Thread forming tool with annular ridge

1. A thread forming tool comprising an elongated body defining a center longitudinal axis, said body having adjacent a first end, a connector portion and adjacent a second end a thread forming portion, said thread forming portion comprising at least one non-helical annular ridge extending substantially about a circumference of said body, wherein said body has a non-circular shape in a cross-sectional plane oriented perpendicular to said body at an axial center of said at least one annular ridge.

2. A thread forming tool according to claim 1 , wherein said non-circular shape includes at least three lobes.

3. A thread forming tool according to claim 2 wherein said at least one annular ridge is oriented perpendicular to the axis.

4. A thread forming tool according to claim 1 wherein said at least one annular ridge is oriented perpendicular to the axis.

5. A thread forming tool according to claim 1 wherein said body includes a plurality of flanks, a flute formed in an outer surface of at least one of said flanks, the flute extending generally along the axis for conducting cooling fluid and intersecting said at least one ridge to render said at least one ridge discontinuous in the circumferential direction.

6. A thread forming tool according to claim 1 wherein said at least one annular ridge comprises a plurality of annular ridges spaced axially apart by annular grooves.

7. A thread forming tool according to claim 1 wherein said body comprises solid carbide.

8. A thread forming tool comprising an elongated body defining a center longitudinal axis, said body having adjacent a first end thereof a connector portion and adjacent a second end thereof a thread forming portion, the thread forming portion comprising at least one non-helical annular ridge extending substantially about a circumference of said body and oriented perpendicular to said axis, wherein said body has a non-circular shape in a cross-sectional plane oriented perpendicular to said body at an axial center of said at least one annular ridge, said non-circular shape including at least three lobes.

9. A method of forming a thread in a workpiece, said method comprising:

A) introducing into an opening of the workpiece a thread forming tool comprising at least one non-helical annular ridge extending substantially about a circumference of said body, wherein said body has a non-circular shape in a cross-sectional plane oriented perpendicular to said body at an axial center of said at least one annular ridge, wherein the opening has a diameter larger than a maximum diameter of said tool;

B) rotating said tool about said axis; and

C) during step B, moving said tool circularly around a circumference of said opening and simultaneously axially into said opening.