Drill and method for manufacturing cut workpiece

Abstract

A drill according to a non-limiting aspect of the present disclosure is rod-shaped and extends from a leading end to a rear end along an axis of rotation. The drill has a cutting edge located on the leading end side and a discharge groove extending from the cutting edge toward the rear end. The cutting edge has a first edge, a second edge extending from the first edge toward an outer periphery, and a third edge extending from the second edge toward the outer periphery. The inclination angles of the first edge, second edge, and third edge with respect to the axis of rotation are a first inclination angle, a second inclination angle, and a third inclination angle, respectively. The second inclination angle is smaller than the first inclination angle, and the third inclination angle is smaller than the second inclination angle. The rake angles of the first edge, second edge, and third edge are a first rake angle, a second rake angle, and a third rake angle, respectively. The second rake angle is larger than the first rake angle and the third rake angle.

Description

Drill and cutting process CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2023-168978, filed on September 29, 2023, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to a drill used for cutting a workpiece and a method for manufacturing a cut product.

[0003] A drill disclosed in Japanese Patent Laid-Open No. 2010-115750 (Patent Document 1) has been known as a drill used for cutting workpieces such as metal members. The drill disclosed in Patent Document 1 has a cutting edge located on the tip side. The cutting edge has a main cutting edge located on the rotation axis side and a peripheral cutting edge (deburring edge) located on the outer periphery side. From the viewpoint of suppressing chipping of the cutting edge on the outer periphery side, the inclination angle of the peripheral cutting edge with respect to the rotation axis of the drill is set smaller than the inclination angle of the main cutting edge with respect to the rotation axis of the drill.

[0004] When drilling a workpiece using a drill, burrs may form at the opening of the through hole as the drill penetrates the workpiece. Burrs are particularly likely to form when the inclination angle of the peripheral cutting edge is set small to prevent chipping of the cutting edge. In this case, by gradually reducing the inclination angle of the peripheral cutting edge, chipping of the cutting edge on the outer periphery can be prevented while also preventing the generation of burrs.

[0005] However, if the inclination angle of the peripheral cutting edge is gradually reduced, the thickness of the chips will gradually decrease as they move toward the outer periphery. When the chips have this shape, they are difficult to break up and tend to grow long. This can cause the chips to wrap around the drill, making it difficult to continue drilling.

[0006] The present disclosure has been made in view of the above-mentioned problems, and aims to provide a drill that has good chip breaking properties.

[0007] A non-limiting one-sided drill of the present disclosure has a rod shape extending from a leading end to a trailing end along a rotation axis, the drill having a cutting edge located on the leading end side and a discharge flute extending from the cutting edge to the trailing end.

[0008] The cutting edge has a first blade, a second blade extending from the first blade toward the outer periphery, and a third blade extending from the second blade toward the outer periphery. The inclination angles of the first blade, the second blade, and the third blade with respect to the rotation axis are a first inclination angle, a second inclination angle, and a third inclination angle, respectively. The second inclination angle is smaller than the first inclination angle, and the third inclination angle is smaller than the second inclination angle.

[0009] The first rake angle, the second rake angle, and the third rake angle are respectively a first rake angle, a second rake angle, and a third rake angle, and the second rake angle is larger than the first rake angle and the third rake angle.

