lv02 - foundation skills - issue 1

8/4/2019 LV02 - Foundation Skills - Issue 1

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Student Workbook

LV02

Foundation

Skills

LV02/SWB

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


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Student Workbook for Technical Certificates

Light Vehicle Maintenance and Repair

MODULE LV02

FOUNDATION SKILLS

ContentsPage .. Page

Common Hand Tools: 3 Pressure units 20Air tools 3 Pressure in liquids 21Air ratchet 3 Progress check 2 22Air gun 3Air drill 4 Measuring Equipment: 23

Hand spanners, wrenches and Micrometer 23sockets 4 Using the micrometer 24Special sockets 5 Reading the micrometer 25Torque wrenches 6 Vernier calliper 26Pliers and grips 6 Dial gauge 27Files and filing 7 Feeler gauge 28Using the file 7 Progress check 3 29Hacksaw 8Drills and drilling 9 Principles of Electricity: 30Screw cutting 10 What is electricity? 30Taps 10 The principles of electricity 31Dies 11 Positively charged body 32Thread sizes 11 Conductors, semi-conductors and

Special service tools 12 Insulators 33Progress check 1 13 How is flow of electricity measured? 33

Voltage 34Measurement: 14 Electrical resistance 35Length 14 Ohms Law 36Area 15 Transposing Ohms Law 37Volume 16 Watts 38Exercise 17 Progress check 4 39Pressure: 18What is pressure? 18 (Cont.)

- 1 -Copyright Automotive Skills Limited 2003 LV02: Foundation Skills Issue 1All Rights Reserved


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Page .. Page

Electrical Measurement: 40 Inspection and Fault-findingMultimeters 40 Techniques: 56Unit multipliers 41 Diagnosis techniques 56Multimeter use 41 Driver interrogation 56Progress check 5 43 Gathering information 57Types of circuit 44 Visual inspection 57Series 44 Formulating your diagnostic strategy 58Parallel 44 Progress check 8 60Series parallel 45Progress check 6 46Electrical wiring diagrams 47Japanese manufacturers 47

European manufacturers 50

Locking and Securing Devices: 51Bolts and screws 51Nuts and washers 53Chemical thread locking 54Progress check 7 55



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Common Hand Tools

Air tools

A technicians hand tools are as important to him as surgical instruments areto a surgeon. Without a good selection and perhaps more importantly, a highlevel of skill with respect to use and application, a technician cannot do thejob. Let us study a few of the more common hand tools that a technician islikely to require.

Air ratchet

This tool lends itself particularly well to the removal of screws used in largequantities to secure components, such as those found holding a sump. It israre for such a tool to have any sort of torque regulation, so its use for refittingscrews should be avoiding or carried out with a great deal of care finaltightening should always be carried out with a torque wrench (studied later inthis chapter).

Air gun

This does a similar job to the air ratchet but is generally capable of generatingfar more torque. The torque output is normally adjustable through a knurledknob. Unlike the air ratchet, air guns are designed for use with two hands andare produced with inch, inch and even 1 inch drives. The latter is a prettyfearsome piece of kit and deserves some respect!



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Air drill

This can be used to carry out typical drilling operations and is powered by airpressure 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 toelectrical power tools. The reason is clear when you consider that a vehicletechnician often has to work in damp conditions.

Hand spanners, wrenches and sockets

Spanners (or wrenches) are the technicians bread and butter tools. Thesetools facilitate the removal of the nuts and bolts that secure components to avehicle to enable repair or access.

There are many different types of spanners available, designed for a multitudeof tasks but four of the most commonly used are shown above.

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



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

Sockets are also designed for aiding the removal of nuts and bolts. Unlike aspanner, they cannot be used on their own but have to be used in conjunctionwith a secondary tool such as a ratchet or perhaps a knuckle bar or speedbrace.

The spanner priority should be observed when deciding which tool is bestsuited for the removal of a nut or bolt. Other factors permitting, the choiceshould be in the following order socket, ring spanner, open-ended, andfinally an adjustable spanner if all else has failed! Sockets are available in

varying sizes and shapes such as shallow, standard, deep, six point andtwelve point. Strengthened sockets (impact sockets) must always be usedwith air tools. Standard sockets do not have sufficient strength and couldshatter.

Special sockets

Standard hexagon head bolts are rarely found in areas where there is littleroom to spare and where large amounts of torque are required. It is morecommon to find multi-spline, Torx or Allen key female-headed bolts (discussedlater in this workbook).



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Torque wrenches

A torque wrench is designed to facilitate the accurate and consistenttightening of nuts and bolts. They can also be used for carrying outadjustments where a given amount of resistance to rotation is required on an

assembly (pre-load). Each use requires a different type of torque wrench - aclick type for tightening nuts and bolts and a torque meter for pre-loadadjustment. The picture above shows a click type in use. It is bad practice toclick the wrench several times when tightening a bolt. One click is sufficient. Ifmore 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 typesavailable. Combination pliers are the most common and can be used to carryout 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 forthe job (i.e. electrical pliers for wire cutting and crimping connectors).Electrical pliers provide a limited degree of protection to the user from anelectric shock thanks to the use of insulation on the handles.

