drill

Abstract

The first flank includes a first front flank portion and a first rear flank portion. The second flank includes a second front flank portion and a second rear flank portion. A ridgeline between the first front flank portion and the first rear flank portion is defined as a first ridgeline. A ridgeline between the second front flank portion and the second rear flank portion is defined as a second ridgeline. When viewed in the axial direction, a distance between the first ridgeline and the second ridgeline in a direction perpendicular to the first ridgeline is greater than 0 mm and not greater than 0.03 mm. The ridgeline between the first thinning surface and the first flank, and the ridgeline between the first thinning surface and the second flank constitute a first thinning ridgeline. The ridgeline between the second thinning surface and the first flank, and the ridgeline between the second thinning surface and the second flank constitute a second thinning ridgeline. When viewed in the axial direction, the shortest distance between the first thinning ridge line and the second thinning ridge line in a direction perpendicular to the first ridge line is not less than 0.04 mm and not more than 0.10 mm.

Description

[Technical field]

[0001] The present disclosure relates to a drill. [Background technology]

[0002] International Publication No. WO 2017 / 179689 (Patent Document 1) describes a drill with two tip flanks. The tip flanks include a first tip flank and a second tip flank. When viewed from the tip side in the axial direction, the intersecting ridge between the first tip flank and the second tip flank is linear. When viewed from the tip side in the axial direction, the distance between the intersecting ridge and an extension line of the intersecting ridge on one tip flank of the two tip flanks toward the other tip flank is within a range of 0.04 mm to 0.08 mm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 179689 Summary of the Invention

[0004] The drill according to the present disclosure is a drill that rotates around an axis and includes a first flank, a first thinning surface, a second flank, and a second thinning surface. The first thinning surface is provided rearward in the rotational direction from the first flank. The second flank is provided rearward in the rotational direction from the first thinning surface. The second thinning surface is provided rearward in the rotational direction from the second flank. The first flank includes a first front flank portion and a first rear flank portion. The first rear flank portion is continuous with the first front flank portion. The first rear flank portion is inclined with respect to the first front flank portion. The first rear flank portion is provided rearward in the rotational direction from the first front flank portion. The second flank includes a second front flank portion and a second rear flank portion. The second rear flank portion is continuous with the second front flank portion. The second rear flank portion is inclined with respect to the second front flank portion. The second rear flank portion is provided rearward in the rotational direction relative to the second front flank portion. The second front flank portion is continuous with each of the first front flank portion and the first rear flank portion. The second rear flank portion is continuous with the first front flank portion. The ridgeline between the first front flank portion and the first rear flank portion is defined as a first ridgeline. The ridgeline between the second front flank portion and the second rear flank portion is defined as a second ridgeline. When viewed in the axial direction from the front end to the rear end of the drill, the distance between the first ridgeline and the second ridgeline in a direction perpendicular to the first ridgeline is greater than 0 mm and equal to or less than 0.03 mm. The ridgeline between the first front flank portion and the second rear flank portion constitutes a first chisel region. The ridgeline between the first rear flank portion and the second front flank portion constitutes a second chisel region. The ridgeline between the first front flank portion and the second front flank portion constitutes a third chisel region. The third chisel region is continuous with each of the first chisel region and the second chisel region. The third chisel region is provided at the front end. The ridgeline between the first thinning surface and the first flank surface and the ridgeline between the first thinning surface and the second flank surface form a first thinning ridgeline. The ridgeline between the second thinning surface and the first flank surface and the ridgeline between the second thinning surface and the second flank surface form a second thinning ridgeline. When viewed in the axial direction, the shortest distance between the first thinning ridgeline and the second thinning ridgeline in a direction perpendicular to the first ridgeline is 0.04 mm or more and 0.10 mm or less. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic plan view showing the configuration of a drill according to this embodiment. [Diagram 2] FIG. 2 is a schematic perspective view showing the configuration of the drill according to this embodiment. [Diagram 3] FIG. 3 is a schematic front view showing the configuration of the drill according to this embodiment. [Figure 4] FIG. 4 is an enlarged schematic front view showing region IV in FIG. [Diagram 5] FIG. 5 is a schematic cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is an enlarged schematic view showing region VII in FIG. [Figure 8] FIG. 8 is an enlarged schematic diagram showing region VIII in FIG. [Figure 9] FIG. 9 is an enlarged schematic view showing region IX in FIG. [Figure 10] FIG. 10 is a schematic cross-sectional view showing a state immediately before the drill penetrates the workpiece. [Figure 11] FIG. 11 is a schematic cross-sectional view showing a state in which a hole has been formed in a workpiece using a drill. [Figure 12] FIG. 12 is an enlarged schematic front view showing the configuration of the drill according to Sample 1. As shown in FIG. [Figure 13] FIG. 13 shows the increase in hole diameter from sample 8 to sample 13. [Figure 14] FIG. 14 shows the hole position accuracy in Samples 8 to 13. [Figure 15] FIG. 15 shows the increase in hole diameter from sample 14 to sample 20. [Figure 16] FIG. 16 shows the hole position accuracy in Samples 14 to 20. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] [Problem that this disclosure aims to solve] An object of the present disclosure is to provide a drill that can improve the accuracy of hole drilling and the strength of the drill.

[0007] [Effects of this disclosure] According to the present disclosure, it is possible to provide a drill that can improve the accuracy of hole drilling and the strength of the drill.

[0008] [Outline of the embodiment] First, an overview of the embodiment of the present disclosure will be described.

[0009] (1) The drill 100 according to the present disclosure is a drill 100 that rotates around an axis X, and includes a first flank 10, a first thinning surface 13, a second flank 20, and a second thinning surface 23. The first thinning surface 13 is provided rearward in the rotational direction from the first flank 10. The second flank 20 is provided rearward in the rotational direction from the first thinning surface 13. The second thinning surface 23 is provided rearward in the rotational direction from the second flank 20. The first flank 10 includes a first front flank portion 11 and a first rear flank portion 12. The first rear flank portion 12 is continuous with the first front flank portion 11. The first rear flank portion 12 is inclined with respect to the first front flank portion 11. The first rear flank portion 12 is provided rearward in the rotational direction from the first front flank portion 11. The second flank 20 includes a second front flank portion 21 and a second rear flank portion 22. The second rear flank portion 22 is continuous with the second front flank portion 21. The second rear flank portion 22 is inclined with respect to the second front flank portion 21. The second rear flank portion 22 is provided rearward in the rotation direction with respect to the second front flank portion 21. The second front flank portion 21 is continuous with each of the first front flank portion 11 and the first rear flank portion 12. The second rear flank portion 22 is continuous with the first front flank portion 11. The ridge line between the first front flank portion 11 and the first rear flank portion 12 is defined as a first ridge line 71. The ridge line between the second front flank portion 21 and the second rear flank portion 22 is defined as a second ridge line 72. When viewed in the axial direction 101 from the front end 1 to the rear end 2 of the drill 100, the distance E1 between the first ridgeline 71 and the second ridgeline 72 in a direction perpendicular to the first ridgeline 71 is greater than 0 mm and equal to or less than 0.03 mm. The ridgeline between the first front flank portion 11 and the second rear flank portion 22 constitutes a first chisel region 41. The ridgeline between the first rear flank portion 12 and the second front flank portion 21 constitutes a second chisel region 42. The ridgeline between the first front flank portion 11 and the second front flank portion 21 constitutes a third chisel region 43. The third chisel region 43 is continuous with each of the first chisel region 41 and the second chisel region 42. The third chisel region 43 is provided at the front end 1. The ridgeline between the first thinning surface 13 and the first flank 10 and the ridgeline between the first thinning surface 13 and the second flank 20 form a first thinning ridgeline 15.The ridge line between the second thinning surface 23 and the first flank 10 and the ridge line between the second thinning surface 23 and the second flank 20 constitute a second thinning ridge line 25. As viewed in the axial direction 101, the shortest distance E2 between the first thinning ridge line 15 and the second thinning ridge line 25 in a direction perpendicular to the first ridge line 71 is 0.04 mm or more and 0.10 mm or less.

