TECHNICAL FIELD OF THE INVENTION

The present invention belongs to the technical field of metal cutting. More specifically the present invention belongs to the field of tools for turning comprising a round turning insert.

BACKGROUND OF THE INVENTION AND PRIOR ART The present invention refers to a turning insert according to the preamble of claim 1 . In other words, the present invention relates to a turning insert comprising a top surface, an opposite bottom sur face, a reference plane between the top and bottom surfaces, a center axis intersecting the top and bottom surfaces, a side surface connecting the top surface and the bottom surface, a cutting edge adjacent to the top surface and the side surface, the cutting edge being circular and concentric in relation to the center axis,

wherein the bottom surface comprises a set of radial grooves. In turning of a metal work piece, the metal work piece rotates around a center axis. A turning tool is used to remove material from the metal work piece. The turning tool normally comprises a turning insert. A turning insert may have different shape, depending on fac tors such as the type of turning operation and component design. One common type of turning inserts are round turning inserts, i.e. turning inserts having a circular cutting edge.

US7607867B2 disclose a turning tool comprising a turning insert having a circular cutting edge. The bottom surface of the turning insert comprises a plurality of radial grooves. The inventors have found that there is a need for an improved turn ing insert.

SUMMARY OF THE INVENTION An object of the present invention is to provide a turning insert hav ing a circular cutting edge, which can be indexable in predeter mined positions, which can give improved chip breaking both at low and high feed rates when used in more than one feed direction. At least one of said objects is achieved by a turning insert compris ing a top surface, an opposite bottom surface, a reference plane between the top and bottom surfaces, a center axis intersecting the top and bottom surfaces, a side surface connecting the top surface and the bottom surface, a cutting edge adjacent to the top surface and the side surface, the cutting edge being circular and concentric in relation to the center axis, wherein the top surface comprises a set of first protrusions, wherein a greatest distance from the refer ence plane to the first protrusions is greater than a distance from the reference plane to the cutting edge, wherein the bottom surface comprises a set of radial grooves, wherein the bottom surface com prises a set of flat surfaces, wherein the flat surfaces extend in a plane parallel to the reference plane, wherein in a top view each first protrusion is symmetrical in relation to a line extending be tween the center axis and a mid-point of the first protrusion, where- in the first protrusions are elongated in a direction parallel to the adjacent cutting edge. By such a turning insert, chip breaking and/or chip control may be improved. The first protrusions bends the chip so it becomes more fragile. When turning using a round turning insert, the chip thick ness varies. The thin part of the chip is controlled effeicietly solely by the elongated first protrusions. By such a turning insert, indexing positions can be predetermined.

The turning insert preferably comprises a wear resistant material such as cemented carbide, cubic boron nitride or ceramic. The top surface comprises a rake surface. The bottom surface comprises a seating surface. The reference plane is mid-way between the top and bottom surfaces. The center axis intersecting the top and bot tom surfaces is perpendicular to the reference plane. Preferably, a through hole is concentric with the center axis. The side surface connecting the top surface and the bottom surface comprises a clearance surface. The side surface is preferably conical. In other words, an area of the top surface is preferably greater than an area of the bottom surface. A cutting edge is adjacent to, i.e. connects or borders to the top surface and the side surface. The cutting edge is 360° circular in a top view and is concentric in relation to or with the center axis. The cutting edge may be entirely located in a plane parallel to the reference plane. The top surface comprises a set, i.e. a number of spaced apart first protrusions. A protrusion is a portion of the top surface which protrudes upwards, i.e. in a direction away from the reference plane, in relation to surrounding or adjacent por tions of the top surface. Said first protrusions are spaced apart from the cutting edge. A greatest distance from the reference plane to the first protrusions is greater than a distance from the reference plane to the cutting edge, where said distances are measured per- pendicular to the reference plane. In other words, in a side view, the first protrusions are at least partly above the cutting edge, where the top surface is upwards and the bottom surface is down wards. The bottom surface comprises a set of radial grooves. In other words, said grooves extend towards the center axis. Said grooves preferably intersect the side surface. Said grooves prefera bly have a constant width and height along the length of the groove. Preferably, the set of radial grooves are evenly distributed around the center axis. Preferably, each of said radial grooves are uniform in cross-sections. Preferably, the number of radial grooves is even. Preferably, the number of radial grooves is 6-20, even more prefer ably 6-12, still even more preferably 6. The bottom surface com- prises a set of flat surfaces. Preferably, the number of flat surfaces is equal to the number of grooves. Preferably, the flat surfaces are formed between adjacent pairs of grooves. Preferably, the flat sur faces intersect the side surface. Preferably, the flat surfaces are spaced apart from the center axis. In a top view, each first protru- sion is symmetrical, i.e. mirror-symmetrical in relation to a line ex tending between the center axis and a mid-point of the first protru sion. The first protrusions are elongated in a direction parallel to the adjacent, i.e. closest or neighboring part of the cutting edge. In oth er words, each of the first protrusions are elongated in a direction perpendicular to a radius extending from the center axis to a mid point of the respective first protrusion. Preferably, the first protru sions are evenly spaced around the center axis. Preferably, seen in a side view, the top surface slopes downwards from the cutting edge towards the first protrusions. Preferably, the number of first protrusions is 10 - 40, even more preferably 16 - 32.

