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THE

LABORATORY
WORKSHOP

PLATE I

A

An attic room converted into a laboratory workshop

THE

LABORATORY WORKSHOP

A SIMPLE COURSE

IN APPARATUS MAKING AND

THE USE OF TOOLS

r-

BY

E. H. DUCKWORTH

B.Sr., A.U.C.S.

Insiector of Silence and Technical Education

Colonial Service, Nigeria*
Formerly Senior Science Master
Dean Close School, Cheltenham

AND

R. HARRIES

City and Guilds [Lngmeenng] College
Imperial College of Science and fedmology, London

LONDON
G. BELL & SONS, LTD

1933

Printed in Great Britain by The Camelot Press Limited
London and Southampton

PREFACE

THE writers of this book were responsible for the workshop
practice which formed a distinctive part of the Science Colleges
held at Cheltenham by the Board of Education in 1930 and 19<fl.
It became apparent that many teachers would welcome a book
dealing with the functions of a laboratory workshop and, at the
suggestion of the organiser, Mr. E. G. Savage, II.M.L, this worfc
has been undertaken in order to reach a wider circle than is pos-
sible at a fortnight's Course. :

We wish particularly to stress the fact* that the fundamental
processes needed, even in a complex piece of apparatus, are few in
number and quite simple. We venture to make this point since
it is in danger of being overlooked by manyumen and perhaps even
more by women teachers who often regard a workshop as some-
thing outside their sphere. Our hope is that the book may en-
courage the design and construction of home-made apparatus,
not only because of the pleasures and advantages which tihe use of
a laboratory workshop brings, but also because in these times when
economy is urged and the allocation of money for scientific ap-
paratus is all too small, self-help of this kind seerhs the only way
in which efficient teaching is to be secured.

The apparatus described in Chaps. XI and XII have been selected
to show something of the wide range of equipment that it is pos-
sible to construct, ift very small cost, by the application of the
simple processes described in the earlier chapters. Users of the
book should have little difficulty in applying these processes to
their own requirements.

The line drawings and photographs for the illustrations have
been prepared by the writers.

Our very special thanks arc due to Miss M. A. Reid, B.Sc., who
undertook the reading of the manuscript, correction of the proofs
and the compilation of the index, and whose encouragement and
sympathetic interest has been our never-failing support.

Our thanks are due to the following firms for the drawings of
certain tools in Chapters I and II :

British Tool and Engineering Co., Ltd. (Bench drilling machine,
Item 18).

v

vi PREFACE

Greenfield Tap and Die Corporation (Little Giant screw cutting

appliances, Items 1-7).
C. and J. Hampton, Ltd. (Record vices, Figs. 2 and 3, and

Stanley pattern planes, Items 76 and 77).

Schollhorn and Co. (Bernard pliers, Items 49 and 50).

Other acknowledgements are made under the respective figures.

E. II. DUCKWORTH
11. HARRIES

CONTENTS

CHAP. PAO1C

INTRODUCTION ...... ix

I. THE SELECTION AND GENERAL EQUIPMENT

OF A LABORATORY WORKSHOP ... 1

II. TOOL EQUIPMENT . . . . .14

III. MATERIALS ...... 29

IV. How TO MARK OUT, CUT, FILE, DRILL AND

BEND SHEET METAL, ROD, STRIP AND TUUE 50

V. SCREW CUTTING ..... 78

VI. SOLDERING 102

VII. WOODWORKING ..... 119

VIII. ELECTRIC WIRING AND THE LABORATORY . 136

IX. MISCELLANEOUS PROCESSES THE CUTTING,

^DRILLING AND GRINDING OF GLASS , . 156

X. DRAWINGS AND DESIGNS .... 175

XL APPARATUS DESIGNS .... 187

XII. MORE APPARATUS DESIGNS . . . 226

APPENDIX ...... 240

INDEX ...... 243

LIST OF PLATES

I. A I.ABORATORY WORKSHOP ....

AN ATTIC ROOM CONVERTED INTO A LABORATORY WORKSHOP

Frontispiece

PAGE
II. A. A LABORATORY BENCH CONVERTED TO WORKSHOP USE . .183

B. MICRO-PROJECTOR 183

III. A. RADIATION SWITCH 194

B. SEARLE'S HFAT CONDUCTIVITY APPARATUS . . . 194

IV. A. PROJECTION MICROSCOPE ...... 209

B. SPECTRUM PROJECTION APPARATUS ..... 209

C 1 . SOAP FILM APPARATUS ....... 209

V. A. LARGE B.C. ELECTRO-MAGNET 223

B. LIFTING ELECTRO-MAGNET ...... 223

C ELECTRO-MAGNETIC DIP-NEEDLE ..... 223

D. SYNCHRONOUS MOTOR 223

E. APPARATUS FOR PRODUCING A ROTATING MAGNETIC FIELD 223

VI. A. MODEL TO ILLUSTRATE THE MECHANISM OF A MOTOR-DRIVEN

GARDEN ROLLER 235

B. AQUARIA < 235

C. SMALL TANK 235

D. WHIRLING TABLE WITH STROBIC DISC .... 235

E. SHAKING SAND BOX 235

VII. A. DERRICK CRANE WITH LIFTING ELECTRO-MAGNKT . . 238

B. HAMMER-HEADED CRANE 238

C. TRAVELLING CRANE ....... 238

1). AUTOMATIC RECORDING AUXANOMETER .... 238

VIM. A. MODEL OF A MEDIEVAL SYSTEM OF FARMING . . . 239

B. MODEL OF A CASTLE ....... 239

C. MODEL OF A LAKE VILLAGE 239

D. HISTORICAL MODELS : 239

INTRODUCTION

A SCIENCE laboratory forms part of the recognised equipment of
every up-to-date school and many schools have spent large sums
on elaborate buildings and ready-made apparatus, yet it is quite
rare to find any of these laboratories with a suitably equipped
workshop for the repair and construction of apparatus.

The type of laboratory that has been equipped in every detail
from a catalogue is far too common and rather depressing in its
lack of originality and flexibility.

Most science masters have had the experience of delving into
cupboards and finding a dusty collection of broken balances,
galvanometers and such-like that are no longer in use owing to the
lack of some small screw or essential part. The old apparatus
can be packed up and sent back to the makers for repairs, but
this involves trouble, time and money.

A small workshop enables repairs to be done at negligible
expense without delay and, what is even more important, the
teacher of science with a knowledge of the use t of tools is able to
try experiments that are not found in school text-books *md to
introduce into his teaching a freshness and originality that is often
sadly lacking in these days of certificate examinations.

The modern science student at a University receives little
training in manual dexterity. The lecture experiments are set up
by skilled assistants and the laboratory work seldom calls for
much manipulative skill, with the result that few science masters
or mistresses have an opportunity of learning the use of tools and
the construction and adjustment of apparatus.

The late Sir James Dewar often deplored this lack of ability
in students under his notice. His own dexterity, displayed in his
work and lectures was founded in boyhood days when he tried his
hand at making fiddles. He regarded this early training as tlie
most important part of his education.

During recent years the Board of Education in England has
attempted to remedy this deficiency in the school and university
training of science teachers by the organisation of vacation
courses in laboratory arts. The present writers have had oppor-
tunities of giving instruction at some of these courses and noting

ix

X INTRODUCTION

the special difficulties and requirements of science masters and
mistresses.

It is hoped that this book will assist science teachers to make a
workshop a useful and vitalising part of their equipment.

In general education a laboratory workshop can play an im-
portant part. Most school workshops come under one or other of
three categories. A wood workshop, a metal workshop or an
engineering workshop.

A wood workshop requires no description, a metal workshop is
usually devoted to the making of ornamental articles in sheet metal
and simple forging, and an engineering workshop implies an
equipment of lathes, milling machines and so forth.

Many public schools, with engineering workshops fitted with
machine tools, find a difficulty in providing suitable work of a not
too expensive character for the students to practise on.

Both wood and metal workshops are of value provided they
do not degenerate into places for wearisome exercise in the making
of joints or the shaping of material to set forms, such exercise
pieces to finish up ultimately on a scrap heap.

The wide development of science in schools has given the oppor-
tunity for a new type of workshop, where science and handcraft
are happily linked together, and where students can learn that
general 1 handincss with tools for accurate working in both wood
and metal, which is of value, not only to the future science worker,
but to any man of woman living in the present age of mechanism.
Few boys after leaving school, unless they take up engineering as
a profession, are likely to have the use of workshops equipped with
lathes and machine-tools; on the other hand a Kttle workshop
provided with wood-working tools and mechanic's hand tools for
metal work is readily acquired and provides the owner with a
life-long, pleasurable and most useful hobby, in that it enables him
to make and repair many things required or used in home or
garage.

In a laboratory workshop both staff and students have an
opportunity of making up all sorts of interesting models and
experimental apparatus, of trying out old, almost forgotten,
experiments or attempting new ones. An escape is provided from
the stagnation of examination science and something of the spirit
of a research laboratory is introduced into school studies.

An elaborate, expensive, equipment is not necessary, but it
does include, not only the usual carpenter's tools, but such things
as files, soldering irons and stocks and dies for cutting screw-
threads, also a supply of suitable materials.

INTRODUCTION XI

The omission of a lathe, so far as beginners are concerned, is
rather an advantage than otherwise, since the art of inventing,
improvising and adapting tends to be stimulated by its absence.
A workshop allied to the laboratory helps students to learn the
application of knowledge gained from books or in the lecture room.

A student who has constructed a telephone or microscope
projector, or wrestled with the difficulty of making and adjusting
apparatus to show the interference colours of soap films on a
screen has more real knowledge about these things than one who
has only read text-book descriptions or looked at demonstration
apparatus.

Many schools suffer from lack of science equipment yet, as the
following pages set out to show, it is possible to make a great range
of laboratory equipment at very small cost.

All the apparatus described has been constructed and tested
out by students in England or Nigeria, and some of it has been
exhibited in London at meetings of the Science Masters' Associa-
tion.

The writers hope that the book may serve as a practical guide
to the equipment of a laboratory workshop, provide help to
teachers and students in the use of tools, and give information
regarding the construction of a wide range of apparatus, also hints
on the setting up of interesting experiments that are* seldom
included in text books and arc of value in connection with school
science exhibitions. *

Many of these experiments, especially if demonstrated with
home-constructed apparatus, help to stimulate interest in science
and show something of its romance.

CHAPTER I

THE SELECTION AND GENERAL EQUIPMENT
OF A LABORATORY WORKSHOP

THE selection of a room, or space in the laboratory to be used as a
workshop is subject to various considerations. The workshop
should, if possible, be close to the laboratory. If a separate room
cannot be used, a place can often be found in the laboratory itself,
for preference in the physical laboratory. The fumes of a chemical
laboratory can cause steel tools to rust over-night. An elaborate
building is not necessary; thought should be given to the creation
of a workshop atmosphere; white paint and glazed tiles are
incompatible with the surroundings of a workshop. At the same
time arrangements should be made to keep everything neat and
tidy, since an array of well kept tools and materials, all ready to
hand and not hidden away in store boxes, has a valuable psycho-
logical effect in stimulating ideas. If the workshop is to *be used
by the science staff, a laboratory assistant and a few students
only, quite a small room will suffice. In cold countries provision
should be made for heating during the winter time; it is difficult
to do accurate work with metal if the hands are numb. In warm
countries the Workshop should be as airy as possible.

Many schools already have carpenters' workshops and it is
often an advantage to do most of the woodwork required in this
shop, reserving the laboratory workshop for metal work. This
avoids the dust and litter of sawdust and shavings. Small tools,
little nuts and so on tend to get lost in a mass of shavings. If a
separate room or space cannot be detailed for woodwork, then the
next best thing is to have a separate bench, and if this is not
possible it is always a good rule after using a plane to sweep up
the shavings before going on to other work (Plate HA, page 18o).

A good firm bench is essential. A design for a bench is shown
(Fig. 1). This may be made of pitch pine, deal or wood of similar
type. Deal is quite suitable and cheaper than pitch pine. The
top of the bench should be made of thick wood and be massive
enough to stand the blow of a mallet or hammer without rebound,

A bench, to be used for woodwork, is conveniently^ made lower

Bw i

THE LABORATORY WORKSHOP

Fig 1 A workshop bench

than one for metal work. When using a plane or chisel the worker
requires to stand well over his work. Laboratory metal work
involves much delicate marking out and drilling, a bench that is
too low necessitates uncomfortable stooping. For wood work
a bench height of 2' 6" is recommended and for metal work 3' is
not too high. A bench for combined wood and metal work is
conveniently macte 2' 10" high. It is often possible to convert an
ordinary laboratory bench. To protect the polished top from
the marks and cuts inevitable in a workshop the teak or other
top of good wood can be protected by covering* it with some
planed lengths of cheap wood firmly fastened down with screws.
A laboratory bench free from under-cupboards is to be preferred
since it gives a better standing or sitting position. Drawers on
the other hand are an advantage. The bench must be provided
with a parallel- jaw vice. The number of vices fitted will depend
on the number of workers likely to use the shop at any one time.
A vice to every worker is ideal, but much can be done with one
vice to every two or even three workers; a vice is in such constant
ue that one vice per worker should be aimed at if possible.

A vice with jaws 4* wide of the type shown (Fig. 2), is a useful
size. This may look large and clumsy, but will be found in practice
to be capable of holding small delicate work and it is a great con-
venience to have at least one good strong vice when iron-strip has
to be hammered over and bent without heating or " diam. iron
rods have tQ be provided with a screw-thread.

SELECTION AND EQUIPMENT o

Small vices with jaws 2" wide are quite cheap and will serve for
the majority of purposes, but if possible instal both a large and a
small vice. Vices are made in cast iron and steel. Steel vices are
much stronger and more expensive than cast iron ones. Since a
vice should never be hit with a hammer, cast iron ones are quite
satisfactory if this action be avoided.

The jaws of a good vice should go together fair and square and
be free from side wobble. Much of the wood-making to be done*
in connection with a laboratory workshop can be carried out with

Woodworker's quick -giip
paiallel-jaw \iee

the help of an ordinary parallel- jaw vice, but if space allows it is
useful to instal an ordinary carpenter's vice. A metal vice of the
quick-grip type shown (Fig. 3), is easily attached to a bench and
is a great help.

When attaching a parallel -jaw metnl vice to a bench, select a
firm place near to a bench leg or support. The marking out of the
positions of the holding down bolts or screws requires care. Clamp
a long straight metal bar in a vertical position in the jaws and so
place the vice on the bench that the bar is just clear of the edge of
the bench (Fig. 4). Avoid as far as possible the vice projecting
out over the bench top, at the same time it must project far enough
to enable it to hold long vertical rods that extend below the level
of the bench top. The jaw edges, as seen from above, must be
parallel to the bench top. Test with a long rod clamped in the
jaws in a horizontal position (Fig. 5). A mechanic usually con-
trives to fix his vice at such a height that .he is able to rest his
elbow on the top of it when standing by the side of the bench
(Fig. 6).

