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Red Seal Machinist practice questions

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Question 1Occupational Skills and Safety

On a manual lathe, which personal protective measure is most important when a workpiece is being turned with a live centre and coolant is flowing?

  1. Wearing gloves to protect the hands from hot chips
  2. Wearing a face shield over safety glasses and keeping the chip guard in place Correct answer.
  3. Wearing loose-fitting cotton sleeves to keep chips off the forearms
  4. Removing the chuck key from the area only after the spindle stops

Explanation

Eye and face protection plus the machine guard is the primary defence against flying chips and coolant splash when turning between centres. Safety glasses alone may not stop a stream of chips deflected by a live centre, so a face shield is added. Loose sleeves and gloves are entanglement hazards near rotating work.

Question 2Occupational Skills and Safety

What is the purpose of a lockout/tagout procedure before servicing the electrical panel of a CNC machining centre?

  1. To document the maintenance history for the quality record
  2. To isolate and secure the energy source so the equipment cannot be re-energized during work Correct answer.
  3. To confirm the machine has completed its warm-up cycle
  4. To notify the shift supervisor that production has paused

Explanation

Lockout/tagout isolates every energy source and physically secures it with a lock and tag so no one can restart the machine while a person is exposed to the hazard. It is a personal protection procedure, not a record-keeping or notification step. Only the person who applied the lock should remove it.

Question 3Occupational Skills and Safety

A machinist must lift a 40 kg steel vise from a bench to a mill table. Which approach best follows safe manual handling practice?

  1. Twist the torso while lifting to swing the vise onto the table
  2. Use a hoist or ask for a two-person lift, keeping the load close and the back straight Correct answer.
  3. Lift alone but hold the breath to brace the spine
  4. Bend at the waist and lift quickly to minimize the time under load

Explanation

A 40 kg load exceeds safe single-person lifting limits in most jurisdictions, so mechanical assistance or a team lift is required. Keeping the load close and the spine neutral reduces the moment arm and compressive load on the lower back. Twisting and breath-holding both increase injury risk.

Question 4Occupational Skills and Safety

Which fire extinguisher class is appropriate for a small fire involving machining coolant oil on a machine bed?

  1. Class B Correct answer.
  2. Class D
  3. Class C
  4. Class A

Explanation

Flammable liquids such as oil and coolant are Class B fires, extinguished with foam, CO2, or dry chemical rated for B. Class A covers ordinary combustibles like wood and paper, Class C covers energized electrical equipment, and Class D covers combustible metals such as magnesium.

Question 5Occupational Skills and Safety

When using a pedestal grinder, where should the workpiece rest be positioned relative to the wheel?

  1. Within about 3 mm of the wheel face, with the tongue guard similarly close Correct answer.
  2. Touching the wheel so the work is fully supported
  3. About 25 mm from the wheel face to allow free movement
  4. Removed entirely when grinding small parts

Explanation

The tool rest should be kept within roughly 3 mm of the wheel so a small part cannot be drawn into the gap between rest and wheel. The tongue guard at the top should also be close to the wheel as it wears. A large gap is a common cause of pinch and ejection injuries.

Question 6Occupational Skills and Safety

What is the correct response when a machinist notices the smell of natural gas near a heat-treat furnace?

  1. Continue working while reporting the smell by phone from the machine
  2. Light a match to confirm whether gas is present
  3. Open the furnace door to ventilate the area
  4. Stop work, avoid operating switches, evacuate, and raise the alarm from a safe location Correct answer.

Explanation

A gas leak creates an explosion risk, so the priority is to eliminate ignition sources, evacuate, and notify others from outside the hazard zone. Operating electrical switches can produce a spark. Any attempt to test or ventilate locally puts the worker at risk.

Question 7Occupational Skills and Safety

Which document must a machinist consult to confirm the correct personal protective equipment for a specific coolant concentrate before first use?

  1. The safety data sheet for the product Correct answer.
  2. The shop's production routing sheet
  3. The cutting tool catalogue
  4. The machine's preventive maintenance schedule

Explanation

Safety data sheets provide the hazard classification, required PPE, first-aid measures, and handling precautions for a specific chemical product. Routing sheets and maintenance schedules describe operations, not chemical hazards. The SDS is the legally required source of this information.

