Abstract: A cutting insert for grooving operations having a forward main cutting edge and two opposing side cutting edges extending rearwardly and outwardly from the main cutting edge, each side cutting edge having a variable rake angle.

Abstract: The present invention relates to an indexable cutting insert for an end mill for machining of contours in a workpiece and to a milling tool. The cutting insert is asymmetrical in respect of a line through a hole in the cutting insert. The cutting insert comprises two cutting edge portions. Each cutting edge portion comprises a substantially straight cutting edge and a curved cutting edge along respective intersecting lines between a clearance surface and a rake face. The curved cutting edges have different lengths. The cutting insert has a bottom side and a first and a second opposite corner. The second corner is defined in plane view by a radius that is greater than, preferably at least twice as great as a radius of the first corner.

Abstract: A cutting insert intended exemplarily for use in a face-milling cutter, has an all-around extending rake surface which changes into a plateau surface by an uninterrupted step. The step reaches its greatest height in the corner regions of the cutting insert. The rake surface defines a positive rake angle. The step prevents the produced chips from running onto the plateau surface. As a result of such a measure, a smear-on of material onto the plateau surface from a chip is prevented.

Abstract: A cutting insert includes a polygonal body having an upper chip surface, a bottom surface and a peripheral edge surface extending therebetween. The peripheral edge surface intersects the upper chip surface to form a main cutting edge. The upper chip surface defines a chip face including a chip former comprising a wall extending downwardly from an elevated plateau to a cutting edge having a plurality of chip forming grooves and a rib formed between adjacent chip forming grooves. The chip former of the cutting insert effectively controls the formation of a chip by forming the chip to a desired shape and guiding the chip to an obstruction that impedes chip flow until the chip breaks.

Abstract: A cutting insert for grooving operations includes an elongated clamping portion and a cutting portion. The cutting portion has a chip rake surface and a relief surface meeting at a cutting edge. The relief surface has a plurality of recesses extending to the chip rake surface. In a top view of the cutting insert the cutting edge has the form of a serrated curved cutting edge.

Abstract: A support movable in a predetermined direction carries a cutting insert having a body formed with a front face lying generally in a plane generally parallel to the direction and an arcuate edge face having an inner end merging with the front face, an outer end and defining between the inner and outer ends an arcuate cutting edge. A side face directed forward in the direction defines an outer cutting edge extending transversely of the front face from the outer end of the arcuate cutting edge.

Abstract: A milling cutter for chip removing machining includes a milling cutter body with a number of insert pockets in connection with an end of the milling cutter body. An opposite end of the milling cutter body is adapted to cooperate with a tool attachment. An indexable cutting insert is secured in the cutting insert seats, each indexable cutting insert having two substantially identical main surfaces. Two side surfaces and two end surfaces extend between the main surfaces, each main surface including two cutting insert corners, each cutting insert corner including major cutting edge and a minor cutting edge. Parts of each main surface include rake faces. Parts of each side surface and each end surface include clearance surfaces. The cutting insert has a height between the end surfaces and each main surface includes an associated support surface.

Abstract: A thread cutting insert includes main cutting edges that have a pair of thread cutting edges and wiper thread cutting edges for full profile on side edges of a rake face formed on the insert body respectively. The pair of thread cutting edges is formed in a convex V shape as viewed in a plane facing the rake face, and the wiper thread cutting edges for full profile are connected to posterior ends of the thread cutting edges. An inner portion of a V-shaped projection of the rake face, which is formed on the front side of the wiper thread cutting edge for full profile by the pair of thread cutting edges, is formed not to protrude from the thread cutting edges as viewed in the plane.

Abstract: A double-sided cutting insert, for use in a milling cutter, having two identical opposing end surfaces and two opposing identical major side surfaces with a through bore extending between, and opening out to, the major side surfaces. Major cutting edges are formed at the intersection of each major side surface with each end surface. Adjacent each major cutting edge, in each major side surface, is a primary relief surface. In each cross section of the cutting insert taken in a plane generally perpendicular to the major side surfaces, a line tangent to the primary relief surface at the major cutting edge is inclined to a median plane of the cutting insert at an acute interior angle.

Abstract: A throw-away tip of which two principal surfaces each has a land surface provided along the periphery thereof, a central surface provided on the inside of the land surface, a recess (a chip breaker groove) interposed therebetween, and at least one protrusion that extends from the central surface toward the land surface, wherein height of the land surface is made equal to the height of at least the top surface of the protrusion so that at least the top surface of the protrusion of the central surface and the land surface both serve as contact surface is provided.

