1. Classification by rolling bearing structure type
(1) Bearings are divided into:
1) Radial bearings - mainly used for rolling bearings bearing radial loads, and their nominal contact angles range from 0° to 45°. According to the different nominal contact angle, it is divided into:
Radial contact bearings - radial bearings with a nominal contact angle of 0°;
Radial angular contact bearings - radial bearings with a nominal contact angle greater than 0° to 45°.
2) Thrust bearings - mainly used for rolling bearings bearing axial loads, and their nominal angles are greater than 45° to 90°. According to the different nominal contact angle, it is divided into:
Axial contact bearings - thrust bearings with a nominal contact angle of 90°
Thrust angular contact bearings - thrust bearings with a nominal contact angle greater than 45° but less than 90°.

(2), according to the type of rolling element, the bearing is divided into:
1) Ball bearings - the rolling elements are balls;
2) Roller bearings - the rolling elements are rollers. According to the types of rollers, roller bearings are divided into:
Cylindrical roller bearings - bearings whose rolling elements are cylindrical rollers, the ratio of the length to diameter of the cylindrical rollers is less than or equal to 3;
Needle roller bearings - bearings whose rolling elements are needle rollers, the ratio of the length to diameter of the needle rollers is greater than 3, but the diameter is less than or equal to 5mm;
Tapered roller bearings - roller bearings whose rolling elements are tapered;
Spherical roller bearings - bearings whose rolling elements are spherical rollers.

(3) According to whether the bearing can be adjusted when it is working, it is divided into:
1) Self-aligning bearing - the raceway is spherical, which can adapt to the angular deviation and angular motion between the axis lines of the two raceways;
2) Non-aligning bearings (rigid bearings) - bearings that can resist the offset of the axis line angle between the raceways.

(4) According to the number of columns of rolling elements, the bearings are divided into:
1) Single row bearings - bearings with one row of rolling elements;
2) Double row bearings - bearings with two rows of rolling elements;
3) Multi-row bearings - bearings with more than two rows of rolling elements, such as three-row and four-row bearings.

(5) According to whether the parts can be separated, the bearings are divided into:
1) Separable bearings - bearings with separable parts
2) Non-separable bearings - after the final assembly of the bearings, the rings cannot be separated freely.

(6) The bearing can be divided into various structural types according to its structural shape (such as whether there is a filling groove, whether there is an inner and outer ring and the shape of the ferrule, the structure of the rib, and even whether there is a cage).

2. Classified by rolling bearing size
Bearings are divided into:(1) Miniature bearings - bearings with a nominal outer diameter of 26mm or less;
(2) Small bearings - bearings with a nominal outer diameter ranging from 28 to 55mm;
(3) Small and medium-sized bearings - bearings with a nominal outer diameter ranging from 60 to 115mm;
(4) Medium and large bearings - bearings with a nominal outer diameter ranging from 120 to 190mm;
(5) Large bearings - bearings with a nominal outer diameter ranging from 200 to 430mm;
(6) Extra-large bearings - bearings with a nominal outer diameter of 440mm or more.