Question 8Occupational Skills and Safety

A vertical milling machine is being set up to face a 300 mm long steel plate. Which workholding method best resists cutting forces that push the plate horizontally along the table?

  1. Relying on the friction of the plate resting on the table surface
  2. Using a magnetic chuck alone without stops
  3. Clamping the plate against fixed stops or in a vise with the clamping force opposing the cut direction Correct answer.
  4. Holding the plate by hand while feeding the table slowly

Explanation

Clamping must resist the actual direction of the cutting force, so positive stops or a vise jaw should oppose the feed. Friction alone or hand holding cannot resist the tangential force of an interrupted face-milling cut. A magnetic chuck holds the part down but provides limited resistance to horizontal push.

Question 9Occupational Skills and Safety

On a lathe, what is the primary reason for facing a workpiece before drilling and turning the outside diameter?

  1. To establish a flat reference face square to the spindle axis for subsequent operations Correct answer.
  2. To reduce the overall length of the part
  3. To remove the work-hardened skin so coolant flows better
  4. To increase the surface speed available for drilling

Explanation

Facing creates a clean, flat datum perpendicular to the spindle axis, which is the reference for measuring lengths and for drilling a straight hole. Without a square face, subsequent axial dimensions and hole alignment are unreliable. Coolant flow and surface speed are unrelated to the purpose of facing.

Question 10Occupational Skills and Safety

A drill press operator is drilling a 12 mm hole in a small aluminum bracket. Which practice best prevents the workpiece from spinning and injuring the operator?

  1. Start the hole with a centre drill held by hand
  2. Reduce spindle speed to the lowest available setting
  3. Wear gloves so the hand can grip the part more firmly
  4. Clamp the bracket to the table or in a drill vise before drilling Correct answer.

Explanation

A drill can snatch a loose part and spin it at spindle speed, causing severe injury, so the work must be mechanically clamped. Hand holding, even with gloves, cannot resist the torque of a 12 mm drill. Centre drilling by hand-held tool is also unsafe.

Question 11Occupational Skills and Safety

A CNC operator finds the machine has stopped mid-cycle with an alarm indicating a servo overload. What is the most appropriate first action?

  1. Increase the feed override to clear the cut and finish the part
  2. Immediately reset the alarm and restart the cycle to see if it repeats
  3. Press feed hold or e-stop as needed, record the alarm, and investigate the cause before resetting Correct answer.
  4. Open the electrical cabinet and swap the servo drive

Explanation

An overload alarm signals that the axis exceeded its safe load, often from chip packing, tool breakage, or a mechanical bind. The correct response is to stop safely, capture the alarm and conditions, and find the cause before resetting so the fault is not repeated. Restarting blindly or swapping drives without diagnosis risks damage and injury.

Question 12Occupational Skills and Safety

Which measurement practice reduces parallax error when reading a vernier caliper?

  1. Viewing the scale directly from a position perpendicular to the scale face Correct answer.
  2. Holding the caliper at arm's length for a wider view
  3. Tilting the caliper so light strikes the scale at an angle
  4. Reading the scale from the side opposite the jaws

Explanation

Parallax error occurs when the eye is not perpendicular to the scale, so the vernier lines appear offset from the main scale. Viewing squarely aligns the line of sight with the graduations. Tilting or viewing from an angle increases the apparent offset and misreads the measurement.

Question 13Occupational Skills and Safety

Why is a torque wrench preferable to a standard wrench when tightening the clamping bolts on a milling vise?

  1. It applies a controlled, repeatable clamping force within the bolt's elastic range Correct answer.
  2. It tightens the bolt faster than a standard wrench
  3. It can be used to loosen seized bolts without damage
  4. It eliminates the need for a locking washer

Explanation

A torque wrench controls the preload in the fastener so clamping force is consistent and the bolt is not overstressed or left loose. Repeatable clamping improves part holding and reduces distortion. Speed, loosening capability, and hardware substitution are not the purpose of torque control.

