ABSTRACT
This chapter describes the macrogeometry of involute asymmetric gears, analysis of the gear tooth and mesh parameters utilizing the Direct Gear Design method. In the asymmetric tooth gear mesh, such "tip-tip" interference occurs first at the low pressure angle flanks. Since the Direct Gear Design method utilizes an established standard gear nomenclature and specifications as much as it possible, asymmetric helical gears are typically also specified with the normal tooth section parameters. At certain gear geometry parameter combination, the tips of the mating gears may interfere. However, helical gears are typically specified by parameters in the normal to a tooth line section, because in many cases they are fabricated using the generating rack tooling, for example, hob cutters. Parameters of rack tooling are defined in the normal section and include a normal module or diametral pitch, normal pressure angle, and tooth proportions, like an addendum, whole depth, cutter tip radius, and addendum modification, also known as the X-shift.
