Abstract: In one aspect of the present invention a disc cutter for an earth boring system includes an axle and a sintered polycrystalline ceramic disc disposed about and forming a continuous perimeter around the axle. The disc cutter may be attached to a drill bit comprising a body, working face and plurality of blades. Another aspect of the present invention comprises a method of forming a disc cutter including providing a can of a generally cylindrical shape with a central axis, positioning a column of disposable material, carbide, and crystalline grains in such a manner so when put under high temperature and high pressure a compact in the shape of a disc cutter may be formed and a column from the center axis may be removed. Another method for forming a disc cutter comprises forming a plurality of compacts and bonding the compacts together in a generally toroidal shape.

Abstract: Various downhole drilling tools designed and manufactured at least in part on evaluating respective forces acting on respective groups and sets of cutting elements during simulated engagement with the downhole end of a wellbore and drilling from a first downhole formation into a second downhole formation. Simulating forces acting on each cutting element as the cutting element contacts a downhole formation may be used to force balance downhole drilling tools during transition drilling or non-uniform downhole drilling conditions. Multilevel force balanced downhole drilling tools may be designed using five respective simulations, cutter group level, neighbor cutter group level, cutter set level, group of N (N=3 or N=4) consecutive cutters level and all cutters level. Various cutter layout procedures and algorithms may also be used to design multilevel force balanced downhole drilling tools which may drill faster with higher lateral stability, especially during downhole transiting drilling conditions.

Abstract: A collapsible cutter bit or rock head for use with an underground auger boring machine has an expanded position for cutting rock in front of an underground pipe and a collapsed position for withdrawing the rock head through the underground pipe. The auger boring machine is configured to bore a passage through a body of soil and rock and simultaneously lay the underground pipe in the passage. Forward rotation of the cutter bit causes expansion while collapse of the cutter bit may be driven by reverse rotation of the cutter bit or another mechanism.

Abstract: Polycrystalline compacts include non-catalytic nanoparticles in interstitial spaces between interbonded grains of hard material in a polycrystalline hard material. Cutting elements and earth-boring tools include such polycrystalline compacts. Methods of forming polycrystalline compacts include sintering hard particles and non-catalytic nanoparticles to form a polycrystalline material. Methods of forming cutting elements include infiltrating interstitial spaces between interbonded grains of hard material in a polycrystalline material with a plurality of non-catalytic nanoparticles.

Abstract: A hole opener having a hybrid reaming section for downhole earth boring operations may include a reamer body having an axis of rotation, an outer periphery, and upper and lower ends, a plurality of rolling cutters coupled to the outer periphery and depending downwardly, the rolling cutters defining a rolling cutter cutting profile having a cutting diameter, a plurality of fixed blade cutters coupled to the outer periphery and defining a fixed blade cutter cutting profile having a cutting diameter, each fixed blade cutter being coupled between adjacent rolling cutters. At least one of the fixed blade cutters may be asymmetrically coupled about the axis. The cutting diameter of the fixed blade cutter cutting profile may be larger than the cutting diameter of the rolling cutter cutting profile. At least a portion of the fixed blade cutter cutting profile may be deeper than the rolling cutter cutting profile.

Abstract: A hole opener having a hybrid reaming section for downhole earth boring operations may include a reamer body having an axis of rotation, an outer periphery, and upper and lower ends, a plurality of rolling cutters coupled to the outer periphery and depending downwardly, the rolling cutters defining a rolling cutter cutting profile having a cutting diameter, a plurality of fixed blade cutters coupled to the outer periphery and defining a fixed blade cutter cutting profile having a cutting diameter, each fixed blade cutter being coupled between adjacent rolling cutters. At least one of the rolling cutters may be asymmetrically coupled about the axis. The cutting diameter of the rolling cutter cutting profile may be larger than the cutting diameter of the fixed blade cutter cutting profile. At least a portion of the rolling cutter cutting profile may be deeper than the fixed blade cutter cutting profile.

