JP3835327B2

JP3835327B2 - Drill and manufacturing method thereof

Info

Publication number: JP3835327B2
Application number: JP2002089156A
Authority: JP
Inventors: 正治滝口; 雅行馬渕
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2002-03-27
Filing date: 2002-03-27
Publication date: 2006-10-18
Anticipated expiration: 2022-03-27
Also published as: JP2003285210A

Description

【０００１】
【発明の属する技術分野】
本発明は、ドリル本体の先端部外周に切屑排出溝が形成されるとともに、この切屑排出溝のドリル回転方向を向く内周面の先端に切刃が設けられ、主として金属材よりなる加工物に穴明け加工をするのに用いられるドリルに関するものである。
【０００２】
【従来の技術】
このようなドリルとしては、例えば図４に示すように軸線Ｏを中心として該軸線Ｏ回りにドリル回転方向に回転される概略円柱状のドリル本体１の後端側が工作機械の主軸に把持されるシャンク部２とされるとともに先端側は切刃部３とされ、この切刃部３の外周に一対の切屑排出溝４，４が、軸線Ｏに関して互いに対称となるように、該切刃部３の先端面、すなわちドリル本体１の先端逃げ面５から後端側に向かうに従い軸線Ｏ回りにドリル回転方向の後方側に捩れる螺旋状に形成され、これらの切屑排出溝４，４の内周面のうちドリル回転方向を向く部分の先端側の上記先端逃げ面５との交差稜線部に切刃６が形成された、いわゆる２枚刃のソリッドドリルが知られている。従って、このようなソリッドドリルでは、上記切屑排出溝４内周面のドリル回転方向を向く部分の先端側がこの切刃６のすくい面７となり、切刃６によって生成された切屑は、このすくい面７から切屑排出溝４の内周面を摺接しつつ、該切屑排出溝４の捩れによって後端側に送り出されて排出されることとなる。
【０００３】
ここで、このようなドリルにおける上記切屑排出溝４の後端部における溝底８は、該切屑排出溝４の延びる方向に沿った断面、すなわちこの切屑排出溝４が上述のように捩れている場合にはその捩れに沿った断面において、図４に示すように曲率半径の比較的小さな凹曲線状をなすように後端外周側に切れ上がって切刃部３の外周面に達するように形成され、この溝底８が切れ上がって切刃部３外周面に達した位置が当該切屑排出溝４の後端とされる。これは、このような切屑排出溝４の溝底８が、図４に示すように円板状の研削砥石Ｇをその中心軸Ｘ回りに回転させてその外周を該切屑排出溝４の内周面に摺接させつつ該研削砥石Ｇと上記ドリル本体１とを上記軸線Ｏ方向に向けて相対移動（通常は、研削砥石Ｇを固定したままドリル本体１を移動させて、図４に矢線Ａで示すように研削砥石Ｇがドリル本体１の先端逃げ面５から後端側に向かうように相対移動）させることによって形成され、切屑排出溝４の後端部では所定の位置まで切屑排出溝４が形成されたところで研削砥石Ｇの回転を止めて切屑排出溝４から抜き出すためであり、従ってこの後端部において溝底８の上記断面がなす凹曲線の曲率半径は、この研削砥石Ｇの半径ｒに略準じたものとなる。なお、切屑排出溝４が上述のように捩れている場合は、この研削砥石Ｇの外周が切屑排出溝４の捩れに沿うように該研削砥石Ｇに軸線Ｏに対して所定の振り角が与えられ、ドリル本体１をこの切屑排出溝４の捩れに合わせて軸線Ｏ回りに回転させつつ該軸線Ｏ方向に相対移動させることにより、研削を行う。
【０００４】
【発明が解決しようとする課題】
ところで、このようなソリッドのドリルによる穴明け加工では、上記切刃６の外周端９が軸線Ｏ回りになす円の直径すなわちこの切刃６の外径Ｄに対して切刃部３の長さが、５×Ｄ程度の通常のものから、近年では１０×Ｄ以上、場合によっては２０〜２５×Ｄにも及ぶ長いものが用いられるようになってきており、従来はガンドリルによって行われていた深穴の加工をこのようなソリッドドリルにより行って加工効率の向上を図ることが多くなっている。しかしながら、そのような切刃部３が長くて深穴加工を行うドリルでは、切刃６の外周端９から上記切屑排出溝４の後端まで軸線Ｏ方向の長さすなわち切屑排出溝長さＬも同じように長くなり、このため切刃６によって生成された切屑が上記切屑排出溝４を通って排出される長さも長くなって切屑詰まりを生じ易い。そして、一旦このような切屑詰まりを生じると、切刃部３の先端側では詰まった切屑によってドリル本体１の回転に対する抵抗が増大するのに対し、ドリル本体１後端側の上記シャンク部２は工作機械の主軸に把持されて回転駆動力が与えられ続けているため、これらの間の切刃部３の後端部に大きな捩りの力が作用してしまい、切屑排出溝４の溝底８が上述のように曲率半径の小さな断面凹曲線状に切れ上がっていてドリル本体１の肉厚が削がれていることとも相俟って、この切屑排出溝４の後端部分でドリル本体１が折損してしまうことが多かった。
【０００５】
本発明は、このような背景の下になされたもので、上述のような切刃部の長いドリルにおいても切屑詰まりによって折損が生じたりすることのないドリルおよびその製造方法を提供することを目的としている。
【０００６】
【課題を解決するための手段】
