Rotary cutting tool

Abstract

This rotary cutting tool comprises an outer peripheral cutting edge, a front cutting edge, and a rake face to which a groove has been provided. With respect to the front cutting edge, the outer peripheral cutting edge is positioned in a first direction that is parallel to an axis and goes from a front end of the rotary cutting tool toward a rear end of the rotary cutting tool. The rake face comprises a first rake face portion linked to the outer peripheral cutting edge. The groove comprises a first side wall surface linked to the first rake face portion. A ridge line between the first side wall surface and the first rake face portion is taken to be a first ridge line. In a cross section that is perpendicular to the axis and intersects the groove and that is viewed in the first direction, a virtual line that is perpendicular to the first rake face portion and passes through the first ridge line is taken to be a first virtual line. In the cross section, a tilt angle of the first side wall surface with respect to the first virtual line is 35° to 60°.

Description

Rotary cutting tool

[0001] The present disclosure relates to a rotary cutting tool. This application claims priority based on International Application PCT / JP2024 / 036660, which was filed on October 15, 2024. All the descriptions described in the application are incorporated herein by reference.

[0002] Japanese Utility Model Publication No. 58-44135 (Patent Document 1) describes a gun drill in which a chip breaker is provided on the rake face of a cutting edge tip.

[0003] Japanese Utility Model Publication No. 58-44135

[0004] The rotary cutting tool according to this disclosure is rotatable about an axis. The rotary cutting tool comprises an outer cutting edge, a front cutting edge, and a rake face. The front cutting edge is connected to the outer cutting edge. The rake face is connected to both the outer cutting edge and the front cutting edge. The outer cutting edge is parallel to the axis with respect to the front cutting edge and is located in a first direction from the front end of the rotary cutting tool toward the rear end of the rotary cutting tool. The outer cutting edge is parallel to the axis, or the outer cutting edge is provided with a back taper. The slope of the back taper is 1° or less. A groove is provided on the rake face. The groove is connected to the front cutting edge. The groove extends along a first direction, or, when viewed perpendicular to the rake face, the direction in which the groove extends is inclined at an angle of 1° or less with respect to the first direction. The rake face has a first rake face portion and a second rake face portion. The first rake face portion is connected to the outer cutting edge. The first rake face is located between the outer cutting edge and the groove. The second rake face is located opposite the first rake face relative to the groove. The groove has a first side wall surface and a second side wall surface. The first side wall surface is connected to the first rake face. The second side wall surface is connected to the second rake face. The ridge line between the first side wall surface and the first rake face is defined as the first ridge line. The ridge line between the second side wall surface and the second rake face is defined as the second ridge line. In a cross section perpendicular to the axis and intersecting the groove, viewed in a first direction, a virtual line perpendicular to the first rake face and passing through the first ridge line is defined as the first virtual line. In the cross section, a virtual line perpendicular to the second rake face and passing through the second ridge line is defined as the second virtual line. In the cross-section, the first side wall is inclined clockwise around the first edge with respect to the first imaginary line. In the cross-section, the second side wall is inclined counterclockwise around the second edge with respect to the second imaginary line. The inclination angle of the second side wall with respect to the second imaginary line is 10° or more and 60° or less. The inclination angle of the first side wall with respect to the first imaginary line is 35° or more and 60° or less. When viewed perpendicular to the rake face, the distance from the outer cutting edge to the groove in a direction perpendicular to the first direction is 0.05 mm or more and 0.2 mm or less.

[0005] Figure 1 is a schematic plan view showing the configuration of a rotary cutting tool according to the first embodiment. Figure 2 is an enlarged perspective schematic view showing the configuration of a rotary cutting tool according to the first embodiment. Figure 3 is an enlarged schematic view showing region III in Figure 2. Figure 4 is a schematic front view showing the configuration of a rotary cutting tool according to the first embodiment. Figure 5 is an enlarged schematic plan view showing region V in Figure 1. Figure 6 is a schematic cross-sectional view along the line VI-VI in Figure 5. Figure 7 is a schematic cross-sectional view along the line VII-VII in Figure 5. Figure 8 is a schematic cross-sectional view showing the configuration of a rotary cutting tool according to the second embodiment. Figure 9 is a schematic cross-sectional view showing the configuration of a rotary cutting tool according to the third embodiment. Figure 10 is a schematic front view showing the configuration of a first modified example of the rotary cutting tool according to this embodiment. Figure 11 is a schematic front view showing the configuration of a second modified example of the rotary cutting tool according to this embodiment. Figure 12 is a schematic plan view showing the configuration of a third modified example of the rotary cutting tool according to this embodiment. Figure 13 is an enlarged schematic plan view showing the configuration of a fourth modified example of the rotary cutting tool according to this embodiment. Figure 14 is a schematic front view showing the configuration of a fifth modified example of the rotary cutting tool according to this embodiment. Figure 15 is an enlarged schematic plan view showing the configuration of a fifth modified example of the rotary cutting tool according to this embodiment. Figure 16 is a schematic plan view showing the configuration of the rotary cutting tool according to the fourth embodiment. Figure 17 is a schematic perspective view showing the configuration of the rotary cutting tool according to the fourth embodiment. Figure 18 is an enlarged schematic plan view showing region XVIII in Figure 16. Figure 19 is an enlarged schematic side view showing the rotary cutting tool as seen in the third direction shown in Figure 18. Figure 20 is a schematic plan view showing the configuration of the rotary cutting tool according to the fifth embodiment. Figure 21 is a schematic front view showing the configuration of the rotary cutting tool according to the fifth embodiment. Figure 22 is an enlarged schematic plan view showing region XXII in Figure 20. Figure 23 is an enlarged schematic side view showing the rotary cutting tool as seen in the third direction shown in Figure 22. Figure 24 is a schematic plan view showing the configuration of the rotary cutting tool according to the sixth embodiment. Figure 25 is a schematic perspective view showing the configuration of the rotary cutting tool according to the sixth embodiment. Figure 26 is an enlarged planar schematic view showing region XXVI in Figure 24. Figure 27 is a schematic cross-sectional view along the line XXVII-XXVII in Figure 26. Figure 28 shows the results of the cutting evaluation using a rotary cutting tool on the sample.

[0006] Even when grooves such as chip breakers are provided on the rake face of a rotary cutting tool, the chips can sometimes become excessively long. The purpose of this disclosure is to provide a rotary cutting tool capable of improving chip breaking performance.

[0007] According to this disclosure, it is possible to provide a rotary cutting tool capable of improving chip breaking performance. First, an outline of the embodiment of this disclosure (also referred to as this embodiment) will be described.

[0008] (1) The rotary cutting tool according to the present disclosure is rotatable about an axis. The rotary cutting tool has an outer cutting edge, a front cutting edge, and a rake face. The front cutting edge is connected to the outer cutting edge. The rake face is connected to both the outer cutting edge and the front cutting edge. The outer cutting edge is parallel to the axis with respect to the front cutting edge and is located in a first direction from the front end of the rotary cutting tool toward the rear end of the rotary cutting tool. The outer cutting edge is parallel to the axis, or the outer cutting edge has a back taper. The slope of the back taper is 1° or less. A groove is provided on the rake face. The groove is connected to the front cutting edge. The groove extends along a first direction, or, when viewed perpendicular to the rake face, the direction in which the groove extends is inclined at an angle of 1° or less with respect to the first direction. The rake face has a first rake face portion and a second rake face portion. The first rake face portion is connected to the outer cutting edge. The first rake face is located between the outer cutting edge and the groove. The second rake face is located opposite the first rake face relative to the groove. The groove has a first side wall surface and a second side wall surface. The first side wall surface is connected to the first rake face. The second side wall surface is connected to the second rake face. The ridge line between the first side wall surface and the first rake face is defined as the first ridge line. The ridge line between the second side wall surface and the second rake face is defined as the second ridge line. In a cross section perpendicular to the axis and intersecting the groove, viewed in a first direction, a virtual line perpendicular to the first rake face and passing through the first ridge line is defined as the first virtual line. In the cross section, a virtual line perpendicular to the second rake face and passing through the second ridge line is defined as the second virtual line. In the cross-section, the first sidewall is inclined clockwise around the first ridge with respect to the first imaginary line. In the cross-section, the second sidewall is inclined counterclockwise around the second ridge with respect to the second imaginary line. The inclination angle of the second sidewall with respect to the second imaginary line is between 10° and 60°. The inclination angle of the first sidewall with respect to the first imaginary line is between 35° and 60°. The distance from the outer cutting edge to the groove in the direction perpendicular to the first direction, viewed perpendicular to the rake face, is between 0.05 mm and 0.2 mm. This improves chip breaking performance.

[0009] (2) In the rotary cutting tool described in (1) above, when the arithmetic mean roughness of the first sidewall surface and the rake face is measured along the first direction, the arithmetic mean roughness of the first sidewall surface may be 0.05 μm or more and 1 μm or less, and the arithmetic mean roughness of the first sidewall surface may be greater than the arithmetic mean roughness of the rake face. By having an arithmetic mean roughness of 0.05 μm or more for the first sidewall surface, the chip breaking performance can be effectively improved. By having an arithmetic mean roughness of 1 μm or less for the first sidewall surface, chip clogging in the first groove can be prevented.

[0010] (3) In the case of the rotary cutting tool according to (1) or (2) above, the depth of the groove in the direction perpendicular to the rake face may be 0.01 mm or more and 0.5 mm or less. By having a groove depth of 0.01 mm or more perpendicular to the rake face, the chip breaking performance can be effectively improved. By having a groove depth of 0.5 mm or less perpendicular to the rake face, the time required to form the first groove can be shortened.

[0011] (4) In the case of a rotary cutting tool according to any of (1) to (3) above, the width of the groove in the direction perpendicular to the first direction when viewed perpendicular to the rake face may be 0.1 mm or more and 2 mm or less. By having a groove width of 0.1 mm or more in the direction perpendicular to the first direction (third direction) when viewed perpendicular to the rake face, the chip breaking performance can be effectively improved. By having a groove width of 2 mm or less in the third direction, the time required to form the first groove can be shortened.

[0012] (5) In the rotary cutting tool according to any of (1) to (4) above, the groove may have a third side wall surface and a fourth side wall surface. The third side wall surface may be connected to the first side wall surface. The third side wall surface may be located opposite the first ridge line with respect to the first side wall surface. The fourth side wall surface may be connected to the second side wall surface. The fourth side wall surface may be located opposite the second ridge line with respect to the second side wall surface. In cross-section, the third side wall surface may be inclined clockwise with respect to the first side wall surface around the connection point between the first side wall surface and the third side wall surface. In cross-section, the fourth side wall surface may be inclined counterclockwise with respect to the second side wall surface around the connection point between the second side wall surface and the fourth side wall surface. This makes it possible to improve the strength of the rotary cutting tool.

[0013] (6) In the rotary cutting tool according to any of (1) to (4) above, the groove may have a bottom surface, a first corner curved surface, and a second corner curved surface. The first corner curved surface may connect the first side wall surface and the bottom surface. The second corner curved surface may connect the second side wall surface and the bottom surface. This makes it possible to improve the strength of the rotary cutting tool.

[0014] (7) A rotary cutting tool relating to any of (1) to (6) above may be formed from a single component.

[0015] (8) A rotary cutting tool according to any of (1) to (6) above may have a main body and a cutting edge tip. The cutting edge tip may be attached to the main body. The cutting edge tip may have an outer cutting edge, a front cutting edge and a rake face.

[0016] (9) In the rotary cutting tool described in (8) above, the cutting edge tip may be formed from one of the following: a diamond sintered body, a cemented carbide, or cubic boron nitride.

[0017] (10) The rotary cutting tool relating to any of (1) to (9) above may be a reamer.

[0018] (11) In the rotary cutting tool according to (10) above, the reamer may further have a relief face. The relief face may be connected to the front cutting edge. The front cutting edge may have a straight cutting edge portion. The straight cutting edge portion may be connected to the outer cutting edge. The ridge line between the rake face and the relief face may have a portion that extends along the direction from the outer cutting edge toward the axis when viewed perpendicular to the rake face. When viewed perpendicular to the rake face, the above portion may be located in a first direction with respect to the straight line that coincides with the straight cutting edge portion.

[0019] (12) The rotary cutting tool relating to any of (1) to (9) above may be an end mill.

[0020] (13) The rotary cutting tool relating to any of (1) to (9) above may be a boring tool.

[0021] (14) The rotary cutting tool according to (12) or (13) above may further have a tip surface and a relief surface. The relief surface may be connected to the front cutting edge. When viewed perpendicular to the axis, the tip surface may be located in a first direction relative to the relief surface.

[0022] (15) The rotary cutting tool relating to any of (1) to (9) above may be a drill for machining cast holes. The inclination angle of the second side wall surface with respect to the second imaginary line may be 35° or more and 60° or less.

