Abstract: A method for simulating the drilling performance of a roller cone bit drilling an earth formation may be used to generate a visual representation of drilling, to design roller cone drill bits, and to optimize the drilling performance of a roller cone bit. The method for generating a visual representation of a roller cone bit drilling earth formations includes selecting bit design parameters, selecting drilling parameters, and selecting an earth formation to be drilled. The method further includes calculating, from the bit design parameters, drilling parameters and earth formation, parameters of a crater formed when one of a plurality of cutting elements contacts the earth formation. The method further includes calculating a bottomhole geometry, wherein the crater is removed from a bottomhole surface.

Abstract: The present invention generally relates to positioning and/or orienting inserts on a gage row and/or a first inner row to optimize the duty among inserts on the gage row and/or insert row of cutting a sidewall and bottom hole of a bore hole such that wear and breakage of inserts are reduced and the life of the bit is enhanced.

Abstract: Disclosed are a variety of arcuate-shaped inserts for drill bits, and in particular, for placement in rolling cone cutters of drill bits. The arcuate inserts include 360 degree or ring-shaped inserts, as well as inserts of smaller arcuate length. The arcuate inserts may include stress relieving discontinuities such that, upon assembly into the cone, the arcuate inserts fragment in a controlled and predicted manner into shorter arcuate lengths. The arcuate inserts are suitable for use in all surfaces of the rolling cone cutter, and in other locations in drill bits, and may have specialized cutting surfaces and material enhancements to enhance their cutting duty performance.

Abstract: Disclosed are cutter elements for a drill bits having particular, but not exclusive, application on the nose portion of the cone cutters of a rolling cone bit. The cutter elements include a base, a cutting portion, and a plurality of cutting lobes extending radially from the cutting portion. Each lobe includes a forward-facing cutting face and trailing portion having a trailing surface that intersects the cutting face in a nonlinear cutting edge. The trailing surface is non-planar and recedes away from the cutting edge. In certain embodiments, the trailing surface is a partial dome shaped surface. The trailing portion provides strength and buttresses the cutting edge. A drill bit employing such cutter elements in the nose region of its rolling cones, either as a single element or in a circumferential row of such cutters, will aggressively attack the core regions of the borehole bottom.

Abstract: A method of forming a tooth rock bit is disclosed. In one embodiment, the method includes attaching the at least one cutting element to a surface of a cone, and depositing a hard facing layer on at least one cutting element prior to the attaching.

Abstract: Compacts are oriented in certain places on roller cones of an earth boring bit to increase the number of compacts in certain rows. The compacts that are pressed into holes in rows on the cones. The compacts are of tungsten carbide and have a cutting end axis and a barrel axis. The barrel axis intersects the cutting end axis at an obtuse angle. In one of the cones, the barrel axis of at least some of the compacts is rotated to have less inclination than the barrel axis of the compact nearest to it. The nearest compact may be in the same row or an adjacent row. Also, at least some of the compacts may be asymmetrical, with a cutting end axis that diverges from a barrel axis.

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: A rolling cone drill bit is provided that has gage inserts on the first row from the bit axis to cut to full gage diameter that have a cutting portion enhanced with a layer of super abrasive material. The gage cutting surface has a center axis that is canted to be more normal to the gage curve such that its point of contact at gage is away from the thinner portion of the layer of super abrasive material.

Abstract: The present invention relates to providing a drill bit stabilizing system and methods which overcome the above noted problems. The at least one stabilizing member is biased to a second extended operating position. The body member further comprises at least one fixed stabilizing surface positioned in axially spaced relationship to the at least one movable stabilizing member. In another aspect, the invention is directed to a drill bit stabilizing system comprising a body member and at least one stabilizing member, being moveable from an extended operating position to a retracted position within the body member. The at least one stabilizing member comprises outer contact faces adapted to engage the walls of a bore hole when in an operating position, and an inner slide surface adapted to slidingly engage a corresponding slide surface formed in the body member. There is also provided a method of drilling a bore hole using a drill bit rotated in conjunction with a drill string.