上記課題を解決してこのような目的を達成するために、本発明のドリルは、軸線回りに回転されるドリル本体の先端部外周に切屑排出溝が形成され、この切屑排出溝の内周面の先端側に形成されたすくい面と上記ドリル本体の先端逃げ面との交差稜線部に切刃が形成されたドリルにおいて、上記切刃の外周端から上記切屑排出溝の後端までの上記軸線方向の切屑排出溝長さＬを上記切刃の外径Ｄに対して２５×Ｄ以上とするとともに、上記切屑排出溝の溝底を、この切屑排出溝の後端から上記軸線方向先端側に向けて上記切屑排出溝長さＬのＬ／２の範囲内で後端外周側に切り上げはじめて、この切屑排出溝の延びる方向に沿った断面において曲率半径が上記切刃の外径Ｄに対し１０×Ｄ以上の凹曲線をなしてその上記後端に達するように形成したことを特徴とする。従って、このようなドリルでは、切屑排出溝の後端部における溝底が、上述のような曲率半径のきわめて大きい凹曲線状の断面をなすようにして後端外周側に切り上げられているので、この切屑排出溝の後端部においてドリル本体の肉厚が削がれる部分が小さく、すなわち心厚を大きくすることができ、これにより当該部分のドリル本体の捩れに対する剛性や強度を確保して、折損が生じるのを防ぐことができる。
【０００７】
また、このような構成のドリルを製造するために、本発明のドリルの製造方法は、軸線回りに回転されるドリル本体の先端部外周に切屑排出溝が形成され、この切屑排出溝の内周面の先端側に形成されたすくい面と上記ドリル本体の先端逃げ面との交差稜線部に切刃が形成され、上記切刃の外周端から上記切屑排出溝の後端までの上記軸線方向の切屑排出溝長さＬが上記切刃の外径Ｄに対して２０×Ｄ以上とされたドリルの製造方法であって、上述のように円板状の研削砥石を回転させてその外周を上記切屑排出溝内に摺接させつつ該研削砥石と上記ドリル本体とを上記軸線方向に向けて相対移動させることによって上記切屑排出溝の溝底を形成するとともに、切屑排出溝の後端から上記軸線方向先端側に向けて切屑排出溝長さＬのＬ／２の範囲内で、上記研削砥石を上記ドリル本体の後端外周側に該研削砥石の外径よりも大きな曲率半径の凹曲線を描いて切り上がるように相対移動させることを特徴とする。従って、このような製造方法によれば、ドリルの切屑排出溝後端部においてその溝底の断面がなす凹曲線の曲率半径を、従来の研削砥石の半径に準じた曲率半径よりも大きくすることができ、この切屑排出溝後端部におけるドリル本体の肉厚（心厚）を大きく確保することができる。
【０００８】
【発明の実施の形態】
図１ないし図３は、本発明のドリルおよびその製造方法の一実施形態を示すものである。本実施形態のドリルは、そのドリル本体１１が超硬合金等の硬質材料によって軸線Ｏを中心とした概略円柱状をなし、その先端側（図１および図３において左側）が切刃部１２とされるとともに、後端側（図１および図３において右側）はシャンク部１３とされている。そして、この切刃部１２の外周には、該ドリル本体１１先端の先端逃げ面１４から後端側に向けてシャンク部１３の直前まで、軸線Ｏ方向に後方に向かうに従いドリル回転方向Ｔの後方側に螺旋状に捩れる一対の切屑排出溝１５，１５が軸線Ｏに関して互いに対称となるように形成され、この切屑排出溝１５の内周面１６のうち先端のドリル回転方向Ｔ側を向く部分がすくい面１７とされて、このすくい面１７と上記先端逃げ面１４との交差稜線部に切刃１８が形成されている。
【０００９】
なお、この切刃部１２の長さは、本実施形態では、上記切刃１８の外周端１９が軸線Ｏ回りになす円の直径すなわち切刃１８の外径Ｄに対して少なくとも５×Ｄ以上、上述のように深穴を穴明けする場合には２０〜２５×Ｄとされており、従って切刃１８の外周端１９から切屑排出溝１５がその後端側で切れ上がって切刃部１２の外周面に達する位置すなわち切屑排出溝１５の後端２０までの軸線Ｏ方向の長さ、つまり切屑排出溝長さＬも、同じように５×Ｄ以上、あるいは１０×Ｄ以上または２０〜２５×Ｄ以上と長く設定される。さらに、ドリル本体１１内には、その後端から先端側に向けて一対の切削油剤の供給路２１，２１が、切屑排出溝１５，１５を避けるように螺旋状に形成されていて、それぞれ上記先端逃げ面１４に開口させられている。
【００１０】
また、この切刃部１２の周方向における切屑排出溝１５，１５の間の外周面には、そのドリル回転方向Ｔ側において螺旋状に捩れた切屑排出溝１５との交差稜線部に、マージン部２２が形成されている。このマージン部２２は、その外周面が上記切刃１８の外径Ｄと等しい外径の断面円弧状をなし、周方向に小さな一定幅で切刃部１２の全長に渡って切屑排出溝１５に沿うように延設されている。さらに、このマージン部２２のドリル回転方向Ｔ後方側には、該マージン部２２の上記外周面に対して一段ドリル本体１１の内周側に後退するようにして、小さな外径の断面円弧状をなす外周逃げ面２３が形成されている。なお、上記切刃１８やマージン部２２および外周逃げ面２３も、切屑排出溝１５，１５と同様に軸線Ｏに関して対称に一対ずつ形成されている。また、これらマージン部２２や外周逃げ面２３にはバックテーパが与えられていてもよい。
【００１１】
さらに、本実施形態では、上記切屑排出溝１５の溝底２４が、この切屑排出溝１５の捩れに沿ったドリル本体１１の断面において、切刃部１２先端の上記先端逃げ面１４から後端側に向けて延びる部分では軸線Ｏに平行、または後端側に向かうに従い内周側に向けて極僅かに傾斜する直線状に形成される一方、後端側のシャンク部１３の近傍では外周側に切り上げられて切刃部１２の外周面に至り上記後端２０に達するようにされている。そして、この切屑排出溝１５の溝底２４は、この切屑排出溝１５が切刃部１２の外周面に達したその後端２０から上記軸線Ｏ方向先端側に向けて上記切屑排出溝１５の長さＬのＬ／２の範囲Ｍ内で後端外周側に切り上がりはじめるようにされ、さらに図１に示すように直線状をなして後端２０に達するように形成されている。ただし、この溝底２４が後端外周側に直線状に切り上がり始める部分の断面は、極短い範囲で、この直線と先端側の軸線Ｏに平行または後端側に向かうに従い内周側に傾斜する直線とを滑らかに結ぶ凹曲線状とされている。
【００１２】
