Claims
- 1. A drag-type drill bit comprising:
- a bit body adapted for rotative movement in a pre-determined direction in use and having an operating end face;
- and a plurality of cutting members mounted in said bit body, each of said cutting members having
- a stud portion disposed in a respective recess in said bit body and defining the inner end of said cutting member,
- and a cutting face generally adjacent the outer end of the cutting member facing outwardly through said end face of said bit body and terminating in an outermost cutting edge,
- the centerline of said stud portion being rearwardly inclined from said outer end to said inner end with respect to said direction of movement in use--taken at the midpoint of said cutting edge--at a first angle from 80.degree. to 30.degree. inclusive;
- and said cutting face being oriented such that the tangent to said cutting face at the midpoint of said cutting edge and in the central plane of the cutting member, is disposed at a second angle, from 18.degree. to 75.degree. inclusive, with respect to the centerline of said stud portion.
- 2. The apparatus of claim 1 wherein said cutting face has a back rake angle at said cutting edge of about -20.degree., and wherein said second angle is from 38.degree. to 75.degree. inclusive.
- 3. The apparatus of claim 1 wherein said cutting face has a back rake angle at said cutting edge of about -10.degree., and wherein said second angle is from 28.degree. to 65.degree. inclusive.
- 4. The apparatus of claim 1 wherein said cutting face has a back rake angle at said cutting edge of about 0.degree., and wherein said second angle is from 18.degree. to 55.degree. inclusive.
- 5. The apparatus of claim 1 wherein said first angle is from 65.degree. to 50.degree. inclusive, and wherein said second angle is from 25.degree. to 60.degree. inclusive.
- 6. The apparatus of claim 5 wherein said cutting face has a back rack angle at said cutting edge of about -20.degree., and wherein said second angle is from 45.degree. to 60.degree. inclusive.
- 7. The apparatus of claim 5 wherein said cutting face has a back rack angle at said cutting edge of about -10.degree., and wherein said second angle is from 35.degree. to 50.degree. inclusive.
- 8. The apparatus of claim 5 wherein said cutting face has a back rake angle at said cutting edge of about 0.degree., and wherein said second angle is from 25.degree. to 40.degree. inclusive.
- 9. The apparatus of claim 1 wherein said end face of said bit body includes a plurality of upsets each having a leading edge surface and at least one recess extending through each such leading edge surface, said end face of said bit body further comprising a plurality of flow paths, each of said leading edge surfaces having one of said flow paths extending therealong and inset therefrom;
- and wherein each of said cutting members has its stud portion mounted in a respective one of said recesses, with its cutting face facing generally outwardly along said leading edge surface of said upset.
- 10. The apparatus of claim 9 wherein each of said stud portions has a significant part thereof, opposite said cutting face, embedded in and supported by the material of said bit body in the respective one of said upsets.
- 11. The apparatus of claim 10 wherein the walls of each of said recesses abut the respective stud portion about more than 180.degree. of its periphery measured in a plane transverse to and intersecting said cutting face.
- 12. The apparatus of claim 9 wherein the walls of each of said recesses abut the respective stud portion about more than 180.degree. of its periphery measured in a plane transverse to and intersecting said cutting face.
- 13. The apparatus of claim 9 wherein said upsets are elongate ribs each arranged to have a substantial radial component of direction, with respect to said end face of said bit body, at each point along its length, and wherein said cutting faces are fully exposed along said leading edge surfaces of said ribs.
- 14. The apparatus of claim 13 wherein said bit body has a plurality of circulation ports opening through said end face and communicating with said flow paths, the number of said ports being less than the number of flow paths extending along said leading edge surfaces of said ribs, and at least some of said ports communicating with more than one such flow path.
- 15. The apparatus of claim 14 wherein said bit body has a central longitudinal bore, and wherein said ports are defined by rectilinear bores each intersecting said central bore and each intersecting said end face of said bit body at an angle of about 0.degree. to 40.degree. from the normal to the bit body at the point of such intersection.
- 16. The apparatus of claim 15 wherein each of said ports is located a different radial distance from the centerline of said bit body.
- 17. A drag-type drill bit comprising:
- a bit body adapted for rotative movement in a given direction in use and having an operating end face;
- and a plurality of cutting members mounted in said bit body, each of said cutting members having
- a stud portion disposed in a respective recess in said bit body and defining the inner end of said cutting member,
- and a cutting face generally adjacent the outer end of said cutting member, facing outwardly from said end face of said bit body, and defining an outermost cutting edge;
- the centerline of said stud portion being rearwardly inclined from the outer end to the inner end of said cutting member with respect to said direction of movement in use--taken at the midpoint of said cutting edge--at an angle from 65.degree. to 50.degree. inclusive.
- 18. A cutting member for use in a drag-type drill bit comprising:
- a stud portion defining one end of said cutting member;
- a cutting face generally adjacent the other end of said cutting member and defining an outermost cutting edge;
- said cutting face being oriented such that the tangent to said cutting face at the midpoint of said cutting edge and in the central plane of the cutting member is disposed at an angle from 36.degree. to 60.degree. inclusive with respect to the centerline of said stud portion.
CROSS-REFERENCE TO RELATED APPLICATION
This is a continuation-in-part of U.S. application Ser. No. 443,657, filed Nov. 22, 1982 now U.S. Pat. No. 4,505,342.
US Referenced Citations (7)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
443657 |
Nov 1982 |
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