The sliding contact surface of joint bearing is spherical, which is mainly suitable for swing motion, tilt motion and rotation motion. Rolling bearings Rolling bearings are divided into radial bearings and thrust bearings according to the load direction they can bear or the difference in the nominal contact angle. Among them, radial contact bearings are radial bearings with a nominal contact angle of 0, and radial angular contact bearings are radial bearings with a nominal contact angle greater than 0 to 45. Axial contact bearings are thrust bearings with a nominal contact angle of 90, and thrust angular contact bearings are thrust bearings with a nominal contact angle of more than 45 but less than 90. According to the shape of the rolling elements, it can be divided into ball bearings and roller bearings. Roller bearings are classified according to the types of rollers: cylindrical roller bearings, needle roller bearings, tapered roller bearings and spherical roller bearings. According to whether it can be adjusted during work, it can be divided into self-aligning bearings-the raceway is spherical, which can adapt to the angular deviation between the axis of the two raceways and angular motion bearings and non-aligning bearings (rigid bearings) ---- Bearings that can resist the angular deviation of the axis between the raceways. According to the number of rows of rolling elements, it is divided into single-row bearings, double-row bearings and multi-row bearings. According to whether its components (rings) can be separated, it can be divided into separable bearings and non-separable bearings. According to its structure shape (such as with or without filling groove, with or without the shape of inner and outer ring and ferrule, the structure of ribs, and even with or without cage, etc.) can also be divided into a variety of structural types. According to its outer diameter size, it is divided into miniature bearings (<26mm), small bearings (28-55mm), medium and small bearings (60-115), medium and large bearings (120-190mm), large bearings (200-430mm) and special bearings. Large bearings (>440mm). According to the application field, it is divided into motor bearings, rolling mill bearings, main bearings, etc. According to the material, it is divided into ceramic bearings, plastic bearings and so on. Deep groove ball bearings Deep groove ball bearings are the most representative rolling bearings. Compared with other types of bearings of the same size, this type of bearing has small friction coefficient, high limit speed, simple structure, low manufacturing cost, high precision, no frequent maintenance, large size range and many forms, and it is the most widely used type. Bearing. It mainly bears radial load, but also can bear certain axial load. When it only bears radial load, the contact angle is zero.