RAISED CUTTING SURFACES

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

[0001] The present disclosure generally relates to superabrasive cutters for earth boring bits with multiple raised cutting surfaces.

Description of the Related Art

[0002] US 8,037,951 discloses a cutter for a drill bit used for drilling wells in a geological formation that includes an ultra hard working surface and a chamfer along an edge of the working surface, wherein the chamfer has a varied geometry along the edge. The average geometry of the chamfer varies with cutting depth. A depression in the shaped working surface is oriented with the varied chamfer and facilitates forming the varied chamfer. A non-planar interface has depressions oriented with depressions in the shaped working surface to provide support to loads on the working surface of the cutter when used.

[0003] US 8,132,633 discloses a self positioning cutter element and cutter pocket for use in a downhole tool having one or more cutting elements. The self positioning cutter element includes a substrate and a wear resistant layer coupled to the substrate. The cutter element includes a cutting surface, a coupling surface, and a longitudinal side surface forming the circumferential perimeter of the cutter element and extending from the cutting surface to the coupling surface. The cutter element has one or more indexes formed on at least a portion of the coupling surface. In some embodiments, the index also is formed on at least a portion of the longitudinal side surface. Hence, the coupling surface is not substantially planar. Additionally, at least a portion of the longitudinal side surface does not form a substantially uniform perimeter. The cutter pocket also is indexed to correspond and couple with the indexing of the cutter element.

[0004] US 8,739,904 discloses cutters for a drill bit wherein the cutters have at least one groove in a face of a superabrasive table of the cutters. The cutters may also include ribs adjacent to the at least one groove. [0005] US 9,103,174 discloses cutting elements including a superabrasive table, at least one indentation in a cutting face of the superabrasive table, and at least one spoke extending radially across at least a portion of the at least one indentation. Earth-boring drill bits include such a cutting element. Methods of forming a cutting element include forming a superabrasive table having at least one such indentation and at least one such spoke, and positioning the superabrasive table on a substrate.

[0006] US 2015/0259988 discloses (see Figures 55-57) a cutting element including a substrate, an upper surface of the substrate including a crest, the crest transitioning into a depressed region, and an ultrahard layer on the upper surface, thereby forming a non-planar interface between the ultrahard layer and the substrate. A top surface of the ultrahard layer includes a cutting crest extending along at least a portion of a diameter of the cutting element, the top surface having a portion extending laterally away from the cutting crest having a lesser height than a peak of the cutting crest.

SUMMARY OF THE DISCLOSURE

[0007] The present disclosure generally relates to superabrasive cutters for earth boring bits with multiple raised cutting surfaces. In one embodiment, a cutter for a drill bit includes: a substrate for mounting the cutter to the drill bit; and a cutting table. The cutting table: is made from a superhard material, is mounted to the substrate, has an interface with the substrate at a lower end thereof, and has a working face at an upper end thereof. The working face has a protruding center section and a plurality of protruding ribs. Each rib extends radially outward from the center section to a side of the cutting table. Each rib has a triangular profile formed by a pair of inclined side surfaces and a ridge connecting opposing ends of the side surfaces. The working face further has a plurality of recessed bases located between adjacent ribs and each extending inward from the side.

[0008] In another embodiment, a cutter for a drill bit includes: a substrate for mounting the cutter to the drill bit; and a cutting table. The cutting table: is made from a superhard material, is mounted to the substrate, has an interface with the substrate at a lower end thereof, and has a working face at an upper end thereof. The working face has a protruding center section and a plurality of protruding ribs. Each rib extends spirally outward from the center section to a side of the cutting table. Each rib has a triangular profile formed by a pair of inclined side surfaces and a ridge connecting opposing ends of the side surfaces. The working face further has a plurality of recessed bases located between adjacent ribs and each extending inward from the side.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

[0010] Figure 1A illustrates a cutter, according to one embodiment of the present disclosure. Figure 1 B illustrates a working face of the cutter.

[0011] Figure 2A is a side view of the cutter. Figure 2B is a cross-sectional view of the cutter.

[0012] Figure 3A illustrates a first alternative cutter, according to another embodiment of the present disclosure. Figure 3B illustrates a drill bit having a plurality of the first alternative cutters.

