Abstract: A magnetic chuck assembly comprises top and bottom plates separated by a layer of non-magnetizable material, each plate having magnetizable sections separated by strips of non-magnetic material. A rotor mounted between the top and bottom plates carries a plurality of permanent magnets substantially symmetrically disposed therein. The magnets in each half of the rotor are of the same polarity but those in one half are of opposite polarity to those in the other. When the rotor is turned to a position in which all the magnets of like polarity in one half thereof lie between the magnetizable sections of the plates on the same side of the non-magnetizable strips, the sections become magnetized and hold a magnetizable workpiece in place on the edges of the plate. Switching the rotor to a position in which equal numbers of magnets of opposite polarity lie between the magnetizable sections serves to de-energize the latter and release the workpiece.