Cutting Tools

Abstract

The cutting tool has a main body and a cutting edge layer. The main body is rod-shaped. The cutting edge layer is provided at a front end of the main body. The cutting edge layer forms a cutting edge. The main body is formed of a cemented carbide containing tungsten carbide and cobalt. The cutting edge layer is formed of polycrystalline diamond. In the cemented carbide, the weight of the tungsten carbide divided by the weight of the entire cemented carbide is a percentage of 90.0% or more and 95.0% or less. In the cemented carbide, the weight of the cobalt divided by the weight of the entire cemented carbide is a percentage of 4.0% or more and 9.0% or less.

Description

[Technical field]

[0001] The present disclosure relates to cutting tools. [Background technology]

[0002] Japanese Utility Model Publication No. 59-183301 (Patent Document 1) discloses a boring tool in which a composite cutting edge tip is brazed into a tip seat provided at the tip of a cylindrical tool body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Jpn. Jpn. Published No. 59-183301 Summary of the Invention

[0004] The cutting tool according to the present disclosure includes a body and a cutting edge layer. The body is rod-shaped. The cutting edge layer is provided at a front end of the body. The cutting edge layer forms a cutting edge. The body is formed of a cemented carbide containing tungsten carbide and cobalt. The cutting edge layer is formed of polycrystalline diamond. In the cemented carbide, the weight of the tungsten carbide divided by the weight of the entire cemented carbide is a percentage of 90.0% or more and 95.0% or less. In the cemented carbide, the weight of the cobalt divided by the weight of the entire cemented carbide is a percentage of 4.0% or more and 9.0% or less. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic plan view showing the configuration of a cutting tool according to this embodiment. [Diagram 2] FIG. 2 is an enlarged schematic view showing region II in FIG. [Diagram 3] FIG. 3 is a schematic side view showing the configuration of the cutting tool according to this embodiment. [Figure 4] FIG. 4 is a schematic front view showing the configuration of the cutting tool according to this embodiment. [Diagram 5] FIG. 5 is a schematic cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a schematic diagram showing the configuration of a cutting tool as viewed along the direction in which the first cutting edge portion extends. [Figure 8] FIG. 8 is a schematic diagram showing the configuration of the cutting tool as viewed along the direction in which the second cutting edge portion extends. [Figure 9] FIG. 9 is a partial cross-sectional schematic view illustrating a state in which the cutting tool according to this embodiment is used. [Figure 10] FIG. 10 is an enlarged schematic view showing a state in which a workpiece is being cut using the cutting tool according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] [Problem that this disclosure aims to solve] When a workpiece is cut using a cutting tool, the body of the cutting tool may vibrate, which may increase the surface roughness of the machined surface of the workpiece.

[0007] An object of the present disclosure is to provide a cutting tool capable of reducing the surface roughness of a machined surface of a workpiece.

[0008] [Effects of this disclosure] According to the present disclosure, it is possible to provide a cutting tool capable of reducing the surface roughness of the machined surface of a workpiece.

[0009] [Overview of the embodiment] First, an overview of the embodiments of the present disclosure will be described.

[0010] (1) The cutting tool according to the present disclosure has a main body and a cutting edge layer. The main body is rod-shaped. The cutting edge layer is provided at the front end of the main body. The cutting edge layer forms a cutting edge. The main body is formed of a cemented carbide containing tungsten carbide and cobalt. The cutting edge layer is formed of polycrystalline diamond. In the cemented carbide, the percentage of the weight of tungsten carbide divided by the weight of the entire cemented carbide is 90.0% or more and 95.0% or less. In the cemented carbide, the percentage of the weight of cobalt divided by the weight of the entire cemented carbide is 4.0% or more and 9.0% or less. Therefore, the vibration of the cutting tool can be suppressed when machining the workpiece. This can reduce the surface roughness of the machined surface of the workpiece.

[0011] (2) According to the cutting tool of (1) above, the percentage of the weight of cobalt in the cemented carbide divided by the weight of the entire cemented carbide may be 5.0% or more and 8.0% or less. This effectively prevents an excessive decrease in the transverse rupture strength of the main body. Therefore, breakage of the main body can be effectively prevented.

[0012] (3) According to the cutting tool of (1) or (2) above, the polycrystalline diamond may contain a plurality of diamond particles. In the polycrystalline diamond, the weight of the binder that binds the plurality of diamond particles divided by the weight of the entire polycrystalline diamond may be 10.0% or less or 0%. This can improve the wear resistance of the cutting edge layer.

[0013] (4) According to the cutting tool of (3) above, in the polycrystalline diamond, the percentage of the weight of the binder divided by the weight of the entire polycrystalline diamond may be 1.0% or less or 0%, which can effectively improve the wear resistance of the cutting edge layer.

[0014] (5) According to the cutting tool of any one of (1) to (4) above, the diameter of the main body may be 6 mm or less. This makes it possible to perform internal machining even when the internal diameter of the workpiece is relatively small.

[0015] (6) The cutting tool according to any one of (1) to (5) above may have a brazing material. The brazing material may join the cutting edge layer and the main body. The brazing material may contain silver, copper, and titanium. This can improve the rigidity of the entire cutting tool.

[0016] (7) According to the cutting tool according to any one of (1) to (6) above, the cutting edge may have a corner cutting edge portion, a first cutting edge portion, and a second cutting edge portion. The corner cutting edge portion may have a first end point and a second end point. The second end point may be opposite to the first end point. The first cutting edge portion may be connected to the corner cutting edge portion at the first end point. The first cutting edge portion may be provided in a direction from the front end to the rear end along the axis of the main body portion with respect to the corner cutting edge portion. The second cutting edge portion may be connected to the corner cutting edge portion at the second end point. The second cutting edge portion may be provided in a direction from the corner cutting edge portion to the axis with respect to the corner cutting edge portion. The cutting edge layer may have a first flank surface. When viewed along the direction in which the first cutting edge portion extends, the first flank surface may be inclined in a direction from the first cutting edge portion toward the axis line with respect to an imaginary line that is perpendicular to an imaginary plane including the corner cutting edge portion and the first cutting edge portion and intersects with the first cutting edge portion, and the angle between the imaginary line and the first flank surface may be 7° or more and 13° or less. When viewed perpendicular to the imaginary plane, the first cutting edge portion may be inclined in a direction from the first end point toward the axis line with the first end point as a fulcrum, and the angle between the axis line and the first cutting edge portion may be 2° or more and 4° or less.

[0017] This makes it possible to effectively reduce the surface roughness of the machined surface of the workpiece while suppressing a decrease in the strength of the cutting edge.

[0018] (8) According to the cutting tool according to the above (7), the cutting edge layer may have a second flank. The second flank may be continuous with the first flank. The second flank may be on the opposite side of the first cutting edge portion with respect to the first flank. When viewed along the direction in which the first cutting edge portion extends, the second flank may be inclined with respect to the imaginary straight line in a direction from the first cutting edge portion toward the axis, and the angle between the imaginary straight line and the second flank may be 20° or more. The width of the first flank in the direction in which the imaginary straight line extends may be 0.4 mm or less. This makes it possible to prevent contact between the cutting edge layer and the workpiece when performing internal diameter machining on a workpiece having a small internal diameter.

[0019] [Details of the embodiment] Hereinafter, the details of an embodiment of the present disclosure (hereinafter also referred to as the present embodiment) will be described with reference to the drawings. Note that in the following drawings, the same or corresponding parts are given the same reference numerals, and the description thereof will not be repeated.

[0020] <Cutting tool configuration> First, the configuration of a cutting tool 100 according to this embodiment will be described.

