JP2002301613A - Drill with diamond sintered material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill with diamond sintered material which can make a quick feed by attaining reduction of cutting resistance. SOLUTION: A cutting blade 5 provided on a diamond sintered material 6 and a thinning surface 10 are formed in a tip end part of a drill main unit 1 rotated around an axial line O, a length L of a cutting blade external peripheral part 5A formed on the diamond sintered material 6 as viewed by the front from an axial line O direction tip end side is set to 60% or more relating to a radius R of the cutting blade 5, and a space M between a pair of the cutting blade external peripheral parts 5A, 5A in a direction orthogonal thereto is set to a range of 0.4 to 1.0 mm, a maximum distance N between a plane Q extended in a direction orthogonal to the cutting blade external peripheral part 5A including the axial line O and an opening edge in a tip end center part C of the drill main unit 1 of the thinning surface 10 is set to a range of 0.2 to 0.6 mm, and a diameter S of a circle R inscribed to the opening edge of the thinning surface 10 in the tip end center part C with the axial line O serving as the center is set to a range of 0.2 to 0.6 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill with a diamond sintered body in which a cutting edge at the tip of a drill body is formed of a diamond sintered body.

[0002]

2. Description of the Related Art Such a diamond sintered body has higher hardness and higher wear resistance than cemented carbide or high-speed steel used as a general tool material. It is often used for the cutting edge of cutting tools such as reamers. The same applies to a drill used for drilling a work material, that is, a chip discharge groove is formed on the outer periphery of a tip portion of a substantially cylindrical drill body which is rotated around an axis, and the chip discharge groove is formed. A diamond sintered body is provided at the tip of the wall face of the discharge groove facing the drill rotation direction, and a cutting edge that reaches from the center of the tip of the drill body to the outer periphery of the drill body through these diamond sintered bodies is formed. Various proposals have been made.

[0003]

However, in such a conventional drill with a diamond sintered body, the purpose is to extend the life of the drill mainly by the high hardness and wear resistance of the diamond sintered body. I was just there. For this reason, for example, in a drill in which a diamond sintered body is simply attached to a cutting edge portion of a conventional general drill, a cutting force is increased and a rotational driving force of the drill is also increased. However, there was a natural limit in improving the drilling efficiency.

The present invention has been made under such a background, and in the above-described drill with a diamond sintered body, rapid cutting is enabled by reducing cutting resistance to improve drilling efficiency. It is an object of the present invention to provide a drill with a diamond sintered body that can be used.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve such an object, the present invention relates to a drill body having a substantially cylindrical outer shape which is rotated around an axis.
A pair of chip discharge grooves are formed on opposite sides of the axis, and a diamond sintered body is provided on at least an outer peripheral portion of a wall surface of the chip discharge grooves facing the drill rotation direction, and a diamond sintered body is provided. A pair of cutting blades extending from the center of the tip end of the main body to the outer periphery of the drill main body through these diamond sintered bodies are formed symmetrically with respect to the axis, and the chip discharge groove is positioned rearward in the drill rotation direction. A drill with a diamond sintered body, in which a thinning surface inclined toward the drill rotation direction toward the distal end side is formed toward a distal end center portion of the drill body at a distal end portion of the wall surface facing the When viewed from the front in the axial direction, the length of the outer periphery of the cutting edge formed on the diamond sintered body among the respective cutting edges is 60% or less of the radius of the cutting edge. With the spacing between the pair of cutting edge outer peripheral portion in a direction perpendicular to the cutting edge peripheral portion (hereinafter, referred to as the cutting edge offset.) The 0.4~1.0mm
And the maximum distance between a plane extending in a direction orthogonal to the outer peripheral portion of the cutting edge including the axis and an opening edge at the center of the tip of the drill body at the thinning surface (hereinafter, referred to as
It is called the thinning depth. ) Is in the range of 0.2 to 0.6 mm, and the diameter of a circle (hereinafter, referred to as thinning core thickness) inscribed in the opening edge at the center of the tip centering on the axis is 0.2 to 0. The range is 6 mm. The length of the outer peripheral portion of the cutting blade, the offset amount of the cutting blade, the thinning depth, and the thickness of the thinning core are all sizes as viewed from the front in the axial direction.

