JP5028757B2 - Throwaway tip - Google Patents

Description

The present invention relates to a throw-away tip used for turning or the like.

The approximately diamond-shaped flat negative chip for turning defined in the ISO standard is formed with four acute corner portions and obtuse corner portions on the upper surface and the lower surface of the approximately diamond shape. In the conventional throw-away tip, the same cutting edge shape is applied to the acute corner portion and the obtuse corner portion.

A plan view of this type of conventional throw-away tip is illustrated in FIG. As shown in the figure, this throw-away tip has a rake face 2 formed on the polygonal surface of the polygonal plate-like chip body 1, and a ridge portion of the polygonal face on which the rake face 2 is formed, A pair of cutting edges 4 extending from the polygonal corner portion C are formed, and the rake face 2 is inclined so as to be gradually depressed as the distance from the cutting edge 4 increases. A land 7 is formed along the cutting edge 4, and the land 7 is inclined so as to be gradually depressed as it is separated from the cutting edge 4 at an inclination angle α smaller than the inclination angle β of the rake face 2. The inclination angle between the rake face 2 and the land 7 is reduced in the direction away from the projecting end of the corner portion C along the cutting edge 4. On the rake face 2, there is a gap between the rake face 2 and the cutting edge 4. The corner portion C A main dot 8 having a convex spherical shape is formed on the end side, and at least a pair of sub-dots 9 having a convex spherical shape are also formed at positions spaced apart from the main dot 8 along the pair of cutting edges 4, respectively. (See, for example, Patent Document 1).

A plan view of another conventional throw-away tip is illustrated in FIG. This throw-away insert has a chip breaker suitable for turning at the 80 ° corner of the CNMG type insert, and a breaker mainly aimed at reducing cutting resistance suitable for milling at the 100 ° corner. It is provided. Specifically, as shown in the figure, a flat land 2 is provided along the cutting edge 1, and the breaker groove 3 that gradually falls from the inner end portion of the land and reaches the hem portion of the central land portion 4 is completely formed. It is provided over the circumference. Further, the breaker projection 5 is the same as that illustrated in the figure at the 80 ° corner a portion, while the breaker groove 3 is further dug down to the rake angle of the rake face 6 at the 100 ° corner b portion. At the same time, a breaker recess 7 is provided which sharpens the cutting edge. The breaker concave portion 7 is provided in a range extending from the cutting edge portion to the central land portion 4 by being biased toward one of the 80 ° corners. (For example, refer to Patent Document 2).
JP 2003-220503 A Noto 3009833

As described above, in the throw-away insert for turning corresponding to the CNMG type and the CNGG type specified in the ISO standard, importance is attached to the high versatility applicable to applications such as copying and corner R machining. An acute angle corner of 80 ° is generally used. Therefore, the radius of curvature of the corner cutting edge of the acute corner portion may be set in the range of 0 mm to 3.2 mm in consideration of the restriction of the shape surface in the above-mentioned application or the cutting performance of cutting resistance and chip disposal. There were many. Especially in finishing applications with small depth of cut, and in turning applications of iron-based metals such as carbon steel and alloy steel that produce continuous chips and have a higher cutting resistance than aluminum alloys and gray cast iron. In consideration of the influence on the property, the radius of curvature is often set in the range of 0.2 mm to 1.6 mm. On the other hand, the radius of curvature of the corner cutting edge of the obtuse corner portion of 100 ° is generally set equal to that of the corner cutting edge of the acute angle corner portion, but cannot be used for the same application as the acute angle corner portion due to shape restrictions. In many cases, it was not generally used. In addition, the shape of the lands provided at the corner and cutting edge, the rake angle of the rake face, and the position and shape of the dots on the rake face are set with emphasis on the cutting performance of the sharp corner part used mainly. It was made. On the other hand, in the obtuse corner portion, since the frequency of use is low as described above, the setting is almost the same as that of the acute corner portion.

By the way, in a throw-away tip having an obtuse angle corner portion represented by conventional CNMG type and CNGG type, the obtuse angle corner portion has a simple outer periphery and end face turning rough without cutting edge shape restrictions during cutting. Suitable for processing applications. However, as described above, since the cutting edge of the obtuse corner portion is substantially the same as the acute corner portion, in the turning roughing process, the chipping resistance, cutting resistance, chip treatment, etc. It could not be said that the cutting performance was satisfactory. In particular, in a throw-away tip used for turning finishing, the obtuse corner portion may be damaged due to premature chipping or chip clogging and cannot be used. In a throw-away tip used for turning rough machining, the application of a relatively obtuse corner portion is allowed, but the cutting performance is not improved compared to an acute angle corner portion, but only comparable. On the other hand, in the throw-away tip shown in FIG. 11, the obtuse corner portion is designed to have a cutting edge shape suitable for milling, which is different from the acute corner portion, but when used for turning roughing, Since the cutting edge strength is insufficient, there is a possibility that the life of the cutting edge may be remarkably shortened due to chipping or chipping of the cutting edge.

