Why Knowing Bearing Clearances Has Become So Important

The size of the working clearance has an impact on the rolling fatigue life, temperature rise, noise, vibration and other performance of the bearing.

The measurement of bearing clearance is generally to apply a specified measurement load to the bearing to obtain a stable measurement value. Therefore, the measured value obtained from the actual clearance (referred to as theoretical clearance) is relatively large, which increases the amount of elastic deformation caused by the measured load. For roller bearings, due to the small elastic deformation, it can be ignored.

The internal clearance of the bearing before the theoretical clearance generally indicates the installation.

When the bearing is installed on the shaft or housing, the theoretical clearance minus the clearance caused by the interference of the expansion or contraction of the retaining ring is called “installation clearance”. The temperature difference inside the bearing caused by the dimensional change after adding and subtracting the installation clearance is called “effective clearance”.

When the bearing is installed, there is a mechanical placement clearance for carrying a specific load, that is, sufficient clearance plus the amount produced by the elastic deformation of the bearing load, which is called “working clearance”.

When the working clearance is slightly negative, the fatigue life of the bearing is the longest, but with the increase of the negative clearance, the fatigue life decreases obviously. Therefore, the selection of bearing clearance generally recommends that the working clearance is zero or slightly larger. The working clearance must also be analyzed in detail according to the usage.