Cutting tool for rotary cutting tool and rotary cutting tool

Abstract

The cutting tool for a rotary cutting tool has a top surface, a bottom surface and an outer peripheral surface. The ridge between the top surface and the outer peripheral surface forms a cutting edge. The cutting edge includes a first line segment, a second line segment, a third line segment, a fourth line segment, a first curved portion, a second curved portion, a third curved portion and a fourth curved portion. The angle formed between the straight line along the first line segment and the straight line along the third line segment is an acute angle. The angle formed between the straight line along the second line segment and the straight line along the fourth line segment is an acute angle. The angle formed between the straight line along the second line segment and the straight line along the third line segment is an obtuse angle. The angle formed between the straight line along the first line segment and the straight line along the fourth line segment is an obtuse angle. The radius of curvature of each of the third curved portion and the fourth curved portion is greater than the radius of curvature of the first curved portion, and greater than the radius of curvature of the second curved portion. In a direction perpendicular to the bottom surface, the distance between the top surface and the bottom surface is equal to the distance between the cutting edge and the bottom surface, or is shorter than the distance between the cutting edge and the bottom surface.

Description

Technical Field

[0001] The present invention relates to a cutting tool for a rotary cutting tool (a cutting tool for a rotary cutting tool) and a rotary cutting tool. Background Art

[0002] Japanese Patent Application Laid-Open No. 2008-178967 (Patent Document 1) discloses a drill having a first throwaway blade and a second throwaway blade. The ratio between the cutting load of the center edge formed by the first throwaway blade and the cutting load of the peripheral edge formed by the second throwaway blade is set to be within the range of A:B=52:48 to 55:45.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-178967 Summary of the invention

[0006] The cutting tool for a rotary cutting tool according to the present invention includes a top surface, a bottom surface, and an outer peripheral surface. The bottom surface is opposite to the top surface. The outer peripheral surface is continuous with each of the top surface and the bottom surface. The ridge between the top surface and the outer peripheral surface forms a cutting edge. The cutting edge includes: a first line segment; a second line segment, which is opposite to the first line segment; a third line segment, which is inclined relative to each of the first line segment and the second line segment; a fourth line segment, which is opposite to the third line segment; a first curved portion, which connects the first line segment and the third line segment; a second curved portion, which connects the second line segment and the fourth line segment; a third curved portion, which connects the second line segment and the third line segment; and a fourth curved portion, which connects the first line segment and the fourth line segment. The angle formed between the straight line along the first line segment and the straight line along the third line segment is an acute angle. The angle formed between the straight line along the second line segment and the straight line along the fourth line segment is an acute angle. The angle formed between the straight line along the second line segment and the straight line along the third line segment is an obtuse angle. The angle formed between the straight line along the first line segment and the straight line along the fourth line segment is an obtuse angle. The radius of curvature of each of the third curved portion and the fourth curved portion is greater than the radius of curvature of the first curved portion, and greater than the radius of curvature of the second curved portion. In a direction perpendicular to the bottom surface, the distance between the top surface and the bottom surface is equal to the distance between the cutting edge and the bottom surface, or is shorter than the distance between the cutting edge and the bottom surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a schematic perspective view showing the structure of a cutting insert for a rotary cutting tool according to the first embodiment.

[0008] Figure 2 It is a schematic plan view showing the structure of a cutting insert for a rotary cutting tool according to the first embodiment.

[0009] Figure 3 is along Figure 2 A schematic cross-sectional view taken along line III-III in FIG.

[0010] Figure 4 is along Figure 2 Schematic cross-sectional view taken along line IV-IV in FIG.

[0011] Figure 5 It is a schematic perspective view showing the structure of a cutting insert for a rotary cutting tool according to a second embodiment.

[0012] Figure 6 It is a schematic plan view showing the structure of a cutting insert for a rotary cutting tool according to a second embodiment.

[0013] Figure 7 is along Figure 6 A schematic cross-sectional view taken along line VII-VII in FIG.

[0014] Figure 8 is along Figure 6 A schematic cross-sectional view taken along line VIII-VIII in FIG.

[0015] Fig. 9 It is a schematic perspective view showing the structure of a rotary cutting tool according to a third embodiment.

[0016] Fig.10 This is a schematic perspective view showing a state where a workpiece is processed using a rotating cutting tool.

[0017] Fig.11 It is a schematic diagram showing the trajectory of the cutting tool set in the center-side cutting tool placement groove and the trajectory of the cutting tool set in the outer peripheral-side cutting tool placement groove.

[0018] Fig.12 yes Fig.11 Schematic enlargement of region XII.

[0019] Fig.13 This is a schematic cross-sectional view showing the flow of chips when a workpiece is cut using a conventional cutting tool.

[0020] Fig.14 This is a schematic cross-sectional view showing the flow of chips when a workpiece is cut using the cutting tool according to the second embodiment.

[0021] Fig.15 This is a schematic cross-sectional view showing the flow of chips when a workpiece is cut using the cutting tool according to the first embodiment.

[0022] Fig.16It is a figure which shows the structure of the cutting tool of sample 1 to sample 7.

[0023] Fig.17 The diagrams are photographs showing chips of workpieces cut by the cutting tools of Samples 1 to 7.

[0024] Fig.18 This is a graph showing the cutting resistance of the cutting tools of Samples 1 to 7.

[0025] Fig.19 This is a graph showing the depth of scratches on the side surfaces of holes formed by the cutting tools of Samples 1 to 7. DETAILED DESCRIPTION

[0026] [Problems to be Solved by the Invention]

[0027] The chip discharge performance varies greatly depending on the workpiece. For example, the chips of carbon steel are relatively easy to cut. On the other hand, compared with carbon steel, the chips of highly viscous workpieces such as stainless steel are difficult to cut. When the drill described in Patent Document 1 is used to process stainless steel, it is difficult to discharge the chips effectively.

[0028] An object of the present invention is to provide a cutting insert for a rotary cutting tool and a rotary cutting tool capable of improving chip discharge performance.

[0029] [Effects of the Invention]

[0030] According to the present invention, a cutting insert for a rotary cutting tool and a rotary cutting tool capable of improving chip discharge performance can be provided.

[0031] [Description of Embodiments of the Invention]

[0032] First, embodiments of the present invention will be described by way of examples.

