Drill

Abstract

This drill rotates about an axis, and has a cutting edge, a thinning surface, and a recessed surface. The cutting edge includes a main cutting edge section and a thinning cutting edge section. The thinning cutting edge section is continuous with the main cutting edge section. The thinning surface is continuous with the thinning cutting edge section. The recessed surface is continuous with the thinning surface. The recessed surface is provided with a coolant supply hole. In a cross section parallel to the axis and including the axis, the receding surface is located rearward from the thinning surface in the axial direction, and the opening edge of the coolant supply hole in the receding surface has a first position and a second position. In a cross section parallel to the axis and including the axis, when the angle that is formed by the axis and a straight line passing through the first position and the second position and that is equal to or less than 90° is defined as a first angle, and the angle that is formed by the axis and the tangent of the thinning surface at the boundary between the thinning surface and the receding surface and that is equal to or less than 90° is defined as a second angle, the first angle is smaller than the second angle.

Description

Drill

[0001] The present disclosure relates to a drill.

[0002] International Publication No. 2022 / 239045 (Patent Document 1) discloses a drill with an oil hole formed therein. The oil hole is provided on the gash surface of the drill.

[0003] International Publication No. 2022 / 239045

[0004] The drill according to the present disclosure is a drill that rotates around an axis, and includes a cutting edge, a thinning surface, and a retreat surface. The cutting edge has a main cutting edge portion and a thinning cutting edge portion. The thinning cutting edge portion is continuous with the main cutting edge portion. The thinning surface is continuous with the thinning cutting edge portion. The retreat surface is continuous with the thinning surface. A coolant supply hole is provided in the retreat surface. In a cross-section parallel to the axis and including the axis, the retreat surface is located axially rearward with respect to the thinning surface, and the opening edge of the coolant supply hole in the retreat surface has a first position and a second position. In a cross-section parallel to the axis and including the axis, an angle formed by the axis and a straight line passing through the first position and the second position, and an angle that is 90° or less is defined as a first angle, and an angle formed by the axis and a tangent line of the thinning surface at the boundary between the thinning surface and the retreat surface, and an angle that is 90° or less is defined as a second angle. In this case, the first angle is smaller than the second angle.

[0005] FIG. 1 is a front schematic view showing the configuration of the drill according to the first embodiment. FIG. 2 is a side schematic view showing the configuration of the drill according to the first embodiment. FIG. 3 is a perspective schematic view showing a part of the first main body region of the drill according to the first embodiment. FIG. 4 is a cross-sectional schematic view taken along line IV-IV of FIG. 1. FIG. 5 is an enlarged schematic view of region V in FIG. 2. FIG. 6 is a front schematic view showing the configuration of the drill according to the second embodiment. FIG. 7 is a perspective schematic view showing a part of the first main body region of the drill according to the second embodiment. FIG. 8 is a front schematic view showing the configuration of the drill according to the third embodiment. FIG. 9 is a perspective schematic view showing a part of the first main body region of the drill according to the third embodiment.

