Cutting insert and machining method

Abstract

The cutting insert includes a rake face (50), a clearance face (70), and a cutting edge (10) formed by a ridge (20) line between the rake face and the clearance face. The cutting edge has a first cutting edge portion (1) for corner machining, a second cutting edge portion (2) for low-depth cutting, a third cutting edge portion (3) for high-depth cutting, a fourth cutting edge portion (4) for finishing surface machining, a first connecting cutting edge portion, a second connecting cutting edge portion, and a third connecting cutting edge portion. The fourth cutting edge portion is disposed between the first cutting edge portion and the second cutting edge portion. The second cutting edge portion is disposed between the fourth cutting edge portion and the third cutting edge portion. Each of the first cutting edge portion, the second cutting edge portion, and the fourth cutting edge portion has a curved shape. The radius of curvature of the first cutting edge portion is 0.1 mm or more and 2.4 mm or less. The radius of curvature of the second cutting edge portion is 3 mm or more. The fourth cutting edge portion has a radius of curvature of 3 mm or more. The third cutting edge portion has a straight line shape.

Description

[Technical field]

[0001] The present disclosure relates to cutting inserts and machining methods. [Background technology]

[0002] International Publication No. WO 2019 / 087496 (Patent Document 1) discloses a cutting insert having a rake face, a flank face, and a chamfer disposed between the rake face and the flank face. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 087496 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when performing high-efficiency machining of hardened steel, the cutting resistance increases, making it easy for chipping to occur on the cutting edge, making it difficult to improve the tool life of the cutting insert.

[0005] An object of the present disclosure is to provide a cutting insert capable of improving tool life. [Means for solving the problem]

[0006] The cutting insert according to the present disclosure has a surface involved in cutting made of a cBN-based sintered body, a diamond-based sintered body, ceramics, cermet, or cemented carbide, and includes a rake face, a clearance face, and a cutting edge formed by a ridge between the rake face and the clearance face. The cutting edge has a first cutting edge portion for corner machining, a second cutting edge portion for low-cutting-depth drawing, a third cutting edge portion for high-cutting-depth drawing, a fourth cutting edge portion for finishing surface machining, a first connecting cutting edge portion connecting the first cutting edge portion and the fourth cutting edge portion, a second connecting cutting edge portion connecting the second cutting edge portion and the fourth cutting edge portion, and a third connecting cutting edge portion connecting the second cutting edge portion and the third cutting edge portion. The fourth cutting edge portion is disposed between the first cutting edge portion and the second cutting edge portion. The second cutting edge portion is disposed between the fourth cutting edge portion and the third cutting edge portion. Each of the first cutting edge portion, the second cutting edge portion, and the fourth cutting edge portion has a curved shape. The radius of curvature of the first cutting edge portion is 0.1 mm or more and 2.4 mm or less. The radius of curvature of the second cutting edge portion is 3 mm or more. The radius of curvature of the fourth cutting edge portion is 3 mm or more. The third cutting edge portion has a straight line shape. Each of the first connecting cutting edge portion, the second connecting cutting edge portion, and the third connecting cutting edge portion has a curved shape. Effect of the Invention

[0007] According to the present disclosure, a cutting insert capable of improving tool life can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic perspective view showing the configuration of a cutting insert according to a first embodiment. [Diagram 2] FIG. 2 is a schematic plan view showing the configuration of the cutting tool according to the first embodiment. [Diagram 3] FIG. 3 is an enlarged schematic view of region III in FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is a schematic perspective view showing the configuration of a cutting insert according to a second embodiment. [Figure 6]FIG. 6 is a schematic plan view showing the configuration of a cutting insert according to a second embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 8 is a schematic cross-sectional view taken along line VIII-VIII in FIG. [Figure 9] FIG. 9 is a schematic cross-sectional view taken along line IX-IX in FIG. [Figure 10] FIG. 10 is a schematic cross-sectional view taken along line XX in FIG. [Figure 11] FIG. 11 is a schematic cross-sectional view taken along line XI-XI in FIG. [Figure 12] FIG. 12 is a schematic diagram showing the first processing method according to the present embodiment. [Figure 13] FIG. 13 is an enlarged schematic view showing the processed state. [Figure 14] FIG. 14 is a schematic diagram showing the relationship between the cutting depth and the side cutting edge angle of the cutting edge. [Figure 15] FIG. 15 is a schematic side view showing the side rake angle of the cutting edge. [Figure 16] FIG. 16 is a schematic diagram showing the second processing method according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure (also referred to as the present embodiment) will be listed and described.

[0010] (1) The cutting insert 100 according to the present disclosure has a surface involved in cutting made of a cBN-based sintered body, a diamond-based sintered body, ceramics, cermet, or cemented carbide, and includes a rake face 50, a clearance face 70, and a cutting edge 10 formed by a ridge line 20 between the rake face 50 and the clearance face 70. The cutting edge 10 has a first cutting edge portion 1 for corner machining, a second cutting edge portion 2 for low cutting edge machining, a third cutting edge portion 3 for high cutting edge machining, a fourth cutting edge portion 4 for finishing surface machining, a first connecting cutting edge portion 11 connecting the first cutting edge portion 1 and the fourth cutting edge portion 4, a second connecting cutting edge portion 12 connecting the second cutting edge portion 2 and the fourth cutting edge portion 4, and a third connecting cutting edge portion 13 connecting the second cutting edge portion 2 and the third cutting edge portion 3. The fourth cutting edge portion 4 is disposed between the first cutting edge portion 1 and the second cutting edge portion 2. The second cutting edge portion 2 is disposed between the fourth cutting edge portion 4 and the third cutting edge portion 3. Each of the first cutting edge portion 1, the second cutting edge portion 2, and the fourth cutting edge portion 4 has a curved shape. The radius of curvature of the first cutting edge portion 1 is 0.1 mm or more and 2.4 mm or less. The radius of curvature of the second cutting edge portion 2 is 3 mm or more. The radius of curvature of the fourth cutting edge portion 4 is 3 mm or more. The third cutting edge portion 3 has a straight shape. Each of the first connecting cutting edge portion 11, the second connecting cutting edge portion 12, and the third connecting cutting edge portion 13 has a curved shape.

[0011] (2) According to the cutting insert 100 according to the above (1), the first connecting cutting edge portion 11, the second connecting cutting edge portion 12 and the third connecting cutting edge portion 13 may each have a radius of curvature of 0.2 mm or more.

[0012] (3) According to the cutting insert 100 relating to (1) or (2) above, the clearance angle of each of the first cutting edge portion 1, the second cutting edge portion 2, the third cutting edge portion 3 and the fourth cutting edge portion 4 may be greater than or equal to 3° and less than or equal to 20°.

[0013] (4) According to the cutting insert 100 according to any one of (1) to (3) above, the flank 70 may have a constraint surface 71 that is constrained by the holder. If the apex angle of the second cutting edge portion 2 is a first angle θ8 and the apex angle of the ridgeline between the constraint surface 71 and the rake face 50 is a second angle θ9, the second angle θ9 may be smaller than the first angle θ8. The second angle θ9 may be 30° or more and 80° or less.

