JP3518315B2 - Indexable insert and indexable drilling tool equipped with indexable insert - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away tip (hereinafter referred to as a tip) suitable for use in drilling, and a throw-away type drilling tool (hereinafter referred to as a punching tool) equipped with the tip. Referred to as)).

[0002]

2. Description of the Related Art As such a tip and a drilling tool, the inventors of the present invention have proposed a tool as shown in FIGS. 8 to 10 in Japanese Patent Laid-Open No. 6-91416. Of these, the chip 1 shown in FIG. 8 is such that the chip body 2 is formed in a substantially rhombic flat plate shape, and the side edge portion of the polygonal surface (rhombic surface) 3 that is the rake face is A pair of cutting blades 4A, 4B having a corner C as an acute-angled end of the polygonal surface 3 are formed in the respective corners C, C so that they are alternately located in the circumferential direction of the polygonal surface 3. Has been done. Further, these cutting edges 4A, 4B are respectively configured by two cutting edge portions 4a, 4b that are bent in a convex shape in the circumferential direction of the polygonal surface 3, and are symmetrical about a diagonal line connecting the corner portions C, C. Further, the cutting edge portion 4a of the cutting edge portions 4a and 4b, which is continuous with the corner portion C, has a cutting edge length shorter than that of the other cutting edge portions 4b.

The tip 1 thus constructed is attached to the tip of a tool body 5 of a drilling tool which is rotated around an axis O and is used for drilling, as shown in FIG. 9, for example. Here, in this drilling tool, a pair of the chips 1 and 1 are attached to the tip of the tool body 5 on opposite sides of the axis O so as to be biased toward the inner circumference side and the outer circumference side of the tool. One of the tips 1A on the inner peripheral side of the tool has one of the corner portions C located above the axis O in the vicinity of the axis O, and the cutting edge 4A connected to the corner C. , 4B, one cutting edge 4A is arranged so as to project toward the tool tip side. On the other hand, the other tip 1B on the outer peripheral side of the tool has its one corner portion C positioned on the outer peripheral side of the tool, and the other cutting edge 4B of the cutting edges 4A, 4B continuous to this corner portion C is the tool. It is arranged so as to project to the tip side. And then these chips 1
A and 1B are cutting edges 4 protruding toward the tool tip side.
The intersection point P of the cutting edge portions 4a and 4b of A and 4B is located at the forefront, and as shown in FIG. ，
4b are arranged so as to overlap.

[0004]

By the way, in the above-described drilling tool in which such a tip 1 is mounted as a pair of tips 1A and 1B, the cutting edge 4 protruding toward the tip end side of the tool.
Since A and 4B have the intersection point P of the cutting edge portions 4a and 4b bent in a convex shape as the leading edge position, in the one cutting edge 4A of the one tip 1A on the inner peripheral side of the tool, the cutting edge portion is formed. 4a is arranged so as to extend toward the tool tip side from the inner peripheral side toward the outer peripheral side, while the cutting edge portion 4 is formed.
b is inclined and arranged so as to extend toward the tool rear end side from the inner peripheral side toward the outer peripheral side. On the contrary, in the other cutting edge 4B of the other tip 1B on the outer peripheral side of the tool, the cutting edge portion 4a is inclined so as to extend toward the tool rear end side from the inner peripheral side toward the outer peripheral side. On the other hand, the cutting edge portion 4b is arranged so as to be inclined so as to extend toward the tool tip side from the inner peripheral side toward the outer peripheral side.

Here, at the time of drilling, each of the above cutting edge portions 4
The loads acting on a and 4b act in a direction perpendicular to these cutting edge portions 4a and 4b, and therefore these cutting edge portions 4a and 4a, which are inclined in opposite directions via the intersection P, are formed.
A load having components that are opposite to each other in the radial direction with respect to the axis O acts on 4b. Moreover,
It is known that the magnitude of this load increases in accordance with the cutting edge length of each of the cutting edge portions 4a and 4b, and that the tool outer peripheral side with a large cutting amount is larger than the tool inner peripheral side,
Therefore, in the other cutting edge 4B of the other tip 1B on the outer peripheral side of the tool, the radial component of the load acting on the cutting edge portion 4a having a short cutting edge length arranged on the outer peripheral side of the tool, and the inside of the tool. Since the radial component of the load acting on the long cutting edge portion 4b arranged on the circumferential side is canceled by each other, the tool body 5 can be bent in the radial direction with respect to the axis O thereof. The force can be suppressed from acting on the other chip 1B.

