The outer ring raceway of self-aligning ball bearings forms a spherical surface whose center is common to the bearing center. The inner ring of the bearing has two raceway. The ball , cage ,and inner ring of these bearings are capable of a shifting in order to compensate for a certain degree of misalignment with the outer ring. As a result, the bearing is able to align itself and compensate for shaft/housing finishing unevenness, bearing fitting error, and other sources of misalignment