Screw for plastic composite lumber

摘要

A fastener for use in conjunction with plastic lumber is provided with an undercut head and radially projecting helical flutes on the shank which combine to contain plastic lumber material displaced by the shank and head beneath the head, permitting a single step installation to produce a finished appearance. The helical flutes have an opposed helical orientation to the screw threads. This opposed relationship causes the flutes to push displaced plastic lumber material away from the screw head while the flutes bore a space for plastic lumber material displaced by countersinking the screw head. The undercut head may be provided with a series of teeth around the underside of the head periphery. The teeth aid in penetrating the surface of the plastic lumber. The teeth also resist backing out of the screw.