Question

When a screw gauge with a least count of 0.01 mm is used to measure the diameter of a wire, the reading on the pitch scale is found to be 0.5 mm and the reading on the head scale is 27 divisions. If the zero error is +0.005 cm, what is the diameter of the wire?

Answer 1

First part of the measurement, P.S.R = 0.5 mm

Head scale division that coincides with the pitch scale axis, H.S.C = 27

Second part of the measurement, H.S.C $\times$ L.C = 27 $\times$ 0.01 mm = 0.27 mm

Measurement with zero error = P.S.R + H.S.C $\times$ L.C = 0.5 + 0.27 = 0.77 mm

Zero error = + 0.005 cm = + 0.05 mm

So, corrected reading = 0.77 – 0.05 = 0.72 mm