Drill bit and method of manufacturing a machined workpiece

Abstract

A drill bit based on an aspect of the invention not limited has a body extending along an axis of rotation from a first end toward a second end. The body has an outer peripheral surface, a cutting edge located on the first end side, a relief surface disposed along the cutting edge on a rear side in a direction of rotation of the axis of rotation, and a flute extending from the cutting edge toward the second end. The cutting edge has a first land, a second land extending from the first land toward the outer peripheral surface, and a third land extending from the second land toward the outer peripheral surface. The relief surface has a first relief surface disposed along the first land and having a first relief angle, a second relief surface disposed along the second land and having a second relief angle, and a third relief surface disposed along the third land and having a third relief angle. The second relief angle is smaller than the first relief angle and the third relief angle.

Description

TECHNICAL FIELD

[0001] This application claims priority to Japanese Patent Application No. 2020-082959 filed May 11, 2020, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present application relates to a drill bit generally used for hole machining of a workpiece, and a method of manufacturing a machined product. As the drill bit, for example, a front-end replaceable drill bit and an integral drill bit can be cited. BACKGROUND

[0003] As a drill bit used when a workpiece such as a metal is subjected to hole machining, for example, a drill bit described in Japanese Patent Application Publication No. 2010-125592 (Patent Literature 1) and International Publication No. 2010 / 086988 (Patent Literature 2) is known. The drill bit described in Patent Literature 1 has a cutting edge and a chamfer edge located on the outer peripheral side with respect to the cutting edge. The drill bit described in Patent Literature 2 has a first cutting edge and a second cutting edge located on the outer peripheral side with respect to the first cutting edge.

[0004] When hole machining is performed using a drill bit, it is sought to improve the accuracy of the machined hole. SUMMARY

[0005] A drill bit according to an aspect of the present application that is not limited has a main body extending from a first end toward a second end along a rotation axis. The main body has an outer peripheral surface, a cutting edge located on the first end side, a relief surface provided on the rear side in the rotation direction of the rotation axis along the cutting edge, and a flute extending from the cutting edge toward the second end. The cutting edge has a first edge, a second edge extending from the first edge toward the outer peripheral surface, and a third edge extending from the second edge toward the outer peripheral surface. The relief surface has a first relief surface provided along the first edge and having a first relief angle, a second relief surface provided along the second edge and having a second relief angle, and a third relief surface provided along the third edge and having a third relief angle. The second relief angle is smaller than the first relief angle and the third relief angle. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 is a perspective view showing a drill bit according to an aspect of the present application that is not limited.

[0007] Figure 2 is a plan view of the drill bit shown in Figure 1

[0008] Figure 3 is a side view of the drill bit shown in Figure 2

[0009] is a side view of the drill bit shown in​Figure 4 is a side view of the drill bit as viewed from the A2 direction Figure 2

[0010] Figure 5 is an enlarged view of the region B1 shown in Figure 1

[0011] Figure 6 is an enlarged view of the region B2 shown in Figure 3

[0012] Figure 7 is a sectional view of the VII-VII section shown in Figure 6

[0013] Figure 8 is a sectional view of the VIII-VIII section shown in Figure 6

[0014] Figure 9 is a sectional view of the IX-IX section shown in Figure 6

[0015] Figure 10 is a schematic diagram showing one step in a manufacturing method of a machined product according to an aspect of the present application.

[0016] Figure 11 is a schematic diagram showing one step in a manufacturing method of a machined product according to an aspect of the present application.

[0017] Figure 12 is a schematic diagram showing one step in a manufacturing method of a machined product according to an aspect of the present application. DETAILED DESCRIPTION

[0018] <Drill bit>

[0019] Hereinafter, a drill bit 1 according to an aspect of the present application will be described in detail using the drawings. However, in each of the drawings referred to below, only the main components necessary for the description of the embodiments are simply shown for the sake of convenience of the description. Therefore, the drill bit 1 can have any of the constituent components not shown in each of the drawings referred to. Further, the dimensions of the components in each of the drawings are not necessarily true to the dimensions of the actual constituent components and the dimensional ratios of the components, and the like.

