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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 09/218,952, filed Dec. 22, 1998 and now issued as U.S. Pat. No. 6,135,219, which is a CIP of Ser. No. 09/074,260 filed May 7, 1998 U.S. Pat. No. 6,098,730 which is a CIP of Ser. No. 08/633,983 filed Apr. 17, 1996 filed as U.S. Pat. No. 5,758,733. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to superabrasive inserts, or compacts, for abrasive cutting of rock and other hard materials. More particularly, the invention pertains to improved interfacial geometries for polycrystalline diamond compacts (PDC&#39;s) used in drill bits, reamers, and other downhole tools used to form bore holes in subterranean formations. 
     2. Background of Related Art 
     Drill bits for oil field drilling, mining and other uses typically comprise a metal body into which cutters are incorporated. Such cutters, also known in the art as inserts, compacts, buttons and cutting tools, are typically manufactured by forming a superabrasive layer on the end of a sintered carbide substrate. As an example, polycrystalline diamond, or other suitable abrasive material, may be sintered onto the surface of a cemented carbide substrate under high pressure and temperature to form a PDC. During this process, a sintering aid such as cobalt may be premixed with the powdered diamond or swept from the substrate into the diamond. The sintering aid also acts as a continuous bonding phase between the diamond and substrate. 
     Because of different coefficients of thermal expansion and bulk modulus, large residual stresses of varying magnitudes and at different locations may remain in the cutter following cooling and release of pressure. These complex stresses are concentrated near the diamond/substrate interface. Depending upon the cutter construction, the direction of any applied forces, and the particular location within the cutter under scrutiny, the stresses may be either compressive, tensile, or shear. In the diamond/substrate interface configuration, any non-hydrostatic compressive or tensile load exerted on the cutter produces shear stresses. Residual stresses at the interface between the diamond table and substrate may result in failure of the cutter upon cooling or in subsequent use under high thermal or fractional forces, especially with respect to large-diameter cutters. 
     During drilling operations, cutters are subjected to very high forces in various directions, and the diamond layer may fracture, delaminate and/or spall much sooner than would be initiated by normal abrasive wear of the diamond layer. This type of premature failure of the diamond layer and failure at the diamond/substrate interface can be augmented by the presence of high residual stresses in the cutter. 
     Typically, the material used as a substrate, e.g., carbide such as tungsten carbide, has a higher coefficient of thermal expansion than diamond matrix. This mismatch of coefficients of thermal expansion causes high residual stresses in the PDC cutter during the high-pressure, high-temperature manufacturing process. These manufacturing induced stresses are complex and of a non-uniform nature and thus often place the diamond table of the cutter into tension at locations along the diamond table/substrate interface. 
     Many attempts have been made to provide PDC cutters which are resistant to premature failure. The use of an interfacial transition layer with material properties intermediate of those of the diamond table and substrate is known within the art. The formation of cutters with non-continuous grooves or recesses in the substrate filled with diamond is also practiced, as are cutter formations having concentric circular grooves or a spiral groove. 
     The patent literature reveals a variety of cutter designs in which the diamond/substrate interface is three dimensional, i.e., the diamond layer and/or substrate have portions which protrude into the other member to “anchor” it therein. The shape of these protrusions may be planar or arcuate, or combinations thereof. 
     U.S. Pat. No. 5,351,772 of Smith shows various patterns of radially directed interfacial formations on the substrate surface; the formations project into the diamond surface. 
     As shown in U.S. Pat. No. 5,486,137 of Flood et al., the interfacial diamond surface has a pattern of unconnected radial members which project into the substrate; the thickness of the diamond layer decreases toward the central axis of the cutter. 
     U.S. Pat. No. 5,590,728 of Matthias et al. describes a variety of interface patterns in which a plurality of unconnected straight and arcuate ribs or small circular areas characterizes the diamond/substrate interface. 
     U.S. Pat. No. 5,605,199 of Newton teaches the use of ridges at the interface which are parallel or radial, with an enlarged circle of diamond material at the periphery of the interface. 
     In U.S. Pat. No. 5,709,279 of Dennis, the diamond/substrate interface is shown to be a repeating sinusoidal surface about the axial center of the cutter. 
     U.S. Pat. 5,871,060 of Jensen et al., assigned to the assignee hereof, shows cutter interfaces having various ovaloid or round projections. The interface surface is indicated to be regular or irregular and may include surface grooves formed during or following sintering. A cutter substrate is depicted having a rounded interface surface with a combination of radial and concentric circular grooves formed in the interface surface of the substrate. 
