Cutting tool and manufacturing method of cutting tool

Abstract

To provide a cutting tool that can suppress the problem of deterioration in processing accuracy resulting from the tool life becoming short, and the problem of sharp rises in a tool cost (tool basic unit) per processing of a product.SOLUTION: A cutting tool comprises a cutting part with a plurality of tool blades, and applies cutting to a workpiece. In the cutting tool, a blade tip shape connecting a rake face and a flank in the tool blade is a shape that turns the stress applied to the blade tip into compressive stress, when subjecting the workpiece to processing.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a cutting tool and a method for manufacturing a cutting tool. [Background technology]

[0002] In recent years, the power source (powertrain) has changed rapidly with the shift to EV in the automobile industry, and there is an increasing demand for gears, which are one of the components, to have low NV (noise and vibration), be compact, and low cost. To meet these demands, high efficiency, high precision, and low cost are required in gear cutting, and as one of the cutting methods, "gear skiving" as described in Patent Document 1, for example, is adopted. In Patent Document 1, a chamfer is formed on the cutting edge of the leading side that comes into contact with the workpiece in advance in a skiving cutter that performs the gear skiving on a workpiece. This is said to suppress damage to the leading edge and extend the tool life. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-39971 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, gear skiving is an intermittent process in which a multi-blade tool is used to machine the tooth grooves one groove at a time, and the rake angle of the tool changes from positive to negative from the start to the end of the groove processing, and the cutting force and cutting heat increase near the end of processing, so that the tool is prone to wear and breakage. In particular, if processing is continued in a state where a small depression is formed and crater wear occurs on the cutting edge, in which the periphery of the depression becomes stepped, the stepped portion is likely to chip and break. Therefore, even in the skiving cutter described in the above Patent Document 1, the effect of extending the tool life was insufficient. For this reason, there was a problem that the shortened tool life caused the processing accuracy to deteriorate and the tool cost (tool unit cost) per processed product to rise. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one embodiment of the present disclosure, there is provided a cutting tool that includes a cutting portion having a plurality of tool blades and that performs cutting on a workpiece, and a cutting edge shape of a cutting edge connecting a rake face and a flank face of the tool blade is such that a stress applied to the cutting edge during machining of the workpiece becomes a compressive stress. According to the cutting tool of this embodiment, the stress applied to the cutting edge during cutting is compressive stress, so that chipping of the cutting edge and the expansion of the chipping can be suppressed, and thus the tool life can be improved. (2) In the above embodiment, a contact length, which is the length of a portion where the flank and the machined surface of the workpiece contact each other in a cross section showing the cutting edge shape in a plane that intersects the rake face and passes through the cutting edge, may be 5 μm or more. According to the cutting tool of this embodiment, by making the length of the portion where the flank and the machined surface of the workpiece contact each other 5 μm or more, the stress applied to the cutting edge can be a compressive stress. (3) In the above embodiment, at least a portion of the cutting edge may be curved. (4) In the above embodiment, at least a portion of the cutting edge may be chamfered. (5) In the above embodiment, the tool blades may be formed in multiple numbers on a circumferential edge portion of the blade portion, and the cutting tool may be a gear cutting tool that processes gear teeth in the workpiece by moving the workpiece and the cutting tool relative to each other while synchronizing a rotation of the workpiece about a central axis of the workpiece and a rotation of the cutting tool about a central axis of the cutting tool. (6) According to a second aspect of the present disclosure, there is provided a method for manufacturing a cutting tool, the method for manufacturing a cutting tool comprising: a preparation step of preparing a base member that serves as a base for the cutting portion; an edge treatment step of scraping the cutting edge by cutting a cutting object for edge treatment using the base member; and a coating step of coating a surface of the cutting edge after the edge treatment step. According to this embodiment of the manufacturing method for a cutting tool, in the edge treatment step, it is possible to easily manufacture an edge shape in which the stress applied to the edge is compressive stress. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a gear machining device according to a first embodiment of the present disclosure. [Diagram 2] FIG. 1 is a diagram illustrating the operation of gear skiving as viewed in the radial direction of the machining tool. [Diagram 3] FIG. 2 is a perspective view showing the entire processing tool. [Figure 4] FIG. 2 is an enlarged view showing a portion of a rake face including a radially outer end portion thereof; [Diagram 5] FIG. 4 is a cross-sectional view showing the cutting edge shape of the central cutting edge. [Figure 6] FIG. 13 is a graph showing the relationship between contact length and maximum principal stress. [Figure 7] FIG. 11 is a diagram showing the change over time in the magnitude of the load applied to the tool blade in the feed direction during machining. [Figure 8] FIG. 11 is a cross-sectional view showing the shape of a cutting edge of a machining tool in a second embodiment. [Figure 9] FIG. 2 is a perspective view showing a schematic view of a tool and a workpiece during machining. [Figure 10] 10 is a cross-sectional view taken along line XX in FIG. [Figure 11] 10 is a cross-sectional view taken along line XX in FIG. [Figure 12] FIG. 11 is a cross-sectional view showing a cutting edge shape of a machining tool in another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A. First embodiment: A1. Overall configuration of the gear processing device 10: The configuration of the gear machining device 10 will be described with reference to Fig. 1. Fig. 1 is a perspective view showing a schematic configuration of the gear machining device 10 to which a cutting tool according to a first embodiment of the present disclosure is applied. As shown in Fig. 1, the gear machining device 10 is, for example, a five-axis machining center having three linear axes and two rotation axes as drive axes for changing the relative position and attitude of a workpiece 1 and a gear machining tool T1 (hereinafter also simply referred to as "cutting tool T1" or "machining tool T1"). In this example, the gear machining device 10 has three orthogonal axes (X-axis, Y-axis, Z-axis) as linear axes, and a B-axis and a Cw-axis as rotation axes. In this example, the B-axis is a rotation axis about the central axis RB of the rotary table 14 which is parallel to the Y-axis, and the Cw-axis is a rotation axis about the central axis Rw of the workpiece 1. The gear machining device 10 also has a Ct-axis which is a rotation axis about the central axis RT of the machining tool T1, and when the Ct-axis is included, the gear machining device 10 becomes a 6-axis machining center.

