【０００１】
【産業上の利用分野】
本願発明は、加工深さがドリル直径の１５〜３０倍程度の深穴加工用ドリルに関し、詳細には、切屑排出作用を円滑にすることにより、ノンステップで加工できる深穴加工用ドリルに関する。
【０００２】
【従来の技術】
一般に用いられているドリル径の２〜３倍程度の通常の穴加工用ドリルでは、切屑がカールした連続切屑が生成され、ドリル径の５倍程度の加工深さで切屑の排出が不能となり、切屑排出溝中に詰まる事で切削トルクの増大を招き、しいてはドリルの折損に至る。そこで、直径の５倍以上の深さを加工する場合、溝形状を通常のコーンケープからパラボリックにした深穴用ドリルが用いられ（例として、実公平３−３３３７５号公報。）、切屑の排出方向をリード方向に制御し、リボン状切屑形状にする事で穴内壁とドリル溝との空間から切屑を排出しやすくし、ドリル径の１０倍程度までノンステップ加工できる深穴用ドリルが使用されている。
【０００３】
また、通り穴加工の際の抜け際のバリ抑制やコバ欠け防止のために、ドリル先端角を２段にしたりテーパ状にしたドリルが用いられ、例として特開平７−８０７１４号公報、特開２０００−２６３３０６号公報、がある。
【０００４】
【発明が解決しようとする課題】
本願発明は、ドリル直径の１５〜３０倍程度の深穴をノンステップで加工できるツイストドリルを検討したところ、切屑排出、特に、切屑排出は刃溝の中途で切屑詰まりを起こし、一度切屑が滞留するとそのまま留まってしまい、ステップ送り等別の工程を入れて排出しなければならないという課題があった。
次に、横型での加工の場合、深穴加工用ドリルは突き出し長さが長く、片持ち梁りの状態となりドリル自重によりドリル先端部が撓み、この状態でドリルを回転させるとドリル溝終端部を頂点とした円錐状にドリル先端が回転とともに振られてしまう。その状態におれる加工穴位置のズレを防止するため、同径以上のドリルでドリル直径の２倍程度の深さに前もって加工されたガイド穴に該ドリルが回転しながら前進し、ガイド穴に倣う際、ガイド穴の入口にドリル切刃外周部が当たり、カジリや振動が発生し切刃にチッピングを誘発させ、しいてはドリルを折損させる場合があり、加工の安全性を損うという課題があった。
【０００５】
【課題を解決するための手段】
本願発明では、上記の課題を解決するため、ドリル直径の１５倍以上の深穴をノンステップ加工できるツイストドリルを鋭意研究した結果、深穴を加工するツイストドリルにおいて、該ドリルの刃部の心厚が先端側から基端側に向けて、厚みが略一定の第一心厚部、第二心厚部とを備え、該第一心厚部の心厚を該第二心厚部の心厚より大とし、且つ、該ドリルの先端角を２段以上としたことを特徴とする深穴加工用ドリルであり、詳細には、第一心厚部の心厚と第二心厚部の心厚とをドリル直径の２％以上８％以下小さくし、該第一心厚部の長さがドリル径の１／２以上１０以下に設け、２段目先端角を１２０°以下６０°以上とし、１段目と２段目の先端角の偏曲点の位置をドリル径の０．５倍以上０．９倍以下に設けることでドリル先端に振れが生じても滑らかにドリル先端をガイド穴に導き加工入口部における安全性を改善した深穴加工用ドリルである。
【０００６】
【発明の実施の形態】
先ず、深穴加工時に切屑詰まりが発生するのは、刃溝の中途であり、本願発明では、ドリル先端部から一定距離までの心厚（以下、第一心厚部と称する。）より、ドリル溝切り上がり部を除く、ドリル溝基端側の心厚（以下、第二心厚部と称する。）を小さくした。この構成により刃溝の容積を拡げ、溝を拡幅することもでき、切屑詰まりを起こしにくくなる。
【０００７】
コーンケーブ溝形状、凹状溝形状、パラボリック溝形状いずれのドリルによる穴加工でも、先端切刃で切削された切屑は、先端切刃より後方のドリル直径の約０．５倍程度の長さの位置でドリル溝と穴内壁により、曲げや圧縮作用を受け、切屑の形状ならびに切屑体積がドリル溝と穴内壁に収まる形に成形される。形成されたチップ状切屑は、ドリルの切削力により溝中に順次押し出されるが、ドリル溝と穴内壁の摩擦抵抗により切屑の押し出される力は減じ、穴深さが深くなるに従って、やがては切屑を押し出す力は失われ切削詰まりを起こす。この切屑詰まりを起こす深さが深穴用ドリルではドリル径の８〜１０倍である。この付近で刃溝容積を拡大することにより、切屑を押し出す力を阻害する摩耗抵抗をより減じる事で改善が図られる。
