| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of a main body metal fitting for a spark plug having an intermediate cylindrical part 21 of a flange profile in which a large diameter hole 8L, a medium diameter hole 8M of a smaller diameter than the large diameter hole 8L, and a small diameter hole 8S of a smaller diameter than the medium diameter hole 8M are formed standing in a row penetrating through the axial center of a cylindrical member and to the tip side from the proximal end side, and protruded outwardly in the diameter direction of the cylindrical member, a tip end side cylindrical part 22 positioned at further tip end side than the intermediate cylindrical part 21, and a proximal end side cylindrical part 23 positioned at further proximal end side than the intermediate cylindrical part 22, in which it can be manufactured at low cost and with high precision while keeping the jig for a long time use. SOLUTION: A metal pipe material P is used as a starting material, and after the pipe material P is worked to have a prescribed length in a first process, the fitting is molded by applying plastic working to the pipe material P. COPYRIGHT: (C)2004,JPO&NCIPI
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