JP2002326111A - Throw away type drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new holder for a throw away tip for a drill having a higher chip discharging function than that of the prior art, in relation to the one-tip type throw away tip having two similar tips. SOLUTION: This throw away type drill comprises the throw away tip 1, a shaft-like drill body 4, and a pair of grappling pieces 21 that are disposed at an end of the drill body 4 and grapple and hold the throw away tip 1. The throw away tip 4 has an inner blade 11 used for cutting the central part of a hole and an outer blade 12 used for cutting the peripheral edge of the hole, and the drill body 4 has a chip handling surface 30 on the inner blade side and a chip treating surface 29 on the outer blade side on the sides of grappling pieces 21. A spot facing part 21c corresponding to the head 3a of a mounting screw 3 is formed in a through-hole 21a formed in the grappling piece 21 having the chip treating surface 29 on the outer blade side.

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 the holder with a screw or the like.

[0003] There are two types of throw-away type drills and one tip 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 chip having an inner blade for cutting the center of a hole and a chip having an outer blade for cutting the periphery of the hole are mounted on the tip of the holder. Then, in the invention described in the above publication, both the inner blade and the outer blade are formed on one chip, and the same chip can be used also as the inner blade chip or the outer blade chip depending on the direction and position of mounting on the holder. Is also configured.

[0004] However, this two-chip type configuration is suitable for a large drill having a large processing diameter, but when it is applied to a small drill having a processing diameter smaller than about φ10, for example, the tip of the holder is required. The problem is that there is not enough space for chip mounting or chip discharge space, or the screws for chip mounting are so small that sufficient mounting strength cannot be obtained. was there.

On the other hand, the one-chip type throw-away type drill (hereinafter, abbreviated as “one-tip drill”) includes:
For example, as described in Japanese Patent Application Laid-Open No. 10-328918, a pair of tips extending in both directions from a top portion facing the drilling direction and located on the rotation axis of the drill, similar to the tip shape of a conventional solid type drill. In general, a tip having a long blade ridge extending over the entire length of the radius of the processing hole is used.

[0006] However, in the above-mentioned chip shape, since the cutting resistance applied to the chip at the time of drilling is large, it is necessary to firmly fix one chip to the tip of the holder with two screws as shown in the figure of the above-mentioned publication. In addition, there is a problem that it is necessary to increase the thickness of the chip, and accordingly, it is not easy to secure a space for chip discharge.

Therefore, the inventor first provided an inner blade for cutting the center of the hole and an outer blade for cutting the peripheral portion of the hole. 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 mounting screw for the holder, a space for chip discharge can be secured.

Therefore, the present inventors have further studied a similar chip and its holder, and have 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 To solve the above problems, the invention of claim 1 of the present invention comprises a mounting screw, a through hole through which the mounting screw is inserted, and a cutting blade at a front end. The formed throw-away tip, 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, and the mounting formed in the thickness direction of the holding piece. A through hole through which a screw is inserted, a chip processing surface formed on a side of the holding piece, and a flute groove formed on an axial rear side of the holding piece continuously with the chip processing surface; The insert has an inner cutter for cutting the center of the hole and an outer cutter for cutting the peripheral portion of the hole.The drill body is provided with a chip processing surface on the inner cutter side and a chip And the outer blade A drill-away drill characterized in that a counterbore corresponding to the head of the mounting screw is formed in the through hole formed in the holding piece provided with the chip processing surface on the side.

According to this configuration, the head of the mounting screw having a large size can be installed on the holding piece side having the outer blade side chip processing surface,
As a result, the inner-chip-side chip processing surface can be installed closer to the center axis of the mounting screw. Therefore, the chip processing space on the inner blade side can be made larger, and the effect of improving the chip discharge performance can be obtained more reliably.

[0013]

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

FIGS. 1A and 1B are exploded perspective views of a throw-away tip and a holder for mounting the throw-away tip according to an embodiment of the present invention, and FIG. 2A is an exploded view of the tip as viewed from the front side. FIG. 2B is an exploded perspective view of the chip viewed from the back side.

As shown in FIG. 2, the indexable insert 1 has an inner blade 11 for cutting a central portion of a hole at a front end in a drilling direction,
An outer blade 12 for shaving the peripheral edge of the hole is formed. The indexable insert 1 is formed by integrally forming a plate-shaped first block 13 forming the inner blade 11 and a plate-shaped second block 14 forming the outer blade 12.

