Thread-cutting masonry screw

摘要

In order to improve the holding force of a self-tapping concrete screw (1) in a hole (2) drilled in concrete (3), the invention proposes formation of the concrete screw (1) with two threads (8, 9) having different external diameters (d1, d2), the spacing (p1) of the thread (8) which has the smaller external diameter (d1) to the thread (9) which has the larger external diameter (d2) when seen from the front end (5) of the screw being smaller than the spacing (p2) of the thread (9) having the larger external diameter to the thread (8) having the smaller external diameter. The threads (8, 9) are preferably sawtooth threads.