JP2001277023A - Throwaway type drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a throwaway type drill in which the discharging property of chips is improved in a one-tip type throwaway tip with two similar tips. SOLUTION: A notched portion is formed in a rear end corner of a first block forming an inner blade cutting a center portion of a hole in a tip. A sectional shape of a flute groove on the inner blade side is of double-arc shape in a drill body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away type drill used for drilling.

[0002]

2. Description of the Related Art As a drill used for drilling, in addition to a normal solid-type drill integrally formed as a whole, a cutting blade is provided on a throw-away tip separate from a drill body (holder). There is a so-called throw-away type drill which is formed so that it can be detachably attached to the tip of a drill body with a screw or the like.

[0003] There are two types of throw-away type drills and one-chip type drills. Of these, the former two-chip type throw-away drills are described in, for example, JP-A-10-29108. As shown in the figure, a tip having an inner blade for cutting a central portion of a hole and a tip having an outer blade for cutting a peripheral portion of the hole are mounted on a tip of a drill body. In the invention described in the above publication, both the inner cutter and the outer cutter are formed on one tip, and the same tip can be used as the inner cutter tip or the outer cutter tip depending on the direction and position of attachment to the drill body. It is also configured.

[0004] However, this two-chip type configuration is suitable for a large drill having a large processing diameter, but if it is to be applied to a small drill having a processing diameter smaller than about φ10, for example, the drill body of the drill body is required. Insufficient space at the tip for chip mounting or chip removal, or too small screws for chip mounting, resulting in insufficient mounting strength There was a problem.

[0005] On the other hand, as the one-chip type throw-away drill (hereinafter abbreviated as "one-chip drill"), for example, as described in Japanese Patent Application Laid-Open No. 10-328918, the tip of a conventional solid-type drill is used. In general, a pair of inserts having a long blade ridge that is similar to the shape and that faces the drilling direction and that extends on both sides from the top located on the rotation axis of the drill and that extends over the entire length of the radius of the processing hole is generally used. It is.

However, in the above-mentioned tip shape, since a large cutting resistance is applied to the tip at the time of drilling, one tip is firmly fixed to the tip of the drill body with two screws as shown in the above-mentioned publication. In addition to the necessity, it is necessary to increase the thickness of the chip, and there is a problem that it is not easy to secure a space for discharging chips.

Accordingly, the inventor has previously provided an inner cutter for cutting the center of the hole and an outer cutter for cutting the peripheral edge of the hole, and an inner cutter for the inner cutter tip in a two-chip type throw-away drill and an outer cutter for cutting. A one-chip type throw-away tip similar to a two-chip type and formed on one tip as an arrangement similar to the arrangement of the outer cutters of the blade tip has been developed (JP-A-11-188518).
No.).

In the one-chip type throw-away insert similar to the above-mentioned two-chip (hereinafter abbreviated as “similar one-tip”), the inner blade only needs to have a length sufficient to cut the center of the hole. Since the blade only needs to have a length sufficient to cut the peripheral portion of the hole, it is possible to reduce the cutting resistance applied to the chip at the time of drilling, as compared with a conventional one-chip drill, By reducing the thickness of the outer blade portion and using one screw for attaching to the drill body, it is possible to secure a space for chip discharge.

Therefore, the present inventor has further studied a similar one chip and a drill body thereof, and as a result, has found that the structure described in the above publication has room for further improvement, particularly in terms of chip dischargeability.

[0010] An object of the present invention is to provide a novel throw-away type drill having a similar chip and having improved chip dischargeability as compared with the conventional one.

[0011]

Means for Solving the Problems and Effects of the Invention In order to solve the above-mentioned problems, the invention of claim 1 of the present invention comprises a plate-shaped throw-away chip and a central portion of a hole provided in the throw-away chip. The first to form the inner blade at the front end
The block and the throwaway tip are also provided,
A second block formed at the front end with an outer blade for shaving the peripheral portion of the hole; a shaft-shaped drill body; and a pair of holding pieces provided at an end of the drill body and holding and holding the throw-away tip. The first block of the indexable insert is provided with a cutaway portion at a rear end corner thereof.

According to this structure, the notch is provided in the first block, and the structure in which the coolant flows through the notch is adopted in the drill, so that the coolant is discharged through the notch as the liquid passage. Can be discharged into the flute groove on the inner blade side. By discharging the coolant into the inner blade side flute groove, it is possible to reliably discharge chips from the inner blade, which are formed in an umbrella-like shape and have poor drainage properties, from the hole.

