Abstract: A PDC bit includes a plurality of blades including primary blades and secondary blades. The included primary blades are set with PDC cutters in accordance with a “single set” methodology. The included secondary blades, however, are set with PDC cutters using a type of “plural set” methodology such that the radial positions of cutters on a secondary blade match the radial positions of cutters on a single set primary which is immediately preceding that secondary blade. Plural secondary blades can be positioned to follow a single primary blade, and the cutters on those plural secondary blades will have radial positions matching the cutters of the immediately preceding single set primary blade.

Abstract: Downhole cutting tools such as blade mills comprise a body having a first end for connection with a rotating component of a drill string and a cutting end for rotation in unison with the body. The cutting end comprises at least two blades, each of the at least two blades comprising a front sidewall surface, a back sidewall surface, an inner end, an outer end, and at least one beveled portion disposed along the front sidewall surface toward the inner end of each of the at least two blades. At least one of the beveled portions comprise at least one cutting element disposed thereon that is disposed across a center point of the face of the cutting end to provide for cutting away an object disposed in a wellbore to occur across a center point of the cutting end.

Abstract: A superabrasive cutter including a superabrasive table having a cutting face in non-perpendicular orientation with respect to a longitudinal axis of the cutter. A superabrasive cutter having a cutting face of a superabrasive table in non-parallel orientation to a back surface thereof.

Abstract: A rolling cone drill bit comprises a bit body and a plurality of rolling cone cutters mounted on the bit body. Each cone cutter includes a plurality of gage cutting elements. Each gage cutting element has a cutting portion extending from a base portion to an extension height. Further, each gage cutting element contacts a gage curve at a gage curve contact point in a composite rotated profile view. Each gage cutting element has a cross-sectional area A1 in a first offset reference plane parallel to a base reference plane and offset from the base reference plane by an offset distance d1 equal to 10% of the extension height. The ratio of A1 to a cross-sectional area Ab of the base portion of each gage cutting element is less than 11%.

Abstract: A cutting element is disclosed that has a sleeve with a first inner diameter and a second inner diameter, wherein the second inner diameter is larger than the first inner diameter and located at a lower axial position than the first inner diameter, a rotatable cutting element having an axis of rotation extending therethrough, the rotatable cutting element at least partially disposed within the sleeve, wherein the rotatable cutting element has a cutting face and a body extending axially downward from the cutting face, at least one hole extending from an outer surface of the body toward the axis of rotation, and a locking device disposed in each hole, wherein the locking device protrudes from the hole to contact the second inner diameter of the sleeve, thereby retaining the rotatable cutting element within the sleeve.

Abstract: A rotary drill bit is disclosed. The rotary drill bit may include a bit body, a cutting pocket defined in the bit body, and a cutting element rotatably coupled to the bit body. The cutting element may be positioned at least partially within the cutting pocket. The rotary drill bit may also include a rotation-inducing member adjacent to the cutting element for inducing rotation of the cutting element relative to the cutting pocket. The rotation-inducing member may include a resilient member or a vibrational member. The rotary drill bit may also include protrusions extending from an interior of the cutting pocket adjacent to an outer diameter of the cutting element. A method of drilling a formation is also disclosed.

Abstract: A rolling cone drill bit for drilling a borehole in earthen formations. In an embodiment, the bit comprises a bit body. In addition, the bit comprises a cone cutter mounted on the bit body and adapted for rotation about a cone axis in a cutting direction. Further, the bit comprises at least one transition insert mounted to the cone cutter. Still further, the bit comprises a first asymmetric insert mounted to the cone cutter. Moreover, the bit comprises a second asymmetric insert mounted to the cone cutter. Each insert includes a cutting surface with a leading side relative to the cutting direction. The leading side of the first asymmetric insert has a leading geometry and the leading side of the second asymmetric insert has a leading geometry that is different than the leading geometry of the first asymmetric insert.

