Rotary tool and method for producing a machine-made product

Abstract

A rotary tool (1), comprising a body (3) which extends along an axis of rotation (R1) from a first end (3a) to a second end (3b) and has a cylindrical shape, wherein the body (3) has: a free space (13) located at the first end (3a), a groove (12) extending from the free surface (13) to the second end (3b) and designed to eject a chip, a cutting edge (11) which is arranged at a section of the clearance surface (13) and the groove (12), and a coolant hole (14) extending from the second end (3b) to the first end (3a) and opening into the open area (13), and the coolant hole (14) has: in a cross-section orthogonal to the axis of rotation (R1) a first section (14A) which projects forward in a rotation direction (R2) of the rotation axis (R1) and towards an outer circumferential side and has a convexly curved shape, a second section (14B) which projects forward in the direction of rotation (R2) and towards a central side and has a convexly curved shape, and a third section (14C) which projects backwards and towards the central side in the direction of rotation (R2) and has a convex curved shape.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a rotary tool for machining a workpiece and a method for producing a machined product. Examples of a rotary tool include an end mill, a drill, and a reamer. BACKGROUND OF THE INVENTION

[0002] Examples of well-known rotary tools for machining workpieces, for example those made of metal, are the drills described in JP 2011 - 020 255 A and JP 2017 - 205 844 A. These drills have a coolant hole extending from a rear end to a tip end, where it terminates. During cutting, coolant can be sprayed from this hole, cooling both the drill and the workpiece.

[0003] Furthermore, from DE 10 2013 205 056 A1, a rotary tool is known with a body that extends along an axis of rotation from a first end to a second end and has a cylindrical shape, wherein the body has: a clearance surface arranged at the first end, a groove extending from the clearance surface to the second end and configured to eject a chip, a cutting edge arranged at an intersection of the clearance surface and the groove, and a coolant hole extending from the second end to the first end and opening into the clearance surface. BRIEF EXPLANATION

[0004] A rotary tool according to one aspect of the present disclosure has a body extending along an axis of rotation from a first end to a second end and having a cylindrical shape. The body has a clearance face located at the first end, a groove extending from the clearance face towards the second end and configured for chip ejection, a cutting edge located at an intersection of the clearance face and the groove, and a coolant hole extending from the second end towards the first end and opening into the clearance face.The coolant hole has, in a cross-section perpendicular to the axis of rotation, a first section which projects forward in a direction of rotation of the axis of rotation and towards an outer circumferential side and has a convex curved shape, a second section which projects forward in the direction of rotation and towards a central side and has a convex curved shape, and a third section which projects backward in the direction of rotation and towards the central side and has a convex curved shape. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view of a rotary tool according to the present embodiment. Fig. 2 is an enlarged view of one in Fig. 1 of the area shown A1. Fig. Figure 3 is a side view of the rotation tool. Fig. Figure 4 is a front view of the rotary tool. Fig. Figure 5 is a cross-sectional view along the arrow line III-III in Fig. 3 and an enlarged partial view. Fig. Figure 6 is a view showing the shape of a coolant hole, using the cross-sectional view along arrow line III-III in Fig. 3. Fig. Figure 7 shows the flow of coolant being discharged from the coolant hole, using the front view of the rotary tool. Fig. Figure 8 is a schematic view showing a process for manufacturing a machined product according to one embodiment. DESCRIPTION OF THE EXECUTION FORMS

[0005] The rotary tool and the method for producing a machined product of an embodiment of the present disclosure are described in detail below with reference to the diagrams. However, each of the figures referred to below is a simplified representation of only those components necessary for describing the embodiments, in order to facilitate the description. Accordingly, the rotary tool may include any components not shown in each of the figures. The dimensions of the components in the figures do not represent the actual dimensions of the components, their proportions, or similar aspects.