[0023] (16) In the case of the rotary cutting tool described in (15) above, the number of grooves provided on the rake face may be one.

[0024] (17) In the case of a rotary cutting tool according to any of (1) to (16) above, the rake face may have a fourth rake face portion. The fourth rake face portion may be connected to each of the first rake face portion and the second rake face portion. Viewed perpendicular to the rake face, the fourth rake face portion may be located in a first direction relative to each of the first rake face portion and the second rake face portion. The groove may have a bottom surface and a fifth side wall surface. The bottom surface may be connected to each of the first side wall surface and the second side wall surface. The fifth side wall surface may be connected to each of the first side wall surface, the second side wall surface, the bottom surface, and the fourth rake face portion. Viewed perpendicular to the rake face, the fifth side wall surface may be located in a first direction relative to the bottom surface.

[0025] (18) In the case of a rotary cutting tool according to any of (1) to (17) above, the width of the groove in the direction perpendicular to the first direction when viewed perpendicular to the rake face may be 0.4 mm or more and 1.7 mm or less.

[0026] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the following drawings, identical or corresponding parts are given the same reference numerals, and their descriptions will not be repeated.

[0027] (First Embodiment) First, the configuration of the rotary cutting tool 100 according to the first embodiment will be described.

[0028] As shown in Figure 1, the rotary cutting tool 100 has a front end 1 and a rear end 2. The front end 1 is the part that faces the workpiece (not shown). The rear end 2 is the part that faces the spindle (not shown) of the machine tool that rotates the rotary cutting tool 100. The rotary cutting tool 100 rotates around axis X. The direction parallel to axis X and moving from the front end 1 to the rear end 2 is called the first direction 101. The direction opposite to the first direction 101 is called the second direction 102.

[0029] The rotary cutting tool 100 is used for processing metallic materials such as aluminum alloys and non-ferrous metals. Specifically, the rotary cutting tool 100 is used, for example, for finishing the inner wall surface of a hole in a metallic material. The rotary cutting tool 100 is, for example, a reamer.

[0030] The rotary cutting tool 100 has, for example, a main body 3 and a plurality of cutting edge tips 4. The main body 3 has a first portion 31 and a second portion 32. The first portion 31 is provided with flutes 9. The flutes 9 extend along a first direction 101. The second portion 32 is connected to the first portion 31. The second portion 32 is located in the first direction 101 relative to the first portion 31. The second portion 32 is a shank.

[0031] Each of the multiple cutting edge tips 4 is attached to the main body 3. Specifically, each of the multiple cutting edge tips 4 is attached to the first part 31. Each of the multiple cutting edge tips 4 is joined to the main body 3, for example, by brazing.

[0032] As shown in Figure 2, the rotary cutting tool 100 has, for example, four cutting edge tips 4. The main body 3 has a first surface 36 and a second surface 37. The first surface 36 and the second surface 37 form flutes 9. For example, the cutting edge tips 4 are located in recesses provided on the first surface 36. The first surface 36 extends along the first direction 101. The second surface 37 is connected to the first surface 36. The second surface 37 may be perpendicular to the first surface 36. The second surface 37 extends along the first direction 101.

[0033] The rotary cutting tool 100 has a tip surface 8. The tip surface 8 is formed by the main body 3. The tip surface 8 is located at the front end of the main body 3. The tip surface 8 faces the workpiece (not shown). The tip surface 8 may be perpendicular to the axis X, for example.

[0034] As shown in Figure 3, the cutting edge tip 4 has an outer peripheral cutting edge 19 and a front cutting edge 18. From another perspective, the rotary cutting tool 100 has, for example, four outer peripheral cutting edges 19 and four front cutting edges 18. The outer peripheral cutting edges 19 are, for example, parallel to axis X (see Figure 1). In other words, the outer peripheral cutting edges 19 extend along the first direction 101. The front cutting edges 18 are connected to the outer peripheral cutting edges 19.

[0035] The cutting edge tip 4 has a rake face 5, an outer peripheral relief face 6, and a front relief face 7. From another perspective, the rotary cutting tool 100 has, for example, four rake faces 5, four outer peripheral relief faces 6, and four front relief faces 7.

[0036] The rake face 5 is connected to the outer cutting edge 19 and the front cutting edge 18, respectively. The rake face 5 is parallel to the first direction 101, for example. The rake face 5 may also be parallel to the first surface 36 of the main body 3.

[0037] The outer peripheral relief surface 6 is connected to the outer peripheral cutting edge 19. From another perspective, the outer peripheral cutting edge 19 is formed by the ridge line between the outer peripheral relief surface 6 and the rake face 5. The outer peripheral relief surface 6 has a first outer peripheral relief surface portion 61, a second outer peripheral relief surface portion 62, and a third outer peripheral relief surface portion 63.

[0038] The first outer peripheral relief surface 61 is connected to the outer peripheral cutting edge 19. The first outer peripheral relief surface 61 extends along the first direction 101. The second outer peripheral relief surface 62 is connected to the first outer peripheral relief surface 61. The second outer peripheral relief surface 62 is located opposite the outer peripheral cutting edge 19 to the first outer peripheral relief surface 61. The second outer peripheral relief surface 62 extends along the first direction 101.

[0039] The third outer periphery relief surface 63 is connected to the second outer periphery relief surface 62. The third outer periphery relief surface 63 is located opposite the first outer periphery relief surface 61 to the second outer periphery relief surface 62. The third outer periphery relief surface 63 extends along the first direction 101.

[0040] The front relief surface 7 is connected to the front cutting edge 18. From another perspective, the front cutting edge 18 is formed by the ridge line of the front relief surface 7 and the rake face 5. The front relief surface 7 has a first front relief surface portion 71 and a second front relief surface portion 72. The first front relief surface portion 71 is connected to the rake face 5 and the outer peripheral relief surface 6, respectively. The second front relief surface portion 72 is connected to the first front relief surface portion 71. The second front relief surface portion 72 is located opposite the outer peripheral relief surface 6 to the first front relief surface portion 71.

[0041] In the rake face 5, a first groove 91 and a second groove 92 are provided. The first groove 91 extends, for example, along the first direction 101. The extending direction of the first groove 91 may be parallel to the extending direction of the outer peripheral cutting edge 19. The first groove 91 is continuous with the front cutting edge 18. In the first relief face portion 71, the first groove 91 is open.

[0042] The second groove 92 extends, for example, along the first direction 101. The extending direction of the second groove 92 may be parallel to the extending direction of the first groove 91. The second groove 92 is continuous with the front cutting edge 18. The second groove 92 is open in the first relief face portion 71 and the second relief face portion 72.

[0043] In FIG. 4, the configuration of the rotary cutting tool 100 as viewed in the first direction 101 is shown. For the sake of convenience of explanation, in FIG. 4, the second portion 32 (see FIG. 1) of the main body portion 3 is not shown.

[0044] As shown in FIG. 4, when viewed in the first direction 101, the shape of the rotary cutting tool 100 may be rotationally symmetric with respect to the axis X. Specifically, when viewed in the first direction 101, the shape of the rotary cutting tool 100 may be, for example, rotationally symmetric four times with respect to the axis X. From another perspective, when viewed in the first direction 101, the shape obtained by rotating the rotary cutting tool 100 by 90° around the axis X may coincide with the shape of the rotary cutting tool 100.

[0045] When viewed in the first direction 101, twice the distance between the outer peripheral cutting edge 19 and the axis X is defined as the diameter D of the outer peripheral cutting edge 19. The diameter D of the outer peripheral cutting edge 19 is, for example, 12 mm.

[0046] In FIG. 5, mainly the configuration of the cutting edge tip 4 as viewed perpendicularly to the rake face 5 is shown. As shown in FIG. 5, when viewed perpendicularly to the rake face ⑤, the direction perpendicular to the first direction 101 is defined as the third direction 103. The third direction 103 is, when viewed perpendicularly to the rake face 5, perpendicular to the first direction 101 and is the direction from the outer peripheral cutting edge 19 toward the axis X (see FIG. 1).

[0047] The scraping surface 5 has a first scraping surface portion 11, a second scraping surface portion 12, a third scraping surface portion 13, and a fourth scraping surface portion 14. The first scraping surface portion 11 is located between the outer peripheral cutting edge 19 and the first groove 91. The first scraping surface portion 11 is continuous with each of the outer peripheral cutting edge 19 and the front cutting edge 18. The first scraping surface portion 11 extends along the first direction 101.

[0048] The second scraping surface portion 12 is located between the first groove 91 and the second groove 92. The second scraping surface portion 12 is located opposite to the first scraping surface portion 11 with respect to the first groove 91. From another perspective, the first groove 91 is provided between the first scraping surface portion 11 and the second scraping surface portion 12. The second scraping surface portion 12 is located in the third direction 103 with respect to the first scraping surface portion 11. The second scraping surface portion 12 is separated from the first scraping surface portion 11. The second scraping surface portion 12 extends along the first direction 101.

[0049] The third scraping surface portion 13 is located opposite to the second scraping surface portion 12 with respect to the second groove 92. From another perspective, the second groove 92 is provided between the second scraping surface portion 12 and the third scraping surface portion 13. The third scraping surface portion 13 is located in the third direction 103 with respect to the second scraping surface portion 12. The third scraping surface portion 13 is separated from each of the first scraping surface portion 11 and the second scraping surface portion 12. The third scraping surface portion 13 extends along the first direction 101.

[0050] The fourth scraping surface portion 14 is continuous with each of the first scraping surface portion 11, the second scraping surface portion 12, and the third scraping surface portion 13. The fourth scraping surface portion 14 is located in the first direction 101 with respect to each of the first scraping surface portion 11, the second scraping surface portion 12, and the third scraping surface portion 13.

[0051] The first groove 91 has a first side wall surface 41, a second side wall surface 42, a first bottom surface 49, and a fifth side wall surface 45. The first side wall surface 41 is continuous with the first scraping surface portion 11. The first side wall surface 41 extends along the first direction 101.

[0052] The second side wall surface 42 is connected to the second rake face portion 12. The second side wall surface 42 extends along the first direction 101. The first bottom surface 49 is connected to both the first side wall surface 41 and the second side wall surface 42. Viewed perpendicular to the rake face 5, the first bottom surface 49 is located between the first side wall surface 41 and the second side wall surface 42. The first bottom surface 49 extends along the first direction 101.

[0053] The fifth side wall surface 45 is connected to the first side wall surface 41, the second side wall surface 42, the first bottom surface 49, and the fourth rake face portion 14. The fifth side wall surface 45 is located between the first bottom surface 49 and the fourth rake face portion 14. Viewed perpendicular to the rake face 5, the fifth side wall surface 45 is located in the first direction 101 relative to the first bottom surface 49.

[0054] The second groove 92 has a sixth side wall surface 51, a seventh side wall surface 52, a second bottom surface 59, and a tenth side wall surface 55. The sixth side wall surface 51 is connected to the second rake face portion 12. The sixth side wall surface 51 extends along the first direction 101.

[0055] The seventh side wall surface 52 is connected to the third rake face portion 13. The seventh side wall surface 52 extends along the first direction 101. The second bottom surface 59 is connected to the sixth side wall surface 51 and the seventh side wall surface 52, respectively. Viewed perpendicular to the rake face 5, the second bottom surface 59 is located between the sixth side wall surface 51 and the seventh side wall surface 52. The second bottom surface 59 extends along the first direction 101.

[0056] The tenth side wall surface 55 is connected to the sixth side wall surface 51, the seventh side wall surface 52, the second bottom surface 59, and the fourth rake face portion 14. The tenth side wall surface 55 is located between the second bottom surface 59 and the fourth rake face portion 14. Viewed perpendicular to the rake face 5, the tenth side wall surface 55 is located in the first direction 101 relative to the second bottom surface 59.

[0057] According to the first embodiment, the width of the first groove 91 in the third direction 103 (first width H1) is, for example, 0.1 mm or more and 2 mm or less. By having a first width H1 of 0.1 mm or more, the volume of the first groove 91 is sufficiently increased. Therefore, chips can easily flow into the first groove 91. This effectively improves the chip breaking performance. Furthermore, it is possible to prevent a decrease in chip breaking performance caused by chips getting stuck in the first groove 91.

[0058] If the first width H1 is excessively large, chips that are curled inward towards the rotary cutting tool 100 by contacting the first side wall surface 41 will have difficulty colliding with the second side wall surface 42. In this case, the chip breaking performance is expected to decrease. By setting the first width H1 to 2 mm or less, chips curled by the first side wall surface 41 will be more likely to collide with the second side wall surface 42. Therefore, the chips can be effectively curled. This improves the chip breaking performance. In addition, by setting the first width H1 to 2 mm or less, it is possible to prevent the volume of the first groove 91 from becoming excessively large. Therefore, in the manufacturing of the rotary cutting tool 100, the time required to form the first groove 91 can be shortened.

