WO2011132686A1

WO2011132686A1 - Gun drill

Info

Publication number: WO2011132686A1
Application number: PCT/JP2011/059662
Authority: WO
Inventors: 公志西川; 賢傑崔
Original assignee: 株式会社タンガロイ
Priority date: 2010-04-19
Filing date: 2011-04-19
Publication date: 2011-10-27
Also published as: JP2013139059A

Abstract

Disclosed is a roughly rod-shaped gun drill (1) provided with a shank portion flow path (4a) which circulates a coolant internally, and a tip portion flow path (4b). On the tip of the gun drill (1) are formed a cutting surface (5), a first flank surface (6a), a second flank surface (6b), a cutting blade (7) and a coolant guide surface (8). A roughly circular first aperture (9a) (a coolant nozzle) is formed in the first flank surface (6a), and a second aperture (9b) (another coolant aperture) is formed spanning the first flank surface (6a) and the coolant guide surface (8), wherein the aperture area of the second aperture is greater than that of the aforementioned first aperture.

Description

Gun drill

The present invention relates to a single-blade gun drill in which a coolant flow passage is formed.

¡When drilling small-diameter deep holes, a gun drill is generally used, and a single-edged gun drill is often used among gun drills. Some single-blade gun drills have a flow passage formed therein so that coolant (cutting oil) supplied from the rear end portion is injected from the front end portion (see Patent Document 1). ). When the coolant is injected from the tip of the gun drill, the frictional force generated between the cutting edge and the hole bottom is reduced, and the cutting edge is also cooled. The coolant also has a function of discharging the generated chips out of the machining hole.

JP 2003-165010 A

Among the effects of the coolant as described above, the chip discharge effect depends on the coolant flow rate passing through the chip discharge groove formed on the side of the gun drill, and the higher the flow rate, the higher the discharge effect.

However, since the space formed between the inner wall of the machining hole and the chip discharge groove is very narrow and long, the pressure loss generated there is large. Therefore, it cannot be said that the current gun drill has sufficient chip discharge capability required for deep hole machining.
As a solution to this problem, a method of increasing the area of the coolant injection port has been attempted, but increasing the area of the injection port leads to a decrease in strength of the tip of the gun drill. It is difficult to secure a sufficient area.

The present invention has been developed in view of the above-described problems. An object of the present invention is to provide a gun drill in which the chip discharge capability is improved by increasing the flow rate of the coolant flowing in the chip discharge groove without reducing the strength of the tip.

In order to solve the above-described problem, the gun drill of the present invention has a flow path for the coolant flowing along the longitudinal direction inside the substantially rod-shaped gun drill having a rotation axis extending in the longitudinal direction. A chip discharge groove for discharging chips is formed on the outer peripheral surface of the gun drill along the longitudinal direction, and a rake face is formed along the longitudinal direction in the chip discharge groove, and the tip of the gun drill is formed. In a one-blade gun drill in which a flank is formed and a cutting edge is formed at the intersection of the flank and the rake face,
A coolant guide surface is formed at the tip of the gun drill, the coolant guide surface intersects the flank surface, and intersects one wall surface defining the chip discharge groove,
The opening on the front end side of the flow passage has first and second openings,
The first opening is formed in the flank;
The second opening is formed to extend from the flank to the coolant guide surface, and an opening area of the second opening is larger than an opening area of the first opening.

According to the gun drill of the present invention, since the flow rate of the coolant passing through the chip discharge groove is larger than that of the conventional gun drill, the chip discharge capability is high. Since the chips are smoothly discharged out of the machining hole, the drill does not bite the chips or the chips are less likely to damage the inner wall of the machining hole.

Also, according to the gun drill of the present invention, the coolant is more efficiently injected onto the cutting edge than the conventional gun drill, so that the cooling ability of the cutting edge is high.

Although the gun drill of the present invention has improved chip discharge capacity and cutting edge cooling capacity compared to the conventional technique, the decrease in strength at the tip is minimized, and general drilling is performed. It can handle enough.