[0013] Figure 4A illustrates a second alternative cutter, according to another embodiment of the present disclosure. Figure 4B is a side view of the second alternative cutter.

[0014] Figure 5A illustrates a third alternative cutter, according to another embodiment of the present disclosure. Figure 5B is a side view of the third alternative cutter.

[0015] Figure 6A is a side view of a fourth alternative cutter, according to another embodiment of the present disclosure. Figure 6B is a cross-sectional view of the fourth alternative cutter. [0016] Figure 7A illustrates a working face of a fifth alternative cutter, according to another embodiment of the present disclosure. Figure 7B is a side view of the fifth alternative cutter.

[0017] Figure 8A illustrates a working face of a sixth alternative cutter, according to another embodiment of the present disclosure. Figure 8B is a side view of the sixth alternative cutter.

DETAILED DESCRIPTION

[0018] Figure 1A illustrates a cutter 1 , according to one embodiment of the present disclosure. Figure 1 B illustrates a working face 5 of the cutter 1. Figure 2A is a side view of the cutter 1. Figure 2B is a cross-sectional view of the cutter 1. The cutter 1 may include a cutting table 2 mounted to a cylindrical substrate 3. The cutting table 2 may be circular and the substrate 3 may be a circular cylinder. The cutting table 2 may be made from a superhard material, such as polycrystalline diamond, and the substrate 3 may be made from a hard material, such as a cermet, thereby forming a compact, such as a polycrystalline diamond compact. The cermet may be a cemented carbide, such as a group VIIIB metal-tungsten carbide. The group VIIIB metal may be cobalt. The cutting table 2 may be formed and mounted to the substrate 3 simultaneously in a single step sintering process or the cutter 1 may be made in a two-step process.

[0019] The cutting table 2 may have an interface 4 with the substrate 3 at a lower end thereof and the working face 5 at an upper end thereof. The substrate 3 may have the interface 4 at an upper end thereof and a lower end for being received in a pocket of a drill bit 15 {Figure 3B). The pocket end of the substrate 3 may have a chamfer 3c formed in a periphery thereof. The interface 4 may have a planar outer rim 4r, an inner non-planar surface 4c, and a shoulder 4s connecting the outer rim and the inner non-planar surface. The non-planar surface 4c of the cutting table 2 may be concave and the non-planar surface of the substrate 3 may be convex.

[0020] The working face 5 may have a plurality of recessed bases 6a-c, a protruding center section 7, a plurality of protruding ribs 8a-c, and an outer edge 9. Each base 6a-c may be planar and perpendicular to a longitudinal axis of the cutter 1. The bases 6a-c may be located between adjacent ribs 8a-c and may each extend inward from a side 1 1 of the cutting table 2. The outer edge 9 may extend around the working face 5 and may have constant geometry. The outer edge 9 may include a chamfer 9c located adjacent to the side 1 1 and a round 9r located adjacent to the bases 6a-c and ribs 8a-c.

[0021] Each rib 8a-c may extend radially outward from the center section 7 to the side 1 1. Each rib 8a-c may be spaced circumferentially around the working face 5 at regular intervals, such as at one-hundred twenty degree intervals. Each rib 8a-c may have a triangular profile formed by a pair of curved transition surfaces 10t, a pair of linearly inclined side surfaces 10s, and a round ridge 10r. Each transition surface 10t may extend from a respective base 6a-c to a respective side surface 10s. Each ridge 10r may connect opposing ends of the respective side surfaces 10s. An elevation of each ridge 10r may be constant.

[0022] An elevation of each ridge 10r may range between twenty percent and seventy-five percent of a thickness of the cutting table 2. A width of each rib 8a-c may range between twenty and sixty percent of a diameter of the cutting table 2. A radial length of each rib 8a-c from the side 1 1 to the center section 7 may range between fifteen and forty-five percent of the diameter of the cutting table 2. An inclination of each side surface 10s relative to the respective base 6a-c may range between fifteen and fifty degrees. A radius of curvature of each ridge 10r may range between one-eighth and five millimeters or may range between one-quarter and one millimeter.

