Double-sided negative cutting insert and milling tool

Abstract

A double-sided negative cutting insert for milling has a secondary basic shape and eight different working positions. The cutting insert (1) comprises an outer peripheral surface (10) extending around the cutting insert between a first main face (2) and a second main face (3) and having four main side faces (11a-11d). A main cutting edge and a surface scraping cutting edge are formed at the intersection of each main side with the first main face (2) and at the intersection of each main side with the second main face (3). Each main side surface comprises a first lateral side surface (13), a central side surface (14) and a second lateral side surface (15), the side surfaces are arranged between the two corner side surfaces (12) one after the other, and the central side surface (14) is located between the first lateral side surface (13) and the second lateral side surface (15), and the central side surface (14) is located between the first lateral side surface (13) and the second lateral side surface (15). The central side surface is slightly recessed relative to the adjacent first and second lateral side surfaces.

Description

Technical Field

[0001] The invention relates to a double-sided negative cutting insert for milling according to the preamble of claim 1. The invention also relates to a milling tool comprising such a double-sided negative cutting insert. Background Art

[0002] A milling tool is a rotary cutting tool which may be provided with one or more cutting inserts which are removably mounted in corresponding insert seats in the tool body of the milling tool. One cutting insert which can be used for shoulder milling and face milling is a double-sided negative cutting insert having a substantially quadratic basic shape of the type defined in the preamble of claim 1. A cutting insert of this type is previously known from US 6 336 776 B1 and is capable of being rotated into eight different working positions, four of which are provided by four sets of different cutting edges formed at the interface between the peripheral surface of the cutting insert and the first main face, and four further working positions are provided by four sets of other different cutting edges formed at the interface between the peripheral surface of the cutting insert and the second main face, wherein each such set of cutting edges comprises a main cutting edge and a surface scraping cutting edge and an intermediate curved corner cutting edge. When one of the cutting edges included in a set of such cutting edges is worn, the cutting insert can be repositioned in its insert seat and mounted in a new working position, while another set of different cutting edges is in an active cutting position.

[0003] Double-sided negative cutting inserts of the type described above provide a large number of different working positions and can be produced in a relatively simple and cost-effective manner. Due to the negative shape of the cutting insert, when the cutting insert is installed in the insert seat in the tool body of the milling tool, the cutting insert must be given a negative axial mounting angle and a negative radial mounting angle, which means that the cutting insert must be mounted axially forward and radially outward in the tool body to obtain clearance. The negative axial mounting angle is necessary to form a relief behind the active surface scraping cutting edge, and the negative radial mounting angle is necessary to form a relief behind the active main cutting edge. Due to the presence of the negative axial mounting angle, the cutting process is more arduous because the cutting insert is more difficult to cut than the corresponding cutting process performed using a cutting insert with a positive axial mounting angle. In order to offset the negative effect of the axial mounting angle, each main cutting edge has a downward slope in the direction away from the corner cutting edge that connects the main cutting edge to the associated surface scraping cutting edge. This downward slope of the main cutting edge, combined with a negative axial and radial insertion angle, will result in an approach angle to the workpiece that is always slightly less than 90°. It is desirable to have this approach angle as close to the 90° value as possible. Summary of the invention

[0004] Purpose of the Invention

[0005] It is an object of the present invention to provide a double-sided negative cutting insert of the above-mentioned type having a novel and advantageous design. SUMMARY OF THE INVENTION

[0007] According to the invention, this object is achieved by a double-sided negative cutting insert having the features defined in claim 1 .

[0008] The double-sided negative cutting insert according to the invention has a substantially quadratic basic shape and can be rotated into eight different working positions and comprises: - a first main face and a second main face, the first main face and the second main face being arranged on opposite sides of the cutting insert and serving as a top face and a bottom face of the cutting insert, wherein the cutting insert has a central axis and a middle plane, the central axis extending between the first main face and the second main face, the middle plane extending perpendicularly to the central axis in the middle between the first main face and the second main face, and wherein the cutting insert has a 90° rotational symmetry about the central axis; - a peripheral surface extending around the cutting insert between the first main face and the second main face substantially perpendicularly to the mid-plane and comprising: • four main side surfaces, a first pair of main side surfaces of the four main side surfaces are arranged opposite to each other on two opposite sides of the cutting insert, and a second pair of main side surfaces of the four main side surfaces are arranged opposite to each other on the other two opposite sides of the cutting insert, wherein the cutting insert has a first transverse plane and a second transverse plane, the first transverse plane extends halfway between the two main side surfaces of the first pair of main side surfaces and contains the center axis of the cutting insert, the second transverse plane extends halfway between the two main side surfaces of the second pair of main side surfaces and contains the center axis of the cutting insert, and wherein each of the first pair of main side surfaces has a 180° rotational symmetry about a first imaginary reference axis, the first imaginary reference axis extends along the intersection line between the middle plane and the second transverse plane, and each of the second pair of main side surfaces has a 180° rotational symmetry about a second imaginary reference axis, the second imaginary reference axis extends along the intersection line between the middle plane and the first transverse plane, and • four corner side surfaces, each of the four corner side surfaces being arranged between two adjacent main side surfaces; - four first main cutting edges formed at intersections between a corresponding one of the four main side surfaces and the first main surface; - four second main cutting edges formed at intersections between a corresponding one of the four main side surfaces and the second main surface; - four first surface scraping cutting edges, the four first surface scraping cutting edges being formed at the intersection of a corresponding one of the four main side surfaces and the first main surface; - four second surface scraping cutting edges, the four second surface scraping cutting edges being formed at the intersection of a corresponding one of the four main side surfaces and the second main surface; - four first curved corner cutting edges, the four first curved corner cutting edges being formed at the intersection between a corresponding one of the four corner side faces and the first main face, wherein each of the first curved corner cutting edges is located between a first one of the first main cutting edges and a first surface scraping cutting edge of the first surface scraping cutting edges; and - Four second curved corner cutting edges, the four second curved corner cutting edges being formed at the intersection between a corresponding one of the four corner side faces and the second main face, wherein each of the second curved corner cutting edges is located between one of the second main cutting edges and one of the second surface scraping cutting edges.

[0009] As mentioned above, the peripheral surface extends between the first and second main faces substantially perpendicular to the mid-plane, ie perpendicular within manufacturing tolerances, which means that every portion of the peripheral surface is perpendicular to the mid-plane within manufacturing tolerances.

[0010] Each of the main side surfaces comprises: a central side surface extending between the first main surface and the second main surface; a first lateral side surface extending between the first main surface and the second main surface and adjoining one of the four corner side surfaces; and a second lateral side surface extending between the first main surface and the second main surface and adjoining another of the four corner side surfaces, the first lateral side surface, the central side surface and the second lateral side surface being arranged one behind the other, wherein the central side surface is located between the first lateral side surface and the second lateral side surface, wherein: • one of the first main cutting edges extends along the first lateral side surface and along at least a major part of the central side surface, • one of the first surface scraping cutting edges extends along at least a portion of the second lateral side surface, • one of the second main cutting edges extends along the second lateral side surface and along at least a major part of the central side surface, and • One of said second surface scraping cutting edges extends along at least a portion of said first lateral side surface.

