LV02 foundation skills issue 1

LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1LV02 kỹ năng nền tảng vấn đề 1

Student Workbook

LV02 Foundation Skills

kap all covers 6/9/03 9:48 am Page 3

Student Workbook for Technical Certificates

Light Vehicle Maintenance and Repair

MODULE LV02 FOUNDATION SKILLS

Contents

Page … Page

Hand spanners, wrenches and Micrometer 23

Special sockets 5 Reading the micrometer 25

Hacksaw 8

Drills and drilling 9 Principles of Electricity: 30

Screw cutting 10 What is electricity? 30

Taps 10 The principles of electricity 31

Thread sizes 11 Conductors, semi-conductors and

Special service tools 12 Insulators 33

Progress check 1 13 How is flow of electricity measured? 33

Bolts and screws 51

Nuts and washers 53

Chemical thread locking 54

Progress check 7 55

Common Hand Tools

Air tools

A technician’s hand tools are as important to him as surgical instruments are

to a surgeon Without a good selection and perhaps more importantly, a high level of skill with respect to use and application, a technician cannot do the job Let us study a few of the more common hand tools that a technician is likely to require

Air ratchet

This tool lends itself particularly well to the removal of screws used in large quantities to secure components, such as those found holding a sump It is rare for such a tool to have any sort of torque regulation, so its use for refitting screws should be avoiding or carried out with a great deal of care – final

tightening should always be carried out with a torque wrench (studied later in this chapter)

Air gun

This does a similar job to the air ratchet but is generally capable of generating far more torque The torque output is normally adjustable through a knurled knob Unlike the air ratchet, air guns are designed for use with two hands and are produced with ⅜ inch, ½ inch and even 1 inch drives The latter is a pretty fearsome piece of kit and deserves some respect!

Air drill

This can be used to carry out typical drilling operations and is powered by air pressure like the other tools described here One key benefit of all air tools is safety From a safety aspect, they win hands down when compared to

electrical power tools The reason is clear when you consider that a vehicle technician often has to work in damp conditions

Hand spanners, wrenches and sockets

Spanners (or wrenches) are the technician’s ‘bread and butter’ tools These tools facilitate the removal of the nuts and bolts that secure components to a vehicle to enable repair or access

There are many different types of spanners available, designed for a multitude

of tasks but four of the most commonly used are shown above

Ring spanners provide more contact between the tool and the nut or bolt and their use is far less likely to result in damage or ‘rounding off’ Open-ended spanners should be used only when a ring spanner is not suitable

Most types of spanners have cranked ends to help location with the flats of a nut or bolt, where access is tight and the nut or bolt can only be moved by a small amount each time

Sockets are also designed for aiding the removal of nuts and bolts Unlike a spanner, they cannot be used on their own but have to be used in conjunction with a secondary tool such as a ratchet or perhaps a knuckle bar or speed brace

The ‘spanner priority’ should be observed when deciding which tool is best suited for the removal of a nut or bolt Other factors permitting, the choice should be in the following order – socket, ring spanner, open-ended, and finally an adjustable spanner if all else has failed! Sockets are available in varying sizes and shapes such as shallow, standard, deep, six point and twelve point Strengthened sockets (impact sockets) must always be used with air tools Standard sockets do not have sufficient strength and could shatter

Special sockets

Standard hexagon head bolts are rarely found in areas where there is little room to spare and where large amounts of torque are required It is more common to find multi-spline, Torx or Allen key female-headed bolts (discussed later in this workbook)

Torque wrenches

A torque wrench is designed to facilitate the accurate and consistent

tightening of nuts and bolts They can also be used for carrying out

adjustments where a given amount of resistance to rotation is required on an assembly (pre-load) Each use requires a different type of torque wrench - a

‘click type’ for tightening nuts and bolts and a ‘torque meter’ for pre-load

adjustment The picture above shows a click type in use It is bad practice to click the wrench several times when tightening a bolt One click is sufficient If more than one click is heard, the bolt could be over-tightened

