Tool for machining a workpiece

Abstract

The present invention relates to a tool (10) for machining a workpiece, having a tool holder (12) extending along a holder longitudinal axis (36) and a cutting insert (14) which can be fastened to the tool holder (12) with the aid of a fastening element (18). The tool (10) is suitable in particular for profiling. On the cutting insert (14), a protrusion (68) is provided which protrudes from a cutting-insert-side support surface (66) and, when the tool (10) is mounted, engages in a recess (40) in the tool holder, said recess being provided in a holder-side support surface (38). Laterally on the protrusion (68) are three cutting-insert-side bearing surfaces (72, 74, 76) oriented transversely to one another, two of which, when the tool (10) is mounted, bear against two holder-side bearing surfaces (44, 46) which form side walls of the recess (40). Furthermore, when the tool (10) is mounted, the cutting-insert-side support surface (66) of the cutting insert (14) bears against the holder-side support surface (38) of the tool holder (12).

Description

Tool for machining a workpiece

[0001] The present invention relates to a tool for machining a workpiece, comprising a tool holder and a cutting plate that can be attached to the tool holder by means of a fastening element.

[0002] The tool according to the invention is designed in particular as a turning tool, especially preferably as a tool for profile turning.

[0003] Tools of this type for profile turning are already widely known. Exemplary cutting inserts for such profile turning tools are marketed by the applicant under the designation "Form cutting inserts S117".

[0004] Profile turning is a well-known turning process, standardized according to DIN 8589 under section 3.2.1.5, and used to produce rotationally symmetrical shapes on the workpiece. In profile turning, the shape of the workpiece is... The shape to be produced is formed as a negative on the tool or the tool's cutting insert. The cutting inserts of such tools are therefore usually custom-made, in which the shape to be produced on the workpiece is ground as a negative into the cutting contour of the insert. Exceptions are standardized profile turning tools for producing grooves, undercuts, or round profiles.

[0005] The general advantage of such profile turning tools is that the profile to be formed on the workpiece can be produced in a single operation. Otherwise, several different tools with differently shaped cutting edges would usually be necessary to produce such profiles, each used to manufacture only individual segments of the profile. Profile turning is therefore very productive and offers short machining times, even for more complex shapes.

[0006] In profile turning, a basic distinction is made between longitudinal and transverse profile turning, as well as between internal and external profile turning, and between parting and cut-off profile turning.

[0007] Depending on the design of the tool, the cutting inserts of such profile turning tools are used "lying down" or "standing up".

[0008] The aforementioned cutting insert, marketed by the applicant under the name "Form-Schneidplatte S117," is a cutting insert designed for "horizontal" use. This means that it is positioned horizontally on the tool holder. It lies flat on the tool holder with one of its two transverse sides, which are comparatively larger than the narrow sides of the cutting insert. The dimension of the cutting insert measured parallel to the cutting direction is therefore smaller than its dimension measured perpendicular to it in the infeed and / or feed direction.

[0009] In contrast, with a "standing" arrangement of the cutting plate, the cutting plate is arranged vertically on the tool holder, whereby the cutting elements used are edges are arranged on the narrow sides of the cutting plate and the extent of the cutting plate in the cutting direction is typically greater than its extent in the infeed and / or feed direction.

[0010] Due to the fundamentally different geometries of "horizontal" and "vertical" cutting inserts, the way the inserts are mounted on the tool holder and their applications differ completely. For larger cutting widths, for example, widths greater than 20 mm, tools with "horizontal" inserts are generally the only option, as tools with "vertical" inserts would require very large inserts, resulting in exceptionally high carbide consumption. Similarly, for machining operations with relatively limited space, such as turning inside bores, "horizontal" inserts are typically the only choice. Since the space required for internal bore machining is limited by the bore's radius, relatively flat inserts must be used.The use of "lying" cutting inserts is therefore significantly more advantageous for this application than the use of "standing" cutting inserts.

[0011] To ensure reliable machining with consistently repeatable results, a stable and consistently repeatable method of clamping the cutting inserts in the toolholder is of paramount importance. Therefore, guaranteeing a stable insert fit depends particularly on an interface between the cutting insert and the toolholder that is specifically designed for the intended application.

[0012] In various previously known tool systems for profile turning, this fundamental problem of securely clamping the cutting insert to the tool holder has not been satisfactorily solved. For example, undesirable relative movements between the cutting insert and the tool holder can occur due to the loads that arise during machining. However, this must be absolutely prevented to achieve the desired machining quality.

