WO2017188379A1

WO2017188379A1 - Endmill

Info

Publication number: WO2017188379A1
Application number: PCT/JP2017/016732
Authority: WO
Inventors: 鈴木　教和; 石黒　力也; 真靖細川; 光太郎坂口
Original assignee: 国立大学法人名古屋大学; 三菱マテリアル株式会社
Priority date: 2016-04-27
Filing date: 2017-04-27
Publication date: 2017-11-02
Also published as: JP2017196694A

Abstract

In the present end mill: four peripheral cutting edges (1) and (2) that are side by side at distances from each other in the circumferential direction of the end mill body comprise two each of first peripheral cutting edges (1) and second peripheral cutting edges (2) that have a different helix angle from the first peripheral cutting edges 1; the first peripheral cutting edges (1) and the second peripheral cutting edges (2) are alternately disposed in the circumferential direction; and in a transverse sectional view of the end mill at a specified location in the cutting edge length ap region of the peripheral cutting edges (1) and (2), four pitch angles A and B that are side by side in the circumferential direction comprise two each of first pitch angles A and second pitch angles B with a different angle from the first pitch angles A, and the two first pitch angles A, A are disposed adjacent to each other in the circumferential direction and the two second pitch angles B, B are disposed adjacent to each other in the circumferential direction.

Description

End mill

The present invention relates to an end mill that can effectively suppress chatter vibration over the entire blade length region.
This application claims priority based on Japanese Patent Application No. 2016-089384 filed in Japan on April 27, 2016, the contents of which are incorporated herein by reference.

Conventionally, for example, an end mill as shown in Patent Document 1 below is known.
The end mill is formed on the outer periphery of the end mill main body having an axial shape and the end mill main body, and toward the side opposite to the tool rotation direction in the circumferential direction around the axis from the tip end in the axial direction of the end mill main body toward the base end side. An extended chip discharge groove, an outer peripheral blade formed on a cross ridge line between the wall surface facing the tool rotation direction in the chip discharge groove and the outer peripheral surface of the end mill body, and a wall surface facing the tool rotation direction in the chip discharge groove and the tip end surface of the end mill body And a bottom blade (tip blade) formed at a crossing ridge line.

The end mill of Patent Document 1 is a so-called unequal lead end mill in which the torsion angles of the outer peripheral blades are different from each other. Such an unequal lead end mill can suppress chatter vibration by suppressing self-excited vibration generated during cutting.

JP 2009-220188 A

However, in a conventional end mill, chatter vibration can be suppressed regardless of where the cutting process is performed in the cutting edge region (full cutting length) of the outer peripheral cutting edge (that is, regardless of the amount of cutting in the axial direction). There was room for improvement. Furthermore, the chatter vibration frequency cannot be known in advance and chatter vibration can be suppressed even in a state where chatter vibration can occur at an arbitrary frequency within a predetermined frequency band. There was room for improvement.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an end mill that can remarkably suppress chatter vibration regardless of the amount of cut.

In order to solve such problems and achieve the above object, the present invention proposes the following means.
That is, the present invention provides an end mill body having an axial shape, and chip discharge formed on the outer periphery of the end mill body and extending in the circumferential direction around the axis as it goes from the distal end in the axial direction of the end mill body toward the base end side. An end mill comprising a groove, a wall surface facing the tool rotation direction in the circumferential direction in the chip discharge groove, and an outer peripheral blade formed on a cross ridge line with the outer peripheral surface of the end mill body, wherein the chip discharge Four grooves are formed in the circumferential direction so as to be spaced apart from each other, and the four outer peripheral blades that are spaced apart from each other in the circumferential direction are twisted between the first outer peripheral blade and the first outer peripheral blade. Two second outer peripheral blades having different angles are included, and the first outer peripheral blades and the second outer peripheral blades are alternately arranged in the circumferential direction, and the outer peripheral blades The axis at a predetermined position in the long region 4 in the circumferential direction with a central angle formed between a pair of virtual straight lines connecting the pair of outer peripheral blades adjacent in the circumferential direction and the axis as a pitch angle in a cross-sectional view perpendicular to the end mill. The two pitch angles include two first pitch angles and two second pitch angles different from the first pitch angle, and the two first pitch angles are Are arranged adjacent to each other in the circumferential direction, and the two second pitch angles are arranged adjacent to each other in the circumferential direction.

The end mill of the present invention includes four outer peripheral blades arranged on the outer periphery of the end mill main body at intervals in the circumferential direction. These four outer peripheral blades each include two first outer peripheral blades and two second outer peripheral blades having different torsion angles, and the first outer peripheral blade and the second outer peripheral blade. The outer peripheral blades are alternately arranged in the circumferential direction. That is, the end mill of the present invention is not an equal lead end mill in which the twist angles of the outer peripheral blades are all the same, but an unequal lead end mill having a plurality of types of twist angles.

Further, in the cross-sectional view of the end mill main body at a predetermined position in the blade length region of the outer peripheral blade, four pitch angles arranged around the axis of the end mill main body (in the end mill cross-sectional view, a pair of adjacent outer peripheral blades, an axis, (Center angle formed between a pair of virtual straight lines) includes two first pitch angles and two second pitch angles having different angles. The two first pitch angles are adjacently arranged in the circumferential direction, and the two second pitch angles are also adjacently arranged in the circumferential direction. That is, the end mill of the present invention is not an equal pitch end mill in which the pitch angles of the outer peripheral blades are all the same, but is also an unequal pitch end mill having a plurality of types of pitch angles.

For this reason, in the end mill of the present invention, the four outer peripheral blades are arranged with special technical features that are not conventionally provided. The arrangement of the outer peripheral blades of the present invention and the effects thereof will be described below with reference to FIGS.
In FIG. 5 schematically showing the arrangement of the outer peripheral blades of the present invention, the cross section of the end mill main body at a predetermined position in the blade length ap region of the outer peripheral blades 1 and 2 (in the example shown, the center (1 / 2))), the pitch angles A and B corresponding to the distance between the outer

peripheral blades

1 and 2 along the end mill circumferential direction (horizontal axis direction) in FIG. The first pitch angle A, the first pitch angle A, the second pitch angle B, and the second pitch angle B are arranged in this order.
The outer peripheral blades alternate in the order of the first outer peripheral blade 1, the second outer peripheral blade 2, the first outer peripheral blade 1, and the second outer peripheral blade 2 in the order opposite to the tool rotation direction T. Accordingly, the torsion angle of the outer peripheral blade is also directed toward the side opposite to the tool rotation direction T, the torsion angle γ1 of the first outer peripheral blade 1, the torsion angle γ2 of the second outer peripheral blade 2, and the first The twist angle γ1 of the outer peripheral blade 1 and the twist angle γ2 of the second outer peripheral blade 2 are alternately arranged in this order.

Accordingly, of the two first pitch angles A and A shown in FIG. 5, one of the first pitch angles A located in the tool rotation direction T and two of the second pitch angles B and B are One second pitch angle B positioned in the tool rotation direction T is the difference between the angles (B−A absolute value) over the entire blade length ap region. | May be expressed as |).

