They can be checked against working standards of measurement ‑ precisely made steel gauge blocks. Note that steel expands when the temperature rises and contracts when, the temperature fails. Thus measuring accurately is affected by changes in temperature.

When using screw pitch gauges, radius gauges or form type gauges, you should, where possible, hold the work piece and gauge in front of a light background. This allows you to clearly see any differences between the work piece and the gauge.

Basic Measuring Tools:

Using Standard Gauges

Screw Pitch Gauges

A screw pitch gauge is used to find the pitch of a thread. It is a series of thin marked blades which have different pitched teeth. Thread pitch gauges also come in the standard thread forms of metric, Whitworth, BSF, UNF, and UNC which allows both the pitch of the thread to be gauged and the form or shape of the thread, to be checked. Each set of screw pitch gauges has the thread form stamped on it.

Measuring Thread Pitch

Before using a screw pitch gauge, you should measure the approximate pitch of the thread with a rule. To do this for metric threads:

• put the rule on the thread parallel to the thread axis.

• line up a major division on the rule with the top or crest of the thread.

• count the number of crests to another major division, usually 20 - 30 mm.

• divide the length between the major divisions by the number of crest counted.

• the answer is the pitch of the thread.

• then choose the gauge closest to this pitch for the first try.

For imperial threads the method is similar except that the pitch is given as threads per inch (TPI) and so the number of crests in one inch are counted.

Screw pitch gauge U

se of screw pitch gauges

Radius Gauges

They are used to check internal and external radii. The gauges are a set of thin blades with a convex (external) and concave (internal) radius of the same size on each blade. The size of the radius is marked on each blade. When the radius on the gauge less than 90 degrees, the gauge is called a fillet gauge.

Using a radius gauge

Radius gauges

Feeler Gauges

They are used to measure or set clearances between mating parts or for measuring the width of small slots or grooves. In a metric set of feeler gauges the thickness ranges from 0.05 mm to approximately 1 mm in varying steps. The gauges can be built up to produce the thickness required. When using the thinner gauges care should be taken to pull the gauge through a gap rather than push, as by pushing, the gauge will tend to bend and wrinkle or possibly if a sideway movement is used the gauge will tear.

Checking clearances with feeler gauges

Feeler gauge

Thickness Gauges

A thickness gauge is used to measure the thickness of material using a plunger and dial. These gauges are used to measure sheet materials such as paper, plastics, cardboard, leather and sheet metals. They must be handled carefully and kept away from dirt and moisture and returned to their storage box immediately after use.

Form or Profile Gauges

These gauges are used to compare shapes. They can be a fixed shape or profile, or an adjustable type as shown. With the adjustable type, the gauge is set to the master shape as shown, and then compared to the shape being checked.

Adjustable profile gauge

Text Box:

Callipers

Callipers are used to transfer measurement:

They consist of two legs that are firmly

screwed or fixed together so that they will

maintain the position in which they are set.

Some types of callipers have a spring‑loaded

joint and an adjusting screw to position the legs.

The accurate transfer of measurement when

using callipers, depends upon the feel of

the callipers against the work. This 'feel' is

the light pressure of the callipers as they pass

over the work.

Skill is needed to obtain the correct 'feel' of

callipers.

Using outside callipers

Text Box:

Outside callipers are used:

• To measure outside diameters

• To measure external dimensions

• To check whether external surfaces are parallel.

Check the diameter of work using outside callipers

and a rule as follows:

• Open the jaws of the callipers until they pass

clearly over the diameter to be measured. The

work must be stationary when taking readings.

• Gently tap the back of one leg of the callipers

against a solid part of the work to slightly close

the jaws.

• Try the new setting over the work.

Keep the callipers at right angles to the axis of the work.

Continue to adjust the callipers and check the setting

until you feel the jaws just bear against the work.

When the adjustment is correct, the calliper jaws touch

so lightly that the weight of the callipers is sufficient

to make them pass over the diameter of the work.

When you have adjusted the callipers to have the correct

'feet' against the work, proceed as follows:

• Place a graduated steel rule flat on a machined or

flat smooth surface.‑

• Hold the callipers so that one jaw is against the end

of the rule. Make sure that the calliper jaws lie on a

line parallel with the edge of the rule.

• Read off the measurement at the other jaw.

Text Box: This measurement will be the diameter of the work.

Practise obtaining the correct 'feel' of the calliper jaws against the work by adjusting the callipers over various diameters. Try setting the callipers on flat parallel material.

Using inside callipers

Inside callipers are used:

• To measure internal diameters

• To measure internal dimensions

• To check whether internal faces are parallel.

Check the inside diameter of a hole using spring inside

callipers and micrometer as follows:

• Hold the callipers lightly in your right hand with your thumb and first finger on the adjusting nut. Support the weight of the callipers with the middle or third finger.

• Place one leg of the callipers just inside and at the bottom of the hole.

• Open the callipers' legs by the adjusting screw until the other leg touches against the top of the hole.

• Rock the callipers slightly on the lower leg and adjust the screw until you obtain the 'feel' of the callipers in the hole.

