Abstract: A cutting structure for a rotary drill bit includes a cutting element 30 having a front layer 32 formed of polycrystalline diamond, bonded to a backing layer 33 formed of tungsten carbide. The cutting element is bonded to a carrier 33 which is formed of a number of detachable individual elements having means holding them in position such that, upon wear of the cutting structure in use, the holding means of an element engaging the formation will eventually fail, causing detachment of that element from the carrier, and thereby reducing the area of the cutting structure in contact with the formation.

Abstract: In the manufacture of a bit body by a powder metallurgy process, a hollow mold is formed in the configuration of at least a portion of the outer surface of the bit body, and elongate pockets of generally V-section are then formed in the interior surface of the mold, to receive portions of thermally stable cutting elements, each of which is of generally triangular cross-section with a flat front face. Each pocket is machined from the mold material by means of a conical tool rotating about its axis, the axis being inclined to the perpendicular in a plane containing the required longitudinal axis of the pocket. The main elongate part of the pocket is formed by translatory movement of the tool along the axis of the pocket, and a flat, generally triangular, end face is then formed by translatory movement of the tool transversely of the axis of the pocket.

Abstract: There is provided a method of manufacturing a rotary drill bit of the kind including a plurality of cutting structures mounted in sockets in the bit body and projecting from the face of the bit. The method comprises providing a clearance between each cutting structure and its socket and filling the clearance with a settable liquid, the settable liquid being such as to solidify at a temperature less than 400.degree. C. and to retain its integrity, after solidification, at least up to a temperature of 180.degree. C. The solidified liquid acts as a gap filler and provides an interference fit between the cutting structure and the socket. Suitable gap filing settable liquids are: anaerobic adhesive, epoxy resin, dental amalgam, tin/lead solder and bismuth/antimony alloy.

Abstract: An elongate cutter for a drag-type drill bit includes a stud defining one end thereof and a cutting formation comprising a cutting face generally adjacent the other end. Length extends from one end to the other, depth extends generally transverse to the cutting face as well as transverse to the length, and width extends transverse to both length and depth. The stud has a cross section transverse to its length such that the cross section cannot be circumscribed by a reference circle whose diameter is equal to the maximum width of the cross section. The cross section also has an assumed section modulus, in the direction of depth, greater than that of the reference circle. The leading side of the cutter comprises a first planar zone adjacent the one end and a second planar zone adjacent the other end, and on which the cutting formation is carried. The maximum lateral dimension of the leading side is generally greater than or equal to the maximum width of the cutter.

Abstract: The body of a rotary drill bit is formed from a matrix formed by a powder metallurgy process, and a plurality of cutting elements are mounted on the bit body, each cutting element being in the form of a disc of superhard material which is thermally stable at the temperature of formation of the matrix. The front surface of each cutting element is engaged by a holding structure on the bit body in front of the cutting element, the arrangement of the holding structure being such that the resistance provided by the holding structure to forward deflection of the portion of the cutting element opposite the cutting edge is less than the resistance to rearward deflection provided by the surface behind the cutting edge. Bending stresses imparted to the cutting element by rearward deflection thereof in the vicinity of the cutting edge are thereby reduced.

Abstract: A method of manufacturing by a powder metallurgy process a rotary drill bit including a bit body having a plurality of cutting elements mounted on the outer surface thereof comprises the steps of forming a hollow mould for moulding at least a portion of the bit body, packing the mould with powdered matrix material, and infiltrating the material with a metal alloy in a furnace to form a matrix. Before packing the mould with powdered matrix material, there are postioned in spaced locations on the interior surface of the mould a plurality of cutting element, each of which is formed of a material, such as a polycrystalline diamond material, which is thermally stable at the temperature necessary to form the matrix. Also positioned in the mould, adjacent the rearward side of each cutting element, is a support material such that, at least after formation of the matrix, the support material has a higher modulus of elasticity than the matrix.

Abstract: A rotary drill bit comprises a bit body having a leading face and a gauge region, a number of blades on the leading face of the bit body, and a number of cutting elements mounted along each blade. A passage in the bit body supplies drilling fluid to nozzles in the leading face of the bit body for cooling and cleaning the cutting elements. Each nozzle is so oriented, and the surface of the bit body in the region in front of each blade is so shaped, as to promote a vortex flow of drilling fluid around said region, with part of the periphery of the vortex extending across the cutting elements on the blade, so that fluid in the periphery of the vortex passes across the cutting elements mounted on each blade before escaping through an exit channel in the gauge region.