[0006] In the present disclosure, the axis of rotation denotes a center of rotation of the rotating tool, and the circumferential direction refers to a direction around the axis of rotation. The radial direction is a direction orthogonal to both the axis of rotation and the circumferential direction. The radially inner side is a direction approaching the axis of rotation, or a side approaching the axis of rotation in the radial direction. The radially outer side is a direction away from the axis of rotation, or a side away from the axis of rotation in the radial direction. The outer circumferential side denotes a side of an outer circumferential surface of the rotating tool, and the central side denotes a side of an inner edge section that has a center of the rotating tool at which the axis of rotation is located. 1. Rotary tool Schematic configuration of a rotary tool 1

[0007] First, a configuration of a rotary tool 1 according to the present embodiment is determined based on the Fig. 1 to 4 described. Fig. Figure 1 is a perspective view of a rotary tool 1 according to the present embodiment. Fig. 2 is an enlarged view of one in Fig. 1 of the area shown A1. Fig. Figure 3 is a side view of the rotation tool 1. Fig. Figure 4 is a front view of rotary tool 1.

[0008] As in Fig. 1 and Fig. As shown in Figure 3, a drill bit can be cited as an example of the rotary tool 1, and the drill bit is represented as the rotary tool 1 in the present embodiment. More precisely, the drill bit shown in Figure 3 is a rotary tool 1. Fig. The drill shown is a flat drill with a point angle of 180 degrees. Examples of rotary tools include end mills and reamers. Of course, the point angle of the drill is not limited to 180 degrees.

[0009] As in Fig. As shown in Figure 1, the rotary tool 1 according to the present embodiment has a body 3 which extends along an axis of rotation R1 from a first end 3a to a second end 3b and has a cylindrical shape. The first end 3a can be replaced by a pointed end 3a and the second end 3b by a rear end 3b. The rotary tool 1 has a body 3. The body 3 is rotatable about an axis of rotation R1 and has a cutting section 10 at the first end 3a, which is an end section in the axial direction to the axis of rotation R1. As shown in Figure 1, the cutting section 10 is located at the first end 3a, which is an end section in the axial direction to the axis of rotation R1. Fig. As shown in Figure 8 and described below, the cutting section 10 performs the cutting in contact with a workpiece T.

[0010] The body 3 of the so-called solid rotary tool 1 can, for example, be made of a hard material. Examples of such hard materials include high-speed steel, cemented carbide, ceramic, cermet, cubic boron nitride (cBN), and polycrystalline diamond (PCD). In the solid version, at least the cutting section 10 can be made of the hard material described above, and the cutting section 10 can be brazed to a metal element. The rotary tool can be a tool commonly referred to as a tool with replaceable tips, consisting of a holder and a cutting insert. In this case, the cutting insert for cutting the workpiece T can, for example, be made of the hard material described above.

[0011] The body 3 can have a section called the shaft section 4 and a section called the main body 5, as shown in Fig. 1 and Fig. Figure 3 shows the shank section 4 being located at the second end 3b, and the main body 5 being located closer to the first end 3a than the shank section 4. The shank section 4 is a section that can be gripped by a rotating spindle or the like in a machine tool. The cutting section 10 is formed on the side of the first end 3a of the main body 5. A groove 12 extending from the first end 3a is formed in a helical shape on an outer circumferential surface of the main body 5.

[0012] Although described in detail below, the rotary tool 1 drills the workpiece T (see Fig. 8), while the shaft section 4 is gripped by a machine tool, rotated in a rotational direction R2 around the axis of rotation R1 and moved to the side of the first end 3a. Cutting section

[0013] As in Fig. 2 and Fig. As shown in Figure 4, the cutting section 10, which is located on the side of the first end 3a, has a cutting edge 11, an opening of a groove 12, a clearance surface 13 and an opening of a coolant hole 14. Fig. Figure 4 is a front view of the rotary tool 1 as seen from the side of the first end 3a. A view from the side of the first end 3a is referred to as a front view.

[0014] The open space 13 is located at the first end of 3a. As in Fig. As shown in Figure 4, the free area 13 in the present embodiment is formed by a first to third free area section 13A, 13B and 13C, which are arranged at the first end 3a and have free angles that increase stepwise towards the rear in the direction of rotation R2. As shown in Fig. As shown in Figure 4, in the present embodiment, a pair of free surfaces 13 are formed symmetrically to each other with respect to the axis of rotation R1 in a front view. The free surface section 13C is a cut surface in the present embodiment.

[0015] The cutting edge 11 is arranged at an intersection of the clearance surface 13 and the groove 12, which is located in the direction of rotation R2 in front of the clearance surface 13. In particular, the cutting edge 11 is formed on a comb section where the first clearance surface section 13A and the groove 12, especially the opening of the groove 12, intersect. In the example of Fig. 4 The cutting edge 11 has a thinning edge 11a on its radially inner side. In the present embodiment, a pair of cutting edges 11 are symmetrical to each other with respect to the axis of rotation R1 in a front view.

