DISK HOLDING DEVICE

PURPOSE:To improve the centering accuracy of disks and to improve the track density, by installing a collet chuck which is in contact with the inner surface of the opening at the center of disks and is equally divided into plural parts in the radial direction, to the center of a turntable. CONSTITUTION:When a disk 1 is placed on a turntable 6, the central opening 3 of a hub 2 can be put on a collect chuck 13 easily because the collet chuck 13 becomes narrower at the top, and thus, the disk 1 is placed on the turntable. When a press board 10 is lowered and the hub 2 is pressed with a clamper 8 through a spring 9, the collet chuck 13 is expanded in the direction of the circumference through a spring 26 and center coma 19 and holds the central opening 3 of the hub 2 at high accuracy. Therefore, the centering accuracy of the disk 1 depends only on the coaxial condition of the outer diameter of the collet chuck 13 with respect to a shaft 11.