Abstract: A double-sided reversible and indexable cutting insert has identical opposing first and second end faces and a peripheral side surface extending therebetween. A clamping through-bore extends between, and opens out to, the first and second end faces. The cutting insert has a median plane between the first and second end faces, and a through-bore axis extending perpendicularly through the median plane. The cutting insert also has a Y-fold rotational symmetry about the through-bore axis. The peripheral side surface has Y major side surfaces and Y minor side surfaces, each minor side surface interconnecting two adjacent major side surfaces. Each minor side surface is a section of a single cylindrical surface having a given radius, the given radius being greater than a minor side surface distance of each minor side surface from the through-bore axis.

Abstract: The present invention relates to a cutting insert for chip removing machining. The cutting insert has a substantially circular cutting edge formed at a transition between an upper side and an edge surface of the cutting insert. The upper side includes a chip surface including at least one chip breaker portion and the edge surface includes a clearance surface having an arrangement for indexing the cutting insert. The chip breaker portion is provided at varying distance from the associated cutting edge. The arrangement is provided in a position relative to a reference line or axis of the tool in order to orient the chip breaker portion in the chip surface to a desired position.

Abstract: An object of the invention is to reliably control chip, particularly that produced in profiling.

Abstract: A cutting tool having a crystalline tip is pressed with a uniform pressure against the outboard surface of a vehicle wheel as the wheel is rotated. The smoothed wheel surface is then chrome plated to provide a cosmetic finish to the wheel face.

Abstract: An indexable cutting insert for chip removal machining, the insert having a polygonal body having opposed lower and upper faces that are mutually interconnected by peripheral faces meeting at rounded corners, which are formed symmetrically with respect to upper face bisectors. The upper face includes a mid portion, which is positioned inside of a chip face. Intersections of the chip face and the peripheral face forming major cutting edges and corner cutting edges. The chip face comprises a row of protrusions. A pair of oblong corner protrusions are provided at each corner area of the chip face. The pair is located symmetrically with respect to an associated bisector of the upper face. Each oblong corner protrusion has a longitudinal axis and at least two peak areas. The peak areas are positioned in line, essentially on the longitudinal axis of each oblong corner protrusion.

Abstract: A ball nose end mill includes a tool body and a throwaway insert mountable on the tool body. The throwaway insert includes a bottom face as a mounting face, an upper face on an opposite side from the bottom face, a side face formed between the bottom face and the upper face, and a cutting edge formed along an intersecting ridge between the upper face and the side face in a substantially arc shape such that the rotational trace of the cutting edge when the throwaway insert is attached to the tool body in use substantially forms a partial spherical surface. An undulating portion, which is formed by alternately arranged concave portions and convex portions, is provided on the upper face so as to intersect the cutting edge. At least one of the concave portions is formed as a deep-concave portion which has a greater depth than that of the others.

Abstract: A cutting tool in which a cutting insert is retained by a retaining screw. The cutting insert comprises a rear surface and a lower surface, both of which are generally V-shaped.

Abstract: An indexable cutting insert (10) having a top surface (12) including a substantially planar central portion (48), a substantially planar bottom surface (14), and a plurality of side surfaces (16, 18, 20, 22). A long cutting edge (24, 26), a corner radius cutting edge (28, 30), a facet radius cutting edge (32, 34), and ramping cutting edge (36, 38) are defined at an intersection between the top surface (12) and one of the side surfaces (16, 18, 20, 22). A margin (87, 89) extends around a nose radius of the cutting insert (10) and blends into a flat surface (94, 96). A margin angle, C, formed by the margins (87, 89) is less than a seating angle, B, formed by the flat surfaces (94, 96).

Abstract: A cutting insert, intended for chip removing machining, includes a body delimited by two opposite, first and second surfaces, which in the operative state of the cutting insert form an actively chip removing top surface and a bottom surface, respectively. The insert also includes at least one side surface, serving as a flank surface, which extends between the first and second surfaces. A cutting edge is formed between the flank surface and at least one of said first and second surfaces, in which a segment is included, which has the purpose of smoothening and facing the machined surface of the workpiece. The smoothening edge segment is divided into at least three different part edge segments, a first of which forms a tangent point and is surrounded by two part edge segments having longer radii (R22, R23) than the first edge part segment.

