JP7541238B2

JP7541238B2 - End Mills

Info

Publication number: JP7541238B2
Application number: JP2020217137A
Authority: JP
Inventors: 誠馬場; 峰史佐井
Original assignee: Moldino Tool Engineering Ltd
Current assignee: Moldino Tool Engineering Ltd
Priority date: 2020-12-25
Filing date: 2020-12-25
Publication date: 2024-08-28
Anticipated expiration: 2040-12-25
Also published as: JP2022102421A

Description

本発明は、エンドミル本体を回転軸方向先端側から見たときに半径方向に連続し、中低勾配角が付いた切れ刃が高硬度鋼の中仕上げ加工する上で、被削材に対する加工面品位の低下を抑制する形態のエンドミルに関するものである。 The present invention relates to an end mill with a cutting edge that is continuous in the radial direction when viewed from the tip side in the direction of the rotary shaft and has a medium to low gradient angle, which suppresses deterioration of the machined surface quality of the workpiece when semi-finishing high-hardness steel.

エンドミル本体の回転軸方向（軸方向）先端部に回転方向に配列し、半径方向に連続する、先端面側から見たときの長さが大きい親刃と小さい子刃の区別がある、複数枚の切れ刃を有するエンドミルがある（特許文献１～３参照）。 There are end mills with multiple cutting edges that are arranged in the direction of rotation at the tip of the end mill body in the axial direction (axial direction), are continuous in the radial direction, and have a distinction between a parent blade that is longer when viewed from the tip face side and a child blade that is shorter (see Patent Documents 1 to 3).

エンドミル本体の先端部を先端面側から見たときの子刃と親刃の切れ刃長さの相違に伴い、逃げ面の広さに対応した肉厚の相違もあり、逃げ面を含めた厚さを有する子刃部分の回転方向の剛性は、逃げ面を含めた親刃部分の回転方向の剛性より低くなる。 When looking at the tip of the end mill body from the tip face side, the cutting edge length of the child blade and the parent blade differs, and there is also a difference in thickness corresponding to the width of the flank, so the rigidity in the rotational direction of the child blade part, which has a thickness including the flank, is lower than the rigidity in the rotational direction of the parent blade part, which includes the flank.

各切れ刃の実際に被削材を切削する部分（切削区間）が、先端部を先端側から見たときの切れ刃長さに対応した長さを有する場合、すなわち切れ刃長さと切削区間が実質的に比例関係にあれば、子刃部分が被削材から受ける抵抗は親刃部分が被削材から受ける抵抗より小さい。この場合、子刃部分と親刃部分の抵抗の差はそれぞれの剛性の差に対応した大きさ（差）になるため、振動数の差が顕著になることはなく、問題視されることもない。 If the portion of each cutting edge that actually cuts the workpiece (cutting section) has a length that corresponds to the length of the cutting edge when viewed from the tip, i.e., if the cutting edge length and the cutting section are substantially proportional, the resistance that the child blade section receives from the workpiece is smaller than the resistance that the parent blade section receives from the workpiece. In this case, the difference in resistance between the child blade section and the parent blade section is a magnitude (difference) that corresponds to the difference in their respective rigidities, so the difference in vibration frequency is not noticeable and is not considered a problem.

一方、多くのスクエアエンドミルやラジアスエンドミルのように子刃と親刃に中低勾配角（すかし角）が付く場合（特許文献２の図５、図６）には、子刃と親刃の見かけ上の長さは相違しながらも、親刃の中心付近は被削材には接触しない状態になる。すなわち、子刃部分と親刃部分の剛性が相違しながらも、それぞれが被削材から受ける抵抗に差が生じないことがある。 On the other hand, when the child blade and parent blade have a medium to low gradient angle (concave angle), as in many square end mills and radius end mills (Figs. 5 and 6 of Patent Document 2), even though the apparent lengths of the child blade and parent blade are different, the center of the parent blade does not come into contact with the workpiece. In other words, even though the rigidity of the child blade portion and parent blade portion differs, there may be no difference in the resistance that each receives from the workpiece.

このため、子刃と親刃が実際に被削材を切削する部分（切削区間）の長さは、子刃と親刃とでは実質的に変わらず、親刃部分が被削材から受ける抵抗と子刃部分が受ける抵抗に差が生じないことがある。親刃部分の抵抗と子刃部分の抵抗に差がなければ、親刃部分の剛性と子刃部分の剛性の差がそのままそれぞれの振動数の差になり、相対的に子刃部分の振動数が多くなるため、被削材の加工面品位に影響が表われる。 Because of this, the length of the part where the child blade and parent blade actually cut the workpiece (cutting section) is essentially the same for the child blade and parent blade, and there may be no difference in the resistance that the parent blade receives from the workpiece and the resistance that the child blade receives. If there is no difference in the resistance of the parent blade and the child blade, the difference in stiffness between the parent blade and the child blade will directly result in a difference in their respective vibration frequencies, and the vibration frequency of the child blade will be relatively higher, which will affect the machined surface quality of the workpiece.

特開平８－１１２７１０号公報（請求項１、段落０００６～０００９、図３～図５）JP-A-8-112710 (Claim 1, paragraphs 0006 to 0009, Figures 3 to 5) 国際公開第２０１６／１５２６１１号（請求項１、段落００１０～００４７、図２～図４）International Publication No. 2016/152611 (Claim 1, paragraphs 0010 to 0047, Figures 2 to 4) 国際公開第２０２０／１９５６６３号（請求項１、段落０００９～００４８、図１、図２）International Publication No. 2020/195663 (Claim 1, paragraphs 0009 to 0048, Figures 1 and 2)

子刃部分の抵抗と親刃部分の抵抗に差がないにも拘わらず、子刃部分の剛性が親刃部分の剛性より小さければ、子刃が被削材を切削するときに子刃部分に生じる振動数が、親刃部分に生じる振動数より多くなり易い。子刃部分の振動数が親刃部分の振動数より多いことは、被削材を切削するときに子刃部分が親刃部分より多く振動することであるから、被削材の加工面品位の低下を招き易い。また子刃部分の振動数が多くなり易いことで、子刃のいずれかの部分に欠けが生じ易くもなる。 Even if there is no difference between the resistance of the child blade portion and the resistance of the parent blade portion, if the rigidity of the child blade portion is less than that of the parent blade portion, the frequency of vibration generated in the child blade portion when the child blade cuts the workpiece is likely to be greater than the frequency of vibration generated in the parent blade portion. If the frequency of vibration of the child blade portion is greater than that of the parent blade portion, the child blade portion vibrates more than the parent blade portion when cutting the workpiece, which is likely to lead to a decrease in the quality of the machined surface of the workpiece. In addition, if the frequency of vibration of the child blade portion is likely to be high, chipping is likely to occur in one of the child blade portions.

本発明は上記背景より、振動数差に影響する親刃部分と子刃部分の剛性差を極力、小さくし、剛性差に起因する、被削材に対する加工面品位の低下を低減する形態のエンドミルを提案するものである。 In light of the above background, the present invention proposes an end mill that minimizes the difference in rigidity between the parent blade and child blade, which affects the difference in vibration frequency, and reduces the deterioration of the machined surface quality of the workpiece caused by the difference in rigidity.

請求項１に記載の発明のエンドミルは、、エンドミル本体の軸方向の先端側に、半径方向中心側から外周側へかけて連続する親刃と、この親刃に前記エンドミル本体の回転方向に隣り合い、前記エンドミル本体を軸方向の先端側から見たときに前記親刃より短い子刃とを備え、前記親刃と前記子刃の各回転方向後方側にギャッシュが形成され、前記各ギャッシュから前記軸方向後端側に切屑排出溝が連続し、
前記子刃の回転方向後方側の前記ギャッシュは前記軸方向の先端側に位置する子刃先端側ギャッシュと、前記軸方向の後端側に位置する子刃後端側ギャッシュとに区分され、
前記子刃先端側ギャッシュと前記子刃後端側ギャッシュとの間の境界線の回転方向前方側の端部は、前記子刃の、逃げ角が最大の逃げ面より回転方向後方側に位置し、
前記親刃の回転方向後方側の前記ギャッシュは前記軸方向の先端側に位置する親刃先端側ギャッシュと、前記軸方向の後端側に位置する親刃後端側ギャッシュとに区分され、
前記親刃先端側ギャッシュと前記親刃後端側ギャッシュとの間の境界線の回転方向後方側の端部は、前記親刃の回転方向後方側に位置する前記子刃の半径方向中心側の端部より前記中心側に位置していることを特徴とする。 The end mill of the invention described in claim 1 comprises a parent blade that is continuous from the center side to the outer periphery side in the radial direction at the axial tip side of the end mill body, and a child blade that is adjacent to the parent blade in the rotational direction of the end mill body and is shorter than the parent blade when viewed from the axial tip side of the end mill body, and a gash is formed on the rear side of each of the parent blade and child blade in the rotational direction, and a chip discharge groove is continuous from each of the gashes to the rear end side in the axial direction,
The gash on the rear side in the rotational direction of the child blade is divided into a child blade tip side gash located on the tip side in the axial direction and a child blade rear end side gash located on the rear end side in the axial direction,
a front end of a boundary between the gash on the tip end side of the child blade and the gash on the rear end side of the child blade is located rearward in the rotational direction from a clearance face of the child blade having a maximum clearance angle ,
The gash on the rear side in the rotational direction of the parent blade is divided into a parent blade tip side gash located on the tip side in the axial direction and a parent blade rear end side gash located on the rear end side in the axial direction,
The present invention is characterized in that the rear end of the boundary line between the gash at the tip end of the parent blade and the gash at the rear end of the parent blade is located closer to the center in the radial direction than the end of the child blade located rearward in the rotational direction of the parent blade .

請求項１の「先端側から見たとき」とは、図１、図４に示すようにエンドミル本体（工具本体）を先端側から回転軸Ｏ反対側のシャンク部３側に向かって見たときの状況を言う。以下では「回転軸Ｏ方向」を単に「軸方向」とも言い、「回転軸Ｏ」を半径方向の中心Ｏとも言う。請求項１の「回転軸方向の先端側」と「回転軸方向の後端側」は工具本体を先端側から見たときの、それぞれ「半径方向中心側」と「半径方向外周側」である。回転方向ｒはエンドミル本体（工具本体）が被削材を切削するときに回転軸Ｏ回りに回転する向きを言う。請求項１の「子刃の、逃げ角が最大の逃げ面」とは、子刃逃げ面の内、逃げ角が最大の逃げ面であり、子刃の逃げ面が１面（２番面）である場合には、その逃げ面を指し、複数面、形成される場合には、最も逃げ角が大きい逃げ面を指す。 In claim 1, "when viewed from the tip side" refers to the state when the end mill body (tool body) is viewed from the tip side toward the shank part 3 on the opposite side of the rotation axis O, as shown in Figures 1 and 4. In the following, the "direction of the rotation axis O" is also simply referred to as the "axial direction", and the "rotation axis O" is also referred to as the center O in the radial direction. The "tip side in the rotation axis direction" and the "rear end side in the rotation axis direction" in claim 1 are the "radial center side" and the "radial outer periphery side", respectively, when the tool body is viewed from the tip side. The rotation direction r refers to the direction in which the end mill body (tool body) rotates around the rotation axis O when cutting the workpiece. In claim 1, "the flank surface of the child blade with the largest clearance angle" refers to the flank surface with the largest clearance angle among the flank surfaces of the child blade, and if the flank surface of the child blade is one surface (second surface), it refers to that flank surface, and if multiple surfaces are formed, it refers to the flank surface with the largest clearance angle.

