JP2006015417A - End mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an end mill capable of surely preventing the occurrence of chattering vibration caused by excessive biting of an outer peripheral cutting blade and chipping or the like caused by the impact at the time of biting while suppressing the increase of cutting resistance and cutting heat. <P>SOLUTION: The outer peripheral cutting blade 5, which is directed to the rear side in the rotating direction T of an end mill body 1 as going toward the rear end side of the end mill, is formed to the outer periphery at the tip side of the end mill body 1 rotated around the axis line O. A margin part 8 or a first flank continuous to the outer peripheral cutting blade 5 and a second flank 9, which has a flank angle larger than the margin part 8 or the first flank, are formed to at least a flank 7 on the tip side of the end mill in the outer peripheral cutting blade 5. The width of the margin part 8 or the first flank on the tip side of the end mill is made to be in the range of 0.01-0.1 mm, and also, that of the flank 7 on the rear end side of the end mill is made smaller than that of on the tip side of the end mill. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an end mill in which an outer peripheral cutting edge is formed on the outer periphery of a tip end portion of an end mill main body.

  As this type of end mill, for example, in Patent Document 1, a first flank is provided along the outer peripheral cutting edge of the end mill, and a second flank connected to the first flank is provided. The width is set to 1/2000 to 1/100 of the end mill blade diameter (specifically, 0.05 mm with respect to the end mill blade diameter of 6 mm), or the clearance angle of the first flank exceeds 2 ° and is 5 ° or less, The clearance angle of the second flank is greater than 10 degrees and 20 degrees or less, and the width of the first flank is 1/100 to 1/10 of the width of the second flank (specifically, the end mill blade diameter is 10 mm). The second flank width of 1.5 mm is 0.06 mm). Patent Document 2 describes an end mill in which a margin portion having a width of 0.05 mm or less is formed on the flank of the outer peripheral cutting edge, and Patent Document 3 further describes an end mill in which a margin portion having a width of 0.04 mm or less is formed. ing.

And among these, in patent document 1, this 1st flank vibration is prevented by providing the 1st flank with a small flank angle along an outer periphery cutting edge, but preventing the chatter vibration when the biting with respect to a work material is too strong, this 1st flank. By setting the width of the surface as small as described above, the increase in the contact width of the first flank with the work material due to the progress of wear is reduced to prevent an increase in the cutting resistance due to friction. It is described that it is possible to prevent the workpiece surface from being roughened due to welding, frictional vibration of the work material, chipping and chipping of the cutting edge, and breakage of the end mill.
JP 2000-246532 A JP-A-5-345212 JP-A-11-277320

  As described above, in order to prevent chatter vibration due to excessive biting of the outer peripheral cutting edge, when the margin part or the first flank having a small flank angle is formed on the flank of the outer peripheral cutting edge, these scrape with the work material. Since it is a part, the cutting resistance is increased and the generation of cutting heat and the like are increased. Therefore, it is desirable to make the width as small as possible as described in Patent Documents 1 to 3. However, on the other hand, it is not easy to reduce the width of the margin part and the first flank over the entire length of the outer peripheral cutting edge because of manufacturing variations.

  In particular, when the width of the first flank is set to 1/2000 of the lower limit with respect to the end mill blade diameter as described in Patent Document 1, the case of the end mill blade diameter of 6 mm or 10 mm described in Patent Document 1 is the first. The width of one flank is less than 0.01 mm, and it is extremely difficult to form such a very narrow first flank and margin with a constant width along the outer peripheral cutting edge. Accordingly, when the width of the margin part or the first flank is reduced to reduce the cutting resistance in this way, if this width becomes too small, the occurrence of chatter vibration due to the biting of the outer peripheral cutting edge is prevented. On the other hand, the finished surface accuracy may be deteriorated, or the outer cutting edge may be chipped or chipped due to the impact at the time of biting.

  The present invention was made under such a background, and while suppressing increase in cutting resistance and cutting heat, chatter vibration due to excessive biting of the outer peripheral cutting edge, chipping due to impact at the time of biting, chipping, etc. The object is to provide an end mill that can be reliably prevented.

