Self-aligning ball bearings have two structures: cylindrical bore and tapered bore. The cage is made of steel plate, synthetic resin, etc. Its characteristics are that the outer ring raceway is spherical and has automatic self-aligning property. It can compensate for the errors caused by non-concentricity and shaft deflection, but the relative inclination of the inner and outer rings shall not exceed 3 degrees. It can withstand large radial loads and certain axial loads.