Abstract:
A rotary tool for drilling subterranean material is disclosed. The rotary tool includes a tool body having a distal crown end comprising a circumferential series of raised cutting blades with recessed junk slots therebetween. Cutting elements are located proximate a leading peripheral edge of the raised cutting blades and cutting control structures are located interiorly of the cutting elements at a leading surface of an adjacent junk slot. Cutting control structures are releasably secured to the tool body in the adjacent junk slot whereby a used rotary tool is refurbishable by removing worn cutting control structures without degradation to the tool body and replacing the worn cutting control structures by installing new cutting control structures in the worn cutting control structures&#39; locations.

Description:
FIELD OF TECHNOLOGY 
       [0001]    The present application relates generally to rotary tools used for drilling subterranean material. More particularly, the present application is directed to a method of manufacturing and repairing rotary tools for drilling subterranean material having cutting control structures releasably secured to the tool body. 
       BACKGROUND 
       [0002]    Fixed-cutter drag-type rotary drill bits having natural and synthetic diamond cutting elements affixed to a distal crown of the bit body have been employed in subterranean drilling for many decades. Rotary drag-type drill bits are typically comprised of a bit body having a shank for connection to a drill string and encompassing an inner channel for supplying drilling fluid to the face of the bit through nozzles or other apertures. Drag bits may be cast and/or machined from metal, typically steel, or may be formed from wear-resistant metal particles (typically tungsten carbide (WC)) infiltrated at high temperatures with a liquefied (typically copper-based) binder material to form a matrix. Such bits may also be formed with layered-manufacturing technology, as disclosed in U.S. Pat. No. 5,433,280 incorporated herein by reference. 
         [0003]    Drag bits herein disclosed include polycrystalline diamond compact (PDC) cutters typically comprised of a large diamond table (usually of circular, semi circular or tombstone shape) which presents a generally planar cutting face. A cutting edge (sometimes chamfered or beveled) is formed on one side of the cutting face which, during boring, is at least partially embedded into the formation so that the formation is received against at least a portion of the cutting face. As the bit rotates, the cutting face moves against the formation and shavings of formation material (cuttings) are sheared off and are forced up the surface of the cutter face. In brittle materials at atmospheric pressure the formation cuttings easily separate from the cutter face and break down into small particles that are transported out of the bore hole via circulating drilling fluid. Another cutting then begins to form in the vicinity of the cutting edge, is forced up the face of the cutting surface, and breaks off in a similar fashion. Such action occurring at each cutting element on the bit removes formation material over the entire face of the bit, and so causes the bore hole to become progressively deeper. 
         [0004]    However, for ductile formations under pressure that exhibit plastic properties, such as highly pressurized deep shales, mudstones, and siltstones, the formation cuttings have a marked tendency to stay intact and adhere to the cutting face of the cutting element. If the cutting is not broken into smaller pieces or removed from the cutting face, the cuttings collect as a mass of cuttings ahead of the PDC cutting elements and eventually clog the junk slots with drilled-up material. Once this phenomenon, termed bit balling, occurs the bit ceases to drill effectively. 
         [0005]    U.S. Pat. No. 6,328,117 to Berzas et al. discloses apparatus for the prevention of bit balling that includes a chip breaker affixed upon fixed-cutter, rotary-type drill bits used in drilling subterranean formations. The chip breaker includes a knife-like protrusion positioned proximate a cutting element and adjacent a fluid course defined by the bit body. As formation cuttings are generated during drilling, the cuttings move over the protrusion and are split or scribed by the protrusion. 
         [0006]    Even in view of such improvements disclosed in the aforementioned prior art, rotary tools are still susceptible to bit balling during drilling of subterranean material. Operating rotary tools at an excessively high great depth of cut (DOC) may generate more formation cuttings than can be consistently broken or cleared from the bit face and back up the bore hole via the junk slots on the face of the bit. Furthermore, chip breakers disclosed in the prior art are exposed to extremely large loads that can cause the chip breaker to either be eroded or entirely removed from the bit body. 
