Self-countersinking screw with cutting receiving pockets

Abstract

A self-countersinking screw including an inverted-conical head portion formed at a top with a cavity adapted to receive a tip of a screwdriver and having a conical bottom, said conical bottom having a plurality of triangular recesses each having a lateral side extending inwardly to form a sharp edge and a space for receiving chips, a threaded portion, and a tapered portion having a large diameter connected with the head portion and a small diameter connected with the threaded portion, whereby the sharp edge will make a countersink on a workpiece when the countersunk head screw is turned therein.

We claim: 
     
       1. A self-countersinking screw having a body with a longitudinal axis, said body comprising in combination: (a) a head which includes screwdriver engaging means at a top face and an underside having an inversely frusto-conical surface;   (b) a threaded stem portion integral with the head and comprising a thread adapted to drive the screw into a workpiece when the threaded stem portion is rotated about said axis in a predetermined direction;   (c) a plurality of generally triangular recesses on said underside, said recesses having straight sides, each said recess being axially spaced from said stem and from said top face;   (d) each recess comprising from the standpoint of said predetermined direction, a generally planar trailing wall forming a linear cutting edge coincident with said frusto-conical underside;   (e) each said recess further including: (i) a leading wall which is generally planer and convergent with said trailing wall in the direction along said underside and towards the axis of the screw;   (ii) a generally planer upper boundary wall extending between upper ends of said trailing wall and said leading wall in a circumferential direction and disposed at a spacing from said top along said frusto-conical surface; and   (iii) a flat, generally triangular bottom.     
     
     
       2. The screw of claim .[.1.]. .Iadd.8.Iaddend., further comprising a tapered intermediate portion tapering in a direction away from the head and disposed between said underside and said stem, said intermediate portion including a large diameter section adjoining said underside, and a small diameter section adjoining said threaded stem portion. 
     
     
       3. The screw as claimed in claim .[.1.]. .Iadd.8.Iaddend., wherein the upper boundary walls are all generally coplanar with a single plane which is generally perpendicular to the axis of the screw and is spaced from said top surface. 
     
     
       4. The screw as claimed in claim .[.1.]. .Iadd.8 .Iaddend.wherein the depth of each said recess increases in the direction from said leading .[.wall.]. .Iadd.boundary .Iaddend.to a corner between said trailing wall and said upper boundary wall. 
     
     
       5. A self-countersinking screw having a body with a longitudinal axis, said body comprising in combination: (a) a head which includes screwdriver engaging means at a top face and an underside having an inversely frusto-conical surface;   (b) a threaded stem portion integral with the head and comprising thread adapted to drive the screw into a workpiece when the threaded stem is rotated about said axis in a predetermined direction;   (c) a plurality of generally triangular recesses on said underside, each said recess being axially spaced from said stem and from said top face;   (d) a tapered intermediate portion tapering in a direction away from the head and disposed between said underside and said stem portion, said intermediate portion including a large diameter section adjoining said underside, and a small diameter section adjoining said threaded stem portion;   (e) each said recess including: (i) from the standpoint of said predetermined direction, a generally planar trailing wall forming a linear cutting edge coincident with said frusto-conical underside;   (ii) a leading wall which is generally planar and convergent with said trailing wall in the direction along said underside and towards the axis of the screw;   (iii) a generally planar upper boundary wall extending between upper ends of said trailing wall and said leading wall in a circumferential direction and disposed at an axial spacing from said top along said frusto-conical surface; and   (iv) a flat, generally triangular bottom.     
     
