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INTERNATIONAL 
LIBRARY of TECHNOLOGY 



A SERIES OF TEXTBOOKS FOR PERSONS ENGAGED IN THE ENGINEERING 
PROFESSIONS AND TRADES OR FOR THOSE WHO DESIRE 
INFORMATION CONCERNING THEM. FULLY ILLUSTRATED 
AND CONTAINING NUMEROUS PRACTICAL 
EXAMPLES AND THEIR SOLUTIONS 



- : tATttE\Y\|QftK; 

: >jlaner'wqrk 

SHAPER.ANTJ'::SL.QttER WORK 

DRILLING* "AMT BORING 

MILLING MACHINES 



SCRANTON 
INTERNATIONAL TEXTBOOK COMPANY 

IB 



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PUBUO UB*ARf 



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M* •• 


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Copyright, 10<)1, by The Colliery Engineer Company. 



Copyright, 1903, by International Textbook Company 



Entered at Stationers' Hall, London. 



Lathe Work, Parts W: Copyright, 1901, by The Colliery Engineer Company. Entered 
at Stationers' Hall, London. 

Lathe Work, Parts 2 and 4: Copyright, 1903, by International Textbook Company. 
Entered at Stationers' Hall, London. 

Planer Work: Copyright, 1901. by The Colliery Engineer Company. Copyright. 
1903, by International Textbook Company. Entered at Stationers' Hall, L« ndon. 

Shaper and Slotter Work: Copyright, 1901, by The Colliery Engineer Company. 
Copyright, 1903, by International Textbook Company. Entered at Stationers' 
Hall, London. . . # 

Drilling and Boring. Parts jif :*• Cfpypfibt, fft^J, tfy *C«X-J:olliery Engineer Com- 
pany. Entered at StatlbriefV^rlatl*. LendonV V* **••*• 

Drilling and Boring, Part 3: Copyright, 19j03f by I^ejinationai. Textbook Company. 

Entered at Stationers' Hall , Londetf. • *• • • I t'.l 

• • ••«••• • • 

Milling- Machine Work. Parts 1-4: • QQpypght**19tft, by The Colliery Engineer Com- 

pany. Entered at Stationers/ NaB, JJbndon+'t I J, 

Milling-Machine Work, Parts 3-5? Copyright*. IlTqgj by J^ternational Text hook Com- 
pany. Entered at Stationers' Hall. London. 



All rights reserved 



2.YV.W 



IB 



PREFACE 



The International Library of Technology is the outgrowth 

of a large and increasing demand that has arisen for the 

Reference Libraries of the International Correspondence 

Schools on the part of those who are not students of the 

Schools. As the volumes composing this Library are all 

printed from the same plates used in printing the Reference 

Libraries above mentioned, a few words are necessary 

regarding the scope and purpose of the instruction imparted 

to the students of — and the class of students taught by — 

these Schools, in cix-er t Stafford eix^ar understanding of 

their salient and unique feat y res ^. 

The only requirement % fQi admission to any of the courses 
offered by the International Correspondence Schools is that 
the applicant shall be able "jtpjread; the English language and 
to write it sufficiently well to make his written answers to 
the questions asked him intelligible. Each course is com- 
plete in itself, and no textbooks are required other than 
those prepared by the Schools for the particular course 
selected. The students themselves are from every class, 
trade, and profession and from every country; they are, 
almost without exception, busily engaged in some vocation, 
and can spare but little time for study, and that usually 
outside of their regular working hours. The information 
desired is such as can be immediately applied in practice, 
so that the student may be enabled to exchange his 
present vocation for a more congenial one or to rise to a 
hieher level in the one he now pursues. Furthermore, he 

• • • 

ni 



w 



PREFACE 



wishes to obtain a good working knowledge of the subjects 
treated in the shortest time and in the most direct manner 
possible. 

In meeting these requirements, we have produced a set of 
hooks that in many respects, and particularly in the general 
plan followed, are absolutely unique. In the majority of 
subjects treated the knowledge of mathematics required is 
limited to the simplest principles of arithmetic and men- 
suration, and in no case is any greater knowledge of 
mathematics needed than the simplest elementary principles 
of algebra, geometry, and trigonometry, with a thorough, 
practical acquaintance with the use of the logarithmic 
table. To effect this result, derivations of rules and 
formulas are omitted, but thorough and complete instruc- 
tions are given regarding how, when, and under what 
circumstances any particular rule, formula, or process 
should be applied; and whenever possible one or more 
examples, such as would be likely to arise in actual practice 
— together with their solutions — are given to illustrate and 
explain its application. . 

In preparing the6^"tektbe6ks^ < Sf*n^^.^een our constant 
endeavor to view the m^jtter'frqfti "the^ftHent's standpoint, 
and to try and anticipate/ evqfyCbingrthat would cause him 
trouble. The utmost pains, have'" "been taken to avoid and 
correct any and all ani$£ddto^5£vp£es6ions — both those due 
to faulty rhetoric and those due to" insufficiency of statement 
or explanation. As the best way to make a statement, 
explanation, or description clear is to give a picture or a 
diagram in connection with it, illustrations have been used 
almost without limit. The illustrations have in all cases 
been adapted to the requirements of the text, and projec- 
tions and sections or outline, partially shaded, or full-shaded 
perspectives have been used, according to which will best 
produce the desired results. Half-tones have been used 
rather sparingly, except in those cases where the general 
effect is desired rather than the actual details. 

It is obvious thit books prepared along the lines men- 
tioned must not only be clear and concise beyond anything 



PREFACE 



. attempted, but they musl 
or reference purposes. They not only give the 

m of information in a minimum space, but this 
tion is so ingeniously arranged and correlated, and 
us are so full and complete, that it ran a 
mailable to the reader. Tii< triples and 

explanatory' remarks, together with the absence of long 
rations and abstruse mathematical calculations, are 
of great assistance in helping one to select the proper for- 
mula, method, or process and in teaching him how and when 
be used. 
Four of the volumes of this library arc devoted to subject) 
ag to shop and foundry practice, The present volume, 
the first of the series, treats on the following subjects: lathe 
i .'1 -l'.tUT work, drilling and boring, 
lling machines. The subjects named have been treated 
from the standpoint of the man running the i 

i and the text is therefore suited not only to the 

the apprentice and the journeyman, but meets fully 

uirements of the foreman, superintendent, 

ring an intimate knowledge of the operation of 

machine tools. This volume, together with the others on 

shop and foundry practice, will prove of gi 

persons engaged in handling, operating, manufacturing, M 

inery. 

aethod of numbering the pages, ems. articles, etc, 

U such that each subject or part, when the subject is divided 

■ 
to make the index intelligible, it was necessary to give each 
or part a number. This number is placed at the top 
page, on the headline, opposite the page number; 
and to distinguish it from the pa^e number it is preceded by 
■ ■ ion mark (§). Consequently, a reference 
. . 26, will be readily found by looking along 
■: tin' headlines until § 37 is found, .■ 
: i § 37 until page 26 is found. 

International Textbook Company 



CONTENTS 

Lathe Work Section Page 

Historical 3 1 

Classes of Lathes 3 3 

The Engine Lathe 3 3 

Plain Cylindrical Turning 3 11 

Centering 3 12 

Squaring the Ends of Work 3 18 

Turning to a Diameter 3 24 

Taper Turning 3 32 

Taper Attachment 3 41 

Boring in the Lathe 4 1 

Use of Chucks 4 4 

Measuring Bored Holes 4 13 

Chucking Tools 4 14 

Boring Bars 4 20 

Boring a Taper 4 25 

Radial Facing 4 26 

Screw Cutting 4 29 

Shapes of Screw Threads 4 32 

Standard Threads 4 36 

Cutting Screw Threads ..... 4 41 

Bolt Cutters 4 43 

Cutting Screws on the Lathe .... 4 47 

The Threading Tool 4 59 

Special Threads 4 5 

Cutting Double or Triple Threads ... 5 11 

Inside Screw Cutting 5 12 

Threading Tapered Work 5 15 

vn 



viii CONTENTS 

Lathe Work — Continued Section Page 

Theory of Cutting Tools ... . . 5 19 

Shape of Cutting Tools 5 25 

Side Rake 5 29 

Forms of Cutting Tool 5 33 

Toolholders 5 37 

Hand Tools 5 47 

Tool Grinders 5 49 

Cutting Speeds 6 1 

Cutting Feed 6 10 

% Errors in Lathe Work 6 16 

Spring of Lathe Tools 6 16 

Spring of the Work 6 20 

Spring Due to Methods of Driving . . 6 21 

Lathe Centers . 6 26 

Errors in Screw Cutting 6 30 

Sliding Fits 6 33 

Driving Fits 6 35 

Forced Fits 6 36 

Shrinking Fits 6 38 

Arbors or Mandrels 6 40 

Ball Turning 6 50 

Turning Cranks 6 50 

Turning Ovals 6 53 

The Turret Lathe ........ 7 1 

Hand Screw Machine 7 3 

Turret Tools and Their Uses .... 7 5 

Monitor Lathes 7 22 

Special Forms of Turret Lathe .... 7 24 

Automatic Screw Machines 7 31 

Special Forms of Lathes 7 32 

Polishing 7 42 

*iling « 4o 

Use of Kmerv . . T -15 

Use of Steady Rest . ... . . 1 47 

m 

Follower Rests 1 49 

Straightening Work 7 51 

Using a Rotating Tool 7 55 



CONTENTS ix 

Planer Work Section Page 

Work of the Planer 8 1 

The Planing Machine 8 1 

Fastening Work to the Platen . . . • 8 7 

Planer Tools 9 1 

Planer Operations 9 9 

Cutting Speed of the Planer 9 20 

Accuracy of Planer Work 9 24 

Special Planer Work 9 28 

Open-Side Planers 9 41 

Shaper and Slotter Work 

The Shaper 9 45 

Classes of Shapers 9 46 

Column Shapers 9 46 

Traveling-Head Shaper 9 50 

Shaper Operations 9 53 

Shaper Tools 9 54 

Holding the Work 9 54 

Taking the Cut ' . . . 9 55 

Spring of the Machine and Work ... 9 60 

The Draw-Cut Shaper 9 61 

Open-Side Plate Planer ,9 62 

Shapers for Special Work 9 64 

The Slotting Machine 9 68 

Slotting Operations 9 70 

Examples of Slotter Work 9 75 

Keyway Cutters 9 79 

Drilling and Boring 

Drilling 10 1 

Development From the Lathe . ... 10 2 

Essential Parts of Drilling Machines . . 10 3 

Principal Functions of Drilling Machines 10 4 

Forms of Tools and Their Uses .... 10 6 

Drilling Tools 10 6 

Machine-Shop Drills 10 9 

Lubrication of Drills . 10 18 



x CONTENTS 

Drilling and Boring — Continued Section Pnge 

Reamers 10 2<» 

Countersinks 10 2K 

Counter bores 10 30 

Spot Facing 10 33 

Taps 10 34 

Devices for Holding Tools 10 35 

Securing Work to the Table of the Simple 

Drilling Machine 10 42 

Types of Drilling Machines and Their 

Uses 11 1 

Boring Machines 11 23 

Horizontal Drilling and Boring Machines 1 1 29 

Cylinder Boring 11 40 

Boring Spherical Bearings 11 44 

Drilling-Machine Operations 12 1 

Lubricating 12 7 

Drill Grinding 12 8 

Drilling and Boring Jigs and Fixtures .12 11 

Miscellaneous Tools and Fixtures ... 12 24 

Tables 12 29 

Morse Taper Shank 12 30 

Morse Tapers 12 31 

Speed and Feed of Drills 12 32 

Cutting Speeds 12 33 

Tap Drills . . * .12 34 

Twist Drills for Pipe Taps 12 35 

. Recent Tests of Twist Drills 12 35 

Milling-Machine Work 

Definitions 13 1 

Construction of Machine 13 4 

Advantages of Milling Machines ... 13 9 

Milling Cutters 13 10 

Classification of Cutters 13 lo 

Construction of Cutters 13 11 

Face Milling Cutters 13 11 

Side Milling Cutters 13 18 



CONTENTS xi 

Milling-Machine Work — Continued Section Page 

Angular Milling Cutters 13 23 

End Milling Cutters 13 25 

Form Milling Cutters 13 20 

Care of Milling Cutters 13 30 

Holding Cutters 13 31 

Preparation of Stock 13 39 

Cutting Speeds 13 40 

Feeds 13 42 

Table of Feeds and Speeds 13 45 

Lubrication 14 1 

Selection of Cutter 14 6 

Limitations and Errors 14 10 

Holding Work 14 12 

Simple Indexing 15 21 

Compound Indexing 15 27 

Differential Indexing 16 5 

Fractional Indexing 16 12 

Spiral Work 16 19 

Natural Functions 16 37 

Special Milling Attachments 16 41 

Talcing the Cut 16 50 

Setting the Machine 16 64 

Special Uses of the Milling Machine . . 16 75 

Comparison of Milling Machines ... 16 79 



LATHE WORK. 

(PART 1.) 



THE LATHE. 



HISTORICAL. 

1. Early Forms of Lathes. — The art of turning, or 
the production of circular or cylindrical pieces by the aid of 
a machine and special tools, has long been known. One of 
the earliest forms of machines of which there is record was 
one used for this purpose. It consisted of a crude wooden 
frame in which the piece to be turned was held by pointed 
wooden or metal pegs passing through the frame and into the 
ends of the piece. The piece was made to rotate upon these 
pegs by wrapping a cord or band about one end of the piece. 
One end of the cord was fastened to a weight or a spring 
pole, while the other was held by the operator or an assist- 
ant. By pulling the cord, the work was made to rotate in 
one direction, the weight or spring pole pulling it back as 
soon as the forward pressure was released. The tools for 
cutting were held in the hand and presented to the work in 
such a way as to cause them to cut the various shapes 
desired. These early machines were called lathes, and the 
simple principle that they involved, i. e., of revolving the 
work upon its axis while being operated upon by the cutting 
tool, is still the fundamental principle in the most modern 
lathes. 

OOmUOMTCO BY INTERNATIONAL TEXTBOOK COMPANY. ENTERED AT STATIONERS' MALL. LONDON 

is 

TIB— 2 



2 LATHE WORK. §3 

2. Slide Rest. — It was not, however, until the inven- 
tion of the slide rest and its application to the lathe, and, 
subsequently, to other forms of machine tools, that the 
rapid growth and improvement in machine-tool construction 
began. The credit for this invention is universally be- 
stowed upon Mr. Henry Maudslay, an Englishman, who was 
born in the year 1TT1 and died in 1831. His slide rest was 
first applied to lathes in 1T94. 

His method was to rix the cutting tool rigidly in a block 
that was fitted into a groove or slide in such a manner that 
it could be moved only in one direction, it being held rigidly 
against all forces tending to move it in any other direction. 
A uniform speed or feed along this line of free motion was 
given by the use of a screw. These few simple principles 
are the ones still employed, and their use has made possi- 
ble the rapid improvements and developments in machine 
construction that have resulted in the wonderfully high 
type represented in the automatic machines of the present 
day. 

3* Development of Lathes. — The early lathe was 
more rapidly developed than the other metal-working ma- 
chines, and consequently was called on to perform many 
operations that could now be more easily performed on 
other types of machines. It not only had to perform its 
own characteristic functions of producing cylindrical, 
tapered, or conical and radial surfaces, but it had to act in 
the capacity of drill press, boring mill, milling machine, and 
grinding machine as well. 

These special forms of machines, which are for the most 
part branch: < from the original lathe, have now become so 
fully developed and adapted to their special work that the 
lathe has been greatly relieved of abnormal duties and can 
now be used almost exclusively in performing its normal 
functions. While the lathe is now assuming its particular 
line of work, it does not follow that its work is less 
complicated or of less importance; it simply admits of a 
greater development and a greater amount of skill. 



§3 LATHE WORK. 8 

CLASSES OF LATHES. 

4* Lathe work probably embraces a greater variety of 
operations than the work of any other machine, and because 
of this fact lathes are divided into different sizes and classes 
specially designed to operate upon some particular class of 
work. Chief among these classes is the engine lathe, which 
might be considered as the typical metal-workers' lathe. 
This same type of lathe, when made with particular care 
and supplied with some extra attachments, is sometimes 
classed as a toolmakers* lathe. Other types of lathes that 
possess some peculiar characteristic are the gap lathe, axle 
hit he, iv heel lathe, turret lathe, bench or precision lathe, and 
some other types specially designed for a particular duty, 
all of which will be described. 

In operating any of the above-named lathes, it will be 
found that the underlying principles necessary for success- 
fully completing a piece of work on any machine are simi- 
lar, and that if the engine lathe be thoroughly mastered, the 
others may be successfully handled with a little practice. 
The principal differences will be found to arise from the size 
and peculiar shapes of the work. 



THE ENGINE LATHE. 



GENERAL. DESCRIPTION. 

S. In discussing the work of the lathe, the standard 
engine lathe of medium size, from 16-inch to 24-inch swing, 
will be considered first. 

The term engine lathe generally indicates that the lathe 
is driven by some power other than foot power, that the tool 
motion is controlled by power feeds, and that the lathe is 
equipped with a leadscrew used for cutting screw threads. 

ft. Names of Parts. — Fig. 1 represents a standard type 
of screw-cutting. engine lathe with the various parts num- 
bered, and their respective names and duties are as follows: 



4 LATHE WORK. §3 

A A is the bed or shears ; Jl, the headstock complete ; C, the 
tailstock complete; D, the carriage; F, the apron; E, E, the 
legs; /, the live center; .', the dead center; 3, the driving 
cone ; -J, the driving gear keyed to spindle ; 5, the back gear ; 




6, the handle for throw 

7, the tiiee y'.aw: v. ' 
stud; 1", the large I 



;ing the back gears 
mid. or swindle: 



or "out"; 
pj.ui.nv. ■-. -l iv-ecl-eime t-n 
feed-rod: II. the i'ecd-nxl; 



LATHE WORK. 



inge gear on stud used in screw cutting; IS, 
angc gear on leadscrew used in screw cutting; V,, an 
. 
■adscrew used in screw cutting; /'.. a 
ravening carriage by hand; 17, a knob for throw 
automatic feed from feed-rod; 18 t a lever forthron 
■ ■', a hand crank f 
tO, a knob for throw 
rhe tool post for holding the cutting tool; ...'■', a 
clamping tsilstock to the bed j4; IBS, a hand wheel 
i [nek spindle and dead center; 2',, a lever 
tock for reversing direction of fead-moti 
feed-rack securely fastened to the lathe 1"'!; . .-''<', a handle 
r operating compound rest cross-feed ; and 87, an adjust- 
ing screw for setting over tailstock spindle. 

7. The Carriage. — The carriage is divided into two 

!. part Miscalled the saddle. Il 
fully fitted Lhe Lop of the lathe h 

id the tool, and receivesall the strain and 
hfust exerted in cutting the work. The 
»llcd the apron. This is secured to the saddle by screws. 
ni ■■!" tin- bed and contains the ■ 
iugh wl ition is transmit ti 

-rack .-'■' -mil tlie split nut which en] 
■ miing threads. 

8, The Feed.— :'- operate lhe feud or cause the can 

malically along the lathe lied, I In- knob 17 
rating a friction clutch inside lhe apron. 
ows in the feed and power is then trans- 
: ml tone '>' tu the fei d-rod com 
and so along the rod to 1 1 

i of the feed-mol i i aj . 

ing cither in the 

■ ■ 
■ 

I that U'-ars X-.s .,' ami .', rotate 



LATHE WORK, 
in the same direction, while gears Nos. 2 and £ rotate in 



the opposite d 



From this wc may see that if the 



bcr of gears in a 

are even, the 

and last gears 

revolve in opposite 
■ Flo. n, .. . , ., ., 

directions, while if 

the number of gears are odd, the first and last gears revolve 

in the same direction. 



03333 E ; 




and the gears by 
which the direction ..f the feed-motion is controlled. 

Fig. 4 is a detailed end view of the same heudstnek. Gear 
Ko. 1 is keyed to the spindle, while gear No. ,1 is keyed to 
the stud or change-gear spindle ft. An arm pivoted on the 
Stud spindle '.' carries the gears J and .}. When the handle;: 
is up, motion is transmitted from the gear mi the headsiock 
spindle, through gear „' in gear .7. Tln-n, having three 
gears in the train, the tir-l and la-t gear have the same 
direction. When the handle- is pushed down, as in Fig. 5. 



§3 LATHE WORK. 7 

gear 2 is moved away from gear J, and gear 4. which was 
before revolving idly, is brought against gear J. Motion is 
then transmitted from gear 1 to 4, from 4 to %, and frofn S 
to S, so that while in this position there are four gears in 




the train and the motions of the first and last gears are in 
opposite directions. In Fig. 1 this same reversing mechan- 
ism is used, but the gearing is placed inside the frame of the 
headstock. 

9. The Speed. — The various speeds of the lathe are 
controlled by the belt running on different steps of the 
cone 3, Fig. 1, and by the use of the back gears. 

10. The Back Gears. — Fig. G is a horizontal section 
through the headstock, illustrating the operation of the back 
gears. The back gears b and c are rigidly fixed to the ends 
of a hollow quill, this quill being supported on an eccentric 
shaft on brackets at the back of the headstock. By partly 
rotating this eccentric shaft by means of the hand lever e, 
the back gears b and c can be brought forwards to engage 
with the gears a and d. The cone is fitted to revolve freely 
on the spindle, and carries with it gear a. Gear d is keyed 
to the spindle and revolves with it. When the back gears 
are out, the cone may be attached to the driving gear d by 
means of a block f, which may be moved into a radial slot 
cut in the end of the cone. When thus connected, the cone 
and spindle revolve together. When the back gears are to 



e LATHE WORK. § 3 

be used, this block is dropped out of the slot and the cone is 
again free to revolve on the spindle. The back gears are 
next brought forwards to engage with the cone and spindle 
gears. Power is then transmitted from the cone and gearn 
to gears b and c, and from gear c to the driving gear </, and 
so to the spindle. Because of the different sizes of the back 
gears, the speed is much reduced; the ratio of speed with the 




back gears out to the speed with the hark gears in, the belt 
remaining on the same step of the cone, is aboul 10 to 1 on 
lathes of about Ki-inch swing. This change by the intro- 
duction of the back gears not only reduces the speed but at 
the same time increases the power, making it possible to take 
much deeper cuts on the work. 

11. Double and Triple Gearing. — When a greater 
change of speed is desired than can be obtained with the 
ordinary set of back gears, a second combination of gears of 
different ratios is introduced whereby the speed may be re- 
duced still more. When this combination is used, the lathe 
is said to be double back-geared. 



J8 LATHE WORK. 9 

Pig. 7 shows a double back-geared headstock. The gears 
b and c are free to slide on a feather on the back-gear shaft, 
so that -when moved to one position, b meshes with a on the 
cone spindle, giving one rate of speed. When b and c are 
moved to the other end of their seat, c meshes with d. Gears 




r and d, being of a different proportion in diameter from b 
and a, give a different rate of speed. 

On the larger and more powerful lathes, a third combina- 
tion is used and it is said to be triple geared. Fig. 8 illus- 
trates a gear of this type. The first portion of the gear- 
ing is similar to that already described, but the triple gearing 
is obtained by means of an internal gear a attached to the 



LATHE WORK. 



§3 




face plate b, which is oper- 
ated by a pinion on the 
shaft d, thus producing a 
slow speed. 

1 2. Tailstock. — In 

the simple engine lathe, 
as shown in Fig. 1, the 
tailstock is secured to the 
bedplate by a clamp bolt 
22 and can be moved by 
loosening this and sliding 
the tailstock to the desired 
position by hand. In the 
case of large lathes, this 
would be difficult or im- 
possible, and siimc special 
method is necessary. In 
tlie form shown in Fig. 8, 
an arm / is attached to 
the tailstock and provided 
with a hand wheel e, which 
operates the gearing ar- 
ranged to engage with the 
rack J. By this device 
the tailstock can easily 
be moved by hand. In 
some c;iscs, arrangement 
is made for connecting 
the traverse mechanism 
with the leadscrcw so 
that the tailstock may 
be moved by power. In 
the form shown in Fig. 1, 
the tail spindle is moved 
in or out by means of the 
hand wheel .'•?; but in the 
form shown in Fig. X, the 



§3 LATHE WORK 11 

tailstock becomes of such extreme length that it is not always 
convenient to operate the spindle by the hand wheel g % and 
the auxiliary hand wheel h with the shaft i and gearing at k 
is provided, thus enabling the operator to control the spindle 
while he is close to the center. 

13. Feed-Sere w Supports. — In the case of a small 
lathe, as shown in Fig. 1, the feed-screw and feed-rod, i5and 
11, are simply supported at the ends and in the apron. In 
the case of long or heavy lathes, additional supports, as 
shown at /, Fig. 8, become necessary. Sometimes several of 
these supports are arranged along the lathe. 

14. Tool Posts. — In most lathes, the tool is secured in 
the ordinary tool post of the form shown at 21 % Fig. 1, and 
at n y Fig. 8, but in large lathes it is sometimes desirable to 
turn work that cannot be swung over the carriage. In such 
a case, the device illustrated in Fig. 8 is used. It consists 
of an auxiliary slide tn placed at the front end of the car- 
riage, and the tool post o. Such a tool post is located con- 
siderably below the line of the lathe centers, and, in order 
to obtain the proper cutting angles for the ordinary tools, 
the surface upon which the bottom of the tool rests is inclined 
at such an angle that a plane passing through the bottom of 
the tool would pass approximately through a line joining the 
centers. 



PLAIN CYLINDRICAL TURNING. 

15. Example of Turning. — In discussing this first 
exercise in lathe work, it may be well to have in mind some 
particular piece that is to be finished. A plain cast-iron 
cylinder 12 inches long, 
2 inches in diameter, 
finished round, true, and 
parallel, according to the Fl °- 9 - 

drawing, Fig. 9, has been selected. The stock may be 
finches in diameter and long enough to " square up" or 
to have the ends finished smooth when it is the correct 




12 



LATHE WORK. 



§3 



size. Work of this character, such as bolts, studs, spindles, 
shafts, etc., that have been forged, cut from the bar, or cast 
very near the finished length, is held in the machine between 
the lathe centers, holes having been previously drilled and 
reamed in the ends of the work for the reception of the 
lathe centers. 



CENTERING. 



LOCATING CENTERS. 

16. Centering by Dividers. — The operation of loca- 
ting, drilling, and reaming the center holes is one of impor- 
tance and requires careful attention. Various methods are 
used for locating center holes, depending on the shape of the 
piece and the number of pieces to be centered. If the stock 
is round and true, the center may be roughly located by 

placing the work on a flat surface 
and using a pair of dividers, set 
to about half the diameter of the 
m^^^pj^ work, for scribing lines on the 
^^^^^P en d> as shown in Fig. 10. To do 
^Fmm this, the dividers are drawn across 
^^F the chalked end of the work, 

^W scribing one line; the work is 

w given a quarter revolution and 

another line is scribed, and so on 
until there are four lines intersecting, as shown. The 
center of the inscribed square is approximately the center 
of the work, provided the dividers were held at the same 
angle with the work each time a line was scribed. A prick- 
punch mark made in the center of the square locates the 
trial center. 

1 7. Centering by Surface Gauge. — Instead of the 
dividers, a surface gauge or scriber block may be used for 
scribing the lines. Fig. 11 shows how a surface gauge a 
may be used for centering a bolt b. In this niece, it is de- 
sirable to make the center true with the stem or shank of 



Fig. 10. 



LATHE WORK. 



the bolt. The head cannot always be depended on to be 
forged true with the shank. The bolt is placed in the V's 
of two blocks c, c, as shown in Fig. 11. These blocks should 




hold the bolt high enough from the bench or table so that 
the head will not touch when the bolt is revolved in the V's. 
The scriber point of the surface gauge is then set to about 
the center of the work and the four lines are scribed, inter- 
secting as shown, 

IS. Centering by Hermaphrodites. — Another 
method of locating the center is by the use of hermaphro- 
dites, as shown in Fig. 12. The hermaphrodites are set so 
thai the pointed leg comes near the 
center of the work. With the other 
leg at the respective points a, b, c, 
and (/, four arcs are scribed, intersect- 
ing as shown. The center e of this 
inscribed polygon is the approximate 
center. 

1 19. Centering by Cup Centers. 
When there are many pieces to be 
centered, time can be saved in locating 
the centers by the use of a cup center, 
shown in Fig. 13. The conical opening 
in the end is placed over the end of the .. 
*ork, as shown, and a light blow on 




14 



LATHE WORK. 



the prick punch p with a hammer is sufficient to mark the 
point. If the end of the work to be centered is untrue, as 
in Fig. 14, or if the device is not held true on the end, as in 
Fig. 15, it will r.ot locate the center accurately. The line 
a b shows the center line of the work, and c d the center 




line of the punch. Fig. 16 shows a centering device that 
insures that the punch and the work will be held in line, 
but does not overcome errors due to untrue ends, as shown 
in Fig. 14. 

20. Testing Location of Centers. — When the 
"stock," or the rough piece to be finished, is very close to 
the finished size, it is best to test the accuracy of the loca- 
tion of the centers before they are actually drilled and 
reamed. This may be done in the case of light work by 
supporting it between the centers of the lathe, allowing the 
points of the lathe centers to enter the prick-punch marks 
made in the ends of the work. While thus supported, the 
work should be revolved rapidly by drawing the hand 
quickly across it. While the work is thus spinning on the 



§3 



LATHE WORK. 



15 



center points, chalk is held against it so that the chalk will 
just touch. If there is an untrue end or a high side, the 
chalk will mark the high place. Thus, the work is tested 
and the center mark moved, if necessary, until the work 
will run with sufficient accuracy to insure the correct loca- 
tion of the centers. 

21. Changing: Center Marks. — The center marks 
in the ends may be changed slightly in location by using a 
prick punch and slanting it in 
the direction in which it is 
desired to move the mark, as 
shown in Fig. 17 (a), or the 
prick punch may be held at one 
side of the center, as shown 
at (b). In the latter case, the 
point of the punch will move 
toward the old center when 
struck, but will draw the center 
to one side as desired. When 
the centers are satisfactorily 
located, they should be made 
quite large with the punch for 
the purpose of making a start- 
ing point for the drill. If only a very small mark is made 
in locating the center, the drill may not start in the desired 
place but begin drilling at some other point. 





FlO. 17. 



FORMING CENTERS. 

22. Centering Machines. — When there are large 
quantities of work to be centered, much time and expense 
can be saved by the use of special centering machines. A 
type of one of these machines is shown in Fig. 18. These 
machines render the methods of locating centers just de- 
scribed unnecessary. The one illustrated is fitted with a 
universal chuck #, which holds the work to be centered 
accurately in line with one spindle of the machine. If the 



16 LATHE WORK. g3 

work is long, the end is supported in the V-shaped rest b. 
When in this position, the work is drilled and reamed, there 
being two spindles, c carrying a drill and d a reamer, which 
can be alternately brought in line with the center of the 
work. After the machine is once adjusted, it will drill and 
ream all pieces to the same depth and size. 




23. Drilling and Reaming on the Lathe or Drill 

Press. — If a centering machine is not at hand, the drilling 
and reaming may be dene on a sniail sensitive drill press or 
on a speed lathe. Ordir.arily. this operation consists of first 
drilling a \.>'.e from , ! , :■■ \ inch in diameter about 1 inch 
deep and then iean::::g the end < I the hole with a reamer 
of the form shown in Fig. 1:' t<*1 or Fig. !•» (/•). This 
practice has been almost entirely abandoned in the case 



LATHE WORK. 



small work by the introduction of the combination drill 



ant 

. 

5 



method saves time 




and reamer shown in Fig. 
res that the 
?amcd position of the 
ill be axially true 
drilled position. 
bis is a very important 
point when accurate lathe 
work is to be done. 



2-4. C © r r e « t I 
Formed Center IIole». 
Fig. 20 (<i) shows a sec- no. M. 

ugh a properly formed center hole and shows how 
it should fit the lathe center. It will be noticed that it is 
framed to an angle of 60° to lit perfectly the angle of Hie 
lathe center; also that the drill hole extends into the work 
■officiently deep to prevent the extreme point of the lathe 
center from bearing against the work. 

The practice employed by some workmen of forming the 

titer hole by simply making a very large prick-punch mark 

into the end of the work is a practice that should not he 




since it is impossible to produce accurate work with 

,ach center holes; besides, the work will soon wear or break 

■ jits of the lathe centers. 

When very large center holes arc required for supporting 

. y pieces, particularly in cast iron.it is an excel- 

nt plan to cut several oil channels, as if. Fig, 2i> (/<). It is 

I to fill (he end of the renter h..le b with wool, felt, 

sal urated with oil. 



18 



LATHE WORK. 



§3 



HOLDING WORK BETWEEN CENTERS. 

25. Precautions. — After centering, the work is ready 
for the lathe. A lathe dog, Fig. 21, is slipped on one end 
of the work, a drop of oil put in the center hole of the other 
end, and the tailstock adjusted to the proper position for 
holding the work between the centers. Care must be taken 
in adjusting the dead center. The proper adjustment is 
such that the work is free to turn, and at the same time is 
held so tight that there is no lost motion. The operator 
must also see that the tail of the dog fits loosely in the notch 





Fig. 21. 



Fig. 22. 



of the face plate. Sometimes the tail of the dog pinches in 
the face plate in such a manner as to hold the work off from 
the live center, as shown in Fig. 22. This prevents the 
work from running true. In adjusting the tailstock on the 
bed, it should be clamped in such a position that it will not 
be necessary to run the tailstock spindle out very far to 
reach the work, as greater rigidity is secured by keeping the 
spindle well in the tailstock. 



SQUARING THE ENDS. 

26. All work turned between the centers of a lathe 
should have its ends %k squared up " or made Hat and true 
before attempting to turn the cylindrical surfaces. 



§3 



LATHE WORK. 



19 



THE TOOL. 

Tool. — The tool used for this kind of work 
is shown in Fig. 23 and is 
known as a right-hand 
slde> tool or knife tool. 





f"T -*■.— „_ - 





Fig. 23. 



Grinding; the 
Tool. — Lathe tools are 
ground for two purposes: 
firsts to secure the desired 
form and shape; and, 
second^ to make the tool sharp. After a tool is once cor- 
rectly shaped, there should be as little grinding as possi- 
ble, in order that the original shape may be preserved. 
Much grinding needlessly wears away the tool. Fig. 24 
shows an end view of a side tool correctly shaped and illus- 
trates how it is presented to the work as seen from the back 
of the lathe. The cutting edge of the tool is at the center 
of the work. It will be noticed that the face of the tool A B 
is ground flat and at an angle to the line C D, which is par- 
allel to the side of the shank. This angle, formed by the 





Fig. iu. 



Fig. 25. 



lines A B and C D y is the angle of side rake. The top 
face denoted by the line J: I 7 is usually ground to make an 
angie with the face A B of about G0° for cast iron and 55° for 
wrought iron or soft steel. When sharpening the tool, the 
most grinding should be done on the top face /: F, care being 
taken to preserve the original shape of the tool. Fig. 25 
shows how a careless workman may round the face A /> of 
the tool in attempting to make the cutting edge sharp, with 



20 



LATHE WORK. 



§3 



the result that the tool cannot cut because of the high 
place //, which touches the face of the work first. After a 
tool is ground on an emery wheel or grindstone, it should be 
sharpened by the use of an oilstone, to give it a keen edge. 



SETTING THE TOOL. 

29. General Considerations. — For roughing cuts, 
the tool should be clamped in the tool post so that the cut- 
ting edge A />', Fig. 20, makes 
an angle of from 10° to 15° with 
the end of the work. The tool 
should be clamped as close to 
the cutting edge as possible, 
in order to give rigidity to the 
tool. The tool should be ad- 
justed for height, so that the 
cutting edge is level with the 
center of the work. 




U* J 



Fn;. *J0. 

30« Rlse-aiid-Full West. — Various means are adopted 
for adjusting the height of the tool, depending on the style 
of lathe and carriage. Fig. 27 shows a very common form 
u s e d on small sizes of 
lathes. This is known as 
the rise-and-fall rest. 
The rest is composed of 
two parts, one a resting on 
the bed of the lathe, while 
the upper part b is hinged 
at the points/,/, and car- 
ries the toul block. By 
means of the adjusting 
screw .»-, this upper part 
may be raised or lowered and the tool set at any desired 
height. This is one of the most convenient forms of tool 
rest u^ed t-r small work. A weight is frequently attached 
to the under side of b by a link passing through a. The 




Fig. 37. 



LATHE WORK. 



sight should be heavy enough to hold the top part down. 
atb.es fitted up in this manner are called weighted-rest 
atlien. 



Fig. as represents another type of 
This style is used 
s type, the height of 



31. 1 »i;.ii. Rest, 
iel rest, known as the plai 
larger lathes 
point is adjusted 
Afore clamping in the tool 
lost, by means of wedges, 
■rashers, or rings under the 
ml, as described in the 
allowing articles. 

32. A<1J ustments 
Height of Tool.— 

Fig. 29 («) shows one style 

adjustment commonly 

iscd. The tool rests on a chip n, which is convex on ils 

inder side. This chip fits the tup of a concave ring b, 

its on the tool block. The tool point o can be set 

ithin given limits, and the chip a under the 

■_.! will rock to a position that will give a Hat bearing fur 





r iu.-:I].h| ..f adjusting (In: hi:ight 
re.ideil and htted tu the I hi in bit/ b, 



22 LATHE WORK. § :* 

which fits over the tool post. By rotating the nut n 9 the 
thimble b may be raised or lowered to any desired position. 
This form has an advantage over the style previously 
described in that it gives a level or flat bearing for the tool 
and keeps it in a horizontal position at all times. There are 
numerous other styles of tool-post adjustment that vary 
little in principle and accomplish the same purpose. 



TAKING THE CUT. 

33* Classification of Cuts. — On all machine work 
there are two classes of cuts used, namely, the roughing cut 
and the finishing cut. The roughing cut is, as its name 
implies, the first heavy cut taken over the work for the pur- 
pose of blocking out or roughing the work very close to size, 
the object being to remove the excessive metal in the short- 
est possible time. Roughing cuts are therefore made as 
heavy and as deep as the machine will drive. The finishing 
cut is the last cut taken on the piece and is intended for 
finishing the work to exact size and at the same time ma- 
king it smooth and true. In order to obtain these results, 
the tool must be very sharp and keen. 

34. Roughing Cuts. — When using the side tool, the 
cut is started at the center of the work. The tool is moved 

side wise by moving the carriage 
by hand until the tool has a deep 
cut — deep enough to cut well 
under the skin and scale if the 
stock is cast iron. The tool is 
held in this position by holding 
the carriage still, while being 
Fig. ao. drawn from the center by means 

of the cross-slide. These operations are repeated until the 
desired amount of metal is cut frmn the end. If much is 
cut from one end, a burr will be !« ft around the center hole 
as shown at /', Fig. ">n. This burr may easily be removed bv 
using the point of the toi.I, after having first loosened the 




LATHE WORK 






dead center to admit the tool, as shown. The tool is fed 
sidewise, in the direction of the arrow, by hand, and, at the 
same lime, the dead center is fed in, to keep the (Ti 

g off. This will cause chips and shavings to get 
into the center hole, which should be carefully removed 
before any turning is done along the cylindrical surface uf 
the work. After each end is roughed off and the 
very close to length, the center holes should again he drilled 
and reamed, if necessary, to make them of the proper size 
to stand the strain when taking the heavy cuts on the 
outside. 

;J5. Finishing Cuts. — Before taking a finishing cut, 
the tool should be reground if necessary and then made 

■! sharp with an oilstone. In order to make the cuts 
it is better, in grinding, to slightly curve the edge 



*= 



HH 



^ 



of the tool near the point, as shown in Fig. 31. The tool 
same- as for roughing cuts, with the exception that 
ing edge m.ikt's such an angle that the end of the 
■: i>r tangent to this curve 
int of the tool o. If the 
U >- t<">l is not rounded or 
tirved, it will leave deep marks on 
i work, as shown in :i somewhat 
d form in Fig. '■••;, the dis- 
•■•■•■n the marks represent- 
ng the movement of the tool for fii. sa. 

i i it ion "( the work. In some cases, when the work 
. eter or when true square faces are not 
'quired, the edge of the tool is ground straight and set flat 



gle that the end of the 



24 LATHE WORK. § 3 

with the end of the work, as shown in Fig. 33. When the 
tool is thus set, it is fed in the direction of the arrow, that 
is, sidewise to the work and not drawn out from the center. 
The "squareness" of the end will then depend on the way 
in which the tool was set. 

36. By setting the tool as in Fig. 31, so that only a small 
portion of the point cuts, and then drawing the tool out 
from the center, the squareness of the end is insured, be- 
cause of the accuracy of the cross-feed. If, however, in 
making the cut, the tool and carriage are jarred or moved 
away from the work, or if the tool dulls, or springs in the 
tool post, the work will not be true. The work may be 
tested with sufficient accuracy for ordinary work by putting 
a scale or straightedge across the end, when, by holding it 
to the light, it will be easy to detect any slight error. If the 
lathe continues to make the work concave or convex after 
the spring of the carriage and tool have been cared for, the 
lathe centers will probably be found out of line. After the 

centers are lined up, the difficulty 
will probably disappear. 




TURNING TO A DIAMETER. 



THE TOOL. 

37. Shape of Tool. — The tool 
selected for the outside cylindrical 
turning in this case is called a dia- 
mond point or front tool. . Very 

much depends on its exact shape 
and the way it is held in the tool 
post and presented to the work. 
These tools will be discussed in full later. For the oresent, 
the typical form represented by the diamond point will 
be considered. Fig. 34 shows this tool as ordinarily formed. 
The cutting is done by the edge A B and the point O 
shown in plan. 



§3 



LATHE WORK. 



25 




Fig. 85. 



Grinding* — The tool is sharpened by grinding the 

top face E JF and the faces shown by the lines A B and CD, 

Care should be taken in grinding the front faces that the 

same amount be ground off the heel 

of the tool as at the point, so that 

the slope of the front of the tool, 

shown by the line G //, be kept the 

same. When the tool becomes dull, 

there is a tendency to hurry the 

grinding operation and make the 

cutting edges sharp by rounding the 

front faces, so that the tool v soon appears as shown in Fig. 35. 

While this may make the cutting edge sharp, it entirely 

changes the cutting conditions of the tool. 

After grinding the three faces E F 9 A B, and CD, Fig. 34, 
they will form a sharp point at O and a sharp edge along 
the line G H. This edge should be rounded along its entire 
length, so that the point of the tool will be rounded as shown 
in plan in Fig. 34. 

In grinding lathe tools when the tool is held in the hand, 
the point should be finished by holding it, when applied to 
the grindstone or emery wheel, as shown in Fig. 36. This 
allows the water to strike the cutting edge first, keeping it 





Fig. 86. Fig. 37. 

cool; it also sets in the correct direction the grain of the 
tool caused by the cutting particles of the emery wheel. 
The tool should never be held as shown in Fig. \Yt when 
grinding by hand, as there is danger that it will catch 
between the wheel and the rest and cause much damage. 



LATHE WORK. 



§3 



SETTING TRE TOOL. 

39. Position of Tool. — The tool should be clamped 
n the tool post as close to the cutting edge as possible, to 




give it rigidity. The shank is generally set about square 
with the work, as shown in Fig. 38. 

40. Height of Tool. — Very much depends on the 
height of the tool. The correct height is governed by the 
angle of front rake or the slope of front edge of the tool G H, 
Fig. 34. Fig. 30 shows a tool at the correct height for 
turning a piece to the diameter shown by the inner circle. 




In this case, if a line A Ji lie drawn from the center of the 
work A, through the point of the tool O, it will be found 
that the front of the tool G H is tangent at this point O. 



§3 



LATHE WORK. 



27 



If the tool should be raised, keeping the front of the 
tool G H at the same angle to the work, it would bring the 




PlO. 40. 

cutting point above the work, as shown in Fig. 40. It is 
obvious that in this position it would be impossible for the 
tool to cut. 

Fig. 39 shows the exact position for a perfect tool, pro- 
vided it would remain sharp. In practice, the tool dulls 
and the point rounds off slightly, so that it is customary to 
set the tool slightly below this theoretical point. This theo- 
retical height varies with every diameter of work. Fig. 41 




Fig, 41. 



shows a tool correctly set for a piece of large diameter. 
The dotted lines show the same tool at the same height 
moved in to cut on a smaller piece shown by the dotted 
lines. It will readily be seen that the tool cannot cut work 



28 LATHE WORK. §3 

of such small diameter when its point C is so far above the 

work. It will also be seen that the 
point of the tool should be lowered as 
the diameter decreases, the point O 
following along the line A B until it 
finally reaches the axis of the work. In 
clamping the tool in the tool post, care 
should be taken that the point of the 
tool does not touch the work. When 
it does touch and the tool is clamped 

down, the edge is liable to be cracked off, as shown in 

Fig. 42. 




TAKING THE CUT. 

41. Roughing Cuts. — Roughing cuts are taken to 
reduce the work very close to size in the shortest time, after 
which the work is finished to the exact diameter and at the 
same time made smooth. 

When it is possible to remove the excessive amount of 
material at one cut, it should be done. Whether this can be 
done or not depends on the power of the machine and the 
strength of the tool, and on the strength of the piece to with- 
stand a heavy cut without springing or breaking. Some 
pieces are so frail that a number of light cuts are required 
to remove an amount of material that under more favorable 
conditions could easily be taken off at one cut. Whatever 
the amount removed may be, there should be left from -fa 
to ^ inch in diameter over the finished size for the finishing 
cut. Only in special cases or on rough work is it allowable 
to rough and finish work with the same cut. 

42. In making the first cut, the tool is started at the end 
of the work and fed by hand until it begins to cut. The 
feed is then thrown in and the tool moves along until a short 
piece is turned on the end. This part is calipered, and if 
correct, the lathe runs on until the tool has fed about half 
the length of the work. The work will then be as shown in 
Fig. 43, the part a being rough, and the part b turned. It 



30 



LATHE WORK. 



§3 



cut, as just described, than to take a number of cuts on 
one end before reversing. The speed of the work depends 
on certain conditions that will be treated of later. For this 
particular piece, F'g. 9, which is 2 inches in diameter, it should 
make about 75 revolutions per minute, provided the casting 
is soft. The feed should be comparatively coarse, making a 
thick shaving. 

43. Fintnhtnft Cuts. — In taking the finishing cut, 
considerable skill must be exercised, since if the piece is 
once made loo small, there is no remedy, and if cut rough 
and untrue, it requires much extra labor to complete it. 

The tool should always be resharpened for the finishing 
cut. Its shape remains much the same as for roughing, ex- 
cept that the top face may be given a little more slant or 
top rake. 

The shape for tools for roughing and finishing cuts will 
be described more fully when considering the theory of cut- 
ting tools. The shapes of tools and also the feed vary con- 
siderably, so that what may be considered good practice for 
this piece would not be the best for heavier work. 



FINISHING TO AX EXACT SIZE. 

44. I t mc of Calipers for Measuring. — The diameter 
of the work is measured by the use of special gauges or by 

calipers. When calipers are used, they 

are adjusted to correct size by trying 

them over a standard cylindrical gauge 

«>1" the desired size, or thev mav be set 

to size by the use o\ a scale. When 

sett mi: calipers by the use of a scale, 

they should be held as shown in Fig. 45. 

It will be noticed that the point of one 

le^ oi" the calipers comes against the end 

oi the scale Hy means of the thumb 

n:-.:. :hr calipers arc ac.;;:sted so that 

the »*ihi':- point of the calipers comes 

i\. *N i'm v. will*, the desired hr.e v " the scale. 




LATHE WORK. 

are must be taken to hold the calipers true and to makt 
he adjustment such that by looking squarely by the point 

r the caliper, it will appear to split the mark on the scale. 

he thickness of a tine on a steel scale is equal to 

inch, and in many instances this amount would be 
ufficient to cause considerable trouble. 

45. Adjusting the Tool. — The lathe tool is set to 

turn the correct diameter by a series of careful trials. A 

light cut is first taken 00 the end, running along far enough 

to give sufficient length of turned part to caliper. The 

lathe is stopped and this part carefully calipered, If found 

to be loo large, the lathe is again started, the feed thrown 

out, and the carriage and tool moved back to the starting 

point, The tool is moved forwards an amount determined 

' the judgment of the operator and another cut taken. 

The work is again calipered, and if found to be correi 1. the 

. irted and the cut proceeds; if the worh is still too 

irge, the previous operation is repeated until the correct 

is obtained. It should be noticed that if, after 

Ig the work, it is found necessary to take another 

■ ross-fecd screw must not be used except to advance 

ii the tool is moved away from the cut, the 

itimating how much to turn the 

move the tool in a little deeper than it 

last cut. 



46. After the roughing cut, the work should be calipered 

>ng its entire length to see if it is all of the same diameter. 

i than the other, it may result from either 

F two causes. The lathe centers may be out of line, or the 

' may have worn away enough to cause a notice- 

c difference of diameter. If the centers are out of line, 

'liter must be moved until the two sides of the 

irlt are parallel. Care must be taken, however, to locate 

tly, in ordei that the center may not be 

lOved when the tool is at fault, The adjustment of the 

i center will be considered later. 



33 LATHE WORK. §3 

CALIPERING. 

47. Great skill and delicacy of touch may be acquired 
by careful calipering,and differences in diameter of .001 inch 
may be detected with ordinary spring calipers. • There are 
two chances for error in calipering: jirst- by incorrectly 
setting the calipers, and, st\ m onJ % by not properly handling 
them. 

Assuming that the calipers are correctly adjusted, they 
are held lightly between the thumb and lingers and passed 
gently over the work a number oi times. It is obvious that 
the diameter of a cylinder must be measured at right angles 
to its axis, and if measured at any other angle, as along the 
line C I\ Fig. 40, it would be incorrect. The calipers are 
therefore turned slightly from side to side until the position 

p ^ is found where the calipers pass 

— -- - - over the easiest. This position. 

which aot\?ars to be the small- 
est diameter, is the correct one. 
When the w. rk is cf the correct 
Fw * size and the c rrect position is 

fr,\::..-] m the calipers will jus: pass over with a very gentle 
press*.: rr--. I: the pressure is sufficient t ■•» h.'.i the weight 
of the :ali::er> or i: force is required t> rush them over 
the w rk. it is t :-;■ iarce. Calir-ers ntav verv easiiv be 
= :, r .: r.g m a r. i it is an eas y matter t • to roe them over work 
-> r r i i- . h :■■•'■ Lar.c~. When the ca livers have been set 
:: rr. a £a-;;e. :r - e T r< >«:-u.c :^ turr.ec so that they ct 
- -.-■: ■» :r"x with the same pressure and feeiir.g that they fit the 

**-6 - 




TAPER TURNING. 

4S. Exprc^sinu the Taper. — Taper is expressed by 

«■« -•••■•■ 

* . .--: -. - i.-T.T. .-:. r..; ^> £ in Co to 

- 4.. - • - - -- - ...?• .. «I?C\ lilalW 

. _ • - mm * mm — m. m »..«.«...M.. a ...^ \^ m «A ^ — 



£- . 



* - - - ■ " i " S.' *■ 



S 



-.___, ^- » » •«* 



st*:^ :t,i case, ii 



§3 



LATHE WORK. 



33 






FlO. 47. 




— J— < 



measured 1 foot apart, the difference in diameters will be 
2 inches. It matters not how large a piece may be, pro- 
vided this ratio of diame- 
ter is maintained. Fig. 47 
shows a number of pieces 
of different diameters but 
all of the same taper. 
Their lengths are the 
same, and the difference 
of diameters at the two 
ends is constant. 

Fig. 48 shows pieces of 
different lengths but still 
of the same taper. The 
fifst piece, 1 inch long, 
has a difference of £ inch in diameter at the ends. The next 
piece, 2 inches long, has f inch difference of diameter at the 

ends ; the third piece, 
4 inches long, has f inch 
difference in diameter. If 
the piece were 12 inches 
long, the difference of 
diameter at the ends 
would be if or 1£ inches 
taper to the foot. It may 
thus be seen how taper 
expressed in one denomination may be reduced to another 
denomination. Thus, to reduce taper per foot to taper per 
inch divide by 12. To reduce taper per inch to taper per foot 
multiply by 12. 

49. Standard Tapers. — Tapers are often spoken of 
by numbers or by the names of particular makers. For ex- 
ample, the Brown & Sharpe taper of a given number, or 
the Morse taper of a given number. The Brown & Sharpe 
taper is supposed to be a taper of £ inch to 1 foot and the 
number of the taper indicates a particular diameter. The 
Morse taper was intended to be £ inch to 1 foot and the 

T IB— 4 





Fig. 48. 



:H 



LATHE WORK. 



§3 



numbers indicate different sizes. Unfortunately, the first 
standards were inaccurate and, consequently, the different 
numbers of Morse tapers are not the same and no one 
of them is exactly £ inch to 1 foot, as originally intended. 



METHODS OF TURNING TAPERS. 

50. Classification of Methods. — There are four 
methods for turning tapers in common use, which are as 
follows: firsts the dead center may be set out of line with 
the live center; second, a lathe provided with a special 
taper attachment may be employed; third, a special turn- 
ing lathe in which the headstock and tailstock may be set at 
an angle to the line of tool feed-motion may be employed; 
fourth, the taper may be turned with the aid of a compound 
rest. 

The first method is applicable only for outside turning, 
while the other three may be used for turning and boring. 



SKTTIXG OVKH THE TAILSTOCK. 

51. Construction of the Tailstock. — The tailstock 

of a hit he is so constructed that the spindle and dead center 
may be moved to bring it either exactly in line with the live 
center, for parallel turning, or out of line with the live center 
for taper turning. 

Fig. -11) show* an end view of a tailstock. The part a is 
lilted to the lathe bed. The part b is fitted accurately to 

pari a and may be moved toward either 
the front or the back of the lathe. The 
part b is moved by turning the adjust- 
ing screw c at the front. When it 
is desired to turn a taper, the tailstock 
h* undamped by loosening the nut d 9 
whi.ii damps it t«> the bed, and the 
ill ,i'l cenicr is moved out of line an 
ain«-uu; that has been previously cal- 
culated . i t". mi r,d bv trial to be correct. 




Ki-. I' 



53 



LATHE WORK. 



52. Estimating the Amount of Set-Over. — The 

amount that a center should be moved to turn a given taper 



eC 



can be easily calculated. Suppose it is desired to turn a 
taper J inch to the foot on the piece shown in Fig. 50. This 
means that in 1 foot length the differ- 
ence of diameter is J inch, and since the 
piece is 1 foot long, it will be necessary 
to move the dead center out of line and 
toward the front of the machine one- 
half of this half inch, or | inch. It 
must be understood in turning that if 
we take a cut i inch deep, we reduce I, 
the diameter £ inch. Moving the dead 
center toward the tool £ inch is equiva- 
lent to taking a shaving or cut £ inch 
deep. The amount that a center is 
set out of line may easily he measured 



by moving the two 
each other and measui 




nters close to 
gfrom point to point v 
as in Fig. 51, 




ith a scale, 
,r by means 
the tailstock, 
as shown in Fig. 52. 

53. Suppose the piece 
to he as shown in Fig. 53. 
Here the taper is $ inch 
to 1 fiu it and the piece 
is hi inches long. If the 
Pw -» piece were 13 inches long. 

it could at once be estimated that the center should be set 
out of line f inch, but since the piece is less than ]'i inches 
' on Bi i > ncn would not lie correct, as it would turn the 
taper too blunt. We must here reduce the taper per foot 



3(i 



LATHE WORK. 



S3 



6 



T 
i 



to taper per inch by dividing by 1*2. Dividing } by 12 
equals £ X ^ = ■** = rV inch; x \ x inch to the inch is there- 
fore equal to 2 inch to the 
foot. Multiplying the total 
length of the piece between 
centers by 10, { \ x 1 = J J = 
3 inch, the taper in a piece 
10 inches long. Since the center is set over half the 
amount of the taper, divide g by 2, which gives r 5 T inch, 
the amount that the center should be moved out of line. 



Fig. 55. 




Fn.. M. 



54. Setting by Notches. — When the taper per foot 
is not given but when we have the diameters, with the 
distance between them, 
another method may be 
used. Suppose a piece 
as shown in Fig. 54 is 
to be finished. Notches 
are first cut in the stock, 
as shown at a and /\ Fig. 55. The dotted lines indicate the 
shape of the finished piece. One much is cut $ inch from 

the end, until the di- 
ameter at the bottom is 
1J inches, and the sec- 
ond notch is cut 3£ 
inches from the first 
until it measures 1 T \ 
inches at the bottom. 
These notches define the taper, and from these diameters, 
measurements are taken for setting the lathe, as will be 
shown later. 

When the work is prepared, it is put between the center 
and a to..l held in the tool post, the same as for turning. 
The dead rentrr is moved an amount estimated by judg- 
nv nt. The t'»-il is then moved opposite one notch of the 
W'-rk, as at »/, l ; i-. .">♦'.. and the distance from the point of 
t'r.r t". '1 t«» the bottom of the notch is measured. The tool 
and carriage are then moved opposite the second notch b 9 







§3 



LATHE WORK. 



37 



and the same measurement taken. If the measurements 
arealike, the work is correctly set; if not, the dead center 
must be adjusted until they are the same. After each ad- 
justment of the tailstock, the work must be measured from 




each notch. It is not right to measure with the tool in 
position a, and then adjust the tailstock until the measure- 
ment at b is the same, for it will be seen that in changing 
the measurement at b the measurement at a will also 
change, although not so rapidly. 

Various methods are employed for taking the measure- 
ments from the work to the point of the tool. An ordinary 
scale or a pair of inside calipers may be used. When cal- 
ipers are used, it is better to use the butt end of the tool, or 
some flat surface, as it is easier to measure between surfaces 
than between points. 




55. Caliper Tool. — A 


till better way is to have 


special caliper tool, as shown 


ii Tin. 57. It consists ..f 


shank b like an ordinary lath 


c t....l, i<j ilic end of whi.h 



38 



LATHE WORK. 



§3 



pivoted a pointer/, which can be moved like the leg of a 
caliper. The tool is clamped to the tool post and adjusted 
so that the rivet e on which the pointer swings is at the 
same height as the axis of the work. When it is desired to 
test the work, the pointer is brought opposite one of the 
notches and the tool is adjusted by means of the cross-feed 
screw until the end of the pointer just touches the work, as 
shown. The nurled knob a is connected with the pointer 
and is used for moving it in calipering. After the tool is 
adjusted for one position, the pointer is dropped so that it 
can be moved to the other position, where it will at once 
indicate whether the work is correctly set or not. 



56. Setting: by Turning Parallel to Two Diam- 
eter*. — Sometimes tapered work is set by turning to two 
diameters, as shown in Fig. 58, the work being turned to 

the smallest diameter 



Y 



V 



r 



31 



a 






* 



Fig. 56. 



of the taper up to its 
beginning, and then 
from this point to the 
head of the taper the 
work is turned to 
the largest diameter 
of the taper, as shown. After this, the tool may be set to 
the points a and b y as in the case of setting by notches. 
This method has the advantage that a large portion of the 
stock is removed while the work is between centers that 
are in line, and fits the centers of the work perfectly. 

57. Setting With a Model Piece. — When a model 

taper has been furnished, the lathe may be set directly from 
it. The model is put t>ct\veen the lathe centers, and the 
dead center is adjusted so that the measurements from 
t;.e >•::.: «»t" a tool in the U>ol post to the taper model 
re::. : :.- o»n>tant a> the carriage and tool are moved along 
:•.- !'.n^'::. When close measurements are desired, the tool, 
or. "•,«.•:«;■■. -onie article with a rounded end, is brought close 
\'. •.;.•_■ ::.o'iei. >o that it loosely pinches a piece of tissue 



§3 



LATHE WORK. 



\yj 



paper. The tool and the paper are moved along the length 
of the taper and tested at various places by pulling the 
paper. If the paper slips between the tool and the taper 
model with about the same pull at all places, it is correct. 
White this method of turning tapers by setting over the tail- 
stock is a very common one, it is by no means the best, 
ance there are some very objectionable features. 



OBJECTION TO SETTING OVER LATHE CENTERS. 

58. Wear of Centers. — Fig. 59 shows a section through 
wrk when the centers are set out considerably. It will be 
s«d that the dead center touches the work in only two 



points. Since the work rotates about the dead center, there 

is a tendency to wear away the center hole and the lathe 

«nter. Much wear would result in a shape as shown in 

Fig- 60. The front side of the point of the center is worn 

"ay and a groove formed at the 

tack, while the center hole is worn 

intoa bell shape. The live center 

revolves with the work, so that 

the Wearing action between it and 

'he center is somewhat different. 

On the dead center the work has 

a stating motion, while on the 

I™ center it has a reciprocating i 

that the live center is worn evenl 

"iter hole is worn into about the sa 

c^ter hole. 




i. The result is 
around, and the 
ape as the dead- 



40 



LATHE WORK. 



§3 



This wear on the center holes is verv undesirable. It 
makes it difficult to turn a true taper, and if a part of the 
work has been turned true and parallel, it will be found to 
run untrue on the worn center holes. The result is that 
after a taper has been turned, the tapered part and the par- 
allel part do not run true with each other. Besides this, if 
the lathe centers become much worn, it will be necessary to 
grind them before parallel or true work can again be turned. 

59. Different Tapers for Different Lengths of 
Work. — When it is desired to turn the same taper on a 
number of pieces of different lengths, it will be found that 
the center must be adjusted or reset for each length of work. 
When the lathe is adjusted to turn a given taper or work of 
a particular length, it will be found that if the work is a 
little longer or shorter, it will change the taper. Suppose 
that in Fig. CI, a b represents the line of lathe centers for 




Fig. 61. 

turning parallel work. Assume that the dead center is set 
out of line \ inch, as shown by the line c d. 

Any piece that may be turned with the dead center thus 
set will have a difference of diameter at its ends of \ inch. 
If the piece be 1 inch long, so that the dead center is in 
position e y the taper will be \ inch to the inch. If the piece 
be 2 inches long, so that the dead center is in position/", 
the taper will be £ inch to 2 inches, or J inch to the inch. 
If the piece is 3 inches long, so that the dead center is in 
position^, the taper will be 4- inch to 3 inches, or 2 inches 
to the foot. These three tapers may be compared by refer- 
ence to the outlines. It is evident that anv slight difference 
in the distances between centers in turning two pieces of 



§3 LATHE WORK. 41 

work will make a difference of taper that can readily be 
detected when fitting work. If, in two pieces of the same 
length, one is centered and reamed with much deeper center 
holes than the other, it will allow the lathe centers to come 
closer together. This will cause a slight error. In es- 
timating the amount that a dead center should be set over, 
as previously described, this error is often neglected, as the 
work is usually tested before the finishing cut is taken, and 
any slight error is corrected. 

GO. Amount of Taper Possihle.-^-The amount of 
taper that can be turned between centers by setting over 
the center is limited by the total length of work and the 
amount of adjustment possible in the tailstock. Suppose the 
greatest amount of " set-over " in the tailstock is 2 inches. 
This will make a difference of diameter at the ends of the 
work of 4 inches. If we should wish to turn a taper of 1 inch 
to the foot, the greatest length of shaft on which we could 
turn it is 4 feet, and if the shaft or work should be longer 
than this, it would be necessary to use some other method 
of turning the taper. 



TAPER ATTACHMENT. 

61. Principle of Taper Attachment. — Very many 
of the objections that arise in taper turning due to the set- 
ting of the dead center are eliminated by the use of the 
taper attachment. The principle is simple. It consists 
primarily of a jguide bar supported by brackets on the back 
of the lathe. This bar so controls the movement of the cut- 
ting tool that as it is fed along the bed it is made to advance 
or recede from the work. 

Fig. 62 shows a taper attachment applied to a lathe as 
seen from the back. This particular carriage is fitted with 
a taper attachment and a compound rest &, a device also 
used for turning tapers. The peculiarity of this carriage 
for the taper attachment is that it requires an extra slide. 



LATHE WORK. 



§3 



62. Oeacrlptlon. — Fig. liU shows a side elevation of a 
carriage with this form of taper attachment. The saddle a 




'['■■ this i* !iiii-d tin' extra cross-slide b, 
ii- l-.i.k and is ■-.iiiim-tril iv.ithabolt rand 



§3 LATHE WORK. 43 

shoe s to the guide bar g. The cross-feed screw is attached 
at the front end of the slide b, and operates the tool block c 9 
which is fitted so as to slide upon part b. When the cross- 
feed screw is turned, the tool moves as in the ordinary car- 
riage. When part b moves, it carries the tool with it. The 
movement of part b and, consequently, the movement of the 
tool, is controlled by the angularity of bar g. If this bar 
is set parallel to the V's of the lathe bed, there will be no 
motion of part b across the lathe and the tool will turn the 
work parallel. Suppose this guide bar to be 2 feet long and 
pivoted in the center. If the bar be turned at such an angle 
that the ends are out of line \ inch, and the carriage be 
moved along from the center of the bar to the end, then the 
part b and the tool will be moved across the lathe bed \ inch. 
This will be equivalent to setting over the center £ inch, 
which on a piece 1 foot long would turn a taper of £ inch to 
the foot. If the carriage moved the whole length of the 
tar, or 2 feet, the tool would move across the lathe bed 
i inch, which would give a taper of \ inch in 2 feet, which 
is the same as before. It will be seen from this that when 
the attachment is once set, it will turn the same taper on 
pieces of any length. 

63. Adjusting: to Turn a Given Taper. — In adjust- 
ing this style of taper attachment, the scale shown at the 
end of the bar g y Fig. 02, is used. A line at the center 
marked o indicates the mid-position, when the bar is par- 
cel with the lathe bed V's. The scale indicates taper in 
e, ghths of an inch to the foot, so if a taper of \ inch to the 
foot is desired, the clamping bolts (not shown) that pass up 
through the slots in the end brackets are loosened and the 
adjusting screw d is turned until the pointer on the bar 
has moved over four marks. The bar is then clamped in 
place and all is ready to proceed with the cut. When the 
lathe is used for ordinary parallel work, the taper attach- 
ment is usually disconnected by removing the screw e from 
toe block j, and the part b is clamped in its slide by tighten- 
,n gthe setscrews f on the side. 



44 



LATHE WORK. 



§* 



4. Advantage*. — The advantages of the taper attach- 
ment are apparent. By keeping the lathe centers in line 
while turning, the work centers do not wear untrue, the 





Km. 64. 



lathe renters are nut subject t<> undue wear, and arc con- 
stantly in line when a change is made tmm taper to straight 
work. When these attachments become much worn, there 
may be some lust liiutiun in the parts. This will cause the 



\ 



LATHE WORK. 



!- 



lathe to turn parallel for a short distance on the end, until 
the lost motion is taken up. This trouble can easily Lie over- 
come by starting ttic cm Ear enough beyond the end of the 
■ that by the lime the carriage anil tool nave fed up 
•> the work, all the lost motion has been taken up. In prao- 
s this movement of the tool and carriage is made by hand 
j save time. 



SPECIAL TAPER.Tl'KMIVG LATHE. 

65. A more perfect arrangement for taper turning is 

Sound in lathes specially designed for this purpose. Such a 

is represented in plan and elevation in Fig. <ii. In 

nne, the beadstock and tailstock are fitted to the 

plate or secondary bed. This plate is fitted to the 

ig pivoted in the center in such a manner 

■■.- be s.*l at an angle with the V's of the main lied 

. which tiic carriage runs. This secondary bed is set by 

ncans of a si'ate at the end, in much the same manner as 

i attachment. 

.. may at first appear that the taper is produced by 

.citing over both headstock and tailstock, it is quite differ- 

. the method first described. In this style of ma- 

hine, the axes of the headstock and tailstock spindles are 

; hat all the desirable features found in the 

'.ml here, while the trouble due to 

a in the parts is avoided. 



TVRMVfi TAI'LH WITH A COMPOl'KI) BEST. 

«6. L'ims of Compound Best.— When the taper is very 

inch to the inch, it can best lie turned by 

compound rest. Such a rest is very clearly 

tsists of ,111 extra slide fur carrying 

: u the place of I he !"<>! 

- <\iv.i slide rests on a 

lase and can : ■ laud 



46 



LATHE WORK. 



§3 



of the tool block may be in a line at any angle with the 
regular cross-feed. 

In Fig. 02, the usual cross-slide is operated by means of 
the handle //, while the compound slide is operated by the 
handle/. 

67. Setting the Compound Rest. — The base of the 
compound rest is usually graduated with degrees, so that it 
may easily be set at any desired angle. When the angle in 
degrees of a taper is not known, it may be found by making 
a drawing of the work. 

68. Example of Turning With Compound Rest. — 

Suppose it is desired to turn the piece as shown in Fig. 65. 

If the drawing has been 
accurately made, the angle 
may be measured with a 
bevel protractor ; if only a 
sketch with dimensions is 
given, the angle may be 
laid off as follows: Draw 
two lines a b and c d y Fig. 66, 
at right angles to each 
other, intersecting at 0. 
On a b lay off from o a dis- 
tance 8 inches, equal to 
the distance between the 

given diameters. On c d lay off 7 inches, equal to half the 

difference of diameters, or equal 

to the difference of radii. Draw 

a line through these two points. 

If a protractor is at hand, the 

angles may be measured; if not, 

a bevel may be set equal to 

angle v. With the bevel, the 

c<»m{H>und rest may be set at the 

proper angle by using it as shown 

in Fig. i;7. The beam of the 

bevel is held against the face plate while the compound^ 




Pig. 66. 




Fig. GO. 



jj3 LATHE WORK. 47 

rest ia swung to the angle indicated by the blade of the 
beveL This method of setting the compound rest is also 
used when boring tapered holes. 




TURNING TAPER BY USB OF TWO FEED-MOTIONS. 

69. Another method of turning tapers is to use the two 
feeds at once. The longitudinal feed is thrown in and the 
tool may be fed by hand. Sometimes the two feeds ma,y be 
worked automatically, but the method is not generally used, 
« it is difficult to proportion the rates of feeds to turn a 
correct taper. 



POSITION OF TOOL. 

70, General Directions. — The operation of turning 
a taper after the machine has been set is similar to that of 
turning a plain cylinder. The difference will be found in 
"k shape of the tool and in the manner of setting it. This 
l»lter exception is of sufficient importance to warrant the 
'tttement of the following rule: 

71. Setting: the Tool. — In setting a tool for tinning 
"'"per, the point of the tool should be at the same height as 
'basis of the work. 



4P 



LATHE WORK. 



53 



Since the position of the tool is fixed at n given height in 
taper turning, the tool should be forged with little front 
rake or clearance, keenness being given by increasing its top 
rake. If the tool is set above the center, it will make the 
large end of the work too small. It will also make the sides 




of tlie taper curved, as shown by the dotted lines hij in 
Fig. lis. Suppose that we have turned a taper, as shown by 
the full lines, with the tool correctly set at the center. The 
line ah represents the path of the point of the tool, and is 
equal to the length of the piece. The line a* b' also shows 
the path <>f the point of the tool and represents exactly the 
»m>>uni that the t"<>l recedes from the axis of the work in 
traveling along its length. With the machine once set, 
these conditions of tool travel will be repeated whether the 
too] is set high or low. 

72. Suppose that the tool is set much above the center, 
as at c, and adjusted to cut the same diameter at the small 
em! lis bef-re. The path of the tool will then be along the 
linn-/ equal to. 7 A When the tool has reached the point d, 
it will alfi li.tvi- in. 1 vi d along the line «■'*/' to the point </', a 
diMaiirc e.pial to <i'h\ A i-in-li: drawn through tf repre- 
sen;s Hi.- diann-lir that the i....| is turning when it leaves 
the work at./. This will be seen to be somewhat smaller 



S3 



LATHE WORK. 



49 



thin the correct diameter obtained when the tool is properly 
seL In the same manner we may find the exact diameter 
that the tool may be turning at any point along the taper. 
Suppose we wish to find the diameter that the tool will 
turn in the middle of the piece when the tool is set above 
the center and follows the path cd. Divide the line c' d' in 
halves, which will give the point k '. Describe a circle 
about the center through this point, and it will indicate the 
diameter at this point. This diameter may be transferred 
to the side elevation by dividing the line cdin halves and 
erectingaperpendicular^yat the dividing point. With ok 
as a radius, lay off points i on the line ef, each side of the 
center line a b. These points will be found to fall inside the 
true taper. In like manner, points may be found at any 
place along the length of the work, and they will all fall 
inside the true taper. If a line be drawn through these 
points, it will represent the curve to which the work will be 
turned. 



PITTING THE TAPER. 

73. Methods of Testing. — After the roughing cut 
ins been taken on a tapered piece, and before it is near the 
finished size, it should be tested in the piece it is intended 
to fit. The taper is carefully placed in the tapered hole. 



and first tested by the : 
"» small, as at c. Fig. CO, 
it can be detected by rock- 
ing the work in the hole. 
The plug will just fill the 
hole at the end a, and while 
the imperfect fit cannot 
Ik seen, it can easily be 
felt. In this particular 
case, the indications are 
that the dead center was mo 
he moved back a very sliglv 
o«r the work. After this 



of feeling. If one end is much 




out of line. It should 
ind another cut taken 
work should again be 



50 LATHE WORK. §3 

tested, and if there is no perceptible wabble, the fit may be 
tested still more closely by drawing three chalk lines along 
its length. The work is then placed in the hole and given a 
turn or two in a direction opposite the motion it had in the 
lathe. Upon removing the work, it will be seen that the 
chalk has rubbed off and is black at one end or the other, 
depending on which end was too large. In this way the 
work is tested and the lathe adjusted until the fit is satis- 
factory. 

74. It should be observed that the work is tested and 
the machine accurately adjusted before the piece is turned 
to size. If the machine should be incorrectly set, and the 
piece at once turned to size at the small end, it might be 
found that the work was too small at the large end, and for 
this mistake there would be no remedy. In most cases it 
will be found that tapers must fit the hole exactly and go in 
a certain distance, up to a shoulder, as at b> or until the 
end c just comes through. If the taper is turned too small, 
even though it is a correct taper, it will allow the work to 
go in too far, which, in many cases, is as bad as an incorrect 
fit. In practice, the plug is left slightly large, so that it 
does not go in quite the desired amount. The final fitting 
is usually done by filing, or by grinding on a grinding 
machine, the filing or grinding being just enough to remove 
the tool marks. In fine fitting, the thickness of a chalk line 
is sufficient to make an error of some importance, so a sub- 
stitute is used. One-half of the tapered piece along its 
length is coated with a very thin coat of Prussian-blue 
marking, it being applied with the finger and nearly all 
rubbed oil, so that there is just enough left to give it color. 
The work is then tested in the hole or gauge and given a 
turn. Ii." the marking is evenly distributed about the piece, 
it indicates a perfect bearing; but if it is rubbed off at one 
place only, it shows that it is too large at that point. 



LATHE WORK. 



BORING IN THE LATHE. 

1. Definition. — The operation of turning or producing 
internally true cylindrical or conical surfaces is known as 
l>»riiti£. Tin's operation is performed by causing the work 
to turn upon its axis while held in a chuck or bolted to a 
:, the tool being fixed in the lathe carriage; or, by 
fixing the work securely to the carriage, while the tool 
revolves upon a bar placed between the lathe centers. 



HOLDING THE WORK. 



CHUCKS. 

2. General Considerations. 

nay best be held in th 

■ the lathe 

■ 
lot* are 

ated by means nf 



Small regular work 
tat be eliuek. The lathe chuck in 




2 



LATHE WORK. 



§4 




^BMS^ 




Fig. 2. 



screws or by a scroll. Fig. 1 shows a common form of lathe 
chuck. Fig. 2 shows a section of the same chuck with one 

jaw and its screw re- 
moved and placed 
above the chuck. 
These lathe chucks 
are made as large as 
3 feet in diameter. 
Work that would re- 
quire the use of very 
large chucks may be 
better operated upon by fastening or bolting it to the face 
plate of the lathe. 

Chucks are made with two, three, or four jaws. Chucks 
similar to those shown in Fig. 2 may have the jaws reversed 
by unscrewing and putting them in in reversed position. 

3. Classification of Chucks. — Chucks are classed as 
independent* combination, or universal chucks. Indepen- 
dent chucks are so arranged that each jaw is moved with 
an adjusting screw independent of the other jaws. Uni- 
versal chucks are so constructed that when one jaw moves, 
the others move in the same direction a corresponding 
distance. Combination chucks are so constructed that they 
may be used either as independent or as universal chucks. 

4. I' nl versa I and Combination Chucks. — Fig. 3 
shows a combination chuck with a partial section moved 
from the back. A pinion a is cut on each adjusting screw, 
and thrM 1 pinions engage with a circular rack b in the back 
of tlu* chuck. When one adjusting screw is turned, the rack 
is i ota led and each screw is turned an equal amount, thus 
moviiH'. e.u h jaw a corresponding distance. To make this 
chuck independent, the lack must be lifted out of mesh with 
i lie pinion'. »mi the m lews. The ring c rests against the 
ba« L ft tin i.n L .'■ a\u\ cams ./project from the back of this 
mir When the it ue. is partially rotated by means of the 
Limb . . t lie . .mi . .:' di up into pockets, tlvcs aV.owinjj the ring 
and the tat 1. i" iu.»\e a\\a\ ! : oin t'le pinions sufficiently to 



LATHE WORK. 



scngage. When this is done, each screw is disengaged 

M.l the chuck is independent. When the ring is partly 

-t a led in the opposite direction, the cams lift the ring and 

lat the latter again engages the pinions, and the 

buck is again unlvcr- 

After using a 

i chuck as 

independent chuck 

or irregular work, the 

5 will be out of true. 

jaws true, 

djust each to a circle 

brawn upon the 

ice of the chuck, and 

i throw Mn' r.iL-k tiilo 

r. Combination chucks 

■ some classes of irregular work. The chuck i^- made 

dependent, and after the work is once set true, the cumbi- 

i be thrown in. When the work is removed, U^ 

irs will all open together, occupying a relative position. I f 

! next piece of work is set in the chuck in the same posi- 

i in relation to the jaws as the first, the jaws can be 

and the work will run true the same as the pre- 

i nek may be constructed like the 

3 with the ring r left out and the rack b 

he gears or the jaws may be moved by a 

is a flat disk with a spiral groove cut in it. 




■ 1 adv intage 



5. Independent Chucka.— 1 u this style of chuck, the 

y irregular shapes. When 

use an independent chuclt on work of 

, regular shape, the difficulty of carefully centering each 

ided by marking two jaws of the chuck (in 

chuck) after the first piece has been 

ion. When the piece is finished, it can be 

■ the marked jaws, the succeeding 

□ position, and ilie. marked jaws tightened. 

ond |iie<;e being properly set. This 



4 LATHE WORK. §4 

operation may be repeated for any number of pieces that 
are alike. By this device, the one great objection to the 
use of the independent chuck is overcome, and work may 
be centered almost as quickly as in the universal chuck. 

6. Advantages of the Different Classes. — Inde- 
pendent chucks are generally stronger and better adapted 
to irregular forms of work than either of the other types. 

Universal chucks are best adapted to regular work; they 
save much time because of the ease and rapidity with which 
the work may be centered. 

Combination chucks answer for both purposes, but require 
a little more care to keep them in proper condition. 



isi: OF CHICKS. 

7. Selection of Chuck for Work. — If the hole is to 
be bored concentric with the outside of the work, the uni- 
versal chuck can be used. If the. work does not run satis- 
factorily, it can be partly turned around in the chuck and 
tried in various positions. If this is not sufficient to make 
the part to be bored run sufficiently true, pieces of paper or 
brass can be placed between a jaw of the chuck and the 
work. When this amount of trouble is necessary, an inde- 
pendent chuck would be the better one to use. 

8. Setting Work in an Independent Chuck. — To 

set a piece in an independent chuck, if the work is at all 
heavy, it can be held against the chuck by using a block of 
wood bet wren the work and the dead center, as shown in 
Fig. 4. This will hold the work from falling out while the 
jaws are being adjusted. The jaws are tightened enough to 
hold the work. The lathe is started at a moderately fast 
spied and the work tested by holding chalk against the side 
of the work. If the work is untrue, the chalk will touch only on 
th<- hiiih <id<\ This indicates that the work should be moved. 
If the chalk touches the work as shown by the line a b, it 



» 



LATHE WORK. 



would indicate that the jaw opposite jaw / should be loosened 
and jaw 1 tightened, thus moving the work across the face 




of the chuck. If the chalk touches between the two jaws, 
Iben the two opposite jaws must be loosened and the two front 
ones tightened a corresponding amount. The amount that 
each jaw is moved should be observed, as it will help to de- 
termine the amount of subsequent movements. When the 
TOrk is to be turned or faced on a number 
of faces, each face should be considered in 
setting the work before beginning to turn 
any one face. For example, take the cone 
pulley, Fig. 5. Here the hole must be bored 
true, and the inside and outside of the cone 
bored and turned. If the casting is perfectly 
true, the work may be set by any one face 
and the others will naturally run true, but 
this is not apt to . be the case. All parts Fig. 5. 

should be tested to see if there is enough stock, and to see 
if the faces run true enough to turn to size. 

9. Example of Chuck In k-— Suppose a disk, as shown 
in Fig. 6 (a), with a hole cored very much to one side, is to 
be bored and turned to a given size. If set in the chuck so 
that the outside runs perfectly true, the cored hole would 
he so out of true that it could not be finished. If the cored 
hole is set to run true, then the outside could not be finished 




6 



LATHE WORK 



§4 



all over. In such a case, the work should be so set that both 
the outside and the cored hole run out of true. By thus 
dividing up the eccentricity, it will be found that the work 





w 



(ti 



Pig. a 



can be finished all over to the desired size, as shown by the 
dotted lines, Fig. 6 (b). 

10. Spring of Work From Pressure of Jaws. — 

When the work is light or frail, there is much danger of 

springing because of 
the pressure of the jaws 
necessary to hold the 
piece. In chucking a 
piece, advantage should 
be taken of the shape of 
the work in order to 
have the jaws of the 
chuck come against the 
more solid parts. For 
example, in chucking a 
pulley, it should be so 
set that the jaws come 
opposite the arms of the 
pulley. Suppose that a 
ring is held in the chuck, as shown in Fi^ r . 7. When the jaws 
are tightened, the work is sprung opposite each jaw. If a cut 
is taken, the work will be bored true and round while under 
pressure of the jaws. When this pressure is removed, it 




Fig. 7. 



{4 



LATHE WORK. 



will be found that the work will no longer be true but will 

spring back to its normal shape. This will cause the work 

to be untrue, as shown in Fig. 8, the dotted lines indicating 

the true circle. In such 

cases, the jaws of the chuck 

should be loosened before 

taking the finishing cut, so 

that the pressure will be 

just sufficient to hold the 

work. 




Fig. 8. 



11. Care of Lathe 

Chucks. — Lathe chucks 

should be treated with care, 

especially universal chucks, 

since their value depends in 

many cases on their ability 

to hold the work true. When these chucks are abused by 

hammering or by unduly heavy strains, they become sprung 
and thus lose their characteristic value. In putting a chuck 
on the lathe, it should be held carefully against the nose of 
the spindle while the lathe is turned by hand. It is not 
good practice to start the lathe by power and hold the chuck 
against the spindle, expecting the thread in the chuck to 
catch squarely on the lathe; neither is it good practice to 
let the spindle screw into the chuck up to the thread with a 
bang. This often causes the chuck to stick so tightly to the 
spindle that it becomes quite difficult to remove it. When 
the chuck does stick on the spindle, it may be loosened by 
running the lathe backwards at the slowest speed and in- 
serting a block of wood between the jaw of the chuck and the 
lathe bed. 



SPECIAL CHUCKS. 



12. Some work is of such shape that the ordinary lathe 
chuck will not hold it with sufficient rigidity' to take heavy 
cuts. In this case, special chucks may be made, when 



8 



LATHE WORK. 



§4 



there are enough pieces to be turned to warrant the cost. 

For example, the cone pulley shown in Fig. 5 may best be 

held in a special chuck. Such 
a chuck is shown in Fig. 9. 
This chuck consists of a bell- 
shaped casting a, which is 
fitted to the spindle b of the 
lathe. The outer end is bored 
to receive the work c, which 
is held in place by setscrews d 
at the sides. This form of 
chuck holds the work with 
great rigidity and makes pos- 
sible the taking of heavy cuts 
that could not otherwise be 

accomplished. For special work, other forms of chucks may 

be devised that dejxmd on the shape of the work. 




Pig. 0. 



CHICKING ON THE FACE PLATE. 

It). I t hc of Face Plate. — When the work is large or 
heavy, or for other reasons cannot be held in the chuck, it 
may Ik* fastened to the face plate by means of special blocks, 
Irolts, or strips used for that purpose. It is essential in set- 
ting work on the face plate that it is secured firmly, so that 
it will not slip or change its position because of its weight 
• ir the pressure of the Ux)l. 



II. A<U tint able Jawn for Face Platen. — For 

•<rurin«: work ujx>n the face plate, and in order to enable 
i hi- ojKTator to successively chuck similar pieces with the 
li ;r i amount of labor, adjustable jaws are frequently 
t Limped on the fare plate. These adjustable jaws usually 
lohi t «»t a l>liH*k, a^ <j, V\£. 10, in which jaws b work. The 
IiIimK-. .in- rl.imprd to the fa co plate by means of T bolts c. 
I In- ivall\ make-: a special form of chuck of the face plate. 
A liice plate lit ted with t hose adjustable jaws is shown in 
I'lj.- 11 The j.iwN have the advantage that they can be 



10 LATHE WORK. § 4 

as shown in Fig. 12. These consist of castings s bolted to 
the face plate and provided with setscrews r for securing 
the work. The shoulder below the points of the setscrew 
should be turned off so that the dimension a is equal on all 
of them. This will enable the operator to place work against 
these shoulders during chucking. 

15. Example of Clamping Regular Work. — Fig. 13 
illustrates a very simple method of clamping a large flange 
to a face plate when it is only desired to bore the hole in the 
center of the flange and to face the hub /, the surface r being 
left rough. This method will do very well where the back 
face of the flange maybe clamped directly to the face plate 
or on parallel blocks, and where but a single hub is to be oper- 
ated upon. If it becomes necessary either to face the surface r 
or to oj>eratc upon a number of pieces, it is best to use jaws 
similar hi those illustrated in Figs. 11 and 12. 




Uoekur-Anii.— Whvn it is desired 

i similar to the one shown in Fig. 14, 
ii-.ln -d 1 iy using I hiw cbucking-block 
•li.iwn in Fij;. 12. These arc placed 



H 



LATHE WORK. 



11 



at c, c and bear against three sides of the large hub of 

the rocker-arm. The work is held securely against the 

face plate by means of the two clamps d, d, as shown in 

Fig. 14. Fig. 15 is a section on the line a b, Fig. 14, and shows 

the arrangement of the clamps and blocking; e is the arm, 

d, d are the clamps, g, g the blocks, and /, / the bolts. 

Care should be taken to see that the blocks g are of exactly 

the height of the work, so that the 

damps d will set level or parallel to 

the face plate. The bolts / should 

be placed as close to the work as 

possible. If much strain is brought 

upon the work e by the clamps d, it 

is evident that there will be danger 

of springing the arm between its 

hubs or bosses. To overcome this, 

a block may be fitted under the arm, 

or a planer jack / may be adjusted 

under the arm, as shown in Fig. 15. 

In order to balance the portion of 

the rocker-arm extending to one 

side of the center and the clamps 

and bolts d and /, a counterweight w Fk " 1j 

wy be attached to the opposite side of the face plate, as 

shown, and adjusted in or out until it balances the whole 

°sctly. Such work as this, which has a number of faces 

•hat must be finished in certain relations to one another, 

'bould be laid out before attempting to set it in the chuck 

o 1 " on the face plate. In Fig. 14, the work is to be bored to 

the circle indicated by the dotted lines, and may be set so 

toat it will run true with this circle by testing with a scriber 

or point held in the tool post. 

17. Use of Paper on a Face Plate. — When a fin- 
"shed surface is to be clamped against the face plate or any 
other metal surface, the danger of its slipping can be greatly 
reduced by putting a sheet of paper between the two sur- 
faces. If this precaution is not taken, it will be found 







J • 



12 



LATHE WORK. 



H 




Fig. 16. 



almost impossible to damp the work so that it will resist the 
action of the boring tools. 

18. Pulley Clamp. — Pulleys that have to be bored 
and turned can be clamped by means of the arms. Fig. 16 

illustrates a clamp intended for 
this purpose. The block a is 
bolted to the face plate and 
supports an adjustable damp c 
having a turned portion that 
fits into a socket in the block j, 
and is secured by the 9etscrew d. 
The pulley arm b is hdd in 
the damp c by the 9etscrew e. 
Similar damps can be devised 
for holding a great variety of 
irregularly shaped work. 

1!K Annie Plate. — A very convenient attachment for 
laee-plale work is the angle plate, as shown at a. Fig. 17. 
This angle plan* is made so 
that iis two faces make an 
angle of W* with each other. 
When it is desired to finish 
two faces of a piece square 
wittt each other, as. for in- 
stance, the tlanges of a pipe 
ellmw, one face is clamped to 
I In 1 angle plate as shown. This 
In ili h the other face oi the 
•■II iow in ?-ueh a jwsition that 
ii will be cut square wi:h the 
fit --t lace This angle plate 
max In- iimv! to givat advar.- 
Itij. t.n manv opvratior.s i:i 

l.ii f |>l.l1t- WOlk 

Hi.- itii-th.Hl'. of fast c:\ir.g work :c the lathe face plate are 
niuiil.il i«- !lh»v !iv, ta^icr/.ng work 
hi In the la He \^\ \\\c Km-.v.v; r.v.'.i. 







planer. 



$ 4 LATHE WORK. 13 


TAKING 


THE CUT. 


20. The Tool. -Suppose 


a shaft collar 2 inches long is 


to be bored 1££ inches in diameter. The tool used is a 


tool, as shown in 




' 


Fig. 18. The tool is L 


■ d rigidly in the tool ' 


i i that it lies parallel l 


f 


■■ lathe V's and so ' 


■ ^v^^v^v ^ 


that it will pass through 


the bole in the work. The 
tool should be set as low as 


Pic. IS. 


possible in the hole. 


-I. Roughing and l-'i 

at the front end. Roughing 


nishlng. — The cut is started 


cuts should be taken as heavy 


ible. They can never 


be taken very heavy because 


: of the tool. 


After the first cut. the hole 


to see if it is boring parallel. If it is 


to be tapered, lighter 


cuts should be taken. Some- 


i he hole may be made 


parallel by reversing the direc- 


■ ed, which will .start the cuts at the back end of 


the hole. 




MEASURING 


SORBD HOLES. 


'2'1. l"»c of Calipers mid Gauges. — Greater skill is 


required for measuring the 


diameters of holes than for 




measuring outside work. 




The holes may be nn-.i.-.- 


^^_ 


ured by the use of plug 




g~ gauges, limit gauges, or 


^fT*"^" "3 


T inside calipers. When in- 


J* <*^"^5B 


' side calipers are used, they 


\ J *-*""'""^""^*\. V""" 


may be set from a stand- 




ard ring gauge, from a 




» scale, or from a pair of 




i outside calipers that have 




y previously been set from a 




scale. When setting inside 







14 



LATHE WORK. 



§4 










Fig. 20. 



calipers from a scale, one end of the scale should be held 
squarely against a block, as shown in Fig. 19, and the 
caliper adjusted to the line on the scale. When work is 
measured with inside calipers that have been set from 

outside calipers, there 
are three chances for 
error: first, in adjust- 
B ing the outside calipers; 
second, in transferring 
the size to the inside 
calipers; third, in the 
final measuring. It 
will be seen bv refer- 
ence to Fig. 20 that in order to measure accurately, the 
calipers must be held in line with the axis .4 B of the work. 
If the calij)crs are held in any other line, as, for example, 
C A the hole would appear too large, since, with one point 
reating against the work at b, the other point a would be in 
the position a'. When the solid plug gauge is used for test- 
ing, extreme care is necessary. If the hole is the exact 
size, the gauge will enter only when its axis is held exactly 
in the line A B\ because of this, the work is often bored too 
large, since sufficient care is not used in making the trial. 

If, in caliporing a hole, it appears to be very close to size, 
a second cut may lie run through without adjusting the tool 
deeper. A sufficient amount may often be removed by this 
second cut, its depth deluding on the spring of the tool 
during the previous cut. When the work is large enough 
to admit heavy tools, they should be used to avoid the spring 
as much as possible. 



CIIUCKIXr. TOOLS. 

2ft. Method of Holding Cli ticking Tools.— When 

the holes are small, tt inches or less in diameter, they can be 
more rapidly and accurately bored by using special 1 wring, 
or cluickiiiir, tools. These tonus may be held in a special 
holder on the carriage, or in the tailslock in place of the 



LATHE WORK. 

dead center. The latter method is the more common,. 
When a chucking tool Is to be held in the Uitatock, rati 

should be taken that it is perfectly in line with the live 
spindle, otherwise trouble will be encountered. 



PLAT imil.l.S AND KBAMER9. 

24. Flat lirills and Holders. — For rough boring in 
cored holes, the flat drill shown in Fig. 21 is sometimes 

used. This drill may ._.. 

be made from flat bar ]J| If' j \ L] 

steel with the point * \kJ£M > U 

ground like the point 

of an ordinary flat drill. The other end has a large center 

hole for receiving the dead center. In using the drill, a 

specially made holder is employed, as shown in Fig. 22. 

This holder consists of a flat piece of 

X^^^^B iron or steel wiih one end bent at an 

/%'1P^*> angle. A slot a is cut through this end 

Syf./ sufficiently large to allow the drill to 

■ "/ pass through. 

25. Operating a Plat Drill. — 
When used, the holder. Fig. 22, is 
clamped in the tool post so that the opening a comes oppo- 
site the center of the hole in the 
I lie drill is passed through 
the opening a and held against 
the work by pressure of the dead 
center. The holder beeps the drill 
■living. In starting the 
cm, there will he a tendency for 
the drill to wabble, owing to the i 
; ity of the cored hole. In | 
order to start the drill true, 

irrench is used on the 
shown in Fig. 23. By 
pulling on the wrench in the direc- 
tion of the arrow, the drill is 

TlB-0 




16 



LATHE WORK. 



§4 




'TOT 



■s 









T 



(•) 



rotated sufficiently to make it pinch in the holder. While 
in this position, the drill is fed into the work until the entire 
cutting edge is in metal, after which the wrench is taken off 
the drill. Holding with the wrench causes the drill to start 
true. When once started, this drill cuts well, but the hole 
will not be truly cylindrical. 

26. Flat Reamers, or Turned Drills.— To finish 
the hole more perfectly, a flat reamer, or turned drill, 

shown in Fig. 24 (a), may be used in the same manner as 

the flat drill. This 
reamer is made of 
flat bar steel and 
turned parallel on 
the sides c and d to 
a diameter equal to 
the diameter of the 
desired hole. The 
cutting edges are 
at a and b. This 
reamer is sometimes covered with wood, so that it will just 
follow the hole being bored. These wooden faces are used 
to keep the reamer from chattering and to guide it so that 
the holes will be more nearly accurate. Such wood-covered 
reamers are sometimes called wood reamers. 

27. Cannon Drills. — Fig. 24 (b) shows a cannon 
drill. Half the face is cut away, as shown at <r, while b is 

the cutting edge. 




Pig. tt. 



ROSE AM) FLUTED REAMERS. 

28. Rose Reamers. — A better form of tool for cored 
holes, known as a rose" reamer, is shown in Fig. 25. The 




Fir. STi 



part marked a is ground round and parallel to the diameter 
of the desired hole. This form of reamer will generally 



|1 LATHE WORK. 

produce holes slightly larger than the size, due to the wear 
■.mer on the walls of the hole. 

2H. Three-Fluted Chucking Reamer. — For deep 
botes, the tnrec-fluted chucking reamer shown in 

Pig. 26 is an excellent tool. Because of the spiral flut 

i^^f^WTm — r 



Ihere is less danger of the shavings clogging than there is 
in the style shown in Fig. '-J5. The cutting is done by the 
edges rt, and the chips pass away through the larger flutes; 
the small flutes b are formed for clearance and to allow the 
il or other lubricant to flow to the point of the 

;iO. Fluted Chucking Reamer. — Fig, 27 represents 
-. fluted chucking reamer for finishing holes smooth 
uid true to standard size. In this form of reamer, the cut- 
"ig edges are along the lines a h. When used in connection 




^ 



j the rose reamers, the latter should leave about .005 inch 
meter f<>r this reamer to remove in finishing. Since it is 
toiled fi>r finishing holes to exact diameter, it should be 
I with considerable care. The cutting speed and the 
b therefore reduced. 

Shell Chucking Reamers.— Fig. 28 (<j) shows a 

1 Cb ticking reamer of the; rose-reamer type, and in 

shown a shell reamer of the fluted or finish - 

These reamers are cheaper and in many 

a more convenient than the solid reamers just described. 








- -m . !■— — 




■w*^ 


m 




- 

9 t^mg 3 


«MM 


~ *~— ~T ~-~ - 


<fr_ 






. 1 

■ 
. is way 



mmmiry to hav* t 



LATHE WORK. 



33. Starting Chucking Reamers True. — If the 

cored bole does not run true, the chucking reamer will not 




start true, the tendency being to follow the cored hole. When 
it is desired to start the reamer true, it may be done by using 
a common boring tool and boring out the mouth of the hole 
to nearly the correct size, so that the reamer will enter 
i inch or so. This will give a bearing all around and hold 
the reamer true. 

34. Drilling Solid Material.— The tools thus far 
described, with the exception of the fiat drill, are for enlar- 
ging holes that have been previously drilled or cored. The 
flat drill will pierce a hole in the solid metal as well as it will 
follow cored holes, but it will not cut as freely as the twist 
drill. Twist drills are often used in the lathe in a special 
holder or socket fitted in the tailstock, the drill being fed into 
the work the same as the chucking tools just described. 

35. Starting a Twist Drill. — It is essential that the 
twist drill be started to run true and that its point be cen- 
tered before the outer corner of the drill has begun to cut. 
After the outside comer of the drill has entered the work, 



20 LATHE WORK. g 4 

its position cannot be changed. It is well to make the start- 
ing points true by using a tool in the tool post, as shown 
in Fig. 31. This tool is forged with a thin flat point and 




ground like the point of a flat drill. The hole is started 
true with the tool, after which the twist drill in the tailstock 
will follow in the hole previously started. When this start- 
ing tool is not at hand, the twist drill may be started true 
by placing the butt of an ordinary lathe tool in the tool post 
and adjusting it so that it just touches the twist drill. This 
will steady the point of the drill sufficiently, so that in most 
cases it will start true. 



BORING WITH A BORING BAR BETWEEN 
CENTERS. 

36. Use of Boring Bur. — When the work is heavy or 
the holes comparatively long, the work of boring can quite 
often be accomplished by reversing these operations, clamp- 
ing the work to the carriage and revolving the tool in 
the work. When this is done, a bar is passed through the 
work and held between the centers. This bar is called 
a boring bar. It carries the blades or cutters that do the 
boring. The boring of an engine cylinder furnishes a good 
example of a typical operation performed in this manner. 



j4 LATHE WORK. 21 

TYPES OP BORING BARS. 

37. Borinfc Bars With Fixed Cutters.— There are 
two types of boring bars; one has a fixed cutter in the cen- 
ter that may project sufficiently to cut only on one end, or it 
may project equally on each side of the bar and cut at each 
end. Such a bar is shown in Fig. 32. The cutter is fitted 
into a rectangular slot and held in place by a key k driven 
in at the back. The cutter blade should previously be turned 



N 



-&J3- 



-v 



ZDd 



to the desired diameter before hardening. The cutting is 
done by the points or edges a and b. When this style of bar 
s used, it must be twice as long as the hole to be bored, since 




there must be room for work at one side of the cutter before 
starting, and room for it to pass beyond the cutter after the 
cut is finished. 



/ 



22 



LATHE WORK. 



§4 



When the work is large so that the cutter would project 
a considerable distance beyond the bar, it is best to fix a 
cutter head to the bar. Such a head is shown in Fig. 33. 
It consists of a cast-iron collar carefully fitted to the bar 
and kept from turning by a key and setscrew. There are 
generally four blades or cutters a inserted in the head and 
held in place by the setscrews s, s; 6, 6 are setscrews for 
adjusting the blades. It will be seen that by tightening 
these screws, which stand against the ends of the blades, 
the blades will be pushed out of their sockets. As the blade 
becomes short, pieces must be put between the screw and 
the blade to make the screws effective. 

38. I*orIng Barn With Sliding Heads.— When 

much heavy boring is done, the second type of boring bar, 
shown in Fig. 34, is more desirable. This bar a is fitted with 
a head h, which slides upon the bar a. The head is kept 





Pig. 34. 

from rotating on the bar by means of a key that slides in 
a spline cut the entire length of the bar. Four cutting tools b 
are used and held in place by setscrews r. Clamps or wedges 
are often used for holding the tools in the head. A feed- 
screw s y supported in bearings at either end of the bar, passes 
through a nut in the sliding head. By revolving this feed- 
screw, the head is moved along the bar. This feed-screw 
is generally set in a slot cut in the side of the bar. By doing 
this, the screw is protected. 

39. Boring an Kngine Cylinder. — Fig. 35 shows 
the general scheme of using this type of bar when boring an 



I* 



LATHE WORK. 



23 



engine cylinder. The cross-slide is removed from the lathe 
and the work set upon blocking and clamped with bolts in 
its correct position. Considerable care should be exercised 
in setting this class of work upon the machine, to see that 
it is so set that all faces can be finished in their correct rela- 
tion to one another and to correct sizes. It will be seen 
that the bar passes through the work, is held between the 
lathe centers, and is driven with a dog. One of the various 
methods of operating the feed mechanism is by means of the 
star feed, as shown in Fig. 34. A star wheel w is fastened 
to the end of the feed-screw. This revolves with the bar. 
A pin /, Fig. 35, is fastened in some convenient place so 




FIG. 85. 



that for each revolution of the work it strikes one of the 
arms in the star wheel and gives it a partial revolution. 
When a coarser feed is desired, two or more pins may be 
arranged to act one after the other. This revolves the feed- 
screw and so gives feed-motion to the head. Another 
method of revolving the feed-screw is to put a gear-wheel 
in the place of the star wheel. A second gear is fixed to 
the lathe center so that it gears with the wheel on the feed- 
screw. As the bar revolves, the gear and the feed-screw 
rotate about the fixed gear, thus revolving the feed-screw 



24 LATHE WORK. §4 

upon its axis. If the gears are of the same size, the screw 
will make one revolution for each revolution of the bar. 
By varying the proportion of these gears, various rates of 
feed may be obtained. 

This form of bar is more desirable for large work than the 
type of bar with the fixed head. Because of the sliding 
head, the bar need be but a little longer than the work to 
be bored. This shortening of the bar gives it greater rigid- 
ity. When the bar has a sliding head, the work does not 
need to be fastened to the carriage of the lathe, but may be 
more securely bolted to the lathe bed. This also adds to 
the rigidity of the work. 



TAKING A CUT WITH THE BORING BAR. 

40. Adjusting the Tools. — After the work has been 
carefully set, so that it is known to be correct, the cut is 
started at one end. One tool is used at first until a sufficient 
depth of cut is obtained and a short distance bored into the 
work. After this true place is turned, the other tools are 
carefully adjusted so that they each do their share of the 
work. 

4 1 . Shape of the Boring Tools. — The tools for the 
roughing cuts are ground round on the point similar to the 
diamond point. Very little clearance should be given. The 
first roughing cuts are generally made deep, with a moder- 
ately fine feed. The finishing cuts are made with a very 
coarse feed. The finishing tool, therefore, has a broad cut- 
ting edge with a minimum of clearance. 

42. Spring of the Bar and Work. — It will be seen 
that the boring bar held between the lathe centers is lim- 
ited in its power by the strength of the lathe center. When 
each of the four tools is doing its share of the work, the bar 
is well balanced in the cut and the strain on the lathe cen- 
ters is small. If the cut is very heavy on one side and light 
on the other, the opposite cuts will be unbalanced, the 
heavier cut tending to spring the bar away and into the 



§4 LATHE WORK. 25 

lighter cut on the opposite side. This action will bring a 
great strain upon the centers of the lathe. Special boring 
mills have been designed for this class of work and will do it 
better and more rapidly than the lathe. At the same time, 
the lathe is always at hand for special jobs when boring 
mills or boring lathes are not available. 



BORING TAPERS. 

43. Boring With Taper Attachment or Com- 
pound Rest. — Taper boring is often best done on the lathe. 
If the work is held in the chuck, the taper may be bored by 
using the taper attachment. For this, the attachment is 
set in the same way as for taper turning, and the operation 
of taking the cut is the same as in boring cylindrical holes. 
When the holes to be bored are short or an abrupt taper is 
desired, the compound rest may be used. For some kinds 
of work, taper chucking reamers are used. They are held 
in the tailstock the same as the ordinary chucking tools. 

44. Reaming Tapers. — Tapers may be reamed by a 
tool or tools inserted in the cutter head of a boring bar. 
The tools must be in the form of blades as long as the hole, 
and set so that their cutting edge is at the desired angle. 

45. Boring Tapers With a Boring Bar. — When 
the boring bar with the sliding head is used, a taper hole 
may be bored in work fastened to the carriage or bed by 
setting over the headstock end of the bar. This is accom- 
plished by fastening a false center c, Fig. 3G, to the face 
plate, which may be adjusted at any distance from the true 
center of the lathe. The amount that this center is to be 
set out of line may be estimated the same as the amount 
that the dead center is set out of line in plain taper turning. 
When the bar is thus set out of line, it will be noted that 
but one cutter point / can be used. This should be so set 
that when the false face-plate center c is at the front and at 
the same height as the dead center, the cutter point/ is also 
at the same height. 



26 



LATHE WORK. 



§* 



The boring bar shown in Fig. 36 {&) may be used for 
either straight or tapered holes. The bar a is fastened to 




Fin. 36. 

the dead spindle b so that it Cannot rotate. It is provided 
with a T or dovetail slot its entire length, which carries a 
sliding cutter. This cutter has lugs c which engage the 
end of a feeding piece d held in the tool post e. The work/" 
may be clamped to the face plate g as shown. As the 
feeding piece d is fed along the lathe, it will force the sliding/ 
cutter fitting the T or dovetail slot to feed along the bar a, 
so that the cutting point A will bore either a tapered or 
a cylindrical hole, depending upon the position of the dead 
center. The live center rotates in a stationary bar and 
hence it should be hardened and supplied with oil. It is 
also necessary to feed the tool post in by means of the cross- 
slide as the cut advances so as to prevent the lugs c from 
passing out of contact with the feeding piece d. 



RADIAL FACING. 



FACING OF REVOLVING WORK. 

46. Definition of Radial Facing. — When a true 
flat surface is produced with a lathe, it is called a radial 
face. The end of a piece that is squared up between cen- 
ters is a radial face, but the term radial facing is gener- 
ally applied to larger pieces of work that have to be held in 
the chuck or on the face plate. 



LATHE WORK. 27 

47. Precautions to be Taken In Radial Facing. — 

There are two important points in all facing. First, all end 
play of the lathe spindle must be taken up. Second, the 
carriage must be clamped upon the V's, thus preventing 
the tool from moving away from the work. 



48. Tools Used and Their Shape.— Tools for radial 

facing do not need as great a clearance angle on the front; 

i. e., they do not require as 

much front rake as when 

turning cylindrical shapes. In 

shape the tools for radial 

facing are similar to planer or 

shaper tools, especially when 

they are used for facing from 

the outside toward the center. 

This point is taken up more 

fully under "Forms of Cut- 
ting Tools." Quite a large vm.sr. 

variety of tools can be used for radial facing, and in most 

cases a bent tool is preferable, because it can be heid in the 
tool post closer to the 
cutting edge, thus giv- 
ing greater stiffness. 
In Fig. 37 a front ele- 
vation of a tool pre- 
sented to the work for 
radial facing is given, 
the front rake being 
shown by the line G H. 
The tool point a is 
placed about level 
with the center of the 
work. Fig. 38 gives a 
plan of the same tool 
illustrating how it 
Pro. sa "▼ should be set. The 

uM make an angle of 30° to 45° with the face 



28 LATHE WORK. §4 

of the work, and the cutting edge should be presented 
to the work as indicated by the line E F. The type of tool 
shown should be fed from the outside toward the center, the 
tool being set the same height as the center of the work. 
The tool may be fed either by hand or by means of a power 
feed. 

For finishing radial surfaces, the side tool may be employed, 
or a special square-nosed tool may be used. The square- 
nosed tool has the advantage that it can be fed in either direc- 
tion. If the feed and the cut are heavy, care must be taken 
that the tool docs not spring into the work. 

49. Cutting Speeds for Radial Facing. — In radial 
facing, the cutting speed of the tool will vary according to 
the diameter of the work at the point where the tool is oper- 
ating, the number of revolutions per minute remaining the 
same; hence it is evident that, as the tool advances toward the 
center, the cutting speed will decrease. For this reason, on 
large surfaces, it may be advantageous to sjxxxi up the lathe 
as the tool advances toward the center. 



FACING OF STATIONARY WORK. 

50. Holding Stationary Work for Facing. — When 
the work to be operated ujxm is so large that it cannot be 
swung upon the face plate, it may be bolted to the carriage 
or lathe bed and faced by means of a rotating tool or cutter. 
The work must Ixj blocked up to the proper position and 
then bolted securely, so that there will be no chance of its 
moving during the facing. 

51. Facing Arms. — For facing the ends of cylinders 

as shown in Fig. 35, a facing arm is used, as shown in 
Fig. 31). This arm is fastened to the boring bar and rotates 
with it. On one side of the arm is fitted a tool block a, 
which slides in a guide. This tool block carries the cutting 
tool />. Feed -motion is given by means of a screw operated 
by the star wheel t\ which is made to rotate partly for each 
revolution of the bar. In this way, the tool is fed entirely 



across the face of the work. When a facing arm is not at 
a cross-slide of some sort is fastened to the face plate 
of the lathe. Very 
iflen the compound 
fastened to 
the face plate so that 
the slide may be used 
for feeding a tool 
across the face of the 
work. 

S2. Reason for 

Facing Before 

Boring, — When a 

piece of work held 

i a chuck or on a 

face plate is to be 

ind faced, it 

test to do the PlG » 

facing first, or at least take a roughing cut before doing the 

luring. This gives a better chance to start chucking tools 

and also furnishes a belter edge for calipering the hole. 

he tool has a greater leverage on the work 

ind, hence, a greater tendency to displace it. For this 

nil facing and outside turning should be done before 

hiring. 




SCREW CUTTING. 

S3. Definition*.— The point of a thread i 

. I 
. .meter of a thread is the diameter measured over 
■ ■ ■■■ ./of tin. bolt, Fig. -10, ln-fore the 

The diameter at the root of the thread 



: pro- 



Thc root of the thread is the bottom of the space b where 
the thread* unite, Fig 40 
The bcllfHt of a thread is the vertical distance // from 
erool to the point, Fig 40 



■ 

A rl 



LATHE WORK. 



H 

A ritfhl-hnnil threat! is one that is turned in the 
direction of the hands of a dock when it is being screwed 
the common thl 

A left-hand thread 
turns in the opposite 
direction from a right- 
hand thread. 

A *lntrlc thread 
has one spiral groove 
cut around the bolt. 
This leaves one spiral 
projection or thread, 
Fig- -in. 

A double thread 
spiral grooves 
spiral 




Fin. 40. 



cut around the bolt. This leaves 

threads. Fig. 41 shows a double thread. One thread is cut 

farther along the 

bolt than the other, 

to show how the first 

thread is cut. 

A triple thread 
has three spiral 
grooves and, con- 
leqttentlfi th ree 
spiral projections or 

A single thread 
m. i f be Illustrated 
by (rinding a string 

around ,i lead pencil. 

The string will represent the thread of the screw. If two 
strings be wound ;i l the same time about the pencil, i 
them side by side, I he strings will represent 
If three or four strings be used. .i triple m ,i quadruple 
thread will be i]ln H 

'I'll-- pitch of a chit nd is the distance between any two 
toe thread, measured parallel to the axis; it i* equal 




Rio. a. 



LATHI- WORK. 



1 divided by the number of turns the thread makes in 
advancing 1 inch, 

54. Measuring Screw Threads. — It is customary to 
designate a screw thread by the number of turns it makes 
about the axis in advan- 
inch along the axis. 
42 shows a screw 
i with a scale against 
i that the first thread 
me opposite the end of 
BC&le and the fifth 
•ad opjwisite the 1-ineh 
Lines drawn down 
i the end and from the 
mark would divide 
and fifth thread in 




"WA VVWV\ 



Fie. 42. 



VWVs 



middle, leaving only four complete threads between 
marks. There are, therefore, only 4 threads per inch 
screw and the pitch is j inch. In counting the threads 
include both the first and hist threads. 

a double-threaded screw, as shown in Fig. 41. 
is taken, making two threads per inch or 
| inch pitch. In triple- 
threaded screws, as in 
Fig. 43. every third thread 
is counted. 

Double and triple threads 
are used when a very coarse- 
pitch screw of small diame- 
ter is desired. By cutting a 
number of threads in the 
place of one large thread, 
! can keep the coarse pitch without cutting very deep 
ig. 43 shows a section of a screw with 
ends The- dotted lines show the depth to which 
.iry to cut a single thread of the same 



— 



33 



LATHE WORK. 



M 



SHAPES OF SCREW THREADS. 

55. Common Forms of Threads. — There are four 
forms of screw threads in common use. They are the sharp, 
or V, thread, the United States standard, also known as the 
Sellers, or Franklin Institute, thread, the British standard, 
known also as the Whitivorth thread, and the square thread. 
Besides these forms there are some other forms, such as the 
ratchet thread, the acme thread, and some others. These 
last named, however, are used only for special purposes. 

The two forms that are most commonly used in the 
United States are the V thread and the United States 
standard. These are used on commercial bolts and screws 
and whenever fastening devices are required in machine 
construction. 



i* — p 




FIG. 44. 



56. Shape of V Thread. — Fig. 44 is a section through 

a part of a V thread, showing 
its exact shape. It will be seen 
that the sides of the thread are 
straight and make an angle of 60° 
with each other, and 60° with the 
center line of the screw. These 
side faces meet and form a sharp 
point a and a sharp corner b at 
the root ; hence its name, sharp, or V, thread. 

