A data storage device (10) includes a stator (20), a rotor (40), a disk (80), and a clamp (60) attaching the disk to the rotor. The rotor includes a hub (48) forming a shoulder (57) at a top portion thereof. A recess (56) is defined in the top portion of the hub and surrounded by the shoulder. An outer diameter of the recess is equal to or larger than a diameter of a central opening (82) of the disk. The disk is seated on the shoulder of the hub. The clamp includes a bottom fixing part (62) fixedly attached to the hub in the recess, a cylindrical wall (64) abutting an inside of the shoulder and the disk in the central opening, and a pressing part (66) extending through the central opening of the disk and pressing on the disk thereby ensuring that the disk can rotate with the rotor.