Earth-boring tools having pockets for receiving cutting elements therein and methods of forming such pockets and earth-boring tools
Methods of forming cutting element pockets in earth-boring tools include machining at least one recess to define at least one surface of a cutting element pocket using a cutter oriented at an angle to a longitudinal axis of the cutting element pocket. Methods of forming earth-boring tools include forming a bit body and forming at least one cutting element pocket therein using a rotating cutter oriented at an angle relative to a longitudinal axis of the cutting element pocket being formed. Earth-boring tools have a bit body comprising a first surface defining a lateral sidewall of a cutting element pocket, a second surface defining an end wall of the cutting element pocket, and another surface defining a groove located between the first and second surfaces that extends into the body to enable a cutting element to abut against an area of the lateral sidewall and end wall of the pocket.
The present invention relates generally to earth-boring tools and methods of forming earth-boring tools. More particularly, the present invention relates to methods of securing cutting elements to earth-boring tools and to tools formed using such methods.
BACKGROUND OF THE INVENTIONRotary drill bits are commonly used for drilling bore holes or wells in earth formations. One type of rotary drill bit is the fixed-cutter bit (often referred to as a “drag” bit), which typically includes a plurality of cutting elements secured to a face region of a bit body. Generally, the cutting elements of a fixed-cutter type drill bit have either a disk shape or, in some instances, a more elongated, substantially cylindrical shape. A cutting surface comprising a hard, super-abrasive material, such as mutually bound particles of polycrystalline diamond forming a so-called “diamond table,” may be provided on a substantially circular end surface of a substrate of each cutting element. Such cutting elements are often referred to as “polycrystalline diamond compact” (PDC) cutting elements or cutters. Typically, the PDC cutting elements are fabricated separately from the bit body and secured within pockets formed in the outer surface of the bit body. A bonding material such as an adhesive or, more typically, a braze alloy may be used to secured the cutting elements to the bit body.
The bit body of a rotary drill bit typically is secured to a hardened steel shank having an American Petroleum Institute (API) thread connection for attaching the drill bit to a drill string. The drill string includes tubular pipe and equipment segments coupled end to end between the drill bit and other drilling equipment at the surface. Equipment such as a rotary table or top drive may be used for rotating the drill string and the drill bit within the bore hole. Alternatively, the shank of the drill bit may be coupled directly to the drive shaft of a down-hole motor, which then may be used to rotate the drill bit.
Referring to
The drill bit 10 may further include an API threaded connection portion 30 for attaching the drill bit 10 to a drill string (not shown). Furthermore, a longitudinal bore (not shown) extends longitudinally through at least a portion of the bit body 12, and internal fluid passageways (not shown) provide fluid communication between the longitudinal bore and nozzles 32 provided at the face 20 of the bit body 12 and opening onto the channels leading to junk slots 16.
During drilling operations, the drill bit 10 is positioned at the bottom of a well bore hole and rotated while drilling fluid is pumped through the longitudinal bore, the internal fluid passageways, and the nozzles 32 to the face 20 of the bit body 12. As the drill bit 10 is rotated, the PDC cutting elements 18 scrape across and shear away the underlying earth formation. The formation cuttings mix with and are suspended within the drilling fluid and pass through the junk slots 16 and up through an annular space between the wall of the bore hole and the outer surface of the drill string to the surface of the earth formation.
The bit body 12 of a fixed-cutter rotary drill bit 10 may be formed from steel. Such steel bit bodies are typically fabricated by machining a steel blank (using conventional machining processes including, for example, turning, milling, and drilling) to form the blades 14, junk slots 16, pockets 22, buttresses 24, internal longitudinal bore and fluid passageways (not shown), and other features of the drill bit 10.
The cutting elements 18 of an earth-boring rotary drill bit often have a generally cylindrical shape. Therefore, to form a pocket 22 for receiving such a cutting element 18 therein, it may be necessary or desirable to form a recess into the body of a drill bit that having the shape of a flat-ended, right cylinder. Such a recess may be machined into the body of a drill bit by, for example, using a drilling or milling machine to plunge a rotating flat-bottomed endmill cutter into the body of a drill bit along the axis of rotation of the cutter. Such a machining operation may yield a cutting element pocket 22 having a substantially cylindrical surface and a substantially planar end surface for disposing and brazing a generally cylindrical cutting element 18 therein.
