CHAMFERING METHOD FOR HOLE

Japanese Patent JP3757601

B2

PROBLEM TO BE SOLVED: To uniformly chamfer the total periphery of an edge part for a short time by pressing a ball to one edge of a hole to perform the deformation processing on an edge part of the hole, and then grinding the edge part. SOLUTION: A nozzle body 1 of a fuel injection nozzle is totally formed into the almost cylindrical shape, a lower point part 2 is tapered and closed, and a hole part of small diameter almost semispherically projecting to the point side, is formed on the pointmost of the point part on the shaft center position. The hole part 3 comprises a plurality of holes of small diameters, that is, the nozzle holes 4. A die 6 is lowered, the specific pressure is applied to the die 6, the balls 16 are strongly pressed to the edge parts 19 of the nozzle holes 4 for the deformation processing of the edge parts 19, and then the edge parts 19 are lightly ground. As mentioned in the above, by performing the deformation processing on the edge parts 19 before the edge parts are ground, the grinding time can be reduced, that is, the time necessary for the total chamfering can be remarkably reduced.