JPH11293303A - Manufacture of drill with hole and drill with hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cemented carbine-made drill with hole which can surely a cutting oil solution even in the case the hole has small diameter, by surely forming a press formed body of the drill with hole, in which particularly the internal diameter of a twisted hole is extremely small diameter, by an extrusion press formation. SOLUTION: Raw material to be pressed obtd. by kneading the cemented carbide raw material and petroleum-based wax in a kneading device 2 is extruded and press-formed with a screw 9 for extruding through a mold 11 provided with a spiral pin 13 in an extrusion press device 4 provided with a jacket part 8 where warm water and cold water are supplied while controlling the temp. of the raw materials so that the temp. difference from the m.p. of the petroleum wax becomes in the range of 20-30 deg.C, to form the press formed body, in which the twisted hole is formed. In this way, the cemented carbide-made drill with the twisted hole having <=0.5 mm internal diameter formed on the inside, is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill having a cutting edge made of cemented carbide having a small outer diameter of a cutting edge and having a torsion hole formed therein as a supply path for a cutting oil or the like. The present invention relates to a manufacturing method and a drill with holes.

[0002]

2. Description of the Related Art In this type of drill, a so-called twist drill is generally well known, in which a spiral groove for discharging chips is formed on the outer periphery of a cylindrical drill body having a cutting edge formed at the tip. Further, among such twist drills, there is known a drill with a hole in which a torsion hole serving as a supply path for a cutting fluid or the like is formed so as to be twisted along the spiral groove. Here, when manufacturing a drill with a hole having such a twisted hole, when the drill is formed from a steel material or the like, a straight hole parallel to the central axis of a cylindrical material serving as the material of the drill is formed. A method is employed in which the hole is formed into a twisted hole by twisting the hole around the center axis in a hot state or the like, but the drill is manufactured by powder metallurgy such as cemented carbide. , Such a method cannot be adopted.

Therefore, as a method of manufacturing a drill with a hole made of cemented carbide having such a twisted hole, for example, Japanese Patent Application Laid-Open Nos. 54-159791 and 63-109 are disclosed.
No. 908 or Japanese Unexamined Patent Publication (Kokai) No. 2-34702 is provided with a pin for spirally twisting a press raw material obtained by adding a plasticizer for imparting fluidity to a raw material powder to be a raw material of a cemented carbide and kneading it. By extruding and pressing while rotating through the core, a cylindrical press-formed body with a twisted hole formed inside is formed, and by firing this press-formed body, a drill with a hole having a twisted hole is manufactured. A way to do that has been proposed.

[0004]

In the case where a pressed material is extruded and press-formed to form a press-formed body, the outer diameter of the cutting edge of the drill to be manufactured is small, for example, 3 mm or less. When the inner diameter of the torsion hole formed in the above has to be reduced to, for example, 0.5 mm or less, the outer diameter of the press-formed body and the inner diameter of the torsion hole formed in the press-formed body must also be reduced. . And with this, the inner diameter of the mold, which determines the outer diameter of the press-formed body, also becomes smaller, so even if a plasticizer is added to the cemented carbide raw material to give fluidity, the pressed raw material is clogged due to clogging It is hard to be pushed out from
Unless a high press pressure is applied, the press-formed body will not be extruded from the mold.

However, the outer diameter of the cutting blade is small,
In the case of manufacturing a drill with a hole in which the inner diameter of the torsion hole is 0.5 mm or less, the above-mentioned pin provided on the core for forming the torsion hole in the press-formed body is also usually ultrafine having a diameter of 0.6 mm or less. Inevitably, when such a high press pressure is applied to a mold having such a fine pin provided in the core, there arises a problem that the pin is broken or deformed. On the other hand, by increasing the amount of plasticizer added to the cemented carbide raw material, the fluidity of the press raw material was increased,
If the press-formed body is to be easily extruded from the mold, the shape of the extruded press-formed body is impaired and deformed, so that it becomes impossible to fire a desired drill.

The present invention has been made under such a background. In a method of manufacturing a drill having a hole for forming a press-formed body from a press raw material by the above-described extrusion press, particularly, the inner diameter of the twisted hole is extremely small. Provided is a method for manufacturing a drill with a hole, which can surely form a press-formed body of a drill with a hole having a small diameter by extrusion press molding, and can reliably supply a cutting oil or the like even with a small diameter. The aim is to provide a possible drill with a hard metal.

