drill

Abstract

The drill comprises a center drill and a cutting insert. The center drill has a central cutting edge. The cutting insert has an outer cutting edge. If the tool diameter is twice the distance between the outer peripheral end of the outer cutting edge and the axis in the radial direction, the outer diameter of the center cutting edge is between 0.3 and 0.6 times the tool diameter. When viewed along the axis, the angle between the direction parallel to the main cutting edge portion of the center cutting edge and the direction radially outward from the axis and the direction from the axis toward the outer peripheral end of the outer cutting edge is between 30° and 50°. The center drill has an outer peripheral surface and a chip control surface provided on the outer peripheral surface. When viewed along the axis, the angle of the chip control surface with respect to the direction from the axis toward the outer peripheral end of the outer cutting edge is between 80° and 100°.

Description

Technical Field

[0003]

[0001] The present disclosure relates to a drill.

Background Art

[0002] Japanese Patent Publication No. 2016-508889 (Patent Document 1) describes a drill system having a holder body and a drill head.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The drill according to the present disclosure is a drill that rotates around an axis and includes a center drill and a cutting insert. The center drill has a central cutting edge. The cutting insert has an outer cutting edge. When the tool diameter is defined as twice the distance between the outer peripheral end of the outer cutting edge and the axis in the radial direction, the outer diameter of the central cutting edge is 0.3 times or more and 0.6 times or less of the tool diameter. When viewed in the direction along the axis, the angle formed by the main cutting edge portion of the central cutting edge, which is parallel to the axis and faces radially outward from the axis, and the direction from the axis to the outer peripheral end of the outer cutting edge is 30° or more and 50° or less. The center drill has an outer peripheral surface and a chip control surface provided on the outer peripheral surface. When viewed in the direction along the axis, the angle of the chip control surface with respect to the direction from the axis to the outer peripheral end of the outer cutting edge is 80° or more and 100° or less.

Brief Description of the Drawings

[0005] [Figure 1] FIG. 1 is a perspective schematic view showing the configuration of the drill according to the present embodiment. [Figure 2] FIG. 2 is a front schematic view showing the configuration of the drill according to the present embodiment. [Figure 3]Figure 3 is a schematic plan view showing the configuration of the center drill. [Figure 4] Figure 4 is an enlarged view of region IV in Figure 2. [Figure 5] Figure 5 is a schematic side view showing the configuration of the drill according to this embodiment. [Figure 6] Figure 6 is an enlarged view of area VI in Figure 5. [Figure 7] Figure 7 is an enlarged view of area VII in Figure 6. [Figure 8] Figure 8 is an enlarged view of region VIII in Figure 4. [Figure 9] Figure 9 is a schematic front view showing the arrangement of the guide pads. [Figure 10] Figure 10 is an enlarged schematic diagram of region X in Figure 5. [Figure 11] Figure 11 is a schematic perspective view showing the configuration of the head. [Figure 12] Figure 12 is a schematic bottom view showing the configuration of the head. [Figure 13] Figure 13 is a schematic side view showing the configuration of the holder. [Figure 14] Figure 14 is a schematic front view showing the configuration of the front end of the holder. [Figure 15] Figure 15 is a schematic perspective view showing the head attached to the holder. [Modes for carrying out the invention]

[0006] [Description of Embodiments in this Disclosure] First, embodiments of this disclosure (also referred to as these embodiments) will be described.

[0007] (1) The drill according to the present disclosure is a drill that rotates about an axis and comprises a center drill and a cutting insert. The center drill has a central cutting edge. The cutting insert has an outer cutting edge. If the tool diameter is twice the distance between the outer peripheral end of the outer cutting edge and the axis in the radial direction, the outer diameter of the central cutting edge is 0.3 times or more and 0.6 times or less the tool diameter. When viewed in the direction along the axis, the angle between the direction parallel to the main cutting edge portion of the central cutting edge and radially outward from the axis and the direction from the axis toward the outer peripheral end of the outer cutting edge is 30° or more and 50° or less. The center drill has an outer peripheral surface and a chip control surface provided on the outer peripheral surface. When viewed in the direction along the axis, the angle of the chip control surface with respect to the direction from the axis toward the outer peripheral end of the outer cutting edge is 80° or more and 100° or less.

[0008] (2) According to the drill described in (1) above, in the direction along the axis, the shoulder of the center drill is located in front of the apex of the cutting insert, and the distance between the shoulder of the center drill and the apex of the cutting insert may be greater than 0 and less than or equal to 1 mm.

[0009] (3) In the case of the drill according to (1) or (2) above, the cutting insert may have a rake face connected to the outer cutting edge and an outer surface connected to the rake face. Viewed in a direction perpendicular to the rake face, the outer cutting edge has a scraping edge formed by an arc-shaped cutting edge portion and a linear cutting edge portion connected to the arc-shaped cutting edge portion, the radius of curvature of the arc-shaped cutting edge portion is 0.3 mm or more, and the length of the linear cutting edge portion may be 0.5 mm or more and 3 mm or less. Viewed in a direction along the axis, the outer surface has an arc-shaped side surface portion connected to the outer cutting edge, the radius of curvature of the arc-shaped side surface portion may be 0.2 times or more and 0.5 times or less the tool diameter.

[0010] (4) In the case of a drill according to (1) or (2) above, the drill may be equipped with guide pads. The number of guide pads may be equal to or greater than the number of cutting inserts. When viewed in the direction along the axis, the angle between the direction from the axis toward the center of the guide pad and the direction from the axis toward the outer peripheral end of the outer cutting edge may be 10° or more and 80° or less. When viewed in the direction along the axis, the distance between the center of the guide pad and the outer peripheral end of the outer cutting edge may be 0.1 times or more and 1 time the tool diameter. When viewed in the direction along the axis, the guide pad may have a planar surface portion and an arc-shaped surface portion connected to the planar surface portion. The value obtained by subtracting the diameter of the arc-shaped surface portion from the tool diameter may be 0.1 mm or more and 1 mm or less.

[0011] (5) In the case of a drill according to (1) or (2) above, the drill may be equipped with a holder having a chip evacuation groove formed therein. When viewed in the direction along the axis, the angle between the direction from the axis toward the center of the end point of the chip evacuation groove and the direction from the axis toward the outer peripheral end of the outer cutting edge may be 40° or more and 90° or less.