[0010] 1 is a perspective view showing an unrestricted one-sided drill of the present disclosure; FIG. 2 is an enlarged view of a region II shown in FIG. 1; FIG. 3 is a plan view of the drill shown in FIG. 1 as viewed from the tip side; FIG. 4 is a side view of the drill shown in FIG. 3 as viewed from direction IV; FIG. 5 is an enlarged view of a region V shown in FIG. 4; FIG. 6 is the same enlarged view as FIG. 5; FIG. 7 is a side view of the drill shown in FIG. 3 as viewed from direction VII; FIG. 8 is an enlarged view of a region VIII shown in FIG. 7; FIG. 8 is the same enlarged view as FIG. 5; FIG. 9 is a cross-sectional view of cross-section X of the drill shown in FIG. 9; FIG. 10 is a cross-sectional view of cross-section XI of the drill shown in FIG. 9; FIG. 11 is a cross-sectional view of cross-section XII of the drill shown in FIG. 9; FIG. 12 is a schematic view showing one step in a method for manufacturing an unrestricted one-sided machined product of the present disclosure; FIG. 13 is a schematic view showing one step in a method for manufacturing an unrestricted one-sided machined product of the present disclosure; FIG. 14 is a schematic view showing one step in a method for manufacturing an unrestricted one-sided machined product of the present disclosure; FIG. 15 is a schematic view showing one step in a method for manufacturing an unrestricted one-sided machined product of the present disclosure;

[0011] <Drill> A non-limiting example of a drill 1 according to the present disclosure will be described in detail below with reference to the drawings. However, for the sake of convenience, the drawings below show only the main components necessary for explaining the embodiment in a simplified form. Therefore, the drill 1 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 or the dimensional ratios of the components.

[0012] In a non-limiting aspect, a solid drill may be shown as an example of the drill 1. However, the drill 1 is not limited to a solid drill, and may be, for example, a replaceable tip drill.

[0013] 1 to 12, the drill 1 may have a rod shape extending from a tip end 1a to a rear end 1b along a rotation axis O1. The drill 1 is rotatable around the rotation axis O1. Note that the arrow Y1 in FIG. 1 and other figures may indicate the rotation direction of the rotation axis O1, or may indicate the rotation direction of the drill 1 around the rotation axis O1.

[0014] The drill 1 may have a shank portion 3 and a cutting portion 5. The shank portion 3 can function as a portion that is gripped by a rotating spindle of a machine tool. The shank portion 3 may be designed according to the shape of the spindle of the machine tool.

[0015] The cutting portion 5 may be located on the tip 1a side relative to the shank portion 3. The cutting portion 5 is capable of coming into contact with a workpiece, and can function as a portion that plays a major role in cutting (e.g., drilling) the workpiece.

[0016] The drill 1 is not limited to a specific size. For example, when the outer diameter of the cutting portion 5 is defined as D, the maximum value of D may be set to approximately 1 to 30 mm. Furthermore, when the length of the cutting portion 5 in the direction along the rotation axis O1 is defined as L, L may be set to approximately L=0.8D to 40D.

[0017] The drill 1 may have a cutting edge 7 and a flute 9, as a non-limiting example shown in Figure 2. These parts may be located in the cutting part 5.

[0018] The cutting edge 7 may be located on the side of the tip 1a. The cutting edge 7 can function as a portion that cuts the workpiece in cutting processing. There may be only one cutting edge 7, or there may be multiple cutting edges 7. When there are multiple cutting edges 7, the number of cutting edges 7 may be 2 to 4.

[0019] When there are multiple cutting edges 7, the multiple cutting edges 7 may be positioned so as to be rotationally symmetrical about the rotation axis O1 when viewed from the tip 1a side. For example, as in a non-limiting example shown in Figure 3, when there are two cutting edges 7, the two cutting edges 7 may be positioned so as to be rotationally symmetrical about 180° about the rotation axis O1 when viewed from the tip 1a side. In this case, the drill 1 has high linearity when cutting a workpiece.

[0020] The discharge grooves 9 may extend from the cutting edge 7 toward the rear end 1b, as in the non-limiting examples shown in Figures 5 and 8. The discharge grooves 9 may function as a portion for discharging chips generated by the cutting edge 7 to the outside. The discharge grooves 9 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 grooves 9 may have a concave curved shape. The number of discharge grooves 9 may be the same as the number of cutting edges 7.

[0021] The cutting edge 7 may have a first edge 11, a second edge 13, and a third edge 15, as shown in a non-limiting example in Figure 2. The second edge 13 may extend from the first edge 11 toward the outer periphery 17. The third edge 15 may extend from the second edge 13 toward the outer periphery 17.