[0010] (2) According to the drill 100 according to (1) above, the length L3 of the third chisel region 43 as viewed in the axial direction 101 may be 23% or more and 55% or less of the shortest distance E2.

[0011] (3) According to the drill 100 according to the above (1) or (2), the cutting edge diameter D of the drill 100 may be 3 mm or less.

[0012] (4) The drill 100 according to (3) above may include a first chip discharge surface 19 and a second chip discharge surface 29. The first chip discharge surface 19 may be provided in a spiral shape around the axis X. The first chip discharge surface 19 may be continuous with the first flank surface 10. The second chip discharge surface 29 may be provided in a spiral shape around the axis X. The second chip discharge surface 29 may be continuous with the second flank surface 20. Each of the first chip discharge surface 19 and the second chip discharge surface 29 forms a chip discharge groove. The length of each of the first chip discharge surface 19 and the second chip discharge surface 29 in the axial direction 101 may be 2 times or more and 10 times or less the cutting diameter D.

[0013] (5) According to the drill 100 according to (4) above, the ridgeline between the first flank 10 and the first chip discharge surface 19 may form the first cutting edge 51. The ridgeline between the second flank 20 and the second chip discharge surface 29 may form the second cutting edge 52. At the outermost end 91 of the first cutting edge 51, the rake angle θ11 of the first cutting edge 51 in the radial direction of the drill 100 may be not less than −18° and not more than −9°. At the outermost end 92 of the second cutting edge 52, the rake angle θ12 of the second cutting edge 52 in the radial direction of the drill 100 may be not less than −18° and not more than −9°.

[0014] (6) According to the drill 100 of any of (1) to (5) above, when viewed in the axial direction 101, the angle θ3 between the first ridge 71 and the third chisel region 43 may be greater than the angle θ1 between the first ridge 71 and the first chisel region 41, and may also be greater than the angle θ2 between the first ridge 71 and the second chisel region 42.

[0015] (7) According to the drill 100 according to any one of (1) to (6) above, the angle θ3 between the first ridge 71 and the third chisel region 43 as viewed in the axial direction 101 may be greater than or equal to 50° and less than or equal to 80°.

[0016] (8) According to the drill 100 according to any one of (1) to (7) above, the angle θ1 between the first ridge line 71 and the first chisel region 41 as viewed in the axial direction 101 may be greater than or equal to 40° and less than or equal to 60°. The angle between the first ridge line 71 and the second chisel region 42 as viewed in the axial direction 101 may be greater than or equal to 40° and less than or equal to 60°.

[0017] [Details of the embodiment] Hereinafter, an embodiment of the present disclosure (hereinafter also referred to as the present embodiment) will be described in detail with reference to the drawings. Note that in the following drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated.

[0018] First, the configuration of the drill 100 according to this embodiment will be described. Fig. 1 is a schematic plan view showing the configuration of the drill 100 according to this embodiment. As shown in Fig. 1, the drill 100 according to this embodiment mainly has a front end 1, a rear end 2, a first cutting edge 51, a first chip discharge surface 19, a second chip discharge surface 29, an outer peripheral surface 9, a shank 7, a second flank surface 20, and a second thinning surface 23. The drill 100 according to this embodiment is, for example, a drill for metal processing.

[0019] As shown in Fig. 1, the first chip discharge surface 19 is provided in a spiral shape around the axis X. The second chip discharge surface 29 is provided in a spiral shape around the axis X. The first chip discharge surface 19 and the second chip discharge surface 29 each form a chip discharge groove. Specifically, the first chip discharge surface 19 forms a first chip discharge groove 93. The second chip discharge surface 29 forms a second chip discharge groove 94.

[0020] The outer peripheral surface 9 is continuous with each of the first chip discharge surface 19 and the second chip discharge surface 29. The outer peripheral surface 9 has a first outer peripheral surface portion 16 and a second outer peripheral surface portion 26. The first outer peripheral surface portion 16 is provided in a spiral shape around the axis X. The second outer peripheral surface portion 26 is provided in a spiral shape around the axis X. The first cutting edge 51 is provided at a position close to the front end 1 of the drill 100. The second thinning surface 23 is continuous with each of the second flank surface 20, the second outer peripheral surface portion 26 and the first chip discharge surface 19.

[0021] The front end 1 of the drill 100 is a portion facing a workpiece. The rear end 2 of the drill 100 is a portion facing a tool spindle (not shown) that rotates the drill 100. The shank 7 is a portion that is attached to the tool spindle. An axis X passes through the front end 1 and the rear end 2. The drill 100 rotates around the axis X. In this specification, the direction from the front end 1 to the rear end 2 is defined as the axial direction 101. The axial direction 101 is a direction along the axis X. A direction perpendicular to the axial direction 101 and toward the axis X is defined as the radial inner direction. Conversely, a direction perpendicular to the axial direction 101 and away from the axis X is defined as the radial outer direction.

[0022] 1, the length of the first chip discharge surface 19 in the axial direction 101 is defined as a first length L1. The first length L1 is, for example, 10 mm. The length of the second chip discharge surface 29 in the axial direction 101 is defined as a second length L2. The second length L2 is substantially the same as the first length L1.

[0023] Fig. 2 is a schematic perspective view showing the configuration of the drill 100 according to this embodiment. As shown in Fig. 2, the drill 100 according to this embodiment has a first flank 10, a first thinning surface 13, and a second cutting edge 52. The first flank 10 is continuous with a first chip discharge surface 19 (see Fig. 1) and a first outer peripheral surface portion 16. The ridgeline between the first flank 10 and the first chip discharge surface 19 forms a first cutting edge 51. The first chip discharge surface 19 close to the first cutting edge 51 functions as a rake face.

[0024] The first thinning surface 13 is continuous with each of the first flank 10, the first outer peripheral surface portion 16, and the second chip discharge surface 29. The second flank 20 is continuous with each of the first flank 10, the first thinning surface 13, and the second chip discharge surface 29. The ridgeline between the second flank 20 and the second chip discharge surface 29 forms a second cutting edge 52. The second chip discharge surface 29 closer to the second cutting edge 52 functions as a rake surface.

[0025] As shown in FIG. 2, the first flank 10 has a first front flank portion 11 and a first rear flank portion 12. The first front flank portion 11 is, for example, planar. The first front flank portion 11 is continuous with the first cutting edge 51. From another perspective, the ridgeline between the first front flank portion 11 and the first chip discharge surface 19 (see FIG. 1) constitutes the first cutting edge 51. The first rear flank portion 12 is, for example, planar. The first rear flank portion 12 is continuous with the first front flank portion 11. The ridgeline between the first front flank portion 11 and the first rear flank portion 12 is defined as a first ridgeline 71. The first ridgeline 71 is, for example, linear.

[0026] The second flank 20 has a second front flank portion 21 and a second rear flank portion 22. The second front flank portion 21 is, for example, planar. The second front flank portion 21 is continuous with the second cutting edge 52. The second front flank portion 21 is, for example, planar. The second rear flank portion 22 is continuous with the second front flank portion 21. The ridge line between the second front flank portion 21 and the second rear flank portion 22 is defined as a second ridge line 72. The second ridge line 72 is, for example, linear.

[0027] 2, the outer peripheral surface 9 has a first margin surface 18 and a second margin surface 28. From another perspective, the drill 100 has only one pair of margin surfaces. The first margin surface 18 is continuous with each of the first outer peripheral surface portion 16 and the first chip discharge surface 19. The ridgeline between the first margin surface 18 and the first chip discharge surface 19 constitutes a first leading edge 17.

[0028] The second margin surface 28 is continuous with each of the second outer peripheral surface portion 26, the second flank surface 20, and the second chip discharge surface 29. The ridge line between the second margin surface 28 and the second chip discharge surface 29 constitutes a second leading edge 27.