[0014] (5) According to the cutting insert 100 according to any one of (1) to (3) above, the flank 70 may have a constraint surface 71 that is constrained by the holder. If the apex angle of the second cutting edge portion 2 is a first angle θ8 and the apex angle of the ridgeline between the constraint surface 71 and the rake face 50 is a second angle θ9, the second angle θ9 may be smaller than the first angle θ8. The first angle θ8 may be 35° or more and 85° or less.

[0015] (6) According to the cutting insert 100 according to the above (4) or (5), the clearance angle of the constraint surface 71 may be 0°.

[0016] (7) A processing method according to one embodiment of the present disclosure is a processing method using a cutting insert described in any one of (1) to (6) above, wherein in a drawing process in which a workpiece is machined using the second cutting edge portion 2, a side rake angle of the second cutting edge portion 2 may be greater than or equal to -20° and less than or equal to 20°.

[0017] (8) According to the machining method of (7) above, in a drawing process in which a workpiece is machined using the third cutting edge portion 3, the side rake angle of the third cutting edge portion 3 may be greater than or equal to -20° and less than or equal to 20°.

[0018] (9) According to the processing method of (7) or (8) above, the second cutting edge portion 2 may be within a range of 0.15 mm or less from a position closest to the workpiece in a direction perpendicular to the rotation axis. In a drawing process in which the workpiece is processed using the second cutting edge portion 2, the side cutting edge angle of the second cutting edge portion 2 may be 70° or more and 89° or less.

[0019] (10) According to the machining method of (7) or (8) above, the third cutting edge portion 3 may be located in a range of 0.05 mm to 0.5 mm from a position closest to the workpiece in a direction perpendicular to the rotation axis. The side cutting edge angle of the third cutting edge portion 3 may be 60° to 85°.

[0020] (11) According to any one of the machining methods (7) to (10) above, the minimum value of the side cutting edge angle of the second cutting edge portion 2 may be the same as the side cutting edge angle of the third cutting edge portion 3.

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific example of a cutting insert according to an embodiment of the present disclosure will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated.

[0022] (First embodiment) FIG. 1 is a perspective schematic diagram showing the configuration of the cutting insert according to the first embodiment. As shown in FIG. 1, the cutting insert 100 according to the first embodiment has a blade member 6 and a base metal 7. The blade member 6 is attached to the base metal 7. The blade member 6 is involved in cutting. The planar shape of the base metal 7 is not particularly limited, but is, for example, a rhombus. The blade member 6 is joined to an acute corner portion of the base metal 7. The base metal 7 is made of, for example, cemented carbide or cermet. The cutting insert 100 according to this embodiment is formed by joining the blade member 6 to an acute corner portion of the base metal 7, but the entire cutting insert 100 may be formed of the blade member 6.

[0023] The present disclosure is also applicable to cutting inserts 100 having polygonal shapes other than a diamond shape. Since the cutting edge shape is common, only a diamond-shaped cutting insert 100 is illustrated. A counterbore 8 is formed by partially recessing a part of the upper surface at an acute corner of the base metal 7. The blade member 6 is joined to the base metal 7 at the counterbore 8 by a joining means such as brazing.

[0024] The blade member 6 is composed of a cBN-based sintered body, a diamond-based sintered body, ceramics, cermet, or cemented carbide. The cBN-based sintered body is a sintered body containing cBN (cubic boron nitride) at a volume ratio of 10% to 99.9%. The diamond-based sintered body is a sintered body containing diamond at a volume ratio of 10% to 99.9%. The ceramic is not particularly limited, but for example, ceramics such as alumina (Al2O3), silicon nitride (Si3N4), and titanium carbide (TiC) can be preferably used. The cermet is not particularly limited, but for example, nitride-based cermet and carbide-based cermet can be preferably used.

[0025] The cutting insert 100 according to this embodiment has a rake face 50, a flank 70, a cutting edge 10, and a bottom surface 60. The cutting edge 10 is formed by a ridge 20 between the rake face 50 and the flank 70. The ridge 20 has two cutting edges 10, two first ridge portions 21, and two second ridge portions 22. The cutting edge 10 is a part of the ridge 20. The flank 70 has a first flank portion 30, a second flank portion 40, and a restraining surface 71. The first flank portion 30 is continuous with the cutting edge 10. The second flank portion 40 is continuous with each of the first flank portion 30 and the bottom surface 60.

[0026] The cutting edge 10 has a first cutting edge portion 1 for corner machining, a second cutting edge portion 2 for low-depth cutting, a third cutting edge portion 3 for high-depth cutting, and a fourth cutting edge portion 4 for finishing surface machining. The fourth cutting edge portion 4 is disposed between the first cutting edge portion 1 and the second cutting edge portion 2. The second cutting edge portion 2 is disposed between the fourth cutting edge portion 4 and the third cutting edge portion 3.

[0027] 2 is a schematic plan view showing the configuration of the cutting tool according to the first embodiment. The schematic plan view shown in FIG.

[0028] As shown in FIG. 2, the first cutting edge portion 1 has a curved shape. The first cutting edge portion 1 is curved so as to be convex outward. The first cutting edge portion 1 is a corner cutting edge portion. The curvature radius of the first cutting edge portion 1 is 0.1 mm or more and 2.4 mm or less. The curvature radius of the first cutting edge portion 1 is not particularly limited, and may be 0.2 mm or more and 2.2 mm or less, 0.4 mm or more and 2.0 mm or less, or 0.6 mm or more and 1.8 mm or less.

[0029] The fourth cutting edge portion 4 has a curved shape. The radius of curvature of the fourth cutting edge portion 4 is 3 mm or more. The radius of curvature of the fourth cutting edge portion 4 is not particularly limited, but may be 5 mm or more, 10 mm or more, 20 mm or more, or 40 mm or more. The radius of curvature of the fourth cutting edge portion 4 may be 80 mm or less, 70 mm or less, or 60 mm or less.

[0030] The second cutting edge portion 2 has a curved shape. The radius of curvature of the second cutting edge portion 2 is 3 mm or more. The radius of curvature of the second cutting edge portion 2 is not particularly limited, but may be 5 mm or more, 10 mm or more, 20 mm or more, or 40 mm or more. The radius of curvature of the second cutting edge portion 2 may be 80 mm or less, 70 mm or less, or 60 mm or less. The radius of curvature of the second cutting edge portion 2 may be different from or the same as the radius of curvature of the fourth cutting edge portion 4.

[0031] The third cutting edge portion 3 has a straight line shape. The length of the third cutting edge portion 3 may be longer than the length of the second cutting edge portion 2. The length of the second cutting edge portion 2 is the length measured when the curved second cutting edge portion 2 is made straight. The length of the third cutting edge portion 3 is, for example, 0.5 mm or more and 5.0 mm or less.

[0032] 2, the rake face 50 has a first rake face portion 51 and a second rake face portion 52. The first rake face portion 51 is formed of a blade member 6. The second rake face portion 52 is formed of a base metal 7. A through hole 5 is formed in the second rake face portion 52.

