Abstract: A method of manufacturing a spark plug (1) including a disposing step, a contacting step, and a deforming step. In the disposing step, a mounting screw portion (30) is inserted into a gasket (50) and the gasket (50) is disposed between the mounting screw portion (30) and a seat portion (32). In the contacting step, from a front end side, a jig (60) is brought into contact with the gasket (50) disposed by the disposing step, and the jig (60) is moved toward the rear end side until a load applied to the jig (60) from the gasket (50) reaches a predetermined set load. In the deforming step, after the contacting step, the jig (60) is further moved toward the rear end side by a predetermined set distance XS. Consequently, the gasket (50) is pressed by the jig (60) and an inner edge portion (55) of the gasket (50) is deformed inward in a radial direction of the gasket (50).

Abstract: A method of manufacturing a spark plug (1) including a disposing step, a contacting step, and a deforming step. In the disposing step, a mounting screw portion (30) is inserted into a gasket (50) and the gasket (50) is disposed between the mounting screw portion (30) and a seat portion (32). In the contacting step, from a front end side, a jig (60) is brought into contact with the gasket (50) disposed by the disposing step, and the jig (60) is moved toward the rear end side until a load applied to the jig (60) from the gasket (50) reaches a predetermined set load. In the deforming step, after the contacting step, the jig (60) is further moved toward the rear end side by a predetermined set distance XS. Consequently, the gasket (50) is pressed by the jig (60) and an inner edge portion (55) of the gasket (50) is deformed inward in a radial direction of the gasket (50).