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

Automotive Mechanics (Volume I)(Part 1, chapter3) Tools and their use Tools and their use 33 Tools for turning 34 Tools for holding and gripping 38 Tools for hammering and driving 39 Tools for cutting and forming 41 Tools for drilling and reaming 44 Tools for threading 46 Tools and materials for grinding and abrading 48 Tools for pulling and pushing 51 Special service tools 51 Technical terms 51 Review questions 51

Tools and their use

Chapter 3

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

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,

hammer-ing, cutthammer-ing, formhammer-ing, drillhammer-ing, grindhammer-ing, threadhammer-ing,

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, adjust-able 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 3.1 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 3.2 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 3.3 Ring spanners DIS

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

one-twelfth 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.

Socket accessories

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

( 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.

figure 3.4 Socket spanners DIS

figure 3.5 Socket handles and accessories DIS

figure 3.6 Special ring spanners DIS

figure 3.7 Use of adjustable spanner

Spanner sizes

Spanners are marked with the size of the nut or head

of the bolt on which they will be used This is the

Adjustable spanners

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.

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.

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.

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).

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.

figure 3.8 Spanner size – ‘A’ is the dimension across the

flats of the nut or bolt head

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

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.

Screwdrivers

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

figure 3.11 Angular torque wrench and socket spanner

pointer

degree plate

square socket

square drive

socket spanner

figure 3.12 An Allen screw and wrench

figure 3.13 Pipe wrenches DIS

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

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.

■ 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.

Torx bit

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.

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.

Tools for holding and gripping

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.

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.

figure 3.15 Screwdriver blades

(a) correctly ground (b) badly ground

figure 3.16 A torx bit for use with special bolt heads

hexagonal head flutes

figure 3.17 Two types of wheel brace

(a) tool-kit wheel brace (b) cross wheel brace

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.

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.

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.

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

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.

figure 3.19 Circlip pliers for external and internal

circlips DIS

figure 3.20 T Type es s o off p plliie er rs s a and tto ongs s

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

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

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.

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.

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.

figure 3.22 Clamps

(a) G-clamps (b) toolmakers clamp (c) hand

vice DIS

figure 3.23 The wrong and right ways to grip and use a

hammer

figure 3.24 Various types of hammers DIS

figure 3.25 Hammers with rubber and plastic heads

rubber hammer

plastic-tip hammer

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.

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

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

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 3.26 A centre punch and a range of pin punches

DIS

figure 3.27 Punches

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

the pin figure 3.28 Hacksaws DIS

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.

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 3.30 Types of cold chisels

figure 3.31 Cold chisels

(a) chisel requiring grinding (b) chisel after

grinding