JP2003275913A - Drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain good chip disposal performance without causing chip clogging by producing segmented chips. <P>SOLUTION: A subsidiary groove 16 is formed to open to a wall face 15A facing to the front side of a chip disposal groove 15 in a drill rotating direction T and to an outer periphery face 13 of a cutting edge portion 12. A flank is given to a wall face 16B facing to the subsidiary groove 16 on the outer periphery side of a drill body in the drill rotating direction T. A cutting edge 19 consists of a cutting edge inner periphery portion 17 formed on an intersecting ridge portion between a front-end region of the wall face 15A facing to the front side of the chip disposal groove 15 in the drill rotating direction T and a front-end flank 14 and a cutting edge outer periphery portion 18 formed on an intersecting ridge portion between a front-end region of the wall face 16A facing to the front side of the subsidiary groove 16 in the drill rotating direction T and the front-end flank 14. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill used for drilling a work.

[0002]

2. Description of the Related Art Generally, a drill used for drilling is made of a hard material such as high-speed steel or cemented carbide, and has an outer peripheral surface at the tip of a drill body that is rotated around an axis and has a substantially cylindrical shape. In addition, a pair of chip discharge grooves are formed. Then, these chip discharge grooves are spirally twisted with a constant lead toward the rear side in the drill rotation direction around the axis from the tip flank of the drill body toward the base end side,
Further, a pair of cutting blades are formed at the ridge line portion where the tip side region of the wall surface of the chip discharge groove facing the front side in the drill rotation direction and the tip flank face intersect.

[0003]

Since the pair of cutting edges are formed in a long linear shape extending from the periphery of the axis on the flank of the tip to the outer peripheral surface of the drill body, they have the above-mentioned configuration. When drilling is performed using a drill,
The width of the chips generated by the cutting edge becomes large, and chips with such a large width are clogged in the chip discharge groove, and good chip discharge performance cannot be maintained, which hinders drilling. It will end up coming. In particular, such a tendency becomes remarkable in the drilling of deep holes in which the tip of the drill body in which the chip discharge groove is formed must be inserted inside the drilled hole for a long time. There were even things that couldn't be done. Moreover, since such a cutting edge is formed so as to reach the outer peripheral surface of the drill body, a large chip generated by the cutting edge comes into contact with the inner wall surface of the machining hole, There is also a problem that the inner wall surface is damaged and the surface roughness is reduced.

Here, for example, JP-A-11-13832
There are stepped drills such as those disclosed in No. 0 and Japanese Patent Laid-Open No. 2001-54810, and such a stepped drill has a small diameter portion in which the outer diameter is further reduced at the tip portion of the drill body. And a step portion at the location where the small diameter portion and the base end side are connected, the cutting blade inner peripheral portion formed at the tip of the small diameter portion and the cutting blade outer periphery formed at the step portion. A cutting edge is constituted by the part. When performing drilling using such a stepped drill, it is possible to generate chips by dividing them in the width direction by the cutting blade inner peripheral portion and the cutting blade outer peripheral portion that configure the cutting blade. However, when it becomes necessary to perform re-grinding due to wear of the cutting blade inner peripheral portion and the cutting blade outer peripheral portion, between the flank surface continuous to the cutting blade inner peripheral portion and the flank surface continuous to the cutting blade outer peripheral portion. Each had to be reground, which was not an effective solution.

The present invention has been made in view of the above problems, and provides a drill capable of maintaining a good chip discharging property without causing chip clogging by dividing chips to generate chips. To aim.

