Six Matters Of Bearing Clearance

The so-called bearing clearance refers to the amount of movement when the bearing is not installed on the shaft or bearing box, and the inner or outer ring of the bearing is fixed, and then the fixed party does radial or axial movement. According to the direction of movement, it can be divided into radial clearance and axial clearance.

Six matters of bearing clearance:
1. The operating clearance (called working clearance) has an impact on the rolling fatigue life, temperature rise, noise, vibration and other performance of the bearing.
2. When measuring the clearance of bearings, in order to obtain stable measurement values, the specified measurement load is generally applied to bearings. Therefore, the measured value obtained is larger than the true gap (called theoretical gap), that is, the amount of elastic deformation caused by the measured load is increased. For roller bearings, because the elastic deformation is small, it can be ignored.

3. The internal clearance of bearings before installation is generally expressed by theoretical clearance.

4, from the theoretical clearance minus the bearing installed on the shaft or inside the shell due to interference with the expansion or contraction of the ring clearance is called “installation clearance”. The clearance after adding or subtracting the dimensional change caused by the temperature difference inside the bearing on the installation clearance is called “effective clearance”.

5. The bearing is installed with the clearance when it is placed under a certain load on the machinery, that is, the effective clearance plus the elastic deformation generated by the bearing load is called “working clearance”.

6. 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 also decreases significantly. Therefore, when selecting the clearance of bearings, it is generally appropriate to make the working clearance zero or slightly positive. In addition, when the rigidity of the bearing needs to be improved or the noise needs to be reduced, the working clearance should be further negative, and when the bearing temperature rises sharply, the working clearance should be further positive, etc., and the specific analysis must be done according to the conditions of use.