[0020] Note that, in an aspect not limited, as an example of the drill bit 1, a monoblock drill bit can be shown. However, the drill bit 1 is not limited to a monoblock drill bit, and can be, for example, a front-end replaceable drill bit or the like.

[0021] The drill bit 1 can be, for example, Figures 1-4 ​​​​​​The main body 3 can extend from a first end 3a toward a second end 3b along the rotation axis O1. In other words, the main body 3 can be a bar shape extending from the first end 3a to the second end 3b along the rotation axis O1. Generally, the first end 3a is referred to as a "front end", and the second end 3b is referred to as a "rear end". In addition, the main body 3 is rotatable about the rotation axis O1. Note that, Figure 1 The arrow Y1 in FIG. 1 indicates a rotation direction of the rotation axis O1.

[0022] The main body 3 can have a shank 5 and a cutting portion 7. The shank 5 can be held by a rotating spindle of a machine tool. The shank 5 can be designed according to a shape of the spindle in the machine tool.

[0023] The cutting portion 7 can be located on the first end 3a side with respect to the shank 5. The cutting portion 7 can be in contact with a workpiece, and can play a major role in cutting processing (e.g., hole processing) of the workpiece.

[0024] An outer diameter D of the cutting portion 7 is not limited to a particular value. For example, a maximum value of the outer diameter D can be set to 2 to 50 mm. In addition, a length L of the cutting portion 7 in a direction along the rotation axis O1 can be set to L = 1.5D to 12D.

[0025] The main body 3 can also have an outer peripheral surface 9, a cutting edge 11, a relief surface 13, and a flute 15 as shown in an example not limited to FIG. 2. Figure 5 The cutting edge 11 can be located on the first end 3a side. The relief surface 13 can be provided along the cutting edge 11 on a rear side in the rotation direction Y1 of the rotation axis O1. The flute 15 can extend from the cutting edge 11 toward the second end 3b. Note that the outer peripheral surface 9, the cutting edge 11, the relief surface 13, and the flute 15 can also be located in the cutting portion 7.

[0026] The cutting edge 11 can be used to cut the workpiece in cutting processing. The cutting edge 11 can have a first edge 17, a second edge 19, and a third edge 21. The first edge 17, the second edge 19, and the third edge 21 are also referred to as main cutting edges. The second edge 19 can extend from the first edge 17 toward the outer peripheral surface 9. The third edge 21 can extend from the second edge 19 toward the outer peripheral surface 9. Note that the first edge 17 can be away from the rotation axis O1. As shown in an example not limited to FIG. 3, Figure 3 and Figure 6 As shown in an example not limited to FIG. 4, the second edge 19 can be inclined with respect to the first edge 17, and the third edge 21 can be inclined with respect to the second edge 19 when viewed from a direction orthogonal to the rotation axis O1. The third edge 21 can be connected to the outer peripheral surface 9.

[0027] The number of the first blades 17 can be one, but can also be plural. In the case where the number of the first blades 17 is plural, the number thereof can be 2 to 5. The same applies to the second blades 19 and the third blades 21. As shown in the example not limited to the one shown in FIG. 2, the drill bit 1 can also be a so-called double-blade type drill bit. Figure 2

[0028] In the case where the number of the first blades 17 is plural, the plural first blades 17 can be disposed in a manner to be rotationally symmetrical with respect to the rotation axis O1 when viewed from the front side of the first end 3a. Specifically, as shown in the example not limited to the one shown in FIG. 3, in the case where the number of the first blades 17 is two, the two first blades 17 can be disposed in a manner to be rotationally symmetrical at 180° with respect to the rotation axis O1 when viewed from the front side of the first end 3a. In this case, the straight running property of the drill bit 1 when cutting a workpiece is high. The same applies to the second blades 19 and the third blades 21. Figure 2

[0029] The first blade 17 can be a linear shape or a curved shape, or a shape in which a linear shape and a curved shape are combined when viewed from the front side of the first end 3a. The same applies to the second blades 19 and the third blades 21.