Specifically, in FIG. 5, the first pitch angle A on one side (left side / tool rotation direction T side) at a predetermined position (ap1 / 2) in the blade length ap region is gradually decreased toward the tip side of the blade length ap. Thus, the pitch angle θ1 is set at the tip position (ap0) of the blade length ap region. Further, the second pitch angle B on one side (left side / tool rotation direction T side) at a predetermined position (ap1 / 2) in the blade length ap region is gradually reduced toward the tip side of the blade length ap, and the blade length The pitch angle θ3 is set at the tip position (ap0) of the ap region.
In this case, the angle difference | BA | at the predetermined position of the blade length ap and the angle difference | θ3-θ1 | at the tip position of the blade length ap are equal to each other. Also, at the base end position (ap1 not shown) of the blade length ap region, the difference in angle is the same as described above, and the difference in angle is also equal in the other blade length ap regions.
That is, the difference between the first pitch angle A and the second pitch angle B is constant over the entire blade length ap region.

Further, of the two first pitch angles A and A shown in FIG. 5, the other first pitch angle A located on the side opposite to the tool rotation direction T, and the two second pitch angles B, Of B, the other second pitch angle B located on the opposite side of the tool rotation direction T is constant in the difference | BA− between each other over the entire blade length ap region. .

Specifically, in FIG. 5, the first pitch angle A on the other side (right side / opposite to the tool rotation direction T) at a predetermined position (ap1 / 2) in the blade length ap region is directed toward the tip side of the blade length ap. Accordingly, the pitch angle θ2 is set at the tip position (ap0) of the blade length ap region. Further, the second pitch angle B on the other side (right side / opposite to the tool rotation direction T) at a predetermined position (ap1 / 2) in the blade length ap region is gradually increased toward the tip side of the blade length ap. The pitch angle θ4 is set at the tip position (ap0) of the blade length ap region.
In this case, the angle difference | BA | at the predetermined position of the blade length ap is equal to the angle difference | θ4-θ2 | at the tip position of the blade length ap. Also, at the base end position (ap1 not shown) of the blade length ap region, the difference in angle is the same as described above, and the difference in angle is also equal in the other blade length ap regions.
That is, the difference between the other first pitch angle A and the other second pitch angle B is constant over the entire blade length ap region.

Also, the difference in angle between one first pitch angle A and one second pitch angle B | B−A |, and the other first pitch angle A and the other second pitch angle B The angle difference | BA | is equal to each other. Furthermore, this relationship is maintained over the entire blade length ap region.
Specifically, for example, at the tip position (ap0) of the blade length ap region, the angle difference | θ3-θ1 | and the angle difference | θ4-θ2 | And the same as each other.

Moreover, in FIG. 6 which shows the arrangement | sequence of another outer periphery blade included in this invention typically, in the blade length ap area | region of the

outer periphery blades

1 and 2, the cross section of an end mill main body in a predetermined position (in the example of illustration ap1 / 2), pitch angles A and B corresponding to the distance between the outer

peripheral blades

1 and 2 along the end mill circumferential direction (horizontal axis direction) in FIG. 6 are directed toward the side opposite to the tool rotation direction T. The first pitch angle A, the second pitch angle B, the second pitch angle B, and the first pitch angle A are arranged in this order.
The outer peripheral blades alternate in the order of the first outer peripheral blade 1, the second outer peripheral blade 2, the first outer peripheral blade 1, and the second outer peripheral blade 2 in the order opposite to the tool rotation direction T. Accordingly, the torsion angle of the outer peripheral blade is also directed toward the side opposite to the tool rotation direction T, the torsion angle γ1 of the first outer peripheral blade 1, the torsion angle γ2 of the second outer peripheral blade 2, and the first The twist angle γ1 of the outer peripheral blade 1 and the twist angle γ2 of the second outer peripheral blade 2 are alternately arranged in this order.

Accordingly, of the two first pitch angles A and A shown in FIG. 6, one of the first pitch angles A located in the tool rotation direction T and two of the second pitch angles B and B are The difference between the other second pitch angles B located on the opposite side of the tool rotation direction T and the angle | BA− ||

Specifically, in FIG. 6, the first pitch angle A on one side (left side) at a predetermined position (ap1 / 2) in the blade length ap region is gradually reduced toward the tip side of the blade length ap, and the blade length ap The pitch angle θ1 is set at the tip position (ap0) of the region. In addition, the second (right) second pitch angle B at a predetermined position (ap1 / 2) in the blade length ap region is gradually reduced toward the tip side of the blade length ap, and the tip position of the blade length ap region ( In ap0), the pitch angle is θ3.
In this case, the angle difference | BA | at the predetermined position of the blade length ap and the angle difference | θ3-θ1 | at the tip position of the blade length ap are equal to each other. Also, at the base end position (ap1 not shown) of the blade length ap region, the difference in angle is the same as described above, and the difference in angle is also equal in the other blade length ap regions.
That is, the difference between the first pitch angle A on one side and the second pitch angle B on the other side | B−A | is constant over the entire region of the blade length ap region.

In addition, of the two first pitch angles A and A shown in FIG. 6, the other first pitch angle A located on the side opposite to the tool rotation direction T and the two second pitch angles B, Of B, one second pitch angle B positioned in the tool rotation direction T is constant in the difference | BA− of the angle over the entire blade length ap region.

Specifically, in FIG. 6, the first (right) first pitch angle A at a predetermined position (ap1 / 2) in the blade length ap region is gradually increased toward the tip side of the blade length ap, and the blade length ap is increased. The pitch angle θ2 is set at the tip position (ap0) of the region. In addition, one (left side) second pitch angle B at a predetermined position (ap1 / 2) in the blade length ap region is gradually increased toward the tip side of the blade length ap, and the tip position of the blade length ap region ( In ap0), the pitch angle is θ4.
In this case, the angle difference | BA | at the predetermined position of the blade length ap is equal to the angle difference | θ4-θ2 | at the tip position of the blade length ap. Also, at the base end position (ap1 not shown) of the blade length ap region, the difference in angle is the same as described above, and the difference in angle is also equal in the other blade length ap regions.
That is, the difference between the other first pitch angle A and one second pitch angle B is constant over the entire blade length ap region.

Also, the difference between the first pitch angle A and the second pitch angle B on the other side | B−A | and the difference between the first pitch angle A on the other side and the second pitch angle B on the other side. The angle difference | BA | is equal to each other. Furthermore, this relationship is maintained over the entire blade length ap region.
Specifically, for example, at the tip position (ap0) of the blade length ap region, the angle difference | θ3-θ1 | and the angle difference | θ4-θ2 | And the same as each other.

As a result of extensive research on the end mill, the inventor of the present invention, in order to suppress a specific frequency that generates chatter vibration at the time of cutting, each of the difference of the angle corresponding to the frequency It came to the knowledge that it was effective to set it as the arrangement | sequence of the outer periphery blade made into the pitch angle. That is, by setting the difference between the angles between the four outer peripheral blades, the phase difference of the regenerative vibration can be shifted between the outer peripheral blades, thereby suppressing the occurrence of self-excited vibration near the resonance frequency. As a result, chatter vibration can be suppressed.
The “difference in angle corresponding to a specific frequency” can be obtained based on vibration calculation theory or can be obtained from an experimental value (experience value). The “specific frequency” specifically indicates a frequency band within a predetermined range, for example, a range of 300 to 900 Hz.

