Indexable cutting insert

Abstract

The proposed technology relates to an indexable cutting insert (10) for a cutting tool. The cutting insert (10) includes a first side surface (12) and an opposite second side surface (14), and a peripheral surface (16) extending between the first side surface (12) and the second side surface (14). The cutting portion (18) includes a first cutting face (24) and an opposite second cutting face (26), a flank face (28) extending between the first cutting face (24) and the second cutting face (26), a first cutting edge (20) between the first cutting face (24) and the flank face (28), and a second cutting edge (22) between the second cutting face (26) and the flank face (28). The cutting portion (18) is bisected by a first plane (AA') transverse to the first side surface (12), and the cutting portion (18) has a double concave cross-section transverse to the first plane (AA').

Description

Technical Field

[0001] The proposed technology generally relates to the field of cutting tools in turning or lathe machining applications. Additionally, the proposed technology specifically relates to cutting inserts or replaceable tips for cutting tools, and particularly to indexable cutting inserts. Background Art

[0002] In turning or lathe machining applications, indexable cutting inserts are known, which means that the cutting insert can be quickly and easily repositioned on the toolholder to a new orientation. Such a cutting insert has at least two cutting edges, and indexing switches the cutting edge engaging the workpiece. The number of cutting edges typically limits the minimum size of the cutting insert, and the larger the number of cutting edges, the larger the minimum size must be.

[0003] In some applications (e.g., grooving and parting applications), indexable cutting inserts with shorter and smaller cutting widths are required. This can be achieved by reducing the scale of the cutting insert. However, this typically results in a reduction in the stability and strength of the cutting insert. It also reduces the ability to transfer heat from the cutting edge. Summary of the Invention

[0004] Object of the Invention

[0005] The aim of the proposed technology is to achieve an indexable cutting insert that is shorter and has a narrower cutting width while maintaining strength, stability, and heat transfer capabilities. Summary of the Invention

[0007] According to a first aspect of the proposed technology, an indexable cutting insert for a cutting tool is provided. The cutting insert includes: a first side surface and an opposite second side surface, and a peripheral surface extending between the first side surface and the second side surface. The cutting insert further includes: a cutting portion, which includes: a first cutting face and an opposite second cutting face, a flank face extending between the first cutting face and the second cutting face, a first cutting edge between the first cutting face and the flank face or separating the first cutting face and the flank face, and a second cutting edge between the second cutting face and the flank face or separating the second cutting face and the flank face. The cutting portion is bisected by a first plane transverse to the first side surface.

[0008] Preferably, the cutting tool is a turning tool for turning applications (e.g., lathe machining). The cutting tool can be a grooving or parting cutting tool.

[0009] The first cutting edge and the second cutting edge may extend from the first side surface to the second side surface. The first cutting edge, the second cutting edge, the first cutting face, the second cutting face, and the flank face are understood to be located on or form part of the peripheral surface. The peripheral surface may surround the entire cutting insert.

[0010] The cutting face is understood to face the workpiece or the cutting direction during use. The cutting tool may be configured for machining a workpiece that rotates relative to a rotational axis. This means that the cutting direction is opposite, or the cutting face faces the tangential direction of the rotating workpiece. This also means that the first side surface and the second side surface are aligned transversely to the rotational axis of the rotating workpiece during use.

[0011] The flank face is understood to face the new or machined surface of the workpiece during use. The first cutting face and / or the second cutting face may be transverse to the flank face. The side surface is understood to extend over the entire length and height of the cutting insert. The width of the cutting insert is understood to correspond to the spacing or distance between the first side surface and the second side surface.

[0012] The cutting portion bisected by the first plane is understood to encompass the first plane that divides the cutting portion into two congruent parts, or the cutting portion consists of a first congruent part and a second congruent part with respect to the first plane transverse to the first side surface. The first plane may cut the flank face in the two congruent parts.

[0013] Congruent parts are understood here to encompass the shapes of parts that can be transformed into each other by reflection and / or rotation. The first cutting edge and the second cutting edge being located on the same cutting portion means that the cutting insert is double-sided, and the cutting insert can be used with either the first side surface or the second side surface facing the toolholder for the cutting insert.

[0014] The cutting portion may have a proximal end and a distal end, and the first cutting edge and the second cutting edge, and / or the flank face may be located at the distal end of the cutting portion. It should be understood that the proximal end and the distal end are on opposite sides of the cutting portion.

