JPH11235606A - Indexable insert and indexable drill with the indexable insert - Google Patents

Abstract

(57) [Abstract] [Problem] To improve machining hole accuracy. SOLUTION: A corner portion C of an upper surface 13 to be a rake face
The cutting edge length a of the cutting edge portion 15a connected to the corner portion C is longer than the cutting edge length b of the other cutting edge portion 15b in one of the cutting edges 15A intersecting with the other cutting edge 15B. The cutting edge length c of the cutting edge portion 15c connected to C is shorter than the cutting edge length of the other cutting edge portions, and the inner peripheral side tip 11A connects the corner portion C to the axis O of the tool body 11.
The outer peripheral side tip 11B positions the corner portion C on the outer peripheral side of the tool while causing the other cutting edge 15B to protrude toward the distal end side of the tool. The other cutting blades 15b, 15d of the cutting blades 15A, 15B overlap each other in the rotation locus around O, and are mounted on the tool inner peripheral side and the tool outer peripheral side of the tool main body 21 in a biased manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away insert (hereinafter referred to as a "tip") which is particularly suitable for drilling, and a throw-away type drilling tool having the insert mounted thereon (hereinafter referred to as a "drilling tool"). ).

[0002]

2. Description of the Related Art As such a tip and a drilling tool, the inventors of the present invention have proposed the one shown in FIGS. 8 to 10 in JP-A-6-91416. Among them, the chip 1 shown in FIG. 8 has a chip main body 2 formed in a substantially rhombic flat plate shape, and the ridge of a polygonal face (rhombic face) 3 serving as a rake face has: A pair of cutting edges 4A, 4B having an acute angle end of the polygonal surface 3 as a corner C are formed at the corners C, C so as to be alternately positioned in the circumferential direction of the polygonal surface 3. Have been. Further, these cutting edges 4A, 4B are respectively constituted by two cutting edge portions 4a, 4b bent in a convex shape in the circumferential direction of the polygonal surface 3, and symmetrically with respect to a diagonal line connecting the corner portions C, C. The cutting edge portion 4a connected to the corner portion C among the cutting edge portions 4a and 4b is formed to have a shorter cutting edge length than the other cutting edge portions 4b.

[0003] The insert 1 constructed as described above is attached to the tip of a tool body 5 of a drilling tool rotated about an axis O, for example, as shown in FIG. Here, in this drilling tool, a pair of the chips 1 and 1 are attached to the tip end of the tool body 5 on the opposite sides with respect to the axis O, and are biased toward the inner circumferential side and the outer circumferential side of the tool. One of the inserts 1A on the inner peripheral side of the tool has one of the corners C located in the vicinity of the axis O beyond the axis O and the cutting edge 4A connected to the corner C. , 4B are arranged such that one cutting edge 4A protrudes 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 and 4B connected to this corner portion C is used as the tool. It is arranged so as to protrude toward the distal end. And 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, 4b of A, 4B is located at the forefront, and the other cutting edge portions 4b of the cutting edges 4A, 4B on the rotation locus around the axis O as shown in FIG. ,
4b are arranged to overlap.

[0004]

By the way, in such a drilling tool in which such a chip 1 is mounted as a pair of chips 1A and 1B, the cutting blade 4 protruding toward the tool tip side.
Since A and 4B have the point of intersection P of the cutting edge portions 4a and 4b bent in a convex shape as the foremost position, the one cutting edge 4A of the one tip 1A on the tool inner peripheral side has the cutting edge portion. 4a is arranged to be inclined so as to extend toward the tool tip as going from the inner peripheral side to the outer peripheral side.
b is inclined so as to extend from the inner peripheral side toward the outer peripheral side toward the tool rear end side. On the other hand, the other cutting edge 4B of the other tip 1B on the outer peripheral side of the tool is inclined so that the cutting edge portion 4a extends toward the rear end of the tool from the inner peripheral side toward the outer peripheral side. On the other hand, the cutting edge portion 4b is arranged to be inclined so as to extend toward the tool tip from the inner peripheral side toward the outer peripheral side.