         [0007]    It is therefore necessary to provide the industry with an apparatus and method for breaking down and dispersing formation cuttings that collect on the body of fixed-cutter drag-type rotary tools regardless of the size, shape or composition of the cutting and regardless of the type of subterranean material encountered by the rotary tool. Fixed-cutter drag-type rotary tools such as rotary drill bits, casing bits, reamers, bi-center rotary drill bits, reamer wings, down-hole milling tools, bi-center drill bits, or other drilling tools known in the art for utilizing cutting elements may benefit from the present disclosure and, as used herein, the term “rotary drill bit” encompasses any and all such apparatuses. 
       SUMMARY 
       [0008]    The application herein provides apparatus and methods for releasably securing cutting control structures to a tool body of a rotary tool for drilling subterranean material. The rotary tool includes a tool body having a distal crown end comprising a circumferential series of raised cutting blades with recessed junk slots therebetween. Cutting elements are located proximate a leading peripheral edge of one of said raised cutting blades and cutting control structures are located interiorly of said cutting elements at a leading surface of an adjacent junk slot. The cutting control structures provide a means for splitting, breaking, twisting and/or diverting cuttings, chips or shavings that collect on the cutting face of a cutting element during drilling of subterranean material. The cutting control structures are releasably secured to the tool body in an adjacent junk slot whereby a used rotary tool is refurbishable by removing and replacing worn cutting control structures without degradation to the tool body. The embodiments disclosed herein permit rapid removal and replacement of cutting control structures that become worn or removed during drilling of subterranean material. The embodiments disclosed herein also enable easy modification of the location of cutting control structures in field operations thereby optimizing the position of cutting control structures depending on the drilling conditions. Furthermore, a variety of cutting control structures such as splitters, breakers, diverters and wedges can be configured on a single tool body for optimal break-up and dispersion of cuttings during drilling operations. 
         [0009]    The foregoing and other objects, features and advantages of the disclosure will become more readily apparent from the following detailed description of the preferred embodiments as disclosed herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Embodiments of the present application will now be described, by way of example only, with reference to the attached Figures, wherein: 
           [0011]      FIG. 1  is a perspective side view of a first embodiment rotary-type drill bit in accordance with the present disclosure; 
           [0012]      FIG. 2  is a partial sectional view of a second embodiment of a rotary-type drill bit illustrating cutting control structures mounted on a carrier releasably secured to the bit body; 
           [0013]      FIG. 3  is a partial sectional view of a formation chip being modified by a cutting control structure on a drill bit in accordance with the present disclosure; 
           [0014]      FIG. 4  is a perspective view of the cutting control structures mounted to a carrier on a cutting blade of a rotary-type drill bit; 
           [0015]      FIG. 5  is another perspective view of the cutting control structures mounted to a carrier on a cutting blade of rotary-type drill bit; 
           [0016]      FIG. 6  is a perspective view of a carrier having cutting control structures mounted thereon; 
           [0017]      FIGS. 7A-7C  are examples of single cutting control structures releasably securable to a bit body; 
           [0018]      FIG. 8  is an example of a removable cutting control structure according to the present disclosure with a press fit engagement to the bit body; 
           [0019]      FIG. 9  is a second example of a removable cutting control structure according to the present disclosure with a press fit engagement to the bit body; 
           [0020]      FIG. 10  is an example of a removable cutting control structure according to the present disclosure with a screw engagement to the bit body; and 
           [0021]      FIG. 11  is a partial sectional view of a removable cutting control structure that is welded, brazed, press fit or shrink fit into a recess in the bit body according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    It will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the example embodiments described herein. However, it will be understood by those of ordinary skill in the art that the example embodiments described herein may be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Also, the description is not to be considered as limiting the scope of the embodiments described herein. 
         [0023]    Referring to  FIG. 1 , a drill bit  10  in accordance with the present disclosure comprises a body  12  having a threaded connection  14  at a proximal end  16  thereof and a crown  18  at a distal end  20  thereof. The crown  18  includes a plurality of longitudinally extending blades  22  that define a plurality of fluid courses  23  with adjacent junk slots  24  thereinbetween. Along each blade  22 , proximate the distal end  20  of the body  12 , is a plurality of cutting elements  25  attached to the leading peripheral edge  27  of the blades  22  and oriented to cut into a subterranean formation upon rotation of the bit  10 . 