The present invention has been made in view of the above problems, and its purpose is to strengthen the obtuse corner portion more than the acute corner portion and improve the cutting edge life in turning rough machining, thereby reducing the frequency of use of the obtuse corner portion. The aim is to provide a throw-away tip that is highly economical and improved.

In order to solve the above-mentioned problem, the first invention is a substantially polygonal flat plate shape, at least one of the opposing polygonal surfaces is a rake surface, and a corner portion having an arc shape at a corner portion of the polygonal surface. In the throw-away tip in which a cutting edge and a pair of linear main cutting edges extending from the corner cutting edge are formed, and the outer peripheral surface connected to the corner cutting edge and the main cutting edge is a flank face, At least one corner portion of the rake face is an obtuse corner portion, and the radius of curvature Rd of the corner cutting edge of the obtuse corner portion is the curvature of the corner cutting edge of the acute corner portion formed in the corner portion excluding the obtuse corner portion. The throw-away tip is characterized by being larger than the radius Re.

In addition, the second invention has a substantially polygonal flat plate shape, and an arcuate corner cutting edge at a corner portion of the opposing polygonal surface, and a pair of linear cuttings extending from the corner cutting edge, respectively. A throw-away tip in which a breaker groove having a land is formed inside the corner cutting edge and the main cutting edge, and an outer peripheral surface connected to the corner cutting edge and the main cutting edge is a flank surface And at least one corner portion of the rake face is an obtuse corner portion, and a land width Wd of the land provided in the obtuse corner portion is provided in an acute corner portion formed in a corner portion excluding the obtuse corner portion. The throw-away tip is characterized by being larger than the land width We of the land.

In the first and second inventions described above, a right-angled corner portion that forms a right angle is included in the obtuse angle corner portion.

According to the first aspect of the invention, the obtuse corner portion is provided with a corner cutting edge having a larger radius of curvature than the acute corner portion, so that the cutting edge strength is increased, and a long life is achieved in the turning roughing of the outer periphery and end face. Therefore, the use frequency of the obtuse corner portion is increased and the economy is improved. In the first invention, the radius of curvature Rd of the corner cutting edge of the obtuse corner portion is preferably in the range of 0.8 to 6.4 mm, particularly preferably in the range of 1.6 to 6.4 mm. If the radius of curvature Rd is less than 0.8 mm, the effect of extending the cutting edge life may not be obtained. If the radius of curvature Rd exceeds 6.4 mm, the contact length between the corner cutting edge and the work material May increase the cutting resistance.

According to the second aspect of the invention, the obtuse corner portion is provided with a wider land than the acute corner portion, so that the strength of the cutting edge is increased and the outer periphery and the end face have a long life in turning roughing. The frequency of use of the obtuse corner portion is increased and the economy is improved. When the curvature radius Rd of the corner cutting edge of the obtuse corner portion is larger than the curvature radius Re of the corner cutting edge of the acute corner portion, the obtuse corner portion has an extremely long life due to further improved cutting edge strength. It becomes.

In the second invention, a rake face having a positive rake angle αd is formed in the breaker groove formed in the obtuse corner portion, and the rake angle αd is in a range of 5 ° to 30 °. preferable. By setting the rake angle α within the above range, the cutting resistance is greatly reduced in the obtuse corner portion, the load on the cutting edge is reduced, and the fracture resistance is improved. Furthermore, the vibration and chatter during cutting are suppressed, the limit area of cutting conditions is increased, and cutting with higher efficiency becomes possible. The reason why the rake angle α is limited to the above range is that the cutting resistance is reduced and the fracture resistance of the cutting edge is taken into consideration. When the rake angle α is less than 5 °, the cutting resistance is not sufficiently reduced. If the rake angle α exceeds 30 °, the edge strength of the obtuse corner portion may be reduced, and the chipping resistance may be deteriorated.

Furthermore, in the second invention, it is preferable that the land width Wd of the land formed in the obtuse corner portion is in a range of 0.2 mm to 0.5 mm. This is to increase the fracture resistance of the obtuse corner portion in rough machining, particularly high feed machining. If the width Wd of the reinforced land is less than 0.2 mm, the effect of increasing the fracture resistance may not be obtained. If the width Wd of the reinforced land exceeds 0.5 mm, the cutting resistance may increase or the chip disposal property may deteriorate.

