An improved disk stack assembly for a hard disk drive (HDD) includes a generally cylindrical hub with flange having a downward sloping conical flange surface. The conical flange surface is defined between a radially inner circular ridge and a radially outer circular edge. The bottom disk in the stack is in contact with the flange inner circular ridge. The disk stack assembly also includes a disk clamp with a contact surface having a contact rim that is in contact with either the radially inner portion of the top disk in the stack or a spacer ring. The clamp contact rim is located at approximately the same radial distance from the hub's central cylindrical axis as the flange circular ridge so that the clamping force is applied to the disks close to the area where the disk stack is supported on the conical flange surface.