     Drilling operations subject the cutters on a drill bit to extremely high stresses, often causing crack initiation and subsequent failure of the diamond table. Much effort has been devoted by the industry to making cutters resistant to rapid deterioration and failure. 
     Each of the above-indicated references, hereby incorporated herein, describes a three-dimensional diamond/substrate interfacial pattern which may accommodate certain of the residual stresses in the cutter. Nevertheless, the tendency to fracture, defoliate and delaminate remains. An improved cutter having enhanced resistance to such degradation is needed in the industry. 
     SUMMARY OF THE INVENTION 
     The present invention provides a drill bit cutter having a diamond/substrate interface which has enhanced resistance to fracture, defoliation, and delamination. The invention also provides a cutter with a pattern which helps to break up and isolate the areas of high residual stress throughout the interfacial area and having the diamond table with a reduced stress level. The invention still further provides a cutter with enhanced bonding of the diamond table to the substrate. 
     The invention comprises a cutter having a superabrasive layer overlying and attached to a substrate. The interface between the superabrasive layer and the substrate is configured to enable optimization of the radial compressive prestressing of the diamond layer or table. The interface configuration preferably incorporates a three-dimensional interface having radial members or ribs and at least one generally annular member such as a circular or polygonal member, or an irregularly shaped annular member comprising a combination of curved and straight geometrical segments, arranged in a preselected pattern. Preferably, the radial and nonradial members are interconnected at junctions therebetween such that the diamond table is in nearly uniform radial and circumferential compression. Thus, the desired lowering of the high residual stress of the diamond table within the interior and exterior thereof results in a biaxial compressive prestress and in the vicinity of the interface occurs upon cooling from a high-temperature, high-pressure manufacturing procedure used in forming the cutter. 
     A decrease in residual radial and circumferential compressive prestress of the diamond table along at least the interface of the table and the substrate counteracts the forces superimposed upon the table during drilling or when conducting other downhole operations, depending on the tool in which the cutter is mounted. The resistance to delamination is also increased. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The following drawings illustrate various embodiments of the invention, not necessarily drawn to scale, wherein: 
     FIG. 1A is a perspective view of an exemplary drill bit incorporating one or more drill bit cutters of the invention; 
     FIG. 1B is an isometric view of an exemplary drill bit cutter of the invention; 
     FIG. 2 is an isometric exploded view of an exemplary drill bit cutter of the invention; 
     FIG. 3 is a cross-sectional side view of a drill bit cutter of the invention, as taken along line  3 — 3  of FIG. 2; 
     FIG. 4 is a cross-sectional side view of a drill bit cutter of the invention, as taken along line  4 — 4  of FIG. 2; 
     FIG. 5 is an isometric exploded view of another exemplary drill bit cutter of the invention; 
     FIG. 6 is a cross-sectional side view of another exemplary drill bit cutter of the invention, as taken along line  6 — 6  of FIG. 5; 
     FIG. 7 is a cross-sectional side view of another exemplary drill bit cutter of the invention, as taken along line  7 — 7  of FIG. 5; 
     FIG. 8 is a plan view of an interface between a diamond table and a substrate of an additional exemplary drill bit cutter of the invention and FIG. 8A is a plan view of a variant of the interface of FIG. 8; 
     FIG. 9 is a plan view of an interface between a diamond table and a substrate of another exemplary drill bit cutter of the invention; 
     FIG. 10 is a plan view of an interface between a diamond table and a substrate of an additional exemplary drill bit cutter of the invention; 
     FIG. 11 is an isometric exploded view of another drill bit cutter of the invention; 
     FIG. 12 is a plan view of an interfacial area on a substrate of another drill bit cutter of the invention; 
     FIG. 13 is a cross-sectional side view of a substrate of another drill bit cutter of the invention, as taken along line  13 — 13  of FIG. 12; 
     FIG. 14 is a cross-sectional side view of a substrate of another drill bit cutter of the invention, as taken along line  14 — 14  of FIG. 12; 
     FIG. 15A is a front view of another drill bit cutter embodying the present invention; 
     FIG. 15B is a front view of yet another drill bit cutter embodying the present invention; and 
     FIG. 16 is an isometric exploded view of yet another drill bit cutter embodying the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The several illustrated embodiments of the invention depict various features which may be incorporated into a drill bit cutter in a variety of combinations. 
