Variable thread knurl fastener

1. A fastener, comprising:

a shank having a point at a first end and a head at a second end defining a total fastener length, the shank including a first section having a first diameter, the first section of the shank including a thread , the thread in the first section adjacent to the first end and including a first region having multiple turns about the shank in said first section and having a first thread angle, and a second region between the first region and the second end having multiple turns of the thread, the thread in the second region with a second, different thread angle smaller than the first thread angle, at least a portion of the thread in the first region having a serrated edge;

a first cylindrical knurl having a first end and a second end, the knurl limited in position to the first region of the first section of the shank and within an area of the first thread angle, the first cylindrical knurl having knurling comprising a plurality of straight ridges, each of the ridges extending along a knurl length between the first end of the knurl and the second end of the knurl and being parallel to the total fastener length of the shank, each of the ridges having a symmetrical cross-section relative to a radial axis extending perpendicular to the shank and having a height no greater than a first knurl diameter minus the diameter in the first section; and

a second section of the shank comprising a thread free region, the second section including a second knurl having a second knurl diameter;

wherein the thread has a diameter which is 1.5-1.75 times the first diameter of the shank, wherein the first knurl diameter and the second knurl diameter each have a maximum diameter of 1.3 times the first diameter of the shank, such that the first and second knurl diameters are less than the diameter of the thread.

2. The fastener of claim 1 wherein the first knurl is longer than the second knurl.

3. The fastener of claim 1 wherein the first section begins at and extends from the point toward the head, and wherein each thread angle is formed by a leading and trailing edge of the thread, each edge being non-normal with respect to a surface of the shank.

4. The fastener of claim 1 wherein the second knurl is provided in second section closer to the first section than the head.

5. A fastener, comprising:

a shank having a tip at a first end and a head at a second end defining a fastener length, the shank including

a first section having a first section length and diameter formed at the first end and having a contiguous helical thread, the contiguous helical thread having multiple turns about the shank and a first thread angle in a first region of the first section, the first region being adjacent the tip and extending toward the second end, and the contiguous helical thread having multiple turns about the shank and a second thread angle smaller than the first thread angle in a second region of the first section having the diameter, the second portion region positioned between the first region and the second end;

the first section including a first cylindrical knurl having straight knurling comprising a plurality of straight ridges, each of the ridges extending along a knurl length between a first end of the first cylindrical knurl and a second end of the first cylindrical knurl, each end of the first cylindrical knurl being positioned within the first region of the first section and thereby limited to a position within the first region, the straight ridges defining a knurl diameter, the knurl length comprising a portion of the length of the shank and parallel to the length of the shank, each of the ridges having a symmetrical cross-section relative to a radial axis extending perpendicular to the shank and having a height no greater than the first knurl diameter minus the first diameter in the first section; and

a second, thread free section having a second section length between the first section and the head, the second section including a second knurl having a second knurl diameter,

wherein the thread has a diameter which is 1.5-1.75 times the first diameter of the first section, wherein the first knurl diameter and the second knurl diameter each have a maximum diameter of 1.3 times the first diameter, such that each knurl diameter is less than the diameter of the thread.

6. The fastener of claim 5 the second knurl comprising a second plurality of separated straight ridges, each of the ridges extending along a second knurl length which is a portion of the length of the shank and parallel to the length of the shank, the second knurl having a length longer than the first knurl.

7. The fastener of claim 6 wherein first knurl has diameter which may be the same as or different than a diameter of the second knurl by a ratio of 0.8-1.2.

8. The fastener of claim 6 wherein the first angle is in a range of about 55-65 degrees and the second angle is in a range of about 30-45 degrees.

9. A fastener, comprising:

a shank having a tip at a first end and a head at a second end, the first end and second end defining a fastener length, the shank having a first diameter between the tip and the second end and including

a first fastener section including a contiguous helical thread formed from and beginning at the tip and extending toward the second end, the contiguous helical thread having multiple turns about the shank having said first diameter, the contiguous helical thread having a first thread angle in a first region of the first region which is adjacent the tip and extending toward the second end, and a second thread angle smaller than the first thread angle in a second region of the contiguous helical thread;

a first cylindrical knurl positioned in the first fastener section of the shank along a knurl length between a first end of the first cylindrical knurl and a second end of the first cylindrical knurl, each end of the first cylindrical knurl being positioned within the first region of the first section, the first cylindrical knurl thereby limited to a position within the first region, the first cylindrical knurl having a first knurl diameter greater than the first diameter of the shank and comprising a first plurality of separated straight ridges, each of the ridges having a symmetrical cross-section relative a radial axis extending perpendicular to the shank and extending along the first knurl length which is a portion of the length of the shank and parallel to the length of the shank, the first cylindrical knurl having a height no greater than the first knurl diameter minus the first diameter in the first region;

a second knurl provided in a second, thread-less fastener section at a distance on the shank apart from the first knurl, the second knurl comprising a second plurality of separated straight ridges, each of the ridges extending along a second knurl length which is a portion of the length of the shank and parallel to the length of the shank, the second knurl having a second knurl diameter; and

wherein the helical thread has a diameter which is 1.5-1.75 times the diameter of the shank, wherein the first knurl diameter and the second knurl diameter have a maximum diameter less than the diameter of the thread.

10. The fastener of claim 9 wherein the second knurl has a length greater than a length of the first knurl.

11. The fastener of claim 10 wherein the first knurl diameter is defined by a top of each of said ridges of said first knurl and is 1.1-1.3 times said diameter of the shank.

12. The fastener of claim 11 wherein the first knurl diameter is related to the second knurl diameter by a ratio of 0.8-1.2.

13. The fastener of claim 12 wherein the first angle is in a range of about 55-65 degrees and the second angle is in a range of about 35-45 degrees.