Abstract: A toolholder for removing material from a workpiece wherein the workpiece and toolholder are rotatable with respect to one another. The toolholder includes a body having a plurality of pockets. A roughing insert is carried in one of the pockets of the body. The roughing insert presents a roughing edge. The roughing insert is of a first grade. A finishing insert is carried in another of the pockets of the body. The finishing insert presents a finishing edge. The finishing insert is of a grade different than that of the roughing insert.

Abstract: A cutting element which has a metal carbide stud having a conic tip formed with a reduced diameter hemispherical outer tip end portion of said metal carbide stud. A layer of polycrystalline material, resistant to corrosive and abrasive materials, is disposed over the outer end portion of the metal carbide stud to form a cap. An alternate conic form has a flat tip face. A chisel insert has a transecting edge and opposing flat faces. It is also covered with a PDC layer.

Abstract: A drill bit for cutting hard and abrasive materials has cutting lips formed from sintered polycrystalline diamond (PCD) or polycrystalline cubic boron nitride (PCBN) contained in one or more inserts installed in a drill bit blank. The inserts are made by forming depressions in the upper surface of a matrix slab of tungsten carbide, filling the depressions with fine mesh grains of diamonds or cubic born nitride, subjecting the slab to heat and pressure sufficient to fuse the grains to one another and to the surrounding matrix walls, and then cutting the matrix slab to remove individual inserts containing an elongated vein having an exposed PCD or PCBN surface supported by at least one and preferably two or more side walls of tungsten carbide. A rectangular slot having side walls parallel to one another and equidistant from the diameter of a cylindrical drill bit blank is cut into one transverse end wall of the blank, and one or more inserts placed in the slot.

Abstract: A drill to cut hardly machinable materials has major flanks extending in a backward direction of rotation from major cutting edges with an ascending slope and ultra-hard cutting grains adhered to said major flanks, at least. When the rotating drill contacts the work-piece, the ultra-hard cutting grains adhered to the most backward part of the major flanks to the direction of rotation cut the work-piece at first. As the ultra-hard cutting grains of the major flanks drop off by the cutting, actual cutting parts move to adjacent part forward of the rotation of the major flanks. Finally, major cutting edges take over the cutting of the work-piece.

Abstract: A metal cutting insert is made by performing a sintering operation to form a substrate having a longitudinal axis and superhard abrasive bodies bonded thereto at longitudinally spaced locations. The substrate and superhard bodies are sliced-through in directions perpendicular to the axis to form inserts having superhard body portions on both side surfaces of the insert.

Abstract: An improved coated hard alloy tool having a substrate made of a hard alloy, and a multi-layer ceramic coating film provided on the surface of the substrate, the coating film including at least one oxide layer. The top several layers of the coating film are missing partially or completely in an area where the tool is brought into frictional contact with a workpiece. At least one oxide layer (such as Al.sub.2 O.sub.3 layer) is included in the missing layers. This increases wear resistance of the coated hard alloy tool.

Abstract: Wear resistant rotary machining tools including twist drill bits, slot drill bits, thread taps, end mills and reamers are disclosed. The tools comprise a body of cemented tantalum, titanium tungsten carbide (1) having a layer of abrasive polycrystalline diamond or cubic boron nitride compact (2) bonded to a convex curved surface of the tool body. The twist drill bits of the invention comprise a layer of abrasive compact of substantially uniform axial thickness extending over substantially the whole top surface of the tip of the drill bit. Methods of manufacturing the wear resistant tools are also disclosed.

Abstract: A single-blade reamer is guided in a hole by means of at least one guide fillet. The guide fillet is provided with a coating of cubical boron nitride (CBN) in the region of its guide surface facing the wall of the hole. The guide fillet thus withstands heavier loads, so that the reamer is suitable in particular for the economical machining of hardened steel alloys.

