CUTTING INSERT AND TOOL HAVING SUCH A CUTTING INSERT

Abstract

Cutting insert for a tool for machining. The cutting insert is particularly suitable for grooving tools for grooving turning. The cutting insert has a chip breaker geometry in its cutting region, which enables both machining of full cuts and machining of partial cuts as well as machining of webs. In particular, due to the shape of a chip cavity provided in the cutting region and due to the presence of a negative chamfer, very short chips can be produced in all three machining variants, so that a high level of process reliability is ensured and long tool lives are made possible.

Claims

1. A cutting insert for a tool for machining, wherein the cutting insert comprises in a cutting region: a main cutting edge that is rectilinear and runs orthogonally to a longitudinal direction of the cutting region; a chamfer having three part regions that are all arranged in a common chamfer plane, wherein a first of the three part regions is arranged adjacent to a first end of the main cutting edge, a second of the three part regions extends along at least a majority of the main cutting edge and parallel thereto, and a third of the three part regions is arranged adjacent to a second end of the main cutting edge; a chip cavity configured as a recess which is laterally delimited by the first and the third part regions of the chamfer, is delimited at its front end region facing the main cutting edge by the second part region of the chamfer, and is delimited in its rear region opposite the front end region by a wall; wherein the chip cavity including the wall is arranged mirror-symmetrically to a plane of symmetry that is oriented orthogonally to the main cutting edge and runs through a center point of the main cutting edge, wherein the chip cavity including the wall is arranged below the chamfer plane and does not intersect the chamfer plane, wherein the wall comprises five wall regions which adjoin one another in incremental order and in sequence, wherein a first of the five wall regions and a fifth of the five wall regions are configured so as to be mirror-symmetrical to one another relative to the plane of symmetry, wherein a second of the five wall regions and a fourth of the five wall regions are configured so as to be mirror-symmetrical to one another relative to the plane of symmetry, and wherein a third of the five wall regions is divided into two mirror-symmetrical halves by the plane of symmetry, wherein a profile line of the wall, which results from an intersection of the wall with an imaginary plane oriented orthogonally to the plane of symmetry and running along the longitudinal direction, has a first part portion arranged in the first wall region, a second part portion arranged in the second wall region, a third part portion arranged in the third wall region, a fourth part portion arranged in the fourth wall region, and a fifth part portion arranged in the fifth wall region, wherein the first, third and fifth part portions are each concave, and wherein the second and fourth part portions are rectilinear or convex, and wherein at least one point on the first part portion has a smaller distance from the main cutting edge than all points on the second, third and fourth part portions, and wherein all points on the second and fourth part portions have a smaller distance from the main cutting edge than all points on the third part portion.

2. The cutting insert as claimed in claim 1, wherein all points on the first part portion have a smaller distance from the main cutting edge than all points on the second, third and fourth part portions.

3. The cutting insert as claimed in claim 1, wherein the five part portions each define a curve which is continuous and differentiable.

4. The cutting insert as claimed in claim 1, wherein the five wall portions do not merge into one another tangentially.

5. The cutting insert as claimed in claim 1, wherein the first part portion is curved more strongly than the third part portion.

6. The cutting insert as claimed in claim 1, wherein the third part portion is longer than the first part portion, the second part portion, the fourth part portion, and the fifth part portion.

7. The cutting insert as claimed in claim 1, wherein the second part region of the chamfer directly adjoins the main cutting edge.

8. The cutting insert as claimed in claim 1, wherein the first part portion of the profile line directly adjoins the first part region of the chamfer, and wherein the fifth part portion of the profile line directly adjoins the third part region of the chamfer.

9. The cutting insert as claimed in claim 1, wherein a first boundary line between the chip cavity and the first part region of the chamfer, viewed in top view, runs at a first angle α relative to the main cutting edge, wherein 30°≤α≤90°.

10. The cutting insert as claimed in claim 1, wherein a plurality of protrusions are arranged in the chip cavity and protrude upward from a base surface arranged in the chip cavity, and wherein the protrusions are arranged parallel to one another in a row along the main cutting edge.

11. The cutting insert as claimed in claim 10, wherein the plurality of protrusions comprise an uneven number of protrusions.

12. The cutting insert as claimed in claim 10, wherein the protrusions directly adjoin the second part region of the chamfer.

13. The cutting insert as claimed in claim 10, wherein the protrusions each have a surface portion which lies in the chamfer plane.

14. The cutting insert as claimed in claim 1, wherein the chip cavity is configured so as to be concave in any section parallel to the plane of symmetry.

