Cutting insert and cutting tool having same

Abstract

The invention provides a cutting insert and a cutting tool capable of improving the machining resistance of a corner part during drilling. The cutting insert (3) has a substantially polygonal plate shape, includes a first long side (11U) and a second long side (12U), and a first short side and a second short side located between the first long side and the second long side, and has a first end surface (10U) and a second end surface (10L) facing each other. Furthermore, the first end surface and the second end surface have a first cutting edge (31) extending from the first long side to a first corner section (Cn1) located between the first long side and the first short side, and a second cutting edge (32) extending from the second long side to a second corner section (Cn2) located between the second long side and the first short side. Further, the radius of curvature R3 of a third corner section (Cn3), which sandwiches the first long side and is located on the opposite side of the first corner section (Cn1), is larger than the radius of curvature R1 of the first corner section.

Description

Technical Field

[0001] The present invention relates to a cutting blade and a cutting tool having the cutting blade. Background Art

[0002] An end mill is a cutting tool for milling a workpiece to be cut, and it is well known that a detachable cutting blade is mounted on a mounting seat provided on its main body. The present applicant has proposed an example of such an end mill, which has a plurality of cutting blades, any one of the center cutting edge and the outer peripheral cutting edge of the cutting blade can be used, and the cutting blade can be reversed inside and outside and reused (see Patent Document 1).

[0003] Prior Art Documents

[0004] Patent Document

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-30401

[0006] Technical Problem

[0007] The end mill having the above-mentioned conventional cutting blade is a double-sided type center cutting edge blade replaceable multi-functional machining end mill, and in particular has the following advantages: excellent economy and the cutting blade can be stably fixed to the main body of the cutting tool as compared with the prior art.

[0008] Figure 5 FIG. is a schematic cross-sectional view schematically showing an example of a state in which a workpiece to be cut is drilled (drilled) using the cutting blade provided in the existing end mill. This cross-section corresponds to a plane cross-section including the rotation axis AX (central axis of the hole 61) of the end mill when machining a hole 61 in a solid workpiece 6. In addition, in this figure, the installation states of the cutting blades 5A and 5B are also shown. These cutting blades themselves have the same shape.

[0009] In this case, the cutting blade 5A functions as a center cutting edge, which has an inner cutting edge and a main cutting edge. In the state where the cutting blade 5A is mounted on the main body of the cutting tool, the inner cutting edge extends from the outer peripheral surface of the main body toward the rotation axis, and the main cutting edge is located on the outer peripheral surface. On the other hand, the cutting blade 5B functions as an outer peripheral cutting edge, which has a main cutting edge, and the main cutting edge is located on the opposite side of approximately 180° from the main cutting edge of the center cutting edge. The cutting blades 5A and 5B are substantially rectangular parallelepipeds, and center cutting edges and outer peripheral cutting edges are formed opposite to each other at the ridge line portions of the front surface (for example, the upper surface) and the side surface, and the same center cutting edges and outer peripheral cutting edges are also formed on the back surface (for example, the lower surface), and have a total of 4 usable cutting edges.

[0010] As Figure 5As shown, when drilling a workpiece with such an end mill, a cylindrical core column 6T can remain near the center of the machining bottom surface 6B. The core column 6T is a deliberately left part after cutting to ensure that the cutting speed of the cutting blade 5A near the rotation axis AX is not zero. Specifically, by slightly retracting the cutting blade 5A towards the inner side of the drawing of Figure 5 such that the cutting edge does not pass through the rotation center (rotation axis AX), the core column 6T remains after cutting. As the drilling process progresses, the core column 6T is broken at the corner Cn on the tool center side of the cutting blade 5A. At this time, if the cutting blade 5A has a core-retaining design (referred to as "core-offset design" in Japanese) that allows offset from the central axis, there is a tendency for the load during the removal of the core column 6T to be too high. Additionally, according to the inventor's opinion, when referring to the main machining method of the core column 6T, a method of squeezing and breaking the core column 6T by the corner Cn can be considered. Based on this, in the drilling of the workpiece, it is desired to improve the machining resistance of the corner Cn on the tool center side of the central cutting edge.