[0022] The first blade 11 may also be called a main cutting blade. The second blade 13 and the third blade 15 may also be called chamfering blades. The second blade 13 may be connected to the first blade 11. The third blade 15 may be connected to the second blade 13. The third blade 15 may be connected to the outer periphery 17.

[0023] The cutting edge 7 may be chamfered or honed. For example, as shown in a non-limiting example in Figure 3, the first blade 11 may be honed. Also, the end of the second blade 13 on the first blade 11 side may be honed.

[0024] 5 , the inclination angle of the first blade 11 with respect to the rotation axis O1 may be a first inclination angle θ11a. The inclination angle of the second blade 13 with respect to the rotation axis O1 may be a second inclination angle θ13a. The inclination angle of the third blade 15 with respect to the rotation axis O1 may be a third inclination angle θ15a. The second inclination angle θ13a may be smaller than the first inclination angle θ11a, and the third inclination angle θ15a may be smaller than the second inclination angle θ13a.

[0025] In this case, the inclination angles of the second blade 13 and the third blade 15, which are located closer to the outer periphery 17 than the first blade 11 that can function as the main cutting edge, are smaller than that of the first blade 11. As a result, a large cutting load is less likely to be applied to the second blade 13 and the third blade 15 compared to the first blade 11. Therefore, chipping of the second blade 13 and the third blade 15 is more likely to be suppressed.

[0026] Furthermore, when cutting a workpiece, if the cutting edge 7 is viewed from the front in the rotation direction Y1 of the rotation axis O1, a force that pushes out chips generated by the cutting edge 7 in a direction perpendicular to the cutting edge 7 is likely to act on the chips. If the inclination angle of the first cutting edge 11 that can function as the main cutting edge is relatively large, a force that pushes out the workpiece in roughly the same direction as the direction of travel of the drill 1 is likely to be applied. Therefore, the pushed-out portion is likely to be cut off in the next cutting process.

[0027] If the second blade 13 and the third blade 15, which are located closer to the outer periphery 17 than the first blade 11 and function as the main cutting edge, have a smaller inclination angle than the first blade 11, a force pushing the workpiece in a direction generally perpendicular to the direction of travel of the drill 1 (toward the outer periphery 17) is likely to be applied. This may lead to the generation of burrs at the opening of the through hole. However, if the third blade 15, which is located closer to the outer periphery 17 than the second blade 13, has a smaller inclination angle than the second blade 13, chipping of the second blade 13 and the third blade 15 is suppressed, and burrs are also likely to be suppressed. Specifically, even if uncut portions are left behind during cutting by the first blade 11 and the second blade 13, these uncut portions are easily removed by the third blade 15. As a result, burrs are more likely to be suppressed.

[0028] As shown in a non-limiting example in Fig. 10, the rake angle of the first blade 11 may be a first rake angle θ11b. As shown in a non-limiting example in Fig. 11, the rake angle of the second blade 13 may be a second rake angle θ13b. As shown in a non-limiting example in Fig. 12, the rake angle of the third blade 15 may be a third rake angle θ15b. The second rake angle θ13b may be larger than the first rake angle θ11b and the third rake angle θ15b (see Figs. 10 to 12).

[0029] In this case, the second rake angle θ13b is relatively large, and therefore the sharpness of the second cutting edge 13 is high. Therefore, portions that are likely to lead to burrs due to being pushed out are less likely to occur in the workpiece.

[0030] Furthermore, the relatively small first rake angle θ11b increases the durability of the cutting edge 7. Because the first blade 11 is located closer to the rotation axis O1 than the second blade 13, the cutting speed of the first blade 11 is slower than the cutting speed of the second blade 13, and a relatively large torque is likely to be applied to the first blade 11. In this case, because the first rake angle θ11b is relatively small, the thickness of the first blade 11 is likely to be secured, and durability is likely to be improved.