ここで、このようなドリルの切屑排出溝１５は、ドリル本体１先端側の溝底２４の断面が軸線Ｏに平行または後端側に向かうに従い内周側に僅かに傾斜した部分を形成するところまでは、従来と同様に円板状の研削砥石Ｇに切屑排出溝１５の捩れに合わせた砥石振り角を与えて回転させつつその外周部を切屑排出溝１５内に摺接させ、さらにこの切屑排出溝１５の捩れに合わせてドリル本体１１を捩りながら先端逃げ面１４側から軸線Ｏ方向後端側に向けて軸線Ｏに平行または後端側に向けて僅かに内周側に向かうようにドリル本体１と研削砥石Ｇとを図１に矢線Ｂで示すように相対移動させることにより形成される。そして、上記実施形態のドリルを製造する際の本発明の製造方法の一実施形態においては、この切屑排出溝１５の溝底２４が上記範囲Ｍ内で後端外周側に切れ上がる部分では、ドリル本体１１を捩りながら図１に実矢線Ｃで示すように研削砥石Ｇを軸線Ｏ方向後端側に相対移動させつつドリル本体１１の外周側にも相対移動させて、該研削砥石Ｇをドリル本体１１の後端外周側に直線状に切り上がるように相対移動させ、上記後端２０を経て切屑排出溝１５から抜け出るようにする。なお、このように切屑排出溝１５の後端部が切り上げられることにより、該切屑排出溝１５後端部の切刃部１２外周面への開溝部は、図４に示した従来のドリルのように研削砥石Ｇの外周部断面形状がそのまま転写されることなく、図１あるいは図３に示すように後端２０に向けて漸次先細りとなるような形状を呈することとなる。
【００１３】
従って、このような製造方法によって製造された上記実施形態のドリルでは、切屑排出溝１５の後端側の上記範囲Ｍにおいて溝底２４が、上述のように後端外周側に向けて断面直線状をなすように切り上げられているので、その後端２０の位置が同じで研削砥石Ｇの外径も同じであれば、従来のドリルと比べてこの溝底２４が切れ上がる部分の軸線Ｏから該溝底２４までの距離を大きくすることができ、これに伴いドリル本体１１の肉厚（心厚）も大きく確保してその剛性や強度の向上を図ることができる。このため、その長さが上述のように長くされた切刃部１２の先端側において切屑詰まりが生じた際に、シャンク部１３の直前のこの切屑排出溝１５の溝底２４が切れ上がる部分に大きな捩れの力が作用しても、これによってドリル本体１１がこの部分から折損してしまうのを防止することができ、ツイストドリルによる深穴の穴明け加工をより確実かつ円滑に行うことが可能となる。
【００１４】
また、このようなドリルを製造する際の上記実施形態の製造方法においては、従来と同様に研削砥石Ｇをドリル本体１１に対してその軸線Ｏ方向に相対移動させておいて、切屑排出溝１５が切れ上がる部分で上述のように後端外周側に直線状に相対移動させるだけでよく、例えばこの切れ上がり部分を異なる砥石によって形成したりするのに比べて効率的かつ容易に上述のような切屑排出溝１５を形成することができる。さらに、本実施形態によれば、この切屑排出溝１５の切り上がり部分の切刃部１２外周面への開溝部が上述のように後端２０に向けて先細り形状となるので、ドリル本体１１の周方向においてもこの後端２０近傍で切屑排出溝１５の溝幅を小さくしてその肉厚を確保することができ、この部分におけるドリル本体１１の剛性や強度の一層の向上を図って、折損等の発生をより確実に防止することが可能となる。
【００１５】
ただし、本実施形態のドリルおよびその製造方法においては、このように研削砥石Ｇを図１に矢線Ｂで示すように直線状にドリル本体１１の後端外周側に相対移動させることにより、切屑排出溝１５の溝底２４も断面直線状に切れ上がって後端２０に達するようにしているが、図１に破矢線Ｄで示すようにこの切屑排出溝１５の後端２０から軸線方向Ｏ先端側に向けて切屑排出溝長さＬのＬ／２の範囲Ｍ内で、上記研削砥石Ｇをドリル本体１１の後端外周側に該研削砥石Ｇの半径ｒよりも大きな曲率半径Ｒの凹曲線を描いて切り上がるように相対移動させることにより、この切屑排出溝１５の切れ上がり部分における断面が、その曲率半径Ｒが上記切刃１８の外径Ｄに対し１０×Ｄ以上の凹曲線状をなして後端２０に達するように形成してもよい。しかして、このようなドリルにおいても、この切屑排出溝１５の切り上がり部分におけるドリル本体１１の肉厚（心厚）を従来よりも大きく確保することができるので、当該部分におけるドリル本体１１の剛性および強度の向上を図ることができ、切屑詰まりが発生したときの折損を防止することができる。
【００１６】
なお、これらのドリルおよびその製造方法においては、切屑排出溝１５の溝底２４がドリル本体１１の後端外周側に切れ上がり始める位置を、切屑排出溝１５の後端２０から軸線方向Ｏ先端側に向けて切屑排出溝長さＬのＬ／２の範囲Ｍ内としているが、これは、この範囲Ｍよりも先端側で溝底２４が外周側に切れ上がり始めると、切屑排出溝１５の溝深さが切刃部１２の先端側で浅くなりすぎて頻繁に切屑詰まりが発生し易くなり、たとえ上記構成によってドリル本体１１の折損には至らないとしても、円滑かつ安定した穴明け加工に支障を来すおそれが生じるからである。ここで、このように先端側での切屑排出溝１５の溝深さを確実に確保するには、例えば上記切屑排出溝長さＬが１０×Ｄの場合は上記範囲Ｍが切屑排出溝１５の後端２０から軸線方向Ｏ先端側に向けて切屑排出溝長さＬのＬ／３程度に、また切屑排出溝長さＬが２０×Ｄの場合は上記範囲Ｍが後端２０から軸線方向Ｏ先端側に向けて切屑排出溝長さＬのＬ／５程度にされるのが望ましい。また、この切り上がり部分の溝底２４の断面を凹曲線状とした上記ドリルにおいて、その曲率半径Ｒが切刃１８の外径Ｄに対して１０×Ｄを下回るほど小さいと、従来の研削砥石Ｇの半径ｒに準じた曲率半径で溝底が切れ上がるドリルと変わらなくなって、確実な折損防止を図ることができなくなるおそれがある。
【００１７】
