JPH10180518A - Throw-away type drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve favorable chip discharging performance. SOLUTION: An outer blade tip 17a and an inner blade tip 17b of similar form and sizes are installed on tips of a pair of chip dicharging grooves in a drill main body 11. To an outer blade 23a of the outer blade tip 17a and an inner blade 23b of the inner blade tip 17b, second cutting blades 25 are connected to a chevron shaped first cutting blade 24 through steps 24a. The outer blade tip 17a is positioned on the outer circumferential side of the drill main body 11, and the inner tip 17b is positioned on the inner side, where the outer blade 23a is protruded more on the tip side than the inner blade 23b.

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 and the like.

[0002]

2. Description of the Related Art Conventionally, an example of a throw-away type drill is disclosed in Japanese Utility Model Laid-Open Publication No. 54-88992. This drill will be described with reference to FIGS. 9 and 10.
The drill 1 includes a shank portion 2 and a blade portion 3, and a pair of linear or helical chip discharge grooves (flutes) 4 along the rotation axis O of the drill body 1 a is provided on the outer peripheral surface of the blade portion 3. It is formed from the base end to the distal end surface. A substantially triangular plate-shaped throw-away tip 6 is attached to the tip end of each chip discharge groove 4 on the tip end surface 3 a of the blade portion 3. The throw-away tip 6 is a positive tip having a substantially equilateral triangular plate shape, and a ridge portion between an upper surface 7 and a side surface opposing a lower surface serving as a seating surface is a cutting edge 8, and each cutting edge 8 forming three ridges is provided. Has a chevron shape in plan view that protrudes toward the tip end with its central portion 8a as the vertex. When cutting is performed with the indexable insert 6 mounted on the drill 1, chips are generated by the cutting blades 8 of the indexable insert 6, and are discharged through the chip discharge groove 4 to the base end side.

[0003]

However, when drilling using such a drill 1, it is necessary to bring the cutting start point of each cutting edge as close to the rotational center O of the drill body 1a as possible. This is preferable for reducing the cutting torque at the time of attachment and preventing the loss of the cutting blade. In addition, to increase the rigidity of the drill 1, it is necessary to increase the core thickness. However, when the core thickness is increased, the cross-sectional area of the chip discharge groove 4 is inevitably reduced, so that the cutting edge 8 generates However, there is a disadvantage that chips are easily clogged. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a throw-away type drill which has a good chip flow and chip discharge property and is less likely to cause chip clogging.

[0004]

According to the present invention, there is provided a throw-away drill in which a throw-away tip is attached to a tip end surface of a drill body, wherein a cutting edge protruding from the tip of the throw-away tip is provided. A substantially angled first cutting edge and a second cutting edge connected to the first cutting edge via a step, wherein the first and second cutting edges generate separated chips during cutting. It is characterized by having made it. Increasing the core thickness to increase the drill rigidity reduces the cross-sectional area of the chip discharge groove and makes it easier for the chips to be clogged, but in the present invention, the chips generated by the cutting blade are generated in a separated thin state. Therefore, even in a narrow chip discharge groove, the chip flow is good, the chip is hardly clogged, and the chip can be smoothly discharged.

[0005] The throw-away tip is an inner cutter tip and an outer cutter tip having the same shape and the same size. The inner cutter tip is located inside the rotation axis of the drill body, and the cutting edge is an inner cutter. The blade tip may be located on the outer peripheral side with respect to the rotation axis of the drill body, and the cutting blade may be an outer blade. Since the outer cutter tip and the inner cutter tip are constituted by the same throw-away tip, the cost is low. Further, the cutting edge may be provided with a lead angle because the first cutting edge projects more toward the tip end than the second cutting edge. By providing the cutting edge with a lead angle formed by the first cutting edge, the workpiece comes into contact with the workpiece from a position close to the rotation axis of the drill body, and the impact and cutting resistance at the time of biting are small. Further, one of the inner blade and the outer blade may be disposed so as to protrude from the other to the tip side in the rotation axis direction. One of the inner blade and the outer blade starts cutting first when biting, so the impact at the time of biting is small.

[0006]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIGS. 1 is an overall view of a throw-away type drill according to an embodiment, FIG. 2 is an enlarged view of a cutting edge portion in FIG. 1, FIG. 3 is a front end view of the drill shown in FIG. 1, and FIG. 5 is a plan view of the throw-away tip, and FIG. 6 is a sectional view of the tip shown in FIG.
7 is an enlarged view of the breaker groove of FIG. 6, FIG.
FIG. 3 is a diagram showing a cutting state by a drill. 1 to 4, a drill body 11 of a throw-away drill 10 is shown.
Is formed of a shank portion 12 and a blade portion 13. The drill tip shown in FIG. 3 is provided with a pair of substantially fan-shaped lands 14 through a core thick portion 14a. Chip discharge grooves 15 are formed facing each other, and the chip discharge grooves 15 are formed by spirally cutting the outer peripheral surface along the rotation axis O of the drill body 11. Each chip discharge groove 15
Is substantially fan-shaped at the distal end of the drill body 11 when viewed from the distal end, but has a circular arc-shaped cross section at the proximal end close to the shank 12 as shown in FIG. The cross section is formed so as to gradually change.