[0011] Therefore, an object of the present invention is to provide a cutting blade and a cutting tool having the cutting blade, which can improve the machining resistance of the corner on the tool center side when drilling a workpiece, thereby effectively suppressing defects and the like at this part. Summary of the Invention

[0012] To solve the above problems, the present invention adopts the following structure.

[0013] [1] A cutting blade provided by the present invention is generally in the shape of a polygonal plate (e.g., generally a cuboid), including a first long side and a second long side, a first short side and a second short side located between the first long side and the second long side, and having opposite first and second end faces. Additionally, the first and second end faces have a first cutting edge and a second cutting edge. The first cutting edge extends from the first long side towards the first corner located between the first long side and the first short side, and the second cutting edge extends from the second long side towards the second corner located between the second long side and the first short side. Further, the radius of curvature R3 of the third corner located on the opposite side of the first corner with the first long side in between is greater than the radius of curvature R1 of the first corner.

[0014] As described above, when drilling a workpiece, it is possible to leave a residue such as Figure 5The core post 6T shown can be broken at the third corner portion on the tool center side of the center cutting edge. In contrast, in the present invention, when the cutting blade is mounted on the cutting tool, the first corner portion and the third corner portion are located on the tool outer peripheral side and the tool center side respectively, and the radius of curvature R3 of the third corner portion is larger than the radius of curvature R1 of the first corner portion. Therefore, the machining tolerance for the load when removing the core post 6T is improved. Thus, when drilling the workpiece to be machined, chipping and the like of the third corner portion can be effectively suppressed.

[0015] [2]In addition, specifically, the cutting blade may further have relatively arranged short side faces, the short side faces are connected to the first end face and the second end face, and include a first short side and a second short side. At this time, the short side faces may be inclined relative to the plane perpendicular to the first end face and the second end face. Further, it is preferably that the clearance angle on the first short side is a positive angle, and the clearance angle on the second short side is a negative angle. It should be noted that in the present invention, "the clearance angle is a positive angle" means that the inner angle formed by the two intersecting faces is an "acute angle", and "the clearance angle is a negative angle" means that the inner angle formed by the two intersecting faces is an "obtuse angle".

[0016] [3]Furthermore, in such a structure, it is preferable that the first cutting edge and the second cutting edge on the first end face and the first cutting edge and the second cutting edge on the second end face form a 180° rotationally symmetric relationship around a specified axis passing through the cutting blade.

[0017] [4]In addition, in this 180° rotationally symmetric relationship, more specifically, the positional relationship between the first corner portion on the first end face and the third corner portion on the second end face, and the positional relationship between the third corner portion on the first end face and the first corner portion on the second end face can be opposite to each other across the short side faces. With such a structure, the cutting blade of the present invention can be used as a double-sided standard and replaceable multi-functional end mill for machining, making the cutting blade have the advantages of excellent economy and being able to be stably fixed on the main body of the cutting tool.

[0018] [5]In addition, in the above structure, the cutting blade may have a chip breaker formed on the rake face associated with the first cutting edge. The chip breaker includes a first chip breaker and a second chip breaker. The position of the first chip breaker is closer to the first corner portion side than the center of the first long side, and the position of the second chip breaker is closer to the third corner portion side than the center of the first long side. At this time, it is more preferable that the maximum width W cmax of the second chip breaker is greater than the maximum width W pmax of the first chip breaker. Herein, the "width of the chip breaker" in the present invention means the width in the direction of the first short side in the top view of the cutting blade.

