Cutting tool and method for manufacturing cut workpiece

Abstract

The present invention provides a cutting tool that exhibits excellent discharging of chips. A cutting tool according to one aspect of the present disclosure has a body section, and a first cutting section that is fixed to the body section. The body section has a trunk section that is positioned toward a rear end, and a branch section that extends from the trunk section toward a tip end. The branch section has a first branch section that extends rearward in the rotation direction of a rotary axis toward the tip end, and a second branch section that extends forward in the rotation direction of the rotary axis toward the tip end. The first cutting section is fixed to the body section at a portion where the first branch section and the second branch section intersect.

Description

Cutting tool and method for manufacturing machined product

[0001] The present disclosure relates to a cutting tool and a method for manufacturing a machined product. Examples of cutting tools include rotary tools such as boring tools. Boring tools can be used to machine the inner surface of a cylindrical workpiece.

[0002] A cutting tool described in Patent Document 1 is known as a boring tool, which is an example of a rotary tool. The cutting tool described in Patent Document 1 has a center tube and an annular cutting ring. The cutting ring has leading and trailing arms and a cutting head. An opening is formed in the center tube to reduce the weight.

[0003] U.S. Patent Publication No. 2021 / 0060665

[0004] A cutting tool according to one aspect of the present disclosure has a main body portion extending along a rotation axis from a tip end to a rear end, and a first cutting portion fixed to the main body portion and having a first cutting edge, the main body portion having a trunk portion located on the rear end side and a branch portion extending from the trunk toward the tip, the branch portion having a first branch portion extending rearward in the rotation direction of the rotation axis as it approaches the tip, and a second branch portion extending forward in the rotation direction of the rotation axis as it approaches the tip, the first cutting portion being fixed to the main body portion at a portion where the first branch portion and the second branch portion intersect.

[0005] FIG. 1 is a perspective view of a cutting tool according to a non-limiting embodiment of the present disclosure, as viewed from the rear end side. FIG. 2 is a perspective view of the cutting tool shown in FIG. 1, as viewed from the tip side. FIG. 3 is a front view of the cutting tool shown in FIG. 1, as viewed from the tip side. FIG. 4 is a side view of the cutting tool shown in FIG. 1, as viewed from the direction of arrow A4 shown in FIG. 3. FIG. 5 is a cross-sectional view taken along the arrows VI-VI shown in FIG. 5. FIG. 6 is a cross-sectional view taken along the arrows VII-VII shown in FIG. 4. FIG. 7 is an enlarged perspective view of a region in which a first cutting portion and a third cutting portion are located in the cutting tool shown in FIG. 1. FIG. 8 is a schematic explanatory view showing one step of a method for manufacturing a machined product according to a non-limiting embodiment of the present disclosure.

[0006] In cutting processes, further improvement in chip evacuation is required. In particular, for boring tools, the space for chip evacuation is limited, and there is a high demand for further improvement in chip evacuation.

[0007] Hereinafter, a cutting tool and a method for manufacturing a machined product according to an embodiment of the present disclosure will be described in detail 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 cutting tool may include optional components not shown in the drawings. Furthermore, the dimensions of the components in the drawings do not faithfully represent the actual dimensions of the components, the dimensional ratios of the components, etc.

[0008] 1 to 7, the configuration of a non-limiting example of a cutting tool 1 according to this embodiment will be described. The cutting tool 1 is, for example, a rotary tool, and a specific example is a boring tool. The boring tool can be used to cut the inner surface of a cylindrical workpiece.

[0009] 1 and 2, the cutting tool 1 has a rotation axis O1. The rotation axis O1 is an axis about which the cutting tool 1 rotates, and is not a tangible object of the cutting tool 1. The cutting tool 1 rotates around the rotation axis O1 in a rotation direction O2 to cut a workpiece 103 (see FIG. 9), which will be described later.

[0010] The cutting tool 1 may include a main body 10 and a cutting portion 20 fixed to the main body 10. The main body 10 may extend from a tip 10A toward a rear end 10B along a rotation axis O1. The main body 10 may have a trunk 11 located on the rear end 10B side and branch portions 12 extending from the trunk 11. The branch portions 12 may extend toward the tip 10A.

[0011] 1 to 7 , the cutting tool 1 may have, as the cutting portion 20, a first cutting portion 21 having a first cutting edge 21a. The cutting tool 1 may have, as the cutting portion 20, a second cutting portion 22 having a second cutting edge 22a. The second cutting portion 22 may be located closer to the tip 10A than the first cutting portion 21 and closer to the rotation axis O1 than the first cutting portion 21.

