Drill heads, indexable drills and drills

Abstract

The drill 100 has a tip surface 11, an outer peripheral surface 5, a cutting edge 1, a flute surface 4, and a thinning surface 40. The cutting edge 1 has a major cutting edge portion 65, a first thinning cutting edge portion 61, a second thinning cutting edge portion 62, and a third thinning cutting edge portion 63. The first thinning cutting edge portion 61 is linear and is formed by the ridgeline between the first thinning rake surface portion 41 and the first flank surface portion 51. The second thinning cutting edge portion 62 is linear and is formed by the ridgeline between the second thinning rake surface portion 42 and the first flank surface portion 51. The third thinning cutting edge portion (63) is curved and located between the first thinning cutting edge portion (61) and the second thinning cutting edge portion (62), and is formed by the ridge line between the third thinning rake surface portion (43) and the first relief surface portion (51).

Description

[Technical Field]

[0001] The present disclosure relates to a drill head, an indexable tip drill, and a drill. [Background technology]

[0002] International Publication No. 2022 / 201298 (Patent Document 1) describes a drill. The drill described in Patent Document 1 has a main cutting edge and a thinning cutting edge. The thinning cutting edge extends linearly. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 201298 Summary of the Invention

[0004] The drill according to the present disclosure is a drill that rotates around a central axis and includes a tip end and a rear end that are ends in a direction along the central axis, a tip face at the tip, an outer circumferential surface connected to the tip face, a cutting edge on the tip face extending from the outer circumferential surface toward the central axis, a flute face formed on the outer circumferential surface and extending around the central axis from the tip face toward the rear end, and a thinning face connected to the tip face and the flute face. The tip face has a first flank portion connected to the cutting edge and a second flank portion located on the opposite side of the flute face from the first flank portion. The thinning face has a thinning rake face connected to the first flank portion and a thinning heel face connected to the second flank portion. The thinning rake face has a first thinning rake face portion connected to the thinning heel surface, a second thinning rake face portion connected to the flute surface, and a third thinning rake face portion connecting the first thinning rake face portion and the second thinning rake face portion. The cutting edge has a major cutting edge portion, a first thinning cutting edge portion, a second thinning cutting edge portion, and a third thinning cutting edge portion. The major cutting edge portion is connected to the outer peripheral surface and is formed by the ridgeline between the first flank face portion and the flute surface. The first thinning cutting edge portion is linear and is formed by the ridgeline between the first thinning rake face portion and the first flank face portion. The second thinning cutting edge portion is linear and is formed by the ridgeline between the second thinning rake face portion and the first flank face portion. The third thinning cutting edge portion is curved, located between the first thinning cutting edge portion and the second thinning cutting edge portion, and is formed by the ridgeline between the third thinning rake face portion and the first relief face portion. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic perspective view showing the configuration of a drill according to a first embodiment. [Figure 2] FIG. 2 is a perspective schematic view showing the configuration of the drill head. [Figure 3] FIG. 3 is a schematic front view showing the configuration of the drill head. [Figure 4] FIG. 4 is a schematic rear view showing the configuration of the drill head. [Figure 5]FIG. 5 is a schematic front view showing an example of the configuration of the cutting edge. [Figure 6] FIG. 6 is a schematic front view showing another example of the configuration of the cutting edge. [Figure 7] FIG. 7 is a cross-sectional schematic view showing the axial rake angle of the first thinning rake face portion. [Figure 8] FIG. 8 is a cross-sectional schematic view showing the axial rake angle of the second thinning rake face portion. [Figure 9] FIG. 9 is a cross-sectional schematic diagram showing the axial rake angle of the flute face. [Figure 10] FIG. 10 is a perspective schematic view showing the configuration of the holder. [Figure 11] FIG. 11 is a schematic perspective view showing the overall configuration of a drill according to the second embodiment. [Figure 12] FIG. 12 is an enlarged perspective schematic view showing a partial configuration of a drill according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0007] (1) A drill according to the present disclosure is a drill that rotates around a central axis and includes a leading end and a trailing end that are ends along the central axis, a leading end face at the leading end, an outer peripheral surface connected to the leading end face, a cutting edge extending from the outer peripheral surface on the leading end face toward the central axis, a flute surface formed on the outer peripheral surface and extending around the central axis from the leading end face toward the trailing end, and a thinning surface connected to the leading end face and the flute surface. The leading end face has a first flank portion connected to the cutting edge and a second flank portion located on the opposite side of the flute surface from the first flank portion. The thinning surface has a thinning rake face connected to the first flank portion and a thinning heel face connected to the second flank portion. The thinning rake face has a first thinning rake face portion connected to the thinning heel surface, a second thinning rake face portion connected to the flute surface, and a third thinning rake face portion connecting the first thinning rake face portion and the second thinning rake face portion. The cutting edge has a major cutting edge portion, a first thinning cutting edge portion, a second thinning cutting edge portion, and a third thinning cutting edge portion. The major cutting edge portion is connected to the outer peripheral surface and is formed by the ridgeline between the first flank face portion and the flute surface. The first thinning cutting edge portion is linear and is formed by the ridgeline between the first thinning rake face portion and the first flank face portion. The second thinning cutting edge portion is linear and is formed by the ridgeline between the second thinning rake face portion and the first flank face portion. The third thinning cutting edge portion is curved, located between the first thinning cutting edge portion and the second thinning cutting edge portion, and is formed by the ridgeline between the third thinning rake face portion and the first relief face portion.