Based on the above-described knowledge, the present invention employs a configuration that maintains the above-described angle difference that can cancel a specific frequency over the entire blade length ap region. Specifically, as described with reference to FIGS. 5 and 6, by using a special configuration in which the angle difference | BA is constant over the entire blade length ap region, Regardless of the depth of cut, the specific frequency to be canceled can be stably suppressed.
Furthermore, the frequency of chatter vibration cannot be known in advance, and conventionally, even in a state where chatter vibration can occur at an arbitrary frequency within a predetermined frequency band, the end mill of the present invention can be used. According to this, chatter vibration can be stably suppressed over the entire predetermined frequency band.

Here, in order to deepen the understanding of the present invention, a comparative example (conventional end mill) shown in FIG. 7 will be described. In FIG. 7, at a predetermined position in the blade length ap region, the four pitch angles A and B are directed to the opposite side of the tool rotation direction T, and the first pitch angle A, the second pitch angle B, and the first The pitch angle A and the second pitch angle B are alternately arranged in this order.
Of the two first pitch angles A and A, one of the first pitch angles A located in the tool rotation direction T and two of the second pitch angles B and B in the tool rotation direction T. One of the second pitch angles B that is positioned is an angle difference | BA− that can suppress a specific frequency only at a predetermined position (ap1 / 2) in the blade length ap region.

Specifically, in FIG. 7, the first pitch angle A on one side (left side) at a predetermined position (ap1 / 2) in the blade length ap region is gradually decreased toward the tip side of the blade length ap, and the blade length ap The pitch angle θ1 is set at the tip position (ap0) of the region. In addition, one (left side) second pitch angle B at a predetermined position (ap1 / 2) in the blade length ap region is gradually increased toward the tip side of the blade length ap, and the tip position of the blade length ap region ( In ap0), the pitch angle is θ2.
In this case, an angle difference | BA | at a predetermined position of the blade length ap and an angle difference | θ2-θ1 | at the tip position of the blade length ap are different from each other. Also, at the base end position (ap1 not shown) of the blade length ap region, the difference in angle is different as described above, and the difference in angle is also different in the other blade length ap regions.
That is, the difference between the first pitch angle A on one side and the second pitch angle B on the other side is changed over the entire blade length ap region.

In addition, of the two first pitch angles A and A shown in FIG. 7, the other first pitch angle A located on the side opposite to the tool rotation direction T, and the two second pitch angles B, Of B, the other second pitch angle B located on the side opposite to the tool rotation direction T is an angle at which a specific frequency can be suppressed only at a predetermined position (ap1 / 2) in the blade length ap region. The difference is | B−A |.

Specifically, in FIG. 7, the first (right) first pitch angle A at a predetermined position (ap1 / 2) in the blade length ap region is gradually decreased toward the tip side of the blade length ap, and the blade length ap The pitch angle θ1 is set at the tip position (ap0) of the region. Further, the second (right) second pitch angle B at a predetermined position (ap1 / 2) of the blade length ap region is gradually increased toward the tip side of the blade length ap, and the tip position of the blade length ap region ( In ap0), the pitch angle is θ2.
In this case, an angle difference | BA | at a predetermined position of the blade length ap and an angle difference | θ2-θ1 | at the tip position of the blade length ap are different from each other. Also, at the base end position (ap1 not shown) of the blade length ap region, the difference in angle is different as described above, and the difference in angle is also different in the other blade length ap regions.
That is, the difference between the other first pitch angle A and the other second pitch angle B is changed over the entire blade length ap region.

In FIG. 7, the difference between the first | left-side first pitch angle A and the other (right-side) second pitch angle B is similar to the above. It is varied over the entire long ap region. Also, with respect to the other (right side) first pitch angle A and the one (left side) second pitch angle B, the difference between the angles | BA is equal to the blade length ap region, as described above. Can be changed throughout.

In such a conventional end mill, when cutting is performed at a portion other than a predetermined position in the blade length ap region (a cutting amount other than the cutting amount corresponding to the predetermined position), a specific frequency cannot be suppressed, The occurrence of chatter vibration cannot be suppressed.

On the other hand, in the present invention, the following remarkable effects which are not obtained by the conventional end mill are exhibited. That is, at a predetermined position (ap1 / 2 in FIGS. 5 and 6) in the blade length ap region, effective pitch angles A and B are set to specific frequencies for which the occurrence of self-excited vibration is desired to be suppressed. A simple configuration in which the pitch angles A and A and the second pitch angles B and B are arranged adjacent to each other in the circumferential direction, and the outer

peripheral blades

1 and 2 having different twist angles are alternately arranged in the circumferential direction. By manufacturing the end mill, the end mill effectively suppresses the occurrence of self-excited vibration for the specific frequency not only at a predetermined position of the blade length ap region but also over the entire region of the blade length ap region. Can do it. That is, chatter vibration can be stably suppressed regardless of the amount of cut in the axial direction of the end mill, and the manufacture of the end mill is not complicated.

In the present invention, the following effects can also be obtained.
In the present invention shown in FIGS. 5 and 6, the difference in angle between the first pitch angles A and A | A−A |, the difference in angle between the second pitch angles B and B | B−B | In the blade length ap region, at positions other than a predetermined position (ap1 / 2 in the illustrated example), | A−A | ≠ 0 and | BB | ≠ 0 (that is, unequal division). That is, even when paying attention to the combination of the first pitch angles A and A and the combination of the second pitch angles B and B, reproduction is performed at most positions (other than the predetermined position) in the blade length ap region. An effect can be obtained. For this reason, the present invention has a more robust effect than the conventional general unequal read (the area where the effect can be obtained for suppressing the reproduction effect can be expanded).

On the other hand, in the comparative example shown in FIG. 7, the difference in angle between the first pitch angles A and A | A−A | and the difference in angle between the second pitch angles B and B | B−B | Is | A−A | = 0 and | BB | = 0 (that is, equally divided) over the entire blade length ap region. For this reason, it is not effective in suppressing the reproduction effect.

Furthermore, the end mill according to the present invention makes it easy to suppress not only the specific frequency but also the occurrence of self-excited vibration when the frequency changes because the outer peripheral blades are unequal leads. In other words, the effect of suppressing a specific frequency is obtained, and the effect of suppressing a frequency other than the specific frequency is also achieved. Therefore, the effect of suppressing chatter vibration becomes particularly remarkable.

In the end mill of the present invention, it is preferable that the predetermined position in the blade length region is a portion other than the tip portion in the blade length region.

In this case, at the tip of the blade length region, for example, as shown in FIGS. 5 and 6, the angles of the pitch angles θ1 to θ4 can be made different from each other. That is, the tip portion of the edge length region of the outer peripheral blade is a position that starts to be cut into the work material, and is a place that is frequently used for cutting, and when the pitch angles are all different in the tip portion, the present invention The above-described effect of suppressing chatter vibration is more likely to be particularly remarkable, which is preferable.

