1. Selection of bearing type: The bearing type is generally selected by the user's technicians according to the use conditions and load bearing of the supporting products. The business personnel mainly know whether the user's actual load is in line with the selected bearing. 

If the bearing does not meet the use requirements, they should advise the customer to change the model as soon as possible, but unless it is a special product, generally there will be no problem in the selection of the model.

2. Selection of bearing clearance: when purchasing bearings, users generally only tell what type and grade they are in, and rarely ask for clearance of bearings. 

Business personnel must ask about the use conditions of bearings, the speed and temperature of bearings , fit tolerance are directly related to the selection of bearing clearance. 

Generally, motors with a speed below 3500 rpm mostly use CM clearance, such as high-temperature and high-speed motors, require a relatively large clearance. 

After assembly, the bearing clearance will be reduced due to the expansion of the inner hole and the reduction of the outer circle. The reduction of clearance = interference × 60% (except that the bearing chamber is made of aluminum). 

For example, the clearance of the bearing before assembly is 0.01mm, and the interference during assembly is 0.01mm, then the clearance of the bearing after assembly is 0.004mm. 

Theoretically, the noise and service life of the bearing will reach the best state when there is zero clearance, but in actual operation, considering the temperature rise and other issues, it is better for the bearing to have a clearance of 0.002mm-0.004mm after assembly.

3. Selection of grease: The selection of grease is generally based on the bearing speed, temperature resistance, noise requirements and starting torque, etc., requiring business personnel to have a good understanding of the performance of various greases.

4. Selection of bearing seal type: The lubrication of bearings can be divided into oil lubrication and grease lubrication. 

Oil-lubricated bearings are generally used as formal bearings, and grease-lubricated bearings are generally sealed with dust covers or rubber seals. The dust cover is suitable for parts with high temperature or good use environment. 

There are two types of seals: contact seal and non-contact seal. Not as good as contact.