In order to obviate the inconvenience and loss of time involved in the ordinary mode of fixing upon a lathe-chuck certain special kinds of work, such as thin steel disks or small circular-saws, the chuck may be converted into a temporary magnet, so that the articles, when simply placed on the face of the chuck, are held there by the attraction of the magnet; and, when finished, can be readily detached by merely breaking the electric current and demagnetizing the chuck. The face-plate of the magnetic chuck is composed of a central core of soft iron, surrounded by an iron tube, the two being kept apart by an intermediate brass ring; and the tube and core are each surrounded by a coil of insulated copper wire, the ends of which are connected by two brass contact-rings that encircle the case containing the entire electro-magnet thus formed. These rings are grooved, and receive the ends of a pair of metal springs connected with the terminal wires of a battery, whereby the chuck is converted into an electro-magnet capable of holding firmly on its face the article to be turned or ground. For holding articles of larger diameter, it is found more convenient to use an ordinary face-plate, simply divided into halves by a thin brass strip across the centre; a horseshoe-magnet, consisting of a bent bar of soft iron, with a coil of copper wire around each leg, is fixed behind the face-plate, each half of which is thus converted into one of the poles of the magnet. The whole is inclosed in a cylindrical brass casing, and two brass contact-rings, fixed around this casing, are insulated by a ring of ebonite, and are connected with the two terminal wires of the magnet-coils. A similar arrangement is also adapted for holding work upon the bed of a planing or drilling machine, in which case the brass contact-rings may be dispensed with, and any desired number of pairs of the electro-magnetic face-plates are combined so as to form an extended surface large enough to carry large pieces of work. For exciting the electro-magnet, any ordinary battery that will produce a continuous current of electricity can be used.