[0006]

In order to solve the above-mentioned problems and to achieve such an object, the present invention is to discharge chips on the outer peripheral surface of a drill body having an outer diameter and a substantially cylindrical shape rotated around an axis. A groove is formed, and a wall surface facing the drill rotation direction front side of the chip discharge groove and a sub-groove opening to the outer peripheral surface of the drill body are formed, and the wall surface of the sub-groove facing the drill body outer peripheral side is formed. Is provided with relief in the direction of drill rotation, and the inner peripheral portion of the cutting edge formed at the ridge line intersecting the tip side flank and the tip side region of the wall surface facing the drill rotation direction front side of the chip discharge groove. A cutting edge is formed by a tip edge region of a wall surface of the auxiliary groove facing the front side in the drill rotation direction and a cutting edge outer peripheral portion formed at a ridge line intersecting with the tip flank. With this configuration, the wall surface of the auxiliary groove facing the outer peripheral side of the drill body is inclined toward the inner peripheral side of the drill main body toward the rear side in the drill rotating direction. The outer peripheral part of the cutting edge formed on the ridge of the intersection of the wall facing the front side and the flank of the cutting edge is the cutting edge formed on the ridge of the intersection of the wall facing the front side in the drill rotation direction of the chip discharge groove and the flank of the tip. Since the chips are not continuous to the inner peripheral part of the blade and chips are generated at each of the outer peripheral part of the cutting blade and the inner peripheral part of the cutting blade, a chip having a large width is not generated unlike the conventional case, and the width of the chip is reduced. It is possible to generate by dividing into directions. As a result, the chips that have been cut into smaller widths are more easily conveyed and discharged to the base end side of the drill body by the chip discharge groove, and good chip discharge performance can be maintained, making it possible to drill deep holes. There is no problem even when performing processing. Also,
Chips that are generated on the outer periphery of the cutting edge and tend to come into contact with the inner wall surface of the machined hole do not increase in width as in the case of using a conventional drill, but are divided in the width direction and become smaller in width. Since the chips are chips, the inner wall surface of the processed hole is not damaged and the surface roughness can be improved. Furthermore, since the cutting blade inner peripheral portion and the cutting blade outer peripheral portion constituting the cutting blade are both located on the same tip flank, when the cutting blade inner peripheral portion and the cutting blade outer peripheral portion are worn. In this case, it is only necessary to re-grind the tip flank, and the sharpness of the inner peripheral portion of the cutting blade and the outer peripheral portion of the cutting blade can be restored by re-grinding once.

Further, in the present invention, in a cross section orthogonal to the axis of the drill body, an outer peripheral end of a wall surface of the chip discharge groove facing the front side in the drill rotation direction and a wall surface of the auxiliary groove facing the front side in the drill rotation direction. The distance a in the radial direction of the drill body from the outer peripheral edge of the is 0.05 with respect to the outer diameter D of the cutting edge.
(D) ^1/2 ≤ a ≤ 0.3 (D) ^1/2 is set in the range. Here, if the distance a is too small,
As the length of the inner peripheral portion of the cutting blade becomes too large, the width of the chips generated at the inner peripheral portion of the cutting blade also becomes large, and the effect obtained by dividing the chips becomes weak, while the distance a becomes large. If it is too large, the outer peripheral length of the cutting edge becomes too large, and the width of the chips generated by the outer peripheral part of the cutting edge also becomes large, increasing the width of the chips that are likely to come into contact with the inner wall surface of the machined hole. This may damage the wall surface. Therefore, in the present invention, the distance a is set to 0.05
(D) ^1/2 ≤ a ≤ 0.3 (D) ^1/2 By setting the optimum range, chips can be cut into a suitable width,
It is possible to improve the roughness of the inner wall surface of the processed hole.

Further, according to the present invention, in a cross section orthogonal to the axis of the drill body, the outer peripheral edge of the wall surface of the chip discharge groove facing the front side in the drill rotation direction and the wall surface of the auxiliary groove facing the front side in the drill rotation direction. A distance b in the circumferential direction of the drill main body from the outer peripheral edge of the outer peripheral edge of the wall surface facing the front side in the drill rotation direction of the chip discharge groove and the outer peripheral edge of the wall surface facing the front side in the drill rotation direction of the auxiliary groove. With respect to the radial distance a of the drill body, 0.5a ≦ b ≦ 3a is set. Here, if the distance b is too small, the outer peripheral portion of the cutting edge and the inner peripheral portion of the cutting edge are formed as if they were continuous cutting edges, and there is a possibility that the chips cannot be divided in the width direction. If b is too large, the size of the sub-groove becomes too large, which may reduce the rigidity of the drill body. Therefore, in the present invention, by setting the distance b within the range of 0.5a ≦ b ≦ 3a,
It is possible to stably divide the chips and keep the rigidity of the drill body high.

