Drill bit

Abstract

The first flank surface includes a first front flank surface portion and a first rear flank surface portion. The second flank surface includes a second front flank surface portion and a second rear flank surface portion. The ridge line between the first front flank portion and the first rear flank portion is a first ridge line. The ridge line between the second front flank portion and the second rear flank portion is a second ridge line. When viewed in the axial direction, the distance between the first ridge line and the second ridge line in the direction perpendicular to the first ridge line is greater than 0 mm and 0.03 mm or less. The ridge line of the first grinding face and the first rear tool face and the ridge line of the first grinding face and the second rear tool face form a first grinding ridge line. And the ridge line of the second grinding surface and the first rear cutter surface and the ridge line of the second grinding surface and the second rear cutter surface form a second grinding ridge line. The shortest distance between the first polishing ridge line and the second polishing ridge line in the direction perpendicular to the first ridge line is 0.04 mm or more and 0.10 mm or less when viewed in the axial direction.

Description

Technical Field

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

[0002] A drill bit having two front flank faces is described in International Publication No. 2017 / 179689 (Patent Document 1). The front flank face includes a first front flank face and a second front flank face. When viewed from the front end side in the axial direction, the intersection ridge line between the first front flank face and the second front flank face is linear. When viewed from the front end side in the axial direction, among the two front flank faces, the interval between the extension line of the intersection ridge line in one front flank face toward the other front flank face and the intersection ridge line is in the range of 0.04 mm to 0.08 mm.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: International Publication No. 2017 / 179689 Summary of the Invention

[0006] The drill bit involved in the present disclosure is a drill bit that rotates around an axis, and includes a first flank face, a first grinding face, a second flank face, and a second grinding face. The first grinding face is disposed behind the first flank face in the rotational direction. The second flank face is disposed behind the first grinding face in the rotational direction. The second grinding face is disposed behind the second flank face in the rotational direction. The first flank face includes a first front flank face portion and a first rear flank face portion. The first rear flank face portion is connected to the first front flank face portion. The first rear flank face portion is inclined with respect to the first front flank face portion. The first rear flank face portion is disposed behind the first front flank face portion in the rotational direction. The second flank face includes a second front flank face portion and a second rear flank face portion. The second rear flank face portion is connected to the second front flank face portion. The second rear flank face portion is inclined with respect to the second front flank face portion. The second rear flank face portion is disposed behind the second front flank face portion in the rotational direction. The second front flank face portion is connected to the first front flank face portion and the first rear flank face portion respectively. The second rear flank face portion is connected to the first front flank face portion. The ridge line between the first front flank face portion and the first rear flank face portion is defined as the first ridge line. The ridge line between the second front flank face portion and the second rear flank face portion is defined as the second ridge line. When viewed in the axial direction from the front end to the rear end of the drill bit, the distance between the first ridge line and the second ridge line in the direction perpendicular to the first ridge line is greater than 0 mm and 0.03 mm or less. The ridge line between the first front flank face portion and the second rear flank face portion constitutes the first chisel edge region. The ridge line between the first rear flank face portion and the second front flank face portion constitutes the second chisel edge region. The ridge line between the first front flank face portion and the second front flank face portion constitutes the third chisel edge region. The third chisel edge region is connected to the first chisel edge region and the second chisel edge region respectively. The third chisel edge region is disposed at the front end. The ridge line between the first grinding face and the first flank face and the ridge line between the first grinding face and the second flank face constitute the first grinding ridge line. The ridge line between the second grinding face and the first flank face and the ridge line between the second grinding face and the second flank face constitute the second grinding ridge line. When viewed in the axial direction, the shortest distance between the first grinding ridge line and the second grinding ridge line in the direction perpendicular to the first ridge line is 0.04 mm or more and 0.10 mm or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a top view schematic diagram showing the configuration of the drill bit according to the present embodiment.

[0008] Figure 2 is a perspective view schematic diagram showing the configuration of the drill bit according to the present embodiment.

[0009] Figure 3 is a front view schematic diagram showing the configuration of the drill bit according to the present embodiment.

[0010] Figure 4 is showingFigure 3 Enlarged front view schematic diagram of Region IV.

[0011] Figure 5 It is Figure 4 Cross-sectional schematic diagram along line V-V.

[0012] Figure 6 It is Figure 3 Cross-sectional schematic diagram along line VI-VI.

[0013] Figure 7 It represents Figure 6 Enlarged schematic diagram of Region VII.

[0014] Figure 8 It represents Figure 3 Enlarged schematic diagram of Region VIII.

[0015] Figure 9 It represents Figure 3 Enlarged schematic diagram of Region IX.

[0016] Figure 10 Cross-sectional schematic diagram showing the state before the drill bit penetrates the workpiece to be cut.

[0017] Figure 11 Cross-sectional schematic diagram showing the state where a hole is formed in the workpiece to be cut using a drill bit.

[0018] Figure 12 Enlarged front view schematic diagram showing the structure of the drill bit related to Sample 1.

[0019] Figure 13 Represents the amount of increase in the hole diameter in Samples 8 to 13.

[0020] Figure 14 Represents the hole position tolerance in Samples 8 to 13.

[0021] Figure 15 Represents the amount of increase in the hole diameter in Samples 14 to 20.

[0022] Figure 16 Represents the hole position tolerance in Samples 14 to 20. Detailed implementation mode

[0023] [Problems to be solved by the present disclosure]

[0024] The object of the present disclosure is to provide a drill bit that can improve the accuracy of hole machining and can improve the strength of the drill bit.

[0025] [Effects of the present disclosure]

[0026] According to the present disclosure, it is possible to provide a drill bit that can improve the accuracy of hole machining and can improve the strength of the drill bit.

[0027] [Summary of Embodiments]

[0028] First, a summary of the embodiments of the present disclosure will be described.

[0029] (1) The drill bit 100 involved in the present disclosure is a drill bit 100 that rotates around the axis X, and includes a first flank 10, a first grinding surface 13, a second flank 20, and a second grinding surface 23. The first grinding surface 13 is disposed behind the first flank 10 in the rotational direction. The second flank 20 is disposed behind the first grinding surface 13 in the rotational direction. The second grinding surface 23 is disposed behind the second flank 20 in the rotational direction. 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 connected to 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 disposed behind the first front flank portion 11 in the rotational direction. 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 connected to 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 disposed behind the second front flank portion 21 in the rotational direction. The second front flank portion 21 is respectively connected to the first front flank portion 11 and the first rear flank portion 12. The second rear flank portion 22 is connected to 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 the first ridge line 71. The ridge line between the second front flank portion 21 and the second rear flank portion 22 is defined as the second ridge line 72. When observing in the axial direction 101 from the front end 1 to the rear end 2 of the drill bit 100, the distance E1 between the first ridge line 71 and the second ridge line 72 in the direction perpendicular to the first ridge line 71 is greater than 0 mm and is 0.03 mm or less. The ridge line between the first front flank portion 11 and the second rear flank portion 22 constitutes the first chisel edge area 41. The ridge line between the first rear flank portion 12 and the second front flank portion 21 constitutes the second chisel edge area 42. The ridge line between the first front flank portion 11 and the second front flank portion 21 constitutes the third chisel edge area 43. The third chisel edge area 43 is respectively connected to the first chisel edge area 41 and the second chisel edge area 42. The third chisel edge area 43 is disposed at the front end 1. The ridge line between the first grinding surface 13 and the first flank 10, and the ridge line between the first grinding surface 13 and the second flank 20 constitute the first grinding ridge line 15. The ridge line between the second grinding surface 23 and the first flank 10, and the ridge line between the second grinding surface 23 and the second flank 20 constitute the second grinding ridge line 25. When observing in the axial direction 101, the shortest distance E2 between the first grinding ridge line 15 and the second grinding ridge line 25 in the direction perpendicular to the first ridge line 71 is 0.04 mm or more and 0.10 mm or less.

