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.

In thesame way as bearing lubrication, excessive or too little grease will causebearing temperature changes, resulting in bearing damage; similarly, bearingclearance is too large or too small, the bearing's working life and even thestability of the entire equipment operation will be reduced.

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

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

Theclearance when the bearing is mounted on the machine to withstand a certainload, that is, the clearance after the effective clearance plus the elasticdeformation caused by the bearing load is called the "workingclearance".

When theworking clearance is slightly negative, the bearing has the longest fatiguelife. However, as the negative clearance increases, the fatigue life decreasessignificantly. Therefore, when selecting a bearing clearance, the workingclearance is generally zero or slightly positive.

Inaddition, when it is necessary to increase the rigidity of the bearing orreduce the noise, the working clearance should further take a negative value;when the bearing temperature rises sharply, the working clearance shouldfurther take a positive value.

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

Thechoice of specific clearance depends on the technical standards for equipmentinstallation.

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