Maintenance Tools and Service Basics flashcards

$\tau =rF\sin \theta$: r is distance from fastener center (m), F is force (N), $\tau$ in N·m (or lb-ft). At 90° it is just $rF$: 20 N at 0.30 m gives 6 N·m; at 30° only half as much.

$T_w=T_s\times \frac{L}{L+E}$, L = wrench length, E = crowfoot reach. For 45 N·m, L = 0.40 m, E = 0.05 m: set 40 N·m. Turning the crowfoot 90° to the handle removes the need to correct.

Six-point: grips the flats over a larger area, least likely to round a stubborn bolt. Twelve-point: grips nearer the corners but fits at twice as many positions, helpful when swing room is tight.

Drive size is the square hole for the handle (commonly 1/4, 3/8 or 1/2 inch). Opening size is the fastener it fits (for example 14 mm). The two numbers are unrelated.

Use it only to tighten to a spec, never to loosen stuck bolts. Stop at the click, pull smoothly at the grip, keep it calibrated, and store a click type at its lowest setting. Finish lug nuts with it, not an impact wrench, in a star pattern.

Feeler gauge: small gaps (valve clearance, plug gap). Micrometer: precise outside size such as rotor thickness. Dial indicator: runout, with $TIR=\text{max}-\text{min}$; +0.05 and -0.03 mm gives 0.08 mm.

Voltage: across the part, in parallel, circuit running. Current: open the circuit and put the meter in series (or use a clamp meter). Resistance: power off and part isolated; OL means open circuit.

No. A jack only lifts and can leak down or roll. Chock the wheels that stay on the ground, set rated jack stands in pairs at the support points, lower the car onto them and check it is steady before going under.