[0030] (2) According to the drill bit 100 described in the above (1), when observing in the axial direction 101, the length L3 of the third chisel edge area 43 can be 23% or more and 55% or less of the shortest distance E2.

[0031] (3) According to the drill bit 100 described in the above (1) or (2), the cutting edge diameter D of the drill bit 100 can be 3 mm or less.

[0032] (4) The drill bit 100 described in the above (3) can be provided with a first chip fluting surface 19 and a second chip fluting surface 29. The first chip fluting surface 19 can be arranged in a spiral shape around the axis X. The first chip fluting surface 19 can be connected to the first flank 10. The second chip fluting surface 29 can be arranged in a spiral shape around the axis X. The second chip fluting surface 29 can be connected to the second flank 20. The first chip fluting surface 19 and the second chip fluting surface 29 respectively form chip fluting grooves. The respective lengths of the first chip fluting surface 19 and the second chip fluting surface 29 in the axial direction 101 can be 2 times or more and 10 times or less of the cutting edge diameter D.

[0033] (5) According to the drill bit 100 described in the above (4), the ridge line between the first flank 10 and the first chip fluting surface 19 can form a first cutting edge 51. The ridge line between the second flank 20 and the second chip fluting surface 29 can form a second cutting edge 52. At the outermost peripheral 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 bit 100 can be -18° or more and -9° or less. At the outermost peripheral 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 bit 100 can be -18° or more and -9° or less.

[0034] (6) According to the drill bit 100 described in any one of the above (1) to (5), when observed in the axial direction 101, the angle θ3 formed by the first ridge line 71 and the third chisel edge region 43 can be larger than the angle θ1 formed by the first ridge line 71 and the first chisel edge region 41, and larger than the angle θ2 formed by the first ridge line 71 and the second chisel edge region 42.

[0035] (7) According to the drill bit 100 described in any one of the above (1) to (6), when observed in the axial direction 101, the angle θ3 formed by the first ridge line 71 and the third chisel edge region 43 can be 50° or more and 80° or less.

[0036] (8) According to the drill bit 100 described in any one of the above (1) to (7), when observed in the axial direction 101, the angle θ1 formed by the first ridge line 71 and the first chisel edge region 41 can be 40° or more and 60° or less. When observed in the axial direction 101, the angle formed by the first ridge line 71 and the second chisel edge region 42 can be 40° or more and 60° or less.

[0037] [Detailed content of the embodiment]

[0038] Hereinafter, the details of the embodiments of the present disclosure (hereinafter also referred to as the present embodiment) will be described based on the accompanying drawings. It should be noted that the same or corresponding parts are denoted by the same reference numerals in the following drawings and will not be described repeatedly.

[0039] First, the configuration of the drill bit 100 according to the present embodiment will be described. Figure 1 It is a top view schematic diagram showing the configuration of the drill bit 100 according to the present embodiment. As Figure 1 shown, the drill bit 100 according to the present embodiment mainly includes a front end 1, a rear end 2, a first cutting edge 51, a first chip flute surface 19, a second chip flute surface 29, an outer peripheral surface 9, a shank 7, a second flank 20, and a second relief surface 23. The drill bit 100 according to the present embodiment is, for example, a drill bit for metal processing.

[0040] As Figure 1 shown, the first chip flute surface 19 is provided in a spiral shape around the axis X. The second chip flute surface 29 is provided in a spiral shape around the axis X. The first chip flute surface 19 and the second chip flute surface 29 respectively form chip flutes. Specifically, the first chip flute surface 19 forms a first chip flute 93. The second chip flute surface 29 forms a second chip flute 94.

[0041] The outer peripheral surface 9 is connected to the first chip flute surface 19 and the second chip flute surface 29 respectively. 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 bit 100. The second relief surface 23 is connected to the second flank 20, the second outer peripheral surface portion 26, and the first chip flute surface 19 respectively.

[0042] The front end 1 of the drill bit 100 is the portion facing the workpiece to be cut. The rear end 2 of the drill bit 100 is the portion facing a tool spindle (not shown) that rotates the drill bit 100. The shank 7 is the portion mounted on the tool spindle. The axis X passes through the front end 1 and the rear end 2. The drill bit 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 the direction along the axis X. The direction perpendicular to the axial direction 101 and toward the axis X is defined as the radially inner side. Conversely, the direction perpendicular to the axial direction 101 and away from the axis X is defined as the radially outer side.

[0043] As Figure 1 shown, the length of the first chip flute 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 flute 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.

[0044] Figure 2 is a perspective view showing the configuration of the drill bit 100 according to the present embodiment. As Figure 2 shown, the drill bit 100 according to the present embodiment has a first flank face 10, a first relief face 13, and a second cutting edge 52. The first flank face 10 is connected to the first chip flute face 19 (refer to Figure 1 ) and the first outer peripheral face 16. The ridge line between the first flank face 10 and the first chip flute face 19 forms the first cutting edge 51. The first chip flute face 19 near the first cutting edge 51 functions as a rake face.

[0045] The first relief face 13 is connected to the first flank face 10, the first outer peripheral face 16, and the second chip flute face 29, respectively. The second flank face 20 is connected to the first flank face 10, the first relief face 13, and the second chip flute face 29, respectively. The ridge line between the second flank face 20 and the second chip flute face 29 forms the second cutting edge 52. The second chip flute face 29 near the second cutting edge 52 functions as a rake face.

[0046] As Figure 2 shown, the first flank face 10 has a first front flank face portion 11 and a first rear flank face portion 12. The first front flank face portion 11 is, for example, planar. The first front flank face portion 11 is connected to the first cutting edge 51. From another perspective, the ridge line between the first front flank face portion 11 and the first chip flute face 19 (refer to Figure 1 ) forms the first cutting edge 51. The first rear flank face portion 12 is, for example, planar. The first rear flank face portion 12 is connected to the first front flank face portion 11. The ridge line between the first front flank face portion 11 and the first rear flank face portion 12 is defined as the first ridge line 71. The first ridge line 71 is, for example, linear.

[0047] The second flank face 20 has a second front flank face portion 21 and a second rear flank face portion 22. The second front flank face portion 21 is, for example, planar. The second front flank face portion 21 is connected to the second cutting edge 52. The second front flank face portion 21 is, for example, planar. The second rear flank face portion 22 is connected to the second front flank face portion 21. The ridge line between the second front flank face portion 21 and the second rear flank face portion 22 is defined as the second ridge line 72. The second ridge line 72 is, for example, linear.

[0048] As Figure 2 shown, the outer peripheral face 9 has a first land face 18 and a second land face 28. From another perspective, the drill bit 100 has only a pair of land faces. The first land face 18 is connected to the first outer peripheral face 16 and the first chip flute face 19, respectively. The ridge line between the first land face 18 and the first chip flute face 19 forms the first leading edge 17.

[0049] The second land face 28 is respectively connected to the second outer peripheral face 26, the second flank face 20, and the second chip flute face 29. The ridge line between the second land face 28 and the second chip flute face 29 forms the second leading edge 27.

[0050] The first outer peripheral face 16 is respectively connected to the first flank face 10, the first grinding face 13, and the second chip flute face 29. The second outer peripheral face 26 is respectively connected to the second flank face 20, the second grinding face 23, and the first chip flute face 19.

[0051] Figure 3 It is a front view schematic diagram showing the structure of the drill bit 100 according to the present embodiment. Figure 3 The shown front view schematic diagram shows the structure of the drill bit 100 observed along the axis direction 101. For ease of explanation, in Figure 3 , the shank 7 is not shown. As Figure 3 shown, the first grinding face 13 is provided behind the first flank face 10 in the rotational direction. The second flank face 20 is provided behind the first grinding face 13 in the rotational direction. The second grinding face 23 is provided behind the second flank face 20 in the rotational direction. The first flank face 10 is provided behind the second grinding face 23 in the rotational direction.