[0059] The first width H1 may be, for example, 0.4 mm or more and 1.7 mm or less. The first width H1 may be, for example, 0.3 mm or more, or 0.5 mm or more. The first width H1 may be, for example, 1.8 mm or less, 1.5 mm or less, or 1.0 mm or less. The first width H1 is the same as the distance in the third direction 103 between the first rake face portion 11 and the second rake face portion 12.

[0060] The width of the second groove 92 in the third direction 103 (second width H2) is, for example, 0.1 mm or more and 2 mm or less. The second width H2 may be the same as the first width H1, or it may be different from the first width H1. The second width H2 is the same as the distance in the third direction 103 between the second rake face portion 12 and the third rake face portion 13.

[0061] The distance from the outer cutting edge 19 to the first groove 91 in the third direction 103 (first distance E1) is, for example, 0.1 mm. The first distance E1 is the same as the width of the first rake face portion 11 in the third direction 103.

[0062] The first distance E1 is 0.05 mm or more and 0.2 mm or less. The first distance E1 may be 0.07 mm or more, 0.09 mm or more, or 0.1 mm or more. The first distance E1 may be 0.18 mm or less, or 0.16 mm or less.

[0063] The distance between the first groove 91 and the second groove 92 in the third direction 103 (second distance E2) is, for example, 0.1 mm. The second distance E2 may be, for example, 0.05 mm or more and 0.5 mm or less. The second distance E2 may be the same as the first distance E1, or it may be different from the first distance E1. The second distance E2 is the same as the width of the second rake face portion 12 in the third direction 103.

[0064] According to the first embodiment, when the arithmetic mean roughness (Ra) of the first sidewall surface 41 is measured along the first direction 101, the Ra of the first sidewall surface 41 is, for example, 0.05 μm or more and 1 μm or less. Ra is a surface property parameter specified in JIS (Japanese Industrial Standards) B0601:2013.

[0065] By having a Ra of 0.05 μm or more on the first sidewall 41, the frictional force between the chip and the first sidewall 41 can be sufficiently increased. This allows the shear angle of the chip to be reduced. As a result, the thickness of the chip can be increased. Consequently, the chip breaking performance can be effectively improved. By having a Ra of 1 μm or less on the first sidewall 41, it is possible to prevent the frictional force between the first sidewall 41 and the chip from becoming excessively large. Therefore, the chip can be easily discharged from the first groove 91. As a result, clogging of the first groove 91 with chips can be prevented.

[0066] In measuring the Ra of the first sidewall surface 41, the roughness curve of the first sidewall surface 41 is measured along the first direction 101. The Ra of the first sidewall surface 41 is measured using this roughness curve. The measurement distance is set to 0.5 mm. The measurement start position is set to a position on the first sidewall surface 41 where the distance from the front cutting edge 18 in the first direction 101 is 0.1 mm.

[0067] The Ra of the first sidewall 41 may be, for example, 0.1 μm or more, or 0.2 μm or more. The Ra of the first sidewall 41 may be, for example, 0.8 μm or less, or 0.6 μm or less. The Ra of the first sidewall 41 is greater than the Ra of the scoop face 5.

[0068] When the Ra of the second side wall surface 42 is measured along the first direction 101, the Ra of the second side wall surface 42 is, for example, 0.05 μm or more and 1 μm or less. Similarly, the Ra of the first bottom surface 49, the fifth side wall surface 45, the sixth side wall surface 51, the seventh side wall surface 52, the second bottom surface 59, and the tenth side wall surface 55 is, for example, 0.05 μm or more and 1 μm or less.

[0069] When the Ra of the first side wall surface 41 and the rake face 5 are measured along the first direction 101, the Ra of the first side wall surface 41 is greater than the Ra of the rake face 5. In other words, the Ra of the rake face 5 is less than the Ra of the first side wall surface 41. This prevents the Ra of the rake face 5 from becoming excessively large. If the Ra of the rake face 5 is excessively large, chips may be welded to the portion of the rake face 5 that is close to the machined surface of the workpiece. The machined surface becomes cloudy due to the welded chips damaging the machined surface or due to the welded chips adhering to the machined surface. According to the first embodiment, since the Ra of the rake face 5 is prevented from becoming excessively large, the clouding of the machined surface can be prevented.

[0070] Because the Ra of the first side wall surface 41 is greater than the Ra of the rake face 5, the frictional force generated between the first side wall surface 41 and the chip is greater than the frictional force generated between the first rake face portion 11 and the chip. Therefore, on the first rake face portion 11, the speed at which the chip flows becomes relatively fast and the thickness of the chip becomes relatively thin. On the other hand, compared to the first rake face portion 11, the speed at which the chip flows becomes slower and the thickness of the chip becomes thicker on the first side wall surface 41. Because the chip flow is faster on the first rake face portion 11, which is closer to the outer cutting edge 19, compared to the first side wall surface 41, the chip is more likely to curl in a fan shape toward the inside of the rotary cutting tool 100. This is thought to improve the chip breaking performance.

[0071] The Ra of the scoop face 5 is, for example, 0.04 μm or less. The Ra of the scoop face 5 may be, for example, 0.02 μm or less, or 0.01 μm or less. The Ra of the scoop face 5 is not particularly limited, but for example, 0.002 μm or more.

[0072] The measurement of Ra of the rake face 5 can be performed using the same method as the measurement of Ra of the first side wall surface 41 described above. Specifically, the roughness curve of the rake face 5 is measured along the first direction 101. The Ra of the rake face 5 is measured using this roughness curve. The measurement distance is set to 0.5 mm. The measurement start position is set to a position on the rake face 5 where the distance from the front cutting edge 18 in the first direction 101 is 0.1 mm. In measuring the Ra of the rake face 5, for example, the Ra of the first rake face portion 11 is measured.

[0073] The outer cutting edge 19 is located in a first direction 101 relative to the front cutting edge 18. Viewed perpendicular to the rake face 5, the front cutting edge 18 is inclined in a third direction 103 relative to the outer cutting edge 19. From another perspective, viewed perpendicular to the rake face 5, the front cutting edge 18 is inclined clockwise relative to the outer cutting edge 19 around the connection point between the front cutting edge 18 and the outer cutting edge 19 (cutting edge connection point 90). The front cutting edge 18 has a first straight cutting edge portion 21, a first concave cutting edge portion 22, a second straight cutting edge portion 23, a second concave cutting edge portion 24, and a third straight cutting edge portion 25.

[0074] The first straight cutting edge portion 21 is connected to the outer peripheral cutting edge 19. The first straight cutting edge portion 21 is formed by the ridge line between the first rake face portion 11 and the first front relief face portion 71 (see Figure 3).

[0075] The first concave cutting edge portion 22 is connected to the first straight cutting edge portion 21. The first concave cutting edge portion 22 is formed by the ridge line between the first groove 91 and the first front relief surface portion 71. Specifically, the first concave cutting edge portion 22 is formed by the ridge line between each of the first side wall surface 41, the first bottom surface 49, and the second side wall surface 42 and the first front relief surface portion 71.

[0076] The second straight cutting edge portion 23 is connected to the first concave cutting edge portion 22. The second straight cutting edge portion 23 is located opposite the first straight cutting edge portion 21 with respect to the first concave cutting edge portion 22. The second straight cutting edge portion 23 is formed by the ridge line between the second rake face portion 12 and the first front relief face portion 71.

[0077] The second concave cutting edge portion 24 is connected to the second straight cutting edge portion 23. The second concave cutting edge portion 24 is located opposite the first concave cutting edge portion 22 with respect to the second straight cutting edge portion 23. The second concave cutting edge portion 24 is formed by the ridge line between the second groove 92 and the front relief surface 7. Specifically, the second concave cutting edge portion 24 is formed by the ridge line between the sixth side wall surface 51 and the first front relief surface portion 71 and the second front relief surface portion 72 (see Figure 3), and by the ridge line between the second bottom surface 59 and the seventh side wall surface 52 and the second front relief surface portion 72.

[0078] The third straight cutting edge portion 25 is connected to the second concave cutting edge portion 24. The third straight cutting edge portion 25 is located opposite the second straight cutting edge portion 23 with respect to the second concave cutting edge portion 24. The third straight cutting edge portion 25 is formed by the ridge line between the third rake face portion 13 and the second front relief face portion 72 (see Figure 3). The third straight cutting edge portion 25 may be located at the front end 1 of the rotary cutting tool 100.

[0079] When viewed perpendicular to the rake face 5, the angle between the axis X (see Figure 1) and the first straight cutting edge portion 21 is defined as the cutting angle θ11. The straight line 111 shown in Figure 5 is a straight line parallel to the axis X. The straight line 112 is a straight line that coincides with the first straight cutting edge portion 21 when viewed perpendicular to the rake face 5. The cutting angle θ11 is, for example, either 45° or 75°. The cutting angle θ11 may also be, for example, 10° or more and 85° or less. When viewed perpendicular to the rake face 5, the angle between the first straight cutting edge portion 21 and the outer peripheral cutting edge 19 is the angle obtained by subtracting the cutting angle θ11 from 180°.

[0080] Viewed perpendicular to the rake face 5, the straight line 112 coincides with the second straight cutting edge portion 23. In other words, viewed perpendicular to the rake face 5, the first straight cutting edge portion 21 and the second straight cutting edge portion 23 are on the same straight line. Viewed perpendicular to the rake face 5, the first concave cutting edge portion 22 is concave in the first direction 101 with respect to the straight line 112. Viewed perpendicular to the rake face 5, the straight line 112 is spaced apart from the third straight cutting edge portion 25. Viewed perpendicular to the rake face 5, the third straight cutting edge portion 25 extends along the direction toward axis X (Figure 1) from the outer peripheral cutting edge 19. Specifically, the third straight cutting edge portion 25 extends along the third direction 103. Viewed perpendicular to the rake face 5, the second concave cutting edge portion 24 is concave in the first direction 101 with respect to a straight line (not shown) that coincides with the third straight cutting edge portion 25.

[0081] Figure 6 shows the configuration of the cutting edge tip 4 in a cross section (first cross section CS1) that is perpendicular to the axis X and intersects the first groove 91, and is viewed in the first direction 101. As shown in Figure 6, the first bottom surface 49 may be, for example, parallel to the rake face 5. The ridge line between the first side wall surface 41 and the first rake face portion 11 is defined as the first ridge line 81. In the first cross section CS1, a virtual line perpendicular to the first rake face portion 11 and passing through the first ridge line 81 is defined as the first virtual line 95.

[0082] In the first section CS1, the first side wall surface 41 is inclined clockwise around the first ridge line 81 with respect to the first imaginary line 95. The inclination angle of the first side wall surface 41 with respect to the first imaginary line 95 (first inclination angle θ1) is 35° or more and 60° or less. The first inclination angle θ1 may be, for example, 38° or more, or 40° or more. The first inclination angle θ1 may be, for example, 57° or less, or 50° or less.

[0083] The ridge line between the second side wall surface 42 and the second rake face portion 12 is defined as the second ridge line 82. In the first cross section CS1, the imaginary line perpendicular to the second rake face portion 12 and passing through the second ridge line 82 is defined as the second imaginary line 96.

[0084] In the first cross-section CS1, the second side wall surface 42 is inclined counterclockwise around the second ridge line 82 with respect to the second imaginary line 96. The inclination angle of the second side wall surface 42 with respect to the second imaginary line 96 (second inclination angle θ2) is 10° or more and 60° or less. The second inclination angle θ2 may be, for example, 15° or more, 20° or more, or 25° or more. The second inclination angle θ2 may be, for example, 55° or less, 50° or less, or 45° or less.

[0085] According to the first embodiment, the depth of the first groove 91 in the direction perpendicular to the rake face 5 (first depth F1) is 0.01 mm or more and 0.5 mm or less. In the direction perpendicular to the rake face 5, the first depth F1 is the longest distance between the surface forming the first groove 91 and the rake face 5.

[0086] By having a first depth F1 of 0.01 mm or more, the area of ​​the first side wall surface 41 can be made sufficiently large. This makes it easier for chips to come into contact with the first side wall surface 41. As a result, the chips can be sufficiently curled inward of the rotary cutting tool 100. The curled chips are thought to be fragmented by colliding with the portion of the workpiece surface that is to be cut or with the second side wall surface 42. In addition, by having a first depth F1 of 0.01 mm or more, the volume of the first groove 91 is sufficiently increased. Therefore, chips can easily flow into the first groove 91. As a result, the chip breaking performance can be effectively improved.

