Abstract: Enhanced inserts are formed having a cylindrical grip and a protrusion extending from the grip. An ultra hard material layer is bonded on top of the protrusion. The inserts are mounted on a rock bit and contact the earth formations off center. The ultra hard material layer is thickest at a critical zone which encompasses a major portion of the region of contact between the insert and the earth formation. Transition layers may also be formed between the ultra hard material layer and the protrusion so as to reduce the residual stresses formed on the interface between the ultra hard material and the protrusion.

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 planar or convex heel, gage, or cutting element comprising one or more layers of superhard materials bonded to a metal-carbide substrate. The substrate's perimeter is inclined and comprises one or more circumscribing grooves or furrows, or flutes, in order to permit the bonding of superhard materials below the plane of the major interface, thereby reinforcing the perimeter of the element itself. This heel, gage, or cutting element is useful in drilling applications for the oil, gas, geothermal, and mining industries.

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 method and apparatus for improved attachment of an ultra-hard compact, especially a two-layer disk-type PCD compact, to a tool or support surface with a mechanical connection. In general the ultra-hard compact is provided with a tool-engaging threaded end protruding from the compact. The threaded end may be facilitated by a post fitted into a blind hole in the ultra-hard compact, or may be facilitated by a threaded sleeve permanently attached to the ultra-hard compact. In any case, when the ultra-hard compact is threadably engaged into a tool or support surface, the fastening means is hidden with only the wear resistant materials of the ultra-hard compact exposed.

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: Superhard material enhanced inserts and methods of making the same have been disclosed. The enhanced insert includes a body portion adapted for attachment to the earth-boring bit and a top portion for contacting an earthen formation to be drilled. The top portion includes a substrate and a layer of superhard material over a portion of the substrate other than in central region of the outer lateral face. For example, a layer of polycrystalline diamond is provided in the leading transition of the top portion, whereas the trailing transition and the central region of the outer lateral face of the top portion are substantially free of polycrystalline diamond.

Abstract: Superhard material enhanced inserts include a body portion adapted for attachment to the earth-boring bit and a top portion for contacting an earthen formation to be drilled. The top portion includes a substrate and a layer of superhard material over a portion of the substrate other than in the outer lateral face. For example, superhard material is provided on the leading edge, the leading face, the crest, the trailing edge, and the trailing face, but not on a portion of the outer lateral face of the top portion. Suitable superhard materials include boron nitride and diamond.

Abstract: A drill bit has a plurality of cemented carbide buttons embedded in a front end of the drill body. Each button includes a cemented carbide body having a rear mounting portion embedded in the drill body, and a symmetrically shaped crushing end protruding from the drill body. The buttons are oriented at a first acute angle of from about 35° to about 55° relative to the rotational center axis of the drill bit. The crushing end of the button includes at least one annular groove defining axially spaced local maximum points at each side of the groove. An imaginary line touching the maximum points defining a second acute angle relative to the center line of the button. The second angle is smaller than the first acute angle.

Abstract: A high-performance drilling stabilizer is provided that is high in both wear resistance and strength. Blades are bonded to a stabilizer body. The blade is split into at least two segments. The blade segments are bonded to the stabilizer body to form the blade. A laminate made of cemented carbide and having a laminate structure made up of at least two layers is bonded to the top of each of the blade segments. The laminate has a thickness of between 1 mm and 5 mm. The cobalt contents of the respective layers decrease stepwise from the innermost layer toward the outermost layer.

Abstract: Cutting elements providing a relatively constant superabrasive area in contact with the formation responsive to weight on bit during a substantial portion of the useful life of a circular cutting face cutting element or other cutting element exhibiting a non-linear cutting edge, for example, from about 5% diametrical wear to in excess of about 30% diametrical wear in the case of a circular cutting element, measured across the cutting face. The superabrasive table of the cutting element is configured, internally, externally, or both, to vary in depth radially and laterally, as required, so that an increase in width of the contact or wear flat area with the formation and the variation in table depth as the cutting element wears, are substantially offsetting. The rate of penetration of a drill bit so equipped may thus be maintained at a desirable magnitude without a substantial increase in weight on bit as the cutting element wears, since the superabrasive contact area is maintained relatively constant.