[0052] As Figure 3 shown, the drill bit 100 can be substantially bilaterally symmetric with respect to the axis X. The shape of the first flank face 10 after rotating 180° around the axis X is substantially the same as the shape of the second flank face 20. Similarly, the shape of the first grinding face 13 after rotating 180° around the axis X can also be substantially the same as the shape of the second grinding face 23. Observed along the axis direction 101, the second ridge line 72 is substantially parallel to the first ridge line 71.

[0053] The first front flank face portion 11 is connected to the second grinding face 23. The ridge line between the first front flank face portion 11 and the second grinding face 23 forms the first grinding cutting edge 61. The first grinding cutting edge 61 is connected to the first cutting edge 51. The first grinding cutting edge 61 is provided radially inward with respect to the first cutting edge 51. The first front flank face portion 11 is separated from the first grinding face 13.

[0054] The first rear flank face portion 12 is provided behind the first front flank face portion 11 in the rotational direction. The first rear flank face portion 12 is connected to the first grinding face 13. The ridge line between the first rear flank face portion 12 and the first grinding face 13 is defined as the third ridge line 73. The first rear flank face portion 12 is separated from the second grinding face 23.

[0055] The second front flank face 21 is connected to the first grinding face 13. The ridge line between the second front flank face 21 and the first grinding face 13 forms a second grinding cutting edge 62. The second grinding cutting edge 62 is connected to the second cutting edge 52. The second grinding cutting edge 62 is disposed radially inward relative to the second cutting edge 52. The second front flank face 21 is separated from the second grinding face 23.

[0056] The second rear flank face 22 is disposed behind the second front flank face 21 in the rotational direction. The second rear flank face 22 is connected to the second grinding face 23. The ridge line between the second rear flank face 22 and the second grinding face 23 is defined as a fourth ridge line 74. The second rear flank face 22 is separated from the first grinding face 13.

[0057] As Figure 3 shown, when observed along the axial direction 101, the first outer peripheral face 16 is disposed radially outward relative to the first grinding face 13. When observed along the axial direction 101, the second outer peripheral face 26 is disposed radially outward relative to the second grinding face 23.

[0058] When observed along the axial direction 101, the first cutting edge 51 is curved. Specifically, the first cutting edge 51 may also be arc-shaped. When observed along the axial direction 101, the first cutting edge 51 is recessed rearward in the rotational direction. When observed along the axial direction 101, the second cutting edge 52 is curved. Specifically, the second cutting edge 52 may also be arc-shaped. When observed along the axial direction 101, the second cutting edge 52 is recessed rearward in the rotational direction.

[0059] The outermost peripheral end of the first cutting edge 51 is defined as a first outermost peripheral end 91. The outermost peripheral end of the second cutting edge 52 is defined as a second outermost peripheral end 92. When observed along the axial direction 101, the first outermost peripheral end 91 and the second outermost peripheral end 92 may be arranged in a straight line with the axis X. When observed along the axial direction 101, the distance between the first outermost peripheral end 91 and the axis X and the distance between the second outermost peripheral end 92 and the axis X are substantially the same.

[0060] When observed along the axial direction 101, the distance between the first outermost peripheral end 91 and the second outermost peripheral end 92 is defined as 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. There is no particular limitation on the upper limit of the cutting edge diameter D. For example, it may be 2 mm or less, or it may be 1 mm or less. There is no particular limitation on the lower limit of the cutting edge diameter D. For example, it may be 0.1 mm or more, or it may be 0.5 mm or more.

[0061] The length of the first chip removal surface 19 in the axial direction 101 (the first length L1) is, for example, 2 times or more and 10 times or less the cutting edge diameter D. The first length L1 can, for example, also be 3 times or more and 5 times or less the cutting edge diameter D. There is no particular limitation on the lower limit of the first length L1. For example, it can be 2.5 times or more the cutting edge diameter D, or it can be 4 times or more the cutting edge diameter D. There is no particular limitation on the upper limit of the first length L1. For example, it can be 8 times or less the cutting edge diameter D, or it can be 6 times or less the cutting edge diameter D.

[0062] The length of the second chip removal surface 29 in the axial direction 101 (the second length L2) is, for example, 2 times or more and 10 times or less the cutting edge diameter D. The second length L2 can, for example, also be 3 times or more and 5 times or less the cutting edge diameter D. There is no particular limitation on the lower limit of the second length L2. For example, it can be 2.5 times or more the cutting edge diameter D, or it can be 4 times or more the cutting edge diameter D. There is no particular limitation on the upper limit of the second length L2. For example, it can be 8 times or less the cutting edge diameter D, or it can be 6 times or less the cutting edge diameter D.

[0063] As Figure 3 shown, the ridge line between the first chip removal surface 19 and the second grinding surface 23 is defined as the fifth ridge line 75. When observing in the axial direction 101, the fifth ridge line 75 is recessed toward the front in the rotation direction. When observing in the axial direction 101, at the first point 121 on the first grinding cutting edge 61, the fifth ridge line 75 overlaps with the first grinding cutting edge 61. From another perspective, when observing in the axial direction 101, the fifth ridge line 75 extends from the first point 121 toward the front in the rotation direction relative to the first grinding cutting edge 61. When observing in the axial direction 101, a straight line passing through the first point 121 and parallel to the first ridge line 71 is defined as the first imaginary line 111. When observing in the axial direction 101, the first cutting edge 51 is disposed in the rotation direction front relative to the first imaginary line 111.

[0064] As Figure 3 shown, the ridge line between the second chip removal surface 29 and the first grinding surface 13 is defined as the sixth ridge line 76. When observing in the axial direction 101, the sixth ridge line 76 is recessed toward the front in the rotation direction. When observing in the axial direction 101, at the second point 122 on the second grinding cutting edge 62, the sixth ridge line 76 overlaps with the second grinding cutting edge 62. From another perspective, when observing in the axial direction 101, the sixth ridge line 76 extends from the second point 122 toward the front in the rotation direction relative to the second grinding cutting edge 62. When observing in the axial direction 101, a straight line passing through the second point 122 and parallel to the first ridge line 71 is defined as the second imaginary line 112. When observing in the axial direction 101, the second cutting edge 52 is disposed in the rotation direction front relative to the second imaginary line 112. As Figure 3 shown, the direction toward the radially inner side and parallel to the first ridge line 71 when observing in the axial direction 101 is defined as the side view direction 102.

[0065] Figure 4 is an enlarged front elevation view showing Figure 3 region IV. As Figure 4 shown, the second front flank 21 is connected to the first front flank 11 and the first rear flank 12 respectively. The second rear flank 22 is connected to the first front flank 11. The second rear flank 22 is separated from the first rear flank 12.

[0066] The ridge line of the first front flank 11 and the second rear flank 22 forms a first chisel edge region 41. When observed along the axial direction 101, the first chisel edge region 41 is, for example, linear. The ridge line of the first rear flank 12 and the second front flank 21 forms a second chisel edge region 42. When observed along the axial direction 101, the second chisel edge region 42 is, for example, linear. The second chisel edge region 42 is separated from the first chisel edge region 41.

[0067] The ridge line of the first front flank 11 and the second front flank 21 forms a third chisel edge region 43. The third chisel edge region 43 may intersect the axis X. The third chisel edge region 43 has a first end 81 and a second end 82. At the first end 81, the third chisel edge region 43 is connected to the first chisel edge region 41 and the second ridge line 72 respectively. The second end 82 is located opposite to the first end 81. At the second end 82, the third chisel edge region 43 is connected to the second chisel edge region 42 and the first ridge line 71 respectively. The third chisel edge region 43 is disposed radially inward with respect to the first chisel edge region 41. The third chisel edge region 43 is disposed radially inward with respect to the second chisel edge region 42.

[0068] When observed along the axial direction 101, a straight line extending in the direction of the second ridge line 72 is defined as a third imaginary line 113. When observed along the axial direction 101, the third imaginary line 113 is located in front of the first ridge line 71 in the rotational direction with respect to the first ridge line 71. When observed along the axial direction 101, in the direction perpendicular to the first ridge line 71, the distance between the first ridge line 71 and the second ridge line 72 is defined as a first distance E1. The first distance E1 is the distance between the third imaginary line 113 and the first ridge line 71 when observed along the axial direction 101. The first distance E1 is greater than 0 mm and 0.03 mm or less. There is no particular limitation on the lower limit of the first distance E1. For example, it may be 0.005 mm or more, or 0.01 mm or more. There is no particular limitation on the upper limit of the first distance E1. For example, it may be 0.027 mm or less, or 0.023 mm or less.