[0012] The cutting tool 1 may further include a third cutting portion 23 having a third cutting edge 23 a as the cutting portion 20. The third cutting portion 23 may be located rearward of the first cutting portion 21 in the rotation direction O2 and at the same distance from the rotation axis O1 as the first cutting portion 21.

[0013] The cutting tool 1 may further include a fourth cutting portion 24 having a fourth cutting edge 24a as the cutting portion 20. The fourth cutting portion 24 may be located closer to the rear end 10B than the first cutting portion 21 and at the same distance from the rotation axis O1 as the first cutting portion 21.

[0014] 8, the first cutting section 21 may have a cutting insert 201 having a cutting edge, a cartridge 202, and a holding section 203. The second cutting section 22 to the fourth cutting section 24 may also have the cutting insert 201, the cartridge 202, and the holding section 203, similar to the first cutting section 21.

[0015] The cutting insert 201 is attached to the cartridge 202. The cartridge 202 may have a pocket on the side of the tip 10A for attaching the cutting insert 201, and the cutting insert 201 may be attached to this pocket. The cartridge 202 is not limited to a particular shape, and may be in the shape of a rod, a polygonal plate, a polygonal column, or the like.

[0016] The cartridge 202 is attached to the holder 203. The holder 203 may be formed as a part of the main body 10.

[0017] In the case where the first cutting portion 21 to the fourth cutting portion 24 are configured to include cutting inserts 201, the cutting insert 201 of the first cutting portion 21 has a first cutting edge 21a, and the cutting insert 201 of the second cutting portion 22 has a second cutting edge 22a. Furthermore, the cutting insert 201 of the third cutting portion 23 has a third cutting edge 23a, and the cutting insert 201 of the fourth cutting portion 24 has a fourth cutting edge 24a.

[0018] The cutting insert 201 is not limited to a specific shape, and may be a diamond-shaped plate, a triangular plate, etc. The shapes of the cutting inserts 201 may differ among the first cutting portion 21 to the fourth cutting portion 24.

[0019] When the cutting insert 201 has a diamond-shaped plate shape or a triangular shape, the first cutting edge 21a may be located at the intersection of two side surfaces that sandwich the vertex on the tip 10A side of the cutting insert 201 in the first cutting portion 21. Cutting can be performed by bringing this first cutting edge 21a into contact with the workpiece 103 (see FIG. 9).

[0020] The second cutting portion 22 to the fourth cutting portion 24 are similar to the first cutting portion 21. In other words, when the cutting insert 201 has a diamond-shaped plate shape or a triangular shape, the second cutting edge 22a, the third cutting edge 23a, or the fourth cutting edge 24a may be located at the intersection of two side surfaces that sandwich the vertex on the tip 10A side of each cutting insert 201. Cutting can be performed by bringing the second cutting edge 22a, the third cutting edge 23a, or the fourth cutting edge 24a into contact with the workpiece 103 (see FIG. 9).

[0021] Examples of the material of the cutting insert 201 include cemented carbide and cermet. Examples of the composition of the cemented carbide include WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co. Here, WC, TiC, and TaC may be hard particles, and Co may be a binder phase.

[0022] The cermet may be a sintered composite material in which a ceramic component is combined with a metal. An example of the cermet is a titanium compound mainly composed of titanium carbide (TiC) or titanium nitride (TiN). The material of the cutting insert 201 is not limited to the above composition.

[0023] The surface of the cutting insert 201 may be coated with a film formed by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The film may have a composition of titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al ２ O ３ ) and the like can be mentioned.

[0024] The cutting tool 1 may also include a plurality of first cutting portions 21. As shown in Fig. 3, in a configuration including two first cutting portions 21, the first cutting portion 21 and the other first cutting portion 21 may be disposed in positions facing each other across the rotation axis O1.

[0025] A plurality of the second cutting portions 22 to the fourth cutting portions 24 may also be provided, similar to the first cutting portion 21. As shown in Fig. 3, in a configuration in which two of each of the second cutting portions 22 to the fourth cutting portions 24 are provided, the second cutting portion 22 to the fourth cutting portion 24 and another second cutting portion 22 to the fourth cutting portion 24 may be disposed in positions facing each other across the rotation axis O1.

[0026] 1 to 7 , the main body 10 to which the cutting unit 20 is fixed may have a trunk 11 located on the rear end 10B side and branch portions 12 extending from the trunk, and the branch portions 12 may extend toward the tip 10A. The above-mentioned first cutting portion 21, second cutting portion 22, and third cutting portion 23, which are the cutting unit 20, may be fixed to the branch portions 12.