At the time of drilling, each of the cutting blades 4
The load acting on the cutting edges 4a, 4b will act in a direction perpendicular to these cutting edges 4a, 4b, and thus these cutting edges 4a, 4b, which are inclined in opposite directions via the intersection P.
Loads having components opposite to each other in the radial direction with respect to the axis O act 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 outer peripheral side of the tool having a larger cutting amount is larger than the inner peripheral side of the tool.
For this reason, 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 shorter cutting edge length disposed on the outer peripheral side of the tool and the inside of the tool Since the radial components of the load acting on the long cutting edge portion 4b arranged on the peripheral side are offset each other, the tool body 5 is bent in the radial direction with respect to the axis O thereof. The force acting on the other chip 1B can be suppressed.

However, in the one cutting edge 4A protruding toward the tool tip side of the one tip 1A on the tool inner circumference side, the cutting edge portion 4a having a short cutting edge length is located on the tool inner circumference side where the cutting amount is small. 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, which has a large cutting amount, so that the tip 1A has a larger load toward the inner peripheral side of the tool. It is inevitable that a force acting on the tool body 5 to bend toward the other chip 1B will be applied. When such a force acts, the tool body is radially wobbled during drilling. Therefore, the bore formed by the drilling tool has an inner diameter larger than a predetermined bore diameter. Is greatly expanded, and concentricity is also impaired. For this reason, there is a problem that it is difficult to obtain higher machining hole accuracy with the above-described conventional chip 1 and the drilling tool on which the chip 1 is mounted.

The present invention has been made under such a background, and in particular, when used for drilling, a force is exerted on the insert to cause the tool body to bend radially with respect to its axis. Drilling tools that can suppress drilling and provide a higher accuracy in drilling by suppressing the runout of the tool body during drilling. It is intended to provide.

[0008]

In order to solve the above-mentioned problems and to achieve the above object, a chip of the present invention comprises a polygonal flat chip-shaped chip body having a polygonal face, which is a rake face. In a chip in which at least a pair of cutting edges intersecting the corners of the polygonal surface are formed on the side ridges, a plurality of cuttings that bend the pair of cutting edges convexly in a circumferential direction of the polygonal surface. The cutting edge length of the cutting edge portion connected to the corner portion is longer than the cutting edge length of the other cutting edge portion on one of the pair of cutting edges.
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 length of the other cutting edge portion.
Further, the drilling tool of the present invention is a drilling tool equipped with a tip having such a configuration, wherein a pair of the above-mentioned tips are provided on a tip end portion of a tool body rotated around an axis, and the pair of opposite sides of the above-mentioned axis are interposed therebetween. The tool is detachably mounted on the tool inner peripheral side and the tool outer peripheral side so as to be detachable, and one of the chips on the tool inner peripheral side has the corner portion positioned near the axis, and With the cutting blade protruding toward the tool tip,
The other tip on the outer peripheral side of the tool has the corner portion positioned on the outer peripheral side of the tool so that the other cutting edge projects toward the tip end of the tool, and the other cutting edge of the other cutting edge on the rotation locus around the axis. The blade portions are arranged so as to overlap.

However, according to the chip having the above-described configuration, by mounting the chip on the tool body of the drilling tool as described above, one of the chips on the inner peripheral side of the tool projects toward the tip of the tool. In the cutting edge of the above, a cutting edge portion connected to the corner portion having a longer cutting edge length is disposed on the inner peripheral side of the tool with a small acting load, and the cutting edge length is short on the outer peripheral side of the tool with a large load acting. Are arranged so that the components of the load acting on both the cutting edges in the radial direction with respect to the axis of the tool body are offset, and a force such that one of the tips bends the tool body in the radial direction. Can be suppressed. On the other hand, in the other chip on the outer peripheral side of the tool, a cutting edge portion connected to a corner portion having 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 The other cutting edge having a longer cutting edge length is arranged on the peripheral side, so that the other insert does not generate a force to bend the tool body in the radial direction. It is possible to obtain higher machining hole accuracy by preventing runout in the direction.

