JP2002370113A - Drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill capable of stabilizing a machining condition and improving the machining accuracy and efficiency. SOLUTION: An outer peripheral part of a drill body 1 is provided with rough cutting edges 10, 20 having point angles of 180 deg. or more and axially arranged in steps. The outer peripheral part of the drill body 1 is provided with finishing edges 30 positioned on rear parts of the rough cutting edges 10. The finishing edges 30 are made of a diamond sintered body or a boron nitride sintered body. The outer peripheral part of the drill body 1 is provided with guide pats 40 slidable on inner peripheral faces of bored holes. The point angles of the rough cutting edges 10, 20 are determined within a range of 180-200 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a drill.

[0002]

2. Description of the Related Art An example of a conventional drill will be described. FIG. 17 shows a side view of the drill, and FIG. 18 shows a front view thereof. The drill shown in FIG. 17 is a straight-edged drill,
A cutting portion 2 and a shank portion 4 are provided integrally with a drill body 1. As shown in FIG. 18, the cutting unit 2 includes two blades 3. The blade 3 has a cutting blade 5 and a pad 6 extending from the tip to the side edge. The tip angle 5θ (see FIG. 17) of the cutting blade 5 is 180 ° or less, for example, 120 °.
Is set to Groove 8 between both blades 3
(See FIG. 18) guides the cutting oil to the cutting portion and discharges the cut chips. Conventionally, in addition to the above, on the outer peripheral portion of the same drill as the above-mentioned drill (see FIGS. 17 and 18), it is located in a plane located behind the cutting edge and perpendicular to the axis of the drill. There is one provided with an outer cutting blade (for example, see Japanese Patent Application Laid-Open No. 58-149115). Further, the above drill (see FIGS. 17 and 18)
There is a drill provided with a cutting tool located on the outer peripheral portion of the same drill as that described above and located in a plane perpendicular to the axis of the drill and behind the cutting blade (for example, see Japanese Patent Application Laid-Open No. 9-150315). However, at the start of machining, any drill is still drilled with the same cutting edge as the above-mentioned drill (see FIGS. 17 and 18).

[0003]

In FIG. 19, which schematically shows the state of drilling, the workpiece W to be drilled is, for example, a material made of aluminum die-cast, and has a cast hole (called a pilot hole). ) H. The pilot hole H is a hole that penetrates the workpiece W, and drills, that is, cuts, a machining allowance P around the pilot hole H. In such a case, misalignment between the drill (drill body 1) and the prepared hole H of the workpiece W during processing is inevitable.

Therefore, at the start of machining, machining is performed by only one cutting edge 5 (see FIG. 17) (referred to as single-edged machining). For this reason, the “drill tipping” (see the two-dot chain line 1 in FIG. 19) such that the drill main body 1 is inclined is likely to occur, and the rotation of the drill (drill main body 1) becomes unstable and the vibration tends to increase. . As described above, when the machining state becomes unstable due to the inclination, vibration, or the like of the drill, the machining accuracy is deteriorated, and the machining efficiency is reduced.

[0005] In addition to the workpiece W, as shown in a blind hole in a sectional view of FIG.
In the case where the machining allowance P including a is drilled with a bottom, the same problem as described above occurs. Further, the same problem as described above also occurs when the surrounding machining allowance P including the bottom Ha of the bottomed pilot hole H1 is drilled in a penetrating manner.
Further, as shown in the sectional view of FIG.
The same problem as described above also occurs when the surrounding machining allowance P including the bottom Hb is drilled in a penetrating manner from the bottom Hb side.

An object of the present invention is to provide a drill capable of improving machining accuracy and machining efficiency by stabilizing a machining state.

[0007]

The above object can be attained by a drill having the features described in the claims. That is, according to the drill described in claim 1, the rough cutting edge provided on the outer peripheral portion of the drill body has a tip angle of 180 ° or more. Therefore,
Even if the workpiece is misaligned with respect to the prepared hole, single-edge processing at the start of processing can be prevented. Thereby, the processing state of the drill is stabilized, so that processing accuracy and processing efficiency can be improved.

Further, according to the drill described in the second aspect, the bottom of the bottomed prepared hole of the workpiece can be drilled by the bottom cutting edge having a tip angle of 180 ° or less.