Abstract: Superabrasive inserts are disclosed. More particularly, a superabrasive insert may comprise a superabrasive layer bonded to a substrate at an interface. Further, the superabrasive layer may include a central substantially planar surface, a peripheral side surface, and an arcuate peripheral surface extending between the central substantially planar surface and the peripheral side surface. In one embodiment, the arcuate peripheral surface may comprise a lateral extent and an extension depth, wherein a ratio of the lateral extent to the extension depth is at least about 1.5. In another embodiment, an arcuate peripheral surface may comprise a substantially circular arc, wherein the substantially planar surface is tangent to the substantially circular arc and a tangent reference line to the substantially circular arc forms an angle of at least about 10° with the peripheral side surface. Subterranean drilling tools (e.g., drill bits) including at least one superabrasive insert are disclosed.

Abstract: A downhole cutting tool may include a tool body; a plurality of blades extending azimuthally from the tool body; and a plurality of cutting elements disposed on the plurality of blades, the plurality of cutting elements comprising: at least two conical cutting elements comprising a substrate and a diamond layer having a conical cutting end, wherein at least one of the at least two conical cutting elements has a positive back rake angle, and at least one of the at least two conical cutting elements has a negative back rake angle.

Abstract: An earth-boring tool includes a bit body having a face on which two different types of cutters are disposed, the first type being cutting elements suitable for drilling at least one subterranean formation and the second type suitable for drilling through at least one elastomeric component of a casing string, as well as a casing shoe and cement. Methods of drilling with an earth-boring tool include engaging and drilling an elastomeric component using at least one abrasive cutting structure.

Abstract: A drill bit for drilling a borehole in earthen formations comprising a bit body having a bit axis and a bit face. In addition, the drill bit comprises a primary blade extending radially along the bit face, the primary blade including a cutter-supporting surface that defines a blade profile in rotated profile view extending from the bit axis to an outer radius of the bit body. The blade profile is continuously contoured and includes a plurality of concave regions. Further, the drill bit comprises a plurality of cutter elements mounted to the cutter-supporting surface of the primary blade. Each cutter element on the primary blade has a forward-facing cutting face with a cutting edge adapted to penetrate and shear the earthen formation.

Abstract: A PDC bit includes a plurality of blades. A blade includes a primary cutter row and a secondary cutter row. Primary PDC cutters on the primary cutter row are set in accordance with a single set methodology. Backup PDC cutters on the secondary cutter row are set in accordance with a methodology wherein a radial position of each backup PDC cutter in the secondary cutter row is offset from a radial position of each primary PDC cutter in the primary cutter row. The blade further includes a tertiary cutter row. Additional backup PDC cutters on the tertiary cutter row are set in accordance with a methodology wherein a radial position of each additional backup PDC cutter in the tertiary cutter row is offset from a radial position of each primary PDC cutter in the primary cutter row. The backup cutter setting methodology is effectively radially positions the included backup PDC cutters (in the secondary cutter row and/or tertiary cutter row) between primary PDC cutters in the primary cutter row.

Abstract: A drill bit for cutting casing employing a plurality of discrete, abrasive particulate-impregnated cutting structures having cutting structures therein extending upwardly from abrasive particulate-impregnated blades, which define a plurality of fluid passages therebetween on the bit face. Additional cutting elements may be placed in the inverted cone of the bit surrounding the centerline thereof.

Abstract: A drill bit includes a bit body having a face on which two different types of cutters are disposed, the first type being cutting elements suitable for drilling at least one subterranean formation and the second type being at least one of an abrasive cutting structure and an abrasive cutting element suitable for drilling through a casing shoe, reamer shoe, casing bit, casing or liner string and cementing equipment or other components, as well as cement. Methods of forming earth-boring tools include disposing at least one abrasive cutting structure or element on the earth-boring tool. Methods of drilling with earth-boring tools including drilling with at least one abrasive cutting structure or element.

Abstract: A method of manufacturing a tool component, which is typically a cutting element or a gauge stone in a rotary drill bit, including a layer of ultra-hard abrasive material bonded to a substrate, the layer of ultra-hard abrasive material comprising a pair of opposed end surfaces, an upper surface defined between the end surfaces, and at least one curved and tapered cutting edge defined at the intersection of the respective end surfaces and the upper surface. The respective cutting edges of the tool component and the respective end surfaces leading to the cutting edges are generally wedge-shaped, the upper surface of the layer following generally the same or a similar profile, at least in the region of the cutting edges.