[0009] The gear machining device 10 includes a tool spindle 11 that supports a machining tool T1 and is rotatable about a Ct axis, and is movable in the Y-axis and Z-axis directions. The gear machining device 10 further includes a workpiece spindle 12 that supports a workpiece 1 and is rotatable about a Cw axis, is rotatable about a B axis, and is movable in the X-axis direction. The gear machining device 10 includes a machining control unit 13 that controls the machining of gear teeth, etc. In this embodiment, a case will be described in which the machining control unit 13 controls the machining of gear teeth on the workpiece 1 by skiving. Note that the configuration is not limited to the above, and the tool spindle 11 and the workpiece spindle 12 may be configured to be relatively movable.

[0010] A2. Skiving: Skiving will be described with reference to Fig. 2. Fig. 2 is a diagram for explaining the operation of gear skiving as viewed in the radial direction of the machining tool T1. In skiving, as shown in Fig. 2, the central axis RT of the machining tool T1 is set to have an intersection angle θ with an axis parallel to the central axis Rw of the workpiece 1. In addition, when viewed from the X-axis direction, the central axis RT of the machining tool T1 and the central axis Rw of the workpiece 1 are parallel to each other.

[0011] Then, while synchronizing the rotation of the workpiece 1 about its central axis Rw and the rotation of the machining tool T1 about its central axis RT, the machining tool T1 is fed in the direction of the central axis Rw of the workpiece 1 relative to the workpiece 1, thereby machining gear teeth on the workpiece 1. In skiving, each tooth groove portion of the workpiece 1 is machined only once by the machining tool T1 while the workpiece 1 makes one rotation.

