Rotary tool and method for manufacturing cut workpiece

Abstract

A rotary tool according to one non-limiting aspect of the present disclosure comprises a rod-shaped main body that extends along an axis of rotation from a tip end toward a rear end. The main body has a cutting edge positioned on the tip end side and a discharge groove extending from the cutting edge toward the rear end. The cutting edge has one or a plurality of main cutting edges and one or a plurality of sub cutting edges. The main cutting edge has a linear inner cutting edge, a linear outer cutting edge positioned on the outer peripheral side of the inner cutting edge, and a recessed connecting cutting edge connecting the inner cutting edge and the outer cutting edge. The sub cutting edge has a linear shape.

Description

Rotary tool and method for manufacturing machined product CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2024-027539, filed on February 27, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to a rotary tool and a method for manufacturing a machined product. Examples of the rotary tool include a drill and an end mill. Examples of the end mill include a radius end mill and a square end mill.

[0003] An end mill described in Japanese Patent Laid-Open No. 2004-237365 (Patent Document 1) is known as a rotary tool used for milling a workpiece. The end mill described in Patent Document 1 has one main cutting edge (long cutting edge), two sub cutting edges (short cutting edges), and a discharge groove (chip discharge groove). The main cutting edge and sub cutting edge are each linear. The discharge groove has a flat main cutting surface located along the main cutting edge and a flat sub cutting surface located along the sub cutting edge.

[0004] In Patent Document 1, because the parent rake face is flat, it is difficult to achieve both the ability to discharge chips generated by the parent cutting edge and the durability of the parent cutting edge. This is because, when the rake angle of the parent rake face is increased, the durability of the part of the parent cutting edge located near the rotation axis tends to decrease, and, when the rake angle of the parent rake face is reduced, the flow of chips tends to stagnate in the part of the parent cutting edge located away from the rotation axis.

[0005] A non-limiting one-sided rotary tool of the present disclosure has a rod-shaped body extending along a rotation axis from a tip end to a rear end. The body has a cutting edge located on the tip side and an ejection groove extending from the cutting edge toward the rear end. The cutting edge has one or more main blades and one or more sub-blade. The main blade has a linear inner blade, a linear outer blade located on the outer periphery of the inner blade, and a concave connecting blade connecting the inner blade and the outer blade. The sub-blade is linear.

[0006] 1 is a perspective view showing one non-limiting rotary tool of the present disclosure; FIG. 13 is an enlarged view of region II shown in FIG. 1; FIG. 2 is an enlarged view of region III shown in FIG. 2; FIG. 14 is a plan view of the rotary tool shown in FIG. 1 as viewed from the tip side; FIG. 4 is an enlarged view of region V shown in FIG. 4; FIG. 15 is a plan view of the rotary tool shown in FIG. 1 as viewed from the tip side; FIG. 4 is a side view of the rotary tool shown in FIG. 4 as viewed from direction VII; FIG. 4 is a side view of the rotary tool shown in FIG. 4 as viewed from direction VIII; FIG. 16 is a view of a main cutting edge of the rotary tool shown in FIG. 1 as viewed from the front in the rotation direction of the rotary shaft; FIG. 17 is an enlarged view of region X shown in FIG. 17; FIG. 18 is a view of a sub cutting edge of the rotary tool shown in FIG. 1 as viewed from the front in the rotation direction of the rotary shaft; FIG. 19 is an enlarged view of region XII shown in FIG. 11; FIG. 19 is a plan view of the rotary tool shown in FIG. 1 as viewed from the tip side; FIG. 19 is a cross-sectional view of cross section XIV of the rotary tool shown in FIG. 13; FIG. 19 is a cross-sectional view of cross section XV of the rotary tool shown in FIG. 13; FIG. 20 is a cross-sectional view of cross section XVI of the rotary tool shown in FIG. 13; FIG. 21 is a cross-sectional view of cross section XVII of the rotary tool shown in FIG. 13; FIG. 22 is a cross-sectional view of cross section XVIII of the rotary tool shown in FIG. 13; Fig. 14 is a cross-sectional view of the XIX cross section of the rotary tool shown in Fig. 13. Fig. 15 is a schematic view showing one step in a method for manufacturing a machined product with one surface, which is not limited to the present disclosure. Fig. 16 is a schematic view showing one step in a method for manufacturing a machined product with one surface, which is not limited to the present disclosure. Fig. 17 is a schematic view showing one step in a method for manufacturing a machined product with one surface, which is not limited to the present disclosure.

