AGMA 20FTM07 [ Active ]

ISO/TS 6336-22 (Calculation of load capacity of spur and helical gears — Part 22: Calculation of micropitting load capacity) is the ISO technical specification containing a proposal for a calculation for the risk of micropitting in gear sets. This document was originally published in 2010 as ISO/TR 14179-1 and added to the ISO 6336 suite of documents in 2018. It assesses micropitting risk through a safety factor that is calculated as the minimum specific film thickness in the contact zone divided by a permissible specific film thickness. A sliding parameter is used to adjust the film thickness in the contact zone to the region of highest sliding, which is where micropitting has been observed. The permissible specific film thickness is best determined through experience or testing, but there is an option to estimate it based on the lubricant’s failure load stage in FVA-FZG micropitting testing. This paper is a case study to compare the results of the calculation to applications that have experienced micropitting in the field. For these examples, the method does not predict micropitting because of limitations in the Method B formulation.