JP2014083641A - Ball end mill and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball end mill that makes cut surface roughness after cutting work sufficiently proper, and a method of manufacturing the same.SOLUTION: A ball end mill includes: a first round surface 22 that is provided along a ball blade 18 and that is equivalent to a part of a spherical surface of a partial spherical part 16a; a flank 24 that is provided on the other side of the ball blade 18 with respect to the first round surface 22 and that is equivalent to a diameter smaller than a diameter dimension of the spherical surface; and a second round surface 26 that is provided on the other side of the first round surface 22 with respect to the flank 24 and that is equivalent to a part of the spherical surface of the partial spherical part 16a.

Description

  The present invention relates to a ball end mill and a method for manufacturing the same, and more particularly to an improvement for making a machined surface roughness sufficiently good after cutting by the ball end mill.

  A ball end mill in which at least one ball blade is formed in a partial spherical portion provided at the tip of a tool body is known. For example, it is a spherical blade end mill described in Patent Document 1. Such a ball end mill is used, for example, by being attached to a well-known machining center to enable cutting of a three-dimensional free-form surface. Widely used for cutting materials.

Japanese Patent Laid-Open No. 11-156622

  By the way, in the machining of the mold using the ball end mill, the machined surface after cutting is usually polished. In particular, since a mirror surface is required for a mold for a design surface or the like, the necessity for such a polishing process is high. However, in the conventional technique, the cost required for the polishing process has been a problem. In other words, since sufficient cutting surface roughness cannot be obtained by cutting with a conventional ball end mill, it is necessary to perform finish polishing manually, but this has the adverse effect of requiring human or time costs for the polishing technique and processing time. was there. In order to eliminate such an adverse effect, it is conceivable to perform the same processing using a diamond or a CBN tool, but this causes a new adverse effect that the tool cost is increased. For this reason, there has been a demand for the development of a ball end mill that has a sufficiently good surface roughness after cutting, but such a ball end mill has not been developed yet.

  The present invention has been made in the background of the above circumstances, and the object of the present invention is to provide a ball end mill and a method of manufacturing the ball end mill that have a sufficiently good surface roughness after cutting. It is in.

  In order to achieve such an object, the gist of the first invention is a ball end mill in which at least one ball blade is formed in a partial spherical portion provided at the tip of a tool body, wherein the ball A first round surface corresponding to a part of the spherical surface of the partial spherical portion provided along the blade, and a diameter of the spherical surface provided on the opposite side of the ball blade with respect to the first round surface. A flank corresponding to a smaller diameter, and a second round surface corresponding to a part of the spherical surface of the partial spherical portion provided on the opposite side of the first round surface with respect to the flank. It is characterized by this.

  Thus, according to the first invention, the first round surface corresponding to a part of the spherical surface of the partial spherical portion provided along the ball blade, and the ball with respect to the first round surface. A flank corresponding to a diameter smaller than the diameter of the spherical surface provided on the opposite side of the blade, and a spherical surface in the partial spherical portion provided on the opposite side of the first round surface with respect to the flank. Since the second round surface corresponding to a part is provided, the surface roughness after cutting is good due to the burnishing effect (burnishing) of the first round surface and the second round surface. In addition, since the flank is provided between the first round surface and the second round surface, tool wear can be suppressed and occurrence of chatter vibration and the like can be suitably suppressed. That is, it is possible to provide a ball end mill that makes the surface roughness after cutting sufficiently satisfactory.

  The gist of the second invention subordinate to the first invention is that the width dimension of the first round surface is within a range of 0.01 mm or more and 0.10 mm or less. If it does in this way, the surface roughness after cutting can be made as good as possible by necessary and sufficient burnishing.

  The gist of the third invention subordinate to the first invention to the second invention is that the width dimension of the flank is the round width of the ball blade from the cutting edge to the heel. It is 1/2 or more. If it does in this way, by providing sufficient flank, tool wear can be controlled and generation of chatter vibration etc. can be controlled more suitably.