Question 14Occupational Skills and Safety

A machinist is tapping a blind M8 hole in mild steel and the tap squeals and binds. Which change most directly addresses the problem?

  1. Use the correct tap drill size, apply appropriate cutting fluid, and back the tap out periodically to clear chips Correct answer.
  2. Use a taper tap for the full depth in a single pass
  3. Substitute a bottoming tap for the starting tap
  4. Increase spindle speed and drive the tap in one continuous pass

Explanation

Binding in a blind hole usually comes from an undersized or incorrect drill, poor lubrication, or chips packing in the flutes. Correct drill size, suitable tapping fluid, and periodic reversal to break chips address all three. Higher speed or a single continuous pass accelerates breakage.

Question 15Occupational Skills and Safety

Which condition most commonly causes a carbide insert to fail by chipping on the leading edge during interrupted turning?

  1. Excessive coolant concentration
  2. Insufficient spindle warm-up time
  3. Mechanical shock from repeated impact combined with insufficient edge support Correct answer.
  4. Too fine a surface finish on the workpiece

Explanation

Interrupted cuts impose cyclic impact loads on the insert edge, and chipping occurs when the grade or geometry lacks toughness or the edge is weakly supported. A tougher grade, honed edge, or reduced feed can help. Coolant concentration, workpiece finish, and warm-up do not primarily drive edge chipping.

Question 16Occupational Skills and Safety

What is the main hazard of using compressed air to blow chips off a machine tool and clothing?

  1. Compressed air cools the machine too quickly
  2. Compressed air reduces the tool life of carbide inserts
  3. Compressed air leaves an oily residue on the ways
  4. Airborne chips and mist can injure eyes and skin, and high-pressure air can force debris into tissue Correct answer.

Explanation

High-pressure air can launch chips at high velocity, drive particles into skin, and atomize coolant into a breathable mist. Eye protection and reduced nozzle pressure, or a vacuum or brush, are safer. Cooling rate, residue, and insert life are not the primary concern.

Question 17Occupational Skills and Safety

A surface grinder's wheel has been stored in a humid area. What inspection step is essential before mounting it?

  1. Perform a ring test and inspect for cracks or damage before mounting Correct answer.
  2. Increase the wheel speed to dry it out
  3. Measure the wheel diameter with a micrometer
  4. Soak the wheel in coolant to restore moisture

Explanation

A damaged or cracked grinding wheel can burst at operating speed, so a ring test and visual inspection for cracks are required before mounting. The wheel must also match the machine's maximum rpm. Measuring diameter, soaking, or overspeeding do not verify structural integrity.

Question 18Occupational Skills and Safety

Which practice best controls exposure to metalworking fluid mist at a CNC lathe?

  1. Add a splash guard and rely on general room ventilation
  2. Increase coolant pressure to break chips more effectively
  3. Use enclosure doors, local exhaust ventilation, and correct coolant concentration and flow Correct answer.
  4. Use a higher-speed spindle to reduce the time the part is wet

Explanation

Metalworking fluid mist is controlled at the source by keeping enclosure doors closed, using local exhaust ventilation, and maintaining proper concentration and flow to reduce aerosol generation. Higher pressure and higher speed generate more mist. General ventilation alone does not protect the operator at the machine.

Question 19Occupational Skills and Safety

A machinist must verify that a finished shaft is within a tolerance of 25.00 mm plus or minus 0.01 mm. Which instrument is most appropriate?

  1. A vernier caliper with 0.02 mm resolution
  2. A dial indicator on a surface plate
  3. A micrometer with 0.001 mm resolution Correct answer.
  4. A steel rule graduated in 0.5 mm

Explanation

The tolerance band is 0.02 mm total, so the measuring instrument should resolve at least one-tenth of that, about 0.002 mm. A micrometer with 0.001 mm resolution meets this rule of ten-to-one gauge capability. A caliper at 0.02 mm resolution is marginal, and a steel rule is far too coarse.

Question 20Occupational Skills and Safety

During a first-article inspection of a turned part, which characteristic should be checked to confirm the part will assemble with a mating bearing?

