JP2003039220A - Boring tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance boring precision and a lifetime of a boring tool. SOLUTION: At the tip of the outside circumference of the main part of a tool which is nearly cylindrical, scraps discharge grooves are formed symmetrically and twistedly with the axis of rotation O of the main part of the tool, and cutting edges 5 are formed respectively in the intersection ridgeline parts of the wall surface which face to the rotational direction of each scraps discharge groove and a tip of a major flank 4. A thinning face 4a is formed at the internal perimeter side of the tool in the tip of the major flank 4, and the inner circumference portion of the cutting edge 5 which is bent to the side of the axis of rotation O by this thinning face 4a and reaches the cutting edge 5 of another side is set to a thinning edge 6. A chisel 7 is formed among the cutting edge 5 and the size of the chisel 7 along the direction of the thinning edge 6 is made into within the limits of 0.10 to 0.25 mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool such as a drill suitable for drilling a difficult-to-cut material which is easily work hardened.

[0002]

2. Description of the Related Art As shown in FIGS. 10 and 11, a conventional drilling tool 21 has a pair of chips that are twisted around a rotation axis O1 on the outer periphery of the tip of a tool body 22 that is rotated about the rotation axis O1. The grooves 23, 23 are formed symmetrically with respect to the rotation axis O1, and the cutting edge 25 is formed on the ridge line portion where the wall surface 23a of each chip discharge groove 23 faces the tool rotation direction and the tip flank 24. . In the tool body 22, a thinning surface 24a is formed on the tool inner peripheral side of the tip flank 24, and the inner peripheral side portion of the cutting edge 25 is bent by the thinning surface 24a toward the rotation axis O1 side to rotate the rotation axis O1. The thinning blade 26 is connected to the front flank 24 on the front side (outer peripheral side) of the thinning blade 26, and a chisel 27 is formed between the inner circumferential ends of the thinning blades 26. Here, the dimension X1 of the chisel 27 in the direction substantially orthogonal to the thinning blade 26 is defined as X dimension, and the dimension Y1 of the chisel 27 along the thinning blade 26 is defined as Y dimension. Further, the Y dimension when the thinning blades 26 do not face each other is positive, and the Y dimension when at least a part of the thinning blades 26 faces each other is negative. In addition, in FIG. 11, the shape of the vicinity of the chisel 27 is schematically shown.
Actually, the size of the vicinity of the chisel 7 is very small.

The above-mentioned difficult-to-cut materials (for example, Ti alloy,
For drilling Ni-based alloys, heat-resistant alloys, non-ferrous metals such as Al), the tip angle α1 of the cutting edge 25 is 14 as a general shape.
A drilling tool having a tip clearance angle γ1 of the tip clearance surface 24 of 10 ° and a radial thinning angle δ1 of 30 ° is used. As such a drilling tool, the cutting edge shape is a general shape, but the honing amount of the cutting edge is reduced in order to reduce welding of chips to the cutting edge at the time of cutting, for example, with a cutting edge diameter of 10 mm. 0.05mm when the normal honing amount is 0.10mm
There are things that are suppressed. Further, the twist angle θ1 of each chip discharge groove 23 is made larger than usual to improve the chip dividing property due to the interference with the inner surface of the chip discharge groove 23, improve the chip discharge property, and reduce the cutting resistance. There is a plan.

[0004]

However, if the honing amount of the cutting edge is simply reduced in the drilling tool,
The load applied to the cutting edge during cutting increases and the tool life shortens. Further, the twist angle θ1 of the chip discharge groove 23
If the value is increased, the torsional rigidity of the tool main body 22 is lowered, and the tool main body 22 is apt to shake during drilling, and the drilling accuracy is reduced. Further, since the rigidity of the tool main body 22 is low and the runout is generated, the load applied to the tool main body 22 is increased, so that the tool life is shortened.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a drilling tool having improved drilling accuracy and tool life.