[0013] Furthermore, from an economic perspective, it would be desirable to design such cutting inserts for profile turning as indexable inserts with several identical cutting edges, so that one and the same cutting insert can be used multiple times by clamping it in different orientations on the tool holder. If one of the cutting edges wears, such indexable inserts can be removed from the tool holder and then re-clamped in the tool holder in a different position, in which another, previously unworn cutting edge is used.

[0014] It is therefore an object of the present invention to provide a tool for machining a workpiece which eliminates or at least largely overcomes the aforementioned disadvantages. In particular, it is an object of the present invention to provide a tool for machining a workpiece in which the interface used to clamp the cutting insert to the tool holder is structurally improved to enable a stable insert seat, and in which the cutting insert is designed as an indexable insert with several cutting edges that can be used consecutively.

[0015] This problem is solved according to the invention by a tool according to claim 1, in which the tool holder has a cutting insert receptacle in a side surface for receiving the cutting insert, which comprises a recess formed in a support surface on the holder side. A base surface of the recess is penetrated by a holder-side mounting bore, the axis of which runs transversely to the longitudinal axis of the holder and which serves to receive the fastening element. The recess is laterally bounded by two holder-side contact surfaces extending transversely to the base surface and oriented transversely to each other. The cutting insert has a plurality of identical cutting edges arranged in a common cutting plane, which are formed at a transition between a top surface and a circumferential side of the cutting insert, are arranged at an angle to each other, and extend transversely to each other.The cutting insert has a cutting-edge bearing surface on one of its undersides, opposite the top surface, which is aligned parallel to the cutting plane. Furthermore, the cutting insert has a projection extending from the cutting-edge bearing surface, which, when the tool is mounted, is inserted into the recess and on which three laterally aligned, cutting-edge contact surfaces are located. The cutting insert is arranged in a grid pattern. It also features a centrally located mounting hole extending through the extension, penetrating both the top and bottom surfaces. The axis of this hole is orthogonal to the cutting plane and serves to accommodate the mounting element. When the tool is mounted, the cutting insert's bearing surface rests against the holder's bearing surface. When the tool is mounted, one of the three cutting insert-side bearing surfaces rests against one of the two holder-side bearing surfaces. A second of the three cutting insert-side bearing surfaces rests against a second of the two holder-side bearing surfaces.

[0016] The tool according to the invention thus has a cutting insert that is arranged "lying" on the tool holder. This cutting insert is designed as an indexable insert, which has a plurality of identical cutting edges that are arranged at an angle to each other at the transition between the top and the circumferential side of the cutting insert.

[0017] In other words, the cutting plate of the tool according to the invention has at least two identical cutting edges. Preferably, the tool according to the invention has at least three identical cutting edges. Particularly preferably, the tool according to the invention has exactly three identical cutting edges. Depending on the embodiment, however, the cutting plate of the tool according to the invention can also have four, five, six or more identical cutting edges, all of which lie in a common cutting plane.

[0018] Preferably, the cutting insert of the tool according to the invention is designed to be rotationally symmetrical about the axis of the mounting hole on the cutting insert side. Accordingly, the cutting edges of the cutting insert are preferably offset from each other by a constant angle. In other words, one of these cutting edges can be mapped onto another of these cutting edges by rotating it by a constant angle about the axis of the mounting hole on the cutting insert side. The respective angle of rotation depends on the number of cutting edges and results from the quotient of 360° divided by the number of identical cutting edges.

[0019] In the preferred embodiment of the cutting insert with exactly three identical cutting edges, these can be aligned by rotating them 120° around the axis of the bore on the cutting insert side. According to this preferred embodiment, the cutting insert is preferably as a whole rotationally symmetrical by 120° around the axis of the mounting bore on the cutting insert side.

[0020] The number of contact surfaces on the cutting insert side preferably corresponds to the number of cutting edges provided on the cutting insert. The contact surfaces on the cutting insert side are also preferably offset from each other by a constant angle (for example, 120°) around the axis of the mounting hole on the cutting insert side.

[0021] Furthermore, it should be noted that the term "transverse" in this context does not necessarily mean orthogonal, but rather any spatial orientation of two objects (e.g. surfaces or sections) that enclose an angle greater than 0° between each other, i.e., are not parallel to each other.

[0022] In the tool according to the invention, for example, the bore axis of the holder-side mounting bore runs transversely, i.e., not parallel, but preferably orthogonally to the longitudinal axis of the holder. The two holder-side contact surfaces run transversely, i.e., not parallel, but preferably orthogonally to the base of the recess. The two holder-side contact surfaces are oriented transversely, i.e., not parallel, but preferably at an acute angle to each other. The cutting edges arranged on the cutting insert run transversely, i.e., not parallel to each other, and preferably form an acute angle with each other. The same applies to the (at least) three cutting insert-side contact surfaces.