Lockwire pliers are used for the application of lockwire. This material is usedto secure nuts and bolts found on machinery subject to a great deal of

vibration - the wire prevents them shaking loose. It is commonly found onmilitary vehicles and aircraft.



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Files and filing

The file is a form of hand operated milling tool. It can be used for shapingmetal objects and dressing rough edges. The body and heel are all cuttingfaces, whilst the tang is provided for the fitting of a handle. All cutting portionsare hardened and tempered, whereas the tang is usually left in a softenedcondition.

Using the file

Flat Square

RoundFlat triangle

Before using the file, ensure that the handle is secure by striking it lightly on ahard surface. Apply the file to the work surface holding the handle with themaster hand. Guide the tool with the other. Move the file tangentially to thework surface whilst applying light, even pressure. The ability to file a surfaceflat will only develop with a great deal of practice! Work surface lines can beeliminated by rubbing chalk on the teeth of the file. Regular use of chalkreduces the cutting depth and also reduces the likelihood of pinning (this iswhere 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 fileregularly during use.



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Hacksaw

A technicians role often requires the use of a hand cutting saw, such as ametal hacksaw. It is commonly used to cut off rods, bolts and studs.

The replaceable blades are commonly made of alloy steel. This givesexcellent cutting properties but also provides a large amount of strengthshould the blade be accidentally twisted.

For most operations, a blade with 24 teeth per inch is ideal (this specificationis still quoted in imperial measurement only). It is important when replacing ablade to ensure that the cutting teeth face forward. This ensures that theremoval of metal occurs on the forward (and most powerful) stroke. An arrowon 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 issuch that a slip cannot cause the vice or work piece to be punched with thehand.



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Drills and drilling

Drills are used to form holes in a variety of operations such as number-platefitting, mud flap fitting and sheared bolt removal. There are many differenttypes of drill, but the most commonly used example is the twist drill The flutesformed by the twist of the drill aid swarf clearance. Most good quality twistdrills are made from high speed steel (HSS) and have excellent wearproperties.

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 isused, the hole that results will often exceed this because of unavoidablemovement 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 drillcentre - and to prevent drift.



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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 formaking internal threads are known as screwing taps, while those for makingexternal threads on cylindrical parts are known as screwing dies.

Taps

Keep the tapstraight

Will result in adrunken thread

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

The taper tap has the last five or six threads ground away to ease passage ofthe tap into the drilled or prepared hole. This tap should be screwed in as faras it will go to form the bulk of the thread. The second cut tap is then used tobring the thread out to the correct finished dimensions. In general, a plug tapis used for finishing a thread in a blind hole.

When cutting a new thread, it is important that the hole is drilled to the correctdiameter 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 thecorrect tapping size. Tapping hole tables are available. These indicate thetwist drill required for any size of thread and the most popular of these ismarketed under the Zeus brand.

When cutting the thread, apply a little cutting lubricant to the tap. For cuttingthreads in steel, normal engine oil is fine. Use paraffin for aluminium alloys.Ensure that the tap is perpendicular to the work surface (and remains thisway) otherwise a drunken thread will result. Screw the tap in two or threerevolutions followed by one full backwards revolution this backwardsrevolution detaches any cut swarf and clears the flutes. Without a periodic

reverse action, the thread will be very rough.



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Dies

Dies are designed to cut external threads. The cylindrical material that is toreceive the thread should be finished to an appropriate diameter (as with taps)in order to receive the appropriate die. Again, size tables should beconsulted.

With round split dies, a certain amount of adjustment is possible on theformed thread size, using the three screws provided on the diestock. Theseenable the split die diameter to be altered slightly. The same techniqueshould be employed in the use of the die as that used with a tap (two to threerotations forward and then one back). The appropriate cutting lubricantshould also be used.

Thread sizes

Metric thread sizes are available in either fine or coarse variants. Thegeometry 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).



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Special service tools

There are many types of special service tools. What distinguishes them fromgeneral 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.



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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

socket

adjustable spanner

ring spanner.

3. What is the correct name for a tool that is designed to cut internalthreads?

4. What is the difference between a high impact socket and a normal

socket?

5. After you have used a torque wrench how should the wrench bestored?



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Measurement

Length

he S.I (Systme Internationale) unit of length is the metre. This unit of lengthtoo large for the majority of automotive applications, so the metre is dividedto smaller parts:

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 toecimally: 0.01mm (1 hundredth of a millimetre).

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

1 metre

1 cm

1hundredth

1 cm1 cm

1hundredth

1 mm

1tenth

1 mm1 mm

1tenth

0.01mm

1hundredth

0.01mm0.01mm

1hundredth

0.001mm1t

enth

0.001mm0.001mm1t

enth

1 hundrethof millimetre

1 thousanthOf millimetre

1 hundrethof millimetre

1 thousanthOf millimetre

TisinOEEd

Eis



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rr

Let us assume that this circle has a radius of 10cm. The area is calculated in

he formula is:

his means that 314.2 square centimetres would fit exactly inside the circle.

