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outer. groove. The sides of the outer groove are separate rings that are 
held in a frame, one fixed and the other adjustable by means of a screw 
thread cut on the inside of the frame, and a corresponding one cut on the 
outside of the ring. Adjustment of the bearing to the balls is gotten by 
means of this ring. This gives a four-point bearing in which the balls 
travel in planes perpendicular to the axis of the shaft. The balls were .5 
inch in diameter. 
The roller bearings used were of the form shown in fig. 2, in which, 
however, is shown a bearing having four sets. In the test, only one set 
Fig. 1. 
was used, as this was the unit in building the bearing. This consists 
of a cage holding fourteen small rolls, of hardened steel, each .315 inch in 
diameter and .625 inch long. These are separated from one another in the 
cage by brass bars. During the operation of the bearing the only friction 
between the cage and rolls ought to be that induced by the weight of the 
cage. It was found that the heavier loads caused the cage to become badly 
worn where there was contact between the ends of the rolls and the cage. 
The cage and rolls are held in a cylinder of steel that is carefully bored, 
