Self-drilling and thread-forming screw

Claim 2

In a drill and thread forming screw having a head portion, a shank portion with an outstanding thread thereon, a longitudinal axis, and a formed metal drilling portion centered on the axis at the end of the shank having side extremity surfaces and drilllike end surfaces, the improvement wherein said drilling portion comprises: metal cutting means having at least two cutting edges each extending uninterruptedly from a side extremity surface of the drilling portion to the longitudinal axis, said cutting edges meeting each other at said axis providing continuous cutting means from one side extremity surface through the axis to an opposite side extremity surface of the drilling portion; formed metal means supporting the cutting edges for drilling purposes and including an exposed surface extending generally longitudinally from each cutting edge to the shank portion; a pair of rounded surfaces each extending from a side extremity surface around the drilling portion to end abruptly at an exposed surface forming a pair of longitudinal extending pockets with said exposed surfaces along which chips may egress, each pocket having means adjacent to the cutting edge providing a relatively abrupt change in direction for breaking chips into small pieces.

Claim 3

In a drill and thread forming screw having a head portion, a shank portion with an outstanding thread thereon, a longitudinal axis, and a formed metal drilling portion centered on the axis at the end of the shank having side extremity surfaces and drill-like end surfaces, the improvement wherein said drilling portion comprises: metal cutting means having at least two cutting edges each extending uninterruptedly from a side extremity surface of the drilling portion to the longitudinal axis, said cutting edges being the extremities of exposed surfaces and meeting each other at said axis providing continuous cutting means from one side extremity surface through the axis to an opposite side extremity surface of the drilling portion; formed metal means in trailing position to said edges supporting each of the cutting edges along its entire extent for drilling purposes and including a solid mass of metal shaped generally as a pair of longitudinal, offset half cylinders one for each cutting edge, each surmounted at the end by a section of an oblique cone, the cutting edge being an element of the surface of the cone section, the cylindrical axis of each half cylinder being radially displaced from said longitudinal axis.

Claim 4

In a drill and thread forming screw having a head portion, a shank portion with an outstanding thread thereon, a longitudinal axis, and a formed metal drilling portion centered on the axis at the end of the shank having side extremity surfaces and drill-like end surfaces, the improvement wherein said drilling portion comprises: metal cutting means having at least two cutting edges each extending uninterruptedly from a side extremity surface of the drilling portion to the longitudinal axis, said cutting edges being the extremities of exposed surfaces and meeting each other at said axis providing continuous cutting means from one side extremity surface through the axis to an opposite side extremity surface of the drilling portion; formed metal means in trailing position to said edges supporting each of the cutting edges along its entire extent for drilling purposes and including a solid mass of metal shaped generally as a pair of longitudinal, offset half cylinders one for each cutting edge, each surmounted at the end by a section of an oblique cone, the cutting edge being an element of the surface of the cone section, the cylindrical axis of each half cylinder being radially displaced from said longitudinal axis.

Claim 5

The screw of claim 2 wherein the apex of each cone section is centered on the longitudinal axis of the screw.

Claim 6

In a drill and thread forming screw having a head portion, a shank portion with an outstanding Thread thereon, a longitudinal axis, and a formed metal drilling portion centered on the axis at the end of the shank having side extremity surfaces and drill-like end surfaces, the improvement wherein said drilling portion comprises: metal cutting means having at least two cutting edges each extending uninterruptedly from a side extremity surface of the drilling portion to the longitudinal axis forming together a pointed drilling end with an apex on said axis, said cutting edges being the extremities of exposed surfaces and meeting each other directly at said axis providing continuous cutting means from one side extremity surface through the axis to an opposite side extremity surface of the drilling portion; and formed metal means in trailing position to said edges supporting each of the cutting edges along its entire extent for drilling purposes, said formed metal means having a curved outer surface extending abruptly away from said exposed surface at generally a right angle and curling outwardly to said side extremity.

Claim 7

In a drill and thread forming screw having a head portion, a shank portion with an outstanding Thread thereon, a longitudinal axis, and a formed metal drilling portion centered on the axis at the end of the shank having side extremity surfaces and drill-like end surfaces, the improvement wherein said drilling portion comprises: metal cutting means having at least two cutting edges each extending uninterruptedly from a side extremity surface of the drilling portion to the longitudinal axis forming together a pointed drilling end with an apex on said axis, said cutting edges being the extremities of exposed surfaces and meeting each other directly at said axis providing continuous cutting means from one side extremity surface through the axis to an opposite side extremity surface of the drilling portion; and formed metal means in trailing position to said edges supporting each of the cutting edges along its entire extent for drilling purposes, said formed metal means having a curved outer surface extending abruptly away from said exposed surface at generally a right angle and curling outwardly to said side extremity.

Claim 8

In a drill and thread forming screw having a head portion, a shank portion with an outstanding thread thereon, a longitudinal axis, and a formed metal drilling portion centered on the axis at the end of the shank having side extremity surfaces and drill-like end surfaces, the improvement wherein said drilling portion comprises: metal cutting means having at least two cutting edges each extending uninterruptedly from a side extremity surface of the drilling portion to the longitudinal axis, said cutting edges being the extremities of exposed surfaces and meeting each other at said axis providing continuous cutting means from one side extremity surface through the axis to an opposite side extremity surface of the drilling portion; formed metal means in trailing position to said edges supporting each of the cutting edges along its entire extent for drilling purposes and including a solid mass of metal behind each cutting edge, each such mass being generally shaped with a rounded outer surface curling from the side extremity to abrupt intersection with one of said exposed surfaces, said rounded surface extending over the length of the drilling portion and in generally conical form at the material entering end of the drilling portion with an apex of the conical form being on the axis of the fastener and the cutting edge being an element of the surface of such conical form, said mass of metal being positioned relative to the cutting edge of the opposite exposed surface exposing such edge from the side extremity continuously to said longitudinal axis.

Claim 9

In a drill and thread forming screw having a head portion, a shank portion with an outstanding thread thereon, a longitudinal axis, and a formed metal drilling portion centered on the axis at the end of the shank having side extremity surfaces and drill-like end surfaces, the improvement wherein said drilling portion comprises: metal cutting means having at least two cutting edges each extending uninterruptedly from a side extremity surface of the drilling portion to the longitudinal axis, said cutting edges being the extremities of exposed surfaces and meeting each other at said axis providing continuous cutting means from one side extremity surface through the axis to an opposite side extremity surface of the drilling portion; formed metal means in trailing position to said edges supporting each of the cutting edges along its entire extent for drilling purposes and including a solid mass of metal behind each cutting edge, each such mass being generally shaped with a rounded outer surface curling from the side extremity to abrupt intersection with one of said exposed surfaces, said rounded surface extending over the length of the drilling portion and in generally conical form at the material entering end of the drilling portion with an apex of the conical form being on the axis of the fastener and the cutting edge being an element of the surface of such conical form, said mass of metal being positioned relative to the cutting edge of the opposite exposed surface exposing such edge from the side extremity continuously to said longitudinal axis.

Claim 10

In a drill and thread forming screw as defined in claim 5 wherein the rounded outer surface of the metal mass behind each cutting edge has an involute shape viewed in section taken normal to the axis of the fastener.

Claim 11

In a drill and thread forming screw as defined in claim 5 wherein the material entering end of the drilling portion is relatively blunt with the included angle between the two cutting edges extending across such end being between 120* and 160*.