JP4243087B2 - Throw away tip and rotary tool using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a throw-away tip mounted on a throw-away end mill used as a rotary tool.
[0002]
[Prior art]
As a throw-away end mill used as a rotary tool, for example, a throw-away end mill in which a throw-away tip is attached to the end portion of an end mill main body as shown in FIG. 17 is known.
[0003]
FIGS. 13 to 16 show a conventional throw-away tip 51, FIG. 13 is a perspective view thereof, FIG. 14 is a top view, FIG. 15 is a side view of the long side, and FIG. GG sectional drawing, FIG.16 (b) is HH sectional drawing of FIG. 14, FIG.16 (c) shows JJ sectional drawing of FIG. As shown in FIG. 17, the throw-away tip 51 is mounted on the end mill body 56 with the long side cutting edge 52 as a main cutting edge, that is, an outer peripheral cutting edge. (For example, refer to Patent Document 1.)
The long side surface portion includes a first side surface 53 that is continuous with the cutting edge ridge line and has a clearance angle, and a second side surface 54 that is disposed on the chip bottom surface 58 side of the first side surface.
[0004]
Here, the main cutting edge 52 of the throw-away tip 51 is configured with a curved curve protruding outward from the tip when the tip is viewed from above, so that the throw-away tip 51 is attached to the end mill body 56 in the positive or negative axial direction. When the end mill body 56 is rotated around the axis 57 of the end mill body 56 when mounted with a rake angle, the rotation locus of the main cutting edge 52 becomes substantially cylindrical, and the rotation locus As a result, the perpendicularity of the machining wall surface of the work material can be finished with high accuracy by bringing the axial cross section as close as possible to the straight line.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-84708
[Problems to be solved by the invention]
However, in the case of the throw-away tip as described above, as shown in FIG. 16, there is a retracted inclined surface 55 between the first side surface 53 and the second side surface 54 at any position of the main cutting edge 52, In other words, since the first side surface 53 has a shape protruding from the second side surface 54, the cutting blade strength is not sufficient, and the cutting blade is used when processing is used for relatively severe cutting conditions such as high feed processing. There was a problem that many deficiencies occurred.
[0007]
Further, since the second side surface 54 serving as a restraining surface when attaching the tip to the end mill main body 56 is formed of a curved surface, there is a problem that the tip attachment is likely to be unstable.
[0008]
The present invention has been made to solve the above-described problems of the prior art, and in a throw-away tip capable of accurately finishing the perpendicularity of the machining wall surface of a work material and a rotary tool using the same , a cutting tool is provided. The purpose is to ensure the processing stability by improving the strength of the blade and improving the accuracy of the tip.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the throw-away tip according to claim 1 is a throw-away tip that is used by being attached to a holder, and is formed by a side surface and an upper surface of a tip body that forms a substantially parallelogram in plan view. A corner R cutting edge is formed at two corners opposed to each other diagonally among the corners of the crossed ridge, and a long side cutting edge that is a main cutting edge and a Sarae on both sides of the corner R cutting edge. A short-side cutting edge as a blade is provided, and the main cutting edge has a convex curve outward from the chip when viewed from the top surface of the chip, and is inclined so as to gradually approach the bottom surface side as the distance from the corner R cutting edge portion increases. In the throw-away tip, the side surface on the main cutting edge side has a convex curved surface continuous to the main cutting edge, and in the central portion along the main cutting edge among the side surfaces on the main cutting edge side , Convex curved surface continues to the bottom And connected Te, the both end portions adjacent to the central portion, as characterized by continuously the corner portions at both ends of the side surface of the main cutting edge side and a flat surface which is recessed from the convex curved surface Yes.
[0010]
According to such a configuration, the perpendicularity of the machining wall surface of the work material during shoulder machining or grooving can be accurately finished, and the main cutting edge protruding outward from the chip when viewed from the top of the chip is a convex curved surface. Since it is reinforced by the side of the shape, chipping of the main cutting edge is suppressed and the life of the chip can be extended. In addition, since the thickness of the chip near the screw hole can be increased, the effect of dispersing the uneven clogging of the raw material at the time of molding of the chip can be obtained, so that the deformation of the chip can be suppressed and flat. The depressed flat surface serving as a constraining surface enables stable constraining to the chip seating surface of the end mill main body, and the perpendicularity of the workpiece can be processed with higher accuracy.