Pliers and grips

Pliers can be used for a variety of tasks and there are many different types available Combination pliers are the most common and can be used to carry out any number of operations where increased grip and leverage are required Generally speaking, side cutters can do a large number of jobs adequately, but if there is a specific task in mind, it is wise to consider a specialist tool for the job (i.e electrical pliers for wire cutting and crimping connectors)

Electrical pliers provide a limited degree of protection to the user from an electric shock thanks to the use of insulation on the handles

Lockwire pliers are used for the application of lockwire This material is used

to secure nuts and bolts found on machinery subject to a great deal of

vibration - the wire prevents them shaking loose It is commonly found on military vehicles and aircraft

Files and filing

The file is a form of hand operated milling tool It can be used for shaping metal objects and dressing rough edges The body and heel are all cutting faces, whilst the tang is provided for the fitting of a handle All cutting portions are hardened and tempered, whereas the tang is usually left in a softened condition

Using the file

Round Flat triangle

Before using the file, ensure that the handle is secure by striking it lightly on a hard surface Apply the file to the work surface holding the handle with the master hand Guide the tool with the other Move the file tangentially to the work surface whilst applying light, even pressure The ability to file a surface flat will only develop with a great deal of practice! Work surface lines can be eliminated by rubbing chalk on the teeth of the file Regular use of chalk reduces the cutting depth and also reduces the likelihood of pinning (this is where swarf adheres to the file and scratches the work surface) It is also worth noting that a flat file is a rare thing indeed, you should also turn the file

Hacksaw

A technician’s role often requires the use of a hand cutting saw, such as a metal hacksaw It is commonly used to cut off rods, bolts and studs

The replaceable blades are commonly made of alloy steel This gives

excellent cutting properties but also provides a large amount of strength

should the blade be accidentally twisted

For most operations, a blade with 24 teeth per inch is ideal (this specification

is still quoted in imperial measurement only) It is important when replacing a blade to ensure that the cutting teeth face forward This ensures that the removal of metal occurs on the forward (and most powerful) stroke An arrow

on the blade is a fitting aid Whenever cutting material mounted in a vice, ensure that the orientation between the work piece, the vice and the saw is such that a slip cannot cause the vice or work piece to be ‘punched’ with the hand

Drills and drilling

Drills are used to form holes in a variety of operations such as number-plate fitting, mud flap fitting and sheared bolt removal There are many different types of drill, but the most commonly used example is the twist drill The flutes formed by the twist of the drill aid swarf clearance Most good quality twist drills are made from high speed steel (HSS) and have excellent wear

properties

Drilling, as an operation in engineering terms, is an exact science However,

as most drilling operations will be carried out by a technician using a hand drill (either pneumatic or electric), it should be noted that if an 8mm twist drill is used, the hole that results will often exceed this because of unavoidable movement during the drilling So, pick a small drill and work your way up! Always use a centre punch prior to drilling, to aid location of the twist drill centre - and to prevent ‘drift’

Screw cutting

Occasionally, a technician is called upon to create, or perhaps improve, a screw thread There are two types of screwing tools Those designed for making internal threads are known as screwing taps, while those for making external threads on cylindrical parts are known as screwing dies

Taps

Keep the tap straight

Will result in a drunken thread

Taps are designed for cleaning out or forming threads internally The tap consists of a threaded and fluted member, with a square end for mounting in a tap wrench

The taper tap has the last five or six threads ground away to ease passage of the tap into the drilled or prepared hole This tap should be screwed in as far

as it will go to form the bulk of the thread The second cut tap is then used to bring the thread out to the correct finished dimensions In general, a plug tap

is used for finishing a thread in a blind hole

When cutting a new thread, it is important that the hole is drilled to the correct diameter to receive this cut thread The required hole diameter is known as the tapping size Ensure selection of a suitable drill bit to form a hole with the correct tapping size Tapping hole tables are available These indicate the twist drill required for any size of thread and the most popular of these is marketed under the ‘Zeus’ brand

