Abstract: A spark plug and a method of manufacturing the same, where the spark plug has a metal shell, an insulator, a center electrode, a ground electrode, and a gasket located over a threaded portion of the shell and used to seal the spark plug against a cylinder head. Once the gasket is attached on the spark plug, it is shrunk to become a post-formed gasket with an inner diameter that prevents the post-formed gasket from slipping over a threaded portion of the metallic shell. This process may be carried out with a collet type machine that produces a post-formed gasket that is flat and has a substantially uniform thickness, which can improve the sealability of the gasket. This may be important when the spark plug is installed in a cylinder head made from a lost foam casting process or other process that creates a somewhat porous sealing surface.

Abstract: A method of manufacturing a spark plug (20) for being threaded into a cylinder head (28) of an internal combustion engine is provided. The spark plug (20) includes a shell (24) with threads (26) disposed at a predetermined rotational position (a) relative to a shell outer surface (64) and ground electrode (34). The position of the threads (26) relative to the ground electrode (34) places the ground electrode (34) in a desired position in the combustion chamber (22) and relative to components of the engine, thus allowing the ground electrode (34) to provide a robust and reliable ignition. When multiple spark plugs (20) are formed, the threads (26) in each of the shells (24) are repeatedly and accurately formed at the predetermined rotational position (?) by locating the ground electrode (34), threads (26), and dies (76) of a thread forming apparatus (102) in specific locations.

Abstract: A method of manufacturing a spark plug (20) for being threaded into a cylinder head (28) of an internal combustion engine is provided. The spark plug (20) includes a shell (24) with threads (26) disposed at a predetermined rotational position (a) relative to a shell outer surface (64) and ground electrode (34). The position of the threads (26) relative to the ground electrode (34) places the ground electrode (34) in a desired position in the combustion chamber (22) and relative to components of the engine, thus allowing the ground electrode (34) to provide a robust and reliable ignition. When multiple spark plugs (20) are formed, the threads (26) in each of the shells (24) are repeatedly and accurately formed at the predetermined rotational position (a) by locating the ground electrode (34), threads (26), and dies (76) of a thread forming apparatus (102) in specific locations.

Abstract: A spark plug and a method of manufacturing the same, where the spark plug has a metal shell, an insulator, a center electrode, a ground electrode, and a gasket located over a threaded portion of the shell and used to seal the spark plug against a cylinder head. Once the gasket is attached on the spark plug, it is shrunk to become a post-formed gasket with an inner diameter that prevents the post-formed gasket from slipping over a threaded portion of the metallic shell. This process may be carried out with a collet type machine that produces a post-formed gasket that is flat and has a substantially uniform thickness, which can improve the sealability of the gasket. This may be important when the spark plug is installed in a cylinder head made from a lost foam casting process or other process that creates a somewhat porous sealing surface.