Cutting insert, cutting tool, and method for manufacturing cut workpiece

Abstract

The present invention achieves both an improvement in the surface accuracy of a machined surface of a workpiece, and an improvement in the durability of a cutting insert. A main rake face has a linear shape that approaches a reference surface with increasing distance from a land surface in a cross-section perpendicular to an outer edge of an upper surface. The land surface has a first land surface positioned along a corner portion, and a second land surface positioned along a side portion. The first land surface has a first straight portion having a linear shape in a cross-section perpendicular to the corner portion, and the entire second land surface has a convex curved shape in a cross section perpendicular to the side portion.

Description

Cutting insert, cutting tool, and method for manufacturing machined product

[0001] The present disclosure relates to a cutting insert used in cutting a workpiece, a cutting tool, and a method for manufacturing a machined product.

[0002] For example, cutting inserts described in Patent Documents 1 and 2 are known as cutting inserts used in cutting workpieces made of metal or the like. The cutting inserts described in Patent Documents 1 and 2 have a land surface (referred to as a first rake face in Patent Document 1 and as a land in Patent Document 2) located along the outer edge of the upper surface of the cutting insert, and a rake face located along the land surface. The provision of the land surface on the cutting insert increases the cutting edge strength of the cutting edge and improves the durability of the cutting insert. Therefore, cutting inserts with land surfaces are actively used when performing cutting processes in which a large cutting load is applied to the cutting edge, such as medium-rough cutting. In the cutting inserts described in Patent Documents 1 and 2, the shape of the land surface in a cross section perpendicular to the outer edge of the upper surface (hereinafter referred to as the cross-sectional shape of the land surface) is linear, but the cross-sectional shape of the land surface may also be convexly curved.

[0003] International Publication No. WO 2011 / 037186 ​​International Publication No. WO 2015 / 141428

[0004] The cutting insert according to the present disclosure comprises an upper surface, a lower surface located opposite the upper surface, a side surface located between the upper surface and the lower surface, and a cutting edge located at the intersection of the upper surface and the side surface. A virtual axis passing through the centers of the upper surface and the lower surface is defined as the insert central axis, and a virtual plane located between the upper surface and the lower surface and perpendicular to the insert central axis is defined as the reference plane. The upper surface has an outer edge having a convexly curved corner portion and a linear side portion extending from the corner portion, a land surface located along the outer edge, and a linear rake face located along the land surface and linearly shaped so as to approach the reference plane as it moves away from the land surface in a cross section perpendicular to the outer edge. The land surface has a first land surface located along the corner portion and a second land surface located along the side portion. The first land surface has a first linear portion that is linear in a cross section perpendicular to the corner portion. The entire second land surface has a convexly curved shape in a cross section perpendicular to the side portion.

[0005] A cutting tool according to the present disclosure includes a holder and a cutting insert according to the present disclosure. The holder has a rod shape extending from a first end to a second end and has a pocket located on the first end side. The cutting insert is located in the pocket.

[0006] 1 is a schematic perspective view of a cutting insert according to an embodiment of the present disclosure. 2 is a schematic top view of the cutting insert shown in FIG. 1. 3 is an enlarged view of portion III in FIG. 2. 4 is a schematic cross-sectional view taken along line IVA-IVA in FIG. 3. 4B is an enlarged view of portion F1 of IVA in FIG. 4. 5 is a schematic cross-sectional view taken along line VA-VA in FIG. 3. 5B is an enlarged view of portion F2 of VA in FIG. 5. 6 is a schematic cross-sectional view taken along line VIA-VIA in FIG. 3. 6B is an enlarged view of portion F3 of VIA in FIG. 6. 7 is a schematic cross-sectional view taken along line VIIA-VIIA in FIG. 3. 7B is an enlarged view of portion F4 of VIIA in FIG. 7. 8 is a schematic cross-sectional view taken along line VIIIA-VIIIA in FIG. 3. VIIIB of Fig. 8 is an enlarged view of part F5 of VIIIA of Fig. 8. Fig. 8 is a schematic perspective view of a cutting tool according to an embodiment of the present disclosure. Fig. 8 is a schematic view illustrating a method for manufacturing a machined product according to an embodiment of the present disclosure. Fig. 8 is a schematic view illustrating a method for manufacturing a machined product according to an embodiment of the present disclosure. Fig. 8 is a schematic view illustrating a method for manufacturing a machined product according to an embodiment of the present disclosure.

