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

Abstract

To enhance the effect of cooling a cutting edge by a coolant, and to improve the durability and chip dischargeability of a cutting insert. This cutting insert has: an upper surface having a corner and a first side; a corner side surface; and a corner cutting edge. The upper surface further includes a corner land surface extending along the corner cutting edge and inclined upwards away from the corner cutting edge, and a plurality of corner grooves extending from the corner land surface. The plurality of corner grooves have a first corner groove and a second corner groove located closer to the first side than the first corner groove. In a side view of the corner side surface, the lower end of the opening edge of the first corner groove opening on the corner land surface is located higher than the lower end of the opening edge of the second corner groove opening on the corner land surface.

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] An example of a cutting insert used when cutting a workpiece is the cutting insert described in Patent Document 1. During cutting, a coolant, such as a cooling solvent, is usually sprayed toward the cutting insert to remove chips and cool the cutting insert. In order to enhance the cooling effect of the coolant on the cutting edge, the cutting insert described in Patent Document 1 is provided with a groove.

[0003] Japanese Patent Application Publication No. 2014-018891

[0004] The cutting insert according to the present disclosure has an upper surface having a corner and a first side connected to the corner, a corner side surface connected to the corner, and a corner cutting edge located at the corner, and the upper surface further has a corner land surface extending along the corner cutting edge and inclining upward as it moves away from the corner cutting edge, and a plurality of corner grooves extending from the corner land surface toward the inside of the upper surface, the plurality of corner grooves including a first corner groove and a second corner groove located closer to the first side than the first corner groove, and in a side view of the corner side surface, the lower end of an opening edge of the first corner groove opening to the corner land surface is located higher than the lower end of an opening edge of the second corner groove opening to the corner land surface.

[0005] 1 is a schematic perspective view of a cutting tool according to an embodiment of the present disclosure. 2 is a schematic side view of the cutting tool shown in FIG. 1. 3 is a schematic perspective view of a cutting insert according to an embodiment of the present disclosure. 4 is a schematic top view of the cutting insert shown in FIG. 3. 5 is a schematic side view of the cutting insert shown in FIG. 3, as viewed from direction A1 in FIG. 4. 6 is an enlarged view of region VI in FIG. 3, which is a schematic enlarged perspective view of a portion of a cutting insert according to an embodiment of the present disclosure. 7 is an enlarged view of region VII in FIG. 4, which is a schematic enlarged perspective view of a portion of a cutting insert according to an embodiment of the present disclosure. 8 is an enlarged view of region VIII in FIG. 5, which is a schematic enlarged perspective view of a portion of a cutting insert according to an embodiment of the present disclosure. 9 is a cross-sectional view taken along line X-X in FIG. 7. 10 is a cross-sectional view taken along lines XI-A, XI-B, and XI-C in FIG. 7. 11 is a schematic view illustrating a method for manufacturing a machined product according to an embodiment of the present disclosure.

[0006] 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 simplified views of only the components necessary for explaining the embodiments. Therefore, the cutting insert according to the embodiments of the present disclosure may include any components not shown in the drawings referred to. 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. Furthermore, in this disclosure, "parallel" does not mean strictly parallel, but means that an error of about ±5 degrees is allowed.

[0007] <Cutting Tool> A cutting tool 1 according to an embodiment of the present disclosure will be described with reference to Figures 1 and 2. As shown in the example of Figures 1 and 2, the cutting tool 1 according to an embodiment of the present disclosure is a turning tool used for turning a workpiece W (see Figure 12) as a cutting tool. The cutting of the workpiece W includes external diameter machining, internal diameter machining, grooving, cut-off, and the like. The cutting tool 1 may also have a holder 2 attached to a tool post of a lathe and a cutting insert 10 held by the holder 2.

[0008] The holder 2 may have a square bar shape extending from a leading end 2a, which is a first end, to a rear end 2b, which is a second end. The holder 2 may have a bar shape other than a square bar shape, such as a round bar shape. Examples of materials for the holder 2 include metals such as stainless steel, carbon steel, cast iron, and aluminum alloy. A pocket 3 for holding the cutting insert 10 may be located on the leading end 2a side of the holder 2. The length of the holder 2 may be set to, for example, 100 mm to 400 mm.

[0009] The tip 2a of the holder 2 may be provided with an injection port 4 for injecting coolant, in other words, a cooling medium, toward the cutting insert 10. The coolant may be, for example, a water-insoluble or water-soluble oil, and may be appropriately selected depending on the material of the workpiece W. Examples of water-insoluble oils include oil-based, inactive extreme pressure, and active extreme pressure cutting oils. Examples of water-soluble oils include emulsions, solubles, and solutions. The coolant is not limited to a liquid, but may also be a gas such as an inert gas.

