- Inside micrometers are precision measuring instruments that use
a calibrated screw to measure interior distances on a workpiece, such
as the span between two edges, or the diameter of a circle or hole.
Rotations of the micrometer’s screw amplify small distances that cannot
otherwise be measured directly, translating those turns to a measurement
that can then be read from a scale, dial, or electronic display.
Bore gauges are precision measuring instruments used to measure or
transfer measurements of the interior diameter of holes, or bores, in a
workpiece at any depth. Simple bore gauges are used with a caliper to
transfer the hole measurement, while more complex gauges take the
measurement directly and display it through a vernier, dial, or digital