JP2018015861A - Drill body of cutting edge replacing type drill, and cutting edge replacing type drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate manufacturing of a drill body, secure strength, increase chip discharge performance, and improve cooling efficiency by facilitating reaching of a coolant to near a cutting edge.SOLUTION: A chip discharge groove 8 is provided with: a tip side twisted part 8a; a base end side twisted part 8b that has a twist angle θ smaller than that θ of the tip side twisted part 8a, and an intermediate twisted part 8c that is arranged between the tip side twisted part 8a and the base end side twisted part 8b. A coolant hole 10 is provided with: a first coolant hole 11 that is opened in a recess formed in the base end surface 9 of a drill body 2 or the base end surface 9 and that linearly extends in a drill rotational direction toward a tip side in the direction of an axis O; and a second coolant hole 12 that is connected to the tip part of the first coolant hole 11 in the direction of the axis O, that linearly extends in a direction different from the extending direction of the first coolant 11 from the tip part toward the tip side of the drill body 2, and that is opened in the chip discharge groove 8 closer to the tip side than the tip position of the base end twisted part 8b.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a drill body of a blade tip replaceable drill and a blade tip replaceable drill.

2. Description of the Related Art Conventionally, for example, blade tip exchange drills as shown in Patent Documents 1 to 4 below are known.
The blade-replaceable drill has an axial shape and is rotated in the direction of drill rotation in the circumferential direction around the axis, and is attachable to and detachable from the drill body with an insert mounting seat formed at the tip in the axial direction. And a cutting insert having a cutting edge.

A chip discharge groove extending from the distal end in the axial direction to the proximal end side is formed on the outer periphery of the drill body. The chip discharge groove extends in a twisted direction toward the opposite side of the drill rotation direction from the distal end in the axial direction toward the proximal end side, at least at the distal end portion of the drill body.
Further, the drill body is formed with a coolant hole extending through the drill body in the axial direction and through which coolant (oil-based or water-soluble cutting fluid, compressed air, etc.) flows.

JP 2003-285212 A Japanese Patent No. 4802095 Japanese Patent No. 5675991 Japanese Patent No. 5205458

However, the above-described conventional cutting edge-replaceable drill has the following problems.
In patent document 1, the coolant hole is opened in the outer peripheral surface of a drill main body. For this reason, the coolant ejected from the coolant hole may not easily reach the cutting edge, and there is room for improvement in terms of improving the cooling efficiency of the cutting edge.

  In Patent Document 2, the coolant hole extends in parallel with the axis inside the drill body. A coolant hole opens in the chip discharge groove in the vicinity of the tip of the drill formed by twisting the chip discharge groove. In this case, the coolant sprayed from the coolant hole can be directly supplied to the vicinity of the cutting edge, and the cooling efficiency of the cutting edge can be increased. However, in extending the coolant hole parallel to the axis to the vicinity of the tip of the drill, it is necessary to extend a portion other than the tip of the drill in the chip discharge groove parallel to the axis, and it is difficult to maintain good chip discharge performance. .

  In Patent Document 3, a coolant hole extending in the drill body includes a portion parallel to the axis, and a portion that is disposed on the tip side of the portion and is inclined with respect to the axis. Also in this patent document 3, the part corresponding to the part parallel to the said axis line of a coolant hole must be extended in parallel with an axis among chip discharge grooves, and chip | tip discharge property cannot be ensured.

  In Patent Document 4, at the time of drill production, a coolant hole parallel to the axis is formed in the drill body in advance, and a plastic is heated between a pair of tightening positions spaced apart in the axial direction in the drill body. Twist around the axis. Thereby, the coolant hole extending in the drill body forms a spiral between the tightening positions, and forms a straight line at other portions (both ends). However, in this case, a high technique is required for forming the coolant hole, and the manufacture is difficult. In addition, since the twist angle of the chip discharge groove formed according to the position of the coolant hole is constant, the strength of the drill body tends to decrease if the twist is increased to ensure chip discharge. In addition, the pressure loss of the coolant flowing through the coolant hole is large, and it is difficult to increase the coolant flow rate, and it is difficult for the coolant to reach the vicinity of the cutting edge.

  The present invention has been made in view of such circumstances, and the drill body can be easily manufactured, the strength of the drill body can be ensured, the chip discharge performance can be improved, and the coolant is provided near the cutting edge. An object of the present invention is to provide a drill body of a blade-tip replaceable drill that can be easily reached and improve cooling efficiency, and a blade-tip replaceable drill.

One aspect of the present invention is an insert mounting that has an axial shape, is rotated in a drill rotation direction in a circumferential direction around the axis, and a cutting insert having a cutting edge is detachably attached to a tip portion in the axial direction A drill body of a blade-tip-exchangeable drill having a seat formed thereon, and the outer periphery of the drill body is twisted and extended toward the opposite side of the drill rotation direction from the distal end in the axial direction toward the proximal end. A plurality of chip discharge grooves are formed spaced apart from each other in the circumferential direction, and the inside of the drill body opens into a base end surface of the drill body or a recess formed in the base end surface, and the base end surface or the A coolant hole extending from the recessed portion toward the tip end side in the axial direction without passing through the axial line between the circumferentially adjacent chip discharge grooves is formed. A proximal-side twisted portion disposed adjacent to the seat mounting seat, and a proximal end disposed on the proximal side in the axial direction with respect to the distal-side twisted portion and having a twist angle smaller than the twist angle of the distal-side twisted portion A side twisted portion, and the tip-side twisted portion and the proximal-side twisted portion are arranged and connected to each other, from a boundary portion with the tip-side twisted portion to a boundary portion with the proximal-side twisted portion. An intermediate twist portion that gradually decreases in torsion angle, and the coolant hole opens in the base end surface or the recess, and the drill extends from the base end surface or the recess toward the tip end side in the axial direction. A first coolant hole extending linearly toward the rotation direction, and the first coolant hole connected to the tip end portion in the axial direction of the first coolant hole, from the tip end portion toward the tip end side of the drill body, The cooler A second coolant hole that extends linearly in a direction different from the extending direction of the hole and opens into the chip discharge groove on the distal end side with respect to the distal end position of the base end side twisted portion. It is characterized by.
Another aspect of the present invention is a drill body that has an axial shape and is rotated in a drill rotation direction in a circumferential direction around an axis, and an insert mounting seat is formed at a tip portion in the axial direction, and the insert mounting A cutting edge replaceable drill comprising a cutting insert detachably mounted on a seat and having a cutting edge, wherein the drill body of the above-described blade edge replaceable drill is used as the drill body.