[0009]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a side view of a drill according to an embodiment of the present invention, FIG. 2 is a front end view of the drill as seen from the front end side in the axial direction, FIG. 3 is a sectional view taken along the line AA in FIG. 1, and FIG. It is a principal part enlarged view in.

Drill body 10 of the drill according to the present embodiment
Is formed of a hard material such as high-speed steel or cemented carbide into a substantially cylindrical outer shape centered on the axis O, and its base end side (upper side portion in FIG. 1) is a shank portion 11, This shank portion 11 is attached to a rotary shaft of a machine tool, is rotated in a drill rotation direction indicated by a symbol T in the drawing, and is used for drilling.

The tip of the drill body 10 (the lower side portion in FIG. 1) is a cutting edge portion 12.
On the outer peripheral surface 13 of the pair of chips, a pair of chip discharge grooves 15, 15 on opposite sides of the axis O are symmetrical with respect to the axis O from the tip flank 14 of the drill body 10 to the entire length of the cutting edge 12. In addition, it is formed so as to have a spiral shape that is twisted with a constant lead toward the rear side of the drill rotation direction T from the tip flank 14 toward the base end side. In addition, this cutting edge portion 12
Are the chip discharge grooves 15 and 15 (and auxiliary grooves 16 and 1 to be described later).
It is formed so as to be symmetrical with respect to the axis O, including 6).

In the cross section perpendicular to the axis O, the chip discharge grooves 15 and 15 respectively face the drill rotation direction T front side, as shown in FIG. 3, from the outer peripheral surface 13 of the cutting edge portion 12 to the drill rotation direction T. A wall surface 15 </ b> A having a substantially curved cross section that is recessed rearward and approaches the axis O side, and the wall surface 15 </ b> A.
A wall surface 15B which is smoothly connected to A, faces the rear side in the drill rotation direction T, is recessed in the front side in the drill rotation direction T, is separated from the axis O, and intersects the outer peripheral surface 13 and has a substantially curved cross section. Has been done. The wall surfaces 15A and 15A of the chip discharge grooves 15 and 15 which face the front side in the drill rotation direction T have a cutting blade inner peripheral portion 17 to be described later that has a substantially linear shape when the tip flank 14 is formed at a predetermined tip angle. It is formed into a curved line such that

In this embodiment, the outer peripheral surface 13 of the cutting edge portion 12 is adjacent to the outer peripheral surface 13 of the cutting edge portion 12 on the rear side of the chip discharge grooves 15, 15 in the drill rotation direction T.
Also, sub-grooves 16 and 16 are formed so as to open to a wall surface 15A facing the front side of the chip discharge groove 15 in the drill rotation direction T. The sub-grooves 16 and 16 are also formed in the chip discharge groove 1
Like 5 and 15, it is symmetrical with respect to the axis O over the entire length of the cutting edge portion 12 from the tip flank 14 of the drill body 10, and from the tip flank 14 toward the base end in the rearward direction T of the drill rotation. It has a spiral shape that twists with a certain lead.

As shown in FIGS. 3 and 4, the sub-grooves 16 and 16 respectively face the outer peripheral surface 13 of the cutting edge portion 12 toward the front side in the drill rotation direction T as shown in FIGS. 3 and 4 in a cross section orthogonal to the axis O.
From the wall surface 1 that has a substantially linear cross-section that approaches the axis O side from
6A and the wall surface 16A are smoothly connected to each other via a portion having a substantially curved cross section, and face the outer peripheral side of the drill body, and become convex toward the outer peripheral side of the drill body and face the front side of the chip discharge groove 15 in the drill rotation direction T. It is composed of a wall surface 16B that crosses the wall surface 15A and has a substantially curved cross section.