[0033] (1) The cutting tool 100 for a rotary cutting tool according to the present invention includes a top surface 1, a bottom surface 2, and an outer peripheral surface 3. The bottom surface 2 is opposite to the top surface 1. The outer peripheral surface 3 is continuous with each of the top surface 1 and the bottom surface 2. The ridge between the top surface 1 and the outer peripheral surface 3 forms a cutting edge 6. The cutting edge 6 includes: a first line segment 10; a second line segment 20, which is opposite to the first line segment 10; and a third line segment

[0034] 30, which is inclined relative to each of the first line segment 10 and the second line segment 20; the fourth line segment 40, which is opposite to the third line segment 30; the first curved portion 51, which connects the first line segment 10 and the third line segment 30; the second curved portion 52, which connects the second line segment 20 and the fourth line segment 40; the third curved portion 53, which connects the second line segment 20 and the third line segment 30; and the fourth curved portion 54, which connects the first line segment 10 and the fourth line segment 40. The angle formed between the straight line along the first line segment 10 and the straight line along the third line segment 30 is an acute angle. The angle formed between the straight line along the second line segment 20 and the straight line along the fourth line segment 40 is an acute angle. The angle formed between the straight line along the second line segment 20 and the straight line along the third line segment 30 is an obtuse angle. The angle formed between the straight line along the first line segment 10 and the straight line along the fourth line segment 40 is an obtuse angle. The radius of curvature of each of the third curved portion 53 and the fourth curved portion 54 is greater than the radius of curvature of the first curved portion 51, and greater than the radius of curvature of the second curved portion 52. In the direction perpendicular to the bottom surface 2, the distance between the top surface 1 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2, or is shorter than the distance between the cutting edge 6 and the bottom surface 2.

[0035] (2) According to the cutting tool 100 for a rotary cutting tool according to (1) above, the distance between the top surface 1 and the bottom surface 2 in the direction perpendicular to the bottom surface 2 can be equal to the distance between the cutting edge 6 and the bottom surface 2 .

[0036] (3) According to the cutting tool 100 for a rotary cutting tool according to (1) above, the top surface 1 may have a flat portion 50 spaced apart from the cutting edge 6. The flat portion 50 may be located between the cutting edge 6 and the bottom surface 2 in a direction perpendicular to the bottom surface 2.

[0037] (4) According to the cutting tool 100 for a rotary cutting tool as described in any one of (1) to (3) above, the top surface 1 may include: a first land surface 11 continuous with the first line segment 10; a second land surface 21 continuous with the second line segment 20; a third land surface 31 continuous with the third line segment 30; and a fourth land surface 41 continuous with the fourth line segment 40. Each of a width of the third land surface 31 in a direction perpendicular to the third line segment 30 and a width of the fourth land surface 41 in a direction perpendicular to the fourth line segment 40 may be greater than a width of the first land surface 11 in a direction perpendicular to the first line segment 10, and greater than a width of the second land surface 21 in a direction perpendicular to the second line segment 20.

[0038] (5) According to the cutting tool 100 for a rotating cutting tool involved in any one of the above (1) to (4), each of the curvature radius of the third bend 53 and the curvature radius of the fourth bend 54 can be more than 2 times and less than 5 times the curvature radius of the first bend 51, and can be more than 2 times and less than 5 times the curvature radius of the second bend 52.

[0039] (6) According to the cutting tool 100 for a rotary cutting tool according to (1) above, the distance between the top surface 1 and the bottom surface 2 in the direction perpendicular to the bottom surface 2 may be equal to the distance between the cutting edge 6 and the bottom surface 2. The top surface 1 may include: a first land surface 11 continuous with the first line segment 10; a second land surface 21 continuous with the second line segment 20; a third land surface 31 continuous with the third line segment 30; and a fourth land surface 41 continuous with the fourth line segment 40. Each of the width of the third land surface 31 in the direction perpendicular to the third line segment 30 and the width of the fourth land surface 41 in the direction perpendicular to the fourth line segment 40 may be greater than the width of the first land surface 11 in the direction perpendicular to the first line segment 10, and greater than the width of the second land surface 21 in the direction perpendicular to the second line segment 20. Each of the curvature radii of the third curved portion 53 and the curvature radii of the fourth curved portion 54 may be 2 to 5 times the curvature radius of the first curved portion 51 , and may be 2 to 5 times the curvature radius of the second curved portion 52 .

[0040] (7) According to the cutting tool 100 for a rotary cutting tool according to (1) above, the top surface 1 may have a flat portion 50 spaced apart from the cutting edge 6. The flat portion 50 may be located between the cutting edge 6 and the bottom surface 2 in a direction perpendicular to the bottom surface 2. The top surface 1 may include: a first land surface 11 continuous with the first line segment 10; a second land surface 21 continuous with the second line segment 20; a third land surface 31 continuous with the third line segment 30; and a fourth land surface 41 continuous with the fourth line segment 40. Each of the width of the third land surface 31 in a direction perpendicular to the third line segment 30 and the width of the fourth land surface 41 in a direction perpendicular to the fourth line segment 40 may be greater than the width of the first land surface 11 in a direction perpendicular to the first line segment 10, and greater than the width of the second land surface 21 in a direction perpendicular to the second line segment 20. Each of the curvature radii of the third curved portion 53 and the curvature radii of the fourth curved portion 54 may be 2 to 5 times the curvature radius of the first curved portion 51 , and may be 2 to 5 times the curvature radius of the second curved portion 52 .

[0041] (8) A rotary cutting tool according to the present invention includes: the cutting insert 100 for a rotary cutting tool according to any one of (1) to (7) above; and a body portion that holds the cutting insert 100 for a rotary cutting tool.

[0042] [Details of the embodiments of the present invention]

[0043] Next, the details of the embodiments of the present invention will be described with reference to the accompanying drawings. In the following drawings, the same reference numerals represent the same parts or corresponding parts, and the repeated description will not be repeated.

[0044] (First embodiment)

[0045] First, the structure of a cutting insert 100 for a rotary cutting tool according to a first embodiment will be described.

[0046] Figure 1 1 is a schematic perspective view showing the structure of a cutting tool 100 for a rotary cutting tool according to the first embodiment. Figure 1 As shown, the cutting tool 100 for a rotary cutting tool according to the first embodiment mainly comprises: a top surface 1, a bottom surface 2, an outer peripheral surface 3, and an inner peripheral surface 4. The bottom surface 2 is opposite to the top surface 1. The bottom surface 2 is, for example, a flat surface. The outer peripheral surface 3 is connected to each of the top surface 1 and the bottom surface 2. The ridge line between the top surface 1 and the outer peripheral surface 3 forms a cutting edge 6. The top surface 1 is, for example, a rake face. The outer peripheral surface 3 is, for example, a flank face. The inner peripheral surface 4 is connected to each of the top surface 1 and the bottom surface 2. The inner peripheral surface 4 defines a through hole 5. The through hole 5 is open in each of the top surface 1 and the bottom surface 2. The outer peripheral surface 3 surrounds the inner peripheral surface 4.

