Indexable cutting insert

Abstract

The present invention relates to an indexable cutting insert (4) for a blade seat (3) of a tool body (2) of a shoulder milling cutter (1), the cutting insert (4) being generally defined by a triangular top surface (5), a triangular bottom surface (6), and three circumferential surfaces (7) extending between the top surface (5) and the bottom surface (6), wherein on each side of the cutting insert (4), a single one of the three circumferential surfaces extends along the edges of the triangular top surface (5) and the edges of the triangular bottom surface (6), the cutting insert (4) including three cutting corners (8), three main cutting edges (9), and three secondary cutting edges (10) at each of the top surface (5) and the bottom surface (6), wherein each cutting corner (8) connects a main cutting edge (9) and a secondary cutting edge (10), wherein each cutting corner of the cutting corners (8), each main cutting edge of the main cutting edges (9), and each secondary cutting edge of the secondary cutting edges (10) are provided at the intersection of the top surface (5) or the bottom surface (6) with one of the circumferential surfaces (7), and wherein each of the circumferential surfaces (7) includes a planar contact surface (15) defined by the main cutting edge (9) at the top surface (5) and the main cutting edge (9) at the bottom surface (6).

Description

Technical Field

[0001] The present invention relates to an indexable cutting insert for mounting in a blade seat of a tool body of a shoulder milling cutter. The cutting insert is generally defined by a triangular top surface, a triangular bottom surface, and three circumferential surfaces extending between the top surface and the bottom surface. On each side of the cutting insert, a single one of the three circumferential surfaces extends along the edges of the triangular top surface and the triangular bottom surface. The cutting insert includes three cutting corners, three major cutting edges, and three minor cutting edges at each of the top surface and the bottom surface. Each cutting corner connects a major cutting edge and a minor cutting edge. Each of the cutting corners, each of the major cutting edges, and each of the minor cutting edges is disposed at the intersection between the top surface or the bottom surface and one of the circumferential surfaces. Background Art

[0002] Many machine parts have a design that requires machining of metal workpieces to form shoulders arranged at a defined angle relative to a wall surface. For so-called shoulder milling, various types of indexable cutting inserts are known, such as the above-mentioned type of triangular double-sided cutting inserts. A problem with some of these known cutting inserts is that it is difficult to produce machine parts that meet strict tolerances. Summary of the Invention

[0003] It is an object of the present invention to alleviate the above problems and to provide an indexable cutting insert by means of which the ability to produce machine parts that meet strict tolerances can be improved.

[0004] The above object is achieved by the invention defined in claim 1.

[0005] According to a first aspect of the present invention, at least one of the above objects is achieved by an indexable cutting insert for mounting in a blade seat of a tool body of a shoulder milling cutter. The cutting insert is generally defined by a triangular top surface, a triangular bottom surface, and three circumferential surfaces extending between the top surface and the bottom surface. On each side of the cutting insert, a single one of the three circumferential surfaces extends along the edges of the triangular top surface and the triangular bottom surface. The cutting insert includes three cutting corners, three major cutting edges, and three minor cutting edges at each of the top surface and the bottom surface. Each cutting corner connects a major cutting edge and a minor cutting edge. Each of the cutting corners, each of the major cutting edges, and each of the minor cutting edges is disposed at the intersection between the top surface or the bottom surface and one of the circumferential surfaces, and each of the circumferential surfaces includes a planar contact surface defined by the major cutting edge at the top surface and the major cutting edge at the bottom surface.

[0006] The present invention provides a triangular indexable cutting insert, wherein the indexable cutting insert has six sets of cutting edges. After indexing and flipping of the cutting insert, the six sets of cutting edges can be used one after another, such that the total tool life is six times the life of a cutting insert having a single set of cutting edges. Each set of cutting edges includes a main cutting edge for milling a wall surface, a secondary cutting edge for milling a bottom surface, and a cutting corner for milling a corner between the wall surface and the bottom surface of a workpiece to provide a shoulder therein. The cutting corner connects the main cutting edge and the secondary cutting edge.