     
       6. A self-countersinking screw having a body with a longitudinal axis, said body comprising in combination: (a) a head which includes screwdriver engaging means at a top face and an underside having an inversely frusto-conical surface;   (b) a threaded stem portion integral with the head and comprising thread adapted to drive the screw into a workpiece when the threaded stem is rotated about its axis in a predetermined direction;   (c) a plurality of generally triangular recesses on said underside, each said recess being axially spaced from said stem portion and from said top face;   (d) a tapered intermediate portion tapering in a direction away from the head and disposed between said underside and said stem portion, said intermediate portion including a large diameter section adjoining said underside, and a small diameter section adjoining said threaded stem portion;   (e) each said recess including.Iadd.; .Iaddend. (i) from the standpoint of said predetermined direction, a generally planar trailing wall forming a linear cutting edge coincident with said frusto-conical underside;   (ii) a leading wall which is generally planar and convergent with said trailing wall in the direction along said underside and towards the axis of the screw;   (iii) a generally planar upper boundary wall extending between upper ends of said trailing wall and said leading wall in a circumferential direction and disposed at an axial spacing from said top along said frusto-conical surface; and   (iv) a flat, generally triangular bottom;     (f) the upper boundary walls of each said recesses being all generally coplanar with a single plane generally perpendicular to the axis of the screw and spaced from said top surface.   
     
     
       7. A self-countersinking screw having a body with a longitudinal axis, said body comprising in combination: (a) a head which includes screwdriver engaging means at a top face and an underside having an inversely frusto-conical surface;   (b) a threaded stem portion integral with the head and comprising thread adapted to drive the screw into a workpiece when the threaded stem is rotated about said axis in a predetermined direction;   (c) a plurality of generally triangular recesses on said underside, each said recess being axially spaced from said stem portion and from said top face.[., the depth of each said recess increasing in the direction from a leading wall to a corner between a trailing wall and said upper boundary wall.].;   (d) each said recess having a tapered intermediate portion tapering in a direction away from the head and disposed between said underside and said stem portion, said intermediate portion including a large diameter section adjoining said underside, and a small diameter section adjoining said threaded stem portion;   (e) each said recess including: (i) from the standpoint of said predetermined direction, generally planar trailing wall forming a linear cutting edge coincident with said frusto-conical underside;   (ii) a leading wall which is generally planar and convergent with said trailing wall in the direction along said underside and towards the axis of the screw;   (iii) a generally planar upper boundary wall extending between upper ends of said trailing wall and said leading wall in a circumferential direction and disposed at an axial spacing from said top along said frusto-conical surface; and   (iv) a flat, generally triangular bottom so arranged that the depth of each said recess increases in the direction from said leading wall to a corner between said trailing wall and said upper boundary wall;     (f) the upper boundary walls of each said recesses being all generally coplanar with a single plane generally perpendicular to the axis of the screw and spaced from said top surface. .Iadd.   
     
     
       8.  A self-countersinking screw having a body with a longitudinal axis, said body comprising in combination: (a) a head which includes screwdriver engaging means at a top face and an underside having an inversely frusto-conical surface;   (b) a threaded stem portion integral with the head and comprising a thread adapted to drive the screw into a workpiece when the threaded stem portion is rotated about said axis in a predetermined direction;   (c) a plurality of generally triangular recesses on said underside, said recesses having straight sides, each said recess being axially spaced from said stem and from said top face;   (d) each recess comprising from the standpoint of said predetermined direction, a generally planar trailing wall forming a cutting edge coincident with said frusto-conical underside;   (e) each said recess further including: (i) a leading boundary which is convergent with said cutting edge in the direction along said underside and towards the axis of the screw;   (ii) a generally planar upper boundary wall extending between an upper end of said trailing wall and an upper end of said leading boundary in a circumferential direction and disposed at a spacing from said top along said frusto-conical surface; and   (iii) a flat, generally triangular bottom. .Iaddend..Iadd.     
     
     
       9.  A self-countersinking screw having a body with a longitudinal axis, said body comprising in combination: (a) a head which includes screwdriver engaging means at a top face and an underside having an inversely frusto-conical surface;   (b) a threaded stem portion integral with the head and comprising thread adapted to drive the screw into a workpiece when the threaded stem is rotated about said axis in a predetermined direction;   (c) a plurality of generally triangular recesses on said underside, each said recess being axially spaced from said stem and from said top face;   (d) a tapered intermediate portion tapering in a direction away from the head and disposed between said underside and said stem portion, said intermediate portion including a large diameter section adjoining said underside, and a small diameter section adjoining said threaded stem portion;   (e) each said recess including: (i) from the standpoint of said predetermined direction, a generally planar trailing wall forming a linear cutting edge coincident with said frusto-conical underside;   (ii) a leading boundary which is convergent with said cutting edge in the direction along said underside and towards the axis of the screw;   (iii) a generally planar upper boundary wall extending between an upper end of said trailing wall and an upper end of said leading boundary in a circumferential direction and disposed at an axial spacing from said top along said frusto-conical surface; and   (iv) a flat, generally triangular bottom. .Iaddend..Iadd.     
     
