Claims
- 1. A method of designing a bi-center drill bit comprising the steps of designing a bit body, the bit body having a longitudinal axis, a first end adapted to be detachably secured to a drill string, a pilot section on a second, opposite end of the bit body and an eccentric reamer section intermediate the first and second ends, and having a plurality of cutting elements on the pilot section,
defining a first center of rotation of the pilot section about the longitudinal axis, defining a radius of rotation R1 of the drill bit about the first center of rotation, defining a second center of rotation of the pilot section spaced apart from the first center of rotation by a distance D, defining a radius of rotation R2 of the drill bit about the second center of rotation, and setting the relationship between D, R1 and R2 such that R1 is less than the sum of R2 and D.
- 2. The method of designing the bi-center drill bit of claim 1 wherein the cutting elements of the pilot section are arranged upon a plurality of blades formed on the bit body.
- 3. The method of designing the bi-center drill bit of claim 1 wherein the cutting elements of the pilot section are formed of a superhard material.
- 4. The method of designing the bi-center drill bit of claim 3 wherein the superhard material is a preform element with a facing table of diamond bonded to a less hard substrate material.
- 5. The method of designing the bi-center drill bit of claim 4 wherein the facing table of diamond comprises polycrystalline diamond.
- 6. The method of designing the bi-center drill bit of claim 3 wherein the superhard material is natural diamond.
- 7. The method of designing the bi-center drill bit of claim 1 further comprising providing at least two blades extending from the bit body with at least one non-cutting bearing element mounted on each blade and terminating with the non-cutting bearing element extending to the radius of rotation R2.
- 8. The method of designing the bi-center drill bit of claim 7 wherein a maximum included angle about the second center of rotation between the non-cutting bearing elements on two adjacent blades is less than 180 degrees.
- 9. The method of designing the bi-center drill bit of claim 7 wherein the non-cutting bearing elements are in the form of a flush mounted, hard, wear resistant material.
- 10. The method of designing the bi-center drill bit of claim 9 wherein the non-cutting bearing elements are in the form of a flame spray coating containing the carbides of elements selected from the group consisting of tungsten, titanium, iron, and chromium.
- 11. The method of designing the bi-center drill bit of claim 10 wherein the coating is generally uniformly applied over a portion of the at least two blades.
- 12. The method of designing the bi-center drill bit of claim 7 wherein the non-cutting bearing elements are in the form of a protruding insert made of a hard, wear resistant material.
- 13. The method of designing the bi-center drill bit of claim 12 wherein the hard, wear resistant material is cemented tungsten carbide.
- 14. The method of designing the bi-center drill bit of claim 13 wherein the hard, wear resistant material is a preform element with a facing table of diamond bonded to a less hard substrate material.
- 15. The method of designing the bi-center drill bit of claim 2 wherein at least two of the blades extend from the bit body, the blades terminating with a gauge cutting element extending to radius of rotation R1.
- 16. The method of designing the bi-center drill bit of claim 15 wherein at least one of the blades is located at the intersection of radius of rotation R1 and the radius of rotation R2.
- 17. The method of designing the bi-center drill bit of claim 15 wherein the blade located at the intersection of radius of rotation R1 and the radius of rotation R2 has at least one non-cutting bearing element mounted thereon, the non-cutting bearing element extending to the radius of rotation R2.
- 18. A method of designing a bi-center drill bit comprising a bit body, the bit body having a longitudinal axis, a first end adapted to be detachably secured to a drill string, a pilot section on a second, opposite end of the bit body and an eccentric reamer section intermediate the first and second ends, and a plurality of cutting elements on the pilot section, the method comprising,
defining a first center of rotation of the pilot section about the longitudinal axis, defining a radius of rotation R1 of the drill bit about the first center of rotation, defining a second center of rotation of the pilot section spaced apart from the first center of rotation by a distance D, defining a radius of rotation R2 of the drill bit about the second center of rotation, setting the relationship between D, R1 and R2 such that R1 is less than the sum of R2 and D, and fixing a plurality of gauge cutting cutter elements upon the bit body at radius R1.
- 19. The method of designing a bi-center drill bit of claim 18 further comprising
defining a first region of the pilot section centered about the first center of rotation having a radius of D, defining a second region of the pilot section centered about the second center of rotation having a radius of D, and defining a third region of the pilot section formed by the intersection of the first region and the second region, wherein the third region of the pilot section is devoid of cutting elements.
