Skiving cutter

Abstract

The skiving cutter rotates around an axis. In the skiving cutter, multiple cutting edges are arranged in an annular pattern around the axis. The skiving cutter has a base portion and a cutting edge portion. The cutting edge portion is continuous with the base portion. The cutting edge portion is arranged alongside the base portion in a first direction along the axis toward the front of the skiving cutter. The base portion is formed of either cemented carbide or high-speed steel. The cutting edge portion has a cutting edge layer and a cemented carbide layer. The cutting edge layer forms multiple cutting edges. The cemented carbide layer is arranged between the cutting edge layer and the base portion. The cutting edge layer is formed of either cubic boron nitride sintered body, diamond, or special cemented carbide.

Description

[Technical Field]

[0001] The present disclosure relates to a skiving cutter. This application claims priority to Japanese Patent Application No. 2024-081061, filed May 17, 2024. The entire contents of the Japanese Patent Application are incorporated herein by reference. [Background technology]

[0002] As an example of a skiving cutter, Patent Publication No. 2022-045081 (Patent Document 1) describes a skiving cutter in which the tip of the cutting edge is chamfered with a radius of curvature in the range of 20 μm or more and 40 μm or less. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-045081 Summary of the Invention

[0004] The skiving cutter according to the present disclosure rotates around an axis. The skiving cutter has a plurality of cutting edges arranged in an annular pattern around the axis. The skiving cutter includes a base portion and a cutting edge portion. The cutting edge portion is continuous with the base portion. The cutting edge portion is arranged alongside the base portion in a first direction along the axis toward the front of the skiving cutter. The base portion is formed of either a cemented carbide or a high-speed steel. The cutting edge portion includes a cutting edge layer and a cemented carbide layer. The cutting edge layer forms a plurality of cutting edges. The cemented carbide layer is arranged between the cutting edge layer and the base portion. The cutting edge layer is formed of one of cubic boron nitride sintered body, diamond, or a special cemented carbide. The special cemented carbide has tungsten carbide particles and a binder phase. The binder phase includes cobalt. In the special cemented carbide, the percentage of the volume of the binder phase divided by the volume of the entire special cemented carbide is 0.7% or more and 28% or less. In the binder phase, the percentage of the mass of cobalt divided by the mass of the entire binder phase is 50% or more. The binder phase further contains at least one element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a perspective schematic view showing the configuration of a skiving cutter according to the first embodiment. [Figure 2] FIG. 2 is a schematic plan view showing the configuration of the skiving cutter according to the first embodiment. [Figure 3] FIG. 3 is a schematic bottom view showing the configuration of the skiving cutter according to the first embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is an enlarged schematic cross-sectional view showing region V in FIG. [Figure 6] FIG. 6 is an enlarged perspective schematic view showing region VI in FIG. [Figure 7] FIG. 7 is an enlarged schematic plan view showing region VII in FIG. [Figure 8] FIG. 8 is a schematic side view showing the configuration of the skiving cutter as viewed in the direction of the arrow in FIG. [Figure 9] FIG. 9 is a partial cross-sectional schematic view illustrating skiving using a skiving cutter. [Figure 10] FIG. 10 is a schematic plan view illustrating skiving using a skiving cutter. [Figure 11] FIG. 11 is an enlarged cross-sectional schematic view showing the configuration of a skiving cutter according to the second embodiment. [Figure 12] FIG. 12 is an enlarged schematic bottom view showing the configuration of the skiving cutter according to the second embodiment. [Figure 13] FIG. 13 is a schematic cross-sectional view taken along line XIII-XIII in FIG. [Figure 14] FIG. 14 is a schematic cross-sectional view taken along line XIV-XIV in FIG. [Figure 15] FIG. 15 is a first enlarged schematic cross-sectional view showing a modified example of the second embodiment. [Figure 16] FIG. 16 is a second enlarged schematic cross-sectional view showing a modification of the second embodiment. [Figure 17] FIG. 17 is a cross-sectional schematic view showing the configuration of a skiving cutter according to the third embodiment. [Figure 18] FIG. 18 is a perspective schematic view showing the configuration of a skiving cutter according to the fourth embodiment. [Figure 19] FIG. 19 is a schematic plan view showing the configuration of a skiving cutter according to the fourth embodiment. [Figure 20] FIG. 20 is a schematic bottom view showing the configuration of the skiving cutter according to the fourth embodiment. [Figure 21] FIG. 21 is an enlarged schematic diagram showing region XXI in FIG. [Figure 22] FIG. 22 is a schematic cross-sectional view taken along line XXII-XXII in FIG. [Figure 23] FIG. 23 is a schematic cross-sectional view taken along line XXIII-XXIII in FIG. [Figure 24]FIG. 24 is a schematic side view showing the configuration of the blade portion as viewed along the arrow E in FIG. [Figure 25] FIG. 25 is a perspective schematic view showing the configuration of a skiving cutter according to a fifth embodiment. [Figure 26] FIG. 26 is a cross-sectional schematic view showing the configuration of a skiving cutter according to the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Problem to be solved by this disclosure] According to the skiving cutter described in Patent Document 1, the tip of the cutting edge is chamfered with R, which can cause the cutting edge to wear significantly.

[0007] An object of the present disclosure is to provide a skiving cutter that can suppress wear on the cutting edge. [Effects of this disclosure] According to the present disclosure, a skiving cutter capable of suppressing wear of the cutting edge can be provided.

[0008] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0009] (1) A skiving cutter according to the present disclosure rotates around an axis. In the skiving cutter, a plurality of cutting edges are arranged in an annular pattern around the axis. The skiving cutter has a base portion and a cutting edge portion. The cutting edge portion is continuous with the base portion. The cutting edge portion is arranged alongside the base portion in a first direction along the axis toward the front of the skiving cutter. The base portion is formed of either a cemented carbide or a high-speed steel. The cutting edge portion has a cutting edge layer and a cemented carbide layer. The cutting edge layer forms a plurality of cutting edges. The cemented carbide layer is arranged between the cutting edge layer and the base portion. The cutting edge layer is formed of one of cubic boron nitride sintered body, diamond, or a special cemented carbide. The special cemented carbide has tungsten carbide particles and a binder phase. The binder phase includes cobalt. In the special cemented carbide, the percentage of the volume of the binder phase divided by the total volume of the special cemented carbide is 0.7% or more and 28% or less. In the binder phase, the percentage of the mass of cobalt divided by the total mass of the binder phase is 50% or more. The binder phase further contains at least one element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. This can suppress wear of the cutting edge.

[0010] (2) The skiving cutter according to (1) above may have a shaft portion and a plurality of cutting edges. The shaft portion may have an outer peripheral surface. The outer peripheral surface may be provided around the axis. Each of the plurality of cutting edges may be continuous with the shaft portion. Each of the plurality of cutting edges may extend radially outward from the outer peripheral surface. Each of the plurality of cutting edges may form one of a plurality of cutting edges. Each of the plurality of cutting edges may have a first flank portion and a second flank portion. The first flank portion may be formed by a cutting edge portion. The first flank portion may be continuous with the plurality of cutting edges. The second flank portion may be formed by a base portion. The second flank portion may be provided in a second direction, along the axis, toward the rear of the skiving cutter relative to the first flank portion. The cutting edge portion may have a first bottom surface portion and a second bottom surface portion. The first bottom surface portion may be in contact with the base portion. The second bottom surface portion may be continuous with each of the first flank surface portion and the first bottom surface portion. The second bottom surface portion may be provided on the outer side with respect to the base portion. The ridge between the first flank surface portion and the second bottom surface portion may have a first ridge portion, a corner ridge portion, and a second ridge portion. The corner ridge portion may be continuous with the first ridge portion. The corner ridge portion may be provided on the radially outer side with respect to the first ridge portion. The second ridge portion may be continuous with the corner ridge portion. The second ridge portion may be provided in the rotational direction with respect to the first ridge portion. When the length of the second bottom surface portion between the first ridge portion and the second relief surface portion in a cross section perpendicular to the tangent to the first ridge portion when viewed along the axis is defined as the first length, and the length of the second bottom surface portion between the second ridge portion and the second relief surface portion in a cross section perpendicular to the tangent to the second ridge portion when viewed along the axis is defined as the second length, the first length may be the same as the second length.

[0011] This makes it possible to effectively suppress flank wear when the thickness of the chip is substantially the same between two different points on the cutting edge.

[0012] (3) The skiving cutter according to (1) above may have a shaft portion and a plurality of cutting edges. The shaft portion may have an outer peripheral surface. The outer peripheral surface may be provided around the axis. Each of the plurality of cutting edges may be continuous with the shaft portion. Each of the plurality of cutting edges may extend radially outward from the outer peripheral surface. Each of the plurality of cutting edges may form one of the plurality of cutting edges. Each of the plurality of cutting edges may have a first flank portion and a second flank portion. The first flank portion may be formed by a cutting edge portion. The first flank portion may be continuous with the plurality of cutting edges. The second flank portion may be formed by a base portion. The second flank portion may be provided in a second direction, along the axis, toward the rear of the skiving cutter relative to the first flank portion. The cutting edge portion may have a first bottom surface portion and a second bottom surface portion. The first bottom surface portion may be in contact with the base portion. The second bottom surface portion may be continuous with each of the first flank surface portion and the first bottom surface portion. The second bottom surface portion may be provided on the outer side with respect to the base portion. The ridge between the first flank surface portion and the second bottom surface portion may have a first ridge portion, a corner ridge portion, and a second ridge portion. The corner ridge portion may be continuous with the first ridge portion. The corner ridge portion may be provided on the radially outer side with respect to the first ridge portion. The second ridge portion may be continuous with the corner ridge portion. The second ridge portion may be provided in the rotational direction with respect to the first ridge portion. When the length of the second bottom surface portion between the first ridge portion and the second relief surface portion in a cross section perpendicular to the tangent to the first ridge portion when viewed along the axis is defined as the first length, and the length of the second bottom surface portion between the second ridge portion and the second relief surface portion in a cross section perpendicular to the tangent to the second ridge portion when viewed along the axis is defined as the second length, the first length may be different from the second length.

[0013] This makes it possible to effectively suppress flank wear when the thickness of the chip differs between two different points on the cutting edge.

[0014] (4) According to the skiving cutter according to (2) or (3) above, each of the plurality of cutting edges may have a rake face and a rear end face. The rake face may be continuous with the plurality of cutting edges. The rake face may be formed by a cutting edge layer. The rear end face may be opposite the rake face. The rear end face may be formed by a base portion. When viewed along the axis, the rear end face may overlap the rake face.

[0015] (5) According to the skiving cutter according to (2) or (3) above, each of the plurality of cutting edges may have a rake face and a rear end face. The rake face may be continuous with the plurality of cutting edges. The rake face may be formed by a cutting edge layer. The rear end face may be opposite the rake face. The rear end face may be formed by a base portion. When viewed along the axis, the rake face may be provided in the rotational direction relative to the rear end face.

[0016] (6) According to the skiving cutter according to any one of (1) to (5) above, the cutting edge may have a brazing material layer. The brazing material layer may be provided on the base. The cemented carbide layer may be provided on the brazing material layer.

[0017] (7) In the skiving cutter according to any one of (1) to (6) above, the cutting edge layer may have a maximum thickness in the first direction of 0.3 mm or more and 3 mm or less, thereby suppressing wear of the cutting edge portion and breakage of the cutting edge portion.

[0018] (8) The skiving cutter according to any one of (1) to (7) above may have a coating. The coating may cover at least a part of the cutting edge. This can suppress wear of the cutting edge.

[0019] (9) In the skiving cutter according to any one of (1) to (8) above, the curvature radius of the cutting edges in a cross section perpendicular to the cutting edges may be 10 μm or more and 40 μm or less. This makes it possible to prevent damage to the skiving cutter near the cutting edges and to prevent the cutting edges from losing their sharpness excessively.

[0020] (10) In the skiving cutter according to any one of (1) to (9) above, the cutting edge layer may be formed of a cubic boron nitride sintered body. The cubic boron nitride sintered body may contain cubic boron nitride particles. In the cubic boron nitride sintered body, the percentage of the volume of the cubic boron nitride particles divided by the total volume of the cubic boron nitride sintered body may be 50% or more and 100% or less. In the cubic boron nitride sintered body, the average particle size of the cubic boron nitride particles may be 0.01 μm or more and 3 μm or less. This effectively prevents chipping of the cutting edge portion.

[0021] (11) According to the skiving cutter according to (10) above, in the cubic boron nitride sintered body, the percentage of the volume of the cubic boron nitride particles divided by the total volume of the cubic boron nitride sintered body may be less than 100%. The cubic boron nitride sintered body may contain a binder. The binder may contain at least one element selected from the group consisting of titanium, cobalt, aluminum, and zirconium. This effectively suppresses wear of the cutting edge.

