JP2010094766A - Boring tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boring tool for keeping high processing accuracy, smoothly carrying out cutting without increasing cost, and easily having a breaker function. <P>SOLUTION: In a reamer 1 provided with cutting edge tips 25, 28 having diamond sintered compact, first and second cutting edge parts 23, 26 are composed by first and second counterbore parts 24, 27 recessing in a wall face 21 facing forward in a tool rotating direction T of a cutting chip discharge groove 20 and opening outward in a tool diametrical direction, and the first and second cutting edge tips 25, 28. The first and second counterbore parts 24, 27 are composed by first and second bottom faces in which the first and second cutting edge parts 23, 26 are seated with the thickness direction facing the tool rotating direction T and first and second breaker wall faces 24B, 27B standing from the bottom faces to be thicker than the thickness of the first and second cutting edge tips 25, 28 and intersecting with the wall face 21 facing forward in the tool rotating direction T of the cutting chip discharge groove 20. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a hole machining tool that is inserted into a prepared hole formed in advance in a workpiece and used to cut an inner wall surface of the prepared hole.

As one of these types of drilling tools, a reamer in which a cutting edge tip made of a hard material such as a diamond sintered body is attached to the tip of a long cylindrical tool body rotated about an axis by brazing or the like. It has been known.
Such a reamer is rotated around an axis and fed in the axial direction, and is inserted into a prepared hole formed in advance in the work material and cut with a cutting blade so that the prepared hole has a predetermined inner diameter. It processes (for example, refer patent document 1).
JP-A-6-170640

  By the way, in such cutting with a reamer, chips of the material to be cut are generated. In particular, at the time of high-speed cutting, the chips having increased ductility due to thermal softening become long and continuous, so that the chips However, there is a problem that the cutting tool is entangled with the tool main body in an unexpected direction and hinders the cutting process, or the finished surface of the workpiece is damaged, and the smooth cutting process cannot be performed.

In order to prevent this, a method of providing a step as a chip breaker on the cutting edge chip itself and forcibly bending and dividing the generated chips can be considered.
However, there has been a problem that it is difficult to form a chip breaker by processing a high hardness diamond sintered body. In addition, if a step is provided in the cutting edge tip to provide a breaker function, the structure of the cutting edge tip becomes more complicated than necessary, so it is processed compared to a reamer with a cutting edge tip that does not have a step. The accuracy of the surface may be lowered, which is not preferable for a reamer used in finishing processing that requires high accuracy. Furthermore, since the breaker performance depends on the shape of the chip breaker, it is not easy to determine an appropriate shape, and a problem arises that if a chip breaker is provided for each cutting edge chip, the manufacturing cost increases. .

  The present invention has been made in view of such a problem, and in a drilling tool having a cutting edge tip provided with a cutting edge made of a diamond sintered body, a breaker function can be easily provided. An object of the present invention is to provide a drilling tool capable of smoothly performing a cutting process while maintaining high accuracy and without increasing the cost.

In order to solve the above problems, the present invention proposes the following means.
That is, the drilling tool according to the present invention is provided with a cutting edge portion in a tool body that is rotated around an axis, and is inserted into a pilot hole formed in advance in a workpiece to cut the inner wall surface of the pilot hole. In the hole machining tool for forming a machining hole, a chip discharge groove that opens to the front end surface of the tool main body and extends to the rear end side is formed in the tip outer peripheral portion of the tool main body, and the cutting edge portion is A counterbore part recessed from the wall of the chip discharge groove facing forward in the tool rotation direction and opening outward in the tool radial direction, and a cutout attached to the counterbore part and projecting outward in the tool radial direction in a substantially flat plate shape. A cutting edge tip provided with a blade, wherein the cutting edge of the cutting edge tip is made of a diamond sintered body, and the counterbore portion has the cutting edge tip with its thickness direction oriented in the tool rotation direction. The bottom surface to be seated and the thickness of the cutting edge tip from the bottom surface Characterized in that it includes a breaker wall face intersecting a wall surface facing the tool rotating direction forward of hear rising the chip discharge groove.