[0012] (6) The drill according to (1) or (2) above may include a head and a holder that is detachable from the head. The center drill and the cutting insert may each be attached to the head. The head may have a first fastening portion and a second fastening portion. The first fastening portion may have a first contact surface that abuts against the holder at the outermost diameter side of the first fastening portion. The second fastening portion may have a second contact surface that abuts against the holder at the outermost diameter side of the second fastening portion. The outer cutting edge may have a first outer cutting edge portion and a second outer cutting edge portion. When viewed in the direction along the axis, the angle between the direction from the axis toward the outer peripheral end of the first contact surface and the direction from the axis toward the outer peripheral end of the first outer cutting edge is 50° or more and 70° or less, the angle between the direction from the axis toward the outer peripheral end of the second contact surface and the direction from the axis toward the outer peripheral end of the second outer cutting edge is 50° or more and 70° or less, and the length of the first contact surface and the second contact surface may be 0.03 times or more and 0.1 times or less of the tool diameter.

[0013] (7) According to the drill according to the above (1) or (2), the holder may have a third contact surface that contacts the first contact surface, a first anti-counter-rotation wall surface provided at a position inclined at an angle of 70° or more and 110° or less with respect to the third contact surface, a fourth contact surface that contacts the second contact surface, and a second anti-counter-rotation wall surface provided at a position inclined at an angle of 70° or more and 110° or less with respect to the fourth contact surface. When viewed in the direction along the axis, the distance between the first anti-counter-rotation wall surface and the second anti-counter-rotation wall surface may be 0.3 times or more and 0.5 times or less of the tool diameter. The holder and the head may be positioned using pins arranged along the axis.

[0014] Specific examples of embodiments of the present disclosure (hereinafter also referred to as the present embodiments) will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference numerals, and the description thereof will not be repeated.

[0015] FIG. 1 is a perspective schematic view showing the configuration of a drill according to the present embodiment. As shown in FIG. 1, the drill 100 according to the present embodiment mainly includes a center drill 10, a cutting insert 20, a head 40, a holder 30, and a guide pad 5. The drill 100 according to the present embodiment is used, for example, to form a deep hole having a depth of 4 times or more the tool diameter. The drill 100 rotates around an axis A. A direction that is perpendicular to the axis A and radially outward from the axis A is also referred to as a radial direction.

[0016] The center drill 10 is arranged at a position intersecting the axis A in the radial direction. The cutting insert 20 is arranged outside the axis A in the radial direction. Each of the center drill 10 and the cutting insert 20 is attached to the head 40. The guide pad 5 is arranged on the outer peripheral side surface of the head 40. The holder 30 is separable from the head 40. The head 40 is attached to the holder 30. In the direction along the axis A, the head 40 is located in front of the holder 30. A chip discharge groove 31 is formed in the holder 30.

[0017] Figure 2 is a schematic front view showing the configuration of the drill 100 according to this embodiment. The center drill 10 has a central cutting edge 11. As shown in Figures 2 and 3, the central cutting edge 11 has a thinning cutting edge portion 1, a main cutting edge portion 2, and a sub-cutting edge portion 3. The cutting insert 20 has an outer cutting edge 21. As shown in Figure 2, when viewed along axis A, the direction from axis A toward the outer peripheral end of the outer cutting edge 21 (hereinafter also referred to as the first outer peripheral end 22) is defined as the first direction R1. When viewed along axis A, the direction parallel to the main cutting edge portion 2 of the central cutting edge 11 and radially outward from axis A is defined as the second direction R2. When viewed along axis A, the angle between the first direction R1 and the second direction R2 is defined as the first angle θ1. The first angle θ1 is 30° or more and 50° or less. The first angle θ1 may be, for example, 32° or more and 48° or 35° or more and 45° or less.

[0018] As shown in Figure 2, the endpoint 32 of the chip discharge groove 31 is located in the enlarged diameter section 34 (see Figure 5). Looking in the direction along axis A, the direction from axis A toward the center of the endpoint 32 of the chip discharge groove 31 is defined as the third direction R3. Looking in the direction along axis A, the angle between the third direction R3 and the first direction R1 is defined as the second angle θ2. The second angle θ2 is, for example, 40° or more and 90° or less. The second angle θ2 may also be, for example, 45° or more and 85° or 50° or more and 80° or less. The center of the endpoint 32 of the chip discharge groove 31 is the midpoint of the endpoint in the rotational direction of the drill 100.

[0019] As shown in Figure 2, the drill 100 according to this embodiment has two cutting inserts 20. The two cutting inserts 20 are positioned symmetrically twice with respect to axis A as the center of rotation. The holder 30 has chip evacuation grooves 31 corresponding to each cutting insert 20. Note that the number of cutting inserts 20 is not limited to two. The number of cutting inserts 20 may be, for example, one or three or more.

[0020] Figure 3 is a schematic plan view showing the configuration of the center drill 10. As shown in Figure 3, the center drill 10 has a tip portion 18, a first rake face 17, a first relief face 14, a first outer peripheral surface 16, and a thinning surface 4. The central cutting edge 11 is formed by the ridge line between the thinning surface 4 and the first relief surface 14, and the ridge line between the first rake face 17 and the first relief surface 14. The first rake face 17 has a first rake region 17a and a second rake region 17b. In the radial direction, the first rake region 17a is located between the thinning surface 4 and the second rake region 17b. The first rake region 17a is connected to both the thinning surface 4 and the second rake region 17b. The thinning cutting edge portion 1 is formed by the ridge line between the thinning surface 4 and the first relief surface 14. The main cutting edge portion 2 is formed by the ridge line between the first rake region 17a and the first relief surface 14. The secondary cutting edge portion 3 is formed by the ridge line between the second rake region 17b and the first relief surface 14. The secondary cutting edge portion 3 forms the second outer peripheral end portion 12 of the central cutting edge 11.

[0021] The center drill 10 according to this embodiment has two central cutting edges 11. The two central cutting edges 11 are positioned symmetrically twice with respect to axis A as the center of rotation. Each of the two central cutting edges 11 extends axially rearward and radially outward from the tip portion 18. Each of the two central cutting edges 11 is inclined with respect to axis A and the radial direction. In the radial direction, the tip portion 18 is located on axis A.