[0006] [Description of Embodiments of the Disclosure] First, embodiments of the Disclosure (also referred to as these embodiments) will be described. (1) A drill according to the Disclosure is a drill that rotates about an axis and comprises a cutting edge, a thinning surface, and a recessed surface. The cutting edge has a main cutting edge portion and a thinning cutting edge portion. The thinning cutting edge portion is connected to the main cutting edge portion. The thinning surface is connected to the thinning cutting edge portion. The recessed surface is connected to the thinning surface. Coolant supply holes are provided in the recessed surface. In a cross section parallel to and including the axis, the recessed surface is located axially rearward with respect to the thinning surface, and the opening edge of the coolant supply hole in the recessed surface has a first position and a second position. In a cross-section parallel to the axis and containing the axis, if the first angle is defined as the angle between the axis and a straight line passing through the first position and the second position, and which is 90° or less, and the second angle is defined as the angle between the axis and the tangent to the thinning surface at the boundary between the thinning surface and the receding surface, and which is 90° or less, then the first angle is smaller than the second angle. (2) In the drill according to (1) above, the first angle may be 0° or more and 45° or less. (3) In the drill according to (1) or (2) above, if the first distance is defined as the distance between the front end of the drill and the front end of the coolant supply hole in a direction parallel to the axis, then the value obtained by dividing the first distance by the diameter of the cutting edge may be 0.1 or more and 0.7 or less. (4) In a drill according to any of (1) to (3) above, if the distance between the front end of the coolant supply hole and the rear end of the coolant supply hole in a direction parallel to the axis is defined as the second distance, the value obtained by dividing the second distance by the diameter of the cutting edge may be 0.05 or more and 1.08 or less. (5) In a drill according to (1) above, the first angle may be 0° or more and 45° or less. If the distance between the front end of the drill and the front end of the coolant supply hole in a direction parallel to the axis is defined as the first distance, and the distance between the front end of the coolant supply hole and the rear end of the coolant supply hole in a direction parallel to the axis is defined as the second distance, the value obtained by dividing the first distance by the diameter of the cutting edge may be 0.1 or more and 0.7 or less, and the value obtained by dividing the second distance by the diameter of the cutting edge may be 0.05 or more and 1.08 or less.

[0007] Specific examples of embodiments of the present disclosure are described below with reference to the drawings. In the following drawings, identical or corresponding parts are given the same reference numerals, and their descriptions will not be repeated.

[0008] (First Embodiment) Figure 1 is a schematic front view showing the configuration of a drill according to the first embodiment. As shown in Figure 1, the drill 1 according to the first embodiment has a first cutting edge 10, a thinning surface 50, a receding surface 60, a first relief surface 30, and a first outer peripheral surface 70. The first cutting edge 10 has a main cutting edge portion 11 and a thinning cutting edge portion 12. The main cutting edge portion 11 is connected to the first outer peripheral surface 70. The thinning cutting edge portion 12 is connected to the main cutting edge portion 11.

[0009] The drill 1 rotates around axis A (see Figure 2). The direction perpendicular to axis A and radiating outward from axis A is defined as the radial direction. In the radial direction, the main cutting edge portion 11 is located between the thinning cutting edge portion 12 and the first outer peripheral surface 70. When viewed along axis A, the main cutting edge portion 11 may have a portion that is recessed towards the rear in the direction of rotation.

[0010] The thinning surface 50 is connected to the thinning cutting edge portion 12. The recessed surface 60 is connected to the thinning surface 50. The recessed surface 60 is connected to the first outer peripheral surface 70. In the radial direction, the recessed surface 60 may be located between the thinning surface 50 and the first outer peripheral surface 70. The recessed surface 60 is provided with a coolant supply hole 2. Specifically, the opening edge 3 of the coolant supply hole 2 is located on the recessed surface 60. As shown in Figure 1, when viewed in the direction along axis A, the opening edge 3 of the coolant supply hole 2 is surrounded by the outer edge of the recessed surface 60.

[0011] The first relief surface 30 has a first relief surface portion 31 and a second relief surface portion 32. The first relief surface portion 31 is connected to the main cutting edge portion 11 and the thinning cutting edge portion 12, respectively. In the thinning cutting edge portion 12, the first relief surface portion 31 is connected to the thinning surface 50. The second relief surface portion 32 is connected to the first relief surface portion 31. The second relief surface portion 32 may be inclined with respect to the first relief surface portion 31. The second relief surface portion 32 is located rearward in the rotational direction relative to the first relief surface portion 31.

[0012] The drill 1 according to the first embodiment may further have a second cutting edge 13, a second flank surface 20, and a second outer peripheral surface 80. In the radial direction, the second cutting edge 13 is located outside the first cutting edge 10. The second cutting edge 13 is spaced apart from the first cutting edge 10. In the radial direction, the second flank surface 20 is located outside the first flank surface 30. The second flank surface 20 is spaced apart from the first flank surface 30. In the radial direction, the second outer peripheral surface 80 is located outside the first outer peripheral surface 70. The second outer peripheral surface 80 is spaced apart from the first outer peripheral surface 70.