When cutting the thread, apply a little cutting lubricant to the tap For cutting threads in steel, normal engine oil is fine Use paraffin for aluminium alloys Ensure that the tap is perpendicular to the work surface (and remains this way) otherwise a ‘drunken thread’ will result Screw the tap in two or three revolutions followed by one full backwards revolution – this backwards

revolution detaches any cut swarf and clears the flutes Without a periodic reverse action, the thread will be very rough

With round split dies, a certain amount of adjustment is possible on the

formed thread size, using the three screws provided on the diestock These enable the split die diameter to be altered slightly The same technique

should be employed in the use of the die as that used with a tap (two to three rotations forward and then one back) The appropriate cutting lubricant

should also be used

Thread sizes

Metric thread sizes are available in either fine or coarse variants The

geometry of these threads are shown above It is the pitch that varies -

between metric fine and metric coarse Fine has a pitch of 1.25mm and

coarse a pitch of 1.5mm (dimension P above)

Special service tools

There are many types of special service tools What distinguishes them from general hand tools is their task specific design Tools such as gear pullers, ball joint splitters and press tools would be classified as special service tools

Progress check 1

Answer the following questions:

1 What is the correct name for this tool?

2 Put the following four tools in the correct order of preferred use:

• open jaw spanner

ne metre is divided into 100 equal parts called a centimetre

ach centimetre is divided into 10 equal parts called a millimetre

ach millimetre is divided into 100 equal parts and each is referred to

ecimally: 0.01mm (1 hundredth of a millimetre)

ach 0.01mm can be split down further into 10 equal parts and therefore each expressed: 0.001mm (1 thousandth of a millimetre).

0.01mm

1 hun dred th

0.001mm

1 t th0.001mm

1 t th

Area

Width

Height

Width Height

The area of a simple shape, such as a square or rectangle, is calculated by ultiplying its width (or length) by its height

ample, if the square above has a width of 10cm and a height of 10cm,

s area will be:

his is always the case regardless of the size of the circle, because if you

uare’ the radius – this

The ‘2’ in this formula indicates that we have to ‘sq

imply means multiply it by itself e.g

s

2 ‘squared’ would be:2 x 2 = 4

Think of volume as a three-dimensional surface area (area being two

dimensional) If we want to calculate the volume of a regular shape, we must first calculate the area of one end and then multiply this value by the length of the shape

Above is a picture of a cylinder If it is assumed that one end has a radius of 10cm, the surface area of one end will be:

Exercise

n learnt in a vehicle specific application The

iagram above shows a reciprocating piston engine Let us assume that the

e piston is 10cm

the volume through which the piston will sweep (the swept volume):

our answer:

nclude all working o

Let us use what has just bee

Pressure

hat is pressure?

ed

thorough understanding of the concept of pressure will aid understanding of

ove shows a battle tank and a soldier, both on boggy ground

he soldier will weigh, on average, about 90 kilograms and the battle tank

kg) So logic would suggest that of the two, the tank the most likely to sink However, as the tanks large mass (the force) is pread out over such a large surface area (its tracks), the ground pressure enerated is actually far less than that created by the soldier The soldier’s latively small body mass (the force) is concentrated over a very small

urface area – the soles of the boots The soldier sinks, the tank doesn’t

hy does a drawing pin go into a wall but not the thumb? The force present equal – there is as much ‘push’ on the thumb as there is on the wall, but the ressure on the wall is very high as the pushing force is concentrated over a

ny surface area – the point of the pin The large head on the drawing pin preads the pushing force over a relatively large surface area in contact with

e thumb, so the pressure exerted on the thumb is very small

he relationship between pressure, force and area can be expressed

sm all force

Tin y surface area

To the engineer, pressure is a term used to define how much force is exertagainst a specific area The combination of force acting over a surface area creates pressure