The pitch is here denoted by /, the height of the thread 
by //, the diameter of the bolt by d, the diameter at the root 
of the thread, i. e., the diameter of the tap drill, by d v On 
account of the fact that the sides of the thread make equal 
angles with each other and with the center line of the bolt, 
this angle being 00°, the height of the thread divided by the 

pitch equals .800; that is, - = .800, or// = .806/. Also the 

diameter of the bolt at the root of the thread, that is, the 
diameter of the tap drill, is expressed by the following for- 
mula: d x = d—Hh = d — 1.732/. Expressed as a rule this 
would read as follows: 



8* 



LATHE WORK. 



88 



Rule — To find the diameter of the tap drill when the 
diameter of (he bolt and the pitch are given, multiply the 
pitch by 1.782 and subtract the result from the diameter of 
the bolt. 

E x an pus.— Required to find the diameter if tap drill for a 1-inch 
standard bolt that has H threads per inch, or a pitch of 1 in. 

Solution. — Applying the above rule gives 1.732 X j = .3168. Sub- 
tracting litis from the outside diameter -if the bolt gives 1 — .2185 
_- n)H in. as the diameter of the bottom of the thread or the diameter 
of the tap drill. Ana. 



EXAMPLES FOR PRACTICE. 

1. A bolt is [ inch in diameterand has a pitch of fa inch. What 

tap drill is required ? Ans. .5768 in. 

2. What diameter of tap drill is necessary for a bolt fa inch in diam- 
eter, with a pitch of fa inch ? Ans. .2163 in. 



Stt,. As the pitch equals 1 divided by the number of 

i he rule can be expressed more simply by letting « 

equal the number of threads, when the formula can be 

written d, = a '■ . Expressed as a rule this formula 

becomes 

Mule. — To find the diameter of the bottom of the thread, 

ter of the tup drill when the diameter of the 

■ r of threads per inch are given, divide 1.782 
fry the number of threads per inch an,! subtract the quotient 
from the outside diameter of the bolt. 

Exawpi.f. — It is desired to It.td the diameter of the tap drill for a 

1 'ioch standard bolt having H threads per inch. 

i .2165. Subtracting 
diamelei of holt gives 1 — .31 (Hi = THUS in. as the 

■ lom of the thread or the diameter of the tap drill. 

Ans 



-Applying the rule, we get - 



34 LATHE WORK. {4 

EXAMPLES FOB PRACTICE. 

1. A bolt is 1$ inches in diameter and has 11 threads per inch. 
What diameter of tap drill is required ? Ans. 1.4676 in. 

2. What diameter of tap drill must be used to drill a nut for a 
fa inch standard bolt having 14 threads per inch ? Ans. .8188 in. 




Pig. 45. 



57. Shape of United States Standard Thread. — A 

section through a United States standard thread is shown in 

Fig. 45. The shape is 

-^a — - /^j similar to the sharp, or V, 

thread in that the sides are 
straight and form an angle 
of 00° with one another and 
with the center line of the 
bolt. The point and the 
root of the thread, however, are flat. The amount of flat- 
ness is determined by dividing the total height of a sharp, 
or a V, thread into 8 parts. One-eighth of the total height 
is cut from the point and an equal amount filled in at the* 
root, thus making the total height of the United States 
standard three-fourths that of a V thread of the same pitch. 
The letters in Fig. 45 are similar to those in the previous 
illustrations and have the following values: d equals the 
diameter of the screw, d x the diameter at the root of the 
thread, that is, of the diameter of the tap drill, / the pitch, 
// the height of the thread and the number of threads per inch. 
For the United States standard thread, the following 
formulas may be used, the letters in which have the same 
meaning as in Arts. 56 and 56iS 

// = .800 Xp X 1 = .6495/. 
d t = d - % A = d - 1.299/. 

Expressed as a rule this becomes 

Rule. — To find the diameter at the bottom of a United 
States standard thread when the outside diameter and the 
pitch are given, multiply the pitch by 1.299 and subtract the 
product from the outside diameter of the bolt. 



§4 LATHE WORK. 35 

Example. — It is desired to find the diameter of the tap drill for a 
1-inch bolt for United States standard thread, the 1-inch bolt having 
8 threads per inch. 

Solution. — Since there are 8 threads per inch, the pitch is i in. ; 
hence, applying the foregoing rule, i X 1-299 = .1624. Subtracting this 
from 1 in. gives .8876 in. as the diameter of the tap drill. Ana. 



EXAMPLES FOR PRACTICE. 

1. A bolt with United States standard thread is 1| inches in diam- 
eter. What is the diameter at the bottom of the thread, the pitch 
being J inch ? Ans. .94 in. 

%. What is the diameter at the bottom of the thread of a bolt 
4 inches in diameter having a United States standard thread ? The 
pitch is i inch. Ans. 3.567 in. 

57,# When the number of threads per inch, in place of 
the pitch 9 is given, the following formula may be employed: 

1 n 

Expressed as a rule this becomes 

Rule. — To find the diameter at the bottom of the thread or 
the diameter of the tap drill for United States standard 
thread when the diameter of bolt and number of threads per 
inch are given , divide 1.299 by the number of threads per 
inch and subtract the quotient from the diameter of the bolt. 

Examplb. — It is desired to find the diameter at the bottom of the 
thread or of the tap drill for a 1-inch standard bolt that has 8 threads 

per inch. 

1 299 
Solution.— Applying the rule, - 1 g— = .1624; subtracting this from 

the diameter of the bolt gives 1 — .1624 = .8876 in. Ana. 



EXAMPLES FOR PRACTICE. 

1. What is the diameter at the bottom of the thread of a United 
States standard bolt \ inch in diameter, with 9 threads per inch ? 

Ans. .781 in. 

1 What is the diameter of the tap driJl necessary to cut a thread 
for a 3-inch United States standard bolt, with 3* threads per inch ? 

Ans. 2.629 in. 



LATHE WORK. 




§4 

58. Shape of British Standard Thread. — The 

exact shape of the British standard is shown in Fig. 46: 
In this thread the sides 
are straight and form 
an angle of 55° with one 
another. The point and 
root are rounded. The 
total height of a sharp 
thread is divided into six 
equal parts. One part is taken from the point and one part 
filled in at the root. The thread is further shaped by 
rounding the bottom, or root, and top with curves that just 
come tangent to the sides. 

59. Shape of Square Thread. — The square thread, 
as its name implies, is square in section, as shown in 
Fig. 47. The space between the p. &_^ 
threads is also square, so that in 
theory the dimensions a, b, and c 
should all be equal. In practice, 
a is made slightly greater than b. 
In the square thread there is no 

standard relation between the diam- ■ 

eter of the screw and the pitch ; in fact, there is no standard 

pitch. _ 



STANDARD THREADS. 



UNITED STATES STANDARD THREAD. 

60. Origin of a Standard Thread. — Originally, each 
manufacturer adopted his own standard as to thenumber of 
threads per inch and the form of thread. The result was 
that bolts and screws made by different firms were not 
interchangeable, and, in the case of a breakdown, it was 
often very inconvenient to obtain repairs for machines. As 
manufacturing interests became specialized and shops 
exchanged tools and commodities, interchangeability of the 
parts became very desirable, and a number of leading 



LATHE WORK. 



37 



St 

manufacturers brought out special types of threads that 
they tried to have adopted. 

In the year 1864, The Franklin Institute, of Philadelphia, 
appointed a committee to investigate and report upon this 
subject of screw threads. They made a careful investigation, 
and finally recommended a system designed by Mr. William 
Sellers, which was later adopted by the Institute. 

61. Reason for Selecting Present Standard. — In 
determining the exact shape and pitch for a screw, many 
things had to be considered. Among 
these were the best angle for the 
sides, and whether the angle of the 
sides should be equal or not. When 
a bolt has a thread cut on its end, 
the strength of that bolt is reduced 
because of the reduced diameter at 
the root of the thread. It will not 
be any stronger than a bolt equal 
to the diameter at the root of the 
threads. It would therefore seem 
desirable to make the threads shal- F1 ° •■ 

low, so as not to reduce the strength of the bolt. The 
threads then might be of the shape shown in Fig. 48. Sup- 
pose we have this form of thread on a bolt that passes 
through the pieces shown, and it is intended to carry a load 
acting in the direction of the arrow. A nut shown in sec- 
tion holds the bolt in place. As the load is applied, the bolt 
will tend to draw through the nut, and, by so doing, will 
tend to stretch or burst it. The bursting strain on the nut 
will depend on the angle 
of the side of the threads, 
each thread acting like a 
wedge in the nut. It will 
be seen that the bursting 
strain in this case will be 
much greater for a given 
load than it would be if 
as shown in Fig. 49 (a). 





the threads were 



38 LATHE WORK, §4 

Besides, the great bursting strain would cause great friction 
on the thread, and there would be danger, in tightening the 
nut, that the bolt would be twisted off. It is evident, there- 
fore, that a thread having a flat angle is not desirable. The 
sharp acute thread would so weaken the bolt that it is not 
desirable. The friction and the bursting strain on the nut 
might be eliminated by using a ratchet thread, as shown in 
Fig. 49 (6). This would be flat on the under side, relieving 
the nut from the wedge-shaped thread tending to burst the 
nut. The thread would not be deep, so that the bolt would 
not be much reduced in strength after the thread was cut. 
This would at first seem to answer the conditions, but if the 
direction of the load should be changed, these ideal condi- 
tions would vanish. In every case, the workman would 
have to consider the direction of the load before he could 
determine which side of the thread should be flat and which 
side beveled. Furthermore, the nut used for this thread 
would only fit from one side ; if the nut were turned over, 
it would not go on. This and many other considerations 
led to the adoption of a thread with equal angles on either 
side. The angle of 60° was chosen after much considera- 
tion, it being an angle easily obtained and one that seems 
best to answer the conditions. To give the thread dura- 
bility, it was decided to take off the sharp point, since it did 
not add to the strength of the thread. By removing the 
point of the thread in the nut, it made it possible to fill in a 
corresponding amount in the root of the screw. This added 
to the strength of the bolt. The points were left flat 
because of the ease with which the screw could be con- 
structed when compared with the curved points represented 
by the British standard. 

62. United States Standard Threads. — The pitch 
of the screw for different diameters was also considered, and 
a standard number of threads to the inch for various diam- 
eters was adopted. 

The number of threads per inch for the United States 
standard is given in the following table: 



U 



LATHE WORK. 



39 



UNITED STATES STANDARD THREADS. 



Diam. of 

Screw. 

Inches. 


Diam. at 
Root of 
Thread. 
Inches. 


No. of 

Threads 

Per Inch. 


Diam. of 
Screw. 
Inches. 


Diam. at 
Root of 
Thread. 
Inches. 


No. of 
Threads 
Per Inch. 


i 


.185 


20 


2 


1.712 


H 


A 


.240 


18 


n 


1.962 


H 


i 


.294 


16 


H 


2.175 


4 


A 


.344 


14 


2* 


2.425 


4 


i 


.400 


13 


3 


2.629 


H 


A 


.454 


12 


H 


2.879 


H 


f 


.507 


11 


H 


3.100 


H 


f 


.620 


10 


3* 


3.317 


3 


i 


.731 


9 


4 


3.567 


3 


i 


.837 


8 


H 


3.798 


H 


ij 


.940 


7 


H 


4.028 


2* 


u 


1.065 


7 


4f 


4. 255 


H 


it 


1.160 


6 


5 


4.480 


H 


H 


1.284 


6 


H 


4.730 


n 


i| 


1.389 


H 


H 


4.953 


H 


if 


1.490 


5 


5} 


5.203 


81 


ij 


1.615 


5 


6 


5.423 


H 



63. Formal Adoption of United States Standard 
Threads. — This system was authorized for the naval ser- 
vice by the Government in the year 1868. In the year 1871, 
the Master Car Builders' Association recommended it for 
use in the construction of locomotives and cars. The system 
is now entirely used in the United States Navy, and very 
generally used in locomotive and car construction. It has 
been adopted by manufacturers generally. It has not 
entirely taken the place of the V-thread system, however, 
since for very small screws and fine pitches the V thread is 
in many instances more desirable. 

64. Variations in Diameter of Standard Bolts. 

It will be noticed that the United States standard diameters 



/ 



40 LATHE WORK. §4 

of bolts vary by sixteenths, eighths, and fourths of an 
inch. Until recently, many makers used the same number 
of threads per inch, but made the diameter of the bolt t \ or 
j*j inch under or over the standard diameter; thus, a {-inch 
bolt might be fa inch over or under J inch in diameter. 
Taps and dies made according to this system are still in use 
in many blacksmith shops. Fortunately, the confusion 
arising from this cause is rapidly being done away with, and 
manufacturers generally are adopting the single standard 
system and making all their bolts of exactly the nominal 
diameter. The United States standard thread is used on 
commercial capscrews. 



SHARP, OR V, THREADS. 

65. This form of thread has been almost 



sally 



adopted for the making of case-hardened setscrews. The 
number of threads per inch adopted by universal consent is 
slightly different from that employed in the United States 
standard, and is given in the following table: 



at 11* \ \ 


■V 1 ! 


!, 


1 


1 


i 


1 


■ 


M 


"1 


ii 


4 


■I 


■« 


'I 


• 


TJiruail* [■» iS 


16 


, 


„ 


" 


"• 


9 


s 


7 


' 


6 6 


s 


s 


41 


.1 



BRITISH STANDARD. 

fi«. Origin of the System.— In the year 1861, Sir 
Joseph Whit worth, of England, proposed a system of stand- 
ards for screw threads to overcome the evils that were 
arising in England by the use of a great number of indi- 
vidual systems, each individual builder or manufacturer 
having had his own standard up to that time. The system 
that he introduced is now the standard thread used by 
British manufacturers, and the same form has been adopted 



§4 LATHE WORK. 41 

very largely throughout Europe. The rounding of the top 
and bottom of the thread has certain very desirable features, 
since it adds greatly to the strength and durability of the 
screw and does away with the sharp corners, which are more 
liable to be nicked or bruised. 

Most American manufacturers that are accustomed to the 
United States standard consider the difficulty of keeping 
up to standard the necessary tools for producing these 
curved points and roots a sufficient argument against 
the adoption of the British standard screw thread in this 
country. 



CUTTING SCREW THREADS. 

67. Methods of Cutting Threads in Use. — Screw 
threads may be cut on bolts or screws by either one of two 
methods. First, a die may be used that cuts the thread to 
size at one passage over the work. Second, the work may 
be revolved between the centers of a lathe and a single- 
pointed tool held in the tool post passed along the course of 
the thread a number of times, so as to remove the metal a 
little at a time. 

68. Definitions. — When a screw is cut upon the out- 
side of a piece of work, it is called an external, or a male, 
thread. When a thread is cut on the inside of a nut or 
collar, it is called an internal, or a female, thread. 



CUTTING THREADS BY HAND. 

69. General Consideration. — When accuracy of 
pitch is desired, or the screws are long, the thread should be 
cut in a lathe between the centers, but if a limited number 
of short threads is required, these can be advantageously 
cut by hand with dies; while if a large number is required, 
they can be produced by means of a special bolt-cutting 
machine. 



42 



LATHE WORK. 



TO. iIiiikI Mm. Pig. SO shows a dw far 
threads, which is intended to be operated by hand. 

bald in B die holder, as shown in Fig. 
When these hand dies are used, the i 

to be threaded is held in a vise. The i 
is than screwed down on the end of 1 
rod until the desired length of screw 1 
been cut. Some pressure will be i 
saxy to start the die, but, after j 
threads are cut, it will feed it' 
Flc " M as it is revolved. The die shown in 

Fig. 50 is adjustable within certain limits. Fig. 52 shows it 
with one half removed, parts a and b compose the i 
proper. Part c is a guide that slips on the end of the i 





8* 



LATHE WORK. 



43 



dies from the work as it does to cut the thread. Hand-cut 
threads can never be depended on to be true with the axis 
of the work, as the guide does not fit with sufficient accu- 
racy to start the dies perfectly true. Worst of all is the 
inaccuracy of pitch. It is not uncommon to find dies that 
would cut a thread which, if continued for a foot in length, 
would be in error -1 inch. With care, dies can be made that 
will cut short threads with sufficient accuracy of pitch for 
commercial purposes. 

BOLT CUTTERS. 

72. General Description of Bolt Cutter.— Foi 

rapid screw cutting, special machines are used. These 




machines, called bolt cutter**, rotate the dies while the 
work is held in a chuck on the machine. Fig. 53 shows a 
type of bolt cutter called a double-head machine, since 



44 



LATHE WORK. 



§4 



it carries two heads or die holders. Work is clamped hori- 
zontally in the machine in the jaws or chucks d y d by means 
of the large hand pilot wheels a, a. The chuck and work 
are moved up to the dies c, c by means of hand wheels b, b y 
these wheels operating the gears, which engage with the 
racks shown. 

73. Automatic Dies. — The dies used on bolt-cutting 
machines are quite different from the hand dies just described. 
They are automatic in action, so that when the die has cut a 
sufficient length of thread on the bolt, a lever automatically 
opens the die, causing it to cease cutting and allowing the 
work to be freely withdrawn. This saves much time. 
Fig. 54 shows one style of special head for bolt cutters 




Fig. 54. 

designed to hold detachable dies. Dies of various sizes may 
be used in this head for cutting different diameters of bolts. 
Fig. 55 shows the principle of this style of automatic head. 
The body of the head b has four radial grooves cut in the 
end, in which the four cutter dies d can slide. A cap c y 
fastened to the head b with screws, holds the dies in place. 
The outer ends of the dies are beveled, as shown. The 
ring r tits over the head b and partly over the ends of 



s< 



LATHE WORK. 



45 



the dies. When in the position shown in the illustration, 
the dies are open. To close the dies, the ring r is pushed 
in the direction of the arrow, over the ends of the dies to 
the position of the dotted lines. This forces each of the dies 
toward the center. When in this position, the dies are 




1 IH:^ 



ready to cut. Levers are so arranged that after a thread 
of the desired length is cut on a bolt, the ring r is suddenly 
released and moved back to its normal position, as shown. 
This releases the dies, which are as quickly opened by the 
cylindrical portions a. Fig. 64, sliding in the ring r, and the 
dies cease to cut. 

74. Lubrication. — When these machines are being 
used, a stream of lard oil is kept flowing on the dies and the 
work, to keep them cool and to lubricate the cutting edges. 



TAPPING. 

75. Use of Taps. — The operation of cutting internal 
threads is in many respects similar to that of cutting 
external threads. It may be done on the engine lathe, as 
vi'N be described later, or by the use of taps, which may be 
operated either by hand or machine power. The use of taps 
for cutting internal threads is the common practice, and 
only when large or special forms of threads are desired is 
the lathe employed. 



46 LATHE WORK. ' §4 

76. Hand Taps. — Taps are generally made from the 
solid bar of steel. They are accurately threaded and fluted, 



B 



B 



^ — 

^ 



B 



and then tempered. Pig. 56 shows a set of machinists' hand 

taps. A set consists of a taper, a plug, and a bottoming tap. 

77. Tapping a Hole. — When a hole has been drilled 

entirely through a piece, it is only necessary to use the taper 

tap, which may be run entirely through 

?— 'i ■ '■':''■$ the piece being tapped. When a hole 

§ ■ ■ ■ S£ that has been drilled partly through a 

piece is to be threaded to the bottom, as 
; shown in Pig. 57, it is necessary to use 
, ; all three taps. In order to start the 
;■■. thread, it is necessary to use the taper 
. .,../.$& ta P- This is screwed in until it touches 
the bottom of the hole. The plug tap 
is next used, which, when screwed to the 
bottom of the hole, will cut "full" threads somewhat 
deeper, and, for finishing, the bottoming tap is used. 

7H. Machine Tapping. — Por machine tapping, the 
taper tap is used, the principal difference being that it has 
a Imiger shank than the hand taper tap. The machines 
used are similar to those used for bolt cutting. The die 
head is removed ami the taps' are held in suitable chucks in 
the place of the die heads. 



§4 LATHE WORK. 47 

CUTTING SCREWS ON THE LATHE. 

79. Accuracy of Pitch. — When screws of accurate 
pitch or lead are desired, or when screws are desired that 
will be true with the axis of the work, they can be cut with 
more certainty on the lathe than with dies. The accuracy 
of the screw cut will depend on the accuracy of the lead- 
screw in the lathe used. For ordinary threads, the ordinary 
leadscrew is sufficiently accurate. When greater accuracy 
is required for such work as making taps or dies, the making 
of precision screws for measuring instruments, or similar 
work, a leadscrew that has been made with more than ordi- 
nary care and has been tested all along its length must be 
used. 



CAI>CUI.ATING CHANGE GEARS. 

80. The Function of the Leadscrew and Change 

Gears. — When cutting screw threads the carriage is moved 

ty the leadscrew. The leadscrew is caused to revolve, and 

as it works in a nut attached to the carriage, the carriage is 

moved toward or away from the headstock, according to the 

direction in which the leadscrew turns. This nut is split in 

halves, and when it is not desired to move the carriage by 

the leadscrew, a movement of a lever opens the two halves 

of the nut so that they do not engage with the leadscrew. 

It is at once apparent that for every revolution of the 

kadscrew the carriage moves a distance equal to the pitch. 

For example, if a leadscrew has 5 threads per inch, its 

pitch is \ inch, and for every revolution of the leadscrew the 

carriage moves -| inch. If, now, the lathe spindle and with 

it the work on which the thread is to be cut turns exactly 

once while the leadscrew turns once, the thread tool will 

advance \ inch, and the thread thus cut will have a pitch of 

\ inch, or the number of threads per inch cut will be the 

same as the number of threads per inch on the leadscrew, in 

this case 5. If, further, the spindle turns, say, twice as fast 

as the leadscrew does, the work will make two turns while 

the tool advances \ inch. In other words, the resulting 

tib-« 



»t. 



48 LATHE WORK. (4 

thread will have twice as many turns in a given distance, 
say, 1 inch, as the leadscrew has. In the present case, if the 
leadscrew has 5 threads per inch, the resulting screw will 
have 10 threads per inch. If the spindle turns one-half as 
fast as the leadscrew, the leadscrew will make two turns 
while the work makes one tum. The result of this is that 
the distance l>ctwccn any two threads on the work will be 
just twice that on the leadscrew. In other words, the 
resulting pitch will lie H inch, and the number of threads per 
inch will ho 2 j. 

81. In screw cutting the chief object to be attained is 
to make the leadscrew turn slower or faster than the spindle, 




Pk. IH. 



whrllkT the ,-htvw to be cut has a greater pt 
if :!uv;li)^ j«t inch than the leadscrew. This 
ili-ilu-d liy diaiifiinj.; the gears mi the back end 



LATHE WORK. 



of the lathe, will be understood more clearly by referring to 

Fig 68, which shows the arrangement of the gearing. On 

small work the back gears are thrown out and the c 

ley a turns the spindle and with it the gear b, which is keyed 

i the rear end. Gear /' engages with the idler c, which in 

irn engages with gear d. dears ii and e are keyed to .1 

ollow sleeve on the stud and revolve together, Gear f 

idler ,'. which transmits the motion to gear g on 

11 will be noticed that gears b, d, 

il g turn in the same direction, and that gears e and / turn 

i ihe opposite direction. Gearsr, d, ant! // are a part of the 

neehanism used for reversing the direction in which the 

:adscrew turns. As geared now, the lathe will cut a right- 

ul. If. however, the handle j were pushed dowtt, 

^a^ k would engage with gear b and gears c and g would 

irn in the opposite direction to that shown in the cut. and 

::<! would be cut. Gears b and d have the 

Suae number of teeth. Hence the only gears affecting the 

evolutions of the leadscrew with respect to the spindle are 

arse and g. Either or both of these gears can be changed, 

od if changed, they will affect the motion of the leadscrew; 

ailed clianee gears. 

ie cone <r, and with it the lathe spindle and 

revolution. Gear d being the same size 

I gear b will also make one revolution, and as gear e is 

■ stud as ./. ii will likewise make one revo- 

■, were the same size as gear .'. gear g would 

er of threads cut per 

mber of threads per inch 

■ ver, gear^f contains more teeth 

will not make a complete revo- 

1 when lln' : . rumplete revolution; and if 

1' r, the leadscrew (' will make more 

km when the spindle makes one 

Selecting Lite Cliiinyc liears for a Simple- 
;jr».-ii Lathe.— Man) lathes have "ii 1 1 1 .. ■ from •'■ 

iss in ilex plate, on which is stated what 



50 LATHE WORK. §4 

gears are to be used in order to cut any particular number 
of threads per inch. On some lathes this index plate is 
omitted, and it may happen, also, that it is necessary to cut 
a thread which is not given on the index plate. In this case 
it becomes necessary to make a calculation in order to ascer- 
tain whether or not the thread can be cut with the change 
gears in stock. Probably the easiest method of performing 
this calculation is the following: 

Suppose the leadscrew has i.I threads per inch and it is 
desired to cut a screw having ]ti threads per inch. Form a 
fraction whose numerator shall be the number of threads 
per inch in the leadscrew and whose denominator shall be 

the number of threads per inch to be cut, in this case -— . 

3 

Reduce this fraction to its lowest terms, obtaining -. Now 

o 

multiply both terms of this fraction by the same number 
until a new fraction is obtained whose numerator and denom- 
inator shall be numbers corresponding to the number of 
teeth in two gears in stock. In the present case, multiplying 

•I . 3 X 8 24 

both terms of the fraction - bv 8 we obtain -- , = — • 

8 ' 8 X 8 64 

If we have gears in stock having 24 and K4 teeth, we can place 

the '.M-tontli gear on the stud and the ft 4- tooth gear on the 

leadscrew. In many eases there will be several selections 

that •■an be made, while in other cases only one set of gears 

will (Hit the desired thread. 

a 

•NCJ. The work of selecting the gears may be shortened 

in tin- fallowing manner: After reducing the fraction to its 
lowest iiTins, refer to the list giving the number of teeth in 
each of the gears in stork. Ascertain which of the numbers 
are divNibii' by either the numerator or denominator of the 
fra-t:"ti wit is-fit a remainder. Suppose in the preceding 
i a-e i: wa- : '!.!';'■ that among tin- gears in stock was one 
hav-jg *M i-iili. a:v-ther having -y t teeth, another having 
M» t'-eih. ami «... nil. \..\v dividing *M by the numerator 3 
th«_- m-ml: U ^ Multiplying both terms of the fraction by 8 



§4 LATHE WORK. 51 

24 
the result, as previously shown, is — . If we have a gear 

with 04 teeth, it can be placed on the leadscrew and the 
24-tooth gear can be placed on the stud. 

84. Any lathe having its gears so arranged that when 
the lathe is running there is but one change of speed between 
the stud and leadscrew is called a Him pie-geared lathe. 
In explanation of this definition, refer again to Fig. 58. It 
will be seen that when the lathe is running, gear e makes a 
certain number of revolutions in a certain time, say, 1 minute, 
while gear g revolves a greater or less number of times in 
1 minute according to whether it is smaller or larger than 
gear e. It makes no difference how many gears there are 
between c and g f as the speed of gear^ is not affected. In 
fact, in the figure shown, so far as the speed of gear g is 
concerned, gear /"could be removed entirely and gear g 
could mesh directly with gear c. In some simple-geared 
lathes, however, to avoid the use of large gears, the fixed 
gear on the stud is sometimes larger than the gear on the 
spindle. In other words, referring to Fig. 58, gear d is 
sometimes larger than gear b. In such cases gear /; is usually 
placed inside the bearing and gear d is partly or wholly con- 
cealed in the headstock. As a rule, in all such instances, 
gear d has either twice or three times as many teeth as gear b. 

85. Therefore, the first step in calculating the change 

gears is to ascertain whether or not gear d has the same 

number of teeth as gear b. Should it l>c found that gear d 

is larger than gear £, multiply the number of threads per 

inch in the leadscrew by the number of teeth in gear d and 

divide the product by the number of teeth in gear b. Use 

this number in all cases as the numerator of the fraction 

whose denominator is the number of threads per inch to be 

cut. For example, assuming that the leadscrew has threads 

per inch, that gear b on the spindle contains -24 teeth, and 

gear d contains 48 teeth, multiply by 4K and divide by "M, 

4-8 X 
obtaining — wi — = 12. In all cases of calculating the 



52 LATHE WORK. §4 

change gears for a lathe of this kind, 12 would be used for 

the numerator instead of 0. For example, if in the case 

just mentioned it is desired to cut 13 threads per inch, the 

12 
fraction will be -^. Now referring to the set of gears, we 

1 o 

endeavor to find one whose number of teeth is a number 

divisible by 13. Suppose we find one having 52 teeth. 

Dividing 52 by 13, the result is 4, and multiplying both terms 

12 X 4 48 
of the fraction by 4 we obtain -^ . = —-. Hence, if there 

J 13 X 4 52 ' 

is a 4S-to<>th gear in the set, it can be placed on the stud and 

the 52 -tooth gear can be placed on the leadscrew. 

Rule. — 1 . For a simple geared lathe ', form a fraction whose 
numerator is the Number of threads per inch in the leadscrew 
and whose denominator is the number of threads per inch to 
be cut % and reduce this fraction to its lowest terms. 

II. But if there is a fixed gear on the stud that differs in 
size from the gear on the spindle \ multiply the number of 
threads per inch in the leadscrew by the number of teeth in 
the fixed gear on the stud and divide the product by the num- 
ber of tct tit in the gear on the spindle ; use this result as the 
numerator instead of the number of threads per inch in the 
i Cti itse rci*. '. 

III. Find from the list of change gears one y the number 

ot whose teeth is exactly divisible by either the numerator or 
denominator of the fraction last found, and find how many 
timts the number representing the u umber of teeth in the gear 
*c!tctcd CfHi-iins the numerator or denominator of the fraction. 
Multiply ,'.'/' firms of the fraction by this quotient and the 
nn mora ft r ■;/ f he fiat tion will represent the number of teeth 
/■; the el t ■• :.■;#■ .,e.tr on the sfud t and the denominator the num- 
bet it teeth in the gear ,».y the leadscrew. Ff it should so 
ha*p.--': that t-'.e/e are no two gears having the number of teeth 
/■■/.•■/ ;■■ th's n.\ii»ncr % repeat the process until two gears are 
ton-'i hartttg the same number f teeth as are represented by 
tin ;.;/.'',■',;» ccmre>n.j th t - numerator and denominator. 
l he ,„■'."'. tht i;n::;b t t ,-/" who\'e teeth corresponds to the 



LATHE WORK. 63 

numerator, should be placed on the stud and the other gear 
on the leadscrew. 

Example. —Suppose Uie gear on the spindle has 24 teeth and the 
fixed gear on the stud lias 811 teeth. It the lesdacrew has i threads per 
inch, what change gears must be used in order to cut a screw having 
13 threads per inch ? 

Solution, — As the fixed gear on the stud differs in size from the 
gear on the spindle, we proceed as in II of the rule just given, obtaining 
It) 



We therefore use 10 for the i 
mber of threads per inch I 
10 

I teelfa is exactly divisible by la. In other words, there must 

- a gear in stock the number of whose teeth equals 2 X 13 = 39, 

IS multiplied by some other small num- 

■ [ligation, that a gear is found having 62 teeth, 

s 13 is contained four times in 52. multiply both terms of the fraction 

" ' 4 =, - 
* IB X 4 62 



i. obtaining ttj- Now there must be a gear in stock whose 



I by 4, obtaining a = ^. If now there is a gear in stock having 



►Sti. Cutting Fractional Threads.— When the num- 

ili< li !■■ be ml contains a fraction, as for 

Ihe rule just given will still apply. 

be formed in the usual manner. Being a 

instead of a simple one, reduce the com- 

a simple fraction by multiplying both 

n( the compound fraction by 

the fraction in the denominator of the 

—Referring !■■ Fig "■«. in which the rued gear on the stud 
n the spindle, calculate the change gears 
. BCrew having S| threads per inch. Assume that the 
■ inch 

ind 2| for the denom- 
id traction =j. The denominator of the 



£4 LATHE WORK 55 

as tor instance one having a patch of 1 inch or more, it is 
necessary to use compound gearing", both because otherwise 
an extra large number of change gears would be required 
in the set, and because the change gears themselves would 
have to be very large. The same remarks apply to gears 
having a particularly fine pitch, as for instance a pitch of 
^s inch or less. The gearing arrangement in a compound- 
beared lathe is shown in Fig. 51). This is the same lathe as 
was shown in Fig. 5S, but has a different arrangement of 
gears. Usually a simple-geared lathe cannot be converted 
into a compound-geared one. As in Fig. otf, a is the cone 
pulley, b the gear on the end of the spindle, i\ //, and tl arc 
gears attached to the reversing mechanism, c is the change 
gear on the stud, and g the change gear on the leadscrew. 
Instead of connecting c and^ r by an idler gear/*, as in Fig. r>s, 
f meshes with /', Fig. 59, and revolving on the same shaft 
with k and keyed to a hollow sleeve, free to turn on the 
shaft is gear/, which meshes with gear g on the leadscrew; 
gears k and f are both keyed to the same sleeve and revolve 
together. The result of this arrangement is that there is 
a change of speed between c and k and another change 
between f and g. Consequently, a compound-geared lathe 
may be defined as one in which, when the lathe is running, 
there are two changes of speed between the guar on the stud 
and the gear on the leadscrew. With a lathe geared as in 
Fig. 51), four gears may be changed, a change in any one of 
which will affect the motion of the leadscrew. These gears 
arc c % f % t, and g. It should be apparent that a far greater 
range of screw cutting can t>e obtained when there are four 
gears that can be changed than when there are only two 
gears that can be changed. 

88. The process of choosing the proper change gears 
for compound-geared lathes is very similar to that pursued 
in case of simple-geared lathes. The first step is to form a 
fraction that has for its numerator the number of threads 
per inch in the leadscrew, and for its denominator the number 
of threads per inch to be cut. As described in connection 
with simple-geared lathes, if the fixed gear on the stud differs 



.Vi LATHE WORK. §4 

in si/.c from the gear on the spindle, instead of using for the 
numerator of the fraction the number of threads per inch in 
the leadscrew, use for this numerator the number of threads 
per inch in the leadscrew multiplied by the number of teeth 
in the fixed gear on the stud, and divided bv the number of 
teeth in the gear on the spindle. Having found the fraction, 
the next step is to divide it into two fractions whose product 
shall be equal to the fraction first found. Then treat each of 
these two fractions in the same manner as was described in 
connection with simple-geared lathes, for selecting the 
change gears. An example will make the process clear. 

Hi). Suppose that for the lathe shown in Fig. 50, the 
change gears in l lie set are as follows: IS. 18, 36, 39, 42, 48, 
."»!. »'.'•. iii'i. ;■», !»»;, the numbers being the number of teeth in 
the gears. Suppose further that the leadscrew has threads 
per inch and that the fixed gear on the stud has the same 
number of teeth as the gear on the spindle. If it were 
desired to cut a screw having 2? threads per inch, it would 
be found that with the gears in stock, as given above, it 
would be impossible to cut this thread in a simple-geared 
lathe. ThU is easily shown in the following manner. The 
number »>!" threads per inch in the leadscrew being 6 r the 

fraction is , - ": the smallest gear in stock has 18 teeth in 

•>: '.♦ 

it. and is divided by the numerator 2 is 9. Multiplying 

2x9 18 

both terms of the fraction bv 9 the result is- v = ^r t and 

9*9 ol 

there is no jjcar in stock having 81 teeth. If we attempt to 

;:>e the -ear having :JiJ teeth (the next largest in stock), it 

will bi found that on dividing 3U by 2 and multiplying both 

3ti 

term** of the fraction by the quotient 18, the result is — - 

162 

A^ the larue^t gear in stock contains only 96 teeth, the 

re-n'i i» thai there are no gears available for cutting 

m l\ i \v,\ ails. 1 fowever, let us see if the thread can be cut by 

i> : ng .■•impound gearing. The fraction " = , v X .-,- Treat- 

• ' it • 1 

\\\v each of the<e two fractions in the same manner as in the 



§4 LATHE WORK. 57 

case of simple gearing, we divide the number representing 

the number of teeth in the 30-tooth gear by the denominator 

of the first fraction 3, obtaining 12. Multiplying both terms 

24 
of the fraction by 12, we obtain — . As we have in stock no 

of) 

24-tooth gear, we experiment with the 72-tooth gear. 72 -f- 3 

= 24. Multiplying both terms of the fraction by 24, we 

2 X 24 48 
obtain - = ^. As we have a 48-tooth gear we proceed 

to experiment with the other fraction, -. The smallest gear 

o 

in stock is 18; hence, multiplying both terms of the fraction 

1 X 18 18 
by 18, we obtain - = — , and as we have a 54-tooth 

«j X lo o4 

gear, the calculation is completed, the only thing that 
remains now is to determine where the gears are to be 
placed. The fractions themselves determine this. The 
gears represented by the numerators mesh with the gears 
represented by the denominators, and the gears represented 
by the numerators are in all cases the driving gears. It is 
usually more convenient to have the smaller of the two gears 
represented by the numerators on the stud. Therefore, put- 
ting the gear having 18 teeth on the stud, it becomes gear i\ 
Fig. 59. The gear that meshes with this is gear £, which 
has 54 teeth in it. The other gear on the same spindle as 
gear k is gear/", the numerator of the second fraction, which 
has 48 teeth in it. This meshes with gear g, which has 
72 teeth on the leadscrew. So far as the motion of the lead- 
screw is concerned, it does not mattex whether the gear hav- 
ing 18 teeth or the gear having 4* teeth is placed on the stud, 
but the arrangement as selected will probably be easier of ad- 
justment than if the 48-tooth gear were placed on the stud. 
Again, suppose it were desired to cut a screw having 
1 thread per inch. It "would be found impossible to do this 
in a simple-geared lathe in which the gears in stock were 
those previously mentioned, and with a leadscrew having 
B threads per inch. This is very easily accomplished, how- 
ever, when the gearing arrangement is compounded as 



58 LATHE WORK. §4 

g 

shown in Fig. 59. Forming the fraction, it becomes -. This 

3 2 
is equal to - X y. Multiplying both terms of the first frac- 

54 
tion by 18, the result is — , and multiplying both terms of 

18 

72 
the second fraction by 30, the result is — . As we have in 

oo 

stock gears having 18, 54, 72, and 36 teeth, the gear having 
54 teeth will be placed on the stud and made to mesh with 
one having 18 teeth. The gear having 72 teeth will be 
placed next to the gear having 18 teeth, and will mesh with 
one on the leadscrew having 36 teeth. 

■ 

Rule. — Horsing formed a fraction in the manner described 
in the rule for a simple-geared lathe, divide this fraction into 
two fractions whose product shall be equal to the fraction first 
formed. Treat each of these fractions in the manner described 
in the rule for simple-geared lathes. The numerators of the 
two fractions wilt be, respectively, the change gear on the stud 
and the driving gear on the second stud. The denominators 
will be the gear meshing with the change gear on thestud 9 and 
the gear on the leadscrew. 

Example.— With the gears and leadscrew mentioned in Art. 89, 
what gears are required to cut a screw having 40 threads per inch ? 

Solution.— Assuming the fixed gear on the stud to be the same size 

Aft 3 

as the gear on the spindle, the fraction becomes -jr = sy But =: 



3 1 

X .»• The only gear in stock, the number of whose teeth is 

exactly divisible by lo is the one having GO teeth. Hence, since 

tin -:- io _ <», ■'- ' — '.. As it is probably advisable to use the 

1 X 48 

UO-iimth gear, and HO -s- 2 = 4S, the second fraction becomes s - Q 

4S 

- -,. Therefore, the driving gears are 18 and 48 and the driven gears 

are 00 and Ut>. Ans. 

90. Cutting Right-Uand and Left-Hand Threads. 

As kit lu- s arc commonly geared, they will cut a right-hand 
thread when one intermediate gear is used and a left-hand 
thread when two intermediate gears are used. The number 



§1 LATHE WORK. 59 

of teeth in the intermediate gears has no effect on the 
thread cut so long as they are all in one continuous train 
without compounding. In compound -geared lathes the 
compound gears take the place of the intermediate for 
right-hand thread cutting, while for cutting a left-hand 
thread, it is necessary to introduce another intermediate 
gear into the train, either between the driving stud and 
compound stud or between the compound stud and the lead- 
screw. Most lathes have gearing in the head for reversing 
the feed, and in such a case this can be used to reverse the 
motion when cutting left-hand threads. 



THE THREADING TOOL. 

91. Shupe of Threading Tool. — When a screw 
thread is to be cut, the tool is ground and shaped as shown 
in Pig. 60. The tool is ground flat on top. The side 
faces NS and GK are ground to form an angle of 60°, 



ES^ 



^ 



LF 



This angle is tested by using a thread gauge, shown in 
Pig. 61. When the gauge is used to test the angle of the 
point of the tool, it should be held so that it lies flat with 
the top face in the line A B, Fig. 60. If it is desired to 
measure the exact angle that the two faces make with each 
other, the gauge should be held at ri^ht angles to the faces, 
or along the line PQ. It will be apparent that the way the 



LATHE WORK. |4 

tool fits the gauge will depend on the way the gange is held 
to the Wot. In order t<> make the angle at the poifl 
the line A B equal 00", it will be necessary to make the 
: ihe face* along the line^^a little uverW. Little 
. i r, is [i.i id to the exact angle, since the 
angle along tin- line A H i* the important MM The Ugk 
of front rake and clearance of the tool is shown by i 
line EF. Tlii* should Ijc about 15' with the perpendk 
ular C I). 

»2. Grinding Threading Tool.— These tools 

be ground liy th<= tame method used in grinding ordinary 

lathe tools, the gauge being used to teat the angle of the 

point. Whcncvet il is possible, it is letter to grind the 

in machines specially designed for grinding tools. 

il is possible to grind more accurate angl 
and truer faces than it is liy hand 

tt:t. Setting Tlircadlnit Tool.— The tooh 

i In the tool post at such an angle to the work tl 
A', Pig. !H), will make eoj 
with the work. This is accomplished i 
gauge, as shown in Fig. Hi. The back of the gauge 



the 



■ 
■ 




I LATHE WORK. 

,d the work will be an angle of CO". It will therefore 1 
burnt more convenient on some kinds of work to hold the 
jauge as shown in Fig. S3. When one edge of the toot is 
iroperly set, the other edge will be at the correct angle, 
irovided the tool is correctly ground. 



CUTTING THE THREAD. 

94. Operation of Cutting the Thread. —Be fore 

starting the cut, care should be taken that the t".>l is firmly 

clamped in the tool post, that the dog is tight on tin 

nd that all gearing is properly adjusted S" that nothing 

in slip when the cut is being made. The feed should be 

om right to left when the lathe is running forward. This 

ill cut a right-hand thread. The tool is moved forward 

> that the point just touches the work. The lathe is started 

irward and continues in this direction until the tool has fed 

long the work a distance equal to the desired length of 

iread. When the tool reaches that point, it is quickly 

eairn away from the work by a turn of the cross-feed screw 

ilh one hand, while the lathe is quickly reversed by swing- 

ng the shifter handle with the other hand. By reversing 

lathe, the work moves backward and the tool will feed 

: to the starting point. 

»S. Stop for 

• ThreniUns: 
keep the 

deep, a stop is ar- 
mged on 

ihown in 

niog the si 

i large shoulder and nurled head, passes 




LATHE WORK. 



M 



loosely through the stop and screws into the tool block /. 
When the stop is adjusted as shown in the figure, the tool 
and tool block ran be moved away from the work, since the 
screw s is not threaded to the block b. When the block is 
moved forward, it can only move until the head of the 
screw s comes against the stop. 

After the tool has passed over the work and it is desired 
to take a dreper cut, the stop-screw s is unscrewed a partial 
turn ; this will allow the tool to be advanced slightly, depend- 
ing on the amount the screw is turned. After the first cut 
or scratch is made on the work with the point of the tool, 
it is good practice to hold a scale against the threads and 
count the number to the inch to see if the lathe is cut- 
ting correctly. If a mistake is discovered, it can l>c recti- 
fied, but if the error of pitch is not discovered until the 
thread is cut, there is no remedy. 



FITTING THI! THREAD. 

Perfectly Fitted V Threitd. — As was shown 

is sharp at its point and at its root. 
If a 1-inch threat! were being cut, 
the thread would be complete when 
the groove cut by the tool just 
formed the sharp point of the thread. 
It is difficult to know just when this 
pinnt is reached, therefore the work 
is taken from the lathe and tested 
with a gauge or in the piece it is 

represents a section 
hull and nut, showing how 

the faces of the threads 

arh other. 




97. Call perl n 



lit- 



l In- final testing in 
I'sleil by the use of 



LATHE WORK. 



specially prepared calipers. These calipers are made very 
thin on their point, so that they fit into the V's of the 




hread and measure the diameter at the root, as shown in 
p ig. 68. The calipers may be set from a tap or a standard 
gauge. 



US. Effect of Using a Dull Thread! 

I shows a bolt that has been :i u 

ointecl tool. Because of the rounded 

oint of the tool, the threads are 

; at the bottom. When this 

. thread is tested in a per- 

laded nut, as shown, it will 

e seen that it will not enter until the 

ul sufficiently deep to .ill. w 

d root of the thread to pass 

this may hold the work so 

in be detected at 

~st, it is evident that the piece will 

incc there is no bear- b ■- — 

sides of the threads. F10.07. 



\AAAAM 



L/yVVWVj 



89. Effect of Using a Dull Tap.— Fig. ti8 shows 

mother case where the nut to be fitted has been cut with 

ip, which left the threads slightly rounded in the 

When a sharp-threaded screw of full diameter is 

«d in such a nut, it will not enter. By cutting the screw 



64 



LATHE WORK. 



8* 



smaller, it will go in, but the fit will be as shown, -the bear- 
ing being entirely on the points of 
the threads. In practice, when the 
thread has been cut to a sharp point 
and it will not enter, this trouble 
should be looked for, and if it is 
found that the threads in the nut 
are imperfect, the points of the 
screw being cut should be slightly 
rounded with a file. A screw 
thread should fit by bearing on the 
sides of the threads and not on the 
points. 




1 OO. Ad vantage of Larue Tap Holes. — In machine 
construction where holes are drilled and tapped for V threads 
in various parts of castings, 
it is customary to drill the 
holes slightly larger than 
would be necessary to cut 
such a full sharp thread as 
shown in Fig. 05. After the 
holes are tupped, they are 
more nearly the shape shown 
somewhat exaggerated in 
section in Fig. OH. where it 
may be seen that the threads 
are not full on the points. 
When a bolt is being fitted 

to this kind of a tapped hole, the necessity of keeping a very 
sharp point on the tool and cutting the thread sharp at the 
root is not so important. 




lOl. Kffeet of n Slight Difference In Pitch on 

the Pit.— Pig. ?o shows a section through a bolt and nut 
having slightly different pitches. In fitting such a bolt, it 
will In- l.'iiml upon iri.il th.it it enters the nut for a few 
turns iMsih*. growint- [ij-hier .is it i-; sere wo J in, with the 




§4 LATHE WORK. 65 

appearance of being tapered. After more cutting, the bolt 

will pass through the nut, appearing to fit. When the end of 

the bolt is once passed through the 

work, it will not fit any more closely 

as it is screwed along the bolt. When 

a bolt and a nut are of slightly dif- ^'Xfyififify 

ferent pitches, the effect is much more 

noticeable if the nut is long than 

if the nut is short. It may be seen 

from Pig. 70 just what the real contact 

is. In this case, the thread on the bolt ^"Oyty*^ 

is of a coarser pitch than the thread 

on the nut, and bears only on the first 

and last threads of the nut. 

102. Fitting; Threads on the Same Lathe. — When 
two threads are to be cut that are desired to fit each other 
perfectly, the internal thread being long, it is desirable that 
they each be cut on the same lathe. By the use of the same 
lathe, they can be made to have the same pitch, and if there 
is any error in the pitch, it will be the same in each thread. 

103. Putting: Work Back into the Lathe After 
Tcatinu;. — If, after testing the work carefully, it is found 
to be too large, it should be put back into the lathe and a 
sufficient number of light cuts taken to reduce it to the 
desired size. Care must be taken to notice and mark the 
notch in the face plate used for the tail of the dog, and to 
put the dog back in the same position from which it was 
taken. A failure to do this will cause the point of the tool 
to start another thread that will destroy the one nearly 
completed. 

104. Precautions to Observe in Thread Cut- 
ting;- — When cutting screws in a lathe, lard oil should be 
freely applied to the tool and the work. The finishing cuts 
should be light shaving cuts. The tool should be made 
sharp and keen with an oilstone. 



66 LATHE WORK. §4 

RESETTING THE TOOL. ' 

105. When the tool has been removed for sharpening 
or other purpose, it may be reset as follows: Adjust the tool 
in the tool post to fit the gauge, Fig. 62, the same as before 
the thread was started. Turn the lathe forward and note 
whether the tool point comes opposite the cut in the work or 
not. If not, drop the intermediate gear r, Fig. 58, away from 
the gear b on the spindle. Turn the lathe forward until the 
tool comes exactly opposite the notch or thread in the work. 
Bring gears b and c together again, which will throw in the 
feed, and proceed to cut the thread as before. It should be 
noted that the lathe must always be turned forwards. This 
is to take up the slack or backlash in the gears and the lead- 
screw. This backlash can be noted at the time the lathe is 
reversed, when it will be seen that the work may make a 
part of a turn before the tool will start to feed back. This 
will cause the tool to drag behind, and if the tool should be 
brought up to the work when it is running backwards, it 
would not fit in the notch as it did when the lathe was 
running forwards. 

OPENING THE LEAD NUT. 

106. When cutting threads on the ordinary lathe, after 
the thread is once started, the feed-nut is seldom opened 
from the leadscrew. In some cases, however, this is allow- 
able. Suppose that a screw with 10 threads per inch is 
being cut with a leadscrew of (5 threads per inch. If the 
feed-nut is opened and the carriage moved along one notch 
or thread on the leadscrew, so that the nut will just close 
again in the second notch, the carriage will have moved 
\ inch. The point of the lathe tool will also have moved 
\ inch. The second notch or thread on the screw being cut 
is 1 \, inch from the first, so it will be seen that the point of 
the tool has moved a little beyond the notch of the thread 
being cut. If the carriage should be moved 2 threads on 
the leadscrew, the tool point would move along \ inch. This 
position would not correspond with any thread on the screw 
being cut. If we should move it 3 threads and close the nut, 



§4 LATHE WORK. 67 

the tool point would have moved f or ^ inch. At this pointy 
*t would be found that the point of the tool would come 
°Pposite the fifth thread of the screw being cut, which would 
t*^ ^ or \ inch on the screw being cut. If we move along 
6 threads or 1 inch on the leadscrew, we would move 
lO threads or 1 inch on the screw being cut. From this it 
will be seen that in the case of a 6-thread leadscrew cutting 
10 threads, the nut may be opened and the carriage moved 
along, and for every \ inch along the leadscrew the nut may 
again be closed on the thread and the cutting proceed with- 
out damage to the thread; for any other position the nut 
will not close, or, if it does, the tool point will not come 
opposite the thread being cut. If the thread to be cut were 
11 pitch, it would be found that the nut could only be 
closed on the leadscrew at spaces 1 inch apart. If the thread 
to be cut were 2^ pitch, the spaces on the leadscrew would 
be 2 inches apart. If the threads to be cut were 6, 12, 18, 24, 
or any multiple of the pitch of the leadscrew, then the split 
nut might be opened and again closed in any place on the 
screw and the tool point would be found to come opposite the 
thread being cut; for if the tool moved \ inch, it would be 
equal to 2 threads on the 12-thread screw, 3 threads on the 
18-thread screw, 4 threads on the 24-thread screw, and so on. 

107. When cutting a screiv, the number of whose threads 
Per inch is exactly divisible by the number of threads per inch 
*n the leadscrew, the lathe need not be reversed \ but may be 
allowed to run in one direction all the time. When the tool 
has fed to the end of the cut, it is quickly drawn out, while 
the feed is stopped by opening the split nut. The carriage 
is then moved back by hand, the feed thrown in, and the 
operation repeated. 

AN IMPROVED METHOD OF GEARING LATHE FOR 

SCREW CUTTING. 

108. The operation of changing the gears for every 
desired pitch of screw consumes considerable time and offers 
a chance to make mistakes. A new system of gearing has 
been introduced which is applied to small lathes. A lathe 



$4 LATHE WORK. 69 

so geared is shown in Fig. 71. In this system all the 
change gears are on a shaft in the gear-box seen at the 
front of the lathe, directly under the headstock. To change 
from one set of gearing to another, the knob a, which 
moves in the slot in the gear-box, is moved to a position 
indicated by the table. This is a very convenient arrange- 
ment when compared with the older methods. This particu- 
lar lathe possesses another feature that makes it desirable 
for screw cutting, viz., the reversing of the feed-motion by 
a lever in the apron. This makes it possible to keep the 
work running in one direction all the time. 



LATHE WORK. 

(PART a> 



SCREW CUTTING. 



UNITED STATES AND BRITISH STANDARD 

THREADS. 



CUTTING UNITED STATES STANDARD THREADS. 

1. Tool for Cutting: United States Standard 
Threads. — The operation of cutting United States stand- 
ard threads is similar to that of cutting V threads. The 
only difference is in the tool, and that consists of grinding 
a very small portion from the point of the tool. It will be 
seen by reference to Fig. 45, Lathe Work, Part 2, that the 
United States standard thread is flat in the root. The width 
across the flat in the root and also at the point of the thread 
varies for every pitch of thread, since one-eighth the space 
between the threads is removed from the points and filled in 
a * the roots, and this amount would vary with each pitch. 
The tool should therefore be ground to an angle of 60° as 
* or V threads, and the proper amount taken from the point. 
The best way to determine the amount to be removed from 
tn e point is to try the tool into a standard tap or to have a 
gauge to which the tool can be fitted. 

2. United States Standard Thread Gauge. — Such 
a gauge is shown in Fig. 1. The figures opposite the differ- 
e °t notches indicate the notch to be used in shaping the 
tool for that pitch. The following table gives the widths of 

§5 

Por notice of copyright, see page immediately following the title page. 



I 



« 



s 



LATHE WORK. 



§ 



TABLE I. 



UNITED STATES STANDARD SCREW THREADS. 



Diameter of 
Screw. 




i 
i 

i 

f 
i 
i 

l 

H 
U 
i| 
i* 
if 
i* 
i* 

2 

H 
H 
** 

3 

31 
3i 
3* 
4 

5 

H 

6 



Threads 
Per Inch. 




20 
18 
16 
14 
13 
12 
11 
10 
9 



8 
7 
7 
6 
6 

6* 
5 

5 

H 

4 
4 

3* 
H 

H 

3 
3 

n 
n 



Diameter at 
Root of 
Thread. 

r 




.1850 
.2403 
.2936 
.3447 
.4001 
.4542 
.5069 
.6201 
.7307 

.8376 
.9394 
1.0644 
1.1585 
1.2835 
1.3888 
1.4902 
1.6152 

1.7113 
1.9613 
2.1752 
2.4252 

2.6288 
2.8788 
3.1003 
3.3170 

3.5670 
3.7982 
4.0276 
4.^551 

4. 4804 
4.7304 
4. 9530 
5.2030 

5.4226 



Width of 
Flat. 




.0063 
.0069 
.0078 
.0089 
.0096 
.0104 
.0114 
.0125 
.0139 

.0156 
.0179 
.0179 
.0208 
.0208 
.0227 
.0250 
.0250 

.0278 
.0278 
.0313 
.0313 

.0357 
.0357 
.0385 
.0417 

.0417 
.0435 
.0455 

.0476 

. 0500 
.0500 
.0526 
.0526 

.0556 



Double Deptt 
of Thread. 



.0650 
.0722 
.0814 
.0928 
.0999 
.1083 
.1181 
.1299 
.1443 

.1624 
.fB56 
.1856 
.2165 
.2165 
.2362 
.2598 
.2598 

,2887 
.8887 
.8248 
.3248 

.3712 
.3712 
.3997 
.4330 

.4330 
.4518 
.4724 
.4949 

.5196 
.5196 
.5470 
.5470 

.5774 



§5 LATHE WORK. 3 

flats for different pitches and also the diameter of the screw 
at the root of the threads. 




Fig. l. 

3. Cutting United States Standard Threads. — 

When cutting United States standard threads, the cutting 
is continued until the space between the grooves is equal to 
the width of the flat of the desired thread. The mistake is 
sometimes made of cutting until the thread comes sharp 
like a V thread and then cutting off the point. This method 
is incorrect. 



CUTTING BRITISH STANDARD THREADS. 

4. Tool for Cutting: British Standard Threads. — 

The operation of cutting British standard threads is similar 
to that just described. The difference in thread is due to 
the shape of the tool. Every pitch of thread requires a 
tool of particular size and shape, the same as the United 
States standard, but because of the curved point and root of 
the thread (see Fig. 46, Lathe Work, Part 2), the tool is much 
more difficult to make. Fig. 2 shows the plan of a tool as it 
is applied to the work. It will be seen that the point is 
rounded and round corners are formed on the sides of the 



LATHE WORK. 



15 



tool, to form the round points of the threads. These tools 
are thus in reality forming tools, and are sharpened by 
grinding on the top face. 
The tools are formed by 
using a hob shaped like a 
tap, with eight or ten flutes. 
These hobs are accurately 
formed screws before the 
flutes are cut. After the 
hob is fluted and hardened, 
it is held between the lathe 
centers while the blank tool 
is held in the tool post. 
As the hob revolves, the 
tool blank is fed up to it; 
at the same time, it is fed 
along by the leadscrew. By repeating these operations, as 
in cutting a screw, the blank is soon formed into a thread- 
ing tool. After hardening, it is ready to be used to cut the 
desired screw. 




SPECIAL THREADS. 



SQUARE THREADS. 

5. Tool for Cutting Square Threads.— The tool 

used for cutting square threads is similar to a parting tool 

except for its angle of 

side rake, which varies 

for every diameter and 

every pitcli of thread. 

Suppose it is desired to- 

cut a square thread of 

2 threads per inch, as 

shown in Fig. 3. Since 

the thread is J inch 

pitch, the space and 

thread together would be equal to J inch, while the space or 




M 



LATHE WORK. 




PlO.4. 



the thread would each be J inch wide. The tool therefore 
would be ± inch thick. It will be seen from the figure that 
the space between the threads 
slopes to one side, as shown by 
the line c d. The tool, there- 
fore, must have sufficient side 
rake to allow it to run freely in this space. The angle of 
side rake is found by laying off on the line E F, Fig. 4, a 
distance equal to the circumference of the root of the thread. 
At F erect a perpendicular F R, equal to the pitch, 
and draw £ R. Angle R E F is the angle of side rake 






Fig. 5. 

or the slope to one side that the tool blade C D % Fig. 5, 
should make with the line G K. The tool blade should be 
ground thinner at the bottom than at the top, so that the 
sides of the tool will not rub against the sides of the 
thread. 



6. The thread should be cut as deep as it is wide, thus 
making the threads square. When the screws are large and 
it is desired to finish the sides of the threads very smooth, 
the threading tool, Fig. 5, is made a little thinner than the 
desired width of space. After the notch is cut the desired 
depth, a side tool may be used for cutting the side of the 
threads, the blade being set flat with the side. Care must 
be taken that the tool does not catch and spring into the 
work. 



LATHE WORK. 



§5 



THE 2»*, OR ACME, THREAD. 

7. Use of Acme Thread. — In many instances, a 
coarse pitch screw is desired that has but little friction on 
the sides, but is neither a square thread nor a V thread. 
Without a standard, there are apt to be differences in shape 
used by different manufacturers. In order that there may 
be a standard, the 29" screw thread, called the acme 
thread, has been proposed, and is extensively used in 
many places to take the place of square threads. 

8. Shape of Acme Thread. — The sides of the thread 
are inclined 14± , making the included angle 29°. This is 

the angle that is used for 

■ cutting worm- threads. The 
depth of the thread is the 

"1 same as a square thread of 

W the same pitch. Fig. 6 il- 

A lustrates the form of the 
thread, and the accompany- 

,.;' ing formulas and table give 

^ the proportions for threads 

| of various pitches. It will 

I be observed that the top of 

£ the thread does not touch 

■ the bottom of the space. 
K This opening represents the 

clearance, which is provided 
Pio. a. . - _ 

to insure a perfect fit upon 
the sides of the thread. 

». The various parts of 29° screw thread, acme stand- 
ard, are obtained as follows: 

A = widtli of point of tool for screw or tap thread; 

H = width of point of screw or nut thread; 

C = diameter of tap; 

D = diameter of screw; 

E = diameter of screw at root of thread; 

T = number of threads per inch; 

a = depth of thread. 




§8 



LATHE WORK. 



^ = ^^-.0052. E = D - (jt + .02 Y 



B 
C 



T 
.3707 

T ' 
Z7+.02. 



a = 2"7«+ «<>1. 



TABLE II. 





TABLE OP ACME THREAD 


PARTS. 




Number of 

Threads 

Per Inch. 

Linear. 


Depth 

of 

Thread. 

a 


Width at 

Top of 

Thread. 

b 


Width at 

Bottom of 

Thread. 

c 


Space at 

Top of 

Thread. 

d 


Thickness 

at Root 

of Thread. 

e 


1 


.5100 


.3707 


.3655 


.6293 


.6345 


1* 


.3850 


.2780 


.2728 


.4720 


.4772 


i 


.2600 


.1853. 


.1801 


.3147 


.3199 


S 


.1767 


.1235 


.1183 


.2098 


.2150 


i - 


.1350 


.0927 


.0875 


.1573 


.1625 


s 


.11($0 


.0741 


.0689 


.1259 


.1311 


6 


.0933 


.0618 


.0566 


.1049 


.1101 


7 


.0814 


.0529 


.0478 


.0899 


.0951 


8 


.0725 


.0463 


.0411 


.0787 


.0839 


9 


.0655 


.0413 


.0361 


.0699 


.0751 


10 


.0600 


.0371 


.0319 


.0629 


.0681 



SPRING OP THE TOOL WHEN CUTTING A THREAD. 

10. Cause of Spring of the Tool.— When the tool 
15 slender or slightly dull, there is a tendency for the tool 
to spring to one side, away from the work, just at the time 
lt is entering the cut. It will be seen that, as the tool 
torts into the cut for the first half revolution, the cutting 
fc done entirely along one edge. This will tend to spring 
the tool away from the cut. After the work has made a 
complete revolution, the cutting on the two sides of the point 
balance each other and the tendency to spring the tool is 



LATHE WORK. 



85 



reduced. This spring of the tool will make the first thread 
on the work slightly thicker than the others, so that, in 
testing work, the nut may be found to be tight on the 
end, while, after it has passed over this thick thread, the fit 
will be loose. This trouble is very apt to occur when cut- 
ting square threads. The remedy is to run over that part 
of the cut with the tool a few more times, until the thread 
is cut down. This tendency to spring is greatly increased 
when the tool has insufficient side rake or clearance. 



X 



11. Cause of Tools Breaking:. — Sometimes the 
tool will show a tendency to break.. The point of the tool 
may be chipped off from the right side, as shown 
— ^ in plan, Fig. 7. When a tool shows this kind of 
/\ a break, it is evidently caused by the dog slipping. 
It is evident that the breaking strain was in the 
direction of the arrow. When the tool takes a 
heavy cut and the dog slips, the work will stop 
revolving while the lathe and feed continue. 
When the feed continues and the point is in the 
thread, the tool must either slip or break. Some- 
times a tool will break by chipping off the top face, 
as indicated in Fig. 8. 
Fio. 7. This kind of a break in- 
dicates that the lathe was re- 
versed and the work was running 
backwards before the tool was 
withdrawn from the work. In 
many instances, a careful ob- 
servance of results will enable the operator to determine 
the cause of the trouble. 



J. 



Fig. & 




HEIGHT OF TOOL FOR CUTTING THREADS. 

12. Correct Height of Thread-Cutting Tool.— 

When a thread is being cut, the tool should be at such a 
height that if a line is drawn from the center of the work 
through the point of the tool, it will just lie flat with the 



§5 LATHE WORK. if 

top face of the tool. If the tool is correctly ground, this 
position will cut the correct angle of thread. When a see- 
lion of a thread is given, it is always supposed to be taken 
through the axis. Suppose we have a correctly shaped 
thread, Fig. 9, and a section is taken parallel to the axis 
but above it, as shown. By examining the shape of the 
threads at this section, it is seen that the sides are not 
straight, but convex; also that the height of the thread ap- 
pears to be greater at this section than when a section is 
taken on the axis. 




Fig. V. Kir,. 10. 

13. Incorrect Height of Thread-Cutting: Tool. - 
If a tool is correctly ground, and set as much above the 
center as shown by the line A />', Fig. 10, and a thread is 
c ut to a sharp point, it will be found that on this section the 
sides of the threads are straight and form the correct angle 
•itheach other. It will be noticed that on the line CD the 
sides of the thread are concave, as at a, and that they are 
lot as deep as they should be. It will thus be seen that by 
setting the tool above the center, an imperfect thread is 
cut. 



14. It is possible to cut a perfect thread with the 
above the center, provided the tool is correctly shapei 
'oat position. A correct thread could be cut by ma 



tool 



10 



LATHE WORK. 



s 



the sides of a tool curved as in Fig. 1L these curves beir 

taken from the curves of the sectic 
of the threads in Fig. 9. The to 
must be set as much above tl 
center as the section was taken. 



1 5. Top Rake to Tbrcadiii 
Tools. — It will be seen that tl 
ordinarv threading tool that cu 
with its two edges cannot i 




Fig. 11. 



given any top rake or 
keenness. By means • f 
the compound rest set at 
an angle of ti«"'" with the 
center line of the w»-rk, 
as shown in Fig. VI (ci). 
and a tool shown in 
Fig. VI (r). a thread may 
be cut with a tool having 
top rake. The to«»i is 
ground so that the br ad 

CUtUllg edge C P Ilia si eS 

an an^le i«t ■a'" with the 
side \*i the tool, whi'.e the 
lop face is given sl^po 
or ivp side rake. When 
the cut is taken, the 
tool is fed into the work 
by the compound rest. 
Since the rest :< set 
at m alible •.( ■ ■■ . it 
may le seen 
side »'t 

Will :..-' 

t tu uui. 
l»»l'l 



fa .* •. 
• • 1 



♦ N ■ . , ■ 



r 

m 

■ * > 
1 1 







*V. 







I . 



SB 



LATHE WORK. 



11 



CUTTING DOUBLE OR TRIPLE THREADS. 

16. Cutting Double Threads. — When a double 
thread is to be cut, it must be remembered that two threads 
are to be cut in the space that would be required for a 

single thread. 

To cut a double V thread, proceed as in cutting a single 
thread until the space left between the grooves is equal to 
the width of the grooves, as shown in Fig. 13. The work 
is then given half a turn so that the point of the tool will be 
opposite the center of the 
"ncut part, as shown. 
The work may be given 
this half turn by remov- 
ing it and turning it so 
that the tail of the dog 
is in the notch of the face 
plate diametrically oppo- 
site the one used for the 
£r st thread. Another and 
ktter method is to dis- 
connect the feed-gears 
an d then turn the lathe 
** »ork half a turn. 
Su Ppose a change gear 
,i( h 48 teeth is on the F,c ' 13 - 

stud. One of the teeth that meets with the intermediate 
gear may t>e marked with chalk, after which the two gears 
"^y be disconnected. By turning the lathe so that this 
change gear passes over half its number of teeth, or 
'^ teeth, the work will also have made half a revolution. 
the gears are then brought together and the second thread 
cu t the same as the first. If the lathe is compound-geared 
kt^een the spindle and- stud, instead of turning the stud 
^w half a turn, it is turned a proportional part, depending 
on the ratio of the compound. 

'7. Cutting Triple Threads.— To cut triple threads, 
after the first thread is cut, the space between the grooves 




12 



LATHE WORK. 



§5 



should be double the width of the groove. The work is given 
a third of a revolution and'' the second thread cut, after 
which another third of a revolution is given and the third 
thread is cut. A similar method is used for cutting quad- 
ruple threads. 



INSIDE SCREW CUTTING. 

18. Holding: the Work for Inside Screw Cut- 
ting- — When an internal thread is to be cut in the lathe 
the work is held in a chuck or on a flat plate, the same as 
for boring. 

19. Tool for Inside Screw Cutting. — Inside thread- 
ing tools are similar to boring tools except that the point 






friii.'!!. .!■ ■;,: :■;. 




(9) 




Pig. 14. 



is ground to the shape necessary to cut the desired thread. 
In grinding an inside, threading tool for a V or United 




^r*ry > »» r » n » ww w t v w ■ ■ ■ ■ t*i f * 



Fig. 15. 




States standard thread, the point is ground to fit the 
gauge when the back of the gauge is nearly parallel to the 



§5 



LATHE WORK. 



13 




shankof the tool, Fig. 14 (*). If the tool fitted the gauge 

when held in the position shown in Fig. 14 (a), it would 

not go far into the hole before the 

back of the tool would touch the 

wort. Fig. 15 (a) and (6) show 

methods of holding the gauge 

against the work in order to set 

the tool true. Fig. 16 shows the 

result of untrue grinding, which 

necessitates setting the shank of 

the tool at an angle with the axis 

of the hole, and it also shows 

•ww the tool may be pushed so 

far away from its cut at the front, 

*hen running the lathe backwards, l0, 

that the tool will drag in the hole and spoil the first 

threads. 

20. Stop for Inside Screw Cutting. — When cut- 
ting inside threads, the stop shown in Fig. 63, Lathe Work, 
Parts, may be used by taking the screw out of the stop and 
putting it in the tool block so that it comes between the 
tool block and the stop. For inside screw cutting, it is 
necessary to move the tool in an opposite direction, to take 
the tool out of the cut, from that required in outside screw 
c utting. It is therefore necessary to adjust the stop-screw 
50 that the head of the screw comes against the stop. 
Deeper cuts may be made by turning the screw into the tool 
block. 



TESTING IIHSIDE THREADS. 

21. Moving Tool Away From Work. — In most 
cas *s, the work cannot be taken from the lathe and must be 
tested in place. The tool can be moved out «f the way by 
rev ersing the lathe and allowing the carriage to feed back 
tar enough to allow the gauge to be used. This is a very 
s 'ow way and need not be used. Sometimes it is possible to 
fove the tool back, by means of the cross-slide, far enough 



LATHE WORK. 



85 




to allow the gauge to be used. If the tool is brought back 
to the stop after the work has been tested, it will be in place 
to continue the work. 
Another method is to 
open the feed-nut in the 
apron, and move the 
carriage by hand out 
of the way. When this 
is done, some means 
must be provided 
whereby the carriage 
can be brought back to 
the same place and the 
feed-nut locked as be- 
fore. This may be done 
by making a mark on the bed of the lathe, or. better, by 
measuring from the point of the tool to the work, as shown 
in Fig. 1?. After testing, the tool can be moved back so that 
the measurement is the same as before and the feed thrown 
in. Care should be taken that the lathe is not turned while 
the feed-nut is opened, for it will cause trouble in getting 
the feed to start again in the correct place. 

22. When the pitch of screw to be cut is a multiple of 
the pitch of the leadscrew, this care is not necessary, for the 
tool will come correctly into the cut whenever the feed-nut is 
closed on the leadscrew. When cutting these screws of 
multiple pitches of the leadscrew, it is possible to keep the 
lathe running forwards all the time by throwing out the 
feed and moving the tool and carriage by hand back to the 
starting point. This operation will save much time. 

23. Testing Inside Threads With a Gauge.— 

After the cutting tool has been moved away from the 
work, the gauge should bu strewed in, taking care to have 
it exactly in line with the hole. Care slmuM also be taken 
to see that the first thread is not thukiT than the others, 
owing to the spring of the tool at the beginning of the cut. 
Sometimes a tap is used in place of a gauge, and in this case 



§5 



LATHE WORK. 



15 



the tap is sometimes allowed to take a very light cut from 
the hole, especially when square threads are being cut. 
When the tap is used for taking a light cut, in order to finish 
the thread, the tool is usually moved back by means of the 
cross-feed, and the tail-center is introduced into the center 
in the shank of the tap, so as to guide it while it is being 
passed through the work. Sometimes, when the piece is in 
a rather light chuck, the latter may be removed from the 
spindle and the work tried upon the piece that it is to fit. 
This is very often done when the thread being cut is inside 
of a new face plate or chuck back, the work being tried upon 
the spindle of the lathe that it is intended to fit while it is 
still held in the chuck. 



THREADING TAPERED WORK. 

24. Setting: Tool for Threading Tapered Work. — 

In setting the tool for taper turning, the gauge is put against 




Fig. 18. 

the work so that its back is parallel to its axis and the tool 
is set the same as for parallel thread cutting, as shown in 
% 18. 

25. Error in Pitch Due to Setting Over the Tail- 
Center. — If the center is set over, it will give an incorrect 
pitch, and also an incorrect thread. This point will be taken 
up later, under the head of 14 Errors in Lathe Work." 



/ 



16 



LATHE WORK. 



§5 



If a taper thread is cut by setting over the tailstock, the 
pitch of the thread will not agree with the pitch that would 
be cut by the use of the taper attachment. Suppose we 
have the tapered piece, Fig. 19, to be threaded. The piece 
is 2 inches long and should have a thread of 10 pitch. This 
means that for 10 revolutions of the piece, the tool would 




- M> 



Kig. lfc 

advance 1 inch, and, to advance 2 inches, it would require 
20 revolutions; therefore there should be 20 threads on the 
piece. When the taper attachment is used and the lathe is 
properly geared, this result will be obtained. The tool will 
start at the end a, and, after 20 revolutions of the work, will 
have moved 2 inches sidewise, which will bring it to the end t>, 
the carriage moving in a direction parallel to the line CD. 

26. When the dead center is set over, the tapered piece 
will take the position shown by the dotted lines. The 
threading tool will move along parallel to the face of the 
work and also parallel to the center line CD. If the cut is 
started at the end (J as before, 20 revolutions of the work 
will move the tool along the face of the work 2 inches, to the 
point c. It will be seen that there remains a part un- 
threaded, since the taper measured on the slope is greater 
than the true length of the piece measured parallel with its 



a 



LATHE WORK. 



17 



aits. It will therefore require more than 20-turns to carry 
the thread to the end of the piece ; consequently, there will 
be more than 20 threads on the piece. 

Thus, it may be seen that the pitch of the thread on a 
tapered piece depends on whether it was cut by setting over 
the center or by the use of a taper attachment. Tapered 
threads should be cut with a taper attachment whenever 
possible. 



SPECIAL THREADING TOOL. 

27. A threading tool, Fig. 20, by means of which many 
of the difficulties in screw cutting that have been mentioned 
nay be overcome, has recently been placed upon the market. 




h consists of a cutter a, resembling a milling cutter, sup- 
P° r fcd upon a bracket b by a slide c. The device is clamped 
"poll the tool rest of a lathe from which the tool post has 
previously been removed. 



LATHE WORK. 






The cutter a has 10 teeth do its circumference, each one 
which is formed to cut deeper than the 

and gives the thread its gonial width 
to the full depth of the cut. For 
Instance, in Fig. 81, the first tooth 
cuts the full width of the thread to 
Che line /. the second cuts to the 
line 2, and so on until the tenth 
tooth eats to the bottom, to 
(.'M*M'-M</M'-Mnd (/) show the 
shape of the teeth and the corre- 
sponding forms of the thread for the first, second, third, 
fifth, eighth, and tenth cuts, two and one-half times the 
actual size of a T-pitch V thread. 

28. The tool is set up and adjusted for the first cut, as 
shown in Fig. 20, proper side rake for either right-hand or 



"Wj '"■ j/V" 



left-hand thread being given bj means of an ail justing scr« 
on the far side of thedevice, which is nol shown 
rests upon the support d, which holds the top face level w 
in center lineol the screw. When all adjustments! 
been made, both the d si are clamped, , 

1 1: first cut is taken. The rest is then brought ba 
starting point in the usual way. The second tooth 
nit- position anil li't-ltiT.l t iy throwing over the lever * i 
bringing it hack into place. The second cut is then taki 

and 1 1 peration repeated until the tenth tooth has tak< 

its cut. The last tooth may be advanced in steps 1 
means of an eccentric stud and micrometer slop, 
step advances the cutter a Fraction of a thousand 
inch, thus permitting very fine fits and exact duplicates I 

be made. 



§5 



LATHE WORK. 



19 



The special advantage claimed for this tool is that each 
tooth comes to the work in better condition than when a 
single tool is used, the work being distributed over 10 cutting 
edges instead of 1. The finishing tool comes into service 
with a sharp point, while its duty is comparatively light. 
Under these conditions, the lathe can be run at a higher 
speed, since the danger of injuring the tool point by its con- 
tinuous use on every cut has been eliminated. A perfect 
thread can, therefore, be formed in less time without injury 
to the tool. For rough work many shops prefer the ordi- 
nary single tool, the thread being finished with six or seven 
cuts. 



THEORY OF CUTTING TOOLS* 



DISCUSSION OF CUTTING PROPERTIES OF 

TOOLS. 

29. Theory of Cutting Tools Applied to Hand 

Tools. — In discussing a cutting tool from a theoretical 
standpoint, attention will first be given to that part known 





<b> 



FlO. 23. 



*& the cutting wedge, which enters the work and severs 
or removes a part known as the shaving. 



LATHE work, gs 

The nit ling qualities of a tool arc governed larg"! 
dupe of the catting point or cutting edgp. We can bc*t 

■ ■''! the in-: principles il we > onskler the acti I .1 

chisel when cutting a block of wood. If ire 
the center of a block, ;i* shown In I-'in 88, and spa 
tdicated bj the arrow, the chisel will be hsn 
ttM block, bending each side out equally until the bio 
The force required to press the tool into the work will de- 
pend on the strength at the block and th< ins 
ting wedge. It we have two blocks (<i) and (£), Pi ■ 
the same strength, it can easily be proved by I 
tcs that it requires more power to force the blunt wedge b 
into the work than the more acute one a. 



30. Fig. M (<') represents a chisel cuttings block. The 
edge nf the chisel is ground to an a 

dge in Fig. 83 (a). Fig. il {A) rep 
block, being similarly cul with a tool ground with a blunt 
cutting edge, the cutting angle 6 lining equal to tile angle of 




ge h. Fig. 23 (A). In estimating the force necessary 
to push each of the t-»'ls along its cut, it will be seen that 
the blunt tool will require the greater force, as the blunt 
wedge, Fig. 23 (/>), required the greater fon 
the block. In Fig. 21 (■/) the shaving is forced from the 



§5 



LATHE WORK. 



block and slightly bent away, while in Fig. 24 (l>) the sha- 
™gisvery much bent and broken. This bending and break- 
ing of the shaving at the time of severing it from the block 
absorbs an extra amount of power. The direction of the 
force required to turn the shaving is represented graphically 
by drawing a line at right angles to the cutting face of the 
tool. In Fig. 24 (a) the pressure on the face of the tool is 




"i the direction of the arrow c . The intensity of the pres- 
sure varies with the thickness of the shaving. This force 
tetl ds to hold the tool very close to the work, and, if it were 
n °t [or the broad flat face of the tool, it would be pressed 
" ee per into the work. If the angle of the tool be changed, 
35 in Fig. 25 [a), so that the face of the tool /does not touch 
the work except along its cutting edge e, the pressure of the 
shaving would be sufficient to force the tool into the work so 
"■at as the too! moved along it would cut in the direction of 
'he dotted line. 

31. In Fig. 24 {£), in which the tool is very blunt, the 
re sult of this pressure against the tool is quite different, 
"be direction of the pressure of the shaving is at right 
an 8'estothe face of the tool, as shown by the arrow c. It 
we divide this force into two forces, one acting against the 



•J 



1 . 



^ * 



V V. "^ ■ 



* " » ._ 




v"':. _ 



1 .± - 



v: 



: :c 






* ^ : :*e 



a.. 



• m 



:e 



,»._< 



' ■ J ■:. - 






» ■ ■ 



L :rz .«: 



■* *. 






■ * : : ' ■ v : : 

: . v : * : : 
- - - ■ , „ v , 



r i;u:e 



■■-=■ " * 



: " . .* C • .1 JLT1 



":■::. n of 
: ..::> the 

^ IT 

-. • *.*c 



§a LATHE WORK. 23 

a certain line of motion, the cutting action depends as much 
on the position it holds relative to the work as on its exact 

shape. 

33. Angles of Clearance and Keenness. — If we con- 
sider the strength of the two tools shown in Figs. 24 (b) and 
25(4), it can readily be seen that the tool shown in Fig. 24 (b) 
is much the stronger because of the greater support given 
to the cutting edge. In Fig. 25 (b) the cutting edge has 
very little backing or support, and it would break at once. 
When this tool is held and moved as shown in Fig. 24 (a) y it 
is in its strongest position. When it is moved so that its 
face makes an angle with the work, its strength begins to 
decrease as the angle c y Fig. 25 (b), increases. This angle c t 
which the back face of the tool makes with the work, is 
called the angle of clearance. 

H the tool in Fig. 24 (a), which is held in its strongest 
Position, is compared with the tool shown in Fig. 24 (b) y 
it will be seen that the latter is the stronger. This 
strength is due to the support given to the cutting edge 
because of its bluntness. The angle between the cutting 
faces of a tool, a, Fig. 24 (a), and b, Fig. 24 (£), is called 
the angle of keenness of the tool. The strength of a 
cutting tool, therefore, depends on the angle of clearance 
M d the angle of keenness. The angle of keenness of a tool 
should vary with the degree of hardness of the material to 
k cut For turning soft woods, the turning tools are 
pound very keen, or so that the cutting faces make a very 
ac ute angle with each other. In turning metals, the cutting 
^fces are made less keen, depending on the hardness of 
"te metal. In some cases, such as turning chilled cast-iron 
r °Hs, the angle formed by the cutting edges is nearly 90°. 

34. Angles of Rake and Keenness. — Fig. 27 shows 
a diamond point with lines drawn to indicate its angles of 
**« and keenness. A £ is drawn through point O, parallel 
to the base of the tool. CD is perpendicular to A B at O. 
£^is parallel to the top face of the tool at O. H K is 
P*ailel to the front edge of the tool at O. Angle A O E 



LATHE WORK. 



presents the angle of top front rake of the tool 
D // represents the angle of front rake, Anyl' 
represents the angle of keenness. 

7, 




These angles as here described refer to the tool alone. 
When the tool is clamped in the tool post and presented 
in the Murk to take a cut, these angles assume a new rela- 
tion to each other, and the cutting qualities oi I 
dip- ml ini these new relations. Fig. .- 
properly set for cylindrical turning. 

JiS. A "tilts of Uitkc and Kcennum of I.uthc 
Tool* When Applied to Work. — To propcrlj 
the angles of the tool thus set, draw the line A S 
Center of the work through the point of the tool. L>raw 
CD perpendicular to A B at 0. Drafl 
the top face oi the tool through the poinl 0. I >r.-iw UK 
parallel to the edge of the tool. Angle . i 
top rake of the tool. Angle E D equ 

s. Angle D O I! 
■ ■■ ■ 




I 



Tt will be noted I 
difference in drai 
lines in Fig. VI 
begins with drawing 
After tins : 



is properly drawn, the other lines follow in i! 

'.'■. 



\ 5 LATHE WORK. 25 

side, as shown in Fig. 29, the tool has top side rake. The 
angle of top side rake is measured by drawing A B parallel 
to the base of the tool through the point 5, and E F parallel 
to the top face of tool through the point 5. Angle A S E is 
the angle of top side rake. 



CONDITIONS THAT GOVERN THE SHAPE OF THE TOOL,. 

36. General Statement. — These effective angles of 
rake, clearance, and keenness depend on (1) kind of metal 
king cut ; (2) hardness of metal; (3) character of cut, 
whether roughing or" finishing; and (4) particular manner 
in which the tool is set when presented to the work. 

37. Effect of Kind of Metal Being Cut Upon 
Shape of Tool. — This matter will be more thoroughly 
taken up later, but, in general, it may be stated that for 
soft material, such as mild steel, the angles are keener than 
for hard material, such as chilled cast iron, while for some 
Materials that have a tendency to draw the tool in, as brass 
°r copper, the angles may be made very blunt indeed — in 
kct, a negative rake is often given them. 

38. Hardness of Metal. — As before stated, the 

^gle of keenness varies with the hardness of the material. 

Tools for cutting soft steel should be ground with suffi- 

Cle nt keenness to enable them to turn long, curly sha- 
• 

Vln gs. The character of the shaving indicates much 
rc garding the cutting of the tool. When the shavings 
come off in large curls and are very strong, it indicates 
that the tool is properly ground and set in the machine, 
when the shavings come from the work broken in small 
Pteces, it indicates that the tool is laboring because of incor- 
rc ct setting in the machine or incorrect grinding. A word 
°f caution should be given here to those who, for the first 
to&e, experience the delight of seeing a tool, properly 
ground and set, roll off a beautifully curled shaving. Never 
attempt to remove the shaving from the work by taking it 



M LATHE WORK. 

hi the hand and pulling or jerking it. A. good steel shavin 
' M-s are as keen as any Id 
■ tint the shaving will slip through the hand, cut- 

flesh En .1 most painful way. To reraoi 
: from the cut, throw out the feed and the tool wil 
nil the shaving off. 

.'*9. Rouctalnjj or Flnhhtng C«t»^— Theangleof top 

: the nature of the cut, whether roughing 
Pig, 30 shows :i piece of work with the tool s< : 
heavy rou^iiin^ cut. Here the cutting is doafj 




along the edge S of the tool, the point doing a vet 
pari ol the work, it is evident that this to 
id to give keenness all aloi ■ ■ 

done by giving the tool top side rake. 

When the tool is used for a finishing cat, tl 
uol dei p, and most of the cutting is done with the 
the tool 0. In this case, too front rake, a 
should be given, Top side rake and top (root rake ; 
i[ also by the rate of feed used. 

40. Fig, 31 illustrates n isc in which the feed i- 
and the tool poinl broad, so thai the rate 
taon of the work is greatei than ■ lit In sue! 



}5 



LATHE WORK. 




a caw. the Lop front rake should exceed the lop side rake, 
When the feed is fine compared with the. depth of cut, the top 
side rake should be the greater. 

41* Manner In Which 
Tool Is Presented to Work. 
The shape or width of the 

i a tool depends on the 
feed used, and this depends on 
the nature of the work. In fin- 
mall rods, shafts, or spin- 
dles that should be very true, 
the roughing cut is made deep 
coaiae feed as the Work 

tool will stand, while the finishing cut is light and 
the feed comparatively fine. This fine feed is allowable 
very true, and on small work the 
if. and remain sharp up to the end 
of the cut. On large work, the method is different. Deep, 
heavy roughing cuts are taken, as before, but the finishing 
b a tool that has a broad, flat point and a 
very coarse feed. When the work is heavy, this form of 
tool can be used and will turn comparatively true, while on 
work, a broad-nosed tool could not be used at all. 
able to use a broad-nosed tool for finishing, 
tld be done. Il saves much time because of the coarse 
feed thai i i the tool will usually remain sharp 

d erf the cut, unless it is a long one. 
12, Clumne of Front Top Wake to Side Top 
Halie. — The anple of tup rake may be effectively changed 



s^=, 




■om front top rake to side top rake by changing the 
tool with the work. Fig. 32 (a) shows a bra 
finishing tool ground with top tront rake. This may be 



28 



LATHE WORK. 



§5 



changed to a very efficient roughing tool with top side rake, 
by swinging it in the tool post so that it has the position 
shown in Fig. 32 (£). 

Special care should be taken when using a tool set in the 
manner shown in Fig. 32 (£), as if it becomes loose in the tool 
post it will swing into the work and may do great damage. 
It is always best to have the tool post in advance of the 
point at which the tool is cutting so that the tool will rotate 
away from the work if it becomes loose in the tool post. 
When working upon expensive material, the tool should 

never be set as shown in Fig. 32 (£), 
but a regular roughing tool, such 
as will be described later, should be 
employed. 



43. Effect of Height of Tool 
on Angles of Rake and Clear- 
ance. — It is well to study the effect 
of setting the tool at different 
heights, so that any difficulty from 
this cause may be recognized and 
remedied. 

Fig. 33 shows a tool ground flat 
on its top face so that according to 
Fig. 27 it is without top rake. By 
applying this tool at its highest pos- 
sible cutting position, and drawing 
the lines as in Fig. 27, we have an 
effective angle of top rake EO B y and 
an effective angle of keenness EO D. 
Suppose this same tool is next low- 
ered to a position shown in Fig. 34, 
the point of the tool being level with 
the axis of the work. By drawing 
the lines as before, we find that the 
line A B coincides with the line EF t 
so that the tool has no effective 
top rake, and the effective angle of 




Fig. 86. 



§5 LATHE WORK. 2a 

keenness BOD is equal to 90°. At this point, the cutting 
action changes from a shaving to a scraping action, which 
can never admit of a deep cut. Next, suppose the tool to 
be set below the center, as shown in Fig. 35. By drawing 
the lines as before we will find that A B passes into the tool 
below the line E F. In this position, the tool has a nega- 
tive angle of top rake E OB and would do little more than 
scrape the work. 

44. Effect of Height of Tool on Its Strength. — 

The effect of the position of a tool upon its strength can 
also be seen from Figs. 33, 34, and 35. In Fig. 33 the angle 
of clearance D O H \% very small and the cutting edge is 
We ll supported; consequently, the tool is in its strongest 
P°sition. In Fig. 35 the angle of clearance D O H is great, 
and it is easy to see that the cutting edge cannot endure 
m uch pressure. From this it will be seen that a tool is 
strongest when set as high as possible upon the work. 



SIDB RAKE OP SIDE TOOLS. 

45. Determining Clearance Angle for a Side 

TooL—In the case of side tools, as shown in Fig. 24, Lathe 
Work, Part 1, the angle that the side face of the tool A B 
ma kes with the end of the work or with the line CD drawn 
Parallel to the end of the work, is called side rake. In 
theory, this angle of side rake or clearance should vary to 
suit every diameter of work and every amount of feed. 
Having given a rate of feed per revolution of work and a 
£iven diameter, the exact angle of clearance can be esti- 
mated. 

Suppose we have a side tool, with its edge ground straight, 
set to the work as shown in Fig. 33, Part 1, and we wish to 
fin d the necessary angle of clearance at points a, b y and c 
a '° n g its cutting edge, which will allow it to feed in the 
Erection of the arrow at the rate of £ inch per revolution, 
ft is assumed to be understood that if the side tool were 




30 LATHE WORK. § 5 

flat or had no clearance, it could not cut, since it would simply 
lie flat against the work. 

46. To estimate the angle of clearance for point a, draw 
a line A B, Fig. 36, equal to the circumference of the work 
at point a. At B erect a perpendicular and lay off B F 
(I inch) from B equal to the desired feed per revolution. 
Draw a line through A F. The angle B A F indicates 

the required angle 

\ "1 "f °* c ^ earance f° r t^s 

J~b ] c — f b point of the tool. To 

find the correct an- 
gle of clearance for 
point 6, lay off from A a distance A C equal to the circum- 
ference of the work at 6; at i>oint C erect a perpendicular 
and lay off a distance C F' equal to the desired feed. 
Draw A F'. Angle F' A C represents the necessary angle 
for the tool at point 6. To find the angle for point c, pro- 
ceed as before, laying off A D equal to the circumference 
of the work at point c. Angle F" A D will represent the 
necessary angle at this point. It will be observed that the 
angle of clearance changes for each of these points, increas- 
ing as it approaches the point of the tool or the center of 
the work. The correct shape for this face of the tool would 
be a warped surface with little clearance at the heel of the 
tool a, but with considerable clearance at the point. 

In practice, however, the tools are ground nearly flat, with 
sufficient clearance at the point of the tool to let it cut, and 
the rest of the cutting edge will have excessive clearance, 
but not enough to cause any serious objection. 



TOOLS FOR 11RASS WORK. 

47. Shape and Setting: of Tools for Brass Work. — 

The theory of the shapes of tools and the methods of 
applying them to the work, as just described, do not 
seem to be sustained in all cases when applied to tools for 
brass. This is due largely to the peculiar nature of brass 



§6 LATHE WORK 31 

found in its toughness and its flexibility. These qualities 
tend to cause a tool to spring into the work and the 
ork to spring over the tool in such a way as to make 
very untrue cuts. If the work and the tool could be held 
it h sufficient rigidity to avoid all danger of springing, the 
tool could be ground with more keenness than is allowable 
for iron or steel. In practice, it is found that the best 
results are obtained when the tool is ground and 
shown in Fig. 34. This is ground without top rake and 
set at the center of the work. Other shapes of tools aw 
ised for brass, which will be discussed later, but, in most 
the cutting angles remain as here indicated. 



BOBIHO TOOtS, 
48. Working Conditions of Boring Tools.— The 

conditions under which a boring tool must work an: mosl 
mfavorable fuf carrying out the principles that naturally 
lead to good results. The boring tool, because of the long 
slim arm required to reach into the bottom of small holes, 
lacks that rigidity of cutting edge that is essential in rapid 
curate work. 



49. Cutting A mile*. i>l' line in it Tools, 
to Fig. 37, it will be found 
that the angles of rake and 
keenness for a boring tool may 
be defined the same as in a 
diamond point. The line AB 
awil from the axis of the 
work through the point of the 
. E F is drawn along the 
lop face of the tool through 
;he point 0. The angli 

■ —Tits the angle of top 

If the tool I ■ 
. ■ il in the hole, the angle 
f top rake will vary, as shown 
1 Figs, 33, 34, and 35 



-By reference 




32 



LATHE WORK. 



§5 



SO. Spring of Boring: Tools. — The force necessary 
to hold the point of the tool up to the cut depends largely 
on the shape of the point. Fig. 38 (a) shows a well-shaped 

tool for small work. The 
point is narrow and is shaped 
much the same as the point 
of a diamond-pointed tool. 
The force tending to spring 
the tool away from the work 
is in the direction of the 
arrow, at right angles to the 
line A £. Fig. 38 (b) shows 
a tool with the point more 
rounded, with the force tend- 
ing to spring it away from 
the work more at right 
angles to the shank of the 
tool. Fig. 38 (c) shows a 
broad-nosed tool with the 
force acting squarely across 
the shank of the tool. This form of tool would chatter and 
spring away from the work so that it would be difficult to 
do much with it. Single-pointed boring tools as here shown 
should have narrow points, as shown by Fig. 38 (a), and 
should be used with moderately fine feeds. When broad- 
edged boring tools are used with very coarse feeds, they are 
held in boring bars or heads, or in some other way than 
here mentioned. 




Pig. 88. 



51. Height of Boring Tools. — The correct height 
of the boring tool in the work, to give it the strongest 
and the easiest cutting position, is as much below the center 
as it can be set and still have its cutting point cut. This 
is for the same reason that the diamond point is set above 
the center of the work. It is not always safe to set the tool 
in this low position, if the tool is long or springy; for, 
being below the center, if the tool should catch and spring 
down, it would spring into the work more deeply and cause 



§5 LATHE WORK. 33 

trouble. Ordinarily, a boring tool is set at about the center 
of the work, it having been ground so that when thus set 
it will have but little clearance. 

52, Boring Small Holes. — When the hole is small, 
the conditions are more unfavorable. 
Fig. 39 shows a section through work 
with the tool in place. The tool nearly 
fills the hole. When a line A B is 
drawn from the center through the 
point 0, it passes into the tool, show- 
ing that in this position it has nega- 
tive top rake. The best that can be 
done in this case is to grind the top F,G * 39> 

fece back from the edge E t giving the tool a great deal of 
tofsiderike. 




FORMS OF CUTTING TOOLS. 



FORGED TURNING TOOLS. 

53, Diamond-Pointed Tool. — Thus far, the forged 
diamond-pointed tool has been the principal tool con- 
sidered for cylindrical tinning. This has been done because 
the principles that have been shown to govern its cutting 
actions are applied in the same way to other forms of tools, 
^d the similarity of cutting edges will be apparent. 

54# Self-Hardening Steel. — During the last few 
y® 1 *, specially prepared self-hardening or air-hardening 
^ has taken a leading place in the making of lathe and 
planer tools. This steel is so treated in manufacturing that 
it does not require heating and hardening, as does the ordi- 
^f tool steel. By heating it to a dull-red color and allow- 
m 8 it to cool in the open air or in a blast of air, it is made 
ex tra hard. If this kind of steel be plunged into water while 
Jt K hot, it cracks, which spoils the tool. 

Among the advantages of self-hardening steel are: First, 
te hardness will enable it to hold a sharp edge when cutting 



34 



LATHE WORK. 



8« 



very hard material, such as hard castings, castings with a 
heavy scale, steel castings, or similar work. Second, since 
its hardness is little affected by heat, it is possible to run the 
work much faster or at a higher rate of cutting speed than 
is possible with the ordinary tool-steel tool. On account oi 
these facts, it is used almost universally in many shops. 

The objections that are raised against self-hardening steel 
are that it is difficult to forge and that it is expensive, cost- 
ing about four times as much per pound as ordinary tool 
steel. 

55* Shapes of Forged Roughing Tools. — In for- 
ging self-hardening steel, it can only be worked at a low heat, 

- and it is very difficult 

^ to draw or bend it 

into such a shaped tool 
as shown in Fig. 27. 
It is usually heated 
and cut with a hot 
chisel approximately 
to shape, with little 
forging or bending, 
and is finally shaped 
on the grinding wheel. Fig. 40 shows an elevation and 
plan of a front tool as forged from this kind of steel. The 






Pig. 41. 



Pig. 42. 



side A B has been trimmed off to make the cutting edge, 
the point O bent up to give top rake along the line E F y 
and the heel cut off along the line 7/A\ so that little 



§5 



LATHE WORK. 



35 



grinding will be required on the front end of the tool. 
When the tool is ground, it appears as shown in Fig. 41. 
This tool will be seen to possess the same cutting angles as 
shown in Fig. 27, although it is quite different in general 
appearance. Since the point O is at one side, its cutting 
edge is entirely along the edge A B. This designates it as 
a right-liand tool in contrast with one beveled, as shown in 
Fig. 42, which would be called a left-hand tool The ordi- 
nary diamond point, with the point in the center and ground 
without top front rake, may be used to cut in either direc- 
tion. If ground with top side rake, as shown in Fig. 20, to 
cut toward the live center, it is called a right-hand diamond 
point ; if ground sloping the other way, it is called a left- 
liand diamond point. 

56. When heavy cuts and great strength are required, 
the outline of the cutting edge is curved and the point con- 
siderably rounded. This applies particularly to heavy work. 





Pig. 48. Pig. 44. 

^g- 43 shows a form of round nose used for some kinds of 
heavy work. Fig. 44 shows a broad-nosed tool used for 
Wishing when coarse feeds are permissible. 

57. Proper Form for Round-Nosed Tools. — For 

some kinds of work, a round-nosed tool, shown in Fig. 45, 
ls used. This is ground round on its point, and top rake is 
sometimes given by grinding a notch a on the top face, as 
shown.. Grinding the top face of a tool in this way is not 
good practice, as it soon spoils the shape. If a tool is to be 
given top rake, it should be so forged that the top rake can 



LATHE WORK. 



8« 

easily be ground without forming a notch a on the tool. 
Fig. 46 shows how such a tool should be forged. This 



style of forging gives opportunity to grind the top face of 
the tool and keep the angles and shapes constant. Fig. 47 




shows a piece of work of such shape that this form of 
tool is desirable, since it can be set to finish the faces a 
and b at the same setting. When 
top side rake is desired, it should 
be given by setting the tool at an 
angle to the work, as shown in 
Fig. 33 (i>), or by grinding the tool 
as shown in Fig. 48, but never 
allowing a corner or notch to be 
Fio, «. formed as shown in Fig. 45. 




§5 LATHE WORK. 37 

TOOL HOLDERS FOR TURNING TOOLS. 

58. Advantages of Tool Holders. — The expense of 
keeping up a stock of tools forged from the bar, whether of 
ordinary tool steel or of special self-hardening steel, is great, 
and this fact has led to the devising of many forms of 
holders employing small blades of steel to do the cutting. 
The holder is made the same size as the shank of the ordi- 
nary forged tool. They make a very great saving in the 
cost of the steel used, as one holder will be sufficient for 
a great variety of shapes of cutting points, tools, or 
blades. The blades may be of the very finest and most 
expensive quality of steel and still cost far less than the 
forged tool. 

59. Disadvantages of Tool Holders. — The objec- 
tion to these inserted-blade tools or tool holders is that it 
is difficult to find a means of clamping the small blade in 
the holder so that it will have the same rigidity as the forged 
tool. The holders soon wear, allowing the blades to spring. 
This causes trouble. This is caused in many cases by using 
too small a holder to do the work. If heavy holders are 
used and comparatively large blades, the trouble will be 
Partly avoided. 

60. Diamond-Pointed Tool Holders.— Figs. 49 and 

50 show two styles of diamond-pointed tool holders. The 
similarity of Fig. 50 to 
the regular forged dia- 
mond point is readily 
*<*. In Fig. 49 the s ^ 

tool shown has the out- 

lin e of a diamond point FlG - 49 - 

itched over it in dotted lines. From this it will be seen 

that the shapes of the cutting edges are identical. 

61. Grinding of Diamond-Pointed Inserted- 
Blade Tools. — The methods of grinding these two tools 
are quite different. In Fig. 50 the cutting tool is ground 



\ *»■ 




38 LATHE WORK. §5 

entirely on its top face, which corresponds to the face EF y 
Fig. 27. This determines the angle of keenness, and since 
the angle of front rake remains unchanged in the tool, it is 
always set at the same height for a given diameter. 

In Fig. 49 the angle of top rake of the tool is determined 
by the angle at which the tool sets in the holder. Grinding 
should be done entirely along the end of the blade which cor- 
responds to the face H K % Fig. 27. In this case, if we wish 

to increase the keenness of 
the tool, we grind it away at 
the heel. It must be remem- 
bered, however, that the keen- 
ness given the tool by chan- 
ging its angle of front rake will 
not change the effective keen- 
ness when applied to the work, 
°* "k unless the position of the tool 

is changed. Grinding away the heel makes it possible to 
set the point higher on the work. This higher position 
gives an increased angle of top rake and therefore increases 
the effective keenness. Other forms of tool holders are 
made that are similar to these and accomplish the same 
purpose. 




THE PARTING, OR CUTTING-OFF, TOOL. 

62. Forged Parting Tool. — Fig. 51 represents a 
common form of parting tool. This tool is used for cutting 
grooves or notches in work, for cutting square corners, or 
for cutting off work held in a chuck. The cutting edge of 
the tool is along the line A B. The blade is forged and 
ground so that the cutting edge is the thickest part. The 
sides of the blade are each ground with a slight amount of 
clearance, as shown by section CD at (b). The tool is sel- 
dom ground with top rake, keenness being given by varying 
the angle of front rake and changing its height. When this 
tool is used as a cutting-off tool, its theoretical height is 
constantly changing as it approaches the center of the work, 



LATHE WORK. 



»nd so it should be set at the same height as the center of 
the work. 

63. Use of PartinK Tool. — Work held between the 
centers should not be cut in two with this tool. Work may 
be partly out in two if care is used, after which it should be 




taken from the lathe and either broken or sawed apart. 
?'g. 58 shows the too! deep in a cut. Soon the piece will 
become so reduced in diameter that the force required to 




'•>*wthcrut will bend the work. By bending the work at 

ter, it will open the notch on one side and 

CKtte it on the other, so that the tool cannot pass through, 



LATHB WORK. 



J» 



but will become jammed in the cut. This will result in 
either breaking the lathe tool, or the lathe center will be 
broken or torn out of the center hole. 

64. Inserted-Blade Parting Tool. — Inserted -blade 
tool holders are very successfully used for parting tools. 
Fig. 53 shows one style of inserted- blade parting tool. The 
blade is held in the holder by the clamping screw s and is 



still further clamped when the tool holder is clamped in the 
tool post, because of the spring of the tool holder. Fig. 54 
shows another form of bent parting tool with inserted blade. 
The blades for these tools are ground either concave on the 




side or thinner on the bottom edge, to give clearance. They 
are made either from self-hardening steel or regular tool 
steel. When the blades are made from regular tool steel 
and hardened, it is customary to draw the temper along the 
lower edge, which gives the tool toughness — a quality much 
desired. . 



THREADING TOOLS. 

65. Forged Threading Tools. — A good form of 
threading tool for V threads is shown in Fig. 59, Lathe 
Work, Part 2. This has an advantage over the common 
form shown in Fig. 55 in that it does not become thicker 



§5 LATHE WORK. 

each time it is ground. This constant thickness is a desir- 
able feature when threads are to 
be cut very close to a shoulder. 

66. Iuserted-Blade Thread- 
ing; Tools. — Various forms of tool 
holders have been designed for I 
threading tools. Fig. 56 shows one 
of these forms for V threads. The ' 
tool is accurately made and ground *"*■ **■ 

so that the front faces form such an angle with each other 
when the top face is ground flat that the angle of the 
cutting edges will measure 60°. These inserted blades are 
sharpened by grinding the top face. Tool holders are made 



K 





forcutting square threads, blades of various thickness being 
used to cut the various pitches of threads. When coarse 
pitches on small diameters are to be cut, these tools cannot 
* used because of the excessive side rake required on tools 
used for this purpose. 



BENT TOOLS. 

67. Right-Hand or Litft-Hand Tools.— For some 
kinds of work, the straight tools 
that have been described cannot be 
used, and a" class of tools known 
as bent tools becomes necessary. 
These are classed as right-hand or 
left-hand tools, depending on the 
direction they are intended to cut. 




43 



LATHE WORK 



08. Bent Side Tool. — Fig. 57 shows a right-hand 
bent side tool. This form of tool is especially desirable 
when cutting a shoulder that is very close to the lathe dog, 
as shown in Fig. 58. 

69. Bent Parting Tool. — When it is desired to cut 
work very close to a shoulder or the jaws of a chuck, a beat 




parting tool may be used, as shown in Fig. 59. The form 
of tool shown in Fig. 64 is particularly well adapted to this 
class of work. 

70. Bent Round-Nosed Tool. — Round-nosed tool- 
may be bent either right or left, to meet certain condition; 
of work. The right-hand bent round-nosed tool is ofter 
used for facing, and it makes a good inside turning oi 

boring tool. 



DORINQ TOOLS. 

71. Special Holders for Boring Tools. — For boring 
tools special holders with inserted blades are superioi 
to forged tools. Fig. 60 shows a special boring tool that car 
be held in the tool post of the lathe. The blade is held ir 
the end of the bar b by a cap c, which screws over the end oi 
the bar. The bar b can be adjusted in the holder so that il 
will just pass through the work. 



!l LATHE WORK. All 

Fig. CI shows another form of boring tool with inserted 
blade. This form holds the bar b very rigidly in a special 
block bulted on the lathe tool block. 




72. Advantages of Special Holders for Boring 

Tools, — Among the advantages of this type of tools, the 

following may be mentioned. When the holes to be bored 

a bar that nearly fills the hole may be used. It 




m Y be set to project beyond the holder just far enough to 
DUgh the work. This gives the tool the greatest 
rigidity. Furthermore, because of the low posi- 

[ tool, .'. the cutting ai i 



LATHE WORK: | 

i better than could be obtained with the forged tool 
as ordinarily ground. 

For heavy work, the 
=tylc of bar shown in 
Fig. 90 has too much 
Hpring, hence the form 
shown in Fig. fU should 
iyed The lighter 
bar is very handy f-.r 
small work. At time*, 
the clamping block shown 
in Fig. SI 

red to the tool block 
by two bolls. These 
bolts hold the block to- 
*o secure the bar b. 




and do much bcucr and more uniform work than can I 
done by hand. These tools are carefully made so that t 



§5 LATHE WORK. 45 

have the proper clearance along the line G H^ Fig. 64, and 
should be sharpened by grinding entirely on the top face. 
When used, they should be set at the same height as the 
center of the work. On wrought iron or steel, a bountiful 
supply of lard oil should be used. Very complicated forms 
may be produced by the use of forming tools. 



SPRING TOOLS. 

74. Use of Spring Tools. — In most cases, rigidity of 
work and tool is sought for the purpose of producing the 
most accurate and the smoothest surfaces. In a few in- 
stances, the spring or elasticity of a tool is made use of to 
overcome a roughness of cut that cannot otherwise be 
avoided. 

75. Forms of Spring Tools. — Fig. 05 shows a 
tprlog tool, or gooseneck tool, as it is sometimes 
called, applied to the 
work. The tool is set 
level with the center of 

the work. Any tendency , 

°n the part of the tool J 
°r the work to vibrate or 
chatter is taken up by 
toe narrow springy part 
of the tool. # It will be 

^n that this form of tool can never dig into the work, 

• 

Sl nce the pressure of the cut is constantly tending to press 
the edge away in the direction of the arrow, in a circle 
described about the center c. 

Pig. 66 shows another form of spring tool applied to the 
*ork. This form of tool is intended to avoid all danger of 
springing into the work. The tool is so set that as the 
force of the cut bends it down, the point follows the arc of 
toe circle as indicated. This circle is described about the 
P°int of support of the tool. As the tool springs down, 




46 LATHE WORK. § 5 

the point will naturally move away from the work, and so 
prevent its digging into the stock. 




CHATTERING. 

76. Cause of Chattering. — Chattering of the tool, 
which produces a rough corrugated surface on the work, 
may be traced to many sources. The action that occurs 
when chattering takei place is as follows: The tool is caught 
by the work and drawn in so as to cut deeply; when it has 
sprung in a certain depth, the tool and work are placed 
under a strain that causes them to spring apart. These 
performances take place in quick succession and in more or 
less of a rhythmical order, producing at times a musical 
sound, and, at other times, a most discordant noise. This 
springing action that takes place may be traced to different 
causes, as, to the frailty of the work, as in long slender 
shafts or long pieces being turned upon slender arbors; to 
the method of driving or rotating the work ; to looseness of 
the spindle in the heads took bearings, or to looseness in the 
cross-slide of the tool rest; to looseness between the lathe 
centers or to the peculiar shape or manner of setting the 
tool. Broad-edged tools have a greater tendency to chatter 
than narrow ones. 



LATHE WORK. 



■17 




77. Remedies for Chattering. — When a second cut 
is taken on a surface that shows slight chatter marks, they 
may be removed by grinding the tool so that its top fact- has 
a slight angle of top side rake 
just sufficient to keep the broad 
edge of the tool from falling 
into the old chatter marks. If 
in Fig. t!7 the cutting edge of 
the inn! was at first along the Pro. 87. 

line A B, the chatter marks would be parallel to it. These 
chatter marks can generally be removed by giving the tool 
top side rake along the line CD. 

When remedies in the way of adjustment and methods of 
driving have been tried without avail, the spring tool often 
proves successful ia removing the chatter marks. 

I HAND TOOLS OR GRAVERS. 

78. Diamond-Pointed Graver. — Hand tools, as 
eir name implies, are held in the hand while operating 
upon the work. Their cutting action depends on the laws 
of rake and clearance. Their cutting power, compared 
with tools held in a slide 
rest, is very small. Their 
principal use in metal work- 
ing is turning very small 
pins and pivots on such 
lathes as watchmakers' or 
small bench lathes for work- 
ing brass, and for finishing 
curves and pieces of irregu- 
lar outline. Chief among 
these tools is the <iin- 
mmid- pointed Kiaur. 
BOS Of Steel ground with a bevel on the point, as 
hown in Pig. UK. When ihis tool is used for rounding a 
orner such as the end "f :\ bolt or screw, it rests upon one 



48 



LATHE WORK. 



§5 



corner r, Fig. 69, while the edge A B does the cutting. 
The angles of rake and clearance are easily changed to 
give the best results by changing the position of the tool. 




Fig. OB. 

79. Round-Nosed Graver. — Fig. 70 shows a round- 
nosed graver. This tool is used for finishing concave 
curves. The under side lies flat on the rest when it is used. 




Fig. 70. 



Gravers are commonly made from worn-out files of either 
square or rectangular section. Their points can be ground 
to any particular shape best suiting the work. 



8(>. 



TOOLS FOR BRASS. 

Tools for brass are usually drawn out nearly to a 

point similar to a round-nosed tool. 
The top face is made flat, as shown 
in Fig. 71, while the point is ground 
similar to a threading tool with the 
point rounded. Tools with broad 
edges are seldom used for brass un- 
less they are some kind of forming 

no. 7i. tool. The characteristic features of 




LATHE WORK. 



49 



a brass too! are: it is flat on the top, is set at the cen- 
ter of the work so that it has no top rake, and is ground 
with more front rake than similar tools used on iron and 
steel. 



TOOL i;im\iii.ks. 

81. Tool Grinding.— II is a common practice in 
nosl shops for each man to grind his tools to suit himself, 
the grinding being done on grindstones or special emery 
wheels for tool grinding. The result is a very great 
stock of steel, which is necessary to make up the sets of 
the different machines, and an almost infinite num- 
>er of shapes. The best managed shop;; are now adopting 
system whereby the tuols arc systematically and scientific- 
ally ground by one man. All tools are kept in a tool room 
and are checked to the workmen as used. There arc a num- 
ber of automat ic tool grinders on the market designed for 
this purpose, and some of them arc described later. 



82. Mochtne-Cround Tools. — Fig. 72 shows a few 

typical lathe toots as ground upon one of the standard tool 

Fig, 73 showssome typical planer toolsas ground 

upon the same machine, and Fig. 7-i some slotting machine 

«ils, threading, and other special tools. Figs. 75 and 7fl 

■ bartfl that are sent out with Sellers' grinding 

the i Iterance angles for grinding the 

lificrerit tools. The numbers placed opposite the tools in 

78, »nd 74 correspond to similar numbers on the 

■Is in Figs. 75 and 70. In the cast of the 

liing planer tools illustrated in Fig. 76, it will be 

angles are given fur ii. The upper angle 

.. side rake, at right angles to the cutting face, 

ind the lower angle is the top rake in the direction of the 

rts and figures are given simply to 

ihow what is considered good practice in regard to the 

shape of thi 



LATHE WORK. 



§5 




LATHE WORK. 





LATHE WORK. 



§3 




LATHE WORK. 



gX,Lo.^Vj\,'j^<A?JjVl- 




LATHE WORK. 



§5 



jjUgj^fe ?tm Sim tv. 



*u 



5U 



MR 












LATHE WORK. 

