JP2005271167A - End mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the strength of the outer peripheral side of an end cutting edge from being impaired by a chamfering part while the axial rake of the end cutting edge is made larger to the negative angle side than the twisting angle by chamfering the end cutting edge to form a chamfered part especially in a hard helical end mill. <P>SOLUTION: An outer periphery cutting edge is formed extending helical on the rear side in the rotating direction T of an end mill in cutting from the forward to the rear end, and an end cutting edge 8 extended from the inner peripheral side to the outer peripheral side and connected to the tip of the outer peripheral cutting edge is formed at the tip of the end mill body 1. The end cutting edge 8 is provided with a chamfering part 10 formed along the end cutting edge so that the axial rake is made larger to the negative angle side than the helical angle of the outer peripheral cutting edge. On the outer peripheral side of the end cutting edge 8, the chamfering part 10 is bent in the circumferential direction so that the radial rake β of the end cutting edge 8 is substantially equal to the radial rake of the outer peripheral cutting edge. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, an outer peripheral blade that spirally twists is formed on the outer periphery of the end portion of the end mill main body, and a bottom blade that extends from the inner peripheral side to the outer peripheral side and continues to the front end of the outer peripheral blade is formed on the end of the end mill main body. It relates to end mills.

  The end mill generally has a cylindrical shape and a chip discharge groove is formed on the outer periphery of the end portion of the end mill body that is rotated about its central axis, and the outer peripheral side edge of the wall surface that faces the direction of rotation of the chip discharge groove. An outer peripheral blade is formed in the portion, and a bottom blade connected to the distal end of the outer peripheral blade is formed in the tip side ridge portion, and is used for performing cutting processing such as grooving and shoulder cutting on the workpiece. Here, the chip discharge groove is usually formed in a spiral shape twisted around the axis so as to go to the rear side in the rotation direction toward the rear end side of the end mill body. The outer peripheral edge formed on the outer peripheral side ridge portion of the wall surface facing the rotation direction is also formed by being twisted toward the rear side in the rotation direction toward the rear end side of the end mill body, and is predetermined with respect to the axis. The twist angle is given.

Here, among such end mills, in particular, an end mill having an outer peripheral edge having a twist angle of approximately 40 ° or more is generally referred to as a strong twist end mill. In this type of strongly twisted end mill, in Patent Document 1, in order to compensate for the insufficient strength of the tip of the outer peripheral blade that intersects the bottom blade, the axial rake angle of the bottom blade is a positive angle of 0 ° or 0 ° or more. A flat blade in which the tip of the bottom blade is a part of the outer peripheral blade is constituted by, for example, a plane parallel to the rotation axis of the end mill body, and in order to secure the strength of the tip of the flat blade, A tip corner with a chamfered blade has been proposed. However, since the chamfered blade is in contact with the flat blade at an obtuse angle, the chamfered portion of the intersection ridgeline between the outer peripheral flank connected to the rear of the flat blade in the rotational direction and the tip flank connected to the rear of the bottom blade on the outer side in the rotational direction. It is formed by doing.
JP 2000-190120 A

  By the way, in such a strong torsion end mill, not only the insufficient strength of the tip portion of the outer peripheral blade is compensated as described above, but, for example, when cutting a hard material or high speed cutting, it is closer to the rear end side. It is necessary to ensure the strength of the extending outer peripheral blade itself, and therefore the radial rake angle of the outer peripheral blade is often set to a negative angle. Therefore, when the rake face of the outer peripheral blade is directly extended to the tip of the end mill body to form the bottom blade, the rake angle in the radial direction of the bottom blade also becomes a strong negative angle. If the bottom blade itself is chamfered by a plane parallel to the rotation axis and a flat blade that is a part of the outer peripheral blade is formed at the tip (outer peripheral end), the chamfered bottom blade is The rake face of the blade is positioned on the rear side of the bottom blade formed by extending the rake face to the tip as it is, and the radial rake angle is larger on the positive side than the outer edge blade. On the other hand, the strength is impaired, and there is a risk that defects or the like are likely to occur during cutting.

  The present invention has been made under such a background. By forming a chamfered portion by chamfering the bottom blade, the axial rake angle of the bottom blade is set to a negative angle side with respect to the twist angle of the outer peripheral blade. However, the chamfered portion can prevent the strength on the outer peripheral side of the bottom blade from being damaged, and the object is to provide a suitable end mill particularly applicable to the above-mentioned strong twist end mill. It is said.

