AU2020402359A1

AU2020402359A1 - Drill bit

Info

Publication number: AU2020402359A1
Application number: AU2020402359A
Authority: AU
Inventors: Darren Thomson
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-12-10
Filing date: 2020-11-25
Publication date: 2023-10-05
Also published as: CA3161346A1; AU2020402359A9; WO2021113900A1

Abstract

A core drill bit comprising an annular cutting member including (i) at least two cutting elements (34) including a leading face (36) facing the direction of rotation and trailing face (38) facing away from the direction of rotation; (ii) an inner surface (28); (iii) an outer surface (32); (iv) at least one channel (24) extending radially between the at least two cutting elements from an entry point (26) at the inner surface to an exit point (30) at the outer surface; wherein said channel includes a base (40), a leading wall and a trailing wall and wherein the leading wall includes a recess (50) that extends towards the direction of rotation (14). Lift generating elements (100), or foils, located on the outer surface of the shank for enhancing fluid flow away from the annular cutting member.

Description

Drill bit

Field of the Invention

The present invention relates to a drill bit and more particularly to a core drill bit. The present invention also relates to a drilling assembly including the drill bit and to drilling methods using the drill bit and/or drilling assembly.

Background of the Invention

Despite developments in drilling technology over the last thirty years, the rate of penetration (ROP) achieved in hard rock drilling has only improved marginally. The improved ROP can be largely attributed to the improvements in drilling rigs, with the most significant change being drill rigs capable of generated higher rotation speeds which equates to more cuts per minute and hence increased ROP. For example, in the early 1990’s the fastest rotation speed for a diamond drill was around 600rpm and currently they range from 1100 to 2500rpm.

Another key factor that impacts ROP is drill bit wear. Drill bit wear is a natural consequence of the drilling process - drill bits are designed to be consumed during the drilling process. However, optimising drill bit wear can have a marked impact on ROP. One of the key causes of undue drill bit wear is inefficient removal of drill cuttings from the drilling interface - the space between the leading end of the drill bit and the material being drilled.

The present invention seeks to provide improved drill bits or at least provide a useful alternative to currently available drill bits.

Summary of the Invention

According to a first aspect, the present invention provides a drill bit having an axis, the drill bit comprising:

(a) a shank including a trailing end for engaging a drill string for rotating the drill bit around the axis in a direction of rotation; (b) an annular cutting member located on the leading end of the shank and including:

(i) a cutting face for engaging a material to be drilled and including at least two cutting elements, each of said cutting elements including a leading face facing the direction of rotation and a trailing face facing away from the direction of rotation;

(ii) an inner surface;

(iii)an outer surface;

(iv)at least one channel extending radially between the at least two cutting elements from an entry point at the inner surface to an exit point at the outer surface; wherein said channel includes a base, a leading wall and a trailing wall and wherein the leading wall includes a recess that extends towards the direction of rotation;

(c) an aperture centred on the axis and extending through the shank and the annular cutting member.

According to another aspect, the present invention provides a drill bit having an axis, the drill bit comprising:

(a) a shank including a trailing end for engaging a drill string for rotating the drill bit around the axis in a direction of rotation and at least one lift generating element located on the outer surface of the shank for enhancing fluid flow away from the annular cutting member during use;

(b) an annular cutting member located on the leading end of the shank and including:

(i) a cutting face for engaging a material to be drilled and including at least two cutting elements, each of said cutting elements including a leading face facing the direction of rotation and a trailing face facing away from the direction of rotation; (ii) an inner surface;

(iii)an outer surface;

(iv)at least one channel extending radially between the at least two cutting elements from an entry point at the inner surface to an exit point at the outer surface; wherein said channel includes a base, a leading wall and a trailing wall;

According to another aspect of the present invention there is provided a drill assembly comprising a drill bit as described herein.