[0011] When seen in a cross section of the cutting insert taken along the mid-plane, each of the major side surfaces is arranged such that the first lateral side surface of the major side surface extends along a first line, the central side surface of the major side surface extends along a second line, and the second lateral side surface of the major side surface extends along a third line, wherein: • the second line has a first endpoint and a second endpoint, the second line adjoins the first line through the first endpoint, the second line adjoins the third line through the second endpoint, these first endpoint and second endpoint are located on an imaginary straight line reference line, the imaginary straight line reference line extends between a first point and a second point, in the first point, the first line adjoins a corner side surface adjacent to the first lateral side surface of the main side, in the second point, the third line adjoins a corner side surface adjacent to the second lateral side surface of the main side, • the second line is recessed toward the central axis of the cutting insert relative to the imaginary straight reference line and has a deepest portion at a middle portion of the second line, and • The depth of the second line relative to the imaginary straight line reference line gradually increases when viewed from the first end point to the deepest part of the second line, and when viewed from the second end point to the deepest part of the second line, and the depth of the deepest part of the second line relative to the imaginary straight line reference line is 0.01-0.15 mm, preferably 0.01-0.10 mm.

[0012] It turns out that the design of the above-mentioned double-sided negative cutting insert with a slightly concave central side surface on each major side means that, compared to a corresponding double-sided negative cutting insert with conventional planar major sides, the entry angle is closer to the desired 90° value, at least for most of the commonly used cutting depth range.

[0013] Due to the symmetry of the cutting insert, the deepest portion of the central side surface of each major side surface will be centrally located between the first and second lateral side surfaces of the major side surface.

[0014] When the double-sided negative cutting blade is in a working position and one of the first surface scraping cutting edges is in an active surface scraping position, the inactive first main cutting edge on the same main side as the active first surface scraping cutting edge will move closely above the machined workpiece surface smoothed by the first surface scraping cutting edge. In a corresponding manner, when the double-sided negative cutting blade is in a working position and one of the second surface scraping cutting edges is in an active surface scraping position, the inactive second main cutting edge on the same main side as the active second surface scraping cutting edge will move closely above the machined workpiece surface smoothed by the second surface scraping cutting edge. There must be an appropriate gap between the inactive first main cutting edge or the second main cutting edge and the workpiece surface to prevent small fragments of workpiece material from getting stuck between the inactive main cutting edge and the workpiece surface, thereby causing small damage to the inactive main cutting edge. The gap is slightly raised along the concave central side surface of the main side facing the workpiece surface, which will reduce the risk of damaging the inactive main cutting edge.

[0015] In each working position of the double-sided negative cutting insert, one of the four main side surfaces of the cutting insert abuts against a radial support surface in a blade seat in a tool body of a milling tool, while another of the four main side surfaces of the cutting insert abuts against an axial support surface in the blade seat. The design of the main side surfaces having a recessed central side surface between a first lateral side surface and a second lateral side surface on each main side surface means that the first and second lateral side surfaces of the main side surface facing the radial support surface in the blade seat can be used together as two mutually spaced radial abutment surfaces of the cutting insert, and the first and second lateral side surfaces of the main side surface facing the axial support surface in the blade seat can be used together as two mutually spaced axial abutment surfaces of the cutting insert, which provides the cutting insert with good stability in radial and axial directions when installed in the blade seat. The mutually spaced radial abutment surfaces and the central side surface of the intermediate recess, as well as the mutually spaced axial abutment surfaces and the central side surface of the intermediate recess, will also have the effect of being less sensitive to dust and other small particles that may remain on the main sides of the radial support surfaces and axial support surfaces facing the insert seat.

[0016] The above-mentioned center axis of the cutting insert extends between the center point of the first main face and the center point of the second main face. The center point refers to the centroid or geometric center. The cutting insert can be provided with a through hole, which extends through the cutting insert centrally between the first main face and the second main face, wherein the center axis of the through hole coincides with the center axis of the cutting insert.

[0017] The double-sided negative cutting insert according to the present invention may be in the form of a shoulder milling insert or a face milling insert.

[0018] Preferably, each of the main side surfaces has a shape such that the central side surface of the main side surface is tangentially connected to the first lateral side surface of the main side surface and is tangentially connected to the second lateral side surface of the main side surface, which means that there is a smooth transition from each lateral side surface to the adjacent central side surface.

[0019] According to one embodiment of the present invention, preferably, each of the first pair of main side surfaces has such a shape that, when viewed along the first imaginary reference axis in a lateral view of the cutting insert toward the main side surface, the length of the central side surface of the main side surface along the middle plane corresponds to 35-75%, preferably 45-65%, of the width of the cutting insert observed in the lateral view and measured along the middle plane. According to the symmetry of the cutting insert, the length of the central side surface of each of the second pair of main side surfaces corresponds to the length of the central side surface of each of the first pair of main side surfaces.

[0020] According to another embodiment of the present invention, it is characterized in that: - the first lateral side surface of each major side has a shape such that at least a portion of the first line protrudes outwardly from the associated imaginary linear reference line, wherein the highest portion of the first line has a height of 0.001-0.02 mm relative to the associated imaginary linear reference line, and wherein the highest portion is disposed on a raised portion of the associated first lateral side surface; and - The second lateral side surface of each main side has such a shape that at least a portion of the third line protrudes outwardly from the associated imaginary straight line reference line, wherein the highest portion of the third line has a height of 0.001-0.02 mm relative to the associated imaginary straight line reference line, and wherein the highest portion is arranged on a raised portion of the associated second lateral side surface.

[0021] In this case, the above-mentioned radial abutment surface and axial abutment surface of the cutting insert are formed by the highest parts of the first lateral side surface and the second lateral side surface of the main side facing the radial support surface and the axial support surface in the insert seat. Due to the convexity of these highest parts of the first lateral side surface and the second lateral side surface, the requirements for the tolerances of the first lateral side surface and the second lateral side surface of the main side are reduced. The radius of curvature of the convex part of the first lateral side surface and the radius of curvature of the convex part of the second lateral side surface are advantageously at least 25 mm, preferably 25-600 mm, and more preferably 40-100 mm. In addition, or as an alternative, the suitable radius of curvature of these convex parts can be defined relative to the size of the cutting insert. In this case, the radius of curvature of the raised portion of the first lateral side surface and the radius of curvature of the raised portion of the second lateral side surface are advantageously 2 to 10 times larger, preferably 3 to 7 times larger, than the width of the cutting blade, wherein the width of the cutting blade is measured along the middle plane in a lateral view of the cutting blade as observed along the first imaginary reference axis.

[0022] According to another embodiment of the present invention, it is characterized in that: - a second surface scraping cutting edge associated with said first lateral side surface of each major side extends at least along a portion of said raised portion of said first lateral side surface and preferably extends beyond said highest portion of said first lateral side surface; and - A first surface scraping cutting edge associated with said second lateral side surface of each major side extends at least along a portion of said convex portion of said second lateral side surface and preferably extends beyond said highest portion of said second lateral side surface.

[0023] As an alternative, the first and second lateral side surfaces of each major side may be planar, such that the aforementioned first and third lines are both flush with the associated said imaginary rectilinear reference line.

