JP2001277021A - Throwaway type drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a throwaway type drill D which can firmly fit a throwaway tip 1 without using any large screw, and has a large durability to the twist to be effected on the tip 1 and holding pieces 21 and 22. SOLUTION: When the throwaway tip 1 is inserted in a pocket 23 of a drill body 2, and fixed by the screw 3, an alloy tool steel is selected for the material of the screw.

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.

However, an outer blade for cutting the peripheral portion with respect to the center of rotation and an inner blade for cutting the central portion are formed at a front end with a cutting blade for forming one chip, and a through hole for inserting a screw is provided. A throw-away tip, a shaft-shaped drill body, and an end portion of the drill body, which partition the pocket for inserting the tip therebetween, and hold the tip inserted in the pocket with screws. In this case, it is necessary to provide a seating surface of one blade and a rake surface of the other blade adjacent to each other, and a slope between the adjacent seating surface and the rake surface. The screw hole for fixing the chip to the drill body must be an insertion hole that penetrates both seat surfaces of the outer cutter and the inner cutter, while securing the chip discharge space. Let's secure a screw hole size that takes into account Them if, because originally small size of the chip itself, it is difficult to shape corresponding both to respective purposes. For this reason, a design has been required to satisfy appropriate conditions while compromising the two, such as making the sloped step surface somewhat smaller or making the screw hole smaller.

[0010] In particular, since the inner blade including the rotation center becomes umbrella-shaped chips having the vertex at the rotation center side, the chips on the inner blade side have a poor discharge property with respect to the chips on the outer blade side, and a larger discharge amount is obtained. Since space is required, the above problem becomes a serious problem.

Therefore, the inventor of the present invention has examined the similar one chip for further improvement from the viewpoint of chip dischargeability and durability, and as a result, selected a screw material to be used for the chip in order to fix the chip to the drill body. As a result, the above problem has been solved.

[0012]

According to the first aspect of the present invention, there is provided a throw-away type drill having a cutting edge formed at a front end thereof and having a through hole through which a screw is inserted, and a shaft-shaped drill body. And a pair of holding pieces formed at the end of the drill body, between which the tip is inserted, a through hole through which a screw formed on one holding piece is inserted, and a holding piece formed on the other side. And a screw hole into which the set screw is screwed, a throw-away tip is arranged between a pair of holding pieces, and through a through-hole formed in the throw-away tip from the outside of a through-hole formed in one holding piece. A throw-away type drill in which a throw-away tip is fixed to a drill body by inserting and screwing a screw into a screw hole formed in a holding piece on the other side, wherein the screw is made of alloy tool steel. The one in which the features.

According to the first aspect of the present invention, since the screw itself has a large tensile strength, even when the screw is used for a throw-away tip having a limited size or shape,
Even when a large torsion stress is applied to the holding piece for holding the chip during the drilling process, the chip can be held firmly.

According to a second aspect of the present invention, the through hole of the chip has one opening on each of a first seating surface formed on one surface of the chip and a second seating surface formed on the other surface of the chip. This is applied to a chip that is a through hole.

Even with such a chip having only one through-hole, the tensile strength of the screw itself is large.
Great durability can be achieved.

Further, in the invention according to claim 3, the tip itself is applied to a tip having a concave portion which is not in contact with the clamping piece of the drill body on a seat surface attached to the clamping piece of the drill body. is there.

At the time of drilling using a drill, a large torsion force acts not only on the chip itself but also on the holding piece of the drill body holding the chip. Since the tip itself is made of a material having high rigidity, for example, a cemented carbide, the tip itself does not deform, but if a large unacceptable twisting force acts on the holding piece, the holding piece is deformed. This leads to destruction of the chip itself.
In order to prevent this, a concave portion that does not contact the holding piece of the drill body is provided on the seat surface of the tip, and even if a large twisting force that the holding piece cannot accept is applied, this twisting force does not directly act on the chip. It is a chip that has been devised like this.

In a drill using such a tip,
A very large pulling force acts on the screw that fixes the chip itself, but by selecting and using the screw material as in the present invention, sufficient durability is maintained and under severe conditions. Drilling is possible.

