Hand tools, measuring instruments and workshop equipment
Hand tools, measuring instruments and workshop equipment tests tool identification, correct use, care and the interpretation of readings. Expect questions on micrometers, vernier calipers, dial test indicators, feeler gauges, torque wrenches, plastigauge and bore gauges, plus the safe use of bench grinders, presses and lifting gear.
Rules of use
- Select the tool for the task: a six-point socket on a hex nut, a flare-nut spanner on brake pipes, a soft-faced hammer on machined surfaces.
- Never extend a spanner with a pipe to increase leverage; use the correct size or a breaker bar.
- A torque wrench is a measuring instrument: return it to its lowest setting after use and recalibrate after a drop.
- Clean and lightly oil measuring tools, store them in cases, and check zero before use.
Worked example. A metric micrometer has 0.5 mm barrel graduations and a 0.01 mm thimble. The barrel edge shows 7.5 mm and thimble line 28 aligns with the datum. Reading = 7.5 + (28 × 0.01) = 7.78 mm. If the closed micrometer shows its thimble zero one division past the datum, the zero error is +0.01 mm and must be subtracted from every reading.
Traps that cost marks
Reading the thimble on the wrong side of the datum. Using a torque wrench as a breaker bar. Measuring a hot or dirty component. Forgetting calibration. Pulling a feeler gauge leaf through with force instead of adjusting until it drags lightly.