[0047] Figure 2 1 is a schematic plan view showing the structure of a cutting tool 100 for a rotary cutting tool according to the first embodiment. Figure 2 As shown, the cutting edge 6 is substantially parallelogram when viewed in a direction perpendicular to the bottom surface 2. The cutting edge 6 has a first line segment 10, a second line segment 20, a third line segment 30, a fourth line segment 40, a first curved portion 51, a second curved portion 52, a third curved portion 53, and a fourth curved portion 54. The second line segment 20 is opposite to the first line segment 10. The second line segment 20 and the first line segment 10 are substantially parallel. The third line segment 30 is inclined relative to each of the first line segment 10 and the second line segment 20. The fourth line segment 40 is opposite to the third line segment 30. The fourth line segment 40 is inclined relative to each of the first line segment 10 and the second line segment 20. The fourth line segment 40 and the third line segment 30 are substantially parallel. Each of the first line segment 10, the second line segment 20, the third line segment 30, and the fourth line segment 40 extends linearly. Each of the first line segment 10 and the second line segment 20 is a portion used as a center blade. Each of the third line segment 30 and the fourth line segment 40 is a portion used as a peripheral blade.

[0048] like Figure 2As shown, the angle (first angle θ1) formed between the straight line (first straight line L1) along the first line segment 10 and the straight line (third straight line L3) along the third line segment 30 is an acute angle. Similarly, the angle (second angle θ2) formed between the straight line (second straight line L2) along the second line segment 20 and the straight line (fourth straight line L4) along the fourth line segment 40 is an acute angle. In other words, each of the first angle θ1 and the second angle θ2 is greater than 0° and less than 90°. The first angle θ1 and the second angle θ2 are substantially the same. Each of the first angle θ1 and the second angle θ2 is, for example, greater than 75° and less than 85°.

[0049] like Figure 2 As shown, the angle (third angle θ3) formed between the straight line (second straight line L2) along the second line segment 20 and the straight line (third straight line L3) along the third line segment 30 is an obtuse angle. Similarly, the angle (fourth angle θ4) formed between the straight line (first straight line L1) along the first line segment 10 and the straight line (fourth straight line L4) along the fourth line segment 40 is an obtuse angle. In other words, each of the third angle θ3 and the fourth angle θ4 is greater than 90° and less than 180°. The third angle θ3 and the fourth angle θ4 are substantially the same. Each of the third angle θ3 and the fourth angle θ4 is, for example, greater than 95° and less than 105°.

[0050] like Figure 2 As shown, the first curved portion 51 connects the first line segment 10 and the third line segment 30. The second curved portion 52 connects the second line segment 20 and the fourth line segment 40. The third curved portion 53 connects the second line segment 20 and the third line segment 30. The fourth curved portion 54 connects the first line segment 10 and the fourth line segment 40. Each of the first curved portion 51, the second curved portion 52, the third curved portion 53 and the fourth curved portion 54 is arc-shaped. The curvature radius of the first curved portion 51 (the first curvature radius R1) and the curvature radius of the second curved portion 52 (the second curvature radius R2) are substantially the same. The curvature radius of the third curved portion 53 (the third curvature radius R3) and the curvature radius of the fourth curved portion 54 (the fourth curvature radius R4) are substantially the same.

[0051] Each of the curvature radius of the third curved portion 53 (third curvature radius R3) and the curvature radius of the fourth curved portion 54 (fourth curvature radius R4) is larger than the curvature radius of the first curved portion 51 (first curvature radius R1), and larger than the curvature radius of the second curved portion 52 (second curvature radius R2). In other words, the third curvature radius R3 is larger than each of the first curvature radius R1 and the second curvature radius R2. The fourth curvature radius R4 is larger than each of the first curvature radius R1 and the second curvature radius R2.

[0052] Each of the curvature radius of the third curved portion 53 (third curvature radius R3) and the curvature radius of the fourth curved portion 54 (fourth curvature radius R4) may be more than twice and less than five times the curvature radius of the first curved portion 51 (first curvature radius R1), and may be more than twice and less than five times the curvature radius of the second curved portion 52 (second curvature radius R2). In other words, the third curvature radius R3 may be more than twice and less than five times each of the first curvature radius R1 and the second curvature radius R2. The fourth curvature radius R4 may be more than twice and less than five times each of the first curvature radius R1 and the second curvature radius R2.

[0053] The lower limit of each of the curvature radius of the third curved portion 53 and the curvature radius of the fourth curved portion 54 is not particularly limited, but for example, it may be 2.5 times or more, or 3 times or more, the curvature radius of the first curved portion 51 and the curvature radius of the second curved portion 52. The upper limit of each of the curvature radius of the third curved portion 53 and the curvature radius of the fourth curved portion 54 is not particularly limited, but for example, it may be 4.5 times or less, or 4 times or less, the curvature radius of the first curved portion 51 and the curvature radius of the second curved portion 52.

[0054] like Figure 2 As shown, the top surface 1 may include: a first land surface 11, a second land surface 21, a third land surface 31, a fourth land surface 41, a first inclined surface 12, a second inclined surface 22, a third inclined surface 32, a fourth inclined surface 42 and a flat portion 50. The first land surface 11 is continuous with the first line segment 10. The second land surface 21 is continuous with the second line segment 20. The third land surface 31 is continuous with the third line segment 30. The fourth land surface 41 is continuous with the fourth line segment 40. The flat portion 50 is continuous with the inner peripheral surface 4. The flat portion 50 is a convex surface. The flat portion 50 is spaced apart from the cutting edge 6. As shown in FIG. Figure 2 As shown, when viewed in a direction perpendicular to the bottom surface 2, the flat portion 50 surrounds the through hole 5. When viewed in a direction perpendicular to the bottom surface 2, the cutting edge 6 surrounds the flat portion 50.

[0055] The first inclined surface 12 is located between the first land surface 11 and the flat portion 50. The first inclined surface 12 is continuous with each of the first land surface 11 and the flat portion 50. The second inclined surface 22 is located between the second land surface 21 and the flat portion 50. The second inclined surface 22 is continuous with each of the second land surface 21 and the flat portion 50. The third inclined surface 32 is located between the third land surface 31 and the flat portion 50. The third inclined surface 32 is continuous with each of the third land surface 31 and the flat portion 50. The fourth inclined surface 42 is located between the fourth land surface 41 and the flat portion 50. The fourth inclined surface 42 is continuous with each of the fourth land surface 41 and the flat portion 50.

[0056] like Figure 2As shown, each of the width of the third land surface 31 in the direction perpendicular to the third line segment 30 (third land width W3) and the width of the fourth land surface 41 in the direction perpendicular to the fourth line segment 40 (fourth land width W4) may be greater than the width of the first land surface 11 in the direction perpendicular to the first line segment 10 (first land width W1), and may be greater than the width of the second land surface 21 in the direction perpendicular to the second line segment 20 (second land width W2). In other words, the third land width W3 is greater than each of the first land width W1 and the second land width W2. The fourth land width W4 is greater than each of the first land width W1 and the second land width W2. The first land width W1 and the second land width W2 are substantially the same. The third land width W3 and the fourth land width W4 are substantially the same.

