Automotive mechanics (volume i)(part 1, chapter3) tools and their use

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Chapter 3

Tools and their use

Tools for turning
Tools for holding and gripping
Tools for hammering and driving
Tools for cutting and forming
Tools for drilling and reaming
Tools for threading
Tools and materials for grinding and abrading
Tools for pulling and pushing
Special service tools
Technical terms
Review questions


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A mechanic’s tool kit consists of a variety of spanners,
screwdrivers, pliers, hammers, punches and so on,
which must be cared for and used correctly. Incorrect
use of tools will damage the part being worked on, and
could also damage the tool being used.
Good workmanship involves using the correct tool
for the job, carrying out the work in a reasonable time,
and observing good safety practices.
Tools are kept together in a tool box with divided
trays or compartments so that they are clean and sorted
ready for use. Figure 3.1 shows tool boxes and also a
cabinet with a range of mechanic’s hand tools.
As well as personal tools, there are other tools and
equipment in the workshop that are used for various
purposes including turning, holding, bending, hammering, cutting, forming, drilling, grinding, threading,
pulling and lifting.

for tightening or loosening bolts, nuts and screws, or
for turning other threaded parts.
Spanners
Many types of spanners are available: open-end,
socket, ring, combination open-end and ring, adjustable etc. Each type has its particular use.

■ Spanners are also referred to as wrenches.
Open-end spanners
These are the most common type of spanner
(Figure 3.2). The openings, or jaws, are set at an angle
and this permits the spanner to be used in a restricted
space. The bolt or nut is turned as far as the space will
allow and the spanner is then turned over to permit
further movement.
■ For greater control, a spanner should be pulled
rather than pushed. If a spanner has to be pushed,
do so with the open palm of the hand.

figure 3.2

Open-end spanners

DIS

Ring spanners
Ring spanners (Figure 3.3) have a ring at each end
which fits completely around the head of the bolt or
nut being turned.
Ring spanners can be used in restricted spaces
because of the thin section of material at the ring. The
double-hexagonal ring allows a bolt or nut to be
removed or installed where there is a swing of only 30°.

figure 3.1

Tool boxes and tool cabinet

DIS

Tools for turning
Tools used for turning include spanners, screwdrivers,
wrenches and other special equipment, which are used

figure 3.3

Ring spanners

DIS


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chapter three tools and their use

Ring and open-end spanners are a combination,
with a ring at one end and open jaws at the other. The
ring end can be used for loosening a bolt or nut and for
final tightening. The open end can be used at other
times when it is more convenient than a ring spanner.
Socket spanners

These are tubular-type spanners that fit over the nut
(Figure 3.4). They are used with a detachable handle.
Most sockets are a double hexagonal shape internally,
so that the bolt or nut being turned can be moved onetwelfth of a turn at a time, if necessary. The drive-end
of the handle has a square end, which fits into a square
hole in the socket.

figure 3.4

Socket spanners

35

(1/4 inch) for small sockets, up to 25 mm (1 inch) for
large sockets.
Special spanners
Some spanners, like those shown in Figure 3.6, are
designed for special purposes. Ring spanners of
C-shape and S-shape can be used for manifold bolts
and nuts, and also at other places which are hard to
reach with a normal ring spanner.
An offset ring spanner, known as a crow’s-foot
spanner, is somewhat L-shaped. It is used to reach
difficult places.

DIS

figure 3.6

Socket accessories

Special ring spanners

DIS

Adjustable spanners

Handles and other accessories are used with socket
spanners. They include ratchet handles, speed braces,
extension pieces and universal joints (Figure 3.5). The
square driving end of the extension can be 6.4 mm

Spanners with adjustable jaws are available in various
sizes, and are particularly useful for irregular-sized
bolts and nuts. However, they should be used for
special work only, and must not be considered as a
substitute for all spanners. They must be used
correctly, with the jaws adjusted firmly (Figure 3.7).
They are often referred to as shifting spanners.

figure 3.7

Use of adjustable spanner

Spanner sizes
figure 3.5

Socket handles and accessories

DIS

Spanners are marked with the size of the nut or head
of the bolt on which they will be used. This is the


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dimension across the nut or bolt head from one flat
side to the other, sometimes referred to as across the
flats. For open-end spanners, this is the width of the
jaw opening (Figure 3.8).
Metric spanners are marked in millimetres. Typical
markings are 6 mm, 7 mm, 8 mm, 10 mm, 12 mm,
14 mm, 17 mm, 19 mm etc. A set of metric spanners
could range from 6 mm, in steps of 1, 2 or 3 mm, up to
32 mm.
Spanners for bolts with Unified threads are marked
in fractions of an inch. A set of spanners for these
bolts could range from 1/4 inch to 1 inch, in steps of
1

/16 inch.
■ Spanners for bolts with BSF and BSW threads were
marked with the diameter of the bolt. These threads
could still be found on older vehicles of British
manufacture.

figure 3.8

Spanner size – ‘A’ is the dimension across the
flats of the nut or bolt head

When bolts are tightened they are placed under
tension, that is, the bolt is subjected to a tensile or
stretching force. The torque applied will determine
the tension placed on the bolt. The tighter the bolt, the
greater is the tension.
Torque wrenches are used because overtightening
could cause distortion of parts, stripped threads or
broken bolts, while undertightening could allow a bolt
or nut to become loose.
Manufacturers specify the torque for important
bolts and nuts. Using a torque wrench enables the
torque to be measured while tightening. Torque
specifications for bolts and nuts are quoted in newton
metres.
The torque wrench illustrated has a scale, other
designs have a direct reading dial gauge.
About torque
Torque is a twisting or turning force. In Figure 3.10,
a force of 1 N (newton) is applied at right angles to

an arm 1 m long. This produces a torque of 1 Nm
(1 newton metre). The torque can be varied by
altering the length of the arm or by increasing the
force.
Smaller values of torque can be measured in
newton millimetres (Nmm). This is the product of the
force in newtons (N) and the length of the spanner or
arm in millimetres (mm).

