Rotary tool and method for manufacturing cut article

Abstract

To provide a highly versatile rotary tool high in rotary cutting freedom.SOLUTION: This rotary tool has a rod-shaped body extending along a rotary shaft from a tip toward a rear end. The body includes a bottom blade positioned on the tip side, and a discharge groove extending from the bottom blade toward the rear end. The bottom blade includes a first blade of a projected curve shape, and a second blade of a projected curve shape extending from the first blade toward the rotary shaft. The second blade comes closer to the rear end as it approaches the rotary shaft. In a tip view, the curvature radius of the first blade is larger than that of the second blade.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a rotary tool and a method for manufacturing a machined product. Examples of the rotary tool include a drill and an end mill. Examples of the end mill include a radius end mill and a square end mill. [Background technology]

[0002] As a rotating tool used in performing turning on a workpiece, for example, an end mill (square end mill) described in Patent Document 1 is known. The end mill described in Patent Document 1 has a bottom cutting edge that is inclined toward the rear end as it approaches the rotation axis. In addition, the bottom cutting edge has a convex arc shape when viewed from the tip. The convex arc shape of the bottom cutting edge improves the durability of the bottom cutting edge. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-056608 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of so-called milling, in which a rotating tool is moved in a direction perpendicular to the rotation axis, the part of the bottom cutting edge located near the rotation axis hardly comes into contact with the workpiece. Therefore, there is no problem even if the bottom cutting edge has a simple convex arc shape. However, in the case of so-called oblique sinking, the part of the bottom cutting edge located near the rotation axis is likely to come into contact with the workpiece. In such a case, the durability of the above-mentioned part may be reduced. [Means for solving the problem]

[0005] The presently disclosed non-limiting one-sided rotary tool has a rod-shaped body extending along a rotation axis from a tip end to a rear end. The body has a bottom blade located on the tip side and a discharge groove extending from the bottom blade toward the rear end. The bottom blade has a first blade having a convex curved shape and a second blade having a convex curved shape extending from the first blade toward the rotation axis. The second blade approaches the rear end as it approaches the rotation axis. When viewed from the tip end, the radius of curvature of the first blade is larger than the radius of curvature of the second blade. Effect of the Invention

[0006] The above rotary tools have high durability of the bottom cutting edge even in oblique sinking processing, etc. Therefore, they have high degree of freedom in turning processing and are highly versatile. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view of a non-limiting rotary tool of the present disclosure; [Diagram 2] FIG. 2 is an enlarged view of a region II shown in FIG. [Diagram 3] FIG. 2 is a plan view of the rotary tool shown in FIG. 1 as viewed from the tip side. [Figure 4] FIG. 2 is a plan view of the rotary tool shown in FIG. 1 as viewed from the tip side. [Diagram 5] 4 is a side view of the rotary tool shown in FIG. 3 as viewed from a V direction. [Figure 6] FIG. 6 is an enlarged view of region VI shown in FIG. 5. [Figure 7] FIG. 7 is a side view of the rotary tool shown in FIG. 3 as viewed from a direction VII. [Figure 8] FIG. 2 is a plan view of the rotary tool shown in FIG. 1 as viewed from the tip side. [Figure 9] 9 is a cross-sectional view taken along line IX of the rotary tool shown in FIG. 8. [Figure 10] 9 is a cross-sectional view of the rotary tool shown in FIG. 8 taken along the X section. [Figure 11] FIG. 2 is a schematic diagram showing a step in a non-limiting method of manufacturing a one-sided machined product according to the present disclosure. [Figure 12] FIG. 2 is a schematic diagram showing a step in a non-limiting method of manufacturing a one-sided machined product according to the present disclosure. [Figure 13] FIG. 2 is a schematic diagram showing a step in a non-limiting method of manufacturing a one-sided machined product according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] <Rotary tools> Hereinafter, a non-limiting aspect of the rotary tool 1 of the present disclosure will be described in detail with reference to the drawings. However, in each of the drawings referred to below, for the sake of convenience, only the main members necessary for explaining the embodiment are shown in a simplified form. Therefore, the rotary tool 1 may include any component member not shown in each of the drawings referred to. In addition, the dimensions of the components in each drawing do not faithfully represent the dimensions of the actual components and the dimensional ratios of each component.

