Cutting tool and method for manufacturing cut product

Abstract

Provided is a cutting tool excellent in chip dischargeability and excellent in durability. A cutting tool based on one aspect of the present disclosure comprises a body section and a first cutting part and a second cutting part fixed to the body section. The body section includes a trunk part positioned on a rear end side, and a branch part extending toward a tip end from the trunk part. The branch part includes: a first branch part extending rearward in a rotation direction toward the tip end and connected to the trunk part and the first cutting part; a second branch part extending frontward in the rotation direction toward the tip end and connected to the trunk part and the first cutting part; a third branch part extending rearward in the rotation direction toward the tip end and connected to the trunk part and the second cutting part; and a fourth branch part extending frontward in the rotation direction toward the tip end and connected to the trunk part and the second cutting part. The second branch part and the third branch part intersect and are connected at the intersecting sites.

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 includes a main body extending from a tip end to a rear end along a rotation axis, a first cutting portion fixed to the main body and having a first cutting edge, and a second cutting portion fixed to the main body and having a second cutting edge, the first cutting portion being located forward of the second cutting portion in a rotation direction of the rotation axis, the main body having a trunk located on the rear end side and a branch portion extending from the trunk toward the tip end, the branch portion extending rearward in the rotation direction of the rotation axis as it approaches the tip end, and a first branch portion connected to the tip of the shaft, a second branch portion extending forward in the rotation direction of the rotating shaft as it approaches the tip and connected to the trunk and the first cutting portion, a third branch portion extending backward in the rotation direction of the rotating shaft as it approaches the tip and connected to the trunk and the second cutting portion, and a fourth branch portion extending forward in the rotation direction of the rotating shaft as it approaches the tip and connected to the trunk and the second cutting portion, and the second branch portion and the third branch portion intersect and are connected at the intersecting portion.

[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 second 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 further improvement in chip evacuation is highly demanded. However, simply increasing the opening to reduce weight and / or improve chip evacuation may result in a decrease in the overall strength of the cutting tool.

[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 and a second cutting portion 22 having a second cutting edge 22a. The first cutting portion 21 may be located forward of the second cutting portion 22 in the rotation direction O2 of the rotation axis O1. The first cutting portion 21 and the second cutting portion 22 may be located at the same distance from the rotation axis O1.

[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 closer to the tip 10A than the first cutting portion 21 and the second cutting portion 22, and closer to the rotation axis O1 than 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 the second cutting portion 22, and may be located at the same distance from the rotation axis O1 as the first cutting portion 21 and the second cutting portion 22.

[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 multiple pairs of the first cutting portion 21 and the second cutting portion 22. As shown in Fig. 3, in a configuration including two pairs of the first cutting portion 21 and the second cutting portion 22, the first cutting portion 21 and another first cutting portion 21 belonging to another pair may be disposed opposite each other across the rotation axis O1. Similar to the first cutting portion 21, the second cutting portion 22 and another second cutting portion 22 belonging to another pair may be disposed opposite each other across the rotation axis O1.

[0025] A plurality of third cutting portions 23 and a plurality of fourth cutting portions 24 may also be provided. In a configuration including two third cutting portions 23, the third cutting portion 23 and another third cutting portion 23 may be disposed in positions facing each other across the rotation axis O1. As with the third cutting portions 23, in a configuration including two fourth cutting portions 24, the fourth cutting portion 24 and another 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. 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] As shown in Figures 1, 2, 4, and 5, the branch portion 12 may have a first branch portion 121 to a fourth branch portion 124. In Figure 1, the portions corresponding to the first branch portion 121 and the second branch portion 122 are shown surrounded by dotted lines. In Figure 4, the portions corresponding to the first branch portion 121 to the fourth branch portion 124 are shown surrounded by dotted lines. The first branch portion 121 to the fourth branch portion 124 may extend toward the tip 10A.

