| 摘要 |
A method of manufacturing a center electrode of a spark plug, comprising the steps of forming a cylindrical electrode member having a medium diameter portion and a small diameter portion and forming a barrel portion by extruding the medium diameter portion when the value of (S1-S2)/S1×100) is 30 or more, S1 being the cross-sectional area of a cross-section of the medium diameter portion perpendicular to an axial direction, and S2 being the cross-sectional area of a cross-section of each small diameter portion perpendicular to the axial direction.
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