Cutting insert and cutting tool

Abstract

This cutting insert has a first main surface, a second main surface, and an outer peripheral surface. A boundary between the first main surface and the outer peripheral surface forms a first ridge line. A boundary between the second main surface and the outer peripheral surface forms a second ridge line. A virtual ridge line shape formed when the first ridge line and the second ridge line are vertically projected on a virtual plane at an intermediate position between a first plane portion and a second plane portion is in 180° rotational symmetry around each of a first diagonal line and a second diagonal line. Each of a first straight line portion, a second straight line portion, a third straight line portion, and a fourth straight line portion includes a main cutting edge. The first main surface includes a first rake face portion continuous with the main cutting edge. The outer peripheral surface includes a first flank face portion continuous with the main cutting edge. A distance between the first flank face portion and the central axis in a direction perpendicular to the central axis of a through-hole decreases from the first main surface toward the second main surface.

Description

Cutting Inserts and Cutting Tools

[0001] The present disclosure relates to cutting inserts and cutting tools.

[0002] WO 2014 / 208513 (Patent Document 1) discloses a cutting insert having a pair of corner cutting edges located at a pair of corners.

[0003] International Publication No. 2014 / 208513

[0004] The cutting insert according to the present disclosure comprises a first main surface, a second main surface, and an outer peripheral surface. The second main surface is opposite the first main surface. The outer peripheral surface is continuous with each of the first main surface and the second main surface. The first main surface includes a first flat portion. The second main surface includes a second flat portion parallel to the first flat portion. The cutting insert has a through hole extending from the first flat portion to the second flat portion. The boundary between the first main surface and the outer peripheral surface forms a first ridgeline. The boundary between the second main surface and the outer peripheral surface forms a second ridgeline. The first ridgeline includes a first linear portion and a second linear portion opposite the first linear portion. The second ridgeline includes a third linear portion and a fourth linear portion opposite the third linear portion. When viewed in a direction from the first flat portion toward the second flat portion, the first linear portion and the second linear portion are parallel, and the third linear portion and the fourth linear portion are parallel. The shape formed when the first ridge line and the second ridge line are perpendicularly projected onto an imaginary plane located midway between the first and second planar portions is referred to as the imaginary ridge line shape. On the imaginary plane, the imaginary ridge line shape has a first projected straight line portion, a second projected straight line portion, a third projected straight line portion, and a fourth projected straight line portion, which are shapes formed when the first straight line portion, the second straight line portion, the third straight line portion, and the fourth straight line portion are perpendicularly projected onto the imaginary plane. The shape enclosed by the first imaginary line portion extending along the first projected straight line portion, the second imaginary line portion extending along the second projected straight line portion, the third imaginary line portion extending along the third projected straight line portion, and the fourth imaginary line portion extending along the fourth projected straight line portion is a rhombus. The line segment connecting the first intersection of the first imaginary line portion and the third imaginary line portion and the second intersection of the second imaginary line portion and the fourth imaginary line portion forms the first diagonal of the rhombus. The line segment connecting the third intersection point of the first imaginary line portion and the fourth imaginary line portion and the fourth intersection point of the second imaginary line portion and the third imaginary line portion forms the second diagonal of the rhombus. The imaginary ridge line shape is rotationally symmetrical by 180° around each of the first diagonal and the second diagonal. Each of the first straight line portion, the second straight line portion, the third straight line portion, and the fourth straight line portion includes a major cutting edge. The first main surface includes a first rake surface portion continuous with the major cutting edge. The outer peripheral surface includes a first flank surface portion continuous with the major cutting edge. The distance between the first flank surface portion and the central axis in a direction perpendicular to the central axis of the through hole decreases from the first main surface toward the second main surface.

[0005] FIG. 1 is a schematic perspective view showing the configuration of a cutting insert according to a first embodiment. FIG. 2 is a schematic plan view showing the configuration of a cutting insert according to the first embodiment. FIG. 3 is a schematic bottom view showing the configuration of a cutting insert according to the first embodiment. FIG. 4 is a schematic view showing a shape formed when a first ridgeline and a second ridgeline are vertically projected onto an imaginary plane located midway between a first planar portion and a second planar portion. FIG. 5 is a schematic cross-sectional view taken along line V-V in FIG. 2. FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. 2. FIG. 7 is a schematic cross-sectional view taken along line VII-VII in FIG. 2. FIG. 8 is a schematic cross-sectional view taken along line VIII-VIII in FIG. 2. FIG. 9 is a schematic cross-sectional view taken along line IX-IX in FIG. 2. FIG. 10 is a schematic cross-sectional view taken along line X-X in FIG. 2. FIG. 11 is a schematic front view showing the configuration of a cutting insert according to the first embodiment. FIG. 12 is a schematic front view showing the configuration of a cutting tool according to this embodiment. Fig. 13 is a schematic perspective view showing the configuration of a cutting insert according to a second embodiment, Fig. 14 is a schematic front view showing the configuration of a cutting insert according to a second embodiment, and Fig. 15 is a schematic plan view showing the configuration of a cutting insert according to a second embodiment.