That is, at the tip side of the wall surface of the chip discharge groove facing the drill rotation direction, that is, at the rake face of the cutting edge, the length of the cutting edge on the diamond sintered body provided at least on the outer peripheral portion is equal to the length of the cutting edge. If the radius is less than 60% of the radius of the cutting edge, abrasion and welding occur at the cutting edge portion formed at the center of the tip of the drill body on the inner peripheral side of the diamond sintered body, that is, cutting occurs due to wear and welding. This leads to an increase in resistance. The length of the cutting edge on the diamond sintered body may be 100% of the radius of the cutting edge, that is, the entire length of the cutting edge may be formed on the diamond sintered body. Further, even if the offset amount of the cutting edge exceeds 1.0 mm, the rake angle in the radial direction of the cutting edge increases toward the negative angle side, so that the cutting resistance increases. If the diameter is smaller than 4 mm, the thickness of the thinning core, which will be described later, must be reduced, and the edge strength of the drill body becomes insufficient at the center of the tip of the drill body.

On the other hand, a thinning surface which is inclined in the drill rotation direction toward the tip end is formed on the tip end of the wall surface of the chip discharge groove which faces rearward in the drill rotation direction toward the center of the tip end of the drill body. Accordingly, in the center of the tip of the drill body, the opening edge of the thinning surface acts as a cutting edge, so that the thrust load acting most on the center of the tip can be reduced to reduce the cutting resistance. However, when the thinning depth by forming this thinning surface is less than 0.2 mm, or when the thinning core thickness is more than 0.6 mm, the effect of forming this thinning surface is small, and the cutting resistance also increases. Will be invited. On the other hand, if the thinning depth is larger than 0.6 mm or the thinning core thickness is smaller than 0.2 mm, the thickness at the center of the drill body tip cannot be secured, and the edge strength is reduced. Insufficiency will result in damage to the drill body.

The thinning surface has an inclination angle (hereinafter referred to as "thinning") formed by a thinning surface with respect to a straight line perpendicular to the rake surface in a cross section orthogonal to the rake surface and the thinning surface. It is desirable that the angle of inclination of the cutting edge be in the range of 0 to 25 °. If the angle of inclination of the thinning edge falls below 0 ° and overhangs on the rake face, the thinning face is formed. When the opening edge of the above-mentioned opening edge acts as a cutting edge, chips may not be able to be discharged smoothly. Conversely, when the thinning cutting edge inclination angle is greater than 25 °, the tip of the drill body becomes thinner. There is a possibility that the surface is largely cut off and the rigidity is impaired.
In addition, it is desirable that an intersection angle (hereinafter, referred to as a groove angle) between a wall surface of the chip discharge groove facing the tool rotation direction and a wall surface facing the tool rotation direction rear side be in the range of 80 to 120 °, If the groove angle is less than 80 °, the chip discharging property is impaired, while if it is more than 120 °, the rigidity of the drill body may be impaired. Furthermore, an inclination angle (hereinafter, referred to as a thinning angle) formed by the thinning surface with respect to the wall surface facing the rear side in the drill rotation direction of the chip discharge groove.
Is desirably in the range of 15 to 35 °. If the angle is less than 15 °, the above-mentioned thinning depth cannot be obtained unless the width of the thinning surface is increased, and the drill body tip portion 35 ° while lacking rigidity
When the thickness exceeds the above range, the thinning surface comes to block in the outflow direction of the chips generated by the opening edge, which may lead to chip clogging.

[0009]

FIG. 1 to FIG. 4 show an embodiment of the present invention. In this embodiment, the drill body 1 is formed of a hard material such as a cemented carbide in a substantially cylindrical shape with the axis O as a center, and has a rear end side (FIG. 1).
The right side of the figure is a shank portion 2, and this shank portion 2 is attached to a rotating shaft of a machine tool.
It is rotated in the drill rotation direction indicated by the symbol T in the figure and used for drilling. The tip (the left side in FIG. 1) of the drill body 1 is a cutting blade 3, and a pair of chip discharging grooves 4 are formed on the outer periphery of the cutting blade 3 on opposite sides of the axis O. , 4 are formed symmetrically with respect to the axis O over the entire length of the cutting edge 3 from the flank 1A of the drill body 1. The cutting edge 3 is formed symmetrically with respect to the axis O, including the chip discharge grooves 4.

