JP2010201564A - End mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an end mill elongating the life of the end mill and achieving high-precision and high-quality cutting in the end mill with a plurality of end cutting edges irregularly formed in a circumferential direction by preventing a specific end cutting edge from being susceptible to damage such as fracture or chipping. <P>SOLUTION: The plurality of end cutting edges 7 extending from the outer peripheral side to the inner peripheral side are spaced in the circumferential direction at the distal end of an end mill body 1 rotated around an axis O. At least one end cutting edge 7A among these end cutting edges 7 has a larger circumferential distance than an end cutting edge 7B adjacent in a rotating direction T of the end mill, and has a larger negative angle in a radial rake angle α than other end cutting edges 7B. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an end mill in which a plurality of bottom blades from the outer peripheral side toward the inner peripheral side are formed at unequal intervals in the circumferential direction at the end of an end mill main body rotated about an axis.

  As described above, as an end mill in which a plurality of bottom blades are formed at unequal intervals in the circumferential direction, for example, in Patent Document 1, at least one bottom blade of the plurality of bottom blades is the center of rotation of the end mill main body tip. The other bottom blade extends from the position away from the rotation center to the outer peripheral side and extends from the vicinity to the outer peripheral side and has a 0 ° or negative radial rake angle, and the at least one bottom blade What is formed so that a larger rake angle in the radial direction is attached to the positive angle side than the other is disclosed. In such an end mill, a high cutting edge strength is given to the at least one bottom blade extending from the vicinity of the rotation center, and even in the case of inclined cutting, the cutting edge is prevented from being damaged against an excessive cutting load. Can do.

  Also, in Patent Document 2, the twist angle of at least one outer peripheral blade among the plurality of outer peripheral blades is set to a different angle from the other outer peripheral blades, and the circumferential interval between the outer peripheral blades is the length of the blade from the tip of the end mill body. By making it equal in the range of 1/3 thru | or the center part, the thing which the space | interval of the circumferential direction of a bottom blade becomes an unequal space is disclosed. In such an end mill, vibrations cancel each other because the frequency of vibration generated in the end mill body during cutting changes between the bottom edge and the part where the outer peripheral edge is unevenly spaced in the circumferential direction. It is possible to prevent the occurrence of resonance that may occur.

Japanese Utility Model Publication No. 6-66910 Japanese Patent Publication No. 63-62323

  However, among the end mills described in Patent Document 1, a high cutting edge strength is provided by providing the at least one bottom blade with 0 ° or a negative radial rake angle, while other bottom blades. The rake angle in the radial direction is a positive angle, and the circumferential interval between the bottom blade adjacent to the end mill rotation direction and the other bottom blade adjacent to the end mill rotation direction is such that the at least one bottom blade is adjacent to the end mill rotation direction. It is larger than the interval.

  Therefore, the cutting strength of the other bottom blade is smaller than that of the at least one bottom blade even though the cutting amount is larger than that of the at least one bottom blade and a large load is applied. When an excessive cutting load is applied, there is a risk that chipping or chipping is likely to occur. In particular, this Patent Document 1 also proposes a bottom blade formed so as to form a concave curve on the outer peripheral side when viewed from the front end side in the axial direction. Occurrence of defects or the like may be significant on the outer peripheral side. Although this problem is not specifically described in the end mill described in Patent Document 2 regarding the rake angle in the radial direction of the bottom blade, the bottom blade is formed in a concave curved shape in the axial front end view, It can happen as well.

  On the other hand, in the end mill described in Patent Document 1, the at least one bottom blade has a 0 ° or negative radial rake angle, is dull, and has a high resistance despite the high resistance. Since it extends from the vicinity of the rotation center to the outer peripheral side and cuts the entire processing surface by the bottom blade, there is a risk of impairing the accuracy and quality of the processing surface.

  The present invention has been made under such a background. In the end mill in which a plurality of bottom blades are formed at unequal intervals in the circumferential direction as described above, a specific bottom blade is damaged such as chipping or chipping. An object of the present invention is to provide an end mill capable of extending the end mill life by preventing the occurrence of the end mill, and capable of high-precision and high-quality cutting.

  In order to solve the above problems and achieve such an object, the end mill of the present invention has a plurality of bottom blades extending from the outer peripheral side to the inner peripheral side at the tip end of the end mill body rotated around the axis. The at least one bottom blade among the above-mentioned bottom blades has a larger circumferential interval with the bottom blade adjacent to the end mill rotation direction than the other bottom blades, and has a diameter. The direction rake angle is increased to the negative angle side.