  In order to solve the above-described problems and achieve such an object, the present invention provides a rear end side in the rotational direction of the end mill body toward the rear end side of the end mill on the outer periphery of the end mill body rotated about the axis. An outer peripheral cutting edge is formed, and at least a flank on the end mill tip side of the outer peripheral cutting edge is larger than a margin part or a first flank connected to the outer peripheral cutting edge and the margin part or the first flank. A second flank having a clearance angle, and the width of the margin portion or the first flank is in a range of 0.01 to 0.1 mm on the end mill tip side, and the end mill rear end side flank The surface is smaller than the end mill tip side.

  That is, in the end mill that is formed so that the outer peripheral cutting edge is directed toward the rear side in the rotation direction of the end mill body as it goes toward the rear end side of the end mill, the end mill tip side portion of the outer peripheral cutting edge is the rotation direction of the end mill main body. Since it is located on the side, it will first touch the work material and bite. Therefore, on the flank of the outer peripheral cutting edge on the end mill tip side, the first flank having a margin portion or a small flank angle with a width in the range of 0.01 to 0.1 mm which is as small as possible within a range in which manufacturing variations can be prevented. By forming, chatter vibration due to excessive biting of the outer peripheral cutting edge can be prevented, and chipping and chipping of the outer peripheral cutting edge due to impact at the time of biting can also be prevented.

  On the other hand, the outer peripheral cutting edge on the rear end side of the end mill located on the rear side in the rotation direction of the end mill body is guided to the outer peripheral cutting edge on the end mill tip side that bites into the work material in this manner. Since it bites in, the biting does not become stronger than the end mill tip side and impact does not act. Accordingly, the margin portion of the flank and the width of the first flank may be smaller than the end mill tip side even if there is some variation, thereby increasing the cutting resistance and heat of the outer peripheral cutting edge as a whole. It can suppress, and it becomes possible to prevent situations, such as breakage of an end mill.

  Here, in order to make the width of the margin part or the first flank on the flank face of the outer peripheral cutting edge smaller on the rear end side of the end mill than on the front end side of the end mill, the margin part or the first flank face is one. May be formed so that the width thereof gradually decreases from the front end side of the end mill toward the rear end side of the end mill, that is, the margin portion or the first flank gradually decreases toward the rear end side of the end mill. As another example, the width of the margin portion or the first flank may be reduced stepwise from the end mill front end side toward the end mill rear end side.

  Further, the margin portion or the first flank is formed only on the end mill tip side portion of the flank of the outer peripheral cutting edge, and on the rear end side of the end mill, more than the margin portion or the first flank at the end mill tip. A flank having a large flank angle is formed so as to be continuous with the outer peripheral cutting edge, that is, a flank on the rear end side of the end mill is not formed with a margin part or a first flank with a small flank angle, or on the rear end side of the end mill The width of the margin part or the first flank may be zero. When the margin portion or the first flank is formed only on the end mill tip side, the margin portion or the first flank is equal to the outer diameter of the outer peripheral cutting edge in the axial direction from the tip of the outer peripheral cutting edge. It is desirable to form only in the part up to the length, and if it extends to the rear end of the end mill, the cutting resistance may increase.

  In addition, when the first flank and the second flank having a larger flank than the first flank are formed on at least the end mill tip side of the flank of the outer peripheral cutting blade, In other words, when the first flank face that is small but has a flank angle is formed so as to be continuous with the outer peripheral cutting edge, rather than the cylindrical margin portion having no flank angle, the flank angle of the first flank face is formed. Is preferably in the range of 1/4 to 1/2 of the clearance angle of the second flank. That is, if a small clearance angle smaller than ¼ of the clearance angle of the second flank is to be given to the first flank, an error is likely to occur due to manufacturing variations, and conversely the clearance angle of the second flank. Giving a large clearance angle greater than 1/2 of the first flank on the end mill tip side will increase the biting of the work piece, impairing the chatter vibration suppression effect, or causing chipping due to impact when biting It may be difficult to prevent.

  1 and 2 show a first embodiment of the present invention. In this embodiment, the end mill main body 1 is formed in a substantially cylindrical shape centering on the axis O by a hard material such as cemented carbide, and a rear end portion (right side portion in FIG. 1) not shown is a cylindrical shank portion. On the other hand, the tip portion (left side portion in FIG. 1) is the cutting edge portion 2, and the shank portion is attached to the main spindle of the machine tool and is rotated in the end mill rotation direction indicated by the symbol T in the drawing. By being sent out in a direction crossing the axis O, the cutting edge portion 2 performs side cutting, grooving, shoulder cutting and the like on the work material.

