JP2019171514A - Drill - Google Patents

Abstract

To provide a drill that can prevent a coolant hole that opens to a chip discharge groove from being clogged with chips.SOLUTION: The drill comprises: a drill main body 2 with a center shaft O that is rotated in a drill rotation direction T around the center shaft O; a chip discharge groove 8 arranged at an outer periphery of the drill main body 2 and extended from a tip toward a rear end side in a shaft direction; a coolant hole 10, extended through the drill main body 2, which opens to a groove wall of the chip discharge groove 8; and a guide surface 12 arranged between an inner peripheral surface of the coolant hole 10 and the groove wall. In a cross sectional view including an opening part 11 of the coolant hole 10, a distance between a center line C in a hole width of the coolant hole 10 and the guide surface 12 becomes larger as the surface approaches along the center line C in the hole width of the coolant hole toward the groove wall side, and the guide surface 12 is positioned inside in a drill radial direction of the opening part 11.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a drill capable of suppressing clogging of coolant into a coolant hole opened in a chip discharge groove.

  Conventionally, for example, a drilling tool disclosed in Patent Document 1 is known. In this drilling tool, a chip discharge groove is provided from the front end to the rear end of the tool main body, and an opening of the cutting oil supply hole is provided on a wall surface facing the direction opposite to the tool rotation direction of the chip discharge groove.

No. 6-7853

  Conventional drills have room for improvement in terms of suppressing chip clogging in the coolant holes that open in the chip discharge grooves.

  In view of the above circumstances, an object of the present invention is to provide a drill that can suppress clogging of coolant into a coolant hole that opens in a chip discharge groove.

  One aspect of the drill of the present invention includes a drill body having a center axis and rotated in a drill rotation direction around the center axis, and disposed on an outer periphery of the drill body, from an axial front end to a rear end side. A chip discharge groove extending toward the end, a coolant hole extending through the inside of the drill body and opening in a groove wall of the chip discharge groove, and a guide surface disposed between an inner peripheral surface of the coolant hole and the groove wall And in the cross-sectional view including the opening of the coolant hole, the guide surface is located along the hole width center line of the coolant hole and toward the groove wall side, and between the hole width center line and the guide surface. And the guide surface is located inside the opening in the drill radial direction.

According to one aspect of the drill of the present invention, even if chips flow from the outer side to the inner side in the radial direction of the drill with respect to the opening of the coolant hole that opens to the groove wall of the chip discharge groove, the chips are not generated. By being guided by the guide surface, being caught near the opening is suppressed. For this reason, it is suppressed that the chip | tip enters a coolant hole from an opening part, and clogging of the chip | tip of a coolant hole can be suppressed.
In addition, the “hole width center line” in the present specification refers to the center line in the width direction (hole width direction) of the opening of the coolant hole, which appears in a sectional view including the opening.

  The said drill WHEREIN: It is preferable that the said guide surface is located also in the axial direction rear end side among the said opening parts.

  In this case, the chips flowing toward the rear end side in the chip discharge groove are suppressed from being caught near the opening of the coolant hole. Therefore, clogging of the chips into the coolant hole can be further suppressed.

  In the drill, it is preferable that the guide surface is also located on the distal end side in the axial direction of the opening.

  In this case, it is further suppressed that chips are caught near the opening of the coolant hole. Therefore, clogging of the chips into the coolant hole can be further suppressed.

  In the drill, it is preferable that the guide surface is located around the entire opening of the opening.

  In this case, even if the chips flowing in the chip discharge groove flow from any direction with respect to the opening of the coolant hole, the chips are suppressed from being guided to the guide surface and caught in the vicinity of the opening. For this reason, it is possible to further suppress clogging of the coolant holes.

  In the drill, it is preferable that the guide surface has a convex curve shape in a sectional view along the hole width center line.

  In this case, since the guide surface has a convex curved surface shape, chips are less likely to be caught near the opening of the coolant hole.