Preferably, each radial groove is aligned with a mid-point of a first protrusion. In other words, a plane comprising and parallel to the center axis is aligned with a center of a radial groove and intersects a mid-point of a first protrusion.

Preferably, in a top view a distance from the mid-point of the first protrusion to the adjacent cutting edge is 0.3 - 1.0 mm, even more preferably 0.4 - 0.8 mm. By such a turning insert, chip breaking is further improved especially at low feed rates. According to an embodiment, the number of first protrusions is a multiple of the number of radial grooves.

By such a turning insert, chip breaking is more even for each index ing position.

Preferably, the number of first protrusions is two to six times the number of radial grooves. According to an embodiment, a distance between adjacent first pro trusions is smaller than a length of a first protrusion. By such a turning insert, the chip breaking and/or chip control is even further improved, especially at low cutting depths.

In other words, in a top view, adjacent first protrusions are spaced apart by a distance which is less than the maximum length of a first protrusion, i.e. the length measured in a direction perpendicular to a radius intersecting the center axis and a mid-point of the first pro trusion.

According to an embodiment, each first protrusion is convex in a radial cross section and in a cross-section perpendicular to the ra dial cross section.

By such a turning insert, the chip breaking and/or chip control is even further improved.

In other words, a top of the first protrusion is non-flat. At least an upper portion of the first protrusion is convex. A lower portion may be concave, to provide a smooth transformation to a surrounding area of the top surface.

According to an embodiment, the first protrusions are evenly dis tributed around the center axis.

By such a turning insert, the chip breaking and/or chip control is even further improved.

In other words, in a top view, an angle between adjacent first pro trusions is constant, where said angle is measured between radial lines intersecting the center axis and mid-points of adjacent first protrusions. According to an embodiment, the top surface is mirror symmetrical in relation to a plane comprising and parallel to the center axis.

By such a turning insert, chip breaking is more even when used in longitudinal turning in opposite directions.

According to an embodiment, in a top view the first protrusions are oval shaped or substantially oval shaped. By such a turning insert, the chip breaking and/or chip control is even further improved.

Said oval is in a top view elongated in a direction perpendicular to a radius intersecting a mid-point of the respective first protrusion, where said radius intersects the center axis. Preferably, each first protrusion is 2-5 times longer in a direction parallel to the cutting edge than in a radial direction.

According to an embodiment, the top surface comprises a set of second protrusions, wherein a greatest distance from the cutting edge to the first protrusions is smaller than a greatest distance from the cutting edge to the second protrusions.

By such a turning insert, the chip breaking and/or chip control is even further improved. The second protrusions bends or breaks the chip. The second protrusions are raised relative to the first protru sions to ensure chip forming takes place even if the first protrusions lift the chip. The thick part of the chip is partly controlled by the first protrusions, but mainly by the second protrusions.