[0023] The interface provided according to the invention between the cutting insert and the cutting insert holder provided on the tool holder offers various technical advantages.

[0024] Due to the "horizontal" arrangement of the cutting insert, achieved by the cutting insert's support surface on the underside, which is aligned parallel to the cutting plane, resting flat on the holder's support surface, a very flat and space-saving design is possible. This allows the tool according to the invention to be used even in confined machining situations, for example, for machining internal bores.

[0025] During turning operations, the two contact surfaces (cutting-edge side and holder-side) are typically aligned orthogonally to the cutting direction. Accordingly, the majority of the cutting force is transferred to the tool holder at the contact point between these two contact surfaces.

[0026] Since these two contact surfaces can be made relatively large due to their geometry, the force application can be distributed over a relatively large area, thereby reducing the contact pressure between the cutting plate and the tool holder caused by the cutting force.

[0027] The machining forces acting transversely during turning (e.g. feed force and passive force) are essentially absorbed by the holder-side contact surfaces and the corresponding cutting insert-side contact surfaces in the tool according to the invention.

[0028] In this respect, it is advantageous that the contact surfaces and the bearing surfaces are arranged on different parts of the cutting plate or on different parts of the cutting plate holder, which are structurally and spatially separated from each other.

[0029] The holder-side contact surfaces are formed by the side walls of the recess that is integrated into the holder-side bearing surface. The cutting insert-side contact surfaces are located laterally on the extension projecting from the cutting insert-side bearing surface. This separation of the contact and bearing surfaces has a positive effect on the mechanical stability of the insert seat. In particular, this allows A load-induced relative movement between the cutting insert and the tool holder that occurs during machining can be effectively avoided.

[0030] The structural and spatial separation of the support surfaces and contact surfaces also makes it possible for the recess provided in the cutting insert holder and the corresponding extension on the cutting insert to be comparatively small, which also enables a space-saving overall arrangement. If the support surfaces intended to absorb the cutting forces were also located in the recess or on the extension, the recess and extension would have to be significantly larger or more robust.

[0031] The above-mentioned task has therefore been completely solved.

[0032] According to a preferred embodiment, the bearing surface on the cutting plate side completely surrounds the extension. This means that the bearing surface on the cutting plate side does not just surround a part of the extension, but surrounds the extension along its entire circumference.

[0033] This has a tremendously positive effect on the mechanical stability of the insert seat. Firstly, it allows for an increase in the size of the bearing surface on the cutting insert side. Secondly, it effectively prevents the cutting insert from tilting under load, as it is supported all around the extension.

[0034] According to a further embodiment, the mounting surface on the holder side completely surrounds the recess. This means that the mounting surface on the holder side does not just surround part of the recess, but surrounds the recess along its entire circumference.

[0035] This also has a positive effect on the mechanical stability of the insert seat, as the tool holder can support the underside of the cutting insert along its entire circumference around the recess. Furthermore, this also prevents breakouts. Avoid splitting the recess, as the recess is entirely integrated into the solid part of the tool holder.

[0036] Preferably, the holder-side bearing surface and the cutting insert-side bearing surface are each designed as planar surfaces. Equally preferably, the holder-side contact surfaces and the cutting insert-side contact surfaces are each designed as planar surfaces. This allows for a defined, planar contact of the cutting insert with the tool holder.

[0037] According to a further embodiment, the cross-section of the extension, oriented orthogonally to the axis of the mounting hole on the cutting insert side, essentially has the shape of a regular polygon with rounded corners. In the case of a 120° rotationally symmetric cutting insert, the cross-section of the extension preferably corresponds essentially to the shape of an equilateral triangle with rounded corners.

[0038] This design has the advantage that the contact surfaces on the cutting plate side, arranged on the extension, are provided as regular surfaces corresponding to the cutting edges of the cutting plate.

[0039] In one embodiment of the cutting insert with exactly three cutting edges, it is therefore preferred that the contact surfaces on the cutting insert side form an angle of 60° with each other, as is the case with an equilateral triangle. Preferably, the contact surfaces on the holder side also form an angle of 60° with each other according to this embodiment.

[0040] According to a further embodiment, the bore axis of the cutting insert-side mounting bore is aligned orthogonally to the longitudinal axis of the holder.

[0041] Since the bore axis is aligned orthogonally to the cutting plane according to the invention, the cutting plane accordingly runs parallel to the longitudinal axis of the holder according to this embodiment.

[0042] According to a further embodiment, the height of the extension measured parallel to the axis of the mounting hole on the cutting insert side is smaller than the depth of the recess measured parallel to the axis of the mounting hole on the holder side.

