FASTENER INCLUDING FUMBLE-PROOF DRIVE HOLE

摘要

PROBLEM TO BE SOLVED: To provide a fastener including fumble-proof drive hole capable of smoothly releasing a drive tool from the drive hole upon receiving a driving force in a releasing direction.;SOLUTION: This invention is made such that a head part 2 has a drive hole 3 including upright surfaces 3a of hexagonal shape as seen from a top plan view and a release surface 3d extending upward from a bottom part of each of the upright surfaces 3a in a releasing direction with apexes of the hexagonal shape being applied as base points. The release surface 3d is of a curved surface of which slope becomes loose as it approaches to the bottom part. With this configuration, since the upright surfaces 3a have no such a pressure receiving surface as one performing a transmittance function against a drive force in a releasing direction from a hexagonal wrench 4, a top part 4a of the hexagonal wrench 4 takes a roundabout path against the release surface 3d. In this case, an inclination of an edge part 3f of the upright surface 3a formed by the release surface 3d becomes loose as it approaches to the bottom surface 3b. Due to this fact, the extremity end of the hexagonal wrench 4 can ride over the edge part 3f of the upright surface 3a and ride on the release surface 3d and in addition, its sliding action after riding-on also becomes easy and the hexagonal wrench 4 can be released smoothly from the drive hole 3.;COPYRIGHT: (C)2015,JPO&INPIT