[0019] In this structure, in the first chip breaker portion that can be located on the outer peripheral side of the tool, since the distance to the "wall" is relatively close, it is easy to force the chip to curl. On the other hand, in the second chip breaker portion that can be located on the center side of the tool, since the distance to the "wall" is relatively far, it is difficult to force the chip to curl. That is, in this structure, it is easy to adjust as desired to achieve the curling process adapted to the chip thickness. Thus, it is possible to contribute to improving the machining performance of the cutting insert.

[0020] [6] Further, in the above structure, more specifically, it is further preferable that the maximum width W of the second chip breaker portion cmax is less than or equal to 50% of the length of the first short side, so that it is easier to control the shape of the chips generated during drilling.

[0021] [7] A cutting tool provided by the present invention can be effectively constituted by having a main body and the cutting insert of the present invention mounted on the main body. The cutting insert is generally in the shape of a polygonal plate, and includes a first long side and a second long side, a first short side and a second short side located between the first long side and the second long side, and has opposite first end faces and second end faces. In addition, the first end face and the second end face have a first cutting edge and a second cutting edge. The first cutting edge includes a first corner portion between the first long side and the first short side, and extends from the first long side to the first short side. The second cutting edge includes a second corner portion between the second long side and the first short side, and extends from the second long side to the first short side. Further, the radius of curvature R3 of the third corner portion sandwiching the first long side and located on the opposite side of the first corner portion is greater than the radius of curvature R1 of the first corner portion.

[0022] By the present invention, it is possible to improve the machining tolerance of the third corner portion of the cutting insert, so that it is possible to effectively suppress the defect of the third corner portion when drilling the workpiece to be cut. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a perspective view schematically showing the overall structure of the cutting tool provided by the present embodiment.

[0024] Figure 2 is a perspective view schematically showing the overall structure of the cutting tool provided by the present embodiment.

[0025] Figure 3 is a perspective view schematically showing the structure of the cutting insert included in the cutting tool provided by the present embodiment.

[0026] Figure 4 is a plan view (top view) schematically showing the structure of the cutting insert included in the cutting tool provided by the present embodiment.

[0027] Figure 5It is a cross-sectional schematic view schematically showing an example of a state in which a workpiece is drilled using a cutting blade provided in an existing cutting tool.

[0028] Explanation of Main Component Symbols

[0029] Cutting tool 1

[0030] Body 2

[0031] Outer peripheral surface 2P

[0032] Cutting blade 3

[0033] Chip breaker 3B

[0034] First state 3C

[0035] Second state 3P

[0036] Cutting blades (existing) 5A, 5B

[0037] Workpiece 6

[0038] Machined bottom surface 6B

[0039] Core column 6T

[0040] Screw 8

[0041] Second end face (front cutting face) 10L

[0042] First end face (front cutting face) 10U

[0043] First long side face 11

[0044] Second long side face 12

[0045] First long sides 11L, 11U

[0046] Second long sides 12L, 12U

[0047] First short side face (short side face) 13

[0048] Second short side face (short side face) 14

[0049] First short sides 13U, 14L

[0050] Second short sides 13L, 14U

[0051] Front end portion 21

[0052] Rear end portion 22

[0053] First cutting edge 31

[0054] Second cutting edge 32

[0055] Hole 61

[0056] Rotating shaft AX

[0057] Shaft (specified shaft) BX

[0058] Corner part (existing) Cn

[0059] First corner part Cn1

[0060] Second corner part Cn2

[0061] Third corner part Cn3

[0062] Insert grooves D1, D2

[0063] Mounting hole H

[0064] Maximum width W cmax , W pmax

[0065] Rotating direction YA Detailed implementation mode

[0066] Hereinafter, this implementation mode will be described with reference to the accompanying drawings. For the convenience of understanding the description, the same reference numerals are assigned to the same components in the respective drawings, and repeated descriptions are omitted. Figure 1 is a perspective view schematically showing the overall structure of the cutting tool provided in this implementation mode, and is a view observed from the side of the cutting insert installed in the first state described later. In addition, Figure 2 is also a perspective view schematically showing the overall structure of the cutting tool provided in this implementation mode, and is a view observed from the side of the cutting insert installed in the second state described later. Further, Figure 3 and Figure 4 are respectively a perspective view and a plan view (top view) schematically showing the structure of the cutting insert included in the cutting tool provided in this implementation mode.

