Manufacturing method for drills and cut works

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

Cross-Reference to Related Applications

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

[0002] The present disclosure relates to a drill used for cutting a workpiece, and a method for manufacturing a machined product. BACKGROUND ART

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

[0004] In drilling a workpiece using a drill, burrs may be generated at the opening portion of the through-hole when the drill penetrates the workpiece. In particular, when the inclination angle of the peripheral edge is set small in order to suppress chipping of the cutting edge, burrs are likely to occur. At this time, by gradually reducing the inclination angle of the peripheral edge, it is possible to suppress the occurrence of burrs while suppressing chipping of the cutting edge on the outer peripheral side.

[0005] However, when the inclination angle of the peripheral edge is reduced stepwise, the thickness of the chip becomes thinner stepwise toward the outer peripheral side. When the chip has such a shape, the chip is less likely to be divided and tends to elongate. Therefore, the chip may wind around the drill, making it difficult to continue the drilling operation.

[0006] This disclosure has been made in view of the above-mentioned problems and aims to provide a drill with good chip breaking ability. [Overview of the project]

[0007] A drill, not limited to this disclosure, is rod-shaped and extends from the tip to the rear end along the axis of rotation. The drill has a cutting edge located on the tip side and an ejection groove extending from the cutting edge to the rear end.

[0008] The cutting edge has a first blade, a second blade extending outward from the first blade, and a third blade extending outward from the second blade. The inclination angles of the first blade, the second blade, and the third blade with respect to the axis of rotation are the first inclination angle, the second inclination angle, and the 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 rake angles of the first, second, and third cutting edges are the first, second, and third rake angles, respectively. The second rake angle is larger than the first and third rake angles. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view showing one aspect of the drill, not limited to this disclosure. [Figure 2] This is a magnified view of region II shown in Figure 1. [Figure 3] Figure 1 is a plan view of the drill as seen from the tip side. [Figure 4] Figure 3 is a side view of the drill as seen from direction IV. [Figure 5] This is a magnified view of region V shown in Figure 4. [Figure 6] This is an enlarged view of the same figure as Figure 5. [Figure 7] Figure 3 is a side view of the drill as seen from direction VII. [Figure 8]Figure 7 is a magnified view of region VIII shown in Figure 7. [Figure 9] This is an enlarged view of the same figure as Figure 5. [Figure 10] Figure 9 shows a cross-sectional view of the drill in the X-section. [Figure 11] Figure 9 is a cross-sectional view of the XI section of the drill shown. [Figure 12] Figure 9 is a cross-sectional view of section XII in the drill shown. [Figure 13] This is a schematic diagram showing one step in a method for manufacturing a one-sided machined workpiece, not limited to the present disclosure. [Figure 14] This is a schematic diagram showing one step in a method for manufacturing a one-sided machined workpiece, not limited to the present disclosure. [Figure 15] This is a schematic diagram showing one step in a method for manufacturing a one-sided machined workpiece, not limited to the present disclosure. [Figure 16] This is a schematic diagram showing one step in a method for manufacturing a one-sided machined workpiece, not limited to the present disclosure. [Modes for carrying out the invention]

[0011] <Drill> Hereinafter, a drill 1, which is not limited to this disclosure, will be described in detail with reference to the drawings. However, in the drawings referenced below, for the sake of clarity, only the main components necessary for describing the embodiment are shown in a simplified manner. Therefore, the drill 1 may include any components not shown in the drawings referenced below. Furthermore, the dimensions of the components in each drawing do not faithfully represent the dimensions of the actual components or the dimensional ratios of each component.

[0012] In addition, a solid drill may be shown as an example of drill 1, although this is not limited to a solid drill. For example, drill 1 may be a drill with an interchangeable tip.

[0013] The drill 1 may have a rod shape extending from the tip 1a toward the rear end 1b along the rotation axis O1, as in the non-limiting example shown in Fig. 1 to Fig. 12. The drill 1 is rotatable around the rotation axis O1. Note that the arrow Y1 in Fig. 1 and the like 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 part to be gripped by a rotating spindle of a machine tool. The shank portion 3 may be designed according to the shape of the spindle in the machine tool.

