阅读说明：本技术 包括冷却剂通道的、用于金属切削的车削刀具 (Turning tool for metal cutting comprising coolant channels ) 是由 罗尼·洛夫 亚当·约翰松 克里斯特·维克布拉德 于 2019-02-28 设计创作，主要内容包括：一种车削刀具(1)包括刀具本体(2)和车削刀片(3),该车削刀具(1)包括刀片座(4),所述车削刀片(3)被安装在该刀片座(4)中,所述刀片座(4)包括底表面(5)和侧表面(6),该侧表面(6)包括第一表面(13)和第二表面(14),其中,所述第一表面(13)包括接触表面(19),其中,所述接触表面(19)与所述车削刀片(3)的侧表面(9)的一部分接触,所述刀具本体(2)包括冷却剂通道(10),该冷却剂通道(10)在冷却剂通道入口(26)和冷却剂通道出口(11)之间延伸,该冷却剂通道出口(11)通向处在所述车削刀片(3)的所述侧表面(9)和所述刀片座(4)的所述侧表面(6)的所述第一表面(13)之间的空隙(24)。(A turning tool (1) comprising a tool body (2) and a turning insert (3), the turning tool (1) comprising an insert seat (4), the turning insert (3) being mounted in the insert seat (4), the insert seat (4) comprising a bottom surface (5) and a side surface (6), the side surface (6) comprising a first surface (13) and a second surface (14), wherein the first surface (13) comprises a contact surface (19), wherein the contact surface (19) is in contact with a portion of the side surface (9) of the turning insert (3), the tool body (2) comprising a coolant channel (10), the coolant channel (10) extending between a coolant channel inlet (26) and a coolant channel outlet (11), the coolant channel outlet (11) opening into the first surface (13) of the side surface (9) of the turning insert (3) and the side surface (6) of the insert seat (4) ) A gap (24) therebetween.)

1. A turning tool (1) comprises a tool body (2) and a turning insert (3),

the turning tool (1) comprising an insert seat (4), the turning insert (3) being mounted in the insert seat (4),

a longitudinal axis (A1) extending from the rear end (16) to the front end (17),

the insert seat (4) comprises a bottom surface (5) and a side surface (6),

the side surface (6) comprising a first surface (13) and a second surface (14),

wherein the first and second surfaces (13, 14) form an angle (beta) with respect to each other,

the turning insert (3) comprising a top surface (7), an opposite bottom surface (8) and a side surface (9) connecting the top and bottom surfaces (7, 8),

the bottom surface (8) of the turning insert (3) being in contact with the bottom surface (5) of the insert seat (4),

wherein the first surface (13) comprises a contact surface (19),

wherein the contact surface (19) is in contact with a portion of the side surface (9) of the turning insert (3),

the tool body (2) comprises a coolant channel (10),

the coolant channel (10) extending between a coolant channel inlet (26) and a coolant channel outlet (11),

it is characterized in that

The coolant channel outlet (11) opens into a gap (24) between the side surface (9) of the turning insert (3) and the first surface (13) of the side surface (6) of the insert seat (4).

2. The turning tool (1) according to claim 1,

wherein the coolant channel outlet (11) is formed partially or completely in the first surface (13).

3. A turning tool (1) according to any of the preceding claims, wherein the channel outlet (11) is spaced from the side surface (9) of the turning insert (3) by a distance of 0.1-2.0 mm.

4. A turning tool (1) according to any of the preceding claims,

wherein the side surface (6) of the insert seat (4) comprises a third surface (15),

wherein the first surface (13) faces the third surface (15).

5. A turning tool (1) according to any of the preceding claims,

wherein the distance from the contact surface (19) to the top surface (7) of the turning insert (3) is shorter than the distance from the contact surface (19) to the bottom surface (8) of the turning insert (3).

6. A turning tool (1) according to any of the preceding claims,

wherein the contact surface (19) is adjacent to the void (24).

7. A turning tool (1) according to any of the preceding claims,

wherein the distance from the coolant channel outlet (11) to the bottom surface (8) of the turning insert (3) is shorter than the distance from the coolant channel outlet (11) to the top surface (7) of the turning insert (3).

8. A turning tool (1) according to any of the preceding claims,

wherein the distance from the longitudinal axis (A1) to the first surface (13) is greater than the distance from the longitudinal axis (A1) to the second and third surfaces (14, 15), respectively.