15. A tool for machining a workpiece, with a cutting insert and a tool holder which comprises at least one cutting insert receptacle for receiving the cutting insert, wherein the cutting insert comprises in a cutting region: a main cutting edge that is rectilinear and runs orthogonally to a longitudinal direction of the cutting region; a chamfer having three part regions that are all arranged in a common chamfer plane, wherein a first of the three part regions is arranged adjacent to a first end of the main cutting edge, a second of the three part regions extends along at least a majority of the main cutting edge and parallel thereto, and a third of the three part regions is arranged adjacent to a second end of the main cutting edge; a chip cavity configured as a recess which is laterally delimited by the first and the third part regions of the chamfer, is delimited at its front end region facing the main cutting edge by the second part region of the chamfer, and is delimited in its rear region opposite the front end region by a wall; wherein the chip cavity including the wall is arranged mirror-symmetrically to a plane of symmetry that is oriented orthogonally to the main cutting edge and runs through a center point of the main cutting edge, wherein the chip cavity including the wall is arranged below the chamfer plane and does not intersect the chamfer plane, wherein the wall comprises five wall regions which adjoin one another in incremental order and in sequence, wherein a first of the five wall regions and a fifth of the five wall regions are configured so as to be mirror-symmetrical to one another relative to the plane of symmetry, wherein a second of the five wall regions and a fourth of the five wall regions are configured so as to be mirror-symmetrical to one another relative to the plane of symmetry, and wherein a third of the five wall regions is divided into two mirror-symmetrical halves by the plane of symmetry, wherein a profile line of the wall, which results from an intersection of the wall with an imaginary plane oriented orthogonally to the plane of symmetry and running along the longitudinal direction, has a first part portion arranged in the first wall region, a second part portion arranged in the second wall region, a third part portion arranged in the third wall region, a fourth part portion arranged in the fourth wall region, and a fifth part portion arranged in the fifth wall region, wherein the first, third and fifth part portions are each concave, and wherein the second and fourth part portions are rectilinear or convex, and wherein at least one point on the first part portion has a smaller distance from the main cutting edge than all points on the second, third and fourth part portions, and wherein all points on the second and fourth part portions have a smaller distance from the main cutting edge than all points on the third part portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG. 1 shows a perspective view of a first exemplary embodiment of a cutting insert according to the disclosure;

[0055] FIG. 2 shows a perspective view of an exemplary embodiment of a tool according to the disclosure;

[0056] FIG. 3 shows a top view from above onto the first exemplary embodiment of the cutting insert illustrated in FIG. 1;

[0057] FIG. 4 shows a side view of the first exemplary embodiment of the cutting insert illustrated in FIG. 1;

[0058] FIG. 5 shows a detail view of the top view from above, shown in FIG. 3;

[0059] FIG. 6 shows the section B-B indicated in FIG. 4;

[0060] FIG. 7 shows the section A-A indicated in FIG. 3;

[0061] FIG. 8 shows the view of the cutting insert from FIG. 5, wherein further geometric relationships are marked;

[0062] FIG. 9 shows the view of the cutting insert from FIG. 6, wherein further geometric relationships are marked;

[0063] FIG. 10 shows the view of the cutting insert from FIG. 7, wherein further geometric relationships are marked;

[0064] FIG. 11 shows a second exemplary embodiment of the cutting insert in a top view from above, similar to that illustrated in FIGS. 5 and 8; and

[0065] FIG. 12 shows the second exemplary embodiment of the cutting insert in a sectional view, similar to that illustrated in FIGS. 6 and 9.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0066] A first exemplary embodiment of the cutting insert is shown in a perspective view in FIG. 1. The cutting insert is designated as a whole with reference sign 10.

[0067] At its front end, the cutting insert 10 has a cutting region 12 which comes at least partially into contact with a workpiece during machining of the workpiece. The shape of this cutting region 12 is therefore essential for chip formation, i.e. the formation of chips removed from the workpiece.

[0068] In the rear region, the cutting insert 10 has a clamping portion 14. This clamping portion 14 serves for clamping the cutting insert 10 in a tool holder. The clamping portion 14 is configured as a web or bar and preferably has a polygonal or prismatic cross-section.

[0069] FIG. 2 shows an exemplary tool 16 in which the cutting insert may be used. The tool 16 shown in FIG. 2 is designed as a turning tool. This turning tool 16 is particularly suitable for plunge turning or grooving. It is however understood that the tool shown in FIG. 2 is merely an arbitrary example of a plurality of tools in which the cutting insert 10 may be used.