According to the hole drilling tool having such a feature, the breaker wall surface is provided between the cutting edge tip and the wall surface facing the front of the tool discharge direction of the chip discharge groove. The generated chips are forcibly bent by abutting against the breaker wall surface. As a result, the chips are divided into small pieces, so that the chips do not hinder cutting and smooth cutting can be performed.
In addition, by providing a breaker function to the breaker wall surface formed on the tool body itself, it is not necessary to form a breaker groove or the like on the cutting edge chip itself made of a diamond sintered body, thereby reducing the processing cost. This makes it possible to maintain high cutting accuracy.
Furthermore, since the cutting edge of the cutting edge tip is composed of a diamond sintered body, the life of the cutting edge can be greatly extended.

Further, according to the drilling tool according to the present invention, the tool body has a multi-stage columnar shape in which the tip side thereof is successively reduced in diameter, and a first cutting edge portion provided at the tip of the tool body, And a second cutting edge provided on the rear end side of the tool main body with respect to the first cutting edge and having a larger diameter than the first cutting edge.
Thereby, even if the object to be processed is a pilot hole having a multistage cylindrical surface, chips generated by the finishing process can be easily divided, so that a smooth cutting process can be performed.

Furthermore, in the hole drilling tool, the counterbore part of the first cutting edge part is open to the tip surface of the tool body, and the tool body tip side is attached to the cutting edge tip attached to the counterbore part. And a cutting edge that protrudes from the outer peripheral side of the tool body along the diameter direction of the tool body.
According to the hole drilling tool having such a feature, even if the bottom hole has a bottomed hole shape in which the lower hole does not penetrate, the entire bottom surface of the lower hole can be finished by the tip cutting edge.

  Further, in the drilling tool according to the present invention, a coolant supply hole is provided in the tool body along the axial direction, and communicates with the coolant supply hole on a wall surface facing the rear side in the tool rotation direction of the chip discharge groove. In addition, a coolant discharge hole that opens toward the counterbore portion is provided, and is cut out from a wall surface facing the tool rotation direction of the chip discharge groove toward the breaker wall surface on an extension line of the coolant discharge hole. A coolant supply groove is formed.

  According to the hole drilling tool having such a feature, the coolant discharged from the coolant discharge hole passes through the coolant supply groove and is guided to the breaker wall surface. Thereby, since a coolant can be directly applied to the chip | tip which contact | abuts to a breaker wall surface, it becomes possible to cut a chip | tip more effectively in combination with the breaker function by a breaker wall surface.

  According to the drilling tool according to the present invention, the breaker wall surface is provided between the cutting edge tip and the wall surface facing the front of the cutting direction of the chip discharge groove, thereby providing a cutting blade made of a diamond sintered body. It is possible to divide chips easily and reliably without providing a breaker groove or the like in the cutting edge chip itself. Therefore, a breaker function can be easily provided, and smooth cutting can be performed without increasing costs while maintaining high processing accuracy.

Hereinafter, a reamer, which is an embodiment of a drilling tool of the present invention, will be described in detail with reference to FIGS. 1 to 6.
1 is a perspective view of a reamer according to the present embodiment, FIG. 2 is a side view of the reamer according to the present embodiment, FIG. 3 is a view in the direction of arrow A in FIG. 2, and FIG. 4 is a front view of the reamer according to the present embodiment. 5 is an enlarged view of the main part of FIG. 2, and FIG. 6 is an enlarged view of the main part of FIG.

As shown in FIGS. 1 to 3, the reamer 1 has a multi-stage cylindrical tool body 2 that is rotated in the tool rotation direction T around the axis O, and the tip side of the tool body 2 (FIGS. 2 and 3). The left side in FIG. 2 is a processing portion 3 for processing the workpiece, and the rear end side (right side in FIGS. 2 and 3) of the tool body 2 is a shank portion 4 having a substantially cylindrical shape.
At the rear end of the shank portion 4 is formed an attachment portion 5 for attachment to a main shaft of a machine tool (not shown).