[0023] The center section 7 may have a plurality of curved transition surfaces 7t, a plurality of linearly inclined side surfaces 7s, and a plurality of round edges 7r. Each set of the features 7r,s,t may connect respective features 10r,s,t of one rib 8a-c to respective features of an adjacent rib along an arcuate path. The elevation of the edges 7r may be equal to the elevation of the ridges 10r. The center section 7 may further have a plateau 7p formed between the edges 7r. The plateau 7p may have a slight dip formed therein.

[0024] Figure 3A illustrates a first alternative cutter 12, according to another embodiment of the present disclosure. The first alternative cutter 12 may be similar to the cutter 1 except for having an orienting profile 14 formed in a pocket end of a substrate 13. The orienting profile 14 may be polygonal and formed by a plurality of flats 14f and a plurality of round portions 14r for mating with a complementary profile (not shown) formed in the pocket of the drill bit 15. The orienting profile 14 may have a pair of flats 14f and rounds 14r for each rib 8a-c. Each round portion 14r may be aligned with a respective rib 8a-c. The complementary profile of the pocket may be oriented such that when the orienting profiles 14 are engaged, one of the ribs 8a-c is oriented to engage a formation {not shown) for drilling of a wellbore using the drill bit 15. Once the drill bit 15 has become worn, the first alternative cutter 12 may be demounted from the drill bit and rotated to index the orienting profile, and then reengaged with the pocket of drill bit, thereby orienting a new one of the ribs 8a-c to engage the formation.

[0025] Alternatively, the orienting profile 14 may include protrusions formed in the pocket end of the substrate 13 instead of the flats 14f and the pocket of the drill bit may have mating grooves formed therein or vice versa.

[0026] Figure 3B illustrates the drill bit 15 having a plurality of the first alternative cutters 12. The drill bit 15 may include a bit body 16, a shank 17, a cutting face, and a gage section. The shank 17 may be tubular and include an upper piece and a lower piece connected to the upper piece, such as by threaded couplings secured by a weld. The bit body 16 may be made from a composite material, such as a ceramic and/or cermet body powder infiltrated by a metallic binder. The bit body 16 may be mounted to the lower shank piece during molding thereof. The shank 17 may be made from a metal or alloy, such as steel, and have a coupling, such as a threaded pin, formed at an upper end thereof for connection of the drill bit 15 to a drill collar (not shown). The shank 17 may have a flow bore formed therethrough and the flow bore may extend into the bit body 16 to a plenum thereof. The cutting face may form a lower end of the drill bit 15 and the gage section may form at an outer portion thereof.

[0027] Alternatively, the bit body 16 may be metallic, such as being made from steel, and may be hardfaced. The metallic bit body may be connected to a modified shank by threaded couplings and then secured by a weld or the metallic bit body may be monoblock having an integral body and shank.

[0028] The cutting face may include one or more primary blades 18p, one or more secondary blades 18s, fluid courses formed between the blades, the first alternative cutters 12, and a plurality of backup cutters 19. The cutting face may have one or more sections, such as an inner cone, an outer shoulder, and an intermediate nose between the cone and the shoulder. The blades 18p,s may be disposed around the cutting face and each blade may be formed during molding of the bit body 16 and may protrude from the bit body. The primary blades 18p may each extend from a center of the cutting face, across the cone and nose sections, along the shoulder section, and to the gage section. The secondary blades 18s may each extend from a periphery of the cone section, across the nose section, along the shoulder section, and to the gage section. Each blade 18p,s may extend generally radially across the cone (primary only) and nose sections with a slight spiral curvature and along the shoulder section 4s generally longitudinally with a slight helical curvature. Each blade 18p,s may be made from the same material as the bit body 16.

[0029] Alternatively, the blades 18p,s may be radially straight (no spiral curvature).

