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ITI Mechanic Tractor (AITT Theory) study materials
ITI Mechanic Tractor (AITT Theory) study resources

ITI Mechanic Tractor (AITT Theory) practice questions

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Question 1Trade Safety, Health and Environment

Before starting a tractor engine inside a workshop, which practice best controls exposure to diesel exhaust emissions?

  1. Run the engine only long enough to move the tractor outside
  2. Route the exhaust outlet through the workshop ventilation duct
  3. Attach a flexible hose that discharges the exhaust outdoors Correct answer.
  4. Open the workshop door and keep the engine at idle

Explanation

Diesel exhaust contains carbon monoxide, nitrogen oxides and particulate matter, so the safest control is source removal by ducting the exhaust to open air outside the building. Opening a door or idling briefly only dilutes or shortens exposure and does not reliably protect nearby workers.

Question 2Trade Safety, Health and Environment

Which PPE is essential when using a high-pressure water jet to clean a tractor's engine and chassis?

  1. A dust respirator and cotton overalls
  2. Impact-rated eye protection and waterproof clothing Correct answer.
  3. Leather welding gauntlets and a face shield
  4. Anti-vibration gloves and ear plugs

Explanation

High-pressure cleaning throws water, grit and degreasing chemicals back toward the operator, so sealed eye protection and waterproof clothing are the minimum protection. Ordinary overalls soak through and offer no barrier to a high-velocity jet.

Question 3Trade Safety, Health and Environment

What is the correct first action when a tractor's radiator cap must be removed after the engine has been working hard?

  1. Pour cold water over the radiator before touching the cap
  2. Loosen the cap quickly to release pressure in one movement
  3. Remove the cap while the engine is idling to check coolant flow
  4. Cover the cap with a rag and turn it slowly to the first stop Correct answer.

Explanation

Coolant in a hot system is above atmospheric boiling point, so sudden release of pressure causes violent flash boiling and scalding steam. Covering the cap with a cloth and turning it slowly to the first stop lets pressure bleed off before full removal.

Question 4Trade Safety, Health and Environment

In the workshop, what is the primary purpose of colour-coding portable electrical tools and testing them at set intervals?

  1. To identify the tool's voltage rating for the operator
  2. To confirm the tool has been formally inspected and is safe to use Correct answer.
  3. To show the tool has been recently cleaned
  4. To record which technician owns the tool

Explanation

A pat-test label and colour code give visible evidence that the tool has passed an insulation and earth-continuity inspection within its due interval. This lets a user reject equipment that is overdue without opening or testing it.

Question 5Trade Safety, Health and Environment

A mechanic must work under a raised tractor to inspect the transmission. Which support arrangement is acceptable?

  1. The front-end loader lowered to the ground as the only support
  2. Rated axle stands placed under the chassis at the specified points Correct answer.
  3. Wooden blocks stacked under the sump
  4. The hydraulic jack alone, with the handle left in place

Explanation

Hydraulic jacks can creep or fail and must never be the sole support for a person under a machine. Rated stands positioned at the manufacturer's lifting points provide a stable, load-rated support that cannot lose pressure.

Question 6Trade Safety, Health and Environment

A tractor fitted with a front-end loader is driven across a sloping yard. Which practice most reduces the risk of a sideways overturn?

  1. Keep the bucket low, travel slowly and avoid turning across the slope Correct answer.
  2. Carry the loader bucket high to improve the view ahead
  3. Select the highest gear and steer sharply downhill
  4. Increase engine speed to cross the slope quickly

Explanation

A raised loader raises the centre of gravity and shifts the stability envelope, so the bucket should be kept low and the machine driven slowly, ideally straight up or down the slope. Turning across a slope with a raised load is a common cause of sideways rollover.

Question 7Trade Safety, Health and Environment

During a field trial a tractor's PTO guard is found cracked. What is the correct action before the machine is used again?