FIG. 1 is a front view of the single blade gun drill of the present embodiment. 2A is a cross-sectional view taken along the line IIA-IIA in FIG. 2B is a cross-sectional view taken along the line IIB-IIB in FIG. 2C is a cross-sectional view taken along the line IIC-IIC in FIG. FIG. 3 is a side view of the gun drill of FIG. 1 as viewed from the front end side. FIG. 4 is an explanatory diagram for explaining an inclination angle of the coolant guide surface. Drawing 5A is an explanatory view showing the shape of the 1st opening in another embodiment. Drawing 5B is an explanatory view showing the shape of the 1st opening part in another embodiment. Drawing 5C is an explanatory view showing the shape of the 1st opening in another embodiment. Drawing 5D is an explanatory view showing the shape of the 1st opening in another embodiment. FIG. 6 is a diagram illustrating a connection state between the shank portion flow passage and the tip portion flow passage according to another embodiment. FIG. 7A is a front view of the first embodiment. FIG. 7B is a left side view illustrating the shape of the tip of the first embodiment. FIG. 8A is a front view of the second embodiment. FIG. 8B is a left side view illustrating the shape of the tip of the second embodiment. 9A is a front view of Comparative Example 1. FIG. 9B is a left side view showing the shape of the tip of Comparative Example 1. FIG. 10A is a front view of Comparative Example 2. FIG. FIG. 10B is a left side view showing the shape of the tip of Comparative Example 2. 11A is a front view of Comparative Example 3. FIG. FIG. 11B is a left side view showing the shape of the tip of Comparative Example 3.

FIG. 1 is a front view of the single blade gun drill of this embodiment. 2A to 2C are sectional views of the gun drill, and FIG. 3 is a side view of the gun drill as viewed from the tip side.

As shown in FIGS. 1 to 3, the gun drill 1 according to the present embodiment includes a driver 2, and the driver 2 is formed at the rear end of the gun drill 1. The driver 2 functions as a grip when the gun drill 1 is attached to the machine tool. The gun drill 1 is substantially rod-shaped and includes a shank portion 1A and a tip portion 1B attached to the tip of the shank portion 1A, and one V-shaped chip discharge groove 3 is formed on the outer peripheral surface thereof. The chip discharge groove 3 is linearly formed along the rotation axis CL from the tip of the gun drill 1 to the shank portion 1A. The generated chips are swept away by the coolant flowing in the chip discharge groove 3 and discharged out of the machining hole.

As shown in the cross-sectional view of FIG. 1, a flow passage for circulating coolant is formed inside the gun drill 1, and the flow passage is divided into two parts, a shank portion flow passage 4a and a tip portion flow passage 4b. It consists of
The shank portion flow passage 4a is a flow passage that extends to the inside of the driver 2 of the gun drill 1 and is connected to a coolant supply port (supply side opening) formed at an end portion on the side where the driver 2 is provided. It accounts for more than half of the entire road. In the present embodiment, the range indicated by S1 in FIG. 1 is a portion where the shank portion flow passage 4a is formed. As shown in FIG. 2B, the shank portion flow passage 4 a is formed almost entirely along the cross-sectional shape of the shank portion 1 </ b> A of the gun drill 1. In other words, the shank portion 1A has a tubular cross-sectional shape having a substantially constant wall thickness within the range indicated by S1 in FIG. In order to increase the coolant flow rate, it is preferable to make the shank portion flow passage 4a as large as possible as long as the torsional rigidity of the gun drill 1 is not excessively impaired.

The tip part flow passage 4 b is formed continuously with the shank part flow passage 4 a and is connected to a coolant injection port (injection side opening) formed at the tip of the gun drill 1. In the present embodiment, the tip portion flow passage 4b is formed in the range indicated by S2 in the gun drill 1. As shown in FIG. 2A, the tip portion flow passage 4b includes a first tip portion flow passage 4b1 connected to a substantially circular first opening (first injection port) and a second opening (curved in a substantially C shape). 2nd tip part flow path 4b2 connected to (2nd injection port). The first tip portion flow passage 4b1 and the second tip portion flow passage 4b2 are formed so as to extend substantially in parallel along the rotation axis of the gun drill 1 without intersecting each other.

As shown in FIG. 2, a rake face 5, a flank face 6, a cutting edge 7, and a coolant guide face 8 are formed at the tip of the gun drill 1. In the gun drill 1 of the present embodiment, the vicinity of the end of one groove wall of the chip discharge groove 3 functions as the rake face 5, and the generated chip is rounded by the rake face 5 and cut at an appropriate length. The

The flank 6 is composed of a first flank 6a and a second flank 6b, and a cutting edge 7 is formed at the intersection ridgeline between the flank and the rake face 5. In particular, the cutting edge formed at the intersecting ridge line portion between the first flank 6a and the rake face 5 functions as a central edge 7a for cutting the center portion of the machining hole, and the second flank 6b and the rake face 5 The cutting edge formed in the intersecting ridge line portion functions as an outer peripheral blade 7b that cuts the outer peripheral side of the machining hole.