[0007] When the cross-sectional shape of the land surface is linear, the cutting edge is sharpened, the sharpness of the cutting edge is improved, and the surface precision of the machined surface of the workpiece is improved, but chipping and the like are more likely to occur on the cutting edge, raising concerns about a decrease in durability of the cutting insert. Also, when the cross-sectional shape of the land surface is convexly curved, chipping and the like are less likely to occur on the cutting edge, and the durability of the cutting insert is improved, but it is more difficult to improve the sharpness of the cutting edge, raising concerns about a decrease in surface precision of the machined surface of the workpiece. In recent years, there has been a demand for both improved surface precision of the machined surface of the workpiece and improved durability of the cutting insert.

[0008] According to the present disclosure, it is possible to achieve both improved surface accuracy of the machined surface of the workpiece and improved durability of the cutting insert.

[0009] Hereinafter, a cutting insert, a cutting tool, and a method for manufacturing a machined product according to embodiments of the present disclosure will be described in detail with reference to the drawings. However, for the sake of convenience, the drawings referred to below show only the components necessary for explaining the embodiments in a simplified form. Therefore, the cutting insert and cutting tool according to embodiments of the present disclosure may include any components not shown in the drawings referred to. Furthermore, the dimensions of the components in the drawings do not faithfully represent the actual dimensions of the components and the dimensional ratios of each member.

[0010] In the present disclosure, "orthogonal" does not mean strictly orthogonal, but means allowing an error of about ±5 degrees. "Parallel" does not mean strictly parallel, but means allowing an error of about ±5 degrees.

[0011] <Cutting Insert> A cutting insert 10 according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 8. FIG. 1 is a schematic perspective view of the cutting insert 10 according to an embodiment of the present disclosure. FIG. 2 is a schematic top view of the cutting insert 10 shown in FIG. 1. FIG. 3 is an enlarged view of portion III in FIG. 2. IVA in FIG. 4 is a schematic cross-sectional view taken along line IVA-IVA in FIG. 3. IVB in FIG. 4 is an enlarged view of portion F1 of IVA in FIG. 4. VA in FIG. 5 is a schematic cross-sectional view taken along line VA-VA in FIG. 3. VB in FIG. 5 is an enlarged view of portion F2 of VA in FIG. 5. VIA in FIG. 6 is a schematic cross-sectional view taken along line VIA-VIA in FIG. 3. VIB in FIG. 6 is an enlarged view of portion F3 of VIA in FIG. 6. VIIA in FIG. 7 is a schematic cross-sectional view taken along line VIIA-VIIA in FIG. 3. VIIB of Fig. 7 is an enlarged view of a portion F4 of VIIA of Fig. 7. VIIIA of Fig. 8 is a schematic cross-sectional view taken along the line VIIIA-VIIIA of Fig. 3. VIIIB of Fig. 8 is an enlarged view of a portion F5 of VIIIA of Fig. 8.

[0012] As in the example shown in FIGS. 1 and 2 , the cutting insert 10 may be an exchangeable insert used for cutting a workpiece W (see FIG. 10 ). The cutting insert 10 may include an upper surface 12 and a lower surface 14 located opposite the upper surface 12. The upper surface 12 and the lower surface 14 may each be quadrilateral. In other words, the cutting insert 10 may be a quadrilateral plate. The upper surface 12 and the lower surface 14 may each be a polygonal shape other than a quadrilateral, such as a triangular shape or a pentagonal shape. In other words, the cutting insert 10 may be a polygonal plate shape other than a quadrilateral, such as a triangular plate shape or a quadrilateral plate shape. The polygonal shape is not limited to a polygonal shape in the strict sense.

[0013] 1 and 2 , the upper surface 12 and the lower surface 14 may each have a shape that is rotationally symmetrical by a certain angle about the insert central axis CS. In other words, the cutting insert 10 may have a shape that is rotationally symmetrical by a certain angle about the insert central axis CS. The insert central axis CS refers to a virtual axis that passes through the center of the upper surface 12 and the center of the lower surface 14.