[0009] In one non-limiting aspect, the rotary tool 1 is a so-called solid tool, but a tip-replaceable tool may also be used. In another non-limiting aspect, a radius end mill may be used as an example of the rotary tool 1. However, the rotary tool 1 is not limited to a radius end mill, and may be another end mill such as a square end mill.

[0010] The rotating tool 1 may have a main body 3, as in a non-limiting example shown in Figs. 1 to 10. The main body 3 may be rod-shaped extending along a rotation axis O1 from a front end 3a to a rear end 3b. The main body 3 is rotatable around the rotation axis O1. Note that an arrow Y1 in Fig. 1 etc. may indicate the rotation direction of the rotation axis O1, or may indicate the rotation direction of the main body 3 around the rotation axis O1.

[0011] The main body 3 may have a shank portion 5 and a cutting portion 7. The shank portion 5 may function as a portion that is gripped by a rotating spindle of a machine tool. The shank portion 5 may be designed according to the shape of the spindle in the machine tool.

[0012] The cutting portion 7 may be located on the tip 3a side relative to the shank portion 5. The cutting portion 7 is capable of contacting the workpiece and can function as a portion that plays a major role in cutting the workpiece (for example, oblique sinking).

[0013] The size of the main body 3 is not limited to a specific size. For example, when the outer diameter of the cutting part 7 is D, the maximum value of D may be set to about 0.2 to 25 mm. When the length of the cutting part 7 in the direction along the rotation axis O1 is L, L may be set to about L=1.5D to 12D.

[0014] The body 3 may have a bottom cutting edge 9 and a discharge groove 11, as a non-limiting example shown in FIG.

[0015] The bottom cutting edge 9 may be located on the side of the tip 3a. The bottom cutting edge 9 can function as a part that cuts the workpiece in the cutting process. The bottom cutting edge 9 may be only one, or may be multiple. When the bottom cutting edge 9 is multiple, the number of the bottom cutting edges 9 may be 2 to 6.

[0016] In the case where there are multiple bottom blades 9, the multiple bottom blades 9 may be positioned so as to be rotationally symmetrical about the rotation axis O1 in the tip view. For example, as in a non-limiting example shown in FIG. 3, in the case where there are two bottom blades 9, the two bottom blades 9 may be positioned so as to be rotationally symmetrical about the rotation axis O1 by 180° in the tip view. In this case, the linearity of the rotating tool 1 when cutting the workpiece is high. Note that the tip view may refer to a state viewed from the tip 3a side.

[0017] The discharge groove 11 may extend from the bottom cutting edge 9 toward the rear end 3b, as in a non-limiting example shown in Fig. 5 and Fig. 7. The discharge groove 11 may function as a portion for discharging chips generated by the bottom cutting edge 9 to the outside. The discharge groove 11 may extend parallel to the rotation axis O1, or may extend in a spiral shape around the rotation axis O1. In a cross section perpendicular to the rotation axis O1, the discharge groove 11 may have a concave curved shape. The number of discharge grooves 11 may be the same as the number of bottom cutting edges 9.

[0018] Here, the bottom blade 9 may have a first blade 13 and a second blade 15, as in a non-limiting example shown in Fig. 2. The first blade 13 may have a convex curved shape. The second blade 15 may have a convex curved shape extending from the first blade 13 toward the rotation axis O1. When the first blade 13 and the second blade 15 each have a convex curved shape, the durability of the bottom blade 9 is likely to be improved.

[0019] The convex curve shape of the first blade 13 and the second blade 15 may be evaluated by viewing from the tip (see FIG. 3) or from the front in the rotation direction Y1 of the rotation axis O1 (see FIG. 6). The second blade 15 may be connected to the first blade 13.

