JPH11254207A - Indexable inserts and indexable cutting tools - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A plurality of pieces can be mounted on a tool body by providing different blades for one type of insert. A chip has a substantially rectangular plate shape, and two opposing ridges on an upper surface are non-parallel long blades and short blades. The corner angles of the first and second corner portions 10 and 11 in one diagonal direction are the same acute angle α, and 2 in the other diagonal direction.
Corners are made obtuse. The long blades 6 and the short blades 7 are mounted as front blades with the plurality of inserts 1 facing the axis O of the tool main body 21, and the first corner portion 10 and the second corner portion 11 are located outside thereof. By locating the fourth cutting edge 9 and the third cutting edge 8 of each chip 1 as outer peripheral blades, the long blades 6 and the short blades 7 are inclined from the outer corner portions 10 and 11 inward toward the base end. .

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, sometimes referred to as a tip) and a throw-away type cutting tool such as an end mill to which the throw-away tip is mounted.

[0002]

2. Description of the Related Art Conventionally, in a throw-away type end mill in which a plurality of, for example, two, throw-away tips are attached to the tip of a tool body, the end mill is disposed at a position close to an axis which forms a rotation center of the tool body. An inner cutter tip and an outer cutter tip disposed on the outer peripheral side of the tool body are provided.
In the case of the inner blade tip, the front blade protruding from the tip surface of the tool body is located close to the axis, and in the case of the outer blade tip, the front blade protruding from the tip surface of the tool body is located away from the axis and sandwiches the corner. The outer peripheral edge is located on the outer peripheral side and projects from the outer peripheral surface of the tool body. When the tool body is rotated, the rotation trajectories of the two front blades are continuous.

[0003]

By the way, in such an end mill, there is a case where a plurality of indexable inserts are mounted so that two corners can be used by changing corners. Since the shape of the front blade is different between the outer blade tip and the outer blade tip, two types of indexable inserts having different appearance shapes are used. For this reason, a plurality of types of indexable inserts are required as a tip to be mounted and a replacement tip, and there is a disadvantage that the production cost of the insert, the running cost of a cutting tool, and the like become high.

[0004] In view of such circumstances, an object of the present invention is to provide a throw-away insert provided with a plurality of types of cutting blades in which different cutting blades can be arranged. Another object of the present invention is to provide a cutting tool that can arrange a plurality of types of cutting blades using one type of throw-away insert.

[0005]

The indexable insert according to the present invention has a substantially rectangular plate shape, and two opposing edges of the four sides of one surface (upper surface) are non-parallel. And the two corners in one diagonal direction are acutely angled to each other. When mounting this throw-away tip on the tool body of the cutting tool, one tip projects one non-parallel cutting edge from the tip of the tool body as, for example, a front edge, and the other tip uses the other non-parallel cutting edge. For example, if the front blade is mounted so as to protrude from the tip of the tool body, a long blade and a short blade can be used as a front blade and the like, respectively, using a plurality of chips of one type. Note that two corner angles in one diagonal direction may be equal to each other, and in this case, two corner angles in the other diagonal direction may be equal.
The two cutting edges are also non-parallel. The corner portion is a corner blade.

Further, the distance between two corners in one diagonal direction and the other surface (lower surface) opposing one surface (upper surface) is larger than that in the other two corner portions in diagonal direction. Is formed on an inclined surface such that the distance from the other surface gradually decreases from two corner portions in one diagonal direction to a diagonal line connecting the two corner portions in the other diagonal direction. You may. Since the two corner portions in one diagonal direction forming an acute angle are formed to be thicker than the corner portions in the other diagonal direction, the cutting edge strength of these one diagonal corner portions is large. By attaching one of these diagonal corners to the tip of the tool body, the fracture resistance of one of the diagonal corners at the time of biting etc. is improved, and the rake angle of the cutting edge is increased. So the sharpness is improved. Further, the inclined surface may be a convex curved surface. The thickness of the chip is increased and the strength is improved. Note that the inclined surface may be formed in a flat shape or a concave curved shape, or may be formed as a twisted surface. A breaker may be provided on the rake face of the cutting blade including the inclined face.