Abstract: A hole opener having a hybrid reaming section for reaming subterranean wellbores may include a tubular reamer body having a longitudinal axis and upper and lower ends, a rolling cutter mount coupled to the body, a rolling cutter rotatably coupled to the mount, and a fixed blade coupled to the body adjacent the mount. A method of forming a hybrid reamer tool for downhole use may include providing a tubular stem having couplers on the upper and lower ends, coupling a reamer body having an outer periphery to the stem between the stem upper and lower ends, coupling a rolling cutter mount to the outer periphery of the reamer body, the mount having a rolling cutter rotatably coupled thereto, and coupling a fixed blade to the outer periphery of the reamer body adjacent the rolling cutter mount.

Abstract: A hole opener having a hybrid reaming section for downhole earth boring operations may include a reamer body having an axis of rotation, an outer periphery, and upper and lower ends, a plurality of rolling cutters coupled to the outer periphery, the rolling cutters defining a rolling cutter cutting profile having a cutting diameter, a plurality of fixed blade cutters coupled to the outer periphery and defining a fixed blade cutter cutting profile having a cutting diameter, each fixed blade cutter being coupled between adjacent rolling cutters. At least one fixed blade cutter may be asymmetrically coupled about the axis. The cutting diameter of the fixed blade cutter cutting profile and the cutting diameter of the rolling cutter cutting profile may collectively define a gage diameter. At least a portion of the fixed blade cutter cutting profile may be deeper than the rolling cutter cutting profile.

Abstract: A drill bit for drilling a borehole in an earthen formation. In an embodiment, the bit comprises a first blade having a cutter-supporting surface. In addition, the bit comprises a plurality of primary cutter elements with cutting faces mounted to the cutter-supporting surface. The cutting profiles of the cutting faces define an outermost cutting profile P0 in rotated profile view. Further, the bit comprises a stabilizing member having an end distal the cutter-supporting surface. The end includes a tip. The tip is offset from the outermost cutting profile P0 in rotated profile view.

Abstract: An earth boring drill bit comprising a bit body having a bit profile including nose, shoulder, and gage sections; a plurality of fixed cutting elements secured to the body and defining a fixed cutter profile; and a roller cone rotatably secured to the body, the roller cone having a plurality of roller cone cutting elements defining a roller cutter profile, wherein the fixed cutter profile extends beyond the roller cutter profile in at least one of the sections and the roller cutter profile extends beyond the fixed cutter profile in at least one of the sections. The roller cutter profile may extend beyond the fixed cutter profile in the shoulder and gage sections, possibly with the fixed cutter profile extending beyond the roller cutter profile in the nose section and/or a cone section.

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.

Abstract: A hybrid drill bit having both roller cones and fixed blades is disclosed. 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-fracture formation in the weak and highly stressed nose and shoulder sections.

Abstract: A bit body is configured at its upper extent for connection into a drillstring. At least one fixed blade extends downwardly from the bit body, and has a radially outermost gage surface. A plurality of fixed cutting elements is secured to the fixed blade, preferably in a row at its rotationally leading edge. At least one bit leg is secured to the bit body and a rolling cutter is mounted for rotation on the bit leg. At least one stabilizer pad is disposed between the bit leg and the fixed blade, the stabilizer pad extending radially outward to substantially the gage surface. The radially outermost gage surface of each blade can extend axially downward parallel to the bit axis or angled (non-parallel), spirally or helically, relative to the bit axis.

Abstract: A method for designing a fixed cutter drill bit, includes simulating the fixed cutter drill bit drilling in an earth formation, determining radial and circumferential components of imbalance forces on the drill bit and a Beta angle between the radial and circumferential components of the imbalance forces during a period of simulated drilling, and adjusting a value of at least one design parameter for the fixed cutter drill bit at least based upon the Beta angle. To facilitate drill bit design, the Beta angel can be displayed to a drill bit designer. To improve performance, the method can include repeating the simulating, determining, and adjusting to change a simulated performance of the fixed cutter drill bit. A drill bit may be made according to the design resulting from the method.

Abstract: Methods of forming earth-boring rotary drill bits include providing a bit body, providing a shank that is configured for attachment to a drill string, and attaching the shank to the bit body. Providing a bit body includes providing a green powder component having a first region having a first composition and a second region having a second, different composition, and at least partially sintering the green powder component. Other methods include providing a powder mixture, pressing the powder mixture to form a green component, and sintering the green component to a final density. A shank is provided that includes an aperture, and a feature is machined in a surface of the bit body. The aperture is aligned with the feature, and a retaining member is inserted through the aperture. An earth-boring bit includes a bit body comprising a particle-matrix composite material including a plurality of hard particles dispersed throughout a matrix material. A shank is attached to the bit body using a retaining member.