Abstract: An excavating tool has a tungsten carbide insert which is more wear resistant and not subject to breakage because of bring too brittle. The insert has a semispherical tip, a divergent midsection and a base with a conical rear surface. The insert is made with tungsten carbide particles sized between 1 and 8 microns and averaging between 2 and 5 microns, blended with particles of a binder of which the binder comprises 5.5 to 6.5 percent of the blend by weight, and the insert is sintered to a hardness of 89.5 Ra or more.

Abstract: A superabrasive cutting element, the substrate of which is structured with a reduced dimension circumferential portion about which is formed an annular portion of superabrasive material, such as sintered diamond in the form of a polycrystalline diamond compact, to provide a ring- or skirt-like portion of superabrasive material at the perimeter of the cutting element to reduce residual tensile stresses existing at the perimeter of the cutting element after formation.

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: An earth-boring bit has a bit body and at least one cantilevered bearing shaft depending inwardly and downwardly from the bit body. A cutter is mounted for rotation on the bearing shaft and includes a plurality of cutting elements. At least one of the cutting elements has a generally cylindrical body formed of hard metal with a convex cutting end. A plurality of recesses extend longitudinally from the apex to the junction. The recesses are shallow grooves symmetrically spaced about the axis. A layer of super-hard material is formed on the cutting end of the body and overlays the recesses formed thereon.

Abstract: A preform element comprises a substrate having an outer peripheral surface and at least one end surface. At least a portion of the peripheral surface of the substrate has bonded thereto an inner surface of a peripherally extending facing layer of superhard material, such as polycrystalline diamond. The portion of the peripheral surface of the substrate and the inner surface of the peripheral facing layer are provided with inter-engaging formations, such as ribs and grooves, whereby the peripheral facing layer is keyed to the substrate.

Abstract: The present invention relates to a cutting insert for a rock drill bit. The rock drill bit includes a tool body (10) having a front surface (13), and a number of cutting inserts (14), each having a generally cylindrical shank portion. The cutting insert (14) is provided with increased volume portions in its parts being most subjected to wear. The invention also relates to the rock drill bit.

Abstract: A preform cutting element for a rotary drag-type drill bit comprises a front facing table of superhard material having a front surface, a peripheral surface, a rear surface bonded to a substrate of less hard material, and a cutting edge formed by at least part of the junction between the front surface and the peripheral surface. The front surface of the facing table is formed with a chip-breaking formation which is located adjacent the cutting edge and is shaped to deflect transversely of the front surface of the facing table cuttings which, in use, are removed by the cutting edge from the formation being drilled. The chip-breaking formation may comprise a peripheral groove or rebate, or an upstanding ridge or insert.

Abstract: A cutter element that balances maximum gage-keeping capabilities with minimal tensile stress induced damage to the cutter elements is disclosed. The cutter elements of the present invention have a non-symmetrical shape and may include a more aggressive cutting profile than conventional cutter elements. In one embodiment, a cutter element is configured such that the inside angle at which its leading face intersects the wear face is less than the inside angle at which its trailing face intersects the wear face. This can also be accomplished by providing the cutter element with a relieved wear face. In another embodiment of the invention, the surfaces of the present cutter element are curvilinear and the transitions between the leading and trailing faces and the gage face are rounded, or contoured.

