JP5849817B2

JP5849817B2 - Square end mill

Info

Publication number: JP5849817B2
Application number: JP2012073129A
Authority: JP
Inventors: 貴行畔上
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2012-03-28
Filing date: 2012-03-28
Publication date: 2016-02-03
Anticipated expiration: 2032-03-28
Also published as: JP2013202722A

Description

本発明は、エンドミル本体の先端部外周に形成される外周刃と先端に形成される底刃とが、直交、または直交よりも僅かに鋭角に交差するようにされたスクエアエンドミルに関するものである。 The present invention relates to a square end mill in which an outer peripheral blade formed on the outer periphery of a tip end portion of an end mill body and a bottom blade formed on the distal end intersect each other at right angles or slightly at an acute angle.

このようなスクエアエンドミルは、エンドミル本体の先端部外周に、エンドミル本体の先端に開口して後端側に向かうに従いエンドミル回転方向後方側に向かうようにエンドミル本体の軸線に対して捩れる切屑排出溝が形成されて、この切屑排出溝のエンドミル回転方向前方側を向く壁面の外周側辺稜部に外周刃が形成されるとともに、切屑排出溝の先端部には、切屑排出溝の内周部を切り欠くように凹溝状のギャッシュが形成され、このギャッシュのエンドミル回転方向前方側を向く壁面とエンドミル本体の先端逃げ面との交差稜線部に、上記外周刃に対して直交する方向、または直交よりも僅かに鋭角に交差する方向に延びる底刃が形成されたものである。 Such a square end mill has a chip discharge groove that is twisted with respect to the axis of the end mill body so as to open toward the rear end side of the end mill body and toward the rear end side as it goes toward the rear end side. The outer peripheral blade is formed on the outer peripheral side ridge portion of the wall surface facing the front side in the end mill rotation direction of the chip discharge groove, and the inner peripheral portion of the chip discharge groove is formed at the tip of the chip discharge groove. A groove-shaped gash is formed so as to be cut out, and a direction perpendicular to the outer peripheral edge or orthogonal to the intersecting ridge line part of the wall surface facing the front side in the end mill rotation direction of the gash and the end flank of the end mill body A bottom blade extending in a direction slightly intersecting with an acute angle is formed.

ところで、このようなスクエアエンドミルにおいては、上記ギャッシュが、そのエンドミル回転方向前方側を向く上記壁面が外周刃にまで達せずに、切屑排出溝のエンドミル回転方向前方側を向く壁面の途中までに延びていて、このギャッシュの壁面から外周側は、切屑排出溝のエンドミル回転方向前方側を向く壁面と先端逃げ面との交差稜線部に底刃が形成されたものが知られている。 By the way, in such a square end mill, the gasche extends to the middle of the wall surface facing the front side in the end mill rotation direction of the chip discharge groove without the wall surface facing the front side in the end mill rotation direction reaching the outer peripheral blade. In addition, it is known that the outer peripheral side from the wall surface of the gasche is formed with a bottom blade at the intersecting ridge line portion between the wall surface facing the front side in the end mill rotation direction of the chip discharge groove and the tip flank surface.

ところが、そのようなものでは、底刃の外周側では軸方向すくい角が切屑排出溝および外周刃の軸線に対する捩れ角と等しくなるため、この捩れ角が例えば４５°以上の強捩れとなると底刃の外周側における切刃強度が失われて欠損を生じ易くなる。そこで、特許文献１、２には、ギャッシュのエンドミル回転方向前方側を向く壁面を外周刃にまで延長して外周逃げ面に交差させ、外周刃が強捩れでも底刃は全長に亙って軸方向すくい角が小さくなるようにしたものが提案されている。 However, in such a case, on the outer peripheral side of the bottom blade, the axial rake angle is equal to the twist angle with respect to the axis of the chip discharge groove and the outer peripheral blade. Therefore, when this twist angle is a strong twist of 45 ° or more, for example, The cutting edge strength on the outer peripheral side of the metal is lost, and defects are likely to occur. Therefore, in Patent Documents 1 and 2, the wall surface facing the front side in the rotation direction of the end of the gash is extended to the outer peripheral blade and intersected with the outer peripheral flank. Proposals have been made to reduce the rake angle.

特開２００４−２８３９６５号公報JP 2004-283965 A 特開２００８−２００８１７号公報JP 2008-200187 A

これら特許文献１、２に記載されたスクエアエンドミルでは、外周刃のエンドミル回転方向後方側に、逃げ角が極小さい、あるいは逃げ角が０°で外周刃と等しい外径の円筒面状をなす幅狭のマージンを設けて、そのさらにエンドミル回転方向後方側に所定の逃げ角で外周刃の軸線回りの回転軌跡に対して内周側に後退する外周逃げ面を形成している。そして、このうち特許文献２に記載のスクエアエンドミルでは、外周刃の先端部においてギャッシュのエンドミル回転方向前方側を向く壁面の軸線方向の幅がマージンの軸線方向の幅よりも広くなるようにしている。 In these square end mills described in Patent Documents 1 and 2, the clearance angle is extremely small on the rear side in the end mill rotation direction of the outer peripheral blade, or the width forms a cylindrical surface shape having an outer diameter equal to that of the outer peripheral blade with a clearance angle of 0 °. A narrow margin is provided, and an outer peripheral flank face that recedes toward the inner peripheral side with respect to the rotational trajectory around the axis of the outer peripheral blade is formed at a predetermined clearance angle on the rear side in the end mill rotational direction. Of these, in the square end mill described in Patent Document 2, the axial width of the wall surface facing the front side in the end mill rotation direction of the gash at the tip of the outer peripheral blade is made wider than the axial width of the margin. .

