drill

Abstract

To provide a drill that can stably perform high-accuracy drilling, even in drilling a high-hardness material to be ground such as a hard and brittle material.SOLUTION: The drill comprises a blade part 3 extending in an axial direction with a central axis C as a center. The blade part 3 comprises rake faces 5, flank faces 6 and cutting blades 7 arranged at ridge line parts between the rake faces 5 and the flank faces 6. The cutting blades 7 have main cutting blades 10, arranged on a tip surface 3b pointing to a tip side in the axial direction of the blade part 3, whose rake angles are set to negative angles and corner blades 11, arranged at an end part outside in a radial direction of the blade part 3 and connected to the main cutting blades 10, whose rake angles are set to positive angles.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] As a conventional drill, for example, a cutting tool for brittle materials described in Patent Document 1 is known. This cutting tool for brittle materials has a cutting edge disposed on the tool tip surface, and this cutting edge is used to drill holes in high-hardness brittle materials (hereinafter simply referred to as "hard and brittle materials") including, for example, silicon, various ceramics, glass, and cemented carbide materials such as tungsten carbide (WC). In Patent Document 1, the rake angle of the cutting edge is a negative angle over the entire length of the cutting edge in order to suppress chipping and breakage of the cutting edge. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-355710 A Summary of the Invention [Problem to be solved by the invention]

[0004] This type of drill has room for improvement in terms of preventing "edge chipping" that occurs near the inner circumference of the drilled hole when drilling into a workpiece made of hard and brittle materials, etc. In particular, edge chipping is prone to occur when drilling hard and brittle materials such as silicon-based ceramics.

[0005] An object of the present invention is to provide a drill that can perform stable, high-precision drilling even when drilling a workpiece having high hardness, such as a hard and brittle material. [Means for solving the problem]

[0006] One aspect of the drill of the present invention includes a cutting portion extending in the axial direction around a central axis, the cutting portion including a rake face, a clearance face, and a cutting edge disposed on a ridge between the rake face and the clearance face, the cutting edge including a main cutting edge disposed on a tip face facing the tip side in the axial direction of the cutting portion and having a negative rake angle, and a corner edge disposed on a radially outer end of the cutting portion, connected to the main cutting edge, and having a positive rake angle. The corner blade extends in a convex curve shape toward the rear end side in the axial direction as it moves radially outward. . Moreover, one aspect of the drill of the present invention comprises a cutting portion extending in the axial direction around a central axis, the cutting portion comprising a rake face, a clearance face, and a cutting edge arranged on a ridge between the rake face and the clearance face, the cutting edge comprising: a main cutting edge arranged on a tip face facing the axial tip side of the cutting portion and having a negative rake angle; and a corner edge arranged on a radially outer end of the cutting portion, connected to the main cutting edge, and having a positive rake angle, the cutting portion comprising a chip discharge groove opening on the tip face and extending in the axial direction, and a width dimension of a portion of the cutting face located between the main cutting edge and the chip discharge groove decreasing radially outward. In one embodiment of the drill of the present invention, the drill has a cutting portion extending in the axial direction around a central axis, the cutting portion having a rake face, a clearance face, and a cutting edge arranged on a ridge between the rake face and the clearance face, the cutting edge having a main cutting edge arranged on a tip face facing the axial tip side of the cutting portion and having a negative rake angle, and a corner edge arranged on a radially outer end of the cutting portion and connected to the main cutting edge and having a positive rake angle, the main cutting edges having a first main cutting edge and a second main cutting edge arranged radially outward of the first main cutting edge and having both end portions connected to the first main cutting edge and the corner edge, the cutting angle of the second main cutting edge being equal to or greater than the cutting angle of the first main cutting edge, and the second main cutting edge extending radially outward in the circumferential direction around the central axis in the direction of drill rotation. One embodiment of the drill of the present invention includes a cutting edge extending in the axial direction around a central axis, the cutting edge including a rake face, a flank, and a cutting edge disposed on a ridge between the rake face and the flank. The cutting edges include a main cutting edge disposed on a tip face facing the tip side in the axial direction of the cutting edge, the main cutting edge having a negative rake angle, and a corner edge disposed on a radially outer end of the cutting edge, connected to the main cutting edge, the corner edge having a positive rake angle. , the main cutting edge has a first main cutting edge and a second main cutting edge arranged radially outward of the first main cutting edge, both ends of which are connected to the first main cutting edge and the corner edge, the cutting angle of the second main cutting edge is equal to or greater than the cutting angle of the first main cutting edge, the cutting surface has a first cutting surface connected to the first main cutting edge and a second cutting surface connected to the second main cutting edge, and the first cutting surface and the second cutting surface are arranged in a single plane. In one embodiment of the drill of the present invention, the drill has a cutting edge extending in the axial direction around a central axis, the cutting edge having a rake face, a flank, and a cutting edge disposed on a ridge between the rake face and the flank, the cutting edges being a main cutting edge disposed on a tip face facing the tip side in the axial direction of the cutting edge, the main cutting edge having a negative rake angle, and a corner cutting edge disposed on a radially outer end of the cutting edge, connected to the main cutting edge, the corner cutting edge having a positive rake angle. the main cutting edge has a first main cutting edge and a second main cutting edge arranged radially outward of the first main cutting edge, both ends of which are connected to the first main cutting edge and the corner edge, the cutting edge angle of the second main cutting edge is equal to or greater than the cutting edge angle of the first main cutting edge, the flank has a first flank connected to the first main cutting edge and a second flank connected to the second main cutting edge, the first flank is flat and the second flank is convexly curved. In one embodiment of the drill of the present invention, the drill has a cutting portion extending in the axial direction around a central axis, the cutting portion having a rake face, a clearance face, and a cutting edge arranged on a ridge between the rake face and the clearance face, the cutting edge having a main cutting edge arranged on a tip face facing the axial tip side of the cutting portion and having a negative rake angle, and a corner edge arranged on a radially outer end of the cutting portion, connected to the main cutting edge, and having a positive rake angle, the main cutting edges having a first main cutting edge and a second main cutting edge arranged radially outward of the first main cutting edge and having both ends connected to the first main cutting edge and the corner edge, the cutting angle of the second main cutting edge being equal to or greater than the cutting angle of the first main cutting edge, the main cutting edge extending radially outward toward the rear end side in the axial direction, and the second main cutting edge having a smaller inclination angle with respect to the central axis than the first main cutting edge.