[0019]

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 (a) is a front view of a drill throw-away tip 1 according to an embodiment of the present invention, and FIG. 1 (b) is a bottom view showing the front end face of the tip 1 in the drilling direction. It is. 2A is a rear view of the chip 1, and FIG. 2B is a left side view of the chip 1 as viewed from the front. FIG. 3A is a perspective view seen from the front side, and FIG. 3B is a perspective view seen from the back side.

As can be seen from these figures, the indexable insert 1 for a drill of this embodiment has a first seating surface 1b and a second seating surface 1c for attaching two back-to-back surfaces to a drill body. , Both seating surfaces 1b, 1c
Are formed with through holes 1a through which screws for attachment to the drill body are inserted.

As shown in FIG. 1A, an inner blade 11 for cutting the center of the hole in a direction intersecting the drilling (piercing) direction indicated by the black arrow in the drawing, And an outer blade 12 for cutting the peripheral edge of the outer peripheral portion.

When the chip 1 is rotated in the direction shown by the solid line arrow in FIG. 1B for the drilling process around the rotation axis Pv along the drilling direction, the second seating surface 1c
In the area on the front side of the rotation [FIG.
On the right side of the rotation axis Pv], the first rake face 13a is formed by providing a step 50 such that the step is lower than the second seating surface 1c by one step in the rotation direction. .

By forming the first rake face 13a, the first rake face 13a of the projecting portion 13 of the chip 1 which is thinner than the portion in which the through hole 1a is formed.
a, and a first front flank 13b is formed on the front end face in the drilling direction that intersects the first seating surface 1b which is back-to-back with the first front flank 13b.
The above-described inner ridge forms the inner blade 11 described above.

Similarly, in a region on the first seating surface 1b side which is on the front side of rotation [the portion on the right side of the rotation axis Pv in FIG. The second rake face 14a is formed by providing the step 52 so as to be one step lower than the first seating face 1b.

By forming the second rake face 14a, the second rake face 14a of the projecting portion 14 of the chip 1 which is thinner than the portion where the through hole 1a is formed.
a, and a second front clearance surface 14b is formed on the front end surface in the drilling direction intersecting the second seat surface 1c, which is back-to-back with the second front clearance surface 14b, and the second front clearance surface 14b and the second rake surface 14a.
The outer blade 12 is formed by the crossing ridge.

Further, by providing the step as described above, the second seating surface 1c formed in front of the first rake face 13a.
Is a chip pocket for forming a space for discharging chips from the inner blade 11 between the drill body and the drill body. Similarly, by providing a step, the second rake face is formed. A space formed in front of 14a and having a step difference from the first seating surface 1b is a chip pocket which forms a space for discharging chips from the outer cutter 12 with the drill body.

The inner blade 11 has a top 11a facing in the drilling direction.
And blade ridges 12b and 12c extending downward from the top 11a in both the inward and outward directions of the chip 1. On the other hand, the outer blade 12
It is formed in a shape having a top portion 12a facing the drilling direction, and blade ridges 12b and 12c extending downward from the top portion 12a in both the inward and outward directions of the chip 1.

The inner cutter 11 and the outer cutter 12 are used to cut the central portion of the hole by the inner cutter 11 and the peripheral portion of the hole by the outer cutter 12 almost at the same time to perform smooth drilling. The tops 11a and 12a are arranged at substantially the same height in the drilling direction.

Further, the inner blade 11 and the outer blade 12 are formed such that when the tip 1 is rotated about the rotation axis Pv, a blade ridge 11c extending outward of the inner blade 11 and an inner direction of the outer blade 12 are formed. Are arranged so that the rotation trajectories of the blade ridges 12b extending to each other intersect.

In the chip 1 of this example composed of the above-mentioned parts, the thickness of the outer blade 12 side protruding part 14 formed with the second rake face 14a and the second seating face 1c [T ₂ in FIG. ]
However, it is formed to be larger than the thickness [T ₁ in FIG. 1B] of the protrusion 13 on the inner blade 11 side where the first rake face 13 a and the first seat face 1 b are formed (T ₁ < T ₂ ).

The reason for this is that the inner cutting edge directly contributes to cutting is only a part of the cutting edges 11b and 11c, and the outer cutting edge is not used while the corner 11d is not used. It is the cutting edge 12 including the corner 12d that directly contributes to the cutting.
c and part of 12b. Therefore, the corner 12d
In order to prevent the chip from being broken, the outer blade 12 is intensively reinforced to make the chip 1 higher in strength and more durable than the conventional one.