Here, in the cross section which is also orthogonal to the axis O, as shown in FIG. 4, the wall surface 16B of the auxiliary groove 16 facing the outer peripheral side of the drill body is provided with a clearance in the drill rotation direction T. That is, the wall surface 16B is formed to be inclined so as to gradually approach the inner peripheral side of the drill main body as it goes toward the rear side of the drill rotation direction T. In other words, the wall surface 16B of the auxiliary groove 16 facing the outer peripheral side of the drill body
And a wall surface 15A of the chip discharge groove 15 that faces the front side in the drill rotation direction T, that is, the rotation locus R around the axis O formed by the outer peripheral end X of the wall surface 15A is continuous with the outer peripheral end X. The wall surface 16B does not cross the rotation locus R to the outer peripheral side of the drill body.

Further, as shown in FIG. 4, the wall surface 16A of the sub-groove 16 which faces the front side in the drill rotation direction T gradually tapers toward the inner circumference side of the drill body.
It is formed so as to be inclined toward the rear side. In other words, the wall surface 1 facing the drill rotation direction T front side of the sub groove 16
6A and the outer peripheral surface 13 of the cutting edge portion 12, that is, a straight line S connecting the outer peripheral end Y of the wall surface 16A and the axis O.
On the other hand, the wall surface 16A connected to the outer peripheral end Y does not cross the straight line S forward of the drill rotation direction T.

Similarly, in a cross section perpendicular to the axis O, as shown in FIG. 4, the outer peripheral edge X of the wall surface 15A,
A radial distance a of the drill body 10 to the outer peripheral end Y of the wall surface 16A, that is, a distance in the direction along the straight line S is an outer diameter D of a cutting edge 19 described later (a margin portion 1 described later).
0.05) for a virtual circle with 3A as the arc)
(D) ^1/2 ≤ a ≤ 0.3 (D) ^1/2 is set. Further, as shown in FIG. 4, the drill body 10 including the outer peripheral edge X of the wall surface 15A and the outer peripheral edge Y of the wall surface 16A.
The distance b in the circumferential direction, that is, the distance in the direction orthogonal to the straight line S is 0.5 with respect to the distance a in the radial direction.
It is set in the range of a ≦ b ≦ 3a. And the sub groove 1
6 and 16 are opened to the tip flank 14 while maintaining the cross-sectional shape as described above.

Further, the outer peripheral surface 13 of the cutting edge portion 12 defined between the chip discharge groove 15 and the auxiliary groove 16 which is adjacent to the front side of the drill discharge direction T in the circumferential direction is the outer peripheral surface 13 of the auxiliary groove 16. A margin portion 13A continuous to the rear side of T and having an arcuate cross-section centered on the axis O, and the margin portion 13
It is connected to the rear side of the drill rotation direction T of A, intersects with the wall surface 15B of the chip discharge groove 15 facing the rear side of the drill rotation direction T, and has an arc-shaped cross section centered on the axis O slightly smaller than the margin 13A. It is constituted by the second taking surface 13B.

On the other hand, the tip flank 14 has a substantially conical surface centered on the axis O, and the chip discharge groove 15,
It is formed so as to gradually retreat toward the rear side of the drill rotation direction T from the openings of the fifteenth and the sub-grooves 16 and 16 around the axis O to provide relief. Then, as described above, a substantially straight cutting line is formed at the ridge portion where the tip flank surface of the wall surface 15A that faces the front side of the chip discharge groove 15 in the drill rotation direction T and forms a rake face and the tip flank face 14 are intersected. The blade inner peripheral portion 17 is formed. Further, the wall surface 16 facing the front side of the sub-groove 16 in the drill rotation direction T and forming a rake face.
A cutting edge outer peripheral portion 18 having a substantially linear shape is formed in a ridge line portion where the tip end side region of A and the tip flank 14 intersect so as to be substantially parallel to the cutting blade inner peripheral portion 17.

