IL305453B1

IL305453B1 - A cutting insert and an insert holder for it

Info

Publication number: IL305453B1
Application number: IL305453A
Authority: IL
Original assignee: Carmex Prec Tools Limited
Priority date: 2023-08-24
Filing date: 2023-08-24
Publication date: 2024-10-01
Also published as: IL305453B2; IL305453A

Description

305453/ - 1 - CUTTING INSERT AND TOOL HOLDER THEREFOR TECHNOLOGICAL FIELD The present disclosure is concerned with a cutting insert and a tool holder therefore. More particularly, the disclosure is directed to a multipurpose cutting tool.

BACKGROUND ART References considered to be relevant as background to the presently disclosed subject matter are listed below: - US4,775,0- US7,001,1- US7,270,5- US8,708,617 - US20202383- WO050374 Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.

BACKGROUND US4,775,085 discloses an indexable cutting insert for recessing having a triangular basic shape and comprises three cutting edges. Each cutting edge is arranged at a projection which at least partly is asymmetrically arranged relative to a line parallel with the working direction of the insert. The insert has a good accessibility at work pieces having narrow spaces. US7,001,115 discloses a cutting insert for metalworking operations has an insert core with a pair of cutting portions having cutting tips extending therefrom such that a 305453/ - 2 - toolholder having a pocket to accept such a core is suitable to accept different cutting inserts having a common core plus different cutting portions. As a result, for example, an degree. diamond, a 55 degree. diamond and a 35 degree. diamond cutting insert may all be utilized within a common toolholder. The invention is also directed to a toolholder that will accept such a variety of cutting inserts. US7,270,503 discloses a cutting tool for rotating and drilling into solid blocks, comprising a drill shank and a cutting head on one end. The cutting head has a straight, front-face cutting edge extending approximately crosswise in relation to the drill axis. The cutting head also comprises a section protruding from the shank of the drill at a height ranging from at least 5 percent to a maximum of 40 percent of the diameter of the drill and at a width ranging from at least 5 percent to a maximum of 40 percent of the diameter of the drill. The section comprises a straight, lateral cutting edge which merges into a straight, rear-sided cutting edge extending in an approximately parallel manner in relation to the front-faced cutting edge. US8,708,617 discloses an internal groove insert includes a rectangular main body having a top surface, a lower surface, and first to fourth lateral surfaces; and first and second projections each projecting from the adjacent first and second lateral surfaces. The first projection has a first cutting edge at the side of the top surface of the main body, while the second projection has a second cutting edge at the side of the lower surface. The first and fourth lateral surfaces are inclined by an obtuse angle with respect to the top surface, while the second and third lateral surfaces are inclined by an acute angle with respect to the top surface. The central axis of the clamping hole is inclined to be parallel to the insert corner edge where the first and fourth lateral surfaces meet. US2020238397 discloses a cutting insert for drilling includes an upper surface, a lower surface formed on an opposite side of the upper surface, a side surface connecting the upper surface and the lower surface; a cutting edge formed at an intersection of the upper surface and the side surface, and a ridge portion formed to protrude upward from the upper surface to facilitate chip control. The ridge portion includes a ridge body spaced apart from the cutting edge and disposed at a central portion of the cutting insert for drilling; and a ridge extension portion extending from a vicinity of a corner of the ridge body in a direction parallel to the cutting edge. 305453/ - 3 - WO05037472 discloses a tool for producing and/or internally machining boreholes in metallic materials, said tool comprising devices for the internal supply of coolant. The inventive tool consists of a base body comprising a shaft-type section for introducing into the borehole, said section comprising a cutting arrangement with individual cutting edges on one end. At least one cutting corner formed from two cutting edges and defining the diameter of the borehole to be machined projects past the main part of the shaft-type section by a measurement x in the radial direction. Said tool also comprises at least one outlet channel for the coolant, extending approximately in the radial direction and staggered in the longitudinal direction of the shaft-type section, said channels being oriented away from the cutting corner towards the rear, as observed from the boring direction, and respectively forming an angle alpha with the tool axis. According to the invention, from a front view, the outlet channels respectively extend beneath the plane formed by the respective cutting corner and the tool axis. Furthermore, the outlet channels are oriented upwards towards the cutting corner and form an angle ss with the plane. Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.

