JP2018126832A - Taper ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a processing efficiency and a process tolerance, and a processed face quality in rib groove contour line processing.SOLUTION: Plural chip discharge grooves 4, which extend toward a rear end side, are formed on a tip circumference of an end mill body 1 which is rotated around an axis O, a cutting blade 5 is formed on each of outer peripheral edges of wall surfaces of these chip discharge grooves 4 which are directed in an end mill rotation direction T, partial cutting blades 5A of the cutting blades 5 comprise a bottom blade 5a of which a rotation locus around the axis O has a center on the axis O at a tip of the end mill body 1 and which has a semi-spherical shape, and a peripheral cutting edge 5b which extends from a rear end of the bottom blade 5a, of which a diameter of rotation locus around the axis O is gradually increased as approaching the rear end side, and which has a conical shape with the axis O as a center. The remaining cutting blades 5B of the cutting blades 5 comprise an auxiliary peripheral cutting edge 5c of which a rotation locus around the axis O extends to the rear end side from a rear end outer peripheral part of the rotation locus of the bottom blade 5a in the partial cutting blade 5A, and is overlapped on the rotation locus of the peripheral cutting edge 5b.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a tapered ball end mill used for processing a rib groove such as a mold.

  As such a tapered ball end mill, for example, Patent Document 1 discloses a tapered ball end mill including a tip ball blade (bottom blade), an outer peripheral blade continuous with the tip ball blade, and an outer peripheral blade that is not continuous with the tip ball blade. The total number of outer peripheral blades is an even number of 4 or more, and two end ball blades are provided in succession to a pair of outer peripheral blades in a substantially symmetrical position in front view of the end mill. For the outer peripheral blade that is not continuous, the distance between the position of the tip of the outer peripheral blade and the tip of the end mill is the length when measured in the axial direction, and 0.05 to 0.5 mm is added to the radius of the ball blade. It has been proposed that the length and the core thickness of the round 45 ° portion of the tip ball blade be 20 to 50% with respect to the blade diameter of the portion.

  According to such a tapered ball end mill, the distance between the position of the tip of the outer peripheral blade that is not continuous with the tip ball blade and the tip of the end mill is the length when measured in the axial direction, and is equal to the radius of the ball blade. 0.05 to 0.5 mm in length, that is, the tip of the outer peripheral blade that is not continuous with the tip ball blade is located on the rear end side of the end mill body from the rear end of the tip ball blade. Since the tip of the cutting edge deviates from the cutting edge portion where the amount of cutting is large, chipping and chipping of the tip of the outer peripheral blade during cutting can be suppressed, and the surface roughness and tool life of the cutting surface can be improved.

Japanese Patent No. 4573340

  By the way, the rib groove machining by such a taper ball end mill has conventionally been a reciprocating machining as described in Patent Document 1, but in recent years, a predetermined axis is obtained by pick feed set by CAM data. Contour line machining, in which machining is performed with a tool trajectory approaching the workpiece shape for each direction depth, is often used. In such contour processing of the rib groove, the outer peripheral portion of the rear end is frequently used for cutting in the hemispherical rotation trajectory formed by the tip ball blade around the axis of the end mill body.

  However, in the tapered ball end mill described in Patent Document 1, the outer peripheral blades other than the pair of outer peripheral blades that are continuous with the two distal ball blades among the four or more even outer peripheral blades as described above are the tip ball. Instead of being continuous with the blade, the rear end outer peripheral portion of the hemispherical rotation locus is also formed by two tip ball blades. For this reason, especially in the finishing process by contour processing, it is not possible to increase the processing efficiency, and it is difficult to ensure the processing accuracy and the quality of the processed surface.

  The present invention has been made under such a background, and provides a tapered ball end mill capable of improving machining efficiency even in contour machining of rib grooves and the like and obtaining high machining accuracy and machined surface quality. The purpose is that.

  In order to solve the above problems and achieve such an object, according to the present invention, a plurality of chip discharge grooves extending toward the rear end side are formed on the outer periphery of the front end portion of the end mill body rotated about the axis. Cutting edges are formed on the outer peripheral edges of the wall surfaces of the chip discharge grooves facing the end mill rotation direction, and some of the cutting edges of the cutting edges are around the axis at the end of the end mill body. A bottom blade having a hemispherical shape whose rotation locus is centered on the axis, and the axis that extends from the rear end of the bottom blade and gradually increases in diameter as the rotation locus around the axis moves toward the rear end. A conical outer peripheral blade, and the remaining cutting edges of the cutting blades have a rotational trajectory around the axis line from the rear outer peripheral portion of the bottom blade in the partial cutting edge to the rear end side. Auxiliary that overlaps the rotation trajectory of the outer peripheral blade Characterized in that it comprises a circumferential edge.