In some situations, however, difficulties may arise in machining such generally cylindrical cutting element pockets 22. For instance, there may be physical interference between the machining equipment used, such as a multiple-axis milling machine, and the blades of the drill bit adjacent to the blade on which it is desired to machine a cutting element pocket 22. More specifically, the interference may inhibit a desired machining path of a machining tool that is aligned generally along the axis of rotation thereof because at least one of the machining tool and the collet or chuck that retains the machining tool may contact an adjacent blade. As a result, in order to form the desired cutting element pocket 22 by way of a flat-bottomed machining tool, such as an endmill, the machining tool may be required to remove a portion of, for example, a rotationally leading adjacent blade. As a further complication, drill bits often have a radially central “cone” region on the face thereof. In such a cone region, the profile of the face of the drill bit tapers longitudinally away from the direction of drilling precession as the profile approaches the center of the face of the drill bit. Thus, near the center of the bit, use of a flat-bottomed machining tool to form recesses for generally cylindrical cutting elements may be extremely difficult.
As a result of such tool path interference problems, it maybe necessary to orient one or more cutting element pockets 22 on the face of an earth-boring rotary drill bit at an angle that causes the cutting element 18 secured therein to exhibit a backrake angle that is greater than a desired backrake angle.
Methods for overcoming such tool path interference problems have been presented in the art. For example, U.S. Pat. No. 7,070,011 to Sherwood, Jr., et al. discloses steel body rotary drill bits having primary cutting elements that are disposed in cutter pocket recesses that are partially defined by cutter support elements. The support elements are affixed to the steel body during fabrication of the drill bits. At least a portion of the body of each cutting element is secured to a surface of the steel bit body, and at least another portion of the body of each cutting element matingly engages a surface of one of the support elements.
However, there is a continuing need in the art for methods of forming cutting element pockets on earth-boring rotary drill bits that avoid the tool path interference problems discussed above and that do not require use of additional support elements.
BRIEF SUMMARY OF THE INVENTIONIn some embodiments, the present invention includes methods of forming one or more cutting element pockets in a surface of an earth-boring tool such as, for example, a fixed cutter rotary drill bit, a roller cone rotary drill bit, a core bit, an eccentric bit, a bicenter bit, a reamer, or a mill. The methods include using a rotating cutter to machine at least a portion of a cutting element pocket in such a way as to avoid mechanical tool interference problems and forming the pocket so as to sufficiently support a cutting element therein. For example, methods of the present invention may include machining at least a portion of a cutting element pocket using a rotating cutter oriented at an angle to a longitudinal axis of the cutting element pocket to be formed. In some embodiments, a first recess may be machined in a bit body of an earth-boring tool to define a lateral sidewall surface of a cutting element pocket using a rotating cutter oriented at an angle relative to the longitudinal axis of the cutting element pocket being formed. An additional recess may be machined in the bit body to define at least a portion of an end surface of the cutting element pocket. As cutting elements are often generally cylindrical in shape, the lateral sidewall surface and the end surface of the cutting element pocket may be formed so as to enable a generally cylindrical cutting element to simultaneously abut against each of the lateral sidewall surface and the end surface of the cutting element pocket.
In additional embodiments, the methods may include forming a first surface in a bit body that defines a lateral sidewall surface of a cutting element pocket. At least a portion of the first surface may be caused to have a generally cylindrical shape centered about a longitudinal axis of the cutting element pocket. A substantially planar second surface may be formed that defines a back end surface of the cutting element pocket. Further, at least one additional surface may be formed that defines a groove located between the first surface and the second surface. The at least one additional surface may be caused to extend into the bit body in a generally radially outward direction from the longitudinal axis of the cutting element pocket radially beyond the at least a portion of the first surface.
In additional embodiments, the present invention includes methods of forming an earth-boring tool such as, for example, any of those mentioned above. The methods include forming a bit body and using a rotating cutter to machine at least a portion of a cutting element pocket in the bit body in a manner that avoids mechanical tool interference problems and allows the pocket to be formed so as to sufficiently support a cutting element therein, as previously mentioned and described in further detail below.
