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ITI/NCVT Tool & Die Maker (AITT Theory) study materials
ITI/NCVT Tool & Die Maker (AITT Theory) study resources

ITI/NCVT Tool & Die Maker (AITT Theory) practice questions

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Question 1Safety, environment and housekeeping

While dressing a hardened die block on a pedestal grinder, which combination of personal protective equipment is appropriate for the tool and die maker?

  1. Cotton hand gloves and a cloth cap
  2. A loose synthetic apron and open sandals
  3. Safety goggles worn together with a face shield Correct answer.
  4. A wrist watch and a dust mask only

Explanation

Grinding throws high-velocity abrasive particles and sparks toward the face, so eye protection alone is not sufficient for this operation. Safety goggles worn under a full face shield protect both the eyes and the skin of the face, and the guard and tongue of the grinder must also be correctly adjusted before dressing begins.

Question 2Safety, environment and housekeeping

A small fire starts inside the electrical control cabinet of an EDM machine. Which extinguisher is the correct first choice?

  1. Carbon dioxide (CO2) extinguisher Correct answer.
  2. Foam extinguisher
  3. Water stored-pressure extinguisher
  4. Wet sand thrown by hand

Explanation

Carbon dioxide is non-conducting and leaves no residue, so it is suitable for live electrical equipment in a control cabinet. Water and foam are electrically conductive and can cause shock or further short circuits, while sand is only a makeshift measure and contaminates the precision machine.

Question 3Safety, environment and housekeeping

During chipping on a bench, the head of a cold chisel is found to have spread out into a mushroom shape. What is the correct action before continuing the job?

  1. Wrap the head in a cloth and continue the operation
  2. Fit a larger hammer to spread the impact over the head
  3. Continue chipping but strike with lighter hammer blows
  4. Dress the head on a grinding wheel to restore the correct taper Correct answer.

Explanation

A mushroomed head can spall and send sharp metal chips into the operator or nearby workers. The head must be ground back to the original chamfered taper so that the striking face is flat and slightly convex, and the chisel should be re-hardened and tempered if the dressing removes the hardened zone.

Question 4Safety, environment and housekeeping

A die setter is about to run trial blanks on a mechanical power press. Which safeguarding arrangement best protects the operator's hands during the working stroke?

  1. A warning notice fixed on the press frame
  2. Verbal instruction given once at the start of the shift
  3. A fixed guard with an interlock that prevents the stroke while the guard is open Correct answer.
  4. A foot pedal that leaves both hands free

Explanation

The hazard at a power press is the closing die space, and only a guard that physically prevents access or an interlock that stops the stroke can control it. Warning notices and instructions rely on human behaviour and do not prevent a hand from entering the die area during the descent of the ram.

Question 5Safety, environment and housekeeping

After a long milling run, the soluble cutting fluid in the machine sump has become rancid and must be replaced. What is the acceptable way to dispose of the old fluid?

  1. Mix it with the general workshop refuse and place it in the bin
  2. Pour it into the workshop floor drain
  3. Decant it into labelled drums and hand it to an authorised recycler Correct answer.
  4. Burn it in an open drum behind the workshop

Explanation

Waste cutting fluid contains mineral oil, emulsifiers, biocides and metal fines, and it is a controlled waste that must be segregated, labelled and sent to an authorised recycler or treatment facility. Discharging it to a drain or burning it in the open causes water and air pollution and is an offence under environmental legislation.

Question 6Safety, environment and housekeeping

In the 5S system applied to a die-fitting bench, which step refers to removing unnecessary tools, gauges and offcuts so that only items needed for the current job remain?

  1. Seiketsu (standardise)
  2. Seiri (sort) Correct answer.
  3. Seiton (set in order)
  4. Shitsuke (sustain)

Explanation

Seiri is the sorting step in which everything at the workplace is examined and items not required for current production are removed. Seiton then assigns a fixed, marked location to the items that remain, so the two steps are sequential and must not be confused.

Question 7Safety, environment and housekeeping

A hardened die block weighing about 85 kg has to be moved from the storage rack to the press bed. What is the correct handling method?

  1. Drag it on a wooden pallet using a rope
  2. Roll it along the floor on short lengths of bar stock
  3. Lift it by hand with two workers and walk it across the shop floor
  4. Use a crane with rated slings attached to correctly tapped lifting holes in the block Correct answer.