  1. Operate the PTO only at low engine speed
  2. Tape the crack and continue work until the next service
  3. Remove the guard so the shaft can be inspected while running
  4. Replace or repair the guard before any PTO operation Correct answer.

Explanation

A cracked PTO guard cannot contain clothing or limbs drawn into the rotating shaft, and entanglement injuries are severe and often fatal. The guard must be restored to full condition before the PTO is engaged.

Question 8Trade Safety, Health and Environment

When hitching an implement to a tractor's three-point linkage, what is the safest sequence for the operator?

  1. Stand between the tractor and implement to guide the pins by hand
  2. Reverse quickly so the linkage aligns in one movement
  3. Stop the engine, apply the park brake and use the stabilisers to align the arms Correct answer.
  4. Raise the linkage fully and let the implement swing into position

Explanation

Most hitching injuries occur when the operator is crushed between the tractor and implement, so the machine must be immobilised and alignment done with the stabilisers rather than by hand. Shutting down the engine also removes the risk of unintended movement.

Question 9Trade Safety, Health and Environment

A workshop stores diesel, hydraulic oil and solvent in the same area. Which arrangement meets basic fire-safety requirements?

  1. All containers stored together on a timber shelf beside the welding bay
  2. Diesel and solvent stored in open drums to allow vapour to escape
  3. Solvents decanted into unmarked plastic bottles to save space
  4. Flammable solvents in a marked fire-rated cabinet, with all containers bunded and segregated from ignition sources Correct answer.

Explanation

Flammable liquids need a fire-resisting cabinet and segregation from ignition sources, while bunding contains spills of oils and fuels. Keeping them away from hot work such as welding prevents vapour ignition.

Question 10Trade Safety, Health and Environment

A mechanic notices that the hydraulic hose on a loader has a bulging section. What does this indicate and what should be done?

  1. Normal wear; monitor it at each shift
  2. Air trapped in the system; bleed the circuit
  3. Excess oil pressure; reduce the relief valve setting only
  4. Internal reinforcement failure; replace the hose before further use Correct answer.

Explanation

A bulge means the pressure-containing reinforcement has failed locally and the hose can burst without warning, injecting fluid at high pressure. The hose must be replaced, not monitored or adjusted.

Question 11Trade Safety, Health and Environment

Why must a mechanic never use a hand to check for a high-pressure hydraulic leak on a tractor?

  1. The hand cannot feel leaks smaller than one litre per minute
  2. Hydraulic oil is too hot to touch safely
  3. A fine jet can penetrate skin and cause serious injection injury Correct answer.
  4. The oil will damage the skin's natural oils

Explanation

A pinhole leak can inject fluid through the skin at pressures well above 100 bar, causing tissue damage and possible amputation or toxic reaction. Leaks must be traced with cardboard or paper, never with bare skin.

Question 12Trade Safety, Health and Environment

A tractor battery is being charged in the workshop. Which precaution most directly prevents a hydrogen explosion?

  1. Keep the filler caps tight and the charger switched on before connecting
  2. Ensure good ventilation and connect or disconnect the charger with the mains switched off Correct answer.
  3. Charge at the highest available current to shorten the time
  4. Place a damp cloth over the battery during charging

Explanation

Charging releases hydrogen, which forms an explosive mixture with air, and a spark at the charger clamps can ignite it. Ventilation disperses the gas and switching the mains off before making or breaking connections removes the spark source.

Question 13Trade Safety, Health and Environment

Which statement correctly describes the purpose of a roll-over protective structure with a seat belt on an agricultural tractor?

  1. It prevents the tractor from overturning on slopes
  2. It protects the operator only if the belt is worn and the operator stays within the structure Correct answer.
  3. It replaces the need for a cab on all terrain
  4. It allows the operator to jump clear during a rollover

Explanation

A ROPS creates a protected zone around the operator, but it only works when the seat belt restrains the operator inside that zone. Without the belt the operator can be thrown out and crushed by the structure itself.

