JP3686022B2 - Drilling tool with coolant hole - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drilling tool with a coolant hole (hereinafter simply referred to as a drilling tool) in which a coolant hole for supplying a coolant such as a cutting fluid is formed in a tool body and opened at a tip end surface thereof. is there.
[0002]
[Prior art]
In this type of drilling tool, a pair of chip discharge grooves are symmetrical to the above-mentioned axis on the outer periphery of the tip of a substantially cylindrical tool body that rotates around the axis, as a machining hole is formed in a general steel material. The tool is formed so as to be spirally twisted to the rear side in the tool rotation direction toward the tool rear end side, and the tool is formed on the cross ridge line portion between the wall surface of the chip discharge groove facing the tool rotation direction and the tip surface of the tool body. A so-called two-blade twist drill in which a cutting blade reaching the outer periphery of the tool from the inner peripheral side is formed is well known. In such a drilling tool, the tool must be secured to a certain extent in order to ensure that the chip generated in the form of a string or chip during drilling must be secured. The core thickness of the main body cannot be increased so much and is usually about 10 to 30% of the outer diameter of the cutting blade. Therefore, the coolant hole for supplying coolant such as cutting fluid or air to the cutting site is also described above. It is difficult to form the inside of the circle drawn by the core thickness, considering the rigidity of the tool body. A total of two coolant holes, one for each cutting blade, were opened for one tool body on the flank face continuous to the rear side in the tool rotation direction of the blade.
[0003]
[Problems to be solved by the invention]
However, even if the coolant holes are formed in the land portion of the tool body in this way to ensure the rigidity of the tool body, the increase in the diameter and number of the coolant holes themselves does not impair the tool rigidity. However, since the tool body may be twisted and broken due to cutting resistance during drilling, the coolant hole diameter and the number of holes have to be limited. Incidentally, for example, in a drilling tool having an outer diameter of 34.4 mm, coolant holes having a hole diameter of 3.7 mm are formed on the flank surfaces of the two cutting blades. The total cross-sectional area of the coolant hole is only about 2.4% of the cross-sectional area of the machined hole formed by this, so that the coolant supply amount and supply pressure can be increased to improve the efficiency of cooling and lubrication. There was also a limit. In addition, in order to drill a coolant hole in a land portion formed between the spirally twisted chip discharge grooves and twisted in the same manner, the coolant hole must also be spiral with a chip discharge groove and the like. Of course, the formation of the coolant hole is complicated, and the total length of the coolant hole is long, so that the supply of the coolant is also impaired.
[0004]
On the other hand, the inventors of the present invention previously punched a brittle material such as silicon, ceramics, glass, or a cemented carbide material such as tungsten carbide (WC) in Japanese Patent Application No. 2000-331507. As a drilling method to perform drilling, we propose that the drilling tool rotated around the axis is sent to the tip end side in the axial direction with a very small feed amount of 0.025 to 0.15 μm / rev. According to such a drilling method, since the pushing force when the drilling tool is pushed into the work piece is reduced and an excessive load does not act on the work piece, the work piece is Even such brittle materials can prevent edge chipping caused by cracks, cracks and the like. However, when drilling such a brittle material, the processing heat is likely to be trapped in the bore due to the low thermal conductivity of the brittle material, so coolant can be supplied more efficiently to the cutting site. Thus, cooling is an even more important issue.
[0005]
The present invention has been made under such a background, and it is possible to increase the supply amount and supply pressure of the coolant without impairing the rigidity of the tool body, and even when punching a brittle material. However, the object is to provide a drilling tool capable of efficient cooling and lubrication.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve such an object, the present invention reaches the outer periphery of the tip surface from the inner peripheral side of the tool to the front end surface of the substantially cylindrical tool body rotated about the axis. A cutting edge is formed, and a coolant hole drilled from the rear end side of the tool body is opened so that the core thickness of the tool body is 40% or more with respect to the outer diameter of the cutting edge, while orthogonal to the axis. The total area of the coolant hole in the cross section to be set is set in a range of 5 to 30% of the cross-sectional area of the machining hole formed by the cutting blade , and the outer periphery of the tip end of the tool body is twisted around the axis. A chip discharge groove is formed, and the coolant hole is formed in a twist hole shape having a lead different from the twist of the chip discharge groove . Therefore, in such a drilling tool, by increasing the core thickness of the tool body to 40% or more of the outer diameter of the cutting edge, a coolant hole can be drilled inside the core thick circle. It is possible to increase the cross-sectional area of each coolant hole or increase the number of coolant holes without impairing the rigidity of the main body, and the total area of this coolant hole is 5 to 30% of the cross-sectional area of the processed hole. And can be significantly larger than before.