(PART 4.) 



v CUTTING SPEEDS AND FEEDS. 



CUTTING SPEED. 

1/ Meaning of the Term Cutting: Speed. — The 

cuttingspeeds and feeds of machine tools is a subject for 
much careful study. The output of work from a machine 
and the cost of production depend very largely on the cut- 
ting speed used. 

The cutting speed of a machine tool is the speed at 
which it passes over the surface of the work. This speed is 
measured in feet per minute. Before discussing cutting 
speeds, a very clear understanding should be had of its 
exact meaning. Suppose the speed of a lathe is such that 
the tool can cut in 1 minute a shaving that, if it could be 
straightened, would measure 20 feet in length. The cutting 
speed would then be 20 feet per minute. If the speed of 
the lathe were such that the tool would cut a shaving 10 feet 
l° n g in 1 minute, the cutting speed would be 10 feet per 
minute. 

2. Relation Between Cutting Speed and Speed 
of Work. — Cutting speed and the speed of the work must 
n °tbe confused. Two lathes are working and each making 
^revolutions per minute. One is turning a piece 1 inch in 

COTTRIOHTED BY INTERNATIONAL TEXTBOOK COMPANY. ALL RIGHTS RESERVED 

16 



i 



2 LATHE WORK. §6 

diameter and the other a piece 2 inches in diameter. The 
circumference of the 1-inch piece is 3.1416 inches, say 
3.14 inches and that of the 2-inch piece is 6.28 inches. In 
the 1-inch piece the tool passes over 3. 14 inches for each 
revolution and in 50 revolutions it would pass over 50 X 3.14 
or 157 inches = 13 feet 1 inch. The 2-inch piece having 
twice the circumference will pass over twice the distance or 
26 feet 2 inches. These are the cutting speeds when both 
lathes have the same speed. It will thus be seen that the 
cutting speed varies directly with the diameter of the work 
when the speed of the lathe remains constant. 



LIMIT OF CUTTING SPEED. 

3. Factors Limiting the Cutting Speed. — The 

cutting speed should always be as great as the nature of 
the work or the durability of the tool will permit. The limit 
of the cutting speed depends on the durability of the tool. 
A tool that will cut well when the work is running at a low 
cutting speed will not cut well nor endure long when the 
cutting speed is much increased. The limit may be ascer- 
tained by a number of speed trials. At a moderately low 
speed the tool retains its edge, but if the speed be increased, 
the tool will heat at the point, the temper will be started, 
and the point softened and quickly worn away. As soon as 
the cutting point or edge is dulled, the friction increases 
and greater heat is generated, so that in a very short time 
the entire point of the tool will be worn away. 

4. The greatest speed at which the tool will retain its 
cutting edge a sufficiently long time to turn a fair amount 
of work is the limit of cutting speed. Iron or steel 
running at high speeds soon removes the temper so that the 
tool will not cut. Soft pieces of steel that could easily be 
turned at a low speed would, when running rapidly, wear 
away the point of the hardest tool nearly as fast as if the 
tool were brought against a rapidly revolving emery wheel. 



§6 LATHE WORK. 3 

This limit of cutting speed varies greatly. In attempting 
to determine this limit, it will be found that it depends 
largely on, firsts the kind of metal being turned ; second, 
the hardness of that particular piece ; third, the cut, whether 
it be a heavy roughing cut or finishing cut; and, fourth, 
the diameter and length of the work. 

5. Effect of Kind of Metal on Cutting Speed. — 

The cutting speed is greater for soft metals than for hard. 
This is illustrated in the high speed used for wood-cutting 
tools. Copper, brass, babbitt, and similar metals will admit 
of a much higher cutting speed than cast iron or steel. 
One reason why copper will admit of a higher cutting speed 
than iron is because it is softer and less force is required to 
turn the shaving; consequently, less heat is generated at the 
cutting point of the tool. Moreover, copper is such an 
excellent conductor of heat that, as soon as heat is gen- 
erated, it is at once conducted from the point of the tool so 
that the heat cannot accumulate as fast as in iron or steel. 
It will be found in turning iron or steel that the work and 
the shank of the tool keep quite cool, most of the heat being 
concentrated at the point of the tool and in the shaving. 
Whatever the metal being turned, the speed must be slow 
enough to give the heat time to pass into the work 
Wore it becomes sufficient to draw the temper on the 
tool. The reason the tool becomes so much hotter than 
the work is that the tool is constantly cutting, while the 
*ork is continually changing its position and bringing new 
points in contact with the tool. This allows the heated 
P a *t of the work to cool while it is completing the rest 
°f the revolution. The shaving, which is light com- 
pared with the mass of the work, has no way of distrib- 
uting its heat except by radiation, and, consequently, 
*t comes away from the work at a temperature nearly 
eo ,ual to that at the point of the cutting tool. To a 
ttrtain degree, the rotating of a large piece tends to 
*eep the point of the tool cool, for it no sooner severs 
a part of a shaving at one point on the surface of the 

TJB-13 



4 LATHE WORK. §6 

work than a second point is presented to it, and so on around 
the work, the tool constantly being forced into cool metal, 
which, for an instant, would tend to cool the point of the 
tool. 

6. When the tool is exceedingly sharp, a greater amount 
of heat is generated by the force required to turn the sha- 
ving than by the act of severing it. The force required 
to press a sharp tool into the work depends on the angle of 
the side faces, and if a blade could be made infinitely thin, 
with its edge infinitely sharp, it would be found that the 
mere act of severing a shaving would require very little power. 
For illustration, the thin blade of a cheese knife will pass 
easily through a cheese, while a thick, wedge-shaped knife 
will require a heavy pressure. This is caused by the 
necessary bending aside of the parts before the blade can 
enter farther. 

7. It may therefore be assumed that the heat generated 
in taking a cut is due to the bending and turning aside of 

the shaving, and to the friction of the 
^^*~"" shaving on the top face of the tool and 
of the work on the front face. This 
applies to a tool with a sharp edge. 
This fact in part accounts for the pe- 
culiar wear that is sometimes noticed 
Pl °- *• on tools that are considered excellent. 

Fig. 1 shows a tool as it is sometimes worn after taking a cut 
on steel. It will be noticed that the cutting edge a b has 
retained its original sharpness, while immediately behind it 
a small groove c has been worn. 

This peculiar wear may be explained by assuming that the 
cutting edge possessed an unusually fine temper, being of 
sufficient hardness to retain its keen cutting qualities and 
at the same time being tough enough not to break. This 
keen edge severed the shaving with ease and caused but 
little heat. As fast as it entered the work, it was constantly 
coming in contact with cool points. This tended to keep 




s< 



LATHE WORK. 



the edge cool. At the instant the shaving was severed 
or cut loose from the work, it was at once turned from its 
course by sliding on the top face of the tool. The heat thus 
generated slightly softens the top face of the tool, and the 
shaving lends to wear away this top face as it turns and 
slides from the tool. This is more apt to occur when light 
cuUare being taken at high speeds. 
At high speeds, the edge of the tool is more rapidly cooled 
[ the rapid succession at which the cool points on 
Cha srnrk are brought against it. At slower speeds, with 
heavy cuts, the heat from turning the shaving overbalances 
lg action of the work; consequently, the edge of 
the tool becomes hot and suffers from it. It must not be 
inferred from these statements that a tool will stand better 
« a high than at a low rate of speed. Such is not the 
ew. If, in the case of the tool shown in Fig. 1, the speed 
bid been slightly reduced, the tool would have done the 
""rk just as well and would not have been worn on the top 
k«_ This simply shows that in this case the limit or criti- 
cal catting speed had been reached, and increasing it even 
^'ghtly would have ruined the tool. 

8. The power required to force a tool into the cut de- 

Pwdson the angles made by the cutting faces, and the harder 

the material being cut, the less acute 

'i'ould the cutting angle be. This large 

■"'B'eof the cutting faces is necessary 

l " s upport the cutting edge, since, for 

nurd materials, the tool must be exceed- 

,n K'y hard, otherwise the sharp edge 

"ill be pressed down and rounded. This 

a *h»t really does occur as a tool dulls. The keen cutting 

*df* is worn off so that it becomes a rounded surface, as 

" in much exaggerated form at a, Fig. 'I. As soon as 

e keen edge becomes rounded, heat :s generated at this 

Was it is forced to sever the shaving, and the more it 

«nes rounded, the more heat is generated, until at last 

il will cease to cut. If the edge were sufficiently hard 




B . LATHK WORK. §6 

to resist the pressure of very hard material, it would be m 
brittle that, unless the cutting edge were well supported, the 
tool would break. Keen acute angles would cut more easily 
and be more desirable if they would not break. 

9. It is thus seen that for hard, tough materials, hard 
tools with little top rake must be used, while, for softer 
materials, greater keenness or top rake may be given. Be- 
th* grettei power required to force tools having little 

keenness into tin.' work, a greater amount "f heat will be 
developed. Strict the limit of cutting speed is governed by 
tin- amount of krat gmtrattd, it -,■■"'/ ft* seen tkmt the tool 
having t&e greater angle <</ he* mttsi rnnsi be used at a lower 
tfttdtiutn the .icute on.-, otherwise it will pass its keatin 
limit. 

This applies in the same way to cuts taken Upon the s 
kind of material that varies in degree of hardness, 
iron, for instance, will be found to vary a great deal in i 
degree of hardness, some being very soft and M 
hard. 

10. If two pieces be of the same strength or hardness, 
the more acute the tool, the less the power required to Force 
it into the work. With two tools of the same shape, and 
talcing the same depth of cut in materials of different de- 
grees of hardness, the softer material will require the less 
power. This is because of the case wit ii which the shaving 
is bent and turned from the tool. The 
therefore, develops less heat for the same Bhape of tool ; 
depth of cut than the harder material; consequently, 
increased speed may be used. 



11. Uouiihitii; Cuts. — Roughing cuts are gener: 
heavy and the duty of the tool severe. It then 
comes necessary to use slower cutting speeds for rough i 
than for finishing cuts, This reduced cutting 
give a slight increase in lathe power, thereby making it I 
sible to take still heavier cuts when it is net i 



§6 



LATHE WORK. 



7 




12. Finishing Cuts. — Finishing cuts are best made at 
a high cutting speed, especially on gast iron, as it will give 
a smoother surface than can be 
obtained with a slower cut. When 
a slow cutting speed is used on 
cast iron, there is a tendency 
for the shavings to break out of 
the work slightly in advance of the 
cutting edge. This is due to the 
crystalline structure. of the mate- 
rial. This is shown in some- 
what exaggerated form in Fig. 3, 
where a shaving a is shown just as it is breaking from the 
work. When the slow speed is used, the shaving breaks 
slowly from the work and in so doing breaks into the sur- 
face and carries away with it particles of metal that should 
he left. This will leave a surface that is more or less pitted, 
and, should it be desired to finish it by polishing, these little 
pits will be found to be of sufficient depth to make it very 
difficult to obtain a fine polish. When a higher speed is 
used, or the tool is ground with a keener cutting edge, this 
pitting will disappear. 



Pio. 8. 



INFLUENCE OF DIAMETERS ON RESISTANCE TO CUT. 

13, Suppose that a diamond-pointed tool is cutting a cyl- 
inder of the diameter represented by the circle e y Fig. 4, to the 

size represented by the dotted 
lines. The force or pressure on 
the top face of the tool is meas- 
ured in a direction at right angles 
to the face of the tool ; therefore, 
the direction of the force on this 
tool is along the line c o perpen- 
dicular to ao. This line inter- 
sects the circumference of the 
Pio. 4. outer circle at b. Suppose, in the 

second case, that the tool is cutting the same depth of cut 




8 LATHE WORK. [ ■; 

on a smaller cylinder represented by ff. The force of the cut 
will be in the same direction as in the previous case along 
the line c o. The line co intersects this smaller circle at d. 
These lines do and b o graphically represent the relative 
forces required to turn the shaving. In the larger piece, the 
shaving has a backing and support extending from the point 
of the tool to the point b, while, in the smaller piece, the 
shaving is backed only by metal to the point d. It will 
readily be seen that less power will be required to turn 
the shaving on the smaller piece than on the larger one. 
Since this is true, it is theoretically possible to take a deeper 
cut on the small piece with the same power required for the 
original depth of cut on the larger piece. 

14. Average Cutting Speeds. — The cutting speed 
depends on so many conditions that it is impossible to give 
any exact rule that will apply to all cases. Different cut- 
ting speeds have been given for the different metals, but 
these vary greatly. An average, however, has been taken, 
as given in the accompanying table, which gives fair speeds 
that, may be used under favorable conditions for taking 
roughing cuts of medium depth. 

It will be noticed in this table that the cutting speed of 
brass is considerably greater than that of iron ©T steel, also 
that the cutting speed is increased for the small diameters 
of work. The cutting speeds given for cast trot) 
short cuts taken on very soft castings. Long, continu< 
cuts on hard castings would require a cutting speed som 
what below that given in the table. 

15. Relation of the Steel to Cutting Speed. - 

the case of special self-hardening steel, the cutting specc 
of machine tools have been much increased. This is dm 
largely to the amount of heat these tools will atan 
their temper is impaired. With some of the best brands q 
self-hardening steel, the rate of cutting speed, compai 
with that used with ordinary forged and tempered tools, i 
nearly doubled. With these tools, shavings may often 
cut from tool steel at such a high cutting speed that the h 



§6 



LATHE WORK. 



9 



CUTTING 8PBED8. 





Diameter 

of 

Work. 


Cutting Speed 

in Feet 

Per Minute. 


Wrought Iron 
and 

Machine Steel. 


1 

2 
H 


38 
35 
30 
28 
25 


• 

a 
o 

V* 

3 
o 


1 

H 

2 

2* 


45 
45 

40 
40 


Tool Steel. 


1 

1 

1 

1* 


24 
20 
20 
18 


Brass. 


i 
l 

H 


110 

100 

90 

80 



generated will sometimes be sufficient to draw the temper 
color on the steel shaving to a dark blue. This is equiva- 
len t to a temperature of about 550°. 

Ifi. When Low Cutting Speeds Should Be Used. 

"Me in most cases it is desirable to work up to the 
,lm it in cutting speed, it is not in all cases the most ad- 
visable. With a single-pointed turning tool that may be 
Sickly and easily sharpened, it is a desirable thing to do. 
^n the case of special tools intended to perform certain fm- 
ls "ing operations and when the accuracy of the piece depends 



I. 



LATHE WORK. 



86 



to some extent on the action of the special tool, then that 
tool should be favored by using lower cutting speeds. For 
example, consider a reamer that is to finish holi - 
and true and to an exact diameter within a thousandth o( 
an inch. The size of the hole will depend on the sue of the 
reamer, and when the cutting edge is worn away OQe-hali 1 
thousandth of an inch, the reamer will make the holes too 
small. Such a tool should be handled with care and the 
cutting speed sacrificed for the sake of maintaining the 
cutting edge. 

Taps and dies should not be run at such a high cutting 
speed as can be used for lathe tools. Chm ■ 
also be favored, especially if they are intended to n 
a particular size. Due care and judgment must be exerci; 
in each case to get the best results. 



CUTTING I I I l>. 



'.!! 



arc 
are 



17. Definition of Feed.— Tin- feed uf a tool is the 
amount of its side iimvi.-uh.-iu along the length of the bed 
per revolution of tin: work, or the number of re 
required to move the tool sidewise 1 inch. The feed, in 
turning, and the pitch of the screw, in re* cutting, are 
the same; thus, a feed of 10 means that 10 turns of tl 
work feed the tool over the work a sufficii ni i 
finish -,V inch in length. Sometinn-s the finer F< 
designated by a number' corresponding to the nu 
turns necessary to finish 1 inch, as, foi instance, a feed of 10, 
which means thai 10 revolutions will move the tool 1 inch. 

18. Relation Between Peed and MiHerl.il Being 
Cut. — The best feed to use -m a piece of work dtp. 
many conditions. When cylindrical accuracy is da 

wronghl-iron or steel shiifis, n is lust to i 
finishing, since, with a fine feed, it is possible to u 
with a narrow point, The narrow. pointed tool will • ■■■ 
freely and, consequently, with less spring lo the tool z 



§6 LATHE WORK. 11 

the work. Time, however, is of great importance in ma- 
chine work, and sometimes coarser feeds will finish with 
sufficient accuracy. The feed and the width of the point of 
the lathe tool are interdependent, the point of the tool being 
slightly wider than the amount of feed per revolution. 

19. Cast iron will generally admit of broader feeds than 
wrought iron or steel. This is due largely to the difference 
in the action of the shaving on the tool. With cast iron, 
there is a tendency for the shaving to break immediately 
when turned out of its course by the top face of the cutting 
tool. This constant breaking of the shaving tends to relieve 
the tool of undue pressure. In wrought iron or steel, the 
shaving does not break up so easily. When, in turning steel, 
the broad cutting edge of the tool is set parallel to the axis of 
the work, any slight pressure that may tend to spring the 
tool into the work causes the whole broad edge to spring in. 
This causes the tool to take instantly a very much deeper 
hold, and, because of the tenacity of the steel, the tool will 
be carried deeper and deeper until it reaches a point where 
the strain on the tool balances the pressure of the shaving, 
a t which point the tool will continue to cut at this depth. 
K the work is not sufficiently rigid to hold its shape while 
the tool is thus sprung and taking a deep cut, the piece will 
bend slightly. As the hollow side of the bent piece comes 
around to the tool, the cut will grow less until the heavy side 
a ?ain comes around, whereupon the cut will be heavier than 
before, and, in most cases, the work will be ruined. Broad 
c utting-edged tools should never be put on a piece of 
wrought iron or steel, unless the operator is quite sure that 
there is sufficient rigidity to withstand the cut. 



COMPUTATIONS RELATING TO CUTTING SPEEDS. 

20. To Find the Cutting: Speed. — Suppose a shaft 
* mches in diameter is being turned at the rate of 10 revo- 
lutions per minute. It is desired to find the cutting speed of 
the tool in this case. The circumference or distance around 



12 LATHE WORK. § 6 

the shaft is 3.1416 X 4 = 12.5664 inches, say 12.57 inches. 
This is the length of shaving cut in 1 revolution. Multiply- 
ing 12.57 X 10, gives 125.7 inches, the length of shaving in 
inches turned in 1 minute. As the cutting speed is meas- 
ured in feet per minute, 125.7-5-12 = 10.47 feet, say 10, 
the cutting speed. In some cases, for a rough or approxi- 
mate value, 3.1416 is assumed to be 3. Thus, in the above 
case, if a shaft is 4 inches in diameter, its circumference 
will be about 3 times that, or 12 inches equal 1 foot, and if 
it cuts 1 foot of shaving for 1 revolution, it will cut 10 times 
that, or 10 feet for 10 revolutions. 

21. The cutting speed for any lathe may be found by 
applying the following rule: 

Rule. — Find the continued product of the diameter of the 
work, in inches, the number of revolutions per minute, and 
8. 1416 inches ; this result divided by 12 will be the cutting 
speed in feet per minute. 

For example, to find the cutting speed of a shaft 2£ inches 
in diameter, making 75 revolutions per minute, take the 
continued product of the diameter, in inches, the revolu- 
tions per minute, and 3.1416. This gives 2| X 75 X 3.1416 
= 589.05 inches per minute. Dividing by 12, we obtain 

— -^ — = 49 feet per minute, very nearly, as the cutting 
speed in this case. 

22. To Find the Number of Revolutions Re- 
quired to v Give a Desired Cutting Speed. — If a steel 
shaft is 9 inches in diameter, how many revolutions must it 
make to give a cutting speed of 20 feet per minute ? 

The distance around the shaft equals 3. 1410 times its 
diameter, or 3.1416 X 9 = 28.2744 inches, say 28.27 inches; 
therefore, for 1 revolution of the shaft, 28.27 inches of 
shaving will be cut. Twenty feet equals ^40 inches. To cut 
off 240 inches of shaving per minute will require as many 
revolutions as 28.27 is contained in 240, or 8.5, nearly. 
Therefore, the shaft should make 8 J revolutions per minute 



§6 LATHE WORK. 13 

to give a catting speed of 20 feet per minute. As in the 
previous case, the fractions may be neglected when making 
rough calculations and it is desired to save time. 

23. Again, suppose the work to be 1 inch in diameter 
and the cutting speed desired is 20 feet per minute. The 
circumference of the work equals 3.1416 times the diam- 
eter, or 3.1416 inches. The length of the shaving equals 
240 inches. It will take as many revolutions of the work 
to turn 240 inches as 3.1416 is contained in 240, or 76.4 rev- 
olutions per minute. Hence, to find the number of revolu- 
tions per minute that the work should make in order to have 
a certain cutting speed, use the following rule, in which it is 
assumed that the diameter of the work is known : 

Rale. — To find the number of revolutions per minute that 
the work should make to produce a given cutting speed in feet 
per minute, multiply the cutting speed by 12 y thus reducing 
the speed to inches per minute, and divide the product by 
&m$ times the diameter in inches. 

r -td> 

when R = revolutions per minute; 

5 = cutting speed in feet per minute; 
* = 3.1416; 
D = diameter of the work in inches. 

24. How many revolutions should a shaft 2 inches in diam- 
eter make to produce a cutting speed of 30 feet per minute ? 

Applying the rule just given in the preceding article, we 

have, indicating the operations, 

12 X 30 

revolutions per minute = . „ . ,„ - = 57.3. 

r 3.1416 X 2 

Therefore, the work should make 57.3 revolutions. 

25. To Find the Time Required to Take a Cut. 

*" e time required to turn a shaft can also be determined 
w hen its length, the feed, and the number of revolutions 
are given. 



1 1 



LATHE WORK. 



Suppose it is desired to find the time required to turn a 
shaft 10 feet long that is making 25 revolutions per minute 
with a feed of 30, that is, 20 revolutions of the work to move 
the tool along the shaft 1 inch. 

If the tool moves over 1 inch of length of the shaft in 
20 revolutions, to move over 120 inches (the length of the 
shaft in Inches), ii will take 20 times 140, of 9,400 revolutions 
of the work, If the shaft makes 25 revolutions in 1 minute, 
it will take as many minutes as 26 is contained in 2,400, or 
06 minutes, equal 1 hour and 30 minutes. 



—and 



26. When the length of the work, the number of r 
lutions necessary to advance the tool 1 inch — the feed — am 
the number of revolutions per minute are Iraovn, the time 
necessary for the cut is easily calculated by the following rule: 

Unit. — To find the time necessary <<• take a eut of known 
length, multiply the length in inches by the feed {u:, 

>■■:■ necessary for the tool to advance f i<nli) and divide 
the product by the number of revolutions per minute made b 
the Work, 

For example, applying the rule to case mentioned in 1 
last article, the length is 10 feet = 120 inches, the feed is a 
and the number of revolutions per minute is 25. Indicati 
the operations, we have 

time = 120 X 20 -*- 25 = S6 HUBS 

A case more likely to arise in practice is where the leng 
of the work and its diameter are known ami it is pegj 
take the cut at a given speed and feed, the speed being in 
feet pet minute. Supposi 

essary to turn a shaft 6 feet long and 18 inches in diameter, 
using a feed of 20 and a cutting speed of 18 feet per minute. 

We first find the number of revolutions necessary to give 
the cutting speed by the rule in Art, 29* 

Revolutions per minute = 3| ^* x ]8 = 

Substituting this value in the rule just given, 
time = 72 x 20-J-3. 82 = 377 minutes = 6 hours and 17 mum 




§ LATHE WORK. 15 

27. Instead of using the rules given in Arts. 23 and 26, 
the following rule, which is a combination of the two, may 
be employed: 

Rule— The time in minutes is equal to the continued product 
of8.14W, the diameter, the feed, and the length divided by 12 times 
the cuUing speed. 

Applying this rule to the case last mentioned, 

3.1416X18X20X72 ow . 

tune= — — — =377 minutes. 

12X18 

This same result was obtained by the other method. The 
number 12, which is used in the various formulas, is used 
to reduce the cutting speed from feet to inches, but if the 
dimeters in the various problems were given in feet, the 
number 12 would not be needed. For example, how long will 
it take to turn a flywheel 20 feet in diameter, 24-inch face, 
tf a cutting speed of 15 feet and a feed of £ inch are used? 

A feed of £ inch equals a feed of 2. Applying the rule 
given above, and omitting the number 12, since the diameter 
is given in feet, 

.. 3.1416X 20X2X24 OA1 . ^ 01 . 

time* — = 201 mm. = 3 hours 21 mm. 

15 

28, Advantages of Coarse Feeds. — When the fin- 
ishing cut is being taken on a large piece, it is desirable to 
bave the tool retain its sharp edge until the operation is 
completed, so that the last part of the cut will be as smooth 
and true as the first. On heavy work, when the tool dulls 
f° that it becomes necessary to resharpen it before the cut 
15 completed, as it takes some time for the work to make 
a evolution, by the time the tool is adjusted to the same 
dc Pth as before and the feeds arc again working, much time 
is lost. 

-9. Suppose, in" the flywheel just mentioned, a finishing 
cut should be attempted by using a feed of 10. By the time 
the piece was finished, the shaving would be 3.1416X20X10 
*24= 15,080 feet, or nearly 3 miles long. At a cutting 
speed of 18 feet per minute, this would require 13 hours 



16 LATHE WORK. § 6 

68 minutes. It would be impossible to get a tool that would 
stand to cut nearly 3 miles of shaving without getting dull, 
and the time would be considerably more than necessary. 
On such a piece as this, the feed would be increased to nearly 
1 inch per revolution and the speed reduced to about 15 feet 
per minute. This would reduce the length of the shaving 
to 1,508 feet, and at 15 feet per minute would require 100J min- 
utes, or 1 hour 40J minutes. This reduces the time to one- 
tenth the original and makes it possible to use a tool that will 
last throughout the cut. 



ERROR IN LATHE WORK. 



PRECAUTIONS TO BE OBSERVED. 

30. General Consideration. — The chances for error 
in machine work are numerous. No sooner is one difficulty 
overcome than another appears. The workman must never 
take anything for granted regarding the accuracy of a 
machine or the work it is producing until he has made sure 
that all is right by a personal investigation. Even then he 
must be on the watch, or errors will creep in that are unex- 
pected. These small errors that occur in lathe work become 

• 

more numerous and troublesome as the degree of accuracy 
is increased. Things that would not be noticeable in an ordi- 
nary line of work become very important in accurate work. 
Many of the chances for error that occur may be found 
and illustrated in a simple piece of cylindrical turning. They 
may be due to: (1) spring of the tool; (2) spring of the work; 
or (3) inaccurate adjustment of the machine used. 



SPRING OF LATHE TOOLS. 

31. Factors Governing Spring of the Tool. — 

The amount that the tool will spring depends on the posi- 
tion it holds in relation to the work; on the rigidity of the 



§6 LATHE WORK. 17 

tool; on the closeness of fit between the tool block and the 
slide; on the stiffness of the shank of the tool; and on the 
shape of the tool. 

32. Position of the Tool. — It has been shown, Fig. 66, 
Lathe Work, Part 3, that when the point of a tool is set 
above the center of the work, as it bends in its shank the 
point tends to follow in an arc of a circle described about 
the bending point. If this arc cuts into the work, the tool, 
following in that path, will spring deeper into the work. If 
the tool is so located that when it bends or springs, the 
arc described about the bending point moves away from the 
work, then the tool will spring away from the work. It 
would seem from this that the best place to set the point of 
the tool would be level with the center, so that, if the tool 
springs, it will not spring into the work. A tool properly 
shaped for this position would have very little front rake, 
and its keenness would be given entirely by increasing the 
angle of top rake. Such a tool is absolutely required for 
taper turning, but, for ordinary turning, other conditions 
arise, making it objectionable. It may be seen that when 
this tool is used, the total force acting upon it is in a direc- 
tion tangent to the diameter of the work at the point of the 
tool. 

33. When a tool without front rake is used, the force 
will be directly down, or perpendicular to the top of the 
lathe bed, in the direc- up,, 

tion of arrow D C, *-— \~f >^ ?^ \ ~~ F 

Pig. 5. As increased jn^ I \^ 

front rake is given to Jf*\ \ 

th e tool, and it is set Jm y '~~ ~^ ) 

higher on the work, the BBfri;^ lX * Vs *W \ / 

line of force changes its jRj,^J > ^ m j \. >/ 

direction, so that if the ■™J r - * , ^ 

front rake is 30°, the i 

tint of force acting ? lG •»• 

against the point of the tool at O' will be in the direction 

°f the arrow B A. When the force on the tool is in the 



1H 



LATHE WORK. 



t< 



direction of the arrow BA, it tends to force the tool block 
back from the work; this causes some pressure on the cross- 
feed screw. If the tout had still more front rake and were sel 
higher, the pressure on the cross-feed screw would increase, 
and if the tool could be set as high as the point r , the 
force of the cut would be in the direction of the line F F., 
which would be entirely against the cross-feed screw. This 
pressure against the cross-feed i irabte. 

In .Ms the tool block back and takes up the lost mot I 
may be in the screw, so that, when an adjustment is being 
made, any partial turn of the screw at once acts in moving 
the tool block. It also allows the tool to be held in such a 
position that there is little danger that the pressure of 1 
shaving on the top face of the tool will pull the tool ; 
too! block forwards, thus taking up the lost motion in t 
cross-feed screw. 



This 

that 

ieing 
ving 
ch a 

3 




34. It will be seen from Fig. G that when a tool is set at 
the center and ground with much lop rake, the pressure u 
the shaving on the 
face is in the direction i 
the arrow a. This is : 
nearly parallel to 
of the cross-slide that i 
the slide is loose or 
screw has lost motion, 
1 " ■' , ■ tool will tend to slide int< 

the cut. If the tool is set higher, this force on the top fa< 
is in the direction shown in Fig. 7, and there is little ten< 
ency to drag the too] Into 
the cut. Practice, there- 
fore, has settled upon tools 
with a fair amount of front 
rake, which allows them to 
be set above the center of 
the work. This gives the 
desired pressure against 
the cross-feed screw. 




§6 



LATHE WORK. 



19 



35* Spring of the Tool Caused by Variations in 
the Depth of Cut. — If, in turning a piece, an attempt 
is made to finish the 
work very close to size 



with the first cut, leav- 







Pio. a 



rog a very light cut a 

for the last, the follow- — r 

ing results may ensue : 

The tool is started and 

the cut taken for a 

short distance, and, 

by a series of fine cuts, 

the work is brought to 

the desired diameter 

shown at a, Fig. 8. 

The feed is thrown in and soon the to<51 starts in the heavy 

cut. The result is that as soon as the heavy pressure comes 

upon the tool, it causes it to spring and take a still heavier 

cut The piece will therefore be turned smaller in diameter, 

as shown by the dotted lines, and, in many cases, may make 

the piece below the desired size. This is one reason why at 

least -fa inch should be left for finishing. 
Suppose another case in which a casting or a forging has 

a large lump on one side, Fig. 9, which must be turned off. 

Because of the form of the work, the 
shaving will be of different thick- 
nesses, and, consequently, there will 
be different pressures upon the tool. 
This will cause the tool to spring to 
various depths in the work, with the 
result that the piece will be neither 
round nor true. It will be evident that 
a second finishing cut will be necessary 
p 9 if any degree of accuracy is desired. 

36. Methods for Reducing: the Error Due to the 

Spring of the Tool. — The possibilities of error due to the 
springing of the tool are guarded against by using tools with 

TIB -14 




20 LATHE WORK. §6 

heavy shanks, clamping the tool very close to the cutting 
edge, and in adjusting the tool block so that there is no lost 
motion in the slide. With these precautions, work may be 
performed, so far as the tool is concerned, with sufficient 
accuracy for all ordinary machine construction. In dis- 
cussing the spring of the tool, it has been assumed that the 
work was very rigid, so that all the spring occurred in the 
tool. The tool, however, must not be held responsible for 
all error, since much is caused by the spring of the work. 



SPRING OF THE WORK. 

37. Effect of the Weight of the Work on Its 
Spring. — Any action that may cause the work to bend or 
deflect so that its axis is not a straight line will cause the 
work to be untrue. If the piece is short and its diameter 
great, the spring is less than when the work is long and 
slender. 

In long pieces, the weight of the piece between the cen- 
ters is sufficient to demand attention. 

38. Effect of the Force of the Cut on the Spring. 

The force required to turn a shaving acts against the tool, 
tending to spring it down, and reacts in the opposite direc- 
tion, tending to bend or spring the work up. When the tool 
is starting at the end of the work, there is less deflection 
than when it has reached the center. If a bar be supported 
at the two ends and a load applied at the center, it will 
deflect more than if the load is applied very near the ends. 
Because of this greater deflection at the center of the work, 
the tool cannot cut so deeply; consequently, the work, when 
turned, will be larger at the center than at the ends. This 
must be corrected by taking very light finishing cuts, or, in 
the case of long slender pieces, the work must be supported 
by the use of steady rests. 



§6 



LATHE WORK. 



21 



SPRING DUE TO METHOD OF DRIVING. 

39. Action of Bent-Tail Dog in Springing the 

Work. — Probably as much spring in cylindrical work is 
produced by the imperfect methods of driving or rotating 
the work in the lathe as in any other way. 

The ordinary bent-tail dog so commonly used produces a 
variety of strains in the work, some of which are constant 
and some variable. All, however, tend to distort the work. 

These forces may be considered separately. First, there 
is a leverage from the point of the live center. The amount 
of this leverage depends on the length of the live center. 
This is shown in Pig. 10, which represents a side view of a 





— H 



Fig. NX 



piece of work between the centers. The tail of the dog is 
at the back of the machine. Suppose the end b of the piece 
he clamped rigidly so that it cannot turn. If power be 
applied to the lathe, the work will tend to turn in the 
direction of the arrow c. Since it cannot, it puts the piece 
under such a strain that it springs it. The leverage is rep- 
resented by the distance a that the lathe center projects 
heyond the face plate. The force of the face plate, which 
tends to lift the tail of the lathe dog, acts from the point of 
the center as a fulcrum and tends to bend the work down, as 
shown by the dotted lines. If the lathe center were longer, 
there would be a greater force tending to spring the work 
because of the increased length of leverage a. 



22 



LATHE WORK. 



§6 




40. When the tool begins to cut at the end 6, the resist- 
ance of the cut at this point acts the same as if the work 

were clamped at this 
end as just described. 
This produces the 
same effect, though 
not so great, as 
clamping the end, 
for, with a tool, the 
strain can never be 
greater than that re- 
quired to cut the sha- 
ving. As the tool 
feeds along, this re- 
sisting point ap- 
Pl °- n * ' proaches the point of 

the live center or the fulcrum from which the work bends. 
The result is that the amount of spring of the work will 
change. Here we have a changing force tending to spring 
the work; this force depends on the position of the tool 
along the work. 

41. Suppose, in the next case, that the tool is cutting 
in a position midway along the length of the work. A sec- 
tion through the work 
is taken at this point, 
as shown in Fig. 11. 
This shows the tool at 
the front with the tail 
of the dog diametric- 
ally opposite. As the 
work revolves in the 
direction of the arrow, 
the force required to 
turn the shaving is 
made with an upward 
pressure of the tool. 
This force tends to Plo . i& 




LATHE WORK. 

springihe work up in the direction of the arrow A B. The 
lorce required to revolve the work tends to spring the work 
flow, UDce the dog is at the back of the lathe, and the 
(ones act as shown in Fig. 10. In this case, we have two 
forces tending to spring the work in opposite directions and 
tending to balance each other — one. the force of the cut, the 
other, [he pressure on the lathe dog. 

Suppose the work makes half a revolution so that the tail 
of the dog is at the front, as in Fig. 13. While in this posi- 
tion we will have the force of the cut in an upward direc- 
Jon A R as before, but the pressure on the tail of the dog is 
* in the same direction. Hence, we have two forces, 
"ill tending to spring the work up. In the first case, it is 
c difference of the forces that tends to spring the work. 
" the second case, the sum of the forces acted to spring the 
Here, again, because of the varying forces, vari- 
isdegrees of deflection occur. 

42. When a straight-tailed dog and driving pin, as 

in Fig, 13, are used, the conditions are reversed, the 

tltect of the leverage of the bent tail-dog being entirely 

i, s<> that when the dog is at the back, both forces 

■ ring the work up, and when the dog is at the 

: two forces are opposite and tend to balance each 



CORRECT METHODS OF DRIVING THE WORK. 

43. Stralg;tit-Tatl Doss. — Fortunately, these com- 
bated si rains arising from the ordinary methods of dri- 
igthework may be eliminated 

7 changing the driving devices. 
;i shown by Fig, II) 

**J be remedied by using a 
light -tailed dog and a driving 
i in the face plate, as shown 

f Pfj. 13. By this method, a 
lined between the 
a and the dog. This breaks 

« lererage a. Fig. 10, and so eliminates that bending strain. 




24 



LATHE WORK. 



§6 




Fig. 14. 



44. The variable forces represented in Figs. 11 and 12 
may be balanced by using a two-tailed dog and two driving 

pins in the face plate, as shown 
by Fig. 14. When the work is 
thus driven, the two forces at 
the end of the dog balance each 
other, and the only force remain- 
ing that tends to spring the 
work is the upward force of 
the tool. If the pressures at the 
end of the dog do not balance, 
the same trouble that is found 
with the single-tailed dog will appear. Great care, there- 
fore, is necessary in adjusting the driving pins in the face 
plate so that an equal pressure will be brought against each 
pin. This may be accomplished in some instances by mov- 
ing one of the pins in the slot of the face plate in or out 
from the center. Since the tail of the dog and the slots in 
the face plate are not parallel, moving the pin toward the 
center will bring it against the dog, and moving it from the 
center will move it away from the dog. The pressure on 
the pins may be tested with pieces of paper put between 
the dog and the pins. The work is turned backwards by 
hand on the centers, to hold the dog against the pins, and 
the paper tested by pulling. Any inequality in 
pressure may thus be detected. 



45. Equalizing: Dogs. — Instead of ad- 
justing the pins each time, an equalizing: 
dog:, Fig. 15, may be used. In this case, the 
dog is adjusted to the pins by tightening or 
loosening the screws a, b, as may be neces- 
sary. While it is very desirable to drive the 
work by the methods described, the difficulty 
in adjusting the dogs and the uncertainty 
that they will remain as adjusted do not war- 
rant their general use. When some device 
can be used that will automatically balance or 




c 



Fig. l& 



M 



LATHE WORK. 



SB 



equalize the pressure on the pins, this method becomes 
more practicable. Many forms of equalizing dogs have 
been devised. They serve better for small than for large 
work. A very convenient and successful method of equal- 
izing the pressure on the pins when the two-tailed dog 
is used, is by means of the equalizer or driver shown in 
Fig. Ifi. This consists of a plate carrying the driving pins 
/>. p. This plate is fastened loosely to 
the front face of the face plate by means 
of bolts or studs screwed solidly into the 
face plate but fitting loosely in the long 
slots s, J in the driver. These studs 
keep the driver from slipping around on 
the face plate, but give it freedom to 
move a distance along the slots equal to 
their length. Suppose, in using, the 
greater pressure of the dog first comes pig. in. 

against the top pin. The pressure would force the entire 
driver back, which would slide the lower pin up to the dog. 
As soon as the pressures balanced each other, the plate 
would stop sliding and continue to keep up the equilibrium. 




ERRORS IK THE MACHINE. 

46. Poor Adjustment. — Imperfect work may often 
; traced to the poor adjustment of the machine or to the 

fact that the machine is much worn. When the lathe is 

nuch worn, it will be noticed that the spindle is slightly out 
f line with the bed and that it will not bore holes properly 
r face surfaces true. A great deal of wear comes upon the 

atbe bed at a part quite near the lie ads took, since the greater 
*rt "1 T Hie work turned upon the lathe is short, and the car- 
iage moves over this part more than any other. If the gibs 
Bat bold the carriage t" the bed be adjusted so that the car- 
iage is in good adjustment m this worn place, it will be 

found that when longer work is to be turned, the carriage 
will not slide easily along the unworn part of the bed. 



26 



LATHE WORK. 



§6 



47. Accuracy of New Lathes. — In the manufacture 
of lathes, all parts are carefully tested to see if the line of 
the spindles is exactly parallel with the bed, the carriage 
square across the bed, and all parts correct. All these 
tests require that the lathe shall produce work within a limit 
of from .00025 to .001 inch, depending on the kind of work 
for which the lathe is to be used. 

The accuracy of the machine is not so important as the 
skill of the operator, for a skilful and careful workman will 
overcome the inaccuracies of the machine, but the careless 
workman will have trouble even with the best machine. 




Fig. 17. 



LATHE CENTERS. 

48. Shape of Lathe Centers. — Fig. 17 shows the 

most common form of lathe center. The sides A B and CD 

form an angle of 60° with each 
other and 30° with the center 
line. For very heavy work some 
prefer a blunter center, as shown 
in Fig. 18. This form is used 
because of its apparent strength, 
but while there is less danger of 
breaking the point of the center, 

it cannot hold work to run as truly as the 60° angle. The 

cause of the breaking of 60° angle centers is generally 

due to the imperfect fit in the center hole, which brings all 

the strain on the point of the 

center. When the centers are 90°, 

there will be a greater tendency 

to force the centers apart and out 

of the center hole, due to the 

weight of the work and the force 

of the cut, than if the centers 

are shaped as shown in Fig. 17. 

Suppose two pieces of work are 

being turned on lathes with these two forms of centers, 

If each center were backed out of its work the same 







5 « LATHE WORK. 27 

distance, the work on the 90" center would drop more 
out of line than the work on the 60° center; therefore, to 
keep the work up in line with the spindles, the adjustment 
of the 90° center must be closer than for the 60° center. 
Many builders of heavy machinery use a center having a 
7.5" included angle in place of a (10° or a 90" angle. Such a 
center combines many of the good points of both of the 
other forms. 

-49. \ecesslty of True Centers.— The live center 
should run true in the headstoi k. The dead center should 
be sharp and smooth. If a live center were out of line so 
that its point wabbled slightly and a piece of work were 
turned on it, the work might be round and straight, but the 
turned part would not be true with the center hole. A 
piece may be turned to various diameters and shapes on 
untrue centers and the different cuts may all run true with 
each other, provided they were all taken at one setting. If, 
however, the dog had been loosened and the work given a 
half turn, the dog being again clamped, the piece just 
turned will run out of true an amount double the error 
of the live center. When, therefore, a piece is partly fin- 
ished on one machine and then taken to another for final 
finishing, it is necessary that the centers be true on each 
machine. 

50. Hard or Soft Centers. — The dead center is 
always hardened and tempered. The live center may or 
may not he hardened. Some leading manufacturers prefer 
a soft live center, since it may easily be put in place and a 
cut taken from it as it revolves in the hcadstock. 
This makes it practically true and little time is expended in 
truing it, but because of its softness, it is easily made un- 
true by bending or bruising. If a center, after being trued, 
is hardened and tempered and then put back in its place, it 
will be found that ii no lunger runs true, owing to the warp- 
ing or springing of the center in the operation of hardening 
and tempering. To use hardened live centers successfully, 
they must be made true, as they revolve in the spindle, by 



28 LATHE WORK. § 6 

grinding. Sometimes the live center is hardened and the 
temper drawn to such a point that it can just be turned. 

51. Grinding Lathe Centers. — To grind lathe cen- 
ters, a properly constructed grinding machine should be 
used. There are very many forms of center grinders on 
the market that are sufficiently convenient to warrant their 
use in many shops. Fig. 19 shows a very convenient form 
and its application to the lathe. In setting this grinder in 
the lathe, the shank a is passed loosely through the tool post 




of the lathe ; while the lathe centers come into the reamed 
center holes b, b in the grinder. These center holes have 
been so located that they hold the axis of the grinding 
wheel c at an angle of 30° with the axis of the lathe. After 
adjusting the rest to such a height that the shank a bears 
fairly on its bottom, it is clamped rigidly in the tool post. 
The dead center may be removed and the machine adjusted 
so that the emery wheel comes against the lathe center. A 
rubber wheel d is pressed against the cone pulley by the 
handle/. The lathe is run at its fastest speed backwards, 



§6 



LATHE WORK. 



while the emery wheel is moved along the face of the center 
by moving the shaft operated by the knob e. 



52. When both centers are to be trued, the dead center 
should be trued first. It is put in the place of the live 
center, and, while there, ground smooth and true. It is 
well to polish the dead center with emery cloth and oil. 
The live center may next be ground and left in place aftei 
grinding, so that it will run true. Before grinding or tru- 
ing a center, great care should be taken that the center hole 
in the spindle is very clean before the center is put in place. 
If any dirt or specks of shavings are between the center and 
the hole, it will hold the center away at that point and make 
an incorrect fit. The center might be trued while in this 
position and it would run true until the dirt was removed, 

I whereupon it would at once be untrue. 
S3. Removing the Live Center. — Live centers 
should never be removed from the spindle of the lathe un- 
less it is absolutely necessary. When chucks are used on 
lathes, and rods are passed through the spindle, it becomes 
necessary to remove the centers. If only for plain chuck 
work, the center hole should be plugged with waste, as it is 
very difficult to clean the dirt that accumulates from the 
spindle when the hole is left "pen. 

It is often the case that the center hole in the spindle is 
not absolutely true and that if the center be true in one posi- 
tion in the hole, it 
would run untrue if 
;iven a part of a revo- 
lution to another posi- 
In such cases it 
, best to mark a line 
ng the length of the 
he center f>. Fig. 20, 
and draw a radial line.; 
on the nose of the lathe 
spindle. The center 




30 LATHE WORK. § 6 

can always be put in the same relative position to the spindle 
by making the marks a and b coincide, as shown. After 
lathe centers are once made true, they should be cared for. 
Care should be taken to keep the dead center well oiled. 
When the live center appears to be true, but has not been 
recently ground, its truth may be tested by using an indi- 
cator. These indicators will be described later. 

54. Lining Lathe Centers. — Iq order to turn work 
properly between the lathe centers, it is necessary that they 
be "inline" with each other and with the line of tool 
motion. If the centers are much out of line, as they would 
be after turning a taper, they may be roughly set by placing 
the dead center very close to the point of the live center and 
adjusting until the points appear to be opposite, or the dead 
center may be set by the use of the scale or zero mark on 
the tailstock. To adjust the dead center still further, a 
test bar about 1 foot long may be used. It is carefully cen- 
tered with its ends each finished to some one diameter, while 
the middle portion is slightly reduced. This bar is held 
between the lathe centers and the tool adjusted to touch the 
bar at the live-center end. After the tool is thus adjusted, 
the carriage is moved to the dead-center end and the tail- 
stock adjusted so that the tool just touches the bar at this 
end. Instead of using a tool in the tool post, an indicator 
may be used. This will indicate how much the centers are 
out of line. After the centers are lined, the work being 
turned should be carefully calipered as the cut proceeds, to 
be sure that the "lining" was correctly done. 

55. Wear of the Tool. — Sometimes when the centers 
are correctly lined, the work may be slightly tapered, 
growing larger at the headstock end, owing to the wearing 
away of the point of the tool, thus making the work larger. 



ERRORS IN SCREW CUTTING. 

56. Errors Due to Imperfect Leadscrews. — The 

chances for error in cut screws in the lathe are numerous. 
The chief error is the inaccuracy of pitch due to an imperfect 






8" 



LATHE WORK. 



31 



leadscrew. The best remedy for this sort of error is to 
use a leadscrew that is known to be perfect within a given 
limit. All the lathes in a shop should be tested, and all 
particular screw cutting given to those that have the most 
perfect leadscrews. In cutting long screws, the work fre- 
quently becomes heated above the temperature of the lead- 
screw. The result is that the screw being cut will be short 
when cool. The remedy is to keep the work cool with 
plenty of oil or water. 

57. Cutting: Taper Threads. — In cutting taper 
threads, the taper attachment should be used. A true 




taper thread cannot be cut by setting over the center. If the 
point of a thread be followed around a screw, it will be 
found to follow in the line of a true curve. This curve, 
which is made by the sharp point of a V thread, is called a 
helix. If a thread should be so cut that, in following this 
curve, it would advance rapidly along the screw for a part 
*>' a turn, and slowly for another part of the turn, the rate of 
advance not being uniform, then the thread would not be 
a true thread, but would be known as a drunken thread. 

58. Suppose that it is desired to cut a very blunt taper 
by setting over the center, as shown in Fig. 21. Let Fig. 22 
represent an end view of the same piece, with the tailstock 



32 



LATHE WORK. 



§* 




Fig. 22. 



removed and the work still in position. Suppose the line A B 
be drawn through the axis of the work and through the 

lathe dog, as shown. It will be no- 
ticed that the notch in the face plate 
is slightly behind its perpendicular 
position. This is due to the angu- 
larity of the tail of the dog, caused by 
setting over the dead center. This 
angularity may be more clearly seen 
by reference to Fig. 21. Suppose we 
wish to give the work a quarter of a 
turn. As the work and the machine 
revolve, the tail of the dog slides into 
the notch of the face plate until it is 
directly at the front of the lathe in 
a horizontal position. At the end of the next quarter of a 
turn of the work, when the line A B is inverted, as shown 
in Fig. 23, it will be seen that the notch in the face plate 
has passed beyond the lower quarter point. After the next 
hajf turn, the work would be in the position shown in Fig. 22. 
It will be seen that during the first half turn of the work, the 
lathe or face plate made considerably more than half a turn, 
passing through the angle a b c f 
Fig. 23. During the second half turn 
of the work, the face plate did not 
make a complete half turn, as it only 
passed through the angle c d a. 
This shows that the work did not 
revolve at a uniform rate of speed 
with the lathe. While the lathe re- 
volved at a uniform speed, the work 
first dragged behind and then accel- 
erated until at the end of the revo- 
lution they were again together. 
The feed, however, would be mov- 
ing the tool along at a uniform rate of speed. When this 
sort of action takes place in screw cutting, the screw cannot 
be of uniform pitch, but will be a drunken pitch. 




Pig. ft 



§ 6 LATHE WORK. 33 



FITTING CYLINDRICAL WORK. 



KINDS OF FITS AND THEIR USES. 

59, Meaning of the Term Fit. — The expression 
making a fit" may convey a number of meanings to the 
workman. It may mean that when two pieces are put 
together they will be free to slide over each other, or that 
they will be locked together. That which would be called a 
good fit in one instance would be a bad fit in another. 

60. Kinds of Fits. — In ordinary machine construc- 
tion, there are four kinds of fits commonly used. They are : 
(1) working or sliding fit; (2) driving fit; (3) force fit; (4) shrink 
fit- The first is used for parts that work or slide upon one 
bother, such as shafts, spindles, etc. The last three are used 
when the parts are put together with the intention of their 
remaining in a fixed position. 



SLIDING FITS. 

61. Requirements for a Good Sliding: Fit.— The 

most nearly perfect sliding or working cylindrical fits are 

those whose surfaces most nearly approach perfect cylinders. 

There must be sufficient difference in diameter to allow the 

shaft to revolve freely and to admit oil for lubricating. If 

the shaft and bearing were exactly the same diameter, the 

shaft might be turned in the bearing so long as it was kept 

slightly in motion, but as soon as it stopped, it would be very 

difficult to start it again. With such perfect fits, the heat 

. that would be generated by the revolving shaft would cause 

it to expand so that it would be larger than the bearing, and 

this would change the sliding fit to a solid fit. 

62. Allowances in Sliding: Fits. — The closeness of 
the cylindrical fit depends on the diameter of the work, 
the length of hole, and the condition of the surfaces. 
Greater differences in diameter are allowed for large shafts 



34 LATHE WORK. § 8 

than for small ones. In some small machines, spindles 
about i inch in diameter will require not over .0005 inch 
difference in diameter, while a shaft 12 inches would require 
from .005 to .01 inch. 

63. Making Sliding Fits.— To make a good fit, the 
surface should be smooth and true. If the hole or bearing 
is finished by boring, the tool should be made to take a very 
smooth cut. If there is any danger that the work is sprung 
from the chucking, the pressure should be relieved as much 
as possible before taking the finishing cut. The work 
should be tested to determine if it is round and the sides 
parallel. Whenever it is possible to finish holes by reaming, 
it is best to do so. Reaming tends to make the holes a 
standard size and to make the walls of the holes smooth and 
parallel. When a working fit is being made, it is best to 
finish the beaiing first, as it is easier to fit the shaft to the 
hole than to bore the hole to fit the shaft. When gauges 
are at hand, the "cut-and-try " method is done away with, 
since the holes are all reamed to pass the limit gauge and 
the shaft also is turned within limits, so that the pieces will 
fit each other with sufficient accuracy. 

64. Standard or limit gauges are not always used, 
especially when but a few pieces of a size are to be fitted. 

In this case, the hole that has 
been finished must act as the 
gauge for the shaft. The close- 
ness of the fit depends greatly, 
as before stated, on the smooth- 
ness of the surfaces. Suppose the 
bearing has been reamed, but the 
shaft finished with an ordinary 
finishing cut, and the shaft just 
slides easily into the bearing. A 
Flo -* t section through the work showing 

the conditions of the fit is shown in Fig. 24. Here the bear- 
ing touches only upon the points of the tool marks, which 
are shown in somewhat exaggerated form in the figure. It 




M 



LATHE WORK. 



.;;, 



may be seen that if such a fit were allowed to pass, it could 
not wear long, since the pressure would come on the points 
of the tool marks, causing them to wear away rapidly. 
Furthermore, because of the spiral threads or tool marks 
around the work, it would be difficult to keep the bearing 
lubricated, the spiral thread tending to drive the oil out of 
one end or the other of the bearing, depending on the direc- 
tum of the rotation of the shaft. Because of a lack of oil 
and the narrow bearing points, such a fit would soon wear 
loose. 

This same wearing action would take place if the shaft 
were smooth and true, but the bore left with clearly denned 
tool marks. 

65. To make the fit as it should be, the shaft should be 
turned with a smooth cut to such a diameter that it would 
not unite enter the hole because of the projecting tool marks. 
These tool marks should be carefully removed by filing or 
by grinding. The best class of work is now being finished 
on grinding machines, since this method finishes the work 
smooth and true and in less time than it can be done by filing. 
When, however, it is necessary to fit by filing, care should 
be taken that it is evenly done. If the turning is correctly 
done, it will need only a few strokes of the file to remove the 
desired amount. The less filing necessary after the tool 
marks arc removed, the better the chances for a good fit. 



DRIVING FITS. 

66. Meaning of tlie Term Driving Fit. — In a dri- 
ving fit the plug or shaft is made slightly larger than the 
enveloping piece, and they are put together by driving. This 
method is used when the two pieces are intended to keep a 
fixed position In relation to each other. 

67. Allowances for Driving Fltn. — The allowance 
i.ig, which is the difference in diameter, depends on 

the diameter of the work, the lengths of the holes, the con- 
dition of the surfaces, and the strength of the enveloping 



'. 



36 LATHE WORK. §6 

piece. If the holes are long, less difference in diameter is 
required than when the holes are short. When the hole 
and the shaft are each finished smooth, a very slight differ- 
ence in diameter makes a great difference in the closeness of 
fit. If the surfaces are rough, a much greater difference in 
diameter is allowable. When the surfaces are smooth, a dif- 
ference of from .0005 to .001 inch will make a very tight fit 
on work about 1 inch in diameter, while for such a fit as 
shown in Fig. 24, where the surfaces are rough, a difference 
of .002 or. 003 inch will be necessary. When these rough 
pieces are put together, the roughness of the faces is worn 
down as they are driven over each other, so that, if they 
should be driven apart, the surfaces would be found to be 
much smoother than before. 

68* Making a Driving Fit. — When putting pieces 
together with a driving fit, the surfaces should be oiled. 
The piece into which the shaft is to be driven should be 
set upon a firm foundation and the shaft driven to place with 
a hammer or sledge. Care should be taken not to bruise the 
work when driving it; consequently, a block of wood or lead 
is used to strike upon. Sometimes the work is of such shape 
and in such a position that a ram can be rigged for driving 
the pieces together. This consists of a beam supported from 
above by ropes or chains so that it hangs in a horizontal 
position, level with the work. The beam is drawn back and 
then pushed forwards so that its end strikes against the work. 
This makes a very effective way of driving. If the work is 
large and the fit is very close, the driving may be helped by 
using clamps and bolts, which can be arranged to assist in 
drawing or forcing the pieces together. With the combined 
forces of the bolts and the ram, the shaft can be driven to 
place. 

FORCED PITS. 

69. Use of Forced Fits. — When the work is large, and 
there is a large amount to be done, the pieces are forced 
together by hydrostatic pressure. When fits are prepared 



§6 LATHE WORK. 37 

to be put together in this way, they are called forced fits. 

This method of putting pieces together is used for putting 
engine cranks on shafts, or for putting crankpins in the 
cranks, and for a great variety of similar work. It is prob- 
ably used more extensively for putting the wheels on car 
axles than for any other purpose. 

70. Allowances for Forced Fits. — The allowance 
for forced fits is a little more than for driving fits. The 
amount, however, depends on the materials used, the size of 
the hole, its length, and the condition of the surfaces. It is 
the practice of some engine builders, who put the cranks and 
crankpins together with forced fits, to allow about .0025 inch 
difference for each inch in diameter. This requires a pres- 
sure of from 10 to 13 tons per inch in diameter, depending 
on the length of the hole, to force the pieces together. This 
pressure is estimated for diameters that range from 3 to 8 
inches. 

In fitting car wheels and axles, they are required to go 
together within the limits of certain pressures. One rail- 
road company requires that, for certain classes of wheels, 
the pressure required to force the wheel on to the axle shall 
n °t be less than 25 tons nor over 35 tons. On an axle 7 inches 
l° n g and 4J- inches in diameter, an allowance of about 
.007 inch is made. This requires a pressure of about 30 tons 
to press the wheel on. 

71. Making a Forced Fit. — Considerable skill is 
required by the workmen to make these fits, yet, after a 
little practice, they do it rapidly and can tell within a few 
tons the exact pressure that will be required to force the 
wheel into place. In calipering the axles, the exact differ- 
ence is not always measured by the workman. He may use 
a snap gauge that has been made sufficiently large to allow 
for the fit; or, if calipers are used, he may set them the 
correct size and test the work so that a certain pressure is 
required to force them over the work, experience having 
taught him how great this pressure should be. 



38 LATHE WORK. § 6 

SHRINK FITS. 

72. Meaning: of the Term Shrink Fit. — A shrink 
fit refers more particularly to the method of putting the parts 
together than to the fit itself. The pieces are prepared in 
much the same way as for the forced fit. When the pieces 
are put together, the outer piece is heated, which expands 
the hole sufficiently to let the plug drop in. When the outer 
piece again cools, it contracts sufficiently to grip the pin with 
great force. 

73. Use of Shrink Pits. — When the pieces are large 
and strong and of certain shapes, pressure may be used for 
putting them together without danger of bending or dis- 
torting them. On other classes of work there is no chance 
to drive or force the pieces together; for example, putting 
the tires on locomotive wheels. For such large diameters, 
the difference of diameter in the fit would be so great that it 
would be difficult to start the tire on the wheel and very 
fxnverful presses would be required. By heating the tire, it 
expands sufficiently to let it drop over the wheel center with 
l>crfeet freedom. Shrink fits are very often employed on 
small work in shops that have no press to put forced fits 
together. 

74. Allowance for Shrink Fits. — The amount of 
allowance for shrink fits is generally a little more than for 
forced fits. A fair rule for small work in making shrink fits 
is to allow about .003 inch for the first inch in diameter and 
to add .001 inch for each extra inch. The amount allowed 
for locomotive drivers varies, depending on the si2e of the 
wheel and the service. Most locomotive builders allow 
from too to sV inch to the foot in diameter. 

75. Assembling Shrink Fits. — In making a shrink 
fit, the piece that has been bored is heated slightly ur\A 
evenly. Ordinarily, a heat just sufficient to show a dul\ tw\ 
is more than is required. Care should be taken th-** v 
piece is never hot enough to scale. The diameters u 
previously be tested so that there will be no dai\g^ T ^oval 
pieces will not go together when one is heated. |* . ^ tX 



LATHE WORK. oS 

allowance has been made, the pieces sometimes catch before 

the shaft is quite through to the desired place. Unless it is 

. removed, it will bind so that it will be impossible 

to move it either way. This is because the shaft begins to 

expand as s n as it enters the bored piece, and if the differ- 

■ hameter is slight at first, it will be very quickly 
made up by the rapid expansion of the shaft. Thus, it may 
be seen that great speed is necessary in putting the pieces 
together when shrink fits are used. This is especially true 
on small work. When the pieces are larger, such haste 
is not important. 

In shrinking smaller pieces, as soon as the plug is in place, 
water should be applied to keep it cool. The enveloping 
too suddenly or it is liable in crack, 
especially if it be cast iron. If a gear-wheel is being shrunk 
on a shaft and too much water is applied to the shaft and 
the hub of the wheel, there is danger that some of the arms 
will crack. If a cast-iron disk is being shrunk on a shaft 
and the circumference of the disk be rapidly cooled, there 
is danger that a radial crack will appear at the edge. 

76. Building Up Large (iuna. — There is probably 
if making shrink fits than that illustrated 
in the building of the large guns now constructed for the 
army and navy. These guns are built up. or made of a 
number of pieces. The first part is a long tubular piece the 
l c ni- Over this tube is fitted and shrunk a 

n U tT» her of bands or hoops called jackets, and over these is 
fin «^<J another set of hoops. Great skill is required in turn- 
ing- the jackets and the tube so that when the jackets are 
shrunk on, they will exert a certain amount of compressive 
force. This compressive force varies along the length of 
:he tube. A corresponding difference or allowance in the 
fit must be made to give the various pressures desired. The 
average allowance is from .0013 to .0015 inch per foot. It 
may h? spen that great skill is required to bore and turn 
liies^ pieces to the correct size, as a difference of from .001 
to .O02 inch may be sufficient to cause rejection. 



40 



LATHE WORK. 



When ihe jackets or hoops arc put on a gun tut 
first heated by wood or gas fires. When sufficiently hot, tl 
arc dropped over the tube standing on end in a pit. 
gOOti as the jacket is in of water arc tun 

on the tube to keep it cool and to cool the 1 



LATHE ARBORS, OH MANDRELS. 

SOLID ARBORS. 

77. Meanlnjr, of the Term-. Arlmr ;tm1 | 
A lathe nrlmr i- l sh.i: 

turning the outside of bored ptecee by driving the arU. 
into the bored hole I revolving il betwei a thi 

ters. 

The term mun.lrcl isvi ry com 
article, 1 1 nt is also used for designal ing a pie< e or foi 
which the blacksmith forges a ring, lube, or collar, ■ 

or .'i'.\ imilar material i ■ 
terra arbor nevi i 

mandrtt is also used to designate the suppi 
saw or milling cutter 

78. Shape or Form of Soli. I Arlmrs. - Vrhomir 
commonly used on work havin 

■ li, ill 

forms are th< Bolid <<■■* < 
made : 
pio.«. hardem ■ 

Such an arbor is shown in Fig. 25. These 
slightly under sise at the ends, i"i" the 

i,,: put nn. The center hoi 
be carefully made so that they will not l>e 
injured by driving. Pig 

>ogh tin- end of a properly foi m.-d 
center hole in a lathe arbor. It will be 
noticed that the edges oi I lie i 
are well rounded. This form is given to 



._- 



LATHE WORK. 

the center hole so that if the arbor is bruised on the end 
when driving, or from any other cause, there will not be so 
much danger of the center hole being destroyed. If the end 
of the arbor were flat and it should be bruised near the cen- 
ter hole, a slight bump would be raised on one side of the 
hole that would he sufficient to throw the arbor slightly out 
of line. To further preserve the center holes, the arbor is 
hardened. These center holes should be made with great 
care, the angle being 60°, so that they will exactly fit the 
lathe center. In the best made arbors, the center holes are 
ground true after hardening. The centra! portion of the 
arbor is carefully ground to size, being made slightly tapered. 

79. The small end of the arbor is generally about the 
, while the large end is from .002 to .003 inch 
rger, depending on the length of the arbor and the length 
the work to be turned. The large end is distinguished by 
e size of arbor being stamped upon it. These arbors are 
■ound to standard sizes and should fit holes reamed with 
andard reamers. The necessity of keeping them true may 
iadily be seen when a pulley or similar piece is to be turned 
■ut with a part chat has been bored and reamed. It is 
irident tliat if the arbor is untrue, the hole will run untrue 
the work revolves. The rim or part of the work being 
Tied will be cut true with the machine, but will not be 
the bun.-. When the finished pulley is placed on 
true, the rim of the wheel will wabble. It 
n that an untrue arbor will always produce un- 
nd lead to a great deal of trouble. 
\iku- may become untrue from the wear of the center 
from their being sprung when driven into the 
v taking too heavy a cut on the work for which 
ry arc used 

*0. Cure of Centers of Arbors. — Care should be 
he dead center when the arbor is being used, to 

nd to see that the arbor does not expand 
■use ■■! heal sufficiently to make- it grip on the dead 
ter. When there is dangerof spoiling both arbor center 



42 



LATHE WORK. 



§6 



and lathe center, a bronze dead center may be used. The 
bronze is soft enough so that if the arbor becomes dry it 
will simply wear away the bronze without injury to itself. 
For certain classes of work, the accuracy of which would not 
be affected by having the dead center moved slightly during 
the cut, these bronze centers are very good, but, for the 
general run of work, it is better to employ steel centers and 
see that they are well lubricated and not set up too 
closely. 

81* Putting Arbors in the Work. — When an arbor is 
put in a piece of work, it is usually driven in. The hole and 
the arbor are coated with oil, to keep the surfaces from cut- 
ting, and, while the work is well supported upon the driving 
block, the arbor is driven in with a soft-faced mallet or 

hammer. Hard-faced ham- 
mers should never be used 
for driving arbors. Babbitt 
or rawhide-faced hammers 
are the best. If the work is 
small, much driving is not 
necessary. Judgment 
should be used, as it will be 
found that, if the pieces fit 
well, it will take but little 
pressure to force the arbor 
into the work sufficiently to 
keep it from slipping. The 
practice of some workmen 
of driving an arbor as long 
as it can be moved is bad. 
When driving arbors, care 
should be taken to strike 
fair blows on the end, as 
untrue blows are liable to 
spring it. 

82. A far better way of 
putting arbors in the work 




44 LATHE WORK. §6 

cast iron. The ends of such an arbor are drilled and steel 
plugs fitted for the center holes. These plugs are hardened 
after the center holes are correctly made and driven or 
screwed into the cast-iron arbor. When cast-iron boring 
bars are made, it is better to use hardened-steel center plugs. 



EXPANDING MANDRELS. 

86* Advantages of Expanding Mandrels. — While 
the hardened solid steel arbor is the best form, there are 
inconveniences that arise from its exclusive use. In order 
to be prepared for all sizes of work, a very large stock of 
arbors would be necessary. This leads to inconvenience in 
some shops, while in other shops it is beneficial. Shops 
doing a great variety of work where all sizes of holes are 
bored, demand an arbor or mandrel that can be adjusted to 
slight differences of diameter. Shops that are making a par- 
ticular line of work where many pieces are turned to the 
same size are benefited by using the solid arbor; firsts 
because it is more accurate in itself; and, second^ it acts as 
a second check-gauge on the work. If a piece that has been 
bored too large gets into the lot, it cannot be finished, since 
the arbor will not hold the work. When the cost of keeping 
a lot of arbors up to a standard size is considered, the type of 
arbor that will expand within certain limits and fit all sizes 
of holes within these limits is much cheaper than a great 
stock of solid arbors. 

87. Types of Expanding Mandrels. — A number of 
types of expanding mandrels are on the market. Fig. 28 




Pig ». 



shows one type of expanding mandrel. It consists of a 
tapered arbor a, which tits into a tapered split bushing b. 
The bushings are ground round and parallel on the outside. 



§6 LATHE WORK. 45 

As the tapered mandrel is driven into the work and the 
bushing, the latter expands, thus filling the hole. The 
method of splitting the bushing as here shown allows it 
to spring and expand evenly within quite a wide range of 
limits. 

88. Another form of expanding mandrel is shown in 
Fig. 29. This consists of a steel arbor that has been cen- 
tered with the same care found necessary in solid arbors. 




Pig. 29. 

Pour rectangular grooves are cut along its sides, these 
grooves being cut deeper at one end than at the other. A 
sleeve j fits nicely over the arbor. This sleeve has slots cut 
in its sides, which come opposite the grooves cut in the arbor. 
A hardened-steel jaw is fitted into each groove and slot. As 
the sleeve moves along the arbor, it carries the jaws with 
it, and, because of the varying depths of the slots, the jaws 
are moved in or out, depending on the direction the sleeve 
is moving upon the arbor. With this type of mandrel, dif- 
ferent sets of jaws of different heights may be used, which 
W M give it a range for different sizes of holes. When the 
W( >rk is thick enough to be stiff, so that it cannot be sprung, 
these mandrels are very convenient, but if the work on the 
mandrel is slender, there is danger of springing it, due to 
the outward pressure of the four jaws. 

89. Cone Arbora. — For some classes of work, a cone 
mandrel, as shown in Fig. 30, is used. This consists of the 
arbor part a, to which are fitted two cone-shaped pieces c. 
One piece is held from sliding along the arbor by the 
shoulder s. The work is placed between the cones, and the 



46 



LATHE WORK. 



§6 



second cone tightened against the work w by the nut d. 
The cones are kept from turning on the arbor by keys. This 




W/////A 



PlO. 80. 



is a very convenient way of holding work to be turned that 
does not require great accuracy. 

90. Special Expanding Arbor. — Fig. 31 shows 
another form of arbor for carrying bored or cored work that 
is being turned and faced. A heavy bar is drilled and 
tapped so that screws may be put in around the bar, as shown 





FlO. 81. 



at s, s. The circles around the bar in which the screws arc 
placed are at such a point that the screws come near each 
end of the work. The work is adjusted and held in place by 



LATHE WORE. 47 

ng the screws from the bar, thus bringing the 
pressure on the heads of the screws. 

91. itridjrcM in Castings. — When heavy cast work 
has a tapered cored 
hole that would make 
it difficult to use the 
arbors just described, 
it is very good practice 
to cast a bridge across 
the end in which the 
center hole may be 
placed. Such a bridge 
is shown at b, Fig. 32. 
A similar bridge should 
■ be cast at the other end 
of the work. After the turning is done, these bridges can 
easily be broken out if so desired. 







NUT ARBORS. 

92. After a nut is tapped, it is still further finished by 
facing so that it will be true with the thread. This facing 
is usually done by screwing the nut on an arbor that has 
been threaded up to a shoulder. Such an arbor is shown in 
a section in Fig. 33 with the nut 

in place. It will be seen that 
if the nut has not been tapped 
cl—j squarely and that if it fits 

x C loosely on the arbor, it will first 

come against the shoulder at 
the point ti. As soon as this 
point touches, the nut will be 
rocked on the thread so that 
he axis of the nut thread will not be parallel to the axis 
f the arbor. If the nut should be faced while in this posi- 
ion, the face would not be true with the tapped thread. 




LATHE WORK. 



B« 



93. To overcome this difficulty, some sort of equalizing 
washer must be put between the shoulder of the arbor and 
the nut, so that the nut cannot be thrown out of line, but 
will be held back squarely against the threads. Such a 
device is shown in section by Fig. 34. The shoulder of the 
arbor is rounded to a spherical shape, while the equalizing 
washer is concaved to fit the round end of the arbor. This 
makes a joint similar to a ball-and-socket joint. When the 




nut n is screwed against the washer w, and it bears heavier 
on one side than the other, the washer at once rocks on the 
rounded end of the arbor and adjusts itself to the face of the 
nut. Sometimes an equalizing washer, as shown in Fig. 35, 
is used. The shoulder of the arbor in this case is squared. 
On one face of the washer are two projecting points a, a 
diametrically opposite each other. On the other face of 
the washer are two other points b, b diametrically opposite, 
but quartering with those on the first side. When the nut 
is screwed against the washer thus supported, it is free to 
rock in any direction, with the result that it centers itself 
with its threads and not with the face of the arbor. 



LATHE WORK. 







50 LATHE WORK (6 

EXAMPLES OF SPECIAL LATHE WORK. 

94. Bull Turning-— In order to turn balls in engine 
lathes, special appliances are necessary to regulate the f«d, 
Fig. 36 shows such an arrangement applied to turning a 
large cast-iron ball for an engine bearing 

ported on the lathe centers and drivi 
the face plate c. The ball j is made in sections, which lit 
clamped to the mandrel b by the iron bonds ■! I 
is revolved about a diameter, it will generate part of a 
This is practically the principle that is used in 
turning this ball, as the tool e moves in a circle around the 
work while the work rotates with its axis as a di.-i 
the circle in which the tool revolves. On the 
table /, the rotating circular table g is pivoted and carries 
with it. the upright /i that supports the tool post / and tool * 
At k, on the rotating table g, is a wrought -in in band that 
is fastened by capscrews at one end to the tabl 
other end is fastened to the lathe < \ 
turns the carriage is fed away from the ta.il 

.<■ lathe, drawing with it the band k and thui 
the table g about its axis. As the work rotates in ■ 
the tool moves around it in a circular arc. so thai il 

i distance from the point on the axis that is the center 
of the sphere. 

On smaller work, a method similar to this is used, but the 
tool i carried on a table that ha- 
il and is rotated by a worm. The worm may be operated 
by hand or from the feed -mechanism of the lathe, 



a of hoid- 

. eranlcpim 



95. Turning a Crank-Shaft. One method 
ing a large crank-shaft in a lathe while tun:! 
is shown in Fig, 37 The crank-shaft c is so fastened that 
the center line of the crankpin J coincides with tli 
line of the lathe spindle. The damp b that holds one ( 
of the shaft is fastened to the fa< d the < 

that holds the other end of the ..haft has an offset 
into which the dead center i "I the lathe fits. The 

weight W is fastened to one side of the face plal.c to bal; 



it 



LATHE WORK. 



51 



the weight of the shaft. The crankpin d is turned while the 
shaft is held in the position shown. In order to center the 
shaft so as to turn the pin e, the end of the shaft next the 
tailstock must be blocked up, the clamp b loosened from 
the shaft, and the dead center removed from the clamp /. 




The sh.ift is then rotated till the center h on the damp J 
conies to the dead center, when the center is moved into h 
^'J the clamp b made fast to the shaft. The centers g and 
h on the clamp / hold the same relation to one another and 
35 do the center lines of the crankpins. When the 
*haft is fastened in this position it is ready for turning the 



96. Cams.— Cams are usually made on the milling 
machine, but they may sometimes be turned in a lathe. 
A templet is made with the same outline the cam is to have 
when finished, and fastened to the cam-blank. The screw 
in the cross-slide is removed so that the tool post is free to 
slide back and forth across the lathe saddle. A weight holds 
the tool against the work as it revolves with the templet. 
The tool is kept in the correct position by a stop, whieh 
slides oo the templet. This stop causes the tool post to 

T IB— in 



52 



LATHE WORK. 



§« 



slide in and out across the lathe carriage as the stop follows 
the outline of the templet. This process is not very rapid, 
but it will cut cams as accurate as the templet can be made. 

97. Laying Out Centers for Turning Crank- 
Shafts. — The process of locating and preparing the centers 
for a solid crank-shaft is illustrated by Fig. 38 (a) and (b). 



d 






I 








99 
e 










■ 


a 




e 


b 


/ 


f 


b 




t\ 



(a) 0» 

Pig. W. 

The crank-shaft a is centered and the ends turned to size 
for a short distance, to receive the centering blocks e % e 
and to fit the V blocks b, b. The shaft is then placed on 
V blocks b y b on a surface plate and the centering blocks e f e 
are fastened to the finished ends in line with the crank-arms. 
These centering blocks are bored out to a good fit on the 
turned ends of the shaft and are fastened, so that they 
cannot slip, by the setscrews d f d, or in some cases by keys. 
The shaft is then rotated until the center of the crankpin 
is the same distance above the surface plate as the center 
of the shaft and is blocked in this position. A horizontal 
line across the ends of the shaft through its center and 
across the arms c y e is then drawn with a surface guage. <t 
The center of the crankpin c is somewhere on this line and^ 
can be laid off with the scriber or a pair of dividers by 
taking a length equal to the distance from the center of the 
shaft to the center of the crank and laying it off from the 
center of the shaft. When the centers are located on both 
ends, they are drilled and countersunk. The shaft is then 
ready for the lathe and all the lathe work can be completed 
both on the shaft itself, on the crankpin, and on the crank- 
arms. The shaft is turned and the sides /, f of the crank- 
arms are faced when the work is on the centers in the ends 






5» 



LATHE WORK. 



53 



of the shaft. It is then moved to the centers for the crank- 
pin c using the centering blocks e, e with the centers laid 
off on them and is turned and the sides g, g of the crank- 
arms are faced. If the crank-arms are circular disks, they 
may be turned on the outside with a center midway between 
the other two centers. 




98. Turning Ovals. — In turning circular work in the 
lathe, the distance between the center of the work and the 
point of the tool remains 
constant. By referring to 
Fig. 39, it will be seen that 
if abed represents a circle 
with the center at o, and that 
if the tool were located at a, 
that as the work revolved 
uid b approached a, so long 
as the distance from the 
center o remained constant 
the work would be turned to 
a circular form, but if by 
any means the center o ™" ""■ 

could be made to approach the point a as the work revolved 
during one quarter of a revolution and recede from it during 
the next quarter, advance during the third quarter and 
recede during the fourth quarter, it would be possible to 
turn an oval. For instance, if while the portion of the 
work from a to b were passing the tool at a the center of the 
work o could be moved toward the circumference a distance 
equal to be, the tool would cut along the curve ae of the 
ellipse aecf. This is accomplished in a chuck for turning 
ovals by arranging a slide across the face plate and so 
adjusting the parts that it will move the work in or out 
across the face plate so as to produce the desired oval. 

An attachment for turning ovals is illustrated in Fig. 40, 
where it is shown attached to an ordinary lathe headstork. 
The work is secured to the plate a, or held in the chink 
upon a threaded spindle b. Back of the plate a there 




54 LATHE WORK. §6 

two slides at right angles to each other. These are shown at 
c and e. The disk d has a long projection that reaches 
through and is attached to the regular lathe spindle of the 
headstock. The disk d acts as a driver for the plate a, the 
driving being done by means of the slide C. The slide e is 
secured by guides to the slide c. The slide e is also turned 
out on the side toward the headstock to receive a ring that 
is carried on the piece/. When the center of this ring is 
made to coincide with the center of the lathe spindle, the 
plate a and spindle b rotate as in an ordinary lathe; but if 
the piece f is moved across the lathe by means of the 




adjusting screws, one of which is shown at k, the ring 
attached to it will force the slide e to travel back and forth 
across the attachment as the work revolves, and this will 
cause the center of the plate a, and with it the work, to 
move back and forth, first away from and then toward the 
center of the lathe spindle proper. The result will be that 
an ellipse similar to that shown at aecf. Fig. 39, will be 
turned. The amount that the slide / is moved determines 
the amount of eccentricity of the ellipse; that is, the 
amount shown by the line b e, Fig. 39. The block g is 
bolted fast to the front of the headstock. In the form of 



§6 LATHE WORK. 55 

chuck shown the plate a is provided with a screw i y and 
worm-teeth are cut for a short distance at the top of the 
plate. By means of these worm-teeth and the screw i f the 
plate a can be adjusted slightly in relation to the mechanism 
operating it. This device will be found very useful in 
resetting work in the chuck, as it serves to bring the work 
into line with the ellipse generated by the mechanism. This 
form of device is very handy for turning elliptical dies and 
punches, such as are used by jewelers, silversmiths, electri- 
cal-instrument manufacturers, and others. 



LATHE WORK. 

(PART 0.) 

THE TURRET LATHE. 

\ m Characteristic Feature of tbe Turret Lathe. — 
Probably no one machine deserves greater credit for helping 
along the movement toward rapid production, and, conse- 
quently, the reduction of cost of manufactured articles, 
than the turret lathe. Its characteristic feature is found 
in the turret, which is made to bring, in quick succession, a 
number and variety of cutting tools to act on a bar or rod 
passed through the hollow spindle in the headstock and 
held in a chuck. 

2. Action of the Turret. — The turret is mounted on 
a slide, parallel to the line of the live spindle, and occupies 
a position relatively the same as the tailstock on the ordi- 
nary lathe. It is made to slide upon the base either auto- 
matically or by a hand lever or wheel. After the tool, which 
is held in one of the radial holes in the turret, has made a 
certain cut upon the work, the turret is moved back, and, by 
an automatic arrangement, it is undamped and made to rotate 
a part of a turn upon a vertical axis. This partial rotation 
brings the second tool in the turret in line with the work. 
Each full backward movement of the turret causes it to re- 
volve a part of a turn, sufficient to bring the second tool in 
perfect line for the second cut. 

%t 

for notice of copyright, nee page Immediately following the title page. 






•I 



I? 



LATHE WORK. 



3. Various Type* of Turret l.;it lies. — This style of 
turret has been applied to a variety of lathes for various 
kinds of work, so that we have, under ihe head of turret 
lathes, the turret screw machine, plain turret lathe, brass- 
Little, and monitor lathe. Besides these there are 
some other special forms of turret lathes that are adapted 
to certain classes of work. In the screw-machine class are 
the hand and automatic machines. 



HAND SCREW MACHINE. 



4. Character lstics of the Screw Machine. — The 
band screw machine more nearly embodies all the 
[eristics of turret lathes than any other type. Fig. 1 
represents a typical turret screw machine. Its character- 
istic features are, the turret moving on a slide that takes the , 
place of tailstock. a special form of chuck for gripping rods, 
and the rod-feed mechanism The arrangements for supply- 
ing oil to the cutting tools, and for feeding the work into 
position are important features of the screw machine. 

Names of Parts of Serin Machine. — In this 
, Fig. 1, the parts are named as indicated by the fol- 
lowing letters: a, the turret; />, the pilot wheel for moving 
the turret; .-. the stop serew for adjusting the Havel of the 
turret slide; a", a special chuck for holding the rod, or stock; 
, the lever for opening ami closing the chuck d, and for 
eding the rod into the machine; /, supports for holding 
■ng rods; g, the front tool post; h, the back tool post; 
-s-slide; k, the handle for operating the cross-slide; 
'. the distributing pipe for oil; m, the oil tank; w, the clutch 
operating the chuck. 

i. The Screw-Machine Chuck.— The success of the 

•w machine is due largely to the method employed in 

holding tiir vviik; [his method ^ives great rigidity, and at 

time is so simple that the work can be quickly 

clamped or released. 




i 



-A 



of the fid is accomplished by pushing the split collet 
through the tapered hole in the end of the cap b, the 
being screwed to the nose of the lathe spindle. Fig. 

^ shows the collet a removed. 
The collets are made of various 
sizes, depending on the size of 
the rod to be held, and are 
hardened, as is also the cap in 
no. t which they slide. 

7. When gripping the work, the collet is pushed into 
the cap b by means of the hollow tube d, which \ 




through the lathe spindle to the rear end. Pig. 4 shows a 
MCtlofl through the rear end of the spindle and the gripping 



' 



LATHE WORK. 






mechanism. The end of the tube d comes against the two 
levers /, /. These levers are operated by the cone-shaped 
piece in, which slides on the spindle. When m is moved to 
tlit: position indicated, the ends of the levers are forced apart, 
which moves their other ends against the end of the tube d. 
This operation pushes the tube through the spindle and 
against the collet, thus causing it to grip the work. When 
the cone m is moved back, the long ends of the levers spring 
together and relieve the pressure on the end of the tube d. 
Springs are arranged to open the chuck as soon as the cone m 
is removed from under the levers /, /. In this description, 
only the essential points have been mentioned, all unneces- 

The work of the turret screw machine is confined to a class 
of work that can be made on the ends of rods held in the 
chuck. Turret lathes are, therefore, without centers for sup- 
porting the work. The work of the screw machine can be un- 
erstood by following the operations necessary to complete 
: particular piece. The tools used for the turret are 
lite different from those used in the ordinary engine 
a the. 

9. A Typical Piece of Work for Turret Screw 

luctiliies. — Suppose it is desired to make a large number 

ifh a round nurled head, 

ihovrn in Fig. 5. Having decided 

ion the screw to be made, the ma- 

hinc must be set up. 

1(>. Setting Cp the Turret F '° * 

iiuhltic. — This means .setting the various tools in a turret 
nd in the cross-slide, adjusting the stops to determine the 



WORK OP THE TURRET SCREW MACHINE. 



TUDRET TOOLS AND THEIK OSES. 

Class of Work Done on Turret Machines.- 



6 LATHE WORK. §7 

length of cuts, and adjusting the cutter blades to turn 
the correct diameters. A rod is put through the spindle, 
and the chuck is so arranged that the work can be gripped 
rigidly, and also so that when it is released, the feed will 
move the rod through the spindle. 

11. The Stop. — The first tool in the turret to be used 
will be the adjustable stop gauge shown in Fig. 6. This 
stop is so adjusted that when the turret and slide are at the 

full length of their travel 

next the headstock, and 

the work is fed up to the 

stop and gripped in the 

chuck, the correct length 

to make the screw will 

project from the chuck. 

Having clamped the 

fig- •• work, the turret is moved 

back and revolved a part of a turn, which brings the first 

turning tool to place. This turning tool is known as a 

roughing box tool. 





) 



Fig. 7. 

12. Roughing Box Tool. — The roughing box tool 

is shown in Fig. 7. The shank s is held in the turret, 
and the tool, or blade, c is clamped in place by the screws 
a, a. The tool is adjusted to turn the correct diameter by 
a series of careful trials. To support the work while the 
cut is being taken, the back rest r, opposite the tool c, must 




§7 LATHE WORK. 7 

be adjusted so that it just supports the end of the work. 

Fig. 8 shows an end view of the box tool with a section of 

work w in place. This shows how the tool, or blade, c comes 

against the work, and how 

the back rest supports it. 

Turret lathe tools do not 

need so much keenness as 

those on ordinary lathes. 

With this tool, a cut is 

taken over the stem of the 

screw up to the shoulder 
under the head. If the 
bar is iron or steel, a sup- 
ply of lard oil is kept run- 
ning on the work, to keep Fl °- 8 - 
it and the tool blade from heating. When this roughing 
tool has cut a sufficient length, the turret slide comes against 
a stop. This stop is so adjusted that each tool will stop 
when the desired length has been turned. The turret is 
given another partial turn, which brings the second cutting 
tool in line for the cut. This tool is known as the finishing 
box tool. 

1 3. Finishing Box Tool. — The finishing box tool 

acts on the same principle as the roughing box tool, except 
that the blades are made and adjusted to cut similar to a 
broad-nosed lathe tool. The blade for the rough cut is 
ground on the same principle as the roughing tools for lathe 
work. Fig. 9 shows a finishing box tool. This will be seen 
to carry a number of cutters, each of which may be ad- 
justed to cut a given depth by the setscrews a at the end 
of the blades. These blades are used when it is desired to 
finish parts to different diameters at the same time. Each 
blade is so adjusted along the length of the box tool that it 
will turn the desired length of work to that particular 
diameter. For the screw being made, only the first blade in 
the tool will be used. This will be adjusted to finish the 
stem of the screw to the correct diameter. Before cutting 



8 LATHE WORK. §7 

the thread, the end of the stem should be beveled or cham- 
fered. This is done with a pointing tool. 




14. Polntlna Tool. — The pointing tool is similai 

to the roughing box tool shown in Fig. 7. The blade. ! 
ever, instead of being straight on the edge, is beveled to aa 
angle, the same as the desired bevel on the end of the screw. 
The back rest is adjusted on a pointing tool the uune aa 
on other box tools. When brought to the end of the work, 
this tool will cut the desired bevel. 

15. Dies and Die Holders. — The screw is now ready 
to be threaded. On al! the screw machines the threads are 
cut with dies. In order that the threads will be cut an 
exact length on the stem of each screw, a special die holder 
must be used. 

A die holder is shown in Fig. 10. The die holder a lias 
a circular opening into which the dies are fastened by the 
screws .-. The stem 
d passes through ;. 
sleeve, this sleeve 
having a flange or» 
l. The sleeve 
is held in one of 
the holes in the tur- 
; the illustration, 1 




the position show 



§7 LATHE WORK. 9 

holder is free to revolve in the sleeve. When it is used 
and the die pressed against the work, the holder slips back 
in the sleeve until the pins b and c slip by the side of each 
other. Pin c will then keep the die holder from revolving. 
As soon as the holder ceases to revolve, the die will begin 
to cut, and, after cutting a few threads, it will continue to 
screw and feed itself along the work. If provision were 
not made to stop it as the lathe continued to revolve, the 
die would at once screw up to the shoulder on the work and 
destroy the thread. With the holder shown, the die will 
feed upon the work, the turret being made to follow it, until 
the turret slide reaches its stop. The work, however, con- 
tinuing to revolve, will feed the die still farther, and bring 
the holder with it until the pins b and c disengage, where- 
upon the holder again revolves with the work, thus stopping 
the cut. In the meantime, the direction of the lathe is re- 
versed and the turret moved back by hand until the pin / 
engages the notch cut in the end of the sleeve. This 
keeps the holder from turning backwards and so the die is 
backed off the screw. When considerable uniformity of 
size of threads is desired, a second sizing die is run over the 
thread. These operations complete the turret operations 
on the screw. 



CROSS-8L.IDB TOOLS. 

1 6. Nurling Tool. — When the head of a screw is to 
be our led, as in the present case, it is done by pressing 
hardened-steel rollers against the face of the work while it 
revolves. These hardened-steel rollers have teeth, or 
special forms, engraved around their outside, so that when 
pressed against the work they will form the soft metal into 
the desired shape. In the case in hand, the nurling tool 
shown in Fig. 11 is employed and will be described more 
fully later. Nurling tools are held in one of the tool posts 
on the cross-slide. 



LATHE WORK. 



[I 



1 7. Parting Tnol. — The parting tools used in the 
turret lathe are very similar to those used in a regular lathe, 
and are held in one of the tool posts on the cross-slide. 
Combination parting and forming tools are sometimes em- 
ployed. They are intended to round the head and cut off 
the stock .it the same time. 

1 8. Combination of Parting and Nurling Tool — 

Fig. 11 shows a special nurling tool held in the tool post. 




together with a parting tool. The parting tool is clampod 
under the nurling tool, with its blade shown at li. The nurl- 
ing tool is jointed, so that when the parting tool is used, 
the nurl a may be lifted up to the position shown by the 
dotted lines. While the screw is being made, the nurl should 
be turned back and the parting tool used to cut ,. 
notch in the work, which will define the thickni 
head. If the head must he made true, .l light i ;;'■ 
be taken with a back tool held in the bai I; too) |»^st. This 
back t"nl should be shaped the same .is .l broad-no 
tool and set in the tool post upside down, 
on the back of the work when the lalhc is running foi w:w<k 
The stop on the cross-slide should be so ail justed that the 
tool will just cut the head to the desired diameter. The 
nurling tool may then be brought against the work 
pressure of the hand lever, forced against the work until the 



§* 



LATHE WORK. 



11 



teeth in the nurl roll press corresponding grooves in the head 
of the screw. When the work has been properly nurled, the 
parting tool is again brought to place and the screw cut from 
the bar. 

When the parting tool is sharp and working well, it should 
leave the head of the screw bright and smooth, without 
any projection in the center. The parting tool, therefore, 
must be so set that its edge comes exactly in line with the 
axis of the work. If the parting tool is ground square across 



■_ - 

iMiiiniiiinp 

r 



<2> 



Flo. 12. 

its cutting edge, the work will break off before the cut is 
quite finished. This may be avoided by grinding the cut- 
ting edge of ti* e parting tool beveled, as shown in Fig. 12. 
Here it cuts a smaller diameter near the head, and, when the 
work breaks off, it will break at this small diameter. 

19. The operation of making a screw just described is 
but one of a very great variety that may be performed on 
the screw machine. While certain tools were chosen to per- 
form this operation, there are other forms of tools that could 
have been used with the same result. 

TIB— 17 



LATHE WORK. 



I» 



OTHER FORMS OF TURRET TOOLS. 

Solid Hollow Mills. — In place of the roughing 



20. 

box tool, a hollow mill could have been used. Fig. 13 
shows a solid hollow mill, and Fig. 14 shows a holder used 
for it. These mills cut on the edges a, a, and are bored to 
the size that they are intended to turn. As soon as the mill 




begins to cut, the end of the work at once enters it and is 
thereby steadied or supported while the cut is being taken. 
Because of the four cutters on opposite sides of the work, it 
is balanced so that there is less tendency for it to spring than 
when there is but one cutter acting. 



21. Adjustable Hollow Mills. — Fig. 15 shows an 
adjustable hollow mill. By loosening the screws at the 
front and turning the nurled head, the blades a, a can be 




moved toward or from the center, thus making the cut larj 
or smaller. The cutting action of this tool is the same as 



87 



LATHE WORK. 



■ 




that of the solid hollow mill. The cut is taken on the 
end face of the cutter blades, the inner faces acting as guides 
to support the work after it is turned. It is always advi- 
sable to run a finishing box tool over the cut made with a 
hollow mill, since it cannot be depended on to be perfectly 
true. Finishing tools are made in a variety of shapes. 
Fig, If! shows a style of finishing hollow mill that has two 
inserted blades a, a, which do the cutting, while the other 
two blades b, b are simply back rests to steady the work. 

22. Spring Dies.- -Besides the solid dies mentioned, 
other forms are used. Fig. 17 shows a form of hollow 
spring die that is held in the 

holder shown in Fig. 10. When in 
use, this die would tend to spring, 
so that it is necessary to use a ' 
clamp, Fig. 18, that will pass 
around the die and hold it in 

I shape. By means of this clamp, 
the die may be adjusted to make 
slight differences in cutting. When such a form of die is 
employed, considerable time is lost in reversing the ma- 
chine and backing the die from the work. 

23. Automatic Dies. — To overcome the above diffi- 
culty, automatic dies are used, which act on a principle 

similar to that found in the automatic dies 
used on bolt cutters. The die passes over 
the work and cuts the thread, which, when 
completed, automatically opens tin* die and 
releases the work. Fig. 19 shows an excel- 
lent form of automatic die adapted particu- 
larly to turret screw machines. The die 
heads are made in a number of sizes, each 
head taking a variety of sizes of dies. In 
tin- Bgure, the dies if. ./ may be removed by 
taking out the screws s, s and different sizes put in their 
places. They may be set to cut any length of thread 




Fir. 13, 



LATHE WORK. 



8? 



within limits. When the desired length is cut, the die 

automatically opens. To 

close the die, the handle h 

is given a partial turn. 

This die may be adjusted to 

cut threads slightly above 

or below standard size by 

loosening the nut n at the 

back of the die holder and 

moving the pointer to one 

*»»-»• s ide or the other of the zero 

mark. By means of this adjustment, it is possible to cut 

threads as much as ^j inch over or under standard size. 




DRILLING AND TAPPING. 

24. Holding the Tools. — When operations require 
that drilling or tapping be done, the drills or taps are held 
in the turret in the same manner as the other tools. The 
drills may be held in a chuck provided for that purpose. 
When the taps are used, a special tap holder that works on 
the same principle as the special die holder, Fig. 10, is em- 
ployed. This is to keep the taps from running into the 
work too far and breaking. 

25. Many other shapes and kinds of tools may be used 
in the turret, Those that have been mentioned are the 
standard tools, and embody a general principle, which is, 
that the work must be supported while the blades are cut- 
ting. By following this principle, a great variety of shapes 
of tools may be designed and adapted to particular classes 
of work with advantage. 

OTHER FORMS OF CROSS-SLIDE TOOLS. 

26. Forged Forming Tools. — The tools used in the 
cross-slide perform various operations, the more impor- 
tant of which are the forming of irregular surfaces with 





LATHE WORK. 



18 




ning tools, and the cutting of the finished piece from 
he bar with the cutting-off tool. The forming tools may 

forged from bar steel, and filed or machined to the de- 
sired form. When so made, they are 
similar to the forged forming tools used 
in the engine lathe. Tin; main objec- 
tion to the forged forming tool is 
that only a limited amount of grinding 
can be done before the tool will change 
its shape. 

27. Circular Forming Tools. — 

This class of forming tools has been 
brought out both to overcome the ob- 
jections to the forged forming too! and wn.**. 
. account of the ease with which the cutters can be 
inufactured. Pig. 20 illustrates a typical tool of this 
class. Here a circular 
cutter c has been care- 
fully turned and 
formed so that when 
a section is taken out 
— D at its cutting edge, it 
will conform to the 
desired shape of the 
work. A notch is cut 
on one side of the cut- 
ter so that the lower 
face CD, Fig. 21, 
is in a plane that 
would pass slightly 
below the center of 
the cutter^ B. This 
amount A- varies «'ith 
>e diameter of the cutter On a 2-inch cutter, from ^ to J 
iffident. The holder A, Fig 20, is made of such 
at it holds the '.enter of the cutter above the center 
the work, thus bringing the face of the cutter CD, Fig. 21, 




16 



LATHE WORK. 



§7 




Pig. a. 



in line with the center of the work w. The object in cutting 
the notch in the cutter below its center and then raising it 
above the center of the work is to give the tool slight 

clearance. If the two 
circular pieces, the tool 
and the work, be set at 
the same height, Fig. 22, 
they will touch at the 
point O, which is in a 
line joining the cen- 
ters. If we draw a 
tangent to the work 
through the point O 
and another line tangent to the tool through the same 
point, we will find that the two tangents coincide in the 
line CD. When the tool is thus set, it does not have any 
clearance, and can cut only so long as it remains absolutely 
sharp. 

28. Referring to Fig. 21, if we draw a line E F tangent 
to the work through the point of the tool, and the line G H 
tangent to the circular cutter at the point, we will find that 
the lines do not coincide as in Fig. 22, but form an angle. 
The angle HOE is the angle of clearance when the tool is 
thus set. 

Cutting the face of the notch on the tool slightly below 
the center will slightly change the outline of the cutting 
edge, since a section of the cutter on the line A B is dif- 
ferent from the section on the line C D y Fig. 21. If the cut- 
ter is 2£ inches in diameter, the difference in section caused 
by cutting from £ to \ inch below the center line will not 
be sufficient to cause trouble in ordinary work. If an exact 
outline is required, the cutter must be formed to give 
the desired outline on its cutting edge and not on the 
diametrical section. This form of tool is sharpened by 
grinding the top cutting face, after which the cutter is 
revolved sufficiently to bring the cutting edge to the desired 
height. 



§7 



LATHE WORK. 




20. Straigbt-Faced Forming; Tools. — Another style 
f forming tool is shown in Figs. S3 and 24. The heavy 
block, or holder, shown 

in Fig. 23, is bolted to the 

cross-slide. Into tin 

of this tool block is cut a dove- 

tailedslot e, into which is fitted 

the dovetailed part J of the 

forming cutter. Fig. 21. The 

cutter is clamped to the block 

by tightening the bolt .'. which 

has a special clamp head f. rwi ~ "' 

These forming cutters are shaped along the 
front edge the same as ordinary forming tools, 
so that the section across the top cutting face 
gives the desired outline. They are set in the 
holder so that the front face b has a slight 
angle of clearance. The top face a is ground 
fiat and set at the same height as the center 
of the work. This is a very rigid form of tool. 
30. The forming tools just described are 
Pra.M. f e j tr , (he work in such a way that the cutting 

edge follows in a line that would pass through the axis of 

the work ; thus, in Fig. 21, :ls the tool advances to take a 

deeper cut, it moves along the line C D. 



VERTICAl.-SLIDF. FORMING TOOLS. 

31. Vertical Slide for Holding Tools. — Another 
method of operating forming tools is by means of a verti- 
:al slide rest shown in Fig, 25 Here a vertical slide is 
clamped to the back of the ordinary cross-slide. When this 
ilide is used with the forming tool, the cutting edge does not 
move in a line that would pass through the axis of the work, 
nit in a line tangent to the work 
Fig. 26 shows a side elevation with the forming cutter c in 

lie cutting edge follows the line A B as the tc* 
loves down in the slide. This particular movement 



LATHE WORK. 



§» 



very desirable at times. The cutter c is clamped to the 
block b by a bolt d. The slide s carrying the block b travels 




Pio. M. 

on the guide /, being controlled by the lever /. The work 
is shown at w. 



V 



LATHE WORK. 



19 



89. Form of Tool to Prevent Chat terinff.— When 
tools are used as in Fig. 21, the entire cutting edge of the 
tool is acting at once. If the cut is complicated, or the 
edge broad, the work will spring and chatter because of the 
broad cutting edge. When the vertical slide is used, it is 
possible to grind the cutting face of the forming tool with 
considerable slope to one side, which corresponds to the top 
side rake in the diamond-pointed lathe tool. A tool thus 
ground is shown in plan and eleva- 
tion in Fig. 27, and also the shape 
of the work w that this particular 
form of tool would produce. It will 
be seen that as the tool is fed down- 
wards past the work, the edge or 
point a will be the first to cut. When 
the tool is still farther fed along, the 
point a soon cuts to its depth and 
passes by the work, while other 
points along the cutting edge are 
approaching the work. By the time 
that the point b of the cutting edge 
has reached the work, the point a 
and all the other points along the 
edge have passed by, having done 
their respective parts in the cutting. 
This method, therefore, permits the 
use of broad-edged forming tools, 
since the action is a shaving one, 
and whatever the total length of the edge of the forming 
blade may be, only a small part of it cuts at a time. This 
same principle is used on tools that work on a horizontal 
slide and cut on the under side of the work. 




Fig. 27. 



88a Arrangement of Forming Head.— When very 

ich forming is to be done, and greater production is desired 

i can be obtained by the use of the forming tools just 




SHKCIAI. FORMING HEADS. 



LATHE WORK. §7 

described, a special forming head is used that holds two 
forming cutters, one at the front and the other at the back 
of the 
Fig. 28. 



34. Form of Blades Employed. — In. the forming 
attachments using two forming blades, the edges of the 




blades are not exactly alike. In this case, the back toot I 
may be of the desired outline, while the front tool a i 




V 



LATHE WORK. 



21 



similar, but may have notches cut along its face. This is 
shown in Fig. 29, where the cutting edges of the forming tools 
are compared. The back tool b has a regular outline, while 
the edge of the front tool a is slightly broken. The result of 
this is that the shaving is broken, the high parts of the front 
tool doing the cutting at the points * , while the back blade 
takes all the remaining parts. This relieves the strain on 
the work and the cutters very much. When the work is 
nearly completed, the front blade is slightly backed away 
from the work by moving the lever/. This allows the tool 
at the back to finish the work smooth. When two cuts are 
thus taken, the work is quite well balanced, but to still fur- 
ther steady it, a steady rest with V jaws, operated by the 
hand crank g % is used. These types of forming attachments 
are extensively used in bicycle making on such pieces of 
work as hubs, cones, spindles, pedal pins, and similar 
pieces that are cut from the solid bar. 



SPECIAL PARTING TOOLS. 

35* Inverted Parting Tool. — Instead of the regu 
lar parting tool held in the tool 
post for cutting off the finished 
work, a special holder for blades 
may be used, as shown in Fig. 30. 
This tool is intended to be used 
at the back of the machine ; con- 
sequently, the blade is inverted, 
with the cutting edge at e. By 
holding the cutting blade sloping, 
as here shown, the tool will have 
a top rake, which will add to its efficiency. 




PlO. 80. 



36. Combined Parting and Forming Tool. — 

When the head of the piece to be cut off is curved, as in the 
case of round-headed screws, circular forming tools 
may be used. Fig. 31 shows a section through a circular 



22 



LATHE WORK. 



§7 



'"ttwy ■ ■ v/M 




forming tool that could be used for a cutting-off tool, and 

at the same time be a forming tool 
for the head of the work. 

37. Steady Rest for Turret 
Work. — In some cases, a steady 
rest can be used in the turret for 
certain purposes. Suppose the 
piece shown in Fig. 32 were being 
made. The part a would first be 
turned to size. A hardened-steel 
sleeve s 9 shown in section, which 
has been bored to fit over the 
part a, is then slipped over it. 
Fl °* w * This supports the work while the 

part b is being formed, and while the work is being cut off. 






Fig. 88. 



This method of supporting the end of the work may be 
applied to many styles and classes of work. 



UNIVERSAL MONITOR LATHES.. 

38. Description of the Monitor Lathe. — Another 

class of turret lathe that is extensively used for brass work 
and for work that is not made on the ends of rods, is the 



LATHE WORK. 



lathe, shown in Fig. 33. This style of lathe 
t ordinary rod feed and chuck found on the regular 
. The work performed by this class of lathe 
is usually held in a chuck or some special form designed for 







,he particular work at hand. The turret is mounted on a 
double slide, so that it can move along the line of centers, 
or at right angles across the lathe. This gives a combina- 
tion of movements for the turret that are not possible on 
the screw machines. 

39. Chasing Threads. — Besides the method of cut- 
ting screws by holding dies in the turret, this lathe has a 
sjiorial attachment for chasing threads. At the back of 
the lathe, nicely fitted to bearings at either end of the lathe 
bed, is the large circular chaser bar a, Fig. 33, which is free 
in the direction of its length. To the headstock 
t-nd of ihe chaser bar an arm 6 is rigidly attached. On the 
end of the arm b a piece c is attached, on which a few 
threads arc cut similar to those in a half nut. These 
threads engage with the screw d. seen on the stud of the 
lathe. When thus engaged, as the lathe revolves, the 
threads on the piece c follow the threads in the screw d. 



24 LATHE WORK. §7 

This tends to feed or draw the chaser bar a through its 
bearings. To stop the feed, it is only necessary to lift the 
arm and the threads c away from the screw d. The bar can 
then be moved back to its starting point. Near the center 
of the bar a slide rest is attached, as shown at e. Extend- 
ing over the bed to the front is a lever f to be operated by 
hand. 

40. Suppose a center were put in one of the turret holes 
and the work held between centers in order to have a thread 
cut or chased. The tool would be adjusted in the tool post 
of the slide e so that it just touched the work when the piece 
c was against the screw d. As the lathe revolved, the tool 
would be drawn along and would chase a thread on the 
work of the same pitch as the screw d. When the desired 
length of thread has been chased, the lever f at the front 
of the bed is lifted, thus raising the tool from the work and, 
at the same time, the piece c from the screw d. The bar may 
then be moved back to the starting point, the tool moved 
forwards a little on the slides, and the lever f again dropped 
until the piece c engages with the screw d, when the second 
cut may be taken. This operation is repeated until the de- 
sired depth of thread has been chased. It will be seen that 
by this method only short threads can be cut and that the 
screw d must be changed for every desired pitch. These 
screws d are, in reality, shells that fit over the spindle or 
stud. They are made with various pitches of threads and 
are variously called leaders, hobs, or master threads. This 
method is extensively used in cutting the threads on brass 
pipe, valves, or similar work. 



SPECIAL FORMS OF TURRET LATHES. 

41. The Turret Applied to Engine Lathes. — For 

certain chucking operations, the turret may be applied very 
conveniently to an ordinary engine lathe. Suppose a great 
many pulleys are to be bored and the hubs faced. Instead 



S7 



LATHE WORK. 



25 



of changing the tools in the tool post each time it is used 
for boring and reaming, if a turret is used, each tool can 
be kept in its place, thus saving much time. Fig. 34 shows 
a set of tools that may be used in the turret on an engine 
lathe for such work as boring and facing pulleys. Tool (a) 
can be used to ream the ends of the cored hole, and to 
make a starting place for the chucking reamer (£). A fluted 
shell reamer for finishing the holes to size is shown at (c), 







while (*/) and (e) are facing tools, the ends // having been 
turned to just fit the bure of the pulley and to steady the 
tool while the blades k are cutting. In (</), which is the 
roughing facing tool, edges are nicked to break the sha- 
ving, while, in the finishing tool (/), the cutter blade has 
a straight edge. 

42. lilutttration of Turret Lathe Applied to 
Heavy Work. — Fig. 35 shows another application of the 
turret to the lathe. In this case an octagonal turret takes 
the place of the saddle on the lathe. Power feed moves the 
turret automatically along or across the bed, it having the 
same motion as an ordinary tool post in the lathe. In this 
figure an engine cylinder head, 21 inches in diameter, is 
being finished. Special chuck jaws hold the work to the 
face plate, while the blocks a, a, which have been faced off 

ter being bolted to the face plate, aid in sett 




;n laced on 



26 LATHE WORK. $1 

true with the face plate. The turret has flat faces on its 
sides, so that special tool holders can be clamped to it. By 




the use of these holders, facing, turning, and boring tools 
may be held in the turret and brought in quick succession 
to perform their respective duties. 

43. Special Turret Lathe for Heavy Work. — 

Fig. 30 illustrates a chucking lathe designed for the heaviest 
class of work on castings or forgings. The machine is mas- 
sive in design and its power is sufficient to take the heaviest 
cuts. Like all turret lathes, special forms of tools and cut- 
ters are required before work of any kind can be done; bat, 
once the machine is equipped with a set of tools designed 
for a special purpose, its productive capacity is very great. 
Where the number of like pieces to be finished is relatively 
small, it will rarely pay to install one of these powerful ma- 
chines and to equip it with its. expensive special tools; but 
if a considerable number of pieces of any special design are 
to be made, such a machine will be a valuable acquisition to 
the shop equipment. 



§ 7 LATHE WORK. / 29 

44m Boring Cone Pulleys in Turret Lathes. — 

Fig. 37 illustrates the lathe shown in Fig. 30 fitted up to 
bore a cone pulley k. The hub is roughed out by a cutter on 
the bar c and finished by the cutter on the bar d. The steps 
of the cones are bored and the faces finished by the special 
tools a on the bar l>, while the outer edge of the pulley is 
faced and a finishing cut taken on the inside of the largest 
cone by the heads e and/". It will be noticed that all the 
tools are provided with extensions on the ends of the bars, 
which fit bushings in the spindle of the machine or the chuck 
and thus furnish a guide for the end of the bar. This adds 
greatly to the stiffness of the tool and to the effectiveness of 
the machine. At g a series of screws are arranged to act as 
stops for the various tools. Each one of these can be ad- 
justed separately. In the illustration, the carriage // and the 
taper attachment i are not in use. These cone pulleys may 
be finished on the outside on the same machine by mounting 
them on suitable arbors and turning them with special tools 
placed on the carriage A. This example is given simply as 
an illustration of the class of work for which this style of 
machine is adapted* 

-45. Special Turret Lathe for Large Bar Work. 
Fig. 38 illustrates a turret lathe especially designed for 
work on large bars of steel or iron, either round, rectangu- 
lar, or having any other cross-section. The parts of the 
machine are lettered; a is the automatic chuck for holding 
the bar; 6, the lever for operating the chuck and controlling 
the forward feeding of the stock; r, the lever for throwing 
in the back-gear clutch; d, the roller-feed mechanism for 
feeding the bar forwards; e, the turret, which is of special 
construction, being flat on top and having the tools so at- 
tached to it that it is possible to operate on long bars by 
allowing them to pass through the tools and across the top 
of the turret; f shows one of the tool holders; ^ r , the cross- 
slide lever for operating the cross-slide; //, the circular gil 
that holds the flat turret in place; /, the feed-lever for throw- 
ing the automatic feed; j\ the stock stop, which can be. 



) 



30 LATHE WORK. §7 

thrown up, and against which the stock is fed in order to 
obtain the desired length; k, the back stop; /, the stops 
which can be arranged to control the various tools; m, the 




pilot wheel for feeding the carriage by hand. The roller feed 
is so arranged that when the chuck is loosened, the stock is 
fed forwards at once against the stock stop. 

4tf. The turning tools used in this lathe are similar in 
principle to the box tools used on the ordinary screw machine, 
though they are somewhat different in appearance. Fig. 39 



LATHE WORK. 31 

shows an end view of a turning lool for this lathe. The 
bhde d is damped in the tool block b by setscrews. The tool 
block b is pivoted so that it may be rotated by turning ihe 
i c. This operation moves the point of the cutting 



^ 




tool a toward or away from the work. The lever d may 
be used fur quickly moving the tool to or from the work. 
The back rest_/"is adjusted to the work the same as in the 
ordinary box t<",ls. 

This flat style of turret gives great rigidity to the tools 
mil their cutting edges, and this rigidity is not dependent 
n Ihe length of the work. Ordinary box tools can only be 
■wed upon comparatively short work, while this style of tool 
will operate upon much longer stock. 



AUTOMATIC SCREW MACHINES. 

47. Characteristic Feature of Automatic Screw 

Machine*. — The characteristic feature in the automatic 
tuauhlnes is that the movements made by hand when 

■crating the hand screw machine are made automatically 

11 Ihe automatic machines. These movements are brought 

it by a series of cams and levers that control the work- 

f of each part of the machine. The introduction of the 



32 LATHE WORK. § 7 

automatic controlling part makes the machine much more 
complicated than the simple hand machine. 

48. Setting Up Automatic Machines. — Whenever 
a piece of a certain shape is to be made, a special cam must 
be designed that will give the proper movements to the 
parts. Every new shape of work requires a specially de- 
signed cam and a new arrangement of tools. These factors 
also vary for each make of machine. 

The cutting tools are the same in principle for the auto- 
matic as for the hand machines; hence, no special descrip- 
tion of this class of machines is necessary. 

49. When to Use Turret Lathes. — Before a piece of 
work can be successfully performed with the turret machines, 
some special fixtures must be made and the machine adjusted ; 
they then produce finished pieces much faster than the 
engine lathe. 

In determining whether to use the hand turret or auto- 
matic machines, the amount of finished work to be produced 
must be considered. If only a few pieces are to be made, 
it will not pay to make special tools, or even to take the time 
to set up an automatic machine, until the number of pieces 
to be finished has so increased that the saving in time over- 
balances the cost of making special tools and fixtures. 
Hand machines may be employed for a moderate number of 
pieces, but if there are only a very few the engine lathe or 
a chucking machine should be used. 



SPECIAL FORMS OF LATHES. 



POWER-DRIVEN LATHES. 



TOOLMAKER8' LATHE. 

50. General Description of Tool makers' Lathe. — 
The term toolmakers' lathe is applied to lathes having 
from 10 to 16 inches swing, and, in appearance, are sim- 
ilar to the regular screw-cutting engine lathe. They are 
equipped with taper attachment, compound rest, and special 



LATHE WORK. 




chucks, and are made with a greater degree of perfection 
than is the ordinary engine latne. 