In yet additional embodiments, the present invention includes earth-boring tools having a bit body comprising a first surface defining a lateral sidewall surface of a cutting element pocket, a second surface defining an end surface of the cutting element pocket, and at least one additional surface defining a groove located between the first and second surfaces that extends into the bit body in such a way as to enable a cutting element to abut against an area of each of the lateral sidewall surface and the end surface of the cutting element pocket. In some embodiments, the cutting element pockets may be configured to receive a generally cylindrical cutting element therein. For example, in some embodiments, at least a portion of the first surface that defines a lateral sidewall surface of the cutting element pocket may be generally cylindrical in shape and may be centered about a longitudinal axis of the cutting element pocket. In such embodiments, the at least one additional surface may define a groove that extends into the bit body in a generally radially outward direction from the longitudinal axis of the cutting element pocket radially beyond the generally cylindrical portion of the first surface.
While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, various features and advantages of this invention may be more readily ascertained from the following description of the invention when read in conjunction with the accompanying drawings, in which:
The illustrations presented herein are, in some instances, not actual views of any particular cutting element insert, cutting element, or drill bit, but are merely idealized representations which are employed to describe the present invention. Additionally, elements common between figures may retain the same numerical designation.
In some embodiments, the present invention includes methods of forming cutting element pockets that avoid or overcome at least some of the interference problems associated with previously known methods of forming such pockets, as well as the resulting cutting element pockets that are formed using such methods.
In some embodiments, the cutting element that is desired to be secured to the face 54 of the bit body 50 in the cutting element pocket may have a generally cylindrical body comprising a generally cylindrical lateral sidewall surface extending between two substantially planar end surfaces. Such configurations are commonly used for polycrystalline diamond compact (PDC) cutters. As a result, the cutting element pocket to be formed also may have a generally cylindrical shape that is complementary to the cutting element to be secured therein.
As shown in
Referring again to
Referring to
The additional recess or groove 70 may be formed in the bit body 50 using a machining process substantially similar to that previously described with reference to the recess 52 shown in
Referring to
As previously mentioned, the additional recess or groove 70 maybe machined in the bit body 50 using a rotating cutter 56 oriented at a right angle relative to the longitudinal axis 60 of the cutting element pocket 80, as shown in
As previously described, in some embodiments of the present invention, the recess 52 maybe formed prior to the recess or groove 70, and the recess or groove 70 maybe formed in or cause to intersect one or more surfaces of the bit body 50 that are exposed within the recess 52. In additional embodiments, the recess or groove 70 may be formed prior to forming the recess 52, and the recess 52 may be formed in or caused to intersect one or more surface of the bit body 50 that are exposed within the recess or groove 70.
Referring to
As shown in
After forming the recess or groove 70′ and the recess 52′, the first substantially planar surface 66 may define a substantially planar back end surface of the cutting element pocket 80, and the lateral side wall surface 55 may define a lateral side wall surface of the cutting element pocket 80.
Although the cutting element pocket 80 illustrated in
The present invention has utility in relation to earth-boring rotary drill bits having bit bodies substantially comprised of a metal or metal alloy such as steel. Recently, new methods of forming rotary drill bits having bit bodies comprising particle-matrix composite materials have been developed in an effort to improve the performance and durability of earth-boring rotary drill bits. Such methods are disclosed in pending U.S. patent application Ser. No. 11/271,153, filed Nov. 10, 2005 and pending U.S. patent application Ser. No. 11/272,439, also filed Nov. 10, 2005, the disclosure of each of which application is incorporated herein in its entirety by this reference.
In contrast to conventional infiltration methods (in which hard particles (e.g., tungsten carbide) are infiltrated by a molten liquid metal matrix material (e.g., a copper based alloy) within a refractory mold), these new methods generally involve pressing a powder mixture to form a green powder compact, and sintering the green powder compact to form a bit body. The green powder compact may be machined as necessary or desired prior to sintering using conventional machining techniques like those used to form steel bit bodies. Furthermore, additional machining processes may be performed after sintering the green powder compact to a partially sintered brown state, or after sintering the green powder compact to a desired final density. For example, it may be desired to machine cutting element pockets on one or more blades 14 (
After forming one or more cutting element pockets 80 in a bit body 50 of an earth-boring rotary drill bit as previously described, a cutting element 18 may be positioned within each cutting element pocket 80 and secured to the bit body 50. By way of example and not limitation, each cutting element 18 may be secured within a cutting element pocket 80 using a brazing alloy, a soldering alloy, or an adhesive material.