[0016] The groove 12 opens into the open area 13 at the first end 3a, extends from the open area 13 to the second end 3b, as shown in Fig. 1 and Fig. Figure 3 shows the groove 12, which serves to remove chips produced during cutting with the cutting edge 11. In the present embodiment, a pair of grooves 12 extends symmetrically to each other with respect to the axis of rotation R1 as they wind from the clearance face 13 to the second end 3b, and are shaped such that they are cut off before reaching the shank section 4. From the perspective of continuous outward chip discharge, the groove 12 can have a concave curved shape in a cross-section orthogonal to the axis of rotation R1.

[0017] The coolant hole 14 extends inside the body 3 from the second end 3b towards the first end 3a and opens into the free surface 13. The function of the coolant hole 14 is to expel a coolant (cooling fluid) supplied from the second end 3b out of the opening of the first end 3a in order to cool the rotating tool 1 and the workpiece T (see Fig. 8) It is also possible to use the coolant to remove the produced chips.

[0018] In the present embodiment, which is described in Fig. As shown in Figure 4, a pair of coolant holes 14 are provided symmetrically to the axis of rotation R1. The pair of coolant holes 14 opens such that it spans the second free-surface section 13B and the first free-surface section 13A of the free surface 13. The coolant holes 14 are designed such that their shape and size are constant in a cross-section orthogonal to the axis of rotation R1 over the entire length of the body 3. <form des Kühlmittellochs>

[0019] The shape of the coolant hole 14 is described below with reference to the Fig. 5 to 7 described. Fig. 5 is a cross-sectional view along an arrow line III-III in Fig. 3 and an enlarged partial view. Fig. Figure 6 is a view showing a shape of the coolant hole 14, with the cross-sectional view along the arrow line III-III in Fig. 3 is used. Fig. Figure 7 is a view showing a flow of coolant being discharged from coolant hole 14, using the front view of rotary tool 1.

[0020] As in Fig. As shown in Figure 5, the coolant hole 14, in a cross-section perpendicular to the axis of rotation R1, has a first section 14A, a second section 14B, and a third section 14C, each with a convexly curved shape. The first section 14A has a convexly curved shape that projects forward in the direction of rotation R2 and towards the outer circumferential side. The second section 14B has a convexly curved shape that projects forward in the direction of rotation R2 and towards a central side. The third section 14C has a convexly curved shape that projects backward in the direction of rotation R2 and towards the central side. 1) The first section 14A has a convexly curved shape that projects forward in the direction of rotation and towards the outer circumferential side. As a result, the coolant ejected (expelled) from the first section 14A flows towards an outer circumferential side section (radially outer section) of the cutting edge 11, which is located in front of the coolant hole 14 in the direction of rotation R2, as indicated by an arrow Y1 in Fig. 7. During cutting, the rotary tool 1 is rotated at high speed in the direction of rotation R2, so that the centrifugal force acts towards the outer circumferential side. This centrifugal force enables the coolant to be discharged uniformly towards the outer circumferential side section of the cutting edge 11.

[0021] Since the outer circumferential side section of the cutting edge 11 has a large rotational diameter from the axis of rotation R1, the amount of chips produced, the cutting load, and the generation of cutting heat are high, and chipping of an edge tip is also likely. However, the first section 14A allows a large quantity of coolant to be supplied to the outer circumferential side section of the cutting edge 11 and to a cutting section of the workpiece T (see Fig. 8), which is cut from the outer circumference side section to effectively cool the outer circumference side section and the cutting section.

[0022] 2) The second section 14B has a convexly curved shape that projects forward in the direction of rotation and towards a central side. As a result, the coolant expelled from the second section 14B flows towards a section near the center, where the axis of rotation R1 is located, as indicated by an arrow Y2. Fig. 7. In the section near the center, the rotational speed is slow, but heat tends to accumulate. Therefore, it is possible to place a large amount of coolant in the section near the center and in part of the workpiece T (see Fig. 8), which is located in this area, to direct and effectively cool the areas.