According to the drill described in the third aspect, it is possible to drill the prepared hole of the workpiece in a well-balanced manner in the circumferential direction by three or more rough cutting blades arranged at substantially equal intervals in the circumferential direction. it can.

[0010] According to the drill described in claim 4, the inner peripheral surface of the machined hole of the workpiece cut by the rough cutting blade can be finished with high precision by the finishing blade.

According to the drill of the fifth aspect, since the finishing blade is formed of a diamond sintered body or a boron nitride sintered body, the properties of the inner peripheral surface of the machined hole can be improved. At the same time, the life of the finishing blade can be improved.

According to the drill described in claim 6, when drilling, the guide pad of the drill body slides against the inner peripheral surface of the drilled hole, so that the inner peripheral surface of the drilled hole is burnished. At the same time, the drill body is subjected to a self-holding action, that is, a self-bushing action, so that its axis is held at a fixed position. For this reason, the processing state of the drill can be further stabilized.

According to the drill of the present invention, it is possible to obtain a drill excellent in machining performance such as an allowance for enlargement of a machining hole, roughness, and roundness.

[0014]

[Embodiment 1] Embodiment 1 of the present invention will be described. In the first embodiment, the shape of the tip of the drill in the above-described conventional technique is changed, so that the changed portion will be described in detail, and the same portions will be denoted by the same reference numerals, without redundant description. FIG. 1 is a front view of the tip of the drill, FIG. 2 is a side view of FIG.
1 is a side view as viewed in a direction III in FIG. 1, and FIG. 4 is a side view as viewed in a direction IV in FIG.

In the cutting portion 2 of the drill body 1, the outer peripheral portion of each blade portion 3 has its rotation direction (see arrow Y in FIG. 1).
The first rough cutting blade 10 and the finishing blade 3
0 and a second rough cutting edge 20 are formed respectively. Further, the first rough cutting edge 10 and the second rough cutting edge 20 are formed at the same position in the axial direction of the drill main body 1, and the finishing blade 30 is arranged in the axial direction of the drill main body 1 with respect to the two rough cutting edges 10 and 20. It is formed shifted by a predetermined amount backward. The drill body 1 is made of, for example, a cemented carbide.

As shown in FIG. 4, the first rough cutting blade 10
Has a rake face 10a formed on one plane including the axis L of the drill body 1, and a flank face 10b formed with a clearance angle 10θA of, for example, 8 °. Further, the tip angle 10θ (see FIG. 2) of the first rough cutting blade 10 is formed to be 180 ° or more. The outer dimensions of the first rough cutting blade 10 are formed smaller than the outer dimensions of the guide pad 40 (described later) on the outer peripheral portion.

As shown in FIG. 2, the second rough cutting edge 20
Has a rake face 20a formed on one plane including the axis L of the drill body 1 and a flank face 20b formed with a clearance angle 20θA of, for example, 8 °. Further, the tip angle 20θ (see FIG. 4) of the second rough cutting blade 20 is formed to be 180 ° or more. Also, the tip angle 2 of the second rough cutting blade 20
If 0θ is 180 ° + α2 and the tip angle 10θ of the first rough cutting edge 10 (see FIG. 2) is 180 ° + α1, α2 and α1 are set to have a relationship of α2 ≦ α1. In addition,
The second rough cutting blade 20 and the first rough cutting blade 10 are formed at the same position in the axial direction. In addition, two second rough cutting blades 20 and first rough cutting blades 10 are formed two by two in total, and the four rough cutting blades are arranged at substantially equal intervals in the circumferential direction.

As shown in FIG. 3, the finishing blade 30 is located behind the two rough cutting blades 10 and 20 at the axial end of the drill body 1 and has a rake face 30a, for example, a 10 ° angle 30θ.
It has a cutting edge made of A. The outer dimensions of the finishing blade 30 are formed larger than the outer dimensions of the rough cutting blades 10 and 20. The finishing blade 30 is formed of a diamond sintered body or a boron nitride sintered body. The finishing blade 3
0 may be formed integrally with the blade portion 3 or may be formed separately and attached to the blade portion 3 by fixing means such as brazing. Incidentally, when the workpiece is an aluminum material, the finishing blade 30 may be formed of a sintered diamond. When the workpiece is a cast iron material or the like having a high hardness, the finishing blade 30 may be formed of a boron nitride sintered body.