[0007]
If the core thickness is less than 40% of the outer diameter of the cutting edge, it is difficult to make a coolant hole inside the core thickness circle without impairing the rigidity of the tool, and the total area of the coolant hole is 5 of the cross-sectional area of the machining hole. If it is less than%, the coolant supply amount and supply pressure cannot be increased. On the other hand, if it exceeds 30%, it becomes difficult to maintain the tool rigidity no matter how thick the core is. In addition, when drilling a brittle material as described above, a wound or chip-like chip is not generated as in the case of drilling a general steel material, but the work piece is a brittle material. As a result, powdery chips will be generated.Thus, even if the cross-sectional area of the chip discharge groove is reduced by increasing the thickness of the core, good dischargeability can be maintained. On the other hand, since it is important to efficiently supply the coolant as described above in the drilling of such a brittle material, the drilling tool of the present invention is a workpiece made of a brittle material by the above cutting blade. It can be said that it is particularly effective when used for forming the above-mentioned processed holes.
[0008]
By the way, when the core thickness of the tool body is increased in this way, and especially when drilling a workpiece made of a brittle material, the cutting edge is a workpiece as in drilling a general steel material. Instead of cutting the chip and generating chip-wound or chip-shaped chips with a thickness according to the feed amount, the workpiece is scraped into powder as described above to generate chips. The blade is required to have a strength higher than its sharpness. For this reason, on the tip surface of the tool body, the rake face that continues to the tool rotation direction of the cutting blade is directed toward the tool rotation direction side toward the tool rear end side. It is desirable that the cutting edge is inclined so as to give a negative axial rake angle. Therefore, when a negative rake angle is given to the rake face in this way, the cutting hole or the cutting part of the workpiece by the cutting edge is made more efficient by opening the coolant hole at least on the rake face. Coolant can be supplied. Further, in the present invention, since the number of coolant holes can be increased as described above, a plurality of coolant holes are drilled in the tool body, and these are also opened on the flank that continues to the rear of the cutting blade in the tool rotation direction. Of course, it does not matter.
[0009]
And in order to efficiently discharge and process the chips and chips generated in this way , in the present invention, a chip discharge groove is formed on the outer periphery of the tip of the tool body. Since the coolant hole can be drilled inside the thick circle, the chip discharge groove is formed in a spiral shape that twists around the axis of the tool body, while the coolant hole is the twist of the chip discharge groove. The lead is drilled in a different twisted hole shape . Therefore, for example , if this coolant hole is drilled in the shape of a twisted hole of a lead smaller than the twist of the chip discharge groove, the coolant hole can be shortened and the coolant can be supplied more efficiently.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
1 to 3 show a first embodiment of the present invention. In the present embodiment, the tool body 1 is integrally formed of a hard material such as a cemented carbide, and a tip portion 2 that is inserted into a workpiece to perform drilling is gripped by a spindle of a machine tool and a shank portion. The tapered portion 4 has a multi-stage cylindrical shaft shape with the axis O reduced by one step with respect to the rear end portion 3 being formed, and the portion between both end portions 2 and 3 is gradually reduced in diameter toward the front end side. Is tied by Further, in the present embodiment, the tip surface of the tip portion 2 intersects at one intersection point P on the axis O, and is a flat surface or tool inclined toward the rear end side from the intersection point P toward the outer peripheral side. It is composed of four fan-shaped surfaces having a convex curved surface that bulges toward the outer peripheral side of the tip. Accordingly, in the tool body 1, the position of the intersection point P is projected to the most tip side, and the fan-shaped surfaces intersect each other 4. The intersecting ridge lines of the strips are formed so as to recede linearly from the intersection P toward the outer peripheral side toward the rear end, and to extend radially from the intersection P in the front view of the axis O direction.