[0031] Furthermore, because the third rake angle θ15b is relatively small, the drill 1 can be provided with good chip breaking properties for the following reason: Because the third rake angle θ15b is relatively small, chips generated by the third cutting edge 15 (hereinafter referred to as third chips for convenience) flow less smoothly than chips generated by the second cutting edge 13 (hereinafter referred to as second chips for convenience). In other words, a misalignment occurs between the flow of the second chips and the flow of the third chips.

[0032] Due to this misalignment, a force pulling the third chip is applied from the second chip. As described above, since the third inclination angle θ15a is relatively small, the third chip is relatively thin and easily broken up. The chip breakage generated in the third chip progresses to the second chip, and further to the chip generated by the first cutting edge 11, so that the chip breaks up as a whole. For the above reasons, the drill 1 has good chip breakability.

[0033] The first rake angle θ11b may be the same as or different from the third rake angle θ15b. For example, the first rake angle θ11b may be larger than the third rake angle θ15b. In this case, the first blade 11 has a high sharpness, so that the cutting edge 7 is less likely to be left uncut during cutting. Furthermore, the third blade 15 has a high strength, so that the cutting edge 7 is less likely to be chipped.

[0034] Conversely, the third rake angle θ15b may be greater than the first rake angle θ11b (see FIGS. 10 and 12). In this case, the third blade 15 has a high sharpness, and even if uncut portions are left behind during cutting by the first blade 11 and the second blade 13, the uncut portions are stably removed, which makes it easier to prevent burrs from occurring. Furthermore, because the third rake angle θ15b is smaller than the second rake angle θ13b, it is easier to ensure a minimum strength for the third blade 15.

[0035] As shown in a non-limiting example in FIG. 5, the difference between the first inclination angle θ11a and the second inclination angle θ13a may be smaller than the difference between the second inclination angle θ13a and the third inclination angle θ15a. In this case, chips are more likely to be prevented from splitting vertically. This ensures a sufficient width for the chips, further improving chip separability. Furthermore, because chips are less likely to split vertically, split chips are less likely to become tangled, resulting in good chip discharge.

[0036] The difference between the first tilt angle θ11a and the second tilt angle θ13a is a value calculated from the formula: first tilt angle θ11a - second tilt angle θ13a. The difference between the second tilt angle θ13a and the third tilt angle θ15a is a value calculated from the formula: second tilt angle θ13a - third tilt angle θ15a.

[0037] The "inclination angle" may be evaluated as follows. For example, if the cutting edge 7 has a linear shape when viewed from the front in the rotation direction Y1 of the rotation axis O1, the angle formed between an imaginary line along the cutting edge 7 (or the cutting edge 7) and the rotation axis O1 (or an imaginary line O1a parallel to the rotation axis O1) may be evaluated. Furthermore, if the cutting edge 7 does not have a linear shape when viewed from the front in the rotation direction Y1, the angle formed between an imaginary line connecting both ends of the target portion of the cutting edge 7 and the rotation axis O1 (or an imaginary line O1a parallel to the rotation axis O1) may be evaluated.

[0038] In the non-limiting example shown in Fig. 5, the first blade 11 has a concave shape when viewed from the front in the rotation direction Y1, but for ease of visual understanding, the imaginary line connecting both ends of the first blade 11 used to evaluate the "tilt angle" is omitted. Also, in the non-limiting example shown in Fig. 5, the second blade 13 and the third blade 15 each have a linear shape when viewed from the front in the rotation direction Y1.

[0039] The "tilt angle" is not limited to a specific value. For example, the first tilt angle θ11a may be set to 45 to 90°. The second tilt angle θ13a may be set to 15 to 60°. The third tilt angle θ15a may be set to 1 to 10°.