[0030] The shapes of the first blade 17, the second blades 19, and the third blades 21 can be the same, or can be different, respectively, when viewed from the front side of the first end 3a. For example, as shown in the example not limited to the one shown in FIG. 4, the first blade 17 can be a concave curved shape when viewed from the front side of the first end 3a. The second blades 19 can be linear shapes. The third blades 21 can be convex curved shapes. Figure 2

[0031] The lengths of the first blade 17, the second blades 19, and the third blades 21 can be the same, or can be different, respectively. For example, as shown in the example not limited to the one shown in FIG. 5, the length of the second blade 19 can be longer than the length of the first blade 17. The length of the third blade 21 can be longer than the length of the second blade 19. The third blade 21 can also be the longest among the cutting blades 11. Figure 2

[0032] The grooves 15 can function to discharge chips generated by the cutting blades 11 to the outside. The grooves 15 can extend in parallel with the rotation axis O1, or can extend spirally around the rotation axis O1. The number of the grooves 15 can be one, or can be plural.

[0033] ​​​​The groove 15 can be connected with the cutting edge 11. In this case, the cutting property to the workpiece is high. In addition, a rake face connecting the groove 15 and the cutting edge 11 can be provided. In this case, the discharge direction of the chip generated by the cutting edge 11 is easily stabilized. From the viewpoint of smoothly discharging the chip to the outside, the groove 15 can be a concave curved shape in a cross section orthogonal to the rotation axis O1.

[0034] The depth of the groove 15 is not limited to a particular value. For example, the depth of the groove 15 can be set to 10 to 40% with respect to the outer diameter of the main body 3 (the cutting portion 7). The depth of the groove 15 can also be a value obtained by subtracting the distance from the rotation axis O1 of the bottom of the groove 15 from the radius of the main body 3 (the cutting portion 7) in a cross section orthogonal to the rotation axis O1. The bottom can be a portion of the groove 15 closest to the rotation axis O1.

[0035] The flank face 13 can have a first flank face 23, a second flank face 25, and a third flank face 27. The first flank face 23 can be provided along the first edge 17. The second flank face 25 can be provided along the second edge 19. The third flank face 27 can be provided along the third edge 21.

[0036] Note that the first flank face 23 can be connected with the first edge 17, and in addition, can be distanced from the first edge 17. Similarly, the second flank face 25 can be connected with the second edge 19, and in addition, can be distanced from the second edge 19. The third flank face 27 can be connected with the third edge 21, and in addition, can be distanced from the third edge 21. For example, as in the example not limited as shown in Figure 2 , the first flank face 23 can be connected with the first edge 17, the second flank face 25 can be connected with the second edge 19, and the third flank face 27 can be connected with the third edge 21.

[0037] The flank face 13 can have a "clearance angle". The "clearance angle" can also be defined as follows. First, in the portion of the cutting edge 11 as the object, a cross section orthogonal to the cutting edge 11 can be indicated. For example, as in the example not limited as shown in Figures 6-9 , cross sections orthogonal to the first edge 17, the second edge 19, and the third edge 21, respectively, can be indicated. Note that in the case where the drill 1 is a so-called double-edge type drill, two first edges 17 or the like can also be provided. In order to easily visually understand the positional relationship of each portion, in Figures 6-9 , the reference numeral indicating one portion is labeled "a", and the reference numeral indicating the other portion is labeled "b". For example, in Figure 6 and Figure 7 , the first edge 17 on one side is indicated by the reference numeral 17a, and the first edge 17 on the other side is indicated by the reference numeral 17b.

