Abstract: A metal cutting insert incorporates a polycrystalline diamond or a polycrystalline cubic boron nitride material as a pre-formed discrete cutting tip which wraps around the nose of the insert. The insert may further incorporate an integral chipbreaker.

Abstract: According to the present invention there is provided a body at least partially coated with one or more refractory layers of which at least one layer essentially consist of &agr;Al2O3. Said &agr;Al2O3 layer consists of essentially equiaxed grains with an average grain size of <1 &mgr;m and with a bimodal grain size distribution with coarser grains with an average grainsize in the interval 0.5-1 &mgr;m and finer grains with an average grainsize of <0.5 &mgr;m. The Al2O3 layer further contains striated zones containing titanium (>5 at %) but no nitrogen or carbon. This particular microstructure is obtained by temporarily stopping the gases needed for the growth of the Al2O3 layer and introducing TiCl4.

Abstract: A ceramic member is constituted with a zirconia-containing ceramic material containing 20% by volume or more of a zirconia series ceramic phase mainly composed of a zirconium oxide. The zirconia-containing ceramic material satisfies: KC/(dA)≧5 by using an exponential value A set within a range from −0.41 to −0.37 width, d being an average grain size (unit: &mgr;m) and KC being a fracture toughness value (unit: MPa·m½). An edge portion appearing in the form of a ridge is formed at an intersection between two edge forming surfaces 4a and 5 to the outer surface of the member, and the edge portion is formed as a sharp edge portion E having a width w of 0.15 mm or less for the top end of the edge appearing on a cross section taken along an arbitrary plane in perpendicular to the direction of the ridge.

Abstract: The present method involves heating a blank, a shank and a welding material in an instantaneous heating process wherein a temperature instantaneously rises at a rate of 500-1000° C./min.; and cooling the blank and the shank at a temperature of 700-1200° C. for a short period of time thus integrating the blank and shank into a cutting tool. The instantaneous heating process is preferably a light heating process by a halogen lamp. A welding chamber for the blank controls both pressure and atmosphere, and is provided with a desired degree of vacuum. In this manner, a thermal deterioration of a diamond blank, a welding metal or a shank material is prevented.

Abstract: A coated milling insert particularly useful for milling in low and medium alloyed steels with or without abrasive surface zones during dry or wet conditions at high cutting speed, and milling hardened steels at high cutting speed. The insert is characterized by a WC-Co cemented carbide with a low content of cubic carbides and a highly W-alloyed binder phase and a coating including an innermost layer of TiCxNyOz with columnar grains and a top layer of TiN and an inner layer of &kgr;-Al2O3.

Abstract: A laser beam is directed onto a bonding surface of a steel tool body to form a molten melt pool. Particles of high speed steel alloy are flowed into the melt pool and melt in the melt pool. The laser beam is moved along the bonding surface to form solid lines of high speed steel laser cladding metallurgically bonded to the cutter portion at the bonding surface and to each other. The cladding is abraded to form the cutting edge of a composite cutting tool.

Abstract: A cutting insert is provided with a combination coating, comprising a wear-protection coating and an indicating layer. The indicating layer preferably is provided on the tool flank or flanks, meaning for radial inserts on the side surfaces and for tangential inserts on the bottom or top surface. The indicating layer is sensitive enough, so that even a short-term use of the adjacent cutting edge leaves clear traces on the indicating layer. In the process, the indicating layer is discolored and/or worn down, so that underlying layers or materials with different colors become visible. As a result of the clear color contrast or brightness contrast, used cutting edges can be identified immediately. The use of the tool flanks as indicating surfaces has proven to be particularly advantageous because a tribological and possibly unfavorable coating can be provided, without this having a negative influence on the processing result of the cutting insert.

Abstract: A thin layer of carbide containing an ultra-hard component, such as diamond, is applied to a formed compact for a drilling tool. The compact is then subjected to a high-temperature, high-pressure process to bond it to the added layer. This process allows the use of an underlying substrate which has a lower binder content than previously possible. The compact provides superior cutting ability, as even if the diamond-enhanced layer wears through, the carbide can provide enhanced hardness.

Abstract: A coated cemented carbide tool, and a method for making the same, wherein the as-sintered substrate is formed by sintering in an atmosphere having at least a partial pressure and for a part of the time a nitrogen partial pressure.

