| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a screw with a bit engagement hole extensively elongating a service life of a punch forming a step part in a blade engagement groove, not causing buckling or the like of a fiber flow, and of a shape with superior biting characteristics. Ž<P>SOLUTION: The bit engagement hole 4 is equipped with a center hole part 5 formed along an axis line N passing through an axis of a shaft part 1, and a plurality of the blade part engagement grooves 6 radially extending from the center hole part 5. A groove end wall of the blade part engagement groove 6 is equipped with an inclined plane part 71 inclined in a direction approaching the axis line N toward a bottom 51 of the center hole part 5, and a parallel part 73 connected to the inclined plane part 71 via an inclined step part 72 and extending toward a head top face 31. The inclined step part 72 is composed such that it is slanted in a direction wherein an inner end becomes deeper than an outer end with respect to an orthogonal line orthogonal to the axis line N. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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