[0022] (12) The skiving cutter according to (1) above may have a shank and a plurality of cutting edges. The shank may have an outer peripheral surface. The outer peripheral surface may be arranged around the axis. Each of the plurality of cutting edges may be connected to the shank. Each of the plurality of cutting edges may extend radially outward from the outer peripheral surface. Each of the plurality of cutting edges may form one of a plurality of cutting edges. Each of the plurality of cutting edges may have a rake face and a flank. The rake face may be connected to the plurality of cutting edges. The rake face may be formed by a cutting edge layer. The flank may be connected to the rake face via a plurality of cutting edges. In each of the plurality of cutting edges, a point located at the outermost periphery as viewed along the axis may be defined as the outermost point. In each of the plurality of cutting edges, in a cross section including the axis and passing through the outermost point, an angle formed by the rake face and a straight line perpendicular to the axis may be between 0° and 40°. In each of the plurality of cutting edges, the angle between the ridge line of the flank and the axis when viewed in a direction perpendicular to the axis and from the outermost periphery toward the axis may be between 0° and 40°, thereby suppressing wear of the cutting edge.

[0023] (13) In the skiving cutter according to any one of (1) to (12) above, the cutting edge layer may be formed of diamond. The diamond may be a polycrystalline diamond containing a plurality of diamond particles. In the diamond, the percentage of the volume of the plurality of diamond particles divided by the total volume of the diamond may be 80% or more and 100% or less. This prevents the strength of the cutting edge layer from being excessively reduced.

[0024] (14) According to the skiving cutter according to (13) above, the average particle size of the plurality of diamond particles may be 0.01 μm or more and less than 100 μm, thereby preventing the strength of the cutting edge layer from being excessively reduced.

[0025] (15) In the skiving cutter according to any one of (1) to (12) above, the cutting edge layer may be formed of diamond. The diamond may be a single crystal diamond. This can improve the strength of the cutting edge layer.

[0026] [Details of the embodiments of the present disclosure] Next, the details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated.

[0027] (First embodiment) First, the configuration of the skiving cutter 100 according to the first embodiment will be described.

[0028] As shown in Fig. 1, the skiving cutter 100 has a plurality of cutting edges 1, a shaft portion 10, and a plurality of cutting edges 6. The skiving cutter 100 rotates around an axis O. The plurality of cutting edges 1 are arranged in an annular shape around the axis O.

[0029] The shank 10 is a portion facing a tool spindle (not shown) that rotates the skiving cutter 100. The shank 10 extends, for example, along an axis O. Each of the multiple cutting edges 6 is connected to the shank 10. The multiple cutting edges 6 are arranged in an annular shape around the axis O. Each of the multiple cutting edges 6 forms one of the multiple cutting edges 1. From another perspective, in the skiving cutter 100, the number of cutting edges 1 is the same as the number of cutting edges 6.

[0030] The skiving cutter 100 is used, for example, to process metal materials. Specifically, the skiving cutter 100 is used, for example, to process hardened steel. The skiving cutter 100 is used, for example, to process high-hardness materials. More specifically, it is used, for example, to process high-hardness materials having a hardness of 50 HRC or more on the Rockwell hardness C scale (HRC).

[0031] As shown in FIG. 1 , the shank 10 has a first outer peripheral surface 56 and a second outer peripheral surface 57. The first outer peripheral surface 56 is provided around the axis O. The first outer peripheral surface 56 includes an interface between the shank 10 and each of the plurality of blade portions 6. The first outer peripheral surface 56 is annular. The first outer peripheral surface 56 surrounds the axis O.

[0032] The second outer peripheral surface 57 is provided in a second direction 102 relative to the first outer peripheral surface 56. The second outer peripheral surface 57 is annular. The second outer peripheral surface 57 surrounds the axis O. The second direction 102 is a direction toward the rear of the skiving cutter 100 along the axis O. Conversely, the direction toward the front of the skiving cutter 100 along the axis O is defined as a first direction 101. The first direction 101 and the second direction 102 are parallel to each other.

[0033] The shaft portion 10 has a first front end surface 51 and a second front end surface 52. The first front end surface 51 intersects with, for example, the axis O. The second front end surface 52 is annular. The second front end surface 52 surrounds the axis O. The second front end surface 52 is continuous with a first outer peripheral surface 56.

[0034] Each of the multiple blade portions 6 extends radially outward from the first outer peripheral surface 56. In this specification, the radially outward direction is a direction perpendicular to the axis O and extending from the axis O toward the first outer peripheral surface 56. Conversely, the direction perpendicular to the axis O and extending from the first outer peripheral surface 56 toward the axis O is referred to as the radially inward direction.

[0035] Each of the plurality of cutting edges 6 has a rake face 5 and a flank face 4. From another perspective, the skiving cutter 100 has a plurality of rake faces 5 and a plurality of flank faces 4.

[0036] The flank 4 is provided in the second direction 102 relative to the cutting edge 1. The flank 4 is continuous with the rake face 5. The ridgeline between the flank 4 and the rake face 5 forms one of the multiple cutting edges 1. From another perspective, the rake face 5 is continuous with the multiple cutting edges 1. The flank 4 is continuous with the multiple cutting edges 1. The flank 4 is continuous with the rake face 5 via the multiple cutting edges 1.

[0037] The skiving cutter 100 has a plurality of bottoms 9. The plurality of bottoms 9 and the plurality of cutting edges 1 form the outer peripheral edge of the skiving cutter 100. The plurality of cutting edges 1 and the plurality of bottoms 9 are arranged alternately around the axis O. From another perspective, each of the plurality of bottoms 9 is provided between two adjacent cutting edges 1 among the plurality of cutting edges 1.

[0038] The plurality of bottoms 9 are provided radially inward of the plurality of cutting edges 1. A portion of each of the plurality of bottoms 9 is formed by a ridge line between the second front end surface 52 and the first outer peripheral surface 56.

[0039] 2, when the skiving cutter 100 is viewed in the second direction 102 (hereinafter also referred to as a plan view), the shape of the first front end face 51 is, for example, circular. In the plan view, the second front end face 52 surrounds the first front end face 51. When viewed along the axis O, the cutting face 5 is provided radially outward from the second front end face 52. When viewed along the axis O, the multiple cutting edges 1 are provided on the outermost periphery of the skiving cutter 100.

[0040] In each of the plurality of cutting portions 6, the point located on the outermost periphery as viewed along the axis O is defined as the outermost periphery point 89. In each of the plurality of cutting portions 6, as viewed along the axis O, the outermost periphery point 89 is located at a position where the distance from the axis O is greatest. For ease of explanation, only one outermost periphery point 89 is shown in FIG. 2 , but in the skiving cutter 100, the number of outermost periphery points 89 is equal to the number of the plurality of cutting portions 6.

[0041] 3 shows the configuration of the skiving cutter 100 as viewed in a first direction 101. As shown in FIG. 3, each of the plurality of cutting portions 6 has a first rear end face 61. The first rear end face 61 is continuous with the flank face 4. In each of the plurality of cutting portions 6, the first rear end face 61 is located opposite the rake face 5 (see FIG. 2).

[0042] The shaft portion 10 has a second rear end surface 62 and a third rear end surface 63. The second rear end surface 62 is continuous with the first rear end surface 61. When viewed in the first direction 101 (hereinafter also referred to as a bottom view), the second rear end surface 62 is annular. The first rear end surface 61 extends radially outward relative to the second rear end surface 62. The third rear end surface 63 intersects with the axis O, for example. When viewed from the bottom, the shape of the third rear end surface 63 is, for example, circular.

[0043] As shown in FIGS. 1 to 3, the skiving cutter 100 has a spur gear shape. Specifically, the extending direction of each of the multiple cutting portions 6 is substantially parallel to the axis O. From another perspective, as shown in FIGS. 2 and 3, when viewed along the axis O, the first rear end surface 61 overlaps the cutting face 5. In other words, when viewed in the first direction 101 or the second direction 102, the first rear end surface 61 overlaps the cutting face 5. When viewed along the axis O, the first rear end surface 61 is spaced apart from the multiple cutting edges 1. The skiving cutter 100 having a spur gear shape is used in processing a workpiece to form a helical gear.

[0044] The cross section shown in Fig. 4 is a cross section that is perpendicular to the multiple cutting edges 1 and includes the axis O. Hereinafter, the cross section that is perpendicular to the multiple cutting edges 1 and includes the axis O will also be referred to as a first cross section CS1. As shown in Fig. 4, the skiving cutter 100 mainly has a base portion 2 and multiple cutting edges 3.

[0045] The base portion 2 forms, for example, a portion of each of the plurality of blade portions 6 and the shank 10. The base portion 2 forms a first front end surface 51, a second front end surface 52, a first rear end surface 61, a second rear end surface 62, and a third rear end surface 63. In the second direction 102, the base portion 2 extends, for example, from the first front end surface 51 to the third rear end surface 63.

[0046] The base 2 is formed from either a cemented carbide or a high-speed steel. Specifically, when the base 2 is formed from a cemented carbide, the cemented carbide forming the base 2 contains tungsten carbide and cobalt. In the cemented carbide forming the base 2, the weight of tungsten carbide divided by the weight of the entire cemented carbide is 90.0% or more and 95.0% or less, and the weight of cobalt divided by the weight of the entire cemented carbide is 4.0% or more and 9.0% or less. When the base 2 is formed from a high-speed steel, the base 2 is formed from SKH51 or SKH55.

[0047] SKH51 and SKH55 are high-speed steels specified in JIS (Japanese Industrial Standards) G 4403:2015.

[0048] Each of the multiple cutting edges 3 is connected to the base 2. In this specification, two members being connected refers to a state in which the two members are at least in contact with each other by sintering, fastening, or the like. The two connected members may be integral or separate. The multiple cutting edges 3 form multiple cutting edges 1. Specifically, each of the multiple cutting edges 3 forms one of the multiple cutting edges 1. Each of the multiple cutting edges 3 is arranged alongside the base 2 in the first direction 101. The multiple cutting edges 1 are provided at the front end of the skiving cutter 100.

[0049] The plurality of cutting edges 3 form a part of each of the plurality of cutting portions 6. From another perspective, each of the plurality of cutting portions 6 is formed by the cutting edge portion 3 and the base portion 2.

[0050] 4, in the first cross section CS1, the flank 4 is inclined radially inward with respect to the axis O. Specifically, in the first cross section CS1, the distance in the first direction 101 between the flank 4 and the axis O decreases with increasing distance from the cutting edge 1.

[0051] The first front end surface 51 is, for example, perpendicular to the axis O. The second front end surface 52 is provided in a first direction 101 relative to the first front end surface 51. The second front end surface 52 is inclined in the first direction 101 relative to a plane perpendicular to the axis O. The rake face 5 is provided in the first direction 101 relative to the second front end surface 52. The rake face 5 is inclined in the first direction 101 relative to a plane perpendicular to the axis O.

[0052] The first rear end surface 61 is inclined in a first direction 101 with respect to a plane perpendicular to the axis O. The second rear end surface 62 is provided in a second direction 102 with respect to the first rear end surface 61. The second rear end surface 62 is inclined in the first direction 101 with respect to a plane perpendicular to the axis O.

[0053] The third rear end surface 63 is provided in the second direction 102 relative to the second rear end surface 62. The third rear end surface 63 is opposite the first front end surface 51. The third rear end surface 63 may be parallel to the first front end surface 51, for example. The third rear end surface 63 is perpendicular to the axis O, for example.

[0054] The second outer peripheral surface 57 is continuous with the second rear end surface 62 and the third rear end surface 63. The second outer peripheral surface 57 is provided in a second direction 102 relative to the first outer peripheral surface 56. The second outer peripheral surface 57 extends along the first direction 101.

[0055] As shown in Fig. 5, the cutting edge portion 3 has a brazing filler metal layer 23, a cemented carbide layer 22, and a cutting edge layer 21. The brazing filler metal layer 23 is provided on the base portion 2. The brazing filler metal layer 23 is composed of at least one element selected from the group consisting of Ag (silver), Cu (copper), In (indium), Ti (titanium), and Zr (zirconium). The cemented carbide layer 22 is provided on the brazing filler metal layer 23. In the cemented carbide constituting the cemented carbide layer 22, the tungsten carbide content is 90.0% or more and 95.0% or less, and the cobalt content is 4.0% or more and 9.0% or less.

[0056] The cutting edge layer 21 is provided on the cemented carbide layer 22. From another perspective, the cemented carbide layer 22 is provided between the cutting edge layer 21 and the base portion 2. The cutting edge layer 21 is separated from the brazing material layer 23 by the cemented carbide layer 22. The cutting edge layer 21 forms the rake face 5. The cutting edge layer 21 is formed of one of a cubic boron nitride (cBN) sintered body, diamond, and a special cemented carbide. The cBN sintered body, diamond, and special cemented carbide will be described in detail below.