As shown in FIG. 1, the first flank 6a intersects the second flank 6b at an obtuse angle, and its intersection IS_1 becomes the most distal end of the gun drill 1, and the rear end of the gun drill 1 increases as the distance from the intersection IS_1 increases. Inclined to the side. Further, the intersecting portion IS_1 is also inclined to the rear end side of the gun drill 1 with the intersection IS_2 between the center blade 7a and the outer peripheral blade 7b as a vertex. In other words, this will be described with reference to FIG. 3. The intersection IS_1 is inclined so as to go to the back side of the drawing as it is away from the intersection IS_2. Further, the first flank 6a is inclined so as to go to the back side of the paper as it gets away from the intersection IS_1 with the second flank 6b. By forming the first flank 6a in this way, a space is secured between the machining hole bottom and the first flank 6a during machining. Similar to the first flank 6a, the second flank 6b is also inclined so as to go to the back side of the page as the distance from the intersection IS_1 with the first flank 6a increases. Further, the intersection IS_1 between the first flank 6a and the second flank 6b is formed at a position deviated from the rotation axis CL of the gun drill 1. Therefore, the center blade 7a and the outer peripheral blade 7b intersect at an obtuse angle, and these intersections IS_2 are also necessarily located at a position deviated from the rotation axis CL of the gun drill 1.

The coolant guide surface 8 intersects the flank 6a at an obtuse angle, and also intersects the wall surface 5b of the chip discharge groove 3 that does not function as the rake surface 5. In other words, the coolant guide surface 8 is inclined so as to go to the back side of the paper surface as the distance from the intersection IS_3 with the flank 6a increases. In the present embodiment, the coolant guide surface 8 is a flat surface.

Chamfering is applied to the edge of the tip of the gun drill 1. By chamfering the edge, the portion is difficult to chip.

As shown in FIG. 3, the first opening 9 a is formed in a substantially circular shape and is formed in the flank 6, and in the direction of rotation of the gun drill about the rotation axis CL, the first opening 9 a is It is formed in front of the second opening 9b. The 1st opening part 9a is arrange | positioned in the position which can ensure distance as much as possible with the 2nd opening part 9b mentioned later. Preferably, the first opening 9a is a plane in contact with the outer end of the outer peripheral blade 7b (a plane perpendicular to a straight line passing through the rotation axis CL and the outer end of the outer peripheral blade 7b) G in the flank 6; These are formed only in a region parallel to the plane G and between the plane F including the rotation axis CL. The 1st opening part 9a is arrange | positioned in the position which can ensure distance as much as possible with the 2nd opening part 9b mentioned later. In addition, you may form in any position in the flank 6 if the distance between the 1st opening part 9a and the 2nd opening part 9b can be ensured.

The shape of the second opening 9b is such that the second opening 9b extends along the circumferential direction around the rotation axis CL, and has an inner diameter side that is a concave curved curve toward the outer circumference. This part is composed of a curved curve. That is, when a circle with a predetermined diameter is moved in the circumferential direction along a circle with a predetermined radius centered on the rotation axis CL, it substantially coincides with the locus drawn by the circle with the predetermined diameter. The second opening 9b is formed across the first flank 6a and the coolant guide surface 8, and does not extend to the cutting edge 7 side of the virtual plane F. The opening area of the second opening 9b is larger than the opening area of the first opening 9b. Thereby, the flow rate of the coolant flowing out from the coolant guide surface is increased, and the cooling effect on the front side of the cutting edge that is likely to increase in temperature is enhanced.

FIG. 2C is a sectional view taken along the line IIC-IIC in FIG. As shown in FIG. 2C, in the gun drill 1 of this embodiment, the shank portion flow passage 4a and the tip portion flow passage 4b are on the supply port side of the tip portion flow passages 4b1 and 4b2 when viewed from the direction of the rotation axis CL. Are in a positional relationship in which they are respectively included inside the outline of the opening on the injection port side of the shank portion flow passage 4a. When the shank portion flow passage 4a and the tip portion flow passage 4b are designed in such a positional relationship, the pressure loss generated when the coolant moves from the shank portion flow passage 4a to the tip portion flow passage 4b is minimized. Can be suppressed.