GENERAL DESCRIPTION A first aspect of the present disclosure is directed to a cutting insert having a polygonal body with a top face, a bottom face and a concentric throughgoing fastener bore, extending therebetween; a positioning member disposed at least at the bottom face, and having an equilateral triangular shape defining a positioning circumscribed circle and extending coaxial with said fastener bore; three cutting tips projecting from said body, each cutting tip configured with a first cutting edge and a second cutting edge, defining between them a cutting nose; wherein each first cutting edge of the three cutting tips extends along a respective edge of a first equilateral triangle, and wherein each second cutting edge of the three cutting tips extends along a respective edge of a second equilateral triangle; wherein a first circumscribed circle of the first equilateral triangle is coaxial with a second circumscribed circle of the second equilateral triangle; and wherein 30 305453/ - 4 - said first circumscribed circle and second circumscribed circle are coaxial with the positioning circumscribed circle. The cutting insert is generally a symmetric triangular body with three cutting tips, each comprising two cutting noses, a first cutting edge and a second cutting edge, wherein the first cutting edge of each cutting tip is tangentially oriented and is disposed over a respective side of an equilateral triangle having a circumcircle coaxial with a positioning member of the cutting insert. The cutting tips are polygonal-shaped, each comprising a first cutting edge, a second cutting edge, and a third cutting edge, with a first cutting nose extending between the first cutting edge and the second cutting edge, and a second cutting nose extending between the second cutting edge and the third cutting edge. The second cutting nose of each cutting tip extends along an imaginary line originating from a facing first cutting nose of a facing cutting tip and coextending along a first cutting edge associated with said facing cutting tip. The term ‘facing cutting nose’ denotes a cutting nose of a cutting tip disposed nearest to a third cutting edge of a respective cutting tip. Likewise, the term ‘facing first cutting edge’ denotes a cutting edge extending nearest to third cutting edge of a respective cutting tip. The term ‘extension edge’ denotes a portion extending between an end of a first cutting edge and a facing/neighboring cutting nose. The second cutting edge of each cutting tip extends approximately parallel with an extension edge of a facing first cutting edge. The cutting edges of the cutting insert are each configured with a chip breaker extending at a top face of the cutting insert, at least along a portion of the respective cutting edge. Side edges of the cutting insert extending below the respective cutting edges, are formed with a side relief flank, wherein a top cutting edge extends outwardly with respect to a corresponding bottom edge. The arrangement is such that each cutting tip of the cutting insert is configurable for performing a variety of machining operations, comprising one or more of facing, taper turning, external/internal turning, forming, chamfering, parting, threading, profiling, boring, drilling, grooving, single point milling, etc. 305453/ - 5 - A second aspect of the disclosure is directed to a cutting insert holder for a cutting insert, said holder comprising a longitudinal shank extending along a longitudinal axis with a cutting tool support portion at a front end thereof, said cutting tool support portion comprising a flat cutting insert seat surface with a recessed portion at a rear portion thereof; and a duty cutting tip support extension laterally projecting from a side wall of the cutting tool support portion and coplanar with the cutting insert seat surface; a positioning portion extending from said cutting insert seat surface and comprising upright extending side walls; said positioning portion having an equilateral triangular shape, with a coaxial threaded bore having a bore axis normal to the cutting insert seat surface and offset from the longitudinal axis; wherein the cutting insert seat surface and the duty cutting tip support extension are configurable for supporting bottom surface portions of a cutting insert, and the side walls of the positioning portion are configured for snugly engaging with side walls of a positioning member of the cutting insert. According to a particular configuration, the second aspect of the disclosure is directed to a cutting insert holder for a cutting insert, said holder comprising a longitudinal shank extending along a longitudinal axis with a cutting tool support portion at a front end thereof, said cutting tool support portion comprising a major surface having at a front end thereof a cutting insert seat surface depressed from said major surface, said cutting insert seat surface comprises a recessed portion configurable for accommodating and supporting a first cutting tip of a cutting insert, two side walls at respective sides of the recessed portion, at least partially encompassing two second cutting edges of the cutting insert; a front seat portion for supporting a second cutting tip of the cutting insert, and a duty cutting tip support extension laterally projecting from a side wall of the cutting tool support portion and coplanar with the cutting insert seat surface, configurable for supporting a duty cutting tip of the cutting insert, whereby the seat surface is coplanar and configurable for supporting a three cutting-tip triangular cutting insert; a positioning portion extending from said cutting insert seat surface, said positioning receptacle having an equilateral triangular shape, with a threaded bore; and further wherein when a cutting insert is secured over said cutting insert seat surface, a third second cutting edge and a third cutting tip of the cutting insert project from an edge of the cutting insert seat surface. The term ‘duty cutting tip’ of a cutting insert refers to a cutting tip of a cutting insert securely mounted to a cutting insert holder, said duty cutting tip configured for 305453/ - 6 - machining operations and wherein cutting edges of said duty cutting tip extend beyond edges of the cutting insert holder. When a particular cutting tip is a duty cutting tip, other cutting tips of the cutting insert do not project from edges of the major surface of the cutting insert holder. By a particular design of the cutting insert holder, the duty cutting tip support is polygonal-shaped, and is configured for supporting a duty cutting tip of a cutting insert, wherein at an assembled position all cutting edges and cutting noses of the duty cutting tip extend beyond edges of the third cutting tip support. The arrangement is such that the cutting insert holder is useful for holding a cutting insert of the aforementioned type, wherein it can be used for performing a variety of machining operations, comprising one or more of facing, taper turning, external/internal turning, forming, chamfering, parting, threading, profiling, boring drilling, grooving, single point milling, etc. At an assembled position of a cutting insert over the cutting insert holder a top edge of a cutting edge of the cutting insert does not extend above the major surface of the cutting insert holder. Any one or more of the following features, designs and configurations can be associated with any one or more of the aspects of the present disclosure, individually or in various combinations thereof: • The top face and the bottom face of the cutting insert are parallel with one another; • The cutting insert can be symmetric about the top face and the bottom face, whereby both faces thereof can be utilized for machining operations, hence doubling the number of cutting edges; hence, where the cutting insert is an equilateral triangular than it comprises six cutting edges (three at each face) and six cutting tips; • Where the cutting insert is symmetric about the top face and the bottom face, the top face is defined as a bottom face when the bottom face is used as a top face, and vice versa; • The cutting tips of the cutting insert can be indexable; • Indexing the cutting tips can be by any visible and/or touchable indicia; 305453/ - 7 - • The cutting tips of the cutting insert can be symmetrically disposed about the bore axis; • The cutting tips of the cutting insert can be disposed radially; • The cutting tips of the cutting insert can be disposed tangentially; • The first cutting edge and the second cutting edge can be disposed at an angle of about 80° - 88° with respect to one another; • The second cutting edge and the third cutting edge can be disposed at an angle of about 83° - 89° with respect to one another; • The angle between a side edge of the first equilateral triangle and a corresponding neighboring side edge of the second equilateral triangle can be about 83.7°; • The first cutting edge can be disposed at an angle of about 20° with respect to a neighboring side edge of the triangular positioning member, and the second cutting edge can be disposed at an angle of about 3.7° with respect to a neighboring side edge of the triangular positioning member; • At an assembled position, an extension edge portion of a facing first cutting edge extends parallel with the longitudinal axis of the cutting insert holder; • At an assembled position, a heel of each side relief flank of one or more of the cutting edges of a duty cutting tip can extend beyond edges of the duty cutting tip support extension; • The threaded bore of the cutting insert holder can be coaxially disposed at the positioning portion, with a bore axis extending perpendicular to said longitudinal axis and offset therefrom; • The first cutting nose and the second cutting nose of each cutting tip can be identical or different, as far as cutting radius or cutting angle; • The cutting insert can be configured with cutting tips, each having a different cutting nose; • At an assembled position the top surface of the cutting is coplanar with the major surface of the cutting insert holder; • At an assembled position the cutting edge of the cutting insert extends below the major surface of the cutting insert holder; 305453/ - 8 - • The throughgoing fastener bore of the cutting insert can be configured with a screw-support shoulder; • The positioning member of the cutting insert and the positioning portion of the cutting insert holder are configured for bearing and transmitting loads and forces extending during a machining operation between a workpiece and the cutting insert holder for forces, for true positioning of the cutting insert over the cutting insert holder, and for indexable positioning of the cutting insert with respect to the cutting insert holder; • The positioning portion of the cutting insert holder can be configured with a tapering cross-section, for snugly engaging with the positioning member of the cutting insert; • The positioning member of the cutting insert can be configured with a cross-section, for snugly engaging with the positioning portion of the cutting insert holder; the side walls can be parallel with the bore axis, or slightly taper; • One of the positioning member and the positioning portion can be one of a depression and a projection, and the other one of the positioning member and the positioning portion can be an other one of a projection or depression; • The two side walls at the respective sides of the recessed portion, wherein one side wall extends towards and terminates at a side wall of the cutting tool support portion, and the other side wall extends towards and terminates at a front seat portion of cutting insert seat surface; • The cutting tool holder can be configured with a replaceable mounting plate comprising a positioning member for interacting with a positioning member of a cutting insert; • A spacer shim, namely a replaceable mounting plate, can be configured for positioning between a bottom face of the cutting insert and a top face of the cutting insert seat surface of the cutting insert holder; • The shim can comprise at either or both of a top face and a bottom face thereof a positioning portion, and further wherein each of said positioning portion can configured as either a projecting positioning portion or a depressed positioning portion; 305453/ - 9 - • At an assembled position the cutting insert is secured and fastened over the tool support portion, wherein bottom face portions of the cutting insert bare over top surface portions of the cutting insert seat surface, and side walls of the positioning member of the cutting insert bare against respective side walls of the positioning portion of the cutting tool support portion; • The cutting insert holder can be made of high-quality steel or a combination of sintered material shank with a front portion thereof made of high-quality steel; • The cutting tool support portion can be configured with an insert clamp, for clamping arresting a cutting insert; the insert clamp can be used instead or in combination with a fastener screw; • The bottom face of the cutting insert is generally flat and can be configured with depressed zones symmetrically distributed, to assure proper surface contact of the cutting insert over a flat cutting insert seat surface of a cutting insert holder. Said depressed zones substantially do not bare forces imparted to the cutting insert during machining operations; • The chip breaker of the first cutting edge almost merges with the chip breaker of the second cutting edge, with a separating ridge extending therebetween; • The assembly comprising cutting tool holder and the cutting insert can be used for turning operations (i.e. wherein the assembly is kept fixed and operates about a rotating workpiece), and for milling operations (i.e. wherein the assembly is rotatably displaceable about a fixed workpiece); • The first cutting edge can be inclined such that an end portion at the second cutting tip is disposed elevated from an extension edge of said first cutting edge.

