JP4807521B2 - Twist drill - Google Patents

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JP4807521B2
JP4807521B2 JP2007143491A JP2007143491A JP4807521B2 JP 4807521 B2 JP4807521 B2 JP 4807521B2 JP 2007143491 A JP2007143491 A JP 2007143491A JP 2007143491 A JP2007143491 A JP 2007143491A JP 4807521 B2 JP4807521 B2 JP 4807521B2
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thinning
drill
cutting edge
center
thinning portion
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JP2008296313A (en
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直宏 中村
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Sumitomo Electric Hardmetal Corp
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この発明は、先端中心部の切れ刃の強度を維持しながらチゼルエッジの縮小によるスラストの低減や求心性向上を可能にした金属加工用のツイストドリルに関する。   The present invention relates to a twist drill for metal processing that enables reduction of thrust and improvement of centripetality by reducing the chisel edge while maintaining the strength of the cutting edge at the center of the tip.

金属加工用のツイストドリルについては、シンニング処理を施してスラストの低減、食い付き性や求心性の向上などを図ることが従来から行われている。図９〜図１３に、従来用いられているシンニング形状の一例を示す。図１１は、Ｘ形シンニングであり、図９のハッチング入れ部分をドリルの軸線ＣＬに対してα（図１０参照）の逃げ角をもつように加工してシンニング面６ａ，６ｂ間にβの開き角を有する溝（図１２参照）を生じさせている。片方のシンニング面６ａは逃げ面５に連なり、他方のシンニング面６ｂは、シンニング部切れ刃３ａ（シンニングによって生じる切れ刃）を生じさせてそのシンニング部切れ刃のすくい面となる。 Conventionally, twist drills for metal processing have been subjected to a thinning process to reduce thrust and improve biting and centripetalness. 9 to 13 show examples of conventionally used thinning shapes. FIG. 11 shows X-shaped thinning, in which the hatched portion of FIG. 9 is machined to have a clearance angle α (see FIG. 10 ) with respect to the axis CL of the drill, and β is opened between the thinning surfaces 6a and 6b. A groove having a corner (see FIG. 12 ) is generated. One thinning surface 6a continues to the flank 5 and the other thinning surface 6b generates a thinning portion cutting edge 3a (cutting edge generated by thinning) and becomes a rake face of the thinning portion cutting edge.

図１３のシンニングは、切れ刃３を所定の芯上がり量（＝先端芯厚ｔの１／２）をもつ刃にするとともに、シンニング部６を、ドリル中心Ｏを越えて反対側切れ刃の逃げ面５側に入り込ませている。 In the thinning of FIG. 13 , the cutting edge 3 is changed to a blade having a predetermined center rising amount (= 1/2 of the tip core thickness t), and the thinning portion 6 is moved beyond the drill center O to escape the opposite cutting edge. It enters the surface 5 side.

これらのほかに、下記特許文献１〜３が開示しているようなシンニング形状も提案されている。これら特許文献のうち、文献１のドリルは、シンニング部切れ刃とシンニング部の逃げ面側の稜線とがなす角を１２０°〜１７０°の範囲に設定してシンニング処理によって作り出される切屑排出用の空間（この発明で言うシンニング部の溝）を大きくし、それにより、先端中心部で生成される切屑の排出性を向上させて食い付きの安定性や直進性を高めている。   In addition to these, thinning shapes as disclosed in the following Patent Documents 1 to 3 have also been proposed. Among these patent documents, the drill of Document 1 is used for chip discharge generated by a thinning process by setting an angle formed by a thinning portion cutting edge and a ridge line on the flank side of the thinning portion within a range of 120 ° to 170 °. The space (the groove of the thinning portion referred to in the present invention) is enlarged, thereby improving the discharge performance of chips generated at the center of the tip, and improving the biting stability and straightness.

