TOOL FOR CUTTING MACHINING

Abstract: The present invention relates to a tool for cutting machining, a cutting insert (10K) and a method for mounting such a cutting insert. The cutting insert (10K) is intended for chip removing machining and comprises at least one cutting edge (14). The cutting insert (10K) consists of injection molded cemented carbide and comprises first means (15) for clamping the cutting insert against a holder. The means (15) is integrated with the cutting insert. One side of the insert (11) opposite said first means (15; 27) comprises at least one key grip (17) intended to cooperate with a key at clamping of the cutting insert (10A-10L) against the holder.

Description: TOOL FOR CUTTING MACHINING Background of the invention The present invention relates to a tool for cutting machining, a cutting insert and a method for mounting such a cutting insert, according to the preambles of the independent claims. Prior art Traditionally circular indexable inserts are used down to about 5 mm in diameter. The smallest circular indexable inserts are to be regarded as rings of cemented carbide in order to obtain space enough to accommodate the screw, which holds the cutting insert in the cutting insert pocket. Through WO 98/13161 is previously known a ball nose milling cutter comprising a milling head attached via a pull rod to a shank. The milling head comprises of injection molded cemented carbide and has a cutting edge which extends towards the rotational axis of the tool. The milling head has a thread, which is integral with and thereby made in the same material as the cutting edge. The milling head comprises a key grip consisting of diametrical opposite planar surfaces. Through WO 95/33590 is previously known an injection molded cutting insert with an integral thread. Through US-A- 5,496,137 is previously known an end mill with a head having an integral thread and manufactured in accordance with an older technique. The problem of prior art tools is that if these tools are of small dimensions then less strength is obtained and the tools are difficult to manipulate. Objects of the invention One object of the present invention is to provide a tool for cutting machining having advantages of the prior art tools. Another object of the present invention is to provide a tool for cutting machining and a cutting insert with improved strength and which is easy to manipulate. Still another object of the present invention is to provide a tool for cutting machining and a cutting insert, the designs of which make the cutting insert to be clamped harder during machining. Still another object of the present invention is to provide a method to easily mount such a cutting insert. These and other objects have been achieved by a tool for cutting machining, a cutting insert and a method for mounting such a cutting insert as defined in the appended claims with reference to the drawings. Description of the drawings Fig. 1A shows a cutting insert according to the present invention in a side view. Fig. 1 B shows the cutting insert in a top view. Figs. 2A-2C show a turning tool according to the present invention in a side view, in a top view, in a perspective view, respectively. Fig. 2D shows a cross-section according to line II in Fig. 2B. Fig. 2E shows an alternative embodiment of a cutting insert according to the present invention in a side view. Fig. 2F shows an alternative embodiment of a cutting insert according to the present invention in a perspective view. Fig. 3A shows an alternative embodiment of a tool according to the present invention in a cross-section. Fig. 3B shows an alternative embodiment of a cutting insert according to the present invention in a perspective view. Fig. 4A shows an alternative embodiment of a cutting insert and a tool according to the present invention in a cross-section. Fig. 4B shows an alternative embodiment of a cutting insert and a tool according to the present invention in a cross-section. Fig. 4C and 4D show the cutting insert in Fig. 4A in cooperation with different kinds of nuts. Figs. 5A and 5B show an alternative embodiment of a cutting insert according to the present invention in a side view and in a top view, respectively. Fig. 6 shows an alternative embodiment of a cutting insert according to the present invention in a top view. Figs. 7A and 7B show an alternative embodiment of a cutting insert according to the present invention in a side view and in a top view, respectively. Figs. 8A and 8B show an alternative embodiment of a cutting insert according to the present invention in cross-section and in a top view, respectively. Fig. 9 shows an alternative embodiment of a cutting insert according to the present invention in a cross-section. Figs. 10A and 10B show an alternative embodiment of a tool according to the present invention in a cross- section, according to line X in Fig. 10B and in a top view, respectively. Figs. 11A- 11C show an alternative embodiment of a turning tool according to the present invention in an end view, in a side view and in a perspective view, respectively. Figs. 12A-12C show an alternative embodiment of a milling tool according to the present invention in an end view, in a side view and in a perspective view, respectively. Figs. 13A-13C show an alternative embodiment of a milling tool according to the present invention in an end view, in a side view and in a perspective