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 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 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 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. 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.