Wherein the coolant channel outlet (11) is formed in the first surface (13).

9. A turning tool (1) according to any of the preceding claims,

wherein the coolant channel outlet (11) is arranged to direct a flow of coolant in a direction away from the rear end (16) and away from the bottom surface (5) of the insert seat (4).

10. A turning tool (1) according to any of the preceding claims,

wherein the turning tool (1) comprises a shim (12),

and wherein the bottom surface (5) of the insert seat (4) is defined by a top surface of the shim (12).

11. A turning tool (1) according to any of the preceding claims,

wherein the turning insert (3) is arranged symmetrically or substantially symmetrically around a centre axis (A2) of the turning insert (3),

wherein the central axis (A2) intersects the top and bottom surfaces (7, 8),

wherein the distance from the longitudinal axis (A1) to the first surface (13) of the insert seat (4) is larger than the distance from the longitudinal axis (A1) to the central axis (A2) of the turning insert (3),

wherein the first surface (13) of the insert seat (4) faces the centre axis (A2) of the turning insert (3).

12. A turning tool (1) according to any of the preceding claims,

wherein the tool body (2) comprises a portion (22) which is tapered in top view such that its width decreases in a direction away from the rear end (16),

wherein the boundary surface of said portion is the first surface (13) of the insert seat (4).

13. A turning tool (1) according to any of the preceding claims,

wherein the top surface (7) of the turning insert (3) comprises a protrusion (23), wherein the protrusion is spaced from the side surface (9) of the turning insert (3), wherein the distance from the bottom surface (8) of the turning insert (3) to the protrusion (23) is larger than the distance from the bottom surface (8) of the turning insert (3) to the intersection between the top surface (7) and the side surface (9) of the turning insert (3).

14. A turning method comprising the steps of:

providing a turning tool (1) according to any of the preceding claims,

providing a metal workpiece (20);

rotating the metal workpiece (20) about a rotational axis (R1) of the metal workpiece (20);

setting the longitudinal axis (A1) of the turning tool (1) perpendicular to the axis of rotation (R1) of the metal work piece (20);

-supplying a coolant to the coolant channel (10) such that a flow of coolant is directed from the coolant channel outlet (11) towards the side surface (9) of the turning insert (3) such that the flow of coolant is deflected towards a first surface (13) of the insert seat (4);

and moving the turning tool (1) in a direction parallel or substantially parallel to the axis of rotation (R1) such that a machined surface (21) is formed by a portion of the turning insert (3), wherein the longitudinal axis (a1) of the turning tool (1) is in front of the machined surface (21) being formed.

15. The turning method of claim 14, further comprising the steps of:

-setting the entry angle (a) of the turning insert (3) to at least 3 ° but not more than 30 °.

Technical Field

The invention belongs to the technical field of metal cutting. More particularly, the invention is in the field of turning tools for metal cutting in machines such as CNC machines.

Background

The present invention relates to a turning tool according to the preamble of claim 1. In other words, the invention relates to a turning tool comprising a tool body and a turning insert, the turning tool comprising an insert seat in which the turning insert is mounted, the longitudinal axis extending from a rear end to a front end, the insert seat comprising a bottom surface and a side surface, the side surface comprising a first surface and a second surface, wherein the first surface and the second surface form an angle with respect to each other, the turning insert comprising a top surface, an opposite bottom surface and a side surface connecting the top surface and the bottom surface, the bottom surface of the turning insert being in contact with the bottom surface of the insert seat, a portion of the side surface of the turning insert being in contact with the side surface of the insert seat, the tool body comprising a coolant channel, the coolant channel extending between a coolant channel inlet and a coolant channel outlet.

Such a turning tool is known from EP 3153261a1, wherein the turning tool comprises a turning insert mounted in an insert seat formed in a tool body. The coolant channel may be provided as shown in fig. 8 below the turning insert to a coolant channel outlet spaced from the insert seat. As shown in fig. 2, the turning tool is advantageously used for longitudinal turning, forming a machined surface.

While the above turning tool and machining method have been found to provide significant positive benefits, the present inventors have found that there is a need for an improved turning tool. In particular, the inventors have found that, especially in longitudinal turning during long cutting times, such as shafts having a length of more than 300mm, for example, there is a need for a turning tool that can be used for a longer time.