[0010] The cutting insert 10 may be located in the pocket 3 of the holder 2. The cutting insert 10 may be fixed to the pocket 3 of the holder 2 by a clamping member 5. The clamping member 5 may be provided with an injection port 6 for injecting coolant toward the cutting insert 10. The cutting insert 10 may be fixed to the pocket 3 of the holder 2 by a fixing screw instead of the clamping member 5.

[0011] <Cutting Insert> The configuration of the cutting insert 10 according to the embodiment of the present disclosure will be described with reference to Figures 3 to 11. As in the examples shown in Figures 3 to 5, the cutting insert 10 according to the embodiment of the present disclosure may have a base portion 11 for attachment to the pocket 3 of the holder 2. The base portion 11 may have a base portion upper surface 12 and a base portion bottom surface 13 located opposite the base portion upper surface 12. The base portion upper surface 12 and the base portion bottom surface 13 may each be a substantially polygonal shape, such as a substantially square shape. In other words, the base portion 11 may have a substantially polygonal shape, such as a substantially square shape.

[0012] The base 11 may have a plurality of side surfaces located between the base top surface 12 and the base bottom surface 13, and any of the plurality of side surfaces may be a corner side surface 26 described below. The base 11 may have a through hole 14 in its center for inserting the clamp member 5 or fixing screw described above. The through hole 14 may be open on the side of the base top surface 12 and the side of the base bottom surface 13.

[0013] The cutting insert 10 according to the embodiment of the present disclosure may have a cutting portion 20 that comes into contact with a workpiece W to perform cutting. As in the examples shown in Figs. 3 and 4 , the cutting portion 20 may be provided at two opposing corners of the base portion 11. Alternatively, the cutting portion 20 may be provided at only one of the corners of the base portion 11. Alternatively, the cutting portion 20 may be provided at each of the corners of the base portion 11.

[0014] 3 and 4, the cutting portion 20 is located at the intersection of the base portion top surface 12 and the side surface of the base portion 11, but is not limited to this configuration. For example, the cutting portion 20 may be located at the intersection of the base portion bottom surface 13 and the side surface of the base portion 11. Furthermore, the cutting portion 20 may be located at the intersection of the base portion top surface 12 and the side surface of the base portion 11, and at the intersection of the base portion bottom surface 13 and the side surface of the base portion 11, respectively.

[0015] Examples of the material of the cutting portion 20 include hard materials such as cBN (Cubic Boron Nitride) and PCD (Polycrystalline Diamond). The cutting portion 20 may be joined to the base portion 11 with a brazing material. Examples of the material of the base portion 11 include cemented carbide and cermet.

[0016] Examples of cemented carbide compositions include WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co. WC-Co is produced by adding cobalt (Co) powder to tungsten carbide (WC) and sintering the resulting mixture. WC-TiC-Co is produced by adding titanium carbide (TiC) to WC-Co. WC-TiC-TaC-Co is produced by adding tantalum carbide (TaC) to WC-TiC-Co. Cermets are sintered composite materials that combine ceramic components with metals. Specific examples of cermets include those primarily composed of titanium compounds such as titanium carbide (TiC) and titanium nitride (TiN).

[0017] The surface of the cutting insert 10 may be coated with a film by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The material of the film may be, for example, titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), or alumina (Al ２ O ３ ) etc.

[0018] (Cutting portion) A specific configuration of the cutting portion 20 of the cutting insert 10 according to the embodiment of the present disclosure will be described with reference to Figures 6 to 11. As in the examples shown in Figures 6 and 8, the cutting portion 20 of the cutting insert 10 may have a cutting portion upper surface (upper surface) 21, which is the upper surface of the cutting portion 20. The cutting portion upper surface 21 may function as a rake surface for channeling chips. The cutting portion upper surface 21 may constitute the upper surface of the cutting insert 10 together with the base portion upper surface 12 (see Figures 3 to 5).

[0019] The cutting portion upper surface 21 may have a corner 22 and a first side 23 connected to the corner 22. The corner 22 may be curved. The first side 23 may be straight or slightly curved. The cutting portion upper surface 21 may also have a second side 24 connected to the corner 22 on the opposite side to the first side 23.

[0020] The cutting portion 20 may have a corner side surface 26 connected to the corner 22. The corner side surface 26 may function as a clearance surface. The cutting portion 20 may have a first side surface 27 connected to the first side 23, and the first surface 27 may function as a clearance surface. The cutting portion 20 may have a second side surface 28 connected to the second side 24, and the second surface 28 may function as a clearance surface.

[0021] The cutting portion 20 may have a corner cutting edge Ec located at the corner 22. The corner cutting edge Ec may be located at the intersection of the cutting portion upper surface 21 and the corner side surface 26. The corner cutting edge Ec may be located over the entire area or a part of the corner 22. As shown in the example of FIG. 8, the corner cutting edge Ec may have a rounded surface that has been honed to increase the rigidity of the cutting edge.

