Uncertainty analysis of calibration of geometrical gauges

On the calibration of geometrical gauges, such as a ball plate, using a coordinate measuring machine, a gauge block is simultaneously used for compensating the scale error and maintaining traceability to the length standard. A mathematical model of this calibration procedure is presented in accordance with Guide to the Expression of Uncertainty in Measurement (GUM). By considering uncertainty of the calibration, the danger of using a single gauge block is pointed out both theoretically and experimentally, and a solution to avoid the danger is also presented.