JP2019098444A - End mill - Google Patents

Abstract

An object of the present invention is to maintain good chip discharging performance, to obtain an effect of suppressing chatter vibration in a wide frequency band, and to improve machining accuracy under various cutting conditions. A plurality of outer peripheral blades 1 and 2 arranged alternately in the circumferential direction include two or more first outer peripheral blades 1 having different torsion angles α between a distal end portion 1a and a proximal end portion 1b. , A change point CP at which the torsion angle α changes in the blade length region, including the same number of second outer peripheral blades 2 as the first outer peripheral blades 1 having a constant twist angle β different from the torsion angle α. A pitch angle θn adjacent to the tool rotation direction T of the first outer peripheral blade 1 in a cross-sectional view of each end mill at a first predetermined position on the more distal side and a second predetermined position on the proximal side than the change point CP; There are at least two kinds of angle combinations (θn, α) with the torsion angle α of the first outer peripheral blade 1, the pitch angle θn adjacent to the tool rotation direction T of the second outer peripheral blade 2, There are at least two kinds of combinations (θn, β) of angles with the twist angle β of the two outer peripheral blades 2. [Selection] Figure 4

Description

  The present invention relates to an end mill capable of effectively suppressing chatter vibration.

Conventionally, for example, an end mill as shown in Patent Document 1 below is known.
The end mill has a shaft-like end mill main body, a chip discharge groove formed on the outer periphery of the end mill main body, and extending in the circumferential direction around the axis from the tip end of the end mill main body in the axial direction An outer peripheral blade formed on the edge of the cross ridge line between the wall surface facing the direction of tool rotation in the tool rotation direction and the outer peripheral surface of the end mill body, and a bottom formed on the edge of the cross ridge line And a blade.

The end mill of Patent Document 1 has a first cutting edge (peripheral cutting edge) with a constant twist angle, a cutting edge portion from the tip to the center and a cutting edge from the center to the base The twist angle of one cutting edge portion is set to be smaller than the twist angle of the first cutting edge, and the other cutting edge portion is set to be larger than the twist angle of the first cutting edge. The second cutting edges (outer peripheral blades) are alternately formed in the circumferential direction.
As described above, when the plurality of cutting edges (peripheral cutting edges) are formed into unequal twists (unequal leads), the cutting forces and action times by these cutting edges are different from each other in the circumferential direction and axial direction of the end mill, The effect of suppressing the self-excitation vibration generated at the time of cutting and suppressing the chatter vibration can be obtained. And the patent document 1 provided the 2nd cutting edge in which a twist angle differs by the front end side part and the base end side part, and while forming a several cutting edge in unequal twist, the front end side of these cutting edges In the end part of the end and the end part on the proximal end side, the groove width of the chip discharge groove is prevented from being narrowed excessively and the chip discharge performance is secured.

JP-A-63-105814

  However, in the above-described conventional end mill, there is room for improvement in that chatter vibration can be further suppressed when cutting the work material with the outer peripheral blade.

  The present invention has been made in view of such circumstances, and can suppress chatter vibration in a wide frequency band while maintaining good chip dischargeability, and processing accuracy under various cutting conditions The purpose is to provide an end mill that can improve the

  One aspect of the present invention is an end mill main body having an axial shape, and an outer circumference formed on an outer periphery of the end mill main body and extending in a circumferential direction around the axial line from the tip end in the axial direction of the end mill main body An end mill including a plurality of blades, wherein the plurality of outer peripheral blades are formed spaced apart from each other in the circumferential direction, and a plurality of the outer peripheral blades are provided with a distal end portion and a proximal end portion of the outer peripheral blade Have two or more first outer peripheral blades different in twist angle α, and a constant twist angle β different from the twist angle α of the first outer peripheral blade, and the same number as the number of the first outer peripheral blades A second outer peripheral blade is included, and the first outer peripheral blade and the second outer peripheral blade are alternately arranged in the circumferential direction, and a twist in a blade length region of the first outer peripheral blade Perpendicular to the axis at a first predetermined position distal to the change point at which the angle α changes In each of the end mill cross sectional view and the end mill cross sectional view at a second predetermined position proximal to the change point, a pair connecting the pair of the outer peripheral blades adjacent in the circumferential direction and the axis line Between the first outer peripheral edge and the second outer peripheral edge adjacent to the tool rotation direction in the circumferential direction of the first outer peripheral edge, with the central angle formed between the imaginary straight lines as the pitch angle θ n At least two kinds of combinations (θ n, α) of the pitch angle θ n and the twist angle α of the first outer peripheral blade formed in the second outer peripheral blade and the second outer peripheral blade A combination of the pitch angle θ n formed between the second outer peripheral blade and the first outer peripheral blade adjacent in the tool rotation direction and the twist angle β of the second outer peripheral blade (θ n , Β) are characterized by at least two or more.

The end mill according to the present invention is provided with two or more first outer peripheral blades and second outer peripheral blades alternately arranged at intervals in the circumferential direction on the outer periphery of the end mill main body. In addition, the first outer peripheral blade and the second outer peripheral blade have the same number, and the total number of outer peripheral blades is, for example, four blades, six blades, eight blades, and so on. The twist angle α of the first outer peripheral blade and the twist angle β of the second outer peripheral blade are different in size (α 互 い に β). 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 (unequal twist) end mill having a plurality of types of twist angles α and β. Further, among the twist angles α of the first outer peripheral blade, the twist angle α (twist angle α ₁ shown in FIGS. 4 and 7) of the tip end portion and the twist angle α of the base end portion (FIGS. 4 and 7) The torsion angles α ₂ ) shown in FIG.

  The inventor of the present invention has conducted intensive studies on end mills, and as a result, in order to effectively suppress the frequency at which chatter vibration occurs during cutting, it is necessary to shift the phase difference of regenerative vibration between a plurality of outer peripheral blades. Preferably, this makes it possible to suppress the occurrence of self-excited vibration occurring around the resonance frequency, and as a result, it has been found that chatter vibration can be suppressed.

Based on the above-described findings, the present invention is a predetermined position on the tip side of the change point (change point CP shown in FIGS. 4 and 7) at which the twist angle α changes in the blade length region of the first outer peripheral blade In each cross-sectional view of the end mill body at a predetermined position (a predetermined position) and a predetermined position (second predetermined position) proximal to the change point, a special configuration satisfying the following conditions was used.
That is, when a plurality of pitch angles (division angles) aligned around the axis of the end mill main body is θ n, the first outer peripheral blade and the first outer peripheral blade in the end mill cross sectional view at the first predetermined position The pitch angle θ n formed between the second outer peripheral blade adjacent in the tool rotational direction (that is, the pitch angle θ n adjacent to the first outer peripheral blade in the tool rotational direction) and the tip side portion of the first outer peripheral blade Type of combination (θ n, α (α ₁ )) of the twist angle α (twist angle α ₁ ) and the angle of at least two, and the tool rotation of the second outer peripheral blade and the second outer peripheral blade The pitch angle θ n formed between the first outer peripheral blade adjacent in the direction (that is, the pitch angle θ n adjacent to the tool rotation direction of the second outer peripheral blade), and the twist angle β of the second outer peripheral blade The combination of angles (θ n, β) is at least two or more. And, in an end mill cross-sectional view at the second predetermined position, a pitch angle θ n formed between the first outer peripheral blade and the second outer peripheral blade adjacent to the first outer peripheral blade in the tool rotation direction. That is, a combination of the angle (θ n, α (t) of the pitch angle θ n) adjacent to the tool rotation direction of the first outer peripheral blade and the twist angle α (twist angle α ₂ ) of the base end side portion of the first outer peripheral blade A pitch angle θ n (that is, at least two types of α ₂ )) is formed between the second outer peripheral blade and the first outer peripheral blade adjacent to the second outer peripheral blade in the tool rotation direction (that is, There are at least two or more types of combinations (θ n, β) of angles of the pitch angle θ n) adjacent to the tool rotation direction of the second outer peripheral blade and the twist angle β of the second outer peripheral edge.

Specifically, each pitch angle θn combined with the twist angle α (twist angle α ₁ ) of the tip side portion of the plurality of first outer peripheral blades at the first predetermined position in the blade length region of the outer peripheral blade is For example, there are two or more types of θ ₁ , θ ₂ ,..., And each pitch angle θ n combined with the twist angle β of the plurality of second outer peripheral blades is, for example, two or more types of θ ₁ , θ ₂ ,. Each pitch angle θn combined with the twist angle α (twist angle α ₂ ) of the proximal end portion of the plurality of first outer peripheral blades at the second predetermined position in the blade length region of the outer peripheral blade is, for example, θ _1, the theta _2, ... and two or more, each pitch angle θn combined with the helix angle β of the plurality of second peripheral cutting edge, for example theta _1, theta _2, is ... and two or more types.

Here, in the above description, the pitch angle combined with the twist angle α (α ₁ ) of the tip end portion of the first outer peripheral blade is “θ n”, and the twist angle α (α of the base end portion of the first outer peripheral blade _The same variable name "θn" is used for each pitch angle, assuming that the pitch angle to be combined with ₂ ) is "θ n" and the pitch angle to be combined with the twist angle β of the second outer peripheral blade is "θ n" It does not mean that the pitch angles θ n have the same value. In the present invention, each pitch angle θ n may be rephrased as follows in order to make it clearer which “pitch angle θ n” points to which pitch position of which peripheral blade (which part).
That is, the pitch angle θ n combined with the twist angle α (α ₁ ) of the tip end portion of the first outer peripheral blade is “pitch angle θ (α ₁ , n) at the first predetermined position”, “first outer circumference pitch angle theta in the distal portion of the blade (alpha _1, n) ", or simply may be paraphrased as" pitch angle θ (α _1, n) ". Further, the pitch angle θn combined with the twist angle α (α ₂ ) of the base end side portion of the first outer peripheral blade is “pitch angle θ (α ₂ , n) at the second predetermined position”, “first pitch angle theta in the proximal portion of the outer peripheral edge (alpha _2, n) ", or simply may be paraphrased as" pitch angle θ (α _2, n) ". In addition, the pitch angle θn combined with the twist angle β of the tip side portion of the second outer peripheral blade is “pitch angle θ (β, n) at the first predetermined position”, “tip side portion of the second outer peripheral blade The pitch angle θ (β, n) in the above may be reworded simply as “pitch angle θ (β, n)”. Further, the pitch angle θn combined with the twist angle β of the proximal end portion of the second outer peripheral blade is “pitch angle θ (β, n) at the second predetermined position”, “proximal end of the second outer peripheral blade It may be rephrased as pitch angle theta (beta, n) in a side portion, or simply as "pitch angle theta (beta, n)."

  As described above, in the present invention, the types of combinations of angles (θ n, α) are two or more in each of the end mill cross section at the first predetermined position and the end mill cross section at the second predetermined position. And, since there are two or more kinds of combinations of angles (θ n, β), for example, when the total number of outer peripheral blades is four, a total of four combinations of angles can be made at each predetermined position. Since the combination of the respective angles exerts chatter vibration suppression effects in different frequency bands, according to the present invention, the chatter vibration suppression effects can be obtained over a wide range in the axial direction and in a wide frequency band, Machining accuracy can be improved under various cutting conditions. According to the analysis results, the suppressing effect of the chatter vibration by the end mill of the present invention was remarkably remarkable several times as large as that of the conventional unequal lead / uneven pitch end mill.

  Furthermore, the frequency of chatter vibration can not be known in advance, and conventionally, chatter vibration may occur at any frequency within a predetermined frequency range that generates chatter vibration. According to the end mill of the invention, it is possible to suppress chatter vibration over the entire range of the predetermined frequency band.

  As described above, the first outer peripheral blade has different twist angles α at the tip end side and the base end side of the change point, while exhibiting excellent suppression effect of chattering vibration. At the distal end and the proximal end, the width of the chip discharge groove can be prevented from becoming excessively narrow. Thereby, the chip dischargeability is well maintained.

  In the end mill, it is preferable that an angle difference between the twist angle α of the tip end portion of the first outer peripheral blade and the twist angle α of the base end portion is 40 ° or less.

In this case, the twist angle α (the twist angle α ₁ shown in FIGS. 4 and 7) of the distal end portion of the first outer peripheral blade and the twist angle α of the proximal end portion of the first outer peripheral blade (FIGS. Since the angle difference | α ₁ −α ₂ | with the twist angle α ₂ ) shown in 7 is 40 ° or less, the following effects can be obtained.
That is, since the angle difference | α ₁ −α ₂ | is 40 ° or less, the inclination of the twist angle α is too sharp in either the distal end portion or the proximal end portion of the first outer peripheral blade. It can be suppressed from becoming too loose. Thus, it is possible to reliably prevent such a defect that the groove width of the chip discharge groove becomes excessively narrow at the end on the tip end side or the end on the base end side of the first outer peripheral blade. In addition, it is possible to maintain cutting performance well by preventing the sharpness from being impaired even in the portion where the twist angle α is made small among the tip end portion and the base end portion of the first outer peripheral blade. it can.

  In the end mill, it is preferable that an angle difference between the twist angle α of the tip end portion of the first outer peripheral blade and the twist angle α of the base end portion is 5 ° or more and 35 ° or less.

In this case, the twist angle α (the twist angle α ₁ shown in FIGS. 4 and 7) of the distal end portion of the first outer peripheral blade and the twist angle α of the proximal end portion of the first outer peripheral blade (FIGS. Since the angle difference | α ₁ −α ₂ | with the twist angle α ₂ ) shown in 7 is 5 ° or more and 35 ° or less, the following effects can be obtained.
That is, since the angle difference | α ₁ −α ₂ | is 5 ° or more, it is necessary to enhance the chatter vibration suppressing effect in different frequency bands between the distal end portion and the proximal end portion of the first outer peripheral blade. Can. Thereby, the suppression effect of chatter vibration can be stabilized in a wide frequency band. In particular, it is possible to surely enhance the vibration suppressing effect at the low incision at which chatter vibration easily occurs.
Further, since the angle difference | α ₁ −α ₂ | is 35 ° or less, the groove width of the chip discharge groove is excessively narrow at the tip end side or the base end side of the first outer peripheral blade. It is possible to more reliably prevent such a failure. Moreover, the sharpness can be sufficiently enhanced also in the portion of the distal end side and the proximal end side of the first outer peripheral blade, in which the twist angle α is reduced.