Torque wrenches
Torque wrenches are used to tighten bolts and nuts to
a specified torque. Figure 3.9 shows a torque wrench
in use. It has a scale on the handle, which is
graduated in newton metres, and also a pointer. The
bar of the wrench bends as a turning force is applied
to the handle, but the pointer does not. This moves
the scale in relation to the pointer, which shows the
torque.

figure 3.9

Using a torque wrench to tighten an axle nut

figure 3.10

A force of 1 N applied in the direction of the
arrow will produce a torque of 1 Nm

Angular torque wrench
An angular torque wrench is shown in Figure 3.11.

This is used for some particular bolts in conjunction
with a torque wrench. It has a shaft with a square hole
at the top to take a handle and a square drive at the
bottom for a socket spanner. It also has a degree plate
and a pointer to show the angle through which the
shaft is turned.
After a bolt has been tightened to a specified
torque, an angular torque wrench is then used to turn
the bolt through a specified angle. This applies
additional tension to the bolt.


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chapter three tools and their use

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degree plate
pointer
square
socket

figure 3.13

Pipe wrenches

DIS

Screwdrivers
square drive

socket spanner

figure 3.11

Angular torque wrench and socket spanner

Other wrenches
Allen wrenches
These are also referred to as Allen keys (Figure 3.12)
and are designed to fit into a recessed hexagonal head
of an Allen head screw or bolt.
Allen screws are used for particular purposes, such
as for grub screws on pulleys, and the adjustments of
some automatic transmissions.

figure 3.12

A number of screwdrivers are shown in Figure 3.14.
Screwdrivers are identified by the length of the blade
and the shape of the end of the blade.
The screwdrivers Figure 3.14(a) and (b) are
general-purpose screwdrivers of 150 mm and

100 mm length, with blades to suit screws with a
single slot. The screwdriver in Figure 3.14(c) is only
50 mm long and is designed for use in confined
places. The three small screwdrivers in Figure 3.14(d)
have thin blades and are used for electrical work and
small screws.
Phillips head screws, or recessed-head screws, have
cross-slots and so require special screwdrivers with a
suitably shaped end, as Figure 3.14(e), (f ) and (g).
Many screws are of this type.
Care of screwdrivers
The tip of a screwdriver for slotted screws must be
correctly shaped, with the sides almost parallel at the
tip (Figure 3.15). If the sides are tapered, the tip will be
forced out of the slot as it is being turned, causing

An Allen screw and wrench

Pipe wrenches
These have an adjustable jaw to enable the wrench to
fit a range of sizes of pipes or tubes. The hardened
jaws are serrated to enable them to grip the pipe, but
the serrations can mark and damage the surface of the
pipe if the wrench is not used carefully. This type of
wrench is shown in Figure 3.13.

figure 3.14

Screwdrivers
(a) and (b) plain (c) short (d) electrical (e),

(f) and (g) Phillips DIS


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figure 3.15

Screwdriver blades
(a) correctly ground (b) badly ground

damage to the slot and making the screw difficult to
tighten or to remove.
The blade of a damaged screwdriver can be
restored to shape using a grinding wheel.

figure 3.17

Two types of wheel brace
(a) tool-kit wheel brace (b) cross wheel brace

Tools for holding and gripping

■ Select a screwdriver that fits snugly into the screw
head. One that is too large or too small will be
difficult to use and will damage the screw slot.

In many workshop operations, one part of a component
has to be held while working on another part. Various
tools can be used for this purpose, including pliers,
clamps, vices, and fixtures.

Torx bit

1. Pliers. Pliers shown in Figure 3.18 are designed for
various purposes – to hold, cut, bend and so on.
They should not be used on the heads of bolts or
nuts because this will cause damage and spanners
will no longer fit.

This is a tool with flutes that fit into recessed heads
of torx bolts. These are special bolts that are used
for particular applications. A torx bit is shown in
Figure 3.16. One end is hexagonal to fit into a socket
spanner so that it can be turned and the other end is
fluted to fit into the recess in the torx-bolt head.
hexagonal head

figure 3.16

flutes

A torx bit for use with special bolt heads

Wheel braces
Two types of wheel brace are shown in Figure 3.17.
The brace in Figure 3.17(a) has a socket on one end
to fit the wheel nut or bolt and a lever on the other to
remove hubcaps, wheel covers or trims. This type of
wheel brace is commonly part of a car tool kit.
The cross wheel brace in Figure 3.17(b) has four
sockets enabling it to be used on four different-sized
wheel nuts or bolts.
Air-operated impact wrenches, set to the correct
torque, are used in workshops where a large amount of
wheel changing is carried out.

figure 3.18

Various pliers for gripping and cutting

DIS

2. Circlip pliers. These special pliers (Figure 3.19) are
used to remove and replace circlips or snap rings.


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chapter three tools and their use

Circlips (or snap rings) fit into grooves in shafts or
housings. External circlip pliers expand the circlip
for removal from a shaft, while internal pliers
contract the circlip for removal from a groove in the
bore of a housing.

