JP7750804B2 - Drill and cutting process - Google Patents

Description

This disclosure relates to rotary tools used in cutting workpieces and methods for manufacturing machined products. Examples of rotary tools include drills and reamers.

Drills described in Patent Documents 1 to 3 are known as rotary tools used to cut workpieces such as metals. All of the drills described in Patent Documents 1 to 3 have a discharge flute extending from the tip to the rear end. Chips generated at the tip flow through the discharge flute toward the rear end and are discharged to the outside.

Japanese Utility Model Application Publication No. 62-188313 Japanese Patent Application Publication No. 03-142118 Japanese Patent Application Publication No. 09-501109

If chips fly out from the tip of the rotary tool (drill), they may damage the machined surface of the workpiece. Furthermore, if chips do not easily fly out from the rear end of the drill, they may become clogged. Therefore, it is desirable for chips to be difficult to eject from the tip of the drill, and easy to eject from the rear end of the drill.

For example, the drills described in Patent Documents 1 to 3 do not solve the above-mentioned problem because the radial rake and heel angles disclosed in each embodiment are set. (See Figure 3 of Patent Document 1, Figure 3 of Patent Document 2, Figure 3 of Patent Document 3, etc.)

The non-limiting one-sided rotary tool disclosed herein has a rod shape extending from the tip to the rear end along a rotation axis, and includes a cutting edge located near the tip, a discharge groove extending from the cutting edge toward the rear end, a first outer peripheral surface adjacent to the discharge groove at the front end in the rotation direction of the rotation axis, and a second outer peripheral surface adjacent to the discharge groove at the rear end in the rotation direction. The discharge groove has a first region located near the tip and a second region located near the rear end. In a first cross section passing through the first region and perpendicular to the rotation axis, the angle formed by the discharge groove and the first outer peripheral surface is an acute angle, and the angle formed by the discharge groove and the second outer peripheral surface is also an acute angle. In a second cross section passing through the second region and perpendicular to the rotation axis, the angle formed by the discharge groove and the first outer peripheral surface is an acute angle, and the angle formed by the discharge groove and the second outer peripheral surface is an obtuse angle.

With the above drill, chips are difficult to discharge to the outside at the tip end, but are easily discharged to the outside at the rear end.

1 is a perspective view showing a rotary tool according to an embodiment; FIG. 2 is a plan view of the drill shown in FIG. 1 as viewed from the A1 direction. FIG. 2 is a plan view of the drill shown in FIG. 1 as viewed from the A2 direction. 4 is a cross-sectional view taken along the line IV-IV shown in FIG. 2. 3 is a cross-sectional view taken along the line VV shown in FIG. 2. 6 is a cross-sectional view taken along the line VI-VI in FIG. 2. FIG. 2 is a schematic diagram illustrating a step in a method for manufacturing a machined product according to an embodiment. FIG. 2 is a schematic diagram illustrating a step in a method for manufacturing a machined product according to an embodiment. FIG. 2 is a schematic diagram illustrating a step in a method for manufacturing a machined product according to an embodiment.

The rotary tool of the embodiment will be described in detail below with reference to the drawings. Furthermore, for the sake of convenience, the figures referenced below show only the main components constituting the embodiment in a simplified form. Therefore, the rotary tool may include optional components not shown in the figures referenced in this specification. Furthermore, the dimensions of the components in the figures do not faithfully represent the actual dimensions of the components or the dimensional ratios of each component. While the rotary tool shown in this embodiment is a drill, the configuration of the rotary tool shown in this embodiment may also be applied to a reamer or end mill, for example.

The drill 1 of this embodiment, as shown in the example in Figure 1, has a generally cylindrical body 3 extending along a rotation axis O1 from a tip end 3A to a rear end 3B. The body 3 can perform drilling while rotating in a rotation direction O2 around the rotation axis O1.

In the example shown in Figure 1, the main body 3 has a cutting portion 5 located on the tip 3A side and a shank portion 7 located on the rear end 3B side of the cutting portion 5. There are no particular limitations on the shapes of the cutting portion and shank portion, but since the main body in this embodiment is approximately cylindrical, the cutting portion and shank portion are also approximately cylindrical.