[0036] The first branch portion 121 may extend rearward in the rotation direction O2 of the rotation axis O1 as it approaches the tip 10A, and may be connected to the trunk 11 and the above-described first cutting portion 21. The second branch portion 122 may extend forward in the rotation direction O2 of the rotation axis O1 as it approaches the tip 10A, and may be connected to the trunk 11 and the first cutting portion 21. In this case, the above-described holding portion 203 of the first cutting portion 21 may be formed at a portion where the first branch portion 121 and the second branch portion 122 intersect.

[0037] The third branch portion 123 may extend rearward in the rotation direction O2 of the rotation axis O1 as it approaches the tip 10A, and may be connected to the trunk 11 and the above-described second cutting portion 22. The fourth branch portion 124 may extend forward in the rotation direction O2 of the rotation axis O1 as it approaches the tip 10A, and may be connected to the trunk 11 and the second cutting portion 22. In this case, the above-described holding portion 203 of the second cutting portion 22 may be formed at a portion where the third branch portion 123 and the fourth branch portion 124 intersect.

[0038] The second branch portion and the third branch portion may intersect with each other and be connected at the intersecting portion, which will be hereinafter referred to as an "intersecting portion P1."

[0039] If the inside of the main body 10 is hollowed out and the cutting part 20 is fixed to the branch parts 12, chip discharge is excellent, but there is a risk of a decrease in the holding force for the cutting part 20. With the above configuration, the first cutting part 21 is held by both the first branch part 121 and the second branch part 122, and the second cutting part 22 is held by both the third branch part 123 and the fourth branch part 124. Therefore, the holding force for the first cutting part 21 and the second cutting part 22 can be increased compared to a configuration in which the first cutting part 21 is held by only either the first branch part 121 or the second branch part 122, or a configuration in which the second cutting part 22 is held by only either the third branch part 123 or the fourth branch part 124.

[0040] Furthermore, when comparing the first branch portion 121 and the second branch portion 122 during cutting, a greater load is applied to the first cutting portion 21, which is located forward in the rotational direction O2, than to the second cutting portion 22. Furthermore, the load applied to the first cutting portion 21 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 121. As described above, by connecting the second branch 122, which is subjected to the greatest load among the first to fourth branches 121 to 124, with the third branch 123 at the intersection P1, the load applied to the second branch 122 can be distributed to the third branch 123. This allows the first cutting portion 21 to be firmly supported without unnecessarily thickening the branches 12, which act as a barrier to chip flow, thereby improving chip discharge performance and durability of the cutting tool 1.

[0041] 1 and 4 , the second branch 122 may intersect with the third branch 123 at a position closer to the first cutting portion 21 and the second cutting portion 22 than to the trunk 11. Furthermore, the third branch 123 may intersect with the second branch 122 at a position closer to the first cutting portion 21 and the second cutting portion 22 than to the trunk 11. For example, an intersection point P1 where the second branch 122 and the third branch 123 intersect may be located closer to the first cutting portion 21 and the second cutting portion 22 than to the trunk 11.

[0042] In a configuration in which the intersecting portion P1 is located near the trunk portion 11, the effect of distributing the load applied to the second branch portion 122 to the third branch portion 123 is small. In the above configuration, by locating the intersecting portion P1 near the first cutting portion 21 and the second cutting portion 22, the load applied to the second branch portion 122 can be effectively distributed to the third branch portion 123.

[0043] 4 , the second branch 122 may be thicker than the first branch 121, and the fourth branch 124 may be thicker than the third branch 123. In other words, the area of ​​a cross section of the first branch 121 and the second branch 122 taken in a direction perpendicular to the extension direction may be larger for the second branch 122 than for the first branch 121. Similar to the relationship between the first branch 121 and the second branch 122, the area of ​​a cross section of the third branch 123 and the fourth branch 1242 taken in a direction perpendicular to the extension direction may be larger for the fourth branch 124 than for the third branch 123.