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 between the cutting edge length of the cutting edge portion connected to the corner portion and the cutting edge length of the other cutting edge portion in the other cutting edge is set to 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 tip is mounted on a drilling tool as described above and drilling is performed, the load at the time of processing is increased. This is because there is a possibility that components in the radial direction with respect to the axis of the tool main body may not be reliably canceled.
Further, in the chip, the cutting edge length of the cutting edge portion connected to the corner portion in the one cutting edge is 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 blades that intersect one corner can be set to have substantially the same cutting edge length.For example, when the chip main body is formed in a rhombic flat plate shape as in the conventional chip, It becomes possible to form two pairs of the cutting blades having the same cutting edge length at the side ridges of the polygonal surface (rhombic surface). Furthermore, if the cutting edge portions adjacent to each other in the circumferential direction of the polygonal surface are formed so as to all intersect each other at an obtuse angle, chipping of the chip body at the intersection of the cutting edge portions can be prevented. .

On the other hand, in the drilling tool having the above configuration,
By arranging the pair of tips so that the tip positions of the cutting blades projecting toward the tool tip side are slightly shifted in the axial direction, the cutting edges of the pair of chips simultaneously bite into the workpiece. Therefore, the impact acting on the tool main body from the chip at the time of the biting can be dispersed, and a situation in which the tool main body oscillates due to the impact can be prevented.

[0012]

1 to 3 show one embodiment of a chip according to the present invention. The chip 11 of the present embodiment has a chip body 12 formed in a substantially rhombic flat plate shape from a hard material such as a cemented carbide, and the upper surface 13 forming the rhombus is a rake face. The four side surfaces 14 arranged around the periphery 13 are flank surfaces, and the intersection ridge line between the upper surface 13 and the side surface 14
A pair of corners C, C located diagonally on the upper surface 13
Are alternately arranged in the circumferential direction of the upper surface 13. In addition,
The chip 11 according to the present embodiment has a
4 is a positive tip having a clearance angle with respect to the cutting edges 15A and 15B in advance, and the clearance angle is formed so as to increase by one step from the upper surface 13 of the chip body 12 toward the lower surface 16 side. I have. In addition, from the center of the upper surface 13 of the chip body 12 to the lower surface 16,
A mounting hole 17 through which a clamp screw for mounting the chip main body 12 to a tool main body of a drilling tool described later is formed.
7 is formed so as to be axially symmetric with respect to the central axis.

Further, the side surfaces 14 of the chip main body 12.
Are formed so as to be bent one step at an obtuse angle in the circumferential direction of the upper surface 13.
Cutting edge 15A, 15B formed at the ridge line intersecting with
1 is formed from a pair of cutting blade portions 15a, 15b and cutting blade portions 15c, 15d bent at an obtuse angle through an intersection P as shown in FIG. ing. Therefore, the upper surface 13 of the chip main body 12 is strictly formed in an octagonal shape as shown in FIG. 1 in plan view when viewed from the direction facing the upper surface 13. One of the pair of cutting edges 15A and 15B intersecting the corner C of the upper surface 13
5A is a pair of cutting blades 15 intersecting via the intersection P.
a, 15b, the cutting edge portion 15a connected to the corner portion C
Is longer than the cutting edge length b of the cutting edge portion 15b on the opposite side, while the other cutting edge 15B is opposite to the cutting edge length c of the cutting edge portion 5c connected to the corner portion C. Are formed to be shorter than the cutting edge length d of the opposite cutting edge portion 5d.