[0011]
The throw-away tip according to claim 2 is configured such that both ends of the main cutting edge are formed by a cutting edge ridge line parallel to the bottom surface, and a parallel cutting on the side close to the bottom surface among cutting edge ridge lines parallel to the bottom surface. One of the depressed flat surfaces is formed on the side surface at a position corresponding to the edge line of the blade.
[0012]
According to this configuration, the cutting edge ridge line that is parallel to the bottom surface is formed continuously to the center portion of the main cutting edge that is inclined so as to approach the bottom surface, whereby the strength due to the reduction in the thickness of the chip. Can be suppressed. Further, in normal processing, among the main cutting edge, from the corner R cutting edge portion to the inclined cutting edge portion through the cutting edge ridge line parallel to the bottom surface adjacent to the corner R cutting edge portion, is often used. There is no problem in the cutting edge strength even if one of the recessed flat surfaces is provided on the side surface at a position corresponding to the parallel cutting edge ridge line on the side closer to the bottom surface.
[0013]
Further, the throw-away tip according to claim 3 is provided at a corner portion at a cross ridge line portion with the bottom surface of the depressed flat surface formed on the side surface at a position corresponding to the parallel cutting edge ridge line on the side close to the bottom surface. It is characterized in that a flat cut portion is provided which gradually becomes wider as it gets closer.
[0014]
According to this configuration, it is possible to prevent interference between the bottom side corner portion of the tip and the work material in a state where the tip is attached to the end mill body with a positive axial rake angle.
[0015]
According to a fourth aspect of the present invention, in the throw-away tip, the convex curved surface at the center is continuous from the main cutting edge and has a clearance angle, and from the first side to the bottom side. and consists of a second side clearance angle different clearance angle disposed and the first side is attached to, as comprising the said flat surface continuously to the corner portions of both ends of the second side Yes.
[0016]
According to such a configuration, the perpendicularity of the machining wall surface of the work material during shoulder machining or grooving can be accurately finished, and the main cutting edge protruding outward from the chip when viewed from the top of the chip is a convex curved surface. Since it is reinforced at the second side surface, chipping of the main cutting edge is suppressed and the life of the chip can be extended. In addition, since the thickness of the chip near the screw hole can be increased, the effect of dispersing the uneven clogging of the raw material at the time of molding of the chip can be obtained, so that the deformation of the chip can be suppressed and flat. The depressed flat surface serving as a constraining surface enables stable constraining to the chip seating surface of the end mill main body, and the perpendicularity of the workpiece can be processed with higher accuracy.
[0017]
The throw-away tip according to claim 5 is characterized in that a clearance angle of the first side surface is smaller than a clearance angle of the second side surface.
[0018]
According to such a configuration, the cutting edge strength can be increased, and as a result, the life of the chip can be extended.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0024]
6 to 10 show an embodiment of the present invention. FIG. 6 is a perspective view of the throw-away tip 20 according to this embodiment, FIG. 7 is a plan view, FIG. 8 is a side view of the long side, and FIG. 7A is a cross-sectional view taken along the line AA in FIG. 7, FIG. 9B is a cross-sectional view taken along the line BB in FIG. 7, FIG. 9C is a cross-sectional view taken along the line CC in FIG. 4 is a side view of the end mill in a state where the away tip 20 is mounted on the end mill body 37. FIG.
[0025]
In FIG. 6, the throw-away tip 20 according to the present embodiment has corners R at two corners opposite to each other diagonally among the corners of the crossed ridge formed by the side surface and the upper surface of the tip body having a substantially parallelogram shape. A cutting edge portion 2 is formed, and a long-side cutting edge 22 that is a main cutting edge and a short-side cutting edge 23 that is a Sarah edge are provided on both sides of the corner R cutting edge portion 2. Further, a screw hole 25 for fixing a chip screw that penetrates to the bottom surface 24 is formed in the center portion of the upper surface of the chip.
