| 摘要 |
PROBLEM TO BE SOLVED: To prevent transmission of the movement of a rotational shaft to a main shaft even if whirling or the like of the rotational shaft occurs, to stabilize the main shaft to normally rotate thereby to make the tool suitably operate. SOLUTION: A radial direction and a thrust direction of the main shaft 3 are supported in a non-contact manner by using two air bearings 41, 42. The main shaft 3 and the rotational shaft 5 rotatably driven by belt drive are linked by means of a coupling 7, so that the rotations of the rotational shaft 5 is transmitted to the main shaft 3, and the movement of the rotational shaft 5 other than the rotation is allowed while preventing the transmission of the movement to the main shaft 3.
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