Abstract: A cutting tool has a chip breaker, disposed in the region of the chip face, for preventing uncontrolled chip formation. The chip breaker is disposed at a certain spacing from the cutting edge of a diamond layer that is applied to a substrate body. In prior art versions, a joint remained between the chip breaker and the diamond layer, and chips could penetrate the joint and become stuck there. To prevent this, the diamond layer, in the region of the chip breaker, is recessed down to the substrate body and that the chip breaker is applied there directly to the substrate body. In this way, a chip breaker can be disposed with a good hold in the vicinity of the cutting edges without sacrifices in terms of the strength of the cutting layer.

Abstract: There are disclosed a coated cutting tool which comprises a base material of a hard alloy comprising a hard phase of tungsten carbide and at least one material selected from a carbide, nitride and carbonitride of a metal selected from the Group 4, 5 and 6 of the Periodic Table and a mutual solid solution thereof and a binder phase of at least one element selected from Fe, Ni and Co, and a hard coating film formed on the surface of the base material by a CVD method, wherein the hard coating film has a columnar crystal layer comprising at least one material selected from a carbide, nitride and carbonitride of titanium, the columnar crystal layer contains large-sized particles and small-sized particles, and the ratio of the amounts of the large particles to the small particles is 3 to 50; and a method for producing the same which comprises forming the hard coating film by at least one coating film of a carbide, carbonitride and carbonitroxide of titanium using a hydrocarbon gas containing ethane as a carbon elem

Abstract: The invention is to prolong the life time of tools dramatically by (1) considerably improving the flaking resistance of the coating layer at the time of cutting, (2) increasing the wear resistance and crater resistance of the coating layer itself, and (3) enhancing the breakage strength of the coating layer in comparison with the conventional coating cutting tools. In order to achieve the object, the coated cemented carbide of the invention has the following structure in the coating layer on the surface of the cemented carbides: The outer layer has an Al2O3 layer practically having an &agr;-type crystal structure. The Al2O3 layer has a region where &agr;-type and &kgr;-type crystal grains coexist in the first row of the crystal grains that grow on the inner layer. In addition to that, the crystal grains of &agr;-Al2O3 in the region include no pores.

Abstract: A tool component is provided which has particular application in mining picks and drag bits. The component comprises an abrasive compact having a flat working surface presenting a cutting edge around its periphery, and an opposite surface bonded to a cemented carbide substrate along an interface. A recess is provided which extends into the abrasive compact from the interface and is filled with abrasive compact. The recess has a central portion and an outer portion which completely surrounds, and is shallower than the central portion. The central portion defines, in plan, at least one substantially wedge-shaped configuration, the configuration having a narrow end coincident with a side surface of the component and the sides extending into the component and diverging from the narrow end.

Abstract: The cutting member comprises WC, two or more solid solutions of WC and compounds selected from carbides, nitrides and carbonitrides of metals of the groups 4a, 5a and 6a in the Periodic Table, and at least one metal of the iron group; and at least one of the two or more solid solutions being a solid solution having a high Nb or Zr content, whereby the wear resistance and plastic deformation resistance are improved in case of cutting hardly machinable materials such as stainless steel, thereby making it possible to prolong the service life of the cutting member.

Abstract: A coated cemented carbide cutting tool (indexable inserts) for the wet or dry milling, particularly at high cutting speeds, of stainless steels of different composition and microstructure, but also for the milling of non-stainless steels such as low carbon steels and low and medium alloyed steels is disclosed. The coated WC−Co based cemented carbide insert includes a specific composition range of WC+Co without any addition of cubic carbides by a low W-alloyed Co binder and by a narrow range defined average WC grainsize, and a hard and wear resistant coating including a multilayered structure of sublayers of the composition (TixAl1−x)N with repeated variation of the Ti/Al ratio.

Abstract: The present invention provides a coated sintered body which can be used in precious machining hardened steel. The coated PCBN cutting tool comprises a substrate which contains not less than 35 volume % and not more than 85 volume % of CBN, and a hard coated layer formed on the substrate. The hard coated layer comprises at least one compound layer consisting of at least one element selected from a group of 4a, 5a, 6a elements of the periodic table and Al, and at least one element selected from a group of C, N and O. The thickness of the layer is not less than 0.3 &mgr;m and not more than 10 &mgr;m. The center-line mean roughness of the hard coated layer is not more than 0.1 &mgr;m.

