Screw for fibrous material

摘要

The thread (15) of a wood or the like screw has pairs of V-shaped recesses (22, 23) in the edge of a selected intermediate length of the thread (17). Each pair defines a W-shaped cutout (19, 20, 11). The cutouts (19-21) extend into only a part of radial width of the thread (15). There are three cutouts (19-21) at each convolute (17) of the intermediate length. Depending on the length of the shank of the screw, there are three to five convolutes (17). The thread sections (16) at the tip (11) and at the head (13) of the screw are smooth. Each cutout defines a cutting tooth (24) which facilitates the driving of the screw into the workpiece. The recesses (22, 23) provide cavities for fibrous debris generated by the respective tooth (24). When the screw is in place, the teeth (24) are resiliently pressed axially toward the thread produced in the workpiece to reduce the loosening tendency of the installed screw.