[0022] The cutting portion 20 may have a first cutting edge E1 located on the first side 23. The first cutting edge E1 may be located at the intersection of the cutting portion upper surface 21 and the first side surface 27. The first cutting edge E1 may be located over the entire area or a portion of the first side surface 27. The cutting portion 20 may have a second cutting edge E2 located on the second side 24. The second cutting edge E2 may be located at the intersection of the cutting portion upper surface 21 and the second side surface 28. The second cutting edge E2 may be located over the entire area or a portion of the second side surface 28. As in the example shown in FIG. 8 , the first cutting edge E1 and the second cutting edge E2 may have surfaces that have been subjected to homing to increase the rigidity of the cutting edge.

[0023] The cutting portion upper surface 21 may have a corner land surface 30. As shown in the example of Fig. 8, the corner land surface 30 may extend along the corner cutting edge Ec and be inclined upward as it moves away from the corner cutting edge Ec. In other words, the corner land surface 30 may be a negative land.

[0024] The corner land surface 30 may be located on the outer edge of the cutting portion upper surface 21. The corner land surface 30 may have a function of increasing the strength of the corner cutting edge Ec. When viewed from above, the corner land surface 30 may be set as a band-shaped region with a width of, for example, about 0.03 mm to 0.5 mm.

[0025] The cutting portion upper surface 21 may have a first land surface 31 and a second land surface 32. The first land surface 31 may extend along the first cutting edge E1 and be inclined upward as it moves away from the first cutting edge E1. The second land surface 32 may extend along the second cutting edge E2 and be inclined upward as it moves away from the second cutting edge E2.

[0026] 6 and 7, the cutting portion upper surface 21 may have a flat surface 33 located more inward of the cutting portion upper surface 21 than the corner land surface 30. The flat surface 33 may be located more inward of the cutting portion upper surface 21 than the corner land surface 30 located on the outer edge of the cutting portion upper surface 21, that is, on the side of the base portion upper surface 12 (see FIGS. 3 to 5).

[0027] 6 and 7 , the cutting portion upper surface 21 may have a plurality of corner grooves 40 extending from the corner land surface 30 toward the inside of the cutting portion upper surface 21. Each of the plurality of corner grooves 40 may function as a coolant reservoir for storing coolant. The number of the plurality of corner grooves 40 is not limited to a specific value.

[0028] The cutting portion upper surface 21 is configured to have a plurality of corner grooves 40, so that the coolant can be efficiently supplied to the corner cutting edge Ec, thereby enhancing the cooling effect of the coolant on the corner cutting edge Ec.

[0029] 7 , the corner grooves 40 may be formed on both sides of the perpendicular bisector L of the corner cutting edge Ec. That is, a first group G1 made up of the corner grooves 40 may be formed on one side of the perpendicular bisector L, and a second group G2 made up of the corner grooves 40 may be formed on the other side of the perpendicular bisector L.

[0030] For the sake of convenience, the following description will focus on the corner grooves 40 included in the first group G1, and will omit a description of the corner grooves 40 included in the second group G2. In the case of the corner grooves 40 included in the second group G2, the first side 23 may be replaced with the second side 24 in the following description of the corner grooves 40 included in the first group G1.

[0031] 6 and 7 , each of the multiple corner grooves 40 may be spaced apart from the corner cutting edge Ec. Each of the multiple corner grooves 40 may be connected to the corner land surface 30. Each of the multiple corner grooves 40 may be connected to a flat surface 33. When multiple corner grooves 40 are connected to the flat surface 33, coolant tends to flow from the flat surface 33 into each of the multiple corner grooves 40. As a result, coolant tends to accumulate in each of the multiple corner grooves 40.

[0032] The multiple corner grooves 40 may include a first corner groove 41 to a fourth corner groove 44. The second corner groove 42 may be located closer to the first side 23 than the first corner groove 41, the third corner groove 43 may be located closer to the first side 23 than the second corner groove 42, and the fourth corner groove 44 may be located closer to the first side 23 than the third corner groove 43.

[0033] 8 and 9, the opening edge 41a may open to the corner land surface 30 of the first corner groove 41, and the opening edge 42a may open to the corner land surface 30 of the second corner groove 42. Also, as in the example shown in Figures 8 and 9, in a side view of the corner side surface 26, a lower end 41aa of the opening edge 41a of the first corner groove 41 may be located higher than a lower end 42aa of the opening edge 42a of the second corner groove 42. In a side view of the corner side surface 26, the lower the lower end of the opening edge of the corner groove 40 is located, the closer the corner groove 40 is to the corner cutting edge Ec.