[0007] <Rotary Tool> A non-limiting aspect of the rotary tool 1 of the present disclosure will be described in detail below with reference to the drawings. However, for the sake of convenience, the drawings referred to below show only the main components necessary for explaining the embodiment in a simplified form. Therefore, the rotary tool 1 may include any components not shown in the drawings referred to. Furthermore, the dimensions of the components in the drawings do not faithfully represent the actual dimensions of the components, the dimensional ratios of the components, etc.

[0008] In one aspect, the rotary tool 1 is a so-called solid tool, but a tip-exchangeable tool may also be used. In another aspect, a square end mill may be used as an example of the rotary tool 1. However, the rotary tool 1 is not limited to a square end mill, and may be another end mill such as a radius end mill.

[0009] The rotary tool 1 may have a main body 3, as shown in a non-limiting example in FIGS. 1 to 19 . The main body 3 may be rod-shaped and extend along a rotation axis O1 from a front end 3 a to a rear end 3 b. The main body 3 is rotatable around the rotation axis O1. Note that the arrow Y1 in FIG. 1 and other figures may indicate the rotation direction of the rotation axis O1, or may indicate the rotation direction of the main body 3 around the rotation axis O1.

[0010] The main body 3 may have a shank portion 5 and a cutting portion 7. The shank portion 5 can function as a portion that is gripped by a rotating spindle of a machine tool. The shank portion 5 may be designed according to the shape of the spindle in the machine tool.

[0011] The cutting portion 7 may be located on the tip 3a side relative to the shank portion 5. The cutting portion 7 is capable of coming into contact with the workpiece, and can function as a portion that plays a major role in cutting (e.g., drilling) the workpiece.

[0012] The main body 3 is not limited to a specific size. For example, if the outer diameter of the cutting portion 7 is D, the maximum value of D may be set to approximately 3 to 16 mm. Furthermore, if the length of the cutting portion 7 in the direction along the rotation axis O1 is L, L may be set to approximately L=1.1D to 3D.

[0013] The body 3 may have a cutting edge 9 and a discharge groove 11, as a non-limiting example shown in Figure 2. These parts may be located in the cutting portion 7.

[0014] The cutting edge 9 may be located on the side of the tip 3a. The cutting edge 9 can function as a part that cuts the workpiece in the cutting process. The cutting edge 9 may also be called a bottom edge.

[0015] The discharge grooves 11 may extend from the cutting edge 9 toward the rear end 3b, as in the non-limiting example shown in Figures 7 and 8. The discharge grooves 11 may function as a portion for discharging chips generated by the cutting edge 9 to the outside. The discharge grooves 11 may extend parallel to the rotation axis O1, or may extend in a spiral shape around the rotation axis O1. In a cross section perpendicular to the rotation axis O1, the discharge grooves 11 may have a concave curved shape. The number of discharge grooves 11 may be the same as the number of cutting edges 9.

[0016] The cutting blade 9 may have a main blade 13 and a secondary blade 15, as in the non-limiting example shown in Figures 2 and 4. The main blade 13 may extend from the outer periphery 17 side to the rotation axis O1. Furthermore, the main blade 13 may not intersect with the rotation axis O1. The secondary blade 15 may extend from the outer periphery 17 side toward the rotation axis O1. The secondary blade 15 may not extend to the rotation axis O1. When viewed from the front of the tip 3a, the secondary blade 15 may be shorter than the main blade 13.