Explanation

A load of this mass exceeds safe manual handling limits, and die blocks are usually provided with tapped lifting holes for eyebolts. The block should be lifted with a crane or hoist using slings and shackles rated for the load, with the lifting points checked for thread condition and full engagement before the lift.

Question 8Safety, environment and housekeeping

In an oxy-acetylene welding set used for die repair, where should a flashback arrestor be fitted to protect the acetylene cylinder?

  1. At the torch nozzle only
  2. Inside the blowpipe handle
  3. At the midpoint of the acetylene hose
  4. At the regulator outlet on the cylinder side of the hose Correct answer.

Explanation

A flashback arrestor at the regulator outlet stops a flame travelling back along the hose from reaching the cylinder and causing a cylinder explosion. Many sets also carry a second arrestor at the torch end, but the cylinder-side unit is the one that protects the cylinder itself and must be kept in place.

Question 9Safety, environment and housekeeping

A hydraulic press used for die spotting has a pressure relief valve on the main ram circuit. How should this valve be maintained?

  1. Set at or below the rated capacity and checked at planned intervals Correct answer.
  2. Adjusted upwards whenever a job needs more force
  3. Removed and replaced by a plug to simplify the circuit
  4. Blanked off once the press is commissioned

Explanation

The relief valve is the primary protection against overloading the frame, seals and dies, so its setting must never exceed the rated capacity of the press. It should be sealed or locked after setting and its operation verified during planned maintenance, because a drifting setting allows pressure to rise to destructive levels.

Question 10Safety, environment and housekeeping

Before commissioning a newly installed die-sinking EDM machine, what must be verified about its protective earthing?

  1. That the earth conductor is the same colour as the phase conductors
  2. That the earth is disconnected during dielectric tests
  3. That the earth wire is connected only at the machine end
  4. That the earth continuity resistance is low and within the limit specified for the machine Correct answer.

Explanation

Protective earthing provides the low-resistance path that lets fault current operate the protective device and keeps touch voltage safe. The continuity between the machine frame and the earth bar must be measured and found within the specified limit before the machine is energised, and the result recorded.

Question 11Safety, environment and housekeeping

A trainee is about to start a drilling machine after clamping a die plate in the machine vice. What must be done with the chuck key immediately before switching on the spindle?

  1. Remove the chuck key and place it in its holder Correct answer.
  2. Rest it on the drill table beside the machine vice
  3. Leave it in the chuck so the drill can be tightened during cutting
  4. Hand it to a nearby operator to hold during the operation

Explanation

A chuck key left in the chuck becomes a projectile the moment the spindle starts and can strike the operator or a bystander. The safe routine is to remove the key and return it to its holder before switching on, and to use a spring-loaded key where available.

Question 12Safety, environment and housekeeping

During die fitting, a bottle of soluble cutting oil is knocked over and spreads across the operator's standing area. What is the correct immediate action?

  1. Cover the spill with dry metal swarf so the floor looks clean
  2. Continue working and clean up at the end of the shift
  3. Wash the oil into the floor drain with water
  4. Stop work, isolate the area and absorb or clean the spill before continuing Correct answer.

Explanation

Oil on a standing area destroys foot grip and is a common cause of slips in a die shop. Work should stop, the area should be isolated and the spill absorbed or cleaned with a suitable absorbent before work resumes.

Question 13Safety, environment and housekeeping

An operator uses a compressed air blow gun to clear chips from a die block on the bench. Which practice is acceptable?

  1. Reduce the pressure and wear eye protection, blowing chips away from people Correct answer.
  2. Hold the nozzle against the die face and blast at full line pressure
  3. Use the gun to clean the machine slideways without any guard
  4. Direct the jet at the operator's overalls to remove clinging chips

Explanation

Compressed air can force chips into the eyes and skin and can inject air under the skin if pointed at a person. Pressure should be reduced to a safe level, eye protection worn and the jet directed away from operators.

Question 14Safety, environment and housekeeping

A new vitrified grinding wheel is to be mounted on a bench grinder for sharpening die chisels. Which check must be made before mounting?

