433A safety, tools and measuring practice questions.

Five free practice questions on safety, tools and measuring: block A of the Red Seal 433A Industrial Mechanic Millwright exam, about 25 of its 135 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.

01The questions

1. Recall · Uses fastening and retaining devices

   A millwright removes a hex-head cap screw from a crusher flywheel guard and finds six evenly spaced radial lines on the head. What does the marking indicate?

   1. A metric class 6.8 bolt; the lines count the tenths of tensile strength.
   2. SAE grade 8, roughly equivalent to metric 10.9.
   3. SAE grade 5, roughly equivalent to metric 8.8.
   4. A grade 2 low-carbon bolt with six manufacturer identification marks.
   Show the answer

   B. Correct. In the SAE system, three radial lines mark grade 5 (medium carbon, quenched and tempered, about 830 MPa / 120 ksi minimum tensile) and six lines mark grade 8 (alloy steel, about 1 030 MPa / 150 ksi). Metric bolts carry numbers instead: 8.8 is close to grade 5 and 10.9 to grade 8, where the first number is roughly the tensile strength in hundreds of MPa and the second the yield-to-tensile ratio. A replacement must be the same grade or higher, never lower.

   Why not the others

   A. Metric property classes are stamped as numbers (8.8, 10.9, 12.9), never as radial lines. Radial lines are the SAE inch system.

   C. Grade 5 has three radial lines. Confusing three and six lines matters: a grade 5 bolt in a grade 8 location has about 20 percent less tensile strength and will not hold the same preload.

   D. Grade 2 heads carry no radial lines at all, only the manufacturer's mark. Radial lines are the strength grade, not a maker's identification.

2. Recall · Uses shop machines

   A millwright is setting up a pedestal grinder for sharpening drills and chisels. What is the largest acceptable gap between the work rest and the face of the wheel?

   1. 6 mm (1/4 in)
   2. 13 mm (1/2 in)
   3. 3 mm (1/8 in)
   4. 25 mm (1 in)
   Show the answer

   C. Correct. The work rest is adjusted to within 3 mm (1/8 in) of the wheel so the work piece cannot be dragged down between the rest and the wheel. The gap opens as the wheel wears, so the rest is re-adjusted regularly, always with the wheel stopped. The tongue (spark) guard at the top of the wheel is kept within 6 mm (1/4 in).

   Why not the others

   A. 6 mm (1/4 in) is the limit for the adjustable tongue guard above the wheel, not the work rest. A 6 mm gap at the rest is enough to trap a drill shank or a finger.

   B. A gap this large lets small work pieces tip into the wheel and jam, which can shatter the wheel. This is the kind of gap seen on neglected grinders where the rest was never re-set as the wheel wore.

   D. At 25 mm (1 in) the rest gives no protection at all; the work can be pulled straight down between the rest and the wheel. The rest exists to close this gap.

3. Procedural · Performs lock-out/tag-out and zero-energy state procedures

   A millwright has opened the main disconnect for a belt conveyor drive at a mine and applied a personal lock and tag. Before starting work on the drive, what is the required final step to confirm a zero-energy state on the electrical source?

   1. Try to start it from the local control with everyone clear, then return the control to off.
   2. Wait five minutes for the motor to cool and any residual current to dissipate.
   3. Ask the control-room operator to confirm the drive shows 'stopped' on the screen.
   4. Check that the disconnect handle is in the off position and the tag is legible.
   Show the answer

   A. Correct. Locking the disconnect is not the same as proving it worked: the wrong disconnect may have been opened, or a control circuit may be fed separately. The try-start (attempting to operate the equipment from its normal control) verifies zero electrical energy; the control is then returned to off so the machine cannot start when power is restored. Other energies on a conveyor (an inclined belt, a gravity take-up counterweight) must be blocked or released and verified separately.

   Why not the others

   B. There is no residual current in a de-energized induction motor to wait for, and waiting proves nothing about whether the disconnect actually isolated the circuit. Verification is an action (try-start or a qualified test), not a delay.

   C. A 'stopped' status means the motor is not running, not that it cannot start. Zero energy is verified at the equipment by the person who will work on it, not by a remote indication.

   D. A handle in the off position shows what was intended, not what happened. Disconnect linkages fail and mislabelled disconnects exist; only trying to operate the equipment proves it is dead.