[0020] The second blade 15 may approach the rear end 3b as it approaches the rotation axis O1, as in a non-limiting example shown in Fig. 6. When the second blade 15 has the above configuration, the first blade 13 may function as a main part of the bottom blade 9. In addition, as in a non-limiting example shown in Fig. 3, the radius of curvature of the first blade 13 may be larger than the radius of curvature of the second blade 15 when viewed from the tip.

[0021] The second blade 15 is located relatively closer to the rotation axis O1 than the first blade 13, and therefore has a relatively slow rotation speed. Therefore, there is a risk that a large cutting load will be applied to the second blade 15. However, when the second blade 15 has the above configuration, it is easy to avoid a wide range of the second blade 15 biting into the workpiece at the same time. Therefore, the durability of the second blade 15 is improved. Therefore, the durability of the bottom blade 9 of the rotary tool 1 is high even in oblique sinking processing. In addition, the length of the bottom blade 9 is unlikely to be excessively long because the first blade 13 is configured with a relatively gentle curve. Therefore, the width of the chips is unlikely to be excessively long, and the chips are unlikely to clog. As a result, the degree of freedom in turning is high and the tool is highly versatile.

[0022] The respective radii of curvature of the first blade 13 and the second blade 15 in the leading end view are not limited to specific values. For example, the radius of curvature of the first blade 13 in the leading end view may be set to 0.2 to 12.5 mm. Also, the radius of curvature of the second blade 15 in the leading end view may be set to 0.07 to 10 mm.

[0023] The first blade 13 and the second blade 15 may each have a convex arc shape with a constant radius of curvature when viewed from the tip. When viewed from the tip, a point where the radius of curvature changes from the first blade 13 to the second blade 15 may be the boundary between the first blade 13 and the second blade 15.

[0024] When viewed from the tip, the length of the first blade 13 may be the same as or different from the length of the second blade 15. For example, as shown in a non-limiting example in FIG. 3, when viewed from the tip, the first blade 13 may be longer than the second blade 15. In this case, the length of the first blade 13 that can function as a main part of the bottom blade 9 is ensured to be long, so that it can be used for high-feed processing, for example, and is highly versatile. In addition, the length of the first blade 13, which is a relatively gentle curve, is ensured to be long, so that the surface accuracy of the processed surface can be improved.

[0025] The end 9a on the tip 3a side of the bottom cutting edge 9 may be located on the first cutting edge 13, as in a non-limiting example shown in FIG. 6. The end 9a may be the part of the bottom cutting edge 9 farthest from the rear end 3b. When the end 9a is located on the first cutting edge 13, the first cutting edge 13, which is a relatively gentle curve, is likely to come into contact with the workpiece. Therefore, the surface accuracy of the machined surface can be improved. The end 9a may be located farther from the rotation axis O1 than the center 13a of the first cutting edge 13.

[0026] The bottom blade 9 may further have a third blade 17, as shown in a non-limiting example in FIG. 2. The third blade 17 may have a convex curved shape extending from the first blade 13 toward the outer periphery 19 of the main body 3 (cutting portion 7). The convex curved shape of the third blade 17 may be evaluated when viewed from the tip (see FIG. 3) or when viewed from the front in the rotation direction Y1 (see FIG. 6). The third blade 17 may be connected to the first blade 13.

[0027] When viewed from the tip, the radius of curvature of the first blade 13 may be the same as or different from the radius of curvature of the third blade 17. For example, as shown in a non-limiting example in FIG. 3, when viewed from the tip, the radius of curvature of the first blade 13 may be larger than the radius of curvature of the third blade 17. When the first blade 13 is configured with a relatively gentle curve, the length of the bottom blade 9 is unlikely to be excessively long, and chips are unlikely to clog. Also, when the radius of curvature of the third blade 17 is relatively small, the length of the first blade 13 is likely to be long.

[0028] The radius of curvature of the third blade 17 in the distal end view is not limited to a specific value. For example, the radius of curvature of the third blade 17 in the distal end view may be set to 0.01 to 2 mm. The third blade 17 may have a convex arc shape with a constant radius of curvature when viewed from the distal end. When viewed from the distal end, the location where the radius of curvature changes from the third blade 17 to the first blade 13 may be the boundary between the first blade 13 and the third blade 17.