[0067] <Outline of cutting tool 1>

[0068] As Figure 1 and Figure 2As shown, the cutting tool 1 is an end mill that can perform both milling and drilling (drill bit machining) on a workpiece to be machined. On the rotatably driven main body 2, cutting blades 3, 3, for example, are mounted in pairs to form the cutting tool 1. The main body 2 is a component that constitutes substantially the whole of the cutting tool 1, and is formed of, for example, steel. The main body 2 is integrally formed by a front end portion 21 and a rear end portion 22 that are both substantially cylindrical. The cutting blades 3, 3 are mounted on blade grooves D1, D2 provided in a notch portion of the front end portion 21. The main body 2 is held by a machine tool (not shown), and when machining a workpiece (not shown) as well, it is driven to rotate around a rotation axis AX. It should be noted that the rotation axis AX coincides with the central axis of the substantially cylindrical main body 2. In addition, in Figure 1 and Figure 2 , a circular arrow symbol is used to indicate the rotation direction YA of the cutting tool 1 during machining.

[0069] Both of the cutting blades 3, 3 are substantially rectangular parallelepiped, and have the same shape that can be replaced with each other (please refer to Figure 3 and Figure 4 described later), and can be detachably (replaceably) fastened to any one of the blade grooves D1, D2 of the main body 2 by, for example, screws 8. In addition, as shown in Figure 1 and Figure 2 , the cutting blade 3 mounted in the blade groove D1 in a horizontally placed state (first state 3C) extends from the outer peripheral surface 2P of the main body 2 along the front end side to the rotation axis AX or its periphery. On the other hand, the cutting blade 3 mounted on the blade groove D2 in a vertically placed state (a state orthogonal to the horizontal placement: second state 3P) is located on the outer peripheral side substantially 180° opposite to the cutting blade 3 arranged in the first state 3C, and extends from the outer peripheral surface 2P of the main body 2 along the front end side to the middle of the rotation axis AX.

[0070] There is no particular limitation on the material of the cutting blade 3. For example, it is preferably formed of cemented carbide as a whole. In addition, for the part of the cutting blade 3 that at least includes a first cutting edge 31 and a second cutting edge 32 described later, for example, it can be formed of any one of hard materials such as a sintered body containing cermet, ceramic, and cubic boron nitride, a material having a coating formed by PVD or CVD on the surface of these hard materials, and a material containing a single crystal diamond or a sintered body of diamond.

[0071] <Specific Structure of the Cutting Blade 3>

[0072] Next, a more specific structure of the cutting blade 3 will be described. As shown in Figure 3 and Figure 4As shown, the cutting blade 3 includes a first end face 10U (upper surface shown in the figure), a second end face 10L (lower surface shown in the figure), a first long side face 11, a second long side face 12, a first short side face 13 and a second short side face 14 connecting the first end face 10U and the second end face 10L. In addition, each cutting blade 3 is provided with a mounting hole H for fixing it to the blade groove D1, D2 by screws.

[0073] Furthermore, if Figure 1 and Figure 2 As shown, when the cutting insert 3 is mounted on the main body 2 in the first state 3C, the second end face 10L, the second long side face 12 and the second short side face 14, or the first end face 10U, the second long side face 12 and the first short side face 13 are the parts that are restrained by abutting against the insert groove D1 of the main body 2. On the other hand, when the cutting insert 3 is mounted on the main body 2 in the second state 3P, the second end face 10L, the first long side face 11 and the second short side face 14, or the first end face 10U, the first long side face 11 and the first short side face 13 are the parts that are restrained by abutting against the insert groove D2 of the main body 2.