The cutting portion 5 includes the portion that comes into contact with the workpiece and plays a primary role in cutting the workpiece. The shank portion 7 is the portion that is gripped by a rotating spindle or the like in a machine tool, and may be designed according to the shape of the spindle.

The outer diameter of the cutting portion 5 of the embodiment can be set to, for example, 8 mm to 33 mm. Furthermore, as shown in Figures 1 and 2, when the drillable depth of the drill 1 of the embodiment is LA and the outer diameter (machining diameter) is D, the relationship between LA and D in the main body 3 of the embodiment can be set to, for example, LA/D = 1.5 to 12. In the example shown in Figures 1 and 2, the drillable depth LA refers to the length of the portion of the cutting portion that extends from the tip 3A of the drill 1 toward the rear end 3B and has a diameter smaller than the machining diameter D.

The cutting portion 5 has a cutting edge 9, a discharge groove 11, and an outer peripheral surface 13. As shown in Figures 2 and 3, the cutting edge 9 is located on the tip 3A side of the main body 3. The cutting edge 9 is generally called the tip edge. The discharge groove 11 is a groove that extends from the cutting edge 9 toward the rear end 3B. The outer peripheral surface 13 is a surface located on the outer periphery of the cutting portion 5.

Here, Figure 2 is a plan view of the drill 1 viewed from a direction perpendicular to the rotation axis O1, which may also be referred to as a side view. Figure 3 is a plan view of the drill 1 viewed from the direction in which the rotation axis O1 extends, which may also be referred to as a front view.

The cutting edges 9 are provided for cutting the workpiece. As shown in FIG. 3, the cutting edges 9 extend from the rotation axis O1 side toward the outer peripheral surface 13 side. Here, as shown in FIG. 3, if the cutting portion 5 has multiple cutting edges 9, one of the multiple cutting edges 9 is designated as the first cutting edge 9A, and the cutting edge 9 located rearward of the first cutting edge 9A in the rotation direction O2 is designated as the second cutting edge 9B.

The drill 1 shown in this embodiment is a so-called indexable drill, consisting of a holder and an insert, but the drill disclosed herein is not limited to a throw-away drill, and may also be a so-called solid drill, in which the holder and insert are integrally formed.

The discharge groove 11, commonly called a flute, is provided to discharge chips toward the rear end 3B. For this reason, the surface located on the rear side in the rotation direction O2 is generally inclined toward the rear of the rotation direction O2 as it approaches the rear end 3B. In the example shown in Figure 1, the discharge groove 11 extends from the cutting edge 9 toward the rear end 3B in a twisted manner around the rotation axis O1, but it may also extend straight.

Note that "extending in a twisted manner" means that the discharge groove 11 extends in a spiral shape from the cutting edge 9 toward the rear end 3B, as shown in Figure 1. The discharge groove 11 may have portions that are not twisted. When the discharge groove 11 extends in a twisted manner, the twist angle of the discharge groove 11 is not limited to a specific value and can be set, for example, to approximately 10° to 35°.

In the example shown in Figure 2, when the cutting portion 5 has multiple discharge grooves, the one extending from the first cutting edge 9A toward the rear end 3B is referred to as the first discharge groove 11A, and the one extending from the second cutting edge 9B toward the rear end 3B is referred to as the second discharge groove 11B. For convenience of explanation, unless otherwise specified, the discharge groove 11 described below refers to the first discharge groove 11A in this embodiment.

The outer peripheral surface 13 is a surface area located at the outer edge of the cutting portion 5. In the drill 1 of this embodiment, the outer peripheral surface 13 in a cross section perpendicular to the rotation axis O1 has an arc shape. The cutting portion 5 has a first outer peripheral surface 13A and a second outer peripheral surface 13B as the outer peripheral surface 13. The first outer peripheral surface 13A is located forward of the discharge groove 11 in the rotation direction O2 of the rotation axis O1 and adjacent to the discharge groove 11. The second outer peripheral surface 13B is located rearward of the discharge groove 11 in the rotation direction O2 of the rotation axis O1 and adjacent to the discharge groove 11.