  On the outer periphery of the cutting edge portion 2, a plurality of strips (two strips in the present embodiment) twisted to the rear side in the end mill rotation direction T around the axis O as it goes from the front end to the rear end side of the end mill body 1. Chip discharge grooves 3 are formed at equal intervals in the circumferential direction, and an outer peripheral cutting edge 5 having a rake face 4 as a rake face 4 is formed on the outer peripheral side ridges of the wall surfaces of the chip discharge grooves 3 facing the end mill rotation direction T. Similarly to the chip discharge groove 3, it is formed in a spiral shape that twists at a constant twist angle toward the rear side in the end mill rotation direction T around the axis O as it goes toward the rear end side of the end mill body 1. In addition, a bottom blade 6 having a rake face as the wall surface is also provided at a ridge portion on the tip side of the wall surface of the chip discharge groove 3 from the tip of the outer peripheral cutting blade 5 in the present embodiment substantially perpendicularly to the axis O in the present embodiment. That is, the end mill of this embodiment is a two-blade square end mill.

  Further, a flank (outer flank) 7 of the outer peripheral cutting edge 5 is formed on the rear side in the end mill rotation direction T of the outer peripheral cutting edge 5 formed as described above, in other words, the outer peripheral cutting edge 5. Is formed at the intersection ridge line portion of the flank 7 and the rake face 4. Here, in the present embodiment, the flank 7 has a margin portion 8 that continues from the outer peripheral cutting edge 5 to the rear side in the end mill rotation direction T, as shown in FIG. 2 flank 9, and further the rear side of the second flank 9 in the end mill rotation direction T is moved backward by one step toward the inner peripheral side of the end mill body 1 with respect to the second flank 9. The outer peripheral cutting edge 5 is connected to the rake face 4.

  The margin portion 8 is also referred to as a first flank that is not provided with a flank angle (the flank angle α is 0 °) with respect to the second flank surface 9 provided with a clearance angle β as shown in FIG. That is, it is formed on a cylindrical surface centering on the axis O of the end mill body 1. In the present embodiment, the width A of the margin portion 8 is gradually reduced from the front end of the outer peripheral cutting edge 5 toward the rear end side of the end mill as shown in FIG. The width A of the portion 8 is made smaller at the flank 7 on the end mill rear end side than on the end mill front end side. Further, the width A of the margin portion 8 is in a range of 0.01 to 0.1 mm on the end mill tip side.

  In this embodiment, the width A of the margin portion 8 is made sufficiently smaller than the width B of the second flank 9 over the entire length of the cutting edge portion 2, but the width of the flank 7 as a whole. Since W is constant over the entire length of the cutting edge portion 2, the width B of the second flank 9 is made larger on the rear end side of the end mill than on the front end side, contrary to the width A of the margin portion 8. It becomes. Further, the margin portion 8 may be formed over the entire length from the front end to the rear end of the outer peripheral cutting edge 5, but as described above, a width of 0.01 to 0.1 mm at the end mill front end side. If A is secured, the width A becomes 0 on the way to the rear end side of the end mill, and the entire flank 7 is formed only by the second flank 9 having the flank angle β on the rear end side. It may be configured.

  When cutting is performed while rotating the end mill body 1 in the end mill rotation direction T as described above by the end mill configured as described above, the end mill is directed toward the rear end side of the end mill toward the rear side in the end mill rotation direction T. The outer peripheral cutting edge 5 is cut into the work material from the tip and is cut toward the rear end side of the end mill as the end mill body 1 rotates. In the end mill having the above-described configuration, the margin portion 8 is 0.01 to 0.1 mm so as to continue to the outer peripheral cutting edge 5 on the flank 7 on the end mill distal end side of the outer peripheral cutting edge 5 that first bites on the work material. Therefore, it is possible to prevent the occurrence of chatter vibrations by preventing the biting of the work material from becoming too strong, and to improve the finished surface accuracy. The edge strength of the outer peripheral cutting edge 5 on the side can be strengthened to prevent the occurrence of chipping and chipping due to impact at the time of biting.

