There are differences between the two bearings in structure and application. The outer raceway of the self-aligning bearing is a spherical ball centered on the bearing center, so when the inner ring and the outer ring stagger a certain Angle, the roller still rolls on the sphere, so the distance between the roller and the bearing center will not change, nor will there be stuck or wear, so it is called the self-aligning bearing. Self-aligning bearings can be applied to both ends of the longer shaft, suitable for avoiding fulcrum and shaft with insufficient bending stiffness. And the outer ring rolling of deep groove ball bearings is not spherical, so it can not automatically self-aligning, so it is suitable for short shafts with larger stiffness.