JP2003291016A - Throwaway type drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately machine by stably guiding a drill body into a machine hole even when cutting edges of a pair of tips are arranged nearer to inner and outer peripheries. <P>SOLUTION: A pair of tips 6, 7 are arranged on a tip part of a drill body 1 rotated around an axis O such that rotation loci of the cutting edges 9, 11 overlap along the inner and outer peripheries. An outer peripheral side face 10 extending from outer peripheral and 9B of the cutting edge 9 to the rear end side in the direction of the axis O is formed on the tip 6 so as to protrude to the tip part outer periphery of the drill body 1, while a recess 12 moving back in the direction of the axis O for the rotation locus of the cutting edge 9 of the tip 6 and an outer peripheral side face 13 extending from outer peripheral end of the recess 12 to the rear end side in the direction of the axis O and protruding to the tip part outer periphery of the drill body 1, having an identical outside diameter at the outer peripheral side face 10 of the tip 6 as that from the axis O, are formed on the tip 7. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw away type drill (hereinafter referred to as a drill) in which a pair of throw away chips (hereinafter referred to as "chips") are detachably attached to the outer periphery of the tip of a drill body. It is about.

[0002]

2. Description of the Related Art In this type of drill, the cutting edge of one of the above-mentioned tips is arranged at an outer periphery of the tip of the drill body while the cutting edge of the other tip is the tip of the drill body. Of the one of the above-mentioned ones by arranging them so as to be biased toward the inner peripheral side of the Various proposals have been made in which the outer peripheral side of a processed hole is cut by the cutting edge of a chip and the inner peripheral side of the processed hole is cut by the cutting edge of the other chip to perform hole processing. Therefore, according to such a drill, the chips generated by the cutting edge of each chip are divided into the width of about 1/2 of the inner radius of the machined hole, so that a good chip discharging property can be obtained. It is possible to achieve such effects.

[0003]

By the way, the above-mentioned pair of tips attached to such a drill are usually of the same shape and the same size due to problems in management thereof. On the outer peripheral side of the part, only the one tip is attached so that the outer peripheral end of the cutting blade projects, and the diameter of the circle formed by the outer peripheral end of the cutting blade around the axis is the cutting blade of the drill. It was supposed to be the diameter. However, in such a drill, only the side surface portion of the one tip that is continuous with the outer peripheral end of the cutting edge hits the inner periphery of the processing hole to guide the drill body, and the drill body is located on the opposite side of the outer peripheral edge with the axis line. Since a space is provided between the outer peripheral surface of the drill body and the inner periphery of the machined hole, the tip portion of the drill body becomes uneven and becomes unstable. On the other hand, in a drill in which the cutting edges are unevenly arranged on the inner and outer circumferences, the loads acting on the drill body during drilling also differ in size and direction, and the cutting edges are arranged symmetrically. Since it is not offset like a drill installed, there is a risk that the drill body will easily chatter due to the load during this drilling process, leading to deterioration of the processing accuracy.

The present invention has been made under such a background, and even in the drill in which the cutting edges of the pair of chips are unevenly arranged on the inner and outer circumferences of the tip of the drill body as described above,
An object of the present invention is to provide a drill that can stably guide a drill body into a drilled hole during drilling and can obtain high drilling accuracy.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems and to achieve such an object, the present invention provides a pair of chips at the tip of a drill body which is rotated around an axis and a cutting edge thereof. Is attached to the tip side of the drill body so as to be attachable to and detachable from each other on opposite sides of the axis line, and the cutting edge of one tip is biased to the outer peripheral side of the tip of the drill body,
The cutting edge of the other tip is arranged unevenly on the inner peripheral side of the tip of the drill body, and the rotational trajectories of the cutting edges around the axis are overlapped with each other so as to be continuous in the radial direction from the axis. Of these, one of the chips is formed so that the outer peripheral side surface extending from the outer peripheral end of the cutting edge to the axial rear end side is projected to the outer periphery of the tip portion of the drill body, and the other chip is formed. On the outer peripheral side of the cutting edge, a recess recessed in the axial direction with respect to the rotational trajectory of the cutting edge of the one tip, and a drill extending from the outer peripheral end of the recess to the axial rear end side. It is characterized in that the outer peripheral side surface of the one tip is formed so as to protrude to the outer periphery of the tip portion of the main body and the outer peripheral side surface having an equal outer diameter from the axis.