Volume

Think of volume as a three-dimensional surface area (area being twodimensional). 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 ofthe shape.

Above is a picture of a cylinder. If it is assumed that one end has a radius of10cm, the surface area of one end will be:

3.142 x 10 x 10 = 314.2cm

If it is now assumed that its length is 10cm, the volume of the cylinder will be:

314.2cm x 10 = 3142cm

the following way:

TTherefore:

3.142 x 10 x 10 = 314.2cm

T

LengthLength



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Exercise

n learnt in a vehicle specific application. Theiagram aboveshows 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 beeddiameter of the bore is 9 cm (assume a perfect circle) and that the stroke ofthCalculate

Y(I ut)



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Pressure

hat is pressure?

ed

thorough understanding of the concept of pressure will aid understanding of

oveshows 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 tankthe most likely to sink. However, as the tanks large mass (the force) ispread out over such a large surface area (its tracks), the ground pressureenerated is actually far less than that created by the soldier. The soldierslatively small body mass (the force) is concentrated over a very small

urface area the soles of the boots. The soldier sinks, the tank doesnt.

hy does a drawing pin go into a wall but not the thumb? The force presentequal 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 any 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 withe thumb, so the pressure exerted on the thumb is very small.

he relationship between pressure, force and area can be expressedathematically as follows:

his formula means that to calculate pressure, force is divided by area. It isssential that vehicle technicians understand this formula. Remember it!

W

Very large surface area

Largeforce

small

force

Tiny 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 areacreates pressure.

Aany number of vehicle systems.

The diagram abT

about 60 tonnes (60,000issgresWispti

sthTm

Te



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A worked example.

ous diagram, the surface pressure produced by the tank

nd the soldier can be calculated:

he soldier:

Weight = 90 kg

Surface area of boots = 0.01 m

he tank:

Referring to the previ

aT

Pressure = 90kg divided by 0.01m = 9000 kg/m surface pressure

T

Weight = 60,000 kg

Surface area of tracks = 9m

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



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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 imperialnit. 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/m. To help you identify with

ly 10 Newtons in each kilogram (9.81 tobe exact). So, N/m of pressure is roughly a tenth of a kilogram acting overa surface area of 1 square metre not a huge amount.

1 N/m is referred to as 1 Pascal

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

,000,000 N/m 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. Pleaserefer to the exact tyre pressure specification for each vehicle.)

uto 30 p.s.i buTh S.I unit of forcePthis unit a little better, there are rough

10.1 MPa is1 Bar is 15 p.s.i

15 p.s.i is 100 kPa



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Pressure in liquids

ou can squeeze a large volume of gas into

small space by pressurising it. The outward push on the container createdpushes 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 vehicley 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

pointue to this even pressure exertion. Due to this property and the

nt at one endf a car into piston movement at the other end (i.e. a hydraulic brakingystem). Hydraulics is the study of pressure in fluids.

Gases are highly compressible. Y

aby this pressure is entirely uniform e.g. the pressurised gasccar would be a rather odd shape!

Fapplications it is bccontainer.

The breaking bottle is likely to start breaking at the containers weakestdincompressibility of fluids, confined fluids when pressurised act as amechanical link and are capable of transferring piston movemeos



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Progress check 2


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

100mm10cm

80mm

100mm

5



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LV02: Foundation Skills Issue 1All Rights Reserved

Measuring Equipment

nding of the units of measurement, we will

tudy measuring equipment. An ability to use measuring equipmentura aul. Measuring

quipment will always fall into one of two groups those capable of directeasurement and those that are capable only of giving a comparative valuene dimension compared to another).

icrometer

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

lime ternal,ternal, combination and depth micrometers.

he principle of the micrometer can be seen in the above diagram. If we havend 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 oftation. 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

sacc tely is essential in work such as engine overhem(o

M

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

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

min

1 turn1 turn

0.5mm0.5mm

Ta fixed nut (i.e. it cannot rotate) ahre pitch of 0.5mm, each full rt0ro

o

- 23 -Copyright Automotive Skills Limited 2003


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Using the micrometer

It is vital that a micrometerperation to ensure that when the spindle is screwed into full contact with thece 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 especiallyhen carrying out a series of comparative measurements where consistencyf application is important. Any zero errors can be rectified by rotating theuter sleeve with a C spanner.

combination micrometer can be configured as a 0 to 25mm, 25 to 50mm, 5075mm, 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 measuringces - when the micrometer is zeroed - is already 25mm, so the measuringnge 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 beorrected initially through the adjustment of the collars at the anvil end of theame. Fine adjustment can then be carried out in the normal way with a C

he

is zeroed before use. This is a straightforwardofa

liTwoo

Interc

hangeableanvils

Atoa

sfaradcfrspanner. This prevents excessive adjustment from being carried out on theouter sleeve, which would result in the datum line on the sleeve being on twrong side of the micrometer.


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Reading the micrometer

ith 50 equi-spaced graduations, so each

A shows a movement of one graduationfaces is therefore 0.01mm.