[0006] [Description of an embodiment of the present disclosure] First, an embodiment of the present disclosure (also referred to as the present embodiment) will be described.

[0007] (1) A cutting insert according to the present disclosure includes a first main surface, a second main surface, and an outer peripheral surface. The second main surface is opposite the first main surface. The outer peripheral surface is continuous with each of the first main surface and the second main surface. The first main surface includes a first flat portion. The second main surface includes a second flat portion parallel to the first flat portion. The cutting insert has a through hole extending from the first flat portion to the second flat portion. The boundary between the first main surface and the outer peripheral surface forms a first ridge line. The boundary between the second main surface and the outer peripheral surface forms a second ridge line. The first ridge line includes a first linear portion and a second linear portion opposite the first linear portion. The second ridge line includes a third linear portion and a fourth linear portion opposite the third linear portion. When viewed in a direction from the first flat portion toward the second flat portion, the first linear portion and the second linear portion are parallel, and the third linear portion and the fourth linear portion are parallel. The shape formed when the first ridge line and the second ridge line are perpendicularly projected onto an imaginary plane located midway between the first and second planar portions is referred to as the imaginary ridge line shape. On the imaginary plane, the imaginary ridge line shape has a first projected straight line portion, a second projected straight line portion, a third projected straight line portion, and a fourth projected straight line portion, which are shapes formed when the first straight line portion, the second straight line portion, the third straight line portion, and the fourth straight line portion are perpendicularly projected onto the imaginary plane. The shape enclosed by the first imaginary line portion extending along the first projected straight line portion, the second imaginary line portion extending along the second projected straight line portion, the third imaginary line portion extending along the third projected straight line portion, and the fourth imaginary line portion extending along the fourth projected straight line portion is a rhombus. The line segment connecting the first intersection of the first imaginary line portion and the third imaginary line portion and the second intersection of the second imaginary line portion and the fourth imaginary line portion forms the first diagonal of the rhombus. The line segment connecting the third intersection point of the first imaginary line portion and the fourth imaginary line portion and the fourth intersection point of the second imaginary line portion and the third imaginary line portion forms the second diagonal of the rhombus. The imaginary ridge line shape is rotationally symmetrical by 180° around each of the first diagonal and the second diagonal. Each of the first straight line portion, the second straight line portion, the third straight line portion, and the fourth straight line portion includes a major cutting edge. The first main surface includes a first rake surface portion continuous with the major cutting edge. The outer peripheral surface includes a first flank surface portion continuous with the major cutting edge. The distance between the first flank surface portion and the central axis in a direction perpendicular to the central axis of the through hole decreases from the first main surface toward the second main surface.

[0008] (2) According to the cutting insert according to (1), the first ridge may include a minor cutting edge connected to the major cutting edge. The outer peripheral surface may include a second flank portion connected to the minor cutting edge. The second flank portion may have a shape recessed toward the central axis.

[0009] (3) According to the cutting insert of (1), the first ridge may include a minor cutting edge connected to the major cutting edge, a fifth linear portion parallel to the third linear portion, and a ridge portion between the fifth linear portion and the minor cutting edge. When viewed in a direction from the first flat portion to the second flat portion, the ridge portion may have a shape that is concave toward the central axis.

[0010] (4) In the cutting insert according to any one of (1) to (3) above, the first flank portion may be flat.

[0011] (5) According to the cutting insert according to (1) above, the first ridge may include a minor cutting edge connected to the major cutting edge, a fifth straight line portion parallel to the third straight line portion, and a ridge portion between the fifth straight line portion and the minor cutting edge. The outer peripheral surface may include a second flank portion connected to the minor cutting edge. The second flank portion may have a shape recessed toward the central axis. When viewed in a direction from the first flat surface portion toward the second flat surface portion, the ridge portion may have a shape recessed toward the central axis. The first flank portion may be planar.

[0012] (6) A cutting tool according to the present disclosure includes the cutting insert according to any one of (1) to (5) above and a body to which the cutting insert is attached.

[0013] Specific examples of embodiments of the present disclosure will now be described with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals and descriptions thereof will not be repeated.

[0014] (First embodiment) Fig. 1 is a perspective schematic view showing the configuration of a cutting insert according to the first embodiment. As shown in Fig. 1, the cutting insert 1 according to the first embodiment has a first main surface 100, a second main surface 200, and an outer peripheral surface 30. The second main surface 200 is opposite the first main surface 100. The outer peripheral surface 30 is continuous with each of the first main surface 100 and the second main surface 200. The boundary between the first main surface 100 and the outer peripheral surface 30 forms a first ridge line 10. The boundary between the second main surface 200 and the outer peripheral surface 30 forms a second ridge line 20. A through hole 2 is formed in the cutting insert 1. The through hole 2 opens to each of the first main surface 100 and the second main surface 200.