[0026]
The main cutting edge 22 is configured with a convex curve on the outer side of the chip as viewed from the top of the chip, whereby the perpendicularity of the processing wall surface of the work material can be accurately finished.
[0027]
Further, the main cutting edge 22 is inclined so as to gradually approach the bottom surface 24 as it is separated from the corner R cutting edge portion 21, thereby increasing the axial rake angle when the tip 20 is attached to the end mill body 37. Even if not, since the chip 20 itself has a rake angle in the axial direction, the sharpness can be improved and the cutting resistance can be reduced. Further, the fact that the rake angle in the axial direction when the tip 20 is attached to the end mill main body 37 described above can be minimized, the thickness of the holder below the tip seating surface can be secured, so that the rigidity of the holder can be maintained.
[0028]
Further, the side surface 26 of the main cutting edge 22 is formed as a convex curved surface.
[0029]
Further, flat surfaces 29 and 30 that are recessed from the surface of the side surface 26 are formed continuously to the corner portions 27 and 28 at both ends of the side surface 26. Here, as shown in FIGS. 9A and 9C, the flat surfaces 29 and 30 are formed from the side surface 26 through the lead-in inclined surface 31, respectively. On the other hand, the central portion of the main cutting edge 22 has no pull-in inclined surface as shown in FIG. 9B, and the side face 26 is continuously connected to the bottom face 24. The cutting edge defect is suppressed without impairing the cutting edge strength.
[0030]
Further, the flat surfaces 29 and 30 serve as constraining surfaces when the holder is attached. However, the chip can be restrained more stably than the constraining on the curved surface, and the processing of the constraining surface on the holder side is more than that of the curved surface processing. There is also an advantage that the flat surface processing can be easily performed.
[0031]
Further, the flat surfaces 29 and 30 that are depressed at both ends of the side surface 26 are formed, and the central portion between them is a convex curved surface of the side surface 26, so that the thickness of the chip near the screw hole 25 can be increased. The effect of dispersing the unevenness of the clogging of the raw material at the time of molding of the chip is obtained, whereby the deformation of the chip at the time of firing can be suppressed, and the depressed flat surfaces 29 and 30 that become flat constraining surfaces In addition, it is possible to reliably and stably restrain the tip seating surface of the end mill body, and as a result, the perpendicularity of the workpiece can be processed with higher accuracy.
[0032]
As shown in FIG. 8, both ends of the main cutting edge 22 are constituted by cutting edge ridge lines 32 and 34 parallel to the bottom surface 24. The cutting edge ridge line 32 parallel to the bottom surface 24 on the corner R cutting blade 21 side is for maintaining the strength of the corner R cutting blade portion 21 that is always used for processing, and further polishing the chip bottom surface 24. This is also to prevent wobbling of the chip when doing. The cutting edge ridge line 34 parallel to the bottom surface 24 close to the other bottom surface 24 side suppresses a decrease in strength due to a decrease in the thickness of the chip 20. In normal processing, the corner cutting edge 21 of the main cutting edge 22 passes through a cutting edge ridge line 32 parallel to the bottom surface 24 adjacent to the corner cutting edge 21 to the inclined cutting edge portion 33. Therefore, even if one of the recessed flat surfaces 30 is provided on the side surface 26 at a position corresponding to the parallel cutting edge ridge line 34 on the side closer to the bottom surface 24 from there, there is a problem with the cutting edge strength. Absent. Further, when machining is performed with such a depth of cut, the machining load becomes large, so it is general to use with lower cutting conditions.
[0033]
Further, the crossed ridge line portion of the depressed flat surface 30 formed on the side surface 26 at the position corresponding to the parallel cutting edge ridge line 34 on the side close to the bottom surface 24 gradually increases as the corner portion 28 is approached. A flat cut portion 35 is provided so as to be wide. Accordingly, it is possible to prevent interference between the bottom side corner portion 36 of the tip 20 and the work material in a state where the tip 20 is attached to the end mill body 37 with a positive axial rake angle.