Brief Description of the Drawings

Figure 1A is a perspective view, from the leading end, of a drill bit according to one embodiment of the first aspect of the present invention;

Figure 1B is a perspective view, from the trailing end, of the drill bit in Figure 1A;

Figure 1C is an end view, from the leading end, of the drill bit of Figure 1A;

Figure 1D is a side view of the drill bit of Figure 1A, shown with the leading end facing down;

Figure 1E is another version of Figure 1C to show how the angle of the channel is determined; and

Figure 1F is another version of Figure 1D showing how the angle of the path between adjacent lift generating element is determined.

Detailed Description of the Invention

According to a first aspect, the present invention provides a drill bit having an axis, the drill bit comprising: (a) a shank including a trailing end for engaging a drill string for rotating the drill bit around the axis in a direction of rotation;

(ii) an inner surface;

(iii)an outer surface;

Applicant has found that the combination of features of the present invention, such as the recess in the leading wall of the channel, enhances the removal of fragments of drilled material created during drilling. Whilst the present invention is not limited to any mechanism of action, applicant understands that the drill bit of the invention operates to reduce pressure in the channel and more particularly at the entry point of the channel and thus improves the removal of the fragments away from the drilling interface. Applicant also understands, although again is not bound by this, that the combination of features of the present invention avoids or reduces the formation of certain flows, such as vortexes, that also result in sub-optimal removal of the fragments.

Preferably, the recess is located at or near the entry point of the channel. Preferably, the recess has an arcuate or curve shaped cross section.

When the recess has an arcuate shaped cross section, it may be circular arcuate shaped cross section or elliptical arcuate shaped.

The recess may also have an angular shaped cross section. When the recess has an angular shaped cross section, it preferably defines an obtuse angle, more preferably an angle of about 120°-175° or 140°-170°.

Preferably, the recess spans the entire height of the channel.

Preferably, the recess is formed in the trailing face of the cutting element.

Preferably, the channel comprises the space defined between two adjacent cutting elements. In this form of the invention, the leading wall of the channel may comprise the trailing face of a first cutting element and the trailing wall of the channel may comprise the leading face of a second cutting element adjacent to the first cutting element.

Preferably, the channel comprises a main axis extending between the entry point and the exit point that defines an angle offset to a radial axis of the annular cutting member. Preferably, said angle is an acute angle such as at least 10°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80° or 85°.

Preferably, the channel comprises a main axis, defined by the main axis of the trailing wall of the adjacent cutting element extending between the entry point and the exit point that defines an angle offset to a radial axis of the annular cutting member. Preferably, said angle is an acute angle such as at least 10°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30°, 35°, 36°, 37°, 38°, 39°, 40°, 41°, 42°, 43°, 44°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80° or 85°.

Applicant has found that the angle at which the fluid is deflected by the channel is important to the performance of the drill bit. Preferably, the end of the leading wall at the entry point defines the recess. Preferably, the leading wall of the channel comprises at least two profiles.

Preferably, the leading wall of the channel comprises a first profile, adjacent to the entry, and a second profile that extends from the first profile towards the exit.

Preferably, the leading wall of the channel comprise a curved profile.

Preferably, the first profile of the leading wall comprises the recess.

Preferably, the second profile of the leading wall is substantially flat or straight.

Preferably, the second profile of the leading wall is curved.

Preferably, the leading wall comprises a third profile extending from the second profile to the exit. Preferably, the third profile of the leading wall is curved or arcuate.

Preferably, the end of the leading wall at the exit point is curved or arcuate.

Preferably, the end of the trailing wall at the entry point is curved or arcuate.

Preferably, the trailing wall of the channel comprises at least two profiles.

Preferably, the trailing wall of the channel comprises a first profile, adjacent to the entry, and a second profile that extends from the first profile towards the exit.

Preferably, the first profile of the trailing wall is curved or arcuate.

Preferably, the second profile of the trailing wall is substantially flat or straight.

Preferably, the annular cutting member comprises at least one insert of a relatively hard material.

Preferably, the relatively hard material is tungsten.

Preferably, the at least one insert is located on the outer surface of the annular cutting member.