[0014] The cutting insert 10 may include a plurality of side surfaces 16 located between the upper surface 12 and the lower surface 14. The plurality of side surfaces 16 may be connected to the upper surface 12 and the lower surface 14, respectively. The side surfaces 16 may function as clearance surfaces.

[0015] The cutting insert 10 may include a mounting hole 18 extending from the upper surface 12 to the lower surface 14. One opening of the mounting hole 18 may be located in the center of the upper surface 12, and the other opening of the mounting hole 18 may be located in the center of the lower surface 14. The central axis of the mounting hole 18 may coincide with the insert central axis CS.

[0016] The cutting insert 10 may include a cutting edge E located at the intersection of the top surface 12 and the side surface 16. The cutting edge E may be located at the entire intersection of the top surface 12 and the side surface 16, or may be located at a portion of the intersection.

[0017] As shown in the example in Figures 1 and 2, the top surface 12 may have an outer edge 12p that is the contour of the top surface 12. The outer edge 12p of the top surface 12 may have a first corner 20 as a corner portion and a second corner 22 as another corner portion. The first corner 20 and the second corner 22 may be positioned alternately on the outer edge 12p of the top surface 12. The first corner 20 and the second corner 22 may each have a convex curved shape that protrudes outward when viewed from above. The top view is synonymous with viewing the top surface 12 from the front. The outward direction refers to the direction away from the insert center axis CS.

[0018] 1 and 2 , the outer edge 12p of the top surface 12 may have two sides 24 extending from each of the first corners 20. Each of the sides 24 may be connected to a second corner 22. Each of the sides 24 may have a linear shape when viewed from above. The term "linear shape when viewed from above" does not necessarily mean a strictly linear shape when viewed from above, but also includes a slightly curved shape.

[0019] 1 to 3, the top surface 12 may have a land surface 26 located along the outer edge 12p. Note that the term "located along" refers to a state in which the two target areas extend in the same direction. Therefore, the two target areas may be separated from each other or may be in contact with each other.

[0020] For example, the land surface 26 being located along the outer edge 12p means that the land surface 26 extends in accordance with the shape of the outer edge 12p. In this case, the land surface 26 may be connected to the outer edge 12p, or may be slightly spaced from the outer edge 12p.

[0021] Since the cutting edge E is located at the outer edge 12p, the land surface 26 may be located along the cutting edge E. The land surface 26 may have a function of increasing the cutting edge strength of the cutting edge E. A part of the land surface 26 may have a function as a rake face. The land surface 26 may be connected to the cutting edge E.

[0022] As shown in the examples of FIGS. 1 to 5 , the top surface 12 may have a primary rake face 28 located along and inside the land surface 26. The primary rake face 28 may primarily function as a rake face. The primary rake face 28 may be connected to the land surface 26. In a cross section perpendicular to the outer edge 12p of the top surface 12, the primary rake face 28 may have a linear shape inclined relative to the reference plane BF so as to approach the reference plane BF as it moves away from the land surface 26. The reference plane BF is an imaginary plane located between the top surface 12 and the bottom surface 14 and perpendicular to the insert center axis CS. In FIGS. 4(a) to 8(c), the primary rake face 28 is illustrated in bold and has a linear shape in each cross section.

[0023] 1 to 3 , the top surface 12 may have a connecting surface 30 located along and inward of the main rake face 28. The connecting surface 30 may function as a rake face. The connecting surface 30 may be connected to the main rake face 28. The connecting surface 30 may have a shape recessed toward the reference plane BF in a cross section perpendicular to the outer edge 12p of the top surface 12.

[0024] 1 to 3 , the upper surface 12 may have a raised surface 32 located along the connecting surface 30 and on the inside of the connecting surface 30. The raised surface 32 may have a function of curling chips to improve chip discharge. The raised surface 32 may be connected to the connecting surface 30. In a cross section perpendicular to the outer edge 12p of the upper surface 12, the raised surface 32 may be inclined with respect to the reference plane BF so as to move away from the connecting surface 30.

[0025] 1 and 2 , the upper surface 12 may have an upper end surface (boss surface) 34 that surrounds one opening of the mounting hole 18. The upper end surface 34 may be perpendicular to the insert central axis CS. The upper end surface 34 may be connected to the rising surface 32 at a position more inward than the rising surface 32.