Abstract: The profile turning tool is used for rough-turning and dressing circumferential and flat surfaces, in particular of workpieces made of light metals. It consists of a holder (10) with a receiver (16) for a diamond cutting head (18) as well as a claw (20), which is embodied as a chip breaker, engages a longitudinal groove (26) in the holder (10) and braces the cutting head (18) by means of a tightening screw (22). The groove (26) is located directly behind the cutting head (18). In longitudinal section, its base has an arcuate, concave shape and represents a pivot bearing for the claw (20) that has a correspondingly shaped underside and is guided on the lateral walls of the groove (26). The tightening screw (22) extends in front of the center of the arc with play through a hole in the claw (20).

Abstract: A throwaway-type cutting tool including a tool body having a distal end, and a plurality of throwaway tips mounted to the distal end. Each of the plurality of throwaway tips including a plate of a substantially rectangular shape. The plate has a corner angle of two adjacent corner cutting edges of a first side in a surface being to 90° or less, and two opposing ridges on the first side including the two adjacent corner cutting edges are defined as cutting edges which are in a non-parallel orientation to each other. Each of the plurality of throwaway tips have a cutting edge arranged to project toward the distal end. The two adjacent corner cutting edges on the first side in each of the plurality of throwaway tips are arranged to project toward an outer periphery of the distal end of the tool body.

Abstract: A cutting insert for milling cam shafts includes first and second surface interconnected by a third surface, and at least one cutting edge. The cutting edge includes a straight first cutting edge section, a straight second cutting edge section, and a generally convex third cutting edge section, all adjoining one another. The first section extends along the junction between the first and third surfaces. The second section extends along the junction and includes a first end adjoining an end of the first section. The second is inclined at an obtuse angle from one end of the first section in a direction away from the third surface. The third section extends along the junction and adjoins a second end of the second section. The third section is of generally convex shape and extends over an angular range greater than 90°. The first, second and third sections lie in the third surface.

Abstract: A cutting insert, intended for drills, in particular long hole drills, includes a cutting edge from which a concavely curved, chip removing surface extends up to a ridge where the curved surface transforms into a top side of the cutting insert. A number of long narrow chip-embossing formations (e.g., grooves or beads) extend from the chip removing surface to the top side with the purpose of producing, in the underside of the chip, long narrow embossments in the form of either ridges or flutes in order to stiffen the chip and make it more prone to breakage.

Abstract: A throwaway insert enables reduction in cutting force and improves chip separation ability without sacrificing the strength of cutting edge thereof. An upper face of the throwaway insert is provided with an undulating portion, which is formed by alternately arranged concave portions and convex portions, so as to provide a wavy shape to the cutting edge. The undulating portion comprises four concave portions, i.e., a first deep-concave portion, a first shallow-concave portion, a second deep-concave portion, and a second shallow-concave portion. The first deep-concave portion and the second deep-concave portion are located so that effective cutting region of the cutting edge is divided into three portions having lengths substantially equal to each other, and the second deep-concave portion is made deeper than the first deep-concave portion.

Abstract: A cutting insert having an upper and a lower base face; side walls adjoining the faces; at least one cutting edge formed at an intersection of the upper face and a side wall; and at least one cutting corner formed at an intersection of an adjacent pair of side walls. A chip control structure is formed in the upper face extending along the cutting edge from the cutting corner for at least an effective cutting length of the cutting edge. A land surface spaces the chip control structure from the cutting edge. The chip control structure includes multiple radially spaced grooves, wherein the grooves of the chip control structure have a depth generally decreasing from the land toward the center of the insert.

Abstract: An indexable insert for application to turning of a cast iron product, including a first minor cutting edge 21 having a radius Ra and a second minor cutting edge 22 having a radius Rb successively provided between an arcuate nose cutting-edge 12 having a nose radius R and a linear cutting edge 16 so as to extend from the nose tip to the linear cutting edge 16. At a connection point P1 between the arcs assumed by the cutting edges 12 and 21, a smaller intersectional angle &thgr;x of a tangent T12 and a tangent T21 to the respective arcs is 1° or less. Also, at a connection point P2 between the arcs assumed by the cutting edges 21 and 22, a smaller intersectional angle &thgr;y of the tangent T21 and a tangent T22 to the respective arcs is 1° or less. The radii R, Ra, and Rb are set to the dimensional relationships “Ra>R, Ra falls within a range of 3 mm to 20 mm, and Rb≧1.5Ra.

