Turning insert

Abstract

A turning insert includes a top surface, an opposite bottom surface, and a reference plane located parallel to and between the top and the bottom surfaces. A nose portion includes a convex nose cutting edge, and a first and a second cutting edge. The nose cutting edge connects the first and second cutting edges. The first and second cutting edges form a nose angle of 71-85° relative to each other. The nose portion has a third convex cutting edge adjacent to the first cutting edge and a fourth cutting edge adjacent to the third convex cutting edge. The fourth cutting edge forms an angle of 10-30° relative to a bisector. The distance from at least a portion of the fourth cutting edge to the reference plane increases at an increasing distance from the nose cutting edge. A second protrusion is arranged between the nose cutting edge and the first protrusion.

Claims

1. A turning insert comprising: a top surface; an opposite bottom surface, wherein a reference plane located parallel to and between the top surface and the bottom surface, wherein a center axis extends perpendicular to the reference plane; a side surface connecting the top surface and the bottom surface; and a nose portion including a convex nose cutting edge, a first cutting edge and a second cutting edge, wherein the nose cutting edge connects the first and second cutting edges, wherein as seen in a top view the first and second cutting edges form a nose angle of 71-85° relative to each other, wherein a bisector extends equidistantly from the first and second cutting edges, wherein the nose portion includes a third convex cutting edge adjacent to the first cutting edge and a fourth cutting edge adjacent to the third convex cutting edge, wherein as seen in the top view the fourth cutting edge forms an angle of 10-30° relative to the bisector, wherein the bisector intersects the nose cutting edge at a nose cutting edge center point, wherein the third convex cutting edge and the fourth cutting edge are connected by a first transition point, wherein the first cutting edge and third convex cutting edge are connected by a second transition point, the top surface including a first protrusion, wherein the first protrusion includes a first chip breaker wall facing the fourth cutting edge, the first chip breaker wall being arranged between an upper border line and a lower border line, wherein a distance from at least a portion of the fourth cutting edge to the reference plane increases at an increasing distance from the nose cutting edge, wherein a second protrusion is arranged between the nose cutting edge and the first protrusion, wherein the second protrusion intersects the bisector, wherein the second protrusion includes a second chip breaker wall, and wherein a distance from the second chip breaker wall to the reference plane is shorter than a distance from the upper border line of the first chip breaker wall to the reference plane.

2. The turning insert according to claim 1, wherein an angle which the first chip breaker wall forms in relation to the reference plane increases away from the bisector.

3. The turning insert according claim 1, wherein in a side view a distance from the nose cutting edge center point to the first chip breaker wall is greater than a distance from the second transition point to the first chip breaker wall, wherein said distance from the nose cutting edge center point to the first breaker wall is measured along a first line parallel to the reference plane and intersects the nose cutting edge center point and in the top view is perpendicular to the cutting edge tangent at the nose cutting edge center point, wherein said distance from the nose cutting edge center point to the first breaker wall is 1.3-2.3 mm, wherein the distance from the second transition point to the first chip breaker wall is measured along a second line parallel to the reference plane and intersecting the second transition point and in the top view perpendicular to the cutting edge tangent at the second transition point, and wherein said second mentioned distance is 0.7-1.3 mm.

4. The turning insert according to claim 3, wherein an angle which the first chip breaker wall forms in relation to the reference plane at the first line is 15-25°.

5. The turning insert according claim 1, wherein in a side view a distance from the second transition point to the first chip breaker wall is greater than a distance from the first transition point to the first chip breaker wall, wherein said distance from the second transition point to the first chip breaker wall is measured along a second line parallel to the reference plane and intersecting the second transition point and in the top view is perpendicular to the cutting edge tangent at the second transition point, wherein said distance from the first transition point to the first chip breaker wall is measured along a third line parallel to the reference plane and intersecting the first transition point and in the top view perpendicular to the cutting edge tangent at the first transition point, and wherein said second mentioned distance is 0.6-1.2 mm.

