| 摘要 |
A screw includes a rod-shaped portion, and a spiral-shaped thread winding around the rod-shaped portion. The rod-shaped portion has a straight portion, and a front end portion tapering towards a pointed front end. Several cutting trenches are formed on the rod-shaped portion for cutting bits off a workpiece with which when the screw is being screwed into the same. The tapering front end portion is provided with a notch, and cutting teeth are provided on that portion of the thread corresponding to the tapering front end portion. Cut-off bits of a workpiece can be received in the trenches as well as the cutting teeth so that the same can't have excessive resistance against the screw. |
