Abstract: An inexpensive steel cutting tool with excellent cutting characteristics and cutting life is provided to have a cutting part having a chamfered cutting edge and a surface hardening layer formed therein, wherein surface treatment is performed by forming a sufficiently thick surface hardening layer on the surface of steel base material, or by forming a hard coating film on the surface hardening layer.

Abstract: A cutting tool (200, 202) has a longitudinally extending shaft portion (208) with a chucking part (204) and a cutting head (206). A cutting edge (220) is formed on the cutting head (206). The cutting edge (220) includes at least one cutting portion. A rake surface (224) is formed adjacent to at least one of the cutting portions (220) with the rake face being at a rake angle in the range from about −10° to about 10°. A clearance face (226) is formed adjacent to the at least one cutting portion opposite the rake face (224). The clearance face (226) is at a clearance angle in the range from about 10° to about 50°. An edge radius between the rake face and the clearance face is at a radius of from about 0.0003 to about 0.0040 inch.

Abstract: A cutting tool (500) has a longitudinally extending shaft portion (588) with a chucking part (509) and a cutting head (506). A pressed powder cutting insert (518) with a cutting edge (520) is on the cutting head (506). The cutting edge (520) includes at least one cutting portion. A rake surface (524) is formed adjacent to at least one of the cutting portions (520) with the rake face (524) being at a rake angle from about 0° to 10°. A clearance face (526) is formed adjacent to the at least one cutting portion opposite the rake face (524). The clearance face (526) is at a clearance angle from about 10° to 50°. An edge radius (540) between the rake face (524) and the clearance face (526) is at a radius of from about 0.0015 to about 0.004 inch. The edge radius 540 is formed during pressing of the powder to form the insert, thus, enabling the insert to be directly braised into the cutting head (506).

Abstract: A cutting tool, especially a drill, milling cutter, screw tap, reamer and core drill, comprising a shaft and a cutting member on which at least one cutting edge is provided for machining a workpiece, the cutting member being provided with a slide layer which has a lower hardness than a base layer of the cutting member.

Abstract: A first embodiment of a non-adjustable single cylindrical lip boring tool includes a shank, a body, a straight side lip, and a front cutting edge. The shank is formed on an end opposite the body. The straight side cutting lip is formed on the body. The straight side lip has a radially convoluted relief which blends into the body. A second embodiment of a non-adjustable single cylindrical lip boring tool includes a shank, a body, a helical side lip, and a front cutting edge. The shank is formed on an end opposite the body. The helical side lip is formed around the body. The helical side lip has a radially convoluted relief which blends into the body. Both embodiments of the non-adjustable single cylindrical lip boring tool may be sharpened on a hand grinder.

Abstract: A reamer including; a generally cylindrical cutter body having (a) a flute formed in an outer circumferential surface of the cutter body and extending from an axially distal end of the cutter body toward an axially proximal end of the cutter body, (b) a cutting blade portion positioned at a longitudinally distal end of a downstream one of widthwise opposite edges of the flute as viewed in a rotating direction of the reamer, and (c) a guide portion having a guide surface which is circumferentially adjacent to the flute and which circumferentially extends over at least 240° about an axis of the cutter body. The guide surface is a part of the outer circumferential surface of the cutter body.

Abstract: A cutting tool (200, 202) has a longitudinally extending shaft portion (208) with a chucking part (204) and a cutting head (206). A cutting edge (220) is formed on the cutting head (206). The cutting edge (220) includes at least one cutting portion. A rake surface (224) is formed adjacent to at least one of the cutting portions (220) with the rake face being at a rake angle in the range from about −10° to about 10°. A clearance face (226) is formed adjacent to the at least one cutting portion opposite the rake face (224). The clearance face (226) is at a clearance angle in the range from about 10° to about 50°. An edge radius between the rake face and the clearance face is at a radius of from about 0.0003 to about 0.0040 inch.

Abstract: A center cutting or plunging end mill or ball nose end mill has one or more spiral grooves and flutes in the walls of a mill body of cemented tungsten carbide. Each groove includes polycrystalline diamond or cubic boron nitride formed in situ along a leading edge of each flute. Such a groove extends across the cutting end of the mill so that the mill can be used for center cutting or plunging. The vein of diamond-like material may extend to the center of the mill body or may extend almost all of the way to the center, leaving an area of tungsten carbide exposed at the center of the mill body. A high temperature-high pressure press is used for forming the polycrystalline diamond-like veins in situ within the grooves in the mill.