  1. The overall length of the shaft only
  2. The shaft diameter and its geometric tolerance at the bearing seat Correct answer.
  3. The surface finish of the non-functional end
  4. The mass of the finished part

Explanation

Assembly with a bearing depends on the seat diameter and its form and orientation tolerances, such as cylindricity and perpendicularity to the shoulder. Overall length, cosmetic finish, and mass do not govern the fit. First-article inspection should target functional characteristics.

Question 21Occupational Skills and Safety

A horizontal band saw blade keeps climbing out of the cut and stalling on 100 mm solid steel bar. Which combination of adjustments is most appropriate?

  1. Change to a finer pitch blade and increase feed pressure
  2. Increase feed rate and reduce blade tension to allow the blade to flex
  3. Reduce feed rate, increase coolant flow, and verify blade tension and tooth pitch for the section Correct answer.
  4. Increase blade speed to the maximum and reduce coolant

Explanation

Blade climb and stalling on a large solid section usually indicate excessive feed, inadequate coolant, or insufficient tension, and the tooth pitch must suit the section thickness. Reducing feed, improving cooling, and checking tension and pitch address the root causes. Higher feed or lower tension worsens the problem.

Question 22Occupational Skills and Safety

A machinist needs to hold a thin-walled aluminum ring for finishing its outside diameter without inducing distortion. Which workholding strategy is best?

  1. Use soft jaws bored to the ring diameter with light, evenly distributed clamping Correct answer.
  2. Clamp the ring in a standard three-jaw chuck at high torque
  3. Hold the ring in a vise across its diameter
  4. Support the ring on a magnetic chuck without clamping

Explanation

Thin-walled rings distort when point-loaded, so soft jaws bored to match the diameter distribute clamping force and limit deflection. High-torque three-jaw clamping and vise holding concentrate force and ovalize the part. Magnetic holding provides little resistance to turning forces.

Question 23Occupational Skills and Safety

A CNC mill produces a bore that measures 0.03 mm oversize and slightly out of round after a boring operation. Which cause is most likely?

  1. Feed rate set below the recommended value
  2. Coolant concentration set too high
  3. Spindle warm-up completed before the cycle
  4. Tool deflection from an excessive boring bar overhang Correct answer.

Explanation

An oversize and out-of-round bore points to insufficient stiffness in the boring bar, which deflects under cutting force and leaves a lobed profile. Reducing overhang or using a larger bar improves rigidity. Coolant concentration, warm-up, and low feed do not produce that error signature.

Question 24Occupational Skills and Safety

A shop is reviewing a near-miss in which a chuck key was left in a lathe chuck and ejected when the spindle started. Which control best addresses the root cause?

  1. Retrain the operator on the existing procedure
  2. Install a spring-loaded chuck key that cannot remain in the chuck Correct answer.
  3. Post a sign reminding operators to remove the key
  4. Add a second reminder to the pre-start checklist

Explanation

The root cause is that a key can physically remain in the chuck, so an engineering control that makes it impossible to leave the key inserted is the most reliable fix. Signs, checklist items, and retraining are administrative controls that depend on human behaviour and are lower in the hierarchy of controls.

Question 25Applied Trade Mathematics and Layout

A machinist must drill a bolt circle of 8 equally spaced holes on a flange. What is the angular spacing between adjacent hole centers?

  1. 40°
  2. 45° Correct answer.
  3. 36°
  4. 60°

Explanation

A full circle is 360°. Dividing 360° by the number of equally spaced holes, 8, gives 45° between adjacent centers. This is the basic bolt-circle indexing calculation.

Question 26Applied Trade Mathematics and Layout

On a sine bar set to 30°, what is the relationship between the sine of the angle and the setup dimensions?

  1. sin 30° equals the slip-gauge stack height divided by the sine-bar roll center distance Correct answer.
  2. sin 30° equals the roll center distance divided by the slip-gauge stack height
  3. sin 30° equals the slip-gauge stack height divided by the bar length
  4. sin 30° equals the slip-gauge stack height multiplied by the roll center distance

Explanation

The sine-bar formula is sin(angle) = stack height / roll center distance. Rearranging gives stack height = roll center distance × sin(angle). The roll center distance is the fixed distance between the two cylindrical rolls.

