| 摘要 |
<p>A sheet screw comprising a screw head, a threaded shank connected at its top to the screw head, a substantially pyramidal end extending from the bottom of the threaded shank to terminate in a point, the pyramidal end having a tip portion disposed adjacent the point, and a base portion disposed between the tip portion and the bottom of the threaded shank, the tip portion being regularly polygonal in cross section and having a certain number of edges with an obtuse angle extending divergently from the point toward the base portion, the base portion having a smaller number of rounded ridges relative to the number of flat sides and the same number of edges of the tip portion, and each of curved outer surfaces of the rounded ridges becoming wider as it approaches the bottom of the threaded shank.</p> |
