JP3967213B2

JP3967213B2 - Drill

Info

Publication number: JP3967213B2
Application number: JP2002193468A
Authority: JP
Inventors: 泰笹川; 浩司柾本; 淳一斉藤; 賢一谷島; 健佐藤
Original assignee: Ibiden Co Ltd; Mitsubishi Materials Corp
Current assignee: Ibiden Co Ltd; Mitsubishi Materials Corp
Priority date: 2002-07-02
Filing date: 2002-07-02
Publication date: 2007-08-29
Anticipated expiration: 2022-07-02
Also published as: JP2004034213A

Description

【０００１】
【発明の属する技術分野】
本発明は、被削材に穴明け加工を施すために用いられるドリルに関し、とくに、プリント基板や、微少な金属部品、プラスチック等の被削材に小径深穴の孔部を穴明け加工するのに用いられる小型ドリルに関するものである。
【０００２】
【従来の技術】
一般に、小型ドリルは、穿孔すべき穴がきわめて小径であり、軸線回りに回転されるドリル本体の先端側部分に例えば直径０．０１〜３．１７５ｍｍ程度の小径棒状の刃先部が設けられ、後端側部分にドリル本体を工作機械の回転軸に把持するための比較的大径のシャンク部が刃先部と一体にまたはろう付けや締まり嵌め等で接続されて設けられている。刃先部の材質は、通常、超硬合金が採用され、シャンク部は超硬合金やスチール等の鋼材が採用されている。
【０００３】
このような小型ドリルとしては、従来より、刃先部に２条の切屑排出溝が形成され、これら切屑排出溝のドリル回転方向前方側を向く壁面と刃先部の先端逃げ面との交差稜線部にそれぞれ切刃が形成された２枚刃のものがよく用いられているが、２枚刃の小型ドリルでは、その芯厚が薄くならざるを得ず、ドリル本体の剛性が小さくなって、刃先部の折損や穴曲がりによる穴位置精度の低下がとくに生じやすいという問題がある。
【０００４】
これに対し、ドリル本体の剛性を大きく確保できる小型ドリルの一例として、実開平７−３３５１４号公報に開示されているようなものがあり、このような小型ドリルは、刃先部に１条の切屑排出溝が形成されているとともに、切屑排出溝のドリル回転方向前方側を向く壁面と刃先部の先端逃げ面との交差稜線部に１つの切刃が形成されて１枚刃とされたものである。
また、刃先部の先端逃げ面は、切刃からドリル回転方向後方側に向かって、平面状をなす第１逃げ面及び第２逃げ面と、円錐面状をなすとともに先端逃げ面の半分以上を占める第３逃げ面とが周方向に沿って順次配列されることによって構成されており、これらの第１〜３逃げ面に対しては、被削材の穴明け加工の際に、この被削材と接触することがないように、十分な逃げが与えられている。
【０００５】
【発明が解決しようとする課題】
しかしながら、上記のような１枚刃の小型ドリルでは、被削材の穴明け加工の際に、この被削材に接触して切削に作用している切刃が１枚だけであるため、そのドリル本体の安定した状態を保ちづらく、ドリル本体の振れが生じて高い直進性を得ることができなくなってしまう。これにより、上記のようなドリル本体の剛性を大きく確保できる１枚刃ドリルであっても、依然として良好な穴位置精度を得ることができないのが現状であった。
【０００６】
また、昨今では、穴明け効率をより高めるため、重ねて加工する被削材の重ね枚数の増加（加工穴の深穴化）、さらには、配線密度の高密度化などによる加工穴の小径化が進んでおり、このため、穿孔する加工穴の穴径が小さく、穴深さと穴径との比が大きい小径深穴加工が増加してきている。
それゆえ、穿孔する加工穴の穴径が１ｍｍ以下、穴深さと穴径との比が５以上となるような小径深穴加工になってくると、使用する小型ドリルもその剛性を確保しづらくなっていくので、もともとドリル本体の剛性を確保しづらい上記の２枚刃ドリルでは、その剛性不足ゆえに穴位置精度のさらなる低下を招いてしまうのはもちろんのこと、上記のような１枚刃ドリルであっても、穴位置精度の低下が顕著になってしまう。
【０００７】
本発明は、上記のような課題に鑑みてなされたもので、ドリル本体の剛性を高く保つことができるとともに、良好な穴位置精度を得ることができるドリルを提供することを目的とする。
【０００８】
【課題を解決するための手段】
上記の課題を解決して、このような目的を達成するために、本発明は、軸線回りに回転されるドリル本体の先端側部分である刃先部の外周に、この刃先部の先端から後端側に向けて延びる切屑排出溝が形成され、この切屑排出溝のドリル回転方向前方側を向く壁面と前記刃先部の先端逃げ面との交差稜線部に切刃が形成されてなるドリルにおいて、前記切屑排出溝が１条のみであり、前記刃先部を前記軸線方向の先端側から見たとき、前記軸線を通って前記切刃と平行なＸ軸に前記軸線上で直交するＹ軸を挟んで、前記切刃と反対側の領域にある前記先端逃げ面部分が、周方向に沿って配列された複数の逃げ面からなる多段面状とされていて、被削材の穴明け加工の際に、前記先端逃げ面部分を構成する複数の逃げ面同士の交差稜線のうちの少なくとも１つが、前記被削材に接触することを特徴とするものである。
このような構成とされた本発明では、刃先部に設けられる切屑排出溝が１条のみであるために、刃先部に２条の切屑排出溝が設けられたドリルに比べて芯厚が厚くなって、ドリル本体の剛性を高く保つことができる。さらに、被削材の穴明け加工の際には、１枚の切刃だけでなく、上記のＹ軸を挟んで、この切刃と反対側の領域にある逃げ面同士の交差稜線が被削材に接触することになるから、ドリル本体の振れを生じさせずに安定した状態を保つことができ、ドリル本体の直進性を高めることができる。
【０００９】
また、前記被削材に接触する交差稜線の外周端と前記先端逃げ面の最先端との間の前記軸線方向での距離と、前記切刃の外周端と前記先端逃げ面の最先端との間の前記軸線方向での距離との差が、前記被削材の穴明け加工の際に前記ドリル本体に与えられる１回転当たりの送り量よりも大きく設定されていることが好ましく、このような構成とすると、穴明け加工の際に被削材と接触する交差稜線に対して、被削材との適度な接触状態を与えることが可能となる。ここで、上記の距離の差がドリル本体に与えられる１回転当たりの送り量よりも小さくなってしまうと、この交差稜線と被削材との干渉がひどくなってしまう。
【００１０】
また、とくに、被削材に穿孔する穴の穴径が１ｍｍ以下、かつ、穴深さと穴径との比が５以上とされるような小径深穴加工に用いられる小型ドリルのように、刃先部の最大外径Ｄが１ｍｍ以下、かつ、刃先部の有効刃長Ｌと刃先部の最大外径Ｄとの比Ｌ／Ｄが５以上とされていて、ドリル本体の剛性を確保しづらく、穴位置精度の低下を招きやすい場合に、本発明を有効に活用することができる。
【００１１】
【発明の実施の形態】
以下、本発明の実施形態を添付した図面を参照しながら説明する。
図１は本発明の実施形態による小型ドリルの刃先部の要部拡大側面図、図２は図１におけるＩ方向矢視図、図３は図２におけるＩＩ方向矢視図である。
【００１２】
本実施形態による小型ドリルのドリル本体は、その後端側部分が工作機械の回転軸に把持されるシャンク部とされているとともに、先端側部分が刃先部１０とされている。
この刃先部１０は、図１〜図３に示すように、軸線Ｏ回りに回転される軸線Ｏを中心とした略多段円柱状をなし、その先端側部分に位置する第１刃先部１０Ａと、第１刃先部１０Ａの外径Ｄよりも一段小さい外径を有して第１刃先部１０Ａの後端側に段差を介して連なる第２刃先部１０Ｂとから構成されている。つまり、刃先部１０は、いわゆるアンダーカットタイプとされており、この刃先部１０の最大外径Ｄは、第１刃先部１０Ａの外径Ｄ（後述するマージン部２５を円弧とする仮想の円の外径）となっている。なお、刃先部１０の最大外径Ｄは、１ｍｍ以下に設定されている。
