Patent ID: 9343878
Filing Date: 2016-05-17
CPC Classification: H01T

Claim Text:
1. A method of manufacturing a metallic shell for an ignition plug, the metallic shell having a tubular shape, extending in a direction of an axial line, and having a threaded portion on its outer circumferential surface to be engaged with a mounting hole of a combustion apparatus, the method comprising: a metallic shell tubular intermediate forming step of forming a metallic shell tubular intermediate by providing a tubular portion to a metallic shell intermediate that is to become the metallic shell for an ignition plug, and a rolling step of performing rolling on the metallic shell tubular intermediate using rolling dies to form the thread portion, wherein the metallic shell tubular intermediate forming step comprises the steps of: the rolling step comprises the steps of: inserting a bearing member into the metallic shell tubular intermediate for nipping the metallic shell tubular intermediate in cooperation with working surfaces of the rolling dies; rolling simultaneously at least the first tubular portion and the second tubular portion such that a post-rolling radial eccentricity between a center axis of the first tubular portion and a center axis of the second tubular portion becomes smaller than a pre-rolling radial eccentricity between the center axis of the first tubular portion and the center axis of the second tubular portion; and providing a diametral difference between an inside diameter of the metallic shell tubular intermediate and an outside diameter of the bearing member to be 0.8 mm or less in a radial cross sections of the first tubular portion and the second tubular portion.