また、特許文献２，３のドリルは、図１３のシンニングと同様に、芯上がりの切れ刃を有するドリルのシンニング部を、ドリル中心を越えて反対側切れ刃の逃げ面側に入り込ませてドリルの正面視で所定量オーバーラップさせたものであって、切れ刃側シンニング面と逃げ面側シンニング面が連なる部分（この発明では、溝底と言う）を凹曲面で形成することで先端中心部において生成される切屑の排出性を向上させている。なお、特許文献２，３のドリルは、前記凹曲面のＲ半径については０．１ｍｍ〜０．５ｍｍ、シンニング部のオーバーラップ量は０〜０．１ｍｍ、中心対象位置にあるシンニング部切れ刃間の切れ刃長手直角方向の距離は０〜０．３ｍｍ、チゼルエッジの幅は０〜０．１ｍｍの範囲にあるのが好ましいとしている。
特開２００５−１６９５７２号公報 特開２００３−２６６２２５号公報 特開２００７−１０１１号公報 Further, the drills of Patent Documents 2 and 3 are similar to the thinning of FIG. 13 , in which the thinning portion of the drill having a centering cutting edge is inserted into the flank side of the opposite cutting edge beyond the drill center. The center of the tip is formed by forming a portion where the cutting edge side thinning surface and the flank side thinning surface are continuous (referred to as a groove bottom in this invention) with a concave curved surface. This improves the discharge of chips generated in the process. In addition, the drills of Patent Documents 2 and 3 have an R radius of the concave curved surface of 0.1 mm to 0.5 mm, an overlap amount of the thinning portion is 0 to 0.1 mm, and between the thinning portion cutting edges at the center target position The distance in the direction perpendicular to the cutting edge length is preferably 0 to 0.3 mm, and the width of the chisel edge is preferably in the range of 0 to 0.1 mm.
JP 2005-169572 A JP 2003-266225 A JP 2007-1011 A

図１１のＸ形シンニングは、切れ刃３をドリル中心Ｏに近づけてチゼルエッジの幅を縮めることができ、食い付き性や求心性を良くすることができるが、シンニング処理によって作り出される溝が小さいため先端中心部での切屑排出性に問題があり、切屑詰まりが発生してスラスト（スラスト力）の上昇、それによる中心部切れ刃の欠損が起こる。 The X-shaped thinning of FIG. 11 can reduce the width of the chisel edge by bringing the cutting edge 3 closer to the drill center O, and can improve the biting property and centripetality, but the groove created by the thinning process is small. There is a problem in chip dischargeability at the center of the tip, and clogging occurs, resulting in an increase in thrust (thrust force), resulting in a chip in the center.

また、図１３のシンニング形状は、シンニング部に形成される溝が大きく、切屑排出性が良くなってスラストが低減されるが、中心部の強度を確保するために先端芯厚ｔを厚くする必要があり、チゼルエッジの幅ｗが大きくなって求心性の低下、それによる穴曲がり（加工穴の曲がり）が起こり易い。剛性の低いロングドリルでは特に、その穴曲がりが顕著に現われる。 In addition, the thinning shape of FIG. 13 has a large groove formed in the thinning portion, which improves chip discharge and reduces thrust, but it is necessary to increase the tip core thickness t in order to ensure the strength of the center portion. And the width w of the chisel edge is increased, the centripetality is lowered, and the hole bending (bending of the processed hole) is likely to occur. Especially in the long drill with low rigidity, the bending of the hole appears remarkably.

さらに、特許文献１が開示しているドリルは、シンニング部の逃げ面側の稜線をドリルの回転方向前方に延び出させてシンニング部に生じる溝を大きくしているため、先端中心部の切れ刃のバックメタル量が減少して先端中心部の強度が低下する。その先端中心部の強度は、シンニング部加工後の先端芯厚とシンニング部の溝底を構成する凹曲面のＲ半径の大きさにも左右され、２箇所のシンニング部をドリル中心側に寄せるほど弱くなる。このため、先端中心部に強度が要求されるときにはチゼルエッジの短縮を犠牲にせざるを得ず、スラストの低減と先端中心部強度の確保を両立させるのが難しい。   Furthermore, since the drill which patent document 1 discloses is extending the ridgeline by the side of the flank of a thinning part ahead of the rotation direction of a drill, and the groove | channel which arises in a thinning part is enlarged, the cutting edge of a tip center part The amount of the back metal is reduced, and the strength at the center of the tip is lowered. The strength of the center of the tip depends on the thickness of the tip core after the processing of the thinning portion and the R radius of the concave curved surface constituting the groove bottom of the thinning portion, and the two thinning portions are brought closer to the center of the drill. become weak. For this reason, when strength is required at the center of the tip, shortening of the chisel edge must be sacrificed, and it is difficult to achieve both reduction of thrust and securing of strength of the tip center.

