Tools, Equipment, and Shop Practices
Tools, Equipment, and Shop Practices tests whether you can measure, fasten, machine, and lift to specification. Expect questions on micrometers, vernier calipers, dial indicators and bore gauges, torque procedures and torque-to-yield fasteners, fastener grades, thread repair, bearing and seal installation, hydraulic presses, and the safe use of bench grinders, drill presses, and compressed air.
Measure, then decide
- A metric micrometer reads 0.01 mm; read the barrel in 0.5 mm steps and add the thimble value. A vernier caliper typically resolves 0.02 mm and is a general-purpose tool, not a precision substitute for a micrometer.
- A dial indicator reads runout, endplay, and backlash. A bore gauge or inside micrometer measures cylinder and housing bores; measure at several depths and two axes at 90 degrees to catch taper and out-of-round.
- Precision tools are calibrated at 20 degrees Celsius. A hot engine block or a cold unheated shop shifts readings.
Torque and fasteners
- Torque produces clamp load. Lubricated threads can raise clamp load 20 to 30 percent over dry threads at the same wrench setting, so follow the manual's stated condition.
- Use a torque wrench in the middle to upper part of its scale, torque in stages and in a crossing pattern, and never use a torque wrench to loosen fasteners.
- SAE grade 5 heads carry three radial marks and grade 8 carries six; metric property class 8.8, 10.9, and 12.9 are stamped on the head.
- Torque-to-yield bolts stretch into the plastic range and must be replaced, then tightened to a torque plus a specified angle.
- Tap drill size for metric threads is major diameter minus pitch; imperial sizes follow the same approximate rule with the thread pitch in inches.
- Install bearings by pressing or driving on the race that carries the interference fit, never through the rolling elements. Heat bearings in clean oil or with an induction heater; do not exceed the manufacturer's temperature limit.
Worked example
You must tap an M12 x 1.75 hole in a bracket. Tap drill = 12 minus 1.75 = 10.25 mm, and the standard stock size is 10.2 mm, giving roughly 75 to 80 percent thread engagement. Using a 10.5 mm drill removes too much thread and weakens the joint; using 10.0 mm overloads the tap and risks breakage. The reasoning is that thread engagement, not hole size alone, carries the load.
Traps that cost marks
- Applying dry-thread torque values to lubricated or plated fasteners.
- Reusing torque-to-yield bolts or final-drive stretch bolts.
- Pressing a bearing by its outer race when the interference is on the shaft.
- Leaving a bench grinder tool rest far from the wheel; it should sit close to the wheel face, with the tongue guard adjusted as well.