         [0024]    The drill bit  10  as illustrated in  FIG. 1  is of a drag bit that can include polycrystalline diamond compact (PDC) cutters typically comprised of a large diamond table usually of circular, semi-circular or other shape) which presents a generally planar cutting face. While this type of drill bit is illustrated, the disclosure as contained herein can be equally applied to other types of tools used in drilling or otherwise modifying a subterranean material. These subterranean materials can include man-made material such as concrete and steel among other materials. Other examples of tools to which this disclosure could apply have been indicated in the background. 
         [0025]    As illustrated, the fluid courses  23  and adjacent junk slots  24  are defined by the following surfaces: a first, leading side wall  26 , a second, trailing side wall  28  and a bottom surface  30 . The leading side wall  26  provides a surface adjacent the cutting face  29  of the cutting elements  25 . A plurality of cutting control structures  31  are each releasably secured to the leading side wall  26  interiorly of a cutting element  25 . In addition, each cutting control structure  31  preferably has a longitudinal axis L that is in substantial alignment with the center C of the adjacent cutting face  29  so that, as formation cuttings are generated during drilling, the cutting control structure  31  modifies the size, shape or directional path of the cutting that comes in contact with the cutting control structure  31 . It is noted that the orientation or  65  alignment of the longitudinal axis L relative to the cutting face  29  may be engineered based on the location of the cutting element  25  on the bit  10  and the predicted direction of formation cutting generation over the cutting face  29 . Accordingly, as formation cuttings, also referred to herein as shavings or formation chips, are cut by the cutting elements  25 , the cuttings slide over the cutting face  29  and across the leading side wall  26  adjacent the cutting elements  25 , are modified by the cutting control structures  31 , and are carried away by drilling fluid flowing through the fluid course  23 . 
         [0026]    In hard drilling applications that involve drilling hard subterranean material, the cutting control structures  31  may be formed from at least one of the group comprising polycrystalline diamond compact (PDC), thermally stable polycrystalline diamond (TSP), cubic boron nitride (CBN), polycrystalline cubic boron nitride (PCBN), carbide and ceramics. In soft drilling applications that involve drilling relatively softer material, the cutting control structures  31  may be formed from at least one of the group comprising copper, aluminum and plastic. Furthermore, cutting control structures  31  include splitters, breakers, diverters and/or wedges. A chip breaker  31  or splitter  31  includes a knife-like protrusion positioned proximate a cutting element  25 . As formation chips, shavings or cuttings are generated during drilling, the cuttings move over the protrusion and are split or scribed by the protrusion. Chip diverters and wedges include a blunt protrusion that is generally wedge-shaped and positioned proximate a cutting element  25 . As formation chips, shavings or cuttings are generated during drilling, the cuttings move over the protrusion and are deflected or dispersed from the cutting face  29 . Other suitable geometries for splitters, breaker, diverters and wedges will be discussed in further detail below. 
         [0027]    The cutting control structures are especially useful in ductile formations under pressure, such as pressurized shales, mudstones, and siltstones; the cuttings of those materials have a marked tendency to stay intact and adhere to the cutting face of the cutting element. If the cutting is not broken into smaller pieces or removed from the cutting face, the cuttings collect and build up as a mass of cuttings ahead of the cutting elements and eventually clog the junk slots with material. As described herein, the cutting control structures encourage at least one of breaking apart, splitting, and divergence of the cutting from the cutting surfaces. 
         [0028]    In a second embodiment shown in  FIG. 2 , cutting control structures  31  are fixably mounted to a carrier  50  at an upper surface  52  of an exposed end  51  of the carrier  50 . The cutting control structures  31  are fixably mounted to the carrier  50  and positioned relative to a cutting element  25  such that the cutting control structures  31  lie in a potential flow path of cuttings generated by the operating cutting element  25 . The carrier  50  is releasably secured to the leading side wall  26  such that the upper surface  52  of the carrier  50  is elevated above the leading side wall  26 . As a result, at least a portion of the cutting control structures  31  lie in an elevated plane relative to the cutting element  25  and can be configured to project over the cutting face  29  of the cutting element  25  to enhance the dispersion of cuttings from the cutting face  29 . While in the illustrated embodiment the carrier  50  has a top surface  52  that is raised relative to the face of the leading side wall  26 , the carrier  50  can be mounted approximately flush with the leading side wall  26  and a portion of the cutting control structure  31  that lies above the cutting element can be configured to project over the cutting face  29  of the cutting element  25 . 
