Thread Gages
Thread gages are critical to the validation of correct size of threaded parts. If either of the mating parts is not made to the correct thread specifications the assembly will either not fit together or be so loose the assembly will come apart.
Working thread plug gages are used to insure the threaded hole complies to specification, normally either a 2B or 3B classification.
Thread Ring Gages are used to ensure the external threads conform to the Class of Fit requirements. Both a Go Ring and Not Go Ring are required.
Thread Setting Plug Gages are only used to determine if a ring gage is within tolerance. They are not used to check a work piece.