Ball bearing retainers (also known as a cages or ball separator – these are used interchangeably) are components in ball bearings that separates the balls, maintain the balls symmetrical radial spacing, and in most cases, holds the bearings together. Cages can also be utilized in providing lubrication by acting as a reservoir for oils, or by supplying a solid film via the cage material itself or a coating on the cage. The designer’s selection of the appropriate cage design for the application is essential in achieving the desired life and performance of the bearing.

So what can go wrong with these components? A couple common issues are hooping and hang-up, which we’ll review below.

Hooping

The phenomena when the retainer wobbles like a hula-hoop causing torque spikes in the rotating assembly. The retainer should track in a true circumferential plane concentric with the pitch diameter of the balls.

Hang-up (Wind-up)

When an axial load is applied to static bearings that have the axis of their shaft in a horizontal mode, the balls fall downward to a position where they are unequally spaced prior to the load being applied. When the axial load is applied it squeezes the balls between the inner and outer raceways. Now that the balls are held securely in unequally spaced positions they cause the retainer to bind. This binding is called “retainer hang-up.” Once bearing rotation commences the retainer is stressed and some of the balls may skid causing damage that will initiate premature bearing failure.

Want to know more about retainers, failure points or anything bearing-related? Let our team of experts help! Contact them here with any questions you have!