  In the end mill, the change point is in the range of 30% to 70% in the blade length region, with the tip end position being 0% and the base end position being 100% in the blade length region of the first outer peripheral blade. It is preferable that it is arrange | positioned.

In this case, since the change point at which the twist angle α changes in the first outer peripheral blade is disposed in the range of 30% to 70% in the blade length region of the first outer peripheral blade, the following effects can be obtained. Play.
That is, since the change point is arranged in the range of 30% or more in the blade length region of the first outer peripheral blade, it is possible to prevent the blade length of the proximal end portion of the first outer peripheral blade from becoming too long. . As a result, it is possible to reliably avoid such a situation that the groove width of the chip discharge groove becomes too narrow at the proximal end side of the outer peripheral blade.
Moreover, since the said change point is arrange | positioned in 70% or less of range in the blade length area | region of a 1st outer periphery blade, it can prevent that the blade length of the front end side part of a 1st outer periphery blade becomes long too much. As a result, it is possible to reliably avoid such a situation that the groove width of the chip discharge groove becomes too narrow at the tip end side of the outer peripheral blade.

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

  In this case, it is easy to make all the pitch angles of the outer peripheral blades different from each other at the tip of the blade length region. The tip portion of the blade length region of the outer peripheral blade is a position at which cutting starts in the work material and is a portion frequently used for cutting, and if all the pitch angles are different at this tip portion, the above-mentioned chattering vibration It is preferable because the effect of suppressing is likely to be particularly remarkable.

  Further, in the end mill, it is preferable that the first predetermined position is a central portion between the tip in the blade length region and the change point.

  In this case, the first predetermined position for setting the pitch angle θ n on the tip side of the change point of the first outer peripheral blade is at the central portion between the tip of the blade length region of the first outer peripheral blade and the change point. Because of this, it is possible to suppress that the groove width of the chip discharge groove adjacent to the outer peripheral blade becomes too small at the tip and the change point of the first outer peripheral blade. Therefore, the chip discharging property can be more stably enhanced while suppressing the occurrence of chatter vibration as described above.

  In the end mill, it is preferable that the second predetermined position is a central portion between the base end in the blade length region and the change point.

  In this case, the second predetermined position for setting the pitch angle θ n on the base end side of the change point of the first outer peripheral blade is the center of the base end of the blade length region of the first outer peripheral blade and the change point Since it is a part, it can suppress that the groove width of the chip discharge groove adjacent to the outer peripheral blade becomes too small at the base end and the change point of the first outer peripheral blade. Therefore, the chip discharging property can be more stably enhanced while suppressing the occurrence of chatter vibration as described above.

  Further, in the end mill, it is preferable that the twist angle α at the tip end side of the change point of the first outer peripheral blade is smaller than the twist angle α at the base end side of the change point.

  In this case, the change point of the first outer peripheral blade is formed to protrude in the tool rotation direction of the end mill, and it is easy to form the first outer peripheral blade with a grindstone or the like at the time of manufacturing the end mill.

  In the end mill, when the total number of the outer peripheral blades is N, the type of the combination (θ n, α) of the angles is (N / 2) in the end mill cross sectional view at the first predetermined position. The number is preferably one.

In this case, the twist angle α (twist angle α ₁ shown in FIGS. 4 and 7) at the tip end portion of the first outer peripheral blade, and the pitch angle θ n adjacent to the tool rotation direction of the first outer peripheral blade The type of combination of angles (θ n, α (α ₁ )) is half of the total number N of peripheral blades. That is, since the pitch angles θn adjacent to each other in the tool rotational direction are all different from each other at the tip side of the plurality of first outer peripheral blades, the chatter vibration suppression effect is wider in that frequency band Can be obtained by

  In the end mill, when the total number of the outer peripheral blades is N, the type of the combination (θ n, β) of the angles is (N / 2) in the end mill cross sectional view at the first predetermined position. The number is preferably one.

  In this case, the type of combination (θ n, β) of the twist angle β at the tip end portion of the second outer peripheral blade and the pitch angle θ n adjacent to the tool rotation direction of the second outer peripheral blade is outer peripheral It is half of the total number N of blades. That is, since the pitch angles θn adjacent to each other in the tool rotation direction are all different from each other at the tip side of the plurality of second outer peripheral blades, the chatter vibration suppression effect is wider in that frequency band Can be obtained by

  In the end mill, when the total number of the outer peripheral blades is N, the type of the combination (θ n, α) of the angles is (N / 2) in the end mill cross sectional view at the second predetermined position. The number is preferably one.

In this case, a twist angle α (twist angle α ₂ shown in FIGS. 4 and 7) at the proximal end portion of the first outer peripheral blade, and a pitch angle θ n adjacent to the tool rotation direction of the first outer peripheral blade The kind of the combination of angles (θ n, α (α ₂ )) is half of the total number N of peripheral blades. That is, since the pitch angles θn adjacent to each other in the tool rotation direction are all different from each other in the proximal end portion of the plurality of first outer peripheral blades, the chatter vibration suppression effect has a wider frequency It can be obtained in the band.

  In the end mill, when the total number of the outer peripheral blades is N, the type of the combination (θ n, β) of the angles is (N / 2) in the end mill cross sectional view at the second predetermined position. The number is preferably one.

  In this case, the type of the combination (θ n, β) of the twist angle β at the proximal end portion of the second outer peripheral blade and the pitch angle θ n adjacent to the tool rotation direction of the second outer peripheral blade is It is half of the total number N of peripheral blades. That is, since the pitch angles θn adjacent to each other in the tool rotational direction are all different from each other in the proximal end portion of the plurality of second outer peripheral blades, the chatter vibration suppression effect has a wider frequency. It can be obtained in the band.

  ADVANTAGE OF THE INVENTION According to the end mill of this invention, the suppression effect of chattering vibration can be acquired in a wide frequency band, maintaining chip | tip discharge property favorable, and processing accuracy can be improved in various cutting conditions.

It is a perspective view showing a square end mill concerning a 1st embodiment of the present invention. It is the side view (top view) which looked at the square end mill of FIG. 1 from the radial direction. It is the front view which looked at the square end mill of FIG. 1 toward the proximal end side from the front end. It is a figure which shows typically the arrangement | sequence of the outer periphery blade of the square end mill of 1st Embodiment. It is a figure which shows the AA cross section of FIG. 2, and is an end mill cross-sectional view in the 1st predetermined position of the square end mill of 1st Embodiment. It is a figure which shows the BB cross section of FIG. 2, and is an end mill cross-sectional view in the 2nd predetermined position of the square end mill of 1st Embodiment. It is a figure which shows typically the arrangement | sequence of the outer peripheral blade of the square end mill of the modification of 1st Embodiment. It is a figure which simplifies and shows the square end mill of the modification of a 1st embodiment, (a) End mill transverse cross section in a 1st predetermined position, (b) End mill transverse cross section in a 2nd predetermined position. It is a graph showing the relationship between the amount of cuts in the axial direction (vertical axis), frequency (horizontal axis), and the number of regenerations (regeneration vibration) at the time of cutting using the square end mill of the first embodiment. When cutting using the square end mill of a 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 regenerations (regeneration vibration). It is a figure which simplifies and shows the square end mill of a 2nd embodiment, and (a) End mill transverse cross section figure in the 1st predetermined position, (b) End mill transverse cross section figure in the 2nd predetermined position. It is a figure which simplifies and shows the square end mill of a 2nd embodiment, and (a) End mill transverse cross section figure in the 1st predetermined position, (b) End mill transverse cross section figure in the 2nd predetermined position. It is a figure which simplifies and shows the square end mill of a 2nd embodiment, and (a) End mill transverse cross section figure in the 1st predetermined position, (b) End mill transverse cross section figure in the 2nd predetermined position. It is a figure which simplifies and shows the square end mill of a 3rd embodiment, and (a) End mill transverse cross section in a 1st predetermined position, (b) End mill transverse cross section in a 2nd predetermined position is expressed. It is a figure which simplifies and shows the square end mill of a 3rd embodiment, and (a) End mill transverse cross section in a 1st predetermined position, (b) End mill transverse cross section in a 2nd predetermined position is expressed. It is a figure which simplifies and shows the square end mill of a 3rd embodiment, and (a) End mill transverse cross section in a 1st predetermined position, (b) End mill transverse cross section in a 2nd predetermined position is expressed. It is a figure which simplifies and shows the square end mill of a 3rd embodiment, and (a) End mill transverse cross section in a 1st predetermined position, (b) End mill transverse cross section in a 2nd predetermined position is expressed. It is a figure which simplifies and shows the square end mill of a 3rd embodiment, and (a) End mill transverse cross section in a 1st predetermined position, (b) End mill transverse cross section in a 2nd predetermined position is expressed. It is a figure which simplifies and shows the square end mill of a 3rd embodiment, and (a) End mill transverse cross section in a 1st predetermined position, (b) End mill transverse cross section in a 2nd predetermined position is expressed.

First Embodiment
Hereinafter, the square end mill 20 which is an example of the end mill which concerns on 1st Embodiment of this invention is demonstrated with reference to FIGS. The square end mill 20 of the present embodiment is a cutting tool (turning tool) that performs cutting (turning) on a work material made of a metal material or the like.
The present invention is not limited to the square end mill 20, but is applied to various other end mills such as radius end mills, ball end mills (including taper ball end mills, long neck end mills, taper neck end mills, etc.). It is possible.

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

  In the square end mill 20, a shank portion 3b having a cylindrical shape in the end mill main body 3 is attached to a spindle of a machine tool such as a machining center, and is rotated about the axis O in a tool rotation direction (end mill rotation direction) T by the spindle. The square end mill 20 is given a cut in the direction of the axis O and a feed in the radial direction orthogonal to the axis O along with the above rotation, and cuts it into the work material with the blade portion 3a. Perform various processing.

  When cutting a work material by the square end mill 20, coolant is supplied toward the blade portion 3a of the square end mill 20 and the processing surface (work portion) of the work material. As the coolant, for example, an oil-based or water-soluble cutting fluid, compressed air or the like is used. The coolant may be supplied from the main shaft of the machine tool to the blade portion 3a and the processing surface through the inside of the end mill main body 3, or may be supplied from the outside of the end mill main body 3 to the blade portion 3a and the processing surface.

[Definition of Direction (Direction) Used in This Embodiment]
In the present embodiment, the direction along the axis O of the end mill body 3 (the direction in which the axis O extends) is referred to as the axis O direction. Further, in the direction of the axis O, the direction from the shank 3b to the blade 3a is referred to as the tip side, and the direction from the blade 3a to the shank 3b is referred to as the proximal side.
Moreover, the direction orthogonal to the axis line O is called radial direction. In the radial direction, the direction approaching the axis O is referred to as the inner side in the radial direction, and the direction separating from the axis O is referred to the outer side in the radial direction.
Further, the direction of rotation around the axis O is referred to as the circumferential direction. Of the circumferential direction, the direction in which the end mill body 3 is rotated by the spindle of the machine tool during cutting is called the tool rotation direction T, and the opposite rotation direction is the side opposite to the tool rotation direction T (anti-tool rotation Direction).

[Chip discharge groove]
A plurality of 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. In the example of the present embodiment, four chips discharge grooves 4 are formed in the end mill main body 3.

  The chip discharge groove 4 extends in the circumferential direction as it goes from the tip along the direction of the axis O of the end mill body 3 to the proximal side. In the example of the present embodiment, the chip discharge groove 4 is opened at the tip end surface of the end mill main body 3 and is gradually twisted in the direction opposite to the tool rotation direction T as it goes from the tip surface to the base end. , Extends in a spiral. The chip discharge groove 4 is cut up to the outer periphery of the end mill main body 3 at the end on the proximal end side of the blade portion 3 a. In other words, in the end mill main body 3, a region where the chip discharge groove 4 is formed along the direction of the axis O is taken as the blade portion 3a.

  Each chip discharge groove 4 has a wall surface facing the tool rotational direction T, and a portion adjacent to the cutting edge of the wall surface is a rake surface. Specifically, among the rake surfaces of the cutting edge, portions of the cutting edge adjacent to the later-described outer peripheral blades 1 and 2 and the bottom blade 9 are respectively the rake surface 4 a of the outer peripheral blades 1 and 2 and the bottom blade 9 It is considered as the rake face 4b. The rake face 4 b of the bottom blade 9 is formed on the gash 7 of the chip discharge groove 4.

  A groove-shaped gash 7 is formed at the tip of the chip discharge groove 4 in the direction of the axis O. As shown in FIG. 3, in a front view of the end mill main body 3 as viewed from the tip end of the end mill main body 3 in the direction of the axis O, the gashes 7 extend along the radial direction. The radially inner end of the gash 7 is disposed in the vicinity of the axis O, and extends gradually from the radially inner end toward the proximal end in the direction of the axial O (in the radial direction) ( In other words, the groove depth gets deeper).

  The number of gasses 7 corresponds to the number of chip discharge grooves 4, and four gasses 7 are formed in the example of this embodiment. Among the gashes 7, a pair of gashes 7 adjacent to each other in the circumferential direction (a set of gashes 7) communicate with each other at radially inner end portions of the respective gashes 7. Moreover, thereby, the blade length of the two bottom blades 9 (short blades) cut out by (the set of) the gash 7 among the four bottom blades 9 is the two bottom blades 9 (long The blade length is shorter than the blade length.

[Cutting edge]
In the blade portion 3a, a plurality of cutting edges are formed at intervals in the circumferential direction. Each of these cutting edges has an outer peripheral edge 1 or 2 and a bottom edge 9. Each cutting blade is substantially L-shaped as a whole by connecting the outer peripheral blade 1 or 2 and the bottom blade 9 to each other. The number of cutting edges corresponds to the number of the chip discharge grooves 4, and in the example of the present embodiment, four (four sets) of cutting edges are provided. That is, the square end mill 20 of the present embodiment is a four-blade end mill.

[Outer peripheral blade]
Among the cutting edges, the outer peripheral blades 1 and 2 are formed on the outer periphery of the blade portion 3a of the end mill main body 3 and extend in the circumferential direction from the tip of the end mill main body 3 in the axial direction O toward the proximal end. A plurality of outer peripheral blades 1 and 2 are formed at intervals in the circumferential direction.