【００１３】
そして、刃先部１０の外周には、その先端から後端側に向けて延びるようにして刃先部１０の先端逃げ面１２及び外周面に開口する１条の切屑排出溝１１が軸線Ｏを含まないように形成されており、この切屑排出溝１１は、刃先部１０の先端から後端側に向かうにしたがいドリル回転方向Ｔ後方側に向けて軸線Ｏを中心として螺旋状にねじれている。
ここで、刃先部１０における切屑排出溝１１が形成された部分の軸線Ｏ方向での長さ、すなわち、切削に使用できる刃先部１０の有効刃長Ｌは、刃先部１０の最大外径Ｄ（第１刃先部１０Ａの外径Ｄ）に対する比Ｌ／Ｄが５以上となるように設定されている。
【００１４】
また、切屑排出溝１１におけるドリル回転方向Ｔ前方側を向く壁面の先端側領域がすくい面１１Ａとされ、このすくい面１１Ａの先端縁、すなわち、すくい面１１Ａと刃先部１０の先端逃げ面１２との交差稜線部には、軸線Ｏ付近から径方向外方側へ向かって延びて、刃先部１０の外周面と交差する略直線状をなす切刃１３が形成されている。
この略直線状をなす切刃１３には、径方向外側に向かうにしたがい軸線Ｏ方向の後端側及びドリル回転方向Ｔ後方側へ向かうような傾斜が付けられていて、切刃１３が芯上がりとなるように配置されている。
【００１５】
ここで、刃先部１０の先端逃げ面１２の形状を説明するため、刃先部１０を軸線Ｏ方向の先端側から見たときについて考え、図２に示すような仮想のＸ−Ｙ軸を導入する。
このＸ−Ｙ軸は、軸線Ｏ上で互いに直交して交差することによって軸線Ｏを原点とするとともに、そのＸ軸を切刃１３と平行に位置させており、また、Ｘ軸については、Ｙ軸を挟んで切刃１３の位置している領域（図２中、右側）を正の領域とし、Ｙ軸については、Ｘ軸を挟んで切屑排出溝１１が開口している領域（図２中、上側）を正の領域としている。
【００１６】
先端逃げ面１２は、図２に示すように、複数の平坦な逃げ面から構成された多段面状をなしており、具体的には、切刃１３からドリル回転方向Ｔ後方側に向かって、平坦面である第１〜４逃げ面１４Ａ，１４Ｂ，１４Ｃ，１４Ｄが周方向に沿って順次配列されて配置され、かつ、軸線Ｏ付近に、平坦面である逆側第１逃げ面１４Ｅが配置されるとともに、この逆側第１逃げ面１４Ｅと第４逃げ面１４Ｄとのドリル回転方向Ｔ後方側に、平坦面である逆側第２逃げ面１４Ｆが配置されることによって構成されていて、合計６つの平坦面からなる多段面状をなしている。
【００１７】
第１逃げ面１４Ａは、その面上における最も軸線Ｏに近い点が軸線Ｏに一致するようにして、Ｘ，Ｙがともに正の領域内に配置されており、この第１逃げ面１４Ａのドリル回転方向Ｔ後方側には第２逃げ面１４Ｂが連なっている。
第１逃げ面１４Ａと第２逃げ面１４Ｂとの交差稜線１５は、Ｘ軸上に沿って位置し、かつ、軸線Ｏを内周端１５Ａとするとともに、この内周端１５Ａから径方向外方側へ向かって略直線状に延びて、刃先部１０の外周面に交差する点を外周端１５Ｂとしている。
【００１８】
なお、第１逃げ面１４Ａのドリル回転方向Ｔ前方側の稜線、つまり、第１逃げ面１４Ａと切屑排出溝１１におけるドリル回転方向Ｔ前方側を向く壁面の先端側領域であるすくい面１１Ａとの交差稜線をなす切刃１３は、Ｘ，Ｙがともに正の領域内でＸ軸と平行に位置し、かつ、軸線Ｏ付近を内周端１３Ａとするとともに、この内周端１３Ａから径方向外方側へ向かって略直線状に延びて、刃先部１０の外周面に交差する点を外周端１３Ｂとしている。
【００１９】
第２逃げ面１４Ｂは、その面上における最も軸線Ｏに近い点が軸線Ｏに一致するようにして、Ｘが正，Ｙが負の領域内とＸ，Ｙがともに負の領域内とに亘って配置されており、この第２逃げ面１４Ｂのドリル回転方向Ｔ後方側には第３逃げ面１４Ｃが連なっている。
第２逃げ面１４Ｂと第３逃げ面１４Ｃとの交差稜線１６は、Ｘ，Ｙがともに負の領域内に位置し、かつ、逆側第１逃げ面１４Ｅが形成されている分だけ軸線Ｏから離間した位置を内周端１６Ａとするとともに、この内周端１６Ａから径方向外方側へ向かってドリル回転方向Ｔ前方側へ傾斜しつつ略直線状に延びて、刃先部１０の外周面に交差する点を外周端１６Ｂとしている。
【００２０】
第３逃げ面１４Ｃは、Ｘ，Ｙがともに負の領域内に配置されており、この第３逃げ面１４Ｃのドリル回転方向Ｔ後方側には第４逃げ面１４Ｄが連なっている。第３逃げ面１４Ｃと第４逃げ面１４Ｄとの交差稜線１７は、Ｘ，Ｙがともに負の領域内に位置し、かつ、逆側第１逃げ面１４Ｅが形成されている分だけ軸線Ｏから離間した位置を内周端１７Ａとするとともに、この内周端１７Ａから径方向外側へ向かってドリル回転方向Ｔ前方側へ傾斜しつつ略直線状に延びて、刃先部１０の外周面に交差する点を外周端１７Ｂとしている。
【００２１】
なお、第２逃げ面１４Ｂと第３逃げ面１４Ｃとの交差稜線１６と、第３逃げ面１４Ｃと第４逃げ面１４Ｄとの交差稜線１７とを比較したとき、それらの内周端１６Ａ，１７Ａの位置（各交差稜線１６，１７上において最も軸線Ｏに近い位置）については、交差稜線１７の内周端１７Ａの方が交差稜線１６の内周端１６Ａよりも軸線Ｏから離間しており、また、径方向外方側へ向かうにしたがいドリル回転方向Ｔ前方側へ向かう傾斜は、交差稜線１７の方が交差稜線１６よりも小さくなっている。
【００２２】
第４逃げ面１４Ｄは、Ｘ，Ｙがともに負の領域内とＸが負，Ｙが正の領域内とに亘って配置されており、この第４逃げ面１４Ｄのドリル回転方向Ｔ後方側には逆側第２逃げ面１４Ｆが連なっている。
第４逃げ面１４Ｄと逆側第２逃げ面１４Ｆとの交差稜線１８は、Ｘが負，Ｙが正の領域内に位置し、かつ、逆側第１逃げ面１４Ｅが形成されている分だけ軸線Ｏから離間したＹ軸上の位置を内周端１８Ａとするとともに、この内周端１８Ａから径方向外方側へ向かってドリル回転方向Ｔ後方側へ傾斜しつつ略直線状に延びて、刃先部１０の外周面に交差する点を外周端１８Ｂとしている。
【００２３】
逆側第１逃げ面１４Ｅは、その面上における最も軸線Ｏに近い点が軸線Ｏに一致するようにして、Ｘ，Ｙがともに負の領域内で、第２〜４逃げ面１４Ｂ，１４Ｃ，１４Ｄに囲まれるようにして軸線Ｏ付近に配置されており、この逆側第１逃げ面１４Ｅのドリル回転方向Ｔ後方側には、第４逃げ面１４Ｄと同じく、逆側第２逃げ面１４Ｆが連なっている。
逆側第１逃げ面１４Ｅと逆側第２逃げ面１４Ｆとの交差稜線１９は、Ｘ軸上に沿って位置し、かつ、軸線Ｏを内周端１９Ａとするとともに、この内周端１９Ａから径方向外方側へ向かって略直線状に延びて、第４逃げ面１４Ｄと逆側第２逃げ面１４Ｆとの交差稜線１８と交差する点（＝交差稜線１８の内周端１８Ａ）を外周端１９Ｂとしている。
【００２４】
また、この逆側第１逃げ面１４Ｅは、Ｘ，Ｙがともに負の領域内において、第２〜４逃げ面１４Ｂ，１４Ｃ，１４Ｄとに囲まれて配置されているため、Ｘが負，Ｙが正の領域内に位置する逆側第２逃げ面１４Ｆとの交差稜線１９を有するだけでなく、第２逃げ面１４Ｂとの交差稜線２０、第３逃げ面１４Ｃとの交差稜線２１、第４逃げ面との交差稜線２２をも有している。
【００２５】
逆側第１逃げ面１４Ｅと第２逃げ面１４Ｂとの交差稜線２０は、Ｘ，Ｙがともに負の領域内に位置し、かつ、軸線Ｏを内周端２０Ａとするとともに、この内周端２０Ａから径方向外方側へ向かって略直線状に延びて、第２逃げ面１４Ｂと第３逃げ面１４Ｃとの交差稜線１６と交差する点（＝交差稜線１６の内周端１６Ａ）を外周端２０Ｂとしている。
【００２６】
逆側第１逃げ面１４Ｅと第３逃げ面１４Ｃとの交差稜線２１は、Ｘ，Ｙがともに負の領域内に位置し、かつ、第２逃げ面１４Ｂと第３逃げ面１４Ｃとの交差稜線１６の内周端１６Ａ（交差稜線２０の外周端２０Ｂ）と、第３逃げ面１４Ｃと第４逃げ面１４Ｄとの交差稜線１７の内周端１７Ａとを結んだＸ軸と平行な略直線とされている。