6. The turning insert according to claim 5, wherein an angle which the first chip breaker wall forms in relation to the reference plane at the second line is 23-35°.

7. The turning insert according to claim 5, wherein an angle which the first chip breaker wall forms in relation to the reference plane at the third line is 30-40°.

8. The turning insert according to claim 1, wherein in a side view a distance from the nose cutting edge center point to the second chip breaker wall is shorter than a distance from the first transition point to the first chip breaker wall wherein the distance from the nose cutting edge center point to the second chip breaker wall is measured along a first line parallel to the reference plane and intersecting the second transition point and in the top view is perpendicular to the cutting edge tangent at the second transition point, and wherein the distance from the first transition point to the first chip breaker wall is measured along a third line parallel to the reference plane and intersecting the first transition point and in the top view perpendicular to the cutting edge tangent at the first transition point.

9. The turning insert according to claim 1, wherein the second protrusion in the top view is elongated in a direction perpendicular to the bisector.

10. The turning insert according to claim 1, wherein the top surface includes a land surface extending between an inner border line thereof and the cutting edge portions, and wherein the land surface forms a constant positive rake angle which is 6-16°.

11. The turning insert according to claim 1, wherein a distance from at least a portion of the third convex cutting edge to the reference plane is decreasing at an increasing distance from the nose cutting edge, wherein in a side view, a lowest point of the third and fourth cutting edges is the first transition point, or a point within 1.00 mm from the first transition point, wherein a distance between the upper and lower border lines is decreasing away from the nose cutting edge, wherein said distance between the upper and lower border lines is measured in the top view perpendicular to the fourth cutting edge, and wherein the distance from the first cutting edge to the reference plane is decreasing at an increasing distance from the nose cutting edge.

12. The turning insert according to claim 1, further comprising a second nose portion, wherein as seen in the top view the turning insert is 120° or 180° symmetrical or substantially 120° or 180° symmetrical, the nose portion being symmetrical in relation to the bisector.

13. A turning tool comprising: a turning insert according to claim 1; and a tool body, the tool body including a front end, an opposite rear end, a main extension along a longitudinal axis extending from the front end to the rear end, an insert seat formed in the front end in which the turning insert is mountable such that in a top view a distance from the fourth cutting edge of an active nose portion to the longitudinal axis of the tool body is shorter than the distance from the second cutting edge of an active nose portion to the longitudinal axis of the tool body, wherein the bisector of the active nose portion forms an angle of 40-50° relative to the longitudinal axis.

14. A method to generate a cylindrical surface on a metal work piece, the method comprising the steps of: providing a turning tool according to claim 13; rotating the metal work piece around a rotational axis; positioning the first cutting edge of an active nose portion such that the first cutting edge forms a smaller angle relative to the rotational axis of the metal work piece than the angle formed by the second cutting edge relative to the rotational axis of the metal work piece; positioning the longitudinal axis of the tool body perpendicular to the rotational axis of the metal work piece; and moving the turning insert in a direction parallel to the rotational axis such that the first cutting edge is active and is ahead of the surface generating nose cutting edge in the direction of movement of the turning insert, such that the fourth cutting edge is active at an entering angle of 10-45°, such that a lowest point of the third and fourth cutting edges is active, and such that a cylindrical surface is formed.

15. The method according to claim 14, further comprising the steps of selecting the work piece material to be a steel having a Carbon content of maximum 0.20 wt. %, and selecting cutting data such that a feed rate is 0.4-0.7 mm/rev and/or a cutting depth is less than or equal to 1.0 mm.

Description

DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be explained in more detail by a description of embodiments of the invention and by reference to the accompanying drawings.

(2) FIG. 1 is a perspective view showing a turning insert according to a first embodiment.

(3) FIG. 2 is a second perspective view showing the turning insert in FIG. 1.

(4) FIG. 3 is a top view of the turning insert in FIG. 1.

(5) FIG. 4 is a side view of the turning insert in FIG. 1, taken in the direction indicated by arrow A in FIG. 3.