In the present embodiment, the chip discharge grooves 4, 4 have wall surfaces 4A, 4B in a cross section orthogonal to the axis O.
Is an L-shape, and the intersection angle formed by the wall surfaces 4A and 4B in the cross section, that is, the groove angle α is 80 to
The angle is set to 120 °, and is set to 90 ° in the present embodiment. In this embodiment, the chip discharge groove 4 is formed so as to extend straight and parallel to the axis O. However, for example, the chip discharge groove 4 is twisted rearward in the drill rotation direction T around the axis O toward the rear end side. Spiral shape. Also,
The outer peripheral surface of the cutting edge portion 3 defined between the chip discharge grooves 4 and 4 in the circumferential direction has an arc-shaped cross-section centered on the axis O at portions adjacent to the chip discharge grooves 4 and 4 in the circumferential direction. And a portion inside thereof has an arcuate cross-section centered on an axis O having a slightly smaller diameter than the margin portion on the rear end side of the cutting edge portion 3. The distal end side of the portion 3 is formed by a pair of rectangular flat surfaces which intersect each other so as to be bent at an obtuse angle in the circumferential direction and extend in the direction of the axis O.

On the other hand, the flank 1A of the front end is
, And is formed so as to gradually retreat from the opening of the chip discharge groove 4 toward the rear side in the drill rotation direction T around the axis O to provide clearance. . Further, cutting edges 5 and 5 are formed at the intersection ridges between the tip flank 1A and the wall surfaces 4A and 4A of the chip discharge grooves 4 and 4, that is, at the tip edges of the wall surfaces 4A and 4A. The cutting edges 5A, 5A are formed on the diamond sintered bodies 6, 6, respectively. That is, in the present embodiment, the wall surface 4A
A concave portion 7 which is recessed by one step and is open to the tip flank 1A and the outer peripheral surface is formed, and the diamond sintered body 6 and the cemented carbide 8 are layered in the concave portion 7 to form a layered sintered body. The binder 9 is attached by brazing the cemented carbide 8 to the drill body 1 with the diamond sintered body 6 oriented in the drill rotation direction T.

The surface of the layered sintered body 9 facing the drill rotation direction T of the portion of the diamond sintered body 6 is flush with the wall surface 4A and is the rake face 6A of the outer peripheral cutting edge 5A. At the same time, the surface facing the front end side of the layered sintered body 9 is provided with clearance so as to be flush with the front clearance surface 1A,
The cutting edge outer peripheral portion 5A is formed at the intersection ridge line of these surfaces. Thus, as shown in FIG.
In a front view as viewed from the front end in the direction, the length L of the cutting edge outer peripheral portion 5A formed on the diamond sintered body 6 is equal to the length of both cutting edge outer peripheral portions 5A, 5A of the pair of cutting edges 5, 5. hand,
The radius R of the cutting edge 5, that is, the outer peripheral end of the cutting edge 5 is the axis O
In this embodiment, L / R is set to 0.85 (the length L is set to 85% with respect to the radius R). I have. In other words, in the present embodiment, for each cutting edge 5, a portion of 60% or more from the outer peripheral end is a cutting edge outer peripheral portion 5A formed on the diamond sintered body 6 portion. The outer peripheral surface of the layered sintered body 9 is also formed so as to be flush with the outer peripheral surface on the tip side of the cutting blade 3. Further, since the distal flank 1A is formed in a substantially conical shape as described above, the cutting blades 5, 5 are substantially arranged from the distal center portion C around the axis O on the distal flank 1A toward the outer peripheral side. The cutting edges 5, 5 are given a predetermined tip angle by being inclined linearly toward the rear end side.

Further, the outer peripheral portions 5A, 5A of the cutting edge formed on the diamond sintered body 6 in this manner are arranged in parallel with each other in the above-described front view since the cutting edge portion 3 is symmetric with respect to the axis O. However, these cutting edge outer peripheral portions 5
A and 5A are located on the drill rotation direction T side with respect to a plane P including the axis O and parallel to the outer peripheral portions 5A and 5A of the cutting blades. The rake angle θ in the direction is set on the negative angle side. And in the front view, these cutting blade outer peripheral portions 5A,
An interval between the pair of cutting edge outer peripheral portions 5A, 5A in a direction orthogonal to 5A, that is, a direction orthogonal to the plane P, that is, the cutting edge offset amount M is in a range of 0.4 to 1.0 mm. I have.