Abstract: A metalworking apparatus includes a threading insert with a channel-less chip breaker and a holder for holding the threading insert. The threading insert includes (i) one cooling channel disposed on the top side of the threading insert for each crest and each valley, which terminates near the cutting region, and (ii) a ceramic coating on at least the cutting region of crests and valleys, with each cooling channel being uncoated.

Abstract: A directly pressed cutting insert for chip removing machining includes a top surface, a bottom support surface, and edge surfaces interconnecting the top and support surfaces. The top surface comprises a chip surface. A cutting corner is formed by the intersection of two of the edge surfaces and includes a first cutting edge. One of the two edge surfaces includes a first clearance surface having a first clearance angle. The first edge surface includes a second clearance surface having a second clearance angle, which is greater than the first clearance angle. Each of the first and second clearance surfaces connects to the same first cutting edge.

Abstract: A metal cutting insert having a pair of cutting portions disposed on either side of a shank portion which also includes a clamping structure engageable by a tool holder by which the metal cutting insert is held in an operative position. Each cutting portion includes a circular cutting edge that is defined by the juncture of a circular clearance surface and a frusto-conical, positive rake surface. The cutting edge is located in a common horizontal plane. A plurality of elongate spaced apart, radially directed recesses are symmetrically spaced with respect to the cutting edge and include outer ends that merge with the frusto-conical rake surface and inner ends which merge with a plateau-like surface having an upper surface located at a level higher than the cutting edge. The plateau-like surface defines a discontinuous circular edge in the form of arcuate ridges.

Abstract: A cutting insert intended for heavy turning operations has a top side, a bottom side, a front surface disposed between the top and bottom sides, and a cutting edge disposed in the area between the top side and the front surface. The cutting insert includes a comparatively thick front part having a chip breaker positioned behind the edge and a rear part, which is thinner than the front part and tapers rearwardly therefrom. Disposed in the top side of the rear part is a recess for receiving a clamping unit to fix the cutting insert in a co-operating sear of a holder.

Abstract: A cutting insert, intended for chip removing machining includes a cutting geometry surface having a cutting edge from which extends a primary chamfer that transforms into a chip removing surface. The chip removing surface is inclined in a inwards/downwards direction in order to permit sinking of a chip being formed, and transforms into a deflection surface arranged to initiate deflection of the chip from the cutting insert. The angle of inclination of the chip removing surface does not exceed 18°. The level difference in elevation between the primary chamfer and the chip deflection surface amounts to maximally 0.20 mm.

Abstract: A cutting insert for grooving and parting as well as profiling and longitudinal turning of metallic work-pieces, includes a shaft part and at least one cutting head. There is a front end surface at the front end of the cutting insert, and a rear end surface at the rear end of the cutting insert. The shaft part includes a top side, a bottom side and side surfaces extending between the tope and bottom two sides. The cutting head carries a cutting edge defined by the intersection between a chip surface and a clearance surface. The cutting edge has a circular shape and has mainly a constant curvature between the ends thereof. The chip side of the cutting head is provided with a first chip-forming device placed immediately inside the cutting edge.

Abstract: The invention relates to a cutting insert, especially for milling camshafts, said cutting insert having at least one cutting edge. The aim of the invention is provide a cutting insert that allows for considerable savings as compared to conventional cutting inserts.

Abstract: A stump cutter includes a rotary drum, holders mounted on the drum, and cutting bits mounted in respective bores of each holder for rotation relative thereto. Each cutting bit includes a shank having a pocket formed in a front end thereof in which the cutting tip is brazed, wherein an outer lip of the shank tightly grips an outer side surface of the cutting tip with a thermal shrink fit. The cutting tip includes a circular cutting edge formed by the intersection between portions of the front surface and side surface of the cutting tip, which surface portions intersect at a ninety degree angle. The front surface of the cutting tip includes raised radial ribs spaced circumferentially therearound for inducing rotation of the cutting bit during a cutting operation.

Abstract: A cutting insert includes an upper, lower and side surfaces and at least one cutting edge formed at an intersection of the upper surface with the side surface. A rake face of the insert is formed with one or more undulated chip forming grooves extending along the cutting edge and comprising a succession of alternating depressed and raised portions. Each depressed and raised portion is radially aligned with a central axis of the insert along the entire width of the chip forming groove.

