What is pitch diameter?
Taps, dies, bolts, and other helically threaded parts are defined by a number of measurement parameters. Some typical thread dimensions include pitch, depth, angle, and major and minor diameters. Among these dimensions, the pitch diameter is considered to be one of the most crucial.
The pitch diameter (also known as the effective diameter) is used to determine whether two threaded parts could be successfully mated together. Properly mated parts will demonstrate equal distance between thread flanks when in contact. Pitch diameter refers to the width of the cylinder as it intersects the midpoint of the major and minor diameters, known as the pitch line.
Pitch diameters are an essential component in determining the compatibility between internally and externally threaded parts-nuts and bolts, for example-and are also used as an important frame of reference for other thread measurements.