This arrangement is seldom possible in a laboratory workshop
where the vice is likely to be used by people of different height.

Small vices can be secured to the bench top with strong counter-
sunk head wood screws, but a better arrangement,* essential in

4 THE LABORATORY WORKSHOP

the case of large vices, is to fasten them down with nuts and bolts.
Note the diameter of the holes in the base of the vice, one is
usually uncovered only when the jaws are partly opened. Obtain
some iron or bright-steel Whit worth bolts of a size to just pass
through these holes and of a length about longer than the
combined thickness of bench top and vice base.

Suppose a f " diam. bolt has been found to be suitable. Mark
'the position of the vice bolt holes as described above and with the
help of a f " diam. bit held in a carpenter's brace, bore holes in the
bench at those places.

Put the vice in position; if the bolts are a little difficult to get
through the wood, although holes of the correct diameter have
been bored, just tap them through with a hammer. Sometimes
in fitting a vice to a laboratory bench it will be found that the
under support of the bench top or a drawer (Fig. 7), will prevent
the vice being fixed in such a way as to project far enough. In
this case it may be necessary to cut some of the wood away from
the inside with the help of a wood chisel or gouge to give room for
a nut and washer (Fig. 8). If everything is in order, put washers
on the bolts and tighten up the nuts with a spanner. If a bolt
tends to turn round as a spanner is used on the nut, then use two
spanners, one to hold the bolt and the other to turn the nut.

Sometimes it will be found that the screw-thread on the bolt does
not extend far enough to enable the nut to be tightened up. In
this ca^se remove the bolt and cut more thread on it with the help
of a die (see screw cutting< Chapter V). Failing the use of a die
find a nut with an inside diameter large enough to pass over the
bolt thread and use it as a packing piece with walhers on cither
side (Fig. 9).

Bench and vice having been provided for, the next consideration
is the arrangement of tools. It is wise to study economy of move-
ment and have all commonly used tools as near to hand as possible.
Much time can be saved in selecting the correct tools and in
tidying up, if unnecessary walking about the workshop can be
avoided.

It is much better to keep all tools out and ready for immediate
use than to store them in boxes and drawers. If displayed in
definite positions the loss of tools is readily detected and they are
easily examined for rust.

The skilled craftsman knows instinctively what tools to use for
any particular piece of work and may almost be compared with a
musical composer selecting the right note. It is surprising the
number of tools that may be called into use for the completion

SELECTION AND EQUIPMENT

Fig. 4. Fig. 5.

Method of determining the correct position of bolt holes when attaching
a viee to a bench

No room for nut of
holding down bolt

Fig. 7.

Bench,

Fig. 6.
Method of testing a vice for height

Wood cut away to
~ive room for nut
'washer

Fig. 8.

Packing nut

Fig. 9.

Method of usiyg holding-down

bolts that are not threaded far

enough df wn the stem

THE LABORATORY WORKSHOP

Method
of con-
structing
Type 3

Dowel Rods
Type 2

TypeS

Fig. 10. Wooden tool racks

Fig. 11. A metal clip form of tool rack

Nail
without,
a head

Ordinary
nails

A Shou!dr S^u^-e Hook

Fig, 13. Tool holders

A Cup Hook

Fig. 12.
Tool holders

SELECTION AND EQUIPMENT 7

of quite simple apparatus, hence the necessity for tools arranged
ready to hand.

Tools like files, hammers and chisels can be held in loops of
leather strap, wooden racks or metal clips.

feather straps can be purchased quite cheaply at a harness
maker's in long lengths without metal buckles and are easily made
up into loops of different sizes to suit the tools; they can be
attached to woodwork with round-headed brass or iron screws.
Holes for the screws to pass through the leather can be made with
a bradawl.

Wooden racks are cheaper to provide than leather loops and in
some respects are more satisfactory (Fig. 10).

Tool dealers sell metal clips for holding tools, a few of these are
often handy (Fig. 11).

Large tools like saws and a carpenter's brace are readily sus-
pended on shoulder square hooks, cup hooks or nails (Fig. 12).
Steel rules can hang from nails that have had their heads cut off
(Fig. 13).

As far as possible arrange to keep the bench top clear of tools,
except of course when work is in progress.

If the wall facing the bench be made of brick or concrete some
difficulty will be experienced in attaching tool holders. , In this
case it is best to cover the wall to a height of a few feet with
wooden boards. The wall will have to be plugged, the method of
doing this is described in Sec. 201. It is wise to keep tke floor
space as clear as possible to simplify Sweeping up. A shelf under
the bench is handy for storing boxes of oddments and a shelf about
6" wide, opposite the bench and about 2' above it provides a
useful place for plane's, small tools and tools of odd shape that do
not readily slip into loops or other holders.

Cupboards are useful to store paint tins and brushes that tend
to become unsightly, also to keep from the dust objects that have
just been enamelled. Cupboards, also drawers, require periodic
overhaul to prevent them becoming the abode of litter. Provide
plenty of shelves for the storage of screws, nails and such like.

The bench used for woodwork should be fitted with a benjch
stop to enable wood to be planed. Ready-made, metal bench stops
can be obtained. When these are used beginners are very liable
to chip bits out of plane irons by continuing to plane when the
edge of the stop has come flush with the wood being worked on
(Fig. 14).

An alternative method is to bore a row of vertical holes in the
bench top and fit these with dowel rods (Fig. 15). Thfe rods should

8

THE LABORATORY WORKSHOP

be left about 1' long. With the help of a mallet they can be
knocked up from below to any required height. They readily
prevent work slipping, do not get in the way, and no possible
injury can be done to either the job or the plane.

Metal stob too
high A

Wood being
planed

Metal Bench Stop
Fig. 14.

Racks should be made to carry a supply of strip, rod and sheet
metal. ^Two types are shown (Fig. 16). Odds and ends of waste
metal should not be thrown away, but kept in a special box. One
box for brass and copper, another for iron and steel. Great
economy can often be effected by using up odd bits instead of
cutting into new supplies.

Screws arc best bought in gross packets and are Always rather
difficult to keep tidy and sorted. The advantage of leaving the
screws in their original packets is that the lengths and size numbers
are printed on the packets.

It is often necessary to
return unused screws to
packets. It is trouble-
some to compare a screw
held in the hand with the
particulars on a label.

. For this reason it will be

Fig. 15. A fool-proof and very efficient , , . .

form of bench stop foiind advantageous to

store the screws in labelled

glass jars. Sorting is simplified, the stock remaining in reserve
can be noted and iron screws are preserved from rust.

Old jam and honey pots with screw tops are excellent for the
purpose and 'are cheap to replace if broken.

,

s l} apart

SELECTION AND EQUIPMENT

9

Wooden. Bar
pivoted at one
end enabling"
long- lengths
of metal to be
readily
-withdrawn.

Bars to
prevent short

lengths from

falling-

out

A rack of the umbrella stand type for holding metal supplies
The rack can be placed against a wall

A rack for holding metal supplies
Fig. 16.

The chief disadvantage of a pot is that it has to be tilted up to
get out the contents, for this reason rectangular shaped tins a/e
sometimes preferable.

Craven A cigarette tins form excellent screw containers. They
we a gay red, free from unsightly lettering on the sides. The name
is enamelled and not pressed out on the lid. Also the latter, being
domed, gives good store space for the odd screw that is often so
difficult to return to a packet that is nearly full attd slightly
disarranged.

10 THE LABORATORY WORKSHOP

The top of the tin should be painted over with black cycle
enamel and the nature of the contents neatly printed in block
lettering, using a fine brush and white enamel.

Old glass vaseline pots with enamelled screw tops make good
containers for tiny nuts, washers and other small supplies.

If the shelf used for storing screw bottles be subject to vibration
from the work bench it is wise to fit it with a raised strip of wood
to prevent the bottles gradually slipping off.

When screws and small nuts have been used it is often found
that some have been left out after the main tidying up has been
effected. Time is saved if these are not returned to the correct
pot or tin at once, but placed in a special open tin of mixed screws
and nuts that is sorted out every month or so. One tin can be kept
for wood screws and another for metal screws.

Some workers are very wasteful of emery and glass paper.
When this has been used it should not be thrown away unless dirty
or quite worn out. A special box or drawer should be kept for it.

A workshop requires good illumination.

If electric light be used, provide lamps for general illumination

r~\

Fig. 17. An electric lamp holder with push-bar
type of switch

and for a concentrated light on the work bench and vice. Metal
shades, white enamelled on the inside, and of a shape to cut out
all direct light are recommended for the latter purpose. They are
somewhat expensive; a cheap, but less durable substitute is
p^vided by cardboard ones.

Bench lights should be fitted with holder switches. Holder
switches of the push bar type (Fig. 17) are much to be preferred
to holder switches of the turn type. The former can be worked
with one hand and the flexible connection is not bent when the
switch is operated.

It is best to provide a separate soldering table or at any rate
reserve a special place on the bench for soldering. This table or

SELECTION AND EQUIPMENT

11

bench place should be well removed from shavings. If a blow-
lamp be used for heating soldering irons the latter precaution is
most important to avoid danger from fire. Blow-lamps, unless
carefully started up, are liable to squirt out a flaming jet of liquid
paraffin (kerosene) and should always, on first pumping, be directed
away from inflammable material. A soldering table covered with
a piece of Uralite, a commonly used building material made of
cement and asbestos, is particularly useful. A hot soldering iron
can be placed on the table without fear of burning anything, little
pellets of solder can be dropped on it and are readily picked up for
use. If a whole table be not used for soldering a Uralite roofing

A wooden sawing stool

tile measuring about 12" square forms a suitable cover to part of
the main bench.

An ordinary laboratory-stool should be available, sometimes a
very steady hand is required and it is an advantage to sit down at
the bench. *

If the sawing of wood be not done in a carpenter's shop, or if the
wood-shop is not near at hand or always available the wood can
be supported on two laboratory stools or even chairs, but as these
are very likely to get cut into by careless or over vigorous workers
it is best to make two sawing-stools of the type shown (Fig. 18).

A supply of tincture of iodine, bandages and a pair of fine
tweezers should be kept in a first-aid cabinet. Slight cuts ai;e
fairly common in a workshop and should not be neglected. Brass
filings and chips however small should always be extracted and for
this the tweezers are useful. Brass is much more liable to cause
festering than either iron or steel.

A scrap-box for odds and ends can play a most important part
in a laboratory workshop and provision should be made for such a
store. As subsequent chapters show many apparently useless

12 THE LABORATORY WORKSHOP

oddments can be put to good use and often save much time and
trouble in making up special parts.

The floor may be of wood planks, wood blocks, cement or even
hardened mud, but in any case should be capable of being swept
clean. The dust from woodworking is sometimes troublesome, this
is largely obviated by treating the floor with a dust allayer such
as Florigene. A cement floor should be sprinkled with a water-
ing can before sweeping operations start. The last but by no
means the least important part of the general equipment of a
laboratory workshop is the provision of adequate facilities for
cleaning up.

Old rags or cotton waste are handy for mopping up oil and paint.
If these are not available it may be found that expensive glass
cloths and dusters will be taken for the purpose.

One or two soft floor brushes are required and every bench
should have a hand brush. Each brush should have a hole drilled
through its handle, so that a loop of strong cord can be inserted.
The brush can then be hung up and stored with the bristles off
the ground.

It is not easy to sweep up filings without the help of a dust-pan.
A piece of sheet tin plate may be bent up to form its equivalent.
Two fla,t pieces of wood arc handy for gathering up shavings and
putting them in a waste box.

It may appear jmnecessary to mention brushes and such domes-
tic items yet the cleaning up process plays an important part in a
workshop.

After working for some hours the bench will get littered with
tools and it becomes difficult to find just the one required. When
this happens it is always wise to stop work for a few minutes and
tidy up, returning tools to their proper positions in holders and on
shelves.

If small nuts and other parts are dropped on the floor they can
usually be recovered by sweeping up. In any case it is always wise,
as a measure of economy, to look over the last sweepings for odd
screws, nuts and bolts and return them to their respective bottles
or tins.

If gaps exist in thye floor boards they should be filled in with
slips of wood or valuable parts may be lost.

A rule should be made for one's own use and for the instruction
of others that the workshop be left clean, tidy and in perfect order
after each day's work.

A clean tidy workshop, no less than a laboratory, promotes clear
thinking ami accurate work.

SELECTION AND EQUIPMENT 13

Dr. Gladstone in his delightful sketch of Michael Faraday 1
under the heading, 'His Method of Working,' writes :

"He would put away each tool in its own place as soon as done
with, or at any rate when the day's work was over, and he would not
unnecessarily take a thing away from its place: thus, if he wanted
a perforated cork, he would go to the drawer which contained the
corks and cork-borers, make there what he wanted, replace the
bores, and shut the drawer. No bottle was allowed to remain
without its stopper; no open glass might stand for a night without
a paper cover; no rubbish was to be left on the floor; bad smells
were to be avoided if possible; and machinery in motion was not
permitted to grate.

"In working, also he was very careful not to employ more force
than was wanted to produce the effect. When his experiments
were finished and put away, he would leave" the laboratory and
think further about them upstairs.

"This orderliness and this economy of means he not only prac-
tised himself, but he expected them also to be followed by any
who worked with him; and it is from conversation with those that
I have been enabled to give this sketch of his manner of working.
This exactness was also apparent in the accounts he kept with the
Royal Institution and Trinity House, in which he entered every
little item of expenditure with the greatest minuteness of detail."

1 Michael Faraday, by ,T. H. Gladstone, Ph.D., F.H.S., Macmillan & Co.,
1873. Now out ol print, but can sometimes be obtained second-hand.

CHAPTER II
TOOL EQUIPMENT

WHEN choosing tools it is always wise to select one with a maker's
name or trade-mark stamped on it in preference to one not so
marked. A tool that a maker is ashamed to put his name on is
usually bacjly tempered or otherwise poor. A good quality tool
will last a lifetime if properly used.

Beware of combination tools that are supposed to function as a
hammer at one end, a screwdriver at the other and half a dozen
other things in between. Such tools, with a few exceptions, are
never used by workmen. In the case of young people selecting
tools and starting to build up the nucleus of a little home-workshop
it is wise to select a good mechanic's or carpenter's tool in prefer-
ence to the cheap, but usually worthless 6d. store article. The
best policy is to obtain tools from a dealer who does a good trade
with men who have to live by the use of tools or from one of the
large London firms engaged in dealing with engineering concerns;
some of these are prepared to give substantial discount rates to
schools, colleges and laboratory workers.

