Abstract: A disc includes a disc substrate having a major surface operating as a signal recording portion and having a substantially circular center opening in the major surface, and a hub mounted on the disc substrate for closing the center opening in the disc substrate. The hub includes an inner rim portion having a spindle opening at its center and an outer rim portion connected to an outer side of the inner rim portion for extending from the inner rim portion via a step difference towards the side of insertion in the spindle opening. When the hub is set on a disc table, the outer rim portion protruded on the side from which the spindle is inserted into the spindle opening with a step difference approaches a magnet provided on the disc table to increase the force of suction by the magnet so that the magnetic disc is chucked with respect to the disc table solely by the force of the magnet.

Abstract: A disc includes a disc substrate having a major surface operating as a signal recording portion and having a substantially circular center opening in said major surface, and a hub mounted on the disc substrate for closing the center opening in the disc substrate. The hub includes an inner rim portion having the spindle opening at its center and an outer rim portion connected to an outer side of the inner rim portion for extending from the inner rim portion via a step difference towards the side of insertion in the spindle opening. When the hub is set on the disc table, the outer rim portion protruded on the side from which the spindle is inserted into said spindle opening with a step difference approaches to a magnet provided on the disc table to increase the force of suction by the magnet so that the magnetic disc is chucked with respect to the disc table solely by the force of suction by the magnet.