Abstract: A cutting element which has a metal carbide stud having a conic tip formed with a reduced diameter hemispherical outer tip end portion of said metal carbide stud. A layer of polycrystalline material, resistant to corrosive and abrasive materials, is disposed over the outer end portion of the metal carbide stud to form a cap. An alternate conic form has a flat tip face. A chisel insert has a transecting edge and opposing flat faces. It is also covered with a PDC layer.

Abstract: A drill to cut hardly machinable materials has major flanks extending in a backward direction of rotation from major cutting edges with an ascending slope and ultra-hard cutting grains adhered to said major flanks, at least. When the rotating drill contacts the work-piece, the ultra-hard cutting grains adhered to the most backward part of the major flanks to the direction of rotation cut the work-piece at first. As the ultra-hard cutting grains of the major flanks drop off by the cutting, actual cutting parts move to adjacent part forward of the rotation of the major flanks. Finally, major cutting edges take over the cutting of the work-piece.

Abstract: A cutter body for counter sink drilling fiber reinforced plastic materials, such cutter body having a pilot portion at a distal end of the cutter body and a countersinking section formed adjacent to the pilot portion in a region on the base end side of the cutter body. The countersinking section comprises three unit machining sections disposed with equal angular intervals in the circumferential direction of the cutter body. Each unit machining section comprises an abrasive layer formed by electrodepositing diamond abrasive grains on a conical surface in turn provided on the cutter body with a chip discharge groove and a finishing edge overhanging from the abrasive layer by an amount t and disposed in order successively rearward in the direction of rotation of a drill or cutter. The finishing edge is formed on a hard sinter, which contains diamond grains as a main ingredient, on a laminar sinter.

Abstract: A cutting tool is provided which comprises a tungsten carbide body or core (2) to which is soldered, brazed or otherwise bonded at least one strip of tungsten carbide (3) that is ground to form a cutting edge or blade. A tough non-vibrating core is thus provided for use with a very hard blade separately replaceable. A method of forming the body or core (2) involves forming a pre-sintered preform, grinding one or more flutes in the preform and subsequently hardening the preform into a fully sintered state ready for use to receive one or more cutting blades.

Abstract: A cutter shell for cutting a circular opening in a metal object formed of a tubular boring portion and a head portion. The boring portion has a tubular sidewall and teeth at the forward circumferential end. The sidewall is of thickness not greater than the teeth. The head portion has an outer circumferential perimeter secured to the tubular portion rearward circumferential end, the head portion being attachable to a boring bar by which the cutter shell is rotated. A circumferential abrasive band is affixed to the exterior circumferential surface of the tubular sidewall for engagement with the wall of a hole as the hole is cut in an object by the teeth to smooth and round out the hole for improved cylindricality.

Abstract: A spade in a bit body is disclosed to have a planar body shaped with two intersecting cutting faces. The cutting faces extend to side faces defining spade width for cutting a hole to gauge. Inserts positioned in the body are at the comer of the spade. The inserts are formed of very hard material, and provide longer life.

Abstract: A drill bit for cutting hard and abrasive materials has cutting lips formed from sintered polycrystalline diamond (PCD) or polycrystalline cubic boron nitride (PCBN) contained in one or more inserts installed in a drill bit blank. The inserts are made by forming depressions in the upper surface of a matrix slab of tungsten carbide, filling the depressions with fine mesh grains of diamonds or cubic born nitride, subjecting the slab to heat and pressure sufficient to fuse the grains to one another and to the surrounding matrix walls, and then cutting the matrix slab to remove individual inserts containing an elongated vein having an exposed PCD or PCBN surface supported by at least one and preferably two or more side walls of tungsten carbide. A rectangular slot having side walls parallel to one another and equidistant from the diameter of a cylindrical drill bit blank is cut into one transverse end wall of the blank, and one or more inserts placed in the slot.