[0015] The cutting portion may have a bi-concave cross-section extending between a first cutting face and a second cutting face and / or laterally or perpendicularly to a first plane. The bi-concave cross-section helps to improve the tangential side clearance at the cutting edge. The width of the cutting portion increases non-linearly from the center of the cutting portion towards the cutting faces. The increase in width is maximum at the cutting faces. This means that at a given tangential side clearance angle, the width at the center under the bi-concave cross-section is greater than the width at the center under a linear geometry. Thus, the bi-concave geometry helps to improve the strength of the cutting portion or, alternatively, helps to reduce the cutting width while maintaining the strength. The greater width at the center also helps to improve heat transfer. In some applications, it is estimated that the strength can be maintained with a 25% to 35% reduction in the cutting width compared to a conventionally ground cutting blade having a linear geometry. The cutting blade can be made narrower, which helps to reduce the material cost in manufacturing the cutting blade and thus helps to reduce the production cost. This also means that less material is removed from the workpiece in a cutting or parting application, which helps to reduce the application cost when using the cutting blade.

[0016] The bi-concave cross-section means that the cross-section has a minimum width at the center between the first cutting face and the second cutting face (where the first plane bisects the cutting portion) and a maximum width at the first cutting face and the second cutting face. The width at the bisect formed by the first plane of the cutting portion can be smaller by a factor in the range of 0.3 to 0.8 times, 0.4 to 0.7 times, or 0.5 to 0.6 times than the width at the first cutting face and the second cutting face or at the first cutting edge and the second cutting edge.

[0017] The cutting portion may have a cross-section extending between a first cutting face and a second cutting face and / or extending laterally to the first plane, which is recessed on a first side surface. Similarly, the cross-section extending between the first cutting face and the second cutting face and / or laterally to the first plane may be recessed on a second side surface. The resulting geometry has the same advantages as the bi-concave geometry described above.

[0018] The term "laterally to" is understood to cover "oriented at a right angle". The cutting portion having a cross-section is understood to cover a cutting portion having a cross-section along a part of the bisect formed by the first plane of the cutting portion or along the entire bisect formed by the first plane of the cutting portion. Alternatively, it should be understood to cover a cutting portion having a cross-section along a part between the proximal end and the distal end of the cutting portion or between the proximal end and the distal end or the flank of the cutting portion. The bisect formed by the first plane is understood to cover the intersection formed by the first plane. For example, this means that it covers the line at which the first plane meets the cutting portion in the first side surface. The shape and / or dimensions of the cross-section may vary along the part of the bisect, along the entire bisect, or between the proximal end and the distal end of the cutting portion.

[0019] According to a second aspect of the proposed technology, a replaceable cutting insert for a cutting tool is provided, wherein the cutting insert includes: a first side surface and an opposite second side surface, and a peripheral surface extending between the first side surface and the second side surface. The cutting insert further includes: a cutting portion. The cutting portion may include a first cutting face, a flank face, and a first cutting edge between the first cutting face and the flank face. The cutting portion may have a proximal end and a distal end. The first cutting edge and / or the flank face are located at the distal end of the cutting portion.

[0020] According to a third aspect of the proposed technology, a cutting tool assembly is provided, the cutting tool assembly including: a cutting tool configured to rotate a workpiece relative to a rotational axis; and a replaceable cutting insert according to a first aspect of the proposed technology, wherein the cutting tool is further configured to support the cutting insert and orient the cutting insert during use of the workpiece or during machining or cutting of the workpiece such that a first plane is transverse to the rotational axis or at a right angle to the rotational axis.

[0021] According to a fourth aspect of the proposed technology, there is provided a use of a cutting insert according to a first aspect of the proposed technology for machining a rotating workpiece, wherein the cutting insert (10) is oriented such that a first plane is transverse to the rotational axis of the rotating workpiece.

[0022] Detailed Description

[0023] Further details of a first aspect of the proposed technology are described below.

[0024] The cutting portion may be bisected by a second plane transverse to or perpendicular to the first plane. The second plane may be aligned with the first side surface, or may be centered between the first side surface and the second side surface and extend in the same direction as the first side surface and the second side surface. The cutting portion bisected by the second plane is understood to cover a second plane that divides the cutting portion into two congruent parts, or the cutting portion consists of a third congruent part and a fourth congruent part relative to the second plane.