[0015] Fig. 2 is a schematic plan view showing the configuration of the cutting insert 1 according to the first embodiment. As shown in Fig. 2, the first main surface 100 has a first flat surface portion 103, a first rake face portion 101, and a second rake face portion 102. The through hole 2 opens to the first flat surface portion 103. The first flat surface portion 103 is planar. The first rake face portion 101 is continuous with the first flat surface portion 103. The second rake face portion 102 is continuous with each of the first flat surface portion 103 and the first rake face portion 101.

[0016] 3 is a bottom schematic view showing the configuration of the cutting insert 1 according to the first embodiment. As shown in FIG. 3, the second main surface 200 has a second flat surface portion 203, a third rake face portion 201, and a fourth rake face portion 202. The second flat surface portion 203 is parallel to the first flat surface portion 103. The through hole 2 opens to the second flat surface portion 203. The through hole 2 extends from the first flat surface portion 103 to the second flat surface portion 203. The second flat surface portion 203 is planar. The third rake face portion 201 is continuous with the second flat surface portion 203. The fourth rake face portion 202 is continuous with each of the second flat surface portion 203 and the third rake face portion 201.

[0017] As shown in FIG. 2 , the first ridge 10 has a first linear portion 11, a second linear portion 12, a fifth linear portion 15, and a sixth linear portion 16. The second linear portion 12 is located opposite the first linear portion 11. When viewed in a direction from the first flat portion 103 toward the second flat portion 203, the first linear portion 11 and the second linear portion 12 are parallel to each other. The through hole 2 is located between the first linear portion 11 and the second linear portion 12. The sixth linear portion 16 is located opposite the fifth linear portion 15. When viewed in a direction from the first flat portion 103 toward the second flat portion 203, the fifth linear portion 15 and the sixth linear portion 16 are parallel to each other. The through hole 2 is located between the fifth linear portion 15 and the sixth linear portion 16.

[0018] As shown in FIG. 2 , the first ridge 10 has two first major cutting edges 51, two first minor cutting edges 17, two first ridge portions 18, and two first corner portions 19. The first of the two first major cutting edges 51 is a part of the first straight portion 11. The first of the two first major cutting edges 51 may be the entire first straight portion 11. The second of the two first major cutting edges 51 is a part of the second straight portion 12. The second of the two first major cutting edges 51 may be the entire second straight portion 12. The first major cutting edge 51 is continuous with the first rake face portion 101. The first minor cutting edge 17 is continuous with the second rake face portion 102.

[0019] The first ridge portion 18 is continuous with the first minor cutting edge 17. In the direction along the first ridge line 10, the first minor cutting edge 17 is located between the first ridge portion 18 and the first major cutting edge 51. The fifth straight line portion 15 is continuous with the first ridge portion 18. In the direction along the first ridge line 10, the first ridge portion 18 is located between the fifth straight line portion 15 and the first minor cutting edge 17. When viewed in the direction from the first flat surface portion 103 to the second flat surface portion 203, the first ridge portion 18 has a shape that is concave toward the central axis D. When viewed in the direction from the first flat surface portion 103 to the second flat surface portion 203, the first minor cutting edge 17 has a shape that is convex outward.

[0020] The first corner portion 19 is continuous with the first straight line portion 11. In the direction along the first ridge line 10, the first straight line portion 11 is located between the first minor cutting edge 17 and the first corner portion 19. The sixth straight line portion 16 is continuous with the first corner portion 19. In the direction along the first ridge line 10, the first corner portion 19 is located between the sixth straight line portion 16 and the first straight line portion 11. When viewed in the direction from the first flat surface portion 103 toward the second flat surface portion 203, the first corner portion 19 has an outwardly convex shape.

[0021] As shown in FIG. 3 , the second ridge line 20 has a third linear portion 23, a fourth linear portion 24, a seventh linear portion 21, and an eighth linear portion 22. The fourth linear portion 24 is located opposite the third linear portion 23. When viewed in a direction from the second flat portion 203 toward the first flat portion 103, the third linear portion 23 and the fourth linear portion 24 are parallel to each other. The through hole 2 is located between the third linear portion 23 and the fourth linear portion 24. The eighth linear portion 22 is located opposite the seventh linear portion 21. When viewed in a direction from the second flat portion 203 toward the first flat portion 103, the seventh linear portion 21 and the eighth linear portion 22 are parallel to each other. The through hole 2 is located between the seventh linear portion 21 and the eighth linear portion 22.

[0022] As shown in FIG. 3 , the second ridge 20 has two second major cutting edges 52, two second minor cutting edges 27, two second ridge portions 28, and two second corner portions 29. The first of the two second major cutting edges 52 is part of the third straight portion 23. The first of the two second major cutting edges 52 may be the entire third straight portion 23. The second of the two second major cutting edges 52 is part of the fourth straight portion 24. The second of the two second major cutting edges 52 may be the entire fourth straight portion 24. The second major cutting edge 52 is continuous with the third cutting surface portion 201. The second minor cutting edge 27 is continuous with the fourth cutting surface portion 202.

