JP4417520B2 - Throw-away drill - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a throw-away drill used for drilling.
[0002]
[Prior art and issues]
As a drill used for drilling, in addition to a normal solid type drill that is integrally formed as a whole, a cutting blade is formed on the drill body (holder) and a separate throw-away tip and drilled. There is a so-called throw-away type drill that can be detachably attached to the tip of the main body with a screw or the like.
[0003]
This throw-away type drill is classified into a two-chip type and a one-chip type. Among these, the former two-chip type throw-away type drill is described in, for example, Japanese Patent Laid-Open No. 10-29108. As described above, two tips, that is, a tip having an inner blade that cuts the central portion of the hole and a tip having an outer blade that cuts the peripheral portion of the hole are mounted on the tip of the drill body. In the invention described in the above publication, both the inner blade and the outer blade are formed on one tip, and the same tip can be used as the inner blade tip or the outer blade tip depending on the orientation and position of mounting on the drill body. It is also configured.
[0004]
However, although this two-chip type configuration is suitable for a large drill having a large machining diameter, for example, if this is applied to a small drill having a machining diameter smaller than about φ10, a tip is inserted at the tip of the drill body. There is a problem that sufficient space for mounting or chip discharge cannot be secured, or the screws for chip mounting are very small and sufficient mounting strength cannot be obtained. It was.
[0005]
On the other hand, the one-chip type throw-away drill (hereinafter referred to as “one-chip drill”) is similar to the tip shape of a conventional solid-type drill as described in, for example, Japanese Patent Laid-Open No. 10-328918. In general, a chip using a pair of tips having a long edge over the entire length of the radius of the processing hole, which extends in the drilling direction and extends from the top located on the rotation axis of the drill to both sides, is generally used.
[0006]
However, since the cutting force applied to the tip during drilling is large in the above-described tip shape, it is necessary to firmly fix one tip to the tip of the drill body with two screws as shown in the drawing of the above publication. In addition, there is a problem that it is not easy to secure a space for chip discharge correspondingly because it is necessary to increase the thickness of the chip.
[0007]
Therefore, the inventor first determines the inner blade for cutting the center portion of the hole and the outer blade for cutting the peripheral edge portion of the hole, and the inner blade of the inner blade tip and the outer blade tip of the two-chip type throwaway drill. A one-chip type throw-away tip similar to a two-chip type formed on a single chip in the same arrangement as the outer cutter has been developed (Japanese Patent Laid-Open No. 11-188518).
[0008]
In the one-chip type throw-away tip similar to the above-mentioned two tips (hereinafter abbreviated as “similar one-chip”), the inner blade only needs to have a length sufficient to cut the center of the hole, and the outer blade also has Since it suffices to have a length sufficient to cut the peripheral edge of the hole, it is possible to reduce the cutting resistance applied to the chip during drilling compared to the conventional one-chip drill, and the inner and outer blades It became possible to secure a space for chip discharge by reducing the thickness of the part and using one screw for attaching to the drill body.
[0009]
Therefore, as a result of further examination of the similar one tip and its drill body, the inventor has room for further improvement in the structure described in the above publication, particularly in terms of strength of the cutting edge portion and chip dischargeability. I found out.
[0010]
It is an object of the present invention to provide a novel throw-away drill that relates to a similar tip and that has a stronger cutting edge than conventional ones and improved chip discharge performance.
[0011]
[Means for Solving the Problems and Effects of the Invention]
As a result of diligent investigations on chip discharge performance, the present inventors have found that if the chip discharge direction changes instantaneously for some reason and moves toward the bottom of the hole, the chips will escape to the front of the drill body. It has been found that entering between the surface and the bottom of the hole causes clogging of chips.
Even if the chips momentarily go to the bottom of the hole, they do not reach the point where they enter between the front clearance surface of the drill body and the bottom of the hole, and the chips guide the flute toward the flute groove by the tip pocket. It has been found that chip evacuation does not deteriorate if possible.
[0018]
Next, as a result of intensive studies on the chip discharge performance, the present inventors have found that when the chip discharge direction changes instantaneously for some reason and moves toward the bottom of the hole, It has been found that entering between the front flank and the bottom of the hole may cause clogging of chips. Even if the chips momentarily go to the bottom of the hole, they do not reach the point where they enter between the front clearance surface of the drill body and the bottom of the hole, and the chips guide the flute toward the flute groove by the tip pocket. It has been found that chip evacuation does not deteriorate if possible.
