Hand tools, measuring instruments and workshop equipment
Domain focus
This domain tests selection, use, care and calibration of hand tools, measuring instruments and workshop equipment. Expect questions on least count, zero error, torque practice, lifting equipment and the difference between precision measurement and rough checking.
Core rules
- Use the tool for its designed purpose: a torque wrench tightens to a setting, not a breaker bar; a micrometer measures small external dimensions with a ratchet stop.
- A vernier caliper commonly has a least count of 0.02 mm; a micrometer 0.01 mm; a dial indicator reads runout and backlash.
- Check zero before measuring, clean measuring faces, avoid heat and burrs, and record readings with the correct unit and resolution.
- Torque in the specified sequence, often from centre outward, and use the correct lubricant or thread condition stated in the manual.
- Inspect jacks, stands, slings and presses before use; never exceed rated capacity.
Worked example
A metric vernier caliper has a main scale reading of 12 mm and the 34th vernier division coincides with a main-scale line. Least count is 0.02 mm, so the vernier contribution is 34 × 0.02 = 0.68 mm. The reading is 12.68 mm. If the jaws are closed and the instrument reads 0.04 mm, that zero error must be subtracted from later readings unless the caliper is adjusted.
Traps
Forgetting zero error; reading the wrong vernier line; using a micrometer without cleaning the faces; over-tightening a torque wrench after the click; measuring a hot or worn part and treating it as nominal; using an external micrometer for a bore.