As a result, the inner peripheral portion 17 of the cutting blade is substantially straight and does not extend from the periphery of the axis O on the tip flank 14 to the outer peripheral surface of the drill body and does not reach the outer peripheral surface 13 of the cutting edge 12.
And a substantially linear cutting blade outer peripheral portion 18 which is located on the rear side of the cutting blade inner peripheral portion 17 in the drill rotation direction T and reaches the outer peripheral surface 13 of the cutting edge portion 12, with the axis O interposed therebetween. The pair of cutting blades 19, 19 of the drill according to the present embodiment are formed symmetrically. Moreover, when viewed from the tip side in the direction of the axis O, the rotation locus of the cutting blade inner peripheral portion 17 around the axis O and the rotation locus of the cutting blade outer peripheral portion 18 around the axis O are arranged so as to overlap each other. ing.

Further, since the tip flank 14 has a substantially conical surface shape, the cutting blade inner peripheral portion 1 constituting the cutting blade 19 is formed.
7 and the cutting blade outer peripheral portion 18 are provided with an inclination so as to gradually recede toward the base end side as it goes toward the outer peripheral side of the drill body,
As a result, the cutting edges 19 and 19 are given a predetermined tip angle. Further, the tip flank 14 has a pair of cutting blades 19, 1.
9 is formed by two surfaces respectively connected to the rear side of the drill rotation direction T, and these two surfaces intersect with each other on the axis O, so that the chisel passing on the axis O and extending in the direction orthogonal to the axis O 20 is defined, and this chisel 20 is cut up in a portion of the cutting blade inner peripheral portion 17 on the inner peripheral side of the drill body.

According to the drill having the above-described structure according to the present embodiment, the drill rotation direction T of the chip discharge groove 15 is set.
A wall surface 16 that is open on both the wall surface 15A facing the front side and the outer peripheral surface 13 of the cutting edge portion 12 and that faces the outer peripheral side of the drill body.
Sub-groove 16 provided with relief in B in the rotation direction of the drill
Since the sub-groove 16 is formed, the outer peripheral portion 18 of the cutting edge formed at the ridge line intersection of the wall surface 16A facing the front side in the drill rotation direction T of the sub-groove 16 and the tip flank surface 14, and the drill rotation of the chip discharge groove 15. The inner peripheral edge portion 17 of the cutting edge formed at the ridge line intersection of the wall surface 15A facing the front side in the direction T and the tip flank surface 14 is formed discontinuously and intermittently. It is possible to generate different chips in each of the cutting blade inner peripheral portion 17 and the cutting blade outer peripheral portion 18.

Therefore, in the present embodiment, it is possible to generate chips that are divided in the width direction without generating chips having a large width as in the conventional case, and the chips are divided and the width is reduced. The chips are easily carried to the base end side of the drill body 10 and discharged by the chip discharge groove, so that the risk of chip clogging can be reduced. Further, the chips generated in the outer peripheral portion 18 of the cutting edge are discharged to the base end side of the drill body 10 not only in the space of the sub-groove 16 but also in the space of the chip discharge groove 15. It is possible to further improve the chip discharging property.
By doing so, it becomes possible to perform drilling while maintaining good chip discharge performance, and even in the drilling of deep holes, there is no hindrance and machining is performed while maintaining a good working state. You can continue.

Further, the chips generated in the outer peripheral portion 18 of the cutting edge and which are likely to come into contact with the inner wall surface of the machined hole are chips which are divided in the width direction and have a reduced width. Therefore, when a conventional drill is used. As described above, the chips having a large width do not damage the inner wall surface due to contact with the inner wall surface of the processed hole, and the inner wall surface roughness can be improved.