Try moving the top leg at right angles to the other

movement. This will ensure that 'feel' is being obtained

directly opposite the bottom leg.

Graduated Measuring Tools

Steel Rules

Steel rules measure lengths to a degree of accuracy of approximately ± 0.5 mm. As a common instrument, it is often misused. The end of the rule must be maintained with its edge square and sharp. A common error is caused by not sighting across the rule at right angles to the graduations. This is called parallax error.

Measuring Tapes

Like any other measuring device care is essential for reliable operation. The blade or tape must be cleaned as it is withdrawn into the housing otherwise it may be difficult to withdraw or if the tape is dirty when it is withdrawn the markings on the tape may be obliterated or damaged causing difficulty in reading.

Depth Gauge

It can be used to measure the depth of holes, slots, or the distance from an edge to another surface.

Vernier Callipers

Standard vernier callipers measure to within 0.05 mm (0.002 in) and 0.02 mm (0.001 in). Digital callipers are available with an accuracy up to 0.01 mm (0.0005 in).

They can be used to measure outside, inside and depth features. They must be stored in a clean, dry place preferably in the pouch or box in which they were originally bought. It is essential that the corners of the inside and outside jaws are protected against damage otherwise inaccurate readings will result.

Hold the vernier so that you are looking at the scale at an angle and in line with the graduated line. Look along rather than at the line. Move into a position where the light strikes from the back of the vernier scale at about the same angle as your line of sight.

Vernier callipers can be read from zero up to the length of the main scale, often 250 millimetres or more. They may also have provision for taking depth readings.

Reading a Vernier:

• Read the main scale to the left of the zero of the vernier in millimetres.

• Now look at the vernier scale below. Note which one of the vernier divisions is opposite a line on the main scale.

• Each of the lines on the vernier scale represents adivision that is 0.02 of a mm shorter than those of the main scale. Multiply the number of the line on the vernier scale by 0.02 and add the result to the reading

of the main scale.

The next sketch shows the reading on a vernier. There are 37 full divisions on the main scale to the left of the zero. This equals 37 millimetres.

The thirty‑third line on the vernier scale is opposite a line on the main scale giving:

33 x 0.02 = 0.66mm

Now add 0.66 mm to the main scale reading of 37 mm to give a total reading of 37.66 mm.

Certain metric verniers with the vernier scale 49 mm long have each fifth line of the vernier scale numbered from 1 to 10. As each division on the vernier scale represents 0.02 mm, then the fifth line representing 5 x 0.02 which equals 0.1 mm is marked number 1. The tenth line is marked 2, the fifteenth line marked 3, and so on to the end of the scale.

Read this type of scale as follows:

Text Box: • Read the main scale as before.

•

Read the numbered divisions of the vernier scale as tenths of a millimetre.

• Complete the reading by adding the extra 0.02 lines.

Example of a vernier settings:

The main scale reads 60 millimetres. The vernier shows the fifth line which represents 0.5 mm, plus 3 extra divisions which represent:

3 x 0.02 = 0.06 mm.

Total reading is 60

+ 0.5

+0.06

= 60.56 mm

Some metric verniers have their main scale divided into millimetres and half millimetres, with the vernier scale made 24.5 mm long and divided into 25 equal parts.

The length of each vernier division is therefore one twenty‑fifth of 24.5 mm which equals 0.98 of a mm.

The vernier scale divisions are again 0.02 of a mmshorter than the corresponding main scale millimetredivisions,

The last sketch shows the reading of a vernier reading to 0.02 of a millimetre. It has a vernier scale 24.5 mm long.

There are 37 major divisions on the main scale to the left of the zero, which equals 37 mm. There is also one half‑millimetre division which equals 0.5 mm.

37 + 0.5 = 37.5 mm

The eighth line on the vernier scale is opposite a line on the main scale. Multiply 8 by 0.02 which represents 0.16 and add this to the reading of the main scale.

Main scale 37.50

Vernier scale + 0.16

Total reading =37.66 mm

Exercise – Practice reading the Vernier as shown below:

Text Box:

Micrometers

Text Box: They enable veryaccurate measurements to be taken. Outside micrometers are used to measure:

• Outside diameters

• Thickness of material

• Lengths of parts.

They are available in various sized frames. All sizes, however, have a measuring range limited to the length of the thread on the spindle.The range is 0 to 25 millimetres.

The principal parts of a micrometer are:

Frame

Anvils

Spindle and Thread

Sleeve or Barrel

Thimble.

A knurled collar or a small lever on the frame can be used to lock the spindle in the barrel.

After the anvils have been set against the work being measured, tighten the spindle lock. This prevents any movement of the spindle while you are reading the micrometer scale.

Remember to loosen the clamp before attempting to take any further readings.

Text Box: Principles of a micrometer:

The principle of a micrometer that reads to 0.01 of a millimetre is explained below.

Hold a 0‑25 mm outside micrometer by the frame between thumb and first finger of your left hand. Keep the graduations on the sleeve towards you.

Loosen the spindle lock.