However, in the one cutting edge 4A protruding toward the tool tip side of the one tip 1A on the inner circumference side of the tool, the cutting edge portion 4a having a short cutting edge length is located on the inner circumference side of the tool having a small cutting amount. On the other hand, the cutting edge portion 4b having a long cutting edge length is arranged on the outer peripheral side of the tool having a large cutting amount, so that the tip 1A has a larger load toward the inner peripheral side of the tool. It is unavoidable that a force acts to bend the tool body 5 to the other tip 1B side due to the addition of the force. And, due to such a force acting, since a radial deviation occurs in the tool body during drilling, the drilled hole formed by the drilling tool has an inner diameter smaller than the predetermined drilled hole diameter. Also greatly expands and the concentricity is lost. Therefore, there is a problem in that it is difficult to obtain higher machining hole accuracy with the conventional chip 1 and the drilling tool in which the chip 1 is mounted.

The present invention has been made under such a background, and a force for bending the tool main body in the radial direction with respect to the axis thereof acts on the tip particularly when used for drilling. By providing a tip that can prevent the drilling, and by mounting such a tip, it is possible to suppress the deflection of the tool body during drilling and to obtain a higher drilling accuracy. It is intended to be provided.

[0008]

In order to solve the above problems and to achieve such an object, the chip of the present invention has a polygonal flat plate-shaped rake face of a polygonal face. In a chip in which at least a pair of cutting edges intersecting a corner portion of the polygonal surface is formed at a side edge portion, the pair of cutting edges is provided with a plurality of cutting edges bent in a circumferential direction of the polygonal surface. Consists of a blade portion, among these pair of cutting blades, one of the cutting blades has a cutting blade length that is continuous with the corner portion and is longer than a cutting blade length of another cutting blade portion,
The other cutting edge is characterized in that the cutting edge length of the cutting edge portion connected to the corner portion is shorter than the cutting edge lengths of the other cutting edge portions.
Further, the drilling tool of the present invention is a drilling tool in which a tip having such a configuration is mounted, and a pair of the tips is provided at the tip of the tool body rotated about the axis, and the tips are opposite to each other. , The tool inner peripheral side and the tool outer peripheral side are biasedly detachably mounted, one of these chips is located on the inner peripheral side of the tool, and the corner portion is located near the axis. While protruding the cutting edge to the tool tip side,
The other tip on the outer peripheral side of the tool has the corner portion located on the outer peripheral side of the tool so that the other cutting edge projects toward the tool tip side, and the other cutting edge of the other cutting edges in a rotation locus around the axis. It is characterized in that the blades are arranged so as to overlap each other.

According to the tip having the above structure, however, by mounting the tip on the tool body of the drilling tool as described above, one of the tips on the inner peripheral side of the tool projects toward the tip of the tool. In the cutting edge of, the cutting edge part is arranged on the inner peripheral side of the tool where the acting load is small, and the cutting edge part is connected to the corner part where the cutting edge length is increased, and the cutting edge length is short on the outer peripheral side of the tool where large load acts Since the cutting edge part of is arranged, the force component that cancels the component of the load acting on both cutting edge parts in the radial direction with respect to the axis of the tool body, and causes one of the chips to bend the tool body in the radial direction. Can be suppressed. On the other hand, in the other tip on the outer peripheral side of the tool, the cutting edge part connected to the corner part with a short cutting edge length is arranged on the outer peripheral side of the tool with a large load as in the conventional case, and the inside of the tool with a small load is arranged. Since another cutting edge part with a long cutting edge length is arranged on the peripheral side, no force is generated in the other tip to bend the tool body in the radial direction. It is possible to prevent the occurrence of runout in the direction, and to obtain a higher hole accuracy.