Abstract: A drilling tool for boreholes in solid material, with a drill shaft with at least one cutter arranged at the end of the drilling tool and at least one recess which extends in the axial direction from the end of the drill tool, to conduct chips from the borehole. At least one of the cutters is made of a coated cermet cutting material.

Abstract: A machining tool and method of making same includes a blank that is formed to a shank and which is provided with machining faces. The machining faces are configured to expose material of a PCD or PCBN element that is formed in a recess in the blank and fused to the blank using material from the transition group of elements, such as cobalt. The recess has a configuration that is defined by side walls, a base wall, and end walls, so as to define a mold in which the PCD or PCBN material is formed into an element that becomes fused with the blank. Such fusing is achieved by leaching of the cobalt into the PCD or PCBN element during the application of heat. Thus, no additional fabrication process is required for joining the PCBN or PCD material to the blank.

Abstract: A drilling tool includes a tool head having at least one chip groove and a tool shank. A slotted sleeve is placed on the tool shank and closely surrounds the chip groove. The edges adjacent the slot lie on solid material of the tool shank. The chip grooves and the sleeve form channels for carrying away the chips removed at the workpiece machining base. Owing to the slot, the sleeve can be gently spread apart and pushed onto the tool shank from the end having the enlarged tool head.

Abstract: A drilling tool is proposed comprising a shaft which has both a chuck shaft suitable for fitting in machine tools and a drill-holding shaft, known per se, with chuck grooves and (optionally) coolant ducts. A replaceable drill bit (1) is fitted in a positive fit and detachably on the shaft. The drill bit can consist of a homogenous material and has cutting edges (2) inclined radially outwards and backwards; these cutting edges can be formed in one piece from the drill bit material or are composed of blades mounted in the central region and made from the drill bit material and complementary blades orignating from a cutter plate screwed onto the drill bit. The invention proposes that the cutting edges (2) should be aligned symmetrically about the drill bit axis and the cutting edges should be in cutting engagement over the entire radius of the bore to be drilled.

Abstract: A shank adapter for a rock drill, which is used to connect one end of a drill string to a rock drill, has a chuck end (10) made from one piece of material and an opposite, threaded end (16) made from another, different, material. The chuck end and the threaded end are permanently joined to one another in one stage of manufacturing.

Abstract: An improved solid cemented carbide ball nose end mill is provided which enables a cutting of a quenched or hardened difficult-to-machine material without any chipping or break of edge under the condition of a high speed and high load cutting. The improved end mill comprises a substantially semi-spherical ball nose portion provided with such cutting edges as to form a virtually S-shaped symmetrical configuration as viewed from the tip end and a tool body integral with said ball nose portion and having a peripheral cylindrical portion being provided with no peripheral cutting edge and a shank at the rear end thereof. The cutting edges extending from the tip end of the ball nose portion to the respective terminals positioned at the furthest at the vicinity of the border between the ball nose portion and the tool body are formed in the ball nose portion only. Preferably, each of a rake angle and a relief angle of the cutting edge is set between 0.degree. and -10.degree., and between 6.degree. and 16.degree.

Abstract: A boring bar includes a shaft and a head which carries a cutting insert. The head includes a conical protrusion which fits in a correspondingly shaped recess of the shaft and is secured therein by an adhesive joint in order to damp vibrations.

Abstract: A drill for forming bores in constructional components and including a tubular stem (2; 22; 32; 42) having an axially extending through-channel (3; 23; 33; 43) which opens into at least one suction opening (7; 11; 27; 37; 47), a shank (5) provided at a rear end of the stem for connecting the drill to a drilling tool (M), and a drilling head (8; 28; 38; 48) having lips (9; 29; 39; 49) and formed entirely of a cutting material and substantially butt-joined to the stem (2; 22; 32; 42) at a free front end of the stem (2; 22; 32; 42), with at least one suction opening being formed by a mouth opening of a front channel (12; 26; 36; 46) which is limited, at least partially by a material of the drilling head (8; 28; 38; 48) and a mouth surface of which, at least partially is arranged in a circumferential region of at least one of the stem (2; 22; 32; 42) and the drilling head (8; 28; 38; 48).