Specifically, in the blade portion 3a, the number (four) of the outer peripheral blades 1 and 2 corresponding to the number (four rows) of the chip discharge grooves 4 are arranged at intervals in the circumferential direction. Each outer peripheral blade 1, 2 is directed gradually to the opposite side of the tool rotation direction T as it goes from the tip of the end mill main body 3 to the base end side along the chip discharge groove 4 adjacent to the tool rotation direction T. It twists and extends helically.
The rotation trajectory obtained by rotating the outer peripheral blades 1 and 2 around the axis O has one virtual cylindrical surface shape with the axis O as a center.

  The outer peripheral blades 1 and 2 are formed at intersecting ridges of the wall surface of the chip discharge groove 4 facing the tool rotation direction T and the outer peripheral surface of the end mill main body 3. The outer peripheral blades 1 and 2 extend along the outer peripheral edge of the wall surface of the chip discharge groove 4 in a spiral shape. Specifically, among the wall surfaces of the chip discharge groove 4 facing the tool rotational direction T, the outer peripheral blades 1 and 2 are the rake surface 4a located at the end on the radially outer side and the outer peripheral surface of the blade 3a. It is formed in the cross ridge of the peripheral flank 5 adjacent to the side opposite to the tool rotation direction T of the chip discharge groove 4.

  On the outer peripheral surface of the blade portion 3a, an outer peripheral flank 5 is formed between the chip discharge grooves 4 adjacent to each other in the circumferential direction. In the illustrated example, the width (length in the direction orthogonal to the outer peripheral blades 1 and 2) of the outer peripheral flank 5 is substantially constant along the extending direction (blade length direction) of the outer peripheral blades 1 and 2 .

In the side view (plan view) of the square end mill 20 shown in FIG. 2 and the view schematically showing the arrangement of the outer peripheral blades 1 and 2 shown in FIG. 4 (a view showing the end mill outer periphery in a planar form), In the plurality of outer peripheral blades 1 and 2 provided in the blade portion 3a of the end mill body 3, two or more first outer peripheral blades 1 having different twist angles α between the tip end side portion 1a and the base end side portion 1b of the outer peripheral blade 1 And the second outer peripheral blade 2 having a constant twist angle β different from the twist angle α of the first outer peripheral blade 1 and the same number as the number of the first outer peripheral blades 1.
In the example of this embodiment, as four peripheral cutting edge 2, and a proximal portion 1b having a distal portion 1a and the twist angle alpha _{2 (provided} that α ₁ ≠ α ₂₎ having a twist angle alpha ₁ Two first outer peripheral blades 1 and two second outer peripheral blades 2 having a twist angle β (where α ₁ ≠ β, α ₂ ≠ β) are included.
The first outer peripheral blade 1 and the second outer peripheral blade 2 are alternately arranged in the circumferential direction.

  The first outer peripheral blade 1 has a changing point CP (Changing point) at which the twist angle α changes in the blade length direction. In the present embodiment, of the first outer peripheral blade 1, the cutting edge portion located on the distal end side from the change point CP is referred to as the distal end side portion 1a, and the cutting edge portion located on the proximal end side from the change point CP is proximal end It is called side part 1b.

Further, in the present embodiment, the formation region of the outer peripheral blades 1 and 2 along the direction of the axis O of the end mill main body 3 is referred to as a blade length region (hereinafter sometimes referred to as a blade length ap region). Of the blade length ap region of the first outer peripheral blade 1, the tip end position is 0% (ap = 0), the base end position is 100% (ap = 1), and the change point CP of the first outer peripheral blade 1 is , 30% or more and 70% or less in the blade length ap area.
In the example of this embodiment, the twist angle alpha ₁ of the distal portion 1a which is located from the first peripheral cutting edge 1 of the change point CP on the distal end side, located on the proximal side of the change point CP of the proximal portion 1b It is smaller than the twist angle α _2. For this reason, the change point CP of the first outer peripheral blade 1 is formed to project in the tool rotational direction T.

Further, the twist angle alpha ₁ of the first peripheral cutting edge 1 of the distal portion 1a, difference angle between the twist angle alpha ₂ of the proximal portion 1b (angle difference) is 40 ° or less. The difference between the angles is preferably 5 ° or more and 35 ° or less. The difference between the angles referred to herein, is the absolute value of alpha _{1-.alpha. 2,} simply in the following description | may be represented as _| α ₁ -α _2. That is, in this embodiment, 0 ° <| α ₁ −α ₂ | ≦ 40 °, and preferably 5 ° ≦ | α ₁ −α ₂ | ≦ 35 °.

In addition, the difference between the twist angle α of the first outer peripheral blade 1 and the twist angle β of the second outer peripheral blade 2 (here, the difference is an absolute value of α-β, and in the following description, it is simply used. For example, it may be 5 ° ≦ | α-β | ≦ 25 °, preferably 10 ° ≦ | α-β | ≦ 20 °.
Specifically, the difference | α ₁ −β | of the angle between the twist angle α ₁ at the tip end portion 1 a of the first outer peripheral blade 1 and the twist angle β of the second outer peripheral blade 2 is 5 ° ≦ | α ₁ −β | ≦ 25 °, preferably, 10 ° ≦ | α ₁ −β | ≦ 20 °. Further, the difference | α ₂ −β | of the angle between the twist angle α ₂ at the proximal end portion 1 b of the first outer peripheral blade 1 and the twist angle β of the second outer peripheral blade 2 is 5 ° ≦ | α ₂ −β | ≦ 25 °, preferably 10 ° ≦ | α ₂ −β | ≦ 20 °.

In the example of this embodiment, the twist angle alpha ₁ of the first peripheral cutting edge 1 of the distal portion 1a has been smaller than the beta second torsion angle of the peripheral cutting edge 2 of (α _{1 <β).} Further, the twist angle alpha ₂ of the first peripheral cutting edge 1 of the proximal portion 1b, are larger than the helix angle of the second peripheral cutting edge _{2 β (α 2> β)} .
Twist angle alpha ₁ of the first peripheral cutting edge 1 of the distal portion 1a is constant over the entire length of the distal end portion 1a, the twist angle alpha ₂ of the first peripheral cutting edge 1 of the proximal portion 1b, said It is constant over the entire length of the proximal portion 1b. Further, the twist angle β of the second outer peripheral blade 2 is constant over the entire length of the second outer peripheral blade 2.

In the side view of the end mill main body 3 shown in FIG. 2 (when the end mill main body 3 is viewed from the radial direction), the “twist angle” in the present embodiment refers to the axis O and the outer peripheral blades 1 and 2 (twisted The acute angle and the obtuse angle formed between the wire and the helical wire are the acute angle.
In the example of the present embodiment, since the outer peripheral blades 1 and 2 extend in the direction opposite to the tool rotation direction T along the direction of the axis O from the tip to the proximal end, the outer peripheral blades 1 and 2 The twist angle of is a positive angle (positive angle).

[Pitch angle of outer peripheral blade]
In the present embodiment, in an end mill cross-sectional view perpendicular to the axis O shown in FIGS. 5 and 6, a pair of imaginary straight lines connecting the pair of outer peripheral blades 1 and 2 adjacent in the circumferential direction and the axis O The central angle (angle shown by the symbols θ ₁ and θ ₂ ) formed in the above is called “pitch angle (division angle) θn”.
FIG. 5 is a cross-sectional view of an end mill at a predetermined position on the tip end side of the change point CP where the twist angle α changes in the blade length ap region of the first outer peripheral blade 1 (hereinafter referred to as the first predetermined position). Represents Specifically, it is an A-A cross section of FIG. 2 and is a cross-sectional view of an end mill at a first predetermined position indicated by “First PP (Predetermined position)” in the graph of FIG. 4.
Further, FIG. 6 shows an end mill cross section at a predetermined position (hereinafter referred to as a second predetermined position) on the proximal side of the change point CP where the twist angle α changes in the blade length ap region of the first outer peripheral blade 1 It represents a figure. Specifically, it is a B-B cross section of FIG. 2 and is a cross-sectional view of an end mill at a second predetermined position indicated by “Second PP (Predetermined position)” in the graph of FIG. 4.

  Then, in the end mill cross sectional view at the first predetermined position shown in FIG. 5 and the end mill cross sectional view at the second predetermined position shown in FIG. A combination (θ n, α) of the pitch angle θ n formed between the second outer peripheral blade 2 adjacent to the tool rotation direction T of the outer peripheral blade 1 and the twist angle α of the first outer peripheral blade 1 And the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the tool rotational direction T of the second outer peripheral blade 2 The kind of the combination (θ n, β) of the angle with the twist angle β of the second outer peripheral blade 2 is at least two or more.

More specifically, as shown in FIG. 5, the end-side portion 1 a of the first outer peripheral blade 1 and the end-mill cross-sectional view at the first predetermined position located on the tip side of the change point CP in the blade length ap region The pitch angle θ n formed between the second outer peripheral blade 2 adjacent to the tool rotation direction T of the first outer peripheral blade 1 (that is, in the tool rotation direction T of the tip side portion 1 a of the first outer peripheral blade 1) At least two types of combinations (θ n, α ₁ ) of angles of an adjacent pitch angle θ n) and a twist angle α ₁ of the tip side portion 1 a of the first outer peripheral blade 1 are at least two. The pitch angle θ n formed between the outer peripheral blade 2 and the tip side portion 1 a of the first outer peripheral blade 1 adjacent to the tool rotation direction T of the second outer peripheral blade 2 (that is, the tool of the second outer peripheral blade 2) A combination of the pitch angle θ n) adjacent to the rotational direction T and the twist angle β of the second outer peripheral blade 2 (θ n Type beta) is at least two or more.
And, as shown in FIG. 6, in the end mill cross-sectional view at the second predetermined position located on the proximal side of the change point CP in the blade length ap region, the proximal end portion 1b of the first outer peripheral blade 1 Pitch angle θ n formed between the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T (that is, the tool rotational direction of the proximal end portion 1 b of the first outer peripheral blade 1) At least two types of combinations (θ n, α ₂ ) of angles of pitch angle θ n) adjacent to T and twist angle α ₂ of the proximal end portion 1 b of the first outer peripheral blade 1 are, A pitch angle θ n formed between the second outer peripheral blade 2 and the base end side portion 1b of the first outer peripheral blade 1 adjacent to the tool rotation direction T of the second outer peripheral blade 2 (that is, the second outer peripheral blade) Combination of the pitch angle θ n) adjacent to the tool rotation direction T of the blade 2 and the twist angle β of the second outer peripheral blade 2 (θ n, β Type is at least two or more.

As shown in FIGS. 2 and 4, in the present embodiment, the first predetermined position in the blade length ap region is a portion other than the tip portion in the blade length ap region. Specifically, the first predetermined position is a central portion between the tip (ap = 0) and the change point CP in the blade length ap area. That is, the first predetermined position is a central portion between the tip of the first outer peripheral blade 1 (the tip side portion 1a) and the change point CP along the blade length direction.
The second predetermined position is the central portion between the base end (ap = 1) and the change point CP in the blade length ap region. That is, the second predetermined position is a central portion between the base end along the blade length direction of (the proximal end portion 1b of) the first outer peripheral blade 1 and the change point CP.

As shown in FIG. 5, the end mill cross-section view of a first predetermined position of the cutting edge length ap region, the four pitch angle θn arranged in the circumferential direction, the first pitch angle theta _1, first The second pitch angle θ ₂ which is different from the second pitch angle θ ₁ is included two by two. The two first pitch angles θ ₁ and θ ₁ are disposed adjacent to each other in the circumferential direction, and the two second pitch angles θ ₂ and θ ₂ are disposed adjacent to each other in the circumferential direction.
In other words, in the end mill cross-sectional view of the first predetermined position, the four pitch angles θ ₁ and θ ₂ are the first pitch angle θ ₁ , the first pitch angle θ ₁ , and the second pitch angle around the axis O theta _2, are arranged in a second pitch angle theta _2, the order of.

Further, as shown in FIG. 6, in the end mill cross-sectional view at the second predetermined position in the blade length ap region, the four pitch angles θn aligned in the circumferential direction are the first pitch angle θ ₁ , the first pitch angle theta ₁ and the second pitch angle theta ₂ which angle is different, but includes two by two. The two first pitch angles θ ₁ and θ ₁ are disposed adjacent to each other in the circumferential direction, and the two second pitch angles θ ₂ and θ ₂ are disposed adjacent to each other in the circumferential direction.
That is, in the end mill cross-sectional view of the second predetermined position, the four pitch angles θ ₁ and θ ₂ are the first pitch angle θ ₁ , the first pitch angle θ ₁ , and the second pitch angle around the axis O theta _2, are arranged in a second pitch angle theta _2, the order of.
In the example shown in FIGS. 5 and 6, as compared with the first pitch angle theta _1, second the pitch angle theta ₂ is large, it is not limited thereto, the first compared to the pitch angle theta _1, the second pitch angle theta ₂ may be reduced.

More specifically, in FIGS. 4 to 6, four outer peripheral blades 1 and 2 are sequentially moved in the direction opposite to the tool rotation direction T, and the outer peripheral blade No. 1 is not. In the example shown in the drawings, when represented by I to IV, the outer peripheral blade No. I, III is the first peripheral cutting edge 1, the helix angle of these peripheral cutting edge 1 of the distal portion 1a is alpha _1, the helix angle of the proximal portion 1b is alpha _2. In addition, even-numbered peripheral blade No. II and IV are the second outer peripheral blades 2, and the twist angle of these outer peripheral blades 2 is β.