Furthermore, in the second invention, a breaker wall surface that is oriented toward the corner cutting edge and protrudes upward from the surface of the breaker groove is formed on the bisector of the obtuse corner portion. It is preferable that a horizontal distance Dd between the branch point and the bulge start point of the breaker wall surface is in a range of 0.8 mm to 5.0 mm. In this case, the chip is improved in chip disposal by contacting and curling the breaker wall surface. If the distance Dd is less than 0.8 mm, there is a risk of increasing cutting resistance due to chip clogging during rough machining, and if the distance Dd exceeds 5.0 mm, the effect of chip curling by the breaker wall surface is reduced, and chip disposal is possible. May get worse.

Furthermore, in the first and second inventions described above, at least the corner cutting edge and the main cutting edge of the obtuse corner portion are provided with a round honing made of a single arc in a cross-sectional view orthogonal to the cutting edge. And the radius of curvature Rh of the arc is preferably in the range of 0.05 mm to 0.50 mm. This is for improving the fracture resistance of the obtuse corner portion in the intermittent machining in which a high load is intermittently applied to the cutting edge. If the radius of curvature Rh of the arc is less than 0.05 mm, the effect of improving the fracture resistance may not be obtained, and if it exceeds 0.50 mm, the cost for forming the round honing may increase. There is a possibility that the sharpness is lowered and the cutting resistance is increased.

Alternatively, at least the cutting edge of the obtuse corner portion has a curved shape in a cross-sectional view orthogonal to the cutting edge, and the curved face rake face side width Ls is larger than the flank face side width Ln. Is formed along the cutting edge, the rake face side width Ls of the curved portion is in the range of 0.08 mm to 0.50 mm, and the flank face side width Ln is 0.04 mm to 0. .. preferably in the range of 20 mm. This is to improve the fracture resistance of the obtuse corner portion in the intermittent machining in which a high load is intermittently applied to the cutting edge, as in the case of forming the round honing described above. If the width Ls on the rake face side of the curved honing is less than 0.08 mm or the width Ln on the flank face side is less than 0.04 mm, the effect of increasing the fracture resistance may not be obtained. If the surface side width Ls exceeds 0.50 mm or the flank side width Ln exceeds 0.20 mm, the cost for forming the curved honing may increase, and the sharpness may increase. May decrease and cutting resistance may increase.

Next, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are diagrams for explaining the first embodiment, FIG. 1 is a plan view, and FIG. 2 is a cross section taken along line S1-S1 in FIG.
3 to 6 are diagrams for explaining the second embodiment, FIG. 3 is a perspective view, FIG. 4 is a plan view, FIG. 5 is an enlarged plan view of a corner portion, and FIG. (a), (b) is the S2-S2 line cutting part end view in FIG. 4, respectively, and the S3-S3 line cutting part end view. FIGS. 7A and 7B are diagrams showing the usage state of the first and second embodiments, in which FIG. 7A is a diagram showing a state of roughing turning on the outer periphery, and FIG.

As shown in FIG. 1, the throw-away tip 1 of the first embodiment has a substantially rhombic flat plate shape, the rhombus surfaces are formed symmetrically on the front and back, and the throw-away tip passes through the axis of the rhombus surface. 1 is formed symmetrically with respect to a plane including an axial center extending in the thickness direction of 1 and a bisector of each corner portion 4. Furthermore, the present throw-away tip 1 has each diamond-shaped surface formed of a flat plane as a rake surface 2 selectively, and when viewed from a direction orthogonal to the diamond-shaped surface, each corner portion 4 has a circular shape. An arcuate corner cutting edge 5a and a pair of linear main cutting edges 5b each formed from the outer side of the rhombus surface extending from the corner cutting edge 5a are formed. The corner cutting edge 5a and the main cutting edge The outer peripheral surface which continues to 5b is made into the flank 3, and each rhombus surface is provided with two acute angle corner portions 4A forming 80 ° and obtuse angle corner portions 4B forming 100 °, respectively. These are CNMG-type and CNGG-type throw-away tips according to ISO standards, in which a mounting hole 12 having a circular cross section is formed. In the following description, the corner cutting edge 5a and the main cutting edge 5b formed in each corner portion 4A, 4B are collectively referred to as a cutting edge 5. In the present throw-away tip 1, at least the cutting edge 5 is made of a hard material such as cemented carbide, cermet or ceramic, or a material such as an ultra-high pressure sintered body such as a diamond sintered body or a cubic boron nitride sintered body. Composed.