Abstract: New cutting structures for roller cone drill bits. In one aspect, a drill bit includes a bit body, roller cones attached to the bit body and able to rotate with respect to the bit body, and a plurality of cutting elements disposed on each of the roller cones, such that axial force on the bit during drilling is substantially balanced between the cones. In another aspect, a drill bit includes a plurality of cutting elements disposed on each roller cone such that the amount of work performed by each cone during drilling is substantially the same as the amount of work performed by each of the other cones. In yet another aspect, a drill bit includes a plurality of cutting elements disposed on each roller cone such that distribution of axial force on the bit is optimized.

Abstract: A drill bit including a roller cone and a plurality of cutting elements. The roller cone is affixed to a bit body and is arranged circumferentially about a bit axis of rotation. In one aspect, the cutting elements are arranged so that the crests of at least half of the cutting elements are within about 10 degrees of perpendicularity to the bit axis when each of these cutting elements is in a downwardmost rotary orientation. In another aspect, the roller cone and the cutting elements are arranged so that crests on the cutting elements define a substantially flat profile. Substantially flat in this aspect includes the profile having an endmost angle, either at the gage side or the centerline side, with respect to perpendicular to the bit axis, of less than about 11 degrees.

Abstract: A roller cone for a drill bit is disclosed which includes a cone body having a plurality of sockets. An interior portion of at least one of the sockets is treated on an interior surface of the socket to provide a residual compressive stress proximate the interior of the socket to reduce stress cracking. Forms of treating include shot peening, laser shock peening and hammer peening. In one embodiment, the socket is treated over approximately the lower 50 percent of the lateral wall. In another embodiment, the socket is treated on the bottom surface from the lateral wall inward approximately 33 percent of the diameter of the socket. Another aspect of the invention is a roller cone for a drill bit including a cone body having a plurality of sockets formed in the cone. In this aspect, an interior portion of at least one of the sockets is locally annealed on an interior surface of the socket. In one embodiment, the socket is locally annealed over approximately the lower 50 percent of the lateral wall.

Abstract: A fracture and wear resistant rock bit is disclosed, which includes a bit body, and at least one roller cone disposed on the bit body adapted such that at least one row of cutting elements disposed on the at least one roller cone defines a gage row. At least one cutting element disposed on the gage row has a fracture toughness of at least 20 ksi (in)0.5 and a wear number of at least 1.5.

Abstract: A drill bit is assembled to the makeup end of a drill string by means of a breakable washer comprising a ring-shaped body having an inner diameter and an outer diameter. A radially extending first surface of the ring-shaped body is planar and substantially perpendicular to a centerline axis through the body. A second radially extending surface has an angle with reference to the first surface that results in a radially diverging configuration.

Abstract: A fixed cutter drill bit particularly suited for plastic shale drilling includes rows of cutter elements arranged so that the cutting tips of the cutters in a row are disposed at leading and lagging angular positions so as to define a serrated cutting edge. The angular position of the cutting tips of cutters in a given row may be varied by mounting cutters with different degrees of positive and negative backrake along the same blade. Preferably, within a segment of a given row, the cutters alternate between having positive backrake and negative backrake while the cutters mounted with positive backrake are more exposed to the formation material than those mounted with negative backrake. Nozzles are provided with a highly lateral orientation for efficient cleaning. The positive backrake cutter elements have a dual-radiused cutting face and are mounted so as to have a relief angle relative to the formation material.

Abstract: A method for optimizing drilling performance of a roller cone drill bit is disclosed. The method includes simulating drilling with the bit in a selected earth formation to determine at least one drilling performance parameter. The orientation of at least one non-axisymmetric cutting element on the bit is adjusted and the simulating the drilling and determining the at least one performance parameter are repeated. The adjusting and simulating the drilling are repeated until the at least one performance parameter is determined to be at an optimum value. In one embodiment, the performance parameter includes rate of penetration.