[0030] The first alternative cutters 12 may be leading cutters for each blade 18p,s. The first alternative cutters 12 may be mounted in pockets formed along leading edges of the blades 18p,s, such as by brazing. The backup cutters 19 may be mounted in pockets formed along of portions of the blades 18p,s in the shoulder section, such as by brazing. The backup cutters 19 may extend into portions of the blades 18p,s in the nose section. Each backup cutter 19 may be aligned with or slightly offset from a respective first alternative cutter 12. Each backup cutter 19 may include a superhard planar cutting table, such as polycrystalline diamond, attached to a hard substrate, such as a cermet, thereby forming a compact, such as a polycrystalline diamond compact (PDC). The cermet may be a carbide cemented by a Group VI 11 B metal. [0031] One or more ports 20 may be formed in the bit body 16 and each port may extend from the plenum and through the bottom of the bit body to discharge drilling fluid (not shown) along the fluid courses. A nozzle 21 may be disposed in each port 20 and fastened to the bit body 16. The ports 20 may include an inner set of one or more ports disposed adjacent to the center of the cutting face and an outer set of one or more ports disposed at the periphery of the cone section.

[0032] The gage section may include a plurality of gage pads 22 and junk slots formed between the gage pads. The junk slots may be in fluid communication with the fluid courses formed between the blades 18p,s. The gage pads 22 may be disposed around the gage section and each pad may be formed during molding of the bit body 16 and may protrude from the outer portion of the bit body. Each gage pad 22 may be made from the same material as the bit body 16 and each gage pad may be formed integrally with a respective blade 18p,s.

[0033] Alternatively, the drill bit 15 may have non-profiled pockets along the leading edges of the blades 18p,s and the cutters 1 may be used therewith instead of the first alternative cutters 12. Each cutter 1 may be held at the proper orientation during brazing in the respective pocket.

[0034] Figure 4A illustrates a second alternative cutter 23, according to another embodiment of the present disclosure. Figure 4B is a side view of the second alternative cutter 23. The second alternative cutter 23 may include a cutting table 24 attached to a cylindrical substrate 25. The cutting table 24 may be circular and the substrate 25 may be a circular cylinder. The cutting table 24 and substrate 25 may be made from the materials discussed above for the cutting table 2 and substrate 3, respectively.

[0035] The cutting table 24 may have the interface 4 with the substrate 25 at a lower end thereof and a working face at an upper end thereof. The substrate 25 may have the interface 4 at an upper end thereof and a lower end for being received in the pocket of the drill bit 15. The pocket end of the substrate 25 may have the chamfer 3c formed in a periphery thereof. [0036] The working face may have a plurality of recessed bases 26a-c, a protruding center section 27, a plurality of protruding ribs 28a-c, and an outer edge 29. Each base 26a-c may be parabolic. The bases 26a-c may be located between adjacent ribs 28a-c and may each extend inward from a side 31 of the cutting table 24. The outer edge 29 may extend around the working face and may have constant geometry. The outer edge 29 may be a chamfer connecting the side 31 to the cutting face.

[0037] Each rib 28a-c may extend radially outward from the center section 27 to the side 31. Each rib 28a-c may be spaced circumferentially around the working face at regular intervals, such as at one-hundred twenty degree intervals. Each rib 28a-c may have a triangular profile formed by a pair of linearly inclined side surfaces 30s and a round ridge 30r. Each side surface 30s may extend from a respective base 26a-c to a respective ridge 30r. Each ridge 30r may connect opposing ends of the respective side surfaces 30s. An elevation of each ridge 30r may increase from the side 31 to the center section 27.

[0038] A maximum elevation of each ridge 30r may range between twenty percent and seventy-five percent of a thickness of the cutting table 24. A width of each rib 28a-c may range between twenty and sixty percent of a diameter of the cutting table 24. A radial length of each rib 28a-c from the side 31 to the center section 27 may range between fifteen and forty-five percent of the diameter of the cutting table 24. An inclination of each side surface 30s relative to the respective base 26a-c may range between fifteen and fifty degrees. A radius of curvature of each ridge 30r may range between one-eighth and five millimeters or may range between one-quarter and one millimeter. An inclination angle of each ridge 30r may range between one and ten degrees.

[0039] The center section 27 may have a plurality of linearly inclined side surfaces 27s, a plurality of parabolic faces 27f, a plurality of termini 27t, and a plateau 27p. Each set of the features 27f,s may connect respective features 30s of one rib 28a-c to respective features of an adjacent rib along a curved path. Each terminus 27t may receive an inner end of a respective ridge 30r. The termini 27t may be formed between the faces 27f. The plateau 27p may be located adjacent to inner edges of the parabolic faces 27f and the termini 27t. The plateau 27p may have an elevation slightly greater than the maximum elevation of the ridges 30r.

