Earth-boring tools having pockets for receiving cutting elements and methods for forming earth-boring tools including such pockets

Methods of forming cutting element pockets in blades of earth-boring tools include forming a first recess and a second recess intersecting at a location defining the a back of the pocket using a cutter oriented in a manner so as to avoid tool path interference with adjacent blades. A filler material is disposed in the second recess to the location of the back of the pocket. Earth-boring tools including such cutting element pockets.

FIELD OF THE INVENTION

The present invention relates generally to earth-boring tools and methods of forming earth-boring tools. More particularly, embodiments of the present invention relate to methods of securing cutting elements to earth-boring tools and to tools formed using such methods.

BACKGROUND

Rotary 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. Referring toFIG. 1, a conventional fixed-cutter earth-boring rotary drill bit100includes a bit body102that has generally radially projecting and longitudinally extending wings or blades104, which are separated by junk slots106.

A plurality of cutting elements108is positioned on each of the blades104. Generally, the cutting elements108have either a disk shape or, in some instances, a more elongated, substantially cylindrical shape. The cutting elements108commonly comprise a “table” of super-abrasive material, such as mutually bound particles of polycrystalline diamond, formed on a supporting substrate of a hard material, conventionally cemented tungsten carbide. Such cutting elements are often referred to as “polycrystalline diamond compact” (PDC) cutting elements or cutters. The plurality of PDC cutting elements108may be provided within cutting element pockets110formed in rotationally leading surfaces of each of the blades104. The PDC cutting elements108may be supported from behind (taken in the direction of bit rotation) by buttresses112, which may be integrally formed with the bit body102. Conventionally, a bonding material such as an adhesive or, more typically, a braze alloy may be used to secure the cutting elements108to the bit body102.

The bit body102of a rotary drill bit100typically is secured to a hardened steel shank having an American Petroleum Institute (API) thread connection114for attaching the drill bit100to a drill string (not shown). The drill string includes tubular pipe and component 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 to the drive shaft of a down-hole motor, which then may be used to rotate the drill bit, alone or in combination with rotation of the drill string from the surface.

During drilling operations, the drill bit100is positioned at the bottom of a well bore hole and rotated. Drilling fluid is pumped through the inside of the bit body102, and out through the nozzles116. As the drill bit100is rotated, the PDC cutting elements108scrape across and shear away the underlying earth formation material. The formation cuttings mix with the drilling fluid and pass through the junk slots106, 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 body102of a fixed-cutter rotary drill bit100may 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 blades104, junk slots106, pockets110, buttresses112, and other features of the drill bit100.

As previously described, the cutting elements108of an earth-boring rotary drill bit often have a generally cylindrical shape. Therefore, to form a pocket110for receiving such a cutting element108therein, it may be necessary or desirable to form a recess into the body of a drill bit that has 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 end mill 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 pocket110having a substantially cylindrical surface and a substantially planar inner end surface for disposing and brazing a generally cylindrical cutting element108therein.

In some situations, however, difficulties may arise in machining such generally cylindrical cutting element pockets. 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. This is particularly true when cutting element pockets are to be formed in the center, or “cone” region, of the bit face. As illustrated inFIG. 2, attempting to machine a cutting element pocket in blade204at a low angle and in the direction of the arrow may not be possible because of interference with blade206. More specifically, the interference caused by blade206may inhibit the use of a desired machining path for 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 adjacent blade206. As a result, in order to form the desired cutting element pocket by way of a flat-bottomed machining tool, such as an end mill, the machining tool may be required to remove a portion of adjacent blade206.

As a result of such tool path interference problems, it may be necessary to orient one or more cutting element pockets on the face of an earth-boring rotary drill bit at an angle that causes the cutting element secured therein to exhibit a back rake angle that is greater than a desired back rake angle. A lower, or more aggressive, back rake angle than that conventionally obtainable using the foregoing machining technique may be preferred to improve the rate of penetration while drilling.

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 INVENTION

In 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 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 a first recess in a bit body of an earth-boring tool to define a lateral sidewall surface of a cutting element pocket. A second recess may be machined in the bit body to define at least a portion of a shoulder at an intersection with the first recess. Additionally, a filler material may be disposed within the second recess to define at least a portion of an end surface of the cutting element pocket.