As shown in
Referring to
By way of example and not limitation, the filler material 84 shown in
In additional embodiments, the filler material 84 may comprise a hardfacing material (e.g., a particle-matrix composite material) and may be applied using a welding process (e.g., arc welding processes, gas welding processes, resistance welding processes, etc.) or a flamespray process. By way of example and not limitation, any of the hardfacing materials described in pending U.S. patent application Ser. No. 11/513,677, filed Aug. 30, 2006, the disclosure of which is incorporated herein in its entirety by this reference, may be used as the filler material 84, and may be applied to the bit body 50 as described therein. Furthermore, in some embodiments, the filler material 84 may comprise at least one of a welding alloy, a solder alloy, or a brazing alloy, and hardfacing material may be applied over the exposed surfaces thereof to minimize or prevent wear during drilling operations. Such layered combinations of materials may be selected to form a composite or graded structure between the cutting element 18 and the surrounding bit body 50 that is selected to tailor at least one of the strength, toughness, wear performance, and erosion performance of the region immediately surrounding the cutting element 18 for the particular design of the drilling tool, location of the cutting element 18 on the drilling tool, or the application in which the drilling tool is to be used.
In yet other embodiments, at least a portion of the filler material 84 may be or comprise a preformed solid structure that is constructed and formed to have a shape corresponding to that of at least a portion of a recess or void within the cutting element pocket 80 around the cutting element 18. As a non-limiting example, the filler material 84 shown in
Such a preformed solid structure maybe separately fabricated, positioned at a location within the cutting element pocket 80 selected to fill a space or void, and secured to one or more surrounding surfaces of the bit body 50. The preformed solid structure maybe secured to one or more surrounding surfaces of the bit body 50 using, for example, an adhesive, a brazing process, a flamespray process, or a welding process. In some embodiments, a preformed solid structure may be positioned within the cutting element pocket 80 and secured to the bit body 50 after securing a cutting element 18 in the cutting element pocket 80. In additional embodiments, such a preformed solid structure may be positioned within the cutting element pocket 80 and secured to the bit body 50 prior to securing a cutting element 18 in the cutting element pocket 80. In yet other embodiments, one or more such preformed solid structures maybe secured to a cutting element 18 prior to securing the cutting element 18 within the cutting element pocket 80.
In some embodiments, such a preformed solid structure may comprise a relatively abrasive and wear-resistant material such as a particle-matrix composite material comprising a plurality of hard particles (e.g., tungsten carbide) dispersed throughout a metal or metal alloy matrix material (e.g., a nickel or cobalt based metal alloy), so as to further prevent wear of the material surrounding the cutting element 18 during drilling operations.
While the present invention has been described herein in relation to embodiments of earth-boring rotary drill bits that include fixed cutters, other types of earth-boring tools such as, for example, core bits, eccentric bits, bicenter bits, reamers, mills, roller cone bits, and other such structures known in the art may embody teachings of the present invention and may be formed by methods that embody teachings of the present invention, and, as used herein, the term “bit body” encompasses bodies of earth-boring rotary drill bits, as well as bodies of other earth-boring tools including, but not limited to, core bits, eccentric bits, bicenter bits, reamers, mills, roller cone bits, as well as other drilling and downhole tools.
By using embodiments of cutting element pockets 80 of the present invention, cutters (primary cutters and backup cutters) may be secured to the face of a bit body at practically any location thereon, and the cutting element pockets 80 may be configured to provide any selected backrake angle to a cutting element secured therein, without encountering mechanical tool interference problems. As a result, earth-boring drilling tools, such as the earth-boring rotary drill bit 90 shown in
Furthermore, while the present invention has been described herein with respect to certain preferred embodiments, those of ordinary skill in the art will recognize and appreciate that it is not so limited. Rather, many additions, deletions and modifications to the preferred embodiments may be made without departing from the scope of the invention as hereinafter claimed. In addition, features from one embodiment may be combined with features of another embodiment while still being encompassed within the scope of the invention as contemplated by the inventors. Further, the invention has utility with different and various bit profiles as well as cutter types and configurations.
Claims
1. A method of forming a cutting element pocket in an earth-boring tool, the method comprising:
- machining a first recess in an earth-boring tool and defining a lateral sidewall surface of a cutting element pocket using a rotating cutter oriented at an angle relative to a longitudinal axis of the cutting element pocket;
- machining a second recess in the earth-boring tool and defining at least a portion of an end surface of the cutting element pocket; and
- forming the lateral sidewall surface and the end surface of the cutting element pocket to enable a generally cylindrical cutting element to simultaneously abut against an area of each of the lateral sidewall surface and the end surface of the cutting element pocket.