(6) FIG. 5 is a top view of the turning insert in FIG. 1.

(7) FIG. 6 is a partially enlarged view of a cross section taken along the line B-B in FIG. 5.

(8) FIG. 7 is a partially enlarged view of a cross section taken along the line D-D in FIG. 5.

(9) FIG. 8 is a partially enlarged view of a cross section taken along the line C-C in FIG. 5.

(10) FIG. 9 is a schematic view showing a turning method using a turning tool comprising the turning insert in FIG. 1.

(11) FIG. 10 is a chip chart from turning using a known turning insert.

(12) FIG. 11 is a chip chart from turning using the turning insert according to the first embodiment.

(13) All turning insert figures have been drawn to scale.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(14) Attention is now drawn to FIGS. 1-9, which show a turning insert 1 according to a first embodiment. The turning insert 1 comprises a top surface 8 and an opposite bottom surface 9, where a reference plane RP is located parallel to and between the top surface 8 and the bottom surface 9. The top surface 8 is or comprises a rake face. The bottom surface 9 functioning as a seating surface.

(15) A center axis A1 extends perpendicular to the reference plane RP. A screw hole having openings in the top surface 8 and the bottom surface 9 is concentric with the center axis A1.

(16) A side surface 13 connects the top surface 8 and the bottom surface 9. A nose portion 15 comprises a convex nose cutting edge 10, a first cutting edge 11 and a second cutting edge 12. The nose cutting edge 10 connects the first 11 and second 12 cutting edges. In a top view, as seen in FIG. 2, the first 11 and second 12 cutting edges on the same nose portion 15 forms a nose angle α of 71-85° relative to each other, which nose angle α in FIG. 2 is 80°.

(17) In a top view, the nose cutting edge 10, which is part of the nose portion, is located at a largest distance from the center axis A1, i.e. at a larger distance from the center axis A1 than all other parts of the turning insert, except for the nose cutting edge which is part of a second nose portion 15′.

(18) In a top view, imaginary lines coinciding with the first and second cutting edges 11, 12, respectively, converge at a point outside the turning insert 1. A bisector 7 extends equidistantly from the first 11 and second 12 cutting edges. The bisector 7 intersects the center of the nose cutting edge 10 and the center axis A1 of the turning insert 1.

(19) The nose portion 15 comprises a third convex cutting edge 60 adjacent to the first cutting edge 11 and a fourth cutting edge 61 adjacent to the third convex cutting edge 60. In a top view, as in FIG. 3, the fourth cutting edge 61 forms an angle β of 10-30° relative to the bisector 7. The third convex cutting edge 60 and the fourth cutting edge 61 is connected by a first transition point 20.

(20) The turning insert 1 according to the first embodiment is single sided turning insert, or a positive turning insert. The side surface 13 comprises clearance surfaces which are tapered inward from the top surface 8 to the bottom surface 9. The advantages from the clearance surface arrangement is that out-facing can be performed at small metal work piece diameters, and that larger depth of cut is possible in out-facing.

(21) As seen in e.g. FIG. 4, a distance from at least a portion of the fourth cutting edge 61 to the reference plane RP is increasing at increasing distance from the nose cutting edge 10. A distance from at least a portion of the third convex cutting edge 60 to the reference plane RP is decreasing at increasing distance from the nose cutting edge 10. In a side view as seen in FIG. 4, the lowest point of the third and fourth cutting edges 60, 61 is the first transition point 20, or a point within 1.00 mm from the first transition point 20. The distance from the first cutting edge 11 to the reference plane RP is decreasing at increasing distance from the nose cutting edge 10.

(22) As seen in e.g. FIG. 3, the top surface 8 comprises a first protrusion 30. The first protrusion 30 comprises a first chip breaker wall 34 facing the forth cutting edge 61. The first chip breaker wall 34 is arranged between an upper border line 21 and a lower border line 22.