  2 and 3, a pair of coolant supply holes that open to the rear end of the shank portion 4 and extend to the inside of the processing portion 3 with an interval parallel to the axis O are provided in the tool body 2. 6 and 6 are drilled, and when the mounting portion 5 is attached to the spindle of the machine tool, coolant is supplied from the machine tool side to the coolant supply holes 6 and 6.

  The processing portion 3 has a multi-stage cylindrical shape whose diameter gradually decreases as the tip side thereof approaches the tip of the tool body 2. Thereby, the outer peripheral surface of the processing part 3 includes a small diameter part 11 located at the forefront of the tool body 2, a medium diameter part 12 located on the rear end side of the tool body 2 with respect to the small diameter part 11, and the medium diameter. It is provided with a cylindrical surface centering on three axes O with a large-diameter portion 13 that is located on the rear end side of the tool body 2 relative to the portion 12 and extends to the shank portion 4, and between the small-diameter portion 11 and the medium-diameter portion 12. Between the middle diameter portion 12 and the large diameter portion 13, there are provided a first tapered surface 14 and a second tapered surface 15 that gradually increase in diameter toward the rear end side of the tool body 2.

  Further, on the outer peripheral surface of the processed portion 3, as shown in FIG. 4, in the cross section orthogonal to the axis O, there are two pieces of chip discharge grooves 20, 30 formed by cutting the processed portion 3 into a substantially L shape. It is provided so as to extend from the front end of the processed portion 3 toward the rear end side. These chip discharge grooves 20 and 30 are formed at positions that are substantially symmetric with respect to the axis O, and one chip discharge groove 20 is greatly cut out in a cross section perpendicular to the axis O rather than the other chip discharge groove 30. The shape is made. Each of the pair of coolant supply holes 6 and 6 is formed so as to pass between the chip discharge grooves 20 and 30 in the circumferential direction of the tool body 2.

  One of the chip discharge grooves 20 is formed in a fan shape having a substantially circular arc in cross section so that the wall surface 21 facing the tool rotation direction T and the wall surface 22 facing the tool rotation direction T are orthogonal to each other. A first counterbore part 24 and a second counterbore part 27 are formed so as to be recessed by one step from the wall surface 21 facing forward in the rotation direction T. However, the wall surfaces 21 and 22 are located slightly on the side of the tool rotation direction T from the plane parallel to the wall surfaces 21 and 22 and including the axis O, respectively.

As shown in detail in FIGS. 5 and 6, the first counterbore portion 24 is located at the tip of the tool body 2 and opens to the outer side in the tool radial direction and the tool tip side, and is parallel to the wall surface 21. A first bottom surface 24A (see FIG. 6) that is parallel to the wall surface 21 and retracts to the rear side in the tool rotation direction T from the plane including the axis O, and perpendicularly toward the front side in the tool rotation direction T from the first bottom surface 24A. The first breaker wall surface 24B that rises and is orthogonal to the wall surface 21 is formed, and the opening to the tool tip side is formed so as to slightly exceed the axis O on the inner side in the tool radial direction.
Further, the shape of the first counterbore portion 24 as viewed from the direction facing the wall surface 21 is a substantially rectangular shape whose longitudinal direction is the tool radial direction, but the inside of the four corners in the tool radial direction and after the tool The corner located on the end side is cut out so as to form a convex arc shape.