A throw-away type cutting tool according to the present invention comprises a plurality of throw-away type cutting tools comprising a plurality of throw-away chips each having a tip of a tool main body and a plurality of throw-away tips each having a cutting blade protruding from the tip side. The away insert is the same throwaway insert according to any one of claims 1 to 4, wherein one throwaway insert has one non-parallel cutting edge protruding from the tool body, and the other throwaway insert is non-parallel. The other parallel cutting blade is arranged to protrude from the tool body. Two opposite non-parallel cutting blades of a plurality of the same chips can be mounted on the tool body as, for example, front blades, and only one type of mounting chip and replacement chip need be prepared, so that the cost is reduced. Moreover, the non-parallel cutting blades facing the insert are a long blade and a short blade, and the sharp corners are located outside the long blade or short blade located on the tip side of the tool body. Biting occurs at sharp corners on the outer peripheral side, and since the rotating speed on the outer peripheral side is high, loss of the corners can be suppressed. If the sharp corner portion is thick, the strength of the corner blade (corner portion) is high, and the fracture resistance and sharpness are improved. In the above-mentioned plurality of throw-away inserts, non-parallel cutting blades arranged on the tip side are arranged so as to rise, and at least one of the non-parallel cutting blades has an inner corner portion which is aligned with the rotation axis of the tool body. It may be formed so as to be inclined so as to intersect with another surface (seating surface). In this case, the rake face of the inner corner portion may be an inclined flat surface or a convex curved surface.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a throw-away insert and a throw-away type end mill according to an embodiment of the present invention. FIGS. 1 to 3 show a throw-away tip according to the first embodiment.
6 to 6 show a throw-away type end mill according to the first embodiment. 1 is a plan view of the throw-away tip, FIG. 2 is a side view of the throw-away tip shown in FIG. 1 in the direction A, FIG. 3 is a side view of the throw-away tip shown in FIG. 1 in the direction B, and FIG. FIG. 5 is a side view of the main part of the end mill with the away tip mounted thereon, FIG. 5 is a side view of the main part of the end mill shown in FIG. 4 as viewed from the outer peripheral blade side, and FIG. 6 is a front view of the end mill shown in FIG. A throw-away tip (hereinafter, sometimes referred to as a tip) 1 according to the embodiment shown in FIGS. 1 to 3 has a substantially rectangular plate shape, and has an upper surface 3 opposed to a lower surface 2 forming a seating surface. The four side surfaces 4 are provided so as to be gradually inclined outward from the lower surface 2 toward the upper surface 3 with an inclination angle (a clearance angle) of, for example, 15 °.
It is a positive chip. An insertion hole 5 for bolting is formed in the chip 1 so as to penetrate from the center of the upper surface 3 to the lower surface 2.

The upper surface 3 and the lower surface 2 of the chip 1 are substantially in the form of a parallel plate, and one of the four ridges on the upper surface 3 is a relatively long blade 6, one of the cutting edges constituting the two opposite sides. The other is a relatively short short blade 7. The other two opposite sides are, for example, a first cutting edge 8 and a second cutting edge 9 longer than the long blade 6.
It has been. Moreover, the opposing long blade 6 and short blade 7 are not parallel to each other, and the other opposing first and second cutting blades 8, 9 are also non-parallel. The upper surface 3 is a rake face of each of the cutting blades 6, 7, 8, and 9, and the side face 4 is a flank. The first corner portion 10 and the second corner portion 11 in one diagonal direction of the upper surface 3 are formed such that the long side 6, the second cutting edge 9, the short side 7, and the first blade 8 intersect. , Each corner angle of which is an acute angle α (for example, α = 80 °), and the other diagonal third corner portion 12 and fourth corner portion 1
The corner angles of Nos. 3 are obtuse angles. In addition, each corner part 10, 11, 12, 13 comprises a cutting blade. The corner angles of the first and second corner portions 10 and 11 may not be equal. 1, the intersection angle between the long blade 6 and the short blade 7 is, for example, 10 °, and the intersection angle between the first and second cutting blades 8, 9 is also, for example, 10 °.