[0011]
Here, the four fan-shaped surfaces are different from each other in the central angle of the fan shape formed when viewed from the front in the direction of the axis O, and thereby, the four intersecting ridgelines between the fan-shaped surfaces adjacent in the circumferential direction are the circumferential direction. Are arranged at different intervals. However, in the present embodiment, among the four fan-shaped surfaces, the fan-shaped central angles formed by the pair of fan-shaped surfaces positioned on the opposite side across the intersection point P in the end view in the direction of the axis O are equal to each other. In addition, the pair of intersecting ridge lines located on the opposite side across the intersection point P are formed so as to extend on one straight line as shown in FIG. They are arranged in line symmetry. Further, among these four intersecting ridge lines, the intersection angle of the pair of intersecting ridge lines positioned on the opposite side with respect to the intersection point P is the axis of the other pair of intersecting ridge lines positioned on the opposite side with respect to the intersection point P. The crossing angle with respect to O is larger than the pair of crossing ridgelines, and thus the crossing angle of the crossing angle is larger than the other pair of crossing ridgelines and the four fan-shaped surfaces with a small crossing angle in the rotation trajectory around the axis In this embodiment, the cutting edges 5 and 5 reach the outer periphery of the tool from the intersection P on the inner peripheral side of the tool in the present embodiment. The face is a rake face 6, and the fan-like face connected to the rear side in the tool rotation direction T of the cutting edges 5, 5 is a flank 7.
[0012]
In addition, since the front end surface of the tool body 1 is configured by four fan-shaped surfaces that are inclined toward the rear end side from the intersection P toward the outer peripheral side as described above, the flank 7 is formed from the cutting edge 5. It is formed so as to gradually recede toward the rear end side of the tool as it goes rearward in the tool rotation direction T around the axis O, and a predetermined clearance angle is given to the flank 7, while the rake face 6 is cut in reverse. The blade 5 is formed so as to gradually recede toward the rear end side of the tool as it goes toward the tool rotation direction T, thereby giving the rake face 6 a negative rake angle in the axial direction. Further, in the present embodiment, the central angle of the fan-shaped surface that is the rake face 6 is made larger than the central angle of the fan-shaped surface that is the flank 7.
[0013]
Further, on the outer peripheral surface of the tip portion 2 of the tool body 1, the second cutting surfaces 8 and 8 are formed so as to be recessed one step toward the inner peripheral side of the tool except for the portion where the cutting blades 5 and 5 reach the outer periphery of the tip surface. As shown in FIG. 1, the second picking surface 8 is formed so as to be twisted toward the rear side in the tool rotation direction T from the front end surface toward the tool rear end side. Accordingly, the portion where the cutting edge 5 is left in the portion reaching the outer periphery of the front end surface where the second picking surface 8 is not formed is also twisted to the rear side in the tool rotation direction T from the front end surface toward the tool rear end side. Thus, it is left on the outer periphery of the tip portion 2 in the shape of a bank, and this portion has an outer diameter substantially equal to the outer diameter D of the cutting blade 5 and is used as the margin portion 9 in the drilling tool of this embodiment. . Further, a chip discharge groove 10 having an arcuate cross section is formed on the margin portion 9 on the tool rotation direction T side so as to be further recessed from the second picking surface 8 toward the inner peripheral side of the tool. 3 is formed so as to be twisted to the rear side in the tool rotation direction T as it goes from the front end surface to the tool rear end side, like the margin portion 9 and the second picking surface 8, and is a cross section orthogonal to the axis O as shown in FIG. , The circle that contacts the groove bottom of the chip discharge groove 10 with the axis O as the center is the core thickness circle C of the tool body 1, and the diameter of the core thickness circle C is the core thickness E of the tool body 1. Thus, the core thickness E is set to be 40% or more with respect to the outer diameter D of the cutting blade 5.
[0014]
A coolant hole 11 is formed in the tool body 1 from the rear end surface thereof, that is, from the rear end surface of the rear end portion 3 toward the tool front end side, and is opened to the front end surface. The total area of the coolant hole 11 is set in a range of 5 to 30% of the cross-sectional area of the processed hole formed by the cutting blade 5. In this embodiment, as shown in FIGS. 2 and 3, a plurality (four) of coolant holes 11 are formed in the tool body 1 at substantially equal intervals in the circumferential direction and at approximately equal intervals from the axis O. These coolant holes 11 are formed in a circular cross section having the same inner diameter d, and are all arranged inside the core thick circle C. Further, as shown by a broken line in FIG. It is formed in a spiral shape that twists toward the rear side in the tool rotation direction T as it goes toward the rear end side of the tool with leads equal to the surface 8, the margin portion 9, and the chip discharge groove 10. Therefore, in the present embodiment, the total area 4π × (d / 2) ² = π × d ² of these four coolant holes 11 is the cross-sectional area π × (D / 2) of the processed hole formed by the cutting blade 5. ² ) 5 to 30% of the range. Further, these four coolant holes 11 are opened one by one in the rake surfaces 6 and 6 and the flank surfaces 7 and 7 formed in pairs on the front end surface of the tool body 1.