[0038] In the above cross section, an imaginary straight line passing through the cutting edge 11 and intersecting the locus of rotation of the cutting edge 11 can also be used as the reference line Ll. In the case where chamfering or honing is performed on the cutting edge 11 and the cutting edge 11 is planar or convexly curved when viewed microscopically, an imaginary straight line passing through the end portion of the relief surface 13 side in the cutting edge 11 and intersecting the locus of rotation of the end portion can be used as the reference line Ll. An imaginary straight line intersecting the end portion of the cutting edge 11 side in the relief surface 13 can be used as the evaluation line L2. Also, the angle at which the reference line Ll intersects the evaluation line L2 can be used as the "relief angle".

[0039] The first relief surface 23 can have a first relief angle θl as in the example of the unregulated one shown in FIG. 6. Figure 7 The second relief surface 25 can have a second relief angle θ2 as in the example of the unregulated one shown in FIG. 7. Figure 8 The third relief surface 27 can have a third relief angle θ3 as in the example of the unregulated one shown in FIG. 8. Figure 9 The third relief surface 27 can have a third relief angle θ3 as in the example of the unregulated one shown in FIG. 8.

[0040] Here, the second relief angle θ2 can be smaller than the first relief angle θl and the third relief angle θ3. In the case where the first relief angle θl is relatively large, the cutting edge tip of the first land 17, which is relatively close to the rotation axis Ol, can be made sharp, and thus the cutting resistance can be easily reduced, and the straight running stability of the drill bit 1 can be high. Also, in the case where the third relief angle θ3 is relatively large, the cutting edge tip of the third land 21, which is relatively close to the outer peripheral surface 9, can be made sharp, and thus burrs can be less likely to be generated in the machined hole. Also, in the case where the second relief angle θ2 is relatively small, the action of the drill bit 1 in the direction along the rotation axis Ol can be easily controlled. That is, since the thrust resistance changes drastically at the instant of penetration of the workpiece, the action of the drill bit 1 in the direction along the rotation axis Ol can be difficult to control. However, in the case where the second relief angle θ2 is relatively small, the second relief surface 25 can easily come into contact with the workpiece, and thus the action of the drill bit 1 in the direction along the rotation axis Ol can be easily controlled. Therefore, in the case where the second relief angle θ2 is smaller than the first relief angle θl and the third relief angle θ3, the accuracy of the machined hole can be high.

[0041] The first relief angle θl can be the same as the third relief angle θ3, and can also be different. As in the example of the unregulated one shown in FIG. 6 and FIG. 8, in the case where the first relief angle θl is larger than the third relief angle θ3, the thrust resistance can be effectively reduced in the front end portion where the cutting amount per revolution is large. Therefore, for example, in the case of a workpiece having a large cutting resistance, the straight running stability can be high. Figure 7 Figure 9

[0042] ​​When the first clearance angle θ1 is smaller than the third clearance angle θ3, the third clearance face 27 located on the outer periphery is less likely to contact the workpiece compared to the first clearance face 23 located near the rotation axis O1. That is, even assuming the clearance face contacts the workpiece, the first clearance face 23 located near the rotation axis O1 is more likely to contact the workpiece than the third clearance face 27. Therefore, even if chatter occurs due to contact between the clearance face and the workpiece, it is easier to suppress the chatter to a smaller extent.

[0043] The first rear angle θ1, the second rear angle θ2, and the third rear angle θ3 are not limited to specific values. For example, the first rear angle θ1 can be set to 5–15°. In addition, the second rear angle θ2 can be set to less than 5°. The third rear angle θ3 can be set to 5–20°.

[0044] Alternatively, the first flank face 23 can be a plane, while the second flank face 25 and the third flank face 27 are curved surfaces. In this case, the movement of the drill 1 is easier to control. When the first flank face 23 is a plane, the tip angle of the drill 1 is easily suppressed to a smaller value, thus making it easier for the drill 1 to cut into the workpiece. Furthermore, for example, during machining, the drill 1 is prone to vibration when it penetrates the workpiece. However, when the second flank face 25 and the third flank face 27 are curved surfaces, they easily come into contact with the workpiece when it penetrates. Therefore, the vibration of the drill 1 can be suppressed, and straight-line stability can be easily maintained.