[0007]

Means for Solving the Problems In order to solve the above problems and achieve such an object, the inventor of the present invention provides a plasticizer to be added to a cemented carbide material in an extruded press material. When a petroleum-based wax was employed, attention was paid to the fact that the plasticity of the press raw material changes by heating or cooling the press raw material and controlling the temperature. An experiment was conducted by changing the temperature of the press raw material in the extrusion press in various ways. As a result, the temperature difference of the press raw material with respect to the melting point of the petroleum wax added as a plasticizer was 20 ° C. to 30 ° C. By controlling to the range, it is possible to form a press-formed body of a drill with a hole in which the inner diameter of the torsion hole as described above is a very small diameter by extrusion press forming without causing clogging of the mold. I got it.

Thus, the present invention is based on such findings and is directed to a method for manufacturing a drill with a hole made of cemented carbide having a torsion hole formed therein. By extruding the kneaded press material through a mold having a helical pin while controlling the temperature so that the temperature difference with respect to the melting point temperature of the petroleum wax is in the range of 20 ° C. to 30 ° C., and press-molding. And a press-formed body having a twisted hole formed therein. Therefore, according to the method for manufacturing a drill with a hole having such a configuration, as the outer diameter of the cutting edge becomes smaller in the drill with a hole, the inner diameter of the torsion hole also becomes a very small diameter. Even if the diameter of the pin to be formed has to be extremely fine, by controlling the temperature of the press raw material as described above, optimal press plasticity is given to the press raw material and the press molded body is reliably extruded and pressed. It is possible to do. That is, if the temperature difference is greater than 30 ° C., the plasticity given to the press raw material becomes too small, and the press raw material is clogged unless high press pressure is applied during extrusion press molding. On the other hand, when the temperature difference is less than 20 ° C., the plasticity of the press raw material becomes too large, and the shape retention of the press-formed body is impaired.

Here, in the manufacturing method having the above structure,
The pressing pressure at the time of press-extruded the press material, it is desirable to control the range of ^{80kg / cm 2 ~150kg / cm 2} . That is, if the press pressure is so large as to exceed 150 kg / cm ² , an excessive load may act on the core pin for forming the torsion hole, and the pin may be broken or deformed. If the pressing pressure is lower than 80 kg / cm ² , it is difficult to control the extrusion speed and the rotation speed of the press-formed body, and there is a possibility that the leads of the twisted holes may vary. Further, in order to facilitate the temperature control at the time of the extrusion press of the press material, the temperature at the time of kneading the cemented carbide material and the petroleum-based wax is also the same as that at the time of the extrusion press. Is desirably controlled so that the temperature difference with respect to the melting point temperature of D.C. On the other hand, the drill with a hole of the present invention is a drill with a cemented carbide in which a torsion hole is formed inside which can be manufactured by such a manufacturing method, and the inner diameter of the torsion hole is 0.5 mm. It is characterized in that, even if the outer diameter of the cutting blade is small, the cutting oil can be supplied through the twisted hole, and it is possible to achieve smooth drilling. Become.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows an extrusion press forming machine for a press formed body according to the present embodiment.
The kneading device 2, the vacuum degassing chamber 3, and the extrusion press device 4 are arranged in this order. The kneading device 2 has a double-tubular jacket portion 5 arranged such that one end is opened at the lower end of the raw material inlet 1 and is slightly inclined downward toward the other end (the right side in FIG. 1). A kneading screw 6 that is rotated by a driving device (not shown) is inserted therein, and the other end of the jacket portion 5 is opened at an upper portion of the vacuum deaeration chamber 3.

The vacuum deaeration chamber 3 is disposed so as to extend vertically and is maintained in a negative pressure state by a vacuum suction device (not shown). A pair of feed screws 7 that are rotated by a driving device (not shown) are provided in the vacuum degassing chamber 3, and the press raw material supplied from the kneading device 2 is quantitatively extruded. 4 can be supplied. Further, similarly to the kneading apparatus 2, the extrusion press apparatus 4 has one end opened to the lower end of the vacuum degassing chamber 3 and the other end side (the right side in FIG. 1).
A push screw 9 which is also rotated by a driving device (not shown) is inserted into a double tubular cylindrical jacket portion 8 arranged so as to be inclined downward toward In the molding machine, the inclination angle at which the jacket 8 descends is variable.