[0007] Due to the flat contact surfaces on each side of the cutting insert of the present invention (each of which is defined by the main cutting edge at the top surface and the main cutting edge at the bottom surface), the indexable cutting insert can be firmly held in the toolholder and can provide a stable connection between the cutting insert and the cutting tool body. Another advantage is the improved accuracy of the mounting position of the cutting insert in the toolholder. Thus, due to the cutting insert being less likely to vibrate and due to the precise positioning, machine parts can be produced with more stringent tolerances.

[0008] Advantageously, the contact surfaces of the present invention do not interfere with other design conditions of the cutting insert, such that the cutting insert of the present invention additionally provides enhanced positional accuracy and stability.

[0009] At the intersection of each side surface and the top surface, a single main cutting edge, a single secondary cutting edge, and two cutting corners are provided. Similarly, at the intersection of each side surface and the bottom surface, a single main cutting edge, a single secondary cutting edge, and two cutting corners are provided.

[0010] In an embodiment of the present invention, a part of the top surface and a part of the bottom surface are substantially parallel. In addition, the cutting insert includes an intermediate plane located midway between the top surface and the bottom surface. The intermediate plane extends parallel to the parallel portions of the top surface and the bottom surface.

[0011] In the embodiment, each of the contact surfaces is perpendicular to the intermediate plane. Thus, in this embodiment, in terms of the main cutting edge, the cutting insert is a negative cutting insert.

[0012] In the embodiment, each of the secondary cutting edges is straight.

[0013] In an embodiment of the present invention, the cutting insert includes an intermediate plane intermediate between a top surface and a bottom surface, wherein the cutting insert includes three transitional edges at each of the top surface and the bottom surface, the transitional edges being provided at the intersection between the top surface or the bottom surface and one of the circumferential surfaces, wherein each transitional edge connects a main cutting edge and a sub-cutting edge, and when the main cutting edge and the transitional edge are projected onto the intermediate plane, each transitional edge forms an angle with the main cutting edge to which the transitional edge is connected, wherein when projected onto the intermediate plane, each of the main cutting edges is straight and has a total length, the total length being between a cutting corner and the transitional edge, the main cutting edge being connected to the cutting corner and the transitional edge, and wherein each of the contact surfaces extends along at least two-thirds of the total length of the main cutting edge, the main cutting edge defining the corresponding contact surface at the top surface and the bottom surface.

[0014] In an embodiment, each of the contact surfaces extends along at least two-thirds of the total length of the main cutting edge that defines the corresponding contact surface. In an embodiment, each of the contact surfaces extends along the entire total length of the main cutting edge. By increasing the distance that the contact surface extends along the main cutting edge, the area of the planar contact surface is increased.

[0015] In an embodiment of the present invention, each of the planar contact surfaces extends from a cutting corner connecting the main cutting edge at the top surface to the sub-cutting edge at another circumferential surface to a cutting corner connecting the main cutting edge at the bottom surface to the sub-cutting edge at another circumferential surface. This design results in the area of each of the planar contact surfaces being maximized in the diagonal direction from the cutting corner at the top surface to the cutting corner at the bottom surface.

[0016] In an embodiment of the present invention, in a first circumferential direction, each of the contact surfaces is at least partially defined by a first transitional surface, and in a second circumferential direction, at least partially defined by a second transitional surface. The transitional surfaces are part of the circumferential surface. Each transitional edge is provided at the intersection between the first transitional surface and the top surface or at the intersection between the second transitional surface and the bottom surface. Each of the transitional surfaces connects the contact surface to the flank surface of a sub-cutting edge.

[0017] In an embodiment, the extension of the contact surface in the circumferential direction in the intermediate plane is less than the extension of the contact surface along each of the main cutting edges.

[0018] In an embodiment of the present invention, the top surface and the bottom surface have a common axis of rotational symmetry, wherein each of the circumferential surfaces includes two flank clearance surfaces, wherein a first one of the two flank clearance surfaces intersects the top surface at the secondary cutting edge, and a second one of the two flank clearance surfaces intersects the bottom surface at the secondary cutting edge, and wherein each of the flank clearance surfaces slopes inwardly towards the axis of rotational symmetry starting from the secondary cutting edge. In other words, each of the flank clearance surfaces slopes inwardly towards the axis of rotational symmetry in its extension from the secondary cutting edge towards the intermediate plane. Thus, as seen in a cross-section passing through the flank clearance surface and including the axis of rotational symmetry, any point on the flank clearance surface closer to the secondary cutting edge is farther from the axis of rotational symmetry than any point on the flank clearance surface closer to the intermediate plane.