[0029] The first outer peripheral surface portion 16 is continuous with each of the first flank surface 10, the first thinning surface 13, and the second chip discharge surface 29. The second outer peripheral surface portion 26 is continuous with each of the second flank surface 20, the second thinning surface 23, and the first chip discharge surface 19.

[0030] FIG. 3 is a schematic front view showing the configuration of the drill 100 according to the present embodiment. The schematic front view shown in FIG. 3 shows the configuration of the drill 100 as viewed in the axial direction 101. For convenience of explanation, the shank 7 is not shown in FIG. 3. As shown in FIG. 3, the first thinning surface 13 is provided rearward in the rotation direction from the first flank surface 10. The second flank surface 20 is provided rearward in the rotation direction from the first thinning surface 13. The second thinning surface 23 is provided rearward in the rotation direction from the second flank surface 20. The first flank surface 10 is provided rearward in the rotation direction from the second thinning surface 23.

[0031] 3, the drill 100 may be substantially two-fold symmetric with respect to the axis X. The shape of the first flank 10 rotated 180° with respect to the axis X may be substantially the same as the shape of the second flank 20. Similarly, the shape of the first thinning surface 13 rotated 180° with respect to the axis X may be substantially the same as the shape of the second thinning surface 23. When viewed in the axial direction 101, the second ridge line 72 is substantially parallel to the first ridge line 71.

[0032] The first front flank portion 11 is continuous with the second thinning surface 23. The ridge line between the first front flank portion 11 and the second thinning surface 23 constitutes a first thinning cutting edge 61. The first thinning cutting edge 61 is continuous with the first cutting edge 51. The first thinning cutting edge 61 is provided radially inward with respect to the first cutting edge 51. The first front flank portion 11 is spaced apart from the first thinning surface 13.

[0033] The first rear flank portion 12 is provided rearward in the rotational direction from the first front flank portion 11. The first rear flank portion 12 is continuous with the first thinning surface 13. The ridge line between the first rear flank portion 12 and the first thinning surface 13 is defined as a third ridge line 73. The first rear flank portion 12 is spaced from the second thinning surface 23.

[0034] The second front flank portion 21 is continuous with the first thinning surface 13. The ridge line between the second front flank portion 21 and the first thinning surface 13 constitutes a second thinning cutting edge 62. The second thinning cutting edge 62 is continuous with the second cutting edge 52. The second thinning cutting edge 62 is provided radially inward with respect to the second cutting edge 52. The second front flank portion 21 is spaced apart from the second thinning surface 23.

[0035] The second rear flank portion 22 is provided rearward in the rotational direction from the second front flank portion 21. The second rear flank portion 22 is continuous with the second thinning surface 23. The ridge line between the second rear flank portion 22 and the second thinning surface 23 is defined as a fourth ridge line 74. The second rear flank portion 22 is spaced apart from the first thinning surface 13.

[0036] 3, when viewed in the axial direction 101, the first outer peripheral surface portion 16 is provided radially outward from the first thinning surface 13. When viewed in the axial direction 101, the second outer peripheral surface portion 26 is provided radially outward from the second thinning surface 23.

[0037] When viewed in the axial direction 101, the first cutting edge 51 is curved. Specifically, the first cutting edge 51 may be arc-shaped. When viewed in the axial direction 101, the first cutting edge 51 is recessed rearward in the rotational direction. When viewed in the axial direction 101, the second cutting edge 52 is curved. Specifically, the second cutting edge 52 may be arc-shaped. When viewed in the axial direction 101, the second cutting edge 52 is recessed rearward in the rotational direction.

[0038] The outermost end of the first cutting edge 51 is defined as a first outermost end 91. The outermost end of the second cutting edge 52 is defined as a second outermost end 92. When viewed in the axial direction 101, the first outermost end 91, the second outermost end 92, and the axis X may be aligned on a straight line. When viewed in the axial direction 101, the distance between the first outermost end 91 and the axis X and the distance between the second outermost end 92 and the axis X are substantially the same.

[0039] The distance between the first outermost end 91 and the second outermost end 92 as viewed in the axial direction 101 is the cutting edge diameter D of the drill 100. The cutting edge diameter D is, for example, 3 mm or less. The cutting edge diameter D is, for example, 2 mm. The upper limit of the cutting edge diameter D is not particularly limited, but may be, for example, 2 mm or less, or 1 mm or less. The lower limit of the cutting edge diameter D is not particularly limited, but may be, for example, 0.1 mm or more, or 0.5 mm or more.

[0040] The length of the first chip discharge surface 19 in the axial direction 101 (first length L1) is, for example, two or more and ten or less times the blade diameter D. The first length L1 may be, for example, three or more and five or less times the blade diameter D. The lower limit of the first length L1 is not particularly limited, but may be, for example, 2.5 or more times the blade diameter D, or four or more times the blade diameter D. The upper limit of the first length L1 is not particularly limited, but may be, for example, eight or less times the blade diameter D, or six or less times the blade diameter D.

[0041] The length of the second chip discharge surface 29 in the axial direction 101 (second length L2) is, for example, two or more and ten or less times the blade diameter D. The second length L2 may be, for example, three or more and five or less times the blade diameter D. The lower limit of the second length L2 is not particularly limited, but may be, for example, 2.5 or more times the blade diameter D, or four or more times the blade diameter D. The upper limit of the second length L2 is not particularly limited, but may be, for example, eight or less times the blade diameter D, or six or less times the blade diameter D.

[0042] As shown in FIG. 3, the ridgeline between the first chip discharge surface 19 and the second thinning surface 23 is defined as a fifth ridgeline 75. As viewed in the axial direction 101, the fifth ridgeline 75 is recessed forward in the rotational direction. As viewed in the axial direction 101, the fifth ridgeline 75 overlaps the first thinning cutting edge 61 at a first point 121 on the first thinning cutting edge 61. From another perspective, as viewed in the axial direction 101, the fifth ridgeline 75 extends from the first point 121 forward in the rotational direction relative to the first thinning cutting edge 61. As viewed in the axial direction 101, a straight line passing through the first point 121 and parallel to the first ridgeline 71 is defined as a first virtual line 111. As viewed in the axial direction 101, the first cutting edge 51 is provided forward in the rotational direction relative to the first virtual line 111.

[0043] As shown in FIG. 3, the ridgeline between the second chip discharge surface 29 and the first thinning surface 13 is defined as a sixth ridgeline 76. As viewed in the axial direction 101, the sixth ridgeline 76 is recessed forward in the rotational direction. As viewed in the axial direction 101, the sixth ridgeline 76 overlaps with the second thinning cutting edge 62 at a second point 122 on the second thinning cutting edge 62. From another perspective, as viewed in the axial direction 101, the sixth ridgeline 76 extends from the second point 122 forward in the rotational direction relative to the second thinning cutting edge 62. As viewed in the axial direction 101, a straight line passing through the second point 122 and parallel to the first ridgeline 71 is defined as a second virtual line 112. As viewed in the axial direction 101, the second cutting edge 52 is provided forward in the rotational direction relative to the second virtual line 112. As shown in FIG. 3, a direction toward the inside in the radial direction and parallel to the first ridge line 71 when viewed in the axial direction 101 is defined as a side view direction 102.

[0044] Fig. 4 is an enlarged schematic front view showing region IV in Fig. 3. As shown in Fig. 4, the second front flank portion 21 is continuous with each of the first front flank portion 11 and the first rear flank portion 12. The second rear flank portion 22 is continuous with the first front flank portion 11. The second rear flank portion 22 is spaced apart from the first rear flank portion 12.

[0045] The ridgeline between the first front flank portion 11 and the second rear flank portion 22 defines a first chisel region 41. When viewed in the axial direction 101, the first chisel region 41 is, for example, linear. The ridgeline between the first rear flank portion 12 and the second front flank portion 21 defines a second chisel region 42. When viewed in the axial direction 101, the second chisel region 42 is, for example, linear. The second chisel region 42 is spaced apart from the first chisel region 41.