[0021] FIG. 1 is a schematic plan view showing the configuration of a cutting tool 100 according to this embodiment. The cutting tool 100 is a turning tool that turns a rotating workpiece (not shown) by bringing a cutting edge 10 into contact with the workpiece. Specifically, the cutting tool 100 is, for example, a boring tool. In other words, the cutting tool 100 is used, for example, for processing to enlarge the inner diameter of the workpiece. More specifically, the cutting tool 100 is used, for example, for processing to enlarge the inner diameter of the workpiece and with a relatively small cutting depth.

[0022] As shown in FIG. 1, the cutting tool 100 has a body 3 and a cutting edge layer 4. The body 3 is rod-shaped. The body 3 extends along an axis X. The body 3 has a front end 1 and a rear end 2. The front end 1 is a portion that faces a workpiece. The rear end 2 is a portion that faces a machine tool (not shown) that supports the cutting tool 100.

[0023] The main body 3 extends in a direction from the front end 1 to the rear end 2 along the axis X. In this specification, the direction from the front end 1 to the rear end 2 along the axis X is also referred to as a first direction 101. The length L1 of the main body 3 in the first direction 101 is, for example, 30 mm or more. The main body 3 is made of a cemented carbide. The cemented carbide is a sintered body containing tungsten carbide particles as a main component. The specific composition of the cemented carbide forming the main body 3 will be described later.

[0024] The cutting edge layer 4 is provided on the front end 1 of the main body 3. The cutting edge layer 4 forms a cutting edge 10. The cutting edge layer 4 is made of polycrystalline diamond. The specific composition of the polycrystalline diamond that forms the cutting edge layer 4 will be described later.

[0025] <Composition of cemented carbide> The cemented carbide forming the main body 3 contains tungsten carbide (WC) and cobalt (Co). The cemented carbide contains a hard phase and a binder phase. The hard phase is substantially composed of WC particles. The binder phase bonds the WC particles to each other. The binder phase contains Co and the like. In this specification, the percentage of the weight of a component contained in a substance divided by the weight of the entire substance is referred to as the content of that component in the substance.

[0026] The WC content in the cemented carbide forming the main body 3 (WC content) is 90.0% or more and 95.0% or less. The WC content may be, for example, 91.0% or more, or 93.0% or more. The WC content may be, for example, 94.7% or less, or 94.3% or less.

[0027] The content of Co in the cemented carbide forming the main body 3 (Co content) is 4.0% or more and 9.0% or less. The Co content may be, for example, 5.0% or more and 8.0% or less, or 5.0% or more and 7.0% or less. The Co content may be, for example, 4.3% or more, or 4.7% or more. The Co content may be, for example, 8.5% or less, 7.5% or less, or 6.5% or less.

[0028] The sum of the WC content and the Co content may be, for example, 98% or more, or 99% or more. The sum of the WC content and the Co content may be 100% or less than 100%. From another perspective, the cemented carbide forming the main body 3 may contain components other than WC and Co. The binder phase may contain, for example, TiC (titanium carbide), TaC (tantalum carbide), NbC (niobium carbide), or the like. The cemented carbide forming the main body 3 may contain inevitable impurities.

[0029] <Composition of polycrystalline diamond> The polycrystalline diamond forming the cutting edge layer 4 contains a plurality of diamond particles. The polycrystalline diamond forming the cutting edge layer 4 may be polycrystalline sintered diamond (PCD: Poly-Crystalline Diamond) or binderless polycrystalline diamond (hereinafter also referred to as BLPCD).

[0030] PCD is composed of, for example, a binder and multiple diamond particles. BLPCD is polycrystalline diamond in which multiple diamond particles are bonded together without a binder. In other words, BLPCD does not contain a binder. The binder is composed of Co. The binder may contain inevitable impurities such as TiC in addition to Co. The polycrystalline diamond forming the cutting edge layer 4 may be nano-polycrystalline diamond. Nano-polycrystalline diamond refers to polycrystalline diamond in which the grain size of multiple diamond particles is on the order of nanometers.

[0031] The content of the binder in the polycrystalline diamond forming the cutting edge layer 4 (binder content) is, for example, 0%. When the polycrystalline diamond is BLPCD, the binder content is 0%. From another perspective, the polycrystalline diamond may be composed of a plurality of diamond grains and inevitable impurities.

[0032] The binder content may be 10.0% or less. The binder content may be, for example, 0.01% or more, or 0.1% or more. The binder content may be, for example, 5.0% or less, 1.0% or less, or 0.5% or less.

[0033] The WC content, Co content, and binder content can be measured by the following measurement method using an energy dispersive X-ray spectroscopy (EDX) attached to a field emission scanning electron microscope (FE-SEM). For example, Gemini450 manufactured by ZEISS and Ultim Max manufactured by Oxford Instruments can be used as the FE-SEM and EDX.

[0034] When measuring the WC content and the Co content, first, the main body 3 is embedded in a resin. The main body 3 is cut to expose a cross section of the main body 3. The exposed cross section is then polished to prepare a polished surface for observation. Five arbitrary locations (five fields of view) of the polished surface for observation are observed at a magnification of 3000 times using EDX to perform elemental analysis. This allows the content (weight %) of each element to be determined. The composition of the cemented carbide forming the main body 3 can be identified by determining the average value of the values ​​of the above five fields of view for each element. The WC content and the Co content can be determined using the identified composition of the cemented carbide. The resin for embedding the main body 3 can be a thermosetting resin or the like.

[0035] A conventionally known method can be used for polishing the cross section of the main body 3. For example, a smoothed polished surface for observation can be obtained by subjecting the cross section of the main body 3 to ion milling treatment using argon ions. The conditions for the ion milling treatment using Ar ions are, for example, as follows. Accelerating voltage: 6kV Irradiation angle: 0° to 5° from a plane parallel to the cross section of the main body 3 Irradiation time: 6 hours

[0036] Similarly, when measuring the binder content, the composition of the polycrystalline diamond forming the cutting edge layer 4 can be identified by using the above-mentioned measurement method for the cutting edge layer 4. The binder content can be determined using the identified composition of the polycrystalline diamond. Specifically, the Co content in the polycrystalline diamond can be taken as the binder content.

[0037] <More specific configuration of cutting tools> Fig. 2 is an enlarged schematic view showing region II in Fig. 1. Fig. 3 is a schematic side view showing the configuration of the cutting tool 100 according to this embodiment. As shown in Figs. 2 and 3, the main body 3 has a seat surface 31, a side wall surface 32, an outer circumferential surface 33, and a front end surface 34.

[0038] The seating surface 31 is, for example, flat. The side wall surface 32 is continuous with the seating surface 31. The side wall surface 32 is, for example, perpendicular to the seating surface 31. The seating surface 31 and the side wall surface 32 form a recess 39. The cutting edge layer 4 is disposed in the recess 39.

[0039] The outer peripheral surface 33 has a flat surface portion 36 and a curved surface portion 37. The flat surface portion 36 is flat. The flat surface portion 36 is, for example, parallel to the seating surface 31. The flat surface portion 36 is continuous with the side wall surface 32. The curved surface portion 37 is continuous with each of the seating surface 31 and the side wall surface 32.

[0040] The front end surface 34 is located at the front end 1 of the main body portion 3. The front end surface 34 is continuous with each of the seat surface 31, the side wall surface 32, the flat portion 36, and the curved portion 37.