[0012] A3. Detailed configuration of machining tool T1: Next, a detailed configuration of the machining tool T1 will be described with reference to Fig. 3. Fig. 3 is a perspective view showing the entire machining tool T1. The machining tool T1 of this embodiment is a gear skiving cutter that performs gear cutting on a workpiece 1. As shown in Fig. 3, the machining tool T1 is formed in a helical gear shape with a plurality of tool blades 21 arranged radially by processing to form helical grooves on the outer surface of a base material. The machining tool T1 includes a blade portion Ta and a shaft portion Tb.

[0013] The blade portion Ta has a plurality of tool blades 21 on its circumferential edge. In the plurality of tool blades 21 in the blade portion Ta, the axial end faces form the rake faces 22, and the radial outer surfaces of the tool blades 21 form the front clearance faces 23. In this embodiment, a virtual surface circumscribing the blade portion Ta, i.e., a virtual surface circumscribing each of the radial outer surfaces of the tool blades 21 that form the front clearance faces 23, forms a part of a conical surface. However, the circumscribing surface of the blade portion Ta can also be configured to form a cylindrical surface. Furthermore, a pair of side surfaces connected to the front clearance faces 23 and extending along the cutting groove direction form side clearance faces 24.

[0014] The shaft portion Tb is a cylindrical member. The shaft portion Tb is integrally provided on the end surface of the cutting edge portion Ta opposite to the rake face 22, and is provided coaxially with the cutting edge portion Ta. Note that the "opposite side" corresponds to the opposite side of the workpiece 1 in the Z-axis direction in the state shown in FIG. 1 in which the machining tool T1 is attached to the gear machining device 10.

[0015] Fig. 4 is an enlarged view of a portion of the cutting tool T1 including the radially outer end of the cutting face 22, which is enclosed by a dashed line in Fig. 3. Fig. 4 is a view of the cutting tool T1 viewed from the blade portion Ta side in the direction of the central axis RT. The cutting edge 30 including the radially outer end of the cutting face 22 is configured to have a leading portion 31, a cutting bottom portion 32, and a trailing portion 33.

[0016] The leading portion 31 is a region on the leading side that comes into contact with the workpiece 1 first during machining. The blade bottom portion 32 is a region that is continuous with the leading portion 31 and comes into contact with the workpiece 1 after the leading portion 31. The trailing portion 33 is a region on the trailing side that is continuous with the blade bottom portion 32. The blade bottom portion 32 connects the leading portion 31 and the trailing portion 33.

[0017] Depending on the machining state of the workpiece 1, for example, whether a groove is formed or not, and the depth of the groove, there may be cases where the trailing portion 33 comes into contact with the workpiece 1 at a timing not very different from the timing at which the leading portion 31 comes into contact with the workpiece 1 first. In cutting, basically, the leading portion 31 first comes into contact with the workpiece 1 first, and then the cutting edge portion 32 comes into contact with the workpiece 1 in a process that involves a change in the posture of the tool T. However, this does not mean that the trailing portion 33 has no effect on machining at all. For simplicity, in FIG. 4, the leading portion 31 and the trailing portion 33 are drawn as inclined straight lines.

[0018] FIG. 5 is a cross-sectional view showing the shape of the cutting edge at the bottom 32, and is a cross-sectional view showing the shape of the cutting edge in a plane perpendicular to the rake face 22 and passing through the cutting edge 30. FIG. 5 illustrates the cutting edge in a state in which a crater wear portion 41 is formed on the rake face 22 by shavings during machining. The crater wear portion 41 is a small depression formed on the cutting edge 30, and refers to a portion where the end of the depression is worn in a stepped shape. As machining continues, the rake face 22 is partially worn at a position where shavings flow on the rake face 22. Therefore, the cutting edge 30 has a shape in which the tip of the cutting edge protrudes slightly and the rear side thereof is recessed. The step portion at the boundary between the protrusion and the recess is called a corner portion 42. In FIG. 5, the corner portion 42 is formed at a position approximately 10 to 100 μm from the tip of the cutting edge where the rake face 22 and the front clearance face 23 are continuous. The protrusion amount of the corner 42, in other words, the depth of the crater wear portion 41, is about 5 μm. The corner 42 can also be said to be the tip end of the recess caused by the crater wear portion 41 caused by contact with shavings.