Use the finger and thumb of your right hand

on the knurled part of the thimble to screw it

anti‑clockwise. This moves the spindle to the

right and uncovers the graduations on the sleeve.

Look at the gap between the anvils. It is equal to the uncovered 'length of the datum line.

Look at the datum line on the sleeve. It is graduated into millimetres and half millimetres, from zero up to 25 mm, and each fifth millimetre is numbered.

Turn the thimble until zero is level with the datum line. Note the position of the graduation on the sleeve.

Turn the thimble one complete turn. The thimble will

move along one graduation of the sleeve scale. This

is because the pitch of the thread on the spindle is half a millimetre. Two turns of the thimble move the

spindle one millimetre.

Look at the graduations around the thimble.

There are 50 graduations and each fifth graduation

is numbered

Text Box:

Now wipe the face of the anvils with a piece of clean cloth. Screw the thimble inwards towards the frame until the anvils are touching.

• Close the anvils gently. Never apply force.

• Allow your fingers to slip on the knurled part of the thimble.

• Look at the scales. They should both read zero.

• Open the anvils by turning the thimble to uncover one division on the thimble scale.

The movement of the anvil = 1 of a complete turn. 50

50 of 0.5 mm = 0.01 mm

• Continue turning the thimble until the tenth line of the thimble is level with the datum line.

• Hold the micrometer up to the light. By carefully looking at the anvils you should be able to see a small gap. It is 0.1 of a millimetre.

• Continue turning until the fiftieth line of the thimble is level with the datum line.

The anvils will now be 0.5 of a millimetre apart.

The first graduation on the sleeve will now be visible.

Turn the thimble one more complete turn to open the anvils to 1 millimetre.

If you find that the micrometer does not read zero when the anvils are touching and you are sure that they are clean, the micrometer needs adjusting.

Text Box:

Reading a metric micrometer:

• Read on the barrel scale the number of

millimetres that are completely visible.

• Add any half millimetres that are completely visible.

• Note the number of the graduation on the

thimble scale that is level with the datum line.

• Add the thimble reading to the other reading.

The sketch shows a micrometer set to a reading.

There are 5 millimetres between the zero and the thimble. There is also one graduation of 0.5 of a millimetre. The twelfth fine of the thimble scale is level with the datum line.

The reading of the micrometer would be:

5.0 mm

+ 0.5 mm

+ 0.12 mm

= 5.62 mm

Text Box: Using outside micrometers:

Skill is needed to obtain accurate measurements when using a micrometer.

Excessive pressure during adjustment will:

• Give inaccurate readings

• Cause strain on the thread

• Distort the frame.

As you adjust the micrometer anvils against the work, you should feel a light pressure or resistance against the surface. Develop this 'feel' by constant practice, measuring articles of accurately known size.

Some micrometers have a spring‑loaded ratchet which will ensure constant adjusting pressure.

Accurate measurements can be made with the

assistance of the ratchet, provided the micrometer is kept square to the work.

Measure with an outside micrometer as follows:

Hold the outside micrometer in your right hand,

with the graduations on the main scale towards you.

Support the frame on the lower centre of your

palm. Use the little or third finger to hold the frame

to the palm.

Place the middle finger behind and supporting the

frame.

Keep the first finger and thumb free to adjust the

knurled thimble.

Text Box: Close the anvils until you feel them just touching the work.

Allow your finger and thumb to slip on the knurled thimble to obtain the correct pressure.

Move the work slightly between the anvils or pass the micrometer over the work by moving your wrist.

Make any further adjustment of the thimble until you obtain the right 'feel'.

When you are satisfied with the feel of the anvils against the

work, proceed as follows:

• Remove your fingers from the thimble.

• Turn the micrometer towards you.

• Read the measurement.

Sometimes‑ it may be more convenient to hold the

micrometer with both hands by:

• Supporting the frame between the fingers and thumb

of your left hand

• Using the thumb and finger of your right hand to adjust

the thimble.

Exercsie - Read the Micrometers 1. to 10. shown below:

Text Box:

Care During Use

When using any measuring instrument, whether it be a gauge or a graduated instrument, the points listed should be carefully followed.

1 Never drop the instrument

2 When not in use leave the instrument in its case or on a clean rag, never on a hard steel bench

3 Never allow dirt, filings, cutting oils or any other foreign substances to come in contact with the instrument

4 Do not put the instrument on top of or under other instruments or tools

5 Never measure moving objects.

6 Ensure that the instrument is correctly set to zero before use

Storage Procedures

Correct storage procedures will lead to long and reliable service from any gauge or graduated measuring device. The following points should be observed when storing these instruments.

1 Clean the instrument thoroughly during and after use

2 Lightly oil or wrap the instrument in oiled paper

3 Store the instrument in is own case or in a box where it is protected from outside damage

4 Store the instrument in a dry place away from corrosive chemicals or solvents

Marking Out And Making A Component

Hammers

Hammers impart a force either directly or indirectly through another tool such as a chisel or punch to a workpiece. The most common hammers used are:

Soft Faced Hammers

Hammers with copper, rawhide or plastic are suitable for panel beating, shaping thin metal sheet and assembling finished parts to give a light force fit. Soft Headed Hammers (rubber) are suitable for positioning work where you do not want the hammer to rebound

Claw Hammers

Claw hammers with jaws at the reverse of their heads are suitable for nailing, striking all metal chisels and extracting nails.

