Bearing clearance (internal clearance) means that the bearing is before the shaft or bearing housing is installed.
The total distance that a bearing ring can move relative to another ring in a certain direction. According to the direction of movement, it can be divided into radial clearance and axial clearance, as shown in Figure 1.
The internal clearance of the bearing before installation must be distinguished from the internal clearance (run clearance) of the bearing when it reaches the operating temperature after installation. The original internal clearance (before installation) is usually larger than the operating clearance. This is due to the difference in the degree of fit involved in the mounting coordination. The difference in the thermal expansion of the inner and outer rings of the bearing and related components causes the expansion and contraction of the inner and outer rings.
Bearing internal clearance and specified value
The size of the internal clearance (also referred to as play) in the operation of the rolling bearing greatly influences the bearing performance such as fatigue life, vibration, noise, and temperature rise.
Therefore, the internal clearance of the bearing is selected and it is an important research project for the bearing that determines the size of the structure.
In order to obtain a stable test value, give the bearing a specified test load and then test the clearance. Therefore, the measured clearance value is larger than the theoretical clearance (in radial clearance, also called geometrical clearance), that is, the amount of elastic deformation induced by giving the test load (called test clearance Show differences).
In general, the clearance before installation is specified by the theoretical internal clearance.
Internal clearance selection
The following points should be taken into account when selecting the most suitable clearance according to the conditions of use:
(1) Coupling of the bearing with the shaft and housing causes a change in clearance.
(2) The change in clearance due to the temperature difference between the inner and outer rings during the operation of the bearing.
(3) The material used for the shaft and the housing affects the change of the bearing clearance due to the different expansion coefficients.
For bearings that normally work normally, the radial clearance of the basic group should be given priority. However, for bearings that work under special conditions, such as high temperature, high speed, low noise, low friction, etc., the radial clearance of the auxiliary group can be selected. For precision bearings, spindle bearings for machine tools, etc. use smaller radial clearances. Bearings have special requirements for bearings, bearings can meet customer needs.