51. Special Chucks. — The special chucks found on 
toolmakers' lathes are used £or holding rods or bars ot 
different sizes. They 
are similar in princi- 
ple to those used on 
turret screw ma- 
chines. The collets 
shown in Figs. 2 
and 3 are known as 
push - In collets, 
that is, they are 
pushed into a taper 
hole to close them. 
Another style of col- 
let that works on the 
same principle is the 
draw-In collet. In 
the draw-in collet, 
the bevel on the large 
end slopes in an op- 
posite direction from 
that shown in Fig. 3, 
so that, to close the 
chuck, it is drawn 
into a tapered hole 
in the headstock. 
This latter style is 
very commonly used 
on tool makers' 
lathes. 

BBNCfl LATHES. 

52. General 
Description of the 

When small work must lie finished with 




g 7 LATHE WORK. 80 

rabte accuracy, the ordinary engine lathe is too large 
and clumsy, and the hand lathe dues not possess the accuracy 
or the attachments necessary to do the work. To finish this 
class of work, the bench, or precision, lathe, Fig. tO, may 
This lathe is fitted with a double slide rest with 
automatic feed. The slide rest may be removed and an- 
lachment supplied in its place for special milling 
operations. For cutting threads, a chaser bar is provided. 
This chaser bar is operated as the one described in connec- 
tion with turret lathes, Fig. 33. Special draw-in collets are 

■■: holding small rods. These lathes, while not in 
reality watchmakers' lathes, are similar to them. They are 
intended only for light work. 



GAP LATHES. 

53. Special Feature of the Gap Lathe — A style 
of lathe that is often seen in shops where large lathes of 
considerable swing are seldom needed, is shown in Fig. 41. 
This is known as the gap lathe. Its principal feature is 
the second bed a, which slides upon the main bed (>. 
When ordinary work is to be turned, the top bed is 
moved up very close to the face plate, nearly closing the 
gapjf. It is then Ufied as an ordinary lathe. When a par- 
ticularly large piece is to be turned, the upper bed is moved 
away from the headstock by turning the hand wheel c, thus 
opening the gap,? - and giving the lathe its full swing over 
the main bed b. 



TWO-SPINDLE LATBB. 

5 1. l)i*tliiLCuiHhliij£ Characteristic* of the Two- 

Spindle I.athv. — X style of lathe that in many cases 

. | he same purpose is the twn-spfndle lathe shown 

in Fig. 42. For ordinary work, the lower set of spindles a, b 

., but when the piece is too large to be swung on the 



86 LATHE WORK. §7 

lower set of spindles, the high ones c, (/are used and the tool 
post blocked up by using a special cross-slide. 

55. Blocking Up of Lathes. — It is common practice 
in lathe work, when the piece to be operated upon is a 
little too large to be swung in the largest lathe, to block 
up the headstock and tailstock by putting under them 




wooden or iron blocks until the centers are sufficiently high 
above the bed to allow the work to swing. The gap lathes 
and the two-spindle lathes are intended to take the place of 
the blocked-up lathe. Thus far, the lathes mentioned have 
been of the same type as the standard engine lathe, with 
only slight modifications. 



AXLE LATHES, 

56. General Description of tbe Axle Lathe. — 

Specially designed machines are often made when there is 
enough of a particular kind of work to warrant them. Car 
axles may be turned on an ordinary engine lathe, but it is 
possible to do the work much faster on one of a special de- 
sign, such as is shown in Fig. 13. This axle lathe is 



LATHE WORK. 



39 



designed so that the two ends of llie axle may be turned at 

the same time. To accomplish this, the driving head is 

placed in the center of the lathe bed. This allows the work 

to be turned on dead centers — a very desirable thing when 

accuracy is desired— and it also leaves the ends free, so that 

. til may be taken on each end at the same time. The 

iving head is operated by gearing connected by a shaft 

th the cone pulley seen at the left. The axle shown in 

place in the lathe is handled by means of the overhanging 

crane. 

57. Method of Driving the Work.— After the work 
is adjusted between the centers, the dog or driver is put in 
place. This should be an equalizing dog, or a two-tailed 
dog operated by an equalizing device, so that the force 
•equired to drive the work will not spring the axle. Chucks 
used, as they spring the work. Means are pro- 
ded for keeping a large supply of soda water flowing on 
tool during the cut. 



Will II. LATHES. 

58. Fig. a shows a style of lathe especially designed 

turning locomotive driving wheels after they have 

■ecn pressed on to an axle. This lathe is designed with 

no driving heads and two tool rests, thus enabling the 

to turn both driving wheels at the same time. It 

will be noticed that there are no feed-rods along the bed lo 

operate the tool carriages, as found in ordinary lathes. 

The tool carriage ordinarily used is similar to the compound 

li e it may be turned on its base and set at any 

angle. Two sinks allow the tool to be moved in 

o directions, at right angles to each other. Screws for 

noving the slides are operated by a lever a connected to the 

J-screws by ratchets h. These levers are moved auto- 

■ by levers and cams in a separate mechanism 

>ove the lathe to which they are connected by chains. 

r the wheels on the axles are put between the centers, 



40 LATHE WORK. §7 

the drivers c shown on each face plate are so adjusted 
against each wheel that it is driven from its face plate. 
These lathes may also be used for boring the tires of locomo- 
tive driving wheels, the tires being bolted to the face plate 
and bored and faced, as in ordinary face-plate work. This 
method of boring tires is not often employed, as they can 
be bored much better on a boring mill. 



PULLEY LATHES. 

59. Fig. 45 shows a type of lathe specially designed 
for turning pulleys. The lathe has two tool rests so that 




two tools may be used, one at the front and one at the back 
of the machine. Special driving dogs attached to the face 
plate drive the pulley by its arms. 




HAND, OK SPEED, LATHES. 
BO. General Description of the Hand Lathe.— 
Hand lathes, or speed lathes, are the smaller sizes of 
■ led for such 
ions a 
performed with 
held in the hand, 
such ope 

require a higher speed 
of work than can be 
obtained by the ordi- 
nary turning lathe. 
: lathes are with- 
k gears or slide 
rests. Fig. 40 shows a 
andard type of hand 
It is mounted 
1 a table, which makes 
t convenient place for 
holding tools and 
ork. 

Uhc of the Hand Lathe. — Work that is of irreg- 

ar ouUbw, requiring the use of hand gravers, is often 

mshed on this type of lathe. When a small chuck is fitted 

. the spindle of the lathe, it is very handy for turning or 

ointing small rods and pins, and a variety of similar work. 

rifling may also be done very conveniently on certain 

i of work. When much drilling is to be done, a ta.il- 

: with a lever attachment for feeding the spindle is 

; convenient than the screw attachment. 

When the lathe is used for 
drilling or reaming center 
holes, the drill is held in a 
chuck and the work pressed 
against the drill by the tail- 
stock spindle. 

When holes are to be 





48 



LATHE WORK. 



§* 



drilled in thin flat pieces, a pad center, Fig. 47, can 
be used in place of the cone center. When holes are 
to be drilled diametrically through rods or tubes, a forked 

center, or V block, Fig. 48, 
aids in holding the work 
true. 

63. Hand Slide 

PIG - *■ Rest. — Fig. 49 shows a 

band slide rest that is often used on these hand lathes. 

The ordinary hand rest is removed and this is clamped in 





Pio. 49. 



its place. A small tool can be held in the tool post, and for 
light work it is very convenient. 



POLISHING. 

64* Object of Polishing. — One of the principal uses 
for which the speed lathe is adapted is polishing cylindrical 
work. The various parts of a machine are polished to add 
to its attractiveness and beauty, and not to add to the per- 
fection of its movements or to increase its efficiency. Parts 
of the machine that are fitted to each other, or are in unseen 



§7 LATHE WORK. 43 

places, should not be polished. When a piece is well pol- 
ished, it is smooth and true, free from scratches, possesses 
brilliancy, is even in its appearance, and free from bright- 
and dull-colored streaks. 



FILING. 

65* General Consideration. — When a cylindrical 
piece is to be polished, it should be finished with a very 
smooth finishing cut on the lathe. It is next made smooth 
by filing* Just enough filing should be done to remove the 
tool marks, care being taken not to scratch the work. This 
scratching often occurs and is called pinning. Pinning is 
caused by the filings collecting in the teeth of the file and 
forming little balls of metal. When the file is passed over 
the work, these little balls of shavings will catch in the sur- 
face and produce deep scores or scratches. This will occur 
every time the file passes over the work until the file is 
cleaned. For cleaning the teeth of the file, a file card should 
be used. A file card is similar to a very stiff brush with very 
fine steel wires taking the place of the bristles. When the 
card is used, it is drawn across the file so that the wires fol- 
low in the spaces between the teeth. Ordinarily, this oper- 
ation will clean the file, but if it does not, and the little bright 
spots of shavings are still seen, they must be picked out with 
a piece of soft-iron wire that has been flattened on the end. 
The flat end is laid on the file and moved across it in such a 
way that it will get under the ball of shaving and remove it. 

66. Files for Lathe Work. — The best files to use for 
lathe work are the mill files. These are single-cut and there 
is less danger of their pinning than with the double-cut files. 
They also cut smoother. 

67. Avoiding Pinning:. — Pinning may be more or less 
avoided by properly holding the file on the work. When 
filing, the point of the file should be held to the right 
so that it is at an angle to the work, as shown in 

T IB— 19 



f 



§7 LATHE WORK. 45 

circumference. While the file is being drawn back for the 

second stroke, the work begins its second revolution and the 

file again cuts half of the circumference of the work. It will 

also be on the same side of the work. In this case, the file 

has cut twice on one side of the work, and has entirely skipped 

the opposite side. This will be continued so long as the rate 

of file strokes and revolutions of the work are the same. It 

may be seen from this that to keep the work nearly true, the 

file strokes should be slow enough to allow the work to make a 

number of revolutions for each stroke of the file. 



USB OP RMBHY. 

70. Use of a Polishing stick. — After the tool marks 
have been removed by filing, the piece is treated with a 
coarse piece of emery cloth, which will remove the file marks. 
After the file marks have been removed, a finer grade of 
emery is used until the coarser emery marks have been 
removed, and so on, using finer grades of emery until the 
desired polish is obtained. Emery cloth should be pressed 
very hard against the work by using a polishing stick, which 
is passed over the tool rest of the lathe and under the work, 
the emery cloth being held between the stick and the work. 
By pressing down on the outer end of the stick, the emery 
doth can be brought with great pressure against the work. 

71. Speed for Polishing. — The speed for polishing 
is quite different from that used for filing. The higher the 
speed the better, provided the work and the machine are 
balanced so that the high speed does not shake the machine 
too badly. When polishing, the stick should be moved so 
that it will not remain in one position on the work, but will 
move back and forth, in order that the lines cut by the par- 
ticles of emery will be constantly crossing and recrossing 
one another. Oil should be supplied to the work and the 
emery, in a quantity sufficient to keep the surface moistened, 
but not so that it will be thrown from the machine in great 
quantities. 



LATHE WORK. 




72. Care of the Center*. — When a piece "f 
»cing polished, so much heat may be generated as t 
; to expand along its entire length. If, in 

.he dead center has been made fairly tight, it will become 
icked in the end of the work, the oil having betfB 
out, and will be twisted off. This should be carefully 
guarded against by keeping the centers free and well Oded 

73. Finishing a PollMied Surface. — When the 

piece is nearly finished, the pressure of the emery is reduced 
and the movement along the length uf the work is slower. 
For the finest grades of polish, fine emeus cloth is used and 
siill liner polishes are produced by using rottetwtooe. Net 
much machine work is carried to that perfection of polish 
that requires crocus cloth or rotlenstone for finishing. A 
very high polish may be obtained by using a much worn 
piece of No, o or 00 emery cloth. 

Grain emery is often used in the place of emery cloth 
Bare wood, or pieces of lead on the face of the wood, 
to hold the emery against the work. The particles of 




embed themselves in the soft wood or in the lead and so arc 
held from being thrown from the work. Oil is used a- 
before- 



§7 



LATHE WORK. 



47 



74. Polishing Clamp. — For plain cylindrical work, a 
very convenient and effective way of holding the emery 
against the work is brought about by fastening two pieces 
of wood together at the end with a leather hinge. The two 
inside faces of the pieces are cut out at a short distance from 
the hinged end, so that they will fit over the shaft, as shown 
in Fig. 51. By pressing the outer ends together, consider- 
able pressure is brought against the shaft. Either emery 
cloth or grain emery may be used with this device. 



SPECIAL LATHE WORK. 



USE OF STEADY REST. 

75. General Considerations. — When long shafts 
are to be turned, it is necessary to support them along their 
length. If there is.no support, they will bend and vibrate 
so that it will be very difficult to take a cut from them. 
Fig. 52 shows a form of steady rest that is usually supplied 
with engine lathes. When in use, this steady rest is bolted 
to the top of the lathe 
bed at a place where it 
is desired to support the 
shaft. The rest is made 
in two parts, with a 
hinge a at the back and 
a latch or clamp b at 
the front. After the 
steady rest is clamped 
on the bed, the latch is 
undamped and the top 
half turned back so that 
the shaft can be put 
in the lathe between 
the centers. The top 
half is then closed and 
clamped in place. If 
the shaft be perfectly 
true, the jaws c of the FIG . 52. 




48 LATHE WORK. §7 

steady rest may be adjusted so that they just touch it 
Screws d stand against the ends of the jaws and hold them 
against the work. After the jaws have been adjusted so 
that they all touch the shaft, but do not spring it, they 
are clamped by the bolts e y which pass through the jaws and 
the rest. The jaws should be oiled where the shaft turns on 
them. 

76. Spotting the Shaft. — If the shaft does not run 
perfectly true, a spot must be turned on it that does run 
true and the jaws of the steady rest adjusted to the spot. 
If the steady rest were adjusted to a place that did not run 
true at first, it would be found that after it was adjusted, the 
shaft would appear to run true and would continue to do so 
until the jaws were again loosened, when the shaft would 
spring to its natural shape and wabble as before. When a 
shaft is to be spotted for the steady rest, a very fine light 
cut is made (of any diameter so long as it is true) to give 
the jaws a fair bearing. 

If the shaft is quite long and it is desired to put the steady 
rest near the middle of the shaft, it may be found that a cut 
cannot be taken in the middle of the shaft to spot it because 
of its extreme flexibility. Cuts near the end of the shaft, 
where it is better supported by the lathe centers, may be 
taken. In such a case, a cut would be taken near the dead 
center and a spot made. Having the shaft thus spotted, the 
steady rest may be adjusted to this place and the second 
spot turned farther along. In this way, the spots may be 
moved along the shaft until the middle is reached. 

77. The Cat Head. — On some classes of work, it is 
desirable to use the steady rest on a part that does not run 
true and it is not desirable to spot the place on the shaft. In 
such a case, a device called a cat head is adjusted on the 
shaft. A cat head is a collar that fits loosely over the shaft 
to the place where the steady rest is to be adjusted, and is 
here clamped upon the shaft by a number of setscrews, as 
shown in Fig. 53. By varying the adjustment of the set- 
screws at the ends, the cat head may be set to run true. 



LATHE WORK. IS 

Afier it has been set, the jaws of the steady rest may be 
adjusted to it the same as to a larger shaft. In the case of 
the slim shaft just mentioned, the cat head may be used 
instead of making the series of spots from the end. 

If the shaft is long, it may be necessary to use two or 
more steady rests. When the tool and carriage have fed up 




to the steady rest, it must be moved to another position to 
allow the cut to pass. It is difficult to turn long shafts and 
lave them remain straight, even if the spots are turned 
rith great care. When the shaft is rolled, its surface is 
lore or less under tension,' and, as it is turned, this tension 
* removed, thus allowing the shaft to spring so that the spot 
hat was turned true when the shaft was rough is untrue 
after it is turned. 



FOLLOWER RESTS. 

78, Another method of supporting shafts while being 

by the use of the follower rust. Such a style 

f rest is shown in Fig. 54. This rest is bolted securely to 

.he carriage and travels with it. When it is used, a cut of 

c desired diameter is started at the end of the shaft. 

en is a spot is made true, the two jaws c, c are carefl 



LATHE WORK. 



8' 



adjusted to the work w. Since there is a tendency to 
spring the shaft away from the tool, it will be seen that the 
two jaws are sufficient to support the work. 

79. Solid Bushings. — Another method of supporting 
the work is by means of the follower rest supplied with 





bushings, so that as soon as the end of the shaft is turned, 
it enters a rigid bearing. Such a follower rest is shown in 
Fig. 55. Bushings b bored to different diameters are used 
for different sizes of shafts. This style of follower rest 
gives a very perfect support for the shaft. When used, the 
tool is set slightly in advance of the follower. The closer 
the tool is set to the follower rest, the less danger there is 
of its chattering. 



SHAFTING LATHES. 

80. Special Shafting Turner. — When much shaft- 
ing is to be turned, a regular shafting lathe is used. 
These lathes have very long beds and the carriage is fitted 
with a shafting turner. The shafting turner consists of 
a follower rest with bushings to fit around the shaft, similar 
to that shown in Fig. 55. It also has two, three, or four 



S 7 LATHE WORK. 51 

tool slides, so that an equal number of tools may be used to 
cut at once. When used, two or three roughing tools pre- 
cede, and one finishing tool follows the rest. Thus, the 
shaft is roughed and finished at one cut. 

81, Torsion in the Shaft. — Much power is required 
to taie a cut with four tools cutting at the same time, and, 
in the case of a long shaft, the torsion in it, when the tools 
are at the beginning of the cut, is considerable. To over- 
come this, long shafts are driven from both ends. 



STRAIGHTENING. 

82, Straightening Machines, — After the shafts are 
turned, they are apt to be crooked for the reasons mentioned 
above. They are straightened on a regular shafting 
straights ner, which consists of a number of conical rolls 
so arranged that, as the shaft is revolved and drawn be- 
tween the rolls, it is bent and straightened. 

83. Straightening Small Work. — A special straight- 
ener is not always necessary in order that a shaft may be 
made true. Small straightening presses may be used for 
bending the crooked shaft to make it straight. These 
straightening presses are so constructed that the shaft to 
be straightened may rest upon two supports from 1 to 3 
feet apart, depending on the size of the straightener. An 
arm projects from behind the machine, midway between the 
points of support, and over the shaft in such a way that a 
vertical screw may be used for pressing the shaft down. 
When the shaft is to be straightened, it is supported be- 
tween the centers of the lathe, and, while revolving slowly, 
itis marked with chalk on the high side. It is then removed 
from the lathe, taken to the straightener, and bent suffi- 
ciently to make it straight. A number of trials may be 
necessary to make the shaft run true. If the bend is a 
short kink, then all the straightening should be done at that 







52 LATHE WORK, 

place, but if the original crook is a long sweep, the work 
should be straightened by a series of applications of the 
press along the work. These presses are sometimes sup- 
ported on wheels and set directly on the lathe bed. After 
the work is tested, the press is moved along the bed to the 
crooked place on the shaft, and, after loosening the lathe 
centers, the machine is used for straightening the work. 



84. If such a press is not at hand, a shaft may 
straightened after marking by taking it from the lathe am 
resting it upon two solid blocks of wood, with the marked 
part up between the blocks. A third block is rested on the 
shaft between the supporting blocks, and is struck a blow 
with a hammer or sledge. Care must be taken not to de- 
liver too heavy a blow or the work will be more crooked 
than before. 



mi 



- 

een 



85. Sometimes, when the proper straightening devii 
are not at hand, slender work may be straightened between 
the lathe centers, but such practice injures the lathe and 
should not be used except in special cases. The work is re- 
volved between the lathe centers and the high side marked. 
A bar or lever is then put over a tool in the tool post and 
under the work in such a way that when the lever is pushed 
down by hand the work will he sprung up. By turning the 
work so that the marked part is down, it can be so sprung 
that, after a number of trials, it will run quite true. If the 
bend is a long uniform one, it can be straightened by simply 
bending or springing the bar as just indicated. If the shaft 
appears to have a short bend, while either side of the bend 
appears to be straight, this short bend can be taken out by 
springing up the shaft with the lever, as described, and 
striking a few blows with the hammer on the top of the 
shaft on the bent part. The hammering should be light at 
first or the bar will be found to be bent as badly as it was 
before, but to the opposite side. This hammering has a 
peening action that tends to slightly stretch the shaft on thi 
side struck. 



shaft on the 



LATHE WORK. 



53 




86. Straightening Lead screws. — This method of 
peening is sometimes used for straightening large or long 
lathe leadscrews after they have been 
[hrt-adctl. A special tool is used for 
peening the threads, as shown. in Fig. 
84. This tool is made thin at its edge, 
bo thai it will go between the threads 
down to the root. It is concave, so 
that it fits around the screw for a 
short distance. When the- screw is 
tested and found to be untrue, it is 
sprang up with the lever at the bent 
place, and, while held in this sprung 

fen i >f the threads on the top side are peened with 
tile pceiiing tool and a hammer. With some skill, a screw 
that was badly bent may be quickly straightened. It may 
that this method of straightening screws will not 
do when the pitch of the leadscrew must be accurate, since 
it will slightly stretch the screw. For ordinary purposes, 
however, the stretching of the screw caused by slight peening 
would be so little that it would scarcely be perceptible. 
The most accurate leadscrews are always straightened with- 
out peening. 



I'SB OF STEA1>V WEST IM CHUCKING. 

S7. Application ..f Steady Rest to Barn.— Fig. 57 

shows how a bar may be held when it is desired to operate 
on the end for boring or turning. In adjusting a steady 
.; bar is held by one end in the chuck, while the 
other end is supported on blocks of wood at a height equal 
to that of the dead center. The steady rest is moved very 
close to the chuck and the jaws adjusted to touch the bar. 
■ jaws are adjusted, the steady rest is opened by 
turning back the top, but without changing the adjustment 
of the jaws. It is then moved down the bar and clamped in 
the desired place. By this method of adjusting the jaws, 



54 LATHE WORK. §7 

the work is held in line with the headstock spindle. This 
method of supporting work is often used for very large 




pieces, and, when necessary, very large and heavy steady 
rests are used. 

88. Application of Steady Rest to the Turning 
and Boring of Large Guns. — The forgings for large 
guns are usually operated upon while one end is sup- 
ported' in and driven by a chuck, and the body of the 
piece rests on one or more 
steady rests. These 
steady rests are of a 
specially heavy design. 
Fig. 58 illustrates one of 
them supporting the 
inner tube for a 12-inch 
gun, a being the tube 
and b a large chucking 
drill used for boring the 
inside of the tube. In 
this gun work, the 
roughing and finishing 
Pl0 ^ tools are specially de- 

signed drills and reamers, 
and the cutting speeds are very slow, it having been found 
that speeds exceeding 6 or 8 feet per minute are usually un- 
profitable, on account of the fact that they cause excessive 
wear and breakage of the costly tools. 




&^ 



LATHE WORK. 




TIWXING IIV MEANS OF A UOTAT1NG TOOL. 

&{J. Occasionally a job has to be done that requires the 
turningof a trunnion, or projection, upon a large and heavy 



Pig. S3. 
casting. If such a casting b were placed in the lathe and 
rotated upon centers, it would require a very large lathe to 
do the work. Fig. 69 illustrates a method by means of 
which tlus difficulty has been successfully overcome. The 
casting in question is long and heavy and is supported 
at one end upon a regular carriage a, and at the farther 
end upon a special carriage not shown in the illustra- 
tion. The work requires that the portions c, d, and e be 
turned to three different diameters. They are roughed by 
means of a tool attached to the specialarmyattached to 
the face plate g. After the three diameters have been 
roughed out, the face plate g is unscrewed from the spindle 
and the attachment k, shown in the foreground, substituted 
for it. This attachment carries hollow mills, as shown at i. 
The mill shown at i is intended for finishing the portion c, 
, after this portion is finished, the mill shown at J is 
ubstituted to finish the portion if, and the mill shown at k 
> finish the portion e. The tool or mill always revolves at 
he same distance from the face plate or end of the spindle, 
work being fed into or past the revolving too! by means 
ilinary feed upon the carriage u. 



\ 



1 

1 



PLANER WORK. 



(PART 1.) 



WORK OF THE PLANER. 



THE MACHINE. 

\ m Action of the Planer. — The natural function of the 
planer is to produce a flat surface. This is accomplished by 
causing tne wor ^, which is fastened to a table that has a 
reciprocating motion, to pass back and forth under a cut- 
ting tool ; the tool is fed across the work at right angles to 
the line of motion of the table. 

2. Names of Parts. — A standard type of a modern 
planer is shown in Fig. 1. This machine consists of a 
platen a, which slides in V-shaped guides on top of the 
bed q. Heavy housings d, b are securely bolted to the 
bed, the movable cross-rail c being bolted to the front 
face of the housings. The cross-rail carries one or more 
d, d (two in this case) ; these saddles have the 
Leads r, e attached to them. Each head has a slide 
that is operated by the down-feed handle/. For holding 
the tool, each head is provided with suitable tool clamps, 
as g. g- The saddles can be moved along the cross-rail by 

CD Wit INTERNATIONAL TEXTBOOK COMPANY. ALL ftlQHTB RESERVED 

28 



+ 



PLANER WORK. 



means of feed-screws; for feeding by hand each feed- 
screw has a feed-screw handle h. The platen is driven 




by gearing operated by belts placed on the driving: pul- 
leys / and reversing pulleys m. The direction in which 



PLANER WORK. 

the platen moves is changed by tappets/ /, which engage 
the reverting lever i, which is connected in turn to the 
iHilt-shifdnic levers i; k. The cross-rail may be raised 
or lowered by means of screws within the housings; these 
screws are operated simultaneously by bevel sears o, o, 
one [y.iir of which is fastened to the screws mentioned, while 
the other pair is fastened to the shaft r. This shaft is 
driven by spur gearing, which, in turn, is driven by a belt 
placed un the pulley/. 



METHODS OF DRIVING. 

3, Two Methods Commonly Used. — There are two 
methods of imparting motion to the planer table or platen. 
One is by a system of spur gearing, in which the power 
.-.ted from the belts to the table by means of 
gears. Planers thus driven are called spur-geared planers. 
The other method is by means of a spiral gear that en- 
gages with a rack on the under side of the platen. The 
driven by gears and shafts, which, in turn, are 
driven by the belts. From the kind of driving mechanism 
used, such planers are called spiral-geared planers. 

4- Spur-Geared Planers. — Fig. 2 shows how the 

driving gears are arranged on a spur-jjeared planer. 

Three shafts pass through the bed and have their bearings 

* 'he ends. Shaft / projects through the front side of 

bed sufficiently to receive the driving pulleys / 

and m, Pigs. 1 and 2. This shaft, near the back side of the 

ies the pinion a, Fig. 2, which engages with the 

spur gear b on shaft %. Near the center of shaft 2 is a 

which engages and drives a spur gear e carried on 

shaft S. This gear is the largest and heaviest in the train 

: and is sometimes called the bull-wheel. On 

under side of the platen, and between the guides, or 

is a rack/, which engages with the bull-wheel 

ion of tht.s^'Mis when the belt-driven 
are moving in the direction indicated by the arrow 




A 



■I PLANER WORK. S§ 

it will be found that the table will move in the din 
the arrow u. In order to reverse the direction ■ 
two belts are used; one of these is an open belt and the 
Other is a crossed belt It will be seen by reference \ a 
Figs. 1 and 2 that there are two pulleys of each size on 
the shaft, one of each set being a loose pulley. When oiw 
belt is rotating the shaft 1 in one direction, the other belt 
runs in an opposite direction on the loose pulley of the other 




set. When the reversing occurs, the driving belt is runoff 
the tight pulley to the loose pulley beside it, while the other 
belt is moved from its loose pulley to the fixed pulley beside it. 
This at once changes the direction of rotation of the shafts, 
and, consequently, the direction of motion of the machine. 
When the end of the stroke is reached, the reversing lever; 
at once change the belts back to the original position and 
the planer moves forwards as before. 

5. Quick Return. — It will be noticed in Figs. 1 Rod a 

that the driving pulley / and the return-stroke pulley ut 
have different diameters. The pulleys on the counter- 
shaft to which these are belted also have different diam- 
eters. By this combination, the planer is made to run 
backwards on the return stroke at a rate of speed ! 



18 PLANER WORK. 5 

limes as great as the forward, or cutting, speed. When 
planers are thus designed, they are said to have a quick- 
return motion. This method saves considerable time 
HW the old-style machines, which required as much time 
for the return stroke as for the forward stroke. 

6. Spiral-Geared Planers. — In the spiral-geared 

planers, two driving belts running in opposite directions 




0t > tight and loose pulleys are used, the same as in the 

pur-geared planers. Fig. 3 shows a top view of a spiral- 

Reared planer. The 

*C driving pulleys 

r * shown at / and m. 

*t*ill be noticed that 

*i« shaft that carries 

l he pulleys is parallel 

ll) the line of motion 

"' the platen, while in 

"it spur-geared planer 

*o»n it was at right 

W (W to it. On the 

belt-pulley 




PLANER WURK. 



II 

shaft is a small bevel gear a, which engages with a lafgt 
bevel gear I on the shaft c. On the other end of the shaft e 
is a spiral gear, or worm, f, which engages with the rack 
on the under side of the platen and is shown in dotted 
lines in the illustration. It may tie noticed by examining 
the threads of a worm or any screw, as, for instance, that 
Shown in Fig. 4, that the threads are not square with the 
avis nf the screw, but make some other angle than 90°, as 
shown by the line O D; the angle depends on the diameter 
of the screw and its pitch. On account <>f this [act, in i 
spiral -geared planer, the shaft ,* is set at such an angle that 
the line of the threads is at right angles to the line «( 
motion of the platen, in '11011- to give a direct pull. The 
rack on the under side of the table is specially cut, so that 
the worm lits it correctly. It is claimed that these spiral 
geared planers are very smooth in their action. 



7. 



SIZE OF PLANERS, 

Definition. — The size of a planer is indicated by 



I 



width and height of the largest piece that will pass thrd 
its housings and the length of the longest piece tha 
planed on its table. Thus, a 40" X 40" X 10' planer means 
that a piece 40 inches square will go through the housll 
and the table will take a piece 10 feet long. 

8. Planer HeadH. — Ordinarily, planers an: 
with but one head, but when specially ordered for partici 
work, two heads may be used on the cross-rail, as s 

Fig. 1. Large planers are frequently equipped with I 
heads, two being placed upon the cross-rail, as sh 
Fig. 1, and the other two, called side bcail*, on the housi 
below the cross-rail. These side heads are usL-d when I 
undercuts are being made, or when it is desired to fa 
sides at the same time that the top is being finished, 
are some other types of planers used for special kind: 
work, but they are modifications of the standard 
shown in Fig. 1. 



PLANER WORK. 



FASTENING WORK TO THE PLATEN. 



THE 1>[ AMI* CHUCK. 



9. When a piece is to be planed, it must be i 
ened to the platen in some 
manner. This operation is 
tailed setting the work. 
The manner of holding 
the work on the platen de- 
pends on the shape and 
size of the work. It may 
be held in a regular planer 
chuck or vise, by the use 
of bolts and clamps, by 
pins and jacks, or by spe- Pio.5. 

ctftl holding devices designed for the purpose. 



:urely fast- 




IO. Description.— Fig. 6 shows a common type of 

plattM 1 cliu«b. It is fastened to the platen by bolts that 

ay be slipped into slots at its sides, one of which is shown 

The base of the chuck is circular, and is made in two 

so that by unclamping the two bolts, one of which is 

novrn at b, the other being at the opposite side of the 

buck, the top part may be swiveled around in order that 

lie jaws may be set at any angle. The bottom of the 

upper part is graduated to degrees for determining the 

angle when setting the jaws. One jaw c is fixed ; the other 

jaw d may be moved to the proper position to hold the work. 

When work is to be held in the vise, the jaw d is moved 

■ In: work, and the block c is moved against the rear 

of the jaw. The block c is kept from slipping back by 

means of the strips/. /, which drop into the notches cut in 

the chuck, as shown. The nuts k, k in the jaw d are now 

screwed down, and it is tightened against the work by means 

of the setscrews^, g. Finally, the nuts k, k are tightened 

once more. 



8 



PLANER WORK. 



§8 



11. Square Planing. — Suppose that a rough cast- 
iron block 2£ inches square is to be planed square and true. 
If it is desired that the block be made with considerable 
accuracy, it should be planed all over with roughing cuts 
before any finishing cuts are taken. The work is put in a 
chuck and a cut taken over one side. After the work is 
planed on one side, it is given a quarter turn in the chuck, 
and is then clamped for planing the second side. Before 
taking the cut, it must be known that the finished side of 
the work is set perpendicular to the table, so that the cut on 
the second side will be square with the one previously fin- 
ished. When the planer chuck is true and in good shape, 
the jaw c will be square with the bottom of the chuck, so 
that if work with a flat face be clamped against it and a cut 
is taken, the planed surface will be square with the flat face 
in contact with the jaw. 

If the work is not true, care must be taken in clamping 
it, or the finished face will not be held squarely against the 
jaw. Suppose the work w to be tapered, as shown in 




Pio. & 

Fig. 6. The face k of the work is finished, but the face / is 
rough. When the jaws are tightened against the work, the 
pressure will come against the work at the edges of the 
jaws, while, at the bottom, the jaws will not touch the work. 
If the jaws are tightened, they will remain in the same posi- 
tion relative to the work, so that even though the face k 
has been planed, it will not be held flat against the jaw c. 
When a cut is taken with the work thus held, the latter will 
not be square with the finished face. If it is found that 



§8 



PLANER WORK. 



9 



this condition exists, the work may be made to come flat 
against the jaw by putting thin pieces of packing / (strips 
of paper or tin) between the jaw d and the lower edge of the 
work, as shown. This will cause pressure against the lower 
edge of the work and hold it squarely against the jaw c. 

1 2. Instead of putting the packing pieces / between the 
jaw rfand the work, Fig. 6, a false jaw /with a rounded 




Pig. 7. 



face, shown in Fig. 7, may be used. This rounded face 
will allow the work to turn slightly so as to bring its finished 
face squarely against the jaw c. 

^ no false jaw is available, the same end may be attained 
by placing a straight piece of copper or iron wire between 
the work and the movable jaw. The wire should be long 
enough to touch the jaw and work at every point of contact. 




Pig. a. 

13. Another source of error that must be guarded 

a ?ainst is caused by the jaw d rising slightly from its seat 

*hen the screws £• are tightened. Fig. 8 shows, somewhat 

exaggerated, the result of tightening the screws g on the 

work before the bolts k are tightened sufficiently to hold the 



m\ 



10 



PLANER WORK. 



§ e 



jaw d to its seat. In this case, the faces k and / of the wo 
are parallel, but the lifting of the jaw d will throw the wo 
out of true with the jaw c y and if a cut is taken over the 
top, the work will not be square. 

14. If the work projects beyond the ends of the vise 
jaws, the setting of the finished side may be tested by put- 
ting the stock of a try square / on the platen and pushing" 
the blade against the finished side k y as shown in Fig. 9 




PIG. ft. 

If the blade is in contact only at the top, or at the bottom 
of the finished side k, it shows that the piece is not properly 
chucked. In order to bring the finished face square, strips 
of paper or tin may be put between the work and the jaw c 
at the top or bottom of the jaw. 

15. Making Sides Parallel. — If the work is large 
enough to allow it to be set flat on the bottom of the chuck, 
as shown in Fig. 6, it will usually be near enough true to 
be planed parallel. To make sure that the work is fairly 
bedded, that is, in contact with the bottom of the fixed jaw, 
it is well to put pieces of paper under each end of the piece 
and after the jaws are properly tightened, to strike the top face 
of the work with a lead or Babbitt hammer. It can be deter- 
mined by the sound if the piece is down solid ; also the pieces 
of paper can be tested by pulling to see if they are tight. 

When the work projects beyond the sides of the chuck, 
the bottom of the work may be set parallel to the bed by 
tapping with a hammer and testing by calipering, as shown 
in Fig. 10. If the work is short and cannot be planed on its 




88 PLANER WORK. 11 

tupfaee when set down on the bottom of the vise, it must 
be held up. To set it true so that the top face may he 
planed parallel with the bottom face, its setting may be 



§8 



inside calipers, measuring from the bottom of the 
■ huck to the under finished face, and adjusting the work by 
tapping it with a soft hammer until the measurements are 
the same at all points. 

18. Use of Parallel Strips. — A much quicker way is 
t»u$e parallel strips b, b, Fig. 11, under the work w, and 
sei the work down on these strips. Parallel strips are thin 
pieces of cast iron or steel that have been carefully machined 
so that the opposite faces are parallel with each other. 






jffiq lffTr 



They a re made of various sizes and thicknesses, to be used 
,or different thicknesses of work, and are usually made in 
Nft After the roughing cut is taken over the top face of 
'he *ork, it is well to caliper its thickness at the ends to 
ffla kesure that it is being planed parallel. 

'". L'se of the Surface Gauge. — Suppose that one 
8 « of a tapering piece of work is to he planed. Then a 
line is |jjd out and marked by prick-punch marks to aid in 



12 



PLANER WORK. 



§8 



setting the work correctly in the vise jaws. For testing the 
setting, a surface gauge, one design of which is shown at 
5 in Fig. 12, may be used. A surface gauge consists of a 
heavy base b with a flat face that carries a standard c of 
some kind, to which a pointer / is attached by a clamping 
device in such a manner that it can be moved along the 
standard and clamped anywhere. In addition, the pointer 

Q 



IS 



jQl 




jQl 





PlG. 12. 

can be swiveled around the clamping device. In use, the 
pointer p is adjusted to one end of the line a drawn on the 
work, which in Fig. 12 is shown held in the planer chuck. 
The base resting fairly on the platen, the surface gauge is 
now moved to the other end and it is noted if the pointer 
coincides again with the line a. If it does not do so, the 
work is shifted by tapping it lightly with a hammer and 
the testing and shifting is repeated until the surface gauge 
shows the line a to be parallel to the platen. 

18. When a number of tapering pieces are to be planed, 
tapered strips may be used in the vise to set the work on, 
in the same way that parallel strips are used to produce 
parallel work. When these tapered strips are used, the 
work is bedded fairly on them; there is then no necessity of 
setting each piece separately by the aid of a surface gauge. 



§8 



PLANER WORK. 



13 



19. A surface gauge may not only be used in setting work 
to aline, but is also well adapted for testing the parallelism of 
surfaces with the platen. For instance, let a piece c having 
the profile shown in Fig. 13 be held in the chuck, and let it 
be required to adjust it so that its surfaces a and b are both 
the same height above the platen. Then the contact point 
of the surface gauge is placed on the surface b y while the 



p 



i 



1 1 

!! 



<k 



ua JjlpF^ a ^p£ 




Pig. 18. 



base rests fairly on the platen ; the surface gauge is now 
placed on the other side of the work in the position shown in 
dotted lines, and it is observed if the contact point touches 
the surface a. If it does not do so, the work is moved as 
required; the contact point is readjusted, and the setting of 
a and b is tested again. This operation is repeated until 
the surface gauge shows a and b to be at the same height 
above the platen. 

20. Special Jaws. — For some classes of work, spe- 
cial jaws may be made and fastened to the regular jaws of 
^ e planer chuck for holding particular shapes of work. 
But if many such pieces are to be made, it is better to make 
a s Pecial jig, or holding device. 

21. Truing the Planer Chuck. — When it is found 
that the planer vise is out of square, thus causing the work 
to be held untrue, the vise should be trued by taking a very 



i 



14 



PLANER WORK. 



§8 



light, smooth cut over the jaw c 9 Fig. 5, and also over the 
bottom of the jaw on which the work rests. Before this 
cut is taken, the chuck should be cleaned thoroughly, and 
care should be taken that there are no chips or dirt between 
it and the planer platen. 



BOLTS AND CLAMPS. 

22. Method of Applying. — If the work is large, or for 
other reasons cannot be held in the ordinary chuck, it may 
be fastened to the platen by bolts and clamps. T slots 
are cut in the top of the platen to receive the boltheads, and 
holes are provided for pins to keep the work from slipping. 

23. Fig. 14 shows a part of a planer platen with a flat 
block a fastened to it by the use of bolts b, b and clamps c y c 




Pig. li. 

resting on packing-blocks d, d. These clamps are pieces of 
flat bar iron 2 inches by £ inch, or of similar proportion, 
with holes drilled near the ends for the bolts to pass 
through. When applying clamps to a piece of work, care 
should be taken to adjust them so that the bolts come very 
near the work, as shown in Fig. 14; also that the packing- 
blocks d y d are the same height as the work, or slightly 
higher. Fig. 14 also shows how stop-pins e y e are used to 
prevent the work from sliding along the platen while a cut 
is being taken. The stop-pins are merely removable pins 
inserted in holes drilled in the platen. 

24. Imagine that in Fig. 14 the piece a is the pack- 
ing-block, and that d is the work. Then, with the bolt b 



§8 



PLANER WORK. 



15 




(a) 



close to the packing-block, the tightening of the nut will 
cause the clamp to grip the block tightly, while the work 
will be left comparatively loose. For this reason, the bolt 
should always be placed as close as possible to the work. 
Now, if the packing-block is too low, the bolt must bend 
when the nut is tightened, owing to the clamp sloping 
downwards. Furthermore, the tendency will be for the 
clamp to push the work away. 

This is shown in Fig. 15 (a). It will be observed that as 
the nut on the bolt is screwed down, the clamp bears only 
against the edge of the 
work and the packing- 
block, and that the pres- 
sure is acting not directly 
at right angles to the 
platen, but at an inclina- 
tion to it. In conse- 
quence of this, there is a 
tendency for the work to 
slide away from the 
clamp. Since the clamp 
»s m line contact with the 
extreme edge of the work, 
!t is very likely to mar the edge badly. For these reasons, 
car e must always be taken to make the packing-block 
high enough to insure a fair bearing of the clamp on the 
w ork. When the packing-block is just the same height 
as the work, and the clamp is bent and applied with its 
convex side downwards, as shown in Fig. 15 (£), or when 
the clamp is so thin as to readily bend when the nut is 
ll ghtened, the same effect will be had as if the packing- 
block were too low. That is, there will be a tendency to 
P u sh the work away and also to mar the edge. Now, if 
t" e packing-block is slightly higher than the work, the edge 
°* the clamp will be in contact with the surface of the work, 
an d any tightening of the nut will, by reason of the bending 
°* the clamp, bring it in more intimate contact with the 
surface of the work. 




to 

Fig. 15. 



PLANER WORK. 



25. Shapes of Planer Bolts. — Planer bolts are ordi- 
narily made with large square and flat heads; they are 
slipped into the T slots in the platen from the ends. This 
form of head is the strongest. It sometimes occurs in 
clamping work to the platen that when heavy work is set in 
place, it is desired to apply a bolt and clamp to some part of 
the inside of the work without moving the latter. For this 
purpose, a special form of bolthead is used that allows the 
bolt to be slipped into the T slot from above, instead of 
from the ends. Fig. 16 (a) shows such a bolthead; two 
opposite sides are cut away so that it will drop into the slot. 
After it is in place, it is given a quarter turn, so that the 
head comes under the lips of the T slot. The bolt is kept 
from revolving when the nut is tightened by the ends of the 
head coming against the sides of the T slot. 

Another method of applying clamping bolts to such places 
is by means of a T-shaped nut, as shown in Fig. lti (&). 



£MJ 







This nut may be slipped along the T slot and under the 
work to the de=ired place, after which a bolt may be screwed 
into it. 

26. Bent Clamps. — Besides the common flat clamp 
shown at c in Fig. 14, the bent clamp a shown in Fig. 1? is 
often used. A bent clamp is convenient when it is desired 
to keep the end of the bolt out of the way of the tool as it 
passes over the work, or when no bolts long enough for 




§8 PLANER WORK. 17 

a straight clamp are available. It is a rather expensive 
clamp totnake and does not possess any particular advan- 
tages over a straight clamp; for this reason, it is rarely u^ed 




thickness art t 




by experienced planer hands, except for work where 
straight clamp will not answer. 

27. When a number of pieces of the 

be planed, a clamp may be 

made as shown in Fig. 18. 

This clamp has one end 

tent over at a right angle; 

the bottom is cut off paral- ^^^^^^^^ 

W to the top, so that when 

■, , , no. is. 

" rests squarely on the 

table, the top of the clamp will be level. With this style of 

damp, packing-blocks are unnecessary. 

28. U Clamps.— Fig. 19 shows a form of clamp that is 
desired to remove the clamp 
without removing the nut fruit 
the bolt. This clamp is made 
of square iron and is bent into 
a U shape, with an opening 
sufficiently wide to allow it to 
slide over the shank of a bolt. 
nient on account of the fai E 



ver y convenient when it 




Fio. 19. 

I' will also be found conv 




18 PLANER WORK. § 8 

that the bolt can be moved along the clamp in order to get the 
bolt into the most desirable position. Likewise, the clamp 
can be moved to suit the work in case the bolt must occupy 
a certain position. Taking it all around, this is probably 
the most useful form of clamp for general work, since it has 
the widest range of application. It is applied in the same 
manner as the ordinary flat clamp. Always place a washer 
between the clamp and the nut used for tightening it, in 
order to have a fair bearing for the nut. 

29. Finger Clamps With Bolts It often occurs that 

some flat face is to be finished all over when the work is of 

such a shape that there is 
no place to put the clamps 
except on the top face. In 
that case, the work is often 
planed as far as the clamps 
allow; the clamps are then 
moved to the planed part 
*** and the cut is continued. 

Sometimes, however, it is possible to drill holes in the 
side of the work and use finger clamps, which save 
much time. Fig. 20 shows a side view of a piece of work a 
with a finger clamp b in place. The clamp has one end 
forged or turned round so that it will fit loosely into the 
drilled hole. If these holes are drilled into the solid cast- 
ing, they may be filled after the work is finished. The 
conditions of each particular case will determine whether 
a finger clamp can be used or not. When it is inadvisable 
or objectionable to drill holes for them, the work must be 
held in some other manner. 




30. Shape. — A very convenient method of fastening 
work to the planer is by the use of planer pins, or screw 
plugs, one of which is shown in Fig. 21. One end a is 



PLANER WORK. 



turned round to fit the holes in the platen, while the other 
is left square and tapped for a steel setscrew b. Fig. 22 





On 



d 



shows the same style of pin made to fit in the T slot of a 
planer platen. 
31. Method of Usin^.— Fig. 23 (a) and (£) shows how 

they may be used. In Fig. i'-i (.;), pinner strip a, which 
a been previously planed square, is bolted to the platen so 
it the edge against which the work bears will be true with 




we line of cut. Sometimes two pins like c, c are used in 

the strip a. In Fig. 23 (a) the planer strip a is 

provided with a tongue that fits the T slots and is bolted to 

I platen, while in Fig. 23 (/') tiie planer strip is 

made a tight fit in the slot. The work h is put 

e strip, and t wo pins c, c with setscrews are put in 



PLANER WORK. § 8 

: holes in the platen and the screws set up against the 
work. The screws push the work against the planer strip. 
While the friction will be sufficient to hold the work against 
light cut, it would he pretty sure to slip under a moder- 
ately heavy one, and hence stop-pins d, d should be placed 
in front of the work to prevent any longitudinal move- 
ment. 

32. Toe DogH. — Thin work may be fastened to the 
platen by screw pins and toe dogs. The toe dogs used for 
this class of work are 
shown in Fig. 2i. They 
are usually made of tool 
steel with one end flat- 
tened to press against the 
work and the other cupped 
to receive the end of the 
setscrew. The thin end 
may be hardened, so that 
its edges n, a will cut into the work and thus be kept from 
slipping. Some persons prefer a wedge-shaped edge, like 
that of a chisel, on the flattened end. For holding work 
that is finished on its edges, it is advisable to make the toe 
dogs of soft iron to prevent them from marring the work. 

A number of pins and dogs may be put on each side of 
the work. It may be seen, by referring to Fig. 25 (a), that 




as the screws a, a are tightened, there is a tendency to push 
the work b down on the platen, thus holding it securely. 



33. The slant of toe dogs must not be so great that the 
tightening of the setscrew will tend to turn the outer end 



§8 



PLANER WORK. 



21 



upwards about the edge in contact with the work. In gen- 
eral, the inclination of a line drawn from the point of con- 
tact to the point of the setscrew should not exceed 10°. 

34. Toe dogs are sometimes applied to work held in the 
planer vise. They are then placed between the jaws of the 
vise and the work, so that the tightening of the movable 
jaw will press the work to the bottom of the vise. In some 
cases, toe dogs may be used in connection with a planer 
strip; being then placed on one side of the work only, they 
will push the work against the planed side of the planer 
strip and down on the platen at the same time. 

35. Since toe dogs do not hold the work very tightly in 
the direction of the cut, it is always advisable to put stop- 
pins in front of the work to keep it from slipping. 

A thin strip or straightedge may be used with or in place 

of toe dogs for holding work. Fig. 25 (b) shows a piece 

of work a held on a planer table by the straightedge b and 

the toe dogs c. The straightedge rests against a planer 

strip d or against two blocks bolted down in the same 

manner. The piece b is inclined as shown, so as to keep 

the work in contact with the table. A straightedge may 

be used in a similar manner for holding work in a planer 

chuck. 

36. Clamping Round Work. — If a shaft is to have a 
keyway or spline cut along its length, it may be clamped to 
the table in the manner shown in Fig. 26. Here the shaft a is 




FIG. 26. 



held in one of the T slots in the platen, and bent clamps b y b 
arc applied to each side. To keep the clamps from slipping 



22 



PLANER WORK. 



§8 



down on the sides of the shaft, stop-pins /, / are put in 
the platen to hold the clamps in place. If one clamp is made 
much tighter than the others, there is a tendency to spring 
the work, especially if there are many clamps along the 
side. The stop-pins may be made with an enlarged cylin- 
drical head to prevent their slipping through the platen. 
The shoulder at the junction of the head and shank may be 
beveled slightly ; this allows the point of a screwdriver or 
pinch bar to be used for prying them out of the hole. 



37. A better method of holding long shafts that are to be 
splined is to have a long planer strip a bolted to the platen, 
as shown in Fig. 27. This is beveled as shown so that 




Fig. *7. 

when the shaft is pressed against it by the setscrew, it is 
held down firmly. By this method the shaft is kept 
straight. 

To prevent the points of the setscrews from marring the 
shaft, a guard piece b should be placed in front of each set- 
screw. When the point of the setscrew is much higher 
than the axis of the shaft, it may be necessary to put a 
packing-block c between the lower end of the pin and the 
guard strip. The center of the setscrew should be at least 
as high as the axis of the work, or slightly above it; other- 
wise, there will be a tendency for the shaft to rise up when 
the setscrews are tightened. As the pressure of the cut is 
considerable, a stop-pin should be placed in front of the shaft. 



PLANER WORK. 



38. V Blocks. — If a shaft has different diameters, it 
may not be possible to 
hold it by the methods de- 
scribed. V blocks may 
then be used for support- 
ing the shaft, as shown in 
Fig. 28. A number of 
these blocks are planed 
exactly alike, and have 
tongues on the bottom 
that fit the T slots in the 
platen and insure correct alinement. These blocks are put 
on the platen in such positions that the parts of the shaft to 
he supported that have equal diameters will rest in them. 




PI.ASF.R tENTERS, 

39. Construction and Use. — Fig. 20 shows a set of 
planer centers used for certain classes of work. These 
centers are clamped to the platen ; tongues on their bottom, 
ff hich fit the T slots, insure that they are in line with each 
other and with the line of motion of the platen. The work 




is held between them in the same way that it would be held 
between lathe centers. A dog is fastened to the work and the 
tail is held in the slot in the arm a. Referring to Fig. "i'i («), 
a *orm-wheel b is shown. This is rigidly fastened to the 



PLANER WORK. §8 

headstock spindle; by means of a worm engaging the worm- 
wheel and a handle c fastened to the worm, the headstock 
spindle may be revolved by hand. The worm d is shown 
clearly in the end view given at (b). By examining this end 
view, it will be noticed that several concentric rows of holes 
are drilled into the worm-wheel, the holes in each row being 
spaced equidistant. A movable arm e is fastened to the frame 
of the headstock in such a manner that it can be rigidly 
clamped. This arm carries on one end a latch pin/", which 
has a small cylindrical projection that fits the holes in the 
worm-wheel. By means of the holes and latch pin, quite a 
number of equal divisions of the circle may be obtained. 

in. To Find What Divisions Can Be Obtained. — 

To find if a given number of equal divisions can be obtained 
with the number of holes in the various rows, use the fol- 
lowing rule: 

Kulc. — Divide successively the number of holes in each row 
by the number of parts into which a circle is to be divided, 
[f the quotient is a whole number, the proposed number of 
parts can be obtained. The quotient is the number of holes 
which the latch pin must be advanced. Never count the hole 
the latch pin is in when starting to make a change. 

Example, — There being 72, 64, and 66 holes in the three rows on 
the worm-wheel, can a circle be divided into 14 parts ? 

Solution. — Dividing 72 by 14, we get fifr as 'he quotient. As this 
is not an integral (whole) number, try the row having 64 holes. hi\ i- 
ding 64 by 14 we get 4fV as the quotient. Since this is not a whole 
number, try the last row. Dividing 56 by 14, we get 4 as the quotient, 
which is a whole number. This shows that, by moving the worm- 
wheel 4 holes at a time in the row having 56 holes, we can obtain 
14 equal divisions. Ana. 



am; I i: PLATES. 

41 . How Angle Plates Arc Used. — For some classes 
of work, an angle plate, shown at a in Fig. 30, is very 
convenient. This angle plate is planed so that the two 




PLANER WORK. 



outer surfaces make an angle of 60° with each other. When 
used, one face is bolted to the platen, as shown in the illus- 
tration, and the work is bolted to the side of the angle plate. 




lien one side of a piece of work has been finished and ail- 
her side is to be finished square with it, the work is bolted 
ith its finished surface against the angle plate by bolts and 
amps, used in the same way as when fastening work to the 
ate 11. 

42. The angle plate is especially adapted to work where 
ic surface opposite the side to be finished has such a shape 
lat it cannot be conveniently bolted directly to the platen, 
j occurs, for instance, in the piece shown in the figure. ■ It 
ill be seen that the under side is a curved surface. 

43. Planer Jacks. — When the work projects a con. 
lerable distance from the angle plate, it should be Bup 
>rted near the free end in order to prevent it from springing 

way from the cut. Planer Jacks are very convenient 
t this purpose; one of these is shown applied at 6 in 
ig. JO. 

44. One form of a planer jack is shown in Fig. 81, 
consists of a base a tapped to receive the screw b. 



PLANER WORK. 



!*• 



through the head of 



hich two holes are drilled at right 
angles with each other, to admit 
the adjusting pin shown. A cap 
i is attached to the head by a 
ball-and-socket joint, to allow the 
cap to adjust itself to any slight 
inclination of the surface to which 
it is applied. The cap may be 
checkered, as shown, in order to 
prevent it from slipping. These 
jacks may be made in various 
Pio. ft. heights to suit conditions. 

45. To Keep Work From Slipping. — Under a 
heavy cut there is danger, where two planed surfaces are 
placed together, that the work will slip. This danger may 
be lessened by placing a piece of paper between the sur- 
faces before clamping. 




CLAMPING BV CLVI7CG. 

46. Very thin and flat work that is to be planed 3 
over its top surface cannot be held very readily by 1 
dogs. If straight clamps are put on top, they must 1 
shifted after part of the surface has been planed, 
many cases, however, such work may be held without a 
clamps at all by a method that for want of a belt 
name may be called sluing. The edges of the work, s 
the platen right around the edges of the work, are care- 
fully cleaned and made fairly bright with coarse emery 
cloth. Melted rosin is then applied around the edges; 
this, if the surfaces to which it is applied are absolutely 
free from grease, will stick surprisingly well to them, and 
will offer enough resistance to hold the work securely 
against a light cut. Melted shellac, sealing wax, or pitch 
may be used instead of the rosin; the rosin is usually 
easier to obtain and is cheaper. This method of fastening 
obviates any danger of springing the work in clamping. 







PLANER WORK. «7 

SPRING OP THE WORK IK CLAMPING. 

-47. Flat Bearings. — So f.ir it has been assumed that 
the face of the work is true, so that it has a large fiat sur- 
face bearing against the jaw of the chuck or on the planer 
platen. Such, however, is seldom the case. When the 
casting or forging is first put on the platen, it rarely touches 
1 more than three points, and when the rough piece is cor- 
rectly set for the cut, probably not more than one point 
actually touches the platen, the other points being supported 
t packing or blocking. 

-48. Packing Under the Work. — When a clamp is 
ised, there should be a support under the work at that 
prevent springing it. Suppose the piece shown in 
Fig. 33 is to be clamped to the platen. The piece is crooked 
OH the bottom, so that it touches only at the points d and b. 
If clamps be applied at the ends of the work and then tight- 
ned, the work will spring down at the ends, bending around 
i points of support a and b. If a cut is taken over the 



work while it is thus sprung, it will be found upon releasing 
he clamps that it will spring back nearly to its original 
id, hence, the planed part will no longer be straight. 
Vhcn clamping work that dues not touch the platen directly 
nder the clamp, a blocking piece or packing piece should 
r put under the work at that point, so that when the 
clamp is tightened, the end cannot spring down. Paper or 
sheet iron is often used for packing. In many cases, a thin 
i or copper wedge is found convenient for packing up 
,nd also for setting the work. 



PLANER WORK. 



88 



CARE IN SETTING I III WORK. 

49. Position on the Bed. — When a large piece is to 
be planed or finished on a number of surfaces, it should be 
so set that all the surfaces can be finished in their proper 
relation to each other. The work should be laid out by 
drawing lines on the various surfaces to indicate the amount 
of metal that is to be removed. The work is then set to 
these lines so that all the surfaces can readily be worked 
upon. 

Suppose a lathe bed is to be planed. In this case, the 
top and bottom parts should be planed parallel. It may be 
found that the bed is considerably warped and twisted 
After the bed is put on the planer, it is leveled up by the 
use of shims, or wedges, under the ends and sides until 
it has a fair bearing. For testing the top face of the 
bed, or the face about to be planed, the surface gauge may 
be used at the end and along the sides to see that the work 
averages the same height. When the work is adjusted will 
the wedges and packing so Lhat the top face appears about 
level, the clamps are applied, care being taken that they a 
over the packing pieces. 

50. RewetUne. — If a piece has been planed true and 
is turned over on the platen, it may be found that it does 
not remain true but is slightly warped, so that there is <j 
slight amount of rocking motion when the work rests on the 
platen. In such cases, the piece should be supported on 
thin pieces of paper at the four corners. It will be found by 
pulling the pieces of paper that two are tight and two an 
loose. More paper should be put under the loose cornel 
until the papers at the four corners are all pinched with th 
same pressure. When care is used, it is possible to give . 
very even bearing. 

51. Use of a Level. — When a surface that has bi-cn 
removed from the platen after planing is to be set again, it 
may be set level and tested by the use of the surface gauge. 
The work is often of such shape that the surface gauge 



I 



PLANER WORK. 2!) 

annot be used. In such cases, a spirit level may be employed. 
Tien the level is used for setting work, the platen should 
irst be tested with it to see that the platen itself is level. 
Planers should be set so that the platen is level in the direc- 
on of its length and width. If the platen is set level, the 
work may be set by the use of the level. 

When the level is not at hand, or cannot be used, a tool 
nay be clamped in the head and adjusted so as to almost 
ouch the work at one corner. The work can then be moved 
nder the tool by moving the machine, preferably by hand, 
nd if there is any unevenness in height, it will be apparent. 



SPECIAL JIGS FOH HOLDING WORK. 

52. When there are a number of pieces to be finished, it 
s generally preferable to make a special Jig for holding the 
work. By doing this, much time may be saved. In devi- 
sing special jigs for holding work, the aim should be to hold 
the work securely and accurately, and at the same time to 
have the jig so simple that the work may be changed quickly 

rnd easily. 
53. Planing a Number of Pieces at Once. — Much 
time can often be saved by setting a number of pieces on 
the platen so that they will all be planed at the same time. 
This is especially true when much time is required to adjust 
the tool to the cut. After it is adjusted to one piece of 
work, the tool runs the whole length of the table, cutting 
:ach piece of work to the desired shape. 
Fig. 33 shows very clearly how a number of pieces may 
on the platen at the same time and a number of cuts 
Inken over all of them. In this case, eleven pump frames 
with cylinders cast on their ends are so arranged that they 
may all be planed at the same time. Each casting is care- 
fully set and clamped in place, care being taken in setting 
hat the space between them is as small as possible. The 
laner used has four heads. The two heads on the cross-rail 



30 PLANER WORK. 

work on the top of the cylinders, planing the valve seats and 
the joint for the steam and water chests. On either side, 
a head is used for squaring down the end for the cylinder 
heads. All the feeds in this case are automatic. 




nut 
P la< 



54. Special .lacks or Unices for lliuh Work, 
Fig. 34 shows two large pillow-blocks for a steam engi 
supported on the planer white a cut is being taken off thei 
bottom faces. The pieces, being quite high and havinj 
narrow bases, have a tendency to tip when a heavy cut 
being taken. To avoid this, after the work is set. the 
■pedal planer Jacks shown at a are employed. This 
particular form of jack is very convenient for this and simi 
lar classes of work. By placing the end b of the jack a 
one of the holes in the planer platen and swinging the othi 
end c into some angle of the ccsting, then by turning tl 
nut <i the jaw c is forced out against the casting. By 
placing two jacks under the end of a large casting in the 



I 




PLANER WORK. 



a 



the sliank of g and a washer C is sometimes used next the 
out for the nut to turn against. The piece d is simply a 
piece of gas pipe and may be of any desired length. The 
pieces n, b, and e are picked up and the pin on either a or c 
put into a hole in the planer platen. Then the gas pipe is 
put on the other pin and the screw g is slipped into the other 
end of the gas pipe. The whole jack is then turned to the 
desired position and tightened by the nut /"until the work 
is properly supported. 

55. Example of Clamping Heavy Work.— Fiff. 3(1 
shows a piece of work that, because of its peculiar shape 
and great weight, is difficult to hold on the platen with- 
out some special device. The two pieces shown are the 
■ of the frame that supports the cylinder of a ver- 
tical engine. A yoke a is here used to support the upper 
sada "i the frames. This yoke is bolted to the platen and 
the end of the casting rests in it. The flange on the casting 
keeps it from slipping down, while setscrews b at the side of 
the yoke are used for adjusting the work. The lower end of 
the casting overhangs the table. It is kept from slipping 
along the platen, when a cat is being taken, by the use of .i 
heavy bar r, which is bolted to the platen. A setscrew d in 
the end ci tin- bat is used to make slight adjustments when 
setting the work true. Planer jacks r, r are also used to 
keep the work from slipping and tipping. The clamps for 
holding the work down are shown at /and g. When such 
heavy work as this is securely braced and rests fairly on a 
special fixture or special holding device, its weight helps to 
hold it down, so that very heavy clamps are not necessary. 



PLANER WORK. 



PLANER TOOLS. 

1. Cutting Principle. — In the case of planer tools 

the principles underlying the cutting operations do not differ 
materially from those of lathe tools, with the exception of 
the fact that planer tools always work on a flat surface and 
hence the angle of front rake Of clearance cannot be varied 
by changing ihe position of the tool. The shape of planer 
Eoola varies somewhat and is determined by the kind of 
be cut, the hardness of the metal, and whether the 
cut being taken is a roughing or finishing cut. 

2. Anisic* uf Kake and Clearance. — -A common 
form of (orged planer tool is shown in Fig. 1 (it) and (4). If 
through the point o of the tool a line a b be drawn perpen- 

to the surface of the work and a line cd parallel fed 
the surface of the work, the angle dvf will be the angle <if 
el**ranc«f or front ruk«. In this case the line ab coin- 
cides with tht top face of the tool, hence the tool has no top 

ike. In Fig. I (b) the bottom of the tool is shown. 
The line gh is drawn at right angles lo the line of motion of 

net platen, and the line ki is drawn along the front 
face of the tool. The angle hvi is the angle uf Hide rake. 
It will be seen thai the angle of front rake cannot be varied. 
The angle of side rake, also, depends on the grinding of the 
tool and ! tools cannot be varied, by setting. 

the planer tool always has a constant angle of clear- 
ance and a constant angle of keenness that cannot bt 
§9 

For Hotter i.( copyright, n.-e page ImmsdiMely Following ihc tills p»b». 
T I II -22 



PLANER WORK. 






varied by changing the position of the tool in relation to th 
work. In the case of some tools having a curved cuttin 

edge, it is possible to vary the angle of sid^ 
rake slightly by changing the position of the 
tool. The position of the planer tool rela- 
tive to the work corresponds to that of a 
lathe tool when the point is set level with 
the center. Tools for planer work are 
forged with from three to five degrees of 

J clearance. 

The keenness of a planer tool depends 
I \ largely on the angles of top front rake and 
f/t/w f top side rake. The strength of a planer 
^^' tool depends on its angle of clearance and 
' a) the angle of top rake. 




3. Forged Roughing Tools. — Ordi- 
narily roughing tools for planer work are 
of the form shown in Fig. 1, though for 

/I m heavy roughing a tool of the form shown 

* in Fig. 2 is frequently employed. In this 

FlG " lm tool it will be noticed that the cutting edge 

has been formed by upsetting the end of the tool so as to 
bring the cutting edge above the upper surface of the shank 
of the tool and the nietal has not been cut away or reduced 
back of the cutting edge, as in the tool shown in Fig. 1; 
this results in a very much stiffer tool. The amount of 
rake, or clearance, given to these tools depends on the hard- 
ness of the metal to be cut and also, to some extent, on the 
depth of the cut. In the tool shown in Fig. 2, the cutting is 
done entirely along 
the edge A fi t while 
the back edge CD 
coincides very nearly 
with the shank. This 
form of tool will turn 
a chip up and away from the surface of the work; it will 
also produce a nearly flat chip, which is easier to bend 



c ^ 




Fig. 2. 



§9 



PLANER WORK. 



than a curved chip. The objections to the form of tool 
shown in Fig. 1 are that the surface being cut is a curve and 
hence the chip will not roll away from the tool as freely and 
also the stock back of the cutting edge is so reduced that the 
tool loses much of its stiffness. 




Pio. 8. 



&• For very heavy roughing work a form of tool known 
as the clam-shell tool is frequently used. This is shown 
» n Fig. 3. It will be seen that the cutting 
e dge of this tool is very much like that of 
the tool shown in Fig. 1 (a). The cutting is 
done along the outer curved edge. The tool 
is forged like an ordinary straight-side tool 
an d is then bent to the desired curve. The 
principal advantage that this tool possesses 
,s that it requires less work in grinding, 
owing to the fact that there is a smaller 
su rface of metal to be ground away on the upper face of the 
tool to produce a sharp cutting edge; also it is easier to 
draw the cutting edge above the face of the tool than it is to 
u pset the whole end of the tool, as in the case of the form 
shown in Fig. 2. The cutting edge may be made practically 
straight, as in the tool shown in Fig. 2. 

5, Forged Finishing Tools. — -"For finishing cuts on 

cast iron, a broad square-nosed tool of 
the form shown in Fig. 4 is used for 
surfacing; this tool is given a little top 
front rake. For finishing wrought iron 
and steel, a similar tool having a much 
narrower point is frequently used. Some- 
times for finishing wrought iron or steel 
a tool similar to that shown in Fig. 1 
is used, in which case the curve at o is 
made much flatter and at times the 
point of the tool is ground perfectly 
pig. 4. fl at £ or one-eighth inch or so, blending 

into a curve at each side. 




PLANER WORK. 



6. For finishing side cuts, the siile tool is em] 
me [or heavy work is shown In Fig. .'> (,i). Th 
s forged thin along its cutting edge A B \ 




that it [a thick at the back, to give ii strength; the cut- 
ting face t is ground thin and is given enough i teai 
that tin- tool can be made to cut along iis entire i ■:■ 
cutting edge A B slopes back from ih< shank ol the tool sou 
to givea shearing i ul ; this is ad\ a ■ ount ••( llw 

fact that ii gives less shock when entering or lei 
cut, .is the cutting starts near the corner A' and I 

ry to move the I gradually inci ■ 

cut is being taken. At the end of the stroke the tod 
gradually runs out of the cul with I ■ 

■ 
the 'Hi tends to push the work down on the plati n ■■ 
reduce the liability of the work from clipping. 

Sometimes it is necessary to finish a side cul 
shoulder, in which case a tool ul tin 
cannot be used, owing to the form of the i 
l'i,r ml h work, ;i tool i>{ i In 1..1 m shown in H ..■ 
employed, in whh h i ase the ■ lilting ■ 
shank of the tool and the general form of ; I 
similar to the Bide tool used in lathe work, ki 
gained entirely by front and top rake, 

7. Tool holders, of which man) form ai 
planer wot k, ai e i spi dally scrvh cable 01 
fact that the inserted blades used in them require a much 







|! 



PLANER WORK. 



■mount of steel than would be necessary if the 

t of the forged type. Self-hardening steel 
pita BiceKeot results on planer work, espe- 
cially for roughing cuts, and self-hardening 
"*•! tools are very largely used in the tool 
wltferg, Any tool holder intended for use in 
W planer should have a very stiff shank and 
'hould he so arranged as to hold the cutter, or 
k' a <le, firmly and support it close to the cut- 
''"gedge. A common form is shown in Fig. 6. 
j te ' >f holder the blade may be set 
' n line with the shank for flat surfaces, or it 
'"'V 1 ' lie turned to either side for right-hand or 
ef '-hand cutting. In some cases it is well to 
" IK the tool so that the shank travels in 
"I'ance of the blade; this is done to avoid the 
^"ger of the tool's springing into the wink, or F1 °- ■■ 

•"tcring, which is liable to occur when the cutting edge is 
far in advance of the point of support 
or when cutting a broad surface. This 
matter will be taken up more fully under 
the heading, " Spring of Planer Tools. " 




8. Ganjr, Planer Tool*. — Where 

only a single planer tool is used, it is 
sometimes impossible to increase the 
feed greatly without bringing an exces- 
sive strain upon the tool and planer 
head; besides, an excessive feed results 
in a rough surface and in badly breaking 
off the edge of the work where the cut 
runs nut. It is mainly to increase the 
capacity of planers that multiple-head 
planers have been brought out, and in 
large work it is no uncommon tiling to 
BC< two tools in heads upon the cross- 
1 one tool on each housing operating on the casting 
Mat!) pieces of work are of such a form 



PLANER WORK. 




that it is impossible to get two heads over then 

mum time and yet it would be advantageous If a 

feed could be used, To meet these requirements, the 

|[uni; plantr tool, ODC form "I win- ■ 

Fig. 7, has been brought out. This consists oi 

nary shank a to which an adjustable head b is attached. 

This head is pivoted on a pin oppoeit* tin ■ 

the shank c< and can be adjusted by means of clamp 

Bcrawa ' bo that the cutting edges <i of the tool) 

only slightly it) advance of each other, or so that - ■ 

will take a considerable cut. The tools t are all ground Id 

.1 gauge and are brought into their proper position in the 

head by clamping the shank a in the tool block and allowing 

the points of the tools 1 to rest upon the platen, after won b 

they are secured in place by the sctscrews/. The ret 
offered by a cu! varies, probably, at least as the squan 
thickness of the chip, and as a consequence a cut givil | 

J inch thick would, I hew 

offer sixteen times 

the resistance offered by a 

chip ^ inch thii I 

this it will be seen that by 

Fl °- B - using the multiple-tod head 

ble to take heavy roughing cuts, using an apparently 

. . si feed, and at the same time have the chips cut thin 

by the individual tools. Pig. 8 shows the waj in a 

four tools of the gang divide up the cut between them. 

9. sprliiu of Pinner Toole, Owing to the fact th, 
the cutting edge of a planer tool is llsllalh in advi 
point of support, there is more or less ol a ! . 
to spring into the work, This is well ill- 
Fig. 9, where the tool bends about the point a, th 
the tool Following the arc J /■'. It will be noticed that I 
arc cuts deeply into the work. In the foi 
the cutting edge is considerably in advan 
support, hence the tendency to spring in i 
this tendency becomes less as the cutting edge is brouj 
more nearly beneath the point of support, if the cult 



PLANER WORK. 



edge is carried back of the point of support, the tool will 
liaw a tendency to spring away from, or out of, the work; 
when in this position it is called an underhung tool. Such 



£: 



%^f 



L 



a tool is shown in Fig. 10, where, however, it is only carried 
tock of a plane passing through the point a. If the tool 





12 , J. 


/' 


K. 


V Js* 



"sad is loose on the cross-rail or there is any spring in the 
cross-rail, the whole tool head may tend to rotate about the 
P°"it b, in which case the tool will swing into the work along 



PLANER WORK. 



J' 



the arc fi /■'; if the head is perfectly rigid, the point of tli? 
tool will tno*e along the arc A B, and heno will ad b nd I 
t-iitcr deeper into the work. Sometimes, in ordb 
further reduce the tendency of the tool to enter th 
the edge is carried well back, or underhung, M 
Fig. 11. In this c.iso rotation about the points a or c would 




carry the point of the tool along the arcs A B and CD, 
uf whit ii would tend to lift it om of the work. 

i : 1 1. .mi the point b would only tend to carry I In 

the tool into the work very slightly Of i ourse the pencil I 
cannot he determined definitely, as can the points a and t, 
and depends on the style of the cross-rail and the fit of the 
bead Upon it, but in a m>uU sliff planer there should be link 
or no tendency to motion from this cause. 

It). Special Forms of Finishing Tool-. 
nosed or special nnlshlniE toota, if forged fromaolid stock, 
are very expensive. On this account various forms of spc- 
ciil tools, iii which the cutting edges are formed 
pii Ms of sice! boiled or clamped to a hold* I 
Fig IS shows three tools of this class. The one shown « 

■ (<*) is intended for finishing verj 
The steel tool a is clamped to the shank d by two capscrews. 






PLANER WORK. B 

'he '.lilting is done by the edge be. The tool shown at 
'ig. VI (b) is intended for finishing a narrower flat sui fai ■> ■, 
aving a square corner. The cutting is done along the edge 
c and the steel tool a is made square with the four cutting 
dges, so that any one of them can be brought into the posi- 
ion be. The tool shown at Fig. 13 (c) is intended for fin- 
ihinp a lillet of large radius. The cutter a is circular in 




orm, the cutting being done along the edge be. The cut- 
can be rotated on the clamping bolt and clamped in 
ay desired position, so that all parts of the edge can be used 
■fore sharpening. All these special tools are underhung, 
hat is, the steel tool proper is clamped to the back side of 
he shank. Cutters or blades having an irregular outline 
nay also be used on shanks similar to those shown in Fig. Vi. 



PLANiSU OPERATIONS. 



TAKING A CUT. 



I'l, \ M-. SUUFACING. 

Clamping the Tool. — When taking a cut over a 

■ tool should be rigidly clamped to the 

ool block, so that the i ntting edge projects as little beyond 

.■ I'.n.'l block lis is necessary to insure rigidity of the work. 

Phe cross-rail should be adjusted as close to the work as 

practicable, and should be clamped rigidly to the housings. 



10 



PLANER WORK. 



ft 



The tool is adjusted by means of the down-feed handle sc 
that it will take the desired depth of cut. Care should be 
taken to see that all parts of the planer are so adjusted that 
there is no lost motion. The screws in the gibs of the 
down-feed slide should be tightened so that the head can be 
fed up and down with no shake or lost motion, and the gibs 
fitting the cross-rail of the planer should also be tightened sc 
that the planer head can be fed along the crosshead freely, 
but without any lost motion. Usually at the beginning of a 
cut the tool is fed to the work by operating the feed-screw by 
hand. After the cut is started the automatic feed is thrown in. 

Action of tbe Feed-Motion. — The feed-motion 
is operated by the rack », Fig. 13, at the 
side of the housing, which is connected 
with the feed-disk at its lower end by a 
connecting-rod. This connecting-rod is 
pivoted to a block that slides in a slot cut 
in the disk; the block is operated by a 
screw handle. For each stroke of the 
planer, the disk makes a partial turn, and 
the rack will be alternately moved up and 
down. When the block in the disk is 
moved to the end of the slot, the rack 
will have its greatest travel. As the block 
is moved toward the center of the disk, 
the amount of throw decreases until tht 
block reaches the center, where it is zero. 
The amount of throw and the movement 
of the rack determine the rate of feed. 

13. Details of Peed-Motion. — A 

top and side view of the feed-motion at 
the end of the cross-rail of the planei 
are shown in Fig. 13. The teeth of tb< 
rack u engage the teeth of the gear v. 
The gear v is attached to the shaft tt; 
which is free to turn in its bearing anc 
carries the gear / and ratchet wheel x. The gear / is 




§9 PLANER WORK. 11 

loose on the shaft w f while the ratchet x is keyed fast 
to the shaft. On the outside of the gear / is a pawl y 
that engages the ratchet wheel x. The gear / meshes 
with the gear s on the feed-screw. When the rack 
is moved down in the direction of the arrow the gear v 
revolves, carrying with it the ratchet wheel x. When the 
pawl y is engaged, the ratchet wheel / is rotated in the 
direction of the arrow, thus turning the gear s 9 and with it 
the feed-screw. When the rack u moves up again, it turns 
the gear v back, but the pawl y slips over the ratchet 
wheel; consequently, the feed-screw remains at rest. With 
wch stroke of the machine a similar movement occurs. To 
reverse the direction of the feed, the pawl y is moved so 
that its opposite end engages the ratchet wheel x. The 
feed may be stopped entirely by setting the pawl y in 
mid-position, so that neither end engages the ratchet 
wheel 

14. Depth of Cut. — In planer work, as in lathe work, 
r °ughing and finishing cuts are taken. The first cuts are 
ma de deep, and the feed is consequently fine when com- 
pared with the finishing cut. It should, however, be as 
heavy as the tool will stand without heating, and as great as 
the machine will drive without danger of springing or bend- 
ing the work. 

15. Feeds for Roughing and Finishing Cuts. 

™he amount of feed that can be taken under different con- 
ations depends largely on the metal being cut and the kind 
°* cut being taken. The resistance that a chip offers to a 
too] as it is cut from the solid and turned past the tool 
spends on the thickness of the chip more than on its width, 
an <l also on the character of the metal. In planing some 
me tals, such as cast iron, a very heavy feed cannot be used, 
,n some cases, on account of the fact that the great resist- 
an ce offered by the thick chip causes the metal to break out 
,n advance of the point of the tool, thus causing pits or 
^dentations in the surface of the work being planed. If 



12 PLANER WORK. §9 

the thickness of the chip can be reduced without reducing 
the feed, a greater surface can be covered in less time; this 
is illustrated in Fig. 14. If a tool were set with its cutting 
edge perpendicular to the work, so that it would cut out the 
block acdb, it would have a feed equal to<?£, and would 
have to turn a chip whose thickness is also equal to a b. The 
depth of the cut in this case is a c. If the same tool were 
arranged with its cutting edge at an angle of 45°, as shown 
in Fig. 14 (£), and given a feed a b equal to that shown in 




pig. u. 

Fig. 14 (a), the chip would have a thickness shown along 
the line c d, which would only be about three-fourths of the 
feed as shown by the lineal. The breadth of chip, how- 
ever, would be equal to a c. According to a principle in 
geometry, if the feed of a b remains constant and the depth of 
the cut is the same, the area of the chip ab dc, Fig. 14 (<?), 
or a bfc, Fig. 14 (b) % will remain the same, and hence the 
amount of metal removed in each cut will be the same ; but 
owing to the fact that the thickness has been reduced one- 
fourth, the resistance offered to the tool will be very greatly 
reduced. On this account, the cutting edge of planer tools 
intended for roughing work are usually set at an angle to 
the surface to be cut, as shown by the line A /?, Fig. 2. 
From this it will be seen that the feed which can be 
given to a roughing tool depends to a large extent on 
the angle that the cutting edge forms with the surface 
of the work. 

Finishing cuts should always be light, and the feed that 
can be given depends on the character of the metal being 
cut. In finishing wrought iron and steel, it is necessary to 



§fl 



PLANER WORK. 



nparativety narrow finishing tools with a correspond* 
gly fine feed. In finishing cast iron, very broad finishing 
s may be used, and a feed nearly equal to the width of 
the tool. 



lfi. Cblpplng the Edge of (lie Work. — When taking 
,1 roughing cut, there is a tendency for the tool to break "IT 
the edge of the work just as 
the tool is leaving it. This 
breaking of the edge often 
nuch below the fin- 
ished surface, and leaves a 
iad-louking piece of work. 
It may be avoided by beret* 
- edge of the work, as 
shown at*, in Fig- 15. The F,G ' * 

SVe] Btartfl at the Hue that indicates the depth of cut and 
runs back at an angle of about 15°. When the tool comes 
to the beveled edge, the force of the cut begins to decrease, 
so that by the time the edge of the work is reached, there is 
little of it to break. 




SI III-: CUTS OK DOWN CUTS. 

1 7. SeUinjE the Tool.— The sides of the casting may 

! finished by feeding a properly shaped tool down over the 

sides of the work. In Fig. Hi a casting is shnwn fastened to 

! platen of the planer. The upper surface a has 

finished in the ordinary manner and it is desired to finish 

the sides c and b square with the finished face a; a too) of 

■ shown at / may be used for this purpose. It should 

B set in the tool blink so that its edge extends far enough 

leyond the t".>l clamps to pass entirely over the surface to 

d before the tool block comes in contact with the 

account of the fad that the cutting edge of the 

iol extends so far beyond the tool block, it is impossible to 

I s in facing down as it is when working on 

i Hat surface. 



14 



PLANER WORK. 



8 



When taking a side cut, it is necessary to swing the to 
block to one side, as shown in Fig. 16. The tool blocks ai 
clamps are pivoted on a pin placed at the center of that ctrc 
of which the arc containing the bolts e forms a part. 1 
loosening these bolts, the head may be swung to the desin 




angle. When the pressure of the cut is released and t 
tool is on the back stroke, it is free to swing along t 
arc A B, as shown in Fig. 17. As the work passes back u 
der the tool, the point of the tool tends to swing away frc 
the work when planing Hat surfaces. 






■ 



§ 9 PLANER WORK. 15 

When cutting; a side face, the tool tends to rise the same 
as when cutting horizontal surfaces; but if the swing of the 
point of the tool and 
the (ace of the work 
are in the same verti- 
cal plane, the tool 
point will rub against 
the face of the work 
instead of swinging 
away from it. It is 
for this reason that the 
head is swung into 
the position shown in 
Pig. 16. As the tool 

must always swing in I , „,.^.^ ,1~, 

1 plane perpendicular ; 
to the pin ie, Fig. 17, 

* is evident that as F,a "' 

'he work goes back under the tool, the point will swing away 
from the work. In Fig. 16 the center line of the pin is rep- 
resented by the line A B, and the center line of the tool by 
the line CD. 

When planing a surface on the opposite side of the work, 
Mifir, Fig. 16, tfae tool head and tool block must be swung 
m the direction opposite to that shown in Fig. 16. A handy 
ru le to remember is that when taking any side cut, the top 
°f tie tool block must be swung away from the surface to 



18, Testing the Squareness of the Head. — When 
fating down cuts that are intended to be square with the 
to P face of the platen, the down-feed slide of the head should 
he examined to see that it is perpendicular with the platen. 
Thisslide, or head, isonaswiveled base clamped to the saddle, 
"tan usually be swung around to make any angle with a 
Position perpendicular to the platen. The base is graduated, 
M that when set perpendicular, two zero marks come 
^ether. If the head is not set perpendicular, it may be 



16 



PLANER WORK. 



§» 



loosened by unclamping the four nuts£, /, m, and n, Fig. 16; 
it is then adjusted to the correct position and clamped again. 
The squareness of the head and the accuracy of the work are 
assured by proceeding in the following manner: A finishing 
cut is taken over the surface a. Fig. 16, and a side tool sub- 
stituted and a finishing cut taken down the face or side b. 
A try square is applied to the two finished surfaces, and 
if b is not square with a, the vertical slide is adjusted and 
trial cuts made until b is made square with a. 



CUTTING BEVELS. 



19. Swinging the Head. — When a beveled cut, that 
is, a cut at any other angle to the surface of the platen than 




00°, is to he made, the head is swung around so that the 
lino i if down feed makes the desired angle with the table. 
Suppose it is desired to bevel a piece at an angle of 60° with 



§9 



PLANER WORK. 



17 



the top of the platen. Then the head is moved through 30°, 
as shown in Fig. 18, when the tool will be fed down at 60°. 
The graduations are not the same on all planers. On this 
account, care must be taken to be sure that the proper angle 
with the surface of the platen is obtained. 

When cutting bevels, the tool block must be swung around 
as shown in Fig. 18. A very easy rule to remember as to 
which way to swing the tool block when making side cuts or 
undercuts is the following: Always swing the top of the 
tool block aivay front the surface to be planed. 

In making down cuts, especially in roughing cuts, the tool 
should invariably be fed downwards while cutting, but never 
upwards. On a fine finishing cut, this is not so essential. 
The objection to feeding upwards is that during the return 
motion the tool is liable to catch in the work before it has 
time to swing clear. 

20. Planer-Head Graduations. — Planer heads are 
graduated in degrees from zero to 90; that is, a quarter of 



I 




e 




A 



ifW 



5 = 

7 



M 



}Q 



(c) 



Pig. 19. 



a circle is divided into 90 equal parts, which are laid off as 
shown at g, Fig. 19. On some planers, the graduations are 
numbered from zero to 90°, zero being at the side, Fig. 19 (/;),- 

T ID— 23 



18 



PLANER WORK. 



§• 



in other cases, the graduations are numbered from 90 to 
zero, Fig. 19 (c). In order to set the planer head *•, Fig. 19, 
to feed down at any given angle, it is necessary to know 
either the horizontal angle c or the vertical angle *•, Fig. 20 (a). 
If the horizontal angle c is 35° and the graduations are as 
shown in Fig. 19 (6)> the head must be set to 90° — 35°, or 
55°. If the graduations are as shown at Fig. 19 (c), the 
head will be set to 35°. If the loose side, or gib, d, Fig. 20 (a), 




S3 

L 



<V«1 




i i 



4*- 



!& 



Vl 



» • 

i i 



fa) 



r*j 



Pio. so. 



is to be planed, it is usually set on edge against an angle 
plate or block, as shown in Fig. 20 (/>) ; when so set the 
angles are reversed and it will be necessary to set the planer 
head just the opposite from the way in which it should beset 
for planing the angles shown in Fig. 20 (a). For instance, 
if the graduation on the planer head were such that in 
order to plane the angle c it would be necessary to set the 
planer head to the 55° graduation mark when the piece a 
was set flat on its face, it would be necessary to set the head 
to :jo° to plane the piece d when it was set as shown at 
Fig. 20 {b). 



UNDEHCUT8. 



21. Spring of the Tool. — When making undercuts, 
or when cutting T slots, the results of the springing of the 
tool are reversed. In Fig. U it was shown that when the 
tool bent, it sprung down into the work, the top of which 



PLANER WORK. 



19 



is represented by the line wk. If this line is assumed to 

represent the under surface of a piece of work, it will be 

seen that during a cut when the tool springs down in 

/■', 11 will spring away from the work, anil <<n the 

itroks the tool block will lift and swing the point oi 

the tool in the arc CD, thus throwing the too] into the 

1 i ausing it to catch and lift the work off the table, 

■ 






22. UIocIUiik the Tool.— When an ordinary beat tool 
i-; used fot undercutting, the t'»>l must be blocked so that it 

II DOt spring bacfc on the return stroke. This may be 

mplished by having the shank of the tool long enough 

a block may be driven between it and the head; this 
ill keep the point from rising. 

23. Cutting T Slots.— When cutting T slots, a tool 
made as shown in Fig. 2] may be used ; the tool must then be 
blocked in some con- 
venient way to pre- 
vent its rising daring 
the backward stroke. 
Instead of blocking 
the toot, it is better 
to make the stroke of 
the planer long enough 

I at the tool will 
. nee "in 

lot .it each end. 
When the machine is 
on the return stroke, the tool may be heid up by swinging 
the too] block upwards to allow the tool to pass over the 
he tool being dropped again at the beginning of 
the next stroke, 

A limp ■ the place of the hand for holding 

the tool up is shown iii Fig. 23. Two pieces of sheet metal 
are hinged together at a; one pie< ■ 
and the othei • left free to swing. When a cut 




20 



PLANER WORK. 



§9 



C 

c 






is being taken, the loose end b drags on the work, as 
shown in Fig. 22 (a). As soon as the tool and the hinged 

part b pass by the 
work, the part b 
drops down. On the 
return stroke, it 
strikes the end of the 
work and lifts the 
tool up, as shown in 
Fig. 22 (*), so that it 
drags over the top. 
When the cut again 
starts, the tool enters 
the slot while part b 
drags over the work 
as before. 

For some heavy 
undercutting, a heavy 
bar is clamped in the 
tool clamp. This bar 
is fitted with a special 
tool block at its lower 
end, which carries a 
small tool and is so 
arranged that, at the 
backward stroke of 
the planer, it allows 
the tool to spring 
away from the cut. In 
the case of large planers the side heads usually answer much 
better for undercutting and also for side facing. 




■ .; j*« v. .y rf '• 






: v* ■* 



FlQ. 22. 



CUTTING SPEED OF THE PLANER. 

24. Limit of Speed. — The cutting npeed of planer 
tools is governed by the same laws that govern the speed of 
lathe tools. The speed must not be so high as to cause the 
tool to heat and to become dull too quickly. It should vary 



§9 PLANER WORK. 21 

with the hardness of the metal cut, the kind of metal, and 
with the kind of cut; that is, it should in general be slower 
for a roughing cut than for a finishing cut. With ordinary 
steel tools the following speeds may be considered good prac- 
tice: For brass, 100 feet per minute; for cast iron, 45 feet 
per minute; for wrought iron and machine steel, 35 feet per 
minute; for tool steel, 20 feet per minute; for chilled iron, 
2 feet per minute. 

With the ordinary planer, there is no way of varying the 
cutting speed after it has once been determined and the 
machine has been erected. In belting a new planer, a cut- 
tmg speed is selected that is slow enough for very hard 
metals and heavy cuts, and ever after the planer must run 
at that same slow speed, whether it be used for planing steel 
°r for finishing a brass casting. This puts the planer at a 
disadvantage. In order to make planers suitable for hard 
metal and heavy cuts, they are usually belted to run at a 
speed of from 18 to 20 feet per minute. 

25. Variable-Speed Countershaft. — If a planer is 
fitted with some device for changing or varying the speed, it 
results in a very great saving of time on many classes of 
work. One of the most common devices of this kind is 
the Reeves variable-speed countershaft, which is shown in 
% 23. 

This appliance consists of a rectangular frame that sup- 
P° r ts two parallel shafts a, b y on which are located the two 
cones c y c and d, d that rotate with the shafts, but can be 
mov ed along them. The apexes of the cones are toward 
each other. The cones are held in position by means of the 
" ars e, e that are pivoted to the frame at the points f y f. 
"hen these bars are placed with their ends g, g in the posi 
t,o n shown in the figure, the cones c, c on the shaft a are 
m,) ved together, while the cones d, d on the shaft b are moved 
a I ,ar t. An endless belt //// runs between these cones and 
tra 'ismits power from one shaft to the other. This belt is 
* ( -pt from squeezing down between the cones by blocks of 
w wd fastened across it to stiffen it. Power from the line 



22 



PLANER WORK. 



§» 



shaft is transmitted by a belt to the pulley /, which drives 
the shaft b and the cones d, d. When in the position shown, 
that is, when the cones d y d are far apart on the shaft b y the 
belt // is quite close to the shaft. Consequently, the belt is 
driven at a slow rate of speed, or just as if it were mounted 
on a small driving pulley. The cones c 9 c on the shaft a are 




Pig. 23. 



close together, and the belt // takes a position near their 
circumference. In consequence of this, the shaft a will be 
driven at a slower speed than the shaft b. If c y c are moved 
apart, the cones d, d will approach each other, an,d the 
belt // will come nearer the center of the shaft a and will move 
farther from the center of the shaft b. This causes the 
shaft a to revolve faster. 

The application of this device to a planer is shown in 
Fig. 24. The reversing pulley r, Figs. 23 and 24, is put on 



PLANER WORK. 



33 



the constant -speed shaft b, thus giving a constant-speed 
return motion to the planer. The driving pulley s for 
the forward motion of the planer is on the variable- 
speed shaft a. The sprocket wheel /, which is operated 
from below with a chain, is fastened to a right-and-left- 
hand screw j, Pig. 23, by means of which the bars e, e 
are rotated about /,/ in order to obtain any desired rate 




of speed. With this device, it is possible to adjust the 
speed of a planer to suit the conditions of work, as is 
done in lathe work. The adjustment should be made 
while the machine is running. In some cases a planer is 
driven by a pair of cone pulleys, which afford several 
changes of speed. 



PLANER WORK. 



ACCURACY OF PLANER WORK. 

26. Krcctlni; a Planer. — In erecting u new 

[.liincr. It should be si;i mi a brick or stone I 
hi, ii'ii should be removed and the bed carefully leveled by 
testing the V guides. Care should be taken that tin- 
the bed rest fairly on the foundation, so that thii ■ 
00 tendency to twist the bed or put it in wind, as 
it. is called. It the planer is well set at first, it will 
remain true for a long time. Detailed i 
the erection of both large and small planers ari 
a ting. 

27. Errors In (lie Platen. — After a planer I 

in w for some time the platen becomes out of true. This 
is caused bj the driving in of the stop-pins, the 
bundling of work, and the general hammering that ilii. 1 top "I 
a plateD receives. All these abuses tend to peon tl 
the platen and stretch it, thus causing it to spring 
sidcrably in the middle. When the platen springs up in the 
middle, it bears only on its ends; therefore, when 
cut, when- the end <>t the platen runs over the end of the 
bed, is taken, the ends of the platen drop down 
ilus occurs, ii is impossible to plain- work straij 
true. 

In such a case, the platen should have a light 
ovei its top surface to make it true. When taking a CW to 
true a platen, the first cut should never be deep enough to 
cut its entire length. It is better to take a nnmnei 
Cuts, for the reason that if a heavy cul is taken at the begin- 
ning, it will be found as the cut proceeds that the 
in tli" top of the platen is gradually released an I 
platen will slowly spring back to its natural 
the time the cut has been fed across, the platen has sprt 
back tn its original shape and the front edge, 
made straight at the beginning, will be found to in 
Another light cut will be necessary to finish the plat« 
■might and true. 




ga PLANER WORK. 

!i< ton taking a cul over .1 platen, the cross-rail should be 
tested for alinement with tbe trays, and if not in perfect con- 
dition it should I"-- adjusted to the ways and not to the table. 
This always injures tin: accuracy "t angles and parallelism 
of work done on the machine!. 

'iH. Krrorln (tie CritHH-Hitil. — Before a planer platen 

bj planing, the cross-rail should be tented to see if 

el and parallel sritfa the platen, Phi cross-rail is 

lowered and kept level by the elevating strews in 

th< housings These screws have the same pitch, so that 

when the cross-rail is moved, each end moves the same 

amount; the cross-rail is thus kept parallel with the bed. 

times happens that heavy cuts are taken when the 

Cross- rail is nut securely clamped to the housings; a strain 

en bn night upon tin* elevating screws and the nuts, 

■■■ 1 ross-rail oui of adjusl ment. When the 

■rail is not parallel i" the platen, it will cause the work 

1 ii Iter at ■ edge than al tbe other, 'l be 

is-rail ma) be tested by adjusting n tool in the head so 

: 1! just l:< lids a piece of paper on a cylindrical niece laid 

e of the V guides and.tben running the bead over the 

r rail and testing the tool over the same cylindrical 

..- laid in the othei V II Hie rail is not parallel to thi 

it must be made s" by facing off the huh • >[ one of the 

.■■ top of the adjusting screws, or adjusting one •>( 

i ..11 tin- borisontal shaft that connects the s, rows. 

irs should always be turned soas to raise thecrass rail 

when making .\n adjustment, as this lakes up all lost 



2». Boring of <hc Planter.— In some of the old 

the bed and housings were exceedingly 

■ eorouared with the rigidity of design shown in 

.. r Willi the modern planer in good adjust - 

■ danger o( error due to I he distortion or 

f ol the machine, al leasl when taking light finishing 

Ii the cross-rail or the head 1- loose, 1 hi n 

springing into the work. 



26 PLANER WORK. §9 

30. Spring of Work Due to Clamping. — The great- 
est error is usually due to the spring of the work, which is 
not only caused by improper clamping, but also by the releas- 
ing of internal stresses that have been set up in casting or 
forging. This point is again emphasized, as a serious dis- 
tortion of the work may be produced by a very slight pres- 
sure of the clamps. 

31. Spring of Work Due to Its Weight. — The 

weight of the piece is often sufficient to cause a considerable 
deflection. Suppose that a long cast-iron piece similar in 
shape to the bed of the planer, as, for instance, that shown 
in Fig. 25, is supported only at its two ends. Assume that 




FlO. 26. 

the clamps are applied carefully, so that the work is not 
sprung in clamping, but that the piece is left unsupported 
at the center. Then, the weight of the work in this case 
may cause it to bend down considerably in the center. When 
the tool presses on the top in taking a cut, the pressure of 
the tool will still further press the center of the work down- 
wards. The result will be that if the piece is turned over 
on its side, it will be relieved of the weight that tended to> 
deflect it ; the finished face will then be found* to be far 
from straight. In such a case as this, jacks or supports 
should be put under the work to support it throughout its 
length. 

32. Internal Stresses. — Another source of error that 
prevents a planer from planing a straight surface is that 
which arises in cast or forged work from the releasing of 
internal stresses ; these stresses are created in castings 



PLANER WORK. 



27 



and forgings by uneven cooling of the pieces. There is a 
surface tension in the skin, or scale, of the casting or forg- 
ing, and usually there also exist local stresses, due to uneven 
hammering or cooling of the piece, which tend to warp it 
out of shape. These stresses usually act in different direc- 
tions, with the result that when one is removed, the remain- 
ing stresses cause the piece to change slightly in shape. 
The action of these internal stresses manifests itself very 
strongly when finishing a long, thin casting straight and 
parallel 

Suppose a casting which is straight be clamped carefully, 
so that when it is laid on the platen it has a fair bearing, and 
a cut is taken over the top so that it is straight. Upon 
removing the clamps, the piece may spring up in the i enter, 
as shown somewhat exaggerated in Fig. 2(i [a). Before the 





1 — ~~ 


a 








f«y 










\ 






'" 








. 




'* 



as planed, the surface tension in the two sides a and b 
was about equal; consequently, the piece remained straight. 
Upon taking a cut over one side, as />, part of the surface 
rod and, i onsequently, .i pari of the surface tension 
was relieved. The side if being now under the greater sur- 
'■'ii. the result is a bending of the work, a 
r the piece is turned over, as shown in Fig. 2(i (f>), and 



28 PLANER WORK. § 

carefully clamped with pieces under the ends, so that it will 
not be sprung in clamping, and if a cut is' now taken over^ 
the surface a as deep as the cut taken over the surface b, it 
will be found upon releasing the clamps that the work will 
again change its form, this time springing back to about its 
normal shape. The face b will again be nearly straight and 
the face a curved, as shown in Fig. 26 (c). After the first 
cuts are taken and the skin is removed, there is less ten- 
dency for the work to change its shape. Because of this 
change of form in work, due to the removal of the surface 
tension, it is always desirable to take all the roughing cuts 
before any finishing cuts are taken. If the work is very 
thick and heavy, and the surfaces small, there is less danger 
of the work changing its shape than on light, thin work 
that is machined all over. It is a good rule, however, 
whenever it is possible, to rough out the work all over before 
any finishing cuts are taken. 



SPECIAL PLANER WORK. 

33o Work Too Long for the Platen. — It occasion- 
ally occurs that a piece of work is too large to be handled 
upon the planer in the ordinary way, and in such cases spe- 
cial rigs or devices must be used. When pieces longer than 
the stroke of the planer are planed, one end of the work is 
clamped to the platen while the other end extends beyond. 
When the free end overhangs very much, it is supported on 
bearings or rollers. After one end is planed, the work is 
moved along the platen, so that the finished part projects and 
the unfinished part is planed. Considerable skill and care is 
necessary in resetting the work, so that the two parts when 
finished will be as true as though the work had been planed 
without resetting. 

34. Work Too Wide for the Housings.— When 
work is too wide to pass between the housings and is not 
very long, a special extension head may be made, as shown 



§» 



PLANER WORK. 



n Fig. 27. A bracket a is fitted to the slide of the down 
: the tool block b is then attached to the outer end of 
Itet or extension head. The bracket is made long 
nough to reach over the work when the latter is very close 




(^ " '"^^ **&p y 



> the housings. The spring of the long arm and the lack 
f rigidity in the cross-rail make it rather difficult to take a 
eavy cut; the device will do the work, however, when no 
ana is at hand. 

35. Special ttiic for Pinning Curved Surfaces. 

or some kinds of work, special devices and rigs may be 

evised to save time. Fig. 2-8 shows an end view of a planer 

tied with a rig devised for planing a curved surface on a 

A special long head a is pivoted above the work 

b\ i he distance from the point of the tool to b 

is made equal t" the radius of the arc to be planed. The 

regular planer head with the down feed is attached to the 

lower end of the special head, which is gibbed to the curved 

<>f the cross-rail so that it can slide freely as it swings 

■ut the center /'. In operation, the cross-feed motion is 



30 



PLANER WORK. 



§» 



used as in ordinary planing ; the tool is adjusted to the work 
by the regular down feed. A curved surface is produced by 




Pig. 88. 



this device as easily as a flat surface is planed on an ordinary 
planer. 



36. Planing Links. — When planing links, it is 

necessary to arrange the work in such a manner that it will 
travel through a curved path so that the planer tool may 
cut the desired curve. This may be accomplished in several 
ways. Probably the simplest method of planing a link is that 
illustrated in Fig. 29, where the work a is bolted to an auxil- 

a 

iary table b. This table is rigidly attached to a bar c, which 
is provided with a long slot d for the purpose of allowing the 
pivot pin e to be adjusted to any" radius that may be desired. 
The pivot pin c is securely attached to a fixed support. In 
the device shown the outer end of the bar c is supported 



£9 



PLANER WORK. 



31 



by the guide /, along the upper edge of which it is free to 
slide. The radius of the link being planed is determined by 
the position of the pivot pin e about which the bar c rotates. 
The plate b is held between strips g, which are bolted to 
the planer table as shown. These strips are so adjusted 
that they hold the plate b down on the surface of the planer 
table, and also prevent any motion in the direction of the 
length of the platen. As the platen moves backwards and 




forwards the plate b rotates about the center c, and in so 
"°' n S slides backwards and forwards across the platen. 
Sometimes much more elaborate devices, having carefully 
adjusted gibs, are provided for this work; but in any case 
the edge of the plate b must be an arc of a circle having a 
diameter equal to the distance between the clamp pieces g 
The one great advantage of this device is that the exact 
radius nf the link can be determined and the machine set up 
accurately without much difficulty. The greatest disad- 
vantage is that the bar c must extend a long distance to one 



32 PLANER WORK. § 9 

side of the planer, and hence, prevents the placing of a 
number of planers close together. 

37. Another device for planing links is shown in Figf. 30. 
In this case the work is fastened to a plate a that is attached 
to the planer table by a pin that works in a suitable bearing 
in the center of the plate, as shown at b. The plate a is free 
to rotate about b, and slides on the base c, suitable ways 
being provided, as shown at (/and e. At one corner of the 




plate a there is a stud f, the upper end of which is fitted with 
a block that slides in the groove in the guide g. This guide 
is attached to the lower side of the cross-rail of the planer 
and can be adjusted to any desired angle with the cross-rail. 
If the guide g is placed parallel with the length of the planer 
platen, the plate a will not rotate about the pin b, and the 
tool will plane straight parallel work. By placing the guide g 
at an angle, however, the plate a is made to rotate about 
the pin b. By varying this angle, the amount of rotation of 
the plate about its center can be governed, and the curv- 
ature of the link varied within certain limits. It is not 
practicable to plane links of very short curvature by this 



is 



PLANER WORK. 



33 



device, but for ordinary engine links it has proved very sat- 
isfactory. One advantage of the device is that it is entirely 
self-contained, that is it does not extend beyond the sides 
of the planer, and hence planers can be placed as close 
together as though they had no such device attached to 
them. One disadvantage is that it is sometimes difficult to 
adjust the slides so that it will exactly duplicate links of a 
given curvature. The device is generally set by trial, 

38. Pinning Spirals. — Sometimes it becomes neces- 
sary l" plane a spiral. This may be accomplished by the 
"vice shown in Fig. 31, in which is represented an ordinary 




planer with a pair of planer centers a, b placed upon it. 
i c is placed between the centers, but is not secured 
■ either of them. A bar d is fastened along the 
t)a «of the planer, being clamped at one end to the planer 
and at the other end to a suitable device on the 
Ed, Another bar e. is clamped to one end of the 
9 bich the spiral is to be i tit. This bar e is kept 
: with the bar i/by clamping any suitable weight/ 



H 



PLANER WORK. 



M 



to ii* 'niter end. As the plalen travels backwards and for- 
wards, the bar < slides on the top of the bar d, and on 
KCCotUll of Che inclined position of the bar d, forces the 
work . i" make a partial revolution with each ■troh 
planer, By varying the angle of the bar d, the po 
tii.- revolution made fur .1 -ii-n amount of planer 1 1 I 

per the angle formed by the bar rf, 
ih, steeper will be the pitch of the spiral. The planing is 
done with a tool formed so as to produce the desin 
By this device, spirals having a very loil| 
thai cannot be cut OB an ordinary milling machine can be 
produced very satisfactorily, but it is impossible to pcodue 
spirals aai iftch, The centers a, £aiust be n 

placed that the work c will be in tine with the ptal 
tbe tipper edge of the bar i/ must be well lubricated. 



'•'•i*. Special Gauge* for Setting Planer T....K. 

Winn many pieces are to be planed to the same size and 
■btpe "ii I lie sjiinc planer, am! when the faces to be finished 
are somewhat complicated, which involves careful adjust- 
ment of the tool for each piece, a special gauge may be used 
[or setting the tool, As an illustration of the applii 
such a deviee, .1 luol-setling gauge used in planing latr. 
beds is given. When a lot of lathe beds of I he H 
.ii ate be made, they arc usually required to be planed alii 
The problem of planing the top erf B lathe bed with foi 
V shaped ways on it so that the ways are accural! 
with refer en c< to one another, is one that req 
able care in the setting of the tool. The problem 
becomes more difficult when a number of lathe beds are i 
be planed so that the ways are exactly alike on all of thci 
ft can l". solved very readily, however, by the use i ; 
setting gauge made tn the correct cross-section of a finished 
lathe bed, This gauge a, which may be made of cast irt 
is bolted to the platen in line with the lathe-bed i 
Shown in Fig .>\! (a); space enough is left between it i 
d of the work for the planer to reverse 
iching thi ■ he n n I, Is roughed < 



O 



PLANER WORK. 



35 



'h' 1 platen is run back far enough so that the tool is brought 
directly over the gauge. 

Suppose it is desired to finish the outer side of one of the 
IPs. The tool is then adjusted so that it just pinches a 
ii^sue paper placed between it and the gauge, as 
shown in Fig. 3-J {(>). the head having been previously set to 
plant the correct bevel. The tool is now fed up away from 
the gauge, and, after the stroke of the platen is adjusted to 




1 "' fte correct length, the tool is fed down over the face of 
the w«rk in the direction of the arrow in Fig. 32 (b). In a 
inniat manner, the tool is set for each of the other faces, 
an< > the work is thus planed in accordance with the gauge. 
g the tool with a piece of paper between it and the 
■"Hfc the tool can be carefully adjusted to the gauge; at 
'"fwme time, a slight amount is lefl to be removed in filing 
'"d fitting. It may be seen that, by the use of a tool-setting 



PLANER WORK. 



gauge, all the beds planed will be alike; furthermore, the 
tool can be easily and quickly set. 

40. 1'lanlnjj Dovetails. — Screw machine beds are 
frequently provided with a dovetail guiding surface for the 
head as shown in Fig. 3a (a). The heads that fit on this 




are frequently made to fit without any adjustment, that is, 

without any fibs, and aa a consequence the work must he 

■ liijir accurately. Of course the groove on the head that fits 

mi the bed must be planed to lit accurately over the pro- 

jectton ii. The bearing comes upon the surfaces b, c, d. 

The casting for work of this kind is usually uf the furra 

shown by t lie dotted lines, so that the first operation must 

In- tin- taking of > roughing cut over the surfaces f. r, fi, 

and g % in order to remove the scale. This may be taken 

with any suitable tool, usually a round-nosed tool, though 

frequently a tool without side rake is used so that it can be 

fed in either direction. The bottom of 

roughed off. After this, the bed is carefully reset and tfli 

work "f finishing is commenced. A squat 

used to finish the surfaces e, b\ the tool may be Gi 

the surfaces t and both of them finished. In order ;■ 

the correct distance between the surfaces e, b it is well to u 

,1 setting block k, Fig, 33 (b), which is set oi 

and the planer tool adjusted to its upper face i, when i 

be set right for finishing the surface A 

After the surfaces b, ., Fig. S3 (ii), have been \- 
Gssary to rough out the stock in from oi tfa 
c, </. This may be done with an offset roughing tool of \ 
form shown in Fig. 34 {<>). The cutting is done by l 



■ 




Sfl PLANER WORK. 

faces a, b and the tool ground with little or no top rake and 

with no side rake. The planer < — 

head is set over to the required 

angle and the stock removed 

by successive cuts, as shown in J 

i, in which the doited .// 
■ iws the required form n ^^ '«> 
of the groove. After all the 
stock has been roughed out, PlG ' M ' 

the portion of the surface e. Fig. 33 (c), that is under the 
dovetail and hence could not be finished by the square-nosed 
tool, is finished by a tool of the form shown in Fig. 34 (b). 
In this tool is virtually an offset square-nosed tool, the cut- 
ting being done by the face n, the face b being cut away so 
tut it can work under the bevel surface of the dovetail. 

The bevel surfaces c and d. Fig. 33 (a), are finished with 
an ordinary side tool using a fairly coarse feed. One side of 
the work is always finished first. 

Frequently for laying out the work a gauge of the form 
shown in Fig. 35 is used. The two parts of the gauge a, b 
are fitted accurately to one another. 
The portion a is laid against the 
end of the work and a line scribed 
around it before any undercutting is 
done. 

After the surface c, Fig. 33 (», 

has been completed, the head should 

be swung vertically and the side too] 

tlMl1 '" finish the face h perpendicular to the face b. It is 

"portent to do this at the same setting at which the other 

finished, as frequently the face It is the only sur. 

uce jo which the workman can refer in making measure- 

u fitting the work, and if the surface of a bed 

injured or worn and requires redressing, the sur- 

isiially the only one by which he can set the casting 

ktc Ufately for refitting. After one side of the dovetail has 

other side is planed in a similar manner, the 

i being similar to those shown in Fig. 34 (./) and (b), 





PLANER WORK. | I 

bttt forged to the opposite hand. From this it will be seen 
thai foi planing I dovetail it is necessary to have one or 
more roughing tools, a Mt "f offset right-hand and '< 

tools for working under the groove, and right-hand and left- 
hand side tools. In planing the second side of the dovetail, 
thi portion b of the gauge shown in Fig. 35 is sometimes 

■ I by setting one edge of it against the finisl 
of the work at the end and scribing inside of the other edge, 
thongh usually the roughing and first finishing cuts are 
taken to the lines laid OUI with the part a and the part b is 
used only for testing the fit of the work during finishing 
If the side e. Pig. 88 u\, is planed first, the final Btt 

be done on the face d. Sometimes in place of fitting (he 
work to a gauge the final fit is made by using one of the 
piece* that i> to work upon the slide a as a gauge. Of 
course, in planing, no attempt should be made to make the 
pieces work together freely, as some stock must always be 
Icii fin the fitter to remove when fitting the pieces. 

Frequently, especially in heavy work, parts that an 
Joined by dovetails similar to those shown in Pig. :; 

no! fitted directly to one ao ither, 
, j but a gib is introduced, as shown 

■: ~—ff I ate, Fig. 3(S, The dovetail pie 

i Sk ^'-«E=-U are pl' rim '*' ' m< l fitted togethei 

j a manner similar to that alrc« u . 

described, with the exception of the 
' ' fact that both pieces arc fitted tr> 

*«»•**■ gauges similar to thai 

After this a strip or gib c is planed to fit bet wee 
i he pieces as shown. In the case of a gib, this strip is I 
in place by means of setscrews, as shown at <i. i 
"I the setscrews fit into recesses opposite the center of t 
stripe This arrangement allows of considerable ai 
for the taking up of wear between the surfaces upon the pier 
■ . a also simplifies the planing considerably on account ■ 
the fact that the fit is already made upon the piei 

The sizing block shown at i; Fig. 33 (/'). is usually r 
of hardened steel and accurately ground to shape. It should 



awn 

2 



80 



PLANER WORK. 



39 



also be marked with dimensions for which it is made. 
Instead of using a sizing block of this character a regular 
depth gauge is frequently employed for measuring from the 
surface b to the surface e. 

41. Planing the Ways of Lathes. — The V guides 
on lathes form quite a difficult planer operation on account 
of the fact that there are four V's that must be accurately 
spaced and fitted. Fig. 37 shows the ordinary V's necessary 




FIG. 87. 

u Pon a lathe. The V's a, b are intended for guiding the tail- 
stock and headstock, and c y d for guiding the carriage. It 
is absolutely necessary that the four ways be parallel and 
that a y b and c, d be accurately spaced, but it is not abso- 
lutely necessary that the two sets be accurately spaced with 
elation to each other; that is, the distances between a, c 
an d &, d may vary somewhat, provided the spacing of each 
pairofV's remains constant. Of course only a very slight 
va riation is allowed in this matter, but the only effect of 
variation here would be to 
mov e the carriage from 
on e side to the other in 
Nation to the line of 
Indies of the headstock 
an d tail-stock. Ordinarily 
cac h pair of V's is planed 
U P independent of the 
°ther pair. Sometimes a 
c °mplete gauge of the 
form shown in Fig. 38 (a) is used. The objection to this is 
that there are four bearing surfaces, and if three of them 





<*) 



V 



Fig. 38. 



PLANER WORK. 



come into contact it is difficult to tell whether there is a 
perfect bearing between thein and make the fourth one come 
accurately to a fit. In starting the work many builders 
prefer to use a gauge of the general form shown in Fig. 38 (b). 
This gauge has two inclined surfaces a, b, which are brought 
in contact with one side of the V's; the gauge is then 
reversed and used on the other side of the V's. If considered 
necessary, a gauge of the form shown at Fig. 38 {a) may be 
used for final testing. 