[0041] As shown in FIG. 2, the cutting edge 10 has a corner cutting edge portion 8, a first cutting edge portion 6, and a second cutting edge portion 7. The corner cutting edge portion 8 is provided in a direction opposite to a first direction 101 with respect to the body portion 3. The corner cutting edge portion 8 has a first end point 81 and a second end point 82. In the corner cutting edge portion 8, the second end point 82 is opposite to the first end point 81. The first end point 81 is located in the first direction 101 with respect to the second end point 82. At the first end point 81, the first cutting edge portion 6 is continuous with the corner cutting edge portion 8. The first cutting edge portion 6 is provided in the first direction 101 with respect to the corner cutting edge portion 8.

[0042] In FIG. 2, the dashed line indicates an imaginary plane 95. The imaginary plane 95 includes the first cutting edge portion 6 and the corner cutting edge portion 8. From another perspective, the first cutting edge portion 6 and the corner cutting edge portion 8 are, for example, substantially on the same plane. The imaginary plane 95 may include the axis line X. In FIG. 2, the configuration of the cutting tool 100 viewed perpendicularly to the imaginary plane 95 is shown. When viewed perpendicularly to the imaginary plane 95, the direction from the first end point 81 toward the axis line X is set as the second direction 102. The second direction 102 is perpendicular to the axis line X. The imaginary plane 95 extends, for example, along each of the first direction 101 and the second direction 102.

[0043] 2, the corner cutting edge portion 8 is curved when viewed perpendicularly to the imaginary plane 95. When viewed perpendicularly to the imaginary plane 95, the corner cutting edge portion 8 may be, for example, arc-shaped. When viewed perpendicularly to the imaginary plane 95, the radius of curvature of the corner cutting edge portion 8 is, for example, 0.05 mm or more and 0.5 mm or less.

[0044] 2, the first cutting edge portion 6 is, for example, linear. When viewed perpendicularly to the imaginary plane 95, the first cutting edge portion 6 is inclined in the second direction 102 with respect to the axis X, with the first end point 81 as a fulcrum. From another perspective, when viewed perpendicularly to the imaginary plane 95, the distance between the first cutting edge portion 6 and the axis X becomes shorter as the distance from the first end point 81 increases. The first imaginary straight line 91 shown in FIG. 2 is a straight line parallel to the axis X.

[0045] When viewed perpendicularly to the imaginary plane 95, the inclination angle of the first cutting edge portion 6 with respect to the axis X is defined as a first angle θ1. The first angle θ1 is, for example, 2° or more and 4° or less. The first angle θ1 may be, for example, 2.3° or more, or 2.7° or more. The first angle θ1 may be, for example, 3.7° or less, or 3.3° or less.

[0046] The first cutting edge portion 6 is provided in a direction opposite to the second direction 102 with respect to the outer peripheral surface 33 of the main body portion 3. In the second direction 102, the first cutting edge portion 6 is provided between the outer peripheral surface 33 and the first end point 81.

[0047] The second cutting edge portion 7 is provided in a second direction 102 relative to the corner cutting edge portion 8. From another perspective, the second cutting edge portion 7 is provided in a direction from the corner cutting edge portion 8 toward the axis X. At a second end point 82, the second cutting edge portion 7 is continuous with the corner cutting edge portion 8. From another perspective, in the cutting edge 10, the corner cutting edge portion 8 is between the first cutting edge portion 6 and the second cutting edge portion 7.

[0048] The second cutting edge portion 7 is, for example, linear. When viewed perpendicularly to the imaginary plane 95, the second cutting edge portion 7 is inclined in the first direction 101 with respect to the second imaginary straight line 92, with the second end point 82 as a fulcrum. When viewed perpendicularly to the imaginary plane 95, the second imaginary straight line 92 is a straight line perpendicular to the axis X.

[0049] When viewed perpendicularly to the imaginary plane 95, the inclination angle of the second cutting edge portion 7 with respect to the second imaginary line 92 is set to a second angle θ2. The second angle θ2 is, for example, 3°. The second angle θ2 may be, for example, not less than 2° and not more than 4°.

[0050] When viewed perpendicularly to the imaginary plane 95, the front end surface 34 of the body portion 3 may be substantially parallel to the second cutting edge portion 7. The front end surface 34 is located in a first direction 101 relative to the second cutting edge portion 7. In the first direction 101, the second cutting edge portion 7 is provided between the front end surface 34 and the second end point 82.

[0051] As shown in FIG. 2, the cutting edge layer 4 has a rake face 11 and a curved surface 18. The rake face 11 is continuous with the cutting edge 10. Specifically, the rake face 11 is continuous with each of the corner cutting edge portion 8, the first cutting edge portion 6, and the second cutting edge portion 7. The rake face 11 is, for example, planar. The rake face 11 extends along, for example, an imaginary plane 95. The curved surface 18 is continuous with the rake face 11. When viewed perpendicularly to the imaginary plane 95, the curved surface 18 is, for example, arc-shaped.

[0052] 3, the cutting edge layer 4 has a bottom surface 41, a first flank surface 12, a second flank surface 19, and a corner flank surface 13. The bottom surface 41 is opposite to the rake face 11. A direction perpendicular to the imaginary plane 95 and extending from the rake face 11 toward the bottom surface 41 is defined as a third direction 103.

[0053] The first flank 12 is continuous with the first cutting edge portion 6. The first cutting edge portion 6 is formed by a ridge between the first flank 12 and the rake face 11. The first flank 12 is provided in a third direction 103 with respect to the rake face 11. The second flank 19 is continuous with each of the first flank 12 and the bottom face 41. The second flank 19 is provided in the third direction 103 with respect to the first flank 12. From another point of view, the second flank 19 is opposite the first cutting edge portion 6 with respect to the first flank 12. In the third direction 103, the second flank 19 is provided between the first flank 12 and the bottom face 41.

[0054] The corner flank 13 is continuous with the corner cutting edge portion 8. The corner cutting edge portion 8 is formed by a ridgeline between the corner flank 13 and the rake face 11. The corner flank 13 is continuous with each of the first flank 12 and the second flank 19. The curved surface 18 is continuous with each of the rake face 11, the first flank 12, the second flank 19, and the bottom surface 41.

[0055] As shown in FIG. 3, the front end surface 34 has a first front end surface portion 21 and a second front end surface portion 22. The first front end surface portion 21 is continuous with the flat portion 36. When viewed in the second direction 102, the first front end surface portion 21 extends along the third direction 103. The second front end surface portion 22 is provided in the third direction 103 with respect to the first front end surface portion 21. When viewed in the second direction 102, the second front end surface portion 22 is inclined in the first direction 101 with respect to the first front end surface portion 21. Note that FIG. 3 shows the configuration of the cutting tool 100 viewed in the second direction 102.

[0056] Fig. 4 is a schematic front view showing the configuration of the cutting tool 100 according to this embodiment. Fig. 4 shows the configuration of the cutting tool 100 as viewed in a first direction 101. As shown in Fig. 4, the cutting edge layer 4 has a third flank 14 and a side surface 42. The third flank 14 is continuous with the corner flank 13, the bottom surface 41, and the second cutting edge portion 7.

[0057] The third flank 14 is provided in a third direction 103 relative to the second cutting edge portion 7. The second cutting edge portion 7 is formed by a ridge between the third flank 14 and the rake face 11 (see FIGS. 2 and 3). The side surface 42 is continuous with each of the third flank 14, the bottom surface 41, and the rake face 11 (see FIGS. 2 and 3).

[0058] As shown in FIG. 4, when viewed along the axis X, the second cutting edge portion 7 may be parallel to the second direction 102. When viewed along the axis X, the corner cutting edge portion 8 may be straight. When viewed along the axis X, the corner cutting edge portion 8 may be parallel to the second direction 102. The bottom surface 41 may be parallel to, for example, an imaginary plane 95. When viewed along the axis X, the curved surface portion 37 of the main body portion 3 is, for example, arc-shaped. The flat surface portion 36 of the main body portion 3 is, for example, parallel to the second direction 102. The second front end surface portion 22 is continuous with the first front end surface portion 21.