Preferably, the at least one insert is located on the at least one cutting element, such as on an outer face of the at least one cutting element. Preferably, the cutting elements comprise a leading end that comprises a raised profile.

Preferably, the raised profile has a main axis in the direction of rotation.

Preferably, raised profile includes a plurality of ridges.

Preferably, the ridges have a flat upper surface.

Preferably, the annular cutting member is formed of a first matrix material.

Preferably, the first matrix material comprises a metal that is relatively soft compared to diamond or tungsten.

Preferably, the annular cutting member further comprises a second material that is harder than the first matrix material

Preferably, the first matrix material is impregnated with the second material.

Preferably the second material is diamond, carbonado diamond or polycrystalline diamond (PCD).

Preferably, the shank comprises a threaded portion at its trailing end for fitting the drill bit to a drill string.

Preferably, the drill bit further comprises at least one lift generating element located on the outer surface of the shank for enhancing fluid flow away from the annular cutting member during use.

Preferably, the lift generating element projects from or is raised, relative to the outer surface of the shank.

Preferably, the lift generating element comprises a foil.

Preferably, the foil comprises a leading portion comprising an arcuate portion facing the direction of rotation. Preferably, the foil is located on the shank such that its main longitudinal axis and hence its leading portion is oriented at an angle offset to the main vertical or longitudinal axis of the drill bit. Preferably said angle is about 65-75°. Preferably, the foil comprises a trailing portion extending away from the leading portion.

Preferably, the trailing portion of the foil extends away from the annular cutting member.

Preferably, the trailing portion of the foil tapers away from the leading portion.

Preferably, the trailing portion of the foil comprises an upper edge facing away from the annular cutting member and a lower edge facing towards the annular cutting member.

Preferably, the upper edge of the trailing portion of the foil is straight or substantially straight.

Preferably, the lower edge of the trailing portion of the foil is curved or arcuate. When the lower edge is curved or arcuate it is preferably only slightly curved.

Preferably, the lift generating element comprises at least one insert of a relatively hard material.

When the lift generating element is a foil, the at least one insert may be located on the leading portion of the foil and or the upper edge of the trailing portion of the foil.

Preferably, the drill bit comprises a plurality of lift generating elements arranged around the outer surface of the shank to define a path therebetween for the fragments of drilled material. In this regard, during use of the drill bit, the fragments of drilled material can be transferred away from the annular cutting member via an annulus between the drill bit and the inner surface of a drilled hole.

Preferably, the plurality of lift generating elements are spaced equidistantly from each other.

Preferably, the plurality of lift generating elements comprises, 3, 4 or 5 lift generating elements. Preferably, the trailing portion of a first lift generating element overlaps with a leading portion of a second lift generating element, adjacent thereto.

Preferably, the path is at least 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17 mm wide at its widest point.

Preferably, the path comprises a main axis with an angle of about 10°, 15°, 20°, 25°, 26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, 35° 36°, 37°, 38°, 39°, 40°, 41°, 42°, 43°, 44°, 45°, 50°, 55°, 60°, 65°, 70°, 75° or 80° to the vertical.

According to another aspect the present invention also provides a drill bit having an axis, the drill bit comprising:

(ii) an inner surface;

(iii)an outer surface;

(c) an aperture centred on the axis and extending through the shank and the annular cutting member. In this aspect of the invention the lift generating element may comprise one or more of the preferred features of the lift generating element as described with reference to the first aspect of the invention.

The lift generating element provided on the shank of the drill bit described herein may be included in other parts of a drill assembly such as a drill string. Inclusion of the lift generating element along the drill string will improve the fluid flow along the outside of the drill string. Thus, according to another aspect of the present invention there is provided a drill assembly comprising:

(a) a drill bit as described herein; and

(b) at least one other drilling component including a lift generating element, as described herein, located on the outer surface thereof for enhancing fluid flow therealong during use.

Preferably, the at least one other drilling component includes a plurality of lift generating elements.

Preferably, the plurality of lift generating elements are located equidistantly around the at least one other drilling component such as around the outer circumference or outer surface thereof.