[0022] The first relief surface 14 has a first relief surface portion 14a and a second relief surface portion 14b. The first relief surface portion 14a is connected to the central cutting edge 11. The second relief surface portion 14b is connected to the first relief surface portion 14a. The second relief surface portion 14b is located behind the first relief surface portion 14a in the rotational direction. The second relief surface portion 14b is spaced apart from the central cutting edge 11.

[0023] The first outer surface 16 is connected to the first relief surface 14. The first outer surface 16 has a margin 19, a chip control surface 13, and a flat side surface 15. The margin 19 is connected to the first relief surface portion 14a. The chip control surface 13 is connected to the second relief surface portion 14b. The chip control surface 13 is flat. The chip control surface 13 is inclined with respect to the second relief surface portion 14b. The flat side surface 15 is connected to both the chip control surface 13 and the second relief surface portion 14b. The flat side surface 15 is inclined with respect to both the chip control surface 13 and the second relief surface portion 14b.

[0024] Figure 4 is an enlarged view of region IV in Figure 2. As shown in Figure 4, when viewed in the direction along axis A, the trajectory T1 of the first outer peripheral end 22 of the outer cutting edge 21 is circular when the drill 100 rotates around axis A. The tool diameter C is twice the radial distance between the first outer peripheral end 22 of the outer cutting edge 21 and axis A. The tool diameter C is the same as the diameter of the trajectory T1.

[0025] When viewed in the direction along axis A, the trajectory T2 of the second outer peripheral end 12 of the central cutting edge 11 is circular when the drill 100 rotates around axis A. The outer diameter of the central cutting edge 11 is defined as the central cutting edge diameter B. The central cutting edge diameter B is twice the distance between the second outer peripheral end 12 of the central cutting edge 11 and axis A in the radial direction. The central cutting edge diameter B is the same as the diameter of the trajectory T2.

[0026] The central cutting edge diameter B is between 0.3 and 0.6 times the tool diameter C. For example, the central cutting edge diameter B may be between 0.32 and 0.58 times the tool diameter C, or between 0.35 and 0.55 times the tool diameter C.

[0027] In the radial direction, a portion of the central cutting edge 11 overlaps with the outer cutting edge 21. From another perspective, when the drill 100 rotates around axis A, a portion of the trajectory of the central cutting edge 11 intersects with the trajectory of the outer cutting edge 21.

[0028] As shown in Figure 4, the center drill 10 has a chip control surface 13. The chip control surface 13 is the surface that comes into contact with the chips cut by the cutting insert 20. The chip control surface 13 controls the direction of the chip flow. Specifically, the chip control surface 13 controls the direction of the chip flow so that the chips enter the chip discharge groove 31.

[0029] When viewed in the direction along axis A, the angle of the chip control surface 13 with respect to the first direction R1 is defined as the third angle θ3. The third angle θ3 is between 80° and 100°. The third angle θ3 may also be, for example, between 82° and 98°, or between 84° and 95°.

[0030] Figure 5 is a schematic side view showing the configuration of the drill 100 according to this embodiment. As shown in Figure 5, the holder 30 has a main body portion 33, an enlarged diameter portion 34, and a shank portion 35. In the direction along axis A, the enlarged diameter portion 34 is located between the main body portion 33 and the shank portion 35. The outer diameter of the enlarged diameter portion 34 is larger than the outer diameters of the main body portion 33 and the shank portion 35, respectively. Chip discharge grooves 31 are provided in the main body portion 33 and the enlarged diameter portion 34.

[0031] The shank portion 35 is attached to the tool spindle (not shown). The shank portion 35 forms the rear end of the drill 100. The center drill 10 forms the front end of the drill 100. In the direction along axis A, the direction from the front end to the rear end is axially rearward. In the direction along axis A, the direction from the rear end to the front end is axially forward.

[0032] Figure 6 is an enlarged view of region VI in Figure 5. The enlarged view shown in Figure 6 is perpendicular to the rake face (hereinafter also referred to as the second rake face 23) of the cutting insert 20. As shown in Figure 6, the outer cutting edge 21 of the cutting insert 20 has a first front cutting edge portion 61, a second front cutting edge portion 62, and a vertex portion 63. In the radial direction, the first front cutting edge portion 61 is located outside the second front cutting edge portion 62. In the radial direction, the first front cutting edge portion 61 is located between the first outer peripheral end portion 22 and the vertex portion 63. At the vertex portion 63, the first front cutting edge portion 61 is connected to the second front cutting edge portion 62.

[0033] The first front cutting edge portion 61 extends so that it is positioned axially rearward as it moves radially outward from the apex portion 63. Conversely, the second front cutting edge portion 62 extends so that it is positioned axially rearward as it moves radially inward from the apex portion 63. From the perspective of both the first front cutting edge portion 61 and the second front cutting edge portion 62, the apex portion 63 is the furthest forward in the axial direction.

[0034] As shown in Figure 6, along axis A, the central cutting edge 11 is located in front of the outer cutting edge 21. More specifically, along axis A, the shoulder 12 of the center drill 10 is located in front of the apex 63 of the cutting insert 20. The shoulder 12 of the center drill 10 corresponds to the second outer peripheral end 12 of the central cutting edge 11. The shoulder 12 of the center drill 10 is located at the triple intersection of the first rake face 17, the first relief face 14, and the margin 19. Along axis A, the distance between the shoulder 12 of the center drill 10 and the apex 63 of the cutting insert 20 is defined as the first distance D. The first distance D is greater than 0 and less than or equal to 1 mm. The first distance D may be, for example, 0.9 mm or less, or 0.8 mm or less.

[0035] Figure 7 is an enlarged view of area VII in Figure 6. The enlarged view shown in Figure 7 is perpendicular to the second rake face 23. As shown in Figure 7, the cutting insert 20 has a second rake face 23. The second rake face 23 is connected to the outer cutting edge 21. Viewed perpendicular to the second rake face 23, the outer cutting edge 21 has a scavenging edge 64. The scavenging edge 64 is connected to the first front cutting edge portion 61. The scavenging edge 64 is formed by an arc-shaped cutting edge portion 28 and a linear cutting edge portion 26. The linear cutting edge portion 26 is connected to the arc-shaped cutting edge portion 28.