[0025] On the cutting portion, the first side surface may be concave and define or have the shape of a part of the surface of a first cylinder, the axis of which first cylinder is in the first plane. Additionally, on the cutting portion, the second side surface may be concave and define or have the shape of a part of the surface of a second cylinder, the axis of which second cylinder is in the first plane. The first cylinder and / or the second cylinder may be an elliptical cylinder.

[0026] The elliptical cylinder has or each of the first cylinder and the second cylinder may have a transverse cross-section that is elliptical or forms an ellipse. It should be understood that the transverse cross-section is perpendicular to the axis of the elliptical cylinder. It should also be understood that the transverse cross-section has two foci that do not coincide or overlap. This means that the cross-section does not define or form a circle. The cross-section may have an eccentricity greater than 0.5, 0.8, or 0.9. The eccentricity of the cross-section may be less than 0.95 or 0.97. It has been found that the specified eccentricity provides a good balance between cutting width, strength, and heat transfer capacity. The cross-section may have a semi-minor axis that is parallel or collinear with or lies in the first plane. The cross-section may have a semi-major axis that is transverse to or perpendicular to the first plane. It has been found that this also provides a good balance in terms of the functionality of the cutting blade.

[0027] The first cylinder and the second cylinder may be congruent. Portions of the surface of the first cylinder and portions of the surface of the second cylinder may be congruent. The axis of the first cylinder and / or the axis of the second cylinder may define an angle in the range of 0.5° to 4° or in the range of 1° to 3° relative to the second plane. The first cylinder and the second cylinder may exhibit reflection symmetry and / or rotational symmetry relative to the second plane.

[0028] The cutting portion may have a radial side clearance angle in the range of 0° to 4°, in the range of 0.5° to 3°, or preferably in the range of 1° to 2.5°. The radial side clearance angle is understood to encompass the angle between the second plane and the line that is tangent to the first side surface at the first cutting edge, at the flank face, and / or at the second cutting edge and in a plane parallel to the first plane.

[0029] The cutting portion may have a tangential side clearance angle in the range of 2.5° to 10° or 4° to 8°. The tangential side clearance angle is understood to encompass the angle between the second plane and the line that is tangent to the first side surface at the first cutting edge, at the first cutting face, at the second cutting face, and / or at the second cutting edge and in a plane perpendicular or transverse to the first plane and the second plane.

[0030] The axes of the first cylinder and the second cylinder may diverge in the direction of the flank face. Alternatively or additionally, the cutting portion may have an increasing width between the first side surface and the second side surface towards the flank face. This has the effect that the cutting blade has an increasing radial side clearance from the cutting edge or from the flank face, which is advantageous in grooving and parting. Workpieces with a larger diameter can be cut off, and the geometry helps to improve chip flow.

[0031] The flank face can be recessed and / or curved inwards relative to the cutting portion, e.g. along the intersection between the flank face and the first plane. This has the effect that the cutting insert has a positive rake angle relative to both the first cutting edge and the second cutting edge during use, since the flank face is located between the first cutting edge and the second cutting edge.

[0032] The first cutting face can have a first rake face portion juxtaposed with or located at the first cutting edge. The first rake face portion can be recessed and / or curved inwards relative to the cutting portion or relative to the first cutting face. The second cutting face can have a second rake face portion juxtaposed with or located at the second cutting edge. The second rake face portion can be recessed and / or curved inwards relative to the cutting portion or relative to the second cutting face. The first side surface and / or the first rake face portion can define a positive rake angle relative to the workpiece in the intended orientation during use. Similarly, the second side surface and / or the second rake face portion can define a positive rake angle relative to the workpiece in the intended orientation during use.

[0033] Each cutting edge can extend from the first side surface to the second side surface, or be located at or pass through the peripheral surface. The first cutting edge and the second cutting edge can have equal lengths. The first cutting edge and the second cutting edge can be parallel. The first cutting edge and the second cutting edge can define the maximum cutting width of the cutting portion. The flank face can have a non-finite width, meaning that it does not form an edge parallel to the first plane between the first cutting edge and the second cutting edge.

[0034] Further details of the first and second aspects of the proposed technique are described below.

[0035] The cutting insert can have a base portion, where the cutting portion is attached to the base portion at the proximal end of the cutting portion.