Preferably the drilling component comprises at least two sets of the plurality of lift generating elements, wherein each set is located at different locations along the length of the drilling component or drill string. Preferably, the sets are spaced equidistantly from each other along the length of the drilling component or drill string.

Preferably, the at least one other drilling component is a reamer, a drill pipe or a drilling conduit.

The present invention also provides a drill assembly including a drill bit as described herein.

Advantages

Whilst not limited to the following applicant believes the present invention has a number of advantages including one or more of the following: (i) more efficient transfer of drill cuttings away from the drill bit;

(ii) more efficient transfer of drill cuttings by increased velocity of fluid in the annulus;

(iii) higher drill bit rotation speeds;

(iv) improved ROP;

(v) attenuating or removing the formation of undesirable fluid flows in or around the drill bit such as vortexes;

(vi) attenuating or removing the undesirable grinding/re-grinding of drill cuttings at the drilling interface and/or in the annulus by the reamer and/or other parts of the drill string; and

(vii) enables the use of lower viscosity drilling fluids and hence lower operating pressures.

General

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. The invention includes all such variation and modifications. The invention also includes all of the steps and features referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features.

Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference, which means that it should be read and considered by the reader as part of this text. That the document, reference, patent application or patent cited in this text is not repeated in this text is merely for reasons of conciseness. None of the cited material or the information contained in that material should, however be understood to be common general knowledge.

The present invention is not to be limited in scope by any of the specific embodiments described herein. These embodiments are intended for the purpose of exemplification only. Functionally equivalent products and methods are clearly within the scope of the invention as described herein.

The invention described herein may include one or more range of values (e.g. size etc). A range of values will be understood to include all values within the range, including the values defining the range, and values adjacent to the range which lead to the same or substantially the same outcome as the values immediately adjacent to that value which defines the boundary to the range.

Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

For the purposes of the present invention the terms “leading” and “trailing” relate to positions relative to movement. Preferably, when used in relation to features of the annular cutting member, the terms refer to positions relative to a rotational direction of movement. For example, the phrase “leading face” refers to a face facing in the direction of rotational movement and the phrase “trailing face” refers to a face facing away from the direction of rotational movement. Preferably, the phrase “trailing end” when used in relation to the shank refers to the end of the shank that is distal to the drilling direction (not the rotational direction) of the drill bit, whereas a “leading end” refers to an end that is proximal to the drilling direction of movement.

Other definitions for selected terms used herein may be found within the detailed description of the invention and apply throughout. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the invention belongs.

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. In the various Figures the same reference numerals have been used to identify similar elements. Detailed Description of the Preferred Embodiments

An embodiment of the first aspect of the present invention is a drill bit in the form of a core drill bit, generally indicated by the numeral 10, in Figures 1A-1F.

The core drill bit 10 has an aperture in the form of a hollow 11 in its generally cylindrical body. The hollow 11 is centred on an axis in the form of central axis 12 around which, in use, the core drill bit 10 is rotated by a drill string (not shown) in a direction of rotation 14. During drilling, the hollow 11 receives a sample from the material being drilled.

The core drill bit includes a shank 16 with a trailing end 18 that includes an attachment means in the form of a threaded portion 20 to enable the core drill bit 10 to be conveniently attached and detached from the drill string. In this regard, the core drill bit 10 could be attached to a reaming tool, a drill pipe or any other component of the drill string.

On the leading end of the shank 16 is an annular cutting member in the form of a cutting head 22 that includes a cutting face including nine channels 24 spaced equally around the cutting head 22. The channels 24 are of uniform shape and size and extend radially from an entry point 26 at the inner surface 28 of the cutting head 22 to an exit point 30 at the outer surface 32 of the cutting head 22. It will be appreciated that the cutting head 22 could include other numbers of channels 24 depending on requirements such as 2, 3, 4, 5, 6, 7, 8 or 10 or more.

