The bearing clearance has a significant impact on the bearing life, temperature rise, noise, etc. Therefore, it is necessary to select the appropriate clearance according to the working conditions and performance requirements. The clearance of bearings is divided into radial clearance and axial clearance, which respectively represent the displacement of one sleeve fixed and the other sleeve from one extreme position to another in the radial and axial directions. The radial clearance of bearings includes the original clearance in the free state before bearing installation, the assembly clearance after installing the main shaft and bearing seat, and the working clearance formed under load during operation. For ball bearings, the suitable working clearance is close to zero; For roller bearings, a small amount of working clearance can be maintained. In components that require good support rigidity, bearings should have a certain amount of preload. This is the principle for determining the radial clearance of bearings.
For radial thrust ball bearings and tapered roller bearings, they are usually installed face-to-face or back-to-back, with the internal clearance or preload determined by the axial position of a certain bearing ring. Starting from the zero clearance condition, the specified clearance can be obtained by adjusting the thickness of the gasket on the outer ring of the bearing or loosening or tightening the back nut on the shaft. There is a fixed relationship between the axial clearance and radial clearance of this type of bearing, and satisfying one of the values is sufficient.
When choosing bearing clearance, the following aspects should also be considered:
1. Working conditions of bearings, such as load, temperature, speed, etc;
2. Requirements for the performance of bearings, such as rotational accuracy, friction torque, vibration, and noise;
When the bearing is in interference fit with the shaft and housing holes, it leads to a reduction in bearing clearance;
4. When the bearing is working, the temperature difference between the inner and outer rings leads to a decrease in bearing clearance;
5. Due to the different expansion coefficients of the shaft and housing materials, the bearing clearance decreases or increases;
6. Due to the large temperature difference between the inner and outer rings of the bearing, deep groove ball bearings need to withstand large axial loads or improve their centering performance, requiring an increase in maximum speed and a reduction in bearing friction torque;
When the basic group cannot meet the usage requirements, auxiliary group clearance should be selected. The large clearance auxiliary group is suitable for interference fit between bearings, shafts, and housing holes, while the small clearance auxiliary group is suitable for situations that require high rotational accuracy, strict control of axial displacement of housing holes, and reduction of vibration and noise.

• Previous：How to choose lubricating grease for bearings? Method for selecting bearing lubricating grease
• Next：What is the monitoring of the working status of rolling bearings