本発明におけるエンドミルは、少なくとも、エンドミル本体を先端側から見たときに切れ刃が存在していればよく、先端側から見たときの切れ刃は底刃のみの場合も、コーナーＲ刃のみの場合もあり、それらの組み合わせを含む。「親刃」は回転方向に配列する複数枚の切れ刃の内、工具本体（切れ刃）を先端側から見たときの切れ刃長さ（刃自体の長さ）が最も大きい切れ刃を指し、「子刃」は親刃より切れ刃長さが相対的に小さい残りの切れ刃を指す。親刃は１枚の場合と複数枚の場合がある。切れ刃はエンドミル本体に複数枚、形成されるから、子刃は親刃の枚数に応じ、複数枚の場合と１枚の場合がある。親刃が複数枚ある場合、切れ刃長さが最も大きい同一長さの切れ刃が複数枚あることになる。子刃が複数枚ある場合、子刃の切れ刃長さは等しい場合と等しくない場合がある。切れ刃数が３枚の場合の図８に示す例では、１枚の親刃の回転方向前方側と回転方向後方側のそれぞれに、切れ刃長さの相違する子刃が形成されている。 The end mill in the present invention is sufficient if there is at least a cutting edge when the end mill body is viewed from the tip side, and the cutting edge when viewed from the tip side may be only a bottom edge or only a corner R edge, and includes a combination of these. The "parent edge" refers to the cutting edge that has the longest cutting edge length (the length of the blade itself) when the tool body (cutting edge) is viewed from the tip side among the multiple cutting edges arranged in the rotation direction, and the "child edge" refers to the remaining cutting edge that has a relatively shorter cutting edge length than the parent edge. There may be one parent edge or multiple parent edges. Since multiple cutting edges are formed on the end mill body, there may be multiple child edges or one child edge depending on the number of parent edges. When there are multiple parent edges, there will be multiple cutting edges of the same length with the longest cutting edge length. When there are multiple child edges, the cutting edge lengths of the child edges may or may not be equal. In the example shown in Figure 8, where there are three cutting edges, child blades with different cutting edge lengths are formed on both the front and rear sides of a single parent blade in the direction of rotation.

「親刃」と「子刃」は外周刃６を含み得る。コーナーＲ刃５の外周側には外周刃６が連続する。親刃４１と子刃４２がコーナーＲ刃５を有する場合、エンドミル１は図示するようなラジアスエンドミルになるが、親刃４１とコーナーＲ刃５の境界、及び子刃４２とコーナーＲ刃５の境界は必ずしも明確には表れないこともある。コーナーＲ刃５がなく、親刃４１と子刃４２の外周側に外周刃６が連続する場合、エンドミル１はスクエアエンドミルになる。 The "parent blade" and "child blade" may include an outer peripheral blade 6. The outer peripheral blade 6 is continuous with the outer periphery of the corner R blade 5. When the parent blade 41 and child blade 42 have a corner R blade 5, the end mill 1 becomes a radius end mill as shown in the figure, but the boundary between the parent blade 41 and the corner R blade 5, and the boundary between the child blade 42 and the corner R blade 5, may not always be clearly visible. When there is no corner R blade 5 and the outer peripheral blade 6 is continuous with the outer periphery of the parent blade 41 and child blade 42, the end mill 1 becomes a square end mill.

「子刃の回転方向後方側のギャッシュが回転軸Ｏ方向の先端部側に位置する子刃先端側ギャッシュ８と、回転軸Ｏ方向の後端側に位置する子刃後端側ギャッシュ１０とに区分され」とは、子刃先端側ギャッシュ８が相対的に軸方向先端側に、子刃後端側ギャッシュ１０が軸方向後端側にそれぞれ位置し、図２－（ｂ）に例示するように２段に形成されていることを言う。親刃の回転方向後方側のギャッシュ（親刃先端側ギャッシュ９と親刃後端側ギャッシュ１１）も同様である（請求項２）。 "The gash on the rear side of the rotational direction of the child blade is divided into a child blade tip gash 8 located at the tip end side in the direction of the rotation axis O, and a child blade rear end gash 10 located at the rear end side in the direction of the rotation axis O" means that the child blade tip gash 8 is located relatively toward the axial tip side, and the child blade rear end gash 10 is located relatively toward the axial rear end side, and is formed in two stages as shown in Figure 2-(b). The same applies to the gash on the rear side of the rotational direction of the parent blade (parent blade tip gash 9 and parent blade rear end gash 11) (Claim 2).

子刃が被削材を切削するときに被削材から抵抗を受けて振動する部分は、子刃の逃げ面を含み、子刃４２と、子刃の回転方向後方側の子刃先端側ギャッシュ８とで区画された領域（部分）であると考えることができる。この子刃部分はまた、子刃のすくい面４２ａから子刃逃げ面４２ｂの回転方向後方側のギャッシュ面（子刃先端側ギャッシュ面８ａと子刃後端側ギャッシュ面１０ａ）までの領域（部分）であるとも言える。以下、子刃が振動する部分である「子刃のすくい面から逃げ面の回転方向後方側のギャッシュ面までの領域」を子刃部分と言い、「切れ刃部分」とも言う。 The part of the blade that vibrates when it receives resistance from the workpiece when cutting the workpiece includes the flank of the blade, and can be considered to be the area (part) partitioned by the blade 42 and the gash 8 on the tip side of the blade on the rear side in the rotational direction of the blade. This blade part can also be said to be the area (part) from the rake face 42a of the blade to the gash surface on the rear side in the rotational direction of the blade flank face 42b (the gash surface 8a on the tip side of the blade and the gash surface 10a on the rear side of the blade). Hereinafter, the part of the blade that vibrates, "the area from the rake face of the blade to the gash surface on the rear side in the rotational direction of the flank face", is referred to as the blade part, and is also referred to as the "cutting edge part".

同様に親刃が被削材を切削するときに被削材から抵抗を受けて振動する部分は、親刃の逃げ面を含み、親刃４１と、親刃の回転方向後方側の親刃先端側ギャッシュ９とで区画された領域（部分）であると言える。親刃部分はまた、親刃のすくい面４１ａから親刃逃げ面４１ｂの回転方向後方側のギャッシュ面（親刃先端側ギャッシュ面９ａと親刃後端側ギャッシュ面１１ａ）までの領域（部分）であるとも言える。以下、親刃が振動する部分である「親刃のすくい面から逃げ面の回転方向後方側のギャッシュ面までの領域」を親刃部分と言い、「切れ刃部分」とも言う。 Similarly, the part of the parent blade that vibrates when it receives resistance from the workpiece when cutting the workpiece includes the flank of the parent blade, and can be said to be the area (part) partitioned by the parent blade 41 and the parent blade tip gash 9 on the rear side in the rotational direction of the parent blade. The parent blade part can also be said to be the area (part) from the rake face 41a of the parent blade to the gash surface on the rear side in the rotational direction of the parent blade flank 41b (parent blade tip gash surface 9a and parent blade rear end gash surface 11a). Hereinafter, the part of the parent blade that vibrates, "the area from the rake face of the parent blade to the gash surface on the rear side in the rotational direction of the flank face", is referred to as the parent blade part, and is also referred to as the "cutting edge part".

ここで、子刃先端側ギャッシュ８と子刃後端側ギャッシュ１０との間の境界線８２の回転方向前方側（切屑排出溝７側）の端部が子刃逃げ面の内、最も逃げ角が大きい逃げ面（４２ｃ）より回転方向後方側に位置することで（請求項１）、境界線８２が逃げ面に接続する場合（例えば、図１、図２、図４、図５中、二点鎖線で示す軌跡を描く場合）より、子刃部分の体積と、子刃部分の回転方向後方側と軸方向後端側の肉厚が増すため、子刃部分の回転方向の剛性が大きくなる。この結果、子刃が被削材を切削するときの、子刃部分の振動数が、境界線８２の回転方向前方側の端部が、子刃逃げ面に接続している場合より低下し、振動しにくくなる。「境界線８２の回転方向前方側の端部が、逃げ角が最大の逃げ面より回転方向後方側に位置する」とは、切れ刃を先端側から見たときの状況を述べている。 Here, the end of the boundary line 82 between the tip end gash 8 and the rear end gash 10 of the blade is located rearward in the rotation direction from the flank surface (42c) with the largest clearance angle among the blade flank surfaces (claim 1). This increases the volume of the blade portion and the thickness of the blade portion in the rotation direction rear side and the axial rear end side compared to when the boundary line 82 is connected to the flank surface (for example, when the path is shown by the two-dot chain line in Figures 1, 2, 4, and 5), and therefore increases the rigidity of the blade portion in the rotation direction. As a result, the vibration frequency of the blade portion when the blade cuts the workpiece is lower than when the end of the boundary line 82 on the front side in the rotation direction is connected to the blade flank surface, making it less likely to vibrate. "The end of the boundary line 82 on the front side in the rotation direction is located rearward in the rotation direction from the flank surface with the largest clearance angle" describes the situation when the cutting edge is viewed from the tip side.

子刃部分の振動部分が、子刃と子刃先端側ギャッシュ８とで区画された領域によってある程度、決められることの考えに立てば、子刃部分の剛性は境界線８２の回転方向前方側端部の切屑排出溝７との接続位置によって、または境界線８２自体の軌跡の描き方等によって調整可能である、とも言える。とすれば、境界線８２の回転方向前方側の端部が切屑排出溝７と軸方向後端側、または回転方向後方側で交わる程、子刃部分の肉厚が増すため、子刃部分の剛性が増すことになる。 If we consider that the vibration part of the child blade part is determined to some extent by the area partitioned by the child blade and the gash 8 at the tip of the child blade, it can also be said that the rigidity of the child blade part can be adjusted by the connection position of the forward end of the boundary line 82 in the rotation direction with the chip discharge groove 7, or by the way the trajectory of the boundary line 82 itself is drawn. If this is the case, the thickness of the child blade part increases as the forward end of the boundary line 82 in the rotation direction intersects with the chip discharge groove 7 at the rear end in the axial direction or the rear side in the rotation direction, and therefore the rigidity of the child blade part increases.

境界線８２の回転方向前方側の端部が切屑排出溝７と軸方向後端側で交わる程、子刃先端側ギャッシュ８の最も深い部分（線）を含む平面、または親刃に回転方向に対向する子刃先端側ギャッシュ面８ａの、図２－（ｂ）に示す回転軸Ｏとのなす鋭角の角度θ１が、切屑排出溝７側に位置する子刃後端側ギャッシュ面１０ａがなす角度θ２より相対的に大きくなる。結果として、子刃先端側ギャッシュ８の占める容積が増え、子刃部分全体の肉厚が大きくなる。 The closer the front end of the boundary line 82 in the rotational direction intersects with the chip discharge groove 7 at the rear end in the axial direction, the greater the acute angle θ1 between the plane including the deepest part (line) of the gash 8 at the tip of the child blade, or the gash surface 8a at the tip of the child blade facing the parent blade in the rotational direction, and the rotation axis O shown in FIG. 2(b) becomes, compared to the angle θ2 between the gash surface 10a at the rear end of the child blade located on the chip discharge groove 7 side. As a result, the volume occupied by the gash 8 at the tip of the child blade increases, and the thickness of the entire child blade portion becomes greater.