The nine channels 24 in the cutting head 22 form nine cutting elements in the form of cutting parts 34. Each cutting part 34 is of uniform shape and size and spaced equally around the cutting head 22 and has a body with a leading face 36 facing the direction of rotation a trailing face 38 facing away from the direction of rotation 14 and a leading face comprising a raised profile in the form of a series of ridges 39 that have a flat upper surface.

Each cutting part 34 also includes inserts of relatively hard material in the form of four tungsten inserts 41 located at the base of the cutting part 34 on the outer surface 32 thereof. As with the number of channels 24, It will be appreciated that the cutting head 22 could include other numbers of cutting parts 34 depending on requirements such as 2, 3, 4, 5, 6, 7, 8 or 10 or more.

Each channel 24 comprises a main axis 80 extending between the middle of the entry point 26 and the middle of the exit point 30 that defines an angle 82 of about 25-30° offset to the radial axis 84 of the cutting head 22. The main axis 80 and how angle 82 is determined is best illustrated in Figure 1E.

The angle of the channel 24 can also be defined with reference to a main axis 90, defined by the main axis of the trailing wall of the adjacent cutting element that defines an angle 92 of at least about 35-40° offset to a radial axis 84 of the cutting head 22. The main axis 90 and how angle 92 is determined is best illustrated in Figure 1E.

Each channel 24, includes a base defined by a contoured surface, such as a convex surface 40, a leading wall formed by the trailing face 38 of one cutting part 34 and a trailing wall formed by the leading face 36 of an adjacent cutting part 34. The leading wall 38 comprises three profiles, a first profile 60 adjacent to the entry point 26, that includes a recess in the form of arcuate recess or notch 50 that extends the entire height of the leading wall/trailing face 38, towards the direction of rotation, a second profile 62 that is essentially straight and extends from the first profile towards the exit point 30 and a third profile 64 that is arcuate and extends from the second profile 62 to the exit.

Whilst in the embodiment, the channels 24 are defined by the spaces between adjacent cutting parts 34, the channels 24 could include separate trailing and leading walls discrete from the cutting parts 34.

The cutting head 22 is formed of a matrix material in the form of a relatively soft metal that is impregnated with a harder material in the form of diamond or PCD.

The core drill bit 10 further comprises a plurality of lift generating elements in the form of four foils 100 located on and raised from the outer surface of the shank 16. The four foils 100 are arranged around the outer surface of the shank 16 and spaced equidistantly. The space 110 between each pair of adjacent foils 100 defines a path for fragments of drilled material produced during the drilling process. The foils 100 enhance fluid flow away and hence the transfer of drilled material away from the cutting head 22, during use, with drilled material being transferred away from the cutting head 22 via an annulus between the core drill bit 10 and the inner surface of a drilled hole. Preferably, the path defined by the space 110 comprises a main axis 112 with an angle 113 of about 35° offset to the main vertical or longitudinal axis 116 of the core drill bit 10. The main axis 112 and how angle 113 is determined is best illustrated in Figure 1F.

Each foil 100 includes a leading, arcuate portion 102 facing the direction of rotation and a tapered, trailing portion 104 extending away from the leading arcuate portion 102 and the cutting head 22. Each foil 100 is located on the shank such that its main longitudinal axis 105 and hence its leading arcuate portion is oriented at an angle offset to the main vertical or longitudinal axis of the drill bit 116 at an angle 101 of about 65-75°. The main axis 116 and how angle 101 is determined is best illustrated in Figure 1F. The upper edge 105 of the trailing portion 104 is straight and the lower edge 107 of the trailing portion 104 is arcuate.

Each foil 100 includes at least one insert of a relatively hard material in the form of tungsten inserts 112 located in the leading, arcuate portion 102 and tungsten inserts 114 in the tapered, trailing portion 104 at the edge thereof.

Applicant also understands, although again is not bound by this, that the lift generating elements described herein alone and/or in combination with other features of the present invention improves fluid flow and hence also improves the removal of drilled fragments which in turn can improve ROP.