     
       10.  A self-countersinking screw having a body with a longitudinal axis, said body comprising in combination: (a) a head which includes screwdriver engaging means at a top face and an underside having an inversely frusto-conical surface;   (b) a threaded stem portion integral with the head and comprising thread adapted to drive the screw into a workpiece when the threaded stem portion is rotated about its axis in a predetermined direction;   (c) a plurality of generally triangular recesses on said underside, each said recess being axially spaced from said stem portion and from said top face;   (d) a tapered intermediate portion tapering in a direction away from the head and disposed between said underside and said stem portion, said intermediate portion including a large diameter section adjoining said underside, and a small diameter section adjoining said threaded stem portion;   (e) each said recess including: (i) from the standpoint of said predetermined direction, a generally planar trailing wall forming a linear cutting edge coincident with said frusto-conical underside;   (ii) a leading boundary which is convergent with said cutting edge in the direction along said underside and towards the axis of the screw;   (iii) a generally planar upper boundary wall extending between an upper end of said trailing wall and an upper end of said leading boundary in a circumferential direction and disposed at an axial spacing from said top along said frusto-conical surface; and   (iv) a flat, generally triangular bottom:     (f) the upper boundary walls of each said recesses being all generally coplanar with a single plane generally perpendicular to the axis of the screw and spaced from said top surface. .Iaddend..Iadd.   
     
     
       11.  A self-countersinking screw having a body with a longitudinal axis, said body comprising in combination: (a) a head which includes screwdriver engaging means at a top face and an underside having an inversely frusto-conical surface;   (b) a threaded stem portion integral with the head and comprising thread adapted to drive the screw into a workpiece when the threaded stem is rotated about said axis in a predetermined direction;   (c) a plurality of generally triangular recesses on said underside, each said recess being axially spaced from said stem portion and from said top face;   (d) each said recess having a tapered intermediate portion tapering in a direction away from the head and disposed between said underside and said stem portion, said intermediate portion including a large diameter section adjoining said underside, and a small diameter section adjoining said threaded stem portion;   (e) each said recess including: (i) from the standpoint of said predetermined direction, a generally planar trailing wall forming a linear cutting edge coincident with said frusto-conical underside;   (ii) a leading boundary which is convergent with said cutting edge in the direction along said underside and towards the axis of the screw;   (iii) a generally planar upper boundary wall extending between an upper end of said trailing wall and said leading boundary in a circumferential direction and disposed at an axial spacing from said top along said frusto-conical surface; and   (iv) a flat, generally triangular bottom so arranged that the depth of said recess increases in the direction from said leading boundary to a corner between said trailing wall and said upper boundary wall;     (f) the upper boundary walls of each said recesses being all generally coplanar with a single plane generally perpendicular to the axis of the screw and spaced from said top surface. .Iaddend..Iadd.12. A self-countersinking screw having a body with a longitudinal axis, said body comprising in combination:   (a) a head which includes screwdriver engaging means at a top face and an underside having an inversely frusto-conical surface;   (b) a threaded stem portion integral with the head and comprising a thread adapted to drive the screw into a workpiece when the threaded stem portion is rotated about said axis in a predetermined direction;   (c) a plurality of generally triangular recesses on said underside, said recesses having straight sides, each said recess being axially spaced from said stem and from said top face;   (d) each recess comprising from the standpoint of said predetermined direction, a generally planar trailing wall forming a linear cutting edge coincident with said frusto-conical underside;   (e) each said recess further including: (i) a leading boundary which is convergent with said cutting edge in the direction along said underside and towards the axis of the screw;   (ii) a generally planar upper boundary wall extending between an upper end of said trailing wall and an upper end of said leading boundary in a circumferential direction and disposed at a spacing from said top along said frusto-conical surface; and   (iii) a flat, generally triangular bottom. .Iaddend.