[0069] As Figure 4As shown, the ridge line (the third ridge line 73) between the first grinding surface 13 and the first flank 10, and the ridge line (the second grinding cutting edge 62) between the first grinding surface 13 and the second flank 20 form the first grinding ridge line 15. The first grinding ridge line 15 is connected to the second chisel edge region 42. When observed along the axial direction 101, the first grinding ridge line 15 is recessed inward in the radial direction. The point on the first grinding ridge line 15 that is closest to the axis X in the direction perpendicular to the first ridge line 71 when observed along the axial direction 101 is designated as the third point 123. The third point 123 is, for example, located on the third ridge line 73.

[0070] The ridge line (the first grinding cutting edge 61) between the second grinding surface 23 and the first flank 10, and the ridge line (the fourth ridge line 74) between the second grinding surface 23 and the second flank 20 form the second grinding ridge line 25. The second grinding ridge line 25 is connected to the first chisel edge region 41. When observed along the axial direction 101, the second grinding ridge line 25 is recessed inward in the radial direction. The point on the second grinding ridge line 25 that is closest to the axis X in the direction perpendicular to the first ridge line 71 when observed along the axial direction 101 is designated as the fourth point 124. The fourth point 124 is, for example, located on the fourth ridge line 74.

[0071] When observed along the axial direction 101, the distance between the third point 123 and the fourth point 124 in the direction perpendicular to the first ridge line 71 is designated as the second distance E2. When observed along the axial direction 101, the second distance E2 is the shortest distance between the first grinding ridge line 15 and the second grinding ridge line 25 in the direction perpendicular to the first ridge line 71. The second distance E2 is 0.04 mm or more and 0.10 mm or less. There is no particular limitation on the lower limit of the second distance E2. For example, it may be 0.05 mm or more, or 0.053 mm or more. There is no particular limitation on the upper limit of the second distance E2. For example, it may be 0.09 mm or less, or 0.085 mm or less. The second distance E2 is larger than the first distance E1.

[0072] The length of the third chisel edge region 43 when observed along the axial direction 101 is designated as the third length L3. From another perspective, the third length L3 is the distance between the first end portion 81 and the second end portion 82 when observed along 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 (the first value) obtained by dividing the third length L3 by the second distance E2 is 23% or more and 55% or less. There is no particular limitation on the lower limit of the first value. For example, it may be 28% or more, or 35% or more. There is no particular limitation on the upper limit of the first value. For example, it may be 50% or less, or 45% or less.

[0073] As Figure 4As shown, when observing along the axis direction 101, a straight line that is parallel to the first ridge line 71 and intersects the first chisel edge region 41 is defined as the fourth imaginary line 114. When observing along the axis direction 101, among the angles formed by the fourth imaginary line 114 and the first chisel edge region 41, the angle that is an acute angle is defined as the first angle θ1. From another perspective, the first angle θ1 is the angle formed by the first ridge line 71 and the first chisel edge region 41 when observing along the axis direction 101.

[0074] The first angle θ1 is, for example, 40° or more and 60° or less. There is no particular limitation on the lower limit of the first angle θ1. For example, it can be 43° or more, or it can be 47° or more. There is no particular limitation on the upper limit of the first angle θ1. For example, it can be 57° or less, or it can be 53° or less.

[0075] As Figure 4 shown, when observing along the axis direction 101, a straight line that is parallel to the first ridge line 71 and intersects the second chisel edge region 42 is defined as the fifth imaginary line 115. When observing along the axis direction 101, among the angles formed by the fifth imaginary line 115 and the second chisel edge region 42, the angle that is an acute angle is defined as the second angle θ2. From another perspective, the second angle θ2 is the angle formed by the first ridge line 71 and the second chisel edge region 42 when observing along the axis direction 101.

[0076] The second angle θ2 is, for example, 40° or more and 60° or less. There is no particular limitation on the lower limit of the second angle θ2. For example, it can be 43° or more, or it can be 47° or more. There is no particular limitation on the upper limit of the second angle θ2. For example, it can be 57° or less, or it can be 53° or less.

[0077] When observing along the axis direction 101, the angle formed by the first ridge line 71 and the third chisel edge region 43 is defined as the third angle θ3. The third angle θ3 is an acute angle. The third angle θ3 is larger than the first angle θ1. From another perspective, when observing along the axis direction 101, the first chisel edge region 41 is inclined rearward in the rotational direction with respect to the third chisel edge region 43. The third angle θ3 is larger than the second angle θ2. From another perspective, when observing along the axis direction 101, the second chisel edge region 42 is inclined rearward in the rotational direction with respect to the third chisel edge region 43.

[0078] The third angle θ3 is, for example, 50° or more and 80° or less. There is no particular limitation on the lower limit of the third angle θ3. For example, it can be 55° or more, or it can be 60° or more. There is no particular limitation on the upper limit of the third angle θ3. For example, it can be 75° or less, or it can be 70° or less.

[0079] Figure 5 is a schematic cross-sectional view along the Figure 4 V-V line. Figure 5The cross-section shown includes axis X and is parallel to the first ridge line 71 when observed in the axial direction 101. In this specification, the cross-section that includes axis X and is parallel to the first ridge line 71 when observed in the axial direction 101 is defined as the first cross-section CS1. As Figure 5 shown, in the first cross-section CS1, the first front flank 11 is, for example, linear. In the first cross-section CS1, the straight line extending in the direction in which the first front flank 11 extends is defined as the sixth imaginary line 116. In the first cross-section CS1, the second front flank 21 is, for example, linear. In the first cross-section CS1, the straight line extending in the direction in which the second front flank 21 extends is defined as the seventh imaginary line 117.

[0080] Among the angles formed by the sixth imaginary line 116 and the seventh imaginary line 117, the angle that is an obtuse angle is defined as the fourth angle θ4. The fourth angle θ4 is the angle formed by the first front flank 11 and the second front flank 21. The fourth angle θ4 is the tip angle of the drill 100. The fourth angle θ4 is, for example, 140°. The fourth angle θ4 may also be 120° or more and 160° or less. In the first cross-section CS1, axis X substantially bisects the angle formed by the first front flank 11 and the second front flank 21.

[0081] Figure 6 is a schematic cross-sectional view along Figure 3 the VI-VI line. Figure 6 The cross-section shown is parallel to axis X and intersects the first ridge line 71. When observed in the axial direction 101, Figure 6 the cross-section shown is perpendicular to the first ridge line 71. From another perspective, Figure 6 the schematic cross-sectional view shown represents the configuration of the drill 100 when observed from the side view direction 102 (refer to Figure 3 ). In this specification, the cross-section that is parallel to axis X and intersects the first ridge line 71 is defined as the second cross-section CS2.

[0082] As Figure 6 shown, the first rear flank 12 is inclined with respect to the first front flank 11. Specifically, in the second cross-section CS2, the first rear flank 12 is inclined with respect to the first front flank 11 in the axial direction 101. Similarly, the second rear flank 22 (refer to Figure 3 ) is inclined with respect to the second front flank 21 (refer to Figure 3 ).

[0083] As Figure 6 shown, in the second cross-section CS2, the first front flank 11 and the first rear flank 12 may each be linear. Similarly, in the cross-section that is parallel to axis X and intersects the second ridge line 72 (refer to Figure 3)In the intersecting cross-section, the second front flank 21 and the second front flank 21 can be linear respectively.

