RELATIVE THICKNESS OF GREASE AND OIL FILMS IN ROLLING BEARINGS.

A method for measuring the thickness of grease films between the rollers and rings of rolling bearings is described. Measurements in two designs of bearing show that a grease can initially form thicker films than can its base oil but that, without frequent relubrication, the grease films become slightly the thinner with time. The thinning of grease films, which is attributed to partial starvation, is accompanied by a reduction in viscous friction. Except in critical applications, where the thickest films are required, the consequences of partial starvation associated with grease lubrication can be advantageous.