Question 14Trade Safety, Health and Environment

A mechanic is asked to arc-weld a repair on a tractor chassis. Which combination of controls is required before striking the arc?

  1. Wear sunglasses and weld in the open yard without screening
  2. Screen the area, remove or protect fuel lines and drain flammable liquid, and connect the work return clamp directly to the workpiece Correct answer.
  3. Weld with the fuel tank in place and rely on the workshop extractor fan
  4. Leave the battery connected and the fuel tap open to speed the job

Explanation

Welding near fuel systems requires removal or protection of lines and tanks, screening of the arc to protect others, and a work return clamp on the workpiece to prevent stray current paths. These controls address fire, fume and electric shock together.

Question 15Trade Safety, Health and Environment

A workshop floor becomes contaminated with hydraulic oil during a repair. What is the correct immediate response to control slip risk?

  1. Spread sawdust and leave it until the end of the week
  2. Wash the oil into the yard drain with water
  3. Contain and absorb the spill, clean the area with a suitable degreaser, and dispose of the absorbent as hazardous waste Correct answer.
  4. Cover the area with a sheet of cardboard

Explanation

Oil spills must be contained and absorbed promptly, then the floor cleaned so the slip hazard is removed. The contaminated absorbent is hazardous waste and must go through the proper disposal route rather than drains or general refuse.

Question 16Trade Safety, Health and Environment

A mechanic must replace a fan belt on a tractor engine. Which shutdown and isolation routine best protects against unexpected starting and stored energy?

  1. Switch off the ignition key and leave the transmission in neutral
  2. Stop the engine, remove the key, disconnect the battery earth lead and ensure all rotating parts have stopped Correct answer.
  3. Remove the key only, with the battery still connected
  4. Lower the loader and leave the engine idling while the belt is changed

Explanation

Full isolation requires the engine stopped, the key controlled, and the battery earth disconnected so the starter cannot be operated by another person. Confirming that all rotating parts and stored hydraulic pressure have been released prevents residual-energy injury.

Question 17Engineering Drawing, Materials and Hand Tools

In a first-angle orthographic projection drawing of a tractor component, where is the top view placed relative to the front view?

  1. Above the front view
  2. To the left of the front view
  3. Below the front view Correct answer.
  4. To the right of the front view

Explanation

In first-angle projection the object is imagined between the observer and the plane, so the view obtained by looking from above is projected onto the plane beneath the object and appears below the front view. This is the standard layout used on most Indian workshop and AITT drawing sheets.

Question 18Engineering Drawing, Materials and Hand Tools

A drawing of a plough share is dimensioned as 250 mm at a scale of 1:5. What length should the line measure on the drawing sheet?

  1. 5 mm
  2. 250 mm
  3. 1250 mm
  4. 50 mm Correct answer.

Explanation

A scale of 1:5 means one unit on the drawing represents five units on the actual object, so the drawing length equals the true length divided by 5. Dividing 250 mm by 5 gives 50 mm on the sheet.

Question 19Engineering Drawing, Materials and Hand Tools

Which line type is used to show the hidden internal bore of a hydraulic lift cylinder in an orthographic view?

  1. Continuous thin wavy line
  2. Dashed thin line Correct answer.
  3. Continuous thick line
  4. Chain thin line

Explanation

Hidden edges and outlines that are not visible in a given view are drawn with short dashes of thin line, so the internal bore appears as a dashed line. Continuous thick lines are reserved for visible outlines.

Question 20Engineering Drawing, Materials and Hand Tools

A file with a single row of parallel diagonal cuts across its face is best described as which cut?

  1. Rasp cut
  2. Double cut
  3. Single cut Correct answer.
  4. Curved cut

Explanation

A single-cut file has one set of parallel teeth running diagonally across the face and is used for sharpening and fine finishing where a smooth surface is wanted. Double-cut files carry two intersecting sets of cuts for faster metal removal.

Question 21Engineering Drawing, Materials and Hand Tools

Which property of a material describes its ability to be drawn into thin wires without fracture?

