METHOD FOR MANUFACTURING SPARK PLUG

PROBLEM TO BE SOLVED: To provide a method for manufacturing a spark plug capable of crimping and fixing a main metal fitting to an insulator while preventing plastic deformation of a threaded portion in an axial direction.SOLUTION: While engaging a threaded portion of a main metal fitting with an engaging portion of a jig, a surface on the distal end side of a seat portion is brought into contact with a receiving portion of the jig. In the jig, an axial distance of the engaging portion with respect to the receiving portion is constrained. Since at least the threaded portion positioned on the radially outer side of the surface on the rear end side of the shelf portion of the threaded portion is engaged with the engaging portion, the threaded portion can be constrained in the axial direction. Therefore, the main metal fitting can be caulked and fixed to an insulator while preventing plastic deformation of the threaded portion in the axial direction.SELECTED DRAWING: Figure 2 【課題】ねじ部の軸方向の塑性変形を防ぎながら主体金具を加締めて絶縁体に固定できるスパークプラグの製造方法を提供すること。【解決手段】治具の係合部に主体金具のねじ部を係合しつつ、座部の先端側の面を治具の受け部に当接する。治具は、受け部に対する係合部の軸方向の距離が拘束されており、ねじ部のうち、少なくとも棚部の後端側の面の径方向外側に位置するねじ部を係合部に係合するので、ねじ部を軸方向に拘束できる。よって、ねじ部の軸方向の塑性変形を防ぎながら主体金具を加締めて絶縁体に固定できる。【選択図】図２