         [0029]    In another embodiment, the carrier  50  is releasably secured to the leading side wall  26  such that the upper surface  52  of the carrier  50  is flush-oriented with the leading side wall  26  of the adjacent junk slot  24 . Additionally, the cutting control structures  31  can be configured such that they do not project over the cutting face  29  of the cutting element  25 , thereby easing disengagement and replacement of worn cutting control structures  31 . 
         [0030]      FIG. 3  illustrates a means for releasably securing the cutting control structure  31  to the leading side wall  26 . A carrier  50  comprises an exposed end  51  having an upper surface  52  and anchoring end  55  having a top anchoring portion  54  and a releasable anchorage  56 . The cutting control structure  31  is fixably mounted to the carrier  50  at the upper surface  52  of the exposed end  51  of the carrier  50 . The releasable anchorage  56  includes a substantially cylindrical portion  57  for releasably securing the carrier  50  to a retention recess  82  within the leading side wall  26 . The retention recess  82  can be formed by boring a threaded cylindrical passage into the leading side wall  26 . The substantially cylindrical portion  57  of the releasable anchorage  56  is threaded to releasably secure the carrier  50  to the retention recess  82  by screwing the substantially cylindrical portion  57  into the retention recess  82 . Additionally, a top anchoring portion  54  of the anchoring end  55  of the carrier  50  can have a larger cross-sectional area compared to the cylindrical portion  57  or other portions of the releasable anchorage  56 . The top anchoring portion  54  is configured to fit within a top portion recess  80  that accommodates the top anchoring portion  54 . Increasing the cross-sectional area of the top anchoring portion  54  increases the surface area contacting the leading side wall  26 , thereby distributing the stresses and loads exerted on the carrier  50  during drilling. 
         [0031]    In another embodiment, to further secure the carrier  50  to the leading side wall  26 , the retention recess  82  can be formed by boring a threaded cylindrical passage through the leading side wall  24  and through a rear surface of the cutting blade. The carrier  50  is releasably secured to the retention recess  82  by screwing the substantially cylindrical portion  57  into the retention recess  82 . In at least one embodiment the distal end  58  of releasable anchorage  56  can also be fastened with a nut to the rear surface of the cutting blade (not shown). 
         [0032]    In other embodiments, the carrier  50  can be releasably secured to the bit body  12  by welding, brazing, bonding, using studs, shrink fitting a portion of the carrier  50  to the bit body  12  and/or friction fitting a portion of the carrier  50  to the bit body  12 . For example, the upper surface  52  of the exposed end  51  of the carrier  50  could be welded, brazed and/or bonded around its perimeter. In another embodiment, it is also possible to braze the top anchoring portion  54  of the cutting control structure  31  within the retention recess  82 . Other mechanisms that secure the releasable anchorage  56  of the cutting control structure include the implementation of threaded engagements, locking mechanisms, studs, friction fitting, press fitting and the like. 
         [0033]    As illustrated in  FIG. 3 , formation cutting  40  may be both split and lifted or split, lifted and twisted and/or dispersed from leading side wall  26  by cutting control structure  31  relative to cutting face  29  of cutting element  25  and leading side wall  26 . By splitting and lifting the cutting  40  away from leading side wall  26 , the unsupported portion  44  of the cutting  40  that is exposed to the flow of drilling fluid is weakened by drilling fluid penetrating into cracks and pores and can be relatively easily broken away from the rest of the cutting  40  by the force of drilling fluid flowing through the fluid course. Segments  42  of cutting  40 , one of which is viewable in  FIG. 3  with the other directly therebehind, will typically have two additional sides  41  exposed to the action of the drilling fluid for further break-up of segments  42  away from the rest of the cutting  40 . The cutting control structure  31  can further deflect and/or disperse the cutting from the cutting face  29  into an adjacent junk slot  24  (not shown). Therefore, the cutting control structures  31  of this embodiment may modify the shape, size or directional path of the cuttings generated while drilling. 