[0006]

In order to achieve the above object, a drilling tool according to the present invention comprises a pair of chip discharge grooves twisted around a rotation axis on the outer periphery of the tip of a tool body rotated around the rotation axis. Is formed symmetrically with respect to the rotation axis, and in the drilling tool in which the cutting edges are formed at the ridges intersecting the wall surface of each chip discharge groove that faces the tool rotation direction and the flank face, A thinning surface is formed on the peripheral side, and the inner peripheral side portion of the cutting edge is bent to the rotation axis side by this thinning surface to become a thinning blade that crosses the rotation axis and reaches the other cutting edge side. The dimension of the chisel formed between the thinning blades in the direction along the thinning blades is 0.10 mm to 0.2.
It is characterized in that it is within the range of 5 mm.

In the drilling tool thus constructed, the thinning surface is formed on the tool inner peripheral side of the tip flank, so that the inner peripheral side portion of the cutting edge is bent to the rotation axis side and rotated. It is a thinning blade that crosses the axis and reaches the other cutting edge side. That is, the Y dimension of the chisel formed between the thinning blades with the thinning blades facing each other is negative. Thereby, the space formed between the thinning surface and the thinning blade becomes wider, and the chips scraped off from the work material by the thinning blade are easily discharged to the space formed between the thinning surface and the thinning blade. Therefore, the chip discharging property is improved. Here, when the size of the chisel formed between these thinning blades in the direction along the thinning blade is smaller than 0.10 mm (when the Y dimension of the chisel is larger than -0.10 mm), The space formed between the thinning blade and the thinning blade becomes narrow, and the dischargeability of the chips scraped off from the work material by the thinning blade at the time of drilling is reduced. Furthermore, if the space formed between the thinning surface and the thinning blade becomes narrower in this way, the chips are more likely to be crushed in this space, so that under the influence of this, runout easily occurs in the tool body and hole machining Since the accuracy is lowered and the runout is generated, the load applied to the tool main body is increased and the tool life is shortened. When the size of the chisel along the thinning blade is larger than 0.25 mm (the size of the chisel in the Y direction is -0.25 mm).
Smaller than that), the strength of the chisel is reduced and the tool life is shortened. Therefore, the dimension of the chisel formed between the thinning blades in the direction along the thinning blades is within the range of 0.10 mm to 0.25 mm.

Further, the tip angle α of the cutting edge is 125 ° to 1
It may be within the range of 35 °. In this case, since the tip angle α of the cutting edge becomes small, the cutting edge easily bites into the work material during drilling, and the tool body hardly swings. Here, if the tip angle α of the cutting edge is smaller than 125 °, the strength of the cutting edge is reduced and the tool life is shortened. Further, when the tip angle α of the cutting edge is larger than 135 °, the cutting edge is less likely to bite the work material during drilling and the tool body is likely to swing.
Therefore, the tip angle α of the cutting edge is preferably within the range of 125 ° to 135 °.

Further, the tip clearance angle γ is 10 at the tip clearance surface.
It may be formed in a conical surface shape with the apex located on the axis of rotation within the range of 20 ° to 20 °. In this case,
Since the tip clearance surface is conical, the tip clearance angle γ
Can be increased to reduce the blade angle of the cutting blade to improve the sharpness, and at the same time, the wall thickness of the cutting edge can be secured to secure the strength. If the tip clearance angle γ is smaller than 10 °,
The cutting angle of the cutting blade is too large and the cutting resistance becomes large, resulting in poor sharpness. If the tip clearance angle γ is greater than 20 °, the wall thickness of the cutting edge becomes too thin and the strength of the cutting edge decreases. For this reason, it is preferable that the tip clearance angle γ of the tip flank is within the range of 10 ° to 20 °.

The size of the chisel in the direction substantially orthogonal to the thinning blade (X size of the chisel) may be in the range of 0.05 mm to 0.25 mm. In this case, the space formed between the thinning surface and the thinning blade becomes wider, and the chips scraped off from the work material by the thinning blade are discharged into the space formed between the thinning surface and the thinning blade. Since it becomes easier, the chip discharging property is further improved. Here, when the size of the chisel in the direction substantially orthogonal to the thinning blade is smaller than 0.05 mm,
The strength of the chisel is reduced and the tool life is shortened.
If this dimension is larger than 0.25 mm,
The space formed between the thinning surface and the thinning blade becomes narrow, and the dischargeability of chips scraped off from the work material by the thinning blade during drilling is reduced. Furthermore, if the space formed between the thinning surface and the thinning blade becomes narrower in this way, the chips are more likely to be crushed in this space, so that the tool body is susceptible to runout under the influence of this and the hole When the machining accuracy is reduced and the runout is generated, the load applied to the tool body is increased and the tool life is reduced. Therefore, the dimension of the chisel formed between the thinning blades in the direction substantially orthogonal to the thinning blades (X dimension of the chisel) is 0.0
It is preferable to set it within the range of 5 mm to 0.25 mm.