In the first embodiment, the radius of curvature Re of the arc constituting the corner cutting edge 5a of the acute angle corner portion 4A is 0.8 mm as viewed from the direction orthogonal to the rhombus surface, while the obtuse angle corner portion 4B The radius of curvature Rd of the arc constituting the corner cutting edge 5a is 1.6 mm which is larger than the acute angle portion 4A. This is because the strength of the corner cutting edge 5a of the obtuse corner part 4B is higher than that of the acute corner part 4A, and the cutting edge life in the turning rough machining of the outer periphery and end face is extended. Therefore, the problem that the cutting edge life is shortened when the obtuse corner portion of the conventional throw-away insert is used for the roughing machining is solved. As the radius of curvature Rd of the corner cutting edge 5a relative to the cutting becomes relatively large, the average cutting thickness and the maximum cutting thickness of the corner cutting edge 5a become smaller and the effect of extending the cutting edge life becomes higher. Assuming that the minimum cutting depth in rough machining is 0.5 mm, the radius of curvature Rd should be 0.8 mm or more, and the cutting resistance is increased by increasing the contact length between the corner cutting edge 4A and the work material. In order to prevent this, it may be 6.4 mm or less. The radius of curvature is particularly preferably 1.6 mm or more in order to reliably obtain the effect of extending the cutting edge life in turning roughing with a cutting depth exceeding 1 mm. For the purpose of the present invention, the radius of curvature Re of the corner cutting edge 5a of the acute corner portion 4A satisfies the relative magnitude relationship with the radius of curvature Rd of the corner cutting edge 5a of the obtuse corner portion 4B. For example, it can be arbitrarily determined according to the application of the acute corner portion 4A, and generally speaking, consideration of shape surface restrictions in copying and corner R machining, or cutting performance of cutting resistance and chip disposal From the range of 0 mm to 3.2 mm, it is used for finish machining applications with a small depth of cut, as well as continuous chips, which have higher cutting resistance than aluminum alloys and gray cast iron, etc. When used for turning applications, the range is 0 to 1.6 mm.

Further, a honing 6 is formed along the cutting edge 5 in the cutting edge 5 formed at least on the obtuse corner portion 4B. This is because the fracture resistance in intermittent processing in which a high load is intermittently applied to the cutting edge of the cutting blade 5 is taken into consideration. As shown in FIG. 2A, the honing 6 has an arc shape that smoothly connects the rake face 2 and the flank face 3 in a cross section perpendicular to the cutting edge 5. It is a round honing 6A of 05 mm. The radius of curvature Rh of the arc is 0.05 mm or more in order to surely prevent chipping or chipping of the cutting edge, and 0.50 mm or less in order to increase cutting resistance and reduce the processing cost of the round honing 6A. Is preferred. Further, as shown in FIG. 2 (b), an arc having a radius of curvature Rs continuous to the rake face 2 and an arc having a radius of curvature Rn equal to or less than the radius of curvature Rs connected to the flank 3 are smoothly connected. Even when a curved honing 6B in which a straight line is smoothly connected between these arcs is applied, the same effect as the round honing 6A can be obtained. In the curved honing 6B, in order to avoid an increase in cutting resistance and an increase in the flank wear width at the beginning of cutting, the rake face side width Ls is larger than the flank face side width Ln, and the rake face side width. Ls is in the range of 0.08 mm to 0.50 mm, the flank width Ln is in the range of 0.04 mm to 0.20 mm, and the radius of curvature Rn of the arc connected to the flank 3 is 0.03 mm to 0. It is preferable to be in the range of 20 mm. The honing 6 may be formed over the entire circumference of the cutting edge 5 formed on the periphery of the rake face 3 including the acute corner portion 4A. As described above, the round honing 6A or the curved honing 6B on the cutting edge 5 formed in the obtuse corner portion 4B increases the strength of the cutting edge of the cutting edge 5, reduces the concentrated load due to cutting resistance, and further In order to suppress damage caused by dropping off the adherend of the cutting material, chipping and chipping of the cutting blade 5 are extremely effectively prevented.

Next, a second embodiment will be described. In the following description, the description of the same configuration as that of the first embodiment is omitted, and the same reference numerals are given to the drawings. The throw-away tip 1 of the second embodiment is substantially the same as that of the first embodiment with respect to its constituent material and outer shape, but has the following characteristic configuration. A breaker groove 8 having a land 7 is formed along the cutting edge 5 on the inner side of the cutting edge 5 formed on the periphery of each rhombic surface in an opposing relationship. Further, a boss surface 11 is formed inside the breaker groove 8 via a breaker wall surface 10b rising obliquely upward from the breaker groove 8. The boss surface 11 is composed of a flat surface higher than the cutting edge 5 and is formed so as to surround the attachment hole 12. The boss surface 11 acts as a seating surface when the throw-away tip 1 is mounted on the tool body. Further, both the corner cutting edges 5a in the obtuse corner portion 4B and the acute corner portion 4A are formed from arcs having a curvature radius of 0.8 mm.