  In the drill, it is preferable that the guide surface has a concave curve shape in a cross-sectional view along the hole width center line.

  In this case, since the guide surface has a concave curved surface shape, the guide surface can be easily formed (with few cutting passes) by a ball end mill or the like. That is, the guide surface can be easily formed and the manufacturing of the drill (drill body) can be simplified while the guide surface has a function of preventing chips from being caught near the opening of the coolant hole.

  In the drill, it is preferable that the guide surface is linear in a sectional view along the hole width center line.

  In this case, since the guide surface has a chamfered shape, the guide surface can be easily formed (with few cutting passes) by an end mill or the like. That is, the guide surface can be easily formed and the manufacturing of the drill (drill body) can be simplified while the guide surface has a function of preventing chips from being caught near the opening of the coolant hole.

  In the drill, it is preferable that the opening is disposed in a wall portion facing a direction opposite to the drill rotation direction in the groove wall of the chip discharge groove.

  In this case, it becomes easy to supply the coolant directly from the coolant hole toward the cutting edge. Moreover, since the opening part of a coolant hole is arrange | positioned away from the cutting blade cut into a work material in a drill circumferential direction, it becomes difficult to contact a chip with respect to an opening part, and chip clogging is suppressed more.

  The drill preferably includes a cutting insert that is detachably attached to the tip of the drill body and has a cutting edge.

  In this case, the cutting insert is a detachable drill head or cutting tip, and the drill is a blade-tip replaceable drill. For this reason, when the cutting insert reaches the end of its life due to chipping of the cutting edge or the like, the machining accuracy can be maintained well by replacing it with another new cutting insert. Further, a plurality of types of cutting inserts having various cutting blades can be prepared and selectively used according to the type of workpiece and the processing form.

  According to the drill of one aspect of the present invention, it is possible to suppress clogging of the chip into the coolant hole opened in the chip discharge groove.

It is a perspective view which shows the blade-tip-exchange-type drill which concerns on one Embodiment of this invention. It is a perspective view which shows the principal part of the blade-tip-exchange-type drill of FIG. It is a front view which shows a blade-tip-exchange-type drill. It is a side view which shows the principal part of a blade-tip-exchange-type drill. It is sectional drawing which shows the VV cross section of FIG. It is a figure explaining the effect | action of a guide surface. It is a figure explaining the effect | action of a guide surface. It is sectional drawing which shows the modification of a blade-tip-exchange-type drill. It is sectional drawing which shows the modification of a blade-tip-exchange-type drill. It is sectional drawing which shows the modification of a blade-tip-exchange-type drill.

  Hereinafter, a blade-tip replaceable drill 1 that is an example of a drill according to an embodiment of the present invention will be described with reference to the drawings.

[Schematic configuration of the blade tip type drill]
As shown in FIG. 1 to FIG. 5, the blade tip replaceable drill 1 of the present embodiment has an axial shape having a central axis O, is rotated in a drill rotation direction T around the central axis O, and is axially distal. A drill body 2 having an insert mounting seat 3 formed thereon, and a cutting insert 4 detachably mounted on the insert mounting seat 3 and having a cutting edge 5. The drill body 2 is made of steel, for example, and the cutting insert 4 is made of cemented carbide, for example.

The drill body 2 is disposed at a position different from the shank portion 6 which is detachably mounted on the main shaft or the like of the machine tool, and the axial shank portion 6, and an insert mounting seat 3 and a chip discharge groove 8 which will be described later are formed. The blade part 7 is provided.
In the example of the present embodiment, the insert mounting seat 3 has a groove shape extending in the drill radial direction at the distal end portion of the drill body 2, and is formed on the distal end surface and the outer peripheral surface (both outer sides in the drill radial direction) of the drill body 2. Open.