[0023] 3) The third section 14C has a convexly curved shape that projects rearward and toward the center in the direction of rotation. As a result, the coolant expelled from the third section 14C flows toward the groove 12, which is located behind the coolant hole 14 in the direction of rotation R2, as indicated by arrow Y3. Fig. 7. The coolant, which is expelled from the rear of the coolant hole 14 in the direction of rotation R2, is probably directed towards the outer circumferential side due to centrifugal force.

[0024] If the third section 14C projects towards the outer circumferential side, the coolant is likely to be discharged to the outside of the body 3 without flowing into the groove 12, which is located downstream of the coolant hole 14 in the direction of rotation R2. However, by forming the third section 14C in a shape that is convex towards the central side, a larger quantity of coolant can be directed into the groove 12, which is located downstream in the direction of rotation R2, even when centrifugal force is applied. As a result, a greater quantity of coolant can be supplied from the third section 14C towards the groove 12, which is located downstream in the direction of rotation R2, and the chips can be discharged advantageously.

[0025] The coolant hole 14 not only has an opening section in the free area 13, as in Fig. 4 shown, but also a first section 14A to third section 14C in a cross-section that is far removed from the open area 13, as in Fig. 3 and Fig. Figure 5 shows that, for example, the coolant hole 14 has the first section 14A to the third section 14C only in the vicinity of the opening section in the free area 13, and that the shape of the coolant hole 14 is circular in the cross-section furthest from the free area 13. In this case, a flow loss increases due to the change in the shape of the coolant hole 14 in the cross-section. For this reason, there is concern that the effects of the first section 14A to the third section 14C described above cannot be sufficiently achieved.

[0026] However, if the coolant hole 14 has the first section 14A to the third section 14C at a large distance from the free area 13 in cross-section, the flow path loss within the coolant hole 14 is likely to be suppressed. Therefore, the effects of the first section 14A to the third section 14C described above are easily achieved.

[0027] By bringing the coolant hole 14 into the shape described above, it is not only possible to connect the rotary tool 1 and the workpiece T (see Fig. 8) to cool by means of the coolant discharged from coolant hole 14, but also to carry away the chips produced by means of the coolant.

[0028] As in Fig. As shown in Figure 5, the coolant hole 14, in a cross-section orthogonal to the axis of rotation R1, can further comprise a fourth section 14D and a fifth section 14E, each having a concave curved shape, or only one of the fourth section 14D and one of the fifth section 14E. The fourth section 14D is located between the first section 14A and the second section 14B and has a concave curved shape recessed towards the inside of the coolant hole 14. The fifth section 14E is located between the second section 14B and the third section 14C and has a concave curved shape recessed towards the inside of the coolant hole 14.

[0029] The narrowing of a space between the first section 14A and the second section 14B, each of which has a convex curved shape, at the fourth section 14D, which has a concave curved shape, allows for a narrowing of the outlet direction for the coolant supplied by the first section 14A and the second section 14B. This narrowing of the outlet direction also increases the momentum of the coolant. Similarly, the narrowing of a space between the second section 14B and the third section 14C, each of which has a convex curved shape, at the fifth section 14E, which has a concave curved shape, also narrows the outlet direction for the coolant supplied by the second section 14B and the third section 14C. This narrowing of the outlet direction also increases the momentum of the coolant.

[0030] As in Fig. As shown in Figure 6, an end section 14A-1 of the first section 14A, which is located at the front in the direction of rotation R2, can be located further from the axis of rotation R1 than an end section 14C-1 of the third section 14C, which is located at the rear in the direction of rotation R2. That is, the end section 14A-1 is located further from the axis of rotation R1 on the outer circumferential side (radially outer side) than the end section 14C-1. Fig. 6. The end section 14A-1 and the end section 14C-1 are highlighted by black dots.

[0031] With such a configuration, the first section 14A for supplying the coolant towards the outer circumferential side section of the cutting edge 11 is located close to the outer circumferential side and makes it possible for a larger quantity of coolant to be supplied towards the outer circumferential side section of the cutting edge 11 in order to cool the outer circumferential side section more effectively.

[0032] As in Fig. As shown in Figure 6, all sections 14A, 14B, and 14C, from the first to the third, can be arc-shaped, and the radii of curvature of the arc shapes can satisfy a relationship between the first section 14A > the second section 14B > the third section 14C. That is, the first section 14A has an arc shape with a first radius of curvature, the second section has an arc shape with a second radius of curvature, and the third section has an arc shape with a third radius of curvature. The first radius of curvature is larger than the second radius of curvature, and the second radius of curvature is larger than the third radius of curvature.

