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ITI/NCVT Mechanic Motorcycle (AITT Theory) study materials
ITI/NCVT Mechanic Motorcycle (AITT Theory) study resources

ITI/NCVT Mechanic Motorcycle (AITT Theory) practice questions

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Question 1Occupational Safety, Health and Environment

While servicing a motorcycle in the workshop, a technician notices a small petrol spill on the floor. What is the most appropriate immediate action under good workshop safety practice?

  1. Cover the spill with a cloth and continue working
  2. Leave it to evaporate naturally before continuing
  3. Absorb the spill with an approved spill kit and dispose of the waste correctly Correct answer.
  4. Wash the spill into the floor drain with water

Explanation

Petrol is highly flammable and its vapour can ignite from a spark or hot surface, so a spill must be contained and removed at once using an approved absorbent material. The contaminated absorbent is then treated as hazardous waste rather than being washed away or left to evaporate. Prompt containment protects both the technician and others in the workshop.

Question 2Occupational Safety, Health and Environment

Which type of fire extinguisher is the correct choice for a burning petrol fire in a motorcycle workshop?

  1. Water (Class A) extinguisher
  2. Foam (Class B) extinguisher
  3. Carbon dioxide or dry powder extinguisher Correct answer.
  4. Wet chemical extinguisher

Explanation

Petrol is a flammable liquid, so the fire is a Class B fire. Carbon dioxide and dry powder extinguishers are suitable for Class B fires and for electrical equipment, making them appropriate in a workshop. Water and wet chemical types are intended for other classes and can spread a liquid fuel fire.

Question 3Occupational Safety, Health and Environment

A technician must lift a motorcycle engine from a bench to a stand. Which technique best reduces the risk of back injury?

  1. Bend the back, keep the legs straight and twist while lifting
  2. Keep the load close to the body, bend the knees and lift with the legs Correct answer.
  3. Hold the engine at arm's length to keep it clear of the body
  4. Lift quickly with a jerking motion to overcome the weight

Explanation

Safe manual handling keeps the load close to the trunk, uses the leg muscles with bent knees and avoids twisting the spine. Holding a heavy engine at arm's length greatly increases the load on the lower back. A smooth lift with the legs reduces the strain on the spine.

Question 4Occupational Safety, Health and Environment

What is the main purpose of wearing safety goggles when using a compressed-air blow gun to clean a motorcycle engine?

  1. To protect the eyes from flying debris and fluid particles Correct answer.
  2. To reduce noise from the air jet
  3. To improve visibility of small components
  4. To prevent dust from entering the lungs

Explanation

A compressed-air jet can propel metal particles, dirt and solvent droplets at high speed, so eye protection is essential. Safety goggles shield the eyes from these projectiles. Respiratory protection, not goggles, addresses dust entering the lungs.

Question 5Occupational Safety, Health and Environment

In a workshop, a red-coloured fire extinguisher is normally provided for which purpose?

  1. Water extinguisher for Class A fires Correct answer.
  2. Dry powder extinguisher for all fire classes
  3. Foam extinguisher for flammable liquids
  4. Carbon dioxide extinguisher for electrical fires

Explanation

Under the common colour-coding convention, a red body indicates a water extinguisher, which is intended for Class A fires involving solid combustibles such as wood, paper and textiles. Other media are identified by a coloured band on the body. Water must not be used on live electrical equipment or flammable liquid fires.

Question 6Occupational Safety, Health and Environment

A technician is about to use a two-post motorcycle lift for the first time. Which check is most important before raising the machine?

  1. Check that the workshop floor has been swept
  2. Ensure the lift has been used earlier the same day
  3. Confirm the lift's safe working load and that the motorcycle is correctly secured Correct answer.
  4. Ask a colleague to stand on the lift to test it

Explanation

Every lifting device has a rated safe working load, and the motorcycle must be within that limit and properly clamped or strapped before it is raised. Correct securing prevents the machine from slipping or toppling. A visual check of the lift and its locking mechanism is also part of the pre-use inspection.

Question 7Occupational Safety, Health and Environment

Why should a motorcycle engine never be run in a closed workshop without adequate ventilation?