In carrying out the work in the case of most medium-sized 
lathes it would take an excessive amount of time to use an 

I . ordinary round-nosed tool of the form shown in 

Fig. 32 (b) and feed it along the face of the V's 
by setting the head over to the proper angle. 
On this account a tool of the form shown in 
Fig. 39 is frequently used. These are forged 
right hand and left hand and are really simply 
offset square-nosed tools with considerable top 
rake. The cutting is done along the edge a, 
and it is necessary to have both right-hand and 
left-hand tools. One of these tools is set to the 
proper angle and fed against one side of one of 
I the V's and a roughing cut taken over it of suffi- 
cient depth to remove all the scale and show 
clean metal; then by means of a gauge of the 
form shown in Fig. 38 (/'), one side of the other V of the 
pair being worked upon is roughed out. The gauge for 
the other pair of V's is then taken and the corresponding 
sides of them roughed out. The other hand tool is then 
clamped in the tool block and the other sides of all four V's 
roughed out to their respective gauges. 

The surfaces c between the V's and/, g outside of the V's 
should be finished with a square -nosed tool before the V's are 
finished and a cut should also be run over the flat top // of 
the V's. The finishing of the V's is done with an ordinary 
side toot and with a head set over to the proper angle; i 
the finishing, as coarse a feed as practicable should be use 
For setting all roughing tools a gauge of the form s 




>uld be used, 
■rm shown in 





§9 PLANER WORK. 41 

Fig. 32 (a) may be used, but gauges of the form shown in 
Fig. 38 (a) and (b) will be found convenient for the final 
fitting of the Vs. 

The planing of the V grooves in the headstock and tail- 
stock is carried on in a manner similar to that necessary in 
planing the V's already 
described. When planing 
V's in the headstock and 
tail-stock after the sides 
are finished, a square- 
nosed tool should be taken Pl °- 40, 
and a slight recess cut in the bottom of the groove, as shown 
at fl, Fig. 40. This is to make sure that the surfaces of the 
V's on the headstock and carriage will always come in contact 
w ith those on the lathe and that there will be no danger of 
the bottoms of the grooves coming in contact. This space 
is serviceable in distributing the lubricant when lubricating 
the V's of a machine. 

In setting any gauges that bear on two or more surfaces, 
11 is well to put pieces of paper of uniform thickness under 
the bearing surfaces of the gauges and then see if the 
gauges hold all the pieces of paper with uniform pressure 
when they are in contact with the surfaces to be tested. 



OPEN-SIDE PLANERS. 

^2. Planing Wide or Irregular Work. — A device 
* or planing work too wide for the housings of an ordinary 
P'aner is shown in Fig. 27, but this device is limited in its 
a PPlication. To overcome these objections, the open-side 
Ptener, illustrated in Figs. 41 and 42, has been brought 
° u t- This consists of one heavy upright a rigidly attached 
to the bed b, which carries an ordinary platen c. The 
Pkten, however, is usually made somewhat heavier than 
w °uld be the case with an ordinary planer having the same 
Wl dth of platen. The cross-rail r/is supported from one end 
only by a housing, or post, a. Fig. 42 shows a back view of 



PLANER WORK. §9 

the machine illustrating the heavy brace casting fitted 
between the upright, or post, a and the cross-rail d in order 
to give a cross-rail as stiff as that ordinarily obtained by the 
use of two housings. One or more planer heads e are 
attached to the cross-rail, as shown in Fig. 41. To support 




the end of work that overhangs the planer table, an auxiliary 
rest / is provided, which runs upon a series of rollers^ - on 
the top of the I beam //. The I beam A, together with the 
auxiliary rest that it supports, can be moved toward or away 
from the planer bed b by adjusting il along the supports » 
Both the bed b and the supports (should be placed upon l 



I a 



PLANER WORK. 



•13 



same rigid foundation. The platen c is driven by a spiral 
gear operating in a rack under the table, the spiral gear 
being driven by bevel gears in the case/, Fig. 42. In the 
planer shown in Fig. 41, a tool head is placed on the vertical 




. u ■hown at k. Such a planer as this will be found 
1 useful for many special classes of work that are too 
,d to be carried on an ordinary planer, or are so irreg- 
in shape that they cannot be supported on a regular 



5HAPI:R AND SLOTTER WORK. 



THE SHAPER. 



DISTINCTIVE FEATUHE9. 

1. Comparison of Planer and simper. — Both the 
laner and the shaper are used to produce flat surfaces, and 
5th are adapted to about the same class of work. In fact, 

I many cases a piece of work may be done equally well on 
ither the planer or shaper. This is especially true in the 

ise of small work. 

The principal points of difference between the planer and 
te shaper are found in the relation that the motions of the 
iol and work bear to each other, and in the method of 
btaining the feed. In the planer the tool is stationary 
.uring the stroke and the work is moved past the tool in 
■ I .lei to take the cut. In the shaper the work is stationary 
uring the cut and the tool passes over it. In the planer 
te I"-] feeds ndewise during the return stroke of the work. 

II the column shaper, which is the most common type, the 
■ork feeds udewiae during the return stroke of the tool, 
'he shaper is generally adapted to a lighter class of work 
ian the planer, or for work that does not require a long 
j-oke of the tool. 

B» 

For notice of copyright, sec pag.- immediately Following ihu title psKe. 



40 SHAPER AND SLOTTER WORK. • 9 

CLASSES OF SHAPEHS. 

2. Types nf Sbapers. — The ordinary types of shapcrs 
may be divided into column shapers and traveling-head 

jtafitrs, the distinction being made largely on a< ■ 
the style of the frame of the tool and the feed. In thr 
column sliaper the work is fed sidewise during the return 
stroke of the tool, while in the traveling-head shaper the 
ln;nl [a fed sidewtse during the return stroke of the tool. 

Column shapers may also be divided ini 
c rait I- ■ shaper s and geared shapers, the division depending mi 
the method of driving the tool. There are also several 
special types "f shapers, or machines belonging to the 
shaper class, that will be considered after the work of ibt 
ordinary shaper lias been discussed. 



COLUMN SHAPERS. 



l.H*NKEIMIVr\ SMM'I'.K. 



3. Construction of Simper.— This class of shaper 
consists of a column A, Fig, 1, that supports the driving 
mechanism and the various stationary and movable parts of 
the machine; a movable ram B that carries the cut 
at one end; and a movable table /: to which tt» 
fastened. The rani />' slides in Hat bearings [omed on tOg 
of the column; at its front end it carries the shaper head I), 

which gives the down feed. This shaper bead is so arranged 

ili.it it ran be swiveled around to make any angle with the 
top surfaci ••[ the table. The ram is moved to and fro over 
the work by the driving mechanism within the column, which 
is operated by belting from a countershaft tr> tin: cone pul- 
ley/. The length of stroke and the position of the ram with 
reference to the work are adjustable. The shaper head 
carries a tool block H similar to that of a planer, 
table E is fastened by bolts to a saddle .'A which is giW 
to the cross-rail /and can be moved along it cither by 



. 



!» SHAPER AND SLOTTER WORK. 47 

r 'f by an automatic feed. The cross-rail can be raised or 
lowered by means of a screw on the vertical slide G, which 
forms part of the column, and can be clamped to it at any 
point. The table E usually has a removable vise F fitted to 




*0 assist in supporting the table, a screw jack N is 
illy Bttached to the base of the machine. The 
i Feed fr>r each stroke of the ram can be adjusted by 
ttie position of a slide that can be locked by the 

"*• Driving Mechanism. — The driving mechanism of 

an sftaper shown in Fig. 1 is illustrated by the two 

. Pig. 2. A is the column or main frame, 

n 'he ram that carries at the front end the swivel piece C. 




A 



in SHAI'ER AND SLOTTER WORK. gB 

Tha slide D carries the tool holder //. The block a [| 
sri.nr-.il to the ran B by the stud b and the tightener handler, 
This block a Is lapped and fitted to the screw d. The 
screw d can he rotated by the hand wheel /and the bevel 

By this means the block a can be moi 
tbi ram and placed at any desired position. This 
the operator to adjust the position 'if the ram OYM 

a of the length of the cutting stroke I : 

in tin- ["■■■ill i< .11 -i:.,» n i.i- I 1 ■■ li: HI ill- 

stroke, the cutting will take place at or near tin 

the tabic. Ry means of the block a and the screw d, the 




ram can be so adjusted that this cut will take phu e 

en. I of the table. Especially in die work, il is frequently d 

advantage to be able to i ut to an 

out cutting the who]< face of the work, or to col cl< 

round boss or other projection on the work. This i 

the changing of the position of the stroke ■ 

uf the tool. The roller block a< arrics the pin ■-:. up 

are mounted the rollers //. These rolli rs form .1 connection 

between the ram and the vibrating arm and red 

friction The vibrating arm i is slotted si 

the driving gear k by the crank pin /, funned upon the 



g 9 SHAPER AND SLOTTER WORK, 48 

block /'. This block /' is secured in suitable bearings so 
ih.it it can be moved across the face of the gear k. If the 
crankpin / is placed farther from the center of the gear k, 
tin length of the stroke of the ram B will be increased, 
while if the crankpin / is drawn toward the center of the 
gear fc, the length of the stroke of the ram will decrease 
until the pin / reaches the center of the gear k, when the 
stroke will become zero. In order to adjust this crankpin, 
the screw » and gears o and /> are provided. The gear p is 
mounted upon the shaft q, one end of which is squared to 
receive a crank. A locknut A", Fig. 1, is provided on the 
shaft, so that when the gear / has been placed in the desired 
position, the shaft q can be locked and further motion pre- 
vented. The graduated scale r on the body of the machine 
and the pointer s on the ram serve to show when the proper 
position for the desired stroke is reached. The vibrating 
arm i is made very stiff and is provided with a clamp piece /, 
intended to prevent any spring in the arm. This clamp 
piece is shown partly broken away in Fig. 2 so as to show 
the gears behind it. The pinion u and shafts v and w, 
together with the clutch lever y, are a part of the back-gear 
arrangement. The rest of this back-gear arrangement is 
not shown, since il is on the side of the section toward the 
front of the machine, and hence could not be seen in this 

... 

5. Construction of Shaper.— The geared sbapcr 

differs from the crank-driven column shaper only in the 

method employed for driving the ram. In the geared 

attached to the under side of the rain; the 

■■\ 3pur gearing in the same manner as a 

spur-geared planer. The motion of the ram may be 

i by a reversing belt that is alternately shifted, 

together with the driving belt, from the tight to the loose 

this method is similar to that employed for opera- 

: the platen of a spur-geared planer. In some shaper 



1.1 .llil'.H -hi III. If. 



5D 



SHAPER AND SLOTTER WORK. 



designs the reversing is accomplished by friction clutchi 
ulii< li alternately grip and release the pulleys carrying tss 
driving and reversing belts. These Erictioa dutches ate 
operated b] tappets attached to the rams; tlie ta 
movable and can b< clamped anywhere along the ram. Tbjej 
determine by their position the length of the strolci 
post! >i Hie ram .a the beginning ami end of the strol 



TH,\vi;i.i\<;-in:.\i> shapkr. 



6. Construction of Sluiptr. — A style of shape: 
known as a traveling-bead abaper is used to 
extent for work beyond the range of the column 







Such a shuper is shown in Fig. 3. It has a very rigid box 
bed a, which carries the ram b on top and one or more 
tables on its side, The ram is mounted on a saddle k. 



§9 



SHAPER AND SLOTTER WORK. 



51 






which can be moved along the bed either by hand or by an 
automatic feed. The line of motion of the saddle is at right 
angles to the line of motion of the ram; the tool is fed 
across the work by moving the saddle. The shaper head c 
is Fastened to the end of the ram in the same manner as in a 
column shaper. Vertical slides m, m, which can be moved 
along horizontal ways on the front of the bed and clamped 
thereto, carry the table e and the vise d. The table and 
vise can be moved in a vertical direction by means of screws, 
and can be rigidly clamped to the vertical slides in any posi- 
tion. The work when small is either fastened to the table 
nr lull! in the vise; if large, both may be used for support- 
ing and holding it, 

With this type of shaper, it is possible to take cuts on 
quite heavy work, since the work, on account of being sta- 
tionary during machining, may be supported by jacks or 
by blocking placed on the floor. This cannot be done very 
well with a column shaper, where the work is usually sup- 
ported entirely by the table with which it moves. 

Many shapers of this class are provided with a stud, 
between the table e and the vise d, for holding work that is 
to be finished to a radius. The stud is sometimes provided 
with an automatic feed that turns it through a small portion 
■ if a revolution after each stroke of the tool. By this device 
;niy curved work having a radius less than the distance from 
ter of the stud to the bottom of the ram can be 
finished. The stud is sometimes made removable, so as 
to leave a hole through which lung shafts can be placed. 
Ices it possible to cut keyways near the center of 
long shafts. 



7. Driving Mechanism. — Fig. 4 is a right-hand side 
view of the machine shown partially in section. Corre- 
sponding parts have been lettered alike in Figs. 3 and i. 
Power is transmitted from a line shaft or countershaft by a 
>e!t to the cone pulley /, which is fastened to a splined 
laft J extending along the back of the bed. The shaft 
•ries a pinion i; which has a feather fitted to the spline, 



sa 



SHAPER AND SLOTTER WORK. 



and consequently is free to slide along the shaft, but ' 

forced to rotate with it. The pinion k meshes with the gear / 

The gear f carries a crankpin I, which is mounted on a sIL ^k3 
and can be clamped to the gear at any distance from t ~B* 
center within its range. A connecting-rod n is attached *: 
the crankpin and also at «' to a block fitted to a slot in t- S~» 
ram b\ the block can be clamped to the ram in any posit i «> 




within the range given by the length of the slot. By vary- 
ing the position of the crankpin i, the length of stroke of 
the ram can be adjusted; in order to change the position of 
the ram so that the tool will pass over the surface to ber 
machined, the block at «' is loosened and the ram pushed io- 
or out by hand until it is in the desired position, when the? 
block is again clamped to the ram. 



8. Quick-Return Motion. — The geared shaper is fre- 
quently provided with a quick-return motion, as shown in 
Fig. 4. The gear f revolves on a large pin or hub v. The 
piece w is secured to « by the eccentric pin /, and is pro- 
vided with a slot in its back in which the driving pin r is free 
to slide. As /"revolves it forces «- to revolve about /. but 
owing to the eccentric position of /, the pin i makes one half 



59 SHAPER AND SLOTTER WORK. 53 

revolution while the gear is revolving through the angle or t t 
and the other half while the gear is revolving through the 
angle Isa. By making the former the return stroke and the 
latter the forward stroke, the tool is given a slow advance 
and a quick return. 

SHAPER OPERATIONS. 

CUTTING SPEEDS. 
'•>■ Influence of Style of Simper on Cutting Speed. 

'he proper cutting speeds of shaper tools are the same as 
; kuier tools. In a crank-shaper, the average speed 
Willi:- ram varies with the length of the stroke, since, with 
the belt on a given step of the cone, the shaper will make a 
Mutant number of strokes per minute, whether they be 
'"»K r>r start. 

Suppose the shaper makes 60 strokes per minute and the 
SIr, fes are 1 foot long. Then the tool moves 1 foot for- 
**ftisand 1 foot backwards in 1 second, or 2 feet per revolu- 
ll0[l i this is equal to a cutting speed of 120 feet per minute. 
Appose the length of stroke is changed so that it is 1 inch 
" m £: but that the machine continues to make CO revolutions 
f* r minute. Then, in 1 stroke, the tool moves 2 inches, 
: "''l in 80 strokes it would move 120 inches, or 10 feet. 
*™%, in one case, the cutting speed was 120 feet per 
""lute and in the other case it was 10 feet per minute, 
""ten, since the average cutting speed depends on the length 
ike, it follows that a constant average cutting 
'peed can only be kepi by varying the number of strokes 
r* r minute. For this reason, crunk-shapers are always sup- 
plied with a cone pulley for the driving belt. 
' n geared shapers, the cutting speed does not vary with 

. 'ii stroke, but remains constant, as is the case in 
planers. Pot this reason, geared shapers do not require cone 
NfeyS in order to keep the cutting speed constant. Cone 

c often put on geared shapers to provide different 
speeds for different metals. 




54 SHAPER AND SLOTTER WORK. §9 

SHAPER TOOLS. 

lO. Relationship Between Shaper and Planer 
Tools. — As the cutting action of the planer and shaper is 
the same, the same class of tools can be used on both. In 
the shaper, as in the planer, the shank of the tool is always 
in a plane perpendicular to the line of motion of the tool or 
the work, and hence the angle of clearance always remains 
constant. 

Special tool holders and inserted blade tools may be used 
in the shaper as well as in the planer. Tool holders, or in 
fact any tools, cannot be used effectively both on lathe and 
planer or shaper work, on account of the fact that the angle 
of front rake, or clearance, is constant in the shaper and 
planer and varies in the lathe. 



HOLDING THE WORK. 

11. The Vise. — Most of the work done on the shaper 
is held in the chuck or vise. The methods employed for 
setting the work square and true, so that it may be planed 
square and parallel, are the same as those used in setting 
work in the planer vise. 

There are some vises especially made for shaper work. 
As a rule, the planer vise is provided with no method of 
adjusting the vise on the base after the work is clamped in 
position, but shaper vises are usually provided with a screw 
by means of which the vise proper and the work can be 
adjusted. Such a vise is shown in Fig. 5. The base of the 
vise a is clamped to the shaper table. By means of the 
graduated circle shown at £, the body of the vise c can be 
set at any desired angle with the slide r. When set to the 
desired angle, the vise is clamped to the slide by means of 
the nuts shown in the pockets at the sides. The slide e can 
he fed back and forth across the base a by a screw operated 
by the handle d. The body of the vise c is provided with 
a fixed jaw g and a movable jaw h. The movable jaw is 
adjusted by means of the screw t\ which is operated by the 



SHAl'ER AND SLOTTER WORK. 5a 

wrench f. After the jaw // is in the desired position, it is 
rcured by a clamp nut k. The jawsj^ and // have remov- 
ble steel faces. For work on cylindrical pieces, one of the 




emovable jaw faces is sometimes replaced by a V-shaped 
ock that will facilitate the holding of any cylindrical 
aiece of work. 

12. Cliimpint; Work. — When work is of such a form 
hat it cannot be held in a vise, the vise is removed and the 

work fastened to the table. This is done with bolts, straps, 
nd clamps in a manner similar to that in which work is 
istenedon the platen of the planer table. Sometimes toe 
lamps and plugs are also employed. With traveling-bead 
bapere, very large castings or forgings that have small sur- 
ices to be machined are frequently blocked up in front of 
he machine on suitable jacks and blocking, and clamped 

either to the table or front of the machine and then oper- 

ited on by the tools. 



TAKING THE CUT. 
1 3. Etang« of Utility of the Shaper. — For short 
uts on pieces of relatively small size, the shaper is usually 
■tier adapted than the planer. For cnttin 

>r for cuts that terminate close to a shoulder, the 



shaper possesses the advantage that it can be more readily 
set to take a particular length of stroke, and it will then cul 
that exact length of stroke each time. This is true partic- 
ularly of the crank-shapers, but only to a limited extent is 
it true of geared shapers. On the planer or geared shaper 
the reversing point is not positive, because of the uncer- 
tainty in the slip of the belts and the gripping of the pulleys 
by the friction clutches. 

14. Cutting » Key way. — Whenever a cut terminates 
in the metal, a notch must be cut at the end so that the 
!<k>1 will pass out of the cut each time. Suppose that a key- 
way is to be cut in the end of a shaft, as shown in Fig. ('■ (a). 




The keyway should first be laid out by scribing tines i 
indicate its width and depth. At the place where the key- 
way terminates in the shaft, a circle is described equal Id 
diameter to the width of the keyway. In this circle a hole 
is drilled, as shown in Fig. « {/>), cipial in depth to that of 
the keyway. The work is then set in the vise or clamped to 
the table, so that the lines on the end that indicate the sides 
of the finished keyway arc perpendicular to the shaper table. 
In the case of a fairly large keyway, or when no tool of the 
right width is at hand, slots are cut along the outside edges 
of the keyway, as shown in Fig. 6 (<-). This work is doi 
with a parting tool. After the slots have been cut, l 



§ 9 SHAPER AND SLOTTER WORK. 

melal shown at a. Fig. 6 [e), is removed with a square- 
pointed tool. If an attempt is made to take such a cut as 
s shown in Fig. 6 without first drilling or otherwise cutting 
nit a place for the tool to run into, and thus cut off the 
tying, each shaving will clog the slot slightly, so th;it 
i few strokes the tool will strike with great force 
tgmtOSt solid metal. If the cut is continued, the tool will 
break, or the work will be pushed from the machine. 

Large keyways are usually cut with several settings of 
the tool, as shown in Fig. ti. Small keyways are often cut 
by using a too! just the width of the slot. When the key- 
way is finished at one cut, it is well to drill two holes at the 
end and chip out between them so that the tool can be 
lifted clear of the work for the back Stroke. With a single 
hole there is danger of the work catching the tool. When 
the kcyway is cut the entire length of the work, there is no 
difficulty in lifting the tool for tin: back stroke. In some 
cases the keyway is planed a liitic narrower than desired, 
with the square-nosed tool, and the sides are finished with a 
side tool. 



15. Cutting to a Shoulder. — Suppose that it is 
necessary to take a cut over the piece of work shown in 
Fig. 7, and that the surface c is to be partly removed up to 




e line A li, as indicated by the dotted lines. Refore this 
n be taken on tii" shaper, it will !"■ necessary to cul ■< 
■ ,i: I B i qua! in depth to the amount to be removed. 

-■ '-in with .i i old ■ hisel and a ha ei oi 

by first drilling a hole at a and then cutting the gToove on 



SHAPER AND SLOTTER WORK. 



)i 



the shaper wilh a parting tool. The part of the surface? 
indicated by dotted lines can then be easily planed 
In castings, when it is known that such cuts as these are to be 
taken, much work can be saved by coring out a space where 
the cut lata terminate. This saves the time reqi 
cutting a groove with the chisel or by planing. 

16. Clamping Work to the Smlillc. — Work that is 

COO high to be placed on the shaper table, or work that can- 
not be clamped to the table on account of its 
iH(|n.iuly be clamped to the saddle. An ewnpji ol 
is shown in Fig. 8, which shows a pair of legs for a lathe 



clamped in position for shaping the tipper surface. The 
[able and vise are removed and the work a s.-> ui 
saddle by bolts and blocking. This method of holding wc 
is similar to attaching it to an angle plate fastened to i 
planer platen. 




SHAPER AND SLOTTER WORK. 



6!) 



When work is clamped against the front of the saddle, it 
, not always possible to test the setting with a surface 
ange. This is also occasionally the case when rather large 
; clamped to the top of the table. Then the setting 
the work may be tested by means of a level or by a 
minted wire, a scriber. or a tool held in the tool post, while 
ring the ram by hand. In some instances, the ram can 
run out until it extends clear over the work; a surface 
angc can then be inverted and held up against the bottom 
: the ram, along which it is moved in order to test the 
«tting of the work. 

1 7. Rack Cutting. — In some cases the shaper may be 
used as a rack cutter. The vise is set with the jaws at right 
angles to the line of motion of the tool, and the rack blank 
is clamped in it. A tool having its cutting edge formed to 
give the correct shape of tooth is set in the tool post, and is 
fed down into the work, thus cutting out the space between 
two teeth of the rack. The work is then moved sidewise 
the correct distance to cut the second space, and the tool is 
again fed into the work to the same depth as before. 

For comparatively rough work, the spacing of the teeth 
may be laid out on the face of the rack, and the tool set as 
near as can be judged to the marks by moving the saddle 
by means of the feed-screw. A better way is to use the 
feed-screw as a spacing device. When the feed-screw is 
used for spacing the teeth, it is treated as a micrometer 
The pitch of the screw is measured and a calcula- 
tion made to see how many turns and what part of a turn 
will be necessary to advance the work one tooth. To make 
the fraction of a turn, it is necessary to provide some kind of 
index on the feed-screw. Frequently one of the change 
;ears belonging to a lathe can be clamped on the screw and 

ied as an index plate. 

Example, — Let it tie required to cut a rack to mesh with a 4 diame- 

J pitch gear. (The circular pitch, or distance from the center of 
the center of the next on ihe pitch line, for 4 diametral 
is equal to 7W5 inch.) The work is to be done in a shaper having 

h reads per inch on the feed-screw for the saddle. 



SHAPER AND SLOTTER WORK. 



Solution— If the feed- 
the leadscrew will advance 
cular pitch of the rack i 
= 8«> = V» 



On has 4 threads per inch, each turn of 
che saddle 1+4 = .35 inch. As the cir- 
.785 inch, it will be necessary to make 

irns of the feed-screw to move the work 



from one tooth of the rack to the next. A 50-tooth gear may be 
attached to the leadscrew and the screw given three turns and then 
moved far enough to carry seven teeth of the gear past some fixed 
point. If no 50-tooth gear is at hand, it will be necessary to select 
another ; as s ' fl is very nearly 1, it would not result in a serious error if 
the screw were only given 3j revolutions. To accomplish tliix I 
28-tooth gear could be used and the screw given three turns and then 
moved four teeth farther. 



SPRING OF MACUINB AND WORK. 

18. Sprlnjt of tbe Ram. — The chances that the tool 

and the work will spring are greater in the shaper than in 
the planer. In the shaper, there is a tendency for the tool 
to spring away from the cut; this is due to the lack of abso- 
lute rigidity in the ram, and also to the looseness of the 
guides in which the ram slides. When the stroke is very 
long, the tendency of the ram to spring is greater than when 
the stroke is short. This is due to the fact that in a long 
stroke the ram has to extend a long way from the column. 
When taking a short stroke, the work should always be set 
as close to the column as possible. 

On account of the excessive spring of long shaper rams, 
the average stroke of shapers is about 10 to 16 inches, and 
few exceed 30 inches. When the stroke of a shaper exceeds 
30 inches, it is necessary to make the ram very heavy and 
rigid. 



19. SprlnK of the Work. — The spring of the work 
itself and the sag of the table supporting it, especially if 
increased by any looseness of the gibs holding the saddle to 
the cross-rail, are fruitful sources of error. Errors due to 
these causes are made still larger by the action of the cut- 
ting tool, which, in forcing its way through the work, tei 
to spring it still farther away from the machine. 





§9 SHAPER AND SLOTTER WORK. 

SPECIAL SHAPERS. 



THE DKAW.CUT SHAPER. 
20. Description of Draw-Cut Shaper.— In order 
to overcome as far as possible the errors due to the spring- 
ing Iway uf the work and the table as the toot advances, 
diapers have been designed in which the cutting is done 
during what would be termed the return stroke in the ordi- 
nary shaper. In other words, the tool, instead of being 
pushed across the work by the ram. is drawn across. From 
Ih is fact, machines of this class derive the name of draw- 
cut hit a fters. 




Fig. 9 is an illustration of such a machine. It will be 

noticed that in general appearance it does not differ from 

[nary column shaper. Since it is intended to cut 



62 SHAPER AND SLOTTER WORK. §9 

while the shaper head is moving toward the body of the 
machine, the tool block a is reversed on the ram b in order 
to allow the tool to swing away from the work while the 
ram is moving outwards. When the ram draws back into 
the machine, the tool block swings to its seat. As a matter 
of course, the tool must be set in the opposite direction from 
that which it occupies in the ordinary shaper; that is, its 
cutting edge must be toward the ram. 

2 1 • Advantages of the Draw-Cut. — For some kinds 
of work a draw-cut possesses distinct advantages. When a 
cut is being taken, the pressure due to the tool forcing its 
way through the metal is exerted toward the machine; in 
the case of work clamped to the saddle especially, it tends to 
hold the work more securely. Furthermore, in case of work 
bolted to the table or held in the vise, this pressure partly 
relieves the cross-rail of the stresses to which it is subjected 
by the weight of the table, vise, and work. In many cases, 
great rigidity can be secured by putting blocking or jacks 
between the work and the face of the machine, thus greatly 
reducing the spring of the work and the machine during the 
cutting operation. 

OPEN-SIDE PLATE PLANER. 

22. Description of Open-Side Plate Planer.— A 

modification of a planing machine designed for planing the 
edges of steel and iron plates is shown in Fig. 10. This 
machine is known as an open-side plate planer. 
Though commonly called a planer, it is really a modifica- 
tion of the shaper, on account of the fact that the work 
remains stationary during the cutting operation, while the 
tool moves. 

The machine illustrated is arranged to plane one side and 
one end of the plate at the same setting. The plate is sup- 
ported on the tables a and b y and is held in place by jacks j 
that butt against the girder c. The traveling head //car- 
ries the tools for planing the edge of the work. It is pro- 
vided with two tool heads set in opposite directions, so that 



C4 SHAPER AND SLOTTER WORK. 

I he tool in one cuts when the head is travelil 

Mi, n and the tool in the other when the bea 

the opposite direction. These tool heads are conti 

the screws e and/". The head d elides on ■. 

fed backwards and forwards by :i screw driven by the pulW 

v. As there are t<«pis to cut in each din i 
pulleys at w are both the same size. For phmin^ : 
the plate, a head i fitting on a guide I- is provide 
guide k is adjustable through an angle oi about 10° each 
way, and can be clamped to the base -' This provides for 
the planing of the ends of plates si angles slightly more n 
less than 90° with their edges. The head i is proi ■ 
a single tool clamp, and cutting is done in our direction 
only. As the tool on i cuts in one direction only, a quick- 
return motion is provided by driving the fi 
cutting stroke by the pulley m and on the return stroke by 
the pulley ii The length i.f cut made by (he loots in either 
head is adjusted by shifting the tappets e and /< so I 
the blocks r r at the proper lime to shift Uu 



BHAPER8 FOR SPECIAL WORK. 
23. I -sc of Shapera for 8p*elal Work.— In manu- 
facturing any sjiecial line of machinery thi cosl at 
can very often !"■ greatly reduced by employing ape ■ 
for carrying on certain operations Tools of I 
are especially serviceable for this class of work. i 
two general classes of special shapers, nam< ly, portable and 
stationary. For very large work portable shaperi are very 
Ii.mhIv for planing small bosses and other si 
eastings, the shaper being liolted to the cast i 
operating or being bolted loan iron flooi or floor pi a I 
side of the casting. Such tools are generally e]ei trii all) 
i] riven or driven by a rope belt. Very often such :i ! a< 
placed upon a casting on the erecting floor and 
machine operations carried on while the work of ereel 
progress, or two or more of the portable special machic 
be operating on the casting at once Fhi special shapers at 



SHAPER AND BLOTTER WORK. 65 

e stationary type are usually somewhat larger than the port- 

. and are occasionally provided with more than one 

, so that more than one surface can be finished at a 



24. Exumplc Of Sliaper for Special Work. — The 

nts of large flywheels are frequently joined by links, 
. shown in Fig. 11. The faces a, a of the segments are 



J to the correct angle, so that when placed together 

aJte a closed joint at the hub and rim, as shown at bb. 

At the rim the segments are held together by steel links 

placed on each side of the wheel in suitable recesses. One 

of these links is shown at d. The links are placed in the 

recesses while hot, and on cooling they shrink, thus drawing 

the joints closely together. The shrinkage allowance that 

isary to hold segments together in calculated, and the 

links are made so that the distance e, Fig. II, is the same in 

In order that the heads of the links may have a good 

:aring on the shoulders f, c of the recesses, it is necessary to 

: hcse shoulders to exact dimensions and make sure 

at the shoulders are an exact distance from the surface b b. 

i one shop the problem of properly machining these recesses 



66 SHAPER AND SLOTTER WORK. §» 




OS SHAPER AND SLOTTER WORK. g 9 

or arm, o. The machine is provided with power feeds bo* " 
for vertical and horizontal cuts, the slide e being arranged * * 
feed the tool horizontally and the slide k to feed the to*- 3 
vertically. When feeding by hand, the horizontal feed # 
controlled by a crank on the shaft n and the vertical fee'' 
by a crank on the shaft m. The rams c and d, though botf^ 
driven by the same mechanism, can be operated independ -*^ 
ently of each other. The castings for the wheels are core<^^ 
out at the back of the surface to be cut, so as to allow the^" 
tool an opportunity to run out of the cut at the back end oC 
its stroke. By means of this machine the surface c against 
which the shoulders of the links bear, as shown in Fig. 11, 
and also the vertical surface against which the bodies of the 
links bear near c, are machined so as to fit the links accu- 
rately. While such special machines frequently cost a large 
sum of money, the saving that they effect more than pays 
for the investment where the line manufactured is of such a 
nature that there is a considerable amount of duplicate work. 



THE SLOTTING MACHINE. 

25. Characteristic Feature* of the Slotting 

Machine. — The slot t Inn machine is a modification of 

the shaper and is similar to it in many respects. In the 

slotting machine, however, the rain moves vertically instead 
of horizontally. It is used for finishing flat or curved sur- 
faces at right angles to a horizontal surface of the work. 
The slotting machine derives its name from the fact that it 
was originally intended for cutting slots or beywaya in 
gears or pulleys, hut it is now used for a large variety of work, 
where it is desired to produce vertical, fiat, or curved sur- 
faces. A machine of this class is illustrated in Fig. 11. It 
consists of a rigid frame M, carrying a platen or table Aon 
which the work is secured. The tool is clamped to the 
head L, on the end of the ram A. Power is transmitted to 
the ram from the pulley E, through a pair of gears -V to the 
crank-disk B. The crankpin is adjustable in a slut in the 
crank-disk B. The connecting-rod C t:ikes hold of the pin P. 



59 



SHAPER AND SLOTTER WORK. 



69 



The pin P is adjustable in the slot in the ram A, so that the 
position of the ram in relation to the work can be changed 
so as to cause the tool to cut at any desired portion of the 
»ork. The length of the stroke is determined by the posi- 
tion of the pin O in the slot in B. The ram is provided with 
a counterbalance weight D. The platen F is mounted on a 




™* that can be moved longitudinally in two directions at 
ri ght angles to each other across the base of the frame .If. 
™M platen'/ 7 can also be rotated by means of a circular 
™* Q and a worm controlled by the handle //. Power feed 
^provided by means of a rod and telescopic shaft as shown 
at C, G and a suitable set of gearing on the front of the 
machine. The amount of feed is controlled by adjusting a 



pin in the slot Upon the crank-plate K. The slotter is very 

similar to the crank-shapei . both in the manner of driving 
the ram and in the adjustment of the feed for the table. 
The end of the ram L carries two sets of tool clamp 
provide for fastening tools in two different positions at right 
angles to each other. 

2i$. Setting the Ham. — When adjusting the slotter ram 
for a given piece of work, the ram should be so adjiu 
the edge of the too! will pass by the lower edge of the work. 
but not touch the platen. To set the ram, it should be let 
down so that the tool rests on a piece of wood or soft metal 
on the platen. The machine is then turned by hand so thai 
the crankpin is at the lowest part of the stroke, after 
which the bolt /'is tightened. When the ram is raised, the 
spacing strip may be removed from under the tool, and, for 
each stroke, the tool will stop short of the platen a distance 
equal to the height of the spacing strip. 



8I.OTTKR OPERATIONS, 

27. Setting the Work. — In planer work, a surface 
gauge can be used and the work set so that the line indica- 
ting the edge of llit- surface to be machined is parallel with 
the platen. The setting of slotter work cannot be tested in 
this way, because the line of motion of the tool is . 
angles to the surface of the platen instead of parallel to il 
The work must be clamped to the platen, so that the line 
indicating the edge of the surface to be cut, shown by the 
dotted line A A, Fig. 16, is perpendicular to the platen. 
This may be tested with a square. Parallel strips, or 
blocks, i, c must be put under the piece in order to raise it 
above the platen, so that the tool may pass entirely over the 
surface to be machined. After the work is set true, a tool 
is clamped in the ram, and the work is brought und 
that the tool point just comes to the line scribed on the 
work. The setting of the work is then tested by moving 
the platen past the tool point, and noting if the line follows 
the tool point. If it fails to do so, the platen, and hence 



SHAPER AND SLOTTER WORK. 



the work, may be revolved so that the point of the tool w 
just follow the line. The work will then be set, and ! 

ready for the cutting operation. 




Bolts, pins, angle plates, and special holding devices may 
be used for holding work on the slotter platen in the same 
*»y thal'they are used on the planer platen or shaper table. 

28. Clamping the Work. — The work to be operated 
oa is clamped to the platen in the same manner in which 
w °fk is clamped to a planer platen or shaper table. The 
M me care is necessary in setting the work true and clamping 
11 » that it will not be sprung out of shape. 

The work for the slotter should be laid out with lines to 
•irk to. These lines are necessary in setting the work, on 
^ount of the fact that when a flat surface is to be planed, 
Wit lin e indicating the finished edge of that surface must be 
Ml parallel to one of the slides of the table. 

2W. Cutting Circular Surfaced — When cutting cir- 
cular surfaces on the slotter, the work must be set so that 
"* Utis coincides with the axis of rotation of the platen. 
Rk instance, if a cylindrical surface having a radius of 
10 inches is to be finished in the slotter, the work must be 



SHAPER AND SLOTTER WORK. 



|i 



set so that the center around which the radius is ■ ■■ 

is in the axis of rotation of the table, and the pi. il 

be id justed bo thai the point of the tool is at a 

10 inches from the center. The feeding is done by rotating 

the platen slightly after each down stroke of the ram. 

To aid in setting work having cylindrical surfaces, con 
centric circles are usually marked on the platen and may be 
used u guides ; or, a cylindrical stake may be fitted to the 
center hole of the platen and used to measure from. In 
either case, after the work is set, it is best-to revolve it pa« 
the point of the tool to be sure that it is correctly set. This 
applies to internal as well as external cylindrical surfaces. 



30. Blotter Too In.— Many of the tools used for the 
slotter are different in appearance from those used for cither 
planer or shaper work. The cutting edge is formed on the 
end of the bar so that it cut* 
when pushed endwise, and it 
Js therefore under compression. 
Fig. l(i ((») shows a forged rough- 
ing tool for Hie Blotter. The 
shank is generally made square, 
and the end is forged so that it 
about like a parting tool To* 
cutting face that turns the ■ha- 
ving is on the end. To Bhi 
angles of rake and clearance in 
»— this tool, draw the line A H in 

" ^S LwJ F ' g ' 1G *"' I ,aral,rl to the to P o( 

*~ ^w tne P' aten; £ D perpendicular to 

A B at the point O of the tool; 

long the end of th 

and !I K along the side of the tool. The angle D O K is 

the angle of clearance, and the angle ISO J' the angle of 

front rake. It may be sei n from tins that these angles are 

measured at right angles to the direction in which they are 

measured on a planer, shaper, or lathe tool. When I 

slotter tool is carried at the end of the ram so that its si 




SHAPER AND SLOTTER WORK. 



. 



D □ 



is at right angles to the line of motion, the clearance angl 
and the angle of front rake are measured in the same way as 
on a planer tool. When slotter tools are 
forged from the bar, they are made with 
narrow points for roughing cuts and 
wide points for finishing cuts, as is done 
I" planer work. It is not possible, how- 
ever, to use such coarse feeds for finish- 
ing work on the slotter as can be done 
<>n the planer. 

For the slotter, a good roughing tool 
for flat work may be forged with the 
blade diagonally across the shank of the 
tot, as shown in Fig. 16 (£). 

When slotter tools for cutting key ways 
are forged from the solid bar, they are 
shaped as shown in Fig. 17, the cutting 
edge being along the line A B. If the 
slots are long, it requires a long, slim P" - "• 

blade to reach through the work. When such slim tools are 
. used, they spring away from the work 

^-_ |"M^ considerably, and, consequently, time 

and care is necessary to complete the 

31. Slotter Bars 'With Fixed 

Tools. — The ordinary forged slotter 

tools require a large amount of steel, 

are heavy to handle, difficult to main- 

jlt tain in good condition, and require a 

-P^ large amount of space for storing them, 

on account of their size. To permit the 

use of small steel tools in the slotter, 

-\ various forms of slotter bars have been 

i-U devised, one of the most common forms 

Fia K of which is shown in Fig. 18. This 

consists of a rectangular body a, through which the bolt b is 

fitted. The bolt b is held in position by a nut and washer ate. 






D 



SHAPER AND SLOTTER WORK. 



The lower end of the bolt is slotted to receive the tool a 
The tool rests against the head of the bolt e. The bar a 
uped to an ordinary slotter head by the regular 



clamps f and g. The bolt b 



s^- 



be revolved in such a way 
that the tool ^extends froi 
the bar at any desired angle 
This device facilitates the use 
of ordinary small planer or 
shaper tools in the slotter. 
The bar a can be adjusted up 
or down under the clamps 
and g to some extent. 

While this makes a fai: 
rigid bar for short work, 
is not practicable for a lot 
bar, and hence bars of tb< 
form shown in Fig. 19 are fre- 
quently used. In this case the 
regular clamps have been re- 
moved from the slotter head 
and two special clamps B, B 
substituted for them. These 
are held against the end of 
the ram by the bolts £,£. The 
slotter bar c passes througl 
holes in the clamps and 
held in position by tl 
bolts a, a. A small steel t 
is fitted in a slot in the lower 
end of the bar c and secured 
by a setscrew, as shown. 
The cylindrical form of the 
bar c permits of its being 
rotated so as to bring the 
tool or cutter to any desired 
angle of the work. This will be found advantageous when 
slotting out irregular forms having internal angles, i 
as square holes The cutter blades or tools are rigid 




. ne 
ool 





filed in both of the forms of bars shown in Figs, 18 and 19, 
iiud hence, on the return stroke the tool drags over the 
wort. If the tool is sharp, it will usually cut true enough so 
that the bar will be sprung very little on the return stroke, 
and the dragging of the tool will not injure the edge of the 
tool materially. If, however, the tool is given too much 
top rake, the edge may break or crumble off on the return 
stroke. The feeding of the work does not occur until 
lias returned to the top of the stroke, and hence 
the edge is out of harm's way during the operation of 
feeding. 

32. Slotter Bars With Tool Blocks. — Some heavy 
slotter bars are made with tool blocks in the lower end that 
«c pivoted in the same way that the tool block on the head 
°f ashaper or planer is pivoted, so that on the return stroke 
the tool will lift away and not drag on the surface of the 
"ork. In such a bar the weight of the tool would naturally 
cause the block to hang away from the work at all times, 
and hence it is necessary to provide springs for holding the 
block against its seat. Sometimes the slotter tools them- 
selves are drilled and fitted on pins and held in place by 
springs, so that the tool itself becomes a swinging block. 
Cut DU8I be taken with bars of this class to see that the 
springs always hold the block or tool against its seat, and to 
4Void the possibility of dirt accumulating under the tool or 
block, for if the tool is not firmly seated when the cut 
begins, it will come down against its seat suddenly and is 
liable to gouge into the work. 



EXAMPLES OP SLOTTER WORK. 

33. Stacking Work. — Frequently a number of pieces 
of the same class are to be finished at once. If these pieces 
.re thin, much time may be saved by piling up a number of 
them and clamping all to the platen so that the cut may 
extend across the entire pile. Fig. 20 shows an illustration 



76 SHAPER AND SLOTTER WORK. §9 

of this class of work in which two engine links a and b have 
been placed one upon the other and clamped to the slotter 
table, parallel strips being placed under the work, as shown 
at c, c, and the tool set so as to cut both pieces at one time. 
Care must be taken in setting the parallels to see that they 
are placed so that the work is supported close to the clamps, 
thus reducing the tendency to spring. In the piece shown 
five parallel strips are used and the work is secured by bolts 




through the regular bolt holes of the piece. Frequently 
the work is secured by means of blocks and clamps. It is 
possible to pile up as many pieces as the stroke of the 
machine can accommodate. Locomotive frames and similar 
pieces are usually finished in this way, and frequently spe- 
cial slotting machines having several heads that can operate 
on different parts of the frame at the same time are pro- 
vided for such work as slotting locomotive frames. 

34. T&klnfE Two Cuts at Once. — Fig. 21 shows a 
piece of work clamped to the platen and ready for the cut. 
The work is a U-shaped forging that is to be finished on its 
inside surfaces. The curved part of the piece has been 
bored to a diameter equal to the width between the surfaces 
when finished. A very heavy slotter bar b is used with a 
blade a, which projects at each side. This blade is made 
the correct length, and with cutting points at each end; 
when set so that it will just pass through the bored part, it 



SHAPER AND SLOTTER WORK. 77 

; correctly set to take the finishing cut, which it does by 
utting both surfaces at the same time. 




35. Gear-'Cutting on the Slotter. — The slotting ma- 

i ten used for special kinds of work. It is well adapted 
for cutting internal gears or for cutting very large spur gears. 
Fig. 22 shows a part of a slotter and a large internal gear 
that it is cutting, A part of the gear is shown at it. This 
rests on a plate c that has been accurately notched with as 
nany notches in its periphery as there are teeth to be cut 
the gear. The plate is fastened to the gear, and is 



n 



SHAPER AND SLOTTER WORK. 



1 1 



mounted on the platen of the slotter. Clamps 
ened to the platen for clamping this index plate and fol 
carrying the stop-pin that holds the index plate in place. 
A stop e with check-nuts on either side is used to regulate 
the depth of each tooth. The cutter or tool used for this 
gear is shaped to the correct outline to the teeti 
Cllttcl /"is carried in a Special block fastened to the end of 
the ram. A similar tool block is shown at g and a tool at k. 







As soon as one tooth space is cut, the stop-pin in the clamp d 
is pulled from the index plate and the blank is revolved until 
the stop-pin will slip into the next notch of the index plate. 
After clamping, a second notch is cut in the blank, and so 
on until all the teeth are finished. 

Very large gears may be cut in this way when supported 
properly on bearings away from the platen, so that the edg< 
of the blank rests on the platen and is free to slide on its 
outer support an amount equal to the depth of the tooth. 



89 



SHAPER AND BLOTTER WORK. 



79 



The action of the slotter is in so many respects similar to 
that of the shaper and planer that a thorough understand- 
ing of these will enable one in a short time to successfully 
handle the slotter. 



KEVWAY CUTTERS. 

36. Description of Key way Cutter.— Another form 

of machine similar to the slotter and the draw-cut shaper is 

he key way cutter. This machine is especially designed for 

utting key ways in the hubs of gears, pulleys, or similar pieces. 




\^ ^\\\\W\ X 



. 23 shows a keyway cutler operating on the hub of a 
ulley, part of the rim being removed to show the hub. 



SHAPER AND SLOTTER WORK. 



cutter bar a is operated from beneath by a ram 
driven by gearing, in a manner stm 
that in which a geared shapcr is driven, 
A table b supports the work, which is fed 
automatically against the cutter c in the bar. 
The overhanging arm d, < i.. 
on the column c, gives support to the upper 
end of the cutter bar. The cutter bar is in 
two parts, which may be screwed together. 
Fig. 24 shows the parts unscrewed, and also 
shows the method of clamping the cutter in 
the bar. The cutter passes through the slotu 
and is clamped by the setscrew b. These bars 
are made in various sizes to accommodate 
different sizes of work. 

Fig. i5 shows a cutter for cutting key ways. 
The shank 5 fits the cutter bar, while the 
part C does the cutting, the cutting edge 
being along the line A B. These cutter 
blades are accurately made of different 
tting key ways of standard sizes. When 



Flo. H 
widths for 

sharpened, the sides are not 
gPOund, the grinding being 
done on the bottom face. 



37. Cutting Rucks on 
u Keywity Cutter. — While 

tin- k.-yway cutter is designed 
particularly for certain classes 
of work, it is possible to do a 
number of other classes of 
work on ihe machine, A 

method of fitting up the machine for cutting racks i 
trated in Fig. 26. A cutter black that will produce tin 
desired tooth form is used and the rach clamped to the 
table, as shown in the illustration. The graduated feed- 
screw a is used to space the teeth and the CTOfl 
screw b to set the work for the proper depth of tooth. 




SHAPER AND SLOTTER WORK. 



By the use of specially formed cutters and some special 
attach mem*, many kinds of work similar to racks can be 
lone on the keyway cutter. 




Fig. X 

38. Machine Broaching- — In order to work more rap- 
idly, machine broaching is sometimes resorted to. This is 
practically cutting with a multiple tool head. The machines 
used for this class are similar to the draw-cut shaper shown in 
T the keyway cutter shown in Fig. 23. The broach 
consists of a number of tools, the cutting edge of each being 
set slightly in advance of the one in front of it. Sometimes 
all the teeth are formed on a single piece of steel, when the 
broach has the appearance of a coarse -toothed saw. The 
broach is drawn past the work and each tooth takes a cut. 
The back of the broach bar is firmly supported so that it 
cannot spring away from the cut. By this device it is pos. 
sible to cut a keyway with a s'erv few strokes of the machine 



DRILLING AND BORING. 



DRILLING. 



HISTOHICAL. 

1. Prehistoric Drill. — The principle of drilling holes 
by means of a revolving tool was known in prehistoric time. 
The form of machine used was a type 
of bow drill, which is still found in 
some smaller manufacturing and re- 
pair shops. The primitive drill may 
still be seen among the Pueblo Indians 
in the form shown in Fig. 1. A 
round piece of hard wood a is split at 
the bottom and a piece of flint or iron b 
inserted and bound into place; the 
point of the drill is formed with scra- 
ping edges. The upper end of the 
stick is pointed and, when drilling, 
rests against a flat stone or piece of 
wo#d c, which has a slight depression 
in it to receive this point. The drill ' "' ' 

is rotated by means of a bow, the string of which is given 
\ single turn around the stick, as shown. To operate the 
Irill, the piece c is held in one hand, thus furnishing the 




! in 



»of copyright, Bee pag* in 



2 DRILLING AND BORING. g 1< 

necessary pressure and giving the proper direction, wL ilc 
with the other hand, the bow is drawn back and for-^li, 
rotating the drill alternately in opposite directions. T* I* is 
instrument, in hands that are skilled in its use, has p» ro- 
duced marvelous results. Beads, shells, etc. are drilled in 
a manner that produces the highest admiration for thaese 
primitive workmen. 



DEVELOPMENT FROM THE LATHE. 

2. Prehistoric Lathe. — The modern machine-shoP 
drill has its origin in the lathe, from which all other forr** s 
of machine tools have been developed. 

The lathe, in a very primitive form, was known in prehi^* 
toric time. Its earliest form consisted of a piece of woo^^* 
supported horizontally upon two wooden pillars and rotate 
by means of a string. The material to be worked 
attached to this revolving part, which moved in opposit 
directions as the string was wound or unwound. As th 
tool could cut only while the work was running in on 
direction, it had to be withdrawn and brought up alter — ' 
nately as the direction of motion changed. 

3* Development of Modern Drill. — While the prin- 
ciple of the lathe is very old, it was not until a compar — * 
atively recent date that power was applied to it, and the^ 
modern shop tool, which rotates continuously in one direct 
tion, was developed. It was some time after the power* 
lathe had made its appearance that the drilling machine was 
brought into use. 

The step from the lathe to the drilling machine was 
simply a change in the arrangement of the head. In the 
lathe, the piece to be worked is usually rotated with the 
spindle, while the cutting is done with a fixed tool. In 
boring holes, the tool may be rotated with the spindle, while 
the part to be drilled is pressed against it. When used in 
this way, the lathe is a drilling machine with a horizontal 
spindle, and the only difference between the lathe when 



SW 



DRILLING AND BORING. 



thus used and the ordinary drilling machine is that, in the 
letter, tht spindle stands in a vertical position and the work 
is supported upon a horizontal table. 



ESSENTIAL PARTS OF DRILLING MACHINES. 

4. Essential Parts. — The modern drilling machine 
consists of a revolving spindle to which a device for holding 
tiic too] is attached, a table upon which the work is sup- 
da device for feeding the tool into the material to 

b drilled. 

5. Arrangement of Parts. — The arrangement of 
ie parts is shown in Fig. 2. In this simple drilling ma- 
rine, the spindle a is held in a 
rcrtical position by a frame b 
"d column c. The spindle is 
rotated by means of a belt run- 
°' n gona pulley d, which is con- 
«ted to the upper end of the 
'Pmdle by means of a spline. 
"he pulley is held vertically be- 
l »wn the two arms e and /, 
''"'s permitting the spindle to 

tin the pulley while turning. 
The tool A is held in a chuck or 
**ktigon the lower end of the 
•pindleand moves vertically and 
with the spindle, The 
art to be drilled is held upon 
* table i. 

The principal parts of the 
filling machine have been men- l0 ' 8 ' 

but it is still necessary to devise some means 

■.; the tool through tht- material. This is usually 

one liy lowering the tool .is it cuts its way; although, as 

II be seen later, in a few cases the table is raised while 




4 DRILLING AND BORING. g 10 

the tool is held in a fixed position. Fig. 2 shows a very 
simple method by which the spindle may be raised or low. 
cred by means of a hand lever. The spindle is made te Cfr 
volve in a sleevey and is held vertically in it by means trf 
the collars k and /, which are fixed to the spindle. Tht 
sleeve has a rack m upon its outer side, which euga 
a pinion upon the inner end of the shaft n. This shaft has 
its bearing in the lower arm of the frame t>, aud 
upon its outer end a hand lever o. The sleeve is free to 
move in a vertical direction as the pinion is turned by meant 
of the lever, but it is kept from rotating by the rack. The 
spindle is lowered by moving the lever in the directional 
the arrow /», thus rotating the pinion and carrying down tht 
rack with which it engages. 

The machine receives its power from a belt running from 
the pulley (/over a pair of idlers q to the pulley r. Attached 
to r is another pulley s, which is Iwltcd to a CQUO 
Bvei v part of a drilling machine should be . 
siUi-, .is :i utv sli'jln spring in any »f the parts cause! ri.n.- 
curacies in the work. 



PRINCIPAL FUNCTIONS OP DKII.I.IM, 
MACHINES. 

«. Purpose of DrltllnfE Machine*.— The drilling 

mac ti Hit was brought into use primarily for the purpose of 
sinking circular holes into a solid body, which is called 
drilling; but with its development it has been found thai 
it can be used advantageously for other operations, such as 
reaming; countersinking; counter boring, spot facing, tapping, 
center drilling, etc. 






7. Causes of Irregularity In Drilled Hole*. 

varying iiardncss ., I" \ In- metal, blow holes in castings, 
slight imperfections in the formation of the tool tend to 
make a drilled hole imperfect. Sometimes the bjoli 
quite straight, or it may not be quite round, or the si 
may be rough 



DRILLING AND BORING. 5 

8. Reaming. — In order to overcome these defects 
where absolute accuracy is necessary, another tool, called a 

cr, is passed through the hole. This operation is 
known as reaming. 

9. Countersinking. — In other case?;, it is necessary to 
enlarge the upper end of the hole, as shown in Fig. 3 (<?). 



10. Counter boring. — When the sides of the enlarged 
lole are carried down straight and a shoulder is formed at 
he bottom, as ahown in Fig. 3 {b), the operation is called 
:ountcr boring. 

11. Spot Facing. —When it is necessary to finish a body 

■ uly a small distance about a drilled hole, to form 
. smooth surface for the head or nut of a bolt, or a bearing 




m 



for the hub of an adjacent part, it is called spot facing, as, 
instance, the bearings for the nuts a, n on the cylinder 
head. Fig. 4, are produced by facing the spots b, b. 



DRILLING AND BORING. 



11 



12. Facing. — When the ends of hubs are finished 
a revolving cutter, it is simply called facing, as, for instance, 
in the case of the rocker-arm in Fig. 5, where the surfaces 
a, a are faced to receive the pin b and washer c. 

13. Tapping. — When internal screw threads are 
in a piece of metal, the operation is called tappli 
The hardened-steel screw, which is grooved or fluted loi 



tudinally, as shown in Fig. 6, and with which the thread 
formed, is called a tap. 



14. Center Drilling. — When a center in a piece 

lathe work is formed with a drill and reamer, it is 
center drilling. 



FORMS OF TOOLS AND THEIR USES. 



DRILLING TOOLS. 
15. Classen of Drills. — The drill, which is one of 
most largely used tools found in a machine shop, is made 
a number of forms, which may be classified under the t 
heads/,)/ drills and twist drills. 

10. Common Characteristics. — These differei 
forms have three essential characteristics that are common 
to all. First, there must be one or more cutting edges that 
separate the small particles of material from the body eith« 
by scraping or cutting. Second, there must be a cent 
leading point about which the cutting edges revolve 
which guides the drill through the material. This is 
tained by tapering the cutting edges toward the cen 



f JO 



DRILLING AND BORING. 



as shown in Fig. 7. The angle a of this taper vanes for 
d/lFerent classes of work, but for ordinary drilling it is 
made between 60° and 60°. The Morse Twist 
Drill Company recommends 59°, while Wra. 
Sellers & Co. recommend 62°. Third, there 
must be a clearance back of the cutting edge. 
Fig. 8 represents the point of a flat drill, in 
which b is the clearance angle, sometimes 
called the angle of relief. This angle should 




-=* 



be large enough so that the stock back of the cutting edge 
witt clear at all times. 

17. Early Form of Drill. — The earliest form of ma- 
chine-shop drill consisted of a flat piece of steel drawn down 



nn 



<j y 




"**■ at one end, as shown in Fig. 9, and ground to the desired 
shape. This class of drill is still largely used in various 
fonas and is known as the flat drill. 



DRILLING AND BORING. 



i used in the 



18. Double Scraping BiIkc- The form i 
bow drill is shaped as shown in Fig. 10. The edges arc 
beveled on both sides, thus permitting the drill to be rotated 
in either direction while both edges cut equally well. This 
form is still used by watchmakers for drilling small holes 
with a drill that runs backwards and forwards alternately. 
One great objection to this drill lies in the shape of the 
tint; edges and the corners at the outer end of the eultir; 
edges. The metal is removed by scraping rather than t 
cutting, and a heavy pressure is r«q 
make it work satisfactorily. These condition! 
wear the scraping edges so i hat frequent Brio 

j is necessary, and every time 
ground, the width serosa the flat, part i; 
duced, thus reducing the diameter of the 

will drill. This difficulty may be overcom 
by making the sides parallel for a short i 
"^^" tailce above the outer corners, as shown 

Fl °" Fig. 11. The parallel sides also form guidi 
for the drill, thus insuring a straighter and better hole. 



19. Single Cutting Bdee. — Another form of dri 
that may be revolved in either direction is shown in Fig. 12. 
It is made from a round bar by grinding 
one end to a cone of the required taper 
and grinding away one side to the center 
line, as shown. This drill has the disadvan- 
tage of cutting on only one edge at a time, 
but the angle of the edge is such thai it 
cuts more freely than the scraping edges. 
The parallel sides guide the dril 
accurately and a fairly straight and round 
hole of the same diameter is formed, no 
matter how often the drill may be ground. 
These two types of drills, however, are F|C '*- 

seldom used in the modern machine shop, as other i 
that will cut when revolving in only one direction have t 
found more efficient. 



Innvn i 



$10 



DRILLING AND BORING. 
MACHINE-SHOP DRILLS. 



FLAT DRILLS. 

20. Form of Drill Point. — The simplest and most 

cheaply made machine-shop drill is the ordinary flat drill 
shown in Fig. 13. When rightly formed, 

i type of drill does very excellent 
work. It is, however, a hand-made tool 
and is often so poorly formed and so 
imperfectly ground that its work is not 
satisfactory. 

11 order that a drill may cut equally 
on both sides and form a smooth, round 
hole, the point must be in the center, 
the cutting edges must make equal 
angles with the center line, and must be 
of the same length and have equal 
clearance angles. 

21. Results of Improperly 
Formed Drills. — All these require- 
ments must be carefully observed. It 
is not sufficient to have the point in the 
center of the drill, because different 
angles of the cutting edges will cause the 
drill to cut 011 one side only, as shown in fig- i». 

Fig. H(«), thus throwing twice the intended depth of cut 
upon the one cutting edge. It also causes a crowding 
against one side, and a tendency to throw the center of the 
drill out of its correct position. The angles which the cut- 
ting edges make with the center line may be equal, but if 
the lengths of the cutting edges are not equal, it will result 
in the condition shown in Fig. 14 (t>). The hole will be 
larger than the drill, and the outer end of the long side of 
the cutting edge must do double duty, which soon dulls it, 
causes crowding, and makes a rough hole. 

When both the angles with the center line and the lengths 
of the cutting edges are unequal, the hole will be larger 




than ihe OHM, ami the effect will be an shown iii 1 

AH the work will be done by the short side ami I 

end of the long side. Unequal clearance angles will cause 

one side to cut more freely than the other, thus distribute 

the work unequally. Under a given pressure, the side wil 



"T 



tei 



the greater clearance angle tends to take a deeper cut 1 
the other, while there is less metal to support its i.ulliii 
edge. This edge wears away more rapidly than the othei 
resulting in unsatisfactory working conditions. 

22. Symmetrical dm Inn ICnd. — The culling ende) 
a ifrili must In- symmetrical in every respect in order tod 
accurate work. It should also be as thin at the point as thi 
material to be drilled and the i 
of the drill will pi i 
ful examination of flat-drill pole 
will show that the catl 
ab&n&cd. Fig. 16, stand oft' 
site sides of the center tine \ 
J f L ,, 9 the clearance angles are equal, t 

^^W.r^^ two planes representing the clej 
jnff i,-i ance 

b J perpendicular to the axis of t 
dull 



23. \dvautages of Thin Point. — It will readily be 
seen that the cutting edges extend only to b and </, and 
between these two points the edge has equal dean 

both sides, producing an edge resembling that of a cold chisel. 
When rotated, it is simply a scraping edge, and the pressor* 
required to force it throngh the metal at the rate at which the 
drill should cut is very great compared with the pr«. sa 
ijuired upon the cutting edges proper. This scraping edge 
also wears away very quickly, which necessitates additional 
pressure. It becomes evident, then, that, in order to do the 
work with the least loss of power, the scraping edge b J 
must be made as short as possible. This is accomplished 
when the point is made very thin. 

On the other hand, when it is made too thin, the cutting 
edges are not supported sufficiently well, and break away, 
making frequent dressing and grinding necessary. No 
definite rule for the thickness of the point can be given, 
since it depends largely on the grade of steel used in the 
tool and the quality of the material to he drilled. Experi- 
ence and care in observing the action of the drill and tht 
working conditions alone will enable one to determine the 
correct thickness. 

24. Grooved Drill Point. — Sometimes grooves are 
formed in the end of the drill, as shown in Pig. 16, thus 
providing curved cutting edges, which, 
when properly shaped, remove almost 
entirely the scraping edges. This prac- 
tice, however, tends to weaken the inner 
ends "f the cutting edges by removing 
the supporting metal, and it is generally 
thought to be better simply to make the 
end of the drill as thin as practicable. 




25. Parallel Sides.— Flat drills, to ! * 3 

give the best results, should have the pm ' '*■ 

sides a b, Fig. 17 [a), parallel, \ inch or more above the 
cutting edges This parallel portion should be rounded to 
fit the circumference of the hole. Drills are often used 



DRILLING AND BORING. 




with the corners projecting beyond the body, as shown in 
Fig. IT (A), and with the 
sides beveled, as shown in 
Fig. 17 (<"). Drills formed 
in this way make ragged 
holes, and when there are 
soft or hard spots or blow 
holes in the material 
drilled, they run off to one 
side, making holes that 
are neither straight, 
round, nor smooth. The 
simple precaution of ma- 
king the sides parallel for a 
short distance and round- 
ing the edges to fit the 
desired hole, as shown in 
p '° "■ Fig. 17 (a), will, when 

the point is rightly formed, obviate this difficulty almost 

entirely. 

26. Drill Shank. — The portion of the drill between 
the flattened part and the upper end is called the shank. 
It should be somewhat smaller than the hole, in order 1 
work freely in it. In the case of comparatively shallow holes, 
the flat part should extend to a point high enough so that 
the cuttings or chips can work out. The shank should 
round. The corners of any angular section draw the chips 
under them and clog the drill. Even with a round shank 
and a perfectly formed drill, there will be more c 
clogging in a deep hole, and it is often necessary to back out 
the drill and remove the cuttings. 

27. Lipped Drills. — In the kind of drill just con- 
sidered, the front of the cutting edge is either perpendicu- 
lar to the direction of travel, as shown in Fig. 18 (a), or, if 
the drill is tapered toward the point, it may have a slight 
negative front rake, as shown in Fig. 18 (£). In order to 
gain the advantage of a better cutting edge, a groove is 



I to 



DRILLING AND BORING. 



l:i 



sometimes ground above the cutting edge, as shown in 
Fig. 19 (<j). A section through c d is shown in Fig. 19 {(>). 

The same end may be ac- 
complished by dressing the 
drill with the cutting edge 
lipped, as shown in Fig. 19 (c). 
Fig. 1!) (i/) shows a section 
through e f. In both of these 
iscs, care must be taken to F,a - ]8 - 

ave enough metal back of the cutting edge to withstand 
he cutting strain. 





28. Twisted Flat Drills.— One disadvantage in these 

trills is that grinding reduces the lip, and necessitates fre- 
quent dressing. This objection may be overcome by twist- 
ng the end of the drill into a spiral, as shown in Fig. 19 (/). 
this way, the same angles of the cutting edges may be 
obtained, while the shape is not altered by grinding, until 
he entire spiral is ground away. The spiral also assists in 
irrying the cuttings away from the drill point. 



TWIST DRILLS, 

29. Commercial Twist Drills. — The fact that a 
>iral drill requires no dressing and removes its cuttings 
las led to an almost universal use of the twist drill, 
■ the commercial spiral drill is called. Fig. 20 (a) 



DRILLING AND BORING. 

illustrates an ordinary commercial drill of this type. 

is made from round stock, the spiral flutes being cut with 
a milling Cutter. The surface between 
the flutes is backed off slightly from near 
the cutting edges a, a. Fig. 31 (*), to the 
backs b, b of the other flutes, leaving on!) 
narrow strips a c the full diameter of the 
drill. This is done to reduce th. 
surface on the side of the hole, lritfJ< 
enough surface is left to form a perfect 
guide, owing to the fact that the bear- 
ing ac runs in a spiral around the 

In some drills a narrow bearing strip 
is left, as shown in Fig. 20 (/>), the clear- 
ance being cut away, concentric with tbi 




Fig.W. Fio. n. 

bearing surface, as illustrated in Fig. 21 (b). Twist drills 
are manufactured in such a large variety of sizes, are found 
so efficient, and can be bought at such a small cost that 
they are rarely made in the tool room. 

30. Precautions In Grinding. — The irregularities 
that arise from imperfect grinding, which have been men- 
tioned in connection with the treatment of the cutting 
edges of flat drills, are applicable to the twist drill as well. 
The dangers suggested are, however, almost entirely over- 
come by the use of special grinding machines. 



STRAIGHT-FLUTED DRILLS. 

31. A Htruitciit-fiutcd drill lias been found 
viceable for drilling thin plates and brass. With a t 
drill there is a tendency to plunge forwards as the dril' 



DRILLING AND ItORING. 



comes through the plate. This is overcome by having a 
lri!l formed like the twist drill, but with straight 
nstcad of spiral flutes, as shown in Fig. 22. 



r key- 



I 



SLOT *NP TEAT DRILLS. 

32. Forms of Slot Drills.— In drillin 
chines where a feed perpendicular to the i 
line of the spindle may be secured, slot, 
way, drills are often used. These are made in a 
number of different forms. In Fig. 23, (a), (/>), 
({"), and [d ) show four different kinds, all of which 
are quite satisfactory in metal of uniform hardness. 

133. Advantages of Some Forma. — In 
sinking these drills into the metal, holes are 
formed as shown in Fig. 23 (*■), (/), (,i?), and (//). 
The central cores in Fig. 23 (c) and {/) form 
guides for the drill, which, in metal of varying 
hardness, have been found of great advantage. 

Blot drills are used largely in forming keyways, 
or slots, in shafts. They are sunk into the metal F,0 * 5a - 
a sufficient depth for a longitudinal cut and are then fed 



B* 



/Mi 



ir^ 



1 U 




ngthwise along the shaft, thus cutting 
Tib— a* 



h; 



DRILLING AND BORING. 



I ' 



this depth throughout the entire length of the slot. The 
drill is then lowered enough to furnish another longitudinal 
cut and the operation is repeated until the required titpti 
is obtained. 

34. Tent Drills.— The drills shown in Fig. 23 {<-) 
and (</) may be nsud in squaring the bottoms i 

made by an ordinary twist 

I l^| to be planed or chipped. The 

I teat drill, shown in Fig. 24, is 

1 I I ■ used for this same purpose, 

\ I / \ '""■ ,na y ** e ,,set ' *" r ''""'"s 

\ ■ / \ the entire depth of the hole* 

\J / ' \ required. The teat « is 

I ground to a point, being u- 

W , i __J pered in l>oth dir« i 

* a acts as a guiding point for the 

■"•* drill. The cutting ft 

of the same form as those shown in Pig. 23 (tr) and (</). 



AKNVLAR CUTTERS. 

35. Single Tool. — An annular cutter that is used 
very generally for removing large bodies of metal . 
ting large holes in boiler plates, rod ends, etc. is shown ii 



C3 



ised 




§10 



DRILLING AND BORING. 



17 



Fig. 25. The tool a is practically a cutting-off tool, with 
the proper side rake to clear the circular sides of the hole. 
A holer is first drilled for the guide pin b y after which the 
stock around the hole c is removed as a washer with a hole 
in the center. 

36, Double Tool. — Sometimes two tools are used, one 
on each side of the center, as shown in Fig. 26. This bal- 
ances the side thrust upon the center pin b and reduces it to 
a minimum, besides doubling the capacity of the tool. 

37. Spring: Center. — In light work, such as cutting 
holes in boiler plates, the necessity of drilling the center 
hole may be avoided by 
using a tool like the one 
shown in Fig. 27. The 
center pin rests in a 
punch mark, thus form- 
m g a guide for starting 
tta cutting tools, while 
a spring that acts upon 
the end of the pin per- 
m its it to recede as the 
tool travels through the 
Plate. This device op- 
crates very nicely in 

comparatively small FlG ' *' 

holes in light plates, but for large holes or very heavy stock 

a solid center pin, running in a drilled hole, is necessary. 







DRILL SHANKS. 

38. Straight Shank. — On ordinary flat drills, the 
shanks shown in Fig. 28 (a) and (6) are most commonly used. 
* n Pig. 28 (a) the shank is straight and slightly flattened 
a * a in order to furnish a good bearing for the setscrew. 
The end of the screw often cuts a burr at the bearing point, 
w hich prevents the easy removal of the drill, and to avoid 
this the shank may be turned down slightly at the bearing 



DRILLING AND BORING. § w 

point of the screw, as shown at a. Fig. 28 (6). The shoulder 
also prevents the tool from dropping out of the socket when 
the screw becomes slightly loose. 




39. Taper Shank. — Fig. 28 (f) and (/) shows t 
shank tapered. The taper is so made that it will hold the 
drill from dropping out of the socket, while the flat end, or 
tang, at the top, which fits into the hole in the socket, pre- 
vents the drill from turning in the socket. There are sev- 
eral tapers used by different makers of drills. The Morse 
Twist Drill Company uses a taper of about g inch to the 
foot. Some makers have a key inserted in the socket to 
assist the tang in preventing the drill from turning. This 
calls for a corresponding keyway in the drill as shown 
a. Fig. 28 ((/). 



LUBRICATION OF DRILLS. 

40. Requirements. — Cast iron and brass are drill* 
rithout lubricating the drill point; in fact, in cast in 
ir icant causes the fine cuttings tu cake and choke I 



DRILLING AND BORING. 

drill. Tn drilling: wrought iron and steel, on the other hand, 
the drill point should be thoroughly lubricated. 

41. Application of Lubricants. — The lubricant is 
usually applied by dropping it into the hole and permitting 
it to run down along the sides of the hole and the drill. 
This method has been found rather unsatisfactory, as the 
cuttings, in working their way to the surface, tend to 
carry the lubricant up, and in some cases 
very little, if any, reaches the drill point 
where it is most needed. 

Fig. 29 (a) shows a very simple method 
by means of which better lubricating con- 
ditions are obtained. Two spiral grooves 
a, a are cut parallel with the flutes b, b, 
thus forming separate channels for the 
lubricant There is some danger of these 
grooves becoming clogged by fine par- 
ticles that work around the drill, and 
small brass tubes are brazed into the 
grooves as shown, in order U> insure an 
unobstructed flow. Fig. 20 {{>) shows a 
drill with holes running through the solid 
metal. 

42- Provision fur Supplying I.u- 
orlcants.— The lubricants may be carried 
to the holes in the drill through the chuck 
or through a small attachment placed just (a - 

he chuck. Fig. 30 illustrates an 
attachment that is frequently used. A collar a 



\.i 




le lower end of the drill socket, 



, and is kept from 



20 DRILLING AND BORING. § H 

revolving with the spindle by means of a pipe that res 
against the column of the machine and through which th 
oil is conveyed to the collar. Inside of the collar, an< 
immediately over a pair of holes in the socket that corn 
spond to the upper holes in the drill, a circular groove b 
turned, thus forming a connection between the outer pipe 
and the drill. The oil is supplied by means of an oil pum 
under sufficient pressure to insure a steady flow to the dri 
point, and is carried to the attachment by means of a fle 
ible tube. 



REAMERS. 

43. Purpose of Reamers. — Drilled holes are rarely 
formed perfectly round or straight, and with each grinding 
of the drill, especially when the grinding is done by hand, 
the diameter is liable to vary slightly. It is therefore 
necessary, in work where accuracy is required, to true the 
hole. This is done by passing a tool called a reamer 
through it. 

44. Flat Reamers. — Reamers are made in various 
forms. The simplest of these consists of a flat piece of 
steel turned accurately to the diameter of the hole, with 
the cutting edges shaped much like those of the ordinary 

twist drill, but with a greater 




i 



Fig. 31. 



angle between the cutting 
edges. Fig. 31 illustrates 
this type. It is used fre- 
quently because of its cheap- 
ness, but despite its cheap- 
ness it is not an economical 

tool, as it does not produce a hole of sufficient accuracy for 

the better grades of machine work. 

45. Fluted Reamers. — A better type of reamer is 
shown in Fig. 32. It consists of a piece of round steel with 
flutes cut lengthwise. For the general run of work, the 




DRILLING AND BORIXG. 



mes are so shaped that the catting faces lie in radial planes, 
s shown in Fig 33 (a). 



46. t'ndercut Faces. — Fluted reamers are sometimes 
made with the cutting faces cat under, as shown in 7 
This is not right, as the slightest spring causes the cutting 
edges to run more deeply into the metal, resulting in an in- 
jured or enlarged hole, and sometimes in a broken reamer. 




47. Curved Cutting Facen. — Reamers with curved 
cutting faces n, f>, illustrated in Fig. 33 (f). are object ion - 

ble, as they have a negative front rake that is increased by 
Tinding. 

48. Brass Reamer. — Fig. 33 {d) illustrates a reamer 

] fur brass when a sufficiently large amount of 
to he done \n warrant the expense of a special 
Tilt- faces, in sizes of about \ inch to 1 inch in 
diameter, are set forwards from the radial line about ,' r 
inch, and are made parallel to it, thus giving a negative front 
rake. For larger sizes, the faces are set forwards a corre- 
sponding amount. 

4i>. Number of Cutting Edges. — A reamer should 

always have enough cutting edges to gaide itself in a straight 

ugh the hole. There should never be I 

' where the diameter is large enough to make it 

practicable there should be more. The number ut edges 



22 DRILLING AND BORING. 

should be even and not odd, as this makes it possible to 
caliper the reamer. 

SO. Hounded or Tapered End*. — The ends of the 
cutting edges should be rounded slightly, as shown at a, 
Fig. 34. This creates a tendency for the reamer 
to keep working toward the center of the hole. 
This same advantage is secured by making the 
lower end with a slight taper, J inch or more 
long, as shown at a b. Pig. 35. 



am- 
the 



51 . Depth of Cut. — In all classes of re; 
ing, the holes should be drilled as nearly to 
finished size as possible, so that the reamer need 
take only a light finishing cut. This preserves 
the edges, avoids frequent grinding, and length- 
ens the life of the reamer. An allowance of 
,' ( inch of stock is sufficient for the reamer in 
holes having a diameter of 1 inch or less, while 
in holes having diameters between 1 and 2 inches, 

3^ jnch is enough. For sizes above 2 inches in diameter it is 
sidered best to finish the hole with a boring bar 

and cutter, except in cases where the hole passes through 



two adjoining parts. In such cases, a long reamer may he 
used for finishing. Holes above 3 inches arc sometimes 
finished with large shell reamers. 



TAPER »i vMius 

52. Soltd Taper Reamers. — Tapered holes for 
dowel pins and various other purposes have brought taper 
rcamcrtt into very general use. They are fluted and made 



DRILLING AND BORING. 



ke a straight reamer, except that the sides are tapered. 
. 36 (a) illustrates a reamer of this type. 



jKHMsmrm 



53. Heavy Duty of Taper Reamer.— The duty of a 

:r reamer is heavier than that of a straight reamer, 
ince it must remove a larger body of metal. The drilled 
ilc if straight and must he a little smaller than the small 
id of the reamed hole. The amount of metal that must 
: removed is represented by the part acb in Fig. 37, and 
spends on the taper required. 

54. Roughing Reamer. — Where the taper is great, 
roughing reamer, Fig. 36 {b), is first used to remove 

:e excess of metal. This is followed by a finishing reamer, 




ig. 30 (a), which should take only a very light finishing cut. 
i some shops, it is customary to relieve the reamer in 
:avy work by counterboring steps, as shown in Fig, 38. 
riis is a rather dangerous proceeding, as the cutting edges 



DRILLING AND BORING. g 10 

of the reamer are liable to be injured. It is also a great 
waste of time. By the use of the step reamer shown in 
Fig. 39, the metal can 
■ be removed more easily 
| and rapidly than with 
drill. The small 
F|G w end a of this reamer 

is made the size of the drilled hole. The edges b, e, ti, and c 
are the lower ends of the steps and form the cutting edges. 
The diameters are made from y^ inch to -^^ inch less at 
the top of each step than at the bottom, to provide for 
clearance and to insure the free operation of the tool. There 
is also clearance on the bottom, as shown at f, g. This 
reamer should be followed by the roughing reamer shown in 
Fig. 36 (b) to remove the steps and the coarse tool marks, 
and to enlarge the hole so that it can be finished with the 
reamer shown in Fig. 36 (a). In holes of very slight taper, 
the roughing reamer is not generally used, but even here, 
when a large number of holes are to be reamed, it is advis- 
able to use it, as it preserves the cutting edges and the 
accuracy of the finishing reamer. 

55. Care of Reamers. — The most serious difficulty 
met with in reaming is the maintenance of the full diameter 
of the cutting edges, and in order to keep them in good 
condition as long as possible, the greatest care should be 
taken in their use. This is especially necessary with fin- 
ishing reamers, which may be rendered useless by a very 
little wear or a slight injury. Reamers should never be 
pounded or jerked sidewise when in a hole, and when not in 
use, they should always be kept on wooden shelves, or on :i 
wooden board, or other support, if at the machine. 

56. Inserted Blades. — A form of reamer that is 
gradually growing in favor is illustrated in Fig. 40. The 
cutters, which are made of steel, are dovetailed into a solid 
body. In reamers of 5 or 6 inches diameter, the body is 
sometimes made of cast iron. The special advantage of this 
form lies in the ease with which an injured blade may 



: renewed. In the solid rraraer, a cracked or broken cut* 
a g edge, <*r any slight warping, throws the whole reamer 
it of use. In this form, the injured part is simply driven 
it of the dovetail, a new one is inserted, and the reamer if 



good as when it was new. This is especially advan- 
tageous in the larger sizes, which are very expensive. 

Inserted blades are, however, not practicable in the 
■ sices, as there is not stock enough to support the 
blades properly. Opinion as to the minimum siie in which 
they can safely be used varies; ordinarily, they are not used 
in reamers less than 1 i inches in diameter. 



10 



DRILLING AND BORING. 



ADJUSTABLE REAUEBS, 

57. Advantages of Adjustable Reamers. — When 
solid reamers are used, it is customary to make the diameter 

s much larger than the desired diameter as the limit of 
error in the working fit will permit, and to use it until the 
diameter has been reduced to the inside limit of error, after 
which it must be worked over or discarded. For the best 
grades of machine work, where the permissible variation is 
reduced to a minimum, the life of such a reamei 
short. 

58. A Simple Adjustable Reamer. — For this rcttOn, 
reamers with adjustable cutting edges have been found 



much more satisfactory than the solid type. Fig. 41 shows 
one type of adjustable reamer. The reamer [s ■ 



36 DRILLING AND BORING. 

to the desired size by means of a ground tapered plug t 
acts upon the blades <?, and is locked by the lockout 6 t 
t lie adjustment has been made. With this type, 
amount of wear or the reduction of dhutti 
ing can readily be taken up. 

59. Adjustable Reamer for Different Sit 

Hole*. — An adjustable reamer that can 

accurately adjusted may take the place of a number of s 

reamers. Fig. i'i (a) and (l') shows a reamer espc d 

for this purpose. The blades a are held in the body b b 







3? 




dovetails in which the blades lit on the sides and bottoi 
The part of the body of the reamer thai forms the I 
ol the dovetails slnpes toward the eentci 
deeper nearest the nut. Then as the blade! 
toward the shank they are forced "in and the dial 
the reamer is enlarged. A collars, which lit, into notches 
in the blades, determines their posi the diam- 

eter of the reamer. By having diffcrenl sets of blades, am 
collars of different lengths, such a reamer may be used for 
number of sizes and will do fairly accurate work. Fig. \% [1 
shows a section through ./. of Fig. 1.' [a). For cxtrt 
accuracy the solid reamer is best Sometimes xdjui 
reamers are so arranged that forcing the blades toward t 
point expands them, the nut being placed back of the blade; 

60. Expansion Reamer.— Another aljn-i 
of reamer, known as the expansion reamer, is shown il 
Fit;. 43. The reamer is drilled fur a taper plug in 
lower end, and the sides are slotted, as shown. The | 



1 10 DRILLING AND BORING. 27 

is threaded, and, when screwed into the end of the reamer, 
expands it. Reamers of this kind are made as small as 
i inch in diameter, while the reamer illustrated in Fig. -11 
is not made smaller than J inch. The adjustment also 
is very easily made, and, by taking a number of cuts, a 
large amount of metal may be removed. The hole is not, 
however, very accurate. The expanding plug enlarges the 



middle of the reamer most, and the cutting edges taper 
toward the ends, resulting in curved cutting edges with- 
out a straight portion to guide them. Any unevenness 
in the structure of the metal causes the reamer to run 
out of its true course. Where accuracy is essential, this 
kind of reamer should never be used for the finishing cut, 
but should be followed by a finishing reamer. 



SHELL AM) ROSB RRAMERS. 

61. Fig. 44 (<j) shows an ordinary shell reamer, and 
Fig. 44 (o) a rose shell reamer. Both of these have 
already been described in Art. 31, Lathe Work, Part 2. 




They are sometimes fitted to shanks, which in turn fit drill 
sockets, and are used in drilling machines. The rose reamer 
s especially well adapted to removing a large amount of 



DRILLING AND BORING. 



Ilfl 



metal in this way, but usually does not leave the hole 
smooth, and should therefore be followed by a finishing 
reamer. 

The rose reamer shown in Fig. 44 (b) has a flute for every 
second cutting edge. Many persons prefer to have a flute 
for each cutting edge, claiming that it adds to the efficiency 
of the reamer. Rose reamers are therefore often made this 
way. If the rose reamer is used for horizontal work, as 
in a horizontal drill or lathe, the chips will clog in the short 
flutes; hence, each cutting edge should have a flute. 



COUNTERSINK. 

62. Definition. — It is frequently necessary to enlarge 
the end of a drilled hole to take the taper head of a bolt or 
other machine part, as shown in Fig. 3 (u). This operation 
is known as countersinking. 

63. Drill as a Countersink. — The tools used in 
countersinking resemble very closely the various forms of 
drills. In some shops and for some classes of work, the 
point of a drill is simply ground to the desired taper. 
When the cutting edges are properly formed, the metal 
uniform, and the surface smooth, very good results are 
obtained in this way, but for general use it is better to 
have a countersink that is guided by a center pin. 

64. Pin Countersink. — A flat countersink provided 
with a pin a, which fits the hole and holds the tool perfectly 
central under all conditions, is illustrated in Fig. 45. This 
same style of tool is sometimes made with four cutting 
edges, as illustrated in Fig. 46. 

65. Pin and Collar Countersink. — Where a coun- 
tersink of the same taper is occasionally required in 
holes of different diameters, a tool as shown in Fig. 4? i 
found very serviceable. The pin a, instead of fitting the 






DRILLING AND BORING. 29 

ioIe, becomes the bearing of a set of collars c, which are 
urncd on the outside to fit the different holes in which 
he tool is to be used. The collars in this form of tool 




ire secured by a screw b anil washer </. The cutting edges 
nay be made of any type desired, but four edges, as shown 




the illustration, are perhaps the most desirable, there 
«ing enough cutting edges v, guide properly, while the 



80 DRILLING AND BORING. § lC^ 

construction is very simple. Turning the cutting edget^^ 
back, as shown, forms a bearing for the top of the collar andK 
facilitates the grinding. In some cases, collars are simply* - 
slipped over the pin of an ordinary countersink. 



66. Combined Reamer and Countersink. — I 

plate work, reaming and countersinking may be done at the 
same time with the combination tool shown in Fig. 48. The 
lower end a is made like an ordinary fluted reamer, while 
the countersink h is formed with four cutting edges grouni 
to the desired angle. 



67. Center Countersinks. — Milled and half-round 

countersinks, as shown in Kig. 49 (it), (/>), and {c), are used 
almost entirely in enlarging centers in lathe work, but these 
styles may be used for ordinary countersinking as well. 



-Im 
the 
The 
Mies 

unci 



COl 'STBHHORH. 



68. Ordinary Types. — Counterborlns consists 

enlarging a hole at one end so that the enlarged part has 
parallel sides and a flat bottom, as illus- 
trated in Fig. 3 (A). For small counter- 
bores, any of the pin countersinks already 
described, with the cutting faces ground 
at right angles to the center line, as in 
Fig. 50, are frequently used. 



. 




69. Double-End Cutter. — A bctt< 
counterbore, Fig. 51, is made from a 
bar of steel with a rectangular hole cut 
through it, into which a flat cutter a is 
inserted and held by means of a key &, 
The lower end of the bar is made to tit the 
hole without any play, while the length of 
tlit .utter represents the diameter of th« 
This cutter cms on both sides of the bar. 



= 



to 



DRILLING AND BORING. 



it project the same 






id great care must be taken to ha 
■lance on each side, and to 
tve the cutting edges ground 

i that both sides will take an 
|ual cut. 

7)1. Single-End Cutter. — 

his style of countering- is 
metimes made with the cutter 
rojecting on one side only. 
he latter tool is used very gen- 
ally in boring holes in horizon- 
l drilling and boring machines, 
d is usually called a bering bar 
d cutter. fig. si. 

7 1 . Milled End of Bar. — Sometimes the lower end of 
ic boring bar and of the pin on the pin counterbore is made 
ith the corners slightly rounded and serrated. This is 

pecially useful when the hole is drilled slightly under size 
r is not perfectly round, as it enables the boring bar to cut 
way enough metal to permit it to turn freely. 

72. Counterbore for Lijcbt Work. — A very useful 

ol for counterboring is illustrated in Fig. 52 (*/). A ci'rcu- 
ar hole a is drilled in the bar b, in which a circular piece of 
tool steel c is inserted and held in place by a pin d. The bar 
13 then put in a lathe and the ends of the tool c turned up to 
the desired diameter. The ends are backed off and the cut- 
ting edges ground as shown. The lower end of the bar is 
turned to the diameter of the hole below the counterbore, to 
form a guide for the tool. . 

This tool gives very good results when operated with care 
and on light cuts, but the cutter is not heavy enough to 
stand a very heavy strain. The breaking of the cutter is, 

iwever, not a serious matter, as it can be replaced with 

ry little loss of time and at small expense. 

Counterbore With Cliontfeiilile Tool. — This 
me style of cutter may be used with tliu device shown 




88 



DRILLING AND BORING. 



10 



in Fig. 53 (/>) without danger of breaking under ordinary 
usage. The bar b has a hole a drilled into it as in Fig. 52(<»). 
and immediately above this a slot c is formed. The tool ** 
is made with an angle on top, as shown, and a support c for 
the cutter is shaped to lit this angle and the slot c when tb«s 



-> 



•e::;: :3«*d& 




i 



tool stands in its proper position. A wedge/ holds the tool 
and its supporting piece rigidly in place, while the pin g 
prevents any end motion of the cutter. The piece e shoul 
run the entire length of the cutter, in order to furnish 
much support for the ends of the tool as possible. 

A set of cutters and supports of different lengths may be 
made for use in the same bar, thus providing counterbores 
of a number of sizes at a very small cost, A set of collars 
for the bar end that will fit various holes will render this tool 
available for a large range of work. 

74. Special Counter bore. — Another tool that 
sometimes used in counterboring, and is available for a brc 
range of work, is shown in Fig. 53. The body a has grooves h 
running lengthwise, into which blades c, with side projec- 
tions d, are fitted. The blades are held in place longitudi- 
nally by the hooked ends c, which fit a corresponding gn » >vc 
in the nut/. An opening g at the end of the nut permits 
the blades to enter when the nut is turned to the rig 




DRILLING AND BORING. 



33 



iition. When the blades are ali in place, they are moved 
the right location on the body by screwing up the nut/", 
i are locked in place by the locknut h. 

'.t will be seen that by making sets of blades of different 
;s and providing center pins i of corresponding sizes, a 
of counterbores covering a wide range of work may be 
>vided. While this tool is more expensive than the one 




>wn in Fig. 53 (£), it has the advantage of being available 
or smaller holes, since the size of the center pin may be 
made miidi smaller. This tool will therefore cover a broader 
r:tnye of work, and, when once constructed, can be used 
until the greater part of the blades is worn away, thus 
avoiding the expense of frequent renewals. 



SPOT FACING. 

75. Definition. — A very common drilling-machine 
operation is the facing of spots about drilled holes, to form 
smooth surfaces for the heads or nuts of bolts or other ma- 
chine parts, When the faced area is quite small and the 
facing is done with a rotating cutter, the operation is called 
a pot facing. 

76. Fonnn of Cutters.— The cutters are the same as 
those used for counterboring, and the only difference in the 



94 



DRILLING AND BORING. 



in 




operation lies in the depth of the cut. A counterbore mai 
be of any depth, but the spot facing is only carried deep 
enough to form a smooth bearing surface. The bar with 
inserted cutter is especially well adapted to spot facing 
flanges of cylinders, cast-iron pipe flanges, etc. 

77. Spot Facing Lower Side of Flange. — Fig. 54 
shows a piece of pipe on which the flanges must be Spot 
faced on 

side. The flange) 
arc drilled in tb 
ordinary way, after 

which the drill ii 
removed from the 
socket and the cut- 
ter bar put in it* 
place. The cutter 
is then remoted 
from tin- bar. tin- 
F,0 ' M " ii.n pas 

the hole, and the cutter again put back ini 

bar with its cutting edges toward the flange. Thefacingu 

done by feeding the drill spindle bat : 



CENTER DRILLS. 

78. Although center drilling is essentially a drilling- 
machine operation, it is so closely a lathe wort 
lint it has been discussed under tli.n bead, 
of tools and their various uses arc found in An. 23| E >' 
Work, Part 1. 



TAPS. 

79. The forms of taps used in drilling machines re- 
semble those employed with the lathe. In holes that donot 
run through the material, taper and plug tape, Fig. SS, 

are required, the former to -start the thread and the Utter 



S 10 DRILLING AND BORING. 35 

to complete it to near the bottom. When a full thread 
roust be rim all tbe way to the bottom of the hole, the plug 
tap is followed by a bottoming tap, shown in Fig. 55. 
In the case of holes that pass through the material, the taper 




H 


himiMllllllllllMIMllllHI 


"*"■ 




H 


tllllllMIIIIHIIIIMlllllllllMI 




rt^WWlAAAAA, AAAAAAAAA 




H 


iHHiMiUMiimiiiiniHmmnni 


" W * 8 B »M lns 

FIG.M. 

tap alone may be used. In high-speed machines, such as 
pneumatic drills, a long taper tap gives the best results, on 
account of the fact that less material is removed by each 
. the work being distributed along the length of the tap, 
The shanks of taps that are to be employed in the drilling 
machine exclusively may be made to fit the spindle or a 
collet of the machine for which they are intended. When 
they are required for general use, special sockets are needed 
to receive the square shank of the tap. 

DEVICES FOR HOLDING TOOLS. 

SO. Straight Socket With Set screw. — Various 

devices for holding tools in drilling-machine spindles have 
been brought into use. One of the earliest of these — still 
found in some shops — consists of a hole drilled in the bot- 
tom of the spindle, with a setscrew holding the drill, as 
shown in Fig. 5G. This device has several disadvantages. 
The drill may press on one side of the screw and in a 



DRILLING AND BORING 






direction that tends to loosen it. To prevent this, the screw 
is jammed Upon llie drill, causing a burred shank that it it 
difficult to remove. When the shank 
does not fit the socket CUtac 
pressure of the screw on orn 
throws (lie drill off the ceQta . 
spindle and results in the crampin. 
of iiic drill and a poorly forirn I 
and often in an injured or hroken drill 




81. Taper Shank. — A very s; 

pie and efficient means of holding the 
drill, known as the Caper aliank, 
shown in Fig. 57. The drill spindle a is made aritfa a 
hole b at the lowei end. At the upper end, the hole is made 




flat on two sides to receive a tang or flattened 
the upper end of the drill shank. 
The taper that is in most common use for drill 



I in 



DRILLING AND BORING. 



B? 



known as the Morse taper and is about £ inch per foot. This 
aper is just great enough to hold the drill when put into 
place with a quick motion of the hand or under slight 
pressure, The drill shank must, of course, be made with 
EBCisely the same taper as that in the spindle, so that the 
ntirc surface will be in contact. The tang at the top of 
drill shank must also fit snugly, as it takes practically 
ill the torsional strain that comes upon the drill when 
cutting, the tapered surface taking only a very small part. 
The drill is removed by driving a taper key c into the slot d 
Ed ill-. 1 spindle. The slot tl is so located that the point of 
the key just passes over the end of the tang, but when the 
body of the key is driven in, it forces the drill out. 



82. Drill Sockets or Collets. 
not be made with the same size 
of shank; consequently, it is 
necessary to have a number of 
drill sockets or collets, 
Pig. 58 («) and (/■), to take the 
sizes of drills that do not fit 
iplndle. The upper end 
f the socket is made to fit the 
■ he next larger size 
while the lower end 
i made to fit the desired drill. 
Collets are also found very 
«rviceable where it is desir- 
hle to use a drill with one 
nd of shank in a spindle in- 
ended for another. Fig 58(c) 
i collet lor a taper- 
bank drill and a straight 
pindle. 



-All sizes of drills can- 



1 



83. Pin-Grip Socket. — A form of drill socket that 

he drill to be changed while the spindle is running 

s shown in Fig. 5'J. The shank of the socket a is made to 



H 



DRILLING AND BORING. 






fit the taper of the spindle b. A collet c is road.; to 

the shank of the drill ./. The body of the SOt 

. 1 1 = t straight to receive the collet, which is held in 

tWD pins (hat enter the groove/and are control! 

collar^. To remove the collet, the collar g is raised with 

one hand, while the drill is in motion, and the collet is re- 

moved with the other hand. 




Fig. CO shows a partial section of the socket. The collar/ 
is bored out to form an internal cam. When the coll 
its lowest position, it holds the pins A, h in, as shown, their 
points entering thegrooveyin the collet. When, 
to the position Vindicated by the dotted line*, the i 
k-al force tends to throw the pins out, thus relieving I 
collet. The ends of the pins arc tapered, so that theweJg 
of the collet or drill will assist in moving them out when t 



(10 



DRILLING AND BORING. 



:he centrifugal 



machine is running at a slow speed and the < 
force alone is not sufficient. The collar is brought back by 
its own weight when relieved by the band. The collet c is 
made with a tang./, which stands between the two pins k, k, 
thus causing it to rotate with the spindle. 

84. K«y-Grlp Socktst.— In very heavy work, the tang 
sometimes yields to the torsional strain and is twisted. 
Pig. HI illustrates a device that grips the body of the shank 
as well as the end. The illustration shows the grip socket 




^"ispart cut away, thus exposing all the working parts. 
The shank and tang are of the ordinary taper type. A key- 
**£« is cut into the shank of the drill with a circular cut- 
making the bottom the arc of a circle. The key b, 
wi| ich (its the bottom of the keyway and also a slot in the 
•octet, is held in place by a collar c, which is bored eccen- 
trical^ and which, when in the position shown, causes the 
"<7 to grip the shank with a tendency to keep it from work- 

.-. rll as preventing it from 
turning in the socket. To remove 
™ drill, the collar is turned to a 
P° s >tion where the key is free to 
'""ve om Of the drill shank, and the 
,r| H is driven out in the usual way. 
Ihis device can be used with any of 
^ standard taper-shank drills by 
* lm Ply milling in the keyway. 

&S. Light Drill Chuck.— Sep- 

* ra k chucks that grip the drill on 
l *° «r more sides are found very 




II) 



DRILLING AND BORING. 



{10 



satisfactory for the lighter grades of work, and a large 
number of different kinds have been made. Fig. 63 repre- 
sents a type that is largely used for small drills. The bodr 
of the chuck a is attached to the drill spindle either by 
means of a screw or a taper shank, as dew ril 
three holes b converging toward the center line, as shown, 
are three jaws d, which, when forced forwards by tk- 
nut c, close in upon the drill shank and grip it firmly. The 
jaws are so formed that the parts that grip the drill art 
|dw*ys parallel and therefore grip vatious slz<;s equally *el 
The nut is held in and turned with the collar f, which b 
Burled on the outside to furnish a better grip for the hand 

8tt. Heavy Drill Chuck.— Another form 

that has given excellent satisfactipn and it used for heavier 
work than the one just described, is shown in Fig. 63. The 
body of the chuck has a 
slot a cut across the lower 
end, in which two jaws b,i 
are free tn move toward 
and away from the center. 
These jaws are controlled 
by means of a screw e, one 
end of which has a right- 
hand thread and engages 
with the thread on one jaw, 
while the other end has a 
left-hand 

gages with the other jaw. 
The jaws are so guided that 
the faces are always parallel, and drills of any diameter that 
will enter the chuck are gripped equally well. A hole in the 
plate t\ which is screwed to the bottom of the body, is large 
enough to take only the largest diameter of drill for which 
the chuck is designed. A plate / immediately above the 
jaws contains a slot g made to fit the tang on the upper end 
of the drill shank, thus preventing the drill from slipping it 
the chuck. 




DRILLING AND BORING. 



87. Safety Drilling and Tapping Device.— A very 
efficient safety device for drilling ami tapping is illustrated 
!n Fig. 64. A shank «, which 
is tapered to fit the spindle 
with which it is to be used, 
has upon its lower end an 
enlarged part that is threaded 
on the outside and bored out 
to form a friction seat for a 
socket b. A cap c, which has 
internal thread to fit the 
external thread on a, clamps b 

■etween itself and a, form- 
another friction surface 

between b and c. Two fiber 
washers </and e are placed be- 
tween a and b and b and c, 

ispectively. The cap e is 
tightened on the washers until 
the friction obtained is suffi- 
cient lo drive the drill or tap, 

nd is held in adjustment by 

, , , , , FIG. M. 

he check-nut //. 

Two spanner wrenches are required to make the adjust- 

Drill and tap sockets that fit the required drills or 

aps are made to fit the socket b and are kept from dropping 

out by the catch pin /, which enters the grooves in and « in 

s drill and tap sockets, and is held in place by a spring 

.uid retaining screw. The sockets are driven by means of 

two feathers. The tap shank is made about tJj inch smaller 

in diameter than the tap socket/", thus allowing the tap to 

own feed without injury to the thread, and to 

enter itself with the hole without binding, while a catch 

pin o, held in place by a flat spring, engages with a groove 

tap .mil keeps it from dropping out until a force 

greater than its own weight is applied. A specimen of 

he taps used, marked i, shows how the shank is con- 

■ucted,/ being the groove for the catch pin. The drill 




42 DRILLING AND BORING. {1 

sockets £; which are made in various sizes to take different 
sized drills, have a standard taper and a slot/ at the upper 
end to receive the tang. 

88. Automatic Reverse Tapplna Chucks. — Where 
a large amount of tapping is done, much time may be saved 
by the use of a device that will reverse the tap and back 
it out, either when the tap bottoms or sticks, or when it 
has run the required depth. Several such devices are on 
the market and many of thera give very good results. In 
one class, the mechanism is so designed that the tap travels 
with the spindle while running forwards, but as soon as it 
meets with more than a certain amount of resistance, a 
reversing gear, or set of gears, is thrown into action and 
the tap is backed out at an increased speed. In another 
class, the tap is also reversed and backed out when it has 
run a stated depth. Such a device, it will be seen, is a safety 
provision as well as a means of saving a targe amount of time. 



SECURING WORK ON THE TABLE OF THE 
SIMPLE DRILLING MACHINE. 

89. Securing the work properly on the table of a drill- 
ing machine is one of the important parts of drilling. A 
piece that is not properly set or not well secured will not 
be well drilled, although all other conditions may be perfect. 

(M>. The Table. — The table of the ordinary drill 
press should furnish a perfectly plane surface standing at 
right angles to the center line of the spindle. It should 
also be provided either with holes through which bolts 
may be passed or radial slots for T-headed bolts, so tl 
work may be clamped rigidly upon it. 

01. Securing the Work. — A plain piece of work, 
which the holes are to be drilled at right angles to a plane 
upon which the piece may rest, may be secured very simply 
in the following manner: The piece n. Fig. C5, which is to 
be drilled, is laid upon the table b, with two parallel pi< 
of iron c, c under it to raise it far enough from the 









(10 



DRILLING AND BORING. 



43 



:rges from the 




prevent injuring the latter when the drill e 

piece. Two clamps 

d, d are then placed 

*ilh one end upon the 

pitce over the paral- 
lels, and the other end 

upon bliwks or screw 

jacks*,* of the same 

height as the top of 

the piece. Bolts / / 

ar e then put through 

"ie clamps and the 

*Mo, w near to the 
■Wl as the holes will 
Permit, and the nuts 
•crowed down until the 
c 'atnps press firmly up- 
0,1 the piece and hold 
" rigidly enough to 
prevent any slipping 
* h 'le the drill is pass- 
ta S through it. 

.Th e above illustra- F,Q ° 5 " 

'on embodies the essential features of clamping. A piece 
^at always be set so that the center line of the hole to be 
(r, "ed j 3 parallel to the center line of the spindle, and must 

^lamped rigidly in that position. Great care must be 

er i to have all the supports so adjusted that the piece will 

spring out of shape when the clamps are tightened down. 

Tegular parts that have not a plane surface upon which 
r «st must be supported with jacks or blocks at different 
'^t-s. When pieces that are too large to be supported 
tlr ely upon the table are to be drilled, the overhanging 

*W must be blocked up, to prevent any undue strain upon 
e tabic or any spring in the piece itself. 







fr 


a 


1 


• 












b 





**3. Plain Chun 

nl Ung a hole a little 



rhe clamps are often made by 
r than the bolt in a piece of flat_ 



44 



DRILLING AND BORING. 



§10 



iron of suitable length. This kind of clamp is sometimes 
made with an offset, as shown in Fig. 66 (a), which serves the 
double purpose of forming a shoulder to prevent the work 
from rotating and of lowering the clamp-bolt nut so that it 
does not interfere with other parts. 

93. U Clamp. — A more convenient clamp is made of a 
piece of square iron bent in the form of a U, as shown in 
Fig. 66 (b), the inside width being just great enough to take 
the bolt freely. Such a clamp can be removed and replaced 
without taking the nut off the bolt. In some cases, the 
other form is of advantage, however, and both are found 
among the accessories of a drilling machine. The U clamp 
is often made without the offset at the end, shown in the 
illustration. 





t— r 




(a) 




D 



D 




(b) 
Fio. 66. Fig. 67. 

94. Screw Jack. — The screw jacks mentioned 
above consist of a cast-iron foot a, Fig. 67, which has a 
tapped hole running vertically through it and a square-head 
bolt /;, with a thread cut the entire length of the body, 
screwed into it. The top of the bolthead should be faced 
to form a good bearing surface, and the corners rounded to 



DRILLING AND BORING. 

■event any digging when adjusting the height. The 
ottom of the foot is sometimes left rough, but it is better 
> have it finished. 

95. Parallels. — The parallels used in blocking up 
he work should be care- 
illy planed and should 

made of rectangu- 
ar cross-section and in 
pairs. Sometimes par- 
allels are made with the 
width exactly twice the 
thickness. It is conve- 
nient to have the width 
each pair equal to 
thickness of the 
xt larger. Fio. es. 

96. V Blocks for Supporting Cylindrical Pieces. 
ylindrical parts are usually supported on V blocks a, 

. The V blocks should be made in pairs, so that a 
iece resting upon them may be exactly parallel to the drill 
table. It is usually of advantage to make the block wide 
nough to support short pieces with a single clamp, as shown 
I Fig. 68. A hole b drilled at the point of the V will form 
. clearance in planing. The two sides of the V usually 
ake an angle of 90° with each other. 

97. Angle Plates. — Pieces with a plane surface at 
right angles to the surface to be drilled are usually attached 





to an angle plate by means of clamps, as illustrated i 



u 



DRILLING AND BORING. 



Fig. 69. If the overhanging pari is too long, it should 
blocked or jacked up and clamped at another ; 
away from tin- angle plate as possible. The angle must, 
course, be firmly bolted to the table. 

98. C Clamps — The style of clamp show 

is known ai -i C clamp 
is shown on a larger* 

— n \ in Fig- 70. 

I | I 9S. Special An* 

tSNttH pflBlQ Plateja.— Angalai 

*" "^ — ^ an frequently supports 
F,li * on angle plates ■ 

inclination as the piece. For instance-, thi 
is clamped i<> an angle plate b of the same inclination, i 
bringing the surface to be drilled parallel ta . 

1IH). Vie*. — A vine as shown in Fig. 78 is often m 
for supporting the work. Ii is convenient i 
tin- bottom of a piece is irregular and >■ 
sides that the vise may grip between the jaws a, a. A lug 
on each Bide forms a convenient means of clamping theF\ 
to the table. 

101. Universal Vise— Fig. 73 shows a unite*,, 
viae that may be bolted to the table of a drilling mac},,,,. 




and may be rotated both in a horizontal and in a vertfol 
plane. The two circles a and b are graduated, as shorn. 
Such a vise is especially useful where holes must be ilrlllal 



DRILLING AND BORING. 



J t different angles in the same piece. The piece can be set 
either horizontally or vertically, and, by having the circles 




graduated, it can be rotated to any desired angle without 
resetting. 

102. Necessity of Clumping Rigidly. — When a 

piece has been set and adjusted in a vise, the jaws and all 
partstbatare liable to move should be tightened securely. 
In a good vise, provision is always 
made for clamping every joint. In 
the universal vise shown, for instance, 
11 is not safe to depend on the adjust- 
ing screws to hold the work, and the 
clamping screws should always be 
dr awn tight when all adjustments 
h av e been made. 

1 03. Drilling Parts To* 
*tb»;r. — When two adjoining pieces 

; to be drilled so that the holes in 
" e two are to match perfectly, they 
"^uld be drilled together whenever 
""acticable. This insures a perfectly 
'tinuous hole, and avoids a great 
a ' of awkward and expensive fitting. 

l©4» Jigs ami Fixtures In 

n »facturing, where pieces are du- 

1 in large numbers, special Jlj-s and fixtures are 
"*« for holding and drilling the work. Some of these will 
' c °nsidcred later. 




Fio.73. 



\ 



DRILLING AND BORING. 

(PART 2.) 



TYPES OF DRILLING MACHINES 
AND THEIR USES. 



DRILLS FOR LIGHT AND HEAVY WORK. 



SIMPLE DRILLING MACHINES. 

1. Up to the present time, only the simplest type of 
drilling machine has been considered — one that embodies 
only the principal features of the elementary drill. 

2. Necessity of More Flexible Arrangement. — It 
is evident that in our modern practice there is need of a 
more flexible machine — one that will accommodate a broader 
range of work than the simple machine described. 

3. Adjustable Table. — The great difference in the 
size of the work, and the various angles at which holes must 
be drilled, have demonstrated the need of an adjustable 
table that Can be moved vertically, swung about the column, 
and rotated about its own center, while in some forms of 
drills it may be tilted to different angles. 

4. Variable Cutting speed. — It has already been 
seen that nearly all materials possess qualities that make it 
necessary to use different cutting speeds in order to work 
them efficiently. It is obvious also that a drill of large 
diameter must be run more slowly than a smaller one, the 
revolutions per minute being inversely proportional to the 

MTED ST INTCftMATIONAL TEXTBOOK COMPANY. ALL RIGHT* RESERVED 

J 11 



8 DRILLING AND BORING. § 



diameter of the drill. To illustrate : A drill t inch in 
eter may make twice as many revolutions per minute as 
drill 1 inch in diameter, and four times as many as on 
2 inches in diameter, in the same material. Provision mus - 
therefore be made for a number of different speeds, any on* 
of which may readily be thrown in by the operator. 

5. Variable Feed. — A more flexible means of feedin 
must also be provided. It is frequently necessary to have a 

, greater pressure upon the drill than the hand lever described 
will furnish, and power feeds, in which the rate of feed can 
be varied, as well as other methods of feeding by hand, have 
been brought into use. 

6. Movable Spindle. — It is of very great advantage, 
too, in some classes of work to be able to move the spindles 
to accommodate the work, and this has been accomplished 
in several different ways. It is evident, however, that 
every machine need not embody all these features, but all 
these and others are seen in the various machines found in 
well-equipped shops. The peculiar features of each machine 
are determined by the class of work it has to perform. It 
must alwavs be remembered that the machine is made for 
the work and not the work for the machine, and, in distrib- 
uting the work to the various machines, whether drilling 
machines or other machine tools, the adaptation of the 
machine to each piece must be considered. 



MEDIUM-CLASS DRIIJL. 

7. Fig. 1 illustrates a machine that is largely used for 
light and medium-class work, and one or more of this gen- 
eral type is found in every good machine shop. This 
machine differs somewhat from the elementary machine 
described, yet it embodies the same essential features. 

8. Driving Gear. — The spindle <?, Fig. 1, is driven by 
means of a pair of bevel gears £, b and a belt running on 
a pair of stepped or cone pulleys r, c. The four steps on 



11 



DRILLING AND BORING. 



le cones furnish four different speeds, any one of which 
iay be obtained by simply throwing the belt to the desired 
ep. A belt running from the pulleys d and e to a coun- 
irshaft transmits the power to the drill. Either d or e 




runs loose upon its shaft. When the belt is on the loose 
pulley, the drill stands still. To start up the drill, tin- belt is 
shifted from the loose to the tight pulley, which is keyed 
gidly to the shaft, and therefore transmits the power to 
pulley c and to the drill. 




DRILLING AND BORING. 



511 

9. Feed. — In addition to the lever feed already described, 
a wheel feed is provided, This consists of a hand wheel/ 
keyed to a shaft that has IU tearing in the hub ^*, and on 
the other end carries a worm //, which engages with a worm- 
gear * mounted on the lever shaft j. It will be seen that a 
much greater pressure can be put upon the drill point with 
the I...'..! «!;<■ !..!i'l«'..!m than with 1 he lever, ami [l 

, ___. . . ^ fore used for the heavier work. 

"3^JX while Willi small drills and 

inati rials that .if.- ■■ i:-ll ■ 
the lever is used. 

Provision for using cither 
method at will is made as fol- 
lows: An eccentric hushing in 
the bearing g, in which the 
hand wheel and ■ 
carried, may he rotated 
moving the small hand lever, 
thus carrying the i 
until the worm k does not en- 
gage with the gear i 
illustrates DOW this i 
a represents the hand wheel 
and worm-shaft; 6, the bush- 
ing; <-, the bearing; an 
worm-gear. When 6 El 
position shown, the ■ 
worm-gear engage with each other, but when b is turned i» 
the position shown by the dotted lines, the shaft a and the 
worm arc carried with it and the worm and worm-gear are 
out of contact. The shall j. Fig 1, is then free tube 
turned by the hand lever. When it is desired to use the 
wheel, the lever must be disengaged. In the 
shown, the hand lever turns the shaft j by means of tlie 
spring latch /, which engages with a notched wheel m keyed 






toy. 



Todis 



"gage 



the lever, it i 



necessary simply to hold 



the latch in its raised position. This is done by means o 
catch at the top of the lever. 



II DRILLING AND BORING. 5 

10. Table. — The table n is supported on the arm 

id may be rotated about its center, while both arm and 
.ble revolve about the column p. The table may be raised 
id lowered by means of a gear that engages with the rack q, 
id is turned through the medium of a worm and worm-gear 
ith a wrench or crank applied to the square r. The drill 
•ot s is used as an auxiliary table upon which work that is 
•o large for the table « may be placed. 

11. Adjustment and Clamping. — Thisarrangenient 
ill accommodate a wide range of work, while all operations 
id adjustments are under the complete control of theoper- 

or. It must be remembered, however, in dealing with 
iese machines, that as the machine is made more flexible, 
i as to accommodate a wider range of work, a larger number 

parts and joints are introduced, and greater care must be 
ken to keep every part in perfect adjustment. When a 
ece is set, and the table moved so that the drill is exactly 
intral with the hole to be drilled, the table should be 
-mly clamped by tightening the bolts in all its movable 
■ints. 



HEAVY TYPE OF IUJII.I.. 

12. A heavier machine of this same type is shown in 
ig. 3. The driving mechanism is furnished with a back 
,t i7, in order to supply a greater variety of speeds. 
he bevel gears driving the spindle are enclosed at 6. 