         [0034]      FIGS. 4 and 5  illustrate an embodiment with cutting control structures  31  fixably mounted to a carrier  50  at an upper surface  52  the exposed end  51  of the carrier  50 .  FIG. 4  provides a perspective view of the cutting face  29  of the cutting elements  25 .  FIG. 5  provides a side perspective view of the cutting elements  20  along with cutting control structures  31 . The carrier  50  is releasably secured to the leading side wall  26 . In the illustrated embodiment, the adjacent cutting control structures  31  are spaced apart on the carrier  50  at distance-X that is not equivalent to the spacing distance-Y between adjacent cutting elements  25 . The spacing between adjacent cutting control structures  31  relative to the spacing between adjacent cutting elements  25  may vary in order to optimized the contact between cutting control structures  31  and cuttings based on the directional path (such as line A) that cuttings follow during drilling of subterranean material. The spacing between adjacent cutting control structures  31  relative to the spacing between adjacent cutting elements  25  may be maintained such that the angle between the directional of path of two flow patterns of cuttings across a pair of adjacent cutters is constant across the pair of adjacent cutters  25  and a pair of corresponding adjacent cutting control structures  31 . In another embodiment, the adjacent cutting control structures are spaced apart on the carrier  50  at distance-X substantially equal to a spacing distance-Y between cutting elements  25  on the raised cutting blade. Maintaining an equivalent distance between adjacent cutting control structures  31  relative to the distance between adjacent cutting elements  25  is useful if adjacent cutting elements  25  are arranged substantially linearly and/or produce a flow pattern of cuttings in a substantially linear directional path. 
         [0035]    While the embodiments shown in  FIGS. 2 ,  4 , and  5  have three cutting control structures mounted on the top surface  52  of the carrier  50 , other arrangements of the cutting control structures are considered within the scope of this disclosure. For instance, a pair of cutting control structures  31  can be affixed to the carrier  50 . Additionally, the cutting control structures  31  can be arranged such that more than three are provided on the carrier. As will be described below, the cutting control structures  31  can also be individually releasably secured to the tool body. 
         [0036]      FIG. 6  illustrates another embodiment of a carrier  50  with a plurality of cutting control structures  31  fixably mounted to the carrier  50 . The carrier  50  comprises an exposed end  51  having an upper surface  52  and anchoring end  55  having a top anchoring portion  54  and a releasable anchorage  56 . The cutting control structures  31  are fixably mounted to the carrier  50  at the upper surface  52  of the carrier  50 . The releasable anchorage  56  comprises a substantially cylindrical and threaded portion  62  for releasably securing the carrier  50  to the bit body  12 . In accordance with this embodiment, the carrier  50  may be secured to the bit body by screwing the substantially cylindrical and threaded portion  62  into a threaded recess in the bit body. The carrier  50  may be unscrewed and replaced with another carrier  50  when one or a plurality of cutting control structures  31  become worn or broken from use in drilling subterranean material, thereby making a drill bit  10  refurbishable. 
         [0037]      FIGS. 7A-7C  illustrate several other embodiments of cutting control structures  31  in accordance with the present disclosure. In  FIG. 7A , the cutting control structure  31  is illustrated as having a cone-shaped protrusion or protuberance  30 . The cutting control structure  31  includes an exposed end  51  having an upper surface  52  and an anchoring end  55  having a top anchoring portion  54  and a releasable anchorage  56 . The releasable anchorage  56  comprises a substantially cylindrical and threaded portion  62  for releasably securing the cutting control structure  31  to the bit body  12 . In accordance with this embodiment, the cutting control structure  31  can be secured to the bit body  12  by screwing the substantially cylindrical and threaded portion  62  into a threaded recess in the bit body  12 . The cutting control structure  31  can be unscrewed and replaced with another cutting control structure  31  when the cutting control structure  31  becomes worn or broken from use in drilling subterranean material, thereby making a drill bit  10  refurbishable. Although the cutting control structure  31  is not mounted to a carrier in this embodiment, one or more cutting control structures  31  illustrated in this embodiment can be mounted to a carrier that is releasably secured to the bit body in any number of ways herein disclosed. 