[0084] Figure 7 is a magnified schematic view of Figure 6 region VII. As Figure 7 shown, the third chisel edge region 43 is provided at the tip 1 of the drill bit 100. When observed in the side view direction 102, the third chisel edge region 43 is substantially perpendicular to the axis X. When observed in the side view direction 102, the first chisel edge region 41 is inclined with respect to the third chisel edge region 43 in the axial direction 101. When observed in the side view direction 102, the inclination angle of the first chisel edge region 41 with respect to the third chisel edge region 43 is set as the fifth angle θ5. The fifth angle θ5 is, for example, 3° or more and 15° or less.

[0085] When observed in the side view direction 102, the second chisel edge region 42 is inclined with respect to the third chisel edge region 43 in the axial direction 101. When observed in the side view direction 102, the inclination angle of the second chisel edge region 42 with respect to the third chisel edge region 43 is set as the sixth angle θ6. The sixth angle θ6 is, for example, 3° or more and 15° or less.

[0086] Figure 8 is a magnified schematic view of Figure 3 region VIII. As Figure 8 shown, when observed in the axial direction 101, the tangent line of the first cutting edge 51 in the first outermost end 91 is set as the first tangent line 131. When observed in the axial direction 101, the straight line passing through the first outermost end 91 and the axis X (refer to Figure 3 ) is set as the eighth imaginary line 118.

[0087] When observed in the axial direction 101, the first tangent line 131 is inclined rearward in the rotation direction with respect to the eighth imaginary line 118. Among the angles formed by the first tangent line 131 and the eighth imaginary line 118 when observed in the axial direction 101, the angle of the acute angle is set as the first rake angle θ11. From another perspective, at the outermost end 91 of the first cutting edge 51, the rake angle of the first cutting edge 51 in the radial direction of the drill bit 100 is set as the first rake angle θ11. The first rake angle θ11 is negative.

[0088] At the outermost end of the cutting edge, the fact that the rake angle of the cutting edge in the radial direction of the drill bit 100 is "positive" means that when observed in the axial direction 101, with respect to the straight line passing through the axis X and the outermost end, the tangent line of the outermost end of the cutting edge is inclined forward in the rotation direction of the drill bit 100. On the contrary, at the outermost end of the cutting edge, the fact that the rake angle of the cutting edge in the radial direction of the drill bit 100 is "negative" means that when observed in the axial direction 101, with respect to the straight line passing through the axis X and the outermost end, the tangent line of the outermost end of the cutting edge is inclined rearward in the rotation direction of the drill bit 100.

[0089] The first rake angle θ11 is, for example, -18° or more and -9° or less. The first rake angle θ11 can also be, for example, -14° or more and -10° or less. There is no particular limitation on the lower limit of the first rake angle θ11. For example, it can be -16° or more, or it can be -13° or more. There is no particular limitation on the upper limit of the first rake angle θ11. For example, it can be -9.5° or less, or it can be -11° or less. When observed in the axial direction 101, the first land face 18 is provided on the radially outer side with respect to the first flank face 10, the first outer peripheral face 16, and the second outer peripheral face 26 respectively. When observed in the axial direction 101, the first land face 18 is provided in front of the first outer peripheral face 16 in the rotational direction.

[0090] Figure 9 It represents Figure 3 an enlarged schematic view of the region IX. As Figure 9 shown, when observed in the axial direction 101, the tangent line of the second cutting edge 52 in the second outermost end 92 is set as the second tangent line 132. When observed in the axial direction 101, the straight line passing through the second outermost end 92 and the axis X (refer to Figure 3 ) is set as the ninth imaginary line 119. When observed in the axial direction 101, the ninth imaginary line 119 can overlap with the eighth imaginary line 118 (refer to Figure 8 ).

[0091] When observed in the axial direction 101, the second tangent line 132 is inclined rearward in the rotational direction with respect to the ninth imaginary line 119. When observed in the axial direction 101, among the angles formed by the second tangent line 132 and the ninth imaginary line 119, the angle that is an acute angle is set as the second rake angle θ12. From another perspective, at the outermost end 92 of the second cutting edge 52, the rake angle of the second cutting edge 52 in the radial direction of the drill bit 100 is set 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.

[0092] The second rake angle θ12 is, for example, -18° or more and -9° or less. The second rake angle θ12 can also be, for example, -14° or more and -10° or less. There is no particular limitation on the lower limit of the second rake angle θ12. For example, it can be -16° or more, or it can be -13° or more. There is no particular limitation on the upper limit of the second rake angle θ12. For example, it can be -9.5° or less, or it can be -11° or less. When observed in the axial direction 101, the second land face 28 is provided on the radially outer side with respect to the second flank face 20, the first outer peripheral face 16, and the second outer peripheral face 26 respectively. When observed in the axial direction 101, the second land face 28 is provided in front of the second outer peripheral face 26 in the rotational direction.

[0093] Next, the effects of the drill bit 100 according to the present embodiment will be described.

[0094] According to the drill bit 100 according to this embodiment, it has a first chisel edge region 41, a second chisel edge region 42, and a third chisel edge region 43. The third chisel edge region 43 is connected to the first chisel edge region 41 and the second chisel edge region 42 respectively. The third chisel edge region 43 is provided at the tip 1. Therefore, when using the drill bit 100 to machine a workpiece to be cut, the third chisel edge region 43 first contacts the workpiece to be cut. In addition, according to the drill bit 100 according to this embodiment, the distance (first distance E1) between the first cutting edge 71 and the second cutting edge 72 is 0.03 mm or less. When observed in the axial direction 101, the shortest distance (second distance E2) between the first grinding edge 15 and the second grinding edge 25 in the direction perpendicular to the first cutting edge 71 is 0.10 mm or less.

[0095] By making the first distance E1 0.03 mm or less, the length of the third chisel edge region 43 can be suppressed from becoming excessively long. Therefore, it is possible to suppress the contact area between the drill bit 100 and the workpiece to be cut from becoming excessively large at the beginning of the hole machining using the drill bit 100. Therefore, the cutting-in property of the drill bit 100 can be improved. Therefore, the swing of the drill bit 100 can be suppressed during hole machining. Therefore, the amount of enlargement of the hole diameter and the hole position accuracy of the hole machined using the drill bit 100 can be improved respectively. As a result, the accuracy of hole machining can be improved. By making the second distance E2 0.10 mm or less, the lengths of the first chisel edge region 41 and the second chisel edge region 42 can be suppressed from becoming excessively long. Therefore, it is possible to suppress the forces respectively loaded on the first chisel edge region 41 and the second chisel edge region 42 from the workpiece to be cut from becoming excessively large at the initial stage of hole machining. Therefore, the swing of the drill bit 100 can be suppressed during hole machining. As a result, the accuracy of hole machining can be improved.

[0096] Furthermore, according to the drill bit 100 according to 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, the periphery of the tip 1 of the drill bit 100 can be suppressed from becoming excessively sharp. Therefore, the periphery of the tip 1 of the drill bit 100 can be suppressed from being damaged. As a result, the strength of the drill bit 100 can be improved. By making the second distance E2 0.04 mm or more, the wall thickness of the periphery of the tip 1 of the drill bit 100 can be made thicker. Therefore, the drill bit 100 can be suppressed from being bent. As a result, the strength of the drill bit 100 can be improved.

[0097] According to the drill bit 100 according to this embodiment, the length (third length L3) of the third chisel edge region 43 can be 23% or more and 55% or less of the second distance E2. Therefore, the hole position accuracy of the hole formed using the drill bit 100 can be improved.

[0098] According to the drill bit 100 according to this embodiment, the cutting edge diameter D of the drill bit 100 can be 3 mm or less. Generally, in machining using a drill bit 100 with a relatively small cutting edge diameter D, an oily coolant is often supplied by external oil supply. In this case, compared with the case where the coolant is supplied by internal oil supply, the temperature of the drill bit 100 tends to become higher. Therefore, in a drill bit 100 with a relatively small cutting edge diameter D, in order to reduce the friction between the drill bit 100 and the workpiece to be cut, the number of land surfaces is often set to two (a pair). In this case, compared with the case where the number of land surfaces is four (two pairs) or more, the drill bit 100 becomes more likely to wobble. As a result, the accuracy of hole machining decreases. According to the drill bit 100 according to this embodiment, even when the cutting edge diameter D is 3 mm or less, a decrease in the accuracy of hole machining can be suppressed.