  In order to achieve the above object, the gist of the fourth invention is a method of manufacturing a ball end mill in which at least one ball blade is formed in a partial spherical portion provided at the tip of a tool body, A spherical grinding step of grinding a spherical surface in the partial spherical portion, a first round surface corresponding to a portion along the ball blade in the spherical surface, and a second portion corresponding to a portion of the spherical surface facing the ball blade. And a flank grinding step for grinding a flank corresponding to a smaller diameter than the diameter of the spherical surface. In this way, the first round surface and the second round surface can be made to have good surface roughness after cutting by the burnishing effect (burnishing) of the first round surface and the second round surface. By forming the flank surface between the second round surfaces, it is possible to suppress tool wear and suitably suppress the occurrence of chatter vibrations. That is, it is possible to provide a method for manufacturing a ball end mill that makes the surface roughness after cutting sufficiently satisfactory.

It is the front view which looked at the ball end mill which is a suitable example of the present invention from the direction perpendicular to an axis. It is the figure which looked at the blade part with which the ball end mill of FIG. It is a fragmentary sectional view explaining in detail the partial structure of the blade part with which the ball end mill of FIG. 1 was equipped. It is process drawing explaining the principal part of an example of the manufacturing method of the ball end mill of FIG. It is a figure explaining the test which the present inventors etc. performed in order to verify the effect of the present invention, and shows the composition of the sample and the test result of each sample. It is a figure explaining the other test which this inventor etc. performed in order to verify the effect of this invention, and has shown the roughness curve of the pick feed direction of the cut surface after the cutting by the conventional product. It is a figure explaining the other test which this inventor etc. performed in order to verify the effect of this invention, and has shown the roughness curve of the feed direction of the cut surface after the cutting by the conventional product. It is a figure explaining other tests which the present inventors conducted in order to verify the effect of the present invention, and shows a roughness curve in the pick feed direction of the work surface after cutting by the ball end mill of the present embodiment. Yes. It is a figure explaining other tests which the present inventors performed in order to verify the effect of the present invention, and shows the roughness curve of the feed direction of the work surface after cutting by the ball end mill of this example. .

  The ball end mill of the present invention is preferably used for cutting for processing a three-dimensional curved surface including a processing surface and a cavity of a mold. Preferably, it is suitable for machining a die by a contouring method in which cutting is performed along a curved surface to be processed, or a contouring method in which cutting is performed while gradually changing the height of a portion to be processed. Although it is used, it is widely used for various other work materials.

  As the material for the ball end mill of the present invention, cemented carbide or high-speed tool steel is preferably used, but other materials may be used. It is desirable to coat the surface of the blade portion or the like with a hard coating such as TiAlN, TiN, or TiCN as necessary.

  The ball end mill of the present invention is preferably a two-blade ball end mill in which two ball blades are formed in a partial spherical portion, but the present invention is also applicable to a multi-blade ball end mill having three or more ball blades. It is preferably applied.

  In the ball end mill of the present invention, the round, that is, the first round surface and the second round surface correspond to a part of the spherical surface in the partial spherical portion, in other words, the same spherical diameter surface of the partial spherical portion. is there.

  The ball blade provided in the ball end mill of the present invention may be provided in a spiral shape twisted in the direction opposite to the cutting direction as it goes from the end on the axial center side toward the outer periphery, in other words, away from the tool tip. Desirably, an outer peripheral cutting edge twisted at a predetermined twist angle, for example, is smoothly connected to the outer peripheral end portion.

  The ball end mill of the present invention preferably includes a shank portion grinding step for grinding the shank portion, a neck / partial spherical portion grinding step for grinding the neck portion and the partial spherical portion, and a groove portion and an outer peripheral portion in the partial spherical portion are ground. The groove / peripheral portion grinding step, the spherical grinding step for grinding the spherical surface in the partial spherical portion, the gash grinding step for grinding the gash in the partial spherical portion, and the portion along the ball blade in the spherical surface. A flank grinding step of grinding a flank corresponding to a smaller diameter than the diameter of the spherical surface between the first round surface and a second round surface corresponding to a portion of the spherical surface facing the ball blade. Are produced by a manufacturing process including

  The manufacturing process of the ball end mill according to the present invention preferably includes a lapping process in which at least one of the spherical surface ground by the spherical grinding process and the flank surface ground by the flank grinding process is lapped. . In other words, the first round surface and the second round surface in the ball end mill of the present invention are preferably obtained by lapping the surfaces thereof.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings used for the following description, the dimensional ratios and the like of each part are not necessarily drawn accurately.