  1. The fuel will evaporate faster
  2. Exhaust gas contains carbon monoxide, an odourless toxic gas Correct answer.
  3. The engine will overheat more quickly
  4. The spark plugs will foul more rapidly

Explanation

Engine exhaust contains carbon monoxide, which is colourless, odourless and can cause unconsciousness or death in an enclosed space. Running engines indoors therefore requires effective extraction or ventilation to the outside. Opening a door may not be sufficient, so a proper exhaust extraction system is preferred.

Question 8Occupational Safety, Health and Environment

A technician is handling used engine oil drained from a motorcycle. What is the correct environmental practice?

  1. Mix it with workshop sweepings and place it in general waste
  2. Pour it down the sink with plenty of water
  3. Store it in a labelled container for recycling or authorised disposal Correct answer.
  4. Burn it in an open container behind the workshop

Explanation

Used oil contains contaminants and must be collected in a clearly labelled, closed container and passed to a licensed recycler or disposal contractor. Pouring it into drains pollutes watercourses, and burning it releases harmful emissions. Segregating waste oil also allows it to be re-refined.

Question 9Occupational Safety, Health and Environment

What is the correct way to store a compressed gas cylinder used for welding in a motorcycle workshop?

  1. Store it upright and secured with a chain or strap, away from heat Correct answer.
  2. Keep it loose so it can be moved quickly in an emergency
  3. Lay it horizontally on the floor near the workbench
  4. Store it next to the petrol storage cabinet for convenience

Explanation

Compressed gas cylinders should be stored upright and restrained so they cannot fall, with the valve cap fitted when not in use. They must be kept away from heat sources and flammable stores. Securing the cylinder prevents the valve from being sheared off and the cylinder from becoming a projectile.

Question 10Occupational Safety, Health and Environment

A technician notices that the insulation on the mains lead of a portable inspection lamp is frayed, exposing the conductors. What should be done?

  1. Take the lamp out of service and report it for repair or replacement Correct answer.
  2. Continue using the lamp but keep the damaged part away from metal
  3. Wrap the damaged section with insulating tape and continue using it
  4. Use the lamp only for short periods to reduce the risk

Explanation

Damaged insulation on mains-powered equipment removes the barrier between the user and live conductors, creating a risk of electric shock. The equipment must be withdrawn from use, tagged and reported so it can be repaired or replaced by a competent person. Taping over damage is not an acceptable permanent repair.

Question 11Occupational Safety, Health and Environment

When using a bench grinder to sharpen a tool, which practice best protects the operator?

  1. Use the side of the wheel for heavy grinding
  2. Wear gloves and stand in line with the wheel
  3. Stand to one side of the wheel, keep the guard and tool rest adjusted close Correct answer.
  4. Stand directly in line with the wheel and remove the guard for access

Explanation

Standing to one side reduces exposure if the wheel bursts, while the guard and correctly adjusted tool rest limit the gap and prevent the work from being drawn in. The tool rest should be kept close to the wheel and the gap small. Gloves near rotating machinery create an entanglement risk.

Question 12Occupational Safety, Health and Environment

A technician develops a rash on the forearms after repeated contact with cleaning solvent while washing motorcycle parts. What is the most appropriate first response?

  1. Increase the solvent concentration to clean the parts faster
  2. Stop contact with the solvent, wash the skin and report the condition Correct answer.
  3. Continue working but apply barrier cream each morning
  4. Ignore it because skin irritation is not a work-related concern

Explanation

Solvents can cause contact dermatitis by removing natural oils from the skin, so exposure must be stopped and the affected skin washed gently. The condition should be reported so that the cause can be assessed and controls such as gloves or substitution introduced. Early reporting prevents the condition from becoming chronic.

Question 13Occupational Safety, Health and Environment

Which document should a technician consult to find the correct personal protective equipment and first-aid measures for a chemical used in the workshop?

  1. The tool inventory register
  2. The motorcycle service manual
  3. The workshop duty roster
  4. The material safety data sheet for the chemical Correct answer.

Explanation

The material safety data sheet, now often called the safety data sheet, provides hazard information including required PPE, first-aid measures, handling and storage precautions. It is the primary reference for safe use of a chemical. Service manuals and rosters do not contain chemical hazard data.

Question 14Occupational Safety, Health and Environment

A workshop has a small first-aid kit. Which item is essential for treating a minor cut to a technician's hand?

  1. A torque wrench
  2. A tin of spray paint
  3. A sterile dressing and adhesive plasters Correct answer.
  4. A bottle of engine oil

Explanation

A first-aid kit should contain sterile dressings and adhesive plasters to cover cuts and prevent contamination and infection. The other items listed are workshop tools or materials with no first-aid purpose. A first-aid kit should also be checked regularly and restocked.