[0013] As shown in Figure 1, the drill 1 according to the first embodiment has two first cutting edges 10, two first relief surfaces 30, two thinning surfaces 50, two recessed surfaces 60, two second cutting edges 13, and two second relief surfaces 20. When viewed in the direction along axis A, the two first cutting edges 10, the two first relief surfaces 30, the two thinning surfaces 50, the two recessed surfaces 60, the two second cutting edges 13, and the two second relief surfaces 20 may have a shape that is symmetrical twice with axis A as the center of rotation.

[0014] As shown in Figure 1, the first relief surface 30 has a rear edge 90 located behind the first cutting edge 10 in the rotational direction. The rear edge 90 of the first relief surface 30 is located in front of the thinning surface 50 and the receding surface 60 in the rotational direction. The rear edge 90 has a first boundary line 53 and a second boundary line 63. The first relief surface 30 is connected to the thinning surface 50 at the first boundary line 53. The first relief surface 30 is connected to the receding surface 60 at the second boundary line 63. Viewed along axis A, the second boundary line 63 may extend along the first boundary line 53. The second boundary line 63 may be connected to the first boundary line 53.

[0015] Figure 2 is a schematic side view showing the configuration of a drill 1 according to the first embodiment. As shown in Figure 2, the drill 1 has a front end 5 and a rear end 6. The axis A extends from the front end 5 along the rear end 6. The drill 1 has a main body portion 8 and a shank portion 7. The front end 5 is formed by the main body portion 8. A chip evacuation groove surface 4 is formed on the main body portion 8. The shank portion 7 is connected to the main body portion 8. The rear end 6 is formed by the shank portion 7. The chip evacuation groove surface 4 is not formed on the shank portion 7.

[0016] The direction from the front end 5 to the rear end 6 is considered to be axially rearward. The direction from the rear end 6 to the front end 5 is considered to be axially forward. The shank portion 7 is located axially rearward relative to the main body portion 8.

[0017] The main body portion 8 has a first main body region 81 and a second main body region 82. The second main body region 82 is connected to the first main body region 81. In the direction along axis A, the second main body region 82 is located between the first main body region 81 and the shank portion 7. The first cutting edge 10, the thinning surface 50, the receding surface 60, the first relief surface 30, and the first outer peripheral surface 70 are formed by the first main body region 81. The second cutting edge 13, the second relief surface 20, and the second outer peripheral surface 80 are formed by the second main body region 82.

[0018] As shown in Figure 1, the diameter of the first cutting edge 10 is defined as the first diameter D1. Viewed along axis A, the first diameter D1 is twice the distance between the outer circumference of the first cutting edge 10 and axis A. The diameter of the second cutting edge 13 is defined as the second diameter D2. Viewed along axis A, the second diameter D2 is twice the distance between the outer circumference of the second cutting edge 13 and axis A. The second diameter D2 is larger than the first diameter D1. The second diameter D2 may be 1.3 times or more the first diameter D1, or 1.6 times or more the first diameter D1. The second diameter D2 may be 2.2 times or less the first diameter D1, or 2 times or less the first diameter D1.

[0019] Figure 3 is a schematic perspective view showing a part of the first body region 81 of the drill 1 according to the first embodiment. As shown in Figure 3, the chip evacuation groove surface 4 is connected to the main cutting edge portion 11. The main cutting edge portion 11 is formed by the ridge line between the chip evacuation groove surface 4 and the first relief surface 30. A part of the chip evacuation groove surface 4 functions as a rake surface.

[0020] The thinning surface 50 is connected to the chip discharge groove surface 4. The thinning surface 50 has a first thinning surface portion 51 and a second thinning surface portion 52. The first thinning surface portion 51 is connected to the thinning cutting edge portion 12. The second thinning surface portion 52 is connected to the first thinning surface portion 51. The second thinning surface portion 52 is spaced apart from the thinning cutting edge portion 12. In the radial direction, the second thinning surface portion 52 may be located further out than the first thinning surface portion 51.