Here, in the above-mentioned tip, the ratio of the cutting edge length of the cutting edge portion connected to the corner portion to the cutting edge length of the other cutting edge portion of the one cutting edge is 1: 1.1. The ratio of the cutting edge length of the cutting edge portion connected to the corner portion to the cutting edge length of the other cutting edge portion in the other cutting edge is 1. It is desirable to set in the range of 1: 1 to 1.5: 1. This is because when the ratio of the cutting edge lengths of these cutting edge portions deviates from the above range, when the chip is mounted on a drilling tool as described above or when drilling is performed, the load at the time of processing This is because the component in the radial direction with respect to the axis of the tool body may not be canceled out with certainty.
Further, in the chip, the cutting edge length of the cutting edge portion connected to the corner portion in the one cutting edge is made longer than the cutting edge length of the cutting edge portion connected to the corner portion in the other cutting edge. In this case, the pair of cutting edges that intersect one corner portion can be set to have substantially equal cutting edge lengths, for example, when the tip body is formed in a rhombic flat plate shape like the conventional tip, It becomes possible to form two pairs of the above-mentioned cutting edges having the same cutting edge length on the side ridges of the polygonal surface (diamond surface). Furthermore, if the cutting edge portions that are adjacent to each other in the circumferential direction of the polygonal surface are formed so as to intersect each other at an obtuse angle, it is possible to prevent chipping of the chip body at the intersection of the cutting edge portions. .

On the other hand, in the drilling tool having the above structure,
By arranging the pair of chips so that the tip positions of the cutting blades projecting toward the tool tip side are slightly displaced in the axial direction, the cutting blades of the pair of chips simultaneously bite the workpiece. It is possible to disperse the impact that the tip exerts on the tool body at the time of this bite, and to prevent a situation in which the tool body shakes due to such impact.

[0012]

1 to 3 show an embodiment of a chip of the present invention. The tip 11 of the present embodiment has a tip body 12 formed of a hard material such as cemented carbide in a substantially rhombic flat plate shape, and the rhombic upper surface 13 is a rake surface and the upper surface The four side surfaces 14 arranged around 13 are flanks, and the ridges intersecting with the upper surface 13 and the side surfaces 14 ...
A pair of corner portions C, C located on the diagonal of the upper surface 13
Two pairs of cutting blades 15A and 15B intersecting with each other are alternately arranged in the circumferential direction of the upper surface 13. In addition,
The chip 11 of the present embodiment has a side surface 1 which is the flank surface.
4 is a positive tip having a clearance angle with respect to the cutting edges 15A and 15B preliminarily provided, and this clearance angle is formed so as to become larger from the upper surface 13 of the chip body 12 toward the lower surface 16 side. There is. Further, from the center of the upper surface 13 of the chip body 12 to the lower surface 16,
A mounting hole 17 is formed through which a clamp screw for mounting the chip body 12 on a tool body of a drilling tool, which will be described later, is inserted.
It is formed so as to be axisymmetric with respect to the central axis of 7.

Further, the side surface 14 of the chip body 12 ...
Are formed so as to be bent one step at an obtuse angle in the circumferential direction of the upper surface 13, and accordingly, the upper surface 1
The cutting edges 15A and 15B formed on the ridge line intersecting with 3
Is also formed from a pair of cutting blade portions 15a, 15b and cutting blade portions 15c, 15d which are bent in a convex shape at an obtuse angle through an intersection point P as shown in FIG. ing. Therefore, the upper surface 13 of the chip body 12 is strictly formed in an octagonal shape as shown in FIG. 1 when seen in a plan view from a direction facing the upper surface 13. One of the pair of cutting blades 15A, 15B intersecting the corner C of the upper surface 13 is one of the cutting blades 1A.
5A is a pair of cutting edge portions 15 that intersect each other through the intersection point P.
Of the a and 15b, the cutting edge portion 15a connected to the above corner portion C
The cutting edge length a is formed longer than the cutting edge length b of the opposite cutting edge portion 15b, while conversely, the other cutting edge 15B is the cutting edge length c of the cutting edge portion 5c continuous to the corner portion C. Is shorter than the cutting edge length d of the cutting edge portion 5d on the opposite side.