(23) The top surface of the first protrusion 30 is flat and parallel to the reference plane RP. The first protrusion 30 is the part of the top surface 8 of the turning insert 1 which are located at the greatest distance from the reference plane RP.

(24) As seen in e.g. FIG. 5, a distance D1 between the upper border line 21 and the forth cutting edge 61 is decreasing away from the nose cutting edge 10, where said distance D1 is measured in a plane perpendicular to the reference plane RP and perpendicular to the fourth cutting edge 61. Said upper border line 21 preferably extend in a plane which is parallel to the reference plane. Said distance D1 decreases from a maximum value of 0.3-0.5 mm to a minimum value of 0.0-0.1 mm.

(25) The turning insert 1 comprises a nose portion 15 and an opposite second nose portion 15′. In other words, the turning insert comprises two opposite and identical, or substantially identical, nose portions 15, 15′ formed 180° relative each other around the center axis A1 of the turning insert 1. Thus, in a top view as seen in e.g. FIG. 3, the turning insert 1 is 180° symmetrical. The first, second and fourth cutting edges 11, 12, 61 are linear or straight or substantially linear or straight. The nose portion 15 is symmetrical in relation to the bisector 7. Further, as seen in e.g. FIG. 3, the radius of curvature of the third cutting edge 60 is greater than the radius of curvature of the nose cutting edge 10.

(26) In a side view, such as in seen in FIG. 4, the fourth cutting edge 61 slopes upwards, such that the fourth cutting edge 61 has the lowest point thereof closer to the nose cutting edge 10. In other words, the distance from the fourth cutting edge 61 to the reference plane RP varies in such a way that that this distance is increasing at increasing distance from the nose cutting edge 10.

(27) Further, the first, second and third cutting edges 10, 11, 60 are in a side view sloping downwards, i.e. in an opposite direction compared to the fourth cutting edge 61, such that in relation to the bottom surface 9, the nose cutting edge 10 is further away than the first and second cutting edges 11, 12, which in turn are further away than the third cutting edges 60. In this context, that a cutting edge is further away than another cutting edge refers to the respective mid-points of said cutting edges.

(28) Bisectors 7 extend equidistantly from each pair of first 11 and second 12 cutting edges. Each bisector 7 intersects the center axis A1, and the bisectors 7 extend in a common direction.

(29) As seen in e.g. FIG. 1, a second protrusion 44 is arranged between the nose cutting edge 10 and the first protrusion 30. The second protrusion 44 intersects the bisector 7. The second protrusion 44 comprises a second chip breaker wall 35.

(30) The second protrusion 44 is in a top view, as seen in e.g. FIG. 3, elongated in a direction perpendicular to or substantially perpendicular to the bisector 7 and is oval shaped or substantially oval shaped.

(31) As seen in FIG. 6, a distance from the second chip breaker wall 44 to the reference plane RP is shorter than a distance from the upper border line 21 of the first chip breaker wall 34 to the reference plane RP.

(32) In a top view as seen in e.g. FIG. 3, the first, second and fourth cutting edges 11, 12, 61 are linear or straight or substantially linear or straight, and the radius of curvature of the third cutting edge 60 is greater than the radius of curvature of the nose cutting edge 10.

(33) FIG. 5 show lines B-B, D-D and C-C, which intersects and are tangent to the nose cutting edge center point 52, the second transition point 53, and the first transition point 20, respectively.

(34) FIG. 6 show a cross section taken along the line B-B (the bisector 7) in FIG. 5, where a first line 46 intersect the nose cutting edge center point 52. FIG. 7 show a cross section taken along the line D-D in FIG. 5, where a second line 47 intersect the second transition point 53. FIG. 8 show a cross section taken along the line C-C in FIG. 5, where a third line 48 intersect the first transition point 20.

(35) As seen in FIGS. 6-8, an angle γ, δ, ε which the first chip breaker wall 34 forms in relation to the reference plane RP is increasing in a direction away from the bisector 7.

