Physics
How to Use a Micrometer Screw Gauge
A micrometer screw gauge measures very small lengths, such as the diameter of a wire or the thickness of paper, correct to 0.01 mm. It works on the screw principle: each full turn of the thimble moves the spindle forward by a fixed distance called the pitch.
Least count = pitch ÷ number of divisions
Observed reading = MSR + (CSR × least count)
Correct reading = observed reading − zero error
This activity uses a screw gauge with a pitch of 1 mm and 100 divisions on the circular scale. MSR means main scale reading and CSR means circular scale reading.
- Learn the parts of the screw gauge.
- Find the least count.
- Check the zero error.
- Close the jaws on a wire.
- Read the scales and correct the result.