view, respectively. Figs. 14A-14C show an alternative embodiment of an additional milling tool according to the present invention in an end view, in a side view and in a perspective view, respectively. Fig. 15A shows an alternative embodiment of a cutting insert according to the present invention in a perspective view. Fig. 15B shows the cutting insert in Fig. 15 in a cross-section. Figs. 15C and 15D show alternative cross-sections of a cutting insert according to Fig. 15A. Fig. 16 shows an alternative embodiment of a cutting insert according to the present invention in a perspective view. Detailed description of preferred embodiments of the invention In Figs. 1 A and 1 B is shown a cutting insert 10A according to the present invention, which insert preferably is intended for longitudinal turning. The cutting insert 10A has a round geometry of so called R type. The cutting insert has an upper side 11 and a substantially planar, opposite lower side 12, interconnected by a cylindrical edge surface 13. The cutting insert has a circular cutting edge 14 formed along a line of intersection between the upper side 11 and the edge surface 13. The cutting insert 10A has a center line CL. The cutting insert comprises means 15 to be used for clamping the cutting insert against a holder. The diameter of the cutting insert is considerable larger than the diameter of the means 15. The means 15 is integrated with the cutting insert and thereby performed in the same material as the cutting edge 14. This has been obtained through injection molding with suitable equipment and subsequent sintering. The cutting insert is made by mixing powder of sintered hard alloy with an organic binder, such as plastic, and by shaping the mixture into pellets or granules. Said pellets or granules are cast by means of an injection molding process, whereafter the obtained product is sintered at a temperature of 1300 to 1500°C. The injection molding technique has been more closely described in EP 96913765.2, the contents of which hereby is incorporated in the present description. The means 15 projects perpendicularly from the center part of the lower side 12. The means 15 comprises of an externally threaded spigot 16 the center axis of which substantially coincides with the centeriine CL of the cutting insert. In the shown embodiment the thread has one entrance and one exit. Alternatively the thread may have at least two entrances and at least two exits of the type as is shown in Fig. 3B. This can also be expressed as that the means 15 comprises one or more external, helically shaped grooves. The upper side 11 of the cutting insert 10A or the side of the insert 11 opposite said means 15 comprises at least one key grip 17. The key grip 17 has the shape of a profiled recess 18 intended to cooperate with a key during clamping of the cutting insert against the holder. The key grip 17 has a center axis, which substantially coincides with the centeriine CL of the cutting insert. The profile of the key grip is of the type Torx® or an Allen key, or similar, that is a profile which comprises more than two surfaces for driving, preferably six such surfaces. Consequently, the centeriine of the means 15 substantially coincides with the centeriine of the key grip 17. The grip 17 is arranged within an imaginary cylinder 24, the diameter of which substantially corresponds to the average diameter of the thread 16. Likewise can be noted that the cutting edge 14 preferably is provided in one plane. The cutting edge 14 surrounds the key grip 17 by being provided radially outside of and at a distance from the key grip relative to the centeriine CL. Figs. 2A-2D show a turning tool 19A according to the present invention comprising a holder 20A and the cutting insert 10A. The holder 20A comprises a shank having one end being provided with a cutting insert pocket while the other end is provided to be fastened in a machine for turning. The holder is made of steel. The cutting insert pocket comprises a bottom surface 21 and a side support surface 22, Fig. 2D. The holder 20A comprises means for clamping the cutting insert in the cutting insert pocket in the shape of a threaded hole 23, which extends substantially perpendicularly to the plane of the bottom surface 21. The thread in the hole 23 has one entrance and one exit in the shown embodiment. Alternatively the thread may have at least two entrances and at least two exits. This can also be expressed as that the means 23 comprises one or more internal, helically shaped grooves. The hole 23 is provided centrally in the substantially round bottom surface. The side support surface 22 is part-cylindrically concave in order to fit the convex edge surface 13 of the cutting insert. Mounting of the cutting insert 10A in the holder 20A is done as follows. The cutting insert is brought in direction towards the bottom surface 21 of the cutting insert pocket such that the centeriine of the spigot 15 is aligned with the centeriine of the hole 23. The cutting insert is pushed towards the cutting insert pocket such that the threads abut against each other. Subsequently, the cutting insert 10A and the associated threaded spigot 15 are rotated as a one- piece unit by hand or with the aid of a suitable key, not shown, in engagement with the key grip 17, until the lower side 12 of the cutting insert abuts against the bottom surface 21 of the cutting insert