特許文献２，３が開示しているドリルは、シンニング部の溝底を凹曲面で形成して中心部での切屑排出性を高めているが、ドリルの場合、中心部の切削速度は０に近く、切屑は切削と言うよりは押し潰されるような状況で生成されて反対側切れ刃の逃げ面と被削材との間に入り込もうとするため、シンニング部をドリル中心部でオーバーラップさせることと、シンニング部の溝底を凹曲面で形成することだけでは十分でなく、先端中心部での切屑詰まりが起き易い。特に、切削送りが高くなると切屑の厚みが増し、反対側切れ刃の逃げ面と被削材との間に噛み込まれ易くなる。その噛み込みが起こると溶着が起こってスラストが高まり、中心切れ刃部の欠損に結びつく。   In the drills disclosed in Patent Documents 2 and 3, the groove bottom of the thinning part is formed with a concave curved surface to improve the chip discharging performance at the center part. In the case of a drill, the cutting speed at the center part is zero. Nearly, the thinning part is overlapped at the center of the drill because the chip is generated in a situation where it is crushed rather than cut and tries to enter between the flank face of the opposite cutting edge and the work material. In addition, it is not sufficient to form the groove bottom of the thinning portion with a concave curved surface, and chip clogging is likely to occur at the center of the tip. In particular, as the cutting feed increases, the thickness of the chips increases, and it becomes easy to be caught between the flank of the opposite cutting edge and the work material. When the bite occurs, welding occurs and the thrust increases, which leads to a loss of the center cutting edge.

要するに、従来の技術では、先端中心部も含めた刃先強度の確保とスラストの低減や求心性向上のためのチゼルエッジの縮小を両立させることができない。   In short, with the conventional technology, it is impossible to achieve both the securing of the cutting edge strength including the center portion of the tip and the reduction of the chisel edge for the purpose of reducing thrust and improving centripetality.

そこでこの発明は、金属加工用ツイストドリルを改善の対象にして、そのドリルの先端中心部の刃先強度を維持しながらチゼルエッジを十分に小さくしうるようにすることを課題としている。   In view of this, an object of the present invention is to improve a metal processing twist drill so that the chisel edge can be made sufficiently small while maintaining the cutting edge strength at the center of the tip of the drill.

上記の課題を解決するため、この発明においては、ドリル中心を間に挟んで片側と反対側にそれぞれ切れ刃を有し、さらに、各切れ刃に対応させた切屑排出溝と、チゼルエッジの幅を縮めるシンニング部を有するツイストドリルにおいて、前記シンニング部の溝底、即ち、切れ刃側シンニング面と逃げ面側シンニング面が交差した部分を凹曲面で形成し、各切れ刃のシンニング部を、ドリル中心を越えて反対側切れ刃の逃げ面側に入り込ませてドリルの正面視でシンニング部切れ刃が延びる方向に所定量オーバーラップさせ、さらに、各シンニング部のドリル先端に位置する部分に、前記チゼルエッジの幅をさらに縮める副シンニング部を設け、前記切れ刃を所定の芯上がり量をもつ刃として構成し、前記副シンニング部を、ドリルの正面視で、シンニング部切れ刃に対して所定の角度をもってドリル中心側に入り込むように形成した。 In order to solve the above-described problems, in the present invention, the cutting center has a cutting edge on one side and the opposite side with the center of the drill in between, and further, a chip discharge groove corresponding to each cutting edge, and the width of the chisel edge. In the twist drill having a thinning portion to be shrunk, a groove bottom of the thinning portion, that is, a portion where the cutting edge side thinning surface and the flank side thinning surface intersect is formed with a concave curved surface, and the thinning portion of each cutting edge is formed at the center of the drill. The chisel edge is inserted into the flank side of the opposite cutting edge over a predetermined amount so as to overlap by a predetermined amount in the direction in which the thinning part cutting edge extends in the front view of the drill, width further sub thinning portion is provided to reduce the of, constitute the cutting edge as a blade having a predetermined center of the object volume, the sub thinning section, a front view of the drill It was formed so as to enter the drill center side at a predetermined angle with respect to thinning portion cutting edge.

このツイストドリルの副シンニング部は、切れ刃に刃先強化用のネガランドを形成し、そのネガランドに連ならせてネガランドの延長上に設けることができる。 The sub-thinning portion of the twist drill can be provided on the extension of the negative land by forming a negative land for reinforcing the cutting edge on the cutting edge and connecting to the negative land.

その副シンニング部のドリル正面視におけるシンニング面間の開き角は、９０°以上が好ましい。   The opening angle between the thinning surfaces in the front view of the drill of the sub-thinning part is preferably 90 ° or more.