[0006] In such a drill, however, the cutting edge of one of the above-mentioned tips is arranged so as to be offset toward the outer peripheral side, and the cutting edge is provided so as to be offset toward the inner peripheral side of the other tip. And, since the concave portion on the outer peripheral side is retracted with respect to the cutting edge of one of the chips, it does not act as a cutting edge. Can be generated. And
On the other hand, on the outermost periphery of the other tip, the outer peripheral side surface of the one tip is equal to the outer diameter from the axis, that is, the outer peripheral side surface having an outer diameter equal to the outer diameter of the cutting edge of the drill, It is formed so as to extend from the outer peripheral edge of the recess to the rear end side, and the outer peripheral side surfaces of both of these tips hit the inner periphery of the processing hole, so that the tip of the drill body is guided while being supported from both sides across the axis. Will be done,
It is possible to perform stable drilling without causing chattering.

Here, the amount of retreat of the concave portion of the other tip relative to the rotation locus of the cutting edge of the one tip is set to be larger than the feed amount per one rotation of the drill body, and specifically, 0. It is desirable to set it in the range of 3 to 1.0 mm. That is, if the amount of retreat is so small as to be less than 0.3 mm, the recess may hit the bottom of the machined hole cut by the cutting edge of one tip, and conversely the amount of retreat is less than 1.0 mm. If it is also large, the distance from the outer peripheral side of one insert hitting the inner circumference of the machining hole to the outer peripheral side connecting to the concave part of the other tip hitting the inner circumference of the machining hole becomes long, and the drill body may become unstable during that time. There is.

Further, the cutting edge of the other tip disposed on the inner peripheral side extends toward the tip side from the inner peripheral side of the drill main body toward the outer peripheral side, and then the rear end via the apex. If it is formed so as to form a chevron toward the end side, when the cutting edge of the other tip is projected to the tip side more than the cutting edge of one tip and bites into the work piece, this apex is pinched Since the cutting loads that act on the cutting edge portions on both sides of the cutting edge cancel each other out, it is possible to ensure stability when biting. However, in this case, the apex of the chevron formed by the cutting edge is 0.05 to the outer diameter D of the cutting edge of the one throw-away tip in the radial direction from the axis.
It is desirable that the apex is located in the range of 0.25 × D. If the apex is on the inner peripheral side of this range, a large thrust load may act on the apex and the apex may be crushed. If it is on the outer peripheral side of the range, the amount of chips produced by this other tip becomes too large,
There is a possibility that an imbalance of the cutting amount may occur between the one of the chips.

[0009]

1 to 13 show one embodiment of the present invention. In the present embodiment, the drill body 1 has a substantially multi-stage cylindrical shape centered on the axis O, and its rear end is a shank portion 2 having a flat surface 2A parallel to the axis O on the outer periphery of the cylinder. From the portion 2 to the tip side (left side in FIG. 1), a disk-shaped collar portion 3 whose diameter is expanded by one step from the shank portion 2 in order toward the tip side.
A, and a truncated cone-shaped portion 3B whose diameter is gradually reduced toward the tip side,
The small-diameter columnar portion 3C is formed coaxially with the axis O to form the cutting edge portion 3. A pair of chip discharge grooves 4 and 4 are provided on the outer periphery of the cutting edge portion 3 on opposite sides of the axis O between the tip of the cylindrical portion 3C and the middle of the truncated cone portion 3B. Cage, these chip discharge grooves 4,
Chips 6 and 7 are removably attached by clamp screws 8 to chip attachment seats 5 and 5 formed on the wall surface of the tip of 4 facing the direction T of the drill rotation. In the drill body 1, a cutting oil supply hole 1A is bored from the shank portion 2 at the rear end toward the tip side along the axis O, and two supply holes 1A are provided in the cutting edge portion 3. To the rear side of the tip mounting surface of the cutting edge portion 3 (the front end surface of the drill body 1) in the drill rotation direction T of the tip mounting seats 5 and 5.