Abstract: A bearing element for a rotary, earth boring drag bit effectively reduces an exposure of at least one adjacent cutting element by a readily predictable amount, as well as a depth-of-cut (DOC) of the cutter. The bearing element has a substantially uniform thickness across substantially an entire area thereof. The bearing element also limits the amount of unit force applied to a formation so that the formation does not fail. The bearing element may prevent damage to cutters associated therewith, as well as possibly limit problems associated with bit balling, motor stalling and related drilling difficulties. Bits including the bearing elements, molds for forming the bearing elements and portions of bodies of bits that carry the bearing elements, methods for designing and fabricating the bearing elements and bits including the same, and methods for drilling subterranean formations are also disclosed.

Abstract: 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.

Abstract: Earth-boring tools comprise a body having a face at a leading end. A plurality of cutting elements are disposed over the face and configured as a plurality of kerfing pairs comprising two or more cutting elements disposed at substantially the same radial position relative to a bit axis, wherein each of the at least two cutting elements follows substantially the same cutting path when the bit is rotated about its axis. Earth-boring tools are further configured so that a summation of a lateral force generated during drilling by each cutting element of the plurality of cutting elements is directed toward a side of the body.

Abstract: A drill bit for drilling a borehole in earthen formations comprising a bit body having a bit axis and a bit face. In addition, the drill bit comprises a primary blade extending radially along the bit face, the primary blade including a cutter-supporting surface that defines a blade profile in rotated profile view extending from the bit axis to an outer radius of the bit body. The blade profile is continuously contoured and includes a plurality of concave regions. Further, the drill bit comprises a plurality of cutter elements mounted to the cutter-supporting surface of the primary blade. Each cutter element on the primary blade has a forward-facing cutting face with a cutting edge adapted to penetrate and shear the earthen formation.

Abstract: A cutter for a fixed cutter drill bit including a substrate and an ultrahard material layer disposed on an end surface of the substrate, the ultra hard material layer having an upper surface opposite the substrate end surface and a peripheral surface such that the upper surface intersects the peripheral surface along a peripheral edge. The peripheral edge continuously increases and decreases in height as measured from a plane perpendicular to a longitudinal axis of the cutter.

Abstract: A drill bit has cutting elements with multiple cutting surface geometries that are positioned so that their cutting profiles overlap, but do not completely contain or engulf one another. The different cutting surface geometries and the specific overlap create a zone of high density in the middle regions of the cutting profiles and low density in the periphery, resulting in a cutting profile that becomes sharper with increasing wear. Such an arrangement is more effective and stable as the drill bit encounters hard and abrasive formation materials. Moreover, cutting elements with larger axial volumes may be combined with cutting elements having smaller axial volumes.

Abstract: A fixed cutter drill bit and a method for designing a fixed cutter drill bit includes simulating the fixed cutter drill bit drilling in an earth formation. A performance characteristic of the simulated fixed cutter drill bit is determined. A side rake angle distribution of the cutters is adjusted at least along a cone region of a blade of the fixed cutter drill bit to change the performance characteristic of the fixed cutter drill bit.

Abstract: In an embodiment, a drill bit for drilling a borehole comprises a bit body having a bit axis and a bit face. In addition, the drill bit comprises a primary blade extending radially along the bit face. Further, the drill bit comprises a plurality of primary cutter elements mounted to the primary blade. The primary blade is free of backup cutter elements. Still further, the drill bit comprises a secondary blade extending radially along the bit face. Moreover, the drill bit comprises a plurality of primary cutter elements mounted to the secondary blade. In addition, the drill bit comprises a first plurality of backup cutter elements mounted to the secondary blade in a first backup row that trails the primary row. Further, the drill bit comprises a second plurality of backup cutter elements mounted to the secondary blade in a second backup row that trails the first backup row.

Abstract: A rotary drill bit or other drilling tool for drilling or reaming through subterranean formation and comprising a body comprising a distal end and gage areas near a proximal end thereof and comprising longitudinally upward extensions of a plurality of blades or legs. A longitudinally trailing, radially inwardly extending surface is associated with at least some gage pads or legs at the longitudinally trailing ends thereof. Protective structures in the form of superabrasive elements comprising a plurality of thermally stable polycrystalline diamonds, or so-called “TSPs” (thermally stable products) are secured to a trailing surface of at least one gage pad. PDC elements may be employed in combination with the TSPs. Non-diamond structures may also be employed, in lieu of or in conjunction with diamond structures, particularly if drilling of ferrous metal casing components is contemplated.