[0021] The recessed surface 60 is connected to the chip discharge groove surface 4. The recessed surface 60 has a first recessed surface portion 61 and a second recessed surface portion 62. The first recessed surface portion 61 is connected to the second thinning surface portion 52. In the radial direction, the first recessed surface portion 61 may be located outside the second thinning surface portion 52. The second recessed surface portion 62 is connected to the first recessed surface portion 61. In the radial direction, the second recessed surface portion 62 may be located outside the first recessed surface portion 61. The second recessed surface portion 62 is spaced apart from the second thinning surface portion 52.

[0022] The first outer peripheral surface 70 has a first margin portion 71, a second margin portion 72, and an outer peripheral end surface portion 73. The first margin portion 71 is connected to the first relief surface portion 31, the first cutting edge 10, and the chip discharge groove surface 4. The second margin portion 72 is located behind the first margin portion 71 in the rotational direction. The second margin portion 72 is connected to the second relief surface portion 32. The outer peripheral end surface portion 73 is connected to the first margin portion 71 and the second margin portion 72, respectively. In the radial direction, the first margin portion 71 and the second margin portion 72 are located outside the outer peripheral end surface portion 73.

[0023] As shown in Figure 3, the first boundary line 53 has a first boundary region 54 and a second boundary region 55. The first boundary region 54 is the boundary between the thinning surface 50 and the first relief surface 31. The second boundary region 55 is the boundary between the thinning surface 50 and the second relief surface 32. Similarly, the second boundary line 63 has a third boundary region 64 and a fourth boundary region 65. The third boundary region 64 is the boundary between the first recessed surface 61 and the second relief surface 32. The fourth boundary region 65 is the boundary between the second recessed surface 62 and the second relief surface 32. The fourth boundary region 65 is located on the extension of the second boundary region 55.

[0024] Figure 4 is a schematic cross-sectional view along the line IV-IV in Figure 1. The cross-section shown in Figure 4 is parallel to and includes axis A. The cross-section shown in Figure 4 intersects the thinning surface 50, the recessed surface 60, and the opening edge 3 of the coolant supply hole 2. In the cross-section shown in Figure 4, the recessed surface 60 is located axially rearward relative to the thinning surface 50. The opening edge 3 of the coolant supply hole 2 on the recessed surface 60 has a first position 41 and a second position 42. In the direction along axis A, the first position 41 is located axially forward of the second position 42. In the direction along axis A, the first position 41 is located between the front end 5 of the drill 1 and the second position 42. In the radial direction, the second position 42 is located outward from the first position 41.

[0025] The straight line passing through the first position 41 and the second position 42 is defined as the first straight line L1. In the cross-section shown in Figure 4, the angle between axis A and the first straight line L1, which is 90° or less, is defined as the first angle θ1. In the cross-section shown in Figure 4, the tangent to the thinning surface 50 at the boundary between the thinning surface 50 and the receding surface 60 is defined as the second straight line L2. In the cross-section shown in Figure 4, the angle between axis A and the second straight line L2, which is 90° or less, is defined as the second angle θ2. The first angle θ1 is smaller than the second angle θ2.

[0026] The first angle θ1 is, for example, 0° or more and 45° or less. The first angle θ1 may be 10° or more, 15° or more, 20° or more, 25° or more, or 28° or more. The first angle θ1 may be 40° or less, or 34° or less. The first angle θ1 may be 28° or more and 34° or less.

[0027] Figure 5 is an enlarged schematic diagram of region V in Figure 2. As shown in Figure 5, the front end of the coolant supply hole 2 in the direction parallel to axis A is the third position 43. The rear end of the coolant supply hole 2 in the direction parallel to axis A is the fourth position 44. The distance between the front end 5 of the drill 1 and the third position 43 in the direction parallel to axis A is the first distance W1. The distance between the third position 43 and the fourth position 44 in the direction parallel to axis A is the second distance W2.

[0028] The value obtained by dividing the first distance W1 by the first diameter D1 of the first cutting edge 10 is, for example, 0.1 or more and 0.7 or less. The value obtained by dividing the first distance W1 by the first diameter D1 may be 0.2 or more, or 0.3 or more. The value obtained by dividing the first distance W1 by the first diameter D1 may be 0.6 or less, or 0.5 or less. The value obtained by dividing the first distance W1 by the first diameter D1 may be 0.2 or more and 0.7 or 0.1 or more and 0.6 or less.