しかしながら、そのような特許文献２に記載のスクエアエンドミルでは、ギャッシュのエンドミル回転方向前方側を向く壁面が、マージンから内周側に後退する外周逃げ面に亙って交差させられて、その交差稜線部に外周刃の先端部が形成されるため、外周逃げ面に交差する外周刃の最先端部では、先端側に向かうに従い外周刃がエンドミル本体の内周側に向けて傾斜してしまい、外周刃の外径が小さくなって加工精度が損なわれてしまう。これは、マージンを設けずに、外周刃のエンドミル回転方向後方側に直接内周側に後退する外周逃げ面を形成したスクエアエンドミルにおいて、ギャッシュのエンドミル回転方向前方側を向く壁面を外周逃げ面に交差させた場合も同様である。 However, in such a square end mill described in Patent Document 2, the wall surface facing the front side in the rotational direction of the end of the gasche is crossed over the outer peripheral flank that recedes from the margin toward the inner peripheral side, and the crossed ridgeline Since the tip of the outer peripheral blade is formed in the part, the outer peripheral blade inclines toward the inner peripheral side of the end mill body toward the front end side at the most distal portion of the outer peripheral blade that intersects the outer peripheral flank. The outer diameter of the blade is reduced and the processing accuracy is impaired. This is a square end mill that has an outer peripheral flank that is retracted directly to the inner peripheral side on the rear side in the end mill rotation direction of the outer peripheral blade without providing a margin. The same applies when crossing.

一方、特許文献１に記載のスクエアエンドミルでは、ギャッシュのエンドミル回転方向前方側を向く壁面が外周逃げ面に交差した部分も含め、外周刃の全長に亙ってエンドミル回転方向後方側にマージンを設けており、このため外周刃の先端部でも外径を一定とすることができる。しかしながら、マージンは上述のように逃げ角が極小さいか０°であって外周刃と等しい外径の円筒面状をなすものであるので、このようなマージンが外周刃の全長に亙って設けられていると、マージンが被削材の加工面に摺接することによって切削抵抗の増大を招いてしまう。 On the other hand, in the square end mill described in Patent Document 1, a margin is provided on the rear side in the end mill rotation direction over the entire length of the outer peripheral blade, including the portion where the wall surface facing the front side in the end mill rotation direction of the gasche intersects the outer peripheral clearance surface. Therefore, the outer diameter can be made constant even at the tip of the outer peripheral blade. However, since the margin is a cylindrical surface having an outer diameter that is as small as 0 ° or equal to the outer peripheral blade as described above, such a margin is provided over the entire length of the outer peripheral blade. If this is done, the margin will slidably contact the work surface of the work material, leading to an increase in cutting resistance.

また、これら特許文献１、２に記載のスクエアエンドミルのように、ギャッシュのエンドミル回転方向前方側を向く壁面を外周逃げ面にまで延長して交差させたものでは、外周刃の先端部において外周刃の捩れ角（軸方向すくい角）が急激に変化する角部が形成されることになり、切削時にこの角部に負荷が集中することによってチッピング等を生じるおそれもある。 In addition, as in the square end mills described in Patent Documents 1 and 2, the wall surface facing the front side in the rotation direction of the end of the gasche is extended to the outer peripheral flank, and the outer peripheral blade at the tip of the outer peripheral blade. A corner portion in which the torsion angle (axial rake angle) of the steel plate changes abruptly is formed, and there is a risk that chipping or the like may occur due to concentration of a load on the corner portion during cutting.

本発明は、このような背景の下になされたもので、切屑排出溝や外周刃の捩れ角が大きくても底刃や外周刃に欠損やチッピングを生じることがなく、また外周刃の全長に亙って外径を一定として加工精度を維持することができるとともに、切削抵抗の増大を招くことのないスクエアエンドミルを提供することを目的としている。 The present invention has been made under such a background. Even if the twist discharge angle of the chip discharge groove and the outer peripheral blade is large, the bottom blade and the outer peripheral blade are not damaged or chipped, and the entire length of the outer peripheral blade is increased. Accordingly, it is an object of the present invention to provide a square end mill that can maintain the machining accuracy with a constant outer diameter and that does not cause an increase in cutting resistance.