【０００８】
より好ましくは、第二心厚部と第一心厚部の差をドリル直径の２％以上とすることによりこの作用を確実なものとする。ドリルの第一心厚部と第二心厚部の心厚の差がドリル径の１０〜１５倍程度の穴深さで切屑詰まりが発生し、心厚の差が８％以上では相対的に第二心厚部の心厚が薄くなり、ドリルの剛性が不足し加工時にドリルが撓んだり柄部に与えられた回転トルクを切刃に充分に伝達できずドリルに捩れが生ずる為、ドリル心厚の差を２％以上８％以下とした。また、第一心厚部、第二心厚部の略一定とは、回転軸と略平行に設けても、通常のウェブテーパでも逆のウェブテーパであっても良く、また、ドリル製作上の都合により発生する１００ｍｍにつき±０．２ｍｍ程度の勾配なら、切屑の押し出す力を大幅に減じたり、ドリル剛性を大きく損う事はない。
【０００９】
第一心厚部の長さは、ドリルリードの１／２以下では切刃で生成された切屑を充分に成形し、方向を整える事が出来ず起点の位置がドリルリードの５リード以上ではドリル溝と穴内壁による切屑擦過の摩擦が大きく、切屑詰まりを解消できないため、第一心厚部の長さはドリルリードの１／２以上５以下の範囲とした。
【００１０】
横型加工の際、ドリルは自重によりドリル先端部が撓み、その状態に回転の円心力が加わって、ドリル先端部にはフレが発生する。この状態では、加工穴位置ズレ防止の為にすでに加工されたガイド穴とドリル軸心にズレが生じており、ガイド穴入口にドリル外周部が当たり、その際にカジリや振動が発生し切刃をチッピングさせるので、先端角を２段以上とし２段目先端角を１２０°以下にする事で、ドリル先端をスムーズにガイド穴へ導き、加工の安全性を図る事ができる。特に、切刃外周部が鋭利な凹状溝形状のドリルや脆い超硬合金製のドリルには効果がある。２段目の先端角が１２０°以上では、ガイド穴に対しての向心性が劣り、切刃コーナの角度が１２０°と小さく、強度的に劣りチッピングの危険性があるので１２０°以下とした。また、２段目の先端角が６０°以下ではガイド穴に対しての向心性と切刃コーナの角度が１５０°になり強度的に優れるが切刃の有効捩れ角が小さくなり、切削性の低下を招くので６０°以上とした。
【００１１】
更に、１段目先端角と２段目先端角の偏曲点の位置がドリル中心側に近づくに従い向心性は向上するが、２段目先端角の切刃が長くなりその結果生成される切屑の幅が広くなり、切屑のボリュームが増す事で、切屑の排出性を阻害する。また、０．９倍以上では２段目先端角部の幅が狭く向心性の効果が乏しいので偏曲点の位置をドリル径の０．５倍以上０．９倍以下とした。更に、該ドリルにクーラントホールを設けてクーラントとして油性切削油、水溶性切削油、ミスト及びエアー等々を送ることにより、穴明け加工によって生ずる切削熱を冷却し、また潤滑性を高め切屑排出をよりスムーズに行うことが出来る。以下、実施例に基づき本発明を具体的に説明する。
【００１２】
【実施例１】
本発明例１としてコーンケーブ溝形状で図２に示す心厚構成を有したコバルトハイス製ストレートシャンク深穴ドリル、すなわちドリル径＝６．０ｍｍ、溝長＝２２０ｍｍ、全長＝３００ｍｍ、第一心厚部＝０．４×Ｄ、第二心厚部＝０．３７×Ｄ、第一心厚部の長さ＝６×ドリル径、ドリル捩れ角＝４０°、表面処理＝ＴｉＡｌＮコーティング、一段目先端角＝１１８°、二段目先端角＝９０°、先端角の偏曲点＝０．８×Ｄを製作した。また、比較例２、３として、本発明例１のドリルと同仕様で二段目先端角を６０°、５０°とし製作した。
【００１３】
