Self-aligning ball bearings have two rows of balls, a common sphered raceway in the outer ring and two deep uninterrupted raceway grooves in the inner ring. They are available open or sealed. The bearings are insensitive to angular misalignment of the shaft relative to the housing (fig. 1), which can be caused, for example, by shaft deflection.

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.