[0057] In a cross section perpendicular to the cutting edges 1, each of the cutting edges 1 is, for example, arc-shaped. In a cross section perpendicular to the cutting edges 1, the curvature radius A of the cutting edges 1 is 10 μm or more and 40 μm or less. The curvature radius A may be, for example, 12 μm or more, or 15 μm or more. The curvature radius A may be, for example, 38 μm or less, or 35 μm or less.

[0058] As shown in FIG. 5 , each of the plurality of cutting edges 6 has a first flank portion 7 and a second flank portion 8. The first flank portion 7 and the second flank portion 8 form a flank 4. The first flank portion 7 is formed by the cutting edge portion 3. Specifically, the first flank portion 7 is formed by a cutting edge layer 21, a cemented carbide layer 22, and a brazing material layer 23. The first flank portion 7 is continuous with the plurality of cutting edges 1.

[0059] The second flank portion 8 is formed by the base portion 2. The second flank portion 8 is provided in the second direction 102 relative to the first flank portion 7. The second flank portion 8 is continuous with the first flank portion 7, for example. The second flank portion 8 is continuous with the first rear end face 61 (see FIG. 4). The first flank portion 7 and the second flank portion 8 are smoothly connected, for example.

[0060] Each of the plurality of cutting edges 6 has a connecting surface 66. The connecting surface 66 connects the rake face 5 and the second front end surface 52. The connecting surface 66 is smoothly connected to each of the rake face 5 and the second front end surface 52.

[0061] The base portion 2 has a bearing surface 20 and a side wall surface 55. The bearing surface 20 is in contact with the cutting edge portion 3. Specifically, the bearing surface 20 is in contact with the brazing filler metal layer 23. The brazing filler metal layer 23 is provided on the bearing surface 20. The bearing surface 20 is, for example, planar. The bearing surface 20 is, for example, perpendicular to the axis O. In the first cross section CS1, the distance in the first direction 101 between the rake face 5 and the bearing surface 20 decreases with increasing distance from the cutting edge 1.

[0062] The side wall surface 55 is continuous with each of the bearing surface 20 and the connecting surface 66. The side wall surface 55 is, for example, perpendicular to the bearing surface 20. The side wall surface 55 is in contact with the cutting edge portion 3. Specifically, the side wall surface 55 is in contact with each of the cutting edge layer 21, the cemented carbide layer 22, and the brazing material layer 23.

[0063] The cutting edge portion 3 has a first bottom surface 30. The first bottom surface 30 is in contact with the base portion 2. Specifically, the first bottom surface 30 is in contact with the bearing surface 20 of the base portion 2. The first bottom surface 30 is covered by, for example, the base portion 2. The first bottom surface 30 is formed by a brazing material layer 23. The first bottom surface 30 is, for example, planar. The first bottom surface 30 is, for example, perpendicular to the axis O.

[0064] The maximum thickness (first thickness H1) of the cutting edge layer 21 in the first direction 101 is, for example, 0.3 mm or more and 3 mm or less. The first thickness H1 may be, for example, 0.5 mm or more, or 1 mm or more. The first thickness H1 may be, for example, 2.5 mm or less, or 2 mm or less. The first thickness H1 is the longest distance in the first direction 101 between the interface between the cutting edge layer 21 and the cemented carbide layer 22 and the multiple cutting edges 1.

[0065] The maximum thickness (second thickness H2) of the cemented carbide layer 22 in the first direction 101 is, for example, 0.5 mm or more and 5 mm or less. The second thickness H2 is the longest distance in the first direction 101 between the interface between the cutting edge layer 21 and the cemented carbide layer 22 and the interface between the cemented carbide layer 22 and the brazing material layer 23.

[0066] The maximum thickness (third thickness H3) of the brazing material layer 23 in the first direction 101 is, for example, 0.01 mm or more and 0.05 mm or less. The third thickness H3 is the longest distance in the first direction 101 between the interface between the cemented carbide layer 22 and the brazing material layer 23 and the first bottom surface 30.

[0067] As shown in Fig. 5, the first cross section CS1 may pass through the outermost point 89. From another perspective, the cross section shown in Fig. 5 is a cross section that includes the axis O (see Fig. 4) and passes through the outermost point 89. A straight line 99 shown in Fig. 5 is a straight line perpendicular to the axis O. In the cross section that includes the axis O and passes through the outermost point 89, the angle formed by the straight line 99 and the rake face 5 is defined as the rake angle φ1.

[0068] In each of the multiple cutting edges, the rake angle φ1 is, for example, 0° or greater and 40° or less. The rake angle φ1 may be, for example, 5° or greater and 15° or less. The rake angle φ1 may be, for example, 3° or greater, or 8° or greater. The rake angle φ1 may be, for example, 30° or less, 18° or less, or 13° or less.

[0069] As shown in FIGS. 6 and 7, each of the plurality of cutting edges 1 is formed by a first cutting edge portion 11, a second cutting edge portion 12, and a corner cutting edge portion 13.

[0070] The second cutting edge portion 12 is provided in the rotational direction R relative to the first cutting edge portion 11. The second cutting edge portion 12 faces the first cutting edge portion 11. The corner cutting edge portion 13 connects the first cutting edge portion 11 and the second cutting edge portion 12. The corner cutting edge portion 13 is provided radially outward from each of the first cutting edge portion 11 and the second cutting edge portion 12. In each of the multiple cutting edges 1, the corner cutting edge portion 13 is provided between the first cutting edge portion 11 and the second cutting edge portion 12. In a plan view, the corner cutting edge portion 13 is, for example, arc-shaped.

[0071] As shown in FIG. 6 , the first flank portion 7 has a first portion 71, a first corner surface portion 73, and a second portion 72. The ridgeline between the first portion 71 and the rake face 5 forms the first cutting edge portion 11. The first corner surface portion 73 is continuous with the first portion 71. The ridgeline between the first corner surface portion 73 and the rake face 5 forms the corner cutting edge portion 13. The second portion 72 is continuous with the first corner surface portion 73. The ridgeline between the second portion 72 and the rake face 5 forms the second cutting edge portion 12.

[0072] The second flank portion 8 has a third portion 81, a second corner surface portion 83, and a fourth portion 82. The third portion 81 is continuous with the first portion 71 and the first rear end surface 61 (see FIG. 3). The second corner surface portion 83 is continuous with the first corner surface portion 73, the first rear end surface 61, and the third portion 81. The fourth portion 82 is continuous with the second portion 72, the first rear end surface 61, and the second corner surface portion 83. The connecting surface 66 is continuous with the first outer peripheral surface 56. The ridge line between the connecting surface 66 and the first outer peripheral surface 56 forms part of the bottom portion 9. As shown in FIG. 6, a line on the flank 4 that passes through the tip of each of the multiple cutting edges 6 is defined as a ridge line 88 of the flank 4.

[0073] Fig. 8 is a side schematic view showing the configuration of the skiving cutter 100 as seen in the direction of arrow D in Fig. 2. The direction of arrow D is perpendicular to the axis O and is a direction from the outermost point 89 toward the axis O.

[0074] 8, when viewed perpendicular to the axis O and in a direction from the outermost point 89 toward the axis O, the ridge line 88 is located midway between the boundary line (first boundary line 26) between the first portion 71 and the first corner surface portion 73 and the boundary line (second boundary line 27) between the second portion 72 and the first corner surface portion 73. From another perspective, when viewed in a direction perpendicular to the axis O and from the outermost point 89 toward the axis O, the distance between the ridge line 88 and the first boundary line 26 is the same as the distance between the ridge line 88 and the second boundary line 27 in the direction perpendicular to the ridge line 88.

[0075] Similarly, when viewed perpendicular to the axis O and in a direction from the outermost point 89 toward the axis O, the ridge line 88 is located midway between the boundary line (third boundary line 28) between the third portion 81 and the second corner surface portion 83 and the boundary line (fourth boundary line 29) between the fourth portion 82 and the second corner surface portion 83. From another perspective, when viewed perpendicular to the axis O and in a direction from the outermost point 89 toward the axis O, the distance between the ridge line 88 and the third boundary line 28 is the same as the distance between the ridge line 88 and the fourth boundary line 29 in the direction perpendicular to the ridge line 88.

[0076] The ridge line 88 may be parallel to the axis O, for example. In other words, when viewed in a direction perpendicular to the axis O and from the outermost periphery point 89 toward the axis O, the angle formed by the ridge line 88 and the axis O may be 0°, for example. The first corner surface portion 73 extends along the ridge line 88. The second corner surface portion 83 extends along the ridge line 88.

[0077] (cBN sintered body) Next, the cBN sintered body will be described in detail. The cBN sintered body contains cBN particles. In the cBN sintered body, the percentage (cBN particle content) obtained by dividing the volume of the cBN particles by the volume of the entire cBN sintered body is, for example, 50% or more and 100% or less. The cBN particle content may be, for example, 70% or more, 80% or more, or 90% or more. The cBN particle content may be, for example, 99% or less, or 97% or less.

[0078] The average particle size of cBN particles (D 50 ) is, for example, 0.01 μm or more and 3 μm or less. The average particle size of the cBN particles may be, for example, 0.03 μm or more, or 0.08 μm or more. The average particle size of the cBN particles may be, for example, 2 μm or less, 1.5 μm or less, or 0.7 μm or less.

[0079] The cBN sintered body may contain a binder. The binder bonds the cBN particles. When the cBN sintered body contains a binder, the cBN particle content in the cBN sintered body is less than 100%. The cBN sintered body may be composed of cBN particles and a binder, or may be composed of cBN particles, a binder, and unavoidable impurities.

[0080] The binder contains at least one element selected from the group consisting of titanium (Ti), cobalt (Co), aluminum (Al), and zirconium (Zr). Specifically, the binder contains at least one element selected from the group consisting of titanium nitride (TiN), cobalt, titanium carbide (TiC), titanium carbonitride (TiCN), aluminum oxide (Al2O3), zirconia (ZrO2), and aluminum nitride (AlN).

[0081] (cBN particle content) The cBN particle content of the cBN sintered body can be confirmed by performing structural observation, elemental analysis, etc. on the cBN sintered body using an energy dispersive X-ray spectroscopy (EDX) attached to a scanning electron microscope (SEM). The SEM can be a JEOL "JSM-7800F" (trade name). The EDX can be an Octane Elect EDS system. Hereinafter, the EDX attached to the SEM will also be referred to as SEM-EDX. Specific measurement methods are as follows:

[0082] (A1) First, a cBN sintered body is cut at an arbitrary position to prepare a sample containing a cross section of the cBN sintered body. A focused ion beam device, a cross-section polisher device, or the like can be used to prepare the cross section. Next, the cross section is observed at 1000x magnification using an SEM to obtain a backscattered electron image. In the backscattered electron image, areas where cBN particles are present appear as black areas, and areas where binder is present appear as gray and / or white areas.

[0083] (B1) Next, the backscattered electron image is binarized using image analysis software ("WinROOF" by Mitani Corporation). In the image after binarization, the areas where cBN particles exist (black areas in the backscattered electron image) become dark fields, and the areas where the binder exists (gray and / or white areas in the backscattered electron image) become bright fields. A measurement area (70 μm × 100 μm) is set in the image after binarization. The area ratio of pixels originating from the dark field (pixels originating from cBN particles, pixels originating from the black areas in the backscattered electron image) to the total area of the measurement field is calculated. The cBN particle content can be determined by regarding the calculated area ratio as a volume ratio.

[0084] It has been confirmed that as long as measurements are made on the same cutting edge layer 21 using the above method, there is no variation in the measurement results even if the measurement location is changed arbitrarily.

[0085] (Binding material) The fact that "the binder contains at least one element selected from the group consisting of Ti, Co, Al, and Zr" can be identified by XRD (X-ray diffraction). That is, "the binder contains at least one element selected from the group consisting of Ti, Co, Al, and Zr" means that at least one element selected from the group consisting of Ti, Co, Al, and Zr is present in the binder to an extent that it can be detected by XRD.

[0086] (average particle size of cBN particles) The average particle size of cBN particles can be determined as follows. First, a sample containing a cross section of a cBN sintered body is prepared in accordance with the method for determining the cBN particle content described above, and a backscattered electron image is obtained. Next, image analysis software ("WinROOF (ver. 7.4.5)" by Mitani Corporation) is used to calculate the equivalent circle diameter of each dark field (corresponding to cBN) in the backscattered electron image. It is preferable to calculate the equivalent circle diameter of 100 or more cBN particles by observing five or more fields of view.

[0087] Next, the circle-equivalent diameters are arranged in ascending order from smallest to largest to determine the cumulative distribution. The particle size at which the cumulative area accounts for 50% of the cumulative distribution is the average particle size. The circle-equivalent diameter refers to the diameter of a circle with the same area as the measured cBN particle.

[0088] (diamond) Next, we will explain the details of diamond. Diamond is either polycrystalline diamond or single-crystal diamond (SCD).