Abstract: An earth-boring bit comprising a bit body configured at its upper extent for connection into a drillstring. A selected number of fixed blades extend downward from the bit body and a selected number of rolling cutters are mounted for rotation on the bit body. A plurality of rolling-cutter cutting elements are arranged on each rolling cutter and a plurality of fixed-blade cutting elements are arranged on each fixed blade. The selected number of fixed blades exceeds the selected number of rolling cutters by at least one.

Abstract: A drill bit is disclosed that in one aspect includes a cutting device on a selected section of the drill bit, which cutting device is configured to cut formation on the high side of a wellbore during drilling of the wellbore. In one aspect, the cutting device comprises a cutting element disposed on a substantially non-rotating member placed around the selected section. In another aspect, the selected section may be a gage section of the drill bit.

Abstract: The invention disclosed and taught herein is directed to an improved hybrid drill bit having at least two rolling cutters, each rotatable around an axis of rotation, at least one of the rolling cutters having a high pin angle, and at least one fixed blade. The increase in the pin angle can encompass pin angles above 39 degrees to less than 393 degrees. In at least one embodiment, the improved drill bit expands the capabilities of a hybrid bit to allow the rolling cutters to engage a shoulder portion and/or gage portion of the bit profile and assist the fixed blade(s) in these areas.

Abstract: The present invention relates to a system and method for automated or “robotic” application of hardfacing to the surface of a steel-toothed cutter of a standard earth-boring rock bit or a hybrid-type rock bit. In particular, the system incorporates a grounded adapter plate and chuck mounted to a robotic arm for grasping and manipulating a rock bit cutter, particularly a hybrid rock bit cutter, beneath an electrical or photonic energy welding source, such as a plasma arc welding torch manipulated by a positioner. In this configuration, the torch is positioned substantially vertically and oscillated along a horizontal axis as the cutter is manipulated relative along a target path for the distribution of hardfacing. Moving the cutter beneath the torch allows more areas of more teeth to be overlayed, and allows superior placement for operational feedback, such as automatic positioning and parameter correction.

Abstract: A hybrid drill bit having secondary backup cutters positioned with high side rake angles.

Abstract: The invention disclosed and taught herein is directed to an improved hybrid drill bit and associated elements having at least two rolling cutters, each rotatable around separate spindles on the bit, and at least one fixed blade. The improved drill bit expands the pilot pin to journal diameter ratio within the body of the rolling cutter, but within the confines of the allowable space of the rolling cutter.

Abstract: The present invention discloses a tri-cone drill bit comprising: three head sections with upper parts thereof jointed together to form a bit body, three cones rotatably mounted to lower ends of the head sections respectively, nozzle sockets designed on the bit body between respective head sections and each having a hole in which a nozzle is mounted, wherein gage cutters are mounted to an upper trailing side of each head O.D. surface to form a gage holding surface thereon, and a leading side of each head section is backwardly slanted as a whole. The design of gage surface at trailing sides of head sections increases the bit's stability, reduces lateral vibration and also reduces tendency of bit deflection in horizontal drilling applications and effective working life of the bit is improved. Backward slant of leading sides of head sections facilitates upward carrying of drilling cuttings and improves drilling efficiency.

Abstract: An earth-boring bit comprising a bit body is cofigured at its upper end for connection into a drillstring. A fixed blade depends axially downwardly from the bit body. An axially extending slot is formed in the bit body adjacent the fixed blade. A bit leg is received and retained in the slot by engagement between the slot and correspondingly shaped bit leg, wherein the bit leg cannot be removed from the slot except by axial movement relative to the bit body. A rolling cutter is secured to the bit leg at its lower extent. A fastener secures the bit leg against movement relative to the bit body and extends through oblong apertures in the bit leg and into the bit body, wherein the bit leg can be moved axially relative to the bit body to adjust the projection of the rolling cutter relative to the fixed blade. The slot defines a pair of generally opposed sides connected by a third side, the generally opposed sides being inclined toward one another to define a dovetail that corresponds with the shape of the bit leg.