[0027] With this configuration, main body 10 is hollowed out, and in the area of ​​branch 12, there is no part separating the inside and outside of main body 10, that is, no part that acts as a barrier when chips generated in cutting section 20 flow toward rear end 10B, except for branch 12. Therefore, chips cut by first cutting section 21, second cutting section 22, and third cutting section 23 flow from the hollowed inside of main body 10 through the wide openings between branch sections 12 toward rear end 10B and are discharged.

[0028] This significantly improves chip discharge compared to cutting tools that have a shaft that extends along the rotation axis at the center of the main body. Also, compared to cutting tools that have a hollow shaft and an opening on the outer periphery of the shaft that communicates with the internal hollow space, there are significantly fewer areas that act as barriers to the flow of chips, improving chip discharge.

[0029] Furthermore, since the first cutting portion 21, the second cutting portion 22, and the third cutting portion 23 are each supported only by the branch portions 12, the generated chips enter the inside of the main body portion 10 through the gaps between the branch portions 12 and flow inside the main body portion 10. Therefore, the amount of chips flowing outside the main body portion 10, where the machined surface of the workpiece 103 (see FIG. 9) is located, can be reduced, and the risk of damaging the machined surface can be reduced.

[0030] As shown in Figures 2 and 6, the stem 11 may be hollow. That is, the stem 11 may have a shape in which the interior is hollowed out and only the outer periphery remains. For example, the stem 11 may have a cylindrical shape with a hole 11A formed in its center along the rotation axis O1. Furthermore, the stem 11 may be located on a portion of the outer periphery of the main body 10, and the portion of the outer periphery of the main body 10 where the stem 11 is not located may be open.

[0031] For example, as shown in Figures 2 and 4, the stem 11 may have a triangular or trapezoidal opening 14 that convex from the distal end 10A toward the proximal end 10B when viewed from the direction of arrow A4 in Figure 3. In other words, as shown in Figure 5, the stem 11 may have a shape that is divided into triangular portions that convex from the proximal end 10B toward the distal end 10A when viewed from the direction of arrow A3 in Figure 3. As shown in Figures 1 and 2, a pair of such triangular portions may be arranged opposite each other across the rotation axis O1.

[0032] As shown in Figure 3, the directions of arrows A1 and A3 are perpendicular to the rotation axis O1, and are 180° apart from each other. The directions of arrows A2 and A4 are perpendicular to the rotation axis O1, and are 180° apart from each other. The directions of arrows A1, A2, A3, and A2 are each offset by 90° from the rotation direction O2.

[0033] In this way, by hollowing out the trunk 11 and providing an opening 14 that communicates with the outside of the main body 10, chips cut by the first cutting section 21, the second cutting section 22, and the third cutting section 23 in the trunk 11 are discharged to the rear end 10B side through the opening 14. This makes it possible to achieve a configuration that has even better chip discharge properties.

[0034] 6, the trunk 11 may be curved with the side where the rotation axis O1 is located facing inward. The trunk 11 may also be shaped to bulge away from the rotation axis O1 from the rear end 10B toward the front end 10A. The opening 14 described above may open toward the rear end 10B. The thickness of the plate-shaped portion of the trunk 11 does not have to be uniform, and the portion where the branch portion 12 is connected may be thicker than the other portions. The outer and inner surfaces of the trunk 11 may be smooth.

[0035] 1, 2, 4, and 5, the branch portion 12 may have a first branch portion 121 and a second branch portion 122. In FIGS. 1 and 4, the portions corresponding to the first branch portion 121 and the second branch portion 122 are shown surrounded by dotted lines.

[0036] The first branch 121 and the second branch 122 may extend toward the tip 10A. The first branch 121 may extend rearward in the rotation direction O2 of the rotation axis O1 as it approaches the tip 10A. The second branch 122 may extend forward in the rotation direction O2 of the rotation axis O1 as it approaches the tip 10A.

[0037] The first branch portion 121 and the second branch portion 122 intersect on the side of the tip 10A, and the above-described first cutting portion 21 may be fixed to the main body portion 10 at a portion P1 where the first branch portion 121 and the second branch portion 122 intersect. In this case, the above-described holding portion 203 of the first cutting portion 21 may be formed at the portion P1 where the first branch portion 121 and the second branch portion 122 intersect.