And in FIG. The outer peripheral blade No. 1 adjacent to the tip end side portion 1 a of the first outer peripheral blade 1 shown in FIG. 1 and the tool rotation direction T of the first outer peripheral blade 1. The pitch angle θ n formed between the outer peripheral blade 2 and the second outer peripheral blade 2 indicated by IV is θ ₁ . The combination of the twist angle α ₁ of the tip end portion 1 a of the first outer peripheral blade 1 I and the pitch angle θ n is (θ ₁ , α ₁ ). In addition, outer peripheral blade No. An outer peripheral blade No. 1 adjacent to the distal end side portion 1 a of the first outer peripheral blade 1 shown in FIG. Pitch angle θn formed between the second peripheral cutting edge 2 as shown in II is _{θ 2 (θ 1 ≠ θ 2} ), thus peripheral cutting No. The combination of the twist angle α ₁ of the tip end portion 1 a of the first outer peripheral blade 1 of III and the pitch angle θ n is (θ ₂ , α ₁ ).
That is, at the first predetermined position, the pitch angle θ n formed between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent in the tool rotation direction T of the first outer peripheral blade 1, and There are two kinds of combinations (θ n, α (α ₁ )) of angles of twist angle α (α ₁ ) of the outer peripheral blade 1 of ₁ .

Further, in FIG. An outer peripheral blade No. 2 adjacent to the second outer peripheral blade 2 indicated by II and the tool rotation direction T of the second outer peripheral blade 2. The pitch angle θ n formed between the first outer peripheral blade 1 and the distal end side portion 1 a of the first outer peripheral blade 1 is θ ₁ . The combination of the twist angle β of the second outer peripheral blade 2 of II and the angle of the pitch angle θ n is (θ ₁ , β). In addition, outer peripheral blade No. An outer peripheral blade No. 4 adjacent to the second outer peripheral blade 2 indicated by IV and the tool rotation direction T of the second outer peripheral blade 2. The pitch angle θn formed between the first outer peripheral blade 1 and the tip end portion 1a of the first outer peripheral blade 1 is θ ₂ (θ ₁ ≠ θ ₂ ). The combination of the twist angle β of the second outer peripheral blade 2 of IV and the angle of the pitch angle θ n is (θ ₂ , β).
That is, at the first predetermined position, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T; There are two types of combinations (θ n, β) of angles with the twist angle β of the outer peripheral blade 2 of two.

The constitution described hereinabove, in the first predetermined position shown in FIGS. 4 and 5, the pitch angle theta _1, theta _1, theta _2, along the theta ₂ is the circumferential direction (horizontal direction of the graph in FIG. 4) This Line up in order. The pitch angles θ ₁ , θ ₁ , θ ₂ , θ ₂ are arranged in the circumferential direction only at the “first predetermined position” on the tip side of the change point CP in the blade length ap region.

Moreover, in FIG. The outer peripheral blade No. 1 adjacent to the proximal end portion 1 b of the first outer peripheral blade 1 shown in FIG. 1 and the tool rotation direction T of the first outer peripheral blade 1 is shown. The pitch angle θ n formed between the outer peripheral blade 2 and the second outer peripheral blade 2 indicated by IV is θ ₁ . Angle of the combination of the twist angle alpha ₂ and the pitch angle θn of the first peripheral cutting edge 1 of the proximal portion 1b of the I _is, (θ _1, α ₂₎ is. In addition, outer peripheral blade No. The outer peripheral blade No. 1 adjacent to the proximal end portion 1 b of the first outer peripheral blade 1 and the tool rotation direction T of the first outer peripheral blade 1 shown by III. Pitch angle θn formed between the second peripheral cutting edge 2 as shown in II is _{θ 2 (θ 1 ≠ θ 2} ), thus peripheral cutting No. Angle of the combination of the twist angle alpha ₂ and the pitch angle θn of the first peripheral cutting edge 1 of the proximal portion 1b of the III is (θ _{2, α 2).}
That is, at the second predetermined position, the pitch angle .theta.n formed between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent in the tool rotational direction T of the first outer peripheral blade 1, and There are two types of combinations (θ n, α (α ₂ )) of angles of twist angle α (α ₂ ) of the outer peripheral blade 1 of 1.

Further, in FIG. An outer peripheral blade No. 2 adjacent to the second outer peripheral blade 2 indicated by II and the tool rotation direction T of the second outer peripheral blade 2. The pitch angle θ n formed between the base end portion 1 b of the first outer peripheral blade 1 shown by I and the outer peripheral blade No. ₁ is θ ₁ . The combination of the twist angle β of the second outer peripheral blade 2 of II and the angle of the pitch angle θ n is (θ ₁ , β). In addition, outer peripheral blade No. An outer peripheral blade No. 4 adjacent to the second outer peripheral blade 2 indicated by IV and the tool rotation direction T of the second outer peripheral blade 2. The pitch angle θn formed between the first outer peripheral blade 1 and the proximal end portion 1b of the first outer peripheral blade 1 is θ ₂ (θ ₁ ≠ θ ₂ ). The combination of the twist angle β of the second outer peripheral blade 2 of IV and the angle of the pitch angle θ n is (θ ₂ , β).
That is, at the second predetermined position, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T; There are two types of combinations (θ n, β) of angles with the twist angle β of the outer peripheral blade 2 of two.

From the above-described configuration, at the second predetermined position shown in FIGS. 4 and 6, the pitch angles θ ₁ , θ ₁ , θ ₂ , θ ₂ along the circumferential direction (horizontal axis of the graph in FIG. 4) Line up in order. In the blade length ap region, the pitch angles θ ₁ , θ ₁ , θ ₂ and θ ₂ are arranged in the circumferential direction only at the “second predetermined position” on the base end side of the change point CP.

In the first of each end mill cross-section view of the predetermined position and the second predetermined position, the angle difference (difference here between the pitch angle theta ₁ and the pitch angle theta _2, the maximum pitch angle θn and minimum pitch angle θn a difference between the absolute value of the words theta ₁ - [theta] ₂ simply in the following description |. θ ₁ -θ ₂ | may be represented by), for example _{0 ° <| θ 1 -θ 2} | ≦ 20 °, preferably 5 ° ≦ | θ ₁ −θ ₂ | ≦ 15 °.

Further, in the present embodiment, when the total number of the outer peripheral blades 1 and 2 is N, the type of combination of angles (θ n, α (α ₁ )) is ( N / 2). That is, the pitch angle θ n adjacent to the tool rotation direction T of the tip end side portion 1a of each first outer peripheral blade 1 in the first outer peripheral blade 1 of half (N / 2) of the total number N of the outer peripheral blades 1 and 2 The two are all different from one another.
Further, when the total number of the outer peripheral blades 1 and 2 is N, in the end mill cross-sectional view at the first predetermined position, there are (N / 2) kinds of combinations of angles (θ n, β). In other words, all the pitch angles θn adjacent to each other in the tool rotation direction T of each second outer peripheral blade 2 in the second outer peripheral blade 2 of half (N / 2) of the total number N of the outer peripheral blades 1, 2 mutually It is different.
Specifically, in the present embodiment, the total number N of the outer peripheral blades 1 and 2 is four, and at the first predetermined position, there are (N / 2) kinds of combinations of angles (θ n, α (α ₁ )) That is two. Also, there are (N / 2), that is, two types of combinations of angles (θ n, β).

In addition, when the total number of the outer peripheral blades 1 and 2 is N, the type of combination of angles (θ n, α (α ₂ )) is (N / 2) in an end mill cross sectional view at the second predetermined position. Is one. That is, the pitch angle adjacent to the tool rotation direction T of the base end side portion 1b of each first outer peripheral blade 1 in half (N / 2) of the total number N of the outer peripheral blades 1 and 2 in the first outer peripheral blade 1 θ n are all different from one another.
Further, when the total number of the outer peripheral blades 1 and 2 is N, in the end mill cross-sectional view at the second predetermined position, the number of types of combinations of angles (θ n, β) is (N / 2). In other words, all the pitch angles θn adjacent to each other in the tool rotation direction T of each second outer peripheral blade 2 in the second outer peripheral blade 2 of half (N / 2) of the total number N of the outer peripheral blades 1, 2 mutually It is different.
Specifically, in the present embodiment, the total number N of the outer peripheral blades 1 and 2 is four, and at the second predetermined position, there are (N / 2) kinds of combinations of angles (θ n, α (α ₂ )) That is two. Also, there are (N / 2), that is, two types of combinations of angles (θ n, β).

The peripheral blades 1 and 2 of the above-described embodiment and the twist angles α (α ₁ , α ₂ ), β and pitch angle θ n thereof are shown as pattern 1 in Table 1 below.

[Bottom blade (tip blade)]
As shown in FIGS. 1 to 3, among the cutting edges, a bottom blade (tip blade) 9 is formed at the tip of the blade portion 3 a of the end mill main body 3 and extends along the radial direction. The bottom blades 9 are formed in a plurality at intervals in the circumferential direction. The radially outer end 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.

  Specifically, in the blade portion 3a, a number (four) of bottom blades 9 corresponding to the number (four rows) of the chip discharge grooves 4 are arranged at intervals in the circumferential direction. In the example of the present embodiment, a pair of long blades (bottom blades 9 not cut out by the gashes 7) and a pair of short blades (diameters by the gashes 7 are cut out in the four bottom blades 9). And a bottom blade 9). The inner ends (radially inner end edges) of the pair of long blades are disposed close to the axis O. A gash 7 (a connecting portion between the gashes 7) is disposed between the inner ends of the pair of short blades and the axis O.

Further, in a side view of the end mill main body 3 shown in FIG. 2, the bottom blade 9 extends gradually and slightly proximally toward the radially inner side from the outer end (radially outer end edge) There is.
The rotation trajectory obtained by rotating the bottom blade 9 around the axis O has a virtual conical surface (taper surface) shape that gradually inclines toward the proximal side as it goes radially inward from the outer end of the bottom blade It is eggplant.

  The bottom blade 9 is formed at a cross ridge line between a wall surface of the chip discharge groove 4 facing the tool rotational direction T and the tip surface of the end mill body 3. The bottom blade 9 extends linearly along the leading edge of the wall surface of the chip discharge groove 4. Specifically, the bottom blade 9 is a rake surface 4b located at the end on the tip end side of the wall surface facing the tool rotational direction T in the gash 7 of the chip discharge groove 4 and the tip surface of the blade portion 3a It is formed in the cross ridge line of the tip flank 8 adjacent on the opposite side to the tool rotation direction T of the gash 7.

  On the tip end face of the blade portion 3a, a tip end flank 8 is formed between the chip discharge grooves 4 adjacent to each other in the circumferential direction. In the illustrated example, the width (length in the direction orthogonal to the bottom blade 9) of the tip flank 8 is substantially constant along the extending direction (blade length direction) of the bottom blade 9.

[Modification of this embodiment]
Here, a modified example of the present embodiment included in the present invention will be described with reference to FIGS. 7 and 8. The same components as those described above will not be described in detail and only differences will be described below.
FIG. 7 is a view schematically showing the arrangement of the outer peripheral blades 1 and 2 (a plan showing the end mill outer periphery in a planar form), and FIGS. 8 (a) and 8 (b) are blade portions of the end mill main body 3. It is an end mill cross-sectional view which simplifies and shows 3a (as a mere two-dot chain line circle). 8 (a) is a cross-sectional view of an end mill at a predetermined position (first predetermined position) on the tip end side from the change point CP where the twist angle α changes in the blade length ap region of the first outer peripheral blade 1 8B shows an end mill cross-sectional view at a predetermined position (second predetermined position) proximal to the change point CP where the twist angle α changes in the blade length ap region. There is.
In this modification, the arrangement (positional relationship) of the outer peripheral blades 1 and 2 and the pitch angles θ ₁ and θ ₂ is different from FIGS. 4 to 6 of the above-described embodiment.

Specifically, in this modification, in FIG. The outer peripheral blade No. 1 adjacent to the tip end side portion 1 a of the first outer peripheral blade 1 shown in FIG. 1 and the tool rotation direction T of the first outer peripheral blade 1. The pitch angle θ n formed between the outer peripheral blade 2 and the second outer peripheral blade 2 indicated by IV is θ ₁ . The combination of the twist angle α ₁ of the tip end portion 1 a of the first outer peripheral blade 1 I and the pitch angle θ n is (θ ₁ , α ₁ ). In addition, outer peripheral blade No. An outer peripheral blade No. 1 adjacent to the distal end side portion 1 a of the first outer peripheral blade 1 shown in FIG. Pitch angle θn formed between the second peripheral cutting edge 2 as shown in II is _{θ 2 (θ 1 ≠ θ 2} ), thus peripheral cutting No. The combination of the twist angle α ₁ of the tip end portion 1 a of the first outer peripheral blade 1 of III and the pitch angle θ n is (θ ₂ , α ₁ ).
That is, at the first predetermined position, the pitch angle θ n formed between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent in the tool rotation direction T of the first outer peripheral blade 1, and the first There are two kinds of combinations (θ n, α (α ₁ )) of the twist angle α (α ₁ ) of the outer peripheral blade 1 and the angle of (θ n, α (α ₁ )).

Further, in FIG. An outer peripheral blade No. 2 adjacent to the second outer peripheral blade 2 indicated by II and the tool rotation direction T of the second outer peripheral blade 2. Pitch angle θn formed between the first peripheral cutting edge 1 of the distal portion 1a indicated by I is theta _2, therefore the peripheral cutting edge No. The combination of the twist angle β of the second outer peripheral blade 2 of II and the pitch angle θ n is (θ ₂ , β). In addition, outer peripheral blade No. An outer peripheral blade No. 4 adjacent to the second outer peripheral blade 2 indicated by IV and the tool rotation direction T of the second outer peripheral blade 2. The pitch angle θn formed between the first outer peripheral blade 1 and the tip end portion 1a of the first outer peripheral blade 1 is θ ₁ (θ ₁ ≠ θ ₂ ). The combination of the twist angle β of the second outer peripheral blade 2 of IV and the angle of the pitch angle θ n is (θ ₁ , β).
That is, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent in the tool rotation direction T of the second outer peripheral blade 2 at the first predetermined position, and the second There are two kinds of combinations (θ n, β) of the angles of the twist angle β of the outer peripheral blade 2 and the angle.

From the above-described configuration, at the first predetermined position shown in FIGS. 7 and 8A, the pitch angles θ ₁ , θ ₂ , θ ₂ and θ ₁ are in the circumferential direction (horizontal axis direction of the graph in FIG. 7). Line up in this order along. The pitch angles θ ₁ , θ ₂ , θ ₂ and θ ₁ are arranged in the circumferential direction only at the “first predetermined position” on the tip side of the change point CP in the blade length ap region.

