AGMA is happy to announce the publication of two new documents: AGMA 925-B22, Effect of Tribology and Lubrication on Gear Surface Distress, written by a subcommittee of the AGMA Helical Gear Rating Committee, and, AGMA 943-A22, Tolerances for Spur and Helical Racks, written by the AGMA Gear Accuracy Committee.
Point-surface-origin (PSO) macropitting occurs at sites of geometric stress concentration (GSC) such as discontinuities in the gear tooth profile caused by micropitting, cusps at the intersection of the involute profile and the trochoidal root fillet, and at edges of prior tooth damage, such as tip-to-root interference. When the profile modifications in the form of tip relief, root relief, or both, are inadequate to compensate for deflection of the gear mesh, tip-to-root
interference occurs. The interference can occur at either end of the path of contact, but the damage is usually more
severe near the start-of-active-profile (SAP) of the driving gear.
Surface coatings or finishing processes are the future technologies
for improving the load carrying capacity of case hardened gears. With
the help of basic tests, the influence of different coatings and finishing
processes on efficiency and resistance to wear, scuffing, micropitting,
and macropitting is examined.