[0036] The base portion can be configured to be attached to a toolholder. The cutting insert can include only a single cutting portion. This means that the cutting edges are located at the same end of the cutting insert, which has the effect that the cutting insert is shorter, thereby allowing a smaller toolholder. Compared with a indexable cutting insert having cutting edges on opposite sides of the base portion, the reduction in the estimated length can be up to 35%. Additionally, the cutting insert can include only a single base portion.

[0037] The cutting portion can have a smaller width between the first side surface and the second side surface than the base portion.

[0038] The cutting portion can have a width that increases from the proximal end to the distal end of the cutting portion between the first side surface and the second side surface. Additionally or alternatively, the first side surface and the second side surface can diverge from each other from the proximal end to the distal end of the cutting portion. This has the effect that the cutting insert has an increasing side clearance from the cutting edge or from the flank face towards the base portion.

[0039] The base portion may have a through - circular hole between a first side surface and a second side surface. The through - circular hole may be configured to receive a screw for fixing the cutting blade to the toolholder. The axis of the circular hole may be in a first plane. Additionally or alternatively, the circular hole may be transverse or perpendicular to a second plane. The base portion may have a first beveled or tapered edge between the circular hole and the first side surface and a second beveled or tapered edge between the circular hole and the second side surface. The first beveled edge and the second beveled edge may be configured to mate with the tapered head of the screw for fixing the cutting blade to the toolholder.

[0040] In a first aspect of the proposed technology, the base portion may be bisected by a first plane transverse to the first side surface. In a second aspect of the proposed technology, the base portion may be bisected by a first plane transverse to the first side surface. The base portion bisected by the first plane is understood to cover the first plane that divides the base portion into two congruent parts, or the base portion consists of a first congruent part and a second congruent part with respect to the first plane transverse to the first side surface. The first plane may cut the through - circular hole into the two congruent parts. Congruent parts are understood here to cover shapes of parts that can be transformed into each other by reflection and / or rotation.

[0041] The base portion may have a first planar portion or a first planar surface portion on the first side surface and a second planar portion or a second planar surface portion on the second side surface, wherein the first planar portion and the second planar portion are parallel. The through - circular hole may pass between the first planar portion and the second planar portion. The first planar portion and the second planar portion are intended to abut against a plane on the toolholder and may constitute the maximum contact surface between the cutting blade and the toolholder.

[0042] At each point on the base portion between the first side surface and the peripheral surface, the first side surface may be at a right angle to the peripheral surface. Similarly, at each point on the base portion between the second side surface and the peripheral surface, the second side surface may be at a right angle to the peripheral surface. This means that no material is lost due to chamfering the edges of the base portion, which contributes to easier and cheaper manufacturing.

[0043] The base portion may have a portion in the form of a sector of a ring with a uniform thickness. The sector of the ring may correspond to a circular sector with a sector angle in the range of 60° to 180°, in the range of 90° to 180°, in the range of 120° to 180°, or in the range of 150° to 180°. A circular sector with a sector angle of 180° is understood to correspond to a semi - disk, and a circular sector with a sector angle of 60° is understood to correspond to one - sixth of a circle. The portion in the form of a sector of a ring may have a uniform radial thickness.

[0044] The base portion may have a proximal end and a distal end, wherein the base portion is attached to the cutting portion at the distal end of the base portion. It is understood that the proximal end and the distal end are located on opposite sides of the base portion. A portion shaped as a sector of a ring may be located at the proximal end of the base portion. A circular hole may form or define the inner surface of the sector of the ring, and a portion of the peripheral surface may form or define the outer surface of the ring.

[0045] On the base portion, a portion of the peripheral surface may be convex and define or have the shape of a portion of the surface of a third cylinder, the axis of which is in the first plane. The axis of the third cylinder may be collinear with the axis of the circular hole. Alternatively or additionally, the third cylinder and the circular hole may be concentric.

[0046] The base portion may have a circular profile at the proximal end of the base portion. The peripheral surface may be a smooth surface on the base portion. A smooth surface is understood to cover a surface without sharp features such as corners or edges. The peripheral surface may curve around the base portion in a single dimension. This means that the peripheral surface curves only in the second plane and not in the first plane.

[0047] The cutting portion may have a thickness transverse to the first plane that increases or substantially increases from the proximal end of the cutting portion to the distal end or at a point at the distal end. The effect of any rake face portion on the thickness may be negligible.