[0036] As shown in Figure 7, when viewed in a direction perpendicular to the second rake face 23, the arc-shaped cutting edge portion 28 is arc-shaped, and the straight cutting edge portion 26 is straight. The radius of curvature of the arc-shaped cutting edge portion 28 is defined as the first radius of curvature H1. The first radius of curvature H1 is, for example, 0.3 mm or more. The first radius of curvature H1 may also be, for example, 0.4 mm or more, or 0.5 mm or more. The first radius of curvature H1 may also be, for example, 1 mm or less.

[0037] The linear cutting edge portion 26 is connected to the arc-shaped cutting edge portion 28 at the first outer peripheral end portion 22. The linear cutting edge portion 26 extends along a direction parallel to the axis A. The length of the linear cutting edge portion 26 is, for example, 0.5 mm or more and 3 mm or less. The length of the linear cutting edge portion 26 is defined as the third length G3. The third length G3 may be, for example, 0.7 mm or more and 2.8 mm or less, or 0.9 mm or more and 2.6 mm or less.

[0038] Figure 8 is an enlarged view of region VIII in Figure 4. The enlarged view shown in Figure 8 is perpendicular to axis A. The cutting insert 20 has an outer surface 65. The outer surface 65 is connected to the second rake face 23 and the second flank face 25, respectively. As shown in Figure 8, when viewed along axis A, the outer surface 65 has an arcuate side portion 24 and a linear side portion 27. The arcuate side portion 24 is connected to the outer cutting edge 21. The linear side portion 27 is connected to the arcuate side portion 24. The arcuate side portion 24 is located between the outer cutting edge 21 and the linear side portion 27. The radius of curvature of the arcuate side portion 24 is set to the second radius of curvature H2. The second radius of curvature H2 is, for example, 0.2 times or more and 0.5 times or less of the tool diameter C. The second radius of curvature H2 may be, for example, 0.23 times or more and 0.47 times or less the tool diameter C, or 0.26 times or more and 0.44 times or less.

[0039] Figure 9 is a schematic front view showing the arrangement of the guide pads. The schematic front view shown in Figure 9 is perpendicular to axis A. As shown in Figure 9, the drill 100 has two guide pads 5. The two guide pads are positioned, for example, in a way that is symmetrical twice with respect to axis A as the center of rotation.

[0040] As shown in Figure 9, when viewed along axis A, the direction from axis A toward the center of the guide pad 5 is defined as the fourth direction R4. The center of the guide pad 5 is the midpoint of the guide pad 5 in the rotational direction. When viewed along axis A, the angle between the fourth direction R4 and the first direction R1 is defined as the fourth angle θ4. The fourth angle θ4 is, for example, between 10° and 80°. The fourth angle θ4 may also be, for example, between 15° and 75°, or between 20° and 70°.

[0041] In the drill 100 according to this embodiment, the number of guide pads 5 is the same as the number of cutting inserts 20, but it does not have to be the same as the number of cutting inserts 20. Specifically, the number of guide pads 5 may be greater than the number of cutting inserts 20. For example, there may be two cutting inserts 20 and four guide pads 5.

[0042] As shown in Figure 9, when viewed along axis A, the guide pad 5 has a planar surface portion 91 and an arc-shaped surface portion 92. The arc-shaped surface portion 92 is connected to the planar surface portion 91. In the rotational direction, the arc-shaped surface portion 92 is located on both sides of the planar surface portion 91.

[0043] In the radial direction, the first outer peripheral end 22 of the cutting insert 20 is located outside the arc-shaped surface portion 92 of the guide pad 5. When viewed in the direction along axis A, twice the distance between axis A and the arc-shaped surface portion 92 is defined as the diameter J of the arc-shaped surface portion 92. The diameter J of the arc-shaped surface portion 92 is the diameter of the trajectory of the arc-shaped surface portion 92 when the drill 100 rotates. The value obtained by subtracting the diameter J of the arc-shaped surface portion 92 from the tool diameter C is, for example, 0.1 mm or more and 1 mm or less. The value obtained by subtracting the diameter J of the arc-shaped surface portion 92 from the tool diameter C may be, for example, 0.2 mm or more and 0.9 mm or less, or 0.3 mm or more and 0.8 mm or less.

[0044] Figure 10 is an enlarged schematic diagram of region X in Figure 5. As shown in Figure 10, the distance between the center of the guide pad 5 and the first outer peripheral end 22 of the outer cutting edge 21 in the direction along axis A is defined as the second distance E. The second distance E is, for example, 0.1 to 1 times the tool diameter C. The second distance E may also be, for example, 0.2 to 0.9 times the tool diameter C, or 0.3 to 0.8 times the tool diameter C. In the direction along axis A, the center of the guide pad 5 is the midpoint between the front end and the rear end of the guide pad 5. The guide pad 5 is fixed to the head 40 using fixing screws 66.

[0045] Figure 11 is a schematic perspective view showing the configuration of the head 40. Figure 12 is a schematic bottom view showing the configuration of the head 40. As shown in Figures 11 and 12, the head 40 has a head front surface 41, a head rear surface 42, a head outer peripheral surface 43, a first fastening portion 71, and a second fastening portion 72. The center drill 10 and the cutting insert 20 are each attached to the head front surface 41. The head rear surface 42 is located on the opposite side of the head front surface 41. The head rear surface 42 faces the holder 30. The head outer peripheral surface 43 is connected to both the head front surface 41 and the head rear surface 42. The head outer peripheral surface 43 is provided with a guide pad placement groove 44 where the guide pad 5 is placed. The head rear surface 42 is provided with a pin insertion hole 45.

[0046] The first fastening portion 71 and the second fastening portion 72 are each provided on the rear surface 42 of the head. The first fastening portion 71 has a first contact surface 71a, a first non-contact surface 71b, a first outer peripheral region 71d, and a first inner peripheral region 71e. The first contact surface 71a is connected to the first outer peripheral region 71d. The first non-contact surface 71b is connected to the first inner peripheral region 71e. The first contact surface 71a is connected to the first non-contact surface 71b. In the radial direction, the first contact surface 71a is located outside the first non-contact surface 71b. The first contact surface 71a contacts the holder 30 at the outermost diameter side of the first fastening portion 71. The first non-contact surface 71b does not contact the holder 30.