In the example shown in Figure 3, the first outer peripheral surface 13A and the second outer peripheral surface 13B are located on two outer peripheral surfaces separated by the first discharge groove 11A and the second discharge groove 11B, respectively. On the other hand, for example, if the cutting portion 5 has only one discharge groove 11, the first outer peripheral surface 13A and the second outer peripheral surface 13B may be located on the same outer peripheral surface.

When the cutting portion 5 has one or more cutting edges 9, the number of discharge grooves 11 and outer peripheral surfaces 13 in the cutting portion 5 may correspond to the number of cutting edges 9. In the example shown in Figures 2 and 3, the number of cutting edges 9 is two, and the number of discharge grooves 11 and outer peripheral surfaces 13 is also two. The cutting portion 5 may have three or more cutting edges 9, three or more discharge grooves 11, and three or more outer peripheral surfaces 13.

In the example shown in Figure 2, the cutting edge 9, discharge flutes 11, and outer peripheral surface 13 of the drill 1 shown in this embodiment are rotationally symmetric about the rotation axis O1, specifically, 180° rotationally symmetric about the rotation axis O1. However, the cutting edge 9, discharge flutes 11, and outer peripheral surface 13 may also be asymmetric about the rotation axis O1.

The discharge groove 11 has a first region 15 located on the side of the leading end 3A and a second region 17 located on the side of the rear end 3B. Here, when the length from the end (leading end portion S1) located on the leading end 3A side of the outer peripheral surface 13 to the end (rear end portion S2) located on the rear end 3B side of the workable depth LA is defined as LB, the first region 15 refers to the region of the discharge groove 11 located at a position moved 0 to (LB/6) from the leading end portion S1 toward the rear end 3B, and the second region 17 refers to the region of the discharge groove 11 located at a position moved 0 to (LB/6) from the rear end portion S2 toward the leading end 3A.

Also, as shown in Figure 2, the discharge groove 11 may have a portion on the rear end 3B side where the width in the circumferential direction of the rotation axis O1 decreases from the front end 3A toward the rear end 3B. In this case, as shown in Figure 2, the rear end S2 refers to the end located on the rear end 3B side excluding that portion.

As shown in Figure 2, the IV-IV cross section and the V-V cross section represent cross sections at a location LB/8 moved from the tip end S1 toward the rear end 3B and a location LB/8 moved from the rear end S2 toward the tip end 3A, respectively.

Furthermore, Figure 4 is a view of a cross section perpendicular to the rotation axis O1 in the first region 15, i.e., a first cross section, and Figure 5 is a view of a cross section perpendicular to the rotation axis O1 in the second region 17, i.e., a second cross section.

Here, let us assume that the point where the Nth outer peripheral surface 13T and the discharge groove 11 meet on the Mth cross section is the contact point PMN, the tangent line to the Nth outer peripheral surface 13T that passes through this contact point PMN is the imaginary straight line JMN, and the tangent line to the discharge groove 11 that passes through the contact point PMN is the imaginary extension line KMN. The angle between the imaginary straight line JMN and the imaginary extension line KMN is expressed as θMN. Note that M is an integer between 1 and 3, and N is 1 or 2. Furthermore, T is A when N=1, and B when N=2.

The cutting portion 5 may have a chamfered surface between the outer peripheral surface 13 and the discharge groove 11. In this case, θMN may be defined by taking the point where the outer peripheral surface 13 and the chamfered surface meet on the imaginary straight line JMN as the contact point PMN, and taking the point where the discharge groove 11 and the chamfered surface meet on the imaginary extension line KMN as the contact point PMN.

In the first cross section, the angle between the discharge groove 11 and the first outer peripheral surface 13A is an acute angle, and the angle between the discharge groove 11 and the second outer peripheral surface 13B is also an acute angle. Here, if the above angles cannot be uniquely identified because the discharge groove 11 or the outer peripheral surface 13 is arc-shaped in the first cross section, they may be evaluated using the angle θ11 between the imaginary line J11 and the imaginary extension line K11 and/or the angle θ12 between the imaginary line J12 and the imaginary extension line K12. In the example shown in Figure 4, θ11 corresponds to the angle between the discharge groove 11 and the first outer peripheral surface 13A, and θ12 corresponds to the angle between the discharge groove 11 and the second outer peripheral surface 13B. In the example shown in Figure 4, both θ11 and θ12 are acute angles.