pocket. Then the key must be used to firmly tighten the cutting insert against the bottom surface in order to create a pre-tension in the more elastic steel threads in the hole 23. In the preferred embodiment the cutting insert 10A has a diameter about 4 mm, a metric thread M2.2 and a key grip T07. More generally the interval for the diameter of the cutting insert lies in area 3-5 mm. The thread may be of any type and optionally right-hand or left-hand. A type of thread which fits sintered cemented carbide well is a rope thread, see Fig. 2E. The thread in Fig. 2E is a left-hand thread, which in connection with the round cutting edge 14 tends to tighten to the threaded connection during machining. Alternatively, the thread of the spigot 15 can be replaced by one or more helically shaped grooves, the circumferential dimension of which is smaller than 360°. This groove or these grooves shall then fit with corresponding protrusion/s in the hole of the holder in order to create a bayonet coupling, according to Fig. 2F, which enables indexing of the cutting insert into at least two positions with a fresh cutting edge. Indexing of the cutting insert may alternatively be achieved by providing a shim between the bottom surface of the holder and the lower side of the cutting insert. The thickness of the shim is chosen to half of the pitch of the thread in order to achieve indexing by 180°. In Fig. 3A is shown an alternative embodiment of a tool 19B according to the present invention. The difference between this embodiment and the above-described tool is partly that the cutting insert 10B has a positive basic geometry and partly that the side support surface is missing. Thereby all cutting forces are received by the bottom surface and the thread in the holder 20B. In Fig. 4A is shown an alternative embodiment of a cutting insert 10C and a tool 19C according to the present invention. The difference between this embodiment and the above-described tool according to Fig. 3A is that both the spigot and the hole of the holder comprise cylindrical guiding surfaces 25 and 26, respectively, provided radially beyond the imaginary cylinder 24. The diameters of the guiding surfaces 25, 26 are adapted for mutual slide fit. In this case all cutting forces are received by the bottom surface, the guiding surfaces 25, 26 and the thread in the holder. In Fig. 4B is shown an alternative embodiment of a cutting insert 10C and a tool 191 according to the present invention. The difference between this embodiment and the above-described tool according to Fig. 4A is that the thread in the holder now has been replaced by a thread in a loose nut having a Torx ® grip. The nut and the cutting insert 10C are rotated relative to each other in order to mount or dismount the cutting insert. Fig. 4C shows the nut and the cutting insert 10C from Fig. 4A. Fig. 4D shows an alternative nut with external Allen grip and the cutting insert 10C from Fig. 4A. In Figs. 5A and 5B is shown an alternative embodiment of a cutting insert 10D according to the present invention. The difference between this embodiment and the above-described tool according to Fig. 3A is that the edge surface or the clearance surface of the cutting insert is concave and comprises two mutually circumferential portions in order to guide breakage towards their line of intersection. In Fig. 6 is shown an alternative embodiment of a cutting insert 10E according to the present invention in a top view. The difference between this embodiment and the above-described tools is that the key grip comprises of a hexagonal recess, a so-called Allen grip. In Figs. 7A and 7B is shown an alternative embodiment of a CUTTING insert 10f according to the present invention. The difference between this embodiment and the above-described tool according to Fig. 3A is that the key grip includes a profiled projection on the cutting insert. The projection comprises a male portion for a so-called Torx ® connection. The projection shall cooperate with a female portion of similar but inverted geometry. The projection also serves as a chip former or chip breaker. Alternatively, the projection may consist of a male portion an Allen key connection, that is a projection with a hexagonal cross-section. The projection may however be considered as an inferior technical solution than the earlier described recess at tools of small diameters and small chip spaces. In Figs. 8A and 8B is shown an alternative embodiment of a cutting insert 10G according to the present invention. The difference between this embodiment and the above-described tool according to Fig. 3A is that the helically formed grooves now are performed in a center recess 27 in the cutting insert. The recess 27 surpasses in the mid portion of the cutting insert into the key grip recess. The thread of the recess shall cooperate with a screw in the holder. The screw is firmly anchored in the holder or rotatable in the holder. The recess may include one or more internal, helically shaped grooves. In Fig. 9 is shown an alternative embodiment of a cutting insert 10H according to the present invention. The difference between this embodiment and the above-described tool according to Figs. 8A and 8B is that the key grip is a projection. In Figs. 10A and 10B is shown an alternative embodiment of a tool 19D according to the present invention with a cutting insert 10D according to Figs. 5A