A worked example

ous diagram, the surface pressure produced by the tank

nd the soldier can be calculated:

• Surface area of tracks = 9m²

Pressure = 60,000kg divided by 9m² = 6666.66 kg/m² surface pressure

Pressure units

The unit of pressure that most people are familiar with is probably P.S.I This

is an abbreviation for pounds per square inch, so is most certainly an imperial nit Most people will know that on average, a light vehicle tyre will be inflated

t what is that in Bar? Or how about Pascals?

e is the Newton and the S.I unit of distance is the metre ressure, therefore, should be expressed in N/m² To help you identify with

ly 10 Newtons in each kilogram (9.81 to

be exact) So, N/m² of pressure is roughly a tenth of a kilogram acting over

a surface area of 1 square metre – not a huge amount

1 N/m² is referred to as 1 Pascal

1000 N/m² is therefore 1 kPa (kilo Pascal or 10,000 Pascals)

,000,000 N/m² is therefore 1MPa (Mega Pascal or 1,000,0000 Pascals)

1 Bar (100 kPa)

So, on average, a light vehicle tyre will be inflated to 200 kPa or 2 Bar!

(This is only an example to aid the understanding of pressure units Please refer to the exact tyre pressure specification for each vehicle.)

Pressure in liquids

ou can squeeze a large volume of gas into small space by pressurising it The outward push on the container created

pushes the ontainer walls equally, everywhere If this were not the case, the tyres on a

luids cannot be compressed (they actually can, but in the majority of vehicle

y a negligible amount) Like a gas, the pressure that is reated in the fluid pushes uniformly on its container and at 90 degrees to the

point

ue to this even pressure exertion Due to this property and the

nt at one end

f a car into piston movement at the other end (i.e a hydraulic braking

ystem) Hydraulics is the study of pressure in fluids

Gases are highly compressible Y

incompressibility of fluids, confined fluids when pressurised act as a

mechanical link and are capable of transferring piston moveme

o

s

Progress check 2

Answer the following questions:

1 How many millimetres

2 How many p.s.i is 20 kPa?

What is the unit of force?

are there in a metre?

3 What is the study of pressure in liquids referred to as?

4 What is the volume of the regular shape pictured below?

10cm

80mm

100mm 10cm

80mm

100mm

5

Measuring Equipment

nding of the units of measurement, we will tudy measuring equipment An ability to use measuring equipment

quipment will always fall into one of two groups – those capable of direct easurement and those that are capable only of giving a comparative value

ne dimension compared to another)

icrometer

he micrometer is a tool capable of direct measurement, to within

ternal, combination and depth micrometers

he principle of the micrometer can be seen in the above diagram If we have

nd we have a bolt screwed into it with a

ad evolution that the bolt completes will see it 5mm further to the left or to the right, dependent upon the direction of

tation The position of the ‘moving face’ of the bolt when compared to that

f a fixed face (the anvil) then becomes a measured dimension

Now that you have a good understa

an accuracy of 0.01mm (a micro-metre or one hundredth of a

il tre) There are many different types available such as ex

m

in

1 turn 0.5mm

T

a fixed nut (i.e it cannot rotate) a

hre pitch of 0.5mm, each full r

t

0

ro

o

Using the micrometer

It is vital that a micrometer

peration to ensure that when the spindle is screwed into full contact with the

ce of the anvil (using the ratchet stopper to prevent over tightening) the zero

ne on the thimble lines up perfectly with the datum line on the outer sleeve

he ratchet stopper should always be used when practicable – especially hen carrying out a series of comparative measurements where consistency

f application is important Any ‘zero errors’ can be rectified by rotating the uter sleeve with a C spanner

combination micrometer can be configured as a 0 to 25mm, 25 to 50mm, 50 75mm, 75 to 100mm, 100 to 125mm or a 125 to 150mm micrometer This is chieved using interchangeable anvils with different lengths Fitting the

econd longest anvil in the kit ensures that the gap between the measuring ces - when the micrometer is zeroed - is already 25mm, so the measuring nge would be 25 to 50mm Zeroing such a micrometer involves the use of istance pieces and any zero error in excess of about 0.03mm should be orrected initially through the adjustment of the collars at the anvil end of the ame Fine adjustment can then be carried out in the normal way with a C