[0029] When viewed from the tip, the length of the first blade 13 may be the same as or different from the length of the third blade 17. For example, as shown in a non-limiting example in FIG. 3, when viewed from the tip, the first blade 13 may be longer than the third blade 17. In this case, the length of the first blade 13 that can function as a main part of the bottom blade 9 is ensured to be long, so that it can be used for high-feed processing, for example, and has excellent versatility. In addition, the length of the first blade 13, which is a relatively gentle curve, is ensured to be long, so that the surface accuracy of the processed surface can be improved.

[0030] When viewed from the front end, the radius of curvature of the second blade 15 may be the same as or different from the radius of curvature of the third blade 17. For example, as in a non-limiting example shown in Fig. 3, when viewed from the front end, the radius of curvature of the second blade 15 may be larger than the radius of curvature of the third blade 17. In this case, even in a situation where the second blade 15 is used in oblique sinking processing, the durability of the second blade 15 is likely to be improved.

[0031] When viewed from the front end, the length of the second blade 15 may be the same as or different from the length of the third blade 17. For example, as in a non-limiting example shown in Fig. 3, when viewed from the front end, the second blade 15 may be longer than the third blade 17. In this case, even in a situation where the second blade 15 is used in oblique sinking machining, it can also be used for high feed machining, etc., and is highly versatile.

[0032] The discharge groove 11 may have a rake face 21, as a non-limiting example shown in Figures 9 and 10. The rake face 21 may be located along the bottom cutting edge 9. The rake face 21 may function as a portion through which chips flow during cutting.

[0033] The rake angle θ of the bottom cutting edge 9 may be a positive value. In this case, the sharpness of the bottom cutting edge 9 is improved, and the surface precision of the machined surface can be improved.

[0034] When the rake face 21 is located behind the bottom cutting edge 9 in the rotation direction Y1, the rake angle θ at the bottom cutting edge 9 may be evaluated as a positive value. The rake angle θ may be evaluated based on the angle between the rake face 21 and a virtual straight line L1 parallel to the rotation axis O1 in a cross section perpendicular to the bottom cutting edge 9 and parallel to the rotation axis O1 when viewed from the tip. The rake angle θ is not limited to a specific value. For example, the rake angle θ may be set to -10 to 10°.

[0035] The rake angle θ of the first blade 13 may be larger than the rake angle θ of the second blade 15 (see Figs. 9 and 10). In this case, the sharpness of the first blade 13, which can function as the main part of the bottom blade 9, is improved, thereby improving the surface accuracy of the machined surface. In addition, the rake angle θ of the second blade 15, which is located relatively closer to the rotation axis O1 than the first blade 13 and therefore has a relatively slower rotation speed, is relatively smaller. In this case, the strength of the second blade 15 is increased, thereby improving the durability of the bottom blade 9.

[0036] The main body 3 may further have a chisel edge 23, as a non-limiting example shown in Fig. 3. The chisel edge 23 may extend from the bottom cutting edge 9 toward the rotation axis O1. The chisel edge 23 may function as a portion for crushing the workpiece.

[0037] The chisel edge 23 may have a straight line shape. The chisel edge 23 may be connected to the bottom blade 9 (the second blade 15). The chisel edge 23 may extend to the rotation axis O1.

[0038] The radius of curvature of the first blade 13 when viewed from the front in the rotation direction Y1 of the rotation axis O1 may be the same as or different from the radius of curvature of the first blade 13 when viewed from the tip. For example, the radius of curvature of the first blade 13 when viewed from the front in the rotation direction Y1 (see FIG. 6) may be larger than the radius of curvature of the first blade 13 when viewed from the tip (see FIG. 3). When the radius of curvature of the first blade 13 when viewed from the front in the rotation direction Y1 is relatively large, the surface accuracy of the machined surface is likely to be improved. Also, when the radius of curvature of the first blade 13 when viewed from the tip is relatively small, it is likely to be avoided that a wide range of the first blade 13 bites into the workpiece at the same time. Therefore, the durability of the first blade 13 is improved and chatter vibration is likely to be suppressed.