     The invention is a superabrasive drill bit cutter  20  such as a polycrystalline diamond compact (PDC) which has a particular three-dimensional interface  50  between superabrasive, or diamond, table  30  and substrate  40 . The interface  50  between the superabrasive layer or table  30  and the substrate  40  is configured to enable optimization of the radial and circumferential compressive stresses of the diamond layer or table  30  by the substrate  40 . 
     It should be understood that when the diamond table  30  and substrate  40  are joined, or stated differently, cojoined at a periphery, to form interface  50 , therebetween is substantially completely filled, i.e. there are preferably essentially no spaces remaining unfilled between the superabrasive diamond, or compact, table and the substrate material. 
     In FIGS. 1A and 1B is shown an exemplary, but not limiting, rotary drill bit  10  which incorporates at least one cutting element or drill bit cutter  20  of the invention. The illustrated drill bit  10  is known in the art as a fixed cutter or drag bit useful for drilling in earth formations, and is particularly suitable for drilling oil, gas, and geothermal wells. Cutting elements  20  of this invention may be advantageously used in any of a wide variety of drill bit  10  configurations which use cutting elements. Drill bit  10  includes a bit shank  12  having a tapered pin end  14  for threaded connection to a drill string, not shown, and also includes a body  16  having a face  18  on which cutting elements  20  may be secured. Bit  10  typically includes a series of nozzles  22  for directing drilling mud to the face  18  of body  16  for removal of formation cuttings to the bit gage  24  and to facilitate passage of cuttings through junk slots  26 , past the bit shank  12  and up the annulus between the drill string and the well bore toward the surface or to the surface to be discharged. It should be understood that cutting elements of the present invention, including cutting elements  20 , can be installed in roller-cone style drill bits wherein cutting elements are preferably installed on a rotatable roller-cone so as to movingly engage and cut the formation. 
     As depicted in FIGS. 2 through 4, a typical cutter  20  of the invention is cylindrical about longitudinal central axis  28  thereof Cutter  20  comprises a diamond table  30  with cutting face  34  and an interfacial surface  32  adjacent an interfacial surface  42  of substrate  40  that is able to withstand high applied drilling forces because of a high strength of mutual affixation between the diamond table  30  and substrate  40  provided by the present invention. The interfacial surfaces  32  and  42 , when taken together, are considered to be the interface  50  between diamond table  30  and substrate  40 . Interface  50  is generally non-planar, i.e., having three-dimensional characteristics, and includes portions of diamond table  30  which extend into and are accommodated by substrate  40 , and vice versa. The table  30  may be formed of diamond, a diamond composite, or other superabrasive material. Substrate  40  is typically formed of a hard material such as a carbide, and preferably a tungsten carbide. 
     As shown in FIGS. 2-4, cutter  20  has a three-dimensional substrate surface pattern  46  which mates, or cojoins, with three-dimensional diamond table surface pattern  36 . 
     In accordance with the invention, surface patterns  36 ,  46  comprise complementary raised, or protrusive, portions  52  and depressed, or receptive, portions  54  which include at least one annular member, such as complementary annular members  60 A,  60 B of which individual annular members can be circular, polygonal, or a combination of both and which are positioned about a pattern axis  48 . Pattern axis  48  may coincide with cutter central axis  28 . Each annular, circular, polygonal, or combination thereof, member  60  comprises a ring; i.e. it has a relatively thin radial width  78  preferably less than or approximately equal to the thickness of diamond table  30 . A plurality of radial members  70  generally radiates outwardly from pattern axis  48 , each radial member  70  intersecting the annular member, or members,  60 . Furthermore, radial members  70  may either have a constant or changing width  82  with width  82  being about 0.04 to 0.4 times the cutter diameter  80 . Stated differently, width  82  preferably does not exceed the approximate maximum thickness of diamond table  30 . However, width  82  can exceed the preferred ranges if desired. 
     The number of radial members  70  may vary from about three to about twenty-five or more. Typically, the number of radial members  70  is about six to fifteen, depending upon suitability for the particular usage conditions. 
     As shown in the embodiment of FIGS. 2-4, two concentric polygonal annular members  60 A,  60 B are uniformly joined by radial members  70 , wherein neither the circular, nor annularly shaped, members  60 A,  60 B, or radial members  70  extends outwardly to the periphery  56  of cutter  20 . In these figures, polygonal annular members  60 A,  60 B and intersecting radial members  70  project from diamond table  30 . 
