KR20160079502A - Indexable Drill - Google Patents

Abstract

The present invention relates to an indexable drill, and more particularly to an indexable drill capable of machining a hole in a workpiece.
The indexable drill according to the embodiment of the present invention can secure a larger chip discharge space constituting the indexable drill so as to smooth chip discharging and ensure that the flute has a constant flute helix angle across the whole area, And the flute has a rotation angle of 90 to 115 degrees to improve the quality of the processing and the concave shape is applied to the flute extension portion of the flute to improve the durability of the indexable drill .

Description

[0002] Indexable Drill [0003]

The present invention relates to an indexable drill, and more particularly to an indexable drill capable of machining a hole in a workpiece.

Generally, the indexable drill forms a cut-in portion and a shank on both sides of the flange with respect to the flange. A flow path is formed inside the indexable drill, and the coolant flows through the flow path.

Further, a plurality of flutes are formed at the notch portions, and cutting inserts are mounted at the outer end portions of the flutes.

The cutting insert can be distinguished according to the position in which it is mounted. More specifically, the inner cutting insert is mounted on the side near the center of rotation of the indexable drill, and the outer cutting insert is mounted on the far side of the rotation center.

The flute is used for cutting chips generated by the cutting insert and discharging the generated chips.

However, the general indexable drill as described above has the following problems.

Indexable drills with internal cutting inserts and external cutting inserts should be provided with sufficient chip clearance and capable of providing sufficient flow rate of cutting fluid in order to achieve good performance.

In order to secure the chip discharge space, the flutes must be formed deeply. However, since the oil holes are formed inside the indexable drill, the flutes and the oil holes must be able to maintain a proper distance.

Further, in order to secure a sufficient chip discharge space and to supply a sufficient amount of cutting oil, a drill body twisting technique is applied to form a flute helix angle of 10 degrees or more. However, in order to apply a body twisting technique, An additional process is required and the manufacturing cost is increased by 20% or more. In addition, there is a problem that a dedicated equipment for twisting the drill body is required.

On the other hand, the chips generated by the cutting process continuously strike the wall surface of the chip pocket, thereby causing wear on the chip pocket portion. As the wear progresses, grooves may be generated, and in particular, the chip pocket portion on the side where the cutting insert for external use is mounted wears more severely.

On the other hand, in the indexable drill, a groove is formed in the chip pocket portion due to wear of the chip pocket portion, and the indexable drill may be broken if the groove is gradually enlarged.

Korean Patent Publication No. 10-2011-0075303 (Jul. 2011)

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to at least partially solve the above problems and / or disadvantages and to provide at least the advantages below. So as to improve the machining quality by allowing the flute to have a rotation angle of 90 to 115 degrees and to improve the durability of the indexable drill by applying a concave surface shape to the flute extension portion of the flute The present invention is directed to an indexable drill.

The present invention has been made in view of the above problems, and it is an object of the present invention to at least partially solve the problems in the conventional arts. There will be.

According to an aspect of the present invention, there is provided an indexable drill comprising: a flange; A shank 120 formed on one side of the flange 110; A notch 130 formed on the other side of the flange 110; First and second flutes 131 and 132 formed to have a flute helix angle (a) and a rotation angle (b) on the outer circumferential surface of the entire length of the notch portion 130; First and second pockets (133, 134) formed on one side of the ends of the first and second flutes (131, 132); First and second flute extensions 141 and 142 formed at the ends of the first and second flutes 131 and 132 and each of which is concavely and concave at a position spaced apart from the first and second pockets 133 and 134; An oil hole (200) formed from the shank (120) to the notch (130); And first and second cutting inserts (310, 320) installed in the first and second pockets (133, 134), respectively.

In the indexable drill according to the embodiment of the present invention, the flute helix angle (a) may be the same in all the sections of the first and second flutes 131 and 132.

The indexable drill according to the embodiment of the present invention is characterized in that the flute flute helix angle a is set such that the length L1 of the notch 130 is at least twice the outer diameter D of the notch 130, If it is less than 3 times, it may be 19 to 20 degrees.

The indexable drill according to an embodiment of the present invention is characterized in that the flute flute helix angle a is set such that the length L1 of the notch 130 is at least three times the outer diameter D of the notch 130 If it is less than 4 times, it may be 18 to 19 degrees.