[0046] The ridgeline between the first front flank portion 11 and the second front flank portion 21 defines a third chisel region 43. The third chisel region 43 may intersect with the axis X. The third chisel region 43 has a first end 81 and a second end 82. At the first end 81, the third chisel region 43 is continuous with the first chisel region 41 and the second ridgeline 72, respectively. The second end 82 is opposite the first end 81. At the second end 82, the third chisel region 43 is continuous with the second chisel region 42 and the first ridgeline 71, respectively. The third chisel region 43 is provided radially inward with respect to the first chisel region 41. The third chisel region 43 is provided radially inward with respect to the second chisel region 42.

[0047] When viewed in the axial direction 101, a straight line extending in the direction in which the second ridge line 72 extends is defined as a third virtual line 113. When viewed in the axial direction 101, the third virtual line 113 is located forward of the first ridge line 71 in the rotational direction. When viewed in the axial direction 101, a distance between the first ridge line 71 and the second ridge line 72 in a direction perpendicular to the first ridge line 71 is defined as a first distance E1. The first distance E1 is the distance between the third virtual line 113 and the first ridge line 71 when viewed in the axial direction 101. The first distance E1 is greater than 0 mm and equal to or less than 0.03 mm. The lower limit of the first distance E1 is not particularly limited, but may be, for example, 0.005 mm or more, or 0.01 mm or more. The upper limit of the first distance E1 is not particularly limited, but may be, for example, 0.027 mm or less, or 0.023 mm or less.

[0048] As shown in FIG. 4, the ridgeline (third ridgeline 73) between the first thinning surface 13 and the first flank surface 10 and the ridgeline (second thinning cutting edge 62) between the first thinning surface 13 and the second flank surface 20 form a first thinning ridgeline 15. The first thinning ridgeline 15 is continuous with the second chisel region 42. When viewed in the axial direction 101, the first thinning ridgeline 15 is recessed radially inward. A point located on the first thinning ridgeline 15 and closest to the axis X in a direction perpendicular to the first ridgeline 71 when viewed in the axial direction 101 is defined as a third point 123. The third point 123 is located on the third ridgeline 73, for example.

[0049] The ridge line (first thinning cutting edge 61) between the second thinning surface 23 and the first flank 10 and the ridge line (fourth ridge line 74) between the second thinning surface 23 and the second flank 20 constitute a second thinning ridge line 25. The second thinning ridge line 25 is continuous with the first chisel region 41. As viewed in the axial direction 101, the second thinning ridge line 25 is recessed radially inward. A point located on the second thinning ridge line 25 and closest to the axis X in a direction perpendicular to the first ridge line 71 as viewed in the axial direction 101 is defined as a fourth point 124. The fourth point 124 is located on the fourth ridge line 74, for example.

[0050] The distance between the third point 123 and the fourth point 124 in the direction perpendicular to the first ridge 71 as viewed in the axial direction 101 is defined as the second distance E2. As viewed in the axial direction 101, the second distance E2 is the shortest distance between the first thinning ridge 15 and the second thinning ridge 25 in the direction perpendicular to the first ridge 71. The second distance E2 is 0.04 mm or more and 0.10 mm or less. The lower limit of the second distance E2 is not particularly limited, but may be, for example, 0.05 mm or more, or 0.053 mm or more. The upper limit of the second distance E2 is not particularly limited, but may be, for example, 0.09 mm or less, or 0.085 mm or less. The second distance E2 is greater than the first distance E1.

[0051] The length of the third chisel region 43 as viewed in the axial direction 101 is the third length L3. From another perspective, the third length L3 is the distance between the first end 81 and the second end 82 as viewed in the axial direction 101. The third length L3 is 23% or more and 55% or less of the second distance E2. In other words, the percentage (first value) of the value obtained by dividing the third length L3 by the second distance E2 is 23% or more and 55% or less. The lower limit of the first value is not particularly limited, but may be, for example, 28% or more, or 35% or more. The upper limit of the first value is not particularly limited, but may be, for example, 50% or less, or 45% or less.

[0052] 4, a straight line that is parallel to the first ridge line 71 and intersects with the first chisel region 41 as viewed in the axial direction 101 is defined as a fourth imaginary line 114. An acute angle among the angles that the fourth imaginary line 114 and the first chisel region 41 form as viewed in the axial direction 101 is defined as a first angle θ1. From another perspective, the first angle θ1 is the angle that the first ridge line 71 and the first chisel region 41 form as viewed in the axial direction 101.

[0053] The first angle θ1 is, for example, 40° or more and 60° or less. The lower limit of the first angle θ1 is not particularly limited, but may be, for example, 43° or more, or 47° or more. The upper limit of the first angle θ1 is not particularly limited, but may be, for example, 57° or less, or 53° or less.

[0054] 4, a straight line that is parallel to the first ridge line 71 and intersects with the second chisel region 42 in the axial direction 101 is defined as a fifth imaginary line 115. An acute angle among the angles that the fifth imaginary line 115 and the second chisel region 42 make in the axial direction 101 is defined as a second angle θ2. From another perspective, the second angle θ2 is the angle that the first ridge line 71 and the second chisel region 42 make in the axial direction 101.

[0055] The second angle θ2 is, for example, 40° or more and 60° or less. The lower limit of the second angle θ2 is not particularly limited, but may be, for example, 43° or more, or 47° or more. The upper limit of the second angle θ2 is not particularly limited, but may be, for example, 57° or less, or 53° or less.

[0056] When viewed in the axial direction 101, the angle between the first ridge 71 and the third chisel region 43 is a third angle θ3. The third angle θ3 is an acute angle. The third angle θ3 is greater than the first angle θ1. From another perspective, when viewed in the axial direction 101, the first chisel region 41 is inclined backward in the rotational direction with respect to the third chisel region 43. The third angle θ3 is greater than the second angle θ2. From another perspective, when viewed in the axial direction 101, the second chisel region 42 is inclined backward in the rotational direction with respect to the third chisel region 43.

[0057] The third angle θ3 is, for example, 50° or more and 80° or less. The lower limit of the third angle θ3 is not particularly limited, but may be, for example, 55° or more, or 60° or more. The upper limit of the third angle θ3 is not particularly limited, but may be, for example, 75° or less, or 70° or less.

[0058] FIG. 5 is a schematic cross-sectional view taken along line VV in FIG. 4. The cross section shown in FIG. 5 is a cross section that includes the axis X and is parallel to the first ridge line 71 when viewed in the axial direction 101. In this specification, the cross section that includes the axis X and is parallel to the first ridge line 71 when viewed in the axial direction 101 is referred to as the first cross section CS1. As shown in FIG. 5, in the first cross section CS1, the first front flank portion 11 is, for example, linear. In the first cross section CS1, a straight line extending in the direction in which the first front flank portion 11 extends is referred to as the sixth virtual line 116. In the first cross section CS1, the second front flank portion 21 is, for example, linear. In the first cross section CS1, a straight line extending in the direction in which the second front flank portion 21 extends is referred to as the seventh virtual line 117.

[0059] Among the angles formed by the sixth virtual line 116 and the seventh virtual line 117, an obtuse angle is defined as a fourth angle θ4. The fourth angle θ4 is an angle formed by the first front flank portion 11 and the second front flank portion 21. The fourth angle θ4 is a tip angle of the drill 100. The fourth angle θ4 is, for example, 140°. The fourth angle θ4 may be 120° or more and 160° or less. In the first cross section CS1, the axis X substantially bisects the angle formed by the first front flank portion 11 and the second front flank portion 21.