[0019] According to this embodiment, the cutting insert is positive with respect to each of the secondary cutting edges. According to this embodiment, a positive insert at the secondary cutting edge enables a cutting tool including a tool body equipped with at least one indexable cutting insert to be tilted and inserted. In addition, the sloping flank clearance surfaces avoid collisions between the cutting insert and the workpiece while maximizing the area of the planar contact surface.

[0020] In an embodiment of the present invention, each of the flank clearance surfaces is a planar surface.

[0021] In an embodiment of the present invention, each of the triangular top surface and the triangular bottom surface has three-fold symmetry. However, in the embodiment, the top surface and the bottom surface are arranged such that the angular position of the cutting corner on the top surface relative to the cutting corner on the bottom surface is twisted relative to each other. However, in this embodiment, the top surface and the bottom surface have a common axis of rotational symmetry. The twisted positioning of the cutting corners of the top surface and the bottom surface allows for a positive cutting insert with respect to the secondary cutting edge.

[0022] In an embodiment of the present invention, each of the flank clearance surfaces extends from the secondary cutting edge to an intermediate plane that is intermediate between the top surface and the bottom surface. The extension of the flank clearance surface from the respective secondary cutting edge to the intermediate plane improves the clearance of the secondary cutting edge. In the embodiment, each of the flank clearance surfaces terminates at the intermediate plane.

[0023] In an embodiment of the present invention, the top surface includes a planar top support surface, and the bottom surface includes a planar bottom support surface. In addition to the planar contact surfaces on the circumferential surface, providing planar support surfaces on the top surface and the bottom surface enhances the mechanical positioning stability and / or positioning accuracy of the cutting insert when mounted in a blade seat of a tool body.

[0024] In an embodiment, each of the secondary cutting edges at the top surface projects above the top support surface along the entire length of the secondary cutting edge, wherein each of the secondary cutting edges at the bottom surface projects above the bottom support surface along the entire length of the secondary cutting edge, wherein each of the primary cutting edges at the top surface projects at least partially above the top support surface, wherein each of the primary cutting edges at the top surface slopes towards the top support surface from an adjacent cutting corner that connects the primary cutting edge to the secondary cutting edge, wherein each of the primary cutting edges at the bottom surface projects at least partially above the bottom support surface, and wherein each of the primary cutting edges at the bottom surface slopes towards the bottom support surface from an adjacent cutting corner that connects the primary cutting edge to the secondary cutting edge. In other words, the secondary cutting edges are raised above the respective top surface or bottom surface along their entire extent, and at least a portion of each primary cutting edge is raised above the respective top surface or bottom surface. By disposing the cutting edges above the respective support surfaces, the area of the planar support surfaces on the top and bottom surfaces is increased.

[0025] In an embodiment of the present disclosure, the top support surface and the bottom support surface are parallel.

[0026] In an embodiment of the present invention, wherein each of the primary cutting edges projects at least partially above the respective planar support surface, the primary cutting edge and the respective planar support surface (i.e., the top support surface or the bottom support surface) form an angle in the range from 5 to 15° or from 8 to 12°. This angle is measured in a plane perpendicular to the respective contact surface, or in other words, between the cutting edge and a line perpendicular to the normal of the respective support surface.

[0027] The primary cutting edge that forms an angle with respect to the top support surface or the bottom support surface can mount the cutting blade at the tool body such that the primary cutting edge provides a positive effective axial angle.

[0028] In an embodiment of the present invention, the top surface and the bottom surface each include a primary chip surface and a secondary chip surface, wherein each primary cutting edge defines a primary chip surface, and each secondary cutting edge defines a secondary chip surface, wherein each primary chip surface and each secondary chip surface form an angle in the range from 0° to 45° with the respective support surface (i.e., the top support surface or the bottom support surface), and wherein each primary chip surface rises in the direction towards the primary cutting edge, and each secondary chip surface rises in the direction towards the secondary cutting edge. This design of the chip surface strengthens the cutting edge by increasing the wedge angle of the respective cutting edge that defines the chip surface.