[0040] The "rake angle" may be defined as follows. First, it may represent a cross section perpendicular to the cutting edge 7 at a target portion of the cutting edge 7. For example, as in the non-limiting examples shown in FIGS. 10 to 12, it may represent a cross section perpendicular to the center of each of the first blade 11, the second blade 13, and the third blade 15. If the cutting edge 7 has been chamfered or honed, the rake angle may be evaluated based on the point of the machined portion that is closest to the rotation axis O1.

[0041] In the above cross section, a line connecting the cutting edge 7 and the rotation axis O1 may be defined as a first imaginary line L1. A imaginary line passing through the cutting edge 7 and tangent to the rake face 21 of the discharge groove 9 may be defined as a second imaginary line L2. The angle at which the first imaginary line L1 and the second imaginary line L2 intersect may be defined as a "rake angle."

[0042] In addition, if the cutting edge 7 has been chamfered or honed and the cutting edge 7 is a flat surface or a convex curved surface when viewed microscopically, the first virtual straight line L1 and the second virtual straight line L2 may each pass through the end of the cutting edge 7 on the side of the cutting face 21.

[0043] The "rake angle" is not limited to a specific value. For example, the first rake angle θ11b may be set to 5 to 30°. The second rake angle θ13b may be set to 20 to 45°. The third rake angle θ15b may be set to 5 to 30°.

[0044] The flank 19 of the drill 1 may extend rearward in the rotation direction Y1 from the cutting edge 7, as in a non-limiting example shown in FIG. 8 . The flank 19 can function as a portion that avoids contact with the workpiece and reduces cutting resistance. The flank 19 may be connected to the cutting edge 7.

[0045] The rake face 21 in the discharge groove 9 may be located along the cutting edge 7, as in a non-limiting example shown in Figures 10 to 12. The rake face 21 can function as a portion through which chips flow during cutting. The rake face 21 may be connected to the cutting edge 7.

[0046] 3, the first blade 11 may have a concave shape when viewed from the tip 1a side. In this case, even if uncut portions are left behind during cutting by the first blade 11, the uncut portions are less likely to be pushed out toward the outer periphery 17. Therefore, the generation of burrs is more likely to be suppressed.

[0047] Furthermore, the second blade 13 may have a convex shape when viewed from the tip 1a side. In this case, the second blade 13 easily bites into the workpiece. This results in good cutting performance by the second blade 13. In particular, when the second rake angle θ13b is relatively large, the strength of the second blade 13 is likely to decrease, so good cutting performance by the second blade 13 tends to improve the durability of the second blade 13.

[0048] Also, when viewed from the side of the tip 1a, the first blade 11 may be concave and the second blade 13 may be convex. When the first blade 11 is concave, the uncut material is less likely to be pushed out toward the outer periphery 17 as described above, and further, when the second blade 13 is convex, the second blade 13 can cut the workpiece well, which makes it easier to suppress the generation of burrs.

[0049] 6 , the first blade 11 may be longer than the second blade 13 and the third blade 15 in the direction along the rotation axis O1. That is, the length W11 of the first blade 11 may be longer than the length W13 of the second blade 13 and the length W15 of the third blade 15 in the direction along the rotation axis O1. In this case, it is possible to ensure a relatively long first blade 11 that can function as a main cutting edge.

[0050] 6 , the third blade 15 may be longer than the second blade 13 in the direction along the rotation axis O1. That is, the length W15 of the third blade 15 may be longer than the length W13 of the second blade 13 in the direction along the rotation axis O1. In this case, the surface precision of the inner peripheral surface of the machined hole is high.

[0051] 5, the first blade 11 may be longer than the second blade 13 and the third blade 15 in a direction perpendicular to the rotation axis O1. Also, the second blade 13 may be longer than the third blade 15 in a direction perpendicular to the rotation axis O1.

[0052] 3, the radial rakes of the first blade 11, the second blade 13, and the third blade 15 may each be set to a positive value. In this case, it becomes easier to design a configuration in which the second rake angle θ13b is larger than each of the first rake angle θ11b and the third rake angle θ15b.