  Therefore, in the end mill having such a configuration, the radial rake angle is set to the at least one bottom blade in which the circumferential interval between the bottom blades adjacent to the end mill rotation direction is larger than that of the other bottom blades. Since it is made larger on the negative angle side than the other bottom blades, a high cutting edge strength can be ensured, so that it is possible to prevent the occurrence of chipping and chipping even when a large load is applied during cutting.

  On the other hand, other bottom blades whose rake angle in the radial direction is larger than the at least one bottom blade to the positive angle side have a large load because the circumferential interval between the bottom blades adjacent to the end mill rotation direction is small. It does not act, can prevent damage to all bottom blades and can improve end mill life, and can give high cutting accuracy and processing quality by giving sharpness to other cutting blades. It becomes possible.

  Here, it is preferable that the at least one bottom blade has a shorter radial length with respect to the axis than the other bottom blades. By shortening at least one bottom blade whose radial rake angle is increased to the negative angle side and cutting resistance is increased in this way, the resistance acting on the entire end mill body can be reduced, and the radial rake angle is increased to the positive angle side. Other bottom blades that are large and sharp are long, and the machining surface of the bottom blade can be finished with high accuracy and high quality over the entire surface.

  Further, the at least one bottom blade may be formed in a straight line shape when viewed from the front end side in the axial direction, and the other bottom blade may be formed in a concave curve shape on the outer peripheral side. As a result, at least one bottom blade with a large load during cutting can ensure a higher cutting edge strength and prevent the occurrence of damage, while other bottom blades with less cutting load have It becomes possible to give a sharper sharpness and promote higher quality cutting.

  As described above, according to the present invention, it is possible to secure a sufficient cutting edge strength for a bottom blade having a large load during cutting, thereby preventing damage such as chipping and chipping from being easily generated, and a bottom having a small load. A sharp cutting edge can be given to the blade, which makes it possible to obtain a machined surface with excellent machining accuracy and machining quality while improving the end mill life.

It is the front view seen from the axial direction front end side which shows the 1st Embodiment of this invention. It is a side view of a 1st embodiment. It is the front view seen from the axial direction front end side which shows the 2nd Embodiment of this invention. It is a side view of 2nd Embodiment.

  In the first embodiment of the present invention shown in FIGS. 1 and 2, the end mill body 1 is formed of a hard material such as cemented carbide and has a substantially cylindrical shape centering on the axis O, and a rear end side portion ( The right side portion in FIG. 2 is a cylindrical shank portion 2 and the tip side portion (left side portion in FIG. 2) is a cutting blade portion 3, and the shank portion 2 is held by the main spindle of the machine tool and is axial. While being rotated in the end mill rotation direction T around O, it is fed in a direction crossing the axis O, and in some cases, is also fed to the tip end side in the axial direction, so that the cutting edge 3 cuts the work material. I will give it.

  On the outer periphery of the cutting edge portion 3, a plurality (four in this embodiment) of chip discharge grooves 4 that are twisted toward the rear side in the end mill rotation direction T around the axis O from the front end to the rear end side are formed. The wall surface 4A facing the end mill rotation direction T side of the chip discharge grooves 4 has a concave curve shape recessed in the rear side in the end mill rotation direction T in the cross section orthogonal to the axis O, and is formed at the outer peripheral side ridge portion. The outer peripheral blades 5 are respectively formed. Therefore, the wall surface 4A is the rake face of the outer peripheral blade 5, and in this embodiment, the four outer peripheral blades 5 spiral in accordance with the twist of the chip discharge groove 4 in which the wall surface 4A to be the rake face is formed. It is formed to be twisted into a shape.

  On the other hand, the end portion of the end mill body 1 is formed with a gash 6 extending from the chip discharge groove 4 to the inner peripheral side, and a wall surface 6A facing the end mill rotation direction T of the gash 6 has a concave curved cross section. The wall surface 4A of the chip discharge groove 4 is formed so as to be cut out in a planar shape until reaching the outer periphery of the end mill body 1, and the end mill body is respectively formed on the tip side ridge portion of the wall surface 6A from the tip of the outer peripheral blade 5. A bottom blade 7 extending to the inner peripheral side of 1 is formed.

  Therefore, in the present embodiment, the wall surface 6A of the gash 6 is used as the rake face of the bottom blade 7, and the plurality of (four strips) bottom blades 7 as in the outer peripheral blade 5 are arranged in the direction of the axis O as shown in FIG. The end mill body 1 is formed so as to extend linearly from the outer peripheral side to the inner peripheral side when viewed from the side. Here, in the end mill of the present embodiment, the rotation trajectory of the outer peripheral blade 5 around the axis O is substantially cylindrical with the axis O as the center, and the outer peripheral blade 5 and the bottom blade 7 have the same rotation trajectory. It is a square end mill that is substantially orthogonal.