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: An earth-boring bit of the rolling cutter variety is provided with hard gage inserts that protrude from the gage surface of the cutter to engage the side of the borehole for holding gage. The gage insert has a substantially flat face with sharp cutting edges formed thereon and has cutting surfaces that define a negative rake angle with respect to the sidewall of the borehole that is being sheared by the gage insert. The cutting surfaces are comprised of multiple chamfers. The face, cutting edge, and cutting surfaces of the gage insert are formed of a super-hard and abrasion-resistant material such as polycrystalline diamond or cubic boron nitride. The body of the insert is formed of a hard, fracture-tough material such as cemented tungsten carbide. The improved gage inserts provide an actively cutting gage surface that engages the sidewall of the borehole to promote shearing removal of the sidewall material.

Abstract: A method of manufacturing preform elements comprises the initial step of forming a preliminary component including a facing table of superhard material having a front face, a peripheral surface, and a rear surface bonded to a less hard substrate. The rear surface of the facing table and the front surface of the substrate are formed with inter-engaging projections and recesses to provide a non-planar interface between the substrate and facing table. There are then cut from the preliminary component a plurality of separate preform elements each having a facing table and substrate with a non-planar interface between them. The configuration of the non-planar interface of the preliminary component may vary with distance from its center, so that the non-planar interface of each preform element also varies in configuration across the width of the element.

Abstract: Drill bit cutters and drill bits equipped with the cutters. The cutter is mounted on a bit to present the formation with a radiused, curving, side wall cutting face that is concave in one dimension and convex in another dimension. In a preferred form, the cutting face is in the form of a portion of a surface of revolution generated by an arc segment that is concave relative to the axis of revolution. The cutting face is formed on a layer of polycrystalline diamond disposed on a substrate of tungsten carbide. In another side wall cutter arrangement, a standard cylindrical cutter with a diamond cap is mounted to present the curved cylindrical side of the cap to the formation. Curved side wall cutting faces cut more efficiently than the usual flat end face of conventionally mounted cutters. A major portion of the diamond volume in a side mounted cutter trails the point of cutting face engagement with the formation to provide impact resistance and an increased diamond wear area.

Abstract: A cutting element for use in drilling subterranean formations. The cutting element includes a superabrasive table between about 0.070 inch and 0.150 inch thickness, mounted to a supporting substrate. The superabrasive table includes a two-dimensional cutting face having a cutting edge along at least a portion of its periphery, and a rake land extending forwardly and inwardly from the cutting edge at an angle of between about 10.degree. and 80.degree. to the longitudinal axis of the cutting element for a width, measured along the surface of the rake land, of not less than about 0.050 inch. The interface between the superabrasive volume and the substrate, taken to the rear of the cutting edge, is located no less than about 0.015 inch to the rear of the cutting edge.

Abstract: A superabrasive cutting element, the substrate of which is structured with a reduced dimension circumferential portion about which is formed an annular portion of superabrasive material, such as sintered diamond in the form of a polycrystalline diamond compact, to provide a ring- or skirt-like portion of superabrasive material at the perimeter of the cutting element to reduce residual tensile stresses existing at the perimeter of the cutting element after formation.

Abstract: A cutting element has a substrate with a non-planar, non-linear surface bonded to a superhard element. The substrate provides one or more non-linear grooves radially mounted in spaced relationships on the surface of the substrate. Each groove has a generally curved shape that unfurls from a first circle on the substrate towards a perimeter of the substrate. The groove shape is defined by complex functions, examples of which include high order polynomials and involutes. The depth and width of the groove varies, generally in an increasing manner, along the path from the first circle towards the substrate perimeter. Further, the pitch of the groove also varies along the path from the first circle towards the substrate perimeter.

Abstract: An improved surface finish for non-planar drill inserts or cutting elements is provided for use on inserts used in the drilling and boring of subterranean rock formations. This new surface finish provides an insert with improved wear characteristics, a decrease in heat generation, a decrease in frictional work loss, and a minimization of failure inducting surface cracks. This invention accomplishes these objectives by a process of polishing the cutting or contact surface of the insert to a very high degree of smoothness.