[0019] As shown in Fig. 5, the cutting edge shape at the cutting edge bottom portion 32 is a curved shape that is tangent to the rake face 22 and the front clearance face 23. In the cross section shown in Fig. 5, when the rake face 22, the front clearance face 23, and the cutting edge 30 are viewed on the same plane, a portion where the machining surface 2 of the workpiece 1 and the front clearance face 23 come into contact is defined as a contact portion C.

[0020] In the first embodiment, the contact area C is a continuous curve. The length of the contact area C in the state (cross-sectional state) shown in FIG. 5 is defined as the "contact length". More specifically, in the first embodiment, the "contact length" refers to the length of the portion present on the front clearance face 23 side when the angle θ2 between the rake face 22 and the front clearance face 23 is halved to halve the area in a cross section on a plane perpendicular to the rake face 22 and passing through the cutting edge 30. In FIG. 5, the straight line that halves the angle θ2 between the rake face 22 and the front clearance face 23 is shown as a straight line S. The cutting edge 30 is machined so that the contact length is 5 μm or more.

[0021] In FIG. 5, the blade bottom 32 is described as an example, but the cross-sectional shapes of the leading portion 31 and the trailing portion 33 have the same contact length as the blade bottom 32. However, the leading portion 31, the blade bottom 32, and the trailing portion 33 do not need to satisfy the condition that the contact length is 5 μm or more (hereinafter also referred to as the "contact length condition"). It is sufficient that at least one of the portions satisfies the contact length requirement. The blade bottom 32 is a portion that is more likely to wear out than other portions and is also easier to inspect. From this perspective, it is preferable that the blade bottom 32 satisfies the contact length condition. On the other hand, the leading portion 31 and the trailing portion 33 are portions that have a greater impact on the processing quality. From this perspective, it is preferable that the leading portion 31 or the trailing portion 33 satisfies the contact length condition.

[0022] The cutting edge 30 can be processed by, for example, blasting. In the well-known blasting, the cutting edge 30 can be processed to have a desired contact length by appropriately adjusting the discharge pressure of the abrasive grains, the diameter of the abrasive grains, and the exposure time. In FIG. 5, arrows A1 and A2 show examples of the discharge direction of the abrasive grains sprayed onto the cutting edge in the blasting. Arrow A1 shows discharge from the lateral direction, and arrow A2 shows discharge from the oblique direction. When discharged from the oblique direction, the cutting edge tip generally has a beautiful curved shape, and the cutting edge shape of this embodiment can be processed. When discharged from the lateral direction, the cutting edge tip may have some discontinuous parts and may not be curved in some parts.

[0023] Next, the reason for setting the contact length to 5 μm or more will be described. FIG. 6 is a graph showing the relationship between the contact length and the maximum principal stress applied to the cutting edge 30. In FIG. 6, the horizontal axis represents the contact length, and the vertical axis represents the maximum principal stress. FIG. 7 is a graph showing the change in the magnitude of the load in the feed direction applied to the tool blade during machining over time while machining one groove, with the horizontal axis representing time and the vertical axis representing load. As shown in FIG. 7, the load in the feed direction gradually increases from the start of machining to a maximum, and decreases just before the end of machining. The maximum principal stress shown in FIG. 6 is the maximum principal stress at the timing Tm when the load in the feed direction during machining is maximum. In FIG. 6, the analysis results of the first embodiment are shown by circles and dashed lines. The multiple circles are plotted by analyzing the maximum principal stress by changing the R shape of the roundness of the cutting edge 30, that is, by changing the contact length. In FIG. 6, a positive maximum principal stress indicates that the stress applied to the cutting edge 30 is a tensile stress, and a negative maximum principal stress indicates that the stress applied to the cutting edge 30 is a compressive stress.