Furthermore, in the second cross section, the angle between the discharge groove and the first outer peripheral surface is an acute angle, and the angle between the discharge groove and the second outer peripheral surface is an obtuse angle. Here, if the above angle cannot be uniquely identified in the second cross section because the discharge groove 11 or the outer peripheral surface 13 is arc-shaped, evaluation may be performed using the angle θ21 between the imaginary line J21 and the imaginary extension line K21 and/or the angle θ22 between the imaginary line J22 and the imaginary extension line K22. In the example shown in Figure 5, θ21 corresponds to the angle between the discharge groove 11 and the first outer peripheral surface 13A, and θ22 corresponds to the angle between the discharge groove 11 and the second outer peripheral surface 13B. In the example shown in Figure 5, θ21 is an acute angle, and θ22 is an obtuse angle.

For ease of explanation, in the drill 1 of this embodiment, the angle (θ12 to θ32) between the discharge flute 11 and the second outer peripheral surface 13B will be referred to as the radial rake, and the angle (θ11 to θ31) between the discharge flute 11 and the first outer peripheral surface 13A will be referred to as the heel angle.

When drilling a deep hole using a rotary tool (drill 1), the tip of the drill 1 is located inside the drilled hole, so if chips fly out from the tip 3A of the drill 1, there is a high possibility that the chips will collide with the inner wall surface (machined surface) of the drilled hole, potentially damaging the machined surface. Therefore, it is desirable that the radial rake of the discharge flute 11 be acute-angled on the tip 3A side of the drill 1 to prevent chips from flying out.

On the other hand, if chips are difficult to eject to the outside at the rear end 3B of the drill 1, they may become clogged. Therefore, it is desirable that the radial rake of the discharge flute 11 at the rear end 3B of the rotary tool be obtuse so that chips can be easily discharged to the outside.

In addition, it is desirable that the heel angle of the discharge flute 11 be acute on the rear end 3B side of the drill 1. This is because the rear portion of the discharge flute 11 in the rotational direction O2 rotates toward the front in the rotational direction O2, so when chips are discharged from the front side of the discharge flute 11 in the rotational direction O2, there is a possibility that the chips will collide with the rear portion of the discharge flute 11 in the rotational direction O2.

In the drill 1 according to this embodiment, in the first cross section, the angle between the discharge groove 11 and the first outer peripheral surface 13A is an acute angle, and the angle between the discharge groove 11 and the second outer peripheral surface 13B is an acute angle; and in the second cross section, the angle between the discharge groove 11 and the first outer peripheral surface 13A is an acute angle, and the angle between the discharge groove 11 and the second outer peripheral surface 13B is an obtuse angle.

Drill 1 has the above-described configuration, which provides excellent performance in that chips are less likely to be discharged to the outside from the tip end 3A of drill 1, and more easily discharged to the outside from the rear end 3B of drill 1.

Note that angles θ11, θ12, θ21, and θ22 are not limited to any specific value. For example, angle θ11 can be set to 45 to 75 degrees. angle θ12 can be set to 30 to 60 degrees. angle θ21 can be set to 15 to 45 degrees. angle θ22 can be set to 90 to 120 degrees.

The cutting section 5 may further include a third region 19 located between the first region 15 and the second region 17. Here, the third region 19 refers to the region of the discharge groove 11 at the midpoint between the positions of the first cross section and the second cross section in the direction of extension of the rotation axis O1. In the example shown in Figure 2, the VI-VI cross section represents a cross section at a location moved D/2 from the leading end S1 toward the rear end 3B.

Also, Figure 6 is a diagram of a cross section perpendicular to the rotation axis in the third region, i.e., a third cross section. In the third cross section, the angle between the discharge groove and the first outer peripheral surface may be an acute angle. Also, in the third cross section, the angle between the discharge groove and the second outer peripheral surface may be an acute angle or an obtuse angle.