  On the other hand, in the flank 7 of the outer peripheral cutting edge 5 on the rear end side of the end mill where a large impact or the like does not act because it is cut into the work material so as to be guided to the end side of the end mill, the margin portion 8 has a width A smaller than that at the tip end side of the end mill. Therefore, while preventing chipping and chipping on the rear end side of the end mill, the entire outer peripheral cutting edge 5 has an increased cutting resistance due to the margin 8 and The accompanying cutting heat can be suppressed, and as a result, the end mill body 1 can be prevented from being broken and the tool life can be extended. In addition, the width A of the margin portion 8 thus reduced on the rear end side of the end mill does not have to be formed with a predetermined width with such a strict accuracy. For example, the width A is directed toward the rear end side of the end mill as in this embodiment. Even when the width A is gradually reduced, there are some errors due to manufacturing variations, the reduction rate of the width A is changed, or the width A becomes 0 in the middle as described above. Since the margin portion 8 may not be formed, the flank 7 can be formed relatively easily.

  Here, if the width A of the margin part 8 on the end mill tip side is so small that it is less than 0.01 mm, the biting when the outer peripheral cutting edge 5 on the end mill tip side bites the work material for the first time is too strong. There is a possibility that chatter vibration may occur, and there is a possibility that chipping or chipping may occur in the outer peripheral cutting edge 5 due to the impact at the time of biting. On the other hand, if the width A of the margin portion 8 on the end mill tip side is larger than 0.1 mm, cutting resistance and cutting heat may not be sufficiently reduced in the entire outer peripheral cutting edge 5, The width A of the margin portion 8 that is larger than the rear end side at the end mill front end side is in the range of 0.01 to 0.1 mm as described above.

  Further, in the present embodiment, the width A of the margin portion 8 is gradually reduced toward the rear end side of the end mill, and even if there is a slight error or a variation in the reduction rate as described above, the outer peripheral cutting edge Since the cutting force acting on 5 can be continuously reduced toward the rear end side of the end mill, the cutting force changes suddenly at a specific portion of the outer peripheral cutting edge 5 and the load is concentrated. No chipping or chipping is likely to occur. When the width A of the margin portion 8 is gradually reduced toward the rear end side of the end mill in this way, the outer diameter of the outer peripheral cutting edge 5 (the diameter of the cylinder formed by the outer peripheral cutting edge 5 around the axis O, that is, the end mill blade diameter). ) Although it depends on the size of D, it is sufficient that the width A is larger than the rear end side of the end mill in the range of 0.01 to 0.1 mm at least at the tip of the outer peripheral cutting edge 5.

  By the way, in the first embodiment, the clearance angle 7 connected to the peripheral cutting edge 5 on the clearance surface 7 of the peripheral cutting edge 5 is 0 ° and the clearance angle β continuous to the margin section 8 (α <β The second flank 9 is formed so that the width A of the margin portion 8 is in the range of 0.01 to 0.1 mm on the end mill end side, and is smaller than the end end side on the end mill rear end side. However, instead of the margin portion 8, as in the second embodiment of the present invention shown in FIGS. 3 and 4, the clearance angle β of the second flank 9 is larger than 0 ° at least on the end mill end side. Is formed such that the first flank 10 having a small flank angle α is connected to the outer peripheral cutting edge 5 with a width A of 0.01 to 0.1 mm, and the width A of the first flank 10 is set to the rear end of the end mill. By gradually decreasing it toward the side, the end side of this end mill should be It may be made smaller. In the second embodiment, the same reference numerals are assigned to portions common to the first embodiment shown in FIGS. 1 and 2 and the description thereof is omitted.

  Here, the clearance angle α given to the first clearance surface 10 only needs to be smaller than the clearance angle β of the second clearance surface 9, but if the difference from the clearance angle β is too small, that is, If the ratio of the clearance angle α to the clearance angle β is too large, the biting of the outer peripheral cutting edge 5 on the work material on the tip side of the end mill becomes too strong, causing chatter vibration and easily causing chipping and chipping. On the contrary, if the difference from the clearance angle β is too large, that is, if the ratio of the clearance angle α to the clearance angle β is too small, the first clearance surface with such a small clearance angle α is surely provided with the width A as described above. It may be difficult to form with. Therefore, when the first flank 10 is formed on the flank 7 instead of the margin portion 8, the flank angle α is in a range of ¼ to ½ of the flank angle β of the second flank 9. It is desirable that