Disclosure of Invention

It is an object of the present invention to provide an improved turning tool which can be used for longer periods of time, especially in longitudinal turning during long periods of cutting.

This object is achieved by the turning tool initially defined, which is characterized in that the coolant channel outlet opens into a space between a side surface of the turning insert (3) and a first surface of a side surface of the insert seat.

With such a turning tool, the inventors have found that the risk of plastic deformation of the insert seat is reduced, thereby increasing the time during which the turning tool, and in particular the tool body, can be used.

With such a turning tool, the temperature is the temperature of the insert seat, and in particular the temperature of the contact surface. Thus, the risk of deformation of the tool body is reduced if the tool body is made of a material whose yield strength decreases with increasing temperature.

The turning tool is suitable for longitudinal turning of a rotating metal workpiece, i.e. turning with a feed direction parallel to the axis of rotation of the metal workpiece. The turning tool is preferably also adapted for turning in a direction perpendicular to and away from the axis of rotation of the rotating metal workpiece, wherein the longitudinal axis is perpendicular to the axis of rotation. In other words, the turning tool is adapted for longitudinal turning using a first cutting edge adjacent to the nose cutting edge, and preferably for turning in a direction perpendicular to and away from the axis of rotation of the metal workpiece to be machined (machined out) using a second cutting edge adjacent to the nose cutting edge, wherein the nose cutting edge is between and connects the first cutting edge and the second cutting edge, and wherein the longitudinal axis of the turning tool is perpendicular to the axis of rotation of the metal workpiece.

The turning tool comprises a tool body, preferably made of steel, and a turning insert, preferably made of a wear resistant material, such as cemented carbide, cermet or cubic boron nitride. The turning tool is suitable for machining metal workpieces.

The turning tool comprises an insert seat, also called insert pocket, in which the turning insert is removably mounted or clamped by means of e.g. screws, clips or bars.

The turning tool preferably comprises exactly one insert seat.

The rear end of the turning tool is a coupling portion adapted to be connected to a machine interface of a machine tool, such as a CNC lathe. The rear end may include a tapered polygon and a flange. The rear end may be square in cross-section.

The longitudinal axis extends from the rear end toward the front end. The longitudinal axis is the geometrical centre axis of the rear end (i.e. the coupling part).

The distance from the longitudinal axis to the turned distal end portion is greater than the distance from the longitudinal axis to the distal end portion of the tool body. By means of such a turning tool, outward machining is possible.

The blade seat opens towards the front end.

The insert holder includes a bottom surface and a side surface. At least a part of the bottom surface and the side surface, respectively, is a contact surface or a support surface for contact with the turning insert. The bottom surface of the insert seat may be a part of the tool body. Alternatively, the bottom surface may be in the form of the top surface of a shim or pad. Such a shim or shim plate is preferably made of cemented carbide.

The side surface comprises a first surface and a second surface, wherein the first surface and the second surface form an angle with respect to each other, wherein said angle is preferably 50 ° -160 °, even more preferably 100 ° -150 °. Each of the first and second surfaces preferably comprises a contact surface or a support surface. The side surface is preferably part of the tool body.

The turning insert includes a top surface, an opposite bottom surface, and a side surface connecting the top surface and the bottom surface. The top surface includes a rake surface. The top surface preferably comprises chip breaking means, preferably in the form of one or more protrusions or recesses. The side surfaces include clearance surfaces. A cutting edge is formed at the intersection between the top surface and the side surface. The bottom surface of the turning insert, which may be flat or non-flat, is in contact with the bottom surface of the insert seat.

The top surface of the turning insert is preferably 120 deg. symmetrical or 180 deg. symmetrical in top view.

The first surface comprises a contact surface, wherein the contact surface is in contact with a portion of the side surface of the turning insert. In other words, the side surface of the turning insert comprises at least one, preferably two support surfaces. Preferably, the side surface of the turning insert is in contact with a portion of the second surface.

The side surfaces of the turning insert extend uninterrupted from the top surface to the bottom surface. In other words, the side surface of the turning insert is a continuous surface, i.e. without any through-hole.

The tool body includes a coolant channel formed therein. Thus, the coolant channels are internal coolant channels.

The coolant channel extends between a coolant channel inlet, preferably open in the rear end, and a coolant channel outlet formed in the first surface of the insert seat.

The coolant channel outlet is preferably circular or substantially circular in cross-section, preferably 0.5-3 mm in diameter.