(36) As seen in FIGS. 6 and 7, a distance 40 along the first line 46 from the nose cutting edge center point 52 to the first chip breaker wall 34 is greater than a distance 41 along the second line 47 from the second transition point 53 to the first chip breaker wall 34. Said first mentioned distance 40 is 1.3-2.3 mm, more precisely 1.8 mm. Said second mentioned distance 41 is 0.7-1.3 mm, more precisely 1.0 mm.

(37) As seen in FIG. 6, an angle γ which the first chip breaker wall 34 forms in relation to the reference plane RP at the first line 46 is 15-25°, more precisely 30°.

(38) The first, second and third lines 46, 47, 48 in FIGS. 6-8 are each parallel to the reference plane RP.

(39) As seen in FIGS. 7 and 8, a distance 41 along the second line 47 from the second transition point 53 to the first chip breaker wall 34 is greater than a distance 42 along the third line 48 from the first transition point 20 to the first chip breaker wall 34. Said second mentioned distance 42 is 0.6-1.2 mm, more precisely 0.9 mm.

(40) As seen in FIG. 7, an angle δ which the first chip breaker wall 34 forms in relation to the reference plane RP at the second line 47 is 23-35°, more precisely 29°.

(41) As seen in FIG. 8, an angle ε which the first chip breaker wall 34 forms in relation to the reference plane RP at the third line 48 is 30-40°, more precisely 35°.

(42) As seen in FIGS. 6 and 8, a distance 43 along the first line 46 from the nose cutting edge center point 52 to the second chip breaker wall 35 is shorter than a distance 42 along the third line 48 from the first transition point 20 to the first chip breaker wall 34. Said first mentioned distance 43 is 0.5-1.1 mm, more precisely 0.8 mm.

(43) As seen in e.g. FIG. 3, the top surface 8 comprises a land surface 45 extending between an inner border line 55 thereof and the cutting edge portions 10, 11, 12, 60, 61. As seen in FIG. 8, the land surface 45 forms a constant or substantially constant positive rake angle λ which is 6-16°, more precisely 11°.

(44) In FIG. 9, it is shown a turning tool 3 comprising the turning insert 1 according to the first embodiment and a tool body 2. The tool body is made from steel. The tool body 2 comprising a front end 44 and an opposite rear end (not shown). A main extension of the tool body 2 is along a longitudinal axis A2 extending from the front end 44 to the rear end. An insert seat 4 is formed in the front end 44. The turning insert 1 is mounted or mountable in the insert seat 4 such that in a top view, as shown in FIG. 9, the distance from the forth cutting edge 61 of an active nose portion 15 to the longitudinal axis A2 of the tool body is shorter than the distance from the second cutting edge 12 of an active nose portion 15 to the longitudinal axis A2 of the tool body. As seen in FIG. 9, one nose portion 15, located closer to the rotational axis A3 than the opposite inactive nose portion 15′, is active. Active means that the nose portion as placed such that it can be used for cutting chips from the metal work piece 50.

(45) The bisector 7 of the active nose portion 15 forms an angle θ in the range of 40-50° relative to the longitudinal axis A2.

(46) The distance from the forth cutting edge 61 of the active nose portion 15 to the longitudinal axis A2 of the tool body is shorter than the distance from the second cutting edge 12 of the same active nose portion 15 to the longitudinal axis A2 of the tool body 2.

(47) The turning insert 1, seen in top view, is securely and removably clamped in the insert seat 4 or pocket in the tool body 2 by means of a screw (not shown), having a center axis thereof which coincide or substantially coincide with the center axis A1 of the turning insert 1.

(48) The tool body 2 is may at least partly be in the form of a square shank, which in cross section, in a plane perpendicular to the longitudinal axis A2, is square shaped. The sides of the square may have a length of e.g. 25 mm. Alternatively, the tool body may be rectangular in cross section. Alternatively, the tool body may be configured in any other suitable shape where the shape in different cross sections vary. The longitudinal axis A2 is located at the center of such cross section. The tool body may have a shape comprising e.g. a substantially conical or substantially frustoconical or tapered rear part suitable to be clamped in a tool spindle in a CNC-machine. In such case, the longitudinal axis A2 is located at the center of such cone. For example, the rear part of the tool body may be shaped in accordance to ISO 26623, or in any other way which is known in the industry under the name of “CAPTO”.