3. Feed. — This machine is supplied with a rapid 
nd-levcr feed operated by the lever c, a hand-wheel 
»l operated by the wheel d t and a power feed operated 
by means of a belt running on the cone pulleys e and/, the 
latter being keyed to the main driving shaft, thus transmit- 
ting the power to a pinion and rack on the spindle, through 
the bevel pinion and gear^-and //and the worm and worm- 
■'./. The power feed is thrown in and out by means of 
clutch *, which is controlled by the pin / running up 
ougb. the vertical feed-shaft. When both the power and 



C DRILLING AND BORING. 

hand. wheel feeds are to be thrown out, in order to use tl 
rapid hand-lever feed, the hearing m is moved out in 
direction of the arrow n, by turning the rod a with wl 




the bearing is connected, tin.- hearing/* being pivoted so** 
to permit the bearing m to swing. A counterweight s bal- 
ances the weight of the spindle and reduces the friction ol 
the feeding device. 

14. Table. — The table swings about the column as in 
Fig. 1, but, instead of rotating about its own center, it hasa 

Straight-line adjustment in the direction of the it 

of the arm, which permits a straight line of holes to be 



DRILLING AND BORING. t 

led without moving the arm. The table is raised and 
ered by means of a crank q connecting through gears 
li a screw in the column that carries the nut r upon 
ch the arm rests. 

RADIAL DRILLS. 

SIMPLE RADIAL UK ILL. 

5. A machine that is designed for a class of work 
t cannot well be mounted upon a drill-press table, either 




mse of its size or weight, is shown in Fig. 4 and is called 
iclial drill. 




8 DRILLING AND BORING. § 11 

16. Driving Gear. — The spindle is carried in a head 
that traverses back and forth upon a radial arm a, which is 
hinged upon a vertical slide s on the column b. The spindle 

is driven by means of a 
belt c f which runs over 
pulleys x on the shaft d 
and y on the end of the 
arm, while an intermediate 
FlG - B - pulley that travels with 

the head, and about which the belt is carried by means of 
an idler, transmits the motion to the spindle. The plan of 
the belt c is shown in Fig. 5. The driving pulley x is splined 
upon the shaft d y while the pulley^ is supported on the outer 
end of the arm*?; £ represents the driving pulley on the 
drilling head, and w represents the idler. The motion is 
transmitted either to the spindle direct or through back 
gears shown at/, Fig. 4. A counterweight / balances the 
weight of the spindle, thus relieving the feeding device. 
The head is traversed by means of a hand wheel v, which 
has a worm on the other end of its shaft engaging with the 
rack g. 

17. Feed. — Both hand feed and power feed are pro- 
vided. The former is operated by the hand wheel h on the 
oblique shaft i, which has a wormy* on its end that engages 
with a rack on the upper end of the spindle. The power feed 
is obtained by means of a worm on the spindle running in a 
worm-gear, and is connected with the oblique shaft i by 
means of the gears, worm, and worm-gear at k. The hand 
feed or power feed is thrown in as desired by means of the 
hand wheels / and ;;/ and the pin «. 

In the larger sizes of this type of machine, a power trav- 
erse for the head is also furnished, taking its power from 
a screw in the radial arm #, which is connected with the 
vertical shaft d by means of a pair of bevel gears. The arm a 
and slide $ are raised by means of a screw in the column 
that runs in a nut attached to the slide between the guides 
f the upright. The power is transmitted to this screw 



§ 11 DRILLING AND BORING. 2 

through the gearing at <?, and is controlled by the handle / 
on the lower end of the vertical rod q. 

18. Foot-Plate and Table. — The work for which this 
type of drill is used is usually large and is generally sup- 
ported on the foot-plate r, which is finished and fitted with 
slots for T-head bolts. The table s is, however, provided for 
smaller pieces, or pieces that require side support. It is 
finished and has slots for supporting work on the top and 
sides. For light work, its own weight is sufficient to hold 
it in place, but for very heavy cuts, or where there is a 
tendency to tip, it should be bolted down. 

19. Setting the Work. — The same general rules that 
apply to ordinary drill-press work apply to the radial drill. 
The work must always be so set that there will be no spring 
in the piece when the clamps are tightened, and should be 
so placed that as much work as possible may be done with- 
out resetting. 



GEAR-DRIVEN RADIAL DRILL. 

20. The general type of radial drill already described is 
often driven by means of gearing and rods instead of the 
teltSHand^. The power is transmitted directly from the 
main driving cone to a vertical rod in the center of the col- 
um n, then, by means of gears at the top of the column, to a 
vertical rod corresponding to d, Fig. 4. Another pair of 
bevel gears connect this rod with a horizontal rod on the 
arm a, which is geared to the spindle in the drilling head. 



RADIAL DRILL WITH OUTER COLUMN. 

21. The type of radial drill mentioned above has ac- 
quired a large place in drilling operations, and for work 
where extreme accuracy is not essential, it has given ex- 
tent satisfaction. There are cases, however, where the 
s PHng of the various overhanging parts causes errors that 



10 



DRILLING AND BORING. 



§ 



are objectionable, and, to overcome this spring, a supportii 
column at the outer end of the radial arm is sometim 
added. Fig. 6 represents such a machine, which is called 
radial drill with outer column. The column a wi 
the radial arm b swings in an arc about the center of the ma 
column c y and, when moved to the right position, it 




Fig. 6. 

clamped to the bed by means of the bolts d y thus forming 
solid support for the arm. A simple device for moving 1 
outer column consists of a lever c linked to the foot of 1 
column, as shown. The lower end of the lever enters a sei 
of holes/ in the bed, thus forming a series of fulcrums 
the lever as the column is drawn along. 



DRILLING AND BORING. 



side frc 



i the c 



e outer cnlumn and the provision for moving 

s machine is substantially I lie same as an ordinary gear- 

i radial drill. The power is transmitted tO the spindle 

gh a pulley that connects with a vertical rod in the 

r of the column e. This rod is geared to an outer ver- 

I rod that moves with the radial arm through the gears 

The power is transmitted to the cone / through a pair 

.•el gears, thence by belt to the cone «, which is con- 

cted either directly or through back gears o to a hori- 

ntal shaft/, which is connected through gearing with the 

illing head q. 



UNIVERSAL TABLE. 

22. It is often necessary to drill holes at an angle in 
dial machines. For the 
smaller pieces, a universal 
ttalilc. Fig. 7, may be used, 
«o which the piece is set 
tilted to the desired 
le. The table is bolted 
the foot-plate by the lugs 
It may be turned 
its center upon the 
cle b, while the top can be 
at an angle, as shown, by 
ans of the handle c and a 
and worm-gear d. 
amping bolts on each circle 
1 the table firmly in place fjg ;. 

to it has been adjusted to a desired position. 



IMV1CHSAI. RADIAL DRILL. 

t3. In large work that cannot be supported upon a unt- 
sal table, R radial drill with an arm that can be rotated 
ut its own center, and equipped with a head that can be 




12 DRILLING AND BORING. flll 

thrown to anj angle, u soon n in Fig. 8, hat 
useful, The rotation of the arm is obtained by pi 

center of the shaft e Such a machine is called a 
universal radial drill. Thecircle », upon which the srm 
is rotated, is graduated in di^rees, and, as the arm mar U 
turned through the entire circle, an adjustnu u 




angle may be made very quickly and accurately. The cin lei 
on the head is also graduated, thus furnishing a ready 
means of setting the spindle to almost any conceivable angle. 
This machine, while differing from the radial drills already 
described in some details, maintains the same gene 
stniction. A careful inspection of the illustration 
readily explain the utility of all the parts. 



DRILLING AND BORING. 



25. Splndlcn In One Plane. — Fig. 8 illustrates a 
in ichtae "i" this type with six spindles thai 
lines all in one plane. The spun 

Laftab) means of worms at ■. the shaft 

a connecting with the driving cone / through the gears i 
and i. The motion for the feed is taken from the snafu, 
running in the cross-rail, and is transmitted to each spindle 
by gearing and clutches at ./, the feed-shaft *- being driven 
from the shaft a by a belt on the cone pulleys rand /, which 
also furnish the t sriable feed 

The table on the machine shown is not movable, 
work of a moderate depth can be drilled in it. This same 
general type of machine is, however, frequently m 
an adjustable tabic. The spindles can be moved i 

ail and adjusted to any dial 
range of the machine, while any number of holes from one 
to six may be drilled at the same tine. 

Thiatypeof machine is used principally for plate woik, 
structural iron, and other light work requiring a large 
number of holes in a straight line. Modified forma are nscd 
lai ;;■ I) for drilling locomotive : ■ 

and for tapping nuts in large numbers in bolt and sal 
factories. 



26. Universal Adjustable Spindles. — Multiple- 
spindle drills arc frequently made with universal adjust- 
it hie spindles. The universal joints allow 

be ved in and out as well as along the cross-rail, 

arrangement, holes that are not in line with one 
may be drilled at one setting, or if the holes 
d and are far enough apart, half : 
■ ■''I with drills and the other half frith 
. so that when [he holes are drilled the piece may 
be moved to the other set of spindles and finished 
taking it off the machine. 

Jigs should always be used in drilling with universal 
joint spindles, since the short lower bcai 
become slightly worn or may not be in perfect adjustment. 



II 



DRILLING AND BORING. 



ntroducing inaccuracies. A well-constructed jig guides 
c drill perfectly and avoids this danger. 
7. Vertical Flange-t>rllllnK Machine. — A very 

«ful multiple-spindle drill is shown in Fig. 10. Here the 
lindles may be adjusted about the center of the main dri- 
ing spindle tf. The drill spindles are all equipped with 




universal joints and each one moves independently of the 
others. This enables the machine to drill as many holes H9 
there are spindles in one circle, or the spindles may be 
arranged in two or more circles or set irregularly, as desired. 
This machine is designed Cor drilling engine cylinders, pipe 
flanges, valve bodies, etc., but it may be used for almost 
any work where such a grouping of drills is desirable. The 
illustration shows a piece of pipe clamped upon the drill 



Ifl 



DRILLING AND BORING. 



table with jig attached and drills insert--: 
inn. The power is transmitted to the spindles by a spur 
gear on the main spindle a, and a small pinion on the tipper 
end of each of the drill spindles enclosed in the upper pari n' 
the head b. The drill spindles are held vertically 

the upper and lower bearing! 
The feed is obtained by lower 
ing the entire head 6. Thi> 
i b either by meansof 
the pilot wheel c, or by power 
by means of a belt running 
on the cone pulleys d and t. 

28. Horizontal I" Ian if*. 
Drilling Machine — Mid- 
tipte-spindJe drilling machiaa 
with two hi *ds 
(ally upon a long bed, intewM 
especially for drilling thr two 
ends of engine cylini 
etc. at the same time, bavt 
recently been placed on tit 
market. The const 
the heads is prai 
same as that shown in Fig. 10, 
the only difference being Uttt 
they are placed horizon tally on 
the bed. The work is held 
a table between the two lie; 




(I on 



si:\sitivi: [mil i -. 
29. The drilling machines 
already described have been 
designed for the heavier grades of work. There is, how- 
ever, a large amount of light work in a machine sh 
which drills must Iw used, and which is too small to stand the 
strain of heavy machines. Tin- 1ms lul in the devcto 
a lighter and more sensitive class called wnsliivt drill*. 



i n 



DRILLING AND BORING. 



17 



Fig. 11 illustrates a machine of this class. The power is 

ansmitted directly to the spindle by means of belts, while 
he speeds are varied by the use of the ordinary cone pul- 
leys. The feed isof the simple, hand-lever, pinion-and-rack 
ype, already described, which is the most sensitive arrange- 
nent in use, any variation in the working conditions of the 
Irill point being readily felt with the hand upon the lever. 

he table a of the drill shown has no vertical adjustment, 
ut may be swung about the center of the post, out of the 
■ay of the center line of the spindle, so as to permit long 
pieces to be set upon the lower table b. The lower table and 
he lower spindle bracket c are both adjustable vertically, 
hus permitting pieces of greatly varying lengths to be taken 
nto the machine. 

This class of machine is used largely for center drilling in 
hops where a special machine for this purpose is not avail- 
,ble. The funnel-shaped piece d, commonly called a cup 

nter. is a special device for centering the lower end of a 

aft that has been cut off straight. The shank is set in a 
lole in the center of the lower table />, the center line of 

hich coincides with the center line of the spindle. The 

upped-out top of d is made a perfect internal cone, with its 

a the center of rotation of the spindle. A shaft that is 

t into this cup and is held with its center under the drill 
at the upper end will, therefore, have its center line in the 
axis of rotation, and a hole drilled into it, when held in this 
position, will be concentric with the outside of the shaft 

r rough out its entire length. 
30. Introductory. — In recent years there has been a 
marked development in light, portable machines for drilling 
and kindred purposes. The extreme lightness of their con- 
struction and the small space that they occupy have made 
hem available for much of the work that was formerly done 
t hand, and a large amount of time and hard labor may 



POUTAULIi DRILLS. 



18 DRILLING AND BORING. g 11 

be saved through their use. Most of these machines are 
so light that they can be carried about and operated by 
one man. 

31. Classes of Machines. — These machines may be 
classed under three heads, deriving their names from the 
manner in which they are driven, viz.: pneumatic drills, 
electric drills, and flexible-shaft drills, 

32. Pneumatic Drills. — Portable pneumatic tools 
are made in a large number of different forms. Some are 




driven by means of oscillating cylinders, others by means of 
vanes, acting through gearing that gives the proper reduc- 
tion of speed. 

Fig. 12 shows one of the oscillating cylinder type set up 
for drilling. The cylinders and gearing arc enclosed in a 
(■.!-■- ,?. The air, which for this class of work is generally 
compressed to about 80 pounds per square inch, is brought 
from the air compressor or storage reservoir to the drill 
through a rubber tube b, the tube usually being protected 
by means of wire wound spirally about it. The drill is 



§11 



DRILLING AND BORING. 



19 



fed by means of a screw c and is operated as indicated in 
the illustration. The air is turned on or off and the flow 
regulated by means of a valve d, which is controlled by the 
hand of the operator. This type of machine will drill and 
ream holes up to 3 inches in diameter, and may be used 
for various other operations, such as tapping, grinding 
steam joints, boring in wood, etc. 

33. Electric Drills. — Electric machines that are 
used for the same operations embody the same general 




features as the pneumatic machines, the difference being 
that an electric motor is substituted for the air motor. 



30 



DRILLING AND BORING. 



j^^|B|g^»- 



34. Flexible Shaft*— Fig. 13 illustrate ■ HM 
■baft and drilling machine set up ready for UH, Thep 
is transmitted to the shaft ih rough a rope drive, the r 
ning from the pulley b on the driving end of the shaft, i 
a pair of idlers c hung from the ceiling, to a pair of idlers i 

attached to the floor, 

thence to the pulley <- on Uu 
ountershaft , By either 

lengthening or shortening the 
bing the idlers d \<> 

the floor, the pulley / 
moved to any location within the reach of the driving rope 
A variable speed is obtained by means of the step pulley i 
Tin* shaft is made by winding successive layers of wire in 
opposite directions about a center wire, as shown [n Fig 14, 
the outside being covered with leather. 

35. Drilling Machine. —The drilllnK machine 

used with the flexible shaft is sho* S, It con- 

sists Mt a pair of bevel gears a and b mounted in a frame r, 
a spindle ii, feed-screw r, and wheel/. The bevel pinion d, 
which is covered by a guard, is attached to the flexible shaft, 
while the bevel wheel b is splined upon the spindle d. 
drill is iield in the spindle in tile u-i: 

The illustration shows how the machine is set Up 
drilling with the flexible abaft, by means of which it may ' 
operated at any angle. This machine may also be used I 
drilling horizontal holes in a vertical drill press, or for dr 
ing vertical holes in a horizontal machine, by an ki 
directly to the drilling-machine spindle instead of the flexible 
shaft. 

:tl>. Electrically Driven Flexible Shaft. - 

there is no running shaft available, the flexible shaft i 
receive its power from any convenient port 
a small electric motor mounted upon a suitable trucl 
shaft is connected to the motor by means of a a 

in order that the arrangement may be as flexible a 
possible. 



i li 



DRILLING AND BORING. 



81 



37. Heavy Portable Machine Tools The tend- 

ncy toward larger units in manufactories of various sorts 

introduced a new phase in machine-tool operations. 

Parts that are too heavy to be machined in the ordinary 




stationary machine tools are now met with quite commonly 
in machine shops. This has led to the use of large cast-iron 
floors upon which the work is placed, and portable machine 
tools, which may be carried to the floor and set up in any 
position to accommodate the worlc. 

Fig. 16 illustrates a case where a 135-ton flywheel was 
to be drilled at intervals along the rim for the purpose of 
joining the sections in which it was cast. The individual 
parts were machined and fitted together, but, to make the 
oints, several 2-inch holes had t< i be drilled through 26 inches 
[ solid metal. An ordinary radial drill was lifted from its 



DRILLING AND BORING. 



base and set upon the rim, as shown. When the hole: 
one joint were drilled, it was moved to the next joint and 
operation repeated, until all the joints were completed. 




rope drive was used in tniiismU'.ini; the power to the d 
The idlers were attached .n thece:;ter of the wheel, ther 
making it possible to r.i ve ;:*.e machine to any point on 
rim without changing the length of tbe rope. 



DRILLING AND BORING. S3 

BORING MACHINES. 

INTRODUCTORY. 

38. It has already been stated that the machine tools 
the present day have their origin in the lathe, which 
ands out as the parent machine tool. Some of the differ- 
nt machines developed have passed through various stages 
nd forms in the course of their evolution and have become 
stinctive types in themselves, bearing in their general ap- 
^arance no resemblance to the machine from which they 
ere derived. 

This is especially noticeable in machines used in boring 
terations, these being regarded by the present-day observer 
a distinctive type of machine tool in themselves. Two 
bdivisions have even been made, each division represent- 
\ a type of boring machine adapted to a certain class of 
These two types, namely, vertical and horizuntat 
machines, are so widely different in their construction 
at the most careful observation is necessary to establish 
■ relationship. While they are known as boring ma- 
ines, they both perform other operations. The vertical 
designed for turning as well as boring, and is often 
a boring and turning mill. The horizontal type 
ally performs drilling and some classes of milling opera- 
a.ii as boring, hence the name horizontal faring, 
tiling, and milling machines. 



VERTICAL BORING MACHINE. 

I.I.M 1/ 11. DESCRIPTION. 

9. Introductory- — Fig. \~ represents the ordinary 
-ticui iKirinu and turning mill found in up-to-date 
:hine shops. The work is clamped upon a rotating table 
i ided with slots for T-head bolts and a circu- 
hole in the center, as shown. The cutting is done by 



24 DRILLING AND BORING. 

means of tools in the tower ends of the boring bars b 
there being on the machine illustrated two of these ba 
carried in two saddles upon a cross-rail c. 




40. Control of Cutting Tools. — The tools are n 
and lowered by means of the hand wheels d, d, or by p- 
through the rods t, e, which are geared to the boring 



u 



DRILLING AND BORING. 



25 



id connect by me.ins of gearing at f and a friction wheel 
id disk at g, through the bed of the machine to the driving 
me k. The tools are fed horizontally by means of the 
rews i, i", which traverse the saddles upon the cross-rail. 
hese screws may be operated either by hand, with the 
indies J, J, or by power through the gearing at /"and fric- 
an wheel and disk at g, already referred to. Reversing 
rvices are provided, and the whole machine is entirely 
ider the control of the operator. The cross-rail is raised 
id lowered by power through the pulley and gearing at k. 

41. Control of Peed. — The rate of feed is regulated 
1 the friction wheel and disk at g. The wheel can be 
lised and lowered by turning the hand wheel /, while the 
jsition of the disk does not change. It will be seen that as 
le wheel approaches the circumference of the disk, it will 
ake more revolutions per revolution of the disk than when 
:ar the center. When the wheel is carried below the cen- 
r of the disk, the direction of motion is reversed, while the 
ime range of speeds is obtained by moving it toward the 
rcumference. A great variety of both vertical and hori- 
>ntal feeds in either direction is thus obtained, while 
utches and reversing mechanisms in the saddles place the 
k>1 perfectly under the operator's control. Counterweights 
■e provided wherever possible, in order that all parts may 
: operated easily. 

42. Arrangement of Peed. — The feeds are so ar- 
inged that one tool may be turning the outside of a piece 

while the other is boring, or they may both be either boring 

or turning on the same or different diameters, or one tool 

lay be facing the top while the other may be either boring 

turning. When working on different diameters, the tool 

the smaller diameter has a slower cutting speed than 

.t cutting on the larger, and the speed must, therefore, 

adjusted for the larger diameter. These operations are 

ually the same as tln.se carried on in the lathe, and the 

tools used for these operations in the two machines are 

identical. 



26 DRILLING AND BORING. S *1 

4:t. Tunic. — The tiihic is rotated by n 
bsnul gear on its lower side, and a pinion that is connected 
through a pair of bevel gears to the driving cone h. A back 
gear like that on a lathe is provided, which, with I 
ent steps on the cone, furnishes 1 I 

The table is supported in the center upon a ton . 
spindle running in a bearing near the top and inotl 
ing at the bottom, while a step bearing at the lower end 
takes the thrust. The rim of the table runs In a : 
the bed, which is flooded with oil, and, when running slowly 
on heavy work, the greater part of the weight is taken on 
this rim. 

Provision is made for raising and lowering the table when 
running at high speeds on light work, so thai 
is taken by tin' spindle. A screw />< connects with a wedge 
under the thrust bearing by means of a nut and lei 
by turning the screw in one direction, the wedge is forced 
in, while rotation in the opposite direction withdraws it. 
Conical turning or boring may be done by Betting the bi 
at an angle, as shown at the right hand i>( Fig. 17. 






i \ i i \>io\ iini'iv; mill. 
44. In shops where there is occasionally a piec* 
diameter to be turned, but where there is not ei 
ill is class of woi k to warrant the purchase of a l*rg< 
mill, an extension Itorlnjr mill may be used to advantage 
On an extension mill, the bed 0, Pig. 17, is mad* with in 
extension at the back and ways "ii top, on which I h 
in^-s n rest, ami on which they may bemOVi 
accommodate a larger piece upon the table. The i 
is, of course, carried bank with [he housings, and, 
to do boring, it is necessary to use a vertical boring I 
ported from an arm attache. 1 to the cross-rail ami | ■ 
the center of the table. As the table revolvi 
shu i-l si ill. A hub at the center of the work mav | 
by using an ordinary facing head, such as is used i] 



§11 



DRILLING AND BORING. 



2? 



he ends of cylinders on a horizontal boring mill. This 
uple provision in a mill designed for the average work o| 
i shop will enable larger pieces to be machined at a com- 
laralively small increase of cost fur machine tools. 



BORING AND TtlVHMQ OPERA 

45. Setting tliu Work.— The horizontal table of the 
KHlDg mill makes the setting of the piece differ from that 

the lathe and resemble the setting upon the drilling- 
; table. The piece must, of course, be set perfectly 
■entral with the center of rotation as in the lathe, and must 
blocked up and clamped as on a drilling-machine table, 
l jaws as in corresponding lathe opcralionn. When 
urning and boring a flat part, aa an engine-crank disk, for 
nstance, the part is held in jaws precisely as a piece of 
Hilar form would be held on a lathe face plate. When 
he center of such a piece has been bored, the top faced, 
and as much of the outside turned as the jaws will permit. 
the piece is turned over, trued up with the center, again 
gripped in the jaws, and the remaining parts finished. 

Wheu a piece is held in this way, it is always well to use 
one or more drivers, to prevent the piece from yielding to 
the tangential pressure of the tool and slipping in the jaws. 
Irregular pieces call for some ingenuity on the part of the 
operator, but the principles involved are the same as those 
in the case described. 

46. The following principles may be taken as a guide in 
all emergencies. The piece must always be set with the 
circumference to be finished exactly concentric with the 
center of rotation, and the center line must be perpendicular 
to the plane of the table. If the lower surface is irregular, 
it must be blocked up, so that the conditions mentioned 
above arc true, and must then be either gripped with jaws 
or clamped as in the drill press, drivers being provided to 

ke the twisting strain. The drivers may be simply angles, 
y devices to prevent the part from turning on the table. 




DRILLING AND BORING. 



Care must also be taken so that the piece shall not I 

sprung out of its true shape when clamped down. 

47. Example of Setting. — Fig. 18 illustrates how an 
ular piece may be secured on the table. Before setting 
i piece, the table must be carefully cleaned and lowered so 
that the weight is taken on the outer rim. When this is 
neglected, there is danger of injuring the step bearing ami 
also of springing the tabic. The piece is then placed on the 
table, set approximately central, and leveled up by blocking 
at regular intervals. In Fig. 18, screw jacks a are used to 
leveling up. When the piece is approximately level, a tool 




is brought very near the circumference to be turned, 
the table is rotated slowly. Careful observation of the dis- 
tance between the part and the tool will show in which 
direction it must be moved in order to bring it perfectly 
central. At the same time, the distance from the tool to 
the upper surface may be observed and the piece brought 
level as well. Several trials may be necessary before the 
correct position is obtained. Jaws b, which are supported 
upon extension arms c, which in turn are bolted to the 



11 DRILLING AND BORING. 29 

able if, are used for centering and clamping. The jaws 
-ire equipped with adjusting screws e to control the grip f. 
The jaws are also provided with clamping bolts (not shown) 
by means of which they are secured after being adjusted. 
4S. All adjustments having been made, two drivers, one 
n each side of the center, are set against any available sur- 
face. In the illustration, an angle g is set against a lug h 
■;nped on the table, as shown. The piece having 
""« been properly secured, it may be well to test the setting 
again, and to look over all bolts, so as to be sure that every 
put is fastened securely, after which the machine may be 
tUtted, the speeds properly adjusted, and the tools fed as 
required. The cutting conditions are the same as in a simi- 
lar operation in a lathe. 

Tlit piece shown is held by three vertical jacks a, three 
jaws^, and two drivers^ - . On pieces where a flange orally 
uther surface upon which a clamp may secure a hold is avail- 
able, clamps are used in preference to the jaws, drivers being 
applied to prevent any sliding on the table. In some cases, 
gfct of the part, together with the clamp, furnishes 
grip enough on the surface of the table to prevent any slip- 
P ln gi but this grip is very uncertain, and it is better not to 
depend on it entirely. Other special boring operations are 
described in Drilling and Boring, Part 3. 



HORIZONTAL DRILLING AND BORING 
MACHINES. 

■49. Introductory. — Horizontal drilling operations are 
*o closely associated with horizontal boring that they will 
oe considered together. Nearly all horizontal machines are 
designed for drilling, boring, and milling, the spindle being 
""■pied for any of these operations. The economy of such 
*° arrangement is evident when it is considered that the 
™rh]g operation requires that a hole, sufficiently large to 
troiit a boring bar to be passed througli it, be previously 
1, either by coring or drilling. 



30 DRILLING AND BORING. §11 

Small holes, up to about 'i inches in diameter, are usually 
drilled, and a machine that will do both the drilling and boring 
with one setting saves a large amount of time. Resetting, or 
moving to another machine, frequently takes more time and 
requires a larger number of men than the drilling or boring, 
while in the meantime the machine is standing idle and the 
additional service of a power crane is often necessary. For 
this same reason, it is an advantage to be able to perform a 
milling operation at the same time. It will be observe^ 
that these three operations require practically the sanwfe 
spindle action, and can, therefore, be carried on in thesam^ 
machine. It is economy to have machine tools so arrange:*} 
that the greatest possible amount of work may be done with 
one setting. This should always be borne in mind when 
selecting and arranging machines, as well as in their oj>cra- 

50. Drilling and Boring. — It has already been stat«^l 

that drilling consists of sinking circular holes in solid iv» a_ 
terial. Boring, as understood in a machine shop, consist* 
of enlarging and truing a hole that has previously b^* n 
made. This is done by supporting, independently of the pi^ ce 
to be bored, a bar that carries one or more cutters, f " c 
center of the bar thus forms the center of the bored hol*s in ' 
dependently of the center of the original hole. Where * 
center of the new hole does not correspond with the cef» let 
of the original hole, the heavy cut on one side will cans*? *'" 
bar to spring and the hole will neither be perfectly r<->"-* ni 
nor straight. One or two light cuts after the roughing ^ u 
has been taken usually true it up. When the cut is une *" * fll 
therefore, provision should be made for a finishing cut- '•J' 
using a cutter slightly smaller than the desired hole for "*' lc 
first cut. 

51. Simple Boring Bar. — There are two differ^ 1 " 
styles of bars used in this operation. The simplest of th*-* sr 
is used almost entirely for the smaller holes, and resr*"' 
bles, in construction, the counterbore already described "' 
Art. 69, Drilling and Soring, Part l. 



DRILLING AND BORING. 

Fig, 19 represents this type of bar. The end a is made 
to Gt either the spindle or some device attached to it. The. 
W should be as large as the hole will permit, in order 



CLUB 



-i|3±- 



ti ^~* 

Fig. in. 

"iat the spring may be reduced to a minimum. The mate- 
rial for the bar should be selected with a view to its stiff- 
"ess. For the larger sizes, cast iron is often used because 
°f its great rigidity. 

52. Cutter Slot, Cutter, and Key — At the middle 
°f the bar, a rectangular slot is formed to receive the cutter 
^ and a key c, which holds the cutter in place. The back of 
'he cutter and the front of the key are slightly tapered in 
°rder to wedge the key in the slot, the two ends of which 
a <"e parallel and perpendicular to the center line. When the 
cutter has been fitted, it should be turned up in the bar, 
"taking the ends parallel. The cutting should all be done 
r *n the front edges, which are formed with the proper clear- 
*n« angles. The outer corners are usually rounded 
"ightly. 
When no adjustment of the cutter is required, it is well to 
"*■ it into the slot with a slight taper running from the out- 
side .jf the bar, as shown by the dotted line it This enables 
't to be removed and replaced, or allows other cutters that 
°ave been similarly fitted to be inserted in its stead. This 
W 'I1 not do for cutters that require adjustment, as the ta- 
rred sides hold them firmly in one position. This advantage 
,s . however, so great that it is generally thought better 
I* r actice to have a set of cutters of different sizes properly 
nt ted to the bar than to use the adjustable form. 

53. Location of Cutters.— The cutter is placed at the 
middle of the bar, since this type travels through the work, 
'he work extends its full length beyond the cutter in both 



j 



3a 



DRILLING AND BORING. 



I 



directions as the latter reaches the ends of tlie work. 
pair of slota similar to that at the middle arc put near 

ends of the liar, where the ends of the piece art; i 

anil fating cutlcrsare inserted. Thus, the boring 

will he done with the unu bai ami with a single setting 

of the piece. 

54. Length of Bar. — This type of bar should be some- 
what more than twice the length of the work, in ■ 

there may be room for 
setting the cutter wlirn 
the " r urk stands at either 
end. 



3 




55. Nut Support 
for Cutter. 

boring bar and COttO 

of this same i :. 

possess some excelled'. 
Pro. so. , 

features, are shown in 

Fig. 20. The cutter a is notched with tapered sides to fii 

corresponding tapers on the bar, as shown. A nut c and 

collar b arc used to hold the cutler instead of the ordinary 

key. A better support for the cutter is thus provided, 

while the danger of injury due to the use of the hammer 

in setting the cutter is entirely eliminated. 

56. Boring Bar Wltli Traveling Head. — Another 
form of boring bar that is used in boring boli 

lively lart;e diameter isshowu in Fig. St. Thebu ■ 

ally made of cast iron, cored out so as to furnish the greatest 

stiffness with a minimum weight. A bead !> is ban 

the bar and turned on the mil side to a diameter somewhat 

smaller iban the diameter to be bored. One or mor 

tools c are let into the head, as shown, and are held 

by the straps and tap bolts at :i. 

57. Boring Henri. — The head is traversed by meansof 
a screw <-, which runs in a slot In the side of the bar, and a 



in 



DRILLING AND BORING. 



33 




not on the inside of the head. The slot is made large enough 
so that the nut is free to travel 
from end to end as the screw' 
is rotated. The head is rotated 
with the bar by means of a key 
in the head and a spline that 
runs the entire length of the bar, 
diametrically opposite the feed- 
screw. Bearings /, / support 
the screw at each end, while it 
is rotated with reference to the 
bar by means of a star feed, 
acting through the gears at k. 



68. Rotation of Bar and 

Support of Outer End. — The 

bar is rotated by attaching it to 

the spindle of a boring mill, or 

■ by means of special gearing. 

$ The outer end of the bar is sup- 

S ported by a bearing carried upon 

a pedestal that can be moved on 

the floor to suit the position of 

the head, and adjusted to any 

desired height. 



59. Facing Head. —This 
type of bar is generally equipped 
with a facing head, as described 
in Art. 70, that is clamped to 
the bar, as shown. This head 
receives its feed in the direction 
of the length of the bar by mov- 
ing the whole bar and spindle 
endwise. The facing tool is fed 
radially by means of a star feed, 
as described in the article men- 
tioned. 



DRILLING AND BORINtJ. 



til 



HO. Head. — One of the simplest types of drilling and 
boring machines is Illustrated in Fig, 98. The general ar- 
rangement of the liwntl resembles very closely that of a 
lathe, the cone pulley and baclc gear being the same. Instead 
of the ordinary face plate, there is an attachment on the 




Fro. u. 

end of the spindle for supporting either a drill or a boring 
bar. The spindle runs through the center of the cone and 
iasosplined ili.it, while it rotates with the driving gear, it 
may be fed through it by means of the screw a, which is 
turned either by the hand wheel b through the si 
gearing shown or by power through the gearing at c. 

HI. Borlnff-BarSupport. — An OUti 
a support fur the outer end of the boring bar. Slot 
in the head and the side of the table, as shown, permit thb 
bearing to be moved as mar to the work as possible, in order 
to prevent any unnecessary spring in the bar. 

H2. Table.— The table is supported at the outer end 
and provision is made for vertical, side, and longitudinal 
adjustment by means of the screws r, e, f, and ,, 
ively, 

H.X Setting the Work and Tool*. — The work, 
which is set upon the table h, can be drilled and bored in 



§11 



DRILLING AND BORING. 



96 



position, then moved to another position and the 
*ation repeated without resetting. The work is fast- 
ned on the table precisely as it is on a vertical drill, rare 
icing taken to have the center line of the hole in perfect 

line with the center of the spindle. It is well, also, to 
;uard against the work slipping endwise by setting a dog, 
: other support, solidly against each end. The tools used 
i this style of drill, aside from the boring bar, are the 
ame as those used for similar operations in the machines 

already considered. 



POST HR1LL. 

tt-4. Another form of machine that is used very largely 
midline shops for work not requiring extreme accu- 
racy is shown in Fig. 23. The driving parts are supported 




I two posts, which give this i hiss the name of post drill, 
riie spindle a, with the driving part !>, may I"- adjusted 



N DRILLING ANT) BORING. $ 1J 

vertically by means of a rai It i on tbe [Hist, while the work, 

which is set upon ,1 table (/equipped with wheels ud 

mounted upon a track, is adjusted horizontally b< 

the entire carriage along the track. In the 

shown, the carriage is moved by means of a bar that fits 

the hales shown in the hub e of the wheel Dearest 

Tin' machine is driven by means of a belt /, which runs 

oref an Idler g and a driving pulley on the spindle a. then 

over another idler //, down through the floor, and up again 

at i. 

The essential features of the driving mechanism are the 
m horizontal boring and drilling machines, although 
Lhe details are necessarily quite different. 

This machine is used very largely fordriUing flanges, spot 
facing, etc., and is especially useful on parts that are too 
high to he drilled in an ordinary machine tool. The posts 
are carried high enough to accommodate any work I 
he handled in tlie shop, the tops being supported by means 
of braces carried from the side walls or ceiling. 



HORIZONTAL ri.OOM MILLS. 

6S. General Arrangement. — A type of b 
boring, drilling, and milling machine that is used quite 
extensively in shops doing heavy work is illustrated in 
Fig. 24. The boring bar a and feed mechanism are carried 
in a head !>, supported on a column c, which, in turn, rest* 
on the bed d. The power is transmitted to thi 
through the cone pulley and back gear at e, and is carried 
by means of shafting and gears to the boring bar. The 
machine is so constructed that the head may he moved 
vertically on the column, and the column horizontally on 
lhe bed, while the boring bar moves in and out through 
the head. 

The work is set on a floor h, which is provided with 
T slots, as shown. The outer end of the boring ha 
ported in a bearing/ mounted on the column g, which rests 



DRILLING AND BORING. 



on the floor. The column and bearing may be moved to 
any location on the bed, and adjusted to any desired height. 




66. Floor. — The floor of this typeof machine is some- 
times made very large, so as to accommodate more than 
one machine. A good arrangement consists of two ma- 
chines set at right angles to each other, the one being of 

heavy class designed principally for boring on large 



DRILLING AND BORING. 



diameters, while the other is somewhat lighter and is espe- 
ally adapted for drilling operations. 

Double-Head Machine. — Machines have been 
lesigned with a heavy boring head on one side of the col- 
i and a drilling head on the other, with the driving 
mechanism so arranged that either one can be thrown in 
will. With this arrangement, only one head can be op- 
ated at a time, and the experience of users of such a 
lachine seems to indicate that better results are obtained 
/ mounting the two heads on separate columns, so that 
•oth may be operated at once. 

<»N. Setting: and Fastening Work. — The same prin- 
ciples that have already been mentioned in connection with 
he securing of the work on the tables of other machines 
y to this class of machine as well. It is necessary to set 
t perfectly level, and to line up the center line of 
wsed hole with the center line of the boring bar. 
Parallels and blocks, or wedges, are used to raise the work 
to a suitable height, and to level it up. When it is properly 
set, clamps are applied, as shown in Fig. 25. 

. Example of Setting lipand Fastening Work. 

25 represents an engine bed set up on a large floor 
md being operated on by a boring bar connected with a 
large horizontal boring machine. The bed a is mounted on 
parallels b, b near each end of the bed, which are clamped 
to the floor plate by means of the clamp c, and the bed is 
clamped to the upper parallels with the clamps d, d. A pair 
of pipe jacks e, e running out from the corners, as shown, 
guards against both side and end motion. A duplicate set 
of parallels, clamps, and jacks, at the other end, which is 
not shown, holds the bed rigidly in place. 

70. Arrangement of Boring Bar and Cutter. — 

The illustration shows the boring bar /, the boring head^ 
with two tools //, k in position, the traversing screw /, the 
iuter bearing j with the front of its supporting column k, 
he facing head / with the tool m clamped on the tool slide «, 



: 



40 DRILLING ANI> BORING. 

the feed-screw i>, the star/, and the star feed-poet <j, 
last being bolted to the floor. 

The boring bar is connected to the spindle by means of a 
special socket r. One end of the socket fits the spindle and 
the other end is bored out to receive the boring bar.' which 
is gripped and held central by means of four setscrews/, 
The illustration shows a typical piece of work fnr this class 
of machine, and the usual method of supporting and hold- 
ing it. 



MM I l\<; OPBRATIONM IN lioitivc Mil.is. 

71. The milling done in horizontal boring machines 
similar to that done in the heavier types of milling n 
Solid cutters are used for the smaller work, ai 
inserted-tooth cutters, resembling the heads used i 
planers, are usually employed in facing large surfaces. The 
horizontal boring machine is especially well adapted for 
facing irregular surfaces, the horizontal and verticil feedi 
being so arranged that either one or both may be thrown En 
at the same time, thus permitting any path within the range 
of the machine to be followed. 



. 



CYLINDER BOWING. 






72. Setting L'p Work. — Engine, pump, or other 
cylinders in which a reciprocating piston must 
should always be bored in the position in which they arc to 
be used. The cylinder of a vertical engine should be bored 
standing on its end, while the cylinder of a h 
engine should be bored in a horizontal position, 
cylinders, especially, there is considerable 'spring due to 
their weight, which will tend to produce an oval shape wh( 
a cylinder that has been bored in a vertical po^if 
on its side, or when a cylinder bored in a horizontal posit i 
is set on end. When the boring is done in its working p 
tion, this difficulty is practically eliminated. 



u 



DRILLING AND BORING. 



41 



73. Tools for Finishing Cut. — The working sur- 
ace should be very carefully bored in order that there may 
« no unevenness or irregularities of any sort. There is 
ome difference of opinion, however, as to the best course to 
itirsue to attain this end. Some claim that the finishing 
nt should be taken with a square-nosed tool in order that 
he surface may be perfectly smooth, while others prefer a 
ounded diamond point, claiming that the narrow point is 
:ss affected by unevenness in the structure of the metal, 
nd that the slight ridges formed tend to reduce theamount 
i metal En actual contact, and are an advantage rather than 

detriment. The ridges also tend to draw the oil under 
he piston, thus affording Letter lubricating conditions. 

74. Continuous Travel on Finishing Cut. — All 
hop men agree that whatever tool is used for the finishing 

ul. it si Id run continuously from one end of the cylinder 

o the other. The heating due to the action of the tool 
auses enough expansion thru even a short stop will leave a 
otieeable ridge, and long stops often make it necessary 
3 bore the whole length over again. For this reason, 
ylinder-boring machines should be run by an independent 

engine or other motor. 

75. Machines Employed In Cylinder Boring. — 
Cylinders are bored in lathes, vertical and horizontal boring 
mills, or special machines built for that purpose, depending 
on tin amount of this class of work that is to be done. Ex- 
cept in shops where a specialty is made of one or more types 
of machines, either a lathe or an ordinary vertical or hori- 
zontal boring mill is used. 



OMM.ISS BXGINH CrUMtRR-BOUING MACHINE. 

7fl. A machine for boring large Corliss engine 
oyllndero is shown in Fig. SO. Two adjustable boring 
bars ,i and b, standing at right angles to the main 
spindle r, are provided for boring the ports, while the 
main spindle c bores the cylinder proper. An outboard 



SH 



DRILLING AND BORING. 



41 



bearing d for the main boring bar, which is mounted < 
i verticil slide on the column e, is raised and lowered to 
■;uit the spindle by means of the wheel f. The main spindle 
is driven through the 
cone and back gear 
at g, while the main 
head h is raised and 
lowered by means of 
a belt running on the 
pulleys /', which con- 
nect with the head by 
means of a vertical 
shaft through a worm 
and worm-gear at j. 
The small heads and 
boring bars a and b 
are operated through 
the cone and gearing 
at^and shafting and 
gears in the bed / and 
column m. The col- 
umn n, with its bear- 
ings, forms an outer 
support for the two 
boring bars a and b. 
The cylinder is sup- 
ported on the paral- 
lels o and/. 

VERTICAL 

CVH1VDER-BORING 

MACHINE. 

77. In shops hav- 
ing a large amount 
of vertical cylinder 
boring to be done, 
special machines are 
sometimes employed ; 




44 DRILLING AND BORING. § 11 

these machines are so constructed that the cylinder stands 
on a heavy floor plate, to which it is clamped. The boring 
is done by a vertical bar, the upper end of which, together 
with the driving mechanism, is carried by heavy columns. 
These machines are sometimes so constructed that the bar 
and a portion of the driving mechanism may be lifted out of 
the way while the cylinder is being placed in the machine. 
Such heavy machines are usually run by an independent 
engine or other motor. 



VERTICAL BORING BAR. 

78. In shops where the amount of work does not war- 
rant the purchase of an expensive machine, a vertical boring 
bar, like the one shown in Fig. 27, may be used. The 
cylinder is supported on the stand a, and is clamped between 
it and the four-arm bracket b at the top, which also forms 
the guide for the boring bar c. The bar is rotated by means 
of a large bevel gear d and a bevel pinion (not shown) that 
connects with a pulley from which the machine receives its 
power. The cutter head e is fed by means of the ordinary 
feed-screw/" and the reduction gearing^ and h shown at the 
top of the bar. 



BORING SPHERICAL BEARINGS. 

79. The boring of internal spherical surfaces is accom- 
plished by means of a revolving boring bar that carries a~ 
tool on an arm that moves in an arc about a point in the^ 
center of the bar, the axis of rotation of the arm intersecting" 
the center line of the bar at right angles. 

80. Special Boring Bar. — Fig. 28 illustrates a device 
designed for this purpose. A boring bar a has a double-end 
arm b b pivoted on the axis c, which stands at right angles 
to the center line of the bar. The arm b b carries on its 
outer ends two tools */, d t set in and clamped as shown. 

It will be seen that if the arm b is turned about its axis C 



DRILLING AND BORING. 



45 



tile ill.- b, ir ,7 is rotating, the tool points will bore an 

Uernal spherical surface. In order to secure this motion, 

e arm is const rue ted with the segment of a worm-gear e 

one side. A worm f engages with this worm-gear, so 

hen the worm is rotated, the arm swings about the 

c, causing the tool points to travel in an arc about 

: same center. The worm f is revolved by a star g 

trough, the gears U and /. A post on the floor operates the 




>tar in the usual way. The worm f is supported in tivo 
flanged bushings j and k, while the arm b is pivoted on a 
through bolt. The end / of the boring bar is made to fit the 
spindle of a large horizontal boring mill in which it is used, 
while the end m fits the outer bearing. Narrow round' 
nosed tools are usually employed with a fine feed, so as to 
. smooth surface. For the roughing cuts, the two 
lay be used, but for the finishing cut, it is best to use 
ne tool only. 

81. Portable Borlnir Devices. — When the Amount 
■paerical boring to be done does not warrant the 



DRILLING AXD BORING. 



construction of a bar as JBrnMrstu S in Fig- *8, or in c 
■fere a portable arrangement b neci—irj-, a boring 
may be fitted op a* sbowr. m F'g 19. An ordinary bono; 
bar a, with ha feed-acre* and gearing: ' *n<l f . ani - , ""'' : 
bead d, rt fitted np with a forked arm e, which is pivotal 
on both aides of the bar. so that the axis of rotation of the 
arm and the center line of the bar intersect at right angles. 




The arm e carries a tool /and is connected with the head i 
by thr link g. The boring bar is rotated by means of the 
worm-gear A and a worm and pulley that are not shown. 
As the screw 6 is routed, the? head d is moved along H 
bar, and the link g- causes the arm e to swing about its 

■ (, when both bar and screw are rotated, the tool * 
form tii' desired spherical surface. 

The illustration shows the bar mounted on a large engine 

ready to bore the spherical bearing Jj. The bar i 

supported on two brackel i I to the ends of thi 

and is kept from moving endwise by means of 
worm-gear // on one end and the collar ion the other > 



DRILLING AND BORING. 

(PART 3.) 



DRILLING-MACHINE OPERATIONS. 



DRILLING, BORING, AND TAPPING. 




DRILLING. 

1. Laying: Out. — In many modern machine shops, the 
laying: out of all the work is done in a special department 
and the work is sent to the machine tools ready for the 
operation. For the drilling machine, the cen- 
ter of the required hole is marked; a circle 
equal to the diameter is scribed about it and 
light prick-punch marks put at the center 
and at intervals about the circumference, as 
shown in Fig. 1. The diameter and character 
of the hole are also marked, usually with fio. i. 
chalk. The marks on Fig. 1 indicate that a 1 J-inch reamed 
hole is required. 

2. Enlarging: the Center Mark. — When the work 
reaches the drill, the operator enlarges the center a with a 
large center punch, to form a guide for the drill point when 
beginning the cut. It is practically impossible to start the 
drill in the center of the hole without the assistance of this 
deep center mark. 

For notice of copyright, see page immediately following the title page. 
T IB— 33 



DRILLING AND BORING. 



3. Adjusting Uic Work and Table. — The piece 

now ready tot the dull, and is mounted Utd da::i 

table aa already explained. The drill table i ^ then swung 

about and adjusted until the center mark ■ 

under the drill point, the drill having, in the meantime, 

been run down to make sure that the [joint coin' 
the center. The table is then i ■ vent any 

motion while drilling, the machine started, and the drill 
fed into the work. 

4. Starting the Drill. — When the drill has OM 

menced Cutting, any u 

or varying hardm 
or imperfection in the 'i ; 
tends toca (w&yfftei 

the true centcrof the bole 
,;. drill rims down, making a c 
link' as shown in Fig. 2, . 
''"' ency away ft the i i ■ 

be observed by raising the drill point slightlj and I 

brushing away the chips, If the outer circle made by d 

drill is not concentric 

with the circle of punch 

marks, the drill has run 

off (row the desired 

center, and must he 

brought back. Adraw- fig.s. 

ing chisel, shown hi Fig 

is simply a narrow round-nosed chisel with which I 
is cut away on the side toward which the drill poii 
drawn, as shown in Fig. 4. The cutting should 

quite near the center, a 

removed there H ill draw : 

when the cutting ts done near the c i re u in f cretin 
The drill is again lowered and the resu 

observed. If the circle should aol I ■■ 

trie, the chisel is again used and the drill txfc 
this operation is repeated until the hole coincides crac 




m 



; [l 



DRILLING AND BORING. 



with the circle when the drill lias entered to its full diameter. 

The punch marks are cut away equally all around the cir- 
umference when the drill has been properly started. The 
rill is then fed through the piece, or to the desired depth, 

either by hand or by power, and when the cut is finished, 
: is backed out by hand. 

5. Advantages of Power Feed. — All drill presses of 
e heavier types should be so constructed that either hand 

power feed may be used at will. In light work, enough 

pressure can be furnished by hand to cause the drill to cut 

to its full capacity, but in the heavier work a greater pres- 

needed. It is contended by some that the average 

rkman will accomplish more by feeding by hand than by 

>tng a power feed, since the tendency seems to be to set 

le feed at its finest rate, although most drill presses are 

ovided with gearing that will furnish two or more rates. 

his is the fault of the operator and not of the method. 

he power feed should be so set that the drill will work up to 
limit, which it is impossible to accomplish with a hand feed 

hen large drills are used. 

The power feed has several advantages over the hand feed 
for all sizes of drills. With a hand feed, the drill will leap 
forwards as the point emerges from the material, often 
causing a rough hole and injury to the drill. The same 
is true when it enters a blow hole. In drilling flanges, the 
drill frequently breaks through on one side, and, when the 
cutting edges stand at a certain angle, the drill runs forwards 
easily and the next instant takes a heavy cut on one side 
only. It is evident that this condition will sooner or later 
result in an injured drill. With the power feed, all this is 
avoided, as the drill has a fixed rate of advance, In using 
the power feed, care must be taken to sue that the drill Iain 
proper working condition. 

6. Lead Hole*. — In using large drills, time may be 
saved by drilling a small hole at the center fur the entire 
depth of the hole, the diameter of this small hole being made 
at least equal to the length of the scraping edge at the point 




* DRILLING AND BORING. 

of the large drill. The small center bole is called a head 

hole. This hole will permit all the preasui ■ 

cutting edges proper, and all the power ii 
applied directly in removing th 
Thedrillwill thus cut more rapidly than 
it will when required to remove the meul 
from before its center. 

When the large drill runs ou 1 . o 
at the start, il is necessary to draw it over 
with a drawing chisel. In this case, a 

groove running the full length of the conical surface should 

be cut as shown in Fig. 5. 

7. Drilling l>ct|> Holes. — In drilling deep holes 

through ;i piece of work, ii may be necessary to go deeper 

than the length of the flutes in the drill of 

the required size. If the hole is not too 

deep, i he drill may be backi d oul and the 

hole cleaned at short intervals. When 

the hole is very deep, however, I 

be saved by running the drill down as far 

as the chips will discharge, then drilling 

the remaining depth with s smaller drill, 

making a hole a* shown in Fig, 0. The 

first drill is then put back into the ma- **°- *■ 

chine and the entire hole drilled to the h. . 
The second drill must be small enough so that Lhei 

work out around it, but tnusi not he so small thai 

made by the larger drill that follows it cannot dropo 

at the bottom. In one instance, where a lj;;-im-h note was 

drilled through 2'3 inches of solid cast iron, a 11 

was employed to drill the small hole and gave good n 




8. Method* of Reaming. 
that reaming consists ol trail 
reamer. The hole has been prei 



■It has already Uecns 
up :i hole by me ■ 

d or bored, and, 



■ 
results. 

:n stated 



; ll 



DRILLING AND BORING. 



s it is a matter of economy to do as much work as possible 
t same setting, the reaming is often 
e in the same machine that was used 
for the drilling or boring. The rough- 
ing reamer is usually made with a shank 
that can be used in a drill press, and is 
run at a slow speed and fed carefully by 
hand. For very accurate work, the 
reamer should be operated by hand, but 
may be guided by a center in the drill 
spindle, as shown in Fig. 7. The reamer a 
is turned with a wrench and is followed 
up by the center b, which also furnishes 
the necessary pressure. 

9. Care Necessary in Reaming. — Reaming should be 

Mi the greatest care. Undue forcing of the reamer, 
. any side pressure, or any irregular or jerking motion, tends 
to injure both the reamer and the hole. A very steady and 
ativeJy slow motion under a light pressure gives the 
best results. In some cases, the weight of the reamer and 
the wrench is sufficient to furnish the feed, although some 
additional pressure is usually necessary. 

10. Machine Reaming. — In cases where a large num- 
ber of holes arc to be reamed, it is done with one reamer, 
operated by a drill press and fed with the power feed. This 
should, however, be done only in cases where there isenough 
work of this kind to enable the operator to know exactly 
what speed and feed to use, and to set his machine properly. 
The holes, too, must be drilled very carefully, in order that 

tere may be no great variation in the duty of the reamer. 



TAPPING. 

11. Forms of Taps Used. — The forms of taps used 

i the drilling machine are the same as those used in the 
ithe, except that in the former the shank is usually made 



DRILLING AND BORING. J U 

with a standard taper or other form adapted for drill chuck; 

or sockets, while in the lathe the square-end ta| 

The devices for holding taps in the 

are explained in Arts. 87 and 88, Drilling and Borwg^ 

Part 1. 

In ordinary machine tapping, a taper tap gives the best 
results. When the thread runs through the material, the 
tap is run either entirely through or until a thread of the 
full diameter is formed. When the hole does not run through 
and the thread must run as near the bottom as ;>■ ■ - 
taper tap is used to start the thread, and is followed by a 
plug and bottoming tap. 

12. Spaed of Spindle. — As in reaming, the speed d 
the spindle must be slow, and, after the tap is Btai 
pressure should be put upon it by the feeding device. The 
tap should be perfectly free to take its own feed. 

13. Correct 81m of Drilled Hole. — It is a very 

important matter in lapping that the hole should be so 
drilled that a full thread will be formed without removing 
an excessive amount of metal. When the hole is drilled 
too small, it is very hard to start the tap, and, when it is 
Btarted, the work is so heavy that tlie Up is frequently in- 
jured, while the amount of time and energy required is far 
greater than is necessary. 

It is claimed by some, however, that the hole B 
drilled larger fur cast iron than for wrought iron and necl. 
and that a thread about three-quarters full in th< i 
cast iron is stronger than a full thread, owing to the danger 
of crushing the points of the thread and perhaps | 
the lap in case a full thread is attempted. 

A hole that is too largo is equally objectionable, as the 
threads will not be of the full depth, and will, therefore, 
be imperfect and weak. The lap runs very easily, how- 
ever, when the hole is large, and for this reason there is 
a tendency toward making it large, even a1 
in the strength of the thread. This should, however, never 



$ 13 DRILLING AND BORING. 7 

be permitted, as the perfect form of the thread should be 
maintained under all conditions. Tables Vand VI, Art. 47, 
give the sizes of drills to be used for taps of various sizes. 



14. Countersinking, counterborlag, and facing 

are carried on very much as ordinary drilling. The tool is 

Inserted m the drill socket, the hole brought central with 

the spindle, and the tool is fed down to the desired depth. 

The speed should, however, be reduced to a suitable point 

r the outside diameter of the cutting edges of the tool 

cd. Center drill! ni; is fully considered in Art. 23, 

ttke Work, Part 1, and Art. 29, Drilling and Boring, 

art 2. 

LUBRICATING. 

t 5. The subject of lubrication of drills has already been 
I in Ails. *Oto 42, Drilling and Boring, Part I. 
'he same conditions with regard to lubrication that have 
Ben mentioned exist in the use of countersinks, counterbores, 
icing tools, and center drills. In working cast iron and 
;. ihese tools, no lubrication is necessary; in fact, 

retards the work in the case of cast iron. Wrought 
mi and sled, however, always require lubrication. In 
laming and tapping, some form of lubricant should be used 
ith al! metals. 

Usually, the lubricant is dropped on the cutting edges 
■kh an ordinary oil can, but in multiple-spindle machines, 
nd occasionally in single-spindle machines, a tank, with a 
ibe leading to the tool, is attached to the machine frame. 
"he Row is controlled by means of a valve in the tube. A 
nail pump carries the hihricant from the table of the 
lachlne back to the tank, thus providing a means of using 
le same lubricant over and over again, and of flooding 
ic cutting edges without undue waste of the lubricating 
laterial. 



DRILLING AND BORING. 



§1* 



DRILL GRINDING. 
16. Form of Drill Point. — The form of drill point 

that will give the best results has already been en u side red in 
Drilling ami Boring, Part 1. It is very important that 
this form shall be maintained whenever the drill is ground. 
The drill point should always be perfectly symmetrical, 
and when cutting, should produce similar cuttings on each 
side. 

1 7. Hand Grinding. — To grind a drill by hand so that 
the above conditions may be fulfilled requires the great- 
est skill and care. Hand grinding is usually done by 
holding the tool on the grinder without any gauge, and 
depending only on the eye for the correct cutting and 
clearance angles. Sometimes a fiat drill is tested by press- 
ing the one cutting edge against a smooth piece of wood, 
while holding the drill in a certain position, then turning 
it and pressing the other edge on the same mark, still main- 
taining the same position of the shank. If the two mark- 
coincide, the drill is supposed to be well ground. The accu- 
racy of this test depends entirely on the skill of the work- 
man, but remarkably good results are often obtained in 
this way. 

1 8. Measuring the Cutting and Clearance 
Angles of Twist Drills. — The test given above is nut a 
very sure one, and it is better in the case of a twist drill 
to use a gauge, or a protractor, set at the required angle. 
as shown in Fig. 8 (a). By turning the drill so as to bring 
the protractor from a to b, the clearance angle may be 
observed, and in this way the two sides may be compared. 

Another method often used is illustrated in Fig. 8 (/>). 
The point of the drill is set on a plane surface or 
straightedge, and a scale held against its side, as shown 
The heights of the corners </ from the point are thus me; 
ured. If the two sides are alike, the drill is turned, and tl 
heights of the corners b are measured, thereby determining 
whether the clearance angles are equal. The scale is then 



i-n 



. 



512 



DRILLING AND BORING. 



laid along the cutting edges, and if all three correspond- 
ing measurements agree on both sides, the point is sym- 
metrical. 




'**. Ancle and Length of Scraping Edge. — The 

ar *oce angle determines the angle of the line a b, 
£• 9 (a), in which the planes of the clearance faces inter- 



,_ This illustration shows about the correct 

When 



ingle. 



the angle is too small, as in Fig. 9 (b), or too great, 
Fig. 9 {c), the drill will not work well. 




In order to give strength to the drill, the center is made 
thicker as it approaches the shank, and it is obvimis that as 
the cutting edges are ground back, the length of the line a i\ 

* 9 {")• increases. When this increase becomes objec- 
tionable, the flutes should be ground out until the point 




10 



DRILLING AND BORING. 



[I! 

reduced to Its original thickness. In this operation, care 
must be taken not to change the shape of the flute. 

2<>. Machine Grinding. — As may be expected from 
the methods employed, hand grinding is generally Dot Bat* 
factory, and machines that obviate the difficulties mrt with 
in hand grinding have been 
brought into very genera] 
use. The 

in Fig. 10 may be taken 
as a fair representative of 
twist-drill grinding ma- 
chines. 

21. Twlttt-Orlll 
Grinding UaoUiM. — 
The grinding wheel a, 
which is rotated by means 
of a belt, is supported on a 
column b at a convenient 
height from the floor. The 
drillisheldontWoV--ii.<! ed 
supports e. c ami 
rest '/, all of which are bi-lil 
on an arm e, which is sup- 
ported in a bearing 
whose axis the arm e is free 
to swing. The bearing / 
is supported on t h 
the arm g and may be moved nearer or farther away I 
wheel a by sliding the arm endwise in its bearing, while it 
may be clamped at any pOS 

22. Grinding Twist Drills.— To grind the drill, it is 
laid "ii the V's c, c and the end rest d'w adjusted to hold the 
drill near the wheel. The lip of the drill is laid ,. 
gauge that is hidden behind the upper V, and the arm t i> 
rotated about the axis/". The drill is fed slowly toward the 
wheel by turning the screw /; until the drill is groan 
dasfwd edge. 




I 






§12 DRILLING AND BORING. 11 

23. Form of Clearance Face. — It is evident from 

this construction that the metal back of the cutting edge 

will be ground away in the form of an arc of a circle, and 

not in a plane surface as in hand grinding. This has been 

thought objectionable, but the use of these machines has 

demonstrated that if the radius is properly adjusted for each 

size of drill, the arc immediately back of the cutting edge 

will be so flat, and will approximate so closely to a plane, that 

the supporting edge is practically not weakened. As the 

ar c runs farther away from the cutting edge, it, of course, 

Aviates more from the true clearance angle, but before any 

deviation is noticeable, the arc has run so far back that the 

support of the cutting edges is not affected. 

24. Length of Radius. — The length of the radius is 

ac tyusted by moving the arm g in or out of the bearing, the 

Potion being determined by a very ingenious little device 

s «o\vn at i. In order to make the adjustment for the drill, 

" e ^rm^is loosened and drawn out a short distance. The 

u PPer V, £, is then loosened and moved up until the opening 

^Ween the projection /and the projection/ on the arm c just 

P eri Xiits the drill to pass through. The V is clamped in that 

Y^^tion, and the arm g is again moved in until the lip gauge, 

r ^^dy mentioned, just clears the wheel. The end ntst d 



In 

^lien set to the proper position, and the drill laid on the 
3nd ground, as explained above. 



v s 



T^hese adjustments can be made with very little loss of 
. ,****. and a perfectly symmetrical drill point is assured. It 
claimed that a machine of this type will grind drills 
^ging from £ inch to 2£ inches in diameter. 



^**ILLING AND BORING JIGS AND FIXTl/WKS. 



DRILLING JIG*. 

25. Drilling Duplicate Pieces. — buplkat': pi"'.es 

^**ay be drilled by the use of drilling Jig*. A dr:!l:r.g 

J*g is a device or fixture that may be t':m:#'/rar:Iy a'.ta'.r.':'! 

*o the work, and acts a=, a guide for th'; drill ir* ar*y tl-.S.r-A 



i 

L 



DRILLING AND BORING. 




position. The guiding of the drill is accomplished by means 
of steel bushings placed over the positions of the required 
holes. It is obvious that in this way a large amount of time 
otherwise devoted to laying out may be saved, and, when 
the jig is well made, a degree of accuracy may be attained 
that is impossible by any other means, The economy of 
such a device depends on the number of pieces to be drilled 
and the cost of the jig. 

26. Construction of .1 Ir. ■ - The body of the jig is 
usually made of cast iron, but, in order to prevent undue 

wear of the holes, hardened-steel 

bushings d, Fig. 13, which fit 
f|j both the jig and the drill snugly, 
are inserted. These bushings arc 
generally made with a shoulder, 
as shown in Fig. 11, and with the 
" FlG - l1, inner corner slightly rounded, to 

avoid injury to the drill when entering. Jigs arc frequently 

used from both sides, the bushings being set as shown i 

Fig. IS) and the inside corners being rounded on both em 
In drilling two adjacent parts, ; 

for instance, the flange and head of \ 

a cylinder, the head may be drilled 

first, and may then be used as a jig 

for drilling the cylinder, or as a 

templet for marking the holes. 

When a large number of duplicates 

are to be made, however, it is better to use a jig for 1 

the cylinder and head. 

27. Ji|E for Drilling* Flanges With Regular! 
Spaced Holes. — Fi^^£ 
13 illustrates a flange 

I and a jig b of the for ■ 
that is very general 7 
used for this class <^* 
work. A Hp c on I 
circumference fits 1 





19 



DRILLING AND BORING. 



LB 



mgc ami holds the jig central. When in the desired posi- 
m, a clamp is applied to keep the jig in place while the 
illing is being done. When the holes are equally spaced 
i the same circle, and the adjoining flange or head is of 
e same diameter, it may be drilled with the same jig, 
us insuring a continuous hgle when the two parts are put 
igether. 

28. JlK for Drilling Flange* Wltb Irregularly 

paced Holes. — When the holes are not regularly spaced, 

is evident that they 
innot he drilled by 
irning the jig over, as 
IggeStAd in Art. 27; 
onsequently, it is 
ecessary to make the 
g with a lip on each 
de and with bushings 
;t in, as shown in ""' ™" 

ig. 14, so that each side of the jig will fit one of the 
Ijacent flanges. It is evident that when the flange a is 



1 


1 


i 


1 1 1 i . i 1 1 i 


;lE 


b' 


nn 


1 i ■ 






JJ 




rilled with the side a' of the jig against it, and the flange b 



DRILLING AND BORING. 



|U 



willi the side //' against it, l lie holes in [be two flanges till 
meet perfectly, however irregularly thej i 

29. Example of Drilling With Jlr- 

mfiuntcil on a drilling-machine table, a jig for drilling the 
hub and hub plate of a locomotive wheel, in which 
are not regularly spared. The plate a is supported on par- 
allels b resting on the table c. The jig </ has a Up 
side, to fit the bores of both the plate and the w \u 
Bet-in bushings are shown at g. A single clamp /"holds both 
jig and plate in place. 

30. Outside and Inside Jig-— Fig. 10 (a) ih 
used in drilling two parts, one of which has a pray 
which must fit into a bored hole b on the other. The jig it 



_LU 



\MT 







II 1 r- 






') B - 


15 ' 



= 



made with a counterbore c on one side, which «rfD 
projection a, and a projection don the Othi 
bore b. This same arrangemenl may at used In drilling 
parts of different sizes, as, for instance, a manhole and its 
cover, as shown in Fig. 10 (/>). 

• II- Jlg» for Irregular Surfaces. — The ji 

thus far are intended fur circular pieces, but the principle 
in v ilvcd may be applied to pieces of any form, wit 
regular or irregular surfaces. Fig. 17 shows a right-hand 
and left-hand jig used in drilling parts of the s&dd 
vertical boring mill. One of the pieces is shown at ■», ; 
number of them are piled up ;it b. Two of these pie 



j 13 



DRILLING AND BORING. 



15 



one a right-hand c and one a left-hand d — are bolted on 
the floor plate of a radial drill, with the jigs in place ready 
for drilling. All the holes in the two pieces are drilled 
without moving either piece. The upper surface of the 




Fio i 



saddle being uneven, several holes are required on the level e, 
and others on the level f. The illustration shows how the 
jig is formed to fit the uneven surfaces. 

For holes that are to he reamed, two bushings art pm- 
vided, one for the drill and the other for the reamer. The 
drilling hushing is made smaller than that for the reamer, 
the difference in their diameters being equal to the allow- 
ance for reaming. 



nORING FIXTURES. 

32. Fixture for Boring Duplex Pump Cylinders. 
Fig. 18 shows a fixture that produces practically the same 
result as a jig. Although it does not form a positive 
for the boring tool, it so holds the work as to properly locate 
the holes. It is a device for holding a pair of pump cylin- 
ders while they are being bored in a double-head machine, 
which is also double-ended, boring the four cylinders at the 
same time. The cutters at the two cuds of the machine 



u 



DRILLING AND BORING. 



(11 



rotate in opposite directions, thus lessening the V. n 
move. In Fig. 18 a shows the device empty, while b shows 
a pair of cylinders mounted in the machine. Tin: i 
rest on a pair of cross-ban e, e supported cm four adjusting 
The end adjustment, is made by means of a screw 4 
at each end, only one of which is seen, while the side adjust- 
ment is made by means of the four screws r, e, e, e. Thr 
fixture is set on the table, as shown, the two tongues// 




fitting into corresponding slots, to prevent any slipping and 
to insure perfect alinement on the table. The fi) 
clamped on the table by means of the bolts . 
cylinders are in place, and the adjusting screws are set ne 
tightly, the cylinders are held securely by meai 
'lamps h, h. The illustration shows a roughing cutter r 
just entering the cylinder and a pair of finishing cutters /y 
lying on the top of the machine. 

33. Special Borlos Fixture. — Fig. 19 illustrates a 

special fixture for boring the connecting-rod-pin b 



gas-engine pisto 



is lit 1,1 between the 



/-shaped castings b and it. The one castings is bolted firmly 



§ 13 



DRILLING AND BORING. 



17 



against the side of the rest, as shown, while the other cast- 
ing b is loose. The piston is placed between the V's, as 
shown, and when set in its correct position, b is drawn up 
against it by the two end bolts </, and the clamping bolts e 
are tightened. The boring bar/" is then passed through the 




Fig. 19. 

V's and the piston, and the holes are bored in the usual way. 
This arrangement insures a hole that is perfectly central 
and square with the piston. For larger pistons, a single V 
is used in a larger lathe, the piston being simply clamped 
against it. A fixture like this can be employed on either a 
lathe or a boring mill. 



DRILLING AND BORING LOCOMOTIVE CONNECTING-RODS. 

34. In drilling and boring the ends of locomotive con- 
necting-rods and similar work, a machine with two heads 
supported on a common cross-rail, so that the spindles may 
be set at any position along the cross-rail, is frequently 
employed. 

Fig. 20 shows the table of such a machine with a connect- 
ing-rod a fastened upon it. In the illustration, the one spin- 
dle is fitted with a drill b to form a guide hole for the pin f 
of the annular cutter, while the other spindle is equipped 
with an annular cutter c, as described in Art. 3*J, Drilling 
and Boring, Part 1, with two tools e, e to remove the body of 



18 DRILLING AND 


BORING. i a 


the metal from the boie, the 


hole having previously been 


formed for the center pin/ 


The hole formed by 






lar cutter is finished 






with the reamer d, 






which 






sertcd-tooth type. 




The holes in Um 


— » IkM 




reamer are made 


1 




simply ti>reduce the 
weight. The piece 
is held on the table 
by mttUI 
clamps ,f and h, the 
end i being laid fiat 
<>n the ntrfai 

the end/resting on 


Hi ||\ \ 


1 


,\ parallel 1-, which 

is equal in tfaii 
j to the verti. 
^ tance between tbt 


U TO 


\| 


11 111 


\ 


£ two lower (". 


H \ 


v 


3S. C i . 


ffr] |1 1 


\! 


parallels / of differ- 


- _ fjf^flr 


I 


ent thickness 
often ttw d ■ 


___Jgcy 


' \ \ 


ing up the ends at 
the rod, cai i 


IWrl/-, 


1 


of rod having it> 

1 OWU : ■ . 

I The inside diameter 
of the parallel is 


1 




somewhat greater 
\ than : 

1 lie 

bole in the rod, in 

order that the sap- 


port may not be affected when 


the 


block of metal is removed. 



I 12 



DRILLING AND BORING. 



IS 



FIXTURES FOR SUPPORTING \M> ROTATING WORK. 

36. V Supports. — Fig. 21 shows a very useful device 
for drilling cylinders. Two pedestals a of a suitable height 
are placed on the base of the drilling machine at a sufficient 
distance apart to accommodate the work to be drilled. Two 
V-shaped bearings b are placed on the pedestals, and are so 
lined up that the center of a shaft lying on them will lie in 




the center lines of the drill spindles. The drills will, there- 
fore, always drill radial holes in a cylinder whose shaft rests 
on these V's and it is necessary simply to lay out the holes, 
drop the cylinder with its shaft in place, adjust the drill 
spindles to the right distance apart, and drill in circles 
about the cylinder, as indicated by the rows of holes shown. 



20 



DRILLING AND BORING. 



8« 



the cylinder being turned on the V's until each 

set of holes comes under the drills. The cylinder I* kept 

from working endwise by the bar <, which is set against ihv 

hub and clamped to the pedestal. The cylinder 

this illustration is a crushing roll for anthracite coal 

When the holes are drilled, they must be reamed ] 

teeth are inserted. 

37. Holler Supports. — Fig. 22 illustrates a roll set up 
ready for reaming in a radial drill. It is supported on foot 
rollers a, held in two frames d, d, one at each end of the roll. 
The first row of holes is adjusted vertically above the aiis 




of the roll by means of a surface gauge, with which a set at 
holes on opposite sides of the center are brought an equal 
distance from the floor. When this; adjustment has been 
made, a pin b is inserted in a hole about the height of the 
center line, and a block c is so fitted I hat the pin i e 



DRILLING AND BORING. 



21 



$ia 

This acts as a stop to prevent the roll from turning. When 
one row of holes is reamed, the pin is moved down one row 
and then brought up by turning the roll until it again rests 
on the block, thus furnishing a very simple means for 
adjusting each successive row. 

38. Heavy Center*. — Fig. 23 shows a very good device 
for holding heavy parts with circular ends, such as pump 
chambers, under a radial drill. Two uprights «, a, with 
two cones b, b, provided with roller bearings, support the 
work, the cones entering the ends of the work, as shown. A 
rod t [iassing through the center of the cones and the cast- 
ing keeps the uprights from spreading. The piece is set in 
the correct position for drilling one set of flanges, the tie- 
rod c is tightened, and all the holes in this plane are then 




Fig. ml 

drilled. The rod is then loosened slightly, and the piece 
turned until another set of holes comes into position, whenc 
is again tightened, and the drilling on this face is performed. 
This operation is repeated until all the holes are drilled. 
The rollers in the hub d reduce the friction of the bearings 
so that heavy pieces may be turned with comparative ease. 
When any regular series of spaces is required, a special 
ndex may be attached at one end, to facilitate the setting. 



DRILLING AND BORING. §13 

39. Double Face Plate. — A double face plate, for the 

purpose of supporting work that has faced circular flanges 
with regularly spaced bolt 
holes, is shown in Fig. 24. 
Two face plates a and b 
are supported by means of 
1 a bearing on each side of 
the bracket c, which may- 
be clamped on the floor 
plate of a drilling machine. 
The flanged piece </, which 
is to be drilled and faced 
e,f, and g, and at corre- 
sponding points opposite e 
and f, is attached to the 
face plate by means of 
three arms ft, bolted to the plate by bolts i, and to the 
flanges by bolts j. 

The face plates are rotated to the right position for drilling, 
where they are held in place by the latch k, which enters 
notches in the plates. By placing notches at proper points, 
holes may be drilled at any angle. In the piece shown, the 
holes are drilled at right angles to each other, and the face 
plates are held in position by the notches at k and /. The 
plates are rotated by means of bars inserted in a series of 
holes m, n, o, etc. about the circumference. 




40. The illustration shows only one piece attached to 
the plate a. In doing work, ordinarily, another piece is 
attached to the plate b, thereby balancing the device so as 
to prevent springing the bracket c, or cramping while turn- 
ing to a new position. This also permits twice as many 
holes to be drilled without moving the face plate as when 
only one piece is attached, while the service of the power 
crane is required only one-half as often. 

The face plates may be made to take pieces of various 
sizes by moving the arms ft to suitable positions. A series of 
holes r for the bolts i are provided in the face plates shown, 



5 12 



DRILLING AND BORING. 



23 



j accommodate pieces of different sizes. A large variety 
f work may be supported in this way by means of suitable 
A key s under each arm, which fits into a corre- 
sponding keyway, as shown at t, together with the bolt i, 
locates the arm positively. When the piece is enough out 
of balance to prevent turning it, counterweights may be 
attached to the face plates, as in balancing work in the lathe. 



41. Trunnion Supports Fig. 25 shows a fixture of 

this class fo* drilling duplex pump cylinders. The cylinders 
, b are held by means of two plates e, which, on one side, 
,ave projections entering the ends of the cylinders, and, on 
he other side, trunnions d, which rest on V's on the 




uprights e, e of the frame of the fixture, Bolts f,f hold 
the plates c in place and form guides for the jig g, by 
nie;tns of which holes are drilled in the hubs // and i. When 
the Suture is in position for drilling, the trunnions are fast- 
ened by means of the clamps n. 

The illustration shows the bushing j and the drill k in 
lace, ready to drill the hole. The hub (" is supported on the 



24 



DRILLING AND BORING. 



g 12 



lower side by a piece of pipe /. When both the hubs A and i 
are drilled, the jig,? is moved away from the hubs in the 
direction of the arrow**//, and the ends of the hubs are faced 
by means of a double-end cutter. The clamp « is then 
loosened and the cylinders turned on the trunnions d to the 
next position to be drilled. The four holes o, o, o t o are 
drilled by means of the jig />, which is lying on the floor, 
while the four holes q, q, q, q are drilled with the jig s 
attached as shown. These cylinders have holes to be drilled 
on four sides, and must be set in as many positions, When 
the piece is once set up for one position, it is a simple 
matter to move it to any of the other positions. Screw 
jacks r are used in adjusting and holding the work, 
piece may be set in position by means of a square or level. 



MISCELLANEOUS TOOLS AND FIXTURES. 



TREPANNING DRILL. 

42. Fig. 26 illustrates a special hollow drill designed (o 
the purpose of removing test bars from a solid piece. Th 
drill is run into the metal as far as the central core wil 
permit, when it is withdrawn and, at a point that will cut ol 
the core at the bottom, a hole is drilled at right angles to i 




Pic M. 

with an ordinary twist drill. The core is then taken nut am 
turned up to the proper dimensions for testing purposes. 
The point a of this form of trepanning; drill can easily be- 
removed from time to lime, at small expense. It is made 
hardened steel and is screwed to a soft-steel body b. 



is made of 



DRILLING AND BORING, 



25 



HlllltlMJ TOOL. 

43. A very useful hubblng tool is shown in Fig. 27. 
A hub a of the piece h is lo be finished as shown at c. The 
tool with which this is done consists of a center har d, which 
fits the bore of the hub, and a tool e supported on the arm/! 




As the tool is rotated about the center of the pin, it cuts a 
perfect circle. The device is attached to the spindley'of a 
heavy drilling machine, the work being fastened upon the 
table. The radius at which the tool cuts is regulated by the 
adjusting screw g and a clamp /' f. 



SPECIAL BXTBHfl 



44. On a boring mill it is necessary at times to 
urn work that is larger in diameter than the bori ng-mill 
table. Fig. 18, Drilling and Boring, Part 8, shows how 
uch a piece may Lie carried by means of extension arms. 



86 



DRILLING AND BORING. 



§1! 



There are, however, cases where the extension arms must 
project so far beyond the edge of the table, and where the 
weight is concentrated so near the end, that additional sn[>. 
port is needed to firevent objectionable springing. Fig, if 




suggestsa means of providing such support when the center 
of the piece is open, .is in t he case shown. The tabled oi 
the boring mill is of the ordinary type, with radial slot 



I IS DRILLING AND BORING. 27 

The extension arms b are bolted to the table in the ordinary 
At the center of the table a pillar c, with a flanged 
tot that is bolted to the table, furnishes the upper support 
'ox diagonal tie-rods d whose lower ends are bolted to the 
irms, thus forming an additional support. Tnrnbuckles t 
i the tie-rods permit the arms to be adjusted approxi- 
tately level, after which a light surface cut may be taken 
a true them up perfectly. The piece may then be fastened 
any convenient way that its shape will permit, and 
turned up. 

This is a comparatively inexpensive and very efficient shop 
expedient, which, however, may or may not be a means of 
:conomy, depending on the number of pieces for which it 
:an be used and the cost of having the work done in a shop 
quipped for it. Shop expedients are frequently resorted to 
when the work could have been done outside more cheaply. 
Ireat caution should be exercised in the construction of 
ihop expedients, in order that true economy may be 
practiced. 



FIXTUBF.S FOR TURNING SPHERICAL SURFACE. 

45. A special fixture for turning a spherical surface on 
a vertical boring mill is shown in Fig. 28, an ordinary verti- 
■ ,il baring mill being used. The machine has two saddles. 
One of them a has bolted to it a bracket c, which carries a 
pin d, around which swings the link t. The saddle is so 
clamped to the cross-rail that the point d lies in a vertical 
line forming the axis of rotation of the table. The other 
saddle b is detached from the cross-feed screw in the cross- 
rail, and is free to move. A bracket f, having a roller on 
each end that bears on the cross-rail, is attached to the 
saddle so as to carry its weight, thus reducing the friction 
urn] providing a free motion along the rail. The boring 
bar g has an arm // attached near its upper end, which car- 
ries the fulcrum I of the link f. The link e continues to a 
pointy, where a vertical link k is pivoted. At the lower end, 
k cafces hold of the lever / at m. The iever / is pivoted at « 




table is rotated and the boring bar is fed down. In < 
to accomplish this, the length of the link *and the ver 
distance between the pivots /and « must both be equ 
the vertical distance between the center of the sphere I 
turned and the pivot rf; the distance if i must be equi 
the distance from Ihe center of the sphere to the piv 



} U DRILLING AND BORING. 39 

iat is, the sum of ihe radius of the sphere and the distance 
: the tool point from its pivot «, and the distance ij must 
e equal to the distance « m. 

As the bar g is fed up, the saddle b will travel toward 
the center when turning the upper half of the sphere, in 
order to permit the point i to swing about its center d, 
and the point n travels in an arc of the same radius about 
the center of the sphere. As the bar g moves down from 
the center of the sphere q, the saddle b will again travel 
toward the center of rotation. 

It is obvious that if the distance d i is made equal to the 
sum of the required radius of the sphere and the distance 
from the tool point to the pivot «, the tool will form a per- 
fect sphere of the required radius. It is evident, too, that 
the center line of the link « m will always point to the 
center of the sphere, and the tool will cut at the same point, 
as it travels along. In this work, a narrow, round-nosed tool 
is used with a comparatively light feed, so as to insure a 
smooth surface. 



TABLES. 

47. The following tables are reprinted from the publi- 
cations of the manufacturers whose names appear at the 
head of each. 

Tables I and II give actual dimensions of Morse tapers 
and taper shanks. Table I gives dimensions relating to the 
taper of the shank and the thickness of the tang. In 
Table II, Figs, (a) and (b) refer to the taper of the socket 
alone, while (c) and (d) refer to the shank, the tang, the 
slot, and the key, Dimension Cot Table I must not be 
confused with d of Table II; C, Table I, is to be used in 
forming the taper only, while d is the width of the par- 
allel end of the tang, which is somewhat smaller than the 
small end of the taper. 

Table III deals with the speed of drills of sizes ranging 
■fr inch to % inches in diameter, working in wft 
;ecl, iron, and brass. It will be observed that the 



DRILLING AND BORING. 



IB 



recommended for iron is somewhat higher, ami 
for brass about twice as high, as thai Eo* BOl 

The data preceding Tabic III has reference to t ' 
drills and the necessity of using lubricants when d 
steel and wrought and malleable iron. 

Table IV shows the number of revolutions iw 
give a cutting speed of a certain number of feet per oiinuic 
for drills of various diameters. This table is applicable to 
any tool traveling along a circular path. 

Tables V and VI give the diameters of drills for taps cf 
different diameters for V, U. S. Standard, Whitworth, and 
pipe threads. 

The decimal equivalents of the numbers of tho \ 
tad Bta l-wlrc gauge are given in Table VI oi \fiasnring 
[nstrumtnts. 



TABLE 1 



MOUHF. TAI'KR SHARKS. 

' Twist Drill ami M<tfkint Ci'mfiaity.) 





















No. 


A 


B 




D 


E 


12 Indie* 


1 


*A 


H 


:;■..' 




li 


.600 


a 


»A 


n 


set 


.TOO 


I 


,60« 


3 


SJ 


■■',". 


.7M 


.1438 


:, 


.60S 


4 


H 


I! 


m 


1 341 


it 


.02.1 


5 


6 


5! 


i 44-; 


1.748 


« 


.630 


6 


8A 


s 


a. or? 


a. ti'i 


s 


.626 



DRILLING AND BORING. 



1 ^ — * — ;#. 




r i vi i 




iU_ZZjAi 


^ 


q U a- —J 


^ r™™™™B 


b 



jo laquuiN 




H..HI.. 


-i|3U[ jad jsdej. 




B333S1 


'inoj jad .ladHj, 




ggwncs 


Hldaa ^ueqg 


> 


ss£ra„ 


■ 


■= 


■O OOHrXW 


.>n8uox JOJ 
H!H )°«<!P»H 


•<: 


.*«««... 


■aiiSuoj, 

jnesjujioiqx 


; 


S—ea— 


■anSuoj, 
jo j.ii.iuiEiri 


s=~aa. 


anSmy, 
fo quills'] 


k 


-=«- r— - - 




'- 


" : . ' ' ' ' 1 a 


jn i|i3u3T 


s 






■< 


^-~st.- 


■BiOM 

jo mrfaa 


5; 


*»««» 


quvqS !■■' 


"5 


«*-„ J 


■qidsa 

8n[,i pjEpuEis 


•V 


? ,- h ;<-c«c^. 


■JMpog j<i 

|,u : .I |* iu«r,[ 


- 




■pug i[t;ius »B 
8"H 3" 'u^'n 




'-'■"" '''.I, 

JO J- pi [ill II [J 




h ........ 



_ 



DRILLING AND BORING. 






T mili: III. 



the speed juhd ki:i;i> of nun-LS. 
Drill Company.} 

This tabic haa been compUed from memoranda furnish*,: 

request, by about 500 of the best known and most successful minn- 
'ii this o.untry- We believe that these speeds aha 

^.ri .-.j/i-i/ inn l-.-r unliiiiiry circumstances. A feed o( 1 iiiL'h ba I 

Itt revolul lould ba required according to 

the drill. At these speeds it will be neicssary to use plenp- 

a solution of oil, potash, and water, when drilling steel, wrought. <n 

malleable In 

It is based on a speed of periphery <>f the drill dI 1V> Ui< r pi 
for steel, H tor Iron, and SO feet per mbraU 

It will be found advisable to vary the speed given In the b 
uii.ii. ai cording as the material to be drilled is more or It*- i 





Speed 


Speed 


■ 


Hi.lini'lrf 


Speed 




,>r 


!,„ Suit 


for 


[01 


of 


for Soft 




... 


Drill. 


Steel 


Iron 


Brass. 


Prill. 


■ 


Iron 


Bran. 


A 


1,834 


J,I'!S 


i.cis 


li'r 


[08 


i M 


■ 


i 


9 1 S 


1,064 [,834 


H 


[09 


UK 


. 


A 


>:< is 




1A 


n 


1 |i) 




i 


i/.i. 


,-.;:■; 


sua 


n 


m 


106 


181 


A 


SOS 


435 


780 


iA 


a: 


101 


174 


1 


SM 


355 


606 


is 


k:i 






A 


860 


804 




iA 


SI. 


■ 


1 


r;s 


360 


156 


il 


76 


■ 


A 


303 


336 


4l>, f . 


'A 


. 




1 


18S 


■.'i:; 


:;,;;, 


i| 


70 




11 


im; 


I'.M 


939 


1H 


68 


rfl 


i 


IJ53 


177 


304 


'1 


0.i 




U 


M» 


[64 S80 


Mi 


63 




I 


ISO 


■ 


■s 


60 


71 ia 


H 


i-;j 


1 49 24.1 


Ml 


V.I 




i 


114 


I :;:i J»fi 


■i 


■ 





voltttluH pern 









TABLE IV. 












CUTTING SPEEDS. 










(Fr 


«m fieaman &• Smith.) 






a&c 


5 1 lO 


» 


20 1 25 1 30 


35 1 -lO 


- 


SO 


DJ_ 


Revolutluns per Minnie 


1 


18 '-' 


16.4 


114.6 


169 9 


191.1 


199 :l 


267.5 303.7 


344.0 


889 2 


t 


3n. tl 


01.9 


ui s 


122.5 


IBS.] 


188 7 


814.8 214 1) 


275.5 


:w, i 


| 


■-'■1.4 


r.n.M 


7H .:} 


mi. t 




1 62 . .' 


178.0 808.4 


888 a 


254.2 


! 


8i a 


i:; B 


(15 r, 


81 ;; 


urn I 


130.9 


152.71 174.5 


l'.Mi :l 


916 ;i 


19.1 


;w.a 


57,3 


76.4 


1)5 5 


114.6 


188.8 158.9 


172.D 


191.1 


1* 


17.0 


B4 


51.0 


us. .I 


«.-, (1 


1H2.II 


119.0 


l:lil ii 


198 


170,0 


l| 


15.:) 


341.6 


IB 8 


61 - 


78, S 


III S 


toe ii 


122.5 


137 4 


153.1 


!! 


18.9 


27.8 


41.7 


55.6 


60.5 


63.3 


97,2 


111.1 


125 U 


138.9 


12.7 


25.4 


be i 


5i t. s 


63 7 


76,8 




101.7 


114.6 


127.1 


I| 


11.8 


23.5 


35.0 


17 il 


58.8 


70.5 


M,2 


98.9 


105.7 


117.4 


It 


10.9 


81.6 


89,7 


46.6 


515 


66.6 


76.4 


B7.8 


98.2 


109.1 


1 


10.9 


20.4 


80.6 


■m.7 


50.9 


81.1 


71 a 


81.5 


91.9 


101. 9 


2 


9.6 


16 i 


2* 7 




47.8 


57.3 


66 9 


7(1 1 


86.0 


95.5 


2* 


8 .1 


17.i> 


25,4 


34 J) 


■12.1 


51.0 


59.4 


m.o 


76.9 


66 ii 


2* 


7.6 




22.8 


80.6 


38,9 


45.8 


53.5 


81.2 


68.8 


70.3 


M 


S.9 


139 


■>,].* 


BT.8 


34 7 


41.7 


48 6 


68.6 


02.5 


69.5 


? 


6.4 


12 7 


19.1 


25.5 


Bi a 


88.2 


44 6 


51 11 


57.3 


63.7 


»t 


B.6 


111.!) 


16.4 


21.8 


27 3 




88.S 


43 .6 


49.1 


54.5 


4 


4.6 


9.8 


14.3 


19.1 


23.9 


28^7 




B8.9 


43 I) 


47.8 


4* 


4.9 


8.5 


12.7 


16.8 


21.2 


25 I 


w.a 


M B 




42 4 





8.8 


7.6 


11.5 


15.3 


19.1 




26.7 


30.6 


ill 1 


B8.S 


Si 


8.5 


6.9 


10.4 


18.9 


17 1 


2D a 


24.3 


27.8 


31.3 


34.7 


6 


B.9 


8,4 


0.6 


12.7 


16.9 


19.1 


.... ... 






31.8 


? 


■! 7 


5.5 


8.1 


in '..• 


13 


16 4 


10 1 


81.8 


24.6 


27.3 


8 


2.4 


4.8 


7.9 


9.6 


11.0 


14 3 


16 7 


19.1 


31.1 


93. 8 


9 


2.1 


4.9 


6.4 


8.5 


in ii 


12 7 


14.8 


17.0 


71' 1 


21.2 


10 


1.9 


:■;.-< 


5.7 


7.11 


:i i; 


11.0 


13.4 


15.3 


17,9 


19.1 


11 


i ; 


a s 


5 2 


6.9 


6.1 


10.4 


18.9 


13.9 


15.8 


17 4 


19 


1.6 


8.2 


■I B 


6.4 


3.0 


9.6 


11. 1 


12.7 


14.8 


15.9 


13 


1.5 


2.0 


4 -1 


5.0 


7.3 




10.9 


11.8 


I8.S 


14.7 


14 


1.4 


8.7 


4.1 


5.5 


6.6 


M.I 


(i ii 


10.9 


12.8 


13 6 


IS 


1.8 


2.6 


3 8 


B.I 


6.4 


7.(1 


S.9 


10.2 


11 5 


18.7 


18 


1,9 


2.4 


B.a 


4,8 


ii 


: 2 


B.4 


9.6 


Hi .7 


11.9 


17 


1 1 


2 1 


3.4 


4,6 


5,6 


6 7 


7.9 


9.0 


10.1 


11.2 


18 


1.1 


2.1 


3.2 


4,2 


5.3 


6.4 


7.4 


B.G 


9.8 


10.6 


19 


1.0 


2.0 


8,0 


4.0 


5,0 


6.0 


7.0 


8.0 


9.1 


10.1 


20 


1.0 


1.9 


2.9 


8.8 


48 


5 7 


6 7 


7,6 


B.6 


9.0 


SI 


M 


1.8 


S . 1 


B.6 


4.5 


5 


6.4 


7.3 


8.1 


9.1 


S3 


.9 


1.7 


2 6 


8.5 


4.8 


5.2 


8.1 


0,9 


1.8 


8.7 


u 


.8 


1 7 


2.5 




4 1 


5.0 


5.8 


6.6 


7.5 


8.3 


34 


.a 


1 11 


2.-1 


B.2 




4.8 


6.6 


6.4 


7,2 


a n 


20 


.8 


1 s 


! 8 


3.1 


s!s 


4.8 


5 8 


6.1 


6.9 


7.6 


H 


.■; 


1.5 


9,9 


1 9 


B.I 


4 4 


5.1 


5 Ii 


ii.ii 


7,8 


27 


.-: 


1.4 


9.1 


2.* 


8.0 


•1 2 


5.0 


5 7 


B.4 


7.1 


28 


: 


14 


3 


9 ) 


8.4 


4.1 


4.8 


5.5 


ii 1 


6 8 


29 


.7 


1.8 


9.0 


•1 •'. 


3.:i 


4.0 


4.8 


5.2. 


5.1) 


6 


30 


.8 


1 :: 


l.fl 


3.5 


8.2 


3.8 


4 5 


5 1 


5 7 


6,4 




















T1B-M 



TABLE V. 



TAP 1 

{From New Process Twist Drill Company.) 
The following table shows the different sizes of drills 
be mad When J lull thread is to be tapped. The siies give 
ticallj correct. 



% 



11 13 

10 11 13 

in ii ia 



I \ 



1* 



II 1 



12 



DRILLING AND BORING. 



35 



TABLE VI. 



TWIST DRILLS FOR PIPE TAPS. 

(First three columns from Standard Tool Company.) 

The sizes of twist drills to be used in boring holes to be 
re 3med with pipe reamer and threaded with pipe tap are 
as f ollo W s: 



Size. 
**iches. 



Number of 

Threads 

Per Inch. 



i 


27 


i 


18 


I 


18 


i 


14 


} 


14 


1 


11* 


u 


Hi 


1* 


1H 


2 


11* 


H 


8 


3 


8 


3* 


8 


4 


8 



Size of Drill. 



.3281 
.4531 
.5937 

.7187 
.0375 
1.1875 
1.4687 
1.7187 
2.1875 
2.6875 
3.3125 
3.8125 
4.3125 



Size of Drill In 
Nearest ^ Inch. 



H 
H 

tt 

52 
H 
ift 
HI 
iff 
aft 

3ft 

m 

4ft 



OTE. — A drill jff inch larger than the size given in the table is 
etimes used when one 6i the given size is not available. 



RECENT TESTS OF TWIST DRILLS. 

**48. Bickford Experimental Feeds and Speeds. 

: has recently been shown by experiments made by the 
1 ckford Drill Company that with drilling machines of very 
-iff design, heavier feeds may be used than have heretofore 
^«n used in ordinary practice, and that the breaking of 



M 



DRILLING AND BORING. 



81 



drills has been due largely to the spring of the drilling 
machine. 

It must not be inferred, however, that these experimental 
feeds can be used in ordinary machines, as t-xn 
stiffness in the horizontal arm and vertical aai 
■ required to use them successfully. Even with such macbloa 
it may not be wise to use them in ordinary practice, and it 
is probable that slightly lighter feeds may be e:-.: 
for general use with machines of strong design. 

The results of these experiments are given below, as they 
will Ntggvtt approximately the feeds that can safely be 
taken in machine tools of great rigidity. Many 41 
tested to destruction in ordinary cast iron, and some tests 
were made in machinery steel with larger drills but very 
few broke. In one case a 1/g-inch drill turned a shaving 
of machinery steel ^ r inch in thickness and stopped the 
machine, but the drill did not break. 

Table VII gives the feeds used in ordinary cast iron 
without the least injury to the drills. These feeds are 
almost four times as great as those generally advocated at 
the present time. 

Table VIII gives the feeds at which the drills broke. 

Table IX gives the speeds at which the drills were run. 



TABLE VII. 



fto* 
. 1 to 1( 



§12 



DRILLING AND BORING. 



37 



TABLE VIIL 



PBBDS AT WHICH THE DRILLS BROKE IN ORDINARY 

CAST IRON. 





Feed Per Revo- 




Feed Per Revo- 


Size of Drill. 


lution at Which 


Size of Drill. 


lution at Which 


Inch. 


Drill Broke. 


Inch. 


Drill Broke. 




Inch. 




Inch. 


A 


.007 


A 


.035 


A 


.010 


i 


.047 


I 


.014 


A 


.064 


A 


.020 







TABLE IX. 



THE SPEEDS AT WHICH THE DRILLS WERE RUN. 





Revo- 


Cutting 




Revo- 


Cutting 


Size of 


lutions 


Speed Feed 


Size of 


lutions 


Speed Feed 


Drill. 


Per 


Per 


Drill. 


Per 


Per 




Minute. 


Minute. 




Minute. 


Minute. 


i 


267 


35 


1* 


61 


28 


i 


222 


36 


2 


51 


26 


i 


184 


36 


n 


42 


25 


I 


153 


35 


H 


35 


23 


1 


128 


33 


H 


29 


21 


n 


106 


31 


3 


24 


19 


H 


88 


29 


H 


20 


17 


i* 


73 


28 


H 


17 


15 



JNG-MACHINE WORK. 

(PART 1.) 

INTRODUCTION. 

DEFINITIONS. 

1. Milling may be defined as the process of removing 
uetal by a cutting tool that is rotated about its own axis 
and has one or more cutting edges that are successively 
irougbt against the work. Any machine in which this 
s is performed is called a milling machine. 
Milling machines are made in a great variety of forms to 
ult different conditions and requirements; they are given 
special names in accordance with the class of service for 
which they are intended, and also in accordance with their 
:sign. 



CLASSIFICATION OF MILLING OPERATIONS, 

2. The cutting operations grouped under the general 
term oi "milling "are plain milting, side nulling, angular 
milling, grooving, form milling, profiling, and routing. 

The first threi- operations named are performed on, and 
result in the production of, plane surfaces; curved or irreg- 
ular surfaces an- produced by the last three uperations. 

H. Plain millliitr may be denned as the performing of 
ilie cutting operation mi a plane surface that is parallel to 
he axis of rotation of the cutting tool. 
§13 



a MILLING-MACHINE WORK. & 13 

1. suit milling is always understood i" mean that tkc 
catting operation is performed on a plane surfac 
ptrfendicular to the ;isi^ of rotation of the cutting tooL 

S. Anirniiir mill inn invariably refers to tin 
ing of plana surfaces ai an inclination to the axis ■ ■ 

0l Hi.' CUtt : 

tt. Groo*lAC i" a certain sen 
term thai refers to the cutting of grooves 
may have any profile and follow .1 

irregular path. 

7. Form milling is a 1 lass of milling in which 1 
surfaces operated on are nol plane, I mi which hai 1 
profile throughout the direction in which ; 
against the cutter. This is rnoal horizontal 

diroctton, but may occasionally be 1 veftic 



■ 



S. I'r.iniliui is usually understood to be n 
operation In which the woi k is guided in ■ 
path by .i templet having .1 suitabh 

W. Routing is a 111 opcraiii 

in which iln- work is presented to the '-ut tc-r and 1 
guided by hand, whence n follows that the result dcp< 
entirely on the skill of the operator 

1 0. The defi 1 

a lani c « h h 1 he mosi 

in, mi ill; .!■■■ epted agr< 1 meni 1 

hi' expected thai some people will use the terms in a ilif 

on sense. 



CLASSIFICATION ill MILLING MltlMMs, 

11. Milling machines ma) ' - classifieds 
'. nmUispindlt, and sptcioL 

12. Plain mllHiin nine ti Iocs ari 

finishing of surfaces that inquire the motion of the work 
be in a straight line during the culling ope 




MILLING-MACHINE WORK. 



J 



i arranged that the work can be fed to the cutting 
>ol, or vice versa, in a vertical direction, and also in two 
•rizontal directions at right angles to each other. The 
3 of rotation of the cutting tool is normally horizontal. 

13. Vertical milling machine** derive their name 
om the fact that the axis of rotation of the cutting tool is 
ertical. They are usually so arranged that the cutting 
iol can be fed toward or away from the work in a vertical 

direction, white the work can be fed to the cutting tool in 
two horizontal directions at right angles to each other. In 
some cases the machine is so arranged that the work can be 
revolved in a horizontal plane for the purpose of finishing 
circular surfaces. 

14. Universal milling machines are so called by 
virtue of the fact that the numerous attachments furnished 
with them adapt these machines to a very wide range of 
work; they can be used for almost every conceivable mill- 
ing operation within the capacity of the machine. The 

of rotation of the cutting tool is usually horizontal; 
t work can be fed to the cutting tool in a vertical direc- 
i, and also in two horizontal directions ; the angle between 
he latter can be changed within the limits imposed by the 
iesign of the machine. By means of special devices the 
work can be rotated at the same time that it is moved 
longitudinally in a horizontal direction; this adapts the 
lachine for the production of helical and spiral work. The 
work can also be rotated in these machines through a 
definite part of a revolution for each individual cutting 
operation. 

The special devices fitted to a universal milling machine 
may also be applied to a plain or a vertical milling machine, 
which are thus to some extent converted into universal 
milling machines. They will rarely have as wide a range of 

pplication, however, as a machine especially designed to he . 
i universal milling m 

15> Multlsplndle milling machines, as implied 
the name, are fitted with two or more spindles that 



4 MILLING-MACHINB WORK- 1 13 

carry the cutting tools. Each spindle, and hence each cut- 
ting tool, is usually made to be independently ad 
relation to the work. In most machines of this class, tin 
work can be moved in a straight line in one dire : 
Multispindlc milting machines are intended for 
several surfaces simultaneously, and are usually employed 
for heavy work only. 

16. Special milling machines may take any con- 
ceivable form that will adapt them for the class of work for 
which they arc designed, but no matter in what mannet 
they are constructed, the principles of operation will be the 
same as those of any regular milling machines. 



CONSTRUCTION OF MACHINE. 






ESSENTIAL PARTS. 

17. A milling machine consists of certain essential 
parts, which in some form or mher must exist in any of iti 
numerous niodifu'.iii mi is. The essi ntial parts are the /raw, 
the spindle, tin; table, the fced-mtchanism, and the cutting 
tool. The function of the frame 

spindle, table, ind feed-mechanism, The spindle, which by 
suitable means is revolved in bearings provided for it in ihc 
frame, carries the cutting tool. The function <>i 
is to serveas a support for the work, win. h 
either directly to the table or to holding de 
it. The feed-mechanism serves to move the work 
cutting tool; it may operate directly upon lh.: 
upon the spindle, or upon both. The function of the 
ting tool is self-explanatory. 






CONSTRUCT lOM. 

18. The universal milling machine is the most advanced 
form for general work, ami i mlimlies all rhc features found 
in other types. For this reason it is here selected and 



813 MILLING-MACHINE WORK. 



described. As far as the universal machines of various 
lakes are concerned, their general arrangement is similar 




. that of the machine illustrated in Fig. 1 ; they differ only 
n the design of the details, which are modified in accordance 



MILLING-MACHINE WORK. 



with the personal experience anil judgment of their respect' 
ive designers. 

19. Referring to the figure, it is seen that the gener^* 
form of the frame a is that of a column or pillar. Th* s 
frame carries the horizontal spindle b near its top. Thu ^ 
spindle is driven by a belt from a line shaft or countershaft^- '* 
the belt is placed on the cone pulley c. The particula- *" 
design of machine shown is back-geared in order to provid -^^ 
for a larger number of speed changes. The back gearing l & 
similar to that employed for engine lathes and is operated i^^"*- 
the same manner, in this case by a handle. In the machin -^ 
illustrated, the back gears are protected by light metE^»- ' 
guard* shown at d and e. The spindle is bored out taperin -^g 

at the front end to receive the shank of the cutting tool i ^ * 

an arbor to which the cutting tool is attached. Anadjus-^K^ • 
ablearm, or outboard bearing sliding in bearings parall »-~^l 
to the spindle, can be used for supporting the free end «^^f 
the arbor when heavy cuts arc taken; when not in use it c^m_ ^i 
be swung out of the way. The arm can be rigidly clampe^= •*! 
in position after it has been adjusted. 

20. A vertical slide is formed on the front of the frame a""^! 
a kneef is fitted to this slide, which is in a plane at rig ~* ~ lt 
angles to the axis of the spindle. The lop of the knee is -^E*' 
right angles to the surface of the slide on the frame, aB^*'' 
carries the clamp bed //, which can be moved along it ir» a 
straight line parallel to the axis of the spindle by means of t *-"* e 
cross- feed screw 1, Thekncc i;i:i be raised and lowered 'fc^*/ 
turning the e.eva ting: screw;; fur t lie sake of convenient— ~*' 
this is operated from the front of the knee by turning t *~* e 
shaft k, which carries a bevel gear that meshes with one ^^* n 
the elevating screw. A detachable handle / fits the squi^- *~ e 
end of /' and k. The cross-feed screws and elevating sere; '**' s 
are supplied with dials graduated to indicate movements t>/ 
thousandths of an inch. 

21. The clamp lied A carries the saddle m, which * s 
pivoted to it, and which can be rotated through an arc *>* 
about 45°; suitable clamping devices are provided fo-f 



I u 



MILLING-MACHINE WORK. 



tiping the saddl 
which it may he si 
Gorms a bIMo that re 



to the clamp bed i 



■ posit it 



to 



in any \ 
ng. The upper part of the saddle 
ives the table n; this slides in a line 
parallel to the top surface of the knee. The table can be 
moved by means of the feed-screw a, which is operated by 
the handle shown. The top of the clamp bed is graduated 
into degrees; a zero mark on the saddle, by its coincidence 
with the zero line of the graduation, indicates when the line 
of motion of the table is at right angUs to the axis of the 
spindle, and by its coincidence with the other graduations 
shows how many degrees the line of motion differs from its 
position at right angles with the axis of the spindle. 

22. The table is fitted with a detachable Index head/ 
Utd A detachable tallstock q. The index head and tail- 
Stock are fitted with centers between which work may be 
placed. The spindle of the index head can be rotated by 
means of a worm-wheel and worm ; it is so arranged that it 
can be swung in a vertical plane around the axis of the 
worm from slightly below a horizontal position to somewhat 
beyond a vertical position. On the bottom of the index 
head are tongues that fit a longitudinal T slot in the table; 
they insure that the axis of the index-head spindle is always 
in the same vertical plane as the line of motion of the table. 
The front end of the index-head spindle is often threaded to 

iceive face plates, chucks, or special devices for holding 
spindle is almost invariably made hollow, and is 
>red out tapering to receive a live center or arbors. 

23. When it is necessary to set the spindle In the index 
■ad at an angle to the line of motion of the table, owing to 

he form of the work clamped to the index head, the head 
i detached from the table ; a raising block r is bolted 
> the table in such a position that one of its two T slots 
I Bt the required angle, and the index head is attached 
i that T slot of the raising block. When the diameter 
f the work is so large that it cannot be attached to the 
index head if the latter is fastened directly to the table, 
the index head is raised by moans of the raising block 



MILLING. MACHINE WORK. 



$13 



When no raising block is available, parallel strips may be 
used for the same purpose. The tailstock q has the dead 
center mounted in a block fitted to a slot of the tailstock. 
This block can be raised or lowered a certain ftffi 
order to bring the dead center in line with the live center 
when tapering work is placed between lliem. 

24. A mlltlnic-mucbtne viae s, which can be rotated 
and then clamped in any position to the table, is used for 
holding work. When comparatively slender work is to t* 
milled between the centers, it will naturally sprifl 

the cutting operation. This tendency is counteracted by 
placing a center rest or steady rest / on the tabic and 
adjusting it properly to support the work. An oil tauk is 
shown at it. 

25. The machine shown is provided with an automatic 
feed for the table, which, by means of ad j 

can be made to stop at a predetermined point. A vertira! 
feed for the knee is also provided. The knee and t 
bed may be clamped rigidly to their slides ;it any p 
suitable arrangement. Adjustabli o provided 

for the knee and table; they arc used when a Dtl 
duplicate pieces arc to be milled, and the feeding is 
by hand. 

26. The inside of the frame of universal milling 
chines usually serves asa cupboard in which cutters, change 
gears, collets, arbors, wrenches, and other small parts may 
be conveniently kept. 

27. When milling machines of different types are care- 
fully examined, they will be found to have son- 
features of the universal milling machine embodied i 
in one form or another, In one case the cutting tool i 
be fed to the work, and in another case the work may be fi 
to the cutting tool; in one case the feeding may be J 
ptished by a lever operatin ■h and r 
another case the feeding may be done by turning a fct 
screw; no matter, however, in what form the essential 






§13 MILLING-MACHINE WORK. 9 

parts appear and what their construction may be, it will be 
found that the fundamental principles and the function of 
the essential parts are the same in each case. 

Furthermore, a person that can operate one type of 
machine successfully can, after getting accustomed to the 
methods of adjustment of another type, operate it with 
equal ease. As far as special methods of adjustment are 
concerned, they can always be readily traced out by a little 
intelligent study. For this reason, no attempt is here made 
to describe all the different types and the subclasses of each 
type in detail. 



ADVANTAGES OF MILLING MACHINES. 

28. It was conceded for a long time that milling was 
superior to other processes of machining by reason of the 
fact that by the use of properly formed cutting tools, pieces 
°f work having an intricate profile could be duplicated within 
such small limits of variation as to be interchangeable. 
This could be done at a rate of speed that was not feasible 
with any other method of machine work, and consequently 
at a lower time cost per piece. The milling machine can 
truly be said to have been the most potent factor that made 
P^sible the application of the interchangeable system to the 
cc °nomic production of work done in large quantities, as 
° re arrns, sewing machines, typewriters, etc. As a matter 

fret, the milling machine was developed originally in 

ar &iories manufacturing small firearms, and for a long time 

as Unknown outside of them. Of late years, it is gradually 

c °niing recognized that the process of milling cannot 

. y be applied to a great variety of work usually performed 

*he planer, shaper, slotter, and lathe, but that also, by 

as On of the multiplicity of cutting edges and the continu- 

s Cutting operation, the work in many instances can be 

Whined by milling at a much lower time cost. 

^©. While intelligent superintendence, i. e., the making 
*he tools and special fixtures for the milling machines, 



10 



MILLING. MACHINE WORK. 



lu 



calls for skill of .1 very high order, the fad rem 

machine operate 
ties, the actual placing ol the work into it, 
and removing the ■ fely entrusted to 

lively unskilled labor after the mat nine b 
adjusted by a skilled workman. In audi a 

tender can often look after seTeral roachi 
out Inconvenience. In consequence of this, there ■ 
: reducl [on [a 1 be laboi cost pec piece. 
30. When the milling machine is used as a su 
For other ma< nine tools, on work other than duplicate work, 
the machine cannot be placed in the charge ■ 

sons if its product i - to 1 

machine tools. In such rases, then 
called Eor as is required £01 

1 ool (i hose place is taken by the milling ma 



Mil MM. CUTTERS, 



CLASSIFICATION OF ClTTKIiS. 

31. The cutting tool used for milling is known a* a 
mlllliitr. cutter. Milling cutter ictice may 
be classified as plain mill 1 common, 
axial, and surf act milling cutlers, suit milling cut t 

called fate <>r bull ■ ■ ■■..■■,..-.. 

cutters, ai ■' Side mills and 1 

called radial mills. Any one of these cutters may n 

an inserted-looth, a shank, or a shell cutter, and it may be 

fastened to the spindle of the milling machine by h 

Iglt to the 
spindle or to ,1 shank fitted to the latter, or, finally, it mat- 
be formed with a shank I hat fits the 

32. Milling cnttcTS an; ■! . lent -tan octocl and left. 

handed in accordance with I heir direi 1 1 

cutting. In order to tell 






§13 MILLING-MACHINE WORK. 11 

or left-handed, lay it down flat with the side of the cutter 
up which is intended to face the driving cone of the machine. 
Then if the cutter must revolve in the direction in which 
the hands of a watch move, it is right-handed ; when it 
must revolve in a direction opposite to that in which the 
hands of a watch move, it is left-handed. 



CONSTRUCTION OF CUTTERS. 




PLAIN MILLING CUTTERS. 

33. Slitting Saw. — A plain milling cutter may be 

defined as one intended for machining surfaces parallel to 
tn e axis of rotation of the 
c "tter. The simplest form 
°* a plain milling cutter is 
the slitting saw shown in 
* '£• 2. This saw is clamped 
ktween washers to an arbor ; 
a number of cutting edges are 
f° r med on its periphery by 
ser rating it. These cutting 
e(J ges are ground after hard- 
ening so that they all are ex- 
ac *ly the same distance from 

tIle axis, in order that each cutting edge will do the same 
a mount of work. Slitting cutters, like the one shown, are 
& r ound with clearance on the sides; that is, they are made 
s,l £htly thinner at the center than at the periphery, so that 
ee P slots can be cut, or stock can be cut off , without having 
the sides of the cutter bind in the slot. 

*M. Screw Slotting Cutter. — When shallow slots 

re to be cut, as, for instance, the slots in screw heads, the 

u Uer is made with teeth having a much finer pitch; the 

lcies are then usually left parallel, in order to save expense 

taking the cutter. This kind of a cutter is given the 

TlB-30 



It MILLING-MACHINE WORK. 1 IS 

name of ncrtw slotting culler, si net; it is most frcquentlv 
used for that purpose. While used by some for en 
stock, it is not as well adapted for this purpose as the slit- 
ting cutter, since on thick slock the sides of the cutter, 
especially if the teeth are at all dull, will bind in the stocit 
being sawed. 

35. Parts of Hie Culler. —The term pitch, when 
applied to the teeth "f a milling culler, refers to the dis- 
tance between adjacent cutting edges. Since In milling 
cutters the teeth are equally spaced, the pitch can be found 
by dividing the circumference of the cutter by the 
of teeth. The plane represented by the line a b is called the 
front face of the tooth. In American practice, ii is ftlaw! 
invariably made radial; that is, the front face lies on a 
plane that passes through the axis of the cutter. In tide 
milling cutters, this rule is occasionally departed from for 
the purpose of throwing ihe chips in a certain dl 
The surface a «', Fig. 2, is called the top face of the toolh; 
the angle included between a b and a a' varies [ 
to 87°, thus giving a clearance of from 3° to 5°. The edged 
is the cutting edge and (he surface whose edge 
the back of the tooth. The cutter, in order to cut, num 
rotate so that the front faces of the teeth move toward Wk 
work, or in the direction of the arrow x. 

