3 points micrometer is a variant of inside micrometer, which is a high precision gauge especially designed to make measurements of holes diameter in each stage of processing, from production to testing.
The instrument body is constituted by a cylinder, inside of which a rod commands feelers that protrude radially in respect to the instrument axis. The measurement accuracy and the instrument centring relative to the hole are ensured by these three points of contact, out of phase between them of 120°, while the clutch guarantees the repeatability and a constant measuring pressure.