  On the other hand, in these first and second embodiments, the width A gradually decreases as the margin portion 8 of the first embodiment or the first flank 10 of the second embodiment moves toward the end end side of the end mill. Thus, the width A is smaller on the rear end side of the end mill than on the front end side of the end mill. This is different from the margin portion 8 of the third embodiment shown in FIGS. As in the first flank 10 of the fourth embodiment shown in FIG. 8, the width A of the margin 8 or the first flank 10 is set to a range of 0.01 to 0.1 mm on the end mill tip side. The end mill may be made smaller in the stepwise direction from the end mill front end side toward the rear end side of the end mill so that the end mill rear end side becomes smaller than the front end side. In the third and fourth embodiments, the same reference numerals are assigned to the parts common to the first and second embodiments, and the description thereof is omitted.

  Here, in the third and fourth embodiments, the margin 8 or the first flank 10 is formed with a constant width A only in a predetermined range of the flank 7 of the outer peripheral cutting edge 5 on the end mill tip side. In addition to this, on the rear end side of the end mill, a clearance surface 7 having a larger clearance angle than the margin portion 8 on the front end side of the end mill or the first clearance surface 10 (for example, as shown in FIG. 9 common to both embodiments) The second flank 9) having a clearance angle β is formed so as to be directly connected to the outer peripheral cutting edge 5, that is, the margin portion 8 or the first flank 10 becomes smaller in one step toward the rear end side of the end mill. The width A is 0 on the rear end side of the end mill, that is, the margin 8 or the first flank 10 is not formed on the rear end side of the end mill. However, the width A of the margin portion 8 or the first flank 10 on the end mill rear end side is gradually reduced toward the rear end side.

  Therefore, also in the end mills of the second to fourth embodiments configured as described above, the margin portion 8 having the width A of 0.01 to 0.1 mm or the first portion so as to be connected to the outer peripheral cutting edge 5 on the end mill tip side. The flank 10 is formed, and the width A of the margin 8 or the first flank 10 is smaller on the rear end side of the end mill than on the front end side of the end mill (particularly, the width A in the third and fourth embodiments). As in the first embodiment, the increase in cutting resistance and cutting heat is suppressed, and the biting of the outer peripheral cutting edge 5 is prevented from becoming excessively strong, as in the first embodiment. Chipping and chipping can be prevented. Further, in the second and fourth embodiments in which the first flank 10 is formed so as to be continuous with the outer peripheral cutting edge 5 instead of the margin portion 8, the flank angle on the first flank 10 is small as described above. Since α is added, the cutting resistance can be further reduced while suppressing the excessive biting and improving the chipping resistance by strengthening the cutting edge.

  On the other hand, in the third and fourth embodiments in which the width A of the margin portion 8 or the first flank 10 is gradually reduced toward the rear end side of the end mill, the width A is constant in each stage. In addition, the flank 7 can be easily formed on the rear end side of the end mill as long as it is narrower than the front end side of the end mill even if there are some errors due to manufacturing variations. Here, the margin portion 8 or the first flank 10 has a width A that is gradually reduced in two or more steps toward the rear end side of the end mill, or such a margin portion. 8 or the first flank 10 may be formed over the entire length of the outer peripheral cutting edge 5, but in particular from the end mill front side toward the rear end side as in the third and fourth embodiments. When the width A is set to 0 in one step from 0.01 to 0.1 mm, the margin portion 8 or the first flank 10 may be formed only on the flank 7 on the end mill tip side. The molding becomes easier, and it is possible to further reduce the cutting resistance.

  When the margin portion 8 or the first flank 10 is formed only on the flank 7 on the end mill tip side in this way, the margin portion 8 having a flank angle α of 0 ° or the first flank having a small flank angle α. In the third and fourth embodiments in which the width A of the margin portion 8 or the first flank 10 is constant on the tip end side of the end mill, for example, the width A is, for example, after the end mill when the portion where the portion 10 is formed is too long. Since the cutting resistance on the end mill tip side tends to increase compared to the first and second embodiments that gradually decrease toward the end side, the margin portion 8 or the first portion formed only on the end mill tip side in this way. The flank 10 has a length L from the front end of the outer peripheral cutting edge 5 toward the rear end side of the end mill in the direction of the axis O of the end mill body 1 to a length equal to the outer diameter D of the outer peripheral cutting edge 5. Ru Desirable. However, even if the length L is too short, there is a possibility that excessive biting and chipping resistance cannot be sufficiently improved. Therefore, the length L is ¼ or more of the outer diameter D. Is more desirable.