[0044] As described above, 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. With the above configuration, it is possible to increase the durability of the second branch portion 122, which is subjected to a large load. Furthermore, in the first branch portion 121, by not making the portion that acts as a barrier to the flow of chips unnecessarily large, it is possible to improve the dischargeability of chips.

[0045] 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.

[0046] As with the first branch portion 121 and the second branch portion 122, the load applied to the second cutting portion 22 during cutting is greater on the fourth branch portion 124, which supports the rear of the second cutting portion 22 in the rotation direction O2, than on the third branch portion 123. With the above configuration, the durability of the fourth branch portion 124, which is subjected to a large load, is increased, and the third branch portion 123 can have good chip discharge properties.

[0047] This reduces the number of areas that act as barriers to the flow of chips, while firmly supporting the first cutting portion 21 and the second cutting portion 22, thereby increasing durability.

[0048] 4, a portion 122-1 located closer to the tip 10A than the intersection of the second branch 122 and the third branch 123 may be formed thicker than a portion 122-2 located closer to the rear end 10B than the intersection of the second branch 122 and the third branch 123. In other words, the portion 122-1 located closer to the tip 10A than the intersection P1 may be formed thicker than the portion 122-2 located closer to the rear end 10B than the intersection P1.

[0049] When the portion 122-1 is relatively thick, the rigidity for holding the first cutting part 21 can be increased against the principal component force, which is the load applied in the opposite direction to the rotation direction O2 during cutting. Also, when the portion 122-2 is relatively thin, it is easy to ensure space for discharging chips.

[0050] Furthermore, in the cutting tool 1, the first branch portion 121 to the fourth branch portion 124 may each have a linear shape. A linear shape of the branch portion 12 is more resistant to bending than a bent shape. Therefore, by adopting the above configuration, it is possible to make the branch portion 12 less likely to bend even when a load is applied during cutting processing.

[0051] Furthermore, in the cutting tool 1, the first branch portion 121 to the fourth branch portion 124 may be formed so as to move away from the rotation axis O1 toward the tip 10A. By adopting such a configuration, the overall length can be shortened, and even if the diameter is the same, the configuration can be made less likely to bend and more resistant to loads.

[0052] 1 to 5, the branch portion 12 may have a fifth branch portion 125 extending from the first branch portion 121 and / or the second branch portion 122, or the third branch portion 123 and / or the fourth branch portion 124 toward the tip 10A. In this case, the above-described holding portion 203 of the third cutting portion 23 may be formed on the third branch portion 123.

[0053] According to the above configuration, when a large diameter hole 104 is drilled in a workpiece 103 (see FIG. 9 ) using the first cutting unit 21 and the second cutting unit 22, a small diameter hole 105 can be drilled using the third cutting unit 23. Since the small diameter hole 105 can be drilled simultaneously in the process of drilling the large diameter hole 104, there is no misalignment between the large diameter hole 104 and the small diameter hole 105, allowing for accurate formation. This also reduces the number of processes.

[0054] Furthermore, in a configuration in which the fifth branch 125 supporting the third cutting portion 23 extends from the trunk 11, the fifth branch 125 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.

[0055] In addition, in a configuration including two third cutting portions 23, the third cutting portion 23 and another third cutting portion 23 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 fifth branch portions 125 to each other.

[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 second cutting portion 22, and the fourth cutting portion 24 of the cutting tool 1, and forming a small diameter hole 105 by the third cutting portion 23.

[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> A cutting tool according to a first aspect of the present disclosure includes a main body extending from a tip end to a rear end along a rotation axis, a first cutting portion fixed to the main body and having a first cutting edge, and a second cutting portion fixed to the main body and having a second cutting edge, the first cutting portion being located forward of the second cutting portion in a rotation direction of the rotation axis, the main body including a trunk located on the rear end side and a branch portion extending from the trunk toward the tip end, the branch portion extending rearward in the rotation direction of the rotation axis as it approaches the tip end, and a cutting tool including the trunk and the first cutting portion a first branch portion connected to the tip of the shaft, a second branch portion extending forward in the rotation direction of the rotating shaft as it approaches the tip and connected to the trunk and the first cutting portion, a third branch portion extending backward in the rotation direction of the rotating shaft as it approaches the tip and connected to the trunk and the second cutting portion, and a fourth branch portion extending forward in the rotation direction of the rotating shaft as it approaches the tip and connected to the trunk and the second cutting portion, and the second branch portion and the third branch portion intersect and are connected at the intersecting portion.