Abstract: A cutting element which has a metal carbide stud having a plurality of ridges formed in a reduced or full diameter hemispherical outer end portion of said metal carbide stud. The ridges extend outwardly beyond the outer end portion of the metal carbide stud. A layer of polycrystalline material, resistant to corrosive and abrasive materials, is disposed over the ridges and the outer end portion of the metal carbide stud to form a hemispherical cap.

Abstract: A diamond coated drill bit capable of drilling small holes and then reaming the holes to their correct size. The tapered tip of the drill bit has a coarse diamond grit coating which enables it to initiate a hole. The drill bit then gradually grinds the hole to the proper size with a grinder having coarse diamond grit bonded to its surface which is at a predetermined taper. The final diameter of the hole is controlled by using a fine grit diamond reamer above the tapered grinder portion. The grinder applies a radial load to the composite material resulting in no fiber breakout or splintering. The tapered grinder and the reamer are formed on a machined-flat portion of the drill bit which enables coolant to circulate down to the grinding area and allows the easy removal of debris.

Abstract: A cutting tool having a diamond film cutting edge is disclosed. The tool may have a shear cutting angle of up to 25.degree. while maintaining its durability and achieving a high degree of cutting efficiency.

Abstract: The tool for machining bore transitions includes a holder drivable rotatably through at least one rotation, and drivable in an advance stroke and in a return stroke; and a spring wire having at least two resilient arms with overlapping movable free end, the spring wire being bent into a hairpin shape so as to have a stem or bent end portion structured to be inserted and held in the holder and a cutting medium provided on the free ends of the resilient arms for machining the bore transitions. The holder can advantageously be provided with a slot for the stem, threaded bolts which engage between the resilient arms of the spring wire and a spring which spring-loads the side of the spring wire inserted in the slot.

Abstract: Diamond cutting tools such as a diamond core drill and a disk-shaped diamond saw which are used to grind and cut hard articles in order to bore or cut hard articles. The diamond cutting tools comprise a tool body and a diamond blade portion attached to an outer end of the tool body. The diamond blade portion has a plurality of outer cuts formed at an outer end thereof and a plurality of inner slots formed under and between the outer cuts and higher than the bottoms of outer cuts by a certain depth. The diamond cutting tools can carry out effectively boring or cutting work until the expensive diamond blade portion is completely worn away.

Abstract: The invention provides a method of manufacturing a twist drill having a cutting insert. The method includes the steps of providing a cutting insert which has a prismatic shape and which comprises a layer of abrasive compact which is bonded to a cemented carbide backing. The insert has on a first facet a cutting edge formed by the abrasive compact layer, and on a second facet a seating surface formed predominantly by the cemented carbide backing. The first and second facets define a predetermined first angle with each other. A twist drill is provided, having a seat in its flank. The seat defines a support surface adapted to receive a seating surface of the insert, and is inclined at a predetermined second angle to the face of the drill. The insert is bonded into the seat, so that the cutting edge of the insert defines the major cutting edge of the drill and the first facet of the insert coincides with the face of the drill. The invention includes cutting inserts and twist drills produced by the method.

Abstract: A tool for processing holes has a shaft which can be clamped in a drive element for executing a forward stroke into a working position within a hole, a return stroke, and an at least rotating working motion of the tool, two support elements arranged on the shaft, wires clamped at one end of the shaft between the support elements and being sprung bowing away from the shaft in an arc shape, the wires being coated with a cutting medium. One of the support elements is axially adjustable relative to the shaft. The shaft has axially positioned slots distributed on a circumference in two regions axially offset from one another. The shaft also has an axial hole leading out from both ends of the shaft and extending into the regions. The support elements are formed as limit stops inserted in the axial hole and each end just short of an entry of the hole into an area of the slots. The wires have ends extending through the slots and coming to rest on the limit stops.