  FIG. 1 is a front view of a ball end mill 10 according to a preferred embodiment of the present invention as viewed from a direction perpendicular to the axis. As shown in FIG. 1, the ball end mill 10 of the present embodiment includes a cylindrical shank portion 12, a neck portion 14, and a blade portion 16 that is provided at the tip of a tool body and that is involved in cutting work. In preparation. The ball end mill 10 is preferably such that the shank portion 12, the neck portion 14 and the blade portion 16 are integrally formed by polishing a material such as cemented carbide or high-speed tool steel.

  FIG. 2 is a view of the blade portion 16 provided in the ball end mill 10 as viewed in the axial direction from the tool tip side. The blade portion 16 provided in the ball end mill 10 is a partial spherical portion 16a at least partially corresponding to a spherical surface having a specified diameter, and the partial spherical portion 16a has a circumference around an axis or the like. Two ball blades 18 are provided at an angular interval (180 ° interval in this embodiment). The ball blade 18 is preferably cut in the cutting direction of the ball end mill 10 (in the example shown in FIG. 2, as shown in FIG. It is provided in a spiral shape that is twisted in the opposite direction. The outer peripheral edge of the ball blade 18 is smoothly connected to the outer peripheral cutting edge 20 continuously twisted at a predetermined twist angle, for example, continuously with the ball blade 18. Preferably, the surface of the blade portion 16 is coated with a hard coating such as TiAlN, TiN, or TiCN as necessary.

  FIG. 3 is a partial cross-sectional view (for example, an axial center) showing a portion of the blade portion 16 cut along a plane corresponding to a great circle of a spherical surface in the partial spherical portion 16a in order to explain in detail the partial configuration of the blade portion 16. Is a cross-sectional shape having a central angle of 45 °). In FIG. 3, the spherical surface of the partial spherical portion 16a is indicated by a broken line. As shown in FIGS. 2 and 3, the partial spherical portion 16a includes a first round surface 22 provided along the ball blade 18 and corresponding to a part of the spherical surface of the partial spherical portion 16a, and A flank 24 corresponding to a diameter smaller than the diameter of the spherical surface provided on the opposite side of the ball blade 18 with respect to the first round surface 22, and the first round surface 22 with respect to the flank 24. And a second round surface 26 corresponding to a part of the spherical surface of the partial spherical portion 16a provided on the opposite side. In other words, in the blade portion 16, the first round surface 22 and the second round surface 26 are not flank surfaces, and come into contact (sliding) with the work surface of the work material during cutting by the ball end mill 10. It is configured to be contacted.

  The width dimension w1 of the first round surface 22, that is, the margin width along the ball blade 18, is preferably in the range of 0.01 mm or more and 0.10 mm or less, and more preferably 0.015 mm or more and 0. .05 mm or less. The width dimension w2 of the flank 24 is preferably the round dimension w0 (see FIG. 2) of the portion of the ball blade 18 having a width on the bank from the cutting edge to the heel. It is 1/2 or more of the width w0. As shown in FIG. 2, the round width w0 is a width dimension from the end of the first round surface 22 on the ball blade 18 side to the end of the second round surface 26 opposite to the ball blade 18. (= W1 + w2 + w3). In other words, assuming that the width dimension of the first round surface 22 is w1, the width dimension of the second round surface 26 is w3, the width dimension w2 of the flank 24 satisfies the following expression (1). . More preferably, the width dimension w2 of the flank 24 is not more than 4/5 of the round width w0.

  w2 ≧ (w1 + w2 + w3) / 2 (1)

  As specific dimensions of the ball end mill 10 of the present embodiment, the shank portion 12 has a cylindrical shape with a diameter of about 6 mmφ and a length of about 40 mm, for example. The neck portion 14 has a cylindrical shape with a diameter dimension of about 3.85 mmφ and a length dimension of about 4 mm, for example, and the diameter dimension gradually decreases from the shank portion 12 toward the neck portion 14 as shown in FIG. A tapered portion is provided. The blade portion 16 has, for example, an axial length (blade length) of about 4 mm and a diameter of about 4 mmφ, and the spherical surface of the partial spherical portion 16a corresponds to, for example, a diameter of about 2 mm. . The rake angle of the ball blade 18 is, for example, about 5 °. The twist angle of the outer peripheral cutting edge 20 is, for example, about 30 °. The width w1 of the first round surface 22 is, for example, about 0.015 to 0.05 mm. The width dimension w2 of the flank 24 is, for example, about 0.55 to 0.85 mm. The width dimension w3 of the second round surface 26 is, for example, about 0.25 to 0.45 mm.