[0060] Fig. 6 is a schematic cross-sectional view taken along line VI-VI in Fig. 3. The cross-section shown in Fig. 6 is parallel to the axis X and intersects with the first ridge line 71. When viewed in the axial direction 101, the cross-section shown in Fig. 6 is perpendicular to the first ridge line 71. From another perspective, the schematic cross-sectional view shown in Fig. 6 shows the configuration of the drill 100 as viewed in a side view direction 102 (see Fig. 3). In this specification, the cross-section parallel to the axis X and intersecting with the first ridge line 71 is referred to as the second cross-section CS2.

[0061] As shown in Fig. 6, the first rear flank portion 12 is inclined relative to the first front flank portion 11. Specifically, in the second cross section CS2, the first rear flank portion 12 is inclined in the axial direction 101 relative to the first front flank portion 11. Similarly, the second rear flank portion 22 (see Fig. 3) is inclined relative to the second front flank portion 21 (see Fig. 3).

[0062] As shown in Fig. 6, in the second cross section CS2, each of the first front flank portion 11 and the first rear flank portion 12 may be straight. Similarly, in a cross section that is parallel to the axis X and intersects with the second ridge line 72 (see Fig. 3), each of the second front flank portion 21 and the second front flank portion 21 may be straight.

[0063] 7 is an enlarged schematic diagram showing region VII in FIG. 6. As shown in FIG. 7, the third chisel region 43 is provided at the front end 1 of the drill 100. When viewed in a side view direction 102, the third chisel region 43 is substantially perpendicular to the axis X. When viewed in the side view direction 102, the first chisel region 41 is inclined in the axial direction 101 with respect to the third chisel region 43. When viewed in the side view direction 102, the inclination angle of the first chisel region 41 with respect to the third chisel region 43 is set to a fifth angle θ5. The fifth angle θ5 is, for example, 3° or more and 15° or less.

[0064] As viewed in the side view direction 102, the second chisel region 42 is inclined in the axial direction 101 with respect to the third chisel region 43. As viewed in the side view direction 102, the inclination angle of the second chisel region 42 with respect to the third chisel region 43 is set to a sixth angle θ6. The sixth angle θ6 is, for example, not less than 3° and not more than 15°.

[0065] Fig. 8 is an enlarged schematic view showing region VIII in Fig. 3. As shown in Fig. 8, when viewed in the axial direction 101, a tangent to the first cutting edge 51 at the first outermost end 91 is defined as a first tangent 131. When viewed in the axial direction 101, a straight line passing through the first outermost end 91 and the axis X (see Fig. 3) is defined as an eighth virtual line 118.

[0066] When viewed in the axial direction 101, the first tangent 131 is inclined rearward in the rotational direction with respect to the eighth imaginary line 118. When viewed in the axial direction 101, an acute angle among the angles formed by the first tangent 131 and the eighth imaginary line 118 is defined as the first rake angle θ11. From another perspective, at the outermost peripheral end 91 of the first cutting edge 51, the rake angle of the first cutting edge 51 in the radial direction of the drill 100 is defined as the first rake angle θ11. The first rake angle θ11 is negative.

[0067] A "positive" rake angle of the cutting edge in the radial direction of the drill 100 at the outermost peripheral end of the cutting edge means that, when viewed in the axial direction 101, the tangent to the cutting edge at the outermost peripheral end is inclined forward in the rotation direction of the drill 100 with respect to a straight line passing through the axis X and the outermost peripheral end. Conversely, a "negative" rake angle of the cutting edge in the radial direction of the drill 100 at the outermost peripheral end of the cutting edge means that, when viewed in the axial direction 101, the tangent to the cutting edge at the outermost peripheral end is inclined backward in the rotation direction of the drill 100 with respect to a straight line passing through the axis X and the outermost peripheral end.

[0068] The first rake angle θ11 is, for example, -18° or more and -9° or less. The first rake angle θ11 may be, for example, -14° or more and -10° or less. The lower limit of the first rake angle θ11 is not particularly limited, but may be, for example, -16° or more, or may be -13° or more. The upper limit of the first rake angle θ11 is not particularly limited, but may be, for example, -9.5° or less, or may be -11° or less. When viewed in the axial direction 101, the first margin surface 18 is provided radially outward relative to each of the first flank surface 10, the first outer peripheral surface portion 16, and the second outer peripheral surface portion 26. When viewed in the axial direction 101, the first margin surface 18 is provided forward in the rotational direction relative to the first outer peripheral surface portion 16.

[0069] Fig. 9 is an enlarged schematic diagram showing region IX in Fig. 3. As shown in Fig. 9, when viewed in the axial direction 101, a tangent to the second cutting edge 52 at the second outermost end 92 is a second tangent 132. When viewed in the axial direction 101, a straight line passing through the second outermost end 92 and the axis X (see Fig. 3) is a ninth imaginary line 119. When viewed in the axial direction 101, the ninth imaginary line 119 may overlap with the eighth imaginary line 118 (see Fig. 8).

[0070] When viewed in the axial direction 101, the second tangent 132 is inclined backward in the rotational direction with respect to the ninth imaginary line 119. When viewed in the axial direction 101, an acute angle among the angles formed by the second tangent 132 and the ninth imaginary line 119 is defined as the second rake angle θ12. From another perspective, at the outermost peripheral end 92 of the second cutting edge 52, the rake angle of the second cutting edge 52 in the radial direction of the drill 100 is defined as the second rake angle θ12. The second rake angle θ12 is negative. The second rake angle θ12 is substantially the same as the first rake angle θ11.

[0071] The second rake angle θ12 is, for example, -18° or more and -9° or less. The second rake angle θ12 may be, for example, -14° or more and -10° or less. The lower limit of the second rake angle θ12 is not particularly limited, but may be, for example, -16° or more, or may be -13° or more. The upper limit of the second rake angle θ12 is not particularly limited, but may be, for example, -9.5° or less, or may be -11° or less. When viewed in the axial direction 101, the second margin surface 28 is provided radially outward with respect to each of the second flank surface 20, the first outer peripheral surface portion 16, and the second outer peripheral surface portion 26. When viewed in the axial direction 101, the second margin surface 28 is provided forward in the rotational direction with respect to the second outer peripheral surface portion 26.

[0072] Next, the effects of the drill 100 according to this embodiment will be described. The drill 100 according to this embodiment has a first chisel region 41, a second chisel region 42, and a third chisel region 43. The third chisel region 43 is continuous with each of the first chisel region 41 and the second chisel region 42. The third chisel region 43 is provided at the front end 1. Therefore, when a workpiece is machined using the drill 100, the third chisel region 43 comes into contact with the workpiece first. In addition, according to the drill 100 according to this embodiment, the distance (first distance E1) between the first ridgeline 71 and the second ridgeline 72 is 0.03 mm or less. When viewed in the axial direction 101, the shortest distance (second distance E2) between the first thinning ridgeline 15 and the second thinning ridgeline 25 in a direction perpendicular to the first ridgeline 71 is 0.10 mm or less.

[0073] By setting the first distance E1 to 0.03 mm or less, the length of the third chisel region 43 can be prevented from becoming excessively long. This can prevent the contact area between the drill 100 and the workpiece from becoming excessively large immediately after the start of hole drilling using the drill 100. This can improve the biting ability of the drill 100. This can prevent the drill 100 from swinging during hole drilling. This can improve both the enlargement margin of the hole diameter and the hole position accuracy of the hole drilled using the drill 100. As a result, the accuracy of hole drilling can be improved. By setting the second distance E2 to 0.10 mm or less, the length of each of the first chisel region 41 and the second chisel region 42 can be prevented from becoming excessively long. This can prevent the force applied from the workpiece to each of the first chisel region 41 and the second chisel region 42 from becoming excessively large at the beginning of hole drilling. This can prevent the drill 100 from swinging during hole drilling. As a result, the accuracy of hole drilling can be improved.