[0087] If the first depth F1 is excessively deep, the volume of the first groove 91 becomes excessively large. In this case, chips that flow into the first groove 91 are less likely to be discharged from the first groove 91, making it easier for chips to clog the first groove 91. Consequently, the cutting load on the rotary cutting tool 100 increases. As a result, the chip curling action becomes unstable due to the occurrence of chatter, etc. According to the first embodiment, by setting the first depth F1 to 0.5 mm or less, it is possible to prevent chips from clogging the first groove 91. Also, if the first depth F1 is excessively deep, the time required to form the first groove 91 in the manufacturing of the rotary cutting tool 100 increases. By setting the first depth F1 to 0.5 mm or less, the time required to form the first groove 91 can be shortened. By having a first width H1 of 0.1 mm or more and a first depth F1 of 0.01 mm or more and a first depth F1 of 0.5 mm or more, it is thought that chip clogging will be less likely to occur even when the machining allowance exceeds the groove width, and the effect of chip fragmentation will be obtained.

[0088] The first depth F1 may be, for example, 0.02 mm or more, 0.05 mm or more, 0.08 mm or more, or 0.1 mm or more. The first depth F1 may be, for example, 0.45 mm or less, or 0.35 mm or less.

[0089] The cross-sectional shape of the second groove 92 may be the same as the cross-sectional shape of the first groove 91. Specifically, the second bottom surface 59 may be parallel to the rake face 5. The ridge line between the sixth side wall surface 51 and the second rake face portion 12 is defined as the third ridge line 83. In the first cross-section CS1, a virtual line perpendicular to the second rake face portion 12 and passing through the third ridge line 83 is defined as the third virtual line 97.

[0090] In the first cross-section CS1, the sixth side wall surface 51 is inclined clockwise around the third ridge line 83 with respect to the third imaginary line 97. The inclination angle of the sixth side wall surface 51 with respect to the third imaginary line 97 (sixth inclination angle θ6) is, for example, 35° or more and 60° or less.

[0091] The ridge line between the seventh side wall surface 52 and the third rake face portion 13 is defined as the fourth ridge line 84. In the first cross section CS1, the imaginary line perpendicular to the third rake face portion 13 and passing through the fourth ridge line 84 is defined as the fourth imaginary line 98.

[0092] In the first section CS1, the seventh side wall surface 52 is inclined counterclockwise around the fourth ridge line 84 with respect to the fourth imaginary line 98. The inclination angle of the seventh side wall surface 52 with respect to the fourth imaginary line 98 (seventh inclination angle θ7) is between 10° and 60°.

[0093] The depth of the second groove 92 in the direction perpendicular to the rake face 5 (second depth F2) is 0.05 mm or more and 0.5 mm or less. In the direction perpendicular to the rake face 5, the second depth F2 is the longest distance between the surface forming the second groove 92 and the rake face 5.

[0094] The first outer peripheral relief surface 61 may be a margin. In the first cross section CS1, the angle between the first outer peripheral relief surface 61 and the first rake face 11 may be, for example, 90°. The angle between the first outer peripheral relief surface 61 and the first rake face 11 may be, for example, 85° or more and 90° or less. In the first cross section CS1, the second outer peripheral relief surface 62 is inclined clockwise with respect to the first outer peripheral relief surface 61 around the ridge line between the first outer peripheral relief surface 61 and the second outer peripheral relief surface 62.

[0095] Figure 7 shows the configuration of the cutting edge tip 4 in a cross section (second cross section CS2) that is parallel to the first direction 101 and intersects the first bottom surface 49, and is viewed in the third direction 103. As shown in Figure 7, the ridge line between the fifth side wall surface 45 and the fourth rake face portion 14 is defined as the fifth ridge line 85. In the second cross section CS2, a virtual line perpendicular to the fourth rake face portion 14 and passing through the fifth ridge line 85 is defined as the fifth virtual line 99.

[0096] In the second section CS2, the fifth side wall surface 45 is inclined clockwise around the fifth ridge line 85 with respect to the fifth imaginary line 99, for example. The inclination angle of the fifth side wall surface 45 with respect to the fifth imaginary line 99 (fifth inclination angle θ5) is, for example, 15°. The fifth inclination angle θ5 may be, for example, 0° or more and 60° or less. The fifth side wall surface 45 may extend along the fifth imaginary line 99. Although not shown, the configuration of the tenth side wall surface 55 may be substantially the same as the configuration of the fifth side wall surface 45.

[0097] Next, the material of the rotary cutting tool 100 will be described. The main body 3 is formed of, for example, a cemented carbide. The cutting edge tip 4 is formed of, for example, a diamond sintered body, a cemented carbide, or cubic boron nitride (cBN). In this specification, the diamond sintered body is either PCD (Poly-Crystalline Diamond) or nanocrystalline diamond.

[0098] The PCD contains multiple diamond particles and a metal binder. In the PCD, the average particle size (D ５０ The average particle size (D) of the diamond particles is greater than 0.5 μm. Nanocrystalline diamond is formed from multiple diamond particles. In other words, nanocrystalline diamond does not contain a binder. In nanocrystalline diamond, the average particle size (D) of the diamond particles is greater than 0.5 μm. ５０ The thickness of the grooves is, for example, between 10 nm and 0.5 μm. In the manufacture of the rotary cutting tool 100, the first groove 91 and the second groove 92 are formed, for example, using a laser.

[0099] Next, the operation and effects of the rotary cutting tool 100 according to the first embodiment will be described. The rotary cutting tool 100 according to the first embodiment has an outer cutting edge 19, a front cutting edge 18, and a rake face 5. A first groove 91 is provided in the rake face 5. The first groove 91 extends along a first direction 101. The first groove 91 is connected to the front cutting edge 18. The first groove 91 has a first side wall surface 41 and a second side wall surface 42. In the first cross section CS1, the first side wall surface 41 is inclined clockwise around the first ridge line 81 with respect to the first imaginary line 95. The inclination angle of the first side wall surface 41 with respect to the first imaginary line 95 (first inclination angle θ1) is 35° or more and 60° or less.

[0100] Normally, the chips generated by the cutting edge 18 and the outer peripheral cutting edge 19 cutting the workpiece come into contact with the first side wall surface 41 of the first groove 91. This changes the direction in which the chips flow. However, if the first inclination angle θ1 is excessively large, the change in the direction in which the chips flow is small. Therefore, the chips cannot be sufficiently broken up. According to the first embodiment, by setting the first inclination angle θ1 to 60° or less, the change in the direction in which the chips flow when they come into contact with the first side wall surface 41 can be increased. This improves the chip breaking performance.

[0101] If the first inclination angle θ1 is excessively small, the thickness of the portion of the rotary cutting tool 100 closest to the outer cutting edge 19 becomes excessively thin. Consequently, the strength of the portion of the rotary cutting tool 100 closest to the outer cutting edge 19 is excessively reduced. This can cause the cutting edge to chip. According to the first embodiment, by setting the first inclination angle θ1 to 35° or more, it is possible to prevent a reduction in the strength of the portion of the rotary cutting tool 100 closest to the outer cutting edge 19. This prevents chipping of the cutting edge.

[0102] If the inclination angle of the second side wall surface 42 (second inclination angle θ2) is excessively small, chips flowing along the first side wall surface 41 will collide with the second side wall surface 42, making it easier for chips to get stuck in the corners of the first groove 91. According to the first embodiment, the second inclination angle θ2 is 10° or more. As a result, chips can easily flow along the second side wall surface 42. This makes it easier for chips to be discharged from the first groove 91. As a result, it is possible to prevent chip clogging in the first groove 91.

[0103] If the width of the first groove 91 does not change, the depth of the first groove 91 (first depth F1) becomes shallower as the second inclination angle θ2 increases. From another point of view, the area of ​​the first side wall surface 41 decreases as the second inclination angle θ2 increases. Therefore, if the second inclination angle θ2 is excessively large, it becomes difficult for the chips to come into contact with the first side wall surface 41. This reduces the chip breaking performance. According to the first embodiment, the second inclination angle θ2 is 60° or less. Therefore, it is possible to prevent a decrease in chip breaking performance.

[0104] According to the first embodiment, the outer peripheral cutting edge 19 extends along the first direction 101. The first groove 91 also extends along the first direction 101. Therefore, when the cutting edge of the rotary cutting tool 100 is resharpened, it is possible to prevent a change in the relative position between the outer peripheral cutting edge 19 and the first groove 91. This prevents a change in the chip breaking performance of the rotary cutting tool 100 even when the cutting edge of the rotary cutting tool 100 is resharpened.

[0105] According to the first embodiment, the distance from the outer peripheral cutting edge 19 to the first groove 91 in the third direction 103 (first distance E1) is 0.05 mm or more and 0.2 mm or less. By having a first distance E1 of 0.05 mm or more, the thickness of the portion of the rotary cutting tool 100 close to the outer peripheral cutting edge 19 in the third direction 103 can be made sufficiently thick. This improves the strength of the portion of the rotary cutting tool 100 close to the outer peripheral cutting edge 19.

[0106] Since the first distance E1 is 0.2 mm or less, the distance between the outer cutting edge 19 and the first groove 91 is sufficiently close. Therefore, chips can easily flow into the first groove 91. This effectively improves chip breaking performance.

[0107] (Second Embodiment) Next, the configuration of the rotary cutting tool 100 according to the second embodiment will be described. The rotary cutting tool 100 according to the second embodiment differs from the rotary cutting tool 100 according to the first embodiment mainly in that the first groove 91 has a third side wall surface 43 and a fourth side wall surface 44, and is substantially the same as the rotary cutting tool 100 according to the first embodiment in other respects. The differences from the rotary cutting tool 100 according to the first embodiment will be mainly described below.

[0108] As shown in Figure 8, according to the rotary cutting tool 100 of the second embodiment, the first groove 91 has a third side wall surface 43 and a fourth side wall surface 44.

[0109] The third side wall surface 43 is connected to the first side wall surface 41. The third side wall surface 43 is located opposite the first ridge line 81 to the first side wall surface 41. The third side wall surface 43 connects, for example, the first side wall surface 41 and the first bottom surface 49. In the first cross section CS1, the length L of the first side wall surface 41 in the direction perpendicular to the rake face 5 is, for example, 0.5 times or more and 0.9 times or less the first depth F1 (see Figure 6).

[0110] In the first section CS1, the third side wall surface 43 is inclined clockwise with respect to the first side wall surface 41 around the connection point (first connection point 86) between the first side wall surface 41 and the third side wall surface 43. Specifically, in the first section CS1, the third side wall surface 43 is inclined clockwise around the first connection point 86 with respect to a virtual line (not shown) that overlaps the first side wall surface 41. From another point of view, the inclination angle of the third side wall surface 43 with respect to the first virtual line 95 (third inclination angle θ3) is greater than the first inclination angle θ1 (see Figure 6). The third inclination angle θ3 is less than 90°.

[0111] The fourth side wall surface 44 is connected to the second side wall surface 42. The fourth side wall surface 44 is located opposite the second ridge line 82 to the second side wall surface 42. The fourth side wall surface 44 connects, for example, the second side wall surface 42 to the first bottom surface 49.

[0112] In the first section CS1, the fourth side wall surface 44 is inclined counterclockwise with respect to the second side wall surface 42 around the connection point (second connection point 87) between the second side wall surface 42 and the fourth side wall surface 44. Specifically, in the first section CS1, the fourth side wall surface 44 is inclined clockwise around the second connection point 87 with respect to a virtual line (not shown) that overlaps the second side wall surface 42. From another point of view, the inclination angle of the fourth side wall surface 44 with respect to the second virtual line 96 (fourth inclination angle θ4) is greater than the second inclination angle θ2 (see Figure 6). The fourth inclination angle θ4 is less than 90°.

[0113] The second groove 92 has an eighth side wall surface 53 and a ninth side wall surface 54. The eighth side wall surface 53 is connected to the sixth side wall surface 51. The eighth side wall surface 53 is located opposite the third ridge line 83 to the sixth side wall surface 51. The eighth side wall surface 53 connects, for example, the sixth side wall surface 51 and the second bottom surface 59.

[0114] In the first section CS1, the eighth side wall surface 53 is inclined clockwise with respect to the sixth side wall surface 51 around the connection point (third connection point 88) between the sixth side wall surface 51 and the eighth side wall surface 53. From another point of view, the inclination angle of the eighth side wall surface 53 with respect to the third imaginary line 97 (eighth inclination angle θ8) is greater than the sixth inclination angle θ6. The eighth inclination angle θ8 is less than 90°.

[0115] The ninth side wall surface 54 is connected to the seventh side wall surface 52. The ninth side wall surface 54 is located opposite the fourth ridge line 84 to the seventh side wall surface 52. The ninth side wall surface 54 connects, for example, the seventh side wall surface 52 to the second bottom surface 59.

[0116] In the first section CS1, the ninth side wall surface 54 is inclined counterclockwise around the connection point (fourth connection point 89) between the seventh side wall surface 52 and the ninth side wall surface 54 with respect to the seventh side wall surface 52. From another point of view, the inclination angle of the ninth side wall surface 54 with respect to the fourth imaginary line 98 (ninth inclination angle θ9) is greater than the seventh inclination angle θ7 (see Figure 6). The ninth inclination angle θ9 is less than 90°.

