Bearing Clearance Of Ball Bearings
Jul 03, 2022| Bearing clearance (internal clearance) refers to the total distance that a bearing ring can move in a certain direction relative to another ring before the bearing is not installed with the shaft or bearing housing. According to the moving direction, it can be divided into radial clearance and axial clearance.
A distinction must be made between the internal clearance of the bearing before installation and the internal clearance (running clearance) of the bearing when the operating temperature is reached after installation. The original internal clearance (before installation) is usually larger than the running clearance, which is caused by the difference in the degree of fit involved in the installation fit, and the difference in thermal expansion of the inner and outer rings of the bearing and related components causing the inner and outer rings to expand or contract.
Bearing internal clearance and specified value
The size of the internal clearance (also known as clearance) of the rolling bearing in operation has a great influence on the bearing performance such as fatigue life, vibration, noise, and temperature rise.
Therefore, selecting the internal clearance of the bearing is an important research project for the bearing that determines the structural size.
Generally, in order to obtain a stable test value, the specified test load is given to the bearing, and then the clearance is tested. Therefore, the measured clearance value is larger than the theoretical clearance (in radial clearance, also known as geometric clearance), that is, one more elastic deformation caused by the test load (called test clearance and show the difference).
Usually, the clearance before installation is specified as the theoretical internal clearance.
Selection of Internal Clearance
The following points should be considered when selecting the most suitable clearance according to the conditions of use:
(1) Changes in clearance caused by the fit of the bearing, the shaft and the housing.
(2) Changes in clearance due to the temperature difference between the inner and outer rings during bearing operation.
(3) The material used for the shaft and the housing affects the change of the bearing clearance due to the different expansion coefficients.
Generally, for bearings that work normally, the radial clearance of the basic group should be used first. However, for bearings that work under special conditions, such as high temperature, high speed, low noise, and low friction, the radial clearance of the auxiliary group can be selected. Select a smaller radial clearance for precision bearings, machine tool spindle bearings, etc. If there are special requirements for bearing clearance, the bearing can meet the needs of customers.