In the gun drill 1 of the present embodiment, a part of the second opening 9b extends from the first flank 6a to the coolant guide surface 8, so that the energy loss of the coolant flowing through the chip discharge groove 3 is minimized. become. That is, in the conventional gun drill, the coolant injected from the injection port once collides with the bottom of the machining hole and then flows into the chip discharge groove. Therefore, when the coolant collided with the bottom of the machining hole, a part of the energy that the coolant had was lost, and as a result, the flow rate of the coolant passing through the chip discharge groove was reduced.

On the other hand, in the gun drill 1 of this embodiment, since the opening (injection port) is formed also in the coolant guide surface 8, the coolant injected from there once collides with the hole bottom of the machining hole. Although there is no change until now, a large space near the coolant guide surface 8 is secured, so that a large amount of coolant is guided to the chip discharge groove 3 with minimal energy loss. Therefore, the coolant flows through the chip discharge groove 3 at a larger flow rate than in the past.

Furthermore, the cooling effect of the coolant is enhanced by forming a part of the second opening 9b to extend to the coolant guide surface 8. That is, in the case of the conventional injection method, when passing through a narrow space, the coolant receives heat from the bottom of the processing hole where the coolant has become hot, and the coolant temperature has already risen before the cutting edge is cooled. However, in the gun drill 1 of the present embodiment, a large amount of coolant injected from the second opening 9b formed in the coolant guide surface 8 into a wide space is applied to the cutting edge 7 from the chip discharge groove 3 side. Therefore, the temperature rise of the coolant is suppressed and the cooling effect of the coolant is enhanced. Further, considering the relative rotation direction with respect to the machining hole of the gun drill 1, the second opening 9 b formed in the coolant guide surface 8 is located closest to the cutting edge 7 in the forward direction of the cutting edge 7. Accordingly, the amount of coolant directly applied to the rake face 5 is increased, and the cooling effect of the cutting edge 7 is increased. Furthermore, the second opening 9b formed in the coolant guide surface 8 is positioned farther from the machining hole bottom than the conventional gun drill, and the coolant guide surface 8 is open toward the chip discharge groove 3. Therefore, the rake face that rotates before the sprayed coolant reaches the bottom of the machining hole can move to the coolant arrival point, and the frequency at which the coolant directly collides with the rake face 5 is greatly increased. For this reason, the gun drill 1 of the present embodiment has a higher cooling effect than the conventional gun drill.

Further, since the first opening 9a is formed in the first flank 6a, the coolant sprayed from here is from the side opposite to the second opening 9b across the cutting edge 7, that is, the flank 6 side. To the cutting edge 7 directly.

As described above, the coolant is applied in a large amount to the cutting edge 7 from two different directions, so that the temperature of the cutting edge 7 of the gun drill 1 of the present embodiment is less likely to rise than the conventional gun drill.

The second opening 9b is formed close to the coolant guide surface 8 side, and the first opening 9a is formed only in the flank 6 so that the space between the second opening 9b and the first opening 9a is increased. A sufficient wall thickness can be secured. Thus, the gun drill 1 can have a rigidity that is applicable to cutting under normal cutting conditions.

FIG. 4 is an explanatory diagram for explaining the inclination angle of the coolant guide surface. As shown in FIG. 4, when the coolant guide surface 8 is viewed in parallel to the center blade 7a, that is, the center blade 7a, it is 30 ° or more and 45 ° or less with respect to the straight line F1 orthogonal to the rotation axis CL. It is preferable to be formed so as to intersect within a range. That is, when the angle θ in FIG. 4 is 30 ° or more and 45 ° or less, the coolant is more effectively guided to the chip discharge groove 3.

The gun drill of the present invention includes not only the above-described embodiment but also various other ones. For example, as shown in FIGS. 5A to 5D, the first opening has a triangular shape (see FIG. 5A), a substantially triangular shape with rounded corners (see FIG. 5B), a semicircle (see FIG. 5C), and an arcuate shape (see FIG. 5D). ) Etc. are possible. That is, as long as it is formed only in the flank 6, the first opening 9 a may have any shape. Naturally, the flow rate of the coolant increases as the area of the first opening 9a increases. The shape of the 1st opening part 9a is adjusted so that the coolant which injected and turned up at the hole bottom of the processing hole may reach the cutting blade 7 in a larger amount.