[0034] The cutting load on the corner cutting edge Ec is small on the side closer to the first side 23 where the cutting edge angle is small, and increases toward the center of the corner cutting edge Ec where the cutting edge angle is large. The center of the corner cutting edge Ec is the part through which the perpendicular bisector L (see FIG. 7) passes. In other words, the center side of the corner cutting edge Ec is an area where the chips are thick and the cutting load is large, and the side closer to the first side 23 is an area where the chips are thin and the cutting load is small.

[0035] Therefore, if the lower ends of the plurality of corner grooves 40 are configured uniformly low in order to ensure a cooling effect, a sufficient thickness cannot be ensured at the center of the corner cutting edge Ec, resulting in a decrease in durability. Conversely, if the lower ends of the opening edges of the plurality of corner grooves 40 are configured uniformly high in order to emphasize durability, the cooling effect will be insufficient.

[0036] In the case of the first corner groove 41 and the second corner groove 42, the first corner groove 41 is located in an area where the cutting load is greater than that of the second corner groove 42. With the above configuration, the first corner groove 41, which is located in an area where the cutting load is greater, can be separated from the corner cutting edge Ec to ensure durability. Furthermore, with the above configuration, the second corner groove 42, which is located in an area where the cutting load is smaller than that of the first corner groove 41, can be positioned closer to the corner cutting edge Ec to ensure a cooling effect.

[0037] Furthermore, with the above configuration, the difference in flow velocity between the inside and outside of the chips generated at the corner cutting edge Ec increases, promoting chip curling without increasing resistance and improving chip discharge performance.

[0038] Specifically, when the cutting portion upper surface 21 has a plurality of corner grooves 40, chips are more likely to be drawn into these corner grooves 40. In such a case, the plurality of corner grooves 40 can function as guides, which makes it easier to stabilize the direction in which the chips flow.

[0039] Furthermore, as the chips are drawn into the corner grooves 40, streaks are formed along the corner grooves 40. The formation of these streaks hardens the chips, which tends to stabilize their behavior. Therefore, when a difference in flow speed occurs between the inside and outside of the chips generated by the corner cutting edge Ec, the curling of the chips can be stably promoted.

[0040] In other words, the above configuration enhances the cooling effect of the corner cutting edge Ec by the coolant, while improving the durability of the corner cutting edge Ec, in other words, the cutting insert 10, and also improving the chip removal performance.

[0041] 9, dots are added to lower ends 41aa to 44aa and centers 41ab to 44ab of the lower edges of the opening edges 41a to 44a of the first corner groove 41 to the fourth corner groove 44. In the following, the lower end of the opening edge of the corner groove 40 may be simply referred to as the lower end of the corner groove 40, and the center of the lower edge of the opening edge of the corner groove 40 may be simply referred to as the center of the corner groove 40.

[0042] 8 and 9, the opening edge 43a may open to the corner land surface 30 of the third corner groove 43. Furthermore, as in the example shown in Figures 8 and 9, the lower end 42aa of the opening edge 42a of the second corner groove 42 may be located higher than the lower end 43aa of the opening edge 43a of the third corner groove 43 in a side view of the corner side surface 26.

[0043] With this configuration, in a side view of the corner side surface 26, the lower ends of the multiple corner grooves 40 are positioned gradually lower as they approach the first side 23, that is, closer to the corner cutting edge Ec. Therefore, corner grooves 40 located in areas where the cutting load is relatively large can be spaced away from the corner cutting edge Ec to ensure durability. Also, corner grooves 40 located in areas where the cutting load is relatively small can be positioned closer to the corner cutting edge Ec to further enhance the cooling effect of the corner cutting edge Ec.

[0044] 8 and 9 , the opening edge 44a may open to the corner land surface 30 of the fourth corner groove 44. In addition, in a side view of the corner side surface 26, the lower end 43aa of the opening edge 43a of the third corner groove 43 may be located higher than the lower end 44aa of the opening edge 44a of the fourth corner groove 44.

[0045] Also, as in the example shown in Figure 9, in a side view of the corner side surface 26, the lower end 41aa of the opening edge 41a in the first corner groove 41 may be located closer to the first side 23 than the center 41ab of the lower edge of the opening edge 41a.

[0046] 7, in a plan view of the cutting portion upper surface 21, the lower edge of the opening edge 41a of the first corner groove 41 is closer to the corner cutting edge Ec on the side closer to the first side 23 than on the side closer to the center of the corner cutting edge Ec. As a result, the lower edge of the first corner groove 41 is farther from the corner cutting edge Ec in areas where the cutting load is heavy and closer to the corner cutting edge Ec in areas where the cutting load is lighter, thereby ensuring the durability of the corner cutting edge Ec and improving the cooling effect of the corner cutting edge Ec.

