Tooth proportions for fine-pitch gearing are similar to those of coarse pitch gearing except in the matter of clearance. This standard is applicable to external spur and helical gears with diametral pitch of 20 through 120 and a profile angle of 20 degrees. It provides a system of enlarged pinions which use the involute form above 5 degrees of roll. Data on 14-1/2 and 25 degree profile angle systems, and a discussion of enlargement and tooth thicknesses are provided in annexes. In addition, it addresses, in a new annex, an analysis of comparative systems of selecting tooth thicknesses of pinions.