[0048] In a first aspect of the proposed technique, the first cutting face may have a first flat surface portion and the second cutting face may have a second flat surface portion, wherein the first flat surface portion and the second flat surface portion diverge from each other from the proximal end of the cutting portion towards the distal end. The first flat surface portion and the second flat surface portion may define an angle therebetween in the range of 6° to 18°, in the range of 8° to 16°, or in the range of 10° to 12°. The first flat surface portion and the second flat surface portion may extend from the proximal end of the cutting portion to the distal end of the cutting portion, or respectively to a first rake face portion and a second rake face portion. This has the effect that the cutting blade can cut a workpiece with a larger diameter, or the cutting blade can be made smaller while maintaining the diameter of the workpiece. The thickness increasing towards the proximal end of the cutting portion, together with the above-described cylindrical geometry of the first side surface and the second side surface, has the effect that the tangential side clearance angle is maximum at the first cutting edge and the second cutting edge and decreases towards the proximal end of the cutting portion, thereby synergistically contributing to improving the cutting geometry. The increasing thickness also helps to generate a larger rake face angle, thus improving the chip flow from the cutting.

[0049] The thickness of the cutting portion transverse to the first plane at the first cutting edge and the second cutting edge or the distance between the first cutting edge and the second cutting edge may be 3 to 10 times greater than the width of the cutting portion parallel to the first plane at the first cutting edge and the second cutting edge or 3 to 10 times greater than the cutting width defined by the first cutting edge and / or the second cutting edge. Here, the width is understood to be less than the thickness. The length of the cutting edge determines the cutting width, and the term "width" is used for the corresponding dimension of the cutting portion.

[0050] The cutting insert may form a one-piece body. This means that there is a seamless transition between the base portion and the cutting portion. This also means that the cutting insert is made of a single piece of material.

[0051] The cutting insert may be sintered or cemented carbide. The sintered or cemented carbide may be tungsten carbide. The cutting portion may be a ground portion. The base portion may be an unground portion. The ground portion should be understood as a portion that is shaped or formed partially or entirely by grinding. The unground portion should be understood as a portion that has not been ground.

[0052] It should be noted that the geometric features of the base portion can be regarded as independent of the convex double-sided geometry of the cutting portion. Different parts of the cutting insert have been described above, and it should be understood that different cutting portions may overlap. Description of the Drawings

[0053] A more complete understanding of the above and other features and advantages of the proposed technology will be apparent from the following detailed description of the preferred embodiments in conjunction with the accompanying drawings, wherein:

[0054] Figure 1 is a perspective view of an embodiment of the cutting insert,

[0055] Figure 2 is Figure 1 a top view of the cutting insert of

[0056] Figure 3 is Figure 1 a side view of the cutting insert of

[0057] Figure 4 is Figure 1 a front view of the cutting insert of Detailed Description of the Preferred Embodiments

[0058] Figures 1 to 4Shows different views of an embodiment of a cutting insert 10 according to the proposed technology. The cutting insert 10 is intended for turning applications. The cutting insert 10 consists of a one-piece body of sintered tungsten carbide. The cutting insert 10 has a first side surface 12 and an opposite second side surface 14, and a peripheral surface 16 extending between the first side surface 12 and the second side surface 14. The first side surface 12 and the second side surface 14 extend along the entire length of the cutting insert 10, and the peripheral surface 16 surrounds the entire cutting insert 10. The cutting insert is divided into a single cutting portion 18 and a single substrate portion 38. The cutting portion has been shaped by grinding, while the substrate portion 38 has been shaped during the sintering process.

[0059] The cutting portion 18 has a proximal end 34 and a distal end 36. The cutting portion 18 is attached to the substrate portion 38 at the proximal end 34 of the cutting portion 18. Similarly, the substrate portion 38 has a proximal end 52 and a distal end 54. The substrate portion 38 is attached to the cutting portion 18 at the distal end 54 of the substrate portion 38.