On the other hand, as shown in FIG. 3, the tip end of the wall surface 4B facing the rear side in the drill rotation direction T of the chip discharge groove 4 intersects the wall surface 4B at an obtuse angle toward the tip end. A thinning surface 10 that is inclined toward the drill rotation direction T is formed toward the tip center portion C of the drill body 1. Here, the inclination angle of the thinning surface 10 with respect to the wall surface 4B, that is, the thinning angle β is constant within a range of 15 to 35 °, and the tip flank 1A has a conical surface shape as described above. As a result, the width W of the thinning surface 10 is formed so as to gradually increase from the outer peripheral side toward the center C of the distal end.
However, the thinning surface 10
Is a ridge line crossing with the tip flank 1A, that is, the opening edge of the thinning surface 10 on the tip flank 1A side draws a curve protruding toward the axis O in the front view and approaches the axis O. Then, the cutting edge is formed so as to be cut substantially linearly and intersect with the inner peripheral end of the outer peripheral portion 5A of the cutting blade. The unit 5B. On the other hand, this tip center portion C
The opening edge of the other thinning surface 10 to the tip flank 1A is slightly inclined in the drill rotation direction T toward the inner peripheral side when viewed from the front, and smoothly forms a convex curve of the opening edge on the tip center portion C side. The opening edge portion is chamfered 11.

In the front view, assuming a plane Q including the axis O and extending in a direction perpendicular to the outer peripheral portions 5A, 5A of the cutting blades, that is, a plane Q orthogonal to the plane P in the axis O, The depth to the position where the thinning surface 10 is most deeply receded from Q, that is, the thinning depth N which is the maximum distance between the plane Q and the opening edge of the thinning surface 10 (excluding the chamfered portion 11). Is in the range of 0.2 to 0.6 mm. Also, the cutting edge inner peripheral portions 5B, 5B of the both cutting edges 5, 5 do not protrude to the opposite side beyond the axis O in front view,
Thus, the axis O is provided between the inner peripheral portions 5B of the cutting blades.
A chisel portion 12 that intersects the thinning surface 1 around the chisel portion 12, that is, the tip center portion C around the axis O in the front view.
The thinning core thickness S, which is the diameter of the circle D inscribed in the opening edge of 0, is also in the range of 0.2 to 0.6 mm.
Furthermore, as shown in FIG. 4, a cross section orthogonal to the rake face 6A (the face facing the drill rotation direction T side of the diamond sintered body 6) of the outer peripheral cutting edge portion 5A of the cutting blade 5 and the thinning face 10. In this, the thinning surface 10 is formed such that the thinning cutting blade inclination angle γ with respect to the straight line X perpendicular to the rake face 6A is in the range of 0 to 25 °,
That is, the thinning surface 10 is formed so as to extend perpendicular to the rake face 6A along the straight line X, or the rake face 6A side in the range where the thinning cutting edge inclination angle γ is 25 ° or less as shown in FIG. Is formed so as to gradually retreat as it goes toward the outer peripheral side of the drill body 1.

However, in the drill with the diamond sintered body thus configured, the cutting edge 5 is viewed from the front.
The length L of the cutting edge outer peripheral portion 5A formed on the diamond sintered body 6 is 60% or more of the radius R of the cutting edge 5 and the cutting edge offset amount M is 0.4 to 1 0.0mm
And the thinning depth N is 0.2 to 0.6.
mm and thinning thickness S is 0.2 ~
Since it is set to the range of 0.6 mm, the diamond sintered body 6 having high hardness and high wear resistance is used to extend the life of the drill, while promoting the reduction of cutting resistance when drilling by the drill. Thus, the drill body 1 can be rapidly traversed at the time of machining and machining efficiency can be improved.