Abstract: A blank material for a drill having a cutting edge and a drill produced from this blank material. The blank material comprises a first blank material having a twisted groove formed on the outer circumference of a columnar base metal sinter and filled with a superhigh pressure sinter, the base metal sinter and the superhigh pressure sinter being sintered and affixed together into one body, and a second blank material composed of a base metal sinter, and the first and the second blank materials are sintered and affixed together at the end faces at superhigh pressure and high temperature. A drill is manufactured by fixing a shank material to the blank material, and forming a twisted cutting edge and a front edge part continuing therefrom, the cutting edge being formed on the superhigh pressure sinter on the first blank material and the front edge part being formed on the second blank material.

Abstract: A rotary cutting tool has a plurality of helical channels located in the body of the rotary cutting tool. Individual cutter segments are bonded within each helical channel to form a continuous helical cutting edge that is machined to a finished state. An area of the tool body adjacent to the helical channel is removed to create helical flutes. Preferably, the segments are cut from disks of polycrystalline diamond (PCD) or polycrystalline cubic boron nitride (PCBN).

Abstract: A tool bit for machining a hard material includes a carrier member (1) supporting polycrystalline diamond platelets (2) with the platelets including a hard metal base member (2a) and a diamond-type layer (2b) supported by the base body. At least the diamond-type layer (2b) is covered by a hard metal layer (3). The hard metal layer (3) serves a carbon diffusion block, whereby the tool bit can be used for machining ferroalloys. Without such a hard metal layer (3) chemical wear occurs due to carbon interaction.

Abstract: Disclosed are methods for applying durable markings to wearing surfaces, such as concrete factory floors, roadways, terrazzo or ceramic tile floors, or for imparting particular floor surface qualities, such as providing a non-skid surface. A diamond surface drill bit rotating at, for example, 2500 to 5000 rpm is employed to form dry recesses in the surface, which recess is immediately receptive to adhesive for attaching a premolded insert, or to an insert formed in situ, such as an insert of an acrylic polymer. The disclosed surface drill bit has a cutting end with two general types of diamond-impregnated cutting element segments attached. Attached around the periphery of the cutting end are peripheral gauge cutting element segments of arcuate configuration spaced from each other.

Abstract: A cutting insert for a rotary cutting tool comprises a body of tungsten carbide, with layers of polycrystalline diamond on opposite sides of the body. The diamond layers overlap across the centre-line of the insert. The cutting insert is shaped for retention at the end of the rotary cutting tool so that the first and second sides of the cutting insert are substantially parallel to the axis of the cutting tool, and the diamond layers are offset from one another across the width of the body so that they define the lips or major cutting edges of the cutting tool.

Abstract: A method, machine tool and boring bar for machining bores in a series of concentric journals for a camshaft in a cylinder head or block of an engine. The boring bar has an elongate and cylindrical body with a single cutting insert at one end for machining all of the journals one at a time and a plurality of circumferentially spaced and longitudinally extending bearing pads on the body which, when the insert is machining one journal, are received in the previously machined journals to radially constrain and support the boring bar. The other end of the bar is received in a chuck or drive spindle of the machine tool which rotates and advances the boring bar through the journals to machine them. Each workpiece is located and clamped in the machine tool with its series of journals to be machined substantially concentric with the axis of rotation of the insert of the boring bar.

Abstract: A high performance drill bit is presented for precision drilling of holes in hard-to-drill materials, such as a carbon fiber reinforced plastic material. The drill is a gun drill type having a pair of flat flutes and a pair of air holes for delivering coolant and/or lubricant. The main feature of the drill is the provision of two pairs of cutting edges formed on the intersecting ridges formed at the leading sides of the flank surfaces with the flute surfaces. At the tip of the drill bit, a pair of primary cutting edges, having a point angle .alpha., is disposed. It is followed by another pair of secondary cutting edges, having a point angle .beta., where .alpha.>.beta.. Physically, this means that the secondary cutting edges are inclined more toward the drill axis than the primary cutting edges. The secondary cutting edge is followed further by another flank surfaces which are even more inclined toward the drill axis.