[0099] Figure 10 is a cross-sectional schematic view showing the state of the drill bit 100 just before penetrating the workpiece to be cut. As Figure 10 shown, during hole machining, just before the drill bit 100 penetrates the workpiece to be cut 99, a remaining portion 98 of the workpiece to be cut 99 is formed. The remaining portion 98 is the portion that has not been cut by the cutting edge of the drill bit 100. Figure 11 is a cross-sectional schematic view showing the state in which a hole is formed in the workpiece to be cut 99 using the drill bit 100. As Figure 10 and Figure 11 shown, when the drill bit 100 penetrates the workpiece to be cut 99, the remaining portion 98 receives a load in the direction along the machining direction A of the drill bit 100. Due to this load, the remaining portion 98 undergoes plastic deformation. As a result, a burr 97 is formed in the workpiece to be cut 99. The distance between the point on the burr 97 that is farthest from the surface of the workpiece to be cut 99 and the surface of the workpiece to be cut 99 in the machining direction A of the drill bit 100 is defined as the height H of the burr 97. The height H of the burr 97 is preferably low.

[0100] According to the drill bit 100 according to this embodiment, at the first outermost peripheral end 91, the rake angle (first rake angle θ11) of the first cutting edge 51 in the radial direction of the drill bit 100 can be -18° or more and -9° or less. At the second outermost peripheral end 92, the rake angle (second rake angle θ12) of the second cutting edge 52 in the radial direction of the drill bit 100 can be -18° or more and -9° or less. By making the first rake angle θ11 and the second rake angle θ12 be -18° or more respectively, the sharpness of the cutting edge at the outermost peripheral end can be improved. As a result, the height H of the burr 97 can be reduced.

[0101] Furthermore, by setting the first rake angle θ11 and the second rake angle θ12 to -9° or less respectively, it is possible to suppress a reduction in the strength of the cutting edge around the outermost peripheral end. Therefore, even after drilling a plurality of holes using the drill bit 100, it is possible to suppress a reduction in sharpness caused by chipping of the cutting edge. As a result, even after drilling a plurality of holes using the drill bit 100, it is possible to suppress an increase in the height H of the burr.

[0102] Example 1

[0103] (Sample preparation)

[0104] First, drill bits 100 related to Sample 1 and Sample 2 were prepared. The drill bit 100 related to Sample 1 was set as a comparative example. The drill bit 100 related to Sample 2 was set as an example.

[0105] In the drill bits 100 related to Sample 1 and Sample 2, the first distance E1 changed. In the drill bit 100 related to Sample 1, the first distance E1 was set to 0.12 mm. Figure 12 It is an enlarged front view schematic diagram showing the configuration of the drill bit 100 related to Sample 1. Figure 12 The enlarged front view schematic diagram shown corresponds to Figure 4 the enlarged front view schematic diagram shown. As Figure 12 shown, the drill bit 100 related to Sample 1 does not have the first chisel edge region 41 and the second chisel edge region 42. In the drill bit 100 related to Sample 1, the percentage (first value) of the value obtained by dividing the length (third length L3) of the third chisel edge region 43 by the second distance E2 was set to 113%.

[0106] The configuration of the drill bit 100 related to Sample 2 was set to the configuration of the drill bit 100 according to the present embodiment (refer to Figure 4 ). In the drill bit related to Sample 2, the first distance E1 was set to 0.02 mm. The first value was set to 32%.

[0107] In the drill bits 100 related to Sample 1 and Sample 2, the cutting diameter D was set to 2 mm. The lengths of the first chip flute surface 19 and the second chip flute surface 29 were each set to 5 times the cutting diameter D. The second distance E2 was set to 0.07 mm. The first rake angle θ11 and the second rake angle θ12 (hereinafter, also simply referred to as the rake angle) were each set to -12°.

[0108] (Evaluation method)

[0109] Next, the amount of hole diameter enlargement and hole position accuracy were evaluated using the drill bit 100 related to Sample 1 and Sample 2. Specifically, using the drill bit 100 related to Sample 1 and Sample 2, holes were formed in the workpiece to be cut. The diameter of the formed holes was measured. The value obtained by subtracting the cutting edge diameter of the drill bit 100 from the diameter of the formed holes was defined as the amount of hole diameter enlargement. Twice the value of the distance between the target position of the center of the hole and the position of the center of the formed hole was defined as the hole position accuracy.

[0110] In the evaluation of the amount of hole diameter enlargement and hole position accuracy, the workpiece to be cut was SCM415. SCM415 is an alloy steel specified by JIS (Japanese Industrial Standards) G 4053:2016. The depth of the hole was set to 6 mm. The cutting speed was set to 38 m / min. The feed rate was set to 0.04 mm / rev.

[0111] (Evaluation results)

[0112] Table 1

[0113]

[0114] Table 1 shows the amount of hole diameter enlargement and hole position accuracy in Sample 1 and Sample 2. As shown in Table 1, the amount of hole diameter enlargement in Sample 2 is smaller than that in Sample 1. The hole position accuracy in Sample 2 is smaller than that in Sample 1.

[0115] Based on the above results, it was confirmed that the drill bit 100 related to the example can reduce the amount of hole diameter enlargement and hole position accuracy respectively compared with the drill bit 100 related to the comparative example.

[0116] Example 2

[0117] (Sample preparation)

[0118] Next, drill bits 100 related to Samples 3 to 7 were prepared. The drill bits 100 related to Samples 3, 6, and 7 were set as comparative examples. The drill bits 100 related to Samples 4 and 5 were set as examples.

[0119] In the drill bits 100 related to Samples 3 to 7, the first distance E1 changed. In the drill bits 100 related to Samples 3 to 7, the first distance E1 was set to 0 mm or more and 0.10 mm or less. The first value was set to 0% or more and 113% or less.

[0120] In the drill bits 100 related to Samples 3 to 7, the cutting edge diameter D was set to 2 mm. The lengths of the first chip flute surface 19 and the second chip flute surface 29 were each 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°.

[0121] (Evaluation method)

[0122] Next, using the drill bits 100 involved in Samples 3 to 7, the cutting-in shape was evaluated. Specifically, using the drill bits 100 involved in Samples 3 to 7, holes were formed in the workpiece to be cut. The depth of the holes was set to about 0.3 mm. At the part of the workpiece to be cut where the drill bit 100 contacted, the shape of the trace (cutting-in shape) where the drill bit 100 contacted was confirmed. When the cutting-in property of the drill bit 100 was good, the cutting-in shape became circular. In the evaluation of the cutting-in shape, the workpiece to be cut was SCM415. The cutting speed was set to 38 m / min. The feed rate was set to 0.04 mm / rev.

[0123] The amount of increase in the hole diameter and the hole position accuracy were evaluated using the drill bits 100 involved in Samples 3 to 7. Specifically, the amount of increase in the hole diameter and the hole position accuracy were measured respectively using the above evaluation method.

[0124] The respective numbers of machined holes of the drill bits 100 involved in Samples 3 to 7 were evaluated. Specifically, using the drill bits 100 involved in Samples 3 to 7, a plurality of holes were formed in the workpiece to be cut. The number of holes was set to a maximum of 600. When the breakage of the drill bit 100 was confirmed, the number of holes formed until the breakage was confirmed was measured as the number of machined holes. When the breakage of the drill bit 100 was not confirmed, the number of machined holes was set to 600. In the evaluation of the number of machined holes, the workpiece to be cut was SCM415. The depth of the holes was set to 6 mm. The cutting speed was set to 38 m / min. The feed rate was set to 0.04 mm / rev.