【００２７】
逆側第１逃げ面１４Ｅと第４逃げ面１４Ｄとの交差稜線２２は、Ｘ，Ｙがともに負の領域内に位置し、かつ、第３逃げ面１４Ｃと第４逃げ面１４Ｄとの交差稜線１７の内周端１７Ａと、第４逃げ面１４Ｄと逆側第２逃げ面１４Ｆとの交差稜線１８の内周端１８Ａ（逆側第１逃げ面１４Ｅと逆側第２逃げ面１４Ｆとの交差稜線１９の外周端１９Ｂ）とを結んだＹ軸と平行な略直線とされている。
【００２８】
これにより、逆側第１逃げ面１４Ｅは、互いに平行な第３逃げ面１４Ｃとの交差稜線２１及び逆側第２逃げ面１４Ｆとの交差稜線１９と、これら交差稜線２１，１９に直交して交差する第４逃げ面１４Ｄとの交差稜線２２と、交差稜線２１，１９に傾斜して交差する第２逃げ面１４Ｂとの交差稜線２０とを４つの辺とした略直角台形状（略四角形状）をなすことになる。
【００２９】
逆側第２逃げ面１４Ｆは、その面上における最も軸線Ｏに近い点が軸線Ｏに一致するようにして、Ｘが負，Ｙが正の領域内とＸ，Ｙがともに正の領域内とに亘って配置されており、この逆側第２逃げ面１４Ｆのドリル回転方向Ｔ後方側には切屑排出溝１１のドリル回転方向Ｔの前方側部分が開口させられている。
逆側第２逃げ面１４Ｆのドリル回転方向Ｔ後方側の稜線、つまり、逆側第２逃げ面１４Ｆと切屑排出溝１１におけるドリル回転方向Ｔ後方側を向く壁面との交差稜線２３は、刃先部１０の外周面と交差する点を外周端２３Ｂとしているとともに、この外周端２３Ｂから径方向内方側へ向かってドリル回転方向Ｔ前方側に凸となるように湾曲しつつ延びて、軸線Ｏ付近で切刃１３と交差する点（＝切刃１３の内周端１３Ａ）を内周端２３Ａとしている。
【００３０】
逆側第２逃げ面１４Ｆは、Ｘ，Ｙがともに正の領域内に至るようにも配置されているため、第１逃げ面１４Ａとの交差稜線２４を有しており、この交差稜線２４は、Ｘ，Ｙがともに正の領域内に位置し、かつ、軸線Ｏを内周端２４Ａとするとともに、この内周端２４Ａから径方向外方側へ向かって略直線状に延びて、切屑排出溝１１に交差する点（＝交差稜線２３の内周端２３Ａ＝切刃１３の内周端１３Ａ）を外周端２４Ｂとしている。
また、この逆側第２逃げ面１４Ｆと第１逃げ面１４Ａとの交差稜線２４と、逆側第１逃げ面１４Ｅと第２逃げ面１４Ｂとの交差稜線２０とは、軸線Ｏに関して互いに略反対側に向かって延びるように配置されている、つまり、これら交差稜線２４と交差稜線２０とが略同一直線上に配置されるようになっている。
【００３１】
先端逃げ面１２は、先端面視については、図２に示すように、第１〜４逃げ面１４Ａ，１４Ｂ，１４Ｃ，１４Ｄ及び逆側第１，２逃げ面１４Ｅ，１４Ｆからなる６つの平坦な逃げ面が上述したように配置されることによって多段面状に構成されているのであり、また、側面視については、図１及び図３に示すように、これら６つの平坦な逃げ面に対して、それぞれ軸線Ｏに近づくにしたがい軸線Ｏ方向の先端側に向かうような傾斜が付けられているとともに、これら平坦な逃げ面同士が交差してできる交差稜線にも、それぞれ軸線Ｏに近づくにしたがい（径方向内方側へ向かうにしたがい）軸線Ｏ方向の先端側へ向かうような傾斜が付けられている。
【００３２】
これにより、面上における最も軸線Ｏに近い点を軸線Ｏ上に位置させている４つの逃げ面、すなわち、第１，２逃げ面１４Ａ，１４Ｂ及び逆側第１，２逃げ面１４Ｅ，１４Ｆ同士が交差してできる１点（４つの交差稜線１５，１９，２０，２４同士が交差してできる１点＝内周端１５Ａ，１９Ａ，２０Ａ，２４Ａ）が、先端逃げ面１２において軸線Ｏ方向の最も先端側に突出した最先端とされるとともに、この最先端が軸線Ｏ上に位置させられている。
【００３３】
また、これら４つの逃げ面（第１，２逃げ面１４Ａ，１４Ｂ及び逆側第１，２逃げ面１４Ｅ，１４Ｆ）同士の交差稜線１５，１９，２０，２４のうち、軸線Ｏを挟んで互いに略反対側に位置する一対の交差稜線２０，２４に与えられた傾斜（軸線Ｏに近づくにしたがい軸線Ｏ方向の先端側に向かうような傾斜）は、互いに略同一に設定されているとともに、他の交差稜線１５，１９に与えられた傾斜よりも小さく設定されている。
このため、これら軸線Ｏ上に内周端１５Ａ，１９Ａ，２０Ａ，２４Ａを位置させている４つの交差稜線１５，１９，２０，２４のうち、一対の交差稜線２０，２４が、軸線Ｏ方向の最も先端側に位置して、所定の先端角が与えられたチゼルエッジをなすことになる。
【００３４】
また、刃先部１０の側面視について、図１及び図３に示すように、切刃１３の外周端１３Ｂと先端逃げ面１２における最先端（＝内周端１５Ａ，１９Ａ，２０Ａ，２４Ａ）との軸線Ｏ方向での距離ａと、（第１逃げ面１４Ａと第２逃げ面１４Ｂとの）交差稜線１５の外周端１５Ｂと先端逃げ面１２における最先端との軸線Ｏ方向での距離ｂとを比較すると、ａ＜ｂとなるように設定されており、切刃１３のドリル回転方向Ｔ後方側に連なる第１逃げ面１４Ａと第２逃げ面１４Ｂとには、切刃１３からドリル回転方向Ｔ後方側に向かうにしたがい順次大きくなるような逃げ角が与えられている。
なお、本実施形態においては、例えば、第１逃げ面１４Ａの逃げ角が１５゜に設定されるとともに、第２逃げ面１４Ｂの逃げ角が４０゜に設定されている。
【００３５】
さらに、刃先部１０の側面視について、図１及び図３に示すように、（第２逃げ面１４Ｂと第３逃げ面１４Ｃとの）交差稜線１６の外周端１６Ｂと先端逃げ面１２における最先端との軸線Ｏ方向での距離ｃと、（第３逃げ面１４Ｃと第４逃げ面１４Ｄとの）交差稜線１７の外周端１７Ｂと先端逃げ面１２における最先端との軸線Ｏ方向での距離ｄと、（第４逃げ面１４Ｄと逆側第２逃げ面１４Ｆとの）交差稜線１８の外周端１８Ｂと先端逃げ面１２の最先端との軸線Ｏ方向での距離ｅと、（逆側第２逃げ面１４Ｆと切屑排出溝１１におけるドリル回転方向Ｔ後方側を向く壁面との）交差稜線２３の外周端２３Ｂと先端逃げ面１２の最先端との軸線Ｏ方向での距離ｆとを比較すると、これら距離ｃ，ｄ，ｅ，ｆのうち、距離ｄが最も小さくなるように設定され、また、距離ａ，ｂを含めて比較すると、ａ＜ｂ＜ｄ＜ｃ，ｅ＜ｆとなるように設定されており、第２〜４逃げ面１４Ｂ，１４Ｃ，１４Ｄ及び逆側第２逃げ面１４Ｆには、距離ｃ，ｄ，ｅ，ｆに対応するような逃げが与えられている。
【００３６】
ここで、上記の交差稜線１６，１７，１８，２３は、軸線Ｏ方向の先端側から見たときにＸが負の領域内（Ｙ軸を挟んで切刃１３と反対側の領域内）に位置しているため、これら交差稜線１６，１７，１８，２３のうちで、先端逃げ面１２の最先端との軸線Ｏ方向での距離が最も小さい外周端１７Ｂを有する交差稜線１７が、軸線Ｏ方向の先端側から見たときのＸが負の領域内において、軸線Ｏ方向の最も先端側に位置していることになる。
【００３７】
また、刃先部１０において、切屑排出溝１１を除く外周面は、切屑排出溝１１におけるドリル回転方向Ｔ前方側を向く壁面と交差する軸線Ｏを中心とした断面略円弧状をなすマージン部２５と、このマージン部２５のドリル回転方向Ｔ後方側に連なって、切屑排出溝１１のドリル回転方向Ｔ後方側を向く壁面の外周側稜線部と交差するとともにマージン部２５がなす円弧よりも一段小さい外径を有する軸線Ｏを中心とした断面略円弧状をなす二番取り面２６とから構成されている。
これらマージン部２５と二番取り面２６とは、切屑排出溝１１と同様に、刃先部１０の先端から後端側に向かうにしたがいドリル回転方向Ｔ後方側に向けて軸線Ｏを中心として螺旋状にねじれるように形成されており、刃先部１０の有効刃長Ｌ全域に亘って形成されている。
【００３８】
なお、軸線Ｏ方向の先端側から見たときに、二番取り面２６が先端逃げ面１２に交差している部分が、Ｘが負，Ｙが正の領域内に位置しているため、上記の交差稜線１８，２３は、二番取り面２６と交差する点を外周端１８Ｂ，２３Ｂとする一方、上記の切刃１３及び交差稜線１５，１６，１７は、マージン部２５と交差する点を外周端１３Ｂ，１５Ｂ，１６Ｂ，１７Ｂとしていることになる。
