JP2010023144A - Chip for lathe turning - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tip enabling coarse processing and finish processing by a single tip, being capable of effectively using all corners, and being excellent in economical efficiency. <P>SOLUTION: A tip for lathe turning has a plurality of blade edges, at least two blade edges of the blade edges has the same edge angles, the edge angles are not more than 90°, and the blade edges having the same edge angles have two kinds of nose radiuses. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cutting tool used for turning.

  In cutting, it is known that selection of the nose radius of a cutting tool is very important (Patent Document 1, Patent Document 2, etc.). For example, in Patent Document 1, the size of the corner radius (nose radius) influences the cutting edge life, dimensional accuracy, and the like, and an optimum one must be selected according to the type of workpiece and the machining conditions. For example, there is a problem that a great loss such as a defective product may occur.

As a cutting tool that can cope with the type of work material and multiple machining conditions, a cutting tool is proposed in which the nose radius of the sharp corner portion of the chip is Re and the nose radius of the obtuse corner portion is Rd as shown in FIG. (For example, Patent Document 3). The cutting tool disclosed in Patent Document 3 enhances the obtuse corner portion more than the acute corner portion and improves the cutting edge life in turning roughing (turning roughing), thereby increasing the frequency of use of the obtuse corner portion and making it economical. The purpose is to improve.
JP-A-11-235607 Japanese Patent Laid-Open No. 2001-322022 JP 2007-7736 A

  In recent years, the performance of cutting tools such as chips has been improved year by year, and the life of individual chips has become longer. Under such circumstances, the cutting tool as proposed in Patent Document 3 can cope with a plurality of cutting conditions and the like. For example, when an acute corner portion has reached the end of its life, cutting corresponding to the corner portion is performed. In order to do this, it was necessary to replace the chip with the obtuse corner portion unused. In this case, the chip | tip which has an unused obtuse angle | corner corner part had to be stored as an inventory. In addition, since the life in the rough turning is taken into consideration as described above, different types of cutting such as cutting and finishing are not possible.

  The present invention has been made in view of the above-described problems, and provides a chip having excellent economical efficiency that enables roughing and finishing with one chip and can effectively use all corners. For the purpose.

  The turning tip of the present invention has a plurality of cutting edges, and at least two of the cutting edges have the same cutting edge angle, the cutting edge angle is 90 degrees or less, and has the same cutting edge angle. The cutting edge has at least two types of nose radii.

  The nose radius of the cutting edge at each corresponding corner of the facing rake face of the turning tip is preferably the same, and it is preferable that the corner of each rake face has a different nose radius.

  The turning tip is a negative tip, and the nose radius of the cutting edge in the same rake face of the negative tip is preferably the same.

Moreover, it is preferable that the side surface of the turning tip is unpolished.
In the present invention, the maximum nose radius is preferably an integral multiple of the minimum nose radius among the at least two types of nose radii, and the maximum nose radius is more than twice the minimum nose radius. It is preferable.

  According to the present invention, since a single tip is provided with cutting edges having the same shape (cutting edge angle) but different only nose radii, it is possible to perform roughing and finishing of the work material with the same tip. . As a result, the processing efficiency can be improved, and all corners of the chip can be used effectively.

<Turning insert>
The turning tip of the present invention can be effectively used as a cutting edge exchange type cutting tip for turning, and can be configured to include, for example, a base material and a coating formed on the base material. When a coating is included, the target work material can be varied by adjusting the composition of the coating, and for example, it is useful as a cutting edge exchangeable cutting tip for turning such as steel and cast iron. be able to.