[0043] Accordingly, the cutting insert rests perpendicular to the bore axis only with its cutting-side bearing surface against the holder-side bearing surface. The extension projecting from the cutting-side bearing surface, however, does not touch the base of the recess. This creates a mechanically well-defined bearing surface for the cutting insert.

[0044] According to a further embodiment, the extension has a planar end face extending transversely to the cutting plate-side contact surfaces, which is penetrated by the bore and aligned orthogonally to the bore axis of the cutting plate-side mounting bore.

[0045] The mounting hole on the cutting plate side preferably runs centrally through the extension and thus also centrally through the planar end face.

[0046] According to a further embodiment, the two holder-side contact surfaces each have a first distance from the bore axis of the holder-side mounting bore, wherein the recess is further bounded laterally by a side surface running transversely to the base surface and transversely to the two holder-side contact surfaces, which has a second distance from the bore axis of the holder-side mounting bore that is greater than the first distance.

[0047] The aforementioned side surface also forms a side wall of the recess. Unlike the two mounting surfaces on the holder side, which form the remaining side walls of the recess, this side surface is located at a greater distance from the axis of the mounting hole on the holder side. A cross-section of the recess oriented orthogonally to the axis of the mounting hole on the holder side essentially has the shape of an isosceles triangle with rounded corners.

[0048] This ensures that, when the tool is mounted, only two of the three cutting-edge contact surfaces are in contact with the tool holder or the holder-side contact surfaces. The third cutting-edge contact surface, however, is positioned at a distance from the aforementioned side surface of the recess when the tool is mounted.

[0049] It is understood that this third cutting-edge contact surface, which has no contact with the tool holder, can be a different one of the three cutting-edge contact surfaces depending on how the cutting edge is mounted on the tool holder (i.e., which of the multiple cutting edges is used). Accordingly, all three surfaces are referred to as cutting-edge contact surfaces in this context, even though, in the assembled state according to this design, only two of the three cutting-edge contact surfaces are in contact with the tool holder.

[0050] According to the last-mentioned design, the recess is slightly larger than the corresponding projection on the cutting plate. More precisely, the cross-section of the recess, oriented orthogonally to the axis of the mounting hole on the holder side, is larger than the cross-section of the projection, also oriented orthogonally to the axis of the mounting hole on the cutting plate side.

[0051] This makes it easier to insert the extension into the recess. Furthermore, it creates a precisely defined contact surface on the two engaging contact surfaces on the cutting plate side.

[0052] According to a further embodiment, a first of the plurality of cutting edges is arranged in a region of the cutting plate projecting laterally from the tool holder in the mounted state of the tool, wherein the first cutting edge has a shorter distance from the side surface than from the two holder-side contact surfaces.

[0053] This so-called "first cutting edge" is the cutting edge of the insert currently used for machining. The insert rests against the toolholder with its two contact surfaces that are furthest away from the cutting edge being used for machining. This further improves the mechanical stability of the insert seat. The insert is, in effect, pulled away from the active cutting edge and into the toolholder.

[0054] According to a further embodiment, the height of the extension, measured parallel to the axis of the mounting hole on the cutting insert side, is less than 40% of the total height of the cutting insert measured parallel to it. Particularly preferred is a height of the extension that is less than 35% of the total height of the cutting insert. It is especially preferred that the height of the extension is 25-35% of the total height of the cutting insert.

[0055] The extension is therefore relatively low in height. Consequently, despite the extension being attached to the cutting insert, a comparatively flat cutting insert can be achieved. This preserves the suitability of the cutting insert for machining in confined spaces.

[0056] According to a further embodiment, the cutting insert holder is arranged in a recess provided on the tool holder, which has a side wall oriented transversely to the holder-side support surface, partially surrounding the holder-side support surface, and which surrounds two of the majority of the cutting edges of the cutting insert when the workpiece is mounted.

[0057] This recess is larger than the depression in the holder-side bearing surface, as it at least partially surrounds the holder-side bearing surface. The side wall of this recess serves primarily to protect the two inactive cutting edges of the cutting insert, preventing damage before they are used as active cutting edges for machining.

[0058] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0059] An embodiment of the present invention is shown in the drawings and is explained in more detail in the following description. The drawings show: Fig. 1 shows a perspective view of an embodiment of the tool according to the invention; Fig. 2 shows a top view of the tool shown in Fig. 1 together with a workpiece shown in section, which is machined using the tool according to the invention; Fig. 3 is an exploded view of the tool shown in Fig. 1; Figs. 4a-4d show different views of a cutting insert usable in the tool from Fig. 1 according to a first embodiment; Figs. 5a-5d show different views of a cutting insert usable in the tool from Fig. 1 according to a second embodiment; Figs. 6a-6b show a tool holder of the tool shown in Fig. 1 in a perspective view (Fig. 6a) and in a top view (Fig. 6b); Fig. 7 shows part of a longitudinal sectional view of the tool shown in Fig. 1; Fig. 8 shows part of a longitudinal sectional view of the structure shown in Figs. 6a and 6b. Tool holder; and Fig. 9 shows a longitudinal sectional view of the cutting plate shown in Fig. 4a-4d.