39

5. Tongs. Long-handled tongs (Figure 3.20(c)) are
used to hold hot objects, such as parts being
welded. The jaws are shaped to enable the tongs to
be used with either flat or round objects.
Bench vice

figure 3.19

Circlip pliers for external and internal
circlips DIS

Bench vice (Figure 3.21) are used to support parts
while they are being dismantled or reassembled. To
avoid marking or damaging the finished surfaces of
parts that are to be clamped in the vice, caps of soft
metal are placed over the steel jaws of the vice. These

are referred to as soft jaws.
Vice are also used to hold material while it is being
sawn, filed, drilled, chiselled or worked in some other
way. Some vice have offset jaws which enable long
objects to be held vertically.

3. Multigrip pliers. These long-handled pliers have
jaws that can be adjusted for size (Figure 3.20(a)).
They are a useful tool for holding, bending and
turning, but should not be used as a substitute for a
spanner as the serrated jaws will tear the corners off
the bolt or nut.
4. Vice-grip pliers. These pliers (Figure 3.20(b)) have
a double-lever action which gives the jaws a very
tight grip. The size of the jaw opening can be
adjusted by means of a knurled screw on the end of
the handle.
figure 3.21

Types of bench vice

DIS

Clamps
Clamps are used for holding parts together while they
are being assembled, drilled or welded. For example,
two pieces of steel that are to be drilled and bolted
together would be clamped together during the drilling
operations to ensure that the holes in both pieces are in
correct alignment.

There are many different designs of clamps, some
of which are shown in Figure 3.22.

Tools for hammering and driving
These include hammers, and tools such as punches and
chisels that are used with hammers.
Hammers
figure 3.20

Types of pliers and tongs
(a) Multigrip pliers (b) vice-grip pliers
(c) tongs DIS

Hammers should be gripped at the end of the handle,
and not near the head. The face of a hammer should
strike the object squarely, as shown in Figure 3.23.


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part one introduction to motor vehicles

figure 3.24
figure 3.22

Clamps
(a) G-clamps (b) toolmakers clamp (c) hand
vice DIS

Various types of hammers

DIS

4. Sledgehammer. This is a heavy hammer with a long
handle which has little application in automotive
work.
5. Soft-head hammer. This is used for striking
surfaces that can easily be marked or damaged.
When reassembling parts, a soft-faced hammer is
sometimes needed (Figure 3.25).
■ The faces or heads of soft hammers can be of
rubber, plastic, lead, brass or copper.
rubber hammer

figure 3.23

The wrong and right ways to grip and use a
hammer

All hammers must be used with care. Careless use
of a steel hammer will bruise or injure the surface
being hammered, and large hammers or strong blows,

unless necessary, can cause considerable damage.
For reasons of safety, the hammer head should
always be securely fixed to the handle. The hole in the
head is elongated, and belled at the top and bottom, so
that a wooden handle can be inserted and then
expanded by a wedge of wood or metal.
Types of hammers are shown in Figure 3.24. These
are:
1. Ballpein hammer. This is the type most commonly
used in workshops. The flat face of the hammer is
used for striking punches and chisels and also for
general work. The ballpein is round and is used
for riveting.
2. Crosspein hammer. This has a wedge-shaped pein
instead of a ball. It is useful for work in corners that
would not be accessible with a ballpein.
3. Panel hammer. This is a specially shaped hammer
that is used with a dolly for beating out damaged
body panels.

plastic-tip hammer

figure 3.25

Hammers with rubber and plastic heads

Punches
Various punches are used to drive out rivets or pins,
align parts for assembly, and mark locations of holes to
be drilled. These are shown in Figure 3.26.

1. Centre punches. These are used for marking a hole
location prior to drilling. The punch mark starts the
drill in the right place. With no punch mark, the point
of the drill will wander over the surface of the work
and will probably start to drill in the wrong place.
Centre punches are also used for marking parts
before they are dismantled. A light punch mark on
mating parts enables them to be reassembled in the
original position.


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chapter three tools and their use

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because they are less liable to bend than long pin
punches.
3. Drifts. Drifts are larger-sized punches that are used
to remove shafts. These are made by cutting a
length of about 150 mm to 200 mm from a piece of
round stock. This could be mild steel, brass, copper
or aluminium. The softer materials prevent damage

to the end of the shaft that is being removed or
replaced.

Tools for cutting and forming
Tools under this heading include hacksaws, chisels,
files, drills and tinsnips.
Hacksaws

figure 3.26

A centre punch and a range of pin punches
DIS

2. Starting and pin punches. These are shown in
Figure 3.27. Starting punches are tapered and are
used to start a pin from a hole. Once the pin has
been started, a pin punch is then used to drive it
from the hole.
The shank of a pin punch is either hexagonal or
round, and the end parallel. For automotive work,
pin punches range in size from about 3 mm to
12 mm in diameter. Starting punches are used

Hacksaws are used for cutting metals. Three types are
shown in Figure 3.28. They have replaceable blades
and a frame that is adjustable for various blade lengths.
Blades are made with different numbers of teeth
(see Figure 3.29). Using a blade with the wrong
number of teeth will not only make the job more
difficult but will damage the teeth or break the blade.

The blade should be placed in the hacksaw frame and
tightened to the correct tension. Insufficient tension
will cause the blade to bend and probably break.
■ The teeth of the blade should point away from the
handle so that they will cut when the hacksaw is
pushed forward.
Cutting
A hacksaw should generally be used at around sixty
cutting strokes per minute and the full length of the

figure 3.27

Punches
(a) punch starting a pin (b) punch removing
the pin

figure 3.28

Hacksaws

DIS


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blade should be used wherever possible. On the
forward or cutting stroke, move the hacksaw evenly
and with uniform pressure. Lift the blade very slightly
on the return stroke to avoid wear on the back of the
teeth. Do not twist or bend the blade when cutting
because this could cause it to break.
Figure 3.29 shows blades with the correct and
incorrect pitch for different types of work. The teeth
should be flat across the work. A blade with the correct
number of teeth will provide chip clearance.
A general rule is that two or more teeth should
always be in contact with the work. If a coarse blade
is used on a thin section, the teeth will straddle the
work making cutting difficult and causing the teeth to
break.