本発明例１、比較例２〜３のドリル各々３本を、切削速度＝４０ｍ／ｍｉｎ、１回転の送り＝０．０９ｍｍ／ｒｅｖ、水溶性切削油、ガイド穴＝φ６×１２ｍｍ、横型マシニングセンター（３．７ｋｗ、ＢＴ３０）を用いて、Ｓ５０Ｃ生材をノンステップで１８０ｍｍ（３０Ｄ）を１０穴加工し、切削の状況と加工穴入口のカジリの状態を確認した。その結果、いずれも１８０ｍｍ加工出来たが、本発明例１、比較例２においては機械ロードの変動幅も１〜４％で安定していたが、比較例３においては機械のロードが１１〜１５％の変動中で不安定であった。また、加工ワーク入口のカジリの状況を確認したところ本発明例１、比較例２、３ともにカジリの痕跡が観られなかった。
【００１４】
【実施例２】
本発明例３として、凹状溝形状で図２に示す心厚構成を有したオイルホール付合金製ストレートシャンク深穴ドリル、すなわちドリル径＝６．０ｍｍ、溝長＝１８０ｍｍ、全長＝２５０ｍｍ、第一心厚部＝０．４×Ｄ、第二心厚部＝０．３７×Ｄ、第一心厚部の長さ＝５×ドリル径、ドリル捩れ角＝３０°、表面処理＝ＴｉＡｌＮコーティング、一段目先端角＝１４０°、二段目先端角＝１２０°、先端角の偏曲点＝０．８×Ｄを製作した。また比較例４〜７として、本発明例３のドリルと同仕様で二段目先端角を１３０°、９０°、６０°、５０°とし製作した。
【００１５】
本発明例３、比較例４〜７のドリル各々３本を、切削速度＝８０ｍ／ｍｉｎ、１回転の送り＝０．１２ｍｍ／ｒｅｖ、水溶性切削油、ポンプ吐出圧力＝２Ｍｐａ、ガイド穴＝φ６×１２ｍｍ、横型マシニングセンター（３．７ｋｗ、ＢＴ３０）を用いて、Ｓ５０Ｃ生材をノンステップで１５０ｍｍ（２５Ｄ）を１０穴加工し、切削の状況と加工穴入口のカジリの状態を確認した。その結果、いずれも１５０ｍｍ加工出来たが、本発明例３、比較例４、５、６においては機械ロードの変動幅も１〜２％で安定していたが、比較例７においては機械のロードが８〜１２％の変動中で不安定であった。また、加工ワーク入口のカジリの状況を確認したところ、比較例４にカジリの痕跡が観られたが、それ以外には観られなかった。また、比較例４のドリルの３本中１本の切刃外周部に微少なチッピングが観られた。
【００１６】
比較例８〜１１として、本発明例３のドリルで同仕様で先端角の偏曲点をドリル径の０．９５×Ｄ、０．９×Ｄ、０．５×Ｄ、０．４×Ｄで製作した。各々３本実施例２と同様に穴加工し、切削の状況と加工穴入口のカジリの状態を確認した。その結果、比較例１１以外はいずれも１５０ｍｍ加工出来たが、比較例１１は機械ロードが上昇し５０％を超え、折損の危険性があるので加工途中で中止した。また、加工ワーク入口のカジリの状況を確認した処、比較例８にカジリの痕跡が観られたがそれ以外には観られなかった。また、比較例１１のドリルの３本中２本の切刃外周部に微少なチッピングが観られた。
【００１７】
【発明の効果】
本願発明を適用することにより、第二心厚部の刃溝及び穴内壁と切屑の摩擦を減少し、切屑の押し出す力を長く維持出来るうえ、横型加工におけるガイド穴進入時のドリルのカジリを防止し切削の安全性を図りつつ、ノンステップでドリル直径の３０倍の切削加工が可能になった。
【図面の簡単な説明】
【図１】図１は、本発明例のドリルの正面図を示す。
【図２】図２は、図１の断面図を示す。
【図３】図３は、本発明例の切屑形態を示す。
【図４】図４は、比較例の切屑形態を示す。
【符号の説明】
１ 第一心厚部
２ 第二心厚部
３ １段目先端角
４ ２段目先端角
５ 偏曲点[0001]
[Industrial application fields]
The present invention relates to a drill for deep hole machining whose machining depth is about 15 to 30 times the diameter of the drill, and in particular, to a drill for deep hole machining that can be machined non-step by smoothing the chip discharging action.