[0026] 2, the land surface 26 and the top end surface 34 may each be symmetrical with respect to the insert center line CL. The main rake face 28, the connecting surface 30, and the rising surface 32 may each be symmetrical with respect to the insert center line CL. The insert center line CL is a virtual line that passes through the vertices of the two first corners 20 and the insert axis CS when viewed from above.

[0027] 1 and 2 , the cutting edge E may have a first cutting edge Ea located at the first corner 20 and a second cutting edge Eb located at the side portion 24. The first cutting edge Ea may be located over the entire first corner 20 or may be located over a portion of the first corner 20. The second cutting edge Eb may be located over the entire side portion 24 or may be located over a portion of the side portion 24.

[0028] As shown in the examples of Figures 3, VIA in Figure 4, VA in Figure 5, VIA in Figure 6, VIIA in Figure 7, and VIIIA in Figure 8, the land surface 26 may have a first land surface 36 located along the first corner 20 and a second land surface 38 located along the side 24. The land surface 26 may have a third land surface 40 located along the side 24 between the first land surface 36 and the second land surface 38. The boundary between the first land surface 36 and the third land surface 40 is illustrated in Figures 5A and 5B.

[0029] As shown in the examples in FIGS. 3 , 4A (IVA), 4B (IVB), 5A (VA), and 5B (VB), the first land surface 36 may have a first linear portion 36s that is linear in a cross section perpendicular to the first corner 20 (a cross section perpendicular to the outer edge 12p of the top surface 12). The first linear portion 36s of the first land surface 36 may be inclined with respect to the reference plane BF in a cross section perpendicular to the first corner 20 so as to approach the reference plane BF with increasing distance from the first corner 20. The first land surface 36 may also have a first arc portion 36c that is arc-shaped in a cross section perpendicular to the first corner 20. The first arc portion 36c of the first land surface 36 may be connected to the side surface 16. In FIGS. 4B (IVB) and 5B (VB), the first linear portion 36s of the first land surface 36 is emphasized using a thick line.

[0030] In a cross section perpendicular to the first corner 20, the inclination angle θ1 of the first linear portion 36s of the first land surface 36 with respect to an imaginary plane VF perpendicular to the insert center axis CS may be smaller than the inclination angle α1 of the major rake face 28. Furthermore, the width T1 of the first land surface 36 in a direction perpendicular to the first corner 20 may increase toward the side 24 in a top view. The length M1 of the first linear portion 36s of the first land surface 36 in a cross section perpendicular to the first corner 20 may increase toward the side 24. Note that, because the reference plane BF is perpendicular to the insert center axis CS, the imaginary plane VF is parallel to the reference plane BF. Therefore, for example, the inclination angle θ1 may be replaced with the inclination angle of the first linear portion 36s with respect to the reference plane BF.

[0031] As shown in the examples of Fig. 3 , Fig. 7 VIIA, Fig. 7 VIIB, Fig. 8 VIIIA, and Fig. 8 VIIIB, the entire second land surface 38 may have a convex curved shape that protrudes upward in a cross section perpendicular to the side portion 24 (a cross section perpendicular to the outer edge 12p of the top surface 12). The second land surface 38 may have a second arc portion 38c that is arc-shaped in a cross section perpendicular to the side portion 24. The second arc portion 38c of the second land surface 38 may be connected to the side surface 16.

[0032] The width T2 of the second land surface 38 in a direction perpendicular to the side portion 24 may increase with increasing distance from the first corner 20 in a top view. The second arc portion 38c of the second land surface 38 may be connected to the side surface 16. The radius of curvature R1 of the first arc portion 36c of the first land surface 36 and the radius of curvature R2 of the second arc portion 38c of the second land surface 38 may be the same. "The two radii of curvature R1, R2 being the same" means that, taking into account manufacturing errors and the like, the difference between the two radii of curvature R1, R2 is within a range of ±5% of the average value of the two radii of curvature R1, R2.