[0007] In the drill of the present invention, the rake angle of the main cutting edge is a negative angle, so that the cutting edge angle of the main cutting edge can be made large. The cutting edge strength of the main cutting edge can be stably increased, and even when drilling a workpiece made of a hard and brittle material, chipping and damage of the main cutting edge can be suppressed, and the drilling can be performed efficiently. For example, even when drilling a workpiece made of a hard and brittle material such as silicon nitride ceramics or alumina ceramics, the occurrence of chipping of the cutting edge can be suppressed.

[0008] The corner cutting edge cuts the inner periphery of the machined hole in the workpiece. According to the drill of the present invention, the rake angle of the corner cutting edge is a positive angle, so that the sharpness of the corner cutting edge is improved and edge chipping near the inner periphery of the machined hole is suppressed. For example, even when drilling a workpiece made of a hard and brittle material such as Si-based ceramics, edge chipping of the machined hole can be suppressed, and machining accuracy can be improved. As described above, the drill of the present invention can perform stable and high-precision drilling even when drilling a workpiece having high hardness, such as a hard and brittle material. In the above drill, the corner edge extends in a convex curve toward the rear end side in the axial direction as it moves radially outward. In this case, because the corner blade is convexly curved, the inclination angle of the corner blade with respect to the central axis decreases toward the rear end in the axial direction. This reduces the thrust force acting on the inner circumference of the drilled hole when the corner blade penetrates the drilled hole. This more reliably prevents chipping of the edge of the drilled hole (especially the exit side). In the above drill, the cutting edge portion is provided with a chip discharge groove that opens to the tip surface and extends in the axial direction, and the width dimension of the portion of the cutting face located between the main cutting edge and the chip discharge groove decreases radially outward. During drilling, the amount of chips supplied from the cutting blade increases toward the radially outer side of the rake face (the part where the peripheral speed is higher). In the above configuration, the width of the rake face decreases toward the radially outer side, so that the chips are efficiently guided from the rake face into the chip discharge groove, resulting in good chip discharge performance.

[0009] In the above drill, the main cutting edge has a first main cutting edge and a second main cutting edge arranged radially outward of the first main cutting edge, both ends of which are connected to the first main cutting edge and the corner edge, and the cutting edge angle of the second main cutting edge is equal to or larger than the cutting edge angle of the first main cutting edge. do.

[0010] In this case, the cutting edge strength of the second main cutting edge, which is farther from the central axis than the first main cutting edge and has a faster peripheral speed (cutting speed) during drilling, is increased. This reduces chipping and damage to the main cutting edge, allowing for efficient and stable drilling.

[0011] In the above drill, the second main cutting edge extends in a drill rotation direction in a circumferential direction around the central axis as it moves radially outward. do.

[0012] In this case, the center height of the second main cutting edge rises toward the outside in the radial direction. Therefore, even if the perpendicular cutting edge angle of the second main cutting edge (the cutting edge angle of the cross section perpendicular to the cutting edge length direction along which the cutting edge extends) is approximately constant along the cutting edge length direction, the effective cutting edge angle that appears on the cross section along the drill rotation direction (the imaginary cylindrical surface centered on the central axis) becomes larger toward the outside in the radial direction of the second main cutting edge. In other words, the greater the distance from the central axis of the second main cutting edge and the greater the peripheral speed, or cutting speed, during drilling, the larger the effective tool angle and the greater the strength of the cutting edge, thereby further reducing chipping and damage to the second main cutting edge.

[0013] In the above drill, the rake face has a first rake face connected to the first main cutting edge and a second rake face connected to the second main cutting edge, and the first rake face and the second rake face are disposed in a single plane. do.

[0014] In this case, the configuration of the rake face can be simplified, and problems such as localized concentration of cutting load on a portion of the main cutting edge can be suppressed, thereby further suppressing chipping of the cutting edge of the main cutting edge.

[0015] In the above drill, the flank has a first flank connected to the first main cutting edge and a second flank connected to the second main cutting edge, the first flank being flat and the second flank being convexly curved. do.

[0016] In this case, since the first flank is flat, it is easy to form the first flank when manufacturing the drill. Also, since the second flank is convexly curved, it is easy to form the second main cutting edge in a curved shape. This makes it easy to smoothly connect, for example, the second main cutting edge and the corner edge. In the above drill, the main cutting edge extends radially outwardly toward the rear end side in the axial direction, and the second main cutting edge has a smaller inclination angle with respect to the central axis than the first main cutting edge. In this case, it becomes easier to smoothly connect the second main cutting edge and the corner edge, and chipping, breakage, and the like at the connection portion between them is suppressed.

[0017] In the above drill, the second main cutting edge has a cross section perpendicular to the cutting edge length direction. The above It is preferable that a cutting edge angle increases from the first main cutting edge toward the corner edge along the cutting edge length direction of the second main cutting edge.

[0018] The more radially outward the second main cutting edge is, i.e., the closer it is to the corner edge, the faster the circumferential speed (cutting speed) in the drill rotation direction during drilling. With the above configuration, the right-angle tool angle of the second main cutting edge increases from the first main cutting edge to the corner edge along the cutting edge length direction, so chipping and damage to the second main cutting edge are more stably suppressed.

[0021] In the above drill, when the cutting edge is viewed in the axial direction, it is preferable that a connection portion between the second main cutting edge and the corner edge protrudes in a drill rotation direction in a circumferential direction about the central axis.

[0022] In this case, the connection between the second main cutting edge and the corner edge protrudes in the direction of rotation of the drill, so that the twist angle (axial rake angle) of the corner edge can be increased accordingly, which improves the sharpness of the corner edge.

