| 摘要 |
A wood screw is characterised in that its core (2) is generally cylindrical with a diameter which does not exceed that of a prebored hole, that it comprises two threads, viz. a main thread (3) and an auxiliary thread (4), of which the former protrudes considerably more from the circumference of the core than the latter and both of which are formed as sharp threads, i.e. are thin in relation to their depth, and that the front end of the cylindrical core is provided with a recess (5) having an edge (8) acting as a cutter. |