The indexable insert 1 according to the present embodiment is configured as described above. Next, an end mill 20 on which a plurality of indexable inserts 1 are mounted will be described with reference to FIGS. At the end of the tool body 21 of the end mill 20, an axis O
, Two recessed grooves 22 and 23 which are cut out in a substantially fan-shaped cross section are provided. Each of the concave grooves 22 and 23 extends from the outer peripheral surface of the tool body 21 in the longitudinal direction at the intermediate portion to the distal end surface 21a.
The chip mounting seat 24a is formed on the surface of one of the concave grooves 22 facing the rotation direction, and the chip mounting seat 24b is also formed on the surface of the other concave groove 23 facing the rotation direction. . The above-mentioned indexable insert 1 is attached to one of the tip mounting seats 24a by using the long blade 6 as a front blade so as to protrude from the distal end surface 21a of the tool body 21 to the distal end side, and this is referred to as a main insert 1A. The throw-away tip 1 is mounted on the other tip mounting seat 24b with the short blade 7 as a front blade protruding from the distal end surface 21a of the tool body 21 to the distal end side, and this is referred to as an auxiliary tip 1B.

The main chip 1A is disposed such that the first corner portion 10 is disposed outside the distal end, and the second cutting edge 9 projects along the outer peripheral surface of the tool body 21 so as to be substantially parallel to the axis O. The outer peripheral edge of the tool body 21
The long blade 6 protruding from the distal end from 1a is inclined at an angle α with respect to the axis O so as to gradually approach the base end from the outer periphery toward the direction of the axis O, and the other end of the long blade 6 forms an obtuse angle. The corner 12 intersects the axis O. Therefore, the first all-blade 8 and the side surface 4 located inside are gradually inclined outward, for example, at an inclination angle of 10 ° from the distal end side toward the proximal end side in a direction gradually separated from the axis O. Further, the sub-tip 1B has a second corner portion 11 disposed outside the distal end, and the first all-blade 8 is disposed so as to protrude along the outer peripheral surface of the tool body 21 so as to be substantially parallel to the axis O. The short blades 7 projecting from the distal end surface 21a of the tool body 21 to the distal end side are inclined at an angle α so as to gradually approach the base end side from the outer peripheral side toward the axis O direction. The fourth corner portion 13 at the other end is separated outward from the axis O. Therefore, the second cutting edge 9 located on the inside and the side surface 4 thereof are inclined inward from the distal end side toward the base end side in a direction gradually approaching the axis O, for example, at an inclination angle of 10 °.

Further, the main tip 1A and the sub tip 1B are mounted so that the axial rake angle becomes positive as shown in FIG. 5 for the second cutting edge 9 and the first cutting edge 8 forming each outer peripheral edge. (Only the second cutting edge 9 is shown in FIG. 5). As shown in FIG. 6, the main chip 1A and the sub chip 1B have the long blades 6 and the short blades 7 forming the front blades positioned on a radius line centered on the axis O, and have a radial rake angle of 0 °. Have been.

Since the indexable insert 1 and the end mill 20 according to the present embodiment are configured as described above, if the workpiece is cut by rotating the tool body 21 about the axis O, the tool body 21 The long blade 6 and the short blade 7 projecting to the tip end bite the work material at the corners 10 and 11 on the outer peripheral side. Since this region rotates at a higher speed than the vicinity of the axis O, the cutting at the time of biting is performed. Cutting with low resistance and no breakage. Further, by sending the tool main body 21 to the front end side in the direction of the axis O, rotary cutting can be performed like a drill by the long blade 6 and the short blade 7 whose rotation trajectories overlap. In addition, by feeding the tool body 21 in the lateral direction, the first cutting edge 8 and the second cutting edge 9 serving as the outer peripheral blades perform feed cutting, while the finish cutting is performed at the corner portions 10 and 11 of the long blade 6 and the short blade 7. it can. Then, even when the cutting edge of either of the inserts 1A and 1B is damaged or worn, the same indexable insert 1 may be replaced and mounted.

According to the present embodiment, as described above, by providing a plurality of the same chips 1, the long blade 6 and the short blade 7 can be mounted on the tool body 21 as different types of cutting blades. Since a plurality of different types of cutting blades can be arranged and configured with one type of insert 1 and only one type of replacement insert needs to be stored, the manufacturing cost of the insert and the running cost of the cutting tool are reduced. Moreover, since the corner angles of the opposing first and second corner portions 10 and 11 are acute, the inner side surface 4 of the sub-tip 1B gradually extends from the tip of the tool body 21 toward the base end in the mounted state. Even if it is inclined to the O side, since the inner side surface 4 of the main chip 1A is gradually inclined away from the axis O from the distal end of the tool main body 21 toward the base end side, the two chips 1A, 1B The thickness of the center portion 26 of the tip end of the tool body 21 sandwiched therebetween can be equally secured along the axis O, and the rigidity of the tool body 21 can be secured.