[0008] (2) According to the drill according to (1) above, the axial rake angle of each of the first thinning rake face portion and the second thinning rake face portion may be not less than −7° and not more than 7°.

[0009] (3) According to the drill according to (1) or (2) above, when the tip surface is viewed along the central axis, the amount of recession of the main cutting edge portion relative to an imaginary line connecting the connection point between the main cutting edge portion and the outer peripheral surface and the connection point between the second thinning cutting edge portion and the main cutting edge portion may be between −0.01 and 0.02 times the diameter of the cutting edge.

[0010] (4) According to the drill according to (1) or (2) above, when the tip surface is viewed along the central axis, the distance between an imaginary line extending the second thinning cutting edge portion toward the outer peripheral surface and the outer end point of the main cutting edge portion may be 0.01 times or less the diameter of the cutting edge.

[0011] (5) In the drill according to (1) or (2) above, the major cutting edge portion may have a first major cutting edge region and a second major cutting edge region located on the opposite side of the central axis from the first major cutting edge region. The first thinning cutting edge portion may have a first thinning cutting edge region located between the first major cutting edge region and the central axis and a second thinning cutting edge region located between the second major cutting edge region and the central axis. When the tip surface is viewed along the central axis, the angle formed by the direction extending outward along the first thinning cutting edge region and the direction from the central axis toward the outer end point of the second major cutting edge region may be 141° or greater and 155° or less.

[0012] (6) According to the drill according to (1) or (2) above, the value obtained by dividing the length of the first thinning cutting edge portion by the sum of the length of the main cutting edge portion and the length of the second thinning cutting edge portion may be 0.19 or more and 0.25 or less.

[0013] (7) A drill head according to the present disclosure is a drill head that rotates around a central axis and includes: a mounting surface that is an end surface in a direction along the central axis; a tip surface that is the surface opposite the mounting surface in a direction along the central axis; an outer circumferential surface that is continuous with the mounting surface and the tip surface; a cutting edge extending from the outer circumferential surface on the tip surface toward the central axis; a flute surface formed on the outer circumferential surface and extending around the central axis from the tip surface toward the mounting surface; and a thinning surface that is continuous with the tip surface and the flute surface. The tip surface has a first flank portion that is continuous with the cutting edge and a second flank portion that is located on the opposite side of the flute surface from the first flank portion. The thinning surface has a thinning rake surface that is continuous with the first flank portion and a thinning heel surface that is continuous with the second flank portion. The thinning rake face has a first thinning rake face portion connected to the thinning heel surface, a second thinning rake face portion connected to the flute surface, and a third thinning rake face portion connecting the first thinning rake face portion and the second thinning rake face portion. The cutting edge has a major cutting edge portion, a first thinning cutting edge portion, a second thinning cutting edge portion, and a third thinning cutting edge portion. The major cutting edge portion is connected to the outer peripheral surface and is formed by the ridgeline between the first flank face portion and the flute surface. The first thinning cutting edge portion is linear and formed by the ridgeline between the first thinning rake face portion and the first flank face portion. The second thinning cutting edge portion is linear and formed by the ridgeline between the second thinning rake face portion and the first flank face portion. The third thinning cutting edge portion is curved, located between the first thinning cutting edge portion and the second thinning cutting edge portion, and is formed by the ridgeline between the third thinning rake face portion and the first relief face portion.

[0014] (8) A tip-replaceable drill according to the present disclosure includes the drill head described in (7) above and a holder attached to a mounting surface.

[0015] [Details of the embodiments of the present disclosure] The details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant descriptions will not be repeated.

[0016] (First embodiment) First, a description will be given of the configuration of the drill according to the first embodiment. The drill according to the first embodiment is a tip-exchangeable drill.

[0017] FIG. 1 is a schematic perspective view showing the configuration of a drill according to a first embodiment. As shown in FIG. 1, a drill 100 according to the first embodiment is rotated around a central axis A. The drill 100 has a tip end 101 and a rear end 102. The tip end 101 and the rear end 102 are ends of the drill 100 in the direction of the central axis A. The rear end 102 is located on the opposite side of the tip end 101 in the direction of the central axis A.

[0018] The drill 100 has a drill head 10, a holder 20, and a fixing member 30. The drill head 10 forms a tip 101 of the drill 100. The holder 20 forms a rear end 102 of the drill 100. The drill head 10 is attached to the holder 20 using the fixing member 30.

