Thread Plug Gauges and Thread Ring Gauges

Thread plug gages are used to check tolerances of threaded parts according to a certain specification. These highly specific calibration tools are used to assure the assembly of mating parts and provide quality control and conformity to standards. Most have two ends: a GO and a NO GO. The GO end must screw all the way on, while the NO GO end must not. The class of fit for each gage measures the amount of tolerance allowed for that class.