[0023] The second ridge portion 28 is continuous with the second minor cutting edge 27. In the direction along the second ridge line 20, the second minor cutting edge 27 is located between the second ridge portion 28 and the second major cutting edge 52. The eighth straight line portion 22 is continuous with the second ridge portion 28. In the direction along the second ridge line 20, the second ridge portion 28 is located between the eighth straight line portion 22 and the second minor cutting edge 27. When viewed in the direction from the second flat surface portion 203 toward the first flat surface portion 103, the second ridge portion 28 has a shape that is concave toward the central axis D. When viewed in the direction from the second flat surface portion 203 toward the first flat surface portion 103, the second minor cutting edge 27 has a shape that is convex outward.

[0024] The second corner portion 29 is continuous with the eighth straight line portion 22. In the direction along the second ridge line 20, the eighth straight line portion 22 is located between the second ridge line portion 28 and the second corner portion 29. The third straight line portion 23 is continuous with the second corner portion 29. In the direction along the second ridge line 20, the second corner portion 29 is located between the third straight line portion 23 and the eighth straight line portion 22. When viewed in the direction from the second flat surface portion 203 toward the first flat surface portion 103, the second corner portion 29 has an outwardly convex shape.

[0025] As shown in FIG. 2 , when viewed in a direction from the first flat surface portion 103 toward the second flat surface portion 203, the first linear portion 11, the second linear portion 12, the third linear portion 23, the fourth linear portion 24, the fifth linear portion 15, the sixth linear portion 16, the seventh linear portion 21, and the eighth linear portion 22 are each linear. The seventh linear portion 21 is parallel to the first linear portion 11. The seventh linear portion 21 is located between the first linear portion 11 and the through hole 2. The eighth linear portion 22 is parallel to the second linear portion 12. The eighth linear portion 22 is located between the second linear portion 12 and the through hole 2. The fifth linear portion 15 is parallel to the third linear portion 23. The fifth linear portion 15 is located between the third linear portion 23 and the through hole 2. The sixth linear portion 16 is parallel to the fourth linear portion 24. The sixth linear portion 16 is located between the fourth linear portion 24 and the through hole 2 .

[0026] As shown in FIG. 1 , the outer peripheral surface 30 has a first flank portion 31, a second flank portion 32, a third outer peripheral region 33, a fourth outer peripheral region 34, a fifth outer peripheral region 35, and a sixth outer peripheral region 36. The first flank portion 31 is continuous with a first rake face portion 101. The first major cutting edge 51 is formed by the ridgeline between the first rake face portion 101 and the first flank face portion 31. The second flank face portion 32 is continuous with a second rake face portion 102. The first minor cutting edge 17 is formed by the ridgeline between the second rake face portion 102 and the second flank face portion 32. The second flank face portion 32 is continuous with the first flank face portion 31.

[0027] The third outer peripheral region 33 is continuous with the first ridge portion 18. The fourth outer peripheral region 34 is continuous with both the second flank portion 32 and the third outer peripheral region 33. The fifth outer peripheral region 35 is continuous with both the fourth outer peripheral region 34 and the second ridge 20. The fourth outer peripheral region 34 is located between the fifth outer peripheral region 35 and both the second flank portion 32 and the third outer peripheral region 33. The sixth outer peripheral region 36 is continuous with both the first ridge 10 and the second ridge 20. The sixth outer peripheral region 36 is continuous with both the third outer peripheral region 33 and the fifth outer peripheral region 35.

[0028] 4 is a schematic diagram showing the shape formed when the first ridge line 10 and the second ridge line 20 are perpendicularly projected onto an imaginary plane located midway between the first flat surface portion 103 and the second flat surface portion 203. The shape formed when the first ridge line 10 and the second ridge line 20 are perpendicularly projected onto an imaginary plane located midway between the first flat surface portion 103 and the second flat surface portion 203 is referred to as an imaginary ridge line shape 300. The imaginary ridge line shape 300 is indicated by a solid line in FIG. 4.

[0029] On the imaginary plane, the imaginary ridge line shape 300 has a first projected straight line portion 311, a second projected straight line portion 312, a third projected straight line portion 323, and a fourth projected straight line portion 324, which are shapes formed when the first straight line portion 11, the second straight line portion 12, the third straight line portion 23, and the fourth straight line portion 24 are vertically projected onto the imaginary plane, respectively. On the imaginary plane, the imaginary ridge line shape 300 has a fifth projected straight line portion 315, a sixth projected straight line portion 316, a seventh projected straight line portion 321, and an eighth projected straight line portion 322, which are shapes formed when the fifth straight line portion 15, the sixth straight line portion 16, the seventh straight line portion 21, and the eighth straight line portion 22 are vertically projected onto the imaginary plane, respectively.

[0030] 4, when viewed in a direction from the first planar portion 103 toward the second planar portion 203, a straight line extending along the first projected straight line portion 311 is defined as a first imaginary line portion A1. Similarly, a straight line extending along the second projected straight line portion 312 is defined as a second imaginary line portion A2. Similarly, a straight line extending along the third projected straight line portion 323 is defined as a third imaginary line portion A3. Similarly, a straight line extending along the fourth projected straight line portion 324 is defined as a fourth imaginary line portion A4.