[0015]
The drilling tool configured as described above is fed to the front end side in the direction of the axis O while the rear end 3 of the tool body 1 is gripped by the main spindle of the machine tool and rotated around the axis O as described above. For example, it is used for drilling a workpiece made of a brittle material such as single crystal silicon. However, it is desirable that the feed amount of the tool body 1 to the front end side in the direction of the axis O at this time is set to a very small value of 0.025 to 0.15 μm / rev as described above, and more preferably the tool body 1. Step feed processing is performed in which the workpiece is gradually cut into the workpiece while repeating feeding and retreating. In particular, when used for drilling a brittle material in this way, diamond coating or electrodeposition is performed on at least the surface of the tip 2 of the tool body 1, or at least the tip 2 is sintered with diamond. Desirably formed by the body. In the drilling process, coolant such as cutting fluid or air is supplied from the machine tool side through the coolant holes 11..., And is ejected from the opening formed on the front end surface of the tool body 1.
[0016]
Therefore, in the drilling tool configured in this way, the core thickness E of the tool body 1 is 40% or more of the outer diameter D of the cutting blade 5, which is significantly larger than the conventional one. Since a large rigidity can be secured, even if the total area of the coolant holes 11 is increased to 5 to 30% of the cross-sectional area of the machining hole, the rigidity of the tool body is prevented from greatly decreasing, and the cutting force reduces the tool. It is possible to prevent the situation where the main body 1 is twisted and broken. Then, by increasing the total area of the coolant holes 11 in this way, according to the drilling tool, it is possible to increase the supply amount and supply pressure of the coolant supplied from the coolant holes 11. In addition, the coolant can be sufficiently supplied to the cutting edge 5 and the part to be cut of the work piece thereby to cool and lubricate the cutting edge 5, thereby preventing the cutting blade 5 from being worn by the processing heat and the deterioration of the processing accuracy and cutting resistance. It is possible to improve the processing efficiency by reducing the above. This is particularly effective in drilling a brittle material in which processing heat tends to be trapped in the processing hole as described above. In addition, in the present embodiment, the coolant holes 11 are formed inside the core thickness circle C of the tool body 1, so that a sufficient thickness is also formed between the coolant holes 11 and the outer peripheral surface of the tool body 1. As a result, the tool rigidity can be ensured and the damage thereof can be surely prevented.
[0017]
Here, the core thickness E of the tool body 1 is set to 40% or more of the outer diameter D of the cutting blade 5 as described above. If the core thickness E is less than 40% of the outer diameter D, the coolant holes 11. This is because sufficient tool rigidity cannot be ensured when the area is increased to 5 to 30% of the cross-sectional area of the processed hole. In the present embodiment, since the second face 8 and the chip discharge groove 10 are formed on the outer periphery of the distal end portion 2 of the tool body 1, the core thickness E is smaller than the outer diameter D of the cutting blade 5, that is, The core thickness E does not become 100% of the outer diameter D. However, if chip discharge is ensured by performing, for example, step feed processing as described above at the time of drilling, these two steps are taken. Without forming the surface 8 or the chip discharge groove 10, the outer periphery of the tip 2 may be formed in a columnar shape so that the core thickness E is equal to the outer diameter D and becomes 100%. Further, the total area of the coolant holes 11 is set to 5 to 30% of the cross-sectional area of the processed hole. If the area is less than 5%, the coolant supply amount and the supply pressure cannot be increased sufficiently. If the percentage exceeds 50%, even if the core thickness E of the tool body 1 is 40% or more of the outer diameter D of the cutting blade 5, the rigidity of the tool body 1 may not be ensured reliably.