As shown in FIG. 1, the first rough cutting edge 10 and the second rough cutting edge 2
A total of six guide pads 40 continuous with the finishing blade 30 and the finishing blade 30, respectively, are formed. Each guide pad 40
Is formed so as to be slidable on the inner peripheral surface of a drilled hole (called a processing hole) of the workpiece.

A case in which a hole is drilled in a workpiece by the above-described drill will be described. In FIG. 5, which schematically shows the processing state of the drill, at the start of processing, the prepared hole H
Irrespective of the presence or absence of misalignment of the drill (drill body 1) with respect to, the well-balanced cutting from the circumferential direction by the first rough cutting blade 10 and the second rough cutting blade 20 (see FIG.
The drill (drill body 1) is positioned at a predetermined position on the workpiece W. At this time, the first rough cutting edge 10 of the drill body 1 has a tip angle 10θ of 180 ° or more (see FIG. 2), and the second rough cutting edge 20 has a tip angle 20 of 180 ° or more.
θ (see FIG. 4). Thereby, single-edge processing can be prevented, and the processing state of the drill is stabilized.

With the progress of the drilling in the stable machining state, the prepared hole H, ie, the machined hole H2 (see FIG. 5), of the workpiece W cut by the two rough cutting blades 10, 20 (see FIG. 1). ) Is cut to the target diameter by the finishing blade 30 (see FIG. 1).

Also, a total of six guide pads 40 (see FIG. 1) are in sliding contact with the inner peripheral surface of the processing hole H2 (see FIG. 5) of the workpiece W. Thus, the inner peripheral surface of the processing hole H2 is subjected to a burnishing process (a so-called polishing process). At the same time, the drill body 1 is subjected to a self-holding operation, that is, a so-called self-bushing operation, so that its axis (axis L) is held at a fixed position, so that the processing state of the drill is stabilized.
Thereafter, the drill may be advanced to a predetermined position.

The lubrication and cooling effects can be obtained by supplying an oil such as cutting oil to the cutting portion through the groove 8 (see FIG. 1) of the drill body 1.

The performances that have been found to be effective in a comparison test between the above-described drill and a conventional drill (see FIGS. 17 and 18) are listed below. FIG. 6 shows a characteristic diagram of the roundness of the machining hole entrance. In FIG. 6, the horizontal axis indicates the depth (mm) from the entrance of the processing hole H2 (see FIG. 5), and the vertical axis indicates the roundness (μm) of the processing hole entrance. The characteristic line L1 is a measurement result of the roundness of the hole drilled by the drill of the present embodiment, and the characteristic line L2 is the roundness of the hole drilled by the conventional drill (see FIGS. 17 and 18). It is a measurement result of the degree.

As is clear from FIG. 6, according to the drill of the present embodiment, it is recognized that the accuracy of the roundness at the entrance of the machined hole is approximately twice as high as that of the conventional drill. This is considered to be a result of the first rough cutting blade 10 and the second rough cutting blade 20.

FIG. 7 is a comparison diagram of the positional accuracy of a machined hole. In FIG. 7, the horizontal axis and the vertical axis show the positional deviation amount (μm) of the processing hole with the processing origin being “0” (zero). A point L3 indicates a center position (referred to as a prepared hole position) of the prepared hole H (see FIG. 5). And ◆
The mark indicates the measurement result of the positional deviation amount of the machined hole by the drill according to the present embodiment, and the mark ▲ indicates the conventional drill (FIG.
8) is a measurement result of the positional deviation amount of the machined hole according to FIG.

As is apparent from FIG. 7, according to the drill of the present embodiment, the accuracy of the positional deviation of the machined hole is improved by about 5 times compared with the conventional drill. This is considered to be a result of the first rough cutting blade 10 and the second rough cutting blade 20 and the six guide pads 40.