さらに、この種のドリルの切刃部１２の表面には、特にその切刃１８や先端逃げ面１４、マージン部２２等の耐摩耗性を向上させるために、該切刃部１２の全長に渡って例えばＴｉＣ、ＴｉＮ、ＴｉＣＮ、ＴｉＡｌＮの１種または複数種よりなる硬質被膜を被覆することが行われるが、このような硬質被膜の表面粗さは被覆したままの状態において２〜４μｍと比較的粗く、従ってそのような硬質被膜が切屑排出溝１５の内周面１６にも被覆されたままの状態であると、切屑排出の際の抵抗が増大してやはり切屑詰まりを生じやすくなってしまう。そこで、このような硬質被膜を切刃部１２の表面に被覆する場合には、そのうち切屑排出溝１５の内周面１６に、例えばダイヤモンド粒子を含んだペーストをブラシに塗布して該内周面１６を磨いたりすることによりポリッシュ加工を施し、これによって該内周面１６の表面粗さを、硬質被膜が被覆されたままの先端逃げ面１４やマージン部２２、あるいは外周逃げ面２３の上記表面粗さよりも小さく、すなわち滑らかにするのが望ましい。
【００１８】
【発明の効果】
以上説明したように、本発明によれば、たとえ切刃部の長さが長くて深穴を加工するような場合でも、切屑排出溝が切れ上がる部分においてドリル本体の肉厚を確保してその剛性および強度の向上を図ることができ、切屑詰まりによってこの部分に大きな捩れの力が作用してもドリル本体の折損を防止することが可能となる。
【図面の簡単な説明】
【図１】本発明のドリルおよびその製造方法の一実施形態におけるドリル本体１１の側面図と切屑排出溝１５の捩れに沿った断面図、および研削砥石Ｇの相対移動とを合わせて示した図である。
【図２】図１に示す実施形態のドリルの切刃部１２を先端側からみた拡大正面図である。
【図３】図１に示す実施形態のドリルの螺旋状に捩れた切屑排出溝１５を軸線Ｏに沿って真っ直ぐとなるように示した側面図である。
【図４】従来のドリルおよびその製造方法におけるドリル本体１の側面図と切屑排出溝４の捩れに沿った断面図、および研削砥石Ｇの相対移動とを合わせて示した図である。
【符号の説明】
１１ドリル本体
１２切刃部
１４先端逃げ面
１５切屑排出溝
１８切刃
２０切屑排出溝１５の後端
２４切屑排出溝１５の溝底
Ｏドリル本体１１の軸線
Ｔドリル回転方向
Ｄ切刃１８の外径
Ｌ切屑排出溝長さ
Ｍ切屑排出溝１５の後端２０から軸線Ｏ方向先端側に向けて切屑排出溝長さＬのＬ／２の範囲[0001]
BACKGROUND OF THE INVENTION
In the present invention, a chip discharge groove is formed on the outer periphery of the tip of the drill body, and a cutting edge is provided at the tip of the inner peripheral surface of the chip discharge groove facing the drill rotation direction. The present invention relates to a drill used for drilling.
[0002]
[Prior art]
As such a drill, for example, as shown in FIG. 4, the rear end side of a substantially cylindrical drill body 1 that is rotated around the axis O in the rotation direction of the drill is held by the spindle of the machine tool. The cutting edge portion 3 is formed as a shank portion 2 and has a cutting edge portion 3 on the tip side, and a pair of chip discharge grooves 4 and 4 are symmetric with respect to the axis O on the outer periphery of the cutting edge portion 3. Are formed in a spiral shape that twists toward the rear side in the drill rotation direction about the axis O as it goes from the front end flank 5 of the drill body 1 toward the rear end side, and the inner periphery of these chip discharge grooves 4, 4. There is known a so-called two-blade solid drill in which a cutting edge 6 is formed at an intersecting ridge line part with the tip flank 5 on the tip side of the portion facing the rotation direction of the drill. Accordingly, in such a solid drill, the tip side of the inner peripheral surface of the chip discharge groove 4 facing the drill rotation direction becomes the rake face 7 of the cutting edge 6, and the chips generated by the cutting edge 6 are the rake face. 7, while being in sliding contact with the inner peripheral surface of the chip discharge groove 4, the chip discharge groove 4 is twisted to be sent to the rear end side and discharged.
