JP3668023B2 - Small-diameter throwaway drill - Google Patents

Description

【００３５】
この実験の結果を表１に示す。
【００３６】
表１に示す如く、本発明の範囲外である試料１（ｌ／Ｌが０．７より大きい）と試料３（ｄが０．０５ｍｍより小さい）はいずれも不合格であったのに対して、残りの本発明品はすべて合格であった。
【００３７】
【発明の効果】
叙上のように本発明によれば、ホルダーの前端部に設けたスリット内に板状体のインサートを装着してなるスローアウェイドリルであって、上記スリットの対向内壁面から奥端面にかけてインサートとホルダーとの非当接間隙領域を設けたことにより、加工中にインサートにかかる捩れ負荷を低減し、もってドリルの耐抗折力を向上せしめることができた。また、ホルダーがよく撓むので、被削材への食いつきのときにインサートにかかる衝撃も緩和され、刃先寿命が長くなった。
【図面の簡単な説明】
【図１】本発明の小径スローアウェイドリルを構成するドリルインサートの斜視図である。
【図２】本発明の小径スローアウェイドリルの斜視図である。
【図３】図２のＸ矢視図である。
【図４】図３のＹ視図である。
【図５】２枚のインサートを装着した従来のスローアウェイドリルの平面図である。
【図６】１枚のインサートを装着した従来の小径加工用のスローアウェイドリルの平面図である。
【符号の説明】
１ ドリルインサート
２ 内切刃
３ 外切刃
４、５ すくい面
６、７ コーナーＲ部
８ 突出部
９ａ ボルト固定孔
９ｂ 凹部
１０ スローアウェイドリル
１１ ホルダー
１１ａ 中心軸
１２ 前端部
１３ 固定用ボルト
１３ａ 固定中心
１４ ポケット
１５ スリット
１５ｂ 奥端面
１５ｃ 対向内壁面
Ａ 非当接間隙領域
Ｈ 全厚み
γ 屈曲角
β テーパー角度
ｄ 間隙[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a small diameter throw-away drill for drilling.
[0002]
[Prior art]
As a drill tool for drilling holes, a tool in which an outer peripheral outer blade insert and an inner peripheral inner blade insert are detachably mounted so that the rotational trajectories of the tool body intersect each other has been generally used. It was.
[0003]
FIG. 5 shows such a throw-away drill T.
[0004]
The drill insert 20 to be mounted on the throw-away drill T has a cutting edge formed on the ridge portion of the upper surface 21, and as shown in FIG. The blade insert 22 and the inner blade insert 23 are mounted with the upper surface 21 facing in the same rotational direction. Further, among the cutting blades formed on the outer blade insert 22 and the inner blade insert 23, the rotation trajectory of the cutting blade that becomes the bottom cutting blade 25 intersects and covers from the center axis T1 to the side surface T2 of the throw-away drill T. .
[0005]
On the other hand, in the case of machining a small-diameter hole of φ10 or less, the screw has to be very small, and such a shape could not be used because of its strength. One that attaches one piece to the front end has been used. FIG. 6 shows such a throw-away drill S for small-diameter processing. As shown in FIG. 6, the thin plate-like insert 30 is wider than the holder diameter, and is formed on the upper and lower ridge sides of the front end. A cutting blade 31 in which the inner cutting blade and the outer cutting blade are integrated is formed.
[0006]
However, as a problem of the throw-away drill S for small diameter machining, since the rear end portion of the insert 30 is hidden in the holder and is difficult to see, it relates to whether or not the rear end surface of the insert is in contact with the opposing surface of the holder. Positioning cannot be confirmed visually, so a process such as polishing is necessary to control the diameter of the hole of the bolt of the insert with very high accuracy, and there is a problem that the manufacturing cost is excessive. there were.
[0007]
Therefore, the present inventor is biased by an elastic body such as a spring in a small-diameter throwaway drill in which a plate-shaped drill insert is mounted with a fixing bolt in a slit provided in the front end portion of the holder. We have developed a small-diameter throw-away drill that uses engagement sliding contact between a positioning ball and the corresponding conical dimple.