[0034]
1 to 5 show another embodiment of the present invention. FIG. 1 is a perspective view of a throw-away tip 1 according to this embodiment, FIG. 2 is a plan view, and FIG. 3 is a side view of a long side. 4A is a cross-sectional view taken along the line AA in FIG. 2, FIG. 4B is a cross-sectional view taken along the line BB in FIG. 2, FIG. 4C is a cross-sectional view taken along the line CC in FIG. FIG. 2 is a side view of the end mill in a state where the throw-away tip 1 of the embodiment is mounted on the end mill body 19.
[0035]
In FIG. 1, the throw-away tip 1 according to this embodiment has corners R at two corners opposite to each other diagonally among the corners of the crossed ridge formed by the side surface and the top surface of the tip body having a substantially parallelogram shape. A cutting edge portion 2 is formed, and a long-side cutting edge 3 as a main cutting edge and a short-side cutting edge 4 as a Sarah blade are provided on both sides of the corner R cutting edge portion 2. Further, a screw hole 6 for fastening a chip screw penetrating to the bottom surface 5 is formed in the center portion of the chip upper surface.
[0036]
The main cutting edge 3 is composed of a curved curve protruding outward from the chip when viewed from the top of the chip, whereby the perpendicularity of the machining wall surface of the work material can be finished with high accuracy.
[0037]
Further, the main cutting edge 3 is inclined so as to gradually approach the bottom surface 5 as the distance from the corner R cutting edge portion 2 increases, so that the axial rake angle when the tip 1 is attached to the end mill body 19 is increased. Even if not, since the chip 1 itself has a rake angle in the axial direction, the sharpness can be improved and the cutting resistance can be reduced. Further, the fact that the axial rake angle when attaching the tip 1 to the end mill body 19 described above can be minimized, the thickness of the holder below the tip seating surface can be secured, so that the rigidity of the holder can be maintained.
[0038]
Further, the side surface of the main cutting edge 3 is continuous with the main cutting edge 3 and has a clearance angle, and the first side face 7 is continuous with the first side face 7 from the first side face 7 to the bottom face 5 side. The second side surface 8 is disposed and has a clearance angle larger than the clearance angle of the first side surface 7. In addition, the first side surface 7 and the second side surface 8 are formed by convex curved surfaces. ing.
[0039]
Further, flat surfaces 11 and 12 that are recessed from the surface of the second side surface 8 are formed continuously to the corner portions 9 and 10 at both ends of the second side surface 8. Here, as shown in FIGS. 4 (a) and 4 (c), the flat surfaces 11 and 12 are formed on the flat surfaces 11 and 12 through the pull-in inclined surface 13 from the first side surface 7, respectively. Yes. On the other hand, since the central portion of the main cutting edge 3 is directly connected to the second side face 8 without passing through the inclined surface as shown in FIG. The cutting edge loss is suppressed without impairing the strength of the cutting edge 3.
[0040]
Further, the flat surfaces 11 and 12 serve as constraining surfaces when the holder is mounted. However, stable chip constraining is possible compared to constraining on a curved surface. There is also an advantage that the flat surface processing can be easily performed.
[0041]
Further, flat surfaces 11 and 12 which are depressed at both ends of the second side surface 8 are formed, and the central portion between them is a convex curved surface of the second side surface 8 so that the thickness of the chip near the screw hole 6 is increased. Because it can be taken large, the effect of dispersing the unevenness of the clogging of the raw material at the time of molding of the chip can be obtained, whereby the deformation of the chip at the time of firing can be suppressed, and the depressed flat surface which becomes a flat constrained surface 11 and 12 enable reliable and stable restraint to the chip seating surface of the end mill body, and as a result, the perpendicularity of the workpiece can be machined with higher accuracy.
