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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 " "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
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 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
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