Cold chisels
Cold chisels are made in a number of different shapes.
The flat chisel is the one most commonly used. The
other chisels shown in Figure 3.30 are for special
purposes, such as cutting grooves and chipping in
corners or other inaccessible places.
A flat chisel can be used to cut off the heads of
rivets or rusted bolts by holding the chisel at a suitable
angle to start the cut under the head to be removed.

To cut thin steel plate up to about 4 mm thick, the
plate is gripped vertically in the jaws of a vice and
the chisel held at about 30° to the horizontal, with the
cutting point resting on the vice jaws at an angle of
about 45° to the work. The cut is commenced from the
edge of the work, and the chisel moved along the vice
jaws as the metal is sheared through.

figure 3.30

Types of cold chisels

Care of chisels
The end of a chisel is made with a long taper and the
point of the chisel is sharpened by grinding it to a
suitable angle. The head is dressed to a slight taper.
A chisel that has mushroomed because of repeated
hammer blows should be dressed on a grinding
wheel so that the turned-over metal is removed
(Figure 3.31).

figure 3.29

Hacksaw blades for various cutting jobs –
blades with the correct tooth pitch are on the
left and those with incorrect tooth pitch are on the right

figure 3.31

Cold chisels

(a) chisel requiring grinding (b) chisel after
grinding


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chapter three tools and their use

Wad punches
These are hollow punches used for cutting holes in
gasket materials and thin metal such as shim brass or
shim steel. To cut a clean hole, the material is placed
on a piece of wood or block of lead and the punch hit
sharply with a hammer. Wad punches are available in a
range of sizes for various diameter holes (Figure 3.32).

coarseness. When the file has two series of cuts across
its face, it is known as a double-cut file (Figure 3.35).

figure 3.35
figure 3.32

Wad punches

43

Single-cut and double-cut files

DIS

Files
A typical file with the various parts named is shown in
Figure 3.33. Files are cutting tools with a large number
of cutting teeth. Files have many uses, and so there are
files with different cuts.

Files are also classified according to their shape.
They may be flat, triangular, square, half-round or
round. They can be either parallel, or tapered from the
heel to the tip.
■ The tang of a file should always be fitted with a
handle. Metal handles clamp on to the tang, but
wooden handles are also used.
Use of files

figure 3.33

A typical file, with parts named

The term cut refers to the cuts that have been made
across the face of the file to form the file teeth. When
the cuts are relatively far apart, the file is termed
a rough or coarse file. When they are close together,
the file is termed a smooth file. The coarser the file, the

more metal it will remove with each file stroke.
Figure 3.34 illustrates four different file cuts. When
only one series of cuts is made across the face of the
file, it is known as a single-cut file, regardless of its

figure 3.34

Types of file cuts

Coarse files are used for roughing to size. They
remove metal quickly, but leave behind large scratch
marks which must then be removed with a fine file.
Work being filed must be held securely. Articles
that are small enough should be held in a vice, and soft
jaws should be used to protect the part from damage.
There are two ways of using a file: cross-filing and
draw-filing.
Cross-filing When cross-filing, the forward (cutting)
stroke should be smooth and firm, with the right
amount of pressure applied by each hand to keep the
file flat and cutting.
On the return stroke, the pressure on the file should
be relieved, so that it slides over the work. Dragging
the file back over the work can chip the cutting edges
of the teeth.
If the file is not cutting, the teeth can be cleaned
with a filecard. This is a special brush with short wire
bristles. Tapping the edge of the file on the bench also
helps to keep it clean.
Draw-filing Draw-filing is a finishing operation. One

hand is placed at each end of the file and the file is
placed across the work. It is then drawn back and forth
without being lifted on the return stroke.


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This method is used where very little metal has to
be removed from the edges or surfaces. It produces a
fine finish with small scratches running parallel to the
edges of the work. Draw-filing is also useful for
checking the flatness of a surface – a light draw-file
will show up the high and low spots.
■ When filing steel, a coating of chalk on the file will
produce a finer finish.
Tinsnips and bolt cutters
Tinsnips are shown in Figure 3.36. They are used for
cutting sheet metal and other thin materials.
Boltcutters (Figure 3.37) are used to cut bolts and
metal rod. They have long handles and a double-lever

action which produces a strong cutting action at the
jaws.

1. The point is the surface at the cutting end of the
drill. It must be ground to the correct angles to cut
properly.
2. The body has two grooves known as flutes, which
spiral around the body. These allow the chips of
drilled material to curl and escape. They also allow
lubricant to reach the cutting edge.
3. The shank is the part of the drill without flutes.
Smaller drills have parallel (straight) shanks
which are gripped in the chuck of the drill.
Larger drills have tapered shanks which fit into a
tapered hole in the spindle of a drilling machine
(Figure 3.39).

figure 3.39
figure 3.36

figure 3.37

Tinsnips

Drill shanks

DIS

Bolt cutters

DIS

Tools for drilling and reaming
Drills are used for drilling holes in all types of
material. They are used with portable electric drills or
bench-mounted drilling machines. The most common
type is the twist drill. Reamers are used to finish holes
to size after they have been drilled.