Further, in FIG. The outer peripheral blade No. 1 adjacent to the proximal end portion 1 b of the first outer peripheral blade 1 shown in FIG. 1 and the tool rotation direction T of the first outer peripheral blade 1 is shown. The pitch angle θ n formed between the outer peripheral blade 2 and the second outer peripheral blade 2 indicated by IV is θ ₁ . Angle of the combination of the twist angle alpha ₂ and the pitch angle θn of the first peripheral cutting edge 1 of the proximal portion 1b of the I _is, (θ _1, α ₂₎ is. In addition, outer peripheral blade No. The outer peripheral blade No. 1 adjacent to the proximal end portion 1 b of the first outer peripheral blade 1 and the tool rotation direction T of the first outer peripheral blade 1 shown by III. Pitch angle θn formed between the second peripheral cutting edge 2 as shown in II is _{θ 2 (θ 1 ≠ θ 2} ), thus peripheral cutting No. Angle of the combination of the twist angle alpha ₂ and the pitch angle θn of the first peripheral cutting edge 1 of the proximal portion 1b of the III is (θ _{2, α 2).}
That is, at the second predetermined position, the pitch angle θ n formed between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent in the tool rotation direction T of the first outer peripheral blade 1, and There are two kinds of combinations (θ n, α (α ₂ )) of the twist angle α (α ₂ ) of the outer peripheral blade 1 and the angle of (θ n, α (α ₂ )).

Moreover, in FIG. An outer peripheral blade No. 2 adjacent to the second outer peripheral blade 2 indicated by II and the tool rotation direction T of the second outer peripheral blade 2. The pitch angle θ n formed between the first outer peripheral blade 1 and the proximal end portion 1 b of the first outer peripheral blade 1 is θ ₂ . The combination of the twist angle β of the second outer peripheral blade 2 of II and the pitch angle θ n is (θ ₂ , β). In addition, outer peripheral blade No. An outer peripheral blade No. 4 adjacent to the second outer peripheral blade 2 indicated by IV and the tool rotation direction T of the second outer peripheral blade 2. The pitch angle θn formed between the first outer peripheral blade 1 and the base end side portion 1b of the first outer peripheral blade 1 is θ ₁ (θ ₁よ っ て θ ₂ ). The combination of the twist angle β of the second outer peripheral blade 2 of IV and the angle of the pitch angle θ n is (θ ₁ , β).
That is, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent in the tool rotation direction T of the second outer peripheral blade 2 at the second predetermined position, and the second There are two kinds of combinations (θ n, β) of the angles of the twist angle β of the outer peripheral blade 2 and the angle.

From the above configuration, at the second predetermined position shown in FIGS. 7 and 8B, the pitch angles θ ₁ , θ ₂ , θ ₂ and θ ₁ are in the circumferential direction (horizontal axis direction of the graph in FIG. 7). Line up in this order along. In the blade length ap region, the pitch angles θ ₁ , θ ₂ , θ ₂ , and θ ₁ are arranged in the circumferential direction only at the “second predetermined position” on the base end side of the change point CP.

The peripheral blades 1, 2 and their twist angles α (α ₁ , α ₂ ), β and pitch angle θ n in this modification are shown as pattern 2 in Table 1 above.

  And also in this modification, in each of the end mill cross sectional view at the first predetermined position shown in FIG. 8A and the end mill cross sectional view at the second predetermined position shown in FIG. 8B. A pitch angle θn formed between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T, and a twist angle of the first outer peripheral blade 1 The combination of the angle of α and the angle (θ n, α) is at least two types, and the first outer peripheral blade adjacent to the second outer peripheral blade 2 and the tool rotation direction T of the second outer peripheral blade 2 The combination (θ n, β) of the pitch angle θ n formed between 1 and the twist angle β of the second outer peripheral blade 2 is at least two or more.

[Operation and effect according to the present embodiment]
The square end mill (end mill) 20 of the present embodiment described above has the first outer peripheral blade 1 and the second outer peripheral blade 2 alternately arranged at intervals in the circumferential direction on the outer periphery of the end mill main body 3 Each has two or more. The first outer peripheral blade 1 and the second outer peripheral blade 2 have the same number, and the total number N of the outer peripheral blades 1 and 2 is four (four blades) in the example of the present embodiment. The twist angle α of the first outer peripheral blade 1 and the twist angle β of the second outer peripheral blade 2 are different in size (α 互 い に β). That is, the square end mill 20 of the present embodiment is not an end mill of equal leads where the twist angles of the outer peripheral blades are all the same, but an end mill of unequal leads (unequal twist) having plural types of twist angles α and β. is there. Further, among the twist angles α of the first outer peripheral blade 1, the twist angle α of the distal end side portion 1a (twist angle α ₁ shown in FIGS. 4 and 7) and the twist angle α of the base end side portion 1b (FIG. 4) And the twist angles α ₂ ) shown in FIG. 7 are different in size from each other.

The inventor of the present invention has conducted intensive studies on the end mill, and as a result, in order to effectively suppress the frequency that generates chattering vibration during cutting, the phase difference of the regenerative vibration is made between the plurality of outer peripheral blades 1 and 2. It is preferable to shift, and as a result, it is possible to suppress the occurrence of self-excited vibration generated near the resonance frequency, and as a result, it is possible to obtain the knowledge that the chatter vibration can be suppressed.
In addition, the "frequency which generates chattering vibration" has concretely shown the frequency band of the predetermined range, for example, is the range of 300-900 Hz. Hereinafter, this range may be referred to as a predetermined frequency band.

Based on the above-described findings, in the present embodiment, in the blade length ap region of the first outer peripheral blade 1, the predetermined position (first predetermined position) on the tip side from the change point CP where the twist angle α changes and the change point In each cross-sectional view of the end mill main body 3 at a predetermined position (second predetermined position) proximal to the CP, a special configuration satisfying the following conditions was used.
That is, when a plurality of pitch angles (division angles) aligned around the axis O of the end mill body 3 is θ n, the first outer peripheral blade 1 and the first outer periphery are viewed in cross section at the first predetermined position. A pitch angle θ n formed between the second outer peripheral blade 2 adjacent to the tool rotation direction T of the blade 1 (that is, a pitch angle θ n adjacent to the tool rotation direction T of the first outer peripheral blade 1); The second outer peripheral blade 2 has at least two types of combinations (θ n, α (α ₁ )) of the twist angle α (twist angle α ₁ ) of the tip side portion 1 a of the outer peripheral blade 1 and Pitch angle θ n formed between the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotation direction T (that is, the pitch angle adjacent to the second outer peripheral blade 2 in the tool rotation direction T) The kind of combination (θ n, β) of the angles of θ n) and the twist angle β of the second outer peripheral blade 2 is at least One or more. And the pitch formed between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent to the tool rotation direction T of the first outer peripheral blade 1 in the end mill cross-sectional view at the second predetermined position The angle between the angle θ n (that is, the pitch angle θ n adjacent to the tool rotation direction T of the first outer peripheral blade 1) and the twist angle α (twist angle α ₂ ) of the proximal end portion 1 b of the first outer peripheral blade 1 Of the combination (θ n, α (α ₂ )) of at least two, and the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the tool rotational direction T of the second outer peripheral blade 2 Combination of the pitch angle θ n (that is, the pitch angle θ n adjacent to the tool rotational direction T of the second outer peripheral blade 2) and the twist angle β of the second outer peripheral blade 2 (θ n, The type of β) is at least two or more.

Specifically, it is combined with the twist angle α (twist angle α ₁ ) of the tip side portions 1a of the plurality of first outer peripheral blades 1 at a first predetermined position in the blade length ap region of the outer peripheral blades 1, 2 Each pitch angle θ n is, for example, two or more types such as θ ₁ , θ ₂ ,... And each pitch angle θ n combined with the twist angle β of the plurality of second outer peripheral blades 2 is, for example, θ ₁ , θ ₂ ,. And two or more. In addition, each pitch combined with the twist angle α (twist angle α ₂ ) of the proximal end portions 1 b of the plurality of first outer peripheral blades 1 at the second predetermined position in the blade length ap region of the outer peripheral blades 1, ₂ angle θn is, for example theta _1, theta _2, ... and is 2 or more, each pitch angle θn combined with the helix angle of the plurality of second peripheral cutting edge 2 beta is, for example theta _1, theta _2, ... and 2 It is more than kind.

Here, in the above description, the pitch angle combined with the twist angle α (α ₁ ) of the distal end portion 1a of the first outer peripheral blade 1 is “θ n”, and the twist of the proximal end portion 1b of the first outer peripheral blade 1 is The pitch angle combined with the angle α (α ₂ ) is “θ n”, and the pitch angle combined with the twist angle β of the second outer peripheral blade 2 is “θ n”, using the same variable name “θ n” for each pitch angle However, this does not mean that these pitch angles θ n have the same value. In the present embodiment, each pitch angle θ n may be rephrased as follows in order to make it clearer which “pitch angle θ n” points to which pitch position of which peripheral blade (which portion). .
That is, the pitch angle θn combined with the twist angle α (α ₁ ) of the tip end portion 1a of the first outer peripheral blade 1 is set to “pitch angle θ (α ₁ , n) at _first predetermined position”, “first The pitch angle θ (α ₁ , n) at the tip end portion 1 a of the outer peripheral blade 1 may be reworded as “pitch angle θ (α ₁ , n)”. Further, the pitch angle θn combined with the twist angle α (α ₂ ) of the base end side portion 1b of the first outer peripheral blade 1 is “pitch angle θ (α ₂ , n) at the second predetermined position”, The pitch angle θ (α ₂ , n) of the proximal end portion 1 b of the outer peripheral blade 1 may be reworded as “pitch angle θ (α ₂ , n)”. Further, the pitch angle θn combined with the twist angle β of the tip end portion (the portion located on the tip end side from the change point CP) of the second outer peripheral blade 2 is set to “pitch angle θ (β, n at first predetermined position “,“ Pitch angle θ (β, n) at the tip side portion of the second outer peripheral blade 2 ”, or simply“ pitch angle θ (β, n) ”. Further, the pitch angle θn combined with the twist angle β of the base end side portion (the part located on the base end side from the change point CP) of the second outer peripheral blade 2 is set to “pitch angle θ (β at a second predetermined position , N), “pitch angle θ (β, n) at the proximal end portion of the second outer peripheral blade 2”, or simply “pitch angle θ (β, n)”.

In this embodiment, since the square end mill 20 is a four-blade end mill, as shown in Table 1, a combination of the angle between the pitch angle θ n and the twist angle α (θ n, α (α ₁ or α ₂ ) There are two types of), and there are two types of combinations ([theta] n, [beta]) of the pitch angle [theta] n and the twist angle [beta]. That is, at each of the first and second predetermined positions, there are two types (θ ₁ and θ _{2 in the} example shown in Table 1) of pitch angles θn combined with the twist angle α (α ₁ or α ₂ ), There are two types of pitch angles θn combined with the twist angle β (in the example shown in Table 1, θ ₁ and θ ₂ ).

  As described above, in the present embodiment, two or more types of combinations (θ n, α) of angles are provided in each of the end mill cross sectional view at the first predetermined position and the end mill cross sectional view at the second predetermined position. Since there are two or more kinds of combinations of angles (θ n, β), and the total number N of the outer peripheral blades 1 and 2 is four as in the present embodiment, for example, A total of four combinations can be made. Since the combination of the respective angles exerts chatter vibration suppression effects in mutually different frequency bands, according to the present embodiment, it is possible to obtain chatter vibration suppression effects in a wide frequency band over a wide range in the axis O direction. The machining accuracy can be improved under various cutting conditions. According to the analysis results, the suppressing effect of the chatter vibration by the square end mill 20 of the present embodiment is remarkably remarkable several times as large as that of the conventional unequal lead / uneven pitch square end mill.

  Furthermore, the frequency of chatter vibration can not be known in advance, and conventionally, chatter vibration may occur at any frequency within a predetermined frequency range that generates chatter vibration. According to the square end mill 20 of the embodiment, it is possible to suppress chattering over the entire area of the predetermined frequency band.

What is shown in FIG. 9 is the index of the cutting amount mm (vertical axis), frequency Hz (horizontal axis), and the number of regenerations RF (the chatter vibration suppression effect by the square end mill 20 of this embodiment, and the lightness and darkness It is an analysis result representing the relationship of “displayed” (details will be described later). The rotation speed of the spindle was set to 2500 rpm. From this analysis result, it was found that, in the case of the square end mill 20 of this embodiment, for example, when the cutting amount exceeds 5 mm, the number of regenerations RF is suppressed to 0.3 or less over substantially the entire frequency of 300 to 900 Hz. In addition, even when the cutting amount is 5 mm or less, the number of reproductions RF is suppressed to 0.3 or less over a wide range of frequencies of 500 to 700 Hz.
As described above, according to the end mill 20 of the present embodiment, the number of regenerations RF can be effectively suppressed over substantially the entire predetermined frequency band that generates chatter vibration, and generation of chatter vibration is significantly suppressed. Was confirmed.

The reproduction number RF will be described.
It can be considered that the regeneration effect is small when the sum of the complex vectors that can be represented using the phase delay ε _{j, l} of the regeneration vibration at each cutting edge is the regeneration number RF and the absolute value | RF | is small. . The definition equation of the reproduction number RF is shown in the following equation (1). In addition, when an equal pitch tool is used, the reproduction effect is maximized, and the number of reproductions | RF | becomes 1. ε _{j, l} means the phase delay in the l-th minute cutting edge axially divided by N _z in the j-th cutting edge of the N _t single-bladed tool. The phase delay can be expressed by the following equation (2) using the pitch angle Δθ _{j, l at the} same minute cutting edge _, the frequency f _{c of} chatter vibration and the spindle rotational speed n.