Reading the micrometer

ith 50 equi-spaced graduations, so each

A shows a movement of one graduation faces is therefore 0.01mm

eading of 0.49mm The first graduation ble (0.5mm) but the graduation on the

hort of the 0.5mm point to

It can be seen that three whole visible – these represent whole bove the datum – 0.5mm

The thread pitch of the micrometer is 0.5mm Therefore, each full rotation of

the thimble increases the distance between the measuring faces by 0.5mm

The thimble is itself marked off w

C

single graduation is the equivalent of 0.01mm

The micrometer pictured in Figure

and the gap between the measuring

The micrometer in Figure B shows a r

above the horizontal datum line is visi

thimble reads 49 Therefore the micrometer is just s

the tune of one graduation – 0.49mm

Figure C shows a reading of 3.56mm

graduations below the datum line are

millimetres – and one graduation is visible a

Therefore, the coarse reading is 3.5mm However it can be seen that the

thimble reading is 0.06mm so this has to be added to the coarse reading:

• 3mm + (above the line)

• 0.5mm + (below the line)

• 0.06mm (on the thimble)

• Reading – 3.56mm

t can be

a second choice to that of the micrometer

d depths, all from a single scale

ero line on the vernier scale lines up perfectly ith the zero line on the main scale At this point, the jaws are touching

g the zero’ of the calliper, there is no method for djusting it

ach graduation on the vernier scale is worth 0.02mm The general principle

er is to read off whole millimetres, by counting off on the main scale using the zero mark on the vernier as the datum If the zero mark does not align perfectly with a whole millimetre mark, then find a pair of

graduations on the main and vernier scale that do Read off the difference from there

Vernier calliper

A vernier calliper is capable of measurement to within 0.02mm I

seen from this that it should be

Reading such a calliper is also, to a large degree, a matter of personal

interpretation This is another factor that contributes to its inaccuracy The major advantage of this tool is its adaptability It can be used for measuring outside diameters, inside diameters an

It can be seen from that the z

dial gauge or dial test indicator (DTI) is only capable of direct measurement

a few situations - mostly, they provide the user with comparative values hey can, however, be used in conjunction with other measurement

he dial above measures down to 0.01mm The bezel is marked off with one

undred graduations Therefore, each full sweep of the needle represents

mm plunger movement It can be seen that from the zero point, the

ad adopted the position represented by the red line, by moving

om the zero point in a clockwise direction, then plunger movement would

Dial gauge

A

in

T

equipment - such as a micrometer - to arrive at a direct measurement valu

A dial gauge is a device that turns lateral movement (straight) into the rotarsweep of a needle on a dial face, using a clockwork mechanism Throu

knowledge of the internal gearing, the manufacturer of the instrument can mark off the dial with graduations These represent a given amount of

movement of the plunger

anti-fr

have been 0.6mm (plunger in) However, if the needle had adopted that position by moving in an anti-clockwise direction, the plunger would have moved only 0.4mm (plunger out)

es

Feeler gauges are designed to measure the

come as a set, and each blade has a differe

can be ascertained by offering up the f

blades), until they fit the gap with the correct amount of resistance The

Feeler gaug

size of a gap or clearance They

nt thickness The size of a gap eeler gauges, (or even a combination of biggest problem with the accuracy of this tool is ‘getting a feel’ for how much resistance represents the correctly selected blade or combination of blades

A very good way to get familiar with this procedure is to set a micrometer to the thickness of a blade and to place that blade between the measuring faces

of the micrometer Move the blade backwards and forwards, until there is aclear understanding of how much pull is required

ck 3

nswer the follo

What is part A called?

What does DTI stand for?