The coolant channel outlet is preferably arranged opposite or substantially opposite to the side surface of the turning insert.

The coolant channel outlet opens into a void or cavity or gap between the side surface of the turning insert and the first surface of the insert seat. In other words, there is a gap between a part of the first surface and a part of the side surface of the turning insert facing the first surface. Thus, the clearance is arranged between the side surface of the turning insert and the first surface of the side surface of the insert seat.

The coolant channel outlet is arranged to direct a flow of coolant towards the side surface of the turning insert, whereby said flow of coolant is deflected towards the first surface of the insert seat. In other words, the side surface of the turning insert facing the first surface, where the coolant flow exits from the coolant channel outlet, is arranged to deflect the coolant flow towards the first surface.

The void includes an outlet. The void is preferably open to the front end. In other words, the interspace is preferably open, such that at least a part of the coolant flow leaves the interspace in a direction away from the rear end.

According to one embodiment, the coolant channel outlet is formed partially or completely in the first surface.

With such a cutting tool, the inventors have found that the risk of deformation of the tool body is further reduced.

According to one embodiment the channel outlet is at a distance from the side surface of the turning insert of 0.1-2.0 mm.

With such a cutting tool, the inventors have found that the risk of deformation of the tool body is further reduced.

According to one embodiment, the side surface of the insert holder comprises a third surface, wherein the first surface faces the third surface.

By such a cutting tool, the performance in turning perpendicular to and away from the axis of rotation of the metal workpiece is improved, since the third surface can comprise a contact surface for such a machine direction.

In top view, the first surface is preferably parallel or substantially parallel to the third surface.

According to one embodiment, the distance from the contact surface to the top surface of the turning insert is shorter than the distance from the contact surface to the bottom surface of the turning insert.

In other words, the contact surface to the top surface of the turning insert is shorter than the distance from the contact surface to the bottom surface of the turning insert.

According to one embodiment, the contact surface is adjacent to the void.

By means of such a cutting tool, the wear of the contact surfaces can be further reduced.

According to one embodiment, the distance from the coolant channel outlet to the bottom surface of the turning insert is shorter than the distance from the coolant channel outlet to the top surface of the turning insert.

Preferably, the coolant channel outlet intersects a plane comprising the bottom surface of the turning insert.

According to one embodiment, the distance from the longitudinal axis to the first surface in which the coolant channel outlet is formed is larger than the distance from the longitudinal axis to the second and third surfaces, respectively.

According to one embodiment, the coolant channel outlet is arranged to direct the flow of coolant in a direction away from the rear end and away from a bottom surface of the insert seat.

By means of such a turning tool, the temperature of the active nose portion of the turning insert is reduced, thereby increasing the time in which the turning tool can be used.

In other words, the coolant channel outlet is arranged to direct the flow of coolant in a forward direction and in an upward direction, wherein the top surface of the turning insert is above the bottom surface of the turning insert.

According to one embodiment, the turning tool comprises a shim and the bottom surface of the insert seat is defined by the top surface of the shim.

Thus, the turning tool comprises a shim or shim (hip plate). The shim is arranged between the bottom surface of the turning insert and the tool body. The bottom surface of the shim is in contact with the cutter body.

Both the turning insert and the shim are arranged inside the cavity or cut-out of the tool body.

The shim is preferably made of cemented carbide.

According to one embodiment, the turning insert is arranged symmetrically or substantially symmetrically about its central axis, wherein said central axis intersects the top surface and the bottom surface, wherein the distance from the longitudinal axis to the first surface of the insert seat is larger than the distance from the longitudinal axis to the central axis of the turning insert, and wherein the first surface of the insert seat faces the central axis of the turning insert.

The turning insert is arranged symmetrically around said centre axis such that the top surface of the turning insert is preferably 120 deg. symmetrical or 180 deg. symmetrical in top view.

Preferably, the distance from the longitudinal axis to the outlet of the coolant channel is greater than the distance from the longitudinal axis to the centre axis of the turning insert in top view.

According to one embodiment, the tool body comprises a portion which is tapered in top view such that its width decreases in a direction away from the rear end, and wherein the boundary surface of said portion is the first surface of the insert seat.

Thus, the portion is limited by a boundary surface, which is defined by the first surface of the insert seat. The portion is bounded by a second boundary surface opposite the first surface of the insert seat. The distance from the longitudinal axis to the first surface of the insert seat is smaller than the distance from the longitudinal axis to said second boundary surface.