[0074] The first end surface 10U has a first long side 11U, a second long side 12U, a first short side 13U, and a second short side 14U, and these four sides respectively define the boundaries between the first end surface 10U and the first long side surface 11, the second long side surface 12, the first short side surface 13, and the second short side surface 14. Similarly, the second end surface 10L has a first long side 11L, a second long side 12L, a first short side 14L, and a second short side 13L, and these four sides respectively define the boundaries between the second end surface 10L and the first long side surface 11, the second long side surface 12, the first short side surface 13, and the second short side surface 14. According to such structural features, the first cutting edge 31 and the second cutting edge 32 of the first end face 10U and the first cutting edge 31 and the second cutting edge 32 of the second end face 10L form a 180° rotational symmetric (i.e., double rotational symmetric) relationship with each other around the axis BX that passes through the center of the cutting blade 3 and substantially extends along the first short sides 13U, 14L and the second short sides 14U, 13L. In this way, the axis BX is equivalent to an example of a "prescribed axis that is assumed to penetrate the cutting blade".

[0075] Among them, the first cutting edge 31 on the first end face 10U side includes a first corner portion Cn1 located between the first long side 11U and the first short side 13U, and extends from the first long side 11U to the first short side 13U. Similarly, the first cutting edge 31 on the second end face 10L side includes a first corner portion Cn1 located between the first long side 11L and the first short side 14L, and extends from the first long side 11L to the first short side 14L. When drilling the workpiece 6, the first cutting edge 31 in the first state 3C mainly functions as a cutting edge for cutting the bottom surface. In addition, asFigure 1 and Figure 2 As shown in Figure 2 , when the cutting blade 3 is fixed to the main body 2 in the first state 3C, the first corner portion Cn1 is located on the outer peripheral side of the tool, and the third corner portion Cn3, which sandwiches the first long sides 11U and 11L and is located on the opposite side of the first corner portion Cn1, is located on the center side of the tool (near the rotation axis AX).

[0076] In the present embodiment, the radius of curvature R3 of the third corner portion Cn3 is larger than the radius of curvature R1 of the first corner portion Cn1. In addition, in the above-described 180° rotational symmetry relationship, the positional relationship between the first corner portion Cn1 on the first end face 10U and the third corner portion Cn3 on the second end face 10L is opposite to each other across the short side face 13, and the positional relationship between the third corner portion Cn3 on the first end face 10U and the first corner portion Cn1 on the second end face 10L is also opposite to each other across the short side face 14.

[0077] On the other hand, the second cutting edge 32 on the first end face 10U side includes a second corner portion Cn2 located between the second long side 12U and the first short side 13U, and extends from the second long side 12U to the first short side 13U. Similarly, the second cutting edge 32 on the second end face 10L side includes a second corner portion Cn2 located between the second long side 12L and the first short side 14L, and extends from the second long side 12L to the first short side 14L. When milling the workpiece 6, the second cutting edge 32 in the second state 3P mainly functions as a cutting edge for machining the circumferential surface.

[0078] In addition, as Figure 3 and Figure 4 shown, the first short side face 13 and the second short side face 14 are inclined faces, that is, they are inclined with respect to the plane perpendicular to the first end face 10U and the second end face 10L. In this structure, the first short sides 13U and 14L are used as part of the first cutting edge 31 and part of the second cutting edge 32, and the clearance angle of the first short sides 13U and 14L is a positive angle. In contrast, the second short sides 14U and 13L are not used as the first cutting edge 31 and the second cutting edge 32, and the clearance angle of the second short sides 14U and 13L is a negative angle.