[0023] In the drill, it is preferable that the radial dimension of the first main cutting edge is 40% or more and 50% or less of the radius of the cutting edge.

[0024] When the radial dimension of the first main cutting edge is 40% or more of the radius of the cutting edge, a large cutting edge length of the first main cutting edge is ensured, and hole drilling can be performed more efficiently. When the radial dimension of the first main cutting edge is 50% or less of the radius of the blade portion, the cutting edge lengths of the second main cutting edge and the corner edge other than the first main cutting edge can be ensured to be large, and the functions provided by the second main cutting edge and the corner edge can be stably performed.

[0025] In the above drill, it is preferable that the radial dimension of the main cutting edge is 70% or more and 80% or less of the radius of the cutting edge.

[0026] When the radial dimension of the main cutting edge is 70% or more of the radius of the cutting edge, a large cutting edge length of the main cutting edge is ensured, and hole drilling can be performed more efficiently. When the radial dimension of the main cutting edge is 80% or less of the radius of the cutting portion, the cutting edge length of the corner cutting edge other than the main cutting edge can be ensured to be large, and the function of the corner cutting edge can be stably achieved.

[0027] In the above drill, it is preferable that the main cutting edge extends radially outward from the central axis when viewed in the axial direction.

[0028] In this case, since the main cutting edge passes along the central axis, no chisel edge or chisel thinning (hereinafter, abbreviated as chisel edge, etc.) is formed near the central axis of the tip surface of the cutting portion. Therefore, according to the above configuration, chipping of the cutting portion caused by the chisel edge, etc. is suppressed. Effect of the Invention

[0033] According to a drill of one aspect of the present invention, even when drilling a workpiece having a high hardness, such as a hard and brittle material, it is possible to perform stable and high-precision drilling. [Brief description of the drawings]

[0034] [Figure 1] FIG. 1 is a perspective view showing a part of the drill of the present embodiment. [Diagram 2] FIG. 2 is a front view showing a part of the drill. [Diagram 3] FIG. 3 is a side view showing a part of the drill. [Figure 4] FIG. 4 is a cross-sectional view showing a cross section taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is a cross-sectional view showing a VV cross section of FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. [Figure 7] FIG. 7 is a cross-sectional view showing a cross section taken along line VII-VII of FIG. [Figure 8] FIG. 8 is an image showing a drilled hole (the 50th hole) drilled by the drill (example) of this embodiment in a workpiece made of a hard and brittle material. [Figure 9] FIG. 9 is an image showing a hole (the 50th hole) drilled in a workpiece made of a hard and brittle material by a conventional drill (conventional example). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] A drill 1 according to an embodiment of the present invention will be described with reference to the drawings. The drill 1 according to the present embodiment is suitable for drilling a workpiece made of a hard and brittle material. Specifically, the hard and brittle material is a brittle material with high hardness, such as silicon nitride ceramics such as sialon, alumina ceramics, Si ceramics, and single crystal silicon.

[0036] As shown in Fig. 1, the drill 1 is columnar or axially shaped about a central axis C. The drill 1 includes a shank portion 2 and a cutting edge portion 3. The shank portion 2 and the cutting edge portion 3 are disposed at different positions in the direction in which the central axis C extends.

[0037] [Direction definition] In this embodiment, the direction in which the central axis C of the drill 1 extends is referred to as the axial direction. Within the axial direction, the direction from the shank portion 2 to the cutting portion 3 is referred to as the axial tip side or simply the tip side, and the direction from the cutting portion 3 to the shank portion 2 is referred to as the axial rear end side or simply the rear end side. The direction perpendicular to the central axis C is called the radial direction. Within the radial direction, the direction approaching the central axis C is called the radially inner direction, and the direction away from the central axis C is called the radially outer direction. The direction rotating around the central axis C is called the circumferential direction. Among the circumferential directions, the direction in which the drill 1 is rotated during hole drilling is called the drill rotation direction T, and the direction opposite to the drill rotation direction T is called the counter-drill rotation direction. In this embodiment, the direction in which a cutting edge 7 of the blade portion 3, which will be described later, extends is called the blade length direction.

[0038] [Shank part] The shank portion 2 is columnar and extends in the axial direction about a central axis C. The shank portion 2 is removably held, for example, by a spindle of a machine tool or a chuck of a drilling press (hereinafter, abbreviated to the spindle or the like) (not shown). The drill 1 cuts into the workpiece with the cutting portion 3 to perform hole drilling by feeding the shank portion 2 axially toward the tip side while rotating the shank portion 2 by the spindle or the like in a drill rotation direction T.

[0039] [Blade] 1 to 3, the cutting portion 3 has a generally columnar shape extending in the axial direction about a central axis C. The diameter of the cutting portion 3, i.e., the blade diameter, is smaller than the diameter of the shank portion 2. In this embodiment, the diameter of the cutting portion 3 is, for example, 2 mm or less. In other words, the drill 1 is a so-called small diameter drill.

[0040] At least the end (tip) 3a of the blade portion 3 on the tip side in the axial direction is made of, for example, sintered diamond (Polycrystalline diamond, PCD) or single crystal diamond. In this embodiment, the part of the blade portion 3 located on the tip side of the boundary line indicated by the symbol B in Fig. 1 and Fig. 3 is made of PCD or single crystal diamond. Note that instead of or in addition to the configuration of this embodiment, at least the tip 3a of the blade portion 3 may be provided with a diamond coating film.

[0041] The cutting portion 3 has a chip discharge groove 4, a rake face 5, a flank face 6, a cutting edge 7, a margin 8, and a chamfer surface 9. The chip discharge groove 4 is recessed radially inward from the outer circumferential surface of the cutting portion 3 and has a groove shape extending in the axial direction. The chip discharge groove 4 opens to a tip end face 3b facing the tip side in the axial direction of the cutting portion 3. Specifically, the chip discharge groove 4 extends spirally in the direction opposite to the drill rotation direction as it moves from the tip end face 3b toward the rear end side in the axial direction. A plurality of chip discharge grooves 4 are provided in the cutting portion 3 at intervals from each other in the circumferential direction. In this embodiment, two chip discharge grooves 4 are provided at equal pitch in the circumferential direction.