In addition, the other end of the jacket portion 8 in the extrusion press device 4 is provided with a mold having an inner diameter corresponding to the outer diameter of the press-formed body to be formed on the inner peripheral portion of the jacket portion 10 having a double tubular shape. A holder 12 on which an 11 is formed is attached. Further, the mold 11 includes:
At the center thereof, a core 14 having a pair of pins 13, 13 made of synthetic fiber or metal, which is twisted in a spiral shape to form a twisted hole inside the press-formed body, is attached. On the inner peripheral surface of the mold 11, a number of spiral grooves 15 are formed for rotating and extruding the press-formed body in accordance with the twist of the twisted hole formed by the pins 13. Here, in the extrusion press molding machine, the inner diameter of the mold 11 is set such that the outer diameter of the cutting edge is 3 mm or less in a drill formed by sintering a press-formed body formed by extrusion press molding. The torsion angles of the pins 13, 13 and the grooves 15 are further set so that the torsion angle (lead angle) of the torsion hole of the fired drill is 30 ° or less.
Is set so that the inner diameter of the twist hole of the drill is 0.5 mm or less.

The kneading device 2, the extruding press device 4, and the respective jacket portions 5, 8,
Hot water or cold water for temperature control, each controlled to a predetermined temperature, is supplied and circulated between the double pipes formed by 10, whereby the cemented carbide held in the kneading device 2 The temperature of the raw material and the petroleum wax as a plasticizer, the press raw material held in the extrusion press device 4, and the temperature of the press molded body extruded from the holder 12 are as follows.
The temperature is maintained and controlled at a predetermined temperature. The press-formed body extruded from the holder 12 is automatically cut to a predetermined length and aligned.

Next, an embodiment of the production method of the present invention using such an extrusion press molding machine will be described. In the present embodiment, first, WC powder as a cemented carbide material, Co and other additives as a binder, and a petroleum-based wax as a plasticizer are charged at a predetermined ratio from a raw material inlet 1. While being kept at a predetermined temperature by the hot and cold water supplied to the jacket portion 5 in the kneading device 2, the mixture is stirred by the kneading screw 6 to be uniformly kneaded, and is sent out to the other end side of the jacket portion 5 as a press material. Here, the ratio of the cemented carbide raw material and the petroleum wax to be charged is 100: 2 to 10 by weight.
It is desirable to set about 0: 4. The temperature difference between the melting point of the petroleum-based wax and the cemented carbide material and the petroleum-based wax kneaded in the kneading device 2 is in the range of 20 ° C. to 30 ° C. due to the hot / cold water supplied to the jacket portion 5. Is controlled so that

The press material obtained by kneading the cemented carbide material and the petroleum-based wax in this way is introduced into the vacuum deaeration chamber 3 from the other end of the jacket portion 5 of the kneading device 2, and the air contained during kneading is removed. After the volatile components are degassed in vacuum, they are quantitatively supplied to the extrusion press device 4 by the feed screw 7. The press raw material supplied to the extrusion press device 4 is heated and cooled by the hot / cold water supplied to the jacket portion 8 and has a temperature difference of 20 ° C. to 30 ° C. with respect to the melting point temperature of the petroleum-based wax. While the temperature is controlled so as to be within the range of ° C., it is extruded to the other end by the extruding screw 9 and extruded from the mold 11 of the holder 12 attached to the other end.

At this time, the press material is given appropriate plasticity by controlling the temperature in the extrusion press device 4 as described above.
The temperature is controlled in the same way by hot and cold water supplied to 0, so that extrusion press molding is performed while maintaining this plasticity. In addition, the press pressure at the time of this extrusion press molding adjusts the supply amount of the press raw material by the feed screw 7 from the vacuum degassing chamber 3 to the extrusion press device 4 and the extrusion speed by the extrusion screw 9 of the extrusion press device 4. By doing so, in this embodiment, 80 kg
/ cm ^{2 to} 150 kg / cm ² .