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 30 305453/ - 10 - Fig. 1A is a perspective view of a cutting tool assembly according to the present disclosure, comprising a cutting insert holder accommodating a cutting insert; Fig. 1B is an enlargement of the portion marked 1B in Fig. 1A; Fig. 1C is a top elevation of the portion illustrated in Fig. 1B; Fig. 1D is a side elevation of Fig. 1C, taken in direction of arrow 1C; Fig. 1E is a front elevation of Fig. 1C, taken in direction of arrow 1E; Fig. 1F is an enlargement of the portion marked 1F in Fig. 1E; Fi1. 1G is a bottom elevation of Fig. 1D, taken in direction of arrow 1F; Fig. 2 is an exploded perspective view of the cutting tool according to the present disclosure: Fig. 3A is an enlargement of the portion marked 3A in Fig. 2; Fig. 3B is a top elevation of the portion illustrated in Fig. 3A; Fig. 4A is a top perspective view of the cutting insert according to an example of the disclosure; Fig. 4B is a top elevation of the cutting insert of Fig. 4A; Fig. 4C is a bottom elevation of the cutting insert of Fig. 4A; Fig. 4D is a bottom perspective view of the cutting insert of Fig. 4A; Fig. 4E is a side elevation in direction of arrow 4E in Fug. 4B; Fig. 5 is a section along line V – V in Fig. 4A; Fig. 6 is a bottom elevation of the cutting insert of Fig. 4A, superimposed with some diagram lines; Fig. 7is a section along line VII – VII in Fig 1C; Fig. 8A is a top perspective view of yet an embodiment of a cutting insert according to of the disclosure, wherein a top face and a bottom face thereof are symmetric; Fig. 8B is a bottom perspective view of the cutting insert seen in Fig. 8A; Fig. 9A is a bottom perspective view of a cutting insert according to an embodiment of the disclosure, wherein a positioning member is configured as a depression; Fig. 9B is a cutting tool support portion of a cutting tool holder configured for use in conjunction with a cutting insert of Fig. 9A; 305453/ - 11 - Fig. 9C is a longitudinal section through a cutting tool assembly comprising an insert and a cutting tool holder according to Figs. 9A and 9B, respectively; Figs. 10A illustrates a mounting plate for use with a cutting tool holder and a cutting insert according to an embodiment of the disclosure; Fig. 10B illustrates themounting plate of Fig. 10A mounted on a cutting tool holder; Fig. 10C illustrates a cutting insert according to the present disclosure, secured to a cutting tool holder shown in Fig. 10B; Fig. 10D is a section along line X – X in Fig. 10C; Figs. 11A to 11D are examples of cutting inserts according to the disclosure, with different cutting tips; Figs. 12A to 12H illustrate different machining operations on a workpiece, utilizing a cutting tool according to the disclosure; Fig. 13A is a perspective view of a front portion of a cutting tool assembly according to a modification of the disclosure; Fig. 13B is a section of the portion shown in Fig 13A, along a longitudinal axis thereof; and Fig. 13C is a perspective view of the front portion of the cutting insert holder.