The radial thinning angle δ may be within the range of 10 ° to 20 °. In this case, since the tip angle β of the thinning blade becomes small, the thinning blade easily bites into the work material during drilling, and the tool body 2 is less likely to swing. Here, if the radial direction thinning angle δ is smaller than 10 °, the blade edge strength of the thinning blade is reduced and the tool life is shortened.
If the radial thinning angle δ is larger than 20 °,
During drilling, the thinning blade is less likely to bite into the work material, and the tool body 2 is likely to run out. Therefore, it is preferable that the radial thinning angle δ be within the range of 10 ° to 20 °.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a drilling tool according to the present invention will be described below with reference to FIGS. 1 to 4. In the present embodiment, an example in which the present invention is applied to a drill will be described. Here, FIG. 1 is a side view showing the shape of the drill according to the present embodiment, FIG. 2 is an enlarged view of the tip of the drill shown in FIG. 1, FIG. 3 is a front view of the drill shown in FIG. 1, and FIG. FIG. 4 is an enlarged view of FIG. 3.

The drill 1 shown in this embodiment is a two-blade twist drill, and has a substantially columnar tool body 2 formed of a hard material such as steel or cemented carbide on the outer periphery of the tip.
A pair of chip discharge grooves 3 and 3 are formed so as to be symmetrical with respect to the rotation axis O of the tool body 2 and to be twisted rearward in the tool rotation direction T at the time of machining toward the rear end side of the tool body 2. Here, in the present embodiment, the twist angle θ of the chip discharge groove 3 is set to 25 ° to 35 °. Further, the tool body 2 has an oil hole 2a communicating from the base end side to the tip flank 4
Is provided. Cutting edges 5 are formed at the ridges of intersections between the wall surface 3a of each chip discharge groove 3 facing the tool rotation direction T and the tip flank 4. Here, when the outer diameter of the cutting edge is D, the core thickness of the tool body 2 is, for example, 0.2 × Dmm to
It is set within the range of 0.35 × Dmm. In the present embodiment, the cutting edge outer diameter D is 8.6 mm. In the present embodiment, the core thickness is 0.25 × Dmm.

The tip angle α of the cutting edge 5 is 125 ° to 135 °.
The angle is within the range of °, and the tip of the tool body 2 is sharper than that of the conventional drill. This makes it easier for the cutting edge 5 to bite into the work material during drilling and makes it difficult for the tool body 2 to swing. Here, the tip angle α of the cutting edge 5
Is less than 125 °, the cutting edge strength will decrease.
Tool life will be shortened. Also, the tip angle α of the cutting edge 5
Is greater than 135 °, the cutting edge 5 is less likely to bite into the work material during drilling, and the tool body 2 is likely to run out. Therefore, the tip angle α of the cutting edge 5 is 1
It is preferably within the range of 25 ° to 135 °.

The tip clearance surface 4 has a tip clearance angle γ of 1
It is formed in the shape of a conical surface with the apex located on the axis of rotation within the range of 0 ° to 20 °, and the tip clearance angle γ is increased to reduce the blade angle of the cutting blade 5 to improve the sharpness. At the same time, the thickness of the cutting edge is secured to secure the strength. Here, if the tip clearance angle γ is smaller than 10 °, the blade angle of the cutting blade 5 becomes too large, the cutting resistance becomes large, and the sharpness deteriorates. If the tip clearance angle γ is greater than 20 °, the wall thickness of the cutting edge becomes too thin and the strength of the cutting edge decreases. Therefore, the tip clearance angle γ of the tip flank is 1
It is preferably within the range of 0 ° to 20 °.

