Variable wall thickness collar

1. A collar, comprising: a first end and a second end opposite the first end, a longitudinal axis extending from the first end to the second end, and a shank extending from the first end to the second end and including an interior surface and an exterior surface, wherein the interior surface of the shank includes a first interior surface extending from the first end to a first interior inflection point, a second interior surface extending from the first interior inflection point to a second interior inflection point, and a third interior surface extending from the second interior inflection point to the second end, wherein the exterior surface of the shank includes a first exterior surface extending from the first end to a first exterior inflection point, and a curvilinear exterior surface extending from the first exterior inflection point to a second exterior inflection point, and wherein the curvilinear exterior surface and an imaginary line extending from the first exterior inflection point to the second exterior inflection point form a first area that is sized and shaped to receive forward extrusion of the collar as the collar is being installed.

2. The collar of claim 1 , wherein each of the first and third interior surfaces is oriented parallel to the longitudinal axis, and the second interior surface is oriented oblique to the longitudinal axis.

3. The collar of claim 2 , wherein the first interior surface and the first exterior surface form a first zone having a first thickness, and wherein the curvilinear exterior surface and a first area on the interior surface adjacent to the curvilinear exterior surface form a second zone having a second thickness.

4. The collar of claim 3 , wherein the second thickness of the second zone is less than the first thickness of the first zone.

5. The collar of claim 4 , wherein the exterior surface includes a protrusion positioned proximate to the second end.

6. The collar of claim 5 , wherein second thickness of the second zone increases as the collar is being installed.

7. The collar of claim 6 , wherein the exterior surface includes a third exterior surface, and wherein the protrusion extends longitudinally from the second exterior inflection point to the third exterior surface.

8. The collar of claim 7 , wherein the third exterior surface terminates at a flange.

9. The collar of claim 5 , wherein the protrusion is an annular protrusion.

10. The collar of claim 9 , wherein the annular protrusion is ring-shaped.

11. The collar of claim 10 , wherein the annular protrusion is curvilinear in shape.

12. The collar of claim 1 , wherein the first interior surface and the third interior surface are each cylindrical in shape, and the second interior surface is frusto-conical in shape.