| 摘要 |
Stable high speed rotation of magnetic recording media is obtained by improving the manufacturing accuracy of a step portion formed in a center core for a magnetic disc between a standardizing surface portion that abuts a spindle to perform standardizing positioning, and an attraction surface portion that approaches a magnet and is attracted thereby. The center core consists of a standardizing surface portion that performs standardizing positioning in its central portion, an attraction surface portion that faces a magnet at a different height than the standardizing surface portion via a step portion, and a collar portion that is fixed to the magnetic recording media at the outer peripheral portion thereof. The step portion between the standardizing surface portion and the attraction surface portion is formed to be a multiple step drawn form. <IMAGE> |