  1. Brittleness
  2. Ductility Correct answer.
  3. Hardness
  4. Malleability

Explanation

Ductility is the capacity of a metal to undergo permanent deformation in tension, allowing it to be drawn into wire. Malleability is the related property of being flattened into sheets under compression.

Question 22Engineering Drawing, Materials and Hand Tools

A vernier calliper main scale reads 24 mm and the 6th vernier division coincides with a main scale division. If the least count is 0.02 mm, what is the reading?

  1. 24.60 mm
  2. 30.00 mm
  3. 24.12 mm Correct answer.
  4. 24.06 mm

Explanation

The vernier contribution equals the coinciding division number multiplied by the least count, that is 6 × 0.02 mm = 0.12 mm. Adding this to the main scale reading of 24 mm gives 24.12 mm.

Question 23Engineering Drawing, Materials and Hand Tools

In a multi-view drawing, a line inclined to both the horizontal plane and the vertical plane appears in the front view as a line inclined to the reference line. What is its true length obtained from?

  1. The front view length directly
  2. The top view length directly
  3. A construction using the projected lengths and the difference in heights Correct answer.
  4. The sum of the front and top view lengths

Explanation

When a line is inclined to both reference planes, neither view shows true length. True length is found by the rotation or auxiliary-plane construction, combining the projected length with the difference in height or distance between end points.

Question 24Engineering Drawing, Materials and Hand Tools

A hexagonal head bolt is to be drawn in a view showing the true shape of the hexagon. How many visible edges of the hexagon appear in that view?

  1. Six Correct answer.
  2. Two
  3. Three
  4. Four

Explanation

When the hexagon is viewed perpendicular to its plane, all six sides are visible as the true shape of the hexagon. In the other common view, only three or four faces are seen depending on orientation.

Question 25Engineering Drawing, Materials and Hand Tools

Which material is most suitable for the cutting teeth of a hand hacksaw blade used on mild steel?

  1. Cast iron
  2. Copper
  3. Low carbon steel
  4. High carbon steel hardened and tempered Correct answer.

Explanation

Hacksaw blades need teeth that stay sharp and resist wear, so high carbon steel hardened and tempered to a suitable toughness is used. Low carbon steel is too soft to hold a cutting edge.

Question 26Engineering Drawing, Materials and Hand Tools

A drawing carries the symbol 'Ø' before a dimension. What does this symbol indicate on a tractor shaft drawing?

  1. Square section
  2. Radius
  3. Diameter Correct answer.
  4. Spherical radius

Explanation

The symbol Ø placed before a numerical value indicates a diameter, so Ø40 means a circular feature of 40 mm diameter. Radius is shown by R and square sections by a square symbol.

Question 27Engineering Drawing, Materials and Hand Tools

During a tension test, a mild steel specimen shows a clear yield point before elongation continues. What does the yield point indicate about the material?

  1. The material has reached its ultimate breaking stress
  2. The material has fully work-hardened
  3. The material has become perfectly elastic again
  4. The material has begun to deform plastically with little increase in load Correct answer.

Explanation

At the yield point the specimen changes from elastic to plastic behaviour, so elongation continues while the load stays nearly constant. The ultimate stress and necking occur later in the test.

Question 28Engineering Drawing, Materials and Hand Tools

A centre punch is being used before drilling a hole in a tractor bracket. Why is the punch mark made first?

  1. To increase the drill diameter
  2. To harden the surface before drilling
  3. To remove the need for a drilling machine
  4. To prevent the drill from wandering off the marked centre Correct answer.

Explanation

A centre punch produces a small conical depression that guides the drill point, preventing it from slipping away from the layout mark. The drill then starts accurately at the intended location.

Question 29Engineering Drawing, Materials and Hand Tools

Which of the following is a ferrous metal commonly used for tractor chassis brackets because it is weldable and reasonably strong?