[0042] The cutting edge 7 is disposed on the ridge between the rake face 5 and the flank 6. A plurality of cutting edges 7 are provided on the cutting portion 3 at intervals in the circumferential direction. In this embodiment, two cutting edges 7 are provided at equal intervals in the circumferential direction. That is, the drill 1 of this embodiment is a two-blade twist drill.

[0043] As shown in FIGS. 2 and 3, the cutting edge 7 has a main cutting edge 10, a corner edge 11, and a leading edge (peripheral edge) 12. The main cutting edge 10 is disposed on the tip surface 3b facing the tip side in the axial direction of the cutting portion 3. The main cutting edge 10 extends in a substantially radial direction on the tip surface 3b. As shown in FIG. 2, the main cutting edge 10 extends radially outward from the central axis C when viewed from the axial direction. That is, the radial inner end of the main cutting edge 10 is located on the central axis C. The radial inner ends of each of the main cutting edges 10 of the multiple cutting edges 7 are connected to each other on the central axis C. For this reason, in this embodiment, no chisel edge or the like is formed near the central axis C of the tip surface 3b of the cutting portion 3. The radial dimension of each main cutting edge 10 is 70% to 80% of the radius of the cutting portion 3 (i.e., 1 / 2 the blade diameter).

[0044] The main cutting edge 10 has a negative rake angle over the entire length in the blade length direction. The rake angle of the main cutting edge 10 is, for example, -70° or more and -60° or less (i.e., a negative angle of 60° or more and 70° or less, and the same applies below), and more preferably -67° or more and -63° or less. As shown in Figs. 4 to 6, the blade angle α of the main cutting edge 10 in a cross section perpendicular to the blade length direction (perpendicular blade angle) is, for example, 110° or more and 145° or less, and more preferably 120° or more and 130° or less. As shown in FIG. 3, the main cutting edge 10 extends radially outward and then axially toward the rear end side.

[0045] The main cutting edge 10 has a first main cutting edge 10a and a second main cutting edge 10b. The first main cutting edge 10a extends in the radial direction when viewed from the axial direction, as shown in Fig. 2. The radial dimension of the first main cutting edge 10a is 40% to 50% of the radius of the blade portion 3. As shown in Fig. 3, the first main cutting edge 10a extends from the central axis C toward the radially outward direction and toward the rear end side in the axial direction. The first main cutting edge 10a is linear. The tip angle θ between the first main cutting edges 10a of the multiple main cutting edges 10 is, for example, 120° to 150°, and more preferably 130° to 140°.

[0046] The second main cutting edge 10b is disposed radially outward of the first main cutting edge 10a. The second main cutting edge 10b has both ends in the cutting edge length direction connected to the first main cutting edge 10a and the corner edge 11. As shown in Fig. 2, the second main cutting edge 10b extends in the drill rotation direction T as it moves radially outward. That is, the center height of the second main cutting edge 10b becomes higher as it moves radially outward. As shown in FIG. 3, the second main cutting edge 10b extends radially outward and then axially toward the rear end side.

[0047] The second main cutting edge 10b is curved and extends in a curved shape. Specifically, the second main cutting edge 10b is a concave curve recessed in the direction opposite to the drill rotation direction when viewed from the axial direction as shown in Fig. 2. Also, the second main cutting edge 10b is a convex curve bulging toward the tip side in the axial direction when viewed from the radial direction as shown in Fig. 3.

[0048] As shown in Figures 4 to 6, the cutter angle α2 of the second main cutting edge 10b is equal to or larger than the cutter angle α1 of the first main cutting edge 10a. The perpendicular cutter angle α2 of the second main cutting edge 10b in a cross section perpendicular to the blade length direction increases from the first main cutting edge 10a toward the corner edge 11 along the blade length direction of the second main cutting edge 10b. Specifically, the cross section of the second main cutting edge 10b shown in Figure 6 is located radially outward from the cross section of the second main cutting edge 10b shown in Figure 5 (see Figure 3), and the cutter angle α2 shown in Figure 6 is larger than the cutter angle α2 shown in Figure 5. That is, in the main cutting edge 10 of this embodiment, the cutting edge angle α increases toward the corner edge 11 along the cutting length direction of the main cutting edge 10 .

[0049] In Fig. 3, the tip angle between the second main cutting edges 10b of the multiple main cutting edges 10 is equal to or smaller than the tip angle θ between the first main cutting edges 10a. As shown in Fig. 3, when viewed from the radial direction, of the acute angle and the obtuse angle formed between the second main cutting edges 10b and the central axis C, the acute angle (inclination angle) is smaller than the acute angle between the first main cutting edges 10a and the central axis C. In other words, the second main cutting edges 10b have a smaller inclination angle with respect to the central axis C than the first main cutting edges 10a.

[0050] The corner edge 11 is disposed at the radially outer end of the cutting portion 3 and is connected to the main cutting edge 10. The corner edge 11 extends in a convex curve toward the rear end in the axial direction as it moves radially outward. As shown in Figures 1 and 2, the twist angle of the corner edge 11 increases from the connection with the main cutting edge 10 toward the rear end in the axial direction. Specifically, the corner edge 11 is connected to the radially outer end of the second main cutting edge 10b. As shown in Fig. 2, when the cutting portion 3 is viewed from the axial direction, a connection portion 13 between the second main cutting edge 10b and the corner edge 11 has a convex shape that protrudes in the drill rotation direction T.

[0051] The corner edge 11 has a positive rake angle (normal angle) over the entire length in the blade length direction. The rake angle of the corner edge 11 is, for example, 5° or more and 25° or less, and more preferably 10° or more and 22° or less. As shown in Fig. 7, the blade angle (right-angle blade angle) β of the corner edge 11 in a cross section perpendicular to the blade length direction is, for example, 45° or more and 65° or less, and more preferably 58° or more and 62° or less.