The top surface comprises a set of preferably at least partly spaced apart second protrusions. The second protrusions protrude in a di rection away from the reference plane in relation to at least some adjacent portions of the top surface. According to an embodiment, a distance from the reference plane to the first protrusions is smaller than a distance from the reference plane to the second protrusions. By such a turning insert, the chip breaking and/or chip control is even further improved. The second protrusions are raised relative to the first protrusions to ensure chip forming takes place even if the first protrusions lift the chip. A distance from the cutting edge to top portions of the respective first protrusions is smaller than a distance from the cutting edge to top portions the respective second protrusions. In other words, in a side view at least portions of both the first protrusions and the sec ond protrusions is above the cutting edge, where the top surface is upwards, and the bottom surface is downwards. Further, in the same view, at least portions of the second protrusions are above all portions of the first protrusions.

According to an embodiment, the first protrusion comprises a first surface facing the cutting edge, wherein the second protrusions comprises a second surface facing the cutting edge, wherein a greatest angle of the first surface in relation to the reference plane is smaller than a greatest angle of the second surface in relation to the reference plane.

By such a turning insert, chip breaking and/or chip control is further improved. At high feed and/or for the thick part of the chip, a steep er angle of the second surface of the higher second protrusion en sures a more aggressive bending of the chip.

Formulated differently, in radial cross sections, the maximum angle of the second protrusion is greater than the maximum angle of the first protrusion, where said angles are measured in relation to the reference plane. Said cross sections intersect respective mid-points of the respective first and second protrusions. Said angles are measured in respective radial planes intersecting mid-points of the first and second protrusion, respectively. Said first and second sur faces are chip forming- and/or chip breaking surfaces.

According to an embodiment, the number of first protrusions is equal to the number of second protrusions, wherein the first protru sions are identical or substantially identical, wherein the second protrusions are identical or substantially identical, wherein the first protrusions are smaller than the second protrusions when seen in a top view, wherein the first protrusions are at a constant distance or substantially constant distance from the center axis, wherein the second protrusions are at a constant distance or substantially con stant distance from the center axis, wherein the second protrusions extend radially from a circular or substantially circular ring concen tric with the center axis.

By such a turning insert, chip breaking and/or chip control is further improved.

The surface around the hole is preferably raised to the top of the second protrusions in order to increase resistance to wear of the second protrusions. In other words, said circular ring decreases the wear of the second protrusions.

The first protrusions are thus identical or substantially identical in shape. The second protrusions are thus identical or substantially identical in shape. The first and second protrusions, respectively, more precisely mid-points of respective first and second protru sions, are at a constant distance or substantially constant distance from the center axis. The second protrusions extend radially, to- wards the cutting edge, from a circular or substantially circular ring, i.e. a circumferential portion, concentric with the center axis. Said ring is preferably raised in relation to the cutting edge. Said ring is preferably raised in relation to the first protrusions. According to an embodiment, the first and second protrusions radi ally overlap when seen in a top view, wherein the first and the sec- ond protrusions, respectively, are uniformly distributed around the center axis.

By such a turning insert, chip breaking and/or chip control is further improved.

The first and second protrusions thus partially overlap radially when seen in a top view. In other words, there exist radii which intersect a first protrusion and a second protrusion, seen in a top view, where said radii extend from the center axis to the cutting edge. The first and the second protrusions, respectively, are uniformly or evenly distributed around the center axis. In other words, adjacent pairs of first protrusions form a constant angle, 360° divided by the number of first protrusions, in relation to the center axis when seen in a top view. In a corresponding manner, adjacent pairs of second protru sions form a constant angle, 360° divided by the number of second protrusions, in relation to the center axis when seen in a top view. Said angles are equal.

In other words, radially overlap means that the sum of radial angles a1 , a2 for the first protrusions and the second protrusions exceeds

360°.

According to an embodiment, the radial grooves are aligned with mid-points of first or second protrusions.

By such a turning insert, chip breaking can be more even when ma chining in opposite directions longitudinally.

In other words, each radial groove is aligned with mid-points of first protrusions or mid-point of second protrusions. In other words, a plane comprising and parallel to the center axis is aligned with a center of a radial groove and intersects a mid-point of a first protru sion or a mid-point of a second protrusion. According to an embodiment, a turning tool comprises a tool body and a turning insert according to one of the above described em bodiments, wherein the turning tool comprises an insert seat, wherein the insert seat comprises a bottom surface and a rear sur face, wherein the turning insert is mounted in the insert seat, wherein the bottom surface of the insert seat comprises a first ridge, wherein the side surface of the turning insert is in contact with the rear surface of the insert seat, wherein the first ridge is in side one of the radial grooves formed in the bottom surface of the turning insert.