【００３９】
以上のような構成とされた小型ドリルは、そのドリル本体が軸線Ｏ回りに回転されつつ、軸線Ｏ方向の先端側に向かって送りが与えられることにより、刃先部１０に形成された１枚の切刃１３で被削材を切削するとともに、この切刃１３にて生成される切屑を切屑排出溝１１に沿って刃先部１０の後端側に排出して、小径深穴の孔部を穴明け加工していく。
【００４０】
ここで、上記の交差稜線１５，１６，１７，１８，２３と先端逃げ面１２の最先端との軸線Ｏ方向での距離ｂ，ｃ，ｄ，ｅ，ｆのそれぞれと、上記の切刃１３の外周端１３Ｂと先端逃げ面１２の最先端との軸線Ｏ方向での距離ａとの差ｂ−ａ，ｃ−ａ，ｄ−ａ，ｅ−ａ，ｆ−ａについては、ドリル本体が軸線Ｏ回りに１回転するごとに、このドリル本体が軸線Ｏ方向の先端側に向かって移動させられる送り量Ｆ［μｍ／ｒｅｖ．］よりも大きくなるようにそれぞれ設定されている。
【００４１】
この穴明け加工の際には、まず、軸線Ｏ上に位置する先端逃げ面１２の最先端（内周端１５Ａ，１９Ａ，２０Ａ，２４Ａ）が最初に被削材に接触して食い付き、その後、被削材との接触箇所が、軸線Ｏから一対の交差稜線２０，２４（チゼルエッジ）に沿って径方向外方側へ延びて、最終的に、交差稜線２４の外周端２４Ｂに交差している切刃１３の内周端１３Ａから外周端１３Ｂに至るようにして、切刃１３の略全長が被削材に接触することにより、この切刃１３で被削材が切削されて穴明け加工が進行していくのである。
【００４２】
また、このとき、軸線Ｏ方向の先端側から見たときのＹ軸を挟んで切刃１３と反対側の領域（Ｘが負の領域）について、刃先部１０の先端逃げ面１２が、第２〜４逃げ面１４Ｂ，１４Ｃ，１４Ｄ及び逆側第２逃げ面１４Ｆとが周方向に沿って配列されてなる多段面状とされているとともに、これらの逃げ面同士の交差稜線１６，１７，１８のうちの１つである交差稜線１７が、軸線Ｏ方向の最も先端側に位置させられていることから、この交差稜線１７の少なくとも径方向内方側の一部分（例えば、約半分程度の長さ）が、切刃１３と同様に被削材に接触するようになっている。
【００４３】
このように、穴明け加工の際に、交差稜線１７を被削材に接触させるため、本実施形態においては、この交差稜線１７の外周端１７Ｂと先端逃げ面１２の最先端との軸線Ｏ方向での距離ｄと、切刃１３の外周端１３Ｂと先端逃げ面１２の最先端との軸線Ｏ方向での距離ａとの差ｄ−ａが、例えば、２〜２００［μｍ］の範囲に設定され、また、ドリル本体に与えられる送り量Ｆが、例えば、１〜１００［μｍ／ｒｅｖ．］に設定されている。
【００４４】
上記のような本実施形態の小型ドリルでは、その刃先部１０に設けられた切屑排出溝１１が１条のみであるために、刃先部１０の芯厚を十分に大きく確保できることとなり、２条の切屑排出溝が設けられた小型ドリルと比較して、ドリル本体の剛性を圧倒的に高く保つことが可能となり、剛性不足に起因する刃先部１０の折損や穴曲がりを抑制することができる。
【００４５】
さらに、この小型ドリルを用いて被削材に穴明け加工を施すときには、刃先部１０に形成された１枚の切刃１３だけでなく、第３逃げ面１４Ｃと第４逃げ面１４Ｄとの交差稜線１７における径方向内方側の約半分程度が、被削材に接触するようになっている。
これにより、切刃１３の位置しているＸ，Ｙがともに正の領域に対して、軸線Ｏを挟んで反対側となるＸ，Ｙがともに負の領域内に位置する交差稜線１７が、ドリル本体の振れを抑制するように被削材に接触することになり、被削材の穴明け加工中、ドリル本体の安定した状態を継続して維持することが可能となる。
【００４６】
それゆえ、本実施形態の小型ドリルでは、剛性を大きく確保できるのに加えて、ドリル本体の振れを生じさせることなく安定した状態を保ち続けることができるので、穿孔する加工穴の穴径が１ｍｍ以下、かつ、穴深さと穴径との比が５以上となるような小径深穴加工に用いられる場合のように、刃先部１０の最大外径Ｄが１ｍｍ以下、かつ、刃先部１０の有効刃長Ｌと刃先部の最大外径Ｄとの比Ｌ／Ｄとの比が５以上に設定されていたとしても、高い穴位置精度を得ることができるのである。
【００４７】
また、被削材に接触する交差稜線１７の外周端１７Ａと先端逃げ面１２の最先端との軸線Ｏ方向での距離ｄと、切刃１３の外周端１３Ｂと先端逃げ面１２の最先端との軸線Ｏ方向での距離ａとの差ｄ−ａが、穴明け加工の際にドリル本体に与えられる送り量Ｆよりも大きく設定されていることによって、この交差稜線１７と被削材との適度な接触状態を保つことが可能となっている。
逆に、上記の距離の差ｄ−ａが送り量Ｆよりも小さくなると、交差稜線１７と被削材との干渉がひどくなって、穴明け加工に支障をきたしてしまうおそれがある。
【００４８】
なお、本実施形態においては、穴明け加工の際に被削材と接触させる逃げ面同士の交差稜線を、第３逃げ面１４Ｃと第４逃げ面１４Ｄとの交差稜線１７の１つのみとしているが、これに加えて、第２逃げ面１４Ｂと第３逃げ面１４Ｃとの交差稜線１６の少なくとも径方向内方側部分を被削材と接触させるようにしてもよい。
この被削材に接触させる逃げ面同士の交差稜線については、軸線Ｏ方向の先端側から見て、Ｙ軸を挟んで切刃１３と反対側の領域内における先端逃げ面１２部分が、周方向に沿って配列された複数の逃げ面から構成されることによって、この領域内（より好ましくは、Ｘ，Ｙがともに負の領域内）に少なくとも１つ以上存在していればよい。
【００４９】
また、本実施形態においては、刃先部１０をアンダーカットタイプのもので説明しているが、これに限定されることなく、刃先部１０の外径Ｄがその先端から後端まで一定とされたストレートタイプであってもよいし、刃先部１０の外径が先端から後端側に向かうにしたがい徐々に小さくなるようなバックテーパを有していてもよい（この場合、刃先部１０の先端部分の外径が最大外径Ｄとなる）。
【００５０】
さらに、本実施形態においては、刃先部の最大外径Ｄが１ｍｍ以下、かつ、有効刃長Ｌと最大外径Ｄとの比Ｌ／Ｄが５以上となるような小型ドリルについて説明したが、この範囲に限定されることなく、これより大きい最大外径Ｄをもつドリルや、Ｌ／Ｄが５より小さいドリルにおいても本発明を適用することで上述したような効果を奏することができる。
【００５１】
【発明の効果】
本発明によれば、刃先部に設けられた切屑排出溝が１条のみであることによって、ドリル本体の剛性を高く保つことができるのに加え、被削材の穴明け加工の際には、１枚の切刃だけでなく、この切刃と略反対側の領域に位置する逃げ面同士の交差稜線まで被削材と接触させるようにしたことによって、ドリル本体の振れを生じさせずに安定した状態を継続して維持することができるので、ドリル本体の直進性を高めて良好な穴位置精度を得ることができる。
【図面の簡単な説明】
【図１】本発明の実施形態による小型ドリルの刃先部の要部拡大側面図である。
【図２】図１におけるＩ方向矢視図である。
【図３】図２におけるＩＩ方向矢視図である。
【符号の説明】
１０刃先部
１１切屑排出溝
１２先端逃げ面
１３切刃
１４Ａ第１逃げ面
１４Ｂ第２逃げ面
１４Ｃ第３逃げ面
１４Ｄ第４逃げ面
１４Ｅ逆側第１逃げ面
１４Ｆ逆側第２逃げ面
１７第３逃げ面と第４逃げ面との交差稜線
Ｏ軸線
Ｔドリル回転方向[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drill used for drilling a work material, and in particular, drilling a hole portion of a small-diameter deep hole in a work material such as a printed circuit board, a minute metal part, or plastic. It is related with the small drill used for.