[0047] Similarly, the second fastening portion 72 has a second contact surface 72a, a second non-contact surface 72b, a second outer peripheral region 72d, and a second inner peripheral region 72e. The second contact surface 72a is connected to the second outer peripheral region 72d. The second non-contact surface 72b is connected to the second inner peripheral region 72e. The second contact surface 72a is connected to the second non-contact surface 72b. In the radial direction, the second contact surface 72a is located outside the second non-contact surface 72b. The second contact surface 72a contacts the holder 30 at the outermost diameter side of the second fastening portion 72. The second non-contact surface 72b does not contact the holder 30.

[0048] As shown in Figure 9, the cutting insert 20 has a first cutting insert portion 20a having a first outer cutting edge portion 21a and a second cutting insert portion 20b having a second outer cutting edge portion 21b. The direction from axis A toward the outer peripheral end portion 22a of the first outer cutting edge portion 21a is the sixth direction R6, and the direction from axis A toward the outer peripheral end portion 22b of the second outer cutting edge portion 21b is the eighth direction R8.

[0049] As shown in Figure 12, when viewed along axis A, the direction from axis A toward the outer peripheral end of the first contact surface 71a is defined as the fifth direction R5, and the direction from axis A toward the outer peripheral end of the second contact surface 72a is defined as the seventh direction R7. When viewed along axis A, the angle between the fifth direction R5 and the sixth direction R6 is defined as the fifth angle θ5. When viewed along axis A, the angle between the seventh direction R7 and the eighth direction R8 is defined as the sixth angle θ6. Each of the fifth angle θ5 and the sixth angle θ6 is, for example, between 50° and 70°. Each of the fifth angle θ5 and the sixth angle θ6 may also be, for example, between 52° and 68°, or between 54° and 66°.

[0050] The first contact surface 71a and the second contact surface 72a are parallel to the radial direction. Viewed along axis A, the length of the first contact surface 71a is defined as the first length G1. Viewed along axis A, the length of the second contact surface 72a is defined as the second length G2. Each of the first length G1 and the second length G2 is, for example, 0.03 times or more and 0.1 times or less the tool diameter C. Each of the first length G1 and the second length G2 may also be, for example, 0.035 times or more and 0.095 times or less the tool diameter C, or 0.04 times or more and 0.09 times or less the tool diameter C.

[0051] Figure 13 is a schematic side view showing the configuration of the holder 30. Figure 14 is a schematic front view showing the configuration of the front end of the holder 30. The holder 30 has a pin 37, a holder front surface 85, a holder outer peripheral surface 38, a third contact surface 83, a first anti-reverse rotation wall surface 81, a fourth contact surface 84, and a second anti-reverse rotation wall surface 82. The pin 37 is provided on the holder front surface 85. The pin 37 is arranged along axis A. The pin 37 extends axially forward from the holder front surface 85.

[0052] When the head 40 is attached to the holder 30, the third contact surface 83 comes into contact with the first contact surface 71a. The first anti-reverse rotation wall surface 81 is positioned at an angle of 7 degrees θ7 relative to the third contact surface 83. When the head 40 is attached to the holder 30, the fourth contact surface 84 comes into contact with the second contact surface 72a. The second anti-reverse rotation wall surface 82 is positioned at an angle of 8 degrees θ8 relative to the fourth contact surface 84.

[0053] The seventh angle θ7 and the eighth angle θ8 are, for example, between 70° and 110°. The seventh angle θ7 and the eighth angle θ8 may also be, for example, between 75° and 105°, or between 80° and 100°.

[0054] The third contact surface 83 and the fourth contact surface 84 are substantially parallel. The first anti-reverse rotation wall surface 81 and the second anti-reverse rotation wall surface 82 are substantially parallel. When viewed in the direction along axis A, the distance between the first anti-reverse rotation wall surface 81 and the second anti-reverse rotation wall surface 82 is defined as the third distance F. The third distance F is, for example, 0.3 times or more and 0.5 times or less of the tool diameter C. The third distance F may also be, for example, 0.32 times or more and 0.48 times or less of the tool diameter C, or 0.34 times or more and 0.46 times or less of the tool diameter C.

[0055] Figure 15 is a schematic perspective view showing the head 40 attached to the holder 30. As shown in Figure 15, the pin 37 provided in the holder 30 is inserted into the pin insertion hole 45 provided in the head 40. The holder 30 and the head 40 are positioned using the pin 37 which is positioned along axis A. By designing the tolerance of the fitting portion of the pin 37 to be smaller than the tolerance of the fitting portions of the first anti-reverse rotation wall surface 81 and the second anti-reverse rotation wall surface 82, the positioning of the head 40 and the holder 30 is, in principle, performed by the pin 37.

[0056] In the above embodiment, the holder 30 is provided with a pin 37 and the head 40 is provided with a pin insertion hole 45, but this disclosure is not limited to the above embodiment. For example, the holder 30 may be provided with a pin insertion hole and the head 40 may be provided with a pin. Alternatively, the holder 30 and the head 40 may be fastened together by providing a protrusion on the holder 30 and a recess on the head 40, or by providing a recess on the holder 30 and a protrusion on the head 40.

[0057] A first fastening screw mounting hole 93 is provided on the outer peripheral surface 38 of the holder. A second fastening screw mounting hole 94 is provided on the first non-contact surface 71b of the first fastening portion 71 of the head 40 (see Figure 11). A fastening screw (not shown) having a conical head is inserted into the first fastening screw mounting hole 93 and the second fastening screw mounting hole 94. This fixes the first fastening portion 71 to the holder 30. Similarly, the second fastening portion 72 is fixed to the holder 30 using a fastening screw (not shown). This attaches the head 40 to the holder 30. The first fastening screw mounting hole 93 and the second fastening screw mounting hole 94 are located at axially offset positions. When the head 40 is fastened to the holder 30, the head 40 is pulled axially relative to the holder 30. The above fastening structure makes it possible to increase the area of ​​the axial contact surface between the head 40 and the holder 30.

[0058] In the above embodiment, the holder 30 and the head 40 are configured to be separable, but this disclosure is not limited to the above embodiment. For example, the holder 30 and the head 40 may be integrally formed and not separable.