[0042]
As shown in FIG. 3, both ends of the main cutting edge 3 are constituted by cutting edge ridge lines 14 and 16 parallel to the bottom surface 5. The cutting edge ridge line 14 parallel to the bottom surface 5 on the corner R cutting blade 2 side is for maintaining the strength of the corner R cutting blade portion 2 that is always used for processing, and further polishing the chip bottom surface 5. This is also to prevent wobbling of the chip when doing. The cutting edge ridge line 16 parallel to the bottom surface 5 close to the other bottom surface 5 side suppresses a decrease in strength due to a decrease in the thickness of the chip 1. In normal machining, the corner cutting edge 2 of the main cutting edge 3 passes through a cutting edge ridge line 14 parallel to the bottom surface 5 adjacent to the corner cutting edge 2 to the inclined cutting edge 15. Therefore, even if one of the recessed flat surfaces 12 is provided on the second side surface at a position corresponding to the parallel cutting edge ridge line 16 on the side closer to the bottom surface 5 from there, the cutting edge strength is obtained. no problem. Further, when machining is performed with such a depth of cut, the machining load becomes large, so it is general to use with lower cutting conditions.
[0043]
Further, the crossed ridge line portion of the depressed flat surface 12 formed on the second side surface at a position corresponding to the parallel cutting edge ridge line 16 on the side closer to the bottom surface 5 is closer to the corner portion 10. A flat cut portion 17 is provided so as to gradually increase. Accordingly, it is possible to prevent interference between the bottom corner portion 18 of the tip 1 and the work material when the tip 1 is attached to the end mill body 19 with a positive axial rake angle.
[0044]
In addition, as shown in FIG. 11, flat restraining surfaces 38 and 39 are provided on the tip mounting portions to which the tips 1 and 20 are attached in the end mill main bodies 19 and 37, and the flat restraining surfaces 38 and 39 are provided. An escape portion 40 is provided between 39. Here, the flat constraining surfaces 38 and 39 and the depressed flat surfaces 11, 12 and 29, 30 on the side of the chips 1 and 20 are overlapped and constrained, so that more stable constraining is possible. Further, the second side surface 8 existing between the recessed flat surfaces 11 and 12 on the chip 1 side and the side surface 26 existing between the recessed flat surfaces 29 and 30 on the chip 20 side are formed by the end mill. Since it is attached so as to fit in the escape portion 22 on the main body 19, 37 side, problems such as interference do not occur when the chip is mounted.
[0045]
FIG. 12 shows a cross-sectional view at the center of the main cutting edge when the clearance angle of the second side surface is smaller than the clearance angle of the first side surface as another embodiment of the present invention. In this case, when the tip is mounted with a large axial rake angle attached to the end mill body, the clearance angle of the flank can be secured, so that flank wear is suppressed. However, from the viewpoint of maintaining the cutting edge strength of the chip, it is desirable that the clearance angle of the flank adjacent to the cutting edge ridge line is small.
[0046]
As mentioned above, although embodiment of this invention was illustrated, this invention is not limited to the said embodiment, It cannot be overemphasized that it can be made arbitrary, unless it deviates from the objective of invention.
[0047]
【The invention's effect】
As described above , according to the throw-away tip of claim 1, the perpendicularity of the processing wall surface of the work material at the time of shoulder processing or grooving can be finished with high accuracy, and the main cutting edge is formed on the top surface of the chip. Since the main cutting edge protruding outward from the chip is reinforced by the convex curved side surface, chipping of the main cutting edge can be suppressed and the life of the chip can be extended.
In addition, since the thickness of the chip near the screw hole can be increased, the effect of dispersing the uneven clogging of the raw material at the time of molding of the chip can be obtained, so that the deformation of the chip can be suppressed and flat. The depressed flat surface serving as a constraining surface enables stable constraining to the chip seating surface of the end mill main body, and the perpendicularity of the workpiece can be processed with higher accuracy.
[0048]
According to the throw-away tip of claim 2, the cutting edge ridge line parallel to the bottom surface is formed continuously to the center portion of the main cutting edge that is inclined so as to approach the bottom surface. A decrease in strength due to a decrease in the thickness of the chip can be suppressed.
