AIA NAS727

This specification covers blank configurations, gear data and tolerances for 20° fine pitch spur gears having standard addendums as depicted in NAS726 and used extensively in airborne computers and control instruments where low-inertia, low-torque characteristics are required. The specification is not intended to cover gears wherein the gear drives a pinion having less than 17 teeth which require special attention to be given to the relative length of the arc of recess to the arc of approach.

Classifications. Because of the transient nature of gear classification terminology resulting from rapid technical advances, this specification and its related standard avoids the use of AGMA-ASA gear quality classifications. Instead numerical values for total composite error and tooth-to-tooth composite error according to AGMA Standards are used to identify gear quality.