A study of the catalogue, of one of the large London tool dealers
can be most instructive, but at the same time rather bewildering.

The number of different hammers, files, screwdrivers and so on
that can be bought, makes selection by tha inexperienced a little
difficult. This chapter is to indicate just those tools that have
been found most useful in a laboratory workshop.

The number of tools that might be bought and found useful is
almost unlimited. If time is no object it is possible to make almost
anything, even a bicycle, with little other equipment than a hack-
saw and file, but few of us have the leisure of a prisoner of war or
the patience of primitive peoples who, as all know, often produce
Wonderful results with the help of simple tools.

Now it is possible to use a tool in many different ways and for
more than one purpose. A file can be used to file, but the tang
end is sometimes handy for enlarging holes. On the other hand
the tang end of a file, uncovered by a handle, when the tool is used
for its norwaal purpose, can inflict an unpleasant cut and it is much
better to spend a few pence and buy a proper tool for enlarging

14

TOOL EQUIPMENT 15

holes. A multiplicity of screwdrivers is unnecessary, but at the
same time a reasonable selection is required. A screwdriver strong
enough for screwing together a packing case is scarcely suitable
for carrying out the delicate adjustment of a moving coil galvano-
meter or tightening the tiny screws of a spectacle frame.

When a reasonable outfit of tools has been gathered together
and possibly selected during a number of years with the care of a
connoisseur, it is wise, before farther purchases are made, to ask
oneself 'Will it enable me to increase the range, accuracy or
efficiency of my work ?'

Certain American firms are world famous for the precision and
beauty of construction of mechanic's fine tools; during recent
years one or two Sheffield firms have turned their attention to this
line of manufacture and are now producing a good range of such
tools at competitive prices.

Lists of tools are given. List 'A' is of tools that should find a
place in every science laboratory that can be regarded as reason-
ably equipped. It is also the equipment that the private experi-
menter or the home mechanic who wishes to do domestic or garage
repairs should start to accumulate.

A drilling machine and a big 4" vice, in addition to a 2J" one,
are not absolutely essential. The drilling machine is the more
important of the two and is invaluable, not only as a saver of time
and labour, but as an aid to accuracy.

List 'B' is of additional tools that will be found very useful and
can well be added as funds permit.

If the workshop is to be used by several workers a more liberal
supply of certain tools will be necessary; some tools are in constant
use while others are les frequently employed.

The third column in the lists indicates a satisfactory supply
for twelve students.

Certain special tools, not included in these lists, but described
and illustrated in other parts of the book can be purchased if and
when the need for them arises.

The prices shown are only approximate, current prices can
always be obtained from a tool dealer.

The cost of American tools to buyers in England is increased b^
duties and it is well to enquire if a satisfactory English made
substitute has appeared on the market.

TenJ twenty or thirty pounds spent on tools and workshop
materials may, at first sight, appear excessive, but as pointed out
in the Board of Education publication Science in Senior Schools 1
1 H.M. Stationery Office, 1/6.

16

THE LABORATORY WORKSHOP

it is money wisely expended. Money in the case of new labora-
tories, is often wasted on over- elaborate furniture, benches and so
on. Tools are more important than furniture. With wise control
of expenditure on furniture all the tools needed can be bought and
the total cost of the laboratory need not exceed what is now often
paid. <-

If tools are available, much money can be saved over the pur-
chase of completed pieces of apparatus and in repairs. The know-
ledge of materials to be gained in a workshop is a valuable asset
to science teaching, other advantages have been pointed out in the
Introduction.

LIST 'A'

Item

No.

1

2
3

4
5
6

7

19
20

21
22
23

No. reqd.
No. for 12
reqd. workers

DESCRIPTION

Approx. Price
single tool or

set

Whit-

9

4

4

10

4

4

11

4

4

12

4

4

18

4

4

14

4

4

15

4

4

16

4

4

ir

1

3

18

1

2

Whit-

2 Stocks and Adjustable Dies \" f

worth. One taper tap per size
2 Stocks and Adjustable Dies J" -^

worth. One taper tap per size
2 Stocks and Adjustable Dies. Size 0123

456 and 9. Brit. Ass. One taper tap per

size
2 Whitworth right hand taper taps Y . .

2JJ *
> " "Iff

2 ..

2 Drop-Forged Adjustable Wrenches, Jaws open

2 Set carbon steel, twist drills on metal stand,

Twist Drills carbon steel

A"

A' ......

i" ......

A" ......

Hand Drill to take drills up to " 12 /- to

Bench type drilling machine with chuck to
take drills up to y ...... 1 to

2 sets 2 sets Spare springs for chuck of drilling machine . .
Ref. Ch. I,
Fig. 2 'Record' Parallel Vice with 4" jaws

* > > > *2 > * * * *

1 "3 Jeweller's small hand shears, straight blades
13 .... .. .. curved blades

s. d.
1 14
100

100
6
6
6

2

12 6
2*
2*

3

3

3

5

10
3

16 6

7 9

1 6

2

TOOL EQUIPMENT

17

OZ3.
Wrench for Wiutworth taps

WKitwortH adjustable die

No. 8 Carbon steel twist drills
on metal stand

BAdie
Nos 1-6 Screw cutting tools

No. 17. Hand drill

No. 7. Drop-forged adjustable wrench

Nos. 22 and 23 Jeweller's snips, straight and curved blades

Nos. 24 and 25. Tinman's snips

No 28.
Engineer's cross pane hammer

L

No. 29. Engineer's ball pane hammer

Cw

No. 18. Bench type drilling
machine

18 THE LABORATORY WORKSHOP

Approx. Price
No. rcqd. single tool or

Item

No. for 12

DESCRIPTION Set

No.

reqd. workers

S.

d.

24

1

3

Tinman's Snips, 12" straight . .

3

25

]

2

,, 0"

1

9

26

1

3

Hall Pane Hammer with handle, 3oz.

27

1

3

Ooz.

28

1

4

Engineer's Hammei Cross Pane with handle,

IJlbs

2

29

1

4

Engineer's Hammer Ball Pane with handle,

lib

1

4

80

1

3

Cold Chisel, y diam. octagon, length ft"

6

81

1

3

Woodworker's Viee, 'Record* 8" (See Fig. 3) . .

15

32

1

2

Jeweller's Saw Frame to take fret saws

2

6

83

3 doz.

i OTO

4

84

3

o

1

,, ,, ,, wood . . . . . . ,,

4

35

1

Hack Saw Frame for 12" saws

3

6

30

2 do/.

2 doz

. Blades 24 teeth to the inch 12"(doz.)

2

3

37

2

2 ,,

32 ,, 12" ,,

2

3

88

1

File 12" bastard hand

1

3

39

1

6

,, 10" second cut hand

1

2

40

1

6

,, 10" smooth hand

1

3

41

1

6

,, 6" smooth ,,

8

42

1

,, 8" half round second cut

10

43

2

6

,, 6" round second cut

44

2

,. *>"

9

45

2

,, (>" square ,, ,,

40

2 sets

3do/.

Assoi tment of 4" small files in sets of six

1

9

47

24

7

Handles, with metal fei rules, selected to fit

c above files . . . . . . . (doz.)

1

9

48

/,!

2

Carborundum stone for sharpening wood tools

(combination fine and coarse) 7" x 2" x 1" . .

5

3

49

1

3

Round-nose Pliers, 4J"

2

50

1

2

Cutting Pliers, OJ" ,

3

6

51

1

4

Firm Joint Callipers outside 4"

2

3

52

1

4

,, ,, ,, inside 4"

2

3

53

1

5

Toolmaker's Dividers, 6"

5

9

54

1

6

Centre Punch, line, bright knurled . .

6

55

1

,, ,, medium ,, ,,

6

56

1

6

Engineer's Bught Steel Try Squares, Size 3"

2

9

57

]

Pocket Scribe

9

58

1

4

12* Steel Rule, divided inches and millimetres,

Chesterman's stainless

2

59

1

6

6" Steel Rule, divided inches and millimetres,

Chesterman's stainless

1

5

do

1

2

Hand Saw, 24", Spear and Jackson

8

01

1

3

Tenon Saw, 12", ., ,,

5

02

1

2

Keyhole Saw

3

03

1

2

Spare blade for Keyhole Saw

04

1

2

Fretsaw frame 12" (Hobbies)

3

05

1

4

Carpenter's Brace 8", with ratchet

6

00

1

3

Brace Bit. Auger i" . .

1

3

07

1 '

3

t
. .

1

3

08

1

3

\"

,, ,, 2 * * * ' * * *

1

5

TOOL EQUIPMENT

19

No. 30. Cold chisel

No 48. Carborundum stone

No 32. Jeweller's saw frame

No 35. Hack haw

38.

NS45.

No. 46. Jeweller's files

20

THE LABORATORY WORKSHOP

No. 49. Round-nose

pliers No 54 centre punch,

fine point

No. 50. Cutting
pliers

No. 51. Outside
callipers

No. 55. Centre punch
medium point

No 52. Inside [_|

callipers No 50 Stcel try squtire

No. 53. Tool maker's
dividers

No. 57. Pocket scribe

No 66 if 68 Auger bit

5)

No 69V 71 Centre bit

Nos. 58 and 59. Steel rules

No 73 Countersink for hand or machine drill

No 72 Countersink rose bit

No. 70.
Stanley pattern smooth plane

N"o 75 Bradawl

No. 77. Stanley pattern jack plane

TOOL EQUIPMENT 21
Approx. Price

Item No.

No. reqd. single tool or

No.

reqd.

for 12

DESCRIPTION

set

workers

s.

d.

69

1

3

Brace Bit Centre f"

4

70

1

3

> 2 ' * * * * *

4

71 *

1

3

,, ,, ,, j . . . . . . . .

5

72

2

4

Countersink Brace rose bit f "

5

73

1

5

Countersink for hand or machine drill. Angle

82, Shank -fa, Body f"

6 '

74

1

2

Gimlet (medium size)

6

75

1

3

Bradawl (medium size), with handle

6

76

1

3

Bailey or Stanley Pattern Plane, Smooth 9"

7

9

77

1

3

Jack 13J" . .

10

9

78

1

3

Wood Chisel with handle J" firmer . .

8

79

1

3

> ) ?> "2 ' '

10

80

1

3

Screwdriver, Cabinet 6"

9

81

1

3

,, ,, LA

1

9

82

1

3

,, Jewellers'

1

83

1

2

Electrician's Turn-screw -fy " point

1

2

84

1

3

Carpenter's Mallet, 18oz.

1

6

85

1

3

Square 9"

3

6

86

1

1

Glazier's Diamond or wheel glass cutter. (See

Chap. IX)

87

1

3

Soldering Iron, 8oz.

1

9

88

1

3

16oz.

3

89

1

4

Engineer's Oil Can

1

90

1

3

Lancashire Taper Broach, J", with handle . .

7

91

1

3

i
5>

1

92

1

3

Brazing Lamp for Paraffin, 1 pint, inclined

burner. (Not required when gas i available)

10

6

93

1

3

Pliers, long flat nose, 4"

1

6

94

1

3

Firmer Gouge, handled y

1

4

95

1

1

Gouge Slip Stone for above

1

8

LIST C B'

96 1 2 Patent Expansion Drill for Iron Brace shank.

(See Fig. 65) 46

97 1 1 Combination Square, English and Metric, 6' . . 126

98 1 1 Burner Tap f *, Screwplate and Reamer. (See

Fig. 123)

99 1 1 High Speed Bench Grinder for Hand. Size of

Wheel, 5" x I" 5 9

100 1 3 File Brush v . . . . 4

101 1 1 Spirit Level, 8" 19

102 1 1 Sliding Bevel, 7 J" 30

103 . 1 2 Spokeshave, Beechwood, Brass Plated on face,

2" 16

104 1 1 Plumber's Shave Hook, Triangular .. .. 10

105 1 2 Screw Nose Centre Bit for Brace V .. v 10

106 1 1 Best Black Gas Pliers, T 20

107 1 3 Wood Chisel with handle, \" 10

22

THE LABORATORY WORKSHOP

N?60 Handsaw.

N61 Tenon savsr.

No 65 Carpenter's Square

N89 Engineers oil can

N62 Keu.Kole saw.

N 90 Lancashire Taper Broach

* No 78 Wood Chisel

No SO Cabinet Screwdr.

No 82 Jeweller's Screwdriver

No 83 Electrician's Turn-screw

O *

river

'9.92 BrazingLamp

N?93 Pliers- Long flat nose

N94 Firmer gouge

N?.9S Gouge slip stone

TOOL EQUIPMENT

23

No. 97. Combination square

Xo. 99 Bench grinder

No 100 File brush No 101 5 P mt Level

No 303 Spokeskave

No. 102 Sliding- Bevel ^ j O4 pj uin bers Shave Hook

No. 105 Screw Nose Centre bit

No. 1O9 Celluloid protractor

w ssors

No. Ill Embroidery Scissors

No. 108 Nail Set

No. 116. j Wire gauge

24 THE LABORATORY WORKSHOP

Approx Price

Item No. No. reqd. single tool or

No. reqd. for 12 DESCRIPTION set

workers s. d.

108 1 2 Nail Set, -J" tip 6

109 1 2 Celluloid Protractor . . . . . . . 9

110 1 2 Scissors, Cutting out, 6J" 40

111 1 2 Embroidery, Fine Points . . . . 1 6

112 1 1 Rawlplug Tool Holder and Bit, No. 8 size.

(See Sec. 201) 1 10

113 1 1 Wall Drill, Size \". (See Fig. 295) .. .. 6

114 1 1 Box of 100 Assorted Hawlplugs, Size 8. (See

Sec. 201) 20

115 1 2 Vice for use in conjunction with drilling

machine. (See Fig. 128) 12

116 1 1 Circular Impenal Standard Wire Gauge, 1-3(5 7

117 1 1 Mitre Cutting Block. (Sec Fig. 224) . . 10

118 1 2 Twist Drill with bit stock \" (Fig. 212) . . 9

119 1 2 i" 13

The use of the different tools is fully described in subsequent
chapters, but at this stage a few observations on the tools them-
selves will not be out of place.

Items 1, 2 and 3.

'Little Giant' taps and dies are some of the best tools of this
description manufactured. Various Sheffield firms are now
making screw cutting tools. 'Little Giant' dies have the advan-
tage of collets that guide the tool and prevent the formation of
drunken threads (see Sec. 94 Chapter V).

Dies of this type are made by G. and J. Hall, Hereford Street,
Sheffield. Other makers of taps and dies are Joseph Robson and
Sons, Mary Street, Sheffield, and the British Tap & Die Co. Ltd.,
Town Road, London, N.9.

Items 4, 5 and 6. Taps.

Small size taps are liable to get broken. It is useful to keep a few
spares in store.