  1. Measure the wheel diameter with a vernier caliper
  2. Soak the wheel in coolant for 24 hours
  3. Spin the wheel on the spindle with the guard open
  4. Ring test the wheel and inspect it for cracks or damage Correct answer.

Explanation

A cracked or damaged vitrified wheel can burst at operating speed. Ring testing a clean, dry wheel with a light tap and inspecting it for cracks before mounting is the standard check; a wheel that does not ring clearly must be rejected.

Question 15Safety, environment and housekeeping

A die-sinking EDM machine is cutting a cavity using kerosene dielectric. Which control is required for the mist and vapour produced at the work tank?

  1. Local exhaust ventilation at the work tank Correct answer.
  2. Opening the shop doors during machining
  3. Covering the work tank with a cloth during cutting
  4. A disposable dust mask worn by the operator

Explanation

EDM dielectric mist and vapour can irritate the respiratory tract and are a fire and health hazard. Local exhaust ventilation at the work tank captures the mist at source, whereas general shop ventilation only dilutes it.

Question 16Safety, environment and housekeeping

A die is to be spotted and repaired inside a mechanical power press. The main isolator has been switched off. What completes a correct lockout/tagout procedure before hands enter the die space?

  1. Press the emergency stop button and leave the isolator unlocked for a quick restart
  2. Lock the isolator with a personal lock, attach a tag and verify that the press cannot be started Correct answer.
  3. Ask a colleague to watch the control panel while the work is done
  4. Switch off the isolator and rely on the key being kept in the supervisor's desk

Explanation

Lockout is not complete when the isolator is merely switched off, because another person can restore power. A personal lock, a tag and a verified test that the press cannot be started, including release of stored hydraulic or pneumatic energy, are required before hands enter the die space.

Question 17Engineering materials and heat treatment

In the iron–carbon equilibrium diagram, plain carbon steel containing about 0.8% carbon is classified as:

  1. hypereutectoid steel
  2. eutectoid steel Correct answer.
  3. white cast iron
  4. hypoeutectoid steel

Explanation

In the iron–carbon equilibrium diagram, the eutectoid composition is about 0.8% carbon, where austenite transforms to pearlite on slow cooling. Steels below this value are hypoeutectoid and contain proeutectoid ferrite, while steels above it contain proeutectoid cementite. White cast iron is a much higher-carbon material, not a plain carbon steel.

Question 18Engineering materials and heat treatment

Which quenching medium removes heat from a hardened tool most slowly under otherwise identical conditions?

  1. Oil at room temperature
  2. Still air Correct answer.
  3. Water at room temperature
  4. Brine solution

Explanation

Cooling severity depends on the medium and its condition: brine is the most severe, followed by water, oil, and still air. Still air transfers heat by natural convection and radiation only, so it removes heat most slowly and gives the slowest cooling rate among the listed media. The other media cause faster cooling and therefore greater risk of distortion and cracking.

Question 19Engineering materials and heat treatment

What is the primary purpose of tempering a hardened carbon tool steel?

  1. To increase the carbon content of the surface
  2. To convert pearlite into austenite
  3. To relieve quenching stresses and improve toughness Correct answer.
  4. To refine the austenite grain size before quenching

Explanation

Tempering is a controlled reheating after hardening, usually below the lower critical temperature. It relieves quenching stresses, reduces brittleness, and adjusts hardness and toughness to the service requirement. It does not add carbon, refine prior austenite grains, or convert pearlite to austenite.

Question 20Engineering materials and heat treatment

In the AISI designation O1 tool steel, the letter O indicates a tool steel that is:

  1. oil-hardening cold-work steel Correct answer.
  2. water-hardening cold-work steel
  3. air-hardening cold-work steel
  4. molybdenum high-speed steel

Explanation

The AISI letter prefix identifies the tool steel group and the hardening medium or application. O stands for oil-hardening cold-work tool steel, W for water-hardening, A for air-hardening, and M for molybdenum high-speed steel. The number identifies a specific grade within that group.