[0117] According to the second embodiment, the first groove 91 has a third side wall surface 43. The third side wall surface 43 is connected to the first side wall surface 41. In the first cross section CS1, the third side wall surface 43 is inclined clockwise around the first connection point 86 with respect to the first side wall surface 41. This allows the angle of the corner of the first groove 91 to be increased in the first cross section CS1. Therefore, the strength of the corner of the first groove 91 can be improved. As a result, the strength of the rotary cutting tool 100 can be improved.

[0118] According to the second embodiment, the first groove 91 has a fourth side wall surface 44. The fourth side wall surface 44 is connected to the second side wall surface 42. In the first cross section CS1, the fourth side wall surface 44 is inclined counterclockwise around the second connection point 87 with respect to the second side wall surface 42. This allows the angle of the corner of the first groove 91 to be increased in the first cross section CS1. Therefore, the strength of the corner of the first groove 91 can be improved. As a result, the strength of the rotary cutting tool 100 can be improved.

[0119] According to the second embodiment, the second groove 92 has an eighth side wall surface 53. The eighth side wall surface 53 is connected to the sixth side wall surface 51. In the first cross section CS1, the eighth side wall surface 53 is inclined clockwise around the third connection point 88 with respect to the sixth side wall surface 51. This allows the angle of the corner of the second groove 92 to be increased in the first cross section CS1. Therefore, the strength of the corner of the second groove 92 can be improved. As a result, the strength of the rotary cutting tool 100 can be improved.

[0120] According to the second embodiment, the second groove 92 has a ninth side wall surface 54. The ninth side wall surface 54 is connected to the seventh side wall surface 52. In the first cross section CS1, the ninth side wall surface 54 is inclined counterclockwise around the fourth connection point 89 with respect to the seventh side wall surface 52. This allows the angle of the corner of the second groove 92 to be increased in the first cross section CS1. Therefore, the strength of the corner of the second groove 92 can be improved. As a result, the strength of the rotary cutting tool 100 can be improved.

[0121] (Third Embodiment) Next, the configuration of the rotary cutting tool 100 according to the third embodiment will be described. The rotary cutting tool 100 according to the third embodiment differs from the rotary cutting tool 100 according to the first embodiment mainly in that the first groove 91 has a first corner curved surface 47 and a second corner curved surface 48, and is substantially the same as the rotary cutting tool 100 according to the first embodiment in other respects. The differences from the rotary cutting tool 100 according to the first embodiment will be mainly described below.

[0122] As shown in Figure 9, according to the rotary cutting tool 100 of the third embodiment, the first groove 91 has a first corner curved surface 47 and a second corner curved surface 48.

[0123] The first corner curved surface 47 connects the first side wall surface 41 and the first bottom surface 49. The first corner curved surface 47 is smoothly connected to both the first side wall surface 41 and the first bottom surface 49. In the first cross section CS1, the first corner curved surface 47 may be arc-shaped.

[0124] The second corner curved surface 48 connects the second side wall surface 42 and the first bottom surface 49. The second corner curved surface 48 is smoothly connected to both the second side wall surface 42 and the first bottom surface 49. In the first cross section CS1, the second corner curved surface 48 may be arc-shaped.

[0125] The second groove 92 has a third corner curved surface 57 and a fourth corner curved surface 58. The third corner curved surface 57 connects the sixth side wall surface 51 and the second bottom surface 59. The third corner curved surface 57 is smoothly connected to both the sixth side wall surface 51 and the second bottom surface 59. In the first cross section CS1, the third corner curved surface 57 may be arc-shaped.

[0126] The fourth corner curved surface 58 connects the seventh side wall surface 52 and the second bottom surface 59. The fourth corner curved surface 58 is smoothly connected to both the seventh side wall surface 52 and the second bottom surface 59. In the first cross section CS1, the fourth corner curved surface 58 may be arc-shaped.

[0127] According to the third embodiment, the first corner curved surface 47 connects the first side wall surface 41 and the first bottom surface 49. This improves the strength of the corner of the first groove 91. Therefore, chipping of the rotary cutting tool 100 can be prevented. Similarly, the second corner curved surface 48 connects the second side wall surface 42 and the first bottom surface 49, thereby improving the strength of the corner of the first groove 91. As a result, the strength of the rotary cutting tool 100 can be improved.

[0128] (First Modification) As shown in Figure 10, the rotary cutting tool 100 may be formed from a single component. In other words, the rotary cutting tool 100 may be, for example, a solid reamer. The rotary cutting tool 100 according to the first modification of this embodiment is formed from, for example, a cemented carbide.

[0129] (Second Modification) As shown in Figure 11, the second embodiment and the third embodiment may be combined as appropriate. Specifically, for example, the first groove 91 may have a third side wall surface 43 and a second corner curved surface 48. The second corner curved surface 48 may connect the second side wall surface 42 and the third side wall surface 43. The first groove 91 does not have a first bottom surface 49. The second groove 92 may have an eighth side wall surface 53 and a fourth corner curved surface 58. The fourth corner curved surface 58 may connect the seventh side wall surface 52 and the eighth side wall surface 53. The second groove 92 does not have a second bottom surface 59.

[0130] (Third Modification) As shown in Figure 12, the outer peripheral cutting edge 19 may be provided with a back taper. Specifically, each of the four outer peripheral cutting edges 19 may be provided with a back taper. From another point of view, the diameter of the outer peripheral cutting edge 19 may decrease as you move from the front end 1 to the rear end 2. In other words, the distance between the outer peripheral cutting edge 19 and the axis X in the direction perpendicular to the axis X may decrease as you move from the front end 1 to the rear end 2. When viewed perpendicular to the rake face 5, the outer peripheral cutting edge 19 is inclined counterclockwise around the cutting edge connection point 90 with respect to a straight line 114 that passes through the cutting edge connection point 90 and is parallel to the axis X.

[0131] The back taper gradient θ10 is 1° or less. The gradient θ10 is the angle between the axis X and the outer cutting edge 19. The straight line 113 shown in Figure 12 is a straight line that coincides with the outer cutting edge 19. The straight line 114 is a straight line parallel to the axis X. The angle between the straight line 113 and the straight line 114 is the same as the gradient θ10.

[0132] The gradient θ10 may be, for example, 0.5° or less, or 0.3° or less. The gradient θ10 may be, for example, 0.002° or more, or 0.004° or more. When the gradient θ10 is 0°, the outer cutting edge 19 is parallel to the axis X.

[0133] The back taper gradient θ10 may be expressed in the form Y / 100. A back taper gradient θ10 of Y / 100 means that the diameter of the outer cutting edge 19 decreases by Y mm per 100 mm of length in the first direction 101. The gradient θ10 may be, for example, 4 / 100 or less, or 2 / 100 or less. The gradient θ10 may be, for example, 0.01 / 100 or more, or 0.015 / 100 or more.

[0134] (Fourth Modification) As shown in Figure 13, when viewed perpendicular to the rake face 5, the direction in which the first groove 91 extends may be inclined with respect to the first direction 101. The direction in which the first groove 91 extends is the direction in which the first ridge 81 extends. The direction in which the first groove 91 extends is, for example, inclined to the third direction 103 with respect to the first direction 101. The direction in which the first groove 91 extends may be inclined with respect to the direction in which the outer peripheral cutting edge 19 extends. When viewed perpendicular to the rake face 5, the direction in which the second groove 92 extends may be inclined with respect to the first direction 101. The direction in which the second groove 92 extends is the direction in which the third ridge 83 extends.

[0135] The inclination angle (angle θ12) of the direction in which the first groove 91 extends with respect to the first direction 101 is 1° or less. The angle θ12 may be 0.5° or less, or 0.3° or less. The angle θ12 may be 0.002° or more, or 0.004° or more. The angle θ12 is the same as the angle between the straight line 115 parallel to the axis X and the first ridge line 81.

[0136] The direction in which the first groove 91 extends may be inclined in a direction opposite to the third direction 103. The direction in which the first groove 91 extends may be inclined with respect to the first direction 101, and a back taper may be provided on the outer cutting edge 19.

[0137] (Fifth Modification) As shown in Figure 14, the rotary cutting tool 100 may have, for example, two first cutting edge tips 4a and two second cutting edge tips 4b. Each of the two first cutting edge tips 4a and the two second cutting edge tips 4b is attached to the main body 3. When viewed in the first direction 101 (see Figure 1), the shape of the rotary cutting tool 100 may be twice symmetric about the axis X.

[0138] The configuration of the first cutting edge tip 4a is substantially the same as that of the cutting edge tip 4 described above (see Figures 2 to 7), except for the second distance E2 (see Figure 5). Specifically, the first cutting edge tip 4a has a first outer peripheral cutting edge 19a and a first rake face 5a. The first outer peripheral cutting edge 19a and the first rake face 5a correspond to the outer peripheral cutting edge 19 and the rake face 5, respectively. The first rake face 5a is provided with a first groove 91 and a second groove 92.

[0139] The second cutting edge tip 4b has a second rake face 5b. From another perspective, the rotary cutting tool 100 has, for example, two first rake faces 5a and two second rake faces 5b.

[0140] The configuration of the second cutting edge tip 4b is substantially the same as that of the cutting edge tip 4 (see Figures 2 to 7) described above, except for the number of grooves provided on the second rake face 5b. Specifically, the second cutting edge tip 4b has a second outer peripheral cutting edge 19b. The second outer peripheral cutting edge 19b and the second rake face 5b correspond to the outer peripheral cutting edge 19 and the rake face 5, respectively. A third groove 93 is provided on the second rake face 5b.

[0141] Figure 15 is an enlarged schematic plan view showing the configuration of the rotary cutting tool 100 as seen along arrow A in Figure 14. The direction of arrow A is perpendicular to the second rake face 5b. In Figure 15, the second cutting edge tip 4b is shown using a solid line, and the first cutting edge tip 4a is shown using a dashed-dot line. Specifically, in Figure 15, the dashed-dot line shows the shape of the first cutting edge tip 4a when the rotary cutting tool 100 is rotated 90° around axis X.

[0142] As shown in Figure 15, the second cutting edge tip 4b has a second front cutting edge 18b. The second front cutting edge 18b has a fourth straight cutting edge portion 26, a third concave cutting edge portion 27, and a fifth straight cutting edge portion 28.

[0143] The fourth straight cutting edge portion 26 is connected to the second outer peripheral cutting edge 19b. The fourth straight cutting edge portion 26 is formed by the ridge line between the second rake face 5b and the first front relief face portion 71 (see Figure 14). The third concave cutting edge portion 27 is connected to the fourth straight cutting edge portion 26. When viewed perpendicular to the second rake face 5b, the third concave cutting edge portion 27 is concave in the first direction 101. The third concave cutting edge portion 27 is formed by the ridge line between the third groove 93 and the first front relief face portion 71 and the second front relief face portion 72 (see Figure 14). The fifth straight cutting edge portion 28 is connected to the third concave cutting edge portion 27. The fifth straight cutting edge portion 28 is connected to the second rake face 5b.

[0144] The first cutting edge tip 4a has a first front cutting edge 18a. The first front cutting edge 18a corresponds to the front cutting edge 18 (see Figure 5) described above. Specifically, the first front cutting edge 18a has a first straight cutting edge portion 21, a first concave cutting edge portion 22, a corner cutting edge portion 29, a second concave cutting edge portion 24, and a third straight cutting edge portion 25. In Figure 15, the first straight cutting edge portion 21 and the third straight cutting edge portion 25 overlap with the second front cutting edge 18b.

[0145] As shown in Figure 15, when the external shape of the second cutting edge tip 4b is superimposed with the external shape of the first cutting edge tip 4a when the rotary cutting tool 100 is rotated 90° around axis X, the third groove 93 is located between the first groove 91 and the second groove 92. In other words, the third groove 93 does not overlap with either the first groove 91 or the second groove 92. The distance between the third groove 93 and the second outer cutting edge 19b (third distance E3) is greater than the width of the first groove 91 (first width H1, see Figure 5).

[0146] When the second front cutting edge 18b and the first front cutting edge 18a are superimposed when the rotary cutting tool 100 rotates 90° around axis X, the fourth straight cutting edge portion 26 of the second front cutting edge 18b connects the first straight cutting edge portion 21 and the corner cutting edge portion 29 of the first front cutting edge 18a. The fourth straight cutting edge portion 26 is located in a second direction 102 relative to the first concave cutting edge portion 22 of the first front cutting edge 18a. The corner cutting edge portion 29 is located in a second direction 102 relative to the third concave cutting edge portion 27. The fifth straight cutting edge portion 28 is located in a second direction 102 relative to the second concave cutting edge portion 24.