[0033] The cutting insert according to this embodiment has two cutting edges 10. When viewed along a straight line perpendicular to the cutting face 50, the through hole 5 is located between the two cutting edges 10. Each of the two cutting edges 10 may have one first cutting edge portion 1, two second cutting edge portions 2, two third cutting edge portions 3, and two fourth cutting edge portions 4. The first cutting edge portion 1 may be located between the two fourth cutting edge portions 4.

[0034] When viewed along a straight line perpendicular to the cutting face 50, each of the two cutting edges 10 may have a shape that is symmetrical with respect to a straight line (a diagonal line of the cutting insert) passing through the two first cutting edge portions 1. Each of the two cutting edges 10 may have a shape that is two-fold symmetric with respect to an axis passing through the through hole 5.

[0035] As shown in Fig. 2, the first ridges 21 and the second ridges 22 are formed by a base metal 7. The cutting edge 10 is formed by a blade member 6. The two first ridges 21 face each other. Similarly, the two second ridges 22 face each other. When viewed along a straight line perpendicular to the rake face 50, each of the two first ridges 21 and each of the two second ridges 22 has a linear shape.

[0036] Of the two third cutting edge portions 3, the first third cutting edge portion 3 may be connected to the first ridge portion 21, and the second third cutting edge portion 3 may be connected to the second ridge portion 22. The length of the first ridge portion 21 may be longer than the length of the third cutting edge portion 3 connected to the first ridge portion 21. The length of the second ridge portion 22 may be longer than the length of the third cutting edge portion 3 connected to the second ridge portion 22.

[0037] As shown in FIG. 2, the apex angle of the second cutting edge portion 2 is a first angle θ8. Specifically, when viewed along a straight line perpendicular to the rake face 50, the first angle θ8 is an angle formed by a straight line passing through both ends of each of the two second cutting edge portions 2. The flank face 70 has a constraint surface 71 that is constrained by the holder (see FIG. 1). The clearance angle of the constraint surface 71 is, for example, 0°. The clearance angle of the constraint surface 71 is the angle of the constraint surface 71 with respect to a plane perpendicular to the rake face 50. The apex angle of the ridge between the constraint surface 71 and the rake face 50 is a second angle θ9. Specifically, when viewed along a straight line perpendicular to the rake face 50, the second angle θ9 is an angle formed by the first ridge portion 21 and the second ridge portion 22.

[0038] The first angle θ8 is, for example, 70°. The first angle θ8 may be 35° or more and 85° or less, 45° or more and 80° or less, or 55° or more and 75° or less. The second angle θ9 is smaller than the first angle θ8. The second angle θ9 is, for example, 55°. The second angle θ9 may be 30° or more and 80° or less, 35° or more and 70° or less, or 40° or more and 60° or less.

[0039] At the contact point between the first ridge portion 21 and the third cutting edge portion 3, the third cutting edge portion 3 may be inclined with respect to the first ridge portion 21. Similarly, at the contact point between the second ridge portion 22 and the third cutting edge portion 3, the third cutting edge portion 3 may be inclined with respect to the second ridge portion 22. The apex angle of the third cutting edge portion 3 may be smaller than the first angle θ8. The apex angle of the third cutting edge portion 3 may be larger than the second angle θ9. The apex angle of the third cutting edge portion 3 is the angle formed by the two third cutting edge portions 3 when viewed along a straight line perpendicular to the rake face 50.

[0040] FIG. 3 is an enlarged schematic diagram of region III in FIG. 1. As shown in FIG. 3, the cutting edge 10 has a first connecting cutting edge portion 11, a second connecting cutting edge portion 12, and a third connecting cutting edge portion 13. The first connecting cutting edge portion 11 connects the first cutting edge portion 1 and the fourth cutting edge portion 4. The first connecting cutting edge portion 11 is located between the first cutting edge portion 1 and the fourth cutting edge portion 4. The second connecting cutting edge portion 12 connects the second cutting edge portion 2 and the fourth cutting edge portion 4. The second connecting cutting edge portion 12 is located between the second cutting edge portion 2 and the fourth cutting edge portion 4. The third connecting cutting edge portion 13 connects the second cutting edge portion 2 and the third cutting edge portion 3. The third connecting cutting edge portion 13 is located between the second cutting edge portion 2 and the third cutting edge portion 3.

[0041] When viewed along a straight line perpendicular to the rake face 50, each of the first connecting cutting edge portion 11, the second connecting cutting edge portion 12, and the third connecting cutting edge portion 13 has a curved shape. Each of the first connecting cutting edge portion 11, the second connecting cutting edge portion 12, and the third connecting cutting edge portion 13 is curved so as to be convex outward. The radius of curvature of the third connecting cutting edge portion 13 may be larger than the radius of curvature of each of the first connecting cutting edge portion 11 and the second connecting cutting edge portion 12.

[0042] The radius of curvature of each of the first connecting cutting edge portion 11, the second connecting cutting edge portion 12, and the third connecting cutting edge portion 13 may be, for example, 0.2 mm or more. The radius of curvature of each of the first connecting cutting edge portion 11, the second connecting cutting edge portion 12, and the third connecting cutting edge portion 13 may be, for example, 0.3 mm or more, or 0.5 mm or more. The radius of curvature of each of the first connecting cutting edge portion 11, the second connecting cutting edge portion 12, and the third connecting cutting edge portion 13 may be less than 3 mm, or less than 2 mm.

[0043] The first connecting cutting edge portion 11 may have a different radius of curvature from the adjacent first cutting edge portion 1 and the adjacent fourth cutting edge portion 4. The second connecting cutting edge portion 12 may have a different radius of curvature from the adjacent second cutting edge portion 2 and the adjacent fourth cutting edge portion 4. The third connecting cutting edge portion 13 may have a different radius of curvature from the adjacent second cutting edge portion 2 and the adjacent third cutting edge portion 3.

[0044] As shown in Fig. 3, the first flank portion 30 has a first flank region 31, a second flank region 32, a third flank region 33, a fourth flank region 34, a fifth flank region 35, a sixth flank region 36, and a seventh flank region 37. The first flank region 31 is continuous with the first cutting edge portion 1. The second flank region 32 is continuous with the second cutting edge portion 2. The third flank region 33 is continuous with the third cutting edge portion 3. The fourth flank region 34 is continuous with the fourth cutting edge portion 4.

[0045] The fifth flank region 35 is connected to the first connecting cutting edge portion 11. The sixth flank region 36 is connected to the second connecting cutting edge portion 12. The seventh flank region 37 is connected to the third connecting cutting edge portion 13. The first flank region 31, the second flank region 32, the third flank region 33, the fourth flank region 34, the fifth flank region 35, the sixth flank region 36, and the seventh flank region 37 are formed by the blade member 6.

[0046] The second flank portion 40 has a first side region 41, a second side region 42, a third side region 43, a fourth side region 44, a fifth side region 45, a sixth side region 46, and a seventh side region 47. The first side region 41 is continuous with the first flank region 31 and the bottom surface 60. The second side region 42 is continuous with the second flank region 32 and the bottom surface 60. The third side region 43 is continuous with the third flank region 33 and the bottom surface 60. The fourth side region 44 is continuous with the fourth flank region 34 and the bottom surface 60.

