| 摘要 |
The contact angle alpha of ball 15 with respect to ball screw grooves 13, 14 is predetermined to a range of from not smaller than 35° to not greater than 45°. In this arrangement, the contact ellipsoid 15 a of ball 15 can be prevented from running onto the beveled surface 18 a of land area even when a thrust load acts on screw shaft 11 or nut 12 . Accordingly, it is possible to provide a ball screw device which is not subject to easy generation of exfoliation due to hydrogen embrittlement caused by metal contact accompanying sudden rise of pressure on the contact area of ball screw groove with ball.
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