Next, a second embodiment of the present invention will be described with reference to FIGS. 7 to 12, and the same or similar parts as those in the first embodiment will be described using the same reference numerals. Omitted. 7 is a plan view of the throw away tip according to the second embodiment, FIG. 8 is a side view of the throw away tip shown in FIG. 7 in the direction A, and FIG. 9 is a side view of the throw away tip shown in FIG. 10 is a side view of a main part of an end mill to which the throw-away tip shown in FIG. 7 is attached, FIG.
Is a side view of a main part of the end mill viewed from the outer peripheral blade side, and FIG. 12 is a front view of the end mill shown in FIG. A throw-away tip (hereinafter, may be referred to as a tip) 30 according to the second embodiment shown in FIGS. 7 to 9 has a substantially square plate shape similar to the tip 1 according to the above-described first embodiment in plan view. The upper surface 3 faces the lower surface 2 forming the seating surface.
First and second corner portions 31 and 32 having a corner angle of acute angle α located in one diagonal direction in plan view, and third and second corner portions having two obtuse corner angles located in the other diagonal direction. Four corner portions 33 and 34 are provided.

Moreover, the first and second corner portions 31, 32
Are the third and fourth corner portions 33, 34 (height hb, h
The height from the lower surface 2 is higher than b), and they are the same heights ha and ha, respectively. On the upper surface 3, the distance from the first and second corner portions 31, 32 to the diagonal line L gradually decreases with respect to the diagonal line L connecting the third and fourth corner portions 33, 34. For example, flat inclined surfaces 35a and 35b are formed, and one inclined surface 35a is a rake surface of the long blade 6 and the second cutting edge 9, and the other inclined surface 35b is the short blade 7 and the first It is a rake face of the cutting blade 8. Therefore, the throw-away tip 30 has the maximum thickness at the first and second corner portions 31 and 32 and the minimum thickness at a portion along the diagonal line L connecting the obtuse corner portions 33 and 34.

The indexable insert 30 according to the present embodiment has the above-described configuration. Next, an end mill 40 equipped with the indexable insert 30 is shown in FIG.
This will be described with reference to FIGS. At the tip of the tool body 21 of the end mill 40, one of the tip mounting seats 24a and 24b provided on the surface of each of the concave grooves 22 and 23 facing the rotation direction is provided with the above-described throwaway tip. Reference numeral 30 denotes the long blade 6 at the tip end surface 21a of the tool body 21.
And is mounted with the thick first corner portion 31 positioned on the outer peripheral side of the distal end, and the second cutting blade 9 is an outer peripheral blade. This is the main chip 30A
And On the other tip mounting seat 24b, the throw-away tip 30 causes the short blade 7 to protrude from the distal end surface 21a of the tool body 21 toward the distal end as a front blade, and the thick second corner portion 32 to be positioned on the outer peripheral side of the distal end. The first blade 8 is an outer peripheral blade. This is referred to as a sub chip 30B. In this case, the main chip 30A has a large thickness at the first corner portion 31 located outside the distal end,
The edge of the corner portion 31 has a high strength, and has high fracture resistance when biting. In addition, in the sub chip 30B, since the second corner portion 32 located on the outer side of the tip is made thick, the strength of the blade of the corner portion 32 is large, and the chipping resistance is high at the time of biting.

Since the indexable insert 30 and the end mill 40 according to the second embodiment have the above-described configurations, in addition to the functions and effects of the first embodiment,
When the indexable insert 30 is mounted on the tool body 21, the first and second corner portions 3 located outside the distal end are provided.
The thickness of the blades is high because the thicknesses of the first and second corners are larger than the third and fourth corner portions 33 and. Moreover, since the first and second corner portions 31 and 32 in the diagonal direction of the chip 30 have the same height, the upper surface 3 is brought into contact with a planar jig when the lower surface 2 is polished during chip production. If so, the flatness of the lower surface 2 can be easily obtained, and the polishing accuracy is high. Moreover, when the indexable insert 30 is mounted on the end mill 40, the first and second corners 31A, 30B of the main and sub-tips 30A, 30B that bite into the work material at the start of cutting have large wall thicknesses. High chipping resistance of the blade.
In addition, the second cutting edge 9 and the first cutting edge 8 forming the outer peripheral edge are the first and second corner portions 31 having the acute angle on the distal end side with respect to the fourth and third corner portions 34 and 33 having the obtuse angle on the proximal end side. , 32 are larger in wall thickness, the axial rake angle is larger than that of the first embodiment, and the sharpness of outer peripheral cutting is improved.

