This information sheet provides a means to describe the appearance of powder metal gear teeth when
they wear or fail. The study of powder metal gear tooth wear and failure has been hampered by the
inability of two observers to describe the same phenomenon in terms that are adequate to assure uniform
interpretation.
The term “gear failure” is subjective and a source of considerable disagreement. For example, a person
observing gear teeth that have a bright, mirrorlike appearance may believe that the gears have “run-in”
properly. However, another observer may believe that the gears have failed by polishing wear. Whether
the gears should be considered failed or not depends on how much change from the original condition is
tolerable.
This information sheet provides a common language to describe powder metal gear wear and failure and
serves as a guide to uniformity and consistency in the use of that language. It describes the appearance
of powder metal gear tooth failure modes and discusses their mechanisms, with the sole intent of
facilitating identification of gear wear and failure. The purpose of the information sheet is to improve
communication between users and manufacturers for failure and wear analysis. Since there may be many
different causes for each type of powder metal gear tooth wear or failure, it is not possible in the
information sheet to identify a single cause for each type of wear or failure, nor to prescribe all possible
remedies.