[0059] Next, the operation and effects of the drill 100 according to this embodiment will be described. According to the drill 100 of this embodiment, the outer diameter of the central cutting edge 11 is between 0.3 and 0.6 times the tool diameter C. If the outer diameter of the central cutting edge 11 is less than 0.3 times the tool diameter C, the length of the overlapping portion between the center drill 10 and the cutting insert 20 in the radial direction becomes excessively short. This increases the vibration of the drill 100, making the cutting process unstable. If the outer diameter of the central cutting edge 11 is greater than 0.6 times the tool diameter C, the length of the overlapping portion between the center drill 10 and the cutting insert 20 in the radial direction becomes excessively long. This widens the gap between the center drill 10 and the cutting insert 20, increasing the likelihood of chips getting stuck in the gap. By setting the outer diameter of the central cutting edge 11 to be between 0.3 and 0.6 times the tool diameter C, it is possible to improve the stability of the cutting process while reducing the possibility of chips getting stuck in the gap between the center drill 10 and the cutting insert 20.

[0060] According to the drill 100 of this embodiment, when viewed in the direction along axis A, the angle between the direction parallel to the main cutting edge portion 2 of the central cutting edge 11 and extending radially outward from axis A, and the direction extending from axis A towards the outer peripheral end of the outer cutting edge 21, is 30° or more and 50° or less. If this angle is less than 30°, the center drill 10 will be closer to the cutting insert 20, making it easier for chips to get stuck in the gap between the center drill 10 and the cutting insert 20. If this angle is greater than 50°, the center drill 10 will be further away from the cutting insert 20, requiring a larger capacity for the chip discharge groove 31 for the center drill 10. Therefore, there is a concern that the rigidity of the drill 100 may be excessively reduced. By setting this angle to 30° or more and 50° or less, the possibility of chips getting stuck in the gap between the center drill 10 and the cutting insert 20 can be reduced without excessively reducing the rigidity of the drill 100.

[0061] According to the drill 100 of this embodiment, the angle of the chip control surface 13 with respect to the direction from axis A toward the outer peripheral end of the outer cutting edge 21, when viewed in the direction along axis A, is 80° or more and 100° or less. If the angle is less than 80°, the center drill 10 becomes closer to the cutting insert 20, making it easier for chips to get stuck in the gap between the center drill 10 and the cutting insert 20. If the angle is greater than 100°, it becomes difficult to provide a margin 19 on the outer peripheral surface of the center drill 10. By setting the angle to 80° or more and 100° or less, it is possible to provide a margin 19 on the center drill 10 while reducing the possibility of chips getting stuck in the gap between the center drill 10 and the cutting insert 20.

[0062] According to the drill 100 of this embodiment, in the direction along axis A, the shoulder portion 12 of the center drill 10 is located in front of the apex portion 63 of the cutting insert 20, and the distance between the shoulder portion 12 of the center drill 10 and the apex portion 63 of the cutting insert 20 may be greater than 0 and less than or equal to 1 mm. This makes it difficult for the cone-shaped chips formed when the drill 100 penetrates the workpiece to adhere to the drill 100.

[0063] According to the drill 100 of this embodiment, the outer cutting edge 21 has a finishing edge 64 formed by an arc-shaped cutting edge portion 28 and a linear cutting edge portion 26 connected to the arc-shaped cutting edge portion 28, and the radius of curvature of the arc-shaped cutting edge portion 28 is 0.3 mm or more. This prevents the finishing edge 64 from chipping. The length of the linear cutting edge portion 26 is 0.5 mm or more and 3 mm or less. By setting the length of the linear cutting edge portion 26 to 0.5 mm or more, the runout of the drill 100 can be reduced by the effect of the linear cutting edge portion 26 guiding the drill 100 to the wall surface of the machined hole (hereinafter also referred to as the guiding effect). By setting the length of the linear cutting edge portion 26 to 3 mm or less, it is possible to prevent the guiding effect from becoming excessive and increasing the cutting resistance.

[0064] According to the drill 100 of this embodiment, the radius of curvature of the arc-shaped side portion 24 is 0.2 times or more and 0.5 times or less the tool diameter C. By setting the radius of curvature of the arc-shaped side portion 24 to 0.2 times or more the tool diameter C, a guiding effect can be exerted, thereby reducing the runout of the drill 100. By setting the radius of curvature of the arc-shaped side portion 24 to 0.5 times or less the tool diameter C, it is possible to prevent the guiding effect from becoming excessive and increasing the cutting resistance.

[0065] According to the drill 100 of this embodiment, the number of guide pads 5 is equal to or greater than the number of cutting inserts 20. When viewed in the direction along axis A, the angle between the direction from axis A toward the center of the guide pad 5 and the direction from axis A toward the outer peripheral end of the outer cutting edge 21 is between 10° and 80°. This allows the inner wall of the hole formed in the workpiece by the cutting inserts 20 and the guide pads 5 to be supported in a balanced manner, thereby reducing the magnitude of vibration of the drill 100.

[0066] According to the drill 100 of this embodiment, the distance between the center of the guide pad 5 and the outer peripheral end of the outer cutting edge 21 is between 0.1 and 1 times the tool diameter C. As a result, even when the cutting insert 20 extends outside the machining hole when the surface where the exit of the machining hole formed in the workpiece is inclined, the guide pad 5 contacts the inner wall of the machining hole, thereby reducing vibration of the drill 100.

[0067] According to the drill 100 of this embodiment, the value obtained by subtracting the diameter of the arc-shaped surface portion 92 from the tool diameter C is 0.1 mm or more and 1 mm or less. This allows the guide pad 5 to contact the inner wall of the hole without excessively increasing the cutting resistance between the inner wall of the machined hole and the guide pad 5.

[0068] In the drill 100 according to this embodiment, the angle between the direction from axis A toward the center of the end point 32 of the chip evacuation groove 31 and the direction from axis A toward the outer peripheral end of the outer cutting edge 21 is 40° or more and 90° or less. By setting this angle to 40° or more, the force acting on the cutting insert 20 and the center drill 10 can be withstood. Therefore, the magnitude of vibration of the drill 100 can be reduced. By setting this angle to 90° or less, the length of the chip evacuation groove 31 formed in the holder 30 can be shortened. Therefore, the rigidity of the drill 100 can be maintained at a high level.