Here, in order to deepen the understanding of the present embodiment, a comparative example (conventional square end mill) will be described.
Although not particularly illustrated, in the square end mill of the comparative example, the twist angle α (twist angle α ₁ ) of the tip side portions 1a of the plurality of first outer peripheral blades 1 at the first predetermined position in the blade length ap region. each pitch angle θn in combination with, for example a one theta ₁ only, the pitch angle θn combined with the helix angle of the plurality of second peripheral cutting edge 2 beta is, for example, one type of theta ₂ only. Specifically, referring to FIG. 4, at the first predetermined position, the pitch angle is θ ₁ , θ ₂ , θ ₁ , θ ₂ along the circumferential direction (in the direction of the horizontal axis of the graph). Arrange alternately.
Each pitch angle θn combined with the twist angle α (twist angle α ₂ ) of the proximal end portion 1b of the plurality of first outer peripheral blades 1 at the second predetermined position in the blade length ap region is, for example, θ is one type of only _1, the pitch angle θn combined with the helix angle of the plurality of second peripheral cutting edge 2 beta is, for example, one type of theta ₂ only. To explain with reference to FIG. 4, at the second predetermined position, the pitch angles are alternately arranged along the circumferential direction (in the direction of the horizontal axis of the graph) with θ ₁ , θ ₂ , θ ₁ , θ ₂ .

In the square end mill of this comparative example, it is confirmed from the analysis result shown in FIG. 10 that chatter vibration occurs with the number of regenerations RF exceeding 0.3 over a wide range of the frequency band when the cutting amount is 10 mm or less. The In particular, when the cut amount is 5 mm or less, chatter vibration occurs over substantially the entire frequency band.
On the other hand, according to the square end mill 20 of the present embodiment, the occurrence of chatter vibration can be effectively suppressed over substantially the entire frequency band.

Moreover, in the square end mill 20 of this embodiment, the following remarkable effects and effects which can not be obtained by the conventional square end mill are exhibited. That is, at the first predetermined position and the second predetermined position in the blade length ap region, the pitch angles θ ₁ and θ ₂ effective for the specific frequency at which it is desired to suppress the occurrence of the self-excited vibration is set. pitch angle theta _1, theta ₁ between a second pitch angle theta _2, together with the adjacent arrangement theta ₂ between the respectively circumferentially alternately twist angle alpha, beta have different peripheral cutting edge 2 between the circumferential direction By manufacturing the square end mill 20 with a simple configuration of arranging, this end mill can not only the first and second predetermined positions of the blade length ap region but also the specific frequency over the entire blade length ap region. On the other hand, the occurrence of self-excitation vibration can be effectively suppressed.

This first peripheral cutting edge 1 between the pitch angle difference at the first predetermined position | and, second peripheral cutting edge 2 difference of the pitch angle between | _| theta ₁ - [theta] ₂ theta ₁ - [theta] _{2 |} and This is because the generation of self-oscillation is suppressed by maintaining the entire tip side portion from the tip (ap = 0) of the blade length ap region to the change point CP. The first outer peripheral edge 1 between the pitch angle difference at the second predetermined position | and, second peripheral cutting edge 2 difference of the pitch angle between | _| theta ₁ - [theta] ₂ theta ₁ - [theta] _{2 |} and is This is because the entire proximal end portion from the change point CP of the blade length ap region to the proximal end (ap = 1) is maintained, and the occurrence of self-oscillation is suppressed.
That is, according to the present embodiment, chatter vibration can be stably suppressed regardless of the cut amount in the direction of the axis O of the square end mill 20, and the end mill can be based on the first and second predetermined positions. Because it can be designed, it does not complicate the manufacture of the end mill.

Then, according to the present embodiment, the first outer peripheral blade 1 has different twist angles α (α (α) on the tip end side and the base end side of the change point CP while exhibiting excellent suppression effect of chattering vibration as described above. ₁ and α ₂ ), it is possible to prevent the width of the chip discharge groove 4 from becoming excessively narrow at the tip end side and the base end side end of the outer peripheral blades 1 and 2 . Thereby, the chip dischargeability is well maintained.

Further, in the present embodiment, the twist angle α (twist angle α ₁ ) of the distal end side portion 1a of the first outer peripheral blade 1 and the twist angle α (twist angle α ₂ of the base end side portion 1b of the first outer peripheral blade 1) Since the angle difference | α ₁ −α ₂ | with the above is 40 ° or less, the following effects can be obtained.
That is, since the angle difference | α ₁ −α ₂ | is 40 ° or less, the inclination of the twist angle α is abrupt in any of the distal end portion 1 a and the proximal end portion 1 b of the first outer peripheral blade 1. It can be controlled to become too loose or too loose. As a result, it is possible to reliably prevent such a defect that the groove width of the chip discharge groove 4 is excessively narrowed at the end on the tip end side or the end on the base end side of the first outer peripheral blade 1. In addition, in the tip end side portion 1a and the base end side portion 1b of the first outer peripheral blade 1, the sharpness is also impaired in the portion where the twist angle α is reduced (the tip end side portion 1a in the example of this embodiment). Cutting performance can be maintained well.

Further, when the angle difference | α ₁ −α ₂ | is 5 ° or more and 35 ° or less, the following operation and effect can be further achieved.
That is, since the angle difference | α ₁ −α ₂ | is 5 ° or more, frequency bands in which the suppression effect of chatter vibration is different between the distal end portion 1 a and the proximal end portion 1 b of the first outer peripheral blade 1 are different. Can be enhanced by Thereby, the suppression effect of chatter vibration can be stabilized in a wide frequency band. In particular, it is possible to surely enhance the vibration suppressing effect at the low incision at which chatter vibration easily occurs.
Further, since the angle difference | α ₁ −α ₂ | is 35 ° or less, the groove width of the chip discharge groove 4 is excessive at the end of the tip end side or the base end side of the first outer peripheral blade 1. Can be more reliably prevented from becoming so narrow. Further, the sharpness is sufficiently enhanced also in the portion (the tip side portion 1a in the example of the present embodiment) of the tip side portion 1a and the base end side portion 1b of the first outer peripheral blade 1 in which the twist angle α is reduced. be able to.

Further, in the present embodiment, in the blade length ap region of the first outer peripheral blade 1, the change in the twist angle α is 0% at the tip end position (ap = 0) and 100% at the base end position (ap = 1). Since the point CP is disposed in the range of 30% to 70% in the blade length ap region, the following effects can be obtained.
That is, since the change point CP is arranged in a range of 30% or more in the blade length ap region of the first outer peripheral blade 1, the blade length of the proximal end portion 1b of the first outer peripheral blade 1 becomes too long Can be prevented. As a result, it is possible to reliably avoid such a situation that the width of the chip discharge groove 4 becomes too narrow at the proximal end side of the outer peripheral blades 1 and 2.
In addition, since the change point CP is disposed within a range of 70% or less in the blade length ap region of the first outer peripheral blade 1, the blade length of the tip side portion 1a of the first outer peripheral blade 1 becomes too long. Can be prevented. As a result, it is possible to reliably avoid such a situation that the groove width of the chip discharge groove 4 becomes too narrow at the tip end side of the outer peripheral blades 1 and 2.

Further, in the present embodiment, since the first predetermined position in the blade length ap region is a portion other than the tip end portion in the blade length ap region, the following effects can be obtained.
That is, in this case, it is easy to make the pitch angles of the outer peripheral blades 1 and 2 different from each other at the tip of the blade length ap region. Among the blade length ap regions of the outer peripheral blades 1 and 2, the tip end is a position to start cutting into the work material, and is a portion frequently used for cutting, and all the pitch angles are different at this tip portion It is preferable because the effect of suppressing the above-mentioned frequent vibration tends to be particularly remarkable.

  Further, in the present embodiment, the first predetermined position for setting the pitch angle θn on the tip side of the change point CP of the first outer peripheral blade 1 is the tip of the blade length ap region of the first outer peripheral blade 1 ( Since it is the central portion between ap = 0) and the change point CP, the groove width of the chip discharge groove 4 adjacent to the outer peripheral blades 1 and 2 becomes too small at the tip of the first outer peripheral blade 1 and the change point CP. You can suppress such things. Therefore, the chip discharging property can be more stably enhanced while suppressing the occurrence of chatter vibration as described above.

  Further, in the present embodiment, the second predetermined position for setting the pitch angle θ n on the base end side of the change point CP of the first outer peripheral blade 1 is the basis of the blade length ap region of the first outer peripheral blade 1. Since it is a central portion between the end (ap = 1) and the change point CP, the groove width of the chips discharge groove 4 adjacent to the outer peripheral blades 1 and 2 is the proximal end of the first outer peripheral blade 1 and the change point CP. It is possible to suppress things that become too small. Therefore, the chip discharging property can be more stably enhanced while suppressing the occurrence of chatter vibration as described above.

Further, in the present embodiment, the twist angle α (α ₁ ) on the tip side of the change point CP of the first outer peripheral blade 1 is smaller than the twist angle α (α ₂ ) on the end side of the change point CP. The change point CP of the first outer peripheral blade 1 is formed to project in the tool rotation direction T. Therefore, at the time of manufacturing the square end mill 20, the first outer peripheral blade 1 can be easily formed by a grindstone or the like.

Further, in the present embodiment, when the total number of the outer peripheral blades 1 and 2 is N, in the end mill cross section at the first predetermined position, there are (N / 2) kinds of combinations of angles (θ n, α) Because of this, the following effects can be achieved.
That is, in this case, the angle between the twist angle α (twist angle α ₁ ) at the tip end portion 1 a of the first outer peripheral blade 1 and the pitch angle θn adjacent to the tool rotation direction T of the first outer peripheral blade 1 The type of combination (θ n, α (α ₁ )) is half of the total number N of the outer peripheral blades 1 and 2. That is, since the pitch angles θn adjacent to each other in the tool rotational direction T at the tip end portions 1a of the plurality of first outer peripheral blades 1 are all different from each other, the chatter vibration suppression effect is further increased by that amount. It can be obtained in a wide frequency band.

Further, in the present embodiment, when the total number of the outer peripheral blades 1 and 2 is N, in the end mill cross section at the first predetermined position, there are (N / 2) kinds of combinations (θn, β) of angles Because of this, the following effects can be achieved.
That is, in this case, the combination (θ n, β) of the angle of the twist angle β at the tip end portion of the second outer peripheral blade 2 and the pitch angle θ n adjacent to the tool rotation direction T of the second outer peripheral blade 2 The type is half of the total number N of the outer peripheral blades 1 and 2. In other words, the pitch angles θn adjacent to each other in the tool rotation direction T at the tip end portions of the plurality of second outer peripheral blades 2 are all different from each other, so the chatter vibration suppression effect is wider It can be obtained in the frequency band.

Further, in the present embodiment, when the total number of the outer peripheral blades 1 and 2 is N, in the end mill cross section at the second predetermined position, there are (N / 2) kinds of combinations of angles (θ n, α) Because of this, the following effects can be achieved.
That is, in this case, the angle between the twist angle α (twist angle α ₂ ) at the base end side portion 1b of the first outer peripheral blade 1 and the pitch angle θn adjacent to the tool rotation direction T of the first outer peripheral blade 1 The type of combination (θ n, α (α ₂ )) of the above is half of the total number N of the outer peripheral blades 1 and 2. That is, in the proximal end portion 1b of the plurality of first outer peripheral blades 1, the pitch angles θn adjacent to each other in the tool rotational direction T are all different from each other, so the chatter vibration suppression effect It can be obtained in a wider frequency band.

Further, in the present embodiment, when the total number of the outer peripheral blades 1 and 2 is N, in the end mill cross section at the second predetermined position, there are (N / 2) kinds of combinations of angles (θ n, β) Because of this, the following effects can be achieved.
That is, in this case, a combination of the twist angle β at the proximal end portion of the second outer peripheral blade 2 and the pitch angle θn adjacent to the tool rotation direction T of the second outer peripheral blade 2 (θ n, β) Type is half the total number N of the outer peripheral blades 1 and 2. That is, in the base end side portions of the plurality of second outer peripheral blades 2, the pitch angles θn adjacent to each other in the tool rotational direction T are all different from each other, so the chatter vibration suppression effect is further increased accordingly It can be obtained in a wide frequency band.

Further, in this embodiment, the difference (angular difference) | α−β | of the angle between the twist angle α of the first outer peripheral blade 1 and the twist angle β of the second outer peripheral blade 2 is 25 ° or less. Specifically, since the angle difference | α ₁ −β | is 25 ° or less and the angle difference | α ₂ −β | is 25 ° or less, the following effects can be obtained.
That is, in this case, it is possible to suppress that the groove width becomes too small at any of the tip portion of the chip discharge groove 4, the vicinity of the change point CP, and the base end.
Moreover, in order to make the above-mentioned effect more remarkable and to stabilize the function by unequal read, preferably, 10 ° ≦ | α−β | ≦ 20 °. Specifically, it is preferable that 10 ° ≦ | α ₁ −β | ≦ 20 °, and 10 ° ≦ | α ₂ −β | ≦ 20 °.

Further, in this embodiment, at each of the first and second predetermined positions, the difference (angular difference) between the maximum pitch angle θ n and the minimum pitch angle θ n, that is, the difference between the pitch angle θ ₂ and the pitch angle θ ₁ Since θ ₁ −θ ₂ | is 20 ° or less, the following effects can be obtained.
That is, in this case, it is possible to suppress that the groove width becomes too small at any of the tip portion of the chip discharge groove 4, the vicinity of the change point CP, and the base end.
Moreover, in order to make the above-mentioned effect more remarkable and to stabilize the function by unequal pitch, preferably, 5 ° ≦ | θ ₁ −θ ₂ | ≦ 15 °.

Second Embodiment
Next, a square end mill 30 according to a second embodiment of the present invention will be described with reference to FIGS. 11 to 13. The same components as those of the above-described embodiment will not be described in detail and only differences will be described below.

  11 to 13 are end mill cross-sectional views showing the blade portion 3a of the end mill main body 3 of the square end mill 30 in a simplified manner (as a mere two-dot chain line circle). Further, in each of FIGS. 11 to 13, (a) shows an end mill crossing at a first predetermined position on the tip end side from the change point CP where the twist angle α changes in the blade length ap region of the first outer peripheral blade 1. (B) represents an end mill cross-sectional view at a second predetermined position proximal to a change point CP at which the twist angle α changes in the blade length ap region of the first outer peripheral blade 1 (b) It represents.