[0003]
Here, the groove bottom 8 at the rear end portion of the chip discharge groove 4 in such a drill has a cross section along the direction in which the chip discharge groove 4 extends, that is, the chip discharge groove 4 is twisted as described above. In this case, in the cross section along the twist, as shown in FIG. 4, it is formed so as to be cut up to the outer peripheral side of the rear end so as to form a concave curve shape having a relatively small radius of curvature and reach the outer peripheral surface of the cutting edge portion 3. The position where the groove bottom 8 is cut up and reaches the outer peripheral surface of the cutting edge portion 3 is the rear end of the chip discharge groove 4. This is because the groove bottom 8 of the chip discharge groove 4 rotates the disk-shaped grinding wheel G around the central axis X as shown in FIG. 4 so that the outer periphery thereof is the inner periphery of the chip discharge groove 4. The grinding wheel G and the drill body 1 are moved relative to each other in the direction of the axis O while being in sliding contact with the surface (usually, the drill body 1 is moved while the grinding wheel G is fixed, and an arrow line in FIG. As shown by A, the grinding wheel G is formed by relatively moving the grinding wheel G from the front end flank 5 of the drill body 1 toward the rear end side, and the chip discharge groove 4 reaches a predetermined position at the rear end portion of the chip discharge groove 4. This is to stop the rotation of the grinding wheel G when it is formed and extract it from the chip discharge groove 4. Accordingly, the radius of curvature of the concave curve formed by the cross-section of the groove bottom 8 at the rear end is the radius of the grinding wheel G. It is substantially in accordance with the radius r. When the chip discharge groove 4 is twisted as described above, a predetermined swing angle is given to the grinding wheel G with respect to the axis O so that the outer periphery of the grinding wheel G follows the twist of the chip discharge groove 4. Then, the drill body 1 is ground by rotating relative to the direction of the axis O while rotating around the axis O in accordance with the twist of the chip discharge groove 4.
[0004]
[Problems to be solved by the invention]
By the way, in drilling with such a solid drill, the length of the cutting edge portion 3 with respect to the diameter of the circle formed around the axis O by the outer peripheral end 9 of the cutting edge 6, that is, the outer diameter D of the cutting edge 6. However, in recent years, a long length of 10 × D or more, and in some cases as long as 20 to 25 × D has been used from a normal one of about 5 × D, which has been conventionally performed by a gun drill. The processing of deep holes is often performed with such a solid drill to improve the processing efficiency. However, in such a drill in which the cutting edge portion 3 is long and performs deep hole machining, the length in the axis O direction from the outer peripheral end 9 of the cutting edge 6 to the rear end of the chip discharge groove 4, that is, the chip discharge groove length L. Similarly, the length of the chip generated by the cutting blade 6 is increased through the chip discharge groove 4 and the chip is easily clogged. Once such chip clogging occurs, resistance to the rotation of the drill body 1 increases due to clogged chips on the front end side of the cutting edge part 3, whereas the shank part 2 on the rear end side of the drill body 1 Since the rotary drive force continues to be gripped by the main spindle of the machine tool, a large twisting force acts on the rear end portion of the cutting blade portion 3 between them, and the groove bottom 8 of the chip discharge groove 4. As mentioned above, the drill body 1 is cut off at the rear end portion of the chip discharge groove 4 in combination with the fact that the cross section is curved into a concave curve with a small radius of curvature and the thickness of the drill body 1 is cut off. Often broke.
[0005]
The present invention has been made under such a background, and an object of the present invention is to provide a drill that does not cause breakage due to clogging of chips even in a drill having a long cutting edge as described above, and an object of the present invention. It is said.
[0006]
[Means for Solving the Problems]
In order to solve the above problems and achieve such an object, in the drill of the present invention, a chip discharge groove is formed on the outer periphery of the tip of the drill body rotated about the axis, and the inner peripheral surface of the chip discharge groove In the drill in which the cutting edge is formed at the intersection ridge line portion between the rake face formed on the tip end side of the drill and the tip flank face of the drill body, the axis line from the outer peripheral end of the cutting edge to the rear end of the chip discharge groove The length L of the chip discharge groove is set to 25 × D or more with respect to the outer diameter D of the cutting blade, and the groove bottom of the chip discharge groove is moved from the rear end of the chip discharge groove to the front end side in the axial direction. the chip discharge flute first rounded up to the length rear outer circumferential side within the range of L / 2 of the L towards the radius of curvature in a cross section along the direction of extension of the chip discharge groove to the outer diameter D of the cutting edge 10 Forms a concave curve more than × D and reaches the rear end It is characterized by that. Therefore, in such a drill, the groove bottom at the rear end portion of the chip discharge groove is rounded up to the outer peripheral side of the rear end so as to form a concave curved cross section as described above, The portion where the thickness of the drill body is scraped at the rear end portion of this chip discharge groove is small, that is, the core thickness can be increased, thereby ensuring the rigidity and strength against twisting of the drill body of the portion, Breakage can be prevented from occurring.