and 5B. The difference between this embodiment and the above- described tool according to Fig. 2D is substantially that the threaded and enlarged hole of the holder is displaced a distance in direction towards the side support surface such that its center line differ in said direction from the center line of the cutting insert. Since the hole's smallest diameter is larger than the largest diameter of the spigot, the spigot can be entered longer into in the hole of the holder, whereafter rotation of the cutting insert can start. Thereby only the parts of the threads which face away from the side support surface will be in engagement at tightening simultaneously as the edge surface of the cutting insert supports against the side support surface. In this manner a quick screw function is obtained. Said feature can also be obtained by means of mutually substantially identical and conical threads whose centerlines coincide. In Figs. 11A-11 C is shown an alternative embodiment of a tool 19E and a cutting insert 101 according to the present invention. The tool 19e is intended for inside grooving and comprises a cylindrical holder and a grooving insert 101 with a projecting cutting portion. The cutting insert is mounted in the above-described manner and optionally the geometries of the threads may be arranged such that the final position for the cutting edge of the cutting portion is predetermined. In Figs. 12A-12C is shown an alternative embodiment of a tool 19F and a cutting insert 10J according to the present invention. The tool 19F is intended for example for end milling and comprises a cylindrical cutting insert 10J, which does divide each chip. The cutting insert is mounted in the above- described manner and since the cutting insert comprises a number of symmetrically placed cutting portions and is to be rotated there is no need for indexing. Alternatively, the cutting insert is developed as a chip dividing cylindrical end-milling insert, a thread milling insert, a broaching insert, a truncated conical head for end-milling of dove tail slots, wherein the latter has a cone apex directed towards the holder, or similar. Common for all these tool is that they replace conventional end mills in high-speed steel where smaller dimensions (5 to 15 mm in diameter) often are desirable. In Figs. 13A-13C is shown an alternative embodiment of a tool 19G and cutting insert 10B, shown in Fig. 3A, according to the present invention. The tool 19G is intended for example for grooving and it comprises two cutting inserts 10B, whereof one of the cutting inserts overlaps the rotational axis of the tool such that the milling cutter also can drill. In Figs. 14A-14C is shown an alternative embodiment of a tool 19H and cutting insert 10B, showed in Fig. 3A, according to the present invention. The tool 19H is intended for example for face milling and it comprises eight cutting inserts 10B. In Figs. 15A and 15B is shown an alternative embodiment of a cutting insert 10K according to the present invention. The difference between this embodiment and the above-described tool according to Fig. 3A is that the upper side 11 of the cutting insert comprises chip breaker. A reinforcing chamfer is connected to the cutting edge 14. The chamfer further connects to a concave chip surface which is in turn connects to a rising rear surface. Fig. 15 C shows an alternative cross-section similar to Fig. 15B but without a reinforcing chamfer. In Fig. 15C a projection is depicted by a dotted line. A number of separate projections is then provided with even partition along of the chip surface periphery. Fig. 15D shows an alternative cross-section similar to Fig. 15B but without a concave chip surface. A planar chip surface connects to the reinforcing chamfer. In Fig. 15D a recess is depicted by a dotted line. A number of separate recesses is then provided with even partition along the chip surface periphery. In Fig. 16 is shown an alternative embodiment of a cutting insert 10L according to the present invention. The difference between this embodiment and the above-described tool according to Fig. 3A is that the upper side 11of the cutting insert comprises a ring of material which is more wear resistant than cemented carbide, such as cubic boron nitride or diamond. The ring surrounds the key grip. The present invention consequently relates to a tool for cutting machining, a cutting insert with improved strength and ease of handling and a method to easily mount such a cutting insert. More specifically by the cutting insert in itself been designed as a screw or nut the hard to handle screws used today in connection with tools according to known technique with little diameters are avoided. A solution according to the mentioned WO 98/13161 is not suitable for turning tools where there is a side support surface, since the side support surface then obstruct the movement of one arm of the key at rotation. Although the present invention has been described in connection with a preferred embodiment thereof, it will be appreciated by those skilled in the art that additions, modifications, substitutions and deletions not specifically described may be made without departing from the spirit and scope of the invention as defined by the appended claims. Consequently the shown embodiments may be combined into tools and cutting inserts not specifically illustrated in the present patent application.