  The second counterbore part 27 extends in the tool radial direction over the first tapered surface 14, the intermediate diameter part 12, the second tapered surface 15, and the large diameter part 13, which are on the rear end side of the tool body 2 relative to the first counterbore part 24. A second bottom surface 27A that is formed so as to open to the outside and that is parallel to the wall surface 21 and retracts to the rear side in the tool rotation direction T from the plane that is parallel to the wall surface 21 and includes the axis O (see FIG. 6). And a second breaker wall surface 27B that rises perpendicularly from the second bottom surface 27A toward the front side in the tool rotation direction T and is orthogonal to the wall surface 21. The shape of the second counterbore part 27 as viewed from the direction facing the wall surface 21 is such that the contour line located on the outer side in the tool radial direction is the first tapered surface 14, the intermediate diameter portion 12, the second tapered surface 15, and the large diameter portion 13. The contour line located along the tool radial direction and connected to both ends of the contour line is formed in an arc shape that is convex toward the inner side in the tool radial direction.

  The first blade edge 25 and the second cutting edge chip 28 are attached to the first counterbore portion 24 and the second counterbore portion 27 by brazing, so that the first blade portion 23 and the second counterbore portion 28 are attached. The two cutting blade part 26 is comprised. In the present embodiment, the second cutting edge portion 26 has a larger diameter than the first cutting edge portion 23 at all.

The first blade tip 25 has a base portion 25A that is formed in a flat plate shape and is made of a hard material such as cemented carbide. One of the surfaces facing the thickness direction of the base portion 25A is the first counterbore portion 24. The seating surface 25B is seated on the first bottom surface 24A. Further, a sinter surface 25D is formed on the other surface of the base portion 25A by integrally sintering a diamond sintered body 25C over the entire surface, and outer peripheral cutting edges orthogonal to each other at the outer edge portion of the rake surface 25D. 25E and a tip cutting edge 25F are formed.
That is, the first blade tip 25 is seated on the first bottom surface 24A of the first counterbore portion 24 with the thickness direction of the base portion 25A facing the tool rotation direction T. In this state, the outer peripheral cutting edge 25E is It protrudes toward the outer side in the tool radial direction along the outer peripheral surface of the small diameter portion 11, and the tip cutting edge 25F is configured to protrude toward the tool tip side. In the present embodiment, the tip cutting edge 25F extends in a straight line from the outer peripheral side of the small-diameter portion 11 along the diameter direction of the tool body 2 over the axis O so as to slightly exceed the axis O. It is considered a blade.

The second cutting edge tip 28 has a base portion 28A formed of a hard material such as a cemented carbide, like the first blade tip 25, and has a surface facing the thickness direction of the base portion 28A. Is a seating surface 28 </ b> B that can be seated on the second bottom surface 27 </ b> A of the second counterbore portion 27.
On the other surface of the base portion 28A, a diamond sintered body 28C is integrally sintered over the entire surface to form a rake face 28D, and an outer peripheral cutting edge 28E is formed on the outer edge of the rake face 28D. Has been.
That is, the second cutting edge tip 28 is seated on the second bottom surface 27A of the second counterbore 27 with the thickness direction of the base portion 28A in the tool rotation direction T, and the outer peripheral cutting edge 28E is in this state. The first taper surface 14, the medium diameter portion 12, the second taper surface 15, and the large diameter portion 13 are configured to protrude outward in the tool radial direction along the outer peripheral surface. Thereby, the outer peripheral cutting edge 28E is also made into the multistage shape according to the shape of the process part 3. FIG.

  In the present embodiment, both the first breaker wall surface 24B and the second breaker wall surface 27B rise toward the front in the tool rotation direction, which is larger than the thicknesses of the first blade tip 25 and the second cutting blade tip 28. ing. As a result, as shown in FIG. 1, the first breaker wall surface as a step surface between the first blade tip 25 and the second cutting blade tip 28 and the wall surface 21 facing the front in the tool rotation direction T of the chip discharge groove 20. 24B and the second breaker wall surface 27B are exposed.

