Bearing clearance selection

Time: 2018-08-23
Summary: In the same way as bearing lubrication, excessive or too little grease will cause bearing temperature changes, resulting in bearing damage; similarly, bearing clearance is too large or too small, the bearing's working life and even the stability of the entire equipment operation will be reduced.

cylindrical roller bearingIn the same way as bearing lubrication, excessive or too little grease will cause bearing temperature changes, resulting in bearing damage; similarly, bearing clearance is too large or too small, the bearing's working life and even the stability of the entire equipment operation will be reduced.

The amount of expansion of the ferrule or the clearance after contraction due to the interference fit when the bearing is mounted on the shaft or in the casing is referred to as the "installation clearance".

The clearance after adding or subtracting the dimensional variation due to the internal temperature difference of the bearing on the installation clearance is called"effective clearance".

The clearance when the bearing is mounted on the machine to withstand a certain load, that is, the clearance after the effective clearance plus the elasticde formation caused by the bearing load is called the "working clearance".

When the working clearance is slightly negative, the bearing has the longest fatigue life. However, as the negative clearance increases, the fatigue life decreases significantly. Therefore, when selecting a bearing clearance, the working clearance is generally zero or slightly positive.

In addition, when it is necessary to increase the rigidity of the bearing or reduce the noise, the working clearance should further take a negative value;when the bearing temperature rises sharply, the working clearance should further take a positive value.

In order to achieve the most ideal life, the bearing must have a suitable clearance. The clearance value = design clearance (factory clearance) - the amount of clearance reduction caused by the inner ring fit - the clearance reduction of the outer ring due to the fit + (or -) the amount of clearance reduction (or increase) due to temperature difference

The choice of specific clearance depends on the technical standards for equipment installation.

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