2. The method of claim 1, wherein using a rotating cutter comprises using an endmill cutter.
3. The method of claim 2, wherein using an endmill cutter comprises using a ballnose endmill cutter.
4. The method of claim 1, wherein machining a second recess further comprises machining the second recess after machining the first recess.
5. The method of claim 1, wherein machining a second recess further comprises machining the second recess prior to machining the first recess.
6. The method of claim 1, wherein machining a second recess further comprises using the same rotating cutter used to machine the first recess to machine the second recess.
7. The method of claim 6, wherein using the same rotating cutter used to machine the first recess to machine the second recess further comprises orienting the rotating cutter at an angle relative to the longitudinal axis of the cutting element pocket while machining the second recess.
8. The method of claim 1, wherein machining a second recess in the drill bit comprises machining a groove in a surface of the drill bit exposed within the first recess.
9. The method of claim 8, wherein machining a groove comprises machining a groove, at least a portion of the groove having a generally annular shape.
10. The method of claim 1, wherein machining a second recess in the drill bit comprises machining a generally planar recess in the drill bit oriented substantially transverse to the longitudinal axis of the cutting element pocket.
11. The method of claim 10, wherein machining the first recess further comprises causing the first recess to intersect the generally planar recess.
12. The method of claim 1, wherein forming the lateral sidewall surface and the end surface of the cutting element pocket to enable a generally cylindrical cutting element to simultaneously abut against each of the lateral sidewall surface and the end surface of the cutting element pocket comprises causing at least a portion of the second recess to extend in a generally radially outward direction from the longitudinal axis of the cutting element pocket beyond at least a portion of the lateral sidewall surface of the cutting element pocket.
13. A method of forming an earth-boring tool, the method comprising: forming a bit body; and
- forming at least one cutting element pocket in the bit body, comprising: machining a first recess in a surface of the bit body and defining a lateral sidewall surface of a cutting element pocket using a rotating cutter oriented at an angle relative to a longitudinal axis of the cutting element pocket; machining a second recess in the bit body and defining at least a portion of an end surface of the cutting element pocket; and forming the lateral sidewall surface and the end surface of the cutting element pocket to enable a generally cylindrical cutting element to simultaneously abut against an area of each of the lateral sidewall surface and the end surface of the cutting element pocket.
14. The method of claim 13, wherein forming a bit body comprises:
- providing a powder mixture; and
- pressing the powder mixture to form a green bit body.
15. The method of claim 14, wherein at least one of machining a first recess and machining a second recess comprises machining the green bit body.
16. The method of claim 14, wherein forming a bit body further comprises partially sintering the green bit body to form a brown bit body.
17. The method of claim 16, wherein at least one of machining a first recess and machining a second recess comprises machining the brown bit body.
18. The method of claim 17, wherein forming a bit body further comprising sintering the brown bit body to a desired final density.
19. The method of claim 14, wherein forming a bit body further comprises sintering the green bit body to a desired final density.
20. The method of claim 19, wherein at least one of machining a first recess and machining a second recess comprises machining the bit body after sintering the green bit body to a desired final density.
21. The method of claim 14, wherein forming a bit body comprises forming a bit body comprising a particle-matrix composite material.
22. The method of claim 13, wherein forming a bit body comprises forming a bit body predominantly comprised of a metal or metal alloy.
23. The method of claim 22, wherein forming a bit body comprises forming a steel bit body.
24. The method of claim 13, wherein using a rotating cutter comprises using an endmill cutter.
25. The method of claim 24, wherein using an endmill cutter comprises using a ballnose endmill cutter.
26. The method of claim 13, wherein machining a second recess further comprises machining the second recess after machining the first recess.
27. The method of claim 13, wherein machining a second recess further comprises machining the second recess prior to machining the first recess.
28. The method of claim 13, wherein machining a second recess further comprises using the same rotating cutter used to machine the first recess to machine the second recess.
29. The method of claim 28, wherein using the same rotating cutter used to machine the first recess to machine the second recess further comprises orienting the rotating cutter at an angle relative to the longitudinal axis of the cutting element pocket while machining the second recess.
30. The method of claim 13, wherein machining a second recess in the bit body comprises machining a groove in a surface of the bit body exposed within the first recess.
31. The method of claim 30, wherein machining a groove comprises machining a groove, at least a portion of the groove having a generally annular shape.