[0070] The tool 16 shown in FIG. 2 has a tool holder 18 which is designed substantially as a bar in its rear region, and has a cutting insert receptacle 20 in the region of its front end which serves for receiving the cutting insert 10. The cutting insert receptacle 20, in the exemplary embodiment shown in FIG. 2, is configured so as to be self-clamping so that no further fixing means are required for fixing the cutting insert 10 in the cutting insert receptacle 20. In a plurality of further known tool holders however, further fixing means, such as e.g. a clamping screw, are used for clamping the cutting insert 10 in the cutting insert receptacle 20. It is understood that this is also possible in principle with the tool 16 without leaving the spirit and scope of the present disclosure.

[0071] FIGS. 3 to 10 show further views of the cutting insert 10 according to the first exemplary embodiment shown in FIG. 1. As evident in particular from FIG. 3, on its front face end, the cutting insert receptacle 10 has a main cutting edge 22 which is configured so as to be rectilinear. The main cutting edge 22 runs orthogonally to a longitudinal direction of the cutting region 12. This longitudinal direction is shown as a dotted line in FIGS. 3 and 4 and marked with reference sign 24.

[0072] Furthermore, in the cutting region 12, the cutting insert 10 has a chip cavity 26. This chip cavity 26 is configured as a depression or material recess. It extends preferably over the majority of the width of the cutting region 12.

[0073] Furthermore, in the cutting region 12, a chamfer 28 is provided which, because of its orientation, is also known in the trade as a negative chamfer. The chamfer 28 is divided into three part regions 30a-30c. All three part regions 30a-30c of the chamfer 28 are arranged on a common flat plane. This plane is designated here as the “chamfer plane”. The chamfer plane is shown by a dotted line in FIG. 7 and carries reference sign 32. The chamfer plane 32 is oriented at an acute angle relative to the longitudinal direction 24 of the cutting region 12. Since this angle forms a negative rake angle, the chamfer 28 is generally also described as a negative chamfer, as already stated.

[0074] Because of the negative rake angle, the chamfer plane 32 protrudes upward beyond the chip cavity 26. The chip cavity 26 is thus arranged below the chamfer plane 32 and is not intersected thereby.

[0075] The chamfer 28 at least partially surrounds the chip cavity 26. The chamfer 28 preferably runs along the entire length of the main cutting edge 22. A first part region 31a of the chamfer 28 adjoins a first end 34a of the main cutting edge 22. The third part region 30c of the chamfer 28 adjoins the opposite end 34b of the main cutting edge 22. The two part regions 30a, 30c are designed as planar faces which form the two front corner regions of the cutting region 12.

[0076] Towards the front, the two part regions 30a, 30c are delimited by the main cutting edge 22. To the side, the two part regions 30a, 30c are delimited firstly at their respective inside by the chip cavity 26 and at their respective outside by a secondary cutting edge 36a, 36b. The two said secondary cutting edges 36a, 36b form the laterally outer ends of the cutting region 12. The secondary cutting edges 36a, 36b are each connected to the ends 34a, 34b of the main cutting edge 22 via a respective radius 38a, 38b. Instead of radii 38a, 38b, chamfers may also be provided as transitions between the secondary cutting edges 36a, 36b and the main cutting edge.

[0077] The second part region 30b of the chamfer 28 extends between the first part region 30a and the third part region 30c. This second part region 30b of the chamfer 28 extends along at least a majority of the main cutting edge 22 and runs parallel thereto. Preferably, the second part region 30b of the chamfer 28 directly adjoins the main cutting edge 22. This second part region 30b is also configured as a planar face which is arranged in one and the same chamfer plane 32 as the two planar faces formed by the part regions 30a, 30c.

[0078] At its front end facing the cutting edge 22, the chip cavity 26 is delimited by the second part region 30b of the chamfer 28. At its opposite rear end, the chip cavity 26 is delimited by a wall 40. This wall 40 forms the rear region of the chip cavity 26, viewed in the longitudinal direction 24. The wall 40 preferably extends over a majority (more than 50%) of the width of the cutting region 12.

[0079] As a whole, the chip cavity 26 is configured so as to be mirror-symmetrical to a plane of symmetry 41. This plane of symmetry 41 is shown as a dotted line in FIG. 3 and corresponds to the section plane A-A also marked in FIG. 3. The plane of symmetry 41 runs orthogonally to the main cutting edge 22 and has the same distance from both ends 34a, 34b of the main cutting edge 22. The plane of symmetry 41 thus runs through a center point of the main cutting edge 22.