Question 15Occupational Safety, Health and Environment

A technician is about to weld a motorcycle frame in a bay that contains a container of petrol. Why must the petrol be removed before welding begins?

  1. Petrol will cool the weld too quickly
  2. Petrol will damage the welding electrode
  3. Petrol fumes make the weld porous
  4. Petrol vapour is heavier than air and can travel to the weld and ignite Correct answer.

Explanation

Petrol vapour is heavier than air and can flow along the floor to a distant ignition source, including welding sparks and hot slag. Removing the fuel container from the area, or moving the work to a designated hot-work area, prevents ignition of the vapour. A fire watch and suitable extinguisher are also good practice during hot work.

Question 16Occupational Safety, Health and Environment

A workshop stores several chemicals in unlabelled bottles. Which control best prevents accidental mixing or misuse?

  1. Use only small bottles so the quantity is limited
  2. Label every container with its contents and hazard information Correct answer.
  3. Store all bottles together in a single unmarked cupboard
  4. Rely on technicians remembering what each bottle contains

Explanation

Clear labelling of every container with the chemical name and hazard information is a basic requirement for safe handling and prevents mistaken identity. Unlabelled containers are a common cause of accidental mixing and exposure. Secondary containers should be labelled at the point of decanting.

Question 17Hand Tools, Measuring Instruments and Workshop Practice

Which hand tool is used to hold a workpiece securely while it is being filed or hacksawed on a bench?

  1. Bench vice Correct answer.
  2. Ball peen hammer
  3. Cold chisel
  4. Try square

Explanation

A bench vice clamps the workpiece between its jaws so that filing, sawing and chiselling can be done with both hands free. The fixed jaw is integral with the body and the movable jaw is closed by the screw handle. Hammers, chisels and squares are working or checking tools, not holding devices.

Question 18Hand Tools, Measuring Instruments and Workshop Practice

On a metric outside micrometer, one full revolution of the thimble moves the spindle by how much?

  1. 1.00 mm
  2. 0.01 mm
  3. 0.50 mm Correct answer.
  4. 0.05 mm

Explanation

The spindle screw of a standard metric micrometer has a pitch of 0.5 mm, so one complete turn of the thimble advances the spindle by 0.5 mm. The barrel is graduated in 0.5 mm divisions and the thimble has 50 divisions, giving a least count of 0.01 mm. Confusing the pitch with the least count is a common error.

Question 19Hand Tools, Measuring Instruments and Workshop Practice

A Vernier caliper main scale reads 24 mm and the 8th vernier division coincides with a main scale line. If the least count is 0.02 mm, what is the reading?

  1. 24.02 mm
  2. 24.08 mm
  3. 24.16 mm Correct answer.
  4. 24.80 mm

Explanation

The vernier reading equals the coinciding division number multiplied by the least count: 8 x 0.02 mm = 0.16 mm. Adding this to the main scale reading of 24 mm gives 24.16 mm. The division number must be multiplied by the least count, not read directly as a decimal fraction.

Question 20Hand Tools, Measuring Instruments and Workshop Practice

Which measuring instrument is most suitable for checking the internal diameter of a small cylinder bore accurately?

  1. Vernier height gauge
  2. Steel rule
  3. Inside micrometer Correct answer.
  4. Outside micrometer

Explanation

An inside micrometer has measuring faces arranged to contact the bore walls from within, so it reads internal diameter directly with micrometer accuracy. A steel rule is too coarse, an outside micrometer measures external dimensions, and a height gauge measures height above a surface plate.

Question 21Hand Tools, Measuring Instruments and Workshop Practice

A feeler gauge set is used in motorcycle workshop practice mainly to measure which of the following?

  1. Tappet or valve clearance Correct answer.
  2. Battery electrolyte level
  3. Tyre tread depth
  4. Engine oil pressure

Explanation

A feeler gauge consists of thin steel blades of known thickness used to check small gaps such as tappet and valve clearances and spark plug gaps. The blade that slides with slight drag indicates the clearance. It measures a gap, not pressure, depth of tread or fluid level.

Question 22Hand Tools, Measuring Instruments and Workshop Practice

Which file cut is best suited for rapid removal of metal on a rough forging before finishing?