  As such a tip, a so-called positive tip in which the cutting surface is one side and the rake surface is a positive angle with respect to the reference surface, and the cutting surface is both surfaces, and the rake surface is negative with respect to the reference surface. Any of so-called negative chips that are corners may be used. In addition, in the positive tip, there are many types of nose radii and the lifetime is generally long, but such a positive tip has conventionally been provided with two cutting edges having a specific nose radius A and having the same shape. Since it is commercially available as approximately 10 sets, for example, a set having a cutting edge having a nose radius that is not frequently used has to be stored for a long period of time, and is not necessarily cost-effective. On the other hand, in the case of the present invention, since only one of the two cutting edges has a specific nose radius A, the life of the chip is reduced with respect to the specific nose radius A. Necessary. Then, all chips in the set can be used, and problems such as stock keeping are solved. As described above, according to the turning tip of the present invention, since a single tip has a plurality of nose radii, efficient cutting is possible, and the effect of the present invention at a cost is particularly significant in a negative tip.

<Base material>
As the base material for the turning tip of the present invention, a conventionally known material known as the base material for such a tip can be used without any particular limitation. Specifically, cemented carbide (for example, WC-based cemented carbide, WC, including Co, or further including carbonitride such as Ti, Ta, Nb, etc.), cermet (TiC, TiN , TiCN, etc.), high speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, and mixtures thereof), cubic boron nitride sintered body, diamond A sintered body etc. can be illustrated. When a cemented carbide is used as such a base material, the effect of the present invention is exhibited even if such a cemented carbide contains an abnormal phase called free carbon or η phase in the structure. In addition, these base materials may have a modified surface. For example, in the case of cemented carbide, a de-β layer may be formed on the surface, or in the case of cermet, a surface hardened layer may be formed. Even if the surface is modified in this way, the present invention The effect of is shown.

<Coating>
When a film is formed on the substrate of the turning tip of the present invention, the composition of such a film is not particularly limited, and a conventionally known film composed of one layer or two or more layers can be applied. The coating is not limited to the one that covers the entire surface of the substrate, and includes a mode in which the coating is partially formed.

<Cutting edge>
The turning tip of the present invention has a plurality of cutting edges, and at least two of the cutting edges have the same cutting edge angle (vertical angle). By making at least two cutting edges the same cutting edge angle in a plurality of cutting edges, it is possible to perform roughing and finishing with a single chip, so it is possible to dispense with chip replacement for each processing, Efficiency can be increased. In the present invention, the cutting edge refers to a portion having a cutting edge in the corner of the chip, and the cutting edge angle is defined as a chip shape standardized by JIS B 4120 (1998). It is an angle formed by two cutting edge ridge lines at the cutting edge. In the present invention, the same includes substantially the same and does not necessarily mean a complete match. Such substantially the same thing includes an error range, and this error range in the edge angle is ± 30 '.

  The cutting edge angle of the cutting tip of the present invention is 90 degrees or less. As the shape of the turning tip provided with the cutting edge having a cutting edge angle of 90 degrees or less, S type (square, cutting edge angle 90 degrees) standardized by JIS B 4120 (1998) or ISO 1832, T type (regular triangle, cutting edge) 60 degrees), C type (diamond, edge angle 80 degrees), D type (diamond, edge angle 55 degrees), V type (diamond, edge angle 35 degrees), etc., but are not limited to these. As long as the edge angle is 90 degrees or less in a desired shape, any shape may be used.

  In the present invention, the cutting edge having the same cutting edge angle has at least two types of nose radii. As described above, since there are two or more kinds of nose radii of the cutting edge having the same cutting edge angle, it is possible to perform roughing and finishing with a single chip. In addition, when roughing and finishing are performed with a single chip in this way, all corners of the chip are used, and a large number of chips that use some corners as in the past are in stock. There is less to do. The nose radius refers to the reference inscribed circle diameter of each cutting edge standardized according to JIS B 4120 (1998). In the following, the case where the nose radius is a (mm) may be expressed as aR.

  In the present invention, since the nose radii of the same cutting edge angle are different, in order to facilitate the identification, for example, in the negative tip, the nose radius is changed between the upper surface and the lower surface, or each of the corresponding on the upper and lower rake surfaces facing each other. It is effective to keep the cutting edge of the corner to the same nose radius.

