Tools and Equipment
This domain examines correct selection, use, care and reading of hand tools, measuring instruments and workshop equipment. Expect questions on least count, torque, calibration and the consequences of using the wrong tool.
Measuring and torque tools
- A metric vernier caliper commonly has a least count of 0.02 mm; a micrometer has 0.01 mm; a dial indicator usually reads 0.01 mm. Zero or check the instrument before measuring.
- A micrometer reading combines the sleeve and thimble. The sleeve shows whole and half millimetres; the thimble has 50 divisions, each 0.01 mm.
- Torque is force multiplied by perpendicular distance and is measured in newton metres (Nm). Tighten in the specified sequence, usually from centre outwards, and use clean, lightly oiled threads unless the manual says dry.
- A torque wrench is a setting tool, not a breaker bar. Do not use it to loosen stiff fasteners or drop it; recalibrate after misuse.
- Six-point sockets grip flats better than 12-point sockets on damaged nuts. Use flare-nut spanners on brake and fuel lines, not adjustable wrenches.
Worked example
A micrometer sleeve reads 7.5 mm and the thimble lines up with the 24th division. Reasoning: each thimble division is 0.01 mm, so 24 divisions equal 0.24 mm. Add the sleeve reading: 7.5 + 0.24 = 7.74 mm. If the thimble were between marks, estimate the last digit but do not claim more precision than the instrument allows.
Traps
Reading the vernier from the wrong zero, over-tightening a micrometer on a soft surface, measuring a hot engine part, and using a torque wrench as a lever are frequent errors. A calibrated tool is only accurate if it is zeroed and used within its range.