Ball Pein Hammers

The ball pein or engineers hammer is the most common of the hammers used by mechanical trades persons. It has a convex face for striking tools such as punches, chisels, centre punches or the workpiece itself. The opposite end of the hammer head is a hemispherical ball pein used to dome or shape the shanks of rivets or to stretch the surface of a metal workpiece to straighten it.

The weight of the hammer must be chosen to suit the job. For example, where a heavy blow is required in a confined space, a heavy hammer should be used because its large mass will be able to deliver a large amount of energy to the workpiece or tool without being made to move fast.

The hammer handle should be in good condition and of a size that is comfortable to use.

It should be square with the head and fit tightly into the head. The hammer should not be used if either the head or the handle is damaged, because a burred or chipped head will cause injury if it hits the hand holding a tool such as a chisel, while a split handle may injure the hand holding the hammer.

Cross Pein Hammers

A special purpose engineering hammer that comes in a variety of masses up to 450 g (1 lb). Larger sizes are called sledge hammers and are suitable for driving a large shafts out of a pullies etc. The cross pein hammer is also used in confined spaces or for straightening or stretching when the metal is peined at right angles to the direction of stretch or curve.

Text Box:

Ball pein hammer

Cross pein hammer

Cutting Tools

Chisels

Cold chisels are forged from tool steel. Only the point of the chisel is hardened and tempered, the body being left soft. If the head of the chisel were hard it would chip as the result of the hammer blows.

The point of the chisel if formed into a cutting edge. This cutting edge is similar in nature to other cutting edges in that it requires the edge to be sharp.

Cold chisel

Correct cutting angle and position

Clearance or relief angle is shown. The cutting action of a chisel is somewhat different from that of a lathe tool, in that the clearance or relief angle is determined by the operator in the manner that the chisel is held in relation to the work piece. The size of the cutting angle should be about 70° for soft steel; when chipping harder metals the angle should be a little larger and for softer metals it can be ground smaller.

Chisels selection

Flat chisel are used to cut out of thin metal sheet. Diamond‑point and round‑nose chisel chisels can draw‑over a drill point that has begun to cut off centre. Diamond‑points also can chip out a weld that has cracked. Cross‑cut chisels can cut out the length of a narrow groove.

Care Of Chisels

Because chisels are subjected to continual impact loads, they are likely to show signs of metal fatigue or cracking after a period of use. In this condition they will become dangerous as small pieces of metal or splinters may fly off at high speed causing injury to the operator or to people standing nearby.

A new chisel should be used lightly until it is proved to be sound and only then should heavy blows be used on it.

A major problem associated with the use of chisels is the mushrooming of the head due to the fact that the head is soft and the constant hammering on the head distorts the metal as shown in. The head of the chisel should be kept in good repair by keeping the chamfer ground cleanly.

When resharpening a chisel care must be taken not to raise the temperature of the cutting edge above the temper temperature. Ideally when grinding a chisel cutting edge no colour should show on the surface but a very light straw colour would not reduce the hardness of the chisel edge.

Mushrooming is a dangerous condition

Text Box:

Six common chisel shapes

Files

Files are used to reduce or smooth the surfaces of the work. They are made from a high grade tool steel and pass through a process which includes forging, dressing of the surfaces by filing or grinding, forming of the teeth and heat treatment.

They are very hard and brittle and must not be used as levers, packing or wedges, nor should they be hit, because of the danger of shattering.

Outline views of a flat file

Convexity Of A File

Most files are made with their faces slightly “bellied” or convex, along the length.

The belly on a file

Slight warping is likely to occur during heat treatment and if files were cut perfectly flat, one side might be concave after heat treatment and be useless for filling flat.

If perfectly flat in the natural state, the pressure applied at the ends when filing would cause the file to bend and become concave on the cutting face while the operation was in progress.

The convexity of a file restricts the number of teeth which contact the work surface and thus reduces the load required to make the teeth penetrate the surface of the work.

The convexity will make a small allowance for the tendency to rock the file as it is used, and will thus make it easier to file flat.

Single Cut And Double Cut Files

The teeth of a file are formed in one of two ways in that they maybe “single” cut or “double” cut.

Single cut Double cut

The teeth of a single cut file extend from one edge of the file to the other without interruption. This broad, continuous tooth has a scraping action on the work surface and produces a good finish. The teeth of a double cut file are pointed and are able to bite more deeply into the work surface than the single cut file. They are able to cut quickly and do not clog (that is, become “pinned”) as easily as the single cut file. Most files are double cut.

Coarseness Of Cut

For the more commonly used files, the coarseness of cut is defined by name: rough, coarse, bastard, second cut, smooth and dead smooth. The most commonly used grades of cut are bastard, second cut and smooth. Figure 10 shows a comparison between these grades.