[0024] According to another embodiment of the present invention, the central side surface of each main side has at least one concave portion, which is concave in a cross section of the cutting blade taken along the middle plane (MP). The radius of curvature of the concave portion is advantageously 25-200 mm, preferably 50-170 mm. In addition, or as an alternative, a suitable radius of curvature of the concave portion can be defined relative to the size of the cutting blade. In this case, the radius of curvature of the concave portion is advantageously 2-16 times larger, preferably 3-13 times larger, than the width of the cutting blade, wherein the width of the cutting blade is measured along the middle plane in a lateral view of the cutting blade as observed along the first imaginary reference axis.

[0025] According to another embodiment of the present invention, it is characterized in that: - each first surface scraping cutting edge extends along at least a major part of the associated second lateral side surface; and - Each second surface scraping cutting edge extends along at least a major part of associated said first lateral side surface.

[0026] According to another embodiment of the present invention, each of the first pair of main side surfaces has such a shape that: - when viewed along the first imaginary reference axis towards the major side surface in a lateral view of the cutting insert, the first major cutting edge associated with the major side surface is inclined inwardly towards the intermediate plane as seen in a direction from a first end of the first major cutting edge located at an intersection between the first lateral side surface of the major side surface and the first major face towards an opposite second end of the first major cutting edge; and - When viewed along the first imaginary reference axis toward the main side surface in a lateral view of the cutting insert, the second main cutting edge associated with the main side surface is inclined inwardly toward the middle plane, as seen from a first end of the second main cutting edge located at the intersection between the second lateral side surface of the main side surface and the second main surface toward an opposite second end of the second main cutting edge.

[0027] This downward inclination of the first and second main cutting edges will counteract the negative effects associated with the axial setting angle required for the double-sided negative cutting insert. According to the symmetry of the cutting insert, each of the second pair of main side surfaces has a shape corresponding to the shape of each of the first pair of main side surfaces.

[0028] According to another embodiment of the invention, each main side surface of the first pair has a shape such that: - when viewed along the first imaginary reference axis in a lateral view of the cutting insert toward the main side surface, the first main cutting edge associated with the main side surface is inclined inwardly toward the middle plane so that when moving from one of the four corner side surfaces adjacent to the first lateral side surface of the main side surface in a direction toward one of the four corner side surfaces adjacent to the second lateral side surface of the main side surface, The first main cutting edge associated with the main side surface approaches the intermediate plane at least along a portion of the first main cutting edge formed at an intersection between a first lateral side surface of the main side surface and the first main face, and / or The first major cutting edge associated with the major side surface approaches the intermediate plane along at least a portion of the first major cutting edge formed at an intersection between a central side surface of the major side surface and the first major face; and - when viewed along the first imaginary reference axis toward the main side surface in a lateral view of the cutting insert, the second main cutting edge associated with the main side surface is inclined inwardly toward the middle plane so that when moving from one of the four corner side surfaces adjacent to the second lateral side surface of the main side surface in a direction toward one of the four corner side surfaces adjacent to the first lateral side surface of the main side surface, The second main cutting edge associated with the main side surface approaches the intermediate plane at least along a portion of the second main cutting edge formed at the intersection between the second lateral side surface of the main side surface and the second main face, and / or The second main cutting edge associated with the major side surface approaches the intermediate plane along at least a portion of the second main cutting edge formed at an intersection between the central side surface of the major side surface and the second main face.

[0029] This downward inclination of the first and second main cutting edges will counteract the negative effects associated with the axial setting angle required for the double-sided negative cutting insert.According to the symmetry of the cutting insert, each of the second pair of main side surfaces has a shape corresponding to the shape of each of the first pair of main side surfaces.

[0030] According to another embodiment of the present invention, it is characterized in that: - each of said first surface scraping cutting edges extends substantially parallel to said median plane; and - Each of said second surface scraping cutting edges extends substantially parallel to said median plane.

[0031] Thus, each first surface scraping cutting edge has its extension in a plane substantially parallel to the median plane, and each second surface scraping cutting edge has its extension in another plane substantially parallel to the median plane.

[0032] According to another embodiment of the present invention, it is characterized in that: - the first main face comprises a substantially planar first tangential abutment surface, wherein each first corner cutting edge, at least a portion of each first surface scraping cutting edge closest to an adjacent first corner cutting edge, and at least a portion of each first main cutting edge closest to an adjacent first corner cutting edge are arranged further from the mid-plane than the first tangential abutment surface; and - The second main face comprises a substantially flat second tangential abutment surface, wherein each second corner cutting edge, at least a portion of each second surface scraping cutting edge closest to an adjacent second corner cutting edge, and at least a portion of each second main cutting edge closest to an adjacent second corner cutting edge are arranged further from the intermediate plane than the second tangential abutment surface.

[0033] Other advantageous features of the double-sided negative cutting insert according to the present invention will emerge from the following description.

[0034] The invention also relates to a milling tool comprising at least one double-sided negative cutting insert of the above-mentioned type.

[0035] Further advantageous features of the milling tool according to the invention will emerge from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] With reference to the accompanying drawings, embodiments of the present invention will be described in detail below. In the accompanying drawings:

[0037] Figure 1a and Figure 1b 1 is a perspective view of a double-sided negative cutting insert according to an embodiment of the present invention viewed from different directions,

[0038] Figure 1c is observed along the first imaginary reference axis Figure 1a and Figure 1b Side view of the cutting insert,

[0039] Figure 1d is observed along the second imaginary reference axis Figure 1a and Figure 1b Side view of the cutting insert,

[0040] Figure 1e yes Figure 1a and Figure 1b A plan view of the cutting insert from above,

[0041] Figure 1f yes Figure 1a and Figure 1b A plan view of the cutting insert viewed from below,

[0042] Figure 1g is based on Figure 1c The cross-sectional view taken along the line Ig-Ig in FIG.

[0043] Figure 2 is a schematic diagram of a portion of a double-sided negative cutting insert according to an embodiment of the present invention,

[0044] Figure 3is a schematic diagram of a portion of a double-sided negative cutting insert according to an alternative embodiment of the present invention,

[0045] Figure 4a Designed for Figure 1a-1g A perspective view of the backing plate of the cutting insert,

[0046] Figure 4b yes Figure 4a A side view of the pad,

[0047] Figure 5a Is equipped with Figure 1a-1g A perspective view of a milling tool with cutting inserts of the illustrated embodiment, wherein one cutting insert is removed from its insert seat in the tool body of the milling tool,

[0048] Figure 5b yes Figure 5a A detailed enlarged view of a portion of

[0049] Figure 5c Observed from another direction Figure 5b A perspective view of the cutting insert and backing plate shown in FIG.

[0050] Figure 5d yes Figure 5a Plan view of the milling tool,

[0051] Figure 5e yes Figure 5a A side view of the milling tool, and

[0052] Figure 5f yes Figure 5e A detailed enlarged view of a portion of the. DETAILED DESCRIPTION

[0053] Figure 1a-1g An embodiment of a double-sided negative cutting insert 1 according to the invention is shown. The cutting insert 1 is configured for milling and is configured for use in a milling tool, for example Figure 5a-5e A milling tool 50 of the type shown.

