Method for regulating aground electrode position in spark plug

A method for manufacturing a spark plug, the spark plug including:

• a cylindrical insulator having an axial hole penetrating said cylindrical insulator in an axial direction thereof;
• a center electrode inserted into said axial hole of said insulator and having a front end projecting beyond a front end surface of said insulator;
• a metal shell surrounding said insulator;
• and
• a ground electrode fixedly attached to said metal shell by a fixation portion and bent to form a spark discharge gap between a front end portion of said ground electrode and said front end of said center electrode;
• said method comprising:
• measuring an X-directional position of said front end of said center electrode;
• positioning an X-directional position of a regulation member based on said X-directional position of said front end of said center electrode measured in said center electrode position measuring step, said regulation member regulating an X-directional position of a front end surface of said ground electrode when said ground electrode is pressed and bent in a Y direction;
• and
• forming said spark discharge gap using said regulation member to regulate said X-directional position of said front end surface of said ground electrode while pressing and bending said ground electrode in said Y direction with a pressure member so as to form said spark discharge gap;
• wherein:
• said X direction designates, of directions perpendicular to a central axis of said metal shell and perpendicular to a width direction of said fixation portion of said ground electrode, a direction from said fixation portion of said ground electrode toward said central axis of said metal shell;
• and
• said Y direction designates a direction from a front end side of said internal combustion spark plug to a base side thereof along said central axis of said metal shell,
• wherein said regulation member positioning step comprises positioning said X-directional position of said regulation member so that said front end surface of said ground electrode will be located within a deviation range deviating from its predetermined position in said X direction with respect to said front end of said center electrode once said gap forming step has been completed,
• wherein said deviation range is ±0.1 mm,
• wherein said regulation member has a regulation abutment surface which abuts against said front end surface of said ground electrode in said gap forming step, and
• wherein said regulation member moves together with the pressure member when the pressure member presses said ground electrode to bend said ground electrode in the Y-direction.