Claims: Claims 1. Cutting insert for chip removing machining comprising at least one cutting edge (14), the cutting insert (10A-10L) being made form injection molded cemented carbide and comprising first means (15;27) for clamping the cutting insert against a holder, said means (15;27) being integrated with the cutting insert, c h a r a c t e r i z e d i n that one side of the insert (11 ), opposite to said first means (15;27), comprises at least one key grip (17) intended to cooperate with a key at clamping of the cutting insert (10A-10L) against the holder. 2. The cutting insert according to claim 1 , wherein the cutting insert (10A-10L) has a lower side (12) intended to abut against a support surface of the holder, wherein the center part of the lower side connects to said means (15;27). 3. The cutting insert according to claim 1 , wherein the key grip (17) comprises a profiled recess (18) in the cutting insert (10A-10E;10G; 101-101) or a profiled projection on the cutting insert (10F;10H), said key grip having a centeriine. 4. The cutting insert according to claim 3, wherein the profile of the key grip (17) comprises more than two surfaces for driving. 5. The cutting insert according to claim 1 or 2, wherein the means (15;27) comprises one or more, internal or external, helically formed grooves, said means having a centeriine. 6. The cutting insert according to claim 5, wherein the means (15;27) comprises a thread with at least one entrance. 7. The cutting insert according to claim 5 or 6, wherein the means (15;27) comprises a thread with at least two entrances. 8. The cutting insert according to anyone of the preceding claims, wherein the centeriine of the means (15;27) substantially coincides with the centeriine of the key grip. 9. The cutting insert according to claim 2, wherein the cutting edge (14) is formed along a line of intersection between an upper side (11) of the cutting insert and an edge surface (13) of the cutting insert, said cutting insert having a substantially circular basic shape and a circular cutting edge. 10. Tool for chip removing machining comprising a holder (20A-20I) and at least one cutting insert (10A-10L) having at least one cutting edge (14), said tool (19A- 191) comprising means (15,23;27) for clamping the cutting insert against the holder, wherein a first (15;27) of said means is integrated with the cutting insert (10A-10L) and consists of injection molded cemented carbide and a second (23) of said means is connected to the holder (20A-20I), wherein the holder and the cutting insert have cooperating support surfaces (12,21), c h a r a c t e r i z e d i n that one side of the insert (11 ), opposite to said first means (15;27), comprises at least one key grip (17) intended to cooperate with a key at clamping of the cutting insert (10A-10L) against the holder (20A-20I). 11. The tool according to claim 10, wherein the key grip (17) comprises a profiled recess (18) in the cutting insert (10A-10E;10G;10I-10L) or a profiled projection on the cutting insert (10F;10H), said key grip having a centeriine and wherein the centerlines of the means substantially coincide with the center line of the key grip and wherein the cutting insert has a substantially circular basic form and a circular cutting edge. 12. Method for mounting a cutting insert to a holder, wherein the tool (19A-19I) comprises first (15;27) and second (23) means for clamping of the cutting insert (10A-10L) against the holder (20A-20i), wherein a first (15;27) of said means is integrated with the cutting insert (10A-10L) and consists of injection molded cemented carbide and a second (23) of said means is connected to the holder (20A-20I), wherein the holder and the cutting insert have cooperating support surfaces (12,21), c h a r a c t e r i z e d i n that the method comprises the following steps: - one side of the insert (11 ), opposite to said first means (15;23), is provided with at least one key grip (17), - bring the means (15;27,23) in engagement with each other, - bring a key in engagement with the key grip (17), - rotate the key such that the cutting insert (10A-10L) and the first means (15;23) is rotated as a one-piece unit at least until the support surfaces (12,21) abut against each other. 13. The method according to claim 12, which comprises the further step of further rotating still the cutting insert (10A-10L) relative to the holder (20A-20I) by means of cutting forces acting during machining such that the support surfaces (12,21 ) are pressed together harder.

Inventors: JORDBERG JONAS, JORDBERG, JONAS
Applicants: SECO TOOLS AB
Application year: 1999
Main classification: B23B27
IPC codes: B23B27, B23B51, B23C5