Abstract: A method for manufacturing a spark plug comprises: welding a ground electrode to a tip of a metal shell (metallic shell); and removing a welding sag formed on and over inner surfaces of the ground electrode and the metal shell from a work in which the ground electrode is welded to the tip of the metal shell, the welding step including: cutting the welding sag using a working tool while a control unit controls a working position of the working tool with respect to the work; and measuring a remaining quantity of the welding sag after the cutting step and the control unit performing a feedback of a measured value of the remaining quantity of the welding sag measured in the measuring step to a working position of a working tool in the cutting step for the subsequent work.

Abstract: A method for manufacturing a spark plug comprises: welding a ground electrode to a tip of a metal shell (metallic shell); and removing a welding sag formed on and over inner surfaces of the ground electrode and the metal shell from a work in which the ground electrode is welded to the tip of the metal shell, the welding step including: cutting the welding sag using a working tool while a control unit controls a working position of the working tool with respect to the work; and measuring a remaining quantity of the welding sag after the cutting step and the control unit performing a feedback of a measured value of the remaining quantity of the welding sag measured in the measuring step to a working position of a working tool in the cutting step for the subsequent work.