Automotive Tools, Measuring Instruments and Workshop Practice
Measurement and hand tools
The exam checks whether you can select, use and care for workshop equipment. Common measuring tools are the steel rule, vernier caliper, micrometer, dial indicator, bore gauge, feeler gauge, plastigauge and torque wrench. A vernier caliper with a 1 mm main scale and 50 vernier divisions has a least count of 1/50 = 0.02 mm. A metric micrometer usually reads to 0.01 mm. Clean the jaws and workpiece, check zero, and avoid springing the frame. Torque wrenches are for final tightening to specification, not for loosening; click-type wrenches should be stored at the lowest setting.
Workshop practice
Use the correct puller for bearings and pulleys, support the component, and never hammer a shaft end. Taps and dies need the correct tapping drill size and lubricant. A thread pitch gauge identifies metric or imperial threads before you chase damaged threads. For engine work, use a straight edge and feeler gauge to check head warpage, and plastigauge to check bearing clearance. Keep benches clear, store tools after use, and report damaged insulation or mushroomed chisels.
Worked example
A vernier caliper has a 1 mm main scale and 50 vernier divisions, so least count = 0.02 mm. The main scale reads 12 mm and the 13th vernier line coincides: 12 + (13 × 0.02) = 12.26 mm. The reading is 12.26 mm, not 12.13 mm; the vernier number is multiplied by the least count.
Traps
Typical errors are reading the vernier division instead of the coincidence line, ignoring micrometer zero error, using a torque wrench to undo a rusted nut, and measuring a hot engine part. A calibrated instrument used carelessly still gives a wrong answer.