PURPOSE: To prevent the occurrence of dust and head crash due to the damages of a magnetic disk and a clamp mechanism, by covering the surface of the magnetic disk around a hole in the center of a discoid hard substrate with synthetic resin buffers in a ring-like shape.
CONSTITUTION: The clamp hole 2 is drilled in the center of the discoid hard magnetic disk 1 equipped with magnetic thin layers on both surfaces 101 and 102. The synthetic resin buffers 41 and 42 cover both surfaces 101 and 102 of the magnetic disk 1 around the hole 2, thereby covering the surfaces in a ring-like shape. If the clamp mechanism 7 clamps, the synthetic resin buffers 41 and 42 provide a buffer action between a spindle hub 71 constituting the magnetic disk 6 and the clamp mechanism 7, and between a clamp member 72 and a sleeve 8. Thus the magnetic disk 6, the clamp mechanism 7 and the sleeve 8 are never damaged, thereby preventing the occurrence of dust. Dust may occur due to the damages.