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

hort of the 0.5mm point to

It can be seen that three wholevisible these represent whole

bove the datum 0.5mm.

The thread pitch of the micrometer is 0.5mm. Therefore, each full rotation ofthe thimble increases the distance between the measuring faces by 0.5mm.The thimble is itself marked off w

C

A B

single graduation is the equivalent of 0.01mm.

The micrometer pictured in Figureand the gap between the measuring

The micrometer in Figure B shows a rabove the horizontal datum line is visithimble reads 49. Therefore the micrometer is just sthe tune of one graduation 0.49mm.

Figure C shows a reading of 3.56mm.graduations below the datum line aremillimetres and one graduation is visible aTherefore, the coarse reading is 3.5mm. However it can be seen that thethimble 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.



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dial gauge or dial test indicator (DTI) is only capable of direct measurementa few situations - mostly, they provide the user with comparative values.

hey can, however, be used in conjunction with other measuremente.y

gh

ost dial gauges meas accuracy of 0.01mm, but some caneasure down to 0.001mm (one thousandth of a millimetre). It should be

oted that like all high accuracy measuring equipment, the dial gauge is aelicate instrument and should be handled with care.

he dial abovemeasures down to 0.01mm. The bezel is marked off with oneundred graduations. Therefore, each full sweep of the needle representsmm plunger movement. It can be seen that from the zero point, the

ad adopted the position represented by the red line, by movingom the zero point in a clockwise direction, then plunger movement would

Dial gauge

AinTequipment - such as a micrometer - to arrive at a direct measurement valuA 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 canmark off the dial with graduations. These represent a given amount ofmovement of the plunger.

M ure to within anmndTh1numbering is up to a maximum of 50 (0.5mm) in the clockwise and the anti-clockwise direction. This is because the dial gauge is capable of giving ameasurement reading for both directions of plunger movement (in and out). Ifthe needle hfrhave been 0.6mm (plunger in). However, if the needle had adopted thatposition by moving in an anti-clockwise direction, the plunger would havemoved only 0.4mm (plunger out).



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es

Feeler gauges are designed to measure thecome as a set, and each blade has a differecan be ascertained by offering up the fblades), until they fit the gap with the correct amount of resistance. The

Feeler gaug

size of a gap or clearance. Theynt 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 muchresistance represents the correctly selected blade or combination of blades.

A very good way to get familiar with this procedure is to set a micrometer tothe thickness of a blade and to place that blade between the measuring facesof the micrometer. Move the blade backwards and forwards, until there is aclear understanding of how much pull is required.



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ck 3

nswer the follo

. What is part A called?

. What does DTI stand for?

Progress cheA wing questions:

1

2. What dimension does the micrometer display?

A

3



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Principles of Electricity

n that it consists oftoms. An atom has a nucleus that is made up of neutrons and protons.s the name would suggest, neutrons have a neutral charge and thereforelay little part in the behaviour of electricity, so they will be disregarded.rotons have a positive charge that is often abbreviated to +VE.urrounding the nucleus is a number ofelectrons that have a negative chargeVE). These electrons rotate around the nucleus in orbits and are kept ineir orbits through their attraction to the positive charge of the nucleus

issimilar charges attract).

ifferent materials have different numbers of electrons in orbit and the atomsre arranged in different ways in relation to each other. It is this that givesifferent materials their individual properties such as texture, density etc.

he greater the number of electrons a material has in its orbits, the furtherway from the nucleus the electrons in the outer orbits will be. The attractive

e b se outer electrons will be relatively weak.n e tery) is applied to a material constructed in

is way, it will be relatively easy to make these outer electrons break free

om the nucleus and move freely within the material. This movement oflectrons within a material iselectricity.

What is electricity?

What is electricity?

he a given material is deconstructed, it can be seen

Copper atomCopper atom

Hydrogen atom Electron

Nucleus - protons and neutrons

+

-Hydrogen atom Electron


+

-Electron


+

-

Electricity - current

Hydrogen atom

+

-Hydrogen atomHydrogen atom

+

-

External pressure

+

Copper atom

-

+

Copper atom

-Copper atom

-

Strong bondStrong bond

WaApPS(-th

(dDadTaforc etween the nucleus and thef a xternal force (such as a batIth

fre



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The principles of electricity

lectricity is always classified as one of two types static electricity (electricitye

if

two

ns in the outer orbits of the atoms in the make-p of the glass move across to the outer orbits of the atoms in the make-up of

Static electricityStatic electricity

Dynamic electricityDynamic electricity

Ethat does not move) or dynamic electricity (electricity that does move). Thhuman race has had knowledge of electricity for hundreds of years. In theearly days it was discovered that a piece of amber would attract small hairsrubbed with a piece of cloth. Glass, when rubbed, has the same effect.

This effect is known as charging. The surfaces of the materials become filledwith electricity. The action of rubbing the glass rod with the cloth has theeffect of upsetting the balance of electrons in the atomic structure of the

materials. Some of the electrouthe cloth. The cloth therefore has an excess of electrons that lends to it anegative charge. The glass rod has fewer electrons (an excess of protons)and therefore has a positive charge.