[0060] Fig. 1 shows an embodiment of the tool according to the invention in a perspective view. The tool as a whole is designated by the reference numeral 10.

[0061] The tool 10 has a tool holder 12 and a cutting insert 14 detachably attached to the tool holder 12. The cutting insert 14 is secured in a cutting insert receptacle 16, which is located in the region of a front end of the tool holder 12 and is inserted into one of the side faces of the tool holder 12, by means of a fastening screw 18 (see Fig. 3).

[0062] The fastening screw 18, when the tool 10 is mounted, is passed through a fastening bore 20, which is centrally located in the cutting insert 14 and is referred to here as the cutting insert-side fastening bore 20, and is inserted into a fastening bore 22 provided in the tool holder 12, which is provided with a thread 24 corresponding to the fastening screw 18 and is referred to here as the holder-side fastening bore 22, and is screwed in with the thread 24 (see Fig. 7).

[0063] As can be seen particularly in Fig. 2, the fastening screw 18 is arranged eccentrically in the cutting-edge-side fastening bore 20 when the tool 10 is mounted. In other words, the longitudinal axis 26 of the fastening screw 18 is slightly offset from the bore axis 28 of the cutting-edge-side fastening bore 20. However, the longitudinal axis of the fastening screw 18 coincides with the bore axis 30 of the holder-side fastening bore 22. Accordingly, the bore axis 28 of the cutting insert-side mounting bore 20 is also laterally offset by a few tenths of a millimeter (e.g., by 0.1 mm–0.2 mm) parallel to the bore axis 30 of the holder-side mounting bore 22 when the tool 10 is mounted. This causes the cutting insert 14 to experience not only an axial tightening force acting along the longitudinal axis 26 of the mounting screw 18, but also a tightening force acting transversely to it, due to the mounting screw 18. learns, with which the cutting plate 14 is drawn into the cutting plate holder 16.

[0064] In the embodiment shown here, several internal coolant channels are arranged in the tool holder 12, which open into several coolant outlets 32 directed towards the cutting insert 14 to supply it with coolant / lubricant during machining. The coolant channels, not explicitly shown here, preferably run inside the tool holder 12 through a clamping section 34 located at the rear of the tool holder 12. This clamping section 34 serves to clamp the tool 10. The clamping section 34, which is typically elongated, runs along the longitudinal axis 36 of the tool holder 12.

[0065] The cutting insert holder 16, located on the front side of the tool holder 12 opposite the clamping section 34, has a planar surface 38 aligned parallel to the longitudinal axis 36 of the holder, which is referred to here as the holder-side support surface 38. A recess 40 is formed in this holder-side support surface 38. This recess 40 is bounded downwards by a base surface 42, which is aligned parallel to and offset from the holder-side support surface 38. The holder-side mounting bore 22 extends perpendicularly through this base surface 42 of the recess 40.

[0066] The recess 40 is bounded laterally by three planar surfaces 44, 46, 48. These three surfaces 44, 46, 48 form the side walls of the recess 40 and are each oriented transversely, preferably orthogonally, to the base surface 42 of the recess 40.

[0067] As can be seen in particular from Fig. 6b, a cross-section of the recess 40 oriented orthogonally to the bore axis 30 of the holder-side mounting bore 22 has essentially the form of an isosceles triangle with rounded corners, wherein the three surfaces 44, 46, 48 mentioned above form the three legs of the isosceles triangle in this cross-section.

[0068] As explained in detail below, only two of these three surfaces 44, 46, 48 function as lateral contact surfaces against which the cutting insert 44 rests when the tool 10 is mounted. More precisely, these contact surfaces are surfaces 44 and 46. Therefore, surface 44 is referred to here as the first holder-side contact surface 44, surface 46 as the second holder-side contact surface 46, and surface 48 as the side surface 48 of the recess 40.

[0069] A first embodiment of the cutting insert 14 of the tool 10 according to the invention is shown in various views in Figs. 4a-4d and in Fig. 9. Fig. 4a shows the top side of the cutting insert 14 in a perspective view. Fig. 4b shows the underside of the cutting insert 14 in a perspective view. Fig. 4c shows a side view of the cutting insert 14. Fig. 4d shows a top view of the underside of the cutting insert 14. Fig. 9 shows a sectional view of the cutting insert 14, with the section plane running along the axis 28 of the mounting bore 20 on the cutting insert side.