[0054] The cutting insert 1 has a substantially quadratic basic shape and can be rotated to eight different working positions. The cutting insert 1 includes a first main face 2 and a second main face 3, which are arranged on opposite sides of the cutting insert and serve as the top and bottom surfaces of the cutting insert. When viewed in a plan view of the cutting insert 1, the first main face 2 and the second main face 3 have a substantially quadratic shape. The cutting insert has a central axis C extending between the first main face 2 and the second main face 3. A middle plane MP constituting an imaginary plane extends perpendicular to the central axis C in the middle between the first main face 2 and the second main face 3, as shown in FIG. Figure 1c and Figure 1dAs shown, within the manufacturing tolerance range, the first main surface 2 and the second main surface 3 are identical to each other.

[0055] In the embodiment shown, the cutting insert 1 is provided with a through hole 5 which extends through the cutting insert centrally between the first main face 2 and the second main face 3. The through hole 5 is configured to receive a fastening element 6, for example in the form of a screw (see Figure 5a-5c ), by means of which the cutting insert can be releasably fixed to the insert seat 54 of the milling tool 50. The center axis C of the cutting insert 1 coincides with the center axis of the through hole 5. As an alternative, the cutting insert 1 can lack the through hole 5, wherein the cutting insert is configured to be releasably fixed to the insert seat of the milling tool by means of a suitable clamping device.

[0056] The peripheral surface 10 extends around the cutting insert 1 between the first main face 2 and the second main face 3 perpendicular to the middle plane MP. The peripheral surface 10 includes four main side faces 11a-11d and four corner side faces 12, wherein each corner side face 12 is located between two adjacent main side faces 11a-11d. These main side faces include: a first pair of main side faces 11a, 11c, which are located on two opposite sides of the cutting insert 1 opposite to each other; and a second pair of main side faces 11b, 11d, which are located on the other two opposite sides of the cutting insert 1 opposite to each other. Therefore, the two main side faces 11a, 11c in the first pair of main side faces are opposite to each other on opposite sides of the center axis C of the cutting insert 1. In a corresponding manner, the two main side faces 11b, 11d in the second pair of main side faces are opposite to each other on opposite sides of the center axis C of the cutting insert 1. Within the manufacturing tolerance range, the four main side faces 11a-11d are identical to each other.

[0057] A first transverse plane TP1 constituting an imaginary plane extends midway between the two main side surfaces 11a, 11c of the first pair of main side surfaces and contains the center axis C of the cutting insert 1. A second transverse plane TP2 also constituting an imaginary plane extends midway between the two main side surfaces 11b, 11d of the second pair of main side surfaces and contains the center axis C of the cutting insert 1. The first transverse plane TP1 and the second transverse plane TP2 extend perpendicularly to each other and intersect each other along the center axis C of the cutting insert 1. Each main side surface 11a, 11c of the first pair of main side surfaces has a 180° rotational symmetry about a first imaginary reference axis A1 (see Figure 1c ), the first imaginary reference axis A1 extends along the intersection line between the middle plane MP and the second transverse plane TP2, and each main side surface 11b, 11d of the second pair of main side surfaces has a 180° rotational symmetry around the second imaginary reference axis A2 (see Figure 1d ), the second imaginary reference axis A2 extends along the intersection line between the median plane MP and the first transverse plane TP1.

[0058] The cutting insert 1 comprises the following cutting edges: - four first main cutting edges 21 formed at intersections between a corresponding one of the four main side surfaces 11 a - 11 d and the first main face 2 ; - four second main cutting edges 31 formed at intersections between a corresponding one of the four main side surfaces 11 a - 11 d and the second main face 3 ; - four first surface scraping cutting edges 22 formed at intersections of a corresponding one of the four main side surfaces 11 a - 11 d and the first main surface 2 ; - four second surface scraping cutting edges 32 formed at intersections of a corresponding one of the four main side surfaces 11 a - 11 d and the second main surface 3 ; - four first curved corner cutting edges 23, which are formed at the intersection between a corresponding one of the four corner side surfaces 12 and the first main surface 2, wherein each of the first curved corner cutting edges 23 is located between one of the first main cutting edges 21 and one of the first surface scraping cutting edges 22; and - Four second curved corner cutting edges 33, wherein the four second curved corner cutting edges 33 are formed at the intersection between a corresponding one of the four corner side surfaces 12 and the second main surface 3, wherein each second curved corner cutting edge 33 is located between one of the second main cutting edges 31 and one of the second surface scraping cutting edges 32.

[0059] The cutting edges 21, 22, 23 positioned along the periphery of the first main side surface 2 form four different first groups of cutting edges, each such first group of cutting edges comprising a first main cutting edge 21, a first curved corner cutting edge 23 positioned adjacent to the first main cutting edge, and a first surface scraping cutting edge 22 positioned adjacent to the first curved corner cutting edge. The cutting edges 31, 32, 33 positioned along the periphery of the second main side surface 3 form four different second groups of cutting edges, each such second group of cutting edges comprising a second main cutting edge 31, a second curved corner cutting edge 33 positioned adjacent to the second main cutting edge, and a second surface scraping cutting edge 32 positioned adjacent to the second curved corner cutting edge. Thus, the cutting insert 1 is provided with a total of eight different groups of cutting edges, each group of cutting edges comprising a main cutting edge 21, 31 and a surface scraping cutting edge 22, 32, as well as an intermediate curved corner cutting edge 23, 33. In each of these different working positions of the cutting insert 1, a cutting edge in one of the eight different groups of cutting edges constitutes an active cutting edge of the cutting insert.

[0060] Each of the main side surfaces 11a-11d includes: a central side surface 14 extending between the first main surface 2 and the second main surface 3; a first lateral side surface 13 extending between the first main surface 2 and the second main surface 3 and adjoining one of the four corner side surfaces 12; and a second lateral side surface 15 extending between the first main surface 2 and the second main surface 3 and adjoining another of the four corner side surfaces 12; the first lateral side surface 13, the central side surface 14 and the second lateral side surface 15 are arranged one behind the other, wherein the central side surface 14 is located between the first lateral side surface 13 and the second lateral side surface 15. The central side surface 14 adjoins the first lateral side surface 13 at a first end and adjoins the second lateral side surface 15 at an opposite second end. One of the first main cutting edges 21 extends along the first lateral side surface 13 and along at least a portion of the adjacent central side surface 14, one of the first surface scraping cutting edges 22 extends along at least a portion of the second lateral side surface 15, one of the second main cutting edges 31 extends along the second lateral side surface 15 and along at least a portion of the adjacent central side surface 14, and one of the second surface scraping cutting edges 32 extends along at least a portion of the first lateral side surface 13.

[0061] Each first main cutting edge 21 and each second main cutting edge 31 may all extend along the associated central side surface 14 .

[0062] Each first surface scraping cutting edge 22 and each second surface scraping cutting edge 32 preferably extends along at least a majority of the associated second lateral side surface 15 and first lateral side surface 13, respectively, and may extend entirely along the associated second lateral side surface 15 and first lateral side surface 13. Figure 1a-1g In the illustrated embodiment, each of the first surface scraping cutting edges 22 and each of the second surface scraping cutting edges 32 extends parallel to the median plane MP, or at least substantially parallel to the median plane MP.

[0063] The central side surface 14 of each main side surface 11a-11d is slightly recessed relative to the adjacent first lateral side surface 13 and second lateral side surface 15 of the same main side surface, which means that, compared with the first lateral side surface 13 and second lateral side surface 15 of the same main side surface, the central side surface 14 of each main side surface 11a, 11c in the above-mentioned first pair of main sides is closer to the first transverse plane TP1, and compared with the first lateral side surface 13 and second lateral side surface 15 of the same main side surface, the central side surface 14 of each main side surface 11b, 11d in the above-mentioned second pair of main sides is closer to the second transverse plane TP2.