上記課題を解決して、このような目的を達成するために、本発明は、軸線回りに回転させられるエンドミル本体の先端部外周に、上記エンドミル本体の先端に開口して後端側に向かうに従いエンドミル回転方向後方側に向けて延びる切屑排出溝が形成され、この切屑排出溝のエンドミル回転方向前方側を向く壁面は、上記軸線に直交する断面においてエンドミル回転方向後方側に凹んだ凹曲線状をなし、この壁面と上記エンドミル本体の外周逃げ面との交差稜線部には、断面凹曲線状の上記壁面をすくい面とする外周刃が形成されるとともに、上記切屑排出溝の先端部外周側には上記断面凹曲線状をなす上記すくい面が残されていて、上記壁面の少なくとも外周部と上記エンドミル本体の先端逃げ面との交差稜線部には、上記エンドミル本体の外周側で上記外周刃のすくい面を共通したすくい面として該外周刃の先端部に角度をもって交差する底刃が形成されており、上記外周刃の先端部には、該外周刃の上記軸線に対する捩れ角が先端側に向かうに従い漸次小さくなる捩れ角漸減部が形成され、上記外周刃はこの捩れ角漸減部も含めて上記軸線回りの回転軌跡が該軸線を中心とした一定外径の円筒面状をなしているとともに、上記外周逃げ面は、上記外周刃からエンドミル回転方向後方側に向けて、該外周刃の上記軸線回りの回転軌跡に対して内周側に漸次後退するように形成されていることを特徴とする。 In order to solve the above-mentioned problems and achieve such an object, the present invention provides an outer periphery of the tip end of the end mill body that is rotated around the axis, and opens toward the rear end side of the end mill body. A chip discharge groove extending toward the rear side in the end mill rotation direction is formed, and a wall surface facing the front side in the end mill rotation direction of the chip discharge groove has a concave curve shape recessed toward the rear side in the end mill rotation direction in a cross section orthogonal to the axis. None, at the intersection ridge line portion between the wall surface and the outer peripheral flank of the end mill body, an outer peripheral blade having the concave wall surface as a rake face is formed, and on the outer peripheral side of the tip end portion of the chip discharge groove. is not the rake face having the above-described cross-sectional concave-curved is left, the intersecting edge line region with at least the outer peripheral portion and the tip flank of the end mill body of the wall, the end mill body In the outer peripheral side are end cutting edge which intersects at an angle the tip portion of the peripheral cutting edge is formed as a common rake face the rake face of the peripheral cutting edge, the distal end portion of the outer peripheral cutting edge, relative to the axis of the outer circumferential edge A torsional angle gradually decreasing portion is formed which gradually decreases as the torsional angle moves toward the tip side, and the outer peripheral blade includes the torsional angle gradually decreasing portion and a cylindrical surface having a constant outer diameter around the axis including the torsional angle gradually decreasing portion. And the outer peripheral flank is formed so as to gradually recede toward the inner peripheral side with respect to the rotation trajectory of the outer peripheral blade around the axis from the outer peripheral blade toward the rear side in the end mill rotation direction. It is characterized by.

このように構成されたスクエアエンドミルにおいては、外周刃の先端部に、上記軸線に対する捩れ角が先端側に向かうに従い漸次小さくなる捩れ角漸減部が形成されることにより、この捩れ角漸減部で外周刃は凸曲線を描きつつ、先端側に向かうに従いエンドミル回転方向前方側に延びることになる。従って、エンドミル本体後端側の切屑排出溝および外周刃の捩れ角が強捩れであっても、外周刃の捩れ角が急激に変化して角部が形成されるのを防ぎつつ、外周刃の先端部に交差する底刃の外周部の刃物角を大きくすることができ、外周刃や底刃の欠損やチッピングを防止することができる。 In the square end mill configured as described above, a torsion angle gradually decreasing portion is formed at the tip end portion of the outer peripheral blade that gradually decreases as the torsion angle with respect to the axial line moves toward the tip end side. The blade extends toward the front side in the end mill rotation direction toward the tip side while drawing a convex curve. Therefore, even if the twist discharge angle of the chip discharge groove and the outer peripheral blade on the rear end side of the end mill main body is a strong twist, while preventing the outer blade from changing abruptly due to a sudden change in the twist angle of the outer peripheral blade, The blade angle of the outer peripheral portion of the bottom blade intersecting the tip portion can be increased, and the outer peripheral blade and the bottom blade can be prevented from being broken or chipped.

その一方で、外周刃は、この捩れ角漸減部も含めて先端部から後端側に渡り、軸線回りの回転軌跡が該軸線を中心とした一定外径の円筒面状とされるとともに、外周逃げ面は、やはり捩れ角漸減部を含めたこの外周刃からエンドミル回転方向後方側に向けて、外周刃の上記軸線回りの回転軌跡に対して内周側に漸次後退するように形成されていて、すなわちマージンを有することがないので、マージンの摺接による切削抵抗の増大を防ぎつつ、捩れ角漸減部でも外周刃の外径が小さくなるのを防いで、高い加工精度を得ることができる。 On the other hand, the outer peripheral blade extends from the front end portion to the rear end side including the torsion angle gradually decreasing portion, and the rotation trajectory around the axis is a cylindrical surface with a constant outer diameter centered on the axis. The flank face is formed so as to gradually recede from the outer peripheral blade including the gradually decreasing portion of the torsion angle toward the rear side in the end mill rotation direction toward the inner peripheral side with respect to the rotation trajectory around the axis of the outer peripheral blade. That is, since there is no margin, it is possible to prevent the outer diameter of the outer peripheral blade from becoming small even at the portion where the torsional angle gradually decreases while preventing an increase in cutting resistance due to the sliding contact of the margin, and high machining accuracy can be obtained.

ここで、外周刃の先端部は、底刃と交差する外周刃の先端まで上記捩れ角漸減部とされて、捩れ角が先端まで漸次減少するようにされていてもよいが、この捩れ角漸減部の先端側に、上記捩れ角が一定とされた捩れ角一定部を形成し、上記外周刃はこの捩れ角一定部も含めて上記軸線回りの回転軌跡が該軸線を中心とした一定外径の円筒面状をなすようにすることにより、底刃の刃物角が大きくされた範囲を広げて、一層確実に欠損等が発生するのを防ぐことができる。なお、上記捩れ角漸減部によって漸減する外周刃の先端における捩れ角は、０°〜２０°の範囲とされるのが望ましく、０°より小さい負角側となると切削抵抗の増大を招くおそれがある一方、２０°よりも大きいと、外周刃の先端部に連なる底刃の外周部の欠損等を確実に防止することが困難となるおそれがある。 Here, the tip end portion of the outer peripheral blade may be the aforementioned torsion angle gradually decreasing portion to the tip of the outer peripheral blade intersecting with the bottom blade, and the torsion angle may be gradually decreased to the tip. A constant torsion angle portion in which the torsion angle is constant is formed on the tip end side of the portion, and the outer peripheral blade includes the constant torsion angle portion and the rotation trajectory around the axis includes a constant outer diameter centered on the axis. By making the cylindrical surface shape of this, it is possible to widen the range in which the blade angle of the bottom blade is increased, and more reliably prevent the occurrence of defects or the like. In addition, it is desirable that the twist angle at the tip of the outer peripheral blade gradually decreasing by the twist angle gradually decreasing portion is in the range of 0 ° to 20 °. If the negative angle is smaller than 0 °, the cutting resistance may be increased. On the other hand, when it is larger than 20 °, it may be difficult to reliably prevent the outer peripheral portion of the bottom blade connected to the tip portion of the outer peripheral blade from being damaged.