[0059] Fig. 5 is a schematic cross-sectional view taken along line VV in Fig. 1. The cross section shown in Fig. 5 is perpendicular to the axis X. As shown in Fig. 5, the outer shape of the main body 3 is, for example, cylindrical. In this specification, the cylindrical shape refers to a shape including an arc having a central angle of 180° or more at the outer edge of the cross-sectional shape. Specifically, for example, the cylindrical shape includes a case where the cross-sectional shape is circular and a case where the outer edge of the cross-sectional shape is composed of an arc having a central angle of 180° or more and a straight line.

[0060] The axis X passes through the center of the main body 3. Specifically, in a cross section perpendicular to the axis X, the axis X is located at the center of a circle including an arc along the curved surface portion 37, for example. The diameter D1 of the main body 3 is, for example, 6 mm or less. When the main body 3 is cylindrical, the diameter D1 is the longest linear distance between two different points on the curved surface portion 37 in the cross section perpendicular to the axis X. In other words, the diameter D1 is the maximum diameter of the main body 3.

[0061] Diameter D1 may be, for example, 5 mm or less, 4 mm or less, or 3 mm or less. Diameter D1 may be, for example, 1 mm or more, or 2 mm or more. The value obtained by dividing length L1 (see FIG. 1) of main body portion 3 in first direction 101 by diameter D1 is, for example, 3 or more.

[0062] Fig. 6 is a schematic cross-sectional view taken along line VI-VI in Fig. 2. The cross section shown in Fig. 6 is perpendicular to the axis X and intersects with each of the main body 3 and the cutting edge layer 4. As shown in Fig. 6, the cutting tool has a brazing material 5.

[0063] The brazing material 5 joins the cutting edge layer 4 and the main body portion 3. The brazing material 5 is located between the cutting edge layer 4 and the main body portion 3. The brazing material 5 contains, for example, each of silver, copper, and titanium. The brazing material 5 has a first portion 51 and a second portion 52.

[0064] In the third direction 103, the first portion 51 is provided between the bottom surface 41 of the cutting edge layer 4 and the seating surface 31 of the body portion 3. The first portion 51 is in contact with each of the bottom surface 41 and the seating surface 31. The first portion 51 extends along each of the second direction 102 and the first direction 101 (see FIG. 2). In a cross section perpendicular to the axis X and intersecting each of the body portion 3 and the cutting edge layer 4, the seating surface 31 is covered by the first portion 51.

[0065] The second portion 52 is continuous with the first portion 51. The second portion 52 is provided between the side surface 42 of the cutting edge layer 4 and the side wall surface 32 of the body portion 3. The second portion 52 is in contact with the side surface 42 of the cutting edge layer 4 and the side wall surface 32 of the body portion 3. The second portion 52 extends along each of the third direction 103 and the first direction 101. In a cross section perpendicular to the axis X and intersecting each of the body portion 3 and the cutting edge layer 4, the side surface 42 is covered by the second portion 52.

[0066] FIG. 7 is a schematic diagram showing the configuration of the cutting tool 100 as viewed along the direction in which the first cutting edge portion 6 extends. In FIG. 7, the configuration of the cutting tool 100 as viewed along the arrow A shown in FIG. 2 is shown. The arrow A is a direction from the first end point 81 toward the rear end 2 (see FIG. 2) along the direction in which the first cutting edge portion 6 extends. In FIG. 7, a third imaginary straight line 93 is shown. The third imaginary straight line 93 is perpendicular to the imaginary plane 95. The third imaginary straight line 93 intersects with the first cutting edge portion 6. From another perspective, when viewed along the direction in which the first cutting edge portion 6 extends, the third imaginary straight line 93 passes through the first end point 81.

[0067] 7, when viewed along the direction in which the first cutting edge portion 6 extends, the first flank surface 12 is inclined in a second direction 102 with respect to the third imaginary straight line 93. From another perspective, the first flank surface 12 is parallel to the imaginary plane 95 and is inclined in a direction from the first cutting edge portion 6 (see FIG. 2) toward the axis line X (see FIG. 2).

[0068] When viewed along the direction in which the first cutting edge portion 6 extends, the angle between the third virtual straight line 93 and the first flank 12 is defined as a third angle θ3. The third angle θ3 is, for example, 7° or more and 13° or less. The third angle θ3 may be, for example, 9° or more, or 11° or more. The third angle θ3 may be, for example, 12.5° or less, or 12° or less.

[0069] 7, when viewed along the direction in which the first cutting edge portion 6 extends, the second flank surface 19 is inclined in a second direction 102 with respect to the third imaginary straight line 93. From another perspective, when viewed along the direction in which the first cutting edge portion 6 extends, the second flank surface 19 is inclined with respect to the third imaginary straight line 93 in a direction that is parallel to the imaginary plane 95 and from the first cutting edge portion 6 (see FIG. 2) toward the axis X (see FIG. 2).

[0070] When viewed along the direction in which the first cutting edge portion 6 extends, the angle between the third virtual line 93 and the second flank 19 is a fourth angle θ4. The fourth angle θ4 is greater than the third angle θ3. From another perspective, when viewed along the direction in which the first cutting edge portion 6 extends, the second flank 19 is inclined in the second direction 102 with respect to the first flank 12.

[0071] The fourth angle θ4 is, for example, equal to or greater than 20°. The fourth angle θ4 may be, for example, equal to or greater than 25°, or may be equal to or greater than 30°. The fourth angle θ4 may be, for example, equal to or less than 50°, or may be equal to or less than 45°.

[0072] The width H of the first flank 12 in the direction in which the third imaginary straight line 93 extends is 0.4 mm or less. The direction in which the third imaginary straight line 93 extends is the same as the third direction 103. The width H may be, for example, 0.35 mm or less, or 0.3 mm or less. The width H may be, for example, 0.1 mm or more, or 0.15 mm or more.

[0073] FIG. 8 is a schematic diagram showing the configuration of the cutting tool 100 as viewed along the extension direction of the second cutting edge portion 7. In FIG. 8, the configuration of the cutting tool 100 as viewed along the arrow B shown in FIG. 2 is shown. The arrow B is a direction from the second end point 82 toward the axis X (see FIG. 2) along the extension direction of the second cutting edge portion 7. In FIG. 8, a fourth imaginary straight line 94 is shown. The fourth imaginary straight line 94 is perpendicular to the imaginary plane 95. The fourth imaginary straight line 94 intersects with the second cutting edge portion 7. From another perspective, when viewed along the extension direction of the second cutting edge portion 7, the fourth imaginary straight line 94 passes through the second end point 82.

[0074] 8, when viewed along the direction in which the second cutting edge portion 7 extends, the third flank surface 14 is inclined in the first direction 101 with respect to the fourth imaginary straight line 94. When viewed along the direction in which the second cutting edge portion 7 extends, the angle between the fourth imaginary straight line 94 and the third flank surface 14 is set to a fifth angle θ5. The fifth angle θ5 is, for example, not less than 7° and not more than 13°.

[0075] <Cutting tool usage status> Next, an example of a state in which the cutting tool 100 according to this embodiment is used will be described. Fig. 9 is a partial cross-sectional schematic view illustrating a state in which the cutting tool 100 according to this embodiment is used. As shown in Fig. 9, the cutting tool 100 is attached to a machine tool 200. Specifically, the cutting tool 100 is supported by the machine tool 200 by a portion of the main body 3 including the rear end 2 being held by the machine tool 200.