Here, the ratio a: b of 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 the present embodiment. １ ： 1: 1.5
In the present embodiment, the ratio c: d of 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 to 1
It is set in the range of 1.5: 1. Further, in this embodiment, the cutting edge length a of the cutting edge portion 15a connected to the corner portion C of the one cutting edge 15A is equal to the cutting edge length of the cutting edge portion 15c connected to the corner portion C of the other cutting edge 15B. c, and these cutting edges 15a, 15c intersect at an obtuse angle at the corner C, whereby the cutting edges 15a adjacent in the circumferential direction of the upper surface 13 are formed.
15d are formed so as to all intersect each other at an obtuse angle. Further, a chip breaker 18 having a concave circular cross section as shown in FIG.
Are formed so as to go around the peripheral portion along the cutting blades 15A and 15B.

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

Here, the pair of chip mounting seats 23A,
23B is formed so as to be deviated in the radial direction with respect to the axis O toward the inner peripheral side of the tool and the outer peripheral side of the tool. Accordingly, the pair of tips 11, 11 mounted on the tip mounting seats 23A, 23B also has One of the chips 11 is arranged on the inner peripheral side of the tool to form an inner peripheral chip 11A, and the other chip 11 is arranged on the outer peripheral side of the tool to form an outer peripheral chip 11B. The inner and outer chips 11A and 11B are connected to the inner chip 11A.
However, the corner C is positioned near the axis O so that the one corner C is over-centered beyond the axis O, and one of the cuts connected to the corner C with the intersection P as a tip position. While the blade 15A protrudes toward the tool tip, the outer peripheral side tip 11B causes one corner portion C to protrude toward the outer periphery of the tool main body 11 tip, and the intersection P
The other cutting edge 15B is protruded toward the tool tip side with the tip as a tip position, and as shown in FIG. 7 in the rotation trajectory around the axis O, the cutting edges 15b, 15b of the cutting edges 15A, 15B 15d are arranged to overlap.

In this embodiment, the inner peripheral chip 11
A, one of the cutting edges 15A protruding toward the tool tip side of A
The intersection point P, which is the tip position of the other cutting edge 15B protruded toward the tool tip side of the outer peripheral side tip 11B, has a shift amount γ as shown in FIG. It is arranged at a position slightly retracted in the direction of the axis O. Further, in the present embodiment, as shown in FIG.
The one cutting edge 15A of A is disposed so as to be slightly lower than the axis with respect to the axis O, and it is avoided that the chip body 12 of the inner peripheral side tip 11A is disposed on the axis O. On the other hand, the other cutting edge 15 of the outer peripheral side tip 11B
B is positioned so that it slightly rises in the center,
Sufficient clearance is ensured on the side surface 14 which is connected to the corner portion C disposed on the outer peripheral side of the tool and is a flank thereof.

However, in the chip 11 configured as described above, one of the pair of cutting edges 15, 15A intersecting the corner C of the upper surface 13 which is the rake face of the chip body 12, has one of the cutting edges 15A. The cutting edge length a of the cutting edge portion 15a connected to the corner portion C is longer than the cutting edge length b of the other cutting edge portion 15b opposite to the corner portion C, and the other cutting edge 15B has 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 opposite to the corner portion C. Therefore, when such a chip 11 is arranged so as to be deviated toward the inner circumferential side and the outer circumferential side of the tool of the tool body 21 of the drilling tool, the inner circumferential side tip (one chip) 11A as described above The corner C is positioned near the axis O so that the one cutting edge 15A protrudes toward the tool tip, and the outer peripheral side tip (the other tip) 11B positions the corner C toward the outer periphery of the tool. Then, the other cutting edge 15B protrudes toward the tool tip, and the other cutting edges 15b, 15d of the cutting edges 15A, 15B overlap each other on the rotation locus around the axis O. Thus, the radial components of the load acting on both the chips 11A and 11B on the inner and outer peripheral sides of the tool can be offset.

