1. agricultural machinery bearings are classified according to the structural types of rolling bearings. (1) the bearings are divided into 1 parts according to their load directions or nominal contact angles. The radial bearings are mainly used for rolling bearings bearing radial loads, whose nominal contact angles range from 0 to 45. According to the nominal contact angle, it is also divided into radial contact bearings -- the centripetal bearing with a nominal contact angle of 0: the centripetal angular contact bearing -- the nominal contact angle is greater than 0 to 45 of the centripetal bearing. 2) thrust bearing - the rolling bearing, which is mainly used to bear axial load, has a nominal contact angle of more than 45 to 90. According to the nominal contact angle, it is also divided into the axial contact bearing -- the nominal contact angle of 90 thrust bearing: thrust angle contact bearing -- the nominal contact angle is greater than 45, but less than 90 of the thrust bearing. (2) bearing in accordance with the type of its rolling body, divided into: 1) ball bearings - rolling body for the ball: 2) roller bearing - rolling body as a roller. According to the roller bearing roller type, can be divided into: cylindrical roller bearings - rolling body is cylindrical roller bearing, cylindrical roller length and diameter ratio is less than or equal to 3; needle bearings - rolling body is needle bearing, needle length and diameter ratio greater than 3, but Yu Huo is equal to 5mm small diameter tapered roller; bearing, tapered roller bearing is a rolling body; spherical roller bearing rolling body is a spherical roller bearing. (3) if the bearing can be adjusted according to its working time, it can be divided into: 1) the aligning bearing -- the raceway is spherical, and it can adapt to the angular deviation and angular movement of the bearing between the two raceway axis. 2) the non aligning bearing (rigid bearing) -- the bearing that can offset the axis angle of the impedance raceway. (4) the bearing is divided into 1 parts according to the number of rollers: 1) single row bearings -- bearing with a row of rollers; 2) double row bearings, bearing two rows of rolling bearings; 3) multi row bearings, bearing more than two rows of rolling bearings, such as three and four columns. (5) bearing can be separated according to its components, it can be divided into: 1) separable bearing -- bearing with detachable components; 2) non separable bearing ---- bearing can't be separated freely after final matching. (6) the bearing can be divided into many structural types according to its structure and shape, such as whether there is loading grooves, whether there are inner or outer rings and the shape of the ring, the structure of the edge, or even the cage. 2. according to the size of the bearing according to the classification of rolling bearing the outer diameter size, divided into: (1) - Miniature Bearing nominal diameter size in the range of 26mm bearing the following; (2) small bearings - nominal diameter size in the range of 28-55mm bearing; (3) small and medium size bearing - Nominal outside the range of 60-115mm bearing; (4) in large - size bearing nominal diameter range of 120-190mm bearing; (5) large size bearings - nominal diameter range of 200-430mm bearing; (6) large bearings - nominal diameter size range is more than 440mm bearing.