[0076] The length of the part of cutting tool 100 that protrudes from machine tool 200 in first direction 101 is set to protrusion amount L2. Protrusion amount L2 is, for example, 12 mm or more.

[0077] A workpiece 99 is prepared. The workpiece 99 is made of, for example, a cemented carbide. An inner peripheral surface 97 of the workpiece 99 is a surface to be cut using a cutting tool 100. An inner diameter D2 of the inner peripheral surface 97 is, for example, 7 mm or less. A value (L / D) obtained by dividing the protrusion amount L2 by the inner diameter D2 is, for example, 3 or more.

[0078] In machining the workpiece 99, the workpiece 99 rotates around the central axis C of the inner peripheral surface 97. The rotation direction of the workpiece 99 is, for example, clockwise when viewed in a first direction 101. In a second direction 102, an axis X of the cutting tool 100 is located between the central axis C and the inner peripheral surface 97. The cutting tool 100 is moved along an arrow F. The arrow F is the opposite direction to the first direction 101. As a result, the cutting edge 10 comes into contact with the workpiece 99 while the workpiece 99 is rotating.

[0079] FIG. 10 is an enlarged schematic diagram showing a state in which a workpiece 99 is cut using a cutting tool 100 according to this embodiment. As shown in FIG. 10, the workpiece 99 is cut using the corner cutting edge portion 8. As a result, a machined surface 98 is formed. The cutting depth ap of the cutting tool 100 is, for example, 0.1 mm or less. The first cutting edge portion 6 comes into contact with the machined surface 98. As a result, the workpiece 99 is cut using the corner cutting edge portion 8, while the machined surface 98 is finished using the first cutting edge portion 6. As a result, the inner diameter D2 of the workpiece 99 is enlarged.

[0080] Next, the effects of the cutting tool 100 according to this embodiment will be described. When cutting a workpiece, the surface roughness of the machined surface of the workpiece may become excessively large. In this case, for example, the machined surface is polished after the cutting process. This increases the time required to machine the workpiece. For this reason, when cutting a workpiece, it is necessary to reduce the surface roughness of the machined surface. In particular, when the workpiece is a die made of cemented carbide, it is necessary to reduce the surface roughness of the machined surface after the cutting process.

[0081] The cutting tool 100 according to this embodiment has a body 3 and a cutting edge layer 4. The cutting edge layer 4 forms a cutting edge 10. The body 3 is made of a cemented carbide containing WC and Co. The cemented carbide forming the body 3 has a WC content of 90.0% or more and 95.0% or less. The cemented carbide forming the body 3 has a Co content of 4.0% or more and 9.0% or less.

[0082] By making the Co content 9.0% or less and the WC content 90.0% or more, the rigidity of the main body 3 can be improved. Therefore, vibration of the cutting tool 100 can be suppressed when machining the workpiece. This makes it possible to smooth the machined surface of the workpiece. Specifically, the surface roughness of the machined surface of the workpiece can be reduced.

[0083] According to the cutting tool 100 of this embodiment, since the Co content is 4.0% or more, it is possible to suppress an excessive decrease in the transverse rupture strength of the main body portion 3. Therefore, even if a relatively high load is applied to the cutting tool 100 when machining the workpiece 99, it is possible to prevent breakage of the main body portion 3.

[0084] When a cutting tool with a cutting edge formed by polycrystalline diamond is used to process a workpiece, such as a mold made of cemented carbide, the part of the cutting tool close to the cutting edge may be excessively worn due to the relatively high hardness of the cemented carbide. In this case, the shape of the cutting edge may be distorted. Therefore, it may be difficult to process the workpiece for a relatively long time.

[0085] According to the cutting tool 100 of this embodiment, the content of binder in the polycrystalline diamond forming the cutting edge layer 4 is 10.0% or less or 0%. This makes it possible to improve the hardness of the cutting edge layer 4. This makes it possible to improve the wear resistance of the cutting edge layer 4. This makes it possible to suppress wear of the cutting edge layer 4 even when the workpiece is made of a relatively hard material such as cemented carbide. This makes it possible to machine the workpiece for a relatively long time.

[0086] The demand for small diameter screws is increasing with the electrification of automobiles. This has led to a need to use cutting to process small diameter internal diameters in the manufacture of molds. In small diameter internal diameter processing, the diameter of the cutting tool is small, so it has been difficult to simultaneously suppress the vibration of the cutting tool and prevent the cutting tool from breaking.

[0087] According to the cutting tool 100 of this embodiment, the diameter D1 of the main body 3 is 6 mm or less. This allows for inner diameter machining even when the inner diameter of the workpiece is relatively small. Furthermore, according to the cutting tool 100 of this embodiment, even when the diameter D1 of the main body 3 is relatively small, the vibration of the cutting tool 100 can be sufficiently suppressed and breakage of the main body 3 can be prevented as described above.

[0088] The cutting tool 100 according to this embodiment has a brazing material 5. The brazing material 5 bonds the main body 3 and the cutting edge layer 4. The brazing material 5 contains silver, copper, and titanium. This improves the strength of the brazing material 5. This improves the rigidity of the entire cutting tool 100. This makes it possible to suppress vibration of the cutting tool 100 when machining a workpiece. This makes it possible to effectively reduce the surface roughness of the machined surface of the workpiece.

[0089] According to the cutting tool 100 according to the present embodiment, when viewed perpendicularly to the imaginary plane 95, the first cutting edge portion 6 is inclined in the second direction 102 with respect to the axis X, with the first end point 81 as a fulcrum. At the first end point 81, the first cutting edge portion 6 is connected to the corner cutting edge portion 8. When viewed perpendicularly to the imaginary plane 95, the angle (first angle θ1) between the axis X and the first cutting edge portion 6 is 2° or more and 4° or less. By making the first angle θ1 4° or less, excessive reduction in strength of the cutting edge 10 can be suppressed. By making the first angle θ1 2° or more, the first cutting edge portion 6 can be used to perform finishing on the machined surface of the workpiece. As a result, the surface roughness of the machined surface of the workpiece can be effectively reduced.

[0090] According to the cutting tool 100 of this embodiment, the cutting edge layer 4 has a first flank 12. The first flank 12 is continuous with the first cutting edge portion 6. When viewed along the extending direction of the first cutting edge portion 6, an angle (third angle θ3) between a virtual line perpendicular to the virtual plane 95 and the first flank 12 is 7° or more and 13° or less. When the third angle θ3 is 7° or more, excessive friction between the first flank 12 and the workpiece can be suppressed. When the third angle θ3 is 13° or less, excessive reduction in strength of the cutting edge 10 can be suppressed.

[0091] According to the cutting tool 100 of this embodiment, the cutting edge layer 4 has a second flank 19. The second flank 19 is continuous with the first flank 12. When viewed along the first cutting edge portion 6, the angle between the virtual line perpendicular to the virtual plane 95 and the second flank 19 is 20° or more. The width of the first flank 12 in the direction in which the virtual line perpendicular to the virtual plane 95 extends is 0.4 mm or less. Therefore, when performing internal diameter machining on a workpiece having a small inner diameter, it is possible to prevent contact between the cutting edge layer 4 and the workpiece. Specifically, for example, when performing internal diameter machining on a workpiece having an inner diameter of 6 mm or less, it is possible to prevent contact between the cutting edge layer 4 and the workpiece.

[0092] Although the above describes a configuration in which the main body 3 is cylindrical, the configuration of the cutting tool 100 according to the present disclosure is not limited to the above configuration. Specifically, the main body 3 may be prismatic. From another perspective, in a cross section perpendicular to the axis X, the outer circumferential surface 33 may be polygonal. When the main body 3 is prismatic, the diameter D1 of the main body 3 is the diameter of a circumscribing circle of the outer circumferential surface 33 in a cross section perpendicular to the axis X.