[0069] According to the drill 100 of this embodiment, the holder 30 is separable from the head 40. Therefore, if the head 40 is damaged, the head 40 can be replaced and the same holder 30 can be used.

[0070] According to the drill 100 of this embodiment, the head 40 has a first fastening portion 71 and a second fastening portion 72. The first fastening portion 71 has a first contact surface 71a that abuts against the holder 30 at the outermost diameter side of the first fastening portion 71. The second fastening portion 72 has a second contact surface 72a that abuts against the holder 30 at the outermost diameter side of the second fastening portion 72. As a result, when attaching the head 40 to the holder 30, the first contact surface 71a and the second contact surface 72a can each be brought into contact with the holder 30. Therefore, variations in the contact position of the head 40 can be reduced.

[0071] In the drill 100 according to this embodiment, the angle between the direction from axis A toward the outer peripheral end of the first contact surface 71a and the direction from axis A toward the outer peripheral end of the first outer cutting edge portion 21a is 50° or more and 70° or less. The angle between the direction from axis A toward the outer peripheral end of the second contact surface 72a and the direction from axis A toward the outer peripheral end of the second outer cutting edge portion 21b is 50° or more and 70° or less. In the portion of the holder 30 where the chip discharge groove 31 is provided, the rigidity of the holder 30 decreases, making the drill 100 more prone to vibration. If this angle becomes excessively small, the first fastening portion 71 and the second fastening portion 72 move closer to the cutting insert 20 side, reducing the volume of the back metal of the first fastening portion 71 and the second fastening portion 72, and decreasing the strength of fastening the head 40 and the holder 30. Conversely, if the angle becomes excessively large, the volume of the back metal on the third contact surface 83 and the fourth contact surface 84 of the holder 30 decreases, reducing the strength with which the head 40 and the holder 30 are fastened. By setting the angle to 50° or more and 70° or less, the head 40 and the holder 30 can be firmly fastened. As a result, vibration of the drill 100 can be significantly suppressed.

[0072] According to the drill 100 of this embodiment, the length of the first contact surface 71a and the second contact surface 72a is between 0.03 and 0.1 times the tool diameter C. By setting the length of the first contact surface 71a and the second contact surface 72a to 0.03 times or more the tool diameter C, wear of the first contact surface 71a and the second contact surface 72a can be prevented. By setting the length of the first contact surface 71a and the second contact surface 72a to 0.1 times or less the tool diameter C, interference between the first contact surface 71a and the second contact surface 72a and the fastening screws that fasten the first fastening portion 71 and the second fastening portion 72 to the holder 30 can be avoided.

[0073] According to the drill 100 of this embodiment, the distance between the first anti-reverse rotation wall surface 81 and the second anti-reverse rotation wall surface 82 is 0.3 times or more and 0.5 times or less the tool diameter C. By setting the distance between the first anti-reverse rotation wall surface 81 and the second anti-reverse rotation wall surface 82 to 0.3 times or more the tool diameter C, when the head 40 attempts to rotate in reverse, the first fastening portion 71 comes into contact with the first anti-reverse rotation wall surface 81, and the second fastening portion 72 comes into contact with the second anti-reverse rotation wall surface 82, thereby preventing the head 40 from rotating in reverse. Even if the pin 37 or the like is damaged, the first anti-reverse rotation wall surface 81 and the second anti-reverse rotation wall surface 82 prevent the head 40 from spinning freely or flying off relative to the holder 30.

[0074] According to the drill 100 of this embodiment, the holder 30 has a first reverse rotation prevention wall surface 81 and a second reverse rotation prevention wall surface 82, which prevents lateral wobble of the drill 100.

[0075] According to the drill 100 of this embodiment, by setting the distance between the first anti-reverse rotation wall surface 81 and the second anti-reverse rotation wall surface 82 to 0.5 times the tool diameter C or less, it is possible to avoid interference between the first anti-reverse rotation wall surface 81 and the second anti-reverse rotation wall surface 82 and the fastening screws that fasten the first fastening portion 71 and the second fastening portion 72 to the holder 30. Furthermore, it is possible to prevent the first fastening portion 71 and the second fastening portion 72 on the head 40 side from becoming thin-walled and to ensure rigidity.

[0076] According to the drill 100 of this embodiment, the holder 30 and the head 40 are positioned using pins 37 arranged along axis A. When assembling the head 40 to the holder 30, the positioning accuracy of the head 40 in the radial direction can be increased.

[0077] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the embodiments described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope. [Explanation of Symbols]

[0078] 1 Thinning cutting edge section, 2 Main cutting edge section, 3 Secondary cutting edge section, 4 Thinning surface, 5 Guide pad, 10 Center drill, 11 Central cutting edge, 12 Second outer peripheral end (shoulder section), 13 Chip control surface, 14 First relief surface, 14a First relief surface section, 14b Second relief surface section, 15 Flat side surface, 16 First outer peripheral surface, 17 First rake face, 18 Tip section, 19 Margin, 20 Cutting insert, 20a First cutting insert section, 20b Second cutting insert section, 21 Outer cutting edge, 21a First outer cutting edge section, 21b Second outer cutting edge section, 22 First outer peripheral end, 22a, 22b Outer peripheral end, 23 Second rake face, 24 Arc-shaped side section, 25 Second relief surface, 26 Straight cutting edge section, 27 Straight side section, 28 Arc-shaped cutting edge section, 30 Holder, 31 Chip discharge groove, 32 End point, 33 Main body section, 34 Enlarged diameter section, 35 Shank section, 37 Pin, 38 Holder outer circumference, 40 Head, 41 Head front surface, 42 Head rear surface, 43 Head outer circumference, 44 Guide pad placement groove, 45 Pin insertion hole, 61 First front cutting edge section, 62 Second front cutting edge section, 63 Apex section, 64 Removal edge, 65 Outer surface, 66 Fixing screw, 71 First fastening section, 71a First contact surface, 71b First non-contact surface, 71d First outer circumference region, 71e First inner circumference region, 72 Second fastening section, 72a Second contact surface, 72b Second non-contact surface, 72d Second outer circumference region, 72e Second inner circumference region, 81 First anti-reverse rotation wall surface, 82 83 Second anti-reverse rotation wall surface, 84 Third contact surface, 85 Fourth contact surface, 85 Front surface of holder, 91 Planar surface, 92 Arc-shaped surface, 93 First fastening screw mounting hole, 94 Second fastening screw mounting hole, 100 Drill, A Axis, B Center cutting edge diameter, C Tool diameter, D First distance, E Second distance, F Third distance, G1 First length, G2 Second length, G3 Third length, H1 First radius of curvature, H2 Second radius of curvature, J Diameter, R1 First direction, R2 Second direction, R3 Third direction, R4 Fourth direction, R5 Fifth direction, R6 Sixth direction, R7 Seventh direction, R8 Eighth direction, T1, T2 Trajectory, θ1 First angle, θ2 Second angle, θ3 Third angle, θ4 Fourth angle, θ5 Fifth angle, θ6 Sixth angle, θ7 Seventh angle, θ8 Eighth angle.

