JP7632092B2 - drill - Google Patents

Description

The present invention relates to a drill.

A known example of a conventional drill is a cutting tool for brittle materials described in Patent Document 1. 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.

JP 2002-355710 A

With this type of drill, there is room for improvement in preventing "edge chipping" that occurs near the inner circumference of the drilled hole when drilling into a workpiece made of a hard and brittle material. In particular, edge chipping is prone to occur when drilling hard and brittle materials such as silicon-based ceramics.

One of the objectives of the present invention is to provide a drill that can perform stable, high-precision drilling even when drilling hard workpieces such as brittle materials.

One embodiment 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 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 corner edge extending in a convex curve toward the rear end side in the axial direction as it extends 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. and 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 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, 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.

The drill of the present invention has a negative rake angle on the main cutting edge, 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, brittle material, chipping and damage to the main cutting edge can be suppressed, allowing efficient drilling. For example, even when drilling a workpiece made of a hard, brittle material such as silicon nitride ceramics or alumina ceramics, the occurrence of chipping on the cutting edge can be suppressed.

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 silicon-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 hole when the corner blade penetrates the hole. This more stably prevents edge chipping of the hole (especially the hole 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 that is 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 portion 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.

In the above drill, the main cutting edge has a first main cutting edge and a second main cutting edge arranged radially outside the first main cutting edge, both ends of which are connected to the first main cutting edge and the corner edge, and the cutting angle of the second main cutting edge is greater than or equal to the cutting angle of the first main cutting edge.

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 further reduces chipping and damage to the main cutting edge, allowing for efficient and stable drilling.

In the above drill, the second main cutting edge extends radially outwardly and in the drill rotation direction in the circumferential direction about the central axis.

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 substantially 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, i.e., the faster the 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.

In the above drill, the cutting face has a first cutting face connected to the first main cutting edge and a second cutting face connected to the second main cutting edge, and the first cutting face and the second cutting face are arranged in a single plane .

In this case, the configuration of the cutting face can be simplified, and problems such as the cutting load being concentrated locally on one part of the main cutting edge can be suppressed. Therefore, chipping of the cutting edge of the main cutting edge can be further suppressed.

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.

In this case, since the first flank is flat, it is easy to form the first flank during the manufacture of 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, etc. at the connection portion between them is suppressed.

In the above drill, it is preferable that the cutting edge angle in a cross section perpendicular to the blade length direction in which the second main cutting edge extends increases from the first main cutting edge to the corner edge along the blade length direction of the second main cutting edge.

The more radially outward the second main cutting edge is located, 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 perpendicular cutting angle of the second main cutting edge increases as it approaches the corner edge from the first main cutting edge along the cutting edge length direction, so chipping and damage to the second main cutting edge are more stably suppressed.

In the above drill, when the cutting edge is viewed from the axial direction, it is preferable that the connection portion between the second main cutting edge and the corner edge protrudes in the circumferential direction around the central axis in the direction of drill rotation.

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 the twist angle (axial rake angle) of the corner edge can be made larger. This further improves the sharpness of the corner edge.

In the above 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.

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 blade 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.

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.

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.

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.

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 part. Therefore, with the above configuration, chipping of the cutting part due to the chisel edge, etc. is suppressed.

The drill of one embodiment of the present invention can perform stable and highly accurate drilling even when drilling hard workpieces such as brittle materials.

FIG. 1 is a perspective view showing a part of a drill according to the present embodiment. FIG. 2 is a front view showing a part of the drill. FIG. 3 is a side view showing a portion of the drill. FIG. 4 is a cross-sectional view showing a cross section taken along line IV-IV of FIG. FIG. 5 is a cross-sectional view showing the V-V section of FIG. FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. FIG. 7 is a cross-sectional view showing a cross section taken along line VII-VII of FIG. FIG. 8 is an image showing a hole (the 50th hole) drilled in a workpiece made of a hard and brittle material by the drill (example) of this embodiment. FIG. 9 is an image showing a drilled hole (the 50th hole) drilled in a workpiece made of a hard and brittle material by a conventional drill (conventional example).

The drill 1 according to one embodiment of the present invention will be described with reference to the drawings. The drill 1 according to this 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.

As shown in FIG. 1, the drill 1 is columnar or axial 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.

[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. In 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.
A direction perpendicular to the central axis C is called a radial direction. Of the radial directions, a direction approaching the central axis C is called a radially inner direction, and a direction away from the central axis C is called a 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.