[0093] In the above, the configuration in which the body portion 3 and the cutting edge layer 4 are joined by the brazing material 5 has been described, but the cutting tool 100 according to the present disclosure does not need to have the brazing material 5. Specifically, the cutting tool 100 may be a throw-away tool. The body portion 3 and the cutting edge layer 4 may be fastened by, for example, a screw. EXAMPLES

[0094] The present disclosure will be described in more detail below by way of examples, but the present disclosure is not limited to these examples.

[0095] <Sample preparation> First, the effect of the composition of the main body 3 on the surface roughness of the machined surface of the workpiece was investigated. Cutting tools 100 according to Samples 1-1 to 1-5 were prepared. The cutting tools 100 according to Samples 1-1 to 1-3 were examples. The cutting tools 100 according to Samples 1-4 and 1-5 were comparative examples.

[0096] In the manufacture of the cutting tools 100 according to Samples 1-1 to 1-5, first, polycrystalline diamond was prepared. The thickness of the polycrystalline diamond was 0.65 mm. The shape of the polycrystalline diamond was a sector with a central angle of 60° and a radius of 3 mm.

[0097] The polycrystalline diamond and the main body 3 were joined together by a brazing material 5. The polycrystalline diamond was processed using a laser to form a cutting edge layer 4. In this manner, the cutting tools 100 according to Samples 1-1 to 1-5 were prepared.

[0098] [Table 1]

[0099] Table 1 shows the configuration of the cutting tool 100 according to Samples 1-1 to 1-5. As shown in Table 1, in Samples 1-1 to 1-3, the WC content was 92% or more and 94% or less. The Co content was 5% or more and 8% or less. In Samples 1-4 and 1-5, the WC content was 89% or less. In Sample 1-4, the Co content was 12%. In Sample 1-5, the Co content was 6%.

[0100] In samples 1-1 to 1-5, the cutting edge layer 4 was formed of nano-polycrystalline diamond. The binder content of the polycrystalline diamond forming the cutting edge layer 4 was 0%. The diameter of the main body 3 was 3.5 mm. The first angle θ1 was 3°. The clearance angle (third angle θ3) was 10°.

[0101] <Evaluation method> The following cutting evaluation was performed using the cutting tool 100 according to Samples 1-1 to 1-5. Specifically, the cutting tool 100 was attached to the turret of an NC (Numerical Control) lathe. A cylindrical workpiece was fixed to the chuck of the NC lathe. The workpiece was subjected to turning under the following cutting conditions. In the following, HRA refers to Rockwell hardness A scale.

[0102] <Cutting conditions> Work material: Cemented carbide (hardness: HRA88.0, outer diameter: 30 mm, inner diameter: 5 mm, total length: 18 mm) Cutting speed (Vc): 10m / min Depth of cut (ap): 0.025mm Feed per revolution (f): 0.04mm / rev Protrusion amount: 20mm Cutting oil: None (Dry processing) In the above turning process, the surface roughness (maximum height roughness Rz and arithmetic mean roughness Ra) of the machined surface of the workpiece was measured when the cutting distance reached 5.6 m. Rz and Ra were measured using a surface roughness measuring instrument in accordance with JIS (Japanese Industrial Standards) B 0601:2001. It is understood that the smaller the Rz and Ra values, the smoother the sample can finish the machined surface of the workpiece.

[0103] <Evaluation Results>

[0104] [Table 2]

[0105] Table 2 shows the evaluation results for samples 1-1 to 1-5. As shown in Table 2, in samples 1-1 to 1-3, the Rz of the machined surface was 1.832 μm or less. The Ra of the machined surface was 0.337 μm or less. In samples 1-4 and 1-5, the Rz of the machined surface was 2.258 μm or more. The Ra of the machined surface was 0.431 μm or more.

[0106] From the above, it was confirmed that the cutting tool 100 according to the embodiment can reduce the surface roughness of the machined surface of the workpiece, compared to the cutting tool 100 according to the comparative example. It is considered that the cutting tool 100 according to the embodiment has improved rigidity of the main body 3, thereby suppressing vibration of the cutting tool 100 during cutting. It is considered that this enabled the machined surface of the workpiece to be finished smoothly. EXAMPLES

[0107] <Sample preparation> Next, the surface roughness of the machined surface was investigated when the diameter D1 of the main body 3 was 2.5 mm. Cutting tools 100 according to samples 2-1 to 2-5 were prepared. The cutting tools 100 according to samples 2-1 to 2-3 were examples. The cutting tools 100 according to samples 2-4 and 2-5 were comparative examples. The manufacturing method of the cutting tools 100 according to samples 2-1 to 2-5 was substantially the same as the manufacturing method of the cutting tools 100 according to samples 1-1 to 1-5 described above.

[0108] [Table 3]

[0109] Table 3 shows the configuration of the cutting tool 100 according to Samples 2-1 to 2-5. As shown in Table 3, in Samples 2-1 to 2-3, the WC content was 92% or more and 94% or less. The Co content was 5% or more and 8% or less. In Samples 2-4 and 2-5, the WC content was 89% or less. In Sample 2-4, the Co content was 12%. In Sample 2-5, the Co content was 6%.

[0110] In samples 2-1 to 2-5, the cutting edge layer 4 was formed of nano-polycrystalline diamond. The binder content of the polycrystalline diamond forming the cutting edge layer 4 was 0%. The diameter of the main body 3 was 2.5 mm. The first angle θ1 was 3°. The clearance angle (third angle θ3) was 10°.

[0111] <Evaluation method> The following cutting evaluation was performed using the cutting tool 100 according to Samples 2-1 to 2-5. Specifically, the cutting tool 100 was attached to the turret of an NC lathe. A cylindrical workpiece was fixed to the chuck of the NC lathe. The workpiece was subjected to turning under the following cutting conditions.

[0112] <Cutting conditions> Work material: Cemented carbide (hardness: HRA88.0, outer diameter: 30 mm, inner diameter: 5 mm, total length: 13 mm) Cutting speed (Vc): 10m / min Depth of cut (ap): 0.025mm Feed per revolution (f): 0.04mm / rev Protrusion amount: 15mm Cutting oil: None (Dry processing) In the above turning process, the surface roughness (Rz and Ra) of the machined surface of the workpiece was measured when the cutting distance reached 5.6 m. Rz and Ra were measured using a surface roughness measuring instrument in accordance with JIS B 0601:2001.

[0113] <Evaluation Results>

[0114] [Table 4]

[0115] Table 4 shows the evaluation results for samples 2-1 to 2-5. As shown in Table 4, in samples 2-1 to 2-3, the Rz of the machined surface was 2.02 μm or less. The Ra of the machined surface was 0.407 μm or less. In samples 2-4 and 2-5, the Rz of the machined surface was 2.785 μm or more. The Ra of the machined surface was 0.591 μm or more.

[0116] From the above, it was confirmed that the cutting tool 100 according to the embodiment can reduce the surface roughness of the machined surface of the workpiece, compared to the cutting tool 100 according to the comparative example. It is considered that the cutting tool 100 according to the embodiment has improved rigidity of the main body 3, thereby suppressing vibration of the cutting tool 100 during cutting. It is considered that this enabled the machined surface of the workpiece to be finished smoothly. EXAMPLES

[0117] <Sample preparation> Next, the effect of the composition of the main body portion 3 on the transverse rupture strength of the main body portion was investigated. Cutting tools 100 according to Samples 3-1 to 3-3 were prepared. The cutting tools 100 according to Samples 3-1 and 3-2 were examples. The cutting tool 100 according to Sample 3-3 was a comparative example. The manufacturing method of the cutting tools 100 according to Samples 3-1 to 3-3 was substantially the same as the manufacturing method of the cutting tools 100 according to Samples 1-1 to 1-5 described above.