Claims

1. A drill that rotates around an axis, Equipped with a center drill and a cutting insert, The aforementioned center drill has a central cutting edge, The cutting insert has an outer cutting edge and a rake face connected to the outer cutting edge, If the tool diameter is defined as twice the distance between the outer peripheral end of the outer cutting edge and the axis in the radial direction, then the outer diameter of the central cutting edge is 0.3 times or more and 0.6 times or less the tool diameter. When viewed in the direction along the aforementioned axis, the angle between the direction parallel to the main cutting edge portion of the central cutting edge and extending radially outward from the aforementioned axis, and the direction extending from the aforementioned axis toward the outer peripheral end of the outer cutting edge, is 30° or more and 50° or less. The center drill has an outer circumferential surface and a chip control surface provided on the outer circumferential surface, When viewed in the direction along the aforementioned axis, the angle of the chip control surface with respect to the direction from the axis toward the outer peripheral end of the outer cutting edge is 80° or more and 100° or less. Viewed in the direction along the aforementioned axis, the chip control surface is spaced apart from the central cutting edge. The outer cutting edge has a first front cutting edge portion, a second front cutting edge portion, and a vertex portion. In the radial direction, the first front cutting edge portion is located outward from the second front cutting edge portion. The first front cutting edge portion is connected to the second front cutting edge portion at its apex, Viewed in a direction perpendicular to the rake face, the first front cutting edge extends so as it moves radially outward from the apex, it is positioned axially rearward, and the second front cutting edge extends so as it moves radially inward from the apex, Viewed in a direction perpendicular to the rake face, the outer cutting edge has a scraping edge formed by an arc-shaped cutting edge portion connected to the first front cutting edge portion and a straight cutting edge portion connected to the arc-shaped cutting edge portion, the radius of curvature of the arc-shaped cutting edge portion being 0.3 mm or more, and the length of the straight cutting edge portion being 0.5 mm or more and 3 mm or less. The aforementioned straight cutting edge portion extends along a direction parallel to the axis, in the form of a drill.

2. In the direction along the aforementioned axis, The shoulder of the center drill is located in front of the apex of the cutting insert. The drill according to claim 1, wherein the distance between the shoulder of the center drill and the apex of the cutting insert is greater than 0 and less than or equal to 1 mm.

3. The cutting insert has a rake face connected to the outer cutting edge and an outer surface connected to the rake face, Viewed in the direction along the aforementioned axis, The outer surface has an arc-shaped side portion that is connected to the outer cutting edge, The drill according to claim 1 or claim 2, wherein the radius of curvature of the arc-shaped side portion is 0.2 times or more and 0.5 times or less the tool diameter.

4. The drill is equipped with a guide pad, The number of the guide pads is equal to or greater than the number of the cutting inserts. When viewed in the direction along the aforementioned axis, the angle between the direction from the axis toward the center of the guide pad and the direction from the axis toward the outer peripheral end of the outer cutting edge is 10° or more and 80° or less. In the direction along the aforementioned axis, the distance between the center of the guide pad and the outer peripheral end of the outer cutting edge is between 0.1 and 1 times the tool diameter. Viewed in the direction along the aforementioned axis, The guide pad has a planar surface portion and an arc-shaped surface portion connected to the planar surface portion. The drill according to claim 1 or claim 2, wherein the value obtained by subtracting the diameter of the arc-shaped surface from the tool diameter is 0.1 mm or more and 1 mm or less.

5. The drill comprises a holder having a chip discharge groove, Viewed in the direction along the aforementioned axis, The drill according to claim 1 or claim 2, wherein the angle between the direction from the axis toward the center of the end point of the chip discharge groove and the direction from the axis toward the outer peripheral end of the outer cutting edge is 40° or more and 90° or less.

6. The drill comprises a head and a holder that is detachable from the head. Each of the center drill and the cutting insert is attached to the head, The head has a first fastening portion and a second fastening portion. The first fastening portion has a first contact surface that abuts against the holder at the outermost diameter side of the first fastening portion, The second fastening portion has a second contact surface that abuts against the holder at the outermost diameter side of the second fastening portion, The outer cutting edge has a first outer cutting edge portion and a second outer cutting edge portion. Viewed in the direction along the aforementioned axis, The angle between the direction from the axis toward the outer peripheral end of the first contact surface and the direction from the axis toward the outer peripheral end of the first outer cutting edge is 50° or more and 70° or less. The angle between the direction from the axis toward the outer peripheral end of the second contact surface and the direction from the axis toward the outer peripheral end of the second outer cutting edge is 50° or more and 70° or less. The drill according to claim 1 or claim 2, wherein the length of the first contact surface and the second contact surface, respectively, is 0.03 times or more and 0.1 times or less the tool diameter.

7. The holder has a third contact surface that abuts the first contact surface, a first anti-reverse rotation wall surface provided at a position inclined at an angle of 70° to 110° with respect to the third contact surface, a fourth contact surface that abuts the second contact surface, and a second anti-reverse rotation wall surface provided at a position inclined at an angle of 70° to 110° with respect to the fourth contact surface. When viewed in the direction along the aforementioned axis, the distance between the first anti-reverse rotation wall surface and the second anti-reverse rotation wall surface is 0.3 times or more and 0.5 times or less the tool diameter. The drill according to claim 6, wherein the holder and the head are positioned using pins arranged along the axis.

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