  In order to solve the above-described problems and achieve such an object, the present invention twists the outer periphery of the end portion of the end mill body toward the rear side in the end mill rotation direction during cutting from the front end side to the rear end side. A peripheral blade extending from the inner peripheral side to the outer peripheral side and continuing to the distal end of the outer peripheral blade is formed at the tip of the end mill body, and an axial rake angle is formed on the bottom blade. A chamfered portion is formed along the bottom blade that is larger than the torsion angle of the outer peripheral blade along the bottom blade. On the outer peripheral side of the bottom blade, the radial rake angle of the bottom blade is the radial rake of the outer peripheral blade. The chamfered portion is bent in the circumferential direction so as to be substantially equal to the corner.

  Therefore, in the end mill configured as described above, a chamfered portion is formed along the bottom blade, and its axial rake angle is larger than the twist angle of the outer peripheral blade. Even in the case of a strong twist end mill with a large angle, the edge angle of the bottom blade can be secured and sufficient strength can be maintained. And on the outer peripheral side of the bottom blade, the chamfered portion is bent in the circumferential direction of the end mill body, so that the radial rake angle is substantially equal to the radial rake angle of the outer peripheral blade. When the radial rake angle of the outer peripheral blade is set to the negative angle side, the radial rake angle on the outer peripheral side of the bent bottom blade is also set to the negative angle side, and the edge angle is secured by the chamfered portion. In combination with this, it is possible to prevent the occurrence of defects. For this reason, according to the end mill having such a configuration, the tool life can be extended and stable cutting can be promoted over a long period of time.

  In addition, even if the radial rake angle on the outer peripheral side of the bottom blade by the bent chamfered portion and the radial rake angle of the outer peripheral blade do not exactly coincide with each other, the above-described effect can be achieved, for example, the difference between It may be within 3 °. Furthermore, the present invention can be applied to an end mill whose twist angle is not so large as long as the outer peripheral blade extends toward the rear end side of the end mill body so as to be twisted to the rear side in the end mill rotation direction at the time of cutting. In addition, it can be applied to an end mill in which the radial rake angle of the outer peripheral blade or the bottom blade is a positive angle. However, in consideration of the circumstances as described above, the twist angle of the outer peripheral blade is 37 ° to 60 °. In the strongly twisted end mill, the radial rake angle on the outer peripheral side of the bottom blade is made negative by the chamfered portion as the radial rake angle of the outer peripheral blade is made negative. Is.

  1 to 4 show an embodiment of the present invention. In the present embodiment, the end mill body 1 is formed of a hard material such as a cemented carbide and has a substantially cylindrical shape centered on the axis O, and the rear end side (the right side in FIG. 1) is the machine tool for the end mill body 1. A cutting edge 3 is formed on the tip side (left side in FIG. 1), and the axis of the machine tool around the axis O is indicated by the symbol T in FIGS. The workpiece is cut by the cutting blade portion 3 by being sent out while being rotated in the rotation direction shown.

  A plurality of strips (six strips in this embodiment) are twisted on the outer periphery of the cutting edge portion 3 around the axis O from the front end to the rear end side and twisted to the rear side in the rotation direction T of the end mill body 1 during cutting. The chip discharge grooves 4 are formed rotationally symmetrically by a predetermined angle (60 ° in the present embodiment) with respect to the axis O at equal intervals in the circumferential direction. And in the cross ridge line part of the wall surface which faces the rotation direction T side of these chip discharge grooves 4 and the outer peripheral relief surface of the cutting edge part 3 connected to the rotation direction T rear side, that is, on the outer peripheral side ridge part of the wall surface Is formed with an outer peripheral blade 5 that twists toward the rear side in the rotational direction T around the axis O as it goes to the rear end side, similar to the chip discharge groove 4, and its twist angle θ is a strong twist of 37 ° to 60 °. Has been. Moreover, the said wall surface of the chip discharge groove | channel 4 is made into the rake face 6 of this outer periphery blade 5, The radial direction rake angle (alpha) is set to the negative angle as shown in FIG.

