ASTM Distress Rating Manual 21 (Formerly CRC Manual 21)

The objective of this Distress Rating Manual is to provide rating techniques for gear, bearing, and seal components. Over a period of years, there have been many different designs of these assemblies. For the purpose of this Manual, however, only the most common designs have been selected and only their general construction is illustrated to show the nomenclature of the basic parts.
This Manual also incorporates a glossary of terminology and representative photographs of actual component conditions selected to illustrate lubrication-related wear and deposit conditions of gear, bearing, and seal components. Some non-lubrication-related damage is also illustrated.
This Manual provides broad-based methods which permit the user to define, in generally-accepted terms, those conditions usually considered germane to performance, life, reliability, and maintenance of any gear, bearing and seal.