The indexable drill according to the embodiment of the present invention is characterized in that the flute flute helix angle a is set such that the length L1 of the notched portion 130 is not less than four times the outer diameter D of the notched portion 130 If it is less than 5 times, it may be 13 degrees to 14 degrees.

The indexable drill according to the embodiment of the present invention is characterized in that the flute flute helix angle a is set such that the length L1 of the notch 130 is five times or more the outer diameter D of the notch 130 And may be from 11 degrees to 12 degrees.

In the indexable drill according to the embodiment of the present invention, the rotation angle b may be 95 to 115 degrees.

The indexable drill according to the embodiment of the present invention is characterized in that the web thickness w between the first flute 131 and the second flute 132 is set to 17 % ≪ / RTI > to 21%.

In the indexable drill according to the embodiment of the present invention, the radius of curvature of the first flute 131 and the radius of curvature of the first flute extension 141 may be the same.

The indexable drill according to the embodiment of the present invention is characterized in that the indexable drill passes through the center of the first cutting insert 310 and has a cross section perpendicular to the center axis of the cut- The shortest distance c to the one-flute extension portion 141 may be 5% to 15% with respect to the outer diameter D of the cut-in portion 130.

In the indexable drill according to the embodiment of the present invention, the oil hole 200 is formed with a leading oil hole 212 on the side where the cutting oil flows, and a trailing oil hole 214 is formed on the side where the cutting oil is discharged And the rear oil hole 214 is provided in a straight line with an inclination with respect to the center axis of the notch 130. The length L2 of the rear oil hole 214 is set to be longer than the length of the notch 130 L1 to 70% to 85%.

In the indexable drill according to the embodiment of the present invention, the diameter of the rear oil hole 214 may be smaller than the diameter of the front oil hole 212 by 0.2 mm to 0.5 mm.

In the indexable drill according to the embodiment of the present invention, the center of the rear oil hole 214 at the boundary between the front oil hole 212 and the rear oil hole 214 is the center of the front oil hole 214 May be formed at a position within 40% to 70% with respect to the radius of the notch 130 from the center.

The details of other embodiments are included in the detailed description and drawings.

In the indexable drill according to the embodiment of the present invention as described above, since the flute is formed as large as possible, the chip discharge space can be secured to a greater extent, and the chip can be smoothly discharged.

In addition, the indexable drill according to the embodiment of the present invention allows the flute to have a constant flute helix angle across the entire area, thereby further improving the chip discharging action.

In addition, the indexable drill according to the embodiment of the present invention allows the flute to have a rotation angle of 90 degrees to 115 degrees, so that the machined hole is not scraped, and the machining quality can be remarkably improved.

Further, the indexable drill according to the embodiment of the present invention can induce the chip to slip smoothly without hitting the flute extension by applying a concave shape to the flute extension of the flute, thereby further improving the chip discharging action , And furthermore, the durability of the indexable drill can be improved by significantly reducing the impact due to the impact.

1 is a front view and a side view for explaining an indexable drill according to an embodiment of the present invention.
2 to 4 are views for explaining a flute extension in the indexable drill according to the embodiment of the present invention.
5 is a view for explaining the thickness of the web and the positions of the oil holes in the indexable drill according to the embodiment of the present invention.
6 and 7 are views for explaining rotation angles in an indexable drill according to an embodiment of the present invention.
8 is a view for explaining an operation effect of the indexable drill according to the embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the embodiments described below are provided for illustrative purposes only, and that the present invention may be embodied with various modifications and alterations. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the subject matter of the present invention. The accompanying drawings are not necessarily drawn to scale to facilitate understanding of the invention, but may be exaggerated in size.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Like reference numerals refer to like elements throughout the specification.

Hereinafter, an indexable drill according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a front view and a side view for explaining an indexable drill according to an embodiment of the present invention. FIG.

≪ Embodiment 1 >

In the indexable drill 100 according to the embodiment of the present invention, the shank 120 is formed on one side of the flange 110 and the cut-in portion 130 is formed on the other side.

The shank 120 is a portion that is mounted on the arbor. The flange 110 is provided larger than the outer diameter of the shank 120 and the infeed portion 130. The flange 110 can be positioned where the indexable drill 100 is mounted when the indexable drill 100 is mounted on the arbor.

The cut-in portion 130 has first and second flutes 131 and 132 formed on the outer circumferential surface thereof.

The first and second flutes 131 and 132 are formed to have a flute helix angle a and a rotation angle b at the outer circumferential surface of the entire length of the cut-in portion 130. Thus, the indexable drill 100 according to the present invention allows the chip to be smoothly discharged along the first and second flutes 131 and 132.