Of the chips 6 and 7, the chip 6 is one of the chips in this embodiment, and is made of a hard material such as cemented carbide as shown in FIGS. 3 to 7, and has a substantially trapezoidal flat plate shape. The upper surface of the rake face 6A is formed as a rake face 6A, and one side surface connected to the oblique side of the trapezoid formed by the rake face 6A is a flank face 6B. Therefore, the oblique side of the rake face 6A is the cutting edge 9A. The flank 6B is a positive chip having a clearance angle by being inclined so as to gradually recede toward the lower surface side of the chip 6. The above rake face 6A
Has a mounting hole 6C through which the clamp screw 8 is inserted, and an edge portion on the side of the cutting blade 9 has a groove along the cutting blade 9 as shown in FIG. Shaped breaker 6D is formed, and the cutting edge 9 is further subjected to honing. Further, one end portion (upper end portion in FIG. 3) 9A of the cutting blade 9 is bent so as to be orthogonal to the long side portion of the rake face 6A where the one end portion 9A is continuous,
The other end portion (lower end portion in FIG. 3) 9B of the cutting blade 9 is formed in a convex arc shape and is a rake face 6A parallel to the long side portion.
It is designed to be connected to the short side part of.

On the side surface 6E of the tip 6 which is continuous with the short side portion of the rake surface 6A, the other end portion 9B of the cutting edge 9 is formed.
On the side, the outer peripheral side surface 10 of the one chip 6 is formed with a width substantially equal to that of the breaker 6D as shown in FIG. 3 in a plan view facing the rake surface 6A. Here, the side surface 6E is inclined so that the portion on the lower surface side of the chip 6 generally recedes toward the lower surface side similarly to the flank surface 6B, and the rake surface 6 of the upper surface is formed.
For the part on the A side, the part other than the outer peripheral side face 10 is the rake face 6A.
On the other hand, the outer peripheral side surface 10 is smaller than perpendicular to the rake face 6A as shown in FIG.
Further, the side surface 6E is chamfered so as to intersect at a larger angle than the lower surface side portion thereof, so that the outer peripheral side surface 10 is formed so as to project further than the other portion of the side surface 6E as shown in FIG. Will be done. It should be noted that the outer peripheral side surface 10 is provided with an extremely small inclination so as to gradually recede as it is separated from the cutting edge 9 side.

On the other hand, the tip 7 is the other tip in this embodiment, and is made of a hard material such as cemented carbide as shown in FIG. 8 to FIG. It is formed in a substantially pentagonal flat plate shape that is projected in a "-" shape, and the pentagonal upper surface is the rake face 7A, and escapes to the one side surface that is continuous with one side of the "V" shape. The surface 7B is formed, and therefore, the cutting edge 11 is formed on one side of the "V" shape. The other chip 7 is also a positive chip in which the side surface on which the flank 7B is formed is inclined so as to gradually recede toward the lower surface side of the chip 7 and the flank 7B has a clearance angle. , The above-mentioned clamp screw 8 at the center of the rake face 7A.
A mounting hole 7C through which is inserted is provided.

Here, in the other chip 7,
Of the one side of the rake face 7A that is projected in the "V" shape, from one end (upper end in FIG. 8) of the rake face to the other end (lower end in FIG. 8). The part up to the middle is the cutting edge 11, and therefore the cutting edge 1
1 has a mountain shape with the apex point 11A. It should be noted that the cutting edge portion 11C extending from one end portion 11B of the cutting edge 11 that coincides with one end portion of the one side to the apex 11A.
And the cutting edge portion 11E extending from the apex 11A to the other end portion 11D of the cutting edge 11 are formed into a linear shape, respectively.
They intersect obtuse angles through A, and their inclination angles θ are equal to each other, and this inclination angle θ is also equal to the inclination angle θ of the cutting edge 9 formed on the hypotenuse of the rake face 6A of the one tip 6. ing. Further, at the edge of the rake face 7A on the cutting edge 11 side, a grooved breaker 7D which is also parallel to the cutting edge 11C is formed as shown in FIG. 11, and the cutting edge 9 is subjected to honing. Has been done. By forming such a breaker 7D, the cutting edge portion 11 is formed.
As shown in FIG. 9, E is formed so as to incline toward the lower surface side of the chip 7 from the apex 11A toward the other end 11D.