Here, the ratio a: b between the cutting edge length a of the cutting edge portion 15a and the cutting edge length b of the cutting edge portion 15b in the one cutting edge 15A is 1: 1.1 in this embodiment. ~ 1: 1.5
In the present embodiment, the ratio c: d between the cutting edge length c of the cutting edge portion 15c and the cutting edge length d of the cutting edge portion 15d in the other cutting edge 15B is 1. 1: 1 ~
It is set in the range of 1.5: 1. Further, in the present embodiment, the cutting edge length a of the cutting edge portion 15a that is continuous with the corner portion C of the one cutting edge 15A is the cutting edge length of the cutting edge portion 15c that is continuous with the corner portion C of the other cutting edge 15B. The cutting edge portions 15a, 15c are longer than c, and the cutting edge portions 15a, 15c intersect at an obtuse angle at the corner portion C, whereby the cutting edge portions 15a adjacent to each other in the circumferential direction of the upper surface 13 are provided.
˜15d are formed so as to intersect each other at an obtuse angle. Furthermore, as shown in FIG. 3, a chip breaker 18 having a concave arc shape in cross section is provided on the peripheral portion of the upper surface 13.
Are formed so as to go around the peripheral edge along the cutting edges 15A and 15B.

Next, FIGS. 4 to 7 show an embodiment of the punching tool of the present invention in which the tip 11 of the above embodiment is mounted. In the drilling tool of this embodiment, the tool main body 21 is formed in a generally multi-stage cylindrical shape, and the outer periphery of the tip end portion of the tool main body 21 has a central axis O of the tool main body 21 toward the rear end side. A pair of chip discharge grooves 22, 22 twisted rearward in the tool rotation direction T
Are formed symmetrically with respect to the axis O, and have the same shape and the same size on a pair of chip mounting seats 23A and 23B formed on the wall surfaces of the tips of the chip discharge grooves 22 and 22 facing the tool rotation direction T. The pair of chips 11 and 11 of the above-described embodiment has the upper surface 13 serving as the rake surface thereof facing the tool rotation direction T,
The clamp screws 24 inserted into the mounting holes 17 are screwed into the tool body 21 so that they are detachably mounted.

Here, the pair of chip mounting seats 23A,
23B are formed so as to be biased toward the tool inner peripheral side and the tool outer peripheral side in the radial direction with respect to the axis O, and with this, the pair of chips 11 and 11 mounted on these chip mounting seats 23A and 23B, One of the tips 11 is arranged on the inner circumference side of the tool to be the inner circumference side tip 11A, and the other tip 11 is arranged to be biased on the outer circumference side of the tool to be the outer circumference side tip 11B. The inner and outer peripheral chips 11A and 11B are the inner peripheral chip 11A.
However, the corner portion C is located near the axis O so that the corner portion C crosses the axis O and becomes an over-center. While the blade 15A is projected to the tool tip side, the outer peripheral side tip 11B projects one corner portion C to the outer circumference of the tool body 11 tip portion, and the intersection P
7, the other cutting edge 15B is projected toward the tool tip side, and as shown in FIG. 7 in the rotation locus around the axis O, the cutting edges 15b of the mutual cutting edges 15A, 15B, It is arranged with 15d overlapping.