[0015] The cutting portion 5 may be located on the side of the tip 1a relative to the shank portion 3. The cutting portion 5 is capable of coming into contact with a workpiece, and can function as a part that plays a main role in the cutting processing (for example, drilling processing) of 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 about 1 to 30 mm. Further, 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 about L=0.8D to 40D.

[0017] The drill 1 may have cutting edges 7 and discharge grooves 9, as in the non-limiting example shown in Fig. 2. These parts may be located in the cutting portion 5.

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

[0019] If there are multiple cutting edges 7, they may be positioned such that they are rotationally symmetrical with respect to the axis of rotation O1 when viewed from the side of the tip 1a. For example, as shown in the example without limitation in Figure 3, if there are two cutting edges 7, they may be positioned such that they are 180° rotationally symmetrical with respect to the axis of rotation O1 when viewed from the side of the tip 1a. In this case, the straightness of the drill 1 when cutting the workpiece is high.

[0020] The discharge groove 9 may extend from the cutting edge 7 toward the rear end 1b, as shown in the example (not limited to) in Figures 5 and 8. The discharge groove 9 can function as a part for discharging chips generated by the cutting edge 7 to the outside. The discharge groove 9 may extend parallel to the rotation axis O1, or it may extend in a helical shape around the rotation axis O1. In a cross section perpendicular to the rotation axis O1, the discharge groove 9 may have a concave curve 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 blade 11, a second blade 13, and a third blade 15, as shown in the example not limited to Figure 2. The second blade 13 may extend from the first blade 11 toward the outer circumference 17. The third blade 15 may also extend from the second blade 13 toward the outer circumference 17.

[0022] The first blade 11 may also be called the main cutting edge. The second blade 13 and the third blade 15 may each 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 circumference 17.

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

[0024] Here, as shown in the example not limited to Figure 5, the inclination angle of the first blade 11 with respect to the rotation axis O1 may be the first inclination angle θ11a. Also, the inclination angle of the second blade 13 with respect to the rotation axis O1 may be the second inclination angle θ13a. The inclination angle of the third blade 15 with respect to the rotation axis O1 may be the 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 circumference 17 than the first blade 11 that can function as the main cutting edge, are smaller than those of the first blade 11. As a result, the cutting load on the second blade 13 and the third blade 15 is less likely to be greater than that on the first blade 11. Therefore, chipping of the second blade 13 and the third blade 15 is more easily suppressed.

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

[0027] If the second and third blades 13 and 15, which are located closer to the outer circumference 17 than the first blade 11 that can function as the main cutting edge, have a smaller inclination angle than the first blade 11, a force is more likely to be applied that pushes the workpiece in a direction roughly perpendicular to the direction of movement of the drill 1 (towards the outer circumference 17). Therefore, this may lead to the formation of burrs at the opening of the through hole. However, if the third blade 15, which is located closer to the outer circumference 17 than the second blade 13, has a smaller inclination angle than the second blade 13, chipping of the second blade 13 and third blade 15 is suppressed, and the formation of burrs is also more likely to be suppressed. Specifically, even if some material remains after cutting by the first blade 11 and second blade 13, this remaining material is more likely to be removed by the third blade 15. As a result, the formation of burrs is more likely to be suppressed.

[0028] As shown in the example shown in Figure 10, the rake angle at the first cutting edge 11 may be the first rake angle θ11b. Also, as shown in the example shown in Figure 11, the rake angle at the second cutting edge 13 may be the second rake angle θ13b. As shown in the example shown in Figure 12, the rake angle at the third cutting edge 15 may be the 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 Figures 10 to 12).

[0029] In this case, the second rake angle θ13b is relatively large, resulting in high cutting performance of the second cutting edge 13. Therefore, areas prone to burr formation due to extrusion are less likely to occur in the workpiece.