[0002]
[Prior art]
With a normal drill for drilling about 2 to 3 times the diameter of a drill that is generally used, continuous chips with curled chips are generated, and chips cannot be discharged at a processing depth of about 5 times the drill diameter. Clogging in the chip discharge groove leads to an increase in cutting torque, which leads to breakage of the drill. Therefore, when machining a depth of 5 times the diameter or more, a deep hole drill whose groove shape is made parabolic from a normal cone cape is used (for example, Japanese Utility Model Publication No. 3-33375), and chips are discharged. By controlling the direction to the lead direction and making it into a ribbon-like chip shape, it is easy to discharge chips from the space between the hole inner wall and the drill groove, and a deep hole drill that can be non-stepped up to about 10 times the drill diameter is used Yes.
[0003]
Further, in order to suppress burr at the time of through-hole processing and to prevent edge chipping, a drill with a double tip angle or a tapered shape is used, and as an example, JP-A-7-80714, JP No. 2000-263306.
[0004]
[Problems to be solved by the invention]
The present invention examined a twist drill that can process a deep hole about 15 to 30 times the diameter of the drill in a non-step manner. Chip discharge, especially chip discharge, causes chip clogging in the middle of the blade groove, and once the chip stays. There was a problem that it remained as it was, and another process such as step feed had to be put in and discharged.
Next, in the case of horizontal machining, the drill for deep hole drilling has a long projecting length and is in a cantilevered state, and the drill tip is bent by its own weight. The tip of the drill will be swung with the rotation in a conical shape with the apex at the top. In order to prevent misalignment of the drilled hole position in that state, the drill moves forward to a guide hole that has been drilled to a depth of about twice the drill diameter with a drill of the same diameter or larger, When copying, the outer periphery of the drill cutting edge hits the entrance of the guide hole, causing galling and vibration, inducing chipping on the cutting edge, which may break the drill and impair processing safety. was there.
[0005]
[Means for Solving the Problems]
In the present invention, in order to solve the above-mentioned problem, as a result of earnestly researching a twist drill capable of non-step machining a deep hole having a diameter of 15 times or more of the drill diameter, in the twist drill for machining a deep hole, Comprises a first core thickness portion and a second core thickness portion having a substantially constant thickness from the distal end side to the proximal end side, and the thickness of the first core thickness portion is set to the thickness of the second core thickness portion. It is a drill for deep hole drilling characterized in that it is larger and the tip angle of the drill is two or more steps, and more specifically, the core thickness of the first core thick part and the core of the second core thick part The thickness is reduced by 2% or more and 8% or less of the drill diameter, and the length of the first core thickness part is set to 1/2 or more and 10 or less of the drill diameter, and the second stage tip angle is set to 120 ° or less and 60 ° or more. At the tip of the drill, the position of the inflection point of the tip angle of the 1st stage and the 2nd stage should be 0.5 to 0.9 times the drill diameter. It is a deep hole drill that improves the safety at the processing entrance by guiding the tip of the drill smoothly to the guide hole even if runout occurs.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
First, chip clogging occurs during deep hole machining in the middle of the blade groove, and in the present invention, the drill is based on the core thickness from the drill tip to a certain distance (hereinafter referred to as the first core thick part). The core thickness (hereinafter referred to as the second core thickness portion) on the proximal side of the drill groove, excluding the groove rising portion, was reduced. With this configuration, the volume of the blade groove can be increased and the groove can be widened, and chip clogging is less likely to occur.