  According to the drill body of the blade tip replaceable drill of the present invention and the blade tip replaceable drill, the chip discharge groove includes the distal end side twisted portion, the proximal end side twisted portion, and the intermediate twisted portion having different twist angles. The tip side twisted portion has the largest twist angle in the chip discharge groove, and is disposed adjacent to the insert mounting seat. The proximal-side twisted portion has a smaller twist angle than the distal-end-side twisted portion, and is disposed away from the insert mounting seat toward the proximal end side in the axial direction. The intermediate torsion part is located between the tip side torsion part and the base end side torsion part and connects them, and the base end (base end side torsion part) from the tip in the axial direction (boundary part with the tip side torsion part) The torsion angle is gradually reduced toward the boundary part.

  The “twist angle” as used in the present invention refers to a virtual string winding extending in parallel with the chip discharge groove when the drill body is viewed from the radial direction perpendicular to the axis of the drill body (that is, in a side view of the drill). Among acute angles and obtuse angles formed intersecting the axis, it indicates an acute angle. In other words, the twist angle is such that the intersecting ridge line (corresponding to the virtual string winding) formed between the wall surface facing the drill rotation direction in the chip discharge groove and the outer peripheral surface of the drill body is the axis line in the side view of the drill. It is the angle which inclines with respect. In the present invention, the chip discharge groove is twisted and extended toward the side opposite to the drill rotation direction from the tip end in the axial direction toward the base end side, so the twist angle is a positive angle (positive angle).

In a portion adjacent to the insert mounting seat on which the cutting insert is mounted, the chip discharging groove (the tip side twisted portion) has a large twist angle, so that chip discharging performance can be improved.
In addition, in a portion spaced from the insert mounting seat to the base end side in the axial direction, a positive twist angle is given to the chip discharge groove (the base end side twisted portion) while ensuring a certain level of chip discharge performance. The strength (rigidity) of the drill body can be increased by reducing the twist angle.
In addition, in the portion located between the distal end side twisted portion and the proximal end side twisted portion, the twist angle of the chip discharge groove (intermediate twisted portion thereof) is gradually changed, and the distal end side twisted portion and the proximal end side twisted portion Can be connected gently. Thereby, the residence of the chip | tip which flows in the chip discharge groove | channel can be suppressed effectively, and the rigidity of a drill main body is ensured.

  And the coolant hole formed in the inside of a drill main body is extended between the chip | tip discharge grooves adjacent to the circumferential direction (diameter direction inner side of a land part), without passing on an axis line. Specifically, the coolant hole is connected to a linear first coolant hole extending obliquely with respect to the axis, and a leading end portion of the first coolant hole, and the extending direction of the first coolant hole And a second linear coolant hole extending in different directions.

  The first coolant hole is open to a base end surface of the drill body or a recess formed in the base end surface, and coolant supplied from a coolant supply means provided outside the drill is received in the first coolant hole. , Flows through the spindle of the machine tool. The first coolant hole extends from the proximal end surface or the concave portion of the drill body toward the distal end side in the axial direction, so that the first coolant hole extends in the drill rotation direction, and accordingly, according to the twist angle of the proximal end side twist portion of the chip discharge groove. It is easy to incline.

  That is, since the first coolant hole can be extended (substantially in parallel) along the proximal-side twisted portion of the chip discharge groove, the first coolant hole approaches the groove wall (inner wall) of the chip discharge groove. It is possible to extend the first coolant hole long toward the tip side of the drill body while preventing it from passing or being opened in the groove. For this reason, the malfunction that the intensity | strength of a drill main body falls around the 1st coolant hole, or a coolant is sprayed in a chip discharge groove in the position greatly spaced apart from the cutting blade is prevented. In addition, since the connecting portion between the first coolant hole and the second coolant hole (the tip of the first coolant hole) can be disposed at a position close to the tip of the drill body, the second coolant hole is insert-attached. It is easy to open in the chip discharge groove near the seat, and coolant can be accurately supplied near the cutting edge.

Further, the second coolant hole is connected to the distal end portion of the first coolant hole, extends in a direction different from the direction in which the first coolant hole extends, and from the proximal end side twisted portion of the chip discharge groove. Is also open to either the tip side twisted portion or the intermediate twisted portion located on the tip side.
That is, since the second coolant hole is opened in the chip discharge groove at either the tip side twisted portion or the intermediate twisted portion close to the insert mounting seat, the coolant can easily reach the vicinity of the cutting edge. In addition, the second coolant hole opens in either the tip side twisted portion or the intermediate twisted portion having a larger twist angle than the base end side twisted portion in the chip discharge groove, so that the opening area into the chip discharge groove is reduced. It can be kept small.

  Specifically, it is possible to prevent a problem in which the opening portion of the second coolant hole into the chip discharge groove extends so as to tear in the axial direction. That is, according to the present invention, even if the second coolant hole is not greatly inclined with respect to the axis, it is possible to prevent the opening portion into the chip discharge groove from extending greatly vertically and to secure the strength of the drill body. In addition, the appearance (appearance) as a product is maintained well. Thereby, the design condition of the second coolant hole is relaxed, and various drill forms can be supported. Furthermore, the connection angle between the first coolant hole and the second coolant hole can be made gentle (increased toward the obtuse angle side), and the pressure loss of the coolant flowing through the connection portion can be reduced.

In addition, since the first and second coolant holes are each linear, the pressure loss of the coolant flowing through the coolant holes is significantly reduced. For this reason, it is easy to increase the coolant flow rate linearly by increasing the coolant supply pressure or the like, and the coolant can surely reach the vicinity of the cutting edge.
Moreover, at the time of drill manufacture, the first and second coolant holes can be formed using a small diameter drill or the like, and the manufacture of the drill body is easy.

  As described above, according to the present invention, the drill body can be easily manufactured, the strength of the drill body can be secured, the chip discharge performance can be improved, and the coolant can be easily reached near the cutting edge to improve the cooling efficiency. .

  Further, in the drill main body of the blade-tip-replaceable drill, the second coolant hole is opposite to the drill rotation direction from the tip end portion of the first coolant hole in the axial direction toward the tip end side of the drill main body. It is preferable to extend toward the side.

  In this case, it is easy to arrange the cutting edge of the cutting insert mounted on the insert mounting seat and the rake face adjacent to the cutting edge on the extension line of the second coolant hole. Therefore, the coolant ejected from the second coolant hole can be directly supplied to the vicinity of the cutting edge and cooled, and the cooling efficiency can be remarkably increased.