[0047] The fifth side surface region 45 is continuous with the fifth flank region 35 and the bottom surface 60. The sixth side surface region 46 is continuous with the sixth flank region 36 and the bottom surface 60. The seventh side surface region 47 is continuous with the seventh flank region 37 and the bottom surface 60. The first side surface region 41, the second side surface region 42, the third side surface region 43, the fourth side surface region 44, the fifth side surface region 45, the sixth side surface region 46, and the seventh side surface region 47 are formed by the base metal 7.

[0048] FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. 2. The cross section shown in FIG. 4 passes through the midpoints of the two first cutting edge portions 1. A straight line passing through the midpoints of the two first cutting edge portions 1 is a diagonal line of the cutting insert 100. As shown in FIG. 4, the through hole 5 penetrates the base metal 7. The through hole 5 opens on each of the rake face 50 and the bottom face 60. The flank face 70 may be inclined perpendicularly to the rake face 50. Specifically, each of the first flank face portion 30 and the second flank face portion 40 may be inclined perpendicularly to the rake face 50.

[0049] Second embodiment Next, the configuration of the cutting insert 100 according to the second embodiment will be described. The cutting insert 100 according to the second embodiment differs from the cutting insert 100 according to the first embodiment mainly in the configuration in which the clearance angle of the first clearance portion 30 is 3° or more and 20° or less, and other configurations are substantially the same as those of the cutting insert 100 according to the first embodiment. Below, the configurations different from the cutting insert 100 according to the first embodiment will be mainly described.

[0050] 5 is a perspective schematic diagram showing the configuration of the cutting insert according to the second embodiment. As shown in FIG. 5, the flank 70 has a holder restraint surface 71, a first flank portion 30, and a second flank portion 40. The second flank portion 40 is continuous with the holder restraint surface 71. The first flank portion 30 is inclined inward with respect to a plane perpendicular to the rake face 50. The second flank portion 40 is inclined with respect to the holder restraint surface 71. The second flank portion 40 is formed of a base metal. The second flank portion 40 is continuous with each of the first flank portion 30 and the bottom surface 60.

[0051] Fig. 6 is a schematic plan view showing the configuration of a cutting insert according to a second embodiment. Fig. 7 is a schematic cross-sectional view taken along line VII-VII in Fig. 6. The cross section shown in Fig. 7 passes through the midpoints of the two first cutting edge portions 1.

[0052] 7, the clearance angle of the first cutting edge portion 1 (first clearance angle θ1) is the inclination angle of the first clearance region 31 with respect to a plane perpendicular to the rake face 50. The first clearance angle θ1 may be, for example, 3° or more and 20° or less, 5° or more and 18° or less, or 7° or more and 15° or less.

[0053] 8 is a schematic cross-sectional view taken along line VIII-VIII in FIG. 6. The cross section shown in FIG. 8 intersects with each of the two fourth cutting edge portions 4 and is perpendicular to the diagonal line of the cutting insert. As shown in FIG. 8, the fourth flank region 34 is inclined inward with respect to a plane perpendicular to the rake face 50. The clearance angle of the fourth cutting edge portion 4 (fourth clearance angle θ4) is the inclination angle of the fourth flank region 34 with respect to a plane perpendicular to the rake face 50. The fourth clearance angle θ4 may be, for example, 3° or more and 20° or less, 5° or more and 18° or less, or 7° or more and 15° or less.

[0054] 9 is a schematic cross-sectional view taken along line IX-IX in FIG. 6. The cross section shown in FIG. 9 intersects with each of the two second cutting edge portions 2 and is perpendicular to the diagonal line of the cutting insert. As shown in FIG. 9, the second flank region 32 is inclined inward with respect to a plane perpendicular to the rake face 50. The clearance angle of the second cutting edge portion 2 (second clearance angle θ2) is the inclination angle of the second flank region 32 with respect to a plane perpendicular to the rake face 50. The second clearance angle θ2 may be, for example, 3° or more and 20° or less, 5° or more and 18° or less, or 7° or more and 15° or less.

[0055] 10 is a schematic cross-sectional view taken along line XX in FIG. 6. The cross section shown in FIG. 10 intersects with each of the two third cutting edge portions 3 and is perpendicular to the diagonal line of the cutting insert. As shown in FIG. 10, the third flank region 33 is inclined inward with respect to a plane perpendicular to the rake face 50. The clearance angle of the third cutting edge portion 3 (third clearance angle θ3) is the inclination angle of the third flank region 33 with respect to a plane perpendicular to the rake face 50. The third clearance angle θ3 may be, for example, 3° or more and 20° or less, 5° or more and 18° or less, or 7° or more and 15° or less.

[0056] Fig. 11 is a schematic cross-sectional view taken along line XI-XI in Fig. 6. The cross section shown in Fig. 11 intersects with each of the first ridge portion 21 and the second ridge portion 22, and is perpendicular to the diagonal line of the cutting insert. As shown in Fig. 11, the holder restraint surface 71 is perpendicular to the rake face 50. The clearance angle of the holder restraint surface 71 is the inclination angle of the holder restraint surface 71 with respect to a plane perpendicular to the rake face 50. The clearance angle of the holder restraint surface 71 is, for example, 0°.

[0057] Next, a machining method according to the present embodiment will be described. In the machining method according to the present embodiment, a workpiece is machined using the cutting insert 100 according to the present embodiment.

[0058] FIG. 12 is a schematic diagram showing a first processing method according to the present embodiment. As shown in FIG. 12, the cutting insert 100 is attached to the holder 150 using a pressing member 160. The pressing member 160 has a main body portion 162 and an insertion portion 161. The insertion portion 161 is inserted into the through hole 5 of the cutting insert 100. The main body portion 162 has an attachment hole 163. A fastening screw 170 is inserted into the attachment hole 163. As a result, the pressing member 160 is fixed to the holder 150. The pressing member 160 pulls the cutting insert 100 to the holder 150, so that the cutting insert 100 is fixed to the holder 150.

[0059] The cutting insert 100 according to this embodiment is capable of external diameter drawing. The workpiece 200 has an outer peripheral surface 201. The drawing is a process performed while moving the cutting insert 100 in a first feed direction A. The first feed direction A is a direction from the cutting insert 100 toward the holder 150. In the drawing, the workpiece 200 is machined using the cutting edge 10. The first feed direction A is parallel to the rotation axis X of the workpiece 200. The workpiece 200 rotates in a rotation direction R around the rotation axis X.

[0060] Fig. 13 is an enlarged schematic diagram showing a machining state. The enlarged schematic diagram shown in Fig. 13 shows a state seen along a straight line perpendicular to the rake face 50. The cutting edge 10 cuts into the workpiece 200 with a cutting depth ap.

[0061] 13, the side cutting edge angle of the second cutting edge portion 2 in the drawing process is a fifth angle θ5. The fifth angle θ5 is an angle between a tangent to the cutting edge 10 at the contact point between the outer peripheral surface 201 of the workpiece 200 and the cutting edge 10 and a straight line perpendicular to the rotation axis X of the workpiece 200.