[0040] Alternatively, the pocket end of the substrate 25 may have the orienting profile 14 formed therein.

[0041] Figure 5A illustrates a third alternative cutter 33, according to another embodiment of the present disclosure. Figure 5B is a side view of the third alternative cutter. The third alternative cutter 33 may include a cutting table 34 attached to a cylindrical substrate 35. The cutting table 34 may be circular and the substrate 35 may be a circular cylinder. The cutting table 34 and substrate 35 may be made from the materials discussed above for the cutting table 2 and substrate 3, respectively.

[0042] The cutting table 34 may have the interface 4 with the substrate 35 at a lower end thereof and a working face at an upper end thereof. The substrate 35 may have the interface 4 at an upper end thereof and a lower end for being received in the pocket of the drill bit 15. The pocket end of the substrate 35 may have the chamfer 3c formed in a periphery thereof.

[0043] The working face may have a plurality of recessed bases 36a-c, a protruding center section 37, a plurality of protruding ribs 38a-c, and an outer edge 39. Each base 36a-c may be parabolic. The bases 36a-c may be located between adjacent ribs 38a-c and may each extend inward from a side 41 of the cutting table 34. The outer edge 39 may extend around the working face and may have constant geometry. The outer edge 39 may be a chamfer connecting the side 41 to the cutting face.

[0044] Each rib 38a-c may extend radially outward from the center section 37 to the side 41. Each rib 38a-c may be spaced circumferentially around the working face at regular intervals, such as at one-hundred twenty degree intervals. Each rib 38a-c may have a triangular profile formed by a pair of linearly inclined side surfaces 40s and a round ridge 40r. Each side surface 40s may extend from a respective base 36a-c to a respective ridge 40r. Each ridge 40r may connect opposing ends of the respective side surfaces 40s. An elevation of each ridge 40r may decrease from the side 41 to the center section 37.

[0045] A maximum elevation of each ridge 40r may range between twenty percent and seventy-five percent of a thickness of the cutting table 34. A width of each rib 38a-c may range between twenty and sixty percent of a diameter of the cutting table 34. A radial length of each rib 38a-c from the side 41 to the center section 37 may range between thirty and fifty percent of the diameter of the cutting table 34. An inclination of each side surface 40s relative to the respective base 36a- c may range between fifteen and fifty degrees. A radius of curvature of each ridge 40r may range between one-eighth and five millimeters or may range between one- quarter and one millimeter. A declination angle of each ridge 40r may range between one and ten degrees.

[0046] The center section 37 may have a plurality of linearly inclined side surfaces 37s and a plateau 37p. Each side surface 37s may connect the respective side surface 40s of one rib 38a-c to a respective side surface of an adjacent rib along a curved path. The plateau 37p may include a plurality of trapezoidal faces disposed between inner ends of adjacent ridges 40r and a terminus receiving inner tips of the ridges. The plateau 37p may have an elevation slightly less than the minimum elevation of the ridges 40r.

[0047] Alternatively, the pocket end of the substrate 35 may have the orienting profile 14 formed therein.

[0048] Figure 6A is a side view of a fourth alternative cutter 42, according to another embodiment of the present disclosure. Figure 6B is a cross-sectional view of the fourth alternative cutter 42. The fourth alternative cutter 42 may be similar to the cutter 1 except for having a modified interface 45 between a substrate 44 and a cutting table 43 thereof. The substrate 44 may have the modified interface 45 at an upper end thereof and a lower end for being received in a pocket of the drill bit 15. The substrate upper end may have a planar outer rim 44r, an inner mound 44m for each rib 46a-c, and a shoulder 44s connecting the outer rim and each inner mound. A shape and location of the mounds 44m may correspond to a shape and location of the ribs 46a-c and a shape and location of the outer rim 44r may correspond to a shape and location of the bases 47a-c except that the mounds may not extend to a side of the substrate 44. Ridges of the mounds 44m may be slightly above the bases 47a,b (see dashed line in Figure 6B). A height of the mounds 44m may be greater than an elevation of the ribs 46a-c.