[0074] Furthermore, according to the drill 100 of this embodiment, the first distance E1 is greater than 0 mm. The second distance E2 is 0.04 mm or more. By making the first distance E1 greater than 0 mm, it is possible to prevent the periphery of the front end 1 of the drill 100 from becoming excessively sharp. Therefore, it is possible to prevent the periphery of the front end 1 of the drill 100 from being chipped. As a result, it is possible to improve the strength of the drill 100. By making the second distance E2 0.04 mm or more, it is possible to increase the thickness of the periphery of the front end 1 of the drill 100. This makes it possible to prevent the drill 100 from breaking. As a result, it is possible to improve the strength of the drill 100.

[0075] According to the drill 100 of this embodiment, the length of the third chisel region 43 (the third length L3) may be 23% or more and 55% or less of the second distance E2. This can improve the hole position accuracy of the hole formed using the drill 100.

[0076] According to the drill 100 of this embodiment, the cutting diameter D of the drill 100 may be 3 mm or less. Usually, in machining using a drill 100 with a small cutting diameter D, an oil-based coolant is often supplied by external oil supply. In this case, the temperature of the drill 100 is likely to be high compared to when the coolant is supplied by internal oil supply. Therefore, in the drill 100 with a small cutting diameter D, the number of margin faces is often two (one pair) in order to reduce friction between the drill 100 and the workpiece. In this case, the drill 100 is more likely to vibrate compared to when the number of margin faces is four (two pairs) or more. As a result, the accuracy of hole machining is reduced. According to the drill 100 of this embodiment, even when the cutting diameter D is 3 mm or less, the accuracy of hole machining can be suppressed from being reduced.

[0077] FIG. 10 is a schematic cross-sectional view showing a state immediately before the drill 100 penetrates the workpiece 99. As shown in FIG. 10, a remaining portion 98 of the workpiece 99 is formed immediately before the drill 100 penetrates the workpiece 99 during hole drilling. The remaining portion 98 is a portion that is not cut by the cutting edge of the drill 100. FIG. 11 is a schematic cross-sectional view showing a state in which a hole is formed in the workpiece 99 using the drill 100. As shown in FIG. 10 and FIG. 11, when the drill 100 penetrates the workpiece 99, the remaining portion 98 receives a load in a direction along the machining direction A of the drill 100. The load causes the remaining portion 98 to plastically deform. As a result, a burr 97 is formed in the workpiece 99. In the machining direction A of the drill 100, the distance between the point on the burr 97 that is farthest from the surface of the workpiece 99 and the surface of the workpiece 99 is set to the height H of the burr 97. It is preferable that the height H of the burr 97 is low.

[0078] According to the drill 100 according to this embodiment, at the first outermost end 91, the rake angle (first rake angle θ11) of the first cutting edge 51 in the radial direction of the drill 100 may be -18° or more and -9° or less. At the second outermost end 92, the rake angle (second rake angle θ12) of the second cutting edge 52 in the radial direction of the drill 100 may be -18° or more and -9° or less. By setting each of the first rake angle θ11 and the second rake angle θ12 to -18° or more, the sharpness of the cutting edge at the outermost end can be improved. As a result, the height H of the burr 97 can be reduced.

[0079] Furthermore, by setting each of the first rake angle θ11 and the second rake angle θ12 to -9° or less, it is possible to suppress a decrease in the strength of the cutting edge around the outermost peripheral end. This makes it possible to suppress a decrease in the sharpness of the cutting edge due to chipping even after drilling multiple holes with the drill 100. As a result, it is possible to suppress an increase in the burr height H even after drilling multiple holes with the drill 100. EXAMPLES

[0080] (Sample preparation) First, the drill 100 according to Sample 1 and Sample 2 were prepared. The drill 100 according to Sample 1 was used as a comparative example. The drill 100 according to Sample 2 was used as an example.

[0081] In the drill 100 according to Sample 1 and Sample 2, the first distance E1 was changed. In the drill 100 according to Sample 1, the first distance E1 was set to 0.12 mm. FIG. 12 is an enlarged schematic front view showing the configuration of the drill 100 according to Sample 1. The enlarged schematic front view shown in FIG. 12 corresponds to the enlarged schematic front view shown in FIG. 4. As shown in FIG. 12, the drill 100 according to Sample 1 did not have the first chisel region 41 and the second chisel region 42. In the drill 100 according to Sample 1, the percentage (first value) of the value obtained by dividing the length (third length L3) of the third chisel region 43 by the second distance E2 was set to 113%.

[0082] The configuration of the drill 100 according to Sample 2 was the same as that of the drill 100 according to this embodiment (see FIG. 4). In the drill according to Sample 2, the first distance E1 was set to 0.02 mm. The first value was set to 32%.

[0083] In the drills 100 according to Sample 1 and Sample 2, the cutting edge diameter D was set to 2 mm. The length of each of the first chip discharge surface 19 and the second chip discharge surface 29 was set to 5 times the cutting edge diameter D. The second distance E2 was set to 0.07 mm. Each of the first rake angle θ11 and the second rake angle θ12 (hereinafter also simply referred to as the rake angle) was set to -12°.

[0084] (Evaluation method) Next, the hole diameter enlargement allowance and hole position accuracy were evaluated using the drills 100 according to Sample 1 and Sample 2. Specifically, holes were formed in a workpiece using the drills 100 according to Sample 1 and Sample 2. The diameter of the formed hole was measured. The value obtained by subtracting the cutting edge diameter of the drill 100 from the diameter of the formed hole was determined as the hole diameter enlargement allowance. The value twice the distance between the target position of the center of the hole and the position of the center of the formed hole was determined as the hole position accuracy.

[0085] In the evaluation of the hole diameter enlargement allowance and hole position accuracy, the work material was SCM415. SCM415 is an alloy steel specified in JIS (Japanese Industrial Standards) G 4053:2016. The hole depth was 6 mm. The cutting speed was 38 m / min. The feed rate was 0.04 mm / rev.

[0086] (Evaluation Results)

[0087] [Table 1]

[0088] Table 1 shows the hole diameter enlargement and hole position accuracy in Sample 1 and Sample 2. As shown in Table 1, the hole diameter enlargement in Sample 2 was smaller than the hole diameter enlargement in Sample 1. The hole position accuracy in Sample 2 was smaller than the hole position accuracy in Sample 1.

[0089] From the above results, it was confirmed that the drill 100 according to the embodiment can reduce both the enlargement allowance of the hole diameter and the hole position deviation, compared to the drill 100 according to the comparative example. EXAMPLES

[0090] (Sample preparation) Next, the drills 100 according to Samples 3 to 7 were prepared. The drills 100 according to Samples 3, 6, and 7 were used as comparative examples. The drills 100 according to Samples 4 and 5 were used as examples.

[0091] The first distance E1 was changed in the drills 100 according to Samples 3 to 7. In the drills 100 according to Samples 3 to 7, the first distance E1 was set to be 0 mm or more and 0.10 mm or less. The first value was set to be 0% or more and 113% or less.

[0092] In the drills 100 according to Samples 3 to 7, the cutting edge diameter D was set to 2 mm. The length of each of the first chip discharge surface 19 and the second chip discharge surface 29 was set to 5 times the cutting edge diameter D. The second distance E2 was set to 0.08 mm. The rake angle was set to -12°.

[0093] (Evaluation method) Next, the biting shape was evaluated using the drills 100 according to Samples 3 to 7. Specifically, holes were formed in the workpiece using the drills 100 according to Samples 3 to 7. The depth of the holes was about 0.3 mm. The shape of the trace of the contact of the drill 100 (biting shape) was confirmed at the portion of the workpiece where the drill 100 contacted. If the biting ability of the drill 100 is good, the biting shape will be circular. In the evaluation of the biting shape, the workpiece was SCM415. The cutting speed was 38 m / min. The feed rate was 0.04 mm / revolution.

[0094] The hole diameter enlargement allowance and the hole position accuracy were evaluated using the drills 100 according to Samples 3 to 7. Specifically, the hole diameter enlargement allowance and the hole position accuracy were each measured using the above-mentioned evaluation method.