  Further, in the drill main body of the blade-tip replaceable drill, the second coolant hole may open into the chip discharge groove at one of the tip side twisted portion and the tip end portion of the intermediate twisted portion. preferable.

  In this case, the 2nd coolant hole is opened in the chip discharge | emission groove | channel in either the front end side twist part and the front-end | tip part of an intermediate | middle twist part. That is, the twist angle of the tip side twist portion is large, and the twist angle at the tip portion of the intermediate twist portion has a value close to the twist angle of the tip side twist portion and the twist angle is large. It can be surely opened in the chip discharge groove at a portion having a large twist angle. Therefore, it is easy to suppress the opening area of the second coolant hole to be small, and the above-described operational effects become more remarkable.

  Further, in the drill body of the blade-tip replaceable drill, a connection portion between the first coolant hole and the second coolant hole is disposed on a distal end side with respect to the proximal-side twisted portion along the axial direction. Preferably it is.

  In this case, the connecting portion between the first coolant hole and the second coolant hole is located at a position corresponding to one of the tip side twisted portion and the intermediate twisted portion along the axial direction, that is, a position close to the tip portion of the drill body. Be placed. For this reason, it becomes easy to open the second coolant hole in the chip discharge groove near the insert mounting seat, and the coolant can easily reach the vicinity of the cutting edge more reliably.

  Further, in the drill body of the blade-tip-exchangeable drill, it is preferable that a plurality of sets of the first coolant hole and the second coolant hole that communicate with each other are provided in a rotationally symmetrical manner around the axis.

  In this case, the set of the first coolant hole and the second coolant hole that communicate with each other while equalizing the rigidity of the drill body in the circumferential direction is, for example, two in the case of a two-blade drill, in the case of a three-blade drill Can be provided according to the number of cutting edges, and the cooling efficiency of each cutting edge can be fully improved.

  Moreover, in the above-mentioned blade tip replaceable drill, it is preferable that either the cutting edge or a rake face adjacent to the cutting edge is disposed on an extension line of the second coolant hole.

  In this case, the coolant ejected from the second coolant hole can be directly supplied to the vicinity of the cutting edge and cooled, and the cooling efficiency can be remarkably increased.

  Further, in the above-described replaceable drill, the drill body has two chip discharge grooves formed at 180 ° rotationally symmetric positions around the axis, and the cutting insert rotates 180 ° around the axis. Two of the cutting edges are formed at symmetrical positions, and the first coolant hole and the second coolant hole projected onto a virtual plane including the radial outer ends of the two cutting edges and the axis line, The direction in which the first coolant hole is inclined with respect to the axis and the direction in which the second coolant hole is inclined with respect to the axis are opposite to each other. It is preferable that

  In this case, the first coolant hole is inclined with respect to the axis (inclined to the positive angle side) according to the twist angle of the chip discharge groove, and the second coolant hole is Can be inclined with respect to the axis in the opposite direction (inclined to the negative angle side). For this reason, the opening area of the second coolant hole into the chip discharge groove is kept small, or the surface of the cutting insert attached to the insert mounting seat that is easy to cut is disposed on the extension line of the second coolant hole. It is easy to do. Therefore, while ensuring the strength of the drill body, the coolant ejected from the second coolant hole can be supplied directly to the vicinity of the cutting edge, and the cooling efficiency can be significantly increased.

  According to the drill body of the blade-tip replaceable drill of the present invention and the blade-tip replaceable drill, the manufacture of the drill body is easy, the strength of the drill body can be secured, the chip discharge performance can be improved, and the vicinity of the cutting blade Cooling efficiency can be improved by making it easier to reach the coolant.

It is a perspective view which shows the blade-tip-exchange-type drill which concerns on one Embodiment of this invention. It is a front view which shows a blade-tip-exchange-type drill. It is a side view which shows a blade-tip-exchange-type drill. It is (a) XX sectional drawing, (b) YY sectional view, and (c) ZZ sectional view shown by Drawing 3 (a). It is a side view which shows the modification of a blade-tip-exchange-type drill. It is a perspective view which shows the modification of a blade-tip-exchange-type drill. It is (a) side view, (b) side view, (c) back view which shows the modification of a blade-tip-exchange-type drill. It is a perspective view which shows the modification of a blade-tip-exchange-type drill. It is (a) side view, (b) side view, (c) back view which shows the modification of a blade-tip-exchange-type drill.

  Hereinafter, a blade tip replaceable drill 1 according to an embodiment of the present invention and its drill body 2 will be described with reference to the drawings.

[Schematic configuration of the blade tip type drill]
As shown in FIG. 1 to FIG. 4, the blade tip replaceable drill 1 of the present embodiment has an axial shape and is rotated in the drill rotation direction T in the circumferential direction around the axis O, and the tip portion in the axis O direction 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, for example, a steel material, and the cutting insert 4 is made of, for example, a cemented carbide.

The drill body 2 is disposed at a position different from the shank portion 6 that is detachably attached to the main shaft or the like of the machine tool, and the shank portion 6 in the direction of the axis O, and an insert mounting seat 3 and a chip discharge groove 8 to 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 radial direction at the distal end portion of the drill body 2, and opens on the distal end surface and the outer peripheral surface (both radially outer sides) of the drill body 2. ing.

Further, the cutting insert 4 includes a rake face 15 facing the drill rotation direction T, a flank face 16 facing the tip side in the direction of the axis O, and a cutting edge 5 formed at a cross ridge line portion between the rake face 15 and the flank face 16. And. The cutting edge 5 extends along the radial direction orthogonal to the axis O, and is inclined toward the base end side in the axis O direction as it goes radially outward.
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 edges 5 at 180 ° rotationally symmetrical positions about the axis O. Is formed.

  The cutting insert 4 is in a state in which a cutting edge 5 is protruded from the distal end surface and the outer peripheral surface of the drill main body 2, is mounted on the insert mounting seat 3, and is fixed by a clamp screw. The cutting insert 4 of this embodiment may be called a cutting head.

[Definition of direction (direction) used in this embodiment]
In the present embodiment, the direction along the axis O of the drill body 2 (the direction in which the axis O extends) is referred to as the axis O direction. Moreover, the direction (left side in FIG. 3 (a), (b)) which goes to the blade part 7 from the shank part 6 among axial direction O is called a front end side, and the direction (FIG. 3) which goes to the shank part 6 from the blade part 7 The right side in (a) and (b) is called the base end side.
A direction orthogonal to the axis O is referred to as a radial direction. Of the radial directions, the direction approaching the axis O is referred to as the inner side in the radial direction, and the direction away from the axis O is referred to as the outer side in the radial direction.
A direction that circulates around the axis O is referred to as a circumferential direction. Of the circumferential direction, the direction in which the drill body 2 is rotated by the spindle of the machine tool during cutting is called the drill rotation direction T, and the opposite rotation direction to the drill rotation direction T (the anti-drill) Rotation direction).