Further, at the time of the extrusion press molding, the press molded body extruded from the mold 11 is formed by the spiral groove 15 formed on the inner peripheral surface of the mold 11.
The groove 15 is extruded while being rotated so as to be twisted in the spiral direction. Further, as shown in FIGS. 2 and 3, a large number of spiral ridges 22 are formed on the outer periphery of the press-formed body 21 thus extruded and pressed by the grooves 15 of the mold 11. A pair of torsion holes 23, 23 are formed in the inside thereof by means of the twisted pins 13, 13 of the core 14 attached to the mold 11, axisymmetrically with respect to the center axis of the press-formed body 21. .

The press-formed body 21 is cut into a predetermined length as described above, aligned, then degreased, formed into a predetermined shape, and further fired at a high temperature in a sintering furnace. Then, after the ridges 22 on the outer circumference are cut off, as shown in FIGS. 4 and 5, a pair of chip discharge grooves 24, 24 are formed on the cut off outer circumference in the circumferential direction with the twist holes. The chips 23 are formed so as to be spirally twisted, and the cutting edges 25 are sharpened at the tips of the chip discharge grooves 24, 24, and the shank portions 26 are appropriately provided at the rear ends thereof. It is used as a drill 27. Thus, the drill with hole 27 manufactured in this manner forms an embodiment of the drill with hole of the present invention, that is, the inner diameter d of the torsion hole 23 is 0.5.
mm or less, the outer diameter D of the cutting blade 25 is a small diameter of 3 mm or less, and the torsion angle of the torsion hole 23 and the chip discharge grooves 24 and 24 is 30 ° or less.

However, according to the method for manufacturing a drill with a hole having such a configuration, when a press material obtained by kneading a cemented carbide material and a petroleum-based wax as a plasticizer is extruded and press-formed, the press material is made of petroleum. Since the temperature is controlled so that the temperature difference is in the range of 20 ° C. to 30 ° C. with respect to the melting point of the system wax, appropriate plasticity can be given to the press raw material immediately before being extruded from the mold 11. Thus, even if the outer diameter of the cutting blade is small and the inner diameter of the mold 11 must be reduced accordingly, a high pressing force is required to prevent the press material from clogging the mold 11. By applying pressure, the pin 13 of the core 14 may break or deform,
Alternatively, it is possible to reliably extrude and press-press the desired press-formed body 21 by preventing the press-formed body 21 extruded and pressed from being deformed due to loss of shape retention. Becomes

Here, the temperature at the time of extruding and press-molding the press raw material in the above-mentioned production method is set so that the temperature difference with respect to the melting point of the petroleum wax added as a plasticizer is 2
The reason why the temperature is maintained in the range of 0 ° C. to 30 ° C. is that if the temperature of the press raw material increases as the temperature difference falls below 20 ° C., the plasticity of the press raw material becomes too large and the extrusion press forming is performed. This is because the shape retention of the body 21 is impaired, and the press-formed body 21 is deformed immediately after being extruded from the mold 11. On the other hand, when the temperature difference is 3
If the temperature of the press raw material is lower than 0 °, the plasticity of the press raw material is too low and the pin
3 may be damaged, or in some cases, extrusion press molding itself may not be possible.

In the present embodiment, the press pressure at the time of the extrusion press molding is 80 kg / cm ² to 15 kg as described above.
The pressure is set so as to be in the range of 0 kg / cm ² , whereby the press-formed body 21 having a predetermined shape can be formed more reliably. That is, this press pressure is 150kg
If it is larger than / cm ² , an excessive load acts on the pin 13 of the core 14 for forming the torsion hole 23 in the press-formed body 21, whereby the pin 13 may be broken or deformed. On the other hand, if the pressing pressure is lower than 80 kg / cm ² , when the pressed body 21 is extruded while being rotated by the spiral grooves 15 provided on the inner periphery of the mold 11 as described above, It is difficult to constantly control the rotation of the press-formed body 21 with respect to the extrusion speed of the body 21, and accordingly, the press-formed body 21
There is a possibility that the twist angles of the torsion holes 23, 23 formed in the hole may vary.