[0029] In an embodiment of the present invention, the angle between each secondary cutting surface in the secondary chip surface and the corresponding top support surface or bottom support surface is constant.

[0030] In an embodiment of the present invention, the angle between each primary cutting surface in the primary chip surface and the corresponding top support surface or bottom support surface increases or decreases along the primary cutting edge. In an embodiment, the angle between the primary chip surface and the corresponding support surface (i.e., the top support surface or the bottom support surface) is constant along the primary cutting edge.

[0031] In an embodiment, where the secondary chip surface is inclined relative to the corresponding support surface, or where the secondary chip surface is parallel to the corresponding support surface, and where the secondary clearance surface is inclined from the secondary cutting edge towards the axis of rotational symmetry, the inclination of the secondary clearance surface provides a positive design for the secondary cutting edge.

[0032] In an embodiment of the present invention, each secondary cutting edge in the secondary cutting edges is parallel to the top support surface.

[0033] In an embodiment of the present invention, each pair of primary and secondary cutting edges (where the primary and secondary cutting edges are connected by a cutting corner) includes an angle in the range from 85° to 95° or from 89° to 91° when projected into a plane parallel to the top support surface. The angles within the claimed range are considered to be approximately perpendicular. When observing the cutting insert according to this embodiment, the operator will realize that the cutting insert is suitable for shoulder milling to provide a 90° angle between the wall surface and the bottom surface of the workpiece.

[0034] In an embodiment, the triangular cutting insert according to the present invention has primary and secondary cutting edges, where each primary cutting edge has the same length, where each secondary cutting edge has the same length, and where the length of the primary cutting edge is at least twice the length of the secondary cutting edge. In an embodiment, the length of the primary cutting edge is at least 3 times or at least 4 times the length of the secondary cutting edge. Less material is required to provide the same cutting depth compared to a cutting insert where the primary and secondary cutting edges have the same length or nearly the same length.

[0035] At least one of the above - mentioned objects is solved by a shoulder milling cutter, which includes: a cutter body, the cutter body includes a plurality of blade seats; and a plurality of indexable cutting inserts according to any one of the embodiments discussed above, wherein the cutting inserts are mounted on the blade seats. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] From the following description of the embodiments and the drawings, further advantages, features, and applications of the present disclosure will become apparent. The foregoing and the following detailed descriptions of the embodiments of the present disclosure will be better understood when read in conjunction with the drawings. It should be understood that the depicted embodiments are not limited to the precise arrangements and means shown. Unless otherwise noted, like reference numerals in the different figures represent similar or identical parts.

[0037] Figure 1 is a side view of a shoulder milling cutter including an indexable cutting insert according to an embodiment of the present invention.

[0038] Figure 2 is Figure 1 a top view of the indexable cutting insert.

[0039] Figure 3 is Figure 1 and Figure 2 a side view of the indexable cutting insert.

[0040] Figure 4 is when compared with the side view of Figure 3 a side view of the indexable cutting insert of Figures 1 to 3 rotated 30°. Detailed Description

[0041] Figure 1 The shoulder milling cutter of

[0042] is designed to mill a shoulder in a workpiece (not shown), the shoulder having a 90° angle between the wall surface and the bottom surface machined in the workpiece. Figure 1 In

[0043] only a single indexable cutting insert 4 is depicted in one of the blade seats 3, while the remaining blade seats 3 are depicted without cutting inserts 4. Figure 2 Each of the cutting inserts 4 has a basic triangular shape. The cutting inserts 4 have the same top surface 5 and bottom surface 6, such that the top view of the cutting insert 4 will be the same as

[0044] the top view of

[0045] Each of the top surface 5 and the bottom surface 6 includes three sets of cutting edges, where each set of cutting edges is formed by a main cutting edge 9, a secondary cutting edge 10, and a cutting corner 8 connecting the main cutting edge 9 and the secondary cutting edge 10. Therefore, the cutting insert 4 has a total of six sets of cutting edges. Each of the cutting corners 8 and the cutting edges 9, 10 is provided at the intersection of the top surface 5 or the bottom surface 6 and one of the three circumferential surfaces 7.