  Specifically, the nose radius of the cutting edge is preferably set to the same nose radius at each corresponding corner of the rake face facing the top and bottom of the turning tip. When the nose radii of the corresponding corners of the opposing upper and lower rake faces are the same, it is possible to identify the chips while they are in the case, and in particular, the side faces remain unpolished. In some cases, this discrimination is particularly effective.

  Moreover, when making it the same nose radius in each corresponding corner of the rake face which opposes vertically as mentioned above, it is preferable that the nose radius for every corner of each rake face differs. By adopting such a form, it is possible to cope with a wider range of processing.

  In the present invention, when using a negative tip, the nose radius of the cutting edge in the same rake face of the negative tip can be the same. In this case, for example, roughing is performed on one of the rake faces, and then the rake face is changed and finishing is performed, so that the possibility of erroneous selection of the cutting edge is significantly reduced.

<Nose radius>
In the present invention, the size of the nose radius is not particularly limited, but the maximum nose radius is preferably an integral multiple of the minimum nose radius, and the maximum nose radius is at least twice the minimum nose radius. It is preferable that By designing to such a nose radius, it is possible to cope with a wider range of machining with a single chip, and the tool cost can be reduced. Examples of the wide processing include a case where 1.2R or 0.8R is used for roughing and 1.2R or 0.4R is used for finishing. In addition, various parts can be processed, and the optimum nose radius for the processed portion can be selected with a single chip, so that the processing efficiency can be improved.

<Polishing>
As long as the turning tip of the present invention has the shape as described above, it is effective even if at least either the side surface (flank) or the upper and lower rake surfaces are polished. In this case, the turning tip to be polished may consist of only the base material, or a film may be formed on the base material. Note that the effect of the present invention can be obtained even if at least one of the side surface and the upper and lower rake face is subjected to surface treatment instead of polishing. In the case of a chip whose side surface is polished, it is industrially advantageous that the upper and lower cutting edges of the same corner have the same nose radius.

<Marking>
In order to impart discriminability to the cutting edge of the turning tip, it is also effective to make a marking for identification at the corner of each cutting edge of the rake face. Such a marking method is not particularly limited. For example, the marking may be performed at the same time as the press in the manufacturing process of the turning tip, or the marking may be performed by a laser mark or a ball end mill after the processing. In addition, any shape can be adopted as the shape of the marking as long as it is discriminating in correspondence with the nose radius of each cutting edge.

<Chip breaker>
The present invention is effective whether or not the turning chip has a chip breaker, and is effective even if the chip breaker is different for each corner. In addition, even if the cutting edge processing is different for each corner, the effect of the shape of the present invention is exhibited.

  Hereinafter, the present invention will be described in more detail. In the following description of the embodiments, the description is made with reference to the drawings. In the drawings of the present application, the same reference numerals denote the same or corresponding parts.

(Embodiment 1-1)
In Embodiment 1-1, a negative tip (having four cutting edges with a cutting edge angle of 80 degrees) coated with a coating material AC2000 (manufactured by Sumiden Hard Metal Co., Ltd.) on a cemented carbide by a CVD method ( The shape of the cutting edge in the case of using (CNMA 1204 shape) will be described. The negative tip having such a shape is usually shown in a schematic diagram of a typical turning tip of FIG. 1, for example, and as shown in FIG. 1, cutting edges A to D (D in the drawing is a cutting edge). Four cutting edges) (showing cutting edges on the facing rake face of blade B).

  FIG. 2 is a diagram showing an outline of the cutting surface shape of the turning tip in the embodiment 1-1, and FIG. 2A is a schematic top view of the turning tip in the embodiment 1-1. FIG. 2B is a schematic bottom view of the turning tip in the embodiment 1-1. In Embodiment 1-1, the two nose radii on the upper surface of the turning tip are 0.4 mm, and the two nose radii on the lower surface are 1.2 mm. Then, in order to easily confirm the nose radius by visual observation, as the inscription corresponding to the nose radius, when the nose radius is 0.4 mm, an inscription “04” is given (FIG. 2A), and the nose radius Is marked with “12” (FIG. 2B). The side surfaces were not polished.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become.