Bastard

Second Cut

Smooth

These terms, expressing the grade of cut of a file, are related to the size of the file in that a 300 mm second cut file is coarser than a 150 mm second cut file. The cut of very small files is classified by numbers. Nos 00, 0, 1, 2, 3. 4, 5, 6, 7 and 8. No. 00 is the coarsest. The most commonly used grades are Nos 0, 2, 4 and 6.

File Shapes And Types

Files are made in a wide range of shapes and types, some for general purpose use and others for special applications.

The Common File Shapes

Flat File:

Tapered in width and thickness, double cut, used for general purpose filing.

The flat file

Hand File:

Tapered in thickness only, sides parallel, no teeth on one side (i.e. one safe edge), double cut, same application as the flat file.

The hand file.

Square File:

Tapered on all sides, double cut, used for roughing down flat surfaces and enlarging square holes.

The square file

Round File:

Tapered, single or double cut, used for enlarging round or curved holes.

The round file

Half Round File:

Tapered, double cut except that those finer than bastard cut are single cut on the convex surface. It is widely used because of its combination of flat with curved surface and ability to reach into restricted openings.

The half round file

Three Square File:

Tapered, double cut, triangular cross sectional shape, used for filing sharp internal angles.

The three square file

Warding File:

Tapered on edges only, double cut, its thin section allows it to reach into narrow slots.

The warding file

The Size Of A File

The size of a file is specified by its length as measured from the heel to the point.

Classification Of A File

In general, files are classified by length, name or type and grade of cut.

For example: 300 mm flat second-cut file

200 mm half round bastard cut file.

Care Of Files

Storage

Files should be stored in a clean, dry place to avoid the possibility of rusting or having oil or other liquids come in contact with the cutting face.

The cutting edges of a file must be protected from damage by keeping files separated from other files or hard metals. That is, they should not be placed or thrown across each other on the work bench or stored by bundling them together in a draw.

It is good practice to clean files before storage so that they are ready for use when needed.

File Safety

Never use a file as a lever. Files are very hard and brittle and are likely to snap if used in this way.

Never use a file without a correctly fitting handle as the tang of the file is likely to pierce your hand as you push forward on the working stroke.

A poorly fitted handle can come off the tang on the return stroke in which case you may loose balance and fall over or suddenly find yourself pushing forward towards an exposed tang.

Never use a file with a split or splintered handle.

Removal Of Scale

Scale on black steel is hard and abrasive and will quickly spoil the sharpness of the cutting edges. The cutting edges can be protected by removing scale from the surface of the workpiece with the edge of the file or with an old file or in some cases with a hammer and chisel.

Order Of Use

It is good practice, where possible, for the first use of a file to be on softer materials such as brass, bronze or grey cast iron, and after it has lost its initial sharpness to use it on steel.

Pinning

Particles of metal are likely to wedge in between the teeth of a file. This is called “pinning”. These particles of metal may stand higher than the teeth and can cause scratches in the work surface. Pinning can be minimised by rubbing chalk into the face of the file.

Cleaning Files

Files can be brushed and cleaned with a small stiff brush known as a “file card”

Hacksaws

Hacksaw blades are made from alloy tool-steels and high-speed steel. The blades are available in two types. These are:

All hard:

The “all hard” type blade is hardened throughout and is more rigid than the second type. It is recommended where the workpiece is securely supported and an accurate cut is required.

Flexible:

The flexible blade is hardened on the cutting edge only, the remaining portion of the blade being in a toughened state.

The blades are unbreakable in normal use and are preferred where the workpiece is not securely held or where the operator is unable to control the movement of the saw properly.

Pitch Of The Teeth:

Hacksaw blades are made with a range of tooth pitches to enable them to cope with a variety of job situations.

Material to be cut

Hard -

Alloy & High Carbon Steel

Medium Hard -

Mild, Medium Carbon Steel

Up to 3mm

32 TPI

3mm - 6mm

24 TPI

6mm - 13mm

24 TPI

18 TPI

13mm - 25mm

18 TPI

14 TPI

The Hacksaw Frame

The hacksaw frame is either fixed in length to take a certain length of blade or adjustable and able to take a range of blade lengths. The frame shown below is an adjustable frame.

Blade holding piece may be set in any of four positions

All hacksaw frames have a means of tensioning the blade because it is most important that the blade be properly secured.

If the blade is not tight enough the downwards cutting load will unduly bend it and it will likely break. It will also be difficult to guide the blade, during the cut, because of its lack of stiffness. Over tightening of the blade will also lead to blade breakage.

The blade will be sufficiently tight when it cannot be easily deflected by either the fingers or the cutting force.

When the hacksaw is not in use the tension should be let off the blade and frame by loosening the wing nut by one or two turns.

Hacksaws, like any other tool require regular maintenance. The tension piece and wing nut should be cleaned and lightly oiled from time to time and the handle should be checked for any burrs, sharp edges or splinters or cracks if it is a wooden handle.