[0095] The number of holes machined by each of the drills 100 according to Sample 3 to Sample 7 was evaluated. Specifically, a plurality of holes were formed in the workpiece using the drills 100 according to Sample 3 to Sample 7. The maximum number of holes was 600. In cases where damage to the drill 100 was confirmed, the number of holes formed until damage was confirmed was measured as the number of holes machined. In cases where damage to the drill 100 was not confirmed, the number of holes machined was 600. In the evaluation of the number of holes machined, the workpiece was SCM415. The hole depth was 6 mm. The cutting speed was 38 m / min. The feed rate was 0.04 mm / revolution.

[0096] (Evaluation Results)

[0097] [Table 2]

[0098] Table 2 shows the biting shape, hole diameter enlargement, hole position, and number of holes machined for Samples 3 to 7. As shown in Table 2, when the first distance E1 was 0.03 mm or less (Samples 3 to 5), the biting shape was circular. When the first distance E1 was 0.05 mm or more (Samples 6 and 7), the biting shape was irregular. Specifically, the biting shape was triangular.

[0099] As shown in Table 2, when the first distance E1 was 0.03 mm or less (samples 3 to 5), the hole diameter enlargement was 0.018 mm or less. The hole position deviation was 0.016 mm or less. When the first distance E1 was 0.05 mm or more (samples 6 and 7), the hole diameter enlargement was 0.028 mm or more. The hole position deviation was 0.021 mm or more.

[0100] As shown in Table 2, when the first distance E1 was 0 mm (sample 3), the number of drilled holes was 126. Specifically, in sample 3, chipping was observed around the front end 1 of the drill 100. When the first distance E1 was greater than 0 mm (samples 4 to 7), the number of drilled holes was 600. In other words, no breakage of the drill 100 was observed in samples 4 to 7.

[0101] From the above results, it was confirmed that the drill 100 according to the embodiment can improve the biting ability, can reduce the enlargement of the hole diameter and the hole position deviation, and can improve the strength of the drill 100 compared to the drill 100 according to the comparative example. EXAMPLES

[0102] (Sample preparation) Next, the drills 100 according to Samples 8 to 13 were prepared. The drills 100 according to Samples 8 and 13 were used as comparative examples. The drills 100 according to Samples 9 to 12 were used as examples.

[0103] The second distance E2 was changed in the drills 100 according to Sample 8 to Sample 13. In the drills 100 according to Sample 8 to Sample 13, the second distance E2 was set to be 0.030 mm or more and 0.110 mm or less. The first value was set to be 20% or more and 74% or less.

[0104] In the drills 100 according to Samples 8 to 13, the cutting edge diameter D was set to 2 mm. The length of each of the first chip discharge surface 19 and the second chip discharge surface 29 was set to 5 times the cutting edge diameter D. The first distance E1 was set to 0.02 mm. The rake angle was set to -12°.

[0105] (Evaluation method) Next, the hole diameter enlargement allowance, the hole position accuracy, and the number of drilled holes were evaluated using the drills 100 according to Samples 8 to 13. Specifically, the hole diameter enlargement allowance, the hole position accuracy, and the number of drilled holes were measured using the above-mentioned evaluation method.

[0106] (Evaluation Results)

[0107] [Table 3]

[0108] Table 3 shows the hole diameter enlargement allowance, hole position accuracy, and number of machined holes for Samples 8 to 13. FIG. 13 shows the hole diameter enlargement allowance for Samples 8 to 13. In FIG. 13, the horizontal axis shows the second distance E2. The vertical axis shows the hole diameter enlargement allowance. In FIG. 13, the point indicated by P8 shows the hole diameter enlargement allowance for Sample 8. Similarly, the points indicated by P9 to P13 show the hole diameter enlargement allowance for Samples 9 to 13.

[0109] FIG. 14 shows the hole position accuracy in Sample 8 to Sample 13. In FIG. 14, the horizontal axis shows the second distance E2. The vertical axis shows the hole position accuracy. In FIG. 14, a point indicated by P8 shows the hole position accuracy in Sample 8. Similarly, points indicated by P9 to P13 show the hole position accuracy in Sample 9 to Sample 13.

[0110] As shown in Table 3, Figures 13 and 14, when the second distance E2 was 0.100 mm or less (samples 8 to 12), the hole diameter enlargement was 0.016 mm or less. The hole position deviation was 0.028 mm or less. When the second distance E2 was 0.110 mm or more (sample 13), the hole diameter enlargement was 0.019 mm. The hole position deviation was 0.035 mm.

[0111] As shown in Table 3, when the second distance E2 was 0.03 mm (sample 8), the number of drilled holes was 180. Specifically, breakage of the drill 100 was confirmed in sample 8. When the second distance E2 was 0.04 mm or more (samples 9 to 13), the number of drilled holes was 600. In other words, no breakage of the drill 100 was confirmed in samples 9 to 13.

[0112] From the above results, it was confirmed that the drill 100 according to the embodiment can reduce the hole diameter enlargement amount and the hole position deviation, and can improve the strength of the drill 100, compared to the drill 100 according to the comparative example. EXAMPLES

[0113] (Sample preparation) Next, the drills 100 according to Samples 14 to 20 were prepared. The drills 100 according to Samples 14, 15, and 20 were used as comparative examples. The drills 100 according to Samples 16 to 19 were used as examples.

[0114] In the drills 100 according to Samples 14 to 20, the value (first value) obtained by dividing the length of the third chisel region 43 by the second distance E2 was changed. In the drills 100 according to Samples 14 to 20, the first value was set to be 15% or more and 75% or less. The second distance E2 was set to be 0.030 mm or more and 0.150 mm or less.

[0115] In the drills 100 according to Samples 14 to 20, the cutting edge diameter D was set to 2 mm. The length of each of the first chip discharge surface 19 and the second chip discharge surface 29 was set to 5 times the cutting edge diameter D. The first distance E1 was set to 0.02 mm. The rake angle was set to -12°.

[0116] (Evaluation method) Next, the hole diameter enlargement allowance, the hole position accuracy, and the number of drilled holes were evaluated using the drills 100 according to Samples 14 to 20. Specifically, the hole diameter enlargement allowance, the hole position accuracy, and the number of drilled holes were measured using the above-mentioned evaluation method.

[0117] (Evaluation Results)

[0118] [Table 4]

[0119] Table 4 shows the hole diameter enlargement allowance, hole position accuracy, and number of machined holes for Samples 14 to 20. FIG. 15 shows the hole diameter enlargement allowance for Samples 14 to 20. In FIG. 15, the horizontal axis shows the first value. The vertical axis shows the hole diameter enlargement allowance. In FIG. 15, the point indicated by P14 shows the hole diameter enlargement allowance for Sample 14. Similarly, the points indicated by P15 to P20 show the hole diameter enlargement allowance for Samples 15 to 20.

[0120] FIG. 16 shows the hole position degree in Samples 14 to 20. In FIG. 16, the horizontal axis shows the first value. The vertical axis shows the hole position degree. In FIG. 16, the point indicated by P14 shows the hole position degree in Sample 14. Similarly, each of the points indicated by P15 to P20 shows the hole position degree in Samples 15 to 20.

[0121] As shown in Table 4 and FIG. 15, the hole diameter enlargement when the first value was 23% or more and 65% or less (Samples 15 to 19) was smaller than the hole diameter enlargement when the first value was less than 23% or more than 65% (Samples 14 and Sample 20). As shown in Table 4 and FIG. 16, the hole location degree when the first value was 23% or more and 55% or less (Samples 16 to 19) was smaller than the hole location degree when the first value was less than 23% or more than 55% (Samples 14, Sample 15, and Sample 20).

[0122] From the above results, it was confirmed that the drill 100 according to the embodiment can reduce the hole position error compared to the drill 100 according to the comparative example. EXAMPLES

[0123] (Sample preparation) Next, the drills 100 according to Samples 21 to 27 were prepared. The drills 100 according to Samples 21 and 27 were used as comparative examples. The drills 100 according to Samples 22 to 26 were used as examples.

