Thread inserts and gage utilizing same

Claim 1

A gage for measuring the pitch diameter of threads comprising: a supporting structure; a first measuring member; means for mounting said first measuring member on said supporting structure in fixed relationship relative thereto; a second measuring member; means for mounting said second measuring member on said supporting structure for movement relative thereto and generally toward and away from said first measuring member; a first ball carried by one of said measuring members for engaging said threads; the other of said measuring members having first surface means for defining a first slot and second surface means for defining a second slot; second and third balls carried by said first and second slots, respectively, of said other measuring member; said first, second, and third balls being spaced from each other and defining a plane such that when the gage is located in a gauging position the axis of the threads lies substantially in said plane; each of said surface means including an end wall and a pair of spaced sidewalls which diverge as they extend toward said end wall; each of said sidewalls having at least a pair of concave arcuate portions joined by a generally planar section, said second and third balls bearing against the sidewalls and the end wall of the associated slot with said planar sections being oriented to allow said balls to undergo limited movement parallel to the axis of said threads when the gage is located in a gauging position; said balls being sized to be received in the grooves between adjacent threads and in contact with such threads whereby error in the lead of the threads can be compensated for by movement of said second and third balls generally parallel to said axis; and indicator means on said supporting structure for providing an indication of the pitch diameter of the threads.