Furthermore, in this embodiment, the tool rotation direction T of the one chip discharge groove 20 out of the pair of coolant supply holes 6 and 6 is provided on the wall surface facing the tool rotation direction T of the one chip discharge groove 20 in the present embodiment. A total of two coolant discharge holes 7A extending from one coolant supply hole 6 located on the side toward the rear in the tool rotation direction T and inclined toward the first blade part 23 and the second cutting edge part 26, respectively. , 7B are open. A total of 2 cut out from the wall surface 21 facing the front of the tool rotation direction T of the chip discharge groove 20 toward the first breaker wall surface 24B and the second breaker wall surface 27B on the extended lines of the coolant discharge holes 7A and 7B, respectively. Two coolant supply grooves 29A and 29B are formed.
As a result, the coolant supplied to one coolant supply hole 6 is discharged from the coolant discharge holes 7A and 7B, and directly contacts the coolant supply grooves 29A and 29B on the extension line, thereby directly connecting the first blade portion 23. The coolant is supplied into the second cutting edge portion 26.
The coolant discharge hole 7B is extended toward the outer peripheral cutting edge 28E, while the coolant discharge hole 7A is extended toward the tip cutting edge 25F.

On the other hand, in the other chip discharge groove 30, the wall surface (not shown) facing forward in the tool rotation direction T is a surface parallel to the wall surface 21 including the axis O, and is the first in the circumferential direction of the tool body 2. Attachment seats (not shown) are respectively formed at locations corresponding to the cutting edge portion 23 and the second cutting edge portion 26, and the third cutting edge tip 31 and the fourth cutting edge tip 32 are attached to these attachment seats. Thus, a third cutting edge portion 33 and a fourth cutting edge portion 34 are formed. However, the surfaces of the third and fourth cutting edge portions 33 and 34 facing the tool rotation direction T are flush with the wall surface of the other chip discharge groove 30 facing the tool rotation direction T.
The third cutting edge portion 33 corresponds to the first cutting edge portion 23, and the outer diameter of the outer peripheral cutting edge 31 </ b> A of the third cutting edge tip 31 is outside the outer peripheral cutting edge 25 </ b> E of the first cutting edge tip 25. A straight tip cutting edge 31B extending in the diameter direction of the tool body 2 is formed at the tip of the tip body 25 at the same position as the tip cutting edge 25F in the axis O direction. However, unlike the tip cutting edge 25F of the first blade portion 23, the tip cutting edge 31B does not extend to the axis O but is formed only on the outer peripheral side away from the axis O.
Further, the fourth cutting edge portion 34 corresponds to the second cutting edge portion 26, and the outer peripheral cutting edge 32 </ b> A of the fourth cutting edge tip 32 has the same diameter as the outer peripheral cutting edge 28 </ b> E of the second cutting edge tip 28. And shape.
The third cutting edge tip 31 and the fourth cutting edge tip 32 are also formed by brazing a base portion of a layered sintered body obtained by integrally sintering a diamond sintered body to a base portion made of a cemented carbide. The cutting blades 31A, 31B, and 32A are made of a diamond sintered body.

  Further, the outer peripheral surface of the diamond sintered body connected to the outer peripheral cutting edges 25E, 28E, 31A, 32A is a cylindrical surface margin centered on the axis O.

The reamer 1 configured as described above is mounted on a machine tool, rotated in the tool rotation direction T around an axis O, and has a bottomed hole-like prepared hole having a multi-stage cylindrical surface formed in advance on a workpiece. The processing part 3 is inserted from the tip side. At this time, the inner wall surface of the prepared hole is cut by the tip cutting edges 25F and 31B in the reaming direction and by the outer cutting edges 25E, 28E, 31A, and 32A in the outer peripheral direction, and the multi-stage shape at the tip of the processing unit 3 A finished hole with a predetermined inner diameter according to
At this time, in the reamer 1 of the present embodiment, the tip cutting edge 25F of the first blade tip 25 extends from the outer periphery side of the tool body 2 along the axis O along the diameter direction of the tool body 2, and therefore has a bottomed hole. The entire bottom surface of the shaped prepared hole can be finished with the tip cutting edge 25F.
Further, chips generated during the cutting process are sent from the front end of the processed portion 3 to the rear end side and discharged by the chip discharge grooves 20 and 30.

