| 摘要 |
Related to a tamperproof screw to which a conventional general screwdriver cannot couple so that screw tightening is prevented reliably, to a screwdriver bit that can be simply and quickly coupled to the screw and can reliably prevent a come-out phenomenon during screw tightening, and to a header punch for manufacturing the tamperproof screw simply, easily and at low costs. A tamperproof screw ( 10 A) has: inclined portions ( 15 ) that extends from the opening end edge portions ( 12 a) of the bit fitting grooves of a screw head ( 10 a) toward a center portion of the screw neck portion ( 10 b), step portions ( 14 ) provided at intermediate point of the inclined portion, a conical bottom surface ( 13 ) formed at the center portion where the inclined portions meet, and an inverted truncated cone shape hole portion ( 16 ) that reaches the bottom surface as a continuation, except for the step portions ( 14 ), of the inclined portions so that the open end edge portions of the bit engaging grooves take the maximum diameter of the inverted truncated cone shape hole portion. The thus structured tamperproof screw ( 10 A), a screwdriver bit that matches the screw, and a header punch for manufacturing the tamperproof screw are provided.
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