Item 7. Wrenches.
The wrenches obtained should be large enough to turn a |" nut.

Item 8. Set of twist drills.

It is worth buying or making a stand. The drills are kept
sorted and breakages are instantly detected. Metal stands vary
in quality according to the gauge accuracy of the holes provided
for the drilk. Wooden stands are not recommended, damp or hot
conditions soon make the holes inaccurate.

TOOL EQUIPMENT 25

Items 9-16. Extra drills.

It is well to keep some small size drills in reserve, to replace any
belonging to the set (Item 8) that get broken.

Item 17. Hand drill.

The 'Yankee' ratchet hand drill No. 1530 is one of the best tools
of this description. The ratchet is often a great convenience. A
tool without a ratchet, but of English manufacture is the 'Record'
hand drill No. 125 made by C. & J. Hampton, Ltd., Sheffield.

Item 18. Drilling machine.

Obtain a substantial machine designed for bolting down to a
bench, avoid the type made to clamp to a table edge. Many of the
cheap drilling machines on the market have poor bearings and
badly cut gear wheels ; before long they develop wear and become
inaccurate. The 'Britool' No. 10 machine has all its gear parts
enclosed and running in oil, it is made by the British Tool and
Engineering Co., Ltd., Wolverhampton, England.

Item 30. Cold chisel.

Moore & Wright, Sheffield, England, make excellent cold chisels
in nickel-chrome alloy steel. They are sold under the name of
'Surecut' chisels.

Item 35. Hack-saw frame. *

The non-adjustable hack-saw frame is usually more rigid* than

the adjustable type, unless an adjustable one of first class make

be obtained.

A hack-saw frame should hold the blade without any suspicion

of side play or twist.

James Neill & Co., Ltd., Composite Steel Works, Sheffield, make

a good hack-saw frame known as the 'Eclipse', No. 50. R.S.

Items 38-46. Files.

Files are manufactured in great variety. When ordering files
three features have to be taken into account.

1st. The Length. This is always measured exclusive of tho
tang or part that goes into the handle. *

2nd. The Cut. This has reference to the relative degrees of
coarseness of the teeth.

3rd. The Name or Kind. This has reference to the shape.

The chief terms used to describe the cut are: Bastard, Second
Cut, Smooth and Dead Smooth.

26 THE LABORATORY WORKSHOP

A bastard file has much coarser teeth than a second cut one and
is useful for rough work.

Second cut and smooth files are used when work has to be given
a good surface finish.

Dead smooth files are seldom required.

A file with very coarse teeth, designed for filing wood, is known
as a rasp.

The shapes of files commonly in use are given (Fig. 19). A flat
file differs from a hand one in being tapered at one end.

Fig. 19. File sections

Warding files, apart from other uses, are employed by locksmiths
to file the ward notches in keys.

Hand files are made with one narrow side free from teeth. This
is known as a safe edge and is useful when the file has to be used in
a situation where a slight slip might cause injury to neighbouring
work (Fig. 20).

Item 47. File handles.

Files should always be used with handles.

When using a fjle it may catch in the work
and <an unguarded tang end can, in such a
case, give rise to a cut wriest. To fit a handle Flg 2()
on a file first make certain that the handle edge on a file

has a good deep hole for the tang to pene-
trate. If necessary clamp the handle in a, vice and using a twist
drill, make the hole deeper.

Now clamp the file horizontally in a vice, use jaw protectors,
and, with gentle taps, hammer the handle on to the tang. Take
great care to drive it on straight. As it is being put on, view it
now and again from two positions at right angles to one another.

Item 50. Cutting pliers.

Many cheap cutting pliers have badly tempered cutting edges
that soon fail to act. The best pliers are those with a powerful
parallel jaw action known as 'Bernard' pliers. These can be used
for cutting wire or holding work.

Items 51* 52, 53, 54, 55, 56, 57.

Callipers, dividers, centre punches, try square, scriber, A good

TOOL EQUIPMENT 27

range of Engineers' Precision Tools are now made by Moore &
Wright, Sheffield, England.

Item 62. Keyhole saw.

A very good one of improved design is made by the above firm.

Item 65. Carpenter's brace.

Carpenter's braces can now be obtained with jaws capable of
holding an ordinary brace bit or a twist drill with straight shank.
This is a great convenience in increasing the use of the tool. Twist
drills of a size between f " and |" are liable, if used in a small drill-
ing machine, to press on and injure the springs inside the chuck
of the machine. They are readily held in a carpenter's brace
furnished with the improved type of jaws.

Items 76 and 77. Planes.

British made planes of Stanley pattern can now be bought.
Makers: C. & J. Hampton, Ltd., Sheffield.

Items 78 and 79. Wood chisels.

Marples & Sons, Ltd., Sheffield, manufacture best quality
carpenter's tools.

Item 86. Glass cutter. >

Notes on the relative merits of diamond and wheel cuttess are
given in Chapter IX.

Item 89. Oil can.

Moore & Wright ma'ke a satisfactory leak-proof oil can.

Item 92. Brazing lamp.

One of the best brazing lamps on the market is that of Primus
make.

Item 97. Combination square.

The combination squares of the two American firms Starrett,
and Brown and Sharpe are well known to all mechanics for their
beautiful finish and smooth action.

Item 99. Bench grinder.

A bench grinder should have substantial, well protected bear-
ings. The Carborundum Company, Ltd., Trafford Prfrk, Man-
chester, make good machines.

28 THE LABORATORY WORKSHOP

Item 100. File brush.

Sometimes the teeth of a file get clogged up and a file brush is
useful for cleaning purposes. Try to avoid using a new file on
solder or lead.

Item 104. Plumber's shave hook.

This is a useful tool in a laboratory for scraping benches, remov-
ing labels and so on.

Item 115. Vice for drilling machine.

An excellent vice for this purpose is the 'Yankee' No. 990. This
opens to 3" and one jaw has a V groove for holding circular work.

Item 116. Wire gauge.

The usual method of defining the size of a wire is by a gauge
number. The British Imperial Standard (abbreviated to S.W.G.)
was authorised by Act of Parliament in 1883. A No. 7 S.W.G.
wire has a diameter of -5", a No. 36 S.W.G. wire has a diameter of
0076."

In America another gauge is used known as the American or
Brown and Sharpe gauge (abbreviated to B. & S.W.G.).

The following are the names in alphabetical order and addresses
of five London tool merchants that issue illustrated catalogues.
Some of these catalogues are large, expensive volumes to produce
and 5re only supplied to customers such as colleges and engineering
firms, likely to make considerable purchases, but most of the firms
publish abridged catalogues of mechanics' and carpenters' tools.
Many firms, as already stated, are prepared to give substantial
discounts to schools and science workers.

George Adams, 290, High Holborn, W.C.I.
Buck and Hickman Ltd., 2, Whitechapel Road, E.I.
Buck and Ryan, 310-312, Euston Road, London, N.W.I.
R. Melhuish, Ltd., Fetter Lane, Holborn Circus, London, E.C.
S. Tyzack and Son, Ltd., 341, Old Street, Shoreditch, E.C.I.
Some manufacturers will, on request, supply tools direct to
customers.

CHAPTER III
MATERIALS

MUCH time and trouble can be saved by providing the workshop
with a small store of suitable materials; it is annoying to be held
up in the middle of a piece of work for want of a length of metal of
suitable size or for a screw or nut of the correct dimensions and
pitch of thread.

It is well to have scrap boxes where oddments of all descriptions
can be stored. A good scrap box can be a great aid to the designer
and will sometimes save the making of complicated parts. Skilful
use of the hack-saw, file and drill will often change apparent
rubbish into something quite new and useful.

Electrical contractors and garages frequently have oddments
that they are willing to give away or part with for a few pence; for
those who live in London, the hawkers' stalls in Farringdon Street
and the Caledonian Market, devoted to scrap metal and old
instruments, are not, on occasions, to be despised, though they do
not always repay a visit. >

A scrap box need not be a jumble. Most things can be sorted
and arranged methodically. Scrap ebonite in one box, old
terminals in another and so on.

In addition to the utilization of old material, a stock of new
material should be kept available. The more remote a workshop
is from the source of supplies the better should be its store. The
metal merchants' lists present a great range of metals in different
sizes and shapes.

The metals most commonly used in the construction of
apparatus are brass, steel, copper and aluminium; these can be
obtained in the form of sheet, rod and tube.

Some knowledge of the different forms and qualities of material,
and of the measurements used in commerce is, of value to anyone
engaged in a workshop.

SHEET METAL

1. Brass.

Brass sheet is sold by weight. The average retail* price in
England is about 1 /- a pound; but it varies slightly with the

30 THE LABORATORY WORKSHOP

fluctuations of the metal market. The quality of sheet brass
usually required in a workshop is that known as 'Hard Rolled
Brass'. In the thin sizes this is very easy to bend and does so
without cracking. From large metal-traders it is possible to
obtain other qualities, spring hard, half hard and soft. A small,
but sometimes useful supply of spring hard brass can be obtained
from the contacts of old flash lamp batteries. Sheet brass is
manufactured with a smooth matt, or with a polished finish, the
latter is known in the trade as planished brass. When ordering
brass it is necessary to specify the area of the sheet required. The
stock size of a sheet is 4' x 6'. If a whole sheet be not wanted
the merchant will always cut off the amount required. The
thickness of brass is usually defined, not by actual measurements
in inches, but by a gauge number. In England the Imperial
Standard Wire Gauge is employed (Item 116 tool list).
Useful gauges are as follows :

Gauge No. S.W.G. thickness ins. app.
Sheet Brass 20 -036

24 -022

Sheet brass in the lighter gauges, can be bought in coils of width
J" to 1'. This is a very convenient way of purchasing it.
Recommended gauges in 1' widths are :

Gauge No. S.W.G. thickness ins. app.
Sheet Brass rolled in coils 20 -036

22 -028

24 -022

26 -018

30 . 0124

A complete coil weights 28lbs., but any smaller amount can be
bought. If a large flat piece of brass be required it is better to
buy it as an uncoiled sheet and avoid the trouble of having to
remove the curvature.

2. Sheet copper.

The method of gauging and selling copper is similar to that for
'brass. Copper sheet can be obtained coated with a thin layer of
tin on one side. This is useful when a copper vessel has to be
made for domestic purposes, but it has no special advantages for
apparatus construction apart from increased ease in soldering.

Recommended gauge of sheet copper:
No.eO S.W.G. Approx. thickness -036"

The price of copper is about the same as that of brass. A sheet

MATERIALS 31

of brass has greater rigidity than a sheet of copper of equal thick-
ness.

3. Sheet steel.

A useful quality is that known as black, mild steel, sheets
No. ,16 S.W.G. Approx. fa" thick. A standard sheet measures
6' x 24". A piece measuring 6' x 6" is more convenient for cutting
up with hand tools than a big one.

4. Tin plate.

This is the material used in the manufacture of cigarette tins,
petrol tins and such like. It is thin sheet steel that has been
dipped in molten tin to give it a protective coating. It is not
sold by gauge numbers; the thickness of tin plate is usually
denoted by one or more crosses - one cross - two cross and so on.

Useful thicknesses are two cross and three cross. One cross is
very thin, so thin that it can be cut with a pair of strong domestic
scissors.

Professional tinsmiths use five cross for first class work, but
this is rather thick and difficult to cut and bend without special
equipment.

Ix has a thickness of approximately -0148"
2x -0164"

3x -018"

4x -920"

Tin plate is sold wholesale in wooden boxes holding eithe? 100
thin sheets or 56 when the thickness is* greater than three cross.
Such large quantities are seldom required in the laboratory work-
shop. Stock sizes arc 20" x 14", 25" x 17" and 28" x 20".

A single sheet of three cross measuring 28" x 20" costs retail
about 1 /3. Most ironmongers keep tin plate for it is largely used
in the making and repair of tin kettles and cans.

5. Sheet zinc.

Sheet zinc is very easily bent and soldered and is largely used
in the building trade. The manufacturers of sheet zinc use a
special gauge not the Imperial Wire Gauge, so it is wise when
ordering it to specify the approximate thickness required by*
stating the latter in decimals of an inch. An advance in the zinc
gauge number indicates a thicker sheet, this is the reverse of the
S.W.G. numbers, thus -

No. 8 Zinc Gauge corresponds to an approx. thickness of -015"
No. 10 * -020"

No. 12 ,. -026"

32 THE LABORATORY WORKSHOP

Zinc is usually stocked by merchants in rolls measuring 8' x 3',
but small portions can always be bought.

A generally useful gauge is No. 13, Zinc Gauge. This has a
thickness of about -029" so corresponds approximately to No. 22
S.W.G. (-028*).

An advantage of zinc over tin plate is that, apart from superficial
surface oxidation, it does not rust.

6. Sheet aluminium.

The thickness is specified by the use of S.W.G. gauge numbers
or in decimals of an inch. Aluminium is very easily cut with a
metal piercing saw, hack-saw or snips and is particularly useful in
the construction of optical apparatus. It cannot be soldered by
ordinary processes, but is readily joined together by the use of
rivets or small nuts and bolts. It can be purchased in flat sheets.
The stock dimensions of a full sheet are 6' x 3'. Aluminium sheet
is kept by nearly every garage and car-body building shop.

A useful gauge is No. 19, S.W.G. with a thickness of 040" or
No. 18, S.W.G. with a thickness of -048." A square foot in
either of these thicknesses costs about 3 /-. Aluminium sheet of the
above thickness has the advantage of rigidity, with lightness and
ease of working.

METAL IN ROD FORM

7. Brass rod.

Brass can be purchased in rod of circular cross section ranging
from -fa" up to 2J diameter.

Useful sizes are \" diam. Approx. cost per foot Id.

3 " 0/7

99 99 99 10 99 99 99 99 *tUi*

in nJ

99 99 99 99 99 OC*.

99 99 99 & 99 99 99 * 99 Oft.

When a quantity of brass rod is being ordered it is best to obtain
it in lengths of 6|' ; longer lengths are liable to get distorted during
transport. Brass in small diameters can be obtained in the form
of wire. This is usually in coils and not suitable when straight
lengths of more than a few inches are required. It is very useful
for making clamping screws. (See Sees. 85 and 102). Suitable
sizes are |* and &" diameter wire.

8. Copper rod and wire.

Copper rod is seldom required, it is best to use brass; on the
other hand a supply of copper wire known as soft copper wire in

MATERIALS 33

gauges No. 18 and 22, S.W.G. should be available. Soft copper
wire, unlike hard copper wire, is readily twisted without breaking.
It is useful for binding rubber tube connections to prevent them
leaking or slipping off.

9. .Steel rod.

Black Mild-Steel Rod. In circular cross section this form of
rod is very cheap and in such constant use that a good supply
should be kept. It can be bought in any length up to 18'. Six
foot lengths are best for store purposes. The following diameters
are those most likely to be required.