[0064] Each of the main side surfaces 11a-11d has a shape such that, when viewed in a cross section of the cutting insert 1 taken along the midplane MP, a first lateral side surface 13 of the main side surface extends along a first line L1, a central side surface 14 of the main side surface extends along a second line L2, and a second lateral side surface 15 of the main side surface extends along a third line L3, as shown in FIG. Figure 1g , Figure 2 and Figure 3 shown.

[0065] Figure 2 and Figure 3 Very schematically shown is the profile of one of the main side faces 11a-11d of the cutting insert 1 according to two alternative embodiments of the invention, as seen in a cross section of the cutting insert taken along the median plane MP. In order to more clearly illustrate the unique shape of the main side face, Figure 2 and Figure 3 The vertical contour ratio in Figure 2 and Figure 3 The proportions of the horizontal contours are greatly exaggerated.

[0066] The second line L2 has a first end point E1 and a second end point E2, the second line L2 adjoins the first line L1 through the first end point E1, and the second line L2 adjoins the third line L3 through the second end point E2, wherein these first end points E1 and E2 are located on an imaginary straight reference line RL extending between a first point P1 and a second point P2, in which the first line L1 adjoins one of the corner side surfaces 12 located adjacent to the first lateral side surface 13 of the main side surface, and in which the third line L3 adjoins one of the corner side surfaces 12 located adjacent to the second lateral side surface 15 of the main side surface. The second line L2 is recessed toward the center axis C of the cutting insert relative to the imaginary straight reference line RL, and has a deepest portion 16 at a middle portion of the second line L2. When viewed from the first endpoint E1 toward the deepest part 16 of the second line L2, the depth d of the second line L2 relative to the imaginary straight line reference line RL gradually increases, and when viewed from the second endpoint E2 toward the deepest part 16 of the second line L2, the depth d of the second line L2 relative to the imaginary straight line reference line RL also gradually increases, wherein the depth d of the deepest part 16 of the second line L2 relative to the imaginary straight line reference line RL is 0.01-0.15mm, preferably 0.01-0.10mm.

[0067] Each main side surface 11a, 11c of the above-mentioned first pair of main side surfaces has a shape such that, when observed toward the main side surface along the first imaginary reference axis A1 in a side view of the cutting insert 1, the central side surface 14 of the main side surface has a length L along the middle plane MP, which length L corresponds to 35-75%, preferably 45-65%, of the width w of the cutting insert 1 observed in the side view and measured along the middle plane MP.

[0068] Preferably, each of the main side surfaces 11a-11d preferably has a shape in which a central side surface 14 of the main side surface is tangentially connected to a first lateral side surface 13 of the same main side surface and is tangentially connected to a second lateral side surface 15 of the same main side surface.

[0069] The first lateral side surface 13 and the second lateral side surface 15 of each main side surface 11a-11d may be formed as flat surfaces substantially located in the same plane, wherein the first line L1 and the third line L3 are both flush with the associated imaginary straight line reference line RL, as shown in FIG. Figure 3 However, Figure 2As schematically shown in , the first lateral side surface 13 and the second lateral side surface 15 of each main side surface 11a-11d are advantageously curved, at least along a portion of their extension, when viewed in a cross section of the cutting insert taken along the midplane MP. In this case, the first lateral side surface 13 of each main side surface 11a-11d has a shape in which at least a portion of the first line L1 and at least a portion of the third line L3 protrude outwardly from an associated imaginary straight line reference line RL, wherein the height h of the highest portion 17 of the first line L1 and the height h of the highest portion 17 of the third line L3 relative to the associated imaginary straight line reference line RL is 0.001-0.02 mm, and wherein the highest portion 17 is arranged on a raised portion 18 of the first lateral side surface 13 and the second lateral side surface 15, respectively (see Figure 1c and Figure 1d ). The second surface scraping cutting edge 32 associated with the first side surface 13 extends at least along a portion of the raised portion 18 of the first side surface 13 and preferably extends beyond the highest portion 17 of the first lateral side surface. In a corresponding manner, the first surface scraping cutting edge 22 associated with the second side surface 15 extends at least along a portion of the raised portion 18 of the second side surface 15 and preferably extends beyond the highest portion 17 of the second lateral side surface.

[0070] The curvature radius of the convex portion 18 of the first lateral side surface 13 and the second lateral side surface 15 is: - at least 25 mm, preferably 25-600 mm, more preferably 40-100 mm, and / or - 2-10 times larger, preferably 3-7 times larger, than the width w of the cutting insert 1 as seen along the first imaginary reference axis A1 in a lateral view of the cutting insert 1 and measured along the median plane MP.

[0071] The central side surface 14 of each main side surface 11a-11d has at least one concave portion 19 (see Figure 1c and Figure 1d ), when viewed in a cross section of the cutting insert 1 taken along the mid-plane MP, the at least one recessed portion 19 is concave, wherein: - the radius of curvature of the at least one concave portion 19 is 25-200 mm, preferably 50-170 mm, and / or - The radius of curvature of the at least one concave portion 19 is 2-16 times larger, preferably 3-13 times larger, than the width w of the cutting insert observed along the first imaginary reference axis A1 in a lateral view of the cutting insert 1 and measured along the midplane MP.

[0072] exist Figure 1a-1g In the illustrated embodiment, a central portion 20 of the central side surface 14 of each major side surface 11a - 11 is flat or at least substantially flat, wherein the flat central portion 20 is adjoined by two concave portions 19 of the central side surface 14 located on either side of the central portion 20 .

[0073] Each of the first main cutting edge 21 and the second main cutting edge 31 is preferably inclined toward the middle plane MP. Figure 1c and Figure 1d In this case, each of the main side surfaces 11a, 11c in the first pair of main side surfaces has such a shape, namely: - When viewed in a side view of the cutting insert 1 (i.e. in Figure 1c The first main cutting edge 21 on the main side surface is inclined inwardly toward the middle plane MP when viewed along the first imaginary reference axis A1 toward the main side surface (in the lateral view shown in FIG. 1 ), as seen in a direction from a first end of the first main cutting edge 21 located at the intersection between the first lateral side surface 13 of the main side surface and the first main face 2 toward an opposite second end of the first main cutting edge 21; and - When viewed toward the main side along the first imaginary reference axis A1 in a lateral view of the cutting insert 1, the second main cutting edge 31 associated with the main side is inclined inwardly toward the middle plane MP, as seen in a direction from a first end of the second main cutting edge 31 located at the intersection between the second lateral side surface 15 of the main side and the second main face 3 toward the opposite second end of the second main cutting edge 31.