この発明のドリルは、シンニング部の溝底を凹曲面で形成しており、その凹曲面のＲ半径を大きくすることで先端中心部の強度を十分に確保することができる。また、凹曲面のＲ半径を単純に大きくすると先端芯厚が大きくなってチゼルエッジの幅も大きくなり、スラストの上昇や、食い付き性、求心性の悪化の問題が起こるが、第１形態のドリルは、各切れ刃のシンニング部を、ドリル中心を越えてオーバーラップするように反対側切れ刃の逃げ面側に入り込ませ、さらに、各シンニング部のドリル先端に位置する部分に副シンニング部を設けたので、チゼルエッジの幅が小さくなり、これに加えてシンニング部の溝が大きくなって切屑の排出性も良くなり、これらの相乗効果でスラストが低減される。また、チゼルエッジの幅が小さくなることで良好な食い付き性、求心性も確保される。   In the drill according to the present invention, the groove bottom of the thinning portion is formed with a concave curved surface, and the strength of the tip center portion can be sufficiently secured by increasing the R radius of the concave curved surface. In addition, if the radius R of the concave curved surface is simply increased, the tip core thickness increases and the width of the chisel edge also increases, causing problems such as increased thrust, bite and centripetal problems. Makes the thinning part of each cutting edge enter the flank side of the opposite cutting edge so that it overlaps beyond the center of the drill, and further, a sub-thinning part is provided in the part located at the drill tip of each thinning part Therefore, the width of the chisel edge is reduced, and in addition to this, the groove of the thinning portion is enlarged, and the chip discharging property is improved, and the thrust is reduced by a synergistic effect thereof. Moreover, since the width | variety of a chisel edge becomes small, favorable biting property and centripetality are also ensured.

また、正面視において芯上がりした切れ刃に対して所定の角度をもってドリル中心側に入り込むように副シンニング部を形成したので、副シンニング部の大きさや形状を設定する際に刃先強化用ネガランドの大きさ、角度による制約を受けることがなく、設定の自由度が高まってより優れた機能をもつ副シンニング部を設けることが可能になる。 Further, since the relative center of the object the cutting edge in the positive plane view was formed sub thinning portion so as to enter the drill center side at a predetermined angle, the negative land for edge reinforcement in setting the size and shape of the sub-thinning portion Without being restricted by size and angle, it is possible to provide a sub-thinning unit having a more excellent function by increasing the degree of freedom of setting.

なお、副シンニング部を、切れ刃に形成する刃先強化用のネガランドに連ならせてネガランドの延長上に設けるものは、ネガランドの加工と副シンニング部の加工を連続作業で行うことができ、加工工程の短縮が図れる。 In addition, if the secondary thinning part is connected to the negative land for reinforcing the cutting edge formed on the cutting edge and provided on the extension of the negative land, the processing of the negative land and the secondary thinning part can be performed continuously. The process can be shortened.

以下、添付図面の図１〜図８に基づいてこの発明のツイストドリルの実施の形態を説明する。図１に、この発明を適用するドリルの一例の全体を表す。このドリルは、本体部１の先端に着脱自在のヘッドピース２を設け、そのヘッドピース２に切れ刃３，３を設けた刃先交換式のドリルである。切れ刃３，３は、ドリル中心Ｏ（図２参照）を間に挟んで片側と反対側にあり、中心対象形状をなしている。 Hereinafter, an embodiment of the twist drill of the present invention with reference to FIGS. 1 to 8 of the accompanying drawings. FIG. 1 shows an entire example of a drill to which the present invention is applied. This drill is a blade-tip-exchangeable drill in which a detachable head piece 2 is provided at the front end of the main body 1 and the cutting edges 3 and 3 are provided on the head piece 2. The cutting edges 3 and 3 are on the opposite side to one side with the drill center O (see FIG. 2) in between, and form a central target shape.

ヘッドピース２と本体部１には、各切れ刃に対応させた切屑排出溝（ねじれ溝）４，４を設けている。また、ヘッドピース２には、チゼルエッジ８の幅を縮めるシンニング部６，６と、副シンニング部７，７を各切れ刃に対応させて設けている。   The head piece 2 and the main body 1 are provided with chip discharge grooves (twist grooves) 4 and 4 corresponding to the respective cutting edges. The headpiece 2 is provided with thinning portions 6 and 6 for reducing the width of the chisel edge 8 and auxiliary thinning portions 7 and 7 corresponding to the respective cutting edges.

シンニング部６は、切れ刃側シンニング面６ａと逃げ面側シンニング面６ｂとの間に溝を生じさせるものになっている。このシンニング部６のシンニング面６ｂは、逃げ面５のヒール側を削って生じさせた面であって、ドリルの軸心に対して図１０に示したαの逃げ角を付けている。そのシンニング面６ｂとシンニング面６ａとの交差部の溝底６ｃを半径Ｒ（図３参照）の凹曲面で形成している。 The thinning portion 6 is configured to generate a groove between the cutting edge side thinning surface 6a and the flank side thinning surface 6b. The thinning surface 6b of the thinning portion 6 is a surface generated by cutting the heel side of the flank 5 and has a clearance angle α shown in FIG. 10 with respect to the axial center of the drill. A groove bottom 6c at the intersection of the thinning surface 6b and the thinning surface 6a is formed as a concave curved surface having a radius R (see FIG. 3).