[0046] The top surface 5 includes a flat top support surface 11, where each of the secondary cutting edges 10 rises above the level height defined by the flat support surface 11 along its entire extension. Since the cutting corner 8 connects the raised secondary cutting edge 10 to the main cutting edge 9, the main cutting edge 9 is at least partially raised above the flat support surface 11. However, starting from the cutting corner 8, the main cutting edge 9 descends to a level even lower than the level height of the top support surface 11. This inclination of the main cutting edge 9 enables the insert 4 to be mounted at the tool body 2 at a positive effective axial angle.

[0047] Due to the raised geometry, each of the secondary cutting edges 10 includes a secondary chip surface 12, which also rises above the level height defined by the flat support surface 11. Each of the main cutting edges 9 includes a main chip surface 13, which is partially raised above the level height defined by the flat support surface 11. The main chip surface 13 and the secondary chip surface 12 are inclined with respect to the support surface 11 such that the main cutting edge 9 and the secondary cutting edge 10 have a positive wedge angle.

[0048] When the cutting insert 4 is mounted in Figure 1 the pocket 3 of the tool body 2, a set of cutting edges including the cutting corner 8 and the cutting edges 9, 10 is operative. The operative secondary cutting edge 10 is perpendicular to the rotational axis 14 of the tool body 2. When projected into a plane (the plane being parallel to and including the rotational axis and the secondary cutting edge 10), the operative main cutting edge 9 connected to the operative secondary cutting edge 10 through the cutting corner 8 is perpendicular to the operative secondary cutting edge 10.

[0049] Figure 3 The viewing directions of the side views of

[0050] In the center, a single planar contact surface 15 is provided on each circumferential surface 7. Each of the planar contact surfaces 15 is defined by a main cutting edge 9 at the top surface 5 and a main cutting edge 9 at the bottom surface 6. In addition, each of the planar contact surfaces 15 extends in a diagonal direction from a cutting corner 8 at the top surface 5 to a cutting corner 8 at the bottom surface 6.

[0051] As is clearly seen from Figure 3 the side view, each main cutting edge 9 of the first set of cutting edges, which includes the corners 8 and the cutting edges 9, 10, is connected to a secondary cutting edge 10 of the "next set" by a transition edge 16. Thus, each of the top surface 5 and the bottom surface 6 includes three transition edges 16. The transition edge 16 terminates the main cutting edge 9 at one of its ends. When projected into the intermediate plane, the transition edge 16 forms an angle with the main cutting edge 9.

[0052] Since the secondary cutting edge 10 and the main cutting edge 9 are at least partially raised above the level height defined by the support surface 11, the transition edge 16 connecting the main cutting edge 9 to the next secondary cutting edge 10 at the same circumferential surface 7 rises from a level height below the support surface 11 to a level height defined by the secondary cutting edge 10.

[0053] The contact surface 15 is perpendicular to the support surface 11 on the top surface 5 and the bottom surface 6. Thus, the contact surface 15 is perpendicular to the intermediate plane located in the middle between the top surface and the bottom surface. The contact surface 15 forms a clearance surface for the main cutting edge 9. Thus, Figures 1 to 4 the cutting insert is a negative cutting insert with respect to the main cutting edge 9.

[0054] At the intermediate plane, each of the contact surfaces 15 has a circumferential extension that is less than the length of the contact surface 15 at the main cutting edge 9 that bounds the contact surface 15 and along the main cutting edge 9 that bounds the contact surface 15.

[0055] The contact surface 15 is separated from the secondary clearance surface 18 associated with the secondary cutting edge 10 by a transition surface portion 17 in the longitudinal circumferential direction on each of its sides. Each of the secondary clearance surfaces 18 is inclined in its extension towards the intermediate plane starting from the corresponding secondary cutting edge 10, such that the cutting insert 4 is a positive insert with respect to the secondary cutting edge 10.

