The ball bearing cage (also known as a ball bearing retainer or ball separator – they are used interchangeably) is the component of a ball bearing that separates the balls, maintains symmetrical radial spacing of the balls, and, most of the time it holds the bearings together.
Cages can also be used to provide lubrication, either by acting as a reservoir for oils or by providing a solid film through the cage material itself or a coating on the cage. The designer's selection of the appropriate cage for the application is essential to achieving the desired bearing life and performance.
Like every bearing part, the cage has its own terminology that can be esoteric to those who don't work with it regularly. Here are some important terms in the field:
Tabs : For two-piece steel belt clips, tabs (also known as ears) are the protrusions on the male half of a belt clip that are attached to the female half to hold them together.
Ball pocket : The part of the retainer that surrounds and locates the ball. The diametrical clearance between the ball and spherical pockets can be as small as 0.0035″ in miniature and instrument bearings and as small as 0.010″ in larger bearings. Properly designed retainers will cause the ball to contact the pocket exactly on the pitch circle of the balls. If contact occurs above or below the pitch circle, dynamic operating and static bonding torque peaks of the seal may occur.
Slot : For crown seals, the groove is the opening through which the ball passes (during bearing assembly) before entering the ball housing.
Coined ball pocket : In metal crown ball bearing retainers, an oversized ball is pulled through the empty housing to form a spherical surface with which the balls can contact. The retainer is then hardened so that it can be inserted into the bearing without permanently deforming the tabs/ears.
Loose closure : The belt stops must be loosely tightened so that the balls can orient the two halves of the stop. The loose grip (also known as Crimp) ensures less noise as well as lower starting and running torque.