Abstract: A cutting tip has a cutting face and a flank face. A compression face for plastically deforming a workpiece is provided between the cutting face and the flank face. The cutting tip allows work-hardening to be easily performed by plastic deformation of the cut-finished surface during cutting, without adding a separate process step.

Abstract: A tool for chip removing machining includes a holder and a cutting insert removably mounted therein. The insert includes a shaft having opposite ends and defining a first longitudinal center line. A cutting head projects integrally from at least one end of the shaft. The cutting head includes a cutting edge forming an angle of 45° with the first longitudinal center line. Alternatively, or additionally, the cutting head defines a second longitudinal center line forming an angle of 45° with the first longitudinal center line.

Abstract: A cutting insert holder has a lower clamping jaw resiliently connected to an upper clamping jaw. The upper clamping jaw is provided with two elongated spaced apart parallel grooves. The cutting insert is retained in the cutting insert holder by means of a screw which passes through a through bore in the upper jaw of the insert holder, through a through bore in the cutting insert and is threadingly engaged into a threaded bore in the lower clamping jaw. The two elongated ridges in the upper surface of the cutting insert cooperate with the two elongated parallel grooves in the lower surface of the upper clamping jaw.

Abstract: A wear insert for a tool holder includes a top surface and a bottom surface with a dimple disposed in the top surface. A boss is disposed within the dimple. The tool holder for releasably securing the wear insert has a tool holder body including an insert-receiving pocket formed at a forward end. The tool holder body has a bottom and at least one side wall for receiving an insert. The tool holder includes an internally threaded clamp-securing bore formed between an inclined surface and the insert-receiving pocket. A clamp is arranged on the tool holder body and including a lower face with a nose portion having a shaped lip and a clamp contour portion. The clamp also has a threaded aperture formed therethrough. A clamp screw is inserted into the threaded aperture of the clamp.

Abstract: A double negative cutting insert has opposite top and bottom sides between which transverse flank surfaces extend, adjacent to which cutting edges are formed. There are at least four useful major cutting edges, which separately extend from an active operating corner towards a nearby first inactive corner. Each major cutting edge co-operates with a minor cutting edge with the purpose of face machining the surface, that is left after material removal. The cutting insert has an octagonal basic shape, the top and bottom sides thereof having an identical shape with four spaced-apart supporting projections, which are placed near the four inactive corners and have plane abutment surfaces located in a common plane. An individual land adjacent to the major cutting edges has a concavely arched shape in order to provide a positive cutting geometry during operation.

Abstract: A cutting insert for a metalworking operation includes a polygonal body of hard wear resistant material. The body has a top surface and a bottom surface, and therebetween a peripheral wall including adjacent first and second wall portions. The intersection of the first wall portion and the top surface forms a first cutting edge, and the intersection of the second wall portion and the top surface forms a second cutting edge. The first cutting edge and the second cutting edge meet to form a high point which is adapted to engage a workpiece first during the metalworking operation. In one embodiment, the top surface of the cutting insert has a topography that promotes chip control. The topography includes a plain adjacent to the cutting edges, and a plateau on the plain, which is, located inward from the cutting edges. The plateau is elevated relative to the plain and has a sloped side.

Abstract: A reamer for the fine machining of surfaces of drilled holes in metal workpieces has a reamer body and at that body has at least one main blade and at least one auxiliary blade, a chip surface adjoining the blades at one side and a chip deflector step limiting the chip surface. That deflector step falls away in the zone of the auxiliary blade, exhibiting an increasing distance from the auxiliary blade. The chip deflector step rises in the zone of the main blade, exhibiting a decreasing distance from the main blade. The blades, chip surface and deflector step may be on a cutter plate attached to the reamer body or be part of the body itself. The invention also concerns that cutter plate.

Abstract: The present invention provides an indexable insert which can pare away the chip stably without increase of cutting resistance. With this insert, serrations are formed by arranging a plurality of groove portions and ridge portions alternatingly upon side ridge edge portions of the upper surface, with the exception of sloping surfaces which are formed at both end portions in the longitudinal directions of the upper surface. As a result, the cutting edges exhibit wavy shapes which are made up from this plurality of groove portions and ridge portions over the sloping surface, with the exception of these sloping surfaces. Furthermore, the groove portions and the ridge portions of the serrations are made as curved surfaces. This insert is fitted to a tool main body so that the groove portions and the ridge portions of the serrations extend perpendicular to the rotational axis of the tool.