(Embodiment 1-2)
In Embodiment 1-2, the turning tip has the same shape as Embodiment 1-1, except that the nose radii at the same corner of the opposing rake face are the same.

  Specifically, as shown in FIGS. 3 (a) and 3 (b), the two nose radii on the upper surface of the turning tip are 0.4 mm and 1.2 mm, respectively, and the two nose radii on the lower surface are Similar to the nose radius of the upper surface of each corresponding corner, 0.4 mm and 1.2 mm, respectively. Then, in order to ensure the distinguishability of these nose radii, “04” is marked when the nose radius is 0.4 mm as in the embodiment 1-1, and when the nose radius is 1.2 mm. Mark “12”.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become. Further, by providing a cutting edge having the same cutting edge angle and nose radius at the same corner, a single chip can be used for a wider range of processing, and the tool cost can be reduced.

(Embodiment 1-3)
In Embodiment 1-3, the turning tip has the same shape as Embodiment 1-1 except that the nose radii of the four cutting edges are different from each other.

  Specifically, as shown in FIGS. 4A and 4B, the two nose radii on the upper surface of the turning insert are 0.4 mm and 0.8 mm, respectively, and the two nose radii on the lower surface are respectively set. 1.2 mm and 1.6 mm. Then, in order to ensure the distinguishability of these nose radii, “04” is marked when the nose radius is 0.4 mm as in the embodiment 1-1, and when the nose radius is 0.8 mm. “08” is marked, “12” is marked when the nose radius is 1.2 mm, and “16” is marked when the nose radius is 1.6 mm.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become. In addition, by providing cutting edges having different nose radii for all cutting edges, it is possible to deal with a wide range of processing with a single chip, such as roughing and finishing, and processing that requires a specific nose radius.

(Embodiment 2-1)
Embodiment 2-1 uses a round mark as a mark to improve the discriminating ability of the nose radius. When the nose radius is 0.4 mm, one round mark is used (see FIG. )), The same turning tip as in Embodiment 1-1, except that when the nose radius is 1.2 mm, three round marks (FIG. 5B) are added.

  By marking the mark corresponding to the nose radius in this way, it is possible to eliminate the space and complexity for marking the numerical value and maintain the discriminability.

(Embodiment 2-2)
In the embodiment 2-2, a round mark is used as a mark to improve the discriminating ability of the nose radius. As shown in FIGS. 6 (a) and 6 (b), the nose radius is 0. The turning tip is the same as that of Embodiment 1-2, except that one round mark is provided for 4 mm, and three round marks are provided when the nose radius is 1.2 mm.

  By marking the mark corresponding to the nose radius in this way, it is possible to eliminate the space and complexity for marking the numerical value and maintain the discriminability.

(Embodiment 2-3)
In Embodiment 2-3, a round mark is used as an inscription to improve the discriminating ability of the nose radius. As shown in FIGS. 7 (a) and 7 (b), the nose radius is 0.00. One round stamp for 4 mm, two round stamps for nose radius 0.8 mm, three round stamps for nose radius 1.2 mm, nose radius 1 The turning tip is the same as that of Embodiment 1-3, except that four round marks are applied in the case of 6 mm.

  By marking the mark corresponding to the nose radius in this way, it is possible to eliminate the space and complexity for marking the numerical value and maintain the discriminability.

(Embodiment 3)
In the third embodiment, the shape of the cutting edge when using a cermet T1200A and a regular triangular negative tip (TNGA 1604 shape) having six cutting edges (three upper faces and three lower faces) having a cutting edge angle of 60 degrees will be described. To do.