[0070] The cutting insert 14 is designed as an indexable insert. The cutting insert 14 is rotationally symmetrical by 120° to the axis of the bore 28 of the mounting bore 20 on the insert side and has three identical cutting edges 50, 52, 54. All three cutting edges 50, 52, 54 are located at the transition between the top surface 56 and the circumferential surface 58. The three cutting edges 50, 52, 54 lie in a common cutting plane E. The cutting plane E is indicated by a dashed line in Fig. 9.

[0071] Each of these three cutting edges 50, 52, 54 has a cutting edge contour that corresponds to the negative of a profile to be produced on a workpiece using the tool 10 according to the invention. Such a profile 60 is shown schematically in Fig. 2. The profile 60 shown in Fig. 2, which is produced on a workpiece 62 using the tool 10 according to the invention, corresponds here to an internal profile that is inserted into a bore of the workpiece 62.

[0072] A special feature of the production of this profile 60 using the tool 10 according to the invention is that this profile 60 is introduced into the workpiece 62 in only one operation using one and the same tool 10. To ensure this, the cutting contour of each of the three cutting edges 50, 52, 54 is precisely adapted to the shape of the profile 60 to be produced. Accordingly, each of the three cutting edges 50, 52, 54 has several cutting edges oriented transversely to each other.

[0073] In the present embodiment, the cutting edges of the cutting edges 50, 52, 54 are each designed as straight cutting edges. It is understood, however, that one or more of these cutting edges can also be designed as curved cutting edges, depending on the profile to be produced. It is also understood that the cutting insert 14 can be used not only for turning internal profiles but also for turning external profiles.

[0074] On the underside 64 opposite the upper surface 56, the cutting insert 14 has a planar bearing surface 66, which is referred to here as the cutting insert-side bearing surface 66. This cutting insert-side bearing surface 66 runs orthogonally to the bore axis 28 of the cutting insert-side mounting bore 20 and parallel to the cutting plane E.

[0075] Furthermore, the cutting insert 14 has a projection 68 on its underside 64, which extends from the cutting insert-side support surface 66. This projection 68 acts as a counterpart to the recess 40 provided in the cutting insert holder 16. The cutting insert-side mounting bore 20 passes centrally through this projection 68. An end face 70 of the projection 68 is designed as a planar surface, which is penetrated by the cutting insert-side mounting bore 20 and is oriented orthogonally to the bore axis 28 of the cutting insert-side mounting bore 20.

[0076] Furthermore, three surfaces 72, 74, 76, oriented transversely to each other, are arranged laterally on the extension 68, which are hereby designated as the first cutting-plate-side contact surface 72, the second cutting-plate-side contact surface 74, and the third cutting-plate-side contact surface 76. These three cutting-plate-side contact surfaces 72, 74, 76 In the present embodiment, they are aligned at an angle of 60° to each other. They run orthogonally to the cutting-edge support surface 66 and parallel to the bore axis 28 of the cutting-edge mounting bore 20. All three cutting-edge contact surfaces 72, 74, 76 are equidistant from the bore axis 28 of the cutting-edge mounting bore 20.

[0077] While the recess 40 has the cross-section shape of an isosceles triangle with rounded edges, the extension 68 arranged on the cutting plate 14 has, in a cross-section oriented orthogonally to the bore axis 28, the shape of an equilateral triangle with rounded corners.

[0078] The height of the extension 68 is comparatively small compared to the overall height of the cutting insert 14. Preferably, the height h of the extension, measured parallel to the bore axis 28, is less than 40%, and particularly preferably less than 30%, of the height h of the cutting insert 14 measured parallel to it (see Fig. 4c).

[0079] Furthermore, the height h of the extension 68 arranged on the cutting plate 14 is less than the depth t of the recess 40 measured parallel to the bore axis 30 of the holder-side mounting bore 22 (see Fig. 8). As a result, the end face 70 of the extension 68 does not rest against the base surface 42 of the recess 40 when the tool 10 is mounted (see Fig. 7).

[0080] Instead, in the first embodiment, the cutting insert 14, when the tool 10 is mounted, rests with its cutting-side bearing surface 66 flat on the holder-side bearing surface 38 (see Fig. 7). Furthermore, in the first embodiment, the cutting insert 14, when the tool 10 is mounted, rests with two of its three cutting-side bearing surfaces 72, 74, 76 against the holder-side bearing surfaces 44, 46.

