A purpose of the invention is a sheathed glow plug having a center electrode composed by coaxially welding a leading end axial shaft and a rear end axial shaft, wherein an eccentricity of the center electrode is made small and a burr generated in a connecting portion is suppressed.
Since a connecting end (g) of one axial shaft 6 of a center electrode 4 is made smaller in its diameter than a connecting end (f) of the other axial shaft 5, a butting face between the connecting ends becomes small in its area depending on a diameter of the small diameter side connecting end. Therefore, even if a connecting end face has an error of right angle degree with respect to an axis or is a rough face, it follows that its influence can be suppressed because a diameter of the butting face is small, and a resistance welding can be stably performed. Further, even if a burr is generated in a periphery edge of the connecting face by the resistance welding, a generation amount of the burr becomes small because an area of the butting face is small. And, so long as the burr does not protrude than a main diameter of the maximum diameter side axial shaft, it becomes an allowable range, so that a burr removal can be omitted or a simple burr removal work suffices.