Wallboard screws

Claim 1

A WALLBORD SCREW COMPRISING A LONGITUDINALLY EXTENDING SHANK INCLUDING A SUBSTANTIALY CYLINDRICAL BODY SECTION MERGING INTO A FORWARDLY TAPERED SUBSTANTIALLY CONICAL PILOT END SECTION TERMINATING IN A FORWARDLY DISPOSED POINT, DRILL STRUCTURE CARRIED BY THE FRONT PORTION OF SAID PILOT END SECTION AND EXTENDING TO SAID POINT, A SELF-TAPPING THREAD CARRED BY THE REAR PORTION OF SAID PILOT END SECTION AND BY THE FRONT PORTION OF SAID BODY SECTION, AN ENLARGED HEAD TERMINATING THE REAR END OF SAID BODY SECTION, SAID HEAD BEING OF THE COUNTERSINK TYPE INCLUDING A REARWARDLY TAPERED SUBSTANTIALLY CONICAL THRUST SURFACE AND A SUBSTANTIALLY FLAT TOOL-ENGAGING FACE, SAID TOOL-ENGAGING FACE BEING DISPOSED SUBSTANTIALLY NORMAL TO THE AXIS OF SAID SHANK AND HAVING A TOOL-RECEIVING RECESS THEREIN, WHEREBY SAID SCREW MAY BE SET IN A COOPERATING WALLBOARD WITH SAID HEAD IN COUNTERSUNK RELATION THEREWITH AND WITH SAID THRUST SURFACE IN ENGAGEMENT WITH THE THROAT OF THE HOLE IN THE WALLBOARD THROUGH WHICH SAID SHANK EXTENDS AND SAID TOOL-ENGAGING FACE POSITIONED SUBSTANTIALLY FLUSH WITH THE OTHER SURFACE OF THE WALLBOARD, AND A THREAD-LIKE STRUCTURE CARRIED BY SAID THRUST SURFACE, SAID THREAD HAVING A FIRST SUBSTANTIALLY CONSTANT PITCH ALONG THE AXIS OF SAID SHANK, SAID THREAD-LIKE STRUCTURE HAVING A SECOND VARIABLE PITCH ALONG THE AXIS OF SAID HEAD, SAID FIRST PITCH BEING MATERIALLY GREATER THAN SAID SECOND PITCH, SAID THRUST SURFACE AND SAID THREAD-LIKE STRUCTURE BEING LOCATED RADIALLY INWARDLY WITH RESPECT TO A SIMPLE CONE FRUSTUM PROJECTED REARWARDLY FROM THE FRONT END TO THE REAR END OF SAID THRUST SURFACE, WHEREBY SAID THRUST SURFACE AND SAID THREAD-LIKE STRUCTURE HAVE A CONCAVE CONFIGURATION AND A RESULTING COMPOSITE FRICTIONAL AREA THAT IS MATERIALLY GREATER THAN THAT OF THE SIMPLE CONE FRUSTUM MENTIONED, AND WHEREBY SAID THREAD-LIKE STRUCTURE COMPRESSES A COMPLEMENTARY THREAD-LIKE FORMATION INTO THE THROAT OF THE PREVIOUSLY MENTIONED HOLE IN THE WALLBOARD AS SAID SCREW IS SET THEREIN WITH SAID HEAD IN COUNTERSUNK RELATION WHEREWITH.