以上説明したように、本発明によれば、外周刃の先端部に角部が形成されるのを防ぐとともに底刃の外周部における刃物角は大きく確保して、これら外周刃や底刃にチッピングや欠損が生じるのは防止しつつ、切削抵抗の増大を抑えるとともに、外周刃の回転軌跡が先端部で小さくなるのを防いで、加工精度を維持することが可能となる。 As described above, according to the present invention, it is possible to prevent corners from being formed at the tip of the outer peripheral blade and to ensure a large blade angle at the outer peripheral portion of the bottom blade, and to chip the outer peripheral blade and the bottom blade. It is possible to maintain machining accuracy by preventing an increase in cutting resistance and preventing the rotation trajectory of the outer peripheral blade from becoming smaller at the tip portion while preventing the occurrence of defects.

本発明の一実施形態を示す斜視図である。It is a perspective view which shows one Embodiment of this invention. 図１に示す実施形態の側面図である。It is a side view of embodiment shown in FIG. 図１に示す実施形態の拡大正面図である。It is an enlarged front view of embodiment shown in FIG. 図２におけるＹＹ断面図である。It is YY sectional drawing in FIG. 図２におけるＺＺ断面図である。It is ZZ sectional drawing in FIG. 図１に示す実施形態の外周刃の先端部を示す拡大側面図である。It is an enlarged side view which shows the front-end | tip part of the outer periphery blade of embodiment shown in FIG.

図１ないし図６は、本発明の一実施形態を示すものである。本実施形態において、エンドミル本体１は、超硬合金等の硬質材料により軸線Ｏを中心とした概略円柱軸状に一体に形成されていて、その後端部（図１における右上側部分。図２における上側部分）は円柱状のままのシャンク部２とされるとともに、先端部（図１における左下側部分。図２における下側部分）は切刃部３とされている。このようなエンドミルは、シャンク部２が工作機械の主軸に把持されて、軸線Ｏ回りにエンドミル回転方向Ｔに回転されつつ通常は軸線Ｏに交差する方向に送り出され、切刃部３により被削材を切削加工する。 1 to 6 show an embodiment of the present invention. In the present embodiment, the end mill body 1 is integrally formed of a hard material such as cemented carbide in a substantially cylindrical shaft shape with the axis O as the center, and a rear end portion (upper right side portion in FIG. 1; FIG. 2). The upper part) is a cylindrical shank part 2 and the tip part (the lower left part in FIG. 1, the lower part in FIG. 2) is the cutting edge part 3. In such an end mill, the shank portion 2 is gripped by the main spindle of the machine tool, and is rotated in the end mill rotation direction T around the axis O, and is usually fed in a direction crossing the axis O, and is cut by the cutting edge portion 3. Cutting material.

エンドミル本体１先端部の切刃部３の外周には、切刃部３の先端から後端側に向かうに従い軸線Ｏ回りにエンドミル回転方向Ｔ後方側に捩れる４条の切屑排出溝４が、周方向に間隔（本実施形態では等間隔）をあけて形成されている。これらの切屑排出溝４のエンドミル回転方向Ｔを向く壁面は、軸線Ｏに直交する断面において図５に示すようにエンドミル回転方向Ｔ後方側に凹んだ凹曲線をなすようにされている。 On the outer periphery of the cutting edge portion 3 at the tip end portion of the end mill body 1, there are four pieces of chip discharge grooves 4 that are twisted toward the rear side in the end mill rotation direction T around the axis O as it goes from the tip end of the cutting blade portion 3 toward the rear end side. They are formed at intervals (equal intervals in this embodiment) in the circumferential direction. The wall surfaces of the chip discharge grooves 4 facing the end mill rotation direction T have a concave curve that is recessed toward the rear side in the end mill rotation direction T as shown in FIG.

そして、この壁面とエンドミル本体１の外周逃げ面５との交差稜線部には、該壁面をすくい面６として各切屑排出溝４と同様に切刃部３の先端から後端側に向かうに従い軸線Ｏ回りにエンドミル回転方向Ｔ後方側に捩れるとともに、軸線Ｏ回りの回転軌跡が該軸線Ｏを中心とする一定の外径の１つの円筒面状をなす外周刃７が、やはり周方向に間隔（等間隔）をあけて形成されている。この外周刃７の捩れ角θは、後述する先端部を除いて、例えば４５°とされている。 Then, at the intersecting ridge line portion between the wall surface and the outer peripheral flank 5 of the end mill body 1, an axis line from the front end to the rear end side of the cutting edge portion 3, similar to each chip discharge groove 4, with the wall surface as the rake face 6. The outer peripheral blade 7 is twisted to the rear side in the end mill rotation direction T around O, and the outer peripheral blade 7 whose rotation locus around the axis O forms a cylindrical surface with a constant outer diameter around the axis O is also spaced in the circumferential direction. They are formed at equal intervals. The torsion angle θ of the outer peripheral blade 7 is, for example, 45 °, excluding the tip portion described later.

