English and Metric Screw Pitch Gages
Screw pitch gages are among the most useful tools in any mechanics' toolbox. They quickly determine the pitch of various threads. These gages consist of a substantial steel case with several folding leaves at both ends, each leaf having teeth corresponding to a specific pitch, marked on each leaf.
Starrett screw pitch gages are available in a wide range of sizes with different numbers of leaves in various pitch ranges.
V, Unified, American National 60-degree threads
Whitworth Standard 55-degree threads
International Metric Standard 60º threads
English and metric threads are similar in form, but English threads are described in threads per inch and metric threads by the distance from one crest to the next.
All screw pitch gages (except 473 and 476, which have a positive stop design) feature a locking device at both ends of the case, so leaves can be securely locked in position for use. Leaves on most gages have a special narrow design, permitting checking internal threads in nuts, etc., as well as external threads.