Next, according to a second aspect of the present invention, in the first aspect of the present invention, the drill main body is formed so that the drill body penetrates in the axial direction and reaches one of the holding pieces. A liquid passage groove provided on the sandwiching surface, wherein the liquid passage groove and the notch portion partially overlap each other.

According to this configuration, the coolant can be reliably discharged into the inner blade side flute groove through the notch portion, and the liquid passage groove provided on the holding surface of the holding piece allows, for example, the holding piece to be cooled. The cooling hole can be simultaneously discharged to the tip.

According to a third aspect of the present invention, there is provided a plate-like throw-away tip, a first block formed at the front end of the throw-away tip and having an inner blade for cutting a central portion of a hole at a front end thereof. A second block formed at the front end of the outer blade for shaving the peripheral portion of the hole, a shaft-shaped drill body, and a pair of pinches provided at the end of the drill body and holding the throw-away tip therebetween. A piece and
A flute groove formed in the drill body from an axial rear end of the drill body, wherein the flute groove has an inner blade-side flute groove for discharging chips from the inner blade to the outside of the hole and chips from the outer blade. And an outer blade-side flute groove for discharging the outside of the hole, wherein the cross-sectional shape of the inner blade-side flute groove is a two-arc shape.

According to this structure, chips from the inner blade, which are formed in an umbrella-like shape and have poor dischargeability, fit loosely into one of the circular arcs, and the radial swing of the drill body is reduced. Since they are small and are discharged, clogging of chips can be made difficult to occur.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIGS. 1 (a) and 1 (b) are exploded perspective views of a throw-away tip and a drill body for mounting the same according to an embodiment of the present invention, and FIG. 1 (a) is viewed from the front side of the tip. FIG. 1B is an exploded perspective view of the chip viewed from the back side.

With reference to these figures, the indexable insert 1 has an inner blade 11 for shaving the center of the hole at the front end in the drilling direction.
And an outer blade 12 for shaving the periphery of the hole. The indexable insert 1 is a plate-shaped first forming the inner blade 11.
And the plate-shaped second block 14 forming the outer cutter 12 are integrally formed.

First block 13 and second block 14
Has a shape that is shifted from each other in the direction of the plate surface, except for the portions 15 overlapping each other. Through hole 1a penetrating in the thickness direction at the overlapping portion 15
Are formed. This through hole 1 a is for inserting a mounting screw 3 for mounting the tip 1 to the drill body 2.

The chip 1 has two surfaces back-to-back with each other (ie, corresponding to the outer surfaces of the corner blocks 13 and 14).
A first seating surface 1b as a pair of held surfaces and a second seating surface 1b.
The through hole 1a is opened in the first and second seating surfaces 1b and 1c.

Referring to FIG. 2, the tip 1 has a rear seat surface 1d which is received by the bottom of a pocket 23 provided at the rear of the drill body 2 in the drilling direction. Chip 1
The notch 1 continuous between the pair of pinched seating surfaces 1b, 1c is provided at the rear end corner of the first block 13 having the inner blade 11.
On the other hand, referring to FIG. 3 (a) which is a side view of the drill body, and FIG. 3 (b) which is a side view of the drill body in a state where the tip 1 is mounted with the mounting screw 3 from another angle. The drill body 2 has a shaft-shaped drill body 4 and a shank 5 provided coaxially, and the drill body 2 is attached to a tool holder (not shown) on a part of the peripheral surface of the shank 5. A flat surface 5a that functions as a detent when it is turned is formed.

FIGS. 1A and 1B and FIG. 2A
With reference to, at the front end of the drill body 4, a pair of holding pieces 21 and 22 for holding the tip 1 therebetween is formed, and the holding surfaces 26 and 27 of the pair of holding pieces 21 and 22 are formed.
A pocket for inserting the chip 1 is defined therebetween. With the chip 1 inserted in the pocket 23,
Through-hole 21a and through-hole 1 of holding piece 21 holding mounting screw 3
a, and the screw is screwed into the screw hole 22a of the holding piece 22, whereby the tip 1 is held and fixed to the drill body 2.

One of the holding pieces 21 corresponds to the first block 13 forming the inner blade 11, and the holding surface 26 thereof abuts on the first held seat surface 1b as the first block 13. The other holding piece 22 corresponds to the second block 14 forming the outer blade 12, and the holding surface 27 abuts on the second held seat surface 1 c as the held surface of the second block 14.