[0030] Furthermore, because the first rake angle θ11b is relatively small, the cutting edge 7 has high durability. Since the first cutting edge 11 is located closer to the rotation axis O1 than the second cutting edge 13, the cutting speed of the first cutting edge 11 is slower than that of the second cutting edge 13, and a relatively large torque is easily applied to the first cutting edge 11. In this case, because the first rake angle θ11b is relatively small, the thickness of the first cutting edge 11 is easily secured, and its durability is easily improved.

[0031] Furthermore, because the third rake angle θ15b is relatively small, a drill 1 with good chip breaking ability can be provided for the following reason. Because the third rake angle θ15b is relatively small, the chips generated at the third cutting edge 15 (hereinafter referred to as the third chip for convenience) do not flow as smoothly as the chips generated at the second cutting edge 13 (hereinafter referred to as the second chip for convenience). In other words, a discrepancy occurs between the flow of the second chip and the flow of the third chip.

[0032] Due to this misalignment, a pulling force is applied to the third chip 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. The breaking of the chip that occurs in the third chip progresses to the second chip, and then to the chip generated by the first cutting edge 11, thereby breaking the entire chip. For the reasons above, the chip breaking ability in the drill 1 is good.

[0033] The first rake angle θ11b may be the same as the third rake angle θ15b, or it may be different. For example, the first rake angle θ11b may be larger than the third rake angle θ15b. In this case, the first cutting edge 11 has a higher cutting edge, making it less likely for material to remain uncut when cutting with the first cutting edge 11. Also, because the third cutting edge 15 has a higher strength, chipping of the cutting edge 7 is less likely.

[0034] Conversely, the third rake angle θ15b may be larger than the first rake angle θ11b (see Figures 10 and 12). In this case, because the third cutting edge 15 has high cutting performance, even if some material remains after cutting by the first cutting edge 11 and the second cutting edge 13, this remaining material is reliably removed, thus suppressing the generation of burrs. Also, because the third rake angle θ15b is smaller than the second rake angle θ13b, it is easier to ensure the minimum strength of the third cutting edge 15.

[0035] As shown in the example not limited to Figure 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, it is easier to avoid the chip splitting lengthwise. As a result, the width of the chip is ensured, and the fragmentation ability of the chip is further improved. Also, since the chip is less likely to split lengthwise, the situation in which the split chips become entangled with each other is less likely to occur, resulting in good chip evacuation.

[0036] The difference between the first inclination angle θ11a and the second inclination angle θ13a is the value calculated from the formula: First inclination angle θ11a - Second inclination angle θ13a. The difference between the second inclination angle θ13a and the third inclination angle θ15a is the value calculated from the formula: Second inclination angle θ13a - Third inclination angle θ15a.

[0037] The "angle of inclination" may be evaluated as follows: For example, if the cutting edge 7 is linear when viewed from the front in the rotation direction Y1 of the rotation axis O1, the angle between a virtual straight line along the cutting edge 7 (or the cutting edge 7) and the rotation axis O1 (or a virtual straight line O1a parallel to the rotation axis O1) may be evaluated. Alternatively, if the cutting edge 7 is not linear when viewed from the front in the rotation direction Y1, the angle between a virtual straight line connecting the two ends of the target portion of the cutting edge 7 and the rotation axis O1 (or a virtual straight line O1a parallel to the rotation axis O1) may be evaluated.

[0038] In the example shown in Figure 5, the first blade 11 is concave when viewed from the front in the rotation direction Y1, but to facilitate visual understanding, the imaginary straight line connecting both ends of the first blade 11 used for evaluating the "inclination angle" has been omitted. Also, in the example shown in Figure 5, the second blade 13 and the third blade 15 are straight when viewed from the front in the rotation direction Y1.

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

[0040] The "rake angle" may be defined as follows: First, a cross-section perpendicular to the cutting edge 7 may be shown in the target portion of the cutting edge 7. For example, as shown in the unspecified example in Figures 10 to 12, a cross-section perpendicular to the center of each of the first cutting edge 11, second cutting edge 13, and third cutting edge 15 may be shown. If the cutting edge 7 has been chamfered or honed, the rake angle may be evaluated based on the part of the machined portion closest to the rotation axis O1.

