JPH06335813A - End mill - Google Patents

Abstract

PURPOSE:To sufficiently suppress loss or abrasion even under heavy cutting condition by specifying the flank angle at a corner on the tool base side in the comers where a nick and a spiral flute intersect. CONSTITUTION:A cutting chip produced by a tip 5... in cutting process is cut in short pieces by way of a nick 7... formed by the tip 5. A flank angle alphaof a corner 8a as an acute angle on the tool base side in corners of the nick 7 and a spiral flute is set to be larger than a flange angle beta or corner 8b as am obtuse angle on the tool tip side and more than 40 deg.C. Consequently, the nose angle in section perpendicular to the corner 8a becomes larger than the acute angle exhibited by the corner 8a in side view, so that the tip strength is raised.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end mill having an outer peripheral cutting edge formed with a nick for cutting chips.

[0002]

2. Description of the Related Art As this type of end mill, for example, the one described in Japanese Utility Model Laid-Open No. 63-30420 is known. The end mill described in this publication is an end mill in which a tool body is formed with a plurality of twisted grooves and twisted cutting edges, and a large number of nicks are formed in each cutting edge in a direction perpendicular to the rotation axis of the end mill. 30 ° on the acute side of the corner formed by the intersection of this nick and the twist groove.
The above flank angle is provided, and the side edge of the cutting edge portion is provided with a straight line or a round chamfer having a second falling amount in the direction perpendicular to the rotation axis.

In the end mill having such a structure,
Since a relatively large flank angle of 30 ° or more is provided on the acute angle side of the corner where the nick and the twist groove intersect, it is possible to increase the cutting edge strength at the corner portion on the acute angle side, and at the same time, the cutting edge thereof. It is possible to prevent the cutting edge from being damaged by a straight line or a round chamfer provided on the side edge of the part. With these features, the end mill is designed to enable cutting such that the acute side of the corner is used as a main cutting edge to improve machinability and reduce cutting resistance.

[0004]

However, even with such an end mill, under heavy cutting conditions such as high feed and high depth of cut, it is difficult to impart sufficient cutting edge strength to the sharp corners. there were. Therefore, there is a problem that the cutting load or the like generated in such heavy cutting causes chipping or wear at the acute-angled corners, and the life of the end mill is significantly shortened. The present invention has been made under such a background,
An object of the present invention is to provide an end mill capable of sufficiently suppressing chipping and wear even under the above heavy cutting conditions by giving higher cutting edge strength to the acute angle side of the corners where the nick and the twist groove intersect. .

[0005]

In order to solve the above problems and achieve the above object, the present invention provides a plurality of twisted grooves on the outer periphery of a tool body rotated about an axis from the tool tip toward the base end. Is formed, and a cutting edge is formed on the outer peripheral ridge of the wall surface facing the tool rotation direction side of this twist groove, and this cutting edge is inclined in the direction inclined toward the tool tip side toward the tool rotation direction rear side. Form multiple nicks to extend,
The side wall on the tool tip side and the side wall on the tool base end side of this nick are formed in a direction in which they are separated from each other toward the tool outer peripheral side, and the tool base end side of the corner where the nick intersects with the twist groove is formed. Is larger than the flank angle of the corner on the tip side, and is 40 ° at least at the opening edge of the nick on the outer peripheral side of the tool.
It is characterized in that it is set as described above.

[0006]

According to the end mill having such a structure, the corner on the tool base end side of the corner where the nick and the twist groove intersect, that is, the flank angle of the above-mentioned acute angle side corner is the flank of the tip side corner. Since it is formed at a very large angle of 40 ° or more at least at the opening edge portion on the outer peripheral side of the tool, it is possible to increase the cutting edge angle at the corner on the base end side of the tool to improve the cutting edge strength. Can be planned. In addition to this, the nick is formed so as to extend in a direction that inclines toward the tool tip side as it goes to the rear side in the tool rotation direction, and therefore, the cutting edge angle in the cross section orthogonal to the corner on the tool base end side. In other words, the true cutting edge angle of the corner will be set to a larger value, which in combination gives a higher cutting edge strength to the corner on the acute angle side, so that even under heavy cutting conditions such as those mentioned above, It is possible to suppress the loss and wear of the.