[0057] The lower limit of each of the third land width W3 and the fourth land width W4 is not particularly limited, but for example, it may be more than twice the first land width W1 and the second land width W2, or more than three times. The upper limit of each of the third land width W3 and the fourth land width W4 is not particularly limited, but for example, it may be less than 10 times the first land width W1 and the second land width W2, or less than 8 times.

[0058] like Figure 2 As shown, the distance (first distance D1) between the third line segment 30 and the fourth line segment 40 in the direction parallel to the first line segment 10 may be greater than the distance (second distance D2) between the first line segment 10 and the second line segment 20 in the direction parallel to the third line segment 30. The lower limit of the first distance D1 is not particularly limited, but, for example, may be 1.05 times or more of the second distance D2, or may be 1.08 times or more. The upper limit of the first distance D1 is not particularly limited, but, for example, may be 1.5 times or less of the second distance D2, or may be 1.3 times or less.

[0059] Figure 3 is along Figure 2 A schematic cross-sectional view taken along line III-III in FIG. Figure 3 The cross section shown is perpendicular to the first line segment 10 and perpendicular to the bottom surface 2. In the direction perpendicular to the bottom surface 2, the distance between each of the first land surface 11 and the second land surface 21 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2. From another point of view, each of the first land surface 11 and the second land surface 21 is located on an imaginary plane including the first line segment 10 and the second line segment 20. Each of the first land surface 11 and the second land surface 21 is, for example, parallel to the bottom surface 2. The flat portion 50 is, for example, parallel to the bottom surface 2. Each of the first land surface 11 and the second land surface 21 is, for example, parallel to the flat portion 50.

[0060] In the direction perpendicular to the bottom surface 2, the first inclined surface 12 is located between the first land surface 11 and the flat portion 50. The first inclined surface 12 is inclined relative to each of the first land surface 11 and the flat portion 50. The first inclined surface 12 is inclined toward the bottom surface side relative to the first land surface 11. In the direction perpendicular to the bottom surface 2, the second inclined surface 22 is located between the second land surface 21 and the flat portion 50. The second inclined surface 22 is inclined relative to each of the second land surface 21 and the flat portion 50. The second inclined surface 22 is inclined toward the bottom surface side relative to the second land surface 21.

[0061] In the direction perpendicular to the bottom surface 2, the flat portion 50 is located between the cutting edge 6 and the bottom surface 2. Specifically, in the direction perpendicular to the bottom surface 2, the flat portion 50 is located between each of the first land surface 11 and the second land surface 21 and the bottom surface 2. More specifically, in the direction perpendicular to the bottom surface 2, the flat portion 50 is located between each of the first inclined surface 12 and the second inclined surface 22 and the inner peripheral surface 4.

[0062] Figure 4 is along Figure 2 Schematic cross-sectional view taken along line IV-IV in FIG. Figure 4 The cross section shown is perpendicular to the third line segment 30 and perpendicular to the bottom surface 2. In the direction perpendicular to the bottom surface 2, the distance between each of the third land surface 31 and the fourth land surface 41 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2. From another point of view, each of the third land surface 31 and the fourth land surface 41 is located on an imaginary plane including the third line segment 30 and the fourth line segment 40. Each of the third land surface 31 and the fourth land surface 41 is, for example, parallel to the bottom surface 2. Each of the third land surface 31 and the fourth land surface 41 is, for example, parallel to the flat portion 50.

[0063] The third inclined surface 32 is located between the third land surface 31 and the flat portion 50 in a direction perpendicular to the bottom surface 2. The third inclined surface 32 is inclined relative to each of the third land surface 31 and the flat portion 50. The third inclined surface 32 is inclined toward the bottom surface side relative to the third land surface 31. The fourth inclined surface 42 is located between the fourth land surface 41 and the flat portion 50 in a direction perpendicular to the bottom surface 2. The fourth inclined surface 42 is inclined relative to each of the fourth land surface 41 and the flat portion 50. The fourth inclined surface 42 is inclined toward the bottom surface side relative to the fourth land surface 41.

[0064] In the direction perpendicular to the bottom surface 2, the flat portion 50 is located between each of the third land surface 31 and the fourth land surface 41 and the bottom surface 2. More specifically, in the direction perpendicular to the bottom surface 2, the flat portion 50 is located between each of the third inclined surface 32 and the fourth inclined surface 42 and the inner peripheral surface 4. Figure 4As shown, the distance between the outer peripheral surfaces 3 in the direction parallel to the bottom surface 2 may decrease monotonically from the top surface 1 toward the bottom surface 2 .

[0065] like Figure 3 and Figure 4 As shown, in the direction perpendicular to the bottom surface 2, the distance between the top surface 1 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2, or the distance between the top surface 1 and the bottom surface 2 is shorter than the distance between the cutting edge 6 and the bottom surface 2. From another point of view, in the direction perpendicular to the bottom surface 2, the top surface 1 is not located above the cutting edge 6. Further from another point of view, the top surface 1 does not have a raised curved surface portion (chip breaking portion) located above the cutting edge 6, and it should be noted that the direction from the bottom surface 2 toward the top surface 1 corresponds to the upward direction.

[0066] (Second embodiment)

[0067] Next, the structure of the rotary cutting tool cutting tool 100 involved in the second embodiment will be described below. The rotary cutting tool cutting tool 100 according to the second embodiment has the same structure as the rotary cutting tool cutting insert 100 of the first embodiment, except that the distance between the top surface 1 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2. Below, the structure different from the cutting tool cutting tool 100 involved in the first embodiment will be mainly described.

[0068] Figure 5 1 is a schematic perspective view showing the structure of a cutting tool 100 for a rotary cutting tool according to a second embodiment. Figure 5 As shown, the top surface 1 of the cutting insert 100 for a rotary cutting tool according to the second embodiment is a flat surface.

[0069] Figure 6 2 is a schematic plan view showing the structure of a cutting tool 100 for a rotary cutting tool according to a second embodiment. Figure 6 As shown, the top surface 1 is a substantially parallelogram when viewed in a direction perpendicular to the bottom surface 2. The top surface 1 surrounds the through hole 5. The top surface 1 is surrounded by the first line segment 10, the second line segment 20, the third line segment 30, the fourth line segment 40, the first curved portion 51, the second curved portion 52, the third curved portion 53, and the fourth curved portion 54.

[0070] Figure 7 is along Figure 6 A schematic cross-sectional view taken along line VII-VII in FIG. Figure 7The cross section shown in FIG. 1 is perpendicular to the first line segment 10 and is also perpendicular to the bottom surface 2. In the direction perpendicular to the bottom surface 2, the distance between the top surface 1 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2. From another point of view, the top surface 1 is located on an imaginary plane including the first line segment 10 and the second line segment 20. The top surface 1 is parallel to the bottom surface 2, for example.

