Disclosed is a clamp that includes a bolt, a spacer, a shank, an expander and a blocking means. The bolt includes a non-threaded undercut that permits the bolt to rotate in an internally threaded portion of the spacer without threaded engagement between the bolt and the spacer. When used as a clamp, the spacer, shank, expander and blocking means cooperate to deform the expander into a blind side flange and to clamp a work piece between the flange and the spacer. To remove the clamp, the bolt is moved away from the spacer while rotating the bolt in the expander to bring the external threads of the expander into threaded engagement with the internal threads of the spacer. This permits the extraction of the bolt from the blind side expander by maintaining rotational restraint of the expander with the spacer. In several embodiments, a compression spring is positioned between the head of the bolt and the spacer to automatically move the bolt when it is rotated in a loosening direction.