[0007]
Whether drilling with a cone cave groove, concave groove, or parabolic groove, the chips cut with the tip cutting edge are approximately 0.5 times the drill diameter behind the tip cutting edge. The drill groove and the inner wall of the hole are bent and compressed, and the shape of the chip and the chip volume are formed into a shape that fits in the drill groove and the inner wall of the hole. The formed chip-like chips are sequentially pushed into the groove by the cutting force of the drill, but the force by which the chips are pushed out is reduced by the frictional resistance between the drill groove and the inner wall of the hole, and eventually the chips are removed as the hole depth increases. The pushing force is lost and cutting clogging occurs. The depth which causes this chip clogging is 8 to 10 times the drill diameter in the deep hole drill. Improvement is achieved by further reducing the wear resistance that hinders the force of pushing out the chips by enlarging the blade groove volume in this vicinity.
[0008]
More preferably, the difference between the second core thickness portion and the first core thickness portion is 2% or more of the drill diameter to ensure this effect. Chip clogging occurs when the core thickness difference between the first and second core thicknesses of the drill is about 10 to 15 times the drill diameter. Since the core thickness of the second core thickness portion becomes thin, the rigidity of the drill is insufficient, the drill bends during processing, and the rotational torque applied to the handle portion cannot be transmitted sufficiently to the cutting blade, causing the drill to twist. The difference in heart thickness was 2% or more and 8% or less. Further, the substantially constant thickness of the first core thick portion and the second core thick portion may be provided substantially parallel to the rotation axis, or may be a normal web taper or a reverse web taper. If the gradient is about ± 0.2 mm per 100 mm generated by convenience, the force of pushing out chips will not be greatly reduced, and the drill rigidity will not be greatly impaired.
[0009]
If the length of the first core thickness part is 1/2 or less of the drill lead, the chips generated by the cutting blade will be sufficiently formed, the direction cannot be adjusted, and if the starting point is 5 leads or more of the drill lead, the drill will be drilled. Since the friction of the chip scraping by the groove and the inner wall of the hole is large and chip clogging cannot be eliminated, the length of the first core thick portion is set to a range of 1/2 to 5 of the drill lead.
[0010]
During horizontal machining, the drill tip is deflected by its own weight, and a rotational center force is applied to this state, and the drill tip is flared. In this state, the drill hole center is misaligned with the already drilled guide hole to prevent misalignment of the drilled hole, and the outer periphery of the drill hits the guide hole entrance, causing galling and vibration at that time. Since the tip angle is set to two or more steps and the second step tip angle is set to 120 ° or less, the drill tip can be smoothly guided to the guide hole, and processing safety can be achieved. In particular, it is effective for a drill having a concave groove shape with a sharp outer peripheral portion of the cutting edge or a drill made of a brittle cemented carbide. When the tip angle of the second step is 120 ° or more, the centripetal property with respect to the guide hole is inferior, the angle of the cutting edge corner is as small as 120 °, and the strength is inferior, so there is a risk of chipping. . In addition, when the tip angle of the second step is 60 ° or less, the centripetal property with respect to the guide hole and the angle of the cutting edge corner are 150 °, which is excellent in strength, but the effective twist angle of the cutting blade is reduced and the machinability Since it caused a decrease, the angle was set to 60 ° or more.
[0011]
Furthermore, the centripetality improves as the position of the deflection point of the first stage tip angle and the second stage tip angle approaches the drill center side, but the cutting edge of the second stage tip angle becomes longer and the resulting chips Increases the width of the chip and increases the volume of the chips, which impedes chip discharge. Further, when the width is 0.9 times or more, the width of the second stage tip corner is narrow and the effect of centripetality is poor, so the position of the inflection point is set to 0.5 times or more and 0.9 times or less of the drill diameter. Furthermore, by providing a coolant hole in the drill and sending oil-based cutting oil, water-soluble cutting oil, mist, air, etc. as the coolant, the cutting heat generated by drilling is cooled, the lubricity is increased and chip discharge is further improved. It can be done smoothly. Hereinafter, the present invention will be specifically described based on examples.
[0012]
[Example 1]
As Example 1 of the present invention, a cone high groove straight shank deep hole drill having a cone-cave groove shape and a core thickness configuration shown in FIG. 2, that is, drill diameter = 6.0 mm, groove length = 220 mm, total length = 300 mm, first core thick part = 0.4 × D, second core thick part = 0.37 × D, first core thick part length = 6 × drill diameter, drill twist angle = 40 °, surface treatment = TiAlN coating, first stage tip angle = 118 °, second stage tip angle = 90 °, tip angle deflection point = 0.8 × D. Further, as Comparative Examples 2 and 3, the same specifications as those of the drill of Example 1 of the present invention were made with the second stage tip angle being 60 ° and 50 °.