  1. Smooth file
  2. Second cut file
  3. Dead smooth file
  4. Rough file Correct answer.

Explanation

A rough file has coarse, widely spaced teeth that remove metal quickly, leaving a coarse finish that is later refined. Smooth, second cut and dead smooth files have progressively finer teeth for finishing rather than stock removal. Selecting the coarsest cut for roughing is the standard rule.

Question 23Hand Tools, Measuring Instruments and Workshop Practice

What is the included angle of the cutting edge of a standard cold chisel used for cutting mild steel?

  1. 45 degrees
  2. 90 degrees
  3. 60 degrees Correct answer.
  4. 30 degrees

Explanation

A cold chisel for mild steel is ground with an included angle of about 60 degrees, which balances cutting ability against edge strength. Softer metals such as copper or aluminium need a sharper angle near 45 degrees, and harder materials need a blunter angle. The angle is checked with a chisel angle gauge.

Question 24Hand Tools, Measuring Instruments and Workshop Practice

A hacksaw blade marked 18 TPI is best chosen for which type of work?

  1. Cutting wood only
  2. Cutting thick solid sections of mild steel Correct answer.
  3. Cutting thin sheet metal and tubing
  4. Cutting hardened tool steel

Explanation

Teeth per inch indicates tooth pitch: 18 TPI is a coarse blade suited to thick solid sections, where the coarse teeth clear chips and prevent clogging. Fine blades of 24 to 32 TPI are used for thin sections and tubing where coarse teeth would snag. Selecting pitch according to section thickness is the governing rule.

Question 25Hand Tools, Measuring Instruments and Workshop Practice

Which tool is used to cut an internal thread in a drilled hole?

  1. Reamer
  2. Tap Correct answer.
  3. Counterbore
  4. Die

Explanation

A tap is a hardened threaded tool that cuts internal threads when turned into a drilled hole, usually in a set of taper, second and plug taps. A die performs the opposite operation by cutting external threads on a rod. Reamers and counterbores size and shape holes without producing threads.

Question 26Hand Tools, Measuring Instruments and Workshop Practice

For tapping a thread in mild steel by hand, which lubricant is normally recommended?

  1. Dry, with no lubricant
  2. Kerosene
  3. Water
  4. Tallow or soluble cutting oil Correct answer.

Explanation

Tallow or a soluble cutting oil lubricates the tap and flutes, reduces friction and helps produce a clean thread in steel while extending tap life. Kerosene is preferred for aluminium, and water causes rust and poor finish. Lubrication also reduces the risk of tap breakage.

Question 27Hand Tools, Measuring Instruments and Workshop Practice

What is the purpose of a centre punch in layout work?

  1. To check the squareness of a machined edge
  2. To enlarge a drilled hole
  3. To remove a broken stud from a hole
  4. To mark a permanent centre point for drilling Correct answer.

Explanation

A centre punch is struck with a hammer to make a small conical indentation that locates the drill point and prevents it from wandering. It is used after a dot punch or scribed intersection has marked the position. Enlarging holes, checking squareness and extracting studs belong to other tools.

Question 28Hand Tools, Measuring Instruments and Workshop Practice

A surface plate is used in the workshop for which purpose?

  1. Measuring the hardness of a specimen
  2. Holding a workpiece for welding
  3. Grinding chisel edges
  4. Providing a true flat reference surface for marking out and inspection Correct answer.

Explanation

A surface plate is machined and scraped to a true plane and serves as the reference datum for marking out, checking flatness and supporting height gauges. Work is placed on it so that measurements and scribed lines are taken from a common flat base. It is not a hardness tester, welding table or grinder.

Question 29Hand Tools, Measuring Instruments and Workshop Practice

When using a bench grinder to sharpen a cold chisel, which precaution protects the eyes?

  1. Wetting the wheel with water
  2. Wearing tinted sunglasses
  3. Wearing safety goggles and keeping the guard in place Correct answer.
  4. Standing to one side of the wheel

Explanation

Safety goggles shield the eyes from sparks, metal particles and fragments if a wheel bursts, while the guard contains debris. Standing aside and dressing the wheel are related precautions but do not replace eye protection. Sunglasses are not impact rated and offer no protection against flying particles.

Question 30Hand Tools, Measuring Instruments and Workshop Practice

A dial test indicator reading is required to check the runout of a motorcycle wheel rim. Which setup gives a valid reading?