In the end mill of the present invention, it is preferable that a predetermined position in the blade length region is a central portion in the blade length region.

In this case, as shown in FIG. 5 and FIG. 6, a predetermined length ap region of the outer peripheral blade including the two first pitch angles A and A and the two second pitch angles B and B is predetermined. Since the position is the central portion (ap1 / 2) of the blade length ap region, the width of the chip discharge groove adjacent to the outer peripheral blade is reduced at the distal end and the base end of the blade length ap region of the outer peripheral blade. It is suppressed that it passes too much.
Therefore, according to the said structure, chip | tip discharge property can be maintained favorable, suppressing generation | occurrence | production of chatter vibration.

According to the end mill of the present invention, chatter vibration can be remarkably suppressed regardless of the cutting amount or the like.

It is a perspective view which shows the end mill which concerns on one Embodiment of this invention. It is the side view which looked at the end mill of FIG. 1 from radial direction. It is the front view which looked at the end mill of FIG. 1 toward the base end side from the front-end | tip. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 2 (a cross-sectional view of the end mill). It is a figure which shows typically the arrangement | sequence of the outer periphery blade of the end mill of FIG. It is a figure which shows typically the arrangement | sequence of the outer periphery blade | edge of the modification of the end mill of FIG. It is a figure which shows typically the arrangement | sequence of the outer periphery blade of the end mill of a comparative example. (A) A graph showing the relationship between the amount of cut in the axial direction (vertical axis), the frequency (horizontal axis), and the number of regenerations (regenerative vibration) during cutting using the end mill of FIG. 1, (b) of the comparative example It is a graph showing the relationship between the amount of cuts in the axial direction (vertical axis), the frequency (horizontal axis), and the number of reproductions (reproduction vibration) during cutting using an end mill.

Hereinafter, a square end mill 20 which is an example of an end mill according to an embodiment of the present invention will be described with reference to the drawings.
In addition, this invention is not limited to the square end mill 20, For example, it applies to various end mills, such as a radius end mill and a ball end mill (a taper ball end mill, a long neck end mill, a taper neck end mill etc.), etc. Is possible.

[Schematic configuration of square end mill and end mill body]
As shown in FIGS. 1 to 4, the square end mill 20 of the present embodiment has a shaft shape and includes an end mill body 3 made of, for example, cemented carbide or high-speed tool steel.
The end mill main body 3 has a substantially columnar shape, and a blade portion 3a is formed at least at a tip portion along the axis O direction of the end mill main body 3, and a portion other than the blade portion 3a is a shank portion 3b.

In the square end mill 20, a cylindrical shank portion 3b in the end mill body 3 is held by a main shaft or the like of a machine tool, and is rotated in a tool rotation direction (end mill rotation direction) T around an axis O, thereby a metal material or the like. It is used for cutting work (rolling work) of work material consisting of Further, along with the above rotation, the cutting in the direction of the axis O and the feeding in the direction crossing the axis O are given, and the side surface processing, shoulder processing, plunge (longitudinal feeding) processing on the work material by the blade 3a Various processing such as grooving is performed.

Further, when the work material is cut by the square end mill 20, the coolant is supplied toward the blade portion 3a of the square end mill 20 and the work surface (work part) of the work material. As the coolant, for example, an oily or water-soluble cutting fluid or compressed air is used. The coolant is supplied from the main spindle of the machine tool to the blade portion 3a and the machining surface through the inside of the end mill body 3, or is supplied to the blade portion 3a and the machining surface from the outside of the end mill body 3.

[Definition of direction (direction) used in this embodiment]
In the present embodiment, of the directions along the axis O of the end mill body 3 (axis O direction), the direction from the shank portion 3b to the blade portion 3a is referred to as the distal end side, and the direction from the blade portion 3a to the shank portion 3b. It is called the proximal side.
In addition, a direction perpendicular to the axis O is referred to as a radial direction, and a direction approaching the axis O in the radial direction is referred to as a radial inner side, and a direction away from the axis O is referred to as a radial outer side.
Further, the direction that circulates around the axis O is referred to as the circumferential direction. Of the circumferential directions, the direction in which the end mill body 3 is rotated at the time of cutting is referred to as the tool rotation direction T, and the opposite direction is the tool rotation direction. The side opposite to T (counter tool rotating direction) is referred to.

[Chip discharge groove]
Four chip discharge grooves 4 are formed on the outer periphery of the blade portion 3a at intervals in the circumferential direction. These chip discharge grooves 4 are arranged at unequal intervals in the circumferential direction.
Specifically, among the four chip discharge grooves 4, the two chip discharge grooves 4 are arranged at equal intervals in the circumferential direction, and the remaining two chip discharge grooves 4 are arranged at the equal intervals. Are arranged at equal intervals in the circumferential direction, and the chip discharge grooves 4 are arranged at unequal intervals in the end mill as a whole.

The chip discharge groove 4 is twisted and extended in the circumferential direction along the axis O as it goes from the distal end along the axis O direction of the end mill body 3 toward the base end side. The chip discharge groove 4 of the present embodiment opens at the distal end surface of the end mill body 3 and gradually twists and extends toward the side opposite to the tool rotation direction T from the distal end surface toward the proximal end side. The chip discharge groove 4 is rounded up to the outer periphery of the end mill body 3 at the end portion on the base end side of the blade portion 3a.

Each chip discharge groove 4 has a wall surface facing the tool rotation direction T, and a portion of the wall surface adjacent to the cutting edge is a rake surface. Specifically, of the rake face of the cutting edge, the portions adjacent to the outer

peripheral edges

1 and 2 and the bottom edge 9 described later of the cutting edge are the rake face 4a and the bottom edge 9 of the outer

peripheral edges

1 and 2, respectively. The rake face 4b.

A gash 7 is formed at the tip of the chip discharge groove 4 so that the tip is cut out in a groove shape in the radial direction. Specifically, the gash 7 of the present embodiment is formed in a groove shape extending along the radial direction at the tip end portion of the chip discharge groove 4, and the end portion on the radially inner side is at a position close to the axis O. Is arranged.
In this embodiment, four gashes 7 are formed corresponding to the four chip discharge grooves 4, and as shown in FIG. 3, a pair of gashes adjacent to each other in the circumferential direction among these gashes 7. 7, that is, a set of gashes 7 communicate with each other at the radially inner end of each gasche 7. In addition, among the four bottom blades 9, the two bottom blades 9 (short blades) cut out by the gash 7 (the set) have two blades 9 (long blades) that are not cut out by the gash 7. The blade length is shorter than the blade length.

[Cutting edge]
As shown in FIGS. 1 to 4, the blade portion 3a has four cutting edges spaced from each other in the circumferential direction. Each of the cutting blades has an outer

peripheral blade

1 or 2 and a bottom blade 9, which are connected to form one cutting blade having a substantially L shape. That is, the square end mill 20 of the present embodiment has a four-blade blade portion 3a. The number of cutting edges (four) corresponds to the number of chip discharge grooves 4 (four).

