the present invention provides an improvement to a clamp in a disk drive . insertion holes are formed in the clamp , and screws are inserted into the insertion holes to fasten the clamp to the spindle . the bottom of the screw head contacts the clamp surface to apply a force to the clamp . however , the clamp does not contact the entire bottom surface of the screw head . only a portion of the bottom surface of the screw head contacts the clamp to apply a force to the clamp . since the force caused by tightening the screw is applied only to the area contacting the screw , the force diffuses in a non - contact area in an outer portion of the clamp . therefore , disk distortion and deformation are decreased .