Further, in the present embodiment, the kneading device 2
In this case, the cemented carbide material and the petroleum-based wax supplied from the material supply port 1 are heated and cooled by the hot and cold water supplied to the jacket portion 5 so that the temperature difference with respect to the melting point of the petroleum-based wax is in the range of 20 ° C to 30 ° C. And are kneaded. Therefore, according to the present embodiment, the temperature of the press raw material supplied to the extrusion press device 4 is controlled in advance to a temperature to be held in the extrusion press device 4 or a temperature close to this. It is possible to more accurately and easily control the temperature of the press raw material in the extrusion press device 4 and to more reliably perform the extrusion press molding of the press molded body 21. In the extrusion press molding machine according to the present embodiment, the kneading device 2 and the extrusion press device 4 are integrally combined as described above, and the cemented carbide raw material and petroleum as a plasticizer are used. The process from kneading with the system wax to extrusion press molding is performed continuously. For example, the kneading device 2 and the extrusion press device 4 are separated, and the pre-kneaded press material is extruded and press-molded. You may do it.

On the other hand, according to the drill with holes 27 of the embodiment manufactured as described above, the inner diameter d of the torsion hole 23 is determined.
Is 0.5 mm or less, so that even if the outer diameter D of the cutting edge 25 is a small diameter cemented carbide drill having a diameter of 3 mm or less, the torsion holes 23 can be reliably formed. During drilling by the drill 27 with holes, a cutting oil or the like can be efficiently supplied to a cutting portion by the cutting blade 25 through the torsion holes 23, 23, and the drilling is stable and has little cutting resistance. It can be performed. In particular, reducing the cutting resistance during drilling by supplying the cutting oil or the like is effective for preventing breakage of the small-diameter drill as described above. Further, since the inner diameter d of the torsion holes 23 is suppressed to 0.5 mm or less as described above, even when the outer diameter D of the cutting blade 25 is small as in the above-described drill 27 with a hole, the torsion hole 2 is not required.
The effect of preventing the rigidity from being impaired by the formation of 3, 23 can be obtained, and the breakage and the like can be more reliably prevented.

In the method for manufacturing a drill with a hole according to the above embodiment and the drill with a hole 27 according to the above embodiment manufactured by the manufacturing method, the inner diameter of the torsion hole 23 of the drill with a hole 27 manufactured as described above. Although d is set to 0.5 mm or less, the minimum value is desirably set to 0.3 mm or more in view of the size of a diameter usable as the pin 13 of the core 14 and the like. On the other hand, in the manufacturing method and the drill with hole 27 of the present embodiment, the drill with hole 2
Although the outer diameter D of the cutting blade 25 is set to be a small diameter of 3 mm or less, the present invention is not limited by the outer diameter D of the cutting blade 25. For example, even with a drill having a cutting edge whose outer diameter exceeds 3 mm, in a case where particularly high rigidity is required, the drill with a hole of the present invention is applied by applying the manufacturing method of the present invention. It is also possible to manufacture. However, since the present invention is to solve the problem that occurs when manufacturing a small-diameter hole drill as described above, the small-diameter cutting edge 25 has an outer diameter D of 3 mm or less as in the above-described embodiment. It goes without saying that the present invention is effective when applied to the drill 27 having a hole and a manufacturing method for manufacturing the drill 27 having a hole.

[0025]

Next, the effects of the present invention will be specifically described with reference to examples of the present invention. In the present embodiment, an extruding press molding machine having the configuration shown in FIG. 1 was used, and the material of the cemented carbide and the melting point temperature were 50 ° C., 55 ° C., 63 ° C., 70 ° C.
Six types of petroleum waxes of 79 ° C. and 101 ° C. are supplied, and the temperature difference between the melting point temperature and the temperature of the press raw material in the extrusion press device for various petroleum waxes is in the range of 20 ° C. to 30 ° C. With such control, the formability of the extrusion press molding and the state of the formed press molded body were examined. Further, as a comparative example, the extrusion press formability and the state of the press-formed body were examined even when the temperature of the press raw material was outside the above range. The results are shown in Table 1 together with the press pressure during extrusion press molding for each petroleum wax.

However, in the experimental example and the comparative example, the inner diameter of the torsion hole was 0.35 mm and the outer diameter of the cutting edge was 2.
5 mm, and the twist angle of the chip discharge groove and the twist hole is 3 mm.
A press-formed body of a drill having a hole of 0 ° was formed, and the press pressure was controlled such that the extrusion speed of the press-formed body from the mold was 1.3 m / min. Also,
The ratio between the cemented carbide raw material and the petroleum wax fed from the raw material inlet is 100: 2.8 in weight ratio.
It was 5. Further, the inner diameter of the mold was 4.5 mm, and the core pin for forming a torsion hole in the press-formed body was made of nylon and had a diameter of 0.4 mm.