Abstract: A cutting tool assembly for rotary cutting operations comprising a replaceable cutting head and a tool shank, having a common longitudinal axis and mating peripheral surfaces. The cutting head has a cutting head mounting portion at a trailing end thereof and the tool shank has a cutting head receiving portion at a front face thereof. The cutting head mounting portion and the cutting head receiving portion of the tool shank each have at least two coupling portions bound by associated peripheral surfaces of the cutting head and the tool shank and mating in shape and dimensions. Each coupling portion has a base surface, a torque transmission wall and a fixation wall, the fixation wall of each cutting head coupling portion having an angular extension smaller than a corresponding angular distance between adjacent extremities of the fixation walls of two different tool shank coupling portions.

Abstract: A single point drill particularly adapted to producing small diameter deep holes utilizing a peck feed cycle routine. The preferred embodiment features a limited flute length with a depth approximately 1/3 the drill diameter and a dual point edge consisting of a shallow cutting angle and a steep relief angle. A negative rake angle runs along this edge functioning as a knife edge that will cut on opposite rotation, countering the unbalanced forces inherent in a single point tool. A sharpening fixture consisting of 2 parallel slates secured with a T-headed bolt and an anti-rotation pin. The lower plate features a central groove to locate the drill, the upper plate having a short land that facilitates orienting and clamping the drill flute. The forward end of the fixture mimics the drill point allowing the drill to be sharpened on a grinder table or by hand with a suitable abrasive stone or file.

Abstract: An elongate rotary tool including at least one cutting edge that is useful in the machining of workpiece materials is disclosed. The elongate rotary tool comprises a cermet comprising at least one hard component and about 0.2 wt. % to 19 wt. % Co--Ni--Fe-binder. The Co--Ni--Fe-binder is unique in that even when subjected to plastic deformation, the binder substantially maintains its face centered cubic (fcc) crystal structure and avoids stress and/or strain induced transformations.

Abstract: A tool includes a tool body and a cutting portion detachably mounted thereon, the tool being rotatable about a longitudinal center axis. The tool body includes flutes formed in an outer surface thereof, and a pair of forward projections at a front end thereof. The cutting portion includes front flutes formed in an external side thereof, and a pair of recesses extending circumferentially in communication with respective ones of the front flutes. To connect the cutting portion to the tool body, the cutting portion and tool body are converged longitudinally so that the projections enter the front flutes. Then, relative rotation is produced between the cutting portion and tool body to align the front flutes with the rear flutes while causing the projections to enter the recesses and form therewith a bayonet coupling.

Abstract: A rotary tool with a shank comprises a tool body and a tip member Joined to the tool body. A narrow hole starts at an inlet port positioned at an end surface or an outer peripheral surface of the shank to run along the axis of rotation of the tool up to a tip end of said tool body and communicates at the boundary of the tip member and the tool body with an outlet port which opens to the terminal ends of ejection grooves.

Abstract: A mount for interfacing a cutting tool having a generally cylindrical shank portion to a tool holder having a central opening. The mount comprises an elongate, generally cylindrical shank member having first and second ends. The first end is insertable into and securable within the central opening of the tool holder, with the second end including an axially extending bore disposed therein. The shank member is formed to have an outer diameter which slightly exceeds the diameter of the central opening of the tool holder. The bore itself is formed to have a diameter which is slightly less than the diameter of the shank portion of the cutting tool.

Abstract: A shaft tool for metal cutting machining, includes a cutting portion and a shaft portion. The cutting portion includes a fist part formed with a cutting edge, and a second part formed with an external screw thread. The first and second parts are of one-piece integral construction. The shaft portion includes an internal screw thread to which the external screw thread is removably secured.

Abstract: The drill bit according to the present invention provides an advanced, carbide tipped, coolant feed, two-fluted deep hole drill capable of drilling a wider variety of materials deeper and faster than presently known drills of similar construction. Specifically, a deep hole drill bit includes a cutting tip with a fitting end having "V" shaped profile with an apex edge extending along a plane which is substantially aligned with the cutting edges of the cutting tip. The drill bit additionally includes a drill shaft having a distal end adapted to be matingly fitted to the fitting end of the cutting tip. This joint structure allows the shaft to naturally push behind the drill tip to provide enhanced strength and support during drilling. In this manner, the contact area between the drill tip and the shaft is maximized, with the contact area being greatest towards the base of the "V", where the compressive forces are also greatest, i.e., along the cutting edges.