The tip 1 of this embodiment having the above-mentioned parts is provided with a pocket 23 between the pair of holding pieces 21 and 22 at the tip of the drill body 2 as shown by solid arrows in FIGS. 4 (a) and 4 (b). In a state where the seating surfaces 1b and 1c on both sides thereof are positioned by being brought into contact with the holding surfaces 21b and 22b of the holding pieces 21 and 22, respectively.
Then, the screw 3 is inserted through the through hole 1a of the chip 1 and screwed into the screw hole 22a of the holding piece 22, thereby forming the drill body 2
Is fixed to the tip of

In this fixed state, the first rake face 13
a, the holding pieces 2 on the front face of each of the second rake faces 14a
The space for chip discharge formed between the inner cutter 11 and the outer cutter 21 is communicated with spiral flute grooves 24, 25 formed on the peripheral surface of the drill body 2, respectively. 21 from the flute groove 2
The liquid is smoothly discharged through the holes 4 and 25 out of the hole. In addition,
FIG. 7 illustrating the overall image of the indexable drill D
(A) and (b), reference numeral 20 denotes a drill body in which the holding pieces 21 and 22 and the pocket 23 are formed at the end thereof and spiral flute grooves 24 and 25 are formed on the peripheral surface thereof, and reference numeral 26 denotes a drill body. Is a shank integrally formed coaxially with the drill body 20 and held by a chuck of a machine tool or the like, and reference numeral 26a is a flat portion formed on a side surface of the shank 26 for preventing rotation.

When the tip 1 is fixed to the drill body 2 described above with the screw 3 and used for drilling, that is, the tip 1
Is rotated in the direction indicated by the solid arrow in FIG. 5, a cutting force is generated in the opposite direction,
Accordingly, the holding pieces 21 and 22 of the drill body 2 are shown in FIG.
6, a twisting stress (tensile stress for the screw 3) as shown by a white arrow is applied, and the holding pieces 21, 22 are twisted in the direction of the white arrow around the base end thereof, and the tip ends thereof. When the screw 3 cannot deform enough to resist the stress, it breaks. In addition, after the screw 3 is broken, the holding pieces 21 and 22 are freely deformed in the above-described direction, so that the drill body 2 is damaged.

However, in the present invention, the material of the screw 3 is
It is a major feature that the material composed of alloy tool steel is selectively used. This alloy tool steel is
C, Cr, M as main chemical components added to iron
o, V, etc., hardness (HRC50-55)
And a tensile strength (180 to 250 kgf / mm ² ) which are excellent in a well-balanced state, and are used for hot dies and the like. Above all, C: 0.32 to 0.4
2%, Si: 0.80 to 1.20%, Mn: 0.50%
Hereinafter, P: 0.030% or less, S: 0.030% or less,
Cr: 4.50 to 5.50%, Mo: 1.00 to 1.5
SKD61 having 0% and V0.80 to 1.20% as main chemical components is particularly desirable. This fact, WC-C
Using the drill body shown in FIG. 7 with the tip shown in FIG. 1 coated with TiN as a base material using an o-TiC-based cemented carbide as a base material, and using a chromium molybdenum steel (SCM43
For 5), when a hole was drilled with a diameter of 10 mm and a depth of 30 mm, the screw using chromium molybdenum steel (SCM435) broke in 10,000 times, but the SKD61 was used. With the screw, no abnormality occurred in the screw even after 30,000 times of processing.

As described above, by selecting the material of the screw 3, the above-described chip 1 has a special shape,
A seat surface 1b forming a through hole 1a for inserting a screw,
The chip 1 can be firmly fixed even under the condition limited to 1c.

As described above, by selecting and using the material of the screw 3 itself, sufficient twisting can be countered. However, the through-hole 1a through which the screw 3 is inserted is inserted into the holding piece 21, The distance L1 from the distal end 11a of the tip 1 to the center of the through hole 1a is set at a position farther than the base end of the tip 22 as shown in FIG. It is particularly preferable that the diameter φ is approximately 25 to 35% of the diameter φ0, particularly around 30%, because the tensile stress itself applied to the screw can be reduced.
Also, the inner diameter d1 of the through hole 1a of the screw 3 used at this time.
Is preferably about 9.5 to 10.5%, particularly about 10% of the processing diameter φ0 of the chip 1 in order to secure the chip discharge performance and the fixing strength of the screw 3 cut by the chip.