In this embodiment, the inner peripheral side chip 11
One of the above-mentioned cutting edges 15A that is projected toward the tool tip side of A
The intersection point P, which is the tip position of, is a displacement amount γ as shown in FIG. 7 with respect to the intersection point P, which is the tip position of the other cutting edge 15B that is projected toward the tool tip side of the outer peripheral side tip 11B. It is arranged at a position slightly retracted in the direction of the axis O. Further, in the present embodiment, as shown in FIG. 6 in a front view from the tool tip side, the inner peripheral side tip 11 is
One of the cutting edges 15A of A is arranged so as to be slightly decentered with respect to the axis O, and it is avoided that the chip body 12 of the inner peripheral side chip 11A is arranged on the axis O. On the other hand, the other cutting edge 15 of the outer peripheral side chip 11B
On the contrary, B is arranged so that it is slightly raised.
Sufficient relief is secured on the side surface 14 which is continuous with the corner portion C arranged on the outer peripheral side of the tool and which is the relief surface.

However, in the tip 11 constructed as described above, one of the pair of cutting edges 15, 15 intersecting the corner portion C of the upper surface 13 which is the rake face of the chip body 12 has a cutting edge 15A. The cutting edge length a of the cutting edge portion 15a connected to the corner portion C is made longer than the cutting edge length b of the other cutting edge portion 15b on the side opposite to the corner portion C, and at the other cutting edge 15B. The cutting edge length c of the cutting edge portion 15c connected to the corner portion C is shorter than the cutting edge length d of the cutting edge portion 15d on the side opposite to the corner portion C. Therefore, when disposing such a tip 11 in a biased manner on the tool inner peripheral side and the tool outer peripheral side of the tool body 21 of the drilling tool, the inner peripheral side tip (one tip) 11A is The corner portion C is located in the vicinity of the axis O so that the one cutting edge 15A projects toward the tool tip side, and the outer peripheral side tip (the other tip) 11B positions the corner portion C on the tool outer peripheral side. The other cutting edge 15B is projected toward the tool tip side, and the other cutting edge portions 15b and 15d of the cutting edges 15A and 15B are arranged so as to overlap each other in the rotation locus around the axis O. This makes it possible to cancel the radial component of the load that acts on both the tips 11A and 11B on the inner and outer peripheral sides of the tool.

That is, in the inner peripheral side chip 11A,
In the one cutting edge 15A projected toward the tool tip side, a cutting edge portion 15a having a long cutting edge length a is arranged on the inner peripheral side of the tool with a small acting load, and a tool outer periphery with a large acting load is arranged. Since the cutting edge portion 15b having a short cutting edge length b is arranged on the side, both cutting edge portions 15a, 15 are formed at the time of drilling.
Among the loads acting on b, the magnitudes of the radial components with respect to the axis O that act in mutually opposite directions can be made substantially equal. On the other hand, also in the outer peripheral side tip 11B, a cutting edge portion 15d having a long cutting edge length d is arranged on the inner peripheral side of the tool with a small load acting similarly to the conventional one, and a tool outer periphery with a large acting load is arranged. Since the cutting edge portion 15c having a short cutting edge length c is arranged on the side, the both cutting edge portions 15c
It is possible to make the radial components of the loads acting on c and 15d substantially equal to each other. Therefore, the radial components of the loads acting on the respective tips 11A and 11B on the inner and outer peripheral sides of the tool cancel each other out. It becomes possible. Therefore, according to such a tip 11, it is possible to suppress the generation of a force that bends the tool body 21 in the radial direction during drilling, thereby preventing the tool body 21 from swinging during machining. The hole accuracy can be improved.

Further, particularly in the inner peripheral side chip 11A,
In the other cutting edge 11B connected to the corner C arranged near the axis O of the tool body 21, a cutting edge 15c having a short cutting edge length c is arranged on the tip side, and an intersection point P is formed behind it. A cutting edge portion 15d having a long cutting edge length d that intersects the obtuse angle is arranged via the wall surface 23a of the tip mounting seat 23A that abuts the side surface 14 of the tip body 12 connected to these cutting edge portions 15c and 15d. Also, as shown in FIG. 5, the tool body 21 is formed so as to extend from the tip end surface of the tool body 21 to the tool rear end side for a short time, and then bend and extend to the tool outer peripheral side. Therefore, according to the tip 11 having the above-mentioned configuration, in the tool body 21 of the drilling tool in which the tip 11 is mounted on the inner peripheral side of the tool as described above, the tip mounting seat on the inner peripheral side of the tool on which the tip 11 is mounted is mounted. It is possible to secure a sufficient thickness between the wall surface 23a of 23A and the chip discharge groove 22 in which the chip attachment seat 23B on the outer peripheral side of the tool is formed, whereby the rigidity of the tip portion of the tool body 21 is increased. It is also possible to obtain the effect of improving the machining efficiency and promoting more stable drilling.