This electricity will remain static unless the materials are connected with aconductor, upon which it will flow the excess electrons move back to theglass rod. When the electrons are flowing, the electricity has becomedynamic. This is electric current flowing electricity.



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Positively charged body

This diagram sh

wards the body on the right that is insulated from the ground. The positive

at

ows a positively charged body on the left. This body is moved

tocharge of the body on the left attracts the electrons in the body on the right.That results in too few electrons on the right hand side of this body, lending toit a positive charge. This action is known as electrostatic induction.

If we were to ground this charged body by touching it and providing aconnection to the earths surface, electrons will flow from the earth to thecharged body to balance the charged material by providing the electrons thare required.



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Conductors, semi-conductors and insulators

has been see t different materials have differing numbers of electrons in

rbit within an atom. Materials with a large number of orbits will allowlectricity to flow readily (due to the weak attraction) and are known asonductors.

aterials with relatively few orbits will resist electrical current flow (due to thetrong attraction) and are therefore known asinsulators, or sometimes,sistors.

aterials that dont seem to be able to make up their mind are known asemi-conductors.

:

- silver

Semi-conductors:- silicon- germanium.

Insulators (r- bakelite- rubber.

ow is the flow of electricity measured?

pere,

,000,000,000 electrons flow past a given point in a conductor inne second, this is 1 amp of current flow.

25,000,000,000,000,000 electrons is quantified using the unit Coulomb, so 1mp of electrical current flow could also be referred to as 1 coulomb perecond.

amp can also be described in the following way:

amp is the amount of current flowing in a conductor when the conductoras a resistance of 1 ohm and 1 volt of electrical pressure has been applied toat conductor.

It n tha

oecMsreMs

Some examples of conductors, insulators and semi-conductors are as follows

Conductors:- copper

esistors)

HA flow of electrons is referred to as current. The unit of current is the amcommonly abbreviated to the amp.

If 625,000,000o

6as11hth



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Voltage

ssure between two points in a liquid will create flow in thedirection of the lower pressure. Electrical current behaves in a similar way. Ifwe create a difference in electrical pressure between two points in aonductor, current will flow in the direction of the lower electrical pressure.

sure and it generates current flow. A battery is adevice that is capable of creating a difference in electrical pressure.

volt is said to be the amount of electrical pressure applied to a circuit, if 1t circuit has a resistance of 1 ohm.

In the circuit, the battery has created a difference in electrical pressure in theircuit (a circuit is a combination of electrical components and wires which

ssure is at the negative post. Currentows from the positive post to the negative post, generating heat in the lamp

post are attracted to this and flow to it through the circuit. This isnown as electron flow.

his was not discovered until some time after the electrical rules were

it is effectively ignored in vehicle applications.

+ ve

Electricity - voltage

A difference in pre

cVoltage is electrical pres

1amp of current flows when tha

cprovide the current with a route to take).

The area of highest electrical pressure is at the positive post of the batteryand the area of lowest electrical preflfilament as it does so. This type of current flow is known as conventionalcurrent.

In reality, current actually flows from the negative post to the positive! This isbecause the positive post has a positive charge and the electrons at thenegativekTdevised, and as it makes no significant difference to the operation of anelectrical circuit (current is flowing, it doesnt matter which way it flows, workcan still be done)

Water

High

Low

of the lower pressure

Voltage is electrical pressurepressureand creates current flow

A differencein pressure between two points will create flowin the direction

Water

High

Low

Water

High

Low

of the lower pressure

Voltage is electrical pressurepressureand creates current flow

A differencein pressure between two points will create flowin the direction

High pressure

+ veHigh pressureHigh pressure

- veLow pressure

- veLow pressureLow pressure



36/61

l resistance

o

d rather

(Greektter Omega).

ecause resistance in a circuit reduces current flow, that current can do less

Electrica

Resistor

Less current flowmeans: -

Less work done andtherefore the bulb is

dimly illuminated

Electricity - resistance

Water

Resistance reducescurrent flowResistance reducescurrent flow

Resistance is measured in ohms()

The hig ill flowher the resistance, the less current that w

Resistance

WaterWater

Resistance is measured in ohms()

The hig ill flowher the resistance, the less current that wThe hig ill flowher the resistance, the less current that w

ResistanceResistance

flow, less fluid will flow. ElectricalIf a flowing fluid experiences a resistance tcurrent flow is similar; if the flowing electrical current experiences aresistance, less electrical current will flow. As has been seen, electricalresistance is created by the atomic structure of the material concernethan by a physical restriction.

The unit of electrical resistance is the ohm. This is symbolised by leThe ohm can be described as follows:

A material is said to have a resistance of 1 ohm if 1 amp of current flows inthat material when 1 volt of electrical pressure is applied.

Bwork. Bright lamps will be dim; electric motors will be slow etc.