[0071] Figure 8 is along Figure 6 A schematic cross-sectional view taken along line VIII-VIII in FIG. Figure 8 The cross section shown in FIG. 1 is perpendicular to the third line segment 30 and also perpendicular to the bottom surface 2. In the direction perpendicular to the bottom surface 2, the top surface 1 is located on a virtual plane including the third line segment 30 and the fourth line segment 40.

[0072] like Figure 7 and Figure 8 As shown, each of the width of the third land surface 31 in the direction perpendicular to the third line segment 30 (third land width W13) and the width of the fourth land surface 41 in the direction perpendicular to the fourth line segment 40 (fourth land width W14) may be greater than the width of the first land surface 11 in the direction perpendicular to the first line segment 10 (first land width W11), and may be greater than the width of the second land surface 21 in the direction perpendicular to the second line segment 20 (second land width W12). In other words, the third land width W13 is greater than each of the first land width W11 and the second land width W12. The fourth land width W14 is greater than each of the first land width W11 and the second land width W12. The first land width W11 and the second land width W12 are substantially the same. The third land width W13 and the fourth land width W14 are substantially the same.

[0073] (Third embodiment)

[0074] Next, the structure of the rotary cutting tool according to the third embodiment will be described.

[0075] Fig. 9 1 is a schematic perspective view showing the structure of a rotary cutting tool according to a third embodiment. Fig. 9 As shown, the rotary cutting tool 200 according to the third embodiment includes a main body 60 and a rotary cutting tool cutting tool 100. The rotary cutting tool 200 rotates around a rotation axis B. The main body 60 holds the rotary cutting tool cutting tool 100. The rotary cutting tool cutting tool 100 is, for example, the cutting tool 100 according to the first embodiment or the second embodiment.

[0076] The main body 60 has a front end face 61, a rear end face 65, an outer peripheral side surface 62, and a fitting portion 64. The front end face 61 is a portion facing a workpiece. The rear end face 65 faces the front end face 61. The fitting portion 64 is continuous with the rear end face 65. The fitting portion 64 is mounted on a machine tool.

[0077] The main body 60 is formed with an outer peripheral cutting tool placement groove 71, a center cutting tool placement groove 72, and a chip discharge groove 63. The outer peripheral cutting tool placement groove 71 is continuous with each of the outer peripheral side surface 62 and the front end surface 61. The center cutting tool placement groove 72 is continuous with the front end surface 61 and is spaced apart from the outer peripheral side surface 62. The chip discharge groove 63 is spiral. The chip discharge groove 63 is arranged around the rotation axis B.

[0078] In the rotary cutting tool 200, two cutting tools 100 are mounted on a main body 60. Specifically, one cutting tool 100 is mounted on the peripheral cutting tool placement groove 71, and the other cutting tool 100 is mounted on the center cutting tool placement groove 72. In the peripheral cutting tool placement groove 71, the cutting tool 100 is arranged in such a manner that the fourth line segment 40 (peripheral blade) is located axially forward. In the center cutting tool placement groove 72, the cutting tool 100 is arranged in such a manner that the second line segment 20 (center blade) is located axially forward. The mounting screw 73 is arranged in the through hole 5 of the cutting tool 100. The cutting tool 100 is mounted on the main body 60 using the mounting screw 73. The bottom surface 2 of the cutting tool 100 is in contact with the main body 60.

[0079] Fig.10 2 is a schematic perspective view showing a state in which a workpiece is processed using a rotary cutting tool 200. Fig.10 As shown, a rotating cutting tool 200 is used to form a hole 83 in a workpiece 80. The bottom surface of the hole 83 has a center edge cutting area 81 and a peripheral edge cutting area 82. The center edge cutting area 81 is surrounded by the peripheral edge cutting area 82. The center edge cutting area 81 is an area cut by the center edge of the cutting tool 100 set in the center side cutting tool placement groove 72. The peripheral edge cutting area 82 is an area cut by the peripheral edge of the cutting tool 100 set in the peripheral side cutting tool placement groove 71.

[0080] Fig.11 Schematic diagram showing the trajectory of the cutting tool 100 disposed in the center side cutting tool placement groove 72 and the trajectory of the cutting tool 100 disposed in the outer peripheral side cutting tool placement groove 71. Fig.11 As shown, when the workpiece 80 is machined using the rotary cutting tool 200, the trajectory of the cutting tool 100 disposed in the center side cutting tool placement groove 72 and the trajectory of the cutting tool 100 disposed in the outer peripheral side cutting tool placement groove 71 are symmetrical with respect to the rotation axis B. Fig.11 As shown, when viewed in a direction perpendicular to the rotation axis B, the trajectory of the cutting edge 6 of the cutting tool 100 disposed in the center side cutting tool placement groove 72 intersects with the trajectory of the cutting edge 6 of the cutting tool 100 disposed in the outer peripheral side cutting tool placement groove 71 .

[0081] like Fig.11 As shown, when viewed in a direction perpendicular to the rotation axis B, on the right side (on one side) of the rotation axis B, the trajectory of the cutting edge 6 (center edge) of the cutting tool 100 disposed in the center-side cutting tool placement groove 72 and the trajectory of the cutting edge 6 (peripheral edge) of the cutting tool 100 disposed in the peripheral-side cutting tool placement groove 71 intersect each other at a first intersection 91. When viewed in a direction perpendicular to the rotation axis B, on the left side (on the other side) of the rotation axis B, the trajectory of the cutting edge 6 (center edge) of the cutting tool 100 disposed in the center-side cutting tool placement groove 72 and the trajectory of the cutting edge 6 (peripheral edge) of the cutting tool 100 disposed in the peripheral-side cutting tool placement groove 71 intersect each other at a second intersection 92. In the radial direction perpendicular to the rotation axis B, the distance between the first intersection 91 and the second intersection 92 corresponds to the center edge share A2.

[0082] like Fig.11 As shown, when viewed in a direction perpendicular to the rotation axis B, on the right side (on one side) of the rotation axis B, the first peripheral point 93 is located at the outermost periphery of the trajectory of the cutting edge 6 (peripheral edge) of the cutting tool 100 disposed in the peripheral side cutting tool placement groove 71. When viewed in a direction perpendicular to the rotation axis B, on the left side (on the other side) of the rotation axis B, the second peripheral point 94 is located at the outermost periphery of the trajectory of the cutting edge 6 (peripheral edge) of the cutting tool 100 disposed in the peripheral side cutting tool placement groove 71. In the radial direction perpendicular to the rotation axis B, the distance between the first peripheral point 93 and the second peripheral point 94 is the tool diameter A1. The tool diameter A1 corresponds to the diameter of the hole 83 formed in the workpiece. The value obtained by subtracting the center edge share A2 from the tool diameter A1 is the peripheral edge share.