In addition, the first and second pockets 133 and 134 are formed on one side of the ends of the first and second flutes 131 and 132, respectively.

The first and second flutes 131 and 132 are curved and concave at the positions spaced apart from the first and second pockets 133 and 134 at the ends of the first and second flutes 131 and 132, . The first and second flute extension portions 141 and 142 guide the chip to smoothly flow smoothly without damaging the surface of the flute directly after the chips are formed to improve chip discharge.

In the indexable drill 100 according to the embodiment of the present invention, the oil hole 200 is formed from the shank 120 to the cut-in portion 130. The cutting oil flows through the oil hole 200, and the flowing cutting oil is discharged from the front end of the indexable drill 100. [ The coolant cools, lubs and assists in chip evacuation to the part performing the cutting operation.

Meanwhile, the first and second cutting inserts 310 and 320 are installed in the first and second pockets 133 and 134, respectively. Here, the first cutting insert 310 and the second cutting insert 320 may be cutting inserts 300 of the same kind. More specifically, the cutting insert 300, which is different from the position and orientation in which it is installed, acts as a cutting insert when it is disposed near the center axis of the indexable drill 100, ), It functions as a cutting insert for external claws.

≪ Embodiment 2 >

The indexable drill 100 according to another embodiment of the present invention may be such that the flute helix angle a is the same in the entire section of the first and second flutes 131 and 132 as shown in Figs. .

Thus, the indexable drill according to the present invention is such that the first and second flutes 131 and 132 are applied as a single flute helix angle (a) without changing the flute helix angle (a) from the front end to the bottom end, The flow of the chip 600 is not disturbed. That is, by forming the flute helix angle (a) equally between the first and second flutes 131 and 132, the chip 600 is advantageously discharged. Further, since the flute helix angle (a) is uniformly formed between the front and the back of the first and second flutes 131 and 132, the cross-sectional area is uniform across the entire length of the indexable drill 100,

≪ Third Embodiment >

The factors affecting the discharge capability of the chip 600 when the hole is machined using the indexable drill 100 are flute shape (spherical width ratio, web thickness), flute flute helix angle, and cooling oil (discharge flow rate, speed) . The smaller the flute helix angle (a) of the flute is, the lower the chip discharging ability due to rotation is. Particularly, when the material of a material is subjected to hard machining such as mild steel, STS, and forged steel, the chip discharging ability may be lowered.

Therefore, a flute helix angle (a) of 10 degrees or more is required to realize a good chip discharging ability, and if the flute helix angle (a) is more than 20 degrees, the space for forming the flute is narrow.

The present invention provides a technology idea with a good chip discharge capability according to the ratio of the diameter to the length of the indexable drill (100).

More specifically, the indexable drill 100 according to the embodiment of the present invention is characterized in that the flute flute helix angle a is smaller than the outer diameter D of the cut-in portion 130 such that the length L1 of the cut- If it is 2 times or more and 3 times or less, it may be 19 to 20 degrees.

The indexable drill 100 according to the embodiment of the present invention is characterized in that the flute flute helix angle a is set such that the length L1 of the notch portion 130 is not less than three times the outer diameter D of the notch portion 130 Fold, it may be 18 to 19 degrees.

The indexable drill 100 according to the embodiment of the present invention is characterized in that the flute flute helix angle a is set so that the length L1 of the notch portion 130 is not less than four times the outer diameter D of the notch portion 130 Fold, it may be 13 degrees to 14 degrees.

The indexable drill 100 according to the embodiment of the present invention is characterized in that the flute flute helix angle a is larger than the outer diameter D of the notch 130 by five times or more when the length L1 of the cut- And may be 11 degrees to 12 degrees.

<Fourth Embodiment>

The indexable drill 100 according to another embodiment of the present invention may have a rotation angle b of 95 to 115 degrees. As shown in Fig. 6, the rotational angle b means an angular range in which the flutes form a spiral when viewed from the end of the indexable drill 100. As shown in Fig.

Fig. 7 shows an example in which the rotational angle b is varied. Fig. 7 (a) shows an example in which the rotational angle b is 30 degrees. 7 (b) shows an example in which the rotation angle b is 50 degrees. 7A and 7B, it can be seen that the rib does not cover the entire circumference at the flute portion. 8 (b), when the rotational angle b is small as shown in FIGS. 7 (a) and 7 (b), the hole end 510 of the work 500 is torn Can occur.