  1. Magnetic base on the floor with the plunger touching the tyre
  2. Indicator placed on the bench beside the wheel
  3. Magnetic base clamped to a rigid stand with the plunger touching the rim edge Correct answer.
  4. Indicator held by hand against the spinning rim

Explanation

Runout is measured by mounting the indicator rigidly, with its magnetic base on a solid support, and touching the stylus to the rim so any wobble moves the plunger. A rigid mounting is essential because hand-held or loosely placed indicators add their own movement to the reading. The tyre is flexible and would mask true rim runout.

Question 31Hand Tools, Measuring Instruments and Workshop Practice

A micrometer is closed fully on its anvils and the thimble zero is found to be two divisions past the barrel datum line. How should a reading taken with this instrument be corrected?

  1. Ignore the error because micrometers are self-correcting
  2. Subtract 0.02 mm from every reading Correct answer.
  3. Add 0.02 mm to every reading
  4. Add 0.50 mm to every reading

Explanation

A zero error where the thimble reads past zero means the instrument over-reads by that amount, so the error must be subtracted from each measurement. With a least count of 0.01 mm, two divisions equal 0.02 mm. The error is a fixed offset and does not correct itself, and 0.50 mm is the screw pitch, not the error.

Question 32Hand Tools, Measuring Instruments and Workshop Practice

Which combination of tools is required to mark out and then drill a hole at a specified distance from the edge of a flat plate?

  1. Try square, hacksaw and die
  2. Vernier caliper, reamer and tap
  3. Ball peen hammer, cold chisel and file
  4. Steel rule, scriber, centre punch and dot punch Correct answer.

Explanation

Marking out a hole position needs a steel rule to measure the distance, a scriber to draw the intersecting lines, and a dot or centre punch to mark the intersection for the drill. The other sets contain tools for cutting, threading or shaping, none of which establishes a measured hole position.

Question 33Hand Tools, Measuring Instruments and Workshop Practice

Why is a torque wrench preferred over an ordinary spanner when tightening cylinder head bolts?

  1. It prevents the bolt from corroding
  2. It tightens the bolt more quickly
  3. It applies a controlled and uniform clamping load Correct answer.
  4. It allows the bolt to be reused indefinitely

Explanation

A torque wrench signals when a set turning moment is reached, so all head bolts receive the same controlled clamping load and the gasket seals evenly without distortion. Uneven or excessive tightening can warp the head or strip threads. Speed, corrosion resistance and bolt reuse are unrelated to torque control.

Question 34Hand Tools, Measuring Instruments and Workshop Practice

A hole must be finished to a precise diameter with a smooth bore after drilling. Which sequence is correct?

  1. Drill, then tap with a plug tap
  2. Drill, then ream with a reamer slightly larger than the finished size Correct answer.
  3. Drill, then counterbore
  4. Drill, then centre punch the bore

Explanation

Reaming removes a small amount of material to bring a drilled hole to an accurate diameter with a smooth finish, so the hole is first drilled slightly underside and then reamed. Tapping cuts threads, counterboring seats a bolt head, and punching does not size a bore.

Question 35Hand Tools, Measuring Instruments and Workshop Practice

During hacksawing, the blade breaks repeatedly at the same point. Which cause is most likely?

  1. Too much coolant applied to the blade
  2. Blade tension too low, allowing the blade to buckle Correct answer.
  3. Workpiece clamped too rigidly in the vice
  4. Teeth too fine for the section being cut

Explanation

A hacksaw blade must be tensioned firmly; if tension is low the blade buckles and flexes during the stroke and cracks at the same weak point. Correct tension, a suitable pitch and steady stroke prevent this. Coolant and rigid clamping actually help blade life rather than causing breakage.

Question 36Hand Tools, Measuring Instruments and Workshop Practice

A feeler gauge indicates that the valve clearance on a motorcycle engine is 0.10 mm when the specification is 0.15 mm. What does this indicate and what action follows?

  1. Clearance is insufficient, so the adjuster must be backed off to increase it Correct answer.
  2. The feeler gauge is faulty and the reading should be ignored
  3. Clearance is excessive, so the adjuster must be tightened
  4. Clearance is correct and no action is needed

Explanation

A measured clearance of 0.10 mm is smaller than the specified 0.15 mm, so the clearance is too tight and must be increased by backing off the adjuster until the specified blade slides with slight drag. Excessive clearance would call for tightening, and a correct clearance would match the specification.