[0125] (Evaluation results)

[0126]

[0127] Table 2 shows the cutting-in shape, the amount of increase in the hole diameter, the hole position accuracy, and the number of machined holes in 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 cutting-in shape was circular. When the first distance E1 was 0.05 mm or more (Samples 6 and 7), the cutting-in shape was a non-circular shape. Specifically, the cutting-in shape was triangular.

[0128] As shown in Table 2, when the first distance E1 was 0.03 mm or less (Samples 3 to 5), the amount of increase in the hole diameter was 0.018 mm or less. The hole position accuracy was 0.016 mm or less. When the first distance E1 was 0.05 mm or more (Samples 6 and 7), the amount of increase in the hole diameter was 0.028 mm or more. The hole position accuracy was 0.021 mm or more.

[0129] As shown in Table 2, in the case where the first distance E1 is 0 mm (Sample 3), the number of machined holes is 126. Specifically, in Sample 3, a defect was confirmed around the tip 1 of the drill bit 100. In the case where the first distance E1 is greater than 0 mm (Samples 4 to 7), the number of machined holes is 600. In other words, in Samples 4 to 7, no breakage of the drill bit 100 was confirmed.

[0130] Based on the above results, it was confirmed that the drill bit 100 according to the embodiment can improve the cutting-in property as compared with the drill bit 100 according to the comparative example, and can separately reduce the amount of enlargement of the hole diameter and the hole position accuracy, and can improve the strength of the drill bit 100.

[0131] Example 3

[0132] (Sample preparation)

[0133] Next, the drill bits 100 related to Samples 8 to 13 were prepared. The drill bits 100 related to Sample 8 and Sample 13 were set as comparative examples. The drill bits 100 related to Samples 9 to 12 were set as embodiments.

[0134] In the drill bits 100 related to Samples 8 to 13, the second distance E2 was changed. In the drill bits 100 related to Samples 8 to 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.

[0135] In the drill bits 100 related to Samples 8 to 13, the cutting edge diameter D was set to 2 mm. The lengths of the first chip flute surface 19 and the second chip flute surface 29 were each 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°.

[0136] (Evaluation method)

[0137] Next, the amount of enlargement of the hole diameter, the hole position accuracy, and the number of machined holes were evaluated using the drill bits 100 related to Samples 8 to 13. Specifically, the amount of enlargement of the hole diameter, the hole position accuracy, and the number of machined holes were measured using the above evaluation method.

[0138] (Evaluation results)

[0139]

[0140] Table 3 shows the amount of enlargement of the hole diameter, the hole position accuracy, and the number of machined holes in Samples 8 to 13. Figure 13 Shows the amount of enlargement of the hole diameter in Samples 8 to 13. In Figure 13 the horizontal axis represents the second distance E2. The vertical axis represents the amount of enlargement of the hole diameter. In Figure 13Among them, the point shown by P8 represents the amount of increase in the aperture in Sample 8. Similarly, the points shown by P9 to P13 represent the amounts of increase in the apertures in Samples 9 to 13.

[0141] Figure 14 Represents the hole positional tolerance in Samples 8 to 13. In Figure 14 Among them, the horizontal axis represents the second distance E2. The vertical axis represents the hole positional tolerance. In Figure 14 Among them, the point shown by P8 represents the hole positional tolerance in Sample 8. Similarly, the points shown by P9 to P13 represent the hole positional tolerances in Samples 9 to 13.

[0142] As shown in Table 3, Figure 13 and Figure 14 shown, when the second distance E2 is 0.100 mm or less (Samples 8 to 12), the amount of increase in the aperture is 0.016 mm or less. The hole positional tolerance is 0.028 mm or less. When the second distance E2 is 0.110 mm or more (Sample 13), the amount of increase in the aperture is 0.019 mm. The hole positional tolerance is 0.035 mm.

[0143] As shown in Table 3, when the second distance E2 is 0.03 mm (Sample 8), the number of machined holes is 180. Specifically, in Sample 8, breakage of the drill bit 100 was confirmed. When the second distance E2 is 0.04 mm or more (Samples 9 to 13), the number of machined holes is 600. In other words, in Samples 9 to 13, breakage of the drill bit 100 was not confirmed.

[0144] Based on the above results, it was confirmed that the drill bit 100 according to the embodiment can reduce the amount of increase in the aperture and the hole positional tolerance respectively, and can improve the strength of the drill bit 100 compared with the drill bit 100 according to the comparative example.

[0145] Example 4

[0146] (Sample Preparation)

[0147] Next, drill bits 100 related to Samples 14 to 20 were prepared. The drill bits 100 related to Samples 14, 15, and 20 were set as comparative examples. The drill bits 100 related to Samples 16 to 19 were set as embodiments.

[0148] Among the drill bits 100 related to Samples 14 to 20, the value (first value) obtained by dividing the length of the third chisel edge region 43 by the second distance E2 changed. Among the drill bits 100 related to Samples 14 to 20, the first value was set to 15% or more and 75% or less. The second distance E2 was set to 0.030 mm or more and 0.150 mm or less.

[0149] In the drill bit 100 related to Samples 14 to 20, the cutting edge diameter D is set to 2 mm. The lengths of the first chip fluting surface 19 and the second chip fluting surface 29 are each set to 5 times the cutting edge diameter D. The first distance E1 is set to 0.02 mm. The rake angle is set to -12°.

[0150] (Evaluation method)

[0151] Next, the amount of hole diameter enlargement, hole position accuracy, and the number of machined holes were evaluated using the drill bit 100 related to Samples 14 to 20. Specifically, the amount of hole diameter enlargement, hole position accuracy, and the number of machined holes were measured using the above evaluation method.

[0152] (Evaluation results)

[0153]

[0154] Table 4 shows the amount of hole diameter enlargement, hole position accuracy, and the number of machined holes in Samples 14 to 20. Figure 15 Shows the amount of hole diameter enlargement in Samples 14 to 20. In Figure 15 , the horizontal axis represents the first value. The vertical axis represents the amount of hole diameter enlargement. In Figure 15 , the point indicated by P14 represents the amount of hole diameter enlargement in Sample 14. Similarly, the points indicated by P15 to P20 represent the amount of hole diameter enlargement in Samples 15 to 20.

[0155] Figure 16 Shows the hole position accuracy in Samples 14 to 20. In Figure 16 , the horizontal axis represents the first value. The vertical axis represents the hole position accuracy. In Figure 16 , the point indicated by P14 represents the hole position accuracy in Sample 14. Similarly, the points indicated by P15 to P20 represent the hole position accuracy in Samples 15 to 20, respectively.

[0156] As shown in Table 4 and Figure 15 , when the first value is 23% or more and 65% or less (Samples 15 to 19), the amount of hole diameter enlargement is smaller than when the first value is less than 23% or greater than 65% (Samples 14 and 20). As shown in Table 4 and Figure 16 , when the first value is 23% or more and 55% or less (Samples 16 to 19), the hole position accuracy is smaller than when the first value is less than 23% or greater than 55% (Samples 14, 15, and 20).

[0157] Based on the above results, it was confirmed that the drill bit 100 according to the embodiment can reduce the hole position accuracy compared to the drill bit 100 according to the comparative example.

[0158] Example 5

[0159] (Sample Preparation)

[0160] Next, drills 100 related to Samples 21 to 27 were prepared. The drills 100 related to Sample 21 and Sample 27 were set as comparative examples. The drills 100 related to Samples 22 to 26 were set as examples.

[0161] In the drills 100 related to Samples 21 to 27, the rake angle was changed. In the drills 100 related to Samples 21 to 27, the rake angle was set to be -24° or more and -6° or less.

[0162] In the drills 100 related to Samples 21 to 27, the cutting edge diameter D was set to 2 mm. The lengths of the first chip fluting surface 19 and the second chip fluting surface 29 were each 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%.

[0163] (Evaluation Method)

[0164] Next, using the drills 100 related to Samples 21 to 27, the height H of the burrs after machining 300 holes was measured (refer to Figure 11 ). Specifically, in the machining direction of the drill 100, the distance between the point on the burr 97 farthest from the surface of the workpiece 99 and the surface of the workpiece 99 was measured as the height H of the burr. In the evaluation of the height H of the burr, the workpiece was set to SCM415. The depth of the hole was set to 6 mm. The cutting speed was set to 38 m / min. The feed rate was set to 0.04 mm / rev.

