Measuring tips…

1 Interpret the dial

A metric gauge’s long hand usually records 1mm for one full turn, each mark being 0.01mm. Imperial gauges vary, but a turn is likely to record 0.1in and one mark might be as low as 0.0005in.

2 Check end-float

Hubs, gearbox shafts and crankshafts will often have a stated end-float tolerance. Set up the stand on the block or casing. Carefully lever the hub or shaft one way and then the other.

3 Measure run-out

Mount the gauge with the spindle touching the disc face at 90°. Rotate the hub and zero the gauge at the point of maximum deflection. Rotate it again and take a reading at the point of the hand’s greatest deviation.