  1. Bronze
  2. Brass
  3. Mild steel Correct answer.
  4. Aluminium

Explanation

Mild steel is a low carbon ferrous alloy that welds easily and offers adequate strength for brackets and frames. Aluminium, brass and bronze are non-ferrous and are used where their specific properties are needed.

Question 30Engineering Drawing, Materials and Hand Tools

A component is drawn at a scale of 2:1 and measures 80 mm on the sheet. What is its actual length?

  1. 40 mm Correct answer.
  2. 160 mm
  3. 20 mm
  4. 80 mm

Explanation

A scale of 2:1 is an enlarging scale, so the drawing length is twice the actual length. Dividing the drawn 80 mm by 2 gives an actual length of 40 mm.

Question 31Engineering Drawing, Materials and Hand Tools

In an isometric drawing, how are the three principal axes oriented relative to each other?

  1. Two axes at 45° to the horizontal and one vertical
  2. All three axes at 90° to each other
  3. All three axes at 60° to the horizontal
  4. Two axes at 30° to the horizontal and one vertical Correct answer.

Explanation

Isometric projection uses three axes 120° apart, drawn on paper with two axes inclined at 30° to the horizontal and the third vertical. This gives equal foreshortening along all three axes.

Question 32Engineering Drawing, Materials and Hand Tools

A fit is specified as 40 H7/g6 on a drawing of a gearbox shaft and bush. What type of fit does this designation represent?

  1. Clearance fit Correct answer.
  2. Transition fit
  3. Interference fit
  4. Force fit

Explanation

In the hole-basis system, H denotes a hole whose lower deviation is zero, and a lowercase shaft tolerance such as g lies below the zero line. The shaft is therefore always smaller than the hole, giving a clearance fit.

Question 33Engineering Drawing, Materials and Hand Tools

A surface is marked with the roughness symbol Ra 3.2. What does the number represent?

  1. The maximum waviness height in millimetres
  2. The arithmetic mean roughness value in micrometres Correct answer.
  3. The hardness of the surface in HRC
  4. The tolerance on the dimension in millimetres

Explanation

Ra denotes the arithmetic mean deviation of the assessed profile from its mean line, expressed in micrometres. A value of Ra 3.2 therefore specifies the average surface roughness permitted.

Question 34Engineering Drawing, Materials and Hand Tools

A hole of 25.000 mm minimum and 25.021 mm maximum is to be produced. Which tolerance value applies?

  1. 0.021 mm Correct answer.
  2. 0.042 mm
  3. 0.0105 mm
  4. 25.021 mm

Explanation

Tolerance is the difference between the upper and lower limits, so 25.021 − 25.000 gives 0.021 mm. It is always a positive magnitude independent of the basic size.

Question 35Engineering Drawing, Materials and Hand Tools

In a drawing, a threaded hole is shown with a thin continuous line outside the thick continuous line in the plan view. What does this convention represent?

  1. The major diameter of an internal thread Correct answer.
  2. The minor diameter of an internal thread
  3. The thread run-out only
  4. The pitch circle of a bolt head

Explanation

For internal threads in plan view, the major diameter is drawn as a thin continuous circle while the minor diameter is drawn as a thick continuous circle. The thin outer circle therefore shows the major diameter of the tapped hole.

Question 36Engineering Drawing, Materials and Hand Tools

A steel shaft is to be hardened only on its outer surface while retaining a tough core. Which heat treatment process is appropriate?

  1. Case carburising followed by hardening Correct answer.
  2. Normalising
  3. Stress relieving
  4. Full annealing

Explanation

Case carburising adds carbon to the surface layer, so after hardening the skin becomes hard and wear resistant while the low carbon core stays tough. Annealing, normalising and stress relieving do not produce a hard case.

Question 37Basic Fitting, Measurement and Workshop Practice

When filing a mild steel surface with a new single-cut file, what is the main purpose of the file card (file brush) during the job?