  FIG. 8A is a diagram schematically showing the shape of the cutting surface of the turning tip in the third embodiment. In the third embodiment, the three nose radii on the upper surface of the turning tip are 0.05 mm, 0.10 mm, and 0.15 mm, respectively, and the nose radii at the same corner are the upper and lower surfaces for the three nose radii on the lower surface. It processed so that it might become the same. Then, in order to easily confirm the nose radius by visual observation, as the inscription corresponding to the nose radius, when the nose radius is 0.05 mm, “005” is added, and when the nose radius is 0.10 mm. “010” is marked, and when the nose radius is 0.15 mm, “015” is marked (FIG. 8A). The side surface was polished with a diamond grindstone.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become. In addition, when the nose radius is small as in the third embodiment, it can be seen that it is effective to impart discrimination by marking.

(Embodiment 4)
In the fourth embodiment, a circle is used as an inscription to improve the discriminating ability of the nose radius. As shown in FIG. 8 (b), an inscription is provided when the nose radius is 0.05 mm. The same turning as in the third embodiment, except that two round marks are added when the nose radius is 0.10 mm, and three round marks are marked when the nose radius is 0.15 mm. Chip.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become.

(Embodiment 5)
In the fifth embodiment, a diamond-shaped negative chip (VNGA 1604 shape) provided with PVD coating material ACZ310 (manufactured by Sumiden Hard Metal Co., Ltd.) and four cutting edges (two upper faces and two lower faces) having a cutting edge angle of 35 degrees. ) Will be described.

  FIG. 9 is a diagram schematically showing the shape of the cutting surface of the turning tip in the fifth embodiment. In the fifth embodiment, the two nose radii on the upper surface of the turning tip are 0.1 mm and 0.2 mm, respectively, and the two nose radii on the lower surface have the same nose radius at the same corner on the upper and lower surfaces. Was processed as follows. Then, in order to easily confirm the nose radius by visual inspection, the inscription corresponding to the nose radius is marked with “01” when the nose radius is 0.1 mm, and when the nose radius is 0.2 mm. Mark “02”. The side surface was polished with a diamond grindstone.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become. In addition, when the nose radius is small as in the fifth embodiment, it can be seen that it is effective to impart discrimination by marking.

(Embodiment 6)
In the sixth embodiment, a triangular mark is used as a mark to improve the discriminating ability of the nose radius. As shown in FIG. 10, one triangular mark is used when the nose radius is 0.1 mm. The turning tip is the same as that of the fifth embodiment except that two triangular marks are added when the nose radius is 0.2 mm.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become.

(Embodiment 7)
In the seventh embodiment, the shape of the cutting edge when using a cemented carbide H1 (JIS standard) and a diamond-shaped positive tip (DCGT11T3 shape) having two cutting edges (two upper faces) having a cutting edge angle of 55 degrees is used. explain.

  FIG. 11A is a diagram schematically illustrating the shape of the cutting surface of the turning tip according to the seventh embodiment. In Embodiment 7, the two nose radii of the turning tip were set to 0.05 mm and 0.1 mm, respectively. Then, in order to easily confirm the nose radius by visual inspection, as the inscription corresponding to the nose radius, when the nose radius is 0.05 mm, “005” is added, and when the nose radius is 0.1 mm. Mark “01”. The side surfaces were polished with a diamond grindstone.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become.

(Embodiment 8)
In the eighth embodiment, a bar mark is used as an inscription to improve the discriminating ability of the nose radius. As shown in FIG. 11B, the bar mark is 1 when the nose radius is 0.05 mm. The turning tip is the same as that of the seventh embodiment except that two bar marks are added when the nose radius is 0.1 mm.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become.

(Embodiment 9)
In the ninth embodiment, a silicon negative ceramic NS260 (manufactured by SUMITOMO ELECTRIC HARDMETAL) is provided with a square negative chip (SNMA 1204 shape) having eight cutting edges (four upper surfaces and four lower surfaces) having a cutting edge angle of 90 degrees. The shape of the cutting edge when used will be described.