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.

In yet additional embodiments, the present invention includes earth-boring tools having a bit body comprising a first recess defining a lateral sidewall surface of a cutting element pocket, a second recess located rotationally behind the first recess along a longitudinal axis of the cutting element pocket, and a shoulder region at an intersection between the first and second recesses providing a position for an inner end surface of the cutting element pocket. Additionally, a filler material may be disposed within the second recess and abutting the shoulder region, the filler material defining at least a portion of an inner end surface of the cutting element pocket.

DETAILED DESCRIPTION

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 drilling tools including the resulting cutting element pockets that are formed using such methods.

In the following description, certain terminology is used to describe certain features of one or more embodiments of the invention. As used herein, the term “cutting diameter” means the largest diameter of a machine tool cutter, such as a drill bit, a router, or a mill, taken perpendicular to a longitudinal axis of the cutter about which the cutter is rotated while the cutter is used to cut a workpiece. As used herein, the term “rotationally leading surface,” when used with respect to a blade of an earth-boring tool, means a surface on a blade that leads the blade through rotation in a cutting direction of a body of a bit or other subterranean drilling tool about an axis. As used herein, the term “rotationally trailing surface,” when used with respect to a blade of an earth-boring tool, means a surface on a blade that trails the blade through rotation as the blade rotates about the bit or other tool body axis in a cutting direction.

FIG. 3is a plan view of the face of an earth-boring rotary drill bit300illustrating a recess302being formed in a bit body304according to one embodiment. Cutting elements108would not normally be present at this stage of manufacture of bit body304, but are depicted inFIG. 3on several of the blades306for reference and perspective. The recess302may be formed in a blade306on bit body304using a machining process. By way of example, and not limitation, recess302may be formed using a rotating cutter308of a multi-axis milling or drilling machine (not shown). In one embodiment, recess302may be formed by plunging rotating cutter308into bit body304from an entry point at or near the rotationally trailing surface310of blade306. In some embodiments, rotating cutter308may continue through blade306until it exits at or near the rotationally leading surface312of blade306. Because rotating cutter308may enter the bit body304at the rotationally trailing surface310of blade306, the previously described mechanical interference problems associated with machining a recess302in a bit body304may be reduced or eliminated and a cutting element pocket may be created that enables the positioning of cutting elements with a low back rake angle.

The recess302may have a shape that is complementary to, or that corresponds with, an exterior shape of a cutting element to be secured at least partially within the recess302, as described in further detail below. In some embodiments, the cutting element to be secured in a 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 recess302may have a generally cylindrical shape that is complementary to that of the cutting element to be secured therein. In some embodiments, the rotating cutter308may have a cutting diameter that is substantially the same as the diameter of the desired recess302. In other embodiments, the cutting diameter of rotating cutter308may have a cutting diameter substantially smaller than the desired diameter of recess302as will be discussed in more detail below.

FIG. 4is a partial cross-sectional view of a bit body404and illustrates the formation of a cutting element pocket414by forming first recess402that extends through the blade406from a location on or near a rotationally trailing surface410of the blade406to portions of one or both of the rotationally leading surface407and the outer surface409of blade406. Rotating cutter408may enter blade406from the location at or near the rotationally trailing surface410. The rotating cutter408may be oriented along a longitudinal axis411of cutting element pocket414as the first recess402is formed in blade406. Rotating cutter408may form first recess402by machining in the directions of the arrows as rotating cutter408is rotated. First recess402may define at least a portion of a lateral sidewall surface413of cutting element pocket414.

As can be appreciated fromFIG. 4, first recess402is substantially the same diameter throughout and, thus, there may be no definition as to where a cutting element pocket may end. In other words, there may be no back surface of the cutting element pocket414against which a cutting element placed therein may rest and be supported during drilling of a subterranean formation. Such a back surface of the cutting element pocket414may be formed as described in further detail below.

