To what reference is a dial indicator calibrated?

A dial indicator is calibrated to a master or reference part to ensure accuracy and reliability in measurements. This calibration process involves comparing the dial indicator's readings against a known standard that represents a precise measurement. By using a master part, which has defined and verified dimensions, operators can confirm that the dial indicator provides correct readings at specific measurement points. This is crucial in precision engineering and quality control since any inaccuracies in measurement can lead to poor fitting of components or unacceptable product quality. The master part serves as a traceable standard, and regular calibration to it ensures that the dial indicator maintains its precision over time.