how micrometers work
Measurements. Micrometers measure micro distances. Micro distances are small enough to make a typical ruler or tape measure inadequate. Micrometers are used in machining and mechanical engineering.
A micrometer may have its measurements marked in an inch scale, a metric scale or a vernier scale. Inch scales have 40 threads for each inch. Each turn moves axially 0.025 of an inch. A metric scale contains 2 threads for every millimeter so that one turn is equal to 0.5 of a millimeter.