The cutting insert 4 includes a rake face 15 that faces the drill rotation direction T, a flank face 16 that faces the tip end side in the axial direction, and a cutting edge 5 that is formed at a cross ridge line portion between the rake face 15 and the flank face 16. Have. The cutting edge 5 extends along the drill radial direction. The cutting edge 5 extends while being inclined toward the rear end side in the axial direction as it goes outward in the radial direction of the drill.
In the example of the present embodiment, the blade tip replaceable drill 1 is a two-blade twist drill, and accordingly, the cutting insert 4 has two cutting blades 5 at 180 ° rotationally symmetrical positions about the central axis O. Is formed.

  The cutting insert 4 is mounted on the insert mounting seat 3 with the cutting blade 5 protruding from the tip surface and the outer peripheral surface of the drill body 2, and is fixed by a clamp screw. The cutting insert 4 may be called a drill head or a cutting tip.

[Definition of direction (direction) used in this embodiment]
In the present embodiment, the direction along the central axis O of the drill body 2 (the direction in which the central axis O extends) is referred to as the axial direction. Of the axial directions, the direction from the shank part 6 to the blade part 7 is referred to as the front end side, and the direction from the blade part 7 to the shank part 6 is referred to as the rear end side.
A direction orthogonal to the central axis O is referred to as a drill radial direction. Of the drill radial directions, the direction approaching the central axis O is referred to as the inner side of the drill radial direction, and the direction away from the central axis O is referred to as the outer side of the drill radial direction.
The direction that circulates around the central axis O is called the drill circumferential direction. Of the circumferential direction of the drill, the direction in which the drill body 2 is rotated by the main spindle of the machine tool during cutting is called the drill rotation direction T, and the opposite rotation direction is the direction opposite to the drill rotation direction T (reverse) Called the drill rotation direction).

[Drill body]
A chip discharge groove 8 extending from the axial front end to the rear end side is disposed on the outer periphery of the drill body 2. A plurality of chip discharge grooves 8 are formed on the outer periphery of the drill body 2 at intervals in the drill circumferential direction.

  A coolant hole 10 is formed in the drill body 2 so as to open to the rear end surface 9 of the drill body 2 and extend from the rear end surface 9 toward the front end side in the axial direction. The coolant hole 10 is formed between the land portion 14 formed between the chip discharge grooves 8 adjacent to each other in the drill circumferential direction on the outer periphery of the drill main body 2 and the central axis O (that is, in the drill radial direction of the land portion 14). It has a part located inside. The coolant hole 10 extends inside the drill body 2 and opens in the groove wall (inner wall surface of the groove) of the chip discharge groove 8. The coolant hole 10 has an opening 11 that opens in the groove wall of the chip discharge groove 8.

[Chip discharge groove]
The chip discharge groove 8 opens at the tip end surface of the drill main body 2 and extends in a spiral shape in the direction opposite to the drill rotation direction T from the tip end surface toward the rear end side in the axial direction. The tip of the chip discharge groove 8 is connected to the insert mounting seat 3. In the cross-sectional view of the drill body 2 shown in FIG. 5, the chip discharge groove 8 has a concave curve shape. The groove wall of the chip discharge groove 8 has a concave curved surface shape.

  In the present embodiment, the plurality of chip discharge grooves 8 are arranged at equal intervals (at equal pitches) in the circumferential direction of the drill so as to be rotationally symmetric with respect to the central axis O on the outer periphery of the drill body 2. Specifically, two chip discharge grooves 8 are formed on the outer periphery of the drill body 2 at 180 ° rotationally symmetrical positions about the central axis O.

  The chip discharge groove 8 is cut off on the outer peripheral surface of the drill main body 2 toward the outer side in the radial direction of the drill in the vicinity of the central portion along the axial direction of the drill main body 2 or the portion located on the rear end side of the central portion. Yes. In the drill body 2, a region where the chip discharge groove 8 along the axial direction is formed is the blade portion 7, and a portion located on the rear end side from this region is the shank portion 6.

