Abstract: A metal-capped electrical insulator and method of making same by forming a metal cap on an insulator dielectric by directly casting molten metal round a portion of the dielectric to embed it therein. Before casting the metal (16 or 17), a metal washer (1 ) is placed in contact with the boundary on the insulator at the edge of the portion to be embedded. The washer has a circular groove (2) open on the side through which the molten metal is poured. Before casting, said washer is deformed, by pressing it hard in a metal-casting mould (30) to the dielectric and deflecting the walls (3, 4) of the groove (2) to create an undercut in the metal washer.