[0079] In addition, regarding the first cutting edge 31 of the cutting blade 3, a chip breaker portion 3B is formed on the first end face 10U and the second end face 10L (both are rake faces). Among them, the chip breaker portion 3B is composed of an imaginary portion (first chip breaker portion) and an imaginary portion (second chip breaker portion). The imaginary portion (first chip breaker portion) is located on the side closer to the first corner portion Cn1 (outer peripheral side of the tool) than the center of the first long sides 11U and 11L, and the imaginary portion (second chip breaker portion) is located on the side closer to the third corner portion Cn3 (center side of the tool) than the center of the first long sides 11U and 11L. At this time, in the present embodiment, the maximum width (Wcmax ) greater than the maximum width (W) of the first chip breaker portion pmax ). More specifically, the maximum width W of the second chip breaker portion cmax is 50% or less (1 / 2 or less) of the length of the first short sides 13U, 14L.

[0080] According to the cutting inserts 3, 3 having the above structure and the cutting tool 1 equipped with the cutting inserts 3, 3, the cutting insert 3 functions as a double-sided standard and replaceable multi-functional end mill. That is, since the cutting inserts 3, 3 can be reused by flipping the first end face 10U and the second end face 10L respectively, and can also be reused by swapping, one cutting insert 3 can be used a total of 4 times. Therefore, the economy of the tool can be improved and the inventory management of the product can be made easier.

[0081] In addition, the radius of curvature R3 of the third corner portion Cn3 that can be located on the tool center side is larger than the radius of curvature R1 of the first corner portion Cn1 that can be located on the tool outer peripheral side. Thus, when the core column 6T as shown in Figure 5 is broken by the third corner portion Cn3 of the cutting insert 3 mounted in the first state 3C during drilling of the workpiece 6, the machining tolerance of this portion can also be improved compared to the prior art. Therefore, during drilling of the workpiece 6, the defect of the third corner portion Cn3 can be effectively suppressed.

[0082] Further, the maximum width W of the second chip breaker portion located on the side closer to the third corner portion Cn3 than the center of the first long sides 11U, 11L cmax is greater than the maximum width W of the first chip breaker portion located on the side closer to the first corner portion Cn1 than the center of the first long sides 11U, 11L pmax . Thus, in the first chip breaker portion that can be located on the tool outer peripheral side, since the distance to the "wall" is relatively close, it is easy to forcibly curl the chip. On the other hand, in the second chip breaker portion that can be located on the tool center side, since the distance to the "wall" is relatively far, it is difficult to forcibly curl the chip. That is, this structure has the advantage of being easily adjusted as desired to achieve curling processing adapted to the chip thickness. This enables further improvement of the comprehensive machining performance of the cutting insert 3.

[0083] The above content has described this embodiment with reference to specific examples, but this is for the purpose of easily understanding the present invention and is not used to limit the interpretation of the present invention. That is, the present invention is not limited to these specific examples, and the content that those skilled in the art have appropriately designed and changed based on these specific examples is also included in the scope of the present invention as long as it has the features of the present invention. In addition, each element, configuration, material, condition, shape, size, scale, etc. possessed by the above-mentioned specific examples are not limited to the given examples as long as there is no special indication, and can be appropriately changed. In addition, each element possessed by the above-mentioned specific examples can be appropriately changed in combination as long as there is no technical contradiction.

[0084] In other words, for example, the cutting blade 3 may not be used in both the first state 3C and the second state 3P, as long as a first cutting edge 31 having at least a first corner portion Cn1 and a third corner portion Cn3 is formed, and the relationship represented by the radius of curvature R3 > the radius of curvature R1 is satisfied. In addition, the front end portion 21 and the rear end portion 22 of the main body 2 may be used as separate components, and the two may be designed as an assembled type (modular type) or a head replacement type, or may be connected by welding or the like. In addition, a plurality of blade grooves D1, D2 may be provided, and a plurality of cutting blades 3 may be installed in their respective grooves. In addition, as for the method of mounting the cutting blade 3 onto the blade grooves D1, D2, a screw-on or level-lock method may be cited, but it is not limited thereto. For example, it may also be brazing. In addition, the arrangement pitch of the plurality of cutting blades 3 is not limited to an equal pitch, and may be arranged at an unequal pitch. In addition, when the cutting blade 3 is used for milling, the chip-breaking portion 3B may be formed mainly to provide a positive rake angle. In this case, the chip may be fragmented without specifically contacting the "wall".