[0007]
Further, in order to manufacture the drill having such a configuration, the drill manufacturing method of the present invention has a chip discharge groove formed on the outer periphery of the tip of the drill body rotated about the axis, and the inner periphery of the chip discharge groove. A cutting edge is formed at the intersecting ridge line portion of the rake face formed on the tip side of the surface and the tip flank face of the drill body, and the axial direction from the outer peripheral end of the cutting edge to the rear end of the chip discharge groove It is a manufacturing method of a drill in which the chip discharge groove length L is 20 × D or more with respect to the outer diameter D of the cutting blade, and the outer circumference is rotated by rotating a disc-shaped grinding wheel as described above. The grinding wheel and the drill body are moved relative to each other in the axial direction while being in sliding contact with the chip discharge groove to form the groove bottom of the chip discharge groove, and the axis line from the rear end of the chip discharge groove. L / 2 of the chip discharge groove length L toward the direction tip side In 囲内, the grinding wheel and wherein the relatively moving as up cut painted concave curve of radius of curvature larger than the outer diameter of the grinding wheel cutting 該研 the rear end outer peripheral side of the drill body. Therefore, according to such a manufacturing method, the radius of curvature of the concave curve formed by the cross section of the groove bottom at the rear end portion of the chip discharge groove of the drill is made larger than the radius of curvature according to the radius of the conventional grinding wheel. It is possible to ensure a large thickness (core thickness) of the drill body at the rear end of the chip discharge groove.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
1 to 3 show an embodiment of a drill of the present invention and a manufacturing method thereof. In the drill according to the present embodiment, the drill body 11 has a substantially cylindrical shape centered on the axis O with a hard material such as cemented carbide, and the tip side (the left side in FIGS. 1 and 3) is the cutting edge portion 12. In addition, the rear end side (the right side in FIGS. 1 and 3) is a shank portion 13. Further, on the outer periphery of the cutting edge portion 12, the drill body 11 has a rear end in the drill rotation direction T as it goes rearward in the direction of the axis O from the front end flank 14 at the front end of the drill body 11 toward the rear end side and immediately before the shank portion 13. A pair of chip discharge grooves 15, 15 that are spirally twisted on the side are formed so as to be symmetrical with respect to the axis O, and a portion of the inner peripheral surface 16 of the chip discharge groove 15 facing the drill rotation direction T side at the tip A rake face 17 is formed, and a cutting edge 18 is formed at an intersecting ridge line portion between the rake face 17 and the tip flank face 14.
[0009]
In this embodiment, the length of the cutting edge portion 12 is at least 5 × D or more with respect to the diameter of the circle formed by the outer peripheral end 19 of the cutting edge 18 around the axis O, that is, the outer diameter D of the cutting edge 18. When the deep hole is drilled as described above, it is set to 20 to 25 × D. Therefore, the chip discharge groove 15 is cut off from the outer peripheral end 19 of the cutting edge 18 on the rear end side, and the cutting edge portion 12 The position reaching the outer peripheral surface, that is, the length in the direction of the axis O to the rear end 20 of the chip discharge groove 15, that is, the chip discharge groove length L is also 5 × D or more, or 10 × D or more, or 20 to 25 ×. Longer than D. Further, in the drill body 11, a pair of cutting fluid supply paths 21, 21 are formed in a spiral shape from the rear end toward the front end side so as to avoid the chip discharge grooves 15, 15, respectively. Opened to the flank 14.
[0010]
Further, on the outer peripheral surface between the chip discharge grooves 15, 15 in the circumferential direction of the cutting edge section 12, a margin portion is formed at a cross ridge line portion with the chip discharge groove 15 spirally twisted on the drill rotation direction T side. 22 is formed. The margin portion 22 has a cross-sectional arc shape with an outer diameter equal to the outer diameter D of the cutting edge 18 and is formed in the chip discharge groove 15 over the entire length of the cutting edge portion 12 with a small constant width in the circumferential direction. It is extended along. Further, on the rear side in the drill rotation direction T of the margin portion 22, a cross-sectional arc shape with a small outer diameter is set so as to recede toward the inner peripheral side of the one-stage drill body 11 with respect to the outer peripheral surface of the margin portion 22. An outer peripheral flank 23 is formed. Note that the cutting edge 18, the margin portion 22, and the outer peripheral flank 23 are also formed in pairs symmetrically with respect to the axis O, like the chip discharge grooves 15 and 15. Further, a back taper may be given to the margin portion 22 and the outer peripheral flank 23.
[0011]
Furthermore, in the present embodiment, the groove bottom 24 of the chip discharge groove 15 is located on the rear end side from the tip flank 14 at the tip of the cutting edge 12 in the cross section of the drill body 11 along the twist of the chip discharge groove 15. In the portion extending toward the rear end side, it is formed in a straight line that is parallel to the axis O or slightly inclined toward the inner peripheral side toward the rear end side, while in the vicinity of the shank portion 13 on the rear end side on the outer peripheral side. It is rounded up to reach the outer peripheral surface of the cutting blade portion 12 and reach the rear end 20. The groove bottom 24 of the chip discharge groove 15 is the length of the chip discharge groove 15 from the rear end 20 where the chip discharge groove 15 reaches the outer peripheral surface of the cutting edge portion 12 toward the front end side in the axis O direction. Within the range M of L / 2 of L, it starts to round up toward the outer periphery of the rear end, and is formed so as to reach the rear end 20 in a straight line as shown in FIG. However, the cross section of the portion where the groove bottom 24 starts to rise linearly toward the outer peripheral side of the rear end is in an extremely short range, and is inclined parallel to the straight line and the axis O on the front end side or toward the inner peripheral side toward the rear end side. It is a concave curve that smoothly connects the straight lines.
