| 摘要 |
The invention provides a screw head having a hexalobular slot ( 2 ) in the upper surface of the screw head, an upper peripheral wall ( 9 ) of hexalobular planform extending down into the screw head, the upper peripheral wall ( 9 ) being parallel or near parallel to the axis of the screw, a sloping transition surface ( 15 ) extending downwardly and inwardly with respect to the lower edge of the upper peripheral wall ( 9 ), and a tapered recess ( 11 ) extending downwardly from the lower edge of the sloping transition surface ( 15 ), in which the dimensions of the screw head are such that when the screw head is engaged by a tool ( 6 ) having upper ( 16 ) and lower engagement ( 17 ) sections, the lower engagement section ( 17 ) is tapered, and there is a 'stick fit' between the surface of the tapered recess ( 11 ) and the external surface of the lower tapered engagement section ( 17 ), and there is no engagement with the sloping transition surface ( 15 ).
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