FIG. 8 is a comparison diagram showing the relationship between the processing accuracy and the processing efficiency. In FIG. 8, the horizontal axis indicates the processing accuracy, and the vertical axis indicates the processing efficiency. The mark ● represents the measurement result of the displacement amount by the drill of the present embodiment, and the mark ○ represents the measurement result of the displacement amount by the conventional drill (see FIGS. 17 and 18).

As is apparent from FIG. 8, according to the drill of the present embodiment, even if the machining efficiency is increased, the machining accuracy is improved without deteriorating as compared with the conventional drill. This is considered to be a result of the first rough cutting blade 10 and the second rough cutting blade 20, the six-point guide pad 40, and the finishing blade 30.

According to the drill described above, the rough cutting blades 10 and 20 (see FIG. 1) provided on the outer peripheral portion of the drill body 1
The tip angle 10θ of 80 ° or more (see FIG. 2), 20θ (FIG. 4)
Reference). Therefore, even if the workpiece W (see FIG. 5) is misaligned with respect to the prepared hole H, single-edge processing at the start of processing can be prevented. This allows
Since the processing state of the drill is stable, processing accuracy and processing efficiency can be improved.

The rough cutting blades 1 are arranged at substantially equal intervals in the axial direction.
By using 0 and 20 (see FIG. 2), the prepared hole H of the workpiece W (see FIG. 5) can be drilled with good balance from the circumferential direction.

Further, the inner peripheral surface of the machined hole H2 (see FIG. 5) of the workpiece W cut by the rough cutting blades 10 and 20 (see FIG. 1) is precisely formed by the finishing blade 30 (see FIG. 1). Can be finished.

Further, since the finishing blade 30 is made of a diamond sintered body or a boron nitride sintered body (see FIG. 1), the properties of the inner peripheral surface of the processing hole H2 of the workpiece W (see FIG. 5). Can be improved, and the life of the finishing blade 30 can be improved.

In drilling, the guide pad 40 of the drill body 1 slides on the inner peripheral surface of the drilled hole H2 (see FIG. 5), so that the inner peripheral surface of the drilled hole H2 is burnished. At the same time, the drill body 1 is subjected to a self-holding action, a so-called self-bushing action,
Its axis is held in place. For this reason, the processing state of the drill can be further stabilized.

The tip angle 1 of the rough cutting blade 10 (or 20)
0θ (see FIG. 2) (or 20θ (see FIG. 4)) is 18
By setting the angle within the range of 0 to 200 °, it is possible to obtain a drill excellent in machining performance such as an allowance for enlargement, roughness, and roundness of the machined hole H2 (see FIG. 5). Specifically, FIG. 9 shows the tip angle 10θ of the rough cutting blade 10 (or 20).
(Or 20θ) and the characteristic diagram of the relationship between the machining allowance of the processing hole H2 (see FIG. 5). In FIG. 9, the horizontal axis represents the rough cutting edge angle (°), and the vertical axis represents the enlargement allowance (μ) of the machining hole.
m). The enlargement margin is a difference between the diameter of the drilled hole and the diameter of the finishing blade 30.

FIG. 10 is a characteristic diagram showing the relationship between the tip angle 10θ (or 20θ) of the rough cutting blade 10 (or 20) and the roughness of the machined hole. In FIG. 10, the horizontal axis indicates the tip angle (°) of the rough cutting blade, and the vertical axis indicates the roughness Rz of the machined hole. The roughness Rz is the roughness of the inner peripheral surface of a drilled hole.

FIG. 11 is a characteristic diagram showing the relationship between the tip angle 10θ (or 20θ) of the rough cutting blade 10 (or 20) and the roundness of the machined hole. In FIG. 11, the horizontal axis indicates the tip angle (°) of the rough cutting blade, and the vertical axis indicates the roundness (μ) of the machined hole.
m). In addition, "conventional" in the cutting edge angle in FIGS. 9 to 11 indicates a drill having a cutting edge angle of, for example, 120 °.

As is clear from FIGS. 9 to 11, the tip angle 10θ of the first rough cutting blade 10 (see FIG. 2) and / or the second
The tip angle 20θ of the rough cutting blade 20 of FIG.
By setting the angle within the range of 00 °, it is possible to obtain a drill excellent in machining performance such as an allowance for enlargement of a machining hole, roughness, and roundness.