[0118] [Table 5]

[0119] Table 5 shows the configuration of the cutting tool 100 according to Samples 3-1 to 3-3. As shown in Table 5, in Samples 3-1 and 3-2, the WC content was 92% or more and 94% or less. The Co content was 5% or more and 8% or less. In Sample 3-3, the WC content was 99%. The Co content was 0.7%.

[0120] In samples 3-1 to 3-3, the cutting edge layer 4 was formed of nano-polycrystalline diamond. The binder content of the polycrystalline diamond forming the cutting edge layer 4 was 0%. The diameter of the main body 3 was 2.5 mm. The first angle θ1 was 3°. The clearance angle (third angle θ3) was 10°.

[0121] <Evaluation method> The following cutting evaluation was performed using the cutting tool 100 according to Samples 3-1 to 3-3. Specifically, the cutting tool 100 was attached to the turret of an NC lathe. A cylindrical workpiece was fixed to the chuck of the NC lathe. The workpiece was subjected to turning under the following cutting conditions.

[0122] <Cutting conditions> Work material: Cemented carbide (hardness: HRA88.0, outer diameter: 30mm, inner diameter: 5mm, total length: 25mm) Cutting speed (Vc): 10m / min Depth of cut (ap): 0.05mm Feed per revolution (f): 0.1mm / revolution Protrusion amount: 27mm Cutting oil: None (Dry processing) In the above turning process, the surface roughness (Rz and Ra) of the machined surface of the workpiece was measured when the cutting distance reached 1 km. Rz and Ra were measured using a surface roughness measuring instrument in accordance with JIS B 0601:2001.

[0123] When the cutting distance reached 1 km, the flank wear width (maximum flank wear width) was measured at the cutting edge portion corresponding to the position where the workpiece cut depth was maximum. The position where the workpiece cut depth was maximum was the position of the cutting edge 10 where the distance between the axis X and the cutting edge 10 in the second direction 102 was maximum. The flank wear width was the width in the third direction 103 of the flank portion where wear was confirmed. It is understood that the smaller the maximum flank wear width, the higher the wear resistance of the cutting edge portion corresponding to the position where the workpiece cut depth was maximum.

[0124] <Evaluation Results>

[0125] [Table 6]

[0126] Table 6 shows the evaluation results for samples 3-1 to 3-3. As shown in Table 6, in samples 3-1 and 3-2, the maximum flank wear width was 14.65 μm or less. The Rz of the machined surface was 4.012 μm or less. The Ra of the machined surface was 0.941 μm or less. In sample 3-3, the main body 3 broke during the cutting process, so the above-mentioned turning process was stopped. Therefore, in sample 3-3, the maximum flank wear width, the Rz of the machined surface, and the Ra of the machined surface could not be measured. On the other hand, no breakage of the main body 3 was confirmed in samples 3-1 and 3-2.

[0127] From the above, it was confirmed that the cutting tool 100 according to the embodiment can prevent breakage of the main body portion 3, compared to the cutting tool 100 according to the comparative example. From another perspective, it was confirmed that the cutting tool 100 according to the embodiment can suppress an excessive decrease in the flexural strength of the main body portion 3. When the Co content is 0.7% or less, the flexural strength of the main body portion 3 decreases excessively, and therefore it is considered that the cutting tool is not suitable for the above-mentioned turning process. EXAMPLES

[0128] <Sample preparation> Next, the influence of the first angle θ1 on the surface roughness of the machined surface and the influence of the third angle θ3 on the maximum flank wear width were investigated. Cutting tools 100 according to Samples 4-1 to 4-4 were prepared. The cutting tools 100 according to Samples 4-1 to 4-4 were examples. The manufacturing method of the cutting tools 100 according to Samples 4-1 to 4-4 was substantially the same as the manufacturing method of the cutting tools 100 according to Samples 1-1 to 1-5 described above.

[0129] [Table 7]

[0130] Table 7 shows the configuration of the cutting tool 100 according to Samples 4-1 to 4-4. As shown in Table 7, in Samples 4-1 to 4-3, the first angle θ1 was 3°. The clearance angle (third angle θ3) was 7° or more and 13° or less. In Sample 4-4, the first angle θ1 was 5°. The clearance angle (third angle θ3) was 10°.

[0131] In samples 4-1 to 4-4, the WC content was 92%. The Co content was 8%. In samples 4-1 to 4-4, the cutting edge layer 4 was formed of nano-polycrystalline diamond. The binder content of the polycrystalline diamond forming the cutting edge layer 4 was 0%. The diameter of the main body 3 was 3.5 mm.

[0132] <Evaluation method> The following cutting evaluation was performed using the cutting tool 100 according to Samples 4-1 to 4-4. Specifically, the cutting tool 100 was attached to the turret of an NC lathe. A cylindrical workpiece was fixed to the chuck of the NC lathe. The workpiece was subjected to turning under the following cutting conditions.

[0133] <Cutting conditions> Work material: Cemented carbide (hardness: HRA88.0, outer diameter: 30mm, inner diameter: 5mm, total length: 18mm) Cutting speed (Vc): 10m / min Depth of cut (ap): 0.025mm Feed per revolution (f): 0.04mm / rev Protrusion amount: 20mm Cutting oil: None (Dry processing) In the above turning process, the surface roughness (Rz and Ra) of the machined surface of the workpiece was measured when the cutting distance reached 1 km. Rz and Ra were measured using a surface roughness measuring device in accordance with JIS B 0601:2001. When the cutting distance reached 1 km, the maximum flank wear width was measured.

[0134] <Evaluation Results>

[0135] [Table 8]

[0136] Table 8 shows the evaluation results for samples 4-1 to 4-4. As shown in Table 8, in samples 4-1 to 4-3, the Rz of the machined surface was 2.017 μm or less. The Ra of the machined surface was 0.372 μm or less. In sample 4-4, the Rz of the machined surface was 2.322 μm. The Ra of the machined surface was 0.469 μm. In samples 4-1 to 4-4, the maximum flank wear width was 14.7 μm or more and 23.2 μm or less.

[0137] From the above, it was confirmed that the samples (samples 4-1 to 4-3) in which the first angle θ1 is 3° can reduce the surface roughness of the machined surface of the workpiece, compared to the sample (sample 4-4) in which the first angle θ1 is 5°. It is considered that the cutting tools 100 in the samples 4-1 to 4-3 were able to machine the machined surface of the workpiece smoothly because the length of the first cutting edge portion 6 that contacts the workpiece is long. It was also confirmed that the maximum flank wear width was reduced as the third angle θ3 was larger. EXAMPLES

[0138] <Sample preparation> Next, the influence of the binder content of the polycrystalline diamond forming the cutting edge layer 4 on the maximum flank wear width and the surface roughness of the machined surface was investigated. Cutting tools 100 according to samples 5-1 to 5-3 were prepared. The cutting tools 100 according to samples 5-1 to 5-3 were examples.

[0139] The manufacturing method of the cutting tool 100 according to sample 5-1 was substantially the same as the manufacturing method of the cutting tool 100 according to the above-mentioned samples 1-1 to 1-5. The manufacturing method of the cutting tool 100 according to samples 5-2 and 5-3 was substantially the same as the manufacturing method of the cutting tool 100 according to the above-mentioned samples 1-1 to 1-5, except for the processing method of the polycrystalline diamond. Specifically, in samples 5-2 and 5-3, the cutting edge layer 4 was formed by processing the polycrystalline diamond using a grinding process.