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

[0042] Furthermore, if the cutting edge 7 is chamfered or honed, and is microscopically flat or convex, the first virtual line L1 and the second virtual line L2 may each pass through the end of the cutting edge 7 on the rake face 21 side.

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

[0044] The flank face 19 in the drill 1 may extend backward from the cutting edge 7 in the rotational direction Y1, as in one example not limited to the one shown in Figure 8. The flank face 19 can function as a portion that avoids contact with the workpiece and reduces cutting resistance. The flank face 19 may be connected to the cutting edge 7.

[0045] The rake face 21 in the discharge groove 9 may be positioned along the cutting edge 7, as shown in the example (not limited to) in Figures 10 to 12. The rake face 21 can function as the area through which chips flow during cutting. The rake face 21 may be connected to the cutting edge 7.

[0046] As shown in the example (not limited to) in Figure 3, the first cutting edge 11 may have a concave shape when viewed from the tip 1a side. In this case, even if some material remains after cutting by the first cutting edge 11, this remaining material is less likely to be pushed out toward the outer circumference 17. Therefore, the generation of burrs is more easily suppressed.

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

[0048] Furthermore, when viewed from the tip 1a side, the first blade 11 may be concave and the second blade 13 may be convex. The concave shape of the first blade 11 makes it difficult for any remaining material to be pushed out toward the outer circumference 17, as described above, and the convex shape of the second blade 13 allows the workpiece to be cut well by the second blade 13, thus making it easier to suppress the generation of burrs.

[0049] As shown in the example not limited to Figure 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 becomes possible to ensure that the first blade 11, which can function as the main cutting edge, is relatively long.

[0050] As shown in the example not limited to Figure 6, the third cutting edge 15 may be longer than the second cutting edge 13 in the direction along the rotation axis O1. That is, the length W15 of the third cutting edge 15 may be longer than the length W13 of the second cutting edge 13 in the direction along the rotation axis O1. In this case, the surface accuracy of the inner circumferential surface of the machined hole is high.

[0051] As shown in the example not limited to Figure 5, the first blade 11 may be longer than the second blade 13 and the third blade 15 in the direction perpendicular to the rotation axis O1. Also, the second blade 13 may be longer than the third blade 15 in the direction perpendicular to the rotation axis O1.

[0052] As shown in the example (not limited to) in Figure 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 is easier to design a configuration in which the second rake angle θ13b is larger than the first rake angle θ11b and the third rake angle θ15b, respectively.

[0053] The cutting edge 7 may further have a fourth cutting edge 23, as shown in the example not limited to Figure 2. The fourth cutting edge 23 may extend from the first cutting edge 11 toward the axis of rotation 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 called a thinning 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 part 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 materials for drill 1 include cemented carbide and cermet. Examples of cemented carbide compositions 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 bonding phase.

[0056] The cermet may be a sintered composite material in which a metal is combined with a ceramic component. Specifically, examples of cermets include titanium compounds mainly composed of titanium carbide (TiC) or titanium nitride (TiN). However, the above materials are not limited to these materials, and the drill 1 is not limited to these materials.

[0057] The surface of drill 1 may be coated with a film using chemical vapor deposition (CVD) or physical vapor deposition (PVD). Examples of film compositions include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al2O3).

[0058] <Method for manufacturing machined parts> Next, a method for manufacturing a one-sided machined workpiece 101, which is not limited to the present disclosure, will be described with reference to the drawings.

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

[0060] (1) The step of positioning the drill 1 above the workpiece 103 (see Figure 13). (2) The step of rotating the drill 1 around the rotation axis O1 in the direction of arrow Y1 and bringing the drill 1 closer to the workpiece 103 (see Figure 13).

[0061] Steps (1) and (2) may be carried out by, for example, fixing the workpiece 103 on the table of a machine tool to which the drill 1 is attached, and bringing the drill 1 closer to the workpiece 103 while it is rotating. In step (2), the workpiece 103 and the drill 1 only need to be relatively close to each other; for example, the workpiece 103 may be brought closer to the drill 1.