[0029] The value obtained by dividing the second distance W2 by the first diameter D1 of the first cutting edge 10 is, for example, 0.05 or more and 1.08 or less. The value obtained by dividing the second distance W2 by the first diameter D1 may be 0.1 or more, or 0.2 or more. The value obtained by dividing the second distance W2 by the first diameter D1 may be 1.00 or less, or 0.95 or less. The value obtained by dividing the second distance W2 by the first diameter D1 may be, for example, 0.1 or more and 1.08 or less, or 0.05 or more and 0.1 or less.

[0030] The drill 1 according to the first embodiment has a first cutting edge 10 and a second cutting edge 13, but this disclosure is not limited to the above configuration. The drill 1 of this disclosure may have a first cutting edge 10 and not have a second cutting edge 13.

[0031] (Second Embodiment) Next, the configuration of the drill 1 according to the second embodiment will be described. The drill 1 according to the second embodiment differs from the drill 1 according to the first embodiment mainly in that the fourth boundary region 65 is not located on the extension of the second boundary region 55, and the other configurations are substantially the same as those of the drill 1 according to the first embodiment. The following description will focus on the configurations that differ from the drill 1 according to the first embodiment.

[0032] Figure 6 is a schematic front view showing the configuration of a drill according to the second embodiment. As shown in Figure 6, the fourth boundary region 65 does not have to be located on the extension of the second boundary region 55 when viewed along axis A. The fourth boundary region 65 may be located forward in the rotational direction compared to the second boundary region 55.

[0033] Figure 7 is a schematic perspective view showing a part of the first body region 81 of the drill 1 according to the second embodiment. As shown in Figure 7, the fourth boundary region 65 may be located forward in the rotational direction of the third boundary region 64. The third boundary region 64 may be located forward in the rotational direction of the second boundary region 55.

[0034] (Third Embodiment) Next, the configuration of the drill 1 according to the third embodiment will be described. The drill 1 according to the third embodiment differs from the drill 1 according to the first embodiment mainly in that the thinning surface 50 is connected to the first outer peripheral surface 70, and the other configurations are substantially the same as those of the drill 1 according to the first embodiment. The following description will focus on the configurations that differ from the drill 1 according to the first embodiment.

[0035] Figure 8 is a schematic front view showing the configuration of the drill 1 according to the third embodiment. Figure 9 is a schematic perspective view showing a part of the first body region 81 of the drill 1 according to the third embodiment. As shown in Figures 8 and 9, the thinning surface 50 is connected to the first outer peripheral surface 70. The receding surface 60 is spaced apart from the first relief surface 30. A part of the thinning surface 50 is located between the second relief surface portion 32 and the receding surface 60.

[0036] As shown in Figure 8, when viewed along axis A, the third boundary line 91, which is the boundary between the second receding surface 62 and the thinning surface 50, may be located behind the first boundary line 53, which is the boundary between the thinning surface 50 and the second relief surface 32, in the rotational direction. As shown in Figure 9, the outer peripheral end of the third boundary line 91, which is the boundary between the second receding surface 62 and the thinning surface 50, may be located behind the outer peripheral end of the first boundary line 53, which is the boundary between the thinning surface 50 and the second relief surface 32, in the axial direction.

[0037] Next, the operation and effects of the drill 1 according to this embodiment will be described. When drilling with the drill 1, a blanking hole (pilot hole) with a bottom surface is formed first, and then the drilling process is carried out to expand the blanking hole. In the initial stages of drilling, the blanking hole is expanded mainly by the outer peripheral edge of the cutting edge scraping the side walls of the blanking hole.

[0038] When using a conventional drill to cut the side wall of a cast-out hole, chips cut by the outer edge of the cutting edge can become lodged between the side wall of the cast-out hole and the outer surface of the drill 1. The lodged chips are pressed against the side wall of the cast-out hole by the outer surface of the drill 1 and become almost fixed in place. Furthermore, as the drill 1 rotates, the coolant supply hole 2, located behind the cutting edge in the direction of rotation, approaches the lodged chips. As a result, the lodged chips can become trapped in the nearby coolant supply hole 2.

