WO2025182277A1 - Rotary tool and method for manufacturing cut workpiece - Google Patents

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

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

The present disclosure relates to rotary tools and methods for manufacturing machined products. Rotary tools include, for example, drills and end mills. End mills include, for example, radius end mills and square end mills.

The end mill described in Japanese Patent Laid-Open No. 2004-237365 (Patent Document 1) is a known rotary tool used when 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 edges are each linear. The discharge groove also has a flat main cutting surface located along the main cutting edge and a flat sub cutting surface located along the sub cutting edge.

In Patent Document 1, because the parent rake face is flat, it is difficult to achieve both the ability to remove chips generated by the parent cutting edge and the durability of the parent cutting edge. This is because, if 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, if 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.

A non-limiting one-sided rotary tool of the present disclosure has a rod-shaped body extending along a rotation axis from the tip to the 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 radially outward of the inner blade, and a concave connecting blade connecting the inner blade and the outer blade. The sub-blade is linear.

FIG. 1 is a perspective view of a non-limiting one-sided rotary tool of the present disclosure. FIG. 2 is an enlarged view of an area II shown in FIG. 1 . FIG. 3 is an enlarged view of region III shown in FIG. 2 . FIG. 2 is a plan view of the rotary tool shown in FIG. 1 as viewed from the tip side. FIG. 5 is an enlarged view of an area V shown in FIG. 4 . FIG. 2 is a plan view of the rotary tool shown in FIG. 1 as viewed from the tip side. FIG. 7 is a side view of the rotary tool shown in FIG. 4 as viewed from a direction VII. FIG. 8 is a side view of the rotary tool shown in FIG. 4 as viewed from a direction VIII. 2 is a view of the main cutting edge of the rotary tool shown in FIG. 1 as viewed from the front in the direction of rotation of the rotary shaft. FIG. FIG. 10 is an enlarged view of an area X shown in FIG. 9 . 2 is a view of a cutting edge of the rotary tool shown in FIG. 1 as viewed from the front in the direction of rotation of a rotary shaft. FIG. 12 is an enlarged view of an area XII shown in FIG. 11 . FIG. 2 is a plan view of the rotary tool shown in FIG. 1 as viewed from the tip side. FIG. 14 is a cross-sectional view of the rotary tool shown in FIG. 13 taken along line XIV. FIG. 14 is a cross-sectional view of the rotary tool shown in FIG. 13 taken along line XV. FIG. 16 is a cross-sectional view of the rotary tool shown in FIG. 13 taken along line XVI. FIG. 17 is a cross-sectional view of the rotary tool shown in FIG. 13 taken along line XVII. FIG. 14 is a cross-sectional view of the rotary tool shown in FIG. 13 taken along the line XVIII. FIG. 14 is a cross-sectional view of the rotary tool shown in FIG. 13 taken along line XIX. 1 is a schematic diagram showing a step in a non-limiting method of manufacturing a one-sided machined product according to the present disclosure. 1 is a schematic diagram showing a step in a non-limiting method of manufacturing a one-sided machined product according to the present disclosure. 1 is a schematic diagram showing a step in a non-limiting method of manufacturing a one-sided machined product according to the present disclosure.

<Rotary tools>
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.

In one aspect, the rotary tool 1 is a so-called solid tool, but there is no problem if it is a tip-replaceable tool. In another aspect, a square end mill can be given 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.

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

The main body 3 may have a shank portion 5 and a cutting portion 7. The shank portion 5 may function as a part 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.

The cutting portion 7 may be located on the tip 3a side of the shank portion 5. The cutting portion 7 is capable of contacting the workpiece and can function as a part that plays a major role in cutting the workpiece (e.g., drilling).

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.

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

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

The discharge groove 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 groove 11 may function as a portion for discharging chips generated by the cutting edge 9 to the outside. The discharge groove 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 groove 11 may have a concave curved shape. The number of discharge grooves 11 may be the same as the number of cutting edges 9.

The cutting blade 9 may have a main blade 13 and a secondary blade 15, as shown in the non-limiting example in Figures 2 and 4. The main blade 13 may extend from the outer periphery 17 side to the rotation axis O1. 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.

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. If there are multiple parent blades 13, the number of parent blades 13 may be around 2 to 3. An unrestricted cutting edge 9 on one surface has one parent blade 13.

There may be only one sub-blade 15, or there may be multiple sub-blade 15. That is, there may be one or multiple sub-blade 15. If there are multiple sub-blade 15, the number of sub-blade 15 may be approximately 2 to 6. An unrestricted cutting edge 9 on one surface has two sub-blade 15.

