Abstract: A method of manufacturing a metal shell assembly for a spark plug including a cylindrical metal shell that extends in a direction of a central axis and which has a screw portion formed in an outer peripheral surface thereof, and a bar-shaped ground electrode that extends from a front end portion of the metal shell, the method including: disposing an intermediate assembly, having the ground electrode provided in a metal shell intermediate body, between a plurality of rolling dies having process surfaces facing each other; forming the screw portion by performing a rolling process on the intermediate assembly by the plurality of rolling dies while the intermediate assembly is interposed between the plurality of rolling dies; and positioning the ground electrode in a circumferential direction about a central axis of the intermediate assembly between the disposing and forming steps.

Abstract: Provided is a technique for limiting the radial displacement between a metal shell and an insulator in a spark plug. At the time of manufacturing a spark plug with a metal shell and an insulator, the metal shell and the insulator are assembled together by, while allowing relative positional displacement between the metal shell and the insulator in an axial direction (O-O), limiting relative positional displacement between the metal shell and the insulator in a radial direction intersecting with the axial direction in such a manner that the amount of deviation between an axis of the metal shell and an axis of the insulator becomes less than or equal to a predetermined level.

Abstract: A method and an apparatus for manufacturing a spark plug. A bending apparatus includes a bending unit having a preliminary bending unit and a main bending unit, and a gap adjusting unit. The main bending unit including pressing unit for pressing a distal end of a ground electrode toward a center electrode, and a gap adjusting unit configured to adjust a relative height position of the distal end of the ground electrode relative to a distal end of the center electrode in an axis line direction. The gap adjusting unit includes a gap adjusting unit for relatively moving the distal end of the ground electrode relative to the center electrode in a direction substantially perpendicular to the axis line direction, and a restricting unit for restricting relative movement of the distal end of the ground electrode relative to the center electrode in the axis direction.

Abstract: Provided is a technique for limiting the radial displacement between a metal shell and an insulator in a spark plug. At the time of manufacturing a spark plug with a metal shell and an insulator, the metal shell and the insulator are assembled together by, while allowing relative positional displacement between the metal shell and the insulator in an axial direction (O-O), limiting relative positional displacement between the metal shell and the insulator in a radial direction intersecting with the axial direction in such a manner that the amount of deviation between an axis of the metal shell and an axis of the insulator becomes less than or equal to a predetermined level.

Abstract: A method of manufacturing a metal shell assembly for a spark plug including a cylindrical metal shell that extends in a direction of a central axis and which has a screw portion formed in an outer peripheral surface thereof, and a bar-shaped ground electrode that extends from a front end portion of the metal shell, the method including: disposing an intermediate assembly, having the ground electrode provided in a metal shell intermediate body, between a plurality of rolling dies having process surfaces facing each other; forming the screw portion by performing a rolling process on the intermediate assembly by the plurality of rolling dies while the intermediate assembly is interposed between the plurality of rolling dies; and positioning the ground electrode in a circumferential direction about a central axis of the intermediate assembly between the disposing and forming steps.

Abstract: A method and an apparatus for manufacturing a spark plug. A bending apparatus includes a bending unit having a preliminary bending unit and a main bending unit, and a gap adjusting unit. The main bending unit including pressing unit for pressing a distal end of a ground electrode toward a center electrode, and a gap adjusting unit configured to adjust a relative height position of the distal end of the ground electrode relative to a distal end of the center electrode in an axis line direction. The gap adjusting unit includes a gap adjusting unit for relatively moving the distal end of the ground electrode relative to the center electrode in a direction substantially perpendicular to the axis line direction, and a restricting unit for restricting relative movement of the distal end of the ground electrode relative to the center electrode in the axis direction.