32. The method of claim 13, wherein machining a second recess in the bit body comprises machining a generally planar recess in the bit body oriented substantially transverse to the longitudinal axis of the cutting element pocket.
33. The method of claim 32, wherein machining the first recess further comprises causing the first recess to intersect the generally planar recess.
34. The method of claim 13, further comprising:
- securing a cutting element within the at least one cutting element pocket; and
- filling at least a portion of a void within at least one of the first recess and the second recess around the cutting element with a filler material.
35. The method of claim 34, wherein filling at least a portion of a void within at least one of the first recess and the second recess around the cutting element with a filler material comprises filling the at least a portion of the void with at least one of a brazing alloy, a soldering alloy, a welding alloy, and a hardfacing material.
36. The method of claim 34, wherein filling at least a portion of a void within at least one of the first recess and the second recess around the cutting element with a filler material comprises filling the at least a portion of the void with a preformed solid structure.
37. The method of claim 36, wherein filling the at least a portion of the void with a preformed solid structure comprises at least one of brazing, welding, and flamespraying the preformed solid structure to the bit body.
38. The method of claim 36, wherein filling the at least a portion of the void with a preformed solid structure further comprises forming the preformed solid structure to comprise a particle-matrix composite material.
39. An earth-boring tool having a bit body comprising:
- a first surface defining a lateral sidewall surface of a cutting element pocket, at least a portion of the first surface having a generally cylindrical shape centered about a longitudinal axis of the cutting element pocket;
- a substantially planar second surface defining a back end surface of the cutting element pocket; and
- at least one additional surface defining a groove located between the first surface and the second surface and extending into the bit body in a generally radially outward direction from the longitudinal axis of the cutting element pocket beyond the at least a portion of the first surface.
40. The earth-boring tool of claim 39, wherein the bit body is predominantly comprised of steel.
41. The earth-boring tool of claim 39, wherein the bit body is predominantly comprised of a particle-matrix composite material.
42. The earth-boring tool of claim 39, further comprising a cutting element secured within the at least one cutting element pocket.
43. The earth-boring tool of claim 42, further comprising a filler material disposed within at least a portion of the at least one cutting element pocket around the cutting element.
44. The earth-boring tool of claim 43, wherein the filler material comprises at least one of a brazing alloy, a soldering alloy, a welding alloy, and a hardfacing material.
45. The earth-boring tool of claim 43, wherein the filler material comprises a preformed solid structure.
46. The earth-boring tool of claim 45, wherein the preformed solid structure is at least one of brazed, welded, and flamesprayed to the bit body.
47. The earth-boring tool of claim 45, wherein the preformed solid structure comprises a particle-matrix composite material.
48. A method of forming an earth-boring tool, the method comprising:
- forming a bit body; and
- forming at least one cutting element pocket in the bit body, comprising: forming a first surface in the bit body defining a lateral sidewall surface of the at least one cutting element pocket and causing at least a portion of the first surface to have a generally cylindrical shape centered about a longitudinal axis of the cutting element pocket; forming a substantially planar second surface defining a back end surface of the cutting element pocket; and forming at least one additional surface defining a groove located between the first surface and the second surface and causing the at least one additional surface to extend into the bit body in a generally radially outward direction from the longitudinal axis of the cutting element pocket beyond the at least a portion of the first surface.
49. The method of claim 48, wherein at least one of forming a first surface, forming a substantially planar second surface, and forming at least one additional surface comprises machining a recess in the bit body using a rotating cutter oriented at an angle relative to the longitudinal axis of the at least one cutting element pocket.
50. The method of claim 49, wherein forming a first surface comprises machining a recess in the bit body using the rotating cutter oriented at an angle relative to the longitudinal axis of the at least one cutting element pocket.
51. The method of claim 49, wherein using a rotating cutter comprises using an endmill cutter.
52. The method of claim 51, wherein using an endmill cutter comprises using a ballnose endmill cutter.
53. The method of claim 48, wherein forming a substantially planar second surface further comprises forming the substantially planar second surface after forming the first surface in the bit body.
Type: Application
Filed: Mar 13, 2007
Publication Date: Sep 18, 2008
Inventors: James L. Duggan (Friendswood, TX), John H. Stevens (Spring, TX), Redd H. Smith (The Woodlands, TX)
Application Number: 11/717,905
International Classification: E21B 10/36 (20060101);