[0052] As shown in Fig. 3, the leading edge 12 is disposed on the outer periphery of the cutting portion 3 and is connected to the corner edge 11. Specifically, the leading edge 12 is connected to the radially outer end and the axial rear end of the corner edge 11. The leading edge 12 extends spirally in the direction opposite to the drill rotation direction toward the axial rear end side. The leading edge 12 has a positive rake angle over its entire length in the cutting edge length direction. The leading edge 12 may be back tapered. In this case, the leading edge 12 is positioned slightly radially inward as it moves toward the rear end in the axial direction.

[0053] 2 and 3, a plurality of cutting faces 5 are provided at intervals in the circumferential direction on the cutting portion 3. In this embodiment, two cutting faces 5 are provided at equal pitches in the circumferential direction. The rake face 5 has a main rake face 21, a corner rake face 22, and a peripheral rake face 23.

[0054] The main rake face 21 is disposed on the tip surface 3b of the cutting portion 3 and is connected to the main cutting edge 10. The main rake face 21 is disposed adjacent to the main cutting edge 10 in the drill rotation direction T. The main rake face 21 is a portion of the rake face 5 located between the main cutting edge 10 and the chip discharge groove 4 adjacent to the main cutting edge 10 in the drill rotation direction T. The main rake face 21 extends along the main cutting edge 10. The main rake face 21 is located in the drill rotation direction T from the main cutting edge 10 toward the rear end side in the axial direction. In other words, the main rake angle of the main rake face 21 is a negative angle, and therefore the rake angle of the main cutting edge 10 is also negative. The width of the main rake face 21, i.e., the width of the portion of the rake face 5 located between the main cutting edge 10 and the chip discharge groove 4, decreases radially outward. In this embodiment, the main rake face 21 is formed of a single plane having a substantially triangular shape.

[0055] The main rake face 21 has a first rake face 21a and a second rake face 21b. That is, the rake face 5 has a first rake face 21a and a second rake face 21b. The first rake face 21a is a portion of the main rake face 21 located on the radially inner side. The first rake face 21a is connected to the first main cutting edge 10a. The second rake face 21b is a portion of the main rake face 21 located on the radially outer side. The second rake face 21b is connected to the second main cutting edge 10b. The first rake face 21a and the second rake face 21b are arranged on a single plane. In other words, the first rake face 21a and the second rake face 21b are integrally formed by a single plane.

[0056] As shown in FIG. 3, the corner rake face 22 is disposed on the outer periphery of the tip of the cutting portion 3 and is connected to the corner edge 11. The corner rake face 22 is disposed adjacent to the corner edge 11 on the radially inner side. The corner rake face 22 is located on a wall portion of the chip discharge groove 4 facing the drill rotation direction T. The corner rake face 22 extends along the corner edge 11. The corner rake face 22 is located in the opposite drill rotation direction as it moves radially inward from the corner edge 11 (see FIG. 7). In other words, the corner rake face 22 has a positive rake angle, which makes the rake angle of the corner edge 11 also positive. The corner rake face 22 is a concave curved surface.

[0057] As shown in FIG. 3, the peripheral rake face 23 is disposed on the outer periphery of the cutting portion 3 and connects to the leading edge 12. The peripheral rake face 23 is disposed adjacent to the radially inner side of the leading edge 12. The peripheral rake face 23 is located on a wall portion of the chip discharge groove 4 facing the drill rotation direction T. The peripheral rake face 23 extends along the leading edge 12. The peripheral rake face 23 is located in the opposite drill rotation direction as it moves radially inward from the leading edge 12. In other words, the peripheral rake face 23 has a positive rake angle, which makes the rake angle of the leading edge 12 also positive. The peripheral rake face 23 is a concave curved surface. The corner rake face 22 and the peripheral rake face 23 are disposed on a single concave curved surface, i.e., the corner rake face 22 and the peripheral rake face 23 are integrally formed by a single concave curved surface.

[0058] 2 and 3, a plurality of flanks 6 are provided at intervals in the circumferential direction on the cutting portion 3. In this embodiment, two flanks 6 are provided at equal intervals in the circumferential direction. The flank 6 has a main flank 31 and a corner flank 32 .

[0059] The main flank 31 is disposed on the tip surface 3b of the cutting portion 3 and is connected to the main cutting edge 10. The main flank 31 is disposed adjacent to the main cutting edge 10 in the counter-drill rotation direction. The main flank 31 extends along the main cutting edge 10. The main flank 31 is positioned toward the rear end side in the axial direction as it moves away from the main cutting edge 10 in the counter-drill rotation direction. This provides the main flank 31 with a clearance angle.

[0060] The main flank 31 has a first flank 31a and a second flank 31b. That is, the flank 6 has a first flank 31a and a second flank 31b. The first flank 31a is a portion of the main flank 31 located on the radially inner side. The first flank 31a is connected to the first main cutting edge 10a. The first flank 31a is flat (see FIG. 4). The second flank 31b is a portion of the main flank 31 located on the radially outer side. The second flank 31b is connected to the second main cutting edge 10b. The second flank 31b is convexly curved (see FIG. 5 and FIG. 6). That is, the first flank 31a and the second flank 31b are formed by different surfaces. The first flank 31a and the second flank 31b are smoothly connected to each other.

[0061] 2 and 3, the corner flank 32 is disposed at the radially outer end of the tip face 3b of the cutting portion 3 and is connected to the corner edge 11. The corner flank 32 is disposed adjacent to the corner edge 11 in the counter-drill rotation direction. The corner flank 32 extends along the corner edge 11. The corner flank 32 is positioned radially inward from the corner edge 11 in the counter-drill rotation direction (see FIG. 7). This provides the corner flank 32 with a clearance angle.