また、このシンニング部６は、ドリル中心Ｏを越えて反対側切れ刃の逃げ面側に入り込ませており、２つの切れ刃のシンニング部６，６は、ドリルの正面視（図３）において、シンニング部切れ刃３ａが延びる方向に所定量Ｙオーバーラップしている。このシンニング部６のドリルの正面視におけるシンニング部の広がり角θは、小さすぎると切屑の排出がスムーズになされず、大きすぎるとバックメタル量が減少して反対側切れ刃の強度に悪影響がでる。その２つのバランスを考えたときのθは、７５°〜１２０°の範囲が適正であった。また、シンニング部６，６のオーバーラップ量Ｙは、０．１２ｍｍ〜１．０ｍｍの範囲が先端部の芯厚の確保とスラスト低減の効果がバランスよく発揮されて適当であった。   Further, the thinning portion 6 is allowed to enter the flank side of the opposite cutting edge beyond the drill center O, and the thinning portions 6 and 6 of the two cutting edges are in front view of the drill (FIG. 3), A predetermined amount Y overlaps in the extending direction of the thinning portion cutting edge 3a. If the spreading angle θ of the thinning portion 6 in the front view of the drill of the thinning portion 6 is too small, chips are not discharged smoothly, and if it is too large, the amount of back metal decreases and the strength of the opposite side cutting edge is adversely affected. . The range of 75 ° to 120 ° was appropriate for θ when considering the balance between the two. Further, the overlap amount Y of the thinning portions 6 and 6 was appropriate in the range of 0.12 mm to 1.0 mm because the effect of ensuring the core thickness at the tip portion and reducing the thrust was well balanced.

副シンニング部７は、各シンニング部６のドリル先端に位置する部分に設けている。その副シンニング部７は、切れ刃３に沿って設けた刃先強化用のネガランド９（図５参照）
に連ならせてネガランド９の延長上に設けており、副シンニング部７の設置によって先端中心のチゼルエッジ８の幅が非常に小さくなっている。 The sub-thinning part 7 is provided in the part located in the drill front-end | tip of each thinning part 6. FIG. The secondary thinning part 7 is a negative land 9 for reinforcing the cutting edge provided along the cutting edge 3 (see FIG. 5).
The width of the chisel edge 8 at the center of the tip is made very small by installing the sub-thinning portion 7.

副シンニング部７は、図４に示す逃げ角εを、シンニング部６の逃げ角αよりも大きくすると好ましく、そのようにすると、逃げ面側シンニング面６ｂや溝底６ｃに対する加工工具の干渉を生じさせずその副シンニング部７を加工することができる。また、副シンニング部７をネガランド９に連ならせてネガランド９の延長上に設けることで、ネガランド９の加工と副シンニング部７の加工を連続的に一工程で行うことができる。   The sub-thinning portion 7 preferably has a clearance angle ε shown in FIG. 4 larger than the clearance angle α of the thinning portion 6, so that the machining tool interferes with the flank-side thinning surface 6 b and the groove bottom 6 c. The sub-thinning part 7 can be processed without doing so. Further, by providing the auxiliary thinning portion 7 on the extension of the negative land 9 so as to be connected to the negative land 9, the negative land 9 and the auxiliary thinning portion 7 can be processed continuously in one step.

溝底６ｃの半径Ｒは、その値が小さすぎると芯厚が薄くなって（図６の実線のＲと比較すると、半径の小さい一点鎖線のｒは芯厚を薄くする）先端中心部の強度が不足し、その値が大きすぎると芯厚が厚くなりすぎてスラスト低減の効果が損なわれるので、適切な値を選択する。その値は、シンニング部６のオーバーラップ量Ｙと同程度、具体的には半径Ｒ＝０．１５〜１．０ｍｍの範囲が特に良かった。一般に多用されている、直径がφ３ｍｍ〜５０ｍｍまでのドリルに採用してその範囲の数値が適切であることを確認したが、この数値は、φ５０ｍｍ以上のドリルにも適用できる。   If the radius R of the groove bottom 6c is too small, the core thickness becomes thin (compared to the solid line R in FIG. 6, the dash-dot line r with a small radius makes the core thickness thinner). If the value is too large and the value is too large, the core thickness becomes too thick and the effect of reducing the thrust is impaired, so an appropriate value is selected. The value was about the same as the overlap amount Y of the thinning portion 6, specifically, the radius R = 0.15 to 1.0 mm was particularly good. Although it is confirmed that the numerical values in the range are appropriate by adopting a drill having a diameter of φ3 mm to 50 mm that is widely used, this numerical value can also be applied to a drill having a diameter of φ50 mm or more.

