| 摘要 |
A countersunk screw has a shank which exhibits the thread and a head which is adjacent thereto, is formed conically on the outside and, on its flat top, is provided with a retaining opening for the screwdriver. The outside of the conical head exhibits groove-shaped indentations, stampings or raised, projecting, sharp-edged beads of such a shape that, when the screw is screwed in, the drilled hole is automatically countersunk and sawdust produced in this way is transported to the surface of the drilled hole.
|
