| 摘要 |
PROBLEM TO BE SOLVED: To provide a technique for enhancing mountability of a spark plug on an internal-combustion engine.SOLUTION: A spark plug 100 includes a shaft-shaped center electrode 10, a ground electrode 13 arranged with a predetermined gap for the tip 11 of the center electrode 10, a cylindrical insulator 20 internally housing the center electrode 10, and a main metal fitting 40 for housing the insulator 20. The ground electrode 13 is fixed to the tip side opening 40t of the main metal fitting 40. The main metal fitting 40 has a thread part 42 to be screwed into the mounting hole of an internal-combustion engine on the tip side, and a tool engaging part 45 with which a tool is engaged on the side closer to the rear end than the thread part 42. A metal nut 50 to be screwed over the thread part 42 is attached to the thread part 42 of the main metal fitting 40. |