[0033] As shown in the examples in FIGS. 3 , VA in FIG. 5 , VB in FIG. 5 , VIA in FIG. 6 , and VIB in FIG. 6 , the third land surface 40 may have a second linear portion 40s that is linear in a cross section perpendicular to the side portion 24 (a cross section perpendicular to the outer edge 12p of the top surface 12). The second linear portion 40s of the third land surface 40 may be inclined with respect to the reference plane BF in a cross section perpendicular to the side portion 24 so as to approach the reference plane BF with increasing distance from the side portion 24. The third land surface 40 may also have a third arc portion 40c that is arc-shaped in a cross section perpendicular to the side portion 24. The third arc portion 40c of the third land surface 40 may be connected to the side surface 16. In VB in FIG. 5 and VIB in FIG. 6 , the second linear portion 40s of the third land surface 40 is illustrated in bold.

[0034] In a cross section perpendicular to the side portion 24, the inclination angle θ2 of the second straight portion 40s of the third land surface 40 with respect to an imaginary plane VF perpendicular to the insert center axis CS may be smaller than the inclination angle α2 of the main rake face 28. The width T3 of the third land surface 40 in a direction perpendicular to the side portion 24 may be constant in a top view. The length M2 of the second straight portion 40s of the third land surface 40 in a cross section perpendicular to the side portion 24 may be constant. As described above, the imaginary plane VF is parallel to the reference plane BF. Therefore, for example, the inclination angle θ2 may be replaced with the inclination angle of the second straight portion 40s with respect to the reference plane BF.

[0035] The radius of curvature R1 of the first arc portion 36c of the first land surface 36, the radius of curvature R2 of the second arc portion 38c of the second land surface 38, and the radius of curvature R3 of the third arc portion 40c of the third land surface 40 may be the same. The three radii of curvature R1, R2, and R3 being the same means that, taking into account manufacturing errors and the like, the maximum difference between the three radii of curvature R1, R2, and R3 is within a range of ±5% of the average value of the three radii of curvature R1, R2, and R3.

[0036] 1 and 2, examples of the material for the cutting insert 10 include cemented carbide and cermet. Examples of cemented carbide compositions include WC-Co, which is produced by adding cobalt (Co) powder to tungsten carbide (WC) and sintering the mixture; WC-TiC-Co, which is produced by adding titanium carbide (TiC) to WC-Co; and WC-TiC-TaC-Co, which is produced by adding tantalum carbide (TaC) to WC-TiC-Co. Cermets are sintered composite materials in which a ceramic component is combined with a metal, and specific examples include sintered composite materials whose main components are titanium carbide (TiC) and titanium nitride (TiN) or other titanium compounds.

[0037] The surface of the cutting insert 10 may be coated with a coating by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The coating may have a composition of titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al ２ O ３ ) etc.

[0038] According to the embodiment of the present disclosure, the first land surface 36 is located along the first corner 20, which will be located near the machining surface of the workpiece W. The first land surface 36 has a first linear portion 36s that is linear in a cross section perpendicular to the first corner 20. Therefore, according to the embodiment of the present disclosure, the first cutting edge Ea of the cutting edge E can be sharpened to improve the sharpness of the cutting edge E and thereby improve the surface precision of the workpiece W.

[0039] According to the embodiment of the present disclosure, the second land surface 38 is located along the side portion 24, which is away from the machining surface of the workpiece W and plays a major role in cutting the workpiece W. The entire second land surface 38 has a convex curved shape in a cross section perpendicular to the side portion 24. Therefore, according to the embodiment of the present disclosure, chipping or the like is less likely to occur on the cutting edge E, and the durability of the cutting insert 10 can be improved.

[0040] In other words, according to the embodiment of the present disclosure, it is possible to achieve both improvement in the surface precision of the workpiece W and improvement in the durability of the cutting insert 10 .

[0041] If the first straight portion 36s of the first land surface 36 approaches the reference plane BF as it moves away from the first corner 20 in a cross section perpendicular to the first corner 20, the first cutting edge Ea can be made sharper, the sharpness of the cutting edge E can be improved, and the surface precision of the workpiece W can be further improved.

[0042] In a cross section perpendicular to the first corner 20, when the inclination angle θ1 of the first straight portion 36s of the first land surface 36 is smaller than the inclination angle α1 of the main cutting face 28, the cutting edge strength of the cutting edge E, particularly the cutting edge strength of the first cutting edge Ea, can be sufficiently increased while ensuring space for the chips to flow, thereby controlling the flow of the chips.

