Patent ID: 8371889

Claim:
A spark plug manufacturing method for manufacturing a spark plug including: a rod-like center electrode extending in an axis line direction; a substantially cylindrical insulator having an axial hole extending in the axis line direction, the center electrode being provided at a front end side of the axial hole; a substantially cylindrical metal shell provided on an outer circumference of the insulator; and a ground electrode which includes a proximal end portion joined to the metal shell, an intermediate portion bent so as to form a spark discharge gap between a distal end portion of the ground electrode and a front end portion of the center electrode, the spark plug manufacturing method comprising: pressing the distal end portion of the ground electrode toward the center electrode by a bending unit so that the ground electrode is bent to adjust a relative height position of the distal end portion of the ground electrode in the axis line direction relative to the front end portion of the center electrode; and adjusting a magnitude of the spark discharge gap which is defined in a direction perpendicular to the axis line by use of a gap adjusting unit for moving the distal end portion of the ground electrode relative to the center electrode, while a restricting unit restricts the relative movement of the distal end portion of the ground electrode relative to the center electrode in the axis line direction, and during the pressing step and the adjusting step, an inner deformation preventing unit of a deformation preventing unit for preventing deformation of the ground electrode is brought into abutment with an inner surface of the proximal end portion of the ground electrode, and an outer deformation preventing unit of the deformation preventing unit is brought into abutment with an outer surface of the proximal end portion of the ground electrode.