The clamped seating surfaces 1b and 1c of the blocks 13 and 14 are arranged back to back with the rake surfaces 13a and 14a, respectively. And these rake faces 13
Chip pockets 21b and 22b for chip processing are formed above the a and 14a and on the side of the holding pieces 21 and 22.

Further, helical flute grooves 24 and 25 are formed on the peripheral surface of the drill body to discharge chips during drilling out of the drilled holes.

Further, a large-diameter first passage pipe 6 is formed from the end of the shank 5 to the base end of the drill body so as to penetrate the center thereof and to have a hole through which a coolant flows. The holding surface 26 of the holding piece 21, which communicates with the first liquid pipe 6 and extends from the base end of the drill body to the bottom of the pocket 23, communicates with the second liquid pipe 7 and holds the holding piece. 21
Liquid passage groove 8 having a one-sided arc shape from the base end to the top end
Are formed.

A major feature of the present invention is that the liquid passage grooves 8 are provided.
Is formed so that a part thereof overlaps with the notch 1g of the chip 1, and this notch 1g is used as a liquid passage, and the coolant is discharged into the inner blade side flute groove 24 for chip discharge. 1 (b)]. Then, by discharging the cooling liquid into the inner cutter side flute 24 groove, it is possible to reliably discharge chips from the inner cutter, which are formed in an umbrella-like shape and are not so well discharged, from the inner cutter. .

Further, the present invention is characterized by the cross-sectional shape of the flute groove in order to improve the chip controllability on the inner blade side.
Hereinafter, this feature will be described.

Referring to FIG. 9 which is a cross-sectional view taken along the line VV of FIG. 1, the cross-sectional shape of the inner cutter side flute groove 24 of the drill body 2 is formed in a two-arc shape. Thus, chips from the inner blade, which are formed in an umbrella-like shape and have poor dischargeability, are loosely fitted to one of the arcs, and the drill body is discharged with a small swing in the radial direction. Therefore, it is possible to make it difficult for chips to be clogged.

Hereinafter, other features of the present invention will be described.

FIG. 4 is a sectional view taken along the line II of FIG.
Referring to FIG. 5 which is a cross-sectional view of I, in the chip 1, the front clearance angle α1 of the inner cutter 11 is larger than the front clearance angle α2 of the outer cutter 12.

This will be described below. The inner blade 11 of the tip 1 needs to increase the front clearance angle α1. This is because the trajectory during machining (spiral motion trajectory) at a specific point on the cutting edge has a larger angle in the direction of piercing. On the other hand, the outer blade 12 may have a smaller front clearance angle as compared with the inner blade since the outer direction of the drilling direction of the trajectory (spiral motion trajectory) at the specific point on the cutting blade is larger toward the outside. For example, referring to FIG. 6, the angle α1 with respect to the drilling direction in the spiral motion trajectory L1 at the point P1 of the inner blade at the time of drilling is the point P2 of the outer blade.
Of the spiral movement trajectory L2 with respect to the drilling direction α
2, a large clearance angle is required on the inner blade 11 side to avoid interference with the hole bottom surface.
A relatively small clearance angle may be used on the outer blade 12 side.

Therefore, in the present invention, attention is paid to this point, and the front clearance angle of the outer cutter 12 is made smaller than the front clearance angle α1 of the inner cutter 11, so that the cutting edge angle can be increased. Thereby, the strength of the outer blade 12 having the corner portion can be improved.

The front clearance angle α1 of the inner cutter and the front clearance angle α2 of the outer cutter are not particularly limited in size as long as α1> α2, but the front clearance angle α1 of the inner cutter is not limited. Is 9 ~
It is preferable that the front clearance angle α2 of the outer cutter is 12 ° and the range of 6 ° to 10 °.

When the front clearance angle β1 of the inner cutter is less than 9 °, interference with the hole bottom tends to occur.
If it exceeds 2 °, the strength of the cutting edge tends to decrease.
When the front clearance angle α2 of the outer cutter is less than 6 °, interference with the bottom of the hole tends to occur. On the other hand, when it exceeds 10 °, the strength of the cutting edge tends to decrease.

Next, referring to FIG. 7 which is a sectional view taken along the line III-III of FIG. 1, and FIG. 8 which is a sectional view taken along the line IV-IV, the end faces of the holding pieces 21 and 22 are adjacent to the chip pockets 21b and 22b. The clearance angle γ1 of the part is smaller than the clearance angle γ2 of the other parts. The chip 1 has such a configuration,
Even if the chips go to the hole bottom side momentarily, it is prevented from entering between the end face of the drill body 2 and the hole bottom. Therefore, the chip dischargeability is good.