Here, in the third cross section, if the above angle cannot be uniquely identified because the discharge groove 11 or outer peripheral surface 13 is arc-shaped, evaluation may be performed using the angle θ31 formed by the imaginary line J31 and the imaginary extension line K31 and/or the angle θ32 formed by the imaginary line J32 and the imaginary extension line K32. In the example shown in Figure 6, θ31 corresponds to the angle formed by the discharge groove 11 and the first outer peripheral surface 13A, and θ32 corresponds to the angle formed by the discharge groove 11 and the second outer peripheral surface 13B. In the example shown in Figure 6, θ31 is an acute angle, and θ32 is an acute angle.

In the cutting portion 5, the angle between the discharge groove 11 and the second outer peripheral surface 13B may increase from the first cross section to the second cross section. Here, the angle between the discharge groove 11 and the second outer peripheral surface 13B increasing from the first cross section to the second cross section does not necessarily have to continue to increase in the strict sense; it is sufficient if θ12 < θ32 < θ22.

In the cutting portion 5, the angle formed by the discharge groove 11 and the second outer peripheral surface 13B may increase at a constant rate from the first cross section to the second cross section. Here, the angle formed by the discharge groove 11 and the second outer peripheral surface 13B increasing at a constant rate from the first cross section to the second cross section satisfies (((θ22 - θ12)/2) + θ12 - 5°) < θ32 < (((θ22 - θ12)/2) + θ12 + 5°).

In the above case, the angle between the discharge flute 11 and the second outer peripheral surface 13B increases toward the rear end 3B of the drill 1, where chip clogging is more likely to occur. This allows the drill 1 to have better chip discharge properties, thereby reducing the risk of damaging the machined surface.

In the cutting portion 5, the angle between the discharge groove 11 and the first outer peripheral surface 13A in the first cross section may be larger than the angle between the discharge groove 11 and the first outer peripheral surface 13A in the second cross section. Furthermore, the angle between the discharge groove 11 and the first outer peripheral surface 13A may increase from the second cross section toward the first cross section. Here, the angle between the discharge groove 11 and the first outer peripheral surface 13A increasing from the second cross section toward the first cross section does not necessarily mean that it continues to increase in the strict sense; it is sufficient if θ21 < θ31 < θ11.

In the cutting portion 5, the angle formed by the discharge groove 11 and the first outer peripheral surface 13A may increase at a constant rate from the second cross section to the first cross section. Here, the angle formed by the discharge groove 11 and the first outer peripheral surface 13A increasing at a constant rate from the second cross section to the first cross section satisfies the relationship (((θ11 - θ21)/2) + θ21 - 5°) < θ31 < (((θ11 - θ21)/2) + θ21 + 5°).

In the above case, if the angle between the discharge flute 11 and the first outer peripheral surface 13A is large at the tip 3A of the drill 1 while the angle between the discharge flute 11 and the second outer peripheral surface 13B is small, the thickness of the drill 1 can be ensured, thereby increasing the durability of the drill 1 and preventing chips from being discharged to the outside. Furthermore, if the angle between the discharge flute 11 and the second outer peripheral surface 13B is large at the rear end 3B of the drill 1 while the angle between the discharge flute 11 and the first outer peripheral surface 13A is small, chips can be more efficiently discharged from the rear side of the discharge flute 11 in the rotational direction O2.

Note that angles θ31 and θ32 are not limited to specific values. For example, angle θ31 can be set to 30 to 60 degrees. Angle θ32 can be set to 60 to 90 degrees.

The first region 15 may have a concave curved shape as a whole in the first cross section . The second region 17 may have a first portion 21 connected to the first outer peripheral surface in the second cross section . The first portion 21 may have a concave curved shape. The second region 17 in the second cross section may have a second portion 23 connected to the second outer peripheral surface 13B and the first portion 21. The second portion 23 may have a linear shape.