FIG. 5illustrates a second recess416being formed in the blade406using a rotating cutter418. In some embodiments, the second recess416may extend partially through the blade406toward the rotationally leading surface407thereof from a location on or near the rotationally trailing surface410of the blade406. At least a portion of the second recess416may be positioned below and be at least partially covered by the outer surface409of blade406. Rotating cutter418may enter blade406from the location at or near the rotationally trailing surface410, and also may be oriented along, and concentric with, the longitudinal axis411of cutting element pocket414in the manner previously described with respect to formation of the first recess402. In some embodiments, the second recess416may have a shape (e.g., round) generally similar to that of the first recess402. The second recess416may be larger than the first recess402in at least one cross-sectional dimension such that a shoulder412is formed at the transition or intersection between the first recess402and the second recess416. The shoulder412may define, or may be used to define, a location of a back surface of the cutting element pocket414being formed, as described in further detail below. As illustrated inFIG. 5, shoulder412comprises a substantially annular shoulder.

By way of example and not limitation, second recess416may be formed by machining a counterbore using a rotating cutter418having a cutting diameter larger than the cutting diameter of rotating cutter408(FIG. 4), as shown inFIG. 5. Rotating cutter418may be oriented along the longitudinal axis411of cutting element pocket414and plunged into the blade406to a desired depth from the rotationally trailing surface410. The depth of second recess416may be determined by designers according to the specific needs of the earth-boring drill bit and the specific length of the cutting elements to be disposed in cutting element pocket414.

In additional embodiments, the rotating cutter used to create the first and/or second recess402,416may be substantially smaller than the recess to be formed. For example,FIG. 6illustrates a partial cross-sectional view of a bit body404having a first recess402formed in blade406with a rotating cutter608. Rotating cutter608may have a cutting diameter that is substantially smaller than the desired diameter of first recess402formed in blade406. In this embodiment, rotating cutter608may be moved in the directions of the arrows shown inFIGS. 6 and 7Bto form first recess402oriented along longitudinal axis411of cutting element pocket414.FIG. 7Aillustrates another rotating cutter608′ of relatively small diameter and having a flat, distal end face being used to enlarge first recess402to form second recess416and shoulder412by machining the blade406generally parallel to, but laterally offset from, longitudinal axis411of cutting element pocket414.

FIG. 7Bis a cross-sectional view of the bit body404shown inFIG. 7Ataken along section line7B-7B shown therein.FIG. 7Billustrates a rotating cutter608inside second recess416. Although first and second recesses402,416are shown as having a circular cross-section, it will be appreciated by one of ordinary skill that first and second recesses402,416may be formed with any cross-section suitable for different shapes and configurations of cutting elements. By way of example, and not limitation, first recess402and/or second recess416may have an ovoid shape, a rectangular shape, a tombstone shape, etc.

Shoulder412is also shown as resulting from a step down in size from the second recess416to the first recess402, wherein, in some embodiments, second recess416has the same or similar geometry as first recess402. For example, first recess402and second recess416each may be generally cylindrical, with second recess416exhibiting a greater lateral extent (diameter) than first recess402. The first recess402and second recess416may each be longitudinally aligned with the axis411. Thus, shoulder412may be formed at a point at the intersection or transition between the first recess402and second recess416. The shoulder412may comprise a surface of the blade406, and may have a generally annular shape in some embodiments. However, it will be apparent to one of ordinary skill in the art that first recess402and the second recess416each may have a variety of different geometries and may differ from the geometry of first recess402and the second recess416as shown in the figures. As a non-limiting example, first recess402may comprise a substantially circular cross-sectional shape, and second recess416may comprise a tombstone cross-sectional shape, as shown inFIG. 8A.FIG. 8Bshows another non-limiting example of an embodiment in which the cross-sectional shape of the second recess416includes a central portion that is substantially identical to the cross-sectional shape and size of first recess402and one or more second regions comprising slots, keyways, or other openings that each extend in a generally radially outward direction beyond the cross-sectional area of the first recess402to create one or more shoulders412at the intersection or transition between the first recess402and the second recess416.