Question 21Engineering materials and heat treatment

During austenitizing for hardening, a tool steel is held at temperature only long enough to:

  1. raise the carbon content above the grade specification
  2. precipitate coarse carbide particles at prior-austenite grain boundaries
  3. complete austenite formation and dissolve the necessary carbides Correct answer.
  4. form martensite by diffusion before the component enters the quench

Explanation

Austenitizing requires enough time at temperature for the ferrite–carbide structure to transform to austenite and for the necessary alloy carbides to dissolve. The hold must be controlled because excessive time causes grain growth, decarburization, and distortion. Martensite forms during quenching, not during the austenitizing soak.

Question 22Engineering materials and heat treatment

Which treatment introduces carbon into the surface of a low-carbon steel die component to produce a hard wear-resistant case?

  1. Stress relieving
  2. Nitriding
  3. Carburizing Correct answer.
  4. Induction hardening

Explanation

Carburizing diffuses carbon into the surface of low-carbon steel at a temperature in the austenite range, producing a high-carbon case after quenching. Nitriding adds nitrogen rather than carbon, induction hardening changes no composition, and stress relieving does not produce a wear-resistant case.

Question 23Engineering materials and heat treatment

Austempering of steel involves quenching from the austenitizing temperature into a bath held in the bainite transformation range, holding until transformation is complete, and then:

  1. reheating to form martensite
  2. cold working to increase hardness
  3. quenching in water to refine the grain
  4. cooling to room temperature without martensitic transformation Correct answer.

Explanation

Austempering quenches the part into a bath at a temperature above the martensite start temperature but within the bainite range. The austenite transforms isothermally to bainite, and the part is then cooled to room temperature without forming martensite. This treatment gives good toughness with relatively low distortion.

Question 24Engineering materials and heat treatment

Martempering (marquenching) of a die steel is carried out by quenching into a salt bath held:

  1. just above the Ms temperature until the section is uniform, then air cool Correct answer.
  2. at room temperature until all austenite transforms to pearlite
  3. well below the Ms temperature until martensite is fully formed
  4. at the austenitizing temperature for several hours before a water quench

Explanation

Martempering interrupts the quench in a salt bath just above the Ms temperature so that the whole section reaches a uniform temperature before transforming. The part is then cooled in air, where martensite forms with reduced thermal gradients and less distortion. It is subsequently tempered in the usual way.

Question 25Engineering materials and heat treatment

Which statement correctly describes hardenability of a tool steel?

  1. It is the resistance of the steel to softening during high-temperature tempering.
  2. It is the depth to which steel hardens under a given cooling rate. Correct answer.
  3. It is the maximum hardness measured on the as-quenched surface.
  4. It is the ability of the steel to be hardened by cold working.

Explanation

Hardenability describes the depth and distribution of hardness obtained when a steel is quenched under specified conditions. It is not the same as maximum hardness, which depends mainly on carbon content, nor is it resistance to softening on tempering. Cold working produces strain hardening, not the quench-hardening response described by hardenability.

Question 26Engineering materials and heat treatment

Which alloying element is mainly responsible for the red hardness of high-speed steel cutting tools?

  1. Aluminum
  2. Silicon
  3. Tungsten Correct answer.
  4. Sulfur

Explanation

Tungsten forms very stable carbides in high-speed steel and slows softening when the tool edge becomes hot, which is the basis of red hardness. Silicon, sulfur, and aluminum do not provide this combination of carbide stability and hot hardness; sulfur is used mainly to improve machinability.

Question 27Engineering materials and heat treatment

For rapid routine hardness checking of a hardened tool steel die block at about 60 HRC, the most suitable test is:

  1. Shore rebound test with a scleroscope
  2. Vickers test with a 10 kgf load and a diamond pyramid
  3. Rockwell hardness on the C scale with a diamond cone indenter Correct answer.
  4. Brinell test with a 10 mm ball and 3000 kgf load

Explanation

The Rockwell C test uses a diamond cone indenter with a 150 kgf major load and gives a direct hardness reading, which makes it the standard shop-floor method for hardened tool steel. A Brinell ball tends to deform on steel above roughly 450 HB, and Vickers is more of a laboratory method. Shore rebound testing is useful for large rolls but is less reliable for a small hardened die block.