(49) In FIG. 9, a method to generate a cylindrical surface 53 on a metal work piece 50 is shown, by means of the turning tool 3. The metal work piece 50 rotates around a rotational axis A3. The first cutting edge 11 of the active nose portion 15 is positioned such that the first cutting edge 11 forms a smaller angle relative to the rotational axis A3 of the metal work piece 50 than the angle formed by the second cutting edge 12 relative to the rotational axis A3 of the metal work piece 50. The longitudinal axis A2 of the tool body 2 is positioned at a constant angle, which is perpendicular to the rotational axis A3 of the metal work piece 50. The turning insert 1 is moved in a direction F1 parallel to the rotational axis A3 such that the first cutting edge is active and is ahead of the surface generating nose cutting edge 10 in the direction of movement of the turning insert 1. The fourth cutting edge 61 is active at a entering angle κ1 of 10-45°, such that the lowest point of the third and fourth cutting edges 60, 61 is active, and such that a cylindrical surface 53 is formed. The first transition point 20 is active, as seen in FIG. 9.

(50) The nose cutting edge 10 is positioned a greater distance from the longitudinal axis A2 of the tool body 2 than all other parts of the turning tool 3. By such an arrangement, the turning tool 3 can be used for turning in a further feed direction, which is perpendicular to and away from the rotational axis 3, without reorientation of the longitudinal axis A2 in relation to the rotational axis A3.

(51) The cutting depth is defined by the difference, in distance from the rotational axis A3, between the cylindrical surface 53 and the surface 52. The surface 52 is the surface of the metal work piece 50 which is to be machined by the turning tool 3 in the turning method. The surface 52 may be cylindrical or substantially cylindrical, resulting in a cutting depth which is constant or substantially constant. Alternatively, the surface 52 may have a distance to the rotational axis 52 which varies along the rotational axis, resulting in a cutting depth which varies during the method.

(52) The feed direction F1, towards the right in FIG. 9, is parallel to the rotational axis A3 and preferably away from an end of the metal work piece 50 which is clamped to the CNC-lathe. The metal work piece 50 is preferably clamped by clamping jaws (not shown, which are pressed against an external surface of the metal work piece 50 at one first end, towards the left-hand side in FIG. 9. An opposite second end of the metal work piece 50, towards the right-hand side in FIG. 9, is preferably a free end.

(53) In said feed direction, the fourth cutting edge 61 is active at an entering angle κ1 of 10-45°, preferably 20-40°, which in FIG. 6 is 25°. The fourth cutting edge 61 is the main cutting edge in said feed direction F1, i.e. the majority of the chips are cut by the fourth cutting edge 61, at least at moderate depth of cut. To a lesser degree, third cutting edge 60, the first cutting edge 11 and the nose cutting edge 10 are also active. The first cutting edge 11 is ahead of the nose cutting edge 10 in said feed direction F1. All parts of the turning insert are ahead of the active nose cutting edge 10 in said feed direction F1. The second cutting edge 11, formed on the active nose portion 15, is inactive.

(54) In the axial turning i.e. the longitudinal turning method shown in FIG. 9, chips are curled and/or directed by both the first, and possibly the third and fourth cutting edges 11, 60, 61, depending on cutting depth, as well as the nose cutting edge 10, the first chip breaker wall 34 and the second chip breaker wall 44 and may e.g. be broken by contact with the chip itself.

(55) The cylindrical surface 53, or rational symmetrical surface, generated or formed at least partly by the nose cutting edge in FIG. 6, has a wavy shape with small peaks and valleys, and the wavy shape is influenced at least partly by the curvature of the nose radius and the feed rate. The wave height is less than 0.10 mm, preferably less than 0.05 mm. A thread profile is not a cylindrical surface 53 in this sense.