- 20. A method of designing a bi-center drill bit comprising a bit body with a first end adapted to be detachably secured to a drill string, a pilot section on a second, opposite end of the bit body, a reamer section intermediate the first and second ends, and a plurality of cutting elements on the pilot section, the method comprising
defining a first center of rotation of the pilot section, defining a first cutting face surface on the pilot section generated by the plurality of cutting elements as they are rotated about the first center of rotation of the pilot section, defining a second center of rotation of the pilot section spaced apart from the first center of rotation by a distance D, defining a second cutting face surface on the pilot section generated by the plurality of cutting elements as they are rotated about the second center of rotation of the pilot section, defining a first region of the pilot section centered about the first center of rotation having a radius of D, defining a second region of the pilot section centered about the second center of rotation having a radius of D, and defining a third region of the pilot section formed by the intersection of the first region and the second region, wherein no cutting elements lying within the third region of the pilot section contact both the first cutting face surface and the second cutting face surface.
- 21. The method of designing the bi-center drill bit of claim 20 wherein the cutting elements are arranged upon a plurality of blades formed on the bit body.
- 22. The method of designing the bi-center drill bit of claim 20 wherein the cutting elements are formed of a superhard material.
- 23. The method of designing the bi-center drill bit of claim 22 wherein the superhard material is a preform element with a facing table of diamond bonded to a less hard substrate material.
- 24. The method of designing the bi-center drill bit of claim 23 wherein the table of diamond comprises polycrystalline diamond.
- 25. The method of designing the bi-center drill bit of claim 22 wherein the superhard material is natural diamond.
- 26. The method of designing the bi-center drill bit of claim 20 further comprising defining a radius of rotation R1 of the drill bit about the first center of rotation, and
defining a radius of rotation R2 of the drill bit about the second center of rotation, wherein a plurality of non-cutting bearing elements are mounted upon the bit body at radius R2 and a plurality of gauge cutting cutter elements are mounted upon the bit body at radius R1.
- 27. The method of designing the bi-center drill bit of claim 26 wherein a maximum included angle about the second center of rotation between any two adjacent non-cutting bearing elements is less than 180 degrees.
- 28. The method of designing the bi-center drill bit of claim 26 wherein the non-cutting bearing elements are in the form of a flush mounted, hard, wear resistant material.
- 29. The method of designing the bi-center drill bit of claim 28 wherein the non-cutting bearing elements are in the form of a flame spray coating containing the carbides of elements selected from the group consisting of tungsten, titanium, iron, and chromium.
- 30. The method of designing the bi-center drill bit of claim 29 wherein the coating is generally uniformly applied over a portion of the at least two blades.
- 31. The method of designing the bi-center drill bit of claim 26 wherein the non-cutting bearing elements are in the form of a protruding insert made of a hard, wear resistant material.
- 32. The method of designing the bi-center drill bit of claim 31 wherein the hard, wear resistant material is cemented tungsten carbide.
- 33. The method of designing the bi-center drill bit of claim 32 wherein the hard, wear resistant material is a preform element with a facing table of diamond bonded to a less hard substrate material.
- 34. The method of designing the bi-center drill bit of claim 26 wherein the gauge cutting elements are formed of a superhard material.
- 35. The method of designing the bi-center drill bit of claim 34 wherein the superhard material is a preform element with a facing table of diamond bonded to a less hard substrate material.
- 36. The method of designing the bi-center drill bit of claim 35 wherein the facing table of diamond comprises polycrystalline diamond.
- 37. The method of designing the bi-center drill bit of claim 34 wherein the superhard material is natural diamond.
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This Application is a divisional of U.S. patent application Ser. No. 09/658,857 filed Sep. 11, 2000 which claims priority from U.S. Provisional Application No. 60/162,179 filed October 1999, and from U.S. Provisional Application No. 60/163,420 filed Nov. 3, 1999.
Provisional Applications (2)
|
Number |
Date |
Country |
|
60162179 |
Oct 1999 |
US |
|
60163420 |
Nov 1999 |
US |
Divisions (1)
|
Number |
Date |
Country |
Parent |
09658857 |
Sep 2000 |
US |
Child |
09683746 |
Feb 2002 |
US |