The accuracy of the finished thread is dependent upon the accuracy of the tapped hole. The insert, When installed, will conform to the geometry of the tapped hole. If it is necessary to gage an installed insert it should only gage after a screw/bolt has been installed and tightened to its recommended seating torque.
S.T.I. gages are for gaging the tapped hole. The gage handle and all gages nibs are marked with the particular size and class of fit. All gages should be maintained with a light lubricant. Any dimensional reference required may be found in the applicable military standard or the H28 Federal Standard or H28 Federal Standard for Thread Forms.
The S.T.I. gage listed are working gages and provide for minimum wear allowance on the pitch diameter of the Go gage. The allowance is two ten-thousandths of an inch and is recommended for production in sizes up to ½ inch. If there is a conflict between two working gages then a reference gage on the minimum basic size should be used as a comparison.
Gages will wear with repeated use. Working Gages are recommended for most application and for best wear life.