[0062] Fig. 14 is a schematic diagram showing the relationship between the depth of cut and the side cutting edge angle of the cutting edge. As shown in Fig. 14, as the depth of cut into the workpiece 200 changes, the side cutting edge angle of the second cutting edge portion 2 changes. Specifically, as the depth of cut into the workpiece 200 increases, the side cutting edge angle of the second cutting edge portion 2 monotonically decreases.

[0063] In a drawing process in which the workpiece 200 is machined using the second cutting edge portion 2, the side cutting edge angle of the second cutting edge portion 2 is less than 90°. In a drawing process in which the workpiece 200 is machined using the second cutting edge portion 2, the side cutting edge angle of the second cutting edge portion 2 may be 70° or more and 89° or less, or 73° or more and 86° or less.

[0064] The second cutting edge portion 2 is used in low-cut drawing. Specifically, the cutting depth of the second cutting edge portion 2 is, for example, 0.15 mm or less. The cutting depth of the second cutting edge portion 2 may be, for example, 0.1 mm or less, or 0.05 mm or less. From another perspective, the second cutting edge portion 2 may be in a range of 0.15 mm or less from the position closest to the workpiece 200 in the direction perpendicular to the rotation axis.

[0065] 14, when the depth of cut into the workpiece 200 changes, the side cutting edge angle of the third cutting edge portion 3 does not change. Specifically, when the depth of cut into the workpiece 200 increases, the side cutting edge angle of the third cutting edge portion 3 is constant. For example, when the depth of cut is in the range of 0.05 mm or more and 0.5 mm or less, the side cutting edge angle of the third cutting edge portion 3 may be constant.

[0066] The side cutting edge angle of the third cutting edge portion 3 is, for example, 60° or more and 85° or less. The side cutting edge angle of the third cutting edge portion 3 may be, for example, 63° or more and 82° or less, or 65° or more and 80° or less. As shown in FIG. 14 , the minimum value of the side cutting edge angle of the second cutting edge portion 2 is the same as the side cutting edge angle of the third cutting edge portion 3.

[0067] The third cutting edge portion 3 is used in high-depth cutting. Specifically, the cutting depth of the third cutting edge portion 3 is, for example, 0.05 mm or more. The cutting depth of the third cutting edge portion 3 may be, for example, 0.1 mm or more, or may exceed 0.15 mm. The cutting depth of the third cutting edge portion 3 may be 0.5 mm or less. From another perspective, the third cutting edge portion 3 may be in the range of 0.05 mm or more and 0.5 mm or less from the position closest to the workpiece 200 in the direction perpendicular to the rotation axis.

[0068] Fig. 15 is a schematic side view showing the side rake angle of the cutting edge. The schematic side view shown in Fig. 15 shows a state seen along a straight line perpendicular to the rotation axis X of the workpiece 200.

[0069] In a drawing process in which the workpiece 200 is machined using the second cutting edge portion 2, the cutting insert 100 is fed in a first feed direction A along a direction parallel to the rotation axis X of the workpiece 200.

[0070] 15, when viewed in a direction perpendicular to the rotation axis X of the workpiece 200, the side rake angle of the second cutting edge portion 2 is an inclination angle of the second cutting edge portion 2 with respect to a straight line C1 parallel to the rotation axis X of the workpiece 200. The side rake angle of the second cutting edge portion 2 is a sixth angle θ6. The sixth angle θ6 may be, for example, -20° or more and 20° or less. The sixth angle θ6 may be -15° or more and 15° or less, or -10° or more and 10° or less.

[0071] In a drawing process in which the workpiece 200 is machined using the third cutting edge portion 3 , the cutting insert 100 is fed in a first feed direction A along a direction parallel to the rotation axis X of the workpiece 200 .

[0072] 15, when viewed in a direction perpendicular to the rotation axis X of the workpiece 200, the side rake angle of the third cutting edge portion 3 is an inclination angle of the third cutting edge portion 3 with respect to a straight line C2 parallel to the rotation axis X of the workpiece 200. The side rake angle of the third cutting edge portion 3 is a seventh angle θ7. The seventh angle θ7 may be, for example, -20° or more and 20° or less. The seventh angle θ7 may be -15° or more and 15° or less, or -10° or more and 10° or less.

[0073] In addition, when the cutting edge 10 advances ahead of the rake face 50 during cutting, the side rake angle is a positive angle. Conversely, when the cutting edge 10 lags behind the rake face 50 during cutting, the side rake angle is a negative angle.

[0074] FIG. 16 is a schematic diagram showing a second machining method according to the present embodiment. As shown in FIG. 16, in the second machining method according to the present embodiment, end face machining and outer diameter machining may be performed. The workpiece 200 has an outer peripheral surface 201 and an end surface 202. The outer peripheral surface 201 is parallel to the rotation axis X of the workpiece 200. The end surface 202 is perpendicular to the rotation axis X of the workpiece 200. The pushing and corner machining are performed while moving the cutting insert 100 in the second feed direction B1. In the pushing and corner machining, the workpiece 200 is machined using the first cutting edge portion 1. The pulling is performed while moving the cutting insert 100 in the third feed direction B2.

[0075] In low-depth cutting, the workpiece 200 is machined using the second cutting edge portion 2. In high-depth cutting, the workpiece 200 is machined using the third cutting edge portion 3. The second feed direction B1 is perpendicular to the rotation axis X of the workpiece 200. The third feed direction B2 is parallel to the rotation axis X of the workpiece 200.

[0076] Next, the effects of the cutting insert 100 and the machining method according to this embodiment will be described.

[0077] The cutting insert 100 according to this embodiment has a second cutting edge portion 2 for low-cut pull machining and a third cutting edge portion 3 for high-cut pull machining. The radius of curvature of the second cutting edge portion 2 is 3 mm or more. The third cutting edge portion 3 has a straight line shape.

[0078] As the cutting depth increases, the load on the cutting edge 10 increases. In low-cut pull machining, the side cutting edge angle of the second cutting edge portion 2 decreases as the cutting depth increases. By reducing the side cutting edge angle as the load increases, chipping of the cutting edge 10 can be suppressed. On the other hand, if the side cutting edge angle becomes excessively small, the stability of the cutting process decreases.

[0079] According to the cutting insert 100 of this embodiment, the third cutting edge portion 3 for high cutting depth drawing has a linear shape. Therefore, in high cutting depth drawing, the side cutting edge angle can be maintained constant regardless of the cutting depth. Therefore, in high cutting depth drawing, the stability of the cutting process can be suppressed from decreasing. Therefore, the cutting insert 100 can have a long life in both low cutting depth drawing and high cutting depth drawing.

[0080] Furthermore, since the cutting insert 100 according to this embodiment has the fourth cutting edge portion 4 for finishing the surface, the roughness of the finished surface can be significantly improved. Therefore, a stable and good surface roughness can be obtained even in high-efficiency machining. Note that high-efficiency machining refers to a process in which the volume of the workpiece 200 that can be removed per unit time is, for example, 10 cm 3 This refers to processing that requires more than 1 / min.

