The functional necessity of a gear pair defines the limits of the deviations of all gear
specifications. Gear quality refers to these permissible limits of deviations. Gear quality
grades are standardised for different normal module/DP ranges and different ranges of
reference diameters in AGMA, DIN, JIS and other standards. AGMA provides 8 grades from
15 to 8, where the higher grade number indicates the better gear accuracy. In DIN and JIS,
a lower grade number means better gear accuracy