JPH08281509A - Tip fop throwaway drill - Google Patents

Abstract

PURPOSE: To improve breaker performance of a plate-shaped tip mounted in a throwaway drill. CONSTITUTION: A breaker 4 mounted in a tip 1 is formed with a first slanted surface 5 which has lower level as it is parted from a cutting blade 2 in a cross section orthogonal with the cutting blade 2 and a second slanted surface 6 which has step between the first slanted surface 5 and which has lower level slope of which is gentler than the first slanted surface 5 and a third slanted surface erected from a bottom to a boss surface 3. At the same time, the second slanted surface 6 is a slanted surface which becomes lower toward an outer periphery from a shaft center in the cross section parallel to the cutting blade 2. Cutting having improved sharpness and reduced cutting resistance may be provided by the cutting effect of the first slanted surface 5 and the reduction effect of non-contacted area with the second slanted surface 6 and chip. The chip is smoothly induced and brought into contact with the third slanted surface 7 and receives reasonable bent deformation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tip having a chisel attached to a throw-away drill, and particularly to reduce cutting resistance.

[0002]

2. Description of the Related Art In a throw-away drill in which a flat tip having a chisel is attached to the tip of a drill body, a conventional tip that is applied to the tip for the purpose of improving chip discharge and reducing cutting resistance. There are two major technical means. One is aimed at the rake effect of the breaker groove provided on the rake face near the cutting edge,
Conventionally, this breaker groove is provided in a shape parallel or nearly parallel to the cutting edge.

Another technical means is to prevent the chips from clogging by making the cutting edges discontinuous, for example, to provide V-shaped grooves, which are usually called nicks, formed in a zigzag pattern at the cutting edges ( U.S. Pat. No. 3,460,409), or one in which the cutting edges have a staggered arrangement of steps (Japanese Patent Application Laid-Open No. 5-5120)
4-39290).

[0004]

In the case of drilling, since the cutting speed is different between the tool center and the outer circumference, the cutting phenomenon is complicated, such as the outflowing chip thickness is not uniform. Difficulty is high. The parallel breaker groove as described in the above-mentioned prior art is poor in general versatility, and chip debris may occur if it deviates from a certain cutting condition. Also, in the case of forcibly breaking chips by using a nick or the like, the chips may grow long and become entangled in the drill body. Chip jamming and entanglement increase the cutting resistance and cause tool damage. It is an object of the present invention to provide a tip for a throw-away drill that exhibits good chip controllability in a wider range of cutting conditions and has reduced cutting resistance.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and relates to a plate-shaped tip mounted on the tip of a throw-away drill body. In this chip, cutting edges are formed on two surfaces forming a tip angle, and a boss surface of the chip is provided with a recess serving as a breaker. The breaker has a cross section orthogonal to the cutting edge,
There is a step between the first inclined surface and the first inclined surface, which becomes lower as the distance from the cutting edge increases, and the second inclined surface becomes gradually lower with a gentler gradient than the first inclined surface and the boss from the bottom. The second inclined surface is constituted by a third inclined surface standing on the surface, and the second inclined surface has a cross section parallel to the cutting edge.
An inclined surface that is lower than the axis toward the outer circumference is used.

Further, the cutting edge is formed so as to be lower than the boss surface, and the second inclined surface is provided with at least one groove arranged in a direction substantially orthogonal to the cutting edge.

[0007]

The present invention has a rake effect by the first inclined surface,
Non-contact action of chips by the step provided between the first inclined surface and the second inclined surface, the attraction effect of chips by these inclined surfaces, and the barrier of the third inclined surface standing up to the boss surface. The action causes a smooth bending deformation of the chips and a reduction in cutting resistance. That is, since the breaker is provided relatively wide and inclined in two directions, it has a high attraction effect, can cope with a wide range of cutting conditions, and prevents chip clogging that is likely to occur in the conventional parallel breaker. . The cutting resistance can be reduced accordingly. By providing the groove on the second inclined surface, the contact area between the chips and the second inclined surface can be further reduced, and the cutting resistance is further reduced.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings.

1 to 3, the chip 1 is a chisel-shaped chip having a flat plate shape and a cutting edge 2 formed on two surfaces forming a tip angle. On the boss surface 3 of the chip 1,
A breaker 4 is formed by providing a recess including the cutting edge 2. In addition, the recess including the cutting edge 2 may be a recess in which the land surface having a minute width is secured, in addition to the case where the cutting edge 2 is directly included and when the strength of the cutting edge is emphasized. .

As shown in FIG. 4, the shape of the breaker 4 becomes lower as it goes away from the cutting edge 2 in a cross section orthogonal to the cutting edge 2 (cross section taken along the line AA in FIG. 2). A second step having a step between the inclined surface 5 and the first inclined surface 5 and gradually lowering with a gentler slope than the first inclined surface 5.
Inclined surface 6 and third inclined surface 7 standing on boss surface 3 from the bottom
Composed of and. At the same time, in the cross section parallel to the cutting edge 2 (cross section taken along the line B-B in FIG. 2), the second inclined surface 6 is an inclined surface that becomes lower toward the outer periphery from the axis, as shown in FIG. . As shown in FIG. 4, if the cutting edge 2 is positioned lower than the boss surface 3, the cutting edge portion will not be ground even if the boss surface 3 which is one reference surface at the time of mounting is ground and finished. , Its shape never changes.