[0043] When the radius of curvature R1 of the first arc portion 36c of the first land surface 36 and the radius of curvature R2 of the second arc portion 38c of the second land surface 38 are the same, variation in the sharpness of the cutting edge E is reduced, and the surface precision of the workpiece W is further improved. In particular, when the radius of curvature R1 of the first arc portion 36c of the first land surface 36, the radius of curvature R2 of the second arc portion 38c of the second land surface 38, and the radius of curvature R3 of the third arc portion 40c of the third land surface 40 are the same, variation in the sharpness of the cutting edge E can be sufficiently reduced, and the surface precision of the workpiece W can be further improved.

[0044] When the width T1 of the first land surface 36 in the direction perpendicular to the first corner 20 increases toward the side portion 24, the portion of the first cutting edge Ea away from the second cutting edge Eb can be made sharper, thereby further improving the sharpness of the cutting edge E and further improving the surface precision of the workpiece W. In particular, when the length M1 of the first straight portion 36s of the first land surface 36 in the cross section perpendicular to the first corner 20 increases toward the side portion 24, the portion of the first cutting edge Ea away from the second cutting edge Eb can be made even sharper, further improving the surface precision of the workpiece W.

[0045] When the width T2 of the second land surface 38 in the direction perpendicular to the side portion 24 increases with increasing distance from the first corner 20, the cutting edge strength of the cutting edge E can be increased in a region of the second land surface 38 that is farther from the first land surface 36. This makes it less likely for chipping to occur on the cutting edge E even in cutting with a large cutting depth (cutting with a large cutting amount), and the durability of the cutting insert 10 can be further improved.

[0046] When the third land surface 40 has the second straight portion 40s having a straight line shape in a cross section perpendicular to the side portion 24, a significant decrease in the sharpness of the cutting edge E can be avoided even under the first machining conditions using the first cutting edge Ea and the second cutting edge Eb, compared to when the entire portion of the land surface 26 along the side portion 24 is the second land surface 38. This makes it possible to improve the surface precision of the workpiece W even under the first machining conditions.

[0047] When the width T3 of the third land surface 40 in the direction perpendicular to the side portion 24 is constant, under the second machining conditions in which the first land surface 36 and the third land surface 40 contribute to chip flow control and the second land surface 38 does not contribute to chip flow control, the chip flow direction is aligned on the third land surface 40. As a result, under the second machining conditions, the chip flow on the third land surface 40 becomes dominant, making it difficult for chips to clog the land surface 26 and improving chip dischargeability.

[0048] <Cutting Tool> A cutting tool 42 according to an embodiment of the present disclosure will be described with reference to Fig. 9. Fig. 9 is a schematic perspective view of the cutting tool 42 according to an embodiment of the present disclosure.

[0049] As shown in FIG. 9 , a cutting tool 42 according to an embodiment of the present disclosure may be a tool used for turning, which is a type of cutting process. Examples of turning processes include external diameter machining, grooving, and cut-off. The cutting tool 42 according to an embodiment of the present disclosure may include a rod-shaped holder 44. The holder 44 may extend from a first end (front end) 44 a to a second end (rear end) 44 b. The holder 44 may be made of a metal material such as steel. The holder 44 may have a pocket 46 located on the side of the first end 44 a. The holder 44 may have a screw hole opening into the pocket 46.

[0050] The cutting tool 42 may include a cutting insert 10 positioned in a pocket 46 of a holder 44. The cutting insert 10 is attached to the pocket 46 of the holder 44 by threading a clamp screw 48 inserted into the mounting hole 18 of the cutting insert 10 into the screw hole of the holder 44 and tightening the clamp screw 48.

[0051] In the present disclosure, the cutting tool 42 used for turning, which is one type of cutting work, is exemplified, but a cutting tool used for milling, which is one type of cutting work, may include the cutting insert 10 as a component.

[0052] <Method for manufacturing machined product> A method for manufacturing a machined product according to an embodiment of the present disclosure will be described with reference to Fig. 10 to Fig. 12. Fig. 10 to Fig. 12 are schematic views illustrating a method for manufacturing a machined product according to an embodiment of the present disclosure.

