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

Abstract

A minor cutting edge of a cutting insert according to an embodiment has a convex curved shape that protrudes upward in a side view, and comprises: a first part including a top portion of the minor cutting edge that protrudes farthest upward; a second part positioned between the first part and a connecting blade; and a third part positioned between the second part and the connecting blade. The second part and the third part each approach a lower surface with increasing distance from the first part. In a side view, a radius of curvature of the second part is greater than a radius of curvature of the first part and a radius of curvature of the third part.

Description

Technical Field

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

Background Art

[0002] As an example of a cutting tool, a so-called rotary tool can be mentioned. Examples of rotary tools include end mills and milling tools.

[0003] As a cutting insert used for a cutting tool, the cutting insert described in Patent Document 1 is known. The cutting insert described in Patent Document 1 is a so-called double-sided insert having cutting edges on the upper surface side and the lower surface side, respectively. The cutting edge in Patent Document 1 has a sub-cutting edge (so-called shear edge) for finishing. The sub-cutting edge has a convex curve shape that protrudes upward in a side view. Patent Document 1 exemplifies, as specific shapes of the sub-cutting edge, an arc shape with a constant curvature and a convex curve shape whose curvature gradually decreases toward both ends in a side view.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The cutting insert according to the present disclosure has an upper surface, a lower surface located on the opposite side of the upper surface, a side surface connected to the upper surface and the lower surface, an upper cutting edge located at the intersection of the upper surface and the side surface, and a lower cutting edge located at the intersection of the lower surface and the side surface. The upper surface has a first corner, a first side connected to the first corner, and a second side connected to the first corner on the opposite side of the first side. The upper cutting edge has a main cutting edge located on the first side and being linear in a top view, a sub-cutting edge located on the second side and being linear in a top view, and a connecting edge located at the first corner, connected to the main cutting edge and the sub-cutting edge, and being convex (convex curve shape) protruding outward in a top view. The sub-cutting edge has a convex curve shape protruding upward in a side view, and includes a first portion including the topmost protruding portion in the sub-cutting edge, a second portion located between the first portion and the connecting edge, and a third portion located between the second portion and the connecting edge. The second portion and the third portion are each configured to approach the lower surface as they move away from the first portion. In a side view, the radius of curvature of the second portion is larger than the radius of curvature of the first portion and the radius of curvature of the third portion.

[0006] The cutting tool according to the present disclosure has a cylindrical shape extending from a first end to a second end along a rotation axis, and includes a holder having a pocket located on the side of the first end, and a cutting insert according to the present disclosure located within the pocket.

[0007] The method for manufacturing a machined product according to the present disclosure includes a step of rotating the cutting tool according to the present disclosure, a step of bringing the rotating cutting tool into contact with a workpiece, and a step of separating the cutting tool from the workpiece.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 9

Embodiments for Carrying Out the Invention

[0009] When attaching a double-sided insert such as the cutting insert described in Patent Document 1 to the holder of a cutting tool, it is necessary to set the axial rake of the cutting insert to a negative value. Therefore, when the shape of the secondary cutting edge is as exemplified in Patent Document 1, the area of the secondary cutting edge that can be used as a scraping edge is limited, and the finish machining of the workpiece may not be sufficient. Therefore, improvement in the surface accuracy (surface roughness) of the machined surface of the workpiece is desired.

[0010] According to the present disclosure, the surface accuracy of the machined surface of the workpiece can be improved.

[0011] Hereinafter, a cutting insert, a cutting tool, and a method of manufacturing a machined product according to embodiments of the present disclosure will be described in detail with reference to the drawings. However, each of the drawings referred to below shows only the components necessary for explaining the embodiments in a simplified manner for convenience of explanation. Therefore, the cutting insert and the cutting tool according to the embodiments of the present disclosure may include any components not shown in the respective drawings referred to. Also, the dimensions of the components in each drawing do not faithfully represent the dimensions of the actual components and the dimensional ratios of the respective members.