Abstract: A rotary drill bit, for drilling wells in subsurface earth formations, and designed for rotation in a given direction, comprises a bit body having an internal passageway for drilling fluid. The bit body has an operating end face and at least one opening through that face communicating with the passageway. Cutters on the bit body form at least one elongate cutting region extending generally radially along a substantial portion of the operating end face. The cutters have cutting surfaces facing in the forward direction and generally continuous cutting edges at the outer extremity of the cutting surfaces. An elongate fence is carried on the bit body, extending generally parallel to the cutting region and spaced from the cutting region in a leading direction.

Abstract: The invention comprises a method of mounting a cutter, having a stud portion defining one end thereof and a cutting formation generally adjacent the other end, in a pocket in a drill bit body member. The method includes the steps of forming a channel extending into the pocket, inserting brazing material into the channel, inserting the stud portion of the cutter assembly into the pocket, then heating the bit body member to cause the brazing material to flow through the channel into the pocket, and finally re-cooling the bit body member. During the assembly of the various pieces required in the steps mentioned immediately above, a spring is used, cooperative between the cutter and the bit body member, to retain the stud portion in the pocket and also to displace the stud portion toward the trailing side of the pocket.

Abstract: A rotary drill bit for use in drilling deep holes in subsurface formations comprises a bit body having a leading face and a gauge region, a plurality of cutting elements mounted at the surface of the leading face of the bit body, a passage in the bit body for supplying drilling fluid to a plurality of openings in the leading face of the bit body, and one or more junk slots in the gauge region of the bit body, whereby drilling fluid emerging from the openings flow over the leading face of the bit body and past the cutting elements thereon, so as to cool and clean the cutting elements before exiting through the junk slot.

Abstract: A method of manufacturing by a power metallurgy process a rotary drill bit including a bit body having an external surface on which are mounted a plurality of preform cutting elements, and an inner passage for supplying drilling fluid to at least one nozzle located in a socket at the external surface of the bit. The method includes the steps of forming a hollow mould for moulding the bit body, packing the mould with powdered material, such as tungsten carbide powder, and infiltrating the material with a metal alloy in a furnace to form a matrix. Before packing the mould with the powdered material, there is positioned in the interior surface of the mould at least one former which projects into the interior of the mould space at the desired location for a nozzle socket, the former having an external screw thread whereby the matrix material packed around the former becomes shaped with a corresponding internal screw thread.

Abstract: A cutting element for a rotary drill bit comprises a thin hard facing layer, defining a front cutting face, bonded to a less hard backing layer. The backing layer is of non-uniform thickness, for example is wedge-shaped, and is thicker adjacent the cutting edge of the facing layer than it is over the rest of the area of the facing layer. The rear surface of the backing layer of the cutting element is bonded to a surface on a carrier which is mounted in the bit body. The backing layer of the cutting element may be formed in two portions: a front portion which is bonded to the hard facing layer and a second, wedge-shaped portion which is bonded subsequently to the rear surface of the first portion.

Abstract: A full bore drag-type well drilling bit comprises a bit body having an operating end face defining a plurality of upsets. Each of the upsets has a leading edge surface and at least one recess extending through the leading edge surface into the upset. The end face of the bit body further comprises a plurality of flow channels, each such leading edge surface having one such flow channel extending therealong and inset therefrom. At least some of the upsets have a plurality of such recesses spaced therealong. The bit body further has a plurality of circulation ports opening through its end face and a plurality of nozzles, each nozzle being mounted in a respective one of the ports. The number of nozzles is less than the number of flow channels. At least some of the nozzles communicate with more than one such flow channel, and the transverse cross-sectional flow area of each of the nozzles is substantially less than those of individual ones of the channels communicating therewith.