Claims

1. A drill bit having an axis, the drill bit comprising:

(a) a shank including a trailing end for engaging a drill string for rotating the drill bit around the axis in a direction of rotation;

(ii) an inner surface;

(iii)an outer surface;

2. A drill bit according to claim 1 wherein the recess is located at or near the entry point of the channel.

3. A drill bit according to claim 1 or 2 wherein the recess has an arcuate cross section.

4. A drill bit according to claim 3 wherein the arcuate cross section is circular.

5. A drill bit according to any one of claims 1 to 4 wherein the recess spans the entire height of the leading wall.

6. A drill bit according to any one of the preceding claims wherein the recess is formed in the trailing face of the cutting element.

7. A drill bit according to any one of the preceding claims wherein the channel comprises the space defined between two adjacent cutting elements.

8. A drill bit according to claim 7 wherein the leading wall of the channel comprises the trailing face of a first cutting element and the trailing wall of the channel comprises the leading face of a second cutting element adjacent to the first cutting element.

9. A drill bit according to any one of the preceding claims wherein the channel comprises a main axis extending between the entry point and the exit point that defines an angle offset to a radial axis of the annular cutting member.

10. A drill bit according to any one of the preceding claims wherein the channel comprises a main axis, defined by the main axis of the trailing wall of an adjacent cutting element extending between the entry point and the exit point that defines an angle offset to a radial axis of the annular cutting member.

11. A drill bit according to claim 9 or 10 wherein the angle is an acute angle.

12. A drill bit according to any one of the preceding claims wherein the end of the leading wall at the entry point defines the recess.

13. A drill bit according to any one of the preceding claims wherein the leading wall of the channel comprise a curved profile.

14. A drill bit according to any one of the preceding claims wherein the leading wall of the channel comprises at least two profiles.

15. A drill bit according to claim 14 wherein the leading wall of the channel comprises a first profile, adjacent to the entry, and a second profile that extends from the first profile towards the exit.

16. A drill bit according to claim 15 wherein the first profile of the leading wall comprises the recess.

17. A drill bit according to claim 15 or 16 wherein the second profile of the leading wall is substantially flat or straight.

18. A drill bit according to claim 15 or 16 wherein the second profile of the leading wall is curved.

19. A drill bit according to any one of claims 15 to 18 wherein the leading wall comprises a third profile extending from the second profile to the exit.

20. A drill bit according to claim 19 wherein the third profile of the leading wall is curved.

21. A drill bit according to any one of the preceding claims wherein the end of the leading wall at the exit point is curved.

22. A drill bit according to any one of the preceding claims wherein the end of the trailing wall at the entry point is curved.

23. A drill bit according to any one of the preceding claims wherein the trailing wall of the channel comprises at least two profiles.

24. A drill bit according to claim 23 wherein the trailing wall of the channel comprises a first profile, adjacent to the entry, and a second profile that extends from the first profile towards the exit.

25. A drill bit according to claim 24 wherein the first profile of the trailing wall is curved or arcuate.

26. A drill bit according to claim 24 or 25 wherein the second profile of the trailing wall is substantially flat or straight.

27. A drill bit according to any one of the preceding claims wherein the annular cutting member comprises at least one insert of a relatively hard material.

28. A drill bit according to claim 27 wherein the relatively hard material is tungsten.

29. A drill bit according to claim 27 or 28 wherein the at least one insert is located on the outer surface of the at least one cutting element.

30. A drill bit according to any one of the preceding claims wherein the cutting elements comprise a leading end that comprises a raised profile.

31. A drill bit according to claim 30 wherein the raised profile has a main axis in the direction of rotation.

32. A drill bit according to claim 30 or 31 wherein the raised profile includes a plurality of ridges.

33. A drill bit according to claim 32 wherein the ridges have a flat upper surface.

34. A drill bit according to any one of the preceding claims wherein the annular cutting member is formed of a first matrix material.

35. A drill bit according to claim 34 wherein the first matrix material is a relatively soft metal

36. A drill bit according to any one of claims 34 or 35 wherein the annular cutting member further comprises a second material that is harder than the first matrix material.