副シンニング部７のドリルの正面視における広がり角η（図３）は、９０°以上にすると先端中心部において生成された切屑が排出され易くなり、また、溝底６ｃとの繋がりが滑らかになって繋ぎ部の強度低下も抑えられて好ましい。ηのより適切な値は９５°〜１２０°程度である。   When the spread angle η (FIG. 3) in the front view of the drill of the sub-thinning portion 7 is 90 ° or more, chips generated at the center of the tip are easily discharged, and the connection with the groove bottom 6c becomes smooth. Therefore, it is preferable that the strength of the joint portion is reduced. A more appropriate value of η is about 95 ° to 120 °.

図７は、ドリルの正面視におけるシンニング部６の広がり角θを、ドリルの正面視における副シンニング部７の広がり角ηよりも大きくした例を表している。この構造は、シンニング部に出来る溝がより大きくなって先端中心部で生成された切屑の排出性がより良くなる。   FIG. 7 shows an example in which the spread angle θ of the thinning portion 6 in the front view of the drill is larger than the spread angle η of the sub-thinning portion 7 in the front view of the drill. With this structure, the groove formed in the thinning portion becomes larger, and the discharge of chips generated at the center of the tip becomes better.

図８は、切れ刃３を所定の芯上がり量（ｔ／２）をもつ刃として構成し、副シンニング部７を、ドリルの正面視で、芯上がりした切れ刃（シンニング部切れ刃３ａ）に対して所定の角度σをもってドリル中心Ｏ側に入り込むように形成したものである。この構造は、副シンニング部７の大きさや形状を設定する際にネガランド９の大きさ、角度（図５のγ）による制約を受けることがなく、設定の自由度が高まってより優れた機能をもつ副シンニング部を設けることができる。チゼルエッジ８の幅は、０〜０．１ｍｍの範囲に設定すると優れた食い付き性や求心性が得られて好ましい。図８の構造は、ネガランド９による設置制約を受けないので、チゼルエッジ８の幅を０にすることも簡単である。図７のドリルの副シンニング部７は、ネガランド９の延長上に設けられているが、図３、図６、図８の副シンニング部７は、この発明では図８の副シンニング部７で代替したものにする。 In FIG. 8, the cutting edge 3 is configured as a blade having a predetermined center rise amount (t / 2), and the sub-thinning portion 7 is turned into a center rising edge (thinning portion cutting edge 3a) in a front view of the drill. On the other hand, it is formed so as to enter the drill center O side with a predetermined angle σ. This structure is not restricted by the size and angle of the negative land 9 (γ in FIG. 5) when setting the size and shape of the sub-thinning portion 7, and the degree of freedom of setting is increased and more excellent functions are provided. An auxiliary thinning portion can be provided. The width of the chisel edge 8 is preferably set in the range of 0 to 0.1 mm because excellent biting property and centripetal property are obtained. The structure of FIG. 8 is not subject to installation restrictions due to the negative land 9, so that the width of the chisel edge 8 can be easily reduced to zero. 7 is provided on the extension of the negative land 9, but the sub-thinning portion 7 of FIGS. 3, 6, and 8 is replaced by the sub-thinning portion 7 of FIG. 8 in the present invention. Make it.

なお、以上の説明は、刃先交換式ドリルを例に挙げて行ったが、この発明は、全体が一体的に形成されるソリッドドリルにも適用できる。   In addition, although the above description gave and demonstrated the blade-tip-exchange-type drill as an example, this invention is applicable also to the solid drill by which the whole is integrally formed.

以下に、より詳細な実施例を示す。
図３の形状のシンニング処理を行った外径φ＝１４ｍｍ、加工穴深さ５Ｄ（Ｄは直径）用の刃先交換式ドリル（発明品１）を製作した。このドリルの寸法諸元は、シンニング部のオーバーラップ量Ｙ＝０．３ｍｍ、ドリル正面視シンニング部広がり角θ＝１０５°、ドリル正面視副シンニング部広がり角η＝１００°、シンニング角δ＝１５０°、ネガランド傾斜角γ＝−２５°、ネガランド設置幅ｗ１＝０．１ｍｍ、チゼルエッジの幅ｗ＝０．０５ｍｍ、シンニング部逃げ角α＝３５°、シンニング部の溝の広がり角β＝１０５°、副シンニング部逃げ角ε＝４５°、シンニング部溝底のＲ半径＝０．５ｍｍである。 A more detailed example is shown below.
A blade-replaceable drill (Invention 1) for an outer diameter φ = 14 mm and a processing hole depth 5D (D is a diameter) subjected to the thinning process of the shape of FIG. 3 was manufactured. The dimensions of this drill are as follows: the overlap amount Y of the thinning portion Y = 0.3 mm, the drill front view thinning portion spread angle θ = 105 °, the drill front view auxiliary thinning portion spread angle η = 100 °, and the thinning angle δ = 150. °, negative land inclination angle γ = -25 °, negative land installation width w1 = 0.1 mm, chisel edge width w = 0.05 mm, thinning portion clearance angle α = 35 °, thinning portion groove spreading angle β = 105 °, The sub-thinning portion clearance angle ε = 45 °, and the R radius of the thinning portion groove bottom = 0.5 mm.