[Drill body]
On the outer periphery of the drill body 2, a plurality of chip discharge grooves 8 that are twisted and extended toward the opposite side of the drill rotation direction T from the distal end in the axis O direction toward the proximal end side are formed at intervals in the circumferential direction. Has been.
Further, inside the drill body 2, an opening is made in the proximal end surface 9 of the drill body 2, and the axial line extends between the chip discharge grooves 8 adjacent in the circumferential direction from the proximal end surface 9 toward the distal end side in the axis O direction. A coolant hole 10 extending without passing over O is formed. Specifically, in the drill cross-sectional view shown in FIGS. 4A to 4C (cross-sectional view perpendicular to the axis O), the coolant hole 10 is a chip adjacent in the circumferential direction on the outer periphery of the drill body 2. It is located between the land portion 14 formed between the discharge grooves 8 and the axis O (that is, radially inward of the land portion 14).

[Chip discharge groove]
As shown in FIGS. 1 to 3, the chip discharge groove 8 is opened at the distal end surface of the drill body 2, and gradually proceeds in the anti-drill rotation direction from the distal end surface toward the proximal end side in the axis O direction. Extending in a spiral. The tip of the chip discharge groove 8 is disposed adjacent to the insert mounting seat 3 formed at the tip of the drill body 2. As shown in FIGS. 4A to 4C, the chip discharge groove 8 has a concave curved inner surface.

  In the present embodiment, the plurality of chip discharge grooves 8 are arranged at equal intervals in the circumferential direction (at an equal pitch) so as to be rotationally symmetric with respect to the 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 main body 2 at 180 ° rotationally symmetrical positions about the axis O.

  In FIG. 1 to FIG. 3, the chip discharge groove 8 extends toward the outer side in the radial direction in the vicinity of the center portion along the axis O direction of the drill body 2 or in the portion located on the base end side of the center portion. 2 is cut off on the outer peripheral surface. In the drill body 2, a region where the chip discharge groove 8 along the direction of the axis O is formed is the blade portion 7, and a portion located on the base end side from this region is the shank portion 6.

  3 (a) and 3 (b), the chip discharge groove 8 is disposed adjacent to the insert mounting seat 3 on the distal end side twisted portion 8a and on the proximal end side in the axis O direction with respect to the distal end side twisted portion 8a. The proximal end side twisted portion 8b having a smaller twist angle than the distal end side twisted portion 8a, and the distal end side twisted portion 8a and the proximal end side twisted portion 8b are arranged so as to be connected gently. An intermediate twisted portion 8c that gradually decreases in twist angle from the boundary portion with the distal-side twisted portion 8a toward the boundary portion with the proximal-side twisted portion 8b.

  The “twist angle” as used in the present embodiment refers to the drill body 2 viewed from the radial direction orthogonal to the axis O of the drill body 2 (that is, a drill as shown in FIGS. 3A and 3B). In a side view), a virtual chord winding (not shown) extending in parallel with the chip discharge groove 8 indicates an acute angle among an acute angle and an obtuse angle formed to intersect the axis O. In other words, the twist angle is an intersecting ridge line formed between the wall surface facing the drill rotation direction T in the chip discharge groove 8 and the outer peripheral surface (land portion 14) of the drill body 2 (corresponding to the virtual chord winding). Is an angle inclined with respect to the axis O in a side view of the drill, specifically, an angle indicated by a symbol θ in FIG. In this embodiment, the chip discharge groove 8 is twisted and extended toward the opposite side of the drill rotation direction T from the distal end in the direction of the axis O toward the proximal end side, so that the twist angle θ is a positive angle (positive angle). ).

The twist angle θ of the chip discharge groove 8 (entire) is, for example, 2 ° to 35 °. In the example of this embodiment, the twist angle θ as the whole chip discharge groove 8 is 5 ° to 30 °.
The twist angle θ of the tip side twisted portion 8a in the chip discharge groove 8 is, for example, 20 ° to 35 °, and more preferably 25 ° to 30 °. In the example of the present embodiment, the twist angle θ of the distal end side twisted portion 8a is 30 ° over the entire length of the distal end side twisted portion 8a, and the twist angle θ is constant along the axis O direction. However, the present invention is not limited to this, and for example, the twist angle θ of the distal end side twisted portion 8a may be gradually reduced from the distal end in the axis O direction toward the proximal end side.

  Moreover, the twist angle | corner (theta) of the base end side twist part 8b among the chip discharge grooves 8 is 2 degrees-15 degrees, for example, More preferably, it is 3 degrees-5 degrees. In the example of the present embodiment, the twist angle θ of the base end side twisted portion 8b is 5 ° over the entire length of the base end side twisted portion 8b, and the twist angle θ is constant along the axis O direction. However, the present invention is not limited to this, and for example, the twist angle θ of the proximal end side twisted portion 8b may be gradually reduced from the distal end in the axis O direction toward the proximal end side. In addition, when the rigidity of the drill main body 2 is easy to ensure, for example, when the overall length of the drill main body 2 in the axis O direction is short, the twist angle θ of the proximal-side twisted portion 8b can be set large (easily close to 15 ° above) Become).

  In the example of the present embodiment, the twist angle θ of the intermediate twisted portion 8c of the chip discharge groove 8 is the tip of the intermediate twisted portion 8c (the boundary portion with the tip-side twisted portion 8a). It is set to the same value (30 °) as the torsion angle θ, and gradually decreases from the distal end toward the proximal end, and at the proximal end of the intermediate twisted portion 8c (the boundary portion with the proximal twisted portion 8b) It is set to the same value (5 °) as the twist angle θ of the side twist portion 8b, and the twist angle θ changes along the axis O direction. When the twist angle θ of the distal twist portion 8a gradually decreases from the distal end in the direction of the axis O toward the proximal end, the twist angle θ at the distal end of the intermediate twist portion 8c is the distal twist It becomes equal to the twist angle θ at the base end of the portion 8a (the minimum value of the twist angle θ of the tip side twisted portion 8a). Further, when the twist angle θ of the base end side twisted portion 8b gradually decreases from the tip end in the axis O direction toward the base end side, the twist angle θ at the base end of the intermediate twist portion 8c is It becomes equal to the twist angle θ at the tip of the end side twisted portion 8b (the maximum value of the twist angle θ of the base end side twisted portion 8b).