Further, in the portion from the other end 11D of the cutting edge 11 to the other end of one side of the rake face 7A having the above-mentioned "V" shape, the side face on which the flank face 7B is formed is As shown in FIG. 8 in a plan view substantially perpendicular to the rake face 7A and facing the rake face 7A, the notch is cut out so as to be parallel to the extension line of the cutting edge portion 11D. In the portion, a recess 12 is formed which is recessed by one step with respect to the extension line of the cutting edge portion 11D. And
The recess 12 and the rake face 7A at the other end of the one side
The ridge line intersecting with the ridge line is formed in a convex arc shape so as to be continuous with the ridge line intersecting with the rake face 7A and the other side face 7E of the tip 7.
The outer peripheral side surface 13 of the other tip 7 is formed on the side of the other end) and on the side of the rake face 7A. here,
Similar to the side surface 6E of the one chip 6, the side surface 7E
Is inclined so that the lower surface side portion of the chip 7 gradually recedes as it goes toward the lower surface side, and the portion of the upper surface on the rake face 7A side is the rake face 7A except the outer peripheral side face 13. While the outer peripheral side surface 13 is chamfered substantially vertically to the rake surface 7A, the outer peripheral side surface 13 is smaller than the vertical surface as shown in FIG. 12 and is chamfered so as to intersect at a larger angle than the lower surface side portion of the side surface 7E. As a result, the outer peripheral side surface 13 is formed so as to project further than the other part of the side surface 7E as shown in FIG. Further, the outer peripheral side surface 13 is provided with an extremely small inclination so as to gradually recede as it is separated from the concave portion 12 side.

In the tips 6 and 7 thus constructed, the rake surfaces 6A and 6B are oriented in the drill rotation direction T, respectively, and the flanks 6B and 7B are directed to the tip side, and the side surface 6 is formed.
The cutting blades 9 and 11 are attached to the tip mounting seats 5 and 5 so that the cutting edges 9 and 11 project toward the tip of the drill body 1 with E and 7E facing toward the outer peripheral side. Here, in this mounted state, the one tip 6 is arranged such that the tip 6 itself is biased toward the outer peripheral side of the drill body 1, and the cutting blade 9 is also biased toward the outer peripheral side of the drill body 1. On the other hand, in the other tip 7, the tip 7 itself is arranged from the vicinity of the axis O on the inner circumference of the drill body 1 to the outer circumference side, but the cutting edge 11 is biased to the inner circumference side of the drill body 1. And the cutting edges 9 and 11 overlap each other in a rotation locus around the axis O as shown in FIG.
It is arranged to be continuous from the axis O of the drill body 1 in the radial direction.