境界線８２の端部が子刃の、逃げ角が最大の逃げ面よりも回転方向後方側（切屑排出溝７側）（実線で示す位置）にあれば、上記した逃げ面に接続する（二点鎖線の位置にある）場合より、子刃部分の剛性が増す、または剛性の調整ができることで、子刃部分の剛性と親刃部分の剛性との差を縮めることが可能である。従って親刃部分が被削材から受ける抵抗と、子刃部分が受ける抵抗に差があまり、あるいはほとんどない場合でも、子刃部分の剛性の調整により、子刃部分と親刃部分の振動数差を低減することが可能になる。 If the end of boundary line 82 is located on the rear side of the flank of the child blade with the largest clearance angle in the direction of rotation (towards the chip discharge groove 7) (position shown by the solid line), the rigidity of the child blade portion is increased compared to when it is connected to the clearance face described above (position shown by the two-dot chain line), or the rigidity can be adjusted, making it possible to reduce the difference in rigidity between the child blade portion and the parent blade portion. Therefore, even if there is little or no difference between the resistance received by the parent blade portion from the workpiece and the resistance received by the child blade portion, it is possible to reduce the difference in vibration frequency between the child blade portion and the parent blade portion by adjusting the rigidity of the child blade portion.

「親刃部分と子刃部分が受ける抵抗に差がない場合」とは、親刃４１と子刃４２の切削に寄与する区間（切削区間）が同等程度で、それぞれが被削材から受ける抵抗に差がない場合を言う。このような状況は例えば図２－（ａ）に示すように親刃と子刃が、半径方向の中心Ｏ側に向かうに従って、軸方向に直交する平面に対して回転軸方向の後端側に向かって傾斜している（中低勾配角（すかし角）αが付く）場合に生じる（請求項３）。請求項３の「親刃及び子刃は、半径方向外周側から中心側に向かうに従い、軸方向先端側から後端側に向かって延在している」は親刃と子刃に中低勾配角αが付くことを述べている。このような場合、親刃部分の剛性と子刃部分の剛性の差がそのまま振動数差として表れるため、被削材の加工面への影響が生じ易い。 "When there is no difference in the resistance received by the parent blade portion and the child blade portion" refers to a case where the sections (cutting sections) that contribute to cutting of the parent blade 41 and the child blade 42 are approximately equal, and there is no difference in the resistance received by each of them from the workpiece. For example, as shown in FIG. 2-(a), the parent blade and the child blade are inclined toward the rear end side of the rotation axis direction with respect to a plane perpendicular to the axial direction as they move toward the center O in the radial direction (a median gradient angle (concave angle) α is provided) (Claim 3 ). "The parent blade and the child blade extend from the axial tip side to the rear end side as they move from the radial outer periphery side to the center side" in claim 3 states that the parent blade and the child blade are provided with a median gradient angle α. In such a case, the difference in rigidity between the parent blade portion and the child blade portion is directly expressed as a difference in vibration frequency, which is likely to affect the machined surface of the workpiece.

それに対し、境界線８２の位置によって子刃部分の剛性と親刃部分の剛性の差を減少させられることで、親刃部分が被削材から受ける抵抗と、子刃部分が受ける抵抗に差があまりない場合でも、子刃部分の振動数と親刃部分の振動数に差を生じさせないようにすることが可能になる。子刃部分と親刃部分の振動数差を生じさせないことで、仕上げ加工や中仕上げ加工における被削材に対する加工面品位の向上が図られる。また子刃部分の剛性を通常より増し、振動数を低減することができることで、子刃のいずれかの部分の欠けを回避することも可能になる。 By reducing the difference in rigidity between the child blade portion and the parent blade portion depending on the position of boundary line 82, it is possible to eliminate the difference in vibration frequency between the child blade portion and the parent blade portion even when there is little difference between the resistance that the parent blade portion receives from the workpiece and the resistance that the child blade portion receives. Eliminating the difference in vibration frequency between the child blade portion and the parent blade portion improves the quality of the machined surface of the workpiece in finishing and semi-finishing processes. Also, by increasing the rigidity of the child blade portion more than usual and reducing the vibration frequency, it is possible to avoid chipping of any part of the child blade.

子刃の回転方向後方側に位置するギャッシュと同様に、親刃の回転方向後方側のギャッシュが、回転軸Ｏ方向の先端部側（半径方向中心側）に位置する親刃先端側ギャッシュ９と、回転軸Ｏ方向の後端側（半径方向外周側）に位置する親刃後端側ギャッシュ１１とに区分されることもある（請求項２）。この場合、図１、図４に示すように親刃先端側ギャッシュ９と親刃後端方側ギャッシュ１１との間に境界線９１が形成される。 Similar to the gash located on the rear side of the child blade in the rotational direction, the gash on the rear side of the parent blade in the rotational direction may be divided into parent blade tip side gash 9 located on the tip side (radial center side) in the direction of the rotation axis O, and parent blade rear end side gash 11 located on the rear end side (radial outer periphery side) in the direction of the rotation axis O (claim 2). In this case, a boundary line 91 is formed between the parent blade tip side gash 9 and the parent blade rear end side gash 11 as shown in Figures 1 and 4.

この場合に、子刃後方のギャッシュの境界線８２の回転方向前方側の端部を、逃げ角が最大の子刃の逃げ面よりも回転方向後方側に位置させつつ（請求項１）、親刃後方のギャッシュの境界線９１の回転方向前方側の端部を、親刃のいずれかの逃げ面（４１ｂ、または４１ｄ）に接続すれば（請求項２）、子刃部分の剛性と親刃部分の剛性との差を縮小させることになる。「境界線９１の回転方向前方側の端部が親刃のいずれかの逃げ面に接続する」とは、切れ刃を先端側から見たときの状況を述べている。 In this case, if the forward end in the direction of rotation of the boundary line 82 of the gash behind the child blade is positioned further backward in the direction of rotation than the flank of the child blade with the largest clearance angle (claim 1), and the forward end in the direction of rotation of the boundary line 91 of the gash behind the parent blade is connected to one of the flanks of the parent blade (41b or 41d) (claim 2), the difference in rigidity between the child blade portion and the parent blade portion will be reduced. "The forward end in the direction of rotation of the boundary line 91 is connected to one of the flanks of the parent blade" describes the situation when the cutting edge is viewed from the tip side.

子刃と親刃を軸方向先端側から見たときの切れ刃長さの相違にのみ注目すれば、子刃部分の剛性が親刃部分の剛性より小さくなるが、境界線９１端部の接続位置の調整により親刃部分の体積（肉厚）を子刃部分の体積（肉厚）より抑えることができるため、それぞれの剛性差が縮められることになる。「境界線９１の回転方向前方側の端部」は境界線９１の切屑排出溝７側の端部でもある。「境界線９１の回転方向前方側の端部を親刃の逃げ面に接続する」とは、親刃を先端側から見たときに境界線９１の端部がいずれかの逃げ面のいずれかの部分に接続することを言う。 If one focuses only on the difference in cutting edge length when the child blade and parent blade are viewed from the axial tip side, the rigidity of the child blade portion is smaller than that of the parent blade portion, but by adjusting the connection position of the boundary line 91 end, the volume (thickness) of the parent blade portion can be made smaller than the volume (thickness) of the child blade portion, thereby reducing the difference in rigidity between the two. The "end portion on the forward side in the rotational direction of the boundary line 91" is also the end portion of the boundary line 91 on the chip discharge groove 7 side. "Connecting the end portion on the forward side in the rotational direction of the boundary line 91 to the flank surface of the parent blade" means that the end portion of the boundary line 91 connects to any part of any flank surface when the parent blade is viewed from the tip side.

更に親刃先端側ギャッシュ９と親刃後端側ギャッシュ１１との間の境界線９１の回転方向後方側の端部を子刃４２の半径方向中心側の端部より回転軸Ｏ（半径方向中心）側に位置させることで（請求項１）、親刃部分の領域の拡大との剛性の増大をより抑えることが可能になる。この結果、親刃部分の剛性の調整が可能になるため、子刃部分の剛性との差をより縮小させることが可能になる。なお、境界線９１の回転方向後方側の端部は子刃側の端部とも言える。「境界線９１の回転方向後方側の端部が子刃の半径方向中心側の端部より回転軸Ｏ側に位置する」とは、切れ刃を先端側から見たときの状況を述べている。 Furthermore, by positioning the rear end of the boundary line 91 between the parent blade tip gash 9 and the parent blade rear gash 11 closer to the rotation axis O (radial center) than the end of the child blade 42 on the radial center side (claim 1 ), it is possible to further suppress the increase in rigidity with the expansion of the parent blade area. As a result, it is possible to adjust the rigidity of the parent blade, and therefore it is possible to further reduce the difference with the rigidity of the child blade. The rear end of the boundary line 91 in the rotation direction can also be said to be the end of the child blade. "The rear end of the boundary line 91 in the rotation direction is located closer to the rotation axis O than the end of the child blade on the radial center side" describes the situation when the cutting edge is viewed from the tip side.

境界線９１の回転方向後方側の端部の位置の調整によって親刃部分の剛性が更に調整されることで（請求項１）、上記した子刃逃げ面４２ｂの形成状態のみでは子刃部分の剛性が親刃部分の剛性より小さくなるような場合でも、親刃部分の剛性と子刃部分の剛性との差を小さくすることが可能になる。境界線９１の回転方向後方側の端部を子刃より回転軸Ｏ寄りに位置させること（請求項１）は、境界線９１の回転方向前方側の端部が親刃逃げ面４１ｂに接続すること（請求項２）と同時になされる（並存する）場合と、独立する場合がある。 By further adjusting the position of the end portion on the rear side in the rotational direction of the boundary line 91, the rigidity of the parent blade portion can be adjusted (claim 1 ), and even in cases where the rigidity of the child blade portion is smaller than that of the parent blade portion only by the formation state of the child blade flank 42b described above, it is possible to reduce the difference in rigidity between the parent blade portion and the child blade portion. Positioning the end portion on the rear side in the rotational direction of the boundary line 91 closer to the rotation axis O than the child blade (claim 1 ) may be performed simultaneously (coexisting together) with the end portion on the front side in the rotational direction of the boundary line 91 connecting to the parent blade flank 41b (claim 2), or may be performed independently.

子刃部分の剛性と親刃部分の剛性の差を縮めることは、端的に言えば、各子刃部分の体積と親刃部分の体積が等しくなるように、または同等程度になるように、境界線８２と境界線９１の端部の位置、または境界線８２、９１の軌跡を調整（設定）すればよいことになる。親刃の切れ刃長さは子刃のそれより大きいから、親刃部分の体積と子刃部分の体積を等しくなるようにするには、切れ刃長さに応じ、相対的に親刃部分の肉厚を小さめにする一方、子刃部分の肉厚を大きめに調整すればよいことになる。この課題解決の一手法が境界線８２と境界線９１の端部位置、または軌跡の調整である（請求項１、２）。「各子刃部分」とは、切れ刃長さが同一とは限らない各子刃部分のことを言う。
To reduce the difference in rigidity between the child blade portion and the parent blade portion, simply adjust (set) the end positions of the boundary line 82 and the boundary line 91, or the locus of the boundary lines 82 and 91, so that the volume of each child blade portion is equal to or approximately equal to the volume of the parent blade portion. Since the cutting edge length of the parent blade is longer than that of the child blade, in order to make the volume of the parent blade portion equal to the volume of the child blade portion, the thickness of the parent blade portion is relatively smaller according to the cutting edge length, while the thickness of the child blade portion is relatively larger. One method for solving this problem is to adjust the end positions or locus of the boundary line 82 and the boundary line 91 (claims 1 and 2 ). "Each child blade portion" refers to each child blade portion whose cutting edge length is not necessarily the same.