37/61

g are

ows when 1 volt is applied to a circuit

volt is said to be the amount of electrical pressure applied when 1 amp of

esistance of 1 ohm

s applied.

nship.hms Law states that the current flowing in a circuit is in proportion to the

oltage applied and inversely proportionate to the resistance. In other words,e greater the voltage the more current that will flow, the greater thesistance, the less current that will flow. This all seems fairly logical!

hms Law can also be stated mathematically as can be seen in the diagrambove. 1 is always used to symbolise current. Strictly speaking A shouldot be used unless we are stating a current flow figure, such as 12A.

ets apply Ohms Law to the above definitions of 1A and check that it works.1V is applied to a circuit that has a resistance of 1, in theory, 1A of current

hould flow:

urrent equals volts divided by resistance, which can be written as I=V/R.he voltage is 1V and the resistance is 1 . Therefore, I=1V/1 and one

ivided by one is one, so 1A of current will be flowing!

Ohms Law

So far we have learnt about current, voltage and resistance. The followintrue:

Ohms law

Ohms law states that:

The current flowing in a ciVoltage applied, and invers

rcuit is in direct proportion to theely proportionate to the resistance

This can be expressed mathematically in the following way:

I = Current - V = Voltage - R = ResistanceI = Current - V = Voltage - R = Resistance

1 amp is said to be the current that flthat has a resistance of 1 ohm

current flows in a circuit that has a r

1 ohm is said to be the amount of resistance that a circuit possesses if 1amp of current flows when 1 volt of electrical pressure i

It can be seen from this that there is most definitely a relationship betweencurrent, voltage and resistance. Ohms Law sums up this relatioOvthre

OanLIfsCT

d



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39/61


40/61

Progress

nswer the following questions:

. Which unit is used to describe electrical pressure?

. If the resistance of a circuit is increased for a given applied voltage,

, what is the voltage applied?

check 4

A

1

2what will happen to the amount of current that will flow?

3. If a circuit has a resistance of 12 ohms and 2 amps of current isflowing

4. Complete the Ohms Law triangle below

V

I ?

W

? V



41/61

Electrical Measurement

multi-meter is capable of measuring a number of electrical units / values.

he selector allows the choice of value the meter is to measure, such asctions

of the he red lead only has to be movedhen measuring current flow normally).

ulti-meter n ave a button that enables the technician to choose the

aximum value to easured (the range of the meter). The above diagramhows the electrical values that this multi-meter can typically read. Startingrm bottom left:

amps AC

amps DC

volts AC

volts DC

300mV DC maximum

ohms

diode tester.

Multimeters

Selector

ATVolts DC. The ports at the bottom of the meter allow for differing conne

multi-meters leads when necessary (tw

M s ormally h

be mmsfo

10A port

300mA port

volts, ohms

And diodes

Common

Hold / AUTORANGESelector

10A port

300mA port

volts, ohms

And diodes

Common

Hold / AUTORANGE

~V~V __----

V

__----V

__----A

__----A

~A~A

3030



42/61


43/61

Ohmmeter

14.4

Remember: Always switch the

An ohmmeteomponent or wire that you want to test.

urrent must not be flowing in the part of the circuit being tested, as this willeriously effect the reading (an ohmmeter measures circuit resistance bypplying a known voltage to a circuit from a battery inside its case andeasuring the resultant current flow). From these two values it can calculatee resistance using Ohms Law in the same way shown previously). If

urrent is flowing in the circuit from a different source (i.e. the vehicle battery)is will seriously effect its calculation.

mmeter

n ammeter (a multimeter with amps selected) must be fitted in series withe circuit whose current you want to measure.

his means that the circuit must be broken and the ammeter must be put intoe circuit. A good ammeter has an extremely small internal resistance so it is

important that you take care not to short a circuit out by putting the ammeteracross the only resistance in a circuit (provide the current with an easier path

to take through the meter). This will at best blow a fuse in the meter, and atworst set it alight!

r (a multi-meter with ohms selected) is always fitted across thecCsamthcthA

AthTth

circuit OFF first

remainder of the circuit

Alwaysdisconnect the

component from the

Close switch

0.00

14.414.414.4


circuit OFF first



0.00


component from the

circuit OFF first



component from the

Close switchClose switchClose switch

Never connect an ammeter across a resistance; a goodammeter has zero internal resistance

Remember:always fit an ammeter

in serieswith the circuit



44/61

Progress check 5

nswer the follo

. What do the following symbols mean?

__

----

V

. autions should you take before

A wing questions:

1

2. How many mV in a volt?

3. How is a voltmeter fitted to a circuit?

4 When using an ohmmeter what prectesting the circuit?

5. Draw a series circuit containing 3 bulbs, a battery, and a switch.



45/61

Types of circuit

The way in which components are connected in a circuit dictates the

properties of the circuit (and the performance of the component). The abilitynt.

Series

he circuit (in this instanceisto Coronation Street is

series one episode after the other!

arallel

his is any circuit that has separate branches from a single power supply.appear to run in parallel with each

other. The circuits derive their name from this.

to recognise different types of circuit is importa

This is any circuit where the components in ts rs) are wired one after the other in the same wire.

reaP

TThe branches pictured in a wiring diagram



46/61

Series parallel

As the name (and the d circuit is a combination of theo previously discussed circuits series and parallel.

iagram) suggest, thistw



47/61

Progress check 6

nswer the followi

. What type of circuit is pictured ?

