In most operating conditions, rolling bearings are used with proper clearance. According to different purposes, there are also internal stresses that are generated in advance when the bearing is installed, so that the bearing can be used under negative clearance. This method of use is called preload.

The benefits of preloading on bearings are reflected in the following aspects:

1. Improve the rotation accuracy. After the bearing is pre-tightened, the internal clearance is eliminated, and each rolling body bears a certain preload, and the ring is supported from all directions, which can improve the rotation accuracy, enable the shaft to be correctly positioned in the axial and radial directions, and improve the shaft. The accuracy of the rotation, such as machine tool spindle bearings and measuring instruments.

2. Improve stiffness. The rolling element and the raceway are all in elastic contact, and the rolling element can be regarded as a spring. Bearings with clearance are supported by only a few springs in the force direction. The pre-tightened bearings are supported by springs in all directions, and have a certain amount of preload. The number of rollings under load is more than when there is clearance, so the rigidity can be improved. In ball bearings, the relationship between the contact deformation of the ball and the channel and the load is nonlinear, and as the preload increases, the contact stiffness increases.

3. Improve bearing life. After preloading, the number of loaded rolling elements increases, and the load on each rolling element decreases. At the same time, the load can be evenly distributed on each rolling element, so the life of the bearing can be improved.

4. Improve bearing damping and reduce noise. Pre-tightening creates a stable oil film between the rolling element and the raceway, improves the damping between the rolling element and the raceway, and can improve the dynamic characteristics of the support structure and reduce noise.

5. Improve the dynamic performance of angular contact ball bearings. In angular contact ball bearings rotating at high speed, proper preloading can prevent the steel ball from spinning, prevent or reduce the slip of the steel ball's revolution, and also control the spin slip of the steel ball.

6. Restrain vibration and friction and wear. The outer spherical bearing is actually a variant of the deep groove ball bearing, which is characterized in that its outer ring outer diameter surface is spherical and can be fitted into the corresponding concave spherical surface of the bearing seat to play a self-aligning role. The outer spherical bearing is mainly used to bear the combined radial and axial load mainly radial load, it is generally not suitable to bear the axial load alone. It is used in the vibration-free processing of low-roughness processing machine tools, or in the mechanism that needs to control friction and wear when starting and stopping frequently.

7. Control the slipping phenomenon of the revolution and rotation of the rolling body. The spherical bearing with seat is also designed with certain self-alignment, easy to install, and has a double-structured sealing device, which can work in harsh environments. The bearing housing is generally formed by casting. Bearings with housings are high-precision component products composed of grease-sealed deep groove ball bearings and bearing housings of various shapes. The bearing assembly can be directly mounted on the main body of the mechanical device through several bolts. It has a self-aligning function and can be used to supplement grease. It is a product that is very easy to install and use, such as the direction used in high-frequency motors. Thrust ball bearings and cylindrical roller bearings on jet engines.

8. Compensation for wear during operation. The bearing will increase the clearance due to wear during operation, which can be compensated by preloading.

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