[0008]
Specifically, a positioning ball urged by an elastic body such as a spring with respect to the opposing surface of the drill insert is rotatably mounted inside the holder. The opposing surface of the drill insert is provided with a conical dimple at a portion corresponding to the ball, and the positioning ball and the conical dimple are engaged and slidably contacted when the fixing bolt is fastened. Thus, the drill insert was configured to be pulled back. The drill insert was installed at a predetermined position by arranging the conical dimple so that the conical apex (bottom point) of the conical dimple is located behind the apex of the positioning ball.
[0009]
[Problems to be solved by the invention]
The prior art by the inventor himself has effectively solved the above-mentioned problems of the small-diameter boring end mills, but has found that the following improvements are desirable.
[0010]
That is, a holder made of a material having a low Young's modulus is easily bent due to cutting resistance during processing, whereas a carbide tip having a high Young's modulus is not easily bent, and a torsional load during drilling is very large on the upper and lower surfaces of the insert. If the torsional load applied to the insert is reduced, the insert is hardly damaged as a result, and the mechanical strength and bending resistance of the drill can be improved.
[0011]
Accordingly, an object of the present invention is to reduce the torsional load applied to the insert during machining and to improve the bending resistance of the drill.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides an inner cutting edge that cuts the inner peripheral side of a machining hole at the front end of a polygonal plate-like body and an outer cutting that cuts the outer peripheral side in a slit provided at the front end of the holder. the insert having both cutting edge, a throwaway drill comprising attached by a single fixing bolt, toward the rear end surface from the opposite inner wall surfaces of the slit, the insert floats against deeper in opposed inner wall surfaces the state, and wherein the the insert and the holder are only set the non-contact gap region not contacting.
[0013]
[Action]
The small-diameter throw-away drill of the present invention is provided with a non-contact gap region between the insert and the holder from the inner wall surface facing the slit to the back end surface.
[0014]
Thereby, the drill insert is in a state of floating with respect to the opposing inner wall surface at the back of the slit, and the contact length between the drill insert and the opposing inner wall surface of the slit in the axial direction of the drill is shortened, so that the holder is easily twisted. Since the holder is easily twisted, most of the torsional load during processing is applied to the holder, and the torsional load applied to the insert is very small.
[0015]
In short, since the contact distance between the insert and the holder in the long axis direction is small, the load on the insert is greatly reduced.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 shows a drill insert 1 according to this embodiment. This drill insert 1 has an inner cutting edge 2 that cuts the inner peripheral side of a machining hole and an outer cutting that cuts the outer peripheral side at the front end of a polygonal plate-like body. A drill insert 1 that also has a blade 3, and the inner cutting blade 2 and the outer cutting blade 3 are formed at substantially the same height at an intermediate position corresponding to the total thickness H of the plate-like body. 2 and rake faces 4 and 5 of the outer cutting edge 3 are provided in a step-down manner. The inner cutting edge 2 is formed to bend in the radial direction at an intermediate position.
[0018]
In addition, the outer cutting edge 3 of the drill insert 1 is provided with a pair of corner R portions 6 and 7 at its corners, thereby forming a protruding portion 8 slightly protruding forward.
[0019]
Here, the corner R portions 6 and 7 refer to those in the range of 60 ° to 105 ° in which the angle formed by the straight line continuous to the curved portion is close to a right angle.
[0020]
Further, a bolt fixing hole 9 a is formed in the flat surface 9 that is greatly raised from the rake face 5 that continues to the outer cutting edge 3 of the drill insert 1. On the other hand, on the side of the rake face 4 of the inner cutting edge 2 of the drill insert 1, a flat surface 9 that is greatly raised from the rake face 4 is provided, and on the rear side of each flat face is a recess that is continuous with the rear end face. 9b is provided.