  Further, in the first and second embodiments, the margin portion 8 or the first flank 10 is made to have a width in the third and fourth embodiments so that the width A gradually decreases toward the rear end side of the end mill. Although A is designed to decrease stepwise, for example, it may be formed to have a constant width A of 0.01 to 0.1 mm on the end mill tip side and gradually narrow on the end mill rear end side. On the contrary, the width A is gradually reduced from the range of 0.01 to 0.1 mm toward the rear end side at the end mill tip side, and the constant width A is set at the end mill rear end side. May be. Further, the first flank 10 and the second flank 9 to which the clearance angles α and β other than the margin portion 8 are given are so-called second straight lines in which at least one of them forms a straight line in a cross section perpendicular to the axis O. Alternatively, it may be a so-called eccentric number 2 forming a convex curve such as an arc having a center eccentric from the axis O. Furthermore, although the two-blade square end mill has been described in the first to fourth embodiments, the present invention may be applied to a multi-blade end mill having three or more blades, a radius end mill, a ball end mill, or the like.

It is a side view of the cutting blade part 2 of the end mill main body 1 which shows the 1st Embodiment of this invention. It is ZZ expanded sectional drawing in FIG. It is a side view of the cutting edge part 2 of the end mill main body 1 which shows the 2nd Embodiment of this invention. FIG. 4 is an enlarged ZZ sectional view in FIG. 3. It is a side view of the cutting edge part 2 of the end mill main body 1 which shows the 3rd Embodiment of this invention. It is ZZ expanded sectional drawing in FIG. It is a side view of the cutting edge part 2 of the end mill main body 1 which shows the 4th Embodiment of this invention. It is ZZ expanded sectional drawing in FIG. FIG. 8 is an enlarged YY sectional view in FIGS. 5 and 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 End mill main body 2 Cutting edge part 5 Peripheral cutting edge 7 Flank face of outer peripheral cutting edge 5 Margin part 9 Second flank face 10 First flank face A Width of margin part 8 or first flank face B Second flank face 9 Width W of flank 7 O axis of end mill body 1 Rotating direction of end mill body 1 D outer diameter of outer peripheral cutting edge L Length of margin 8 or portion where first flank 10 is formed α margin 8 or clearance angle of the first flank 10 β clearance angle of the second flank 9

Claims (6)

  An outer peripheral cutting edge is formed on the outer periphery of the tip end of the end mill body that is rotated about the axis, toward the rear side in the rotational direction of the end mill body toward the rear end side of the end mill. The surface is formed with a margin portion or a first flank that is continuous with the outer peripheral cutting edge, and a second flank that has a larger flank than the margin or the first flank. An end mill characterized in that the flank width is in the range of 0.01 to 0.1 mm on the end mill tip side, and the flank on the rear end side of the end mill is smaller than the end mill tip side.   2. The end mill according to claim 1, wherein a width of the margin portion or the first flank is gradually decreased from the end mill front end side toward the end mill rear end side.   2. The end mill according to claim 1, wherein a width of the margin portion or the first flank is gradually reduced from the end mill front end side toward the end mill rear end side.   The margin portion or the first flank is formed only on the end mill tip side portion of the flank of the outer peripheral cutting edge, and on the rear end side of the end mill, the margin portion or the first flank at the end mill tip. The end mill according to any one of claims 1 to 3, wherein a clearance surface having a larger clearance angle is formed to be continuous with the outer peripheral cutting edge.   The margin portion or the first flank is formed only in a portion from the tip of the outer peripheral cutting edge to a length equal to the outer diameter of the outer peripheral cutting edge in the axial direction. End mill. Of the flank face of the outer peripheral cutting edge, at least on the tip end side of the end mill, a first flank face continuous with the outer peripheral cutting edge and a second flank face having a larger flank angle than the first flank face are formed, The end mill according to any one of claims 1 to 5, wherein a clearance angle of the first clearance surface is in a range of 1/4 to 1/2 of a clearance angle of the second clearance surface.

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