[0056] Each major cutting edge in the major cutting edges 9 has the same total length, and each minor cutting edge in the minor cutting edges 10 has the same total length. When projected onto the intermediate plane, the total length of each major cutting edge in the major cutting edges is approximately 5 times the total length of each minor cutting edge in the minor cutting edges 10. Therefore, the circle inscribed in the triangle will touch each side of the triangle only once. Due to the selected geometry, the inscribed circle will touch each of the said sides at the major cutting edges 9.

[0057] In Figures 1 to 4 the embodiment of, each cutting edge in the major cutting edges 9 and the minor cutting edges 10 is straight.

[0058] The complex geometry of the above-mentioned cutting blade 4 provides a cutting blade 4 that is negative at the major cutting edges 9 and positive at the minor cutting edges 10. The selected geometry allows the contact surface 15 on the circumferential surface 7 to have a large area, thereby enhancing the positioning stability of the blade 4 when installed in the blade seat 3 of the tool body 2. In addition, by raising the cutting edges 9, 10 and the cutting corner 8 above the level of the support surface 11, the area of the support surface 11 is further increased, which in turn enhances the positioning stability of the blade 4 when installed in the blade seat 3.

[0059] Note that, as will be readily understood by those skilled in the art, the features described in connection with one embodiment can also be used in other embodiments.

[0060] Although the present disclosure has been described in detail with reference to the accompanying drawings, this description is merely exemplary and is not to be considered as limiting the scope of protection defined by the claims.

[0061] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" does not exclude a plurality. The fact that some features are claimed in different claims does not exclude their combination. The reference signs in the claims are not to be considered as limiting the scope of protection.

[0062] List of reference signs

[0063] 1 Shoulder milling cutter

[0064] 2 Tool body

[0065] 3 Blade seat

[0066] 4 Cutting blade

[0067] 5 Triangular top surface

[0068] 6 Triangular bottom surface

[0069] 7 Circumferential surface

[0070] 8 Cutting corner

[0071] 9 Major cutting edge

[0072] 10 Minor cutting edge

[0073] 11 Flat support surface

[0074] 12 Minor chip surface

[0075] 13 Major chip surface

[0076] 14 Axis of rotation

[0077] 15 Flat contact surface

[0078] 16 Transition edge

[0079] 17 Transition surface portion

[0080] 18 Minor relief surface

Claims

1. An indexable cutting insert (4) for a blade seat (3) of a tool body (2) of a shoulder milling cutter (1), wherein the indexable cutting insert (4) is defined by: a triangular top surface (5), a triangular bottom surface (6), and three circumferential surfaces (7) extending between the triangular top surface (5) and the triangular bottom surface (6), Among them, on each side of the indexable cutting insert (4), a separate one of the three circumferential surfaces (7) extends along the edges of the triangular top surface (5) and the triangular bottom surface (6), the indexable cutting insert (4) comprises: at each of the triangular top surface (5) and the triangular bottom surface, three cutting corners (8), three major cutting edges (9) and three minor cutting edges (10), wherein each cutting corner (8) connects a major cutting edge (9) and a minor cutting edge (10), wherein each of the cutting corners (8), each of the major cutting edges (9) and each of the minor cutting edges (10) is provided at the intersection between the triangular top surface (5) or the triangular bottom surface (6) and one of the circumferential surfaces (7), characterized in that each of the circumferential surfaces (7) comprises a planar contact surface (15) defined by the major cutting edge (9) at the triangular top surface (5) and the major cutting edge (9) at the triangular bottom surface (6), the triangular top surface (5) and the triangular bottom surface (6) have a common axis of rotational symmetry, wherein each of the circumferential surfaces (7) comprises two secondary clearance surfaces (18), wherein the first of the two secondary clearance surfaces (18) intersects the triangular top surface (5) at a minor cutting edge (10), and the second of the two secondary clearance surfaces (18) intersects the triangular bottom surface (6) at a minor cutting edge (10), and wherein each of the secondary clearance surfaces (18) slopes from the minor cutting edge (10) towards the axis of rotational symmetry, and The top surface (5) of the triangle includes a planar top support surface, and each pair of the main cutting edges (9) and the secondary cutting edges (10) includes an angle in the range from 85° to 95° when projected onto a plane parallel to the planar top support surface. The main cutting edges (9) and the secondary cutting edges (10) are connected by a cutting corner (8). Wherein, at an intermediate plane intermediate between the top surface (5) and the bottom surface (6) of the indexable cutting insert, each of the planar contact surfaces (15) has a circumferential extension that is less than the length of the planar contact surface (15) along the main cutting edge (9) that defines the planar contact surface (15).