[0012] In the present disclosure, the insert central axis refers to a virtual axis passing through the center of the upper surface and the center of the lower surface of the cutting insert. The inner direction or the inner side refers to the direction or the side approaching the insert central axis in the cutting insert. The outer direction or the outer side refers to the direction or the side away from the insert central axis in the cutting insert. Orthogonal does not refer to strict orthogonality, but means allowing an error of about ±5 degrees. Parallel does not refer to strict parallelism, but means allowing an error of about ±5 degrees.

[0013] <Cutting insert> Referring to FIGS. 1 to 4, the cutting insert 10 according to an embodiment of the present disclosure will be described. 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 plan view of the cutting insert 10 shown in FIG. 1. FIG. 3 is a schematic side view of the cutting insert 10 shown in FIG. 1. Note that FIG. 3 is a side view from the direction of front view of the second side described later. FIG. 4 is an enlarged view of part IV in FIG. 3.

[0014] The cutting insert 10 according to an embodiment of the present disclosure is a component of a cutting tool used for cutting a workpiece W (see FIG. 7) made of a metal material or the like. Examples of the cutting of the workpiece W include shoulder cutting, groove cutting, R cutting, and profiling.

[0015] As shown in the examples of FIGS. 1 to 3, the cutting insert 10 may have an upper surface 12 and a lower surface 14 located on the opposite side of the upper surface 12. The upper surface 12 and the lower surface 14 may each be a polygonal shape, for example, an octagonal shape. In other words, the cutting insert 10 may be a polygonal plate shape, for example, an octagonal plate shape. The upper surface 12 and the lower surface 14 may each be a polygonal shape other than an octagonal shape, such as a triangular shape or a quadrangular shape. In other words, the cutting insert 10 may be a polygonal plate shape other than an octagonal plate shape, such as a triangular plate shape or a quadrangular plate shape. The polygonal shape is not limited to the shape of a polygon in a strict sense.

[0016] As shown in the example of FIG. 2, the upper surface 12 and the lower surface 14 may each have a rotationally symmetric shape at a certain angle around the insert central axis CS. The upper surface 12 and the lower surface 14 may have a shape that is symmetric with respect to the front and back reversal. In other words, the cutting insert 10 may have a rotationally symmetric shape at a certain angle around the insert central axis CS, or may have a shape that is symmetric with respect to the front and back reversal.

[0017] As shown in the examples of FIGS. 1 and 3, the cutting insert 10 may have a plurality of side surfaces 16 located between the upper surface 12 and the lower surface 14. The side surfaces 16 may be connected to the upper surface 12 and the lower surface 14. The side surfaces 16 may have a function as a relief surface and may be parallel to the insert central axis CS. The cutting insert 10 is a so-called negative type cutting insert with a relief angle of 0 degrees.

[0018] As shown in the examples of FIGS. 1 to 3, the cutting insert 10 may have a mounting hole 18 penetrating from the upper surface 12 to the lower surface 14. One opening of the mounting hole 18 may be located at the center of the upper surface 12, and the other opening of the mounting hole 18 may be located at the center of the lower surface 14. The central axis of the mounting hole 18 may coincide with the insert central axis CS.

[0019] As shown in the examples of FIGS. 1 and 2, the cutting insert 10 may have an upper cutting edge 20 and a lower cutting edge 22. The upper cutting edge 20 may be located at the intersection of the upper surface 12 and the side surface 16. The lower cutting edge 22 may be located at the intersection of the lower surface 14 and the side surface 16. In other words, the cutting insert 10 may be a double-sided insert provided with the upper cutting edge 20 and the lower cutting edge 22. The upper cutting edge 20 may be located over the entire intersection of the upper surface 12 and the side surface 16, or may be located at a part of the intersection. The lower cutting edge 22 may be located over the entire intersection of the lower surface 14 and the side surface 16, or may be located at a part of the intersection.

[0020] As in the example shown in FIG. 2, the upper surface 12 having a polygonal shape may have a first corner 24 as one of a plurality of corners and a second corner 26 as another one of the plurality of corners. The first corner 24 and the second corner 26 may each have a convex curve shape protruding outward in a top view.