[0007]

1 to 5 show an embodiment of the present invention. In these drawings, the tool body 1 is made of a hard material such as cemented carbide and has a cylindrical shaft shape, and the tip side (right side in FIG. 1) is a blade portion 2 and the base end side is a shank portion 3 It is said that. On the outer circumference of the blade portion 2, there are three twist grooves 4 that are twisted backward from the tip of the tool body 1 toward the base end in the tool rotation direction (indicated by symbol T in the figure).
Are formed at equal intervals in the circumferential direction of the tool body 1, and cutting edges 5 are formed on the outer peripheral ridges of the wall surfaces of these twisted grooves 4 that face the tool rotation direction. The twist angle φ of the cutting edge 5 is set to 40 ° in this embodiment. Further, bottom blades 6 are formed on the tip end surface of the blade portion 2 from the tips of the respective cutting blades 5 toward the center of rotation of the tool body 1. A nick 7 is formed on each cutting blade 5 so as to extend rearward from the cutting edge in the tool rotation direction.
Are formed along the line.

Here, FIG. 3 (a) is a development view of the blade portion 2 of the end mill of this embodiment, and FIG. 3 (b) is a nick 7 ... of each cutting edge 5 ... around the rotation axis O of the tool body 1. FIG. 4 is a diagram showing the rotation loci of the tool. In the present embodiment, the nicks 7 formed on the three cutting edges 5 ... Are arranged to be slightly offset from each other in the direction of the axis O so that they do not overlap or coincide with each other. Also,
By arranging the rotation loci of the nicks 7 ... In such a manner that they are displaced in the direction of the axis O, a distance R is provided between the nicks 7, 7 that are adjacent to each other in the direction of the axis O. However, in the present embodiment, the width W of the interval R in the direction of the axis O is set in the range of 0.1 mm to 0.2 mm, which is the same for all the nicks 7 and 7 having the adjacent rotation loci. As a result, the rotation loci of the nicks 7 ... Are arranged at equal intervals in the direction of the axis O as shown in FIG.

Further, in this embodiment, the other nick 7 located on the tip side of the nick 7 in the direction of the axis O in the rotation locus is the cutting edge 5 on which the nick 7 is formed.
Is formed on the other cutting edge 5 adjacent to the rear side in the tool rotation direction. That is, the nicks 7 formed on each cutting edge 5 are arranged so as to draw a helix around the axis O, being sequentially shifted stepwise toward the tip end side in the axis O direction as it goes rearward in the tool rotation direction. It will be. Therefore, the interval between the adjacent nicks 7, 7 in one cutting edge 5, that is, the pitch P (m of the nicks 7 in one cutting edge 5
m), assuming that the width of the nick 7 in the direction of the axis O is N (mm), P = 3 in a three-blade end mill like this embodiment.
It is represented by x (N + W). And each Nick 7 ...
The nick 7 is formed so as to extend in a direction toward the tip side (lower side in FIG. 3) of the tool main body 1 toward the rear side (right side in FIG. 3A) in the tool rotation direction. The inclination angle, that is, the inclination angle δ formed by the nick 7 with respect to the plane perpendicular to the rotation axis O is set to 3 ° in this embodiment.