[Differences from previous embodiments]
The square end mill 30 of the present embodiment is a six-blade end mill, and the first outer peripheral blade 1 and the second outer peripheral blade 2 are alternately arranged at intervals in the circumferential direction on the outer periphery of the end mill main body 3 There are three for each. That is, in the plurality of outer peripheral blades 1 and 2 formed on the outer periphery of the end mill main body 3, two or more first outer peripheries having different twist angles α between the tip end side portion 1a and the base end side portion 1b of the outer peripheral blade 1 The blade 1 and the second outer peripheral blade 2 having a constant twist angle β different from the twist angle α of the first outer peripheral blade 1 and the same number as the number of the first outer peripheral blades 1 are included.

  Then, in each of the end mill cross sectional view at the first predetermined position shown in FIG. 11 (a) and the end mill cross sectional view at the second predetermined position shown in FIG. 11 (b), the first outer peripheral blade Between the pitch angle θ n formed between the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T and the twist angle α of the first outer peripheral blade 1 The type of combination (θ n, α) is at least two or more, and is formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the tool rotational direction T of the second outer peripheral blade 2 At least two kinds of combinations (θ n, β) of the angles of the pitch angle θ n and the twist angle β of the second outer peripheral blade 2 are used.

More specifically, as shown in FIG. 11A, the tip end side of the first outer peripheral blade 1 in an end mill cross-sectional view at a first predetermined position located on the tip side of the change point CP in the blade length ap region. A pitch angle θ n formed between the portion 1 a and the second outer peripheral blade 2 adjacent to the tool rotation direction T of the first outer peripheral blade 1 (that is, the tool rotation of the tip side portion 1 a of the first outer peripheral blade 1) At least two kinds of combinations (θ n, α ₁ ) of the angles of the pitch angle θ n) adjacent to the direction T and the twist angle α ₁ of the tip side portion 1 a of the first outer peripheral blade 1 are The pitch angle θ n formed between the second outer peripheral blade 2 and the tip side portion 1 a of the first outer peripheral blade 1 adjacent to the tool rotation direction T of the second outer peripheral blade 2 (that is, the second outer peripheral blade Combination of the pitch angle θ n) adjacent to the tool rotational direction T of 2 and the twist angle β of the second outer peripheral blade 2 The types of (θ n, β) are at least two or more.
And, as shown in FIG. 11 (b), the proximal end of the first outer peripheral blade 1 in an end mill cross-sectional view at a second predetermined position located proximal to the change point CP in the blade length ap region. Pitch angle θ n formed between the side portion 1 b and the second outer peripheral blade 2 adjacent to the tool rotation direction T of the first outer peripheral blade 1 (ie, the proximal end portion 1 b of the first outer peripheral blade 1 At least two or more kinds of combinations (θ n, α ₂ ) of the angles of the pitch angle θ n) adjacent to the tool rotation direction T and the twist angle α ₂ of the base end side portion 1 b of the first outer peripheral blade 1 And the pitch angle θ n formed between the second outer peripheral blade 2 and the base end side portion 1 b of the first outer peripheral blade 1 adjacent to the tool rotation direction T of the second outer peripheral blade 2 (that is, Combination of the pitch angle θ n) adjacent to the tool rotation direction T of the outer peripheral blade 2 of 2 and the twist angle β of the second outer peripheral blade 2 The types of θ n and β) are at least two or more.

  Also in the present embodiment, the first predetermined position in the blade length ap region is a portion other than the tip end portion in the blade length ap region. Specifically, the first predetermined position is a central portion between the tip (ap = 0) and the change point CP in the blade length ap area. The second predetermined position is the central portion between the base end (ap = 1) and the change point CP in the blade length ap region.

The square end mill 30 shown in FIGS. 12 (a) and 12 (b) has the same configuration as the square end mill 30 in FIGS. 11 (a) and 11 (b), but FIG. The pitch angle θ n at each of the first and second predetermined positions is different from (b), and the patterns of combinations of angles (θ n, α) and (θ n, β) are different.
The square end mill 30 shown in FIGS. 13 (a) and 13 (b) has the same configuration as the square end mill 30 in FIGS. 11 (a) and 11 (b), but FIG. 11 (a), The pitch angle θ n at each of the first and second predetermined positions is different from (b), and the patterns of combinations of angles (θ n, α) and (θ n, β) are different.
The combinations of the angles in FIGS. 11 (a) and 11 (b) are shown as pattern 1 in Table 2 below, and the combinations of the angles in FIGS. 12 (a) and 12 (b) are shown as pattern 2. The combination of angles in b) is shown as pattern 3.

Specifically, in FIGS. 11A and 11B (pattern 1 in Table 2), the six outer peripheral blades 1 and 2 are sequentially moved in the direction opposite to the tool rotation direction T in the outer peripheral blade No. When represented by I to VI, the first outer peripheral blade 1 and the first outer peripheral blade 1 are provided at the first predetermined position shown in FIG. 11 (a) and the second predetermined position shown in FIG. 11 (b). Combination of the pitch angle θ n formed between the second outer peripheral blade 2 adjacent to the tool rotation direction T of the outer peripheral blade 1 and the twist angle α of the first outer peripheral blade 1 (θ n, α There are three kinds of) (θ ₁ ≠ θ ₂ ≠ θ ₃ ). Also, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T, and the twist of the second outer peripheral blade 2 There are three types of angle combinations (θ n, β) with the angle β and (θ ₁ ≠ θ ₂ ≠ θ ₃ ).

Also, in FIGS. 12A and 12B (pattern 2 in Table 2), the first predetermined position shown in FIG. 12A and the second predetermined position shown in FIG. 12B, respectively. Between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T, and the twist of the first outer peripheral blade 1 There are two types of combinations (θ n, α) of angles α and α (θ ₁ ≠ θ ₂ ). Also, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T, and the twist of the second outer peripheral blade 2 There are two types of angle combinations (θ n, β) of the angle β and the angle (θ ₁ ) θ ₂ ).

Further, in FIGS. 13A and 13B (pattern 3 in Table 2), the first predetermined position shown in FIG. 13A and the second predetermined position shown in FIG. 13B, respectively. Between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T, and the twist of the first outer peripheral blade 1 There are two types of combinations (θ n, α) of angles α and α (θ ₁ ≠ θ ₃ ). Also, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T, and the twist of the second outer peripheral blade 2 There are two types of angle combinations (θ n, β) with the angle β and (θ ₂ ≠ θ ₃ ).

In FIGS. 11 to 13, for convenience of explanation, the difference in angle between the pitch angles θ n is emphasized. Specifically, also in this embodiment, in each end mill cross-sectional view of the first predetermined position and the second predetermined position, the difference (angular difference) between the maximum pitch angle θ n and the minimum pitch angle θ n is 0 °. Larger than 20 °. Preferably, the angle difference is 5 ° or more and 15 ° or less.
Further, in FIGS. 11 to 13, although the plurality of pitch angles θ ₁ , θ ₂ , and θ ₃ are increased in this order, the magnitude relationship between the pitch angles θn is not limited to this.

[Operation and effect according to the present embodiment]
According to the square end mill 30 of the present embodiment described above, the same function and effect as those of the above-described embodiment can be obtained.
Specifically, in the present embodiment, the number of reproductions RF is, for example, 2 as compared with a conventional type end mill (one in which the pitch angle θn of the twist angle α is one type and one in which the pitch angle θn of the twist angle β is one type). It turned out that it can be reduced to about / 5 (40%).

  In particular, as shown in FIGS. 11 (a) and 11 (b), when the total number of outer peripheral blades 1 and 2 is N (six), the angles at the first and second predetermined positions are determined. If the combination of (θ n, α) is (N / 2) (3) or if the combination of angles (θ n, β) is (N / 2) (3) It was confirmed that the remarkable vibration suppressing effect was obtained.

Third Embodiment
Next, a square end mill 40 according to a third embodiment of the present invention will be described with reference to FIGS. 14 to 19. The same components as those of the above-described embodiment will not be described in detail and only differences will be described below.

  FIGS. 14-19 is an end mill cross-sectional view which simplifies and shows the blade part 3a of the end mill main body 3 of the square end mill 40 (as a mere two-dot chain line circle). In each of FIGS. 14 to 19, (a) shows an end mill crossing at a first predetermined position on the tip side of a change point CP where the twist angle α changes in the blade length ap region of the first outer peripheral blade 1 (B) represents an end mill cross-sectional view at a second predetermined position proximal to a change point CP at which the twist angle α changes in the blade length ap region of the first outer peripheral blade 1 (b) It represents.

[Differences from previous embodiments]
The square end mill 40 of this embodiment is an 8-flute end mill, and the first outer peripheral blade 1 and the second outer peripheral blade 2 are alternately arranged at intervals in the circumferential direction on the outer periphery of the end mill main body 3 There are four each. That is, in the plurality of outer peripheral blades 1 and 2 formed on the outer periphery of the end mill main body 3, two or more first outer peripheries having different twist angles α between the tip end side portion 1a and the base end side portion 1b of the outer peripheral blade 1 The blade 1 and the second outer peripheral blade 2 having a constant twist angle β different from the twist angle α of the first outer peripheral blade 1 and the same number as the number of the first outer peripheral blades 1 are included.

  Then, in each of the end mill cross-sectional view at the first predetermined position shown in FIG. 14 (a) and the end mill cross-sectional view at the second predetermined position shown in FIG. 14 (b), the first outer peripheral blade Between the pitch angle θ n formed between the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T and the twist angle α of the first outer peripheral blade 1 The type of combination (θ n, α) is at least two or more, and is formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the tool rotational direction T of the second outer peripheral blade 2 At least two kinds of combinations (θ n, β) of the angles of the pitch angle θ n and the twist angle β of the second outer peripheral blade 2 are used.

Specifically, as shown in FIG. 14 (a), the tip end side of the first outer peripheral blade 1 in an end mill cross-sectional view at a first predetermined position located on the tip side of the change point CP in the blade length ap region. A pitch angle θ n formed between the portion 1 a and the second outer peripheral blade 2 adjacent to the tool rotation direction T of the first outer peripheral blade 1 (that is, the tool rotation of the tip side portion 1 a of the first outer peripheral blade 1) At least two kinds of combinations (θ n, α ₁ ) of the angles of the pitch angle θ n) adjacent to the direction T and the twist angle α ₁ of the tip side portion 1 a of the first outer peripheral blade 1 are The pitch angle θ n formed between the second outer peripheral blade 2 and the tip side portion 1 a of the first outer peripheral blade 1 adjacent to the tool rotation direction T of the second outer peripheral blade 2 (that is, the second outer peripheral blade Combination of the pitch angle θ n) adjacent to the tool rotational direction T of 2 and the twist angle β of the second outer peripheral blade 2 The types of (θ n, β) are at least two or more.
And, as shown in FIG. 14 (b), the proximal end of the first outer peripheral blade 1 in an end mill cross-sectional view at a second predetermined position located proximal to the change point CP in the blade length ap region. Pitch angle θ n formed between the side portion 1 b and the second outer peripheral blade 2 adjacent to the tool rotation direction T of the first outer peripheral blade 1 (ie, the proximal end portion 1 b of the first outer peripheral blade 1 At least two or more kinds of combinations (θ n, α ₂ ) of the angles of the pitch angle θ n) adjacent to the tool rotation direction T and the twist angle α ₂ of the base end side portion 1 b of the first outer peripheral blade 1 And the pitch angle θ n formed between the second outer peripheral blade 2 and the base end side portion 1 b of the first outer peripheral blade 1 adjacent to the tool rotation direction T of the second outer peripheral blade 2 (that is, Combination of the pitch angle θ n) adjacent to the tool rotation direction T of the outer peripheral blade 2 of 2 and the twist angle β of the second outer peripheral blade 2 The types of θ n and β) are at least two or more.

  Also in the present embodiment, the first predetermined position in the blade length ap region is a portion other than the tip end portion in the blade length ap region. Specifically, the first predetermined position is a central portion between the tip (ap = 0) and the change point CP in the blade length ap area. The second predetermined position is the central portion between the base end (ap = 1) and the change point CP in the blade length ap region.

Further, the square end mill 40 shown in FIGS. 15 (a), (b) to 19 (a), (b) has the same configuration as the square end mill 40 of FIGS. 14 (a), (b). 14 (a) and 14 (b), the pitch angles θ n at the first and second predetermined positions are different, and the patterns of combinations of the angles (θ n, α) and (θ n, β) are different. ing.
The combinations of angles in FIGS. 14A and 14B are shown as pattern 1 in Table 3 below, and the combinations of angles in FIGS. 15A and 15B are shown as pattern 2 in FIGS. 16A and 16B. The combination of angles in b) is shown as pattern 3, the combination of angles in FIGS. 17A and 17B is shown as pattern 4, and the combination of angles in FIGS. 18A and 18B is shown as pattern 5, The combination of the angles in FIGS. 19A and 19B is shown as a pattern 6.

Specifically, in FIGS. 14A and 14B (pattern 1 in Table 3), the eight outer peripheral blades 1 and 2 are sequentially moved in the direction opposite to the tool rotation direction T in the outer peripheral blade No. When it is represented by I to VIII, in each of the first predetermined position shown in FIG. 14 (a) and the second predetermined position shown in FIG. 14 (b), the first outer peripheral blade 1 and the first peripheral blade 1 are shown. Combination of the pitch angle θ n formed between the second outer peripheral blade 2 adjacent to the tool rotation direction T of the outer peripheral blade 1 and the twist angle α of the first outer peripheral blade 1 (θ n, α There are four kinds of) (θ ₁ ≠ θ ₂ ≠ θ ₃ ≠ θ ₄ ). Also, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T, and the twist of the second outer peripheral blade 2 There are four types of angle combinations (θ n, β) with the angle β and (θ ₁ ≠ θ ₂ ≠ θ ₃ ≠ θ ₄ ).

In FIGS. 15A and 15B (pattern 2 in Table 3), the first predetermined position shown in FIG. 15A and the second predetermined position shown in FIG. 15B, respectively. Between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T, and the twist of the first outer peripheral blade 1 There are two types of combinations (θ n, α) of angles α and α (θ ₁ ≠ θ ₂ ). Also, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T, and the twist of the second outer peripheral blade 2 There are two types of angle combinations (θ n, β) of the angle β and the angle (θ ₁ ) θ ₂ ).