[0018]
Moreover, in this embodiment, the front end surface of the tool main body 1 is formed by four fan-shaped surfaces, and these fan-shaped surfaces form a rake surface 6 and a flank 7 that are connected to the pair of cutting edges 5 and 5, respectively. The rake face 6 is provided with a negative rake angle in the negative direction and is formed so as to go to the tool rear end side toward the tool rotation direction T side, and two of the four coolant holes 11. Are opened on the rake faces 6 and 6 of the respective cutting edges 5 and 5. For this reason, according to the present embodiment, the coolant sprayed from the coolant holes 11 opening on the rake face 6 is caused to be adjacent to the cutting edge 5 and the cutting edge 5 in the tool rotation direction T behind the coolant holes 11 and the cutting blade 5. As the tool main body 1 rotates, it can be supplied directly and quickly to the cutting site of the workpiece by the cutting blade, thereby promoting more efficient cooling and lubrication. In addition, in this embodiment, two coolant holes 11 and 11 are formed for one cutting blade 5 and four coolant holes 11 are formed in one tool body 1, that is, the number of coolant holes 11 is increased. The total area is increased, and the remaining two coolant holes 11, 11 are opened on the flank 7 spaced from the coolant holes 11, 11 of the rake face 6. It becomes possible to supply evenly to the cutting blade 5 and the cutting site by ejecting it uniformly in the circumferential direction of the distal end surface. Furthermore, since the cutting edge 5 is given a negative rake angle in the negative direction as described above, the cutting edge strength of the cutting edge 5 can be increased to improve the cutting edge strength. For example, it is possible to provide a suitable drilling tool by drilling the brittle material in which the cutting edge 5 is required to be stronger than the sharpness.
[0019]
In this embodiment, the number of coolant holes 11 drilled in the tool body 1 is increased in this way to increase the total area. For example, this is the same as that of the second embodiment shown in FIG. Thus, even if the number of the coolant holes 11 is the same as the conventional two, the total area of the coolant holes 11 in the cross section perpendicular to the axis O is increased by increasing the inner diameter of each coolant hole 11. You may make it enlarge with 5 to 30% of. For example, if the inner diameter of the coolant hole 11 in this case is 2 × d, which is twice the inner diameter d of the coolant hole 11 of the first embodiment, the total area of the coolant holes 11 and 11 in the cross section orthogonal to the axis O is 2π. × (2 × d / 2) ² = 2π × d ^2, and a total area twice as large as that of the first embodiment can be secured. Even in this case, it is desirable that the coolant holes 11 are opened on the rake face 6 that is continuous with the cutting edges 5 and 5 on the tool rotation direction T side. Of course, if the total area of the coolant holes 11 is set within a range of 5 to 30% of the cross-sectional area of the processed hole, both the number and the inner diameter of the coolant holes 11 are increased, or the first The four coolant holes 11 as in the embodiment are drilled, and the inner diameter of the coolant holes 11, 11 opened on the rake face 6 is made larger than the coolant holes 11, 11 opened on the flank 7. May be.
[0020]
On the other hand, in the present embodiment, the second faces 8 and 8 are formed on the outer periphery of the tip 2 of the tool body 1 to leave margin portions 9 and 9 having substantially the same diameter as the outer diameter D of the cutting blade 5. While increasing the friction between the tip 2 inserted in the hole and the inner periphery of the machining hole is prevented by the second picking surfaces 8 and 8, the margins 9 and 9 suppress the deflection of the tip 2 and ensure straightness. be able to. Further, a chip discharge groove 10 is formed on the margin portion 9 on the tool rotation direction T side, and this chip discharge groove 10 is the same as the second face 8 and the margin section 9 are twisted. Since it is formed so as to be twisted to the rear side in the tool rotation direction T as it goes to the rear end side of the tool, in particular, powdery chips generated in the case of drilling the above brittle material, etc. As the tool body 1 rotates, it can be sent to the tool rear end side and efficiently discharged.