In the above-described second embodiment, the inclined surfaces 35a and 35b are formed in a flat shape. Alternatively, the inclined surfaces 35a and 35b may be formed in a convex or concave shape. And the cutting edge angle of the cutting blade is increased, so that the cutting edge strength is also improved. In addition, if it is formed into a concave curved surface, the rake angle of the cutting blade is increased, and the sharpness is further improved. Alternatively, the rake angle may be a twisted surface. In this case, the rake angle of the outer peripheral blades (the first blade 8 and the second cutting blade 9) gradually changes from the distal end toward the proximal end. Further, a breaker groove may be provided on the upper surface 3. In the first and second embodiments, each of the throw-away chips 1A, 1B, 30A, 3
6B, the long blade 6 and the short blade 7 are mounted on the radius line of the tool body 21 passing through the axis O and the radial rake angle is set to 0 °. Instead, the long blades 6 and the short blades 7 may be arranged at positions where the center is raised or lowered. In this case, an uncut portion (core residue) occurs at a portion sandwiched between the two chips during cutting, but if the work material of the core residue is small, it can be peeled off with an end mill. If it is fed sideways, it is also possible to scrape off the remaining part.

Alternatively, as shown in FIG.
The long blade 6 (short blade 7) of (30B ') is arranged above the center, and has a substantially circular arc shape toward the lower surface 2 at the end of the third corner portion 33 located on the axis O side of the long blade 6. The curved R-shaped cutting edge may be formed so as to intersect with the axis O. Alternatively, as shown in FIG. 14 and FIG.
The long blades 6 and short blades 7 of A 'and 1B' are arranged above the center, and the long blades 6 have the third corner 12 inside the upper surface 3 intersecting with the axis O facing the tip of the corner. The inner region 6a of the long blade 6, which forms a tip-side ridge line of the inclined portion 42, gradually inclines toward the lower surface 2 side from the centered position, and gradually becomes closer to the axis O. Will intersect. When the configuration of FIG. 13 and the configurations of FIGS. 14 and 15 are adopted as described above, when the tool body 21 of the end mills 20 and 40 is reduced in diameter, it is inevitable to secure the rigidity of the tip mounting seat portion. 1A ', 1B', 3
It is necessary to dispose 0A 'and 30B' above the center, and even in this case, cutting can be performed near the rotation axis O. In this case, the portion near the axis O of the long blade 6 has a small cutting amount.
There is no loss.

The corner angles α of the acute first and second corner portions 10, 11, 31, 32 in the first and second embodiments are the same, but they need not always be the same. In each of the indexable inserts 1 and 30 in the first and second embodiments described above, the long blade 6, short blade 7, first blade 8, and second cutting blade 9 are linear. May be a convex curve or a concave curve. Further, in each of the above-described embodiments, two indexable inserts 1 and 30 are mounted on the tool body 21 of the end mills 20 and 40. However, the present invention is not limited to this. 30 may be attached and cutting may be performed with each cutting blade. Further, the indexable insert according to the present invention is not limited to the end mills 20 and 40, and can be mounted on various cutting tools such as other types of rolling tools and turning tools.

[0022]

As described above, the indexable insert according to the present invention has a substantially rectangular plate shape, and two opposing edges of the four sides of one surface are non-parallel. Since the corners of the two corners in the diagonal direction are acute with each other, when the indexable insert is mounted on the tool body of the cutting tool, one of the inserts is one of the non-parallel ones. If the cutting edge is projected from the tool body tip as a front blade, for example, and the other tip is mounted with the other non-parallel other cutting blade projected from the tool body tip as a front blade, for example, one type of chip is used. A plurality of types of cutting blades can be arranged and each can be used as a front blade, etc. In this case, since the interval between the plurality of indexable inserts does not narrow in the axial direction, the center of the tip end of the tool body sandwiched between both inserts Thickness Tool rigidity is higher can be coercive.