[0033] With this configuration, the outlet direction of the coolant expelled from each of the first to third sections 14A, 14B, and 14C can still correspond to the cooling or expulsion function required for each section. Therefore, the coolant orifice 14 can more effectively achieve both cooling and chip expulsion via the coolant.

[0034] As in Fig. As shown in Figure 6, the centers of the virtual circles C1 to C3, corresponding to the arc shapes of the first to third sections 14A, 14B, and 14C, are defined as centers C1a to C3a. In this case, a positional relationship between centers C1a and C3a can have an interval between center C1a and center C2a that is shorter than an interval between center C2a and center C3a.

[0035] That is, a virtual circle corresponding to the arc shape of the first section 14A is defined as a first virtual circle C1, a virtual circle corresponding to the arc shape of the second section 14B is defined as a second virtual circle C2, and a virtual circle corresponding to the arc shape of the third section 14C is defined as a third virtual circle C3. A center point of the first virtual circle C1 is defined as a first center point C1a, a center point of the second virtual circle C2 is defined as a second center point C2a, and a center point of the third virtual circle C3 is defined as a third center point C3a. In this case, the distance between the first center point C1a and the second center point C2a is shorter than the distance between the second center point C2a and the third center point C3a.

[0036] Such a configuration places the first section 14A close to the second section 14B and allows a section between a position near a center and an outer circumferential side section of the cutting edge 11 to also be effectively cooled by the coolant ejected from both the first section 14A and the second section 14B.

[0037] In this case, as in Fig. Figure 6 shows that the first virtual circle C1 and the second virtual circle C2 intersect each other, and the third virtual circle C3 can be designed such that it is away from the first virtual circle C1 and the second virtual circle C2.

[0038] With such a configuration, the first section 14A is closer to the second section 14B. As a result, the section between the position near the center and the outer circumferential side section of the cutting edge 11 can be cooled more effectively by the coolant expelled from both the first section 14A and the second section 14B.

[0039] As in Fig. As shown in Figure 6, if the fourth section 14D is provided, the fourth section 14D can be recessed towards the rear in the direction of rotation R2. If the fifth section 14E is provided, the fifth section 14E can be recessed towards the rear in the direction of rotation R2 and towards the outer circumferential side.

[0040] Recessing the fourth section 14D rearward in the direction of rotation R2 minimizes its influence on the flow direction of the coolant supplied by both the first section 14A and the second section 14B, allowing the coolant to flow easily to the cutting edge 11. This narrowing of the outlet direction also increases the coolant's momentum. Recessing the fifth section 14E rearward in the direction of rotation R2 and toward the outer circumference allows the coolant supplied by the second section 14B to flow easily to the cutting edge 11 and the coolant supplied by the third section 14C to flow easily to the groove 12.

[0041] In this case, as in Fig. As shown in Figure 6, the fourth section 14D and the fifth section 14E each have an arc shape, and the radii of curvature of the arc shapes can be smaller than the radii of curvature of the arc shapes of the first section 14A to the third section 14C. In other words, a fourth radius of curvature, which is the radius of curvature of the arc shape of the fourth section 14D, can be smaller than the first, second, and third radii of curvature. A fifth radius of curvature, which is the radius of curvature of the arc shape of the fifth section 14E, can be smaller than the first, second, and third radii of curvature.

[0042] Such a configuration allows the fourth section 14D to have a compact configuration, while the first section 14A and the second section 14B are likely to be wide. Accordingly, it is possible to achieve more effective cooling and chip removal by the coolant, while the discharge direction of the coolant supplied by the first section 14A and the second section 14B is stably controlled. The fifth section 14E has a compact configuration, and the second section 14B and the third section 14C are likely to be wide. Accordingly, it is possible to achieve more effective cooling and chip removal by the coolant, while the discharge direction of the coolant supplied by the second section 14B and the third section 14C is stably controlled.

