In a self-aligning bearing, the inner ring has two raceways and the outer ring has a single spherical raceway with its center of curvature coincident with the bearing axis. This allows the axis of the inner ring, balls and cage to deflect around the bearing center to automatically correct misalignment caused by housing and shaft machining or installation error.

A self-aligning bearing is recommended when the alignment of the shaft and housing is difficult or when the shaft may bend during operation. Brda notes that similar to deep groove ball bearings, most self-aligning ball are for general use.
Depending on the series, most self-aligning bearings can be interchanged with standard ball bearing assemblies. (6200 and 6300 have direct interchanges with the 1200 and 1300 series). “However, if this is not possible, the self-aligning bearing may be wider or can have a tapered bore,” Brda explai

Paul Brda, Application Engineer, NSK Americas explains, “Whereas a ball bearing only has one raceway groove on both the inner and outer ring and is the most common type of rolling bearing.”