子刃４２の切れ刃長さが相違する図８に示す３枚刃の例では、親刃４１の回転方向後方側のギャッシュ９、１１間の境界線９１の回転方向前方側の端部を親刃の逃げ面に接続している（請求項２）。同時に、親刃の回転方向前方側に位置する、切れ刃長さの最も小さい子刃４２の回転方向後方側のギャッシュ８、１０間の境界線８２の回転方向前方側の端部を逃げ角が最大の子刃逃げ面４２ｃの回転方向後方側に位置させている（請求項１）。 In the three-blade example shown in Figure 8, in which the cutting edge lengths of the child blades 42 are different, the front end of the boundary line 91 between the gashes 9 and 11 on the rear side of the parent blade 41 in the rotational direction is connected to the flank of the parent blade (Claim 2). At the same time, the front end of the boundary line 82 between the gashes 8 and 10 on the rear side of the child blade 42 with the shortest cutting edge length, which is located on the front side of the parent blade in the rotational direction, is positioned on the rear side of the child blade flank 42c with the largest clearance angle in the rotational direction (Claim 1).

また切れ刃長さが最小の子刃４２より切れ刃長さが大きい子刃（親刃の回転方向後方側に位置する子刃４２）の回転方向後方側のギャッシュ８、１０間の境界線８２の回転方向前方側の端部を逃げ角が最大の子刃逃げ面４２ｃの回転方向後方側の端部に接続し、境界線８２の回転方向後方側の端部を切れ刃長さが最小の子刃４２の（切れ刃）区間に接続している。 In addition, the front end of the boundary line 82 between the rear gashes 8, 10 of the child blade (child blade 42 located on the rear side of the parent blade in the rotational direction) with a cutting edge length greater than that of the child blade 42 with the smallest cutting edge length is connected to the rear end of the child blade clearance surface 42c with the largest clearance angle, and the rear end of the boundary line 82 is connected to the (cutting edge) section of the child blade 42 with the smallest cutting edge length.

いずれにしても、親刃と子刃を含め、切れ刃の枚数に関係なく、各切れ刃部分の体積が同等になるように境界線８２、９１の端部や軌跡を調整し、中心Ｏから、切れ刃の枚数に応じた複数の半径方向に、各切れ刃の長さ方向を向ければよいことになる。結果として、各切れ刃部分の体積（質量）が中心に関して回転方向に均等に分散し、質量の偏りがなくなるため、いずれかの切れ刃部分が他の切れ刃部分より振動し易くなることがなくなり、各切れ刃部分の剛性差が解消される。図８に示す３枚刃の例では隣接する切れ刃（親刃と子刃）間の中心角は１２０°である。 In any case, regardless of the number of cutting blades, including parent and child blades, the ends and trajectories of the boundaries 82, 91 can be adjusted so that the volume of each cutting blade portion is equal, and the length direction of each cutting blade can be directed in multiple radial directions from the center O according to the number of cutting blades. As a result, the volume (mass) of each cutting blade portion is evenly distributed in the rotational direction about the center, and there is no imbalance in mass, so that no cutting blade portion is more susceptible to vibration than the other cutting blade portions, and the difference in rigidity between each cutting blade portion is eliminated. In the three-blade example shown in Figure 8, the central angle between adjacent cutting blades (parent blade and child blade) is 120°.

工具本体先端部に形成された切れ刃長さが大きい親刃より相対的に切れ刃長さが小さい子刃の回転方向後方側のギャッシュを子刃先端側ギャッシュと子刃後端方側ギャッシュとに区分し、それらの境界線の回転方向前方側の端部を、子刃の、逃げ角が最大の逃げ面より回転方向後方側に位置させているため、子刃部分の肉厚を増すことができる。従って親刃部分の剛性に合わせて子刃部分の剛性を高め、調整することができる。 The gash on the rear side in the direction of rotation of the child blade, which has a relatively shorter cutting edge length than the parent blade, which is formed at the tip of the tool body, is divided into a gash on the tip side of the child blade and a gash on the rear side of the child blade, and the front end of the boundary between them in the direction of rotation is positioned rearward in the direction of rotation from the clearance face of the child blade with the maximum clearance angle, so that the thickness of the child blade portion can be increased. Therefore, the rigidity of the child blade portion can be increased and adjusted to match the rigidity of the parent blade portion.

この結果、中低勾配角が付き、切れ刃長さが異なる親刃と子刃を有しているエンドミルのように、親刃部分が被削材から受ける抵抗と、子刃部分が受ける抵抗に差があまり、あるいはほとんどない場合でも、子刃部分の剛性を調整することで、親刃と子刃との振動数差を低減することができる。 As a result, even in cases where there is little or no difference between the resistance received by the parent blade portion from the workpiece and the resistance received by the child blade portion, such as in the case of end mills that have parent and child blades with medium to low gradient angles and different cutting edge lengths, the difference in vibration frequency between the parent and child blades can be reduced by adjusting the rigidity of the child blade portion.

親刃先端側ギャッシュと親刃後方側ギャッシュとの間の境界線の回転方向前方側の端部が回転方向前方側の子刃の逃げ面より回転方向後方側に位置しているエンドミルの先端面を示した端面図である。This is an end view showing the tip surface of an end mill in which the end portion on the forward side in the rotational direction of the boundary line between the gash on the tip side of the parent blade and the gash on the rear side of the parent blade is located rearward in the rotational direction from the flank surface of the child blade on the forward side in the rotational direction. （ａ）は図１に示すエンドミルをｘ－ｘ線方向に見たときの斜視図、（ｂ）は図２に示すエンドミルの切れ刃部の回転軸Ｏを通る概略的な縦断面図である。2A is a perspective view of the end mill shown in FIG. 1 as viewed in the direction of line xx, and FIG. 2B is a schematic vertical sectional view passing through a rotation axis O of the cutting edge portion of the end mill shown in FIG. 図１に示すエンドミルをｙ－ｙ線方向に見たときの斜視図である。2 is a perspective view of the end mill shown in FIG. 1 as viewed in the y-y line direction. 親刃先端側ギャッシュと親刃後方側ギャッシュとの間の境界線の回転方向前方側の端部が回転方向前方側の子刃の逃げ面より回転方向後方側に位置している他の例のエンドミルの先端面を示した端面図である。This is an end view showing the tip surface of another example of an end mill in which the end portion on the forward side in the rotational direction of the boundary line between the gash on the tip side of the parent blade and the gash on the rear side of the parent blade is located rearward in the rotational direction from the flank surface of the child blade on the forward side in the rotational direction. 図４に示すエンドミルをｘ－ｘ線方向に見たときの斜視図である。5 is a perspective view of the end mill shown in FIG. 4 as viewed in the xx line direction. 図４に示すエンドミルをｙ－ｙ線方向に見たときの斜視図である。5 is a perspective view of the end mill shown in FIG. 4 as viewed in the y-y line direction. 本発明のエンドミルのシャンク部を含めた全体を示した側面図である。FIG. 2 is a side view showing the entire end mill including the shank portion of the end mill of the present invention. １枚の親刃と２枚の子刃を有する３枚刃のエンドミルの例の先端面を示した端面図である。FIG. 2 is an end view showing the tip surface of an example of a three-blade end mill having one parent blade and two child blades.

図１～図６はエンドミル本体の回転軸Ｏ方向の先端側に、半径方向中心側から外周側へかけて連続する親刃と、親刃にエンドミル本体の回転方向ｒに隣り合い、エンドミル本体を回転軸Ｏ方向の先端側から見たときに親刃より短い切れ刃の子刃とを有する切れ刃部２とを備えたエンドミル１の製作例を示す。各親刃と各子刃の回転方向後方側にギャッシュが形成され、エンドミル本体の回転方向ｒに隣り合う親刃と子刃との間に、各ギャッシュから回転軸Ｏ方向後端側に連続する切屑排出溝７が形成される。前記のようにエンドミル１は少なくとも、エンドミル本体を先端側から見たときに切れ刃があればよく、この切れ刃は底刃のみの場合と、コーナーＲ刃のみの場合と、底刃とコーナーＲ刃の組み合わせからなる場合がある。 Figures 1 to 6 show an example of the manufacture of an end mill 1 equipped with a cutting edge section 2 having a parent blade that is continuous from the radial center side to the outer periphery side at the tip side in the direction of the rotation axis O of the end mill body, and a child blade that is adjacent to the parent blade in the direction of rotation r of the end mill body and has a cutting edge shorter than the parent blade when viewed from the tip side of the end mill body in the direction of the rotation axis O. A gash is formed on the rear side of the rotation direction of each parent blade and each child blade, and a chip discharge groove 7 that continues from each gash to the rear end side in the direction of the rotation axis O is formed between the parent blade and child blade adjacent to each other in the direction of rotation r of the end mill body. As described above, the end mill 1 is sufficient to have at least a cutting edge when viewed from the tip side of the end mill body, and this cutting edge may be a bottom blade only, a corner R blade only, or a combination of a bottom blade and a corner R blade.

図面ではまた、図７に示すような金型の隅部の加工に適する、首下長の長い小径エンドミルの例を示しているが、本発明のエンドミル１は図７に示す形態には限られない。図１～図６は図７に示す切れ刃部２の軸方向反対側のシャンク部３を除いた切れ刃部２側の先端部分を示している。図面では特に親刃４１と子刃４２が共に、底刃とこれに連続するコーナーＲ刃５とこれに連続する外周刃６を有する場合（エンドミル１がラジアスエンドミルの場合）の例を示しているが、コーナーＲ刃５がない場合（エンドミル１がスクエアエンドミルの場合）もある。。 The drawings also show an example of a small diameter end mill with a long neck length suitable for machining the corners of a mold as shown in FIG. 7, but the end mill 1 of the present invention is not limited to the form shown in FIG. 7. FIGS. 1 to 6 show the tip portion of the cutting edge portion 2 side excluding the shank portion 3 on the axially opposite side of the cutting edge portion 2 shown in FIG. 7. The drawings particularly show an example in which the parent blade 41 and child blade 42 both have a bottom blade, a corner R blade 5 continuing thereto, and a peripheral blade 6 continuing thereto (when the end mill 1 is a radius end mill), but there are also cases in which the corner R blade 5 is not present (when the end mill 1 is a square end mill). .

