| 摘要 |
It is an object of the invention to provide a method of working an injection hole of an electromagnetic type fuel injection valve so that when extrusion by using a punch is adopted, the punch does not break, even in the case where a central axis line of the injection hole of the electromagnetic type fuel injection valve is inclined to a line perpendicular to a face of a plate-like material to be punched. A front end, tapered portion of the punch is inclined in a direction opposed to a plate-like material relative to a central axis line of the punch to facilitate the punch along a sliding, inner face of a punch holder. While achieving a reduction in production cost, the divergent-shaped injection hole can accurately be formed in the plate-like material. A side force (Fs) is produced when the front end portion of the punch impinges on the plate-like material. The side force (Fs) is canceled by a reaction force (Fr) on a side opposed to the plate-like material and a bending moment potentially causing breakage of the punch is avoided.
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