Abstract: Drill bits for subterranean drilling comprising a bit body including at least one blade that includes a blade face comprising a contact zone and a sweep zone are disclosed. In particular, drill bits including at least one blade that extends at least partially over a nose region of the bit body, a shoulder region of the bit body and a gage region of the bit body and that include a sweep zone that rotationally trails the contact zone with respect to a direction of intended bit rotation about a longitudinal axis of the bit body and include a contact zone that defines a range of about 90% to about 30% of the blade face surface area is disclosed. Additionally, drill bits comprising a sweep zone located at least partially within a gage region are disclosed. Also, methods of off-center drilling and methods of manufacturing drill bits are disclosed.

Abstract: A rotary drill bit is disclosed. The rotary drill bit may include a bit body, a cutting pocket defined in the bit body, and a cutting element rotatably coupled to the bit body. The cutting element may be positioned at least partially within the cutting pocket. The rotary drill bit may also include a rotation-inducing member adjacent to the cutting element for inducing rotation of the cutting element relative to the cutting pocket. The rotation-inducing member may include a resilient member or a vibrational member. The rotary drill bit may also include protrusions extending from an interior of the cutting pocket adjacent to an outer diameter of the cutting element. A method of drilling a formation is also disclosed.

Abstract: Reamer bits have cutters with different effective back rake angles. Drilling systems include a pilot bit and a reamer bit, wherein cutters in shoulder regions of the reamer bit have a greater average effective back rake angle than cutters in shoulder regions of the pilot bit. Methods of drilling wellbores include drilling a bore with a pilot bit, and reaming the bore with a reamer bit having cutters in shoulder regions of the reamer bit that have an average effective back rake angle greater than that of cutters in shoulder regions of the pilot bit. Methods of forming drilling systems include attaching pilot and reamer bits to a drill string, and positioning cutters in shoulder regions of the reamer bit to have an average effective back rake angle greater than that of cutters in shoulder regions of the pilot bit.

Abstract: A drill bit having a bit body, a plurality of blades extending radially from the bit body, a plurality of cutter pockets disposed on the plurality of blades, at least one rolling cutter disposed in one of the cutter pockets, wherein each rolling cutter has a substrate, a cutting face, a cutting edge, and a side surface, and at least one blocker positioned adjacent to each of the at least one rolling cutters on a leading face of the blade, wherein each blocker has a retention end and an attachment end is disclosed. The retention end of each blocker is positioned adjacent to a portion of the cutting face of each rolling cutter to retain the rolling cutter in the cutter pocket and the attachment end is attached to a portion of the blade.

Abstract: A rotary drill bit may include a bit body rotatable about a central axis. The rotary drill bit may also include at least one cutting element coupled to the bit body. The at least one cutting element may have a cutting face, a cutting edge adjacent the cutting face, and a back surface opposite the cutting face. The at least one cutting element may be oriented so that a substantial portion of the cutting edge has a positive clearance angle, which may be defined by a first vector that is normal to the cutting face and a second vector that is tangential to a helical path traveled by the cutting edge during drilling.

Abstract: A hybrid drill bit may have a bit body, at least one blade extending longitudinally and radially outward from the face, at least one rolling cutter assembly mounted on the bit body, at least one primary cutter, and at least one cutter set including a first cutter and a second cutter. The cutter set may be positioned to substantially follow the at least one primary cutter along the cutting path upon rotation of the bit body. At least one cutter of the cutter set may have a high side rake angle.

Abstract: Earth-boring tools include at least one up-drill feature disposed on a transition surface so as to be passive during down drilling and active during up drilling and/or back reaming operations. Systems for down drilling and up drilling with drill bits comprising one or more up-drill features are also disclosed. Furthermore, methods for forming a borehole with an earth-boring tool including such up-drill features and for forming an earth-boring tool comprising such up-drill features are also disclosed.

Abstract: In one aspect of the present invention, a drill bit assembly is configured for downhole drilling. The drill bit assembly comprises an outer bit with a plurality of outer blades and a bore disposed within an outer cutting face. In addition, the outer bit comprises a rotational axis. The drill bit assembly comprises an inner cutting face that is configured to cut a hole with an inner gauge diameter in front of the outer bit. At least one outer blade on the outer bit comprises a central most cutter configured to degrade the inner gauge diameter. The central most cutter is axially and laterally displaced from the second most central cutter on the at least blade such that less than fifty percent of the central most cutter axially and laterally overlaps the second most central cutter.