The example of the indexable drill 100 shown in Fig. 7 (a) shows that the surface quality Ra of the workpiece is Ra of 1.3 占 퐉, and the execution of the indexable drill 100 shown in Fig. 7 (b) For example, the processing quality was found to have a surface roughness Ra of 1.1 m.

On the other hand, FIG. 7 (c) shows that the rotational angle b is larger than that of FIGS. 7 (a) and 7 (b). Specifically, FIG. 7C shows the rotation angle b at 95 degrees. Figure 7 (c) shows that the ribs in the flute region are implemented similar to the circumference but still do not cover the entire circumference. In the embodiment of the indexable drill 100 shown in FIG. 7 (c), the surface quality Ra of the surface quality was 0.9 m. That is, as the rotational angle b increases, the machining quality improves. Also, as shown in Fig. 8 (c), the hole end portion 512 of the blank 500 has no slipping phenomenon and a good quality is realized.

On the other hand, FIG. 7 (d) shows that the rotation angle b is larger than that of FIG. 7 (c). More specifically, FIG. 7 (d) shows the rotation angle b at 115 degrees. Fig. 7 (d) shows that the rib covers the entire circumference at the flute portion. In particular, the rigidity of the indexable drill 100 is improved by covering the entire circumference of the rib. In the embodiment of the indexable drill 100 shown in Fig. 7 (d), the surface quality Ra of the surface quality was 0.85 m. That is, as the rotational angle b increases, the machining quality is remarkably improved. In addition, as shown in FIG. 8 (c), the hole end portion 512 of the material 500 has no slippage and a very good quality is realized.

On the other hand, if the helical rotation angle b of the indexable drill is larger than 115 degrees, there may be a problem that the machining of the rear oil hole 214 becomes difficult.

Therefore, when the indexable drill 100 has a rotation angle b of 95 to 115 degrees, it is possible to produce a good machining quality while still being able to manufacture.

<Fifth Embodiment>

In the indexable drill 100 according to the embodiment of the present invention, the web thickness w between the first flute 131 and the second flute 132 is 17% of the outer diameter D of the cut- To 21%.

As the web thickness w is increased, the rigidity of the indexable drill 100 is improved. However, since the spaces of the first and second flutes 131 and 132 are narrowed, the chip discharge space becomes narrower, There may be a problem.

Conversely, if the web thickness w is reduced, the space of the first and second flutes 131 and 132 may be widened to improve the chip discharging ability, but the rigidity of the indexable drill 100 may be reduced, It is easily damaged.

That is, the web thickness w is a very important factor that determines the performance of the indexable drill 100, but is a very difficult value to set.

The indexable drill 100 according to the embodiment of the present invention sets the web thickness w to 17% to 21% with respect to the outer diameter D of the cut-in portion 130. [

Particularly, if the web thickness w is greater than 17% with respect to the outer diameter D of the cut-in portion 130, the rigidity of the indexable drill 100 can be kept good.

On the other hand, if the web thickness w is larger than 21% of the outer diameter D of the cut-in portion 130, the chip discharging performance of the workpiece such as mild steel or STS having a large chip 600 may be drastically reduced, The processing may be restricted, and there is a fear that the high-feed workability is lowered. Therefore, it is preferable that the web thickness w is less than 21% with respect to the outer diameter D of the infeed portion 130.

<Sixth Embodiment>

In the indexable drill 100 according to the embodiment of the present invention, the curved surface radius of the first flute 131 and the curved surface radius of the first flute extension 141 may be the same.

Thereby, the first flute extension portion 141 can be machined by using the raising tool that processes the first flute 131 when the flute is machined. That is, convenience in manufacturing the indexable drill 100 can be increased.

Likewise, the second flute extension portion 142 can be processed by using a raising tool that has been used to machine the second flute 132. That is, convenience in manufacturing the indexable drill 100 can be increased.

<Seventh Embodiment>

The indexable drill 100 according to the embodiment of the present invention is arranged such that it passes through the center of the first cutting insert 310 and has a first pocket 133 and a first flute extension 130 at a cross section orthogonal to the central axis of the cut- The shortest distance c from the outer circumferential portion 141 to the outer circumferential portion 141 may be 5% to 15% with respect to the outer diameter D of the cut-

If the shortest distance c is 15% or less of the outer diameter D of the cut-in portion 130, the chip 600 may be slidably moved on the curved surface to increase the flow performance of the chip 600.