In this cutting process, coolant is supplied from the machine tool to one coolant supply hole 6, and the coolant passes through the coolant discharge holes 7 </ b> A and 7 </ b> B opened in the chip discharge groove, so that the coolant is completely removed from the first blade portion 23 and the second cutting edge. It is supplied toward the blade part 26. At this time, the tool rotation direction of the other chip discharge groove 30 from the other coolant supply hole 6 out of the pair of coolant supply holes 6 and 6 also to the third cutting edge portion 33 and the fourth cutting edge portion 34. The coolant is supplied from a coolant discharge hole (not shown) formed on the wall surface facing T rear.
As a result, it is possible to improve the lubrication of the cutting process of each of the cutting edge portions 23, 26, 33, and 34 to prevent wear, to prolong the life of each of the cutting edge chips 25, 28, 31, and 32, and to reduce the frictional heat. It can cool and can avoid the seizing of the cut part of a processing hole.

  Here, at the time of high-speed cutting with such a reamer 1, since the chips having increased ductility due to thermal softening are long and continuous without being broken, the chips are directed to an unexpected direction in the tool body. 2 may interfere with the cutting process or damage the finished surface of the workpiece.

  In this regard, in the reamer 1 of the present embodiment, the first and second breaker wall surfaces 24B are provided between the first and second cutting edge tips 23 and 26 and the wall surface 21 facing the front in the tool rotation direction T of the chip discharge groove 20. 28B are provided, the chips generated by the cutting of the cutting edge chips 25, 28 are forcibly bent by coming into contact with the first and second breaker wall surfaces 24B, 28B, respectively. As a result, the chips are divided into small pieces, so that the chips do not hinder cutting and smooth cutting can be performed.

  Moreover, it is necessary to form breaker grooves or the like in the first and second cutting edge tips 25 and 28 themselves by providing the first and second breaker wall surfaces 24B and 28B formed on the tool body 2 itself with a breaker function. Therefore, even if the cutting edges 25E, 25F, and 28E of the first and second cutting edge tips 25 and 28 are formed on the diamond sintered body, it is possible to reduce the processing cost and maintain high cutting accuracy. It becomes.

Furthermore, since the second cutting edge portion 26 has a larger diameter than the first cutting edge portion 23, even in a prepared hole having a multi-stage cylindrical surface as a processing target, chips generated by finishing are easily removed. It becomes possible to cut and perform smooth cutting.
Further, since each of the cutting edges 25E, 25F, 28E, 31A, 31B, and 32B of each of the cutting edge tips 25, 28, 31, and 32 is composed of a diamond sintered body, the life can be greatly extended. it can.

And in the reamer 1 of this embodiment, it cuts out toward the 1st and 2nd breaker wall surface 24B, 27B from the wall surface 21 which faces the tool rotation direction T of the chip discharge groove 20 on the extended line of coolant discharge hole 7A, 7B. Since the coolant supply grooves 29A and 29B are formed, the coolant discharged from the coolant discharge holes 7A and 7B passes through the coolant supply grooves 29A and 29B and reaches the first and second breaker wall surfaces 24B and 27B, respectively. Led.
Thereby, since a coolant can be directly applied to the chips contacting the first and second breaker wall surfaces 24B and 27B, the chips can be more effectively divided in combination with the breaker function by the breaker wall surfaces 24B and 27B. Is possible.

