The main external dimensions of the motor bearing refer to the inner diameter, outer diameter, width or height and chamfering dimensions of the bearing that indicate the outline, and are the necessary dimensions when the bearing is installed on the shaft and in the housing. These main dimensions have been standardized by international standards (ISO15), and GB307 (main dimensions of rolling bearings) is also based on ISO standards. The main dimensions are specified in the national standards, and the dimensions of the specific bearings are listed in the following product catalogues. Dimensions are determined for radial bearings (except tapered roller bearings) d: bearing nominal inner diameter D: bearing nominal outer diameter B: bearing nominal width r: inner ring and outer ring chamfering dimensions The outer dimensions of the bearing conform to the outer dimensions of the radial bearing and overall dimensions of the overall plan; the dimensions of deep groove ball bearings for motors conform to GB/T281, the dimensions of cylindrical roller bearings for motors conform to GB/T283, and the dimensions of spherical roller bearings for motors conform to GB/T288 angular contact for motors The external dimension of the ball bearing conforms to GB/T292. Select the external dimension according to the shaft size, limit rotation, fatigue life or rated static load safety factor, and try to choose the external dimension of the standard bearing to save the cost.