[0081] Since the cross-sectional area of ​​the recess 40 is larger than the cross-sectional area of ​​the extension 68, the third of the three cutting plate-side contact surfaces 72, 74, 76, which in the mounted state of the tool 10 of the side surface 48 The recess 40 is located opposite the side surface 48, and therefore does not rest against it. This is primarily due to the fact that the two holder-side contact surfaces 44, 46 have a first distance from the bore axis 30 of the holder-side mounting bore 22, while the side surface 48 has a second distance from the bore axis 30 that is greater than the first distance.

[0082] As can be seen particularly in Figures 4d and 6b, the cutting-edge support surface 66, according to the first embodiment of the cutting plate 14, surrounds the entire circumference of the extension 68. Likewise, the holder-side support surface 38 surrounds the entire circumference of the recess 40. This results in an extremely stable support for the cutting plate 14, which in particular prevents load-dependent tilting of the cutting plate 14.

[0083] Figures 5a-5d show a second embodiment of the cutting insert 14 in four different views, which correspond to the views in Figures 4a-4d. In contrast to the first embodiment shown in Figures 4a-4d, the cutting insert 14 according to the second embodiment shown in Figures 5a-5d is designed as a sintered cutting insert, which has some design differences due to the manufacturing process.

[0084] Firstly, several raised areas are arranged on the underside 64 of the cutting insert, each of whose end faces forms part of the cutting insert-side support surface 66. The cutting insert-side support surface 66 is thus divided into three segments 66.1, 66.2, and 66.3, which are distributed across the underside 64 of the cutting insert 14. Each of these three segments has a planar surface that lies in a common support plane and together forms the cutting insert-side support surface 66. In other words, the cutting insert 14 has three support surfaces 66.1, 66.2, and 66.3. In contrast to the cutting insert 14 shown in Fig. 4a-4d, the cutting insert 14 shown in Fig. 5a-5d, when mounted on the tool 10, does not rest with its entire surface, which is designated here by reference numeral 67, but rather with its three bearing surfaces 66.1, 66.2, 66.3 on the holder-side bearing surface 38.

[0085] Furthermore, a recess 75 is provided in each of the cutting plate-side contact surfaces 72, 74, 76 arranged laterally on the extension 68. The cutting plate-side contact surfaces 72, 74, 76 are thus also segmented into two segments 72.1, 72.2, 74.1, 74.2, and 76.1, 76.2, respectively. The two segments 72.1, 72.2, 74.1, 74.2, and 76.1, 76.2 of each contact surface 72, 74, 76 are spaced apart from each other, lie in the same plane, and are each separated from each other by one of the recesses. In other words, one could also say that the cutting plate has two first cutting plate-side contact surfaces 72.1, 72.2, two second cutting plate-side contact surfaces 74.1, 74.2 and two third cutting plate-side contact surfaces 76.1, 76.2.

[0086] When the tool 10 is mounted, the cutting insert 14 rests with both segments 72.1, 72.2 or 74.1, 74.2 or 76.1, 76.2 of the respective cutting insert-side contact surface 72, 74, 76 against the respective holder-side contact surface 44 or 48. For example, the two segments 72.1, 72.2 rest against the first holder-side contact surface 44 and the two segments 74.1, 74.2 rest against the second holder-side contact surface 48.

[0087] The three cutting-edge support surfaces 66.1, 66.2, 66.3 are arranged on different sides of the extension 68. In other words, each of these three support surfaces 66.1, 66.2, 66.3 is geometrically assigned to one of the three cutting-edge contact surfaces 72, 74, 76. Thus, in the case of the cutting insert 14 according to the second embodiment shown in Figs. 5a-5d, a kind of three-point support is achieved, which ensures a similarly stable insert seat as in the cutting insert 14 according to the first embodiment.

[0088] Regardless of the design of the cutting insert 14, the entire cutting insert holder 16 is arranged in a recess 78 provided in the tool holder 12, which is laterally bounded by a side wall 80 that partially surrounds the holder-side support surface 38 and is oriented transversely to it. The recess 78, or rather its side wall 80, serves in particular to protect the two inactive cutting edges 52, 54 from damage.