[0019]
Accordingly, the invention of claim 1 is a throw-away tip having a cutting edge formed at the front end, a shaft-shaped drill body, and a pair of clamping pieces provided at the end of the drill body and sandwiching the throw-away tip. And a chip processing surface formed on the side of the clamping piece, and a portion adjacent to the chip processing surface of the clearance angle formed on the front end surface of at least one clamping piece of the drill body is more than the others. The present invention provides a throw-away drill characterized by being formed small.
[0020]
In this configuration, the end face of the sandwiching piece has a clearance angle of the portion adjacent to the chip treatment surface smaller than the clearance angle of the other part, so that the front clearance surface and the hole bottom on the part side adjacent to the chip treatment surface The space between was made smaller. This prevents chips from entering between the end face of the drill body and the hole bottom.
[0021]
According to a second aspect of the present invention, in the first aspect, of the clearance angle formed on the end face of the sandwiching piece, a portion adjacent to the chip treatment surface is within a range of 0 to 5 °.
[0022]
In this structure, the effect which improves the intensity | strength of a cutting blade without making a drill main body interfere with a hole bottom, and makes the discharge property of a chip favorable is remarkable.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[0024]
1 (a) and 1 (b) are exploded perspective views of a throw-away drill according to an embodiment of the present invention, and FIG. 1 (a) is an exploded perspective view as seen from the front side of the tip. (B) is the disassembled perspective view seen from the back side of the chip | tip.
[0025]
With reference to these drawings, the throw-away tip 1 forms an inner blade 11 that cuts the center portion of the hole and an outer blade 12 that cuts the peripheral portion of the hole at the front end in the drilling direction. The throw-away tip 1 is formed by integrally forming a plate-like first block 13 that forms the inner blade 11 and a plate-like second block 14 that forms the outer blade 12.
[0026]
The first block 13 and the second block 14 are shaped so as to be shifted from each other in the plate surface direction, leaving a portion 15 that overlaps each other. A through-hole 1a that penetrates in the plate thickness direction at the overlapping portion 15 is formed. This through hole 1a is for inserting an attachment screw 3 for attaching the tip 1 to the drill body 2.
[0027]
The chip 1 has a first seat surface 1b and a second seat surface 1c as a pair of sandwiched surfaces on two surfaces back to back (that is, corresponding to the outer surfaces of the blocks 13 and 14). The through hole 1a is open to the first and second seat surfaces 1b and 1c.
[0028]
Referring to FIG. 2, the tip 1 includes a rear seat surface 1 d received by the bottom of a pocket 23 provided at the rear portion of the drill body 2 in the drilling direction. The tip 1 is a side view of the drill main body, while having a notch recess 1g continuous between the pair of sandwiched seating surfaces 1b and 1c at the rear end corner of the first block 13 including the inner blade 11. Referring to FIG. 3A and FIG. 3B, which is a side view from another angle of the drill body with the tip 1 attached with the mounting screw 3, the drill body 2 has an axial drill body 4. And a shank 5 are provided on the same axis, and a flat surface 5a that acts as a detent when the drill body 2 is attached to a tool holder (not shown) is provided on a part of the peripheral surface of the shank 5. Is formed.
[0029]
Referring to FIGS. 1 (a) and 1 (b) and FIG. 2 (a), a pair of sandwiching pieces 21 and 22 for sandwiching the tip 1 is formed at the front end of the drill body 4, and these A pocket for inserting the chip 1 is defined between the clamping surfaces 26 and 27 of the pair of clamping pieces 21 and 22. With the tip 1 inserted into the pocket 23, the mounting screw 3 is inserted into the through hole 21 a and the through hole 1 a of the holding piece 21 and screwed into the screw hole 22 a of the holding piece 22. It is pinched and fixed.
[0030]
One clamping piece 21 corresponds to the first block 13 that forms the inner blade 11, and its clamping surface 26 comes into contact with the first seating surface 1 b as the first block 13. The other clamping piece 22 corresponds to the second block 14 forming the outer blade 12, and its clamping surface 27 abuts on the second seating surface 1 c as the clamping surface of the second block 14. Further, chip processing surfaces 21b and 22b for chip processing are formed on the sides of the sandwiching pieces 21 and 22, respectively.