In 2nd Embodiment, the curved honing 6B is formed over the perimeter of the cutting blade 5. As shown in FIG. The curved honing 6B takes into consideration the fracture resistance in intermittent machining in which a high load is intermittently applied to the cutting edge of the cutting edge 5, and the detailed form thereof is the form described in the first embodiment. It is the same. As shown in FIGS. 6A and 6B, in the cross section orthogonal to the cutting edge 5, the curved honing 6B of the obtuse corner portion 4B has a different size from the curved honing 6B of the acute angle corner portion 4A. Is formed. That is, in the acute corner portion 4A, the rake face side width Ls of the curved honing 6B is 0.08 mm, the flank face side width Ln is 0.04 mm, and the radius of curvature Rn of the arc connected to the flank face 3 is 0.04 mm. On the other hand, in the obtuse corner portion 4B, the curved honing 6B is formed with the width Ls of 0.10 mm, the width Ln of 0.05 mm, and the radius of curvature Rn of 0.05 mm. . This is to make the tip of the edge of the obtuse corner 4B more efficient and prevent chipping. The form of the honing 6 is not limited to the curved honing 6B, and may be the round honing 6A described in the first embodiment.

Further, a land 7 that is smoothly connected to the end of the curved honing 6B is formed between the cutting blade 5 and the breaker groove 8 over the entire circumference of the cutting blade 5. The land 7 formed along the cutting edge 5 of the acute corner portion 4A has a land width We of 0.20 mm, and is a so-called positive land that is inclined so as to sink downward as it goes inward. On the other hand, the land 7 formed along the cutting edge 5 of the obtuse corner portion 4B has a land width Wd of 0.25 mm larger than the acute corner portion 4A, and is substantially in the horizontal direction (horizontal direction in FIG. 6). It is a negative land formed to extend. This is to improve the fracture resistance of the obtuse corner portion 4B in the turning rough machining of the outer periphery and the end face, particularly in the high feed machining. It is particularly preferable that the land width Wd of the obtuse corner portion 4B is larger than the land width We of the acute corner portion 4A, and is in the range of 0.2 mm to 0.5 mm. This is because if the land width Wd of the obtuse corner portion 4B is less than 0.2 mm, the effect of improving the fracture resistance may not be obtained. If the land width Wd exceeds 0.5 mm, the cutting resistance increases. It is because there exists a possibility that chip disposal property may deteriorate. In this embodiment, the land 7 in the obtuse corner portion 4B is a so-called negative land extending in the horizontal direction (left and right direction in FIG. 4) with respect to the cutting edge of the cutting edge 5. A negative land may be formed so as to gradually rise as it goes, and preferably the inclination angle is set to a range larger than 0 ° and 30 ° or less (not shown). In this case, the effect of increasing the fracture resistance of the cutting blade 5 is further enhanced. Alternatively, it may be a positive land that is inclined so as to be gradually depressed toward the inside from the blade edge, and preferably this inclination angle is larger than 0 ° and not larger than 20 ° (not shown). In this case, since the cutting resistance acting on the cutting blade 5 is reduced, the chipping resistance of the cutting blade 5 can be prevented from deteriorating.

A rake face 2 is formed at a portion of the breaker groove 8 that continues to the land 7. The rake face 2 has an inclined rake face 2a constituted by a flat plane which is inclined so as to be gradually depressed from the land 7 toward the inside. As shown in FIGS. 6A and 6B, in the acute corner portion 4A, the angle between the inclined rake face 2a and the horizontal line, the so-called rake angle αe is 15 °, whereas the obtuse corner portion. In 4B, the rake angle αd is set to 20 °. As described above, the positive rake angle is given to the inclined rake face 2a of the obtuse corner portion 4B by greatly reducing the cutting resistance during processing, thereby reducing the load on the cutting edge 5 and improving the fracture resistance. This is to improve vibration and chatter during cutting and increase the limit area of cutting conditions to enable high-efficiency cutting. Preferably, the rake angle αd between the inclined rake face 2a of the obtuse corner portion 4B and the horizontal plane is in the range of 5 ° to 30 °. This is because when the rake angle αd is less than 5 °, the cutting resistance is not sufficiently reduced, and when the rake angle αd exceeds 30 °, the edge strength of the obtuse corner portion 4B is lowered and the fracture resistance is deteriorated. Because there is a fear. The inclined rake face 2a is not limited to a flat plane having a constant rake angle αd, and may be a curved rake face that is convex or concave upward (not shown). In this case, the rake angle αd between the tangent line and the horizontal line at the connecting portion between the curved rake face and the cutting edge 5, the honing 6 or the land 7 is preferably in the range of 15 ° to 30 °.