[0019] <Drill head configuration> FIG. 2 is a perspective schematic diagram showing the configuration of a drill head 10. The drill head 10 is made of, for example, cemented carbide. The drill head 10 is rotated around a central axis A. As shown in FIG. 2, the drill head 10 has a cutting edge 1, a mounting surface 12, a tip surface 11, an outer peripheral surface 5, a flute surface 4, and a thinning surface 40.

[0020] The mounting surface 12 is the surface facing the holder 20. The mounting surface 12 is an end surface in the direction along the central axis A of the drill head 10. The tip surface 11 is the surface opposite the mounting surface 12 in the direction along the central axis A. The outer peripheral surface 5 is continuous with the mounting surface 12 and the tip surface 11. The flute surface 4 is formed on the outer peripheral surface 5. The flute surface 4 extends spirally around the central axis A from the tip surface 11 toward the mounting surface 12. The thinning surface 40 is continuous with the tip surface 11 and the flute surface 4.

[0021] The tip face 11 has a first flank portion 51 and a second flank portion 52. The first flank portion 51 is continuous with the cutting edge 1. The second flank portion 52 is located on the opposite side of the first flank portion 51 across the flute surface 4. In the rotation direction of the drill 100, the flute surface 4 is located between the first flank portion 51 and the second flank portion 52. The first flank portion 51 and the second flank portion 52 may be configured as a single conical surface. A step portion may be provided between the first flank portion 51 and the second flank portion 52.

[0022] The thinning surface 40 has a thinning rake surface 44 and a thinning heel surface 45. The thinning rake surface 44 is continuous with a first flank portion 51. The thinning heel surface 45 is continuous with a second flank portion 52. The thinning rake surface 44 and the thinning heel surface 45 are continuous with the flute surface 4.

[0023] The thinning rake face 44 has a first thinning rake face portion 41, a second thinning rake face portion 42, and a third thinning rake face portion 43. The first thinning rake face portion 41 is continuous with the thinning heel face 45 and the third thinning rake face portion 43. The first thinning rake face portion 41 is located between the thinning heel face 45 and the third thinning rake face portion 43. The first thinning rake face portion 41 is spaced apart from the flute surface 4. The first thinning rake face portion 41 is spaced apart from the second thinning rake face portion 42.

[0024] The second thinning rake surface portion 42 is continuous with the flute surface 4 and the third thinning rake surface portion 43. The second thinning rake surface portion 42 is located between the flute surface 4 and the third thinning rake surface portion 43. The second thinning rake surface portion 42 is spaced apart from the thinning heel surface 45.

[0025] The third thinning rake surface portion 43 is continuous with the first thinning rake surface portion 41, the second thinning rake surface portion 42, the flute surface 4, and the thinning heel surface 45. The third thinning rake surface portion 43 connects the first thinning rake surface portion 41 and the second thinning rake surface portion 42. The third thinning rake surface portion 43 connects the second thinning rake surface portion 42 and the thinning heel surface 45.

[0026] Fig. 3 is a schematic front view showing the configuration of the drill head 10. The schematic front view shown in Fig. 3 is a view of the tip surface 11 of the drill head 10 viewed along the central axis A. As shown in Fig. 3, the cutting edge 1 extends from the outer peripheral surface 5 toward the central axis A on the tip surface 11. The cutting edge 1 has a major cutting edge portion 65, a thinning cutting edge portion 64, and a chisel edge 66. The major cutting edge portion 65 is continuous with the outer peripheral surface 5.

[0027] As shown in FIG. 3 , the thinning cutting edge portion 64 has a first thinning cutting edge portion 61, a second thinning cutting edge portion 62, and a third thinning cutting edge portion 63. The first thinning cutting edge portion 61 is linear. The first thinning cutting edge portion 61 is continuous with the chisel edge 66. The second thinning cutting edge portion 62 is linear. The second thinning cutting edge portion 62 is continuous with the major cutting edge portion 65.

[0028] As shown in Figure 3, the third thinning cutting edge portion 63 is curved. The third thinning cutting edge portion 63 has an outwardly convex shape. The third thinning cutting edge portion 63 is continuous with the first thinning cutting edge portion 61 and the second thinning cutting edge portion 62. The third thinning cutting edge portion 63 is located between the first thinning cutting edge portion 61 and the second thinning cutting edge portion 62.

[0029] As shown in Figure 2, the main cutting edge portion 65 is formed by the ridgeline between the first flank portion 51 and the flute surface 4. The first thinning cutting edge portion 61 is formed by the ridgeline between the first thinning rake surface portion 41 and the first flank portion 51. The second thinning cutting edge portion 62 is formed by the ridgeline between the second thinning rake surface portion 42 and the first flank portion 51. The third thinning cutting edge portion 63 is formed by the ridgeline between the third thinning rake surface portion 43 and the first flank portion 51.