[0049] Alternatively, a ridge of each mound 44m may be level with or slightly below the bases 47a-c. Alternatively, any of the other cutters 12, 23, 33 discussed above may have the modified interface 45.

[0050] Figure 7A illustrates a working face of a fifth alternative cutter 48, according to another embodiment of the present disclosure. Figure 7B is a side view of the fifth alternative cutter 48. The fifth alternative cutter 48 may include a cutting table 49 attached to a cylindrical substrate 50. The cutting table 49 may be circular and the substrate 50 may be a circular cylinder. The cutting table 49 and substrate 50 may be made from the materials discussed above for the cutting table 2 and substrate 3, respectively.

[0051] The cutting table 49 may have either the interface {not shown, see interface 4) or the modified interface (not shown, see modified interface 45) with the substrate 50 at a lower end thereof and a working face at an upper end thereof. The substrate 50 may have either interface at an upper end thereof and a lower end for being received in the pocket of the drill bit 15. The pocket end of the substrate 50 may have the chamfer 3c formed in a periphery thereof and an orienting profile 51 formed therein. The orienting profile 51 may include one or more (pair shown) slots for mating with a complementary profile (not shown) formed in the pocket of the drill bit 15.

[0052] Alternatively, any of the other cutters 12, 23, 33, 42 discussed above may have the orienting profile 51.

[0053] The working face may have a plurality of recessed bases 52a-c, a protruding center section 53, a plurality of protruding ribs 54a-c, and an outer edge 55. Each base 52a-c may be parabolic. The bases 52a-c may be located between adjacent ribs 54a-c and may each extend inward from a side 56 of the cutting table 49. The outer edge 55 may extend around the working face and may have constant geometry. The outer edge 55 may be a chamfer connecting the side 56 to the cutting face.

[0054] Each rib 54a-c may extend radially outward from the center section 53 to the side 56. Each rib 54a-c may be spaced circumferentially around the working face at regular intervals, such as at one-hundred twenty degree intervals. Each rib 54a-c may have a triangular profile formed by a pair of curved transition surfaces, a pair of linearly inclined side surfaces, and a round ridge 57. Each transition surface may extend from a respective base 52a-c to a respective side surface. Each transition surface may terminate at the outer edge 55 as opposed to extending to the side 56. Each ridge 57 may connect opposing ends of the respective side surfaces.

[0055] An elevation of each ridge 57 may increase from the side 56 to the center section 53. The elevation of each ridge 57 may increase in a linear fashion at a portion adjacent to the edge 55 and then in a curved fashion as the ridge extends from the adjacent portion toward the center section 53. A ratio between a minimum elevation of the ridges 57 and a maximum elevation of the ridges may range between one-sixth and two-thirds.

[0056] A width of each rib 54a-c may increase from the side 56 to the center section 53. The width of each rib 54a-c may increase in a linear and step-wise fashion at a the edge 55 and then in a curved fashion as the rib extends from the edge toward the center section 53. A ratio between a minimum width of the ribs 54a- c and a maximum width of the ribs may range between one-sixth and two-thirds.

[0057] A maximum elevation of each ridge 57 may range between twenty percent and seventy-five percent of a thickness of the cutting table 49. A maximum width of each rib 54a-c may range between twenty and sixty percent of a diameter of the cutting table 49. A radial length of each rib 54a-c from the side 56 to the center section 53 may range between fifteen and forty-five percent of the diameter of the cutting table 49. An inclination of each side surface relative to the respective base 36a-c may range between fifteen and fifty degrees. A radius of curvature of each ridge 57 may range between one-eighth and five millimeters or may range between one-quarter and one millimeter. An inclination angle of the adjacent portion of each ridge 57 may range between ten and forty degrees. [0058] The center section 53 may have a plurality of curved transition surfaces, a plurality of linearly inclined side surfaces, and a plurality of round edges. Each set of the features may connect respective features of one rib 54a-c to respective features of an adjacent rib along an arcuate path. The elevation of the edges may be equal to the maximum elevation of the ridges 57. The center section 53 may further have a plateau formed between the edges. The plateau may have a slight dip formed therein.