By such a turning tool, rotation of the turning insert may be re- duced. Such a turning tool can be manufactured in an economical manner.

The grooves and the ridge are arranged such that a small rotation, i.e. between 0° and 1 °, even more preferably between 0° and 0.5°, of the turning insert around the center axis thereof is possible. The grooves and the ridge are arranged such that a rotation above 1 °, preferably above 0.5°, is prevented. There is a vertical gap between the first ridge and the turning insert, where vertical means in a di rection parallel to the center axis of the turning insert.

According to an embodiment, the bottom surface of the insert seat comprises one or more support surfaces, wherein the support sur faces extends in a common plane, wherein the flat surfaces of the turning insert is in contact with the support surfaces.

According to an embodiment, a method to machine a metal work piece comprises the steps of providing a metal work piece, provid ing the above described turning tool, rotating the metal work piece around a rotational axis thereof, arranging the turning tool such that the first ridge is oriented perpendicular to the rotational axis of the metal work piece, cutting the metal work piece by moving the turn ing tool in a first direction parallel to the rotational axis of the metal work piece, and cutting the metal work piece by moving the turning tool in a second direction parallel to the rotational axis of the metal work piece, where the second direction is opposite to the first direc tion. The metal work piece rotates in the same direction around the rota tional axis thereof during the machining in the first and second di rections.

DESCRIPTION OF THE DRAWINGS

The present invention will now be explained in more detail by a de scription of embodiments of the invention and by reference to the accompanying drawings.

Fig. 1 is a perspective view of a turning insert

Fig. 2 is a front view of the turning insert in Fig. 1

Fig. 3 is a top view of the turning insert in Fig. 1

Fig. 4 is a magnified view of a section of Fig. 3

Fig. 5 is a is a cross-sectional view taken along line 5-5 of Fig.

3

Fig. 6 is a is a cross-sectional view taken along line 6-6 of Fig.

3

Fig. 7 is a perspective view of the turning insert in Fig. 1 where the bottom surface is shown

Fig. 8 is a bottom view of the turning insert in Fig. 1

Fig. 9 is a schematic cross-sectional view of a turning insert mounted in an insert seat

Fig. 10 is a magnified view of a section of Fig. 9

Fig. 1 1 is a bottom view of the turning insert in Fig. 1 and por tions of a bottom surface of an insert seat

Fig. 12 is a side view of Fig. 1 1

Fig. 13 is a perspective view of an insert seat for the turning in sert in Fig. 1

Fig. 14 is a top view of Fig. 13

Fig. 15 is a side view of Fig. 13

Fig. 16 is a front view of Fig. 13

Fig. 17 is a perspective view of the insert seat in Fig. 13 and the turning insert in Fig. 1

Fig. 18 is a top view of Fig. 17

Fig. 19 is a side view of Fig. 17

Fig. 20 is a front view of Fig. 17

Fig. 21 is a perspective view of a tool body comprising the insert seat in Fig. 13 Fig. 22 is a front view of Fig. 21

Fig. 23 is a side view of Fig. 21

Fig. 24 is a top view of Fig. 21

Fig. 25 is a perspective view of a turning tool comprising the tool body in Fig. 21 and the turning insert in Fig. 1

Fig. 26 is a front view of Fig. 25

Fig. 27 is a side view of Fig. 25

Fig. 28 is a top view of Fig. 25

Fig. 29 is a perspective view of a tool body

Fig. 30 is a front view of Fig. 29

Fig. 31 is a side view of Fig. 29

Fig. 32 is a top view of Fig. 29

Fig. 33 is a perspective view of a turning tool comprising the tool body in Fig. 29, the turning insert in Fig. 1 and the shim in Fig. 43

Fig. 34 is a front view of Fig. 33

Fig. 35 is a side view of Fig. 33

Fig. 36 is a top view of Fig. 33

Fig. 37 is a perspective view of the tool body in Fig. 29 and the shim in Fig. 43