[0030] As shown in FIG. 2 , the point where the first thinning rake face portion 41, the third thinning rake face portion 43, and the thinning heel face 45 meet is defined as the first triple point T1. The point where the second thinning rake face portion 42, the third thinning rake face portion 43, and the flute face 4 meet is defined as the second triple point T2. The point where the third thinning rake face portion 43, the flute face 4, and the thinning heel face 45 meet is defined as the third triple point T3. In the direction along the central axis A, the second triple point T2 may be located between the first triple point T1 and the third triple point T3.

[0031] As shown in FIG. 3, the major cutting edge portion 65 has a first major cutting edge region 65a and a second major cutting edge region 65b. The second major cutting edge region 65b is located on the opposite side of the first major cutting edge region 65a with respect to the central axis A. The central axis A is located between the first major cutting edge region 65a and the second major cutting edge region 65b. The first major cutting edge region 65a and the second major cutting edge region 65b are located in positions of dyad symmetry with respect to the central axis A. The distance between the outer end point of the first major cutting edge region 65a and the outer end point of the second major cutting edge region 65b is the diameter D of the cutting edge 1.

[0032] The first thinning cutting edge portion 61 has a first thinning cutting edge region 61a and a second thinning cutting edge region 61b. The first thinning cutting edge region 61a is located between the first major cutting edge region 65a and the central axis A. The second thinning cutting edge region 61b is located between the second major cutting edge region 65b and the central axis. The first thinning cutting edge region 61a and the second thinning cutting edge region 61b are located at positions that are dyad-symmetric with respect to the central axis A.

[0033] As shown in FIG. 3, when the tip end face 11 is viewed along the central axis A, the direction extending outward along the first thinning cutting edge region 61a is defined as the first direction L1. When the tip end face 11 is viewed along the central axis A, the direction from the central axis A toward the outer end point of the second major cutting edge region 65b is defined as the second direction L2. The angle formed by the first direction L1 and the second direction L2 is defined as the thinning angle θ3. The thinning angle θ3 is, for example, 141° or greater and 155° or less. The thinning angle θ3 may be 143° or greater and 153° or less, or 145° or greater and 151° or less.

[0034] 3, the drill head 10 is provided with a mounting hole 3. The mounting hole 3 is located at the boundary between the second flank portion 52 and the thinning heel surface 45. The mounting hole 3 opens into the second flank portion 52 and the thinning heel surface 45.

[0035] 4 is a schematic rear view showing the configuration of the drill head 10. As shown in FIG. 4, a plurality of grooves 15 are provided in the mounting surface 12 of the drill head 10. Each of the plurality of grooves 15 extends from the outer peripheral surface 5 toward the central axis A. The mounting hole 3 penetrates from the tip surface 11 of the drill head 10 to the mounting surface 12. The mounting hole 3 opens into the mounting surface 12.

[0036] 5 is a schematic front view showing an example of the configuration of the cutting edge 1. In FIG. 5, the direction substantially perpendicular to the major cutting edge portion 65 is shown enlarged compared to the direction substantially parallel to the major cutting edge portion 65.

[0037] 5, when the tip surface 11 is viewed along the central axis A, an imaginary line extending from the second thinning cutting edge portion 62 toward the outer peripheral surface 5 is defined as a first imaginary line B1. When the tip surface 11 is viewed along the central axis A, the first imaginary line B1 may be located forward in the rotational direction of an outer end point 71 of the major cutting edge portion 65. The outer end point 71 of the major cutting edge portion 65 is the connection point between the major cutting edge portion 65 and the outer peripheral surface 5.

[0038] When the tip surface 11 is viewed along the central axis A, the distance between the first imaginary line B1 and the outer end point 71 of the major cutting edge portion 65 is defined as a first distance E. The first distance E may be 0.01 times or less the diameter D of the cutting edge 1. The first distance E may be 0.008 times or less, or 0.006 times or less the diameter D of the cutting edge 1. The first distance E is not particularly limited, but may be 0.001 times or more the diameter D of the cutting edge 1.

[0039] As shown in FIG. 5 , the cutting edge 1 has a second connection point 72, a third connection point 73, a fourth connection point 74, and a fifth connection point 75. The second connection point 72 is the connection point between the main cutting edge portion 65 and the second thinning cutting edge portion 62. The third connection point 73 is the connection point between the second thinning cutting edge portion 62 and the third thinning cutting edge portion 63. The fourth connection point 74 is the connection point between the third thinning cutting edge portion 63 and the first thinning cutting edge portion 61. The fifth connection point 75 is the connection point between the first thinning cutting edge portion 61 and the chisel edge 66.