[0165] Using the drills 100 related to Samples 21 to 27, the amount of increase in hole diameter, hole position accuracy, and the number of machined holes were evaluated. Specifically, the amount of increase in hole diameter, hole position accuracy, and the number of machined holes were measured using the above evaluation method.

[0166] (Evaluation Results)

[0167]

[0168] Table 5 shows the amount of increase in hole diameter, hole position accuracy, the height H of the burrs, and the number of machined holes in the drills 100 related to Samples 21 to 27.

[0169] As shown in Table 5, the height H of the burrs in the case where the rake angle was -18° or more and -9° or less (Samples 22 to 26) was smaller than the height H of the burrs in the case where the rake angle was less than -18° or greater than -9° (Samples 21 and 27).

[0170] Based on the above results, it is confirmed that the height H of the burr can be reduced for the drill bit 100 according to the embodiment compared with the drill bit 100 according to the comparative example.

[0171] It should be considered that the embodiments and examples disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is represented not by the above embodiments and examples but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0172] Explanation of reference numerals:

[0173] 1: Front end;

[0174] 2: Rear end;

[0175] 7: Shank;

[0176] 9: Outer peripheral surface;

[0177] 10: First flank;

[0178] 11: First front flank portion;

[0179] 12: First rear flank portion;

[0180] 13: First grinding surface;

[0181] 15: First grinding edge;

[0182] 16: First outer peripheral portion;

[0183] 17: First leading edge;

[0184] 18: First land surface;

[0185] 19: First chip flute surface;

[0186] 20: Second flank;

[0187] 21: Second front flank portion;

[0188] 22: Second rear flank portion;

[0189] 23: Second grinding surface;

[0190] 25: Second grinding edge;

[0191] 26: Second outer peripheral portion;

[0192] 27: Second leading edge;

[0193] 28: Second land surface;

[0194] 29: Second chip flute surface;

[0195] 41: First chisel edge area;

[0196] 42: Second chisel edge area;

[0197] 43: Third chisel edge area;

[0198] 51: First cutting edge;

[0199] 52: Second cutting edge;

[0200] 61: First regrinding cutting edge;

[0201] 62: Second regrinding cutting edge;

[0202] 71: First ridge line;

[0203] 72: Second ridge line;

[0204] 73: Third ridge line;

[0205] 74: Fourth ridge line;

[0206] 75: Fifth ridge line;

[0207] 76: Sixth ridge line;

[0208] 81: First end;

[0209] 82: Second end;

[0210] 91: First outermost end;

[0211] 92: Second outermost end;

[0212] 93: First chip groove;

[0213] 94: Second chip groove;

[0214] 97: Burr;

[0215] 98: Remaining part;

[0216] 99: Workpiece to be cut;

[0217] 100: Drill bit;

[0218] 101: Axial direction;

[0219] 102: Side view direction;

[0220] 111: First imaginary line;

[0221] 112: Second imaginary line;

[0222] 113: Third imaginary line;

[0223] 114: Fourth imaginary line;

[0224] 115: The fifth imaginary line;

[0225] 116: The sixth imaginary line;

[0226] 117: The seventh imaginary line;

[0227] 118: The eighth imaginary line;

[0228] 119: The ninth imaginary line;

[0229] 121: The first point;

[0230] 122: The second point;

[0231] 123: The third point;

[0232] 124: The fourth point;

[0233] 131: The first tangent line;

[0234] 132: The second tangent line;

[0235] A: The machining direction;

[0236] CS1: The first section;

[0237] CS2: The second section;

[0238] D: The cutting edge diameter;

[0239] E1: The first distance (distance);

[0240] E2: The second distance (the shortest distance);

[0241] H: The height;

[0242] L1: The first length;

[0243] L2: The second length;

[0244] L3: The third length;

[0245] X: The axis;

[0246] θ1: The first angle;

[0247] θ2: The second angle;

[0248] θ3: The third angle;

[0249] θ4: The fourth angle;

[0250] θ5: The fifth angle;

[0251] θ6: The sixth angle;

[0252] θ11: The first rake angle;

[0253] θ12: The second rake angle.

Claims

1. A drill bit that rotates about an axis, wherein, the drill bit includes: a first flank face; a first grinding face that is provided behind the first flank face in the rotational direction; a second flank face that is provided behind the first grinding face in the rotational direction; and a second grinding face that is provided behind the second flank face in the rotational direction, the first flank face includes: a first front flank face portion; and a first rear flank face portion that is connected to the first front flank face portion, is inclined with respect to the first front flank face portion, and is provided behind the first front flank face portion in the rotational direction, the second flank face includes: a second front flank face portion; and a second rear flank face portion that is connected to the second front flank face portion, is inclined with respect to the second front flank face portion, and is provided behind the second front flank face portion in the rotational direction, the second front flank face portion is connected to the first front flank face portion and the first rear flank face portion respectively, the second rear flank face portion is connected to the first front flank face portion, when the ridge line between the first front flank face portion and the first rear flank face portion is defined as a first ridge line and the ridge line between the second front flank face portion and the second rear flank face portion is defined as a second ridge line, when viewed in the axial direction from the front end to the rear end of the drill bit, the 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 0.03 mm or less, the ridge line between the first front flank face portion and the second rear flank face portion forms a first chisel edge region, the ridge line between the first rear flank face portion and the second front flank face portion forms a second chisel edge region, the ridge line between the first front flank face portion and the second front flank face portion forms a third chisel edge region that is connected to the first chisel edge region and the second chisel edge region respectively, the third chisel edge region is provided at the front end, the ridge line between the first grinding face and the first flank face and the ridge line between the first grinding face and the second flank face form a first grinding ridge line, the ridge line between the second grinding face and the first flank face and the ridge line between the second grinding face and the second flank face form a second grinding ridge line, when viewed in the axial direction, the shortest distance between the first grinding ridge line and the second grinding ridge line in a direction perpendicular to the first ridge line is 0.04 mm or more and 0.10 mm or less.

2. The drill bit according to claim 1, wherein, when viewed in the axial direction, the length of the third chisel edge region is 23% or more and 55% or less of the shortest distance.

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

4. The drill bit according to claim 3, wherein, the drill bit includes: a first chip flute surface that is provided in a spiral shape around the axis and is connected to the first flank face; and a second chip flute surface that is provided in a spiral shape around the axis and is connected to the second flank face, The first chip removal surface and the second chip removal surface respectively form a chip removal groove. The respective lengths of the first chip removal surface and the second chip removal surface in the axial direction are more than 2 times and less than 10 times the cutting edge diameter.

5. The drill bit according to claim 4, wherein, A first cutting edge is formed by the ridge line of the first flank and the first chip removal surface. A second cutting edge is formed by the ridge line of the second flank and the second chip removal surface. At the outermost peripheral end of the first cutting edge, the rake angle of the first cutting edge in the radial direction of the drill bit is -18° or more and -9° or less. At the outermost peripheral end of the second cutting edge, the rake angle of the second cutting edge in the radial direction is -18° or more and -9° or less.

6. The drill bit according to any one of claims 1 to 5, wherein, When observed in the axial direction, the angle formed by the first ridge line and the third chisel edge region is larger than the angle formed by the first ridge line and the first chisel edge region, and larger than the angle formed by the first ridge line and the second chisel edge region.

7. The drill bit according to any one of claims 1 to 6, wherein, When observed in the axial direction, the angle formed by the first ridge line and the third chisel edge region is 50° or more and 80° or less.

8. The drill bit according to any one of claims 1 to 7, wherein, When observed in the axial direction, the angle formed by the first ridge line and the first chisel edge region is 40° or more and 60° or less. When observed in the axial direction, the angle formed by the first ridge line and the second chisel edge region is 40° or more and 60° or less.

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