[0021] As in the examples shown in FIGS. 1 and 2, the upper surface 12 may have a first side 28 connected to the first corner 24 and a second side 30 connected to the first corner 24 on the opposite side of the first side 28. The second corner 26 may be connected to the second side 30 on the side opposite to the first corner 24. The first side 28 may be linear in a top view, and may approach the lower surface 14 as it moves away from the first corner 24 in a side view. The second side 30 may be linear in a top view.

[0022] In a top view, the first side 28 and the second side 30 are not limited to a linear shape, and may be, for example, a gently convex curve shape protruding outward. Here, "being a gently convex curve shape" means having a radius of curvature larger than the radii of curvature of the first corner 24 and the second corner 26 having a convex curve shape.

[0023] When the upper surface 12 has a shape that is rotationally symmetric by a certain angle about the insert center axis CS, as in an example shown in FIG. 2, the upper surface 12 may have a plurality of first corners 24 and a plurality of second corners 26. At this time, the plurality of first corners 24 and the plurality of second corners 26 may be alternately positioned along the circumferential direction of the upper surface 12.

[0024] Further, the upper surface 12 may have a plurality of first sides 28 and a plurality of second sides 30. When the upper surface 12 has a plurality of first corners 24, a plurality of second corners 26, a plurality of first sides 28, and a plurality of second sides 30, the evaluation of the radius of curvature described later may be performed by focusing on one extracted from each of these parts so as to have the above-described positional relationship.

[0025] As shown in the examples of FIGS. 1 and 2, the upper surface 12 may have a land portion 32 located at its peripheral portion, and the land portion 32 may be connected to the upper cutting edge 20. The land portion 32 may have a function of enhancing the cutting edge strength of the upper cutting edge 20. The land portion 32 may be a portion adjacent to the upper cutting edge 20 and shown as a straight line in a cross-section orthogonal to the upper cutting edge 20 when viewed from above.

[0026] Further, the upper surface 12 may have a rake face 34 located inside the land portion 32, and the rake face 34 may be connected to the land portion 32. The rake face 34 is inclined with respect to the land portion 32 and may be configured to approach the lower surface 14 as it moves away from the land portion 32.

[0027] As shown in the examples of FIGS. 1 and 2, the upper surface 12 may have a flat bottom surface 36 located inside the rake face 34, and the bottom surface 36 may be connected to the rake face 34. The bottom surface 36 may surround the opening of the mounting hole 18 and may be orthogonal to the insert center axis CS.

[0028] As shown in the examples of FIGS. 1 to 3, the upper cutting edge 20 may have a main cutting edge 38 located on the first side 28. The main cutting edge 38 is a portion that can function as a main cutting edge in the cutting process of the workpiece W. The main cutting edge 38 may be located over the entire first side 28 or a part of the first side 28. The main cutting edge 38 may be linear in a top view.

[0029] As shown in the examples of FIGS. 1 to 4, the upper cutting edge 20 may have a sub-cutting edge 40 located on the second side 30. The sub-cutting edge 40 may have a function as a finishing edge for finishing the machined surface of the workpiece W. The sub-cutting edge 40 may be located over the entire second side 30 or a part of the second side 30. The sub-cutting edge 40 may be linear in a top view.

[0030] As shown in the examples of FIGS. 1 to 3, the upper cutting edge 20 may have a first connecting edge (connecting edge) 42 located at the first corner 24, and the first connecting edge 42 may be connected to the main cutting edge 38 and the sub-cutting edge 40. The first connecting edge 42 may have a convex curve shape that protrudes outward in a top view. Further, the upper cutting edge 20 may have a second connecting edge 44 located at the second corner 26, and the second connecting edge 44 may be connected to the sub-cutting edge 40. The second connecting edge 44 may have a convex curve shape that protrudes outward in a top view.

[0031] As shown in the example of FIG. 4, the sub-cutting edge 40 may have a convex curve shape that protrudes upward in a side view. The sub-cutting edge 40 may have a first portion 40a including the top 40t that protrudes most upward in the sub-cutting edge 40, a second portion 40b located between the first portion 40a and the first connecting edge 42, and a third portion 40c located between the second portion 40b and the first connecting edge 42.