That is, in the inner peripheral side chip 11A,
In the one cutting edge 15A protruded to the tool tip side, a cutting edge portion 15a having a long cutting edge length a is arranged on the inner circumferential side of the tool having a small acting load, and the outer periphery of the tool having a large acting load. The cutting edge portion 15b having a short cutting edge length b is disposed on the side, so that both the cutting edge portions 15a, 15
Among the loads acting on b, the magnitudes of the radial components with respect to the axis O acting in opposite directions can be made substantially equal. On the other hand, in the outer peripheral side tip 11B as well, a long cutting edge portion 15d having a long cutting edge length d is arranged on the inner peripheral side of the tool where the load acting on the tool is small as in the related art. Side, a short cutting edge 15c having a short cutting edge length c is arranged.
The radial components of the loads acting on c and 15d can be made substantially equal in magnitude, and therefore, the radial components of the loads acting on the respective chips 11A and 11B on the inner and outer peripheral sides of the tool cancel each other. It becomes possible. Therefore, according to the insert 11, it is possible to suppress the generation of a force that causes the tool main body 21 to bend in the radial direction at the time of drilling, thereby preventing the tool main body 21 from swaying during the processing. The hole accuracy can be improved.

In particular, in the inner peripheral side chip 11A,
In the other cutting edge 11B connected to the corner portion C arranged near the axis O of the tool main body 21, a cutting edge portion 15c having a short cutting edge length c is disposed on the distal end side, and the intersection P is located behind the cutting edge portion 15c. The cutting edge portion 15d having a long cutting edge length d intersecting at an obtuse angle is disposed, and accordingly, the wall surface 23a of the tip mounting seat 23A abutting on the side surface 14 of the tip main body 12 connected to these cutting edge portions 15c, 15d. Also, as shown in FIG. 5, it is formed so as to extend from the distal end surface of the tool body 21 to the rear end side of the tool, and then bend toward the outer peripheral side of the tool. Therefore, according to the chip 11 having the above-described configuration, in the tool body 21 of the drilling tool in which the chip 11 is mounted on the tool inner circumference side as described above, the chip mounting seat on the tool inner circumference side where the chip 11 is mounted. A sufficient thickness can be ensured between the wall surface 23a of the tool 23A and the chip discharge groove 22 in which the chip mounting seat 23B on the outer peripheral side of the tool is formed. In addition, the effect of improving drilling and promoting more stable drilling can be obtained.

Here, in the tip 11, the cutting edge 1 connected to the corner C at the one cutting edge 11A is provided.
5a and the other cutting edge 15b on the opposite side
The ratio a: b to the cutting edge length b is set in the range of 1: 1.1 to 1: 1.5, and the cutting edge length of the cutting edge portion 15c connected to the corner portion C on 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 cancel radial segments of loads acting on the respective chips 11A and 11B on the inner and outer peripheral sides of the tool. This is because there is a possibility that a force for bending the tool main body 21 may be generated during drilling. For this reason, it is desirable that the ratio a: b and the ratio c: d of the cutting edge lengths ad of the respective cutting edge portions 15a to 15d be set in the above ranges as in the present embodiment.

In the tip 11 of the present embodiment, one of the cutting edges 15A, 15B is located between the pair of cutting edges 15A, 15B.
The cutting edge length a 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 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 into a polygonal flat plate having the same length of each side ridge, such as a rhombic flat plate as in the present embodiment, and the cutting blades 15A, 15B formed on these side ridges. Can be used efficiently for processing.