[0074] The first main face 2 comprises a substantially flat first tangential abutment surface 7a, and the second main face 3 comprises a substantially flat second tangential abutment surface 7b. In the illustrated embodiment, each first corner cutting edge 23, at least a portion of each first surface scraping cutting edge 22 closest to the adjacent first corner cutting edge 23, and at least a portion of each first main cutting edge 21 closest to the adjacent first corner cutting edge 23 are arranged at a greater distance from the middle plane MP than the first tangential abutment surface 7a, and are therefore located at a higher level than the first tangential abutment surface 7a when the cutting insert 1 is positioned with the first main face 2 facing upward. In a corresponding manner, each second corner cutting edge 33, at least a portion of each second surface scraping cutting edge 32 closest to the adjacent second corner cutting edge 33, and at least a portion of each second main cutting edge 31 closest to the adjacent second corner cutting edge 33 are arranged at a distance from the middle plane MP farther than the second tangential adjacent surface 7b, and are therefore located at a higher level than the second tangential adjacent surface 7b when the cutting insert 1 is positioned with the second main face 3 facing upward.

[0075] In the illustrated embodiment, shoulders 8 are provided on the first main face 2 and the second main face 3, wherein the shoulder 8 on the first main face 2 is positioned close to and inside a corresponding one of the first surface scraping cutting edges 22, and the shoulder 8 on the second main face 3 is positioned close to and inside a corresponding one of the second surface scraping cutting edges 32. Each shoulder 8 has a substantially flat top surface 9. The top surface 9 of the shoulder 8 on the first main face 2 is located in a common plane parallel to the middle plane MP. The top surface 9 of the shoulder 8 on the second main face 3 is also located in a common plane parallel to the middle plane MP. The top surface 9 of the shoulder 8 on the first main face 2 constitutes the highest part of the first main face, i.e., the part of the first main face 2 that is located at the longest distance from the middle plane MP. In a corresponding manner, the top surface 9 of the shoulder 8 on the second main face 3 constitutes the highest part of the second main face, i.e., the part of the second main face 3 that is located at the longest distance from the middle plane MP. Therefore, in this case, the tangential adjacent surfaces 7a, 7b on each of the first main surface 2 and the second main surface 3 are located at a lower level than the top surface 9 of the shoulder 8 on the same main surface, that is, on the inner side of an imaginary plane flush with the top surface 9 of the shoulder 8 on the same main surface.

[0076] Figure 5a-5fA milling tool 50 in the form of a face milling tool is shown, which can be used for shoulder milling or face milling, for example. The milling tool 50 includes a tool body 51 and is configured to rotate around an axis of rotation 52. The tool body 51 has a rear end 51a and an opposite front end 51b. The longitudinal axis 53 of the tool body 51 extends between the rear end 51a and the front end 51b of the tool body, wherein the longitudinal axis 53 coincides with the axis of rotation 52 of the milling tool 50. At the rear end 51a, the tool body 51 will be mounted on a rotating spindle or the like of a milling machine, for example, via a tool holder. At the front end 51b, the tool body 51 is provided with a blade seat 54, which is configured to receive a cutting insert 1. In the illustrated example, the tool body 51 is provided with eight blade seats 54, which are evenly distributed around the longitudinal axis 53 of the tool body and are configured to receive corresponding cutting inserts 1. However, as an alternative, in particular depending on the diameter of the tool body, the tool body 51 may be provided with any other suitable number of insert seats 54. For example, a tool body with a smaller diameter may be provided with two insert seats, while a tool body with a larger diameter may be provided with more than eight insert seats.

[0077] The cutting insert 1 is installed in each insert seat 54 in the tool body 51. Figure 5a to Figure 5f In the embodiment shown, the milling tool 50 is provided with Figure 1a to Figure 1g A cutting insert 1 of the type shown. Each cutting insert 1 is configured for releasable mounting on an associated insert seat 54. Each insert seat 54 is provided with a flat tangential support surface 56. Each cutting insert 1 can be designed to have tangential abutment surfaces on the first main face 2 and the second main face 3, which are configured for direct contact with the tangential support surface 56 in the associated insert seat 54. However, in the embodiment shown, a shim plate 40 is arranged between the tangential support surface 56 and the cutting insert 1. The shim plate 40 is detachably fixed against the tangential support surface 56 by means of a tubular screw 41, which extends through a through hole 42 in the shim plate 40 and engages in a threaded hole 55 in the tangential support surface 56 in the insert seat. In the embodiment shown, each cutting insert 1 is fixed to the associated insert seat 54 by means of a fastening element 6 in the form of a screw, which extends through a through hole 5 in the cutting insert 1 and engages in a threaded hole 43 in the tubular screw 41 of the shim plate 40 mounted in the insert seat. As described above, each cutting insert 1 is provided with a flat tangential adjacent surface 7a, 7b on each of the first main surface 2 and the second main surface 3, wherein, when the cutting insert 1 is installed in the insert seat 54 in one of its multiple working positions, the tangential adjacent surfaces 7a, 7b on the main surfaces 2, 3 facing the shim plate 40 are configured to abut against the flat tangential support surface 44 on the shim plate 40.

[0078] Each insert seat 54 is also provided with a radial support surface 57 and an axial support surface 58 .

[0079] In each of the different working positions of the cutting insert 1, the first lateral side surface 13 and the second lateral side surface 15 of one of the main side surfaces 11a-11d are constructed to serve together as the axial adjacent surface of the cutting insert, and abut against the axial support surface 58 in the associated insert seat 54. At the same time, the first lateral side surface 13 and the second lateral side surface 15 of another main side surface 11a-11d are constructed to serve together as the radial adjacent surface of the cutting insert, and abut against the radial support surface 57 in the associated insert seat 54.

[0080] Figure 5f Shows Figure 1a-1g A portion of a cutting insert 1 of the type shown in FIG. 1 , which is mounted in an insert seat 54 of a milling tool 50, is in one of its eight working positions. Thus, Figure 5f The cutting insert 1 shown in FIG. 1 has a slightly concave central side surface 14 on each of the main side surfaces 11 a - 11 d . Figure 5f The approximate position of the active main cutting edge of the corresponding cutting insert with a flat main side surface is shown by the dotted line BL. Figure 5f It can be seen that for Figure 1a-1g For a cutting insert 1 of the type shown in FIG, the approach angle α is very close to 90°, whereas for a corresponding cutting insert having conventionally flat major side surfaces, the approach angle α′ will deviate more from the desired value of 90°.

[0081] The invention is of course not limited in any way to the embodiments described above. On the contrary, many possibilities for modifications of the invention will be apparent to a person skilled in the art without departing from the basic idea of ​​the invention as defined in the appended claims.

