A gage block is used to calibrate an unknown micrometer. The "unknown" is the micrometer and the "known" is the gage block being used. This gage block must have a certificate of traceability to the National Institute of Standards and Technology (NIST).

Why do micrometers need to be calibrated?

Calibration. It is important to check that your micrometer is properly calibrated to ensure that the measurements you take are accurate and reliable. Calibration is often confused with zeroing. Zeroing is ensuring that the instrument's zero lines up correctly.

How is a micrometer calibrated and why is it important?

The micrometer as a tool is used to gauge the thickness of a metal or a material to a very accurate degree. ... When carefully calibrated, a micrometer is capable of gauging the thickness or gauge of a material (often, but not limited to, metal) to a very accurate degree, down to . 001 which is very thin indeed.