Abstract: The present invention relates to a cutting insert for a rock drill bit and a rock drill bit including such a cutting insert. It has the object of increasing the wear resistance of the cemented carbide cutting insert. The inserts are formed with a generally cylindrical shank portion and a convexly formed outer portion. In one embodiment of the invention, the cemented carbide of the insert includes a number of zones and the border between two adjacent zones describes a non-symmetrical path seen both in a cross-sectional side view and in a cross-sectional top view. In a further embodiment, the inserts are also provided with increased volume portions in the parts of the insert being most subjected to wear.

Abstract: A frustum cutting bit arrangement, including a shank portion for mounting in, and to be retained by, a rotary cutting tool body, the shank portion having an axis, an inner axial end, and an outer axial end. A head portion has an axis coincident with the shank portion axis, a front axial end, and a rear axial end, the rear end coupled to the shank portion outer end, and the front end having a conical cavity therein diminishing in diameter from the front end toward the rear end. A frustum cutting insert has an axis coincident with the head portion axis, a forward axial end, a back axial end, and an outer conical surface diminishing in diameter from the forward end toward the back end, the conical cavity and the outer conical surface having substantially the same taper, the frustum cutting insert fitting into the cavity in a taper lock.

Abstract: A manufacturing method and a drill bit composite insert for performing mechanical actions that require high wear and impact resistance are provided. The composite insert has improved interface strength and improved residual stress distribution. These improved features are achieved by chemically and mechanically attaching the layer of abrasion and corrosion resistant polycrystalline material to the substrate that ordinarily is tungsten carbide. The chemical bond is formed during high pressure and high temperature sintering. Mechanically, the abrasion and corrosion resistant layer is attached to the substrate by means of irregularities on the substrate's top surface. These irregularities are designed to distribute stress and minimize the number of features that would lead to crack formation and subsequent failure of the insert.

Abstract: A cutter element having a substantially flat wear face and leading and trailing sections, wherein the leading section is sharper than the trailing section. Sharpness is defined as either a smaller inside angle at the intersection of a pair of planes or as a smaller radius of curvature. The insert of the present invention experiences reduced stress on its trailing portion and therefore is less subject to extreme wear and failure. The present invention can be applied with particular advantage to heel row cutters, but can also be applied to cutters in other rows that primarily ream the borehole wall. The present cutter element can be constructed so as to have either a positive or negative rake angle at its leading section, or to have any of a variety of shapes, depending on the characteristics of the formation in which it is to be used.

Abstract: An earth-boring bit has a bit body. At least one cantilevered bearing shaft depends inwardly and downwardly from the bit body and a cutter is mounted for rotation on the bearing shaft. The cutter includes a plurality of cutting elements, at least one of which has a generally cylindrical element body of hard metal. A pair of flanks extend from the body and converge to define a crest. The crest defines at least one sharp cutting edge at its intersection with one of the flanks.

Abstract: An earth-boring bit has a bit body and at least one cantilevered bearing shaft depending inwardly and downwardly from the bit body. A cutter is mounted for rotation on the bearing shaft and includes a plurality of cutting elements arranged in generally circumferential rows, including inner heel rows, of cutting elements. At least one of the cutting elements in one of the inner rows has a crest at least partially formed of super-hard material that defines a cutting edge and cutting surface for shearing engagement with the bottom of the borehole during drilling operations, the remainder of the cutting end of the element is formed of hard, fracture-tough material for crushing engagement with the bottom of the borehole.

Abstract: A preform cutting element for a rotary drag-type drill bit includes a facing table of polycrystalline diamond having a rear surface bonded to a tungsten carbide substrate. The cutting element is formed with an angled chamfer to form a straight cutting edge on the facing table. The junction between one end of the cutting edge and the remainder of the peripheral surface of the facing table is chamfered in a part-circular arc to provide a smooth transition between the cutting edge and the rest of the peripheral surface. Such transition may reduce the spalling or other damage which may be caused by steady state and impact loads in this region.