[0147] For example, if the rotary cutting tool 100 has only the first cutting edge tip 4a, the first concave cutting edge portion 22 is concave in the first direction 101, which can cause irregularities to form on the bottom surface of the hole when machining. Irregularities are particularly likely to form on the bottom surface of the hole when the material removal amount is large.

[0148] According to a fifth modification of the rotary cutting tool 100 according to this embodiment, when the external shape of the second cutting edge tip 4b is superimposed with the external shape of the first cutting edge tip 4a when the rotary cutting tool 100 is rotated 90° around the axis X, the third groove 93 is located between the first groove 91 and the second groove 92. Therefore, when machining a hole, for example, irregularities caused by the first concave cutting edge portion 22 can be cut using the fourth straight cutting edge portion 26 of the second front cutting edge 18b. Similarly, irregularities caused by the third concave cutting edge portion 27 of the second front cutting edge 18b can be cut using the corner cutting edge portion 29 of the first front cutting edge 18a. Thus, the shape of the bottom surface of the hole can be made flat.

[0149] The cross-sectional shape of the third groove 93 may be the same as the cross-sectional shape of the first groove 91 (see Figures 6 and 7). The third groove 93 has an eleventh side wall surface 64, a twelfth side wall surface 65, a thirteenth side wall surface 66, and a third bottom surface 69. The eleventh side wall surface 64, the twelfth side wall surface 65, the thirteenth side wall surface 66, and the third bottom surface 69 correspond to the first side wall surface 41, the second side wall surface 42, the fifth side wall surface 45, and the first bottom surface 49, respectively. The cross-sectional shape of the third groove 93 may differ from the cross-sectional shape of the first groove 91 to the extent that it produces the same effect as the first groove 91.

[0150] In the above description, the rotary cutting tool 100 had two first cutting edge tips 4a and two second cutting edge tips 4b, but the number of each of the first cutting edge tips 4a and second cutting edge tips 4b is not particularly limited. For example, the rotary cutting tool 100 may have three first cutting edge tips 4a and one second cutting edge tip 4b.

[0151] (Other Modifications) The configuration of other modifications according to this embodiment will be described below. In the above, each of the four cutting edge tips 4 was attached to the main body 3 by brazing, but each of the four cutting edge tips 4 may be fastened to the main body 3 using screws (not shown).

[0152] In the above description, a second groove 92 was provided on the rake face 5, but the rake face 5 does not necessarily have to have a second groove 92. From another point of view, the rake face 5 may have only one groove. Furthermore, the number of grooves provided on the rake face 5 may be three or more.

[0153] The number of cutting edge tips 4 on the rotary cutting tool 100 is not particularly limited. From another perspective, the number of outer peripheral cutting edges 19 and front cutting edges 18 is not particularly limited.

[0154] (Fourth Embodiment) Next, the configuration of the rotary cutting tool 100 according to the fourth embodiment will be described. As shown in Figure 16, the rotary cutting tool 100 according to the fourth embodiment is an end mill. As shown in Figure 17, the rotary cutting tool 100 has, for example, three cutting edge tips 4. Each of the three cutting edge tips 4 has one groove.

[0155] A center hole 79 is provided on the tip surface 8, for example. The center hole 79 is used to position the rotary cutting tool 100 during its manufacture. The center of the center hole 79 may coincide with the axis X.

[0156] The cutting edge tip 4 has a corner cutting edge 16. The corner cutting edge 16 connects the outer peripheral cutting edge 19 and the front cutting edge 18. The cutting edge tip 4 has a corner relief surface 15. The corner relief surface 15 is connected to the outer peripheral relief surface 6 and the front relief surface 7, respectively. As shown in Figures 17 and 18, the corner relief surface 15 is connected to the rake face 5, the first side wall surface 41, the first bottom surface 49, and the second side wall surface 42, respectively. The corner cutting edge 16 is formed, for example, by the ridges of the corner relief surface 15 and the rake face 5, the first side wall surface 41, the first bottom surface 49, and the second side wall surface 42.

[0157] As shown in Figure 18, the corner cutting edge 16 has a curved cutting edge portion 75 and a fourth concave cutting edge portion 76. The curved cutting edge portion 75 is connected to the outer peripheral cutting edge 19. The curved cutting edge portion 75 is formed by the ridge line of the first rake face portion 11 and the corner relief face 15 (see Figure 17). When viewed perpendicular to the rake face 5, the curved cutting edge portion 75 may be arc-shaped. The radius of curvature R (cutting radius) of the curved cutting edge portion 75 is, for example, 0.8 mm.

[0158] The fourth concave cutting edge portion 76 is connected to the curved cutting edge portion 75 and the front cutting edge 18, respectively. The fourth concave cutting edge portion 76 is composed of the corner relief surface 15 and the ridges of the first side wall surface 41, the first bottom surface 49, and the second side wall surface 42.

[0159] Viewed perpendicular to the rake face 5, the front cutting edge 18 is, for example, straight. The front cutting edge 18 is formed by the ridge line between the rake face 5 and the front relief face 7 (see Figure 17). From another perspective, the front relief face 7 is spaced apart from the first side wall surface 41, the first bottom surface 49, and the second side wall surface 42. The front cutting edge 18 is located in the second direction 102 relative to the main body 3.

[0160] The front cutting edge 18 is inclined with respect to the third direction 103. Specifically, viewed perpendicular to the rake face 5, the front cutting edge 18 is inclined in the first direction 101 with respect to a straight line 116 that passes through the connection point between the front cutting edge 18 and the corner cutting edge 16 (fifth connection point 105) and is parallel to the third direction 103. From another point of view, except for the fifth connection point 105, the front cutting edge 18 is located in the first direction 101 with respect to the straight line 116. The fifth connection point 105 may be located at the front end 1 of the rotary cutting tool 100 (see Figure 1). The angle between the front cutting edge 18 and the straight line 116 is, for example, 1°.

[0161] Figure 19 shows the configuration of the rotary cutting tool 100 as viewed perpendicular to the axis X. Specifically, Figure 19 shows the configuration of the rotary cutting tool 100 as viewed in a third direction 103. As shown in Figure 19, as viewed perpendicular to the axis X, the tip surface 8 is located in a first direction 101 relative to at least a portion of the front relief surface 7. As viewed perpendicular to the axis X, the tip surface 8 may be located in a first direction 101 relative to the entire front relief surface 7. As viewed perpendicular to the axis X, the tip surface 8 is located in a first direction 101 relative to a portion of the corner relief surface 15. From another point of view, a portion of the corner cutting edge 16 is located in a second direction 102 relative to the main body 3.

[0162] (Fifth Embodiment) Next, the configuration of the rotary cutting tool 100 according to the fifth embodiment will be described. As shown in Figure 20, the rotary cutting tool 100 according to the fifth embodiment is a boring tool. The diameter of the first portion 31 of the main body 3 is larger than the diameter of the second portion 32. As shown in Figure 21, the rotary cutting tool 100 has, for example, two cutting edge tips 4.

[0163] As shown in Figure 22, the front cutting edge 18 is composed of, for example, a first straight cutting edge portion 21, a first concave cutting edge portion 22, and a second straight cutting edge portion 23. When viewed perpendicular to the rake face 5, the first straight cutting edge portion 21 and the second straight cutting edge portion 23 may be on the same straight line.

[0164] Figure 23 shows the configuration of the rotary cutting tool 100 as viewed perpendicular to the axis X. Specifically, Figure 23 shows the configuration of the rotary cutting tool 100 as viewed in a third direction 103. As shown in Figure 23, as viewed perpendicular to the axis X, the tip surface 8 is located in a first direction 101 relative to a part of the front relief surface 7. From another point of view, a part of the front cutting edge 18 may be located in a second direction 102 relative to the main body 3. The front cutting edge 18 may be located at the front end 1 of the rotary cutting tool 100 (see Figure 20).

[0165] (Sixth Embodiment) Next, the configuration of the rotary cutting tool 100 according to the sixth embodiment will be described. As shown in Figure 24, the rotary cutting tool 100 according to the sixth embodiment is a drill for machining cast holes. In other words, the rotary cutting tool 100 according to the sixth embodiment machines the inner wall surface of a cast hole that does not penetrate the workpiece.

[0166] As shown in Figure 25, the rotary cutting tool 100 has two cutting edge tips 4. The number of grooves provided on the rake face 5 of each of the two cutting edge tips 4 is, for example, one. This prevents the strength of the rotary cutting tool 100 from being excessively reduced.

[0167] The main body 3 has a first relief surface 38 and a second relief surface 39. The first relief surface 38 is connected to the first surface 36. The second relief surface 39 is located behind the first relief surface 38 in the rotational direction of the rotary cutting tool 100. The second relief surface 39 is connected to the first relief surface 38. The second relief surface 39 is inclined in a first direction 101 with respect to the first relief surface 38. Coolant holes 78 are provided in the second relief surface 39.

[0168] The front relief surface 7 has a third front relief surface portion 73 and a fourth front relief surface portion 74. The third front relief surface portion 73 is connected to the rake face 5. The fourth front relief surface portion 74 is located behind the third front relief surface portion 73 in the rotational direction of the rotary cutting tool 100. The fourth front relief surface portion 74 is connected to the third front relief surface portion 73. The fourth front relief surface portion 74 is inclined in the first direction 101 with respect to the third front relief surface portion 73.

[0169] The third front relief surface 73 and the first relief surface 38 may form a plane. The third front relief surface 73 and the first relief surface 38 may be provided side by side on the same plane. The fourth front relief surface 74 and the second relief surface 39 may form a plane. The fourth front relief surface 74 and the second relief surface 39 may be provided side by side on the same plane.

[0170] As shown in Figure 26, the ridge line 80 between the first surface 36 and the first relief surface 38 (see Figure 25) and the second straight cutting edge portion 23 may form a straight line. The ridge line 80, the second straight cutting edge portion 23, and the first straight cutting edge portion 21 may be located on the same straight line.

[0171] As shown in Figure 27, in the first cross-section CS1, the first outer peripheral relief surface 61 may be arc-shaped. In the rotary cutting tool 100 according to the sixth embodiment, the second inclination angle θ2 is, for example, 35° or more and 60° or less.

[0172] Normally, when machining with a drill for casting holes, a large amount of chips are discharged and the machining load is high. Therefore, if the second inclination angle θ2 is excessively small, the ridge line (second ridge line 82) between the second side wall surface 42 and the rake face 5 may chip. According to the sixth embodiment, by setting the second inclination angle θ2 to 35° or more, chipping of the second ridge line 82 can be prevented. This improves the chipping resistance of the rotary cutting tool 100.

[0173] (Sample Preparation 1) The effect of the first groove 91 on chip breaking performance was evaluated. First, rotary cutting tools 100 for samples 1 to 11 were prepared. The rotary cutting tool 100 was a reamer (see Figures 1 to 7). Samples 1, 2, and 8 were comparative examples. Samples 3 to 7 and 9 to 11 were examples.

[0174] In Sample 1, neither the first groove 91 nor the second groove 92 was provided on the rake face 5. In Samples 2 through 11, neither the first groove 91 nor the second groove 92 was provided on the rake face 5.

[0175] In samples 3 to 7 and 9 to 11, the first tilt angle θ1 was between 35° and 60°. In sample 2, the first tilt angle θ1 was 15°. In sample 8, the first tilt angle θ1 was 65°.

[0176] In samples 2 to 11, the depth of the first groove 91 (first depth F1) was between 0.1 mm and 0.4 mm. In samples 2 to 11, the width of the first groove 91 (first width H1) was between 0.4 mm and 1.7 mm. In samples 3 to 7 and 9 to 11, the first width H1 was between 0.7 mm and 1.1 mm. In samples 1 to 8, 10, and 11, the engagement angle θ11 was 75°. In sample 9, the engagement angle θ11 was 45°.

[0177] In samples 2 through 11, the second inclination angle θ2 was 15°. The fifth inclination angle θ5 was 15°. The first distance E1 was 0.1 mm. The second distance E2 was 0.1 mm. In the first cross section CS1, the cross-sectional shape of the second groove 92 was the same as the cross-sectional shape of the first groove 91. In all samples, the rotary cutting tool 100 had four outer cutting edges 19 and four front cutting edges 18. The diameter D of the outer cutting edges 19 was 12 mm.

[0178] In samples 1 to 10, the Ra of the scoop face 5 was 0.01 μm or less. In sample 11, the Ra of the scoop face 5 was 0.005 μm. In samples 2 to 11, the Ra of the first scoop face portion 11 was measured as the Ra of the scoop face 5. In sample 1, the Ra of the scoop face 5 was measured at a position corresponding to the first scoop face portion 11 of the other samples. In samples 1 to 11, the Ra of the first side wall surface 41 was 0.2 μm.

[0179] (Evaluation Method 1) For all samples, the maximum length of the chips generated by reaming was evaluated. Specifically, the inner wall surface of a through hole in the workpiece was machined. The length of each of the multiple chips generated by the machining was measured using a scale. The length of the longest chip was considered the maximum chip length. If the maximum chip length is 10 mm or less, the chip breaking performance is considered to be good.