Further, the inner peripheral portion 1 of the cutting edge which constitutes the cutting edge 19
7 and the outer periphery 18 of the cutting edge are the same tip flank 14
Since it is located on the upper side, even when the inner peripheral edge portion 17 and the outer peripheral edge portion 18 of the cutting edge are worn, it is only necessary to re-grind the tip flank surface 14 once for re-grinding. By the grinding, the sharpness of the cutting blade inner peripheral portion 17 and the cutting blade outer peripheral portion 18 can be restored, and the re-grinding does not take time and effort.

Further, here, the outer peripheral edge X of the wall surface 15A facing the front side in the drill rotation direction T of the chip discharge groove 15 and the auxiliary groove 1 are provided.
If the radial distance a from the outer peripheral edge Y of the wall surface 16A facing the front side of the drill rotation direction T of 6 is smaller than 0.05 (D) ^{1/2 with} respect to the outer diameter D of the cutting edge 19, As the length of the blade inner peripheral portion 17 becomes too large, the width of the chips produced at the cutting blade inner peripheral portion 17 also becomes too large.
The effect obtained by dividing the chips is weakened, and conversely, the distance a is 0.3 with respect to the outer diameter D of the cutting edge 19.
(D) If it is larger than ^1/2, the width of the chips generated by the cutting blade outer peripheral portion 18 becomes too large as the length of the cutting blade outer peripheral portion 18 becomes too large, and the inner wall surface of the machined hole becomes large. The width of the chips, which are likely to come into contact with, increases, which may damage the inner wall surface of the chip and reduce the surface roughness. Therefore, in the present embodiment, as described above, the distance a
Was set to 0.05 (D) ^1/2 ≤ a ≤ 0.3 (D) ^1/2 in the optimum range, so that the chips are cut into an appropriate width and the inner wall surface roughness of the machined hole is It is possible to improve. In order to secure the effect as described above, the distance a is set to 0.1 (D) ^1/2 ≦ a ≦ 0.
It is preferable to set it in the range of 2 (D) ^1/2 .

Further, the circumferential distance between the outer peripheral end X of the wall surface 15A of the chip discharge groove 15 facing the front side in the drill rotation direction T and the outer peripheral end Y of the wall surface 16A facing the front side in the drill rotation direction T of the auxiliary groove 16 is measured. b is 0 .. with respect to the radial distance a.
If smaller than 5a, the cutting blade outer peripheral portion 18 and the cutting blade inner peripheral portion 17
Since it is formed so as to form a continuous cutting edge, there is a possibility that the cutting edge having a substantially linear shape acts on the work piece and the chips cannot be divided in the width direction. In addition, if the distance b is larger than 3a with respect to the distance a, the size of the auxiliary groove 16 becomes too large, which may reduce the rigidity of the drill body 10. Therefore, in this embodiment, as described above,
By setting the distance b in the optimum range of 0.5a ≦ b ≦ 3a, it becomes possible to stably divide the chips and to keep the rigidity of the drill body 10 high. In order to secure the effect as described above, the distance b is preferably set in the range of 1a ≦ b ≦ 2a.

The sub-groove 16 does not have to be provided in the entire area of the cutting edge portion 12, but may be provided only in the range of the effective re-grinding use length of the drill. In addition, the cutting edge 19 and the auxiliary groove 16
The shape is not limited to the shape described in the above embodiment, and may be arbitrarily set as long as it is a shape capable of dividing the chips generated by the cutting blade 19. Further, in the present embodiment, the tip flank 14 is a conical edge, but it may be a flat edge or another shape, and may be thinned if necessary.