That is, first, the cutting edge outer peripheral portion 5
By setting the length of A to be 60% or more of the radius R, the length of the inner peripheral portion 5B of the cutting edge formed on the tip center portion C side of the drill body 1 made of cemented carbide is reduced. By preventing abrasion and welding in the above, it is possible to suppress an increase in cutting resistance due to such abrasion and welding. Secondly, since the cutting edge offset amount M is 1.0 mm or less, the radial rake angle θ of the cutting edge outer peripheral portion 5A is prevented from becoming too large to the negative angle side, so that the cutting edge 5 can be favorably used. While the sharpness can be ensured and the cutting resistance can be reduced, the cutting edge offset amount M is 0.4 mm or more, so that the thinning core thickness S described below is prevented from becoming too small, and While maintaining the strength of the cutting edge inner peripheral portion 5B in C,
Again, an increase in cutting resistance due to wear or the like can be suppressed. Thirdly, since the cutting edge inner peripheral portion 5B is formed by the opening edge of the thinning surface 10, the thrust load acting on the front end center portion C is reduced, and the cutting resistance is also suppressed. , Thinning depth N is 0.2mm
Since the thinning core thickness S is as small as 0.6 mm or less, the thrust load can be reduced more reliably. On the other hand, when the thinning depth N is 0.6 mm or less and the thinning core thickness S is not more than 0.6 mm. Since it is 2 mm or more, the thickness of the drill body 1 at the tip center portion C is prevented from being unnecessarily shaved by the thinning surface 10, and the increase in cutting resistance due to wear and damage of this portion can also be suppressed. It is.

In addition, in the present embodiment, the thinning cutting surface inclination angle γ of the thinning surface 10 is set to 0 ° or more, that is, the thinning surface 10 extends beyond the straight line X in FIG. The inner peripheral portion 5B of the cutting blade
Chips generated by the opening edge of the thinning surface 10 forming the overhanging thinning surface 10
In such a case, a large resistance is not generated due to the rapid curling, and the chip curled in such a manner does not cause clogging to increase the resistance.
On the other hand, since the thinning cutting edge inclination angle γ is set to 25 ° or less, the thinning surface 10 is
Since the opening of the drill body 1 is not too large, that is, the distal end of the drill body 1 is not largely cut off by the thinning surface 10, the rigidity of the drill body 1 in this portion can be reliably ensured.

Further, in this embodiment, since the groove angle α of both wall surfaces 4A and 4B of the chip discharge groove 4 having an L-shaped cross section is set to 80 ° or more, the cross-sectional area of the chip discharge groove 4 is reduced. While it is possible to secure a large size to prevent an increase in resistance due to chip clogging, the groove angle α is set to 120 ° or less, so that the cross-sectional area of the drill body 1 is also secured to prevent the rigidity from being impaired. it can. Further, in the present embodiment, since the thinning angle β is set to 15 ° or more, the width W of the thinning surface 10 increases as shown in FIG. 3 even when the above-described thinning depth N is secured. Too long, so that the rigidity of the tip of the drill body 1 can be prevented from being impaired by such a thinning surface 10 having a large width W, and even if the thinning angle β is 35 ° or less. Therefore, the thinning surface 10 does not stand in the outflow direction of the chips generated by the inner peripheral portion 5B of the cutting edge, and the inclination angle γ of the thinning edge is set to 0 ° or more. Thus, the chips by the inner peripheral portion 5B of the cutting blade can be smoothly discharged.

[0020]

As described above, according to the present invention,
Even for drills with cutting edges formed on a diamond sintered body, not only extend the life of the drill due to the high hardness and wear resistance of the diamond sintered body, but also reduce the cutting resistance during drilling. As a result, the rotational driving force of the drill body can also be reduced, whereby a high feed rate can be given to the drill body, and the processing efficiency of drilling can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a front view of the embodiment shown in FIG. 1 as viewed from a front end side in an axis O direction.

FIG. 3 is a sectional view taken along line YY in FIG. 2;