Fig. 38 is a front view of Fig. 37

Fig. 39 is a side view of Fig. 37

Fig. 40 is a top view of Fig. 37

Fig. 41 is a schematic view of turning using the turning tool in

Fig. 25

Fig. 42 is a schematic view of turning using the turning tool in

Fig. 25

Fig. 43 is a perspective view of a shim

Fig. 44 is a top view of the shim in Fig. 43

Fig. 45 is a front view of the shim in Fig. 43

Fig. 46 is a transparent side view of the shim in Fig. 43

All turning insert figures have been drawn to scale.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Reference is made to Figs. 1-3, 7 and 8 which show a turning insert 1. The turning insert 1 comprises a top surface 2 comprising a rake surface and an opposite bottom surface 3 functioning as a seating surface. A reference plane RP extends mid-way between the top and bottom surfaces 2, 3. A center axis A1 intersects the top and bottom surfaces 2, 3. A side surface 4 connects the top surface 2 and the bottom surface 3. A cutting edge 5 is adjacent to the top surface 2 and the side surface 4. The cutting edge 5 is circular and concentric in relation to a center axis A1. A through hole 36 for a screw extends between the top and bottom surfaces 2, 3. The top surface 2 comprises a set of first protrusions 6.

As can be seen in Figs. 5 and 6, a greatest distance from the refer ence plane RP to the first protrusions 6 is greater than a distance from the reference plane RP to the cutting edge 5.

As can best be seen in e.g. Fig. 8, the bottom surface 3 comprises a set of radial grooves 10 and a set of flat surfaces 19. The flat sur faces 19, arranged to function as support surfaces or contact sur- faces, extend in a plane parallel to the reference plane RP.

In a top view as in Fig. 3, each first protrusion 6 is symmetrical in relation to a line extending between the center axis A1 and a mid point 45 of the first protrusion 6. The first protrusions 6 are elongat- ed in a direction parallel to or substantially parallel to the adjacent cutting edge 5.

The number of first protrusions 6 is a multiple of the number of ra dial grooves 10.

As can be seen in Fig. 4, a distance 41 between adjacent first pro trusions 6 is smaller than a length 42 of a first protrusion 6.

As seen in Fig. 5, each first protrusion 6 is convex in a radial cross section. The first protrusions 6 are evenly distributed around the center axis A1 , and are located at constant distance from the center axis A1 .

As can be seen in Fig. 3, a radial angle ct1 for a first protrusion 6 is greater than a radial angle a2 of a second protrusion 7, where said angles are measured between radial lines intersecting end points of the respective protrusion 6, 7. The first and second protrusions 6, 7 radially overlap when seen in a top view. The sum of radial angles a1 , a2 for the first protrusions 6 and the second protrusions 7 ex- ceeds 360°.

The first and the second protrusions 6, 7, respectively, are uniform ly distributed around the center axis A1.

As can be seen in e.g. Fig. 3 the top surface 2 of the turning insert 1 is mirror symmetrical in relation to a plane comprising the center axis A1. The number of first protrusions 6 is equal to the number of second protrusions 7. The first protrusions 6 are identical. The sec ond protrusions 7 are identical. In a top view the first protrusions 6 are oval shaped or substantially oval shaped. Said oval is in a top view elongated in a direction per pendicular to a radius intersecting a mid-point of the respective first protrusion, where said radius intersects the center axis. In other words, a length 42 of a first protrusion 6 is greater than a width 43 of a first protrusion 6, where said width 43 is measured radially in a top view and where said length is measured perpendicular to said width 43, as seen in Fig. 4.

The top surface 2 comprises a set of second protrusions 7. As can be seen in e.g. Fig. 3, a greatest distance from the cutting edge 5 to the first protrusions 6 is smaller than a greatest distance from the cutting edge 5 to the second protrusions 7. In other words, the first protrusions 6 are closer to the cutting edge 5, while the second pro trusions 7 are closer to the center axis A1 . As can be seen in Figs. 5 and 6, the top surface 2 slopes downwards from the cutting edge

5. As seen in Figs. 5 and 6, a distance from the reference plane to the first protrusions 6 is smaller than a distance from the reference plane to the second protrusions 7. As seen in e.g. Fig. 5, the first protrusion 6 comprises a first surface 8 facing the cutting edge 5. As seen in e.g. Fig. 6, the second protrusions 7 comprises a second surface 9 facing the cutting edge 5. A greatest angle e1 of the first surface 8 in relation to the reference plane RP is smaller than a greatest angle e2 of the second surface 9 in relation to the refer ence plane RP.