[0024] As shown by the dashed line in FIG. 6, according to the analysis performed by the inventors of the present application, it was found that when the contact length is 5 μm or more, the maximum principal stress applied to the cutting edge 30 becomes compressive stress. It is presumed that the chipping of the cutting edge 30 and the spread of the chipping are caused by the action of tensile stress. When the contact area between the front flank 23 and the workpiece 1 is small, the stress from the front flank 23 toward the cutting edge 30 becomes small, and the stress from the chips on the rake face 22 side becomes relatively large, resulting in tensile stress at the corner 42. On the other hand, when the contact length is 5 μm or more and the contact area is large as in the first embodiment, the load from the front flank 23, i.e., the pressing force from the processing surface 2, also acts greatly on the cutting edge 30, and the stress applied to the corner 42 becomes compressive stress overall, so that it is presumed that the occurrence and spread of the chipping are suppressed.

[0025] In the leading portion 31 and the trailing portion 33, the "front clearance 23" in the above description can be replaced with the "side clearance 24" to consider the same phenomenon. The "front clearance" when "the stress applied to the cutting edge becomes a compressive shape" refers to the area near the corner 42 on the rake face 22, which is located at a position slightly shifted from the tip (lower left in FIG. 5) that connects the rake face 22 and the clearance 23, or the area where the corner 42 is expected to occur before the crater wear portion 41 occurs. The "area where the corner 42 is expected to occur" refers to the area shifted approximately 10 to 100 μm toward the back side from the tip of the cutting edge where the rake face 22 and the front clearance 23 are continuous, as described above.

[0026] It is difficult to actually measure whether the stress applied to the corner 42 during machining is compressive stress or tensile stress. Therefore, it is possible to model the shape of the tool blade 21 and confirm the same through simulation.

[0027] According to the cutting tool T1 of the above embodiment, chipping of the tool blade 21 can be effectively suppressed. For example, in a tool blade having a cutting edge with a contact length of less than 5 μm, when machining is continued after the crater wear portion 41 is generated, the cutting chips get caught on the corner portion 42, causing small chipping. Then, there was a problem that the chipping spreads and a large chip occurs at the tip of the cutting edge. In this embodiment, by making the stress applied to the tip of the cutting edge during machining a compressive stress, even if crater wear occurs, the above small chipping and the expansion of the chipping can be suppressed. In other words, since the tool life can be extended, problems such as deterioration of machining accuracy and an increase in the tool cost (tool unit cost) per processed product caused by the shortened tool life can be suppressed.

[0028] B. Second embodiment: Next, a cutting tool T12 according to a second embodiment of the present disclosure will be described with reference to Figs. 8 to 11. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted. In the second embodiment, the shape of the tool blade 21 and the manufacturing method are different from those in the first embodiment.

[0029] As shown in FIG. 8, in the cutting tool T2 of the second embodiment, the cutting edge shape at the cutting edge bottom 32 is not a curved shape but a chamfered shape. The chamfer angle between the rake face 22 and the front clearance face 23 is, for example, 29 degrees. More specifically, the cutting edge shape has a discontinuous point between the rake face 22 and the front clearance face 23, and the discontinuous point is connected by a straight line. In the second embodiment, the contact area C where the processing surface 2 of the workpiece 1 and the front clearance face 23 contact each other is a straight line in the cross section shown in FIG. 8. In the second embodiment, the "contact length" is the length of the portion where the front clearance face 23 and the processing surface 2 contact each other during processing. In the second embodiment, the contact length is 5 μm or more, as in the first embodiment.

[0030] The cutting edge 30 is machined not by blasting, but by attaching a tool T2 to the gear machining device 10 and cutting the workpiece 1. By cutting the workpiece 1, the front clearance 23 of the cutting edge 30 is scraped, and the front clearance 23 is made to conform to the machining surface 2 of the workpiece 1. Hereinafter, the processing in this manufacturing method is referred to as "conformal processing".