Snips

Tin snips or snips are used to cut sheet metal. They come in a variety of styles for different cutting operations.

The two main types of snips are universal snips and aviation snips.

Universal snips Aviation snips

Both these types of snips may be obtained in right hand or left hand cut, and in straight or offset stylet. Th figure below shows the correct side the waste should be on when using right hand or left hand snips.

Safety With Snips

When cutting sheet metal, sharp edges are formed that can cut a hand or finger very easily. Therefore take extra care when cutting with snips, that your hand or fingers are well clear of the sharp metal edges.

Some snips have handles that come together when the snip is closed. Ensure that the palm of your hand will not be nipped by the handles when they come together.

Care Of Snips

Only use snips for the material they were designed to cut. Never use snips to cut wire as the cutting edge will be nicked and further clean cuts will be impossible to make.

Keep the cutting edges in good condition by lightly honing with an abrasive stone or by regrinding on a bench grinder.

The pivot point should be kept lightly oiled and in good adjustment so that the faces of the blades slide together firmly with minimum clearance.

Cutters And Strippers

There is a wide variety of cutters which cut round metals up to approximately 13 mm in diameter, depending on the tool capabilities.

Cutters used for cutting round metals above 3 mm diameter are generally known as bolt cutters whereas cutters that are used to cut round metal below 3 mm diameter are side cutters. A range of cutters and strippers is shown in the figure below.

Strippers are used to remove (strip) the plastic insulation off electrical and other coated wiring.

Hand Taps

Hand taps are used to produce internal threads by hand.

Hand taps are made in sets of three and comprise a “taper” tap, an “intermediate” tap and a “plug” tap.

The driving end of the tap is formed into a square to take a tap wrench.

Taper Plug Bottoming

A set of hand taps

The tap wrench is adjustable to take a limited range of tap sizes; it is also double ended in that the driving force, from the operator’s hands, is applied to each end of the wrench. By applying a driving force to each end of the wrench, (i.e., by using a proper tap wrench and not a spanner) there is less chance of breaking the tap due to bending it, because the force applied by one hand balances the other. It is important to use the correct size wrench for a tap, because a large wrench will multiply the force of the hands up to a level where the tap may be overloaded and broken.

Tap wrench

The Tapping Hole Size

Before a hole can be tapped it must be drilled the correct size to allow sufficient metal in the hole for the thread to be formed by the tap. f too much metal is left in the hole it will make tapping difficult and increase the possibility of breaking the tap.

If not enough metal is left in the hole, the tapped thread will be weak and possibly be stripped when a bolt is tightened into it.

The correct size drill to use is best found by referring to tapping size drill tables and using the recommended size drill for the material and application.

A typical tapping size drill table is shown.

TAPPING DRILL TABLE

(Reproduced from the “Ajax Handbook” with the permission of the Ajax Fastener Co.)

To ease the strain of a tap the minor diameter of a nut thread should be produced by the recommended tapping drill

Dies

Three types of die are in common use:

• The divided disc type which is made in two separate pieces. The two halves are attached to a guide plate which secures then and guides the die squarely onto the shaft to be threaded.

The guide plate and dies are held in an elastic stock.

• The button die, which is a disc in one piece, split on one side, is adjusted by means of a screw.

• The die nut which is either hexagonal or square in shape, is operated by a spanner and is used only for cleaning a thread or for removing burrs. An exception is the pipe threading die nut which is used for thread cutting.

Scrapers

Scrapers are used to remove small inaccuracies in surfaces produced by the ordinary methods of machining such as turning, milling, shaping or planing, or by filing.

The scraper is, therefore, used where curved or flat surfaces must be fitted accurately to each other.

The scraper is sometimes used to give ornamental effects to machine parts even when they are not finished to a high degree of accuracy. Srapers can be made from tool steels or sintered carbide.Tool steels are more commonly used than is sintered carbide, because of their cheapness and ease of sharpening.

Scrapers are made in various forms, as follows:

The Flat Scraper

Flat scrapers are used for scraping flat surfaces. They range in size from about 150 mm to 300 mm or more in length. The tang should be fitted with a file handle.

The flat scraper

The Half Round Scraper

The half round scraper is designed for scraping curved surfaces such as bearings. It is made in a range of sizes.

As with other scrapers it should be fitted with a file handle.

The half round scraper

The Three Square Scraper

These scrapers are also used on curved surfaces, but usually small in diameter. The three square scraper is also used for removing burrs from the mouth of a hole while the job is in the lathe.

Three square scrapers can be easily made from a three square file.

The three square scraper

The Bull-Nose Scraper

Bull-nose scrapers are used for scraping large brasses or half bearings. This scraper, being round on the cutting edge end, can be used with the same action as the flat scraper and can also be used with the same action as the half round scraper. It is very useful as a roughing down scraper, but needs to be followed by a half round scraper for fine fitting.

The bull-nose scraper

Marking Out Tools

Engineer’s Squares

Engineer’s squares are available in a variety of sizes. They are accurately made with an angle of 90°. Squares are used to mark out right angles and to check internal and external right angles.