1 " .3 " 1 " 3 " I "
8 1<> ? 4 8> '2 *

10. Bright drawn mild steel rod.

Black mild steel rod has a dull, rather rough finish. Mild steel
can be obtained in another form known as bright mild steel rod.
This has a smooth surface, the diameter is very uniform, having
been drawn through dies, and such rod can be used for making
axles and other parts requiring an accurate fit. It can well be
kept in the sizes given for black mild steel rod.

11. Cast steel -4555% carbon.

It is not easy to cut a perfect screw thread on mild steel. The
material is fibrous and tends to tear; a better material to use for
the purpose is a quality of steel known in the ti*ade as cast steel
45 -55% carbon. It costs very little more than mild steei and
can be toughened, if necessary, by making it red hot, then plunging
into cold water.

12. Silver steel rod.

If a very strong and accurate steel axle be required a length of
round, silver steel should be obtained. It is sold in standard
lengths 13" long. Silver steel does not contain any silver; the
word silver simply denotes a particular quality of steel. Since
silver steel is very hard special care has to be taken when cutting a
screw thread on it (see Sec. 93). Silver steel has approximately
1% carbon and can be made into tools and be hardened or
tempered.

13. Meccano axle rod.

Ordinary Meccano axle rod made of steel is very useful. It has
a diameter of approx. $%" and can be obtained in good straight
lengths of ll". It is soft enough to enable a screw thread to be
cut on it without difficulty.

Dw

34 THE LABORATORY WORKSHOP

14. Spokes.

Steel bicycle spokes are approximately No/ 15, S.W.G. They
are straight and strong. The diameter corresponding to No. 15,
S.W.G. is -073". On a spoke of this diameter it is possible to cut
a No. 9 British Association screw thread.

Umbrella spokes, being of U section, are light and very strong
for their size.

15. Wrought iron rod.

Wrought iron is expensive and is seldom used except by ship-
building and railway works for high class forging.

Many country ironmongers stock so-called wrought iron for
sale to farmers and blacksmiths. This is usually a poor grade of
small carbon content steel, it can be used instead of black mild
steel, but the latter is to be preferred.

16. Metal in flat and square sections.

Lengths of metal with a rectangular section are known as flat
rods or sometimes in the thin sizes as strip.

Brass, copper, black and bright mild steel and cast steel can be
obtained in this form.

Some useful sections in brass and black mild steel are as follows:

FLAT BRASS ROD FLAT BLACK MILD STEEL

Thickness Breadth ^eperfool Thickness Breadth

A" x \" 3d. t V' x This is sold by

k" x I" 3d. |" x Y weight. Theap-

1" <

Flat copper rod is seldom required. As a general rule brass is to
be preferred.

For the connecting strips of potentiometers and Wheatstone
bridges copper has a slight advantage. It can be obtained from
large metal dealers in all the sizes given for brass.

17. Square, black and bright mild steel and brass rod.

Square section black and bright mild steel can be bought, but
are seldom required, on the other hand square section brass has
many uses in a laboratory workshop.

The following are suitable sizes to keep in stock.

Square brass rod " x J": f * x f *; tf x fr f " x f ".

MATERIALS 35

18. Metal tubes.

Brass, copper and aluminium tubes are readily obtainable in
different diameters and thicknesses. What is known as solid
drawn tube is manufactured without a join. Brass telescope
tubing is so made that the interior is very smooth; it can be
obtained in different sizes so that one tube will slide into the other
with an easy fit. Broadhurst Clarkson, Telescope Makers, of
63, Farringdon Road, London, E.C.I, often have scrap lengths of
telescope tubing for disposal.

The outside diameter is the measurement taken when specifying
brass, copper or aluminium tubes. A complete specification in-
volves an approximate thickness measurement.

If brass tubing be not available so called brass curtain tubing
will sometimes serve in its place. This is steel tube covered with
a thin layer of sheet brass. It is unsatisfactory for screw thread-
ing; the screw cutting tool cuts through and peels off the thin
coating of brass; a poor untidy thread is the result. Brass curtain
tubing is very cheap, it can be obtained in different diameters and
it is usually possible to find a size with an internal diameter that
will just allow a J" diam. rod to slip into it.

19. Solid drawn brass tubing.

Solid drawn brass tubing with an external dimeter of f " and
walls about ^" thick is very useful for making apparatus utilizing
gas fittings (see Sees. 114 and 115). ,

The radiator tubes of motor cars are made of copper, this tubing
is stocked by most garages.

20. Iron pipes.

Occasionally iron pipes are useful in the arrangement of aquaria
and other equipment requiring water. When ordering iron pipes
it is well to bear in mind that the diameter used for measurement
is the internal diameter and not the external as in the case of brass
or copper pipes or tubes.

A half inch iron pipe has an internal diameter of |". The
external diameter may be as much as f ".

21. Special sections, angle and channel.

Metal rods having one of the cross sections illustrated (Figs. 21
to 24), are cheap and extremely useful, especially in the following
sizes and materials.

36

THE LABORATORY WORKSHOP

Fig. 22. Angle steel or iron

Fig. 23 Channel brass

USEFUL SECTIONS, ACTUAL SIZE

Angle-brass *"x fa", \" x fa", i"x &" thick (Fig. 21). The '*
and |" refer to the outside measurements
Angle-steel orjiron f "

K I" thick (Fig. 22).
thick, i"x I", V thick (Fig. 23).
Channel brass I" x -J", ' 3 1 2 " thick will just hold a bound lantern
slide and for this reason is of value in the construction of optical
lanterns.

22. Square tube.

Square tube made of brass (Fig. 24) is occasionally called for, it
is worth keeping a small supply in hand measuring I" x i" and
approximately -fa" thick.

23. Screws for metal.

Up to the year 1841 manufacturers of machinery used screws of
a size and shape of their own designing, and many different types
were in use making the interchange and replacement of parts
very difficult. In this year Sir Joseph Whitworth, a well-known
engineer, introduced a screw thread, now known as the Whit-
worth thread that has been generally adopted and is the thread
commonly found on the majority of nuts and bolts about a motor
car and other heavy machinery.

MATERIALS

37

The shape of the thread is shown (Fig. 25), also the meaning of
the dimensions, pitch and depth as applied to a screw thread.
Simple mathematical relationships connect the pitch, depth and
radius of the curved portions. In this way the exact form of the
thread is clearly defined for a whole series of screws of different
diameters. The angle 55 and the relationships between pitch,
depth and radius remain constant, although the diameter may
change. The diameter of a screw is the measurement shown (Fig.
26). It is measured from the top, not the bottom of the thread.
A thread cut on a bolt or rod is sometimes known as a male thread
and that inside a nut, plate or other fitting as a female thread.

The Whitworth thread was primarily designed for diameters
not less than y. The form of the thread is such that if made on

Pitch P

Fig. 25.
A Whitworth thread

Pitch P

Fig 27.
A British Association thread

a rod of a less diameter than J" an undue depth oftcut is taken with
consequent weakening of the rod, however, for screws not sijbject
to much stress those with \" and ^ " diameter Whitworth threads
are quite serviceable.

The majority of instruments require many small screws for their
construction and for* these another thread called the British
Association (B.A.), is commonly used.

The form is shown (Fig. 27). It will be noted that the angle
differs from the Whitworth thread (47| and not 55); the rela-
tionships between pitch, depth and radius also differ from those
used in the Whitworth thread.

If the thread on a Whitworth screw be compared with the
thread on a B.A. screw of approximately the same diameter it
will be found that the number of threads, or little ridges, per inch
on the Whitworth screw is less than those on the B.A. screw,
although the depth of thread of the Whitworth screw is greater
than the depth of the B.A. one.

The B.A. screw depends for its security and makes up for its
lack of depth by a greater number of threads in a given length
compared with a Whitworth screw of equal diameter.

38 THE LABORATORY WORKSHOP

A Whit worth screw of ^" diameter has 24 threads per inch,
a B.A. screw of approximately equal diameter has 28|.

Battery terminals, the little screws inside electric switches, in
fact in most small electrical apparatus have B.A. threads.

Whitworth (Whit.) threads are defined by the diameter. The
sizes most used in a laboratory workshop are:

I" 3 " I" 3" am l 1"
8 > 10 9 4 9 g clUU o .

British Association (B.A.) threads are defined by numbers.
Those most likely to be used are:

No. 0, 1, 2, 3, 4, 5

Diam. -236" 209" 185" -161" -142" -126"

A Whitworth nut cannot be fitted to a B.A. terminal or bolt with
satisfactory results, although the diameter may be nearly the same.
A B.A. nut must be used with a B.A. bolt and a Whit, nut with a
Whit. bolt.

Many other threads, apart from Whit, and B.A., are used in
the watch, lens, cycle and other specialised industries, but Whit,
and B.A. arc sufficient for most laboratory workshop require-
ments.

Special threads are used for gas fittings and iron water pipes.
These are dealt with in the sections describing screw cutting
(Sees. 114 and 123).

Nuts, screws sxid bolts both Whitworth and B.A. can be pur-
chased in great variety.

B.A. nuts, screws and bdlts are usually made of brass or steel and
Whit, in steel, iron or less commonly brass. The names given to
the different shaped heads are indicated in Fig. 28.

When ordering screws for metal it is necessary to specify five
things. The thread (B.A. or Whit.), the nature of the head, the
material, the gauge number or the diameter and the length. The
length of a cheesehead, button head or hexagon head screw for
metal is the measurement from just below the head to the end of
the threaded part (Fig. 29), but with countersunk head screws the
length is overall.

Sometimes a screw is threaded for its whole length and some-
times for part of its length only (Fig. 29).

A screw, especially in the larger sizes is often referred to as a bolt.

An ordinary Whitworth bolt with hexagon head is shown in
Fig. 30.

A bolt threaded down its whole length is known as a set screw
(Fig. 31)?

On motor cars, nuts, bolts and set screws are used made of steel.

MATERIALS

39

wsaSBfflaaaM cSM!B!i!laiin tilisiuwaall UTOMUTO^ i

Cheesehead G?unt<rsun Button Hexagon^ Fig, 28. Screws for metal
head head heacl

Fig. 29. Screws for metal threaded for part of their
length only

length

toQi Fig. 30. A Whitworth bolt with hexagon head

Hexagon

Fig. 31. A set screw. The thread extends the whole
length of the stem

I** IJ Fig. 32. Two types of forged or pressed nuts

Square

Wm^Nut

Turned Brass
Terminal Nut

Fig. 33.

Spring washer Spring washer A washer of the
Double Coil Single coil ordinary type

Fig. 34.

Carriage bolt
I 'Whit

prill a hole in the
wood equal to the
, diameter of the
Stem of the bolt

Square portion form* a
drive in fit wJ-en th bolt
It hammered into petition

Fig. 35.

These are manufactured with beautiful precision by the use of
special lathes, they have a bright surface and well-cut threads.
They are known as bright steel nuts, bolts or set screws and are
of the best quality.

For cheap work, that does not call for such precision and
strength, it is possible to buy Whit, nuts and bolts forged from
red-hot or pressed from cold steel.

These have a dull black finish and are the nuts and bolts usually
stocked by ironmongers. Two types of forged and pressed nuts
can be obtained, square and hexagon (Fig. 32).

Two types of nuts that are sometimes uspful are wing nuts in
iron or brass and turned brass terminal nuts (Fig. 33).

Usually a nut requires a washer under it. Washers are made in
black steel, bright steel and brass. Pressed or forged Whit, nuts
are usually fitted with black steel washers and bright steel Whit,
nuts with bright steel washers of appropriate size. A washer size
is specified by the diameter of its hole.

40

THE LABORATORY WORKSHOP

When nuts are subject to vibration and must on no account get
loose it is usual to fit them with steel spring washers (Fig. 34).

The washers used with B.A. nuts are made of bright steel or
brass and can be obtained in very small sizes.

When fitting a wooden framework together, it is a help to use
black steel carriage bolts. These have a square portion under the
head and when tapped into a hole of appropriate size in woodwork

length

Length

Fig. 37. How the length of a
wood screw is measured

00 3 4 5 6 8 12

Fig 38. Usual sizes of wood screws

Fig. 39. Types of rivets

Panel pir

Oval Steel

T, ^ Brad

French orWire

il

Fig. 40. Types of nails

will Rot rotate when the nut is tightened (Fig. 35). They are
stocked by all ironmongers*,

24. Screws for wood.

Screws for wood are made in iron and brrfss. Brass screws are
more expensive and not as strong as iron ones, but have the ad-
vantage of not rusting. The heads of screws may be round or
countersunk; a type of screw known as a raised head screw has
recently come into considerable use for motor body fittings and has
a particularly neat appearance (Fig. 36).

The diameter of a wood screw is specified, not in inches but by
a gauge number ranging from 0000 or 4 /O in the very small size
then 3 /O, 2 /O, 0, 1, 2, C 3, 4 up to 40 (Fig. 38).

To define a screw completely it is necessary to state material,
type of head, gauge number and length. A No. 14 screw, has a
diameter of about ", it may have a length of 1", 1 J", 1|", 2", 2J",
2j", or 3", the diameter is constant no matter what the length.

The saftie note with regard to length and diameter applies to
screws of other gauge numbers and diameters. Screws can be

MATERIALS 41

purchased in the small gauge numbers ranging from |" long, then
in the following steps:

3 " 1 " 5 " 3 " 7 " 1 " 5 " 3 " 7" 1 "

10 4 > 1% S > Tfr > 2 8 5 > 8 j

The lengttfof a countersunk screw is the over-all measurement.
The length of a round head screw is measured from the underside of
the head to the point (Fig. 37). Some useful sizes arc as follows:

Iron countersunk head Brass countersunk head

wood screws. wood screws

Length Length

No. 00 i" No G |" No 00 \" No 5 \"

No 3 f" No 8 1", I", 1", No 3 f" No. 6 f"

No 4 \" \\" , If" No 4 |" No. 8 f", 1"

No 5 I" No. 12 2"

As a time-saving guide it is convenient to mount labelled speci-
mens of each of these screws on a board and to hang it up in the
workshop with a note below each screw of the correct drills to use
with it.

The cheapest way of buying screws is in gross packets. They
can also be bought at ironmongers by the dozen. Brass screws
cost about twice as much as iron ones of the same type, gauge and
length.

25. Rivets. ,

Rivets in iron, aluminium or copper may be either bifurcated,
round or snap head, flat head, countersunk head or hose rivets
(Fig. 39). Useful sizes are as follows.

Iron, roynd head rivets \" ', \" , ^" I"
Iron, flat head .. J" > \"

Rivets are usually sold by weight.

