| 摘要 |
<p>A recessed screw (10) has a recess (12) formed in the head (11) of screw, and the recess (12) is defined as a superimposition of two equilaterally-triangular recesses (14) which each have arcuately shaped vertices (13) and are arranged coaxially with a phase shift of 60 DEG around a longitudinal axis of the screw. The recess (12) thus has six grooves 915) alternating with six driven vanes (16) having side walls (16a) extending parallel with the axis, and an inner ridge of each vane is a conically curved sticking wall (18) inwardly slanted towards a bottom of the recess (12). The cross-sectional area (A) of each groove (15) is larger than that (B) of each vane (16). A driver bit has six driving vanes in conformity with the grooves (15) and six valleys each interposed between the adjacent driving vanes and corresponding to the driven vanes (16) in the recess (12), such that a biting action appears between the recess (12) and the bit. The driving vanes (16) can be strengthened, and any conventional bit for Torx screws can be used with the recessed screw. <IMAGE></p> |