[0038] If the inside of the main body 10 is hollowed and the cutting part 20 is fixed to the branch 12, chip removal is excellent, but the holding force for the cutting part 20 may be reduced. In particular, a large load is applied to the first cutting part 21, which is located forward in the rotation direction O2, during cutting. With the above configuration, the first cutting part 21 can be held by both the first branch 121 and the second branch 122, and therefore the holding force for the first cutting part 21 can be increased compared to a configuration in which the first cutting part 21 is held by only either the first branch 121 or the second branch 122. This has the effect of improving the durability of the cutting tool 1 in addition to improving chip removal.

[0039] 5, the first branch portion 121 and the second branch portion 122 may be formed so as to move away from the rotation axis O1 toward the tip 10A. At least one of the first branch portion 121 and the second branch portion 122 may be formed so as to move away from the rotation axis O1 toward the tip 10A.

[0040] The first branch 121 and the second branch 122 may be curved or bent so as to extend along the rotation axis O1 toward the tip 10A and then extend radially outward. However, such a configuration would inevitably increase the length of the first branch 121 and the second branch 122, making them more likely to bend if their thicknesses were the same. By adopting the above configuration, the overall length can be shortened, resulting in a configuration that is less likely to bend and more resistant to loads, even if the thicknesses are the same.

[0041] 4, the second branch portion 122 may be formed to be thicker than the first branch portion 121. In other words, the area of ​​a cross section of the first branch portion 121 and the second branch portion 122 taken in a direction perpendicular to the extending direction may be larger in the second branch portion 122 than in the first branch portion 121.

[0042] The load applied to the first cutting portion 21 during cutting is greater on the second branch portion 122, which supports the rear of the first cutting portion 21 in the rotational direction O2, than on the first branch portion 121. The above configuration increases the durability of the second branch portion 122, which is subjected to a large load. The first branch portion 121 ensures chip discharge by not making the portions that act as barriers to the flow of chips unnecessarily large. This allows the first cutting portion 21 to be firmly supported while minimizing the portions that act as barriers to the flow of chips.

[0043] If the thicknesses of the first branch portion 121 and the second branch portion 122 are not constant, the area values ​​at the cross sections where the cross-sectional area is smallest may be compared.

[0044] 1, 2, and 4, the first branch portion 121 and the second branch portion 122 may have a linear shape. At least one of the first branch portion 121 and the second branch portion 122 may have a linear shape.

[0045] Not only the first branch portion 121 and the second branch portion 122, but also the branch portion 12 has a straight shape that is more resistant to bending than a bent shape. Therefore, by adopting the above configuration, it is possible to make it difficult for the branch portion 12 to bend even when a load is applied during cutting processing.

[0046] 1 to 5, the branch portion 12 may have a third branch portion 123 extending from the first branch portion 121 and / or the second branch portion 122 toward the tip 10A. The second cutting portion 22 described above may be fixed to such a third branch portion 123. In this case, the holding portion 203 described above of the second cutting portion 22 may be formed on the third branch portion 123.

[0047] According to the above configuration, when a large diameter hole 104 is machined in a workpiece 103 (see FIG. 9 ) using the first cutting unit 21, a small diameter hole 105 can be machined using the second cutting unit 22. Since the small diameter hole 105 can be machined simultaneously in the process of machining the large diameter hole 104, there is no misalignment between the large diameter hole 104 and the small diameter hole 105, and they can be formed with high precision. In addition, the number of processes can be reduced.

[0048] Furthermore, in a configuration in which the third branch portion 123 supporting the second cutting portion 22 extends from the trunk portion 11, the third branch portion 123 acts as a barrier to the flow of chips, narrowing the space that serves as a passage for the chips to flow. By adopting the above configuration, it is possible to ensure a wider space that serves as a passage for the chips to flow.

[0049] More specifically, the third branch portion 123 may extend from both the first branch portion 121 and the second branch portion 122, or may extend from the portion P1 where the first branch portion 121 and the second branch portion 122 intersect.

[0050] In addition, in a configuration including two second cutting portions 22, the second cutting portion 22 and another second cutting portion 22 may be connected to each other via a connecting portion 13 that is a part of the main body 10, as shown in Figures 1, 5, and 6. The connecting portion 13 may be axial as shown in the example, or may be formed by connecting the tips of multiple third branch portions 123 to each other.

[0051] The third branch portions 123 may approach the rotation axis O1 as they move toward the tip 10A, or may approach the rotation axis O1 along a direction perpendicular to the rotation axis O1. Alternatively, the third branch portions 123 may intersect midway to form a single branch, with the second cutting portion 22 fixed to the tip of the branch.