また、各切屑排出溝４の先端部には、その内周部をエンドミル本体１の内周側に向けて切り欠くようにして凹溝状のギャッシュ８が形成されている。ここで、本実施形態におけるギャッシュ８は、図２に示すように、上記エンドミル回転方向Ｔ前方側を向く壁面とこれに対向してエンドミル回転方向Ｔ後方側を向く壁面とがギャッシュ８のエンドミル本体１後端内周側の底部において凹曲面を介して結ばれた断面略Ｖ字状をなしており、このうち少なくともエンドミル回転方向Ｔ前方側を向く壁面は平面状とされている。 Further, a concave groove-like gash 8 is formed at the tip of each chip discharge groove 4 so as to cut out the inner peripheral part thereof toward the inner peripheral side of the end mill body 1. Here, as shown in FIG. 2, the gash 8 in the present embodiment has an end mill main body in which the wall surface facing the front side in the end mill rotation direction T and the wall surface facing the rear direction in the end mill rotation direction T face the rear side in the end mill rotation direction T. 1 The bottom part on the inner peripheral side of the rear end has a substantially V-shaped cross section connected through a concave curved surface, and at least the wall surface facing the front side in the end mill rotation direction T is flat.

ただし、ギャッシュ８は切屑排出溝４の内周部にのみ形成されていて、切屑排出溝４の先端部外周側には、上述のように断面凹曲線状をなす外周刃７のすくい面６が残されている。そして、これらギャッシュ８のエンドミル回転方向Ｔ側を向く壁面および外周刃７のすくい面６とされる切屑排出溝４のエンドミル回転方向Ｔ前方側を向く壁面と、切刃部３先端の先端逃げ面９との交差稜線部には、内周側ではギャッシュ８のエンドミル回転方向Ｔ前方側を向く壁面をすくい面１０とし、また外周側では外周刃７のすくい面６を共通したすくい面とする４つの底刃１１が、内周側から外周側に延びて外周刃７の先端部に角度をもって交差するように、やはり周方向に間隔（等間隔）をあけてそれぞれ形成されている。 However, the gash 8 is formed only on the inner peripheral portion of the chip discharge groove 4, and the rake face 6 of the outer peripheral blade 7 having a concave cross-sectional shape as described above is formed on the outer peripheral side of the tip end portion of the chip discharge groove 4. It is left. And the wall surface which faces the end mill rotation direction T side of these gashes 8 and the rake face 6 of the outer peripheral blade 7 and the wall surface which faces the front side of the end mill rotation direction T of the chip discharge groove 4 and the tip flank of the tip of the cutting blade portion 3 9 is a rake face 10 on the inner peripheral side facing the front side of the end mill rotation direction T of the gash 8 and the rake face 6 of the outer peripheral edge 7 is a common rake face 4 on the outer peripheral side. The two bottom blades 11 are also formed at intervals (equal intervals) in the circumferential direction so as to extend from the inner peripheral side to the outer peripheral side and intersect the tip of the outer peripheral blade 7 with an angle.

ここで、これら４つの底刃１１は、軸線Ｏ回りの回転軌跡において、該軸線Ｏに垂直な１つの平面上に略位置し、または内周側に向かうに従い該平面から僅かに後端側に向かうように延び、外周刃７と底刃１１とが回転軌跡において略直交または僅かに鋭角に交差する方向に延びるようにされている。また、底刃１１は、上述のように内周側ではギャッシュ８のエンドミル回転方向Ｔ前方側を向く平面状の壁面をすくい面１０とし、また外周側では外周刃７と共通して断面凹曲線状のすくい面６をすくい面としていることから、図３に示すように軸線方向先端視において、内周側では直線状に延び、外周側ではこの直線に対して凹んだ凹曲線状をなしている。 Here, these four bottom blades 11 are substantially located on one plane perpendicular to the axis O in the rotation locus around the axis O, or slightly toward the rear end side from the plane toward the inner peripheral side. The outer peripheral edge 7 and the bottom edge 11 extend in a direction intersecting substantially orthogonally or slightly at an acute angle in the rotation trajectory. Further, as described above, the bottom blade 11 has a flat wall surface facing the front side in the end mill rotation direction T of the gash 8 on the inner peripheral side as the rake face 10 and a concave concave section in common with the outer peripheral blade 7 on the outer peripheral side. Since the rake face 6 is a rake face, as shown in FIG. 3, in the axial front end view, it extends linearly on the inner peripheral side and forms a concave curve that is recessed with respect to this straight line on the outer peripheral side. Yes.

なお、４条の切屑排出溝４の先端部に形成された４つのギャッシュ８のうち、周方向に１つおきの２つのギャッシュ８Ａは、そのエンドミル回転方向Ｔ前方側に隣接する残りの２つのギャッシュ８Ｂにそれぞれ連通するように、これらのギャッシュ８Ｂの底刃１１の内周側のすくい面１０と先端逃げ面９とを切り欠いて延びるように形成されている。これに対して、残りの２つのギャッシュ８Ｂは、そのエンドミル回転方向Ｔ側に隣接する各ギャッシュ８Ａには連通せず、これらのギャッシュ８Ａに形成された底刃１１の間に先端逃げ面９が残されるように形成されている。 Of the four gashes 8 formed at the tip of the four chip discharge grooves 4, every other two gashes 8A in the circumferential direction are the remaining two adjacent to the front side in the end mill rotation direction T. The rake face 10 and the tip flank 9 on the inner peripheral side of the bottom blade 11 of the gash 8B are formed so as to cut out and extend so as to communicate with the gash 8B. On the other hand, the remaining two gashes 8B do not communicate with the gashes 8A adjacent to the end mill rotation direction T side, and the tip flank 9 is located between the bottom blades 11 formed on these gashes 8A. It is formed to remain.