Abstract: A set of machining tools containing at least two separate tools is provided, one of which is tailored for a certain type of application and the other tailored for another application or use. The first tool is particularly adapted for applications having service requirements where the coating on the basic body of the tool must have high adhesive strength, but need not have high hardness, and the second tool is for service requirements of high hardness for the hard material coating, where the adhesive strength is not important.

Abstract: In a cemented carbide cutting tool made of a tungsten carbide-based alloy comprising 8 to 13 percent by weight of Co and 0.1 to 3 percent by weight of Cr as constituents for forming a binding phase, the balance being tungsten carbide as a constituent for forming a dispersing phase and incidental impurities, the rate of the dispersing phase to the total of the dispersing phase and the binding phase being in a range of 72 to 90 percent by area and the average particle diameter being 1 &mgr;m or less according to measurement of an electron microscopic texture; the dispersing phase of the cemented carbide cutting tool made of a tungsten carbide-based alloy comprises a dispersing phase composed of ultra-fine particles dispersed in a matrix and having a particle diameter of 100 nm or less, and the ultra-fine particles comprise a Co based alloy.

Abstract: A cermet tool that has excellent thermal crack resistance, while maintaining plastic deformation resistance, wear resistance and a long service life even when it is used for intermittent cutting is disclosed. The cermet tool comprises Ni or Ni and Co in a total amount of 4-20 wt. %, Ti in an amount of 50-60 wt. %, V, Cr, Zr, Nb, Mo, Hf, Ta, and W in a total amount of 30-40 wt. %, C in an amount of 5-10 wt. %, and N in an amount of 3-8 wt. %. The carbonitride phase contains grains of a Ti carbonitride phase containing Ti in an amount of 90 wt. % or more with respect to all the metal components of the phase. When the cross-sectional microcrystalline structure of the cermet is observed, the ratio of “total area of grains of the Ti carbonitride phase having a ratio of Dmax/Dmin of 1.5 or more” to “total area of the hard phase” is 50% or more.

Abstract: A polycrystalline diamond compact for use in cutting operations that require improved impact strength and non-uniform edge wear. The compact includes a substrate, with multiple, laterally spaced, abrasive diamond particle areas segregated by different particle sizes bonded to the substrate. The polycrystalline diamond areas formed of finer size diamond particles provide higher abrasion resistance wear at a slower rate thus producing a non-linear cutting, edge to the work zone. The areas of different average size diamond particles, in one embodiment, are arranged in concentric rings with each ring of a different particle size. Alternating rings may be formed of uniform size diamond a particles. The areas also may be in the form of spaced grooves inlaid from the end surface of polycrystalline diamond layers. The polycrystalline diamond layer may also have a non-planar end with the discrete areas radially spaced across the layer.

Abstract: A composite cutting tool for use in the abrasive processing of hard substrates comprising cutting elements wherein diamond particles in a predominantly metallic binder material are agglomerated and sintered during an individual molding process of each of said cutting elements.

Abstract: A cutting insert having a rake surface and a flank surface wherein there is a cutting edge at the intersection of the rake surface and the flank surface. The rake surface exhibits a sufficient degree of surface roughness so as to provide for microscopic chip control. The flank surface exhibits a sufficiently smooth (i.e., a mirror finish) so as to provide for a workpiece surface finish that approaches (or possibly reaches) the theoretical value attributable for the given cutting conditions.

Abstract: The invention concerns a cutting insert for machining, said cutting insert comprising a single or outer layer consisting of a plastics material with solid lubricant particles dispersed therein, preferably sulphides and/or selenides of molybdenum, tungsten and/or titanium. The solid lubricant particles are preferably dispersed in the paint which is applied to the cutting insert by treatment in an immersion bath, spraying, painting or passing through a paint mist and electrostatically.

Abstract: A tool manufactured by brazing a hard sintered body such as a diamond or cBN to a tool substrate through a bonding layer comprising at least one of Ti and Zr by 15-65 wt % and Cu. Two ridges of the tool substrate on both sides each has a first ridge adjacent to and aligned with a ridge of the hard sintered body and a second ridge provided nearer to an inscribed circle of the tool than is the ridge of the hard sintered body. Also, an upright side face and a bottom of each seating groove formed in the tool substrate intersect each other at an angle smaller than the intersecting angle between a back side and a bottom of each hard sintered body.

