| 摘要 |
A wood-screw has an essentially cylindrical shank 2 and its diameter does not exceed the diameter of a drill hole, the screw having two threads, that is a main thread 3 and a secondary thread 4, of which the former projects out significantly further from the circumference of the shank than the latter, and which are both formed as angular threads, that is to say they are thin in relation to their depth, and the front end of the cylindrical shank being provided with a depression with an edge 8 acting as cutting edge. <IMAGE> |