Claims

Patent claims 1. A tool (10) for machining a workpiece, comprising a tool holder (12) extending along a longitudinal axis (36) of the holder and a cutting insert (14) that can be fastened to the tool holder (12) by means of a fastening element (18), wherein the tool holder (12) has a cutting insert receptacle (16) for receiving the cutting insert (14), which comprises a recess (40) formed in a support surface (38) on the holder, wherein a base surface (42) of the recess (40) is penetrated by a holder-side fastening bore (22), the bore axis (30) of which extends transversely to the longitudinal axis (36) of the holder and which serves to receive the fastening element (18), and wherein the recess (40) is laterally delimited by two holder-side contact surfaces (44, 46) that extend transversely to the base surface (42) and are aligned transversely to one another; wherein the cutting plate (14) comprises a plurality of cutting edges arranged in a common cutting plane (E),identical cutting edges (50, 52, 54) which are formed at a transition between an upper side (56) and a peripheral side (58) of the cutting plate (14), are arranged at an angle offset from one another and extend transversely to one another, wherein the cutting plate (14) has, on a lower side (64) opposite the upper side (56), a cutting plate-side support surface (66) which is aligned parallel to the cutting plane (E), and an extension (68) projecting from the cutting plate-side support surface (66), which, in the assembled state of the tool (10), is inserted into the recess (40) and on which three cutting plate-side contact surfaces (72, 74, 76) aligned transversely to one another are arranged laterally, and wherein the cutting plate (14) further has a cutting plate-side fastening bore (20) which extends through the extension (64) and penetrates the upper side (56) and the lower side (64),whose bore axis (28) is aligned orthogonally to the cutting plane (E) and which serves to receive the fastening element (18), wherein the cutting plate-side support surface (66) rests against the holder-side support surface (38) in the mounted state of the tool (10), and wherein a, the first of the three insert-side contact surfaces (72, 74, 76) rests against a first of the two holder-side contact surfaces (44, 46) in the mounted state of the tool (10), and a second of the three insert-side contact surfaces (72, 74, 76) rests against a second of the two holder-side contact surfaces (44, 46) in the mounted state of the tool (10).

2. Tool according to claim 1, wherein the cutting plate-side support surface (66) completely surrounds the extension (68).

3. Tool according to claim 1 or 2, wherein the holder-side support surface (38) completely surrounds the recess (40).

4. Tool according to one of the preceding claims, wherein the holder-side contact surfaces (44, 46) and the cutting insert-side contact surfaces (72, 74, 76) are each designed as planar surfaces.

5. Tool according to one of the preceding claims, wherein a cross-section of the extension (68) aligned orthogonally to the bore axis (28) of the cutting plate-side fastening bore (20) has substantially the shape of a regular polygon with rounded corners.

6. Tool according to claim 4 and 5, wherein the insert-side contact surfaces (72, 74, 76) enclose an angle of 60° with one another.

7. Tool according to one of the preceding claims, wherein the cutting plate-side contact surfaces (72, 74, 76) are aligned parallel to the bore axis (30) of the cutting plate-side fastening bore (22).

8. Tool according to one of the preceding claims, wherein the bore axis (28) of the cutting insert-side fastening bore (20) is aligned orthogonally to the holder longitudinal axis (36).

9. Tool according to one of the preceding claims, wherein a height (h) of the extension (68) measured parallel to the bore axis (28) of the cutting plate-side fastening bore (20) is smaller than a depth (t) of the recess (40) measured parallel to the bore axis (30) of the holder-side fastening bore (22).

10. Tool according to one of the preceding claims, wherein the extension (68) has a planar end face (70) extending transversely to the cutting-plate-side contact surfaces (72, 74, 76), through which the cutting-plate-side fastening bore (20) passes and which is oriented orthogonally to the bore axis (28) of the cutting-plate-side fastening bore (20).

11. Tool according to one of the preceding claims, wherein a cross section of the recess (40) aligned orthogonally to the bore axis (30) of the holder-side fastening bore (22) is larger than a cross section of the extension (68) aligned orthogonally to the bore axis (28) of the cutting insert-side fastening bore (20).

12. Tool according to claim 11, wherein the two holder-side contact surfaces (44, 46) each have a first distance from the bore axis (30) of the holder-side fastening bore (22), and wherein the recess (40) is further delimited laterally by a side surface (48) running transversely to the base surface (42) and transversely to the two holder-side contact surfaces (44, 46), which side surface has a second distance from the bore axis (30) of the holder-side fastening bore (22) that is greater than the first distance.

13. Tool according to claim 12, wherein a first of the plurality of cutting edges (50, 52, 54) is arranged in a region of the cutting plate (14) projecting laterally from the tool holder (12) in the mounted state of the tool (10), and wherein the first cutting edge (50) has a shorter distance from the side surface (48) than from the two holder-side contact surfaces (44, 46).

14. Tool according to one of the preceding claims, a height (h) of the extension (68) measured parallel to the bore axis (28) of the cutting plate-side fastening bore (20) is less than 40% of a total height (H) of the cutting plate (14) measured parallel thereto.

15. Tool according to one of the preceding claims, wherein the cutting plate holder (16) is arranged in a recess (78) provided on the tool holder (12), which has a side wall (80) partially surrounding the holder-side support surface (38) and oriented transversely to the holder-side support surface (38), which, in the mounted state of the tool (10), surrounds two of the plurality of cutting edges (50, 52, 54) of the cutting plate (14).

Images