NSK 21308 EAE4 Pendelrollenlager (40x90x23)

As a spherical roller bearing, this bearing carries very high radial and axial loads and accommodates misalignment. The principal dimensions are 40x90x23 mm at a weight of 0.738 kg; the further technical details are listed in the specification table. Two rows of barrel-shaped rollers run on a common spherical outer raceway; the inner ring and roller set align themselves relative to the outer ring without edge loading arising at the roller ends.

The spherical roller bearing carries load through two rows of barrel-shaped rollers running on a common spherical raceway in the outer ring. Because the centre of curvature of that raceway lies on the bearing axis, the inner ring unit together with both roller rows can swivel within it: misalignment between the shaft seat and the housing bore, as well as a shaft deflected under load, are accommodated without forcing the load out to the roller ends.

Unlike a single-row barrel-shaped design, the inclined roller contact transmits a considerable axial force alongside the radial force, and does so in both directions; this is why the design is found at heavily loaded positions with mixed force direction — in crushers, vibrating screens, drums and roll arrangements. This alignment capability compensates for static misalignment but does not replace a properly machined bearing seat: a continuously shifting misalignment means a constant oscillating movement in the rolling contact and enters into the lubrication design.

Standard bearing steel, once through-hardened, provides the combination of hardness, dimensional stability and fatigue strength for the usual operating temperature range. The normal radial clearance is matched to a cylindrical seat with common fits; if the same bearing type is drawn onto a tapered shaft or an adapter sleeve, the drive-up distance reduces the clearance by design, and it is then the remaining clearance rather than the initial clearance that is the mounting criterion.

The open form brings no sealing element of its own; sealing, initial filling and relubrication rest with the housing, whose seal must permit the alignment movement of the bearing. A lower load limit also has to be observed, below which the rollers slide instead of rolling.