[0012]
Here, the chip discharge groove 15 of such a drill is a place where the cross section of the groove bottom 24 on the front end side of the drill body 1 forms a portion that is slightly inclined toward the inner peripheral side in parallel with the axis O or toward the rear end side. Until then, the disk-shaped grinding wheel G is rotated by applying a grindstone swing angle in accordance with the twist of the chip discharge groove 15 to the disk-shaped grinding wheel G while rotating the outer periphery thereof into the chip discharge groove 15. Drilling so that the drill body 11 is twisted in accordance with the twist of the discharge groove 15, toward the rear end side in the direction of the axis O from the front flank 14 side, or parallel to the axis O or slightly toward the inner end toward the rear end It is formed by moving the main body 1 and the grinding wheel G relative to each other as indicated by an arrow B in FIG. And in one Embodiment of the manufacturing method of this invention at the time of manufacturing the drill of the said embodiment, in the part which the groove bottom 24 of this chip | tip discharge groove | channel 15 cuts out to the rear-end outer peripheral side within the said range M, a drill main body While twisting 11, the grinding wheel G is moved relative to the outer peripheral side of the drill body 11 while moving the grinding wheel G relative to the rear end side in the axis O direction as indicated by the solid arrow C in FIG. 11 is moved relative to the outer peripheral side of the rear end in a straight line so as to exit from the chip discharge groove 15 via the rear end 20. In addition, when the rear end portion of the chip discharge groove 15 is rounded up in this manner, the groove opening portion of the rear end portion of the chip discharge groove 15 to the outer peripheral surface of the cutting blade portion 12 is the same as that of the conventional drill shown in FIG. As shown in FIG. 1 or FIG. 3, the outer peripheral cross-sectional shape of the grinding wheel G is gradually transferred to the rear end 20 so as to gradually taper toward the rear end 20.
[0013]
Therefore, in the drill of the above-described embodiment manufactured by such a manufacturing method, the groove bottom 24 in the range M on the rear end side of the chip discharge groove 15 has a linear cross section toward the outer peripheral side of the rear end as described above. Therefore, if the position of the rear end 20 is the same and the outer diameter of the grinding wheel G is the same, the groove bottom 24 extends from the axis O where the groove bottom 24 is cut as compared with the conventional drill. The distance up to 24 can be increased, and accordingly, the wall thickness (core thickness) of the drill body 11 can be ensured and the rigidity and strength thereof can be improved. For this reason, when chip clogging occurs at the tip end side of the cutting edge portion 12 whose length is increased as described above, it is large at the portion where the groove bottom 24 of the chip discharge groove 15 immediately before the shank portion 13 rises. Even if a twisting force is applied, it is possible to prevent the drill body 11 from being broken from this portion, and the drilling of deep holes by a twist drill can be performed more reliably and smoothly. Become.
[0014]
Moreover, in the manufacturing method of the said embodiment at the time of manufacturing such a drill, the grindstone G is relatively moved with respect to the drill main body 11 in the direction of the axis O as in the prior art, and the chip discharge groove 15 is moved. As described above, it is only necessary to linearly move to the outer peripheral side of the rear end as described above. For example, the chip as described above can be efficiently and easily compared with the case where the broken portion is formed by a different grindstone. A discharge groove 15 can be formed. Furthermore, according to this embodiment, since the groove part to the cutting blade part 12 outer peripheral surface of the cutting edge part 12 of the cutting-up part of this chip discharge groove 15 becomes a taper shape toward the rear end 20 as mentioned above, the drill main body 11 In the circumferential direction, the width of the chip discharge groove 15 can be reduced in the vicinity of the rear end 20 to ensure the thickness thereof, and the rigidity and strength of the drill body 11 in this part can be further improved. Occurrence of breakage or the like can be prevented more reliably.
[0015]
However, in the drill of this embodiment and the manufacturing method thereof, the grinding wheel G is linearly moved relative to the outer peripheral side of the rear end of the drill body 11 as indicated by the arrow B in FIG. The groove bottom 24 of the discharge groove 15 is also cut into a straight section so as to reach the rear end 20. As indicated by the broken line D in FIG. 1, the axial direction O extends from the rear end 20 of the chip discharge groove 15. Within the range M of L / 2 of the chip discharge groove length L toward the tip side, the grinding wheel G is recessed on the outer peripheral side of the rear end of the drill body 11 with a radius of curvature R larger than the radius r of the grinding wheel G. By making a relative movement so as to cut and draw a curved line, the cross section at the cut-up portion of the chip discharge groove 15 has a concave curve shape with a radius of curvature R of 10 × D or more with respect to the outer diameter D of the cutting blade 18. Even if formed so as to reach the rear end 20 There. Thus, even in such a drill, the thickness (center thickness) of the drill body 11 at the cut-up portion of the chip discharge groove 15 can be ensured to be larger than that of the conventional drill, so that the rigidity of the drill body 11 at the portion is increased. In addition, the strength can be improved, and breakage when chip clogging occurs can be prevented.