Question 28Engineering materials and heat treatment

A hardened tool steel punch is to be re-machined and needs to be softened throughout. The appropriate treatment is:

  1. Tempering at 180 °C for one hour
  2. Full annealing followed by slow furnace cooling Correct answer.
  3. Stress relieving at 200 °C after machining
  4. Normalizing in still air from the austenitizing temperature

Explanation

Full annealing heats the steel above its critical temperature, holds it, and cools it very slowly in the furnace. This produces a soft ferrite-carbide structure, relieves internal stresses, and restores machinability. Low-temperature tempering or stress relieving does not soften the hardened structure, and normalizing cools in air, leaving a harder, finer pearlitic structure.

Question 29Engineering materials and heat treatment

In grey cast iron used for machine bases and die-set bodies, most of the carbon occurs as:

  1. fine pearlite lamellae
  2. spheroidal graphite nodules
  3. a cementite network
  4. graphite flakes Correct answer.

Explanation

In grey cast iron the silicon content promotes graphitization, so most carbon separates as graphite flakes rather than combined cementite. These flakes give good damping capacity and machinability, which suits machine bases and die-set bodies. Nodular graphite is characteristic of ductile iron, while a cementite network indicates white cast iron.

Question 30Engineering materials and heat treatment

A die insert is gas-nitrided at about 520 °C. Compared with carburizing, the main practical advantage of this treatment is that:

  1. the process can be completed in a few minutes
  2. the case produced is deeper than a carburized case in the same time
  3. no quenching is required, so distortion is very small Correct answer.
  4. the core strength is increased by nitrogen diffusion

Explanation

Nitriding diffuses nitrogen into the surface at about 500-550 °C, below the lower critical temperature, so the part never becomes austenite and needs no quench. Consequently distortion and dimensional change are very small, which is valuable for finished die inserts. The case is relatively shallow and the core is not strengthened by the nitrogen.

Question 31Engineering materials and heat treatment

AISI D2 tool steel, commonly used for cold-work dies and punches, is:

  1. a high-carbon, high-chromium cold-work tool steel Correct answer.
  2. a shock-resisting tool steel with about 0.5% C
  3. a molybdenum high-speed tool steel
  4. a water-hardening plain carbon tool steel

Explanation

AISI D2 is a cold-work tool steel containing roughly 1.5% carbon and 11-12% chromium, giving high wear resistance and deep hardening. Water-hardening grades carry the prefix W, shock-resisting grades the prefix S, and molybdenum high-speed steels the prefix M. D2 is therefore not a plain carbon or high-speed grade.

Question 32Engineering materials and heat treatment

A hardened die steel is tempered at 400 °C instead of 200 °C. The expected change is:

  1. lower hardness and higher toughness Correct answer.
  2. higher hardness with no change in toughness
  3. higher hardness and lower toughness
  4. no change in hardness but increased distortion

Explanation

Tempering at a higher temperature allows more carbide precipitation and recovery of the martensite, so hardness falls while toughness improves. A die tempered at 400 °C is therefore softer and tougher than the same die tempered at 200 °C. Hardness does not remain unchanged, and distortion is not the purpose of tempering.

Question 33Engineering materials and heat treatment

To determine the effective case depth of a carburized die component, the accepted shop method is to:

  1. examine the fracture surface under a magnifying glass
  2. measure the overall hardness on the Rockwell C scale
  3. weigh the component before and after carburizing
  4. make a microhardness traverse on a polished cross-section Correct answer.

Explanation

Effective case depth is defined by the depth at which a specified hardness, such as 550 HV, is reached. This is measured by making a series of microhardness indentations along a polished and etched cross-section from the surface toward the core. Surface hardness alone gives no depth information, and neither fracture appearance nor weight gain is a quantitative measure.

Question 34Engineering materials and heat treatment

After forging, a carbon steel die blank is normalized mainly to:

  1. retain austenite for dimensional stability
  2. introduce compressive residual stresses at the surface
  3. refine the grain and obtain a uniform structure for machining Correct answer.
  4. produce a hard wear-resistant surface layer

Explanation

Normalizing heats the forging above the critical range and cools it in still air, which refines coarse grains and produces a uniform pearlitic structure. This improves machinability and gives a predictable starting structure before hardening. It does not add a hard surface layer, retain austenite, or deliberately introduce compressive residual stresses.

