Applies to external and internal, involute spur and helical gears for use with parallel shafts, and having normal diametral pitches equal to, or coarser than, 20. The basic rack and tooth form are specified, together with requirements for terminology and notation, first and second preference standard pitches and fundamental tolerances which determine the grades of gear accuracy. Ten grades of accuracy are applied ot each gear element and thus the standard can be applied to meet requirements ranging from coarse commercial applications to precision gears for high-speed and/or high-load applications.

AS B61.1-1974

Specification for spur and helical gears — Basic rack form, pitches and accuracy (diametral pich series)