[0017] There may be only one parent blade 13, or there may be multiple parent blades 13. That is, there may be one or multiple parent blades 13. When there are multiple parent blades 13, the number of parent blades 13 may be about 2 to 3. An unrestricted cutting edge 9 on one surface has one parent blade 13.

[0018] There may be only one child blade 15, or there may be multiple child blades 15. That is, there may be one or multiple child blades 15. When there are multiple child blades 15, the number of child blades 15 may be about 2 to 6. An unrestricted cutting edge 9 on one surface has two child blades 15.

[0019] Here, the main blade 13 may have an inner blade 19, an outer blade 21, and a connecting blade 23, as in the non-limiting example shown in Figures 3 and 5. The inner blade 19 may be linear. The outer blade 21 may be located closer to the outer periphery 17 than the inner blade 19. The outer blade 21 may be linear. The connecting blade 23 may connect the inner blade 19 and the outer blade 21. The connecting blade 23 may be concave. Furthermore, the child blade 15 may be linear. These configurations may be evaluated when the tip 3a is viewed from the front.

[0020] When the parent blade 13 has the above-described configuration, the durability of the inner blade 19 located near the rotation axis O1, where high cutting resistance is likely to be applied to the parent blade 13, is high. Furthermore, the outer blade 21 located on the outer periphery 17 side of the parent blade 13 has high chip dischargeability. Additionally, because the connecting blade 23 connecting these blades has a concave shape, chips generated by the inner blade 19 and chips generated by the outer blade 21 are less likely to interfere with each other. This is because even if chips generated by the inner blade 19 or the outer blade 21 advance along the connecting blade 23 in the discharge groove 11, they are likely to curl in this portion. Therefore, the rotary tool 1 has high chip dischargeability and durability.

[0021] 6, the outer cutter 21 may extend closer to the rotation axis O1 than the child cutter 15. In other words, when the tip 3a is viewed from the front, the outer cutter 21 may be in contact with the end 15a of the child cutter 15 on the rotation axis O1 side, and when a virtual circle C1 is set with the rotation axis O1 as its center, the end 21a of the outer cutter 21 on the rotation axis O1 side may be located inside the virtual circle C1.

[0022] In this case, the durability of the cutting blade 15 is high. Chips are likely to occur at the end 15a of the cutting blade 15 on the side of the rotation axis O1, i.e., the inner end. However, the outer cutter 21 is located at a position corresponding to the inner end in the circumferential direction of the imaginary circle C1, and the outer cutter 21 cuts the workpiece, thereby reducing the cutting load applied to the inner end.

[0023] The radial rake θ19 of the inner cutter 19 may be the same as or different from the radial rake θ21 of the outer cutter 21. For example, as shown in a non-limiting example in Figures 5 and 6, the radial rake θ19 of the inner cutter 19 may be larger than the radial rake θ21 of the outer cutter 21. In this case, the sharpness of the outer cutter 21 is likely to be improved while maintaining the durability of the inner cutter 19.

[0024] The radial rake θ15 of the child blade 15 may be the same as or different from the radial rake θ21 of the outer cutter 21. For example, as shown in a non-limiting example in Figure 6, the radial rake θ15 of the child blade 15 may be the same as the radial rake θ21 of the outer cutter 21. In this case, there is little variation in the dischargeability of chips generated by the main blade 13 and the child blade 15. Therefore, chip dischargeability tends to be stable.

[0025] Note that the radial rakes being the same does not necessarily mean that they are exactly the same, but may mean that a difference of about 1° is allowed between the two radial rakes being compared.

[0026] The radial rake may refer to the angle of inclination relative to the radial direction of the rotation axis O1 when viewed from the front toward the tip 3a. For example, as shown in a non-limiting example in Figures 5 and 6, the radial rake θ19 at the end 19a of the inner cutter 19 on the outer periphery 17 side may refer to the angle between an imaginary line passing through the rotation axis O1 and the end 19a and a tangent to the inner cutter 19 at the end 19a. Note that the inner cutter 19 on one side, which is not limited to this example, has a linear shape. Therefore, the tangent to the inner cutter 19 at the end 19a overlaps with the inner cutter 19.