Abstract: A method for simulating the drilling performance of a roller cone bit drilling an earth formation may be used to generate a visual representation of drilling, to design roller cone drill bits, and to optimize the drilling performance of a roller cone bit. The method for generating a visual representation of a roller cone bit drilling earth formations includes selecting bit design parameters, selecting drilling parameters, and selecting an earth formation to be drilled. The method further includes calculating, from the bit design parameters, drilling parameters and earth formation, parameters of a crater formed when one of a plurality of cutting elements contacts the earth formation. The method further includes calculating a bottomhole geometry, wherein the crater is removed from a bottomhole surface.

Abstract: A rolling cone bit includes at least one cone cutter having a gage row of cutter elements and a first inner row of near but off-gage cutter elements that are positioned so as to divide the sidewall and bottom hole cutting duty so as to enhance bit durability, maintain borehole diameter and improve ROP. The off-gage distance of the first inner row of cutter elements is defined for various bit sizes to optimize the division of cutting duty. The distance that the first inner row of cutter elements are off-gage may be constant for all the cones on the bit or may be varied among the various cones to balance the durability and wear characteristics on all the cones of the bit.

Abstract: A bearing failure indicator for sealed and lubricated rolling cutter earth boring drill bits is disclosed. A plurality of cutting inserts, arranged in a plurality of rows, are secured in the rolling cone cutters. At least two of the rolling cone cutters are intermeshing cutters, arranged such that they have intermeshing rows of cutting inserts. A groove is formed in the intermeshing cutters with a row containing a plurality of generally flat top bearing inserts. In the normal operation of the drill bit, the rows of generally flat top bearing inserts do not contribute to the drilling action of the drill bit. However, when a bearing assembly fails in operation, the generally flat top bearing inserts engage the intermeshing rows of inserts in the adjacent intermeshing cutter causing the drilling torque to increase and thereby providing a signal indicating the bearing has failed.

Abstract: A fixed-cutter drill bit is optimized so that cutter torques are evenly distributed not only during drilling of homogeneous rock, but also in transitional formations.

Abstract: A rolling cone bit includes at least one cone cutter having a gage row of cutter elements and a first inner row of near but off-gage cutter elements that are positioned so as to divide the sidewall and bottom hole cutting duty so as to enhance bit durability, maintain borehole diameter and improve ROP. The off-gage distance of the first inner row of cutter elements is defined for various bit sizes to optimize the division of cutting duty. The distance that the first inner row of cutter elements are off-gage may be constant for all the cones on the bit or may be varied among the various cones to balance the durability and wear characteristics on all the cones of the bit.

Abstract: A variety of large diameter PDC cutters for use in drill bits are disclosed. Specifically, various PDC cutters having a diameter between 19.0 mm and 25.0 mm are disclosed. The various PDC cutters disclosed include an elliptical PDC cutter, wherein a major diameter of the elliptical cutter is selected from a range of 19.0 mm to 25.0 mm, a circular PDC cutter, wherein a diameter of the circular cutter falls between 19.0 mm and 25.0 mm, and a non-planar substrate cutter, wherein a diameter of the non-planar cutter falls between 19.0 mm and 25.0 mm. Additionally, the thickness of the diamond table is increased as compared to prior art PDC cutters. The increase in diamond table thickness results in improved durability and performance.

Abstract: A rotary drill bit for boring a bore hole in an earthen formation includes a bit body having a pin end, a cutting end and a longitudinal axis and including at least two legs extending from the cutting end. Each of the legs includes a leading side surface, a trailing side surface, and a shoulder, and each of the legs further includes a bearing and a cutter cone rotatably supported on the bearing. The bit body further including a fluid flow system that includes a flowway in the pin end. The flowway is in fluid communication with at least one exit port in the cutting end. The bit body further includes a neck between the shoulders and the pin end and a hard, wear-resistant material on at least a portion of the neck.

Abstract: An earth-boring bit for attachment to a drill string has rotatable cones with rows of cutting elements. The cutting elements are arranged in generally circumferential rows on each of the cones and interference fit into apertures in the shell surface. The rows include a heel row of cutting elements on the heel surface of each of the cones, and an adjacent row of adjacent row cutting elements next to the heel row cutting elements. Each heel row cutting element has at least one counterpart adjacent row cutting element that is spaced no farther from it than any other adjacent row cutting element, defining a proximal pair. Each of the cutting elements in each of the proximal pairs has a grip ratio, which is the barrel length divided by the diameter. Some of the proximal pairs having cutting elements with higher grip ratios than other cutting elements. None of the proximal pairs has both cutting elements with higher grip ratios.