Here, the main blade 13 may have an inner blade 19, an outer blade 21, and a connecting blade 23, as shown in the non-limiting example 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. The child blade 15 may also be linear. These configurations may be evaluated when the tip 3a is viewed from the front.

When the parent blade 13 has the above configuration, the inner blade 19 located near the rotation axis O1, where high cutting resistance is likely to be applied, has high durability. Furthermore, the outer blade 21 located on the outer periphery 17 side of the parent blade 13 has high chip discharge performance. 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 outer blade 21 advance along the connecting blade 23 in the discharge groove 11, they are likely to curl in this area. Therefore, the rotary tool 1 has high chip discharge performance and durability.

As shown in a non-limiting example in Figure 6, the outer cutter 21 may extend closer to the rotation axis O1 than the sub-cutter 15. In other words, when viewed from the front of the tip 3a, the outer cutter 21 may be tangent to the end 15a of the sub-cutter 15 on the rotation axis O1 side, and when an imaginary 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 imaginary circle C1.

In this case, the durability of the blade 15 is high. The end 15a of the blade 15 on the side of the rotation axis O1, i.e., the inner end, is prone to chipping. However, the outer cutter 21 is located at a point circumferentially around the imaginary circle C1 that corresponds to the inner end, and the outer cutter 21 cuts the workpiece, thereby reducing the cutting load applied to the inner end.

The radial rake θ19 of the inner cutter 19 may be the same as the radial rake θ21 of the outer cutter 21, or they may be different. 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.

The radial rake θ15 of the child blade 15 may be the same as the radial rake θ21 of the outer blade 21, or they may be different. 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 blade 21. In this case, there is little variation in the discharge performance of chips generated by the main blade 13 and child blade 15. This makes it easier to stabilize chip discharge performance.

Note that "the radial rakes are 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.

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 at which an imaginary line passing through the rotation axis O1 and end 19a intersects with a tangent to the inner cutter 19 at 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 end 19a overlaps with the inner cutter 19.

Furthermore, the radial rake θ21 at the end 21b of the outer cutter 21 on the outer periphery 17 side may refer to the angle at which an imaginary line passing through the rotation axis O1 and end 21b intersects with a tangent to the outer cutter 21 at 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 end 21b overlaps with the outer cutter 21.

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

The radial rake is not limited to a specific 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°.

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

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

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 shown in the non-limiting example 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.

In this case, the relatively small rake angle θ29 of the inner rake face 29 increases the durability of the inner cutting edge 19, and the relatively large rake angle θ31 of the outer rake face 31 tends to improve chip removal. Furthermore, the relatively large rake angle θ31 of the outer rake face 31 tends to improve the sharpness of the outer cutting edge 21, and the surface quality of the machined surface tends to improve.

The rake angle θ27 of the sub rake face 27 may be the same as the rake angle θ31 of the outer rake face 31, or they may be different. For example, as in the non-limiting example shown in Figures 14, 18, and 19, the rake angle θ27 of the sub rake face 27 may be the same as the rake angle θ31 of the outer rake face 31. In this case, variation in the chip flow between the sub rake face 27 and the outer rake face 31 is reduced, making chip discharge more stable.

Note that "the rake angles are 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.

The primary rake surface 25 may further include an intermediate rake surface 33, as shown in Figures 16 and 17 as a non-limiting example. The intermediate rake surface 33 may be located along the connecting blade 23.

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 Figure 16 may be rake angle θ33a. The rake angle θ33 in the non-limiting example shown in Figure 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 on the outer periphery 17 side of the inner cutting edge 19, where stress is likely to concentrate and fracture, is likely to be improved, making chipping less likely.

The rake angle may also be evaluated by the angle between the rake face and an imaginary 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.

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 when viewed from the front 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 straight line L1 and the tangent line L2. Note that if the rake face has a concave curved shape in the above cross section, the rake angle may be evaluated using the same procedure as above.

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

The rake angle is 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 minor 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 rake angles may be evaluated using absolute values.

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

Angles θ1 and θ2 are not limited to specific values. For example, angle θ1 may be set to 165 to 175°. Angle θ2 may be set to 150 to 170°.

When viewed from the front of the tip 3a, the length of the inner cutting edge 19 may be the same as the length of the connecting cutting edge 23, or they may be different. For example, as shown in a non-limiting example in Figure 5, when viewed from the front 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 reducing damage to the center of the tool during plunge cutting.

In addition, when viewed from the front of the tip 3a, the outer blade 21 may be longer than the connecting blade 23. Also, when viewed from the front of the tip 3a, the outer blade 21 may be longer than the inner blade 19.

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

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 also be connected to the cutting edge 9.