[0027] The radial rake θ21 at the end 21b of the outer cutter 21 on the outer periphery 17 side may refer to the angle formed by an imaginary line passing through the rotation axis O1 and the end 21b and a tangent to the outer cutter 21 at the end 21b. Note that the outer cutter 21 on one side, which is not limited to this, has a linear shape. Therefore, the tangent to the outer cutter 21 at the end 21b overlaps with the outer cutter 21.

[0028] The radial rake θ15 at the end 15b of the cutting edge 15 on the outer periphery 17 side may refer to the angle formed by an imaginary line passing through the rotation axis O1 and the end 15b and a tangent to the cutting edge 15 at the end 15b. Note that the cutting edge 15 on one side, which is not limited to this, has a linear shape. Therefore, the tangent to the cutting edge 15 at the end 15b overlaps with the cutting edge 15.

[0029] The radial rakes are not limited to any particular value. For example, the radial rake θ19 of the inner cutter 19 may be set to 4 to 6°. The radial rake θ21 of the outer cutter 21 may be set to 1 to 2.5°. The radial rake θ15 of the secondary cutter 15 may be set to 1 to 2.5°.

[0030] As a non-limiting example shown in Figures 14 to 19, the discharge groove 11 may have a main rake surface 25 and a sub rake surface 27. The main rake surface 25 may be located along the main cutting edge 13. The sub rake surface 27 may be located along the sub cutting edge 15. The main rake surface 25 and the sub rake surface 27 can each function as a portion through which chips flow during cutting.

[0031] The leading rake face 25 may have an inner rake face 29 and an outer rake face 31, as shown in Figures 15, 18, and 19, as a non-limiting example. The inner rake face 29 may be located along the inner cutting edge 19. The outer rake face 31 may be located along the outer cutting edge 21.

[0032] The rake angle θ31 of the outer rake face 31 may be the same as or different from the rake angle θ29 of the inner rake face 29. For example, as in the non-limiting examples shown in Figures 15, 18, and 19, the rake angle θ31 of the outer rake face 31 may be greater than the rake angle θ29 of the inner rake face 29.

[0033] In this case, the durability of the inner cutting edge 19 is high because the rake angle θ29 of the inner rake face 29 is relatively small, and the chip discharge performance is likely to be improved because the rake angle θ31 of the outer rake face 31 is relatively large. In addition, the sharpness of the outer cutting edge 21 is likely to be improved because the rake angle θ31 of the outer rake face 31 is relatively large, and the surface quality of the machined surface is likely to be improved.

[0034] The rake angle θ27 of the secondary rake face 27 may be the same as or different from the rake angle θ31 of the outer rake face 31. For example, as in the non-limiting examples shown in Figures 14, 18, and 19, the rake angle θ27 of the secondary rake face 27 may be the same as the rake angle θ31 of the outer rake face 31. In this case, variations in the chip flow between the secondary rake face 27 and the outer rake face 31 are suppressed, and chip discharge performance tends to be stable.

[0035] Note that the rake angles being the same does not necessarily mean that they are exactly the same, but may mean that a difference of about 2° is allowed between the two rake angles being compared.

[0036] The leading rake face 25 may further include an intermediate rake face 33, as shown in Figures 16 and 17 as a non-limiting example. The intermediate rake face 33 may be located along the connecting edge 23.

[0037] The rake angle θ33 of the middle rake face 33 may increase toward the outer periphery 17. For example, the rake angle θ33 in the non-limiting example shown in Fig. 16 may be rake angle θ33a. The rake angle θ33 in the non-limiting example shown in Fig. 17 may be rake angle θ33b. The rake angles θ33a and θ33b may be such that θ33a<θ33b. In this case, the fracture resistance of the end 19a of the inner cutting edge 19 on the outer periphery 17 side, where stress is likely to concentrate and fracture, is likely to be improved, and chipping is less likely to occur.