Abstract: An elongate cutter for a drag-type drill bit includes a stud defining one end thereof and a cutting formation comprising a cutting face generally adjacent the other end. Length extends from one end to the other, depth extends generally transverse to the cutting face as well as transverse to the length, and width extends transverse to both length and depth. The stud has a cross section transverse to its length such that the cross section cannot be circumscribed by a reference circle whose diameter is equal to the maximum width of the cross section. The cross section also has an assumed section modulus, in the direction of depth, greater than that of the reference circle. The leading side of the cutter comprises a first planar zone adjacent the one end and a second planar zone adjacent the other end, and on which the cutting formation is carried. The maximum lateral dimension of the leading side is generally greater than or equal to the maximum width of the cutter.

Abstract: A drag-type drill bit comprises a bit body having an operating end face and a multiplicity of superhard cutting elements interlocked to the bit body. The cutting elements define a multiplicity of cutting areas dispersed over the operating end face of the bit body in a pattern adapted to cause the cutting areas to cut an earth formation to a desired three-dimensional profile as the bit body is rotated. The cutting areas have back rake angles which become more negative with distance from said profile.

Abstract: The invention comprises a drag-type drill bit including a bit body adapted for rotative movement in a pre-determined direction in use and having an operating end face, and a plurality of cutting members mounted in the bit body. Each of the cutting members has a stud portion disposed in a respective recess in the bit body and defining the inner end of the cutting member, and a cutting face generally adjacent its outer end facing outwardly through the operating end face of the bit body and terminating in an outermost cutting edge. The centerline of the stud portion is rearwardly inclined, from the outer end to the inner end, with respect to the direction of movement in use, taken at the midpoint of the cutting edge, at a first angle from 80.degree. to 30.degree. inclusive. The cutting face is oriented such that the tangent to the cutting face at the midpoint of the cutting edge and in the central plane of the cutting member is disposed at a second angle, from 18.degree. to 75.degree.

Abstract: A method of manufacturing by a powder metallurgy process a rotary drill bit including a bit body having a plurality of cutting elements mounted on the outer surface thereof comprises the steps of forming a hollow mould for moulding at least a portion of the bit body, packing the mould with powdered matrix material, and infiltrating the material with a metal alloy in a furnace to form a matrix. Before packing the mould with powdered matrix material, there are positioned in spaced locations on the interior surface of the mould a plurality of cutting elements, each of which is formed of a material, such as a polycrystalline diamond material, which is thermally stable at the temperature necessary to form the matrix. Also positioned in the mould, adjacent the rearward side of each cutting element, is a support material such that, at least after formation of the matrix, the support material has a higher modulus of elasticity than the matrix.

Abstract: The invention comprises a method of mounting a cutter, having a stud portion defining one end thereof and a cutting formation generally adjacent the other end, in a pocket in a drill bit body member. The method includes the steps of forming a channel extending into the pocket, inserting brazing material into the channel, inserting the stud portion of the cutter assembly into the pocket, then heating the bit body member to cause the brazing material to flow through the channel into the pocket, and finally re-cooling the bit body member. During the assembly of the various pieces required in the steps mentioned immediately above, a spring is used, cooperative between the cutter and the bit body member, to retain the stud portion in the pocket and also to displace the stud portion toward the trailing side of the pocket.

Abstract: A drill bit comprises a bit body having an operating end face. A plurality of self-sharpening cutters are mounted in the bit body and extend through the operating end face. The cutters have cutting faces adapted to engage an earth formation and cut the earth formation to a desired three-dimensional profile. The cutting faces define surfaces have back rake angles which decrease with distance from the profile. The individual cutting faces may be inwardly concave in a plane parallel to the intended direction of motion of the cutter in use. Each of the cutting members has a stud portion disposed in a respective recess in the bit body and defining the inner end of the cutting member, the cutting face being generally adjacent the outer end and having an outer cutting edge. The centerline of the stud portion is rearwardly inclined, from the outer end to the inner end, with respect to the direction of movement in use, taken at the midpoint of the cutting edge, at a first angle from 80.degree. to 30.degree. inclusive.

Abstract: A rotary bit for use in subsurface formations comprises a bit body having a central bore (4), the body having a leading face (1) and a trailing gauge region (2), walls (7) on the bit dividing the face into fluid channels, cutting elements C being present on at least some of the walls, and passageways (5) connecting the bore (4) to openings (6) in the fluid channels. At least two wall portions (7) are arranged relative to each openings (6) so that the fluid emerging from the opening is directed to travel first inwardly towards the central axis of the bit before travelling outwardly to the gauge region (2).