| 摘要 |
A method of producing a metallic shell for a spark plug, including steps of preparing a first intermediate article by using a first die including a first large diameter cavity larger in diameter than a metal blank, a first small diameter cavity smaller in diameter than the metal blank, a curved tapered cavity between the first large diameter cavity and the first small diameter cavity, and an oil drain cavity between the first large diameter cavity and the tapered cavity and substantially same in diameter as the metal blank, wherein the metal blank is inserted in the first large diameter cavity and extruded to allow a configuration of the metal blank to conform to the first large diameter cavity, the oil drain cavity, the tapered cavity and the first small diameter cavity while being pressed by a punch, and preparing a second intermediate article by using a second die. |