（００３）
親刃４１は基本的に図１、図４、図８に示すように切れ刃部２を回転軸Ｏ方向の先端面側から見たときの半径方向中心（回転軸）Ｏ、もしくはその付近から外周側の端部まで連続する。但し、親刃４１は切れ刃部２を先端面側から見たときに相対的に子刃４２より切れ刃長さが大きければよく、必ずしも中心Ｏ付近から形成されている必要はない。切れ刃長さが親刃４１より小さい切れ刃は子刃４２になる。「回転Ｏ方向の先端面」は工具本体（エンドミル１）の先端面のことを言う。以下では「回転軸Ｏ方向」と「先端面」をそれぞれ「軸方向」と「端面」とも言う。子刃４２は親刃４１に工具本体の回転方向ｒに間隔を置き、切れ刃部２を軸方向の端面側から見たときの半径方向中心Ｏより外周寄りの位置から外周側へかけて連続する。 (003)
The parent blade 41 basically continues from the radial center (rotation axis) O or its vicinity to the end on the outer periphery side when the cutting blade portion 2 is viewed from the tip face side in the rotation axis O direction, as shown in Figs. 1, 4, and 8. However, the parent blade 41 only needs to have a cutting edge length relatively longer than the child blade 42 when the cutting blade portion 2 is viewed from the tip face side, and does not necessarily need to be formed from the vicinity of the center O. A cutting edge whose cutting edge length is shorter than the parent blade 41 becomes the child blade 42. The "tip face in the rotation O direction" refers to the tip face of the tool body (end mill 1). Hereinafter, the "rotation axis O direction" and the "tip face" are also referred to as the "axial direction" and the "end face", respectively. The child blade 42 is spaced from the parent blade 41 in the rotation direction r of the tool body, and continues from a position closer to the outer periphery than the radial center O when the cutting blade portion 2 is viewed from the end face side in the axial direction to the outer periphery side.

図１、図４に示す４枚刃の場合、親刃４１と子刃４２はそれぞれ、主に中心（回転軸）Ｏに関して対（点対称）になるように形成される。親刃４１の中心Ｏ側の部分は中心Ｏか、その付近まで連続することから、図面では工具本体の先端部を端面側から見たとき、親刃４１の逃げ面４１ｂ（以下、親刃逃げ面４１ｂ）を、中心Ｏを挟んだ側に位置する親刃逃げ面４１ｂに帯状に連続させている。この場合、中心Ｏを挟んで両側に位置する（対になる）親刃逃げ面４１ｂ、４１ｂが回転方向ｒに幅を持ったまま連続した場合、親刃４１に一定の剛性が確保される。「親刃逃げ面４１ｂ」は図面では親刃２番面である。 In the case of the four-blade tool shown in Figs. 1 and 4, the parent blade 41 and child blade 42 are formed to be paired (point symmetrical) with respect to the center (axis of rotation) O. The part of the parent blade 41 on the center O side is continuous to the center O or its vicinity, so when the tip of the tool body is viewed from the end face side in the drawing, the flank 41b of the parent blade 41 (hereinafter, parent blade flank 41b) is continuous in a strip shape with the parent blade flank 41b located on the side sandwiching the center O. In this case, if the parent blade flanks 41b, 41b located on both sides of the center O (paired) are continuous while maintaining a width in the rotation direction r, a certain rigidity is ensured for the parent blade 41. In the drawing, the "parent blade flank 41b" is the second face of the parent blade.

ギャッシュは隣り合う２つの切れ刃の逃げ面間に位置する。ギャッシュを規定する面は、隣り合う２つの切れ刃のうち回転方向後方側に位置する切れ刃のすくい面（４１ａ、４２ａ）を少なくとも含む。図１～図３はギャッシュが平面によって規定されている場合を示しており、すくい面（４１ａ、４２ａ）と、すくい面以外の面（ギャッシュ面８ａ、９ａ、１０ａ、１１ａ）との境界が明確に表れている。 The gash is located between the clearance faces of two adjacent cutting edges. The surfaces that define the gash include at least the rake face (41a, 42a) of the cutting edge that is located rearward in the direction of rotation of the two adjacent cutting edges. Figures 1 to 3 show a case where the gash is defined by a plane, and the boundary between the rake face (41a, 42a) and the surfaces other than the rake face (gash faces 8a, 9a, 10a, 11a) is clearly visible.

一方、図４～図６はギャッシュが凹曲面によって規定されている場合を示しており、一方の切れ刃から回転後方前方に向かって他方の切れ刃の逃げ面に至るまで、ギャッシュを規定する面に境界が明確に表れていない例を示している。なお、コーナーＲ刃５が形成された場合、図２、図３、図５、図６に示すようにすくい面（４１ａ、４２ａ）の半径方向外周側にコーナーＲ刃５のすくい面５ａが連続し、すくい面５ａの軸方向後端側に外周刃６のすくい面６ａが連続する。外周刃６の回転方向後方側には逃げ面（２番面）６ｂが形成される。 On the other hand, Figures 4 to 6 show cases where the gash is defined by a concave curved surface, and show examples where there is no clear boundary on the surface that defines the gash from one cutting edge toward the rear and forward of rotation to the flank of the other cutting edge. When a corner R blade 5 is formed, as shown in Figures 2, 3, 5, and 6, the rake face 5a of the corner R blade 5 continues to the radial outer side of the rake face (41a, 42a), and the rake face 6a of the peripheral blade 6 continues to the axial rear end side of the rake face 5a. A flank face (second face) 6b is formed on the rear side of the peripheral blade 6 in the rotational direction.

図２、図３、図５、図６に示すように、ギャッシュは軸方向の先端側（半径方向中心側）に位置する先端側ギャッシュ８、９と、軸方向の後端側（半径方向外周側）に位置する後端側ギャッシュ１０、１１とに区分される。図２－（ｂ）に示すように、先端側ギャッシュ８、９を規定する面と後端側ギャッシュ１０、１１を規定する面との間には、表面側（半径方向外周側）に凸の稜線となる境界線８２、９１が存在する。言い換えれば、ギャッシュ８、１０（９、１１）を、先端側ギャッシュの先端と後端側ギャッシュの後端とを通り、且つ軸方向に平行な断面で見たとき、境界線８２、９１に対応する点は、先端側ギャッシュ８、９を構成する直線の先端と、後端側ギャッシュ１０、１１を構成する直線の後端とを結んだ直線に対して、ギャッシュ側（エンドミル本体側と反対側）に位置する。 As shown in Figures 2, 3, 5, and 6, the gashes are divided into leading gashes 8, 9 located at the leading end side (radial center side) in the axial direction, and trailing gashes 10, 11 located at the trailing end side (radial outer periphery side) in the axial direction. As shown in Figure 2-(b), there are boundary lines 82, 91 that are convex ridge lines on the surface side (radial outer periphery side) between the surface that defines the leading gashes 8, 9 and the surface that defines the trailing gashes 10, 11. In other words, when the gashes 8, 10 (9, 11) are viewed in a cross section that passes through the leading end of the leading gashes and the trailing end of the trailing gashes and is parallel to the axial direction, the points corresponding to the boundary lines 82, 91 are located on the gashes side (opposite the end mill body side) with respect to the straight line that connects the leading end of the straight line that constitutes the leading gashes 8, 9 and the trailing end of the straight line that constitutes the trailing gashes 10, 11.

後端側ギャッシュ１０、１１は、先端側ギャッシュ８、９と切屑排出溝７に空間的に連続し、先端側ギャッシュ８、９を規定する面とは異なる面によって規定される。後端側ギャッシュ１０、１１は、図２、図３、図５、図６に例示するように、すくい面４１ａ、４２ａ、またはすくい面４１ａ、４２ａ、及びコーナーＲ刃５のすくい面５ａと、すくい面４１ａ、４２ａから回転方向前方に延在して切屑排出溝７に至る後端側ギャッシュ面１０ａ、１１ａとによって規定される。図２、図３は後端側ギャッシュ面１０ａ、１１ａが平面の場合を、図５、図６は後端側ギャッシュ１０ａ、１１ａが曲面の場合を示している。 The rear end gashes 10, 11 are spatially continuous with the front end gashes 8, 9 and the chip discharge groove 7, and are defined by a surface different from the surface that defines the front end gashes 8, 9. As illustrated in Figs. 2, 3, 5, and 6, the rear end gashes 10, 11 are defined by the rake faces 41a, 42a, or the rake faces 41a, 42a and the rake face 5a of the corner R blade 5, and the rear end gashes 10a, 11a that extend forward in the rotation direction from the rake faces 41a, 42a to the chip discharge groove 7. Figs. 2 and 3 show the case where the rear end gashes 10a, 11a are flat, and Figs. 5 and 6 show the case where the rear end gashes 10a, 11a are curved.

子刃４２の回転方向後方側に位置するギャッシュの内、軸方向先端側に位置する子刃先端側ギャッシュ８は、図２に示すようにギャッシュが平面によって規定されている場合、親刃すくい面４１ａと、親刃すくい面４１ａから回転方向前方に延在し、子刃逃げ面（子刃２番面４２ｂ、子刃３番面４２ｃ）に至る子刃先端側ギャッシュ面８ａとによって規定される。図５に示すように、ギャッシュが曲面によって規定されている場合も同様に、子刃先端側ギャッシュ８は、親刃すくい面４１ａと、子刃先端側ギャッシュ面８ａとによって規定されているが、親刃すくい面４１ａと子刃先端側ギャッシュ面８ａとは明確な境界線がなく、単一な面ともみなせる。子刃３番面４２ｃは子刃４２に連続するコーナーＲ刃５の逃げ面（２番面）５ｂの回転方向後方側に位置するため、コーナーＲ刃５の３番面を兼ねる。 When the gash is defined by a flat surface as shown in FIG. 2, the gash 8 at the tip of the child blade, which is located at the rear side of the rotational direction of the child blade 42, is defined by the parent blade scooping surface 41a and the child blade tip gash surface 8a that extends forward in the rotational direction from the parent blade scooping surface 41a and reaches the child blade relief surface (child blade No. 2 surface 42b, child blade No. 3 surface 42c). Similarly, when the gash is defined by a curved surface as shown in FIG. 5, the child blade tip gash 8 is defined by the parent blade scooping surface 41a and the child blade tip gash surface 8a, but there is no clear boundary between the parent blade scooping surface 41a and the child blade tip gash surface 8a, and they can be considered as a single surface. The child blade No. 3 surface 42c is located on the rear side of the relief surface (No. 2 surface) 5b of the corner R blade 5 that is continuous with the child blade 42, so it also serves as the No. 3 surface of the corner R blade 5.

親刃４１の回転方向後方側に位置するギャッシュの内、軸方向先端側に位置する親刃先端側ギャッシュ９は、図３に示すように親刃４１の回転方向後方側に位置する子刃４２のすくい面４２ａと、子刃４２ａのすくい面４２ａから回転方向前方側に向かって延在して親刃逃げ面４１ｂに至る親刃先端側ギャッシュ面９ａとによって規定される場合もあれば、図５に示すように子刃４２のすくい面４２ａを含まず、子刃の回転方向後方側に位置する子刃先端側ギャッシュ８を規定する先端側ギャッシュ面８ａに直接隣接し、その先端側ギャッシュ面８ａから回転方向前方に向かって延在する親刃先端側ギャッシュ面９ａによって規定される場合もある。親刃先端側ギャッシュ９を規定する面は、図２に示すように平面であっても、図６に示すように曲面であってもよい。 The parent blade tip gash 9 located at the axial tip side of the gash located on the rear side of the parent blade 41 in the rotation direction may be defined by the rake surface 42a of the child blade 42 located on the rear side of the parent blade 41 in the rotation direction and the parent blade tip gash surface 9a extending from the rake surface 42a of the child blade 42a toward the front side in the rotation direction to the parent blade flank surface 41b as shown in FIG. 3, or may be defined by the parent blade tip gash surface 9a that does not include the rake surface 42a of the child blade 42 and is directly adjacent to the tip gash surface 8a that defines the child blade tip gash 8 located on the rear side of the child blade in the rotation direction, and extends from the tip gash surface 8a toward the front in the rotation direction as shown in FIG. 5. The surface that defines the parent blade tip gash 9 may be a flat surface as shown in FIG. 2, or a curved surface as shown in FIG. 6.