The clearance angle γ1 of the portion adjacent to the chip pockets 21b and 22b and the clearance angle γ2 of the other portions are as follows.
The size is not particularly limited as long as the relationship γ1 <γ2 is satisfied, but the clearance angle γ1 of the portion adjacent to the chip pockets 21b and 22b is preferably in the range of 0 ° to 5. When the clearance angle γ1 of the portion adjacent to the chip pockets 21b, 22b is less than 0 °, interference with the hole bottom tends to occur. On the other hand, when the clearance angle exceeds 5 °, the end face of the drill body 2 and the hole bottom are in contact with each other. There is a tendency for chips to easily enter between the gaps.

It should be noted that the end face having such a configuration is as follows.
The holding pieces 21 and 22 need not be both, and may be only one.

Next, referring to FIG.
The upper edge line 27 of the outer cutter side chip pocket 21b is extended outwardly of the upper edge line 25a of the outer edge side flute groove 25 with the overhang amount α (w> 0). This makes it possible to prevent the diameter of the chips from becoming too large by forming a roof (overhanging portion) above the outer blade side chip pockets 21b. This makes it possible to improve the chip discharge performance.

The overhang amount w is not particularly limited, but is preferably in the range of 0.5 to 1.2 mm. If w is less than 0.5 mm, the effect of reducing the diameter of the chip is weak, while if it is larger than 1.2 mm, the chip dischargeability tends to be deteriorated.

The configurations of the throw-away tip and the drill body for the throw-away tip of the present invention are not limited to the above-described examples of the drawings, and may be appropriately designed within the scope of the present invention. Changes can be made.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a throw-away insert and a drill body according to an embodiment of the present invention, wherein (a) is a view from the back side of the insert, and (b) is a view from the front side of the insert. It is.

FIG. 2A is a perspective view of the chip as viewed from the front, and FIG. 2B is a perspective view of the chip as viewed from the back.

FIG. 3A is a front view of the drill body, and FIG. 3B is a side view of the drill body.

FIG. 4 is a sectional view taken along the line II of FIG. 1;

FIG. 5 is a sectional view taken along line II-II of FIG.

FIG. 6 is an explanatory diagram showing a mode of a spiral movement during machining at a specific point of the cutting edge with respect to the tip of FIG. 1;

FIG. 7 is a sectional view taken along the line III-III of FIG. 1;

FIG. 8 is a sectional view taken along the line VI-VI in FIG. 1;

FIG. 9 is a sectional view taken along line VV of FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 chip 2 drill body 1 a through hole 11 inner blade 12 outer blade 13 first block 14 second block 24 inner blade side flute groove 25 outer blade side flute groove 1 g notch 21, 22 sandwiching piece 6, 7 liquid passage hole 8 Fluid channel

Claims (3)

[Claims] 1. A plate-shaped throw-away tip, a first block provided on the throw-away tip and having an inner blade formed at a front end for cutting a central portion of a hole, and a peripheral block of the hole also provided on the throw-away tip. A second block forming an outer blade for shaving a portion at a front end, a shaft-shaped drill body, and a pair of holding pieces provided at an end of the drill body and holding and holding a throw-away tip; A throw-away drill, wherein the first block of the away tip has a notch formed at a rear end corner. 2. The drill body according to claim 1, further comprising: a liquid passage pipe penetrating in an axial direction to reach one of the holding pieces; and a liquid passage groove provided in a holding surface of the holding piece in communication with the liquid flowing pipe. 2. The indexable drill according to claim 1, wherein the liquid passage groove and the cutout part partially overlap each other. 3. A plate-like throw-away tip, a first block provided on the throw-away tip and having an inner blade for cutting a central portion of a hole at a front end, and a peripheral block of the hole also provided on the throw-away tip. A second block formed at the front end with an outer blade for shaving the portion, a shaft-shaped drill body, a pair of holding pieces provided at an end of the drill body and holding the throw-away tip therebetween, A flute groove formed in the drill body from the rear end in the axial direction, wherein the flute groove has an inner blade side flute groove for discharging chips from the inner cutter to the outside of the hole and chips from the outer blade to the outside of the hole. A throw-away drill comprising an outer cutter-side flute groove for discharging, and a cross-sectional shape of the inner cutter-side flute groove having a two-arc shape.