[0083] Fig.12 Yes means Fig.11 A magnified schematic diagram of region XII. Fig.12 In FIG. 1 , the shape indicated by the double-dashed line represents the imaginary corner of the cutting edge 6 when the radius of curvature of the third curved portion 53 is substantially zero. In this case, the first intersection 91 is located at the imaginary intersection 95. Fig.12As shown in FIG. 1 , by increasing the radius of curvature of the third curved portion 53, the first intersection 91 is offset toward the center by a distance A3. As a result, the center edge share A2 can be reduced. The centrifugal force applied to the chips cut by the center edge is smaller than the centrifugal force applied to the chips cut by the peripheral edge. Therefore, the chips cut by the center edge are more difficult to cut than the chips cut by the peripheral edge. Fig.12 As shown, by increasing the curvature radius of each of the third curved portion 53 and the fourth curved portion 54 to reduce the center edge share A2, the cutting balance is adjusted.

[0084] The value obtained by dividing the center edge share A2 by the tool diameter A1 is the center edge share ratio. The center edge share ratio is, for example, 48% or more and 53% or less. The upper limit of the center edge share ratio is not particularly limited, but, for example, it may be 52.5% or less, or it may be 52% or less. The lower limit of the center edge share ratio is not particularly limited, but, for example, it may be 48.5% or more, or it may be 49% or more.

[0085] Next, the effects of the cutting insert 100 for a rotary cutting tool and the rotary cutting tool 200 according to the above-described embodiment will be described.

[0086] Fig.13 1 is a schematic cross-sectional view showing the flow of chips 84 when a workpiece 80 is cut using a conventional cutting tool 100. Fig.13 As shown, the conventional cutting tool 100 is provided with a raised chip breaker 7 arranged at a position higher than the cutting edge 6. The chips 84 of the workpiece 80 cut by the cutting edge 6 are broken by the chip breaker 7 after passing through the rake face. For example, in the case of cutting a highly viscous workpiece 80 such as stainless steel, the chips 84 are broken without being cut by the chip breaker. As a result, the chips 84 cannot be effectively discharged.

[0087] Fig.14 1 is a schematic cross-sectional view showing the flow of chips 84 when the workpiece 80 is cut using the cutting tool 100 according to the second embodiment. Fig.14 As shown, the top surface 1 of the cutting tool 100 of the second embodiment is located at the same height as the cutting edge 6. Therefore, even when cutting a workpiece 80 with high viscosity such as stainless steel, the chips 84 of the workpiece 80 cut by the cutting edge 6 can flow smoothly on the top surface 1. Therefore, it is possible to suppress the chips 84 from being broken. As a result, the chips 84 can be effectively discharged. In other words, the inventors converted the existing concept of cutting off the chips 84 into a concept of making the chips 84 flow smoothly, and then rounding and discharging the chips in the chip discharge groove 63 of the main body 60. As a result, the discharge performance of the chips 84 can be improved.

[0088] Fig.151 is a schematic cross-sectional view showing the flow of chips 84 when the workpiece 80 is cut using the cutting tool 100 according to the first embodiment. Fig.15 As shown, the top surface 1 of the cutting tool 100 of the first embodiment is located at the same height as the cutting edge 6 or at a position closer to the bottom surface side than the cutting edge 6. Therefore, even when cutting a workpiece 80 with high viscosity such as stainless steel, the chips 84 of the workpiece 80 cut by the cutting edge 6 can flow smoothly on the top surface 1. Thus, the chips 84 can be suppressed from being broken. In addition, the top surface 1 has a first land surface 11 and a first inclined surface 12 that is continuous with the first land surface 11 and inclined toward the bottom surface side relative to the first land surface 11. Therefore, compared with the cutting tool 100 of the second embodiment, the contact area (scratching area) between the chips 84 and the top surface 1 can be reduced. Thus, the cutting resistance can be reduced. As a result, the chips 84 can be discharged more effectively.

[0089] In other words, according to the cutting tool 100 for a rotary cutting tool according to the above-described embodiment, in the direction perpendicular to the bottom surface 2, the distance between the top surface 1 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2, or the distance between the top surface 1 and the bottom surface 2 is shorter than the distance between the cutting edge 6 and the bottom surface 2. Therefore, even when cutting a highly viscous workpiece 80 such as stainless steel, the chips 84 of the workpiece 80 cut by the cutting edge 6 can flow smoothly on the top surface 1. Thus, the chips 84 can be suppressed from being broken. As a result, the chip discharge performance can be improved.

[0090] In addition, each of the curvature radius of the third curved portion 53 and the curvature radius of the fourth curved portion 54 is larger than the curvature radius of the first curved portion 51, and larger than the curvature radius of the second curved portion 52. Thus, when the diameter of the rotary cutting tool 200 is changed, it is easy to adjust the center blade share A2 to be within a desired range.

[0091] Furthermore, according to the cutting tool 100 for a rotary cutting tool according to the above-described embodiment, each of the width of the third land surface 31 in the direction perpendicular to the third line segment 30 and the width of the fourth land surface 41 in the direction perpendicular to the fourth line segment 40 can be greater than each of the width of the first land surface 11 in the direction perpendicular to the first line segment 10 and the width of the second land surface 21 in the direction perpendicular to the second line segment 20. Each of the third line segment 30 and the fourth line segment 40 corresponds to a peripheral edge. Each of the first line segment 10 and the second line segment 20 corresponds to a center edge.

[0092] In order to improve the chip discharge performance, it is desirable that the chip 84 has a linear extension shape. After the chip 84 is scratched on the land surface, the chip 84 becomes a linear extension shape. The larger the width of the land surface, the easier it is for the chip 84 to become a linear extension shape. On the other hand, if the width of the land surface is large, the distance that the chip 84 scratches on the land surface becomes longer, thereby increasing the cutting resistance. In order to suppress the increase in cutting resistance, it is desirable that the width of the land surface is small.

[0093] Since the peripheral cutting edge is located on the peripheral side of the rotation axis B, the centrifugal force applied to the chip 84 cut by the peripheral cutting edge is relatively large. In this case, the force of the chip 84 drilling into the inclined surface (the third inclined surface 32 and the fourth inclined surface 42) becomes larger. Therefore, in order to make the chip 84 cut by the peripheral cutting edge have a shape extending in a straight line, it is necessary to increase the width of the land surface (the third land surface 31 and the fourth land surface 41) to a certain extent. On the other hand, since the center cutting edge is located on the center side of the rotation axis B, the centrifugal force applied to the chip 84 cut by the center cutting edge is relatively small. In this case, the force of the chip 84 drilling into the inclined surface (the first inclined surface 12 and the second inclined surface 22) is relatively small. Therefore, in order to make the chip 84 cut by the center cutting edge have a shape extending in a straight line, the width of the land surface (the first land surface 11 and the second land surface 21) does not need to be so large.