As mentioned above, although the reamer which is embodiment of this invention was demonstrated, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, in the present embodiment, the tip cutting edge 25F of the first blade tip 25 extends from the outer peripheral side of the tool body 2 along the axis O along the diameter direction of the tool body 2, and has a bottomed bottom hole. A first counterbore portion 24 is formed so as to form a breaker wall surface 24B as a stepped surface only in the chip discharge groove 20 provided with the center blade, while having a so-called center blade capable of cutting the bottom surface. However, the present invention is not limited to this, and the tip cutting edge is not extended as described above, but is formed only on the outer peripheral side away from the axis O, and finished into a through hole-shaped pilot hole. May be applied. In this case, it is preferable that the two chip discharge grooves are formed symmetrically with respect to the axis O, and a counterbore portion that forms the above-described stepped surface is formed on both of them.
However, the chip discharge groove is not limited to two, and may be one or three or more. Further, the number of coolant discharge holes is not limited to one for each cutting edge, and for example, a plurality of coolant discharge holes may be provided for a cutting edge provided in a counterbore having a large bottom surface.

  Furthermore, in this embodiment, although what processed the process part 3 of the tool main body 2 made multistage column shape was demonstrated, it is not limited to this, You may make a simple column shape.

It is a perspective view of the reamer concerning this embodiment. It is a side view of the reamer concerning this embodiment. It is an A direction arrow directional view of FIG. It is a front view of the reamer concerning this embodiment. FIG. 3 is an enlarged view of a main part of FIG. 2. It is a principal part enlarged view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reamer 2 Tool body 6 Coolant supply hole 7A Coolant discharge hole 7B Coolant discharge hole 20 Chip discharge groove 21 Wall surface 22 facing forward in the tool rotation direction Wall surface 23 facing backward in the tool rotation direction First cutting edge portion (first cutting edge portion )
24 First counterbore portion 24A First bottom surface 24B First breaker wall surface 25 First blade tip 25C Diamond sintered body 25E Peripheral cutting edge 25F End cutting edge 26 Second cutting edge portion (second cutting edge portion)
27 Second counterbore portion 27A Second bottom surface 27B Second breaker wall surface 28 Second cutting edge tip 28C Diamond sintered body 28E Outer peripheral cutting edge T Tool rotation direction

Claims (4)

In a drilling tool in which a cutting blade portion is provided in a tool body rotated around an axis, and is inserted into a pre-formed hole in a workpiece, and the inner wall surface of the prepared hole is cut to form a processed hole. ,
In the outer periphery of the tip of the tool body, a chip discharge groove that opens to the tip surface of the tool body and extends to the rear end side is formed,
The cutting edge portion is recessed from the wall surface of the chip discharge groove facing forward in the tool rotation direction and opened toward the outside in the tool radial direction, and is attached to the counterbore portion, and has a substantially flat plate shape. A cutting edge tip with a cutting edge protruding radially outward,
The cutting edge of the cutting edge tip is composed of a diamond sintered body,
The counterbore part has a bottom surface on which the cutting edge tip is seated with its thickness direction facing the tool rotation direction, and rises larger than the thickness of the cutting edge chip from the bottom surface and faces forward in the tool rotation direction of the chip discharge groove. A drilling tool comprising a breaker wall surface that intersects the wall surface. The tool body has a multi-stage columnar shape in which the tip side is gradually reduced in diameter,
A first cutting edge portion provided at a tip of the tool body, and a first cutting edge portion provided on a rear end side of the tool body with respect to the first cutting edge portion and having a larger diameter than the first cutting edge portion. The drilling tool according to claim 1, further comprising a second cutting edge portion. A counterbore portion of the first cutting edge portion is open to the tip surface of the tool body, and a tip edge blade that protrudes toward the tip end side of the tool body is provided on the cutting edge tip attached to the counterbore portion. ,
3. The drilling tool according to claim 2, wherein the tip cutting edge extends from the outer peripheral side of the tool body over the axis along the diameter direction of the tool body. A coolant supply hole is provided in the tool body along the axial direction,
On the wall surface facing the tool rotation direction rear of the chip discharge groove, a coolant discharge hole communicating with the coolant supply hole and opening toward the counterbore part is provided,
The coolant supply groove notched toward the breaker wall surface from the wall surface facing the tool rotation direction of the chip discharge groove is formed on the extended line of the coolant discharge hole. The hole drilling tool according to claim 1.

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