[0040] The length of the first thinning cutting edge portion 61 is defined as a first length C1. The first length C1 is the distance between the fourth connection point 74 and the fifth connection point 75. The length of the second thinning cutting edge portion 62 is defined as a second length C2. The second length C2 is the distance between the second connection point 72 and the third connection point 73. The length of the major cutting edge portion 65 is defined as a third length C3. The third length C3 is the distance between the outer end point 71 of the major cutting edge portion 65 and the second connection point 72 in the direction along the first virtual straight line B1.

[0041] The value obtained by dividing the first length C1 by the sum of the third length C3 and the second length C2 may be 0.19 or more and 0.25 or less. The value obtained by dividing the first length C1 by the sum of the third length C3 and the second length C2 may be 0.195 or more and 0.245 or less, or 0.20 or more and 0.24 or less.

[0042] 5, the third thinning cutting edge portion 63 has, for example, an arc shape. The radius of curvature R of the third thinning cutting edge portion 63 is, for example, 0.15 times the diameter D of the cutting edge 1. The radius of curvature R of the third thinning cutting edge portion 63 may be, for example, 0.08 to 0.20 times the diameter D of the cutting edge 1, or 0.12 to 0.18 times the diameter D of the cutting edge 1.

[0043] 6 is a schematic front view showing another example of the configuration of the cutting edge 1. In FIG. 6, the direction substantially perpendicular to the major cutting edge portion 65 is shown enlarged compared to the direction substantially parallel to the major cutting edge portion 65.

[0044] 6, when the tip surface 11 is viewed along the central axis A, an imaginary line connecting the connection point (outer end point 71) between the main cutting edge portion 65 and the outer peripheral surface 5 and the connection point (second connection point 72) between the second thinning cutting edge portion 62 and the main cutting edge portion 65 is defined as a second imaginary line B2. When the tip surface 11 is viewed along the central axis A, the recess amount F of the main cutting edge portion 65 with respect to the second imaginary line B2 may be not less than −0.01 times and not more than 0.02 times the diameter of the cutting edge 1.

[0045] As shown by the solid line in Fig. 6, when the main cutting edge portion 65 is curved backward in the direction of rotation, the recess amount F is considered to be positive. Conversely, as shown by the dashed line in Fig. 6, when the main cutting edge portion 65 is curved forward in the direction of rotation, the recess amount F is considered to be negative.

[0046] FIG. 7 is a cross-sectional schematic diagram showing the axial rake angle of the first thinning rake face portion 41. The cross-sectional schematic diagram shown in FIG. 7 is a cross section perpendicular to the first thinning cutting edge portion 61 and parallel to the central axis A. As shown in FIG. 7, the axial rake angle of the first thinning rake face portion 41 may be, for example, positive. The axial rake angle of the first thinning rake face portion 41 is defined as a first rake angle θ1. The first rake angle θ1 is the angle formed between a straight line A1 parallel to the central axis A and the first thinning rake face portion 41. The first rake angle θ1 may be, for example, −7° to 7°, −5° to 5°, or −3° to 3°.

[0047] FIG. 8 is a cross-sectional schematic diagram showing the axial rake angle of the second thinning rake face portion 42. The cross-sectional schematic diagram shown in FIG. 8 is a cross section perpendicular to the second thinning cutting edge portion 62 and parallel to the central axis A. As shown in FIG. 8, the axial rake angle of the second thinning rake face portion 42 may be, for example, positive. The axial rake angle of the second thinning rake face portion 42 is defined as a second rake angle θ2. The second rake angle θ2 is the angle formed between a straight line A1 parallel to the central axis A and the second thinning rake face portion 42. The second rake angle θ2 may be, for example, not less than -7° and not more than 7°, not more than -5° and not more than 5°, or not more than -3° and not more than 3°.

[0048] FIG. 9 is a cross-sectional schematic diagram showing the axial rake angle of the flute surface 4. The cross-sectional schematic diagram shown in FIG. 9 is a cross section perpendicular to the tangent of the major cutting edge portion 65 and parallel to the central axis A. As shown in FIG. 9, the axial rake angle of the flute surface 4 may be positive, for example. The axial rake angle of the flute surface 4 is defined as a fourth rake angle θ4. The fourth rake angle θ4 is the angle formed between the flute surface 4 and a straight line A1 parallel to the central axis A. The fourth rake angle θ4 may be larger than the first rake angle θ1. The fourth rake angle θ4 may be larger than the second rake angle θ2.

[0049] <Holder configuration> FIG. 10 is a schematic perspective view showing the configuration of the holder 20. As shown in FIG. 10, the holder 20 has a front end face 21, a rear end face 22, a holder outer peripheral surface 23, and a holder flute surface 24. The holder 20 extends along a central axis A2. The front end face 21 is located opposite the rear end face 22 in the direction in which the central axis A2 extends. The holder outer peripheral surface 23 is continuous with the front end face 21. The holder flute surface 24 is provided in a spiral shape around the central axis A2. The central axis A2 of the holder 20 coincides with the central axis A of the drill head 10.