26. Nails.

Nails are seldom required in the construction of apparatus, it is
best to use screws, but occasionally they arc wanted, and a few
pounds' weight of different kinds should be kept in stock.

Nails are manufactured in many different lengths and shapes.

The three types shown (Fig. 40) should find a place in the
workshop store.

French or Wire Nails can be used for fastening together packing
cases and other rough work.

The special shape of Oval Steel Brads enable them tobe ham-
mered into a piece of wood with little fear of splitting it; they are

42 THE LABORATORY WORKSHOP

very inconspicuous. Panel pins, used for fine work, are of very
slight construction. *

Wire nails are made in sizes ranging from I"-7" 9 oval steel brads
from y~% and panel pins from \" to 2".

Useful sizes are:

Wire nails, length, 1", 1 *", 2", 2|" Oval steel brads, |". 1", 1$"
Panel pins, f", H"

27. Solder.

The solder required for use with an ordinary soldering iron is the
grade known as tinman's solder. It is sold by weight in cast sticks
about 1' long.

28. Soldering flux.

This can be made from concentrated hydrochloric acid and
scrap zinc (see Sec. 125).

A very good ready-made ilux is 'Baker's Preparation'; this is a
fluid and is sold in tins and stoneware bottles. Fluxite, a paste, is
supplied in tins of the boot polish type.

29. Combined solder and flux.

'BritinoP paste made by Bi-Metals, St. Mary's Works, Eldon Road,
Wood Green, London, N.22, is a combination of both solder and
flux. It is sold vi tins. When not in use it should be kept with
the li*l on and before use should be stirred to incorporate any liquid
flux that may have floated to the top.

30. Carborundum grinding paste.

A convenient form is a duplex tin. One Half of the tin contains
coarse paste and the other half compartment fine paste.

31. Carborundum powder.

This is manufactured in many degrees of disintegration. The
grade known as 100 is the kind required for general use.

32. Vaseline.

This is best bought in pots. The empty pots are useful for
holding small screws.

33. Turpentine.

Obtain this from a reliable paint and colour merchant. Some
of the cheap brands of turpentine are adulterated and leave much
to be desired. When visiting a paint merchant to buy turpentine

MATERIALS 43

go provided with a clean, dry, corked bottle and buy from his
bulk supply.

34. Methylated spirit.

In countries where the tax on methylated spirit makes its use
prohibitive and a Primus blow lamp or stove has to be lit, a fairly
satisfactory substitute is a mixture of 1 part of paraffin (kerosene)
and 1 part of petrol. This of course is not smokeless, but is better
and safer than either of the liquids used alone.

35. Plaster of Paris.

This can be bought from a builder, monumental sculptor or at a
druggist's. It must be kept dry and is best stored in an air-tight
jar.

36. Glass or sand paper.

This is paper treated with glue and sprinkled with powdered
glass, sand is less frequently used in these days. It should be
stored in a dry place or the glue softens and the glass comes off.
If necessary dry it before use. The grade is defined by numbers,
is used for very fine work and 2 for rough work.

Useful grades are No. 1, 1 , fine 2 and double 2.

37. Emery cloth.

This is more durable, but more experisive than glass paper. It
will tear into strips in one or two directions only. Glass paper is
usually used for rubbing down wood and emery cloth for removing
rust and polishing metal. Useful grades are: FF, F and li. FF
has a finer texture than 1 J. Both glass paper and emery cloth can
be bought in single sheets measuring 12" x 10". It is cheaper to
buy it by the dozen sheets or by the quire.

38. Scrap celluloid.

This is used for making celluloid varnish and cement. Old
celluloid set squares can be utilised, if these are not available
celluloid can be purchased from a garage where they do repairs to
motor car hoods and side curtains.

39. Amyl acetate.

This is used as a solvent for celluloid. It can be purchased from
most drug stores and from all chemical dealers.

44 THE LABORATORY WORKSHOP

40. Shellac.

Shellac dissolved in methylated spirit mikes an admirable
varnish for wood or for application to insulated wires to act as an
insulating and binding medium.

Paint shops keep shellac in dry flake form or already dissolved in
spirit.

The solution can be kept in a bottle. It is best to stopper the
bottle with a plug of wood; if a cork be used it is very liable to get
stuck into the opening by the shellac and breaks when an attempt
is made to pull it out.

41. Portland cement.

This can be bought from a builder's merchant. It should be
stored in a dry place.

42. Scrap lead.

This can be got from a builder or plumber.

43. Mica.

Small sheets of mica can be obtained from ironmongers who
stock anthracite and oil stoves. It is used for the repair of the
inspection windows of such stoves.

N.B. Often in commerce wrongly called talc.

44. Rustless steef.

Rustless steel sheet with a polished mirror finish can be bought
in large sheets. In thin 'sizes it can be cut with snips, centre
punched and soldered with the same ease as tin plate. It is much
harder and more difficult to drill than tin njate. Ordinary twist
drills can be used, although if much drilling has to be done, it is
best to use specially hardened drills.

A useful thickness is -024" (No. 23, S.W.G.). The makers of
rustless steel are Thomas Firth & Co., Sheffield.

45. Thin sheet pewter.

This substance is soft and pliable and useful in the construction
of scenic models.

It can be bought" in sheets of various thickness from most
dealers in art workers' supplies.

The average price is 2 /- for a sheet measuring 21" x 15 "%

46. Vulcanised fibre.

Vulcanised fibre, a red coloured substance, a good insulator and
tougher than ebonite, can be bought in sheet, rod and tube form.

MATERIALS 45

It is easily cut with a hack-saw, filed and drilled. A sheet measur-
ing \" x 6" x 6" costs about 1 /6, and a tube of external diameter
|" and internal diameter |" is sold at l|d. an inch. It is stocked by
most garages.

47. Investigation of new materials.

One of the interesting features of a workshop is the possibility of
studying the properties and possible uses of new materials.

To take one example only: the number of advertised glues and
household cements can be counted by the score, a few carefully
controlled tests in laboratory and workshop will soon show that
only a few satisfy the extravagant claims made for them by the
manufacturers.

In recent years many new materials for building engineering and
manufacturing have been developed; a science worker, with an
interest in practical work, can often benefit by a visit to such
exhibitions as The British Industries Fair, London and Birming-
ham sections, the 'Model Engineer' Exhibition, the Machinery,
Building, Shipping and other exhibitions held from time to time.

48. The use of oddments for scientific purposes.

A visit to a 6d. store, a marine dealer's store, a cycle accessory or
ironmonger's shop can be associated with a new interest if one eye
be kept open for the possible use of oddments. *

Glass plates sold for table mats make very good plate glass,* sides
for optical tanks. Curtain stretchers J of the spring type make
potentiometers and flexible steel belts for driving pulleys. Cake
tins can be turned into lantern chimneys and tart tins into a
stethoscope.

49. The workshop store room.

The following is a list of material suitable for a workshop store.

No. reqd. DESCRIPTION Approx. Price

s. d.

1 gross Steel Washers, std. size \" . . . . . . 18

1 fc" 13

1 I" 14

1 I" ..' 1 10

3 dozen ,, \" 10

4 Bolts and Nuts, Whit, steel, Hex. head, ft " x 1" . . 40
4 i"x2" .. .. 50

1 i*x3* 20

1 gross Steel Nuts (Whit worth) " 26

1 JL-" > 2 7

* > > igr *

i r 29

46

THE LABORATORY WORKSHOP

No. reqd.

DESCRIPTION

Approx. Price

f

s. d.

3 dozen

Steel nuts (Wliitworth) J"

18

3

,, ,, ,, "2 . . .

20

1,6' length

Brass Tube int. diam. \"

16

1,0'

V

20

1,0'

V

20

2, 6' lengths

Angle Brass, I" x\" x ^"

80

2, 6'

l"xl"x 3 V

90

ilb. coil

Spring Steel Wire S.W.G., No. 22

16

1 tin

Carborundum Grinding Paste

18

2lb.

Tinman* s Solder

30

1 jar

Baker's Soldering fluid

30

1 Ib.

Glue, Crolid

10

3

Nails Wire, 1"

16

3

,, ,, 1 \"

20

4 *

2"

26

1 ,,

Brads, Oval Steel, y

10

* ,

r

10

6, 0' lengths

Brass Rod, round y diam.

16

0,0

,, ,, -j 3 6 "

36

0,0'

n I"

66

2,6'

,, ,, 1"

60

o, o 7 ,,

Cast Steel -4555% Carbon or Bright Mild

Steel

Rod, y

30

0,0'

Cast Steel -4555% Carbon or Bright Mild

Steel

Rod, -&in.

30

0,0'

Cast Steel -4555% Carbon or Bright Mild

Steel

Rod, y

40

0,0'

CastSteel -45-55% Carbon or Bright Mild

Steel

Rod, I"

46

3,0'*,,

Cast Steel -4555% Carbon or Bright Mild

Steel

Rod, y *

40

0,0'

Flat Black Mild Steel, y x y

60

o, o 7

,, ,> i"xf"

90

o, o'

,, J, 5, 5, A X ^ . . .

90

3, 0' ,,

Black Mild Steel Rod, y diam

3, 6'

r

3, 6'

, ,, J> 2

4,0'

Flat Brass ^ x y

50

4, 6'

,, ,, y x y

60

4,6'

,, 8 X ,f .. .. .. ..

70

, o' ,,

Square Brass, y x J" . .

70

,3'

J"xt"

50

Sheet Brass, 4' x 3', No. 20 Gauge

80

Sheet Copper, 4' x 3', ,, ,,

80

dozen

Tin Plate*, 1 cross, 28" x 20*

60

1 ,

2 cross, 28" x 20"

60

1 gross

Button headed metal screws, y diam. x y

Whit- .

worth

36

1

Button headed metal screws, ^ * diam. x 1"

Whit-

worth

86

1 ^ Nettlefold's pressed bolts and nuts, y diam. x *

(Round head)

23

MATERIALS

47

No. reqd.
1 gross

1

1

1

1

1

1

1

12 sheets
12
12

2 tins
1 Ib.

1

1
4 ,,
4

2 tins

DESCRIPTION Approx.

NettlefokTs pressed bolts and nuts, ^" diam. xl"
(Round head) ..........

Screws, Brass, Countersunk, i", No. 10 . . . .

1", No. 8 .. ..

Round head, f, No. 8 . . . .

,, Iron, Countersunk, ", No. 10 . . . .

,, 1", No. 8 .. ..

, l"No. 7 ., ..

2% No. 7 .. ..

Glass Paper, Fine . . . . . . . . . .

,, Medium ..........

Coarse ..........

Oil, 3 in One (3oz.) ..........

Copper Wire, Soft, S.W.G., No. 18 . . . .

No. 20 ......

Robbialac Black Cycle Enamel ......

Aluminium Paint . , . . . . . . . .

Robbialac Enamel Brushes . . . . . . . .

Roscoe Cylinder Black, No. 1 Sue. (See Sec. 202
Chapter IX) ...........

Price
s. d.

26
20
2 10
26

18
20
20
20
20
18
20
20
20
40
40

50. Meccano Parts.

The following parts are particularly useful in the construction of apparatus.
(Fig. 41.)
No. reqd.

DESCRIPTION

2 dozen Axle Rods, 11J*. .

6 only Gear Wheels, No. 27 ..

6 ,, No. 27a ..

6 . No. 27b . .

2 ,, No. 31 ..

2 ,, Worms, No. 32

4 ,, Flanged Wheel, No. 20

2 ,, Cone Pulley, No. 123 ..
4 ,, Pulley Wheel, No. 22 ..
1 ,, Contrate Wheel, No. 28
1 ,, No. 29

1 ,, Bevel Gear, No. 30
1 No. 30a

1 ,, No. 30c ..

1 ,, Pulley Wheel, No. 21 . .
1 ,, No. 20a

3 dozen Collars with set screws, No.

4 only Face Plate, No. 109

1 Fly Wheel, No. 132
6 Couplings, No. 63

3 dozen Angle Girders, 9J*, No. 8a

2 ,, 3i",No. 9b

50

Approx. Price
A. d.
24
26
26
60
20
10

18

26

10

9

6

9

6

16

4 6

1 4

1 8

2 6
6 6
1 4

48

THE LABORATORY WORKSHOP

Axle Rod

Gear Wheel Contrate Wheel

Cone pulley Coupling- Angle girder

Pulley Wheel Worm.

Collar with
set screw

Bevel Gear

Face plate FlywJieel Pulley Wheel

Fig 41. Meccano parts. Jly courtesy of Meccano Ltd.

51. Miscellaneous stores.

Miscellaneous stores should include, boiled linseed oil, turpen-
tine, methylatecVspirit, vaseline, red lead oxide, scrap lead, shellac,
whhVning, string, insulating tape, needles, thread and office paste.

52. Dealers in workshop supplies.

The tool dealers mentioned at the end of Chapter II supply
materials. It is usually cheaper to buy 'metal in fairly large
quantities than in small lengths or sheets.

Smith & Sons, Ltd., 50, St. John's Square, Clerkenwell, London,
E.C.I, are well known to the scientific instrument trade and keep
supplies of brass, copper and aluminium in every form manufac-
tured.

Steel of every description can be obtained from Walker Steel
Works Ltd., Mary Street, Sheffield.

The following firms issue useful catalogues or price lists, for
which a charge of a few pence is usually made:

George Adams, 290, High Holborn, London, W.C.I; Bond's Ltd.,
254, Euston Road, London, N.W.I; A. J. Culham, 21, Strathmore
Gardens, Romford, Essex; Economic Electric Co., 64, London
Road, Twickenham, Middlesex; Grafton Electric Company, 54,
Grafton Street, Tottenham Court Road, London, W.I; G. Kennion

MATERIALS 49

& Co., 30, Kingsland Road, London, E.2; Wren Tool Co., 49a, York
Road, Ilford, Essex.

Handicrafts Ltd., Weedington Road, Kentish Town, London,
N.W.5, issue a 1 / catalogue every year called 'Handicrafts
Annual.' It gives the prices and particulars of many useful wood-
working materials, such as ply wood, strip wood and dowel rod.

Good second-hand lenses and prisms, including optically worked
prisms, achromatic combinations and condensers can be obtained
from Broadhurst Clarkson & Co., 63, Farringdon Road, London,
E.C.I; also The Miscellaneous Trading Co., Ltd., 13, New Oxford
Street, London, W.C.I.

Wray (Optical Works), Ltd., Ashgrove Road, Rromley Hill,
Kent, manufacture lenses and prisms of all descriptions and some-
times have surplus material that can be purchased at a reduced
rate.

Meccano parts can be bought at most toy shops or from Meccano
Ltd., Old Swan, Liverpool.

Other addresses can be obtained from the advertisement pages
of the Model Engineer and English Mechanics.

It is useful to investigate the possibility of local supplies.
Many ironmongers and jobbing engineers keep a supply of brass,
copper, iron and steel.