  1. To sharpen the file teeth before each stroke
  2. To remove pinning (chips wedged between teeth) so the teeth cut cleanly Correct answer.
  3. To measure the depth of cut achieved
  4. To cool the file after heavy pressure

Explanation

Soft metals like mild steel tend to load the file teeth with small chips, a condition called pinning. Cleaning with a file card keeps the teeth cutting freely and prevents scratching and skidding over the work. A file card does not sharpen, cool, or measure anything.

Question 38Basic Fitting, Measurement and Workshop Practice

A vernier caliper has a main scale with 1 mm divisions and a vernier scale of 50 divisions. What is the least count of the instrument?

  1. 0.5 mm
  2. 0.05 mm
  3. 0.02 mm Correct answer.
  4. 0.1 mm

Explanation

Least count equals the main scale division divided by the number of vernier divisions. With 1 mm main scale divisions and 50 vernier divisions, the least count is 1/50 = 0.02 mm. This is the standard metric vernier caliper resolution.

Question 39Basic Fitting, Measurement and Workshop Practice

In a workshop, which tool is the correct choice for checking the flatness of a cylinder head face on a bench?

  1. Spring divider
  2. Vernier height gauge
  3. Surface plate with dial test indicator or a straight edge and feeler gauge Correct answer.
  4. Outside micrometer

Explanation

Flatness is a form characteristic checked against a known flat reference such as a surface plate, straight edge, or with a dial indicator swept over the surface. Micrometers, height gauges, and dividers measure size or mark positions, not flatness.

Question 40Basic Fitting, Measurement and Workshop Practice

What is the included angle of the point of a standard centre punch used for marking hole positions in mild steel?

  1. 120 degrees
  2. 60 degrees
  3. 90 degrees Correct answer.
  4. 30 degrees

Explanation

A centre punch is ground to approximately a 90 degree included angle so it produces a distinct conical dot that guides a drill. A 60 degree point is typical of a prick punch used for fine layout lines. Steeper or shallower angles give either a weak point or a dot too wide to guide the drill.

Question 41Basic Fitting, Measurement and Workshop Practice

Which operation is performed with a hand reamer after drilling a hole for a dowel pin?

  1. Threading the hole for a bolt
  2. Reducing the hole diameter to an interference fit
  3. Enlarging the hole to remove taper and improve roundness and finish Correct answer.
  4. Chamfering the hole entry

Explanation

Reaming removes a small amount of material to correct taper and out-of-roundness left by drilling, producing an accurate, smooth hole. Reamers do not cut threads, chamfer, or shrink a hole. A typical allowance is a few hundredths of a millimetre under the finished size before reaming.

Question 42Basic Fitting, Measurement and Workshop Practice

Which of these is the correct workshop practice for tightening the cylinder head bolts of an engine during assembly?

  1. Tighten diagonally from the centre outwards in one pass
  2. Tighten all bolts by hand first, then apply final torque in any order
  3. Tighten each bolt fully in turn to the final torque before moving to the next
  4. Tighten in the specified sequence in stages up to the final torque Correct answer.

Explanation

Head bolts are tightened in the manufacturer's specified sequence (usually spiral from the centre outwards) and in stages to the final torque. This distributes clamping load evenly and prevents gasket distortion or head warping. One-pass tightening or arbitrary order causes uneven stress.

Question 43Basic Fitting, Measurement and Workshop Practice

A micrometer reading shows 12.5 mm on the sleeve and the thimble line coincides with the 28th division, with a thimble of 50 divisions and 0.5 mm pitch. What is the reading?

  1. 15.30 mm
  2. 12.28 mm
  3. 12.56 mm
  4. 12.78 mm Correct answer.

Explanation

The thimble value is 28 x (0.5/50) = 28 x 0.01 = 0.28 mm. Adding this to the sleeve reading of 12.5 mm gives 12.78 mm. Each thimble division represents 0.01 mm on a 0.5 mm pitch micrometer.

Question 44Basic Fitting, Measurement and Workshop Practice

A hole is specified as 25.00 +0.02/-0.00 mm. Which measurement indicates the hole is within tolerance?