[0050] The front end face 21 is formed with a plurality of ridges 25 extending from the center of the front end face 21 to the outer circumferential surface 5. The front end face 21 of the holder 20 is disposed opposite the mounting surface 12 of the drill head 10. The plurality of grooves 15 formed in the mounting surface 12 of the drill head 10 are fitted into the plurality of ridges 25 formed in the front end face 21 of the holder 20. As described above, the holder 20 is attached to the mounting surface 12 of the drill head 10.

[0051] (Second embodiment) Next, the configuration of the drill 100 according to the second embodiment will be described. The drill 100 according to the second embodiment is a solid-type drill 100. The drill 100 according to the second embodiment differs from the drill 100 according to the first embodiment in that it is not a tip-replaceable drill, but other configurations are substantially the same as those of the drill 100 according to the first embodiment.

[0052] Fig. 11 is a schematic perspective view showing the overall configuration of the drill 100 according to the second embodiment. Fig. 12 is an enlarged schematic perspective view showing the configuration of a portion of the drill 100 according to the second embodiment.

[0053] As shown in FIGS. 11 and 12 , a drill 100 according to the second embodiment is rotated around a central axis A. The drill 100 has a tip surface 11, an outer peripheral surface 5, flute surfaces 4, and a thinning surface 40. The tip surface 11 is located at a tip 101 of the drill 100. The outer peripheral surface 5 is continuous with the tip surface 11. The flute surfaces 4 are formed on the outer peripheral surface 5. The flute surfaces 4 extend from the tip surface 11 toward a butt end 102 around the central axis A. The thinning surface 40 is continuous with the tip surface 11 and the flute surfaces 4.

[0054] The drill 100 has a cutting edge 1. The cutting edge 1 extends from the outer peripheral surface 5 toward the central axis A on the tip surface 11. The tip surface 11 has a first flank portion 51 that is continuous with the cutting edge 1 and a second flank portion 52 that is located on the opposite side of the flute surface 4 from the first flank portion 51. The thinning surface 40 has a thinning rake face 44 that is continuous with the first flank portion 51 and a thinning heel face 45 that is continuous with the second flank portion 52. The configurations of the tip surface 11, the outer peripheral surface 5, the flute surface 4, the thinning surface 40, and the cutting edge 1 are substantially the same as those of the drill 100 according to the first embodiment.

[0055] The effects of the drill 100 and the drill head 10 according to this embodiment will be described below.

[0056] According to the drill 100 and drill head 10 of this embodiment, the thinning cutting edge portion 64 has a linear first thinning cutting edge portion 61, a linear second thinning cutting edge portion 62, and a curved third thinning cutting edge portion 63. This allows the length of the major cutting edge portion 65 to be longer than the length of the first thinning cutting edge portion 61, compared to when the thinning cutting edge portion 64 is a single linear cutting edge. Therefore, when chips cut by the first thinning cutting edge portion 61 are discharged to the outer periphery, the chips are discharged linearly along the major cutting edge portion 65 due to centrifugal force. Therefore, the centrifugal force makes it easier for the chips to break up. As a result, the chips can be more easily broken up.

[0057] In the drill 100 and drill head 10 according to this embodiment, when the tip surface 11 is viewed along the central axis A, the recess amount F of the major cutting edge portion 65 with respect to an imaginary line connecting the connection point between the major cutting edge portion 65 and the outer peripheral surface 5 and the connection point between the second thinning cutting edge portion 62 and the major cutting edge portion 65 may be between −0.01 and 0.02 times the diameter of the cutting edge 1. This makes the major cutting edge portion 65 substantially linear. As a result, chips are less likely to get caught on the major cutting edge portion 65. Therefore, chips are discharged outward in a linear manner, further improving chip breakability.

[0058] In the drill 100 and drill head 10 according to this embodiment, when the tip surface 11 is viewed along the central axis A, the distance between an imaginary line extending the second thinning cutting edge portion 62 toward the outer peripheral surface 5 and the outer end point 71 of the major cutting edge portion 65 may be 0.01 times or less the diameter of the cutting edge 1. This reduces the step between the major cutting edge portion 65 and the second thinning cutting edge portion 62, allowing chips to be discharged more linearly to the outside. As a result, chip breakability can be further improved.

[0059] In the drill 100 and drill head 10 according to this embodiment, when the tip face 11 is viewed along the central axis A, the angle formed by the direction extending outward along the first thinning cutting edge region 61a and the direction from the central axis A toward the outer end point 71 of the second major cutting edge region 65b may be 141° or greater and 155° or less. This allows the length of the major cutting edge portion 65 to be further longer than the length of the first thinning cutting edge portion 61. As a result, chip breakability can be further improved.