従って、エンドミル回転方向Ｔ後方側に隣接するギャッシュ８Ｂが連通していない上記２つのギャッシュ８Ａの底刃１１は、外周刃７の先端から内周側に向けて、互いに反対側の底刃１１の先端逃げ面９同士が交差する位置まで延びることになり、エンドミル本体１先端において軸線Ｏを越えて延びる長底刃１１Ａとされる。また、この長底刃１１Ａ以外の残りの２つの底刃１１は、その内周端がエンドミル本体１先端において軸線Ｏから間隔をあけて外周側に位置する短底刃１１Ｂとされ、これら長底刃１１Ａと短底刃１１Ｂとは周方向に交互に配置されて、エンドミル本体１は軸線Ｏに関して１８０°回転対称に形成されている。 Therefore, the bottom blades 11 of the two gashes 8A, which are not in communication with the gash 8B adjacent to the rear side in the end mill rotation direction T, of the bottom blades 11 opposite to each other from the tip of the outer peripheral blade 7 toward the inner peripheral side. The end flank surfaces 9 extend to a position where they intersect, and the end mill body 1 has a long bottom blade 11A extending beyond the axis O at the end. Further, the remaining two bottom blades 11 other than the long bottom blade 11A are short bottom blades 11B whose inner peripheral ends are positioned on the outer peripheral side at a distance from the axis O at the end of the end mill main body 1. The blades 11 </ b> A and the short bottom blades 11 </ b> B are alternately arranged in the circumferential direction, and the end mill body 1 is formed to be 180 ° rotationally symmetric with respect to the axis O.

一方、外周刃７の先端部には、図６に示すように外周刃７の軸線Ｏに対する捩れ角θが先端側に向かうに従い漸次小さくなるような捩れ角漸減部７Ａが形成されている。この捩れ角漸減部７Ａは、該捩れ角漸減部７Ａに連なる外周刃７のすくい面６が、軸線Ｏに直交する断面では上述のようにエンドミル回転方向Ｔ後方側に凹む凹曲線状をなすものの、エンドミル本体１の周方向に沿った断面、すなわち軸線Ｏを中心とした円筒面による断面ではエンドミル回転方向Ｔ前方側に凸となる凸曲線を描きつつ、先端側に向かうに従い漸次エンドミル回転方向Ｔに延びるように形成され、このすくい面６と外周逃げ面５とが交差することによって、捩れ角θが先端側に向かうに従い漸減するように形成される。 On the other hand, as shown in FIG. 6, a twist angle gradually decreasing portion 7A is formed at the distal end portion of the outer peripheral blade 7 so that the twist angle θ with respect to the axis O of the outer peripheral blade 7 gradually decreases toward the distal end side. The twist angle gradually decreasing portion 7A has a concave curved shape in which the rake face 6 of the outer peripheral blade 7 connected to the torsion angle gradually decreasing portion 7A is recessed to the rear side in the end mill rotation direction T as described above in a cross section perpendicular to the axis O. In the cross section along the circumferential direction of the end mill body 1, that is, the cross section by the cylindrical surface centered on the axis O, the end mill rotation direction T gradually increases toward the tip side while drawing a convex curve that protrudes forward in the end mill rotation direction T. The rake face 6 and the outer peripheral flank 5 intersect each other, so that the torsion angle θ gradually decreases toward the distal end side.

また、この捩れ角漸減部７Ａの先端側には、先端側に向かうに従い漸減した捩れ角θが一定とされる捩れ角一定部７Ｂが形成されており、この捩れ角一定部７Ｂにおいて外周刃７の捩れ角θは、本実施形態では０°〜２０°の範囲とされている。すなわち、この捩れ角一定部７Ｂではすくい面６の上記周方向に沿った断面が、捩れ角漸減部７Ａにおける同断面がなす凸曲線に接して、先端側に向かうに従い漸次エンドミル回転方向Ｔに延びる、または軸線Ｏに平行に延びる直線状とされ、このすくい面６と外周逃げ面５とが交差することによって捩れ角一定部７Ｂが形成される。 Further, a constant torsion angle portion 7B in which the torsion angle θ gradually decreasing toward the front end side is constant is formed on the distal end side of the torsion angle gradually decreasing portion 7A, and the outer peripheral blade 7 in the constant torsion angle portion 7B. Is set to a range of 0 ° to 20 ° in the present embodiment. That is, in the constant twist angle portion 7B, the cross section along the circumferential direction of the rake face 6 is in contact with the convex curve formed by the same cross section in the twist angle gradually decreasing portion 7A and gradually extends in the end mill rotation direction T toward the tip side. Or a straight line extending parallel to the axis O, and the rake face 6 and the outer peripheral flank 5 intersect to form the constant twist angle portion 7B.