  In the example of this embodiment, the twist angle of the tip portion of the chip discharge groove 8 is larger than the twist angle of the portion located on the rear end side. The “twist angle” refers to an acute angle and an obtuse angle formed when a virtual chord winding (not shown) extending parallel to the chip discharge groove 8 intersects the central axis O when the drill body 2 is viewed from the radial direction of the drill. Among them, it indicates an acute angle. In other words, the twist angle is an intersecting ridge line formed between the wall portion 8a facing the drill rotation direction T in the groove wall of the chip discharge groove 8 and the outer peripheral surface (land portion 14) of the drill body 2 (the imaginary line described above). Is an angle inclined with respect to the central axis O in a side view of the drill. In the present embodiment, the chip discharge groove 8 is twisted and extended in the direction opposite to the drill rotation direction T from the front end in the axial direction toward the rear end side. Therefore, the twist angle is a positive (positive) angle. is there.

[Coolant hole]
The coolant hole 10 is a flow path for coolant (oil-based or water-soluble cutting fluid, compressed air, etc.) formed inside the drill body 2. The coolant hole 10 is connected to coolant supply means provided outside the cutting edge replaceable drill 1 through a spindle of a machine tool or the like.

  The opening 11 of the coolant hole 10 is disposed in the wall portion 8 b facing the direction opposite to the drill rotation direction T in the groove wall of the chip discharge groove 8. The cutting edge 5 and the rake face 15 are located on the distal end side of the opening 11 of the coolant hole 10. That is, the coolant hole 10 opens toward the cutting edge 5 and the rake face 15.

A guide surface 12 is disposed in the opening 11 of the coolant hole 10.
As shown in FIG. 5, the guide surface 12 is disposed between the inner peripheral surface 10 a of the coolant hole 10 and the groove wall of the chip discharge groove 8. The guide surface 12 is connected to the inner peripheral surface 10 a of the coolant hole 10 and the groove wall of the chip discharge groove 8. The guide surface 12 connects the inner peripheral surface 10 a of the coolant hole 10 and the wall portion 8 b facing the direction opposite to the drill rotation direction T in the groove wall of the chip discharge groove 8.

As shown in FIG. 5, in a cross-sectional view of the drill body 2 including the opening 11 of the coolant hole 10, the guide surface 12 extends toward the groove wall side of the chip discharge groove 8 along the hole width center line C. As it goes, the distance from the hole width center line C increases. That is, the guide surface 12 is inclined and extended in a direction away from the hole width center line C as it goes along the hole width center line C of the coolant hole 10 toward the outlet side of the coolant hole 10 (coolant ejection direction). The guide surface 12 is a surface that expands the opening 11 of the coolant hole 10 toward the outlet side.
The “hole width center line C” in the present embodiment refers to the center line in the width direction (hole width direction) of the opening 11 of the coolant hole 10, which appears in a sectional view including the opening 11.

In the example of the present embodiment, as shown in FIG. 5, the guide surface 12 has a convex curve shape in a cross-sectional view along the hole width center line C.
As shown in FIGS. 2 to 5, the guide surface 12 is located on the rake face 15 side in the drill radial direction in the opening 11. That is, the guide surface 12 is located inside the opening 11 in the drill radial direction. The guide surface 12 is also located on the rear end side in the axial direction in the opening 11. The guide surface 12 is also located on the distal end side in the axial direction in the opening 11. The guide surface 12 is also located outside the opening 11 in the radial direction of the drill. In the example of this embodiment, the guide surface 12 is located around the entire opening of the opening 11.

  In the present embodiment, as shown in FIG. 4, the width of the guide surface 12 located on the inner side (the rake face 15 side) of the opening 11 in the drill radial direction when the opening 11 is viewed from the front in the side view of the drill is It is larger than the width of the guide surface 12 located on the outer side (land portion 14 side) in the drill radial direction.