[0038] The rake angle may be evaluated by the angle between the rake face and an imaginary straight line L1 parallel to the rotation axis O1 in a cross section perpendicular to the cutting edge 9 and parallel to the rotation axis O1 when viewed from the front of the tip 3a.

[0039] As a non-limiting example shown in Figures 16 and 17, the intermediate rake face 33 may have a concave curved shape in a cross section perpendicular to the cutting edge 9 and parallel to the rotation axis O1 in a front view of the tip 3a. In this case, a tangent line L2 may be set at the end of the intermediate rake face 33 on the connecting edge 23 side. The rake angle θ33 may then be evaluated based on the angle between the imaginary line L1 and the tangent line L2. Note that when the rake face has a concave curved shape in the cross section, the rake angle may be evaluated using the same procedure as above.

[0040] When the rake face is located rearward of the cutting edge 9 in the rotation direction Y1 of the rotation axis O1, the rake angle may be evaluated as a positive value. When the rake face is located forward of the cutting edge 9 in the rotation direction Y1, the rake angle may be evaluated as a negative value.

[0041] The rake angles are not limited to a specific value. For example, the rake angle θ31 of the outer rake face 31 may be set to 5 to 15°. The rake angle θ29 of the inner rake face 29 may be set to -5 to 5°. The rake angle θ27 of the secondary rake face 27 may be set to 5 to 15°. The rake angle θ33 of the middle rake face 33 may be set to -5 to 15°. The magnitude relationship between the rake angles may be evaluated using absolute values.

[0042] In a front view of the tip 3a, the angle θ1 between the outer cutter 21 and the connecting cutter 23 may be the same as or different from the angle θ2 between the inner cutter 19 and the connecting cutter 23. For example, as shown in a non-limiting example in Figure 5, the angle θ1 may be larger than the angle θ2 in a front view of the tip 3a. In this case, the relatively large angle θ1 makes it easier for chips to flow, which tends to improve chip discharge performance.

[0043] The angles θ1 and θ2 are not limited to specific values. For example, the angle θ1 may be set to 165 to 175°, and the angle θ2 may be set to 150 to 170°.

[0044] In a front view of the tip 3a, the length of the inner cutting edge 19 may be the same as or different from the length of the connecting cutting edge 23. For example, as in a non-limiting example shown in Figure 5, in a front view of the tip 3a, the inner cutting edge 19 may be longer than the connecting cutting edge 23. In this case, the area of ​​the inner cutting edge 19 with a small rake angle increases, thereby preventing damage to the center of the tool during plunge cutting.

[0045] In addition, when viewed from the front of the tip 3a, the outer cutter 21 may be longer than the connecting cutter 23. Furthermore, when viewed from the front of the tip 3a, the outer cutter 21 may be longer than the inner cutter 19.

[0046] As a non-limiting example shown in Figures 9 and 10, the main blade 13 may have a linear shape when viewed from the front in the rotation direction Y1 of the rotation axis O1. Also, as a non-limiting example shown in Figures 11 and 12, the secondary blade 15 may have a linear shape when viewed from the front in the rotation direction Y1.

[0047] The main body 3 may further have a flank 35, as shown in a non-limiting example in Figures 3 and 5. The flank 35 may extend rearward from the cutting edge 9 in the rotational direction Y1. The flank 35 can function as a portion that avoids contact with the workpiece and reduces cutting resistance. The flank 35 may be connected to the cutting edge 9.

[0048] Examples of the material of the main body 3 include cemented carbide and cermet. Examples of the composition of the cemented carbide include WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co. Here, WC, TiC, and TaC may be hard particles, and Co may be a binder phase.

[0049] The cermet may be a sintered composite material in which a ceramic component is combined with a metal. Specifically, the cermet may be a titanium compound mainly composed of titanium carbide (TiC) or titanium nitride (TiN). However, the above materials are only examples and are not limiting, and the main body 3 is not limited to these materials.