Further, the distance between the two corners in one diagonal direction and the other surface facing one surface is larger than that in the other two corners in the diagonal direction. The two corners in the angular direction have a greater distance from the other surface than the two corners in the other diagonal direction, and the two corners in one diagonal direction have two corners in the other diagonal direction. Is formed on the inclined surface so that the distance from the other surface gradually decreases toward the diagonal line connecting the two, so that the cutting edge strength of two corner portions in one diagonal direction is large, and these corner portions are By being attached to the tip of the tool body,
The fracture resistance of these corners at the time of biting and the like is improved, and the rake angle of each cutting edge connected to the corners is increased, so that the sharpness is improved. Further, since the inclined surface is formed as a convex curved surface, the thickness of the chip is increased and the strength is improved.

In the indexable cutting tool according to the present invention, a plurality of indexable inserts may be the same indexable insert according to any one of claims 1 to 4, and one indexable insert is one non-parallel indexable insert. Since the blade is arranged so as to protrude from the tool body and the other indexable insert is arranged so as to protrude from the other non-parallel cutting blade tool body, a plurality of the same non-parallel cutting edges of the same chip are, for example, The blades can be attached to the tool main body as a blade, respectively, and the cost is low. In addition, the cutting edge bites at the sharp corners on the tip side, so that the corners can be prevented from being lost.

[Brief description of the drawings]

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

FIG. 2 is a side view of the throw-away tip shown in FIG. 1 as viewed from a direction A.

FIG. 3 is a side view of the throw-away tip shown in FIG. 1 as viewed from a direction B.

FIG. 4 is a side view of a main part of an end mill to which the throw-away tip shown in FIG. 1 is mounted.

FIG. 5 is a side view of the end mill shown in FIG. 4 as viewed from a direction of an outer peripheral blade.

FIG. 6 is a front view of the end mill shown in FIG.

FIG. 7 is a plan view of a throw-away tip according to a second embodiment of the present invention.

FIG. 8 is a side view of the throw-away tip shown in FIG. 7, as viewed from the direction A.

FIG. 9 is a side view of the throw-away tip shown in FIG. 7, as viewed from the direction B.

FIG. 10 is a side view of a main part of an end mill to which the throw away tip shown in FIG. 7 is attached.

11 is a side view of the end mill shown in FIG. 7 as viewed from a direction of an outer peripheral blade.

FIG. 12 is a front view of the end mill shown in FIG. 7;

FIG. 13 is a front view showing a modified example of a state in which the indexable tip according to the second embodiment is mounted on an end mill.

FIG. 14 is a main part front view showing a modified example of a state in which the indexable tip according to the first embodiment is mounted on an end mill.

FIG. 15 is a front view of the end mill shown in FIG.

[Explanation of symbols]

 1, 30 indexable insert 1A, 1A ', 30A, 30A' main insert 1B, 1B ', 30B, 30B' auxiliary insert 6 long blade 7 short blade 10 first corner portion 11 second corner portion 12 third corner portion 13 Fourth corner 20, 40 End mill 21 Tool body 26 Center of tip L Diagonal line

Claims (5)

[Claims] 1. A substantially rectangular plate-like shape, wherein two opposing edges of four edges of one surface are non-parallel cutting edges, and two corner portions in one diagonal direction. The corners of are throw-away tips that are sharp to each other. 2. The indexable insert according to claim 1, wherein the two corner angles in the one diagonal direction are equal to each other. 3. The two corners in one diagonal direction have a greater distance from the other surface facing the one surface than the two corners in the other diagonal direction, and the one surface is From the two corner portions in one diagonal direction to a diagonal line connecting the two corner portions in the other diagonal direction,
3. The indexable insert according to claim 1, wherein the insert is formed on an inclined surface such that a distance from the other surface is gradually reduced. 4. The indexable insert according to claim 3, wherein said inclined surface is a convex curved surface. 5. A throw-away type cutting tool comprising a plurality of throw-away tips, each of which has a cutting edge protruding from a tip end of the tool main body, the plurality of throw-away tips being attached to the tip of the tool body. The same throw-away insert according to any one of claims 1 to 4, wherein one of the throw-away inserts has one non-parallel cutting edge protruding from the tool body, and the other of the throw-away inserts has the other non-parallel non-parallel. A throw-away type cutting tool, wherein a cutting edge is arranged to protrude from a tool body.