[0032] As shown in the example of FIG. 4, in a side view, the length Lb of the second portion 40b of the sub-cutting edge 40 may be longer than the length La of the first portion 40a and the length Lc of the third portion 40c. The length of the third portion 40c of the sub-cutting edge 40 may be longer than the length of the first portion 40a. Further, the second portion 40b and the third portion 40c of the sub-cutting edge 40 may each approach the lower surface 14 as they move away from the first portion 40a.

[0033] Note that the above "length La" means the width of the first portion 40a in a direction perpendicular to the insert central axis CS when the insert 10 is viewed from the side. Similarly, the above "length Lb" means the width of the second portion 40b in a direction perpendicular to the insert central axis CS when the insert 10 is viewed from the side, and the above "length Lc" means the width of the third portion 40c in a direction perpendicular to the insert central axis CS when the insert 10 is viewed from the side.

[0034] As in the example shown in Fig. 4, in a side view, the radius of curvature Rb of the second portion 40b of the secondary cutting edge 40 may be larger than the radius of curvature Ra of the first portion 40a and the radius of curvature Rc of the third portion 40c. In other words, in a side view, the curvature of the second portion 40b of the secondary cutting edge 40 may be smaller than the curvature of the first portion 40a and the curvature of the third portion 40c. In a side view, the radius of curvature Rc of the third portion 40c of the secondary cutting edge 40 may be larger than the radius of curvature Ra of the first portion 40a. In other words, in a side view, the curvature of the third portion 40c of the secondary cutting edge 40 may be smaller than the curvature of the first portion 40a. Further, the distance D1 from the tip 40t of the secondary cutting edge 40 to the second corner 26 may be shorter than the distance D2 from the tip 40t to the second portion 40b. In Fig. 4, the radius of curvature Ra of the first portion 40a, the radius of curvature Rb of the second portion 40b, and the radius of curvature Rc of the third portion 40c of the secondary cutting edge 40 are schematically illustrated.

[0035] As in the example shown in Fig. 4, the boundary 12e between the second side 30 and the first corner 24 may be closer to the lower surface 14 than the boundary 12p between the second side 30 and the second corner 26. Further, the first corner 24 may have a first connection region 24a connected to the second side 30, and the first connection region 24a may have a concave curve shape that is recessed downward in a side view. The second corner 26 may have a second connection region 26a connected to the second side 30, and the second connection region 26a may have a convex curve shape that protrudes upward in a side view.

[0036] The positions of the boundary 12e and the boundary 12p may be specified by a top view of the cutting insert 10. For example, when the first corner 24 and the second corner 26 are convex curve shapes and the second side 30 is a straight line shape in a top view, a virtual straight line along the second side 30 may be set, and a portion away from this virtual straight line may be regarded as the boundary 12e and the boundary 12p. Further, when the first corner 24 and the second corner 26 are convex curve shapes and the second side 30 is a gentle convex curve shape in a top view, a virtual arc along the second side 30 may be set, and a portion away from this virtual arc may be regarded as the boundary 12e and the boundary 12p.

[0037] As in the examples shown in FIGS. 1 to 3, when the upper surface 12 and the lower surface 14 have a shape that is inversion-symmetric with respect to the front and back, the lower surface 14 may have portions corresponding to the first corner 24, the second corner 26, the first side 28, the second side 30, the land portion 32, and the rake face 34 on the upper surface 12. The configuration of the portions corresponding to the first corner 24, the second corner 26, the first side 28, the second side 30, the land portion 32, and the rake face 34 on the lower surface 14 may be the same as the configuration of the first corner 24, the second corner 26, the first side 28, the second side 30, the land portion 32, and the rake face 34 on the upper surface 12, except that the vertical positional relationship is reversed.