[0039] The radius of curvature of the first blade 13 when viewed from the front in the rotation direction Y1 is not limited to a specific value. For example, the radius of curvature of the first blade 13 when viewed from the front in the rotation direction Y1 may be set to 8 to 215 mm.

[0040] The first blade 13 may have a convex arc shape with a constant radius of curvature when viewed from the front in the rotation direction Y1. When viewed from the front in the rotation direction Y1, a point where the radius of curvature changes from the first blade 13 to the second blade 15 may be the boundary between the first blade 13 and the second blade 15, or a point where the radius of curvature changes from the first blade 13 to the third blade 17 may be the boundary between the first blade 13 and the third blade 17.

[0041] As a non-limiting example shown in FIG. 6, when viewed from the front in the rotation direction Y1 of the rotation axis O1, the radius of curvature of the first blade 13 may be larger than the radius of curvature of the second blade 15. In this case, the durability of the first blade 13, which can function as a main part of the bottom blade 9, is improved. This is because the first blade 13 is configured with a relatively gentle curve, so that cutting load is less likely to concentrate on a specific part of the first blade 13. Also, when the radius of curvature of the second blade 15 is relatively small, it is easy to configure the second blade 15 to be closer to the rear end 3b as it approaches the rotation axis O1. Therefore, in oblique sinking processing, the part at the tip 3a of the main body 3 that intersects with the rotation axis O1 is less likely to come into contact with the workpiece.

[0042] The radius of curvature of the second blade 15 when viewed from the front in the rotation direction Y1 of the rotation axis O1 may be the same as or different from the radius of curvature of the second blade 15 when viewed from the tip. For example, the radius of curvature of the second blade 15 when viewed from the front in the rotation direction Y1 (see FIG. 6) may be larger than the radius of curvature of the second blade 15 when viewed from the tip (see FIG. 3). When the radius of curvature of the second blade 15 when viewed from the front in the rotation direction Y1 is relatively large, the surface accuracy of the machined surface is likely to be improved. Also, when the radius of curvature of the second blade 15 when viewed from the tip is relatively small, it is likely to be avoided that a wide range of the second blade 15 bites into the workpiece at the same time. Therefore, even in a situation where the second blade 15 is used in oblique sinking machining, the durability of the second blade 15 is improved and chatter vibration is likely to be suppressed.

[0043] The radius of curvature of the second blade 15 when viewed from the front in the rotation direction Y1 is not limited to a specific value. For example, the radius of curvature of the second blade 15 when viewed from the front in the rotation direction Y1 may be set to 0.6 to 50 mm. In addition, the second blade 15 may have a convex arc shape with a constant radius of curvature when viewed from the front in the rotation direction Y1.

[0044] The radius of curvature of the third blade 17 when viewed from the front in the rotation direction Y1 of the rotation axis O1 may be the same as or different from the radius of curvature of the third blade 17 when viewed from the tip. For example, the radius of curvature of the third blade 17 when viewed from the front in the rotation direction Y1 (see FIG. 6) may be smaller than the radius of curvature of the third blade 17 when viewed from the tip (see FIG. 3).

[0045] When the radius of curvature of the third blade 17 when viewed from the front in the rotation direction Y1 of the rotation axis O1 is relatively small, it is easy to prevent the thickness of the chips generated by the bottom blade 9 from becoming excessively small. Therefore, it is difficult for the cutting surface to be torn. Also, when the radius of curvature of the third blade 17 when viewed from the tip is relatively large, it is easy to prevent the radial rake of the third blade 15 from changing suddenly. Therefore, it is easy to prevent the cutting load applied to the third blade 15 from changing suddenly, and chatter vibration is easily suppressed.

[0046] The radius of curvature of the third blade 17 when viewed from the front in the rotation direction Y1 is not limited to a specific value. For example, the radius of curvature of the third blade 17 when viewed from the front in the rotation direction Y1 may be set to 0.02 to 5 mm. Furthermore, the third blade 17 may have a convex arc shape with a constant radius of curvature when viewed from the front in the rotation direction Y1.