Further, in the present invention, a screw having a high tensile strength is selectively used for the chip 1 inserted into the pocket 23 between the holding pieces 21 and 22, and has great durability against twisting during processing. are doing. In this case, the drill body 2
When the twisting of the holding piece is larger than necessary, the screw usually breaks first, whereas the strength of the screw is large, so that the screw 3 does not break against the twisting. However, as a result, there is a possibility that the undeformed chip 1 itself may be damaged. For this reason, in the present invention, both seating surfaces 1 b and 1 c of the chip 1
Concave portions 1e and 1f that do not contact the holding surfaces 21b and 22b of the holding pieces 21 and 22 are provided. Specifically, as shown in FIG. 3, 1e and 1f are formed on the rear side of the through hole 1a in the drilling direction. Due to the non-contact concave portions 1e and 1f, even if the holding pieces 21 and 22 are deformed by a very large torsion force, the concave portions 1e and 1f allow the deformation and reduce the stress directly applied to the chip 1. Becomes As a result, breakage of the chip 1 can be reliably prevented even when the screw 3 that is strong against twisting is selected and used.

The configuration of the indexable insert for a drill according to the present invention is not limited to the example shown in the above-described drawings, and design changes can be made as appropriate without changing the paper of the present invention.

[0041]

As described above, according to the present invention, in a throw-away type drill using a one-chip type throw-away tip similar to a two-chip having an inner cutter and an outer cutter, an alloy tool is used as a fixing screw material. By selectively using steel, it is possible to mount a tip having extremely excellent durability without using a large screw, and it is possible to provide a throw-away drill in which a sufficient chip discharge space is secured.

[Brief description of the drawings]

FIG. 1A is a front view of a drill throw-away tip according to an embodiment of the present invention, and FIG.
It is a bottom view which shows the front end surface which faces the perforation direction of the said chip | tip.

2 (a) is a rear view of the chip of the example of FIG. 1, and FIG. 2 (b) is a left side view of the chip as viewed from the front in FIG. 1 (a).

3 (a) is a perspective view of the chip of the example of FIG. 1 as viewed from the front side, and FIG. 3 (b) is a perspective view as viewed from the back side.

FIG. 4 (a) is an exploded perspective view of the structure of attaching the tip of the example of FIG. 1 to the tip of the drill body as viewed from the front side of the tip, and FIG. 4 (b) is an exploded view as viewed from the rear side. It is a perspective view.

FIG. 5 is a bottom view of the state in which the tip of the example of FIG. 1 is attached to the tip of the drill body, as viewed from the front end face side facing the drilling direction.

FIG. 6 is an enlarged front view of a main part of FIG.

FIG. 7A is a front view of a drill body of a throw-away drill according to an embodiment of the present invention, and FIG. 7B is a side view of the drill body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drill throw-away tip 1a Through hole 1b 1st seat surface 1c 2nd seat surface 11 Inner blade 12 Outer blade 13a 1st rake surface 13b 1st flank 14a 2nd rake 14b 2nd flank 101 Recess 2 Drill body 21, 22 Holding piece 21a Through hole 22a Screw hole 23 Pocket 3 Screw P1 Center of chip opening P2 Center of holding piece opening

Claims (3)

[Claims] An insert having a cutting edge formed at a front end thereof and having a through-hole through which a screw is inserted, a shaft-shaped drill body, and an end formed at the end of the drill body, wherein the tip is inserted therebetween. A pair of holding pieces, a through hole through which a screw formed on one side of the holding piece is inserted, and a screw hole into which a screw formed on the other side of the holding piece is screwed. A throw-away tip is arranged in between, and a screw is inserted from the outside of the through-hole formed in the one-side holding piece into a screw hole formed in the other-side holding piece via the through-hole formed in the throw-away tip. A throw-away drill in which the throw-away tip is fixed to the drill body by using the screw as described above, wherein the screw is made of alloy tool steel. 2. The through hole of the chip has a first seating surface formed on one surface of the chip and a second seating surface formed on the other surface of the chip.
The indexable drill according to claim 1, wherein the drill is one through hole having an opening in each of the seating surfaces. 3. The throw-away drill according to claim 1, wherein said both seating surfaces each have a concave portion which is not in contact with the holding piece of said drill body.