Claims

1. A double-sided negative cutting insert for milling, the cutting insert (1) having a substantially quadratic basic shape and being rotatable to eight different working positions, and the cutting insert (1) comprising: - a first main face (2) and a second main face (3), the first main face (2) and the second main face (3), being arranged on opposite sides of the cutting insert (1) and serving as the top face and the bottom face of the cutting insert, wherein the cutting insert (1) has a central axis (C) extending between the first main face (2) and the second main face (3), and a middle plane (MP), the central axis (C) extending between the first main face (2) and the second main face (3), the middle plane (MP) extending perpendicularly to the central axis (C) in the middle between the first main face (2) and the second main face (3), and wherein the cutting insert (1) has a 90° rotational symmetry about the central axis (C); - a peripheral surface (10) extending around the cutting insert (1) between the first main face (2) and the second main face (3) substantially perpendicularly to the midplane (MP) and comprising: • four main side surfaces (11a-11d), a first pair of main side surfaces of the four main side surfaces (11a-11d) being arranged opposite to each other on two opposite sides of the cutting insert (1), and a second pair of main side surfaces of the four main side surfaces (11a-11d) being arranged opposite to each other on the other two opposite sides of the cutting insert (1), wherein the cutting insert (1) has a first transverse plane (TP1) and a second transverse plane (TP2), the first transverse plane (TP1) extending in the middle between two main side surfaces (11a-11d) of the first pair of main side surfaces and containing the center axis (C) of the cutting insert, and the second transverse plane (TP2) extending in the middle between two main side surfaces (11a-11d) of the second pair of main side surfaces The invention relates to a first pair of main side surfaces, wherein each main side surface (11a, 11c) of the first pair of main side surfaces has a 180° rotational symmetry about a first imaginary reference axis (A1), the first imaginary reference axis (A1) extending along the intersection line between the middle plane (MP) and the second transverse plane (TP2), and each main side surface (11b, 11d) of the second pair of main side surfaces has a 180° rotational symmetry about a second imaginary reference axis (A2), the second imaginary reference axis (A2) extending along the intersection line between the middle plane (MP) and the first transverse plane (TP1), and • four corner side surfaces (12), each of the four corner side surfaces (12) being arranged between two adjacent main side surfaces (11a-11d); - four first main cutting edges (21), the four first main cutting edges (21) being formed at the intersection between a corresponding one of the four main side surfaces (11a-11d) and the first main surface (2); - four second main cutting edges (31), the four second main cutting edges (31) being formed at the intersection between a corresponding one of the four main side surfaces (11a-11d) and the second main surface (3); - four first surface scraping cutting edges (22), the four first surface scraping cutting edges (22) being formed at the intersection between a corresponding one of the four main side surfaces (11a-11d) and the first main surface (2); - four second surface scraping cutting edges (32), the four second surface scraping cutting edges (32) being formed at the intersection between a corresponding one of the four main side surfaces (11a-11d) and the second main surface (3); - four first curved corner cutting edges (23), the four first curved corner cutting edges (23) being formed at the intersection between a corresponding one of the four corner side surfaces (12) and the first main surface (2), wherein each of the first curved corner cutting edges (23) is located between one of the first main cutting edges (21) and one of the first surface scraping cutting edges (22); and - four second curved corner cutting edges (33), the four second curved corner cutting edges (33) being formed at the intersection between a corresponding one of the four corner side faces (12) and the second main face (3), wherein each of the second curved corner cutting edges (33) is located between one of the second main cutting edges (31) and one of the second surface scraping cutting edges (32), Features: - Each of the main side surfaces (11a-11d) comprises: a central side surface (14), the central side surface extending between the first main surface (2) and the second main surface (3); a first lateral side surface (13), the first lateral side surface extending between the first main surface (2) and the second main surface (3) and adjacent to one of the four corner side surfaces (12); and a second lateral side surface (15), the second lateral side surface extending between the first main surface (2) and the second main surface (3) and adjacent to another of the four corner side surfaces (12), the first lateral side surface (13), the central side surface (14) and the second lateral side surface (15) being arranged one behind the other, wherein the central side surface (14) is located between the first lateral side surface (13) and the second lateral side surface (15), wherein: • one of the first main cutting edges (21) extends along the first lateral side surface (13) and along at least a major part of the central side surface (14), • one of the first surface scraping cutting edges (22) extends along at least a portion of the second lateral side surface (15), • one of the second main cutting edges (31) extends along the second lateral side surface (15) and along at least a major part of the central side surface (14), and • one of the second surface scraping cutting edges (32) extends along at least a portion of the first lateral side surface (13); and - when viewed in a cross section of the cutting insert taken along the midplane (MP), each of the main side surfaces (11a-11d) is arranged such that the first lateral side surface (13) of the main side surface extends along a first line (L1), the central side surface (14) of the main side surface extends along a second line (L2), and the second lateral side surface (15) of the main side surface extends along a third line (L3), wherein: • the second line (L2) has a first endpoint (E1) and a second endpoint (E2), the second line (L2) is adjacent to the first line (L1) through the first endpoint (E1), and the second line (L2) is adjacent to the third line (L3) through the second endpoint (E2), these first endpoints (E1) and the second endpoint (E2) are located on an imaginary straight reference line (RL), and the imaginary straight reference line (RL) extends between a first point (P1) and a second point (P2), in the first point (P1), the first line (L1) is adjacent to the corner side surface (12) adjacent to the first lateral side surface (13) of the main side, in the second point (P2), the third line (L3) is adjacent to the corner side surface (12) adjacent to the second lateral side surface (15) of the main side, • the second line (L2) is recessed relative to the imaginary straight reference line (RL) toward the central axis (C) of the cutting insert and has a deepest portion (16) at a middle portion of the second line (L2), and • When viewed from the first end point (E1) to the deepest portion (16) of the second line (L2), and when viewed from the second end point (E2) to the deepest portion (16) of the second line (L2), the depth (d) of the second line (L2) relative to the imaginary straight line reference line (RL) gradually increases, and the depth (d) of the deepest portion (16) of the second line (L2) relative to the imaginary straight line reference line (RL) is 0.01-0.15 mm, preferably 0.01-0.10 mm.

2. The double-sided negative cutting insert according to claim 1, characterized in that: Each of the main side surfaces (11a-11d) has a shape such that the central side surface (14) of the main side surface is tangentially connected to the first lateral side surface (13) of the main side surface, and is tangentially connected to the second lateral side surface (15) of the main side surface.

3. The double-sided negative cutting insert according to claim 1 or 2, characterized in that: Each main side surface (11a, 11c) of the first pair of main side surfaces has such a shape that, when viewed along a first imaginary reference axis (A1) towards the main side surface (11a, 11c) in a side view of the cutting insert (1), the length (L) of the central side surface (14) of the main side surface along the middle plane (MP) corresponds to 35-75%, preferably 45-65%, of the width (w) of the cutting insert (1) observed in the side view and measured along the middle plane (MP).

4. The double-sided negative cutting insert according to any one of claims 1 to 3, characterized in that: - the first lateral side surface (13) of each main side surface (11a-11d) has a shape such that at least a portion of the first line (L1) protrudes outwardly from the associated imaginary linear reference line (RL), wherein the highest portion (17) of the first line (L1) has a height (h) of 0.001-0.02 mm relative to the associated imaginary linear reference line (RL), and wherein the highest portion (17) is arranged on a raised portion (18) of the associated first lateral side surface (13); and - the second lateral side surface (15) of each main side surface (11a-11d) has such a shape that at least a part of the third line (L3) protrudes outwardly from the associated imaginary linear reference line (RL), wherein the highest part (17) of the third line (L3) has a height (h) of 0.001-0.02 mm relative to the associated imaginary linear reference line (RL), and wherein the highest part (17) is arranged on a raised part (18) of the associated second lateral side surface (15).

5. The double-sided negative cutting insert according to claim 4, characterized in that: - said second surface scraping cutting edge (32) associated with said first lateral side surface (13) of each major side surface (11a-11d) extends at least along a portion of said raised portion (18) of said first lateral side surface (13), and preferably extends beyond said highest portion (17) of said first lateral side surface; and - said first surface scraping cutting edge (22) associated with said second lateral side surface (15) of each major side surface (11a-11d) extends at least along a portion of said raised portion (18) of said second lateral side surface (15) and preferably extends beyond said highest portion (17) of said second lateral side surface.