[0089] Polycrystalline diamond includes a plurality of diamond particles. Polycrystalline diamond may also include a binder. The binder includes at least one element selected from, for example, iron (Fe), cobalt (Co), and nickel (Ni), and any of their mutual solid solutions. Specifically, the binder is formed of, for example, Co, Co-Fe, Ni-Co, etc. Hereinafter, polycrystalline diamond including a binder is also referred to as polycrystalline sintered diamond or PCD (Poly-Crystalline Diamond).

[0090] Polycrystalline diamond may not contain a binder phase. Hereinafter, polycrystalline diamond without a binder phase is also referred to as binderless polycrystalline diamond or BLPCD. BLPCD is a polycrystalline diamond in which multiple diamond particles are bonded together without a binder. In this specification, polycrystalline diamond includes PCD and BLPCD.

[0091] BLPCDs are fabricated by converting graphite into diamond particles using, for example, high temperature and high pressure (HTHP) synthesis, while simultaneously sintering the diamond particles without using a binder phase. More specifically, BLPCDs are fabricated by directly converting graphite into diamond particles while simultaneously sintering the diamond particles under high temperature and pressure conditions, for example, at temperatures between 1800°C and 2500°C and between 15 GPa and 25 GPa.

[0092] PCD is produced by sintering a mixture of raw powder binder and diamond particles produced by HTHP or other methods, while SCD is produced by HTHP and chemical vapor deposition (CVD) methods.

[0093] When the diamond is polycrystalline diamond, the percentage (diamond particle content) of the volume of diamond particles divided by the volume of the entire diamond is, for example, 80% or more and 100% or less. The diamond particle content may be, for example, 85% or more, 92% or more, or 97% or more. The diamond particle content may be, for example, 99% or less, or 98% or less. The diamond particle content can be measured, for example, using secondary ion mass spectrometry (SIMS).

[0094] In a BLPCD, the percentage of the volume of carbon divided by the volume of the BLPCD excluding impurity elements is 100%. In a BLPCD, the value of the volume of the impurity elements divided by the mass of the entire BLPCD (the impurity element content) is, for example, 5% or less. In a BLPCD, the impurity element content may be 0%.

[0095] If the diamond is polycrystalline, the average diameter of the diamond particles (D 50 ) is, for example, 0.01 μm or more and less than 100 μm. The average particle size of the diamond particles may be, for example, 0.05 μm or more, or 0.1 μm or more. The average particle size of the diamond particles may be, for example, 70 μm or less, 40 μm or less, 10 μm or less, or 1 μm or less.

[0096] The average particle size of the diamond particles can be measured using an SEM and image analysis software. The SEM can be, for example, "JSM-7800F" (product name) manufactured by JEOL Ltd. The image analysis software can be, for example, WinROOF manufactured by Mitani Shoji Co., Ltd.

[0097] Specifically, first, a polycrystalline diamond sample is prepared by cutting the cutting edge layer 21. The surface of the sample is mirror-polished. Next, a backscattered electron image of the mirror-polished surface of the sample is observed using an SEM at a magnification of 5,000 times or more and 20,000 times or less. This allows multiple diamond particles to be identified in the backscattered electron image.

[0098] The circular equivalent diameter of each of the identified multiple diamond particles is calculated using image analysis software. For example, by observing five or more fields of view, the circular equivalent diameter of each of 100 or more diamond particles can be calculated. Next, all the calculated circular equivalent diameters are sorted in ascending order from minimum to maximum to determine the cumulative distribution. The particle diameter at which the cumulative area is 50% in the cumulative distribution is called D 50 The circle equivalent diameter means the diameter of a circle having the same area as the measured area of the diamond particle.

[0099] (Special cemented carbide) Next, the special cemented carbide will be described in detail. The special cemented carbide has tungsten carbide particles and a binder phase. In the special cemented carbide, the percentage (binder phase content) obtained by dividing the volume of the binder phase by the total volume of the special cemented carbide is 0.7% or more and 28% or less. The binder phase content may be, for example, 2% or more, 10% or more, 15% or more, or 20% or more. The binder phase content may be, for example, 27.5% or less, or 25% or less.

[0100] The special cemented carbide may be composed of tungsten carbide particles and a binder phase. In this case, the special cemented carbide may contain unavoidable impurities as long as the effects of the present disclosure are not impaired.

[0101] The binder phase contains cobalt. The binder phase further contains at least one element (first element) selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. The cemented carbide forming the base portion 2 does not contain the first element. In this specification, cemented carbide not containing the first element will be referred to as a "cemented carbide" to distinguish it from special cemented carbide.

[0102] In the binder phase, the percentage (cobalt content) of the mass of cobalt divided by the mass of the entire binder phase is 50% or more. The cobalt content may be 50% or more but less than 100%, 60% or more but 98% or less, or 70% or more but 95% or less.

[0103] In the binder phase, the percentage (first element content) of the mass of the first element divided by the mass of the entire binder phase is, for example, 1% or more and 6% or less.

[0104] The special cemented carbide may not contain an intermetallic compound consisting of two or more elements selected from the group consisting of the first element, cobalt, and tungsten, or a compound consisting of at least one element selected from the group consisting of the first element, cobalt, and tungsten and at least one element selected from the group consisting of carbon, nitrogen, and oxygen. Here, the compound does not contain tungsten carbide. This can prevent a decrease in the hardness and strength of the special cemented carbide.

[0105] Examples of the intermetallic compounds include Co2Si, Co3Si, CoSi, etc. Examples of the compounds include Co3W3C, Co6W6C, etc. Whether the special cemented carbide does not contain any of the intermetallic compounds or compounds described above can be confirmed by performing structure observation and EDX analysis on a cross section of the special cemented carbide.

[0106] The special cemented carbide may contain other phases in addition to the tungsten carbide particles and binder phase. The other phases include, for example, carbides, nitrides, or carbonitrides containing at least one element selected from the group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), and molybdenum (Mo). The other phases include, for example, TiCN, TaC, NbC, ZrC, HfC, and MoC. The other phases may also include a metal or alloy containing at least one element selected from the group consisting of nickel, chromium, and molybdenum.

[0107] The special cemented carbide may be composed of tungsten carbide particles, a binder phase, and other phases. In this case, the special cemented carbide may contain impurities as long as the effects of the present disclosure are not impaired.

[0108] In the special cemented carbide, the percentage of the volume of the other phases divided by the volume of the entire special cemented carbide (content of the other phases) is permissible as long as it does not impair the effects of the present disclosure. The content of the other phases may be, for example, greater than 0% and less than 11%, greater than 0% and less than 7%, or greater than 0% and less than 4%.

[0109] The special cemented carbide may contain impurities. Examples of impurities include iron (Fe), calcium (Ca), silicon (Si), and sulfur (S). In the special cemented carbide, the percentage (impurity content) of the mass of the impurities divided by the total mass of the special cemented carbide is acceptable as long as it does not impair the effects of the present disclosure. The impurity content may be, for example, 0% or more and less than 0.1%. The impurity content can be measured using inductively coupled plasma (ICP) optical emission spectrometry. Shimadzu Corporation's "ICPS-8100" (trademark) can be used for ICP optical emission spectrometry.

[0110] The binder phase content in the special cemented carbide can be measured using the following method. (A2) A special cemented carbide is cut out at an arbitrary position to expose a cross section, which is then polished to a mirror finish using a cross section polisher (manufactured by JEOL Ltd.).

[0111] (B2) The mirror-finished cross section is analyzed using a scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX). This allows the elements contained in the special cemented carbide to be identified. For SEM-EDX, a Carl Zeiss Gemini450 (trademark) can be used.

[0112] (C2) A backscattered electron image is obtained by photographing the mirror-finished cross section with a scanning electron microscope (SEM). The photographed area for the backscattered electron image is set at the center of the cross section of the special cemented carbide. Specifically, the photographed area is set at a position that does not include areas with properties that are clearly different from the bulk part, such as near the surface of the special cemented carbide. The observation magnification is set to 5000x. In other words, the photographed area is set so that it consists only of the bulk part of the special cemented carbide. The measurement conditions are an acceleration voltage of 3 kV, a current value of 2 nA, and a working distance (WD) of 5 mm.

[0113] (D2) The imaging area set in (C2) above is analyzed using an energy dispersive X-ray analyzer attached to the SEM. The distribution of the elements identified in (B2) above in the imaging area is determined. This results in an element mapping image.

[0114] (E2) The backscattered electron image obtained in (C2) above is imported into a computer. Using image analysis software (OpenCV, SciPy), the backscattered electron image is binarized. In the binarized image, tungsten carbide particles are shown in white, and the binder phase is shown in gray or black. Note that the binarization threshold varies depending on the contrast, so it is set for each image.

[0115] (F2) The elemental mapping image obtained in (D2) above and the binarized image obtained in (E2) above are superimposed. This allows the regions of tungsten carbide particles and binder phase to be identified in the binarized image. Specifically, the regions shown in white in the binarized image and containing tungsten (W) and carbon (C) in the elemental mapping image are identified as regions of tungsten carbide particles. The regions shown in gray or black in the binarized image and containing cobalt (Co) in the elemental mapping image are identified as regions of binder phase.

[0116] (G2) One measurement field is set in the binarized image. The measurement field is a rectangle of 24.9 μm × 18.8 μm. Using the image analysis software, the area percentage of tungsten carbide particles and the area percentage of the binder phase are determined. Specifically, the area percentage of tungsten carbide particles is determined by dividing the area of the tungsten carbide particles in the measurement field by the entire measurement field. The area percentage of the binder phase is determined by dividing the area of the binder phase in the measurement field by the entire measurement field.

[0117] (H2) The measurement of (G2) above is performed in five different, non-overlapping measurement fields. In the present disclosure, the average area percentage of tungsten carbide particles in the five measurement fields is taken as the tungsten carbide particle content of the special cemented carbide alloy. The average area percentage of the binder phase in the five measurement fields is taken as the binder phase content of the special cemented carbide alloy.

[0118] If the special cemented carbide contains other phases, the content of the other phases in the special cemented carbide is determined by subtracting the tungsten carbide particle content and binder phase content (volume %) measured by the above procedure from 100%.

[0119] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results, even if the cut-out location of the cross section of the special cemented carbide, the photographing area described in (C2) above, and the measurement field of view described in (G2) above are arbitrarily set and the tungsten carbide particle content and binder phase content are measured multiple times according to the above procedure.

[0120] The method for measuring the cobalt content of the binder phase is as follows: The region where the binder phase exists is identified on the binarized image using the same methods as (A2) to (F2) of the method for measuring the tungsten carbide particle content and binder phase content of the special cemented carbide. A rectangular measurement field of view of 24.9 μm × 18.8 μm is set in the binarized image. The region where the binder phase exists in the measurement field of view is analyzed using SEM-EDX to measure the cobalt content of the binder phase. The above measurement is performed in five different, non-overlapping measurement fields of view. In the present disclosure, the average of the cobalt contents of the binder phase in the five measurement fields of view is defined as the cobalt content of the binder phase.

[0121] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even when the cut-out portion of the cross section of the special cemented carbide and the photographing area described in (C2) above are arbitrarily set and the cobalt content of the binder phase is measured multiple times according to the above procedure.

[0122] The inclusion of the first element in the binder phase is confirmed by the following procedure. The region where the binder phase exists is identified on the image after binarization processing using the same methods as (A2) to (F2) of the method for measuring the tungsten carbide particle content and binder phase content of the special cemented carbide. The region where the binder phase exists is analyzed using SEM-EDX, and if the first element is present in the region where the binder phase exists, it is confirmed that the binder phase contains the first element.

[0123] In the special cemented carbide, the binder phase may contain, in addition to cobalt and the first element, at least one second element selected from the group consisting of iron (Fe), nickel (Ni), and chromium (Cr). The binder phase may consist of cobalt, the first element, and the second element. The binder phase may consist of cobalt, the first element, the second element, and inevitable impurities. The inevitable impurities are, for example, iron (Fe), nickel (Ni), and sulfur (S).

[0124] <Method of manufacturing special cemented carbide> The method for producing the special cemented carbide includes a raw material powder preparation step, a mixing step, a molding step, a sintering step, and a first cooling step. The method for producing the special cemented carbide may further include a HIP (Hot Isostatic Pressing) step and a second cooling step. Each step will be described below.

[0125] <Preparation process> The preparation step is a step of preparing raw material powders of materials constituting the special cemented carbide. Examples of raw material powders include tungsten carbide powder (hereinafter also referred to as "WC powder"), cobalt (Co) powder, first element powder, and alloy powder of the first element and cobalt. Examples of the first element powder include at least one of silicon (Si) powder, phosphorus (P) powder, germanium (Ge) powder, tin (Sn) powder, rhenium (Re) powder, ruthenium (Ru) powder, osmium (Os) powder, iridium (Ir) powder, and platinum (Pt) powder. Other examples of raw material powders that may be prepared include titanium carbonitride (TiCN), nickel-chromium alloy (NiCr), and titanium niobium carbonitride (TiNbCN).