[0052] The second cutting portion 22 may be spaced apart from the trunk portion 11. By having the second cutting portion 22 located on the side of the tip 10A spaced apart from the trunk portion 11, the opening space of the main body portion 10 becomes wider, allowing chips to be discharged more smoothly.

[0053] 1, 2, 4, and 5, the branch portion 12 may have a fourth branch portion 124 and a fifth branch portion 125. In Fig. 4, in addition to the first portion 121 and the second branch portion 122, portions corresponding to the fourth branch portion 124 and the fifth branch portion 125 are also shown surrounded by dotted lines.

[0054] The fourth branch 124 and the fifth branch 125 may extend toward the tip 10A. The fourth branch 124 may extend rearward in the rotation direction O2 of the rotation axis O1 as it approaches the tip 10A. The fifth branch 125 may extend forward in the rotation direction O2 of the rotation axis O1 as it approaches the tip 10A.

[0055] The fourth branch portion 124 and the fifth branch portion 125 intersect on the side of the tip 10A, and the above-mentioned third cutting portion 23 may be fixed to the main body portion 10 at a portion P2 where the fourth branch portion 124 and the fifth branch portion 125 intersect. In this case, the above-mentioned holding portion 203 of the third cutting portion 23 may be formed at the portion P2 where the fourth branch portion 124 and the fifth branch portion 125 intersect.

[0056] 1 , 2 , 5 , and 6 , the branch 12 may have a sixth branch 126 extending radially from the rear end 10B of the trunk 11. The fourth cutting portion 24 may be fixed to the trunk 11 and the sixth branch 126. In this case, the holding portion 203 of the fourth cutting portion 24 may be formed to straddle the trunk 11 and the sixth branch 126.

[0057] Examples of materials for the main body 10 include steel such as stainless steel, cast iron, and aluminum alloy. In particular, when steel is used among these materials, the toughness of the above-mentioned members is high.

[0058] (Method for manufacturing machined product) Next, a non-limiting method for manufacturing a machined product on one side according to the present disclosure will be described with reference to Fig. 9. The method will be described for forming a large diameter hole 104 in a workpiece 103 by the first cutting portion 21, the third cutting portion 23, and the fourth cutting portion 24 of the cutting tool 1, and forming a small diameter hole 105 by the second cutting portion 22.

[0059] The machined product 101 is produced by cutting a workpiece 103. A manufacturing method for the machined product 101 in this embodiment includes the following steps: (1) a step of rotating the cutting tool 1, (2) a step of bringing the cutting tool 1 into contact with the workpiece 103, and (3) a step of separating the cutting tool 1 from the workpiece 103.

[0060] More specifically, first, as indicated by reference numeral 901 in Fig. 9 , the cutting tool 1 may be rotated around the rotation axis O1 in a rotation direction O2 and brought relatively close to the workpiece 103. Next, as indicated by reference numeral 902 in Fig. 9 , at least a portion of the cutting edge of the cutting tool 1 may be brought into contact with the workpiece 103 to cut the workpiece 103. Then, as indicated by reference numeral 903 in Fig. 9 , the cutting tool 1 may be moved relatively away from the workpiece 103 (machined object 101).

[0061] As indicated by reference numeral 901 in FIG. 9, the cutting tool 1 may be moved forward (downward in FIG. 9) while being rotated, thereby bringing the cutting tool 1 closer to the workpiece 103.

[0062] Furthermore, as shown by reference numeral 902 in FIG. 9 , the workpiece 103 may be cut by moving the cutting tool 1 forward with at least a part of the cutting edge in contact with the workpiece 103 .

[0063] 9, the cutting tool 1 may be moved rearward (upward in FIG. 9) while being rotated, thereby moving the cutting tool 1 away from the workpiece 103.

[0064] In each step, the cutting tool 1 is moved to bring the cutting tool 1 into contact with the workpiece 103 or to move the cutting tool 1 away from the workpiece 103, but this is not limited to this case.

[0065] For example, in step (1), the workpiece 103 may be brought closer to the cutting tool 1. In step (3), the workpiece 103 may be moved away from the cutting tool 1. When continuing the cutting process, the cutting tool 1 may be kept rotating, and the step of bringing at least a part of the cutting edge into contact with different locations on the workpiece 103 may be repeated.

