Bearing is one of the most commonly used mechanical parts, bearing the rotation and reciprocating movement of the shaft, so that the movement of the shaft is smooth and support it. If bearings are used, friction and wear can be reduced. On the other hand, if the bearing quality is low, it will cause machine failure, so the bearing is considered to be one of the important mechanical parts.

There are two main types of bearings: sliding bearings and rolling bearings.

Plain bearing:

 Plain bearings are generally composed of a bearing seat and a bearing bush. In plain bearings, the shaft is in direct contact with the bearing surface. It can resist high speed and impact load. Plain bearings are used in engines of automobiles, ships and machines.

It is the oil film that supports the rotation. An oil film is a thin film of oil. When the oil temperature rises or is overloaded, the oil film will thin, causing metal contact and causing burning.

Other features include:

 1. The allowable load is large, the vibration and noise are small, and the operation can be quiet.

 2. By performing lubrication state and maintenance, the service life can be used semi-permanently.

Rolling bearing：

Rolling bearings are equipped with ball or roller (round bar) to reduce friction resistance. Rolling bearings include: deep groove ball bearings, angular contact ball bearings, tapered roller bearings, thrust bearings, etc.

Other features include:

1. Low starting friction.

2. Compared with sliding bearings, there is less friction.

3.Because the size and precision are standardized, they are easy to buy.

 In conclusion, bearings are one of the most commonly used parts (standard parts) in mechanical design. Using bearings well can improve the performance of products and reduce costs, so it is particularly important to master the relevant knowledge of bearings.