Abstract: A roller cone drill bit is shown which includes at least one roller cone rotatably mounted on a journal forming a part of a bit body. The at least one cone having cutting elements disposed at selected locations thereon. The at least one roller cone subtends a journal angle of less than about 35 degrees, and has an offset less than about 0.15 inches. In one embodiment, gage row cutting elements on the at least one roller cone define an oversize angle in a range of about −1.5 to +2 degrees.

Abstract: A rolling cone bit includes at least one cone cutter having a gage row of cutter elements and a first inner row of near but off-gage cutter elements that are positioned so as to divide the sidewall and bottom hole cutting duty so as to enhance bit durability, maintain borehole diameter and improve ROP. The off-gage distance of the first inner row of cutter elements is defined for various bit sizes to optimize the division of cutting duty. The distance that the first inner row of cutter elements are off-gage may be constant for all the cones on the bit or may be varied among the various cones to balance the durability and wear characteristics on all the cones of the bit.

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: Disclosed is a tooth type rolling cutter earth boring drill bit with secondary cutting elements on the tooth surfaces. The secondary cutting elements provide additional, relatively sharp edges that help cut hard rock. The teeth also have convex radiused buttresses at their bases to reduce the stresses the teeth experience when drilling through extremely hard rock. This allows the tooth bit to survive the high loads encountered when drilling hard, tough rock formations, without breaking the teeth. The combination of teeth with secondary cutting elements and convex radiused buttresses at their base provide a tooth type rotary drill bit that has superior resistance to wear and breakage when drilling through hard, tough rock without significantly reducing the drilling rate of penetration when drilling through soft rock.

Abstract: An earth-boring bit for drilling a borehole comprises a bit body having a bit axis, at least two rolling cone cutters rotatably mounted on the bit body, a plurality of inner row cutter elements positioned on at least one cone cutter in a first inner row, a plurality of gage-cutting cutter elements positioned in a first fanned-gage row on a first one of the one cutters, and a plurality of gage-cutting cutter elements positioned in a second fanned-gage row on a second one of the one cutters, wherein the gage-cutting cutter elements on the bit define a gage curve and cutter elements in the first fanned-gage row and the second fanned-gage row contact the gage curve at different points. In one embodiment, each cutter element has an extension, and the extensions of the uppermost fanned-gage row cutter element and the first inner row cutter element define a step distance such that the ratio of the step distance to the extension of the first inner row cutter element is greater than 0.5.

Abstract: A drill bit having a canted or non-canted leg backface, a canted or non-canted seal in the interface between the cone backface and the shirttail, and a canted seal that can be semi-encapsulated so that there is no straight-line path across the seal.

Abstract: An earth-boring bit has rolling cutters, each attached to a bit leg depending from a bit body. Each of the cutters has hardfaced, milled teeth. A spear point is located on one of the cutters. The spear point has a neck that protrudes toward the axis of the bit from a conical portion of the cutter. Blades are located on the spear point with spaces located between the blades. A layer of hardfacing is applied to the entire spear point area including the blades, the spaces and the neck.

Abstract: A rotary drill bit includes a rotary cutter rotatably mounted on a leg. A radial bearing arrangement and an axial bearing arrangement are provided in an interface between the cutter and the leg. The leg includes a filling opening for enabling cylindrical rolling elements of the radial bearing arrangement to be installed. The cutter includes a radial flange which radially overlaps the radial bearing arrangement to secure the cutter on the leg. The flange, which is disposed axially behind the radial bearing arrangement and axially in front of the filling opening, includes a recess for accommodating the passage of the cylindrical rolling elements. A locking element is disposed in the filling opening for preventing dislodgement of the cylindrical rolling elements. The locking element includes a lip which projects axially forwardly of the radial bearing arrangement. The lip is disposed radially inwardly of the flange and terminates axially behind the radial bearing arrangement.