(Peripheral blade)
Outer

peripheral blades

1 and 2 are formed on the intersecting ridge line between the wall surface facing the tool rotation direction T in the chip discharge groove 4 and the outer peripheral surface of the end mill body 3. The outer

peripheral blades

1 and 2 extend in a spiral shape (spiral shape) along the outer peripheral edge of the wall surface of the chip discharge groove 4. The outer

peripheral blades

1 and 2 include a first outer peripheral blade 1 and a second outer peripheral blade 2 having a twist angle different from that of the first outer peripheral blade 1. The first outer peripheral blade 1 and the second outer peripheral blade 2 will be described later separately.

The outer

peripheral blades

1 and 2 are the rake face 4a located at the radially outer end of the wall surface of the chip discharge groove 4 facing the tool rotation direction T, and the chip discharge groove 4 of the outer peripheral surface of the blade part 3a. Are formed on the intersecting ridge line of the outer peripheral flank 5 adjacent to the opposite side to the tool rotation direction T.
On the outer peripheral surface of the blade portion 3a, outer peripheral flank surfaces 5 are formed between the chip discharge grooves 4 adjacent in the circumferential direction. The width of the outer peripheral flank 5 (the length in the direction perpendicular to the outer peripheral blades 1 and 2) is, for example, substantially constant along the extending direction of the outer

peripheral blades

1 and 2.

In the blade portion 3a, a number (four) of outer

peripheral blades

1 and 2 corresponding to the number (four) of the chip discharge grooves 4 are arranged at intervals in the circumferential direction. Each of the outer

peripheral blades

1 and 2 is a lead equal to the chip discharge groove 4 adjacent to the tool rotation direction T, and gradually twists toward the opposite side of the tool rotation direction T from the distal end of the end mill body 3 toward the proximal end side. It extends.
A rotation locus formed by rotating the outer

peripheral blades

1 and 2 around the axis O is a single cylindrical surface centered on the axis O.

2 is a side view of the square end mill 20 shown in FIG. 2 and a diagram schematically showing the arrangement of the outer

peripheral blades

1 and 2 shown in FIG. The four outer

peripheral blades

1 and 2 formed on the blade portion 3a of the main body 3 include two first outer peripheral blades 1 and two second outer peripheral blades 2 having different twist angles. Further, the first outer peripheral blades 1 and the second outer peripheral blades 2 are alternately arranged in the circumferential direction.

2 and 5, the symbol γ1 represents the twist angle of the first outer peripheral blade 1, and the symbol γ2 represents the twist angle of the second outer peripheral blade 2. In the illustrated example, the twist angle γ2 of the second outer peripheral blade 2 is made larger than the twist angle γ1 of the first outer peripheral blade 1. However, the present invention is not limited to this, and the twist angle γ2 may be smaller than the twist angle γ1.

The difference in angle between the twist angle γ1 of the first outer peripheral blade 1 and the twist angle γ2 of the second outer peripheral blade 2 (the absolute value of γ2-γ1; in the following description, it is simply expressed as | γ2-γ1 | For example) 0 ° <| γ2-γ1 | ≦ 20 °, and preferably 2 ° ≦ | γ2-γ1 | ≦ 15 °. By setting the angle difference | γ2−γ1 | to 20 ° or less, it is possible to prevent the groove width from becoming too small at either the tip end portion or the base end portion of the chip discharge groove 4.
In the present embodiment, the twist angle γ1 of the first outer peripheral blade 1 is constant over the entire region of the blade length ap region of the outer peripheral blade 1, and the twist angle γ2 of the second outer peripheral blade 2 is The outer peripheral blade 2 is constant over the entire region of the blade length ap region.
In this embodiment, the formation region of the outer

peripheral blades

1 and 2 along the axis O direction of the end mill body 3 is referred to as a blade length region (this may be referred to as a blade length ap region).

Here, the “twist angle” referred to in the present embodiment refers to the axis O and the outer peripheral blades 1 and 2 (twist) in the side view of the end mill body 3 shown in FIG. 2 (when the end mill body 3 is viewed from the radial direction). Among the acute angles and obtuse angles formed between the coil and the spiral winding), an acute angle is indicated.
In the example of the present embodiment, the outer

peripheral blades

1 and 2 are gradually extended toward the side opposite to the tool rotation direction T from the distal end toward the proximal end side along the axis O direction. The twist angles 1 and 2 are positive angles (positive angles).

[Pitch angle of outer peripheral edge]
In the present embodiment, as shown in FIG. 4, a pair of virtual straight lines connecting the pair of outer

peripheral blades

1 and 2 adjacent to each other in the circumferential direction and the axis O in the end mill cross-sectional view perpendicular to the axis O. A central angle (an angle indicated by reference signs A and B) formed between them is referred to as a “pitch angle” (division angle).

As shown in FIG. 4, four pitch angles A arranged in the circumferential direction in the end mill cross-sectional view at a predetermined position (ap1 / 2 in the illustrated example) in the blade length ap region of the outer

peripheral blades

1 and 2, B includes two first pitch angles A and two second pitch angles B different from the first pitch angle A. The two first pitch angles A and A are adjacently arranged in the circumferential direction, and the two second pitch angles B and B are adjacently arranged in the circumferential direction.

That is, in the end mill cross-sectional view at the predetermined position, the four pitch angles A and B are the first pitch angle A, the first pitch angle A, the second pitch angle B, and the second pitch around the axis O. The pitch angles B are arranged in this order. In the illustrated example, the second pitch angle B is made larger than the first pitch angle A. However, the present invention is not limited to this, and the pitch angle B may be smaller than the pitch angle A.

The difference in angle between the first pitch angle A and the second pitch angle B (which is an absolute value of BA, and may be simply expressed as | BA− in the following description) is, for example, 0 ° <| BA | ≦ 20 °, preferably 5 ° ≦ | BA | ≦ 15 °. By setting the angle difference | B−A | to 20 ° or less, it is possible to prevent the groove width from becoming too small at either the tip end portion or the base end portion of the chip discharge groove 4.

As shown in FIG. 5, the pitch angles A, A, B, and B are arranged in this order along the circumferential direction (the horizontal axis direction in FIG. 5), Only at "predetermined positions". And the said predetermined position is made into parts other than the front-end | tip part in the blade length ap area | region, and in the example of this embodiment specifically, this predetermined position is a center part (namely, ap1 / 2) in a blade length ap area | region. It is said that.

[Bottom blade (tip blade)]
As shown in FIGS. 1 to 3, a bottom blade (tip blade) 9 is formed on the intersecting ridge line between the wall surface facing the tool rotation direction T in the chip discharge groove 4 and the tip surface of the end mill body 3. . The bottom blade 9 extends linearly along the tip edge of the wall surface of the chip discharge groove 4.

