【目的】 点接触の可動軸受でも非常に高い回転数にお いて摩耗がなく荷重に関して最適な玉軸受を提供する。
【構成】 玉軸受の玉３がセラミツクから成り、レース １，２がＸ３０ＣｒＭｏＮ１５−１から成り、半径方向 遊隙が内レース２の穴の直径の０．０００５ないし０． ０００７倍である。
PROBLEM TO BE SOLVED: To optimize the load without any abrasion in an extremely high rotation speed despite of a movable bearing of a point contact by using ceramic for the ball, by using X30CrMoN15-1 for races, and by specifying the range of a clearance in the radial direction of the bearing.
SOLUTION: A ball bearing is constituted of an outer race 1, an inner race 2, and a ball provided between time, and the ball is guided and held by a regular retainer 4. Covers or sealing plates 5 are provided in both end faces of the bearing. The both races 1, 2 are composed of X30CrMoN15-1. The ball 3 is composed of ceramic of a light weight and a clearance of the bearing in the radial direction is set between a range of 0.005-0.007 time as large as the hole diameter of the inner race 2. The ball 3 provides a smaller centrifugal force and a higher rotation speed than those of a steel ball. The setting of the radial clearance well endures the loading in the high rotation speed. The effect of a movable bearing can be thus provided by the flat surface of the rolling contact surface 2' of the inner race 2 and the flat surface of the rolling contact surface 1' of the outer race 1.