Other parts of a drill are the web, which is the metal
between the flutes, and the margin, which is on the
outer edge of the drill. The drill has body clearance
which leaves the margin as a thin edge of metal of the
full diameter of the drill. Without body clearance,
the drill would rub against the side of the hole, overheat, and jam in the hole.
■ The tapers on drill shanks and drilling machines
are known as Morse tapers. They are identified by
numbers. No. 1 and No. 2 Morse tapers are the
sizes likely to be found in automotive workshops.
Sharpening drills

Twist drills

To sharpen a drill, the point of the drill is ground on a
grinding wheel. Two angles are considered, the cutting
angle and the clearance angle (Figure 3.40).

There are three main parts to a twist drill (Figure 3.38).
These are the point, the body and the shank:

1. The cutting angle is the angle of the cutting lips.
For general workshop use, this should be 60° to the

figure 3.38

The parts of a twist drill


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Check the angles produced. If the cutting angle is not
60° approximately, then the drill was not held at the
correct angle to the wheel. If the clearance angle is not
12° to 15°, then the shank of the drill was not lowered
correctly. If one cutting lip is longer than the other,
then both sides have not been equally ground.
figure 3.40

Drill angles

axis of the drill, or an included angle of 120°.
Sharper angles may be used for softer materials.
2. The clearance angle is the clearance obtained by
grinding the surface of the point back from the lip.
An angle of 12° to 15° is satisfactory for general
use. Without this clearance, the end of the drill
would merely rub and not cut.
As well as having the correct angles, the cutting
lips must be the same length. If one cutting lip is
longer than the other, or if the angles are unequal, then
an oversized hole will result.
■ A correctly sharpened drill should form a spiral
chip from each flute when drilling mild steel.
To grind a drill
The following points relate to sharpening a drill by
hand grinding. (Refer also to the later section
‘Grinding a tool’.)
1. Hold the drill lightly, with one hand holding the
shank of the drill and the other supporting the body
of the drill toward the point.
2. Hold the drill horizontally, with the point towards
the face of the grinding wheel and the drill at an
angle of 60° to the wheel. The rest of the grinder is
used to support the fingers.
3. Turn the drill in the hand until one of the lips is
horizontal. Grinding starts from this position.
4. Two actions must now be combined to produce the
required angles:
(a) rotate the drill between the fingers, approximately one-quarter turn, to produce the
spherical surface at the point, keeping the drill

at 60° to the wheel
(b) lower the shank of the drill at the same time to
produce the clearance angle of 12° to 15°.
5. Grind one side of the drill two or three times, then
rotate the drill 180° and grind the other side the
same amount.

Drilling holes
The centre of the hole to be drilled should be punched
with a centre punch. This should be deep enough to
locate the point of the drill so that it will drill in the
correct place. Without a punch mark, the drill could
wander over the work.
■ Before drilling with a large drill, a small pilot hole
is made with a small drill.
Drill speed and feed
The drill speed is its revolutions per minute (rpm) and
the feed is the distance the drill travels into the work
for each revolution.
In automotive workshops, where portable electric
drills and small bench drills are mostly used, a general
rule for drill speed is applied: the harder the metal, the
lower the rpm; the smaller the diameter of the drill, the
higher the rpm.
Where the speed is adjustable, the drill is set to a
moderate speed, the drilling conditions checked, and
the speed then increased or decreased as considered
necessary.
The feed depends on the size of the drill and the
type of material being worked. Large drilling machines

have a power feed. With smaller drilling machines, a
hand lever is used and the feed depends on the
operator, who increases or decreases the force on
the lever according to the size of the drill and the
drilling conditions.
Some common drill faults
Some common drill faults are shown in Table 3.1.
Cutting lubricants
Lubricants are used on drills, taps, dies and other
cutting tools. These prevent wear and overheating and
help to produce a smooth finish.
Soluble oil is diluted with water and is suitable for
use on most materials. Machine tools have a coolant
pump which directs soluble oil onto the cutting tool.
This is a lubricant and also a coolant.
In automotive workshops, holes in mild steel are


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part one introduction to motor vehicles

table 3.1 Drill faults
FAULT

CAUSES

Broken drill

Work not rigid; excessive
feed on small drill

Wearing or chipping of
cutting lip

Speed too fast; material
hard; lack of lubricant

Hole too large

Cutting lips of unequal
length

Only one lip cutting

Unequal cutting angles

Rough finish on hole

Lack of lubricant; dull
cutting edge

Drill will not cut

Requires sharpening;
no lip clearance

figure 3.41

usually drilled dry and engine oil is used when cutting
threads with taps and dies.
Reamers
Reamers have a number of cutting edges. They are
turned by hand with a tap wrench and are used for
finishing holes to an accurate size. The three main
types are parallel reamers, tapered reamers and
expanding reamers.
1. Parallel reamers. These reamers (Figure 3.41(a))
are made to a fixed size. They have a number of
spiral flutes with cutting edges. After drilling a
suitable hole, a fixed-size reamer is wound steadily
through the hole to remove a small amount of
metal. This gives the hole a smooth finish and an
accurate size. Each reamer is made for one particular size, and the hole is finished in one
operation of the reamer.
2. Tapered reamers. Tapered reamers are used to
ream holes so that tapered pins or other tapered
parts can be fitted. Two different tapered reamers
are shown in Figure 3.41. The reamer Figure
3.41(b) is used for finishing a hole with a Morse
taper and Figure 3.41(c) is used for reaming a hole
for a tapered pin.