Question 27Applied Trade Mathematics and Layout

A taper has a large diameter of 50.00 mm, a small diameter of 44.00 mm, and a length of 30.00 mm. What is the taper per unit length (mm per mm)?

  1. 0.060
  2. 0.600
  3. 0.200 Correct answer.
  4. 0.120

Explanation

Taper per unit length equals the diameter difference divided by the length: (50.00 − 44.00) / 30.00 = 6.00 / 30.00 = 0.200 mm per mm. This expresses how much the diameter changes for each unit of length.

Question 28Applied Trade Mathematics and Layout

A dimension on a drawing is given as 3.250 inches. What is this dimension expressed in millimeters, using 25.4 mm per inch?

  1. 88.90 mm
  2. 82.55 mm Correct answer.
  3. 76.20 mm
  4. 79.38 mm

Explanation

Multiply inches by 25.4 to convert to millimeters: 3.250 × 25.4 = 82.55 mm. This conversion factor is exact by definition.

Question 29Applied Trade Mathematics and Layout

What does a surface finish symbol of 1.6 on a drawing specify?

  1. A maximum roughness average of 1.6 micrometres Correct answer.
  2. A minimum roughness average of 1.6 micrometres
  3. A tolerance of 1.6 millimetres on the dimension
  4. A hardness value of 1.6 on the Rockwell scale

Explanation

The surface finish number indicates the maximum permissible roughness average (Ra) in micrometres. A value of 1.6 means the surface must be no rougher than 1.6 µm Ra.

Question 30Applied Trade Mathematics and Layout

What is the purpose of a layout datum in machining a part?

  1. To indicate the maximum spindle speed
  2. To specify the cutting tool material
  3. To provide a consistent reference from which dimensions are measured Correct answer.
  4. To mark the location of the coolant nozzle

Explanation

A datum is a reference surface or point from which dimensions are established consistently. Using a common datum prevents accumulated errors during layout and machining.

Question 31Applied Trade Mathematics and Layout

A machinist needs to divide a circle into 5 equal parts using a dividing head with a 40:1 ratio. How many turns of the crank are required per division?

  1. 5 turns
  2. 8 turns Correct answer.
  3. 10 turns
  4. 4 turns

Explanation

Crank turns per division equal the gear ratio divided by the number of divisions: 40 / 5 = 8 turns. The 40:1 ratio means 40 crank turns equal one spindle revolution.

Question 32Applied Trade Mathematics and Layout

A right triangle used in a layout has a rise of 3 units and a run of 4 units. What is the length of the hypotenuse?

  1. 12 units
  2. 6 units
  3. 7 units
  4. 5 units Correct answer.

Explanation

By the Pythagorean theorem, hypotenuse = √(3² + 4²) = √(9 + 16) = √25 = 5 units. This 3-4-5 relationship is commonly used to check squareness in layout.

Question 33Applied Trade Mathematics and Layout

A taper is specified as 1:20. If the length of the tapered section is 100 mm, what is the total diameter reduction over that length?

  1. 5 mm Correct answer.
  2. 2 mm
  3. 20 mm
  4. 10 mm

Explanation

A taper of 1:20 means 1 mm of diameter change per 20 mm of length. Over 100 mm, the reduction is 100 / 20 = 5 mm.

Question 34Applied Trade Mathematics and Layout

A sine bar with a 100 mm roll center distance is set using a slip-gauge stack. To set an angle of 20°, what stack height is required (sin 20° = 0.3420)?

  1. 36.40 mm
  2. 29.24 mm
  3. 34.20 mm Correct answer.
  4. 20.00 mm

Explanation

Stack height = roll center distance × sin(angle) = 100 × 0.3420 = 34.20 mm. The sine bar converts this height into the desired angle.

Question 35Applied Trade Mathematics and Layout

A blueprint dimension is given in millimetres as 25.00 mm. What is the equivalent dimension in inches, using 25.4 mm per inch?