Question 35Engineering materials and heat treatment

High-speed steel tools are often tempered three times at about 550 °C. The main reason for this multiple tempering is to:

  1. transform retained austenite and precipitate fine alloy carbides Correct answer.
  2. produce a thick oxide layer that improves lubricity
  3. soften the martensite completely for easy regrinding
  4. coarsen the carbides so that wear resistance increases

Explanation

During the first temper, retained austenite transforms to martensite on cooling, and fine alloy carbides precipitate, causing secondary hardening. Repeated tempering ensures that this fresh martensite is also tempered and that the structure becomes stable and tough. Complete softening, oxide formation, or carbide coarsening are not the aims of the treatment.

Question 36Engineering materials and heat treatment

A 1.3% carbon tool steel is considered for a die that must resist repeated impact. Its limited use in this application is mainly because:

  1. it cannot be tempered at all after quenching
  2. coarse carbide networks in the structure reduce toughness Correct answer.
  3. it has too little wear resistance for any die application
  4. it cannot be hardened to a useful hardness

Explanation

A 1.3% carbon steel is hypereutectoid, so excess cementite forms a network or coarse carbide particles along the prior austenite grain boundaries. These brittle carbides act as easy crack paths under impact, so toughness is low even though wear resistance is high. Lower-carbon shock-resisting steels are preferred where repeated impact occurs.

Question 37Engineering materials and heat treatment

In plain carbon tool steel, which element is deliberately controlled to increase hardness and wear resistance after quenching?

  1. Sulphur
  2. Carbon Correct answer.
  3. Manganese
  4. Silicon

Explanation

Carbon is the main hardening element in plain carbon steel because it controls the amount of martensite and carbide that can form during hardening. Increasing carbon within the tool steel range raises attainable hardness and wear resistance after quenching and tempering. Silicon, manganese and sulphur are not used as the principal hardening element in this grade.

Question 38Engineering materials and heat treatment

The Jominy end-quench test on a tool steel specimen is performed to determine its:

  1. Machinability rating
  2. Hardenability Correct answer.
  3. Resistance to abrasive wear
  4. Corrosion resistance

Explanation

In the Jominy test, a standard bar is austenitized and water-quenched at one end, then hardness is measured along its length. The resulting hardness-versus-distance curve shows how rapidly hardness falls as the cooling rate decreases, which is the definition of hardenability. It does not directly measure wear, machinability or corrosion resistance.

Question 39Engineering materials and heat treatment

After tempering, a hardened carbon steel die shows a light straw oxide colour on its cleaned surface. The approximate tempering temperature is:

  1. 150 °C
  2. 400 °C
  3. 230 °C Correct answer.
  4. 200 °C

Explanation

Temper colours are thin surface oxide films whose colour depends on the tempering temperature. Light straw corresponds to approximately 230 °C for carbon steel, so the die was tempered near that temperature. The colour is only a shop guide and should be checked against the specified hardness.

Question 40Engineering materials and heat treatment

A high-carbon cold-work die steel retains too much austenite after quenching, causing dimensional instability. Which treatment is most directly used to transform this retained austenite?

  1. Tempering at 150 °C for 1 hour
  2. Normalizing from 900 °C
  3. Annealing at 750 °C
  4. Sub-zero treatment at about −80 °C Correct answer.

Explanation

Retained austenite is unstable and continues to transform to martensite when the steel is cooled below its martensite finish temperature. A sub-zero or cold treatment at about −80 °C drives this transformation and is normally followed by tempering to relieve the new martensite stresses. Annealing and normalizing reset the structure rather than completing the quench transformation.

Question 41Bench fitting, hand tools and measurement

A try square is used in bench fitting mainly to check:

  1. the squareness of two adjacent surfaces Correct answer.
  2. the pitch of an external screw thread
  3. the diameter of a drilled hole
  4. the included angle of a centre drill

Explanation

A try square has a stock and blade fixed at exactly 90 degrees. It is placed against a datum surface so the blade reveals any departure from squareness on an adjacent surface. It is not a thread, angle, or diameter measuring instrument.

Question 42Bench fitting, hand tools and measurement

Which hand tool is used for scribing circles and arcs on a metal surface during layout?