37. A drill bit according to claim 36 wherein the first matrix material is impregnated with the second material.

38. A drill bit according to claim 36 or 37 wherein the second material is diamond or PCD.

39. A drill bit according to any one of the preceding claims wherein the shank comprises a threaded portion at its trailing end for fitting the drill bit to a drill string.

40. A drill bit according to any one of the preceding claims further comprising at least one lift generating element located on the outer surface of the shank for enhancing fluid flow away from the annular cutting member during use.

41. A drill bit according to claim 40 wherein the lift generating element projects from or is raised, relative to the outer surface of the shank.

42. A drill bit according to claim 40 or 41 wherein the lift generating element comprises a foil.

43. A drill bit according to claim 42 wherein the foil comprises a leading portion comprising an arcuate portion facing the direction of rotation.

44. A drill bit according to claim 43 wherein the foil comprises a trailing portion extending away from the leading portion.

45. A drill bit according to claim 44 wherein the trailing portion of the foil extends away from the annular cutting member.

46. A drill bit according to claim 44 or 45 wherein the trailing portion of the foil tapers away from the leading portion.

47. A drill bit according to any one of claims 44 to 46 wherein the trailing portion of the foil comprises an upper edge facing away from the annular cutting member and a lower edge facing towards the annular cutting member.

48. A drill bit according to claim 47 wherein the upper edge of the trailing portion of the foil is straight or substantially straight.

49. A drill bit according to claim 47 or 48 wherein the lower edge of the trailing portion of the foil is curved or arcuate.

50. A drill bit according to any one of claims 40 to 49 wherein the lift generating element comprises at least one insert of a relatively hard material.

51. A drill bit according to claim 50 wherein the lift generating element is a foil and the at least one insert is located on the leading portion of the foil and or the upper edge of the trailing portion of the foil.

52. A drill bit according to any one of claims 40 to 51 wherein the drill bit comprises a plurality of lift generating elements arranged around the outer surface of the shank to define a path therebetween for the fragments of drilled material.

53. A drill bit according to claim 52 wherein the plurality of lift generating elements are spaced equidistantly from each other.

54. A drill bit according to claim 52 or 53 wherein the plurality of lift generating elements comprises, 3, 4 or 5 lift generating elements.

55. A drill bit according to any one of claims 52 to 54 wherein the trailing portion of a first lift generating element overlaps with a leading portion of a second lift generating element, adjacent thereto.

56. A drill bit according to any one claims 52 to 55 wherein the path is at least 12 mm wide at its widest point.

57. A drill bit according to any one of claims 52 to 56 wherein the path comprises a main axis with an acute angle.

58. A drill bit having an axis, the drill bit comprising:

(ii) an inner surface;

(iii)an outer surface;

(iv)at least one channel extending radially between the at least two cutting elements from an entry point at the inner surface to an exit point at the outer surface; wherein said channel includes a base, a leading wall and a trailing wall; (c) an aperture centred on the axis and extending through the shank and the annular cutting member.

59. A drill assembly comprising:

(a) a drill bit according to any one of the preceding claims; and

(b) at least one other drilling component including a lift generating element located on the outer surface thereof for enhancing fluid flow therealong during use.

60. A drilling assembly according to claim 59 wherein the at least one other drilling component includes a plurality of lift generating elements.

61. A drilling assembly according to claim 60 wherein the plurality of lift generating elements are located equidistantly around the at least one other drilling component.

62. A drilling assembly according to claim 60 or 61 wherein the drilling component comprises at least two sets of the plurality of lift generating elements, wherein each set is located at different locations along the length of the drilling component.

63. A drilling assembly according to claim 62 wherein the sets are spaced equidistantly from each other along the length of the drilling component.

64. A drilling assembly according to any one of claims 59 to 63 wherein the at least one other drilling component is a reamer, a drill pipe or a drilling conduit.

65. A drilling assembly comprising a drill bit according to any one of claims 1 to 58.