[0060] The cutting portion 18 and the substrate portion 38 are bisected by a first plane AA' transverse to the first side surface 12. This means that the first plane AA' divides each of the cutting portion 18 and the substrate portion 38 into two congruent parts, or divides the entire cutting insert 10 into two congruent parts. The bisection by the first plane AA' is indicated by the dashed line AA' in Figure 2 and Figure 4 The congruent parts have 180° reflection and rotational symmetry with respect to the first plane AA', as is evident from Figures 1 to 4 Similarly, the cutting portion 18 and the substrate portion 38 are bisected by a second plane BB' transverse to the first plane AA', which means that the second plane BB' is substantially aligned with the first side surface 12 and the second side surface 14. The second plane BB' divides each of the cutting portion 18 and the substrate portion 38 into two congruent parts, or divides the entire cutting insert 10 into two congruent parts. The bisection by the second plane BB' is indicated by the dashed line BB' in Figure 3 and Figure 4 The congruent parts also have 180° reflection and rotational symmetry with respect to the second plane BB', as is evident from Figures 1 to 4

[0061] The cutting portion 18 has a first cutting surface 24 and an opposite second cutting surface 26. A flank surface 28 extends between the first cutting surface 24 and the second cutting surface 24. The cutting portion further has a first cutting edge 20 between the first cutting surface 24 and the flank surface 28 and a second cutting edge 22 between the second cutting surface 26 and the flank surface 28. The first cutting edge 20, the second cutting edge 22, and the flank surface 28 are located at the distal end 36 of the cutting portion 18. The cutting edges 20 and 22 are parallel and extend from the first side surface 12 to the second side surface 14. The cutting edges define the same cutting width because the first plane AA' and the second plane divide the cutting portion into congruent parts.

[0062] The base portion 38 has a first planar portion 48 on the first side surface 12 and a second planar portion 50 on the second side surface 14. The first planar portion and the second planar portion are parallel. A through-circular hole 42 extends between the first planar portion 48 and the second planar portion 50.

[0063] The first side surface 12 of the cutting portion 18 is concave and has the shape of a part of the surface of a first cylinder, the axis of which is in the first plane AA'. Similarly, the second side surface 14 of the cutting portion 18 is concave and has the shape of a part of the surface of a second cylinder, the axis of which is also in the first plane AA'. The axes of the first cylinder and the second cylinder diverge in the direction from the proximal end 34 to the distal end 36 of the cutting portion 38 or towards the flank surface 28, and in both cases define an angle of 2° relative to the second plane BB'. The first cylinder and the second cylinder are congruent elliptical cylinders. A part of the cross-section of the elliptical cylinder is indicated by the dashed line DD'. The parts of the surfaces of the first cylinder and the second cylinder are congruent.

[0064] The fact that the axes of the elliptical cylinders diverge in the direction of the flank surface 28 means that the cutting portion 18 has an increasing width towards the flank surface 28 between the first side surface 12 and the second side surface 14, and the first side surface 12 and the second side surface 14 diverge from each other from the proximal end 34 to the distal end 36 of the cutting portion 18. The fact that both axes of the elliptical cylinders define an angle of 2° relative to the second plane BB' means that the cutting portion 18 has a 2° radial side clearance angle 64 on either side of the cutting portion 18.

[0065] The fact that both the first side surface 12 and the second side surface 14 are concave and the fact that the elliptical cylinder orientation is in generally the same direction means that the cutting portion 18 has a double-concave cross-section transverse to the first plane AA' along its entire length from the proximal end 34 to the flank 28. In fact, this means that the cutting portion 18 has a cross-section transverse to the first plane AA' that is concave on the first side surface 12 and the second side surface 14. The double-concave cross-section causes the cutting portion 18 to have a tangential side clearance angle 66 of 4°.

[0066] The flank 28 is concave and curved inwardly relative to the cutting portion 18. This results in the cutting portion 18 having a front clearance relative to both the first cutting edge 20 and the second cutting edge 22 during use.

[0067] The first cutting face 24 has a first rake face portion 56 at the first cutting edge 20. Similarly, the second cutting face 24 has a second rake face portion 58 at the second cutting edge 22. Both the rake face portions 56 and 58 are concave and curved inwardly relative to the cutting portion 18 and define a positive rake angle relative to the workpiece in the intended orientation during use.