Abstract: A hybrid earth-boring bit comprising a bit body having a central axis, at least one, preferably three fixed blades, depending downwardly from the bit body, each fixed blade having a leading edge, and at least one rolling cutter, preferably three rolling cutters, mounted for rotation on the bit body. A rolling cutter is located between two fixed blades.

Abstract: A roller cone bit having an elastomeric seal with a self break-in property is disclosed. The elastomeric seal includes abrasive material on a sliding surface for facilitating break-in. Examples of abrasive materials include ground rock, hard metals, tungsten, tungsten carbide, tantalum, tantalum carbide, titanium carbide, titanium nitride, and minerals, diamonds and nanomaterial enhanced diamond.

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.

Abstract: Fracture and wear resistant cutting elements are provided. Examples include a cutting element formed of a wear resistant material having a binder composition and a coarse grain size such that the portion of the cutting element formed of the wear resistant material has a fracture toughness of at least about 18 ksi(in)0.5 and a wear number of at least about 1.8. In a particular example, the wear resistant material has a fracture toughness of at least about 20 ksi(in)0.5. A down hole cutting tool incorporating such cutting elements is also provided.

Abstract: A roller cone drill bit for drilling earth formation may include rows arranged on each of the cones such that when viewed in routed profile, cutting element profiles partially overlap with other cutting element profiles and at least the first three interior rows adjacent a gage row each have a cutting element count selected from the group of 16, 18, 21 and 26 cutting elements.

Abstract: A drill bit for cutting a borehole comprises a bit body. In addition, the drill bit comprises a rolling cone cutter mounted on the bit body and adapted for rotation about a cone axis. Further, the drill bit comprises at least one insert having a base portion secured in the rolling cone cutter and a cutting portion extending therefrom. The cutting portion includes a pair of flanking surfaces that taper towards one another to form an elongate chisel crest including a first crest end, a second crest end, and an apex positioned therebetween. A transverse radius of curvature at the first crest end is less than a transverse radius of curvature at the apex, and a transverse radius of curvature at the second crest end is less than the transverse radius of curvature at the apex.

Abstract: A nozzle includes a nozzle body having an extended, tubular nozzle protrusion terminating at a nozzle exit, the nozzle body having an annular shoulder surrounding a base of the nozzle protrusion. A passage extends through the nozzle body, necking down in cross-sectional area before entering the nozzle protrusion and distally terminating at a nozzle exit, where drilling mud is discharged. A nozzle configured as described is disposed in a nozzle recess of a bit body of a rotary drag bit, the nozzle recess being of sufficient depth to receive the nozzle and recess the annular shoulder of the nozzle body a substantial distance from the bit face. A snap-ring is received in an annular groove in the wall of the nozzle recess and extends inwardly over the annular shoulder of the nozzle body. The nozzle protrusion exit extends to a location proximate the bit face.

Abstract: A drill bit for drilling a borehole with a steerable drilling system, the drill bit comprising a longitudinal axis, and a cutting profile with a leading face section blended with a curved region into a tapered gauge region having a tapered gauge profile. The tapered gauge region being tapered with respect to the longitudinal axis determined by the steerable drilling system. The cutting profile and the gauge profile lie wholly within a bit profile envelope made up of a three dimensional surface of two complimentary conical sections set at the tilt angle and separated by and blended with a rounded section which forms an outermost diameter of the bit profile envelope. The rounded section has a diameter substantially equal to a maximum allowable API diameter for the drill bit, and further has a radius of curvature substantially equal to one-half the diameter.

Abstract: A roller cone drill bit is disclosed which includes a bit body adapted to be coupled to a drill string, a bearing journal depending from the bit body and a single roller cone rotatably attached to the journal. The roller cone has a plurality of inserts disposed thereon. In one aspect, the inserts have an extension length of at least 0.6 inches. A roller cone drill bit is disclosed, including a bit body, a bearing journal depending from the bit body, and a single roller cone rotatably attached to the journal. The roller cone has a plurality of inserts disposed thereon. In another aspect, the inserts are arranged such that at most about 20 percent of the inserts are crossed substantially at centerlines thereof by any single plane which contains the axis of the cone axis 10 and which crosses at least two of the inserts.

Abstract: A drill bit, comprising a bit body, a sensor disposed in the bit body, a single journal removably mounted to the bit body, and a roller cone rotatably mounted to the single journal.

