SCREW FOR USE AS A FASTENER IN FIBROUS MATERIAL SUCH AS WOOD

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 threa d (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 only about three cutouts (19-21) at each convolute (17) of the limited length. The lengths of the thread (16) at the tip and at the head (13) of the screw are smooth. Each cutout defines a cutting tooth (24) which facilitates the driving of t he 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, t he teeth (24) are resiliently pressed axially toward the thread produced in the workpiece to reduce the loosening tendency of the installed screw. The disposition and size of the cutouts (19-21), is about three cutouts per one convolute so as not to unduly impede the torque strength of the screw.