CHAPTER IV

HOW TO MARK OUT, CUT, FILE, DRILL AND BEND
SHEET METAL, ROD, STRIP AND TUBE

63. How to use metal working tools.

THE art of learning to use tools can be gained in various ways.
Some people favour the method of setting students to copy a
number of formal exercises before allowing them to construct any
definite article. This method is liable to be very slow and dull.

In the experience of the writers it is much better to give even
beginners some piece of apparatus to construct and let them learn
the use of the different tools as the need for them arises.

The making of quite a simple piece of apparatus will call for the

O O O

Fig. 43.
Strips of metal cut and drilled by a professional and amateur respectively

use of a surprising number of tools and processes and students
rapidly acquire skill as the work proceeds.

The materials used in apparatus construction are not expensive
and if mistakes are made it is easy to start again after the error of
construction has been pointed out.

The chief difference between the work of an amateur and a pro-
fessional is a matter of degree of accuracy and general finish.

If a professional scientific instrument maker has to construct a
strip of metal with four holes drilled in it his finished work may
look like fig. 42. The edges of the strip will be at right angles to
one another and the holes symmetrically spaced. The work of an
amateur may resemble fig. 43, where the edges are not at right
angles, and the holes have been drilled at random.

If the beginner will take the trouble to measure carefully and
mark out all his work and keep the idea of accuracy ever to the
front of his mind it is possible, with a little initial guidance, to
produce excellent work almost from the start.

At many of the Board of Education summer courses surprisingly

50

TO MARK OUT, CUT, FILE, DRILL AND BEND 51

good work has often been done after a few days' training by men
and women with no previous experience of the use of tools.

The writers' method of instruction to a new group of students is
to gather them together for an initial talk and demonstration of
the use of different tools and after that allow them to start work
and come for additional guidance when they feel in doubt. The
instructor can with advantage move about the workshop and
point out errors or better methods of procedure.

It is suggested that this and other chapters should be studied by
the reader, and a general idea of their contents obtained. This
done the construction of some piece of apparatus should be com-
menced and the chapters used for reference purposes when
difficulties arise. It is hoped that the system adopted of numbered
paragraphs and references in connection with the chapters de-
voted to apparatus will serve much the same function as a living
instructor and enable the reader to acquire rapidly proficiency in
the use of tools while engaged in the construction of some interest-
ing and useful piece of apparatus.

None of the processes are difficult and once they have been
mastered the reader is in a position to construct a great range of
equipment for experimental science.

A complete knowledge of the use of tools, and this applies to
tools for working in wood, metal and other substances can only
come through the finger ends, but much help qfin be gained by
intelligent observation of the way skilled artisans set about Jheir
work. The science worker requires a knowledge of certain parts of
many trades and the student can be well advised to cultivate a
sympathetic, not a superior interest, in the work of such men.
The late Sir Edward Harland, engineer and shipbuilder, used to
say how, as a boy, he liked to assist and observe workmen. He
got to know every workshop and every workman in his native
town and picked up a smattering of a variety of trades, which
afterwards proved of the greatest use to him.

54. Marking out strip brass.

Let us suppose that a strip of brass as illustrated (Fig. 42) has
to be prepared, it can later be used to make a switch (see page 215).
It is possible that a strip long enough for the purpose can be
picked out of the scrap box, thus avoiding the cutting up of new
material.

If no scrap ends can be found take a long length from the store
and place it on the bench. It is possible that one end of 4he long
strip will be square and in good enough condition to use without

52

THE LABORATORY WORKSHOP

further treatment, but usually the ends of store strips are im-
perfeet and have to be eut afresh. This is very often the case with
mild steel or iron that has been cut by the metal dealer with a
hammer and cold chisel (Fig. 44).

Place a small steel square along the side of the strip. Hold the
square firmly to prevent it from slipping and with a steel scriber
scratch a line across the brass strip (Fig. 45).

Scribe^ line

r

y* [/"H^This imperfect en
' is sawn off

Scribe

Fig 44.
Metal strip with an impelled end

Fig. 45

Method of using a small steel square and a scriber
for marking out strip metal

If the strip lias to be three inches long take a small steel rule and
mark a place 3" from the first 1m e. With the square and scriber
draw another scratch at this place.

e

55. . Cutting strip brass.

The marked length now has to be cut off. This is done with a
hack-saw. A hack-saw blade with 22 teeth to the inch is a useful
grade to use. The blade must be fixed firmly in its frame and
arranged so that the teeth point away from the handle.

The length of brass should be held in a vice and so arranged that
the place where the saw cut is to be made is close to the vice jaw.
If this be not done the brass strip will bend under the pressure of
the saw. Hold the strip so that the scratch mark faces upwards
(Fig. 46).

An ordinary steel vice has fine teeth in its jaws and will slightly
injure the surface of the brass. One way of avoiding this is to
provide the vice with a pair of lead, copper, or fibre clamps to fit
over and cover the teeth when delicate work has to be held.
Lead and fibre clamps are sold by vice makers, but it is quite easy
to make a pair from some sheet copper or even tin plate (see
Sec. 73).

Placf the blade of the hack-saw on the far edge of the strip and
about -fa" away from the mark. Use a finger of the left hand to

TO MARK OUT, CUT, FILE, DRILL AND BEND 53

Incorrect method

metal strip

vice vice

jaw I jaw

Correct method (side view)

Correct method scribed mark is

close to the vice jaws

Fig, 46. Incorrect and correct methods of holding a strip of metal
in a vice preparatory to sawing

^"-^ Blade must be arranged
with teeth sloping away
from the handle

position of saw

Scribed line

Apply pressure when saw is moving in this direction

once the cut has been started the Hack Saw is brought
into this position.

Fig. 47. Method of using a hack-saw to cut strip metal

B

Fig. 48.

Fig. 49.

Stages in sawing off a strip of metal preparatory to
filing to exact length

54 THE LABORATORY WORKSHOP

steady the blade and prevent its slipping about while the cut is
being started (Fig. 47).

Once the cut has been started the left hand can be used to grip
the forward part of the saw. Apply pressure on the forward
stroke only and make about 50 strokes a minute.

Do not twist the saw blade or it may snap in half, since it is
made of highly tempered steel.

As the work is nearly cut through go slowly in order to make
a clean final cut and to avoid knocking the fingers by a sudden
collapse of the saw frame downwards.

When a long strip of metal is held in a vice in this way it is
advisable to get someone to hold the long end or otherwise support
it. Less force is then needed to hold the strip in the vice and the
unused length does not suffer distortion.

Remove the long length. The marked length will now appear
as (Fig. 48).

Grip the marked length in the vice with the line AB close to the
jaws, and with the hack-saw used as before make a cut about -3^" to
the right of the line. These processes provide a length of brass as
shown (Fig. 49). The next thing is to file it to the exact length
required.

56. Filing strip brass to size.

Grip the strip, vertically in the vice with one of the ends pro-
jecting about y above the vice jaw (Fig. 50) and with a flat
second cut file, file each end in turn down to the mark. File work
requires care. Use the file with a steady movement, and try to
avoid rocking the tool or the work will become rounded. Hold the
handle in the right hand, grip the far end with the left hand or left
fingers and apply pressure on the forward stroke only.

When brass is being filed in this way difficulty is sometimes
caused by a burr obscuring the view of the mark. To avoid this,
when nearly down to the mark lift the file clear after each forward
stroke. Another way is to grip the strip by its narrow sides and
file down to the mark as shown (Fig. 51). This avoids all trouble
due to burr and careful watch can be kept on the accuracy of the
work. Steady the $le and help to apply pressure by pressing on
its far end with the fingers of the left hand.

57. Drilling strip brass.

Before holes are drilled their positions should be carefully
measured out and marked. This is most important if good
finished work is to be produced.

TO MARK OUt, CUT, FILE, DRILL AND BEND 55

Mark out with the help of a steel rule, a scriber and a small steel
square.

Strip brass has a smooth surface and is easily and clearly marked
with light scratches that can be subsequently removed by a little
polishing with fine glass paper. Suppose the 3" strip of brass has
to be drilled as shown (Fig. 52) mark the lines AB, CD, EF, GH
and IJ using a rule, square and scriber. The centre of AB and IJ
required for drawing a centre line can be found by applying the
millimeter edge of the rule to these lines. When the centres have
been found they must be punched before drilling or the point of

Fig. 50.

Strip of metal ready

for filing to scribed

line

Fig. 51. A method of tiling that avoids the for-
mation of a burr over the scribed guide line

I <3 E C A

J H F D B }
3" ^

Strip to be drilled as shown
in this diagram

Fig. 52. Method of marking out a strip of metal before

centre-punching and drilling

the drill will wander about and not pass through at the exact
place required.

For centre-punching use a punch with a fine point, put the work
on some non-yielding surface to serve as an anvil (Fig. 58), place
the point of the punch on each of the centre marks in turn and give
the top of the punch a sharp blow with a Jib. hammer. This has
the effect of making a tiny dimple at each of the marks.

A useful anvil is provided by a short scrap .length of iron girder
to be obtained for a few pence from a builder or scrap iron mer-
chant.. An ordinary domestic iron used upside down with its
handle fixed on a block of wood or gripped in a vice also makes a
good surface to centre punch on.

Drill the holes with twist drills held in a hand drill or placed in
the chuck of a drilling machine. It is much less tiring to drill

56 THE LABORATORY WORKSHOP

metal using a small drilling machine than a hand drill if the work
is more than &" thick.

The hand drill specified in the list of tools will take twist drills
up to J" and the drilling machine up to |".

Care must be taken when using drills larger than f " in the chuck
of the drilling machine to avoid crushing the three little springs
inside. The writers prefer to avoid the possibility by holding
such drills in the chuck of a carpenter's brace adapted for the
purpose (see note, Item 65 tool list). When using a hand drill
care must be taken to keep it vertical. This is less important
with thin than with thick work.

Place a piece of wood under the work to be drilled to serve as a
protection to the bench top and carefully place the point of the
drill in a centre punch impression before starting to turn the
handle. The impression serves as a guide and by preventing the
drill from wandering about ensures the hole being made in the
correct place.

If the work tends to fly round with the drill, drive one or two
nails into the wooden drilling board or fix a strip of wood on it.
This will stop the work from turning.

When a drill bit has nearly passed through a piece of metal it
will sometimes take an extra deep cut and bind in the work, and
if care be not taken the drill bit, especially if it is a fine one, may
be broken. f

To avoid this, use the hand or machine drill with extra care
when the drill bit is nearly through.

If necessary turn the handle backwards, then gradually work it
in the forward cutting direction again. A hand drill fitted with
a ratchet is particularly useful when a drill bit is tending to bind.
Under such circumstances it is often difficult to keep on turning
the handle round and round; if the ratchet mechanism be put into
action the handle can be given a slight to and fro movement and
the drill bit can be gradually fed forward.

Another way of getting over the difficulty is to reverse the work
and file off the elevated portion made by the penetrating drill-bit.
This will make an opening for the point of the drill-bit when little
difficulty will be experienced in completing the drilling process.

58. Drilling large holes.

If the work has been carefully centre punched before drilling is
started little difficulty will be experienced in making small holes in
correct position. Large drills are not so readily guided by a
centre punch mark, and sometimes to ensure accuracy it is better

TO MARK OUT, CUT, FILE, DRILL AND BEND 57

to start by drilling a small hole right through the work to serve as
a guide for the larger drill. In the case of the piece of work under
review (Fig. 52) before attempting to drill out the central f " diam.
hole, drill a guide hole of about -fa".

Another advantage of using a guide hole in connection with
large drills is that the cutting edge of the large drill obtains more
purchase and the rate of drilling is greatly increased. This is very
marked when iron or steel is being drilled.

59. The general use of twist drills. Use of oil.

Twist drills are not only used for drilling brass but all metals, also
ebonite, fibre and wood. When drilling brass, copper, ebonite,
fibre or wood the drill can be used without oil, but in the case of
iron and steel a few drops of oil, motor car engine oil, should be

put at the place of drilling just
after the drill bit has been
started on the centre punch
hole.

If a piece of thick iron or
steel is being drilled extra oil
may be necessary as the work
proceeds.

Always centre punch metal,
ebonite and Itbre before drill-

TI >* t* xi 3 * i inff- This is a great aid to ac-

Fig. 53. Method of centre-punching a fe 6

strip of metal before drilling curate work.

60. Drilling square brass.

When making a brass clamp as shown in fig. 326 it is necessary
to drill a J" diam. hole through a piece of f " square brass. To do
this, carefully mark out the exact positions of the hole with a
scriber and centre punch the opposite faces of the work (Fig. 54).

Start by drilling a iV" diam. hole right through the work. If
this be done in one operation, from one side only, the drill will
probably get crooked and come out on the opposite face at a place
away from the centre punch mark, so it is best, to drill half through
from one side and half through from the other, the two small
holes meeting at the centre. If this hole is being made with a
drilling machine, rest the work on the iron bedplate of the machine
in order to get a good support ; care must be taken so to arrange
the work that each end is supported. If the piece of brass is
short it may be necessary to unclamp the drill and swing it over

58 THE LABORATORY WORKSHOP

a little to one side so that the end of the work nearest to the hole
will have a support (Fig. 55). <

If a drilling machine be not available take great care
when doing work of this kind with a hand drill to keep the tool
vertical. Sometimes it is a help to get a friend to view the tool
from two positions at right angles and say when it is vertical and
correct for drilling, and to check the position as the drilling pro-
1 ceeds. The work can be conveniently held in a vice, but care must
be taken to clamp it accurately, the top edges being flush with and
parallel with the vice jaws.

One method of giving support to work on a drilling machine is
to rest it on a block of wood. If this be done use a block of hard
wood such as oak, when thick work has to be drilled, otherwise the
pressure of the drill will force the work into the wood and the drill
hole will become inaccurate (Fig. 56).

Once an accurate small hole has been made it is an easy matter
to drill the hole full size. This can be done from one side only,
the small hole will act as a guide.

When a hole has to be drilled in one side of a block of square
brass, first locate the centre by scribing diagonals and centre
punch the position. The block can either be held in a bench vice
and drilled with a hand drill, or clamped in a machine vice and
drilled with the bench drilling machine. In either case care must
be taken to clamjp it vertically.

61. Cutting circles, slots and other holes in thick metal, using a drill and
files.

Thin metal can often be cut with snips (see Sec. 63), but this
method cannot be used with metal that is mufch over -fa" thick.

To cut a circle in thick sheet metal plate first locate the centre
of the circle and centre punch it with a fine punch.

Open out a pair of steel dividers to the required radius, and
placing one point in the centre punch hole describe a circle (1
Fig. 57). The steel dividers will scratch a circle on the metal.
Now describe a second circle of -fa* smaller radius (2) after making
a number of centre punch marks on this (3), drill cut a series of
Y diameter holes (4).

