| 摘要 |
<p>A tamperproof screw to which a conventional general screwdriver cannot couple so that screw tightening is prevented reliably, 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 a header punch for manufacturing the tamperproof screw simply, easily and at low costs. A tamperproof screw (10A) has slope portions (15) extending from opening end edge portions (12a) of bit fitting grooves of a screw head (10a) toward a center part of a screw neck portion (10b), step portions (14) provided at intermediate part of the slope portion, and a conical bottom face (13) formed at the center portion where the slope portions meet. A hole portion (16) having a maximum diameter which is the ones of the opening and edge portions (12a) and an inverted conical trapezoidal shape, extending to the bottom face (13) and adjoining the slope portions except the step portions (14) is formed. The thus structured tamperproof screw (10A), a screwdriver bit matching the screw, and a header punch for manufacturing the tamperproof screw are provided.</p> |