[0047] In this case, as shown in the example of Fig. 9, in a side view of the corner side surface 26, the lower end of the opening edge of each of the plurality of corner grooves 40 that opens into the corner land surface 30 may be located closer to the first side 23 than the center of the lower edge of the opening edge of each of the plurality of corner grooves 40. Specifically, in a side view of the corner side surface 26, the lower end 42aa of the second corner groove 42 may be located closer to the first side 23 than the center 42ab. Also, in a side view of the corner side surface 26, the lower end 43aa of the third corner groove 43 may be located closer to the first side 23 than the center 43ab. Furthermore, in a side view of the corner side surface 26, the lower end 44aa of the fourth corner groove 44 may be located closer to the first side 23 than the center 44ab.

[0048] With this configuration, the position of the lower edge of each of the multiple corner grooves 40 is farther from the corner cutting edge Ec in areas where the cutting load is large, and is closer to the corner cutting edge Ec in areas where the cutting load is small. This further improves the cooling effect of the corner cutting edge Ec while ensuring the durability of the corner cutting edge Ec.

[0049] 7, in a plan view of the cutting portion upper surface 21, the multiple corner grooves 40 may each be spaced apart from the outer edge of the cutting portion upper surface 21. In other words, in a plan view of the cutting portion upper surface 21, the multiple corner grooves 40 may each be located apart from the corner cutting edge Ec.

[0050] With this configuration, all of the multiple corner grooves 40 are spaced apart from the outer edge of the upper surface 21 of the cutting portion, thereby increasing the durability of the corner cutting edge Ec compared to a configuration in which there are corner grooves that intersect with the outer edge of the upper surface 21 of the cutting portion.

[0051] Furthermore, in this case, as in the example shown in FIG. 7, the first corner groove 41 may be farther from the outer edge of the cutting portion upper surface 21 than the second corner groove 42 when viewed from above.

[0052] With this configuration, the first corner groove located in the area where the cutting load is large is spaced apart from the corner cutting edge Ec, while the second corner groove located in the area where the cutting load is small is spaced apart from the corner cutting edge Ec, thereby ensuring the durability of the corner cutting edge Ec and enhancing the cooling effect of the corner cutting edge Ec.

[0053] As shown in the example of FIG. 7, the directions in which the corner grooves 40 extend may be parallel to one another in a plan view of the cutting portion upper surface 21.

[0054] With this configuration, when the plurality of corner grooves 40 play the role of a guide as described above, this role can be enhanced, and the direction in which chips flow is more likely to be stabilized.

[0055] 7, in a plan view of the cutting portion upper surface 21, the multiple corner grooves 40 may each extend in a direction approaching the perpendicular bisector L of the corner cutting edge Ec as they move inward on the cutting portion upper surface 21. In other words, in a plan view of the cutting portion upper surface 21, each of the first corner groove 41 to the fourth corner groove 44 may extend in a direction approaching the perpendicular bisector L.

[0056] With this configuration, when the corner grooves 40 are extended in the direction in which they extend, the angle at which they intersect with the corner cutting edge Ec can approach 90°. That is, the direction in which the chips flow can be made closer to parallel to the direction in which the corner grooves 40 extend. This improves the guiding role of the corner grooves 40.

[0057] 10 , the first corner groove 41 may have a bottom 41c and an outer wall 41d in a first cross section D1 that is parallel to the extension direction of the first corner groove 41 and perpendicular to the plane 33. The outer wall 41d may rise from the bottom 41c and connect the bottom 41c and the corner land surface 30.

[0058] With this configuration, even if the corner cutting edge Ec becomes worn due to cutting processing, the outer wall portion 41d makes it difficult for the corner cutting edge Ec to reach the first corner groove 41, making it possible to create a configuration that can withstand wear.

[0059] As shown in the example of FIG. 10, the first corner groove 41 may have a bottom 41c that is curved upward and convex in the first cross section D1.

[0060] While the direction of chip flow tends to be stable when chips are drawn into the first corner groove 41, there is a risk that the first corner groove 41 may be worn due to friction or that the flow of chips may become stagnant. However, this configuration makes it possible to prevent chips from entering too far into the first corner groove 41 while still ensuring space for coolant to accumulate in the first corner groove 41. This is because the apex of the convex bottom portion 41c reduces chips from entering too far into the first corner groove 41.

[0061] From the viewpoint of efficiently reducing chips from getting too far into the first corner groove 41, the bottom portion 41c in the first cross section D1 may have a convex curved shape that curves upward.

[0062] 10 , in the first cross section D1, the outer wall portion 41d may be inclined so as to approach the outer edge of the cutting portion upper surface 21 with increasing distance from the bottom portion 41c. In other words, the outer wall portion 41d may be inclined so as to approach the corner cutting edge Ec with increasing distance from the bottom portion 41c.

[0063] With this configuration, the coolant accumulated in the first corner groove 41 is more easily supplied to the corner cutting edge Ec.