Further, in this attached state, the cutting edge 11 of the other tip 7 has the one end portion 11B of which is the axis O.
The cutting edge portion 11C extending from the one end portion 11B to the apex 11A extends toward the distal end side toward the outer peripheral side while being arranged so as to be an over center beyond the apex 11A at the most distal end side. A cutting edge portion 11E that is configured to project and further extends to the other end portion 11D through the apex 11A is arranged so as to retreat toward the rear end side toward the outer peripheral side, and a mountain shape that is convex toward the front end side is formed. None, the angle formed by the cutting blade portions 11C and 11E with respect to the plane orthogonal to the axis O is set to the inclination angle θ. On the other hand, in the cutting edge 9 of the one tip 6, the one end portion 9A of the cutting edge 9 is projected to the most distal end of the cutting edge 9, and a portion extending obliquely along the hypotenuse from the one end portion 9A. , The cutting edge 1 of the other tip 7 in the above rotation locus
1 is made to coincide with the extension line of the cutting edge portion 11E, and therefore the angle formed by the cutting edge 9 with respect to the plane orthogonal to the axis O is also the inclination angle θ and the cutting edge 9
The one end 9A serving as the tip of the cutting blade 11 is arranged at a position slightly retracted to the rear end side in the direction of the axis O from the apex 11A serving as the tip of the cutting blade 11, and further arranged on the outer peripheral side of the cutting blade 9. The diameter of the circle formed around the axis O by the other end 9B is
This is the outer diameter D of the cutting edge 9 of this one tip 6 and the outer diameter D of the cutting edges 9 and 11 by the drill of this embodiment.

Further, the outer peripheral side surface 10 of one tip 6 and the outer peripheral side surface 13 of the other tip 7 connected to the other end portion 9B of the cutting edge 9 have an outer diameter (radius) from the axis O thereof. The drill body 1 is made equal to each other
The cutting edge portion 3 at the tip is projected to the outer periphery of the cylindrical portion 3C, but the outer peripheral side surface 13 is the outer peripheral side surface 10 as much as the recess 12 is retracted from the extension line of the cutting edge portion 11E. It is arranged so as to be located on the rear side in the axis O direction with respect to each other, and is arranged so as to overlap each other as shown in FIG. ing. The outer peripheral side surfaces 10 and 13 are inclined such that the side surfaces 6E and 7E including the outer peripheral side surfaces 10 and 13 are retracted toward the lower surface side of the chips 6 and 7, and A relief is provided in the radial direction so as to be gradually separated from the inner circumference toward the rear side in the rotation direction T, and the outer peripheral side surfaces 10 and 13 are also retracted as they are separated from the cutting blade 9 and the recess 12. Due to the slight inclination, a clearance is provided also in the direction of the axis O so as to be gradually separated from the inner periphery of the machined hole toward the rear end side. Further, the amount of recession of the recess 12 of the other tip 7 with respect to the rotation locus of the cutting edge 9 of the one chip 6 (in the present embodiment, the amount of recession of the recess 12 with respect to the extension line of the cutting edge 11E of the other tip 7). E is larger than the feed amount per one rotation of the drill body 1 during drilling in the direction of the axis O, and is set in the range of 0.3 to 1.0 mm. Furthermore, the apex 11A of the cutting edge 11 of the other tip 7 formed into the chevron shape as described above is in the range of 0.05 to 0.25 × D with respect to the outer diameter D in the radial direction from the axis O. It is located at radius R.

Therefore, in the thus constructed drill, the outer peripheral side of the hole bottom of the machined hole is the cutting edge 9 of the one tip 6 and the inner peripheral side is the cutting edge 11 of the other tip 7.
As a result, the chips produced during the hole machining have a width of about 1/2 of the inner radius of the machined hole, and the chips can be reliably and smoothly ejected through the chip ejection grooves 4 and 4. Can be achieved. On the other hand, in the drill having the above configuration, the outer peripheral side surfaces 10 and 13 of both tips 6 and 7 have the same outer diameter from the axis O,
Also, the outer peripheral side surface 13 has the retreat amount E relative to the outer peripheral side surface 10.
It is arranged so as to be slightly retracted by an amount and overlap so that the cutting edge 9 on one of the tips 6 is
After the other end portion 9B of the outer periphery bites into the machining hole and the outer peripheral side surface 10 hits the inner periphery of the machining hole, the outer peripheral side surface 13 of the other tip 7 becomes the machining hole when the drill body 1 is fed by the amount E of retreat. After being inserted and hitting the inner periphery thereof, these outer peripheral side surfaces 10 and 13 act as margins, and the cutting edge portion 3 at the tip of the drill body 1 is supported from both sides across the axis O. Therefore, according to the drill having the above-mentioned configuration, the cutting blades 9 and 11 are arranged unevenly on the inner and outer circumferences of the drill body 1, but the chattering portion 3 is prevented while preventing chattering during drilling. Can be reliably guided straight along the axis O, which makes it possible to perform highly accurate drilling with high straightness and roundness.