Adjustable blade square Engineers trysquare

Combination Set

A combination set is made up of a steel rule, a square head, a protractor head and a centre square head. The steel rule is used in whichever head is needed for the job at hand. The square head will also give accurate 45° angles.

Centre Squares

Centre squares are used to mark out the centre of round material.

Centring a disc

Protractor

A protractor is used for marking and testing angles. They can be ordinary protractors as shown, part of a combination set or vernier protractors.

Scriber

Scribers are made from hardened steel. They are used to mark clear, sharp lines into metal surfaces. A rule, square or other surface is used as a guide for the scriber.

Double edge engineer’s scriber Pocket scriber

Dividers

Dividers have hard points. They are used to scribe clear and sharp circles and arcs into metal surfaces.

Spring dividers Winged dividers

Trammels

Trammels are used to mark out large diameter circles.

Hermaphrodite Callipers (Jenny, Odd Leg Callipers)

Hermaphrodite callipers have a hardened point which is used to scribe lines in metal surfaces. They are used to find the centre of round material or to mark a line parallel to an edge.

Prick And Centre Punches

A prick punch has a smaller diameter point than a centre punch which is ground at an angle of 60º. It is used to lightly mark marking out lines so they don’t disappear during other work. A centre punch is used to make a large indent for starting a drill and is ground at an angle of 90º. A pin punch is used to drive out loosened taper pins. Taper drift punches will drive out tight parallel pins.

Centre punch Prick punch Pin punches

Care Of Hand Tools

Safety

For any job, select and use the hand tool that will allow the job to be done safely and within a reasonable amount of time.

Always use the hand tool for the job it was designed for. Example, do not use tin snips to cut wire instead of side cutters simply because they may be close at hand.

Good job planning will ensure you have the correct tools on hand when required during the job.

Always use the tools safely and wear appropriate safety clothing and personal protective equipment.

Storage

To prevent damage to hand tools during storage, manufacturer’s recommendations should be followed. These usually include:

• protection of cutting edges and points by covering with a soft or plastic covering

• cleaning before storage

• application of a rust inhibitor where appropriate

• store in individual compartments/sleeves to prevent damage through contact with other tools

• release of tension where needed.

Where a number of people share hand tools, the tools should always be returned to the same place in good working order.

Faulty Tool Procedures

Faulty tools should be taken out of service immediately and repaired or replaced at the earliest possible time.

Never put a tool back into store or in a toolbox if it requires repair.

Where a fault is obvious or suspected, a qualified person should determine whether the tool can be repaired or needs to be replaced.

Repairs should only be done by someone with the necessary skills and/or training. Replacement tools should be obtained through normal workplace procedures.

Faulty tools should be tagged or marked so they are not used while faulty.

Faulty tools that cannot be repaired should be made inoperative to prevent accidental use.

Routine Maintenance

Routine maintenance of hand tools involves keeping the tools in good working condition. This may involve:

• sharpening

• removal of burrs or unwanted sharp edges/corners

• cleaning

• lubricating moving parts

• applying rust preventative

• checking and adjusting settings.

Dismantling And Assembling

Safety Reminders

• Always wear safety glasses, safety boots, hair protection and suitable clothing while in the workshop

• Lift the right way

• Do not use a machine fitted with a Danger Tag

• Know where the First Aid station is

• No running or horseplay

• Use ear muffs of plugs for protection against noise.

Special Rules For This Section

• Make sure you select the right type and size of spanner for each job

• Make sure the machine is held securely

• Check the drawing before removing any components to avoid being injured by a flying spring etc.

Mechanical Tools

Spanners

When adjusting nuts and bolts, the correct size and type should always be used. This greatly reduces the risk of damage to the nut or bolt and the spanner. The risk

of personal injury due to a spanner slipping is also minimised

by pulling towards the user.The size is determined by the nut

or bolt it fits. The distance across the flats of a nut or bolt

varies both with the size and the thread system. There are three

thread systems to consider:

Text Box: Metric Standard system

Spanners for metric bolts are marked with the size across the jaw opening, followed by the abbreviation "mm,.e.g. 15 mm.

British system

The nominal size of the bolt is used to identify the spanner.

A spanner to fit a British Standard bolt with a half‑inch nominal diameter would be marked 1/2 BS.

A spanner to fit a heavy series British Standard Whitworth bolt with a seven‑sixteenths of an inch nominal diameter

would be marked 7/16 W.

As the heavy W series will fit one size above a BS series the 7/16 W spanner will also a fit a 1/2 BS bolt.

British Association spanners are made with the size numbers followed by the letters BA.

Unified Standard system

Spanners for Unified bolts are marked:

with a number based on the decimal equivalent of the nominal, factional size across the flats of the hexagon before the sign

AF, e.g. 50 AF; or

with the fractional size across the flats before the sign AF,

e.g. 1/2 AF. As American nuts and bolts now conform to the

Unified Standard, the SAE series spanners are interchangeable

with the Unified series.