         [0038]    In  FIG. 7B , the cutting control structure  31 ′ is illustrated as having an elliptical-shaped protrusion or protuberance  30 ′. The cutting control structure  31 ′ includes an exposed end  51  having an upper surface  72  and an anchoring end  55  having a top anchoring portion  74  and a releasable anchorage  76 . The releasable anchorage  76  comprises a substantially cylindrical and threaded portion  78  for releasably securing the cutting control structure  31 ′ to the bit body  12 . In accordance with this embodiment, the cutting control structure  31 ′ can be secured to the bit body  12  by screwing the substantially cylindrical and threaded portion  78  into a threaded recess in the bit body  12 . The cutting control structure  31 ′ can be unscrewed and replaced with another cutting control structure  31 ′ when the cutting control structure  31 ′ becomes worn or broken from use in drilling subterranean material, thereby making a drill bit  10  refurbishable. Although the cutting control structure  31 ′ is not mounted to a carrier in this embodiment, one or more cutting control structures  31 ′ illustrated in this embodiment can be mounted to a carrier that is releasably secured to the bit body in any number of ways herein disclosed. 
         [0039]    In  FIG. 7C , the cutting control structure  31 ″ is illustrated as a semi-cylindrical shaped protrusion or protuberance  30 ″. The cutting control structure  31 ″ includes an exposed end  51  having an upper surface  72  and an anchoring end  55  having a top anchoring portion  74  and a releasable anchorage  76 . The releasable anchorage  76  includes a substantially cylindrical and threaded portion  78  for releasably securing the cutting control structure  31 ″ to the bit body  12 . In accordance with this embodiment, the cutting control structure  31 ″ can be secured to the bit body  12  by screwing the substantially cylindrical and threaded portion  78  into a threaded recess in the bit body  12 . The cutting control structure  31 ″ can be unscrewed and replaced with another cutting control structure  31 ″ when the cutting control structure  31 ″ becomes worn or broken from use in drilling subterranean material, thereby making a drill bit  10  refurbishable. Although the cutting control structure  31 ″ is not mounted to a carrier in this embodiment, one or more cutting control structures  31 ″ illustrated in this embodiment can be mounted to a carrier that is releasably secured to the bit body in any number of ways herein disclosed. 
         [0040]    In other embodiments the cutting control structures  31  may have substantially rectangular-shaped, diamond-shaped, knifelike protrusions and/or any other shape of protrusion that would be understood by one of ordinary skill in the art as effective in modifying the shape, size or directional path of cuttings formed during drilling of subterranean material. 
         [0041]      FIG. 8  illustrates another means for releasably securing a cutting control structure  31  to the bit body. In accordance with  FIG. 8 , a cutting control structure  31  includes a protrusion  30 , an exposed end  51  having upper surface  52  and an anchoring end  55  having a top anchoring portion  54  and a releasable anchorage  56 . The releasable anchorage  56  is of generally smaller diameter than the top anchoring portion  54 . The releasable anchorage  56  has a locking surface  107 , which has formed thereon a series of sharp edged radial projections  112  such as circular ridges or barbs comprised of a hard material. A retention recess  109  is preformed or drilled in the bit body  12  forming a cavity or socket for insertion of the releasable anchorage  56 . An annular sleeve element  105  of metal or other suitable material may be placed in the retention recess  109  and is shown extending into the retention recess  109  to form a shoulder  114 . The sleeve element  105  has a hardness value less than that of the sharp edged radial projections  112  so that the releasable anchorage  56  may be inserted with force into the sleeve element  105  and retained by friction within the sleeve element  105  by the sharp ridges or barbs  112 . The cutting control structure  31  may be forcibly removed and replaced with another control structure  31  when the cutting control structure  31  becomes worn or broken from use in drilling subterranean material, thereby making a drill bit  10  refurbishable. 