比較のために、同一径、同一長さの図１１のＸ形シンニングを施した従来品１（シンニング部溝底のＲ半径＝０．３ｍｍ、シンニング部のオーバーラップ量Ｙ＝０、チゼルエッジの幅ｗ＝０．０５ｍｍ）と、図１３のシンニングを施した従来品２（芯厚ｔ＝０．２５ｍｍ、シンニング部のオーバーラップ量Ｙ＝０．３ｍｍ、シンニング部溝底のＲ半径＝０．３ｍｍ、チゼルエッジの幅ｗ＝０．３５ｍｍ）も準備した。 For comparison, the conventional product 1 having the same diameter and the same length as shown in FIG. 11 (R radius of the thinning groove bottom = 0.3 mm, thinning overlap Y = 0, chisel edge width) w = 0.05 mm) and the conventional product 2 subjected to the thinning of FIG. 13 (core thickness t = 0.25 mm, overlap amount Y = 0.3 mm of the thinning portion, R radius of the thinning portion groove bottom = 0.3 mm) Chisel edge width w = 0.35 mm) was also prepared.

次に、これらのドリルを用いてＳ５０Ｃの被削材に穴を加工した。そのときの条件として、Ｖ＝１００ｍ／ｍｉｎ、８０ｍ／ｍｉｎ、６０ｍ／ｍｉｎの各切削速度とｆ＝０．２ｍｍ／ｒｅｖ、０．２５ｍｍ／ｒｅｖ、０．３ｍｍ／ｒｅｖの送りを組み合わせ、その条件でのスラストを比較した。その結果を図１４に示す。 Next, a hole was machined in the work material of S50C using these drills. As conditions at that time, V = 100 m / min, 80 m / min, and 60 m / min of cutting speeds and f = 0.2 mm / rev, 0.25 mm / rev, and 0.3 mm / rev are combined, and the conditions The thrust at was compared. The results are shown in Figure 14.

また、各ドリルによる求心性を、Ｘ分力とＹ分力を測定して比較した。その結果を図１５に示す。 Moreover, the centripetal force by each drill was measured by comparing the X component force and the Y component force. The results are shown in Figure 15.

この試験結果から、発明品は従来品１，２に比べてスラストが低減されることがわかる。また、求心性は従来品２に比べると大幅に良くなっており、Ｘ形シンニングを施した従来品１と比較しても遜色のない結果が得られている。   From this test result, it can be seen that the inventive product has reduced thrust compared to the conventional products 1 and 2. In addition, the centripetality is significantly better than that of the conventional product 2, and a result comparable to that of the conventional product 1 subjected to X-shaped thinning is obtained.

この発明のドリルの概要を示す側面図Side view showing an overview of drill of the present invention 図１のドリルの拡大正面図1 is an enlarged front view of the drill of FIG. 図２の中心部を拡大して示す正面図The front view which expands and shows the center part of FIG. 副シンニング設置部を拡大して示す側面図Side view showing enlarged sub-thinning installation section 図３のＩ−Ｉ線に沿った断面図Sectional drawing along the II line of FIG. シンニング部の溝底のＲ半径の違いによる芯厚の違いを比較した図The figure which compared the difference in the core thickness by the difference in R radius of the groove bottom of the thinning part シンニング部の他の例を示す拡大正面図An enlarged front view showing another example of the thinning portion シンニング部のさらに他の例を示す拡大正面図An enlarged front view showing still another example of the thinning portion 従来ドリルの一例を示す正面図Front view showing an example of a conventional drill 図９のドリルのヘッド部の側面図Side view of the head of the drill of FIG. 図９のドリルの中心部（Ｘ形シンニング）を拡大して示す正面図The front view which expands and shows the center part (X-type thinning) of the drill of FIG. 図１０のＩＩ−ＩＩ線に沿った断面図Sectional drawing along the II-II line of FIG. 他のシンニングを施した従来ドリルの中心部を拡大して示す正面図Front view showing an enlarged central part of a conventional drill with other thinning スラストの比較試験結果を示す図The figure which shows the comparison test result of thrust 求心性を現すＸ分力とＹ分力の測定結果を比較した図A comparison of measurement results of X and Y component forces showing centripetal force