[0126] Commercially available raw material powders can be used. The average particle size of the raw material powder is not particularly limited, but can be, for example, 0.5 μm or more and 5 μm or less. The average particle size of the raw material powder is the average particle size measured by the FSSS (Fisher Sub-Sieve Sizer) method. The average particle size can be measured using a "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific.

[0127] <Mixing process> The mixing step is a step of mixing the raw material powders prepared in the preparation step in a predetermined ratio. A mixed powder containing the raw material powders is obtained by the mixing step. The mixing ratio of the raw material powders is appropriately adjusted depending on the composition of the special cemented carbide to be manufactured.

[0128] The raw material powders can be mixed using a conventionally known mixing method such as an attritor, ball mill, or bead mill. Conventional mixing conditions can also be used. The mixing time can be, for example, from 2 hours to 20 hours.

[0129] After the mixing step, the mixed powder may be granulated as necessary. Granulating the mixed powder makes it easier to fill the mixed powder into a die or mold in the molding step described below. A known granulation method can be used for the granulation. For example, a commercially available granulator such as a spray dryer can be used for the granulation.

[0130] <Forming process> The molding step is a step of obtaining a molded body by molding the mixed powder obtained in the mixing step into the shape of the cutting edge layer 21. The molding method and molding conditions in the molding step are not particularly limited and may be general methods and conditions.

[0131] <Sintering process> The sintering step is a step of sintering the compact obtained in the compacting step. Specifically, the compact is heated to 1400°C at a heating rate of 50°C / min and held at 1400°C for 60 minutes.

[0132] <First Cooling Process> In the first cooling process, the sintered compact is cooled to 800°C. The cooling rate is 80°C / min.

[0133] <HIP Process and Second Cooling Process> After the first cooling process, a HIP process and a second cooling process may be performed. This can improve the material strength of the cemented carbide. The HIP process is a process of performing HIP treatment on the cemented carbide after the first cooling process. In the HIP process, the cemented carbide is held at 200 MPa and 1290°C for 60 minutes.

[0134] The second cooling process is a process of cooling the cemented carbide after the HIP process. Specifically, the cemented carbide is cooled to 800°C. The cooling rate is 80°C / min. Thereafter, the cemented carbide is slowly cooled. The cooling rate during slow cooling may adopt general conditions and is not particularly limited.

[0135] In the method for manufacturing a cemented carbide, the heating rate in the sintering process is 50°C / min, which is higher than the general heating rate. Also, the cooling rates in the first and second cooling processes are 80°C / min, which are higher than the general cooling rates. Under these conditions, it is possible to manufacture a cemented carbide in which the binder phase contains 50% by mass or more of cobalt and at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. The inventors have found through intensive studies that the cemented carbide of the present disclosure can be realized by adopting such a heating rate in the sintering process.

[0136] Next, the operation and effect of the skiving cutter 100 according to the first embodiment will be described. As shown in FIGS. 9 and 10, for example, the skiving cutter 100 is arranged such that the axis O of the skiving cutter 100 is inclined at an intersection angle θ with respect to the rotation axis C of the machined surface 91 of the workpiece 90. The machined surface 91 is, for example, the inner peripheral surface of the workpiece 90.

[0137] The skiving cutter 100 rotates around an axis O in a rotation direction R. The workpiece 90 rotates around a rotation axis C along an arrow B. The skiving cutter 100 moves along an arrow F. The direction of the arrow F is from the skiving cutter 100 toward the workpiece 90 along the rotation axis C. The multiple cutting edges 1 come into contact with the machining surface 91. As a result, the multiple cutting edges 1 cut the workpiece 90. As a result, the workpiece 90 is machined into, for example, an internal gear shape.

[0138] During skiving, the cutting edge of the skiving cutter can wear out significantly. For example, when machining a workpiece made of a hard material (hard skiving), the cutting edge can wear out significantly. For example, when machining a workpiece made of hardened steel, the cutting edge can wear out significantly due to the hardness of the hardened steel.

[0139] The skiving cutter 100 according to the first embodiment has a base portion 2 and a cutting edge portion 3. The cutting edge portion 3 is continuous with the base portion 2. The cutting edge portion 3 has a cutting edge layer 21. The cutting edge layer 21 forms a plurality of cutting edges 1. The base portion 2 is formed of either a cemented carbide or high-speed steel. The cutting edge layer 21 is formed of either a cBN sintered body, diamond, or a special cemented carbide.

[0140] For example, compared to the wear resistance of cemented carbide and high-speed steel, the wear resistance of cBN sintered body, diamond, and special cemented carbide is high. Therefore, the skiving cutter 100 according to the first embodiment can improve the wear resistance of the cutting edge 1. This can suppress wear of the cutting edge 1.

[0141] According to the skiving cutter 100 of the first embodiment, wear of the cutting edge 1 can be effectively suppressed even when the workpiece is made of hardened steel with high hardness.

[0142] When machining a workpiece made of a hard material, the force applied to the skiving cutter 100 becomes excessively large. Specifically, the force applied to the cutting edge 1 becomes excessively large, for example. In this case, a portion of the skiving cutter 100 near the cutting edge 1 may be chipped.

[0143] For example, compared to the hardness of cemented carbide and high-speed steel, the hardness of cBN sintered body, diamond, and special cemented carbide is high. Therefore, according to the skiving cutter 100 according to the first embodiment, the hardness of the portion of the skiving cutter 100 close to the cutting edge 1 can be improved. This makes it possible to prevent chipping in the portion of the skiving cutter 100 close to the cutting edge 1.

[0144] Compared to the toughness of cBN sintered body, diamond, and special cemented carbide, the toughness of cemented carbide and high-speed steel is high. Therefore, according to the skiving cutter 100 according to the first embodiment, the base part 2 is formed of either cemented carbide or high-speed steel, which improves the toughness of the base part 2. This makes it possible to prevent the skiving cutter 100 from breaking.

[0145] The cutting edge 3 has a cemented carbide layer 22. Therefore, compared to when the cutting edge 3 is made of only sintered cBN and diamond, the cutting edge 3 can be prevented from breaking.

[0146] The thermal conductivity of cBN sintered body, diamond, and special cemented carbide is higher than that of cemented carbide. Therefore, by forming the cutting edge layer 21 from any one of cBN sintered body, diamond, and special cemented carbide, thermal wear caused by temperature rise of the cutting edge can be suppressed.

[0147] According to the skiving cutter 100 of the first embodiment, the maximum thickness (first thickness H1) of the cutting edge layer 21 in the first direction 101 is 0.3 mm or more and 3 mm or less. When the first thickness H1 is 0.3 mm or more, wear of the flank 4 can be effectively suppressed. When the first thickness H1 is 3 mm or less, breakage of the cutting edge portion 3 can be suppressed.

[0148] According to the skiving cutter 100 of the first embodiment, in a cross section perpendicular to the multiple cutting edges 1, the radius of curvature A of the multiple cutting edges 1 is 10 μm or more and 40 μm or less. When the radius of curvature A is 10 μm or more, the pressure applied to the multiple cutting edges 1 can be reduced. This makes it possible to prevent damage to the portion of the skiving cutter 100 close to the multiple cutting edges 1. When the radius of curvature A is 40 μm or less, it is possible to prevent the sharpness of the multiple cutting edges 1 from decreasing excessively.

[0149] In the skiving cutter 100 according to the first embodiment, the binder phase of the special cemented carbide further contains at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. This improves the hardness and strength of the binder phase and the interface strength between the tungsten carbide particles in the special cemented carbide. This, in turn, extends the tool life.

[0150] The hardness of cBN particles is greater than the hardness of the binder. Therefore, as the cBN particle content in the cBN sintered body increases, the hardness of the cBN sintered body can be increased. According to the skiving cutter 100 of the first embodiment, the percentage of the volume of the cBN particles divided by the total volume of the cBN sintered body is 50% or more. Therefore, the hardness of the cBN sintered body can be sufficiently increased. This effectively prevents chipping of the cutting edge portion 3.

[0151] According to the skiving cutter 100 of the first embodiment, the average particle size of the cBN particles in the cBN sintered body is 3 μm or less. This allows for smaller gaps between the cBN particles. This allows for a smaller thickness of the binder, which has a lower hardness than the cBN particles, in the cBN sintered body. This effectively prevents chipping of the cutting edge 3.

[0152] According to the skiving cutter 100 of the first embodiment, the binder in the cBN sintered body contains at least one selected from the group consisting of Ti, Co, Al, and Zr. This improves the wear resistance of the cBN sintered body. As a result, wear of the cutting edge 3 can be effectively suppressed.

[0153] If the rake angle φ1 is excessively large, the portion of the skiving cutter 100 close to the cutting edge 1 becomes excessively sharp. Therefore, the strength of the portion of the skiving cutter 100 close to the cutting edge 1 decreases excessively. According to the skiving cutter 100 of the first embodiment, the rake angle φ1 is 40° or less. Therefore, it is possible to prevent the strength of the portion of the skiving cutter 100 close to the cutting edge 1 from decreasing excessively.

[0154] According to the skiving cutter 100 of the first embodiment, the rake angle φ1 may be 5° or more and 15° or less. This effectively improves the sharpness of the cutting edge 1. As a result, wear on the part of the skiving cutter 100 close to the cutting edge 1 can be effectively suppressed.

[0155] According to the skiving cutter 100 of the first embodiment, the cutting edge layer 21 may be formed of diamond. The diamond may be polycrystalline diamond. If the diamond particle content in the polycrystalline diamond is excessively low, the strength of the cutting edge layer 21 will be excessively reduced. According to the skiving cutter 100 of the first embodiment, the diamond particle content in the diamond is 80% or more. This makes it possible to prevent the strength of the cutting edge layer 21 from being excessively reduced.

[0156] If the average particle size of the diamond particles is excessively large, the diamond particles may not be sintered properly during diamond production. In this case, the strength of the cutting edge layer 21 decreases. In the skiving cutter 100 according to the first embodiment, the average particle size of the diamond particles is 100 μm or less. This makes it possible to prevent the diamond particles from being sintered properly. This makes it possible to prevent the strength of the cutting edge layer 21 from decreasing.

[0157] (Second embodiment) Next, the configuration of the skiving cutter 100 according to the second embodiment will be described. The skiving cutter 100 according to the second embodiment differs from the skiving cutter 100 according to the first embodiment mainly in that a part of the first bottom surface 30 of the cutting edge portion 3 is provided outside the base portion 2, but in other respects it is substantially the same as the skiving cutter 100 according to the first embodiment. Below, the differences from the skiving cutter 100 according to the first embodiment will be mainly described.

[0158] Fig. 11 shows the cross section shown in Fig. 5. As shown in Fig. 11, a part of the first bottom surface 30 of the cutting edge 3 may be provided outside the base portion. The first bottom surface 30 of the cutting edge 3 has a first bottom surface portion 36 and a second bottom surface portion 37.

[0159] The first bottom surface portion 36 is in contact with the base portion 2. From another perspective, the first bottom surface portion 36 is covered by the base portion 2. In the cutting edge portion 3, the second bottom surface portion 37 is continuous with both the first flank surface portion 7 and the first bottom surface portion 36. The second bottom surface portion 37 is located outward from the base portion 2. The first flank surface portion 7 and the second flank surface portion 8 are spaced apart from each other.

[0160] Fig. 12 shows region XII in Fig. 3. For ease of explanation, Fig. 12 does not show the boundary between the cutting edge layer 21 and the cemented carbide layer 22 and the boundary between the cemented carbide layer 22 and the brazing material layer 23. As shown in Fig. 12, the second bottom surface portion 37 is provided between the first flank surface portion 7 and the second flank surface portion 8.

[0161] The ridgeline between the first relief surface portion 7 and the second bottom surface portion 37 forms a first ridgeline portion 31, a corner ridgeline portion 33, and a second ridgeline portion 32. The first ridgeline portion 31 is formed by the ridgeline between the first portion 71 and the second bottom surface portion 37. The corner ridgeline portion 33 is formed by the ridgeline between the first corner surface portion 73 and the second bottom surface portion 37. The corner ridgeline portion 33 is continuous with the first ridgeline portion 31. The corner ridgeline portion 33 is provided radially outward from the first ridgeline portion 31.

[0162] The second ridge portion 32 is formed by the ridge between the second portion 72 and the second bottom surface portion 37. The second ridge portion 32 is continuous with the corner ridge portion 33. The corner ridge portion 33 is provided between the first ridge portion 31 and the second ridge portion 32. The second ridge portion 32 is provided in the rotation direction R with respect to the first ridge portion 31. The second ridge portion 32 faces the first ridge portion 31.

[0163] The first ridge portion 31 is, for example, curved. A tangent to the first ridge portion 31 when viewed along the axis O is a first tangent 41. The second ridge portion 32 is, for example, curved. A tangent to the second ridge portion 32 when viewed along the axis O is a second tangent 42. The corner ridge portion 33 is, for example, curved. A tangent to the corner ridge portion 33 when viewed along the axis O is a third tangent 43.