Question 37Engineering Materials, Fasteners and Fits

A motorcycle cylinder head is to be held by bolts that must resist repeated combustion pressure without losing clamping load. Which property of the bolt material is most important for this application?

  1. Maximum electrical conductivity
  2. High thermal expansion coefficient
  3. Low hardness to allow thread forming by hand
  4. High fatigue strength with adequate proof stress Correct answer.

Explanation

Bolts under cyclic combustion loading fail by fatigue, so the material needs high fatigue strength plus enough proof stress to keep preload without yielding. Conductivity and thermal expansion do not control clamping durability, and low hardness would promote thread wear and stripping.

Question 38Engineering Materials, Fasteners and Fits

A piston pin must combine a hard, wear-resistant running surface with a tough core that resists shock loading. Which treatment best achieves this combination on a low-carbon steel pin?

  1. Full annealing after machining
  2. Electroplating with soft tin
  3. Anodising of the steel surface
  4. Case carburising followed by quenching and tempering Correct answer.

Explanation

Carburising adds carbon to the surface so that quenching produces a hard case while the low-carbon core stays tough. Anodising applies to aluminium, annealing softens rather than hardens, and soft tin plating gives no load-bearing hardness.

Question 39Engineering Materials, Fasteners and Fits

A fastener is marked 8.8 on its hex head. What does the second figure indicate?

  1. The thread pitch in tenths of a millimetre
  2. The minimum yield strength as a fraction of tensile strength Correct answer.
  3. The nominal thread diameter in millimetres
  4. The maximum service temperature in hundreds of degrees

Explanation

In property class 8.8 the first number gives one hundredth of nominal tensile strength in MPa and the second gives the yield-to-tensile ratio as a decimal. So 8.8 means about 800 MPa tensile and yield at 80 percent of that. The figures never encode diameter, pitch or temperature.

Question 40Engineering Materials, Fasteners and Fits

A shaft of nominal diameter 40 mm is to run in a bearing bush with a close running fit. Using the hole-basis system, which designation pair represents a close running clearance fit?

  1. 40 H7/p6
  2. 40 H7/js6
  3. 40 H7/g6 Correct answer.
  4. 40 h6/H7

Explanation

In the hole-basis system the hole is H and the shaft letter sets the fit type. Lower-case g gives a small clearance, so H7/g6 is a close running fit, while p gives interference and js gives a transition fit.

Question 41Engineering Materials, Fasteners and Fits

Why is a copper washer preferred over a steel washer under the sump drain plug of a motorcycle engine?

  1. Copper has a higher melting point than steel
  2. Copper provides electrical insulation from the crankcase
  3. Copper work-hardens on tightening and locks the thread
  4. Copper deforms to seal minor surface irregularities and resists corrosion Correct answer.

Explanation

A soft copper sealing washer conforms to small imperfections on the plug and sump faces when crushed, giving an oil-tight joint, and it resists corrosion in hot oil. It does not lock threads, copper melts below steel, and it is an electrical conductor rather than an insulator.

Question 42Engineering Materials, Fasteners and Fits

A wheel axle nut on a motorcycle is specified as M14 x 1.5. What does 1.5 represent?

  1. The tolerance grade of the thread
  2. The thread pitch in millimetres Correct answer.
  3. The nut height in millimetres
  4. The spanner size in millimetres

Explanation

In metric thread designation the number after the diameter is the pitch measured in millimetres between corresponding thread crests. Spanner size, nut height and tolerance class are given separately, for example by a tolerance band such as 6g.

Question 43Engineering Materials, Fasteners and Fits

A crown wheel and pinion in a motorcycle final drive is to be made from alloy steel. Which sequence gives the correct order of operations to obtain a tough, wear-resistant gear?

  1. Harden, machine, anneal, then temper
  2. Machine, harden fully, then cold roll the teeth
  3. Soften, machine, harden and temper, then finish grind Correct answer.
  4. Anneal, chrome plate, then machine to size

Explanation

Gear manufacture starts with softening so the blank can be cut, then hardening and tempering develop strength and toughness, and final grinding corrects distortion and sets the tooth form. Machining after hardening is impractical, and plating or rolling after hardening does not correct distortion.