Abstract: A cutting insert having an upper and a lower base face; side walls adjoining the faces; at least one cutting edge formed at an intersection of the upper face and a side wall; and at least one cutting corner formed at an intersection of an adjacent pair of side walls. A chip control structure is formed in the upper face extending along the cutting edge from the cutting corner for at least an effective cutting length of the cutting edge. A land surface spaces the chip control structure from the cutting edge. The chip control structure includes multiple radially spaced grooves, wherein the grooves of the chip control structure have a depth generally decreasing from the land toward the center of the insert.

Abstract: A method for applying cutting elements to a tool for cutting or milling a metal item in a well is disclosed, along with the cutting element used in the method. The tool can include one or more blades extending outwardly or downwardly from the tool for cutting a metal item such as the wall of a casing string, or for removing a predetermined length of a casing string in a cutting action. The blade or blades have cutting elements positioned on the leading faces of the blades to engage the casing string or other metal item in the bore hole. Each cutting element is composed of a plurality of effective cutting faces. Each cutting face can have a substantially triangular shape, or a substantially square shape, or some other geometric shape. The cutting elements can be arranged in a random pattern. Each cutting element can be oriented in a random orientation relative to the blade.

Abstract: A method or process for making polycrystalline diamond or polycrystalline CBN cutting tools (Superabrasives), which have integral chip-breaking features is disclosed. This method involves pressing a die or other like rigid component against either the outer can cover or the diamond or CBN region directly. This invention provides economical manufacture of diamond chip-breaker tools, while avoiding unnecessary EDM EDG, grinding, or laser processes. This process forms the chip-breaker on the upper surface of the diamond region, during or prior to sintering. This invention permits a wide variety of chip-breaker or other diamond surface features, while minimizing cost and processing steps. Disclosed embodiments include: pressing through the can assembly; pressing within the assembly by introducing a rigid component in the can; and pressing two cans together with an intervening rigid component imposing the desired diamond surface features.

Abstract: A cutting insert for chipforming machine has a tip face with a cutting edge. Grooves are formed in the top face and extend toward the cutting edge. Chip-deflecting projections extend upwardly from the top face and are situated in spaces formed between adjacent grooves. A jet of cooling fluid is directed toward inner ends of the grooves and travels between the projections and within the grooves toward the cutting edge.

Abstract: A ceramic cutting tool including a ceramic base member 4 of a tool main body 1 which is formed of a composite ceramic which contains a hard phase dispersed within an alumina matrix phase. The hard phase contains, as a predominant component, one or more elements selected from hard-phase-forming metal elements M in the form of at least one of a carbide, nitride, or boride, or in the form of a solid solution of at least two selected from the carbide, nitride and boride. The hard-phase-forming metal elements M include Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and Si. The surface of the ceramic base member 4 is covered with a coating layer 1f, which contains titanium carbonitride or titanium nitride as a predominant component. The coating layer 1f has an average crystal-grain size of 0.1 to 0.5 &mgr;m as observed on the surface, and an average thickness of 0.5 to 2 &mgr;m. The coating layer 4f is formed by a CVD at a low to medium temperature range of 750 to 900° C.

Abstract: A cutting insert intended for heavy turning operations has a top side, a bottom side, a front surface disposed between the top and bottom sides, and a cutting edge disposed in the area between the top side and the front surface. The cutting insert includes a comparatively thick front part having a chip breaker positioned behind the edge and a rear part, which is thinner than the front part and tapers rearwardly therefrom. Disposed in the top side of the rear part is a recess for receiving a clamping unit to fix the cutting insert in a co-operating sear of a holder.

Abstract: The present invention relates to an indexable cutting insert (10) for the turning of grooves with triangular basic shapes where each insert comer features a projection (16). Each projection supports a transverse cutting edge (17) and connecting diverging cutting edges (18, 19), so that the projection (16) seen in a view directly from above has a symmetrical shape. The one outer side edge (18) of the projection (16) is bordered by an unbroken flat flank surface (22) whilst the connecting flank surface on the other side edge (19) is comprised of two partial surfaces (27, 28) of which the one nearest the edge (19) partial surface (27) has a smaller clearance angle than the partial surface (28) nearest the bottom.