[0062] (3) The step of bringing the drill 1 closer to the workpiece 103 so that the rotating drill 1 comes into contact with the workpiece 103 and forms a machined hole 105 (through hole) in the workpiece 103 (see Figures 14 and 15).

[0063] In step (3), cutting may be performed such that at least a portion of the cutting portion 5 is located inside the machined hole 105. Alternatively, 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 surface finish, 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 area for chip evacuation, and excellent chip evacuation performance can be achieved through this area.

[0064] (4) The step of removing the drill 1 from the workpiece 103 (see Figure 16). In step (4), the workpiece 103 and the drill 1 only need to be separated relatively; for example, the workpiece 103 may be separated from the drill 1.

[0065] By following the above process, it is possible to obtain a workpiece 101 having a highly accurate machined hole 105. Specifically, when a drill 1 is used in the manufacturing method of the workpiece 101, the chip breaking ability is good, which allows for excellent machinability. As a result, it is possible to obtain a workpiece 101 having a highly accurate machined hole 105.

[0066] Furthermore, when the workpiece 103 is cut multiple times, for example, when forming multiple machined holes 105 in a single workpiece 103, the process of bringing the drill 1 into contact with different parts of the workpiece 103 while maintaining the rotating state of the drill 1 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 PE (polyethylene), PP (polypropylene), PC (polycarbonate), and PA (polyamide). In addition, so-called GFRP (Glass Fiber Reinforced Plastics) and CFRP (Carbon Fiber Reinforced Plastics) may be used as resin materials.

[0068] The above exemplifies a method for manufacturing a single-sided drill 1 and a cut workpiece 101, which are not limited to the embodiments described herein. However, it goes without saying that the present disclosure is not limited to the embodiments described above, and any method can be used as long as it does not deviate from the gist of the present disclosure.

[0069] For example, the manufacturing method for the drill 1 and the workpiece 101 may have the following configuration. [1] The drill is rod-shaped and extends along the axis of rotation from the tip to the rear end, and has a cutting edge located on the tip side and an ejection groove extending from the cutting edge to the rear end, the cutting edge having a first cutting edge, a second cutting edge extending outward from the first cutting edge, and a third cutting edge extending outward from the second cutting edge, the inclination angles of the first cutting edge, the second cutting edge and the third cutting edge with respect to the axis of rotation being a first inclination angle, a second inclination angle and a third inclination angle, respectively, wherein 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 cutting edge, the second cutting edge and the third cutting edge are a first rake angle, a second rake angle and a third rake angle, respectively, wherein the second rake angle is larger than the first rake angle and the third rake angle. [2] The drill in [1] above may have a third rake angle that is larger than the first rake angle. [3] The drill in [1] or [2] above has a difference between the first inclination angle and the second inclination angle, and the difference between the second inclination angle and the third Slope It can be smaller than the difference in angles. [4] Any one of the drills described in [1] to [3] above may have a first cutting edge that is concave and a second cutting edge that is convex when viewed from the tip side. [5] Any one of the drills described in [1] to [4] above may have a first cutting edge that is longer than the second and third cutting edges in the direction along the axis of rotation. [6] The drill in [5] above may have a third cutting edge that is longer than the second cutting edge in the direction along the axis of rotation. [7] A method for manufacturing a cut workpiece may include the steps of: rotating one of the drills described in [1] to [6] above around the rotating shaft; bringing the rotating drill into contact with the workpiece; and moving the drill away from the workpiece. [Explanation of Symbols]

[0070] 1. Drill 1a ··Tip 1b...rear end 3. Shank section 5...Cutting part 7...cutting blade 9...Discharge groove 11...1st blade 13...2nd blade 15...Third blade 17... Perimeter 19...Escape 21... Scoop surface 23...4th blade 101...Cutting workpiece 103...Work material 105...machined hole O1... Rotation axis Y1...Direction of rotation θ11a · 1st 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 inclination angle and the second inclination angle is smaller than the difference between the second inclination angle and the third inclination 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.

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