Although the embodiments illustrated inFIGS. 4 through 7Ashow first recess402formed before second recess416when forming cutting element pocket414, a person of ordinary skill in the art will recognize the second recess416may be formed prior to forming first recess402. In these embodiments, a rotating cutter, such as rotating cutter418(FIG. 5) or rotating cutter608′ (FIG. 7A), may be used to form second recess416by machining from the rotationally trailing surface410of blade406along longitudinal axis411of cutting element pocket414until the desired depth and diameter are reached. A rotating cutter, such as rotating cutter408(FIG. 4) or rotating cutter608(FIG. 6), may then be used to form first recess402by entering second recess416from the rotationally trailing surface410of blade406and machining first recess402along longitudinal axis411of cutting element pocket414to the rotationally leading surface407and outer surface409of blade406.

The present invention has utility in relation to earth-boring rotary drill bits and other tools having bodies substantially comprised of a metal or metal alloy such as steel, but also has utility in relation to earth-boring rotary drill bits and other tools. For example, the present invention has utility in bit and tool fabrication methods wherein bodies comprising particle-matrix composite materials are manufactured 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 blades104(FIG. 1) of a bit body formed by such a process while the bit body is in the green, brown, or fully sintered state. However, as with steel-bodied drill bits, interference problems may prevent the formation of the desired cutting element pockets. To overcome such interference problems, methods of the present invention, such as those previously described herein, may be used to for one or more cutting element pockets in one or more blades (such as the blades104shown inFIG. 1) of a bit body formed by such a process while the bit body is in the green, brown, or fully sintered state. Therefore, the present invention also has utility in relation to earth-boring tools having bit bodies substantially comprised of a particle-matrix composite material.

In some embodiments, after forming one or more cutting element pockets in a bit body of an earth-boring rotary drill bit as previously described, a plug or other mass of filler material may be disposed in the second recess416. Additionally, a cutting element may be positioned within each cutting element pocket414and secured to the blade406.FIG. 9is a side, partial cross-sectional view illustrating a cutting element pocket414as defined by first and second recesses402,416. A plug or other mass of filler material902may be disposed in second recess416and may be placed so that at least a portion of a leading face906of the plug or filler material902may abut against shoulder412. At least a portion of the leading face906may be configured to define the back surface (e.g., rear wall) of the cutting element pocket414against which a cutting element904may abut and rest. Filler material902may be used to replace the excess material removed from the bit body404when forming the first recess402and the second recess416, and to fill any portion or portions of the first recess402and the second recess416that are not comprised by the cutting element pocket414. By way of example and not limitation, filler material902may comprise a preformed solid structure that is constructed and formed to have a shape corresponding to that of at least a portion of second recess416.

Filler material902shown inFIG. 9may comprise a preformed solid plug structure that may be positioned behind cutting element904within second recess416and secured within blade406. In some embodiments the preformed solid plug structure may comprise a solid metal or alloy plug, such as a steel plug in the case of a steel body earth-boring drilling tool.

In some embodiments, the preformed solid plug structure may comprise a green powder compact structure or a partially sintered brown structure as described above. In such embodiments, the preformed solid plug structure may be disposed within second recess416, and the preformed solid structure and the blade406may be co-sintered to form a bond between the bit body404and the preformed solid structure. In some embodiments, the blade406also may comprise a green powder compact structure or a partially sintered brown structure prior to such a co-sintering process, while in other embodiments, the bit body404including blade406may be substantially fully sintered (i.e., sintered to a desired final density) prior to such a co-sintering process.

In some embodiments, the preformed solid plug structure may be separately fabricated, of a solid metal or alloy as noted above, positioned within second recess416, and secured to one or more surrounding surfaces of bit body404. The preformed solid plug structure may be secured to one or more surrounding surfaces of bit body404using, for example, an adhesive, a brazing process, a flamespray process, or a welding process. The preformed solid plug structure may be cooled, for example in liquid nitrogen, inserted in second recess416, and allowed to expand during warming to create an interference fit with blade406. In some embodiments, a preformed solid plug structure may be positioned within second recess416and secured to bit body404prior to securing a cutting element904in the cutting element pocket414.