[0064] 10 , in the first cross section D1, the first corner groove 41 may further have an inner wall portion 41e located on the opposite side of the outer wall portion 41d and rising from the bottom portion 41c. The inner wall portion 41e may be formed such that, with respect to a reference axis R that is a virtual straight line perpendicular to the plane 33, the angle θ1 formed between the reference axis R and the outer wall portion 41d is larger than the angle θ2 formed between the reference axis R and the inner wall portion 41e.

[0065] With this configuration, the coolant accumulated in the first corner groove 41 is less likely to leak out from the inner wall portion 41e side, and the coolant is more easily supplied to the corner cutting edge Ec.

[0066] As shown in the example indicated by reference numerals 1101 to 1103 in Figure 11, in the first corner groove 41, the bottom 41c may have the shape of a concave curved surface recessed downward in the second cross section D2 perpendicular to the extension direction of the first corner groove 41.

[0067] The first corner groove 41 may have a central region indicated by reference numeral 1102, an outer region indicated by reference numeral 1103, and an inner region indicated by reference numeral 1101. In the direction in which the first corner groove 41 extends, the outer region may be closer to the outer edge of the cutting portion upper surface 21 than the central region, and the inner region may be farther from the outer edge of the cutting portion upper surface 21 than the central region.

[0068] As shown in the examples indicated by symbols 1101 to 1103 in Figure 11, in the second cross section D2, the radius of curvature of the bottom 41c in the central region may be larger than the radius of curvature of the bottom 41c in the outer region and the radius of curvature of the bottom 41c in the inner region.

[0069] When chips get into the first corner groove 41, the chips are more likely to come into contact with the bottom 41c in the central region than with the bottom 41c in the outer region or the bottom 41c in the inner region. As described above, the radius of curvature of the bottom 41c in the central region, which is relatively likely to come into contact with chips, is large, and the bottom 41c in the central region is gently curved. Therefore, even if chips come into contact with the bottom 41c in the central region, cracks are less likely to occur in the first corner groove 41.

[0070] Furthermore, when the radius of curvature of the bottom 41c at the second cross section D2 in the outer region and the radius of curvature of the bottom 41c at the second cross section D2 in the inner region are relatively small values, it is easier to secure a larger space for coolant accumulation in the first corner groove 41.

[0071] The groove lengths in the extension direction of each of the multiple corner grooves 40 may be the same or different. The groove widths of each of the multiple corner grooves 40 may be the same or different. The groove depths of each of the multiple corner grooves 40 may be the same or different. The groove spacings between the multiple corner grooves 40 may be the same or different. The groove widths of each of the multiple corner grooves 40 may be constant or may not be constant in the length direction. The groove ends of the multiple corner grooves 40 on the inner side of the cutting portion upper surface 21 may be aligned or may not be aligned.

[0072] The cross-sectional shape of each of the corner grooves 40 along the width direction may be V-shaped or rectangular. The length of the corner grooves 40 may be set to, for example, 0.1 mm to 3 mm. The width of the corner grooves 40 may be set to, for example, 0.03 mm to 0.5 mm. The depth of the corner grooves 40 may be set to, for example, 0.03 mm to 0.5 mm.

[0073] <Method for manufacturing a machined product> A method for manufacturing a machined product according to an embodiment of the present disclosure will be described with reference to Fig. 12. Fig. 12 is a schematic diagram for explaining the method for manufacturing a machined product according to an embodiment. As shown in the example of Fig. 12, the method for manufacturing a machined product according to an embodiment 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.

[0074] 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 1 into contact with the rotating workpiece W. The third step is a step of separating the cutting tool 1 from the workpiece W. Examples of materials for the workpiece W include stainless steel, carbon steel, alloy steel, cast iron, and non-ferrous metals. Specific details of the method for manufacturing a machined product according to the embodiment are as follows.

[0075] First, the cutting tool 1 is attached to a tool post (not shown) of a lathe, and the workpiece W is attached to a chuck (not shown) of the lathe. Next, in a first step, as shown in the example indicated by reference numeral 1201 in Fig. 12 , the chuck is rotated to rotate the workpiece W around its axis S. Then, in a second step, as shown in the example indicated by reference numeral 1202 in Fig. 12 , the cutting tool 1 is brought close to the workpiece W, the cutting portion 20 of the cutting insert 10 is brought into contact with the outer peripheral surface of the rotating workpiece W, and the cutting tool 1 is moved downward to cut the workpiece W. In this way, the workpiece W is cut, and its outer diameter is machined.

[0076] Thereafter, in a third step, as shown by reference numeral 1203 in Fig. 12 , the cutting tool 1 is moved radially outward on a circle centered on the axis S, thereby separating the cutting tool 1 from the workpiece W. 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 has excellent cutting ability for the reasons described above, a machined product M with excellent machining accuracy can be produced.

