Rolling Element Bearings and Tolerances

The precise operation of a rolling element bearing increases incrementally as each of the individual components approach "perfection" in its manufacture. The American Bearing Manufacturing Association (ABMA) has established two sets of tolerance classes that define the acceptable minimum and maximum manufacturing ranges for rolling element bearings. These are the ABEC (Annular Bearing Engineering Committee) tolerance classes for ball bearing and RBEC (Roller Bearing Engineering Committee) tolerance classes for roller bearings.

The international bearing community also has an association to regulate international standards, the ISO, or International Standards Organization. ISO and ABMA standards are identical with respect to these tolerances, although they use different class designations. Some manufacturers refer to ABMA designations while NTN and others use ISO designations. Either way, the tolerances are identical.

Bearings manufactured within tighter tolerance ranges provide greater accuracy of shaft rotation and contribute to higher speed capability.