[0081] According to the cutting insert 100 of this embodiment, the clearance angle of each of the first cutting edge portion 1, the second cutting edge portion 2, the third cutting edge portion 3, and the fourth cutting edge portion 4 may be 3° or more and 20° or less. By making the clearance angle of each of the first cutting edge portion 1, the second cutting edge portion 2, the third cutting edge portion 3, and the fourth cutting edge portion 4 a positive angle, the cutting resistance in the thrust force direction can be reduced. Therefore, the dimensional accuracy can be stably improved.

[0082] According to the cutting insert 100 of this embodiment, the flank 70 may have a restraining surface 71 that is restrained by the holder. If the apex angle of the second cutting edge portion 2 is a first angle θ8 and the apex angle of the ridgeline between the restraining surface 71 and the rake face 50 is a second angle θ9, the second angle θ9 may be smaller than the first angle θ8. This makes it possible to increase the side cutting edge angle of the second cutting edge portion 2 while maintaining a high restraining force of the cutting insert by the holder.

[0083] According to the cutting insert 100 according to this embodiment, the clearance angle of the restraining surface 71 may be 0°, which can further increase the restraining force of the cutting insert by the holder.

[0084] According to the machining method using the cutting insert of this embodiment, in the drawing process in which the workpiece 200 is machined using the second cutting edge portion 2, the side rake angle of the second cutting edge portion 2 may be -20° or more and 20° or less. This can reduce the load on the second cutting edge portion 2. As a result, it is possible to suppress damage to the second cutting edge portion 2. Therefore, the life of the cutting insert 100 can be further extended.

[0085] According to the machining method using the cutting insert of this embodiment, in the drawing process in which the workpiece 200 is machined using the third cutting edge portion 3, the side rake angle of the third cutting edge portion 3 may be -20° or more and 20° or less. This can reduce the load on the third cutting edge portion 3. As a result, it is possible to suppress damage to the third cutting edge portion 3. Therefore, the life of the cutting insert 100 can be further extended.

[0086] According to the machining method using the cutting insert according to this embodiment, the second cutting edge portion 2 may be within a range of 0.15 mm or less from the position closest to the workpiece 200 in the direction perpendicular to the rotation axis. In the drawing process in which the workpiece 200 is machined using the second cutting edge portion 2, the side cutting edge angle of the second cutting edge portion 2 may be 70° or more and 89° or less. This can reduce the load on the second cutting edge portion 2. As a result, it is possible to suppress damage to the second cutting edge portion 2. Therefore, the life of the cutting insert 100 can be further extended in the low-cut drawing process.

[0087] According to the machining method using the cutting insert according to this embodiment, the third cutting edge portion 3 may be in the range of 0.05 mm to 0.5 mm from the position closest to the workpiece 200 in the direction perpendicular to the rotation axis. The side cutting edge angle of the third cutting edge portion 3 may be 60° to 85°. This can reduce the load on the third cutting edge portion 3. As a result, damage to the third cutting edge portion 3 can be suppressed. Therefore, the life of the cutting insert 100 can be further extended in high-depth drawing. EXAMPLES

[0088] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples. <Example 1: Low cutting depth machining conditions> Cutting inserts 100 (samples SA1 to SA35 and SB1 to SB9) having the shapes shown in Tables 1 and 2 were produced and evaluated for cutting under the following conditions. The cutting inserts 100 of samples SA1 to SA35 and SB1 to SB9 have a blade member 6 and a base metal 7 (see FIG. 1). In the cutting inserts 100 of samples SA1 to SA35 and SB1 to SB9, the material of the blade member 6 was a cBN-based sintered body.

[0089] In Tables 1 and 2, the first cutting edge, the second cutting edge, the third cutting edge, the fourth cutting edge, the first connecting portion, the second connecting portion, and the third connecting portion correspond to the first cutting edge portion 1, the second cutting edge portion 2, the third cutting edge portion 3, the fourth cutting edge portion 4, the first connecting cutting edge portion 11, the second connecting cutting edge portion 12, and the third connecting cutting edge portion 13, respectively. In Tables 1 and 2, the numerical values ​​listed in each column of the first cutting edge, the second cutting edge, the fourth cutting edge, the first connecting portion, the second connecting portion, and the third connecting portion indicate the radius of curvature of the corresponding portion.

[0090] [Table 1]

[0091] [Table 2]

[0092] The cutting inserts 100 of samples SA1 to SA35 are examples. In the cutting inserts 100 of samples SA1 to SA35, the radius of curvature of the first cutting edge portion 1 was 0.1 mm or more and 2.4 mm or less. The fourth cutting edge portion 4 was curved with a radius of curvature of 3 mm or more. The second cutting edge portion 2 was curved with a radius of curvature of 3 mm or more. The third cutting edge portion 3 was linear. Each of the first connecting cutting edge portion 11, the second connecting cutting edge portion 12, and the third connecting cutting edge portion 13 was curved.

[0093] The cutting inserts 100 of samples SB1 to SB9 are comparative examples. In the cutting insert 100 of sample SB1, the radius of curvature of the first cutting edge portion 1 was 0.09 mm. In the cutting insert 100 of sample SB2, the radius of curvature of the first cutting edge portion 1 was 2.5 mm. In the cutting insert 100 of sample SB3, the radius of curvature of the second cutting edge portion 2 was 2.9 mm. In the cutting insert 100 of sample SB4, the third cutting edge portion 3 was curved with a radius of curvature of 30 mm.

[0094] In the cutting insert 100 of sample SB5, the first connecting cutting edge portion 11 was linear. In the cutting insert 100 of sample SB6, the second connecting cutting edge portion 12 was linear. In the cutting insert 100 of sample SB7, the third connecting cutting edge portion 13 was linear. In the cutting insert 100 of sample SB8, the second cutting edge portion 2 was linear, and the third connecting cutting edge portion 13 and the third cutting edge portion 3 were not formed. In the cutting insert 100 of sample SB9, the third connecting cutting edge portion 13 and the third cutting edge portion 3 were not formed.

[0095] The cutting insert 100 was attached to the holder 150, and the following workpiece 200 was machined under the following cutting conditions. The cutting time (tool life) when the cutting edge 10 of the cutting insert 100 was chipped was evaluated. (Cutting Geometry) Cutting edge inclination angle = -5° (work material) High-hardness steel SCM415 (HRC60), diameter = 85 mm, length = 200 mm (Cutting conditions) Cutting speed: V = 250 m / min, Feed rate: f = 0.5 mm / revolution, Depth of cut: ap = 0.05 mm, Wet (Processing form) External machining (drawing) The results are summarized in Tables 3 and 4. As shown in Tables 3 and 4, the side rake angle of the cutting edge 10 was set to be equal to or greater than -21° and equal to or less than 21°. The side cutting edge angle of the second cutting edge portion 2 was set to be equal to or greater than 69° and equal to or less than 89°. Only in the cutting insert 100 of sample SA35, the side cutting edge angle of the third cutting edge portion 3 was set to be 80°.