[0094] The width of the land surface on the peripheral cutting edge side is greater than that on the center cutting edge side. Thus, in each of the peripheral cutting edge and the center cutting edge, the chips 84 can be formed into a linearly extending shape while suppressing an increase in cutting resistance.

[0095] In addition, according to the rotary cutting tool cutting tool 100 involved in the above-mentioned embodiment, each of the curvature radius of the third curved portion 53 and the curvature radius of the fourth curved portion 54 can be more than 2 times and less than 5 times the curvature radius of the first curved portion 51, and can be more than 2 times and less than 5 times the curvature radius of the second curved portion 52. Thus, in the rotary cutting tool 200 having a practical tool diameter A1, the center blade share A2 and the peripheral blade share A2 can be set to the same level. Thus, when cutting a workpiece 80 with high viscosity such as stainless steel, the cutting resistance can be reduced. In addition, the scratch depth formed on the side of the hole 83 of the workpiece 80 can be reduced.

[0096] <Example>

[0097] (Sample preparation)

[0098] Next, a cutting test is described. In the cutting test, each of samples 1 to 7 was used as the cutting tool 100 .

[0099] Fig.16is a diagram showing the structure of the cutting tool 100 of Samples 1 to 7. Fig.16 As shown, in the cutting tools 100 of samples 1 to 7, the curvature radii (first curvature radius R1 and second curvature radius R2) of the curved portions on the acute angle side are all set to 0.6 mm. In the cutting tools 100 of samples 1 to 7, the curvature radii (third curvature radius R3 and fourth curvature radius R4) of the curved portions on the obtuse angle side are set to 0.6 mm, 0.6 mm, 1.0 mm, 1.4 mm, 1.8 mm, 2.2 mm, and 1.4 mm, respectively.

[0100] In the cutting tools 100 of samples 1 to 7, the ratios of the curvature radius of the curved portion on the obtuse angle side to the curvature radius of the curved portion on the acute angle side are 1, 1, 1.67, 2.33, 3, 3.67, and 2.33, respectively. In the cutting tools 100 of samples 1 to 7, the center edge share ratios are 52.9%, 52.9%, 52.0%, 50.7%, 50.1%, 48.9%, and 50.7%, respectively. The top surface 1 of the cutting tool 100 of sample 1 has a raised chip breaker 7 (see Fig.13 The shape of the top surface 1 of each cutting tool 100 in Samples 2 to 6 was set to a flat shape (see Fig.14 The shape of the top surface 1 of the cutting tool 100 of sample 7 is set to a concave shape (refer to Fig.15 ).

[0101] (Cutting test conditions)

[0102] In the cutting test, a hole 83 was formed in each of the workpieces 80 using a rotary cutting tool 200 having a cutting tool 100 of samples 1 to 7. The machine tool used in the test was M / C BT50. The workpiece 80 used in the test was SUS316L. The drill diameter (Dc) was set to 20 mm. The cutting speed (Vc) was set to 150 m / min. The feed rate (f) was set to 0.08 mm / rev. The depth (L) of each hole was set to 60 mm. Wet machining (2 MPa) was used for machining.

[0103] (Cutting test results)

[0104] <Shape of Chips 84>

[0105] Fig.17 1 is a photograph showing the chips of the workpiece 80 cut by the cutting tool 100 of samples 1 to 7. Fig.17 In each of the upper photographs, the entire chip is shown, while each of the lower photographs shows the chip in an enlarged manner. Fig.17 In cutting, longer chips are obtained by cutting with the center edge, and shorter chips are obtained by cutting with the peripheral edge. Fig.17As shown, the chips of the workpiece 80 cut by the cutting tool 100 of sample 1 are greatly twisted and broken. Therefore, a part of the chips of the workpiece 80 cut by the cutting tool 100 of sample 1 is stuck in the chip discharge groove 63 and cannot be discharged smoothly. On the other hand, the chips of the workpiece 80 cut by the cutting tool 100 of each of samples 2 to 7 are roughly cylindrical and not greatly twisted. Therefore, the chips of the workpiece 80 cut by the cutting tool 100 of samples 2 to 7 are smoothly discharged through the chip discharge groove 63. Therefore, it can be confirmed that the cutting tool 100 of each of the first embodiment and the second embodiment can improve the chip discharge performance of stainless steel.

[0106] <Cutting resistance>

[0107] Fig.18 is a graph showing the cutting resistance of the cutting insert 100 of each of Samples 1 to 7. Fig.18 , Z is the maximum value of the cutting resistance in the direction along the rotation axis B. X is the maximum value of the cutting resistance in the direction perpendicular to Z. Y is the maximum value of the cutting resistance in the direction perpendicular to each of X and Z. The maximum value of the cutting resistance of the cutting blade 100 of sample 2 in the Z direction is greater than the maximum value of the cutting resistance of the cutting blade 100 of sample 1 in the Z direction. The maximum value of the cutting resistance of the cutting blade 100 of sample 2 in each of the X direction and the Y direction is less than the maximum value of the cutting resistance of the cutting blade 100 of sample 1 in each of the X direction and the Y direction.

[0108] In the case of the cutting tool 100 of sample 7, the maximum value of the cutting resistance in the Z direction is the smallest. Therefore, it can be confirmed that the cutting tool 100 of the first embodiment can reduce the cutting resistance in the Z direction. Among the cutting tools 100 of samples 2 to 6, the cutting tool 100 of sample 6 has the smallest cutting resistance in the Z direction. Therefore, it can be confirmed that the cutting resistance in the Z direction can be reduced by reducing the center edge share.

[0109] <Scratch depth on the side of the hole>

[0110] After the hole 83 is formed in the workpiece 80 , the depth of the scratch formed on the side surface of the hole 83 is measured. Fig.19 Graph showing the depth of scratches on the side of the hole 83 formed by the cutting tool 100 of samples 1 to 7. Fig.19As shown in the figure, the scratch depth of the side surface of the hole 83 formed by the cutting tools 100 of samples 2 to 7 is smaller than the scratch depth of the side surface of the hole 83 formed by the cutting tool 100 of sample 1. Therefore, it can be confirmed that the cutting tool 100 in each of the first embodiment and the second embodiment can improve the quality of the hole. In the case of the cutting tool 100 of sample 4, the scratch depth of the side surface of the hole is the smallest.