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

[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.

At least the axial tip end (tip) 3a of the blade portion 3 is made of, for example, sintered diamond (Polycrystalline diamond, PCD) or single crystal diamond. In this embodiment, the portion of the blade portion 3 located on the tip side of the boundary line indicated by the symbol B in Figures 1 and 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.

The cutting portion 3 has a chip discharge groove 4, a rake face 5, a clearance 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 surface 3b facing the tip side in the axial direction of the cutting portion 3. Specifically, the chip discharge groove 4 extends in a spiral shape in the direction opposite to the drill rotation direction as it moves from the tip surface 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.

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. In other words, the drill 1 in this embodiment is a two-blade twist drill.

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 blade 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 main cutting edges 10 of the multiple cutting edges 7 are connected to each other at their radial inner ends 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 blade portion 3. The radial dimension of each main cutting edge 10 is 70% to 80% of the radius of the blade portion 3 (i.e., 1/2 of the blade diameter).

The main cutting edge 10 has a negative rake angle over its 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 Figures 4 to 6, the blade angle (perpendicular blade angle) α of the main cutting edge 10 in a cross section perpendicular to the blade length direction 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.

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 each of 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°.

The second main cutting edge 10b is disposed radially outward of the first main cutting edge 10a. Both ends of the second main cutting edge 10b in the cutting edge length direction are 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 increases 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.

The second main cutting edge 10b is curved and extends in a curved manner. 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 axial tip side when viewed from the radial direction as shown in FIG. 3.

As shown in Figures 4 to 6, the tool angle α2 of the second main cutting edge 10b is equal to or larger than the tool angle α1 of the first main cutting edge 10a. Furthermore, the right-angle tool 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 tool angle α2 shown in Figure 6 is larger than the tool angle α2 shown in Figure 5.
That is, in the main cutting edge 10 of this embodiment, the cutting edge angle α increases as it approaches the corner edge 11 along the cutting edge length direction of the main cutting edge 10 .

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

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 portion 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.

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

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 toward the rear end side in the axial direction.

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 intervals 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 .

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 as a result, the rake angle of the main cutting edge 10 is also negative.
The width dimension of the main rake face 21, i.e., the width dimension of the portion of the rake face 5 located between the main cutting edge 10 and the chip discharge groove 4, becomes smaller toward the outside in the radial direction. In this embodiment, the main rake face 21 is formed of a single plane having a substantially triangular shape.

The main rake face 21 has a first rake face 21 a and a second rake face 21 b. That is, the rake face 5 has the first rake face 21 a and the second rake face 21 b.
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.

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 connects to the corner blade 11. The corner rake face 22 is disposed adjacent to the radially inner side of the corner blade 11. The corner rake face 22 is located on the wall portion of the chip discharge groove 4 facing the drill rotation direction T. The corner rake face 22 extends along the corner blade 11. As the corner rake face 22 moves radially inward from the corner blade 11, it is positioned in the opposite direction to the drill rotation direction (see FIG. 7). In other words, the corner rake face 22 has a positive rake angle, which makes the rake angle of the corner blade 11 positive as well. The corner rake face 22 is a concave curved surface.

As shown in Fig. 3, the peripheral rake face 23 is disposed on the outer periphery of the cutting edge 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 positive as well. The peripheral rake face 23 is a concave curved surface.
The corner rake face 22 and the outer peripheral rake face 23 are disposed on a single concave curved surface. That is, the corner rake face 22 and the outer peripheral rake face 23 are integrally formed by a single concave curved surface.

2 and 3, a plurality of flanks 6 are provided at intervals in the circumferential direction on the cutting edge 3. In the present 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 .

The main flank 31 is disposed on the tip surface 3b of the cutting portion 3 and connects to the main cutting edge 10. The main flank 31 is disposed adjacent to the main cutting edge 10 in the direction opposite to the drill rotation. The main flank 31 extends along the main cutting edge 10. The main flank 31 is positioned toward the rear end in the axial direction as it moves away from the main cutting edge 10 in the direction opposite to the drill rotation. This gives the main flank 31 a clearance angle.

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 convex (see FIG. 5 and FIG. 6).
That is, the first flank surface 31a and the second flank surface 31b are formed by different surfaces. The first flank surface 31a and the second flank surface 31b are smoothly connected to each other.