[0031] When viewed in a direction from the first flat surface portion 103 toward the second flat surface portion 203, the shape enclosed by the first imaginary line portion A1, the second imaginary line portion A2, the third imaginary line portion A3, and the fourth imaginary line portion A4 is a rhombus. The first imaginary line portion A1 and the second imaginary line portion A2 are parallel to each other. The third imaginary line portion A3 and the fourth imaginary line portion A4 are parallel to each other.

[0032] The intersection of the first imaginary line portion A1 and the third imaginary line portion A3 is the first intersection B1. The intersection of the second imaginary line portion A2 and the fourth imaginary line portion A4 is the second intersection B2. The line segment connecting the first intersection B1 and the second intersection B2 forms the first diagonal C1 of the rhombus. The intersection of the first imaginary line portion A1 and the fourth imaginary line portion A4 is the third intersection B3. The intersection of the second imaginary line portion A2 and the third imaginary line portion A3 is the fourth intersection B4. The line segment connecting the third intersection B3 and the fourth intersection B4 forms the second diagonal C2 of the rhombus.

[0033] The first diagonal C1 and the second diagonal C2 intersect at the central axis D. The length of the first diagonal C1 is greater than the length of the second diagonal C2. The lengths of the line segments connecting the first intersection B1 and the fourth intersection B4, the line segments connecting the first intersection B1 and the third intersection B3, the line segments connecting the second intersection B2 and the fourth intersection B4, and the line segments connecting the second intersection B2 and the third intersection B3 are all the same.

[0034] The virtual ridge line shape 300 is rotationally symmetrical by 180° about each of the first diagonal line C1 and the second diagonal line C2. In other words, the shape obtained by rotating the virtual ridge line shape 300 by 180° about the first diagonal line C1 is the same as the virtual ridge line shape 300. Similarly, the shape obtained by rotating the virtual ridge line shape 300 by 180° about the second diagonal line C2 is the same as the virtual ridge line shape 300.

[0035] Fig. 5 is a schematic cross-sectional view taken along line VV in Fig. 2. The cross section shown in Fig. 5 is parallel to the central axis D, includes the central axis D, and is perpendicular to the third linear portion 23.

[0036] 5 , the sixth outer peripheral region 36 is continuous with each of the fifth linear portion 15 and the third linear portion 23. The sixth outer peripheral region 36 is inclined with respect to the first flat portion 103. The angle formed between the first flat portion 103 and the sixth outer peripheral region 36 is greater than 90°. The distance between the central axis D of the through hole 2 and the sixth outer peripheral region 36 in a direction perpendicular to the central axis D increases from the first main surface 100 toward the second main surface 200. In the direction along the central axis D, the first flat portion 103 is located between the second linear portion 12 and the second flat portion 203.

[0037] FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. 2. The cross section shown in FIG. 6 is parallel to the central axis D, includes the central axis D, and is parallel to the third linear portion 23. The first flank portion 31 is continuous with each of the first linear portion 11 and the seventh linear portion 21. The first flank portion 31 is planar. The first flank portion 31 is inclined with respect to the second flat portion 203. The angle formed by the second flat portion 203 and the first flank portion 31 is greater than 90°. The distance between the first flank portion 31 and the central axis D in a direction perpendicular to the central axis D of the through hole 2 decreases from the first main surface 100 toward the second main surface 200. In the direction along the central axis D, the second flat portion 203 is located between the fourth linear portion 24 and the first flat portion 103.

[0038] 7 is a schematic cross-sectional view taken along line VII-VII in FIG. 2. The cross section shown in FIG. 7 is parallel to the central axis D, includes the central axis D, and is parallel to the first diagonal line C1. In the cross-sectional view, the outer peripheral surface 30 is recessed toward the central axis D of the through hole 2. The distance between the outer peripheral surface 30 and the central axis D in a direction perpendicular to the central axis D of the through hole 2 decreases from the first ridge line 10 toward the intermediate position between the first flat portion 103 and the second flat portion 203. The distance between the outer peripheral surface 30 and the central axis D in a direction perpendicular to the central axis D of the through hole 2 decreases from the second ridge line 20 toward the intermediate position between the first flat portion 103 and the second flat portion 203.

[0039] FIG. 8 is a schematic cross-sectional view taken along line VIII-VIII in FIG. 2 . The cross section shown in FIG. 8 is parallel to the central axis D, includes the central axis D, and intersects with the first minor cutting edge 17. The distance between the outer peripheral surface 30 and the central axis D in a direction perpendicular to the central axis D of the through hole 2 decreases from the first ridge line 10 toward the second ridge line 20. In the direction perpendicular to the central axis D, the fourth outer peripheral region 34 is located between the second flank surface portion 32 and the fifth outer peripheral region 35. The fifth outer peripheral region 35 is continuous with the second ridge line portion 28. The second flank surface portion 32 may have a shape that is recessed toward the central axis D. From another perspective, the distance between the second flank surface portion 32 and the central axis D in a direction perpendicular to the central axis D of the through hole 2 decreases from the first ridge line 10 toward the second ridge line 20.