[0068] The first cutting face 24 has a first flat surface portion 68 extending from the proximal end 34 of the cutting portion 18 to the first rake face portion 56. Similarly, the second cutting face 26 has a second flat surface portion 70 extending from the proximal end 34 of the cutting portion 18 to the second rake face portion 58. The first flat surface portion 68 and the second flat surface portion 70 diverge from each other from the proximal end 34 of the cutting portion 18 toward the distal end 36. This means that the cutting portion 18 has a thickness or height transverse to the first plane AA' that increases from the proximal end 34 to the distal end 36 of the cutting portion 18, regardless of the first rake face portion 56 and the second rake face portion 58. The first flat surface portion 68 and the second flat surface portion 70 define an angle of 12° between them. The maximum height of the cutting insert 10 is defined by the distance between the first cutting edge 20 and the second cutting edge 22. The maximum height is approximately eight times the cutting width corresponding to the length of the first cutting edge 20 and the second cutting edge 22.

[0069] The base portion 38 is intended to be attached to the tool holder by receiving a screw in a through-circular hole 42 and operatively connected to a threaded hole in the tool holder. Each of the first flat surface portion 48 and the second flat surface portion 50 of the base portion 38 is intended to be pressed against a flat surface on the tool holder one at a time during use.

[0070] The axis DD' of the circular hole 42 lies in the first plane AA' and is perpendicular to the second plane BB'. The base portion 38 has a first bevel edge 44 between the circular hole 42 and the first side surface 12 and a second bevel edge 46 between the circular hole 42 and the second side surface 14.

[0071] The base portion 38 has a circular profile at its proximal end 52, where a portion 60 is shaped as a sector of a ring having a uniform radial thickness and located at the proximal end 52. This means that a portion 62 of the peripheral surface 16 on the base portion 38 is convex in the second plane BB' and has the shape of a part of the surface of a third cylinder, the axis of which is collinear or coaxial with the axis DD' of the circular hole 42. This also means that the third cylinder and the circular hole 42 are concentric.

[0072] The peripheral surface 16 is a smooth surface on the base portion 38 without any sharp features. The peripheral surface 16 only bends in the second plane BB' around the base portion, which means it only bends in a single dimension. The peripheral surface has the same profile in a cross-section aligned with or parallel to the second surface BB'.

[0073] There is no bevel between the first side surface 12 and the peripheral surface 16 or between the second side surface 14 and the peripheral surface 16. The first side surface 12 and the peripheral surface 16 define a right angle between them at their junction. Similarly, the second side surface 14 and the peripheral surface 16 define a right angle between them at their junction. This means that at every point on the base portion 38 between the first side surface 12 and the peripheral surface 16, the first side surface 12 is at a right angle to the peripheral surface 16, and at every point on the base portion 38 between the second side surface 14 and the peripheral surface 16, the second side surface 14 is at a right angle to the peripheral surface 16.

[0074] List of Reference Signs

[0075] AA' First plane

[0076] BB' Second plane of the first cylinder

[0077] CC' Axis of the circular hole

[0078] 10 Blade

[0079] 12 First side surface

[0080] 14 Second side surface

[0081] 16 Peripheral surface

[0082] 18 Cutting portion

[0083] 20 First cutting edge

[0084] 22 Second cutting edge

[0085] 24 First cutting surface

[0086] 26 Second cutting surface

[0087] 28 Rear flank

[0088] 32 Bisecting point

[0089] 34 Proximal end of cutting portion

[0090] 36 Distal end of cutting portion

[0091] 38 Base portion

[0092] 42 Circular hole

[0093] 44 First bevel edge

[0094] 46 Second bevel edge

[0095] 48 First planar portion

[0096] 50 Second planar portion

[0097] 52 Proximal end of base portion

[0098] 54 Distal end of base portion

[0099] 56 First rake face portion

[0100] 58 Second rake face portion

[0101] 60 Annular portion

[0102] 62 Raised portion of peripheral surface

[0103] 64 Radial side clearance angle

[0104] 66 Tangential side clearance angle

[0105] 68 First flat surface

[0106] 70 Second flat surface.

