Spherical roller bearings have double-row rollers, the outer ring has a common spherical raceway, and the inner ring has two raceways that are inclined at an angle relative to the bearing axis. This ingenious structure makes it have self-aligning performance, so it is not easy to be affected by the angle of the shaft and the bearing box seat on the error or shaft bending. It is suitable for the occasions where the installation error or the shaft deflection causes the angle error. In addition to being able to withstand radial loads, the bearing can also withstand bidirectional axial loads. Spherical roller bearings have cylindrical and conical bores. The taper of the conical cone bore is 1:30 and 1:12. This conical bore bearing is equipped with an adapter sleeve or a withdrawal sleeve. The tapered inner hole self-aligning ball bearing can be easily and quickly assembled on the optical shaft or the stepper shaft.