Abstract: An insert is defined by the present invention. The insert is an elongate cylindrical body having two end faces. At the extended end, the end face supports a PDC layer which is bonded thereto by brazing or sintering and is formed of PDC material to resist impact or shock loading and to provide a long life. The PDC layer is joined to the insert body at a surface which is defined by a central elevated point, the point being relatively small in diameter or is a point, land wherein said straight radial lines extend downwardly and outwardly therefrom. The intercept of the end face with the outer surface of the insert body is an undulating sinusoidal wave form of multiple sinusoidal cycles. This provides a shock resistant insert construction.

Abstract: A cutting element for use in drilling subterranean formations. The cutting element includes a superabrasive table between about 0.070 inch and 0.150 inch thickness, mounted to a supporting substrate. The superabrasive table includes a two-dimensional cutting face having a cutting edge along at least a portion of its periphery, and a rake land extending forwardly and inwardly from the cutting edge at an angle of between about 10.degree. and 80.degree. to the longitudinal axis of the cutting element for a width, measured along the surface of the rake land, of not less than about 0.050 inch. The interface between the superabrasive volume and the substrate, taken to the rear of the cutting edge, is located no less than about 0.015 inch to the rear of the cutting edge.

Abstract: An earth-boring bit has a bit body and at least one cantilevered bearing shaft depending inwardly and downwardly from the bit body. A cutter is mounted for rotation on the bearing shaft and includes a plurality of cutting elements arranged in generally circumferential rows including an outer or heel row of cutting elements. At least one of the cutting elements in the heel row has an outermost surface at least partially formed of super-hard material that defines a cutting edge for shearing engagement with the sidewall of the borehole as the cutters roll and slide over the bottom of the borehole during drilling operations.

Abstract: A fixed cutter drill bit includes a cutting structure having radially-spaced sets of cutter elements. Each cutter in a set has a cutting profile that, in rotated profile, partially overlaps the cutting profiles of each of the other cutters that are in the same set so as to create a region of maximum diamond density. The region of maximum diamond density in a set is defined such that the centerlines of the cutting profiles of the elements in the set pass through the region of maximum diamond density. The cutting profiles of the spaced sets of cutters also may overlap to create border regions of multiple diamond density. The diamond density of border regions is less than or equal to the density in the region of maximum diamond density. Providing such regions of varying diamond density along the bit face tends to increase the bit's ability to resist vibration and provides an aggressive cutting structure, even after significant wear has occurred.

Abstract: A full cutting element including a substantially cylindrical backing and cutter mounted thereon is cut generally along the length thereof to produce a pair of semicylindrical partial cutting elements. In the case of an unused cutting element, each partial cutting clement is mounted on a different semicylindrical tungsten carbide base to produce a substantially cylindrical unit which is mounted on a bit using a low temperature braze. In the case of a used full cutting element, the cutting clement is cut to separate the worn portion from the remainder of the bit and only the unused portion is used to form a cylindrical unit with a corresponding semicylindrical tungsten carbide base. In another aspect, a partial cutting element is received in a pocket formed on a bit body. The pocket includes a pair of opposed side surfaces which substantially flushly abut the curved surfaces of the backing on the partial cutter.

Abstract: A novel form of drill bit is disclosed. The bit (30) comprises a bit body having a leading face (32) and gauge surface (44, 46). Cutting inserts (32, 34, 36) are set into the bit body, each cutting insert being in the form of a segment of a composite PCD (polycrystalline diamond) or PCBN (polycrystalline cubic boron nitride) composite. Thus each insert has a PCD or PCBN compact (40) carried by a carbide backing (42). The PCD or PCBN compact of each insert is exposed at the leading face or at the gauge surface to perform an axial cutting or gauge maintenance function during drilling.