On the other hand, FIG. 4 is an enlarged view of the opening of the nick 7 to the twist groove 4 as seen from the tool rotating direction side. As shown in this figure, the nick 7 has a trapezoidal cross section. The side wall 7a on the tool base end side (left side in FIG. 4) and the side wall 7b on the tool tip side (right side in FIG. 4) are both formed in a planar shape and are on the outer peripheral side of the tool (see FIG. 4, the tool base end side and the tip end side are separated from each other. And among the corners where the nick 7 and the twist groove 4 intersect,
A flank angle α formed by a corner located on the tool base end side and having an acute angle in a side view of the tool body 1 (an intersecting ridgeline portion between the side wall 7a and a wall surface of the twist groove 4 facing the tool rotation direction) 8a is
The angle is larger than the flank angle β formed by the corner 8b located on the tool tip side and having an obtuse angle in the side view (the ridge line intersecting the side wall 7b and the wall surface of the twist groove 4), and is 40 °.
The settings are made as described above. Incidentally, in this embodiment, the flank angle α formed by the corner 8a on the tool base end side is 4
It is set at 5 °, while the corner 8b on the tool tip side
The flank angle β formed by is set to 15 °.

Further, FIG. 5 shows a cross section of the cutting edge 5 orthogonal to the axis O of the cutting edge 5. As shown in FIG. 5, the bottom surface 7c of the nick 7 has an outer periphery of the cutting edge 5. The clearance angle γ is set to be equal to the clearance angle of the clearance surface 5a. That is, in other words, the nick 7 is formed so that the nick depth from the outer peripheral flank 5a is constant. Incidentally, in this embodiment, the clearance angle γ of the bottom surface 7c of the nick 7 is set to be 10 °.

In the end mill having such a structure,
Chips generated by the cutting blades 5 during cutting are shortly divided by the nicks 7 formed in the cutting blades 5 so that good discharge of chips can be promoted. In the end mill of this embodiment, the nick 7 and the twist groove 4 are
Among the corners, the flank angle α of the sharp corner 8a on the tool base end side is set to be 40 ° or more larger than the flank angle β of the obtuse corner 8b on the tool tip side. As a result, the cutting edge angle in the cross section orthogonal to the corner 8a becomes larger than the acute angle exhibited by the corner 8a in the side view, and thus high cutting edge strength can be obtained.

In addition to this, the nick 7 is formed so as to incline toward the tool tip side at an inclination angle δ as it goes to the rear side in the tool rotation direction. Therefore, the corner 8a is formed. The angle of the acute angle shown in the side view of 1 becomes large, and the cutting edge angle in the cross section orthogonal to the corner 8a also becomes larger. Therefore, according to the end mill of the present embodiment, increasing the flank angle α and forming the nick 7 with inclination as described above, together with increasing the true cutting edge angle of the corner 8a. As a result, it becomes possible to give a higher cutting edge strength to the corner 8a having an acute angle. And this
It is possible to prevent the corners 8a from being damaged or worn even during machining under heavy cutting conditions as described above, and it is possible to extend the tool life.

In this embodiment, the inclination angle δ formed by the nick 7 with respect to the rotation axis O of the tool body 1 is set to 3 °. However, if the inclination angle δ becomes too large, the nick 7 is
It is not preferable since the contact of the side wall 7a on the tool base end side with the work material cannot be neglected, resulting in an increase in cutting resistance or the abrasion of the side wall 7a. Therefore, it is desirable that the inclination angle δ is set so that the nick 7 is provided with the inclination as described above in the range of 10 ° or less. Also, in this embodiment, this nick 7
The side wall 7a of the tool base end side is formed in a flat shape, and thereby the corner 8a on the tool base end side is also formed so as to extend linearly as shown in FIG. 4, but at least the corner 8a. If the flank angle α is set to 40 ° or more at the edge portion on the outer peripheral side of the tool, for example, a linear chamfer is formed at the intersection ridge portion between the side wall 7a of the nick 7 and the outer peripheral flank surface 5a of the cutting edge 5. A round chamfer may be applied. Further, when such a configuration is adopted, the flank angle of the corner 8a on the tool base end side on the tool inner peripheral side does not necessarily have to be 40 ° or more.

