| 摘要 |
A self-tapping screw for jointing fiberboard comprises a screw head and a shaft. It may comprise additionally a screw tip. The shaft is partially or entirely wrapped around with a thread, the cross-section of which forms a polygon, such as a pentagon, a hexagon, or a heptagon. The vertices of the cross-section are located at one and the same circumference. The thread has a twisted multi-prismal enveloping surface. The vertex of the thread is a chamfer. The polygonal cross-section causes reduction of the contact area of the screw threads with the object into which the screw is being screwed in. During the tapping procedure, the spiral multi-prismal construction makes bits easier to screw requiring smaller forces to be applied. |