[0080] Because of the symmetry properties of the chip cavity 26, accordingly the wall 40 is also configured so as to be mirror-symmetrical to the plane of symmetry 41. The wall 40 has five wall regions 42, 44, 46, 48, 50 which adjoin one another in incremental order and in sequence. The first wall region 42 is configured so as to be mirror-symmetrical to the fifth wall region 50. These two wall regions 42, 50 form the respective outer end regions of the wall 40. The second wall region 44 is arranged adjoining the first wall region 42. Correspondingly, the fourth wall region 48 is arranged adjoining the fifth wall region 50 and is designed mirror-symmetrically to the second wall region 42. The third wall region 46 is arranged between the second wall region 44 and the fourth wall region 48 and, in the width direction of the cutting insert 10, i.e. viewed transversely to the longitudinal direction 24, forms the middle region of the wall 40. Preferably, this third wall region 46 is superficially the largest of the five wall regions 42-50. The third wall region 46 is divided by the plane of symmetry 41 into two equal-sized, mirror-symmetrical halves.

[0081] A profile line 62, which is illustrated in FIG. 6, serves below for a more detailed explanation of the individual wall regions 42-50 of the wall 40. This profile line 62 results from a section along the section plane B-B marked in FIG. 4. This section plane B-B corresponds to an imaginary plane 64, which is oriented orthogonally to the plane of symmetry 41 and runs parallel to the longitudinal direction 24 of the cutting region 12.

[0082] Correspondingly to the five wall regions 42-50 of the wall 40, the profile line 62 also has five part portions 52, 54, 56, 58, 60. The first part portion 52 of the profile line 62 results from the intersection of the imaginary plane 64 with the first wall region 42. The second part portion 54 of the profile line 62 results from the intersection of the imaginary plane 64 with the second wall region 44. The third part portion 56 of the profile line 62 results from the intersection of the imaginary plane 64 with the third wall region 46. The fourth part portion 58 of the profile line 62 results from the intersection of the imaginary plane 64 with the fourth wall region 48. The fifth part portion 60 of the profile line 62 results from the intersection of the imaginary plane 64 with the fifth wall region 50.

[0083] Correspondingly, the five part portions 52-60 of the profile line 62, like the wall regions 42-50, adjoin one another in incremental order and in sequence. The first part portion 52 is configured so as to be mirror-symmetrical to the fifth part portion 60. The second part portion 54 is configured so as to be mirror-symmetrical to the fourth part portion 58. The third part portion 56 is divided by the plane of symmetry 41 into two equal-sized, mirror-symmetrical halves and forms the middle region of the profile line 62, which connects the second part portion 54 to the fourth part portion 58.

[0084] The first, third and fifth part portions 52, 56, 60 are each configured so as to be concave. The second and fourth part portions 54, 58 are each configured so as to be rectilinear or convex. In the sectional view of the first exemplary embodiment shown in FIG. 6, the second and the fourth part portions 54, 58 are each configured so as to be rectilinear. In the view of the cutting insert 10 according to the second exemplary embodiment, shown in FIG. 12, the second part portion 54 and the fourth part portion 58 are however each configured so as to be convex. Otherwise, the exemplary embodiment shown in FIGS. 11 and 12 does not differ from the first exemplary embodiment shown in FIGS. 3-7.

[0085] The first wall region 42 and the fifth wall region 50 of the wall 40, in comparison with the other wall regions 44, 46, 48, have the shortest distance from the main cutting edge 22. In any case, at least one point on the first part portion of the profile line 62 has a smaller distance from the main cutting edge 22 than all points on the second, third and fourth part portions 54, 56, 58 of the profile line 62. Preferably, all points on the first part portion 52 of the profile line 62 have a smaller distance from the main cutting edge 22 than all points on the second, third and fourth part portions 54, 56, 58 of the profile line 62.

[0086] It is understood that, because of the described symmetry properties of the chip cavity 26 or wall 40, the same distance relationships also apply with respect to the fifth wall region 50 or fifth part portion 60 respectively.

[0087] The third wall region 46 has the greatest distance from the main cutting edge 22. Correspondingly, all points on the second and fourth part portions 54, 58 of the profile line 62 have a smaller distance from the main cutting edge 22 than all points on the third part portion 56 of the profile line 62.

[0088] The individual part portions 52-60 of the profile line 62 are preferably each configured so as to be kink-free. They thus each form a curve which is continuous and differentiable.