The first protrusions 6 are smaller in width, i.e. radially, than the width of the second protrusions 7 when seen in a top view.

The first protrusions 6 are at a constant distance or substantially constant distance from the center axis A1 .

The second protrusions 7 are at a constant distance or substantially constant distance from the center axis A1 .

The second protrusions 7 extend radially from a circular or substan tially circular ring 1 1 , i.e. a ring-shaped protrusion, concentric with the center axis A1 . The first protrusions 6 are spaced apart from said circular ring 1 1.

The radial grooves 10 are aligned with mid-points of first or second protrusions 6, 7.

Figs. 25-28 show a turning tool 13 comprising a tool body 14 and the above described turning insert 1. The tool body 14 is shown in detail in Figs. 21-24. The turning tool 13 comprises an insert seat 15. The insert seat 15 comprises a bottom surface 16 and a rear surface 17. The turning insert 1 is mounted in the insert seat 15.

The bottom surface 16 of the insert seat 15 comprises a first ridge 18.

The side surface 4 of the turning insert 1 is in contact with the rear surface 17 of the insert seat 15,

The first ridge 18 is inside one of the radial grooves 10 formed in the bottom surface 3 of the turning insert 1. The grooves and the ridge are arranged such that a small rotation,

1.e. between 0° and 1 °, even more preferably between 0° and 0.5°, of the turning insert around the center axis thereof is possible. The grooves and the ridge are arranged such that a rotation above 1 °, preferably above 0.5°, is prevented.

The bottom surface 16 of the insert seat 15 comprises support sur faces 21 , 32 extending in a common plane. The flat surfaces 19 of the turning insert 1 is in contact with the support surfaces 21 , 32.

The turning insert 1 is mounted in the insert seat 15 by means of a screw (not shown). As seen in Figs. 9 and 10, the first ridge 18 is smaller than one of the radial grooves 10 when seen in a cross-section perpendicular to the main extension of said one of the radial grooves 10. Said first ridge 18 is inside or contained within said one of the radial grooves 10.

A hole 36 for the screw is connecting the top and bottom surfaces

2, 3 of the turning insert 1. A threaded hole 22 for said screw inter sects the bottom surface 16 of the insert seat 15. The screw preferably comprises a screw head and an external thread. A through hole 36 for the screw is connecting the top and bottom surfaces 2, 3 of the turning insert 1 . The bottom surface 16 of the insert seat 15 comprises a threaded hole 22 for the screw. The screw is at least partly located inside said hole 36 formed in the insert and at least partly inside said threaded hole 22.

The radial grooves 10 intersect the hole 36 formed in the turning insert 1 . The radial grooves 10 extend radially between the hole 36 and the side surface 4.

The bottom surface 16 of the insert seat 15 comprises seat grooves 23. The first ridge 18 is formed between the seat grooves 23. The first ridge 18 and the seat grooves 23 are at least partially located on opposite sides in relation to a plane comprising the support sur faces 21 , 32. The bottom surface 16 of the insert seat 15 comprises a second ridge 24. The first ridge 18 and the second ridge 24 are aligned in a top view as seen in e.g. Fig. 14. The first and second ridges 18, 24 are spaced apart and separated by the hole 22 formed in the bot tom surface 16 of the insert seat 15. The first ridge 18 is longer than the second ridge 24 when seen in a top view. The first ridge 18 and the second ridge 24 are separated by 180° in a top view. The The first ridge 18 and the second ridge 24 are aligned with the lon gitudinal axis A2 of the turning tool 13, or aligned with a line parallel to said longitudinal axis A2, when seen in a top view.

