Abstract: Quick-action clamping, for holding workpieces in machine tools, and the like, is developed via orbital movements of a clamp member as induced by relative rotation of the mated eccentric head portion of a cooperating special machine screw threadedly engaged with a suitable mount. In a simple and economical expression of the clamp in a highly-advantageous low-profile form, the bolt is adapted from a steel hex-socket button-head scap screw, by machining a cylindrical exterior to its head in a laterally-offset relation to the central longitudinal axis of the cap screw, and the eccentric head of that modified screw member is fitted within an accommodating cylindrical recess in a shallow brass nut-like clamp member having "flats" about its periphery.