[0164] Line XI-XI in Fig. 12 indicates the position of the cross section shown in Fig. 11. The cross section shown in Fig. 11 is a cross section perpendicular to third tangent line 43. As shown in Fig. 11, in the cross section perpendicular to third tangent line 43, the length of second bottom surface portion 37 between corner ridge portion 33 and second flank surface portion 8 is defined as third length L3. Third length L3 is, for example, not less than 5 µm and not more than 200 µm.

[0165] 13 is a cross section perpendicular to the first tangent line 41. Hereinafter, the cross section perpendicular to the first tangent line 41 will also be referred to as a second cross section CS2.

[0166] As shown in FIG. 13 , in the second cross section CS2, the length of the second bottom surface portion 37 between the first ridge portion 31 and the second flank surface portion 8 is defined as a first length L1. In the second cross section CS2, the first length L1 is the shortest distance between the first ridge portion 31 and the connection point between the second flank surface portion 8 and the second bottom surface portion 37. The first length L1 is, for example, shorter than the third length L3. The first length L1 is, for example, not less than 2 μm and not more than 150 μm. The first length L1 may be substantially the same length along the entire length of the first ridge portion 31.

[0167] 14 is a cross section perpendicular to the second tangent line 42. Hereinafter, the cross section perpendicular to the second tangent line 42 will also be referred to as a third cross section CS3.

[0168] As shown in FIG. 14 , in the third cross section CS3, the length of the second bottom surface portion 37 between the second ridge portion 32 and the second flank portion 8 is defined as a second length L2. In the third cross section CS3, the second length L2 is the shortest distance between the second ridge portion 32 and the connection point between the second flank portion 8 and the second bottom surface portion 37. The second length L2 may be the same as the first length L1, for example. The second length L2 may be shorter than the third length L3, for example. The second length L2 may be substantially the same length along the entire length of the second ridge portion 32.

[0169] The wear resistance of the second flank portion 8, which is made of cemented carbide or high-speed steel, is lower than the wear resistance of the first flank portion 7, which is made of sintered cBN, diamond, or special cemented carbide. In the skiving cutter 100 according to the second embodiment, the cutting edge portion 3 has a first bottom surface portion 36 and a second bottom surface portion 37. The first bottom surface portion 36 is in contact with the base portion 2. The second bottom surface portion 37 is continuous with both the first flank portion 7 and the first bottom surface portion 36. The second bottom surface portion 37 is provided on the outer side of the base portion 2.

[0170] Therefore, in each of the plurality of cutting edges 6, the second flank portion 8 is located inside the first flank portion 7. This prevents the second flank portion 8 from coming into contact with the workpiece 90 when machining the workpiece 90. As a result, wear on the flank 4 can be suppressed. Specifically, wear on the flank 4 in the tooth trace direction can be suppressed.

[0171] According to the skiving cutter 100 of the second embodiment, the second flank portion 8 can be prevented from coming into contact with the workpiece 90, thereby reducing the frictional force generated between each of the plurality of cutting edges 6 and the workpiece 90. As a result, damage to each of the plurality of cutting edges 6 can be suppressed.

[0172] As the thickness of the chips increases, the frictional force that each of the multiple cutting portions 6 receives from the workpiece 90 increases. Therefore, as the thickness of the chips increases, the flank 4 becomes more susceptible to wear. As the length of the second bottom surface portion 37 in the direction perpendicular to the ridge line between the first flank surface portion 7 and the second bottom surface portion 37 increases, the effect of suppressing wear of the flank 4 increases. On the other hand, if the length of the second bottom surface portion 37 is excessively long, the strength of the cutting edge portion 3 decreases. Therefore, it is necessary to set the length of the second bottom surface portion 37 in accordance with the thickness of the chips.

[0173] The thickness of the chips may be substantially the same between two different points on the cutting edge 1, or may be different. Specifically, the thickness of the chips varies depending on the specifications of the skiving cutter 100 and cutting conditions such as the cross angle θ. In the skiving cutter 100 according to the second embodiment, the first length L1 (see FIG. 12) and the second length L2 (see FIG. 13) are the same. Therefore, when the thickness of the chips is substantially the same between two different points on the cutting edge 1, wear on the flank 4 can be effectively suppressed.

[0174] (Modification of the second embodiment) Next, a modified example of the second embodiment will be described. Figure 15 shows the cross section shown in Figure 13. Figure 16 shows the cross section shown in Figure 14.

[0175] As shown in FIGS. 15 and 16, the first length L1 and the second length L2 may be different. For example, the first length L1 may be shorter than the second length L2. The first length L1 may be, for example, 0 μm. From another perspective, the first flank portion 7 and the second flank portion 8 may be smoothly connected at the second cross section CS2, and the second bottom surface portion 37 may be provided between the first flank portion 7 and the second flank portion 8 at the third cross section CS3. The second length L2 may be longer than the third length L3 (see FIG. 11).

[0176] Conversely, the first length L1 may be longer than the second length L2. The first length L1 may be longer than the third length L3 (see FIG. 11). The second length L2 may be, for example, 0 μm. From another perspective, the first flank portion 7 and the second flank portion 8 may be smoothly connected at the third cross section CS3, and the second bottom surface portion 37 may be provided between the first flank portion 7 and the second flank portion 8 at the second cross section CS2.

[0177] According to the skiving cutter 100 according to the modified example of the second embodiment, when the thickness of the chips varies between two different points on the cutting edge 1, wear on the flank 4 can be effectively suppressed.

[0178] (Third embodiment) Next, the configuration of the skiving cutter 100 according to the third embodiment will be described. The skiving cutter 100 according to the third embodiment differs from the skiving cutter 100 according to the first embodiment mainly in that it has a coating 19, and is substantially identical to the skiving cutter 100 according to the first embodiment in other respects. The following description will focus on the differences from the skiving cutter 100 according to the first embodiment.

[0179] Figure 17 shows the cross section shown in Figure 5. As shown in Figure 17, the skiving cutter 100 may have a coating 19.

[0180] The coating 19 covers at least a portion of the cutting edge portion 3. Specifically, the coating 19 covers the first flank portion 7. The coating 19 may also cover the rake face 5. The coating 19 may also cover a portion of the base portion 2. Specifically, the coating 19 may also cover the second flank portion 8. The coating 19 does not have to cover the rake face 5. The coating 19 is composed of at least one element selected from the group consisting of Ti (titanium), Zr (zirconium), Hf (hafnium), V (vanadium), Nb (niobium), Ta (tantalum), Cr (chromium), Mo (molybdenum), W (tungsten), Al (aluminum), and Si (silicon), and at least one element selected from the group consisting of C (carbon), N (nitrogen), O (oxygen), and B (boron).

[0181] According to the skiving cutter 100 according to the third embodiment, the coating 19 covers at least a part of the cutting edge 3. This makes it possible to suppress wear of the cutting edge 3.

[0182] (Fourth embodiment) Next, the configuration of the skiving cutter 100 according to the fourth embodiment will be described. The skiving cutter 100 according to the fourth embodiment differs from the skiving cutter 100 according to the first embodiment mainly in that it has a helical gear shape, and is substantially identical to the skiving cutter 100 according to the first embodiment in other respects. Below, the differences from the skiving cutter 100 according to the first embodiment will be mainly described.

[0183] 18 to 20, the skiving cutter 100 may have a helical gear shape. Specifically, the extending direction of each of the cutting edges 6 may be inclined in the rotational direction R with respect to the axis O. As shown in FIGS. 19 and 20, when viewed along the axis O, the cutting face 5 is provided in the rotational direction R with respect to the first rear end surface 61. The skiving cutter 100 having a helical gear shape is used in processing a workpiece to form a spur gear.

[0184] As shown in FIG. 18 , the second front end surface 52 may be formed by a plurality of first inclined surfaces 58 and a plurality of second inclined surfaces 59. Each of the plurality of first inclined surfaces 58 is connected to one of the plurality of rake faces 5 via a connecting surface 66 (see FIGS. 6 and 7 ). Each of the plurality of second inclined surfaces 59 is provided between two adjacent first inclined surfaces 58 among the plurality of first inclined surfaces 58. Each of the plurality of second inclined surfaces 59 is continuous with one of the plurality of flank faces 4. The ridge between the second inclined surfaces 59 and the flank face 4 forms a part of the bottom portion 9.

[0185] In FIG. 21 , dashed lines indicate the boundary between the first bottom surface portion 36 and the second bottom surface portion 37. For ease of explanation, the boundary between the cutting edge layer 21 and the cemented carbide layer 22 and the boundary between the cemented carbide layer 22 and the brazing material layer 23 are not shown in FIG. 21 . As shown in FIG. 21 , a portion of the corner cutting edge portion 13 may be linear in bottom view. A portion of the corner ridge portion 33 may be linear in bottom view. For ease of explanation, the base portion 2 is not shown in FIG. 21 .

[0186] Fig. 22 shows the cross section shown in Fig. 13. As shown in Fig. 22, in the second cross section CS2, the first flank portion 7 is inclined with respect to the first direction 101 in a direction from the first bottom surface portion 36 to the second bottom surface portion 37. In the second cross section CS2, the second flank portion 8 is inclined with respect to the first direction 101 in a direction from the first bottom surface portion 36 to the second bottom surface portion 37.

[0187] Fig. 23 shows the cross section shown in Fig. 14. As shown in Fig. 23, in the third cross section CS3, the rake face 5 is inclined in the first direction 101 with respect to a plane perpendicular to the axis O. Specifically, the rake face 5 is inclined such that the distance between the rake face 5 and the first bottom surface 30 increases with increasing distance from the second cutting edge portion 12.

[0188] As shown in Fig. 24, when viewed perpendicular to the axis O and in a direction from the outermost point 89 toward the axis O, the ridge line 88 may be inclined with respect to the axis O. When viewed perpendicular to the axis O and in a direction from the outermost point 89 toward the axis O, the angle formed between the ridge line 88 and the axis O is defined as a twist angle φ2. Note that the direction of arrow E in Fig. 19 is perpendicular to the axis O and is the direction from the outermost point 89 toward the axis O. For ease of explanation, only one cutting edge 6 is shown in Fig. 24.

[0189] The twist angle φ2 is, for example, greater than 0° and equal to or less than 40°. The twist angle φ2 may be, for example, equal to or greater than 5°, or equal to or greater than 15°. The twist angle φ2 may be, for example, equal to or less than 35°, or equal to or less than 30°.

[0190] A skiving cutter 100 may be used to perform groove machining on a workpiece. Grooving is a process in which a cutting edge 1 is brought into contact with the surface of the workpiece to form a groove in the workpiece. If the helix angle φ2 is excessively large, the chips, which have become hot due to cutting, scrape the rake face 5 before their temperature can cool down. This causes excessive thermal damage to the cutting edge 3 near the multiple cutting edges 1. This results in an excessively short tool life.

[0191] According to the skiving cutter 100 of the fourth embodiment, the helix angle φ2 is 40° or less. Therefore, during groove machining, chips are more likely to be discharged in a direction perpendicular to the axis O. Therefore, high-temperature chips are less likely to scrape the rake face 5. This reduces thermal damage to the cutting edge 3 near the multiple cutting edges 1. As a result, wear on the cutting edge 3 can be suppressed.

[0192] (Fifth embodiment) Next, the configuration of the skiving cutter 100 according to the fifth embodiment will be described. The skiving cutter 100 according to the fifth embodiment differs from the skiving cutter 100 according to the first embodiment mainly in that a through hole is provided in the shaft portion 10, and in other respects is substantially the same as the skiving cutter 100 according to the first embodiment. Below, the differences from the skiving cutter 100 according to the first embodiment will be mainly described.

[0193] 25, a recess 95 may be provided in the first front end surface 51. The axis O passes through the recess 95. The first front end surface 51 surrounds the axis O. The first front end surface 51 has an annular shape.

[0194] The shaft portion 10 has a bottom surface (second bottom surface 53) of the recess 95. The second bottom surface 53 is formed by the base portion 2. A first through hole 96, a second through hole 97, and a plurality of fastening holes 98 are provided in the second bottom surface 53.

[0195] The first through hole 96 has a tapered shape. This makes it possible to prevent galling (seizure) when attaching the skiving cutter 100 to a tool spindle (not shown). This allows the skiving cutter 100 to be attached smoothly to the tool spindle. The second through hole 97 serves as a rotation stopper. Specifically, by inserting a part of the tool spindle into the second through hole 97, it is possible to prevent the skiving cutter 100 from rotating relative to the tool spindle. A screw (not shown) that fastens the skiving cutter 100 to the tool spindle is attached to each of the multiple fastening holes 98.

[0196] 26 shows the cross section shown in FIG. 4. As shown in FIG. 26, the axis O passes through the first through hole 96. The first through hole 96 penetrates the second bottom surface 53 and the third rear end surface 63. The base portion 2 forms an inner peripheral surface 54. The inner peripheral surface 54 forms the first through hole 96.