[0062] As shown in Figs. 1 to 3, the margin 8 is disposed on the outer peripheral surface of the cutting portion 3 and is connected to the leading edge 12. The margin 8 is disposed adjacent to the leading edge 12 in the direction opposite to the drill rotation direction. The margin 8 extends spirally along the leading edge 12. The axial tip of the margin 8 is connected to the tip surface 3b. The margin 8 is located on a cylindrical rotation trajectory (not shown) obtained by rotating the leading edge 12 around the central axis C. The margin 8 forms an arc shape centered on the central axis C in a cross section perpendicular to the central axis C.

[0063] The chamfered surface 9 is disposed on the outer peripheral surface of the cutting portion 3 between the margin 8 and the chip discharge groove 4 adjacent to the margin 8 in the counter-drill rotation direction. The chamfered surface 9 is located radially inward from the margin 8. The axial tip of the chamfered surface 9 is connected to the tip surface 3b.

[0064] [Effects of this embodiment] In the drill 1 of the present embodiment described above, the rake angle of the main cutting edge 10 is a negative angle, so that a large cutting edge angle α of the main cutting edge 10 can be ensured. The cutting edge strength of the main cutting edge 10 can be stably increased, and even when drilling a workpiece made of a hard and brittle material, chipping or damage of the main cutting edge 10 can be suppressed, and the hole can be drilled efficiently. For example, even when drilling a workpiece made of a hard and brittle material such as silicon nitride ceramics or alumina ceramics, the occurrence of chipping of the cutting edge can be suppressed.

[0065] The corner edge 11 cuts the inner periphery of the machined hole in the workpiece. According to the drill 1 of this embodiment, the rake angle of the corner edge 11 is a positive angle, so that the corner edge 11 has a sharper cutting edge and chipping near the inner periphery of the machined hole is suppressed. For example, even when drilling a workpiece made of a hard and brittle material such as Si-based ceramics, it is possible to suppress chipping of the edge of the machined hole, and improve the machining accuracy. As described above, the drill 1 of the present embodiment can perform stable and highly accurate drilling even when drilling a workpiece having high hardness, such as a hard and brittle material.

[0066] In this embodiment, the cutting angle α2 of the second main cutting edge 10b is equal to or greater than the cutting angle α1 of the first main cutting edge 10a. In this case, the cutting edge strength of the second main cutting edge 10b, which is farther from the central axis C than the first main cutting edge 10a and has a faster peripheral speed (cutting speed) during drilling, is increased. This further reduces chipping and damage to the main cutting edge 10, allowing for efficient and stable drilling.

[0067] In this embodiment, the second main cutting edge 10b extends in the rotation direction T of the drill as it moves radially outward. In this case, the center height of the second main cutting edge 10b rises toward the outside in the radial direction. Therefore, even if the perpendicular cutting edge angle α2 of the second main cutting edge 10b (the cutting edge angle of the cross section perpendicular to the cutting edge length direction in which the cutting edge 7 extends) is substantially constant along the cutting edge length direction, the substantial cutting edge angle that appears on the cross section along the drill rotation direction T (the imaginary cylindrical surface centered on the central axis C) becomes larger toward the outside in the radial direction of the second main cutting edge 10b. In other words, the greater the distance from the central axis C of the second main cutting edge 10b and the greater the peripheral speed, i.e., the faster the cutting speed, during drilling, the larger the effective tool angle and the greater the cutting edge strength, thereby further reducing chipping and breakage of the second main cutting edge 10b.

[0068] In this embodiment, the first rake face 21a and the second rake face 21b of the main rake face 21 are disposed on a single plane. In this case, the configuration of the main rake face 21, i.e., the rake face 5, can be simplified, and defects such as localized concentration of cutting load on a part of the main cutting edge 10 are suppressed. Therefore, chipping of the cutting edge of the main cutting edge 10 is further suppressed.

[0069] In this embodiment, of the main flank 31, the first flank 31a is flat, and the second flank 31b is convexly curved. In this case, since the first flank 31a is flat, it is easy to form the first flank 31a when manufacturing the drill. Also, since the second flank 31b is a convex curved surface, it is easy to form the second main cutting edge 10b in a curved shape. This makes it easy to smoothly connect the second main cutting edge 10b and the corner edge 11, as shown in FIG. 3.

[0070] In this embodiment, the perpendicular cutting angle α2 of the second main cutting edge 10b increases from the first main cutting edge 10a toward the corner edge 11 along the cutting length direction of the second main cutting edge 10b. The peripheral speed (cutting speed) in the drill rotation direction T during drilling becomes faster at a portion of the second main cutting edge 10b that is located radially outward, i.e., closer to the corner edge 11. According to the above configuration, the perpendicular tool angle α2 of the second main cutting edge 10b increases from the first main cutting edge 10a toward the corner edge 11 along the blade length direction, so chipping and breakage of the second main cutting edge 10b are more stably suppressed.

[0071] In this embodiment, the main cutting edge 10 extends radially outwardly toward the rear end side in the axial direction, and the second main cutting edge 10b has a smaller inclination angle with respect to the central axis C than the first main cutting edge 10a. In this case, the second main cutting edge 10b and the corner edge 11 can be smoothly connected to each other, and chipping, breakage, and the like at the connection portion between them can be suppressed.

[0072] In this embodiment, as shown in FIG. 2, when the cutting portion 3 is viewed from the axial direction, a connection portion 13 between the second main cutting edge 10b and the corner edge 11 protrudes in the rotation direction T of the drill. In this case, the connection portion 13 between the second main cutting edge 10b and the corner edge 11 protrudes in the drill rotation direction T, so that the twist angle (axial rake angle) of the corner edge 11 can be increased accordingly. This further improves the sharpness of the corner edge 11.