Further, according to the drill of the first embodiment, a case is shown in which the machining allowance P including the bottom Hb in the bottomed prepared hole H1 of the workpiece W as shown in FIG. In this case, the same operation and effect as described above can be obtained.

[Second Embodiment] A second embodiment of the present invention will be described. In the second embodiment, a part of the first embodiment is changed, so that the changed part will be described in detail, and redundant description will be omitted. FIG. 12 is a front view of the tip of the drill, FIG. 13 is a side view taken along the line XIII in FIG. 12, and FIG.
12 is a side view as viewed from XIV in FIG. 12, and FIG. 15 is a side view as viewed from XV in FIG.

The drill according to the present embodiment has a bottom cutting edge 50 on the inner periphery of the rough cutting edges 10 and 20 of the drill according to the first embodiment.
Is provided. The bottom cutting edge 50 has a tip angle 50θ of 180 ° or less (see FIG. 13), and has both coarse cutting edges 10 and 20.
It protrudes further forward (upward in FIGS. 13 to 15). The bottom cutting edge 50 has substantially the same configuration as the cutting edge 5 (see FIG. 18) in a conventional drill.

According to the drill of the second embodiment, 180 °
Bottom cutting blade 50 having the following tip angle 50θ (see FIG. 13)
Thereby, for example, the bottom portion Ha of the bottomed prepared hole H1 of the workpiece W as shown in the sectional view of FIG. 16 can be cut, that is, drilled.

The present invention is not limited to the above-described embodiment, but can be modified without departing from the scope of the present invention. For example, in the above embodiment, only one of the rough cutting blades 10 and 20 may be used, or three or more rough cutting blades may be provided. Further, the finishing blade 30 and / or the guide pad 40 can be omitted. The number of the blades 3 is not limited to two, but may be three or more.

[0044]

As described above, according to the drill of the present invention, since the processing state is stable, the processing accuracy and the processing efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a front view showing a drill according to a first embodiment of the present invention.

FIG. 2 is a side view taken along the line II in FIG.

FIG. 3 is a side view as viewed in a direction III in FIG. 1;

FIG. 4 is a side view as viewed from IV in FIG. 1;

FIG. 5 is a schematic diagram showing a drill processing state.

FIG. 6 is a characteristic diagram showing the roundness of a machining hole entrance.

FIG. 7 is a comparative diagram showing positional accuracy of a machined hole.

FIG. 8 is a comparative diagram showing a relationship between processing accuracy and processing efficiency.

FIG. 9 is a characteristic diagram showing a relationship between a tip angle of a rough cutting blade and an allowance for enlarging a processing hole.

FIG. 10 is a characteristic diagram showing a relationship between a tip angle of a rough cutting blade and roughness of a machined hole.

FIG. 11 is a characteristic diagram showing a relationship between a tip angle of a rough cutting blade and a roundness of a machined hole.

FIG. 12 is a front view showing a drill according to a second embodiment of the present invention.

FIG. 13 is a side view as viewed in the direction XIII of FIG. 12;

FIG. 14 is a side view as viewed from XIV in FIG. 12;

FIG. 15 is a side view as viewed in the direction XV of FIG. 12;

FIG. 16 is a sectional view showing a pilot hole of a workpiece.

FIG. 17 is a side view showing a conventional drill.

FIG. 18 is also a front view.

FIG. 19 is a schematic view showing a drill processing state.

FIG. 20 is a cross-sectional view showing another example of a prepared hole of a workpiece.

FIG. 21 is a cross-sectional view showing another example of a prepared hole of a workpiece.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drill main body 10 1st rough cutting blade (rough cutting blade) 10θ Tip angle 20 2nd rough cutting blade (rough cutting blade) 20θ Tip angle 30 Finishing blade 40 Guide pad 50 Bottom cutting blade 50θ Tip angle

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 29, 2001 (2001.6.2
9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

As shown in FIG. 4, the first rough cutting blade 10
Has a rake face 10a formed on one plane including the axis L of the drill body 1, and a flank face 10b formed with a clearance angle 10θA of, for example, 8 °. Further, the tip angle 10θ (see FIG. 2) of the first rough cutting blade 10 is formed to be 180 ° or more. The outer diameter of the first rough cutting blade 10 is formed smaller than the outer diameter of a guide pad 40 (described later) on the outer peripheral portion.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