  In the tapered ball end mill configured as described above, among the plurality of cutting blades formed on the outer peripheral edge of the wall surface facing the end mill rotation direction of the plurality of chip discharge grooves, some of the cutting blades are formed on the end mill body. Along with a bottom blade (tip ball blade) whose rotation trajectory around the axis forms a hemisphere, the remaining cutting blades are auxiliary outer peripheral blades extending from the rear end outer periphery of the hemisphere formed by the rotation trajectory of the bottom blade to the rear end side. Therefore, the rear end outer peripheral portion of the bottom blade rotation trajectory is constituted by both the bottom blades of the partial cutting blades and the auxiliary outer peripheral blades of the remaining cutting blades. That is, since it is possible to increase the number of blades at the outer peripheral portion of the rear end of the bottom blade that is frequently used in contour line processing, it is possible to improve the processing efficiency and obtain high processing accuracy and surface quality.

  Here, the straight line connecting the intersection of the rotation locus around the axis of the tip of the auxiliary outer peripheral blade and the bottom blade and the center of the hemisphere formed by the rotation locus of the bottom blade is the rear end side of the end mill body. However, the crossing angle with respect to the axis of the straight line when tilting and intersecting the axis at the center is in the range of 60 ° to 80 °. Is desirable. When this crossing angle approaches 90 ° beyond the above range, the part of the remaining cutting edge that overlaps the bottom edge of some of the cutting edges at the tip of the auxiliary outer peripheral cutting edge becomes too short and is processed during contour processing. While there is a risk that efficiency, machining accuracy, and machined surface quality cannot be improved sufficiently, if the number falls below the above range, especially when the number of cutting edges is large, the chip discharge groove capacity at the most advanced part of the end mill body May become small and cause clogging of chips or insufficient strength.

  In addition, the end mill body is located on the inner side of the rotation locus of the bottom blade so that the end mill body does not interfere with the machining surface formed by the bottom blade on the tip side of the auxiliary outer peripheral blade of the remaining cutting blade. Have been retreated. Here, in the case where the part of the plurality of cutting blades and the remaining cutting blades are alternately formed in the circumferential direction on the outer periphery of the end portion of the end mill body, auxiliary peripheral blades of the remaining cutting blades The tip side is closer to the flank of the bottom edge of some cutting edges adjacent to the end mill rotation direction of the remaining cutting edges, and to some cutting edges adjacent to the opposite side of the remaining cutting edges in the end mill rotation direction. It is desirable that the bottom blade is formed so as to intersect with the gash wall surface of the bottom blade. By leaving the flank face of the bottom blade in some of the cutting edges at the tip end portion of the end mill body, it is possible to ensure the cutting edge strength at the tip end portion of the end mill body of the bottom blade.

  As described above, according to the present invention, it is possible to improve machining efficiency and obtain high machining accuracy and machined surface quality, particularly in contour machining of rib grooves and the like.

It is a side view which shows one Embodiment of this invention. It is an enlarged side view of the front-end | tip part of embodiment shown in FIG. FIG. 2 is an enlarged front view around the center of rotation when the embodiment shown in FIG. 1 is viewed from the front end side in the axial direction.

  1 to 3 show an embodiment of the present invention. In the tapered ball end mill of the present embodiment, the end mill main body 1 is formed of a hard material such as cemented carbide in a cylindrical shaft shape with the axis O as the center as shown in FIG. 1, and the rear end side (FIGS. 1 and 2). The portion on the right side in FIG. 2 is the shank portion 2 that remains in a cylindrical shape, and the portion on the tip side (the left side in FIGS. 1 and 2) is the cutting blade portion 3. In such a tapered ball end mill, the shank portion 2 is gripped by the spindle of the machine tool and rotated in the end mill rotation direction T around the axis O, and the contour material is applied to a work material such as a die to form a rib. Used to form grooves.