Abstract: In a hollow earth auger head assembly a plurality of bit-holding pockets are provided, spaced circumferentially from one another around an open mouth of an auger head, and bits taken selectively from a multiplicity of types of cutting teeth, have a shank portion that seats in any and all of the pockets. A retaining pin extends chordally, off set from a diameter, through holes in the pocket and into a retaining pin receiver in the bits. In those bits that are intended to rotate in the pocket, the retaining receiver takes the form of an annular channel. In those bits that are not supposed to rotate, the retaining pin extends through a linear passage in or along a flat on the bit shank. In certain embodiments of sockets a chordal plug or weldment defines a space with one flat side against which a tail of the shanks of certain bits designed not to rotate bear.

Abstract: A rotary drag bit for drilling hard rock formations with substantially planar PDC cutting elements having diamond tables backed by substrates which flare or taper laterally outwardly and rearwardly of the cutting edge of the diamond table. A cutting structure defining a "lipped" cutting edge is also disclosed.

Abstract: A drag bit having a plurality of blades or ribs on its end face has one or more pockets milled into the top surfaces of said blades using a ball-nosed end mill to create a plurality of pockets, each having a spherical or a semi-spherical first end and a second end having a semicircular configuration that intersects with the leading edge face of the rib. A bullet-shaped cutting structure having a spherical first end is brazed into each of the pockets. During the manufacturing process, a pin is brazed into cooperating first and second semicircular receptacles in the spherical end of the cutter and in the semi-spherical end of the pocket, respectively, to prevent the cutter assembly from being pushed up out of the pocket during the drilling operation. In an alternative embodiment, a slot is milled into the top surface of the rib to allow use of a ball-nosed end mill having a reduced diameter shank sized to pass through the slot.

Abstract: A cutting bit useful for cutting various earth strata and the cutting insert, which may be made from a polycrystalline diamond composite, for such a cutting bit. The cutting bit has at least one pocket at the axially forward end thereof which receives its corresponding cutting insert. The cutting insert has at least one exposed cutting edge which is of an arcuate shape.

Abstract: A conical insert is disclosed having a cutting tip which includes a spherically shaped apex and a substantially conical surface therebelow. The trailing side of the cutting tip is convex as seen in the longitudinal section taken normal to the apex. The leading side of the cutting tip is either a straight line segment or is concave as seen in the longitudinal section taken normal to the apex.

Abstract: A drill bit, and a cutter for a drill bit, are provided, wherein the cutter will encounter the formation with cutting surfaces of differing rake angles to optimize cutting efficiency. In most circumstances, the cooperating cutters will have differing, positive, and negative or neutral rakes. Cutters of differing rakes may be cooperatively paired on a drill bit such that the portion of a formation which is affected by the action of one cutter may be similarly affected by the operation of the other cutter.

Abstract: An earth-boring bit has a bit body and at least one cutter rotatably secured to the bit body. The cutter has a plurality of teeth formed integrally thereon and arranged in circumferential rows. Each of the teeth includes an outer end, an outer end, a pair of flanks and a crest substantially transversely connecting the ends and flanks. The crests of the at least one of the plurality of teeth has an inverted radius formed therein at at least one intersection of the ends and crest. A wear-resistant material is applied over at least the crest and a portion of at least the ends and flanks of the at least one of the plurality of teeth, wherein the thickness of the wear-resistant material over the inverted radius is substantially greater than elsewhere on the tooth.

Abstract: The present invention relates to diamond drag bits having cylindrical polycrystalline diamond faced inserts with a convex cutting surface, the insert being imbedded in the cutting face of a drag bit. The invention teaches an optimization of the geometry of the cutting face of cutting elements, particularly of the type in which a diamond layer is adhered to a cemented carbide substrate to form a composite, and the composite is bonded to a support stud or cylinder. The convex curvature radius is maximized to the extent that the best shear action on the earthen formation is achieved. The resultant side rake angle assures that each insert remains free of detritus presenting a clean cutting edge to the formation.