Abstract: A tool includes a tool body and a cutting portion detachably mounted thereon, the tool being rotatable about a longitudinal center axis. The tool body includes flutes formed in an outer surface thereof, and a pair of forward projections at a front end thereof. The cutting portion includes front flutes formed in an external side thereof, and a pair of recesses extending circumferentially in communication with respective ones of the front flutes. To connect the cutting portion to the tool body, the cutting portion and tool body are converged longitudinally so that the projections enter the front flutes. Then, relative rotation is produced between the cutting portion and tool body to align the front flutes with the rear flutes while causing the projections to enter the recesses and form therewith a bayonet coupling.

Abstract: A cutting tool assembly for rotary cutting operations comprising a replaceable cutting head and a tool shank, having a common longitudinal axis and mating peripheral surfaces. The cutting head has a cutting head mounting portion at a trailing end thereof and the tool shank has a cutting head receiving portion at a front face thereof. The cutting head mounting portion and the cutting head receiving portion of the tool shank each have at least two coupling portions bound by assiciated peripheral surfaces of the cutting head and the tool shank and mating in shape and dimensions. Each coupling portion has a base surface, a torque transmission wall and a fixation wall, the fixation wall of each cutting head coupling portion having an angular extension smaller than a corresponding angular distance between adjacent extremities of the fixation walls of two different tool shank coupling portions.

Abstract: Sintered silicon nitride articles for cutting tools and the like, having a high relative density, excellent wear resistance and nicking, particularly at high temperatures, and a method for preparing such articles are disclosed. The articles are made by mixing 0.25 to 3.0 vol % of magnesium oxide powder and 0.3 to 2.0 vol % of ytterbium oxide with silicon nitride starting materials, then crushing and mixing, optionally with 1.0%-vol. or less, preferably 0.5%-vol. or more of aluminum oxide powder and adding an organic binder. The article is formed using a metal press to a shape for usage as SNGN120408 tools. The sintered silicon nitride articles for tools are obtained by degasing the shaped articles, subjecting them to a primary firing at 1700 to 1900.degree. C. and 0.3 to 1.0 MPa temperature and pressure, and following with a secondary firing at a temperature which is substantially lower than the primary firing temperature, at a pressure of 100 MPa or greater.

Abstract: A reamer for finish machining a bore formed in a workpiece and method for providing a reamer with an abrasion resistant material. The reamer includes a body defining an outer surface, a cutting blade and guide member each coupled to the body, and an abrasion resistant material coupled to the reamer to form a friction resistant layer having a contact surface thereon. The abrasion resistant material impregnates the reamer to define an intermediate layer of abrasion resistant material intermixed with the reamer. The method includes the steps of assembling the reamer, applying an abrasion resistant material to said reamer, and allowing the abrasion resistant material to impregnate the reamer to define an intermediate layer of abrasion resistant material intermixed with the reamer.

Abstract: A drill including a cutter member and a shank which are formed separately from each other and fixed to each other for rotation as a unit, wherein the shank has an engaging groove formed in a distal end face thereof such that the engaging groove extends in an axial direction of the shank and is aligned with a center of the distal end face, and the cutter member consists of a rectangular plate including a proximal end portion fixed to the shank by engagement thereof with the engaging groove, and a distal end portion which is remote from the shank and which has at least one cutting edge.

Abstract: A drill with a drill point part that contains the drill cutter and is made of a solid hard material. The drill point part is replacably attached to the end face of a drill shaft. The drill shaft is penetrated by a shaft groove which extends in an axial direction of the shaft to accomodate the drill point part and can center the drill point part in the groove region. The drill shaft has grooves on its periphery which run in the axial direction and extend into the region of the shaft groove and continue into the region of the drill point part. The drill point part can be clamped on its side faces corresponding to and opposite the groove flanks in a force-locking manner by an insertion-clamping fit in the shaft groove.

Abstract: A thread cutting die or chaser for use with a power driven thread cutting machine is provided with a protective coating of an ultra hard material such as titanium nitride which is initially excluded from or is subsequently removed from the faces of the thread cutting teeth such as by a regrinding thereof after application of the coating to the die.

Abstract: A drill having an elongated body including a fluted land and a shank. The fluted land includes a plurality of radial grooves of reduced material thickness formed therein to the depth of the flutes. The grooves define discrete segments of the drill. Each segment has a facet which has the relief of a drill tip so that when the exposed drill tip becomes dull, the segment can be broken off at the notch exposing a successive, sharp drill tip. The drill can have the cutting edges coated with an appropriate protective material such as TiN, titanium nitride, titanium carbide, titanium carbonitride or any other appropriate coating material to improve cutting and preserve the edge.

