Pitch Gauge

a gear-measuring instrument used to determine the overall teeth spacing or pitch of spur gears—that is, to measure the average thickness of the teeth.

Measurement of the overall tooth spacing as a parameter to be monitored in evaluating tooth thickness in spur gears was first proposed by E. Wildhaber (USA) in 1923. In 1943, B. A. Taits (USSR) studied variations in overall tooth spacing as a possible means of evaluating part of the kinematic error (in determining the factors that cause nonuniform rotation of gears, particularly inaccuracy of gear-cutting machines).

The overall tooth spacing may be determined by means of any device for measuring linear outside dimensions that has two parallel measuring surfaces that can be inserted into the recesses between the teeth (for example, sliding calipers). This principle is the basis for the design of modern pitch gauges. The designs of pitch gauges vary in the tip shape, type of indicator, and general shape. Attachable gauges with a range of measurement from 0 to 700 mm are usually used. Some machine-tool gear-measuring instruments are equipped with interchangeable tips for measurements of tooth spacing (the measurement limit is usually 320 mm). The most common type is an attachable gauge with a micrometer (a gear-measuring micrometer) and with the measuring surfaces in the form of flat disks. A pitch gauge with a dial indicator is also convenient. The readings of the indicator show both the overall tooth spacing and its fluctuations.