Abstract: A diamond tool which generates little vibrations, can be used in high temperature environments and can be produced with excellent yield has at least a shank portion (2) in contact with a diamond chip (1) and formed from a reaction-sintered silicon carbide material having a thermal expansion coefficient close to that of the diamond chip by using a diamond granule, and a method for producing the diamond tool which comprises contacting a diamond chip with an ingredient layer mixed with a diamond granule and a carbonaceous source, placing a metallic silicon powder on the surface of the layer, and then reaction-sintering it in vacuum or in a non-oxidizing atmosphere by heating, thereby forming a reaction-sintered silicon carbide material having a coefficient of thermal expansion close to that of a diamond chip, at least, in the shank portion at which a diamond chip is in contact.

Abstract: An enlarged diamond table for use as a cutter in rotating drill bits is provided by disposing a plurality of thermally stable or leached polycrystalline diamond (PCD) rod-like elements within a matrix body. In one embodiment the matrix body is impregnated with diamond grit and completely fills the interstitial spaces between the plurality of PCD elements. Generally, the PCD elements have their longitudinal axes arranged in a mutually parallel configuration. The bundle of rod-like diamond elements are in one embodiment in a compact touching array and in another embodiment in a spaced-apart array. In the illustrated embodiment, a bundle of rod-like diamond elements are disposed so that their end surfaces are exposed on the cutting face of the cutting slug. The slug is then in turn mounted on a stud or directly infiltrated into a matrix body bit.

Abstract: A diamond cutting table having the geometric characteristics of larger unleached diamond compact products and yet characterized by the physical properties of smaller leached diamond products is fabricated by forming a diamond cutter incorporating a plurality of polycrystalline diamond (PCD) leached disks. The PCD leached disks are disposed in array in a cutting slug formed of matrix material. The matrix material is disposed between and around the plurality of diamond disks and in one embodiment incorporates a volume distribution of diamond grit. The cutting slug is hot pressed or infiltrated to form an integral mass or table. The diamond table is then bonded to a cutter or directly molded into an integral tooth within a matrix body bit.

Abstract: A method of producing a composite cutting insert for a twist drill includes the steps of cutting an intermediate blank from a composite diamond compact. The intermediate blank comprises a relatively broad tungsten carbide strip with a relatively narrow polycrystalline diamond strip at one edge. First and second cutting insert halves are cut from the intermediate blank, each cutting insert half defining a cutting edge of the diamond material. The cutting insert halves are arranged back-to-back to form a composite cutting insert, with the cutting edges on opposite sides of a central plane. The cutting edges are arranged to define a chevron shaped composite cutting edge. The cutting insert halves are preferably brazed together to form a unitary cutting insert. The invention extends to a method of producing a twist drill including the steps of forming a slot-shaped seat diametrally in the end of a twist drill body, and brazing the composite cutting insert into the seat.

Abstract: The invention provides a method of manufacturing a twist drill having a cutting insert. The method includes the steps of providing a cutting insert which has a prismatic shape and which comprises a layer of abrasive compact which is bonded to a cemented carbide backing. The insert has on a first facet a cutting edge formed by the abrasive compact layer, and on a second facet a seating surface formed predominantly by the cemented carbide backing. The first and second facets define a predetermined first angle with each other. A twist drill is provided, having a seat in its flank. The seat defines a support surface adapted to receive a seating surface of the insert, and is inclined at a predetermined second angle to the face of the drill. The insert is bonded into the seat, so that the cutting edge of the insert defines the major cutting edge of the drill and the first facet of the insert coincides with the face of the drill. The invention includes cutting inserts and twist drills produced by the method.

Abstract: The present invention relates to an electrodeposited reamer tool (1) for use in precision bore processing.In this electroplated reamer tool (1), a work processing portion (3) in a reamer body is constituted by a finishing portion (4) having a cylindrical outer peripheral surface and a cutting portion (5) provided on the distal end side of the finishing portion (4) and having a tapered configuration, and abrasive grains (6) are electrodeposited on the outer peripheral surfaces of the finishing portion (4) and the cutting portion (5).In the electrodeposited reamer tool (1) is inserted into a prepared hole provided in a work, the prepared hole is enlarged by the cutting portion (5), and the inner surface of the bore is finished by the finishing portion (4).Accordingly, it is possible to form a precision bore of a predetermined inner diameter in a work without preprocessing the prepared hole with precision.