[0053] As a non-limiting example shown in Fig. 2, the cutting edge 7 may further include a fourth cutting edge 23. The fourth cutting edge 23 may extend from the first cutting edge 11 toward the rotation axis O1. The fourth cutting edge 23 may be inclined with respect to the first cutting edge 11. The fourth cutting edge 23 may also be referred to as a thinning cutting edge. The fourth cutting edge 23 may be honed.

[0054] The drill 1 may further have a chisel edge extending from the fourth cutting edge 23 toward the rotation axis O1. The chisel edge can function as a portion that crushes the workpiece. The chisel edge may be connected to the fourth cutting edge 23. The chisel edge may extend to the rotation axis O1.

[0055] Examples of the material of the drill 1 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.

[0056] 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 primarily composed of titanium carbide (TiC) or titanium nitride (TiN). However, the above materials are merely examples and the drill 1 may be made of any material other than these.

[0057] The surface of the drill 1 may be coated with a coating using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method, and the coating composition may include, for example, titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (AlO).

[0058] <Method for Manufacturing Machined Product> Next, a non-limiting method for manufacturing the machined product 101 having one surface according to the present disclosure will be described with reference to the drawings.

[0059] The machined product 101 may be produced by cutting a workpiece 103. A method for producing the machined product 101 may include the following steps (1) to (4).

[0060] (1) A step of placing the drill 1 above the workpiece 103 (see FIG. 13 ). (2) A step of rotating the drill 1 around the rotation axis O1 in the direction of the arrow Y1 to bring the drill 1 closer to the workpiece 103 (see FIG. 13 ).

[0061] In steps (1) and (2), for example, the workpiece 103 may be fixed on a table of a machine tool to which the drill 1 is attached, and the drill 1 may be brought closer to the workpiece 103 while rotating. In step (2), the workpiece 103 and the drill 1 may be brought closer to each other, for example, the workpiece 103 may be brought closer to the drill 1.

[0062] (3) A process in which the rotating drill 1 is brought closer to the workpiece 103, thereby bringing the rotating drill 1 into contact with the workpiece 103 and forming a machining hole 105 (through hole) in the workpiece 103 (see Figures 14 and 15).

[0063] In step (3), cutting may be performed so that at least a portion of the cutting portion 5 is located inside the machined hole 105. Also, in step (3), the shank portion 3 may be set to be located outside the machined hole 105. From the viewpoint of obtaining a good finished surface, a portion of the rear end 1b side of the cutting portion 5 may be set to be located outside the machined hole 105. This portion can function as a margin region for chip evacuation, and excellent chip evacuation can be achieved via this region.

[0064] (4) Step of separating the drill 1 from the workpiece 103 (see FIG. 16 ): In step (4), the workpiece 103 and the drill 1 may be separated relatively. For example, the workpiece 103 may be separated from the drill 1.

[0065] By going through the above steps, it is possible to obtain a machined product 101 having a highly accurate machined hole 105. Specifically, when the drill 1 is used in the manufacturing method of the machined product 101, excellent workability can be achieved because chip breakability is good. As a result, it is possible to obtain a machined product 101 having a highly accurate machined hole 105.

[0066] In addition, when cutting the workpiece 103 multiple times, for example, when forming multiple machining holes 105 in one workpiece 103, the process of contacting the drill 1 with different locations on the workpiece 103 while keeping the drill 1 rotating may be repeated.

[0067] Examples of materials for the workpiece 103 include metals and resins. Examples of metals include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals. Examples of resins include polyethylene (PE), polypropylene (PP), polycarbonate (PC), and polyamide (PA). Furthermore, so-called glass fiber reinforced plastics (GFRP) and carbon fiber reinforced plastics (CFRP) may also be used as resin materials.

[0068] The above describes an example of a non-limiting one-sided drill 1 and a method for manufacturing a machined product 101 according to the present disclosure. However, the present disclosure is not limited to the above-described embodiment, and it goes without saying that any method may be used as long as it does not deviate from the gist of the present disclosure.