Abstract: A rolling cone drill bit is provided that has gage inserts on the first row from the bit axis to cut to full gage diameter that have a cutting portion enhanced with a layer of super abrasive material. The gage cutting surface has a center axis that is canted to be more normal to the gage curve such that the its point of contact at gage is away from the thinner portion of the layer of super abrasive material.

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 earth-boring bit has a body with a threaded pin on the upper end for connecting to a drill string. Bit legs are formed symmetrically on the exterior of the body and extend downward. The lower portion of each bit leg is inclined and offset circumferentially from the upper portion. A cutter is mounted to the lower portion of each bit leg for rotation about a cutter axis. Nozzle bosses are located between each bit leg. A flow channel exists on both sides of each nozzle boss. The nozzle boss is inclined in a similar direction to the bit leg.

Abstract: Roller cone drilling wherein the bit optimization process equalizes the downforce (axial force) for the cones (as nearly as possible, subject to other design constraints). Bit performance is significantly enhanced by equalizing downforce.

Abstract: An earth-boring bit has a bit body and at least one cutter rotatably secured to the bit body. The cutter has a cutter shell surface including a gage surface and a heel surface. A plurality of cutting elements inserts are arranged in generally circumferential rows on the cutter. At least one scraper cutting element is secured at least partially to the heel surface of the cutter. The scraper cutting element includes an outermost surface, generally aligned with the gage surface of the cutter, that defines a plow edge or point for shearing engagement with the sidewall of the borehole while redirecting cuttings up the borehole.

Abstract: A method of manufacturing a rolling cone with hard-facing coating for use in drilling boreholes is disclosed. The method includes a step of depositing a layer of hardfacing material by an arc process, e.g., a gas-shielding tungsten arc welding process, a plasma-transferred arc welding process, or a metal inert gas arc welding process, over areas susceptible to erosion on the rolling cone surface. A rolling cone rock bit for drilling boreholes with a layer of hardfacing material deposited by an arc process either on the lands or in grooves or both of the cone surface is provided. Furthermore, a cone for attachment to the bit body of a rock bit with a layer of hardfacing material deposited on selected lands or in selected grooves or both of the cone surface also is provided.

Abstract: A rotary drill bit suitable for directional drilling. The bit includes a bit body from which extend legs carrying rotatable cutters. The body carries primary gage pads, above which secondary gage pads may be either longitudinally spaced or rotationally spaced, or both. Longitudinally leading edges of the gage pads may carry cutting structure for smoothing the sidewall of the borehole. Cutting structure may likewise be disposed on the trailing ends of the gage pads to provide an up-drill capability to facilitate removal of the bit from the borehole. The gage pads provide enhanced bit stability and reduced side cutting tendencies, as well as reducing lateral loading on the rotatable cutters and associated bearing structure and seals. The invention also has utility in bits not specifically designed for directional drilling.

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 fixed cutter drill bit particularly suited for plastic shale drilling includes rows of cutter elements arranged so that the cutting tips of the cutters in a row are disposed at leading and lagging angular positions so as to define a serrated cutting edge. The angular position of the cutting tips of cutters in a given row may be varied by mounting cutters with different degrees of positive and negative backrake along the same blade. Preferably, within a segment of a given row, the cutters alternate between having positive backrake and negative backrake while the cutters mounted with positive backrake are more exposed to the formation material than those mounted with negative backrake. Nozzles are provided with a highly lateral orientation for efficient cleaning. The positive backrake cutter elements have a dual-radiused cutting face and are mounted so as to have a relief angle relative to the formation material.

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: A rotary rock drill bit includes a bit body and three conical roller cutters rotatably mounted thereon. Each roller cutter has at least first, second, and third circumferential rows of buttons spaced apart in the direction of rotation of the roller cutter. The three rows of buttons are arranged successively from a rear end toward a front end of the roller cutter. The buttons of each of the first and second rows have lengths of attack which are longer in a direction of rotation of the roller cutter than in a direction perpendicular thereto. Those longer lengths of attack are also longer than a length of attack of the buttons of the third row in the rotational direction.