A thinning surface 4a is formed on the tool inner peripheral side of the tip flank 4, and the inner peripheral portion of the cutting edge 5 is bent toward the rotation axis O side by the thinning surface 4a, and the rotation axis O is formed. It is a thinning blade 6 that passes over and reaches the other cutting blade 5 side. Here, in the present embodiment, the honing amount applied to the cutting blade 5 and the thinning blade 6 is set to 0 to 0.025 mm in order to prevent the welding of the chips to the cutting edge. A chisel 7 is formed between the thinning blades 6, and the size of the chisel 7 in the direction along the thinning blade 6 is within the range of 0.10 mm to 0.25 mm. That is, the Y dimension of the chisel 7 is -0.25 mm.
To -0.10 mm. Further, the dimension of the chisel 7 in the direction substantially orthogonal to the thinning blade 6 (X dimension of the chisel 7) is within the range of 0.05 mm to 0.25 mm. Here, in FIG. 4, for comparison, the shape of the thinning surface 4a when the Y dimension of the chisel is positive is shown by a chain double-dashed line.

The radial thinning angle δ is within the range of 10 ° to 20 °. As a result, the tip angle β of the thinning blade 6 becomes smaller, so that the thinning blade 6 easily bites into the work material during drilling and the tool body 2 is less likely to swing. Here, if the radial thinning angle δ is smaller than 10 °, the strength of the cutting edge of the thinning blade 6 is lowered and the tool life is shortened. Also,
When the radial thinning angle δ is larger than 20 °, the thinning blade 6 is less likely to bite into the work material, and the tool body 2 is likely to swing. Therefore, it is preferable that the radial thinning angle δ be within the range of 10 ° to 20 °.

In the drill 1 thus constructed, the thinning surface 4 is provided on the tool inner peripheral side of the tip flank surface 4.
By forming a, the portion on the inner peripheral side of the cutting blade 5 is bent to the rotation axis O side and reaches the other cutting blade 5 side beyond the rotation axis O to form the thinning blade 6. That is, the thinning blades 6 are opposed to each other and the Y dimension of the chisel formed between the thinning blades 6 is negative. As a result, the space S formed between the thinning surface 4a and the thinning blade 6 becomes wider, and the chips scraped off from the work material by the thinning blade 6 become thinner.
Will be easily discharged into the space S formed between the thinning blade 6 and the thinning blade 6.

Here, when the size of the chisel 7 formed between the thinning blades 6 in the direction along the thinning blade 6 is smaller than 0.10 mm (the Y dimension of the chisel 7 is-).
If it is larger than 0.10 mm), the thinning surface 4
The space S formed between a and the thinning blade 6 becomes narrow, and the dischargeability of the chips scraped off from the work material by the thinning blade 6 deteriorates. Further, since the space S formed between the thinning surface 4a and the thinning blade 6 is narrowed in this way, the chips are easily crushed in the space S during drilling, and the influence thereof is exerted. The tool body 2 is likely to be shaken, the hole machining accuracy is lowered, and the shake is caused, which increases the load applied to the tool body 2 and shortens the tool life. Also,
The dimension of the chisel 7 along the thinning blade 6 is 0.2.
If it is larger than 5 mm (the size of the chisel 7 in the Y direction
If it is smaller than 0.25 mm), the strength of the chisel 7 is reduced and the tool life is shortened. Therefore, the dimension of the chisel 7 formed between the thinning blades 6 in the direction along the thinning blades 6 is 0.10 mm to 0.2 mm.
It is set within the range of 5 mm.

The dimension of the chisel 7 in the direction substantially orthogonal to the thinning blade 6 (X dimension of the chisel 7) is 0.05 mm.
To 0.25 mm, and a wide space S formed between the thinning surface 4a and the thinning blade 6 is secured, so that the chips scraped off from the work material by the thinning blade 6 are thinned. Surface 4a and thinning blade 6
It will be easily discharged into the space S formed between and. Here, when the size of the chisel 7 in the direction substantially orthogonal to the thinning blade 6 is smaller than 0.05 mm, the strength of the chisel 7 is reduced and the tool life is shortened. Further, if this dimension is larger than 0.25 mm, the space S formed between the thinning surface 4a and the thinning blade 6 becomes small, and the chips scraped off from the work material by the thinning blade 6 become smaller. Ejectability is reduced.
Furthermore, since the chips are easily crushed in the space S formed between the thinning surface 4a and the thinning blade 6 during drilling, the tool body is susceptible to runout under the influence of this and the drilling accuracy is improved. And the deflection causes a large load to be applied to the tool body 2 and the tool life is also shortened. Therefore, the dimension of the chisel 7 formed between the thinning blades 6 in the direction substantially orthogonal to the thinning blades 6 (X dimension of the chisel 7) is 0.05 m.
It is preferable to set it within the range of m to 0.25 mm.