In the above case, because the entire first region 15 located on the tip 3A side of the drill 1 has a concave curved shape, chips can be caught by the concave curved portion of the discharge flute 11, reducing the risk of chips flying out from the tip 3A side of the drill 1. Furthermore, because the second region 17 located on the rear end 3B side of the drill 1 has a linear second portion 23, chips that collide with the second portion 13 can be easily discharged to the outside from the rear end side in the rotational direction of the discharge flute 11, improving chip discharge performance from the rear end 3B side of the drill 1.

The third region 19 in the third cross section may have a third portion 25 connected to the first outer peripheral surface 13A. The third portion 25 may have a concave curved shape. The third region 25 in the third cross section may have a fourth portion 27 connected to the second outer peripheral surface 13B and the first portion 21. The fourth portion 27 may have a linear shape. In the example shown in FIGS. 4 to 6 , the length L2 of the second portion 23 may be longer than the length L4 of the fourth portion 27. The length L3 of the third portion 25 may be longer than the length L1 of the first portion 21.

In the above case, the second portion 23 is relatively long, which improves chip evacuation near the rear end 3B of the drill 1. Furthermore, the third portion 25 is relatively long, which reduces the risk of chips flying out near the tip 3A of the drill 1.

The insert attached to the main body 3 can be made of, for example, cemented carbide or cermet. Examples of cemented carbide compositions include WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co. Here, WC, TiC, and TaC are hard particles, and Co is the binder phase. Cermet is a sintered composite material in which a ceramic component is combined with a metal. Specifically, cermets include titanium compounds primarily composed of titanium carbide (TiC) or titanium nitride (TiN). In the case of a solid drill, the cutting portion 5 may be made of cemented carbide.

The surface of the insert attached to the main body 3 may be coated with a film using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. Examples of the composition of the coating include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), alumina (Al ₂ O ₃ ), etc. In the case of a solid drill, the cutting portion 5 may be coated with a film using a physical vapor deposition (PVD) method.

<Method of manufacturing machined product>
Next, a method for manufacturing a machined product according to an embodiment of the present disclosure will be described in detail using the drill 1 according to the above embodiment as an example. The following description will be given with reference to FIGS. 7 to 9.

A method for manufacturing a machined product according to an embodiment of the present disclosure includes:
(1) a step of rotating the drill 1 around a rotation axis O1;
(2) bringing the cutting edge 9 of the rotating drill 1 into contact with the workpiece 100;
(3) A step of separating the drill 1 from the workpiece 100.

More specifically, as shown in FIG. 7, first, the drill 1 is rotated around the rotation axis O1 and moved in the direction along the rotation axis O1 (Y1 direction), thereby bringing the drill 1 relatively closer to the workpiece 100.

Next, as shown in Figure 8, the cutting edge 9 of the drill 1 is brought into contact with the workpiece 100 to cut the workpiece 100. Then, as shown in Figure 9, the drill 1 is moved in the Y2 direction to move the drill 1 relatively away from the workpiece 100.

In this embodiment, the workpiece 100 is fixed and the drill 1 is rotated around the rotation axis O1 while the drill 1 is brought close to the workpiece 100. Also, in Figure 8, the cutting edge 9 of the rotating drill 1 is brought into contact with the workpiece 100 to cut the workpiece 100. Also, in Figure 9, the drill 1 is moved away from the workpiece 100 while rotating.

In the cutting process using the manufacturing method according to the embodiment of the present disclosure, the drill 1 is moved in each step to bring the drill 1 into contact with the workpiece 100 or to separate the drill 1 from the workpiece 100. Naturally, the present invention is not limited to this configuration.

For example, in step (1), the workpiece 100 may be brought closer to the drill 1. Similarly, in step (3), the workpiece 100 may be moved away from the drill 1. To continue cutting, the drill 1 can be kept rotating, and the process of bringing the cutting edge 9 of the drill 1 into contact with different locations on the workpiece 100 can be repeated.