Further, in the present embodiment, the nicks 7 ... Are arranged so as to be offset in the axis O direction so that a distance R is provided between the nicks 7, 7 adjacent to each other in the axis O direction. This is because, in a three-blade end mill like this embodiment, if the rotation loci of the nicks 7 and 7 of the two cutting blades 5 and 5 are overlapped with each other, the nicks 7 and 7 may overlap with each other. This is because there is a portion left uncut on the machined surface of the work material. Then, in order to remove this uncut residue, it is unavoidable to rely on another one of the cutting blades 5, so that the other one of the cutting blades 5 is overloaded, and depending on the feeding relationship, There is a possibility that the uncut portion of the machined surface cannot be completely removed. However, in the case of an end mill having four or more blades, it is sufficient to prevent the rotation loci of the nicks from overlapping with each other between adjacent cutting edges in the circumferential direction of the tool body. And, for example, in the case of a 4-flute end mill, every other cutting edge nick in the circumferential direction
By forming them so that their rotation loci match,
The pitch P of the nicks at one cutting edge can be reduced to P = 2 × (N + W) with respect to the width N of the nicks and the width W of the interval R.

Further, in order to surely prevent the rotation loci of the nicks 7 and 7 from overlapping as described above and obtain a good machined surface, the width W of the interval R in the axis O direction is the same as that of this embodiment. Therefore, it is desirable that the thickness is 0.1 mm or more. Further, in the present embodiment, as described above, the nicks 7 of the respective cutting blades 5 are arranged so as to sequentially draw a helix toward the tip side of the axis O in the stepwise direction as it goes rearward in the tool rotation direction, This also has the advantage that the flow of chips in the twist groove 4 can be made smooth.

[0017]

As described above, according to the present invention, the nick is formed so as to incline toward the tool tip side as it goes rearward in the tool rotation direction, and the nick intersects the twist groove. The synergistic effect of setting the flank angle of the corner on the tool base end side of the corner to be larger than the flank angle of the corner on the tip side and set to 40 ° or more makes it possible to create a sharp corner on the tool base end side. In fact, it is possible to provide a large edge angle, thereby ensuring the edge strength and providing an end mill with a long tool life that can suppress the occurrence of chipping and wear even under heavy cutting conditions. .

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is an enlarged view of the tip portion of the embodiment shown in FIG. 1 when viewed in the A direction.

FIG. 3 is a development view of (a) blade portion 2 of the embodiment shown in FIG.
(B) It is a figure which shows the rotation locus of the nick 7 around the axis O.

FIG. 4 is an enlarged view of an opening of a nick 7 in the embodiment shown in FIG. 1 viewed from the tool rotation direction side.

5 is a sectional view of the cutting edge 5 in the embodiment shown in FIG.

[Explanation of symbols]

 1 Tool body 4 Twisting groove 5 Cutting edge 7 Nick 8a Corner on the tool base end side 8b Corner on the tool tip side O Rotation axis of the tool body R Distance between the nicks 7 and 7 in the rotation trajectory α Corner 8a flank angle β corner 8b flank angle δ nick 7 inclination angle P pitch of nick 7 at one cutting edge N width of nick 7

Claims (3)

[Claims] 1. A plurality of twisted grooves are formed on the outer periphery of a tool body rotated around an axis from the tool tip toward the base end side, and the outer circumferential ridge portion of the wall surface of the twisted groove facing the tool rotation direction side. Is formed with a cutting edge, and a plurality of nicks extending in a direction inclining toward the tool tip side toward the tool rotation direction rear side are formed on the cutting edge. The side wall and the side wall on the tool base end side are formed so as to be separated from each other toward the outer peripheral side of the tool, and the flank angle of the corner on the tool base end side of the corners where the nick and the twist groove intersect each other. Is larger than the flank angle of the corner on the tip side and is set to 40 ° or more at least at the edge portion on the outer peripheral side of the tool. 2. The end mill according to claim 1, wherein an inclination angle formed by the nick with respect to a plane perpendicular to the axis is set to 10 ° or less. 3. At least in a pair of cutting blades adjacent to each other in the circumferential direction of the tool body, the nicks do not have their rotation loci about the axis line overlap with each other, and the rotation loci extend in the axial direction. The end mill according to claim 1 or 2, wherein the nicks are arranged such that a distance of at least 0.1 mm is provided between adjacent nicks.