[0002]
[Prior art]
Generally, in a small drill, a hole to be drilled has an extremely small diameter, and a tip end portion of a drill body rotated about an axis is provided with a small-diameter rod-like cutting edge portion having a diameter of about 0.01 to 3.175 mm, for example. A relatively large-diameter shank portion for gripping the drill body on the rotating shaft of the machine tool is provided at the end side portion integrally with the blade edge portion or connected by brazing, interference fitting or the like. Cemented carbide is usually used for the material of the blade tip, and steel such as cemented carbide or steel is used for the shank.
[0003]
As such a small-sized drill, conventionally, two chip discharge grooves are formed in the blade edge part, and the cross ridge line part between the wall surface of the chip discharge groove facing the front side in the drill rotation direction and the tip flank surface of the blade edge part is formed. A two-blade type with a cutting edge is often used, but a two-blade small drill must have a thin core, reducing the rigidity of the drill body and reducing the cutting edge. In particular, there is a problem that the hole position accuracy is liable to be lowered due to breakage or bending of the hole.
[0004]
On the other hand, as an example of a small-sized drill capable of ensuring a large rigidity of the drill body, there is one disclosed in Japanese Utility Model Publication No. 7-33514, and such a small-sized drill has a chip on the cutting edge. A discharge groove is formed, and one cutting blade is formed on the intersecting ridge line portion between the wall surface facing the front side in the drill rotation direction of the chip discharge groove and the tip flank of the blade tip portion to form a single blade. is there.
Further, the tip flank of the blade tip portion is formed into a flat first flank and second flank from the cutting blade toward the rear side in the drill rotation direction, and has a conical surface and more than half of the tip flank. The occupying third flank is arranged in order along the circumferential direction, and these first to third flank are formed by cutting the workpiece when drilling the work material. Sufficient escape is provided so that it does not come into contact with the material.
[0005]
[Problems to be solved by the invention]
However, in the single-edged small drill as described above, when the work material is drilled, there is only one cutting blade that contacts the work material and acts on the cutting. It is difficult to maintain a stable state of the drill body, and the swing of the drill body occurs, and high straightness cannot be obtained. As a result, even with a single-edged drill that can ensure the rigidity of the drill body as described above, it is still impossible to obtain good hole position accuracy.
[0006]
In recent years, in order to further improve the drilling efficiency, the number of workpieces to be stacked is increased (drilled holes), and the hole diameter is reduced by increasing the wiring density. For this reason, small-diameter deep hole machining is increasing in which the hole diameter of the drilled hole is small and the ratio of the hole depth to the hole diameter is large.
For this reason, when small-diameter deep hole machining is performed such that the hole diameter of the drilled hole is 1 mm or less and the ratio of the hole depth to the hole diameter is 5 or more, it is difficult for the small drill to be used to ensure its rigidity. Therefore, it is difficult to ensure the rigidity of the drill body. The single blade drill as described above, of course, causes a further decrease in hole position accuracy due to insufficient rigidity. Even so, the deterioration of the hole position accuracy becomes remarkable.
[0007]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a drill that can maintain high rigidity of the drill body and can obtain good hole position accuracy.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve such an object, the present invention provides an outer periphery of a cutting edge portion, which is a tip side portion of a drill body rotated around an axis, on the outer periphery from the front end of the cutting edge portion. In the drill in which a chip discharge groove extending toward the side is formed, and a cutting blade is formed in a cross ridge line portion between a wall surface facing the front side of the drill rotation direction of the chip discharge groove and the tip flank of the blade tip part, There is only one chip discharge groove, and when the cutting edge portion is viewed from the tip end side in the axial direction, the Y axis that is orthogonal to the X axis passing through the axis and parallel to the cutting blade is sandwiched. The tip flank portion in the region opposite to the cutting edge has a multi-step surface shape composed of a plurality of flank surfaces arranged along the circumferential direction, and when drilling a work material , Of the intersecting ridge lines of a plurality of flank faces constituting the tip flank face portion One even without it, and is characterized in that in contact with the workpiece.
In the present invention configured as described above, since only one chip discharge groove is provided in the cutting edge portion, the core thickness is thicker than that of a drill in which two cutting edge discharge grooves are provided in the blade edge portion. Thus, the rigidity of the drill body can be kept high. Furthermore, when drilling a work material, not only one cutting edge but also the ridge line between the flank faces in the area opposite to the cutting edge across the Y axis is cut. Since it comes into contact with the material, it is possible to maintain a stable state without causing the drill body to sway, and the straightness of the drill body can be improved.
[0009]
Further, the distance in the axial direction between the outer peripheral edge of the intersecting ridge line that contacts the work material and the leading edge of the tip flank, and the outer peripheral edge of the cutting edge and the leading edge of the tip flank It is preferable that the difference between the distance in the axial direction between them is set to be larger than the feed amount per rotation given to the drill body at the time of drilling the work material. If it comprises, it will become possible to give a moderate contact state with a work material with respect to the crossing ridgeline which contacts a work material in the case of drilling. Here, if the difference in distance becomes smaller than the feed amount per rotation given to the drill body, the interference between the intersecting ridge line and the work material becomes serious.
[0010]
In particular, the edge of a small drill used for small-diameter deep hole machining in which the hole diameter of the hole drilled in the work material is 1 mm or less and the ratio of the hole depth to the hole diameter is 5 or more is used. The maximum outer diameter D of the part is 1 mm or less, and the ratio L / D between the effective blade length L of the cutting edge part and the maximum outer diameter D of the cutting edge part is 5 or more, and it is difficult to ensure the rigidity of the drill body. The present invention can be effectively used when the hole position accuracy is likely to be lowered.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
1 is an enlarged side view of a main part of a cutting edge portion of a small drill according to an embodiment of the present invention, FIG. 2 is a view taken in the direction of arrow I in FIG. 1, and FIG. 3 is a view taken in the direction of arrow II in FIG.
[0012]
The drill main body of the small drill according to the present embodiment has a rear end portion as a shank portion that is gripped by a rotating shaft of a machine tool, and a tip end portion as a cutting edge portion 10.
As shown in FIGS. 1 to 3, the blade edge portion 10 has a substantially multi-stage columnar shape centered on the axis O rotated around the axis O, and the first blade edge portion 10 </ b> A located at the tip side portion thereof, The second cutting edge portion 10B has an outer diameter that is one step smaller than the outer diameter D of the first cutting edge portion 10A and continues to the rear end side of the first cutting edge portion 10A via a step. That is, the blade edge portion 10 is of a so-called undercut type, and the maximum outer diameter D of the blade edge portion 10 is the outer diameter D of the first blade edge portion 10A (a virtual circle whose arc is a margin portion 25 described later). Outer diameter). The maximum outer diameter D of the blade edge portion 10 is set to 1 mm or less.