A ng question:

1



48/61

lectrical wiring diagE rams

apanese manufacturersJ

= Horn = Short Pin

= Resisto

= Lamp

= Analogue

eter

(Junction Block Connector)

= Battery

= Circuit

Breaker

= M4 Relay

r

M

= Distributor

IIA

= Diode

= Tapped

Resistor

= Ground

= Double

Throw

Switch

= Cigarette

Lighter

= Zener

Diode

= SpliceJoint



49/61

= Ignition = Speaker

= Wiper Park

Switch

= Digital Fuel

Gauge

Switch

= Switch ON

= Motor

= Fuse

= Twin

Bulb

Filament

= LED

= S tch OFF

= DoubleThrow Relay

= t

= T

= T

P

= S

wi

Splice Join

hermistor

ransistor

NP

olenoid



50/61

On the diagram below, three components have been labelled A, B and C.

Identify each one co ly and recrrect ord the answers below:A.

B.

C.


A

B

C


51/61

European manufacturers

Identify the symbols. Write the name alongside each one.



52/61

Devices

There are many different types of locking device available, some of which arepictured here. They are all designed with one primary task in mind holdingcomponents together either permanently or temporarily. A commonmisconception is that a screw has a sharp point and is designed to cut its own

a

bolt with the exception that it is threaded all the way to the bottom of the headand is seldom used in conjunction with a nut (it screws into threadedcomponents). A bolt has a thread ess shank. Only self-tapping screws (cuttheir own thread) have sharp points!

Locking and Securing

Bolts and screws

thread. This is incorrect in engineering terms. A screw is almost identical to

BoltBoltScrewScrew Hex screwHex screw

Coach boltCoach bolt

Countersunk screwCountersunk screwSelf tappingSelf tapping



53/61

Hexagon h

ere only a few years ago. e types and Torx types occur where auring device needs to be accommodated in a tight space (with hexagon

ead devices, space needs to be left around the head to accommodate aocket for the fitting and removal). Tight spaces are now commonplace onght vehicles as manufacturers strive to

to

pitch

strength rating.

specification could

5mm long, M8 coarse thread, strength rating 8.

his is a bolt that is 75mm in le from its threaded end tohas an 8 mm thread diameter and a thread pitch of 1.5mm with a

trength rating that would see it safe up to a torque of 60Nm.

ead bolts and screws are used far less frequently now than they

w Multi-splinsechsli save every gram of weight and exploitevery centimetre of cabin space.

When ordering a bolt (standard design) from the parts department, exprovide the following information if the device you want is not specific to task(such as a main bearing cap bolt):

overall length

diameter

pect

thread

A typical be:

7T ngth the underneath of the head,s



54/61

Nuts and washers

me thread as the bolt to which it is to be

to grip the bolt thread by means of

y the bolts thread. It cuts through the nylon collar at theuld be noted that these nuts should never be re-used.

astellated nuts are designed for use in conjunction with split pins and winghere regular and easy removal is required (seldom used on

odern vehicles). Shear nuts are often the choice where security is an issue,iliser equipment, for example.

ashers are used to spread load and often to reduce the possibility of a bolthaking loose as result of vibration. Tab washers are made of a soft materialluminium alloy) and are bent upward, to fit snugly against the flat of a screw

ead to prevent rotation and loosening of the screw through vibration.

Nuts are also available in several different types. When ordering, ensure therequest is for a nut that has the sa

Nut

Castellated nut

Flanged nut Nylock nut

Wing nut Shear nut

fitted this means both thread diameter and thread pitch. Is it metric fine(1.25mm pitch) or metric coarse (1.5mm pitch)? The flanged nut is designedto spread the compression load a little onto the component surface. TheNylock nut (trade name) is designed

friction generated btop of the nut. It shoCnuts are used wmwith vehicle immob

Flat washer

washer

Spring washer

Penny

Ws(ah



55/61

Chemical thread locking

chemical compounds available. Thesean do anything from locking a thread to prevent loosening as a result of

There are now many different types ofcvibration, to sealing joints and even temporarily sealing radiators, tyres orcylinder blocks!

Always read the instructions thoroughly before use. If unsure of the healthand safety risks, always refer to the COSHH data sheet for that specificproduct.



56/61

Progress check 7

Answer the followi

. When can a split pin be reused?

ng questions:

1. What type of nut is this?

2. What is this locking device called?

3. What is a tab washer for?

4



57/61

Inspection and Fault-Finding Techniques

Char re is seldom productive. Working toocan lead to missing the simple, obvious

ults that would have been identified through a more logical, structuredpproach. With complex systems, a well-structured, logical approach is

quired. This approach should be adhered to throughout diagnosis (simpler difficult) and in most cases the same approach can be used time and again.

river interrogation

he driver of the vehicle probably knows more about the vehicles history thannyone else and will normally have first hand knowledge of the fault. If aehicle develops a fault, simple or complex, the driver will have sensed moref the symptoms than the technician can during workshop diagnosis. It isportant to ask drivers the right kind of questions.