DETAILED DESCRIPTION OF EMBODIMENTS Attention is first directed to Fig. 1A of the drawings, illustrating a cutting tool assembly according to the present disclosure, generally designated 10 , comprising a cutting insert holder 12 accommodating a cutting insert 14 . As can be seen also in Fig. 2, 3A and 3B, the cutting insert holder 12 is an elongate rod typically made of high-quality steel, extending along a longitudinal axis 18 , and comprising a longitudinal shank portion 20 for engaging with a spindle of a turning/milling machine (not shown), and a cutting tool support portion 22 at a front portion of cutting insert holder 12 . By an embodiment, the shank of cutting insert holder 12 can be made of sintered material, however with a front portion thereof made of high-quality steel. The cutting insert holder 12 comprises one or more flushing bores extending from a back end thereof towards the cutting tool support portion 22 , with flushing ports 26A 305453/ - 12 - and 26B aiming at the cutting insert 14 for axial machining operations, and for cutting tip associated operations, respectively. The cutting tool support portion 22comprises a major surface 26 having at a front end thereof a cutting insert seat surface 28 , depressed from the major surface 26 , said cutting insert seat surface 28 comprises a recessed portion 32 at a rear portion thereof, with two side walls 34A and 34B at respective sides of the recessed portion 32 , wherein side wall 34A extends towards and terminates at a side wall 44 of the cutting tool support portion 22 , and the side wall 34B extends towards and terminates at a front seat portion 38of cutting insert seat surface 28 . The cutting insert seat surface 28further has a duty cutting tip support extension 40 laterally projecting from the side wall 44 of the cutting tool support portion 22and coplanar with the cutting insert seat surface 28 . Centrally positioned at the cutting insert seat surface 28 , there is a positioning portion 48 configured as an equilateral triangle depressed portion, having upright side walls 52 extending from a flat bottom surface 50 , parallel with the cutting insert seat surface 28 . Coaxially extending from bottom surface 50there is a threaded fastener bore 56 having a bore axis 58 extending perpendicular to said longitudinal axis 18 and offset therefrom. Further attention is now being made to Figs. 4 to 6, directed to the cutting insert 14 . The cutting insert is 14 , typically made of different materials and coatings, imparting its required parameters such as hardness, toughness, and wear resistance, generally has a symmetric triangular polygonal body having a top face 70 , a bottom face 72 and a concentric throughgoing fastener bore 76 extending therebetween. As seen in Figs. 4A, 4B and 5, the fastener bore 76has a screw retention shoulder 77 . The bottom face 72 is configured with a positioning member 78 which in the illustrated example is a projection from the bottom face 72 in the form of an equilateral triangle defining a positioning circumscribed circle ( 84 in Fig. 6) with a coaxial with the fastener bore 76 and having a fastener bore axis 88 . Positioning member 78 has upright side walls 79 , parallel with the bore axis 88 , and the positioning member 78 is sized for snug fitting within the positioning portion 48 of the cutting tool holder 12 . As can be seen in the drawings, the bottom face 72 of the cutting insert 14 is generally flat, however with three depressed zones 74 , symmetrically distributed over the bottom face 72 . This configuration assures proper surface contact of the bottom surface 305453/ - 13 - 72 over the flat cutting insert seat surface 28 of the cutting insert holder 12,when the cutting insert 14 is secured thereover. The cutting insert 14 has three cutting tips 90 projecting from said body, wherein the three cutting tips are tangentially oriented so as to chase each other (imparting the cutting insert 14 the general appearance of a triskelion). Each cutting tip 90 is configured with a first cutting edge 92 and a second cutting edge 94 , defining between them a first cutting nose 98 . The geometric arrangement is such that the three first cutting edges 92 of each of the three cutting tips 90 extend along a respective edge of a first equilateral triangle ( 100 in Fig. 6), and the three second cutting edges 94 of the three cutting tips 90 extend along a respective edge of a second equilateral triangle ( 102 in Fig. 6), and wherein a first circumscribed circle 106 of the first equilateral triangle 100 is coaxial with a second circumscribed circle 108 of the second equilateral triangle 102 , and wherein said first circumscribed circle 106 and second circumscribed circle 108 are coaxial with the positioning circumscribed circle 84 and fastener bore axis 88 . Where a cutting edge of a first cutting edge 92 ends (i.e. where the chip breaker 120 ends) there is an extension edge 99 , extending towards the third cutting edge 112 of a neighboring cutting tip 90 . Extension edge 99 is substantially parallel with second cutting edge 94 . According to the example illustrated in the drawings, the cutting insert 14 is configured such that the first cutting edge 92 and the second cutting edge 94 are disposed at an angle of about 80° - 88° with respect to one another; the second cutting edge 94 and the third cutting edge 112 are disposed at an angle of about 83° - 89° with respect to one another; the angle between a side edge of the first equilateral triangle 100 and a corresponding neighboring side edge of the second equilateral triangle 102 is in the range of 80° – 88° and typically about 83.7° ; the first cutting edge 92 is disposed at an angle of about 10° to 30° with respect to a neighboring side edge of the triangular positioning member 78 , and the second cutting edge 94 is disposed at an angle of about 3.7° with respect to a neighboring side edge of the triangular positioning member 78 . It is seen that the cutting insert generally has a symmetric triangular polygonal body with three cutting tips 90 , each comprising at least a first cutting noses 98 , a first cutting edge 92 and a second cutting edge 94 , wherein the first cutting edge 92 of each cutting tip 90 is tangentially oriented and is disposed over a respective side edge of an 305453/ - 14 - equilateral triangle 102 having a circumcircle 106 coaxial with the positioning circumscribed circle 84 of positioning member 78 . Further noted, the cutting tips 90 of cutting insert 14 are each configured with a third cutting edge 112 , defining a second cutting nose 114 between said third cutting edge 112 and the first cutting nose 98 . The cutting insert is configured with geometric features imparting it for performing various machining operations, hence the first cutting edges 92 are configured with a chip breaker 120 , the second cutting edges 94 are configured with a chip breaker 122 , and the third cutting edges 112 are configured with a chip breaker 124 . In addition, each of the cutting edges 92 , 94 , and 112 is configured with a side flank 126 , 128 and 130 , respectively, wherein each of the cutting edges projects laterally beyond its respective flank surface. It is seen that the chip breaker 120 of the first cutting edge 92 almost merges with the chip breaker 122 of the second cutting edge 94 , with a separating ridge 123 extending therebetween, said ridge 123 configured for chip splitting. For example, the