Here, in the tip 11, the cutting edge portion 1 which is continuous with the corner portion C in the one cutting edge 11A.
Cutting edge length a of 5a and other cutting edge portion 15b on the opposite side
The ratio a: b to the cutting edge length b of 1 is set in the range of 1: 1.1 to 1: 1.5, and the cutting edge length of the cutting edge portion 15c continuous with the corner C in the other cutting edge 11B. The ratio c: d between c and the cutting edge length d of the other cutting edge portion 15d on the opposite side is set in the range of 1.1: 1 to 1.5: 1. If the ratio a: b or the ratio c: d deviates from the above range, it is difficult to reliably offset the radial line segments of the loads acting on the respective tips 11A and 11B on the inner and outer circumference sides of the tool. This is because there is a possibility that a force for bending the tool body 21 may be generated during the drilling process. Therefore, it is desirable that the ratio a: b and the ratio c: d of the cutting edge lengths a to d of the respective cutting edge portions 15a to 15d be set to the above range as in the present embodiment.

Further, in the tip 11 of this embodiment, one of the cutting edges 15A and 15B is provided between the pair of cutting edges 15A and 15B.
The cutting edge length 15a of the cutting edge portion 15a connected to the corner portion C is set longer than the cutting edge length c of the cutting edge portion 15c connected to the corner portion C of the other cutting edge 15B. 15A and 15B are cutting edge portions 15a and 15d having long cutting edge lengths a and d and cutting edge portions 15b and 1 having short cutting edge lengths b and c, respectively.
5c, the cutting edge length a + b of the one cutting edge 15A and the cutting edge length c + d of the other cutting edge 15B can be set to be substantially equal to each other. Therefore, by adopting such a configuration, the chip body 1
2 can be formed in a polygonal flat plate shape in which the length of each side ridge is equal, for example, a rhombic flat plate shape as in the present embodiment, and the cutting edges 15A and 15B formed in these side ridges. Can be efficiently used for processing.

Further, in the tip 11 of the present embodiment, the cutting edge portions 15a, 15B are formed at the cutting edges 15A, 15B.
b and the cutting edge portions 15c and 15d intersect at an obtuse angle through the intersection point P, respectively, while the cutting edge portions 15a and 15c connected to the corner portions C of the respective cutting edges 15A and 15B also intersect at an obtuse angle at this corner portion C. Therefore, the cutting edge portions 15a to 15d adjacent to each other in the circumferential direction of the upper surface 13 are formed.
All of them are formed so as to intersect each other at an obtuse angle. Therefore, according to the present embodiment, the periphery of the intersection point P, which is projected toward the tool tip side and exerts a shocking load when biting on the workpiece, and the vicinity of the axis O of the tool body 21 and the tool. Around the corner portion C where a large load acts by being arranged so as to project to the outer peripheral side, sufficient chip strength that can withstand these loads can be secured, and the intersection point P and the corner portion C It is possible to prevent the occurrence of defects in the periphery and improve the life of the chip.

On the other hand, in the drilling tool of the above embodiment, the pair of chips 1 mounted on the tip of the tool body 21.
The intersection point P, which is the tip position of one of the cutting blades 15A of the inner tip 11A projected toward the tool tip side of the inner tip 11A, is the tip position of the other cutting blade 15B of the outer tip 11B. It is arranged at a position slightly retracted with respect to the intersection point P in the direction of the axis O. Therefore, when performing drilling with such a drilling tool, first, the cutting edge of the outer peripheral side tip 11B protruding toward the tool tip side. The area around the intersection P of 15B precedes the bite on the workpiece, and immediately thereafter, the area around the intersection P of the cutting edge 15A of the inner peripheral side chip 11A bites on the workpiece. Therefore, according to the drilling tool of the present embodiment, these inner and outer peripheral side tips 11A,
Since 11B is prevented from biting the work piece at the same time, the impact acting on the tool body 21 from the tips 11A and 11B is dispersed during the biting, and the tool body 21 may be shaken by the impact. It is possible to prevent a situation and obtain higher hole drilling accuracy.