The drivers comments can prove valuable, especially with intermittent faults,which are often difficult to locate. Asking the correct questions can produceanswers that can usually save time by preventing unnecessary diagnostic

routines. Customers are normally willing to supply the information, so why notallow them to provide the information required to ease fault diagnosis?

Diagnosis techniques

ging into a fault diagnosis proceduquickly and without logical thoughtfa

Dont rush in!

a

reo

D

Tavoim



58/61

Gathering information

EARTH

IGN

IDLE

ECMVOLTS

INJ

MAP

TPS

Build the puzzle until one of the pieces is missing or doesn't fit

EARTH

IGN

IDLE

ECMVOLTS

INJ

MAP

TPS

Build the puzzle until one of the pieces is missing or doesn't fit

By gathering information about the problematic system, a logical diagnostic

equence can be determined to help identify the fault. The area to bevestigated can be reduced by carefully checking and testing strategic partsf the circuit.

may seem that a large amo data and information is required beforeult diagnosis can begin, but by consulting a circuit diagram, certain sections

f the circuit can be eliminated. The large amount of information that seemedecessary at the start may not be required in the end.

efer back to the information and the diagnostic sequence throughout the test

emember, charging into diagnosis is not always a good idea. Sometimes it

sinoVisual inspection

It unt of faon

Rroutine. It might be necessary to follow a different route if the components aretoo difficult to access or the findings are not as first thought.

Always be prepared to change or rethink the strategy.

Rworks, but more often than not what may be a simple procedure is made moredifficult by missing the more obvious faults. A more logical and structuredapproach will pay dividends.



59/61

Formulating your diagnostic strategy

ere is insufficient information and the technician has a limitednowledge, guesswork has been known to take over. Technicians often

ent that they do not fully understand, or by looking at theuantity of the suspect component that the parts department sells. Thiseans that the parts pers ing the fault! This is a potentially

xpensive (and embarrassing) strategy to adopt, as many parts departmentsill not allow the workshop to return parts once purchased.

the new part ordered is not required (the guess was incorrect) the price ofe part has to be absorbed by one of the parties - the workshop or customer.hen the price of the part is low (i.e. 10.00), the amount can usually be

bsorbed as vehicle diagno

owever, when the price of the part is high (i.e. 200.00), it is a different story.he customer will not absorb the cost. The cost must be absorbed by the

is

ians need to undergo

gular training throughout their workshop life to allow them to service and

the obvious first.hen the electrical circuit being tested has an ECM, there is often a tendency

Many technicians get lost in an attempt to diagnose complex electronicsystems. If th

kcondemn a componqm on is diagnosewIfthWa stics time.

HTworkshop, reducing profit. If this happens on several occasions, confidencelost and electrical/electronic diagnosis is then often contracted to other thirdparty businesses - expensive! The reduction of such work in a workshop willquickly lead to de-skilling of the technical staff. Technic

rerepair modern motor vehicles.

When formulating a diagnostic strategy, prioritise. CheckingWto over complicate matters.

Many workshops do not have equipment capable of testing complex electroniccomponents (i.e. ECM or similar). Therefore, they tend to think that theremainder of the circuit is also complex.



60/61

There may be an electronic component at the centre of the circuit, but themainder usually consists of general electrical items that can be tested with

n ordinary

should be noted that although modern electrical circuits are often fitted withlectronic control modules, the testing of such circuits still requires similarkills to those required when testing simple electrical circuits. Getting boggedown thinking things are complex, can cause frustration if the fault isnt initiallybvious.

ecord results as tests are carried out. By recording the test results at eachtage (correct or incorrect), the diagnostic plan can be reviewed at any time. Ifr any reason diagnosis is interrupted, it is easier to return later and recall thesults instantly. A record of the test results will also assist if another person

asked to continue, without having to repeat the checks.

d

redic

rary willrow into a very large, in depth point of reference.

ata. If the information is good or evenad (an idea is to highlight the bad data) the data can be used as a

y

rea multi-meter (bulbs, switches etc).

ItesdoRsfore

isDiagnostic information is often difficult to access in the independent repairmarket and this type of information can be very valuable. If information andata is collated every time a repair is carried out - whether it is informationfrom repair manuals, information printed off test equipment or data gatheduring test procedures it can be used to construct an effective diagnostlibrary. Few people are blessed with a photographic memory! It may take alittle time to set up in the first instance, but over a short period the libgSome of the information obtained from test equipment data printout lists is notavailable from technical information suppliers and therefore a serviceablevehicle is a unique source of valuable dbcomparison against vehicles to be repaired in the future.

A simple PC is capable of providing an effective database utility at very littlecost. The information can then be catalogued into various categories andquickly referenced.

This approach is virtually guaranteed to increase productivity and profitabilitover time.



61/61

Progress check 8


1. Identify four different methods of diagnostic inspection(The first method has been given).

A. Visual

B.____________?

. What does the term guarantee refer to?

C.____________?

D.____________?

2. What does aural mean?

3

lv02 - foundation skills - issue 1

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