境界線８１は子刃先端側ギャッシュ８と親刃先端側ギャッシュ９との間で、軸方向に直交する平面に対して軸方向先端側に凸の稜線をなし、境界線８１を挟んで子刃先端側ギャッシュ８側の面と親刃先端側ギャッシュ９側の面がそれぞれ子刃先端側ギャッシュ８と親刃先端側ギャッシュ９を規定する。境界線８１を挟んだ両側の面は凹面をなす。凹面は平面と曲面を含む。 The boundary line 81 forms a convex ridgeline on the axial tip side with respect to a plane perpendicular to the axial direction between the child blade tip gash 8 and the parent blade tip gash 9, and the surface on the child blade tip gash 8 side and the surface on the parent blade tip gash 9 side on either side of the boundary line 81 define the child blade tip gash 8 and the parent blade tip gash 9, respectively. The surfaces on both sides of the boundary line 81 form concave surfaces. Concave surfaces include flat and curved surfaces.

親刃先端側ギャッシュ９は親刃逃げ面４１ｂの子刃４２側の境界線４１ｃに沿って形成される。親刃先端側ギャッシュ９の領域、すなわち先端部（切れ刃部２）の端面を見たときの親刃先端側ギャッシュ９の平面積は境界線４１ｃに沿った区間の長さが大きい程、大きくなり、切屑収容能力が増す。このため、切屑収容能力を増す上では境界線４１ｃのより長い区間、例えば境界線４１ｃの全長の内、少なくとも半分以上の区間に沿って形成されることが適切である。図面では親刃先端側ギャッシュ９が境界線４１ｃの全長に沿って形成された場合、すなわち境界線４１ｃの全長が親刃逃げ面４１ｂと親刃先端側ギャッシュ９との境界線である場合の例を示している。 The parent blade tip gash 9 is formed along the boundary line 41c on the child blade 42 side of the parent blade flank 41b. The area of the parent blade tip gash 9, i.e., the end face of the tip (cutting edge portion 2), increases as the length of the section along the boundary line 41c increases, and the chip storage capacity increases. For this reason, in order to increase the chip storage capacity, it is appropriate to form the parent blade tip gash 9 along a longer section of the boundary line 41c, for example, at least half of the entire length of the boundary line 41c. The drawing shows an example in which the parent blade tip gash 9 is formed along the entire length of the boundary line 41c, i.e., the entire length of the boundary line 41c is the boundary line between the parent blade flank 41b and the parent blade tip gash 9.

前記した子刃先端側ギャッシュ８と子刃後端側ギャッシュ１０との間の境界線８２の回転方向前方側（切屑排出溝７側）の端部は、子刃４２と子刃逃げ面４２ｂを含む、厚さを有する部分の剛性を高め、または調整する目的から、子刃４２の、逃げ角が最大の逃げ面の回転方向後方側端部よりより回転方向後方側（コーナーＲ刃５側）に位置させられる。「子刃４２の、逃げ角が最大の逃げ面」は図示するように子刃逃げ面４２ｂの回転方向後方側に子刃３番面４２ｃを有する場合には、子刃３番面４２ｃを指し、子刃３番面４２ｃを有しない場合は子刃２番面４２ｂを指す。 The end of the boundary line 82 between the gash 8 on the tip side of the blade and the gash 10 on the rear side of the blade is located further rearward in the rotational direction (toward the corner R blade 5) than the rear end of the clearance surface of the blade 42 with the largest clearance angle, in order to increase or adjust the rigidity of the thick portion including the blade 42 and the clearance surface 42b. The "clearance surface of the blade 42 with the largest clearance angle" refers to the third blade surface 42c when the clearance surface 42b has the third blade surface 42c on the rear side in the rotational direction of the clearance surface 42b as shown in the figure, and refers to the second blade surface 42b when the clearance surface 42c does not have the third blade surface 42c.

子刃４２部分の「剛性を調整する」とは、子刃４２部分の剛性と親刃４１部分の剛性の差が、それぞれが被削材から受ける抵抗の差に応じて子刃４２部分の剛性を調整することを言う。子刃４２部分の剛性を高める、または調整することは、親刃４１部分の剛性との差を抑制する、あるいは剛性差に伴う振動数差を低減する意味がある。 "Adjusting the rigidity" of the child blade 42 portion means adjusting the rigidity of the child blade 42 portion in accordance with the difference in resistance that the child blade 42 portion and the parent blade 41 portion experience from the workpiece. Increasing or adjusting the rigidity of the child blade 42 portion serves to suppress the difference with the rigidity of the parent blade 41 portion, or to reduce the difference in vibration frequency that accompanies the difference in rigidity.

子刃４２部分の剛性が親刃４１部分の剛性より小さくても、子刃４２部分が被削材から受ける抵抗が、親刃４１部分が被削材から受ける抵抗より小さければ、剛性差が直接、被削材の加工面への影響が大きくなることはない。子刃４２部分と親刃４１部分の剛性差がそれぞれの抵抗差に応じた差であれば、子刃４２部分の振動数と親刃４１部分の振動数の差として明確に表れることはなく、実質的に振動数差に起因して被削材の加工面品位の低下を招くことはない。子刃４２部分の振動数が親刃４１部分の振動数より多ければ、子刃４２部分の振動が被削材の加工面を粗くし易い。 Even if the rigidity of the child blade 42 portion is less than that of the parent blade 41 portion, if the resistance that the child blade 42 portion receives from the workpiece is less than the resistance that the parent blade 41 portion receives from the workpiece, the difference in rigidity will not directly affect the machined surface of the workpiece significantly. If the difference in rigidity between the child blade 42 portion and the parent blade 41 portion corresponds to the difference in their respective resistances, it will not be clearly manifested as a difference in the vibration frequency of the child blade 42 portion and the vibration frequency of the parent blade 41 portion, and there will be no substantial decrease in the quality of the machined surface of the workpiece due to the difference in vibration frequency. If the vibration frequency of the child blade 42 portion is greater than the vibration frequency of the parent blade 41 portion, the vibration of the child blade 42 portion will tend to roughen the machined surface of the workpiece.

これに対し、図２－（ａ）に示すように子刃４２と親刃４１に中低勾配角αが付く場合、子刃４２の半径方向中心部分と同様に、親刃４１の半径方向中心部分は被削材に接触せず、接触しない部分は抵抗を受けないため、子刃４２部分の抵抗と親刃４１部分の抵抗に差が生じないか、生じにくくなる。抵抗差がないにも拘わらず、子刃４２部分の剛性が親刃４１部分の剛性より小さく、剛性差があれば、子刃４２部分の振動数と親刃４１部分の振動数に差が生じるため、被削材の加工面品位を低下させる可能性が高まる。このような場合に、子刃４２部分の剛性を増すか、親刃４１部分の剛性との差が縮まるように調整すれば、振動数差を低減することができる。 In contrast, when the child blade 42 and parent blade 41 have a medium-low gradient angle α as shown in FIG. 2-(a), the radial center portion of the parent blade 41 does not come into contact with the workpiece, as does the radial center portion of the child blade 42, and the non-contacting portion does not receive resistance, so there is no difference or it is difficult to make a difference between the resistance of the child blade 42 portion and the resistance of the parent blade 41 portion. Even if there is no difference in resistance, if the rigidity of the child blade 42 portion is smaller than the rigidity of the parent blade 41 portion and there is a rigidity difference, there will be a difference in the vibration frequency of the child blade 42 portion and the vibration frequency of the parent blade 41 portion, which increases the possibility of reducing the quality of the machined surface of the workpiece. In such a case, the vibration frequency difference can be reduced by increasing the rigidity of the child blade 42 portion or adjusting it so that the difference with the rigidity of the parent blade 41 portion is reduced.

図１、図２に示す例のように子刃先端側ギャッシュ８と子刃後端側ギャッシュ１０、または各ギャッシュ面８ａ、１０ａが平坦面（平面）であると仮定した場合、図２－（ｂ）に示すように子刃先端側ギャッシュ面８ａと回転軸Ｏとがなす鋭角の角度θ１より、子刃後端側ギャッシュ面１０ａと回転軸Ｏとがなす鋭角の角度θ２が小さくなる（θ１＜θ２）。 Assuming that the gash 8 at the tip end of the child blade and the gash 10 at the rear end of the child blade, or each gash surface 8a, 10a, are flat surfaces (planar surfaces) as in the examples shown in Figures 1 and 2, the acute angle θ2 formed by the gash surface 10a at the rear end of the child blade and the rotation axis O is smaller than the acute angle θ1 formed by the gash surface 8a at the tip end of the child blade and the rotation axis O as shown in Figure 2-(b) (θ1 < θ2).

この関係で、図１、図２、図４、図５に示す、子刃先端側ギャッシュ８と子刃後端側ギャッシュ１０との境界線８２が二点鎖線で示す位置にある場合、子刃後端側ギャッシュ１０が子刃先端側ギャッシュ８側へ入り込む形になり、子刃４２部分の肉厚（体積）が小さくなるため、子刃４２部分の剛性が小さくなり易い。この場合、親刃４１前のギャッシュは角度θ２の小さい子刃後端側ギャッシュ１０が優勢になる。それに対し、境界線８２が実線で示す位置にあれば、子刃先端側ギャッシュ８が子刃後端側ギャッシュ１０側へ張り出す形になり、二点鎖線の場合より子刃４２部分の肉厚（体積）が増すため、子刃４２部分の剛性を大きくし易い。この場合、親刃４１前のギャッシュは角度θ１の大きい子刃先端側ギャッシュ８が優勢になる。 In this relationship, when the boundary line 82 between the gash 8 on the tip side of the child blade and the gash 10 on the rear side of the child blade shown in Figures 1, 2, 4, and 5 is located at the position shown by the two-dot chain line, the gash 10 on the rear side of the child blade will intrude into the gash 8 on the tip side of the child blade, and the thickness (volume) of the child blade 42 portion will be smaller, so the rigidity of the child blade 42 portion will tend to be smaller. In this case, the gash in front of the parent blade 41 will be dominated by the gash 10 on the rear side of the child blade with a small angle θ2. On the other hand, when the boundary line 82 is located at the position shown by the solid line, the gash 8 on the tip side of the child blade will protrude toward the gash 10 on the rear side of the child blade, and the thickness (volume) of the child blade 42 portion will be larger than in the case of the two-dot chain line, so the rigidity of the child blade 42 portion will tend to be larger. In this case, the gash in front of the parent blade 41 will be dominated by the gash 8 on the tip side of the child blade with a large angle θ1.