[0069] For example, the manufacturing method of the drill 1 and the machined product 101 may be configured as follows: [1] The drill has a rod shape extending from a front end to a rear end along a rotation axis, and has a cutting edge located on the front end side and a discharge groove extending from the cutting edge toward the rear end, the cutting edge has a first blade, a second blade extending from the first blade toward an outer periphery, and a third blade extending from the second blade toward an outer periphery, the inclination angles of the first blade, the second blade, and the third blade with respect to the rotation axis are a first inclination angle, a second inclination angle, and a third inclination angle, respectively, the second inclination angle is smaller than the first inclination angle and the third inclination angle is smaller than the second inclination angle, and the rake angles of the first blade, the second blade, and the third blade are a first rake angle, a second rake angle, and a third rake angle, respectively, and the second rake angle is larger than the first rake angle and the third rake angle. [2] In the drill of [1] above, the third rake angle may be larger than the first rake angle. [3] In the drill of [1] or [2] above, the difference between the first inclination angle and the second inclination angle may be smaller than the difference between the second inclination angle and the third point angle. [4] In any one of the drills of [1] to [3] above, the first cutting edge may have a concave shape and the second cutting edge may have a convex shape when viewed from the tip side. [5] In any one of the drills of [1] to [4] above, the first cutting edge may be longer than the second cutting edge and the third cutting edge in the direction along the rotation axis. [6] In the drill of [5] above, the third cutting edge may be longer than the second cutting edge in the direction along the rotation axis. [7] A method for manufacturing a machined product can include the steps of rotating any one of the drills [1] to [6] above around the rotation axis, bringing the rotating drill into contact with a workpiece, and removing the drill from the workpiece.

[0070] REFERENCE SIGNS LIST 1... Drill 1a... Tip 1b... Rear end 3... Shank portion 5... Cutting portion 7... Cutting edge 9... Discharge groove 11... First cutting edge 13... Second cutting edge 15... Third cutting edge 17... Outer periphery 19... Relief face 21... Rake face 23... Fourth cutting edge 101... Cutting workpiece 103... Workpiece 105... Machined hole O1... Rotation axis Y1... Rotation direction θ11a... First inclination angle θ13a... Second inclination angle θ15a... Third inclination angle θ11b... First rake angle θ13b... Second rake angle θ15b... Third rake angle

Claims

1. It is a rod-shaped structure that extends from the tip to the rear end along the axis of rotation, The cutting edge located on the tip side, It has a discharge groove extending from the cutting edge toward the rear end, The aforementioned cutting edge is The first blade and, A second blade extending outward from the first blade, It has a third cutting edge extending outward from the second cutting edge, The inclination angles of the first blade, the second blade, and the third blade with respect to the rotation axis are the first inclination angle, the second inclination angle, and the third inclination angle, respectively. The second tilt angle is smaller than the first tilt angle, and the third tilt angle is smaller than the second tilt angle, The rake angles of the first cutting edge, the second cutting edge, and the third cutting edge are the first rake angle, the second rake angle, and the third rake angle, respectively. A drill in which the second rake angle is larger than the first rake angle and the third rake angle.

2. The drill according to claim 1, wherein the third rake angle is larger than the first rake angle.

3. The drill according to claim 1, wherein the difference between the first tilt angle and the second tilt angle is smaller than the difference between the second tilt angle and the third tilt angle.

4. The drill according to claim 1, wherein, when viewed from the tip side, the first blade is concave and the second blade is convex.

5. The drill according to claim 1, wherein the first cutting edge is longer than the second and third cutting edges in the direction along the axis of rotation.

6. The drill according to claim 5, wherein the third cutting edge is longer than the second cutting edge in the direction along the axis of rotation.

7. A step of rotating the drill according to any one of claims 1 to 6 around the rotating shaft, The process of bringing the rotating drill into contact with the workpiece, A method for manufacturing a cut workpiece, comprising the step of separating the drill from the workpiece.