As shown in FIG. 3B, the lengths of the tip discharge portion 8a, the intermediate twist portion 8c, and the proximal twist portion 8b along the axis O direction in the chip discharge groove 8 are increased in this order. ing. That is, the length along the axis O direction of the intermediate twisted portion 8c is larger than the length along the axis O direction of the tip side twisted portion 8a. Further, the length along the axis O direction of the proximal-side twisted portion 8b is larger than the length along the axis O direction of the intermediate twisted portion 8c.
In the example of this embodiment, the length in the axis O direction of the distal end side twisted portion 8a is 10.52 mm, the length in the axis O direction of the intermediate twisted portion 8c is 20.5 mm, and the length in the axis O direction of the proximal side twisted portion 8b. Is 79 mm in length.

[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 blade-tip replaceable drill 1 through a spindle of a machine tool or the like.

  1 to 4, the coolant hole 10 opens in the base end surface 9 of the drill body 2, and extends linearly so as to go in the drill rotation direction T from the base end surface 9 toward the distal end side in the axis O direction. 1 coolant hole 11 is connected to the tip of the first coolant hole 11 in the direction of the axis O, and the extending direction of the first coolant hole 11 from the tip toward the tip of the drill body 2 is defined as The second coolant hole 12 extends linearly in different directions and opens into the chip discharge groove 8 on the distal end side with respect to the distal end position of the proximal end side twisted portion 8b.

  In the present embodiment, the cross-sectional shape of the first coolant hole 11 (the cross-sectional shape perpendicular to the extending direction of the hole) and the cross-sectional shape of the second coolant hole 12 are each circular. In addition, the inner diameter of the second coolant hole 12 is smaller than the inner diameter of the first coolant hole 11.

  As shown in FIG. 2, both the first coolant hole 11 and the second coolant hole 12 are formed at positions separated from the axis O in the drill body 2. A plurality of sets of the first coolant hole 11 and the second coolant hole 12 communicating with each other are provided so as to be rotationally symmetric with respect to the axis O. Specifically, two sets of the first coolant hole 11 and the second coolant hole 12 (that is, the coolant hole 10) are formed in the drill body 2 at a rotationally symmetric position by 180 ° about the axis O. ing.

  As shown in FIG. 3 (b), the first coolant hole 11 is formed in a portion of the drill body 2 corresponding to at least the proximal-side twisted portion 8 b along the axis O direction in the shank portion 6 and the blade portion 7. Is formed. In the present embodiment, the distal end portion of the first coolant hole 11 in the axis O direction (that is, the connection portion between the first coolant hole 11 and the second coolant hole 12) is a proximal-side twisted portion along the axis O direction. It arrange | positions at the front end side rather than 8b. In the illustrated example, the connection portion between the first coolant hole 11 and the second coolant hole 12 is disposed at a portion corresponding to the intermediate twist portion 8c along the axis O direction.

  As shown in FIG. 1 and FIG. 2, in this embodiment, the second coolant hole 12 rotates as the first coolant hole 11 moves from the distal end portion in the direction of the axis O to the distal end side of the drill body 2. It extends to the opposite side of the direction T.

Reference numeral 5 a shown in FIG. 3A represents an outer end (outer peripheral corner) of the cutting edge 5 in the radial direction. When a virtual plane including the radial outer ends 5a of the two cutting edges 5 and the axis O is defined as a reference plane, the first coolant hole 11 and the second coolant hole 12 projected onto the virtual plane (reference plane). Are inclined with respect to the axis O and extend. The direction in which the first coolant hole 11 is inclined with respect to the axis O and the direction in which the second coolant hole 12 is inclined with respect to the axis O are opposite to each other.
Specifically, in FIG. 3A, the first coolant hole 11 is inclined so as to gradually approach the axis O as it goes to the tip side in the direction of the axis O, and the second coolant hole 12 is It is inclined so as to gradually move away from the axis O as it goes toward the tip end side in the direction of the axis O.

  The second coolant hole 12 opens into the chip discharge groove 8 at one of the distal end side twisted portion 8a and the distal end portion of the intermediate twisted portion 8c. As shown in FIG. 3B, in the example of the present embodiment, the second coolant hole 12 opens into the chip discharge groove 8 at the tip of the intermediate twisted portion 8c.

  Further, on the extended line of the second coolant hole 12, either the cutting edge 5 or the rake face 15 adjacent to the cutting edge 5 is disposed. In other words, the second coolant hole 12 opens straight toward either the cutting edge 5 or the rake face 15. In the example of the present embodiment, both the cutting edge 5 and the rake face 15 are arranged on the extended line of the second coolant hole 12.

[Effects of this embodiment]
According to the drill main body 2 and the blade tip replaceable drill 1 of the blade tip replaceable drill 1 of the present embodiment described above, the chip discharge groove 8 includes the distal end side twist portion 8a and the proximal end side twist portion having different twist angles θ. 8b and an intermediate twisted portion 8c. The tip side twisted portion 8 a has the largest twist angle θ in the chip discharge groove 8 and is disposed adjacent to the insert mounting seat 3. The proximal end side twisted portion 8b has a smaller twist angle θ than the distal end side twisted portion 8a, and is spaced from the insert mounting seat 3 toward the proximal end side in the axis O direction. The intermediate twisted portion 8c is located between and connected to the distal end side twisted portion 8a and the proximal end side twisted portion 8b, and from the distal end in the axis O direction (boundary portion with the distal end side twisted portion 8a) to the proximal end ( The twist angle θ is gradually reduced toward the boundary portion with the base end side twisted portion 8b.

For this reason, in the part adjacent to the insert mounting seat 3 to which the cutting insert 4 is mounted, the torsion angle θ of the chip discharge groove 8 (the tip side twisted part 8a) is ensured to be large, so that chip discharge performance can be improved. it can.
Further, in a portion spaced from the insert mounting seat 3 toward the base end side in the axis O direction, a positive twist angle θ is imparted to the chip discharge groove 8 (the base end side twisted portion 8b) so that the chip discharge performance exceeds a certain level. While ensuring the above, it is possible to increase the strength (rigidity) of the drill body 2 by suppressing the twist angle θ to be small.
In addition, in the portion located between the distal end side twisted portion 8a and the proximal end side twisted portion 8b, the twist angle θ of the chip discharge groove 8 (the intermediate twisted portion 8c) is gradually changed, and the distal end side twisted portion 8a and The proximal-side twisted portion 8b can be smoothly connected. Thereby, the residence of the chip | tip which flows in the chip discharge groove | channel 8 can be suppressed effectively, and the rigidity of the drill main body 2 is also ensured.

