| 摘要 |
An object of the present invention is to accurately position a forward end portion of a metallic shell (ground electrode) in relation to a combustion chamber and to implement good airtightness when a spark plug is mounted to a combustion apparatus. A gasket 18 is made of metal, has a solid annular shape, and is provided on the outer circumference of a metallic shell 3 of a spark plug 1 between an externally threaded portion 15 and a seat portion 16 of the metallic shell 3. A method of manufacturing the gasket 18 includes a blanking step of performing blanking on a flat plate of a metal material MM, thereby yielding a ring member RC which is to become the gasket 18, and an annealing step of annealing the ring member RC so as to lower the hardness of the ring member RC below that of the metal member MM, thereby yielding the gasket 18. |