Place the work on a block of iron to serve as an anvil (see Sec. 57)
and with a small cold chisel and hammer cut the metal between the
holes (5). The centre can now be removed.

Clamp the metal plate in a vice and using jaw protectors, take
a half round second cut file and file down to the outer marked
circle. As filing proceeds, unclamp the work and turn it from

TO MARK OUT, CUT, FILE, DRILL AND BEND 59

j|"diam.

Fig. 54.

Method of marking out a
piece of square section
brass preparatory to
drilling

work \_ u _^^ Bed plate

drilling" machine
Work incorrectly supported,
it is liable to tilt

work

opening v Wo ^ k supported at
l n & both ends and so
bed plate arranged that the
drill on passing
through will not cut
into the bed plate

Fig. 55. Incorrect and correct methods of arranging work
on the bed plate of a drilling machine

Softwood . this yields
under the pressure applied
by the drill

Hard,wood
f

i i IIK^ ^gyini i i i

Bedplate of drilling machine

f ,., ^y

Fig. 56. When drilling a strip of metal near one end, support
it on a piece of hard wood

2. Scribed 3. Centre punched ?J g * 5T *

How to cut a circular
opening in a sheet of
thick metal

60 THE LABORATORY WORKSHOP

time to time so that the part being filed is always close to the top
of the vice jaws and has plenty of support (6).

62. To cut a slot or square hole in thick sheet metal.

The method of drilling and filing described for cutting out
circles is applicable to slots, square holes and other openings.

63. Cutting thin sheet metal.

Thin sheet metal, tin plate, copper, zinc, aluminium, brass and
mild steel are readily cut with a pair of tinman's snips. These are
used like a pair of large scissors. The larger the snips the greater
is the leverage obtained and relatively easier becomes the work of
cutting. For small work large snips are clumsy and less accurate
in use than small ones.

Vice

Fig. 58. Method of clamping snips in a vice to obtain
extra leverage when cutting thick metal

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With large snips it is sometimes difficult to cut close to an edge,
the metal tending to turn over. When marking out it is worth
bearing this in mind, and keep all marking out lines at least Y
away from any edges.

The handles of snips come together at 4 the end. Keep the
fleshy part of the hand away from the end, or the skin may be
pinched. Extra leverage can be obtained by clamping one handle
of the snips in a vice. If the sheet to be cut be pushed well up
between the jaws of the snips, close to the fulcrum and pressure
be applied to the far end of the movable handle quite thick metal
can be cut with small snips.

64. Flattening sheet metal.

If a sheet of metal has got bent and requires flattening this is
readily done by placing it on a flat bench top or on the floor and
by beating it out with a wooden mallet. If a wooden mallet be not
available the process can be carried out with an ordinary hammer,
but, in *his case, unless care be taken, the surface of the metal is
liable to be disfigured by hammer marks. A simple and effective

TO MARK OUT, CUT, FILE, DRILL AND BEND 61

way out of the difficulty is to hammer a small block of hard wood
that is moved about over the raised portions of the sheet of metal.

65. Marking out sheet metal.

Sheet metal can be marked out with a scriber, a steel rule and
a square.

Usually a sheet of metal taken straight from the store has at least
one straight edge that can be used to mark out from, but if none
of the edges are straight, start by scribing a straight line with a
steel rule and cut along this line with snips. Once a straight base
line has been obtained other lines can be easily scribed out.

Fig 59.
This shows stages in scribing and cutting out a rectangle in sheet metal

Lines at right angles to the base can be marked with the help of
a small engineer's steel square, a large carpenter's square or a T
square, according to the size of the rectangle that has to be set out.

Figure 59 shows stages in scribing and cutting out a rectangle.

(1) Mark a straight base line AB and cut along tfcis line.

(2) Mark C and E at distance CE one side of rectangle.

(3) Using a square scribe lines CD and EF. If a large rectangle
has to be marked out it is best to use a large carpenter's square
or a T square for marking these lines.

(4s) If necessary, by using a steel rule, extend CD and EF to G and
H. Make CG = EH = required length of side of rectangle.
Check the accuracy of the marking out by measuring the
length of the diagonals and finding if they are equal.
Cut out the rectangle with snips. Do not attempt to cut along CG
and turn the corner to cut GH, but cut straight across the whole
sheet along CG and remove the left hand portion. Make the other
cuts in the same way.

66. Cutting difficulties.

Sometimes when sheet metal is being cut the scrap will curl
around the snips and make it difficult to work them (Fig. 60). If
this happens stop cutting along the guide scratch and snip>off and
remove the curling portion of waste metal.

62 THE LABORATORY WORKSHOP

67. The storage of scrap sheet metal.

Scraps of sheet metal, unless of very irregular shape, can well be
kept in a scrap box for possible future use. Before storing scrap
metal it is wise to trim it up roughly, if this be not done it tends to
get in a tangle and become difficult to sort out.

^^^

Fig 60 A cutting difficulty. The scrap
metal may curl around the snips

68. Cutting circular work.

A good example of circular work is the construction of a sheet
metal collar to fit over a lens, to serve as a shield for cutting out
strong light.

Suppose a collar of the dimensions shown in fig. 61 (a) has to be
made. First determine the diameter of the lens by measuring the
lens mount with a pair of external callipers (c). When taking
such measurements it is convenient to work in cms. and mms.

Read the calliper opening by application of the tips to a steel
rule. Set a paij of steel dividers to the required radius.

Place the sheet of metal to be marked on a flat surface and
centre punch an impression for one point of the dividers. This
will prevent the tool from slipping when describing a circle on the
sheet metal. Describe the circle for the lens opening and the
outer circle.

A circle of 6" radius can be cut out with straight snips, circles of
small radius are more easily cut with curved snips (Item 23 tool
list).

A circular disc having been cut the next thing is to remove the
inner circle. If the metal is tin plate the snips are liable to pro-
duce a sharp edge and before proceeding to cut the inner open-
ing it is a good thing to rub off the sharp edge of the disc with a
small wad of glass paper or emery cloth made by folding a strip
several times over.

This will leave the disc in a comfortable condition to hold.

Place the disc on an anvil and with the help of a cold chisel and
hammer cut an opening for the insertion of a pair of small curved
snips (If). Cut along the dotted line and so remove the central
circular portion: smooth the edge with glass or emery paper and

TO MARK OUT, CUT, FILE, DRILL AND BEND 63

Opening: maxie
'wathacold
dusel

(a.) The collar complete with

opemngto fit Lens **"' v ~ ~*

Fig. 61. The construction of a sheet metal collar to fit
round a lens mount

Correct Incorrect

Fig. 62. Fig. 63.

Correct and incorrect methods of filing the edgjp of a disc

Fig. 64. Stages in cutting an opening in the base of a tin can' to
take an electric lamp holder

64 THE LABORATORY WORKSHOP

try the fit of the collar on the lens mount. If the opening be not
quite large enough, grip the disc in a vice ai&d file it evenly all
round with a second-cut, half-round file. Change the position of
the disc as the filing proceeds, so that the portion being worked on
is always near the jaws of the vice and has plenty of support.

Instead of using a vice the disc can be placed flat on the bench
top with the inner opening projecting sufficiently over the edge to
enable a file to be inserted and worked up and down.

File with care or too much metal may be removed, or removed
unequally. Kvcry now and again try the fit of the collar on the
lens.

The method of placing the disc flat on a bench top and filing may
be used to smooth the outer edges of the collar. If done in this
way, instead of using glass or emery paper, take care to work the
file up and down at right angles to the surface of the disc (Fig. 62).
If used as shown (Fig. 63), the file may slip and the metal disc is
then liable to cut the wrist.

69. To decrease the size of a circular opening in a disc.

If an opening has been cut or filed too large it can be made
smaller by placing the sheet of metal on an anvil and hammering
all round the edge of the opening. This has the effect of spreading
the metal.

70. To cut an opening in the end of a tin can for an electric lamp holder.

Measure the diameter of the lamp holder with callipers (see
Sec. 68). Find the centre of the tin can. This can be done with
a pair of dividers. Support one point of the dividers on the edge
of the tin, if necessary holding it in place with a finger. Open the
dividers out to approximately the radius of the tin. Describe an
arc, scratching a mark on the tin. Move the dividers and describe
two more arcs. The intersection of the arcs enables the centre to
be located fairly accurately (Fig. 64a).

Place the tin over a block of wood held in the vice and put
a punch mark at the centre.

With dividers set to the radius of the lamp holder describe
a circle on the tin (b), using the centre punch mark as a support for
one leg of the dividers. Drill one or two adjacent holes close to
the centre large enough to enable small straight snips to be
inserted (c).

Make a series of radial cuts up to the circle (d) and by bending
the little strips so produced backwards and forwards they can be
broken off, thus leaving a roughly circular opening (e).

TO MARK OUT, CUT, FILE, DRILL AND BEND

65

A little filing with a small, half round second cut file will make
the opening smooth and truly circular (f).

71. To cut holes with a circle cutter.

A very useful tool for cutting circular holes in sheet metal is
depicted (Fig. 65).

The tool is held in a carpenter's brace. The metal to be cut is
centre punched, drilled at the punch mark with a ^" hole and
placed on a piece of fiat board. The cutting part of the tool is set
to the required radius and when rotated with the drill point of the
tool placed in the centre hole, a clean circle can be readily cut out
of quite thick sheet metal.

Fig 65. Expansion drill for cutting large

circular holes in sheet metal
By courtesy of Buck & Hickman Ltd

Fig. 66. Vice jaw clamp. Two
are required for each vice

As a general rule it is best to cut half way through from one
side, remove the work, then complete the cutting fPom the opposite
side. If this be not done, the metal is sometimes liable to tear.

72. Bending sheet metal.

This is a workshop process that is often required and can be
accomplished in various ways.

The following examples will serve to illustrate different processes.

73. Vice jaw clamps. (Fig. 66.)

These are pieces of metal to fit over the serrated surface of the
vice jaws and serve to protect work held in the vice from being
marked.

To make a pair of metal clamps mark out.and then cut with
snips two rectangular pieces of sheet copper or tin plate measuring
about 2" wide and of a length corresponding to the length of the
jaws.

If the vice has 4" jaws make the pieces 4" x 2". Grip one of the
pieces in the vice and hammer it over with an ordinary hamjmer to
conform to the top surface of the vice.

Fw

66

THE LABORATORY WORKSHOP

Fig, 67. A rectangular
section tube

aunp*

B D F H

Fig. 68. Sheet of metal marked
ready for bending into a square
section tube

> mered,

ever a.t right angles

Fig. 69. How to bend the metal for
making a rectangular section tube

Hard woodl

overlap before and,
after hammering

Fig. 70.

Fig. 71.

Treat the second piece in the same way.

Round off the corners with a file.

Copper and tin plate can be bent over at an abrupt right angle in
this way without fear of cracking. Soft brass and zinc can be
similarly treated, but hard brass in sizes greater than V thick is
liable to crack if hammered over at a sharp angle.

74. Making a rectangular section tube. (Fig. 67.)

This can be used in the construction of a small reflecting galvano-
meter lamp or parallel beam apparatus.

Materials. Sheet copper, brass, zinc or tin plate.

Cut a sheet of metal measuring 10J" x 8" and scribe the lines
AB, CP, EF and GH (Fig. 68). Obtain two pieces of hard wood,
planed to rectangle form and measuring about \" thick, 10" long

TO MARK OUT, CUT, FILE, DRILL AND BEND 67

and a little under 2" wide. Clamp these in the vice with the
metal to be bent ss> arranged that the line GH or AB just shows
along one side. Use a wooden mallet and hammer over the short
projecting piece at right angles to the remainder (Fig. 69).

Construct each of the sides in the same way taking care that the
metal does not slip during the hammering over process. The
first blows in each case, should be directed with care and the guide
line examined now and again to make certain that the bend is
being made at the correct place.

The sheet of metal when completely hammered over will have a
section resembling fig. 70. Slip the tube over a length of fairly
hard wood clamped in the vice, and with the narrow end of a
hammer give a series of smart blows to the overlapping portions
of metal. This has the effect of shaping the metal so that the
two portions are brought into the same plane (Fig. 71). The
joint is then soldered together (Sees. 125 and 126).

75. Construction of a chimney cover for a lantern. (Fig. 72.)

Materials. Brass, Copper or Tin Plate.

This chimney cover is in effect a rectangular metal box.

Scribe and cut out a sheet of metal as shown (Fig. 73). Place
the cut out metal on the bench and hold a small rectangular block
of wood with its edge along one of the inside scribed lines (Fig. 74),
bend up the end portion ABCD. This can be doi%e by starting the
bend with the fingers and then hammering the side into a vertical
position with a wooden mallet. With a little care and by keeping
the edge of the block on the guide line a good bend can be effected.

Treat each of the sides in the same way.

Tap the corner edges into close contact, then run solder along
them from the inside. Sharp outside edges and corners can now
be rounded off with the help of a file and fine glass paper.

76. Additional methods of bending sheet metal.

From the scrap heap of an engineer or builder who engages in
structural metal work it is often possible to obtain short lengths of
steel girder of an L or T section that make admirable anvils for the
bending of sheet metal. These lengths can be held in a vice.

A useful home-made aid to sheet metal work consists of two
strips pf rectangular section mild steel measuring 12" x 1" x J"
(Fig. 75).

A series of diam. holes are drilled in corresponding positions
in each of the strips. Metal to be bent is clamped between the
strips by a couple of J" diam. steel nuts and bolts passed through

68 THE LABORATORY WORKSHOP

two of the holes. The strips can be held securely in a vice during
the hammering and bending over of the metal

77. Treatment of edges.

The edges of sheet copper, brass, zinc and aluminium can be
rounded by filing and rubbing with glass paper. Tin plate is not
so easily treated and sharp edges are unpleasant.
v If the lantern cover be made of tin plate it should be marked out
as shown (Fig. 76), an extra J" being allowed all round. The
edges should be bent up at right angles along the J" lines then
hammered over as shown (A and B, Fig. 76). The initial bend at
right angles can be made over the edge of an anvil or, with the
help of clamps, turned up in stages by working along the line with
a pair of flat nosed pliers. The first two methods are preferable.
The turning over of the edges gives extra strength and yields a
smooth edge. The edges having been turned the sides can be
bent up and the cover completed as already described.

78. Construction of a tube.

Sometimes a tube is required for the construction of a solenoid
or an electro-magnet.

If a piece of ready-made tube be not available a satisfactory
substitute can be made from thin sheet metal. Obtain a piece
of wood of circular section of the required inside diameter of the
tube. A length* of dowelling is often suitable. Cut a piece of
sheet copper, or brass of a wid