[0013]
Three drills of Invention Example 1 and Comparative Examples 2 to 3 were each cut at a cutting speed = 40 m / min, feed per rotation = 0.09 mm / rev, water-soluble cutting oil, guide hole = φ6 × 12 mm, horizontal machining center ( 3.7 kw, BT30) was used to machine 10 holes of 180 mm (30D) in a non-step S50C raw material, and the state of cutting and the state of galling at the hole entrance were confirmed. As a result, both of them were able to machine 180 mm, but in Example 1 and Comparative Example 2, the fluctuation range of the machine load was stable at 1 to 4%, but in Comparative Example 3, the machine load was 11 to 15%. % Was unstable. Further, when the condition of galling at the work workpiece entrance was confirmed, no traces of galling were observed in both Example 1 and Comparative Examples 2 and 3.
[0014]
[Example 2]
As Example 3 of the present invention, an oil hole-equipped straight shank deep hole drill having a concave groove shape and a core thickness configuration shown in FIG. 2, that is, drill diameter = 6.0 mm, groove length = 180 mm, total length = 250 mm, first Core thickness = 0.4 × D, second core thickness = 0.37 × D, first core thickness = 5 × drill diameter, drill twist angle = 30 °, surface treatment = TiAlN coating, one step The tip angle of the eye = 140 °, the tip angle of the second stage = 120 °, and the inflection point of the tip angle = 0.8 × D. Further, as Comparative Examples 4 to 7, the same specifications as those of the drill of Example 3 of the present invention were made, and the second stage tip angles were 130 °, 90 °, 60 °, and 50 °.
[0015]
Three drills of Invention Example 3 and Comparative Examples 4 to 7 were each cut at a cutting speed = 80 m / min, feed per rotation = 0.12 mm / rev, water-soluble cutting oil, pump discharge pressure = 2 Mpa, guide hole = φ6 Using a x12 mm, horizontal machining center (3.7 kw, BT30), 10 holes of 150 mm (25 D) were machined from S50C raw material in a non-step, and the cutting condition and the galling state at the machining hole inlet were confirmed. As a result, although 150 mm could be processed in all cases, in Example 3 and Comparative Examples 4, 5, and 6, the fluctuation range of the machine load was stable at 1 to 2%, but in Comparative Example 7, the machine load was stable. Was unstable with a variation of 8-12%. Further, when the condition of galling at the machining work entrance was confirmed, traces of galling were observed in Comparative Example 4, but were not observed otherwise. Further, slight chipping was observed on the outer peripheral portion of one of the three drills of Comparative Example 4.
[0016]
As Comparative Examples 8 to 11, the drill of the invention example 3 has the same specification and the tip angle deflection point is 0.95 × D, 0.9 × D, 0.5 × D, 0.4 × D of the drill diameter. Made with. Each three holes were drilled in the same manner as in Example 2, and the state of cutting and the condition of galling at the hole entrance were confirmed. As a result, 150 mm could be machined except for Comparative Example 11, but in Comparative Example 11 the machine load increased and exceeded 50%, and there was a risk of breakage. In addition, after confirming the galling condition at the machining work entrance, a trace of galling was observed in Comparative Example 8, but no other marks were observed. Further, slight chipping was observed on the outer peripheral portion of two of the three cutting blades of Comparative Example 11.
[0017]
【The invention's effect】
By applying the invention of the present application, the friction between the cutting edge of the second core thick part and the inner wall of the hole and the chip can be reduced, the chip pushing force can be maintained for a long time, and drill galling when entering the guide hole in horizontal machining is prevented. However, it is possible to cut 30 times the diameter of the drill in a non-step manner while ensuring cutting safety.
[Brief description of the drawings]
FIG. 1 is a front view of a drill according to an example of the present invention.
FIG. 2 shows a cross-sectional view of FIG.
FIG. 3 shows a chip configuration of an example of the present invention.
FIG. 4 shows a chip configuration of a comparative example.
[Explanation of symbols]
1 1st core thick part 2 2nd core thick part 3 1st step tip angle 4 2nd step tip angle 5 Bending point