[0060] In the drill 100 and drill head 10 according to this embodiment, the value obtained by dividing the length of the first thinning cutting edge portion 61 by the sum of the length of the major cutting edge portion 65 and the length of the second thinning cutting edge portion 62 may be 0.19 or more and 0.25 or less. This allows the length of the major cutting edge portion 65 and the length of the second thinning cutting edge portion 62 to be relatively long. As a result, the chip breakability can be further improved. [Example]

[0061] <Sample preparation> First, drills 100 of Samples 1 to 3 were prepared. The diameter D of the cutting edge 1 was 18 mm. The drill 100 of Sample 1 was the drill 100 described in Patent Document 1. Specifically, in the drill 100 of Sample 1, the thinning cutting edge portion 64 was a single linear cutting edge. The thinning angle θ3 in the drill 100 of Sample 1 was 160°. The drill 100 of Sample 2 was the same as the drill 100 of Sample 1, except that an X-thinning shape was applied. Specifically, when viewed in the direction along the central axis A, the ridge line between the thinning heel surface 45 and the second flank portion 52 was linear.

[0062] The drill 100 of Sample 3 is the drill 100 according to the first embodiment. As shown in FIG. 2 , the thinning edge portion 64 of the drill 100 of Sample 3 had a linear first thinning cutting edge portion 61, a linear second thinning cutting edge portion 62, and a curved third thinning cutting edge portion 63. The length of the first thinning cutting edge portion 61 was 1.487 mm. The length of the second thinning cutting edge portion 62 was 1.607 mm. The length of the major cutting edge portion 65 was 5.178 mm. The value obtained by dividing the length of the first thinning cutting edge portion 61 by the sum of the lengths of the major cutting edge portion 65 and the second thinning cutting edge portion 62 was approximately 0.22. The radius of curvature of the third thinning cutting edge portion 63 was 0.15 times the diameter of the cutting edge 1. The thinning angle θ3 of the drill 100 of Sample 1 was 149.5°.

[0063] <Cutting test method> Drilling was performed on the workpiece using drill 100 of Samples 1 to 3. The equipment used was a DGM Mori Seiki machining center (model number HSK-A63). The workpiece was rolled steel (JIS SS400). The cutting speed (Vc) was 80 m / min. The feed rate (f) was 0.20 mm / revolution. The through-hole length (H) was 100 mm. A water-soluble internal coolant system was used. The chips generated when the three holes were drilled were collected, and the chip breakage rate was calculated.

[0064] Of the collected chips, three types of chips with different generation mechanisms were excluded. Specifically, the entrance chips, disc-shaped chips, and chips from the breakaway were excluded. The entrance chips are characterized by a series of spirals with more than five layers. The breakaway chips are characterized by the spiral twist at the rear end of the chip becoming looser and thinner, with the length of this part being more than five times the length of the curled part. The chip fragmentation rate was calculated by dividing the mass of the fragmented chips by the total mass of the fragmented and unfragmented chips.

[0065] <Cutting test results>

[0066] [Table 1]

[0067] As shown in Table 1, the chip breakage rates of the drills 100 of Samples 1, 2, and 3 were 63%, 70%, and 96%, respectively. It was also experimentally demonstrated that the drill 100 of this embodiment improves the chip breakage rate.

[0068] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0069] 1 cutting edge, 3 mounting hole, 4 flute surface, 5 outer peripheral surface, 10 drill head, 11 tip surface, 12 mounting surface, 15 groove portion, 20 holder, 21 front end surface, 22 rear end surface, 23 holder outer peripheral surface, 24 holder flute surface, 25 convex portion, 30 fixing member, 40 thinning surface, 41 first thinning rake surface portion 42 second thinning rake face portion, 43 third thinning rake face portion, 44 thinning rake face, 45 thinning heel face, 51 first flank face portion, 52 second flank face portion, 61 First thinning cutting edge portion, 61a First thinning cutting edge region, 61b Second thinning cutting edge region, 62 Second thinning cutting edge region, 63 Third thinning cutting edge portion, 64 Thinning cutting edge portion, 65 Main cutting edge portion, 65a First main cutting edge region, 65b Second main cutting edge region, 66 Chisel edge, 71 Outer end point, 72 Second connection point, 73 Third connection point, 74 Fourth connection point, 75 Fifth connection point, 100 Drill, 101 Tip, 102 Rear end, A, A2 Center axis, A1 Straight line, B1 First virtual line, B2 Second virtual line, C1 First length, C2 Second length, C3 Third length, D Diameter, E First distance, F Recess amount, L1 1st direction, L2 2nd direction, R radius of curvature, T1 1st triple point, T2 2nd triple point, T3 3rd triple point.