Abstract: A deburring tool is constructed of a pair of wire sections resiliently interconnected with each other so that each biases the other against the internal side walls of a bore formed in a workpiece. Abrasive material is provided on either or both of the sections, and rotation of the tool about its longitudinal axis causes engagement of the abrasive material with the area of the bore wall at which burrs are to be removed. The tool can be formed of a single length of wire having a curved portion on which the abrasive material is located, or the tool can assume various other configurations. The single wire version can be used to remove burrs from the interior of very small bores.

Abstract: Disclosed are methods for applying durable markings to wearing surfaces, such as concrete factory floors, roadways, terrazzo or ceramic tile floors, or for imparting particular floor surface qualities, such as providing a non-skid surface. A diamond surface drill bit rotating at, for example, 2500 to 5000 rpm is employed to form dry recesses in the surface, which recess is immediately receptive to adhesive for attaching a pre-molded insert, or to an insert formed in situ, such as an insert of an acrylic polymer. The disclosed surface drill bit has a cutting end with two general types of diamond-impregnated cutting element segments attached. Attached around the periphery of the cutting end are peripheral gauge cutting element segments of arcuate configuration spaced from each other.

Abstract: A drill bit has a throw-away drill bit tip in the form of an insert (21, 31) secured to a shank (22, 32) to be mounted in a drilling tool. The insert (21, 31) is disengageably mechanically connected with the shank (22, 32) without any screws. At least a cutting edge of the insert (21, 31) is made of a diamond or cubic boron nitride sintered body, and the shank (22, 32) is made of steel. Due to this structure, the insert (21, 31) has an excellent wear resistance and an adhesion resistance. The shank (22, 32) has sufficient toughness against breakage. Such a drill bit does not require any resharpening for continuous use during bit life.

Abstract: Polycrystalline diamond has non-uniform quality along the direction of thickness. The diamond near the rake surface is of better quality. The diamond near the fixation surface is of worse quality. The worse diamond near the fixation surface alleviates a strong stress or absorbs an external shock. Owing to the worse diamond near the fixation surface, the diamond tool excels in chip resistance or toughness. The better diamond near the rake surface heightens abrasion resistance, adhesion resistance and strength.

Abstract: A drill bit of a diamond-coated sintered body has a substrate mainly composed of Si.sub.3 N.sub.4 or SiC. At least a wear portion of the bit is coated with a diamond layer. If the bit is of the throw-away kind, an insert is removably secured to a shank. At least the insert or a wear portion thereof is coated with a diamond layer. The sintered body contains a prescribed amount of a sintering assistant or aid selected from MgO, Y.sub.2 O.sub.3 and the like. The diamond coating layer has a thickness of at least 0.1 .mu.m.

Abstract: A drill for use in drilling hard and brittle materials includes a shank and a drilling portion attached to one end of the shank. The drilling portion includes a tapered primary cutting edge, a first secondary cutting surface extending from the primary cutting edge and having an angle of taper substantially identical to that of the primary cutting edge, and a second secondary cutting surface extending from the first secondary cutting surface and containing a line substantially parallel to the central axis of the drill. The primary cutting edge has a first abrasive grain layer, and the first and second secondary cutting surfaces both have a second abrasive grain layer. The first and second abrasive grain layers both have a binder made of material selected from the group consisting of metal, resin and glass. Each abrasive grain in the first abrasive grain layer has a diameter greater than that of each abrasive grain in the second abrasive grain layer.