Tip mounting seats 16a and 16b are formed at the tips of the wall surfaces of the chip discharge grooves 15 facing the rotation direction, and each of the chip has an outer blade tip 17a and an inner blade tip 17 of the same shape and size. 17b is mounted by a clamp member such as a screw. As shown in FIGS. 5 to 7, the throw-away tip 17 has a substantially hexagonal plate shape (or a substantially decagonal plate shape), and the lower surface 1 serving as a seating surface.
9 is the upper surface 20 and the side surface 21 is the lower surface 19.
From the top to the upper surface 20. At the center of the upper surface 20, a hole 22 for screw insertion that penetrates to the lower surface 19 is formed.

On the upper surface 20, a ridge line formed by the substantially mountain-shaped side surface 21 is a cutting edge 23, and the angled first blade 24 and a pair of linear second cutting edges 25 at both ends thereof are each formed with a step 24.
a, the first cutting edge 24 projects outward from the second cutting edge 25, and the entire cutting edge 23 forms a substantially mountain shape. The central top part 24- of the first blade 24-
Around 1, a part of the first cutting edge 24 and the second cutting edge 25 are preferably parallel. The step 24a extends from the upper surface 20 to the lower surface 19. A pair of the cutting blades 23 are formed to face each other, and a pair of side surfaces 21a between the cutting blades 23 are formed to be opposed to each other in a planar shape. On the upper surface 20, a pair of cutting blades 2
7, a breaker groove 26 having a substantially arc shape in a sectional view is formed along the cutting edge 23, for example, as shown in FIG. A land 27 may be formed on the cutting blade 23.

In the indexable drill 10 shown in FIG. 2, the tip mounting seat 16a is formed on the outer peripheral side with respect to the rotation axis O of the drill body 11, and the cutting edge 23 of the mounted outer blade tip 17a is formed by the outer blade. 23a, the outer blade 23
a is formed so as to protrude distally with respect to the distal end surface of the drill body 11. With the tip mounted, the outer blade 2
An appropriate lead angle is set for the first all-blade 24a of FIG. The tip mounting seat 16b is formed on the inner side with respect to the rotation axis O of the drill body 11, and the cutting edge 23 of the mounted inner blade tip 17b is used as the inner blade 23b. It is formed so as to protrude toward the tip end. One second cutting blade 25 of the inner blade 23b is positioned so that its end crosses the rotation axis O.

In the tip mounted state, the outer blade 23a projects more toward the tip side in the rotation axis O direction than the inner blade 23b, and as shown in FIG. 8, the outer blade 23a and the inner blade 23b Shall be continuous. Therefore, cutting is performed by the first cutting edge 24 and the second cutting edge 25 on the outer peripheral side in the outer cutting edge 23a, and cutting is performed by the first cutting edge 24 and the second cutting edge 25 in the inner cutting edge 23b. become. At the start of cutting, the outer blade 23a and the inner blade 23b first come into contact with the workpiece at the central top 24-1 of the first blade 24, respectively. An oil hole 29 is formed in the center of the drill body 11 along the rotation axis O, and is divided into two forks at a tip end thereof, and a pair of openings 29a provided in the pair of lands 14 shown in FIG. 29b.

Since the indexable drill 10 according to the present embodiment is constructed as described above, when drilling with this drill 10, first, the first blade 24a of the outer blade 23a must be To start cutting, but at that time, the central top portion 24-1 of the substantially angled first blade 24 first comes into contact with the work material, thereby reducing the cutting torque at the start of cutting. Can be. Then, a little later, the inner blade 23
The cutting torque at the start of cutting of the inner blade 23b can be similarly reduced by starting the cutting at the central top 24-1 of the first blade 24 of b. Moreover, since the outer blade 23a and the inner blade 23b do not start cutting at the same time, and the outer blade 23a cuts first,
Shock and cutting resistance when biting can be reduced.

Thereafter, the workpiece is cut by the first cutting edge 24 of the outer blade 23a and the second cutting edge 25 on the outer peripheral side, so that the outer blade 2a is cut.
The chips generated in step 3a have a step 24a as shown in FIG.
As a result, the chips generated by the first cutting blade 24 are separated into the relatively wide chips and the second cutting blades 25 are separated into narrow chips. Similarly, the chips generated by the inner blade 23b are also generated in a state of being separated into the chips generated by the first blade 24 and the chips generated by the inner second cutting blade 25. Therefore, even if the cross-sectional area of the chip discharge groove 15 is reduced by, for example, setting the core thickness to be large in order to increase the drill stiffness of the throw-away drill 10, the chip is generated in a state where the chip is finely divided into two, By running in the chip discharge groove 15 after being curled or cut in the breaker groove 26, chip clogging can be suppressed and smooth discharge can be performed.