[0066] Typical examples of the material of the workpiece 103 include hardened steel, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0067] <Summary> The cutting tool in aspect 1 of the present disclosure has a main body extending along a rotation axis from the tip to the rear end, and a first cutting portion fixed to the main body and having a first cutting edge, the main body having a trunk located on the rear end side and a branch extending from the trunk towards the tip, the branch having a first branch extending rearward in the rotation direction of the rotation axis as it approaches the tip, and a second branch extending forward in the rotation direction of the rotation axis as it approaches the tip, the first cutting portion being fixed to the main body at a portion where the first branch and the second branch intersect.

[0068] In a cutting tool according to a second aspect of the present disclosure, in the first aspect, at least one of the first branch portion and the second branch portion becomes more distant from the rotation axis as it approaches the tip.

[0069] A cutting tool according to a third aspect of the present disclosure is the cutting tool of the first or second aspect, wherein the second branch portion is thicker than the first branch portion.

[0070] A cutting tool according to a fourth aspect of the present disclosure is the cutting tool according to any one of the first to third aspects, wherein at least one of the first branch portion and the second branch portion has a linear shape.

[0071] The cutting tool in aspect 5 of the present disclosure is, in any one of aspects 1 to 4, further includes a second cutting portion fixed to the main body portion and having a second cutting edge, the second cutting portion being located closer to the tip than the first cutting portion and closer to the rotation axis, the branch portions further including a third branch portion extending from the first branch portion and / or the second branch portion toward the tip, and the second cutting portion being fixed to the third branch portion.

[0072] In a cutting tool according to a sixth aspect of the present disclosure, in the fifth aspect, the second cutting portion is spaced apart from the stem portion.

[0073] A cutting tool according to a seventh aspect of the present disclosure is any one of the first to sixth aspects, wherein the stem is hollow.

[0074] In the cutting tool of aspect 8 of the present disclosure, in the above-described aspect 7, the stem is located at a portion of the outer periphery of the main body, and the portion of the outer periphery of the main body where the stem is not located is open.

[0075] A method for manufacturing a machined product in aspect 9 of the present disclosure includes the steps of rotating a cutting tool of any one of aspects 1 to 8, bringing the cutting tool into contact with a workpiece, and removing the cutting tool from the workpiece.

[0076] [Additional Notes] The invention according to the present disclosure has been described above based on the drawings and embodiments. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art could easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure.

[0077] REFERENCE SIGNS LIST 1 Cutting tool 10 Main body 10B Rear end 10A Front end 11 Trunk 11A Hole 12 Branch 14 Opening 20 Cutting portion 21 First cutting portion 21a First cutting edge 22 Second cutting portion 22a Second cutting edge 101 Machined object 103 Workpiece 121 First branch 122 Second branch 123 Third branch O1 Rotation axis O2 Rotation direction

Claims

1. A cutting tool having a main body extending along a rotation axis from the tip to the rear end, and a first cutting portion fixed to the main body and having a first cutting edge, wherein the main body has a trunk located on the rear end side, and a branch extending from the trunk toward the tip, wherein the branch has a first branch extending rearward in the rotation direction of the rotation shaft as it approaches the tip, and a second branch extending forward in the rotation direction of the rotation shaft as it approaches the tip, and the first cutting portion is fixed to the main body at a portion where the first branch and the second branch intersect.

2. The cutting tool according to claim 1, wherein at least one of said first branch and said second branch becomes more distant from said rotation axis toward said tip.

3. A cutting tool as described in claim 1 or 2, wherein the second branch portion is thicker than the first branch portion.

4. A cutting tool according to any one of claims 1 to 3, wherein at least one of the first branch portion and the second branch portion is linear.

5. A cutting tool as described in any one of claims 1 to 4, further comprising a second cutting portion fixed to the main body portion and having a second cutting edge, the second cutting portion being located closer to the tip than the first cutting portion and closer to the rotation axis, the branch portions further comprising a third branch portion extending from the first branch portion and / or the second branch portion toward the tip, and the second cutting portion being fixed to the third branch portion.

6. The cutting tool of claim 5, wherein said second cutting portion is spaced from said stem.

7. A cutting tool according to any one of claims 1 to 6, wherein the stem is hollow.

8. A cutting tool as claimed in claim 7, wherein the stem is located on a part of the outer periphery of the main body, and the portion of the outer periphery of the main body where the stem is not located is open.

9. A method for manufacturing a machined product, comprising the steps of: rotating a cutting tool according to any one of claims 1 to 8; bringing the cutting tool into contact with a workpiece; and removing the cutting tool from the workpiece.

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