[0043] As in Fig. As shown in Figure 5, in cross-section orthogonal to the axis of rotation R1, the coolant hole 14 can have a distance (interval) from the coolant hole 14 to the axis of rotation R1 that is greater than the distance (interval) from the coolant hole 14 to the outer circumferential surface of the body 3. That is, the coolant hole 14 can be located close to the outer circumferential surface of the body 3. Such a configuration can have a core thickness of the rotating tool 1 while providing the coolant hole 14.

[0044] As in Fig. As shown in Figure 5, in cross-section orthogonal to the axis of rotation R1, the distance from the coolant hole 14 to the groove 12, which is arranged in the direction of rotation R2 in front of the coolant hole 14, can be greater than the distance from the coolant hole 14 to the outer circumferential surface of the body 3. With such a configuration, the coolant hole 14 can be formed in a position that is closer to the outer circumferential surface of the body 3 than the cutting edge 11 to be cooled. Such a configuration can have a core thickness of the rotary tool 1 while the coolant hole 14 is provided. 2. Method for producing a machined or chip-removing product

[0045] A process for manufacturing a machined product according to an example is described using the following: Fig. 8 described. Fig. Figure 8 is a schematic diagram illustrating a process for manufacturing a machined product of one embodiment. The following describes a process for manufacturing a machined product U by machining the workpiece T with the rotary tool 1.

[0046] The method for producing the machined product U according to an embodiment of the present disclosure may comprise the following steps. In detail, (1) Rotating the rotary tool 1, (2) Bringing the rotary tool 1 into contact with the workpiece T and (3) Separating the rotary tool 1 from the workpiece can be done using baptism techniques.

[0047] More precisely, it is first explained how the reference 801 in Fig. As specified in Figure 8, the workpiece T is prepared directly below the rotary tool 1, and the rotary tool 1, attached to the machine tool, is rotated about the axis of rotation R1. Examples of workpiece T include aluminum, unalloyed steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0048] Next, as indicated by reference 802 in Fig. As specified in Figure 8, the rotary tool 1 and the workpiece T are moved towards each other to bring the rotary tool 1 into contact with the workpiece T, thereby cutting the workpiece T through the cutting edge 11 and forming a machined hole V. A chip from the cut workpiece T is carried outwards through the groove 12. The rotary tool 1 and the workpiece T can be moved relative to each other in any way that is not particularly restricted. For example, the rotary tool 1 can be moved towards the stationary workpiece T, or the workpiece T can be moved towards the stationary rotary tool 1.

[0049] Then, as with reference 803 in Fig. 8, the rotary tool 1 is separated from the workpiece T, whereby the machined product U is produced as the workpiece T formed with the machined bore V.

[0050] The invention according to the present disclosure has been described above with reference to the various drawings and examples. However, the invention according to the present disclosure is not limited to each of the embodiments described above. That is to say, the embodiments of the invention according to the present disclosure can be modified in various ways within the scope shown in the present disclosure, and embodiments obtained by suitable combinations of the technical means disclosed in various embodiments are also included within the technical scope of the invention according to the present disclosure. In other words, a person skilled in the art can easily make various variations or modifications based on the present disclosure. It should be noted that these variations or modifications are included within the scope of the present disclosure. REFERENCE MARK 1 rotary tool 3 bodies 3a First End 3b Second End 10 cutting section 11 Cutting edge 12 Nut 13 open space 14 Coolant hole 14A First Section 14A-1 End section of the first section 14B Second Section 14C Third Section 14C-1 End section of the third section 14D Fourth Section 14E Fifth Section C1 First virtual circle C1a First midpoint C2 Second virtual circle C2a Second midpoint C3 Third virtual circle C3a Third center point R1 axis of rotation R2 Rotation direction< / form>