[Effects of this embodiment]
As shown in FIG. 6, according to the cutting edge replaceable drill 1 of the present embodiment described above, the chip W has a drill diameter with respect to the opening 11 of the coolant hole 10 that opens in the groove wall of the chip discharge groove 8. Even if it flows from the outer side to the inner side in the direction, the chips W are suppressed from being caught in the vicinity of the opening 11 by being guided by the guide surface 12. For this reason, it is suppressed that the chip | tip W approachs into the coolant hole 10 from the opening part 11, and the clogging of the coolant hole 10 can be suppressed.
Further, as shown in FIG. 7, even if the chips W flow from the inner side to the outer side in the drill radial direction with respect to the opening 11 of the coolant hole 10, the chips W are guided to the guide surface 12. Thus, it is possible to suppress the vicinity of the opening 11.

In the present embodiment, the guide surface 12 is also located on the rear end side in the axial direction of the opening 11.
For this reason, the chip W flowing toward the rear end side in the chip discharge groove 8 is suppressed from being caught in the vicinity of the opening 11 of the coolant hole 10. Therefore, chip clogging to the coolant hole 10 can be further suppressed.

In the present embodiment, the guide surface 12 is also located on the distal end side in the axial direction of the opening 11.
For this reason, it is further suppressed that the chips W are caught near the opening 11 of the coolant hole 10. Therefore, chip clogging to the coolant hole 10 can be further suppressed.

In the present embodiment, the guide surface 12 is located on the entire circumference of the opening 11.
For this reason, even if the chip W flowing in the chip discharge groove 8 flows from any direction with respect to the opening 11 of the coolant hole 10, the chip W is guided by the guide surface 12 and caught near the opening 11. It is suppressed. For this reason, it is possible to further suppress clogging of the chips W into the coolant hole 10.

Moreover, in this embodiment, the guide surface 12 is convex curve shape by the cross sectional view which follows the hole-width centerline C.
That is, since the guide surface 12 has a convex curved surface shape, the chips W are less likely to be caught near the opening 11 of the coolant hole 10.

Moreover, in this embodiment, the opening part 11 is arrange | positioned in the wall part 8b which faces the direction opposite to the drill rotation direction T among the groove walls of the chip discharge groove 8. FIG.
For this reason, it becomes easy to supply the coolant directly from the coolant hole 10 toward the cutting edge 5. Moreover, since the opening part 11 of the coolant hole 10 is arranged away from the cutting edge 5 which cuts into the work material in the drill circumferential direction, the chip W is less likely to contact the opening part 11, and chip clogging is further suppressed. Is done.

Moreover, in this embodiment, the cutting insert 4 is attached to the front-end | tip part of the drill main body 2 so that attachment or detachment is possible.
That is, the cutting insert 4 is a detachable drill head or cutting tip. For this reason, when the cutting insert 4 has reached the end of its life due to chipping of the cutting edge 5 or the like, the machining accuracy can be maintained well by replacing it with another new cutting insert 4. Further, a plurality of types of cutting inserts 4 having various cutting blades 5 can be prepared and selectively used according to the type of material to be cut and the processing form.

[Other configurations included in the present invention]
Note that the present invention is not limited to the above-described embodiment. For example, as described below, the configuration can be changed without departing from the spirit of the present invention.

8 to 10 are cross-sectional views (transverse cross-sectional views perpendicular to the central axis O) showing modifications of the blade-tip replaceable drill 1 described in the above embodiment.
As shown in FIG. 8A, the wall 8b facing the direction opposite to the drill rotation direction T of the chip discharge groove 8 forms an obtuse angle with the outer peripheral surface (land portion 14) of the drill body 2. It may be connected to. In this case, the chips flowing on the groove wall of the chip discharge groove 8 from the inner side to the outer side in the radial direction of the drill can easily get over the opening portion 11, and chip clogging can be further suppressed.

