| 摘要 |
PURPOSE:To correct horizontally a flange and to prevent the occurrence of the surface vibration of a sheet-shaped recording medium by stamping and processing the connecting part of the cylindrical part of a central disk and a flange part. CONSTITUTION:The connecting part of a cylinder part 5 of a press-processed central disk 2 and a flange part 6 is stamped and processed by a drag 22 having a punch 28 and a taper surface 26 over a whole circumference. Then, the permanent distortion occurs at the connecting part, the flage 6, in which the sheet- shaped recording media are fitted, is corrected, comed to be horizontal and the surface vibration occurrence at the time of rotating the sheet-shaped recording medium is prevented.
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