[0197] The first through hole 96 extends along the axis O. The diameter of the first through hole 96 increases with increasing distance from the second bottom surface 53. From another perspective, the distance between the axis O and the inner circumferential surface 54 increases with increasing distance from the second bottom surface 53.

[0198] Each of the multiple fastening holes 98 penetrates the second bottom surface 53 and the third rear end surface 63. Each of the multiple fastening holes 98 extends along the second direction 102. The second through hole 97 (see FIG. 25 ) penetrates the second bottom surface 53 and the third rear end surface 63.

[0199] Although the above description has been given of a configuration in which the skiving cutter 100 has a plurality of cutting edges 3, the configuration of the skiving cutter 100 according to the present disclosure is not limited to the above configuration. Specifically, the cutting edges 3 may be formed as a single component. For example, the cutting edges 3 may be annular in shape.

[0200] The cutting edge portion 3 may be detachable from the base portion 2. From another perspective, the cutting edge portion 3 and the base portion 2 may be separate bodies. When the cutting edge portion 3 and the base portion 2 are separate bodies, the cutting edge portion 3 does not need to have the brazing material layer 23. In this case, the cemented carbide layer 22 is in contact with the bearing surface 20 of the base portion 2. For example, when the cutting edge portion 3 is formed of multiple parts, the cutting edge portion 3 may be multiple throw-away tips. [Example]

[0201] (Sample preparation) The influence of the structure of the cBN sintered body on tool life was investigated. First, skiving cutters 100 according to Samples 1-1 to 1-19 were prepared. The skiving cutters 100 according to Samples 1-1 to 1-17 were examples. The skiving cutters 100 according to Samples 1-18 and 1-19 were comparative examples.

[0202] In Samples 1-1 to 1-17, the cutting edge layer 21 was made of sintered cBN, in Sample 1-18, the cutting edge layer 21 was made of TiN, and in Sample 1-19, the cutting edge layer 21 was made of cemented carbide.

[0203] In Samples 1-1 to 1-14, the cBN particle content of the cBN sintered body was 50% or more and 100% or less, and in Samples 1-15 to 1-17, the cBN particle content of the cBN sintered body was 15% or more and 45% or less.

[0204] In Samples 1-1 to 1-12 and 1-15 to 1-17, the average particle size of the cBN particles was 0.01 μm or more and 3 μm or less, and in Samples 1-13 and 1-14, the average particle size of the cBN particles was 4 μm or more.

[0205] In Samples 1-1 to 1-3 and 1-11 to 1-17, the binder was TiN. In Sample 1-4, the binder was Co. In Sample 1-5, the binder was TiC. In Sample 1-6, the binder was TiCN. In Sample 1-7, the binder was Al2O3 and ZrO2. In Sample 1-8, the binder was AlN. In Samples 1-9 and 1-10, no binder was included. In Samples 1-1 to 1-19, the number of cutting edges 6 was 30.

[0206] (Evaluation method) Cutting evaluation was performed using the skiving cutters 100 according to Samples 1-1 to 1-19. Specifically, grooves were cut into a workpiece using the skiving cutters 100. The workpiece was made of hardened steel. Specifically, the workpiece was made of chromium-molybdenum steel equivalent to SCM415 specified in JIS G 4053:2016. Carburizing and quenching were performed as a surface treatment on the workpiece. The hardness of the workpiece was 60 HRC or higher.

[0207] The module of the workpiece was set to 1.5. The pressure angle of the workpiece was set to 20°. The number of teeth of the workpiece was set to 68.

[0208] In groove machining, the sliding speed was 80 m / min. The cutting depth was 0.05 mm. The feed rate was 0.03 mm / rev. The cooling conditions were WET (water-soluble). The intersecting angle θ was 25°. The sliding speed is the relative speed of the skiving cutter to the workpiece at the intersection of the pitch circle of the workpiece and the pitch circle of the skiving cutter 100. The cutting depth is the cutting depth in the tooth depth direction of the workpiece. The feed rate is the movement distance of the skiving cutter per revolution of the workpiece.

[0209] The tool life was determined as the point when chipping occurred in the part of the skiving cutter 100 close to the cutting edge 1 or when the maximum flank wear width reached 0.2 mm. The cutting time until the tool life was reached was measured. The maximum flank wear width was the maximum value of the wear width in the direction of extension of the ridge line 88 of the flank 4.

[0210] (Evaluation results)

[0211] [Table 1]

[0212] The evaluation value column in Table 1 lists relative evaluation values, with the cutting time until the tool life of Sample 1-1 being set at 100%. As shown in Table 1, the evaluation values for the samples in which the cutting edge layer 21 was not formed of a cBN sintered body (Samples 1-18 and 1-19) were 20% or less.

[0213] On the other hand, the samples in which the cutting edge layer 21 was formed of a cBN sintered body (samples 1-1 to 1-17) had an evaluation score of 30% or more. Also, the samples in which the cBN particle content was 50% or more and the average particle size of the cBN particles was 3 μm or less (samples 1-1 to 1-12) had an evaluation score of 60% or more.

[0214] As described above, compared to the sample according to the comparative example, the sample according to the example was able to extend the tool life by suppressing fracture of the cutting edge portion 3. Furthermore, the sample having a cBN particle content of 50% or more and an average particle size of the cBN particles of 3 μm or less was able to effectively extend the tool life. [Example]

[0215] (Sample preparation) The influence of each of the rake angle φ1 and the helix angle φ2 on the tool life was investigated. First, the skiving cutters 100 according to Samples 2-1 to 2-10 were prepared. The skiving cutters 100 according to Samples 2-1 to 2-10 were examples.

[0216] In Samples 2-1 to 2-8 and 2-10, the rake angle φ1 was 0° or more and 40° or less. In Sample 2-9, the rake angle φ1 was 50°. In Samples 2-1 to 2-9, the helix angle φ2 was 0° or more and 40° or less. In Sample 2-10, the helix angle φ2 was 50°. In Samples 2-1 to 2-10, the number of cutting edges 6 was 30.

[0217] (Evaluation method) Cutting evaluation was performed using the skiving cutters 100 according to Samples 2-1 to 2-10. The skiving cutters 100 were used to perform groove machining on workpieces. The workpieces were made of hardened steel. Specifically, the workpieces were made of chromium-molybdenum steel equivalent to SCM415 as specified in JIS G 4053:2016. The workpieces were subjected to carburizing and quenching as a surface treatment. The hardness of the workpieces was 60HRC or higher.

[0218] The module of the workpiece was set to 1.5. The pressure angle of the workpiece was set to 20°. The number of teeth of the workpiece was set to 68.

[0219] In groove machining, the sliding speed was 80 m / min. The cutting depth was 0.05 mm. The feed rate was 0.03 mm / rev. The cooling conditions were WET (water-soluble). The crossing angle θ was 25°.

[0220] The tool life was determined as the time when chipping occurred in the part of the skiving cutter 100 near the cutting edge 1 or when the maximum flank wear width reached 0.2 mm. The cutting time until the tool life was reached was measured.

[0221] (Evaluation results)

[0222] [Table 2]

[0223] The evaluation value column in Table 2 lists relative evaluation values, with the cutting time until the tool life of Sample 2-2 being set at 100%. As shown in Table 2, Sample 2-9, which has a rake angle φ1 of 50°, had an evaluation value of 20%. Sample 2-10, which has a helix angle φ2 of 50°, had an evaluation value of 30%.

[0224] On the other hand, the samples (Samples 2-1 to 2-8) with a rake angle φ1 of 40° or less and a helix angle φ2 of 40° or less had an evaluation score of 60% or more, and the samples (Samples 2-2 to 2-6) with a rake angle φ1 of 5° or more and 15° or less had an evaluation score of 100% or more.

[0225] As described above, by setting the rake angle φ1 to 40° or less and the helix angle φ2 to 40° or less, it was possible to suppress wear of the cutting edge 3 and extend the tool life. In addition, by setting the rake angle φ1 to 5° or more and 15° or less, it was possible to effectively suppress wear of the cutting edge 3. [Example]

[0226] (Sample preparation) The influence of the diamond structure forming the cutting edge layer 21 on the tool life was investigated. First, skiving cutters 100 according to Samples 3-1 to 3-11 were prepared. The skiving cutters 100 according to Samples 3-1 to 3-10 were examples. The skiving cutter 100 according to Sample 3-11 was a comparative example.

[0227] In Samples 3-1 to 3-10, the cutting edge layer 21 was formed of diamond. Specifically, in Samples 3-1 to 3-4 and 3-7 to 3-10, the cutting edge layer 21 was formed of PCD. In Sample 3-5, the cutting edge layer 21 was formed of BLPCD. In Sample 3-6, the cutting edge layer 21 was formed of single crystal diamond. In Sample 3-11, the cutting edge layer 21 was formed of cemented carbide.

[0228] In samples 3-1 to 3-6 and 3-8 to 3-10, the diamond particle content was 80% or more and 100% or less. In sample 3-7, the diamond particle content was 70%. In samples 3-1 to 3-5 and 3-7 to 3-9, the average particle size of the diamond particles was 0.01 μm or more and 50 μm or less. In sample 3-10, the average particle size of the diamond particles was 100 μm.

[0229] In samples 3-1 to 3-4, 3-7 to 3-10, the binder phase was formed by cobalt, while in samples 3-5 and 3-6, the diamond had no binder phase.

[0230] In Samples 3-1 to 3-7 and 3-9 to 3-11, the rake angle φ1 was set to 10°. In Sample 3-8, the rake angle φ1 was set to 50°. In Samples 3-1 to 3-8, 3-10, and 3-11, the helix angle φ2 was set to 20°. In Sample 3-9, the helix angle φ2 was set to 50°. In Samples 3-1 to 3-11, the number of cutting edges 6 was 30.

[0231] (Evaluation method) Cutting evaluation was performed using the skiving cutters 100 according to Samples 3-1 to 3-11. Specifically, grooves were cut into the workpiece using the skiving cutters 100. The workpiece was made of PEEK (Polyether Ether Ketone). The Rockwell hardness (R scale) was 120.

[0232] The module of the workpiece was set to 1.5. The pressure angle of the workpiece was set to 20°. The number of teeth of the workpiece was set to 68.

[0233] In groove machining, the sliding speed was 100 m / min. The cutting depth was 0.2 mm. The feed rate was 0.06 mm / rev. The cooling conditions were WET (water-soluble). The crossing angle θ was 25°.

[0234] The tool life was determined as the time when chipping occurred in the part of the skiving cutter 100 near the cutting edge 1 or when the maximum flank wear width reached 0.2 mm. The cutting time until the tool life was reached was measured.

[0235] (Evaluation results)

[0236] [Table 3]

[0237] The evaluation value column in Table 3 lists relative evaluation values, with the cutting time until the tool life of sample 3-1 being set at 100%. As shown in Table 3, sample 3-11, in which the cutting edge layer 21 was not formed of diamond, had an evaluation value of 5%. On the other hand, the samples in which the cutting edge layer 21 was formed of diamond (samples 3-1 to 3-10) had evaluation values of 10% or more.

[0238] As described above, the tool life of the example samples was longer than that of the comparative example samples, and it is believed that the strength of the cutting edge layer 21 was improved in the example samples.

[0239] As shown in Table 3, Sample 3-7, which had a diamond particle content of 70%, had an evaluation score of 40%. On the other hand, Samples 3-1 and 3-3, which had a diamond particle content of 80% or more, had evaluation scores of 100% or more. As described above, a diamond particle content of 80% or more could extend the tool life. It is believed that a diamond particle content of 80% or more improved the strength of the cutting edge layer 21.

[0240] As shown in Table 3, Sample 3-10, in which the average grain size of the diamond particles was 100 μm, had an evaluation value of 10%. On the other hand, Samples 3-3 and 3-4, in which the average grain size of the diamond particles was 50 μm or less, had evaluation values of 105% or more. As described above, by having an average grain size of the diamond particles of less than 100 μm, it was possible to extend the tool life. In Sample 3-10, it is believed that the average grain size of the diamond particles was 100 μm, which caused poor sintering of the diamond particles.

[0241] As shown in Table 3, Sample 3-8, which had a rake angle φ1 of 50°, had an evaluation score of 25%. On the other hand, Sample 3-3, which had a rake angle φ1 of 10°, had an evaluation score of 105%. As described above, tool life could be extended by keeping the rake angle φ1 at 40° or less.

[0242] As shown in Table 3, Sample 3-9, in which the helix angle φ2 was 50°, had an evaluation score of 35%. On the other hand, Sample 3-3, in which the helix angle φ2 was 20°, had an evaluation score of 105%. As described above, by keeping the helix angle φ2 at 40° or less, the tool life could be extended.