Also, in FIGS. 16A and 16B (pattern 3 in Table 3), the first predetermined position shown in FIG. 16A and the second predetermined position shown in FIG. Between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T, and the twist of the first outer peripheral blade 1 There are two types of combinations (θ n, α) of angles α and α (θ ₁ ≠ θ ₂ ). Also, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T, and the twist of the second outer peripheral blade 2 There are two types of angle combinations (θ n, β) of the angle β and the angle (θ ₁ ) θ ₂ ).

In FIGS. 17A and 17B (pattern 4 in Table 3), the first predetermined position shown in FIG. 17A and the second predetermined position shown in FIG. 17B, respectively. Between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T, and the twist of the first outer peripheral blade 1 There are three types of angle combinations (θ n, α) with the angle α (θ ₁ ≠ θ ₂ ≠ θ ₃ ). Also, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T, and the twist of the second outer peripheral blade 2 There are three types of angle combinations (θ n, β) with the angle β and (θ ₁ ≠ θ ₂ ≠ θ ₃ ).

Also, in FIGS. 18A and 18B (pattern 5 in Table 3), the first predetermined position shown in FIG. 18A and the second predetermined position shown in FIG. 18B, respectively. Between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T, and the twist of the first outer peripheral blade 1 There are two types of combinations (θ n, α) of angles α and α (θ ₁ ≠ θ ₃ ). Also, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T, and the twist of the second outer peripheral blade 2 There are two types of combinations (θ n, β) of angles β and θ (θ ₂ θθ ₄ ).

Also, in FIGS. 19A and 19B (pattern 6 in Table 3), the first predetermined position shown in FIG. 19A and the second predetermined position shown in FIG. 19B, respectively. Between the first outer peripheral blade 1 and the second outer peripheral blade 2 adjacent to the first outer peripheral blade 1 in the tool rotational direction T, and the twist of the first outer peripheral blade 1 There are three types of combinations (θ n, α) of angles α and α (θ ₁ ≠ θ ₃ ≠ θ ₄ ). Also, the pitch angle θ n formed between the second outer peripheral blade 2 and the first outer peripheral blade 1 adjacent to the second outer peripheral blade 2 in the tool rotational direction T and the twist of the second outer peripheral blade 2 There are three types of angle combinations (θ n, β) with the angle β and (θ ₂ ≠ θ ₃ ≠ θ ₄ ).

In FIGS. 14 to 19, for convenience of explanation, the difference in angle between the pitch angles θ n is emphasized. Specifically, also in this embodiment, in each end mill cross-sectional view of the first predetermined position and the second predetermined position, the difference (angular difference) between the maximum pitch angle θ n and the minimum pitch angle θ n is 0 °. Larger than 20 °. Preferably, the angle difference is 5 ° or more and 15 ° or less.
In FIGS. 14 to 19, the plurality of pitch angles θ ₁ , θ ₂ , θ ₃ , and θ ₄ are increased in this order, but the magnitude relationship between the pitch angles θ n is limited to this. Absent.

[Operation and effect according to the present embodiment]
According to the square end mill 40 of the present embodiment described above, the same function and effect as those of the above-described embodiment can be obtained.
Specifically, in the present embodiment, the number of reproductions RF is, for example, 2 as compared with a conventional type end mill (one in which the pitch angle θn of the twist angle α is one type and one in which the pitch angle θn of the twist angle β is one type). It turned out that it can be reduced to about / 5 (40%).

  In particular, as in the example shown in FIGS. 14 (a) and 14 (b), when the total number of outer peripheral blades 1 and 2 is N (eight), the angle at each of the first and second predetermined positions is If the combination of (θ n, α) is (N / 2) (four) or if the combination of angles (θ n, β) is (N / 2) (four) It was confirmed that the remarkable vibration suppressing effect was obtained.

[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, as described below, for example.

In the above-described embodiment, in defining the end mill cross-sectional view at the first predetermined position in the blade length ap area (the total blade length of the outer peripheral blades 1 and 2), this first predetermined position is the blade length ap It is set as a site | part other than the front-end | tip part in area | region, and, specifically, it was set as the center part of the front-end | tip (ap = 0) in edge length ap area | region and change point CP. The present invention is not limited to this, and the first predetermined position may be a tip end side from the change point CP, and may be a part other than the central part.
However, the first predetermined position is a portion other than the tip end portion on the tip end side than the change point CP in the blade length ap region, or the center portion between the tip and the change point CP. It is preferable because the effects described in the above embodiments can be obtained.

Further, in the above-described embodiment, in defining the end mill cross-sectional view at the second predetermined position in the blade length ap area (the total blade length of the outer peripheral blades 1 and 2), the second predetermined position is the blade The central portion between the proximal end (ap = 1) in the long ap region and the change point CP. The present invention is not limited to this, and the second predetermined position may be any position other than the central portion as long as it is proximal to the change point CP.
However, since the second predetermined position is a central portion between the base end and the change point CP on the proximal side of the change point CP in the blade length ap region, the operation and effect described in the above embodiment can be obtained. It is preferable because it can be obtained.

Further, in the embodiment described above, the twist angle α ₁ of the distal end side portion 1a located on the distal end side from the change point CP of the first outer peripheral blade 1 is the proximal end portion 1b located on the proximal end side Is smaller than the twist angle α ₂ , but is not limited thereto. That is, the twist angle alpha ₁ of the first peripheral cutting edge 1 of the distal portion 1a may be larger than the twist angle alpha ₂ of the proximal portion 1b. In this case, the change point CP of the first outer peripheral blade 1 is formed to be recessed toward the opposite side to the tool rotational direction T. According to this configuration, it is possible to enhance the sharpness of (the tip side portion 1a of) the first outer peripheral blade 1 at the time of low cutting.

Further, in the above-described embodiment, the twist angle alpha ₁ of the first peripheral cutting edge 1 of the distal portion 1a is, is less than the second twist angle of the peripheral cutting edge _{2 β (α 1 <β)} , the first outer circumference blades 1 helix angle alpha ₂ of the proximal portion 1b, are greater than the second twist angle of the peripheral cutting edge ₂ β (α _2> β) and the, but not limited thereto. That is, the twist angle alpha ₁ of the first peripheral cutting edge 1 of the distal portion 1a is, the second is larger than the helix angle beta of the peripheral cutting edge 2 (alpha _1> beta), first proximal end side of the peripheral cutting edge 1 portion 1b twist angle alpha ₂ of which may be less than the second twist angle of the peripheral cutting edge _{2 β (α 2 <β)} .
Alternatively, both the twist angle α ₁ of the distal end side portion 1 a of the first outer peripheral blade 1 and the twist angle α ₂ of the base end side portion ₁ b may be larger than the twist angle β of the second outer peripheral blade 2. Further, both the twist angle α ₁ of the distal end side portion 1 a of the first outer peripheral blade 1 and the twist angle α ₂ of the base end side portion ₁ b may be smaller than the twist angle β of the second outer peripheral blade 2.

Also in the above-described embodiment, for convenience of explanation, in FIG. 4, for example, the pitch angle theta ₁ and theta ₂ is used as the pitch angle θn of the first predetermined position, also in the second predetermined position, pitch angle as a pitch angle θn θ ₁ and θ ₂ were used. Here, the pitch angle theta ₁ at the first predetermined position, the pitch angle theta ₁ at the second predetermined position, may be the same value, or may be different from each other. Similarly, the pitch angle theta ₂ in the first predetermined position, the pitch angle theta ₂ at the second predetermined position, may be the same value, or may be different from each other. FIG. 11 (a), the or the pitch angle theta ₁ through? ₃ in (b), FIG. 14 (a), the the pitch angle theta ₁ through? ₄ in (b) also, the same above.

  Further, the present invention is not limited to the types (θ n, α) and (θ n, β) of combinations of angles described in the above embodiments. That is, the present invention is not limited to the patterns 1 and 2 of Table 1 described above, the patterns 1 to 3 of Table 2, and the patterns 1 to 6 of Table 3 described above. , Β) may be used.

Moreover, in the above-mentioned embodiment, although the square end mill 20 of 4 blades, the square end mill 30 of 6 blades, and the square end mill 40 of 8 blades were mentioned as an example, the number of blades of an end mill is limited to these. For example, ten or more blades may be used.
In addition, the total number N of the outer peripheral blades is not limited to an even number but is an odd number, and among them, two or more first outer peripheral blades 1 and second outer peripheral blades 2 having the same number as the first outer peripheral blades 1 And may be included. In this case, the present invention is applicable to an end mill having five or more blades even if the number of blades is an odd number.

Further, in the above-described embodiment, the chip discharge groove 4 is twisted and gradually extends in the direction of the axis O toward the opposite side of the tool rotation direction T along the direction of the axis O in the outer periphery of the end mill body 3 ing. Also, along with this, each of the outer peripheral blades 1, 2 extends in the direction of the axis O in the outer periphery of the end mill body 3 and gradually twists toward the opposite side to the tool rotation direction T as it goes from the tip to the base end. There is. 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 direction of the axis O along the axis O direction on the outer periphery of the end mill main body 3 It may extend. Further, along with this, each of the outer peripheral blades 1 and 2 may be twisted and extended gradually in the tool rotation direction T as it goes from the tip to the base end along the axis O direction on the outer periphery of the end mill main body 3. That is, the twist angle of the outer peripheral blades 1 and 2 may be a negative angle.
According to the present invention, even when the twist angle of the outer peripheral blades 1 and 2 is a positive angle or a negative angle, the above-described excellent effects can be obtained.

  In addition, without departing from the spirit of the present invention, each configuration (component) described in the above-described embodiment, modification, and note may be combined, and addition, omission, replacement, and other configurations can be made. Changes are possible. Moreover, this invention is not limited by embodiment mentioned above, It is limited only by the claim.

  The end mill of the present invention can obtain the suppressing effect of chatter vibration in a wide frequency band while maintaining good chip dischargeability, and can improve processing accuracy under various cutting conditions. Therefore, it has industrial applicability.

1 1st peripheral blade (peripheral blade)
1a The tip side portion of the first outer peripheral blade 1b The base end side portion of the first outer peripheral blade 2 The second outer peripheral blade (outer peripheral blade)
3 End mill body 20, 30, 40 Square end mill (end mill)
ap blade length CP change point N total number of outer peripheral blades O axis T tool rotation direction α twist angle of the first outer peripheral blade α ₁ twist angle of the tip side of the first outer peripheral blade α ₂ base end of the first outer peripheral blade Torsion angle of the side part β Torsion angle of the second peripheral blade θn (θ _{1 to} θ ₄ ) Pitch angle

Claims (12)

A shaft-shaped end mill main body,
An end mill comprising: an outer peripheral blade formed on an outer periphery of the end mill main body and extending in a circumferential direction around the axis from the tip end in the axial direction of the end mill main body toward the base end side,
The outer peripheral blades are formed in a plurality at intervals in the circumferential direction,
The plurality of outer peripheral blades
Two or more first outer peripheral blades having different twist angles α between the distal end side portion and the proximal end side portion of the outer peripheral blade;
The second outer peripheral blade having a constant twist angle β different from the twist angle α of the first outer peripheral blade, and the same number as the number of the first outer peripheral blades;
The first outer peripheral blade and the second outer peripheral blade are alternately arranged in the circumferential direction,
An end mill cross-sectional view perpendicular to the axis at a first predetermined position on the distal end side from the change point at which the twist angle α changes in the blade length region of the first outer peripheral blade, and the proximal side from the change point In each of the end mill cross-sectional views at the second predetermined position,
A central angle formed between a pair of imaginary straight lines connecting the pair of outer peripheral blades adjacent in the circumferential direction and the axis line is a pitch angle θ n
The pitch angle θ n formed between the first outer peripheral blade and the second outer peripheral blade adjacent in the tool rotation direction in the circumferential direction of the first outer peripheral blade, and the first outer peripheral blade At least two kinds of combinations (θ n, α) of the angle of twist α and the angle of θ,
The pitch angle θ n formed between the second outer peripheral edge and the first outer peripheral edge adjacent to the second outer peripheral edge in the tool rotational direction, and the twist angle β of the second outer peripheral edge And an angle combination (θ n, β) of at least two or more types. The end mill according to claim 1, wherein
An end mill characterized in that an angle difference between a twist angle α of a tip end portion of the first outer peripheral blade and a twist angle α of a base end portion is 40 ° or less. An end mill according to claim 1 or 2, wherein
An end mill characterized in that an angle difference between a twist angle α of a tip end portion of the first outer peripheral blade and a twist angle α of a base end portion is 5 ° or more and 35 ° or less. The end mill according to any one of claims 1 to 3, wherein
Assuming that the tip end position is 0% and the base end position is 100% in the blade length region of the first outer peripheral blade,
An end mill characterized in that the change point is arranged in a range of 30% to 70% in the blade length region. The end mill according to any one of claims 1 to 4, wherein
An end mill characterized in that the first predetermined position is a portion other than the tip portion in the blade length region. The end mill according to any one of claims 1 to 5, wherein
An end mill characterized in that the first predetermined position is a central portion between a tip in the blade length area and the change point. The end mill according to any one of claims 1 to 6, wherein
An end mill characterized in that the second predetermined position is a central portion between a base end and the change point in the blade length region. The end mill according to any one of claims 1 to 7, wherein
An end mill characterized in that a twist angle α on the tip side of the change point of the first outer peripheral blade is smaller than a twist angle α on the end side of the change point. The end mill according to any one of claims 1 to 8, wherein
When the total number of the outer peripheral blades is N, the number of combinations (θ n, α) of the angles is (N / 2) in the end mill cross sectional view at the first predetermined position End mill to. An end mill according to any one of the preceding claims, wherein
When the total number of the outer peripheral blades is N, in the end mill cross sectional view at the first predetermined position, the number of combinations (θ n, β) of the angles is (N / 2). End mill to. The end mill according to any one of claims 1 to 10, wherein
When the total number of the outer peripheral blades is N, the number of combinations (θ n, α) of the angles is (N / 2) in the end mill cross sectional view at the second predetermined position End mill to. An end mill according to any one of the preceding claims, wherein
When the total number of the outer peripheral blades is N, in the end mill cross sectional view at the second predetermined position, the number of combinations (θ n, β) of the angles is (N / 2). End mill to.

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