Abstract: A drill bit is provided with a cylindrical body portion fabricated from a plastic material. The body portion is fastened in concentric, end to end relation to a cylindrical cutter fabricated from a metallic material and having an array of cutting elements disposed thereon. The body portion and cutter are preferably tubular, wherein the cutting elements are disposed in an annular array, to facilitate core or crown drilling operations. The wall thickness of the tubular body portion may be increased relative that of the cutter to compensate for wear during drilling.

Abstract: A tool-bit holder (1) for tool bits (3, 5) of cemented carbide or other hard material, in which the tool-bit holder has vibration-damping properties and the bits are specifically oriented. In particular, the tool-bit holder (1) in all essentials consists of a material, e.g. mild steel, with vibration-damping properties. The effect achieved is that the tool-bit holder may be made in one piece. The vibration-damping properties makes it possible to place the bits (3, 5) in a manner which would otherwise cause instability and consequent machining marks on the workpiece.

Abstract: A drill for the insertion of a dental implant is disclosed. The drill includes a rotational drive portion in the form of a metal rod with a first end and a second end. The first end is connected to a drilling apparatus. The second end of the rotational drive portion is connected to an active cutting portion made of plastic overmolded on a second end of the metal rod. The drill further includes a metal insert portion coupled to the active cutting portion to serve as a sharp edge for the active cutting portion.

Abstract: A boring bar device comprising an elongated shank and a chisel head. The shank and chisel head are connected by a mating V-shaped cross-sectional joint wherein a solder shim of a predetermined composition is utilized in conjunction with a brazing process to connect the chisel head to the elongated shank to provide the boring bar device of the invention.

Abstract: A tool for cutting or milling casing in a well is disclosed. It includes a plurality of blades extending outwardly to a substantially radial position for cutting the walls of casing strings and removing a predetermined length of the casing strings in a cutting action. The blades have cutting elements positioned on leading faces of the blades to engage the casing strings in a cutting action without tripping or removal from the bore hole. The cutting elements can be arranged in rows and columns. The cutting elements can be shaped to continually present a sharp cutting edge to the object being milled. The cutting elements can be inclined at a negative axial rake angle to cause the metal chips cut from the object being milled to break off at short lengths. The cutting element can also have surface irregularities to cause the metal chips cut from the casings to break off at short lengths.

Abstract: A method of, and apparatus for, treating an elongate rotary tool that presents a sharp cutting edge are described. The method includes the steps of emitting under pressure from a nozzle an abrasive fluid stream comprising an abrasive grit entrained in a fluid; and impinging the abrasive fluid stream against the sharp cutting edge of the elongate rotary tool for a preselected time so as to transform the sharp cutting edge into a relatively uniformly honed edge. The apparatus includes a rotatable fixture that releasably holds the elongate rotary tool. A nozzle that emits under pressure an abrasive steam. The nozzle and the elongate rotary tool are relatively moveable so that the abrasive stream impinges the entire length of the sharp cutting edge.

Abstract: A tool bit for use in at least one of a drilling and cutting operation is formed of an axially extending carrier member (1) and a cutting member (2). The cutting member (2) has an expansion joint (2a) extending parallel to the axis of the carrier member (1). The expansion joint (2a) is formed by reducing the thickness of the cutting member (2) so that material webs (2b) remain. In the fabrication and formation of the tool bit, the cutting member (2) is a single unit. In the use of the tool bit, due to the expansion joint the cutting member forms individual operating units (2a) affording reduced material expense of the cutting member (2), because of reduced stresses.

Abstract: The invention relates to a rotating shank-type tool (11) with a shank (12), in which at least one main channel (21) for coolant/lubricant extends in the longitudinal direction of the shank and from which, in the end region of the main channel, at least one branch channel (22) leads outward and forms a mouth (23). A cutting head (13) is connected to the shank (12) and has chip grooves (15) and a groove run-out region (16). A sleeve (19) engages over the mouth (23). The end region of the sleeve (19) covers at least the groove run-out region (16) of the cutting head (13). The branch channel mouth (23) is positioned in the shank at a distance from the cutting head (13).