[0111] The embodiments and examples disclosed herein are to be considered in all respects as illustrative rather than restrictive. The scope of the present invention is not represented by the above embodiments and examples, but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0112] Description of the label

[0113] 1 top surface, 2 bottom surface, 3 outer peripheral surface, 4 inner peripheral surface, 5 through hole, 6 cutting edge, 7 chip breaker, 10 first line segment, 11 first land surface, 12 first inclined surface, 20 second line segment, 21 second land surface, 22 second inclined surface, 30 third line segment, 31 third land surface, 32 third inclined surface, 40 fourth line segment, 41 fourth land surface, 42 fourth inclined surface, 50 flat portion, 51 first curved portion, 52 second curved portion, 53 third curved portion, 54 fourth curved portion, 60 main body, 61 front end surface, 62 outer peripheral side surface, 63 chip discharge groove, 64 fitting portion, 65 rear end surface, 71 outer peripheral side cutting tool placement groove, 72 center side cutting tool placement groove, 73 mounting screw, 80 workpiece, 81 center edge cutting area Domain, 82 peripheral edge cutting area, 83 hole, 84 chip, 91 1st intersection point, 92 2nd intersection point, 93 1st peripheral point, 94 2nd peripheral point, 95 imaginary intersection point, 100 cutting tool for rotary cutting tool (cutting tool), 200 rotary cutting tool, A1 tool diameter, A2 center edge share, A3 distance, B rotation axis, D1 1st distance, D2 2nd distance, L1 1st straight line, L2 2nd straight line, L3 3rd straight line, L4 4th straight line, R1 1st curvature radius, R2 2nd curvature radius, R3 3rd curvature radius, R4 4th curvature radius, W1, W11 1st margin width, W2, W12 2nd margin width, W3, W13 3rd margin width, W4, W14 4th margin width.

Claims

1. A cutting tool for a rotary cutting tool, comprising: Top surface; a bottom surface, which is opposite to the top surface; as well as an outer peripheral surface, which is continuous with each of the top surface and the bottom surface, wherein the ridge between the top surface and the outer peripheral surface forms a cutting edge, The cutting edge comprises: Line segment 1, a second line segment, which is opposite to the first line segment, a third line segment, which is inclined relative to each of the first line segment and the second line segment, a fourth line segment, which is opposite to the third line segment, a first curved portion connecting the first line segment and the third line segment, a second curved portion connecting the second line segment and the fourth line segment, a third curved portion connecting the second line segment and the third line segment, and a fourth curved portion connecting the first line segment and the fourth line segment, The angle formed by the straight line along the first line segment and the straight line along the third line segment is an acute angle, The angle formed by the straight line along the second line segment and the straight line along the fourth line segment is an acute angle, The angle formed between the straight line along the second line segment and the straight line along the third line segment is an obtuse angle, The angle formed between the straight line along the first line segment and the straight line along the fourth line segment is an obtuse angle, The radius of curvature of each of the third curved portion and the fourth curved portion is greater than the radius of curvature of the first curved portion and greater than the radius of curvature of the second curved portion, and In a direction perpendicular to the bottom surface, the distance between the top surface and the bottom surface is equal to the distance between the cutting edge and the bottom surface, or is shorter than the distance between the cutting edge and the bottom surface, The top surface comprises: a first land surface, which is continuous with the first line segment, a second land surface, which is continuous with the second line segment, a third land surface, which is continuous with the third line segment, and a fourth land surface, which is continuous with the fourth line segment, and Each of the entire width of the third edge surface in the direction perpendicular to the third line segment and the entire width of the fourth edge surface in the direction perpendicular to the fourth line segment is greater than the entire width of the first edge surface in the direction perpendicular to the first line segment, and greater than the entire width of the second edge surface in the direction perpendicular to the second line segment.

2. The cutting tool for a rotary cutting tool according to claim 1, wherein: In the direction perpendicular to the bottom surface, the distance between the top surface and the bottom surface is equal to the distance between the cutting edge and the bottom surface.

3. The cutting tool for a rotary cutting tool according to claim 1, wherein: The top surface has a flat portion spaced apart from the cutting edge, and The flat portion is located between the cutting edge and the bottom surface in the direction perpendicular to the bottom surface.

4. The cutting tool for a rotary cutting tool according to any one of claims 1 to 3, wherein: Each of the width of the third edge surface in the direction perpendicular to the third line segment and the width of the fourth edge surface in the direction perpendicular to the fourth line segment is more than twice the width of the first edge surface in the direction perpendicular to the first line segment, and more than twice the width of the second edge surface in the direction perpendicular to the second line segment.

5. The cutting tool for a rotary cutting tool according to any one of claims 1 to 3, wherein: Each of the curvature radius of the third curved portion and the curvature radius of the fourth curved portion is not less than 2 times and not more than 5 times the curvature radius of the first curved portion, and is not less than 2 times and not more than 5 times the curvature radius of the second curved portion.

6. The cutting tool for a rotary cutting tool according to claim 1, wherein: In the direction perpendicular to the bottom surface, the distance between the top surface and the bottom surface is equal to the distance between the cutting edge and the bottom surface, The top surface comprises: a first land surface, which is continuous with the first line segment, a second land surface, which is continuous with the second line segment, a third land surface, which is continuous with the third line segment, and a fourth land surface, which is continuous with the fourth line segment, Each of the width of the third land surface in the direction perpendicular to the third line segment and the width of the fourth land surface in the direction perpendicular to the fourth line segment is greater than the width of the first land surface in the direction perpendicular to the first line segment, and greater than the width of the second land surface in the direction perpendicular to the second line segment, and Each of the curvature radius of the third curved portion and the curvature radius of the fourth curved portion is not less than 2 times and not more than 5 times the curvature radius of the first curved portion, and is not less than 2 times and not more than 5 times the curvature radius of the second curved portion.

7. The cutting tool for a rotary cutting tool according to claim 1, wherein: The top surface has a flat portion spaced apart from the cutting edge, In the direction perpendicular to the bottom surface, the flat portion is located between the cutting edge and the bottom surface, The top surface comprises: a first land surface, which is continuous with the first line segment, a second land surface, which is continuous with the second line segment, a third land surface, which is continuous with the third line segment, and a fourth land surface, which is continuous with the fourth line segment, Each of the width of the third land surface in the direction perpendicular to the third line segment and the width of the fourth land surface in the direction perpendicular to the fourth line segment is greater than the width of the first land surface in the direction perpendicular to the first line segment, and greater than the width of the second land surface in the direction perpendicular to the second line segment, and Each of the curvature radius of the third curved portion and the curvature radius of the fourth curved portion is not less than 2 times and not more than 5 times the curvature radius of the first curved portion, and is not less than 2 times and not more than 5 times the curvature radius of the second curved portion.

8. A rotary cutting tool comprising: A cutting tool for a rotary cutting tool according to any one of claims 1 to 7; as well as A main body portion holds a cutting tool for the rotary cutting tool.

Images