  In the cutting of the work material by the ball end mill 10 of the present embodiment configured as described above, the shank portion 12 is attached to a cutting device such as a machining center (not shown) and is driven to rotate around the axis by the cutting device. As a result, the work material is cut by the ball blade 18 and the outer peripheral cutting edge 20 in the blade portion 16. The ball end mill 10 of this embodiment is preferably used for cutting for processing a three-dimensional curved surface including a cavity of a mold. For example, it is suitable for machining of dies by the contour processing method that performs cutting while changing the height of the part to be processed stepwise, etc. Used. Here, the first round surface 22 and the second round surface 26 are not flank surfaces, and are configured to be brought into contact (sliding contact) with the work surface of the work material when the ball end mill 10 performs the cutting process. Therefore, due to the burnishing effect (burnishing) of the first round surface 22 and the second round surface 26, the surface roughness of the cut surface after cutting is 1.2 μm at the maximum height Rz (JIS B 0601: 2001). It can be close to the polished surface as follows. Furthermore, since the flank 24 is provided between the first round surface 22 and the second round surface 26, tool wear can be suppressed and occurrence of chatter vibration and the like can be preferably suppressed.

  FIG. 4 is a process diagram illustrating the main part of an example of the method for manufacturing the ball end mill 10. First, in the shank part grinding process P1, the shank part 12 is ground. Next, in the neck / blade portion grinding step P2, the neck portion 14 and the blade portion 16 (rough shape) are ground. Next, in the groove / outer peripheral portion grinding step P3, the groove portion and the outer peripheral portion of the partial spherical portion 16a are ground. Next, in the spherical grinding process P4, grinding of the spherical surface corresponding to the specified diameter in the partial spherical portion 16a is performed. That is, the spherical surfaces corresponding to the first round surface 22 and the second round surface 26 are ground. The spherical grinding is performed, for example, with a cup-type grindstone having a rounded periphery. Next, in the gash grinding process P5, gash grinding is performed on the partial spherical portion 16a (ball blade 18). Next, in the flank grinding step P6, the first round surface 22 corresponding to the portion along the ball blade 18 on the spherical surface and the second round corresponding to the portion of the spherical surface facing the ball blade 18. Between the surface 26, the flank 24 corresponding to a diameter smaller than the diameter of the spherical surface (see FIG. 3) is ground. The flank 24 is ground by, for example, a flat grindstone. Next, in the lapping step P7, the spherical surface to be ground in the spherical grinding step P4, that is, the first round surface 22 and the second round surface 26 are lapped. In the lapping step P7, the flank 24 that is ground in the flank grinding step P6 is not lapped.

  Here, the manufacturing method of the said ball end mill 10 shown in FIG. 4 is realizable even if the order of each process is replaced. For example, the processing of the shank portion grinding step P1 may be performed after the processing from the neck / blade portion grinding step P2 to the lapping step P7 is performed. The processing of the spherical grinding step P4 may be performed after the processing of the flank grinding step P6. Furthermore, in order to obtain the configuration of the present embodiment relating to the ball end mill 10, the processing of the spherical grinding step P4 and the flank grinding step P6 may be performed, and the processing of the remaining steps is not necessarily required. In particular, the processing of the lapping step P7 may not be performed. Subsequent to the lapping step P7, a coating coating step of coating a hard coating such as TiAlN, TiN, TiCN or the like on the surface of the blade portion 16 or the like may be performed.

  Subsequently, a test conducted by the present inventors in order to verify the effect of the present invention will be described. FIG. 5 shows the configuration of the samples 1 to 10 used in this test (margin width, that is, the width of the first round surface 22, the second corner, whether or not lapping is performed), and the feed direction (cutting) as a test result of each sample It is a figure which shows collectively the maximum height Rz (JIS B 0601: 2001) of the circumferential direction of a material surrounding surface. The inventors prepared Samples 1 to 10 which are ball end mills having a configuration as shown in FIG. 5, and performed a cutting test on each sample under the following cutting conditions. Among the samples 1 to 10 shown in FIG. 5, the sample 1 is a conventional ball end mill (standard product) that does not include the first round surface 22 and has a flank surface formed along the ball blade 18. Samples 2 to 7 include the blade portion 16 on which the first round surface 22, the flank surface 24, and the second round surface 26 are formed, and the width dimension w1 of the first round surface 22 is 0.01 mm or more and 0. A ball end mill within a range of 10 mm or less. Samples 8 to 10 include a blade portion 16 on which the first round surface 22, the flank surface 24, and the second round surface 26 are formed. The width dimension w1 of the first round surface 22 is 0.01 mm or more and 0. A ball end mill as a comparative product that deviates from the range of 10 mm or less.