[0053] As shown in the examples of FIGS. 10 to 12 , the method for manufacturing a machined product according to an embodiment of the present disclosure is a method for manufacturing a machined product M, which is a workpiece W that has been machined, and includes a first step, a second step, and a third step. The first step is a step of rotating the workpiece W around its axis S. The second step is a step of bringing the cutting insert 10 of the cutting tool 42 into contact with the rotating workpiece W to cut the workpiece W. The third step is a step of separating the cutting tool 42 from the cut workpiece W. Examples of materials for the workpiece W include stainless steel, carbon steel, alloy steel, cast iron, and non-ferrous metals. The specific details of the method for manufacturing a machined product according to the embodiment are as follows.

[0054] First, the cutting tool 42 is attached to the tool post of the lathe, and the workpiece W is attached to the chuck of the lathe. Next, as shown in the example of Fig. 10, the chuck is rotated to rotate the workpiece W around its axis S (first step). Then, as shown in the example of Fig. 11, the cutting tool 42 is moved in the direction of arrow D1 to approach the workpiece W, and the cutting insert 10 of the cutting tool 42 is brought into contact with the rotating workpiece W, thereby cutting the workpiece W (second step). This allows a machined surface Wf to be formed on the workpiece W.

[0055] 12 , the cutting tool 42 is moved in the direction of arrow D2 to separate the cutting tool 42 from the workpiece W (third step). This completes the cutting of the workpiece W, and a machined product M can be produced, which is the machined workpiece W. Because the cutting insert 10 of the cutting tool 42 has excellent cutting ability for the reasons described above, a machined product M with excellent machining accuracy can be produced.

[0056] To continue the cutting process, the cutting insert 10 of the cutting tool 42 may be repeatedly brought into contact with different locations on the workpiece W while the workpiece W is being rotated. In the embodiment of the present disclosure, the cutting tool 42 is brought close to the workpiece W, but since it is sufficient that the cutting tool 42 and the workpiece W are brought relatively close to each other, the workpiece W may also be brought close to the cutting tool 42. In this regard, the cutting tool 42 is moved away from the workpiece W in the same manner.

[0057] In one embodiment, (1) the cutting unit includes an upper surface, a lower surface located opposite the upper surface, a side surface located between the upper surface and the lower surface, and a cutting edge located at an intersection of the upper surface and the side surface. When a virtual axis passing through the centers of the upper surface and the lower surface is defined as an insert central axis, and a virtual plane located between the upper surface and the lower surface and perpendicular to the insert central axis is defined as a reference plane, the upper surface has an outer edge having a convexly curved corner portion and a linear side portion extending from the corner portion, a land surface located along the outer edge, and a main rake face located along the land surface and linearly approaching the reference plane as it moves away from the land surface in a cross section perpendicular to the outer edge. The land surface includes a first land surface located along the corner portion and a second land surface located along the side portion. The first land surface has a first linear portion that is linear in a cross section perpendicular to the corner portion. The entire second land surface has a convex curved shape in a cross section perpendicular to the side portion.

[0058] (2) In the cutting insert of (1), the width of the first straight portion in a direction perpendicular to the corner portion may be such that, in a cross section perpendicular to the corner portion, the width approaches the reference plane as it moves away from the corner portion.

[0059] (3) In the cutting insert of (2) above, in a cross section perpendicular to the corner portion, the inclination angle of the first straight line portion with respect to an imaginary plane perpendicular to the insert center axis may be smaller than the inclination angle of the main cutting face.

[0060] (4) In the cutting insert according to any one of (1) to (3), the first land surface may further include a first arc portion connected to the side surface and having an arc shape in a cross section perpendicular to the corner portion. The second land surface may include a second arc portion connected to the side surface and having an arc shape in a cross section perpendicular to the edge portion. The first arc portion and the second arc portion may have the same radius of curvature.

[0061] (5) In the cutting insert according to any one of (1) to (4), the width of the first land surface in a direction perpendicular to the corner portion may increase toward the side portion.

[0062] (6) In the cutting insert of (5), the length of the first linear portion in a cross section perpendicular to the corner portion may increase toward the side portion.

[0063] (7) In the cutting insert according to any one of (1) to (6), the width of the second land surface in a direction perpendicular to the side portion may increase with increasing distance from the corner portion.