Specifically, the bottom blade 9 includes a rake face 4b located at an end portion on the tip end side and a tip end face of the blade portion 3a among the wall surfaces facing the tool rotation direction T of the chip discharge groove 4 (gash 7). The chip discharge groove 4 is formed at the intersecting ridge line with the tip flank 8 adjacent to the opposite side to the tool rotation direction T.
A tip flank 8 is formed between the chip discharge grooves 4 adjacent to each other in the circumferential direction on the tip surface of the blade portion 3a. The width of the tip flank 8 (the length in the direction perpendicular to the bottom blade 9) is, for example, substantially constant along the extending direction of the bottom blade 9.

In the blade portion 3a, a number (four) of bottom blades 9 corresponding to the number (four) of the chip discharge grooves 4 are arranged at intervals in the circumferential direction.
In the present embodiment, in a front view of the end mill main body 3 shown in FIG. 3 (when the front end surface of the end mill main body 3 is viewed from the axis O direction to the front), the bottom blade 9 extends along the radial direction.
The four bottom blades 9 include a pair of long blades (bottom blade 9 not cut out by the gash 7) and a pair of short blades (bottom blade 9 in which the radially inner end is cut off by the gash 7). And are included. Inner ends (end edges on the inner side in the radial direction) of the pair of long blades are arranged close to the axis O.
Gash 7 is disposed between the inner ends of the pair of short blades and the axis O.

In addition, in the side view of the end mill body 3 shown in FIG. 2, the bottom blade 9 gradually extends slightly toward the base end side from the outer end (radially outer edge) toward the radially inner side. . Therefore, the rotation locus formed by the bottom blade 9 rotating around the axis O is a conical surface (tapered surface) that gradually inclines toward the base end side from the outer end of the bottom blade 9 toward the radially inner side. Become.
The bottom blade 9 may extend so as to be included in a plane perpendicular to the axis O. In this case, the rotation locus of the bottom blade 9 is a plane perpendicular to the axis O.
The outer end in the radial direction of the bottom blade 9 is connected to the tip of the outer

peripheral blade

1 or 2 in the direction of the axis O.

[Modification of this embodiment]
Here, the modification of this embodiment included in this invention is demonstrated with reference to FIG. Detailed description of the same components as those described above will be omitted, and only different points will be described below.
6 is a diagram schematically showing the arrangement of the outer peripheral blades 1 and 2 (a diagram showing the outer periphery of the end mill developed in a flat shape). FIG. 5 described above is different from the outer

peripheral blades

1 and 2 and the pitch angle A, FIG. The arrangement (positional relationship) of B is different.

In FIG. 6, a pair of adjacent outer

peripheral blades

2 and 1 that form the pitch angle θ2 (and pitch angle A) shown in FIG. 5 and an adjacent outer peripheral blade 2 that forms the pitch angle θ4 (and pitch angle B), The group (1) is arranged so as to be interchanged with each other. In other words, in the four outer

peripheral blades

1 and 2 shown in FIG. 5, the position of the first outer peripheral blade 1 and the position of the second outer peripheral blade 2 are replaced with each other and arranged as shown in FIG. The end mill is configured as described above.

Specifically, in FIG. 6, four outer

peripheral blades

1, 2 face the opposite side to the tool rotation direction T, and the first outer peripheral blade 1, the second outer peripheral blade 2, and the first outer peripheral blade 1. The second outer peripheral blades 2 are arranged in this order. Further, in the end mill cross-sectional view at a predetermined position (ap1 / 2 in the illustrated example) in the blade length ap region of the outer

peripheral blades

1 and 2, the four pitch angles A and B are directed to the side opposite to the tool rotation direction T. The first pitch angle A, the second pitch angle B, the second pitch angle B, and the first pitch angle A are arranged in this order.

That is, in FIG. 6 as well, as in FIG. 5 described above, the first outer peripheral blades 1 and the second outer peripheral blades 2 are alternately arranged in the circumferential direction. Moreover, in the end mill cross-sectional view perpendicular to the axis O at a predetermined position in the blade length ap region of the outer

peripheral blades

1 and 2, the two first pitch angles A and A among the four pitch angles A and B are The two second pitch angles B and B are adjacently arranged in the circumferential direction.

[Effects of this embodiment]
The square end mill (end mill) 20 of the present embodiment described above includes four outer

peripheral blades

1 and 2 arranged on the outer periphery of the end mill body 3 at intervals in the circumferential direction. These four outer

peripheral blades

1 and 2 include two first outer peripheral blades 1 and two second outer peripheral blades 2 having different torsion angles γ1 and γ2 from each other. The one outer peripheral blade 1 and the second outer peripheral blade 2 are alternately arranged in the circumferential direction. That is, the square end mill 20 of the present embodiment is not an equal lead end mill in which the outer blades have the same twist angle, but an unequal lead end mill having a plurality of types of twist angles γ1 and γ2.

Further, in the cross-sectional view of the end mill body 3 at a predetermined position in the blade length ap region of the outer

peripheral blades

1 and 2, four pitch angles arranged around the axis O of the end mill body 3 (a pair of adjacent ones in the end mill cross-sectional view). The central angles A and B formed between a pair of imaginary straight lines connecting the outer

peripheral blades

1 and 2 and the axis O are the first pitch angle A and the second pitch angle that are different in magnitude from each other. B is included two by two. The two first pitch angles A and A are adjacently arranged in the circumferential direction, and the two second pitch angles B and B are also adjacently arranged in the circumferential direction. That is, the square end mill 20 of this embodiment is not an equal pitch end mill in which the pitch angles of the outer peripheral blades are all the same, but is also an unequal pitch end mill having a plurality of types of pitch angles A and B.

For this reason, in the square end mill 20 of the present embodiment, the four outer

peripheral blades

1 and 2 are arranged with special technical features that are not present. The arrangement of the outer

peripheral blades

1 and 2 and the effect thereof according to this embodiment will be described below with reference to FIGS. 5 and 6.
In FIG. 5 schematically showing the arrangement of the outer peripheral blades of the present embodiment, the cross section of the end mill body 3 at a predetermined position in the blade length ap region of the outer peripheral blades 1 and 2 (in the illustrated example, the center of the blade length ap ( Pitch angles A and B corresponding to the distance between the outer

peripheral blades

1 and 2 along the end mill circumferential direction (horizontal axis direction) in FIG. 5 are opposite to the tool rotation direction T. The first pitch angle A, the first pitch angle A, the second pitch angle B, and the second pitch angle B are arranged in this order.
And the outer

peripheral blades

1 and 2 are directed to the side opposite to the tool rotation direction T, and the first outer peripheral blade 1, the second outer peripheral blade 2, the first outer peripheral blade 1, and the second outer peripheral blade 2. As a result, the torsion angles γ1 and γ2 of the outer peripheral blades are also turned toward the side opposite to the tool rotation direction T, and the torsion angle γ1 of the first outer peripheral blade 1 and the second outer peripheral blade 2 The twist angle γ2, the twist angle γ1 of the first outer peripheral blade 1, and the twist angle γ2 of the second outer peripheral blade 2 are alternately arranged in this order.

Accordingly, of the two first pitch angles A and A shown in FIG. 5, one of the first pitch angles A located in the tool rotation direction T and two of the second pitch angles B and B are With respect to one second pitch angle B located in the tool rotation direction T, the difference in angle | BA is constant over the entire blade length ap region.