[0096] [Table 3]

[0097] [Table 4]

[0098] As shown in Tables 3 and 4, it was confirmed that the cutting inserts 100 of Samples SA1 to SA35 had longer tool life than the cutting inserts 100 of Samples SB1 to SB7.

[0099] As shown by the cutting inserts 100 of samples SA1 to SA3, it was confirmed that when the radius of curvature of the first cutting edge portion 1 was 0.1 mm or more and 2.4 mm or less, the cutting insert 100 had a long tool life.

[0100] As shown by the cutting inserts 100 of samples SA4 to SA6, it was confirmed that when the radius of curvature of the second cutting edge portion 2 was 3 mm or more and 20 mm or less, the cutting inserts 100 had a long tool life.

[0101] As shown by the cutting inserts 100 of samples SA7 to SA9, it was confirmed that when the curvature radius of the fourth cutting edge portion 4 was 3 mm or more and 20 mm or less, the cutting inserts 100 had a long tool life.

[0102] As shown in the cutting inserts 100 of samples SA15 to SA18, it was confirmed that when the clearance angles of each of the first cutting edge portion 1, the second cutting edge portion 2, the third cutting edge portion 3 and the fourth cutting edge portion 4 are 20° or less, the cutting insert 100 has a long tool life.

[0103] As shown by the cutting inserts 100 of samples SA19 to SA22, it was confirmed that when the apex angle of the holder restraint surface 71 was 30° or more and 80° or less, the cutting inserts 100 had a long tool life.

[0104] As shown by the cutting inserts 100 of samples SA23 to SA25, it was confirmed that when the clearance angle of the holder restraint surface 71 was 11° or less, the cutting inserts 100 had a long tool life.

[0105] As shown by the cutting inserts 100 of samples SA26 to SA29, it was confirmed that when the side rake angle of the cutting edge 10 was −20° or more and 20° or less, the cutting inserts 100 had a long tool life.

[0106] As shown by the cutting inserts 100 of samples SA30 to SA32, it was confirmed that when the side cutting edge angle of the second cutting edge portion 2 was 70° or more and 89° or less, the cutting insert 100 had a long tool life. <Example 2: High cutting depth machining conditions> Cutting inserts 100 (samples SC1 to SC36 and SD1 to SD9) having the shapes shown in Tables 5 and 6 were produced and evaluated under the following conditions. The cutting inserts 100 of samples SC1 to SC36 and SD1 to SD9 have a blade member 6 and a base metal 7 (see FIG. 1). In the cutting inserts 100 of samples SC1 to SC36 and SD1 to SD9, the material of the blade member 6 was a cBN-based sintered body.

[0107] In Tables 5 and 6, the first cutting edge, the second cutting edge, the third cutting edge, the fourth cutting edge, the first connecting portion, the second connecting portion, and the third connecting portion correspond to the first cutting edge portion 1, the second cutting edge portion 2, the third cutting edge portion 3, the fourth cutting edge portion 4, the first connecting cutting edge portion 11, the second connecting cutting edge portion 12, and the third connecting cutting edge portion 13, respectively. In Tables 5 and 6, the numerical values ​​listed in each column of the first cutting edge, the second cutting edge, the fourth cutting edge, the first connecting portion, the second connecting portion, and the third connecting portion indicate the radius of curvature of the corresponding portion.

[0108] [Table 5]

[0109] [Table 6]

[0110] The cutting inserts 100 of samples SC1 to SC36 are examples. In the cutting inserts 100 of samples SC1 to SC36, the radius of curvature of the first cutting edge portion 1 was 0.1 mm or more and 2.4 mm or less. The fourth cutting edge portion 4 was curved with a radius of curvature of 3 mm or more. The second cutting edge portion 2 was curved with a radius of curvature of 3 mm or more. The third cutting edge portion 3 was linear. Each of the first connecting cutting edge portion 11, the second connecting cutting edge portion 12, and the third connecting cutting edge portion 13 was curved.

[0111] The cutting inserts 100 of samples SD1 to SD9 are comparative examples. In the cutting insert 100 of sample SD1, the radius of curvature of the first cutting edge portion 1 was set to 0.09 mm. In the cutting insert 100 of sample SD2, the radius of curvature of the first cutting edge portion 1 was set to 2.5 mm. In the cutting insert 100 of sample SD3, the radius of curvature of the second cutting edge portion 2 was set to 2.9 mm. In the cutting insert 100 of sample SD4, the third cutting edge portion 3 was curved with a radius of curvature of 30 mm.

[0112] In the cutting insert 100 of sample SD5, the first connecting cutting edge portion 11 was linear. In the cutting insert 100 of sample SD6, the second connecting cutting edge portion 12 was linear. In the cutting insert 100 of sample SD7, the third connecting cutting edge portion 13 was linear. In the cutting insert 100 of sample SD8, the second cutting edge portion 2 was linear, and the third connecting cutting edge portion 13 and the third cutting edge portion 3 were not formed. In the cutting insert 100 of sample SD9, the third connecting cutting edge portion 13 and the third cutting edge portion 3 were not formed.

[0113] The cutting insert 100 was attached to the holder 150, and the following workpiece 200 was machined under the following cutting conditions. The cutting time (tool life) when the cutting edge 10 of the cutting insert 100 was chipped was evaluated. (Cutting Geometry) Cutting edge inclination angle = -5° (work material) High-hardness steel SCM415 (HRC60), diameter = 85 mm, length = 200 mm (Cutting conditions) Cutting speed: V = 250 m / min, Feed rate: f = 0.5 mm / revolution, Depth of cut: ap = 0.5 mm, Wet (Processing form) External machining (drawing) The results are summarized in Tables 7 and 8. As shown in Tables 7 and 8, the side rake angle of the cutting edge 10 was set to be equal to or greater than -21° and equal to or less than 21°. The side cutting edge angle of the third cutting edge portion 3 was set to be equal to or greater than 59° and equal to or less than 86°. Only in the cutting inserts 100 of samples SD8 and SD9, the side cutting edge angle of the second cutting edge portion 2 was set to be 85°.

[0114] [Table 7]

[0115] [Table 8]

[0116] As shown in Tables 7 and 8, it was confirmed that the cutting inserts 100 of Samples SC1 to SC36 had longer tool life than the cutting inserts 100 of Samples SD1 to SD7.

[0117] As shown by the cutting inserts 100 of samples SC1 to SC3, it was confirmed that when the radius of curvature of the first cutting edge portion 1 was 0.1 mm or more and 2.4 mm or less, the cutting inserts 100 had a long tool life.

[0118] As shown by the cutting inserts 100 of samples SC4 to SC6, it was confirmed that when the radius of curvature of the second cutting edge portion 2 was 3 mm or more and 20 mm or less, the cutting inserts 100 had a long tool life.

[0119] As shown by the cutting inserts 100 of samples SC7 to SC9, it was confirmed that when the curvature radius of the fourth cutting edge portion 4 was 3 mm or more and 20 mm or less, the cutting inserts 100 had a long tool life.