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 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 cutting tool has a compressing segment for imparting a compressive force to produce a non-porous surface layer on a workpiece of porous material. The cutting tool also has a cutting segment to machine the non-porous surface layer for a desired surface finish. Furthermore, a method for machining a workpiece using such a cutting tool may be implemented to produce a non-porous surface layer on a workpiece of porous material and then to produce a desired surface finish.

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 coated hard metal tool includes a hard metal base material having an edged part on an insert ridge portion defining a connecting portion between a flank and a rake face, and a coating film applied to a surface of the hard metal base material. The coating film has a surface-treated part on the insert ridge portion. The coating film is so formed that Rc1/(Rs1+d)<1.0 and Rc2/(Rs2+d)>1.

Abstract: A cutting tool for chip removal machining is composed of hard metal, cermet or ceramic as a sutrate coated with a surface coating being composed of both hexagonal and amorphous boron nitrides. At least an outer most coating is being composed of boron nitrides a thickness of between 1 and 5 .mu.m. The surface has a total thickness which does not exceed 20 .mu.m and at least 20 volume % of the outermost coating is composed of hexagonal boron nitride. The infrared spectrum of the outermost boron nitride layer has absorption lines the wave numbers at 800 to 1400 cm.sup.-1.

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 method of cutting hardened steel using a cBN sintered tool which can improve the surface roughness while maintaining high dimensional accuracy. The upper limit of the tool feed rate is set at such a value that a theoretical surface roughness calculated from the feed rate is between 2/3 and 1/1000 of the target surface roughness. The amount of change of the feed rate between the upper and lower limits of the tool feed rate is set to be between 0.002 and 0.05 mm/rev, and the amount of every feed rate change is set not to be equal to the original feed rate multiplied by an integer. The feed rate is changed forcibly for every number of workpieces for which the total cutting length is between 10 and 1000 meters.

Abstract: A coated turning insert particularly useful for dry and wet machining in low and medium alloyed steels, stainless steels, with or without raw surface zones under severe conditions such as vibrations, long overhang and recutting of chips. The insert is characterized by a WC--Co cemented carbide with a low content of cubic carbides and a rather low W-alloyed binder phase and a coating including an innermost layer of TiC.sub.x N.sub.y O.sub.z with columnar grains and a top layer of TiN and an intermediate layer of .kappa.-Al.sub.2 O.sub.3. The layers are deposited by using CVD-methods.

Abstract: The present invention relates to supported polycrystalline diamond compact cutters (PDC cutters) made under high temperature, high pressure (HT/HP) processing conditions, and more particularly to supported PDC cutters having non-planar cutting surfaces. More specifically, the present invention is for an oriented PDC cutter wherein chips and debris are funneled away from the cutting edge by a raised top surface of the polycrystalline diamond layer (PCD layer). The redirection of the debris is achieved by the creation of high and low regions on the PCD layer, of which there can be a variety of different surface geometry's. Thus, an object of the present invention is to provide a PDC cutter with improved performance through channeling debris away from its cutting edge.

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: The ceramic insert made from a silicon nitride ceramic material and formed with a recess for fastening in the center of its rake face. The recess has a surface roughness Rmax not exceeding 4 .mu.m. The angle between a side face of the recess and a centerline perpendicular to the rake face of the insert is 50-70 degrees. The ratio of the diameter of the recess to the diameter of a circle inscribing the perimeter of the rake face is 30-85%. The recess has a flat or curved bottom. The connecting portion between the side face and the bottom of the recess forms a smoothly curved surface.

Abstract: A cutting insert including a flank face, a rake face, and a cutting edge at the intersection of the flank and rake faces that is useful in the chip forming machining of workpiece materials is disclosed. The cutting insert comprises a cermet comprising at least one hard component and about 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 cutting tool for milling titanium and titanium alloys which includes a substrate that comprises tungsten carbide and cobalt. The substrate further includes cobalt in the range of between 5.7 to 6.3 weight percent and chromium in the range of between 0.3 and 0.5 weight percent. The cutting tool has a coating of tungsten carbide applied to the substrate by physical vapor deposition.