  As shown in FIG. 1, the cutting edge portion 3 is formed in a substantially conical shape having an outer diameter that gradually decreases toward the front end side, and the outer periphery of the cutting edge portion 3 rotates from the front end of the end mill body 1 toward the rear end side. A plurality of chip discharge grooves 4 that are twisted in the direction opposite to the direction T are formed. In this embodiment, four pieces of chip discharge grooves 4 are formed at equal intervals in the circumferential direction. And the cutting edge 5 which makes this wall surface a scoop surface is formed in the outer periphery of the wall surface which faces the end mill rotation direction T of these chip discharge grooves 4, respectively, Therefore, 4 is provided in the end mill main body 1 of this embodiment. A strip cutting edge 5 is formed.

Among these cutting blades 5, every other cutting blade 5 in the circumferential direction is a part of the cutting blade 5A in the present embodiment, and every other cutting blade 5 in the remaining circumferential direction is implemented in this embodiment. The remaining cutting blade 5B in the form is used. The part of the cutting blades 5A includes a bottom blade 5a having a hemispherical shape in which a rotation locus around the axis O at the tip of the cutting blade portion 3 of the end mill body 1 has a center C on the axis O, and a rear of the bottom blade 5a. An outer peripheral blade 5b having a conical shape centering on the axis O whose diameter gradually increases as the rotation trajectory around the axis O moves toward the rear end side so as to match the cone formed by the outer shape of the cutting blade portion 3 extending from the end. I have.
The flank of the outer peripheral blade 5b is a minute second surface (flank surface) having a minute width from the outer peripheral blade 5b to the side opposite to the end mill rotation direction T, and further from the minute second surface opposite to the end mill rotation direction T. It is desirable to provide a large main second surface (flank) having a clearance angle larger than the minute second surface toward the side. By providing such a minute second surface, it is possible to suppress the wear on the minute second surface and increase the wear width of the outer peripheral blade 5b.

  Here, the tip of the chip discharge groove 4 formed on the outer peripheral edge of the wall surface in which the part of the cutting blade 5A faces the end mill rotation direction T is recessed toward the inner periphery as it goes toward the tip of the end mill body 1. A groove-like gash 6 is formed. The bottom blade 5a is formed on the outer peripheral edge of the wall surface 6a facing the end mill rotation direction T of the gash 6, that is, at the intersecting ridge line portion between the wall surface 6a and the flank 7 that is continuous with the end mill rotation direction T of the bottom blade 5a. The rotation trajectory is formed so as to form a hemisphere as described above.

  In this embodiment, when viewed from the front end side in the axis O direction, as shown in FIG. 3, the gash 6 of the bottom blade 5a of the cutting blades 5A of the two strips does not intersect the axis O. It is formed so that it slightly crosses over. Thereby, chip discharge | emission property can be improved more. Further, the flank 7 of the bottom blade 5a has a first flank (second surface) 7a, a second flank (third surface) 7b, and the flank angle sequentially increases toward the opposite side of the end mill rotation direction T. And a third flank (fourth surface) 7c.

On the other hand, the remaining cutting blade 5B has a rotation trajectory around the axis O extending from the rear end outer peripheral portion of the rotation trajectory of the bottom blade 5a in the partial cutting blade 5A toward the rear end side. The auxiliary outer peripheral blade 5c is provided so as to overlap the rotation trajectory of the outer peripheral blade 5b of the cutting blade 5A. That is, the auxiliary outer peripheral blade 5c of the remaining cutting blade 5B extends from the outer peripheral portion in front of the rotation trajectory around the axis O to the rear end of the bottom blade 5a in a part of the cutting blade 5A, to the rear end side. It is formed in the same shape and size so as to overlap with a portion other than the tip of the bottom blade 5a. In addition, the tip of the end mill main body 1 at the portion corresponding to the tip of the bottom blade 5a of a part of the cutting blade 5A on the tip side of the auxiliary outer peripheral blade 5c that does not overlap the rotation locus is the rotation of the bottom blade 5a. It is formed by cutting out so as to recede toward the inner circumference side with respect to the locus.
The flank of the auxiliary outer peripheral blade 5c also has a minute second surface (flank) having a minute width from the auxiliary outer peripheral blade 5c to the side opposite to the end mill rotation direction T, and further from the minute second surface to the end mill rotation direction T. It is desirable to provide a large main second surface (flank) having a larger clearance angle than the minute second surface toward the opposite side. By providing such a minute second surface, it is possible to suppress the wear on the minute second surface and increase the wear width of the auxiliary outer peripheral blade 5c.

