Patent ID: 8834224
Filing Date: 2014-09-16
Classification: B21H,H01T

Abstract:
1. A method of manufacturing a metal shell assembly for spark plug including a cylindrical metal shell that extends in a direction of a central axis and which has a screw portion formed in an outer peripheral surface thereof for threading into an attachment hole of a combustion device, and a bar-shaped ground electrode that extends from a front end portion of the metal shell, the method comprising: disposing an intermediate assembly, having the ground electrode provided in a metal shell intermediate body to be used as the metal shell, between a plurality of rolling dies having process surfaces facing each other; forming the screw portion by performing a rolling process on the intermediate assembly by the plurality of rolling dies while the intermediate assembly is interposed between the plurality of rolling dies; and positioning the ground electrode in a circumferential direction about a central axis of the intermediate assembly between the disposing and forming steps, wherein the positioning is performed after the disposing and before the forming steps.