  The coolant hole 10 formed in the drill body 2 extends between the chip discharge grooves 8 adjacent in the circumferential direction (inside in the radial direction of the land portion 14) without passing on the axis O. Specifically, the coolant hole 10 is connected to a linear first coolant hole 11 extending obliquely with respect to the axis O and the tip of the first coolant hole 11, and the first coolant hole 11. And a second linear coolant hole 12 extending in a direction different from the extending direction.

  The first coolant hole 11 opens in the base end surface 9 of the drill body 2. The coolant supplied from the coolant supply means provided outside the drill is supplied to the first coolant hole 11 in the machine tool. It flows in through the main shaft. The first coolant hole 11 extends from the proximal end surface 9 of the drill body 2 toward the distal end side in the direction of the axis O toward the drill rotation direction T, and thus the proximal end side twisted portion 8b of the chip discharge groove 8 is extended. It is easy to incline according to the twist angle θ.

  That is, since the first coolant hole 11 can be extended (substantially in parallel) along the proximal-side twisted portion 8b of the chip discharge groove 8, the first coolant hole 11 is a groove wall of the chip discharge groove 8. The first coolant hole 11 can be extended long toward the distal end side of the drill body 2 while preventing it from being too close to the (inner wall) or being opened in the groove. For this reason, the malfunction that the intensity | strength of the drill main body 2 falls around the 1st coolant hole 11, or a coolant is sprayed in the chip discharge groove 8 in the position spaced apart from the cutting blade 5 is prevented. Moreover, since the connection part (front-end | tip part of the 1st coolant hole 11) of the 1st coolant hole 11 and the 2nd coolant hole 12 can be arrange | positioned in the position close | similar to the front-end | tip part of the drill main body 2, it is 2nd coolant. It is easy to open the hole 12 in the chip discharge groove 8 near the insert mounting seat 3, and coolant can be accurately supplied near the cutting edge 5.

The second coolant hole 12 is connected to the distal end portion of the first coolant hole 11 and extends in a direction different from the direction in which the first coolant hole 11 extends. It opens to either the tip side twisted portion 8a or the intermediate twisted portion 8c located on the tip side of the side twisted portion 8b.
That is, the second coolant hole 12 is opened in the chip discharge groove 8 at either the tip side twisted portion 8a or the intermediate twisted portion 8c close to the insert mounting seat 3, so that the coolant reaches the vicinity of the cutting edge 5. It can be made easier. Further, the second coolant hole 12 opens in any one of the tip-side twisted portion 8a and the intermediate twisted portion 8c having a larger twist angle θ than the proximal-side twisted portion 8b in the chip discharge groove 8, so that the chip discharge groove The opening area into 8 can be kept small.

  Specifically, it is possible to prevent a problem in which the opening portion of the second coolant hole 12 into the chip discharge groove 8 extends so as to tear in the direction of the axis O. That is, according to the present embodiment, even if the second coolant hole 12 is not greatly inclined with respect to the axis O, the opening portion into the chip discharge groove 8 can be prevented from extending greatly vertically, and the drill body The strength of 2 is ensured, and the appearance (appearance) as a product is also maintained well. Thereby, the design condition of the 2nd coolant hole 12 is eased, and it becomes possible to respond to various drill forms. Furthermore, the connection angle between the first coolant hole 11 and the second coolant hole 12 can be moderated (increased to the obtuse angle side) to reduce the pressure loss of the coolant flowing through the connection portion. .

Further, since the first and second coolant holes 11 and 12 are respectively linear, the pressure loss of the coolant flowing in the coolant hole 10 is remarkably reduced. For this reason, it is easy to increase the coolant flow rate linearly by increasing the coolant supply pressure or the like, and the coolant can surely reach the vicinity of the cutting edge 5.
Moreover, at the time of drill manufacture, the 1st, 2nd coolant holes 11 and 12 can be shape | molded using a small diameter drill etc., and manufacture of the drill main body 2 is easy.

  As described above, according to the present embodiment, the drill body 2 can be easily manufactured, the strength of the drill body 2 can be ensured, the chip discharge performance can be improved, and the coolant can be easily reached near the cutting edge 5 for cooling. Efficiency can be improved.

Moreover, in this embodiment, the 2nd coolant hole 12 goes to the opposite side to the drill rotation direction T as it goes to the front end side of the drill main body 2 from the front-end | tip part of the axis line O direction of the 1st coolant hole 11. FIG. Since it is extended, the following effects are obtained.
That is, in this case, it is easy to arrange the cutting edge 5 of the cutting insert 4 mounted on the insert mounting seat 3 and the rake face 15 adjacent to the cutting edge 5 on the extension line of the second coolant hole 12. Therefore, the coolant ejected from the second coolant hole 12 can be directly supplied to the vicinity of the cutting edge 5 to be cooled, and the cooling efficiency can be remarkably increased.

  Moreover, in this embodiment, the 2nd coolant hole 12 is opened in the chip discharge groove | channel 8 in any one of the front end part of the front side twist part 8a and the intermediate | middle twist part 8c. That is, the twist angle θ of the tip side twisted portion 8a is large, and the twist angle θ at the tip portion of the intermediate twisted portion 8c is also close to the twist angle θ of the tip side twisted portion 8a, and the twist angle θ is large. The second coolant hole 12 can be reliably opened in the chip discharge groove 8 at a portion where the twist angle θ is large. Therefore, it is easy to suppress the opening area of the second coolant hole 12 to be small, and the above-described operational effects become more remarkable.

Moreover, in this embodiment, since the connection part of the 1st coolant hole 11 and the 2nd coolant hole 12 is arrange | positioned in the front end side rather than the base end side twist part 8b along an axis line O direction, the following effect | action There is an effect.
That is, in this case, the connection portion between the first coolant hole 11 and the second coolant hole 12 corresponds to one of the tip side twisted portion 8a and the intermediate twisted portion 8c along the axis O direction, that is, the drill body 2. It is arrange | positioned in the position near the front-end | tip part. For this reason, it becomes easy to open the 2nd coolant hole 12 in the chip discharge groove | channel 8 near the insert mounting seat 3, and it is easy to make coolant reach the cutting blade 5 vicinity more reliably.