[0013]
The outer periphery of the blade edge portion 10 does not include the axis O in the tip flank 12 of the blade edge portion 10 so as to extend from the front end toward the rear end side and the one chip discharge groove 11 opened to the outer peripheral surface. The chip discharge groove 11 is helically twisted about the axis O toward the rear side of the drill rotation direction T as it goes from the front end of the cutting edge portion 10 toward the rear end side.
Here, the length in the direction of the axis O of the portion where the chip discharge groove 11 is formed in the blade edge portion 10, that is, the effective blade length L of the blade edge portion 10 that can be used for cutting is the maximum outer diameter D ( The ratio L / D with respect to the outer diameter D) of the first cutting edge portion 10A is set to be 5 or more.
[0014]
Further, the tip side region of the wall surface facing the front side of the drill rotation direction T in the chip discharge groove 11 is a rake face 11A, and the tip edge of the rake face 11A, that is, the rake face 11A and the tip flank 12 of the cutting edge portion 10 A cutting edge 13 is formed in the intersecting ridge line portion, extending from the vicinity of the axis O toward the radially outward side, and forming a substantially straight shape intersecting the outer peripheral surface of the blade edge portion 10.
The cutting edge 13 having a substantially linear shape is inclined so as to go to the rear end side in the axis O direction and the rear side in the drill rotation direction T as it goes radially outward. It is arranged to become.
[0015]
Here, in order to explain the shape of the tip flank 12 of the blade tip portion 10, a case where the blade tip portion 10 is viewed from the tip end side in the axis O direction is considered, and a virtual XY axis as shown in FIG. 2 is introduced. .
The XY axes intersect with each other at right angles on the axis O, so that the axis O is the origin, and the X axis is positioned in parallel with the cutting edge 13. The region where the cutting blade 13 is located across the axis (right side in FIG. 2) is the positive region, and the Y-axis is the region where the chip discharge groove 11 is open across the X axis (in FIG. 2). , The upper side) is a positive region.
[0016]
As shown in FIG. 2, the tip flank 12 has a multi-stage surface shape composed of a plurality of flat flank surfaces. Specifically, from the cutting edge 13 toward the rear side of the drill rotation direction T, The first to fourth flank surfaces 14A, 14B, 14C, and 14D that are flat surfaces are sequentially arranged along the circumferential direction, and the reverse first flank surface 14E that is a flat surface is disposed near the axis O. The reverse side second flank 14F, which is a flat surface, is arranged on the rear side in the drill rotation direction T between the reverse side first flank 14E and the fourth flank 14D. It has a multi-step shape consisting of a total of six flat surfaces.
[0017]
The first flank 14A is disposed in a positive region so that the point closest to the axis O on the surface coincides with the axis O, and the drill of the first flank 14A is made. A second flank 14B is connected to the rear side in the rotational direction T.
The intersecting ridge line 15 between the first flank 14A and the second flank 14B is located along the X axis, and the axis O is the inner peripheral end 15A, and radially outward from the inner peripheral end 15A. A point that extends substantially linearly toward the side and intersects the outer peripheral surface of the blade edge portion 10 is defined as an outer peripheral end 15B.
[0018]
The ridge line on the front side of the drill rotation direction T of the first flank 14A, that is, the first flank 14A and the rake face 11A that is the tip side region of the wall surface facing the front side of the drill rotation direction T in the chip discharge groove 11. The cutting edge 13 that forms an intersecting ridge line is positioned parallel to the X axis in a region where both X and Y are positive, and the vicinity of the axis O is defined as an inner peripheral end 13A, and radially outward from the inner peripheral end 13A. A point extending substantially linearly toward the side and intersecting the outer peripheral surface of the blade edge portion 10 is defined as an outer peripheral end 13B.
[0019]
The second flank 14B extends so that the point closest to the axis O on the surface coincides with the axis O so that X is positive and Y is negative and X and Y are both negative. The third flank 14C is continuous with the second flank 14B on the rear side in the drill rotation direction T.
The intersecting ridge line 16 between the second flank 14B and the third flank 14C is located from the axis O by the amount that both X and Y are located in the negative region and the opposite first flank 14E is formed. The spaced apart position is defined as an inner peripheral end 16A, and extends substantially linearly from the inner peripheral end 16A while inclining toward the front side in the drill rotation direction T toward the radially outer side. The intersecting point is the outer peripheral end 16B.
[0020]
The third flank 14C is disposed in a region where both X and Y are negative, and the fourth flank 14D is continuous to the rear side of the third flank 14C in the drill rotation direction T. The intersecting ridge line 17 between the third flank 14C and the fourth flank 14D is from the axis O by the amount that the X and Y are both in the negative region and the opposite first flank 14E is formed. The spaced apart position is defined as an inner peripheral end 17A, and extends substantially linearly from the inner peripheral end 17A toward the front side in the drill rotation direction T toward the radially outer side, and intersects the outer peripheral surface of the cutting edge portion 10. The point is the outer peripheral end 17B.
[0021]
When the intersecting ridgeline 16 between the second flank 14B and the third flank 14C and the intersecting ridgeline 17 between the third flank 14C and the fourth flank 14D are compared, their inner peripheral ends 16A and 17A. (The position closest to the axis O on each intersecting ridgeline 16, 17), the inner peripheral end 17A of the intersecting ridgeline 17 is more distant from the axis O than the inner peripheral end 16A of the intersecting ridgeline 16, Further, the inclination toward the front side of the drill rotation direction T as it goes outward in the radial direction is such that the intersecting ridge line 17 is smaller than the intersecting ridge line 16.
[0022]
The fourth flank 14D is disposed over a region where X and Y are both negative and within a region where X is negative and Y is positive. The second flank 14F on the opposite side is continuous.
The intersecting ridge line 18 between the fourth flank 14D and the reverse second flank 14F is located in the region where X is negative and Y is positive, and the reverse first flank 14E is formed. The position on the Y-axis that is separated from the axis O is the inner peripheral end 18A, and extends substantially linearly while tilting from the inner peripheral end 18A toward the radially outer side toward the drill rotation direction T rear side. A point that intersects the outer peripheral surface of the blade edge portion 10 is defined as an outer peripheral end 18B.
[0023]
The reverse first flank 14E is arranged such that the point closest to the axis O on the surface coincides with the axis O, and the second and fourth flank 14B, 14C, 14D is arranged in the vicinity of the axis O so as to be surrounded by 14D. On the rear side in the drill rotation direction T of the reverse side first flank 14E, the reverse side second flank 14F is the same as the fourth flank 14D. It is lined up.
The intersecting ridge line 19 between the reverse first flank 14E and the reverse second flank 14F is located along the X axis, and the axis O is the inner peripheral edge 19A. It extends substantially linearly outward in the radial direction and intersects with the intersection ridge line 18 between the fourth flank 14D and the opposite second flank 14F (= the inner peripheral edge 18A of the intersection ridge line 18) End 19B.
[0024]
The reverse first flank 14E is disposed in the region where both X and Y are negative and surrounded by the second to fourth flank 14B, 14C and 14D. Not only has a cross ridge line 19 with the second second flank 14F located in the positive region, but also has a cross ridge line 20 with the second flank 14B, a cross ridge line 21 with the third flank 14C, and the fourth It also has an intersection ridgeline 22 with the flank.
[0025]
The intersecting ridge line 20 between the reverse first flank 14E and the second flank 14B is located in a region where both X and Y are negative, and the axis O is the inner peripheral edge 20A. Extending from 20A to the radially outward side in a substantially straight line and intersecting the intersection ridgeline 16 of the second flank 14B and the third flank 14C (= the inner peripheral edge 16A of the intersection ridgeline 16) The end 20B is used.
[0026]
The intersection ridge line 21 between the reverse first flank 14E and the third flank 14C is located in a region where both X and Y are negative, and the intersection ridge line between the second flank 14B and the third flank 14C. A substantially straight line parallel to the X axis connecting the inner peripheral end 16A of 16 (the outer peripheral end 20B of the intersecting ridge line 20) and the inner peripheral end 17A of the intersecting ridge line 17 between the third flank 14C and the fourth flank 14D. Has been.
[0027]
The intersection ridgeline 22 between the reverse first flank 14E and the fourth flank 14D is located in a region where both X and Y are negative, and the intersection ridgeline between the third flank 14C and the fourth flank 14D. 17A, the inner peripheral end 18A of the intersecting ridge line 18 between the fourth flank 14D and the reverse second flank 14F (intersection of the reverse first flank 14E and the reverse second flank 14F) It is a substantially straight line parallel to the Y axis connecting the outer peripheral edge 19B) of the ridge line 19.
