| 摘要 |
A method of making an elongate mandrel (1) having an end integral with a drill section (4), the method comprising the steps of: subjecting a single columnar piece of material to the heading process so as to make a blank "N" composed of the mandrel, a short stem (2) having one end integral with the end of the mandrel and having a diameter "D" greater than the diameter "d" of the mandrel, and a flange (3) formed integral with the other end of the stem; then cold forging the stem to produce the drill section having end edges (7a) and (7b) facing the flange; and subsequently trimming the drill section so as to remove the flange (3) together with a scrap (10) resulting from the cold forging of the stem, in such a manner that the mandrel having the integral drill section can be mass produced from the single raw piece, efficiently at a reduced cost.
|