  FIG. 12A is a diagram schematically illustrating the shape of the cutting surface of the turning tip according to the ninth embodiment. In Embodiment 9, the nose radii of the four cutting edges on the upper surface of the turning tip were 0.4 mm, 0.8 mm, 0.8 mm, and 1.2 mm, respectively. The nose radii of the four cutting edges on the lower surface of the turning tip were processed so that the nose radii at the same corner were the same on the upper and lower surfaces. Then, in order to easily confirm the nose radius by visual inspection, the inscription corresponding to the nose radius is marked with “04” when the nose radius is 0.4 mm, and when the nose radius is 0.8 mm. Mark “08” and mark “12” when the nose radius is 1.2 mm. In the ninth embodiment, the marking is performed using a ball end mill. The side surfaces were not polished.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become.

(Embodiment 10)
In the tenth embodiment, in order to improve the discriminating ability of the nose radius, a round mark is used as the marking. As shown in FIG. 12B, the round mark is used when the nose radius is 0.4 mm. For turning the same as in the ninth embodiment except that one circle is engraved, two circles are attached when the nose radius is 0.8 mm, and three circles are engraved when the nose radius is 1.2 mm. Chip.

  In this way, at least two cutting edges have the same cutting edge angle, and by making their nose radii different, it is possible to perform rough machining and finishing with the same shape with a single turning tip. Become.

  Each of the turning tips having the shapes in the above embodiments 1-1 to 10 can be made to handle a wide range of cutting conditions with a single tip as compared with the conventional turning tip as shown in FIG. Is possible.

  As described above, the embodiments of the present invention have been described, but it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic diagram of a typical turning tip. (A) is the upper surface schematic of the turning tip in Embodiment 1-1, (b) is the lower surface schematic of the turning tip in Embodiment 1-1. (A) is the upper surface schematic of the turning tip in Embodiment 1-2, (b) is the lower surface schematic of the turning tip in Embodiment 1-2. (A) is the upper surface schematic of the turning tip in Embodiment 1-3, (b) is the lower surface schematic of the turning tip in Embodiment 1-3. (A) is the upper surface schematic of the turning tip in Embodiment 2-1, (b) is the lower surface schematic of the turning tip in Embodiment 2-1. (A) is the upper surface schematic of the turning tip in Embodiment 2-2, (b) is the lower surface schematic of the turning tip in Embodiment 2-2. (A) is the upper surface schematic diagram of the turning tip in Embodiment 2-3, (b) is the lower surface schematic diagram of the turning tip in Embodiment 2-3. (A) is the schematic which shows the cutting surface of the chip | tip for turning in Embodiment 3, (b) is the schematic which shows the cutting surface of the chip | tip for turning in Embodiment 4. FIG. FIG. 10 is a schematic diagram showing first and second cutting surfaces of a turning tip in a fifth embodiment. FIG. 10 is a schematic diagram showing first and second cutting surfaces of a turning tip in a sixth embodiment. (A) is the schematic which shows the cutting surface of the tip for turning in Embodiment 7, (b) is the schematic which shows the cutting surface of the tip for turning in Embodiment 8. FIG. (A) is the schematic which shows the cutting surface of the turning tip in Embodiment 9, (b) is the schematic which shows the cutting surface of the turning tip in Embodiment 10. FIG. It is a schematic diagram which shows the shape and nose radius of the conventional cutting tool.

Claims (7)

A turning tip having a plurality of cutting edges,
At least two of the cutting edges have the same cutting edge angle, and the cutting edge angle is 90 degrees or less,
The cutting edge having the same cutting edge angle is a turning tip having at least two types of nose radii.   2. The turning tip according to claim 1, wherein the nose radius of the cutting edge at each corresponding corner of the facing rake face of the turning tip is the same.   The turning tip according to claim 2, wherein the nose radius of the cutting edge is different for each corner on each rake face.   The turning tip according to claim 1, wherein the turning tip is a negative tip, and the nose radius of the cutting edge in the same rake face of the negative tip is the same.   The turning tip according to any one of claims 1 to 4, wherein the turning tip has a non-polished side surface.   The turning tip according to any one of claims 1 to 5, wherein the largest nose radius among the at least two kinds of nose radii is an integral multiple of the smallest nose radius.   The turning tip according to claim 6, wherein the maximum nose radius is not less than twice the minimum nose radius.

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