| 摘要 |
PROBLEM TO BE SOLVED: To provide a return-tube type ball screw, satisfying a calculated service life, which is hardly damaged in comparison with conventional ones, even if driven and used under the condition of high load and a short stroke and event though a ball repeatedly collides against a land neighborhood part of a ball screw groove of a screw shaft with large impulse force. SOLUTION: This screw shaft 10 for the return tube type ball screw is carburized and quenched. The ball screw groove 11 of the screw shaft 10 comprises the land neighborhood parts P1 and P2 and a ball-rolling part 19. The surface hardness of the ball-rolling part 19 is set to HRC56-62, and the surface hardness of the land neighborhood parts P1 and P2 is set lower than the surface hardness of the ball-rolling part 19.
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