[0039] As drill 1 moves further downward along the axial direction, it begins to cut the bottom surface of the cast hole. The bottom surface of the cast hole is cut mainly by the cutting edges located towards the center of drill 1 (specifically, the thinning cutting edge portion 12 and the main cutting edge portion 11). The chips cut by the thinning cutting edge portion 12 and the main cutting edge portion 11 pass through the thinning surface 50 and the chip discharge groove surface 4 and approach the coolant supply hole 2 located in the forward direction of rotation. As a result, chips may get stuck in the coolant supply hole 2.

[0040] The drill 1 according to this embodiment has a thinning surface 50 and a recessed surface 60. Coolant supply holes 2 are provided in the recessed surface 60. In a cross-section parallel to and including the axis A, the recessed surface 60 is located axially rearward relative to the thinning surface 50. This prevents chips from getting stuck in the coolant supply holes 2. In particular, in high-efficiency machining, chips tend to be long and are difficult to break apart. Even in such cases, it is possible to prevent chips from getting stuck in the coolant supply holes 2.

[0041] Furthermore, according to the drill 1 of this embodiment, in a cross-section parallel to and including the axis A, the opening edge 3 of the coolant supply hole 2 in the receding surface 60 has a first position 41 and a second position 42. In a cross-section parallel to and including the axis A, if the first angle θ1 is defined as the angle between the axis A and the straight line passing through the first position 41 and the second position 42, and which is 90° or less, and the second angle θ2 is defined as the angle between the axis A and the tangent to the thinning surface 50 at the boundary between the thinning surface 50 and the receding surface 60, and which is 90° or less, then the first angle θ1 is smaller than the second angle θ2.

[0042] When the first angle θ1 is the same as the second angle θ2, the chips that have flowed along the thinning surface 50 will continue to flow toward the coolant supply holes 2 formed in the receding surface 60, making it easier for the chips to enter the coolant supply holes 2. On the other hand, when the first angle θ1 is smaller than the second angle θ2, the direction in which the chips flow can be changed to a direction different from the direction toward the coolant supply holes 2. This prevents the chips from getting stuck in the coolant supply holes 2.

[0043] According to the drill 1 of this embodiment, the first angle θ1 may be 0° or more and 45° or less. This allows the opening area of ​​the coolant supply hole 2 to be increased. Therefore, it is possible to further prevent chips from getting stuck in the coolant supply hole 2.

[0044] According to the drill 1 according to this embodiment, when the distance between the front end 5 of the drill 1 and the front end 5 of the coolant supply hole 2 in the direction parallel to the axis A is the first distance W1, the value obtained by dividing the first distance W1 by the diameter of the drill 1 may be 0.1 or more and 0.7 or less. By setting the value obtained by dividing the first distance W1 by the diameter of the drill 1 to 0.1 or more, it is possible to prevent the chips from being caught in the coolant supply hole 2. By setting the value obtained by dividing the first distance W1 by the diameter of the drill 1 to 0.7 or less, sufficient coolant can be supplied to the cutting edge, so that the cutting edge can be effectively cooled.

[0045] According to the drill 1 according to this embodiment, when the distance between the front end 5 of the coolant supply hole 2 and the rear end 6 of the coolant supply hole 2 in the direction parallel to the axis A is the second distance W2, the value obtained by dividing the second distance W2 by the diameter of the drill 1 may be 0.05 or more and 1.08 or less. By setting the value obtained by dividing the second distance W2 by the diameter of the drill 1 to 0.05 or more, the supply amount of the coolant can be increased. By setting the value obtained by dividing the second distance W2 by the diameter of the drill 1 to 1.08 or less, high strength can be maintained.

[0046] Using the drill 1 according to the first embodiment, drilling was performed. The material of the drill 1 is cemented carbide. The workpiece material is aluminum. First, a pilot hole was formed in the workpiece material. The depth of the pilot hole was 20.7 mm. The peripheral speed (Vc) of the cutting edge in the pilot hole machining was 120 m / min. The pressure of the coolant was 1 MPa.