[0064] (8) In the cutting insert according to any one of (1) to (7), the land surface may further include a third land surface located along the side portion between the first land surface and the second land surface. The third land surface may include a second linear portion having a linear shape in a cross section perpendicular to the side portion.

[0065] (9) In the cutting insert of (8), the width of the third land surface in a direction perpendicular to the side portion may be constant.

[0066] (10) A cutting tool includes a holder having a rod shape extending from a first end to a second end and having a pocket located on the side of the first end, and a cutting insert of any one of (1) to (9) located in the pocket.

[0067] (11) The method includes the steps of rotating a workpiece, bringing the cutting tool of (10) into contact with the rotating workpiece, and moving the cutting tool away from the workpiece.

[0068] The invention according to the present disclosure has been described above based on the drawings and embodiments. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art can easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure.

[0069] 10 Cutting insert 12 Upper surface 12p Outer edge 14 Lower surface 16 Side surface 18 Mounting hole 20 First corner (corner portion) 22 Second corner (other corner portion) 24 Side portion 26 Land surface 28 Main rake face 30 Connecting surface 32 Rising surface 34 Upper end surface 36 First land surface 36s First linear portion 36c First arc portion 38 Second land surface 38c Second arc portion 40 Third land surface 40s Second linear portion 40c Third arc portion 42 Cutting tool 44 Holder 46 Pocket 48 Clamp screw E Cutting edge Ea First cutting edge Eb Second cutting edge

Claims

1. The top surface and a lower surface located opposite the upper surface; and A side surface located between the upper surface and the lower surface; a cutting edge located at an intersection of the top surface and the side surface, When a virtual axis passing through the center of the upper surface and the center of the lower surface is defined as a center axis of the insert, and a virtual plane located between the upper surface and the lower surface and perpendicular to the center axis of the insert is defined as a reference plane, The upper surface is An outer edge having a convex curved corner portion and a straight side portion extending from the corner portion; a land surface located along the outer edge; a main rake face located along the land surface and having a linear shape in a cross section perpendicular to the outer edge so as to approach the reference surface as it moves away from the land surface; The land surface is a first land surface located along the corner portion; a second land surface located along the side portion, the first land surface has a first straight line portion having a straight line shape in a cross section perpendicular to the corner portion, The cutting insert, wherein the entire second land surface has a convex curved shape in a cross section perpendicular to the side portion.

2. The cutting insert according to claim 1 , wherein the first straight portion approaches the reference surface as it moves away from the corner portion in a cross section perpendicular to the corner portion.

3. The cutting insert according to claim 2 , wherein in a cross section perpendicular to the corner portion, an inclination angle of the first straight portion with respect to a virtual plane perpendicular to the insert central axis is smaller than an inclination angle of the main rake face.

4. the first land surface further includes a first arc portion connected to the side surface and having an arc shape in a cross section perpendicular to the corner portion, the second land surface has a second arc portion connected to the side surface and having an arc shape in a cross section perpendicular to the side portion, The cutting insert according to claim 1 , wherein a radius of curvature of the first arcuate portion and a radius of curvature of the second arcuate portion are the same.

5. The cutting insert according to claim 1 , wherein a width of the first land surface in a direction perpendicular to the corner portion increases toward the side portion.

6. The cutting insert according to claim 5 , wherein a length of the first straight portion in a cross section perpendicular to the corner portion increases toward the side portion.

7. The cutting insert according to claim 1 , wherein a width of the second land surface in a direction perpendicular to the side portion increases with increasing distance from the corner portion.

8. the land surface further includes a third land surface located along the side portion between the first land surface and the second land surface, The cutting insert according to claim 1 , wherein the third land surface has a second straight line portion having a straight line shape in a cross section perpendicular to the side portion.

9. The cutting insert according to claim 8 , wherein a width of the third land surface in a direction perpendicular to the side portion is constant.

10. a holder having a rod shape extending from a first end to a second end and having a pocket located on the first end side; A cutting tool comprising: a cutting insert according to claim 1 located in the pocket.

11. Rotating the workpiece; contacting the rotating workpiece with the cutting tool according to claim 10; and removing the cutting tool from the workpiece.