As described above, the shape of the honing 6, the land 7 and the rake face 2 is different between the obtuse corner portion 4B and the acute corner portion 4A. Therefore, an intermediate portion 9 for eliminating the difference in shape is formed between the adjacent obtuse corner portion 4B and the acute corner portion 4A. That is, each of the obtuse corner portion 4B and the acute corner portion 4A is provided between the obtuse corner portion 4B located on the left side of FIG. 5 and the acute corner portion 4A located on the right side. An intermediate portion 9 is formed along the main cutting edge 5b to be connected to each of the honing 6, the land 7 and the rake face 2 provided on the main cutting edge 5b. In the intermediate portion 9, the honing 6, the land 7 and The shape of the rake face 2 gradually changes from the obtuse corner portion 4B toward the acute corner portion 4A, thereby eliminating the difference in form between the corner portions 4A and 4B.

In each corner portion 4, chip breakers 10 </ b> A and 10 </ b> B are formed that protrude upward from the surface of the rake face 2. In the acute corner portion 4A, as can be seen from the plan view of FIG. 4, the chip breaker 10A protrudes from the boss surface 11 toward the corner cutting edge 5a in the bisector direction of the acute corner portion 4A. A hemispherical protrusion 10a is formed at the tip of the ridge so as to rise upward from the surface of the inclined rake face 2a. As shown in FIG. 6B, the horizontal distance De from the cutting edge of the corner cutting edge 5a to the bulging start position of the hemispherical protrusion 10a on the bisector cutting plane is, for example, 0.5 to The distance is set to a small distance in the range of 0.7 mm, and the highest point of the hemispherical protrusion 10a is lower than the corner cutting edge 5a. Therefore, it is excellent in chip disposal in finish cutting to medium cutting, and the load due to scraping with the chips is suppressed.

On the other hand, the chip breaker 10B provided in the obtuse corner portion 4B protrudes from the boss surface 11 toward the corner cutting edge 5a in the bisector direction of the obtuse corner portion 4B, as can be seen from the plan view of FIG. The taper is formed in a tapered shape as it goes to the tip in the protruding direction. Specifically, as shown in FIG. 6 (a), a flat plane continuously extending inward in the horizontal direction from the inclined rake face 2a having a positive rake angle in the bisector cutting plane. The bottom face 2b comprised by this is formed, and the chip breaker 10B protrudes upward from the surface of this bottom face 2b. The chip breaker 10B has a breaker wall surface 10b that protrudes upward and inward from the surface of the bottom surface 2b of the rake face, and the highest point of the breaker wall surface 10b is a boss surface 11 higher than the corner cutting edge 5a. The distance Dd in the horizontal direction from the cutting edge of the corner cutting edge 5a to the rising start position of the breaker wall surface 10b is 2.0 mm. The above configuration takes into consideration the chip disposal in turning roughing of the outer periphery and end face. Preferably, the distance Dd is a relatively large distance in the range of 0.8 mm to 5.0 mm. This is because if the distance Dd is less than 0.8 mm, there is a risk of increasing cutting resistance due to chip clogging during turning roughing, and if the distance Dd exceeds 5.0 mm, the breaker wall surface 10b and the chips may come into contact with each other. This is because the chip disposability may be deteriorated. When the distance Dd is 2.5 mm or less, the breaker wall surface 10b reliably curls the chips, so that extremely high chip disposal is obtained. The hemispherical protrusion provided on the acute corner portion 4A described above can also be applied to the obtuse corner portion 4B, and the highest point of the hemispherical protrusion may be lower than the corner cutting edge 5a. Also in this case, the horizontal distance from the cutting edge of the corner cutting edge 5a to the bulging start position of the hemispherical protrusion is preferably in the range of 0.8 mm to 5.0 mm. Further, the bottom surface 2b of the rake face provided at a position lower than the cutting edge 5 has an effect of reducing the load on the cutting edge 5 by suppressing the friction with the chips. The bottom surface 2b of the rake face is not limited to a flat plane extending in the horizontal direction, but the same effect can be obtained as a curved surface that is concave upward or a flat face that is inclined so as to be gradually recessed as it moves away from the cutting edge 5. Play.