In still other embodiments, filler material902may comprise a foreshortened plug which does not completely fill second recess416when abutting shoulder412, and a welding alloy, a solder alloy, or a brazing alloy may be applied using a corresponding welding, soldering, or brazing process to fill the remainder of second recess416. In such embodiments, a hardfacing material (e.g., a particle-matrix composite material) may be applied using a welding process (e.g., arc welding processes, gas welding processes, resistance welding processes, etc.) or a flamespray process to provide enhanced abrasion and erosion resistance over the filler. 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 filler material902, and may be applied to the blade406of bit body404as described therein. As an example, a particle-matrix composite material comprising particles of tungsten carbide dispersed throughout a metal alloy predominantly comprised of at least one of nickel and cobalt may be used as filler material902.

In such embodiments, as the filler material employed to backfill second recess416behind plug902may comprise at least one of a welding alloy, a solder alloy, or a brazing alloy, and a hardfacing material may be applied over exposed surfaces thereof, such layered combinations of materials may be selected to form a composite or graded structure between the cutting element904and the surrounding bit body404that is selected to tailor at least one of the strength, toughness, wear performance, and erosion performance of the region in the immediate vicinity of cutting element904for the particular design of the drilling tool, location of cutting element904on the drilling tool, or the application in which the drilling tool is to be used.

Cutting element904may be secured within cutting element pocket414such that each cutting element904is positioned in a forward-facing orientation, taken in the intended direction of tool rotation during use. Each cutting element904may include a rear face908which may abut against at least a portion of the leading face906of the filler material902, which defines a back surface of the cutting element pocket414. Thus, filler material902may create a support from behind when cutting element904abuts against leading face906. Cutting element904may further be secured within cutting element pocket414. By way of example and not limitation, each cutting element904may be secured within a cutting element pocket414using a brazing alloy, a soldering alloy, or an adhesive material disposed between the sides thereof and the inner surface of cutting element pocket414, as known in the art.

Recently, new methods of forming cutting element pockets by forming a recess 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. Such methods are disclosed in pending U.S. patent application Ser. No. 11/717,905, filed Mar. 13, 2007, the disclosure of which application is incorporated herein in its entirety by this reference. Referring toFIG. 10, a partial cross-sectional view of a blade406on a bit body404is shown and illustrates the formation of cutting element pocket1014by forming a first recess1002. Cutting element pocket1014may be formed by machining first recess1002using rotating cutter1008oriented at an angle relative to the longitudinal axis1011of cutting element pocket1014and machining into blade406from the outer surface409.FIG. 11Aillustrates a second recess1016being formed in blade406using the same or another rotating cutter1008oriented at an angle relative to the longitudinal axis1011and plunging the rotating cutter1008into blade406from the outer surface409. A shoulder1012at the intersection of first recess1002and second recess1016may also be formed to define the location of a back surface of the cutting element pocket1014being formed.

FIG. 11Bis a cross-sectional view of the bit body404shown inFIG. 11Ataken along section line11B-11B shown therein.FIG. 11Billustrates shoulder1012formed at the intersection of first recess1002and second recess1016. As illustrated inFIG. 12, a plug or other filler material1202may be positioned within the second recess1016so that at least a portion of a leading face1206of the plug or filler material1202may abut against shoulder1012. In some embodiments, at least a portion of the leading face1206may be configured to define the back surface or rear wall of the cutting element pocket1014against which a cutting element1204may abut and rest. In other embodiments the plug or filler material1202may be configured as a pocket (similar to1310inFIG. 13B) into which a portion of cutting element1204may be received, the plug or filler material at least partially surrounding the portion of the cutting element1204. Plug pr filler material1202may be formulated according to any of the material options for plug or filler material902(FIG. 9) as described above. Additionally, plug or filler material1202may be disposed and secured according to any of the methods described above with regards to plug or filler material902. Cutting element1204may be secured within the cutting element pocket in a manner similar to that described above with regard to cutting element904(FIG. 9).

A void1208may be present in the outer surface409of blade406above cutting element1204. Void1208may be filled with plug or filler material1202in some embodiments. In other embodiments, void1208may be filled with a plug or filler material that differs from plug or filler material1202. For example, plug1202may comprise a preformed solid structure while void1208may be filled with a hardfacing material. Any combination of materials as described above with relation to plug or filler material902may be employed to fill void1208.