  As shown in FIG. 8 (b), the wall portion 8b facing the direction opposite to the drill rotation direction T of the chip discharge groove 8 forms an acute angle with the outer peripheral surface (land portion 14) of the drill body 2. It may be connected to. In this case, it is easy to ensure the rigidity of the drill body 2. Then, as shown in FIG. 8 (b), the radius of curvature of the guide surface 12 located on the outer side in the drill radial direction in the opening 11 is in the inner side in the drill radial direction in a sectional view along the hole width center line C. The radius of curvature of the guide surface 12 positioned may be larger. Thereby, the chips flowing from the inner side to the outer side in the radial direction of the drill on the groove wall of the chip discharge groove 8 are less likely to be caught in the vicinity of the opening 11 and chip clogging can be further suppressed.

In addition, in a sectional view along the hole width center line C, the radius of curvature of the guide surface 12 located inside the drill radial direction is larger than the radius of curvature of the guide surface 12 located outside the drill radial direction in the opening 11. It can be large.
In a cross-sectional view along the hole width center line C, the radius of curvature of the guide surface 12 may be the same or different from each other in each part of the entire circumference of the opening 11.

As shown in FIGS. 9A and 9B, the guide surface 12 may have a concave curve shape in a cross-sectional view along the hole width center line C.
In this case, since the guide surface 12 has a concave curved surface shape, the guide surface 12 can be easily formed (with few cutting passes) by a ball end mill or the like. That is, the guide surface 12 can be easily formed and the manufacturing of the drill (drill main body 2) can be simplified while the guide surface 12 has a function of preventing chips from being caught near the opening 11 of the coolant hole 10.

As shown in FIGS. 10A and 10B, the guide surface 12 may be linear in a cross-sectional view along the hole width center line C.
In this case, since the guide surface 12 has a chamfered shape, the guide surface 12 can be easily formed (with fewer cutting passes) by an end mill or the like. That is, the guide surface 12 can be easily formed and the manufacturing of the drill (drill main body 2) can be simplified while the guide surface 12 has a function of preventing chips from being caught near the opening 11 of the coolant hole 10.

  As shown in FIG. 10A, an angle (a depression angle) θ formed between a pair of guide surfaces 12 positioned on both sides in the hole width direction of the opening 11 across the hole width center line C is an obtuse angle. It may be. As shown in FIG. 10B, the angle θ may be an acute angle. Although not particularly illustrated, the angle θ may be 90 °.

The guide surface 12 shown in FIGS. 8 to 10 may be appropriately combined and arranged around the hole width center line C in the opening 11.
Further, the guide surface 12 may have a linear shape combining at least two of a convex curve, a concave curve, and a straight line in a sectional view along the hole width center line C.

  In the above-described embodiment, the example in which the guide surface 12 is arranged over the entire circumference of the opening 11 of the coolant hole 10 has been described, but the present invention is not limited to this. The guide surface 12 should just be arrange | positioned at least inside the drill radial direction among the opening parts 11. FIG. In other words, the guide surface 12 does not need to be disposed in a portion (one place or a plurality of places) other than the inner side in the drill radial direction in the entire circumference of the opening 11. However, as described in the above-described embodiment, it is more preferable that the guide surface 12 is provided in each part of the opening portion 11 so that chip clogging into the coolant hole 10 can be remarkably suppressed.

In the above-described embodiment, an example in which the blade tip replaceable drill 1 is a two-blade twist drill has been described. The cutting insert 4 is formed with two cutting edges 5 at 180 ° rotationally symmetrical positions about the central axis O, and the drill body 2 has a chip discharge groove 8 and a coolant hole 10 that are 180 ° rotationally symmetric, respectively. Two are formed at each position. However, the present invention is not limited to this. That is, the cutting blade 5, the chip discharge groove 8, or the coolant hole 10 does not have to be disposed at a 180 ° rotationally symmetric position around the central axis O. The cutting blade 5, the chip discharge groove 8, or the coolant hole 10 is not limited to the configuration arranged at an equal pitch in the drill circumferential direction, and may be arranged at an unequal pitch. Also, the plurality of coolant holes 10 (and their openings 11) may have different shapes.
Moreover, you may apply this invention to the blade-tip-exchange-type drill of 3 blades or more.