[0050] The surface of the main body 3 may be coated with a coating using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method, and the coating composition may include, for example, titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al2O3).

[0051] <Method for Manufacturing Machined Product> Next, a non-limiting method for manufacturing the machined product 101 having one surface according to the present disclosure will be described with reference to the drawings.

[0052] The machined product 101 may be produced by cutting a workpiece 103. A method for producing the machined product 101 may include the following steps (1) to (4).

[0053] (1) A step of placing the rotary tool 1 above the workpiece 103 (see FIG. 20 ). (2) A step of rotating the rotary tool 1 around the rotation axis O1 in the direction of the arrow Y1 to bring the rotary tool 1 closer to the workpiece 103 (see FIG. 20 ).

[0054] In steps (1) and (2), for example, the workpiece 103 may be fixed on a table of a machine tool to which the rotary tool 1 is attached, and the rotary tool 1 may be brought closer to the workpiece 103 while rotating. In step (2), the workpiece 103 and the rotary tool 1 may be brought closer to each other, for example, the workpiece 103 may be brought closer to the rotary tool 1.

[0055] (3) A process of bringing the rotating tool 1 closer to the workpiece 103, thereby bringing the rotating tool 1 into contact with the workpiece 103 and forming a machining hole 105 (through hole) in the workpiece 103 (see Figure 21).

[0056] In step (3), cutting may be performed so that at least a portion of the cutting portion 7 is located inside the machined hole 105. Also, in step (3), the shank portion 5 may be set to be located outside the machined hole 105. From the viewpoint of obtaining a good finished surface, a portion of the rear end 3b side of the cutting portion 7 may be set to be located outside the machined hole 105. This portion can function as a margin region for chip evacuation, and excellent chip evacuation can be achieved via this region.

[0057] (4) Step of separating the rotary tool 1 from the workpiece 103 (see FIG. 22 ). In step (4), the workpiece 103 and the rotary tool 1 may be separated relatively. For example, the workpiece 103 may be separated from the rotary tool 1.

[0058] By going through the above steps, it is possible to obtain a machined product 101 having a highly accurate machined hole 105. Specifically, when the rotary tool 1 is used in the manufacturing method of the machined product 101, excellent workability can be achieved due to high chip discharge properties and durability. As a result, it is possible to obtain a machined product 101 having a highly accurate machined hole 105.

[0059] In addition, when cutting the workpiece 103 multiple times, for example, when forming multiple machining holes 105 in one workpiece 103, the process of bringing the rotary tool 1 into contact with different locations on the workpiece 103 while keeping the rotary tool 1 rotated may be repeated.

[0060] Examples of the material of the workpiece 103 include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0061] The above provides examples of the non-limiting one-sided rotary tool 1 and the manufacturing method of the machined product 101 of the present disclosure, but it goes without saying that the present disclosure is not limited to the above-described embodiments and can be any as long as it does not deviate from the gist of the present disclosure.

[0062] For example, the rotary tool 1 and the method for manufacturing the machined product 101 may be configured as follows. [1] The rotary tool has a rod-shaped main body extending along a rotation axis from a front end to a rear end, the main body having a cutting edge located near the front end and a discharge groove extending from the cutting edge toward the rear end, the cutting edge having one or more main cutting edges and one or more sub-cutting edges, the main cutting edge having a linear inner cutting edge, a linear outer cutting edge located radially outward of the inner cutting edge, and a concave connecting edge connecting the inner cutting edge and the outer cutting edge, the sub-cutting edges being linear. [2] In the rotary tool of [1] above, the outer cutting edge may extend closer to the rotation axis than the sub-cutting edges. [3] In the rotary tool of [1] or [2] above, the radial rake of the inner cutting edge may be larger than the radial rake of the outer cutting edge. [4] In the rotary tool of [3] above, the radial rake of the sub-cutting edge may be the same as the radial rake of the outer cutting edge. [5] In the rotary tool of any one of [1] to [4] above, the discharge groove may have a main rake face located along the main cutting edge and a secondary rake face located along the secondary cutting edge, and the main rake face may have an inner rake face located along the inner cutting edge and an outer rake face located along the outer cutting edge, and the rake angle of the outer rake face may be larger than the rake angle of the inner rake face. [6] In the rotary tool of [5] above, the rake angle of the secondary rake face may be the same as the rake angle of the outer rake face. [7] In the rotary tool of [5] or [6] above, the main rake face may further have an intermediate rake face located along the connecting cutting edge, and the rake angle of the intermediate rake face may increase toward the outer periphery. [8] In the rotary tool of any one of [5] to [7] above, the angle between the outer blade and the connecting blade may be larger than the angle between the inner blade and the connecting blade in a front view of the tip. [9] In the rotary tool of any one of [1] to [8] above, the inner blade may be longer than the connecting blade in a front view of the tip.