[0047] Next, drilling was performed so as to expand the pilot hole. The rotational speed of the drill 1 was 10,000 revolutions per minute. The peripheral speed (Vc) of the cutting edge was 231 m / min. Between the hole depth of 0 mm and 1.8 mm, the feed per tooth (f) was 0.4 mm / revolution. Between the hole depth of 1.8 mm and 24.1 mm, the feed per tooth (f) was 1.2 mm / revolution.

[0048] After the drilling process was completed, it was confirmed that no chips were caught in the coolant supply hole 2 of the drill 1. As described above, according to the drill 1 according to the present embodiment, it was confirmed that it is possible to prevent chips from being caught in the coolant supply hole 2 in high-efficiency machining where the feed per edge (f) is 1 mm / revolution or more.

[0049] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above-described embodiments, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

[0050] 1 Drill, 2 Coolant supply hole, 3 Opening edge, 4 Chip discharge groove surface, 5 Front end, 6 Rear end, 7 Shank part, 8 Body part, 10 First cutting edge, 11 Main cutting edge part, 12 Thinning cutting edge part, 13 Second cutting edge, 20 Second relief surface, 30 First relief surface, 31 First relief surface part, 32 Second relief surface part, 41 First position, 42 Second position, 43 Third position, 44 Fourth position, 50 Thinning surface, 51 First thinning surface part, 52 Second thinning surface part, 53 First boundary line part, 54 First boundary region, 55 Second boundary region, 60 Retreating surface, 61 First retreating surface part, 62 Second retreating surface part, 63 Second boundary line part, 64 Third boundary region, 65 Fourth boundary region, 70 First outer peripheral surface, 71 First margin part, 72 Second margin part, 73 Outer peripheral end face part, 80 Second outer peripheral surface, 81 First body region, 82 Second body region, 90 Rear end edge, 91 Third boundary line part, A Axis line, D1 First diameter, D2 Second diameter, L1 First straight line, L2 Second straight line, W1 First distance, W2 Second distance, θ1 First angle, θ2 Second angle.

Claims

1. A drill that rotates around an axis, comprising: a cutting edge having a main cutting edge portion and a thinning cutting edge portion connected to the main cutting edge portion; a thinning surface connected to the thinning cutting edge portion; and a recessed surface connected to the thinning surface, wherein the recessed surface is provided with a coolant supply hole; in a cross section parallel to the axis and including the axis, the recessed surface is located axially rearward with respect to the thinning surface; the opening edge of the coolant supply hole on the recessed surface has a first position and a second position; the first angle is defined as the angle formed by the axis and a straight line passing through the first position and the second position, and which is 90° or less; and the second angle is defined as the angle formed by the axis and the tangent to the thinning surface at the boundary between the thinning surface and the recessed surface, and which is 90° or less; the first angle is smaller than the second angle.

2. The drill according to claim 1, wherein the first angle is 0° or more and 45° or less.

3. The drill according to claim 1 or claim 2, wherein, if the distance between the front end of the drill and the front end of the coolant supply hole in a direction parallel to the axis is defined as a first distance, the value obtained by dividing the first distance by the diameter of the cutting edge is 0.1 or more and 0.7 or less.

4. The drill according to any one of claims 1 to 3, wherein, if the distance between the front end of the coolant supply hole and the rear end of the coolant supply hole in a direction parallel to the axis is defined as a second distance, the value obtained by dividing the second distance by the diameter of the cutting edge is 0.05 or more and 1.08 or less.

5. The drill according to claim 1, wherein the first angle is 0° or more and 45° or less, the distance between the front end of the drill and the front end of the coolant supply hole in a direction parallel to the axis is defined as the first distance, and the distance between the front end of the coolant supply hole and the rear end of the coolant supply hole in a direction parallel to the axis is defined as the second distance, the value obtained by dividing the first distance by the diameter of the cutting edge is 0.1 or more and 0.7 or less, and the value obtained by dividing the second distance by the diameter of the cutting edge is 0.05 or more and 1.08 or less.

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