In additional embodiments a cutting element pocket1014may be formed similar to cutting element pocket1014ofFIG. 10, above. A second recess1316may be formed in blade406using the same or another rotating cutter1008oriented at an angle of less than ninety degrees (90°) relative to the longitudinal axis1011of cutting element pocket1014, as shown inFIG. 13A. The second recess1316may be formed by machining in a rear surface1020(FIG. 10) of the cutting element pocket1014at the selected angle. As a non-limiting example, the rotating cutter1008may be oriented at an acute angle of between about ninety degrees (90°) and about thirty degrees (30°) relative to the longitudinal axis1011of the cutting element pocket1014when forming the second recess1316. This angle of cut may provide a second recess1316that is formed below the outer surface409of blade406. In other words, the second recess1316may be entirely or partially covered by the outer surface409of blade406.

As illustrated inFIG. 13B, a plug or filler material1302may be positioned within the second recess1316. Plug or filler material1302may comprise face1306configured to define the back surface or rear wall against which a cutting element1304may abut and rest. Plug or filler material1302may be disposed and secured according to any of the methods described above with regards to plug or filler material902(FIG. 9). Cutting element1304may be secured within the cutting element pocket in a manner similar to that described above with regard to cutting element904(FIG. 9).

A void1308, similar to void1208(FIG. 12), may be present in the outer surface409of blade406above cutting element1304. In some embodiments, void1308may be filled with a plug or filler material that differs from plug or filler material1302. For example, plug1302may comprise a preformed solid structure while void1308may be filled with a hardfacing material. Any suitable combination of materials as described above with relation to plug or filler material902may be employed to fill void1308.

In some embodiments of the present invention, plug or filler material1302may include a pocket1310formed therein and configured to receive a portion of cutting element1304, as illustrated inFIG. 13C. In such embodiments, pocket1310may be configured to fully surround a rear portion of cutting element1304abutting against face1306. By way of a non-limiting example only, the broken lines shown inFIG. 13Cillustrate pocket1310having a cutting element1304positioned therein, the plug or filler material1302fully surrounding a portion of cutting element1304. In other embodiments (not shown), the plug or filler material1302may be configured such that pocket1310may only partially surround cutting element1304at an area proximate the rear portion, as illustrated inFIG. 13C. Additionally, plug or filler material1302may be configured to completely fill or only partially fill void1308. Furthermore, some embodiments of plug or filler material1302may include a rear portion1312that is configured with a particular, selected shape. By way of non-limiting example only,FIG. 13Cillustrates an embodiment having a dome-shaped rear portion1312, the second recess1316being formed to have a complementary configuration to receive the plug or filler material1302.

FIG. 14is a plan view of the face of an embodiment of an earth-boring rotary drill bit1400according to the present invention. The earth-boring rotary drill bit1400includes a bit body1402having a plurality of generally radially projecting and longitudinally extending wings or blades1404, which are separated by junk slots1406extending from channels on the face of the bit body1402. A plurality of primary PDC cutting elements1408are provided on each of the blades1404within cutting element pockets414(FIG. 9). A plurality of secondary PDC cutting elements1408′ are also provided within cutting element pockets414on each of the blades1404rotationally behind the primary cutting elements1408.

By using embodiments of cutting element pockets of the present invention, cutters may be secured to the face of a bit body at relatively low back rake angles without encountering mechanical tool interference problems. As a result, earth-boring drilling tools, such as the earth-boring rotary drill bit1400shown inFIG. 14may be provided that are capable of drilling at increased rates of penetration relative to previously known drilling tools having machined cutter pockets, and similar to rates of penetration achieved using drilling tools having cutter pockets formed in a casting process (e.g., infiltration) used to fabricate so-called “matrix-type” bits. For example, the cutting element pockets414(FIG. 9) on the so-called “cone region” of one or more of the blades1404may be formed using methods described herein, and may be configured such that the PDC cutting elements1408disposed therein are oriented at backrake angles of less than about twenty degrees (20°). For example, the PDC cutting elements1408in the cone region of one or more blades1404of the drill bit1400may be disposed at a back rake angle of between about ten degrees (10°) and about seventeen degrees (17°).

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 “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.

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.