[0045] It should be noted that the plane only needs to be approximately plane, not necessarily a plane in the strict sense. The same applies to curved surfaces. The second flank face 25 and the third flank face 27 can also be convex surfaces.

[0046] like Figure 2 As in the undefined example shown, the boundary between the first flank face 23 and the second flank face 25 can be designated as the first boundary 29. This first boundary 29 can approach the outer peripheral surface 9 from the cutting edge 11 (first edge 17 and second edge 19) in the direction of rotation Y1. In this case, chatter caused by the flank face contacting the workpiece is easily suppressed to a smaller extent. This is because, even assuming the flank face is in contact with the workpiece, the first flank face 23, located near the rotation axis O1, is more likely to contact the workpiece than the second flank face 25. Thus, chatter is easily suppressed to a smaller extent while ensuring the length of the second edge 19. It should be noted that the first boundary 29 can also be curved.

[0047] The boundaries of the second flank face 25 and the third flank face 27 can be used as the second boundary 31. This second boundary 31 can move away from the outer peripheral surface 9 from the cutting edge 11 (second cutting edge 19 and third cutting edge 21) in the direction of rotation Y1. It should be noted that the second boundary 31 can also be curved. The radius of curvature of the curved second boundary 31 can also be smaller than the radius of curvature of the curved first boundary 29.

[0048] When viewed from the front view of the first end 3a, the second flank face 25 may have a first region 33 whose width W narrows radially toward the axis of rotation O1 as it moves toward the rear of the rotation direction Y1, and a second region 35 located further rearward than the first region 33 in the rotation direction Y1 and whose width W widens as it moves toward the rear of the rotation direction Y1. In this case, when the second flank face 25 contacts the workpiece, the heat generated in the first region 33 can be minimized, and the movement of the drill 1 can be effectively controlled. It should be noted that the second region 35 may be connected to the first region 33.

[0049] The maximum value of the width W in the first region 33 can be the same as the maximum value of the width W in the second region 35, or they can be different. For example Figure 2 As shown in the undefined example, when the maximum value of the width W in the first region 33 is greater than the maximum value of the width W in the second region 35, heat generation in the second region 35 is easily suppressed. This is because, when the drill 1 penetrates the workpiece, even if the second flank face 25 contacts the workpiece, excessive contact between the second region 35 and the workpiece can be avoided.

[0050] It should be noted that the second flank face 25 can be connected to the first flank face 23. The third flank face 27 can be connected to the second flank face 25, and can also be connected to the outer peripheral face 9.

[0051] The areas of the first flank face 23, the second flank face 25, and the third flank face 27 can be the same, or they can be different. For example, ... Figure 2 As shown in the undefined example, the area of ​​the second flank face 25 can be larger than the area of ​​the first flank face 23. Furthermore, the area of ​​the third flank face 27 can be larger than the area of ​​the second flank face 25. The area of ​​the third flank face 27 can be the largest among the flank faces 13.

[0052] The flank face 13 may also have a fourth flank face 37, which is disposed along the first flank face 23 behind the rotation direction Y1 and is inclined relative to the first flank face 23. The fourth flank face 37 may also be referred to as the third flank face.

[0053] The fourth flank surface 37 can be connected to the first flank surface 23, and can also be connected to the second flank surface 25. The fourth flank surface 37 can be a flat surface. The inclination angle of the fourth flank surface 37 is not limited to a specific value. For example, the inclination angle of the fourth flank surface 37 can be set to 15 to 35°.

[0054] The cutting edge 11 can have a land 39. The land 39 can function to cut into a workpiece. The land 39 can be located in the cutting edge 11 closest to the rotation axis O1. The land 39 can intersect the rotation axis O1. The land 39 can be located between the two first flank surfaces 23. The land 39 can also be located at the intersection of the two first flank surfaces 23. The land 39 can be the shortest in the cutting edge 11. The land 39 can be linear when viewed from the first end 3a side.