[0077] To continue cutting, the cutting portion 20 of the cutting insert 10 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 1 is brought close to the workpiece W, but since it is sufficient that the cutting tool 1 and the workpiece W are brought relatively close to each other, for example, the workpiece W may be brought close to the cutting tool 1. In this regard, the cutting tool 1 is also moved away from the workpiece W in the same manner.

[0078] <Summary> The cutting insert in aspect 1 of the present disclosure has an upper surface having a corner and a first side connected to the corner, a corner side surface connected to the corner, and a corner cutting edge located at the corner, and the upper surface further has a corner land surface extending along the corner cutting edge and sloping upward as it moves away from the corner cutting edge, and a plurality of corner grooves extending from the corner land surface toward the inside of the upper surface, and the plurality of corner grooves include a first corner groove and a second corner groove located closer to the first side than the first corner groove, and in a side view of the corner side surface, a lower end of an opening edge of the first corner groove that opens into the corner land surface is located higher than a lower end of an opening edge of the second corner groove that opens into the corner land surface.

[0079] In a cutting insert in aspect 2 of the present disclosure, in aspect 1, the plurality of corner grooves further include a third corner groove located closer to the first side than the second corner groove, and in a side view of the corner side surface, the lower end of the second corner groove is located higher than the lower end of the opening edge of the third corner groove that opens into the corner land surface.

[0080] In a cutting insert according to a third aspect of the present disclosure, in the first or second aspect, the plurality of corner grooves are each spaced apart from an outer edge of the upper surface in a plan view of the upper surface.

[0081] In a cutting insert according to a fourth aspect of the present disclosure, in accordance with the third aspect, the first corner groove is farther from the outer edge of the upper surface than the second corner groove in a plan view of the upper surface.

[0082] In aspect 5 of the present disclosure, in any one of aspects 1 to 4, the cutting insert is such that, in a side view of the corner side surface, the lower end of the first corner groove is located closer to the first side than the center of the lower edge of the opening edge of the first corner groove.

[0083] In the cutting insert of aspect 6 of the present disclosure, in aspect 5, in a side view of the corner side surface, the lower end of the opening edge opening to the corner land surface of each of the plurality of corner grooves is located closer to the first side than the center of the lower edge of the opening edge of each of the plurality of corner grooves.

[0084] In a seventh aspect of the present disclosure, in the cutting insert of any one of the first to sixth aspects, the directions in which the corner grooves extend are parallel to one another in a plan view of the upper surface.

[0085] In the cutting insert of aspect 8 of the present disclosure, in the same manner as in aspect 7, when viewed in plan on the upper surface, each of the multiple corner grooves extends in a direction approaching the perpendicular bisector of the corner cutting edge as it moves inward on the upper surface.

[0086] The cutting insert in aspect 9 of the present disclosure is, in any one of aspects 1 to 8, such that the upper surface has a plane located inward of the upper surface relative to the corner land surface, and the first corner groove has, in a first cross section parallel to the direction in which the first corner groove extends and perpendicular to the plane, a bottom portion and an outer wall portion rising from the bottom portion and connecting the bottom portion and the corner land surface.

[0087] In a cutting insert according to an aspect 10 of the present disclosure, in accordance with the aspect 9, the bottom portion in the first cross section has a convex shape curved upward.

[0088] In an eleventh aspect of the present disclosure, the cutting insert is the same as in the ninth or tenth aspect, wherein the outer wall portion is inclined in the first cross section so as to approach the outer edge of the upper surface as it moves away from the bottom portion.

[0089] In aspect 12 of the present disclosure, in any one of aspects 9 to 11, the cutting insert has, in the first cross section, the first corner groove located opposite the outer wall portion and further having an inner wall portion rising from the bottom portion, and the angle formed by the reference axis and the outer wall portion is larger than the angle formed by the reference axis and the inner wall portion, using a virtual straight line perpendicular to the plane as a reference axis.

[0090] A cutting insert in aspect 13 of the present disclosure is, in any one of aspects 9 to 12, such that the bottom portion has a concave curved surface shape recessed downward in a second cross section perpendicular to the extension direction of the first corner groove, and the first corner groove has, in the extension direction of the first corner groove, a central region, an outer region closer to the outer edge of the upper surface than the central region, and an inner region farther from the outer edge of the upper surface than the central region, and the radius of curvature of the bottom portion in the second cross section in the central region is greater than the radius of curvature of the bottom portion in the second cross section in the outer region and the radius of curvature of the bottom portion in the second cross section in the inner region.

[0091] The cutting tool in aspect 14 of the present disclosure has a rod-shaped holder extending from a first end to a second end, the holder having a pocket located at the first end, and a cutting insert of any one of aspects 1 to 13 located in the pocket.

[0092] A method for manufacturing a machined product in aspect 15 of the present disclosure includes the steps of rotating a workpiece, bringing the cutting tool of aspect 14 into contact with the rotating workpiece, and removing the cutting tool from the workpiece.