first cutting edges 92 can be used for drilling/boring, and the first cutting noses 98 can be used for universal turning operations, profiling, facing, chamfering, etc. It is also noted that the first cutting noses 98 and the second cutting noses 114 can be of same or different radii, and yet, one or both of said first cutting noses 98 and the second cutting noses 114 can be pointed (e.g. for threading operations). The cutting insert is symmetric, whereby each of the three cutting tips 90 can be readily used for performing a variety of one or more machining operations, such as facing, taper turning, external/internal turning, forming, chamfering, parting, threading, profiling, boring, drilling, grooving, single point milling, etc. The cutting tips 90 are indexed for easy identification thereof by visible indicia (numbers ‘1’, ‘2’ and ‘3’, respectively depressed on the top face 70 ; best seen in Figs. 4A and 4B). However, the indexing indicia can assume other forms too, e.g. embossing (projections or depressions) of different shapes/patterns. According to a particular design of the cutting insert, the first cutting edge 92 and the second cutting edge 94 are disposed at an angle of about 83° - 89° with respect to one another, and the second cutting edge 94 and the third cutting edge 112 are disposed at an angle of about 80° - 88° with respect to one another. Further noted, the angle between a 305453/ - 15 - side edge of the first equilateral triangle 100 and a corresponding neighboring side edge of the second equilateral triangle 102 is about 83.7°. According to an example of the disclosure, as shown in Fig. 6, the first cutting edge 92 is disposed at an angle of about 20° with respect to a neighboring side edge 95 of the triangular positioning member 78,and the second cutting edge 94 is disposed at an angle of about 3.7° with respect to a neighboring side edge 97 of the triangular positioning member 78 . As can be seen in Fig. 1F, the first cutting edge 92 is inclined, with an end portion at the second cutting tip 94 disposed elevated from an extension edge 99 of said first cutting edge 92 . Namely, said first cutting edge 92 has a portion above a center line CL and a portion extending below CL at an angle α referred to as a ‘side rake angle’, sloping at approximately 1° - 2° with respect to said CL . With further reference made now also to Fig. 7 of the drawings, it is appreciated that a cutting insert 14 can be mounted at the cutting tool support portion 22 at a front portion of cutting insert holder 12 , at one of three respective angular positions, wherein at each position one of the three cutting tips 90 (i.e., cutting tip indexed ‘3’ in Figs. 1B, 2C) bears over duty cutting tip support extension 40 , and wherein another cutting tip (i.e., cutting tip indexed ‘2’ in Figs. 1B, 2C) is received at the recessed portion 32 at a rear portion of the cutting tool support portion 22 , and wherein yet another cutting tip (i.e., cutting tip indexed ‘1’ in Figs. 1B, 2C) is received supported over the front seat portion 38 of cutting insert seat surface 28 . Once placed in position, the cutting insert 14 is arrested and fixed in position by the positioning member 78 snugly bearing against upright side walls 52 of the positioning portion 48 , and a fastener screw 111 prevents unintentional disengagement. Hence, the arrangement is such that once the cutting insert 14 is positioned at the cutting insert seat surface 28 and secured in place by a fastener bolt 111 , the bottom face 72 of the cutting insert tightly bears over top cutting insert seat surface 28 , and the cutting insert assumes its true/absolute position in virtue of side walls 79 of positioning member 78 snugly received and supported by side walls 52 of the positioning portion 48 . It is seen that the bottom face portion of the cutting tip indexed ‘2’ extends over the top cutting insert seat surface 28 an the bottom face portion of the cutting tip indexed ‘1’ extends over the seat portion 38 , and wherein the duty cutting tip portion indexed ’3' bears over 305453/ - 16 - the duty cutting tip support extension 40 . Accordingly, machining forces applied to the cutting insert 14 during machining operations are transferred to the cutting insert holder 12 via the bottom surface portions of the cutting insert bearing over top surface portions of the cutting insert seat surface, and further by side walls 79 of positioning member 78 bearing against side walls 52 of the positioning portion 48 . Also noted, best in Figs. 1D and 1E, at an assembled position of the cutting insert over the cutting insert holder a top edge 93 of a cutting edge 92 ; 94 of the cutting insert 14 does not extend above the major surface 26 of the cutting insert holder. At the assembled position, the recessed portion 32 accommodates one cutting tip 90 (indexed ‘2’ in the drawings), with the two side walls 34A and 34B at least partially encompassing two first cutting edges 92 (namely those associated with cutting tips indexed ‘1’ and ‘2’) of the cutting insert 14. Further attention is directed to Figs. 8A and 8B of the drawings, illustrating a cutting insert according to an embodiment of the disclosure, generally designated 140 . The cutting insert 140 is a two-faced cutting insert, comprising a top face 144 and a bottom face 146 , being a symmetric mirror image of one another and wherein each of the top face 144 and the bottom face 146 are configured with a cutting geometry in accordance with the present disclosure and as discussed hereinabove, hence, doubling the number of cutting tips, and respectively, the number of cutting edges. It is seen that the top face 144 and the bottom face 146 comprise three cutting tips 148T ; 148B , wherein each cutting tip is associated with a first cutting edge 150T ; 150B , a second cutting edge 152T ; 152B , and a third cutting edge 154T ; 154B , with cutting noses disposed between the respective cutting edges, and wherein each cutting edge is configured with a corresponding chip breaker, as discussed hereinabove. The center line 142 of the cutting insert is a bottom edge of a side flank extending between each cutting edge and said center line 142 . The cutting insert 140 is configured with a throughgoing fastener bore 160 having an inside shoulder 162 , whereby the cutting insert can be secured over a cutting insert holder at either a top face or a bottom face orientation, for exploiting all the cutting tips and cutting edges. Also noted, the cutting tips of the top face 144 are indexed ‘1’, ‘2’ and ‘3’, and the cutting tips at the bottom face 146 are indexed ‘4’, ‘5’ and ‘6’, respectively. 