[0140] [Table 9]

[0141] Table 9 shows the configuration of the cutting tool 100 according to Samples 5-1 to 5-3. As shown in Table 9, in Sample 5-1, the binder content was 0%. In Sample 5-2, the binder content was 10%. In Sample 5-3, the binder content was 15%. In Sample 5-1, the cutting edge layer 4 was formed of nano-polycrystalline diamond. In Samples 5-2 and 5-3, the cutting edge layer 4 was formed of polycrystalline diamond.

[0142] In Samples 5-1 to 5-3, the WC content was 92%. The Co content was 8%. The diameter of the main body 3 was 3.5 mm. The first angle θ1 was 3°. The clearance angle (third angle θ3) was 10°.

[0143] <Evaluation method> The following cutting evaluation was performed using the cutting tool 100 according to Samples 5-1 to 5-3. Specifically, the cutting tool 100 was attached to the turret of an NC lathe. A cylindrical workpiece was fixed to the chuck of the NC lathe. The workpiece was subjected to turning under the following cutting conditions.

[0144] <Cutting conditions> Work material: Cemented carbide (hardness: HRA88.0, outer diameter: 30mm, inner diameter: 5mm, total length: 18mm) Cutting speed (Vc): 10m / min Depth of cut (ap): 0.025mm Feed per revolution (f): 0.04mm / rev Protrusion amount: 20mm Cutting oil: None (Dry processing) In the above turning process, the surface roughness (Rz and Ra) of the machined surface of the workpiece was measured when the cutting distance reached 16.8 m. Rz and Ra were measured using a surface roughness measuring instrument in accordance with JIS B 0601:2001. The maximum flank wear width was measured when the cutting distance reached 16.8 m.

[0145] <Evaluation Results>

[0146] [Table 10]

[0147] Table 10 shows the evaluation results for Samples 5-1 to 5-3. As shown in Table 10, the maximum flank wear width was 22.86 μm or less in Samples 5-1 and 5-2. The maximum flank wear width was 171.8 μm in Sample 5-3.

[0148] In samples 5-1 and 5-2, the Rz of the machined surface was 3.886 μm or less. The Ra of the machined surface was 0.646 μm or less. In sample 5-3, the Rz of the machined surface was 15.662 μm. The Ra of the machined surface was 2.448 μm.

[0149] From the above, it was confirmed that the wear resistance of the cutting edge layer 4 can be improved and the surface roughness of the machined surface of the workpiece can be reduced in the samples (Sample 5-1 and 5-2) with a binder content of 10% or less, compared to the sample (Sample 5-3) with a binder content of 15%. In Samples 5-1 and 5-2, the wear resistance of the cutting edge layer 4 is improved by improving the hardness of the cutting edge layer 4. This is considered to have reduced the maximum flank wear width. Therefore, compared to the cutting tool 100 of Sample 5-3, the cutting tool 100 of Samples 5-1 and 5-2 allows long-term cutting.

[0150] In addition, in each of Examples 1 to 5, when the composition of the hard phase in the cemented carbide forming the main body 3 was examined by X-ray diffraction, it was found that the hard phase in all samples was substantially composed of WC particles.

[0151] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims, not the above description, and is intended to include the meaning equivalent to the claims and all modifications within the scope. [Explanation of symbols]

[0152] 1 front end, 2 rear end, 3 main body portion, 4 cutting edge layer, 5 brazing material, 6 first cutting edge portion, 7 second cutting edge portion, 8 corner cutting edge portion, 10 cutting edge, 11 rake face, 12 first flank face, 13 corner flank face, 14 third flank face, 18 curved surface, 19 second flank face, 21 first front end face portion, 22 second front end face portion, 31 seating surface, 32 side wall surface, 33 outer peripheral surface, 34 front end face, 36 flat surface portion, 37 curved surface portion, 39 recess, 41 bottom surface, 42 side surface, 51 first portion, 52 second portion, 81 first end point, 82 second end point, 91 first virtual straight line, 92 second virtual straight line, 93 third virtual straight line, 94 fourth virtual straight line, 95 virtual plane, 97 inner peripheral surface, 98 machined surface, 99 Workpiece, 100 cutting tool, 101 first direction, 102 second direction, 103 third direction, 200 machine tool, A, B, F arrows, C central axis, D1 diameter, D2 inner diameter, H width, L1 length, L2 protrusion amount, X axis line, ap cutting depth, θ1 first angle, θ2 second angle, θ3 third angle, θ4 fourth angle, θ5 fifth angle.

Claims

1. a rod-shaped main body; a cutting edge layer provided at a front end of the main body portion and forming a cutting edge; The main body is formed of a cemented carbide containing tungsten carbide and cobalt, the cutting edge layer is formed of polycrystalline diamond, In the cemented carbide, the percentage of the weight of the tungsten carbide divided by the total weight of the cemented carbide is 90.0% or more and 95.0% or less, The percentage of the weight of the cobalt divided by the total weight of the cemented carbide is 4.0% or more and 9.0% or less, The diameter of the main body is 6 mm or less, A cutting tool, wherein the length of the main body in the direction from the front end to the rear end along the axis of the main body is 30 mm or more.

2. 2. The cutting tool according to claim 1, wherein the percentage of the weight of the cobalt in the cemented carbide divided by the total weight of the cemented carbide is 5.0% or more and 8.0% or less.

3. the polycrystalline diamond comprises a plurality of diamond particles; 3. A cutting tool according to claim 1 or claim 2, wherein in the polycrystalline diamond, the weight of the binder that binds the plurality of diamond particles divided by the total weight of the polycrystalline diamond is 10.0% or less or 0%.

4. 4. The cutting tool according to claim 3, wherein in the polycrystalline diamond, the percentage of the weight of the binder divided by the total weight of the polycrystalline diamond is 1.0% or less or 0%.

5. a brazing material that joins the cutting edge layer and the main body portion, The cutting tool according to claim 1 or 2, wherein the brazing material includes each of silver, copper, and titanium.

6. The cutting edge is a corner cutting edge portion having a first end point and a second end point opposite the first end point; a first cutting edge portion connected to the corner cutting edge portion at the first end point and provided in a direction from the front end to the rear end along the axis relative to the corner cutting edge portion; a second cutting edge portion connected to the corner cutting edge portion at the second end point and provided in a direction from the corner cutting edge portion toward the axis, the cutting edge layer has a first flank surface connected to the first cutting edge portion, When viewed along the direction in which the first cutting edge portion extends, the first flank surface is inclined in a direction from the first cutting edge portion toward the axis with respect to an imaginary line that is perpendicular to an imaginary plane including the corner cutting edge portion and the first cutting edge portion and intersects with the first cutting edge portion, an angle formed between the virtual straight line and the first flank surface is equal to or greater than 7° and equal to or less than 13°; When viewed perpendicular to the virtual plane, The first cutting edge portion is inclined with respect to the axis line in a direction from the first end point toward the axis line, with the first end point serving as a fulcrum, The cutting tool according to claim 1 or 2, wherein an angle formed between the axis and the first cutting edge portion is equal to or greater than 2° and equal to or less than 4°.

7. The cutting edge layer has a second flank surface that is continuous with the first flank surface and is located opposite the first cutting edge portion with respect to the first flank surface, When viewed along the direction in which the first cutting edge portion extends, the second flank surface is inclined with respect to the imaginary straight line in a direction from the first cutting edge portion toward the axis line, an angle formed between the virtual straight line and the second flank surface is 20° or more; The cutting tool according to claim 6 , wherein the width of the first flank in the direction in which the imaginary straight line extends is 0.4 mm or less.

Images