The mounting of the chip 1 shown in this embodiment is performed as follows. That is, there is a groove 8 in the center of the bottom of the chip 1 that extends from the front surface to the back surface, and a countersink 9 penetrates the boss surface 3. The tip 1 is assembled at the tip of the drill body 10 as shown in FIG.
At this time, the drill body 10 has a protrusion that fits into the groove 8 and is fitted therein, and is fixed by screws with a countersunk screw 11 inserted in the countersink hole 9. Drill body 10 with which a countersunk screw 11 is screwed
Since the screw holes are provided so as to be slightly eccentric to the axial center side, the chip 1 is fixed while receiving a force biased toward the axial center side. The force that the chip 1 tends to laterally shift is supported by the protrusion of the fitting groove portion.

According to the throw-away drill having the chip 1 incorporated therein as described above, the gradient of the first inclined surface 5 can be made relatively large, so that the cutting can be performed with excellent sharpness and reduced cutting resistance. Become so. Moreover, since the contact area of the chips that flow through the first inclined surface 5 and flow out is reduced by the step effect with the second inclined surface 6, the cutting resistance is further reduced. Further, the chips are smoothly attracted to the third inclined surface 7, and contact with this, and undergo bending deformation.
As a result, chips are ejected as chips similar to the transition cut type found in twist drills. Since the third inclined surface 7 is separated from the cutting edge 2, there is no chip clogging unlike the conventional parallel breaker groove, and a breaker adapted to a wide range of cutting conditions can be obtained.

Next, FIG. 7 shows another embodiment of the present invention, in which the same parts as those described above are designated by the same reference numerals. This chip 1 has a plurality of grooves 12 which are substantially orthogonal to the cutting edge 2 added to the second inclined surface 6, and the sectional shape along the line C-C is along the line D-D in FIG. The sectional shape is shown in FIG. 9, and FIG. 10 shows the sectional shape taken along the line EE.
The groove 12 further reduces the contact area between the chips and the second inclined surface 6 by the amount of the groove 12 added.

11 and 12 show the results of practical use with a throw-away drill (diameter 25 mm) with the tip 1 attached. The work material was SCM490 (Brinell hardness 120 to 130), the cutting speed was 100 m / min, and the material was used while supplying water-soluble cutting oil. Figure 11
Is the thrust, and FIG. 12 is the result of the torque measurement. It is apparent that both of the products of the present invention are significantly smaller than the conventional product.

[0015]

As described above, according to the present invention, due to the rake effect of the first inclined surface and the effect of reducing the non-contact area between the second inclined surface and the chips, excellent cutting performance and cutting resistance can be obtained. The reduced cutting comes to be performed. Furthermore, the chips are smoothly attracted by these inclined surfaces and
It comes into contact with the inclined surface and undergoes natural bending deformation. As a result, chip breakage is prevented and the breaker is adapted to a wide range of cutting conditions.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a front view of the chip shown in FIG.

FIG. 3 is a plan view of FIG. 2;

4 is a cross-sectional view taken along the line AA of FIG.

5 is a cross-sectional view taken along the line BB of FIG.

6 is a perspective view showing an embodiment of a throw-away drill equipped with the tip of FIG. 1. FIG.

FIG. 7 is a front view showing another embodiment of the present invention.

8 is a cross-sectional view taken along the line CC of FIG.

9 is a cross-sectional view taken along the line DD of FIG.

10 is a cross-sectional view taken along the line EE of FIG.

FIG. 11 is a thrust diagram showing a practical result of the present invention.

FIG. 12 is a torque diagram showing a practical result of the present invention.

[Explanation of symbols]

 1 chip 2 cutting edge 3 boss surface 4 breaker 5 first inclined surface 6 second inclined surface 7 third inclined surface 10 drill body 12 groove

Claims (3)

[Claims] 1. A flat plate-shaped tip 1 to be mounted on the tip of a drill body 10, wherein a cutting edge 2 is formed on two surfaces forming a tip angle, and a boss surface 3 of this tip 1 is In a tip 1 for a throw-away drill having a recess to be a breaker 4, the breaker 4 has a cross section orthogonal to a cutting edge 2,
The first inclined surface 5 has a step between the first inclined surface 5 and the first inclined surface 5, which becomes lower as the distance from the cutting edge 2 increases.
The second inclined surface 6 gradually lowering with a gentler slope
And a third inclined surface 7 standing upright on the boss surface 3 from the bottom, and the second inclined surface 6 is a lower inclined surface toward the outer periphery from the axis in the cross section parallel to the cutting edge 2. Inserts for throw-away drills that are characterized by 2. The insert for a throw-away drill according to claim 1, wherein the cutting edge 2 is formed lower than the boss surface 3. 3. The second inclined surface 6 is provided with at least one groove 12 arranged in a direction substantially orthogonal to the cutting edge 2, and the groove 12 is characterized in that: Tips for throw away drills.