4. Critical · Measures material and components

   An apprentice measures the same 25.000 mm (0.9843 in) gauge block five times with an outside micrometer and gets readings from 24.98 to 25.03 mm. The micrometer was verified against a standard that morning. What is the most likely cause of the scatter?

   1. Room temperature changed between readings.
   2. Inconsistent feel; use the ratchet stop every time.
   3. The gauge block is worn and must be replaced.
   4. The micrometer's spindle thread has worn out.
   Show the answer

   B. Correct. A micrometer that checks against a standard but gives scattered readings on a known block is being closed with different pressure each time. The ratchet stop or friction thimble applies the same force every reading; the same number of clicks, the block square to the anvils, and the frame held (not the thimble) give repeatability within 0.01 mm.

   Why not the others

   A. Five readings take a minute or two; temperature does not swing enough in that time to move a 25 mm block by 0.05 mm (that would take roughly 170 degrees C). Temperature effects are systematic, not random.

   C. Gauge-block wear is measured in tenths of a micrometre, and a worn block would read consistently small, not scattered by 0.05 mm.

   D. Thread wear would have shown as an error against the standard that morning and would be consistent at the same size. Random scatter on a fixed size is technique.

5. Recall · Uses mentoring techniques

   A journeyperson millwright is about to teach a second-year apprentice to dial-indicate a coupling. According to the steps for mentoring a skill, what should come first?

   1. Give written feedback on the apprentice's last alignment.
   2. Identify the point of the lesson and link it to prior knowledge.
   3. Demonstrate the full procedure at working speed without commentary.
   4. Have the apprentice attempt it unaided to reveal weaknesses.
   Show the answer

   B. Correct. The RSOS steps for mentoring a skill are: identify the point of the lesson, link the lesson to what the learner already knows, demonstrate the skill, provide practice, give feedback, and assess skills and progress. Explaining why the alignment matters (bearing and seal life, vibration) and connecting it to the apprentice's rough-alignment experience comes before the demonstration.

   Why not the others

   A. Feedback is the fifth step and follows practice of this skill. Feedback on a previous job may be useful context, but it is not where teaching a new skill starts.

   C. Demonstration is the third step, after the point and the link, and it is done with explanation, at a pace the learner can follow. A silent demonstration at working speed teaches little.

   D. Practice comes after the demonstration, and unaided practice comes only after guided practice. Starting with an unaided attempt on a real coupling risks the equipment and the apprentice's confidence.

02Answer key

03What block A covers

This block covers the shop skills every other task relies on. It includes PPE, confined space and hot-work permits, lockout and zero-energy checks, hand, power and shop tools, grease and lubrication, leveling, fasteners and threadlockers, steel identification and heat treatment, drawings and schematics, micrometers and dial indicators, layout, oxy-fuel cutting, SMAW, GMAW and GTAW welding, and mentoring apprentices.

The Red Seal Occupational Standard names this block “Performs common occupational skills”. It carries 18.5% of the exam, about 25 of the 135 questions, split across six tasks. The share column is each task's weight within the block, as the standard publishes it.

04What the questions turn on

Proving zero energy

A locked disconnect is not proof. Try to start the machine from its local control with everyone clear, then return the control to off. A gauge still showing pressure with the pump stopped means stored accumulator energy: bleed it to zero and block the ram.

Lubricated threads change torque

Most applied torque is spent on friction, so anti-seize on threads specified dry gives far more bolt tension at the same torque. Lubricated values are typically 25 to 30 percent lower. Six radial lines on a cap screw head mark SAE grade 8.

Shop formulas for drilling

Spindle speed is cutting speed x 4 divided by the drill diameter in inches, so a 1/2 in drill at 100 sfpm runs at 800 rpm. Blue chips and a squealing drill mean too much speed. A tap drill is roughly major diameter minus pitch.

Reading runout and roundness

Total indicated runout is the full needle travel in one revolution, highest reading minus lowest, wherever the dial was zeroed. Two diameters taken 90 degrees apart that differ show an out-of-round journal; measure along its length for taper as well.

05The other blocks

The 433A exam has six blocks. Each has its own page of free questions:

The 433A Industrial Mechanic Millwright practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.