In this embodiment, the intersection point P, which is the tip position of the cutting edge 15A of the inner peripheral tip 11A, is
Although it is arranged at a position slightly retracted in the direction of the axis O with respect to the intersection point P which is the tip position of the cutting edge 15B of the outer peripheral side tip 11B, on the contrary, the inner peripheral side tip 11A is arranged.
The same effect can be obtained by arranging the intersection point P of the cutting edge 15A of the above in a position slightly ahead of the intersection point P of the cutting edge 15B of the outer peripheral side tip 11B in the direction of the axis O, that is, the above. A pair of chips 11A and 11B has a cutting edge 15A and 15B projecting toward the tool tip side.
It may be arranged so as to be slightly displaced in the direction. However, if the deviation amount γ in the direction of the axis O is too large, for example, when the processed hole is a blind hole, a large step is formed on the bottom surface of the hole, so the deviation amount γ is 0.02 to 0.02. It is desirable to set it in a very small range of about 0.08 mm.

Further, in the tip 11 of the above-mentioned embodiment, the pair of cutting blades 15A, 15B is composed of the pair of cutting blade portions 15a, 15b and the cutting blade portions 15c, 15d, respectively. The blades 15a to 15d,
Further, it may be configured by a plurality of cutting blade portions. Furthermore, if these cutting edge portions 15a to 15d are formed to be uneven in the thickness direction of the chip body 12,
It is possible to efficiently process chips generated during drilling. Further, in the tip 11 of the present embodiment, the cutting edges 15A, 15 are provided on the periphery of the upper surface 13 which is the rake surface.
Since the groove-shaped chip breaker 18 is formed along B, the substantial rake angle of the cutting blades 15A and 15B can be increased to the conformal side, so that the drilling tool of the above embodiment can be used. When the rake angle is apt to increase toward the negative angle side due to the fact that the rake angle is increased like the chip 11 mounted as the outer peripheral side chip 11B, the sharpness of the cutting edge 15B is prevented from being significantly impaired. be able to.

[0027]

As described above, in the tip of the present invention, one of the pair of cutting edges intersecting the corner portion has the cutting edge length of the cutting edge portion which is continuous with the corner portion of the other cutting edge. In addition to being longer than the cutting edge length of the blade, the cutting edge length of the cutting edge that is connected to the corner of the other cutting edge is shorter than the cutting edge length of the other cutting edges, and such a tip is used as a tool. In a drilling tool that is installed unevenly on the inner circumference side and the tool outer circumference side, one tip on the tool inner circumference side positions the corner part near the axis of the tool body and the one cutting edge on the tool tip side. While projecting, the other tip on the outer peripheral side of the tool positions the corner portion on the outer peripheral side of the tool to project the other cutting edge toward the tool tip side, and the above-mentioned cutting edges of each other in a rotation locus around the axis. By arranging the other cutting edges so that they overlap, It can be allowed to cancel the radial component of the load acting on each chip when machining. Therefore, at the time of drilling with such a drilling tool, it is possible to suppress the generation of a force that bends the tool body in its radial direction, thereby preventing the tool body from swinging and making a drilled hole with a predetermined inner diameter high. It is possible to form with concentricity, and it is possible to improve the accuracy of the processed hole.

[Brief description of drawings]

FIG. 1 is a plan view showing a throw-away tip 11 according to an embodiment of the present invention.

2 is a side view of the embodiment shown in FIG. 1 as viewed in the direction of the arrow Y. FIG.

FIG. 3 is a ZZ sectional view in FIG.