As another embodiment, when viewed from the direction of the rotation axis CL, a part of the tip portion flow passage 4b can be formed to protrude outside the shank portion flow passage 4a. That is, as shown in FIG. 6, it is also possible to connect the tip part flow passages 4b1 and 4b2 so that a part of the opening part protrudes outside the opening part of the shank part flow passage 4a. In this case, as a matter of course, part of the

openings

9a and 9b is formed so as to protrude from the extended line of the shank portion flow passage 4a. However, in this case, the coolant flow rate is increased as compared with the conventional single-blade gun drill, but the coolant flow rate is decreased as compared with the above-described embodiment. However, by shifting the tip portion flow passage 4b toward the outer peripheral side with respect to the shank portion flow passage 4a, the coolant is effectively injected toward the outer peripheral side of the gun drill having a higher cutting speed. As a result, the cooling effect of the outer peripheral blade that tends to become high temperature is enhanced.

In the present embodiment, the first flank 6a is a plane, but it may be formed as two intersecting planes or curved surfaces. That is, for example, on the side opposite to the cutting edge 7 of the virtual plane F, a larger space between the first flank 6a and the machining hole bottom may be secured. Moreover, in the said embodiment, although the center blade 7a and the outer periphery blade 7b crossed the obtuse angle, you may make it cross | intersect an acute angle.

Next, the results of a comparative experiment between the gun drill of the example of the present invention and the gun drill of the comparative example are shown below. The shapes of the example and the comparative example are shown in FIGS. 7A to 11B. In addition, although the comparative example is based on a prior art, in order to confirm the effect of the structure of this invention, it compared with the comparative product which does not belong to a part of prior art. Specifically, Comparative Example 1 and the like in FIGS. 9A and 9B are not related art but are devised products close to the present invention, but are comparative examples outside the scope of the present invention. In Example 2, when viewed from the direction of the rotation axis CL, the edge portion of the tip portion flow passage is formed to protrude outside the shank portion flow passage. In Comparative Example 1, the opening 109a formed across the first flank 6a and the coolant guide surface 8 is formed in a circular shape instead of a curved shape as in the first embodiment. Further, the size of the opening 109b is smaller than the size of the opening 109a. In Comparative Example 2, a single opening 110 having a larger area than the second opening 9b of Example 1 and extending in the circumferential direction is formed only in the first flank 6a. . In Comparative Example 3, the second opening 9b having the same shape as that of Example 1 is formed in the same region as that of Example 1. However, the circular opening having the same shape as the first opening 9a of Example 1 is used. 111 is formed across both of the regions of the first flank 6 a divided into two by the virtual plane F.

The specifications from Example 1 to Comparative Example 3 are shown below.
(Omoto)
Example 1 (see FIGS. 7A and B): Diameter 6 mm
Coolant supply pressure 5 MPa
Area of the first opening 0.665mm ²
Area of second opening 2.015mm ²
Length from the front end to the rear end 200mm
Material Cemented carbide

Example 2 (see FIGS. 8A and 8B): Diameter 6 mm
Coolant supply pressure 5 MPa
Area of the first opening 0.665mm ²
Area of second opening 2.015mm ²
Length from the front end to the rear end 200mm
Material Cemented carbide

Comparative Example 1 (see FIGS. 9A and 9B): Diameter 6 mm
Coolant supply pressure 5 MPa
Total area of the opening (total of the two) 2.27mm ²
Length from the front end to the rear end 200mm
Material Cemented carbide

Comparative Example 2 (see FIGS. 10A and 10B): Diameter 6 mm
Coolant supply pressure 5 MPa
Area of opening 2.934 mm ²
Length from the front end to the rear end 200mm
Material Cemented carbide

Comparative Example 3 (see FIGS. 11A and 11B): Diameter 6 mm
Coolant supply pressure 5 MPa
Area of the first opening 0.665mm ²
Area of second opening 2.015mm ²
Length from the front end to the rear end 200mm
Material Cemented carbide

(Experiment regarding flow rate)
Each gun drill is inserted into a vertically open hole having a hole diameter of 6.05 mm and a depth of 100 mm, and then coolant is supplied to each single-blade gun drill. Supply the coolant for 5 minutes and measure the amount of coolant that has overflowed from the holes during that time. The flow rate is calculated by dividing the measured coolant amount by the coolant supply time. This experiment was repeated 5 times, and the average value was listed in Table 1.

(Experiment on torsional rigidity)
The value of the maximum principal stress generated when a torque of 1 N / m was applied while fixing a position 30 mm from the tip of each gun drill was calculated by computer analysis.
In order to calculate the ratio of the torsional rigidity of another one-blade gun drill to the torsional rigidity of Example 1 from the calculated maximum main stress, the maximum main stress of Example 1 and the maximum main stress of Example 2 are compared The results are shown in Table 1.