Abstract: A coated cutting tool, and a method of producing the same, comprising a substrate which has a roughened surface that presents a surface roughness of between 15 microinches R.sub.a and 125 microinches R.sub.a. A coating is applied to the roughened surface of the substrate by physical vapor deposition. A coated cutting tool having a low cobalt substrate and experiencing long tool life is also discussed.

Abstract: A grinding bit for regrinding a component of a constant velocity universal joint which contains a grinding tip, an arbor, and means for removably attaching said grinding tip to said arbor.The arbor has a length of from about 2.0 to about 4.3 inches, the grinding tip has a length of from about 0.7 to about 1.9 inches, and the length of the arbor exceeds the length of the grinding tip by at least about 1.0 inch. The grinding has a head portion with a substantially arcuate shape and has a substrate coated with a abrasive material.

Abstract: A center cutting or plunging end mill or ball nose end mill has one or more spiral grooves and flutes in the walls of a mill body of cemented tungsten carbide. Each groove includes polycrystalline diamond or cubic boron nitride formed in situ along a leading edge of each flute. Such a groove extends across the cutting end of the mill so that the mill can be used for center cutting or plunging. The vein of diamond-like material may extend to the center of the mill body or may extend almost all of the way to the center, leaving an area of tungsten carbide exposed at the center of the mill body. A high temperature-high pressure press is used for forming the polycrystalline diamond-like veins in situ within the grooves in the mill.

Abstract: The invention relates to a twist drill, especially for metals. It has a substantially cylindrical basic component (1) divided into a shaft (2) and a cutting section (3), the central longitudinal axis (5) of which is the axis of rotation of the twist drill. Several swarf grooves (4, 4') are made in the cylindrical surface of the basic component (1) which extend spirally and continuously from the shaft (2) to the drill tip (6) and bound a swarf chamber (35). The feature of the twist drill is that its drill core diameter tapers continuously from the drill tip (6) to the shaft (2).

Abstract: A metal cutting insert comprises a carbide substrate, and at least one body of superhard abrasive material, such as PCD or PCBN, bonded to an edge surface of the substrate and extending from one side surface to the other side surface of the substrate. There can be a plurality of superhard bodies disposed at respective corners of the substrate. The abrasive material is applied to the substrate in a container and then sintered and simultaneously bonded to the substrate by an elevated pressure/temperature step. Inserts can be made in rod form (i.e., in one piece) and then the rod can be transversely sliced into thin inserts; or the inserts can be made in separate pieces, with or without separators within the container.

Abstract: A tungsten carbide boring bar has a mechanism for securing the cutter insert in a passage in the boring bar. The boring bar has a transverse bore through the body of the tool. A steel plug is received in the bore closely adjacent the position of the insert. The plug has a central threaded passage. A retainer is threadably received in the plug and has an inner end seated in a notch in the shank of the insert to retain the tool in position, and an outer end adapted to receive a turning tool.

Abstract: A milling cutter for milling a workpiece comprising a milling head rotatable about its central longitudinal axis. A milling head carries at least one milling insert of a first grade which presents a cutting edge. The milling head carries a wiper insert of a second grade which presents a wiping edge.

Abstract: A spade drill bit device including an elongated shaft formed for rotation about a longitudinal axis thereof, and a flattened blade portion at one end of said shaft. The blade portion has generally planar and parallel opposing faces, and defines opposing side edges, and an end cutting edge therebetween. The cutting edge includes a pair of opposing side spurs each having spur tip portions positioned at the lateral extremities of the cutting edge and terminates at the corresponding side edge. A cutting edge triangular-shaped center tip is included axially aligned with the longitudinal axis, and having a distal end extending beyond the side spurs. The center tip is defined by downward edge portions extending away from the distal end. The cutting edge further includes respective converging edge portions extending between and connecting each side spur to the center tip.

Abstract: Disclosed is an all-ceramic drill bit which combines the positive properties of ceramic with a tool geometry adapted to the special features of the material. The drill bit is formed with a groove for the shavings which extends in the axial direction linearly along a surface line.

Abstract: A preform element, suitable for use as a cutting element on a rotary drill bit, includes a polycrystalline diamond facing table bonded to a tungsten carbide substrate, the rear surface of the facing table being formed with an array of elongate ribs which project from the facing table into the substrate. The array of ribs includes a plurality of pairs of ribs which extend inwardly away from the periphery of the facing table, each pair of ribs being in a generally V-shaped formation so that the ribs diverge as they extend inwardly away from said periphery. Adjacent pairs of ribs may intersect to provide a generally star-shaped formation.