  Here, a straight line L connecting the intersection Q of the rotation locus around the axis O of the tip P of the auxiliary outer peripheral blade 5c and the bottom blade 5a and the center C of the hemisphere formed by the rotation locus of the bottom blade 5a is shown in FIG. As shown in FIG. 2, as it goes toward the rear end side of the end mill main body 1, it inclines toward the inner peripheral side and intersects with the axis O at the center C. The crossing angle θ formed by the straight line L with respect to the axis O at the center C is preferably in the range of 60 ° to 80 °, and is set to 70 ° in this embodiment.

  Note that the tip of the end mill body 1 cut out as described above on the tip side of the auxiliary outer peripheral blade 5c of the remaining cutting blade 5B as described above is the end mill rotation of the remaining cutting blade 5B in this embodiment. The flank 7 of the bottom blade 5a of a part of the cutting blade 5A adjacent to the direction T and the bottom blade 5a of the part of the cutting blade 5A adjacent to the opposite side of the end mill rotation direction T of the remaining cutting blade 5B. When the gash wall surface (the wall surface facing the direction opposite to the end mill rotation direction T of the gash 6) 6b intersects, the rotation trajectory around the axis O forms the rotation trajectory of the bottom blade 5a of some cutting edges 5A. It is formed so as to have a convex curve shape that recedes inward from the hemisphere.

  In the tapered ball end mill having such a configuration, the rear end outer peripheral portion of the hemispherical rotation locus formed by the bottom blades 5a of some of the cutting blades 5A around the axis O is composed of the bottom blade 5a and the bottom blade 5a. It is comprised by the auxiliary | assistant outer periphery blade 5c of the remaining cutting blade 5B which has the rotation locus | trajectory which overlaps with the rotation locus | trajection to make at the front-end | tip part. For this reason, the outer periphery of the rear end of the bottom blade 5a, which is frequently used when processing contour lines such as rib grooves, can be made into multiple blades, and the feed rate per blade can be increased to improve the processing efficiency. In addition, even if the feed amount is increased in this way, high machining accuracy and machined surface quality can be obtained.

  On the other hand, at the most distal end portion of the end mill body 1 on the distal end side of the auxiliary outer peripheral blade 5c of the remaining cutting blade 5B, the rotation trajectory is continuous with the auxiliary outer peripheral blade 5c in the same manner as the bottom blade 5a. In this embodiment, it is formed so as to recede to the inner side of the hemispherical rotation locus of the bottom blade 5a. For this reason, as in the case of trying to form a bottom blade on the tip side from the auxiliary outer peripheral blade 5c, the number of the gashes 6 at the most distal end portion of the end mill main body 1 increases, leading to a decrease in strength, There is no need to make it small, and chip clogging does not occur.

  Further, in this embodiment, a straight line L connecting the intersection Q of the rotation locus around the axis O of the tip P of the auxiliary outer peripheral blade 5c and the bottom blade 5a and the center C of the hemisphere formed by the rotation locus of the bottom blade 5a is formed. In this center C, the crossing angle θ with respect to the axis O when intersecting the axis O is in the range of 60 ° to 80 °, thereby reliably preventing the strength reduction and chip clogging of the end portion of the end mill body 1. However, it is possible to further improve the processing efficiency, processing accuracy, and processing surface quality.

  That is, when the crossing angle θ exceeds the above range, the portion where the tip of the auxiliary outer peripheral blade 5c overlaps with the bottom blade 5a becomes too short, and the processing efficiency, processing accuracy, and surface quality are sufficiently improved during contour processing. There is a risk that it cannot be improved. On the other hand, when the crossing angle θ is less than the above range, the auxiliary outer peripheral blade 5c extends closer to the foremost end of the end mill main body 1, and the capacity of the chip discharge groove 4 and the gash 6 becomes small, and chip clogging occurs. There is a risk that it will occur or the strength will be insufficient.

  Furthermore, in this embodiment, some cutting edges 5A and the remaining cutting edges 5B of a plurality of strips are alternately formed in the circumferential direction on the outer periphery of the tip portion (cutting blade portion 3) of the end mill body 1. On the other hand, the tip end side of the remaining cutting blade 5B from the auxiliary outer peripheral blade 5c is the flank 7 (third) of the bottom blade 5a of a part of the cutting blade 5A adjacent to the end mill rotation direction T of the remaining cutting blade 5B. The relief surface 7c) and the gash wall surface of the bottom blade 5a of a part of the cutting blades 5A adjacent to the side opposite to the end mill rotation direction T of the remaining cutting blade 5B (the side opposite to the end mill rotation direction T of the gash 6) (Between facing wall 6b) is cut out so as to intersect, and as described above, the rotation trajectory around the axis O is formed in a convex curve shape retreating inward from the hemisphere formed by the bottom blade 5a.