[0016]
In these drills and the manufacturing method thereof, the position at which the groove bottom 24 of the chip discharge groove 15 starts to rise toward the outer peripheral side of the rear end of the drill body 11 is set to the front end side in the axial direction O from the rear end 20 of the chip discharge groove 15. In this case, the chip discharge groove length L is within a range M of L / 2. This is because when the groove bottom 24 starts to be cut toward the outer peripheral side on the tip side from the range M, the groove of the chip discharge groove 15 is formed. The depth becomes too shallow at the tip side of the cutting edge portion 12, and chip clogging is likely to occur frequently. Even if the above configuration does not cause breakage of the drill body 11, it will hinder smooth and stable drilling. This is because there is a risk of coming. Here, in order to ensure the groove depth of the chip discharge groove 15 on the tip side in this way, for example, when the chip discharge groove length L is 10 × D, the range M is equal to the chip discharge groove 15. When the chip discharge groove length L is about L / 3 from the rear end 20 toward the front end side in the axial direction O, and the chip discharge groove length L is 20 × D, the above range M is the axial direction O from the rear end 20. It is desirable to make it about L / 5 of the chip discharge groove length L toward the front end side. Further, in the above-mentioned drill in which the cross-section of the groove bottom 24 at the raised portion is a concave curve, if the curvature radius R is so small that it is less than 10 × D with respect to the outer diameter D of the cutting blade 18, a conventional grinding wheel This is not different from a drill in which the groove bottom is cut off with a radius of curvature corresponding to the radius r of G, and there is a risk that reliable breakage prevention cannot be achieved.
[0017]
Further, the surface of the cutting edge portion 12 of this type of drill is provided over the entire length of the cutting edge portion 12 in order to improve the wear resistance of the cutting edge 18, the tip flank 14, the margin portion 22 and the like. For example, a hard film made of one or more of TiC, TiN, TiCN, and TiAlN is applied. The surface roughness of such a hard film is relatively 2 to 4 μm in the as-coated state. If it is rough and therefore such a hard coating is also covered on the inner peripheral surface 16 of the chip discharge groove 15, the resistance at the time of chip discharge increases and it becomes easy to cause chip clogging. Therefore, when such a hard coating is coated on the surface of the cutting edge portion 12, a paste containing diamond particles, for example, is applied to the inner peripheral surface 16 of the chip discharge groove 15 and then the inner peripheral surface. 16 is polished so that the surface roughness of the inner peripheral surface 16 is changed to the above-described surface of the tip flank 14, the margin portion 22, or the outer peripheral flank 23 with the hard coating covered. It is desirable to make it smaller than roughness, ie smooth.
[0018]
【The invention's effect】
As explained above, according to the present invention, even when the length of the cutting edge is long and a deep hole is machined, the rigidity of the drill body is ensured by securing the thickness of the drill body at the portion where the chip discharge groove rises. The strength of the drill body can be improved, and even if a large twisting force is applied to this portion due to clogging of chips, breakage of the drill body can be prevented.
[Brief description of the drawings]
FIG. 1 is a view showing a side view of a drill body 11, a sectional view along a twist of a chip discharge groove 15, and a relative movement of a grinding wheel G in an embodiment of a drill of the present invention and a manufacturing method thereof. It is.
FIG. 2 is an enlarged front view of a cutting edge portion 12 of the drill according to the embodiment shown in FIG. 1 as viewed from the tip side.
FIG. 3 is a side view showing a spirally twisted chip discharge groove 15 of the drill of the embodiment shown in FIG. 1 so as to be straight along an axis O;
FIG. 4 is a view showing a side view of a drill body 1 in a conventional drill and a manufacturing method thereof, a cross-sectional view along twist of a chip discharge groove 4, and a relative movement of a grinding wheel G.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Drill main body 12 Cutting edge part 14 Tip flank 15 Chip discharge groove 18 Cutting edge 20 Rear end 24 of the chip discharge groove 15 Groove bottom O of the chip discharge groove 15 Drill axis 11 of drill main body 11 Drill rotation direction D Outside of the cutting blade 18 Diameter L Chip discharge groove length M Range of L / 2 of the chip discharge groove length L from the rear end 20 of the chip discharge groove 15 toward the front end side in the axis O direction

Claims

A chip discharge groove is formed on the outer periphery of the tip of the drill body rotated about the axis, and the ridge line portion between the rake face formed on the tip side of the inner peripheral surface of the chip discharge groove and the tip flank of the drill body In the drill in which the cutting edge is formed, the chip discharge groove length L in the axial direction from the outer peripheral end of the cutting edge to the rear end of the chip discharge groove is 20 × D with respect to the outer diameter D of the cutting blade. together are more, the groove bottom of the chip discharge groove, from the rear end toward the axial direction distal end side rear outer circumferential side within the range of L / 2 of the chip discharge groove length L of the chip discharge groove In the cross section along the extending direction of the chip discharge groove, the radius of curvature forms a concave curve of 10 × D or more with respect to the outer diameter D of the cutting blade and reaches the rear end thereof. And a drill.

A chip discharge groove is formed on the outer periphery of the tip of the drill body rotated about the axis, and the ridge line portion between the rake face formed on the tip side of the inner peripheral surface of the chip discharge groove and the tip flank of the drill body A cutting edge is formed, and a chip discharge groove length L in the axial direction from the outer peripheral end of the cutting edge to the rear end of the chip discharge groove is set to 20 × D or more with respect to the outer diameter D of the cutting blade. A drill manufacturing method, in which a disc-shaped grinding wheel is rotated so that the outer periphery of the grinding wheel is in sliding contact with the chip discharge groove, and the grinding wheel and the drill body are relatively moved in the axial direction. In this manner, the bottom of the chip discharge groove is formed, and the grinding wheel is moved within the range of L / 2 of the chip discharge groove length L from the rear end of the chip discharge groove toward the front end side in the axial direction. A larger radius than the outer diameter of the grinding wheel on the outer periphery of the rear end of the drill body Manufacturing method of the drill, characterized in that drawing the radius of the concave curve is relatively moved as up cut.