Abstract: Apparatus for the diamond machining of materials which detrimentally react with diamond cutting tools in which the cutting tool and the workpiece are chilled to very low temperatures. This chilling halts or retards the chemical reaction between the workpiece and the diamond cutting tool so that wear rates of the diamond tool on previously detrimental materials are comparable with the diamond turning of materials which do not react with diamond.

Abstract: A burnishing drill includes a cylindrical drill body connected at its forward end integrally with a shank. The forward end of the drill body includes a first pair of cutting edges inclined radially and rearwardly from the forwardmost central end of the drill body toward the shank at a first cutting angle. A second pair of cutting edges formed of diamond chips are disposed in a plane intersecting the plane in which the first pair of cutting edges are located. The second pair of cutting edges are inclined radially and rearwardly from a position inside a circle including the maximum external margins of the first pair of cutting edges toward the shank at a second cutting angle.

Abstract: A hollow drilling tool is made up of an axially extending tubular carrier part, a cutting body at one end of the carrier part, and guide elements located in the axial direction of the carrier part between the cutting body and the carrier part. The radially outer surface of each guide element is in alignment in the axial direction of the carrier part with the radially outer surface of the cutting body. The guide elements guide the hollow drilling tool in a borehole formed by the cutting body.

Abstract: Piston wrist pin boring tool including semi-finish and finish inserts mounted in individual cartridges adjustably secured in cartridge pockets provided in the boring bar. A carbide shank is brazed to a body provided with a cartridge pocket, and a diamond tip for the finishing insert is provided with a closely controlled flat neutral rake cutting edge supplied with coolant from central passages through the bar.

Abstract: Method of making and tool bit construction; the bit has a diametrical blade implant of a two-phase material: a main phase of cemented carbine with diffusion bonded cubic boron nitride insert phases placed at high stress corners of such blade, limited strictly to the radial cutting zone of the bit without penetrating the centering zone.

Abstract: A novel construction of a single blade fly cutter type generator wheel. The wheel incorporates a single polycrystalline blade. The blade is counterbalanced by a cut-out portion. An abrasive grit material is provided on a surface of the wheel rim which follows the polycrystalline blade. The abrasive grit cooperates with the blade such that it breaks down large turnings generated by the blade during cutting operations to increase efficiency of the wheel and allows the use of only one blade. An improved method for drilling or cutting of composites is provided wherein softer layers of the composites are not adversely affected during the cutting or drilling operation.

Abstract: The brazing seams that attach cutting edge wear inserts on a drill are protected against wear and erosion. The inserts are deliberately differentially sized so that the points where the brazing seams that attach them intersect the cutting edges are differentially spaced from the drill center line. Then, a notch is cut into each cutting edge just wide and deep enough to prevent the brazing seam from contacting the cut. Cutting is still complete, despite the notches, since they do not overlap.

Abstract: The inserts and pockets in an inserted drill are provided with differing curvatures on their arcuate back edges. Consequently, when the insert is aligned in the pocket, a crescent shaped, instead of annular, gap is created, with minimal or no thickness at the outboard ends. Very little braze seam is thus exposed to erosion at the cutting edge, but the braze seam is as strong or stronger than conventionally. It is also easier to maintain the desired thickness of the braze seam during manufacture.

Abstract: A diamond cutter for use in a drill bit having a geometric size and shape normally characterized by unleached diamond product, such as STRATAPAX diamond cutters, can be fabricated by assembling a plurality of prefabricated leached polycrystalline diamond (PCD) elements in an array in a cutting slug. A cutting slug is formed of matrix material which in one embodiment is impregnated with diamond grit. The cutting face of the cutting slug is characterized by exposing at least one surface of each of the PCD elements disposed therein. The diamonds may be set within the cutting slug either in a compact touching array or in a spaced-apart relationship. More than one type of array may also be employed within a single cutting slug. The PCD elements can assume a variety of polyhedral shapes such as triangular prismatic elements, rectangular elements, hexagonal elements and the like. The plurality of diamond elements and the cutting slug are fabricated using hot pressing or infiltration techniques.