[0038] As in the examples shown in FIGS. 1 to 3, when the upper surface 12 and the lower surface 14 have a shape that is inversion-symmetric with respect to the front and back, the lower cutting edge 22 may have portions corresponding to the main cutting edge 38, the sub-cutting edge 40, the first connecting edge 42, and the second connecting edge 44 on the upper cutting edge 20. The configuration of the portions corresponding to the main cutting edge 38, the sub-cutting edge 40, the first connecting edge 42, and the second connecting edge 44 on the lower cutting edge 22 may be the same as the configuration of the main cutting edge 38, the sub-cutting edge 40, the first connecting edge 42, and the second connecting edge 44 on the upper cutting edge 20, except that the vertical positional relationship is reversed.

[0039] Examples of the material of the cutting insert 10 include cemented carbide or cermet. Examples of the composition of the cemented carbide include WC-Co produced by adding cobalt (Co) powder to tungsten carbide (WC) and sintering, WC-TiC-Co obtained by adding titanium carbide (TiC) to WC-Co, or WC-TiC-TaC-Co obtained by adding tantalum carbide (TaC) to WC-TiC-Co. Further, cermet is a sintered composite material in which a metal is combined with a ceramic component, and specifically, examples include sintered composite materials mainly composed of titanium compounds such as titanium carbide (TiC) or titanium nitride (TiN).

[0040] The surface of the cutting insert 10 may be coated with a film using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. Examples of the composition of the film include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), or alumina (Al2O3).

[0041] As in the example shown in FIG. 4, the sub-cutting edge 40 has a convex curved shape that protrudes upward in a side view. The second portion 40b and the third portion 40c of the sub-cutting edge 40 each approach the lower surface 14 as they move away from the first portion 40a. The radius of curvature Rb of the second portion 40b of the sub-cutting edge 40 is larger than the radius of curvature Ra of the first portion 40a and the radius of curvature Rc of the third portion 40c.

[0042] In this case, the second portion 40b, which is a gently curved portion, can be arranged on the central side of the sub-cutting edge 40, and the first portion 40a and the third portion 40c, which are slightly more sharply curved portions, can be arranged on both end sides of the sub-cutting edge 40. Therefore, even if the axial rake angle of the cutting insert 10 is set negative, a wide area from the first portion 40a to the third portion 40c of the sub-cutting edge 40 can be used as a shearing edge.

[0043] According to the example of the embodiment of the present disclosure, the surface accuracy (surface roughness) of the machined surface of the workpiece can be improved. In particular, since the first portion 40a including the top 40t is a slightly more sharply curved portion, the biting of the sub-cutting edge 40 into the workpiece W is improved, and the surface accuracy of the machined surface of the workpiece W can be sufficiently improved.

[0044] Also, among the first portion 40a to the third portion 40c of the sub-cutting edge 40, the third portion 40c located closest to the first connecting edge 42 is a slightly more sharply curved portion. Therefore, according to the example of the embodiment of the present disclosure, during cutting, the biting of the subsequent cutting insert 10 into the workpiece W is improved, the chip thickness is ensured, and the occurrence of so-called chipping can be reduced.

[0045] When the length of the second portion 40b of the sub-cutting edge 40 is longer than the lengths of the first portion 40a and the third portion 40c, the gentle portion of the sub-cutting edge 40 becomes longer, and the surface accuracy of the machined surface of the workpiece W can be further improved.

[0046] When the first connection area 24a of the first corner 24 has a concave curve shape and the second connection area 26a of the second corner 26 has a convex curve shape, the length of the second portion 40b of the sub-cutting edge 40 can be made sufficiently long. According to an example of the embodiment of the present disclosure, the surface accuracy of the machined surface of the workpiece W can be further improved.

[0047] When the length of the third portion 40c of the sub-cutting edge 40 is longer than the length of the first portion 40a, the third portion 40c, which is a gentle portion after the first portion 40a among the sub-cutting edges 40, can be made longer after the first portion 30a. According to an example of the embodiment of the present disclosure, the surface accuracy of the machined surface of the workpiece W can be further improved.

[0048] When the radius of curvature Rc of the third portion 40c of the sub-cutting edge 40 is larger than the radius of curvature Ra of the first portion 40a, stress concentration can be reduced in the third portion 40c to which a cutting load larger than that of the first portion 40a tends to be applied. According to an example of the embodiment of the present disclosure, the durability of the cutting insert 10 can be improved.