[0027]

[Table 1]

From the results shown in Table 1, first, in Comparative Examples 1, 2, 4, 6, and 8 in which the temperature difference between the melting point of the petroleum wax and the temperature of the press raw material was less than 20 ° C., the plasticity of the press raw material was too large. The press-formed body did not have sufficient shape-retaining property and was deformed immediately after extrusion, or the press pressure became too small, causing variations in leads of spiral grooves on the outer periphery of the press-formed body. On the other hand, in Comparative Examples 3, 5, 7, 9, and 10 in which the temperature difference was more than 30 ° C., the plasticity of the press raw material was too low, and the mold was clogged, and the extrusion press forming itself became impossible. Also,
Inspection of the core of the mold at this time revealed that the pins had been deformed or broken.

On the other hand, in Examples 1 to 10 in which the temperature difference with respect to the melting temperature of the petroleum wax was controlled within the range of 20 ° C. to 30 ° C., clogging occurred in the mold, and the moldability of the press-formed body was reduced. The desired press-formed body could be reliably obtained by favorable extrusion press-forming without damaging the steel. However, in Examples 1 and 3 in which the press pressure exceeds 150 kg / cm ² , the load acting on the core pin is large, and the pin is relatively early compared to the other examples. The end of life was reached.

[0030]

As described above, according to the present invention,
An extruding press is performed while controlling the temperature of a press raw material obtained by kneading a cemented carbide raw material and a petroleum-based wax as a plasticizer such that the temperature difference with respect to the melting point of the petroleum-based wax is in the range of 20 ° C to 30 ° C. By molding, even in the case of molding a press-formed body which is fired into a drill body having a small diameter and a twisted hole, the mold may be clogged or a pin for forming the twisted hole may be broken. ,
Alternatively, it is possible to prevent a situation in which the shape retention property of the press molded body is impaired and deformed immediately after the extrusion press, and it is possible to reliably manufacture such a small-diameter hole drill having a twisted hole. Becomes

[Brief description of the drawings]

FIG. 1 is a schematic view of an extrusion press forming machine according to an embodiment of a method for manufacturing a drill with holes of the present invention.

FIG. 2 is a partially broken side view of a press-formed body 21 formed by an embodiment of the method for manufacturing a drill with holes of the present invention.

FIG. 3 is a sectional view of the press-formed body 21 shown in FIG.

FIG. 4 is a partially cutaway side view showing a drill 27 with a hole according to an embodiment of the present invention.

FIG. 5 is a sectional view of the drill with hole 27 shown in FIG. 4;

[Description of Signs] 2 Kneading device 3 Vacuum deaeration chamber 4 Extrusion press device 5, 8, 10 Jacket section 6 Kneading screw 9 Extrusion screw 11 Mold 12 Holder 13 Pin 14 Core 15 Groove 21 Press formed body 23 Twisted hole 25 Cutting edge 27 Drill with hole

Claims (4)

[Claims] 1. A method for manufacturing a drill with a hole made of cemented carbide having a torsion hole formed therein, wherein a press material obtained by kneading a cemented carbide material and a petroleum-based wax is mixed with a melting point of the petroleum-based wax. By extruding and pressing through a mold having a helical pin while controlling the temperature so that the temperature difference with respect to the temperature is in the range of 20 ° C. to 30 ° C., a press-formed body having a twisted hole is formed. A method for manufacturing a drill with holes. 2. A press pressure at the time of press-molding extrusion the pressing material, and controlled in the range of 80kg / cm ² ~150kg / cm ² in claim 1, characterized in that molding the pressed bodies The method for producing a drill with a hole according to the description. 3. The temperature at which the cemented carbide material and the petroleum-based wax are kneaded is controlled so that the temperature difference from the melting point of the petroleum-based wax is in the range of 20 ° C. to 30 ° C. The method for manufacturing a drill with a hole according to claim 1 or 2, wherein 4. A drill with a hole made of cemented carbide having a twisted hole formed therein, wherein the inner diameter of the twisted hole is 0.5 mm or less.