  In these bottom blades 7, at least one bottom blade 7 has a larger circumferential interval with the bottom blade 7 adjacent to the end mill rotation direction T than the other bottom blades 7. In the present embodiment, of the four bottom blades 7, two first bottom blades (bottom blades extending in the left-right direction in FIG. 1) located on opposite sides of the axis O are the at least one bottom. A bottom blade (first bottom blade) adjacent to the end mill rotation direction T rather than the remaining pair of second bottom blades (bottom blades extending in the vertical direction in FIG. 1) 7B, which is the other bottom blade 7. 7A has a second bottom blade 7B, and the second bottom blade 7B has a larger circumferential distance from the first bottom blade 7A) 7.

  Note that the first bottom blades 7A and the second bottom blades 7B are disposed at 180 ° rotationally symmetrical positions with respect to the axis O, that is, in the present embodiment, the first bottom blade 7A and the second bottom blade 7B Are formed alternately. Further, in order to make the circumferential intervals of the bottom blades 7 different from each other as described above, the groove width itself of the chip discharge groove 4 is changed between the first bottom blade 7A and the second bottom blade 7B as shown in FIG. It is good also as what is different in a continuous thing, and the space | interval of the bottom blade 7 of the end mill main body 1 tip | tip may differ so that the twist angle of the chip discharge groove | channel 4 may differ.

  The radial rake angles α and β of the first and second bottom blades 7A and 7B are the radial directions of the first bottom blade 7A in which the distance from the second bottom blade 7B adjacent to the end mill rotation direction T is increased. The rake angle α is larger on the negative angle side than the radial rake angle β of the second bottom blade 7B in which the distance from the first bottom blade 7A adjacent to the end mill rotation direction T is reduced. Here, in the present embodiment, the radial rake angles α and β of the first and second bottom blades 7A and 7B are negative angles.

  Furthermore, in the present embodiment, the second bottom blade 7B extends from the outer peripheral end intersecting the outer peripheral blade 5 toward the inner peripheral side to the vicinity of the axis O at the end of the end mill body 1, whereas The first bottom blade 7A is formed from the outer peripheral end toward the inner peripheral side up to a position slightly separated from the axis O, that is, the first bottom blade 7A is more in the radial direction with respect to the axis O than the second bottom blade 7B. The length is shortened.

  In the end mill configured in this way, the circumferential interval of the bottom blade 7 is directed toward the rear side in the end mill rotation direction T, the distance between the first bottom blade 7A and the second bottom blade 7B, and the second bottom blade. 7B and the first bottom blade 7A are different in size, and the outer peripheral blade 5 connected to the bottom blade 7 also has a different circumferential interval at least on the tip end side of the end mill body 1. It is possible to prevent periodic vibrations from occurring when the bottom blade 7 and the outer peripheral blade 5 bite the work material, and to prevent chattering from being caused by such periodic vibrations.

  Further, in the end mill having the above-described configuration, the circumferential distance between the bottom blade 7 and the second bottom blade 7B adjacent to the end mill rotation direction T of the bottom blade 7 is increased, resulting in a large amount of cutting and a large load during cutting. Since the first rake angle α of the first bottom blade 7A on which the sag acts is larger on the negative angle side than the radial rake angle β of the second bottom blade 7B, the first bottom blade 7A has a higher cutting edge. Strength can be secured. For this reason, it is possible to prevent the first bottom blade 7A from being damaged or chipped by a cutting load, and to improve the end mill life.

  On the other hand, with respect to the first bottom blade 7A, the load acting during cutting becomes relatively small by reducing the circumferential distance between the first bottom blade 7A adjacent to the end mill rotation direction T in the circumferential direction. About the 2 bottom blade 7B, since the radial direction rake angle (beta) is made larger than the radial direction rake angle (alpha) of the 1st bottom blade 7A, sharp sharpness can be given. Therefore, the machining surface is formed on the work material by such a second bottom blade 7B, whereby the accuracy and quality of the machining surface can be improved.

  Moreover, in the present embodiment, the radial length of the first bottom blade 7A on which a large cutting load acts as described above is shorter than the second bottom blade 7B. The cutting force acting on the whole and the cutting load itself can also be reduced. On the other hand, the second bottom blade 7B with low resistance and sharpness is longer than the first bottom blade 7A, and in particular in the present embodiment, extends over substantially the entire length in the radial direction of the end mill body 1 tip. The entire processed surface can be finished with higher accuracy and quality by the second bottom blade 7B.