[10] A method for manufacturing a machined product can include the steps of rotating the rotary tool of any one of [1] to [9] above, bringing the rotary tool into contact with a workpiece, and separating the rotary tool from the workpiece.

[0063] DESCRIPTION OF SYMBOLS 1... Rotating tool 3... Main body 3a... Tip 3b... Rear end 5... Shank portion 7... Cutting portion 9... Cutting edge 11... Discharge groove 13... Main cutting edge 15... Sub cutting edge 15a... End portion on the rotation axis side 15b... End portion on the outer peripheral side 17... Outer periphery 19... Inner cutting edge 19a... End portion on the outer peripheral side 21... Outer cutting edge 21a... End portion on the rotation axis side 21b... End portion on the outer peripheral side 23... Connecting edge 25... Main rake face 27... Sub rake face 29... Inner rake face 31... Outer rake face 33... Middle rake face 35... Escape face 101... Cutting workpiece 103... Workpiece 105... Machining hole O1... Rotation axis Y1... Rotation direction C1... Virtual circle L1... Virtual straight line L2... Tangent

Claims

1. A rotary tool having a rod-shaped main body extending from the tip to the rear end along a rotation axis, said main body having a cutting blade located on the tip side and an ejection groove extending from said cutting blade towards said rear end, said cutting blade having one or more main blades and one or more sub-blade, said main blade having a linear inner blade, a linear outer blade located on the outer periphery of said inner blade, and a concave connecting blade connecting said inner blade and said outer blade, and said sub-blade having a linear shape.

2. The rotary tool according to claim 1, wherein the outer cutting edge extends closer to the rotary shaft than the secondary cutting edge.

3. A rotary tool according to claim 1 or 2, wherein the radial rake of the inner cutting edge is larger than the radial rake of the outer cutting edge.

4. The rotary tool according to claim 3, wherein the radial rake of the secondary cutting edge is the same as the radial rake of the outer cutting edge.

5. A rotary tool according to any one of claims 1 to 4, wherein the discharge groove has a main rake face located along the main cutting edge and a sub rake face located along the sub cutting edge, the main rake face having an inner rake face located along the inner cutting edge and an outer rake face located along the outer cutting edge, and the rake angle of the outer rake face is larger than the rake angle of the inner rake face.

6. The rotary tool according to claim 5, wherein the rake angle of the secondary rake face is the same as the rake angle of the secondary rake face.

7. A rotary tool according to claim 5 or 6, wherein the main rake face further has an intermediate rake face located along the connecting edge, and the rake angle of the intermediate rake face increases toward the outer periphery.

8. A rotary tool according to any one of claims 5 to 7, wherein, in a front view of the tip, the angle formed between the outer cutting edge and the connecting cutting edge is larger than the angle formed between the inner cutting edge and the connecting cutting edge.

9. A rotary tool according to any one of claims 1 to 8, wherein the inner cutting edge is longer than the connecting cutting edge when viewed from the front of the tip.

10. A method for manufacturing a machined product, comprising the steps of: rotating a rotary tool according to any one of claims 1 to 9; bringing the rotary tool into contact with a workpiece; and separating the rotary tool from the workpiece.

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