According to the drill 1 thus constructed,
A portion on the inner peripheral side of the cutting blade 5 is a thinning blade 6 that reaches the other cutting blade 5 side beyond the rotation axis O, and along the thinning blade 6 of the chisel 7 formed between these thinning blades 6. The dimension in the vertical direction is 0.10 mm to 0.25 m
The dimension of the chisel 7 in the direction substantially orthogonal to the thinning blade 6 (X dimension of the chisel 7) is within the range of m.
Since the thickness is in the range of 0.05 mm to 0.25 mm, the space S formed between the thinning surface 4a and the thinning blade 6 is widely secured, and the thinning blade 6 scrapes off the work material. Since the chips are easily discharged to the space S formed between the thinning surface 4a and the thinning blade 6, the chip discharging property is improved. As a result, the influence of chips on the drill 1 during drilling is reduced, and the drill 1 is less likely to run out, so that the drilling accuracy can be improved. Further, since the load applied to the cutting blade 5 and the thinning blade 6 is reduced, the life of the cutting blade can be ensured even if the honing amount of the cutting blade 5 and the thinning blade 6 is small. The amount of honing applied to the blade 6 can be reduced or the honing can be eliminated to prevent the welding of chips to the cutting edge. Further, since the swinging of the drill 1 is less likely to occur in this way, the load applied to the drill 1 can be reduced and the tool life can be extended.

[0022]

EXAMPLES Next, a cutting performance test was conducted for each of the drill according to the embodiment of the present invention (hereinafter referred to as an example) and a conventional drill (hereinafter referred to as a conventional example) to compare the cutting performance. It was The configurations of the example and the conventional example are shown in Table 1 below.

[0023]

[Table 1]

As shown in Table 1, the tip angle of the cutting edge is 140 ° in the conventional example, whereas the tip angle of the cutting edge is 130 ° in the embodiment. Further, in the conventional example, the tip flank has a flank angle of 10 ° to 20 °, and the tilt angle with respect to the plane orthogonal to the rotation axis increases in three steps from the cutting edge toward the rear in the tool rotation direction. On the other hand, in the embodiment, the tip flank is a conical surface with the clearance angle of 16 ° and the apex located on the rotation axis of the tool body. Further, in the conventional example, the radial thinning angle is 30 °.
On the other hand, in the embodiment, the radial thinning angle is set to a smaller value of 13 °. Further, in the conventional example, the cutting blade and the thinning blade are subjected to an angle honing of 30 ° and the honing amount is set to 0.1 mm to 0.15 mm, whereas in the working example, the cutting blade and the thinning blade are subjected to honing. Absent. In the conventional example, the surface of the tool body is coated with TiCN / TiAlN, whereas in the embodiment, the surface of the tool body is coated with TiAlN,
Or, there is no surface coating.

Then, using the examples and the conventional examples, the work material was subjected to drilling, and the state of the cut surface (bottom surface of the processed hole) of the work material at that time was observed. The state of this cut surface is shown in FIG. In FIG. 5, (a) shows the cutting surface according to the conventional example, and (b) shows the cutting surface according to the embodiment. From FIG. 5, it can be seen that in the conventional example, the cutting marks are not circular but are distorted, and the cutting surface is also rough, especially the center position is rough. From this, it can be seen that in the conventional example, the tool body is shaken during drilling. On the other hand, in the example, it can be seen that the traces of the cutting work are close to a perfect circle, the roughness of the cutting work surface is small, and the center position is well processed. From this, it can be seen that in the embodiment, the tool body swings little during drilling.