[0180] The workpiece was wrought aluminum alloy. The material of the wrought aluminum alloy was A6061. A6061 is an aluminum alloy specified in JIS H4000:2014. The length of the through hole was 35 mm. The machining allowance was 0.5 mm. In other words, the inner diameter of the through hole before machining was 11.5 mm.

[0181] Two through holes were machined at a feed rate (f) of 0.2 mm / rev per revolution. Subsequently, two more through holes were machined at a feed rate (f) of 0.3 mm / rev per revolution. External lubrication was used for all through hole machining. A water-soluble coolant was used for lubrication. The cutting speed (Vc) was 100 m / min.

[0182] (Evaluation result 1)

[0183]

[0184] Table 1 shows the evaluation results for samples 1 to 11. Figure 28 is a diagram showing the evaluation results. In this specification, if a chip occurs in the rotary cutting tool 100, "Damage" is indicated in the "Maximum Chip Length" column. In sample 2, the maximum chip length could not be measured due to chipping at the cutting edge. Figure 28 does not show the results for sample 2, where the maximum chip length could not be measured.

[0185] As shown in Table 1 and Figure 28, in Sample 1, the maximum chip length was 50 mm under both the condition where f was 0.2 mm / rev and the condition where f was 0.3 mm / rev. In Sample 8, where the first inclination angle θ1 was 65°, the maximum chip length was 25 mm under the condition where f was 0.3 mm / rev. In samples where the first inclination angle θ1 was between 35° and 60° (Samples 3 to 7 and 9 to 11), the maximum chip length was 7 mm or less under both the condition where f was 0.2 mm / rev and the condition where f was 0.3 mm / rev.

[0186] From the above results, it was confirmed that the sample according to the embodiment can improve chip breaking performance compared to sample 8, in which the first inclination angle θ1 is greater than 60°. Furthermore, it was confirmed that the sample according to the embodiment can improve the strength of the cutting edge compared to sample 2, in which the first inclination angle θ1 is less than 35°.

[0187] (Sample Preparation 2) The effect of the distance from the outer cutting edge 19 to the first groove 91 (first distance E1) on chip breaking performance was evaluated. First, rotary cutting tools 100 related to samples 12 to 18 and the rotary cutting tool 100 related to sample 10 described above were prepared. The rotary cutting tool 100 was a reamer (see Figures 1 to 7). Samples 12, 16, and 18 were comparative examples. Samples 13 to 15 and 17 were examples.

[0188] Compared to sample 10, the first distance E1 differed in samples 12 through 18. Compared to sample 10, the diameter D differed in samples 17 and 18. In all other respects, samples 12 through 18 were substantially the same as sample 10.

[0189] (Evaluation Method 2) In samples 12 to 18, the maximum length of chips generated by reaming was evaluated. The evaluation conditions were the same as those described in Evaluation Method 1 above, except for the machining allowance. The maximum length of chips was evaluated for both a machining allowance of 0.5 mm and a machining allowance of 1 mm. In sample 12, a defect occurred under the 0.5 mm machining allowance condition, so the evaluation under the 1 mm machining allowance condition was not performed.

[0190] (Evaluation result 2)

[0191]

[0192] Table 2 shows the evaluation results for samples 12 through 18 and 10. Note that the "-" in the "Maximum Chip Length" column for sample 12 indicates that evaluation was not performed.

[0193] As shown in Table 2, in the samples where the first distance E1 was 0.21 mm or more (Samples 16 and 18), the maximum chip length was 20 mm or more under all machining conditions. In Sample 12, where the first distance E1 was 0.03 mm, a chip occurred in the portion between the outer cutting edge 19 and the first groove 91 under the condition of a material removal allowance of 0.5 mm. On the other hand, in the samples where the first distance E1 was between 0.05 mm and 0.20 mm (Samples 10, 13 to 15, and 17), the maximum chip length was 15 mm or less under all machining conditions. In particular, in the samples where the first distance E1 was between 0.05 mm and 0.15 mm (Samples 13 and 14), the maximum chip length was 4 mm or less under the condition of a material removal allowance of 0.5 mm.

[0194] Based on the above results, it was confirmed that the sample according to the embodiment can improve chip breaking performance compared to samples 16 and 18, in which the first distance E1 is greater than 0.20 mm. Furthermore, it was confirmed that the sample according to the embodiment can improve the strength of the cutting edge compared to sample 12, in which the first distance E1 is less than 0.05 mm.

[0195] (Sample Preparation 3) The effect of the depth of the first groove 91 (first depth F1) on chip breaking performance was evaluated. First, samples 19 to 25, and the rotary cutting tool 100 related to samples 10 and 11 described above were prepared. The rotary cutting tool 100 was a reamer. Samples 19 to 25 were embodiments.

[0196] Compared to samples 10 and 11, samples 19 through 25 differed in the first depth F1. Compared to samples 10 and 11, sample 22 differed in the second inclination angle θ2. Compared to samples 10 and 11, sample 24 differed in the first inclination angle θ1. In all other respects, samples 19 through 25 were substantially the same as samples 10 and 11.

[0197] (Evaluation Method 3) For all samples, the maximum length of the chips generated by reaming was evaluated. The evaluation conditions were the same as those described in Evaluation Method 1 above.

[0198] (Evaluation result 3)

[0199]

[0200] Table 3 shows the evaluation results for samples 19 to 25, 10, and 11. As shown in Table 3, in sample 19, where the first depth F1 was 0.005 mm, the maximum chip length was 15 mm or more. On the other hand, in samples (samples 20 to 25, 10, and 11) where the first depth F1 was between 0.01 mm and 0.5 mm, the maximum chip length was 10 mm or less. Comparing samples with a first inclination angle θ1 of 45° and a second inclination angle θ2 of 15°, in samples (samples 20, 21, 23, 10, and 11) where the first depth F1 was between 0.01 mm and 0.2 mm, the maximum chip length was 5 mm or less.

[0201] From the above results, it was confirmed that chip breaking performance can be improved by setting the first depth F1 to 0.01 mm or more and 0.5 mm or less. In particular, it was confirmed that chip breaking performance can be effectively improved by setting the first depth F1 to 0.01 mm or more and 0.2 mm or less.

[0202] (Sample Preparation 4) The effect of the first groove 91 on chip breaking performance in the end mill was evaluated. First, rotary cutting tools 100 corresponding to samples 26 to 28 were prepared. The rotary cutting tool 100 was an end mill (see Figures 16 to 19). Samples 26 and 28 were examples. Sample 27 was a comparative example.

[0203] In samples 26 and 28, a first groove 91 was provided on the rake face 5. The first inclination angle θ1 was 45°. The second inclination angle θ2 was 15°. The first depth F1 was 0.1 mm. The first width H1 was 0.7 mm. The first distance E1 was 0.1 mm. The Ra of the first rake face portion 11 was 0.01 μm or less. The Ra of the first side wall surface 41 was 0.2 μm.

[0204] In sample 27, neither the first groove 91 nor the second groove 92 was provided on the rake face 5. In samples 26 to 28, the diameter D was 12 mm. The radius of curvature R of the curved cutting edge portion 75 was 0.8 mm. The rotary cutting tool 100 had three outer cutting edges 19 and three front cutting edges 18.

[0205] (Evaluation Method 4) For samples 26 to 28, the maximum length of chips generated when the workpiece was machined was evaluated. The workpiece was wrought aluminum alloy. The material of the wrought aluminum alloy was A6061.

[0206] In samples 26 and 27, the inner wall surface of a through hole in the workpiece was machined. The length of the through hole was 35 mm. The material removal allowance was 0.5 mm. In other words, the inner diameter of the through hole before machining was 11.5 mm.

[0207] Two through holes were machined under the condition that the feed rate (f) per revolution was 0.1 mm / rev. Subsequently, two more through holes were machined under the condition that the feed rate (f) per revolution was 0.15 mm / rev.

[0208] In Sample 28, side milling was performed on the workpiece. The depth of cut in the longitudinal direction of the tool (ap) was 5 mm. The depth of cut in the radial direction of the tool (ae) was 0.2 mm.

[0209] In all machining operations, external lubrication was used. Water-soluble coolant was used for lubrication. The cutting speed (Vc) was 100 m / min.

[0210] (Evaluation result 4)

[0211]

[0212] Table 4 shows the evaluation results for samples 26 to 28. As shown in Table 4, when machining the inner wall surface of the through hole, the maximum chip length was reduced in sample 26, which has the first groove 91, compared with sample 27, which does not have the first groove 91.

[0213] Based on the above results, it was confirmed that, compared to the comparative example, the sample according to the embodiment can improve chip breaking performance even when the rotary cutting tool 100 is an end mill. Furthermore, the maximum chip length in sample 28 was 5 mm. From these results, it was confirmed that the sample according to the embodiment can improve chip breaking performance even in side milling.

[0214] (Sample Preparation 5) The effect of the first groove 91 on the chip breaking performance of the boring tool was evaluated. First, rotary cutting tools 100 related to samples 29 and 30 were prepared. The rotary cutting tool 100 was a boring tool (see Figures 20 to 23). Sample 29 was an example. Sample 30 was a comparative example.

[0215] In sample 29, a first groove 91 was provided on the rake face 5. The first inclination angle θ1 was 55°. The second inclination angle θ2 was 55°. The first depth F1 was 0.1 mm. The first width H1 was 0.7 mm. The first distance E1 was 0.1 mm. The Ra of the first rake face portion 11 was 0.01 μm or less. The Ra of the first side wall surface 41 was 0.2 μm.

[0216] In sample 30, neither the first groove 91 nor the second groove 92 was provided on the rake face 5. In samples 29 and 30, the diameter D was 28 mm. The cutting angle θ11 was 75°. The rotary cutting tool 100 had two outer cutting edges 19 and two front cutting edges 18.

[0217] (Evaluation Method 5) In samples 29 and 30, the maximum length of chips generated when the workpiece was machined was evaluated. The evaluation conditions were the same as those described in Evaluation Method 1 above, except for the feed rate (f) per revolution. Two through holes were machined with a feed rate (f) of 0.1 mm / rev per revolution. Subsequently, two through holes were machined with a feed rate (f) of 0.15 mm / rev per revolution.

[0218] (Evaluation result 5)

[0219]

[0220] Table 5 shows the evaluation results for samples 29 and 30. As shown in Table 5, the maximum chip length was reduced in sample 29, which has the first groove 91, compared to sample 30, which does not have the first groove 91.

[0221] Based on the above results, it was confirmed that, compared to the sample in the comparative example, the sample in the embodiment can improve chip breaking performance even when the rotary cutting tool 100 is a boring tool.

[0222] (Sample Preparation 6) The effect of the first groove 91 on chip breaking performance in a drill for machining cast holes was evaluated. First, rotary cutting tools 100 corresponding to samples 31 to 37 were prepared. The rotary cutting tool 100 was a drill for machining cast holes (see Figures 24 to 27). Sample 31 was a comparative example. Samples 32 to 37 were examples.

[0223] In sample 31, neither the first groove 91 nor the second groove 92 was provided on the rake face 5. In samples 32 to 37, neither the first groove 91 nor the second groove 92 was provided on the rake face 5.

[0224] Compared to samples 33 to 37, the second tilt angle θ2 was smaller in sample 32. The second tilt angle θ2 in sample 32 was 15°. In samples 33 to 37, the second tilt angle θ2 was 35°. The first width H1 differed in samples 33 to 37.

[0225] In samples 32 to 37, the first inclination angle θ1 was 45°. The first depth F1 was 0.1 mm. The first distance E1 was 0.1 mm. The Ra of the first rake face portion 11 was 0.01 μm or less. The Ra of the first side wall surface 41 was 0.2 μm.

[0226] In samples 31 to 37, the diameter D was 12 mm. The engagement angle θ11 was 75°.

[0227] (Evaluation Method 6) In samples 31 to 37, the maximum length of chips generated by machining was evaluated. Specifically, the inner wall surface of a non-through cast hole in the workpiece was machined. The machining allowance was 3 mm. In other words, the inner diameter of the through hole before machining was 9 mm. Other evaluation conditions were the same as those described in Evaluation Method 1 above.

[0228] (Evaluation result 6)

[0229]

[0230] Table 6 shows the evaluation results for samples 31 to 37. In sample 32, the workpiece was cut, but chipping occurred at the cutting edge. Therefore, in Table 6, the maximum chip length measured for sample 32 is indicated in parentheses along with the word "Dropping".

[0231] As shown in Table 6, the maximum chip length was reduced in samples 32 to 37, which have the first groove 91, compared to sample 31, which does not have the first groove 91. In particular, in samples where the first width H1 is 0.4 mm or more and 1.7 mm or less (samples 32, 33, 35, and 36), the maximum chip length was 10 mm or less.