  On the other hand, at the tip of this cutting edge part 3, that is, the most advanced part of the end mill body 1, a gash 7 is formed so that the tip side opening of each chip discharge groove 4 is sharpened to the inner peripheral side, On the tip side of the wall surface facing the rotation direction T of the chip discharge groove 4 thus widened, that is, on the tip side of the rake face 6, the tip mill extends from the inner peripheral side of the end mill body 1 to the outer peripheral side to the tip of the outer peripheral blade 5. A continuous bottom blade 8 is formed. Further, the bottom edge 8 has an intersecting ridge line portion obtained by extending the rake face 6 and the tip flank 9 at the tip of the cutting edge 3 as they are as shown in FIG. A chamfered portion 10 is formed so as to be scraped off by a parallel plane. Accordingly, the chamfered portion 10 intersects the rake face 6 at an obtuse angle, and the axial rake angle is set to be larger on the negative angle side than the twist angle θ of the outer peripheral blade 5 (in this embodiment, 0). °), the bottom blade 8 is formed at the intersecting ridge line portion between the chamfered portion 10 and the tip flank 9.

  In the present embodiment, the chamfered portion 10 extends from the axis O to the outer peripheral side on the inner peripheral side of the end mill body 1 as shown in FIG. The rake angle in the radial direction is set to 0 °, while the end mill main body 1 is bent at the outer peripheral side toward the rear side in the rotational direction T toward the outer peripheral side. Accordingly, the outer peripheral portion of the bottom blade 8 is also bent so as to go to the rear side in the rotational direction T as it goes to the outer peripheral side of the end mill body 1, thereby causing the radial rake angle of the bottom blade 8 on the outer peripheral side. β is a negative angle, and the radial rake angle β of the bottom blade 8 on the outer peripheral side of the end mill body 1 thus made negative is the same as the radial rake angle α of the outer peripheral blade 5 which is also a negative angle. More specifically, the difference between the rake angles α and β in both radial directions, that is, the absolute value of α−β is within 3 °.

  Here, in the present embodiment, the chamfered portion 10 is formed so as to be bent at an angle with respect to the inner peripheral side while being a plane parallel to the axis O on the outer peripheral side of the end mill body 1. The blade 8 is also bent into a broken line shape in which straight lines intersect with each other from the inner peripheral side toward the outer peripheral side. However, the length of the outer peripheral portion of the bottom blade 8 bent in this way is sufficiently shorter than the inner peripheral side.

  In the end mill thus configured, first, a chamfered portion 10 is formed along the bottom blade 8 such that the axial rake angle is larger than the twist angle θ of the outer peripheral blade 5 on the negative angle side. Is formed at the intersecting ridge line between the chamfered portion 10 and the tip flank 9, so that the bottom blade 8 has a torsion angle θ of the outer peripheral blade 5 even if it is a strong twist end mill having a large positive angle as described above. Can provide a large cutting edge angle to ensure sufficient strength, and can prevent the bottom blade 8 from being damaged due to the shortage of the cutting edge angle. Then, the chamfered portion 10 remains in the axial rake angle larger than the twist angle θ on the negative angle side (0 ° in the present embodiment), and the outer peripheral side of the end mill body 1 is bent to the rear side in the rotational direction T. Accordingly, the outer peripheral side of the bottom blade 8 is also bent backward in the rotational direction T so that the radial rake angle β is substantially equal to the radial rake angle α, which is the negative angle of the outer peripheral blade 5. Therefore, also on the outer peripheral side of the bottom blade 8, it is possible to ensure the crossing angle between the chamfered surface 10 and the outer peripheral flank substantially equal to the crossing angle between the rake face 6 and the outer peripheral flank in the outer peripheral blade 5. This becomes possible, and in combination with the securing of the strength of the bottom blade 8 itself as described above, it is possible to reliably prevent defects and the like. Therefore, according to the above configuration, it is possible to prevent the tool life from being shortened due to the chipping of the bottom blade 8 caused by these, and to provide an end mill having a long tool life capable of stable cutting over a long period of time. Is possible.

  The radial rake angle β of the bottom blade 8 made negative by the bent chamfered portion 10 in this way does not have to be exactly equal to the radial rake angle α of the outer peripheral blade 5, but these radial rake angles If the difference between the angles α and β is too large, the above-mentioned effect cannot be reliably achieved when the radial rake angle α of the outer peripheral blade 5 is large, but conversely the radial rake on the outer peripheral side of the bottom blade 8. When the angle β is large, in this embodiment, the outer peripheral side of the bottom blade 8 causes an increase in cutting resistance, and the bottom blade 8 is greatly bent at the inner and outer periphery, and the strength of the bent portion is lost. There is also a risk of being lost. Therefore, it is desirable that the difference between the rake angles α and β in the radial direction is within a range of 3 ° as described above.