FIG. 4 is a sectional view taken along the line ZZ in FIG. 3;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 drill body 1A tip flank 4 chip discharge groove 4A wall surface of chip discharge groove 4 facing drill rotation direction T 4B wall surface of chip discharge groove 4 facing rearward in drill rotation direction 5 cutting edge 5A cutting edge outer peripheral portion 5B cutting edge Inner peripheral portion 6 Diamond sintered body 6A rake face 10 Thinning surface L Length of cutting edge outer peripheral portion 5A in front view from front end side in axis O direction R Radius of cutting edge 5 M In front view from front end side in axis O direction , A pair of outer peripheral portions 5A in a direction orthogonal to the outer peripheral portion 5A,
The distance between the cutting edges 5A (cutting blade offset amount) N In a front view from the front end side in the direction of the axis O, a plane Q including the axis O and extending in a direction orthogonal to the cutting blade outer peripheral portion 5A and a front center C of the thinning surface 10 Maximum distance from the opening edge (thinning depth) S A circle D inscribing the opening edge at the center C of the tip centering on the axis O in a front view from the tip side in the direction of the axis O.
Α (thinning thickness) α Crossing angle (groove angle) formed by the wall surfaces 4A and 4B of the chip discharge groove 4 β Inclination angle (thinning angle) formed by the thinning surface 10 with respect to the wall surface 4B of the chip discharge groove 4 γ Rake surface In a cross section orthogonal to 6A and the thinning surface 10, an inclination angle (thinning cutting edge inclination angle) formed by the thinning surface 10 with respect to a straight line X perpendicular to the rake surface 6A.

Continuation of the front page (72) Inventor Taichi Aoki 179 Kanegasaki Nishi-Oike, Uozumi-cho, Akashi-shi, Hyogo 1 Inside MMC Kobelco Tool Co., Ltd. (72) Inventor Hiroyoshi Fukuda 179 Kanegasaki-Nishi-Oike, Uozumi-cho, Akashi-shi, Hyogo 1 MMC Kobelco Tools Co., Ltd. (72) Inventor Yuji Kusakabe 179 Kanegasaki Nishi-Oike, Uozumi-cho, Akashi-shi, Hyogo 1 1 MMC Kobelco Tools Co., Ltd. No. 1 MMC Kobelco Tools Co., Ltd. (72) Inventor Takashi Masuda 179 Kanegasaki Nishi-Oike, Uozumi-cho, Akashi-shi, Hyogo Prefecture 1 MMC Kobelco Tools Co., Ltd. (72) Inventor Masayoshi Kawano, Kanagasaki-Nishi, Uozumi-cho, Hyogo Prefecture 179 Oike 1 MMC Kobelco Tools Co., Ltd. F-term (reference) 3C037 BB13 DD01

Claims (4)

[Claims] 1. A pair of chip discharge grooves are formed on the outer periphery of a distal end portion of a substantially cylindrical drill body rotated around an axis on opposite sides of the axis with respect to each other, and drill rotation of the chip discharge grooves is performed. A diamond sintered body is provided on at least the outer peripheral portion on the distal end side of the wall surface facing the direction, and a pair of cuts reaching the outer periphery of the drill main body from the center of the front end of the drill main body, passing over these diamond sintered bodies. The blade is formed symmetrically with respect to the axis, and at the tip of the wall surface facing the drill rotation direction rear side of the chip discharge groove,
A drill with a diamond sintered body having a thinning surface inclined toward a tip rotation side in a direction of rotation of the drill toward a center portion of the tip of the drill body, and a front view from the tip side in the axial direction. In the above, the length of the outer peripheral portion of the cutting edge formed on the diamond sintered body is 60% or more of the radius of the cutting edge, and is orthogonal to the outer peripheral portion of the cutting edge. The distance between a pair of the cutting edge outer peripheral portions in the direction is 0.4 to 1.0 mm, and a plane extending in a direction including the axis and perpendicular to the cutting edge outer peripheral portion and the drill body of the thinning surface The maximum distance from the opening edge at the center of the tip is 0.2 to 0.6
mm, and the diameter of a circle inscribed in the opening edge at the center of the tip centering on the axis is 0.2 mm.
A drill with a diamond sintered body, characterized in that the diameter is in the range of 0.6 mm. 2. In a cross section orthogonal to the rake face continuous with the cutting blade and the thinning face, an inclination angle formed by the thinning face with respect to a straight line perpendicular to the rake face is 0 to 2.
The drill with a diamond sintered body according to claim 1, wherein the drill has a range of 5 °. 3. An intersection angle between the wall surface of the chip discharge groove facing the drill rotation direction and the wall surface facing the drill rotation direction rear side is 8.
The drill with a diamond sintered body according to claim 1 or 2, wherein the drill has a range of 0 to 120 °. 4. An inclination angle formed by the thinning surface with respect to the wall surface of the chip discharge groove facing rearward in the drill rotation direction in a range of 15 to 35 °. The drill with a diamond sintered body according to claim 3.