619 Bearing friction

The friction resistance offered by the different kinds of rolling element bearings is usually quoted in terms of the coefficient of friction so that a relative comparison can be made. Bearing friction will vary to some extent due to speed, load and lubrication. Other factors will be the operating conditions which are listed as follows:

1 Starting friction will be higher than the dynamic normal running friction.

2 The quantity and viscosity of the oil or grease; a large amount of oil or a high viscosity will increase the frictional resistance.

3 New unplanished bearings will have higher coefficient of friction values than worn bearings which have bedded down.

4 Preloading the bearing will initially raise the coefficient of friction but under working conditions it may reduce the overall coefficient value.

5 Pre-lubricated bearings may have slightly higher coefficients than externally lubricated bearings due to the rubbing effect of the seals.

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