thread-gage

from The Century Dictionary.

• noun A gage for deter mining the number of threads to the inch on screws and taps.
• noun A gage used to determine the accuracy of screw-threads, cut by machine, as to depth, pitch, and conformity to standard. If the thread is cut with a taper, as on taps and pipes, a thread-gage is used to test the accuracy of these elements also.