[0243] As shown in Table 3, the evaluation values for the samples in which the diamond was BLPCD or single crystal diamond (samples 3-5 and 3-6) were 130% or more. As described above, tool life could be extended by using BLPCD or single crystal diamond. [Example]

[0244] (Sample preparation) The influence of the configuration of the cemented carbide forming the cutting edge layer 21 on the tool life was investigated. First, skiving cutters 100 according to Samples 4-1 to 4-21 were prepared. The skiving cutters 100 according to Samples 4-1 to 4-16 were examples. The skiving cutters 100 according to Samples 4-17 to 4-21 were comparative examples.

[0245] <Creating the cutting edge layer>

[0246] [Table 4]

[0247] [Table 5]

[0248] [Table 6]

[0249] The cutting edge layer 21 of each sample was fabricated using the conditions shown in Tables 4 to 6. Specifically, first, WC powder, Co powder, first element powder, NiCr powder, and TiNbCN powder were prepared as raw material powders (preparation step). As the first element powders, silicon (Si) powder, rhenium (Re) powder, phosphorus (P) powder, germanium (Ge) powder, tin (Sn) powder, ruthenium (Ru) powder, osmium (Os) powder, iridium (Ir) powder, and platinum (Pt) powder were prepared. The average particle size of each powder was 1 μm.

[0250] A mixed powder was prepared by mixing the raw material powders in the proportions shown in Table 4 using an attritor (mixing step). The mixing time was 10 hours. The proportions (mass%) of the raw material powders shown in Table 1 are the proportions when the total mixed powder is taken as 100 mass%.

[0251] Next, the mixed powder was pressed to produce a molded body having the shape of the cutting edge layer 21 (molding step). Thereafter, the molded body was heated to the temperature shown in the "Holding temperature" column at the heating rate shown in the "Heating rate" column of Table 5. This temperature was maintained for the time shown in the "Holding time" column (sintering step). After the sintering step, the molded body was cooled to 800°C at the heating rate shown in the "Heating rate" column of Table 5 (first cooling step).

[0252] Samples 4-1, 4-3 to 4-21 were subjected to a HIP process and a second cooling process. In the HIP process, the pressure and the temperature were maintained at the pressure and the temperature, respectively, listed in the "Pressure" and "Temperature" columns of Table 6 for the time periods listed in the "Time" column.

[0253] After the HIP process, a second cooling process was carried out. Specifically, the temperature was cooled to 800°C at the cooling rate shown in the "Cooling Rate" column in Table 6. After cooling to 800°C, the compact was slowly cooled to produce the cutting edge layer 21 of each sample.

[0254] In Samples 4-1 to 4-16, the cutting edge layer 21 was formed of the special cemented carbide. The binder phase content in the special cemented carbide was 0.73% or more and 27.20% or less. The binder phase contained cobalt and the first element. The cobalt content in the binder phase was 50% or more and 99% or less.

[0255] In Samples 4-17 to 4-21, the cutting edge layer 21 was formed of a cemented carbide other than the above-mentioned special cemented carbide. Specifically, in Samples 4-17 and 4-18, the binder phase of the cemented carbide forming the cutting edge layer 21 did not contain the first element. In Sample 4-19, the cobalt content in the binder phase was 48%. In Sample 4-20, the binder phase content in the cemented carbide was 0.6%. In Sample 4-21, the binder phase content in the cemented carbide was 28.8%. In Samples 4-1 to 4-21, the number of cutting edges 6 was 30.

[0256] (Evaluation method) Cutting evaluation was performed using the skiving cutters 100 according to Samples 4-1 to 4-21. Specifically, grooves were cut into workpieces using the skiving cutters 100. The workpieces were made of hardened steel. Specifically, the workpieces were made of chromium-molybdenum steel equivalent to SCM415 as specified in JIS G 4053:2016. Carburizing and quenching were performed as a surface treatment on the workpieces. The hardness of the workpieces was 60 HRC or higher.

[0257] The module of the workpiece was set to 1.5. The pressure angle of the workpiece was set to 20°. The number of teeth of the workpiece was set to 68.

[0258] In groove machining, the sliding speed was 80 m / min. The cutting depth was 0.05 mm. The feed rate was 0.03 mm / rev. The cooling conditions were WET (water-soluble). The crossing angle θ was 25°.

[0259] The tool life was determined as the time when chipping occurred in the part of the skiving cutter 100 near the cutting edge 1 or when the maximum flank wear width reached 0.2 mm. The cutting time until the tool life was reached was measured.

[0260] (Evaluation results)

[0261] [Table 7]

[0262] The evaluation value column in Table 7 lists relative evaluation values, with the cutting time until the tool life of sample 4-2 is set to 100%. As shown in Table 7, the evaluation values for the samples in which the cutting edge layer 21 was not formed of the special cemented carbide (samples 4-17 to 4-21) were 40% or less. On the other hand, the evaluation values for the samples in which the cutting edge layer 21 was formed of the special cemented carbide (samples 4-1 to 4-16) were 90% or more.

[0263] As described above, the tool life of the samples according to the examples was longer than that of the samples according to the comparative examples. It is believed that the wear resistance of the cutting edge layer 21 was improved by forming the cutting edge layer 21 from a special cemented carbide.

[0264] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof. [Explanation of symbols]

[0265] 1 cutting edge, 2 base portion, 3 cutting edge portion, 4 flank face, 5 rake face, 6 cutting edge portion, 7 first flank face portion, 8 second flank face portion, 9 bottom portion, 10 shank portion, 11 first cutting edge portion, 12 second cutting edge portion, 13 corner cutting edge portion, 19 coating, 20 bearing surface, 21 cutting edge layer, 22 cemented carbide layer, 23 brazing material layer, 26 first boundary line, 27 second boundary line, 28 third boundary line, 29 fourth boundary line, 30 first bottom surface, 31 first ridge line portion, 32 second ridge line portion, 33 corner ridge line portion, 36 first bottom surface portion, 37 second bottom surface portion, 41 first tangent line, 42 second tangent line, 43 third tangent line, 51 first front end surface, 52 second front end surface, 53 second bottom surface, 54 inner peripheral surface, 55 Side wall surface, 56 First outer peripheral surface, 57 Second outer peripheral surface, 58 First inclined surface, 59 Second inclined surface, 61 First rear end surface, 62 Second rear end surface, 63 Third rear end surface, 66 Connection surface, 71 First part, 72 Second part, 73 First corner surface portion, 81 Third part, 82 Fourth part, 83 Second corner surface portion, 88 Ridge line, 90 Workpiece material, 91 Machined surface, 95 Recess, 96 First through hole, 97 Second through hole, 98 Fastening hole, 99 Straight line, 100 Skiving cutter, 101 First direction, 102 Second direction, A Radius of curvature, B, F Arrows, C Rotation axis, CS1 First cross section, CS2 Second cross section, CS3 Third cross section, H1 First thickness, H2 Second thickness, H3 Third thickness, L1 First length, L2 Second length, L3 Third length, O axis, R direction of rotation, θ intersecting angle, φ1 rake angle, φ2 helix angle.

Claims

1. A skiving cutter that rotates around an axis and has a plurality of cutting edges arranged in an annular shape around the axis, a base portion; A cutting edge portion connected to the base portion and arranged alongside the base portion in a first direction toward the front of the skiving cutter along the axis, the base portion is formed of either a cemented carbide or a high-speed steel, The cutting edge portion is a cutting edge layer forming the plurality of cutting edges; a cemented carbide layer provided between the cutting edge layer and the base portion, the cutting edge layer is formed of one of a cubic boron nitride sintered body, a diamond, and a special cemented carbide; The special cemented carbide has tungsten carbide particles and a binder phase containing cobalt, In the special cemented carbide, the percentage of the volume of the binder phase divided by the volume of the entire special cemented carbide is 0.7% or more and 28% or less, In the binder phase, the percentage of the mass of cobalt divided by the mass of the entire binder phase is 50% or more; the binder phase further comprises at least one element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum; The skiving cutter is a shaft portion having an outer circumferential surface provided around the axis; a plurality of blade portions connected to the shaft portion and extending radially outward from the outer circumferential surface, Each of the plurality of blade portions forms one of the plurality of cutting edges, Each of the plurality of blade portions is a first flank portion formed by the cutting edge portion and connected to the plurality of cutting edges; a second flank portion formed by the base portion and provided in a second direction toward the rear of the skiving cutter along the axis relative to the first flank portion; The cutting edge portion is a first bottom surface portion in contact with the base portion; a second bottom surface portion that is continuous with the first relief surface portion and the first bottom surface portion and is provided on the outer side of the base portion, The ridge line between the first flank portion and the second bottom surface portion is A first ridge portion; a corner ridge portion that is continuous with the first ridge portion and is provided radially outward of the first ridge portion, A skiving cutter, wherein when the length of the second bottom surface portion between the first ridge portion and the second relief surface portion in a cross section perpendicular to a tangent to the first ridge portion as viewed along the axis is defined as a first length, the first length is 150 μm or less.

2. The ridge between the first relief surface portion and the second bottom surface portion has a second ridge portion that is connected to the corner ridge portion and is provided in a rotational direction relative to the first ridge portion, When the length of the second bottom surface portion between the second ridge line portion and the second relief surface portion in a cross section perpendicular to a tangent line of the second ridge line portion as viewed along the axis is defined as a second length, The skiving cutter according to claim 1 , wherein the first length is the same as the second length.

3. The ridge between the first relief surface portion and the second bottom surface portion has a second ridge portion that is connected to the corner ridge portion and is provided in a rotational direction relative to the first ridge portion, When the length of the second bottom surface portion between the second ridge line portion and the second relief surface portion in a cross section perpendicular to a tangent line of the second ridge line portion as viewed along the axis is defined as a second length, The skiving cutter according to claim 1 , wherein the first length is different from the second length.

4. Each of the plurality of blade portions is a rake face connected to the plurality of cutting edges and formed by the cutting edge layer; a trailing surface opposite the rake surface and formed by the base portion; The skiving cutter according to claim 1 , wherein the rear end surface overlaps the rake surface when viewed along the axis.

5. Each of the plurality of blade portions is a rake face connected to the plurality of cutting edges and formed by the cutting edge layer; a trailing surface opposite the rake surface and formed by the base portion; The skiving cutter according to claim 1, wherein the rake face is provided in a rotational direction relative to the rear end surface when viewed along the axis.

6. the cutting edge portion includes a brazing material layer provided on the base portion, The skiving cutter according to claim 1 , wherein the cemented carbide layer is provided on the brazing material layer.

7. The skiving cutter according to any one of claims 1 to 5, wherein the cutting edge layer has a maximum thickness of 0.3 mm or more and 3 mm or less in the first direction.

8. The skiving cutter according to any one of claims 1 to 5, further comprising a coating covering at least a portion of the cutting edge.

9. The skiving cutter according to any one of claims 1 to 5, wherein the curvature radius of the plurality of cutting edges in a cross section perpendicular to the plurality of cutting edges is 10 µm or more and 40 µm or less.

10. the cutting edge layer is formed from the cubic boron nitride sintered body, the cubic boron nitride sintered body contains cubic boron nitride particles, In the cubic boron nitride sintered body, the percentage of the volume of the cubic boron nitride particles divided by the volume of the entire cubic boron nitride sintered body is 50% or more and 100% or less; The skiving cutter according to any one of claims 1 to 5, wherein the cubic boron nitride particles have an average particle size of 0.01 µm or more and 3 µm or less.

11. In the cubic boron nitride sintered body, the percentage of the volume of the cubic boron nitride particles divided by the total volume of the cubic boron nitride sintered body is less than 100%; the cubic boron nitride sintered body contains a binder; The skiving cutter according to claim 10, wherein the bond material includes at least one element selected from the group consisting of titanium, cobalt, aluminum, and zirconium.

12. Each of the plurality of blade portions is a rake face connected to the plurality of cutting edges and formed by the cutting edge layer; a flank surface connected to the rake surface via the plurality of cutting edges, the flank is formed by the first flank portion and the second flank portion, In each of the plurality of blade portions, When the point located on the outermost periphery as viewed along the axis is defined as the outermost periphery point, In a cross section including the axis and passing through the outermost periphery, an angle formed between a straight line perpendicular to the axis and the rake face is equal to or greater than 0° and equal to or less than 40°, 2. The skiving cutter according to claim 1, wherein an angle formed between the ridge line of the relief surface and the axis when viewed in a direction perpendicular to the axis and from the outermost peripheral point toward the axis is greater than or equal to 0° and less than or equal to 40°.

13. the cutting edge layer is formed from the diamond, the diamond is a polycrystalline diamond containing a plurality of diamond grains; 6. The skiving cutter according to claim 1, wherein the percentage of the volume of the plurality of diamond particles divided by the volume of the entire diamond is 80% or more and 100% or less.

14. The skiving cutter according to claim 13, wherein the average particle size of the plurality of diamond particles is equal to or greater than 0.01 μm and less than 100 μm.

15. the cutting edge layer is formed from the diamond, The skiving cutter according to any one of claims 1 to 5, wherein the diamond is a single crystal diamond.

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