[0040] Fig. 9 is a schematic cross-sectional view taken along line IX-IX in Fig. 2. The cross section shown in Fig. 9 is parallel to the central axis D, includes the central axis D, and intersects with the first ridge portion 18. The distance between the outer peripheral surface 30 and the central axis D in a direction perpendicular to the central axis D of the through hole 2 increases from the first ridge 10 toward the second ridge 20. In the direction perpendicular to the central axis D, the fourth outer peripheral region 34 is located between the third outer peripheral region 33 and the fifth outer peripheral region 35. The fifth outer peripheral region 35 is continuous with the second minor cutting edge 27.

[0041] FIG. 10 is a schematic cross-sectional view taken along line X-X in FIG. 2. The cross section shown in FIG. 10 is parallel to the central axis D, includes the central axis D, and is parallel to the second diagonal line C2. In the cross-sectional view, the outer peripheral surface 30 is not recessed toward the central axis D of the through hole 2. From another perspective, in the cross-sectional view, the outer peripheral surface 30 may be convex outward. The distance between the outer peripheral surface 30 and the central axis D in a direction perpendicular to the central axis D of the through hole 2 may increase from the first ridge line 10 toward a midpoint between the first flat surface portion 103 and the second flat surface portion 203. The distance between the outer peripheral surface 30 and the central axis D in a direction perpendicular to the central axis D of the through hole 2 may increase from the second ridge line 20 toward a midpoint between the first flat surface portion 103 and the second flat surface portion 203.

[0042] Fig. 11 is a front schematic view showing the configuration of the cutting insert 1 according to the first embodiment. As shown in Fig. 11 , the first major cutting edge 51 may be linear when viewed in a direction perpendicular to the central axis D. In a direction parallel to the central axis D, the first minor cutting edge 17 is located between the first ridge portion 18 and the first major cutting edge 51. When viewed in a direction perpendicular to the central axis D, the first ridge portion 18 may also be linear. In a direction parallel to the central axis D, each of the seventh linear portion 21 and the second ridge portion 28 is located between the second minor cutting edge 27 and the first ridge portion 18.

[0043] Next, a cutting tool according to this embodiment will be described. Fig. 12 is a schematic front view showing the configuration of the cutting tool according to this embodiment. As shown in Fig. 12, the cutting tool 5 has a body 60 and a cutting insert 1. The cutting tool 5 is rotatable around a rotation axis E. From another perspective, the cutting tool 5 is for milling. The cutting insert 1 is attached to the body 60.

[0044] Specifically, the cutting tool 5 has a plurality of cutting inserts 1. The plurality of cutting inserts 1 are arranged at equal intervals around the rotation axis E of the cutting tool 5. A plurality of insert arrangement grooves 63 are provided in the body 60. One cutting insert 1 is arranged in one insert arrangement groove 63. The cutting inserts 1 are attached to the body 60 using a fastening screw 50. The fastening screw 50 is inserted into the through hole 2 of the cutting insert 1.

[0045] The insert placement groove 63 is formed by a groove side surface 62 and a groove bottom surface 61. The first flat surface portion 103 or the second flat surface portion 203 of the cutting insert 1 is pressed against the groove bottom surface 61. The outer peripheral surface 30 of the cutting insert 1 is pressed against the groove side surface 62. As described above, each of the multiple cutting inserts 1 is attached to the body 60.

[0046] Second Embodiment Next, the configuration of a cutting insert 1 according to a second embodiment will be described. The cutting insert 1 according to the second embodiment differs from the cutting insert 1 according to the first embodiment mainly in that the first major cutting edge 51 is curved, but other configurations are substantially the same as those of the cutting insert 1 according to the first embodiment. The following description will focus on the configurations that differ from the cutting insert 1 according to the first embodiment.

[0047] Fig. 13 is a schematic perspective view showing the configuration of a cutting insert 1 according to the second embodiment. As shown in Fig. 13, the cutting insert 1 according to the second embodiment has a first main surface 100, a second main surface 200, an outer peripheral surface 30, a first ridge line 10, and a second ridge line 20. The first main surface 100 has a first flat surface portion 103, a first rake face portion 101, and a second rake face portion 102. The through hole 2 opens to the first flat surface portion 103.

[0048] Fig. 14 is a schematic front view showing the configuration of the cutting insert 1 according to the second embodiment. As shown in Fig. 14, the first ridge 10 has a first major cutting edge 51, a first minor cutting edge 17, a first ridge portion 18, and a first corner portion 19. The first major cutting edge 51 is continuous with the first flank portion 31. The first minor cutting edge 17 is continuous with the second flank portion 32. The first ridge portion 18 is continuous with the third outer peripheral region 33.

