A disk clamp for securing data storage disks to the hub of a spindle motor in a hard disk drive has a stress distributing cavity to reduce the stress concentration on disk under the screw locations. The cavity may comprise a single, completely circumferential annular slot located in the perimeter side wall of the clamp, or a series of smaller cavities that are angularly aligned with each screw in the perimeter of the clamp. In the case of adding a series of small stress distribution cavities, the load distribution is modulated to higher harmonic components, thus reducing the peak-to-valley value of reaction force on the contact ring by about 20% to 50%.