3. Expanding reamers. These have a number of
straight cutting blades. They are available in
different sizes and each reamer can be expanded
within its particular range. They have adjusting nuts
at each end of the blades which enable the blades to
be expanded.

Hand reamers
(a) parallel reamer (b) Morse taper reamer
(c) taper pinhole reamer DIS

When fitting a pin to a bronze bush, for
example, a number of cuts can be made, each
slightly larger than the previous one. Checking the
size of the hole with the pin after each cut ensures
an accurate fit.
■ The curved flutes of a reamer have a better cutting
action than straight flutes, which have a tendency
to chatter and produce an irregular finish.
Drilling machines
Portable electric drills are used for most workshop
jobs. They may be single-speed or variable-speed.
Single-speed drills run at a fixed speed, usually around
1850 rpm. Variable-speed drills allow the operator to
adjust the speed to suit the particular job or type of
material. A fast speed is selected for smaller drill sizes,
and a slower speed for the larger sizes.
Bench drills have a cast iron base which is bolted to
the bench top. A vertical column supports the electric
motor and drill head at the top of the machine. The

column has an adjustable work table, which can be
moved up and down the column to suit various work
heights.
The drilling speed can be adjusted by selecting
different gears or, in some cases, by changing the drive
belt on stepped pulleys. The feed is applied by means
of a hand lever.

Tools for threading
In the workshop, threads are cut by taps and dies. A set
of tools consists of a stock and dies and also a tap
wrench and taps (Figure 3.42).
Taps
Taps are used to cut internal threads. A square end on
the shank of the tap enables it to be held and turned by
a tap wrench. The tap wrench has adjustable jaws
which are tightened onto the tap to hold it securely.


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chapter three tools and their use

47

when threads have to be cut right to the bottom of
the hole.
To tap a thread in a hole
1. Select a taper tap of the correct size and fit it into
the tap wrench.
2. Enter the end of the tap into the hole and turn with
an even downward pressure until a thread starts to
cut.
3. Use a try square from the face of the work to the
shank of the tap to check that the tap is entering the
hole squarely. Check at two places, 90° apart.

figure 3.42

Stocks and dies
(a) a set of dies and taps (b) stock and die
(c) T-shaped tap wrench (d) die with adjustable guide DIS

The set of stocks and dies shown in Figure 3.42(a)
has one type of tap wrench, while Figure 3.42(c)
shows a T-shaped tap wrench that is used for smaller
diameter taps and for working in awkward places.
There are three taps in a set. These are known as
taper, intermediate or second, and plug or bottoming.
These are shown in Figure 3.43:
1. Taper. A taper tap has the end tapered for about six
threads to allow the tap to start in the hole. It is
used for all work that is thin enough in section to
permit the tap to pass right through to cut a full

thread. It is also used as a first operation in a blind
hole in thick-section material.
2. Intermediate. An intermediate or second tap has
less taper and is used as a second operation in blind
holes to thread closer to the bottom of the hole.
3. Plug. A plug or bottoming tap has virtually no
taper. It is used for the third and final operation

figure 3.43

Hand taps

4. Proceed to cut the thread, but frequently back off
the tap to break the chip and prevent the thread
from being torn. This will also prevent the tap from
jamming.
5. Keep the tap lubricated to obtain a clean thread.
When tapping threads in soft metal such as
aluminium, or if the tap becomes hard to turn, remove
the tap from the hole and clean out the flutes to prevent
it from jamming.
■ Taps are fairly brittle and can be broken if
excessive force is applied.
Tapping size
The size of the hole required for a thread is known as
its tapping size. This is the minor diameter of the
thread, and the drill used would be the next standard
size above this diameter.
There are tables of tapping sizes which show the
drill size for various threads, but a quick workshop

method of finding a suitable drill is to use a nut as a
gauge and select a drill that will not quite pass through
the nut. This drill will leave sufficient metal for a
thread to be cut.
Stock and dies
Dies are used for cutting external threads. They are
held in a stock with a handle to enable the die to be
turned. The die has flutes which form the cutting edges
of the teeth and also allow chips to escape. Button-type
dies are shown in Figure 3.44.
The first two or three threads of the leading edge of
the die are tapered to allow it to be started. The
opposite side of the die has a lead on one thread only
which allows the thread to be cut close to the head of
the bolt.
The stock or the die has a guide with a hole of the


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part one introduction to motor vehicles

figure 3.44

Button dies

same diameter as the rod or bolt being threaded. This
guides the die so that the thread is cut parallel to the
rod or shank of the bolt.
Die nuts (not illustrated) are similar to other dies,
but they are hexagonal in shape and are turned with a
spanner. They are useful for cleaning or restoring
damaged threads, particularly where there is
insufficient room to use a normal stock and die.
To thread a rod
1. Grind or file a taper on the end of the rod to allow
the die to start.
2. With the die in the stock, place it over the end of
the rod. If the guide is adjustable, set it to the size
of the rod.
3. Turn the stock, applying a firm downward pressure
to start the thread. Once two or three threads are
cut, the die will screw itself down the rod.
4. Back the die off a little, about each half-turn or so,
to break the chip. This allows free cutting and
prevents the thread from becoming rough and torn.
5. Keep the die and the rod lubricated while threading.
Tools for removing broken bolts
Screw extractors are used to remove bolts that are
broken below the surface (Figure 3.45(a)).
The first step in using an extractor is to centre
punch the end of the bolt and then drill a hole of the

correct size for the extractor. The hole must be as close
to the centre of the bolt as possible.
The extractor is tapered and has spiral flutes with
sharp edges which form a coarse left-hand thread. It
can be turned with a tap wrench or spanner as
shown.
When the extractor is placed in the drilled hole in
the broken bolt and turned, it screws itself down into
the hole. The sharp edges of the flutes bite into the bolt
so that it can be turned with the extractor and screwed
out of its threaded hole.
There are other workshop methods that can
sometimes be used as shown in Figure 3.45(b). If part

figure 3.45

Removing a broken bolt
(a) with an extractor (b) other workshop
methods

of the bolt is above the surface and the thread is free, it
might be possible to turn it with a pair of pliers. Flats
can be filed so that it can be turned with a spanner, or a
slot cut with a hacksaw so that a screwdriver can be
used.
Depending on the location, and if the break is flush
with the surface, a spot-welded washer or nut could be
used. If the bolt is large enough, it can be tapped on
alternate sides with a hammer and a sharp punch. Tap
on one side and then the other until the bolt loosens.