[0021]
2 to 4 show a small-diameter throw-away drill 10 to which the drill insert 1 is mounted. The small-diameter throw-away drill (hereinafter abbreviated as a drill) 10 is formed in a slit 15 formed in the front end portion 12 of the holder 11. The drill insert (hereinafter abbreviated as insert) 1 is mounted with a single fixing bolt 13, and the width of the insert 1 is made smaller than the diameter of the holder 11, and as shown in FIG. The fixing center 13 a of the fixing bolt 13 is displaced from the center axis 11 a of the holder 11 toward the outer cutting edge 3.
[0022]
Further, since the drill 10 has the fixing bolt 13 displaced in the direction of the outer cutting edge 3 as described above, a very large chip is formed on the rotation direction side of the rake face 4 of the inner cutting edge 2 as shown in FIG. It becomes possible to secure the pocket 14 for discharging. Moreover, since the inner cutting edge 2 is bent in the radial direction at a bending angle γ = 10 ° to 20 °, the pocket 14 can be made larger. In addition, when the bending angle γ is less than 10 °, the chip dischargeability may be deteriorated, and the holder 11 is removed by directing the combined force of the radial load, which will be described later, toward the outer cutting edge 3 side. There exists a possibility that the effect | action bent to the cutting blade 3 side may become weak. On the other hand, when the bending angle γ exceeds 20 °, the lower thickness of the inner cutting edge 2 is reduced, and as a result, the mechanical strength may be reduced.
[0023]
Moreover, since the thickness of the insert 1 will become large when the height of the outer cutting edge 3 and the inner cutting edge 2 differs greatly, there exists a possibility that the mechanical strength of the holder 11 may fall.
[0024]
Further, as shown in FIG. 4, the concave portion 9 b of the insert 1 and / or the concave portion 15 a of the slit 15 causes the concave portion 9 b to float to the inner wall surface 15 c of the slit 15 over the back end surface 15 b of the slit 15. Thus, a non-contact gap region A is formed. Thereby, the contact length between the drill insert 1 and the opposed inner wall surface 15c of the slit 15 in the axial direction of the drill 10 is shortened, and the holder 11 is easily twisted. Since the holder 11 is easily twisted, most of the torsional load during processing is applied to the holder 11, and the torsional load applied to the insert 1 is very small.
[0025]
In short, since the contact length between the insert 1 and the holder 11 in the major axis direction becomes small, the load on the insert 1 is greatly reduced. In order to generate this non-contact gap area A, in addition to the form including both the recess 9b of the insert 1 and the recess 15a of the slit 15, only one of the recess 9b of the insert 1 or the recess 15a of the slit 15 is provided. It is good also as a form provided.
[0026]
Incidentally, the ratio 1 / L of the axial length l of the non-contact gap region A to the longitudinal length L of the insert 1 is preferably in the range of 0.1 to 0.7, particularly 0.4. The range of -0.7 is more preferable. If this ratio 1 / L is excessively increased (the contact length is small), the holder 11 may be deformed, and the binding force of the insert 1 is also reduced, and chattering is likely to occur. On the other hand, if the ratio 1 / L is too small (the contact length is large), the torsional load received by the insert 1 increases and the insert 1 may be easily damaged.
[0027]
Further, the gap d of 0.05 mm or more between the opposed inner wall surface 15 c and the insert 1 on the back end face 15 b of the slit 15 is desirably at least 0.05 mm or more. When the gap d is less than 0.05 mm, the opposing inner wall surface of the slit 15 provided in the holder 11 and the concave portion 9b come into contact with each other, and there is a possibility that the function and effect of the concave portion 9b cannot be achieved. The concave portion 9b may be tapered, and even in that case, the gap d at the rear end is preferably 0.05 mm or more.
[0028]
By the way, the drill 10 is provided with the protrusion 8 of the outer cutting edge 3 on the outermost peripheral side. Although this protrusion 8 is provided with a pair of said corner R parts 6 and 7, this has the effect | action which changes the direction of the radial load of the outer cutting blade 3 to the rotation direction side. As a result, as shown in FIG. 3, the combined force direction of the radial load of the inner cutting edge 2 and the radial load of the outer cutting edge 3 is directed toward the outer cutting edge 3 from the center axis 11a of the holder. It bends toward the cutting edge 3 side. Accordingly, the machining diameter becomes large, and when the drill 10 is pulled out from the machining hole, the outer cutting blade 3 and the hole wall can be pulled out without contact, so that the machining surface can be improved.