[0055] The cutting edge 11 can have a land 39. The land 39 can function to cut into a workpiece. The land 39 can be located in the cutting edge 11 closest to the rotation axis O1. The land 39 can intersect the rotation axis O1. The land 39 can be located between the two first flank surfaces 23. The land 39 can also be located at the intersection of the two first flank surfaces 23. The land 39 can be the shortest in the cutting edge 11. The land 39 can be linear when viewed from the first end 3a side.

[0056] The main body 3 can have a center groove 43 located between the land 41 and the groove 15. The center groove 43 can be provided along the land 41 on the front side in the rotation direction Y1.

[0057] As the material of the main body 3, for example, cemented carbide and cermet can be cited. As the composition of the cemented carbide, for example, WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co can be cited. Here, WC, TiC, and TaC can be hard particles, and Co can be a binder phase.

[0058] In addition, the cermet can also be a sintered composite material in which a metal is compounded in a ceramic component. Specifically, as the cermet, a titanium compound in which titanium carbide (TiC) or titanium nitride (TiN) is the main component can be cited. However, the above-mentioned material is an example and the main body 3 is not limited to these materials.

[0059] The surface of the main body 3 can also be coated with a coating film using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. As the composition of the coating film, for example, titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and aluminum oxide (Al2O3) can be cited.

[0060] <Method for manufacturing cutting tool>

[0061] Next, the use of the cutting tool 1 will be described. Figures 10-12A manufacturing method of the cutting work product 101 according to an aspect of the present application will be described.

[0062] The cutting work product 101 can be produced by performing cutting work on the workpiece 103. The manufacturing method of the cutting work product 101 can include the following processes (1) to (4).

[0063] (1) A process of arranging the drill bit 1 above the prepared workpiece 103 (refer to Figure 10 ).

[0064] (2) A process of rotating the drill bit 1 with the rotation axis O1 as the center in the direction of the arrow Y1, and approaching the workpiece 103 in the Y2 direction with the drill bit 1 (refer to Figure 10 ).

[0065] In the processes of (1) and (2), for example, the workpiece 103 can be fixed on the table of the machine tool on which the drill bit 1 is installed, and the workpiece 103 can be approached to the drill bit 1 in a state where the drill bit 1 is rotated. Note that in the process of (2), the workpiece 103 and the drill bit 1 can be relatively approached, and for example, the workpiece 103 can be approached to the drill bit 1.

[0066] (3) A process of forming the processing hole 105 in the workpiece 103 by further approaching the drill bit 1 to the workpiece 103, and bringing the rotating drill bit 1 into contact with a desired position of the surface of the workpiece 103 (refer to Figure 11 ).

[0067] In the process of (3), the cutting work can also be performed in such a manner that at least a part of the cutting portion 7 of the main body 3 is located in the processing hole 105. In addition, in the process of (3), the shank portion 5 of the main body 3 can be located outside the processing hole 105. From the viewpoint of obtaining a good finish surface, a part of the cutting portion 7 on the second end 3b side can be located outside the processing hole 105. The above-described part can function as an edge region for discharging chips, and excellent chip discharge performance can be achieved through this region.

[0068] (4) A process of separating the drill bit 1 from the workpiece 103 in the Y3 direction (refer to Figure 12 ).

[0069] In the process of (4), as in the above-described process of (2), the workpiece 103 and the drill bit 1 can be relatively separated, and for example, the workpiece 103 can be separated from the drill bit 1.

[0070] In the case where the above processes are performed, the cutting work product 101 having the processing hole 105 with high precision can be obtained.

[0071] Note that in the case where the cutting of the workpiece 103 is performed a plurality of times, for example, in the case where a plurality of processed holes 105 are formed in one workpiece 103, the process of bringing the cutting edge 11 of the drill bit 1 into contact with a different portion of the workpiece 103 can be repeated while the drill bit 1 is kept rotating.

[0072] As the material of the workpiece 103, for example, aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals can be given.

