| 摘要 |
PROBLEM TO BE SOLVED: To improve the productivity by grinding at a high speed, and processing the outer peripheral surface and the inner peripheral surface of a hard disk substrate simultaneously, by increasing the suction force of the hard disk substrate. SOLUTION: A grinding device M is composed being provided with a main shaft 3 supported rotatable to a frame 1; a suction plate 4 provided on the main shaft 3; and a rotary joint 6 provided at the lower side of the main shaft 3. To the suction plate 4, at least more than 50 of suction holes 42 are formed in the radial form on its suction surface 41, long grooves are provided alternately to connect the neighboring suction holes 42, and a hard disk substrate D is sucked. The rotary joint 6 has a fixing part 62 supported to a case body 61; and a movable part 64 rotating together with the main shaft 3; and the opposing plain parts 62a and 64b of the fixing part 62 and the movable part 64 are formed by making the accuracy of the plain degree very high, and further a coating by a cemented carbide or the like is applied, so as to prevent the air mixing in the contacting condition.
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