FIG. 6 shows the chips generated during the above cutting test. In FIG. 6, (a) shows the chips according to the conventional example, and (b) shows the chips according to the embodiment. From FIG. 6, it can be seen that the shape of the chips is not stable and the cutting by the cutting blade is not stable in the conventional example. From this, it can be inferred that the tool body is shaken.
Further, from the shape of the chips, it is presumed that the chips are crushed when discharged. On the other hand, in the embodiment, the shape of the chips is stable, which also shows that the tool body is less likely to swing. Further, it can be seen from the shape of the chips that the chips are not crushed when discharged.

Next, the cutting performance when cutting the work material was measured by each of the example and the conventional example. The result is shown in the graph of FIG. The cutting conditions at this time were that the outer diameter of the cutting edge was 8 mm in both the example and the conventional example, the work material was Inconel 718, and the cutting speed Vc = 20 m /
min, feed rate fr = 0.04 / rev, L / D = 1
5, and emulsion type cutting oil was supplied at 1 MPa. (A) Comparison of enlargement margin As shown in FIG. 7A, in the conventional example, the enlargement margin of the machined hole is about 17 μm to about 43 μm in the first drilling.
m, in the second drilling process, it is about 14 μm to 35 μm, and the expansion margin is large and the expansion amount is not stable. On the other hand, in the example, the first drilling process was about 13 μm to about 17 μm, and the second drilling process was about 22 μm to 25 μm. ing. (B) Surface Roughness Comparison Next, the surface roughness in the vicinity of the entrances of the holes made in these examples and the conventional example was measured. The result is shown in FIG.
Is shown in the graph. As shown in FIG. 7B, in the hole formed by the conventional example, the ten-point average roughness Rz is 5.68μ.
m, and the maximum height Ry was 8.54 μm. On the other hand, in the hole formed by the example, the ten-point average roughness Rz is 3.02 μm and the maximum height Ry is 4.82.
was μm. (C) Roundness Comparison Next, the roundness in the vicinity of the entrances of the holes made in these examples and the conventional example was measured. The result is shown in the graph of FIG. As shown in FIG. 7 (c), in the hole drilled by the conventional example, the vicinity of the inlet has a distorted shape, and the maximum deviation from the target machining diameter is 16.3.
was μm. On the other hand, in the hole drilled by the example, the shape near the entrance was almost a true circle, and the maximum deviation from the target processing diameter was 2.6 μm. From the above results, in the conventional example, it is presumed that the tool body is shaken during the drilling, which reduces the machining accuracy, while in the example, the drilling It is presumed that there is little runout in the tool body at this time, which improves the machining accuracy.

(D) Comparison of Cutting Resistance Next, the cutting resistance when drilling was carried out by these examples and the conventional example was measured. The result is shown in FIG.
The cutting conditions at this time were the same as the above-mentioned cutting conditions, and drilling was performed twice. In the conventional example, the cutting resistance is 0.90 k in both the first and second drilling processes.
On the other hand, in the example, the cutting resistance is 0.80 kW, which is lower than that in the conventional example in both the first and second drilling processes. It is considered that this is because the chip discharge is better in the example than in the conventional example. Further, in the conventional example, the thrust force received during the drilling is 1249
In the embodiment, the thrust force received at the time of drilling is 1053N, 1029N.
From the above, it is clear that the tool body is lower than in the conventional example, and that the tool body is less likely to shake than the conventional example. In the conventional example, the torque generated on the tool spindle during drilling is 3.4.
While 3 Nm and 3.27 Nm, in the embodiment,
It is clear that the values are 2.64 Nm and 2.74 Nm, which are clearly lower than those of the conventional example.

Next, in order to know how the work hardening occurred in the drilled work material, the difference in Vickers hardness in the depth direction of the inner surface of the work hole was measured in the work material. The result is shown in the graph of FIG. The cutting conditions at this time were the same as the above cutting conditions. The Vickers hardness of the work material before processing is 26 as shown by the broken line in FIG.
It was from 0 Hv to 270 Hv. In the processed hole according to the conventional example, the Vickers hardness near the entrance reached about 580 Hv, and the Vickers hardness was 300 Hv or more in the range where the distance to the opening end of the hole was 0.2 mm or less. On the other hand, in the processed hole according to the embodiment, the work hardening near the entrance is small, the maximum is about 350 Hv, and when the distance to the opening end of the hole exceeds 0.07 mm, there is some variation, but work hardening Is rarely seen. From this, it can be inferred that the cutting edge of the example has better sharpness than the conventional example.