  For this reason, the flank 7 of the bottom blade 5a is left as it is on the tip side of the auxiliary outer peripheral blade 5c on the side opposite to the end mill rotation direction T of the bottom blade 5a. In this embodiment, which is a four-flute taper ball end mill in which the remaining cutting blades 5B are formed in two strips, the tip end side of the remaining cutting blade 5B is the same as that of the two-flute taper ball end mill. It can be set as this structure. Therefore, the cutting edge strength of the bottom blade 5a and the strength of the end mill body 1 itself on the tip side of the auxiliary outer peripheral blade 5c can be ensured to prevent the occurrence of defects or the like.

  Next, the effect of the present invention will be demonstrated with examples. In this example, the crossing angle θ is set to 70 ° based on the above embodiment, the crossing angle θ is set to the upper and lower limits of 80 ° and 60 ° within the above range, and slightly below the above range. Five types of tapered ball end mills having an intersection angle θ of 55 ° and 85 ° slightly exceeding the above range were produced. These are designated as Examples 1 to 5 in order from the smallest crossing angle θ to the largest.

  Further, as a comparative example with respect to Examples 1 to 5, the crossing angle θ is 0 °, that is, the four cutting blades 5 all have a bottom blade 5a having a hemispherical rotation locus, and the crossing angle θ. 90 °, that is, the remaining cutting blade 5B overlaps only the outer peripheral blade 5b without having a portion where the rotation trajectory overlaps the bottom blade 5a of some cutting blades 5A, and the crossing angle θ is larger than 90 °. That is, the tip of the outer peripheral blade that is not continuous with the bottom blade (tip ball blade) is at the rear end side of the end mill body from the rear end of the tip ball blade, as in the tapered ball end mill described in Patent Document 1. What was located was made. These are also referred to as Comparative Examples 1 to 3 in descending order of the crossing angle θ.

  The tapered ball end mills of Examples 1 to 5 and Comparative Examples 1 to 3 are made of cemented carbide, the radius of the hemisphere formed by the rotation locus of the bottom blade 5a is 0.5 mm, and the taper angle of the outer peripheral blade 5b is 0. The blade length in the direction of the axis O from the tip of the bottom blade 5a on the axis O of the bottom blade 5a to the rear end of the outer blade 5b was 10 mm, and the twist angle of the outer blade 5b was 25 °.

  Then, with the tapered ball end mills of Examples 1 to 5 and Comparative Examples 1 to 3, rib grooves are formed on the work material made of chromium molybdenum steel (SCM420) by contour processing, and the surface roughness of the groove wall surface at that time is formed. (The arithmetic average roughness Ra in JIS B 0601: 2001) and the maximum driving force required to rotate the tapered ball end mill were measured. The results are shown in Table 1 in order from the smallest crossing angle θ to the largest. The processed rib groove has a groove depth of 10 mm, a groove width of 1.1 mm, a rib groove gradient angle of 0.75 °, and a groove length of 50 mm. The finishing conditions are as follows: the end mill body 1 has a rotational speed of 15000 rpm / min, the feed rate is 750 mm / min, the cutting depth per axis O direction is 0.03 mm, and is a water-soluble cutting fluid. It was a wet process using.

  From Table 1, regarding the surface roughness, in Comparative Example 1 and Examples 1 to 4 where there are many portions where the rotation trajectories of the bottom blades 5a of some of the cutting blades 5A and the auxiliary outer peripheral blades 5c of the remaining cutting blades 5B overlap. Nearly equivalent good results were obtained. In Example 5, the surface roughness tended to be lower than that of Comparative Example 1 and Examples 1 to 4, but the difference was slight.

  On the other hand, in Comparative Examples 2 and 3 in which the remaining cutting blade 5B does not have a portion that overlaps the rotation locus of the bottom blade 5a of some of the cutting blades 5A, the rear end outer peripheral portion of the hemispherical rotation locus is Since only the bottom blades 5a of some of the two cutting blades 5A are formed, the surface roughness is significantly lower than those of Examples 1 to 5 and Comparative Example 1 at the constant feed rate as described above. It was.

