Angular Contact Bearings Review

Angular contact bearings are constructed such that their races and the bearing balls contact points are at some angle relative to the axis of the operating axis of the bearing. Standard operating angles are 15, 30, and 40 degrees. Angular bearings are available in standard imperial ( inch ) and metric ( mm ) sizes.

An angular contact ball bearing uses axially asymmetric races. An axial load passes in a straight line through the bearing, whereas a radial load takes an oblique path that tends to want to separate the races axially. So the angle of contact on the inner race is the same as that on the outer race. Angular contact bearings better support "combined loads" (loading in both the radial and axial directions) and the contact angle of the bearing should be matched to the relative proportions of each. The larger the contact angle (typically in the range 10 to 45 degrees), the higher the axial load supported, but the lower the radial load. In high speed applications, such as turbines, jet engines, and dentistry equipment, the centrifugal forces generated by the balls changes the contact angle at the inner and outer race. Ceramics such as silicon nitride are now regularly used in such applications due to their low density (40% of steel). These materials significantly reduce centrifugal force and function well in high temperature environments. They also tend to wear in a similar way to bearing steel—rather than cracking or shattering like glass or porcelain.

Most bicycles use angular-contact bearings in the headsets because the forces on these bearings are in both the radial and axial direction.

Angular contact bearings are assembled with a preload, which is applied between the inner race, the bearing ball and the outer race. The preload minimizes or removes gaps between the bearing balls and the inner and outer races. Angular contact bearings may operate with heavy thrust loads and moderate radial loads. Angular contact ball bearings are a classification as single row, radial ball bearings. NTN’s designations for the various contact angles are:

Contact Designation and Angle

"C' = 15°
No Designation = 30°
"D" = 40°

Double Row, Angular Contact Ball Bearings
Type BD, 40° Angular Contact Bearing	Type BG, Angular Contact Bearing