Patent ID: 7337689
Filing Date: 2008-03-04
Classification: B62D,F16H,Y10T

Abstract:
1. A ball screw mechanism comprising a screw shaft with a male screw groove formed on an external surface thereof; a nut with a female screw groove formed on an internal surface thereof; plural balls held in the male and female screw grooves of the screw shaft and the nut; and a ball circulation piece fit in a window portion formed in the nut and having a circulation groove formed thereon for circulating the balls; wherein the female screw groove and the circulation groove are machined by moving a tool of a diameter equal to or larger than the diameter of the balls, along the female screw groove so that a step is eliminated at a joint between the female screw groove of the nut and the circulation groove of the ball circulation piece, and wherein an infeed depth of the tool is gradually changed as the tool is moved toward the joint so that boundary lines are formed between a machined surface and a non-machined surface on flanks of the female screw groove and the boundary lines extend at an acute angle to one another.