6. The double-sided negative cutting insert according to claim 4 or 5, characterized in that: - the radius of curvature of the convex portion (18) of the first lateral side surface (13) is at least 25 mm, preferably 25-600 mm, more preferably 40-100 mm; and - the radius of curvature of the convex portion (18) of the second lateral side surface (15) is at least 25 mm, preferably 25-600 mm, more preferably 40-100 mm.

7. The double-sided negative cutting insert according to any one of claims 4 to 6, characterized in that: - the radius of curvature of the raised portion (18) of the first lateral side surface (13) is 2-10 times greater than the width (w) of the cutting insert (1), preferably 3-7 times greater; and - the radius of curvature of the raised portion (18) of the second lateral side surface (15) is 2-10 times greater than the width (w) of the cutting insert (1), preferably 3-7 times greater, The width (w) of the cutting insert (1) is a width measured along the median plane (MP) in a lateral view of the cutting insert (1) observed along the first imaginary reference axis (A1).

8. The double-sided negative cutting insert according to any one of claims 1 to 3, characterized in that: - said first lateral side surface (13) of each main side (11a-11d) has such a shape that said first line (L1) is flush with said associated imaginary straight reference line (RL); and - said second lateral side surface (15) of each main side (11a-11d) has such a shape that said third line (L3) is flush with the associated said imaginary straight reference line (RL).

9. The double-sided negative cutting insert according to any one of claims 1 to 8, characterized in that: The central side surface (14) of each major side surface (11a-11d) has at least one recessed portion (19) which is concave when viewed in a cross section of the cutting insert (1) taken along the median plane (MP).

10. The double-sided negative cutting insert according to claim 9, characterized in that: - the curvature radius of the concave portion (19) is 25-200 mm, preferably 50-170 mm, and / or - The radius of curvature of the concave portion (19) is 2-16 times greater, preferably 3-13 times greater, than the width (w) of the cutting insert (1), the width (w) of the cutting insert (1) being the width measured along the mid-plane (MP) in a lateral view of the cutting insert (1) observed along the first imaginary reference axis (A1).

11. The double-sided negative cutting insert according to any one of claims 1 to 10, characterized in that: - each first surface scraping cutting edge (22) extends along at least a major part of the associated second lateral side surface (15); and - Each second surface scraping cutting edge (32) extends along at least a major part of the associated first lateral side surface (13).

12. The double-sided negative cutting insert according to any one of claims 1 to 11, characterized in that Each of the first pair of main side surfaces (11a, 11c) has a shape such that: - when viewed in a lateral view of the cutting insert (1) along the first imaginary reference axis (A1) towards the main side surface (11a, 11c), the first main cutting edge (21) associated with the main side surface is inclined inwardly towards the mid-plane (MP), as seen in a direction from a first end of the first main cutting edge (21) at the intersection between the first lateral side surface (13) of the main side surface and the first main face (2) towards an opposite second end of the first main cutting edge (21); and - When viewed along the first imaginary reference axis (A1) towards the main side surface (11a, 11c) in a lateral view of the cutting insert (1), the second main cutting edge (31) associated with the main side surface is inclined inwardly towards the middle plane (MP), as seen in a direction from a first end of the second main cutting edge (31) located at the intersection between the second lateral side surface (15) of the main side surface and the second main face (3) towards an opposite second end of the second main cutting edge (31).

13. The double-sided negative cutting insert according to any one of claims 1 to 12, characterized in that Each of the first pair of main side surfaces (11a, 11c) has a shape such that: - when viewed along the first imaginary reference axis (A1) in a lateral view of the cutting insert (1) towards the main side surface (11a, 11c), the first main cutting edge (21) associated with the main side surface is inclined inwardly towards the middle plane (MP) so that when moving from one of the four corner side surfaces (12) adjacent to the first lateral side surface (13) of the main side surface in a direction towards one of the four corner side surfaces (12) adjacent to the second lateral side surface (15) of the main side surface, The first main cutting edge (21) associated with the main side surface approaches the middle plane (MP) at least along a portion of the first main cutting edge (21) formed at the intersection between the first lateral side surface (13) of the main side surface and the first main face (2), and / or The first main cutting edge (21) associated with the main side surface approaches the middle plane (MP) at least along a portion of the first main cutting edge (21) formed at the intersection between the central side surface (14) of the main side surface and the first main face (2); and - when viewed along the first imaginary reference axis (A1) in a lateral view of the cutting insert (1) towards the main side surface (11a, 11c), the second main cutting edge (31) associated with the main side surface is inclined inwardly towards the middle plane (MP) so that when moving from one of the four corner side surfaces (12) adjacent to the second lateral side surface (15) of the main side surface in a direction towards one of the four corner side surfaces (12) adjacent to the first lateral side surface (13) of the main side surface, The second main cutting edge (31) associated with the main side surface approaches the middle plane (MP) at least along a portion of the second main cutting edge (31) formed at the intersection between the second lateral side surface (15) of the main side surface and the second main face (3), and / or The second main cutting edge (31) associated with the main side surface approaches the middle plane (MP) at least along a portion of the second main cutting edge (31) formed at the intersection between the central side surface (14) of the main side surface and the second main face (3).

14. The double-sided negative cutting insert according to any one of claims 1 to 13, characterized in that: - each of said first surface scraping cutting edges (22) extends substantially parallel to said median plane (MP); and - Each of said second surface scraping cutting edges (32) extends substantially parallel to said median plane (MP).

15. The double-sided negative cutting insert according to any one of claims 1 to 14, characterized in that The cutting insert (1) is provided with a through hole (5), which extends through the cutting insert centrally between the first main surface (2) and the second main surface (3), wherein a center axis of the through hole (5) coincides with the center axis (C) of the cutting insert (1).

16. The double-sided negative cutting insert according to any one of claims 1 to 15, characterized in that: - the first main face (2) comprises a substantially flat first tangential abutment surface (7a), wherein each first corner cutting edge (23), at least a portion of each first surface scraping cutting edge (22) closest to an adjacent first corner cutting edge (23), and at least a portion of each first main cutting edge (21) closest to an adjacent first corner cutting edge (23) are arranged further from the midplane (MP) than the first tangential abutment surface (7a); and - the second main face (3) comprises a substantially flat second tangential abutment surface (7b), wherein each second corner cutting edge (33), at least a portion of each second surface scraping cutting edge (32) closest to an adjacent second corner cutting edge (33), and at least a portion of each second main cutting edge (31) closest to an adjacent second corner cutting edge (33) are arranged further from the mid-plane (MP) than the second tangential abutment surface (7b).

17. The double-sided negative cutting insert according to any one of claims 1 to 16, characterized in that In each of the different working positions of the cutting insert (1), the first lateral side surface (13) and the second lateral side surface (15) of one of the main side surfaces (11a-11d) are constructed to be used together as an axial adjacent surface of the cutting insert (1), and at the same time, the first lateral side surface (13) and the second lateral side surface (15) of another main side surface (11a-11d) are constructed to be used together as a radial adjacent surface of the cutting insert (1).

18. The double-sided negative cutting insert according to any one of claims 1 to 17, characterized in that The cutting insert (1) is a shoulder milling insert or a face milling insert.

19. A milling tool comprising at least one double-sided negative cutting insert (1) according to any one of claims 1 to 18.

Images