■ Where the thread is damaged, thread inserts can be
fitted to restore the threaded hole.

Tools and materials for
grinding and abrading
Grinding wheels mounted on bench or pedestal
grinders are used for general grinding jobs and for
sharpening drills, punches and chisels. When fitted
with a wire-wheel brush, a grinder can be used for
cleaning.
Grinding wheels and stones are used on valverefacing machines and for valve-seat grinding. This
equipment is used during cylinder-head reconditioning.
Abrasive stones, or oilstones, are used for honing,
sharpening and smoothing. Abrasive-coated discs and
sheets are used during automotive body and paint
repair work.
Grinding wheels
Grinding wheels are made in a wide range of shapes
and sizes, some of which are shown in Figure 3.46.
The wheel Figure 3.46(a) is a plain wheel of the type
used on bench and pedestal grinders. Grinding


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chapter three tools and their use

figure 3.46

Shapes of grinding wheels
(a) plain (b) bevel (c) and (d) cupped

49

DIS

is performed on the edge of the wheel. The wheel
Figure 3.46(b) is shaped for special work. Wheels
Figure 3.46(c) and (d) are cupped to provide a grinding
face on the side of the wheel.
In addition to the size and shape, grinding wheels
are made with different abrasives, different grain sizes
and different types of bonding material.
1. Abrasive. Aluminium oxide is used for general
grinding, and silicon carbide is used for special
tasks.
2. Grain size. The grain size of the abrasive ranges
from coarse through to very fine.
3. Grade. This is considered in terms of hardness,
from soft to hard.
4. Bond. The bond holds the grains of the wheel
together. The amount, type and strength of the
bond material will determine the hardness of the
wheel.

An enlarged section of a grinding wheel is shown in
Figure 3.47. Illustration Figure 3.47(a) is a relatively
soft-grade wheel, where the grains of abrasive (the
grey areas) are held together by a light bond (black
areas). The white areas are small pores which are
necessary for chip clearance.
The structure of a harder wheel, which has the same
grain size but a heavier and stronger bond, is shown in
Figure 3.47(b).
■ A soft-grade wheel will wear away more quickly
than a hard one, but will not clog as easily.
Replacing a grinding wheel
When a new wheel is to be fitted to a grinder, a wheel
similar to the old one should be used. Check to see
whether any printed markings are visible on the old
wheel that can be used for identification.

figure 3.47

Structure of grinding wheels

DIS

Before mounting a new grinding wheel, it should be
inspected for cracks. It should ring if held lightly and
tapped.
The mounting spindle and flanges should be cleaned
so that the wheel fits easily. A clean blotter disc is fitted
on each side between the wheel and the flanges.
Tighten the nut to hold the wheel firmly, then

replace guards and adjust the work rests so that they
are close to the wheel. Start the wheel, allow it to reach
its full speed, and run for a minute or two. Stop the
wheel and reinspect before using it.
Grinding a tool
To grind a small tool, such as a punch, chisel or
screwdriver, the tool should be used against the edge
of the wheel. The correct and incorrect methods are
shown in Figure 3.48. The grinder should be fitted
with clear shields, although these are not shown in the
illustration. Safety glasses should always be worn
while grinding.
The tool should be supported on the tool rest with
the point upwards against the edge of the wheel and
should be moved slowly across the wheel so that the
full width of the wheel is used. Flat articles are held
flat on the tool rest.
When grinding, do not apply too much pressure
to the work, or hold the tool against the wheel too
long without cooling it in water. Grinding generates
heat and this will quickly affect the temper of small
tools.


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part one introduction to motor vehicles

Grinding wheels can be dressed when the grinding
edge becomes worn or grooved. A special wheeldressing tool is used across the edge of the wheel.
Abrasive is removed until the grinding edge is true.
Diamond dressers are used for some special wheels.
The diamond is harder than the abrasive of the
grinding wheel.
Abrasive stones

figure 3.48

Grinding a tool
(a) correct method of holding the tool against
the wheel (b) incorrect method that could jam the tool
between the rest and the wheel

A sharpening stone for general use has a fine grain on
one side and a coarse grain on the other, as shown in
Figure 3.49(a). The coarse side is used to sharpen blunt
tools and the fine side is used for touching-up and final
sharpening. With the stone placed flat on the bench, a
few drops of oil are applied and the tool to be sharpened is moved back and forth over on the stone. The
full surface should be used to ensure the stone wears
evenly.
Slip stones (Figure 3.49(b)) are tapered and often

have rounded edges. Small burrs can be removed from
the surface of a machined part by stoning them off
with a slip stone.
Other abrasive stones are used for honing engine
cylinders. During engine reconditioning, the cylinder
bores are finished by using a rotary hone which has a
number of abrasive stones or blades.