2. The indexable cutting insert (4) according to claim 1, wherein the indexable cutting insert (4) includes three transitional edges (16) at each of the top surface (5) and the bottom surface (6) of the triangle. The transitional edges (16) are provided at the intersection between the top surface (5) or the bottom surface (6) of the triangle and one of the circumferential surfaces (7). Wherein - each transitional edge (16) connects a main cutting edge (9) and a secondary cutting edge (10), and - when the main cutting edge (9) and the transitional edge (16) are projected onto the intermediate plane, each transitional edge (16) forms an angle with the main cutting edge (9), and the transitional edge (16) is connected to the main cutting edge (9), Among them, when projected onto the intermediate plane, each of the main cutting edges (9) is straight and has a total length, wherein the total length is between the cutting corner (8) and the transitional edge (16), and the main cutting edge (9) is connected to the cutting corner (8) and the transitional edge (16), and wherein each of the planar contact surfaces (15) extends along at least two-thirds of the total length of the main cutting edge (9). The main cutting edge (9) defines the corresponding planar contact surface (15) at the top surface (5) and the bottom surface (6) of the triangle.

3. The indexable cutting insert (4) according to claim 2, wherein, Each of the planar contact surfaces (15) extends along the entire total length of the main cutting edge (9).

4. The indexable cutting insert (4) according to claim 1, wherein, Each of the secondary clearance surfaces (18) extends from the secondary cutting edge (10) to the intermediate plane, which is intermediate between the top surface (5) and the bottom surface (6) of the triangle.

5. The indexable cutting insert (4) according to any one of claims 1-4, Among them, the bottom surface (6) of the triangle includes a planar bottom support surface, Each of the secondary cutting edges (10) at the triangular top surface (5) projects above the planar top support surface over the entire length of the secondary cutting edge (10), and each of the secondary cutting edges (10) at the triangular bottom surface (6) projects above the planar bottom support surface over the entire length of the secondary cutting edge (10). Each of the primary cutting edges (9) at the triangular top surface (5) projects at least partially above the planar top support surface. Each of the primary cutting edges (9) at the triangular top surface (5) slopes towards the planar top support surface from an adjacent cutting corner (8) that connects the primary cutting edge (9) to the secondary cutting edge (10). Each of the primary cutting edges (9) at the triangular bottom surface (6) projects at least partially above the planar bottom support surface, and each of the primary cutting edges (9) at the triangular bottom surface (6) slopes towards the planar bottom support surface from the adjacent cutting corner (8) that connects the primary cutting edge (9) to the secondary cutting edge (10).

6. The indexable cutting insert (4) according to claim 5, wherein, The triangular top surface (5) and the triangular bottom surface (6) each include a primary chip surface (13) and a secondary chip surface (12), where each primary cutting edge (9) defines a primary chip surface (13) and each secondary cutting edge (10) defines a secondary chip surface (12), where each primary chip surface (13) and each secondary chip surface (12) form an angle in the range from 0° to 45° with the planar top support surface and the planar bottom support surface, respectively, and where each primary chip surface (13) rises in the direction towards the primary cutting edge (9), and each secondary chip surface (12) rises in the direction towards the secondary cutting edge (10).

7. The indexable cutting insert (4) according to any one of claims 1 to 4, wherein, Each of the secondary cutting edges (10) is parallel to the planar top support surface.

8. The indexable cutting insert (4) according to any one of claims 1 to 4, wherein, Each of the primary cutting edges (9) has the same total length, where each of the secondary cutting edges (10) has the same total length, and where the total length of the primary cutting edge (9) is at least twice the total length of the secondary cutting edge (10).

9. A shoulder milling cutter (1), comprising: A tool body (2) comprising a plurality of blade seats (3); and a plurality of indexable cutting inserts (4) according to any one of the preceding claims mounted on the blade seats (3).

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