FIG. 4 is a plan view showing an embodiment of a throw-away type drilling tool of the present invention in which the throw-away tips 11 and 11 of the embodiments shown in FIGS. 1 to 3 are mounted.

5 is an enlarged plan view of the tip of the embodiment shown in FIG. 4. FIG.

FIG. 6 is an enlarged front view of the embodiment shown in FIG. 4 from the tool tip side.

FIG. 7 is a diagram showing a rotation locus of the inner and outer circumference side chips 11A and 11B around the axis O of the embodiment shown in FIG.

FIG. 8 is a plan view showing a throw-away tip 1 conventionally proposed.

9 is a plan view of a conventional throw-away type drilling tool equipped with the throw-away tips 1 and 1 shown in FIG. 8. FIG.

FIG. 10 is a view showing a rotation locus of the throw-away tips 1A and 1B around the axis O of the throw-away type drilling tool shown in FIG.

[Explanation of symbols]

11 throw-away tip 12 chip body 13 Upper surface to be a rake face 15A, 15B cutting edge 15a to 15d Cutting edge part 18 chip breakers 21 Tool body C corner section Intersection of P cutting edges 15a to 15d a to d cutting edge length of the cutting edge portions 15a to 15d O Axis of tool body 21 T Tool rotation direction

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Kawade 1528 Nakanishi, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture Mitsubishi Materials Corporation Gifu Factory (56) Reference JP-A-11-207508 (JP , A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B23B 27/14 B23B 51/00

Claims (7)

(57) [Claims] 1. A throw-away tool comprising a polygonal flat plate-shaped chip body, and at least a pair of cutting edges intersecting with a corner portion of the polygonal surface formed on a side edge portion of the polygonal surface serving as a rake surface. In the chip, the pair of cutting blades is constituted by a plurality of cutting blade portions that are bent in a convex shape in the circumferential direction of the polygonal surface, and among the pair of cutting blades, one of the cutting blades has a corner portion at the corner portion. The cutting edge length of the continuous cutting edge part is made longer than the cutting edge length of the other cutting edge part, and the cutting edge length of the cutting edge part continuous with the above corner part is the cutting edge length of the other cutting edge part. Throw-away tip characterized by being shorter than the blade length. 2. The ratio of the cutting edge length of the cutting edge portion connected to the corner portion to the cutting edge length of the other cutting edge portion in the one cutting edge is
The throw-away tip according to claim 1, wherein the throw-away tip is set in a range of 1: 1.1 to 1: 1.5. 3. The ratio of the cutting edge length of the cutting edge portion connected to the corner portion to the cutting edge length of the other cutting edge portion in the other cutting edge is
The throwaway tip according to claim 1 or 2, wherein the throwaway tip is set in a range of 1.1: 1 to 1.5: 1. 4. The cutting edge length of the cutting edge portion connected to the corner portion of the one cutting edge is longer than the cutting edge length of the cutting edge portion connected to the corner portion of the other cutting edge. The throw-away tip according to any one of claims 1 to 3. 5. The cutting edge portions adjacent to each other in the circumferential direction of the polygonal surface are all formed so as to intersect each other at an obtuse angle.
Throw-away tip described in any of. 6. A throw-away type drilling tool equipped with the throw-away tip according to any one of claims 1 to 5, wherein a pair of said throws are provided at the tip of a tool body rotated about an axis. The away inserts are detachably attached to the tool inner peripheral side and the tool outer peripheral side on opposite sides of the axis line so as to be attachable / detachable. The tip positions the corner portion in the vicinity of the axis and causes the one cutting edge to project toward the tool tip side, and the other throw-away tip on the tool outer peripheral side positions the corner portion on the tool outer peripheral side. The other cutting edge is projected toward the tool tip side, and the other cutting edge parts of the mutual cutting edges are arranged so as to overlap each other in a rotation locus around the axis. A throw-away tool for drilling. 7. The throw according to claim 6, wherein the pair of throw-away tips are arranged such that the tip positions of the cutting edges projecting toward the tool tip side are slightly displaced in the axial direction. Away type drilling tool.