Bimetal electrodes for spark plugs or the like and method of making same

摘要

A method of producing bimetal electrodes in which a core of copper is enclosed within an outer covering of a nickel alloy. The alloy is extruded into a relatively small diameter, deep cup by first forming a cylindrical blank with a rounded indentation in one face and thereafter extruding the cup using a punch having an end conforming with said indentation to form a central opening having a diameter at least three times the diameter of the punch. A cylindrical copper core is then firmly seated within the cup, which is then extruded by two stages to form an elongated, cylindrical blank. In one embodiment, the end is finished by trimming away a flaring skirt portion at the open end and thereafter upsetting the blank. In another embodiment, the flared skirt portion of the nickel alloy is bottled inwardly and pressed flat against the exposed end of the core so that no scrap is produced.