[0021]
By the way, in this embodiment, the coolant holes 11... Are the same leads that match the twists of the second picking surface 8, the margin portion 9, and the chip discharge groove 10, and again in the tool rotation direction T toward the tool rear end side. Although it is formed in a spiral shape so as to be twisted to the rear side, when the configuration in which the coolant hole 11 is drilled in the inner periphery rather than the core thickness circle C of the tool body 1 as in this embodiment, Since the coolant hole 11 can be provided without being constrained by the position or twist of the second picking surface 8 or the chip discharge groove 10 on the outer side of the thick core C, the coolant hole 11 is formed in a spiral shape. In addition, it can be formed in a twisted hole shape having different leads from the twisting of the chip discharge groove 10 and the second picking surface 8. Therefore, for example, if the coolant hole 11 is formed so as to be twisted with a lead smaller than the chip discharge groove 10 or the like, the total length along the twist of the coolant hole 11 can be shortened, whereby the coolant is supplied more quickly. Therefore, more efficient cooling and lubrication can be achieved.
[0022]
Further, in the drilling tool adopting the above-described configuration, the coolant hole 11 is not spiraled as described above, but can be drilled in a straight line parallel to the axis O as in the third embodiment shown in FIG. In this case, since the total length of the coolant hole 11 is the shortest, the coolant can be supplied in a shorter time, which is efficient, and the coolant hole 11 is formed in a straight line parallel to the axis O. Therefore, the drilling of the coolant hole 11 can be performed very easily, and therefore, the advantage that the drilling tool can be easily manufactured can be obtained. Furthermore, even if the coolant hole 11 is formed in a spiral shape as in the first embodiment, the screw hole is twisted toward the rear side in the tool rotation direction T as it goes toward the tool tip side as opposed to the first embodiment. In this case, the coolant is pushed out to the tool tip side with the rotation of the tool body 1, so that the coolant can be supplied more quickly. As a result, the supply amount and supply pressure can be further increased.
[0023]
【The invention's effect】
As described above, according to the present invention, the core thickness of the tool body is set to 40% or more of the outer diameter of the cutting edge, and the total area of the coolant holes in the cross section orthogonal to the tool axis is set to 5 of the cross sectional area of the machining hole. By setting it as large as ˜30%, it is possible to increase the coolant supply amount and supply pressure, and to efficiently cool and lubricate the cutting blade and the cutting site. Therefore, even in the drilling of brittle materials where heat of processing tends to be trapped, it is possible to reliably prevent high-precision drilling by preventing wear of the cutting edge, deterioration of machining accuracy, or increase in cutting resistance. Can be performed.
[Brief description of the drawings]
FIG. 1 is a side view showing a first embodiment of the present invention.
FIG. 2 is an enlarged front view showing a front end surface of the embodiment shown in FIG. 1;
3 is a ZZ cross-sectional view in FIG. 1. FIG.
FIG. 4 is an enlarged front view showing a second embodiment of the present invention.
FIG. 5 is a side view showing a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tool body 5 Cutting edge 6 Rake face 7 Flank 10 Chip discharge groove 11 Coolant hole O Axis line T of tool body 1 Tool rotation direction D Outer diameter C of cutting edge 5 Center thickness circle E of tool body 1 Center of tool body 1 Thickness d Inner diameter of coolant hole 11

Claims (4)

A cutting edge that extends from the inner peripheral side of the tool to the outer periphery of the front end surface is formed on the front end surface of the substantially cylindrical tool body that rotates about the axis, and a coolant hole that is drilled from the rear end side of the tool main body. The center thickness of the tool body is set to 40% or more with respect to the outer diameter of the cutting blade, while the total area of the coolant holes in the cross section perpendicular to the axis is determined by the cutting blade. Set in a range of 5 to 30% of the cross-sectional area of the machining hole to be formed , and further on the outer periphery of the tip of the tool body is formed a chip discharge groove that twists around the axis, the coolant hole, A drilling tool with a coolant hole, which is formed in a twisted hole shape having a lead different from that of the chip discharge groove .   The drilling tool with a coolant hole according to claim 1, wherein the hole is formed in a workpiece made of a brittle material by the cutting blade.   On the front end surface of the tool body, the rake face that is continuous in the tool rotation direction of the cutting blade is inclined so as to go to the tool rear end side toward the tool rotation direction side, and the negative cutting direction is applied to the cutting blade. 3. A drilling tool with a coolant hole according to claim 1, wherein a rake angle is provided, and the coolant hole is opened at least on the rake face.   4. A hole with a coolant hole according to claim 3, wherein a plurality of the coolant holes are formed in the tool body and are also opened on a flank face that continues to the rear of the cutting blade in the tool rotation direction. Dawn tool.

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