During machining, the second boundary surface is preferably perpendicular or substantially perpendicular to the axis of rotation of the metal workpiece to be machined.

According to one embodiment, the top surface of the turning insert comprises a protrusion, wherein the protrusion is spaced from the side surface of the turning insert, and wherein the distance from the bottom surface of the turning insert to the protrusion is greater than the distance from the bottom surface of the turning insert to the intersection between the top surface and the side surface of the turning insert.

The protrusion includes a chip breaker wall surface.

According to one embodiment, a turning method comprises the steps of: providing any of the above turning tools; providing a metal workpiece; rotating the metal workpiece about a rotational axis of the metal workpiece; setting a longitudinal axis of the turning tool perpendicular to a rotational axis of the metal workpiece; supplying a coolant to the coolant channel such that a flow of the coolant is directed from a coolant channel outlet towards a side surface of the turning insert such that the flow of the coolant is deflected towards the first surface of the insert seat; and moving the turning tool in a direction parallel or substantially parallel to the axis of rotation such that the machined surface is formed by a portion of the turning insert, wherein the longitudinal axis of the turning tool is in front of the machined surface being formed.

The mobile cutting tool, often referred to as a feed, is moved in a direction parallel or substantially parallel to the axis of rotation, such that the first surface of the insert seat faces in the feed direction. Moving the turning tool in a direction parallel or substantially parallel to the axis of rotation is such that the longitudinal axis of the turning tool is in front of the active nose cutting edge of the turning insert.

The machined surface is formed by metal cutting. The cutting is preferably continuous. The cutting depth is preferably 0.5-10mm, even more preferably 1-3 mm. The feed rate is preferably 0.6-1.2 mm/rev. The cutting speed is preferably 100-500 m/min. The length of the cut is preferably greater than 200mm, for example between 300mm and 1000 mm. The coolant pressure is preferably above 5 bar.

According to one embodiment, the turning method further comprises the step of setting the entry angle (α) of the turning insert (3) to at least 3 ° but not more than 30 °.

Drawings

The invention will now be explained in more detail by the description of different embodiments of the invention and with reference to the drawings.

Fig. 1 is a perspective view showing a turning tool according to a first embodiment.

Fig. 2 is a further perspective view of the cutting tool of fig. 1.

Fig. 3 is a perspective view of the cutting tool of fig. 2 without the turning insert.

Fig. 4 is an enlarged view of the insert holder of fig. 3.

FIG. 5 is a side view of the tool body shown in FIG. 1 with coolant channels and other features shown in hidden lines.

FIG. 6 is similar to FIG. 5, but without hidden lines.

Fig. 7 is a front view of the tool body shown in fig. 6.

FIG. 8 is a top view of the cutting tool shown in FIG. 1 with coolant channels and other features shown in hidden lines.

Fig. 9 is a cross-sectional view taken along line B-B in fig. 8.

Fig. 10 is a cross-sectional view taken along line C-C in fig. 8.

Fig. 11 is an enlarged view of a portion of fig. 10.

Fig. 12 is a plan view showing a turning method including the cutting tool according to the second embodiment.

Fig. 13 is a perspective view of the turning insert of fig. 12.

All turning tool figures are drawn to scale.

Detailed Description

Referring to fig. 1 to 11, a turning tool 1 according to a first embodiment is shown, which turning tool 1 comprises a tool body 2, a turning insert 3 and a shim 12. The turning insert 3 is mounted in an insert seat 4. The bottom surface 5 of the insert seat 4 is defined by the top surface of the shim 12. The insert seat 4 further comprises a side surface 6 formed by the tool body 2. As best shown in fig. 4, the side surface 6 includes a first surface 13, a second surface 14, and a third surface 15 (hidden in fig. 4). The first surface 13 faces the third surface 15 such that the first surface 13 is parallel to the third surface 15 in a top view as seen in fig. 8. Further seen in fig. 8, the first surface and the second surface form an angle β of 125 ° with each other.

As seen in fig. 6 to 8, the longitudinal axis a1 extends from the rear end 16, which comprises a coupling part adapted to be connected to a machine tool, to the front end 17 of the turning tool 1. The longitudinal axis a1 is the geometric center axis of the coupling portion. The blade seat 4 opens towards the front end 17. Fig. 9 and 10 show cross-sectional views along lines B-B and C-C in fig. 8, respectively.