Typical examples of materials for the workpiece 100 include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

1... Drill 3... Body 3A... Tip 3B... Rear end 5... Cutting portion 7... Shank portion 9... Cutting edge 9A... First cutting edge 9B... Second cutting edge 11... Discharge groove 11A... First discharge groove 11B... Second discharge groove 13... Outer surface 13A... First outer surface 13B... Second outer surface 15... First region 17... Second region 19... Third region 21... First part 23... Second part 25... Third part 27... Fourth part 100... Workpiece O1... Rotation axis O2... Rotation direction LA... Machinable depth LB... Length from tip to rear end L1 to L4... Length (of each part) D... Outer diameter (machining diameter)
S1: Leading edge S2: Rear edge P: Contact point J: Imaginary straight line K: Imaginary extension line θ: Angle between the imaginary straight line and the imaginary extension line Y1, Y2: Direction of movement

Claims (9)

It has a rod shape extending from the front end to the rear end along the rotation axis,
A cutting edge located on the tip side;
a discharge groove extending from the cutting edge toward the rear end;
a first outer circumferential surface adjacent to the discharge groove at a front side in the rotation direction of the rotary shaft;
a second outer circumferential surface adjacent to the discharge groove at a rear side in the rotation direction,
The discharge groove is
a first region located on the tip side;
a second region located on the rear end side,
In a first cross section that passes through the first region and is perpendicular to the rotation axis,
The angle formed by the discharge groove and the first outer peripheral surface is an acute angle,
The angle formed by the discharge groove and the second outer peripheral surface is an acute angle,
In a second cross section that passes through the second region and is perpendicular to the rotation axis,
The angle formed by the discharge groove and the first outer peripheral surface is an acute angle,
The angle formed by the discharge groove and the second outer peripheral surface is an obtuse angle,
an angle formed by the discharge groove and the second outer peripheral surface increases at a constant rate from the first cross section toward the second cross section . The rotary tool of claim 1, wherein the angle between the discharge groove and the first outer peripheral surface in the first cross section is larger than the angle between the discharge groove and the first outer peripheral surface in the second cross section. It has a rod shape extending from the front end to the rear end along the rotation axis,
A cutting edge located on the tip side;
a discharge groove extending from the cutting edge toward the rear end;
a first outer circumferential surface adjacent to the discharge groove at a front side in the rotation direction of the rotary shaft;
a second outer circumferential surface adjacent to the discharge groove at a rear side in the rotation direction,
The discharge groove is
a first region located on the tip side;
a second region located on the rear end side,
In a first cross section that passes through the first region and is perpendicular to the rotation axis,
The angle formed by the discharge groove and the first outer peripheral surface is an acute angle,
The angle formed by the discharge groove and the second outer peripheral surface is an acute angle,
In a second cross section that passes through the second region and is perpendicular to the rotation axis,
The angle formed by the discharge groove and the first outer peripheral surface is an acute angle,
The angle formed by the discharge groove and the second outer peripheral surface is an obtuse angle,
a rotating tool , wherein an angle formed between the discharge groove and the first outer peripheral surface in the first cross section is larger than an angle formed between the discharge groove and the first outer peripheral surface in the second cross section . The rotary tool according to claim 3 , wherein an angle formed between the discharge groove and the second outer circumferential surface increases from the first cross section toward the second cross section. The rotary tool according to claim 2 or 3 , wherein an angle formed between the discharge groove and the first outer peripheral surface increases from the second cross section toward the first cross section. The first region has an overall concave curved shape in the first cross section ,
The second region, in the second cross section,
a first portion connected to the first outer peripheral surface and having a concave curved shape;
The rotary tool according to claim 1 or 3 , further comprising: a second portion connected to the second outer circumferential surface and the first portion, the second portion having a linear shape. the discharge groove further includes a third region located between the first region and the second region,
The third region has, in a third cross section perpendicular to the rotation axis,
a third portion connected to the first outer peripheral surface and having a concave curved shape;
a fourth portion connected to the second outer circumferential surface and the first portion and having a linear shape;
The rotary tool according to claim 6 , wherein the second section is longer than the fourth section. The rotary tool of claim 7, wherein the third portion is longer than the first portion. a step of rotating the rotary tool according to claim 1 or 3;
bringing the rotary tool into contact with a workpiece;
and removing the rotary tool from the workpiece.