Claims

1. A drill that rotates around a central axis, a leading end and a trailing end in a direction along the central axis; a tip surface at the tip; an outer circumferential surface connected to the tip surface; a cutting edge extending from the outer circumferential surface toward the central axis on the tip surface; a flute surface formed on the outer peripheral surface and extending around the central axis from the tip surface toward the rear end; a thinning surface connected to the tip surface and the flute surface, the tip surface has a first flank portion connected to the cutting edge and a second flank portion located on the opposite side of the first flank portion across the flute surface, the thinning surface has a thinning rake surface connected to the first flank portion and a thinning heel surface connected to the second flank portion, the thinning rake face has a first thinning rake face portion connected to the thinning heel surface, a second thinning rake face portion connected to the flute surface, and a third thinning rake face portion connecting the first thinning rake face portion and the second thinning rake face portion, The cutting edge is a main cutting edge portion that is continuous with the outer peripheral surface and is formed by a ridge line between the first flank surface portion and the flute surface; a first thinning cutting edge portion that is linear and formed by a ridgeline between the first thinning rake surface portion and the first flank surface portion; a second thinning cutting edge portion that is linear and formed by a ridgeline between the second thinning rake surface portion and the first flank surface portion; a third thinning cutting edge portion that is curved, is located between the first thinning cutting edge portion and the second thinning cutting edge portion, and is formed by a ridge line between the third thinning rake surface portion and the first flank surface portion; a value obtained by dividing the length of the first thinning cutting edge portion by the sum of the length of the main cutting edge portion and the length of the second thinning cutting edge portion is 0.19 or more and 0.25 or less, When the tip surface is viewed along the central axis, the main cutting edge portion curves forward in the rotational direction, and a recess amount of the main cutting edge portion with respect to an imaginary line connecting a connection point between the main cutting edge portion and the outer circumferential surface and a connection point between the second thinning cutting edge portion and the main cutting edge portion is −0.01 times or more of a diameter of the cutting edge, the third thinning rake surface portion is continuous with the flute surface, The drill, wherein the axial rake angle of each of the first thinning rake face portion and the second thinning rake face portion is not less than −3° and not more than 3°.

2. 2. The drill according to claim 1, wherein, when the tip surface is viewed along the central axis, a distance between an imaginary line extending the second thinning cutting edge portion toward the outer peripheral surface and an outer end point of the main cutting edge portion is 0.01 times or less the diameter of the cutting edge.

3. the major cutting edge portion has a first major cutting edge region and a second major cutting edge region on the opposite side of the first major cutting edge region with respect to the central axis, the first thinning cutting edge portion has a first thinning cutting edge region between the first major cutting edge region and the central axis, and a second thinning cutting edge region between the second major cutting edge region and the central axis, 2. The drill according to claim 1, wherein, when the tip surface is viewed along the central axis, an angle formed between a direction extending outward along the first thinning edge region and a direction from the central axis toward an outer end point of the second major cutting edge region is 141° or greater and 155° or less.

4. A drill head that is rotated about a central axis, a mounting surface that is an end surface in a direction along the central axis; a tip surface that is the opposite surface of the mounting surface in a direction along the central axis; an outer peripheral surface that is continuous with the mounting surface and the tip surface; a cutting edge extending from the outer circumferential surface toward the central axis on the tip surface; a flute surface formed on the outer peripheral surface and extending from the tip surface toward the mounting surface around the central axis; a thinning surface connected to the tip surface and the flute surface, the tip surface has a first flank portion connected to the cutting edge and a second flank portion located on the opposite side of the first flank portion across the flute surface, the thinning surface has a thinning rake surface connected to the first flank portion and a thinning heel surface connected to the second flank portion, the thinning rake face has a first thinning rake face portion connected to the thinning heel surface, a second thinning rake face portion connected to the flute surface, and a third thinning rake face portion connecting the first thinning rake face portion and the second thinning rake face portion, The cutting edge is a main cutting edge portion that is continuous with the outer peripheral surface and is formed by a ridge line between the first flank surface portion and the flute surface; a first thinning cutting edge portion that is linear and formed by a ridgeline between the first thinning rake surface portion and the first flank surface portion; a second thinning cutting edge portion that is linear and formed by a ridgeline between the second thinning rake surface portion and the first flank surface portion; a third thinning cutting edge portion that is curved, is located between the first thinning cutting edge portion and the second thinning cutting edge portion, and is formed by a ridge line between the third thinning rake surface portion and the first flank surface portion; a value obtained by dividing the length of the first thinning cutting edge portion by the sum of the length of the main cutting edge portion and the length of the second thinning cutting edge portion is 0.19 or more and 0.25 or less, When the tip surface is viewed along the central axis, the main cutting edge portion curves forward in the rotational direction, and a recess amount of the main cutting edge portion with respect to an imaginary line connecting a connection point between the main cutting edge portion and the outer circumferential surface and a connection point between the second thinning cutting edge portion and the main cutting edge portion is −0.01 times or more of a diameter of the cutting edge, the third thinning rake surface portion is continuous with the flute surface, The drill head, wherein the axial rake angle of each of the first thinning rake face portion and the second thinning rake face portion is not less than −3° and not more than 3°.

5. The drill head according to claim 4; and a holder attached to the mounting surface.

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