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.

Abstract: The member is in the form of a hollow body having a skirt (2) surmounted by a head (1), the entire body exhibiting circular symmetry about an axis (10). The hollow body has an internal ring (5) at an intermediate level between the head and the skirt. The surface of the internal ring is corrugated as traced by a generator line at a constant angle to said axis and moving around a closed corrugated curve situated in a plane orthogonal to said axis. This arrangement provides resistance to torsion forces without requiring any sharp inside edges that are difficult to manufacture in tempered glass.