[0049] When the distance D1 from the top 40t of the sub-cutting edge 40 to the second corner 26 is shorter than the distance D2 from the top 40t to the second portion 40b, the relief surface connected to the second corner 26 on the side surface 16 is less likely to contact the machined surface of the workpiece W. According to an example of the embodiment of the present disclosure, the durability of the cutting insert 10 can be improved.

[0050] When the boundary 12e between the second side 30 and the first corner 24 is closer to the lower surface 14 than the boundary 12p between the second side 30 and the second corner 26, the workpiece W can be gradually brought into contact from the main cutting edge 38 to the sub-cutting edge 40, and a sharp increase in cutting resistance can be suppressed. According to an example of the embodiment of the present disclosure, the durability of the cutting insert 10 can be improved.

[0051] <Cutting tool> Referring to FIGS. 5 and 6, a cutting tool 46 according to an embodiment of the present disclosure will be described. FIG. 5 is a schematic perspective view of a cutting tool 46 according to an embodiment of the present disclosure. FIG. 6 is a schematic perspective view of the cutting tool 46 shown in FIG. 5 viewed from another angle.

[0052] As shown in the examples of FIGS. 5 and 6, the cutting tool 46 according to an embodiment of the present disclosure is a tool that is used for machining a workpiece W (see FIG. 7) and is rotatable about a rotation axis RS. The cutting tool 46 may have a holder 48 that is mounted on the spindle of a machine tool such as a milling machine. The holder 48 may have a cylindrical shape extending from a first end 48a to a second end 48b along the rotation axis RS. Examples of the material of the holder 48 include metals such as stainless steel, carbon steel, cast iron, and aluminum alloy. A plurality of pockets 50 may be circumferentially spaced on the outer peripheral surface of the holder 48. The plurality of pockets 50 may be circumferentially equally spaced or circumferentially unequally spaced. The number of pockets 50 may be one.

[0053] As shown in the examples of FIGS. 5 and 6, the cutting tool 46 may have a cutting insert 10 positioned in the pocket 50 of the holder 48. The cutting insert 10 may be positioned only in one or a plurality of selected pockets 50 in the holder 48. Further, the cutting insert 10 may be fixed to the pocket 50 of the holder 48 by a fixing screw 52 inserted through a mounting hole 18. The cutting insert 10 may be fixed to the pocket 50 of the holder 48 by a clamping member. When performing cutting with the upper cutting edge 20, the lower surface 14 may be used as a seating surface for attaching to the holder 48 (see FIG. 3). When performing cutting with the lower cutting edge 22, the upper surface 12 may be used as the seating surface (see FIG. 3).

[0054] <Method for manufacturing a machined product> Referring to FIGS. 7 to 9, a method for manufacturing a machined product according to an embodiment of the present disclosure will be described. FIGS. 7 to 9 are schematic diagrams for explaining a method for manufacturing a machined product according to an embodiment of the present disclosure.

[0055] As shown in the examples of FIGS. 7 to 9, 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 machined workpiece W, and includes a first step, a second step, and a third step. The first step is a step of rotating the cutting tool 46. The second step is a step of bringing the rotating cutting tool 46 into contact with the workpiece W. The third step is a step of separating the cutting tool 46 from the workpiece W. Examples of the material of the workpiece W include aluminum alloy, stainless steel, carbon steel, alloy steel, cast iron, or non-ferrous metal, etc. And the specific content of the method for manufacturing a machined product according to an embodiment of the present disclosure is as follows.

[0056] As shown in the examples of FIGS. 7 and 8, while rotating the cutting tool 46 in the rotational direction T, it is moved in the direction of arrow FD to approach the workpiece W. Then, while bringing the cutting insert 10 of the rotating cutting tool 46 into contact with the workpiece W, it is moved in the direction of arrow FD. Thereby, the workpiece W is machined by the cutting tool 46, and a machined surface Wf is formed on the workpiece as shown in the example of FIG. 9.