  By the way, in the said 1st Embodiment, although 1st, 2nd bottom blade 7A, 7B is formed so that it may form linear shape seeing from the axis line O direction front side, 2nd implementation shown in FIG. As in the form, the first bottom blade 7A may be linear, while the second bottom blade 7B may be formed to have a concave curve shape when viewed from the front end side in the axis O direction on the outer peripheral side thereof. In the second embodiment, the same reference numerals are assigned to portions common to the first embodiment, and description thereof is omitted.

  Here, in order to form the second bottom blade 7B in a concave curve shape on the outer peripheral side in this way, the first and second bottom blades 7A and 7B are formed to be linear in the first embodiment. The flat wall surface 6A of the gash 6 may not be formed in the chip discharge groove 4 in which the second bottom blade 7B is formed at the tip as shown in FIG. Thereby, about the 2nd bottom blade 7B, since the said wall surface 4A which makes the cross-sectional concave curve shape of the chip | tip discharge groove | channel 4 cross | intersects the front end flank of the end mill main body 1 as it is, it becomes the said 2nd bottom blade 7B, As mentioned above Thus, it can be formed in a concave curve shape on the outer peripheral side.

  Accordingly, in such an end mill of the second embodiment, the cutting edge strength of the first bottom blade 7A is secured in the same manner as in the first embodiment, and the radial rake angle β of the second bottom blade 7B is further corrected. Since it can be set large on the corner side, it is possible to give a sharper sharpness to the second bottom blade 7B and improve the accuracy and quality of the processed surface.

  In particular, a flat wall surface 6A is provided by a gash 6 at the tip of the chip discharge groove 4 like the first and second bottom blades 7A and 7B of the first embodiment and the first bottom blade 7A of the second embodiment. When formed, when the wall surface 6A reaches the tip of the outer peripheral blade 5, the tip of the outer peripheral blade 5 is formed on the wall surface 6A, and the rotation trajectory around the axis O is formed. Is inclined slightly toward the inner peripheral side as it goes toward the tip side.

  However, in this second embodiment, the outer peripheral blade 5 connected to the second bottom blade 7B has a rotational trajectory around the axis O over the entire length up to its tip so that it is cylindrical with the axis O as the center. Since it can be formed, even if a slight uncut residue is left on the processing surface of the outer peripheral blade 5 due to the inclined portion of the tip of the outer peripheral blade 5 connected to the first bottom blade 7A, this is caused by the outer peripheral blade 5 connected to the second bottom blade 7B. Can be scraped off. Therefore, according to the second embodiment, the processing surface by the outer peripheral blade 5 can be formed in parallel to the axis O over the whole, and further highly accurate and high-quality cutting is promoted. It becomes possible.

  In the first and second embodiments, the case where the present invention is applied to a square end mill in which the outer peripheral blade 5 and the bottom blade 7 intersect at a substantially right angle in the rotation locus around the axis O has been described. The present invention can also be applied to a radius end mill in which a convex arcuate corner blade is formed at a corner portion where the outer peripheral blade 5 and the bottom blade 7 intersect. Further, the bottom blade 7 may be provided with a watermark angle so as to be slightly inclined toward the rear end side in the axis O direction toward the inner peripheral side.

DESCRIPTION OF SYMBOLS 1 End mill main body 2 Shank part 3 Cutting edge part 4 Chip discharge groove 4A Wall surface which faces end mill rotation direction T of chip discharge groove 4 5 Peripheral blade 6 Gash 6A Wall surface which faces end mill rotation direction T of Gash 6 7 Bottom blade 7A 1st bottom Blade (at least one bottom blade)
7B 2nd bottom blade (other bottom blade)
O Axis of end mill body 1 End mill rotation direction α Radial rake angle of first bottom blade 7A β Radial rake angle of second bottom blade 7B

Claims (3)

  A plurality of bottom blades extending from the outer peripheral side toward the inner peripheral side are formed at intervals in the circumferential direction at the tip of the end mill body rotated around the axis, and at least one of the bottom blades is the other The end mill is characterized in that the circumferential distance between the bottom blade adjacent to the end mill in the rotational direction of the end mill is larger than that of the bottom blade and the rake angle in the radial direction is increased toward the negative angle side.   The end mill according to claim 1, wherein the at least one bottom blade has a shorter radial length with respect to the axis than the other bottom blades.   The at least one bottom blade is formed in a straight line shape when viewed from the front end side in the axial direction, and the other bottom blade is formed in a concave curve shape on the outer peripheral side. The end mill according to claim 2.

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