[0049] 14 , the first major cutting edge 51 is curved when viewed in a direction perpendicular to the central axis D. When viewed in a direction perpendicular to the central axis D, the first major cutting edge 51 may be curved so as to be convex outward. In a direction parallel to the central axis D, at least a portion of the first major cutting edge 51 is located above the first corner portion 19. The upward direction is the direction from the second main surface 200 toward the first main surface 100.

[0050] As shown in FIG. 14 , when viewed in a direction perpendicular to the central axis D, the first minor cutting edge 17 is located between the first ridge portion 18 and the first major cutting edge 51. When viewed in a direction perpendicular to the central axis D, the first ridge portion 18 may be linear. When viewed in a direction perpendicular to the central axis D, the first minor cutting edge 17 extends so as to intersect with the second linear portion 12. In a direction parallel to the central axis D, the portion of the first minor cutting edge 17 that connects to the first major cutting edge 51 is located above the first corner portion 19. The portion of the first minor cutting edge 17 that connects to the first ridge portion 18 is located below the first corner portion 19. Note that the downward direction refers to the direction from the first main surface 100 toward the second main surface 200.

[0051] Fig. 15 is a plan view schematic diagram showing the configuration of the cutting insert 1 according to the second embodiment. The first ridge line 10 has a first linear portion 11 and a second linear portion 12. As shown in Fig. 15, the first linear portion 11 and the second linear portion 12 are parallel to each other when viewed in a direction from the first flat portion 103 toward the second flat portion 203. The first linear portion 11 includes a first major cutting edge 51. When viewed in a direction from the first flat portion 103 toward the second flat portion 203, the first major cutting edge 51 is linear.

[0052] Next, the effects of the cutting insert 1 and cutting tool 5 according to this embodiment will be described.

[0053] According to the cutting insert 1 of this embodiment, the imaginary ridge line shape 300 formed when the first ridge line 10 and the second ridge line 20 are perpendicularly projected onto an imaginary plane located midway between the first flat portion 103 and the second flat portion 203 is rotationally symmetrical by 180° about each of the first diagonal line C1 and the second diagonal line C2. Each of the first linear portion 11, the second linear portion 12, the third linear portion 23, and the fourth linear portion 24 includes a major cutting edge. This allows the four portions to be used as major cutting edges.

[0054] According to the cutting insert 1 of this embodiment, the outer peripheral surface 30 includes a first flank portion 31 that is continuous with the main cutting edge. The distance between the first flank portion 31 and the central axis D of the through hole 2 in a direction perpendicular to the central axis D decreases from the first main surface 100 toward the second main surface 200. This allows the clearance angle of the first flank portion 31 that is continuous with the main cutting edge to be positive. As a result, sharpness can be improved.

[0055] The cutting insert 1 according to this embodiment has a first main surface 100 and a second main surface 200. The second main surface 200 is located opposite the first main surface 100. The first main surface 100 includes a first flat surface 103. The second main surface 200 includes a second flat surface 203 parallel to the first flat surface 103. The cutting insert 1 has a through hole 2 extending from the first flat surface 103 to the second flat surface 203. As a result, when the cutting insert 1 is attached to the body 60, the first flat surface 103 or the second flat surface 203 is pressed against the groove bottom surface 61 of the insert placement groove 63 provided in the body 60. This increases the contact area between the cutting insert 1 and the body 60. As a result, the cutting insert 1 can be firmly fixed to the body 60. The first main surface 100 also includes a first rake surface 101. The second flat surface 203 is located opposite the first cutting surface 101. Therefore, when the main component of cutting resistance is applied to the first cutting surface 101, the stress can be dispersed by the second flat surface 203. As a result, the groove bottom surface 61 is less likely to undergo plastic deformation.

[0056] According to the cutting insert 1 of this embodiment, the first ridge 10 may include a minor cutting edge that is continuous with the major cutting edge. The minor cutting edge is involved in cutting in oblique machining or helical machining. The outer peripheral surface 30 may include a second flank portion 32 that is continuous with the minor cutting edge. The second flank portion 32 may have a shape that is recessed toward the central axis D. This allows the maximum inclination angle of the cutting tool 5 to be increased in oblique machining or helical machining.

[0057] According to the cutting insert 1 according to this embodiment, the first flank portion 31 may be flat. As a result, when the cutting insert 1 is attached to the body 60, the first flank portion 31 is pressed against the side surface of the insert placement groove 63 provided in the body 60. This increases the contact area between the cutting insert 1 and the body 60. As a result, the cutting insert 1 can be firmly fixed to the body 60.