In the above-described embodiment, the insert mounting seat 3 has a groove shape extending in the drill radial direction at the distal end portion of the drill body 2, and the cutting insert 4 causes the cutting blade 5 to protrude from the distal end surface and the outer peripheral surface of the drill body 2. However, the shapes of the insert mounting seat 3 and the cutting insert 4 are not limited to the example described in the above embodiment.
For example, a pair of chip discharge grooves 8 are provided on the outer periphery of the drill body 2 at intervals in the circumferential direction of the drill, and a square plate shape is formed at the tip of one chip discharge groove 8 of the pair of chip discharge grooves 8. The present invention can also be applied to a blade-tip-replaceable drill in which a cutting insert for an inner blade is formed, and a cutting insert for an outer blade having a rectangular plate shape is attached to the tip of the other chip discharge groove 8. .

  In the above-described embodiment, the blade-tip replaceable drill 1 is taken as an example, but the present invention is not limited to this. The drill of the present invention may be, for example, a solid type (integrated type) drill in which a cutting blade 5 is integrally formed with a drill body 2 made of cemented carbide.

  In addition, in the range which does not deviate from the meaning of this invention, you may combine each structure (component) demonstrated by the above-mentioned embodiment, a modification, and a note, etc., addition of a structure, omission, substitution, others It can be changed. Further, the present invention is not limited by the above-described embodiments, but is limited only by the scope of the claims.

  According to the drill of this invention, the clogging of the coolant to the coolant hole opened to the chip discharge groove can be suppressed. Therefore, it has industrial applicability.

1 ... Cutting edge changeable drill (drill)
DESCRIPTION OF SYMBOLS 2 ... Drill main body 4 ... Cutting insert 5 ... Cutting blade 8 ... Chip discharge groove 8b ... Wall part facing the direction opposite to a drill rotation direction among groove walls of a chip discharge groove 10 ... Coolant hole 10a ... Inner peripheral surface 11 ... Opening 12 ... Guide surface C ... Hole width center line O ... Center axis T ... Drill rotation direction

Claims (9)

A drill body having a central axis and rotated in a drill rotation direction around the central axis;
A chip discharge groove disposed on the outer periphery of the drill body and extending from the front end in the axial direction toward the rear end;
A coolant hole extending through the inside of the drill body and opening in a groove wall of the chip discharge groove;
A guide surface disposed between the inner peripheral surface of the coolant hole and the groove wall,
In a cross-sectional view including the opening portion of the coolant hole, the distance between the guide surface and the hole width center line increases as it goes toward the groove wall along the hole width center line of the coolant hole. ,
The said guide surface is a drill located in the inside of a drill radial direction among the said opening parts. The drill according to claim 1,
The drill in which the guide surface is located also on the rear end side in the axial direction in the opening. The drill according to claim 1 or 2,
The drill in which the guide surface is located also on the distal end side in the axial direction in the opening. The drill according to any one of claims 1 to 3,
The drill in which the guide surface is located around the entire opening of the opening. The drill according to any one of claims 1 to 4,
A drill in which the guide surface has a convex curve shape in a sectional view along the hole width center line. The drill according to any one of claims 1 to 4,
A drill, wherein the guide surface has a concave curve shape in a sectional view along the hole width center line. The drill according to any one of claims 1 to 4,
A drill in which the guide surface is linear in a cross-sectional view along the hole width center line. It is a drill as described in any one of Claims 1-7,
The said opening part is a drill arrange | positioned in the wall part which faces the direction opposite to the said drill rotation direction among the groove walls of the said chip | tip discharge groove | channel. It is a drill as described in any one of Claims 1-8,
A drill comprising a cutting insert that is detachably attached to a tip portion of the drill body and has a cutting edge.

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