An example in which turning rough machining of the outer periphery and end face was actually performed using the throw-away tip 1 made of cemented carbide based on the first and second embodiments described above will be described. FIGS. 7A and 7B are diagrams schematically showing the states of the outer peripheral rough turning and the end face rough turning, respectively. FIG. 8 and FIG. 9 are bar graphs showing the cutting edge life of the first and second embodiments in the turning rough machining. First, using the throw-away tip 1 of the first embodiment, rough turning of the end face by the obtuse corner portion 4B was performed. The comparative throw-away tip (hereinafter referred to as “Comparative Product 1”) is the same as that of the first embodiment except that the radius of curvature of the arc constituting the corner cutting edge in the obtuse corner portion is 0.8 mm. It is. As shown in FIG. 7 (b), the processing form is a substantially square columnar work material made of austenitic stainless steel SUS316 (JIS G4303). A form in which the number of impacts by biting is positively increased is adopted. The processing conditions were a cutting speed (Vc) of 160 m / min, an incision (ap) of 1.0 mm, a feed (f) of 0.15 mm / rev, and wet cutting using a water-soluble cutting fluid. The number of impacts until the cutting edge of the obtuse corner portion of each throw-away tip is lost is shown in the bar graph of FIG. As can be seen from this graph, in the first embodiment, the number of impacts up to the cutting edge life was improved to about 2.2 times that of the comparative product 1. From the relationship between the radius of curvature Rd of the corner cutting edge and the cutting ap, the comparative product 1 was damaged early because a high load was concentrated on the corner cutting edge, whereas in the first embodiment, the corner cutting edge was Since the average cutting thickness and the maximum cutting thickness in 5a are relatively small and the load on the corner cutting edge 5a is reduced, it is possible to realize a long life as described above.

Next, using the throw-away tip 1 of the second embodiment, turning roughing of the outer periphery and the end face by the obtuse corner portion 4B was performed. A conventional throw-away tip used for comparison (hereinafter referred to as “Comparative Product 2”) is a honing, land, or rake face (rake face) provided at an acute corner portion in the throw-away tip 1 of the second embodiment. The shape of the corner) and the chip breaker are also applied to the obtuse corner portion. As shown in FIG. 7 (a), the peripheral turning rough machining is for machining the black skin outer peripheral surface of the work material made of carbon steel for mechanical structure S50C (JIS G4051). The processing conditions were a cutting speed (Vc) of 180 m / min, an average depth of cut (ap) of 2.5 mm, a feed (f) of 0.20 mm / rev, and wet cutting using a water-soluble cutting fluid. The number of machining until the cutting edge of the obtuse corner portion of each throw-away tip is lost is shown in the bar graph of FIG. In turning rough machining of the outer peripheral surface of the black skin, a large load is suddenly applied to the cutting edge due to large variation in cutting. For this reason, the comparative product 2 applied to applications from finishing to medium cutting has a short life due to early chipping because it does not have a cutting edge strength that can sufficiently withstand the roughing. Furthermore, since the chips strongly collided with the hemispherical projections close to the corner cutting edge, there was a problem that the chips became clogged and the cutting resistance due to the collision increased. On the other hand, the obtuse corner portion 4B of the second embodiment has a high cutting edge strength corresponding to the above-described cutting fluctuation, and thus a cutting edge life of about 2.2 times that of the comparative product 2 was obtained. Furthermore, since the rising start position of the breaker wall surface 10b of the chip breaker 10B is provided at a position suitable for rough machining applications, chips to be cut with an appropriate number of turns are generated, and chip disposal is improved. Moreover, the sloping rake face 2a to which the collision of the chips with the breaker wall surface 10b and the positive rake angle α are imparted is very effective in preventing an increase in cutting resistance.

As in the first embodiment, as shown in FIG. 7B, the form of the rough turning of the end surface is a substantially square columnar work material made of austenitic stainless steel SUS316 (JIS G4303). By processing the end face forming the quadrangle, the number of impacts due to the biting of the cutting edge is positively increased. The processing conditions were a cutting speed (Vc) of 150 m / min, an incision (ap) of 1.0 mm, a feed (f) of 0.30 mm / rev, and wet cutting using a water-soluble cutting fluid. The number of impacts until the cutting edge is broken is shown in the bar graph of FIG. This machining mode is a machining mode in which a high load is concentrated in a relatively narrow range of the obtuse corner portion because the cutting is not particularly large but the feed is high in addition to the strong intermittent machining. The comparative product 2 having a low cutting edge strength in the obtuse corner portion has a short life due to the early occurrence of a defect, whereas the obtuse corner portion 4B of the second embodiment has a cutting edge formed by the land 7 and the honing 6. Strengthening contributed to the improvement of the cutting edge life, and it was possible to extend the cutting edge life to about 1.8 times that of Comparative Product 2.