Further, in the tip 11 of the present embodiment, the cutting blades 15A, 15B have the cutting blades 15a, 15b.
b and the cutting edges 15c, 15d intersect at an obtuse angle via the intersection point P, respectively, while the cutting edges 15a, 15c connected to the corner C of each of the cutting edges 15A, 15B also intersect at an obtuse angle at this corner C. Therefore, the cutting edge portions 15a to 15d adjacent in the circumferential direction of the upper surface 13 are formed.
They are all formed to intersect each other at an obtuse angle. For this reason, according to the present embodiment, the vicinity of the intersection P, which is protruded toward the tool tip side and is subjected to an impact load when biting into the workpiece, the vicinity of the axis O of the tool main body 21 or the tool. Sufficient chip strength to withstand these loads can be secured in the vicinity of the corner portion C where a large load acts by being arranged so as to protrude to the outer peripheral side, and the intersection point P and the corner portion C can be secured. It is possible to prevent chipping or the like from occurring in the periphery and to improve the chip life.

On the other hand, in the drilling tool of the above embodiment, a pair of tips 1
The intersection point P, which is the tip position of one cutting edge 15A protruded toward the tool tip side of the inner tip 11A, is the tip position of the other cutting edge 15B of the outer tip 11B. It is arranged at a position slightly retreated in the direction of the axis O with respect to the intersection point P. 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 vicinity of the intersection P of 15B first bites into the workpiece, and immediately thereafter, the vicinity of the intersection P of the cutting edge 15A of the inner peripheral side tip 11A bites into the workpiece. Therefore, according to the drilling tool of the present embodiment, the inner and outer peripheral chips 11A,
Since it is possible to avoid that the tool 11B bites into the workpiece at the same time, the impact acting on the tool body 21 from the chips 11A and 11B at the time of biting is dispersed, and the tool body 21 may run out due to the shock. It is also possible to prevent the situation and obtain a higher drilling accuracy.

In this embodiment, the intersection P, which is the tip position of the cutting edge 15A of the inner peripheral side tip 11A, is
Although it is arranged at a position slightly retreated 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
The same effect can be obtained by arranging the intersection P of the cutting edge 15A at a position slightly preceding in the direction of the axis O with respect to the intersection P of the cutting edge 15B of the outer peripheral side tip 11B. A pair of tips 11A, 11B are arranged such that the tip positions of the cutting blades 15A, 15B protruding toward the tool tip side are aligned with the axis O.
It is sufficient if they are arranged so as to be slightly shifted in the direction. However, if the shift amount γ in the direction of the axis O is too large, for example, if the machined hole is a blind hole, a large step is formed on the bottom surface of the hole, so the shift amount γ is 0.02 to 0.02. It is desirable to set it to a very small range of about 0.08 mm.

In the tip 11 of the above embodiment, the pair of cutting blades 15A and 15B are composed of a pair of cutting blade portions 15a and 15b and a pair of cutting blade portions 15c and 15d, respectively. The blades 15a to 15d
Further, it may be constituted by a plurality of cutting blades. Furthermore, if these cutting blade portions 15a to 15d are formed so as to be uneven in the thickness direction of the chip body 12,
Efficient processing of chips generated during drilling can be achieved. Further, in the chip 11 of this embodiment, the cutting edges 15A, 15
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 toward the regular angle side. In a case where the rake angle tends to increase toward the negative angle side by being disposed above the center as in the case of the tip 11 mounted as the outer peripheral side tip 11B, particularly, the sharpness of the cutting edge 15B is prevented from being significantly impaired. be able to.

[0027]

As described above, in the insert of the present invention, of the pair of cutting blades intersecting the corner, one of the pair of cutting blades has the same length as the other cutting blade connected to the corner. The cutting edge length of the cutting edge portion of the other cutting edge portion is shorter than the cutting edge length of the other cutting edge portion. In a drilling tool mounted on the inner peripheral side and the outer peripheral side of the tool, one tip on the inner peripheral side of the tool has the above-mentioned corner located near the axis of the tool main body and the one cutting edge is on the tip side of the tool. 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 tip end of the tool, and the cutting edge of each other on the 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, when drilling with such a drilling tool, it is possible to suppress the generation of a force that bends the tool main body in the radial direction, thereby preventing the tool main body from oscillating and increasing the processing hole having a predetermined inner diameter. It is possible to form with a concentricity, and it is possible to improve the machining hole accuracy.