Further, in normal processing, among the main cutting edge, from the corner R cutting edge portion to the inclined cutting edge portion through the cutting edge ridge line parallel to the bottom surface adjacent to the corner R cutting edge portion, is often used. There is no problem in the cutting edge strength even if one of the recessed flat surfaces is provided on the side surface at a position corresponding to the parallel cutting edge ridge line on the side closer to the bottom surface.
[0049]
In addition, according to the throw-away tip of claim 3, it is possible to prevent interference between the bottom side corner portion of the tip and the work material when the tip is attached to the end mill body with a positive axial rake angle. I can do it.
[0050]
In addition, according to the throw-away tip of claim 4, it is possible to accurately finish the perpendicularity of the processing wall surface of the work material at the time of shoulder processing or grooving, and the main cutting edge is the tip in the top view of the tip. Since the main cutting edge protruding outward is reinforced by the convex curved second side surface, the main cutting edge is prevented from being lost.
In addition, since the thickness of the chip near the screw hole can be increased, the effect of dispersing the uneven clogging of the raw material at the time of molding of the chip can be obtained, so that the deformation of the chip can be suppressed and flat. The depressed flat surface serving as a constraining surface enables stable constraining to the chip seating surface of the end mill main body, and the perpendicularity of the workpiece can be processed with higher accuracy.
[0051]
According to the throw-away tip of claim 5, the cutting edge strength of the main cutting edge can be increased, and as a result, the life of the tip can be extended.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a throw-away tip of the present invention.
FIG. 2 is a top view of the throw-away tip of FIG.
3 is a long side surface of the throw-away tip in FIG. 1. FIG.
4A is a sectional view taken along line AA, FIG. 4B is a sectional view taken along line BB, and FIG. 4C is a sectional view taken along line CC.
FIG. 5 is a side view when the throw-away tip of the present invention is mounted on the end mill body.
FIG. 6 is a schematic perspective view of another throw-away tip of the present invention.
7 is a top view of the throw-away tip in FIG. 6. FIG.
8 is a long side surface of the throw-away tip in FIG. 6;
9A is a cross-sectional view taken along the line AA, FIG. 9B is a cross-sectional view taken along the line BB, and FIG. 9C is a cross-sectional view taken along the line CC.
FIG. 10 is a side arrangement view when another throw-away tip of the present invention is mounted on the end mill body.
FIG. 11 is a schematic view of a tip mounting portion of the end mill body.
FIG. 12 is a cross-sectional view of the central portion of the main cutting edge in another embodiment of the throw-away tip of the present invention.
FIG. 13 is a schematic perspective view of a conventional throw-away tip.
14 is a top view of the throw-away tip in FIG.
15 is a long side surface of the throw-away tip in FIG. 13;
16A is a sectional view taken along line GG, FIG. 16B is a sectional view taken along line HH, and FIG. 16C is a sectional view taken along line JJ.
FIG. 17 is a side view of a conventional example when the throw-away tip is mounted on an end mill body.
[Explanation of symbols]
1: Throw away tip 2: Corner R cutting edge part 3: Main cutting edge (long edge cutting edge)
4: Sarae blade (short edge cutting blade)
5: Bottom surface 6: Tip side screw hole 7: First side surface 8: Second side surface 9, 10: Corner portion 11, 12: Flat surface 13: Retraction inclined surface 14: Parallel to the bottom surface near the corner R cutting edge portion Cutting edge ridge line 15: Inclined cutting edge ridge line 16: Cutting edge ridge line parallel to the bottom surface on the side close to the bottom surface 17: Flat cut portion 18: Bottom side corner portion 19: End mill body 20: Throw away tip 21: Corner R cutting Blade part 22: main cutting edge (long edge cutting edge)
23: Sarae blade (short edge)
24: Bottom surface 25: Chip side screw hole 26: Side surface 27, 28: Corner portion 29, 30: Flat surface 31: Retraction inclined surface 32: Cutting edge ridge line 33 parallel to the bottom surface near the corner R cutting edge portion: Inclination Cutting edge ridge line 34: Cutting edge ridge line 35 parallel to the bottom surface on the side close to the bottom surface: Flat cut portion 36: Bottom side corner portion 37: End mill main body 38, 39: End mill main body side restraining surface 40: Escape portion 41: End mill main body Side seating surface 42: End mill main body side screw hole 43: First side surface 44: Second side surface 51: Throw away tip 52: Main cutting edge 53: First side surface 54: Second side surface 55: Retraction inclined surface 56: End mill main body 57 : End mill body axis

Claims (6)

A throw-away tip that is attached to a holder and used.