[0089] According to the first exemplary embodiments of the cutting insert 10 shown in FIGS. 5 and 6, the five wall regions 42-50 of the wall 40 do not merge into one another tangentially. Between the individual part portions 52-60 of the profile line 62, kinks thus occur at the respective transition points. According to the second exemplary embodiment of the cutting insert 10 shown in FIGS. 11 and 12, however, such kinks occur only between the first wall region 42 and the second wall region 44, and between the fourth wall region 48 and the fifth wall region 50. The second wall region 44 according to the second exemplary embodiment, however, merges tangentially into the third wall region 46. Similarly, according to the second exemplary embodiment, the third wall region 46 also merges tangentially into the fourth wall region 48.

[0090] Both exemplary embodiments described here of the cutting insert share the feature that the first and fifth part portions 52, 60 of the profile line 62 are preferably curved more strongly than the centrally arranged third part portion 56 of the profile line 62. Similarly, according to both exemplary embodiments shown, it is preferred that the centrally arranged third part portion 56 of the profile line 62 forms the comparatively longest of all five part portions 52-60.

[0091] As already explained in the introduction to the description, the cutting insert 10, in particular because of the described form of the chip cavity 26 and because of the presence of the negative chamfer 28, is suitable both for plunge machining of full cuts and also for plunge machining of part cuts and for the above-mentioned web plunge machining. To clarify the meanings of the different machining variants, a plurality of helper lines 66a-66d are shown in FIG. 11.

[0092] The helper lines 66b and 66c indicate the working region of the cutting insert 10 during a part cut. Here, the cutting insert 10 comes into contact with the workpiece to be machined only along a part portion of the main cutting edge 22. The helper line 66b indicates a part cut which extends starting from the second end 34b of the main cutting edge 22, or starting from the radius 38b, to an arbitrary point on the main cutting edge 22 which lies between the two ends 34a, 34b of the main cutting edge 22. The helper line 66c however indicates a part cut which extends starting from the first end 34a or the radius 38a to an arbitrary point on the main cutting edge 22 which is arranged between the two ends 34a, 34b of the main cutting edge 22. Preferably, 60-80% of the total length of the main cutting edge 22 is used for such part cuts.

[0093] The helper line 66d indicates an exemplary working region during web plunge machining. As the name indicates, during web plunge machining, the cutting insert 10 machines a web provided on the workpiece to be machined. This machining preferably takes place with a central region of the main cutting edge 22 which is symmetrical to the plane of symmetry 41. Depending on the width of the web to be machined, usually 10 60% of the total length of the main cutting edge 22 comes into engagement with the workpiece.

[0094] In a full cut, as indicated by the helper line 66a, a part of the chip removed from the workpiece runs over the part regions 30a and 30c of the negative chamfer 28 arranged in the cutting corners. These part regions 30a, 30c stabilize the cutting corners. The centrally arranged second part region 30b of the negative chamfer 28 stabilizes the central region of the main cutting edge 22. On a full cut, in which the entire main cutting edge 22 is used for machining the workpiece, in particular the first and the third part regions 30a, 30c of the negative chamfer 28 contribute to stabilizing the cutting corners. This allows long service lives. The middle region of the rear wall 40 of the chip cavity 26, i.e. the second, third and fourth wall regions 44, 46, 48, are not loaded or at least only minimally loaded during a full cut. The second, third and fourth wall regions 44, 46, 48 of the rear wall of the chip cavity 26 therefore have no or at least only a very slight influence on machining during a full cut.

[0095] During a part cut, as indicated by the helper line 66b, however, it is essentially the third part region 30c of the negative chamfer 28 and the second wall region 44 which act as functional faces and substantially influence the chip formation. A majority of the chip removed from the workpiece runs over these two mutually opposing faces 30c, 44. In this case too, because of the shape of the two faces 30c, 44, a lateral chip taper can be achieved so that even when machining a part cut, short spiral chips can be produced. The same applies to a part-cut machining as indicated by the helper line 66c. In this case, the first part region 30a of the negative chamfer 28 and the fourth wall region 48 act as mutually opposing functional faces which substantially influence the chip formation.

[0096] In the case of web plunge machining, as indicated for example by the helper line 66d, in particular the middle part of the wall 40, i.e. the concavely curved third wall region 46, is decisive for chip formation or chip forming. In particular, in this case, the second part region 30b of the negative chamfer 28 stabilizes the central region of the main cutting edge 22 which is in engagement with the workpiece to be machined. The concave curvature of the third wall region 46 of the wall 40 in turn ensures a lateral chip taper, which allows a comparatively early chip breakage and hence—even on web plunge machining—guarantees the formation of comparatively short chips.