そして、外周刃７は、これら捩れ角漸減部７Ａや捩れ角一定部７Ｂも含めて、上述のように軸線Ｏ回りの回転軌跡が該軸線Ｏを中心とする一定外径の円筒面状をなすようにされている。また、外周逃げ面５は、このような外周刃７からエンドミル回転方向Ｔ後方側に向けて、外周刃７の外径と等しい外径の円筒面状のマージンを有することなく、漸次エンドミル本体１の内周側に後退するように形成されている。 The outer peripheral blade 7 includes a cylindrical surface with a constant outer diameter centered on the axis O as described above, including the twist angle gradually decreasing portion 7A and the constant twist angle portion 7B. Has been. Further, the outer peripheral flank 5 has a cylindrical surface margin with an outer diameter equal to the outer diameter of the outer peripheral blade 7 from such an outer peripheral blade 7 toward the rear side in the end mill rotation direction T, and gradually the end mill body 1. It is formed so as to recede to the inner peripheral side.

従って、このように構成されたスクエアエンドミルにおいて、外周刃７は、上記捩れ角漸減部７において、すくい面６の上記周方向に沿った断面と同様、図６に示すようにエンドミル回転方向Ｔ前方側に凸となる凸曲線を描きつつ、先端側に向かうに従い漸次エンドミル回転方向Ｔに延びるように形成され、特許文献１、２に記載のスクエアエンドミルのようにギャッシュのエンドミル回転方向前方側を向く壁面が外周逃げ面と交差することによる角部が形成されることがない。 Accordingly, in the square end mill configured as described above, the outer peripheral blade 7 is formed in the twist angle gradually decreasing portion 7 as in the cross section along the circumferential direction of the rake face 6 as shown in FIG. It is formed so as to gradually extend in the end mill rotation direction T as it goes toward the tip side while drawing a convex curve that is convex to the side, and faces the front side in the end direction of the Gash end mill rotation like the square end mills described in Patent Documents 1 and 2. Corners due to the wall surface intersecting the outer flank face are not formed.

また、こうして捩れ角θが漸減することにより、エンドミル本体１後端側では捩れ角θが強捩れであっても、外周刃７の先端部に連なる底刃１１の外周部のすくい面６と先端逃げ面９との交差角、すなわち外周部における底刃１１の刃物角は大きく確保することができ、切刃強度の向上を図ることができる。従って、切削時に底刃１１に欠損が生じたり、上述のような角部において外周刃７にチッピングが生じたりするのを防いで、エンドミル寿命の延長を図ることができる。 Further, by gradually decreasing the twist angle θ in this way, even if the twist angle θ is strongly twisted on the rear end side of the end mill main body 1, the rake face 6 and the tip of the outer peripheral portion of the bottom blade 11 connected to the tip portion of the outer peripheral blade 7. The crossing angle with the flank 9, that is, the blade angle of the bottom blade 11 at the outer peripheral portion can be ensured to be large, and the cutting blade strength can be improved. Accordingly, it is possible to prevent the bottom blade 11 from being chipped during cutting or to prevent the outer peripheral blade 7 from being chipped at the corners as described above, thereby extending the end mill life.

その一方で、外周刃７は、この捩れ角漸減部７Ａや上述の捩れ角一定部７Ｂも含めて、軸線Ｏ回りの回転軌跡が一定外径の円筒状とされており、すくい面６と外周逃げ面５との交差稜線部にこれら捩れ角漸減部７Ａや捩れ角一定部７Ｂが形成されていても、外周刃７が先端側に向かうに従いエンドミル本体１の内周側に向けて傾斜して外径が小さくなることがなく、高精度の加工を行うことができる。また、外周逃げ面５は、マージンを有することなく、捩れ角漸減部７Ａおよび捩れ角一定部７Ｂも含めた外周刃７からエンドミル回転方向Ｔ後方側に向かうに従い漸次エンドミル本体１の内周側に向かうように逃げ角が与えられているので、切削抵抗の低減を図ることができる。 On the other hand, the outer peripheral blade 7 includes a cylindrical shape having a constant outer diameter around the axis O including the torsional angle gradually decreasing portion 7A and the aforementioned torsional angle constant portion 7B. Even when the twist angle gradually decreasing portion 7A and the constant twist angle portion 7B are formed at the intersecting ridge line portion with the flank 5, the outer peripheral blade 7 is inclined toward the inner peripheral side of the end mill body 1 as it goes to the tip side. The outer diameter is not reduced, and high-precision processing can be performed. Further, the outer peripheral flank 5 gradually moves toward the inner peripheral side of the end mill body 1 from the outer peripheral blade 7 including the twist angle gradually decreasing portion 7A and the constant twist angle portion 7B toward the rear side in the end mill rotation direction T without having a margin. Since the clearance angle is given so as to face, cutting resistance can be reduced.

なお、このようにマージンを有することのない外周逃げ面５に、捩れ角漸減部７Ａおよび捩れ角一定部７Ｂを有する外径が一定の外周刃７を形成するには、初めに外周刃７と等しい外径の円筒面に対して、捩れ角θが先端側に向けて漸減した後に一定となるように形成されたすくい面６を交差させるようにして外周刃７の基準線を設定しておき、この基準線に対してエンドミル回転方向Ｔ後方側に向かうに従いエンドミル本体１の内周側に漸次後退するように外周逃げ面５を形成すればよい。 In order to form the outer peripheral blade 7 having the constant outer diameter having the torsion angle gradually decreasing portion 7A and the constant twist angle 7B on the outer peripheral flank 5 having no margin as described above, The reference line of the outer peripheral edge 7 is set so that the rake face 6 formed so as to be constant after the torsion angle θ gradually decreases toward the tip side with respect to the cylindrical surface having the same outer diameter. The outer peripheral flank 5 may be formed so as to gradually recede toward the inner peripheral side of the end mill main body 1 toward the rear side in the end mill rotation direction T with respect to the reference line.