Specifically, in FIG. 5, the first pitch angle A on one side (left side) at a predetermined position (ap1 / 2) in the blade length ap region is gradually decreased toward the tip side of the blade length ap, and the blade length ap The pitch angle θ1 is set at the tip position (ap0) of the region. In addition, one (left side) second pitch angle B at a predetermined position (ap1 / 2) of the blade length ap region is gradually decreased toward the tip side of the blade length ap, and the tip position of the blade length ap region ( In ap0), the pitch angle is θ3.
In this case, the angle difference | BA | at the predetermined position of the blade length ap and the angle difference | θ3-θ1 | at the tip position of the blade length ap are equal to each other. Also, at the base end position (ap1 not shown) of the blade length ap region, the difference in angle is the same as described above, and the difference in angle is also equal in the other blade length ap regions.
That is, the difference between the first pitch angle A and the second pitch angle B is constant over the entire blade length ap region.

Specifically, in FIG. 5, the first (right) first pitch angle A at a predetermined position (ap1 / 2) in the blade length ap region is gradually increased toward the tip side of the blade length ap. The pitch angle θ2 is set at the tip position (ap0) of the region. Further, the second (right) second pitch angle B at a predetermined position (ap1 / 2) of the blade length ap region is gradually increased toward the tip side of the blade length ap, and the tip position of the blade length ap region ( In ap0), the pitch angle is θ4.
In this case, the angle difference | BA | at the predetermined position of the blade length ap is equal to the angle difference | θ4-θ2 | at the tip position of the blade length ap. Also, at the base end position (ap1 not shown) of the blade length ap region, the difference in angle is the same as described above, and the difference in angle is also equal in the other blade length ap regions.
That is, the difference between the other first pitch angle A and the other second pitch angle B is constant over the entire blade length ap region.

Moreover, in FIG. 6 which shows typically the arrangement | sequence of the outer periphery blade which is a modification of this embodiment, among the blade length ap area | regions of the

outer periphery blades

1 and 2, the cross section (in the example of illustration) of the end mill main body 3 in a predetermined position. The pitch angles A and B corresponding to the distance between the outer

peripheral blades

1 and 2 along the end mill circumferential direction (horizontal axis direction) in FIG. The first pitch angle A, the second pitch angle B, the second pitch angle B, and the first pitch angle A are arranged in this order.
And the outer

peripheral blades

As a result of extensive research on the end mill, the inventor of the present invention, in order to suppress a specific frequency that generates chatter vibration at the time of cutting, the difference in angle | BA corresponding to the frequency | B−A | As a result, it has been found that it is effective to arrange the outer

peripheral blades

1 and 2 with the pitch angles A and B. That is, by setting the angle difference | B−A | between the four outer

peripheral blades

1 and 2, the phase difference of the regenerative vibration can be shifted between the outer

peripheral blades

1 and 2, and near the resonance frequency. Generation of self-excited vibration that occurs can be suppressed, and as a result, chatter vibration can be suppressed.
The “difference in angle corresponding to a specific frequency” can be obtained based on vibration calculation theory or can be obtained from an experimental value (experience value). The “specific frequency” specifically indicates a frequency band within a predetermined range, for example, a range of 300 to 900 Hz.

Based on the above findings, the present embodiment employs a configuration that maintains the above-described angle difference | BA− that can cancel a specific frequency over the entire blade length ap region. Specifically, as described with reference to FIGS. 5 and 6, by using a special configuration in which the angle difference | BA is constant over the entire blade length ap region, Regardless of the depth of cut, the specific frequency to be canceled can be stably suppressed.
Furthermore, the frequency of chatter vibration cannot be known in advance, and conventionally, even in a state where chatter vibration can occur at an arbitrary frequency within a predetermined frequency band, the end mill of this embodiment can be used. Accordingly, chatter vibration can be stably suppressed over the entire predetermined frequency band.

Specifically, as shown in FIG. 8A, the cutting amount mm (vertical axis) in the direction of the axis O, the frequency Hz (horizontal axis), and the reproduction number RF (displayed by shading, which will be described in detail later). From the calculation result (analysis result) representing the relationship, according to the square end mill 20 of the present embodiment, for example, over a wide range of frequencies of 450 to 800 Hz, regardless of the depth of cut of 0 to 25 mm, the number of reproductions RF is all less than 0.3. It was confirmed that the occurrence of chatter vibration was significantly suppressed. The rotation speed of the main shaft was 2500 rpm.

The reproduction number RF will be described.
The sum of complex vectors that can be expressed using the phase delay ε _{j, l} of the reproduction vibration at each cutting edge is the reproduction number RF, and it can be considered that the reproduction effect is small when the absolute value | RF | is small. . The following formula (1) shows the definition formula of the reproduction number RF. When using an equal pitch tool, the reproduction effect is maximized and the number of reproductions | RF | is 1. ε _{j, l} means a phase delay in the l-th minute cutting edge obtained by dividing N _z in the axial direction in the j-th cutting edge in the N _t -blade tool. Phase delay can be expressed by the following formula (2) using the frequency f _c and the main shaft rotational speed n of the vibration chatter and pitch angle △ θ _{j, l} in the same micro-cutting edge.

Here, in order to deepen the understanding of the present embodiment, a comparative example (conventional square end mill) shown in FIG. 7 will be described. In FIG. 7, at a predetermined position in the blade length ap region, the four pitch angles A and B are directed to the opposite side of the tool rotation direction T, and the first pitch angle A, the second pitch angle B, and the first The pitch angle A and the second pitch angle B are alternately arranged in this order.
Of the two first pitch angles A and A, one of the first pitch angles A located in the tool rotation direction T and two of the second pitch angles B and B in the tool rotation direction T. One of the second pitch angles B that is positioned is an angle difference | BA− that can suppress a specific frequency only at a predetermined position (ap1 / 2) in the blade length ap region.

In such a conventional square end mill, when cutting is performed at a portion other than the predetermined position in the blade length ap region (a cutting amount other than the cutting amount corresponding to the predetermined position), a specific frequency cannot be suppressed. The occurrence of chatter vibration cannot be suppressed.

Specifically, as shown in FIG. 8B, the calculation result representing the relationship between the cut amount mm (vertical axis) in the axis O direction, the frequency Hz (horizontal axis), and the reproduction frequency RF (displayed by shading). (Analysis result) confirms that, in the square end mill of the comparative example, chatter vibration occurs over almost the entire frequency range of 300 to 900 Hz when the cutting depth is 8 mm or less and the reproduction frequency RF exceeds 0.3. It was. The rotation speed of the main shaft was 2500 rpm.