The tool body 14 comprises a rear end coupling portion 25 suitable to be connected to a machine interface (not shown) of a CNC-lathe (not shown). The coupling portion 25 extends along a longitudinal axis A2 of the turning tool 13. The first and second ridges 18, 24 extends primarily along or parallel to the longitudinal axis A2 of the turning tool 13.

The first ridge 18 has a main extension thereof along or parallel to the longitudinal axis A2 of the turning tool 13 when seen in a top view.

The center axis A1 of the turning insert 1 is perpendicular or sub stantially perpendicular to the longitudinal axis A2 of the turning tool 13.

The first ridge 18, the second ridge 24 and the radial grooves 10 formed in the bottom surface 3 of the turning insert 1 have corre sponding or substantially corresponding shapes in cross sections, as seen in Figs. 9 and 10.

The number of ridges 18, 24 formed in the bottom surface 16 of the insert seat 15 is smaller than the number of radial grooves 10 formed in the bottom surface 3 of the turning insert 1. As seen in Figs. 9 and 10, the first ridge 18 comprises planar ridge side surfaces 26, 27 connected by a ridge crest 28. The ridge side surfaces 26, 27 form an angle of 70 - 1 10° in relation to each other. Each radial groove 10 comprises radial groove side surfaces 29, 30 connected by a radial groove root 31. The radial groove side sur faces 29, 30 form an angle of 70 - 1 10° in relation to each other. Each radial groove 10 is uniform or substantially uniform in cross sections along the length of the radial groove, where the length is in a radial direction. In a corresponding manner, the first and second ridges 18, 24 are uniform or substantially uniform.

A gap is formed at least between one of the pair of adjacent ridge side- and radial groove side surfaces 26, 29, 27, 30. In Fig. 10, a gap is formed between both of said adjacent pairs of side surfaces 26, 29, 27, 30. A gap is always formed between the ridge crest 28 and the radial groove root 31.

The bottom surface 16 of the insert seat 15 comprises two support surfaces 21 , 32 located in a common plane. In a top view as seen in e.g. Fig. 14, an area of the support surfaces 21 , 32 are greater than an area of the ridge or ridges 18, 24.

As seen in e.g. 16, the rear surface 17 of the insert seat 15 com prises two spaced apart rear contact surfaces 33, 34. The rear con tact surfaces 33, 34 are separated by a recess 35.

The tool body 14 may comprise the insert seat 15 as seen in Figs. 21-24. In such a case, the bottom surface 3 and the side surface 4 of the turning insert 1 is partly in contact with the tool body 14, as seen in Figs. 25-28. Alternatively, the turning tool 13 may comprise a shim 37, such as the shim 37 shown in Figs. 43-46. In such case, as seen in Figs. 33-36, the bottom surface 3 of the turning insert 1 is in contact with the shim 37, while the side surface 4 of the turning insert 1 is in contact with the tool body 14. Figs. 41 and 42 schematically show a method to machine a metal work piece 38 by means of any of the above described turning tools 13. The metal work piece 38 rotates in one direction around a rota- tional axis A3 thereof. The first ridge is oriented perpendicular to the rotational axis A3 of the metal work piece 38. Cutting the metal work piece 38 is made by first moving the turning tool 13 in a first direction 39 parallel to the rotational axis A3 of the metal work piece 38, and thereafter cutting the metal work piece 38 by moving the turning tool 13 in a second direction 40 parallel to the rotational axis A3 of the metal work piece 38, where the second direction 40 is op posite to the first direction 39.

In Fig. 41 , one ridge surface 27 as seen in Fig. 10 is in contact with one radial groove side surface 30, while in Fig. 42, one other ridge surface 26 is in contact with one other radial groove side surface 29. Thus, the turning insert have made a rotational movement of a predetermined angle around the center axis thereof when compar ing the end of the pass shown in Fig. 41 and the end of the pass shown in Fig. 42. In other words, in Fig. 41 , there is at least a par tial gap between the other ridge surface 26 and the one other radial groove side surface 29. In a corresponding manner, in Fig. 42 there is at least a partial gap between said one ridge surface 27 and said one radial groove side surface 30. In other words, the ridge crest 28 seen in Fig. 10 forms an angle in a top view in relation to the radial groove root 31. This can be understood from Fig. 1 1.