Open ended spanners have their neads offset at 15º to enable full rotation of a square nut when the shank can move no more than 45ºof arc. Such a spanner will give full rotation of a hexagonal nut when the shank is limited to 30º of arc.

Hexagonal nuts ring spanners (six sided) require 60º before they can be re-engaged.

Double hexagonal ring spanners (twelve sided) require 30º before they can be re-engaged.

Single End Spanner

Single end spanners come in a wide range of sizes from very small (5 mm) to very large (75 mm) or more. They are normally of a heavier construction than other spanners in the larger sizes so that nuts and bolts may be tightened or loosened by hitting the spanner with a hammer.

Single-end spanner

Podge Spanner

The podge spanner is used on bridge and construction work where holes drilled in steel girders have to be aligned so that rivets or bolts may be put through the holes. The tapered point is used to enter the two holes and lever them into alignment.

Podge spanner

Open Ended Spanners

Open ended spanners are available in ranges of imperial and metric sizes. They generally have different sizes on each end. Open ended spanners are usually the easiest to slip over a hexagon but can slip off.

Ring Spanners

Ring spanners are the least likely to slip and/or damage the hexagon they are trying to undo. They also have different sizes on each end. Ring spanners are offset to allow clearance for the operators knuckles. Because of the offset there is a slight tendency for the spanner to roll off the top of the nut when force is applied.

Combination Open End And Ring Spanners

Combination spanners have the same size at both ends. They give the advantages of both the open end and ring spanners in a single tool. Because the spanner is straight with no offset, force is applied directly in line with the nut or bolt head and there is no tendency for a correctly fitting spanner to roll off the top of the nut or bolt head.

Tube Or Box Spanners

Tube or box spanners are made from tubular steel formed at both ends into a hexagon. Because of their thin wall design, they can be used in places where there is little clearance between the nut or bolt head and the clearance hole in which it is located. A spanner can be used on one end to apply force or a bar can be used through the hole in the body of the spanner to apply the force to tighten or loosen the nut.

Socket Spanners

Socket spanners are the fastest way of undoing or doing up a bolt or nut. They are used with a variety of accessories. They are available as 6 point (single hexagon) or 12 point (double hexagon). The 12 point socket enables faster positioning of the socket. Some sockets are available in extended length bodies specifically designed to remove spark plugs from motor engines.

Socket Accessories

Torque Wrench

Torque wrenches are used with sockets to tighten screwed parts to a specified tension.

Adjustable Spanner

The adjustable wrench, commonly called a “shifter” should only be used when a correct sized spanner is not available. Although it is convenient because it can be adjusted, the shifter is more likely to slip and cause damage to both the nut and the operator.

Special Purpose Spanners

There is a variety of special purpose spanners that are readily available. Some of those spanners are shown below.

Half moon spanner Crows foot spanner

“C” spanner Tube nut spanner

Hook spanner

Screw Drivers

Flat screw drivers tips should be a little smaller than the length of the bottom of the screw slot. Slightly hollow‑grinding them allows the tip to clear the top edge of the slot while reducing the amount of downward pressure required when turning the blade. It also brings the faces of the tip almost parallel to the sides of the slot

Screw drivers are available with a straight head, a Phillips head or Posi-drive head. The latter two are unlikely to slip from clean matching recesses but require more downward pressure than flat tip screwdrivers.

Some screwdrivers have insulated blades and handles for use in electrical work.

Straight screwdrivers Phillips screwdriver

Special Drivers

Off set screw drivers are used when space around the screw prevents a standard Phillips or flat stubby screw driver from being used.

Impact Drivers

Impact drivers are used to tighten or loosen screws or nuts by using a hammer blow to the end of the impact driver. The hammer blow keeps the driver bit firmly on the head of the screw whilst a helical slide inside the body turns the driver. Most impact drivers can accept sockets as well as a full range of driver bits.

Impact screwdriver

Hexagon Wrenches

Hexagon wrenches, also known as “Allen” keys, are used to drive screws with a recessed hexagon. The keys are available as an “L” shape “Tee” wrench or as hexagon screwdrivers and usually are supplied in a fold up set in sizes from 1.5 mm to 10 mm. The full range of sizes is from 0.71 mm to 27 mm.

Pliers

There is a wide variety of pliers available. The most commonly used type is combination pliers. They are used to hold flat and round material and to cut small diameter material such as copper wire and shearing split cotter pins.

Other types include:

• long nose - straight and bent

• slip joint or multi-grips

• circlip - internal and external

• locking pliers or vice grips

Pipe Wrenches

Designed to grip pipes or cylindrical couplings, pipe wrenches are available as Stillson pattern, foot print and chain types.

Riveting Tools

Used to install pop rivets, there is a variety of light and heavy duty riveting tools.

Care Of Hand Tools

• use the right tool for the job

• use the tools in a safe way

• store the tools to prevent damage

• return tools to their right place

• repair or mark faulty tools.

• use the tool for the purpose it was designed for; i.e. never use files or screwdrivers as levers

• lubricate tools as necessary and always store tools lightly oiled or wrapped in oiled paper to prevent corrosion