     Also illustrated in FIGS. 2-4 is another feature, wherein diamond table  30  has a peripheral rim  38  which extends downwardly into substrate  40  to circumscribe it. This leaves a raised, or protrusive, portion  58  of substrate  40  which will ultimately prestress the polygonal surface pattern  36  of diamond table  30  in compression upon the solidification and subsequent cooling and depressurization of cutter  20  during the preferred post high-temperature, high-pressure manufacturing process thereof. 
     A preferred feature of the present invention is the exclusion of radial members  70  extending within the generally innermost portion of annular member  60 A. 
     Surface patterns  36 ,  46  may have one or, alternatively, a plurality of concentric or non-concentric polygonal annular members  60 A,  60 B with at least four sides  66 . Preferably, polygonal annular members  60  have at least six sides  66 . 
     Radial members  70  and annular/circular/polygonal members  60 A,  60 B in general are preferably connected at junctions such that the diamond table  30  is in nearly uniform radial and circumferential compression so as to be compressively prestressed. Preferably, the inner portion of the diamond table  30  is placed in radial compression and the exterior of the diamond table  30  is placed in circumferential prestress so that the net result is that the disclosed cutter has a diamond table  30  which has a more favorable state of compression. Such prestressing occurs upon cooling cutter  20  from a high-temperature, high-pressure manufacturing process used in forming the superabrasive compact of the cutter onto the preformed carbide substrate. 
     Any irregularity, or three-dimensional configuration, at the interface may be looked upon as both a projection, or protrusion, of the substrate into the diamond table and the inverse, i.e., a projection, or protrusion, of the diamond table into the substrate. If one defines the interfacial space as that between the two planes defining the relative penetration of each member (table, substrate) into the other member, either the material volume of the diamond table or that of the substrate may predominate, or they may occupy substantially equal portions of the interfacial space. 
     FIGS. 5-7 depict an embodiment in which polygonal annular members  60 A,  60 B and radial members  70  project from substrate  40 , i.e., the inverse of FIGS. 2-4. Another feature shown in FIGS. 5-7 is an absence of peripheral rim  38 . In this embodiment, a spider web-shaped raised, or protrusive surface, pattern  46  of substrate  40  places trapezoidal portions  64  of the diamond table  30  and a central portion  62  into a compressively prestressed condition. 
     FIG. 8 illustrates a “wheel” surface pattern  46  having radial members or spokes  70  connecting an inner annular circular member  60 A and an outer annular circular member  60 B. The entire pattern  61  is spaced from periphery  56  of substrate  40 . FIG. 8A illustrates another “wheel” surface pattern  46  having radial members or spokes  70  connecting an inner annular polygonal member  60 A and an outer annular circular member  60 B. The entire pattern  61 ′ is spaced from periphery  56  of substrate  40 . 
     FIG. 9 depicts a surface pattern  46  having three concentric circular annular members  60 A,  60 B, and peripheral rim  38 , with a plurality of radial members or spokes  70  intersecting and connected to each annular circular member  60 A,  60 B. 
     FIG. 10 shows another feature which may be used. In this embodiment, surface pattern  46  is placed off-center of cutter substrate  40 . Thus, pattern axis  48  and central cutter axis  28  are displaced from each other. In practice, such may be used when the cutter is to be used where impinging forces  72  are applied over a relatively small area, and the pattern axis  48  is closer to the direction from which the forces impinge. 
     If desired, a surface pattern  36 ,  46  utilizing the combination of both a circular annular member  60 A and a polygonal annular member  60 B may be used, not only with respect to the embodiment shown in FIG. 10, or in the other figures but with all embodiments of the present invention. In FIGS. 11-14, another embodiment of the invention is shown with a gear-configured interface  50  of intermeshing diamond table surface pattern  36  and substrate surface pattern  46 . Each of diamond table  30  and substrate  40  has a series of radially projecting members  70  which intersect the outer cutter periphery  56  and an inner circular annular member  60 . The substrate  40  is shown with an annular depression  74  within the inner portion of circular annular member  60 . Diamond table  30  has a complementary projecting member  76  which fits into and is received by annular depression  74 . The particular pattern may be varied in many ways, provided a series of radial members  70  intersects with at least one circular or polygonal annular member  60 . For example, projecting radial members  70  of substrate  40  may be of the same or differing shape, width, and depth as the projecting radial members  70  of the diamond table  30 . 