[0073] In this embodiment, the radial dimension of the first main cutting edge 10a is 40% or more and 50% or less of the radius of the cutting portion 3. When the radial dimension of the first main cutting edge 10a is 40% or more of the radius of the cutting portion 3, a large cutting edge length of the first main cutting edge 10a is ensured, and hole drilling can be performed more efficiently. When the radial dimension of the first main cutting edge 10a is 50% or less of the radius of the blade portion 3, the blade lengths of the second main cutting edge 10b and the corner edge 11 other than the first main cutting edge 10a among the cutting edges 7 can be ensured to be large, and the functions of the second main cutting edge 10b and the corner edge 11 can be stably performed.

[0074] In this embodiment, the radial dimension of the main cutting edge 10 is 70% or more and 80% or less of the radius of the cutting portion 3 . When the radial dimension of the main cutting edge 10 is 70% or more of the radius of the cutting portion 3, the cutting length of the main cutting edge 10 is ensured to be large, and the drilling process can be performed more efficiently. When the radial dimension of the main cutting edge 10 is 80% or less of the radius of the cutting portion 3, the cutting edge length of the corner edge 11 other than the main cutting edge 10 among the cutting edges 7 can be ensured to be large, and the function of the corner edge 11 can be stably achieved.

[0075] In this embodiment, the main cutting edge 10 extends radially outward from the central axis C when viewed in the axial direction. In this case, since the main cutting edge 10 passes along the central axis C, a chisel edge or the like is not formed near the central axis C of the tip surface 3b of the cutting portion 3. Therefore, according to the above configuration, chipping of the cutting portion 3 due to a chisel edge or the like is suppressed.

[0076] In this embodiment, the corner edge 11 has a larger twist angle from the connection portion 13 with the main cutting edge 10 toward the rear end side in the axial direction. In this case, the sharpness of the corner blade 11 increases toward the rear end in the axial direction. The corner blade 11, particularly the rear end in the axial direction, stably improves the machining accuracy of the inner periphery of the machined hole, and further suppresses edge chipping of the machined hole.

[0077] In this embodiment, the corner edge 11 extends in a convex curve toward the rear end side in the axial direction as it extends radially outward. In this case, because the corner blade 11 has a convex curved shape, the inclination angle of the corner blade 11 with respect to the central axis C decreases toward the rear end in the axial direction. This reduces the thrust force acting on the inner circumference of the machined hole when the corner blade 11 penetrates the machined hole. This more stably prevents edge chipping of the machined hole (especially on the exit side of the drilling hole).

[0078] In this embodiment, the width of the portion of the rake face 5 located between the main cutting edge 10 and the chip discharge groove 4 (that is, the main rake face 21) decreases toward the outside in the radial direction. During drilling, the amount of chips supplied from the cutting edge 7 increases toward the radially outer side of the rake face 5 (main rake face 21) (the faster the peripheral speed). In the above configuration, the width of the rake face 5 decreases toward the radially outer side, so that the chips are efficiently made to flow from the rake face 5 into the chip discharge groove 4, resulting in good chip discharge performance.

[0079] [Other configurations included in the present invention] The present invention is not limited to the above-described embodiment, and the configuration may be modified within the scope of the present invention, for example as described below.

[0080] In the above embodiment, the drill 1 has been described as a small-diameter drill having a cutting portion 3 with a diameter (cutting diameter) of 2 mm or less, but is not limited thereto. The drill 1 is not limited to a small-diameter drill, and the cutting portion 3 may have a cutting diameter exceeding 2 mm.

[0081] In the above embodiment, the drill 1 is a twist drill with two blades, but the present invention is not limited to this. The drill 1 may have one blade or three or more blades.

[0082] The drill 1 may have a configuration in which the cutting portion 3 and the shank portion 2 are provided separately from each other and then assembled or integrated by brazing. Alternatively, the drill 1 may have a configuration in which the cutting portion 3 and the shank portion 2 are integrally formed from a single member. The drill 1 may be a replaceable drill in which the cutting portion 3 is detachably attached to the shank portion 2 by a screw or the like. In this case, the cutting portion 3 may be referred to as the drill head 3.

[0083] The present invention may be combined with the various configurations described in the above-mentioned embodiments and modifications, and may include additions, omissions, substitutions, and other modifications, without departing from the spirit of the present invention. The present invention is not limited to the above-mentioned embodiments, but is limited only by the claims. EXAMPLES

[0084] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0085] [Check test for chipping of processed holes] As an example of the present invention, the drill 1 described in the above embodiment was used to drill a workpiece made of a hard and brittle material (Si material). As a conventional example, a drill in which the rake angle of the cutting edge arranged on the tool tip face was a negative angle over the entire length in the blade length direction was used to drill a workpiece made of a hard and brittle material (Si material). In both the embodiment and the conventional example, the cutting conditions were as follows, 50 holes were machined in the workpiece, and the degree (condition) of edge chipping occurring near the inner circumference of the machined holes was confirmed.

[0086] <Cutting conditions> Drill: φ1.5mm PCD drill - Flatness of workpiece: within 40μm per 80mm x 80mm ·Cutting speed: vc=21.7m / min Feed: fr=0.001mm / rev Drilling length: ld = 3.5mm (stop) Step (machining) amount: 0.3 mm Return: 0.2mm from flat surface Cutting fluid: Emulsion AP-EX-E1 [10%] External oil supply

[0087] Fig. 8 is an image showing a machined hole (50th hole) drilled by the drill 1 of the embodiment. Fig. 9 is an image showing a machined hole (50th hole) drilled by the conventional drill. As shown in Figs. 8 and 9, it was confirmed that, compared to the conventional example, the drill 1 of the embodiment example stably suppressed edge chipping near the inner circumference even in the case of the 50th drilled hole. [Industrial Applicability]

[0088] INDUSTRIAL APPLICABILITY The drill of the present invention can perform stable and high-precision drilling even when drilling a workpiece having high hardness, such as a hard and brittle material, and therefore has industrial applicability. [Explanation of symbols]

[0089] 1. Drill 3...Blade part 3b…Tip surface 4...Chip discharge groove 5…Scooping surface 6…Flank 7…Cutting edge 10…Main cutting edge 10a…First main cutting edge 10b…Second main cutting edge 11…Corner blade 13…Connection part 21a…First scooping face 21b…Second scooping face 31a…First relief face 31b…Second flank C…Central axis T…Drill rotation direction α…Cutting edge angle (right-angle cutting edge angle) α1…Cutting edge angle of the first main cutting edge α2…2nd main cutting edge cutting edge angle

Claims

1. The cutting edge portion extends in an axial direction around a central axis, The blade portion is The scooping surface and The relief surface and A cutting edge is disposed on a ridge line between the rake face and the flank face, The cutting blade is A main cutting edge is disposed on a tip surface of the cutting portion facing the tip side in the axial direction, and has a negative rake angle; A corner edge is disposed at an end portion on the radially outer side of the cutting edge, connected to the main cutting edge, and has a positive rake angle. The corner edge extends in a convex curve shape toward the rear end side in the axial direction as it moves radially outward. drill.