[0232] Based on the above results, it was confirmed that, compared to the comparative example, the sample according to the example can improve chip breaking performance even when the rotary cutting tool 100 is a drill for machining cast holes. In particular, it was confirmed that the chip breaking performance can be effectively improved by having a first width H1 of 0.4 mm or more and 1.7 mm or less. It is thought that the moderately large groove width prevented chip clogging. Furthermore, it is thought that the not-too-large groove width prevented a decrease in the chip breaking effect.

[0233] Furthermore, chipping occurred at the cutting edge in sample 32, where the second inclination angle θ2 was 15°. On the other hand, no chipping occurred in samples 33 to 37, where the second inclination angle θ2 was 35°. From these results, it was confirmed that the strength of the cutting edge can be improved by setting the second inclination angle θ2 to 35° or higher.

[0234] (Sample Preparation 7) Next, the influence of the Ra of the rake face 5 and the Ra of the first side wall surface 41 on machining was investigated. First, samples 38 to 43 and the rotary cutting tool 100 related to sample 11 described above were prepared. The rotary cutting tool 100 was a reamer (see Figures 1 to 7). Samples 38 to 43 are examples.

[0235] Compared to sample 11, the Ra of the scoop face 5 differed in samples 38 to 43. Compared to sample 11, the Ra of the first side wall surface 41 differed in samples 40 to 43. In other respects, samples 38 to 43 were substantially the same as sample 11.

[0236] (Evaluation Method 7) For all samples, the maximum length of the chips generated by reaming was evaluated. The evaluation conditions were the same as those described in Evaluation Method 1 above.

[0237] (Evaluation result 7)

[0238]

[0239] Table 7 shows the evaluation results for samples 11 and 38 to 43. As shown in Table 7, compared to sample 40, where the Ra of the first sidewall 41 was 0.03 μm, the maximum chip length was reduced in samples 11, 38, 39, 41, and 42, where the Ra of the first sidewall 41 was 0.05 μm or more. From these results, it was confirmed that the chip breaking performance can be improved by having an Ra of 0.05 μm or more on the first sidewall 41.

[0240] In sample 43, where the Ra of the first sidewall surface 41 was 1.1 μm, the cutting edge chipped. In addition, in sample 43, chip clogging occurred in the first groove 91. It is thought that the excessively large Ra of the first sidewall surface 41 prevented the chips from flowing over the first sidewall surface 41, resulting in chip clogging. Furthermore, it can be said that the chip clogging excessively increased the cutting resistance, leading to chipping of the cutting edge. On the other hand, in samples 11 and 38 to 42, where the Ra of the first sidewall surface 41 was 1 μm or less, no chipping of the rotary cutting tool 100 occurred. From these results, it was confirmed that the strength of the cutting edge can be sufficiently improved by having an Ra of 1 μm or less on the first sidewall surface 41.

[0241] In sample 39, where the Ra of the rake face 5 was 0.08 μm, the inner wall surface of the through hole was cloudy after evaluation. It is thought that the cloudiness of the inner wall surface was caused by chips welding to the rake face 5 due to the excessively large Ra of the rake face 5. On the other hand, in samples 11, 38, and 40 to 43, where the Ra of the rake face 5 was 0.04 μm or less, the inner wall surface of the through hole was not cloudy. From these results, it was confirmed that the occurrence of processing defects can be prevented by having an Ra of the rake face 5 of 0.04 μm or less.

[0242] It should be understood that at least one configuration and feature described in each embodiment and example can be combined with other embodiments and examples, or modified in various ways.

[0243] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope.

[0244] 1 Front end, 2 Rear end, 3 Main body, 4 Cutting edge tip, 4a First cutting edge tip, 4b Second cutting edge tip, 5 Rake face, 5a First rake face, 5b Second rake face, 6 Outer circumference relief face, 7 Front relief face, 8 Tip face, 9 Flute, 11 First rake face section, 12 Second rake face section, 13 Third rake face section, 14 Fourth rake face section, 15 Corner relief face, 16 Corner cutting edge, 18 Front cutting edge, 18a First front cutting edge, 18b Second front cutting edge, 19 Outer circumference cutting edge, 19a First outer circumference cutting edge, 19b Second outer circumference cutting edge, 21 First straight cutting edge section, 22 First concave cutting edge section, 23 Second straight cutting edge section, 24 Second concave cutting edge section, 25 Third straight cutting edge section, 26 Fourth straight cutting edge section, 27 Third concave cutting edge section, 28 Fifth straight cutting edge section, 29 Corner cutting edge section, 31 First section, 32 Second section, 36 First surface, 37 Second surface, 38 First relief surface, 39 Second relief surface, 41 First side wall surface, 42 Second side wall surface, 43 Third side wall surface, 44 Fourth side wall surface, 45 Fifth side wall surface, 47 First corner curved surface, 48 Second corner curved surface, 49 First bottom surface, 51 Sixth side wall surface, 52 Seventh side wall surface, 53 Eighth side wall surface, 54 Ninth side wall surface, 55 Tenth side wall surface, 57 Third corner curved surface, 58 Fourth corner curved surface, 59 Second bottom surface, 61 First outer perimeter relief surface section, 62 Second outer perimeter relief surface section, 63 Third outer perimeter relief surface section, 64 Eleventh side wall surface, 65 Twelfth side wall surface, 66 Thirteenth side wall surface, 69 Third bottom surface, 71 First front relief surface, 72 Second front relief surface, 73 Third front relief surface, 74 Fourth front relief surface, 75 Curved cutting edge, 76 Fourth concave cutting edge, 78 Coolant hole, 79 Center hole, 80 Ridge, 81 First ridge, 82 Second ridge, 83 Third ridge, 84 Fourth ridge, 85 Fifth ridge, 86 First connection point, 87 Second connection point, 88 Third connection point, 89 Fourth connection point, 90 Cutting edge connection point, 91 First groove, 92 Second groove, 93 Third groove, 95 First virtual line, 96 Second virtual line, 97 Third virtual line, 98 Fourth virtual line, 99 Fifth virtual line, 100 Rotary cutting tool, 101 First direction, 102 Second direction, 103 Third direction, 105 Fifth connection point, 111, 112, 113, 114, 115,116 Straight line, CS1 First section, CS2 Second section, D Diameter, E1 First distance, E2 Second distance, E3 Third distance, F1 First depth, F2 Second depth, H1 First width, H2 Second width, L Length, R Radius of curvature, X Axis, θ1 First inclination angle, θ2 Second inclination angle, θ3 Third inclination angle, θ4 Fourth inclination angle, θ5 Fifth inclination angle, θ6 Sixth inclination angle, θ7 Seventh inclination angle, θ8 Eighth inclination angle, θ9 Ninth inclination angle, θ10 Gradient, θ11 Angle of contact, θ12 Angle.

Claims

1. A rotary cutting tool rotatable around an axis, comprising: an outer cutting edge; a front cutting edge connected to the outer cutting edge; and rake faces connected to the outer cutting edge and the front cutting edge, wherein the outer cutting edge is parallel to the axis with respect to the front cutting edge and is located in a first direction from the front end of the rotary cutting tool toward the rear end of the rotary cutting tool; the outer cutting edge is parallel to the axis, or the outer cutting edge is provided with a back taper, the gradient of the back taper is 1° or less; the rake face is provided with a groove connected to the front cutting edge, the groove extends along the first direction, or, when viewed perpendicular to the rake face, the direction in which the groove extends is inclined at an angle of 1° or less with respect to the first direction; and the rake face comprises: a first rake face portion connected to the outer cutting edge and located between the outer cutting edge and the groove; The groove has a second rake face portion located opposite the first rake face portion, and the groove has a first side wall surface connected to the first rake face portion and a second side wall surface connected to the second rake face portion, the ridge line between the first side wall surface and the first rake face portion is defined as the first ridge line, the ridge line between the second side wall surface and the second rake face portion is defined as the second ridge line, in a cross section perpendicular to the axis and intersecting the groove, viewed in the first direction, a virtual line perpendicular to the first rake face portion and passing through the first ridge line is defined as the first virtual line, and in the cross section, a virtual line perpendicular to the second rake face portion and passing through the second ridge line is defined as the second virtual line, in the cross section, the first side wall surface is inclined clockwise around the first ridge line with respect to the first virtual line, and the second side wall surface is inclined counterclockwise around the second ridge line with respect to the second virtual line. A rotary cutting tool in which the inclination angle of the second side wall surface with respect to the second imaginary line is 10° or more and 60° or less, the inclination angle of the first side wall surface with respect to the first imaginary line is 35° or more and 60° or less, and the distance from the outer cutting edge to the groove in a direction perpendicular to the first direction when viewed perpendicular to the rake face is 0.05 mm or more and 0.2 mm or less.

2. The rotary cutting tool according to claim 1, wherein when the arithmetic mean roughness of the first sidewall surface and the rake face are measured along the first direction, the arithmetic mean roughness of the first sidewall surface is 0.05 μm or more and 1 μm or less, and the arithmetic mean roughness of the first sidewall surface is greater than the arithmetic mean roughness of the rake face.

3. The rotary cutting tool according to claim 1 or claim 2, wherein the depth of the groove in a direction perpendicular to the rake face is 0.01 mm or more and 0.5 mm or less.

4. The rotary cutting tool according to any one of claims 1 to 3, wherein the width of the groove in a direction perpendicular to the first direction, when viewed perpendicular to the rake face, is 0.1 mm or more and 2 mm or less.

5. The rotary cutting tool according to any one of claims 1 to 4, wherein the groove has a third side wall surface that is connected to the first side wall surface and is located opposite the first ridge with respect to the first side wall surface, and a fourth side wall surface that is connected to the second side wall surface and is located opposite the second ridge with respect to the second side wall surface, and in the cross section, the third side wall surface is inclined clockwise with respect to the first side wall surface around the connection point between the first side wall surface and the third side wall surface, and the fourth side wall surface is inclined counterclockwise with respect to the second side wall surface around the connection point between the second side wall surface and the fourth side wall surface.

6. The rotary cutting tool according to any one of claims 1 to 4, wherein the groove has a bottom surface, a first corner curved surface connecting the first side wall surface and the bottom surface, and a second corner curved surface connecting the second side wall surface and the bottom surface.

7. The rotary cutting tool according to any one of claims 1 to 6, wherein the rotary cutting tool is formed from a single component.

8. A rotary cutting tool according to any one of claims 1 to 6, comprising a main body and a cutting edge tip attached to the main body, wherein the cutting edge tip has an outer peripheral cutting edge, a front cutting edge, and a rake face.

9. The rotary cutting tool according to claim 8, wherein the cutting edge tip is formed of one of a diamond sintered body, a cemented carbide, or cubic boron nitride.

10. The rotary cutting tool according to any one of claims 1 to 9, wherein the rotary cutting tool is a reamer.

11. The rotary cutting tool according to claim 10, wherein the reamer further comprises a front relief surface connected to the front cutting edge, the front cutting edge has a straight cutting edge portion connected to the outer peripheral cutting edge, the ridge line between the rake face and the front relief surface has a portion that, when viewed perpendicular to the rake face, extends along a direction toward the axis from the outer peripheral cutting edge, and when viewed perpendicular to the rake face, the portion is located in the first direction with respect to a straight line that coincides with the straight cutting edge portion.

12. The rotary cutting tool according to any one of claims 1 to 9, wherein the rotary cutting tool is an end mill.

13. The rotary cutting tool according to any one of claims 1 to 9, wherein the rotary cutting tool is a boring tool.

14. The rotary cutting tool according to claim 12 or 13, further comprising a tip surface and a front relief surface connected to the front cutting edge, wherein, viewed perpendicular to the axis, the tip surface is positioned in the first direction with respect to at least a portion of the front relief surface.

15. The rotary cutting tool according to any one of claims 1 to 9, wherein the rotary cutting tool is a drill for machining cast holes, and the inclination angle of the second side wall surface with respect to the second imaginary line is 35° or more and 60° or less.

16. The rotary cutting tool according to claim 15, wherein the number of grooves provided on the rake face is one.

17. The rotary cutting tool according to any one of claims 1 to 5, wherein the rake face has a fourth rake face portion connected to each of the first rake face portion and the second rake face portion, and the fourth rake face portion is located in a first direction relative to each of the first rake face portion and the second rake face portion when viewed perpendicular to the rake face, and the groove has a bottom surface connected to each of the first side wall surface and the second side wall surface, and a fifth side wall surface connected to each of the first side wall surface, the second side wall surface, the bottom surface, and the fourth rake face portion, and the fifth side wall surface is located in a first direction relative to the bottom surface when viewed perpendicular to the rake face.

18. The rotary cutting tool according to any one of claims 1 to 17, wherein the width of the groove in a direction perpendicular to the first direction when viewed perpendicular to the rake face is 0.4 mm or more and 1.7 mm or less.

Images