Further, in the present embodiment, a plurality of sets (coolant holes 10) of the first coolant hole 11 and the second coolant hole 12 that are in communication with each other are provided in a rotationally symmetrical manner around the axis O. Has an effect.
That is, in this case, the set of the first coolant hole 11 and the second coolant hole 12 communicating with each other while equalizing the rigidity of the drill body 2 in the circumferential direction is used in the case of a two-blade drill as in this embodiment. In the case of two or three-blade drills, for example, three can be provided according to the number of cutting edges 5, and the cooling efficiency of each cutting edge 5 can be fully improved.

  In the present embodiment, either the cutting edge 5 or the rake face 15 adjacent to the cutting edge 5 is disposed on the extended line of the second coolant hole 12. Therefore, the coolant ejected from the second coolant hole 12 can be directly supplied to the vicinity of the cutting edge 5 to be cooled, and the cooling efficiency can be remarkably increased.

Moreover, in this embodiment, the 1st coolant hole 11 and the 2nd coolant hole 12 which were projected on the virtual plane (reference surface) containing the radial direction outer end 5a and the axis line O of the two cutting blades 5 are the axis line O. The direction in which the first coolant hole 11 is inclined with respect to the axis O and the direction in which the second coolant hole 12 is inclined with respect to the axis O are opposite to each other. Since there is, there exists the following effect.
That is, in this case, the first coolant hole 11 is inclined with respect to the axis O according to the twist angle θ of the chip discharge groove 8 (inclined to the positive angle side), and the second coolant hole 12 is The discharge groove 8 can be inclined with respect to the axis O in the opposite direction to the twist angle θ (inclined to the negative angle side). Therefore, the opening area of the second coolant hole 12 into the chip discharge groove 8 is kept small, or the cutting edge 5 of the cutting insert 4 mounted on the insert mounting seat 3 on the extension line of the second coolant hole 12. It is easy to arrange the easy surface 15. Therefore, while ensuring the strength of the drill body 2, the coolant sprayed from the second coolant hole 12 can be directly supplied to the vicinity of the cutting edge 5, thereby significantly increasing the cooling efficiency.

  In the present embodiment, since the inner diameter of the second coolant hole 12 is smaller than the inner diameter of the first coolant hole 11, the flow rate of the coolant flowing in the second coolant hole 12 can be increased, and the second The coolant ejected from the coolant hole 12 can be more easily reached near the cutting edge 5.

[Other configurations included in the present invention]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above-described embodiment, as shown in FIG. 3B, the second coolant hole 12 is opened in the chip discharge groove 8 at the tip portion of the intermediate twisted portion 8c. It is not limited.
Here, what is shown in FIGS. 5A and 5B is a modified example of the blade-tip replaceable drill 1 described in the above embodiment. In this modification, the second coolant hole 12 opens into the chip discharge groove 8 at the tip side twisted portion 8a.

Moreover, in the modification of FIG. 5 (a), (b), the twist angle | corner (theta) as the whole chip discharge groove 8 is 5 degrees-20 degrees.
Specifically, in the chip discharge groove 8, the twist angle θ of the tip side twisted portion 8 a is 20 ° over the entire length of the tip side twisted portion 8 a, and the twist angle θ is constant along the axis O direction. is there. Further, the twist angle θ of the base end side twisted portion 8b is 5 ° over the entire length of the base end side twisted portion 8b, and the twist angle θ is constant along the axis O direction. Further, the twist angle θ of the intermediate twist portion 8c is set to the same value (20 °) as the twist angle θ of the tip twist portion 8a at the tip of the intermediate twist portion 8c (the boundary portion with the tip twist portion 8a). The distance gradually decreases from the distal end toward the proximal end, and the same value as the twist angle θ of the proximal twisted portion 8b at the proximal end of the intermediate twisted portion 8c (the boundary portion with the proximal twisted portion 8b) (5 The twist angle θ varies along the axis O direction.
In this modification, the length of the distal-side twisted portion 8a in the axis O direction is 17.15 mm, the length of the intermediate twisted portion 8c in the axis O direction is 20 mm, and the length of the proximal-side twisted portion 8b in the axis O direction. Is 65 mm.
Also in this modification, the same operational effects as those of the above-described embodiment are obtained.

  Further, in the above-described embodiment, the chip discharge grooves 8 that open to the proximal end surface 9 of the drill body 2 and are adjacent to each other in the circumferential direction from the proximal end surface 9 toward the distal end side in the axis O direction are formed inside the drill body 2. A coolant hole 10 extending without passing on the axis O is formed. Specifically, the first coolant hole 11 in the coolant hole 10 opens in the base end surface 9 of the drill body 2, and Although it has been assumed that it extends linearly from the end face 9 toward the tip end side in the direction of the axis O in the drill rotation direction T, the present invention is not limited to this.

Here, what is shown in FIGS. 6 to 9 is a modified example of the blade-tip replaceable drill 1 described in the above-described embodiment.
In the modification shown in FIGS. 6 and 7, a slit-like groove (concave portion) 17 that is recessed from the base end surface 9 is formed on the base end surface 9 of the drill body 2. The first coolant hole 11 (coolant hole 10) is opened in the inner wall of the groove 17. That is, the first coolant hole 11 of the coolant hole 10 may be opened in a groove (concave portion) 17 formed in the base end surface 9 instead of opening in the base end surface 9 of the drill body 2. In the illustrated example, the groove 17 extends in the radial direction on the base end surface 9, and both ends of the groove 17 are open to the outer peripheral surface of the drill body 2.
In the modification shown in FIGS. 8 and 9, a hole (concave portion) 18 formed of a drill hole or the like recessed from the base end surface 9 is formed on the base end surface 9 of the drill body 2. The first coolant hole 11 (coolant hole 10) opens in the bottom wall of the hole 18. That is, the first coolant hole 11 of the coolant hole 10 may be opened in a hole (concave portion) 18 formed in the base end face 9 instead of opening in the base end face 9 of the drill body 2. In the illustrated example, the hole 18 extends from the base end face 9 toward the distal end side in the axis O direction, and the bottom wall of the hole 18 is disposed at a portion corresponding to the shank portion 6 along the axis O direction.
Also in these modified examples, the same operational effects as those of the above-described embodiment can be obtained. In addition, you may form the recessed part made into shapes other than the groove | channel 17 and the hole 18 which were mentioned above in the base end surface 9. FIG.

  Further, in the above-described embodiment, the second coolant hole 12 moves toward the opposite side of the drill rotation direction T as it goes from the distal end portion of the first coolant hole 11 in the axis O direction toward the distal end side of the drill body 2. However, the present invention is not limited to this. That is, the second coolant hole 12 is connected to the distal end portion of the first coolant hole 11 in the direction of the axis O, and the extending direction of the first coolant hole 11 from the distal end portion toward the distal end side of the drill body 2. As long as it opens in the chip discharge groove 8 on the distal end side with respect to the distal end position of the proximal end side twisted portion 8b, for example, it may extend in parallel to the axis O.