[0031]
In addition, spiral flute grooves 24 and 25 are formed on the peripheral surface of the drill body to discharge chips during drilling to the outside of the processing hole.
[0032]
Furthermore, a large-diameter first liquid passage hole 6 is formed from the end portion of the shank 5 to the base end portion of the drill body so as to penetrate the center of the shank 5 and a hole for flowing a coolant. The clamping surface 26 of the clamping piece 21 that communicates with the fluid passage hole 6 and reaches the bottom of the pocket 23 from the base end of the drill body communicates with the second fluid passage hole 7. A liquid passage groove 8 having a circular arc shape in section extending from the end to the tip is formed.
[0033]
The liquid groove 8 overlaps with the notch recess 1g of the chip 1, and the notch recess 1g is used as a liquid passage to discharge the coolant into the inner blade side flute groove 24 for chip discharge. [Refer to FIG. 1 (b)]. Then, by discharging the coolant into the inner blade side flute 24 groove, it is possible to reliably discharge chips from the inner blade that are formed in an umbrella shape and are not so good in discharging performance. .
[0034]
By the way, an important feature of the present invention is that the strength of the cutting edge and the chip dischargeability are improved by providing a feature in the configuration of the front clearance surface of the tip constituting the throw-away drill. Hereinafter, these features will be described.
[0035]
Referring to FIG. 4 which is a sectional view taken along the line II of FIG. 1 and FIG. 5 which is a sectional view taken along the line II-II, the tip 1 has a front clearance angle α1 of the inner blade 11 greater than a front clearance angle α2 of the outer blade 12. Is also big.
[0036]
This point will be described below. The inner cutter 11 of the tip 1 needs to increase the front clearance angle α1. This is because the drilling direction angle of the trajectory being processed (spiral motion trajectory) at a specific point on the cutting edge increases toward the inside. On the other hand, the outer cutter 12 may have a smaller front clearance angle than the inner cutter because the drilling direction angle of the trajectory being processed (spiral motion trajectory) at a specific point on the cutting blade is larger toward the outer side. For example, referring to FIG. 6, the angle β1 with respect to the drilling direction in the spiral movement locus L1 at the point P1 of the inner blade during drilling is greater than the angle β2 with respect to the drilling direction in the spiral motion locus L2 of the point P2 of the outer blade. Therefore, in order to avoid interference with the bottom surface of the hole on the inner blade 11 side, a large clearance angle is required. On the other hand, a relatively small clearance angle may be used on the outer blade 12 side.
[0037]
Therefore, in the present invention, focusing on this point, it is an important feature that the blade edge angle is increased by making the front clearance angle of the outer blade 12 smaller than the front clearance angle α1 of the inner blade 11. Thereby, the intensity | strength of the outer blade 12 which has a corner part can be improved.
[0038]
The size of the front clearance angle α1 of the inner blade and the front clearance angle α2 of the outer blade is not particularly limited as long as the relationship α1> α2, but the front clearance angle α1 of the inner blade is 9˜. It is preferable that the front clearance angle α2 of the outer blade is within a range of 6 ° to 10 °.
[0039]
When the front clearance angle α1 of the inner blade is less than 9 °, interference with the hole bottom tends to occur, and when it exceeds 12 °, the strength of the cutting blade tends to decrease. Further, when the front clearance angle α2 of the outer blade is less than 6 °, there is a tendency that interference with the hole bottom tends to occur. On the other hand, when it exceeds 10 °, the strength of the cutting blade tends to decrease.
[0040]
In addition, the present invention pays particular attention to the clearance angle of the end face of the drill body, and it is possible to improve the chip dischargeability by the following configuration. The features will be specifically described below.
[0041]
Referring to FIG. 7 which is a sectional view taken along the line III-III in FIG. 1 and FIG. 8 which is a sectional view taken along the line IV-IV, the end faces of the sandwiching pieces 21 and 22 are clearance angles γ1 of the parts adjacent to the chip disposal surfaces 21b and 22b. Is smaller than the clearance angle γ2 of other parts. With such a configuration, the chip 1 is prevented from entering between the end face of the drill body 2 and the bottom of the hole even when chips are instantaneously directed toward the bottom of the hole. Therefore, the chip dischargeability is good.