[0031] The manufacturing method using conformal processing includes, in this order, a preparation step of preparing a base member that is the basis of the blade portion Ta, a shape processing step of processing the shape of the blade portion Ta, an edge treatment step of rubbing the edge by cutting a cutting object for edge treatment using the base member, a cleaning step, a shot process, and a coating step of coating the surface of the blade edge 30. In the edge treatment step performed before the coating step, the blade edge 30 is intentionally abraded using the workpiece 1 to conform to the machining surface 2. The reason why the edge treatment step is performed before the coating step is that the blade is less susceptible to abrasion after coating.

[0032] 9 to 11 are diagrams for explaining parameters of machining conditions in the conforming process. FIG. 9 is a perspective view that shows a schematic diagram of the tool T2 and the workpiece 1 during machining. FIG. 10 is a cross-sectional view taken along line XX in FIG. 9, and is a diagram for explaining the cutting depth dc of the tool T2. FIG. 11 is a cross-sectional view taken along line XX in FIG. 9, and is a diagram for explaining the feed amount fa of the tool T2. In FIG. 11, the current machining trajectory is shown by a thick arrow line L1. Note that the "workpiece 1" in FIG. 9 may be an object to be cut for conforming process, and may be different from the workpiece 1 in the first embodiment.

[0033] In the edge treatment process in the run-in process, for example, the cutting speed is 80 to 200 m / min, the cutting depth dc (see Figure 10) is 0.5 to 2.0 mm, the feed rate fa (see Figure 11) is 0.1 to 0.3 mm / rev, the workpiece width W (see Figures 9 and 10) is 20 to 40 mm, the material of the workpiece 1 is SCM material, and the material of the tool base material is high-speed steel (high-speed tool steel).

[0034] The cutting speed in the conformal processing may be set to be the same as the cutting speed under the actual processing conditions, or may be set to be faster to facilitate scraping. The cutting depth dc is set to be the same as the cutting depth under the actual processing conditions. The feed rate fa is set to be slightly smaller than the feed rate under the actual processing conditions. This is because the feed rate fa is reduced to reduce the resistance and cutting force, thereby preventing cracks in the tool and allowing the tool to gradually conform to the shape of the processing surface 2. Note that the chamfer angle and the numerical values ​​of the above conditions in the conformal processing are merely examples and are not limited, and are appropriately set and changed according to the material and processing shape of the workpiece 1.

[0035] In Fig. 6, the analysis results of the second embodiment are plotted with square marks. The data indicated by square marks are the results of analyzing the maximum principal stress by changing the chamfer length, i.e., the contact length, in the cutting tool T12 having the chamfered cutting edge shape shown in Fig. 8 of the second embodiment. The data indicated by triangle marks are the data from a test tool manufactured by blending with a chamfer angle and a cutting depth of about 1.5 times larger than those of the configuration when the analysis results of the square marks were obtained, and are the results of analyzing the maximum principal stress by changing the contact length in the same manner.

[0036] As shown by the plots of squares and triangles in Fig. 6, the analysis conducted by the inventors of the present application revealed that even in the case of a chamfered shape, when the contact length is 5 μm or more, the maximum principal stress becomes compressive stress, as in the first embodiment. Therefore, when the contact length is 5 μm or more, chipping of the cutting edge 30 can be effectively suppressed.

[0037] According to the cutting tool T12 of the second embodiment, it is possible to obtain the same effects as the cutting tool T1 of the first embodiment. In addition, a cutting edge shape having a chamfered shape can be easily manufactured by the blending process.

[0038] C. Other embodiments: (C1) In the first embodiment, the cutting edge shape at the cutting bottom 32 is a curved shape tangent to the rake face 22 and the front clearance face 23, but at least a part of the cutting edge may be curved. For example, as shown in FIG. 12, the cutting edge may be tangent to the front clearance face 23, have a discontinuous point with the rake face 22, and have a curved shape passing through the discontinuous point, as in the case of tool T3. Alternatively, the cutting edge may be tangent to the rake face 22, have a discontinuous point with the front clearance face 23, and have a curved shape passing through the discontinuous point. Alternatively, the cutting edge may be a curved shape having a discontinuous point on the rake face 22 and the front clearance face 23, and have a curved shape passing through the discontinuous point. In other words, as long as the rounded line of the cutting edge 30 is rounded as a whole and has a curved shape, there is no limitation as to whether it is tangent to the rake face 22 or the clearance faces 23, 24, and a part of it may be linear as shown in FIG. 12.