Further, in the above-described embodiment, the blade-tip replaceable drill 1 is a two-blade twist drill. The cutting insert 4 is formed with two cutting edges 5 at a 180 ° rotationally symmetric position about the axis O, and the drill body 2 has two chip discharge grooves 8 at a 180 ° rotationally symmetric position about the axis O. The two pairs of the first coolant hole 11 and the second coolant hole 12 (coolant hole 10) are also formed at 180 ° rotationally symmetric positions. However, the present invention is not limited to this. That is, the set of the cutting edge 5, the chip discharge groove 8, and the first coolant hole 11 and the second coolant hole 12 may not be arranged at 180 ° rotationally symmetric positions around the axis O. (In other words, they may be arranged at unequal pitches).
The present invention can also be applied to a blade tip replaceable drill 1 having three or more blades. In this case, the cutting edge 5, the chip discharge groove 8, the first coolant hole 11, and the second coolant hole 12 are provided. Each set may be arranged at a rotationally symmetric position around the axis O, or may not be arranged at a rotationally symmetric position.

Further, in the above-described embodiment, the insert mounting seat 3 has a groove shape extending in the 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 radially outer sides) of the drill body 2. The cutting insert 4 is opened and the cutting edge 5 is projected from the front end surface and the outer peripheral surface of the drill body 2 and is mounted on the insert mounting seat 3. These shapes are not limited to those described in the above embodiment.
For example, two chip discharge grooves 8 are formed on the outer periphery of the drill body 2, and a cutting insert for an inner blade having a rectangular plate shape is formed at the tip of each chip discharge groove 8, and the same as the cutting insert for the inner blade. The present invention can also be applied to a blade-tip-replaceable drill and a drill body to which a shaped outer blade cutting insert is detachably mounted.

  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 remark etc., addition of a structure, omission, substitution, others It can be changed. Further, the present invention is not limited by the above-described embodiments, and is limited only by the scope of the claims.

DESCRIPTION OF SYMBOLS 1 Cutting edge exchange type drill 2 Drill main body 3 Insert mounting seat 4 Cutting insert 5 Cutting edge 5a The outer end of a cutting edge in the radial direction (outer corner)
8 Chip discharge groove 8a Tip side twisted part 8b Base end side twisted part 8c Intermediate twisted part 9 Base end face 10 Coolant hole 11 First coolant hole 12 Second coolant hole 15 Rake face 17 Groove (concave part)
18 holes (concave)
O Axis T Drill direction θ Twist angle

Claims (8)

Cutting edge replacement in which an insert mounting seat is formed in which a cutting insert having a cutting edge with a cutting edge is detachably mounted at the tip end portion in the axial direction, which is formed in an axial shape and is rotated in the drill rotating direction in the circumferential direction around the axis. The drill body of the type drill,
On the outer periphery of the drill main body, a plurality of chip discharge grooves extending twisted toward the opposite side of the drill rotation direction from the distal end in the axial direction toward the proximal end side are formed at intervals in the circumferential direction. And
Inside the drill main body, the base end surface of the drill main body or a recess formed in the base end surface opens, and is adjacent to the circumferential direction from the base end surface or the concave portion toward the distal end side in the axial direction. A coolant hole extending between the chip discharge grooves without passing on the axis is formed,
The chip discharge groove is
A tip side twisted portion disposed adjacent to the insert mounting seat;
A proximal-side twisted portion that is disposed closer to the proximal end in the axial direction than the distal-end twisted portion and has a twist angle smaller than the twist angle of the distal-end twisted portion;
It arrange | positions between the said front end side twist part and the said base end side twist part, these are connected, and it twists gradually as it goes to the boundary part with the said base end side twist part from the boundary part with the said front end side twist part. An intermediate twisted portion with a reduced angle,
The coolant hole is
A first coolant hole that opens to the base end surface or the concave portion and extends linearly so as to go from the base end surface or the concave portion toward the distal end side in the axial direction in the drill rotation direction;
The first coolant hole is connected to the tip end portion in the axial direction and extends linearly from the tip portion toward the tip end side of the drill body in a direction different from the extending direction of the first coolant hole. And a second coolant hole that opens into the chip discharge groove on the distal end side with respect to the distal end position of the base end side twisted portion. A drill body of the blade-tip replaceable drill according to claim 1,
The second coolant hole extends from the tip end portion of the first coolant hole in the axial direction toward the tip end side of the drill body so as to go to the opposite side of the drill rotation direction. The drill body of the replaceable cutting edge drill. A drill body of the blade-tip replaceable drill according to claim 1 or 2,
The second coolant hole is opened in the chip discharge groove at any one of the distal end side twisted portion and the distal end portion of the intermediate twisted portion. The drill body of the blade tip replaceable drill according to any one of claims 1 to 3,
The connecting portion between the first coolant hole and the second coolant hole is disposed closer to the distal end side than the proximal-side twisted portion along the axial direction. Body. It is a drill main part of the blade-tip exchange type drill according to any one of claims 1 to 4,
A drill body of a blade-tip-exchangeable drill, wherein a plurality of sets of the first coolant hole and the second coolant hole communicating with each other are provided in a rotationally symmetrical manner around the axis. A drill body having an axial shape, rotated in the drill rotation direction out of the circumferential direction around the axis, and having an insert mounting seat formed at the tip in the axial direction;
A cutting edge replaceable drill comprising a cutting insert detachably mounted on the insert mounting seat and having a cutting edge,
A blade-tip replaceable drill using the drill body of the blade-tip replaceable drill according to any one of claims 1 to 5 as the drill body. It is a blade-tip-exchangeable drill according to claim 6,
One of the cutting edge and the rake face adjacent to the cutting edge is disposed on an extension line of the second coolant hole. The blade tip replaceable drill according to claim 6 or 7,
In the drill body, two chip discharge grooves are formed at 180 ° rotationally symmetrical positions around the axis,
Two cutting edges are formed in the cutting insert at a 180 ° rotationally symmetric position about the axis,
The first coolant hole and the second coolant hole projected on a virtual plane including the radial outer ends of the two cutting edges and the axis extend in an inclined manner with respect to the axis, respectively.
The blade tip replaceable drill characterized in that the direction in which the first coolant hole is inclined with respect to the axis and the direction in which the second coolant hole is inclined with respect to the axis are opposite to each other.

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