On the other hand, in the present embodiment, the following remarkable effects that are not obtained with the conventional square end mill are achieved. That is, at a predetermined position (ap1 / 2 in FIGS. 5 and 6) in the blade length ap region, effective pitch angles A and B are set to specific frequencies for which the occurrence of self-excited vibration is desired to be suppressed. The pitch angles A and A and the second pitch angles B and B are adjacently arranged in the circumferential direction, and the outer

peripheral blades

1 and 2 having different twist angles γ1 and γ2 are alternately arranged in the circumferential direction. By manufacturing the square end mill 20 with a simple configuration, this end mill is effective not only in the predetermined position of the blade length ap region but also in the generation of self-excited vibration for the specific frequency over the entire region of the blade length ap region. Can be suppressed. That is, chatter vibration can be stably suppressed regardless of the amount of cut in the direction of the axis O of the square end mill 20, and the manufacture of the end mill is not complicated.

In the present embodiment, the following effects can also be obtained.
In the present embodiment shown in FIGS. 5 and 6, the difference in angle between the first pitch angles A and A | A−A |, the difference in angle between the second pitch angles B and B | BB | Is | AA− ≠ 0, | BB− ≠ 0 (that is, unequal division) at positions other than a predetermined position (ap1 / 2 in the illustrated example) in the blade length ap region. . That is, even when paying attention to the combination of the first pitch angles A and A and the combination of the second pitch angles B and B, reproduction is performed at most positions (other than the predetermined position) in the blade length ap region. An effect can be obtained. For this reason, this embodiment has a more robust effect than the conventional general unequal read (the area in which the effect can be obtained can be expanded).

Furthermore, the square end mill 20 of the present embodiment makes it easy to suppress not only the specific frequency but also the occurrence of self-excited vibration when the frequency changes because the outer

peripheral blades

1 and 2 are unequal leads. Has been. In other words, the effect of suppressing a specific frequency is obtained, and the effect of suppressing a frequency other than the specific frequency is also achieved. Therefore, the effect of suppressing chatter vibration becomes particularly remarkable.

Further, in the present embodiment, the predetermined position in the blade length ap region is a portion other than the tip portion in the blade length ap region, so the following effects are obtained.
That is, in this case, at the tip of the blade length ap region, as shown in FIGS. 5 and 6, for example, the pitch angles θ1 to θ4 can all be made different from each other. That is, the tip part of the edge length ap region of the outer

peripheral blades

1 and 2 is a position where the cutting starts in the work material and is frequently used for cutting, and the pitch angles θ1 to θ4 are all at the tip part. If they are different from each other, the effect of suppressing the chatter vibration of the present embodiment is more likely to become particularly remarkable, which is preferable.

Moreover, in this embodiment, since the predetermined position is made into the center part in this blade length ap area | region among blade length ap area | regions, there exists the following effect.
That is, in this case, as shown in FIGS. 5 and 6, the blade lengths of the outer

peripheral blades

1 and 2 including the two first pitch angles A and A and the two second pitch angles B and B are included. Since the predetermined position of the ap region is the central portion (ap1 / 2) of the blade length ap region, adjacent to the outer

peripheral blades

1 and 2 at the distal end and the base end of the blade length ap region of the outer

peripheral blades

1 and 2 It is suppressed that the groove width of the chip discharge groove 4 to be reduced becomes too small.
Therefore, according to the said structure, chip | tip discharge property can be maintained favorable, suppressing generation | occurrence | production of chatter vibration.

[Other configurations included in the present invention]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above-described embodiment, the first pitch angle A and the second pitch angle B in the end mill cross-sectional view at a predetermined position in the blade length ap region (the entire blade length of the outer peripheral blades 1 and 2) are as follows. The pitch angles A, A, B, and B are arranged in this order along the circumferential direction, and this predetermined position is a portion other than the tip portion in the blade length ap region, specifically the central portion (ap1 / 2). It was. The present invention is not limited to this, and the predetermined position may be a portion other than the central portion in the blade length ap region, for example, a tip portion.
However, it is preferable that the predetermined position is a portion other than the tip portion in the blade length ap region or a central portion, so that the operational effects described in the above-described embodiment can be obtained.

In the above-described embodiment, the chip discharge groove 4 gradually twists and extends toward the side opposite to the tool rotation direction T along the axis O direction along the axis O direction on the outer periphery of the end mill body 3. Yes. Accordingly, the outer

peripheral blades

1 and 2 gradually twist and extend toward the opposite side of the tool rotation direction T along the axis O direction from the distal end toward the proximal end along the outer periphery of the end mill body 3. . That is, the twist angle of the outer

peripheral blades

1 and 2 is a positive angle (positive angle). However, the present invention is not limited to this, and the chip discharge groove 4 is gradually twisted in the tool rotation direction T along the axis O direction along the axis O direction on the outer periphery of the end mill body 3. It may extend. Further, along with this, the outer

peripheral blades

1 and 2 may be gradually twisted and extended in the tool rotation direction T along the axis O direction on the outer periphery of the end mill body 3 from the distal end toward the proximal end side. That is, the twist angle of the outer

peripheral blades

1 and 2 may be a negative angle (negative angle).
According to the present invention, the above-described excellent effects can be achieved regardless of whether the

outer blades

1 and 2 have a positive angle or a negative angle.

In addition, in the range which does not deviate from the meaning of this invention, you may combine each structure (component) demonstrated by the above-mentioned embodiment, a modification, and a remark etc., addition of a structure, omission, substitution, others It can be changed. Further, the present invention is not limited by the above-described embodiments, and is limited only by the scope of the claims.

1 First outer peripheral blade (outer peripheral blade)
2 Second outer peripheral blade (outer peripheral blade)
3 End mill body 4 Chip discharge groove 20 Square end mill (end mill)
A First pitch angle (pitch angle)
ap Blade length B Second pitch angle (pitch angle)
O Axis T Tool rotation direction γ1 Torsion angle of first outer peripheral blade (twist angle)
γ2 Twist angle (twist angle) of the second outer peripheral blade

Claims

A shaft-shaped end mill body,
A chip discharge groove formed on the outer periphery of the end mill body and extending in the circumferential direction around the axis as it goes from the distal end in the axial direction of the end mill body toward the proximal side;
An end mill comprising a wall surface facing the tool rotation direction in the circumferential direction in the chip discharge groove, and an outer peripheral blade formed on a cross ridge line with the outer peripheral surface of the end mill body,
The chip discharge grooves are formed in four strips at intervals in the circumferential direction,
The four outer peripheral blades arranged at intervals in the circumferential direction include two first outer peripheral blades and two second outer peripheral blades having different helix angles from the first outer peripheral blade. And
The first outer peripheral blades and the second outer peripheral blades are alternately arranged in the circumferential direction,
In the end mill cross-sectional view perpendicular to the axis at a predetermined position in the blade length region of the outer peripheral blade,
As a pitch angle, a central angle formed between a pair of virtual straight lines connecting the pair of outer peripheral blades adjacent in the circumferential direction and the axis line,
The four pitch angles arranged in the circumferential direction include two first pitch angles and two second pitch angles different from the first pitch angles,
Two end pitches are arranged adjacent to each other in the circumferential direction, and two second pitch angles are arranged adjacent to each other in the circumferential direction.
The end mill according to claim 1,
The end mill characterized in that the predetermined position in the blade length region is a portion other than the tip in the blade length region.
The end mill according to claim 1 or 2,
The end mill characterized in that a predetermined position in the blade length region is a central portion in the blade length region.