  Next, when comparing the maximum rotational driving force, contrary to the case of surface roughness, in Comparative Example 1 in which all of the four cutting blades 5 have a bottom blade 5a having a hemispherical rotation locus, In order to perform contour line processing while satisfying the above processing conditions, an extremely large driving force was required as compared with the other Comparative Examples 2 and 3 and Examples 1 to 5. Further, when the tapered ball end mill of Comparative Example 1 after the completion of processing was observed, chip clogging and remarkable wear were observed in the bottom blade 5a, particularly in the vicinity of the rotation center of the inner periphery of the end of the end mill body 1.

  On the other hand, in Examples 2 to 5 and Comparative Examples 2 and 3, it is possible to perform contour processing that satisfies the above processing conditions with substantially the same driving force without requiring a driving force as large as Comparative Example 1. Efficient processing was possible. Further, in Example 1, a large driving force was required as compared with Examples 2 to 5 and Comparative Examples 2 and 3, but the difference was not as large as that of Comparative Example 1.

  Therefore, according to the results of the surface roughness and the maximum rotational driving force, according to Examples 1 to 5, it is possible to achieve both processing efficiency, processing accuracy, and processing surface quality in contour processing, and the crossing angle θ is According to Examples 2 to 4 within the above range, it is recognized that it is possible to improve the processing efficiency, the processing accuracy, and the processing surface quality more reliably.

1 End Mill Body 2 Shank 3 Cutting Edge (End Mill End 1 End)
4 Chip discharge groove 5 Cutting blade 5A Some cutting blades 5B Remaining cutting blade 5a Bottom blade 5b Outer peripheral blade 5c Auxiliary outer peripheral blade 6 Gash 6a Wall surface facing the end mill rotation direction T of Gash 6 6b Gash wall surface (end mill rotation of Gash 6) Wall surface facing away from direction T)
7 Flank of bottom blade 5a 7a 1st flank (No. 2 surface)
7b Second flank (No. 3)
7c Third flank (No. 4)
O End mill body 1 axis T End mill rotation direction C Center of hemisphere formed by rotation trajectory around axis O of bottom blade 5a P Tip of auxiliary outer peripheral blade 5c Q Rotation trajectory around axis O of tip P of auxiliary outer peripheral blade 5c and bottom Intersection L with the blade 5a L Straight line connecting the intersection Q and the center C The intersection angle formed by the straight line L with respect to the axis O

Claims (3)

A plurality of chip discharge grooves extending toward the rear end side are formed on the outer periphery of the end portion of the end mill body rotated about the axis, and the chip discharge grooves are respectively cut on the outer peripheral edge of the wall surface facing the end mill rotation direction. The blade is formed,
Some of the cutting blades have a hemispherical bottom blade whose rotation locus around the axis is centered on the axis at the tip of the end mill body, and extends from the rear end of the bottom blade. An outer peripheral blade having a conical shape centered on the axis, the diameter of which gradually increases as the rotation trajectory around the axis moves toward the rear end side,
Among the cutting blades, the remaining cutting blades have a rotation trajectory around the axis extending from the rear outer peripheral portion of the bottom blade rotation trajectory to the rear end side of the part of the cutting blades to the rotation trajectory of the outer peripheral blade. A taper ball end mill characterized by comprising overlapping auxiliary outer peripheral blades.   The straight line connecting the intersection of the rotation locus around the axis of the tip of the auxiliary outer peripheral blade and the bottom blade and the center of the hemisphere formed by the rotation locus of the bottom blade is an intersection within a range of 60 ° to 80 °. 2. The tapered ball end mill according to claim 1, wherein the axis intersects the axis at the center at a corner.   On the outer periphery of the end portion of the end mill body, the plurality of partial cutting blades and the remaining cutting blades are alternately formed in the circumferential direction, and more than the auxiliary outer peripheral blades of the remaining cutting blades. The tip side is the flank of the bottom edge of the part of the cutting blade adjacent to the remaining cutting edge in the end mill rotation direction and the part of the cutting edge adjacent to the opposite side of the remaining cutting edge in the end mill rotation direction. The tapered ball end mill according to claim 1 or 2, wherein the bottom edge of the blade is notched so as to intersect with the gash wall surface.

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