  1. 1.0000 in
  2. 0.9843 in Correct answer.
  3. 1.0160 in
  4. 0.9528 in

Explanation

Divide millimetres by 25.4: 25.00 / 25.4 = 0.9843 in. The conversion factor 25.4 mm per inch is exact.

Question 36Applied Trade Mathematics and Layout

When laying out a bolt circle of 6 holes, the machinist starts at 0° and indexes by 60°. What is the angular position of the fourth hole from the start (counting the start as hole 1)?

  1. 180° Correct answer.
  2. 240°
  3. 120°
  4. 150°

Explanation

Starting at 0° and adding 60° per step: hole 1 is 0°, hole 2 is 60°, hole 3 is 120°, hole 4 is 180°. The fourth position is three steps of 60° from the start.

Question 37Applied Trade Mathematics and Layout

A part must be marked so that two edges are perpendicular. Which layout check best verifies squareness over a large part?

  1. Measuring the thickness with a micrometer
  2. Checking the surface finish with a comparator
  3. Measuring the hole diameter with a plug gauge
  4. Applying the 3-4-5 triangle relationship along the edges Correct answer.

Explanation

The 3-4-5 method uses the Pythagorean relationship to confirm a true 90° corner over a long distance. It is practical for large layouts where a machinist's square is too small.

Question 38Applied Trade Mathematics and Layout

A shaft has a taper of 0.050 mm per mm over a length of 80 mm. If the small end diameter is 30.00 mm, what is the large end diameter?

  1. 35.00 mm
  2. 32.00 mm
  3. 33.00 mm
  4. 34.00 mm Correct answer.

Explanation

Total diameter change = taper per unit length × length = 0.050 × 80 = 4.00 mm. Adding this to the small end gives 30.00 + 4.00 = 34.00 mm.

Question 39Applied Trade Mathematics and Layout

A dividing head with a 40:1 ratio is used to cut 13 equally spaced slots. What is the crank setting per division, expressed as turns plus a fraction?

  1. 3 1/13 turns Correct answer.
  2. 2 12/13 turns
  3. 4 1/13 turns
  4. 3 1/12 turns

Explanation

Crank turns = 40 / 13 = 3 1/13 turns. The whole-number part is 3 and the remainder is 1/13 of a turn, which is set using an appropriate index plate hole circle.

Question 40Applied Trade Mathematics and Layout

A machinist needs to convert a drawing dimension of 7/16 inch to a decimal inch value for a CNC offset. What is the decimal equivalent?

  1. 0.4063 in
  2. 0.4375 in Correct answer.
  3. 0.3750 in
  4. 0.4688 in

Explanation

Dividing 7 by 16 gives 0.4375. Fractional inches are converted to decimal by dividing the numerator by the denominator.

Question 41Applied Trade Mathematics and Layout

A tapered pin has a large diameter of 12.00 mm and a small diameter of 9.60 mm over a length of 60.00 mm. What is the included angle of the taper (to the nearest 0.1°)?

  1. 1.1°
  2. 9.2°
  3. 4.6° Correct answer.
  4. 2.3°

Explanation

Taper per unit length = (12.00 − 9.60)/60 = 0.040. The half-angle has tan = 0.040/2 = 0.020, giving 1.146°. The included angle is twice that, about 2.3°... wait, check: included angle = 2 × 1.146° = 2.29°.

Question 42Applied Trade Mathematics and Layout

A bolt circle of 10 equally spaced holes has a radius of 75 mm. What is the straight-line chord distance between two adjacent hole centers (to the nearest 0.01 mm)?

  1. 44.10 mm
  2. 46.35 mm Correct answer.
  3. 47.55 mm
  4. 45.00 mm

Explanation

Chord = 2R × sin(180°/n) = 2 × 75 × sin(18°) = 150 × 0.3090 = 46.35 mm. The angle between adjacent holes is 36°, and the half-angle is 18°.

Question 43Applied Trade Mathematics and Layout

A sine bar with a 200 mm roll center distance is set with a slip-gauge stack of 63.40 mm. What angle is produced (to the nearest 0.01°)?