     For ease of illustration, the drawings generally show the interfacial surfaces  32 ,  42  as having sharp corners. It is understood, however, that in practice, it is generally desirable to have rounded or bevelled corners at the intersections of planar surfaces, particularly in areas where cracking may propagate. Furthermore, the various circular and polygonal annular members  60  shown in the figures are illustrative, and annular members  60  may also have geometries incorporating arcuate, or curved, segments combined with straight segments in an alternating fashion, for example, to produce an irregularly shaped, generally annular member if desired. 
     The substrate  40  and/or diamond table  30  may be of any cross-sectional configuration, or shape, including circular, polygonal and irregular. In addition, the diamond table  30  may have a cutting face  34  which is flat, rounded, or of any other suitable configuration. 
     FIG. 15A depicts another embodiment of the present invention wherein a cutter  90  is particularly suitable for, but not limited to, use as a rolling cone insert in a roller cone, or rock, drill bit. Cutter  90  has a carbide, preferably tungsten carbide, substrate  92  and has a superabrasive or diamond table, or compact,  94  shown in phantom placed upon substrate  92  in the manners known and discussed above. The contoured interface between diamond compact  94  and substrate  92  is provided with generally radially oriented grooves  98  preferably extending from preferably planar center  96  toward the outer circumference of cutter  90 . Generally annular, or concentric, grooves  100  extending circumferentially preferably intersect and segment radial grooves  98  into a plurality of interrupted, generally radially oriented grooves to provide the desired compressive prestress within diamond compact  94  and in the vicinity of the interface. More particularly, the interior portion of diamond table, or compact,  94  is preferably placed in radial compression and the exterior portion of the diamond table, or compact,  94  is placed in circumferential compression with the net result of generally biaxial compressive prestresses being distributed throughout the diamond table, or compact,  94  and the interface between substrate  92  to better withstand the various types of primarily tensile forces acting on the cutter when placed in service. Furthermore, radially oriented grooves  98  and/or annular grooves  100  may alternatively be configured to be ribs protruding from substrate  92  and received within diamond compact  94  with such a configuration being shown in FIG.  15 B. As shown in FIG. 15B, cutter  90 ′ can be constructed with the same materials and processes as described with respect to cutter  90  but instead has a substrate  92 ′ also having a diamond table, or compact,  94 ′ shown in phantom placed upon substrate  92 ′ as known in the art. However, the contoured interface between diamond compact  94 ′ and substrate  92 ′ is provided with generally radially oriented raised ribs, or ridges,  98 ′ preferable extending from preferably raised center  96 ′ toward the outer circumference of cutter  90 ′. Generally annular, or concentric, raised portions, referred to as ribs, or ridges,  100 ′ extending circumferentially preferably intersect and join with radial ridges  98 ′ to achieve the same results as described with respect to cutter  90  of FIG.  15 A. In a like manner, diamond compact  94 ′ would have an interface accommodating the raised ridges  98 ′,  100 ′ of substrate  92 ′ but in a reverse pattern as described earlier. When constructing a cutter in accordance with alternative cutter  90 ′, care must be exercised not to allow the ribs, or raised portions, to protrude too far into diamond compact  94 ′ so as to provide a relatively thin, or reduced thickness, compact  94 ′ where such raised portions are placed to make the superabrasive table, or compact,  94 ′ vulnerable to localized chipping or breakage. 
     As can now be appreciated, a cutter interface embodying the present invention provides a cutter which has greater resistance to fracture, spalling, and delamination of the diamond table, or compact. 
     Referring now to FIG. 16, which provides an exploded illustration of yet another cutter embodying the present invention, cutter  102  includes a substrate  104  having a superabrasive compact, or diamond table,  204  removed from interface  150  which includes substrate interface surface  106  having a pattern  107  and diamond table interface surface  206  having a mutually complementary but reverse pattern  207 . Substrate interface pattern  107  includes circumferential rim portion  108  and an inwardly sloping circumferential wall  110  leading to a first raised portion  112 . First raised portion  112  preferably has a generally planar surface, but is not limited to such. Inward of first raised portion  112  is a concentric or annular groove  114  and inward of groove  114  is a second raised portion  116 . As can be seen in FIG. 16, a full-diameter, generally rectangularly shaped slot  118  extending to a preselected depth divides interface pattern  107  into symmetrical halves with slot  118  having walls  120  set apart by a width W. Slot  118  is preferably provided with a generally planar bottom surface  122 . 