Abstract: In one aspect of the present invention, a drill bit assembly for downhole drilling comprises an outer bit comprising a central axis and an outer cutting area and an inner bit disposed within the outer bit and comprising an inner cutting area. The outer bit comprises a first plurality of cutting elements and the inner bit comprises a second plurality of cutting elements wherein an average distance of each cutting element in the first plurality to the central axis forms a first moment arm and an average distance of each cutting element in the second plurality to the central axis forms a second moment arm. A ratio of the inner cutting area to the outer cutting area is substantially equal to a ratio of the outer moment arm to the inner moment arm.

Abstract: The blades of a PDC bit have a nozzle between them preferably oriented laterally across the plane of the cutters on the blade and more preferably in a trough disposed adjacent the row of cutters. The cutting is less likely to adhere to the bit surface because the trough abruptly spaces back the bit surface and the spray being oriented radially preferably into the trough gets between the bit surface and the cutting before it can adhere to the bit surface using the fluid energy to drive the cutting into the junk slot.

Abstract: A method of optimizing drill bit design and an optimized drill bit for drilling a well into an earth formation comprising a bit body; a number of blades spaced around the bit body, each blade having a curved outer edge and a forward face; a first row of cutter pockets recessed into the face along the outer edge of each blade; a second group of cutter pockets recessed into the face of each blade offset from the first row; and a plurality of cutting elements, each cutting element being brazed into a different one of the cutter pockets.

Abstract: A drill bit that includes a body having a lower end face for engaging a rock formation is disclosed. The end face has a plurality of raised ribs extending from the face of the bit body and separated by a plurality of channels therebetween. At least one of the plurality of ribs has a leading portion and a trailing portion, the leading portion comprising a first matrix material impregnated with super abrasive particles and the trailing portion comprising a second matrix material impregnated with super abrasive particles, wherein the first and second matrix materials differ from each other.

Abstract: A hard formation drill bit that includes a plurality of gage cutting elements disposed on the at least one roller cone, wherein at least one of the plurality of gage cutting elements includes a cutting portion. The cutting portion includes a partially spherical leading edge and an obtuse relieved trailing edge, wherein a volume of the partially spherical leading edge is greater than a volume of the obtuse relieved tailing edge. Also, a method of drilling a formation that includes such a drill bit. Also included is an insert and a method of manufacturing a gage cutting element.

Abstract: A cutting tool that includes at least one tungsten carbide cutting element disposed on a support, wherein at least one tungsten carbide cutting element has at least one localized region having a material property different from the remaining region, wherein the at least one localized region having a different material property is prepared by a method including determining at least one localized region needing a variation in a material property different from the remaining region; coating a portion of a surface of the at least one tungsten carbide cutting element with a refractory material such that a surface corresponding to the localized region is left uncoated; and treating the coated cutting element with a selected agent to diffuse the selected agent into the localized region is disclosed.

Abstract: A drill bit includes a bit body having a face on which two different types of cutters are disposed, the first type being cutting elements suitable for drilling at least one subterranean formation and the second type being at least one of an abrasive cutting structure and an abrasive cutting element suitable for drilling through a casing shoe, reamer shoe, casing bit, casing or liner string and cementing equipment or other components, as well as cement. Methods of forming earth-boring tools include disposing at least one abrasive cutting structure or element on the earth-boring tool. Methods of drilling with earth-boring tools including drilling with at least one abrasive cutting structure or element.

Abstract: A drill bit includes a bit body having a face on which two different types of cutters are disposed, the first type being cutting elements suitable for drilling at least one subterranean formation and the second type being at least one of an abrasive cutting structure and an abrasive cutting element suitable for drilling through a casing shoe, reamer shoe, casing bit, casing or liner string and cementing equipment or other components, as well as cement. Methods of forming earth-boring tools are also disclosed.