[0058] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0059] 1 Cutting insert, 2 Through hole, 5 Cutting tool, 10 First ridge, 11 First straight line portion, 12 Second straight line portion, 15 Fifth straight line portion, 16 Sixth straight line portion, 17 First minor cutting edge, 18 First ridge portion, 19 First corner portion, 20 Second ridge, 21 Seventh straight line portion, 22 Eighth straight line portion, 23 Third straight line portion, 24 Fourth straight line portion, 27 Second minor cutting edge, 28 Second ridge portion, 29 Second corner portion, 30 Outer peripheral surface, 31 First relief surface portion, 32 Second relief surface portion, 33 Third outer peripheral region, 34 Fourth outer peripheral region, 35 Fifth outer peripheral region, 36 Sixth outer peripheral region, 50 Fastening screw, 51 First major cutting edge, 52 Second major cutting edge, 60 Body, 61 Groove bottom surface, 62 Groove side surface, 63 Insert placement groove, 100 First main surface, 101 First rake face portion, 102 Second rake face portion, 103 First flat surface portion, 200 Second main surface, 201 Third rake face portion, 202 Fourth rake face portion, 203 Second flat surface portion, 300 Virtual ridge line shape, 311 First projected straight line portion, 312 Second projected straight line portion, 315 Fifth projected straight line portion, 316 Sixth projected straight line portion, 321 Seventh projected straight line portion, 322 Eighth projected straight line portion, 323 Third projected straight line portion, 324 Fourth projected straight line portion, A1 First virtual line portion, A2 Second virtual line portion, A3 Third virtual line portion, A4 Fourth virtual line portion, B1 First intersection, B2 Second intersection, B3 Third intersection, B4 Fourth intersection, C1 First diagonal, C2 Second diagonal, D Central axis, E Rotation axis

Claims

1. A cutting insert comprising: a first main surface; a second main surface opposite the first main surface; and an outer peripheral surface continuous with each of the first main surface and the second main surface, wherein the first main surface includes a first flat portion, and the second main surface includes a second flat portion parallel to the first flat portion, the cutting insert has a through hole extending from the first flat portion to the second flat portion, the boundary between the first main surface and the outer peripheral surface forms a first ridge line, the boundary between the second main surface and the outer peripheral surface forms a second ridge line, the first ridge line includes a first linear portion and a second linear portion opposite the first linear portion, the second ridge line includes a third linear portion and a fourth linear portion opposite the third linear portion, when viewed in a direction from the first flat portion to the second flat portion, the first linear portion and the second linear portion are parallel, and the third linear portion and the fourth linear portion are parallel, a shape formed when the first ridge line and the second ridge line are vertically projected onto an imaginary plane located midway between the first and second flat plane portions is defined as a virtual ridge line shape; in the imaginary plane, the virtual ridge line shape has a first projected straight line portion, a second projected straight line portion, a third projected straight line portion, and a fourth projected straight line portion, which are shapes formed when the first straight line portion, the second straight line portion, the third straight line portion, and the fourth straight line portion are vertically projected onto the imaginary plane; a shape surrounded by a first virtual line portion extending along the first projected straight line portion, a second virtual line portion extending along the second projected straight line portion, a third virtual line portion extending along the third projected straight line portion, and a fourth virtual line portion extending along the fourth projected straight line portion is a rhombus; and a line segment connecting a first intersection point between the first virtual line portion and the third virtual line portion and a second intersection point between the second virtual line portion and the fourth virtual line portion forms a first diagonal of the rhombus; a line segment connecting a third intersection point between the first imaginary line portion and the fourth imaginary line portion and a fourth intersection point between the second imaginary line portion and the third imaginary line portion forms a second diagonal of the rhombus; the imaginary ridge line shape is rotationally symmetrical by 180° around each of the first diagonal and the second diagonal; each of the first straight line portion, the second straight line portion, the third straight line portion, and the fourth straight line portion includes a major cutting edge; and the first main surface includes a first rake face portion connected to the major cutting edge.the outer peripheral surface includes a first flank portion connected to the main cutting edge, and a distance between the first flank portion and the central axis in a direction perpendicular to the central axis of the through hole decreases from the first main surface toward the second main surface.

2. A cutting insert as described in claim 1, wherein the first ridge line includes a minor cutting edge that is continuous with the major cutting edge, the outer peripheral surface includes a second flank portion that is continuous with the minor cutting edge, and the second flank portion has a shape that is concave toward the central axis.

3. A cutting insert as described in claim 1, wherein the first ridge line includes a minor cutting edge connected to the major cutting edge, a fifth straight line portion parallel to the third straight line portion, and a ridge portion between the fifth straight line portion and the minor cutting edge, and when viewed in a direction from the first flat surface portion toward the second flat surface portion, the ridge portion has a shape that is concave toward the central axis.

4. A cutting insert according to any one of claims 1 to 3, wherein the first flank portion is flat.

5. A cutting insert as described in claim 1, wherein the first ridge line includes a minor cutting edge connected to the major cutting edge, a fifth straight line portion parallel to the third straight line portion, and a ridge line portion between the fifth straight line portion and the minor cutting edge, the outer peripheral surface includes a second flank surface portion connected to the minor cutting edge, the second flank surface portion has a shape concave toward the central axis, when viewed in a direction from the first flat surface portion toward the second flat surface portion, the ridge line portion has a shape concave toward the central axis, and the first flank surface portion is flat.

6. A cutting tool comprising: a cutting insert according to any one of claims 1 to 5; and a body to which the cutting insert is attached.

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