また、このように本実施形態では、外周刃７の捩れ角漸減部７Ａのさらに先端側に、漸減した捩れ角θが一定となる捩れ角一定部７Ｂが形成されていて、上述のように底刃１１の刃物角が大きくされた範囲が底刃１１からある程度の幅をもって広がっているので、底刃１１の欠損等をより確実に防ぐことができる。ただし、本実施形態では，このように捩れ角一定部７Ｂを形成しているが、捩れ角漸減部７Ａにおいて捩れ角θが漸減しながら外周刃７が底刃１１に交差するようにされていてもよい。 As described above, in this embodiment, the constant torsion angle portion 7B in which the gradually decreased torsion angle θ is constant is formed further on the distal end side of the torsion angle gradually decreasing portion 7A of the outer peripheral blade 7. Since the range in which the blade angle of the blade 11 is increased extends from the bottom blade 11 with a certain width, it is possible to more reliably prevent the bottom blade 11 from being damaged. However, in this embodiment, the constant twist angle portion 7B is formed in this way, but the outer peripheral blade 7 intersects the bottom blade 11 while the twist angle θ gradually decreases in the twist angle gradually decreasing portion 7A. Also good.

さらに、本実施形態では、この捩れ角漸減部７Ａによって漸減した外周刃７の先端における捩れ角θが０°〜２０°の範囲とされており、これによっても、底刃１１の欠損を防ぎつつ切削抵抗を低減することができる。すなわち、外周刃７先端の捩れ角θが０°を下回る負角となると底刃１１の切れ味が鈍くなって切削抵抗が増大するおそれがあり、逆に捩れ角θが２０°を上回ると底刃１１の刃物角を確保できなくなって欠損等を確実に防止することが困難となるおそれがある。 Furthermore, in this embodiment, the torsion angle θ at the tip of the outer peripheral blade 7 gradually decreased by the torsion angle gradually decreasing portion 7A is in the range of 0 ° to 20 °, and this also prevents the bottom blade 11 from being broken. Cutting resistance can be reduced. That is, when the twist angle θ at the tip of the outer peripheral blade 7 becomes a negative angle less than 0 °, the sharpness of the bottom blade 11 may be dulled and the cutting resistance may be increased. Conversely, when the twist angle θ exceeds 20 °, the bottom blade There is a risk that it will be difficult to reliably prevent defects and the like because the 11 tool angle cannot be secured.

１エンドミル本体
３切刃部
４切屑排出溝
５外周逃げ面
６すくい面（切屑排出溝４のエンドミル回転方向Ｔ前方側を向く壁面）
７外周刃
７Ａ捩れ角漸減部
７Ｂ捩れ角一定部
８ギャッシュ
９先端逃げ面
１０底刃１１のすくい面（ギャッシュ８のエンドミル回転方向Ｔ前方側を向く壁面）
１１底刃
１１Ａ長底刃
１１Ｂ短底刃
Ｏエンドミル本体１の軸線
Ｔエンドミル回転方向
θ 外周刃７の捩れ角 DESCRIPTION OF SYMBOLS 1 End mill main body 3 Cutting edge part 4 Chip discharge groove 5 Outer periphery flank 6 Rake face (Wall faced to the front side in the end mill rotation direction T of the chip discharge groove 4)
7 Peripheral blade 7A Twist angle gradually decreasing portion 7B Constant twist angle portion 8 Gash 9 Tip clearance surface 10 Rake surface of bottom blade 11 (wall surface facing front side of end mill rotation direction T of gash 8)
11 Bottom blade 11A Long bottom blade 11B Short bottom blade O End mill body 1 axis T End mill rotation direction θ Twist angle of outer peripheral blade 7

Claims

A chip discharge groove is formed on the outer periphery of the end portion of the end mill body that is rotated about the axis, and extends toward the rear side in the end mill rotation direction toward the rear end side. The wall surface facing the front side in the end mill rotation direction has a concave curve shape recessed in the rear side in the end mill rotation direction in the cross section perpendicular to the axis, and the cross ridge line portion between the wall surface and the outer peripheral flank of the end mill body has a cross section. An outer peripheral blade having the concave curved wall surface as a rake face is formed, and the rake face having a concave curved section is left on the outer peripheral side of the tip portion of the chip discharge groove, the intersection ridge line between the outer peripheral portion and the tip flank of the end mill body, said peripheral cutting edge as cutting face in common the rake face of the outer peripheral cutting edge at the outer peripheral side of the end mill body A bottom blade that intersects the tip portion with an angle is formed, and a tip portion of the outer peripheral blade is formed with a torsion angle gradually decreasing portion that gradually decreases as the torsion angle of the outer peripheral blade with respect to the axis line moves toward the tip side. The outer peripheral blade has a cylindrical surface with a constant outer diameter centered on the axis including the gradually decreasing portion of the twist angle, and the outer peripheral flank is end mill rotated from the outer peripheral blade. A square end mill, wherein the square end mill is formed so as to gradually recede toward the inner peripheral side with respect to the rotational trajectory around the axis of the outer peripheral blade toward the rear side in the direction.

A constant torsion angle portion having a constant torsion angle is formed on the tip side of the torsion angle gradually decreasing portion, and the outer peripheral blade includes a rotation angle around the axis including the constant torsion angle portion. The square end mill according to claim 1, wherein the square end mill has a cylindrical surface shape with a constant outer diameter centered at the center.

The square end mill according to claim 1 or 2, wherein a twist angle at a tip of the outer peripheral blade is in a range of 0 ° to 20 °.