| 摘要 |
PROBLEM TO BE SOLVED: To provide a locking screw capable of offering reliable locking force. SOLUTION: A composite square thread 10 composed of a second flank surface 13 continuing with both side first flank surfaces 11 at a thread apex angle not more than 40 deg.C and having the trough side formed at a looser angle than the thread apex angle is formed in a desired position of a leg part 4 having a tapering circular guide part 7, an outside diameter of the composite square thread 10 is a thread outside diameter slightly larger than an ordinary thread 14 of the leg part 4, and since the ordinary thread 14 is a looseness preventive screw 1 having the thread apex angle formed by the second flank surface 13, looseness preventive force is improved, and screwing-in force is not enhanced so much to prevent seizure of a screw and a work. An automatic screw fastener for screwing in the screw is not required to use a conventional high torque screw fastener, so that an assembling cost is reduced. Since a guide part is a tapeing circular shape, the screw becomes almost vertical to a prepared hole without inclining, so that the screw is reliably screwed in the prepared hole.
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