Abstract: A polycrystalline diamond cutting element has a non-planar, non-linear interface between a substrate and a table. The substrate has one or more protrusions mounted on the surface of the substrate and in spaced relationship. Each protrusion has a generally curved shape such as a delta or triangular shape that extends from the center of the substrate toward the perimeter of the substrate. The depth of the groove between protrusions generally increases along the path toward the perimeter of the element. Similarly, the depth of each protrusion from groove to groove varies along the path toward the perimeter of the element. A thicker, superhard layer such as a diamond layer is provided toward the circle of the element to increase working life. The resulting cutting element is symmetrical about the central axis to alleviate the need for proper orientation of the cutting element during assembly into a drill bit. In another embodiment, a depression is used in place of the protrusion to form a substrate.

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 cutting tool for milling comprises an insert consisting of a cubic boron nitride sintered body having heat conductivity of at least 400 W/m.K at 120.degree. C. and a thermal expansion coefficient within the range of at least 3.0.times.10.sup.-6 /K and not more than 4.0.times.10.sup.-6 /K in the temperature range of 20.degree. C. to 600.degree. C. According to this cutting tool for milling, sufficient tool life can be attained in high-speed face milling under a wet condition and high-speed end milling under a wet condition.

Abstract: A method of making a diamond-coated insert includes, obtaining a substrate of durable and diamond adherent material having a substantially smooth surface on which is coated a diamond layer using any known CVD technique, and partitioning the diamond covered substrate with a laser beam into multiple inserts with desired geometries. If desired, the insert edges and corners may be thereafter machined or ablated until the desired smoothness and finish are achieved, and a fastening throughbore may be preformed or drilled in the center of each insert. The diamond-coated inserts as formed have a top surface entirely coated by a surface layer of diamond of a first thickness, and at least one rake face which is not diamond-coated beyond the surface layer of diamond.

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 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: An insert made of an ultra-high-pressure sintered compact and including no base metal or support layer is brazed to a tool body under vacuum by use of a Ti-containing activated silver brazing filler metal. This method permits the insert to be securely fixed to the tool body without fear of the insert coming off the tool body even if the tool is a helical one. Because no base metal layer is needed, the manufacturing yield, efficiency and productivity are improved.

Abstract: An abrasive cutting element comprised of an abrasive cutting layer and a metal substrate wherein the interface therebetween has a tangential chamfer, the plane of which forms an angle of about 5.degree. to about 85.degree. with the plane of the surface of the cylindrical part of the metal substrate. The abrasive cutting layer is preferably diamond or cubic boron nitride and the metal substrate is preferably tungsten carbide.

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: A spiral end mill which can mill a substantially sharp inside corner of a work surface and attain a stable working accuracy for a long time. The spiral end mill has a hard sintered compact insert portion, a negative relief face a first circular land provided along the outer periphery of the insert portion, and a second circular land on the negative relief face so as to be continuous with the first circular land. The widths of the two circular lands may be the same as or different from each other, and the helix angle of a back line of the second circular land is less than that of the first circular land. A method of manufacturing the spiral end mill involves machining a relief angle in the outer periphery of the insert portion while changing the helix angle between the negative relief face and the rest of the outer periphery.

Abstract: A cutting tool for machining titanium and titanium alloys which comprises a tungsten carbide-containing substrate alone or with a tungsten carbide tip brazed thereto. The cutting tool further includes a hard coating on either the substrate alone or on the tungsten carbide tip. The coating may be PVD-applied tungsten carbide, CVD-applied boron carbide or PVD-applied boron carbide.

Abstract: A cutting tool assembly comprising an elongated tool shank having, at a side adjacent a leading end thereof, a shank holding portion and an exchangeable adaptor having an insert retaining portion for retaining a replaceable cutting insert and an adaptor mounting portion releasably scoured to the shank holding portion by two clamping screws. The clamping screws are inserted into respective adaptor through bores formed in the adaptor mounting portion and threaded bores formed in the shank holding portion, the threaded bores being substantially aligned with the respective adaptor through bores. One of the adaptor mounting and shank holding portions is formed with a recess and the other one is formed with a protrusion mating with the recess and received therein, the bores passing through the recess and the protrusion and being oriented transversely to an axis of relative rotation of a workpiece with respect to the tool.