3fl. Reversible Cutters,— Any milling cutter that is 
reversible, i. c., which can be placed with either side toward 
the spindle, as is the case with most milling 
to an arbor, will serve for a right-handed cutter or a left- 
handed cutter, depending on which side of the cutter is 
placed toward the spindle. Thus, if the cutter ill 
in Fig. 2 is placed with the side rftoward the 
left-handed cutter; but if the side ./ is pla& 
spindle, it is a right-handed cutter. 

37. Si. ..lulu and Helical Cutting Edge* By 

making the slitting cutter wider, it becomes the pla 
cutter shown in Fig, 3 (a). It seems to be the com 



practice to limit the terms "slitting" and "slotting" cut- 
ters to cutters that are narrower than one-quarter inch; 
»hea wider, they are usually called plain cutters, cylin- 
drical cutters, or parallel cutters. The cutter shown 

in Pig. 3 {a) has straight cutting edges, by which is meant 
that they lie in planes passing through the axis. A milling 
cutter with straight cutting edges will answer very well for 
surfaces that are relatively narrow, say not over 1 inch 
•Me; it also has the advantage that straight cutting edges 




W 



fW 



ar e cheaply produced. On the other hand, each cutting 
cd ge, when in contact with the work, will cut at once 
acr oss the whole width of the surface operated on; conse- 
Quently, considerable power will be needed, and as each 
cu Uirig edge strikes throughout the whole width of the sur- 
'*<*, a distinct blow is struck by it, which will set up 
r '° r ations and prevent, to a large extent, smooth, even 
"""ing, unless the machine is exceptionally rigid and the 
°*k held very securely. 

3fJ. The objections to the straight -tooth cutter have led 
the design of cutters with helical cutting edges; such a 
er is shown in Fig. 3 (b). When a surface is being 
chined, the teeth will commence cutting at one corner, 
the cut will gradually proceed across the surface. In 
sequence of this shaving action, the severity of the blow 
~k by each cutting edge on engaging the work is greatly 
med; experience has also shown that for equal condi- 
ris, less power will be required for a cutter with helical 



14 



MILLING-MACHINE v, 



S13 



cutting edges than (or one with straight cutting edges 
The lessening of the seventy of the blow Struck 
edge on engaging the work means a reduction of v 
and, hence, under equal Conditions, the cutter with helical 
cutting edges will produce a nnool 

39. Definition* of Hells and Spiral. — It is to be 
regretted that it has become the practice atnoi 
writers, and hence among many mechanics, to use the 
terms helix and spiral as synonymous, i. e., as having the 
same meaning. 

In geometry, a helix is a line generated by the rotation 
of ■ [i.iini around an axis, the polnl remaining ai the same 
distance rxora the axis but advancing in the direction of its 
length. The most familiar examples of helixes are sere* 
threads and the grooves of twist di 

A spiral is a line generated by the progressive rotation 
of a point around an axis, the point gradually increasing its 
distance from the axis. When the point rotates, in 
its path is called a plane spiral. The most famili 
jile of a plane spiral is a watch spring, where all convolu- 
tions lie in the l-.i plane. 

When a point rotates around an axis at a continually 
increasing distance from the axis . me tun? 

moves in tin- direction of (he axi 

point follows the surface of a cone, i eooloal 

spiral. Probably the most familiar examples o I 
spiral arc conical bed sprini u ings used for seat- 

ing the water valves in many designs of steam pni 

40. From the definition it will be seuii tli.it a 
particular form of a spiral, and thai a spiral becom 
when the path of the point generating it lies on ;! 

of a cylinder. In this Course the terms helix and spiral will 
be used in their true meaning; that is, in accordance with 
the definitions just given. 

41. Nicked Teeth. — Experience has shown that I 
power required to drive a milling cutter can be grea 
reduced by nicking the teeth of helical milling e-mtc 



MILLING-MACHINE WORK. 



U 



he manner shown in Fig. 4, where the nicks are so arranged 
i cutting edge will be behind a nick. With such 
i cutter, the chips are broken up; that is, instead of one 
ontinuous shaving, a number of separate shavings are 
: by each cutting edge. Since it has been shown by 
xperience that less power is required for a nicked cutter, it 
follows that with the same amount of power available and 
under equal conditions, a much wider and deeper cut can be 







taken than is possible with an ordinary helical cutter. For 
this reason, cutters with nicked teeth are now very gener- 
ally employed for heavy milling where the rapid removal 
of superfluous metal is the prime requisite. It is claimed 
that a surface cannot be machined as smooth with a nicked 
cutter as with a plain cutter; but if the nicked cutter is 
carefully made and kept sharp, there seems to be no reason, 
however, why it cannot produce as good work on a finishing 
cut as a plain cutter. 

42. Built-Up Plain Cuiter*. — The cutters shown in 
Figs. 2, 3, and 4 are solid cutters, which means that they are 
made from a single piece of steel. Solid cutters can be 
obtained as large as 8 inches in diameter and 6 inches wide; 
this size is about their commercial limit. When larger cut- 
ters are wanted, they arc usually made with blades or teeth 
of tool steel that are inserted in a body of inexpensive male- 
rial in such a manner that they can be removed and replaced 
when worn or broken. There are a great many different 
ways in which such cutters may be made. 



u 



MILLING-MACHINE WORK. 



{U 



43- Fig. 5 shows the construction adopted by the Morse 
Twist Drill and Machine Company for cutters of the 
inserted-blade type. Referring to the illustration, it will be 
seen that the blades a, a are inserted in rectangular slots 
cut into the body b. A clamp d is placed between each 
alternate pair of blades; this clamp can be drawn inwards by 




setting up the screws c, c, which operation presses the tiro 
blades against opposite sides of their slots and locks thrm. 
The blades themselves are straight, but their cutting edges 
are helical, in order that the front face of the blades maybe 
radial throughout their length. The cutter here shown is 
intended for heavy work, and, hence, the cutting edges are 
nicked. 

44. An entirely different design of a plain milling cutter 
is shown in Fig. (S, This cutter belongs to the inserted- 
tooth type, and is a logical development of the idea c 
nicking the teeth, inasmuch as each separate tooth is i 
equivalent of the cutting edge between a pair of nicks of a 
inserted-blade cutter. The cutler consists of ■ 
body a in which rows of cylindrical holes are drilled : 
reamed for the reception of the teeth. The hoi 
arranged that a line drawn through the centers of the r. 
of each row and along the cylindrical surface of the c 



I 13 



KILLING-MACHINE WORK. 



17 



a helix. The teeth h, b are cylindrical plugs of tool 
eel that are simply driven into the holes. A cutting edge 
formed by cutting away one-half of that part of the plug 
that projects from the body, and grinding a proper clear- 
ance on its top. It will be observed that while the rows of 
I teeth are in the direction of a helix, the cutting edge of each 
:ooth is in a plane passing through the axis of the milling 
:utter. This is done purposely in order to prevent the teeth 
from turning around their own axis under the pressure of 
the cutting operation. If the front face of the tooth is 
helical, it will commence to cut at one corner; in conse- 
quence of this, there will be a tendency to rotate the tooth 
ound its own axis. 





45. Inserted -blade and inserted-tooth milling cutters 
ire limited as to size only by the capacity of the machine, 
i connection with this it is to be observed that as far as 
results are concerned, the solid cutter will accomplish the 
same thing. For large cutters, however, either the cost of 
the solid cutter is such as to be prohibitive, or it is impossi- 
ble to obtain steel of sufficient size to make a solid cutter. 
Furthermore, in hardening very large pieces of tool steel, 
there is considerable danger of losing them by cracking 
when they are quenched. It is thus seen that the question 
of whether to use a solid or an inserted-tooth cutter is 
simply a question of expense, since neither will produce 
ork that cannot be done as well with the other. When 
comes to a question of maintenance, the inserted -blade 



18 MILLING-MACHINE WORK. 

and inserted-tooth cutter is undoubtedly cheaper in the lot 
run, since new blades or teeth can be fitted at a fraction 
the expense of a solid cutter, at least as far as large cuttet 
are concerned. 




SIDE MILLING CUTTEBS, 

46. Solid Side Mill. — The most common form of a si- 
milling cutter for small work is shown in Fig. 7. By e 

ining the illustratic» ^i 
it will be seen that ht. 
a face milling cutt. -^ 
with additional tee= ~^B 
cut on its sides. — * 
order that the sicil ■* 
may clear the woi" ^ 
they are recessed !—■ ' 
the bottom of t ~^> 
teeth, as shown at c* — 
A side milling cut X^— e 
Fl °- 7 - may operate on t- "^ 

sides of work either by cutting with the cutting ed f^ f 
formed on its periphery or by cutting with the te<^' 
formed on its sides, depending on which way the wortc 
fed to the cutter. When the work is fed in a diroctioi "» 
right angles to the axis of rotation of the cutter, Hit- ts ■ 
on the periphery will do the cutting and the side teeth ■*" 
drag against the work; when the feeding is done in a di*~ 
tion parallel to the axis of rotation, the' side teetli will 
all the cutting. 

47. Straddle aad Gang Mill*. — Two side mill^ 
cutters like the one shown in Art. 46 are often placed 

an arbor, with a washer to regulate the distance betire^* 
them. In this case two opposite sides of the work ^*- ! 
operated on at once; such a combination is called ' 
straddle mill. 

A irjifiK mill consists of two or more cutters assembl*^" 
together on the same arbor. It may be made up entire- *>' 



§13 



MILLING-MACHINE WORK. 



of plain cutters or of a combination of plain and angular 
or side cutters. Gang mills are very useful for milling some 
simple shapes, if plain cutters of the required diameter are 
available, since several surfaces may be operated on at the 
ime. For intricate shapes, special milling cutters are 
often made as gang mills. 

48. Threaded Cutters. — When any milling cutter is 

attached by screwing it to a shank or to the spindle, it 
is absolutely necessary to revolve the cutter in such a direc- 
tion that the cutting operation will tend to lock it more 
ly. From this it follows that any cutter attached by 
screwing is not reversible. Fur instance, consider a plain 
iidc milling cutter that is attached by a left-handed thread, 
hen, this cutter must only be attached so that it will run 
ft-handed. Assume that it is run right-handed. Then, 
soon as the cutter engages the work, the pressure of the 
utting operation will tend to unscrew the cutter; in case 
the cutter is actually unscrewed, the work may be spoiled 
by the cutter digging into it, or the cutter may be broken. 
Particular attention is called to this fact, since a large per- 
centage of the accidents to the work and cutters is due 
to its not having been taken into account. The foregoing 
may be summed up as follows: 

If the thread is left-handed, the cutter must run left- 
nded ; for a right-handed thread, the cutter must run right- 
nded. 

49. It has been explained in Art. 32 what is meant by 
, right-handed and left-handed cutter; it will be well to 
efer again to this article, to make sure that the meaning of 

i terms when applied to milling cutters is properly 
nderslood. 

50. Itiserted-Blade Side Mills.— Small side milling 
utters, say up to 8 inches in diameter, are usually made 

Above that size the difficulty of making a solid 
Utter makes cutters with inserted blades or inserted teeth 
heapcr in 6rst cost and maintenance. Inserted-blade side 



go 



MILLING-MACHINE WORK. 



S13 



milling cutters may be constructed in a great variety of 
ways; for instance, they may be made on the same principle 
as the plain milling cutter shown in Fig. 5, or the blades 
may be inserted and locked in the manner shown in Fig. 8. 
This figure shows the design adopted by the Pratt & Whit- 
ney Company. The blades a, a fit rectangular slots cut 




into the body b. A hole is drilled between every alternate 
pair of blades; these holes are reamed out tapering, to 
receive the taper locking pins c, c. After reaming, slots 
are cut through the reamed holes; the blades are then 
locked by driving the taper pins home. The blades arc 
generally made long enough to allow them to be sharpened 
a great number of times, 

51. Inserted-Tootta Side Mills. — The designs shown 
in Figs. 5 and 8 are used for cutters from 8 to 36 inches in 
diameter. Cutters exceeding the latter size are usually 
made with inserted teeth, although relatively small cutters 
are occasionally made that way on account of low first 
cost. There are various ways in which teeth may be 
inserted in side milling cutters. Probably the cheapest 
construction is to insert cylindrical teeth in the periphery of 
a cast-iron body, as shown in Fig. 9. The teeth a, a have 
their ends formed like planer roughing tools; the holes in 



§13 MILLING-MACHINE WORK. 21 

which they are placed are drilled at an angle of about 60° to 
the axis, in order that the cutting edges of the teeth may 
come in front of the side of the body. The teeth are held 
by setscrews b, 6; owing to their simple shape, they can be 
made quite cheaply, and can be easily replaced. 




52. Fig- 10 shows a radically different construction. The 
teeth a are made of square tool steel and are placed in 
rectangular slots in the bodyr; these slots are parallel to 
the axis of the cutter. The teeth are held by setscrews e t e. 
The particular cutter shown is fastened to the spindle d by 
a key/"; longitudinal movement on the spindle is prevented 
by a screw g, which is placed half into the shaft and half 
into the body. This method of fastening a cutter to the 
spindle is adapted only to cases where the cutter body is 
not intended to be replaced by others of different shape 



53. The particular design of cutter shown is a fine 
example of how, by the use of a properly designed tool, a 
surface may be roughed out and finished by running 
the cutter over it but once. Referring to the illustra- 
tion, two flat-nosed tools b, b are seen so placed ili.it their 
outer corner is slightly inside of the circle passing through 
teeth. The cutting edges of these two toolfl are 



22 MILLING- MACHINE WORK. g 

adjusted in a plane slightly in front of that in which i 

cutting edges of the teeth are placed, In consequence i 
this, the teeth will rough out the work in ■<<'■■■ 




the tools /•, and as the cutter moves past the wo 

tools follow directly behind the teeth and take tfai 

cut. This greatly reduces the time required for the cui 

ting operation. 

54. Cutters designed to take a roughing and 

cut at the same time an: only :ip|jlii able I" wmk which i: 
rigid that there is no danger of its springing 
ci&blc extent by the releasing ol I listing at t 

surface of castings and forgings. Plain milling cntti 
cannot very readily be designed to take a roughing and 
finishing cut at the same time. 

55. Slotting Cutter. — The T-slot cutler shown 
Fig. 11 is a combination of a side milling cutter and a fat 
milling cutter, and is intended for cutting oat T -■■ 

style of cutter is usually made solid, and has a -shank » « 
is tapered tu fit the hole of the milling •machine spindl 



8 13 



The end of the shank is milled to form a tang that enters a 
corresponding recess in the bottom of the hole in the 
spindle, in order that the cutter may be positively driven. 



MILLING-MACHINE WORK. 




All shank cutters must be driven home quite heavily, using 
a lead hammer for this purpose; if this is not done, the 
vibratfons due to the cutting operation will soon loosen the 
cutter and, in consequence, it will dig into the work. 



ANGULAR MILLING CUTTERS. 

56. Classification. — An angular milling; cutter 

may be defined as a cutter intended for the finishing of 
urfaces at an angle other than 90° to the axis of rotation. 
-Angular cutters may be constructed in a great variety of 
■ways and may be solid, or have inserted teeth, or inserted 
"blades. They may be attached to the spindle by clamping 
them to an arbor, by screwing them to a shank, or by screw- 
ing them to the spindle. They may also be made solid and 
with a shank that is either tapered to fit the spindle or that 
is cylindrical ; in the latter case, the shank is held in a chuck. 
Angular cutters may be divided into two genera! classes, 
which are single-angle and, double -angle cutters. 

57. Single-Angle Cutters. — A single-angle cutter is 
one in which one cutting face is at an inclination other than 
a right angle to the axis of rotation. Such cutters are 
known according to the angle included between the inclined 
face and a plane perpendicular to the axis, as 30° cutters, 
45° cutters, etc. Angular cutters of the single-angle class 
are largely used for cutting the teeth of milling cutters, 
counterbores, hollow mills, and similar work having straight 
cutting edges. 



M 



MILLING-MACHINE WORK. 



! ! 




58. A single-angle 60" cutter is shown in Fig. 12. As 
shown in the illustration, it has teeth cut on its side, as well 

as on the angular face. 
Such a cutter can oper- 
ate on two surfaces at 
the same time; that is, 
tt can cut on a surface 
I ] perpendicular to the axis 
of rotation and also on 
a surface at an inclina- 
tion to it. Single-angle 
cutters intended only for 
pl °- a - finishing a surface at an 

inclination to the axis are made without teeth on the side; 

such a cutter is considerably cheaper than the one shown in 

Pig. 13. 

59. Double-Angle Cutters. — A double-angle cutter 
has two cutting faces each at an angle other than 90° with 
the axis. When both faces make the saute angle with the 
axis, the cutter is designated by giving the angle included 
between the two cutting faces. For instance, if the angle is 
60°, the cutter would be called a "00° double-angle cutter." 

GO. When the two cutting faces do not make the same 
angle with the axis, as, for instance, in the cutter shown in 
Fig. 13, the cutter 
is designated by giv- 
ing the angle in- 
cluded betweeneach 
face and a plane per- 
pendicular to the 
axis, as the angles 
a and b in the figure. 
For instance, if the 
angle a is 13° and 
the angle * 48°, the 

cutter would be F '°' "• 

designated as a " 13° and 48" double-angle cutter." 





§13 



MILLING-MACHINE WORK. 



25 



Double-angle cutters are most commonly used for fluting 
taps, reamers, milling cutters with helical teeth, and similar 
work where it is important that the two surfaces operated 
on at the same time be finished equally well. 

61. It must not be inferred that a surface at an angle 
to another one cannot be finished except with an angular 
cutter. In many cases, the work may be chucked in such a 
manner that a plain milling cutter or a side milling cutter 
may be used, and in other cases, the axis of rotation of the 
cutter is adjustable, which allows a plain cutter or side mill 
to be used for angular cuts. 



1 Nl> Mil I l\<. CUTTERS. 

62. Stem Mills. — In its true sense, an end milling 
cutter is one in which the cutting is done by the teeth on its 
end. In practice, however, the term is usually applied to 
shank cutters, often called stem mills, which have teeth 
on the periphery as well as on the end, as, for instance, the 
cutter shown in Fig. 14. By examining the cutter illus- 
trated, it will be seen that it is a combination of a plain mill- 
ing cutter and a side milling cutter, and can be used for 




milling surfaces that are parallel, and also for surfaces per- 
pendicular, to the axis of the cutter. When the work is fed 
to the cutter in a direction parallel to the axis of the latter, 
the teeth on the end will do the cutting, and the cutter will 
act as a true end mill. In most cases, however, the work is 
fed in a direction perpendicular to the axis of the cutter, and 
the cutter will operate in the same manner as a side mill. 
The larger sizes of end mills are made as shell mills ; that is, 
they are in the form of a shell that is fastened to an arbor. 



MILLING-MACHINE WORK. 



§13 



Smaller sizes are made with a taper shank a, as shown in 
Fig. 14, and are driven into a tapering hole in the milling- 
machine spindle. The smallest sizes are made with a cylin- 
drical shank, or stem, and are held in a self-centering 
chuck. While the end mill shown in Pig. 14 has straight 
cutting edges, it is often made with helical edges on the 
periphery. The teeth on the end are almost invariably 
radial. 

63. Cotter Mill. — Fig. 15 shows a peculiarly shaped 
mill that is usually considered as an end mill, although it is 
not very well adapted for cutting with its end. This mil! is 
known as a cotter mill, and is in reality a face cutter with 
two teeth opposite each other. It is particularly adapted 



for cutting narrow and deep grooves ; it cannot be sunk 
endwise into solid metal to any extent, but a hole must be 
drilled where the groove is to start. The cutting is done 
by the edges on the periphery. As there is considerable 
room for the chips, the cutter will not clog very easily. 









FORM MILLING CUTTERS. 

64. Classification. — Any milling cutter intended for 
the milting of surfaces that are not plain surfaces may be 
called a form milling cutter. Such cutters may be 
divided into two general classes, vii. : form cutttrs and 
formed cutters. Both classes will accomplish the same re- 
sult; they differ from each other only in their construction. 

The name form cutter is usually applied to any form 
milling cutter that has the teeth constructed in the same 
manner as the ordinary milling cutter. Form cutters can 
rarely be sharpened without changing their profile to ; 
extent. 




§ 13 MILLING-MACHINE WORK. 27 

Formed cutters are milling cutters that have been 
made with a forming tool applied in such a manner that the 
sharpening of the teeth will not change the profile. 

Form milling cutters may have any one of an infinite 
variety of profiles and may be made solid or several cutters 
may be combined into a gang mill. 

65. Fly Cutter. — The simplest form milling cutter is the 
so-called fly cutter, which is shown in its arbor in Fig. 16. 
The cutter a is set into a rectangular slot in the arbor b, 
and is locked by tightening the two setscrews c, c. The 
front face is radial ; one end of the cutter is filed or turned 
to the profile it is desired to cut. It is seen that the fly 
cutter is simply a one-tooth milling cutter. Clearance is 
given by setting the cutter farther out from the center than 
the position in which it was turned. The fly cutter has the 




£l^ 



U ) 

i i > 



-^ 




Fig. 16. 

advantage of being very cheap in first cost, even when the 
profile is quite intricate; for this reason it is well adapted 
for such work as the making of forming tools for screw ma- 
chines, making a gear with an odd pitch of teeth, and simi- 
lar work that does not warrant the expense of a regular 
form cutter. Since the cutter has only one cutting edge, 
it cannot be expected to last as well or cut as fast as a reg- 
ular cutter; it will reproduce its own shape very exactly, 
however, and will mill quite smoothly if kept sharp. 

66. Interlocking of Teeth. — Fig. 17 shows a form 
cutter that is built up of three pieces, thus forming a gang 
cutter. In order that the cutter will not make a mark 
where the pieces join, the teeth are made to interlock, as 
shown at a, a. By examining the cutter, the similarity of its 

T IB— 37 



28 



MILLING-MACHINE WORK. 



teeth to those of the ordinary milling cutter will be noticed. 
The difficulty of sharpening the teeth without changing -the 

profile of the cutter is apparent. 




67. Gear- Tooth Cutter. — The most familiar forrr» «d 
cutter is the gear milling cutter shown in Fig. 18, which, is 
used for cutting the teeth of gear-wheels. This cutter. as 
are all formed cutters, is sharpened by grinding the f r<^»nt 
face of the teeth. If the precaution of grinding the 




faces radially is observed, the profile will not change ; 
since the method by which it is made insures that the f~^ ro " 
file of all sections taken through a tooth in planes ji. ■**■ 
ing through the axis is exactly the same. The tooth <^'_ • 
Fig. 18, of a formed cutter may be conceived to be bu-*'» 



113 



MILLING-MACHINE WORK. 



U P of an infinite number of thin wedge-shaped plates i 
radial faces, each of which is placed slightly nearer the 
°* the cutter than the one in front of it. In this 
lr *e back of the tooth is made to clear the front, which 
° r ffis the cutting edge. Sharpening the tooth may be 
''<ened to the removal of one or more of the plates of which 
In -e real tooth was conceived to be composed, thus leaving 
'ates that have not worn in readiness to cut. 

68. Formed Gang: Gutters. — Formed cutters may be 
■ade for an endless variety of profiles ; Fig. 19 will serve 
i a suggestion of what can be done. In many cases, 
irmed cutters may be combined with ordinary cutters or 




sev 
fea' 



ith form cutters; the several cutters when assembled to- 

ther will form a gang mill. Formed cutters cannot be 

without a special forming machine or device; for this 

■n they are usually bought of manufacturers that make 

specialty of them. 



i. In practice, a vast variety of milling-machine cut- 
ters will be found that at first will appear unlike any that 
have been illustrated here. When they are analyzed, how- 
ever, they will invariably be found to belong to one of the 
several classes enumerated; in many cases the distinctive 
.tures of several classes may be combined in a cutter. 



30 MILLING-MACHINE WORK. §13 



CARE OF MILLING CUTTERS. 



KEEPING CUTTERS SHARP. 

70. In order that a milling cutter may work to the best 
advantage, it is absolutely essential that it be kept sharp, 
and that all cutting edges be at the same distance from the 
axis of rotation of the cutter. It is not sufficient that the 
cutting edges be at the same distance from the axis of the 
cutter, for if a true cutter is mounted on an arbor that is 
eccentric, i. e., runs out of true, the cutting edges will not 
be at the same distance from the axis of rotation. In con- 
sequence of this, some edges will have to do more work than 
others; experience has shown that if this is the case, the 
cutter can neither be pushed to the full limit of its capacity 
nor can it produce as smooth work as one ground true in 
respect to its axis of rotation. This fact is becoming more 
generally realized, as evidenced by the increasing practice 
of grinding cutters while in place in the milling machine. 



EFFECT OF DULLNESS. 

71. Milling cutters cannot be ground true enough by 
hand to allow the machines to be worked to the best advan- 
tage. A cutter-grinding machine is an essential adjunct 
of the milling machine, and without it the milling machine 
is at a serious disadvantage. A dull cutter is distinctly a 
bad cutter; it should never be used in that condition, but 
should be sharpened as soon as it shows signs of becoming 
dull. A dull cutter will do poor work, will require more 
power to drive it, and will wear out faster than one that 
is kept sharp. The extra power required to drive a dull 
cutter is transformed by friction into heat; this heat tends 
to soften the cutting edges and thus tends to make them 
wear faster. In formed cutters there is, in addition, a 
wearing of the formed surfaces that will shorten the life 
of a cutter more than many sharpenings. 



MILLING-MACHINE WORK. 



72. As an example of what work can be done by a 

utter that is kept sharp, the Brown & Sharpe Manufac- 

uring Company state 

hat the worn-out gear- 

:utter shown in Fig. 20, 
which is 3£ inches in di- 
ameter, has cm 167 cast- 
iron gears, having a face 
3 inches wide, with 64 
teeth of ^diametral pitch. 
This makes a total length 
of cut of 7,472 feet. The 
teeth were cut from the 
solid blank and finished 
in one cut. This per- 
formance, while good, is 
by no means exceptional. 

3 




HOLDING CUTTERS. 



ARBORS. 

73. Construction of Arbor. — The ideal method of 
driving the cutter is to make it a part of the spindle, and 
this is done to some extent in milling machines designed 

Ipecially for side milling. In milling machines intended 
r general work, the cutter must be so made that it can be 
oved, which condition precludes making it a part 
the spindle. 
74. Cutters are most commonly clamped to an arbor, 
hich tn turn is fitted to the spindle and forced to rotate 
with it. A common design of an arbor is shown in Fig. 21. 
It has a taper shank /?, which tits a corresponding hole bored 
in the spindle. The rear end of the shank is flattened to 
irm the tang /, which enters a corresponding slot at 
: bottom of the tapered hole in the spindle, and which 



MILLING-MACHINE WORK. 



813 



is expected to drive the arbor in a positive manner. The 
part of the arbor that projects from the spindle is made 
cylindrical; a nut is placed on the end of the arbor for the 
purpose of clamping the cutter, which is placed between 



bzz g r- i-ffflfe 



removable washers, as b, b. These washers are made t 
different lengths in order to accommodate different width: 
of cutters, and also to allow the cutter to be placed in differ- 
ent positions along the arbor without the necessity of havirij 
a very large number of washers. 

75. Methods of Removing Arbors. — The particul, 

design of arbor shown is provided with a nut directly 
front of the shank. This nut when screwed against the 
front end of the spindle will cause the arbor to be withd 
from the spindle. More commonly, however, the arbor is 
loosened by driving a tapered key behind the shank; in 
some cases the spindle is made hollow and the arbor is thei 
punched out with a rod. 

76. Supporting Arbors. — The front end of the arl 
usually has a countersunk center to allow a dead center 
to be used for supporting it. Occasionally, a cylindri- 
cal teat e. Fig. 21, is formed at the front end; this teat is 
fitted to a bushing held in the outboard bearing and serves 
to support the arbor. When the machine has no outboard 
bearing, the cutter should invariably be placed just as 
close to the spindle as circumstances permit, since an arbor 
is comparatively slender and will spring considerably even 
under a moderate cut. When no way of steadying the end 
of the arbor is available, then in cases where the cutter 
must he placed near the end, the finishing must be done 
by light cuts in order to keep the spring of the arbor withi 
reasonable limits. 



hen 
bor 



§13 MILLING-MACHINE WORK. 33 

77. Driving the Cutter. — In many cases the cutter 
is driven simply by the friction between the sides of the 
washers and the sides of the cutter; this friction is created 
by screwing: up the nut on the end of the arbor. When the 
cutter slips in spite of repeated tightening, it may often be 
made to hold by placing washers made from ordinary wri- 
ting paper between the metallic washers and the cutter. 
Thin brass or copper washers will also be found useful for 
this purpose. 

For heavy cutting, the cutter should be driven by a key; 
a good many arbors have a semicircular groove cut along 
the cylindrical part to take a round key, which may be 
made by cutting off a piece of drill rod to the right length. 
A corresponding semicircular keyway is cut in the bore of 
the cutters. In some cases, the driving is done by a regular 
rectangular feather; the arbor is then splined. 

78. Precautions to be Taken With Arbors. — 

When the end of the arbor is supported either by a bushing 
or by a dead center, there is no chance for the arbor to 
become loose in the spindle, provided the supports are 
properly adjusted. When the end of the arbor is free, how- 
ever, it must be driven home in the spindle quite hard, or it 
will come loose under the vibrations due to the cutting 
operation. Before inserting the arbor, the hole in the 
spindle should be thoroughly cleaned of any chips that may 
have gotten into it, and it should also be free from grease or 
oil. The shank of the arbor must then be cleaned off just 
carefully, and inserted so that the tang enters the corre- 
sponding slot in the spindle. It should be driven home by a 
fair, quick blow with a heavy lead hammer. In nine cases 
out of ten, the coming loose of the arbor, which is here as- 
sumed to have been properly fitted, is due to oil or grease 
on the shank and in the spindle. Hence, if the arbor per- 
ists in coming loose, again clean the shank and spindle 
thoroughly. In some cases, the shoulders of the tang may 
strike the bottom of the hole in thespindle; this can easily 
be discovered by examining the tang. If they do, the arbor 



34 MILLING-MACHINE WORK. § 13 

cannot be driven home properly, in which case the tang 
should be ground off where it bottoms. Chips or dirt be- 
tween the collars may bow the arbor and cause it to run out. 

79. Arbors of the form shown in Fig. 21 are made with 
right-hand and left-hand nuts, and the cutter used on the 
arbor should always have a direction of rotation to suit the 
direction of the thread. That is, select a cutter that runs 
in such a direction that when slipping occurs, the tendency 
will be to tighten the nut, Hence, for a left-hand thread on 
the arbor, the cutter should be left-handed. If the thread 
is right-handed, use a cutter that must run right-handed. 

SO. Shell-Mill Arbor. — Small side mills and end mills 
are often so made as to be held in a manner similar to that in 
which a shell reamer is held; the shell-mill arbor shown in 
Fig. 22 {a) is then used. This arbor has a taper shank to 
fit either the milling-machine spindle or a collet fitted to 



< 



if the cylindrical part 



2 spindle. The shoulder at the end of the cylindrical part 
a, which forms the seat for the cutter, has two projections 
that enter corresponding slots in the cutter and insure posi- 
tive driving. The cutter is confined lengthwise by the head 
of the screw b, which enters a recess in the cutter, thus 
bringing the head below the face of the cutter; this is nec- 
essary for end milling and some kinds of side milling. 

81. Screw Arbor. — Small cutters are often made 
with a threaded hole and are screwed to a screw arbor made 
as shown in Fig. 22 (*). The direction of rotation of the 



113 



MILLING-MACHINE WORK. 



cutter that can be used with a shell-mill arbor and screw arbor 
is determined by the direction of the thread of the screw b, 
Fig. 22 (a), or the screw at the end of the screw arbor. 
That is, for a left-handed thread use a left-handed cutter; 
for a right-handed thread use a right-handed cutter. 

82. Effect of Vibration While it is admitted that 

in an arbor driving a cutter by positive means, as by a key, 
or by projections on the shoulder, there is no danger of the 
nut unscrewing by a slipping of the cutter, experience has 
shown that the vibrations due to the cutting operation tend 
to unscrew the nut, or the screw />, Fig. 22 (a), unless its 
thread is in accordance with the statement made in Art. 8 1 . 
If no cutter having the proper direction of rotation is avail- 
able, the nut or screw must be screwed home as firmly as 
circumstances will permit, and the chance of the cutter 
working loose must be taken. 

Shell-mill arbors and screw arbors are liable to become 
loose for the same reasons as the ordinary arbor; the same 
precautions should be used that were explained in Art. 78. 

83. Arbor for Use Between Centers. — Fig. 23 

shows how a milling arbor may be made if the cutter is to 
be driven between centers, as occurs when a lathe is tem- 
porarily converted into a milling machine. The arbor is 



driven by a dog, the tail of which engages with the face 

plate. Such an arbor may occasionally he used for a regular 
milling machine having an outboard bearing; a live center 
must then be placed in the milling-machine spindle and suit- 
able arrangements made for driving the arbor. 



36 MILLING-MACHINE WORK. 

COLLETS. 

84. Plain Collet. — A collet is a socket used for bush- 
ing down Ihe hole in the milling-machine spindle so that 
smaller arbors or shanks can lie held. Fig. 24 (<?) shows 
how such collets are usually made. The outside fits the 
milling-machine spindle; the inside is bored out true with 



0' 



itside, so that an arbor inserted in the collet will run 
true when the collet is in the machine. The tang of the 
arbor or of the cutter shank projects into ihe slot a ; the 
arbor can be removed from the collet by driving a taper key 
into the slot behind the tang. 

85. With constant use, a collet will enlarge somewhi 
inside, so that the shank of the arbor or cutter v. 
bottom. A thin piece of writing paper may then 
wrapped around the shank; the paper must nut be so widt 
as to lap, hmvever. While this is a makeshift at I 
one that will often prove very handy. The same thing ma' 
be done when the cutter shank or arbor does not bottom i 
the hole, but has its tang projecting so far into the slot i 
that it will nut be possible to get a key in to drive the shanl 
out after it is driven home. The key is usually made ; 
shown in Fig. 2-1 (/>); a hole is drilled near the large end s 
that a chain tan be attached to it and to some Btl 
part of the machine. This insures finding the key whei 
it is wanted. 



g 13 MILLING-MACHINE WORK. 37 

86. Chuck Collet — Small cutters are often made with 
i cylindrical shank, and very small cutters are made from 

rill rod. Such cut- 
lers may be held by r—r — l 

means of the chuck [fa fl a) — a ^7 -1 

ollet shown in Fig. ° i — 1_| 

The front end of Fl0 a 

collet is bored out 
cylindrically, and so that the axis of the cylindrical hole 
oincides with the axis of the shank a. A nut b having a 
ain tapered part is 6tted to the front end, which latter 
s been split into three parts. By reason of the front end . 
being tapered on the outside, the screwing up of the nut b 
will close the split part on the shank of the cutter, thus 
holding it centrally and firmly. 

87. The chuck collet shown is open to one objection, 
which is that all cutters to be used with it must have the 
.ame diameter of shank. If a chuck collet is intended to 
ake straight shanks of varying diameter, a high grade drill 
huck of the Almond or Beach type may be attached to a 
bank fitting the milling-machine spindle. 



CHUCKS AND FACE PLATES. 

88. Self-centering lathe chucks may often be fitted to 
the spindle for holding cutters having larger shanks th^n 
the drill chuck will receive. For some work a single-tooth 
cutter may be mounted in a slot of a face plate fitted to the 
spindle. Such a construction does not differ essentially 
from that of a fly cutter, being simply a fly cutter on a 
larger scale. A cutter attached to a face plate will be 
found of great service in finishing a surface to a circular 
profile having a given radius. While this can be done to 
the best advantage with a regular milling cutter made 
:specially to the required radius, the fact remains that in 
tany cases the expense of making such a cutter is not 



MILLING-MACHINE WORK. 



§13 



warranted by the conditions, and a face-plate cutter will then 
prove an excellent inexpensive substitute. 

89. Fig. 20 shows the general idea of a face-plate cut- 
ter; its similarity to the fly cutter will be apparent. Re- 
ferring to the figure, the face plate a is seen to be threaded 
so as to screw on the spindle. The cutter c is adjustable in 




the slot b, and can be clamped by tightening the nut d. 
The shank of the cutter should have a rectangular cross- 
section so that the cutter will not turn in the slot. 

90. If a circular milling cutter of the right profile, but 
of smaller diameter, is available, the expense of making a 
single-tooth cutter can often be saved by clamping the 
regular cutter to the face plate, passing the clamping bolt 
through the slot in the face plate. The cutter is then 
placed with one of its cutting edges in the position occupied 
by the cutting edge of the fly cutter shown in the illustra- 
tion, and after adjusting it to the required radius, it is 
clamped. Any ordinary bolt may be used for clamping. 
The setting of the cutter so as to mill a given radius is not 



§13 MILLING-MACHINE WORK. :i<.i 

a particularly difficult matter. The cutting edge must be 
set at a distance from the periphery equal to the difference 
in the required radius and the radius of the face plate. 
When the cutter projects considerably from the face of the 
face plate, the blade of a try square may he placed on the 
cutting edge and the stock beld against the face plate; 
the distance from the edge of the blade to the periphery 
may then be measured with a steel rule. 

When a regular milling cutter is used as a fly cutter, it is 
advisable to drive a dowel-pin into the face plate in such a 
position that it will come between two teeth, and thus pre- 
vent rotation under the pressure of the cutting operation. 



PREPARATION OF STOCK. 

9t. The term stock, when used in connection with a 
milling operation, refers to the work in its rough condition. 
The success of the milling operation depends to a large ex- 
tent on the condition in which the stock reaches the milling 
machine. If the stock is hard, either in spots or all over, 
as is the case with unannealed tool steel and often with 
forgings, or if the stock has a hard skin, as is usually the 
case with iron castings and steel castings, the hardness 
will cause the cutter to dull rapidly, which prevents the 
machine being worked to the best advantage. 

92. In some cases, the stock is as soft as it can be ren- 
dered; no further preparation is then feasible or necessary. 
In other cases, the stock can readily be softened and thus 
be put into a better condition for milling. The softening 
may consist of a removal of hard scale by pickling and rat- 
tling, or uniform softening by annealing, or maybe a com- 
bination of these methods. 

93. Iron and steel castings, when they leave the mold, 
usually have a hard, glossy skin, or scale, as it is called, in 
which sand is frequently embedded. This scale, when the 
size of the casting allows it, can- be pretty thoroughly 



40 



MILLING-MACHINE WORK. 



removed by rattling the casting* in a foundry rattler, 
tumbler, as tome cat] it. Castings of a si*e and a 
prohibit tumbling may have the scale softened so that 
will crumble easily by pickling. This is done by placii 
the castings (or from L0 to 16 minutes into an add I 
posed of 1 part of sulphuric acid to 2a parts of boiling wait 
After pickling, the castings must be thoroughly washed 
clean boiling water in order to remove all traces of the acid, 
which would cause them to rust very rapidly. A hi 
ts often found on forgtngs. This may also be removed 
rattling or pickling. 

94. When castings or forgings are found too hard 
mill easily, even after the scale has been removed, they may 
be annealed by healing them very slowly to a dull-red heat, 
and allowing them to cool gradually. The annealing will 
have the further advantage of releasing, to a large extent, 
the internal stresses that have been set up in forging or 
casting. This reduces the extent to which the shape of t 
work will change after machining. 



I 



CUTTING SPEEDS AND FEEDS. 



' 



CUTTING SPBEOS. 

95. Owing to the large variety uf work that may be done 
by milling, no hard and fast rules in regard to proper cul 
ting speed and feed per tooth can be ^'iven as applicable t 
all cases. When much work of the same kind is to he don< 
it is well to experiment a little, starting in with a feed a 
speed that judgment indicates to be conservative, and vai 
ing both gradually until the maximum production at I 
minimum expense per piece has been obtained. 

9fl. The cutting speed depends on several factors, c 
of which is the character of the material to be mill 
its resistance to being severed by the milling cutter. 



3 13 MILLING-MACHINE WORK. 41 

may be stated as a general rule that the harder the material 
the slower the cutting speed must be. Thus, unannealed 
tool steel calls for a low cutting speed, while soft brass 
castings can he advantageously milled at a much higher 
speed. In order to aid the milling-machine operator in 
judging about where to commence to experiment, the 
average cutting speeds for different materials are here given. 
A peripheral (surface) speed of 15 feet per minute can 
rarely be exceeded in unannealed tool steel. If well an- 
nealed, the speed may be increased to 25 feet per minute. 
"Wrought iron, soft machinery steel, and hard white-iron 
castings can be successfully machined at a speed of from 
30 to 40 feet per minute. Medium-hard iron castings, phos- 
fzihor bronze, tobin bronze, aluminum bronze, and similar 
xrery tough copper alloys may stand a cutting speed of 
SO feet per minute, which can be increased to GO feet for 
common, soft gray-iron castings, soft steel castings, and 
■Tialleable-iron castings. Red-brass castings, more com- 
monly but wrongly designated as gun-metal castings, will 
stand a cutting speed of 80 feet per minute; this can be 
easily increased to 100 feet for yellow brass. 

97. Another factor that enters into the selection of a 
proper cutting speed is the presence or absence of provision 
tor carrying away the heat generated in the cutting opera- 
lion. This heat may be carried away by flooding the work 
and cutter with oil or soda water during the milling opera- 
tion; when this is done while a sharp cutter is used, the 
<otting speed may be as much as 50 per cent, in excess of 

that possible in dry milling. 

98. A sharp cutter will easily stand a higher cutting 
speed than a dull one; in this respect a milling cutter is 
analogous to a lathe tool. It may be stated that the duller 
the cutter the more heat will be generated per revolution; 
hence in order to give a chance for this heat to dissipate 
into the work and surrounding atmosphere so that the cut- 
ting edges will not become overheated, the revolutions per 
minute must be lowered. 



MILL1XG-MACHINE WORK. 



em- 
way 

it of 



FEEDS. 

99. The rate of feed depends on the pitch of the t 
the provision made for clearing out the chips, the rigii 
of the work and machine, the manner in which the work 
held, and the degree of finish desired. 

When milling cutters were first made, they were c< 
structed with teeth having a very fine pitch. Experience 
quickly showed that the chips would clog up the spaces be- 
tween the teeth, packing in so closely that the cutter would 
refuse to cut at all except when a very fine Feed 
ployed. Such cutters, instead of cutting, really nibbled a 
little crumbs of metal, as it might be expressed for want 
a better term. It became gradually understood that by 
making the pitch of the teeth coarser, a distinct chip could 
be taken, whose size, so far as the cutter was oo 
was limited only by the size of the space between the teeth 
and the provision made for clearing out this space. Finn 
this the conclusion may be drawn that, other conditions per- 
mitting, the rate of feed per tooth can be greater as thi 
pitch of the teeth is made larger. The rate of feed obi 
ously must never be so large as to break the tooth 

100. The rigidity of the work, that is, its resisl 
to a change of form under the pressure of the cutting o| 
ation, exercises a powerful influence over the rate of fe< 
Therefore, if the work will spring easily, a fine feed must 
be employed; when it is very rigid the feed can be increased 
up to the limit. Likewise, if the work is substantial!; 
held, a coarser feed is permissible than when it is Ughl 
held. 

As stated in Art. 99, the permissible feed is influence 
largely by the space available between the teeth for the re- 
ception of the chip. Evidently, this space can be filled 
either by a heavy and short chip or a fine and long chip 
equal volume. From this the conclusion may be dra' 
that for a shallow roughing cut the feed may be coarse, a 
that increasing the depth of the cut requires a decrease 
the feed. 



tly 

:ed 



I 13 MILLING-MACHINE WORK. 43 

101. The degree of finish desired largely influences the 
choice of feed. As a general rule, it may be stated that for 
roughing out, a relatively low cutting speed and a heavy 
feed will be found advantageous, while for finishing, a 
higher cutting speed and fine feed are needed. The only 
exception is in the case of side milling with inserted-tooth 
or insert ed-blade cutters. Here a wide, flat-nosed cutting 
edge can be used, and, consequently, a very wide feed is 
permissible. 

Another point that must be taken into consideration when 
experimenting for a proper feed and cutting speed for a 
particular job, is the difficulty of resetting some forms of 
gang cutters after sharpening bo that they will cut exactly 
the same shape as before. In such cases, it will occasionally 
prove more economical to use a slower speed and lighter feed 
in order to make the cutter last longer and thus save the 
time required for resetting it after it has been sharpened. 

102. The peripheral speed (the cutting speed) of a 
milling cutter can readily be found in feet per minute by 
multiplying its diameter, in inches, by B.1418 and by the 
number of revolutions per minute, and dividing the product 
by 12. The revolutions per minute can be obtained by 
using a speed indicator, which is an instrument made for 

lis purpose. 

cutter 3 indies in diameter makes 120 revolutions per 
What is its cutting speed in feet per minute ? 

-Applying the rule given in Art. 102, we get 
3X 3.1416 X 120 _ 




v: 



- = 04.95 feet. Ans. 



103. Tables I and II were calculated by Mr. C. C. 
and first published in "Machinery." These tables 

: very useful for finding ihe cutting speeds of milling cut- 
ters when the diameter of the evitter and the number of 
revolutions per minute are known. Likewise, if a cutting 
speed has been selected rind the diameter of the cutter is 
known, the number of revolutions it must make per minute 

T 1 B— 38 



U MILLING-MACHINE WORK. §13 

can be taken directly from the table. These tables are appli. 
cable to lathe work as well, by considering the diameter of 
the work instead of the diameter of the milling cutter. 

1 04« Suppose the diameter of the cutter (or work) is 
given, and a cutting speed has been selected. To find 
the corresponding number of revolutions, look in the first 
line at the top for the nearest diameter. Follow down the 
column headed by the diameter until a cutting speed nearest 
to the one selected is found. In the first column at the 
left will be found the corresponding number of revolutions 
per minute. 

1 OS. When the revolutions per minute and the diameter 
of the cutter (or work) are known, to find the correspond- 
ing cutting speed, look in the first column at the left for the 
nearest number of revolutions. Follow this line to the 
right until the column headed by the diameter is reached. 
In this column and on the same line with the number of 
revolutions, the corresponding cutting speed will be found. 





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MILLING-MACHINE WORK. 

(PART 2.) 



OPERATION OF MILLING MACHINES. 



LUBRICATION. 

1. Purpose of Lubrication. — An ample lubrication 
of a milling cutter during the cutting operation not only 
decreases the friction and thus lessens the heating of the 
work and cutter, but also carries the heat away to an extent 
depending on the character, volume, and method of appli- 
cation of the lubricant employed. 

The carrying away of the heat is probably the chief benefit 
derived from an ample application of a lubricant, experience 
having shown that keeping the cutting edges cool largely 
prevents them from becoming dull. A proper application 
of the lubricant will also quite effectively prevent the chips 
from filling up the spaces between the teeth of the cutter, 
and will consequently permit an increase in the rate of feed. 

2m Materials Requiring Lubrication. — Experience 
has shown* that no lubrication is required for milling ordi- 
nary gray cast-iron and yellow-brass castings. For milling 
wrought iron, steel, steel castings, malleable-iron castings, 
hard cast iron, bronze, copper, and the various tough copper 
alloys, lubrication of some sort is usually either necessary 
or advisable. 

Por notice of copyright, see page immediatel v following the title page. 



MILLING-MACHINE WORK. 



8" 

ers is 

water 



LUBRICANTS. 

3. The lubricant generally used for milling cutters is 
either some oil or a mixture of some oil with soda water 
and other ingredients. While oil alone is probably the best 
lubricant, it is also the most expensive; for this reason, it is 
rarely used for any other than small, fine milling, where 
ample provision may be made for catching most of the 
surplus oil and the chips. A cheap mixture of oil with othei 
ingredients is usually preferred for cases where the surplus 
oil cannot readily be saved. 

4. Pure lard oil is by many conceded to be the 
lubricant for milling cutters, since it has sufficient body ti 
make it adhere well, and, furthermore, it thickens ver; 
slowly from age and use. Its only drawback is the con* - 
paratively high first cost. Some of the so-calied fish 
are considerably cheaper than a good grade of lard oil, and 
are considered by some to be fair substitutes. If most of 
the drippings and chips are caught, the oil may be separate *.l 
by some form of oil separator, of which a number are in the 
market, in which case a high-priced lard oil will oft*=r» 
prove the cheapest in the long run, since its superior lubri- 
cating qualities enable more work to be done. 



METHODS OP I.IIIIJkATIOV. 

5. Choice of Method.— The choice of a method *"** 
applying a lubricant naturally depends on the service ■" 
which the machine is engaged. When only a few pie*^"^ s 
are to be milled, an expensive lubricating system is scare ^s "> v 
advisable; when the machine is constantly employed * '" 
duplicate work, an elaborate lubricating system will usu»l ")' 
pay for itself in a short time by reason of the decrease * n 
cost of maintenance of cutters and increase in production. 

The different methods of applying a lubricant to a mill if"* & 
cutter are by a brush, by a gravity feed, and by a pump. 

6. By Brush. — The simplest method of lubricattc-* 1 
consists of applying the lubricant to the cutter with a brusr ~» • 



§14 



MILLING-MACHINE WORK. 






This method is well adapted to delicate work where light 
cuts are taken. The oil supply being intermittent in this 
case, it must be frequently renewed, the chips at the same 
time being cleared out from between the teeth of the cutter. 
In applying the brush, care must always be taken to so 
apply it that there is no likelihood of the brush being drawn 
toward the work by the cutter; that is, apply it to the side 
of the cutter that runs away from the work. A stiff, long- 
handled, bristle brush is preferable for this work; camel's- 
hair brushes are too soft for an efficient removal of the 
chips. 

7. By Gravity. — In general, a constant lubrication is 
preferable to an intermittent one. For this purpose a can 
or a small tank may be placed at some distance above the 
cutter; a bent drip pipe with a stop-cock in it may be used 
forconveying the lubricant to the top of the cutter. The 
rate of How is then adjusted by turning the BtOp-COck, 
Such a tank is furnished with most milling machines; many 
machines have the table so designed as to catch ;ill the 
drippings and chips. The lubricant is then drained off into 
a suitable receptacle, and after being strained or otherwise 
purified, it may be used again. 

8. When no provision has been made for catching the 
drippings, a suitable drip pan may be placed under the 
work. Such a drip pan may easily be made from a piece of 
sheet tin, bent up to form a box. A piece of brass wire 
gauze having about 80 meshes t-j the inch may be soldered 
to a Frame placed into the drip pan, so that the gauze is 
about 1 inch above the bottom of the pan. This will strain 
the lubricant automatically to a fairly satisfactory extent; 
;ts soon as the drip pan is full, the strainer with the chips is 
lifted off and the strained lubricant poured into the lank. 
After thi? lubricant lias been used a number of times, it 
requires si raining in smiic my re i.Tlirioiit iiMimer. 

9. By Pumping. — A constant stream of lubricant will 
not only keep the cutter sharp for a greater length of time, 
but will also wash the chips out of the cutter. This fact 



Ti )RK. 



■::u-iu ;nl..|'ti.l 
- ! (..r fairlv !•■ 




I u 



MILLING-MACHINE work. 



hrough the pipe system d d and is delivered directly on 
he cutter. In order to accommodate different sizes and 
isitions of the cutter, the upper part of the piping has 
swivel joints and, hence, can be arranged to deliver the 
lubricant where it will be most effective. The quantity of 
lubricant that is discharged can be regulated by the stop- 
cock e. The pump a runs at a constant speed and conse- 
quently delivers a constant volume of lubricant. When 
less than this quantity is used, the rising of the pressure in 
the pipe system will open the relief valve/, and the excess 
will pass back into the tank. In the machine shown, a 
gutter extends around the table, from which the lubricant 
drains into the trough g, and then through the flexible tu- 
bing /( back to the tank. It is thus seen that the lubricant 
is used over and over again; the only lubricant lost is that 
adhering to the chips, but a large percentage of this can be 
recovered if a separator is available. 

11. When the lubricant is supplied iu a constant 
stream, it is well to discharge it as close to the cutter as cir- 
cumstances permit, in order to prevent splashing; it should 
be delivered preferably in such a direction that the issuing 
stream will tend to wash the chips out of the cutter and 
away from the cuts. 

12. Internally Lubricated Cutter. — The advan- 
tages to be derived from a forced system of lubrication so 




pplied as to effectively clear the cutter have led to the 
lesign of internally lubricated cutters. Such a cutter, 

■atented by the Newton Machine Tool Works, is shown in 



MILLING-MACHINE WORK. 



Fig. 3. Referring to the figure, the arbor a is seen to havi 
a central hole drilled into it; this hole extends nearly t 
plane of the shoulder against which the cutter is clamped, 
A number of radial holes, as b, b, are drilled through t 
arbor, and hence the recess within the cutter c is in com 
munication with the central hole of the arbor. A number t 
holes, as (/, d, are drilled in the clearance spaces through 
the shell of the cutter. The lubricant is pumped through a 
tube £ into the arbor and issues in fine streams through the 
holes d, d, thus effectually clearing the cutter of chips and 
applying the lubricant where it is most needed, that i 
directly to the cutting edges. The end of the arbor : 
tapering, and fits atapered hole of the stationary bushing_/", 
which is placed in the outboard bearing. This construc- 
tion allows the arbor to revolve, but prevents any escape of 
the lubricant except through the radial holes in the arbor. 



SELECTION OF CUTTER. 



and 
: is, 

r is 



UiMii riovs i.hmmmm; THE CBOICB. 

13. The selection of u cutter for a job is a matter 
that depends not only on the nature of the work, but also 
on the construction of the machine, the attachments to 
the machine, the rigidity of the work itself, the manner 
in which it can be or is held, and the cutters that are avail- 
able. For instance, if a large surface of a rather springy 
casting is to be finished by milling, it will often be out of 
the question to use a wide cylindrical plain cutter, because 
the pressure of the cutting operation, even with a very fine 
cut, may be sufficient to seriously spring the work. But, if 
a small end mill is used, it may be possible to make a very 
satisfactory job of machining the casting. 

I 4. Some machines are so constructed that only side 
milling cutters can be used, hence the operator has no lait. 
tude at all in the choice of a cutter. Other machines have 
no outboard bearing to support the arbor; it would be a 



§ 14 MILLING-MACHINE WORK. 7 

mistake to select a wide cylindrical plain cutter for finish- 
ing a wide plane surface in such a machine, since the spring 
of the arbor even under a very light cut may be sufficient to 
condemn the work. In such a case, a side mill or end mill 
would probably prove satisfactory. 

15. When surfaces parallel to the line of motion are to 
be finished at an angle to each other, it usually becomes a 
question of attachments, cutters, and type of machine avail- 
able. For .instance, in a plain milling machine it may be 
possible to do the job only by the use of angular cutters; in 
a universal milling machine, when the job may be held 
between centers, it might be done by a cylindrical plain 
cutter, and so on. 

16. When the choice has narrowed down to a certain 
type of cutter, the question of which kind of the chosen type 
of cutter will remove the most stock at the least expense 
often becomes a very pertinent one. Suppose that it has 
been determined that a cylindrical plain cutter is to be used. 
Then, if the surface is narrow, a straight-tooth cutter should 
be selected, and if heavy milling (i. e., the removal of a 
large amount of stock) is required, a nicked cutter or its 
equivalent (an inserted-tooth cutter) would be selected. 

17. When it is a question of whether a plain mill, a side 
mill, or an end mill is to be used, it is to be observed that 
for side milling and end milling less power is usually re- 
quired. Furthermore, when the cutter must pass over 
slender or pointed parts of the work, there is less springing 
and less breaking of the edges with a side cutter or end 
cutter than with a plain cutter. On the other hand, the 
plain cutter will usually produce the work in less time, and 
is the one to use when other circumstances permit it. 

18. Considering now the case of grooving, when the 
groove is straight, it can usually be cut cheapest by plain 
cutters, slitting cutters, or formed cutters, depending on 
the profile of the groove. When the groove follows a heli- 
cal path, it can be cut by an end mill, a form cutter, a 



8 



MILLING-MACHINE WORK. 



§ I 4 



formed cutter, or an angular cutter; when the cross-sect 
of a helical groove is required to be rectangular, a plain m 
ing cutter or slitting cutter cannot be used, but an end 
must be employed instead. When grooves following an 
regular path are to be cut, an end mill will almost invaria. 
have to be used, although it may be possible occasion 
to use plain mills or formed mills for part of the groove. 

From the foregoing statements it will be seen that 1 
selection of a cutter is a matter of judgment, which must: 
based on practical experience with different milling ope 
tions. 



n 
ll- 
ill 
Ir- 

tly 
:lie 



DIAMETER OF CUTTER. 

19. The diameter of the cutter has an appreciable 
influence over the length of time required to machine a sur> 
face. As a general rule, it may be stated that with equal 




sui_ 



m 



«- a 



W 





feeds per minute, a small cutter will pass over a surface? 
less time than a large cutter. In order to show the rea^ 



an 



;i4 MILLING-MACHINE WORK. » 

'■r this statement, Fig. 3 lias been drawn; it shows in dia- 
grammatic form the positions occupied by cutters of differ- 
nt diameters when they begin and cease to cut. Referring 
i Fig. 3 {a), let a be the surface that is to be machined by 
1 mill. Let the circle b represent the diameter of one 
f the two cutters that are available, and let c be the diam- 
:ter of the other. Then, at the beginning of the cut the 
utters will be in the positions shown, and their axes will tie 
t i/and e. Now, in order to pass clear across the surface a, 
he cutter b must advance to b', and its axis will then be 
at d'. It is seen that the length of the path of b is equal to 
the distance d ' tt' ', while the length of the path of c is equal 
to ee\ But, ?e' is much greater than dd', which shows 
that a small cutter will travel over a shorter distance than a 
iarge cutter in order to pass over the same surface. The 
same statement applies to plain cutters, angular cutters, 
formed cutters, etc. 

20. Referring to Fig. 3 {b), assume that the work a is 
to be milled down to the dotted line x y, and that 6 and c 
show the diameter of two plain mills when set to begin cut- 
ting. Then, in orderto pass across the work, the cutler b 
must travel the distance dd', while the cutter i-must travel 
the distance c e, which is greater. 

21. A person must not fall into the error of assuming 
from the foregoing that the mere fact of one cutter being 

I ban the other means in itself that the work can be 
machined quicker in every case by using the smaller cutter, 
since it is only when circumstances permit equal, or nearly 
equal, rates of feed per minute that the smaller cutter will 
have the advantage. Under these conditions, on some 
classes of work a saving as high as 10 per cent, may be ef- 
fected iu the lime cost by the difference of only \ inch in the 
diameters of the cutters. It is well to bear in mind that 
t h i-_- s;Lvin£ effected by the use of the smaller cutter is pro- 
portionally greater for short work than for long work. Re- 
ferring to Fig. 3 (a), the distance saved by the use of the 
smaller cutter is ed-\- d'e'. Evidently, this saving for the 



10 MILLING-MACHINE WORK. $14 

given difference in diameters remains constant, ■■■ 
what the length of the work, and it f6Qo« 

between the saving effected and the total distance 
traveled by the larger cutter becomes less as the I 
t.nu'.' becomes greater, 

22. The minimum size of cutter that can be used is 
naturally governed by practical consider i 

the case of an end null, it must be sufficiently stiti I 
a fair cut without bending; in the case of a plain 
advisability of leaving sufficient stock around the hole of 
the cutter governs its smallest permissible size. Again, a 
short cutter i an usually be smallei i ide cutter, 

since the stresses to which the cutter is subjected by the cm- 
ting operation will, as a general rule, be less severe with a 
narrow than with a wide cutter. 



LIMITATIONS AND BBHOR8. 

2,'t. The limits within which work can In- milled t<. a 
given sise largely depend on the construction of the machine 
and the character of the workmanship, al 
.mil tin- nature "I the work. With a high-grade mat 
first-class condition, and using sharp cutlers 
rigidly held, many jobs can readily he milled will. 
small limit of variation, say ,„'„,•, inch. I:. 

duplicate work done in large quantities, all lining 
can be entirely done away with, since ll is prw 
mil] the work close enough tor a fail lit. Willi a 
machine in poor condition, and dull cutti i 
cannot be obtained, and work done on them will mm 
for considerable hand tilting, not only on 

greattn variation in the size but als a 

quality of the surfai ■ ■■ produced under bu< I 

24. It is not possible to stale definitely what the limit 
should he within which work should be milled to a given 
sine. This limit naturally depends on the purpose of the 



MILLING-MACHINE WORK. 



11 



8" 

work; for comparatively rough work, as milling nuts, bolt- 
heads, the squares on the ends of taps and reamers, etc., a 
limit of mVir ' nCH mav usually be considered as allowable. 
Work (hat is milled only for finish can often vary consider- 
ably from its true size; the amount allowable must obvi- 
ously be determined on the merits of each case. Parts of 
sewing machines, typewriters, firearms, and similar fine, 
small work are usually finished within a limit of -rf^ inch, 
although some parts require to be, and can be, finished within 
a smaller limit. 

25. When milling large work, or finishing a rather wide 
surface with a plain mill, it is not always possible to obtain as 
close an approach to a plain surface as the planer tool with 
its single cutting edyc will produce. One reason for this is 
a lack of rigidity of the machine used; another reason may 
be found in the fact that with a milling cutter, the pressure 
on the work during the cutting operation is many times 
greater than in the case of the planer tool, and, hence, 
there will be more springing of the work. Furthermore, 
when a plain cutter is beginning to take a chip while the 
work is fed against the cutter, the pressure is at first in line, 
or nearly so, with the surface of the work. Now, as the 
tooth doing the cutting advances upwards, the direction of 
the pressure changes, and, being upwards, tends to lift the 
work from its fastenings. This change in the direction of 
the pressure is naturally most marked in deep cuts, and if 
the work yields to a sensible extent, will result i 
surface. 

26. In a planer, shaper, or slotter, howeve 
tion of the pressure never changes, and sim 
much less than with a milling machine, it follows that as 
far as large plane surfaces are concerned, the machine tools 
first mentioned can, in general, be better relied on to pro- 
duce them. As a m.itler of course, with a very rigid 
machine especially designed for surface milling, and with- 

so rigid that deflection will be so small as to be insen- 
a very close approach to a plane surface can be 



i an uneven 



, the direc- 

i intensity is 



MILLING-MACHINE WORK. 

obtained by milling; in general, however, it will be found 

that the planer has slightly the advantage. For this 

it is customary in some places to rough out 

heavy work on some suitable form of a milling machine, 

and then to transfer the work to a planer, « i 

by planing. This will, in many cases, be more eo 

than planing the whole job, since with a properly i 

and handled milling machine, the roughing 

lie done at a fraction of the cost of planing. Wliil 

be conceded that at present the planer has slightly the 

advantage so far as truth of large surfaces is cooo 

can be confidently predicted that in the course of 

the advent of more rigid milling machines, its sup 

will not only disappear, but be surj 

heavy milling machines built today that under i 

conditions will produce true plane surfaces as well as the 

planer. 

27. The commercial limits to the field of usefulness of 
the milling machine arc not known, since new field 
are constantly being found. While it will probably never 
entirely supersede the planer, shaper, or skitter, il a 
be predicted that it wilt more and more take their place for 
a large variety of work as the machine become* betirr 
developed and understood. 



HOLDING WOHK. 






GENERAL PB1NC1PLM. 

28. The work may be held in the milling ma 
attaching it directly to the table, by holding il ii* a 
holding it between renters, or in a chuck or on ■ ■■ 
attached to the index head, and, finally, bj I 

fixtures. No matter in what manner the work is held, 
there are certain conditions that must be fulfllfci 
that the machining can be done successfully. First, 



irder 

I 



work must be held so rigid that it cannot slip under the 
pressure of the cutting operation; second, it must not be 
deformed by the clamping; third, it must be so supported 
ty suitable means that it will not deflect either under its 
own weight or the pressure of the cut; fourth, it must be 
lined up properly so that the machining will take place in 
• he required direction. 



HOLDING WORK ON TABLE. 

29. Eli. Minn Devices — If circumstances permit, the 

b «st way of holding work to a table is to bolt it directly 

*** 't, using bolts with low heads that will slip into the 

' slots of the table. When this cannot be done, clamps 

■^ust be used. Owing to the fact that the pressure due 

tQ the cutting operation is usually much larger than is 

tr *e case in planer work, the work must be held much 

'Shter to prevent its slipping, and, hence, in general, the 

c '»rups should be more rigid and the bolts heavier than 

*°Uld be required for the same job on the planer. Further- 

***° r e, a positive stop or stops should be used whenever 

^^sible. If the table has holes in it, pins similar to planer 

J* ,r »s may be used; in the absence of holes, a bar can usually 

^^ bolted directly to the table to form a stop, and the work 

a ** then be pushed against it. Considerable ingenuity will 

l en be required to so clamp the work that there is no 

^^**ger of its slipping, especially in vertical milling machines 

''en the work that is attached to the table is intended to 

machined all around its circumference in one setting. 

such a case, there will be a tendency to rotate the work. 



"*'vh tendency must be counteracted either by the friction 



^ v *sed by clamping or by stop-pins. 

^4(t. The general character of the clamps, pins, screw 

•^ lr *5, toe dogs, and similar clamping devices used does not 

1 *Ttr in any essential particular from that of the corre- 

^Winding devices used in planer work. Neither is there any 

^*fterence as far as their application is concerned, except 



MILLING-MACHINE WORK. 



that more attention must usually he paid to support 
work on a milling machine than is required for a planer. 

31- Construction <>f ll'Unry Pinner. — An 
of iiuw work may be clamped to ;i milling 
given in Fig. 4. In this case, the machine used belongs m 
a type designed especially for producing flat surfaces by the 
uae of a large side milling cuttci Su< I 
commonly called rotary planers. In the tnaobin 
the bed * has flat ways on top to » 
The saddle carries the spindle and cuttei , 
ing from the belt pulley t. A suiti 
ment allows t lit? saddle to be moved along the bed either by 




hand or automatically; most machines hai s 

puts by means cif which the feed can be si 

determined point. As f;ir as adjusting the cutter for the 

proper depth of cut is concerned, practice varies. 

machines, the spindle and cutter are movable sj 

limited extent, while in others, the table can be i 

a. direction parallel to that of the spindle. Both 

accomplish the same thing and incidentally show 

quently then- arc a number of different ways of pel 

the same operation. In the particular machine shown, (he 

table is moved by means of a feed-screw operate 

handJe A 



I u 



MILLING-MACHINE WORK. 



32. Lining the Work. — The work e is a large bracket ; 
it is intended to machine the surface toward the bed so as 
to be at right angles to the surface that rests upon the 
table. Now, in rotary planers, and also in nearly all mill- 
ing machines, except those of the vertical type, and in some 
special machines, the axis of the spindle is parallel to the 
surface of the table/; and since aside cutter produces a 
surface at right angles to the axis of the spindle, it follows 
from the construction of the machine that if one surface of 
the bracket £ rests upon the table, the other surface will be 
machined at right angles to it. 

33. When it is required that the surface about to be 
machined is to be at right angles to the surface r', the work 
must be fastened in the proper position to accomplish this. 
If the edge of the table that is toward the bed is parallel 
to th< line of motion of the saddle, as is usually the case, a 
try square may be used for lining up the work. The stock 
of the square is then placed against the edge of the table 
and the casting is shifted until its surface e' touches the 
blade of the square throughout its length. In many cases, 
it will be possible to set work square by placing the stock 
of the try square against the edge a' of the bed, which 
naturally is parallel to the line of motion of the saddle, 
since it is a part of the ways on which the saddle slides. 
W. nk may be set parallel to the line of motion by the aid of 
inside calipers applied between a' and the work. When this 
cannot be done, the milling cutter itself may be used for 
testing the setting by having it first in the position shown 
and measuring the distance between some tooth and the 
work. The saddle is then fed along the bed until the tooth 
selected for testing is near the left-hand edge of the work; 
its distance from the work is then measured, and if the two 
measurements agree, the work is correctly set. It will be 

iderstood that the cutter must not be in motion during the 
icess of testing. 

34. Clamping tbe Work. — A job of the nature shown 
I the illustration would most likely be clamped by using 



10 MILLING-MACHINE WORK. 

bolts and clamps, asg, g. These clamps may have one e 
bent to obviate the use of blocking, or they may be straight 
in which case they must be hlorked up. With the ciitle 
revolving in the direction of the arrow x, the pn 
the cut will tend to shift the work in the direct i 
arrnv j>; for this reason, a stop // is bolted to the table and 
against the surface e' of the work. The stop is 
strap having two holes in it; bolts are slipped into a T slot 
in the table and pass through the holes of the strap, which 
h clamped by tightening the nuts on the bolts. It will be 
observed that the strap fs held from slipping 1 
it is wise for this reason to place a piece of manila paper be- 
tween the table and the strap, since expel [i 
that this will greatly increase the resistance to slipping. If 
the table has holes in it for the reception of pins, ii | 
to use pins for stops, since they cannot slip. 

35. Use of \nn-lc Plate for Plain MUlinic Ma. 

cMnet.— Fig, 5 is an example of how a job may be 

to the table of a plain milling machine of the pi] 
using an angle plate to hold the work square with 1 1 
In this case, the work it is a sliding table for a machine tool; 
it has a dovetailed bottom that is to be accurately mi 
so that the bottom surfaces are parallel to the top. A littlr 
study will show that with this type of a machine, the mill- 
ing can be done only with end mills and an angular mill 
fastened to a shank, if the whole bottom is in lie finished in 
one setting, which is necessary if all surfaces of the bottom 
are to be correctly machined. This means thai 
must be set up on edge, and since it would have hu 
small bearing on the milling-machine table, an angle plateA 
can be advantageously used to insure that the bottom will 
be milled parallel to the top, and also to steady the work. 
Since the work has T slots in it, bolts can be slipp 
these; they are then passed through the slots of the ; 
plate in order to bolt the work to it. In case the an| 
plate has no slots that will come opposite the al 
work, the latter could be attached by bolts and clamp; 



MILLING-MACHINE WORK. 17 

the angle plate. The work is held down on the milling- 
machine table by tlie clamps c, c, the rear ends of which 
rest on packing blocks d, d. The pressure of the cutting 




eration in this case tends to overturn the work and 

to slide it along the milling-machine table; the first 

endency is resisted by the angle plate and the second by 



MILLING-MACHINE WORK. §14 

the stops f, e, which are bolted to the table in contact with 
the ends of the work. 

36. Lining the Work. — Lining the work is accom- 
plished, in this case, by a proper lining up of the angle plate. 
Since the surface of the milling-machine table, in all ma- 
chines of the type shown, is parallel to the axis of the 
spindle, the surface of the angle plate that is toward the 
spindle will be at right angles to the axis, if the plate is 
bolted directly to the table; consequently, it only remains 
to line up the plate parallel to the line of motion of the 
table. This can be done by the aid of some suitable tool 
with a blunt point that is held in the spindle. Run out the 
table until the marking point is near one edge of the angle 
plate, say the right-band one; then, by means of the cross- 
feed screw in the knee, move the table toward the mark- 
ing point until a piece of paper will just be nipped between 
the marking point and angle plate. Now run the table 
back until the marking point is near the left-hand edge 
of the angle plate and see if the paper will be nipped again. 
If this is not the case, it shows that the angle plate must be 
shifted; after each shifting, the setting must be tested again 
in the same manner. 

37. Testing tbe Setting of Work. — In milling 
machines arranged for plain or angular milling, as in the 
machine shown in Fig. 5, the setting of work may be 
tested for parallelism with the surface of the table by means*- 
of a surface gauge, which is used exactly as in planer work- 
When for any reason a surface gauge cannot be employed., 
a scriber may be clamped between the washers of the^ 
milling-machine arbor and used for testing the setting by 
moving the table under it. It will be understood that the 
spindle must be stationary during the testing. 

38. A piece of work of the nature shown in Fig. 
could have been set quicker in a vertical milling marhim 
since in such a machine it could have been clamped direct 
to the surface of the table, using finger clamps inserted i 
the T slots of the work for holding it. 




: !i 



MILI.INCMACHINE WORK. 



19 



39. Holding Work in a Vertical Milling Ma- 
chine. — Fig. 6 is an example of how work may be clamped 
to the table e of a vertical milling machine when it is re- 
quired to machine the circumference of the work. In this 
case, the job is the strap for a steam-engine connecting-rod 
that is to be milled with a cylindrical end mill a. In order 




that the end of the mill may clear the table, the work c is 
placed on two parallel blocks /', /', which raise its bottom 
above the table. Short clamps i/, d are placed on top of 
be strap over the clamping bolts, which have previously 
i inserted in the T sluts of the table. The outside of 



MILLING-MACHINE WORK. 



the strap can easily he finished by milling; without chan- 
ging the setting. After the outside is finished, clamps may 
be applied from the outside before the inside clamps are re- 
moved; when these outside clamps have been tightened, the 
inside clamps d, d are removed. By proceeding in this 
manner, the setting of the work will not be changed and 
the inside of the strap will be left clear for milling. 

The straight surfaces of the strap are finished by using 
the regular feeds; the curved end must, however, be fin- 
ished by working both feeds simultaneously by hand, cutting 
to a line previously drawn on the top surface of the strap, 
which line shows the edges of the work when finished. 

40. When a job is held to the table in such a manner that 

it can be machined all around its circumference, it will 
usually be a rather difficult matter to provide positive stops 
that will prevent shifting, and the friction created in clamp- 
ing must be relied on. It may be stated as a general rule, 
that whenever it is possible to use positive stops, it is advisa- 
ble to do so. When friction alone prevents slipping, lighter 
cuts and lighter feeds must be used, and special care is re- 
quired in starting the cut. 

41. Construction of a Vertical Milling Mncliinc. 

The vertical milling machine shown in Fig. fi is one of the 
many designs in the market. The table e is arranged to be 
fed in two horizontal directions at right angles to each others 
its level is fixed. The spindle f is adjustable in a vertical 
direction, and a good support close to the cutter is providedl 
by making the headstock g adjustable. The table is pro 
vided with an automatic feed in both directions; the feed- 
shaft h is driven by belting it to a pulley on the spindle / 
and carries a small friction wheel that is in contact with the 
feed-disk /' and rotates it by friction. The friction wheel on 
the feed-shaft is fitted in such a manner that it can be moved 
along the shaft, and, consequently, its position in regard to 
the center of the disk i may be varied. Since the rate at 
which the feed-disk revolves depends directly on the dis- 
tance of the friction wheel from the center of the disk, it 



MILLING-MACHINE WORK. 21 

i that, by moving the friction wheel to different posi- 
■ns, the rale of feed is varied, and by shifting it past the 
ter of [he feed-disk, the feed is reversed. 



-42. Some vertical milling machines have a removable 

>ttom bearing for the end of the spindle; this corresponds 

the outboard bearing of the horizontal mifling machine 

I serves the same purpose. The vertical milling machine 

not be said to be able to do work that cannot be done on 

horizontal type of machine; it is more convenient, how- 

•er, for work that requires to be finished with end milts, 
ce the work is in plain sight. The job shown in Fig. 6 

!ght have been done in the machine shown in Fig. 5 by 
-apping it to an angle plate; it would not have been in as 
.in sight, however. While the vertical milling machine 
>wn is a plain machine, it is also built as a universal 
ichine. 

-43. The peculiar advantage of the vertical machine for 
work, as far as having the cut in plain sight is con- 
ned, has led to the design of 
:cial attachments for convert- 
f a horizontal machine tem- 
rarily into a vertical spindle 
ichine. Such attachments are 

pplietl by all the makers of 

illing machines on regular _ 

ders, and are a convenient 
keshift for some work, as, for example, the job shown in 
r. 7. This piece of work requires to have its top surface 
d all the surfaces of the recess finished by milling. If a 
rtical spindle machine is available, it should be chosen for 
ing the job; in the absence of one, a vertical milling 
achment may be used on a horizontal machine. When 
such attachment is available for a horizontal machine, 
: work must be fastened to an angle plate. 

Lining the Work. — When it is required that the 
surface of a job be finished parallel to the surface of the 




MILLING-MACHINE WORK. 



milling-machine table, its setting in most cases is most con- 
veniently tested wiili B6u 

wort are to be lined up parallel with either din 
notion ni" the table, the setting may be tested with a pouitei 
damped to the Spindle, traversing the work along the 
pointer. 

In sinrn: cases a large try square may he used J 

blade may be applied to the work while tin Etocl 
! against one of the edges of the table, M : 
usually made exactly parallel bo the line of motion for thi* 
very purpose. 

45. v Doable-Headed MsMttlne — Fig. 8 is an < 
ample showing how work may be held on the table i 
machine that resembles a planer in some respects. 




Plo. 8. 

particular machine is of the multispiodle type, having t 

independently adjustable spindles a and 

can be used for driving an arbor c from both ends, as is ' 



i 14 MILLING-MACHINE WORK. 23 

in this case, The work tl is a side rod for a locomotive, 
which is to be milled out between the ends to an I section. 
Th<! cut that is taken is quite heavy, being about 4J inches 
wide, 1-|\ inches deep, and feeding at the rate of 2 inches 
per minute. In consequence of this, the pressure of the 
cutting operation that tends to slide the work along the 
table is quite heavy. In this case, movement of the work 
is prevented by letting it butt against an angle plate <*, which 
is bolted to the table at the rear, and which, in turn, is pre- 
vented from shifting by struts that are placed between it 
and the end of the table. Owing to the view taken, these 
struts cannot be seen. The work is held down on the tabic 
by bolts and clamps placed at each end; the clamp _^at the 
front end can be plainly seen in the illustration. Jacks g,g, 
each of which has two setscrews, are bolted to the table 
and are used for adjusting and confining the work sidewise. 
A double-headed machine, like the one shown, is wdl 
adapted for finishing two surfaces parallel to each other in 

re passage of the work past the cutters. 
46. Clamping WorkforGroovlnR. — Fig, 9(a)shows 
how cylindrical work may be held on the table of a horizon- 
tal milling machine when a slot or groove is to be milled in 
it in line with the axis of the work. A milling-machine 
strip a, which has a tongue u'at the bottom, is bolted to the 
table with the tongue in one of the T slots. The surface a' 
of the strip is machined parallel to the line of motion of the 
table, hence, any work placed against it is parallel to the 
line of motion. Persons familiar with planer work will 
recognize the milling-machine strip as the device known as 
a planer strip, which is constructed in the same manner and 
serves the same purpose. 

Let b be a shaft in which a key way (shown in dotted lines 
at the top) is to be cut throughout its whole length. Then, 
evidently, the clamps must be clear of the cutler and, 
hence, must be placed about in the position shown. When 
the clamp is tightened on the work, the pressure will be 
exerted along a line as c d, so that the shaft will be held to 



u 



MILLING- MACHINE WORK. 



the table and against the milling- machine strip at the sa 
time. Inconsequence of the direction in which the press 
acts, the clamp tends to slip in the direction of the arrow 
if the clamp used is a U clamp, it will simply slide 
From this it follows that a clamp witb a hole to fit 




clamping bolt must be used. With such a clamp, the s 
ping is resisted only by the resistance of the clamping 1 
to bending; if this bolt is short and stiff, it will usually 
sufficient, but if it is rather long, as must be the case w 
the diameter of the work is large, it will bend. 



MILLING-MACHINE WORK. 



47. Fig. (b) shows how the clamp may be constructed 
a prevent it from slipping back. The clamp is bent and 
ladeof such a length that its rear end y will catch the edge 
of a T slot. Fig. 9 (c) shows a way of accomplishing the 
same thing by the use of a special packing block e, which 
has a projection on it to prevent the clamp from moving, 
and is bolted to the table. The block may be adjusted 
for different heights of work by turning the setscrew /; 
the rear end of the clamp rests on the head of this set- 

Frew. 
48. Adjustable Hacking Block. — Fig. 10 is a sug- 
gestion of how a shaft that is to be splined may be held for 
milling with an end mill in a horizontal machine, or with a 
slotting cutter in a vertical machine. The shaft b is placed 
in one of the T slots of the table, the edges of which, being 
parallel to the line of motion, will line the shaft properly. 
The packing block a is adjustable for height, being made in 



^^ 



r- 




parts that are duplicates of each other, and with saw 
teeth of about ^- to ^-inch pitch on their inclined sides. 
This style of packing block is very little known at present; 
it will be found one of the most useful articles for the mill- 
ing machine, planer, drill press, etc., when much work is 
to be held by clamps. When work is held in the manner 
shown in Fig. 10, there is no tendency for the clamp to 
slip off in clamping, hence, U clamps may be used to 
advantage. 



MILLING. MACHINE WORK 



49. 



HOLDING WOUK IK THE VISE. 

Purpose of tue Vise. — The vise used hi 



machine work isintended for holding small work having t 
parallel surfaces, and can only be used for other 
substituting special jaws for the regular ones. Milling- 
machine vises are made in various ways by the different 
makers; when the machine is used only for plain milling, 
the vise is usually made so that it can be placed on tbc 




machine either wiih its jaws in line or at right angles t 
direction of motion of the table, but not at any other a 
Such a vise is called a plain vise, and is most frequently 
used with plain milling machines, as, for instfcfl 
so-called Lincoln type of machine shown in Fig. 11, which ia 
intended especially for vise milling on duplicate work done 
in large quantities. 

50. Construction of tbe Lincoln Miller. — The dis- 
tinguishing feature of the Lincoln type of machine is a 



§ 14 MILLING-MACHINE WORK. 27 

vertically adjustable horizontal spindle b and a correspond- 
ing outboard bearing d. The table a is movable both in line 
with, and at right angles to, the spindle b; the plain vise c is 
rigidly bolted to the table (with its jaws parallel to the axis 
of the spindle in this case). The Lincoln type of machine 
is especially adapted for short cuts on work that can be held 
in a vise, or in any fixture that is the equivalent of a vise, and 
is capable, with proper handling, of doing very accurate 
work of the class it is intended for, since the design allows 
a very compact, rigid, and comparatively inexpensive ma- 
chine. Machines of this design are largely used in type- 
writer, sewing-machine, and armory work. 

51. Swivel Vise. — For general work, milling-machine 
vises are usually constructed with a swivel base, and are 
then called swivel 
vines. One design of 
such a vise is shown in 
Fig. IS {a). It has a 
movable jaw a and a 
fixed jaw b; the jaw u 
can be set up by the 
screw c and crank 
handle d. The base is 
circular and graduated 
into degrees; it can be 
swiveled around on the 
subbase e and clamped 
to it in any position. 
This subbase is bolted 
to the milling-machine 
table; it usually has 
tongues that fit a T 
slot of the table and 
insure that a zero mark 
on the subbase is in line 
with one, and at right 
ngles to the other, direction 




if motion of the table. The 



MILLING. MACHINE WORK. 



114 



graduation on the base of the vise, as a general rule, is so 
placed that when its zero coincides with the zero mark of 
the subbase, the jaws will In: in tine with the spindle. Con- 
sequently, the reading of the graduation indicates the angle 
included between the vise jaws and the axis of the spindle. 

52. In a regular milling-machine vis..-, 
face of the jaws is always exactly at right angles to 
face of the table; consequently, if any work is held between 
the jaws, its top surface will be milled square with tin: ndei fa 
contact with the vise jaws when a cut is taken in a direction 
across the jaws, and the measurement is made in the dim - 
tiun of the cut. 

63* The milling-machine vise is used in the same man- 
ner as in planer work, and the same appliances and methods 
are employed for lining up the work and holding it fairly 
against the fixed jaw. It must always be remembered, how- 
ever, that the pressure of the cutting operation 
greater in milling-machine work; for tail 
must be clamped very solidly to the bed, and in case a 
cut is taken parallel to the vise jaws, the work must lie 
held very tight. 

54. Universal Vise. — The milling-machine vise shown 
in Fig. 19 (<<■) can only be swiveled in a horizontal plane. 
Toolmakers, however, often have occasion to take rati 
where a vise adjustable in a vertical plane would be not only 
very convenient, but would also allow the work to be held in 
a better manner than is possible if only a swivul > 
hand. Such a vise is shown in Fig. 12 (/<) ; it is km 
ii ni vernal vise. The universal vise shown consists of three 
parts, which are the base a, the knee h b, and the 
The knee is made in two parts, which are hinged together; 
the lower part of the knee can swivel on the bas< j 
be clamped thereto. The vise itself swivels on the upper 
part of the knee. The knee can beopemV 
bring the vise vertical, and can be securely braced in any 
position by the bracing levers <■/, </, which are joined by a 
clamping bolt. This vise can be swung to almost any 



Flo. 18. 



MILLING-MACHINE WORK 29 

position, and, consequently, its range of usefulness is greatly 
extended over thai of the swivel-base vise. 

55. False Jaws*.— In all milling-machine vises, the jaws 

are faced with removable false steel jaws, as /,/, Fig. 12, 

which makes it an easy matter 

to substitute special jaws to 

hold special forms of work. 

Fig. 13 shows such a pair of 

special jaws, with the work a 

i them; it will be sug- 

of other ways in which such jaws may be made. 

The false jaws b, b are fastened to the jaws of the viae by 

BlUster-headed screws that fit the tapped holes c, <~. These 

special jaws not only servo to hold work of a special form, 

bal also support it close to the cut. Thus, is Fig. 13, the 

exposed top surface of the work is to be finished by a 

formed cutter; reference to the illustration shows the top 

at the false jaws to have been made to conform to the 

profile of the work, but clearing it slightly. The rigid 

support of the work prevents any springing and allows a 

wide cut to be taken with very little, if any, chattering. 

5t>. Setting the Vise,— There are two cases that 

rise in practice in setting a vise, which are: setting it at 

given angle to the axis of the spindle, and setting it 

t a given angle to the line of motion of the Cable, In 

plain horizontal milling machines, the two cases do not differ 

in the least, since the construction of the machine insures 

i rhr vise isset in respect : ie spindle, 

it is also set correct for the line of motion of the table. In 

verticil milling machines, and also in universal nulling 

machines, when the table is swung- from its zero position, 

that is, when its line of motion is not at right angles to 

the axis of the spindle, the vise must be lined up with the 

of motion. 

B7. Plain milling-machine vises as a general rule have 

it right angles to each other cut in the bottom; 

gues that fit a T slot of the table are fastened in these 



MILLING-MACHINE WORK. 



slots and insure that the vise jaws are at right angles to, or 
in line with, the line of motion of the table. In horizontal 
machines in which the table cannot be swiveled, as in plain 
milling machines, and also in universal machines when tin- 
table is set at zero, the tongues insure that the vise jaws are 
either at right angles or parallel to the axis of the spindle, 
depending on the position of the vise. 

58. Graduated swivel-base vises usually have the zei 
mark on the base so placed that when it coincides with t 
zero of the graduation, the jaws will be at right angles to 
the line of motion of the table. Hence, to set the jaws in 
line with the line of motion, make the 90° mark coincide 
with the zero mark. 

59. There are various designs of swivel-base vises i 
use that have no graduations. In horizontal machine; 
where the table cannot be swiveled, and in universal 
machines when the table is at zero, the vise may be lined 
so that its jaws are parallel to the axis of the spindle (at 
right angles to the direction of motion of the table) by 



zero 

ithe 

in 
ide 



at 



i r 






; shown in 
to the axis 



placing the fixed jaw a against the arbor b, as shown 
Fig. 14 (a). To place the jaws at right angles to the a: 
of the spindle, apply a try square c to the fixed jaw a and 
the arbor b, as shown in Fig. 14 (b). To set the jaws at a 
given angle other than a right angle, apply a bevel 
tractor to the arbor and fixed jaw. 



§14 



MILLING-MACHINE WORK. 



31 



60. So far it has been supposed that the arbor runs ex- 
actly true. If this is not the case, the vise jaws must be 
set in a slightly different manner. Run back the table 
until one of the corners of the fixed jaw, as b f touches the 
arbor, as shown in Fig. 15 (a). Measure the amount of 
opening between the corner a of the fixed jaw and the 
arbor. Now give the spindle half a turn and move the 
table until the corner a is in contact with the arbor. Meas- 
ure the amount of space between the corner b and the arbor; 





w 



fa} 




Pig. 15. 



if this agrees with the first measurement, the vise is correctly 
set ; otherwise, it must be shifted until the measurements do 
agree. The same operation may be used for setting the 
vise jaws square to the axis of the spindle, or at an angle. 

It has here been supposed that the arbor is bent directly 
at the shoulder. When this is not the case, as, for instance, 
when the arbor has one or more short kinks in it, the 
method of testing the setting that has just been explained, 
should not be relied on. The proper thing to do is to pro- 
cure a true-running arbor. 

©I. A swivel-base vise without a graduation, or a grad- 
uated-base vise that is to be tested for the correction of its 
zero mark, may be set with its jaws parallel to the line of 
motion of a vertical milling-machine table as follows: put 
an arbor in the spindle and move the table until the arbor a, 
Fig. 16 (a), is near one corner of the fixed iaw b. Put a 



MILLING-MACHINE WORK. 



8" 



parallel strip of metal c between the arbor and the vise jaw, 
and by means of the cross-feed, move the vise toward the 
arbor until the feeling piece c just touches the arbor and the 
fixed jaw. Remove the feeling piece and then move the 
table in the direction of its line of motion, which is shown 




K99fl] 



by the arrow x, until the arbor is near the opposite corner 
of the fixed jaw. Insert the feeling piece again and observe 
if it is in contact with the fixed jaw and arbor. If this is 
not the case, or when the feeling piece will not go in, the 
vise must be shifted and the testing repeated. 

62. To set the vise jaws square to the line of motion, 
clamp a try square between the jaws and test along the 
blade, as shown in Fig. 1C (6). To set the vise to an angle 
when the base is not graduated, instead of the try square, 
use a bevel protractor set to the correct angle. 

The method of setting a vise explained in connection with 
Fig. 16 may also be used for horizontal milling machines, 
clamping a heavy bent piece of wire to the arbor and usinjC 
its point for testing. 

63. Holding Round Work.— The regular milling- 
machine vise is not well adapted for holding round work, 
owing to the fact that the jaws are in contact with such 
work only along one line. Hence, if the vise is tightened 
on the work, the jaws will mar it along the lines of contact 



8 » 



MILLING-MACHINE WORK. 



2.1 



If the vise is used for holding round work, the marring 
lessened, and, at the same time, the work may be 
held more firmly by placing strips of soft sheet copper or 
sheet brass between the jaws and the work. 

fi-1. When much round wort is to be done in the vise, 
it will lie- found advisable to make a V-shaped false j.iw, as is 

shown in Fig. 17, which will ^^^__^ 

cause the work to be held /"" ""\* 

along three lines of contact, 

as a, b, and c, and prevent 

it from tipping upwards <>r — 

downwards when a cut is 

taken over its top surface. 

Si rips .if sheet brass may be placed between the jaws and 

the work to prevent marring. 

65. Split Vise Cliuck. — ■ When a large quantity of 
ylindrical Work (.ill pieces having the same diameter) is 



v_J 



nillingdone on ii after the cylindrical surface is 
sely finished, the split vise chuck shown in Fig. 18 
may be used, This is mai 

..■ ulai piece of steel . ii has 
a hole bored through it to fit the 
work and is split on top tti 
out the whole length. In 
Bat sinl..- ■ 

Rxed jaw and the curved surfaced 
against the movable jaw; the vise 
is then tightened somewhat and 
tha chuck holding the work Is seat* 
ed fair on the bottom ■■■ 
r by tapping it lightly with a soft hammer. When this 




.14 



MILLING-MACHINE WORK. 



8» 



The curved s 



has been done, the vise is tightened again, 
face b allows a slight variation in diameter of the work, since 
it allows the chuck to easily adjust itself. At the same 
time, it insures a fair bearing of 
the flat surface against the fixed 
jaw. Fig. 19 is given as a sug- 
gestion of what work may be done 
on a cylindrical job held in a split 
vise chuck. 




66. A Special Vise — Plain 
milling machines are often used 
entirely for making simple cuts on 
cylindrical work; in such a case, 
a special vise may be used, as, 
for instance, the one shown in 
Fig. 20. In this vise, which may 
plt3, ** be made vertical, as, for instance, 

the one shown, when the character of the work makes it a 
more convenient design, the movable jaw a is flat and the 
fixed jaw b is V-shaped ; hence, the work c will be automati- 
cally lined up and firmly held. The resemblance of the v 
jaws to the special jaws shown in Fig. 17 should be noted. 



HOMING WORK WITH INDEX CENTERS, 

67. Types. — Index centers are made in two types 

1 respectively 






suit different classes of work, which are known 
as plain and universal index centers. Each manufacturer 
naturally has designs of his own for each type; they all em- 
body the same general features, however, which are: a live 
Spindle that can be rotated at will through a definite part of 
a revolution, and a tailstock carrying the dead center. The 
distance between the two centers is made adjustable to ; 
commodate different lengths of work. 

68. Plain Index Center*. — Fig. 21 shows one C 
of a set of plain index centers, which consists of an I 



1 1} 



MILLING-MACHINE WORK. 



SB 



head a and a tallatock b. In this particular case, the 
tailstock forms part of the bedplate b', and the index head 
is movable along this bedplate. In many designs, however, 
the index head and taiistock are not placed on a bed, but 
are clamped directly to the table of the milling machine; in 
that case they usually have tongues on the bottom that fit 
a T slot of the table and insure the proper alinement of the 

ndex centers. The headstock a carries the live spindle to 
which an index plate c is fitted. The back of the index 
plate has several concentric rows of holes, which are spaced 

iquidistant in each separate row; an index pin i/is inserted 




i a movable bracket e in such a manner that its pointed 
end may be made to engage with any row of holes. The 
holes in the index plate are used for obtaining divisions of 
the circle, that is, to indicate when the spindle has been re- 
volved a given number of degrees. The divisions obtain- 
able depend on the number of holes in the different rows; 
they are the quotients obtained by dividing the number of 
holes in each row by all the whole numbers by which it is 
divisible. In each case, the divisor shows how many holes 
the index plate must be moved for each division. 

The spindle is placed in line with the dead center, and 
cannot be moved in a vertical plane. It carries a live center 
and a face plate that takes the tail of the dog used for con- 
ning the work; a setscrew/ confines the tail of the dog. 
be dead center has a limited range of adjustment in line 



u 



MILUNO-MACHINE WORK. 



•rttfi the axis to allow work to be placed and renioi 

between the cent! BVing to move the index 

bead. 

Some designs of a plain Index bead allow a ■ 
lathe chuck to be screwed to the lire spindl 

Increases the range at useful- 
ness. Practically all 
allow t iiu live ceauu 
removed ; an arbor or a collet 
may then be inserted for bobl< 
work. 

tttt. rjalvereal I Btlei 

1 1 tad. — Fig, 

consl ■■■■■ ■ 

ilo. hr.nl. 'Pi:.. ■ 

difference trom the plain 
bead is that th« Index-bead 
spindle is movable in U 
ca! plant-, ami can be 
according to 
through an arc of Froi 

1 
the head 

Spindle, is mounted in a cir- 
i nl.ir guide ot the frame t t and 
in. iv l"- i Igidl ■ ■ lamped to il in 

■ if movement The hi s 
graduated into degrees, and a 

. ■ ■ . 
with a graduation mark, I 
many degrees the axis "f i 

■ 

/ is bolted i.i i he table, .mil is i ., ,>rdci 

at i ' n i ilirlercni lengths -j1 work. 




: fram* 



t 14 MILLING-MACHINE WORK. 37 

70. In this particular design, the spindle carrier an 

■ c with holes in it, which may he used for rapid 
ndexing for the most commonly used divisions of the circle. 

. worm-wheel, Which is inside of [he head, is fastened to 
e spindle; a worm, keyed to a shaft, meshes with this 

This shaft carries an index pin •/, which can be 
made to engage with any of the concentric rows of holes of 
the index plate r, which is fastened to the head. The 
spindle is rotated by turning the worm-shaft by means of 
the index pin, which, when withdrawn from the plate, forms 
the handle ■■( a crank. 

real Index heads are often constructed in such man- 
ner thai the feed-screw of the table and the WOrto-shaft 

■ "tinected by suitable gearing; the spindle of the 
■! will then revolve at the same time that the table 

In a straight line, and the combination of these two 
novements will allow helixes and spirals to be cut. Such a 
universal index head is given the name of spiral index 
head. 

Work Done Between Centers.— The work that 
s most commonly done between centers is the fluting of 
apsand reamers; the milling of the spaces of milling cutters; 
: cutting of small gear-wheels and sprocket wheels; the 
tilling of squares on the end of cylindrical tools; the eat- 
ing of abort fceyways, and similar work. 

72. Confining (lit Work.— Work held between the 
centers is caused to rotate with the spindle by a dog; to pre- 
vent any rocking of the work the tail of the dog must be con- 
fined liy a set screw, which is always fitted to the face plate or 
When the tail cannot be confined with the setscrew, 
' wedge may be driven in between the tail ai 
Ordinary lathe dogs are not particularly well 
for milling-machine work, since their tails will 
■arely come opposite the setscrew in the driver. A reg- 
clamp dog will be found to be more satisfactory in 
respectt than th< lathe dog, since not only will it nut 



MILLING-MACHINE WORK.' 



mar the work as much, but it will also allow the tail to 
be brought opposite the setscrew on all kinds of work within 
its range. 



73. Lining the Centers. — The construction of pUifl 

index centers insures that they are always in line 

sal milling-machine centers, however, require lining up in a 

vertical plane when a cut is to be taken parallel to the a*is 

of the work. Their construction insures that a lit 

the live center and the tailstock center will always lie in a 

vertical plane parallel to the line of motion; bonce, 

up sidewise is ever required, if their tongues arc placed il 

a T slot of the table. 



to 



74. There are two cases that may arise in pracii 
which require a slightly different method of procedure 
line the centers up to the same height. When tin | 
center is not movable in a vertical plane, as in the case of 
the taitstocks shown in Figs. 21 and 22, proceed as [ 

Set the index head as closely 
as possible by the xero mirk 
on the frame and the scro of 
the graduation on the head. 
Then place some piece of 
metal, as a in Pig. 23, one 
end of which has been turned 
to run true, between the cen- 
ters, with the turned end 
toward the tailstock. New 
adjust the pointer /of a sur- 
face gauge to just loach a 
feeling strip of paper placed 
on top of the turned end. Next, turn the piece a end fur 
end, set up the tailstock center, and placing the feeling 
strip on a again, notice if the pointer will touch tt. If il 
does not touch, it shows that the spindle has been depressed 
too much and requires raising; conversely, if 
will not pass over the piece, the spindle is loo high. 




§14 MILLING-MACHINE WORK. 

75. When the tailstock is so arranged that the dead 
center is movable in a vertical plane, set the index head 
to zero as accurately as 
possible. Now place a 
true-running milling- 
machine arbor in the 
index-head spindle 
(practically all modern 
milling machines have 
the same taper hole in 
the spindle and index- 
head spindle, and, 
hence, the arbor in- 
tended for cutters may 
be used) and adjust the Pl0 -*' 

pointer/ of a surface gauge to just touch its top near the 
shoulder, as shown in Fig. 24. Shift the surface gauge to 
the end of the arbor; if the pointer just touches the top 
the index-head spindle is set parallel to the line of 
ition of the table. To adjust the tailstock center, use a 
explained in connection with Fig. 23, placing its 
turned end toward the index head at first. Raise or depress 
the tailstock center until the pointer of the surface gauge 
shows it to be of the same height as the live center. When 
centers are in line, the cut will be parallel to the axis of 
work, no matter what kind of a cutter is used. 




I 



TAPER WORK BETWEEN CENTERS. 

Cases Arising: in Practice.— When cuts are to 

; taken at an inclination to the axis of work held between 

illing-machine centers, that is, when tapering work is to 

, the work may be set to the required inclination 

ways depending on the construction of the 

{-machine centers available. 

The cases that may arise in practice are as follows: 

\a) Neither the index-head spindle nor the tailstock is 



MILLING-MACHINE WORK. 

adjustable in ;i vertical plane, as is the case with the pi: 

shown in Fig. 21. (A) The tailstock is adjustable in 
a vertical plane, (c) The index-head spindle may be swung 
in a vertical plane, {d) The index-head spindle may be 
swung in a vertical plane and the tailstock is adjustable 
vertically in the same plane. (V) The index-head spindle 
and the tailstoclc may be swung simultaneously in a verti< 
plane around the center of rotation of the index head. 



Bit 



77. Non -Adjustable Index Head and Tailstock 

Taking 'ip case (a), there are two ways in which tapers 
may be milled, depending on the kind of machine and mill- 
ing cutter available. Using a horizontal machine and a plain 
cutter, the axis of the work a, Fig. 25 (a), may be brought 
to the required inclination to the line of motion x y, by pack- 
ing up under one end of the bed b' , Fig. 21. This preserves 
the true alinement of the centers; that is, the axis of the: 
index-head spindle coincides with the axis of the dead center 
irrespective of the inclination of the axis of the index-head 
spindle to the line of motion. When this is the case, the 
work will always revolve in perfect unison with the spindle; 
that is, the angular movements of the spindle and work will 
always be alike, in consequence of which, it is possible to 
divide tapering work into even divisions. There is no axial 
movement of the tail of the dog during the revolution 
the work, and there is no cramping and springing. 



in of 
Hing 



78. When plain centers are used for a vertical millin 
machine and an end milling cutter is employed, the adjust- 
ment is identical with the one just described. When a plain 
cutter is to be used in a vertical milling machine, or an end 
mill in a horizontal machine, the centers must be shifted 
sidewise; that is, they must be moved in a horizontal plane 
until the horizontal angle between the axis of the work and 
the line of motion of the table is equal to I 
When the bed of the centers has tongues lilting a T slot of 
the table, it will be necessary to interpose parallel 
between the table and the bottom of the bed. 



§i* 



MILLING-MACHINE WORK. 



41 



79. Raising the Tailstock. — Case (b) usually occurs 
with plain centers that are fastened directly to the table, 
and when using a face cutter in a horizontal milling 
machine, or an end mill in a vertical machine. The axis of 




(a) 






Fig. 25. 



the work is then often given the required inclination by 
blocking up either the index head or the tailstock with suit- 
able packing blocks. The position of the centers in that 



42 MILLING-MACHINE WORK. §14 

rase is shown in Fig. 25 (6). Now, in packing up with 
parallel packing blocks, the axis of rotation rs ot the spindle 
remains parallel to the line of motion x y of the table, but 
the axis of the work and spindle are at an inclination to each 
other. This condition is equivalent to that existing in 
lathe work when taper turning is done with the tailstock 
center set over, and the same trouble is experienced as in 
lathe work; that is, the angular movements of the spindle 
and work are not equal. In other words, with the centers 
out of line, it is not possible to obtain even divisions of the 
work with even indexing. The trouble is intensified by the 
fact that the tail of the dog in milling-machine work requires 
to be confined with a setscrew. If the different positions of 
the tail during one revolution of the work be observed care- 
fully, it will be seen that it not only slips to and fro in the 
slot of the driver, but it also has a rocking motion at the 
same time. Now, if the spindle is revolved while the set- 
screw is set against the tail, the latter will be cramped, and 
either must bend or the work must spring. For this reason, 
whenever work held between centers that are not in line 
with each other is revolved, the setscrew should be loosened 
before revolving the index-head spindle and tightened again 
on the completion of the movement. While this will pre- 
vent springing of the work, it will not insure even divisions. 

80. When plain centers or universal centers intended to 
be fastened directly to the table are to be used in a horizon- 
tal machine for taper work where the cutting is to be done 
by an end mill, or by a plain mill in a vertical machine, the 
centers must be shifted sidewise; i. e., in a horizontal plane, 
until the line joining them makes the required horizontal 
angle to the line of motion of the table. For this purpose, 
raising blocks, if available, may be used; in the absence of 
such blocks, the centers may be blocked up on parallel bars. 
In order to obtain even divisions, place the tailstock center 
so that it coincides with the axis of the index-head spindle. 
Instead of fastening the centers separately to the table, it 
will be found much better to have them attached to a 



MILLING-MACHINE WORK. 



temporary bed, which insures their always being in line, and 
swivel the bed upon the table. 

81. Adjustable Index Head. — Case (c) occurs with 
some designs of universal index centers, where the tailstock 
is not adjustable in a vertical plane, and when the work is 
done with a face cutter in a horizontal machine, or an end 
mill in a vertical machine. The index head is then raised or 
depressed to suit the taper. All that can be said for this 
method is that it still further aggravates the evils of unequal 
spacing and cramping of the dog. Comparing equal tapers, 
case (r) will give errors slightly more than double those due 
to case (f>). Whenever the nature of the work allows it at 
all, it is best to place the work between the centers so that 
the index-head spindle is raised above a horizontal plane; 
the tailstock can then usually be blocked up by packing 
Mocks or parallel bars until the axis of rotation of the index- 
head spindle coincides with the dead center, as shown in 
Pig- 25 (d). When this is done, even divisions will be 
obtained and there is no cramping of the dog or springing of 
the work. The only objection to the use of a parallel pack- 
ing block, or parallel bars, for raising the tailstock is that 
l '>e dead center will not have a fair bearing in the counter- 
»ink of the work. When conditions permit, a tapering 
Packing block may be made in order to overcome this 
trouble. 

82. Adjustable Index Head and Tailstock. — When 
tne tailstock center is adjustable in a vertical plane inde- 
pendently of the live center, which is case (d), the tail- 
stock center may be raised until it coincides with the axis 
°' r otation of the spindle. Even divisions may then be 
ot *ained. 

"3. Taper Attachment. — Case (e) involves a special 
construction of the index centers ; Fig. 2(S shows the design 

na t has been adopted by the Brown & Sharpe Manufactur- 
ltl 8 Company for this purpose. In this device, the live cen- 
ler «, which fits the tapering hole of the index-head spindle, 

"*s a large cylindrical collar in front that closely fits a bored 



_ 




u 



hole i 



MILLING-MACHINE WORK. 



§« 






n arm of the bed b. The lailstoek < 
this bed in such a manner that it can he moved along to 
accommodate different lengths of work ; the construction 
of the bed insures that the dead center is always in line 
with the axis of rotation of the live center. In use, the 
live center is driven home in the index-head spindle ; the 
index bead is then raised until the required inclination has 










been reached and the free end of the bed, which swings 
with the index head, is tied to the table by clamping it 
to the bracket d. This bracket has previously been bolted 
to the table. The device shown insures that the a\i- of 
rotation of the live center always coincides with the dead 
center, and, consequently, even divisions may be obtai 

84. Precautions to be Observed. — Tin precauti< 

to be observed in milling taper work between centers wh 
even divisions are to be obtained may be summed up as 
follows : the axis of rotation of the spindle and the axis of 
rotation of the work must coincide. When this cuiiditi 
not attainable, it is impossible to obtain even divisioi 
When the angle of inclination is small, the errors of divisli 
will he very small ; they will rapidly increase, however, 
any increase of the inclination. 

85. It is to be noted that with a constant difference 
elevation between the centers, the angle of incli 
the axis of the work to the line of motion of the table 
cases (b), (c), and (d) will vary for different 1 
work, and, hence, the tailstock center must be moved up 
down for different lengths of work if the angle of inclination 



hen 



■on 
or 



: u 



MILLING-MACHINE WORK 



45 



t to be kept constant. In cases where the two centers are 

Itached to a separate bed that preserves their alinement, 

,»d where the bed is then inclined or swivelcd, as in case (n) 

r (e), for instance, the angle of inclination to the line of 

lotion is not affected by the distance between the centers; 

e., by the length of the work. In case (c), It is to be fur- 

ler noted that no attention must be paid to the graduation 

larks of the index bead ; these do not show the angle of 

" lination between the axis of the work and the line of 

motion of the table. In case (<■/), however, the graduations 

will correctly indicate the angle of inclination, but only 

when the tailstock center has been raised enough to make 

the axes of rotation of the index-head spindle and work 

coincide. As far as case (<•) is concerned, the construction 

insures that the graduation marks correctly indicate the 

inclination. 

86. Milling-Machine Dog.— In Art. 7S* it was men- 
tioned that the tail of the dog will cramp badly when 
taper work is done with the centers set out of iine. The 



Fig. 27 («) overcomes this trouble entirely; 
i pair of special driving jaws to be attached to 
driver or face plate. Referring to the figure, it 



Sh' 

I it require 
the reguh 
is seen that the dog has an offset cylindrical tail that is 
placed between the special jaws a and b, as shown in 
Fig. 27 (5). The jaw a is bolted to the face plate c and car- 
ries a small slide V> which tli" movable jaw b is clamped. 
In use, the dog is placed on the work so thai i he axis of the 
tail is about flush with the end of the work. The tail is 




? 



46 



MILLING-MACHINE WORK. 



now placed in contact with the fixed jaw a, and the movable 
jaw b is pushed against it and locked. Owing to the con- 
struction, the dog can rock freely during the revolution of 
the work and there is a complete absence of cramping or 
bending of the work. This kind of dog produces less error 
in dividing work than the bent-tail dog; it will not, how- 
ever, as is commonly claimed, allow even divisions to be 
made while the centers are out of line. 

87. Lining the Centers for Taper Work. — As 

previously stated, when even divisions are to be produced 
on work done between centers, it is absolutely necessary 
that the centers be in line; that is, the axes of rotation of 
the work and of the index-head spindle must coincide. The 
shifting of the centers to bring them into alinement is a 
matter that naturally depends on their construction and the 
conditions of each case, and no general direction that could 
be given would be of the same value as the exercise of . 
little judgment. Their correct alinement may be tested in 
various ways ; one of the simplest and most accurate 
methods is here given, which has the advantage that it 
requires no special tools whatsoever, is rapid, and does not 
call for the exercise of any special skill. 



88. Place the work 6 
a clamp dog mounted o 



Fig. 28, between thecenters with 
Revolve it until the tail of the 
dog is on top and 
tn the vertical plane 
passing through the 
axis of the work. 
Now adjust the dog 
until the end of the 
tail will just touch 
Fl<1 a - a feeling piece b 

placed between it and the driver c. This feeling piece may 
be a strip of tin, paper, brass, etc. Remove the feeling 
piece and give the index-head spindle one-half turn, thus 
bringing the spot on the driver that was opposite the end 
of the tail to the bottom. Revolve the work one-half 




e 

: 

e 

; 



L,nt gf Motion . 



§1* 



MILLING-MACHINE WORK. 



47 



revolution and observe if the feeling piece will go between 
the driver and the dog. If it does not do so, the tailstock 
center is too low; if it enters freer than it did in the first 
position, the tailstock center is too high, and if it just goes 
in with the same degree of tightness that it did in the first 
position, the centers 
are in line in a ver- 
tical direction. To 
test their alinement 
sidewise, place the 
driver and dog into 
their two horizontal 
positions and apply 
the feeling piece in 
each position. If for 
any reason the work 
itself cannot be used, 
a mandrel of the 
same length as the 
work may be em- 
ployed instead. In 
that case, the size of 
the centers in the 
mandrel must be 
the same as that of 
the centers of the 
work. 



89. Setting 
Taper Work. — 
The cases that arise 
in practice in milling 
taper work between 
centers require the 




(a) 







cut to be taken either parallel to the surface of the work 
or at an inclination to it. When setting the centers so that 
the cut, the depth of which is represented by the dotted 
line at in Fig. 29 (a) y will be parallel to the surface of the 



MILLING-MACHINE WORK. 






work, a surface gauge may tie employed for testing when 
using a horizontal milling machine and a plain cutter, or a 
vertical milling machine and an end mill. 

90. The work having been placed between the centers, 
these are adjusted by eye until the top of the work appears 
about parallel to the surface of the milling-machine table. 
The pointer/, Fig. 2L> (a), of a surface gauge is then ad- 
justed to just touch the work at one end ; the gauge is now 
shifted to the other end, into the position shown in dotted 
lines, and it is noted if the pointer is again m contai t with 
the work. If it does not touch, it shows that the work must 
be raised at the left end, or the right end must be depressed. 
After shifting, the testing is repeated until the surface 
gauge shows the work to be parallel to the line of motion. 

91. When the cut is to be deeper on one end than at the 
other, as indicated by the dotted line a b in Fig. 2!) (A), the 
setting may be tested by a surface gauge and an auxiliary 
test piece r. This test piece should be a very narrow strip 
of metal whose height is made equal to the difference in the 
depth of the cut, at the two ends. Place the block on top 
of the work, holding it parallel to the table and set the 
pointer / of a surface gauge to touch it. Then shift the 
surface gauge to the other end and note whether the pointer 
touches the work. If it does touch, the work is correctly 
set; otherwise, it must be shifted and the testing repeated. 

92. When using a plain cutter in a vertical machine, or 
an end mill in a horizontal machine, the surface gauge can- 
not be readily used for lining the work. In these cases, a 
pointer may be damped to the spindle, or one of the cutting 
edges of the cutter iisulf may be used for testing the setting, 
traversing the work past the selected testing point by moving 
the table. In the case of a plain mill used in a horizontal 
machine, or an end mill used in a vertical machine, the set- 
ting may be tested by the cutter; but, as a generat 

is more convenient to use a surface gauge in the mannei 
explained. 



§14 



MILLING-MACHINE WORK. 



49 



93* On some classes of work, as, for instance, when a 
bevel gear is to be cut between centers, the angle that the 
cut makes with the axis of the work is given. With a uni- 
versal head, raise the index head until the graduations indi- 
cate the given angle ; now place the work between the 
centers and raise the tailstock until it is in line, testing by 
means of the method described in Art. 88. When a special 
attachment like that shown in Fig. 26 is used, the testing is 
superfluous ; all that is required is to set the index head to 
the given angle. 

S4# When the centers are to be set sidewise to a given 
angle, as occurs when using them in a horizontal machine 



L ine of Motio n. 




Line of Motion. 



y 




Fig. 90 



with an end mill, or a vertical machine with a plain mill, 
there are usually no graduations available by which to set 



BO 



MILLING-MACHINE \\ 



the centers. Various expedients may then be adOfM 
instance, a piece of tin, as a. Fig. 30 (a), may be cut so that 
iliu BQglfl b equals the given angle. This is then placed 
against a cylindrical mandrel held between the centers, 
which ;in.- now shifted until a traversing of the table past 
the stationary testing point / shows the side edd 
angle a to be parallel to the line of motion of the table. Tim 
testing point may be a piece of wire clamped to the spindle. 

95. When a bevel protractor of the type shown in 
Fig. 30 {b) is available, it may be set to the required angle 
and placed against a cylindrical mandrel held between the 
centers. Their setting may then be tested by traversing 
the table, and, hence, the blade of the bevel protractor, past 
a stationary testing point /. 