Question 44Engineering Materials, Fasteners and Fits

A steel component is heated and then quenched in oil rather than water. What is the main reason for choosing oil?

  1. Oil chemically hardens the surface by adding carbon
  2. Oil cools faster than water and gives deeper hardness
  3. Oil cools more slowly, reducing the risk of cracking and distortion Correct answer.
  4. Oil keeps the component at a constant temperature during quenching

Explanation

Oil has a lower cooling rate than water, so the thermal shock and the risk of quench cracks and distortion are reduced, which suits alloy steels of moderate hardenability. Oil does not add carbon, does not hold temperature constant, and is slower rather than faster than water.

Question 45Engineering Materials, Fasteners and Fits

A plain carbon steel with 0.8 percent carbon is heated to just above its upper critical temperature and slowly cooled. What structure is obtained?

  1. Spheroidised cementite in a ferrite matrix
  2. Fully pearlitic structure with no proeutectoid phase Correct answer.
  3. Martensite with retained austenite
  4. Coarse pearlite with proeutectoid ferrite

Explanation

At the eutectoid composition of about 0.8 percent carbon, slow cooling from above the critical temperature produces pearlite without any proeutectoid ferrite or cementite. Martensite needs rapid quenching, and spheroidisation needs prolonged tempering near the critical range.

Question 46Engineering Materials, Fasteners and Fits

A locking arrangement is required for a connecting rod bolt that is repeatedly tightened during overhaul. Which method allows reuse without damaging the fastener?

  1. Welding the nut to the bolt end
  2. A self-locking nut with a nylon insert Correct answer.
  3. Peening the bolt end over the nut
  4. Staking the thread into the nut

Explanation

A self-locking nut with a resilient insert grips the thread by friction and can be removed and refitted several times without damaging the thread. Staking, welding and peening are permanent deformations and destroy reusability.

Question 47Engineering Materials, Fasteners and Fits

A bolt and nut assembly is described as M10 with a thread tolerance class 6g for the bolt and 6H for the nut. Which statement about this assembly is correct?

  1. The class 6g bolt will not enter a 6H nut without force
  2. The nut thread is smaller than the basic size at maximum material condition
  3. Both threads have identical limits and always interfere
  4. The bolt thread has an allowance giving clearance at maximum material condition Correct answer.

Explanation

For external threads, a lower-case letter such as g indicates a fundamental deviation below the basic profile, so a 6g bolt has an allowance and clears a 6H nut at maximum material condition. The nut's maximum material limit is at the basic size, and the assembly is designed to screw together by hand.

Question 48Engineering Materials, Fasteners and Fits

Which material is most suitable for a motorcycle fuel tank because it combines formability, low weight and corrosion resistance?

  1. Grey cast iron
  2. Sintered bronze
  3. High-carbon tool steel
  4. Aluminium alloy sheet Correct answer.

Explanation

Aluminium alloy sheet is light, readily pressed and drawn into tank shapes, and resists corrosion, which suits fuel tanks. Cast iron is heavy and brittle in thin sections, tool steel is hard and difficult to form, and sintered bronze is used for bearings rather than sheet structures.

Question 49Engineering Materials, Fasteners and Fits

A bearing surface is required to run with low friction against a steel crankshaft journal with minimal lubrication. Which material property combination is most suitable?

  1. High brittleness with low melting point
  2. High hardness with low thermal conductivity
  3. Good embeddability with conformability and low friction Correct answer.
  4. Strong magnetic permeability with high stiffness

Explanation

Bearing alloys need to embed dirt particles, conform to slight misalignment and present low friction, which is why white metal and bronze bearings are used. Extreme hardness reduces embeddability, and brittleness or magnetic properties do not improve bearing performance.

Question 50Engineering Materials, Fasteners and Fits

A stud is broken flush with the surface of an aluminium crankcase. Which removal approach best avoids damaging the soft aluminium threads?

  1. Drill out the entire stud with an oversized drill
  2. Drive a hardened chisel under the stud and lever it out
  3. Weld a large nut on and apply full torque immediately
  4. Drill centrally, use a left-hand extractor, and apply penetrating oil and gentle heat Correct answer.

Explanation

Centre-punching and drilling centrally, then using a left-hand extractor with penetrating oil and gentle warming of the case, removes the stud with least risk to the aluminium thread. Chiselling or heavy torque tears the soft thread, and an oversized drill removes the parent thread.