[0042]
The clearance angle γ1 of the portion adjacent to the chip treatment surfaces 21b and 22b and the relief angle γ2 of other portions are not particularly limited as long as the relationship of γ1 <γ2, but the chip treatment surface is not limited. It is preferable that the clearance angle γ1 of the portion adjacent to 21b and 22b is in the range of 0 ° to 5. When the clearance angle γ1 of the portion adjacent to the chip-treated surfaces 21b and 22b is less than 0 °, there is a tendency that interference with the hole bottom tends to occur, whereas when it exceeds 5 °, the end surface of the drill body 2 and the hole bottom There is a tendency for chips to easily enter between.
[0043]
In addition, it is not necessary to have both of the sandwiching pieces 21 and 22 to have such a configuration of the end face, and only one of them may be provided.
[0044]
Next, other features of the throw-away drill of this embodiment will be described.
[0045]
Referring to FIG. 9 which is a VV sectional view of FIG. 1, the sectional shape of the inner blade side flute groove 24 of the drill body 2 is formed in a two-arc shape. As a result, chips from the inner blade, which are formed in an umbrella shape and are not so good in discharge, are gently fitted into either one of the arcs, and the drill body is swayed in the radial direction and discharged. Therefore, it becomes possible to make it difficult to generate clogging of chips.
[0046]
Referring to FIG. 3, the drill body 2 is configured such that the upper ridge line 27 of the outer blade side chip processing surface 21 b is outside the point N closest to the drilling direction of the upper ridge line 25 a of the outer blade side flute groove 25. It is something that is overhanging. Thereby, it can suppress that the diameter of a chip becomes large because the roof (overhang | projection part) is formed in the upper part of the outer blade side chip processing surface 21b. Thereby, it is possible to make chip discharge | emission property favorable.
[0047]
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 chip diameter is weak, while if it is greater than 1.2 mm, the chip discharge tends to deteriorate.
[0048]
The configuration of the throw-away drill according to the present invention is not limited to the example of the drawings described above, and can be appropriately changed in design without changing the gist of the present invention.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a throw-away drill according to an embodiment of the present invention, where (a) is a view seen from the back side of the tip, and (b) is a view seen from the front side of the tip. .
2A is a perspective view seen from the front side of the chip 1, and FIG. 2B is a perspective view seen from the back side.
FIG. 3 (a) is a front view of the above throwaway tip drill, and FIG. 3 (b) is a side view of the drill holder.
4 is a cross-sectional view taken along the line II of FIG.
5 is a cross-sectional view taken along the line II-II in FIG.
6 is an explanatory diagram for illustrating a mode of spiral movement during processing at a specific point of the cutting edge with respect to the chip of FIG. 1; FIG.
7 is a cross-sectional view taken along the line III-III of FIG.
8 is a sectional view taken along line VI-VI in FIG.
9 is a cross-sectional view taken along the line VV in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tip 2 Drill main body 1a Through-hole 11 Inner blade 12 Outer blade 21, 22 Clamping pieces 24, 25 Flute grooves 21b, 22b Chip treatment surface

Claims (4)

A throw-away tip with a cutting edge formed at the front end, a shaft-shaped drill body, a pair of clamping pieces provided at the end of the drill body and holding the throw-away tip, and to the sides of the clamping piece A formed chip disposal surface,
A throw-away drill characterized in that, of the clearance angle formed on the front end face of at least one sandwiching piece of the drill body, a portion adjacent to the chip treatment surface is formed smaller than the other. Of the clearance angle formed on the pinching one end face, Suroawe Lee drills according to claim 1, a portion adjacent to chip control surface is being in the range of 0 to 5 °. The throw-away tip includes an inner blade and a first block corresponding to one clamping piece, and an outer blade and a second block corresponding to the other clamping piece,
3. A chip discharge space is provided between the first block and the other block and between the second block and the one block. Suroawe Lee drill described. Wherein the circumferential surface of the drill body, Suroawe Lee drills according to claim 3, wherein the leading space for chip discharge, wherein the spiral flute grooves are formed.

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