305453/ - 17 - The arrangement of cutting insert 140 provides six effective cutting tips and respective cutting edges, whereby when the cutting insert is articulated over the cutting insert holder (not shown) with the top face 144 being active (i.e. facing upwards) then the bottom face 146 bears over the cutting insert seat surface of the cutting insert holder, and when the bottom face 146 is an active cutting face, facing upwards, then the top face 144 serves as a bottom face for bearing over the cutting insert seat surface of the cutting insert holder, as explained hereinabove. Figs. 9A to 9C are directed to an embodiment of the disclosure, wherein cutting insert 180 is configured with a cutting geometry identical with the disclosure hereinabove, with the difference residing in the positioning arrangement. According to the example, rather than the downward projecting positioning member 78 of the previous example, bottom face 182 of the cutting insert 180 is configured a depressed positioning member 184 in the form of an equilateral triangle defining a positioning circumscribed circle (not shown) coaxial with a fastener bore 186 about a center axis 188 , in accordance with the geometry discussed before, and further wherein the positioning member 184 has upright side walls 192 , parallel with the bore axis 188 , rendering the positioning member 184 shaped and sized for snug receiving a positioning portion 202 of the cutting tool holder 200 (Figs. 9B and 9C). A cutting insert seat surface 208 of the cutting tool holder 200 is a substantially flat surface and is configured with a positioning portion 202 configured as an equilateral triangle projecting portion, with upright side walls 204 , and with a coaxially extending threaded fastener bore 210 having a bore axis 212 extending perpendicular to a longitudinal axis 209 of the cutting tool holder 200 and offset therefrom. The positioning portion 202 is shaped and sized for snug receiving within the positioning member 184 of the cutting insert 180 , such that at an assembled position (Fig. 9C), the cutting insert is secured to the cutting tool holder 200 by fastener screw 216 extending through fastener bore 186 and screwed into threaded fastener bore 210 , with the cutting insert fixedly positioned at a substantially zero tolerance and high accuracy positioning. Figures 10A to 10D of the drawings are directed to a positioning shim (i.e. a replaceable mounting plate) according to another aspect of the disclosure. Accordingly, there is disclosed a flat positioning shim 220 , made of hard metal, comprising a flat 305453/ - 18 - bottom face 226 and a top face 228 , with a positioning portion 234 projecting upwards therefrom, said positioning portion 234 configured as an equilateral triangle projecting portion, with upright side walls 236 , being coaxially disposed over a fastener bore 238 , wherein positioning portion 234 mimics a positioning portion integral with the cutting tool holder (e.g. as in Fig. 9B). The arrangement is such that shim 220 can be used for height adjusting in case of a respectively thin cutting insert, or the opposite case, where the shim is removed for giving rise to a deeper cutting insert seat surface, useful for example in case of a thick/double cutting insert. Hence, the positioning shim 220 is shaped and sized for snug fitting over a flat cutting insert seat surface 222 , with its bottom face 226 tightly bearing thereover, and whereupon a cutting insert 14’ is placed over the positioning shim 220 with a bottom surface 182 of the cutting insert bearing tight over the top face 228 thereof. The assembly is fastened by screw 230 extending through the cutting insert 14’ , through the bore 238 of the supporting shim 220 and securely fastened into a fastener bore of the cutting insert holder 224 . It is seen in Figs. 10B and 10C that a top face 214 of cutting insert 14' is substantially coplanar with the major surface 215 of the cutting insert holder 224 , and more so, at the assembled position the cutting edge of the cutting insert extends below the major surface of the cutting insert holder, hence guarding the cutting edge. It is noted that according to an embodiment of the disclosure, not shown, the shim can be a negative image, i.e. comprising a depressed positioning portion (rather than a projecting one) and further wherein one or both of a bottom face and a top face of the shim can be configured with a projecting/depressed positioning portion. Figures 11A to 11D illustrate cutting inserts according to the disclosure, wherein the geometry of the cutting inserts follows the disclosure hereinabove, with the differences residing in the cutting tips of the cutting inserts. In Fig. 11A there is a cutting insert 250 with three pointed (V-shaped) cutting tips 252 . Such a cutting tip is useful for a variety of machining operations, e.g. V-shaped grooving, threading parting, etc. It is noted that the cutting tips 252 are single nosed. In Fig. 11B there is a cutting insert 256 with three flat (rectangle-shaped) cutting tips 258 , each configured with two cutting noses (these can be similar or differ from one another). Such a cutting tip is useful for a variety of machining operations, e.g. turning, grooving, internal/external turning, parting, cut-off, face grooving, boring, drilling, etc. 305453/ - 19 - Fig. 11C illustrates a cutting insert 260 configured with three round-ended, single nosed, cutting tips 262 . Such a cutting insert can be used for external/internal turning, profiling, etc. Fig. 11D illustrates a cutting insert 266 wherein each cutting tip is different, i.e. a rounded cutting tip 268 , a flat/rectangle cutting tip 270 and a V-shaped cutting tip 272 , as discussed hereinabove. With respect to Figs. 12A to 12H there is illustrated a workpiece WP and a cutting tool assembly 10 , comprising a cutting insert holder accommodating a cutting insert according to the present disclosure, wherein each figure depicts different machining operations performable by the tool assembly 10 . In Fig. 12A the cutting tool assembly 10 is illustrated upon performing a bore 280 in the workpiece WP . In Fig. 12B the cutting tool assembly 10 is illustrated upon internal turning/profiling of inside surface 282 of the workpiece WP . In Fig. 12C the cutting tool assembly 10 is illustrated upon external turning/profiling of outside surface 284 of the workpiece WP . In Fig. 12D the cutting tool assembly 10 is illustrated upon front head turning at surface 286 of the workpiece WP . In Fig. 12E the cutting tool assembly 10 is illustrated upon external narrow grooving 288 and external wide grooving 290 of the workpiece WP . In Fig. 12F the cutting tool assembly 10 is illustrated upon internal profile turning at surface 292 of the workpiece WP . In Fig. 12G the cutting tool assembly 10 is illustrated upon external profile turning at surface 294 of the workpiece WP . In Fig. 12H the cutting tool assembly 10 is illustrated upon pre-grooving/cutting at a back end 296 of the workpiece WP . Turning now to Figs. 13A to 13C, there is illustrated a modification of the disclosure, wherein a cutting tool holder 300 is configured at a front portion thereof with tool holder support portion 302 , similar to the disclosure hereinabove, however wherein recessed portion 308 is of increased size and comprises a clamp threaded bore 312 suited for securing an insert clamp 316 by a clamp screw fastener 318 . It is appreciated that the 305453/ - 20 - clamp threaded bore can be alternatively configured at the major surface 320 , whereby a larger clamp design is required. The clamp 316 has a downward facing tongue portion 324 , which at an assembled position is configurable for projecting into and bearing against a socket 326 of insert screw fastener 328 , hence increasing fastening of the cutting insert 330 . Notably, the cutting insert clamping arrangement can be used instead or in addition to the screw fastener 328 . It is further noted that the assembly comprising cutting tool holder and the cutting insert can be used for turning operations (i.e. wherein the assembly is kept fixed and operates about a rotating workpiece), and for milling operations (i.e. wherein the assembly is rotatably displaceable about a fixed workpiece).