[0124] The rake angle was changed in the drills 100 according to Samples 21 to 27. In the drills 100 according to Samples 21 to 27, the rake angle was set to be −24° or more and −6° or less.

[0125] In the drills 100 according to Samples 21 to 27, the cutting edge diameter D was set to 2 mm. The length of each of the first chip discharge surface 19 and the second chip discharge surface 29 was set to 5 times the cutting edge diameter D. The first distance E1 was set to 0.02 mm. The second distance E2 was set to 0.08 mm. The first value was set to 28%.

[0126] (Evaluation method) Next, the burr height H (see FIG. 11) was measured after drilling 300 holes using the drills 100 according to Samples 21 to 27. Specifically, the distance between the point on the burr 97 that was farthest from the surface of the workpiece 99 in the machining direction of the drill 100 and the surface of the workpiece 99 was measured as the burr height H. In the evaluation of the burr height H, the workpiece was SCM415. The hole depth was 6 mm. The cutting speed was 38 m / min. The feed rate was 0.04 mm / rev.

[0127] The drills 100 according to Samples 21 to 27 were evaluated for the enlargement of the hole diameter, the hole position accuracy, and the number of drilled holes. Specifically, the enlargement of the hole diameter, the hole position accuracy, and the number of drilled holes were measured using the above-mentioned evaluation method.

[0128] (Evaluation Results)

[0129] [Table 5]

[0130] Table 5 shows the hole diameter enlargement amount, hole position accuracy, burr height H, and number of drilled holes for the drill 100 of Samples 21 to 27.

[0131] As shown in Table 5, the burr height H when the rake angle was greater than -18° and less than -9° (samples 22 to 26) was smaller than the burr height H when the rake angle was smaller than -18° or greater than -9° (samples 21 and 27).

[0132] From the above results, it was confirmed that the drill 100 according to the embodiment can reduce the burr height H, compared to the drill 100 according to the comparative example.

[0133] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims, not the above description, and is intended to include the meaning equivalent to the claims and all modifications within the scope. [Explanation of symbols]

[0134] 1 front end, 2 rear end, 7 shank, 9 outer peripheral surface, 10 first flank, 11 first front flank portion, 12 first rear flank portion, 13 first thinning surface, 15 first thinning ridge, 16 first outer peripheral surface portion, 17 first leading edge, 18 first marginal surface, 19 first chip ejection surface, 20 second flank, 21 second front flank portion, 22 second rear flank portion, 23 second thinning surface, 25 second thinning ridge, 26 second outer peripheral surface portion, 27 second leading edge, 28 second marginal surface, 29 second chip ejection surface, 41 first chisel region, 42 second chisel region, 43 third chisel region, 51 first cutting edge, 52 second cutting edge, 61 first thinning cutting edge, 62 second thinning cutting edge, 71 first ridge, 72 second ridge, 73 3rd ridge, 74 4th ridge, 75 5th ridge, 76 6th ridge, 81 1st end, 82 2nd end, 91 1st outermost edge, 92 2nd outermost edge, 93 1st chip groove, 94 2nd chip groove, 97 burr, 98 remainder, 99 workpiece, 100 drill, 101 axial direction, 102 side view direction, 111 1st virtual line, 112 2nd virtual line, 113 3rd virtual line, 114 4th virtual line, 115 5th virtual line, 116 6th virtual line, 117 7th virtual line, 118 8th virtual line, 119 9th virtual line, 121 1st point, 122 2nd point, 123 3rd point, 124 4th point, 131 1st tangent, 132 2nd tangent, A machining direction, CS1 1st cross section, CS2 2nd cross section, D Blade diameter, E1 1st distance (distance), E2 2nd distance (shortest distance), H height, L1 1st length, L2 2nd length, L3 3rd length, X axis, θ1 1st angle, θ2 2nd angle, θ3 3rd angle, θ4 4th angle, θ5 5th angle, θ6 6th angle, θ11 1st rake angle, θ12 2nd rake angle.

Claims

1. A drill that rotates about an axis, A first flank surface; a first thinning surface provided rearward in a rotational direction with respect to the first flank surface; a second flank surface provided rearward in the rotational direction with respect to the first thinning surface; a second thinning surface provided rearward in the rotational direction relative to the second flank surface, The first flank surface is A first front clearance portion; a first rear flank portion connected to the first front flank portion, inclined relative to the first front flank portion, and provided rearward in the rotation direction relative to the first front flank portion, The second flank surface is A second front clearance portion; a second rear flank portion connected to the second front flank portion, inclined relative to the second front flank portion, and provided rearward in the rotation direction relative to the second front flank portion, the second front flank portion is continuous with each of the first front flank portion and the first rear flank portion, the second rear flank portion is continuous with the first front flank portion, When a ridge line between the first front flank portion and the first rear flank portion is defined as a first ridge line, and a ridge line between the second front flank portion and the second rear flank portion is defined as a second ridge line, When viewed in an axial direction from the front end to the rear end of the drill, a distance between the first ridge line and the second ridge line in a direction perpendicular to the first ridge line is greater than 0 mm and is not greater than 0.03 mm; a ridgeline between the first front flank portion and the second rear flank portion defines a first chisel region; a ridgeline between the first rear flank portion and the second front flank portion defines a second chisel region; a ridgeline between the first front flank portion and the second front flank portion defines a third chisel region that is continuous with each of the first chisel region and the second chisel region, the third chisel region is located at the front end; a ridge line between the first thinning surface and the first flank surface and a ridge line between the first thinning surface and the second flank surface constitute a first thinning ridge line, a ridge line between the second thinning surface and the first flank surface and a ridge line between the second thinning surface and the second flank surface constitute a second thinning ridge line, A drill, wherein a shortest distance between the first thinning ridge line and the second thinning ridge line in a direction perpendicular to the first ridge line as viewed in the axial direction is 0.04 mm or more and 0.10 mm or less.

2. The drill of claim 1 , wherein a length of the third chisel region in the axial direction is greater than or equal to 23% and less than or equal to 55% of the shortest distance.

3. The drill according to claim 1 or 2, wherein the drill bit diameter is 3 mm or less.

4. a first chip discharge surface that is spirally provided around the axis and is connected to the first flank surface; a second chip discharge surface that is spirally provided around the axis and is connected to the second flank surface, Each of the first chip discharge surface and the second chip discharge surface defines a chip discharge groove, The drill according to claim 3 , wherein a length of each of the first chip discharge surface and the second chip discharge surface in the axial direction is equal to or greater than two times and equal to or less than ten times the cutting edge diameter.

5. a ridge line between the first flank surface and the first chip discharge surface constitutes a first cutting edge, a ridge line between the second flank surface and the second chip discharge surface constitutes a second cutting edge, At the outermost peripheral end of the first cutting edge, a rake angle of the first cutting edge in the radial direction of the drill is −18° or more and −9° or less, The drill according to claim 4, wherein a rake angle of the second cutting edge in the radial direction at an outermost peripheral end of the second cutting edge is greater than or equal to −18° and less than or equal to −9°.

6. 3. The drill according to claim 1, wherein, as viewed in the axial direction, an angle between the first ridge line and the third chisel region is larger than an angle between the first ridge line and the first chisel region, and is also larger than an angle between the first ridge line and the second chisel region.

7. The drill according to claim 1 or 2, wherein an angle between the first ridge line and the third chisel region is equal to or greater than 50° and equal to or less than 80° when viewed in the axial direction.

8. When viewed in the axial direction, an angle between the first ridge line and the first chisel region is greater than or equal to 40° and less than or equal to 60°, The drill according to claim 1 or 2, wherein an angle between the first ridge line and the second chisel region is greater than or equal to 40° and less than or equal to 60° when viewed in the axial direction.