Due to the influence of interference fit and temperature, the working clearance of the bearing is smaller than the natural clearance. The basic radial clearance group is suitable for general operating conditions, normal temperature and commonly used interference fit, that is, the roller bearing shall not exceed k5, m5 (shaft) and K6 (seat hole). When a tight fit is used, the temperature difference between the inner and outer rings is large, and the friction torque needs to be reduced or the alignment performance needs to be improved. Small clearance group.