(Experiment on cutting edge temperature)
Using each single-blade gun drill, a hole having a depth of 100 mm is machined into a S45C cubic block at a cutting speed of 120 m / min, and the temperature of the cutting edge after the machining is measured. This experiment was performed 5 times, and the average value was listed in Table 1.

As shown in Table 1, when Example 1 and Comparative Example 1 are compared, the area of the opening of Comparative Example 1 is 85% of Example 1, whereas the flow rate is 79% of Example 1. It has become. This indicates that the injection performance of the coolant of Example 1 has improved beyond the degree of increase in flow rate due to a simple increase in the opening area.

Further, when Example 1 is compared with Comparative Example 2, the flow rate of Comparative Example 1 is only 84% of Example 1 although the area of the opening is about 9% larger than Example 1. ing. In the first embodiment, this means that a part of the second opening is formed on the coolant guide surface, and the formation of the first opening on the first flank produces a synergistic effect and the injection performance. It shows that improve.

Regarding each single-blade gun drill cutting edge temperature, as shown in Table 1, the temperature of the cutting edge of Example 1 was the lowest, indicating the high cooling performance of Example 1.

The torsional rigidity of Example 1 is slightly larger than that of Comparative Example 1 and smaller than that of Comparative Example 2. However, the torsional rigidity of Example 1 is larger than that of Comparative Example 1 having a torsional rigidity having a practically no problem. Has been shown to have a sufficient size.

DESCRIPTION OF SYMBOLS 1 ... Gun drill 2 ... Driver 3 ... Chip discharge groove 4a ... Shank part flow path 4b ... Tip part flow path 4b1 ... First tip part flow path 4b2 ... Second tip part flow path 5 ... Rake face 6 ... Flank 6a ... 1st flank 6b ... 2nd flank 7 ... Cutting edge 7a ... Center blade 7b ... Outer peripheral blade 8 ... Coolant guide surface 9a ... 1st opening part 9b ... 2nd opening part

Claims

Inside the substantially rod-shaped gun drill having a rotation axis extending in the longitudinal direction, a flow passage for circulating coolant is formed along the longitudinal direction, and a cut for discharging chips on the outer peripheral surface of the gun drill. A chip discharge groove is formed along the longitudinal direction, a rake face is formed along the longitudinal direction in the chip discharge groove, a flank face is formed at the tip of the gun drill, the flank face and the rake face, In a one-blade gun drill with a cutting edge formed at the intersection of
A coolant guide surface is formed at the tip of the gun drill, the coolant guide surface intersects the flank surface, and intersects one wall surface defining the chip discharge groove,
The opening on the front end side of the flow passage has first and second openings,
The first opening is formed in the flank;
The gun drill, wherein the second opening is formed across the flank and the coolant guide surface, and an opening area of the second opening is larger than an opening area of the first opening.
The gun drill according to claim 1, wherein the second opening extends in a circumferential direction about the rotation axis.
The cutting edge has a center edge and an outer peripheral edge,
The central blade and the outer peripheral blade intersect with each other at an angle smaller than 180 °, and the intersection is located at a location deviating from the rotation axis,
The coolant guide surface is formed so as to intersect with a straight line orthogonal to the rotation axis in a range of 30 ° to 45 ° when the coolant guide surface is viewed from a direction parallel to the central blade. The gun drill according to claim 1 or 2, wherein
The flow passage has a shank portion flow passage that communicates with the opening on the supply side, and a tip portion flow passage that is formed continuously with the shank portion flow passage and communicates with the opening on the injection side.
The tip portion flow passage has a first tip portion flow passage that communicates with the first opening, and a second tip portion flow passage that communicates with the second opening,
The gun drill according to any one of claims 1 to 3, wherein the first tip portion flow passage and the second tip portion flow passage are formed apart from each other.
Of the openings of the first tip portion flow passage, the opening communicating with the shank portion flow passage is included in the outline of the opening of the shank portion flow passage when viewed from the rotational axis direction. Formed,
Of the openings of the second tip portion flow passage, the opening communicating with the shank portion flow passage is included within the outline of the opening of the shank portion flow passage when viewed from the rotational axis direction. The gun drill according to claim 4, wherein the gun drill is formed.
The second tip portion flow passage is disposed so that a part of the opening portion of the first tip portion flow passage projects toward the outer peripheral side of the opening portion of the shank portion passage passage when viewed from the rotation axis direction. 6. The gun drill according to claim 4, wherein a part of the opening is disposed so as to protrude to the outer peripheral side of the opening of the shank portion flow passage.