[0030]

According to the drilling tool of the present invention, the inner peripheral portion of the cutting blade is a thinning blade that reaches the other cutting blade side beyond the axis of rotation, and is formed between these thinning blades. The dimension of the chisel to be cut along the thinning blade is within the range of 0.10 mm to 0.25 mm, so that a wide space can be secured between the thinning surface and the thinning blade. Since the chips scraped off from the work material by the thinning blade are easily discharged to the space formed between the thinning surface and the thinning blade, the chip discharging property is improved. This reduces the influence of chips on the drilling tool during drilling,
Since it is difficult for the drilling tool to swing, it is possible to improve the accuracy of drilling. Further, since the load applied to the cutting blade and the thinning blade is reduced, the life of the cutting blade can be secured even if the honing amount of these cutting blade and the thinning blade is small. It is possible to prevent welding of chips to the cutting edge by reducing the amount or eliminating honing. Further, since the boring tool is less likely to swing in this way, the load applied to the boring tool can be reduced and the tool life can be extended.

[Brief description of drawings]

FIG. 1 is a side view showing the shape of a drill (drilling tool) according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a tip portion of the drill shown in FIG.

3 is a front end view of the drill shown in FIG. 1. FIG.

FIG. 4 is an enlarged view of FIG.

FIG. 5 is a view showing a state of a cut surface of a work material by each of the drill of the example according to the present invention and the drill of the conventional example.

FIG. 6 is a diagram showing the shape of chips generated when a work material is drilled by a drill of an example according to the present invention and a drill of a conventional example.

FIG. 7 is a graph showing the cutting performance of each of the drill of the example according to the present invention and the drill of the conventional example.

FIG. 8 is a graph showing the cutting resistance when the work material is drilled by each of the drill of the example according to the present invention and the drill of the conventional example.

FIG. 9 is a graph showing how the hardness of the work material changes when the work material is drilled by each of the drill of the example according to the present invention and the drill of the conventional example.

FIG. 10 is a side view showing the shape of a conventional drilling tool.

11 is a front end view of the drill shown in FIG.

[Explanation of symbols]

1 Drill (drilling tool) 2 Tool body 3 Chip discharge groove 4 Tip flank 4a Thinning surface 5 Cutting edge 6 Thinning blade 7 Chisel O Rotation axis X Chisel X dimension Y Chisel Y dimension α Tip angle of cutting edge β Tip angle of thinning blade γ Tip clearance angle δ Radial thinning angle

Claims (5)

[Claims] 1. A pair of chip discharge grooves twisted about the rotation axis are formed on the outer periphery of a tip end portion of a tool body rotated about the rotation axis symmetrically to the rotation axis, and the tool rotation of each chip discharge groove is performed. In a drilling tool in which a cutting edge is formed at each of the ridges intersecting the wall surface and the tip flank facing each other, a thinning surface is formed on the tool inner peripheral side of the tip flank, and the cutting surface is formed by the thinning surface. A portion on the inner peripheral side of the blade is a thinning blade that is bent toward the rotation axis side and reaches the other cutting edge side beyond the rotation axis line, and the thinning blade of the chisel formed between these thinning blades is The dimension along the direction is from 0.10mm to 0.2
A drilling tool characterized by being within a range of 5 mm. 2. The tip angle α of the cutting edge is 125 ° to 1
3. It is set within the range of 35 °.
The described drilling tool. 3. A tip clearance angle γ of the tip flank is 10
The drilling tool according to claim 1 or 2, wherein the drilling tool is formed in a conical surface shape with an apex located on the axis of rotation within a range of 20 ° to 20 °. 4. The chisel according to claim 1, wherein a dimension of the chisel in a direction substantially orthogonal to the thinning blade is within a range of 0.05 mm to 0.25 mm. Drilling tool. 5. The radial thinning angle δ is from 10 ° to 20.
The drilling tool according to any one of claims 1 to 4, wherein the drilling tool is in the range of °.