[0120] As shown in the cutting inserts 100 of samples SC15 to SC18, it was confirmed that when the clearance angles of each of the first cutting edge portion 1, the second cutting edge portion 2, the third cutting edge portion 3 and the fourth cutting edge portion 4 are 20° or less, the cutting insert 100 has a long tool life.

[0121] As shown by the cutting inserts 100 of samples SC19 to SC22, it was confirmed that when the apex angle of the holder restraint surface 71 was 30° or more and 80° or less, the cutting inserts 100 had a long tool life.

[0122] As shown by the cutting inserts 100 of samples SC23 to SC25, it was confirmed that when the clearance angle of the holder restraint surface 71 was 11° or less, the cutting inserts 100 had a long tool life.

[0123] As shown by the cutting inserts 100 of samples SC26 to SC29, it was confirmed that when the side rake angle of the cutting edge 10 was −20° or more and 20° or less, the cutting inserts 100 had a long tool life.

[0124] As shown by the cutting inserts 100 of samples SC32 to SC35, it was confirmed that when the side cutting edge angle of the third cutting edge portion 3 was 60° or more and 86° or less, the cutting inserts 100 had a long tool life.

[0125] In addition, the cutting inserts 100 of samples SB8 and SD8 had long tool lives under high cutting depth conditions, but did not have long tool lives under low cutting depth conditions. The cutting inserts 100 of samples SB9 and SD9 had long tool lives under low cutting depth conditions, but did not have long tool lives under high cutting depth conditions.

[0126] From the above results, it has been demonstrated that by making the radius of curvature of the first cutting edge portion 1 between 0.1 mm and 2.4 mm, making the fourth cutting edge portion 4 a curved shape with a radius of curvature of 3 mm or more, making the second cutting edge portion 2 a curved shape with a radius of curvature of 3 mm or more, and the third cutting edge portion 3 a straight shape, a long tool life can be obtained under both low and high cutting depth machining conditions.

[0127] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims, not by the embodiments described above, and is intended to include the equivalent meanings of the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0128] 1 first cutting edge portion, 2 second cutting edge portion, 3 third cutting edge portion, 4 fourth cutting edge portion, 5 through hole, 6 blade member, 7 base metal, 8 countersink portion, 10 cutting edge, 11 first connecting cutting edge portion, 12 second connecting cutting edge portion, 13 third connecting cutting edge portion, 20 ridge, 21 first ridge portion, 22 second ridge portion, 30 first flank portion, 31 first flank region, 32 second flank region, 33 third flank region, 34 fourth flank region, 35 fifth flank region, 36 sixth flank region, 37 seventh flank region, 40 second flank portion, 41 first side region, 42 second side region, 43 third side region, 44 fourth side region, 45 fifth side region, 46 sixth side region, 47 seventh side region, 50 rake face, 51 first rake face portion, 52 Second rake surface portion, 60 bottom surface, 70 flank surface, 71 holder restraint surface (restraint surface), 100 cutting insert, 150 holder, 160 pressing member, 161 insertion portion, 162 main body portion, 163 mounting hole, 170 fastening screw, 200 workpiece, 201 outer peripheral surface, 202 end surface, A 1st feed direction, B1 2nd feed direction, B2 3rd feed direction, C1, C2 straight line, R rotation direction, X rotation axis, ap cutting depth.

Claims

1. The surface involved in cutting is made of a cBN-based sintered body, a diamond-based sintered body, a ceramic, a cermet, or a cemented carbide; A cutting insert including a rake face, a flank face, and a cutting edge formed by a ridge line between the rake face and the flank face, The cutting edge is A first cutting edge portion for corner machining; A second cutting edge portion for low cutting depth machining; A third cutting edge portion for high cutting depth machining; A fourth cutting edge portion for finishing surface processing; a first connecting cutting edge portion connecting the first cutting edge portion and the fourth cutting edge portion; a second connecting cutting edge portion connecting the second cutting edge portion and the fourth cutting edge portion; A third connecting cutting edge portion connecting the second cutting edge portion and the third cutting edge portion, The fourth cutting edge portion is disposed between the first cutting edge portion and the second cutting edge portion, The second cutting edge portion is disposed between the fourth cutting edge portion and the third cutting edge portion, Each of the first cutting edge portion, the second cutting edge portion, and the fourth cutting edge portion has a curved shape, The radius of curvature of the first cutting edge portion is 0.1 mm or more and 2.4 mm or less, The radius of curvature of the second cutting edge portion is 3 mm or more, The radius of curvature of the fourth cutting edge portion is 3 mm or more, The third cutting edge portion has a linear shape, Each of the first connecting cutting edge portion, the second connecting cutting edge portion, and the third connecting cutting edge portion has a curved shape, A cutting insert, wherein a radius of curvature of the second cutting edge portion is equal to or smaller than a radius of curvature of the fourth cutting edge portion.

2. The cutting insert according to claim 1 , wherein each of the first connecting edge portion, the second connecting edge portion and the third connecting edge portion has a radius of curvature of 0.2 mm or more.

3. The cutting insert according to claim 1 or 2, wherein a clearance angle of each of the first cutting edge portion, the second cutting edge portion, the third cutting edge portion and the fourth cutting edge portion is equal to or greater than 3° and equal to or less than 20°.

4. The relief surface has a restraint surface that is restrained by a holder, An apex angle of the second cutting edge portion is a first angle; If the apex angle of the ridge between the restraint surface and the rake surface is a second angle, the second angle is smaller than the first angle; The cutting insert according to claim 1 or 2, wherein the second angle is equal to or greater than 30° and equal to or less than 80°.

5. The relief surface has a restraint surface that is restrained by a holder, An apex angle of the second cutting edge portion is a first angle; If the apex angle of the ridge between the restraint surface and the rake surface is a second angle, the second angle is smaller than the first angle; The cutting insert according to claim 1 or 2, wherein the first angle is equal to or greater than 35° and equal to or less than 85°.

6. The cutting insert according to claim 4 , wherein the clearance angle of the constraint surface is 0°.

7. A machining method using the cutting insert according to claim 1 or 2, A machining method, in which a workpiece is machined using the second cutting edge portion in a drawing process, wherein a side rake angle of the second cutting edge portion is greater than or equal to -20° and less than or equal to 20°.

8. The processing method according to claim 7, wherein in a drawing process in which a workpiece is machined using the third cutting edge portion, a side rake angle of the third cutting edge portion is greater than or equal to -20° and less than or equal to 20°.

9. The second cutting edge portion is located within a range of 0.15 mm or less from a position closest to the workpiece in a direction perpendicular to the rotation axis, The machining method according to claim 7, wherein in a drawing process in which a workpiece is machined using the second cutting edge portion, a side cutting edge angle of the second cutting edge portion is 70° or more and 89° or less.

10. The third cutting edge portion is in a range of 0.05 mm to 0.5 mm from a position closest to the workpiece in a direction perpendicular to the rotation axis, The machining method according to claim 7 , wherein a side cutting edge angle of the third cutting edge portion is equal to or greater than 60° and equal to or less than 85°.

11. The machining method according to claim 7 , wherein a minimum value of the side cutting edge angle of the second cutting edge portion is the same as a side cutting edge angle of the third cutting edge portion.

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