By the way, in the present embodiment, the cutting edge 9 of the one tip 6 is arranged so as to coincide with the extension line of the cutting edge portion 11E of the cutting edge 11 of the other tip 7 having the chevron shape in the rotation locus. Therefore, it is possible to shorten the time from when the cutting edge 11 bites the work piece to when the cutting edge 9 bites and drilling is performed by the pair of cutting blades 9 and 11, for example, a blind hole. The advantage of being able to prevent a large step from being left at the bottom of the hole when forming the cutting edge is obtained.
In the rotation locus, the cutting edge 9 is located rearward of the extension line of the cutting edge 11 in the direction of the axis O without matching the extension line of E,
For example, they may be arranged so as to recede in parallel. In this case, however, the retreat amount E from the outer peripheral side surface 10 of the chip 6 to the outer peripheral side surface 13 of the chip 7 is also small, so that the subsequent outer peripheral side surface 13 is not contacted after the preceding outer peripheral side surface 10 hits the inner periphery of the processed hole. The time until hitting can be shortened, and therefore, it becomes possible to promptly and stably support the drill body 1 and promote drilling with higher accuracy.

However, even if the retreat amount E is reduced in this way, the retreat amount E is larger than the feed amount per one rotation of the drill main body 1 at the time of drilling with the drill, specifically as described above. It is desirable that the thickness is 0.3 mm or more. That is, in the other tip 7, the recess 12 which is located on the outer peripheral side of the other end portion 11D of the cutting blade 11 has the one tip 6 located on the tip side thereof.
The cutting edge 9 of this machine is designed so as to advance at a distance from this hole bottom after cutting the hole bottom of the machined hole, so that it does not itself perform cutting, whereas this retreat The amount E is smaller than the feed amount of the drill body 1, or 0.3
If it is smaller than mm, this recess 12 will make the cutting edge 11
It will hit the bottom of the machined hole, which causes a great resistance to the feed of the drill body 1,
In some cases, the feeding itself may become impossible. However, on the other hand, if the retreat amount E is too large, the retreat amount between the outer peripheral side surfaces 10 and 13 of the chips 6 and 7 also becomes large, so that after the preceding outer peripheral side surface 10 hits the inner periphery of the processed hole, It takes longer until the outer peripheral side surface 13 hits and the cutting edge portion 3 is supported, and during this time, the drill body 1 is also in an unstable state. Therefore, the retreat amount E is 1.0 mm or less as described above. Is desirable.

On the other hand, in the other tip 7 of the present embodiment, the cutting edge 11 is formed in a chevron shape.
Since the apex 11A of No. 1 is located closer to the tip side than the one end 9A of the tip of the cutting blade 9 of the one tip 6, in the cutting blades 9 and 11 of the drill, first, the apex 11A starts
1 bites into the workpiece, and the inclination angles θ of the cutting edge portions 11C and 11E on both sides of the apex 11A are equal to each other, so that these cutting edge portions 11C and 11E are formed.
The cutting loads that act on each other cancel each other out,
There is also an advantage that it is possible to prevent the drill body 1 from swinging at the time of this bite and to perform highly accurate processing. However, if the position of the apex 11A is located too much on the outer peripheral side, the cutting edge part 11 on the inner peripheral side is formed.
As the length of C becomes longer, the cutting load cannot be reliably offset between the two cutting edge parts 11C and 11E as described above unless the cutting edge part 11E on the outer peripheral side is also made longer, and as a result, The length of the cutting edge 9 of the tip 6 may be shortened, and the cutting amount may not be balanced between the tips 6 and 7. On the other hand, conversely, if the apex 11A is located too much on the inner peripheral side,
In the vicinity of the axis O on the inner peripheral side of the tip of such a drill, since the cutting speed due to the rotation of the drill body 1 becomes small, a cutting form that crushes the work piece and a large thrust load acts, so that A convex portion such as the apex 11A may be crushed by the thrust load. Therefore, the position of the apex 11A, that is, the radius R from the axis O to the apex 11A is also 0.05 to 0.25 × with respect to the outer diameter D of the cutting edge 9 as described above.
It is desirable that it is set to D.