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 1a is for inserting a mounting screw 3 for mounting the chip 1 to the holder 2.

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

As shown in FIG. 2, the chip 1 has a rear seating surface 1d which is received by the bottom of a pocket 23 provided at the rear of the holder 2 in the drilling direction. Chip 1
As shown in FIG. 1, as shown in FIG. 1, there is a cutout concave portion 1 g continuous between a first seating surface 1 b and a second seating surface 1 c at a rear end corner of a first block 13 having an inner blade 11. A pair of holding pieces 21 and 22 are formed at the front end of the main body 4 for holding the chip 1 therebetween.
A pocket 23 for inserting the chip 1 is defined between the holding surfaces 26 and 27 of the first and second 22. This pocket 2
3 and the mounting screw 3 is held in the
The chip 1 is pinched and fixed to the holder 2 by being inserted into the through hole 21 a and the through hole 1 a and screwed into the screw hole 22 a of the holding piece 22.

One holding piece 21 corresponds to the first block 13 forming the inner blade 11, and its holding surface 26 abuts on the first seating surface 1 b as the first block 13. The other holding piece 22 is a second block 14 forming the outer blade 12.
, The holding surface 27 abuts on the second seat surface 1c as the held surface of the second block 14. Further, on the sides of the holding pieces 21 and 22, an outer blade side chip processing surface 29 is provided.
And the inner blade side chip processing surface 30 and the chip pockets 21b and 22b
Are formed.

On the peripheral surface of the drill body 4, spiral flute grooves 24 and 25 are formed for discharging chips during drilling to the outside of the drilled holes.

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

The liquid passage groove 8 overlaps the notch recess 1g of the chip 1. The notch recess 1g serves as a liquid passage, and the inner cutter side flute groove 24 for discharging the chip with the coolant. [See FIG. 1 (b)]. Then, by discharging the cooling liquid into the inner blade side flute 24 groove, it is possible to reliably discharge chips from the inner blade, which are formed in an umbrella-like shape and have a poor discharge property, out of the hole. .

An important feature of the throw-away drill of the present invention is that the through-hole 21 formed in the holding piece 21 having the outer-cut-side chip-treating surface 29 as shown in FIG.
a, a counterbore 2 corresponding to the head 3a of the mounting screw 3;
1c. Thereby, the head 3a of the mounting screw 3 having a large size can be installed on the holding piece side 21 having the outer blade side chip processing surface 29. As a result, the chip-processing surface 30 on the inner blade side can be installed close to the center axis of the mounting screw 3, so that the chip-processing space on the inner blade 11 side (the chip pocket 22)
b) can be made larger, and the effect of improving the chip discharge performance can be obtained more reliably.

The embodiment of the present invention has been described above.
It is needless to say that the present invention is not limited to the above-described embodiment, and can be in any form without departing from the object of the invention.

[Brief description of the drawings]

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

2A is a perspective view of the chip 1 as viewed from the front, and FIG. 2B is a perspective view of the chip 1 as viewed from the back.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chip 1a Through hole 2 Holder 3 Mounting screw 3a Head 4 Drill body 11 Inner blade 12 Outer blade 21, 21 Nipping piece 21a Through hole 21b Through hole 21b, 22b Chip pocket 21c Counterbore 23 Chip pocket 24, 25 Flute groove 29 Chip processing surface on the outer blade side 30 Chip processing surface on the inner blade side

Claims (1)

[Claims] 1. A mounting screw, a throw-away tip having a through hole through which the mounting screw is inserted and having a cutting edge formed at a front end, a shaft-shaped drill body, and an end portion of the drill body, A pair of holding pieces that hold and hold the throw-away tip, a through hole through which the mounting screw formed in the thickness direction of the holding piece is inserted, a chip processing surface formed on the side of the holding piece, A flute groove formed on the axially rear side of the holding piece continuously to the chip processing surface, the indexable insert has an inner blade for cutting the center of the hole and an outer blade for cutting the periphery of the hole, and The drill body includes a chip processing surface on the side of the inner blade and a chip processing surface on the side of the outer blade, respectively, on the side of the holding piece, and a holding piece including a chip processing surface on the outer blade side. Insert the mounting screw into the through hole Indexable drill, characterized in that the formation of the spot facing portion corresponding to the head.