Volt/bolt null ahead sword for tight frame

摘要

PROBLEM TO BE SOLVED: To provide a sword point bolt wherein even when a hole is opened by the sword point bolt relating to a fold sheet roof material thatched upward of a tight frame with sword point bolt, a hole is opened in a condition almost uniform in length of a plurality of cracks generated when the hole is opened. ;SOLUTION: In a sword point bolt (a) comprising a head part 1, shank 2 and a screw part 3, in an upper part of the screw part 3, a circular protruded part 4 of diameter in a similar degree to a bottom diameter of the screw part 3 is provided to protrude by a prescribed length, a top part 5 of the circular protruded part 4 is formed as a recessed part 7 of reverse cone shape with a center part 6 of the protruded part 4 placed in the lowest, and an outer side peripheral edge part of the top part 5 is formed in sharpened shape.;COPYRIGHT: (C)1998,JPO