[0047] As described above, the second blade 15 may have a convex arc shape with a constant radius of curvature when viewed from the tip. In this case, as shown in a non-limiting example in Fig. 4, the center O2 of the imaginary circle C1 overlapping with the second blade 15 may be located inside the outer periphery 19 of the main body 3 (cutting portion 7) when viewed from the tip. In this case, since the second blade 15 does not have an excessively gentle curve, the durability of the second blade 15 is likely to be maintained during oblique sinking processing, etc.

[0048] The main body 3 may further have a flank 25, as a non-limiting example shown in Fig. 2. The flank 25 may extend rearward from the bottom cutting edge 9 in the rotation direction Y1. The flank 25 may function as a portion that avoids contact with the workpiece and reduces cutting resistance. The flank 25 may be connected to the bottom cutting edge 9.

[0049] The material of the body 3 may include, for example, cemented carbide and cermet. The composition of the cemented carbide may include, for example, 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.

[0050] The cermet may be a sintered composite material in which a ceramic component is combined with a metal. Specifically, the cermet may be a titanium compound mainly composed of titanium carbide (TiC) or titanium nitride (TiN). However, the above materials are only examples and are not limited thereto, and the main body 3 is not limited to these materials.

[0051] The surface of the body 3 may be coated with a coating using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. The composition of the coating may include, for example, titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al2O3).

[0052] <Method of manufacturing machined products> Next, a non-limiting method for manufacturing the one-sided machined product 101 according to the present disclosure will be described with reference to the drawings.

[0053] The machined product 101 may be produced by cutting a workpiece 103. A manufacturing method of the machined product 101 may include the following steps. (1) rotating a rotary tool 1 as typified by the non-limiting embodiment described above; (2) contacting the rotating rotary tool 1 with a workpiece 103; (3) a step of separating the rotary tool 1 from the workpiece 103; The present invention may also include:

[0054] Specifically, first, as in a non-limiting example shown in Fig. 11, the rotating tool 1 may be rotated around the rotation axis O1 and brought relatively close to the workpiece 103. Next, as in a non-limiting example shown in Fig. 12, the bottom cutting edge 9 of the rotating tool 1 may be brought into contact with the workpiece 103 to cut the workpiece 103. Then, as in a non-limiting example shown in Fig. 13, the rotating tool 1 may be moved relatively away from the workpiece 103.

[0055] By going through the above-mentioned steps, it is possible to obtain a machined product 101 having a highly accurate finished surface. Specifically, in the manufacturing method of the machined product 101, when the rotating tool 1 is used, the lathe has a high degree of freedom in the milling process and is highly versatile, so that it is possible to exhibit excellent workability. As a result, it is possible to obtain a machined product 101 having a highly accurate finished surface.

[0056] In the non-limiting example shown in Figs. 11 to 13, the workpiece 103 is fixed and the rotary tool 1 is moved in each process, but the present invention is not limited to this configuration.

[0057] For example, in the step (1), the workpiece 103 may be brought closer to the rotating tool 1. Also, in the step (3), the workpiece 103 may be moved away from the rotating tool 1. When continuing the cutting process, the rotating tool 1 may be kept rotating and the step of bringing the rotating tool 1 into contact with different locations of the workpiece 103 may be repeated.

[0058] Examples of the material of the workpiece 103 include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0059] The above provides an example of a non-limiting one-sided rotating tool 1 and a manufacturing method for a machined product 101 according to the present disclosure. However, the present disclosure is not limited to the above embodiment, and can be any embodiment as long as it does not deviate from the gist of the present disclosure.