  1. Odd-leg caliper
  2. Surface gauge
  3. Outside caliper
  4. Divider Correct answer.

Explanation

A divider has two sharp points that are set to the required radius, with one point centred and the other scribing the circle or arc. Outside calipers measure external sizes, odd-leg calipers scribe lines parallel to an edge, and a surface gauge scribes lines at a set height.

Question 43Bench fitting, hand tools and measurement

A hacksaw blade with 14 teeth per inch is most suitable for sawing:

  1. a thick section of soft mild steel Correct answer.
  2. hardened tool steel plate
  3. thin sheet metal and small tubing
  4. a narrow slot in brass

Explanation

Fewer teeth per inch means a coarser pitch, which gives more chip clearance in thick soft sections. Fine-pitch blades are selected for thin sheet, small tubing, narrow slots, and hard materials where a coarse tooth would catch or strip.

Question 44Bench fitting, hand tools and measurement

A metric vernier caliper has a main scale graduated in 1 mm and a vernier with 50 divisions. Its least count is:

  1. 0.02 mm Correct answer.
  2. 0.01 mm
  3. 0.05 mm
  4. 0.10 mm

Explanation

The least count of a vernier is found by dividing the smallest main-scale division by the number of vernier divisions. For a 1 mm main scale and 50 vernier divisions, the least count is 1 divided by 50, which equals 0.02 mm.

Question 45Bench fitting, hand tools and measurement

An outside micrometer has 0.5 mm sleeve graduations and a 50-division thimble. The sleeve shows 12.5 mm and the thimble reads 24 divisions. The measured size is:

  1. 12.62 mm
  2. 13.00 mm
  3. 12.86 mm
  4. 12.74 mm Correct answer.

Explanation

Each thimble division represents 0.5 mm divided by 50, which is 0.01 mm. The thimble contribution is therefore 24 multiplied by 0.01 mm, or 0.24 mm. Adding this to the sleeve reading of 12.5 mm gives 12.74 mm.

Question 46Bench fitting, hand tools and measurement

For tapping an M10 × 1.5 ISO metric coarse thread, the tapping drill diameter is:

  1. 7.5 mm
  2. 10.0 mm
  3. 9.0 mm
  4. 8.5 mm Correct answer.

Explanation

For an ISO metric thread, the tapping drill diameter is obtained approximately by subtracting the pitch from the nominal diameter. For M10 × 1.5, this gives 10 minus 1.5, or 8.5 mm.

Question 47Bench fitting, hand tools and measurement

A surface gauge used on a surface plate is intended mainly to:

  1. measure the depth of a blind hole
  2. remove burrs from a filed edge
  3. scribe lines parallel to a datum surface Correct answer.
  4. check the pitch of a screw thread

Explanation

A surface gauge carries an adjustable scriber and rests on a surface plate, so it can scribe lines at a fixed height parallel to the plate datum. It is a layout tool, not a depth gauge, thread gauge, or deburring tool.

Question 48Bench fitting, hand tools and measurement

A feeler gauge is used in bench fitting to:

  1. check the included angle of a centre
  2. test the hardness of a chisel edge
  3. measure the outside diameter of a shaft
  4. measure the clearance between mating surfaces Correct answer.

Explanation

A feeler gauge is a set of thin blades of known thickness, and it is inserted into a gap to determine clearance. It does not measure shaft diameter, centre angle, or hardness.

Question 49Bench fitting, hand tools and measurement

In precision measurement, 'wringing' is the operation of:

  1. clamping a micrometer to a stand before reading
  2. lapping a gauge block on a cast iron plate
  3. zeroing a dial indicator by rotating its bezel
  4. joining slip gauges by light rotary pressure Correct answer.

Explanation

Wringing means bringing two cleaned slip-gauge measuring faces together with slight rotary pressure so that they adhere through molecular attraction and a very thin film. This allows gauge blocks to be stacked to build a required size.

Question 50Bench fitting, hand tools and measurement

Prussian blue is applied to a mating surface during bench fitting to:

  1. prevent corrosion on a finished file
  2. show the high spots for scraping Correct answer.
  3. lubricate a tap during thread cutting
  4. colour-code a micrometer thimble

Explanation

Marking compound such as Prussian blue is spread on a mating surface and the part is rubbed against it. The transferred blue marks the high spots, which are then removed by scraping until the bearing is even.