| 摘要 |
PROBLEM TO BE SOLVED: To properly prevent a short circuit and misfiring due to plating peeling on an earth electrode in a spark plug having a center electrode and the earth electrode connected to an installing metal fitting and composed of metal includ ing Cr by 5 wt.% or more, with both a housing and the earth electrode plated. SOLUTION: After applying Ni plating to the installing metal fitting 10 connected with the earth electrode 40, an Ni plating film of a part 44 opposed to at least the center electrode 30 of the earth electrodes 40 is removed by grinding. Thus, since there is no plating on a discharge surface on the earth electrode 40, after removing the plated film, the plating peeling on the discharge surface is not caused at bending of the earth electrode 40 and during the discharge when using an engine.
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