Claims

1. An indexable cutting insert (10) for a cutting tool, comprising: - a first side surface (12) and an opposite second side surface (14), and a peripheral surface (16) extending between the first side surface (12) and the second side surface (14); - a cutting portion (18), the cutting portion comprising: a first cutting face (24) for facing a cutting direction during use and an opposite second cutting face (26), a flank face (28) extending between the first cutting face (24) and the second cutting face (26), a first cutting edge (20) between the first cutting face (24) and the flank face (28), and a second cutting edge (22) between the second cutting face (26) and the flank face (28); - wherein the cutting portion (18) is bisected by a first plane (AA') transverse to the first side surface (12); and - wherein the cutting portion (18) has a cross-section transverse to the first plane (AA'), the cross-section being concave on both the first side surface (12) and the second side surface (14); - wherein on the cutting portion (18), the first side surface (12) is concave and defines a part of the surface of a first cylinder, the axis of the first cylinder being in the first plane (AA'), wherein on the cutting portion (18), the second side surface (14) is concave and defines a part of the surface of a second cylinder, the axis (CC') of the second cylinder being in the first plane (AA'), and wherein the first cylinder and the second cylinder are elliptical cylinders.

2. The cutting insert (10) according to claim 1, wherein the axes of the first cylinder and the second cylinder diverge in the direction of the flank face (28).

3. The cutting insert (10) according to claim 2, wherein each of the first cylinder and the second cylinder has a transverse cross-section forming an ellipse, the transverse cross-section having a semi-major axis transverse to the first plane.

4. The cutting insert (10) according to any one of claims 1 to 3, wherein the cutting portion (18) has a width increasing towards the flank face (28) between the first side surface (12) and the second side surface (14).

5. The cutting insert (10) according to any one of claims 1 to 3, wherein the cutting portion is bisected by a second plane (BB'), the second plane (BB') being transverse to the first plane (AA'), and being centered between the first side surface (12) and the second side surface (14), and extending in the same direction as the first side surface and the second side surface, and wherein the cutting portion (18) has a radial side clearance angle (64) between the second plane (BB') and a line tangent to the first side surface (12) at the first cutting edge (20) and at the second cutting edge (22) and in a plane parallel to the first plane (AA'), the radial side clearance angle being in the range of 1° to 2.5°.

6. The cutting insert (10) according to claim 5, wherein the cutting portion (18) has a tangential side clearance angle (66) between the second plane (BB') and a line tangent to the first side surface (12) at the first cutting edge (20) or at the second cutting edge (22) and in a plane perpendicular to the first plane (AA') and the second plane (BB'), the tangential side clearance angle being in the range of 2.5° to 10° or 4° to 8°.

7. The cutting insert (10) according to any one of claims 1 to 3, wherein the first cutting face (24) has a first rake face portion (56) at the first cutting edge, and the second cutting face (26) has a second rake face portion (58) at the second cutting edge (22), wherein the first rake face portion (56) and the second rake face portion (58) are curved inwards relative to the cutting portion (18).

8. The cutting insert (10) according to any one of claims 1 to 3, wherein the cutting insert (10) has a substrate portion (38), the cutting portion (18) having a proximal end (34) and a distal end (36), the cutting portion (18) being attached to the substrate portion (38) at the proximal end (34) of the cutting portion (18), the first cutting edge (20) and the second cutting edge (22) being located at the distal end (36) of the cutting portion (18), and the substrate portion having a circular profile at the proximal end of the substrate portion.

9. The cutting insert (10) according to claim 8, wherein the substrate portion has a through circular hole (42) between the first side surface (12) and the second side surface (14).

10. The cutting insert (10) according to claim 8, wherein the substrate portion (38) has a sector-shaped portion (60) shaped as a ring, the sector having a sector angle in the range of 60° to 180°.

11. The cutting insert (10) according to claim 10, wherein the sector-shaped portion shaped as a ring has a uniform radial thickness.

12. The cutting insert (10) according to claim 8, wherein the cutting insert (10) has a thickness transverse to the first plane (AA'), and the thickness increases from the proximal end (52) of the substrate portion (38) to the distal end (36) of the cutting portion (18).

13. The cutting insert (10) according to any one of claims 1 to 3, wherein the cutting insert (10) constitutes a one-piece body.

14. The cutting insert (10) according to any one of claims 1 to 3, wherein the cutting insert has sintered or cemented carbide.

15. A cutting tool assembly, comprising: A cutting tool configured to rotate a workpiece relative to a rotational axis; And a replaceable cutting insert according to any one of claims 1 to 14, wherein the cutting tool is further configured to support the cutting insert and orient the cutting insert during use such that the first plane is transverse to the rotational axis.

16. Use of a cutting insert (10) according to any one of claims 1 to 14 for machining a rotating workpiece, wherein the cutting insert (10) is oriented such that the first plane (AA') is transverse to the rotational axis of the rotating workpiece.

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