[0068] A cutting tool according to a second aspect of the present disclosure is the cutting tool according to the first aspect, wherein the second branch portion and the third branch portion intersect at a position closer to the first cutting portion and the second cutting portion than the trunk portion.

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

[0070] In a cutting tool according to aspect 4 of the present disclosure, in any one of aspects 1 to 3, the portion of the second branch located closer to the tip than the portion where it intersects with the third branch is thicker than the portion of the second branch located closer to the rear end than the portion where it intersects with the third branch.

[0071] A cutting tool according to aspect 5 of the present disclosure is any one of aspects 1 to 4, wherein the first branch portion, the second branch portion, the third branch portion, and the fourth branch portion each have a linear shape.

[0072] A cutting tool according to a sixth aspect of the present disclosure is any one of the first to fifth aspects, wherein the stem is hollow.

[0073] In a seventh aspect of the present disclosure, the cutting tool is the same as in the sixth aspect, in that 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.

[0074] A method for manufacturing a machined product in aspect 8 of the present disclosure includes the steps of rotating a cutting tool of any one of aspects 1 to 7, bringing the cutting tool into contact with a workpiece, and removing the cutting tool from the workpiece.

[0075] [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.

[0076] REFERENCE SIGNS LIST 1 Cutting tool 10 Main body 10B Rear end 10A Tip 11 Trunk 11A Hole 12 Branch 14 Opening 21 First cutting portion 21a First cutting edge 22 Second cutting portion 22a Second cutting edge 101 Machined product 103 Workpiece 121 First branch 122 Second branch 123 Third branch 124 Fourth branch O1 Rotation axis O2 Rotation direction

Claims

1. A cutting tool having a main body extending along a rotational axis from the front end to the rear end, a first cutting part fixed to the main body and having a first cutting edge, and a second cutting part fixed to the main body and having a second cutting edge, wherein the first cutting part is located forward in the rotational direction of the rotational axis relative to the second cutting part, the main body having a stem located on the rear end side, and branch parts extending from the stem towards the front end, wherein the branch parts have: a first branch part extending rearward in the rotational direction of the rotational axis as it approaches the front end and connected to the stem and the first cutting part, a second branch part extending forward in the rotational direction of the rotational axis as it approaches the front end and connected to the stem and the first cutting part, a third branch part extending rearward in the rotational direction of the rotational axis as it approaches the front end and connected to the stem and the second cutting part, and a fourth branch part extending forward in the rotational direction of the rotational axis as it approaches the front end and connected to the stem and the second cutting part, A cutting tool, wherein the second branch and the third branch intersect and are connected at the intersecting portion.

2. A cutting tool as described in claim 1, wherein the second branch portion and the third branch portion intersect at a position closer to the first cutting portion and the second cutting portion than the trunk portion.

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

4. A cutting tool described in any one of claims 1 to 3, wherein a portion of the second branch located on the tip side of the portion where it intersects with the third branch is thicker than a portion of the second branch located on the rear side of the portion where it intersects with the third branch.

5. A cutting tool according to any one of claims 1 to 4, wherein the first branch portion, the second branch portion, the third branch portion and the fourth branch portion are each linear.

6. A cutting tool according to any one of claims 1 to 5, wherein the stem is hollow.

7. A cutting tool as claimed in claim 6, 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.

8. A method for manufacturing a machined product, comprising the steps of: rotating a cutting tool according to any one of claims 1 to 7; bringing the cutting tool into contact with a workpiece; and removing the cutting tool from the workpiece.

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