The main body 3 may be made of, for example, cemented carbide or cermet. The cemented carbide may have a composition such as WC-Co, WC-TiC-Co, or WC-TiC-TaC-Co. Here, WC, TiC, and TaC may be hard particles, and Co may be a binder phase.

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 whose main component is 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.

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 may have a composition such as titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and _alumina ( _Al2O3 ).

<Method of manufacturing machined product>
Next, a non-limiting method for manufacturing the one-sided machined product 101 according to the present disclosure will be described with reference to the drawings.

The machined product 101 may be produced by cutting the workpiece 103. The manufacturing method for the machined product 101 may include the following steps (1) to (4).

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

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 relatively close to each other; for example, the workpiece 103 may be brought closer to the rotary tool 1.

(3) A process in which the rotating rotary tool 1 is brought even closer to the workpiece 103, bringing the rotating rotary tool 1 into contact with the workpiece 103 and forming a machining hole 105 (through hole) in the workpiece 103 (see Figure 21).

In step (3), cutting may be performed so that at least a portion of the cutting portion 7 is located within 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 perspective of obtaining a good finished surface, a portion of the rear end 3b of the cutting portion 7 may be set to be located outside the machined hole 105. This portion can function as a margin area for chip evacuation, and excellent chip evacuation can be achieved through this area.

(4) Step of separating the rotary tool 1 from the workpiece 103 (see FIG. 22).
In the step (4), the workpiece 103 and the rotary tool 1 may be separated from each other, for example, the workpiece 103 may be separated from the rotary tool 1 .

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

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 may be repeated while the rotary tool 1 is kept rotating.

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

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

For example, the method for manufacturing the rotary tool 1 and the machined product 101 may be configured as follows.
[1] The rotary tool has a rod-shaped body extending along a rotation axis from the tip to the rear end, the body having a cutting edge located on the tip side and an exhaust groove extending from the cutting edge toward the rear end, the cutting edge having one or more parent blades and one or more child blades, the parent blade having a linear inner blade, a linear outer blade located outer than the inner blade, and a concave connecting blade connecting the inner blade and the outer blade, and the child blade is linear in shape.
[2] In the rotary tool of [1] above, the outer cutting edge may extend closer to the rotary shaft than the secondary cutting edge.
[3] In the rotary tool of the above [1] or [2], the radial rake of the inner cutter may be larger than the radial rake of the outer cutter.
[4] In the rotary tool of [3] above, the radial rake of the secondary 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 has a main rake face located along the main cutting edge and a sub rake face located along the sub cutting edge, and the main rake face has 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 secondary 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 blade, 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, when viewed from the front of the tip, the angle formed by the outer blade and the connecting blade may be larger than the angle formed by the inner blade and the connecting blade.
[9] In the rotary tool according to 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 any one of the rotary tools [1] to [9] above, bringing the rotary tool into contact with a workpiece, and removing the rotary tool from the workpiece.

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... Flank face 101... Cutting workpiece 103... Workpiece material 105... Machining hole O1... Rotation axis Y1... Rotation direction C1... Virtual circle L1... Virtual straight line L2... Tangent line

Claims (10)

a rod-shaped main body extending from a front end to a rear end along a rotation axis;
The body includes:
A cutting edge located on the tip side;
a discharge groove extending from the cutting edge toward the rear end,
The cutting blade is
One or more main blades;
one or more blades;
The main blade is
A linear inner blade,
a linear outer cutter located on the outer periphery side of the inner cutter;
a concave connecting blade that connects the inner blade and the outer blade,
The rotary tool, wherein the secondary blade has a linear shape. The rotary tool according to claim 1, wherein the outer cutting edge extends closer to the rotation axis than the secondary cutting edge. 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. 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. The discharge groove is
a main rake face located along the main cutting edge;
a secondary rake face located along the secondary blade,
The rake face is
an inner rake face located along the inner cutting edge;
an outer rake face located along the outer cutting edge;
5. The rotary tool according to claim 1, wherein a rake angle of the outer rake face is larger than a rake angle of the inner rake face. 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. The primary rake face further includes an intermediate rake face located along the connecting edge,
The rotary tool according to claim 5 or 6, wherein a rake angle of the inner rake face increases toward the outer periphery. 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 blade and the connecting blade is larger than the angle formed between the inner blade and the connecting blade. A rotary tool according to any one of claims 1 to 8, wherein the inner blade is longer than the connecting blade when viewed from the front of the tip. A step of rotating the rotary tool according to any one of claims 1 to 9;
bringing the rotary tool into contact with a workpiece;
and removing the rotary tool from the workpiece.