[0059] Figure 8A illustrates a working face of a sixth alternative cutter 58, according to another embodiment of the present disclosure. Figure 8B is a side view of the sixth alternative cutter 58. The sixth alternative cutter 58 may include a cutting table 59 attached to a cylindrical substrate 60. The cutting table 59 may be circular and the substrate 60 may be a circular cylinder. The cutting table 59 and substrate 60 may be made from the materials discussed above for the cutting table 2 and substrate 3, respectively.

[0060] The cutting table 59 may have either the interface (not shown, see interface 4) or the modified interface (not shown, see modified interface 45) with the substrate 60 at a lower end thereof and a working face at an upper end thereof. The substrate 60 may have either interface at an upper end thereof and a lower end for being received in the pocket of the drill bit 15. The pocket end of the substrate 60 may have the chamfer 3c formed in a periphery thereof and one of the orienting profiles discussed above therein.

[0061] The working face may have a plurality of recessed bases 62a-c, a protruding center section 63, a plurality of protruding ribs 64a-c, and an outer edge 65. The bases 62a-c may be located between adjacent ribs 54a-c and may each extend inward from a side 61 of the cutting table 59. The outer edge 65 may extend around the working face and may have variable geometry. The outer edge 65 may be a round or chamfer connecting the side 61 to the cutting face.

[0062] Each rib 64a-c may extend spirally outward from the center section 63 to the side 61. The spiral curvature of the ribs 64a-c may be clockwise or counterclockwise. Each rib 64a-c may be spaced circumferentially around the working face at regular intervals, such as at one-hundred twenty degree intervals. Each rib 64a-c may have a triangular profile formed by a pair of curved transition surfaces, a pair of linearly inclined side surfaces, and a round ridge. Each transition surface may extend from a respective base 62a-c to a respective side surface. Each ridge may connect opposing ends of the respective side surfaces. An elevation of each ridge may be constant.

[0063] An elevation of each ridge may range between twenty percent and seventy-five percent of a thickness of the cutting table 59. A width of each rib 64a-c may range between twenty-five and seventy-five percent of a diameter of the cutting table 59. An inclination of each side surface relative to the respective base 62a-c may range between fifteen and fifty degrees. A radius of curvature of each ridge may range between one-eighth and five millimeters or may range between one-quarter and one millimeter.

[0064] The center section 63 may have a plurality of curved transition surfaces, a plurality of linearly inclined side surfaces, and a plurality of round edges. Each set of the features may connect respective features of one rib 64a-c to respective features of an adjacent rib along an arcuate path. The elevation of the edges may be equal to the elevation of the ridges. The center section 63 may further have a plateau formed between the edges. The plateau may have a slight dip formed therein.

[0065] Conventional shear cutters generate long cuttings during drilling of soft formations. These long cuttings are difficult to transport from the drill bit, up the annulus, and to surface. The ribs 8a-c, 28a-c, 38a-c, 46a-c, 54a-c, 64a-c of the respective cutters 1 , 12, 23, 33, 42, 48, 58 serve as chip-breakers to prevent formation of long cuttings and facilitate evacuation of the cuttings from the drill bit 15. The ribs 8a-c, 28a-c, 38a-c, 46a-c, 54a-c, 64a-c of the respective cutters 1 , 12, 23, 33, 42, 48, 58 also present a sharp cutting edge for drilling soft formations. For drilling hard formations, the ribs 8a-c, 28a-c, 38a-c, 46a-c, 54a-c, 64a-c of the respective cutters 1 , 12, 23, 33, 42, 48, 58 exert point-loading on the formation, thereby utilizing crack formation and propagation as a failure mode to cut the hard formation. Further, the protruding ribs 8a-c, 28a-c, 38a-c, 46a-c, 54a-c, 64a-c create additional surface area to facilitate cooling of the respective cutting tables 2, 24, 34, 43, 49, 59. Further, conventional shear cutters tend to form wear flats when drilling abrasive formations. The wear flats in turn are susceptible to thermal failure. The ribs 8a-c, 28a-c, 38a-c, 46a-c, 54a-c, 64a-c of the respective cutters 1 , 12, 23, 33, 42, 48, 58 can be indexed to a new rib to discourage formation of wear flats.

[0066] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the invention is determined by the claims that follow.