As seen for example in fig. 1, the turning insert 3 comprises a top surface 7, an opposite bottom surface 8 and a side surface 9 connecting the top and bottom surfaces 7, 8. The side surface 9 of the turning insert 3 extends uninterrupted from the top surface 7 to the bottom surface 8. The coolant flow directed towards the side surface 9 is thus deflected away from the side surface 9 and towards the first surface 13.

The intersection between the top and side surfaces 7, 9 forms a cutting edge comprising a nose cutting edge 25. As seen in e.g. fig. 11, the bottom surface 8 of the turning insert 3 is in contact with the bottom surface 5 of the insert seat 4, wherein the bottom surface 5 of the insert seat 4 is defined by the top surface of the shim 12. With further reference to fig. 11, the first surface 13 comprises a contact surface 19 in contact with a portion of the side surface 9 of the turning insert 3. The distance from the contact surface 19 to the top surface 7 of the turning insert 3 is shorter than the distance from the contact surface 19 to the bottom surface 8 of the turning insert 3.

The second surface 14 comprises a contact surface with the side surface 9 of the turning insert 3.

As seen in fig. 5 and 8, a coolant channel 10 is formed inside the tool body 2, the coolant channel 10 being adapted to carry or convey coolant fluid from a coolant channel inlet 26 formed in the rear end 16 to a coolant channel outlet 11. The coolant channel outlet 11 is formed in the first surface 13.

The coolant channel 10 comprises a plurality of connected coolant channel segments. The coolant channel outlet 11 is the end of a straight coolant channel section with a circular cross-section of constant diameter.

As can be seen for example in fig. 4, the coolant channel outlet 11 opens into the insert seat 4. As seen in fig. 11, the coolant channel outlet 11 opens into a gap 24, wherein said gap 24 is formed between the side surface 9 of the turning insert 3 and the first surface 13 of the side surface 6 of the insert seat 4. The interspace 24 and the coolant channel outlet 11 are below the contact surface 19, at which contact surface 19 the top and bottom surfaces 7, 8 of the turning insert 3 are defined above and below, respectively. The interspace 24 extends as far as the contact surface 19.

As seen in, for example, fig. 4, the tool body 2 comprises a portion 22 which is tapered in top view as in fig. 8, such that its width decreases in a direction away from the rear end 16. The boundary surface of said portion 22 is the first surface 13 of the insert seat 4. Said portion 22 is limited by a second boundary surface opposite the first surface 13 of the insert seat 4.

Attention is now directed to fig. 12, which depicts a turning method. A turning tool 1 according to a second embodiment is provided. The turning tool 1 comprises a tool body 2 and a turning insert 3 shown in detail in fig. 13. The main difference between the turning tool according to the first embodiment and the turning tool according to the second embodiment is that for the turning tool 1 according to the second embodiment the rear end comprises a coupling part, the cross-section of which is square or rectangular.

The metal workpiece 20 is rotated about its axis of rotation R1. The longitudinal axis a1 of the turning tool 1 is perpendicular to the axis of rotation R1 of the metal work piece 20. The coolant fluid is supplied to the coolant channel via a coolant channel outlet, such that the coolant flow is directed from the coolant channel outlet towards the side surface of the turning insert, such that the coolant flow is deflected towards the first surface of the insert seat.

The turning tool is set to cut. The turning tool 1 is moved in a direction parallel to the axis of rotation R1 towards the right hand side in fig. 12 so that the longitudinal axis a1 of the turning tool 1 is in front of the nose cutting edge 25 of the turning insert 3 forming the surface 21 to be machined.

The distance from the longitudinal axis a1 to the first surface 13 is greater than the distance from the longitudinal axis a1 to the second and third surfaces 14, 15, respectively. The turning method comprises the step of setting the entry angle alpha of the turning insert 3 to about 25 deg..

Attention is now drawn to fig. 13, the turning insert 3, which is substantially similar to the turning insert found in the turning tool according to the first embodiment, is 180 ° symmetrical about its central axis a 2. The central axis a2 intersects the top and bottom surfaces 7, 8 and is concentric with the hole for the clamping screw. The top surface 7 of the turning insert 3 comprises a protrusion 23. Said protrusion 23 is spaced from the side surface 9 of the turning insert 3 and comprises a chip breaker wall.