このように境界線８２の回転方向前方側の端部が二点鎖線で示す子刃逃げ面４２ｂ、または子刃３番面４２ｃの回転方向後方側端部より回転方向後方側に位置していれば、二点鎖線の場合より子刃４２部分の剛性を大きくすることができるため、想定する剛性の大きさに応じて境界線８２の回転方向前方側の端部の位置は任意に設定（調整）される。境界線８２の回転方向後方側の端部は図示するように親刃すくい面４１ａ、またはコーナーＲ刃のすくい面５ａに交わる（接続する）。 In this way, if the end of the boundary line 82 on the front side in the direction of rotation is located further rearward in the direction of rotation than the rear end of the child blade flank surface 42b or the third child blade surface 42c shown by the two-dot chain line, the rigidity of the child blade 42 portion can be made greater than in the case of the two-dot chain line, so the position of the end of the boundary line 82 on the front side in the direction of rotation can be arbitrarily set (adjusted) depending on the expected rigidity. The end of the boundary line 82 on the rear side in the direction of rotation intersects with (connects to) the parent blade rake face 41a or the corner R blade rake face 5a as shown.

境界線８２の回転方向前方側の端部が子刃逃げ面４２ｂ、または子刃３番面４２ｃの回転方向後方側端部より回転方向後方側に位置することは、境界線８２の切屑排出溝７側の端部が、子刃逃げ面４２ｂ（子刃３番面４２ｃ）より切れ刃部２の軸方向反対側のシャンク部３側の位置で切屑排出溝７の境界線７１に交わって（接続して）いる、とも言える。境界線８２の端部が切屑排出溝７の境界線７１に交わることで、子刃後端側ギャッシュ１０の容積を小さくできることからも、子刃４２部分の剛性が向上することが言える。 The fact that the front end of the boundary line 82 in the direction of rotation is located rearward of the rear end of the child blade flank 42b or the third child blade surface 42c in the direction of rotation can also be said to mean that the end of the boundary line 82 on the chip discharge groove 7 side intersects (connects to) the boundary line 71 of the chip discharge groove 7 at a position on the shank portion 3 side, axially opposite the cutting edge portion 2, from the child blade flank 42b (third child blade surface 42c). By having the end of the boundary line 82 intersect with the boundary line 71 of the chip discharge groove 7, the volume of the gash 10 on the rear end side of the child blade can be reduced, and therefore the rigidity of the child blade 42 portion can be improved.

子刃４２部分の剛性の調整は境界線８２の親刃すくい面４１ａ側、またはすくい面５ａ側の端部の位置と、切屑排出溝７側の端部の中間区間の軌跡の描き方によっても調整される。図１～図６は境界線８２の回転方向前方側の端部が切屑排出溝７の境界線７１に交わり、回転方向後方側の端部が親刃すくい面４１ａ、またはすくい面５ａに交わっている場合の例を示している。 The rigidity of the child blade 42 can also be adjusted by changing the position of the end of the boundary line 82 on the parent blade rake face 41a side or the rake face 5a side, and the way the trajectory of the intermediate section of the end on the chip discharge groove 7 side is drawn. Figures 1 to 6 show an example in which the end of the boundary line 82 on the front side in the rotation direction intersects with the boundary line 71 of the chip discharge groove 7, and the end on the rear side in the rotation direction intersects with the parent blade rake face 41a or the rake face 5a.

子刃４２前（親刃４２後方側）のギャッシュが親刃先端側ギャッシュ９と親刃後端側ギャッシュ１１とに区分される場合、子刃４２部分の剛性に応じ、親刃４１部分の剛性を調整する上では、前記した境界線９１の回転方向後方側（子刃４２側）の端部を子刃４２の半径方向中心側の端部より半径方向中心Ｏ寄りに位置させることが適切である。境界線９１は親刃先端側ギャッシュ９と親刃後端側ギャッシュ１１との間の境界線である。 When the gash in front of the child blade 42 (rear side of the parent blade 42) is divided into the parent blade tip side gash 9 and the parent blade rear end side gash 11, in order to adjust the rigidity of the parent blade 41 portion according to the rigidity of the child blade 42 portion, it is appropriate to position the end portion on the rotational rear side (child blade 42 side) of the boundary line 91 described above closer to the radial center O than the end portion on the radial center side of the child blade 42. The boundary line 91 is the boundary line between the parent blade tip side gash 9 and the parent blade rear end side gash 11.

切れ刃部２を軸方向の端面側から見たとき、境界線９１の回転方向後方側（子刃４２側）の端部が子刃４２の半径方向中心側の端部より半径方向中心Ｏ寄りに位置する（回転軸Ｏに近い）ことで、子刃４２の半径方向外周側に位置する場合より、親刃４１部分の肉厚（体積）を抑制し、親刃４１部分の剛性の増大を抑制することができる。親刃４１部分の剛性が抑制（調整）される結果、子刃４２部分の剛性との差を縮小させることが可能になる。 When the cutting blade portion 2 is viewed from the end face side in the axial direction, the end portion on the rear side in the rotational direction (child blade 42 side) of the boundary line 91 is located closer to the radial center O (closer to the rotation axis O) than the end portion on the radial center side of the child blade 42, so that the thickness (volume) of the parent blade 41 portion can be reduced and the increase in rigidity of the parent blade 41 portion can be reduced compared to when it is located on the radial outer periphery of the child blade 42. As a result of reducing (adjusting) the rigidity of the parent blade 41 portion, it becomes possible to reduce the difference in rigidity with the child blade 42 portion.

図１～図３は図３に示すように境界線９１の子刃４２側の端部が子刃すくい面４２ａに接続し、親刃先端側ギャッシュ９が子刃すくい面４２ａによって規定（区画）されている場合の例を示している。図４～図６は図６に示すように境界線９１の子刃４２側の端部が子刃すくい面４２ａに接続せず、親刃先端側ギャッシュ９が子刃すくい面４２ａによって規定（区画）されていない場合の例を示している。この例では、境界線９１は子刃先端側ギャッシュを規定するギャッシュ面８ａと親刃先端側ギャッシュを規定するギャッシュ面９ａとの境界線８１に接続している。 Figures 1 to 3 show an example in which the end of the boundary line 91 on the child blade 42 side is connected to the child blade rake surface 42a as shown in Figure 3, and the parent blade tip side gash 9 is defined (partitioned) by the child blade rake surface 42a. Figures 4 to 6 show an example in which the end of the boundary line 91 on the child blade 42 side is not connected to the child blade rake surface 42a as shown in Figure 6, and the parent blade tip side gash 9 is not defined (partitioned) by the child blade rake surface 42a. In this example, the boundary line 91 is connected to the boundary line 81 between the gash surface 8a that defines the child blade tip side gash and the gash surface 9a that defines the parent blade tip side gash.

切れ刃部２を軸方向の端面側から見たとき、境界線９１の子刃４２側の端部が子刃４２の半径方向中心側の端部より半径方向中心Ｏ寄りに位置する（回転軸Ｏに近い）ことは、図１、図４に示すように切れ刃部２を軸方向の端面側から見たとき、境界線９１の子刃４２側の端部が、子刃先端側ギャッシュ８と親刃先端側ギャッシュ９との境界線８１に交わる、とも言える。この関係で、親刃先端側ギャッシュ９は図３、図６が示すように子刃すくい面４２ａより半径方向の中心Ｏ寄りに位置し、子刃先端側ギャッシュ８の回転方向ｒ前方側に隣接している。 When the cutting edge portion 2 is viewed from the axial end face side, the end of the boundary line 91 on the side of the child blade 42 is located closer to the radial center O (closer to the rotation axis O) than the end on the radial center side of the child blade 42. This can also be said to mean that when the cutting edge portion 2 is viewed from the axial end face side as shown in Figures 1 and 4, the end of the boundary line 91 on the side of the child blade 42 intersects with the boundary line 81 between the child blade tip gash 8 and the parent blade tip gash 9. In this relationship, the parent blade tip gash 9 is located closer to the radial center O than the child blade rake face 42a, as shown in Figures 3 and 6, and is adjacent to the front side of the child blade tip gash 8 in the rotation direction r.

この場合、親刃先端側ギャッシュ９が子刃先端側ギャッシュ８の回転方向ｒ前方側に位置することで、親刃４１が切削し、子刃先端側ギャッシュ８内に入り込んだ切屑の一部は親刃先端側ギャッシュ９内に入り（回り）込み得る状態にある。このため、子刃先端側ギャッシュ８内の切屑は子刃先端側ギャッシュ８の切屑排出溝７側に隣接する子刃後端側ギャッシュ１０と親刃先端側ギャッシュ９に分散し得る。 In this case, the parent blade tip gash 9 is located forward in the rotational direction r of the child blade tip gash 8, so that the parent blade 41 cuts and some of the chips that have entered the child blade tip gash 8 can enter (wrap around) the parent blade tip gash 9. Therefore, the chips in the child blade tip gash 8 can be dispersed to the child blade rear end gash 10 adjacent to the chip discharge groove 7 side of the child blade tip gash 8 and the parent blade tip gash 9.

親刃４１部分の剛性を調整し、または抑制し、子刃４２部分と親刃４１部分の振動数差が拡大しないようにする上ではまた、境界線９１の回転方向前方側（切屑排出溝７側）の端部を、親刃４１の回転方向後方側に隣接する逃げ面（親刃逃げ面）４１ｂ、または親刃３番面４１ｄのいずれかの部分に接続することが適切である。 In order to adjust or suppress the rigidity of the parent blade 41 portion and to prevent the difference in vibration frequency between the child blade 42 portion and the parent blade 41 portion from increasing, it is also appropriate to connect the end of the boundary line 91 on the forward side in the rotational direction (the chip discharge groove 7 side) to either the flank surface (parent blade flank surface) 41b adjacent to the rear side of the parent blade 41 in the rotational direction, or to the parent blade No. 3 surface 41d.

この場合、境界線９１の回転方向前方側の端部が親刃逃げ面４１ｂ、または親刃３番面４１ｄに接続することで、境界線９１の端部が親刃逃げ面４１ｂ、または親刃３番面４１ｄの回転方向後方側の端部より回転方向後方側に位置する場合よりは、親刃４１部分の剛性は抑えられる。その上、境界線９１の子刃４２側（回転方向後方側）の端部が子刃４２の半径方向中心側の端部より回転軸Ｏ（半径方向中心）寄りに位置している場合には、境界線９１自体の軌跡の描き方次第で、親刃４１部分の剛性の調整が可能になる。この結果、子刃４２部分と親刃４１部分の剛性差を低減し、子刃４２部分と親刃４１部分の振動数差を縮める（圧縮する）ことが可能になる。 In this case, by connecting the front end of the boundary line 91 in the rotational direction to the parent blade flank 41b or the parent blade No. 3 surface 41d, the rigidity of the parent blade 41 portion is suppressed compared to when the end of the boundary line 91 is located further rearward in the rotational direction than the end of the parent blade flank 41b or the parent blade No. 3 surface 41d in the rotational direction. Furthermore, when the end of the boundary line 91 on the child blade 42 side (rearward in the rotational direction) is located closer to the rotation axis O (radial center) than the end of the child blade 42 on the radial center side, the rigidity of the parent blade 41 portion can be adjusted depending on how the trajectory of the boundary line 91 itself is drawn. As a result, it is possible to reduce the rigidity difference between the child blade 42 portion and the parent blade 41 portion and reduce (compress) the vibration frequency difference between the child blade 42 portion and the parent blade 41 portion.