Corner R cutting edge portions are formed at two corner portions opposite to each other diagonally among the corner portions of the crossed ridge formed by the side surface and the upper surface of the chip body having a substantially parallelogram in plan view. A long-side cutting edge that is the main cutting edge and a short-side cutting edge that is the Sarae blade are provided on both sides of the R cutting edge, and the main cutting edge has a convex curve on the outside of the chip when viewed from the top of the chip. In addition, in the throw-away tip that is inclined so as to gradually approach the bottom side as it is away from the corner R cutting edge portion,
The side surface on the main cutting edge side has a convex curved surface continuous to the main cutting edge,
Among the side surfaces of the main cutting edge side, in the central portion along the main cutting edge, said convex curved surface has continuously connected to said bottom surface, at both ends adjacent to the central portion, said main cutting edge A throw-away tip comprising a flat surface recessed from the convex curved surface continuously at the corners at both ends of the side surface.   Both ends of the main cutting edge are constituted by cutting edge ridge lines parallel to the bottom surface, and the side surface at a position corresponding to a parallel cutting edge ridge line on the side close to the bottom surface among cutting edge ridge lines parallel to the bottom surface. The throw-away tip according to claim 1, wherein one of the depressed flat surfaces is formed.   A plane cut portion that gradually increases as it approaches the corner portion at the crossing ridge line portion with the bottom surface of the depressed flat surface formed on the side surface at a position corresponding to the parallel cutting edge ridge line on the side close to the bottom surface. The throw-away tip according to claim 1 or 2, wherein the throw-away tip is provided. The convex curved surface at the center is a first side surface that is continuous with the main cutting edge and has a clearance angle, and is continuously disposed on the bottom surface side from the first side surface, and the relief of the first side surface. Consisting of a second side with a clearance angle different from the corner,
The throw-away tip according to any one of claims 1 to 3, wherein the flat surface is provided continuously at corner portions at both ends of the second side surface.   The throw-away tip according to claim 4, wherein a clearance angle of the first side surface is smaller than a clearance angle of the second side surface. A rotary tool with a throw-away tip attached to the holder,
The throw-away tip has corner R cutting edge portions formed at two corners opposite to each other diagonally among the corners of the crossed ridge formed by the side surface and the upper surface of the tip body having a substantially parallelogram in plan view. In addition, a long-side cutting edge that is a main cutting edge and a short-side cutting edge that is a Sarah blade are provided on both sides of the corner R cutting edge portion, and the main cutting edge is located on the outer side of the chip in a top view of the chip. It has a convex curve and is inclined so as to gradually approach the bottom side as it is away from the corner R cutting edge, and the side surface on the main cutting edge side has a convex curved surface that is continuous with the main cutting edge. and which, among the side surfaces of the main cutting edge side, in the central portion along the main cutting edge, said convex curved surface has continuously connected to said bottom surface, at both ends adjacent to the central portion, the wherein one convex curved surface continuously to the corner portions at both ends of the side face of the main cutting edge side Includes a recessed and flat surface,
The holder includes a tip attachment portion to which the throwaway tip is attached, and the tip attachment portion has two flat restraint surfaces and a relief portion provided between the two restraint surfaces. And
The rotary tool, wherein the throwaway tip is attached to a holder so that the flat surface is constrained by a flat constraining surface of the holder and the convex curved surface is accommodated in a relief portion of the holder.

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