(56) The work piece 50 shown in FIG. 9 is preferably from a steel having a Carbon content of maximum 0.20 wt. %.

(57) Attention is now drawn to FIGS. 10 and 11, showing photos of chips from turning. The only differences between FIG. 10 and FIG. 11 is that the shape of the chips are different, and that FIG. 10 is a chip chart from the turning insert according to EP3153261A1 (FIGS. 11a-e), while FIG. 11 is a chip chart from the turning insert according to the first embodiment as shown in FIGS. 1-9. Both inserts have a distance in a top view between opposite nose cutting edges which is in the range of 24-26 mm. The chip charts are from turning as shown in FIG. 9 where the entering angle κ1 is 25°. The axis in both FIG. 10 and FIG. 11 are as follows: the x-axis show feed rates; the photos from left to right 0.3; 0.5; 0.7; 1.0 and 1.2 mm/rev. The y-axis show cutting depth; the photos from bottom to top 0.5; 1.0; 2.0; 3.0 and 4.0 mm. The work piece material is a low-carbon steel designated S355J2 according to the standard EN 10025-2:2004. As can be seen from the chip charts, the chips from the turning insert according to the first embodiment, seen in FIG. 11, is an improvement (e.g. shorter chips) over the known turning insert seen in FIG. 10, especially at feed rates within the range of 0.4-0.7 mm/rev, and especially at cutting depths within the range of up to 1.0 mm.

(58) The turning method shown in FIG. 9 is preferably performed using a computerized numerical control (CNC) lathe, where the movement of the tool body 2 and the rotation of the metal work piece 50 is controlled by the computerized numerical control (CNC) lathe. The CNC-lathe execute instructions from a computer program. In other words, said computer program has instructions which when executed by a computer numerical control (CNC) lathe cause the computer numerical control (CNC) lathe to perform the method as described above and/or as shown in FIG. 9. The computer program may be stored on a computer readable medium. Alternatively, a data stream may be representative of the computer program.

(59) Reference is now made to a turning insert according to a second embodiment (not shown). The turning insert according to the second embodiment is double sided, or usable in an upside-down position, in such a way that the top and bottom surface 8, 9 are identical. The area of the top and bottom surfaces 8, 9 are equal in size. The turning insert is mirror-symmetric in relation to the reference plane. The side surfaces of the turning insert extend along lines parallel to the center axis of the turning insert. In all other aspects, the turning insert according to the second embodiment is identical to, or substantially similar to, the turning insert according to the first embodiment.

(60) Reference is now made to a turning insert according to a third embodiment. The turning insert according to the third embodiment comprises three nose portions. Said turning insert is 120° symmetrical. In other words, in a top view, the turning insert is identical or substantially identical if rotated around the center axis by 120° or by 240°. In other aspects, the insert according to the third embodiment is in accordance with the turning insert according to the first embodiment.

(61) For all embodiments, the nose angle α, which is the angle between the first and second cutting edges 11, 12, is 75-85°, the angle β is 10-20°, and the radius of curvature in a top view of the nose cutting edge 10 is smaller than the radius of curvature of the third cutting edge. The transitions between all cutting edges are smooth, without sharp corners. By having a relatively large nose angle α, the strength of the nose cutting edge 10 is increased resulting in less wear. By having a relatively large nose angle α, the entering angle for the first cutting edge 11 is relatively small, 2.5-7.5°, which gives reduced wear of the first cutting edge. By having a relatively small radius of curvature of the nose cutting edge 10, a small radius on the component can be machined, and the turning insert 1 can be used to machine a wider range of shapes.

(62) The invention is not limited to the embodiments disclosed, but may be varied and modified within the scope of the following claims. Words such as top, bottom etc. shall be interpreted as understood by the skilled person. The expression top view shall be understood as the view as seen in FIG. 3.