[0073] Reference Signs:

[0074] 1... drill bit

[0075] 3... main body

[0076] 3a... first end (front end)

[0077] 3b... second end (rear end)

[0078] 5... shank

[0079] 7... cutting portion

[0080] 9... outer peripheral surface

[0081] 11... cutting edge

[0082] 13... flank

[0083] 15... groove

[0084] 17... first edge

[0085] 19... second edge

[0086] 21... third edge

[0087] 23... first flank

[0088] 25... second flank

[0089] 27... third flank

[0090] 29... first boundary

[0091] 31... second boundary

[0092] 33... first region

[0093] 35... second region

[0094] 37... fourth flank

[0095] 39... chisel edge

[0096] 41... dressing edge;

[0097] 43... center groove;

[0098] 101... workpiece;

[0099] 103... workpiece;

[0100] 105... machined hole;

[0101] 01... rotation axis;

[0102] Y1... rotation direction;

[0103] L1... reference line;

[0104] L2... evaluation line;

[0105] θ1... first clearance angle;

[0106] θ2... second clearance angle;

[0107] θ3... third clearance angle.

Claims

1. A drill bit, wherein, The drill bit has a body extending along a rotation axis from a first end toward a second end. The subject has: outer peripheral surface; The cutting edge is located on the first end side; A flank face, which is disposed along the cutting edge on the rear side of the rotation direction of the rotating axis; and A groove that extends from the cutting edge toward the second end. The cutting edge has: First blade; A second cutting edge extends from the first cutting edge toward the outer peripheral surface; as well as The third cutting edge extends from the second cutting edge toward the outer peripheral surface. The flank face has: A first back face is provided along the first cutting edge and has a first back angle; The second back face is provided along the second cutting edge and has a second back angle; as well as The third relief face is provided along the third cutting edge and has a third relief angle. The second rear angle is smaller than the first rear angle and the third rear angle. The first flank face is connected to the second flank face, and the second flank face is connected to the third flank face.

2. A drill bit, wherein, The drill bit has a body extending along a rotation axis from a first end toward a second end. The subject has: outer peripheral surface; The cutting edge is located on the first end side; A flank face, which is disposed along the cutting edge on the rear side of the rotation direction of the rotating axis; and A groove that extends from the cutting edge toward the second end. The cutting edge has: First blade; A second cutting edge extends from the first cutting edge toward the outer peripheral surface; as well as The third cutting edge extends from the second cutting edge toward the outer peripheral surface. The flank face has: A first back face is provided along the first cutting edge and has a first back angle; The second back face is provided along the second cutting edge and has a second back angle; as well as The third relief face is provided along the third cutting edge and has a third relief angle. The second rear angle is smaller than the first rear angle and the third rear angle. When viewed from the main view of the first end side, the second flank face has: The first region narrows radially along the axis of rotation as it moves toward the rear of the direction of rotation. as well as The second region is located further back in the direction of rotation than the first region, and its radial width increases as it moves further back in the direction of rotation.

3. The drill bit according to claim 1 or 2, wherein, The first rear angle is greater than the third rear angle.

4. The drill bit according to claim 1 or 2, wherein, The first rear angle is smaller than the third rear angle.

5. The drill bit according to claim 1 or 2, wherein, The first flank face is a plane, while the second and third flank faces are curved surfaces.

6. The drill bit according to claim 1 or 2, wherein, The first boundary between the first flank face and the second flank face approaches the outer peripheral surface from the cutting edge toward the direction of rotation.

7. The drill bit according to claim 1 or 2, wherein, The second boundary between the second flank face and the third flank face moves away from the outer peripheral surface as it moves from the cutting edge toward the direction of rotation.

8. The drill bit according to claim 2, wherein, The maximum value of the radial width in the first region is greater than the maximum value of the radial width in the second region.

9. A method for manufacturing a workpiece by cutting, wherein, The method for manufacturing the workpiece includes the following steps: Rotate the drill bit according to any one of claims 1 to 8; To bring the rotating drill bit into contact with the workpiece being cut; and This separates the drill bit from the workpiece.

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