Abstract: A three cone roller bit with rolling cone cutters that are provided with both primary and secondary cutting elements. The primary cutting elements extend outwardly from lands on the outer surface of the cutter body. The secondary cutting elements are disposed within grooves on the cutter body so as to either protrude with its cutting surface from the bottom of the groove or be flush or slightly recessed within it. During normal operation, the primary cutter elements of the rolling cone cutters engage the borehole formation. The secondary cutters do not engage the formation. After substantial wear has occurred to the primary cutter elements, and wear begins to occur to the body of the cone cutters, the secondary cutter elements serve as a secondary cutting structure that engages and cuts into the formation.

Abstract: A rotary drill bit for penetrating earth strata wherein the drill bit includes a drill bit body that has an axial forward end. The drill bit body has a hard insert, which is preferably monolithic, that is affixed to the drill bit body at the axial forward end thereof. The hard insert presents at least three discrete leading cutting edges for cutting the earth strata.

Abstract: A rotary-type earth-boring drag bit with cutters oriented at varied rake angles and methods for designing such drag bits. Specifically, cutters that are located sequentially adjacent radial distances from a longitudinal axis of the drill bit have cutting faces that are oriented at rake angles that differ from one another. These cutters may be located on the same blade of the drag bit or on different blades of the drag bit. The rake angles at which the cutting faces of these cutters are oriented may be based, at least in part, on the relative radial distances these cutters are spaced from the longitudinal axis of the drag bit, on the vertical positions of these cutters along the longitudinal axis of the drag bit, or in response to actual or simulated evaluations of the use of the drag bit to drill a subterranean formation.

Abstract: Disclosed is a wear resistant cutting insert for use in rolling cutter drill bits. The insert has a cylindrical shank that is readily fitted in an interfering manner into cylindrical sockets formed in the rolling cutter. The surface of die insert that engages the formation, however, is none-circular, and preferably, oval shaped. To prevent the insert from turning in the socket, a shallow counterbore is formed about the socket that accommodates the shape of the top, non-cylindrical portion of the insert. The depth of the recess is made slightly greater than the length of the shank of the insert so that the load applied to insert during operation is not transmitted through the shank to the bottom of the socket in the cutter.

Abstract: A cutter element for a drill bit. The cutter element has a base portion and an extending portion and the extending portion has either a zero draft or a negative draft with respect to the base portion. The non-positive draft allows more of the borehole bottom to be scraped using fewer cutter elements. The cutter elements having non-positive draft can be either tungsten carbide inserts or steel teeth.

Abstract: An array of chisel-shaped cutting elements are mounted to the face of a fixed cutter bit. Each cutting element has a crest and an axis which is inclined relative to the borehole bottom. The cutting elements have a hardened diamond exterior on all surfaces in contact with the formation. The chisel-shaped cutting elements may be arranged on a selected portion of the bit, such as the center of the bit, or across the entire cutting surface. In addition, the crest on the cutting elements may be oriented generally parallel or perpendicular to the borehole bottom. The chisel shape and crest orientation increase the initial contact area while reducing aggressiveness. These advantages are achieved without increasing cutter density, reducing back rake, or adding depth of cut limiters. Chisel-shaped cutting elements having crests which are oriented perpendicular to the borehole bottom have the added advantage of displacing the material in a plane that is parallel to the bit face.

Abstract: A cutter element for a drill bit. The cutter element has a base portion and an extending portion and the extending portion has either a zero draft or a negative draft with respect to the base portion. The non-positive draft allows more of the borehole bottom to be scraped using fewer cutter elements. The cutter elements having non-positive draft can be either tungsten carbide inserts or steel teeth.

Abstract: A one cone drill bit is equipped with multiple jet flow guiding grooves along the cone. The multiple grooves connects to a circular groove axially centered on the nose end portion of the cone. The circular groove sweep the cuttings and mud flow across the drilled face and up the well borehole.

Abstract: A cutter element for a drill bit. The cutter element has a non-rectilinear crest. The non-rectilinear or curvilinear crest provides an advantageous distribution of the cutting forces across the body of the cutter elements and thus improves bit life. The curvilinear crest also allows the cutter element to more efficiently lift the portion of the formation that is being cut, thereby improving cutting action in certain formations. The cutter elements can have either positive or non-positive draft and can be tungsten carbide inserts.

