ABEC Grade

When choosing the ABEC grade, the factors to be considered are: radial and axial runout requirements, bore and O.D. fits, and audible noise level. The table below shows the bore and O.D. size tolerances and the radial runout limits for each ABEC grade. Grades 3 and 7 are preferred for most standard applications.

Normally, race finish and race geometry are superior in ABEC 5 and higher. National Precision Bearing recommends these grades for precision assemblies where low noise (mechanical or audible), minimal runout and long life are important considerations.

Radial Play

Radial Play is the free internal radial looseness between the balls and the races with no load applied to the bearing in any direction. Radial play is necessary to accommodate differential thermal expansions, the effects of interference fits, and to control axial play and deflection. The chart on page 7-3 of the Engineering Section shows the suggested radial play for some typical applications.

Lubricant

There are literally hundreds of lubricants available for ball bearings; selecting the optimal one is critical. Each has a particular characteristic which makes it suitable for a specific application. Unless torque is a problem, grease is preferred for prelubrication since it is less susceptible to migration and leakage. Grease can increase bearing torque by a factor of 1.2 to 5.0 depending on the grease type and quantity used.