[0028]
Thereby, the reverse first flank 14E intersects the cross ridge line 21 with the third flank 14C parallel to each other and the cross ridge line 19 with the reverse second flank 14F, and is orthogonal to the cross ridge lines 21 and 19. A substantially right trapezoidal shape (substantially rectangular shape) having four sides of an intersecting ridgeline 22 with the intersecting fourth flank 14D and an intersecting ridgeline 20 with the second flank 14B inclined and intersecting the intersecting ridgelines 21 and 19 ).
[0029]
The opposite second flank 14F is such that the point closest to the axis O on the surface coincides with the axis O, so that X is negative and Y is positive and both X and Y are positive. The front side portion of the chip discharge groove 11 in the drill rotation direction T is opened on the rear side of the reverse rotation side T of the reverse second flank 14F.
The ridge line on the rear side of the drill rotation direction T of the reverse second flank 14F, that is, the cross ridge line 23 between the reverse side second flank 14F and the wall surface facing the rear side of the drill rotation direction T in the chip discharge groove 11 is the cutting edge portion. A point intersecting with the outer peripheral surface 10 is an outer peripheral end 23B, and extends from the outer peripheral end 23B toward the radially inner side while curving so as to protrude forward in the drill rotation direction T, and near the axis O The point that intersects the cutting edge 13 (= the inner peripheral end 13A of the cutting edge 13) is taken as the inner peripheral end 23A.
[0030]
Since the reverse second flank 14F is also arranged so that both X and Y reach the positive region, the second flank 14F has a cross ridge line 24 with the first flank 14A. , X and Y are both located in the positive region, and the axis O is set as the inner peripheral end 24A, and extends substantially linearly from the inner peripheral end 24A toward the radially outer side. A point intersecting the groove 11 (= inner peripheral end 23A of the crossing ridge line 23 = inner peripheral end 13A of the cutting edge 13) is defined as an outer peripheral end 24B.
Further, the intersecting ridgeline 24 between the reverse second flank 14F and the first flank 14A and the intersecting ridgeline 20 between the reverse first flank 14E and the second flank 14B are substantially opposite to each other with respect to the axis O. It is arranged so as to extend toward the side, that is, the intersecting ridge line 24 and the intersecting ridge line 20 are arranged on substantially the same straight line.
[0031]
As shown in FIG. 2, the tip flank 12 has six flat surfaces including first to fourth flank surfaces 14A, 14B, 14C, 14D and opposite first and second flank surfaces 14E, 14F. The flank is configured as a multi-stage surface by being arranged as described above, and the side view is shown in FIGS. 1 and 3 with respect to these six flat flank surfaces. As the axis O approaches the axis O, an inclination is given toward the tip side in the direction of the axis O, and the intersecting ridge lines formed by the intersection of these flat flank surfaces also each approach the axis O ( Inclined toward the tip end in the direction of the axis O) as it goes inward in the radial direction.
[0032]
As a result, four flank surfaces that are located on the axis line O closest to the axis line O, that is, the first and second flank surfaces 14A and 14B and the opposite first and second flank surfaces 14E and 14F 1 point formed by intersecting (1 point formed by intersecting four intersecting ridge lines 15, 19, 20, 24 = inner peripheral ends 15A, 19A, 20A, 24A) in the direction of the axis O on the tip flank 12 The cutting edge is projected to the most distal end side, and the cutting edge is positioned on the axis O.
[0033]
Of these four flank surfaces (the first and second flank surfaces 14A and 14B and the opposite first and second flank surfaces 14E and 14F), the crossed ridgelines 15, 19, 20, and 24 sandwich each other across the axis O. The inclinations given to the pair of intersecting ridge lines 20 and 24 located on the substantially opposite sides (inclinations toward the tip side in the direction of the axis O as they approach the axis O) are set to be substantially the same as each other. Is set smaller than the inclination given to the intersection ridgelines 15 and 19.
For this reason, among the four intersecting ridgelines 15, 19, 20, and 24 in which the inner peripheral ends 15A, 19A, 20A, and 24A are positioned on these axes O, the pair of intersecting ridgelines 20, 24 are in the direction of the axis O. The chisel edge which is located on the most distal end side and has a predetermined distal end angle is formed.
[0034]
Moreover, about the side view of the blade edge | tip part 10, as shown in FIG.1 and FIG.3, the outer peripheral end 13B of the cutting blade 13 and the most advanced (= inner peripheral end 15A, 19A, 20A, 24A) in the front end flank 12 are shown. A distance a in the direction of the axis O, and a distance b in the direction of the axis O between the outer peripheral end 15B of the intersecting ridge line 15 (the first flank 14A and the second flank 14B) and the tip of the tip flank 12 In comparison, a <b is set, and the first flank 14 </ b> A and the second flank 14 </ b> B connected to the rear side of the drill rotation direction T of the cutting edge 13 are connected to the drill rotation direction T from the cutting edge 13. A clearance angle is given which gradually increases as it goes backward.
In the present embodiment, for example, the clearance angle of the first clearance surface 14A is set to 15 °, and the clearance angle of the second clearance surface 14B is set to 40 °.
[0035]
Further, as shown in FIG. 1 and FIG. 3, the cutting edge portion 10 has a front end at the outer peripheral end 16B and the tip flank 12 of the intersecting ridge line 16 (the second flank 14B and the third flank 14C) as shown in FIGS. The distance c in the direction of the axis O and the distance d in the direction of the axis O between the outer peripheral end 17B of the intersecting ridge line 17 (the third flank 14C and the fourth flank 14D) and the tip of the tip flank 12 And the distance e in the direction of the axis O between the outer peripheral end 18B of the intersecting ridge line 18 (the fourth flank 14D and the reverse second flank 14F) and the tip of the front flank 12 (the second reverse flank 14F). Comparing the distance f in the axis O direction between the outer peripheral end 23B of the intersecting ridge line 23 and the tip of the tip flank 12 (with the flank 14F and the wall facing the drill rotation direction T in the chip discharge groove 11) Of these distances c, d, e, and f, the distance d is the smallest. In addition, when the comparison is made including the distances a and b, a <b <d <c and e <f are set, and the second to fourth flank surfaces 14B, 14C and 14D and the reverse side are set. The second relief surface 14F is provided with relief corresponding to the distances c, d, e, and f.
[0036]
Here, the intersecting ridge lines 16, 17, 18, 23 are within a region where X is negative when viewed from the front end side in the direction of the axis O (in a region opposite to the cutting edge 13 across the Y axis). Therefore, the intersecting ridge line 17 having the outer peripheral end 17B having the smallest distance in the direction of the axis O from the tip of the tip flank 12 among these intersecting ridge lines 16, 17, 18, and 23 is the axis O. When viewed from the front end side in the direction, X is located closest to the front end side in the direction of the axis O in the negative region.
[0037]
Further, in the cutting edge part 10, the outer peripheral surface excluding the chip discharge groove 11 has a margin part 25 having a substantially arcuate cross section with an axis O intersecting with the wall surface facing the front side of the drill rotation direction T in the chip discharge groove 11; The margin portion 25 is connected to the rear side of the drill rotation direction T and intersects the outer peripheral ridge line portion of the wall surface facing the rear side of the drill rotation direction T of the chip discharge groove 11 and is one step smaller than the arc formed by the margin portion 25. It is comprised from the 2nd picking surface 26 which makes the cross-section substantially circular arc shape centering on the axis line O which has a diameter.
The margin portion 25 and the second picking surface 26 are formed in a spiral shape with the axis O as the center toward the rear side in the drill rotation direction T from the front end to the rear end side of the cutting edge portion 10 in the same manner as the chip discharge groove 11. And is formed over the entire effective blade length L of the blade edge portion 10.
[0038]
In addition, when viewed from the front end side in the axis O direction, the portion where the second picking surface 26 intersects the front end flank 12 is located in a region where X is negative and Y is positive. The intersecting ridgelines 18 and 23 are the outer peripheral ends 18B and 23B at the points intersecting the second picking surface 26, while the cutting edge 13 and the intersecting ridgelines 15, 16, and 17 are the points intersecting the margin portion 25. The outer peripheral ends 13B, 15B, 16B, and 17B are used.
[0039]
The small-sized drill having the above-described configuration has one piece formed on the blade edge portion 10 by feeding toward the distal end side in the direction of the axis O while the drill body is rotated around the axis O. While cutting the work material with the cutting blade 13, the chips generated by the cutting blade 13 are discharged along the chip discharge groove 11 to the rear end side of the cutting edge portion 10, and the hole portion of the small diameter deep hole is formed into a hole. We will process after dawn.