The throw-away tip of the embodiment described above is a throw-away tip such as a CNMG type or a CNGG type defined in the ISO standard, but symbols indicating the shape of the throw-away tip of the ISO standard are C, D, E , M, V, etc. can also be applied to rhombus throwaway chips. Alternatively, the present invention can be applied to a parallelogram throwaway tip such as A, B, or K, or a deformed hexagonal throwaway tip of W. Furthermore, the present invention can also be applied to a throw-away tip having a special shape not defined by the ISO standard as long as at least one obtuse corner portion is formed on a polygonal surface that is a rake face. Needless to say, it is applicable not only to negative chips but also to positive chips.

As mentioned above, although embodiment of this invention was described based on drawing, these are one embodiment to the last, and this invention can be implemented in the aspect which added the various change and improvement based on the knowledge of those skilled in the art. .

It is a top view of a 1st embodiment. It is the S1-S1 line | wire cutting part end elevation in FIG. It is a perspective view of 2nd Embodiment. It is a top view of a 2nd embodiment. It is an enlarged plan view of the second embodiment. (A) is the S2-S2 line end view in FIG. 4, (b) is the S3-S3 line end view in FIG. It is a figure which shows the use condition of 1st and 2nd embodiment, (a), (b) is a figure which shows the state of an outer periphery turning, and the state of an end face turning, respectively. It is a figure which shows the cutting-blade lifetime of 1st Embodiment. It is a figure which shows the cutting-blade lifetime of 2nd Embodiment. It is a top view of the conventional throw away tip. It is a top view of other conventional throwaway tips.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Throw away tip 2 Rake face 2a Inclined rake face 2b Bottom face of rake face 3 Relief face 4 Corner part 4A Sharp corner part 4B Obtuse corner part 5 Cutting edge 5a Corner cutting edge 5b Main cutting edge 6 Honing 6A Round honing 6B Curved honing 7 Land 8 Breaker groove 10A, 10B Chip breaker 10b Breaker wall surface 11 Boss surface Re Curvature radius of corner cutting edge of acute corner Rd Curvature radius of corner cutting edge of obtuse corner

Claims (6)

A substantially polygonal flat plate shape, at least one of the opposing polygonal surfaces is a rake surface and the other is a seating surface, a corner cutting edge having an arc shape at a corner portion of the rake surface;
In the throw-away tip formed with a pair of linear main cutting edges each extending from the corner cutting edge, the outer peripheral surface connected to the corner cutting edge and the main cutting edge as a flank surface,
At least one corner of the rake face
The corner radius of the corner cutting edge of the obtuse corner portion is larger than the radius of curvature Re of the corner cutting edge of the acute corner portion formed in the corner portion excluding the obtuse corner portion,
At least the corner cutting edge and the main cutting edge of the obtuse corner portion are formed with a curved honing having a curved shape in a cross-sectional view perpendicular to the cutting edge,
The curved honing includes an arc having a radius of curvature Rs connected to the rake face and a radius of curvature Rn.
Is a shape formed by smoothly connecting an arc that is smaller than the radius of curvature Rs of the arc and connected to the flank,
When the curved honing is viewed in cross section, the width Ls from the connecting portion between the curved honing and the rake face to the flank is larger than the width Ln from the connecting portion between the curved honing and the rake face to the rake face,
Breaker grooves having lands are formed inside the corner cutting edge and the main cutting edge,
The land width Wd of the land provided in the obtuse corner portion is set to a corner portion excluding the obtuse corner portion.
A throw-away tip, which is larger than a land width We of a land provided at a formed acute corner portion . A rake face having a positive rake angle αd is formed in the breaker groove formed in the obtuse corner portion, and the rake angle αd is in a range of 5 ° to 30 °. The throw-away chip according to 1. The throw-away tip according to claim 1 or 2, wherein a land width Wd of the land formed in the obtuse corner portion is in a range of 0.2 mm to 0.5 mm. On the bisector of the obtuse corner portion, there is formed a breaker wall surface that is oriented toward the corner cutting edge and protrudes upward from the surface of the breaker groove, and the bisector of the corner cutting edge and the protrusion of the breaker wall surface The throw-away tip according to any one of claims 1 to 3, wherein a horizontal distance Dd to the start point is in a range of 0.8 mm to 5.0 mm. The throwaway tip according to any one of claims 1 to 4, wherein a radius of curvature Rd of a corner cutting edge of the obtuse corner portion is 0.8 mm or more and 6.4 mm or less. At least the corner cutting edge and the main cutting edge formed in the obtuse corner part are formed along the cutting edge with a circular honing having an arc shape in a cross-sectional view orthogonal to the cutting edge, and the curvature of the arc The throwaway tip according to any one of claims 1 to 5, wherein the radius Rh is in a range of 0.05 mm or more and 0.50 mm or less.

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