NSK 7217 BW Schrägkugellager (85x150x28)

As an angular contact ball bearing, this bearing carries combined radial and one-directional axial loads and is often used in pairs. The mounting dimensions are 85x150x28 mm and the weight is 1.81 kg; technical details beyond these are shown in the specification table. It is not the radial clearance recorded in the catalogue but the axial play after mounting that determines how stiff and how accurately this arrangement runs.

In an angular contact ball bearing the contact points on the inner and outer ring do not face one another radially but are offset, so that the line of force action runs through the bearing at an angle. This geometry allows radial and axial force to be transmitted at the same time, but ties the axial capacity of the single-row design to one direction: in the opposite direction the bearing can support nothing, and even a purely radial load produces an internal axial component that has to be supported.

From this follows the basic rule of application — a single-row angular contact ball bearing works in pairs or against a second bearing position. How the pair is arranged determines the behaviour of the arrangement: in a back-to-back arrangement the lines of force action diverge outwards and form a wide support base that carries tilting moments; in a face-to-face arrangement they converge inwards, which shortens the support base and treats angular errors more forgivingly; in a tandem arrangement both bearings act in the same direction, share the axial force and call for a third bearing position for the opposite direction.

The normal radial clearance recorded corresponds to the standard class; what becomes effective at the bearing position, however, is the axial play, which is only established by the counter-bearing, its setting and the fits — from a preload without play for high stiffness and close running accuracy to a defined residual play for running that is insensitive to heat.

Rings and balls are made of through-hardened standard bearing steel. The open form leaves sealing, initial filling and relubrication to the surrounding construction; at the same time it keeps the rolling chamber accessible for a directed supply of lubricant, which is made use of at higher speeds.