         [0042]    As shown in  FIG. 8 , the sleeve element  105  does not cover the center bottom region  111  of the retention recess  109 . While in  FIG. 9 , the sleeve element  105  is constructed such that the center bottom region  111  of the retention recess  109  is covered by sleeve element  105 . The shape, size and degree of overlay of the sleeve element  105  in the retention recess  109  can be varied depending upon the degree of support needed in the retention recess  109  and depending on the material used for constructing the sleeve  105  and the locking surface  107 . 
         [0043]      FIG. 10  illustrates another means for releasably securing a cutting control structure  31  to the bit body  12 . The cutting control structure  31  includes a protrusion  30  fixed to an upper surface  52  of an exposed end  51 . The cutting control structure  31  further includes an anchoring end  55  having a top anchoring portion  54  and a releasable anchorage  56 . The releasable anchorage  56  includes a substantially cylindrical and threaded portion  108  for releasably securing the cutting control structure  31  to the bit body  12 . A sleeve  115  is mounted within a cavity  106  formed in the bit body  12 . The sleeve  115  accommodates the top anchoring portion  54  of the cutting control structure  31  and is also shaped to accommodate the corresponding substantially cylindrical and threaded portion  108  of the releasable anchorage  56 . A distal end  110  of the substantially cylindrical and threaded portion  108  of the releasable anchorage  56  passes through the sleeve  115  and is threadably engaged with the bit body  12 . The threaded engagement of the releasable anchorage  56  to the bit body  12  fixes the sleeve  115  to the bit body  12  and allows the sleeve  115  and the cutting control structure  31  to be removed and replaced. 
         [0044]    In other embodiments, the cutting control structure  31  can be releasably secured to the bit body  12  by welding, brazing, bonding, using studs, shrink fitting a portion of the cutting control structure  31  to the bit body  12  and/or friction fitting a portion of the cutting control structure  31  to the bit body  12 . For example, the upper surface  52  of the exposed end  51  of the cutting control structure  31  could be welded, brazed and/or bonded around its perimeter. In another embodiment, it is also possible to braze the top anchoring portion  54  of the cutting control structure  31  within the recess  109  as illustrated in  FIG. 8  and  FIG. 11 . Other mechanisms that secure the releasable anchorage  56  of the cutting control structure  31  shown in  FIG. 8  include the implementation of threaded engagements, locking mechanisms, studs, friction fitting, shrink fitting and the like. 
         [0045]    The methods and systems herein disclosed of releasably securing a cutting control structure  31  are not limited to fixed-cutter rotary drill-bits. The methods and systems herein disclosed can be extended to releasably securing cutting control structures  31  to any down-hole tool that generates cuttings during operation including but not limited to fixed-cutter drag-type rotary tools such as rotary drill bits, casing bits, reamers, bi-center rotary drill bits, reamer wings, down-hole milling tools and bi-center drill bits. Furthermore, the systems and methods herein disclosed are not limited to drilling subterranean formations. The methods and systems herein disclosed can be extended to drilling or cutting any subterranean structure, composition of matter or formation that generates cuttings during downhole operations. 
         [0046]    The embodiments disclosed herein exhibit significant advantages over the prior art. The embodiments disclosed herein permit rapid removal and replacement of cutting control structures that become worn or broken during drilling of subterranean material without degradation to the tool body. The embodiments disclosed herein also enable easy modification of the location of cutting control structures during field operations thereby optimizing the position of cutting control structures depending on the drilling conditions and conditions of the wellbore. Furthermore, a variety of cutting control structures such as splitters, breakers, diverters and wedges can be configured on a single tool body for optimal break-up and dispersion of cuttings during drilling operations, thereby optimizing rate of penetration of the drill bit and alleviating bit balling. 
         [0047]    Example embodiments have been described hereinabove regarding a method and apparatus for repairing or refurbishing fixed-cutter drag-type rotary tools for drilling subterranean material and having cutting control structures releasably secured to the tool body. Various modifications to and departures from the disclosed example embodiments will occur to those having skill in the art. The subject matter that is intended to be within the spirit of this disclosure is set forth in the following claims.