■ Overheating will be shown by discolouration of the
metal being ground, particularly the points of drills
and the ends of punches and screwdrivers.
Safety with grinders
Observe the following safety rules when using
grinders:
1. Wear goggles or a shield.
2. Adjust the safety shields on the machine.
3. Check that the work rest is correctly adjusted
close to the wheel.

figure 3.49

Abrasive stones

DIS

4. Keep the wheel nuts tight.
5. Be observant for wheel damage.

Sheet abrasives and discs

6. Allow the wheel to reach full speed before use.

These types of abrasive (Figure 3.50) are available in
various grains and grades for use by hand or with
sanding or grinding tools. They range from coarse
emery paper to fine wet-and-dry paper. Some sheets
have a fabric backing while others have a paper
backing. Some papers are resistant to oil and water,
while others are not.

7. Stand to the side of the wheel if possible.
8. Do not overload the wheel by using excessive
force on the work.
9. Hold small objects with pliers, not by hand.
10. For heavy grinding, wear leather gloves.


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chapter three tools and their use

51

pressure gauge

(do not exceed limit)
note: use a suitable
shield or guard
operating handle

figure 3.50

oil tank

Abrasive sheet and discs

cable drum handle

Tools for pulling and pushing

keep ram length
as short as possible

Many parts, such as ballraces, collars and gears, are a
tight fit on their shafts and force is needed to remove
and replace them. Pullers and presses are used for this
purpose.

release load from
table adjusting
cables
support work
firmly and squarely
all table support
bars properly

located

Pullers
Three designs of pullers are shown in Figure 3.51. The
large puller in Figure 3.51(a) is arranged as an external
puller; that is, the legs or claws fit over the outside of the
part being pulled. The puller in Figure 3.51(b) is of similar
design, but with three legs. Puller Figure 3.51(c) is a
small, universal type. The legs of most pullers of these
designs can be reversed so that the claws on the ends of
the legs can be used internally as well as externally.

figure 3.51

Three designs of pullers

firmly bolted
to floor

figure 3.52

Using a hydraulic press – note that a suitable
guard or shield must be used with this press

When removing or installing a bearing on a shaft
using a puller or press, care must be taken to make sure
the force is applied between the inner race of the
bearing and shaft. Damage to the ball or roller will
occur if not applied correctly (Figure 3.53).

DIS

Presses
Mechanical presses, or arbour presses, are often used
instead of a puller where the component is removed from
the vehicle. Hydraulic presses are also used. These can
apply much greater force than a mechanical press or
puller.
To remove a bearing from a shaft by means of a
press, the bearing must be suitably supported on the
bed of the press so that it will not be damaged. Force
is then applied to the end of the shaft by the ram of
the press so the shaft can be pressed from the bearing.
Larger presses have a bed that can be raised or
lowered to accommodate articles of different sizes.

figure 3.53

The up ≠ arrows indicate where the bearing or
housing should be supported and the down Ø
arrows indicate where force should be applied


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part one introduction to motor vehicles

Special service tools
Each workshop manual provides information on
special tools that are designed for servicing particular
parts of the vehicle. Many of the tools are essential,
while others make it easier to do certain jobs on the
vehicle. In some instances, a universal puller or other
general item of workshop equipment can be used as a
substitute for a special tool.
Special tools can include pullers, drivers, installers,
guides, gauges, adaptors, adjusters and spring
compressors. Special tools are designed for use on
parts of the engine, transmission, suspension, steering,
brakes and many other components. Some examples of
special tools are shown in Figure 3.54.

3.

Why is a torque wrench used?

4.

What are the graduations on a torque wrench?

5.

What is an angular torque wrench?

6.

Why is the shape of the tip of a screwdriver
important?

7.

How would you select the correct screwdriver
for the job?

8.

Name three types of pliers and state a use for
each one.

9.

Name other tools that are used for holding or
gripping.

10.

Where are circlip pliers used?

11.

Name the various types of hammers.

12.

What is a drift?

13.

What are some of the common tools that are
used for cutting and forming metals?

14.

What is a centre punch?

15.

How would you dress a chisel?

16.

What are soft jaws?

17.

What is a single-cut file?

18.

What is cross-filing?

19.

What is draw-filing?

20.

How would you replace a blade in a hacksaw?

21.

Why are hacksaw blades made with differentsized teeth?

Technical terms

22.

Name the parts of a twist drill.

Offset, speed brace, across the flats, Unified,
hexagonal, double-hexagonal, torque, torque
wrench, angular torque wrench, soft jaws, Phillips
head, torx bit, pein, centre punch, starting punch,
drift, pitch (of teeth), cold chisel, wad punch,
roughing, cross-filing, draw filing, parallel shank,
speed, rpm, feed, portable, pilot hole, taper, Morse
taper, reamer, thread, modification, brittle, tap,
tapping size, die, extractor, grinding, abrasive, grain,
grade, temper, puller, press, service tools.

23.

What is meant by drill speed?

24.

How would you control drill feed?

25.

Note some drill faults and their causes.

26.

Name the three types of thread taps.

27.

What is a die?

28.

Consider how you would make a thread on a
piece of round steel.

29.

What is a screw extractor used for?

30.

What is a reamer?

31.

How would you grind a punch?

32.

Name the sizes of some common spanners, or
wrenches.

What safety precautions would you observe
when using a grinder?

33.

What is meant by a hard or soft grinding wheel?

What is an Allen wrench?

34.

What tools are used for pushing and pulling?

ball joint remover

guide

figure 3.54

coil spring compressor

steering-wheel
puller

bush driver

bearing
installer

Examples of special service tools

Review questions
1.

2.