  1. 24.95 mm
  2. 25.01 mm Correct answer.
  3. 25.03 mm
  4. 24.98 mm

Explanation

The tolerance zone is from 25.00 mm (lower limit) to 25.02 mm (upper limit). Only 25.01 mm falls inside this zone. Values below 25.00 mm or above 25.02 mm are rejects.

Question 45Basic Fitting, Measurement and Workshop Practice

A shaft of 40 mm nominal diameter is to run freely in a bearing bush with a small clearance. Which type of fit is appropriate?

  1. Force fit
  2. Clearance fit Correct answer.
  3. Transition fit
  4. Interference fit

Explanation

A clearance fit always leaves a gap between the shaft and hole, allowing free rotation and lubrication. Interference and force fits intentionally make the shaft larger than the hole for a tight grip. A transition fit may give either clearance or interference and is not used where free running is required.

Question 46Basic Fitting, Measurement and Workshop Practice

What is the correct procedure for setting a dial test indicator to zero before checking shaft runout?

  1. Zero the dial with the stylus fully depressed to its travel limit
  2. Bring the stylus into contact with the reference surface, preload it slightly, then set zero Correct answer.
  3. Zero the dial while the stylus is off the work, then bring it into contact
  4. Zero the dial after taking the first reading at the high point

Explanation

The stylus should contact the reference surface with a small preload so it can follow both rises and falls. Zero is then set on that reference. Zeroing off the work or at the travel limit gives no usable reference or risks overtravel.

Question 47Basic Fitting, Measurement and Workshop Practice

When tapping a blind hole in mild steel by hand, why should the tap be backed off a quarter turn periodically?

  1. To align the tap with the hole axis
  2. To break the chips and prevent the tap from jamming or breaking Correct answer.
  3. To increase the thread pitch progressively
  4. To allow the tap to cool in air

Explanation

Backing off breaks the continuous chip into short pieces so it does not pack in the flutes and jam the tap. Jamming is a common cause of tap breakage in blind holes. Backing off does not change pitch or alignment and is not primarily for cooling.

Question 48Basic Fitting, Measurement and Workshop Practice

A feeler gauge set is being used to check valve clearance. The 0.25 mm blade enters with slight drag and the 0.30 mm blade will not enter. What does this indicate?

  1. The clearance cannot be judged with feeler gauges
  2. The clearance is less than 0.25 mm
  3. The clearance is exactly 0.30 mm
  4. The clearance is between 0.25 mm and 0.30 mm, closest to the 0.25 mm blade Correct answer.

Explanation

The blade that enters with a light drag approximates the gap, while the next size that will not enter sets the upper bound. The true clearance therefore lies between the two blade thicknesses, close to 0.25 mm. This is the standard go/no-go feeler gauge method.

Question 49Basic Fitting, Measurement and Workshop Practice

During hacksawing of a 25 mm mild steel bar, the blade jumps and the teeth clog. What is the most likely cause?

  1. Too many teeth per inch for the section thickness Correct answer.
  2. Insufficient stroke length
  3. Blade fitted with teeth pointing towards the handle
  4. Too few teeth per inch, causing teeth to catch

Explanation

A fine-tooth blade used on a thick section has insufficient chip clearance, so chips pack in the gullets and the blade skates or clogs. For thick sections a coarser pitch (fewer teeth per inch) is selected. Teeth should point forward on the cutting stroke, and stroke length affects speed, not clogging.

Question 50Basic Fitting, Measurement and Workshop Practice

Which drill point angle is standard for general-purpose drilling of mild steel?

  1. 118 degrees Correct answer.
  2. 90 degrees
  3. 140 degrees
  4. 60 degrees

Explanation

A 118 degree included angle is the standard general-purpose drill point for steel and most metals. Flatter points around 140 degrees suit hard or thin materials, while sharper points suit plastics and soft materials. The 90 degree point is used for sheet metal and plastics.