  Further, as described above, a chamfered portion 10 having an axial rake angle larger than the twist angle θ of the outer peripheral blade 5 on the negative angle side is formed along the bottom blade 8, and the radial rake of the bottom blade 8 is formed on the outer peripheral side. The configuration itself in which the chamfered portion 10 is bent in the circumferential direction so that the angle β is substantially equal to the radial rake angle α of the outer peripheral blade 5 is, for example, an end mill having a sufficiently smaller twist angle θ than the above range, or an outer peripheral blade. 5 can also be applied to an end mill in which the radial rake angle α is set to 0 ° or a positive angle, and in the latter end mill, the radial rake angle β of the bottom blade 8 is set to the radial rake angle of the outer peripheral blade 5. In order to make it substantially equal to α, the outer peripheral side of the chamfered portion 10 may be bent toward the rotation direction T with respect to the inner peripheral side. However, in an end mill having a small twist angle θ, a large blade edge angle can be obtained even if the bottom blade 8 is directly formed at the tip of the rake face 6 of the outer peripheral blade 5, so that it is not necessary to form the chamfered portion 10 to ensure strength. In addition, if the outer peripheral side of the chamfered portion 10 is bent in the rotational direction T side in accordance with the radial rake angle α of the outer peripheral blade 5 of 0 ° or a regular angle, there is a risk of insufficient strength on the outer peripheral side. The configuration is particularly suitable when applied to a strongly twisted end mill in which the twist angle θ of the outer peripheral blade 5 is 37 ° to 60 ° and the radial rake angle α is a negative angle as in this embodiment.

  In the present embodiment, the bottom blade 8 extends from the axis O to the outer peripheral side on the inner peripheral side of the end mill body 1 and its rake angle in the radial direction is 0 ° as described above. In the case where a center hole is formed around the axis O, the bottom blade 8 may extend from the periphery of the center hole away from the axis O to the outer peripheral side. The radial rake angle of 8 may be a negative angle. Further, in this embodiment, the chamfered portion 10 is bent at an angle on the outer peripheral side, and the bottom blade 8 is bent in a polygonal line along with this, but the bent portion of the bottom blade 8 is a curved shape such as an arc. The chamfered portion 10 may be bent with a smooth curved surface.

It is a side view of the end mill main body 1 which shows one Embodiment of this invention. It is a front view of the end mill main body 1 front-end | tip of embodiment shown in FIG. It is ZZ sectional drawing in FIG. It is sectional drawing orthogonal to the bottom blade 8 which shows the chamfer 10 of embodiment shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 End mill main body 3 Cutting blade part 4 Chip discharge groove 5 Outer peripheral blade 6 Rake face of outer peripheral blade 5 8 Bottom blade 9 Tip flank 10 Chamfer part O Rotation axis of end mill main body 1 Rotation direction when cutting end mill main body 1 Twist angle of blade 5 α Radial rake angle of outer peripheral blade 5 β Radial rake angle of outer edge of end mill body 1 of bottom blade 8

Claims (3)

  On the outer periphery of the end portion of the end mill body, an outer peripheral blade is formed extending from the front end side to the rear end side so as to be twisted backward in the direction of rotation of the end mill at the time of cutting. A bottom blade that extends from the outer periphery to the tip of the outer peripheral blade is formed, and the bottom blade has a chamfered portion whose axial rake angle is larger than the twist angle of the outer peripheral blade on the negative angle side. The chamfered portion is bent in the circumferential direction so that the radial rake angle of the bottom blade is substantially equal to the radial rake angle of the outer peripheral blade on the outer peripheral side of the bottom blade. End mill characterized by   The end mill according to claim 1, wherein the difference between the radial rake angle on the outer peripheral side of the bottom blade and the radial rake angle of the outer peripheral blade is within 3 °. 3. The end mill according to claim 1, wherein the outer peripheral blade is a strong twist with a twist angle of 37 ° to 60 ° and a rake angle in the radial direction is a negative angle.

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