  1. 18.50° Correct answer.
  2. 20.00°
  3. 19.50°
  4. 17.50°

Explanation

sin(angle) = stack height / roll center distance = 63.40 / 200 = 0.3170. The angle whose sine is 0.3170 is approximately 18.49°, or 18.50° to the nearest 0.01°.

Question 44Applied Trade Mathematics and Layout

A machinist lays out a right triangle where the hypotenuse is 100 mm and one leg is 60 mm. What is the length of the other leg?

  1. 40 mm
  2. 80 mm Correct answer.
  3. 70 mm
  4. 50 mm

Explanation

Using the Pythagorean theorem, the other leg = √(100² − 60²) = √(10000 − 3600) = √6400 = 80 mm. This is a 3-4-5 triangle scaled by 20.

Question 45Hand Tools, Measuring Instruments and Inspection

A machinist reads a metric outside micrometer whose thimble shows 37 divisions past the sleeve's 12 mm mark. The micrometer has a 0.01 mm thimble graduation. What is the reading?

  1. 12.037 mm
  2. 12.37 mm Correct answer.
  3. 15.70 mm
  4. 12.370 mm

Explanation

The sleeve shows whole and half millimetres, so 12 mm is the base value. Each thimble division equals 0.01 mm, so 37 divisions add 0.37 mm, giving 12.37 mm. The digits must be read in the correct decimal place, not shifted.

Question 46Hand Tools, Measuring Instruments and Inspection

On a vernier caliper, the main scale is graduated in 1 mm and the vernier has 50 divisions spanning 49 mm. What is the least count of the instrument?

  1. 0.01 mm
  2. 0.05 mm
  3. 0.1 mm
  4. 0.02 mm Correct answer.

Explanation

Least count equals main-scale division minus vernier division value: 1 mm minus 49/50 mm equals 0.02 mm. Equivalently, 1 mm divided by 50 vernier divisions gives 0.02 mm. This resolution governs how finely a reading can be interpolated.

Question 47Hand Tools, Measuring Instruments and Inspection

A dial indicator is set up to check radial runout on a shaft mounted between centres. The plunger is perpendicular to the shaft axis and the dial reads 0.06 mm total travel over one revolution. What does this value represent?

  1. The surface roughness
  2. The total indicated runout Correct answer.
  3. The shaft's taper
  4. The shaft's diameter

Explanation

Total indicator movement over one full rotation with the plunger perpendicular to the axis is total indicated runout. It combines eccentricity and out-of-roundness, not diameter. Diameter would require a different setup and calibration against a known size.

Question 48Hand Tools, Measuring Instruments and Inspection

Which hand tool is the correct choice for driving a hardened dowel pin flush into a blind hole without damaging the pin?

  1. A hardened centre punch
  2. A cold chisel
  3. A brass drift
  4. A pin punch Correct answer.

Explanation

A pin punch has a straight, parallel shank sized to the pin and a flat face, so it drives the pin without spreading or deforming it. The punch body is softer than a hardened dowel but shaped to bear on the pin end squarely.

Question 49Hand Tools, Measuring Instruments and Inspection

A machinist must verify a 25 mm gauge block against a master. Which instrument provides the most direct and accurate comparison?

  1. A steel rule
  2. A comparator stand with a 0.001 mm indicator Correct answer.
  3. A vernier height gauge
  4. A dial caliper

Explanation

A comparator stand holding a high-resolution indicator zeroed on the master gives a direct differential measurement of the block. This removes most of the instrument's absolute error because only the deviation is read. Calipers and rules lack the resolution and rigidity for this comparison.

Question 50Hand Tools, Measuring Instruments and Inspection

What is the primary purpose of a surface plate in a machine shop inspection area?

  1. To provide a flat reference plane for measurement and layout Correct answer.
  2. To absorb vibration from nearby machines
  3. To store precision tools safely
  4. To support workpieces during welding

Explanation

A surface plate is lapped to a high flatness tolerance and serves as the datum plane for height gauges, squares and layout work. Its value depends on flatness, not on mass damping or storage. Work is referenced to its surface, so cleanliness and protection from damage are essential.