Abstract: The effect of the radial clearance on the life of roller bearing is described. The larger the radial clearance, the shorter the life of the roller bearing. The life equation, which is suitable for computing the life of the roller bearing in mining tri-cone bit, is established. The designer should consider comprehensively the effect of structure data and radial clearance on the life of the roller bearing, in order to make optimum design.

Key words: Dynamic load rating, Radial clearance, Roller bearing life, Tri-cone bit