[0093] [Additional Notes] 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 could 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.

[0094] 1 Cutting tool 2 Holder 2a Tip 2b Rear end 3 Pocket 10 Cutting insert 20 Cutting portion 21 Cutting portion upper surface (upper surface) 22 Corner 26 Corner side surface 30 Corner land surface 33 Flat surface 40 Corner groove 41 First corner groove 41aa, 42aa, 43aa Lower end 41c Bottom portion 41d Outer wall portion 41a, 42a, 43a Opening edge 41c Bottom portion 41d Outer wall portion 41e Inner wall portion 42 Second corner groove 43 Third corner groove D1 First cross section D2 Second cross section Ec Corner cutting edge L Perpendicular bisector R Reference axis θ1 Angle between reference axis and outer wall portion θ2 Angle between reference axis and inner wall portion

Claims

1. A cutting insert having an upper surface having a corner and a first side connected to the corner, a corner side surface connected to the corner, and a corner cutting edge located at the corner, wherein the upper surface further has a corner land surface extending along the corner cutting edge and inclining upward as it moves away from the corner cutting edge, and a plurality of corner grooves extending from the corner land surface toward the inside of the upper surface, wherein the plurality of corner grooves include a first corner groove and a second corner groove located closer to the first side than the first corner groove, and wherein, in a side view of the corner side surface, a lower end of an opening edge of the first corner groove that opens into the corner land surface is located higher than a lower end of an opening edge of the second corner groove that opens into the corner land surface.

2. The cutting insert as described in claim 1, wherein the multiple corner grooves further include a third corner groove located closer to the first side than the second corner groove, and in a side view of the corner side surface, the lower end of the second corner groove is located higher than the lower end of an opening edge of the third corner groove that opens into the corner land surface.

3. The cutting insert according to claim 1 or 2, wherein, in a plan view of the upper surface, the plurality of corner grooves are each spaced apart from an outer edge of the upper surface.

4. The cutting insert according to claim 3, wherein, in a plan view of the upper surface, the first corner groove is farther from an outer edge of the upper surface than the second corner groove.

5. A cutting insert described in any one of claims 1 to 4, wherein, in a side view of the corner side surface, the lower end of the first corner groove is located closer to the first side than the center of the lower edge of the opening edge in the first corner groove.

6. A cutting insert as described in claim 5, wherein, in a side view of the corner side surface, a lower end of an opening edge opening into the corner land surface of each of the plurality of corner grooves is located closer to the first side than the center of the lower edge of the opening edge in each of the plurality of corner grooves.

7. A cutting insert according to any one of claims 1 to 6, wherein the directions in which the corner grooves extend are parallel to each other in a plan view of the upper surface.

8. The cutting insert according to claim 7, wherein, in a plan view of the upper surface, each of the plurality of corner grooves extends in a direction approaching a perpendicular bisector of the corner cutting edge as it moves inwardly of the upper surface.

9. A cutting insert as described in any one of claims 1 to 8, wherein the upper surface has a plane located more inward than the corner land surface, and the first corner groove has, in a first cross section parallel to the direction in which the first corner groove extends and perpendicular to the plane, a bottom portion and an outer wall portion rising from the bottom portion and connecting the bottom portion and the corner land surface.

10. The cutting insert according to claim 9, wherein in the first cross section, the bottom portion has an upwardly curved convex shape.

11. The cutting insert according to claim 9 or 10, wherein, in the first cross section, the outer wall portion is inclined so as to approach the outer edge of the upper surface as it moves away from the bottom portion.

12. A cutting insert as described in any one of claims 9 to 11, wherein, in the first cross section, the first corner groove is located on the opposite side of the outer wall portion and further has an inner wall portion rising from the bottom portion, and an angle between the reference axis and the outer wall portion is larger than an angle between the reference axis and the inner wall portion, the angle being determined based on a virtual straight line perpendicular to the plane.

13. A cutting insert as claimed in any one of claims 9 to 12, wherein the bottom has a shape of a concave curved surface recessed downward in a second cross section perpendicular to the extension direction of the first corner groove, the first corner groove having, in the extension direction of the first corner groove, a central region, an outer region closer to the outer edge of the top surface than the central region, and an inner region farther from the outer edge of the top surface than the central region, and the radius of curvature of the bottom in the second cross section in the central region is greater than each of the radius of curvature of the bottom in the second cross section in the outer region and the radius of curvature of the bottom in the second cross section in the inner region.

14. A cutting tool comprising: a holder having a rod shape extending from a first end to a second end and having a pocket located at the first end; and a cutting insert according to any one of claims 1 to 13 located in the pocket.

15. A method for manufacturing a machined product, comprising the steps of: rotating a workpiece; bringing the cutting tool according to claim 14 into contact with the rotating workpiece; and removing the cutting tool from the workpiece.

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