[0040]
Here, each of the distances b, c, d, e, f in the direction of the axis O between the intersecting ridgelines 15, 16, 17, 18, 23 and the tip of the tip flank 12 and the cutting edge 13 described above. The difference between the distance a in the direction of the axis O between the outer peripheral end 13B and the tip of the tip flank 12 is ba, ca, da, ea, fa, the drill body is the axis A feed amount F [[mu] m / rev. By which the drill body is moved toward the tip side in the direction of the axis O every time one rotation around O is performed. ] Are set to be larger than each other.
[0041]
In the drilling process, first, the leading edge (inner peripheral ends 15A, 19A, 20A, 24A) of the tip flank 12 located on the axis O is first brought into contact with the work material and then bites. The contact point with the work material extends radially outward along the pair of intersecting ridge lines 20 and 24 (chisel edge) from the axis O, and finally intersects the outer peripheral end 24B of the intersecting ridge line 24. When the cutting blade 13 is in contact with the work material so that the entire length of the cutting blade 13 extends from the inner peripheral end 13A to the outer peripheral end 13B, the work material is cut by the cutting blade 13 to make a hole. Is going on.
[0042]
At this time, the tip flank 12 of the blade edge portion 10 is the second flank in the region opposite to the cutting blade 13 (region where X is negative) across the Y axis when viewed from the tip side in the axis O direction. -4 flank surfaces 14B, 14C, 14D and reverse second flank surface 14F are formed in a multi-step surface arrayed along the circumferential direction, and intersecting ridgelines 16, 17, 18 between these flank surfaces Since the intersection ridge line 17 that is one of the two is positioned on the most distal side in the direction of the axis O, at least a part of the intersection ridge line 17 on the radially inner side (for example, about half the length) ) Is in contact with the work material in the same manner as the cutting edge 13.
[0043]
In this way, in order to bring the intersecting ridge line 17 into contact with the work material during drilling, in the present embodiment, the axis O direction between the outer peripheral end 17B of the intersecting ridge line 17 and the most distal end of the tip flank 12 is provided. The difference d-a between the distance d at the outer edge 13B of the cutting edge 13 and the distance a in the direction of the axis O between the outer peripheral end 13B of the cutting edge 13 and the tip of the tip flank 12 is set in the range of 2 to 200 [μm], for example. The feed amount F applied to the drill body is, for example, 1 to 100 [μm / rev. ] Is set.
[0044]
In the small drill according to the present embodiment as described above, since the chip discharge groove 11 provided in the cutting edge portion 10 is only one, the core thickness of the cutting edge portion 10 can be secured sufficiently large. Compared with a small drill provided with a chip discharge groove, the rigidity of the drill body can be kept overwhelmingly high, and breakage and hole bending of the cutting edge portion 10 due to insufficient rigidity can be suppressed.
[0045]
Furthermore, when drilling a work material using this small drill, not only the single cutting blade 13 formed on the cutting edge 10 but also the intersection of the third flank 14C and the fourth flank 14D. About half of the ridgeline 17 on the radially inner side comes into contact with the work material.
Thereby, the crossed ridge line 17 in which both the X and Y on the opposite side of the axis O are located in the negative region with respect to the region where both the X and Y where the cutting edge 13 is located is positive is drilled. It comes into contact with the work material so as to suppress the deflection of the main body, and it is possible to continuously maintain a stable state of the drill main body during drilling of the work material.
[0046]
Therefore, in the small drill of the present embodiment, in addition to ensuring a large rigidity, it is possible to keep a stable state without causing the swing of the drill body. The maximum outer diameter D of the blade edge portion 10 is 1 mm or less and the blade edge portion 10 is effective as in the case of small diameter deep hole machining where the ratio between the hole depth and the hole diameter is 5 or more. Even if the ratio L / D of the blade length L and the maximum outer diameter D of the blade edge portion is set to 5 or more, high hole position accuracy can be obtained.
[0047]
Further, the distance d in the direction of the axis O between the outer peripheral end 17A of the intersecting ridge line 17 that contacts the work material and the leading edge of the tip flank 12, and the outer peripheral edge 13B of the cutting edge 13 and the leading edge of the tip flank 12 The difference d-a from the distance a in the direction of the axis O is set to be larger than the feed amount F given to the drill body at the time of drilling, whereby the intersecting ridge line 17 and the work material It is possible to maintain an appropriate contact state.
On the contrary, if the distance difference da is smaller than the feed amount F, the interference between the intersecting ridge line 17 and the work material becomes serious, and there is a possibility that the drilling process may be hindered.
[0048]
In the present embodiment, the cross ridge line between the flank faces to be brought into contact with the work material at the time of drilling is only one of the cross ridge lines 17 between the third flank face 14C and the fourth flank face 14D. However, in addition to this, at least the radially inward side portion of the intersecting ridgeline 16 between the second flank 14B and the third flank 14C may be brought into contact with the work material.
With respect to the intersecting ridge line between the flank surfaces brought into contact with the work material, the tip flank surface 12 in the region opposite to the cutting edge 13 across the Y axis as viewed from the tip side in the axis O direction is the circumferential direction. It is sufficient that at least one or more flank faces are arranged in this area (more preferably, both X and Y are in the negative area).
[0049]
Moreover, in this embodiment, although the blade edge | tip part 10 is demonstrated with the thing of an undercut type, it is not limited to this, The outer diameter D of the blade edge | tip part 10 was made constant from the front-end | tip to the rear end. It may be a straight type, or may have a back taper such that the outer diameter of the blade edge portion 10 gradually decreases from the front end toward the rear end side (in this case, the tip portion of the blade edge portion 10 The outer diameter is the maximum outer diameter D).
[0050]
Furthermore, in the present embodiment, a small drill in which the maximum outer diameter D of the cutting edge portion is 1 mm or less and the ratio L / D between the effective blade length L and the maximum outer diameter D is 5 or more has been described. Without being limited to this range, the effects described above can be achieved by applying the present invention to a drill having a maximum outer diameter D larger than this range or a drill having an L / D smaller than 5.
[0051]
【The invention's effect】
According to the present invention, since there is only one chip discharge groove provided in the cutting edge portion, the rigidity of the drill body can be kept high, and in addition, when drilling a work material, Stable without causing runout of the drill body by contacting not only one cutting blade but also the intersecting ridgeline of the flank faces located in the area almost opposite to this cutting blade. Since this state can be maintained continuously, it is possible to improve the straightness of the drill body and to obtain good hole position accuracy.
[Brief description of the drawings]
FIG. 1 is an enlarged side view of a main part of a cutting edge portion of a small drill according to an embodiment of the present invention.
FIG. 2 is a view taken in the direction of the arrow I in FIG.
3 is a view in the direction of arrow II in FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Cutting edge part 11 Chip discharge groove 12 Tip flank 13 Cutting edge 14A 1st flank 14B 2nd flank 14C 3rd flank 14D 4th flank 14E Reverse side 1st flank 14F Reverse 2nd flank 17th Crossing ridge line O between axis 3 and flank 4 Axis T Drill rotation direction

Claims

A chip discharge groove extending from the front end of the blade tip portion toward the rear end side is formed on the outer periphery of the blade tip portion, which is a tip side portion of the drill body rotated about the axis, and the front side in the drill rotation direction of the chip discharge groove In the drill in which the cutting edge is formed at the intersecting ridge line part of the wall surface facing the front end flank of the cutting edge part,
The chip discharge groove is only one,
When the blade edge portion is viewed from the tip end side in the axial direction, the Y axis that is orthogonal to the X axis passing through the axis and parallel to the cutting blade is sandwiched between the cutting edge portion and the region opposite to the cutting blade. The tip flank portion is a multi-stage surface composed of a plurality of flank surfaces arranged along the circumferential direction,
A drill characterized in that at the time of drilling a work material, at least one of a plurality of intersecting ridgelines of the flank surfaces constituting the tip flank portion contacts the work material.

The drill according to claim 1,
The distance in the axial direction between the outer peripheral edge of the intersecting ridge line that contacts the work material and the leading edge of the tip flank, and between the outer peripheral edge of the cutting blade and the leading edge of the tip flank The difference from the distance in the axial direction is
The drill is characterized in that it is set to be larger than the feed amount per rotation given to the drill body at the time of drilling the work material.

The drill according to claim 1 or 2,
The maximum outer diameter D of the cutting edge portion is 1 mm or less, and the ratio L / D between the effective cutting edge length L of the cutting edge portion and the maximum outer diameter D of the cutting edge portion is 5 or more. .