Claims

[1] A rotary tool (1) comprising a body (3) which extends along an axis of rotation (R1) from a first end (3a) to a second end (3b) and has a cylindrical shape, wherein the body (3) has: a free space (13) located at the first end (3a), a groove (12) extending from the free surface (13) to the second end (3b) and designed to eject a chip, a cutting edge (11) which is arranged at a section of the clearance surface (13) and the groove (12), and a coolant hole (14) extending from the second end (3b) to the first end (3a) and opening into the open area (13), and the coolant hole (14) has: in a cross-section orthogonal to the axis of rotation (R1) a first section (14A) which projects forward in a rotation direction (R2) of the rotation axis (R1) and towards an outer circumferential side and has a convexly curved shape, a second section (14B) which projects forward in the direction of rotation (R2) and towards a central side and has a convexly curved shape, and a third section (14C) which projects backwards and towards the central side in the direction of rotation (R2) and has a convex curved shape. [2] The rotary tool (1) according to claim 1, wherein an end section (14A-1) of the first section (14A), which is arranged at the front in the direction of rotation (R2), is further away from the axis of rotation (R1) than an end section (14C-1) of the third section (14C), which is arranged at the rear in the direction of rotation (R2). [3] The rotary tool (1) according to claim 1 or 2, wherein the first section (14A) has an arc shape with a first radius of curvature, the second section (14B) has an arc shape with a second radius of curvature, the third section (14C) has an arc shape with a third radius of curvature, the first radius of curvature is larger than the second radius of curvature and the second radius of curvature is larger than the third radius of curvature. [4] The rotary tool (1) according to claim 3, where a virtual circle corresponding to the arc shape of the first section (14A) is defined as a first virtual circle (C1), a virtual circle corresponding to the arc shape of the second section (14B) is defined as a second virtual circle (C2), a virtual circle corresponding to the arc shape of the third section (14C) is defined as a third virtual circle (C3), a center point of the first virtual circle (C1) is defined as a first center point (C1a), a center point of the second virtual circle (C2) is defined as the second center point (C2a), a center point of the third virtual circle (C3) is defined as a third center point (C3a) and a distance between the first midpoint (C1a) and the second midpoint (C2a) is shorter than a distance between the second midpoint (C2a) and the third midpoint (C3a). [5] The rotary tool (1) according to claim 4, where the first virtual circle (C1) and the second virtual circle (C2) intersect and the third virtual circle (C3) is away from the first virtual circle (C1) and the second virtual circle (C2). [6] The rotary tool (1) according to any one of claims 1 to 5, wherein the coolant hole (14) has a fourth section (14D) in cross-section orthogonal to the axis of rotation (R1), which is arranged between the first section (14A) and the second section (14B), which is recessed towards an inside of the coolant hole (14) and has a concave curved shape. [7] The rotary tool (1) according to claim 6, wherein the fourth section (14D) is recessed in the direction of rotation (R2) towards the rear. [8] The rotary tool (1) according to claim 6 or 7, wherein the first section (14A) has an arc shape with a first radius of curvature, the second section (14B) has an arc shape with a second radius of curvature, the third section (14C) has an arc shape with a third radius of curvature, the fourth section (14D) has an arc shape with a fourth radius of curvature and the fourth radius of curvature is smaller than the first radius of curvature, the second radius of curvature, and the third radius of curvature. [9] The rotary tool (1) according to any one of claims 1 to 8, wherein the coolant hole (14) has a fifth section (14E) in cross-section orthogonal to the axis of rotation (R1), which is arranged between the second section (14B) and the third section (14C), is recessed towards an inside of the coolant hole (14) and has a concave curved shape. [10] The rotary tool (1) according to claim 9, wherein the fifth section (14E) is recessed in the direction of rotation (R2) towards the rear and towards the outer circumferential side. [11] The rotary tool (1) according to claim 9 or 10, wherein the first section (14A) has an arc shape with a first radius of curvature, the second section (14B) has an arc shape with a second radius of curvature, the third section (14C) has an arc shape with a third radius of curvature, the fifth section (14E) has an arc shape with a fifth radius of curvature and the fifth radius of curvature is smaller than the first radius of curvature, the second radius of curvature, and the third radius of curvature. [12] The rotary tool (1) according to any one of claims 1 to 11, wherein in cross-section orthogonal to the axis of rotation (R1) a distance from the coolant hole (14) to the axis of rotation (R1) is greater than a distance from the coolant hole (14) to an outer circumferential surface. [13] The rotary tool (1) according to any one of claims 1 to 12, wherein in cross-section orthogonal to the axis of rotation (R1) a distance from the coolant hole (14) to the groove (12) lying in front of the coolant hole (14) in the direction of rotation (R2) is greater than a distance from the coolant hole (14) to an outer circumferential surface. [14] A method for producing a machined product (U), wherein the method comprises: Rotating a rotary tool (1) according to any one of claims 1 to 13, Bringing the rotary tool (1) into contact with a workpiece (T), and Separating the rotary tool (1) from the workpiece (T).

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