[0039] (C2) In the second embodiment, the cutting edge shape at the cutting edge bottom 32 is chamfered and its cross section is composed of a series of straight lines, but it does not have to be entirely straight lines, and some of them may be curved. It is sufficient that at least a part of the cutting edge shape is chamfered.

[0040] (C3) In the gear cutting tools T1, T2 of the above embodiments, the shaft Tb may be cylindrical or conical instead of cylindrical. The gear cutting tools T1, T2 replaceable in the gear cutting device 10 may be a hob cutter, a shaper cutter, or the like, in addition to the above gear skiving cutter. The gear cutting device 10 in this configuration is a device that processes a tooth profile in a workpiece by hobbing or shaping.

[0041] (C4) Also, the tool does not have to be for gear cutting, but may be for cutting. In addition to gear cutting, it may be for turning using a lathe, and the processing may be for drilling holes, grooving, stepping, etc., instead of gear cutting.

[0042] (C5) In the gear cutting tool T1 of the first embodiment, the leading portion 31 and the trailing portion 33 are symmetrical to each other with respect to the cutting edge portion 32, but they may be asymmetrical.

[0043] (C6) In the second embodiment, the gear cutting tool T1 is manufactured by conforming processing. However, the chamfered shape may be formed by processing the cutting edge by grinding or laser processing without using conforming processing.

[0044] The present disclosure is not limited to the above-mentioned embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in each embodiment corresponding to the technical features in each form described in the Summary of the Invention column can be appropriately replaced or combined in order to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0045] Reference Signs List 1...workpiece, 2...machined surface, 10...gear machining device, 11...tool spindle, 12...workpiece spindle, 13...machining control section, 14...rotary table, 21...tool blade, 22...rake face, 23...front relief face, 24...side relief face, 30...blade tip, 31...leading section, 32...blade bottom, 33...trailing section, 41...crater wear section, 42...corner, C...contact area, RT...center axis, Rw...center axis, T1, T2, T3...cutting tool, Ta...blade, Tb...shaft, dc...cutting depth, fa...feed rate

Claims

1. A cutting tool having a blade portion having a plurality of tool blades and configured to perform cutting on a workpiece, The cutting edge shape of the cutting edge connecting the rake face and the flank face of the tool blade is such that the stress applied to the cutting edge during machining of the workpiece is compressive stress. Cutting tools.

2. 2. The cutting tool according to claim 1, wherein a contact length, which is a length of a portion where the flank and a machined surface of the workpiece contact each other, in a cross section showing the cutting edge shape in a plane intersecting the cutting face and passing through the cutting edge, is 5 μm or more.

3. The cutting tool according to claim 1 or 2, wherein at least a part of the cutting edge is curved.

4. The cutting tool according to claim 1 or 2, wherein at least a part of the cutting edge is chamfered.

5. The tool blade is formed on a circumferential edge of the blade portion, The cutting tool is 3. The cutting tool according to claim 1 or 2, which is a gear cutting tool that machines gear teeth on the workpiece by moving the workpiece and the cutting tool relative to each other while synchronizing a rotation of the workpiece about a central axis of the workpiece and a rotation of the cutting tool about a central axis of the cutting tool.

6. A method for producing the cutting tool according to claim 1 or 2, comprising the steps of: a preparation step of preparing a base member that serves as a base for the blade portion; A cutting edge treatment process in which the cutting object for cutting edge treatment is cut using the base member to perform a rubbing treatment on the cutting edge; a coating step of coating the surface of the cutting edge after the cutting edge treatment step; The manufacturing method of the cutting tool having the above structure.

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