[0097] To further improve the chip formation, in the cutting region 12 of the cutting insert 10, a plurality of protrusions 68 may be provided. In the two exemplary embodiments shown here of the cutting insert 10 according to the example, in total five of these protrusions 68 are arranged in the chip cavity 26. The protrusions 68 are arranged parallel to one another in a row along the main cutting edge 22. They protrude from a base surface 70 which is arranged in the chip cavity 26 and preferably configured as a planar face adjoining the second part region 30b of the negative chamfer 28.

[0098] Between the protrusions 68, relative depressions or channel-like passages are formed. The protrusions 68 therefore ensure a type of pre-deformation of the chip before it reaches the rear wall 40 of the chip cavity 26. This contributes to a further improved chip breakage and hence to the formation of even shorter chips. It is understood however that the cutting insert 10 may also be configured without the protrusions 68, without leaving the spirit and scope of the present disclosure.

[0099] Insofar as the protrusions 68 are provided on the cutting insert 10, it is preferred that they directly adjoin the second part region 30b of the negative chamfer 28. Particularly preferably, each of the protrusions 68 has a surface portion which lies in the chamfer plane 32. In other words, the protrusions 68 merge preferably tangentially into the second part region 30b of the negative chamfer 28. This contributes to further stabilizing of the main cutting edge 22.

[0100] Further preferred size relationships and geometric designs of the chip cavity 26 are explained in more detail below with reference to FIGS. 8-10.

[0101] The width d.sub.2 of the chip cavity 26 preferably amounts to 75-95% of the total width d.sub.1 of the cutting insert 10 in the cutting region 12. The width d.sub.3 of the second part region 30b of the negative chamfer 28, which corresponds to the width of the base surface 70, preferably amounts to 60-90% of the total width d.sub.1 of the cutting insert 10 in the cutting region 12. Furthermore, the width d.sub.4 of the protrusions 68 preferably amounts to 5-12% of the width d.sub.3. Thus, preferably, d.sub.1>d.sub.2≥d.sub.3>d.sub.4.

[0102] As evident in particular from FIG. 9, the angle α which the main cutting edge 22 encloses with a boundary line 72, which extends between the chip cavity 26 and the first part region 30a of the chamfer 28, preferably amounts to 30°-90°. It is understood that the opposite boundary line 74, which extends between the third part region 30c of the chamfer 28 and the chip cavity, encloses the corresponding counter angle with the main cutting edge 22.

[0103] FIG. 9 furthermore shows a tangent 76 which touches the second part portion 54 of the profile line 62 at the transition point between the second part portion 54 and the third part portion 56. The marked tangent 78 touches the fourth part portion 58 of the profile line 62 at the transition point between the third part portion 56 and the fourth part portion 58. The tangents 76, 78 cross at a point 80. Furthermore, FIG. 9 shows the tangents 82 and 84. The tangent 82 touches the third part portion 56 of the profile line 62 at the transition point between the second part portion 54 and the third part portion 56. The tangent 84 touches the third part portion 56 of the profile line 62 at the transition point between the third part portion 56 and the fourth part portion 58. The tangents 82, 84 intersect at a point 86. This point 86 has a greater distance from the main cutting edge 22 than the point 80.

[0104] Furthermore, the longitudinal section illustrated in FIG. 10 shows that the chip cavity 26 preferably has a concave curvature in every section parallel to the plane of symmetry 41. Preferably, the second wall region 44 and the fourth wall region 48 are curved more strongly than the third wall region 46. This is illustrated amongst others by the angles β.sub.1 and β.sub.2 shown in FIG. 10. It is also preferred that the first wall region 42 and the fifth wall region 50 are each curved more strongly than the second wall region 44 and the fourth wall region 48 (see angle β.sub.3). Preferably, therefore, β.sub.3>β.sub.2>β.sub.1.

[0105] The main cutting edge 22 is formed at the transition between the chamfer 28 arranged in the chamfer plane 32 and a free face 88. This free face 88 forms the front end face of the cutting insert 10. This chamfer 28 is tilted by an angle γ relative to the free face 88, wherein γ≥90°. Particularly preferably, γ>90°.

[0106] It is to be understood that the foregoing is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

[0107] As used in this specification and claims, the terms “for example,” “e.g.”, “for instance”, “such as”, and “like”, and the verbs “comprising”, “having”, “including” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.