Claims

305453/ - 20 - CLAIMS:

1. A cutting insert having a polygonal body with a top face, a bottom face and a concentric throughgoing fastener bore, extending therebetween; a positioning member being one of a depression and a projection formed at least at the bottom face, and having an equilateral triangular shape defining a positioning circumscribed circle and extending coaxial with said fastener bore; three cutting tips tangentially projecting from said body to form a triskelion-like shape of said cutting insert, each cutting tip configured with a first cutting edge and a second cutting edge, defining between them a cutting nose; wherein each first cutting edge of the three cutting tips extends along a respective edge of a first equilateral triangle, and wherein each second cutting edge of the three cutting tips extends along a respective edge of a second equilateral triangle; wherein a first circumscribed circle of the first equilateral triangle is coaxial with a second circumscribed circle of the second equilateral triangle; and wherein said first circumscribed circle and second circumscribed circle are coaxial with the positioning circumscribed circle.

2. The cutting insert of claim 1, wherein the polygonal body is generally an equilateral triangular body with three cutting tips, each comprising two cutting noses, a first cutting edge and a second cutting edge, wherein the first cutting edge of each cutting tip is tangentially oriented and is disposed over a respective side of an equilateral triangle having a circumcircle coaxial with a positioning member of the cutting insert.

3. The cutting insert of any one of the preceding claims, wherein the cutting tips are polygonal-shaped, each comprising a first cutting edge, a second cutting edge, and a third cutting edge, with a first cutting nose extending between the first cutting edge and the second cutting edge, and a second cutting nose extending between the second cutting edge and the third cutting edge.

4. The cutting insert of claim 3, wherein the second cutting nose of each cutting tip extends along an imaginary line originating from a facing first cutting nose of a facing cutting tip and coextending along a first cutting edge associated with said facing cutting tip.

5. The cutting insert of claim 3, wherein the second cutting edge of each cutting tip extends approximately parallel with an extension edge of a facing first cutting edge. 305453/ - 21 -

6. The cutting insert of any one of the preceding claims, wherein the cutting edges of the cutting insert are each configured with a chip breaker extending at a top face of the cutting insert, at least along a portion of the respective cutting edge.

7. The cutting insert of any one of the preceding claims, wherein the side edges of the cutting insert extending below the respective cutting edges, are formed with a side relief flank, wherein a top, cutting edge extends outwardly with respect to a corresponding bottom edge.

8. The cutting insert of any one of the preceding claims, wherein each cutting tip of the cutting insert is configurable for performing a variety of machining operations, comprising one or more of facing, taper turning, external/internal turning, forming, chamfering, parting, threading, profiling, boring, drilling, grooving, and single point milling.

9. The cutting insert of any one of the preceding claims, wherein the top face and the bottom face of the cutting insert are parallel with one another.

10. The cutting insert of any one of the preceding claims, wherein the cutting insert is symmetric about a centerline extending between the top face and the bottom face, whereby both faces thereof comprise cutting tips and cutting edges for machining operations, hence doubling the number of cutting edges.

11. The cutting insert according to claim 10, wherein the top face and the bottom face are a mirror image of one another, and wherein when the top face is utilized as a machining face, then the bottom face is used for bearing over a cutting insert holder, and vice versa, when the bottom face is utilized as a machining face, then the top face is used for bearing over a cutting insert holder.

12. The cutting insert of any one of the preceding claims, wherein the cutting tips of the cutting insert are indexable.

13. The cutting insert of any one of the preceding claims, wherein the cutting tips of the cutting insert are symmetrically disposed about a fastener bore axis.

14. The cutting insert of any one of the preceding claims, wherein the cutting tips of the cutting insert are radially disposed with respect to a fastener bore axis.

15. The cutting insert of any one of the preceding claims, wherein the first cutting edge and the second cutting edge are disposed at an angle of about 80° - 88° with respect to one another. 305453/ - 22 -

16. The cutting insert of any one of the preceding claims, wherein the second cutting edge and the third cutting edge are disposed at an angle of about 83° - 89° with respect to one another.

17. The cutting insert of any one of the preceding claims, wherein the angle between a side edge of the first equilateral triangle and a corresponding neighboring side edge of the second equilateral triangle is about 83.7°.

18. The cutting insert of any one of the preceding claims, wherein the first cutting edge is disposed at an angle of about 10° to 30° with respect to a neighboring side edge of the triangular positioning member, and the second cutting edge is disposed at an angle of about 3.7° with respect to a neighboring side edge of the triangular positioning member.

19. The cutting insert of any one of the preceding claims, wherein one or more cutting tips of the cutting insert comprise one or two cutting noses.

20. The cutting insert of any one of the preceding claims, wherein one or more cutting tips of the cutting insert comprise two cutting noses, the two cutting noses have a different or a similar cutting radius.

21. The cutting insert of any one of the preceding claims, wherein the cutting tips are each configured with a different cutting nose.

22. The cutting insert of any one of the preceding claims, wherein the throughgoing fastener bore of the cutting insert has a screw-support shoulder.

23. The cutting insert of any one of the preceding claims, wherein the positioning member of the cutting insert is configured for bearing and transmitting loads and forces extending during a machining operation between a workpiece and the cutting insert and for true positioning of the cutting insert over a cutting insert holder, and for indexable positioning of the cutting insert with respect to a cutting insert holder.