As described above, according to the present embodiment, the chips generated by the outer blade 23a and the inner blade 23b are generated in a finely separated manner, so that the core thickness is increased in order to increase the rigidity of the drill 10. Even if the cross-sectional area of the chip discharge groove 15 is reduced, the chip can be smoothly discharged without causing chip clogging. Moreover, since the outer blade 23a is positioned so as to protrude toward the front end in the direction of the rotation axis O with respect to the outer blade 23a and the inner blade 23b, the outer blade 23a is
It hits the work material before 3b, and can reduce the impact and cutting resistance at the time of biting. Furthermore, the outer blade 23a and the inner blade 23b form a first angled blade 24 which comes into contact with the workpiece first in a substantially mountain shape, so that a lead angle can be provided. The top 24-1, that is, the part that is off the rotation axis O and comes into contact with the work material from a relatively low peripheral speed portion, the cutting load at the time of biting is small, and the cutting torque at the start of cutting of each cutting blade is small. There is an advantage that it can be completed.

In the above-described embodiment, the outer blade 23a is located closer to the tip side in the rotation axis O direction than the inner blade 23b. Conversely, the inner blade 23b is positioned closer to the outer blade. 23
It may protrude to the tip side from a. Further, in the embodiment, in the outer blade 23a and the inner blade 23b, the first blade 24 is arranged to protrude toward the front end side in the rotation axis O direction. May protrude toward the distal end side.

In the embodiment, two steps 24a and 24 are provided on both sides of the first blade 24 so that the chips generated by the outer blade 23a and the inner blade 23b are each divided into two.
Although two cutting blades 25 are provided through a, the outer blade 23a and the inner blade 23b are respectively configured. However, three or more steps may be provided and four or more cutting blades may be configured. In this case, chips are generated in a state where the chips are separated into three or more parts. In the embodiment, the throw-away tip 1
0 (outer blade tip 10a, inner blade tip 10b) upper surface 20
Although only the cutting blade is provided, the cutting blade may be provided on both upper and lower surfaces.

[0016]

As described above, in the throw-away drill according to the present invention, the cutting edge protruding from the tip of the throw-away tip has a substantially angled first blade and a step formed between the first blade and the first blade. It has a second cutting edge connected thereto, and the first and second cutting edges generate separated chips during cutting, so even if the cross-sectional area of the chip discharge groove is small, it is generated. Since the chips are generated in a separated and thin state, the chips flow well, are hardly clogged, and can be discharged smoothly.

The throw-away tip is an inner cutter tip and an outer cutter tip having the same shape and the same size. The inner cutter tip is located on the inner side with respect to the rotation axis of the drill body, and the cutting edge is an inner cutter. Since the blade tip is located on the outer peripheral side with respect to the rotation axis of the drill body and the cutting blade is an outer blade, the same throw-away tip can be used, and the cost is reduced. In addition, since the cutting edge is provided with a lead angle because the first cutting edge projects more toward the tip side than the second cutting edge, by providing the cutting edge with a lead angle, the cutting edge is aligned with the rotation axis of the drill body. The work material is hit from a close position, and the impact and cutting resistance when biting are small. In addition, since one of the inner blade and the outer blade is disposed so as to protrude further toward the tip side in the rotation axis direction than the other, the impact is small because one of the inner blade and the outer blade starts cutting first at the time of biting.

[Brief description of the drawings]

FIG. 1 is an overall view of a throw-away drill according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a cutting blade portion in FIG.

FIG. 3 is a front end view of the drill shown in FIG. 1;

FIG. 4 is a sectional view taken along line AA of the drill shown in FIG.

FIG. 5 is a plan view of the throw-away tip.

6 is a cross-sectional view of the chip shown in FIG. 5, taken along line BB.

FIG. 7 is an enlarged view of the breaker groove of FIG. 6;

FIG. 8 is a diagram showing a cutting state by a drill.

FIG. 9 is a side view of a conventional drill.

FIG. 10 is a front end view of the drill shown in FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Throw-away type drill 17 Throw-away tip 17a Outer blade tip 17b Inner blade tip 23 Cutting blade 23a Outer blade 23b Inner blade 24a Step 24 First straight blade 25 Second cutting blade

Continued on the front page (72) Inventor Yasuhiko Kawade Gibe, Kochi-cho, Anpachi-gun, Gifu Prefecture 1528 Nakashinden, Yokoi, Mitsubishi Materials Corporation Gifu Works

Claims (4)

[Claims] 1. A throw-away type drill comprising a drill body having a tip attached to a tip thereof, wherein the cutting edge protruding toward the tip of the throw-away tip has a substantially mountain-shaped first blade and a first blade. A second cutting edge connected via a step to the first and second cutting edges, wherein the first and second cutting edges generate separated chips during cutting. 2. The throw-away tip is an inner cutter tip and an outer cutter tip having the same shape and the same size, wherein the inner cutter tip is located inside a rotation axis of a drill body, and the cutting edge is an inner cutter. The indexable drill according to claim 1, wherein the outer cutter tip is located on the outer peripheral side with respect to the rotation axis of the drill body, and the cutting edge is an outer cutter. 3. The throw according to claim 1, wherein the cutting edge is provided with a lead angle by the first cutting edge protruding more toward the distal end side than the second cutting edge. Away drill. 4. The indexable drill according to claim 2, wherein one of the inner cutter and the outer cutter is disposed so as to protrude from the other to the tip side in the rotation axis direction.