[Cutting conditions]
Work material: STAVAX (registered trademark) 50HRC
-Work material shape: R11mm core shape-Tool shape: R2 ball end mill-Spindle speed: 20000rpm
・ Feeding speed: 1000mm / min
・ Pick feed: 0.1mm
・ Cut amount: 0.05mm
・ Cutting oil: Center-through oil mist

  As shown in the test result of FIG. 5, the first round surface 22, the flank surface 24, and the second round surface 26 are provided with the blade portion 16, and the width dimension w <b> 1 of the first round surface 22 is 0. In Samples 2 to 7, which are ball end mills within a range of 0.01 mm or more and 0.10 mm or less, the surface roughness (maximum height) Rz in the feed direction of the cut surface after cutting is less than 1.2 μm and polished. It can be seen that a good surface roughness close to the machined surface after machining is obtained. In particular, in samples 2 to 5 which are ball end mills in which the width dimension w1 of the first round surface 22 is in the range of 0.015 mm or more and 0.05 mm or less, the surface roughness in the feed direction of the work surface after cutting ( The maximum height (Rz) is less than 1.0 μm, and it can be seen that particularly good surface roughness is obtained. In the sample 1 which is a conventional ball end mill that does not include the first round surface 22 and has a flank (second surface) corresponding to a second angle of 17 ° along the ball blade 18, The surface roughness Rz in the feed direction of the work surface is 1.38 μm, and a sufficiently good surface roughness is not obtained. The blade portion 16 is provided with the first round surface 22, the flank surface 24, and the second round surface 26. The width dimension w1 of the first round surface 22 is in the range of 0.01 mm or more and 0.10 mm or less. In samples 8 to 10 which are ball end mills as deviating comparative products, the surface roughness Rz in the feed direction of the cut surface after cutting is as large as 1.37 to 1.89 μm, which is sufficiently good as in sample 1. The surface roughness is not obtained. This is presumed to be caused by excessively rubbing the cut surface after cutting because the width dimension w1 of the first round surface 22 is relatively wide.

  Subsequently, another test conducted by the present inventors in order to verify the effect of the present invention will be described. The present inventors do not have the first round surface 22, and a second surface (flank) corresponding to a second angle of 17 ° is formed along the ball blade 18, and the width of the second surface. R2 ball end mill conventional product (standard product) with dimensions of 0.1 mm, ball blade rake angle of 5 °, and no coating, and the first round surface 22, relief surface 24 and second round surface 26 are formed. And a ball end mill 10 of the present embodiment in which the width dimension w1 of the first round surface 22 is 0.05 mm, and a cutting test is performed using the respective ball end mills under the cutting conditions. Went.

  6 to 9 exemplify a roughness curve indicating the surface roughness of the work surface after cutting by each sample as a result of the cutting test, and the work surface after the cutting by the conventional product is illustrated. FIG. 6 shows a roughness curve in the pick feed direction, FIG. 7 shows a roughness curve in the feed direction (circumferential direction of the work material circumferential surface), and picks the work surface after cutting by the ball end mill 10 of this embodiment. The roughness curve in the feed direction is shown in FIG. 8, and the roughness curve in the feed direction is shown in FIG. On the work surface corresponding to the roughness curve shown in FIGS. 6 and 7, that is, the work surface after cutting with a conventional product, the 10-point average roughness Ra (JIS B 0601: 2001) in the pick feed direction is 0.309 μm, the maximum The height Rz was 1.725 μm. The ten-point average roughness Ra in the feed direction was 0.214 μm, and the maximum height Rz was 1.379 μm. On the other hand, on the work surface corresponding to the roughness curves shown in FIGS. 8 and 9, that is, the work surface after cutting by the ball end mill 10 of this embodiment, the ten-point average roughness Ra in the pick feed direction is 0.05 μm, the maximum. The height Rz was 0.28 μm. The ten-point average roughness Ra in the feed direction was 0.03 μm, and the maximum height Rz was 0.24 μm. As is clear from these results, the surface roughness of the work surface after cutting by the ball end mill 10 of this embodiment is higher than the work surface after cutting by the conventional product in both the pick feed direction and the feed direction. It is greatly improved and it can be seen that a finish close to the machined surface after polishing is obtained.