図１～図３は境界線９１の回転方向前方側の端部が、親刃３番面４１ｄと親刃先端側ギャッシュ面９ａとの境界線に交わるように境界線９１を形成した場合の例を示す。図４～図６は境界線９１の回転方向前方側の端部が親刃逃げ面４１ｂと境界線４１ｃとの交点、または境界線４１ｃと親刃３番面４１ｄとの交点に交わるように境界線９１を形成した場合の例を示す。 Figures 1 to 3 show an example where the boundary line 91 is formed so that the end on the front side in the rotational direction of the boundary line 91 intersects with the boundary line between the parent blade No. 3 surface 41d and the parent blade tip gash surface 9a. Figures 4 to 6 show an example where the boundary line 91 is formed so that the end on the front side in the rotational direction of the boundary line 91 intersects with the intersection point between the parent blade flank surface 41b and the boundary line 41c, or the intersection point between the boundary line 41c and the parent blade No. 3 surface 41d.

図８は１枚の親刃４１と２枚の子刃４２の３枚刃の切れ刃部２を形成した場合の例を示している。ここでは親刃４１の回転方向前方側の第１子刃４２の切れ刃長さが最も小さく、親刃４１の回転方向後方側の第２子刃４２の切れ刃長さは最小の第１子刃４２の切れ刃長さより大きい。この例でも、第１子刃４２の回転方向後方側に位置するギャッシュ８、１０の境界線８２の回転方向前方側の端部は、第１子刃４２の、逃げ角が最大の逃げ面である子刃３番面４２ｃの回転方向後方側端部より回転方向後方側に位置し、親刃４１の回転方向後方側に位置するギャッシュ９、１１の境界線９１の回転方向前方側の端部は、親刃逃げ面（親刃２番面４１ｂ、または親刃３番面４１ｄ）に接続している。 Figure 8 shows an example of a cutting edge portion 2 having three blades, one parent blade 41 and two child blades 42. Here, the cutting edge length of the first child blade 42 on the front side of the parent blade 41 in the rotation direction is the smallest, and the cutting edge length of the second child blade 42 on the rear side of the parent blade 41 in the rotation direction is greater than the smallest cutting edge length of the first child blade 42. Even in this example, the front end of the boundary line 82 of the gashes 8 and 10 located on the rear side of the first child blade 42 in the rotation direction is located rearward of the rear end of the child blade 3 face 42c, which is the relief face with the largest relief angle, of the first child blade 42, and the front end of the boundary line 91 of the gashes 9 and 11 located on the rear side of the parent blade 41 in the rotation direction is connected to the parent blade relief face (parent blade 2 face 41b or parent blade 3 face 41d).

このようにすることで、中低勾配角が付与され、親刃と子刃とが受ける切削抵抗に差があまりないような場合でも、親刃の剛性と子刃の剛性とを近づけ、剛性差を抑制することができる。また、工具を軸方向先端側から見たときに、境界線９１の回転方向後方側の端部が、第２子刃の回転軸Ｏ側の端部よりも、回転軸Ｏに近くなるように、境界線９１は形成されている。このような構成とすることで、親刃の剛性を抑え、子刃の剛性により近づけるように調整することが可能となる。 By doing so, even when a medium-low gradient angle is imparted and there is little difference in the cutting resistance experienced by the parent blade and the child blade, the rigidity of the parent blade and the child blade can be made closer to each other, suppressing the rigidity difference. Also, when the tool is viewed from the axial tip side, the boundary line 91 is formed so that the end on the rear side of the rotation direction of the boundary line 91 is closer to the rotation axis O than the end of the second child blade on the rotation axis O side. With this configuration, it is possible to suppress the rigidity of the parent blade and adjust it to be closer to the rigidity of the child blade.

図８では切れ刃長さが最小でない子刃４２の回転方向後方側の子刃先端側ギャッシュ８と子刃後端側ギャッシュ１０との間の境界線８２の回転方向前方側の端部を子刃３番面４２ｃの回転方向後方側端部に接続し、境界線８２の回転方向後方側の端部をその側に位置する子刃４２の区間（子刃すくい面４２ａ）に接続している。境界線８２の回転方向前方側の端部は、詳しくは子刃３番面４２ｃと子刃先端側ギャッシュ８との境界線の子刃後端側ギャッシュ１０寄りに接続し、この接続点が子刃３番面４２ｃと子刃先端側ギャッシュ面８ａと子刃後端側ギャッシュ面１０ａとの交点になっている。 In FIG. 8, the front end of the boundary line 82 between the gash 8 on the tip side of the blade 42 on the rear side in the rotational direction of the blade 42 that does not have the shortest cutting edge length and the gash 10 on the rear side of the blade is connected to the rear end of the blade 3 face 42c, and the rear end of the boundary line 82 is connected to the section of the blade 42 located on that side (the blade rake face 42a). More specifically, the front end of the boundary line 82 is connected to the boundary between the blade 3 face 42c and the gash 8 on the tip side of the blade 42 near the gash 10 on the rear side of the blade, and this connection point is the intersection of the blade 3 face 42c, the gash surface 8a on the tip side of the blade, and the gash surface 10a on the rear side of the blade.

この例では切れ刃長さが最小の子刃４２の回転方向後方側の境界線８２の回転方向前方側の端部を子刃３番面４２ｃより回転方向後方側に位置させながら、親刃４１後の境界線９１の回転方向前方側の端部を親刃逃げ面４１ｂ等に接続すると共に、境界線９１の回転方向後方側の端部を子刃４２の区間に位置させることで、切れ刃長さが最小の子刃４２部分の剛性と、親刃４１部分の剛性を同等程度に調整している。一方、切れ刃長さが最小でない子刃４２の回転方向後方側の境界線８２の回転方向前方側の端部を子刃３番面４２ｃに接続し、境界線８２の回転方向後方側の端部を子刃４２の区間に接続することで、切れ刃長さが最小でない子刃４２部分の剛性が、切れ刃長さが最小の子刃４２部分の剛性と同等程度になるように調整している。 In this example, the front end of the boundary line 82 on the rear side of the child blade 42 with the shortest cutting edge length is positioned rearward of the child blade No. 3 surface 42c in the rotational direction, while the front end of the boundary line 91 behind the parent blade 41 is connected to the parent blade relief surface 41b, etc., and the rear end of the boundary line 91 is positioned in the child blade 42 section, so that the rigidity of the child blade 42 part with the shortest cutting edge length and the rigidity of the parent blade 41 part are adjusted to be approximately equal. On the other hand, the front end of the boundary line 82 on the rear side of the child blade 42 with the non-minimum cutting edge length is connected to the child blade No. 3 surface 42c in the rotational direction, and the rear end of the boundary line 82 is connected to the child blade 42 section, so that the rigidity of the child blade 42 part with the non-minimum cutting edge length is adjusted to be approximately equal to the rigidity of the child blade 42 part with the shortest cutting edge length.

１……エンドミル（工具本体）、
２……切れ刃部、３……シャンク部、
４１……親刃、４１ａ……親刃のすくい面、４１ｂ……親刃の逃げ面（２番面）、４１ｃ……親刃４１の逃げ面４１ｂの子刃４２側の境界線、４１ｄ……親刃の３番面、
４２……子刃、４２ａ……子刃のすくい面、４２ｂ……子刃の逃げ面（２番面）、４２ｃ……子刃の３番面、
５……コーナーＲ刃、５ａ……コーナーＲ刃のすくい面、５ｂ……コーナーＲ刃の逃げ面、
６……外周刃、６ａ……外周刃のすくい面、６ｂ……外周刃の逃げ面、
７……切屑排出溝、７１……切屑排出溝７の切れ刃部２側の境界線、
８……子刃先端側ギャッシュ、８ａ……子刃先端側ギャッシュ面、８１……子刃先端側ギャッシュ８の親刃先端側ギャッシュ９寄り（子刃先端側ギャッシュ８と親刃先端側ギャッシュ９との間）の境界線、８２……子刃先端側ギャッシュ８と子刃後端側ギャッシュ１０との間の境界線、
９……親刃先端側ギャッシュ、９ａ……親刃先端側ギャッシュ面、９１……親刃先端側ギャッシュ９と親刃後端側ギャッシュ１１との間の境界線、
１０……子刃後端側ギャッシュ、１０ａ……子刃後端側ギャッシュ面、
１１……親刃後端側ギャッシュ、１１ａ……親刃後端側ギャッシュ面。 1... End mill (tool body),
2: cutting edge portion, 3: shank portion,
41: Parent blade; 41a: Rake face of parent blade; 41b: Flank face (second face) of parent blade; 41c: Boundary line of flank face 41b of parent blade 41 on the child blade 42 side; 41d: Third face of parent blade;
42: child blade, 42a: rake face of child blade, 42b: relief face (second face) of child blade, 42c: third face of child blade,
5: corner R blade; 5a: rake face of corner R blade; 5b: relief face of corner R blade;
6: peripheral cutting edge; 6a: cutting surface of peripheral cutting edge; 6b: relief surface of peripheral cutting edge;
7 ... chip discharge groove, 71 ... boundary line of the chip discharge groove 7 on the cutting edge portion 2 side,
8: gash on the tip side of the child blade; 8a: gash surface on the tip side of the child blade; 81: boundary line of the gash 8 on the tip side of the child blade near the gash 9 on the tip side of the parent blade (between the gash 8 on the tip side of the child blade and the gash 9 on the tip side of the parent blade); 82: boundary line between the gash 8 on the tip side of the child blade and the gash 10 on the rear end side of the child blade;
9: parent blade tip gash, 9a: parent blade tip gash surface, 91: boundary between parent blade tip gash 9 and parent blade rear end gash 11,
10: Rear end gash of child blade; 10a: Rear end gash surface of child blade;
11...gash on the rear end side of the parent blade, 11a...gash surface on the rear end side of the parent blade.

Claims

A parent blade is provided at the axial tip side of the end mill body, the parent blade being continuous from the radial center side to the radial outer periphery side, and a child blade is provided adjacent to the parent blade in the rotational direction of the end mill body and is shorter than the parent blade when the end mill body is viewed from the axial tip side, and a gash is formed on the rear side of each of the parent blade and the child blade in the rotational direction, and a chip discharge groove is continuous from each of the gashes to the axial rear end side,
The gash on the rear side in the rotational direction of the child blade is divided into a child blade tip side gash located on the tip side in the axial direction and a child blade rear end side gash located on the rear end side in the axial direction,
a front end of a boundary between the gash on the tip end side of the child blade and the gash on the rear end side of the child blade is located rearward in the rotational direction from a clearance face of the child blade having a maximum clearance angle ,
The gash on the rear side in the rotational direction of the parent blade is divided into a parent blade tip side gash located on the tip side in the axial direction and a parent blade rear end side gash located on the rear end side in the axial direction,
An end mill characterized in that the rear end of the boundary line between the gash at the tip end of the parent blade and the gash at the rear end of the parent blade is located closer to the center in the radial direction than the end of the child blade located rearward in the rotational direction of the parent blade .

The gash on the rear side in the rotational direction of the parent blade is divided into a parent blade tip side gash located on the tip side in the axial direction and a parent blade rear end side gash located on the rear end side in the axial direction,
The end mill according to claim 1, characterized in that a front end of the boundary between the gash on the tip side of the parent blade and the gash on the rear side of the parent blade in the rotational direction is connected to a flank surface of the parent blade.

The end mill according to claim 1 or 2, characterized in that the parent blade and the child blade extend from the tip side to the rear end side in the axial direction while moving from the radial outer periphery toward the center.