[0029]

As described above, according to the present invention,
The outer peripheral part of the cutting edge formed on the ridge line intersection of the wall surface facing the front side in the drill rotation direction of the auxiliary groove and the tip flank, and the crossing ridge line between the wall surface facing the front side in the drill rotation direction of the chip discharge groove and the tip flank surface. By the inner peripheral portion of the cutting blade formed in the portion, it is possible to generate chips so as to divide them in the width direction. Therefore, the chips that have been cut into smaller widths are easily carried to the base end side of the drill body by the chip discharge groove and easily discharged, so that good chip discharge performance can be maintained, and Even when performing hole drilling, there is no problem. Further, the chips that are easily contacted with the inner wall surface of the machined hole generated by the outer peripheral portion of the cutting edge are chips that are divided in the width direction and have a smaller width, so that the inner wall surface of the machined hole is not damaged, The surface roughness can be improved. Furthermore, since the cutting blade inner peripheral portion and the cutting blade outer peripheral portion forming the cutting blade are both located on the same tip flank, when the cutting blade inner peripheral portion and the cutting blade outer peripheral portion are worn Even in this case, it is only necessary to re-grind the tip flank once, and the time and labor required for re-grinding do not increase.

[Brief description of drawings]

FIG. 1 is a side view of a drill according to an embodiment of the present invention.

FIG. 2 is a front end view of the drill shown in FIG. 1 as seen from the front end side in the axial direction.

3 is a cross-sectional view taken along the line AA in FIG.

FIG. 4 is an enlarged view of a main part in FIG.

[Explanation of symbols]

10 drill body 12 cutting edge portion 13 outer peripheral surface 14 tip flank surface 15 chip discharge groove 15A chip discharge groove wall surface 15B facing the drill rotation direction front side of the chip discharge groove wall surface 16 facing the chip rotation groove drill rotation direction rear side 16 sub-groove 16A sub groove Wall surface 16B facing the front side of the drill rotation direction Wall surface 17 of the auxiliary groove facing the outer circumference side of the drill body 17 Cutting blade inner peripheral portion 18 Cutting blade outer peripheral portion 19 Cutting blade X Outer peripheral edge Y of the wall surface of the chip discharge groove facing the drill rotation direction front side Outer peripheral edge of the wall surface of the sub-groove that faces the front side in the drill rotation direction a. Radial distance of the drill body between the outer peripheral edge of the chip discharge groove and the outer peripheral edge of the sub groove b. The outer peripheral edge of the chip discharge groove and the outer peripheral edge of the sub groove. Circumferential distance O of drill body O axis T Drill rotation direction

Claims (3)

[Claims] 1. A chip discharge groove is formed on the outer peripheral surface of a drill body having a substantially cylindrical outer diameter rotated about an axis, and a wall surface facing the drill rotation direction front side of the chip discharge groove and an outer periphery of the drill body. A sub-groove opening to the surface is formed, and a clearance is given to the wall surface of the sub-groove that faces the outer peripheral side of the drill body in the drill rotation direction. The inner peripheral part of the cutting edge formed at the intersection ridge portion of the tip side region of the facing wall surface and the tip flank surface, and the intersection of the tip side surface and the tip side region of the wall surface of the auxiliary groove facing the drill rotation direction front side. A drill having a cutting edge formed by a cutting edge outer peripheral portion formed on a ridge portion. 2. The drill according to claim 1, wherein, in a cross section orthogonal to the axis of the drill body, an outer peripheral edge of a wall surface of the chip discharge groove facing forward in a drill rotation direction and a drill rotation direction of the sub groove. The distance a in the radial direction of the drill body from the outer peripheral edge of the wall surface facing the front side is 0.05 (D) ^1/2 ≦ a ≦ with respect to the outer diameter D of the cutting edge.
A drill characterized by being set in a range of 0.3 (D) ^1/2 . 3. The drill according to claim 1, wherein, in a cross section orthogonal to the axis of the drill body, an outer peripheral end of a wall surface of the chip discharge groove that faces the front side in the drill rotation direction, and the sub groove. The outer peripheral edge of the wall surface facing the front side in the drill rotation direction is a distance b in the peripheral direction of the drill body, the outer peripheral edge of the wall surface facing the front side in the drill rotation direction of the chip discharge groove, and the drill rotation of the auxiliary groove. The drill is characterized in that it is set in a range of 0.5a ≦ b ≦ 3a with respect to a radial distance a of the drill main body from an outer peripheral end of a wall surface facing the front side in the direction.