Abstract: In one aspect, a cutting structure for a drill bit includes cutters arranged to form a cutter profile. Substantially all of the cutters in a shoulder section of the cutter profile are positioned at a profile angle of at most 65°. In another aspect, substantially all of the shoulder cutters are arranged so that the longitudinal force exerted by each shoulder cutter onto an earthen formation is at least 25 percent of the normal force exerted by the shoulder cutter onto the earthen formation.

Abstract: A rolling cone drill bit includes a cutter element having a cutting portion with a chisel crest and a pilot portion extending beyond the chisel crest. The pilot portion includes a cutting surface that may be generally conical, or form a second chisel crest. The cutting tip of the pilot portion is supported by buttress portions which emerge from and extend beyond the flanks of the chisel crest to provide additional strength and support for the material of the pilot portion that extends beyond the height of the chisel crest.

Abstract: A matrix drill bit and method of manufacturing a matrix bit having back raked cutting elements is disclosed. In one aspect, a matrix drill bit for well drilling includes a matrix bit body that has a front area in a direction of drilling and two or more diamond impregnated cutting blades protruding from the front area of the matrix bit body. The cutting blades each have a front external surface protruding from the front area of the matrix bit body and present a plurality of back raked downhole interface surfaces in the direction of drilling. The downhole interface surfaces span a leading face and a trailing face where the leading face extends to a first height and the trailing face extends to a second height and the first height is greater than the second height.

Abstract: A rotary drag bit exhibiting enhanced cutting efficiency and extended life is provided. The rotary drag bit comprises a bit body having a face surface, and a plurality of cutters coupled to the face surface of the bit body. The plurality of cutters comprises at least one pilot cutter and a rotationally trailing larger, primary cutter at substantially the same radius and, optionally of slightly less exposure. The pilot cutter is sized and positioned to pre-fracture the formation and perform an initial cut, while the primary cutter removes weakened, remaining formation material along the same rotational path. A method to pre-fracture subterranean formations using a rotary drag bit having a pilot cutter configuration is also provided.

Abstract: A drill bit includes a crown defining a central axis. The crown includes at least one segment. The segment includes a planar portion and a plurality of surface features continuous with and extending away from the planar portion. The surface features are discontinuous within the segment with respect to a first arced path defined at a first radial distance from the central axis.

Abstract: A central cutting structure for use with a drill bit includes a plurality of cutters, of which at least one overlaps the center of a supporting member from which the cutters extend. Each cutter has a side rake angle that provides an overlapping relationship with at least one other cutter to provide an aggressive cutting surface for penetrating hard formations.

Abstract: A rotary drag bit includes a primary cutter row comprising at least one primary cutter and a multiple backup cutter group. The multiple backup cutter group comprises a first and second trailing cutter row, each comprising at least one cutter positioned to follow the at least one primary cutter. The rotary drag bit life is extended by the multiple backup cutter groups making the bit more durable and extending the life of the cutters. Further, the cutters of the multiple backup cutter group are configured to selectively engage a subterranean formation material being drilled, providing improved bit life and reduced stress upon the cutters. Other embodiments of rotary drag bits are provided.

Abstract: A superabrasive cutter including a superabrasive table having a cutting face in non-perpendicular orientation with respect to a longitudinal axis of the cutter. A superabrasive cutter having a cutting face of a superabrasive table in non-parallel orientation to a back surface thereof.

Abstract: A drill bit for drilling subterranean formations comprising a drill bit body including a group of primary cutting elements comprising a first primary cutting element and a second primary cutting element radially spaced apart from each other along a first radial axis. The drill bit body further including a group of backup cutting elements comprising a first backup cutting element in a secondary cutting position relative to the first primary cutting element and a second backup cutting element in secondary cutting positions relative to the second primary cutting element, wherein the first and second backup cutting elements are radially spaced apart from each other along a second radial axis different than the first radial axis and comprise a difference in cutting characteristic relative to each other of one of a backrake angle and a siderake angle.

Abstract: A hybrid drill bit having both roller cones and fixed blades is disclosed, and a method of drilling. The cutting elements on the fixed blades form a continuous cutting profile from the perimeter of the bit body to the axial center. The roller cone cutting elements overlap with the fixed cutting elements in the nose and shoulder sections of the cutting profile between the axial center and the perimeter. The roller cone cutting elements crush and pre- or partially fracture formation in the confined and highly stressed nose and shoulder sections.