As shown in FIG. 3, the finishing blade 30 is located behind the two rough cutting blades 10 and 20 at the axial end of the drill body 1 and has a rake face 30a, for example, a 10 ° angle 30θ.
It has a cutting edge made of A. Outer diameter of finishing blade 30
The dimension is formed larger than the outer diameter dimension of both coarse cutting blades 10 and 20. The finishing blade 30 is formed of a diamond sintered body or a boron nitride sintered body. The finishing blade 3
0 may be formed integrally with the blade portion 3 or may be formed separately and attached to the blade portion 3 by fixing means such as brazing. Incidentally, when the workpiece is an aluminum material, the finishing blade 30 may be formed of a sintered diamond. When the workpiece is a cast iron material or the like having a high hardness, the finishing blade 30 may be formed of a boron nitride sintered body.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

FIG. 8 is a comparison diagram showing the relationship between the processing accuracy and the processing efficiency. In FIG. 8, the horizontal axis indicates the processing accuracy, and the vertical axis indicates the processing efficiency. Then, ● mark is a drill of this embodiment, ○ mark is a conventional drill (see FIGS. 17 and 18).

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

As is apparent from FIG. 8, according to the drill of the present embodiment, even if the machining efficiency is increased, the machining accuracy is improved without deteriorating as compared with the conventional drill. This is considered to be a result of the first rough cutting blade 10 and the second rough cutting blade 20, the six-point guide pad 40, and the finishing blade 30. In other words, conventional drills improve machining accuracy.
In order to achieve this, the processing efficiency must be reduced,
The drill according to the present embodiment is clear from FIGS.
Thus, the processing accuracy is greatly improved. From this, FIG.
According to the drill of the present embodiment,
However, it shows that the processing accuracy is improved.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction contents]

According to the drill of the second embodiment, 180 °
Bottom cutting blade 50 having the following tip angle 50θ (see FIG. 13)
Thereby, for example, the bottom portion Ha of the bottomed prepared hole H1 of the workpiece W as shown in the sectional view of FIG. 16 can be cut, that is, drilled. In addition, outside the bottom cutting blade 50
The diameter is set so that the inner peripheral surface of the prepared hole H1 is not machined.
ing.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsuya Kitamura 1-1-1 Kyowa-cho, Obu-shi, Aichi Prefecture Within Ai San Industry Co., Ltd. (72) Inventor Yuji Koyama 1-1-1 Kyowa-cho, Obu-shi, Aichi Prefecture 1 Ai San Industry Co., Ltd. (72) Inventor Tsugio Yoshikawa 6-31 Takaracho, Kariya-shi, Aichi Japan Carbide Co., Ltd. (72) Inventor Akimitsu Hirano 6-31 Takaracho, Kariya-shi, Aichi Japan Nippon Carbide Stock F term in the company (reference) 3C037 BB01 CC08 DD03

Claims (7)

[Claims] 1. A drill characterized in that a rough cutting edge having a tip angle of 180 ° or more is provided on an outer peripheral portion of the drill body. 2. The drill according to claim 1, wherein a bottom cutting edge having a tip angle of 180 ° or less and projecting beyond the rough cutting edge is provided on an inner peripheral portion of the rough cutting edge. Drill characterized by being done. 3. The drill according to claim 1, wherein three or more rough cutting edges arranged at substantially equal intervals in a circumferential direction are provided on an outer peripheral portion of the drill body. And drill. 4. The drill according to claim 1, wherein a finishing blade located behind the rough cutting edge is provided on an outer peripheral portion of the drill body. . 5. The drill according to claim 4, wherein the finishing blade is formed of a diamond sintered body or a boron nitride sintered body. 6. The drill according to claim 1, wherein a guide pad is provided on an outer peripheral portion of the drill body, the guide pad being slidable on an inner peripheral surface of the drilled hole. A drill characterized in that: 7. The drill according to claim 1, wherein a tip angle of the rough cutting edge is set to an angle in a range of 180 to 200 °. Drill.