符号の説明Explanation of symbols

１ 本体部
２ ヘッドピース
３ 切れ刃
３ａ シンニング部切れ刃
４ 切屑排出溝
５ 逃げ面
６ シンニング部
６ａ，６ｂ シンニング面
６ｃ 溝底
７ 副シンニング部
８ チゼルエッジ
９ 刃先強化用ネガランド
Ｏ ドリル中心
ＣＬ 軸線
α シンニング部の逃げ角
β シンニング部の溝の広がり角
γ ネガランドの傾斜角
ε 副シンニング部の逃げ角
η 副シンニング部の広がり角
θ シンニング部の広がり角
σ 副シンニング部の入り込み角
δ シンニング角
ｔ 先端芯厚
ｗ チゼルエッジの幅
ｗ１ ネガランド設置幅
Ｒ 凹曲面で形成される溝底の半径
Ｙ シンニング部のオーバーラップ量 DESCRIPTION OF SYMBOLS 1 Main-body part 2 Headpiece 3 Cutting edge 3a Thinning part cutting edge 4 Chip discharge groove 5 Relief surface 6 Thinning part 6a, 6b Thinning surface 6c Groove bottom 7 Sub-thinning part 8 Chisel edge 9 Negative land O for cutting edge reinforcement Drill center CL Axis line α Thinning Clearance angle β Thinning groove expansion angle γ Negative land inclination angle ε Secondary thinning clearance angle η Secondary thinning expansion angle θ Thinning expansion angle σ Secondary thinning entry angle δ Thinning angle t Tip core Thickness w Chisel edge width w1 Negative land installation width R Radius of groove bottom formed by concave curved surface
Y Thinning overlap amount

Claims (3)

ドリル中心（Ｏ）を間に挟んで片側と反対側にそれぞれ切れ刃（３）を有し、さらに、各切れ刃に対応させた切屑排出溝（４）と、チゼルエッジ（８）の幅（ｗ）を縮めるシンニング部（６）を有するツイストドリルにおいて、
前記シンニング部（６）の溝底（６ｃ）を凹曲面で形成し、各切れ刃のシンニング部（６，６）を、ドリル中心（Ｏ）を越えて反対側切れ刃の逃げ面（５）側に入り込ませてドリルの正面視でシンニング部切れ刃（３ａ）が延びる方向に所定量（Ｙ）オーバーラップさせ、さらに、各シンニング部（６，６）のドリル先端に位置する部分に、前記チゼルエッジ（８）の幅をさらに縮める副シンニング部（７）を設け、
前記切れ刃（３）を所定の芯上がり量をもつ刃として構成し、前記副シンニング部（７）を、ドリルの正面視で、シンニング部切れ刃（３ａ）に対して所定の角度（σ）をもってドリル中心側に入り込むように形成したことを特徴とするツイストドリル。 Each has a cutting edge (3) on one side and the opposite side with the drill center (O) in between, and further, a chip discharge groove (4) corresponding to each cutting edge, and the width (w) of the chisel edge (8) In a twist drill having a thinning portion (6)
The groove bottom (6c) of the thinning part (6) is formed as a concave curved surface, and the thinning part (6, 6) of each cutting edge extends beyond the drill center (O) and the flank (5) of the opposite cutting edge. The thinning portion cutting edge (3a) is overlapped by a predetermined amount (Y) in a direction in which the thinning portion (3a) extends in a front view of the drill, A secondary thinning part (7) for further reducing the width of the chisel edge (8) is provided ,
The cutting edge (3) is configured as a blade having a predetermined centering amount, and the sub-thinning portion (7) is a predetermined angle (σ) with respect to the thinning portion cutting edge (3a) in a front view of the drill. A twist drill that is formed so as to enter the center of the drill. 前記切れ刃（３）に刃先強化用のネガランド（９）を形成し、前記副シンニング部（７）を、前記ネガランド（９）に連ならせて前記ネガランド（９）の延長上に設けた請求項１に記載のツイストドリル。 A negative land (9) for reinforcing the cutting edge is formed on the cutting edge (3), and the sub-thinning part (7) is connected to the negative land (9) and provided on an extension of the negative land (9). Item 2. The twist drill according to Item 1 . 前記副シンニング部（７）のドリル正面視におけるシンニング面間の開き角（η）を９０°以上にした請求項１又は２に記載のツイストドリル。 The twist drill according to claim 1 or 2 , wherein an opening angle (η) between the thinning surfaces in the front view of the drill of the sub-thinning portion (7) is 90 ° or more.
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