  Thus, according to the present embodiment, the first round surface 22 corresponding to a part of the spherical surface of the partial spherical portion 16 a provided along the ball blade 18, and the first round surface 22. A flank 24 corresponding to a smaller diameter than the diameter of the spherical surface, provided on the opposite side of the ball blade 18, and provided on the opposite side of the first round surface 22 with respect to the flank 24. Since the second round surface 26 corresponding to a part of the spherical surface in the partial spherical portion 16a is provided, cutting is performed by the burnishing effect (burnishing) of the first round surface 22 and the second round surface 26. In addition to being able to improve the machined surface roughness after machining, the flank 24 is provided between the first round surface 22 and the second round surface 26 to suppress tool wear. Chatter It is possible to suppress the generation of equal suitably. In other words, it is possible to provide the ball end mill 10 that has a sufficiently good surface roughness after cutting.

  Since the width dimension w1 of the first round surface 22 is in the range of 0.01 mm or more and 0.10 mm or less, the surface roughness after cutting is as good as possible by necessary and sufficient burnishing. can do.

  The width dimension w2 of the flank 24 is not less than ½ of the round width w0, where the width dimension from the cutting edge to the heel of the ball blade 18 is the round width w0, and therefore has a sufficient flank. As a result, tool wear can be suppressed, and chatter vibration and the like can be more suitably suppressed.

  According to the present embodiment, there is provided a method for manufacturing the ball end mill 10 in which at least one ball blade 18 is formed on the partial spherical portion 16a provided at the tip of the tool body, and the spherical surface in the partial spherical portion 16a is ground. A spherical grinding step P4, a first round surface 22 corresponding to a portion of the spherical surface along the ball blade 18, and a second round surface 26 corresponding to a portion of the spherical surface facing the ball blade 18; , A flank grinding step P6 for grinding the flank 24 corresponding to a diameter smaller than the diameter of the spherical surface. That is, it is possible to provide a method for manufacturing a ball end mill that makes the surface roughness after cutting sufficiently satisfactory.

  The preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and may be implemented in other modes.

  For example, the ball end mill of the present invention realizes a surface roughness close to the polished surface with respect to the cut surface after cutting, but after the cutting of the work material by the ball end mill of the present invention, the work surface is polished. May be applied. Even in such an aspect, since the processing can be performed in a shorter time than the polishing of the work material cut by the conventional ball end mill, the effect of the present invention can be achieved.

  In the above-described embodiment, the width dimension w1 of the first round surface 22 is in the range of 0.01 mm or more and 0.10 mm or less, and the width dimension w2 of the flank 24 is ½ or more of the round width w0. Although a certain ball end mill 10 has been illustrated, these numerical ranges show the best embodiment, and even in configurations that deviate from such numerical ranges, the advantageous effects of the present invention are achieved.

  In addition, although not illustrated one by one, the present invention is implemented with various modifications within a range not departing from the gist thereof.

  10: ball end mill, 16a: partial spherical portion, 18: ball blade, 22: first round surface, 24: flank surface, 26: second round surface, P4: spherical grinding step, P6: flank grinding step

Claims (4)

A ball end mill in which at least one ball blade is formed in a partial spherical portion provided at the tip of a tool body,
A first round surface corresponding to a part of the spherical surface of the partial spherical portion provided along the ball blade;
A flank corresponding to a smaller diameter than the diameter of the spherical surface, provided on the opposite side of the ball blade to the first round surface;
And a second round surface corresponding to a part of the spherical surface of the partial spherical portion provided on the opposite side of the first round surface with respect to the flank. .   The ball end mill according to claim 1, wherein a width dimension of the first round surface is in a range of 0.01 mm or more and 0.10 mm or less.   3. The ball end mill according to claim 1, wherein a width dimension of the flank is not less than ½ of the round width when a width dimension from a cutting edge to a heel in the ball blade is a round width. A method of manufacturing a ball end mill in which at least one ball blade is formed in a partial spherical portion provided at the tip of a tool body,
A spherical grinding step of grinding a spherical surface in the partial spherical portion;
Between the first round surface corresponding to the portion along the ball blade in the spherical surface and the second round surface corresponding to the portion on the side facing the ball blade in the spherical surface, than the radial dimension of the spherical surface. And a flank grinding step of grinding a flank corresponding to a small diameter.

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