24. The cutting insert of any one of the preceding claims, wherein side walls of the positioning member extend upright and parallel with the fastener bore axis.

25. The cutting insert of any one of the preceding claims, wherein side walls of the positioning member of the have a tapering cross-section.

26. The cutting insert of any one of the preceding claims, wherein a bottom face of the cutting insert is generally flat and can be configured with depressed zones symmetrically distributed, to assure proper surface contact of the cutting insert over a flat cutting insert seat surface of a cutting insert holder. 305453/ - 23 -

27. The cutting insert of any one of the preceding claims, wherein a chip breaker of the first cutting edge almost merges with a chip breaker of the second cutting edge, with a separating ridge extending therebetween.

28. The cutting insert of any one of the preceding claims, wherein the first cutting edge is inclined, with an end portion at the cutting tip disposed elevated from an extension edge of said first cutting edge.

29. A cutting insert holder for use in conjunction with a cutting insert according to any one of the preceding claims, said cutting insert holder comprising a longitudinal shank extending along a longitudinal axis with a cutting tool support portion at a front end thereof, said cutting tool support portion comprising a major surface having at a front end thereof a cutting insert seat surface comprising a recessed portion configurable for supporting a first cutting tip of the cutting insert, and two side walls at respective sides of the recessed portion, at least partially encompassing two first cutting edges of the cutting insert; a front seat portion for supporting a second cutting tip of the cutting insert; and a duty cutting tip support extension, laterally projecting from a side wall of the cutting tool support portion and configurable for supporting a duty cutting tip of the cutting insert; wherein said recessed portion and said front seat portion and said duty cutting tip support extension are coplanar; and a positioning portion extending from said cutting insert seat surface, said positioning portion having an equilateral triangular shape, with a coaxial threaded bore; and further wherein when a cutting insert is secured over said cutting insert seat surface, a third first cutting edge and a third second edge of the cutting insert project from an edge of the cutting insert seat surface.

30. The cutting insert holder according to claim 29, wherein the duty cutting tip support is polygonal-shaped, is configured for supporting a duty cutting tip of a cutting insert, wherein at an assembled position all cutting edges and cutting noses of the duty cutting tip extend beyond edges of the third cutting tip support.

31. The cutting insert holder according to any one of claims 29 and 30, wherein at an assembled position of a cutting insert over the cutting insert holder, only a first cutting edge and a second cutting edge of a duty cutting tip laterally project from edges of the duty cutting tip support extension.

32. The cutting insert holder according to any one of claims 29 to 31, wherein at an assembled position of a cutting insert over the cutting insert holder, a top edge of a cutting edge of the cutting insert extends below the major surface of the cutting insert holder. 305453/ - 24 -

33. The cutting insert holder according to any one of claims 29 to 32, wherein at an assembled position of a cutting insert over the cutting insert holder an extension edge portion of a facing first cutting edge extends parallel with the longitudinal axis of the cutting insert holder.

34. The cutting insert holder according to any one of claims 29 to 33, wherein at an assembled position of a cutting insert over the cutting insert holder, a heel of each side relief flank of one or more of the cutting edges of a duty cutting tip extends beyond edges of the duty cutting tip support extension.

35. The cutting insert holder according to any one of claims 29 to 34, wherein at an assembled position of a cutting insert over the cutting insert holder, the threaded bore of the cutting insert holder is coaxially disposed at the positioning portion, with a bore axis extending perpendicular to said longitudinal axis of the cutting insert holder and offset therefrom.

36. The cutting insert holder according to any one of claims 29 to 35, wherein the positioning portion of the cutting insert holder is configured for snug engaging with a positioning member of the cutting insert and bearing loads and forces imparted to the cutting insert from a workpiece during a machining operation, and for true positioning of the cutting insert over the cutting insert holder, and for indexable positioning of the cutting insert with respect to the cutting insert holder.

37. The cutting insert holder according to any one of claims 29 to 36, wherein the positioning portion of the cutting insert holder is configured with upright side walls extending parallel with the bore axis, and configured for snugly engaging with corresponding side walls of the positioning member of the cutting insert.

38. The cutting insert holder according to any one of claims 29 to 37, wherein the positioning portion of the cutting insert holder is configured with tapering side walls, for snugly engaging with corresponding side walls of the positioning member of the cutting insert.

39. The cutting insert holder according to any one of claims 29 to 38, wherein the positioning portion is one of a depression and a projection extending from the cutting insert seat surface, and having an axis normal to said surface.

40. The cutting insert holder according to any one of claims 29 to 39, comprising two side walls extending at the respective sides of the recessed portion, wherein one side wall extends towards and terminates at a side wall of the cutting tool support portion, and the 305453/ - 25 - other side wall extends towards and terminates at a front seat portion of cutting insert seat surface.

41. The cutting insert holder according to any one of claims 29 to 40, wherein the cutting insert seat surface is configurable for supporting a replaceable mounting plate, said mounting plate comprising a positioning member for interacting with a positioning member of a cutting insert, and wherein said mounting plate has a through-going bore coaxially extendible with the threaded fastener bore of the cutting insert holder and the fastener bore of the cutting insert.

42. The cutting insert holder according to any one of claims 29 to 41, wherein a replaceable mounting plate is configured for positioning between a bottom face of the cutting insert and a top face of the cutting insert seat surface of the cutting insert holder.

43. The cutting insert holder according to any one of claims 29 to 41, wherein a replaceable mounting plate is configurable with a positioning portion extending at either or both of a top face and a bottom face thereof, and further wherein said positioning portion is configurable as either a projecting positioning portion or a depressed positioning portion.

44. The cutting insert holder according to any one of claims 29 to 43, wherein at an assembled position the cutting insert is secured and fastened over the tool support portion of the cutting insert holder, and wherein bottom face portions of the cutting insert bare over top surface portions of the cutting insert seat surface, and side walls of the positioning member of the cutting insert bare against respective side walls of the positioning portion of the cutting tool support portion.

45. The cutting insert holder according to any one of claims 29 to 44, wherein the cutting tool support portion is configured with an insert clamp, for clamping arresting a cutting insert. 25