[0029]
As shown in FIG. 2, the inner cutting edge 2 is bent in the radial direction at the intermediate portion, but this bending can cause the radial load of the inner cutting edge 2 to be directed somewhat toward the outer cutting edge 3. It is possible to reinforce the action of the protrusion 8.
[0030]
As mentioned above, although embodiment of this invention was illustrated with the figure, this invention is not limited to the above-mentioned embodiment, It cannot be overemphasized that it can be set as arbitrary forms, unless it deviates from the objective of invention.
[0031]
[Experimental example]
Hereinafter, experimental examples based on the present invention will be described.
[0032]
The drill insert 1 shown in FIG. 1 to FIG. 4, wherein the feed is sequentially raised under the following conditions using the drill insert 1 in which the l / L and d are set as shown in Table 1, and the insert is damaged. The previous maximum feed was taken as the limit feed condition, and when the value was 0.15 or more, the test was accepted.
[0033]
Experimental condition f = 0.1, 0.12, 0.15, 0.2
V = 120m / min
Internal lubrication drill: φ10
Grade: PR660 manufactured by Kyocera Corporation
[0034]
[Table 1]

[0035]
The results of this experiment are shown in Table 1.
[0036]
As shown in Table 1, sample 1 (l / L is greater than 0.7) and sample 3 (d is less than 0.05 mm), both outside the scope of the present invention, failed. All the remaining products of the present invention passed.
[0037]
【The invention's effect】
As described above, according to the present invention, it is a throw-away drill in which a plate-like insert is mounted in a slit provided at the front end portion of the holder, and the insert extends from the opposing inner wall surface to the back end surface of the slit. By providing a non-contact gap area with the holder, the torsional load applied to the insert during machining can be reduced, thereby improving the bending resistance of the drill. In addition, since the holder bends well, the impact applied to the insert when biting the work material was alleviated, and the life of the cutting edge was prolonged.
[Brief description of the drawings]
FIG. 1 is a perspective view of a drill insert constituting a small diameter throw-away drill according to the present invention.
FIG. 2 is a perspective view of a small diameter throw-away drill according to the present invention.
FIG. 3 is a view taken in the direction of the arrow X in FIG. 2;
4 is a Y view of FIG. 3;
FIG. 5 is a plan view of a conventional throw-away drill equipped with two inserts.
FIG. 6 is a plan view of a conventional throw-away drill for small diameter machining equipped with one insert.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Drill insert 2 Inner cutting edge 3 Outer cutting edge 4, 5 Rake face 6, 7 Corner R part 8 Projection part 9a Bolt fixing hole 9b Recess 10 Throw away drill 11 Holder 11a Center shaft 12 Front end part 13 Fixing bolt 13a Fixing center 14 Pocket 15 Slit 15b Back end face 15c Opposite inner wall surface A Non-contact gap area H Total thickness γ Bend angle β Taper angle d Gap

Claims (3)

In the slit provided at the front end of the holder, an insert having both an inner cutting edge that cuts the inner peripheral side of the machining hole and an outer cutting edge that cuts the outer peripheral side at the front end of the polygonal plate-like body is provided. a throw-away drill made by mounting a fixed bolt, toward the rear end surface from the opposite inner wall surfaces of the slit, the insert is floated against deeper opposing inner wall surface, not in contact with the insert and the holder diameter indexable drill, characterized in that the non-contact gap region digits set. The small-diameter throw-away drill according to claim 1, wherein a gap of the non-contact gap region on the back end face of the slit is 0.05 mm or more. The small diameter throw-away drill according to claim 1 or 2, wherein a ratio 1 / L of an axial length l of the non-contact gap region to an axial length L of the insert is in a range of 0.1 to 0.7.

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