96. When the two centers are mounted upon a bed, this 
bed will usually have some vertical surface that li 

to a vertical plane passing through the centers. In that 
case the bevel protractor or the tin triangle may be ap- 
plied to that surface, instead of to the mandrel, observing 
the necessary precaution of holding the instrument used 
parallel to the surface of the milling- machine table. 



MILLING-MACHINE WORK. 

(PART 3.) 



USE OF MILLING MACHINE. 



HOLDING AND STEADYING WORK. 

HOLDING WOHK IN A CHUCK. 

1. Mllllng-Machlne Chuck. — As a general rule, the 
chuck used in milling-machine work is a self-centering lathe 
chuck that is fitted to a face plate screwed to the index-head 
spindle. For holding small cylindrical work, a high-grade 
self-centering drill chuck of the Almond or Beach type may 
be fitted to a shank that fits the hole of the index-head 
spindle. Regular independent-jaw lathe chucks may be 
used for the index-head spindle; these have the advantage 
that work held in them can be trued up until its axis 
coincides with the axis of rotation of the spindle. It is 
rarely advisable, however, to fit an independent-jaw chuck 
to the index head unless the milling-machine spindle is 
threaded the same as the index-head spindle; the chuck 
can then be screwed to the milling-machine spindle and 
the work there trued up easily. After truing, the chuck is 
transferred to the index head. It is a very tedious job to 
true work in a chuck while on the index-head spindle, except 
in those machines which are provided with means for dis- 
engaging the worm and worm-wheel. 

2. Self-centering drill chucks, if of a high grade and 
carefully fitted, can be relied on to hold work within their 

i 

for notice o( coprriwM. me pagt 




MIU-INi. HACHINB U'iikk 



! 



capacity very true; they will also stay true for a long time 

if used with ;i reasonable amount of care. Self-centering 

lathe i hacks, even though made with the greatest 

will rarely hold work bo that its axis coincides with the a*i» 

■ if rotation ; in spite of careful use, they v- 

further out of true Per this reason, it is not advi 

use a self-centering lathe chuck for work that reqi 

to be vtxj true In respect to us axis; when tfajstsi 

essential, the work should bctnied up in some otJv > 

as, for instance, by clamping it lo a true-running arbor or 

similar device, 

3. K\amplen of Chuck Work. — There is a great 
variety of work that can advantageously be done with the 
piece held in a chuck, among width may be mentioned the 
milling of squares on the ends of taps and 1 1 

ting of axial grooves on work too long to go betwi 
centers but small enough to pass through the i> 
spindle, milling out the spaces of spring dies and hollo* 
mills, and similar work. A few examples are here | 
Which will act as suggestions as to the cUss of work and t 
kind of cuts for which the chuck is adapted. 

4. Grooving Work Held lo Chuck.— Fig. 1 is a fro 

view, looking in the direction of the line of motion of t 
table, of one style of an i 
dex head, which 
three-jawed chuck 
- which the work b is i 

rectangular cross 

to be milled in the work t 

tather; in other 
words, the work, which may 
be assumed to be a s 
to he Bplined ! 

rth. When the g 

is to terminate In the n 

' ■ ' ■ mill e would have to be t 



BIB 



MILLING-MACHINE WORK. 



D 



Fig. 1. When such a groove is to begin at some 
from the end, a hole slightly smaller than the fin- 
shed width of the groove should be i — 

rilled where the groove is to start; 

is hole should have the same depth 

the groove, and will make it easier 

sink the end mill into the metal. 

>me workmen prefer to drill a hole 

here the groove is to terminate, 

iut there is no particular advantage 

be derived from this practice. If 

s done, il is recommended to drill 

bis hole considerably smaller than ' 

e width of the groove, in order j 

■How the end mill to finish the 
oove nicely. F|G . S . 

5. When the character of the work demands that the 
oovc terminate in the manner shown in the top view 
and longitudinal section 
in Fig. 3 (£), a plain cut- 
ter must be selected. In 
that case (for a horizontal 
milling machine), the cut 
would be taken on top of 
the work, as shown in 
Fig. 3. When a groove 
like that shown in Fig. 
2 {/>) does not begin al 
the end, it can be easily 
cut by dropping the cut- 
ter into the work; no hole 
need be drilled and no 
chipping out is required, 
; the plain cutter wtll easily clear itself of chips. 
ft. Milling Polygons. — When milling a square, or any 
her polygon, on the end of round work held in the chuck, 
ie way in which the cut is to terminate will determine the 





tcr to terminate ea< 
by using an end mi 
of the arrow x in Fig. i (A). 



must be taken over 
the top of the work, 
and will terminate 
in a curved shoulder 
having a radius of 
curvature equal to 
the radius of the cut- 
ter. For some work, 
this may be a de- 
cided advantage, as, 
for instance, when 
millinga punch, since 
this way of termina- 
ting the cut will leave 
the punch very strong 
and greatly reduce its 
liability to crack in 
hardening; for other 
work, again, it may 
be a decided disad- 
vantage. Thus, as- 
sume that the square 
at the end of a tap 
was cut in the man- 
ner illustrated in 
Fig. 4 (n). Then, 
the tap wrench will 
jam on the curved 
shoulders and become 
M difficult to remove, 

In this case, it is bet- 
flat with a shoulder; this may be done 
or a side mill, feeding in the directio 



16 



MILLING-MACHINE WORK. 



When conditions permit a cut to terminate in a shoulder 
curved as shown in Fig. 4 (c), the milling may be done with 
an end mill, a side mill, or a pair of side mills used as strad- 
dle mills, feeding in the direction of the arrow x. In that 
case, the axis of the work should intersect the axis of rota- 
tion of the cutter. Comparing squares and cutters of equal 
size, it will be found that a square made as in Fig. 4 (c) can 
be finished in a fraction of the time that is required for 
finishing it in the manner shown in Fig. 4 (b). The reason 
to be fount! in the difference m the distances the cutter 
has to travel in order to complete the cut; the distance to 
be traveled by the cutter is least when milling as shown in 
Fig. I If). 

8. Circular Cbuck Work. — Fig. 5 is a suggestion of 

what may be done in the way of circular milling, using in 
this case a horizontal ma- 
chine and an end mill. 
The work is shown to an 
ilarged scale in Fig. 
(a); it is required to 
finish the curved sur- 
face a, and also the rest 
of the face. This may be 
done by holding the 
stem b of the work in the 
chuck and using an end 
as shown in Fig. 
5 (6). For finishing the 
curved surface, the axes 
f rotation of the cutter 
nd of the work should 
iot intersect, but the axis 
f the cutter should be 
elow the axis of the work 
distance at least equal 
o the radius of the cen- 
hole in which the 




MILLING-MACHINE WORK. 



S 15 



teeth of an end mill terminate. When cutting the curved 
surface a of the work, the feeding is done by rotating the 
index-head spindle in the direction of the arrow x. As 
soon as the cutter has passed clear over the curved surface, 
the knee of the mill- 
ing machine is 
raised; the work is 
then rotated until 
the face c is vertical. 
By means of the 
cross-feed screw, the 
table is fed toward 
the cutter until the 
required depth of cut 
is reached; the feed- 
ing is then done by 
lowering the knee 
until the curved 
part of the work is 
reached. The index - 
head spindle -is now 
slowly rotated in the 
direction of the 
arrow x until the 
side c ' comes vertical ; 
the knee is then fed 
upwards until the 
cutter has passed 
over c', which com- 
pletes the milling of 
the work. 

The method of fin- 
ishing the piece 
shown in Fig. 5 (a) 
that has just been 
not given as the only way in which this 
done, nor is it claimed to be the best 
given merely for the purpose of suggesting 




explained 
job can t 
way. It i: 



g IB 



MILLING-MACHINE WORK. 



to the operator the character of work that may be done 
in this manner. 

9. Precaution*. — -When cuts are to be taken at one 
side of the center on work held in the chuck, it should 
always be the aim to select the cutter or arrange the machine 
so that the pressure of the cut will not unscrew the chuck 
from the spindle. 

Suppose a cut is taken as shown in Fig. 6 (a), and that the 
chuck is screwed on with a right-hand thread. Then, the 
pressure of the cut will tend to rotate the chuck in the direc- 
tion of the arrow x, that is, left-handed; this will unscrew 
the chuck. For making the cut, the cutter should occupy 
the position shown in Fig. 6 {&); the pressure of the cut 
will then tend to rotate the chuck in the direction of the 
arrowy, and thus tend to screw it home more firmly. 

10. It is not always possible to select the cutter or 
arrange the machine so that the pressure of the cut will not 
tend to unscrew the chuck. A good example of this is the 
hollow mill shown in Fig. 7, which is extensively used in 
turret-lathe and screw-machine work. Such mills, as a gen- 
Tile, cut right-handed, the term right-handed being 




pplied to this mill in accordance with the practice existing 
in regard to milling cutters. It can readily be seen that in 
milling out a hollow mill in order to form the cutting edges, 
the cut must be taken to tin: left of the center, or as in 
Fig. (a). Now. if the chuck is screwed 00 with a right- 
handed thread, there is a tendency to unscrew the chuck. 



H MILLING-MACHINE WORK. §1 

which is quite pronounced on account of the width and 
depth of the cut. For this reason, special care is required 
to jam the chuck firmiy against the shoulder on the index- 
head spindle, when the thread is right-handed, and great 
care must also be exercised when taking the cut. It somi 
times is possible to block the chuck by putting a jack undi 
one of the jaws, and this should be done whenever circui 
stances permit. When a chuck that is fitted to the indi 
head spindle by a shank is available, and is of sufficient si; 
it should be used in preference to a screwed chuck. 

11. Angular Cuts.— Cuts may be made at an angle to 
the axis of work held in the chuck by inclining the universal 
head, as shown in Fig. 8. A great variety of work 
thus be done, as, for instance, milling the teeth on the e: 
of end mills, or the teeth 
sides of solid side mills, milling 
bevel gears, etc. Some varieties 
of work can advantageously be 
held in the chuck, while others 
can be done more readily and 
accurately by using some other 
holding device, as an arbor, 
instance. 

12. In order that the chin 
jaws may not cut into the s 
face of finished work, strips 
PIG - ■• soft copper, brass, or sheet 

may be placed between the jaws and the work. When using 
the chuck, the work should project as little as circum- 
stances permit, both in order to get a fair bearing of thi 
jaws and also to reduce the spring of the work during 
cutting operation. 




rsai 
can 
end 
the 



ARDORS FOR INDEX-HEAD U8K. 

13. MHIinic-Macblne Arbor.— Arbors that are to 
used in the index head may be made in many different ways 
to suit the nature of the job. For holding saw blanks, face 



the 

I 



I u 



MILLING-MACHINE WORK. 



tters, solid side cutters, and other similar cutting tools 
<r the milling machine while milling the teeth in them, a 
egular milling-machine arbor can often be used to ad> 
,ntage. 

On many jobs, such an arbor cannot be used very readily 
account of its being in the way of the milling cutter; in 
such a case, some other design of arbor must be adopted. 
In designing such a special arbor, the nature of the job will 
largely determine its shape, and will usually narrow the 
down to a very limited range of designs. Several 
:pecial designs are here given as suggestions of what may 
2 done. 

14. Expanding Arbors — Fig. 9 (a) is one design of 
special arbor intended for holding work with a central hole 



■ 




tfZ <» 


:fc=l- 



= 



= ) 



m 















1 « 




< 

1 








t~ 


-- 






w 




* 








sucha manner as to allow it to be milled on the side; as, 
r instance, a small side milling culter, or a bevel gear. 



MILLING- MACHINE WORK. 



The front < 



I of the arbor is split into three or more r, 
by slots terminating in holes close to the shoulder. A sere' 
with a tapering head will expand the split end so as to hoi 
the work, which is slipped on the arbor before the screw i 
tightened. The split end of the arbor must be a fair fit i 
the hole of the work before expanding. The arbor show 
will hold the work central, and is cheap in first cost. Its 
disadvantages are that it can be used for only one size of 
hole, and that it will not hold the work as firmly as some 
Other designs. 

1 5. Fig. 9 (/>) shows a design intended to overcome one 
of the disadvantages of the arbor just shown. The end is 
split into three or more parts and is made to fit the hole 
the work; a central hole is drilled clear through the arl 
and is reamed out tapering at the front end. A taper pin 
is fitted to it, and is driven in to expand the arbor. To 
loosen the work, the pin is driven out. This may be done 
with a rod and hammer; the rod may be dispensed with if 
the taper pin is made with a long, straight shank extendi] 
beyond the end of the index-head spindle, as is shown in 
illustration. If the split end before expanding is a fair 
in the hole of the work, it will hold the latter central and 
also very firmly, since a greater pressure, and hence more 
frit tion, can be created by driving the taper pin home than 
it is possible to obtain by tightening a conical-headed screw 
with a screwdriver. This design is perhaps slightly more 
expensive than the previous one, but it is to be preferred 
because it holds the work more firmly. It retains the di 
advantage of being adapted for but one size of hole. 

16. Bushed Expanding Arbor. — A design that 
easily be adapted to various sizes of holes at a comparatively 
slight expense is shown ill Fig. 9 (r). Here the front end of 
the arbor is tapered slightly, so that the included angle 
say, from 2" to 3 s . A bushing c is bored to fit the tapered 
of the arbor, and is turned outside to til tin- hole of the wt 
It is split by an axial slot ei; in order to allow it Id eXj 
easily, several slots, as e and f, may be cut around 



id is 
.leof 
Lrbor 
pin * 
To 
done 
th if 

tz 

irfil 
ew 

: 



: LB 



MILLING- MACHINE WORK. 



11 



circumference. The bushing may be expanded by a bolt ^ 
extending clear through the arbor and having a nut at the 
rear end, or it may be locked by simply driving it home. 
In order to adapt the arbor to a different size of hole, a new 
bushing is the only thing required. The arbor shown must 
be removed from the index-head spindle to change the 
work, since the work can only be removed from the arbor by 
driving it off. A nut may be placed back of the bushing so 
that the work can be forced off without removing the arbor. 

kl7. Chuck Arbor. — Fig. 10 is a design of arbor that 
mid, perhaps, more properly be called a chuck, since it is 
ed to hold work with a cylindrical part. The front end 
of the arbor is bored out to fit the work closely; its outside 
is turned tapering and threaded at the rear. It is split into 
three or more parts (four in this case) and has a sleeve 
x fitted to it. This sleeve nut has holes, as b, b, drilled 







i it to take the pin of a spanner wrench. The work, as, 
for instance, the bevel-gear blank c, is placed in the arbor 
and the nut a is screwed home with a spanner wrench ; this 
causes the split end to hold the work centrally and grip it 
quite firmly. In order to hold the work securely, it is 
necessary that the cylindrical part of the work is a fair fit 
in the hole of the arbor. 

The arbor shown can be adapted to a limited range of 
sizes by fitting concentric split bushings to it; it cannot be 

xpected in that case to grip the work as firmly as it does 

hen no adapting bushing is used. 

TIB— tZ 



MILLING-MACHINE WORK. 



.A 



i WORK ON FACE PLATE, 

18. Use of Face Plate. —For many jobs, it is possible 
to use a face plate for holding the work. When the index- 
head spindle is threaded, the face plate can be screwed to 
it; when this is not the case, it may be fitted to a shank fil 
ting the hole of the index-head spindle. If this is doni 
is not advisable to use a thread for uniting the shank and 
face plate on account of the danger of unscrewing the face 
plate, unless a round key is sunk half into the shank and half 
into the face plate. When a face plate is screwed to the 
index-head spindle, the same precaution must be taken as 
in case of a chuck fastened by screwing; that is, whenever 
circumstances permit, the cut should be taken in such a 
manner that there will be no tendency to unscrew the fat 
plate. 

19. Work is fastened to a face plate and is trued up i: 
the same manner as in lathe work; it must always 
remembered, however, that the pressure of the cut is mu< 
greater than in lathe work, and hence the clamping mi 
be done very carefully. If circumstances permit, stop-pi: 
may be inserted in the face plate to prevent slipping of 
work, or stops may be bolted to it. 

2(1. Lining the Pace Plate. — Most of the face-pla 
work done in a milling machine requires the plane of thi 
face plate to be at right angles to the axis of rotation c 
the milling-machine spindle. The setting may then 1 
tested in the following manner: Place the index-head spindle 
about in line with the milling-machine spindle, as is shown 
in Fig. 11. No particular degree of accuracy is required 
for this; it will be good enough for the purpose if this is 
done as nearly as can be judged by the eye. Fasten a beni 
piece of wire, as a, to the milling-machine spindle in any 
convenient manner; by moving the table, bring the pointed 
end in contact with the face plate, or, if desired, with a 
feeling piece h placed against the face plate. Revolve the 
milling-machine spindle one- half of a revolution, thus bring- 
ing the point of the wire into the position shown in dotted 



S 15 



MILLING-MACHINE WORK. 



13 



lines, and test the distance between the end of the wire and 
the face plate. If it is greater than in the first position, the 
index-head spindle requires shifting in the direction of the 
e; if it is less, the shifting must be done in the direc- 
tion of the arrow/. Test next in two positions at right 




ngles to those shown in the illustration, and shift the index- 
head spindle until the end of the wire remains at a constant 
distance from the face plate during a complete revolution 
of the miHing-machine spindle. The wire used for testing 
should be quite stiff, say about £ inch in diameter. 

21. Example of Face-Plate Work Fig. 12 is an 

example of circular milling that may be done with the 
work clamped to the face plate. Here 
the two slots a and b are circular; the 
slot a has its center of curvature at a' 
and the slot b at b', while the center 
of the work is at c. In order to mill 
the slots, the work must be set so that 
for the slot a, the point a' will coincide 
with the axis of rotation of the index- 
iead spindle ; for the slot b, the point b' 




14 MILLING-MACHINE WORK. § 1 

must coincide with the axis just mentioned. Fine center- 
punch marks may be made at these points; the work can 
then be trued up either with the face plate mounted on the 
milling-machine spindle or temporarily mounted in any 
suitable lathe that is available. The slots should be milled 
with an end mill; the feeding is then done by rotating the 
index-head spindle, and, hence, the face plate. 



HOLDING WORK IN JIGS. 

2-2, Purpose of Jigs. — When a great number of equ, 
pieces are to be finished by milling, and especially when 
their form is such that they cannot be readily held in the 
vise or on the table in a simple and efficient manner, they 
can often be held to advantage in special holding devices 
called milling jigs. 

A properly constructed milling jig should serve simul 
taneously for two different purposes in order to warrant thi 
expense of constructing it. In the first place, it must In 
the work securely without distorting it, leaving the surfat 
to be machined exposed to the cutter; in the second pla< 
the act of clamping must automatically aline the worl 
properly for the subsequent cutting operation. 

Milling jigs may be constructed in a great variety of wa; 
to suit the nature of the work, and no specific rules can be 
given as to how they can best be constructed. A number 
of actual examples are here given; these examples will 
serve as suggestions of what may be done. 

23. Splitting Jig. — Pig. 13 shows a jig designed 
holding shafts for key-seating or splining, plain cuttei 
being used for the purpose; it is intended for milling twi 
shafts simultaneously, as a general rule, but, as will becoi 
apparent when its construction is studied, it can be used 
machining one shaft at a time. Referring to the iltustra 
tion, a false table a is bolted to the milling-machine table 
This false table has two parallel V grooves milled in 
throughout its length; these grooves are parallel to the li 



I 

in 



oer 

,vill 

I 



lit 



MILLING-MACHINE WORK. 



15 



of motion of the milling-machine table. The shafts b, b, 
ich are to be splined or key-seated, are laid into these 
grooves and are clamped by means of the clamps c, c, and d. 
It is thus seen that each shaft is held by two clamps at each 
clamping point. Owing to the way in which the clamps 
must be applied in order to be clear of the milling cutters 
e, e, one clamp would fail to insure a rigid holding of the 




work, since it would not press the work with an equal pres- 
2 against both sides of the V groove. This inequality of 
>ressure is corrected by applying a second clamp opposite 
he first. The jig is adapted for different sizes of shafts by 
; the blocking for the clamps c, c adjustable for 
The blocking consists of studs f,f with nuts 
I on them; the clamps c, c have clearance holes in 
hem for the studs to pass through, and rest on the nuts, 
li are screwed up or down to suit different diameters of 



24. The design shown is so constructed that shafts may 
! automatically lined up so as to have two keyways, or 
plines, cut diametrically opposite each other; the design can 
radily be modified to cut the keyways at any predetermined 



16 



MILLING- MACHINE WORK. 



§1 



angle with each other. For the purpose of insuring 
a correct location of the second keyway, a rectangular 
groove, as g or h, is cut in the false table ; a block i, with a 
tongue that fits the key seat, or spline, previously cut, is 
placed into the groove and the work is then placed on top 
with the key seat, or spline, engaging the tongue of the 
block. 

25. Special Jig- — Fig. 14 (a) shows a machine part 
that is to have a dovetailed groove a cut into the bottom in 
line with the axis of the two holes bored through the stand- 
ards b, b. Owing to the shape of the work, it is rather diffi- 
cult to hold it properly for machining, and it will become a 




rather expensive job if a number of such castings are to be 
finished. The work may, however, be securely held, quickly 
set, and automatically lined up by the use of the jig shown 
in Fig. 14 {b). 

This jig consists of a body c that is bolted to the milling- 
machine table. It has three brackets with V grooves milled 
in the top of them in line with the line of motion of the 
table. A cylindrical mandrel is passed through the holes in 
the standards of the work; this mandrel is then laid into the 
V grooves and clamped by means of the bolts and clamps 
shown. The free end of the work is lined up for height by 
means of the jack-screws d and e, and is finally confined by 
the clamp/*. 



S l- r > 



MILLING-MACHINE WORK. 



2*>. Gib Jl(£. — Fig. 15 shows a jig designed for holding 

s to allow the angle on the edges to be finished with an 

rid mill. The jig consists of a body a, which is bolted to 



JO), y 3x 

a i r 



t, :l 



the table. The upper edge of the body is recessed to bold 
the gib b at the proper angle; two clamps c, c are used for 
holding the gib to the jig. 

t27. Multiple .liu>. — A number of pieces may occa- 
>nally be held at once in a jig in order to have some simple 




peratiou performed i 



them, as, for instance, the 







MILLING-MACHINE WORK. 



squaring up of the ends of rails, as shown in Fig. 16 (a), or 
the squaring up of the ends of round work, as shown in 
Fig. it (l'}. In the first case, ;i yoke <i is bolted to tlie table 
of the milling machine by moans of the studs b, b. Thi 
yoke carries the sctscrews r, c. The rails are confined sid< 
wise by the setscrews d, d, which push each set of rai 
against the central packing-blocks. 

28. In Fig. 10 0). B bracket a is bolted to the table a 
milling machine; the bottom of the bracket lias a recta 
gular opening in which the rods are placed and then confined 
by lightening the setscrew b. Tlie act of lightening tin- 
setscrcw causes the round rods to spread so that the outer 
ones come in contact with the sides of the opening: sint 
each rod is in contact with at least two others, they wills 
be held firmly. 



tlBE OF THE STEADY REST. 

29. Purpose and Application. — As implied by t 

name, the steady rent used in milling-machin 

used for supporting slender work against the pressure of thi 

cutting operation. Steady rests may be made in quite i 



U»' 



K 



f i 



number of ways to suit special jobs; Fig. lfshow-. i 
and incidentally gives its application to wnrk heli.1 
the centers. The steady rest has a base a, which is b 
to the milling-machine table in a position about mitlw 



MILLING-MACHINE WORK. 



It 



n the ends of the work. A flat-ended setscrew 6, 
having a check-nut c, is screwed into the top of the base, and 
is adjusted by turning until it is just in contact with the 
bottom of the work. The check-nut is then set up in order 
to lock the setscrew. 

30. Supporting Work Sidewise. — A flat-ended set- 
screw will support the work in a vertical plane, but will not 
support it sidewise. For some classes of work, 
as, for instance, when fluting small taps held in a 
chuck, it is a decided advantage to support the 
work sidewise as well, since, in that case, the cut 
develops a sidewise bending action. For this pur- 
pose, the steady rest may be made with a setscrew 
having a V groove cut into its end, as shown in 
Fig. 18. Such a setscrew should not be screwed 
into the base, but should closely fit a cylindrical Vla - I8, 
hole reamed in it; a nut c, applied as shown in Fig. 17, is 
lien used for bringing the setscrew in contact with the work. 




ig. 19 shows an application of a steady rest with a 
tided setscrew to work held in a chuck; in this particu- 
case, the work is a tap that is to be fluted. Since the 
k itself will hold the setscrew from turning, there is no 



MILLING-MACHINE WORK. 



need of splining it and fitting a feather to the bu 
occasionally done. 

31. Limitations of Ordinary Steady Rest.— The 
ordinary steady rest supplied by manufacturers, of which 
the one shown in Fig. 17 is an example, will answer very 
well for comparatively stiff work, but since it supports the 
work at one point only, as can be seen by referring to Fig. 17, 
it will, if the work is slender, still allow considerable bend- 
ing of the unsupported parts during the cutting operation. 

32. The ideal steady rest will always support the work 
directly beneath the cutter; this condition can be attained 
in two ways for cylindrical work; that ii, either by a Spe- 
cial steady rest made to suit the nature of the work, and con- 
Structed in such a manner as to support the work through 
Itt whole length, or by a follow rest attached to the frame 
of the machine and adjusted so as to be directly beneath the 
cutter. 

A follow rest is open to practical objections, one of which 
is tli.it it is applicable to none but cylindrical work, and to 
1 1 i.i i onh when the direction of the cut is parallel to the axis 
of the work. Another objection is the difficulty of at tact 

ling it in such a manner as to have a I " 
satisfactory range of application. 



ie axis 
ittacb- 
fairly 



33. Universal Steady Rest.— Fig. 90 shows ho- 
factory universal steady rest applicable to stro 



M5 



MILLING-MACHINE WORK. 



g] 



INDEXING. 



and taper work may be constructed for a horizontal milling 
machine. There are two bases a and 6, which carry jack- 
screws and adjusting nuts. The ends of the jack-screws 
form eyes that are hinged to a supporting bar c, which may 
have a V groove milled in its upper side or be flat on top. 
As shown in the figure, it can readily be adjusted to suit 
taper work. Its range of usefulness can be extended by 
having several bars of different lengths. 

rSIMPlK INDEXING. 
34. Definitions. — There are many designs of index 
heads in the market and in use that differ only in detail and 
arrangement. All these designs make use of at least one of 
two methods of dividing the periphery of circular work into 
equal parts, and some designs make use of both methods. 
The process of dividing the circle by means of the index 
head is known in shop parlance as Indexing. The two 
methods of indexing that are in use may be classified as 
direct indexing and indirect indexing. 

Direct indexing is done by the aid of an index plate 
fastened direct to the index-head spindle; that is, the index 
plate is moved to obtain the divisions. 

In indirect indexing, the index plate is normally sta- 
tionary, and the index-head spindle is rotated by the use of 
suitable gearing. Indirect indexing is divided into two 
classes, which are known, respectively, as simple and com- 
pound indexing. In simple indexing, only one movement 
of the indexing mechanism is required; in compound index- 
ng, two movements are made. 

35. Construction of Indexing Mechanism. — Fig. 

1 shows the indirect indexing arrangement reduced to the 

;lementary form in which it appears in all index heads 

lapted to indirect indexing. The arrangements of the 



MILLING-MACHINE WORK. 



a i 



details may vary in different designs, but the principle in- 
volved is common to all. The index-head spindle a has 
fastened to it a wor-m-wheel b; a worm e, which is keyed to 
the worm-shaft d, meshes with the worm-wheel. The worm- 
shaft carries at one end a radially adjustable crank (, 
which is fitted with a latch pin /having a cylindrical pro- 
jection that fits the holes of the stationary index plate g. 
The index plate is usually kept from rotating by means of 
an axially movable pin, called the stop-pin, which is fitted 




Flo. SI. 

to the frame. This stop-pin can be withdrawn in order 
allow the index plate to be rotated, should this become 
essary. In most designs of index heads, the position of 
stop-pin in respect to the axis of the worm-shaft is fixed 
other words, it can be made to engage with only one row 
circle of holes in the index plate. There are some designs, 
however, where the stop-pin is fitted to the frame of the 
index head in such a manner that it can be shifted to enga 
any row of holes in the index plate. 



: 



36. Calculating Turns of Index Crank Reft 

ring now to the illustration, it will be apparent that the 
part of a revolution made by the index-head spindle for one 
complete turn of the worm-shaft depends on the number of 
teeth of the worm-wheel, and whether the worm 
single thread or a double thread. All modern index h. 




MILLING-MACHINE WORK. 



regularly manufactured use a singe- threaded worm, and 
for these, one turn of the worm will produce that part of 
the revolution of the index-head spindle represented by the 



fraction 



1 



Now 



suppose 



number of teeth in worm-wheel' 
that the latch piny engages the index circle having 20 holes, 
and that it is moved from one hole to the next adjoining one. 
Then, the worm is rotated ^ of a revolution; assuming 
the worm-wheel to have 40 teeth, the index-head spindle 
is revolved J l t Xjl( = -gi-a part of a revolution, and, hence, 
by making successive moves of 1 hole in the index circle 
having 20 holes, a circle is divided into 6-J-» = 800 parts, 

37. Now, suppose that, instead of moving the latch pin 
only 1 hole, it is moved 6 holes. Then, the worm-shaft 
makes ^ of a revolution, the index-head spindle makes 
jiy X A = -g4r °f a turn, and, hence, a circle is divided into 
a -| s =100 parts. From the foregoing explanation of the 
principle involved, the following rule is deduced: 

Rule. — To obtain the number of turns the index crank 

■st make, divide the number of turns required for one rtvth 
m of the index-head spindle by the number of divisions 
tto which the periphery of the work is to be divided. 

Example. — In a certain make of index head, the crank roust make 
) revolutions lo produce 1 revolution of the index spindie. How 
rns must the crank make to divide the periphery of the given 
o 6 parts ? 
Solution. — Applying the rule just given, we get 



40 + 6 = 6J ti 






38. Selecting the Index Circle. — Taking the ex- 
ample of Art. 37, it has been calculated that fi whole turns 
and J of a turn are required. The question now arises: 
How can we measure | of a turn ? For convenience of 
measuring fractional parts of a turn of different values, as 
] of a turn, -fa of a turn, fa of a turn, j of a turn, etc., the 
index plate is provided with several concentric index circles, 
each circle having a different number of holes; several more 



MILLING-MACHINE WORK. 

index plates arc provided in order to extend the range ol 
divisions obtainable. 

39. With the latch pin adjusted to the circle having 
20 holes, as in Fin SI, to measure % of a tttl 
evidently havcto be moved20 X f= 13iholcs. Bus il 
more conventenl and also safer u> move the latch pin an h 
tcgral number of holes; this is done by selecting a suit; 
index circle. The index circle that is to be used is the 
having a number of holes divisible, without a remainder 
lliu ili.'iinrninaH'i of the fraction express)] 
part of a turn of the index crank. Referring again to Pig. 21. 
it is seen that the index circles have '.'". IB, 16, IT, It'., and 
15 holes. It will be noticed thai there arc 
divisible by the denominator 3 of tin fractional part of turn, 
which are the 18-hole and i ■ hole circlet, This shows 
cither one of these two i ircles may l>c used. 

Suppose we use the Em [no; Iff holes. Th< 

r.. make £ of a turn, the latch pin must be moved 15 x f = 

! i i he cii cli ha 
must be moved 18 x |= Wholes, From the foregoing si 
meiiis, the following rule is obtained: 

Hulc. — To measure fractional parts of a turn of the index 
crank, select an index circle having a number of holes that it 
divisible by the denominator of the fraction when reduced It* 
its lowest terms. Multiply the number of holes in the index 
circle thus selected by the fraction to obtain the number of 
holes that the latch pin must lie moved for the fractional part 
of a turn. 

Example.— In a given index head, 40 turns of Ihc Index crank will 
produce one turn of the index-bead spindle. How many t 

link make, and what index circle would be used to <1 
the periphery of work into 28 divisions J 

has the following number of hole? in the various circles. 87, J) 
and 4». 

Sol-CTlott.— By the rule given in Art. 37, to obtain 28 dlvlsioi 
index crank must make (J = H: : : the fraction i 

the tract! il part of a turn to ils lowest terms, we get |. 

according to the rule given in Art. 39, we select the ladn . 



mm. 



8 IB 



MI LUNG-MACHINE WORK. 



having 49 holes, it being the only one having a number of holes divisible 
by 7. The number of holes that the latch pin must be moved is 
«X| = 21. 

Then, to obtain 28 divisions, make one complete turn and move the 
latch pin 81 holes additional in the circle having 49 holes. Ana. 

40. Use of Sector. — The sector is a device used in 
connection with an index plate primarily for the purpose of 
saving the labor of counting the number of holes for each 
move of the latch pin, and incidentally for obviating mis- 
takes in counting. Pig. 28 shows a sector in place on an 




index plate. The sector consists of two radial arms a and b, 
*nich are so put together that the angle included between 
them can be changed; the two arms can be locked by tight- 
ening the screw c. 

After the index crank has been adjusted so that the latch 
pin will drop fairly into the holes of the index circle that 
"M been selected, say the circle having 18 holes in Fig. 22, 
ar °p the latch pin into one of the holes of that circle, as d, 
f °r instance. Bring the arm a against the left side of the 
latch pin and then move the arm /' in the same direction in 



MILLING-MACHINE WORK. §15 

which the latch pin is to turn, as in the direction of the 
,. until the required number of holes in the circle 
p «d is between the latch pin and the arm b. To 
the arms together. Thus, if it is required to HOM 
in the index circle having 18 holes, place the arm b in the 
position it occupies in the illustration. In setting the arms 
of the sector, always observe the precaution of omitting i„ 
count the hole in which the latch pin is EaMTtoft; that is, 
count the hole next to this as the first hole. After the cut 
has been taken, withdraw the latch pin and make the re- 
quired number of whole turns of the index crank, using the 
hole from which the latch pin was withdrawn as the start- 
ing point. Then move the index crank until the latch pin 
will drop into the hole indicated by the arm b of the 
drop it in and immediately revolve the sector until the arm a 
is against the latch pin, or in the position shown It 
lines. 

41. Index TabUH, — The manufacturers of milling 
machines, as a general rule, will furnish tables f 

index heads that give all the divisions that can be obtained 

by simple indirect indexing. In these tables, a 

heading "Number of Turns of Crank," the number of 

turns and, if necessary, fractional parts of ■ itn ;i, 

The fractional part of a turn is usually given as ■ 

the denominator of which gives the numlu i 

index circle that is to be used; the numerator denotes t 

number of holes of thai circle that the latch pi 

moved in addition to the whole turns. When no 

part of a revolution ts required, any index circle may t 

used. If no table is available, the crank movements i 

1"' calculated in the manner explained. 

42. Effect of Changing Elevation off Hm 

When the index head is elevated or depressed while * 

attached to the spindle, it will be found thai 

rotated slightly by the act of changing tii 

change in the angle rotates the worm-wheel about the wot 

which is the same as rotating the worm in the op| 



Us 



MILLING-MACHINE WORK. 



2? 



direction. For this reason, the work must be reset after 
each change of the angle of the index head. This is done 

by rotating it in the required direction by means of the 

index crank. 






COMPOUND INDEXING. 

-43. Operation. — By the method of simple indexing, 
the range of divisions obtainable is limited to certain num- 
bers depending directly on the number of index circles, and 
the number of holes in them, that are available. The range 
°f divisions can, however, be greatly extended by a method 
known as compound Indexing. The fundamental prin- 
ciple underlying compound indexing may be explained as 
follows: In Fig. 21, let the latch pin / be adjusted to the 
20-hole index circle, and let the stop-pin be adjusted to the 
19-hole index circle. Now, withdraw the latch pin and 
n, °Ve the crank one hole, dropping the latch pin into the 
°ole. Withdraw the stop-pin from the index plate and then 
r °tate the index plate one hole, or -j 1 , of a turn, in the same 
r ection in which the index crank was turned. Evidently, 
e *orm c has been rotated ^ + tV = iVf °^ a turn, which 
,s ^ part of a turn that ordinarily could not be measured 
Wlt hout an index plate having a circle with 380 holes. Now, 
instead of moving the index plate in the same direction as 
e index crank, move it in the opposite direction. Then, 
e Worm, as the result of the two movements, will have 
bee 



the 



ee n rotated f f - ,\ 
° r e, could not ordin; 
sl> °Mrn. It is thus se 



y^r of a turn; a result that, as be- 
ly be measured with the index plate 
that compound indexing consists of 
*° successive simple indexing operations; the result of the 
*o operations is either the sum or the difference of the two 
,r **ple indexings. 

-*4. Calculating the Moves. — The moves required 

compound indexing may be calculated by the following 

i, which has been deduced algebraically: 

**ulc. — Factor the number of divisions it is desired to 

Choose an index plate and two circles of holes 



to, 



°bta. 



28 MILLING-MACHINE WORK. §15 

thereon for trial ; take the difference of the number of holes 
in the two circles a nd factor this difference. Draw a hori- 
zontal line under the factors. Xext, factor the number of 
turns of the index crank required for one turn of the index- 
head spindle and write the factors below the horizontal line. 
Factor the number of holes in the two chosen circle's, ana 
write their factors also below the line. Xext, cancel equai 
factors above and below the line. If all factors abovi 
the line cane el \ it is possible to obtain the proposed number 
of divisions by means of the two chosen circles. The number 
of holes to be gone forwards in one circle and backward* 
in the other circle are obtained by multiplying together thi 
remaining factors below the line. Special attention is called 
to the fact that in case all the factors above the line dc 
not cancel out, two other circles must be tried until tht 
desired result is obtained or the possible combinations kavi 
been exhausted. In case the division is feasible y write a ptus 
sign before one move and a minus sign before the other movt 
to signify that they are opposite in direction. 

Example. — It is desired to obtain 91 divisions with an index head to 
which 40 turns of the crank shall produce 1 revolution of the index- 
head spindle. What are the moves that are required in case it is found 
that 91 divisions can be obtained by compound indexing ? 

Solution. — Choose two circles for trial, say those having 21 and 
31 holes. By the rule just given, we have 

91 = 7 X 13 
81 - 21 = 10 = 2 x ? 

40 = 2x2x2x1 
81=31 x 1 
21 = 3 x 7 

It will be noticed that the factor 13 above the line does not cancel 
out: this shows that the proposed division cannot be obtained with 
circles having 31 and 21 holes. By trying different combinations, it 
will be found that circles having 39 and 49 holes will answer; thus: 

n = 7 x 13 
49 — 3V = 10 = 2x5 

40 = 2 x '2 X 2 X * 
49 = 7 x 7 
89 = 3X11 



§15 MILLING-MACHINE WORK. 29 

It is seen that all the factors above the line cancel out. Multiplying 
the remaining factors below the line together, we get 2x2x7x3 = 84; 
that is, in order to obtain 91 divisions, we must go forwards 84 holes in 
the&hole circle, and backwards 84 holes in the 39-hole circle; or, go 
forwards 84 holes in the 39-hole circle and go backwards 84 holes in the 
49-hole circle. Writing the moves as directed in the rule, they are 

+ H - tf or + H - H- Ans - 

45. In case the number of holes in one or both of the 

chosen index circles are prime numbers, it is to be observed 

that the factors will be the number itself and 1. Thus, the 

Actors of 17 are 17 X 1; the factors of 13 are 13 X 1, and 
soon. 

46. Simplifying the Moves. — The counting of a 

* ar ge number of holes, especially for the motion of the index 

Pfete where no sector can readily be used, is a tedious job, 

and errors are very liable to occur in counting. In many 

cas es, the results obtained by the rule in Art. 44 can be 

£ r ^atly simplified by a calculation that only involves a 

knowledge of algebraic addition. 

The rules of algebraic addition are very simple and easily 
rer *iembered. When the signs are alike, add as in ordinary 
a d<iition and prefix the common sign. For instance, the 
su *x* of +21 and +11 is +32, and the sum of —12 and -7 
is —19. 

^^Then the signs are unlike, in order to add, subtract the 
srr *^ller value from the larger value, and prefix the sign of 
"^ larger value. Thus, the sum of +18 and —24 is —6; 
of -+18 and —12 is +6; of -7 and +3 is -4, etc. 

*X*he algebraic addition of common fractions is performed, 

a * tw reduction to a common denominator, by operating upon 

^^ir numerators only; thus, to add +$ and — J, they must 

" r st be reduced to a common denominator. This is 3 X 5 

= 15. Then f = ||, and t = &. Adding +|f and -^, 

w ^ get +^j as the sum. 

47. Taking the example given in Art. 44, the forward 
l&ove is +|4, that is, 84 holes in the circle having 49 holes, 
and the backward move is —ft- Now, it can be shown 



80 MILLING-MACHINE WORK. § 15 

mathematically and by trial that the result will not be altered 
if we add algebraically any convenient number of whole 
turns or a part of a turn, or a whole turn and a part of a turn, 
with a minus sign prefixed, to the forward move, and add 
algebraically the same amount with a plus sign prefixed to 
the backward move. Thus, say, that we add one turn to 
each move. Then, one complete turn = {$ and $$. Per- 
forming the operation we get 

+ H-H 
-tt + H 

+ H - «. 

or 35 holes forwards in the index circle having 49 holes and 
45 holes backwards in the circle having 39 holes. It may 
be possible to reduce these moves to a still simpler form. 
To discover if this is possible, add algebraically one or 
more turns or parts of a turn, or whole turns and part of 
a turn, to each move, prefixing the plus and minus signs 
as previously directed. 

Suppose one turn is added. We then get 

+ H-H 
-H + » 

H "A* 

That is, the one move is 14 holes in the index circle hav- 
ing 49 holes, and the other move is 6 holes in the 39-hole 
circle. It will be observed that the addition of one turn gave 
like signs to the two moves ; this means that both moves must 
be made in the same direction. 

48. In order to obtain 154 divisions by compound in- 
dexing, the 33-hole and 21-hole index circles can be used, 
and the moves are found thus: 

154 = % x jt x ;; 

83-21 = 12 = 2x?x£ 



40 = ?X?X?X5 

33 = 7 s x ;; 
21 = 3 x jr. 



§15 MILLING-MACHINE WORK. 31 

Multiplying the remaining factors together, we get 3x5 

= 15, or moves of + if — fr> or + tf — si 

Simplifying by adding, say, 1 turn to the moves first 
named, we get 

+ H-H 
-tt + H 

In this particular case, an excellent example presents 
itself of still further simplifying the moves by the algebraic 
addition of a fractional part of a turn. Let J of a turn 
be added. Now, $ of a turn, with an index circle having 
21 holes, means £f of a turn of the index crank. Likewise, 
J of a turn with an index circle having 33 holes, means f f of 
a turn of the index crank. Then, adding these values with 
the proper signs prefixed, we get 

+ A-i* 
-tt + tt 

As it does not make the least difference in the result as to 
the direction in which the moves are made, as long as they 
are made in opposite directions (the fact of the signs being 
unlike indicates that they must be opposite in direction), the 
moves may be -j-^- and — ^ without affecting the result. 

The moves may, in this particular case, be still further 
sm *plified by the algebraic addition of $ of a turn. J of a 
turn = fr, and ii. Then, 

+ *-* 

+ A- + A- 
Since the moves have like signs, both moves are to be 
°tade in the same direction. 

49. There is no general rule that can be given for 
determining how much to add algebraically to each move in 
0r der to reduce it to a simpler form. This is purely a 
Matter of judgment and experiment. It is to be observed, 



marked tnat it stiouia not De usea wnen tne r 
divisions can be obtained by direct indexing. The 
for this may be found in the fact that the chances of 
an error are much greater with the compound in 
since, for at least one of the movements, the hol< 
actually be counted. 



MILLING-MACHINE WORK. 

(PART 4) 



USE OF THE MILLING MACHINE. 



INDEXING. 



THE SPIRAL HEAD. 

1. Introduction. — By the use of the improved spiral 
head now furnished by the Brown & Sharpe Company, 
both simple and compound indexing can be performed 
readily. The simple indexing does not differ from that 
already explained, but the differential indexing is accom- 
plished through a train of gearing without having to rotate 
the index plate a certain number of holes by hand each 
time. The system previously explained can be used on the 
new spiral heads, but only the new spiral heads are arranged 
to accomplish differential indexing with the same ease and 
facility that simple indexing is done. Other spiral heads on 
universal milling machines might be changed so as to 
operate the index dial by the index crank in a similar manner 
to that used in the improved index heads. 

2. The Gearing of the Improved Spiral Head. 

The gearing of the improved spiral head is shown in 
Fig. 1. (a) and (b). The index crank is shown at a con- 
nected to the index dial b by the pin that slides in the handle 
of the crank. At c a miter gear is shown to which the index 

§16 

For notice of copyright, see page immediately following the title page. 



VTT.r.rVG-ttACHIXE WORK. 



dial is fastened by screws. The shaft shown at d passes 
through die dial and miter gear; it is not keyed to them. 




but mows freely without affecting their motion. A right- 
Vukk-il worm shown at r is keyed to the shaft and meshes 
^JAb the worm-wheel /, which it operates. The worm-wheel 



Bi« 



MILLING-MACHINE WORK. 



10 this case has 4') teeth, so that by turning the index crank. 

which is rigidly connected to the shaft and worm, 40 times, 

the worm-wheel and index head rotate one complete turn. 

Some index heads are fitted with worm-wheels with 60 

Usttad <>f 40 teeth, but the other arrangements are the same 

^ shown in Fig. 1 (a) and (b). On the outer end of the 

•Piadle^is keyed the spur gear k. The adjustable bracket i 

carries a bushing that is free to turn on the bracket stud, 

and to which are keyed the two spur gears j and k. The 

geary' meshes with the gear //, and the gear k meshes with 

tn e idler/, which is fastened loan adjustable bracket/. The 

= merely to change the direction of motion of the 

gear m, and has no effect on the relative speeds of the gears. 

Keyed to the same shaft with the spur gear m is a miter 

g*ar n that meshes with the miter gear c. At a is shown 

t ' )e styp. pin that can be slipped into the dial to hold it from 

r " L; 'tinjj. In simple indexing, the idler / or the compound 

"^ ars /, k are disengaged from the gear-train, and the stop. 

P" 1 *> is slipped into the dial, thus holding it in position. 

"'hen using the head for differential indexing, the stop- 
™ n o is disengaged from the dial b and the gears put in 
es h, so that when the crank a is turned, the gear-train 
r ^ n smits the motion to the dial. Any of the gears k,j, i; t» 
n be removed and others put in their places to obtain 
'"^rent gear ratios, or in other words, to obtain a different 
, **»ber of revolutions of the index dial to one revolution of 



tb. 



e work. 



51. Effect of Rotating *•>« Index Dial.— When the 

?^* 4 *"ing is arranger! as shown in Fig. 1 {a) and (b), the index . 

' H l rotates in the opposite direction to that of the index 
J r; "ik. If the idler is disengaged and the gears on the 
. r ^cket » are brought into mesh with the gears h, in, the 
ll Mpx dial will rotate in the same direction as the index 
Cr »nk. A spacing collar on the shaft that carries the gear// 

^^ be. removed when only one gear is to be used on the 

" r acket i. The effect, however, is the same as having the 

K^axs/, koi the same size. 



MILLING-MACHINE WORK. 




If the index dial shown in Fig- 2 is H* 
kad the Index crankptn Is rotated in the direction of the 

, it will be necessary for the CTanlcpin CO 

point ■' 40 times, or to make 

in complete revolt 

turn tlie index-head spindle 
once. If, on the other hand, 
the geaiin. 
that the index dial 
once in the same direction 
r Lttilc while the in- 
dex spindle turn 
will l>e necessary for the 
crankpin to pass; 1 1 
only 39 i H 
turn the index- in 
once around, [f 

dial moves in the opposite direction (■■ that of the indei 

' rank, with ill': same gear ratio, then the n. 

point a II times in moving the index spindle one turn. 
The number "f times the index crankpin 

ing point plus thi of a turn it passes beyond 

i hat point lias been appropriately called the 

number. The reason for adding the fracti 

dial thai the index crank passes ovi 

be so geared as to make a fractional number of turns while 

the crank makes 40 complete revolutions. 
For example, suppose the dial n 

the opposite direction to the arrow while thi 

in the same directi 10 complete turn 

indcx-ri ckoning tiunilw r is i '•.'$. which means that : ! ■ 

pin must pass the point a 42 times and go four-fit; i 

way around tin dial again No* 

8 holes '.n the 20-holc circle it will go two-fifths of the way 

around the circle each time. ■•< in oi 

plete turns, it will make as many ] 

in 42$, in- 1 07 times, This principle h;i- 

computing the table that follows: 



§16 



MILLING-MACHINE WORK. 



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MILLING-MACHINE WORK. 



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MILLING-MACHINE WORK. 



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MILLING-MACHINE WORK, 



11 



4. Explanation of the Index Table. — In the first 
column is the number of divisions that it is desired to space 
on the index head, or, in other words, the number of move- 
ments to be made in rotating the work once. In the next 
column is the number of holes in the index circle that should 
be used to obtain the number of divisions indicated in the 
SUDD horizontal line in the first column. In the third 
column, in the same horizontal line as the first two num- 
bers, is a number indicating the number of turns of the 
index crank. This number may be a whole number, a 
fraction, or a whole number and a fraction. In case a frac- 
tion is used, the denominator expresses the number of holes 
in the index circle used and the numerator the number of 
holes the index crankpin is to be set over at each move. 
In the other six columns are numbers representing the 
number of teeth in the gear that will be used in the posi- 
tion indicated by the letter at the head of the column, 
which refers to the position of the gears as shown in Fig. 1. 
When no number is given in any one of the six spaces, no 
gear is to be used in the position indicated at the head of 
the column. In other words, use only those gears specified 
by the number of teeth. Where there is no gear in any 
of the six columns, the indexing is simple and the index 
dial remains stationary. In every such case 40 divided by 
the number in the third column, that is, the number of 
turns or fractional part of a turn the index crank makes, 
will give the number of divisions in the first column. 

Whenever gears are to be used, as shown in the table, the 
indexing is differential, and 40 divided by the number will 
not give the number of divisions in the first column. The 
index-reckoning number already explained can be obtained 
at any time, however, by following the gears through from 
the gear h on the spindle and finding out how many turns 
the index dial makes to each turn of the spindle and in which 
direction. Knowing that It turns with the spindle, or turns 
once while the crank rotates 40 times, if the index dial turns 
in the same direction as the index crank, subtract the numberk 
of turns the dial makes from 40; if in the opposite direction. 



18 



MILLING-MACHINE WORK. 



! I 

ained. 



add. When the index-reckoning number has been ob 
it can be used in the manner previously explained. It 
however, necessary to find the index-reckoning number in 
order to use the table; all that is necessary is to place the 
gears on the shaft where they belong, use the proper index 
dial, draw out the index stop-pin, and space off the number 
of holes given in the third column, as in simple indexing. 



FRACTIONAL INDEXING. 

5. Introduction. — By means of compound or differen- 
tial indexing a great many divisions can be obtained, but in 
some cases neither can be used, or at least not to advantage. 
The method of differential indexing with the special spiral 
head is open to the objection that it requires a gear on 
the spindle in the head and hence it is only possible to 
use this device when the spindle is horizontal. The method 
of differential indexing with the back pin is limited in its 
application on account of the fact that the choice of index 
circles is limited to those in a single plate. 

The essential feature of the fractional-Indexing 
method is the use of two index circles, one of which gives 
a means of obtaining a fraction of a space on the other 
circle. Divisions corresponding to any number divisible 
into two factors, which are also factors of two index-circle 
numbers but neither of which is a common factor of both 
ircles, I'an be obtained by this method. 

0. Description of Fractional Indexing. — Some- 
limes only one index plate is used, but generally two are 
required. Both plates are fastened on with the screws ordi- 
narily used, but to get the two plates on at the same time it 
is necessary to face about ^ inch off the shoulder of the 
sleeve carrying the plates and to omit the ordinary sector. 
This method may be used to advantage for obtaining a large 
number of divisions. For instance, to divide a circle Into 
8, l GO parts on the Brown & Sharpe miller it is necessary to 
move the worm-shaft )fj , or ^j, of a revolution (at each 
division; but as 49 is the greatest number of holes in the 







£7 circle. When both pins an 
CRD be moved half a revoluti 
dropped into a hole, when thi 
jetween two holes, and by m 



pin d being adjusted to the 
withdrawn, the index plates 
n, and the back pin again 
front pin will be half way 
ving it to the first hole in 



advance of it gives the desired half of j",, or -^ of a turn, 

To simplify the turning of the index plates, a gear may 
be placed on the shaft that turns the index plates when cut- 
ting spirals, and which is sometimes called the gear on the 



14 MILUXG-MACHINE WORK. §16 

a\-rms:mJ. and another gear/, with half as many teeth, on 
the idler stud, A pointer is fastened over this idler, and a 
1 . kcd I-' indicate the movement. With both index 
pins removed, the index plates and gears arc free to turn, 
and a revolution of the idler indicates the proper movement 
of Che plates. 

The application of the method to many cases where a 

I small number of divisions is required involves 

i! method of procedure. For example, if 

- i c noted, Erst get the factors 7 and ;i; 7 is 

ID and this can be used for the back index 

■ it of 18, and this can be used for the front 

Pert iT.icimn.il turn for the index crank is y x J 

,',,, which gives a movement for the crank of 

11* holes, on the IS row. \ x 18 = -S* = 24, but f X 18 

= ti» = |JVf. If, then, the index plates are turned 1 of a 

>'., the index pin if, which is stationary, will pass by 

I5f spaces. The 15 spaces are unimportant, but the $ is 

the (faction wanted for the crank movement, and a gear of 

trorm and one of 24 teeth on the stud will 

movement of the plates. 

In this case the movement of the plates is in the same 

direction as the crank, on account of the fact that the frac- 

imder obtained from the movement of the index 

klao the desired fractional movement of the cranks. 

Somct imcs, however, it is more convenient to move the plate 

>I«isite direction and use the difference between the 

il remainder and a whole space for the fractional 

turn of the crank. For example, if it is desired to obtain 

■us in which the factors are 7 and 11, the fractional 

turn is w x A; W = 10 K- and iH x w - 1H- '■■ 

a mm of the plates is inconvenient to indicate with the gears. 

I. sare turned backwards ff, the result is the same, 

(or f| X 31 = Vi* = lfl rV which leaves }Jf of a space to 

turn the crank ahead. 

A uumber that has a factor common to both index circles 

be divided by this method. For erampli 
ST, and I X 2? = W, so that if the plates are moved 1 



§ 16 MILLING-MACHINE WORK. 15 

revolution, the index pin will drop into another hole of the 
27 circle, and nothing is gained by using the two plates. 

The fractional turns obtainable by the back plate are 
halves, thirds, quarters, fifths, sevenths, elevenths, thirty- 
thirds, and forty-ninths, and the number of divisions that 
may be obtained ranges from 51 to 64,680. 

The sector, ordinarily used for counting holes on the index 
plates, cannot be used when both plates are on, but one may 
be made with sheet-steel arms, each arm being riveted to a 
collar; one of these collars fits the index-plate sleeve and the 
other fits the outside of the first collar. The outer collar is 
split so as to clamp on the inner one. This sector is shown 
at g and /, Fig. 3. One of the arms i has the end bent over, 
forming a spring resting on the outside of the index plate, 
which holds the sector in place after it is adjusted. When 
the sector is in use the index pin is first drawn out, the 
index plates are then moved and locked in place by the back 
pin c. The index pin d is then released and allowed to rest 
against the plate, for it is not in the right position to enter 
a hole ; one arm of the sector is then moved into contact with 
the pin, when the other arm will indicate the hole to which 
the pin is to be moved. In Fig. 3 the machine is set up to 
cut a 51-tooth gear. 

7. Explanation of Table for Fractional Index- 
ing. — In Table II is given the number of divisions from 51 
to 400 that are obtainable by this method. The method is 
equally applicable for many higher numbers. In the table, 
the minus sign before the fractional turn of the plates indi- 
cates that the plates are to be moved in the direction oppo- 
site to that of the crank. 

In some cases the idler gear can have more than one tooth 
marked, so as to obtain £, J, -J, or other required parts of a 
revolution, and by this means all the movements required in 
the table can be obtained with the gears belonging to the 
machine, with the single addition of a 4-1 -tooth gear. In 
the table, the first column contains the number of divisions 
obtainable; the second column, the fractional turn of the 



16 


MILLING-MACHINE WORK. 
TABLE II. 

FltACTIdJiAL nSBXIHO. 


lu 


Num- 




Holes on 


Num- 


Prac- 






ber 


Fnw 


Outside Plate. 


ber of 




Getrm 


of 
Divi- 
llMI* 






BcJm 


Turn 
of 

pute& 




UttfCOl 


Turn of 
Crank. 


Number 
in Circle 


— 


Plate. 


Wo™. 


St :.,.!. 


5> 


VxA 


'7 


■3i 


33 


— > 


7^ 


24 


57 


VxA 


'9 


'A 


33 


+i 


;» 


»4 


63 


VxA 


ti 


>>\ 


49 


+! 


28 


*4 


69 


VXA 


2 3 


>3i 


33 


-J 


72 


'4 


77 


W x A 


21 


■°H 


33 


-It 


44 


40 


^ 


VxA 


20 


'31 


33 


-1 


72 


34 


93 


VxA 


31 


'3, 


33 


+i 


72 


*4 


96 


Vx,\ 


16 


H 


33 


-1 


7* 


*4 


99 


ttx A 


18 


7A 


33 


+A 


44 


24 


102 


VxtV 


'7 


'1 


33 


+1 


7* 


*4 


III 


VXA 


37 


■3, 


33 


+1 


72 


*4 


112 


Vx A 


16 


rf 


49 


-H 


28 


*4 


114 


Vx A 


19 


N 


33 


-1 


72 


14 


110 


VxA 


'7 


51 


49 


H 


56 


3* 


1*3 




4' 


Ml 


33 


-1 


7" 


*4 


126 


Vx A 


18 


5» 


49 


+4 


S« 


*4 


129 


VxA 


43 


■3l 


33 


+1 


7' 


*4 


'33 


VxA 


19 


S» 


49 


-4 


18 


*4 


US 


VxA 


*3 


'I 


33 


+1 


72 


»4 


141 


V '•■ A 


47 


■3j 


.13 


+i 


7- 


*4 


M7 


V x A 


49 


>3, 


33 


-i 


72 


*4 


•54 


HxA 


21 


5 A 


33 


+* 


44 


*4 


161 


VXA 


23 


s« 


49 


+» 


18 


*4 


174 


VXA 


29 


<■! 


33 


+1 


7i 


M 


'75 


VxA 


'5 


3) 


49 


-H 


56 


»4 


■ 70 


it x a 


id 


.ii'i 


33 


+A 


44 


;; 


1 k<, 


Vxa 


3" 


H 


33 


-1 


7* 


'4 


18; 




'7 


3, v i 


33 


+A 


44 


24 


189 


VxA 


-'7 


5f 


49 


H 


■s 


*4 


19a 


Vxa 


16 


31 


33 


+, 


7* 


*4 


198 


ttxA 


18 


3 A 


33 


-» 


44 


40 





MILLING-MACHINE WORK. 

TABLE II. -(Continued.) 





Holes on 


Num. 


Frac- 


Gear 








Outside Plate. 


ber of 


tional 


on 


Revo- 








Holes 

Plate. 


Turn 

of 
Plates. 






lutions 




Number 
in Circle. 


Move. 


Worm. 


Stud, 


of Stud 
Gear. 




20 


5* 


49 


+* 


56 


40 


, 




'7 


3) 


33 


-J 


72 


"4 


1 




39 


7l 


20 


+i 


48 


»4 


1 




>9 


3ft 


33 


+A 


44 


40 


. 




3' 


St 


49 


+* 


56 


32 


1 




37 


«! 


33 


-i 


72 


*4 


I 




iG 


'it 


49 


+4 


5« 


'4 


1 




'9 


si 


33 


•H 


7* 


24 


1 




33 


5( 


49 


-* 


28 


"4 


1 




'7 


»t 


49 


■H 


28 


*4 


i 




41 


6| 


33 


-i 


72 


»4 


1 




18 


*f 


49 


+f 


56 


40 


1 




'3 


3ft 


33 


+t"t 


44 


38 


1 




'7 


•1 


33 


-i 


72 


24 


1 




43 


'1 


33 


+i 


72 


24 


1 




37 


5» 


49 


+4 


38 


24 


1 




■9 


•t 


49 


+4 


5° 


3" 


1 




17 


'i 


20 


+1 


48 


24 


1 




39 


St 


49 


+4 


56 


24 


1 




'5 


"ft 


33 


+* 


44 


»4 


1 




33 


3i 


33 


-i 


7* 


24 


t 




47 


'4 


33 


+1 


7 2 


»4 


1 




■9 


'1 


33 


-i 


7' 


«4 


1 




4i 


5t 


49 


+4 


28 


24 


i 




iS 


*i 


20 


+1 


48 


24 


t 




49 


'! 


33 


-i 


73 


24 


1 




37 


3ft 


33 


+A 


44 


32 


1 




43 


5t 


49 


+4 


S" 


40 


1 




"9 


'! 


zo 


+i 


48 


24 


• 




ai 


*n 


33 


+ 1 *r 


44 


32 


1 




3 1 















MILLING-MACHINE WORK. 
TABLE II — (Continued.) 



I If 



ber 
of 
Divi- 


Frac- 

Turn of 
Crank. 


Holes on 

Outside l'lnte. 


Num- 

Holes 

Plate. 


Frac- 
tional 
Turn 

of 
Plates. 


— 


.,„ 


Revo- 
lution 


in Circle. 


Move. 


Worm. 


Stud. 


of Stud 
Gear. 


312 


Ax 


39 














315 


V* A 


2^ 


3) 


49 


+< 


56 


3* 


I 


3*9 


1IXA 


2 9 


3t\ 


. 33 


-if 


44 


40 


I 


3*° 


Ax 


16 














3" 


VxA 


*3 


•I 


49 


+4 


56 


*4 


I 


3*8 


Ax 


4i 














3*9 


VxA 


47 


5, 


49 


■H 


28 


*4 


I 


330 


Ax 


33 






+i 








336 


|x,\ 


11 


'1 


JO 


-H 


48 


*4 


I 


340 


Ax 


17 














34 « 


nx,s 


3" 


3ft 


33 


+ft 


44 


*4 


1 


344 


Ax 


43 














345 


IXA 


*3 


*i 


33 


+i 


72 


"4 


I 


348 


Vx A 


29 


3) 


33 


-1 


72 


■4 


I 


350 


V* A 


'5 


■» 


49 


+ T 


56 


40 


J 


35 * 


fix A 


16 


■A 


33 


+A 


44 


3* 


i 


360 


A x 


18 














3 6 4 


VxA 


39 


4» 


49 


+» 


56 


3» 


I 


368 


VXA 


*3 


>i 


20 


+1 


48 


*4 


I 


37° 


AX 


37 














37* 


'a u X ,', 


3' 


31 


33 


+1 


7* 


*4 


I 


374 


n x ,s 


»7 


>ft 


33 


+ft 


44 


28 


1 


376 


Ax 


47 














37« 


V x A 


27 


»l 


49 


-» 


28 


*4 


I 


380 


Ax 


•9 














3&| 


8 x iS 


16 


>! 


33 


-I 


7* 


*4 


1 


3*5 


ft x A 


21 


'A 


33 


-A 


44 


"4 


J 


39« 


A x 


39 














39* 


A x 


49 














39<"> ?" X A 


18 


1 l"l 


33 


-t-ft 


44 


*4 


I 


400 




20 















§ 16 MILLING-MACHINE WORK. 19 

index crank necessary; the third column, the number of 
holes in the circle to be used on the outside plate ; the fourth 
column, the number of holes the index pin is to be moved 
on the outside plate. The fraction, of course, is obtained 
by the movement of the back plate. The fifth column gives 
the number of holes in the circle to be used on the back 
plate. The sixth column gives the fractional turn necessary 
for the plates. In this case the direction is indicated by the 
sign before the number. The seventh and eighth columns 
give the gears necessary to indicate the fractional turn of 
the plates as given in the sixth column. The ninth column 
gives the number of turns that the gear on the stud must 
make to indicate the proper fraction of a turn for the index 
plates. 



SPIRAL WORK. 



GENERATION OP SPIRALS. 

8. Combination of Movements. — If work held 
between centers, or in the chuck of a universal index head, 
is given a rotary motion and a motion of translation at the 
same time, while the relation between the two motions 
remains constant, a stationary point, in contact with the 
surface of the work, will trace a conical spiral or a helix, 
depending on whether the work is conical or cylindrical. In 
a milling machine, the motion of translation is the motion 
of the milling-machine table, which is caused by rotating 
the feed-screw either by the automatic feed or by hand. 
Now, if the feed-screw is connected by gear-wheels with the 
index-head spindle, it is evident that this spindle, and, 
hence, the attached work, will be rotated by any rotation 
of the feed-screw; since a rotation of the feed-screw causes a 
motion of translation of the milling-machine table, while the 
gearing insures a constant relation between the two motions, 
it follows that a milling cutter operating on the work will 
take a cut that follows a helical or conical spiral path. 



30 



MILLING-MACHINE WORK. 



9. Definitions- — In a spiral or helix, the distant 
advanced in 1 revolution, measured in the direction of t 
axis, is called the pitcu of the spiral or helix, or, 

lend. In milling-machine Work, the lead is always express 
in inches, or in inches and fractional parts of an 
the best modern practice, the term lead is used in prefcren< 
to pitch, and will, hence, be used here. It has bt 
ternary to limit the term pitch to small screws; while in ii 
strict sense it means the distance that the - 
advance in 1 revolution, it has become the practice in s 
shops to apply it to the number of threads pet [l 
screw. In order to prevent any contusion, the term .' 
will here be used exclusively, and will, when applied I 
helix, spiral, or screw thread, always represent the dista 
advanced in one revolution. 

10. Angle of Helix. — A helix is represented by (he 
hypotenuse of a right-angled triangle having adjacent sides 
equal to the lead of the helix and to the circumference of a 
cylinder around which it is wound in such a position that 
the adjacent side representing the lead is in the same plane 




as the axis. Thus, let Fig. i (a) represent a right-a 

triangle cut out of paper, where the adjai 

the sides adjoining the right angle) is eq 

ference of the cylinder ./ in Pig i i-m, and tfa< 

side b is the lead. Then, when this triangle is woui 



g 16 MILLING-MACHINE WORK. 21 

around. r/, as shown in Fig. 4 (b), the side c will form a helix 
having a diameter equal to d, and a lead 6. The angle 
included between the sides b and c is called the tingle of 
the helix. 

11. From trigonometry, it follows that the tangent of 
the angle of the helix is equal to the circumference of the 
cylinder (the length of the side a of the triangle) divided by 
the lead. Hence the following rule: 

Rule. — Divide 3.1^16 times the diameter of the helix by 
the /end. Take the corresponding angle from a table of 
natural tangents. 

Ex ample. —A helix 4| inches diameter has a lead of 10 inches; what 
* the angle of the helix ? 

Solution.— Applying the rule just given, we get 

4*"»! = .««**. 

From a table of natural tangents, the corresponding angle is found 
o be 41° 38', nearly. Ans. 

12. It often occurs that it is required to find what lead 
of helix will give a certain angle of helix, the diameter of 
the helix being known. This may be calculated by the fol- 
lowing rule: 

Uule. — Divide 8.13,16 times the diameter of the helix by 
tke tangent of the given angle. 

Example.— A helix is to have an angle of helix of 80° 46' for a diam- 

:r i..f :lj inches. What is the lead of the helix ? 

Solution.— From a table of natural iangenls, the tangent corre- 
•ponding to 30° 45' is .50484. Applying the rule just given, we get 

The two rules just given apply to helixes only, and should 

not be applied to conical spirals. In a conical spiral, the 

gle of the spiral changes continually throughout its 

lgth; it is smallest at the small end of the spiral and 

;t at the large end. 



23 



MILLING-MACHINE WORK. 



816 

The rate at which the angle changes in a conical s 
depends on the angle included between the sides of the 
cone; when this angle is very small, L e.. when the cone is 
almost a cylinder, the change ill the angle of the spiral is 
extremely small, but it rapidly becomes larger as the angle 
included between the sides of the cone becomes greater. 

13* Connecting Index-Head Spindle and Feed 
Screw. — There are many ways in which the feed-screw 
and index-bead spindle may be connected together by gear- 
ing; since, in nearly all designs of universal index heads, 
the worm-shaft and the feed-screw are at right angles to 
each other, it is necessary in these designs to introduce i 
pair of miter gears, or bevel gears, or a pair of equivalent 
machine elements into the gear-train in order to allow th< 
worm-shaft and feed-screw to be connected together by spur 
gearing. 

Fig. 5 shows one of the simplest designs for connecting 
the feed-screw and index-head spindle together. The 
worm-shaft a carries a miter gear b, which, normally, \± 
free on the worm-shaft. The index plate c is fastened to 
the hub of the miter gear b, and is ordinarily prevented 
from rotating by a stop-pin in the frame of the index head. 
The index crank d is attached to the worm-shaft. Now, if 
the stop-pin is withdrawn, and the latch pin is dropped into 
a hole of the index plate, the worm-shaft and the miter 
gear b are locked together, so that any motion transmitted 
to the miter gear will also be transmitted to the worm-shaft 
and then, through the intervention of the worm-wheel *■ 
the index-head spindle/1 The miter wheel b meshes v 
a miter gear g, which is keyed to the shaft h\ the tirs 
change gear k of the train of spur gearing connecting th< 
spindle and feed-screw is attached to the other end of thi 
shaft h. The first gear is usually called the worm-jwi 
from the fact that it operates the worm. 

A spur gear /, known as the feed-screw sear, is ptac< 
on the feed-screw; the gears k and / are then connect ei 
together by the two gears m and n placed on the same 
sleeve, which is mounted on an adjustable stud fastened in 



16 



MILLING-MACHINE WORK. 



any suitable manner to the frame of the index head or the 
table of the machine. As a general rule, another stud is 
provided on which an idler can be placed. This idler may 
be placed either between k and in, or / and ti; it will not 
change the velocity ratio of the gear-train, but only the 
of the rotation of the index-head spindle, and, 




kence, the direction of advance of the spiral. In most mill- 
ing machines, the introduction of the idler will cause the 
production of a left-handed spiral; owing to the difference 
in construction of the various machines, it is better, how- 
determine this separately for each machine than to 
rely on the presence of an idler as a guarantee of a left- 
handed spiral. 

Since the index-head spindle and the feed-screw are 
positively connected together, the relation between the 



U MILLING-MACHINE WORK. § 16 

rotation of the spindle and the advance of the table remains 
constant, and the resulting helix or spiral will have a uni- 
form lead. Evidently, the lead can only be changed by 
changing the velocity ratio of the gears connecting the 
feed-screw and spindle; since all modern designs of milling 
machines have the gearing that connects the worm-shaft to 
the worm-gear k arranged in such a manner that it cannot 
be changed, it follows that different helixes or spirals can 
only be obtained by changing the gears k, t, m, and ». It 
is customary to call the gear m the first gear on stud, 
and the gear » the second sear on stud. 

It will be observed that the change gears form a train of 
compound Bearing. The reason for the almost universal 
adoption of compound gearing is to be found in the fact 
that, with a given number of change gears, a much larger 
range of combinations is possible than can be obtained with 
a single gear-train. 

As previously stated, the index plate is locked to the 
worm-shaft and rotates with it during the cutting opera- 
tion. Indexing is done after the completion of the cut and 
while the machine is standing still, first locking the index 
plate by inserting the stop-pin, and then turning the index 
crank the required number of turns. The index plate is now 
unlocked by pulling out the stop-pin, and the machine is 
ready for the next turn. 

Fig. 6 shows a more complicated design of a gear-train 
for connecting the index-head spindle and feed-screw. This 
design was adopted by the maker of the particular style in 
which it is found because it allowed a very rigid and com- 
pact construction of the index head. 

The worm-shaft a here carries a spur gear b, which can be, 
and is, locked to the worm-shaft by dropping the latch ptn 
into one of the holes of the index plate c. The spur gear b 
meshes with an idler d carried on a stud; this idler in turn 
drives a spur gear e, which is keyed to one end of the 
shaft/. A spiral gear,? is keyed to the other end of the 
shaft/and meshes with another similar spiral gear A keyed 
to a shaft i, which is at right angles to the worm-shaft, and. 







MILLING-MACHINE WORK. 25 

hence, parallel to the feed-screw. The shaft f carries the 
gear on the worm-stud k, which meshes with the first gear m 
on the stud. The second gear « on the stud rotates with m 




and meshes with the feed-screw gear /. In this gear-train, 
the gears b, d, e, g, and // cannot be changed ; different spirals 
and helixes are produced by changing the change gears k, 
/, in, and «, as in the previous case. 



CALCULATING THE CHANGE GEABB. 

14. Lead <>f the .Machine. — Assume that the machine 
is so constructed that 1 revolution of the worm-shaft will 
produce exactly 1 revolution of the gear on the worm-stud k, 




MILLING-MACHINE WORK. 




5 " 



Fig*. •> and G, an J let the change gears be such that 1 revolu- 
tion of the feed-screw will produce exactly 1 revolution of 
the gear on the worm-stud, and. hence, of the worm-shaft a. 
Then, during 1 revolution of the feed-screw, the milling- 
mfhffiT table will advance a distance equal to the lead of 
the feed-screw, and, at the same time, the index-head 
swindle will be rotated a part of a turn given by the fraction 

To make 1 complete 



tnber of teeth in worm-wheel' 

ion of the index-head spindle, the feed-screw must 
make a number of turnsequal to the number of teeth in the 
worm-wheel. The distance that the table will advance, 
which in the lead of the helix produced under the assumed 
condition*, is given by the product obtained by multiplying 
the lead of the feed-screw by the number of teeth in the 
■.'■.'•]. This particular distance is called the lead of 
Hi. mitchinc. 

Now, suppose that the worm-shaft a. Figs. 5 and 6, is so 
In, i|n geaf on the worm-stud t that 1 revolution 
of the worm-shaft docs not produce 1 revolution of the gear 
on the worm-stud. Then, the distance that the table 
during I revolution of the index-head spindle is 
00 longei given by multiplying the number of teeth of the 
worm-wheel by the lead of the feed-screw. The rule for 
this case becomes as follows: 

Mule. — To find the lead of the machine, multiply the 
number of revolutions of the gear on the WOrtHStmd that is 
required to product I revolution of the index-head spindle 
by the dad of the feed-screw. 

Kxakflk, 1 1 having been found by actual count that 5i; re 

iron the worm-stud are required to produce 1 revolution o 
the index-head spindle, and the feed-screw having a lead of J inch. 
what ia Hit lead "I the machine? 

. ■. —Applying the rule just given, we get 
Mxj = Win. Am 
The rule just given is general, since it takes in any cas 
that is likely to arise, while the first one is limited to the 



I tfl 



MILLING-MACHINE WORK 



special case where the revolutions of the gear on worm-stud 
and worm-shaft are equal. For this reason, the lead of the 
machine should preferably be calculated by the general rule, 
which, incidentally, also takes account of the fact that the 

worm which meshes with the worm-wheel on the index-head 
spindle may be double-threaded. 

15. Simple Gearing. — The lead of the spiral or helix 

having been given, the ratio between the revolutions r.f the 

gear on worm-stud and the revolutions of the feed-screw is 

lead of the spiral 

lead of the machine' 

Then, for simple gearing it only remains to choose gears 
that bave this ratio. This is most conveniently done by 
raising both terms of the ratio to higher terms that corre- 
spond with the teeth of the gears available. 

Example. — The lead of ihe required helix being 14 inches and the 
lead ft the machine 10 inches, what gears may tie used in simple 
gearing ? 

Solution.— By the statement just given, the ralio is f). Since 
gears of 14 and 10 teeth are not usually available, multiply both term, 
say, by 2. This gives jj. or gears having 28 and 20 teeth. Multiply- 
ing by 3, we get {J, or gears having 43 and 30 teeth. By still furl her 
raising the terms of the ratio to higher terms, other gears can be 
ha) will give the required spiral. Ans. 

The question of where each gear of the set is to be placed 
depends on the relation of the lead of the spiral to the lead 
tli the machine. When the lead of the spiral is less than 
the lead of the machine, the gear on worm-stud must be the 
smaller gear of the two; when the lead of the spiral is greater 
than the lead of the machine, the gear on the worm-stud 
must be the larger of the I 

1 «. When the two change gears of the train >->l" simple 
gearing are given, to find Ihe spiral or helix that will be cut, 
the following rule maybe used : 

Uuie. — Multiply the number of teeth of the gear on warm- 
stud <'[>■ the lead of the machine, and divide the product by the 
number of teeth of the feed-screw gear. 



MILLING-MACHINE WORK. 



§H. 



Example. — The gear on worm-stud having iH teeih. and the feed- 
icrew gear 100 teeth, what helix will be cut if the lead of the machine 
s 12 inches ? 

So L ution.— Applying the rule just given, we get 






1 7. CoaipouDd Gearing. — When the machine is com- 

pound-geared, the ratio ; ; — j^-; t-f-. — isilK' cum pound 

lead of the machine 

ratio of the gearing. This ratio must be resolved into 
factors that are raised to higher terms until they correspond 
with the number of teeth of gears that are available. For 
instance, let it be required to cut a spiral with a lead of 
24 inches, the lead of the machine being 10 inches. Then, 
the compound ratio is f J, which resolves into the factors 
| X |. This means that two of the gears that mesh together 
must be in the proportion of 3 to 2, and the other two gears 
in the proportion of 8 to 5. Raising | to a higher term 
by multiplying the numerator and denominator by any 
integral number, say 16, we get 48 and 32 teeth as the 
number of teeth of one pair of gears. Raising | to highei 
terms by multiplying the numerator and denominator 1 
any integral number, say 12, we get 96 and 60 for tbi 
other pair of gears. It is to be observed that there i 
not the slightest necessity of multiplying the terms of 
both factors by the same integral number ; all that 
required is that the two terms of each factor be multi- 
plied by the same number. After factoring the ratio, tin- 
numerators of the factors will represent the driven 
of the gear-train, and the denominators will represent th< 
drivers. 

IS. The question of where cacti pair of meshing gears 
must be placed can easily be answered when it is considtrrei 
that if the lead of the helix tn be cut is smaller than ihe 1. 
of the machine, the gear on worm-stud must run faster tl 
the feed-screw gear. When the lead of the helix is grcatci 



MILLING-MACHINE WORK. 



an the lead of the machine, the gear c 
i dower than the feed-screw gear. 



worm-stud must 



8. When the lead of the spiral or helix is a whole num- 
of inches, it is usually quite easy to factor the compound 
o. This factoring can sometimes be made easier by 
ising the ratio to a higher term by multiplying the numera- 
- and denominator by some number. For instance, the 
itio 4 I is rather difficult to factor as it stands, but by rais- 
j it to a higher term, say by multiplying by 4, we get fg, 
lich readily resolves into the factors J J x f, or V X At or 
1 X 1, or V X f 

Take, now, the case of a spiral having a lead expressed 
whole inches and part of an inch, as, for instance, 
inches. Let the lead of the machine be 13 inches. 

n, the compound ratio is —±, which is a form in which 

s rather difficult to factor. Now, suppose it is raised to a 
gher term, multiplying by a number that will make the 

merator 144 a whole number. In this case, it is obvious 
:at 4, or a multiple of 4, will be the number to use. Raising 

to a higher term by multiplying the numerator and 

denominator by 4, we get J-J as the compound ratio. This 

fidily resolves into quite a number of factors, thus: j X i|, 
A X V, or V X |, or V X f or A X V. or ft X J, etc. 

20. When it is not feasible to factor the compound 
ratio, or to get gear combinations that include available 
gears, the proper gear combination can often only be dis- 
covered by a method that may be aptly described as "cut- 
ting and trying." In many cases it is not possible to cut' 
the required spiral at all, but the machine may often be 
geared to cut a spiral that approaches the desired spiral 
somewhat closely. Here the cut •and- try method must also 
be followed. 

There are two methods of procedure that may be adopted; 

iher three gears of the set are assumed and tbe fourth is 



HI 



30 MILLING-MACHINE WORK. § 16 

calculated, or a combination of four gears is selected and 
the resulting spiral or helix found by calculation. 

When three gears of the set are assumed, the fourth may 
be calculated as follows : 

Rule. — Multiply the lead of the spiral or helix in inches 
by the number of teeth of the feed-screw gear and the first 
gear on stud. Divide the product by the product of the num- 
ber of teeth of the second gear on stud and the lead of the 
machine in inches. The quotient will be the number of teeth 
of the worm-gear. 

Example 1. — If the feed-screw gear has 40 teeth, the first gear on 
stud 82 teeth, the second gear on stud 56 teeth, the lead of the machine 
being 10 inches, and the helix to be cut being 28 inches, what should be 
the number of teeth of the worm-gear ? 

Solution. — Applying the rule just given, we get 

£8 X 40 X 32 



56 X 10 



= 64 teeth. Ans. 



Example 2. — A spiral having a lead of 39 inches is to be cut. The 
feed-screw gear has 40 teeth, the first gear on stud 32 teeth, the second 
gear on stud 56 teeth, and the lead of the machine is 10 inches ; what 
number of teeth should the gear on worm-stud have ? 

Solution. — Applying the rule given and substituting, we get 

T^ = W teeth. 
56 X 10 7 

Since a gear with this number of teeth is an impossibility, the cal- 
culation shows that with the gears selected it is not possible to cut the 
required spiral. If a gear with 89 teeth is available, a fairly close 
approach to the required spiral may, however, be cut. Ans. 

21. When the four gears and the lead of the machine 
are known, the resulting spiral or helix may be calculated as 
follows : 

Rule. — Multiply the lead of the machine by the number 

of teeth of the gear on worm-stud and the second gear on 
stud. Divide this product by the product of the number of 
teeth of the feed-screw gear and the first gear on stud. 



g 16 MILLING-MACHINE WORK. 31 

Example. — In example 2 of Art. 20, it was stated that a fair 
approximation to the required spiral might be cut with a gear on 
worm-stud having 89 teeth. Calculate the spiral that will actually 
be cut. 

Solution. — Applying the rule just given, we get 

10 X 89 X 56 



40X82 



= 38.9375 in. Ans. 



Special attention is called to the fact that it is a mathe- 
matical impossibility to calculate directly what the number 
of teeth of the four change gears should be to produce a 
given spiral. 

Let n' = number of teeth in gear on worm-stud; 
n = number of teeth in second gear on stud ; 
N' = number of teeth in feed-screw gear; 
N = number of teeth in first gear on stud; 
L = lead of machine ; 
S = lead of spiral or helix. 

Then, the equation giving the relation is 

nriL 



S = 



NN'' 



In this equation there are four unknown quantities, viz., 
n, n\ N y and N'. They are not known in terms of each 
other, i. e., their relation is unknown, and, hence, it is 
a mathematical impossibility to solve the equation for 
», n\ N y and N' without assigning values to at least three 
of these factors. 

To sum up: When three gears are given, the fourth can 
readily be calculated, as has been shown. When the four 
gears are given, the resulting spiral or helix is easily com- 
puted. To discover the proper relation between the gears, 
factoring must be resorted to. When factoring fails, the 
cut-and-try method must be adopted and followed until 
either a correct gear combination or one that will give 
an approximation which is considered close enough is 
obtained. 



33 MILLING-MACHINE WORK. 

CTTTWG HELIXES AND SPIRALS. 

22. Cutters and Profiles. — By far the greater part 
of the spiral work done in a milling machine consists • 
the cutting of helical and spiral grooves. Familiar e 

the class of work done are the fluting of helical- 
tooth reamers and of twist drills, the cutting of 
spaces of helical-tooth milling cutters, the cutting of screw 
gears, etc. 

With a helical or spiral groove, its profile (shape) is given 
by the intersection of the groove with a plane perpendicular 
talis kihx or spiral, while with a straight groove that is 
parallel to the axis of the work, its profile is its intersection 
with a plane perpendicular to the axis of the work. This 
must l* carefully borne in mind when selecting a cutter for 
■! spiral gnOVfc 
When the profile <>i too groove is symmetrical, it can be 
cut with either • suitable end mill or a formed cutter of the 
required shape, but when the groove has an unsymmetrical 
profile, an end mill cannot be used. 

> end mill is employed for cutting the groove, the 

1MB arranged to swivel, as is the case in horizontal 

Buffing machines, must beset to zero, i. e., so that 

in a plane perpendicular to the axis 

oi rOWrtllf of the cutler. 

I must be employed for unsymmet- 

\i's. and can also be advantageously used for many 

- res It requires the table to be set to an 

tation of the cutter that is equal to 

the difference between the angle of the helix and 90°. As a 

getter*! rale, the graduations of a milling-machine table are 

d thai when the table is set so that the graduation 

the angle of the helix, it will make the required 

s of rotation of the cutter. A rule for 

lug the angle of the helix has been previously 

. ■ 

If the table is not set to the angle of the helix, the result* 
will not have the same profile as the cutter. 




5 



MILLING-MACHINE WORK. 




'his fact can often be taken advantage of when a cutter of 
the right width is not available and the exact shape of the 
Tofite need not be particularly accurate. 

23. Helical Grooves Witli Parallel Sides. — In mill- 
a helical or spiral groove with the kind of plain cutter 

that will produce a 
straight groove with 
parallel sides, as a 
slitting saw, for in- 
stance, it will be found 

hat the resulting 

roove will not have 

larallel sides, but will 
be about as shown, 

oraewhat exagger- 
ated, in Fig. 7 («). 
From this fact, the 
conclusion is to be 
drawn that when a 
helical or spiral groove 
with parallel sidi 
to be cut, a face cuttei 
EAUllOt lie employed 
an end mill will, how 
ever, be found to an 
rer for this purpose. pio. t. 

24. Helical Grooves With Inclined Sides.— When 

an attempt is made to cut an angular helical groove with a 
;ingle-angle cutter, it will be found that the angle between 

the sides of the groove will not be equal to the angle of the 
utter, but will be about as shown, somewhat exaggerated, 
n Fig. 7 {b). It will further be noticed that the side a of 
he groove is very rough compared with the side b, and that 
i decided burr is thrown up at c. From these facts, the 
inclusions are to be drawn that a single-angle cuttsr can- 
lot reproduce its own profile and that cutting teeth lying 



-SF 



u 



MILLING-MACHINE WORK. 



§16 



in a plane, as those on the right-hand side of the angular 
cutter shown, will not mill a smooth groove. The following 
general conclusions may 
also be drawn from the 
facts stated in this and 
the preceding article. No 
cutter, except an end mill, 
can reproduce its own 
profile in a spiral or helical 
groove when it has teeth 
on one or both sides that 
lie in a plane. From this it 
:ept an end mill, that is required 




follows that < 



to produce its own profile in a helical or spiral groove must 
be wider at the bottom than at the top of the teeth, and no 
teeth must lie in a plane. Hence, when angular grooves 
are to be milled, double-angle cutters should always be used ; 
such cutlers will reproduce their own profile, as shown in 
Fig. 8, and mill both sides of the groove smooth. 



25. Helical Grooves With One Side Radial.— A 
great deal of the spiral work done with angular cutters 
requires one side of the groove to be radial. For this work, 
double-angle cutters must be selected, and they must be set 
sufficiently off center to make 
the required side of the groove 
radial when the cutter is sunk 
into the work to the proper 
depth. Referring to Fig. 9 (a), 
which shows a double-angle 
cutter sunk into the work until 
the side a of the groove is 
radial, the amount that the 
cutter must be set off center 
is the distance h. It can be 
readily shown that this dis- 
tance varies with the depth of the cm ; thus, in order that 
the side a may remain radial for a greater or smaller depth 




§ 16 MILLING-MACHINE WORK. 35 

of cut, the cutter must evidently be shifted radially, that 
is, along the line oc. Then, for a smaller depth of cut, as 
shown in Fig. 9 (b), the distance V that the cutter is off 
center will be greater than b, and for a greater depth of cut, 
this distance will be smaller. 

The distance that the cutter is to be set off center is given 
correctly by the following rule: 

Rule. — Subtract the depth of the cut measured radially 
from the radius of the work and multiply the remainder by 
the sine of the angle included betivecn that side of the cutter 
with which the radial side of the groove is to be cut and a 
plane perpendicular to the axis of the cutter \ as the angle din 
Fig. 9 {b). 

Example. — The angle d t Fig. 9 (b), being 12°, how much should the 
cutter be set off center when the work is 3 inches in diameter and the 
radial depth of the cut .4 inch ? 

Solution. — From a table of natural sines, the sine of 12° is .20791. 
For the class of work usually done, it is near enough to call the 
sine .2. Applying the rule just given, we get 

(J - .4) X .2 = .22 in. Ans. 

» 

26. If the effect of the depth of the cut is left entirely 
out of consideration, the rule for setting the cutter off cen- 
ter becomes: Multiply the diameter by half the sine of the 
angle d y Fig. 9 (b). On this basis, the following approxi- 
mate table has been calculated for the angles most com- 
monly used for double-angle cutters. 

The rules here given for the offset of double-angle cut- 
ters apply to straight grooves as well as to helical grooves. 
In the case of a helical groove, the cutter should be set 
correctly while the line of motion is at right angles to the 
axis of rotation of the cutter; the table is to be swiveled to 
the angle of the helix after setting the cutter off center. 

27. Proper Direction of Rotation of Work. — In 

cutting helical grooves with double-angle cutters having 
unequal angles, the work should always revolve toward that 
side of the cutter where the teeth have the greater angle. 



36 



MILLING-MACHINE WORK. 



§16 



TABLE III. 



TABLE SHOWING OFFSET OF DOUBLE-ANGLE 

CUTTERS. 



Angle. 



Offset. 



12° 


Diameter X .i 


2 7 r 


Diameter X .23 


3°° 


Diameter x .25 


40° 


Diameter x .32 


45° 


Diameter X .35 


48 


Diameter x .37 


53° j 

I 


Diameter X .4 



Fig. 10 shows the four cases that arise in practice ; in each 
case, the side a of the cutter has the greater angle, and the 
work should revolve toward it, or in the direction of the 
arrow x. This statement applies to right-handed and left- 
handed spirals and helixes; the direction of rotation that 



/\ 



N 



K 




A 





FIG. 10. 

will bring the work toward the greater angle of the cutter 
can be secured by a proper arrangement of cutter and feed. 
The object of feeding the work toward the side of the cutter 
having the greater angle is to make the sides of the groove 
smooth; experience has shown that smooth sides cannot be 
obtained except by rotating the work in the manner stated. 



S 16 



MILLING-MACHINE WORK. 



3? 



Great care must be taken in all spiral work to confine the 
work in such a manner that it can neither slip in the direc- 
:ion of its axis nor slip about its axis. Should this happen, 
lot only will the work be spoiled, but most likely the cutter 
and arbor also. When the cut has been completed, before 
running the table back, take the work away from the cutter, 
or vice versa, in order that the cutter may not drag in the 
groove, which will mar and score the latter. 



THE NATURAL FUNCTIONS. 

28. Definitions. — In any circle, as in a, Fig. 11, draw 
any two radii, as ob and oc, so that the angle cob included 
between them is less than 90°. 
From the intersection c of 
the radius oc with the cir- 
cle, drop a perpendicular cd 
on o b. Prolong o c, and at b 
erect a perpendicular to ob 
which will be tangent to the 
circle, prolonging the perpen- 
dicular until it intersects oc 
prolonged in e. 

The line cd is called the 
sine of the angle cob and 
is abbreviated to sin; the 
line od is called the cosine 
af the angle cob and is 
written cos; the line db is called the versed sine of the 
ingle cob and is written versin; the line be is called the 
tangent of the angle cob and is written tan. 

From the center o of the circle, draw a radius of at right 
ingles to ob. Then, the angle foe is called the comple- 
ment of the angle cob, and, evidently, is equal to the 
lifference between cob and 90°. Draw a line tangent to 
:he circle at f i. e., perpendicular to of, and extend it 
antil it intersects oc prolonged at^. The line fg is then 




Fig. 11. 



38 MILLING-MACHINE WORK. 

the tangent of the complement of the angle cob, and is 
called the entailment of the angle cob. It is written cot. 

AH these lines are called functions of the .-initio j their 
relative lengths vary with the magnitude of the angle c o b, 
but the ratio between their lengths and the length of the 
radius remains constant for a given angle, no matter what 
the radius may be. 

Tables have been prepared in which the ratio of th 
lengths of the different functions to the radius for all angle* 
between 0° and 90" is given on the assumption that the 
length of the radius is unity (1). Hence, if the length of 
any other radius is given, the length of the corresponding 
function can always be found by multiplying the valui 
the function for a radius of unity, as taken from the table, 
by the given radius. 

Such tables are called tables of natural function--, 
and those most frequently used are given at the end of 
this volume. Tables of versed sines are not given, but the 
versed sine of any angle can be found by subtracting thi 
value of the cosine of the angle, as taken from the table; 
from 1. 



29. Use of the Tables.— To find a function of an 

angle less than 45", look for the number corresponding to 
the degrees of the angle in the horizontal row at the top of 
the page. Look for the minutes in the first vertical colurr 
at the left and follow it over to the right until the vertic; 
column marked with the number of degrees is reache( 
The value of the function will be found there. 

Example. — Find the cosine of 41' 27'. 

SOLUTION. — The column containing the values of cosines between 
41° and 42' is found to be the second column on page 9 of the tables. 
Opposite 27' and in the second column, we find .7495!) as the value of 
the cosine. Ana. 

To find the value of a function of an angle larger than 45°, 
look for the number of degrees in the bottom horizontal 
column. Look for the minutes in the right-hand vertic 
column: follow the horizontal column thus found to the lei 



lie. 

the 
l of 
ing 

Me, 

ii-. 
of 
the 
the 
Wes, 

f an 
g to 
>pof 
umn 
tical 
hed. 




MILLING-MACHINE WORK. 



of a function is 

i top to < 



until the column containing the degree is reached. The 
value of the function will be found there. 

Example.— Find the tangent of 59" 30'. 

Solution.— The vertical column containing tangents between SB" 
ud 00" is found to be the first column on page 18 of the tables of 
natural tangents. Opposite 36' in the right-hand vertical column, we 
find, in the first column of tangents, the value 1.70446. Ans. 

30. To find the angle when the valut 
given, look first in the columns marked 
■pond with the function until the nearest value is found. 
The number of degrees will be found on top of that column 
and the number of minutes in the first vertical column at 
the left. 

When the value of the function cannot be found thus, it 
Knows that the corresponding angle is greater than 45°. 
Hence, look in the columns marked at the bottom to cor- 
respond with the function until the nearest value is found; 
the degrees will be found at the bottom of the column and 
the minutes in the right-hand vertical column. 

Example 1.— What angle corresponds with a sine having a value of 
.KM57? 

Sull'tiiis.- On page 3 of the tables of sines, in the column headed 
If, we find the value .33458. In the first column on the left hand, we 
find 34' ; hence, the angle is 13" 34', very nearly. Ans. 

Example 2.— What angle corresponds with a tangent having a value 
of 1.33214? 

Solution. — Since this value cannot be found in the columns marked 
••Tangent " at the lop, we must look for it in those marked " Tangent" 
at the bottom. In the column marked 56° at the bottom, on page 17 
of the tables, we find the nearest tangent 1.23190, and in the right- 
■and column 66. Hence, the angle nearest to the given tangent is 



MILLING-MACHINE WORK. 

(PART 5.) 



USE OF MILLING MACHINE. 



SPECIAL MILLING ATTACHMENTS. 

1 . Purpose of Attachments. — The range of work for 
which a milling machine is adapted can be greatly extended 
by means of special attachments. Those in most common 
use are : circular milling attachments, which are used chiefly 
in vertical milling machines for the production of about the 
same kind of work that can be done in a lathe; vertical 
milling attachments, for converting a horizontal milling 
machine temporarily into a vertical machine; and cam- 
cutting attachments, for milling cams to a definite shape by 
the aid of a master cam. A milling attachment is occasion- 
ally applied to a planer, thus converting it into a milling 
machine. 

The list of special milling attachments in use is by no 
means exhausted by those just enumerated, since they may 
take almost any conceivable form suitable for the purpose 
for which they are intended. Few, if any, of these special 
attachments embody features that call for a description; 
most of them are simple modifications of those previously 
enumerated, and have been designed to meet special condi- 
tions and requirements. 

2. Circular Milling Attachment — A common f orm 
of circular milling attachment is shown in Fig. 1. It 

corrmoMTCO by international textbook company, all riohtb bcbcrvco 

Jl« 



42 



MILLING-MACHINE WORK. 



consists of a circular table a fitted to the base b in such a 
manner that it can be rotated about its axis. For this 
purpose, a worm-wheel is placed inside of the base which is 
attached to the table; a worm, operated by the hand wheel c, 
meshes with the worm-wheel and serves to rotate the table. 




The particular form of rotary milling attachment here 
shown is only intended to be rotated by hand; such attach- 
ments are often fitted with an automatic feed, however, that 
can be adjusted to start a-nd stop at any point. 




fio. a. 

3. Fig. 2 shows an application of a circular milling 
attachment differing slightly from that shown in Fig. 1. 
In this case, the work a is a worm-wheel blank that is being 



§16 MILLING-MACHINE WORK. 43 

grooved around its circumference preparatory to cutting the 
teeth. A form cutter b is used for grooving. This joh 
might be done in the lathe ; experience, however, has shown 
that the work can he done as well, and much faster, in the 
milling machine. An automatic feed is of decided advan- 
tage for work that is to be milled around its entire periph- 
ery, or the greater part of it; in the attachment shown, the 
shaft c, which carries the worm, is automatically rotated by 
the feed mechanism. 

4. The class of work that may be done with the aid of a 
circular milling attachment does not differ in general from 
that which can be done in a lathe. In addition, some 
circular work can be done for which the lathe is not at all 
adapted, as, for instance, finishing between the spokes on 
the inside of the rim of hand wheels, ami the cutting of cir- 
cular slots closed at both ends. 

5. Vertical Milling Attachment.— For many-classes 
of milling, a vertical milling machine is of advantage chiefly 
on account of the fact that the operator is better able to 
see the cut. In order to obtain this benefit from a hori- 
zontal machine, it may be fitted with a suitable device for 
transforming it, for the time being, into a vertical spindle 
machine. While such an attachment cannot be expected to 
have as large a range as a vertical milling machine, it will 
greatly extend the range of a horizontal machine, and if 
properly designed, will allow work to be performed that 
cannot be done otherwise except by a special machine, such 
as the cutting of relatively long racks, the cutting of helixes 
having a very large angle of helix, the sawing off of stock 
too long to go into the machine in the ordinary way, that is, 
placed parallel to the spindle, and similar work. 

6. Fig. 3 shows one form of a vertical milling attach- 
ment. Tt consists of a frame <i. which carries a central shaft 
fitted to the hole of the milling spindle and inserted therein. 
The frame of the attachment is secured to the frame of the 
machine in such a manner that it can be turned completely 

T 10 -111 



44 MILLING-MACHINE WORK. 

about the axis of the hori 

clamped in any position. The veri ia carried 

in bearings at tin.- outer end of the frame; being 




angles to the horizontal spindle, it is driven either 
gears or by screw gears, in this particular case being drr 
by the former. 

7. The frame of the attachment isgrad 
and a zero mark placed on the frame of the ma< : 
cates, by its coincidence with the zero of the p ■ 
when the spindle is vertical; i. <■., I, in a 

tical plane, to the horizontal line of motion. Pi 
follows that in this position any end mill will cut a hori 
tal surface parallel to the line of motion, and any pi; 
01 formed mill will cut in a vertical plane parallel to 
line of motion. By swiveling the frame <■'■ ti 
so that the spindle becomes horizontal, i. e., lies in a pi 
parallel to ihe line of motion, vertical surfaces can be 
with an end mill, and horizontal cuts at right angles (oi 
case of a table arranged to swivel, at various angles) to 
line of motion of the table can be taken. 

H. A vertical milling-machine attachment of the Ii 
shown can be used for helixes in three ways, two of whi 



nd 

MS, 



§ 16 MILLING-MACHINE WORK. 45 

incidentally adapt it to cases where the table cannot be con- 
veniently swiveled. In the first place, the attachment may 
be rotated about its axis to suit the angle of the helix; that 
is, it may be set so that the spindle of the attachment makes 
a vertical angle with the line of motion of the table equal to 
the difference between the angle of the helix and 90°. A 
plain mill or formed mill attached to an arbor is then used, 
and the cut is taken on the side of the work. 

In the second place, the attachment may be set with its 
spindle parallel to the line of motion, that is, horizontal. 
In that case, the milling-machine table must be set over 
until its graduation indicates an angle equal to the differ- 
ence between the angle of the helix and 90°. Using a plain 
mill, or a formed mill, or a similar cutter attached to an 
arbor, the cut is then taken on top of the work. 

In the third place, the attachment may be set with its 
spindle vertical, that is, in a plane perpendicular to the line 
of motion. It is then used with an end mill, which is ap- 
plied on top of the work for grooving, and on the side of the 
work for plain milling. 

As a general rule, the first and the third methods given 
will allow a greater range of work to be done and allow 
longer helixes to be cut without interference by the frame 
of the attachment than is possible with the second method. 
Since neither the first nor the third method involves a set- 
ting over of the milling-machine table, they allow a plain 
milling machine to be converted into one adapted for 
spiral work. 

9. Cam Classification. — The cams in most general 
use may be classified as face cams, side cams y and grooved 
cams. A face cam may be defined as a cam that will cause 
motion in a direction at right angles to its axis of rotation, 
as, for instance, the cam shown in Fig. 4 (a). A Hide cam 
may be defined as a cam that will cause motion in the di- 
rection of its axis, as the cam shown in Fig. 4 (?>). A 
grooved cam may have the groove cut into its face, as 
the one shown in Fig. 4 (c) ; in this case, it will cause motion 



46 



MILLING-MACHINE WORK. 



| 16 



in the direction of its axis, anil may be called a groove 
aide cam, since it causes a motion similar to that of a side 
cam. The groove may be cut in the side of the cam 
ever, as shown in Fig. 4 {J) ; in that case, the rootle 
be similar to that caused by a face cam and, hence, it may 
be called a grooved face cam. The term "cylindrical 




cam " is often applied to cams of the kind shown in Fig. 4 (<■). 
Cams of the form shown in Fig. 4 (a) and (d) are often 
called radial cams, and cams that cause motion in the direc- 
tion of their axes, as those shown in Fig. 4 (6) and (c), are 
sometimes called axial cams. 

10. Cam-Cutting Attachment. — Nearly all the 

cam cutting that is done in the milling machine may 
be classified under the heading of duplicate work; in ma- 
king a cam, the shape of the working surface is, as a gen- 
eral rule, determined by a master cam, which serves as 
a guide, or templet, for guiding the work in relation to 
the cutter. 

Fig. 5 shows one form of a cam-cutting attachment i 
place on a milling machine, and will serve lo show the prin 
ciple involved in the construction of nearly all, if not i 
such attachments. 

A false table a is bolted to the regular milling-machine 



§ 1ft 



MILLING-MACHINE WORK. 



47 



t slide i 



, gibbed to the fake table, and is free 1 



table; 

slide along it. The slide b carries a shafts in a bearing 
formed in it; this shaft is at right angles to the line of mo- 
tion of the slide and carries a worm-wheel d with which a 
worm e meshes. The shaft c can be rotated by hand or 
automatically; in the latter case, the pulley f is belted to 
some suitable feed-pulley of the machine. In order that the 
shaft c may be driven automatically in any position of the 
slide, the worm-shaft is splined and is driven by a feather 

attached to a sleeve that carries the pulley/! The shaft c 
is so arranged that it can either be left free to slide in the 
direction of its axis or can be confined longitudinally; in 
the latter case, it can only rotate about its axis. The master 
cam g and the work // are both fastened to the shaft c; a 
roller carried by the stationary bracket * engages with the 
master cam, which is held against the roller by a heavy 
weight k attached to the slide b. It is easily seen that by 




ta 



rtlLUNr,. MACHINE WORK. 



... 

on, and that 



turning the master cam the slide is set in motion, 
a milling cutter will cut the work to an outline depending 
on the shape of the master cam. Willi ilic attachment ill 
the position shown in the illustration, face cams having their 
working surface either on the inside or on the outside, ami, 
also, grooved face cams can be cut. 

11. For milling plain or grooved side cams, a properly 
made master cam is fastened to the shaft e, which is then 
unlocked in order to allow it to slide. The whole attach- 
ment is now turned around until it is at right angles to the 
petition shown hi the illustration. The weight I 
attached to the ahaft e, and the roller in the at 
bracket < engaging with the side of the master cam, the 
shaft and the attached work will slide in and out, as in- 
duced by the master cam, The automatic feed may be 
driven, in this case, from the pulley /. It will be 
■tOOd that when Cutting side cams in this 
atidfl b must be locked to the false table a. 





master cam. 



12. While this device will cut rams from a master 
it will not produce a master cam. This must be pi 
smile other manner Erst; in many i ■ 
master cam are such that it can ad be finished 
to the correct shape by milling, <t, perhaps, the ] 
part can be finished by milling and the rest by filing. 

13. Planer Milling Attachment. — E 

milling attachment used for converting a planer into a n 

ing machine. It consists of a head a and an outbos 

bearing f>, both of which are attached to the regular f 

cross-rail. The head a carries the spindle .-, win, 

out to take an arbor or the shank <>i a cutter. The spin 

is driven from the pulley it by the intervention 

gearing. Since the regular speed of the planer plat 

entirely too high to be suitable for the fee 

will usually have to be ii troducec] in order to lower t 

speed of the platen, or some other equivalent d. 



MILLING-MACHINE WORK. 



be used. The cutter is adjusted for depth of cut by moving 
the cross-rail up or down the housings; the side wise position 




of the cutter is adjusted by moving the regular planer 
head e, 10 which the head a and outboard bearing b are tied 
by the rod/1 

In the particular design of attachment shown, the head a 
is arranged so that it can be swiveled. This allows angular 
cuts to be made with a plain mill or a side mill, and greatly 
extends the range of work that may be done. 

14. The attachment illustrated will quite satisfactorily 
convert a planer into a milling machine; it is rather doubt- 
ful, however, whether such a makeshift will do as much 
and as good work as a regular machine designed especially 
to withstand the strains to which it is subjected by the 
milling operation. On the other hand, it allows work to be 
done in one setting that cannot be done otherwise without 
two separate machines, since it allows some parts of the 
■ be finished by milling, as, for instance, straight 
rrooves having an irregular profile, and allows the rest of 
he work, as undercuts, etc., to be finished by planing. 



MILLING-MACHINE WORK. 
TAKINC THE CUT. 



3 l' 




DIRECTION OF FEED. 

1 5. Methods of Feeding. — There is a great diversity 
of opinion among the huilders of milling machines as to the 
direction the feed should have with respect to the direction of 
rotation of the cutter. Perhaps the majority of builders of 
milling machines is in favor of feeding the work against 
the cutter; that is, with 
the cutter rotating in 
the direction of the ar- 
row x. Fig. 7, they hold 
that the work a should 
be fed in the direction 
of the arrow _y. In this 

case, the tendency of 

the cutter is lo push 

. _ the work away from 

F '°- 7 - the cut. On the other 

hand, there are other builders, among whom may be men- 
tioned the Pratt & Whitney Company, who are in favor of 
feeding the work with the cutter, or if the cutter revolves 
in the direction of the arrow jf, they feed the work b in the 
direction of the arrow s. In this case, there will exist 
tendency to draw the work toward the cutter. 

16. Choice of Method. — It is by no means settled 
to which method of feeding will produce the best results; it 
is probable that under proper conditions just as good results 
can be secured with one method as with the other. From 
this it must not be inferred, however, that a machine built 
and intended for feeding against the cutter is, without fur- 
ther preparation, adapted for the other way of feeding; an 
attempt to do so with such a machine is not likely to be 
repeated by the experimenter on account of the destructive 
results of the experiment. 

As previously stated, by feeding the work in the direction 
of the arrow z, Fig. 1, while the cutter is revolving in the 








§16 MILLING-MACHINE WORK. 51 

direction of the arrow x, that is, feeding with the cutter, 
there will be a tendency to draw the work toward the cut- 
ter. Taking a machine arranged for feeding against the 
cutter and attempting to feed with the cutter, the latter 
will suddenly draw the work toward it at the beginning of 
the cut to an extent depending on the amount of backlash 
between the feed-screw of the milling-machine table and the 
nut in which it works. In consequence of this, the cutter 
will climb up on the work; either the cutter will break, or 
the arbor will be bent, or the work will be broken. In any 
case, the result is exactly what might have been anticipated. 

17. The whole trouble is due to the backlash always ex- 
isting between the feed-screw and its nut; by taking up the 
backlash in the proper manner, or, more correctly speaking, 
by transferring it to a place where it can do no harm, a 
machine built to feed against the cutter can be made to feed 
with the cutter. The usual and most obvious way to pre- 
vent the table from jumping forwards, is to hold it back by 
a heavy weight attached to a cord or chain fastened to the 
table; the cord or chain then passes over a pulley placed in 
line with the table. 

18. Considering the case of a milling machine arranged 
to feed with the cutter, it can be used with impunity for 
feeding against the cutter, on account of the fact that there 
is no tendency for the work to jump toward the cutter. 

19. Milling Work With a Hard Surface.— When 

the work to be milled has a hard surface, as iron castings, 
steel castings, and some forgings, or has a surface in which 
sand is embedded; as is the case with brass and similar cast- 
ings that have not been pickled, the consensus of opinion 
seems to be that it is better to feed the work against the 
cutter, since then the cutting teeth will get in below the hard 
surface, and, working in the soft metal, will keep sharp 
much longer. Assume the tooth ,-, Fig. 7, to lie cutting and 
the surface rfof the work to be covered with a hard scale. 
Then, it can be seen that the tooth c comes up from below 



52 MILLING-MACHINE WORK. § 16 

the scale and instead of cutting through it, will pry the 
scale off and crumble it. In this connection, it may be well 
to mention that a prominent firm states as the result of 
experiments, in feeding with the cutter and against it when 
milling iron castings having a hard scale, that by feeding 
against the cutter, the latter lasted, without sharpening, 
eight times as long on an average as when feeding with 
the cutter. 

When the work to be milled is of uniform hardness 
throughout, the objection of dulling the cutter rapidly by 
feeding with it disappears, and just as good work can be 
done by feeding with the cutter when everything is properly 
arranged for that system of feeding. 



APPLICATION OF THE CUTTER. 

20. General Rule. — There is one general rule in 
regard to taking the cut that applies to either system of 
feeding. This may be stated as follows: Always take the 
cut in such a manner that the cutter cannot draw the zvork 
toward itself. 

In other words, whenever circumstances permit, so 
arrange the feed and machine that neither the cutter, work, 
nor machine will be damaged by any slipping of the work. 

21* Influence of Spring. — Fig. 8 is an example that 
brings out some of the points to be taken into consideration 
in determining the proper direction of the feed. In this 
case, a cylindrical piece of work is held in the chuck; it is 
required to cut a rectangular groove, the bottom of which 
is shown by the dotted line a across the end of the work. 
With the cutter rotating in the direction of the arrow -r, 
and feeding in the direction of the arrow j', i. e., feeding 
with the cutter, there will, obviously, be a tendency to draw 
the work toward the cutter. Now, while it is possible to 
transfer the backlash that allows the work to jump toward 
the cutter to a place where it will do no harm by weighting 



§16 



MILLING-MACHINE WORK. 



53 



J 






the table back, it is not possible to get rid of the 

of the work itself, and of any spring that may exist 

| ndex head carrying the chuck. 

With the cutter rotating as 

shown by the arrow x, it should, 

,n this case, be to the left of the 

work, or in the position shown 

ln dotted lines, and the work 

should be fed against the cutter, 

as shown by the arrow z. The 

WOr k will then spring away from 

tJl ^ cutter, and there will be no 

aa.ngr er f its catching and break- 

in £T the latter. 

*^* rom this example, it is 
^•^ried that the spring of the 
Wo *~lc and of the attachment in 
^^ioh it is held must be taken 
ir **c> consideration, and that al- 
^^^nce must be made for it in determining the 
dlr ^ction of feed. 



spring 
in the 




Fig. 8. 



proper 



^2. Example of Feeding: With the Cutter. — Occa- 
Sl °Hally it is a decided advantage to feed with the cutter 

when the machine can 

be arranged to allow 

this to be done. Thus, 

for instance, consider 

the piece a shown in 

Fig. 9 to be held in the 

vise and resting on the 

packing-block b. It is 

required to rough the 

upper surface down to 

the dotted line shown. 

Then, with the cutter revolving in the direction of the 

arrow x and feeding in the direction of the arrow j\ the 

pressure of the cut is mainly downwards, there being no 




54 



MILLING-MACHINE WORK. 



516 



tendency at all to lift the work. In consequence, the work 
will be pressed firmly against the packing-block. 

As previously stated, no attempt should be made to take 
a cut in this manner unless the machine is arranged to suit 
this method of feeding, and the work is of uniform hardness. 

23. Slipping of Work. — Fig. 10 is an example show- 
ing that there is occasionally a right and a wrong way of 
applying the cutter to the work, even after the direction of 
feed that is considered proper has been adopted. In this 
case, it has been determined to feed against the cutter; the 
work a is held between the vise jaws, as shown, and a cut 
is to be taken at an angle other than 90" with the top 
surface of the work. This particular job occurs in making 
forming tools for fly cutters and formed milling cutters. 
The depth and direction of the cut are given by the dotted 
line b. Now, with 
the cutter above 
the work and rota- 
ting in the direction 
of the arrow x, to 
feed against the 
cutter the feed 
■ v *.' e K'("~'>\ ^ must be as shown 
6 |0. 'vV^' 1 h- by the arrow y. 
-***-* '* While feeding in 
this manner, as- 
sume that the work 
slips, as is very liable 
to happen. Then, the work will rotate about a point some- 
where near c, and the end operated on will move in an arc 
about as de, or toward the cutter. The natural result of 
this will be that something must give way, and either the 
cutter or the work, or both, will be mined. 

In order to overcome the evil effect of slipping, the cutte 
should, in this case, commence to cut at the bottom; I 
should revolve in the direction of the arrow s and the feed 
ing should occur in the direction given by the arrow y'. 




§16 



MILLING-MACHINE WORK. 



case of slipping, the work will then move away from the 
cutter, and there is little likelihood of its being spoiled by it. 

24. The rectangular work