As shown in Figures 2 and 3, the corner relief 32 is located at the radially outer end of the tip face 3b of the cutting portion 3 and connects to the corner edge 11. The corner relief 32 is located adjacent to the corner edge 11 in the direction opposite to the drill rotation. The corner relief 32 extends along the corner edge 11. The corner relief 32 is positioned radially inward as it moves away from the corner edge 11 in the direction opposite to the drill rotation (see Figure 7). This gives the corner relief 32 a relief angle.

As shown in Figures 1 to 3, the margin 8 is disposed on the outer peripheral surface of the cutting edge 3 and connects to the leading edge 12. The margin 8 is disposed adjacent to the leading edge 12 in the direction opposite to the drill rotation. The margin 8 extends in a spiral shape along the leading edge 12. The axial tip of the margin 8 connects 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.

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 direction opposite to the drill rotation. The chamfered surface 9 is located radially inward from the margin 8. The axial tip of the chamfered surface 9 connects to the tip surface 3b.

[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 and 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.

The corner cutting 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 cutting edge 11 is a positive angle, so that the sharpness of the corner cutting edge 11 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 1 of this embodiment can perform stable, high-precision drilling even when drilling a workpiece having high hardness, such as a hard and brittle material.

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 efficient and stable drilling.

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 increases 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 effective 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) increases 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 faster the peripheral speed, i.e., the cutting speed, during drilling, the larger the effective tool angle and the greater the cutting edge strength, thereby further reducing chipping and damage to the second main cutting edge 10b.

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

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 convexly curved, 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.

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 is 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 that chipping and breakage of the second main cutting edge 10b are more stably suppressed.

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, it becomes easier to smoothly connect the second main cutting edge 10b and the corner edge 11, and chipping, breakage, etc. at the connection portion between them is suppressed.

In this embodiment, as shown in FIG. 2, when the cutting portion 3 is viewed in the axial direction, the 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.

In this embodiment, the radial dimension of the first main cutting edge 10 a is 40% to 50% 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.

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 secured large, and the function of the corner edge 11 can be stably achieved.

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 in the vicinity of the central axis C of the tip surface 3b of the cutting portion 3. Therefore, according to the above-mentioned configuration, damage to the cutting portion 3 caused by a chisel edge or the like is suppressed.

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.

In this embodiment, the corner edge 11 extends in a convex curve shape toward the rear end side in the axial direction as it extends radially outward.
In this case, since 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 side 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 suppresses edge chipping of the machined hole (especially the hole exit side).

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 (i.e., the main rake face 21) decreases radially outward.
During drilling, the radially outer portion of the rake face 5 (main rake face 21) (the portion having a higher peripheral speed) receives a larger amount of chips from the cutting blade 7. In the above configuration, the width dimension of the rake face 5 decreases radially outward, 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.

[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.

In the above embodiment, the drill 1 is described as being a small-diameter drill with the diameter (blade diameter) of the cutting portion 3 being 2 mm or less, but this is not limited to this. The drill 1 is not limited to being a small-diameter drill, and the cutting diameter of the cutting portion 3 may be greater than 2 mm.

In the above embodiment, the drill 1 is a two-blade twist drill, but this is not limiting. The drill 1 may have one blade or three or more blades.

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, or 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.

The present invention may be implemented by combining the various configurations described in the above-mentioned embodiments and modifications, etc., without departing from the spirit of the present invention, and addition, omission, substitution, and other modifications of configurations are possible. Furthermore, the present invention is not limited to the above-mentioned embodiments, etc., but is limited only by the scope of the claims.

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

[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). Also, 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.

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

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.

The drill of the present invention can perform stable and highly accurate drilling even when drilling hard workpieces such as brittle materials. Therefore, it has industrial applicability.

1...Drill 3...Blade portion 3b...Tip surface 4...Chip discharge groove 5...Rake face 6...Flank face 7...Cutting edge 10...Main cutting edge 10a...First main cutting edge 10b...Second main cutting edge 11...Corner edge 13...Connection portion 21a...First rake face 21b...Second rake face 31a...First flank face 31b...Second flank face 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…Cutting edge angle of the second main cutting edge

Claims (11)

The cutting edge portion extends in an axial direction around a central axis,
The blade portion is
A 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. The cutting edge portion extends in an axial direction around a central axis,
The blade portion is
A 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. 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 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. 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 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. 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 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. The cutting edge portion extends in an axial direction around a central axis,
The blade portion is
A 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 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. 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 . 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. 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. 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. 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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