[Brief description of the drawings]

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

FIG. 2 is a side view of the embodiment shown in FIG.

FIG. 3 is a sectional view taken along the line ZZ in FIG.

FIG. 4 is a plan view showing an embodiment of a throw-away type drilling tool according to the present invention equipped with the throw-away tips 11, 11 of the embodiment shown in FIGS. 1 to 3;

FIG. 5 is an enlarged plan view of a distal end portion of the embodiment shown in FIG.

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

FIG. 7 is a view showing a rotation locus of the inner and outer peripheral chips 11A and 11B around the axis O of the embodiment shown in FIG. 4;

FIG. 8 is a plan view showing a conventionally proposed indexable insert 1;

9 is a plan view of a conventional throw-away type drilling tool to which the throw-away tips 1 and 1 shown in FIG. 8 are attached.

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. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Throw-away insert 12 Tip main body 13 Top surface to be a rake face 15A, 15B Cutting blade 15a to 15d Cutting blade 18 Chip breaker 21 Tool main body C Corner P Intersection of cutting blades 15a to 15d a to d Cutting blade 15a Cutting edge length of ~ 15d O Axis line of tool body 21 T Tool rotation direction

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiko Kawade 1528 Nakashinda, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture Gifu Works, Mitsubishi Materials Corporation

Claims (7)

[Claims] 1. A throwaway in which at least one pair of cutting edges intersecting a corner portion of a polygonal surface, which is a rake surface of a polygonal flat chip body, is formed on a rake surface of the chip body. In the chip, the pair of cutting blades is constituted by a plurality of cutting blade portions bent in a convex shape in a circumferential direction of the polygonal surface, and one of the pair of cutting blades is in the corner portion. The cutting edge length of the continuous cutting edge portion is made longer than the cutting edge length of the other cutting edge portion, and the other cutting edge portion has the cutting edge length of the cutting edge portion connected to the above-mentioned corner portion. A throwaway insert characterized by being shorter than the blade length. 2. A ratio of a cutting edge length of a cutting edge portion connected to the corner portion to a cutting edge length of another cutting edge portion in one of the cutting edges,
The throw-away tip according to claim 1, wherein the index is set in a range of 1: 1.1 to 1: 1.5. 3. A ratio of a cutting edge length of a cutting edge portion connected to the corner portion to a cutting edge length of another cutting edge portion of the other cutting edge is:
3. The throw-away tip according to claim 1, wherein the index is set in a range of 1.1: 1 to 1.5: 1. 4. A cutting edge length of a cutting edge portion connected to the corner portion of the one cutting edge is longer than a cutting edge length of a 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, characterized in that: 5. The cutting edge portions adjacent to each other in the circumferential direction of the polygonal surface are formed so as to all intersect each other at an obtuse angle.
The throwaway tip according to any one of the above. 6. A throw-away type drilling tool equipped with the throw-away tip according to claim 1, wherein a pair of the throws is provided at a tip end of a tool body rotated about an axis. The away tips are detachably mounted on the opposite sides of the axis with respect to the tool inner peripheral side and the tool outer peripheral side, and these throw away tips are provided on one of the tool inner peripheral sides. The tip positions the corner portion near the axis and causes the one cutting edge to protrude toward the tool tip, and the other indexable tip on the tool outer peripheral side positions the corner portion on the tool outer peripheral side. The other cutting edge is projected to the tool tip side, and the other cutting edge portions of the other cutting edges are arranged so as to overlap with each other in a rotation locus around the axis. Indexable drilling tool. 7. The thrower according to claim 6, wherein the pair of indexable inserts are arranged such that the tip positions of the cutting blades projecting toward the tool tip side are slightly shifted in the axial direction. Away drilling tool.