     In a reverse fashion, the interfacial pattern  207  of interface surface  206  of diamond table  204  is provided with a peripheral rim  208  which cojoins with rim portion  108 , and sloping wall  210  cojoins with sloping wall  110 . First recessed portion  212  separated by protruding concentric ridge  214  and second recessed portion  216  respectively accommodate raised portions  112  and  116  and groove  114  of substrate  104 . Also extending across the full diameter pattern  207  of interface surface  206  of diamond table  204  is a generally rectangular tang, or tab,  218  to correspond and fill rectangular slot  118 . Tang walls  220  likewise cojoin with slot walls  120  and tang surface  222  cojoins with bottom surface  122  of slot  118 . Tang  218 , in combination with slot  118 , in effect provides the previously described interfacial stress optimization benefits of the radially extending grooves and complementary raised portions of the cutters illustrated in the previous drawings. 
     Preferably, width W of slot  118 /tang  218  ranges from approximately 0.04 to 0.4 times the diameter of cutter  102 . However, width W of slot  118 /tang  218  may be of any suitable dimension. Preferably, the depth of slot  118 /tang  218  does not exceed the approximate thickness of superabrasive table  204  extending over substrate  104  in other regions than those directly above slot  118 /tang  218 . In other words, the approximate depth of slot  118 /tang  218  preferably does not exceed the approximate minimum thickness of superabrasive table  204 . However, slot  118 /tang  218  can have any depth deemed suitable. Although slot  118  and tang  218  have been shown to have the preferred generally rectangular cross-sectional geometry including generally planar walls  120 ,  220  and surfaces  122 ,  222 , slot  118 /tang  218  can be provided with other cross-sectional geometry if desired. For example, walls  120  can be generally planar but be provided with radiused corners proximate bottom surface  122  to form a more rounded cross-section. Walls  120  and bottom surface  122  can further be provided with non-planar configurations if desired so as to be generally curved, or irregularly shaped. 
     Correspondingly, tang  218  can be provided with radiused edges where walls  220  intersect surface  222  to provide a tang of a generally more curved cross section than the preferred generally rectangular cross section as shown. Walls  220  and surface  222  can further be provided with non-planar configurations to correspond and complement non-planar configurations chosen for walls  120  and bottom surface  122  of slot  118 . 
     Although cutter  102  is shown with the interfacial end of substrate  104  being generally planar, or flat, across raised portions  116 ,  112  and rim portion  108 , the general overall configuration of substrate interface surface  106  can be dome, or hemispherically, shaped, such as the interfacial ends of substrates  92  and  92 ′ of cutters  90  and  90 ′ respectively illustrated in FIGS. 15A and 15B, yet maintain the preferred interfacial pattern shown in FIG. 16 or variations thereof Similarly, superabrasive table  204  would be reversely configured and shaped to form a generally dome-shaped table, such as tables  94  and  94 ′, and would be disposed over and having a complementary diamond table interface surface  206  to accommodate such a modified substrate interface surface  106 . A modified cutter having such a hemispherically shaped substrate and superabrasive table is particularly suitable for installation and use on roller cone style drill bits in which a plurality of cutters is installed on one or more roller cones so as to be moveable with respect to the drill bit while engaging the formation. 
     Thus, it can be appreciated that a single, large, radially or diametrically extending protrusion and a complementarily configured recessed portion can also be used to achieve the benefits of the present invention. 
     As with cutters  90  and  90 ′, illustrated in FIGS. 15A and 15B respectively, cutter  102  can have patterns  107  and  207  reversed. That is, a tang protruding upwardly from substrate interface surface  106  is disposed into a receiving slot in diamond table interface surface  206 . Similarly, raised portions  112  and  116  could be instead recessed portions to accommodate complementary raised portions extending from diamond table  204 . 
     It will be apparent that the present invention may be embodied in various combinations of features, as the specific embodiments described herein are intended to be illustrative and not restrictive, and other embodiments of the invention may be devised which do not depart from the spirit and scope of the following claims and their legal equivalents.

Summary:
A cutter for a drill bit has a superabrasive member joined to a substrate at a three-dimensional interface. The three-dimensional interface comprises a protrusive pattern of interconnected elements comprising projections of the superabrasive member into the substrate and vice versa. The protrusive pattern comprises at least one generally annular member intersected by a series of generally radially extending members for distributing stresses along the interface, enhancing compressive strength, and enabling optimization of the magnitudes and locations of beneficial residual stresses in the superabrasive member and in the vicinity of the substrate.