Abstract: A rolling cutter drill bit and method for making a rolling cutter drill bit having a cutting insert pressed into a socket, wherein the socket forms a juncture with the curved outer surface of a rolling cutter, and the juncture contacts a plane in contact with the juncture in at least three points located on the juncture.

Abstract: An earth-boring bit has a bit body which connects to a drill string. Three cutters are rotatably secured to a bearing shaft of the bit and a large number of chisel-like cutting elements are secured to each cutter. Each cutting element has a cylindrical base and a cutting end. An elongate crest is located at the tip of the cutting end. A conical chamfer connects the crest and the cutting end. The junction created by the chamfer is non-tangential and reduces the amount of unsupported material at the crest. The conical contour of the chamfer is defined by by a straight line moving in an oval path about the longitudinal axis. The contour of the cutting end avoids abrupt changes and associated stress concentrations. This is achieved by avoiding surfaces of rotation in non-axisymmetric configurations.

Abstract: A steel tooth, particularly suited for use in a rolling cone bit, includes a root region, a cutting tip spaced from the root region and a gage facing surface therebetween. The gage facing surface includes a knee, and is configured such that the cutting tip is maintained at a position off the gage curve. So positioned, the cutting tip is freed from having to perform any substantial cutting duty in the corner on the borehole corner, and instead may be configured and optimized for bottom hole cutting duty. The knee on the gage facing surface is configured and positioned so as to serve primarily to cut the borehole wall. It is preferred that the knee be positioned off gage, but that it be closer to the gage curve than the cutting tip.

Abstract: A roller cone or drag-type drill bit for use in drilling subsurface formations, especially useful for directional drilling, has a bit body with a shank portion for connection to a drill string, and a crown portion. Breaker slots are formed in the bit body at or immediately adjacent to the intersection of the crown portion and the shank portion. This location of the breaker slots allows the drill bit to be relatively shorter than comparable prior art bits with the breaker slots formed in the shank portion. The shorter length permits the present drill bit to be more easily steered in directional drilling applications.

Abstract: A rolling cone bit includes a cone cutter having a pair of adjacent rows of cutter elements that are positioned so as to divide the sidewall and bottom hole cutting duty. The wear resistance, hardness and toughness of the cutter elements in the adjacent rows are optimized depending upon the type of cutting the respective rows perform. In most applications, the cutter elements experiencing more sidewall cutting will have cutting surfaces that are more wear resistant or harder than the cutting surfaces of cutter elements in rows experiencing more bottom hole duty. Likewise, the cutter elements exposed to more bottom hole duty will generally be tougher than those experiencing substantial sidewall cutting. The material enhancements include varying the grades of tungsten carbide used in the cutter elements and by selectively employing layers of super abrasives, such as PCD or PCBN. The cutter elements may be either inserts or steel teeth.

Abstract: A rotary cone drill bit for forming a borehole having a bit body with an upper end portion adapted for connection to a drill string. A number of support arms extend from the bit body. Each support arm has an exterior surface with a stabilizer pad formed as an integral part thereof. A number of cutter cone assemblies equal to the number of support arms are rotatably mounted on respective support arms and project generally downwardly and inwardly from each support arm. A ramp may also be formed on the exterior surface of the support arm as an integral part thereof. Both the stabilizer pad and the ramp preferably have surfaces inclined at an angle from a leading edge of the support arm toward a trailing edge of the support arm such that a fluid flow channel is formed therebetween to direct drilling fluids and cuttings to flow upward in the borehole.

Abstract: A rotary drill bit comprises a bit body, a shank for connection to a drill string, a plurality of cutters mounted on the bit body, and a gauge structure which extends around the bit body and, in use, engages the surrounding formation forming the sides of the borehole being drilled. At least a section of the gauge structure is rotatably mounted on the bit body so that, in use, the gauge section may remain substantially non-rotating in engagement with the formation while the bit body rotates relative to it. The external surface of the non-rotating gauge section may be formed with longitudinal grooves to permit the flow of drilling fluid past the gauge section to the annulus. Alternatively the outer surface of the gauge section may be generally cylindrical, in which case internal passages are provided through the gauge section, and/or the bit body, for the flow of drilling fluid past the gauge section to the annulus.