This item consists of a pair of precision ground triangular prisms with 60 degree included angles. They are used for measuring the pitch diameter of various threads, ranging from 0-20 up to and including 8-pitch. The various triangle peaks are truncated at different lengths so the triangle form can sit properly in the troughs of the various pitch forms (very sharp point for fine threads, and truncated form for larger thread sizes). There is a calibration paper with the triangles for converting the distance measured over the triangle flats to actual thread pitch diameter. The paper includes Metric threads. Obviously, these will only work with 60 degree threadforms.
The triangles are in what appear to be perfect condition and include a ‘keeper’ flexible plastic connector to aid in handling, as well as the fitted plastic container and conversion charts.
Location MB 88
Photo set 725