[0057] Thereafter, as shown in the example of FIG. 9, the cutting tool 46 is further moved in the direction of arrow FD to separate it from the workpiece W. Thereby, the machining of the workpiece W is completed, and the machined product M which is the machined workpiece W can be manufactured. Since the cutting tool 46 has excellent cutting ability for the reasons described above, a machined product M with excellent machining accuracy can be manufactured.

[0058] When continuing the cutting process, in a state where the cutting tool 46 is rotated, the contact of the cutting insert 10 of the cutting tool 46 with different portions of the workpiece W may be repeated. In the embodiment of the present disclosure, the cutting tool 46 is approaching the workpiece W, but since it is sufficient that the cutting tool 46 and the workpiece W approach each other relatively, for example, the workpiece W may be brought closer to the cutting tool 46. In this regard, the same applies when separating the cutting tool 46 from the workpiece W.

[0059] 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. That is, various modifications are possible within the scope shown in the present disclosure, and embodiments obtained by appropriately combining the disclosed technical means are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that those skilled in the art can easily make various deformations or modifications based on the present disclosure. Also, note that these deformations or modifications are included in the scope of the present disclosure.

Explanation of Signs

[0060] 10 Cutting insert 12 Upper surface 12e Boundary between the second side and the first corner 12p Boundary between the second side and the second corner 14 Lower surface 16 Side surface 18 Mounting hole 20 Upper cutting edge 22 Lower cutting edge 24 First corner 24a First connection region 26 Second corner 26a Second connection region 28 First side 30 Second side 32 Land portion 34 Rake face 36 Bottom surface 38 Main cutting edge 40 Sub cutting edge 40a First part 40b Second part 40c Third part 40t Top portion 42 First connection edge 44 Second connection edge 46 Cutting tool 50 Pocket 52 Fixing screw CS Insert central axis RS Rotation axis

Claims

1. An upper surface, a lower surface located on the opposite side of the upper surface, side surfaces connected to the upper surface and the lower surface, an upper cutting edge located at the intersection of the upper surface and the side surface, a lower cutting edge located at the intersection of the lower surface and the side surface, and having the upper surface a first corner, a first side connected to the first corner, a second side connected to the first corner on the opposite side of the first side, and having the upper cutting edge a main cutting edge located on the first side and being linear in a top view, a sub cutting edge located on the second side and being linear in a top view, a connecting edge located at the first corner, connected to the main cutting edge and the sub cutting edge, and being convexly curved and protruding outward in a top view, and having the sub cutting edge being convexly curved and protruding upward in a side view, a first portion including the topmost protruding portion in the sub cutting edge, a second portion located between the first portion and the connecting edge, a third portion located between the second portion and the connecting edge, and having the second portion and the third portion each approaching the lower surface as they are away from the first portion, In a side view, a cutting insert in which a radius of curvature of the second portion is larger than a radius of curvature of the first portion and a radius of curvature of the third portion.

2. The cutting insert according to claim 1, wherein in a side view, a radius of curvature of the third portion is larger than a radius of curvature of the first portion.

3. The cutting insert according to claim 1, wherein a length of the second portion is longer than a length of the first portion and a length of the third portion.

4. The cutting insert according to claim 3, wherein a length of the third portion is longer than a length of the first portion.

5. The upper surface further has a second corner connected to the second side on the opposite side of the first corner, The cutting insert according to claim 1, wherein a distance from the top to the second corner is shorter than a distance from the top to the second portion.

6. The cutting insert according to claim 5, wherein a boundary between the second side and the first corner is closer to the lower surface than a boundary between the second side and the second corner.

7. The first corner has a first connection region connected to the second side, The second corner has a second connection region connected to the second side, The cutting insert according to claim 5, wherein in a side view, the first connection region has a concave curved shape that is recessed downward, and the second connection region has a convex curved shape that protrudes upward.

8. A holder having a cylindrical shape extending from a first end to a second end along a rotation axis, and having a pocket located on the side of the first end. A cutting tool, comprising: the cutting insert according to any one of claims 1 to 7, located within the pocket.

9. A step of rotating the cutting tool according to claim 8. A step of bringing the rotating cutting tool into contact with a workpiece. A method for manufacturing a machined product, comprising: a step of separating the cutting tool from the workpiece.

Images