Abstract: The invention discloses a single cone earth boring bit which is adapted to be used for boring in oil fields, mining and geological prospecting. The single cone earth boring bit is composed of a bit body (1), gauge blocks (2), active cutting gauge teeth (4), passive gauge teeth (3) and knobby cone (6) etc. On the knobby cone (6), there are inserted wear-resistant teeth intermittently or successively, so as to make the wear resistance of the bit cutting system to be matched with the service life of the bearing. At the same time, gauge blocks (2) are provided on the bit body which may be directly made on or welded to the bit body. On the gauge blocks (2), there are inserted common carbide or wear-resistant active cutting gauge teeth (4) and the passive gauge teeth (3) to enhance the gauge-protecting effect of the bit. Such a single cone earth boring bit can significantly increase the footage of the bit and reduce the cost for drilling.

Abstract: A rotary drill arrangement comprising a combination spade drill body having a rotational axis, a shank portion, and a generally planar spade cutter portion with a pair of oppositely directed cutting edges extending radially of the axis, and a rotatable frusto conical cutter mounted on the spade cutter portion adjacent the maximum radial extent of each cutting edge.

Abstract: A method of fabricating rotary bits for subterranean drilling by layering techniques such as are employed in rapid prototyping technology. Thin layers of powder may be sequentially deposited and fused or otherwise bonded to define the bit body, or thin sheets of material may be stacked, bonded and cut. Bit body components may also be formed by the method and subsequently assembled with other components made in like manner or by other methods to produce a bit body. Bits fabricated according to the method are also disclosed.

Abstract: A method of manufacturing a roller cone type drill bit, or main body thereof, includes forging a monolithic main body forging comprising a shank blank extending longitudinally at one end and a plurality of circumferentially spaced leg stubs at the other end; turning the shank blank to form a threaded section; rotatably mounting a respective roller cone on each of a plurality of journal members, each journal member being carried at one end of a respective leg extension; and welding a respective one of the leg extensions to each of the leg stubs. The main body is forged with its longitudinal centerline perpendicular to its flash line, the latter being located well inward of the leg end of the forging.

Abstract: A method of fabricating rotary drag bits for subterranean drilling by layering techniques such as are employed in rapid prototyping technology. Thin layers of powder may be sequentially deposited and fused or otherwise bonded to define the bit body, or thin sheets of material may be stacked, bonded and cut. Bit body components may also be formed by the method, and subsequently assembled with other components made in like manner or by other methods to produce a bit body. Bits fabricated according to the method are also disclosed.

Abstract: A drill bit for drilling a hole in the ground, with cutting elements annular by cutting a core which, when it has reached a certain height, is continuously crushed by teeth on rolling cones. By combining these two processes, cutting and crushing, in this manner an improved drilling advancement is achieved as compared to separate use of these processes. The cutting elements show relatively small variations as to radial positioning, which renders it possible to find a common approximately optimal rotational speed of said elements. The core is weak and may be drilled out relatively easily by the aid of crushing, as compared to drilling pure holes. This is due to the fact that the core geometry causes a more efficient growth of fractures for each tooth penetration, and that the core, due to annular cutting, is free from radial tensions from the surrounding rock formations.

Abstract: An improved earth drilling bit and method that cuts at least one annular kerf ahead of at least one rolling cutter and provides for rock chip removal and bit cooling thereby increasing drilling rate and bit performance. One embodiment of the invention includes a bit body having a lower end forming an annular kerf cutter for cutting an outer annular kerf, an inner drill member positioned concentrically within the bit body having a lower end forming an annular kerf cutter for cutting an inner annular kerf, and at least one rolling cutter mounted to the bit body and extending from the interior of the outer kerf cutter to the longitudinal axis of the drill bit. Other embodiments include a chipway port defined by the drill bit for channeling rock chips away from beneath the bit; baffles for directing and accelerating drilling fluid flow; cutting edges having connecting webbs providing egress for rock chip and drilling fluid; and slots extending along the bit body for reducing surge and swab pressure.

Abstract: The inserts for a roller cone of a multiple cone rock bit are positioned or angled in the cone to attack an earthen formation such that the inserts are subjected to more compressive forces and the formation is subjected to more shear forces as the roller cutters roll over the bottom of the formation.