[0060] For example, the manufacturing method of the rotating tool 1 and the machined product 101 may be configured as follows. [1] The rotating tool has a rod-shaped body extending along a rotation axis from a tip to a rear end, the body having a bottom blade located on the tip side and a discharge groove extending from the bottom blade toward the rear end, the bottom blade having a first blade with a convex curved shape and a second blade with a convex curved shape extending from the first blade toward the rotation axis, the second blade approaching the rear end as it approaches the rotation axis, and when viewed from the tip, the radius of curvature of the first blade is larger than the radius of curvature of the second blade. [2] In the rotary tool according to [1] above, the first blade may be longer than the second blade when viewed from the tip end. [3] In the rotary tool of [1] or [2] above, the end portion of the bottom cutting edge on the tip side may be positioned on the first cutting edge. [4] In any one of the rotating tools [1] to [3] above, the bottom blade may further have a third blade of a convex curved shape extending from the first blade toward the outer periphery of the body, and when viewed from the tip, the radius of curvature of the first blade may be larger than the radius of curvature of the third blade. [5] In the rotary tool according to [4] above, the first blade may be longer than the third blade when viewed from the tip. [6] In the rotary tool according to [4] or [5] above, the second blade may have a larger radius of curvature than the third blade when viewed from the tip. [7] In the rotating tool according to any one of the above items [1] to [6], the discharge groove may have a rake face located along the bottom cutting edge, and a rake angle on the bottom cutting edge may be a positive value. [8] In the rotary tool according to any one of the above [1] to [7], the main body may further have a chisel edge extending from the end cutting edge toward the rotary shaft. [9] In any one of the rotating tools [1] to [8] above, a radius of curvature of the first blade when viewed from the front in the rotation direction of the rotating shaft may be larger than a radius of curvature of the first blade when viewed from the tip.

[10] A method for manufacturing a machined product can include the steps of rotating any one of the rotating tools [1] to [9] above, bringing the rotating rotating tool into contact with a workpiece, and removing the rotating tool from the workpiece. [Explanation of symbols]

[0061] 1. Rotary tools 3. Main unit 3a...Tip 3b...rear end 5. Shank section 7...Cutting part 9...Bottom blade 9a...end 11...Discharge groove 13...1st blade 13a...center 15...2nd blade 17...Third blade 19...Circumference 21....Scooping face 23. Chisel Edge 25...Flank 101...Cutting workpiece 103...Work material O1 Rotation axis Y1 Rotation direction L1: Virtual line C1: Virtual circle O2...center

Claims

1. A rod-shaped main body extending from a front end to a rear end along a rotation axis, The body includes: A bottom cutting edge located on the tip side; a discharge groove extending from the bottom blade toward the rear end, The end blade is A first blade having a convex curved shape; a second blade having a convex curved shape extending from the first blade toward the rotation shaft, The second blade approaches the rear end as it approaches the rotation axis, A rotary tool, wherein, when viewed from the tip, a radius of curvature of the first blade is larger than a radius of curvature of the second blade.

2. The rotary tool according to claim 1 , wherein the first blade is longer than the second blade when viewed from the tip.

3. The rotary tool according to claim 1 , wherein an end portion of the bottom cutting edge on the tip side is located on the first cutting edge.

4. The bottom blade further includes a third blade having a convex curved shape extending from the first blade toward an outer periphery of the main body, The rotary tool according to claim 1 , wherein a radius of curvature of the first blade is larger than a radius of curvature of the third blade when viewed from the tip end.

5. The rotary tool according to claim 4 , wherein the first blade is longer than the third blade when viewed from the tip.

6. The rotary tool according to claim 4 , wherein, in a front end view, a radius of curvature of the second blade is larger than a radius of curvature of the third blade.

7. The discharge groove has a rake surface located along the bottom cutting edge, The rotary tool according to claim 1 , wherein the rake angle of the end cutting edge is a positive value.

8. The rotary tool of claim 1 , wherein the body further includes a chisel edge extending from the bottom cutting edge toward the axis of rotation.

9. The rotary tool according to claim 1 , wherein a radius of curvature of the first blade when viewed from the front in the rotation direction of the rotary shaft is larger than a radius of curvature of the first blade when viewed from a tip end.

10. A step of rotating the rotary tool according to any one of claims 1 to 9; contacting the rotating rotary tool with a workpiece; and removing the rotating tool from the workpiece.

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