If the shortest distance c is 5% or more of the outer diameter D of the cut-in portion 130, the rigidity of the indexable drill 100 can be satisfactorily maintained.

&Lt; Eighth Embodiment >

The indexable drill 100 according to the embodiment of the present invention is provided with the oil hole 200 in two stages and the oil hole 200 can be provided in the number corresponding to the number of the flutes. The oil hole 200 can be distinguished into a leading oil hole 212 and a trailing oil hole 214.

The oil hole 200 may have an inlet 210 at the end of the shank 120 and a coolant supplied from the arbor through the inlet 210.

A plurality of leading oil holes 212 may be provided and a plurality of leading oil holes 212 may be communicated with the inlet portion 210. That is, the coolant introduced through the inlet 210 serves as a guide to be supplied to the plurality of leading oil holes 212.

The rear oil hole 214 is formed on the side where the cutting oil is discharged. Further, the rear oil hole 214 is provided in a straight line, inclined with respect to the center axis of the cut-in portion 130.

That is, the rear oil hole 214 may be provided in an inclined shape so as not to overlap with the first and second flutes 131 and 132. Further, the rear oil hole 214 is provided in a linear shape, which is advantageous in that it is easy to process.

On the other hand, the length L2 of the rear oil hole 214 may be 70% to 85% of the length L1 of the cut-in portion 130.

If the length L2 of the rear oil hole 214 is greater than 70% of the length L1 of the notch 130, the rotational angle b of the first and second flutes 131 and 132 is greater than 95 degrees can do.

On the other hand, as the length L2 of the rear oil hole 214 becomes 70% to 85% of the length L1 of the cut-in portion 130, the longer the length L1 of the cut-in portion 130 becomes, However, if it exceeds 85%, the oblique rear oil hole 214 becomes excessively long, and it may be difficult to arrange the oil hole 214 because of the narrow space.

Therefore, the indexable drill 100 according to the embodiment of the present invention can secure a large rotational angle b and can process the rear oil hole 214 easily.

&Lt; Example 9 &

The indexable drill 100 according to the embodiment of the present invention may be such that the diameter of the rear oil hole 214 is smaller than the diameter of the front oil hole 212 by 0.2 mm to 0.5 mm.

When the oil hole 200 is parallel to the central axis of the indexable drill 100, the machining is easy even if the machining depth is long.

However, since the rear oil hole 214 is oblique to the center axis of the indexable drill 100 and the processing depth is deep, the drill position and machining accuracy for machining the rear oil hole 214 are very important, (Machining center) machining is essential.

The indexable drill 100 according to the embodiment of the present invention is designed such that the front end oil hole 212 is firstly processed for ease of manufacture in order to plan the processing order of the oil hole 200 for the production efficiency, (Not shown).

If the inner diameter of the rear oil hole 214 is equal to or smaller than the inner diameter of the front oil hole 212, the breakage ratio of the through hole at the time of penetration can be increased. Therefore, in order to reduce the drill failure rate when machining the oil hole 200, the diameter of the drill for machining the rear oil hole 214 may be smaller than the diameter of the drill for machining the front oil hole 212. [

On the other hand, if the diameter of the drill for machining the leading end oil hole 212 is excessively larger than necessary, it may be too close to the first and second flutes 131 and 132. Particularly, if the inner diameter of the leading end oil hole 212 is too large when the leading end oil hole 212 is machined, there is a possibility that the inner diameter of the leading oil hole 212 is limited to the first and second flutes 131 and 132. Therefore, Needs to be.

The indexable drill 100 according to the present invention provides a difference in diameter between the leading oil hole 212 and the trailing oil hole 214 from 0.2 mm to 0.5 mm. Thus, the indexable drill 100 according to the embodiment of the present invention can securely process the leading oil hole 212 and the trailing oil hole 214, thereby manufacturing the indexable drill 100 of better quality .

<Tenth Embodiment>

In the indexable drill 100 according to the embodiment of the present invention, the center of the rear oil hole 214 at the boundary portion between the leading oil hole 212 and the trailing oil hole 214 is the center of the trailing oil hole 214 from the center of the leading portion 130, May be formed at a position within 40% to 70% with respect to the radius of the substrate 130.

When the center of the rear oil hole 214 is formed at a position deviating from 40% to 70% with respect to the radius of the cut-in portion 130 from the center of the cut-in portion 130, the distance between the oil hole 200 and the outer- The thickness becomes thin and the manufacturing defective ratio can be increased.