[0085] In addition to this, the first cutting edge 31 on the side of the first end face 10U only needs to extend from the first long side 11U to the first corner portion Cn1, and does not necessarily have to be formed on the first short side 13U. In addition, the first cutting edge 31 on the side of the second end face 10L only needs to extend from the first long side 11L to the first corner portion Cn1, and does not necessarily have to be formed on the first short side 14L. Similarly, the second cutting edge 32 on the side of the first end face 10U only needs to extend from the second long side 12U to the second corner portion Cn2, and does not necessarily have to be formed on the first short side 13U. In addition, the second cutting edge 32 on the side of the second end face 10L only needs to extend from the second long side 12L to the second corner portion Cn2, and does not necessarily have to be formed on the first short side 14L. In other words, the first short sides 13U, 14L may not be used as part of the first cutting edge 31 and the second cutting edge 32.

Claims

1. A cutting insert, wherein: The cutting blade is substantially in the shape of a polygonal plate, and includes a first long side and a second long side, a first short side and a second short side located between the first long side and the second long side, and has a first end face and a second end face opposite to each other; The first end surface and the second end surface have a first cutting edge and a second cutting edge, the first cutting edge extends from the first long side to a first corner portion between the first long side and the first short side, and the second cutting edge extends from the second long side to a second corner portion between the second long side and the first short side; A curvature radius R3 of a third corner portion sandwiching the first long side and located on the opposite side of the first corner portion is greater than a curvature radius R1 of the first corner portion.

2. The cutting insert according to claim 1, wherein The cutting blade has short side surfaces that are arranged opposite to each other, the short side surfaces are connected to the first end surface and the second end surface, and include the first short side and the second short side; The short side surface is inclined relative to a surface perpendicular to the first end surface and the second end surface; The rear angle on the first short side is a positive angle; The rear angle on the second short side is a negative angle.

3. The cutting insert according to claim 1, wherein: The first cutting edge and the second cutting edge of the first end surface and the first cutting edge and the second cutting edge of the second end surface are in a 180° rotationally symmetrical relationship with each other about a predetermined axis that passes through the cutting insert.

4. The cutting insert according to claim 2, wherein: In the 180° rotationally symmetrical relationship, the positional relationship between the first corner portion on the first end surface and the third corner portion on the second end surface, and the positional relationship between the third corner portion on the first end surface and the first corner portion on the second end surface are respectively opposite to each other via the short side surface.

5. The cutting insert according to claim 1, wherein The cutting insert has a chip breaker formed on a rake face associated with the first cutting edge, the chip breaker includes a first chip breaker and a second chip breaker, the first chip breaker is located closer to the first corner portion than the center of the first long side, and the second chip breaker is located closer to the third corner portion than the center of the first long side; The maximum width W of the second chip breaking portion cmax Greater than the maximum width W of the first chip breaking portion pmax .

6. The cutting insert according to claim 5, wherein: The maximum width W of the second chip breaking portion cmax Less than or equal to 50% of the length of the first short side.

7. A cutting tool, wherein: The cutting tool comprises: the subject; and, a cutting blade mounted on the main body; The cutting blade is substantially in the shape of a polygonal plate, and includes a first long side and a second long side, a first short side and a second short side located between the first long side and the second long side, and has a first end face and a second end face opposite to each other; The first end surface and the second end surface have a first cutting edge and a second cutting edge, the first cutting edge extends from the first long side to a first corner portion between the first long side and the first short side, and the second cutting edge extends from the second long side to a second corner portion between the second long side and the first short side; A curvature radius R3 of a third corner portion sandwiching the first long side and located on the opposite side of the first corner portion is greater than a curvature radius R1 of the first corner portion.

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