2. A cutting tool having a blade portion extending in an axial direction around a central axis, The blade portion is The scooping surface and The relief surface and A cutting edge is disposed on a ridge line between the rake face and the flank face, The cutting blade is A main cutting edge is disposed on a tip surface of the cutting portion facing the tip side in the axial direction, and has a negative rake angle; A corner edge is disposed at an end portion on the radially outer side of the cutting edge, connected to the main cutting edge, and has a positive rake angle. The blade portion is provided with a chip discharge groove that opens on the tip surface and extends in the axial direction, A width dimension of a portion of the rake face located between the main cutting edge and the chip discharge groove becomes smaller toward the radially outer side. drill.

3. A cutting tool having a blade portion extending in an axial direction around a central axis, The blade portion is The scooping surface and The relief surface and A cutting edge is disposed on a ridge line between the rake face and the flank face, The cutting blade is A main cutting edge is disposed on a tip surface of the cutting portion facing the tip side in the axial direction, and has a negative rake angle; A corner edge is disposed at an end portion on the radially outer side of the cutting edge, connected to the main cutting edge, and has a positive rake angle. The main cutting edge is A first main cutting edge; a second main cutting edge disposed radially outward of the first main cutting edge, the second main cutting edge having both ends connected to the first main cutting edge and the corner edge; The cutting edge angle of the second main cutting edge is equal to or greater than the cutting edge angle of the first main cutting edge, The second main cutting edge extends in a drill rotation direction in a circumferential direction around the central axis as it moves radially outward. drill.

4. A cutting tool having a blade portion extending in an axial direction around a central axis, The blade portion is The scooping surface and The relief surface and A cutting edge is disposed on a ridge line between the rake face and the flank face, The cutting blade is A main cutting edge is disposed on a tip surface of the cutting portion facing the tip side in the axial direction, and has a negative rake angle; A corner edge is disposed at an end portion on the radially outer side of the cutting edge, connected to the main cutting edge, and has a positive rake angle. The main cutting edge is A first main cutting edge; a second main cutting edge disposed radially outward of the first main cutting edge, the second main cutting edge having both ends connected to the first main cutting edge and the corner edge; The cutting edge angle of the second main cutting edge is equal to or greater than the cutting edge angle of the first main cutting edge, The rake face is A first cutting face connected to the first main cutting edge; A second cutting face connected to the second main cutting edge, The first rake face and the second rake face are disposed in a single plane. drill.

5. A cutting tool having a blade portion extending in an axial direction around a central axis, The blade portion is The scooping surface and The relief surface and A cutting edge is disposed on a ridge line between the rake face and the flank face, The cutting blade is A main cutting edge is disposed on a tip surface of the cutting portion facing the tip side in the axial direction, and has a negative rake angle; A corner edge is disposed at an end portion on the radially outer side of the cutting edge, connected to the main cutting edge, and has a positive rake angle. The main cutting edge is A first main cutting edge; a second main cutting edge disposed radially outward of the first main cutting edge, the second main cutting edge having both ends connected to the first main cutting edge and the corner edge; The cutting edge angle of the second main cutting edge is equal to or greater than the cutting edge angle of the first main cutting edge, The flank surface is A first flank surface connected to the first main cutting edge; A second flank surface connected to the second main cutting edge, The first flank surface is planar, The second flank surface is a convex curved surface. drill.

6. A cutting tool having a blade portion extending in an axial direction around a central axis, The blade portion is The scooping surface and The relief surface and A cutting edge is disposed on a ridge line between the rake face and the flank face, The cutting blade is A main cutting edge is disposed on a tip surface of the cutting portion facing the tip side in the axial direction, and has a negative rake angle; A corner edge is disposed at an end portion on the radially outer side of the cutting edge, connected to the main cutting edge, and has a positive rake angle. The main cutting edge is A first main cutting edge; a second main cutting edge disposed radially outward of the first main cutting edge, the second main cutting edge having both ends connected to the first main cutting edge and the corner edge; The cutting edge angle of the second main cutting edge is equal to or greater than the cutting edge angle of the first main cutting edge, The main cutting edge extends radially outwardly and toward the rear end side in the axial direction, The second main cutting edge has a smaller inclination angle with respect to the central axis than the first main cutting edge. drill.

7. The second main cutting edge has a cutting edge angle in a cross section perpendicular to a cutting edge length direction in which the cutting edge extends, the cutting edge angle increasing from the first main cutting edge to the corner edge along the cutting edge length direction of the second main cutting edge. A drill according to any one of claims 3 to 6.

8. When the cutting edge is viewed from the axial direction, a connection portion between the second main cutting edge and the corner edge protrudes in a drill rotation direction in a circumferential direction around the central axis. A drill according to any one of claims 3 to 7.

9. The radial dimension of the first main cutting edge is 40% or more and 50% or less of the radius of the blade portion. A drill according to any one of claims 3 to 8.

10. The radial dimension of the main cutting edge is 70% or more and 80% or less of the radius of the cutting edge. A drill according to any one of claims 1 to 9.

11. The main cutting edge extends radially outward from the central axis when viewed in the axial direction. A drill according to any one of claims 1 to 10.

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