That is, the positions of the leading oil hole 212 and the trailing oil hole 214 are located inside the ribs of the indexable drill 100 to prevent the first and second flutes 131 and 132 from bursting, So that it is possible to provide the indexable drill 100 of good quality.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. will be.

Therefore, it should be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive, and the scope of the present invention is indicated by the appended claims. The scope of the claims and their equivalents It is to be understood that all changes or modifications that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

An indexable drill according to an embodiment of the present invention can be used for machining holes in a workpiece.

100: indexable drill 110: flange
120: shank 130:
131, 132: first and second flutes 133, 134: first and second pockets
141, 142: First and second flute extensions
200: Oil hole 210: Inflow part
212: leading oil hole 214: trailing oil hole
300: cutting inserts 310, 320: first and second cutting inserts
500: Material 510: hole
512: Hole end 600: Chip
a: flute helix angle
b: rotation angle
c: the shortest distance from the level of the cutting insert center position to the pocket and the flute extension
d: Distance from the center axis to the center of the oil hole
L1: length of the infeed portion
L2: Length of rear oil hole
w: web thickness

Claims (13)

A flange 110;
A shank 120 formed on one side of the flange 110;
A notch 130 formed on the other side of the flange 110;
First and second flutes 131 and 132 formed to have a flute helix angle (a) and a rotation angle (b) on the outer circumferential surface of the entire length of the notch portion 130;
First and second pockets (133, 134) formed on one side of the ends of the first and second flutes (131, 132);
First and second flute extensions 141 and 142 formed at the ends of the first and second flutes 131 and 132 and each of which is concavely and concave at a position spaced apart from the first and second pockets 133 and 134;
An oil hole (200) formed from the shank (120) to the notch (130); And
First and second cutting inserts (310, 320) installed in the first and second pockets (133, 134), respectively;
&Lt; / RTI &gt;
The method according to claim 1,
Wherein the flute helix angle (a) is the same in all sections of the first and second flutes (131, 132).
3. The method of claim 2,
If the length L1 of the notch 130 is 2 to 3 times larger than the outer diameter D of the notch 130, the flute flute helix angle a is 19 to 20 degrees.
And the indexable drill.
3. The method of claim 2,
The flute flute helix angle a is in a range of 18 degrees to 19 degrees when the length L1 of the notched portion 130 is three times or more and four times less than the outside diameter D of the notched portion 130
And the indexable drill.
3. The method of claim 2,
The flute flute helix angle a is in a range of 13 degrees to 14 degrees when the length L1 of the cut-in portion 130 is four times or more and five times smaller than the outer diameter D of the cut-in portion 130
And the indexable drill.
3. The method of claim 2,
If the length L1 of the notch 130 is 5 times or more larger than the outer diameter D of the notch 130, the flute flute helix angle a is in a range of 11 degrees to 12 degrees
And the indexable drill.
The method according to claim 1,
And the rotation angle (b) is 95 to 115 degrees.
The method according to claim 1,
Wherein the web thickness (w) between the first flute (131) and the second flute (132) is 17% to 21% with respect to the outer diameter (D) of the notch (130).
The method according to claim 1,
Wherein a curved surface radius of the first flute (131) is equal to a curved surface radius of the first flute extension portion (141).
The method according to claim 1,
The shortest distance c from the center of the first cutting insert 310 to the first pocket 133 and the first flute extension 141 at a cross section orthogonal to the central axis of the cut-in portion 130 Is 5% to 15% with respect to the outer diameter (D) of the notch portion (130).
The method according to claim 1,
The oil hole 200 is formed with a leading oil hole 212 on the side where the cutting oil flows and a trailing oil hole 214 is formed on the side where the cutting oil is discharged.
The rear end oil hole 214 is provided in a straight line with an inclination with respect to the central axis of the notch portion 130,
, And the length (L2) of the rear oil hole (214) is 70% to 85% of the length (L1) of the notch (130).
12. The method of claim 11,
Wherein the diameter of the rear oil hole (214) is smaller than the diameter of the front oil hole (212) by 0.2 mm to 0.5 mm.
13. The method of claim 12,
The center of the rear oil hole 214 at the boundary between the front end oil hole 212 and the rear oil hole 214 may be 40% to 40% of the radius of the cut- 70%. &Lt; / RTI &gt;

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