[0022]

As described above, according to the present invention,
By arranging the cutting blades on the inner and outer circumferences of the drill body in a biased manner, it is possible to support the drill body in a stable manner and guide it straight while achieving good chip discharge performance. Prevents high-precision hole drilling.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a front view of the embodiment shown in FIG. 1 viewed from the front end side in the direction of the axis O.

FIG. 3 is one chip 6 in the embodiment shown in FIG.
FIG.

FIG. 4 is a front view of the tip 6 shown in FIG. 3 viewed from a flank 6B side.

5 is a side view of the chip 6 shown in FIG. 3 viewed from the side surface 6E side.

6 is a cross-sectional view orthogonal to a cutting edge 9 of the tip 6 shown in FIG.

7 is a partial side view as seen from the direction of the arrow X in FIG.

8 is the other chip 7 in the embodiment shown in FIG.
FIG.

9 is a front view of the chip 7 shown in FIG. 8 viewed from a side surface side where a flank 7B is formed.

10 is a partial side view as seen from the direction of the arrow Y in FIG.

11 is a cross-sectional view orthogonal to the cutting edge 11 of the tip 7 shown in FIG.

FIG. 12 is a partial side view taken along the arrow Z in FIG.

FIG. 13 shows chips 6 and 7 in the embodiment shown in FIG.
It is a figure which shows the rotation locus of.

[Explanation of symbols]

1 drill body 6 One chip 7 Other chip 9,11 cutting edge 11A Cutting edge 11 apex 10,13 outer peripheral side 12 recess O Drill body 1 axis T drill rotation direction D Cutting edge 9 outer diameter E Recession amount of recess 12 from cutting edge 9 R Radius from axis O of top 11A

Continued front page    (72) Inventor Yasuhiko Kawade             1528, Nakashinden, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture             Address Mitsubishi Materials Corporation Gifu Factory             Within F term (reference) 3C037 AA10 BB00 BB17

Claims (3)

[Claims] 1. A pair of throw-away tips are attached to the tip of a drill body rotated around an axis so as to be detachable from each other on opposite sides of the axis, with their cutting edges protruding toward the tip. The cutting edge of one throw-away tip is arranged biased to the outer peripheral side of the drill body tip, while the cutting edge of the other throw-away tip is biased to the inner peripheral side of the drill body tip, And the rotational trajectories around the axis of these cutting blades are overlapped with each other so as to be continuous from the axis in the radial direction,
Of these, the one throw-away tip is formed such that the outer peripheral side surface extending from the outer peripheral end of the cutting edge to the axial rear end side is projected to the outer periphery of the tip end portion of the drill main body, and the other one is formed. The throw-away tip has, on the outer peripheral side of the cutting edge thereof, a recessed portion that retreats in the axial direction with respect to the rotation locus of the cutting blade of the one throw-away tip, and an axial rear end from the outer peripheral end of the recessed tip. And the outer peripheral side surface of the one throw-away tip and the outer peripheral side surface of which the outer diameter from the axis is equalized are formed. Away drill. 2. The amount of recession of the concave portion of the other throw-away tip relative to the rotation locus of the cutting edge of the one throw-away tip is set within a range of 0.3 to 1.0 mm. The throw-away drill according to Item 1. 3. The cutting edge of the other throw-away tip has a chevron shape that extends toward the tip side from the inner peripheral side of the drill main body toward the outer peripheral side and then extends toward the rear end side via the apex. That is, the apex of the chevron formed by the cutting edge is in the radial direction from the axis with respect to the outer diameter D of the cutting edge of the one throw-away tip of 0.05 to 0.
The throw-away drill according to claim 1 or 2, wherein the throw-away drill is located in a range of 25 x D.