JPH0631505A - Boring bar - Google Patents

Abstract

PURPOSE:To suppress vibration caused by cutting, and to prevent occurrence of chatter, or the like, by forming the inner circumferential surface of an insertion hole of a shank and the outer circumferential surface of a damper to be inserted into this hole in tapered surfaces that come into close contact with each other. CONSTITUTION:A head 4 with a cutting edge 8 is screwed to the front end of a damper 11 which is loosely inserted into the insertion hole 2 of a shank 1, and hence vibration generated in the cutting edge 8 at the time of cutting is transmitted to this damper 11 via the head 4. This damper 11 is made of material different from that of the shank 1, and the tapered outer circumference of the damper is in close contact with the tapered part of the insertion hole 2 of the shank 1. For this reason, frictional shock absorbing action arises between the damper 11 and the shank 1. This causes the vibration to be damped and suppressed, and hence the occurrence of chatter can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boring bar used for machining the inner circumference of a prepared hole formed in a work material.

[0002]

2. Description of the Related Art As a boring bar of this type, a head having a cutting edge is integrally formed on the tip of a cylindrical shaft-shaped shank made of steel or cemented carbide, or the head is detachably attached. The composition is known. In such a boring bar, the base end of the shank is attached to and held by a holding stand of a machine tool,
Similarly, a head is inserted into a prepared hole of a work material which is also rotatably supported by a machine tool, and an inner peripheral surface of the prepared hole is cut by a cutting blade provided in the head.

[0003]

By the way, in such a boring bar, especially when a hard material such as cemented carbide is used as the material of the shank, a high tool rigidity can be secured, but the cutting is difficult. The stability limit is low against the vibration caused by the above.Therefore, when the cutting conditions are increased by increasing the cutting speed or increasing the depth of cut or the feed amount, chattering occurs and the machined surface deteriorates. there were. Further, in such a boring bar, the larger the protruding length of the shank from the holding table, the lower the stability limit against vibration. Therefore, for example, when drilling a deep hole, it becomes severe. There was a risk that chattering vibrations would occur, making cutting impossible.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, in which a shank is formed with insertion holes open at both ends thereof in the axial direction,
At least a part of the insertion hole is a tapered portion that expands in diameter toward the tip side or the base end side in the axial direction, and the insertion hole is made of a material different from the material forming the shank. It is characterized in that a damper having a tapered outer peripheral portion in close contact with the head portion is inserted into the head by screwing the tip portion thereof into the head.

[0005]

In the boring bar having such a structure, the head having the cutting edge is screwed onto the tip of the damper loosely inserted into the insertion hole of the shank, so that the vibration generated in the cutting edge during cutting is generated by the head. Propagates to this damper via. Here, this damper is made of a material different from that of the shank, and since the tapered outer peripheral portion is in close contact with the tapered portion of the shank insertion hole, a frictional vibration absorbing action occurs between the damper and the shank. The vibration is damped and suppressed, and the chattering described above can be prevented from occurring.

[0006]

1 to 5 show an embodiment of the present invention. In these drawings, reference numeral 1 is a shank having a substantially cylindrical outer shape made of a hard material such as cemented carbide,
The inner diameter portion is an insertion hole 2 into which a damper to be described later is inserted, and the insertion hole 2 is formed in a tapered shape whose diameter gradually increases from the base end side in the axis O direction of the shank 1 to the tip end side over the entire length thereof. Has been done. That is, in this embodiment, the entire insertion hole 2 is formed as a tapered portion.
The taper of the insertion hole 2 is 1 in this embodiment.
It is appropriately set within the range of 1/00 to 2. Further, on the outer peripheral surface of the shank 1 on the proximal end side, recesses 3 and 3 are formed for hanging a working tool such as a spanner on the shank 1 when adjusting the tension of the damper.

Reference numeral 4 is a head attached to the tip of the shank 1, and a tip pocket 5 and a tip mounting seat 6 having a mounting screw hole (not shown) are formed at the tip of the head 4. There is. A throw-away tip 7 made of cemented carbide or the like is detachably attached to the tip mounting seat 6 with its cutting edge 8 protruding toward the tip and the outer periphery of the head 4 and screwed into the mounting screw hole. It is fixed by a clamp screw 9 to be attached.

The tip surface of the shank 1 is formed as a conical convex surface projecting toward the tip side of the shank 1 in the direction of the axis O. On the other hand, the base end surface of the head 4 is formed into a conical concave surface that is recessed toward the tip end side in the direction of the axis O, and the shank 1 and the head 4 are brazed with these surfaces in close contact with each other. It is joined and integrated. A damper mounting screw hole 10 is formed at the center of the base end surface of the head 4 toward the tip side along the axis O.

On the other hand, reference numeral 11 is a damper,
In this embodiment, the damper 11 is made of a damping alloy such as damping steel material, or a material having vibration absorbing properties such as aluminum and copper. The outer peripheral portion of the damper 11 is gradually expanded in diameter from the base end side in the axis O direction toward the front end side with a taper equal to the taper of the insertion hole 2 over its entire length. The damper 11 is inserted into the insertion hole 2 so as to be in close contact with the inner peripheral surface. Also,
Male screw portions 12A and 12B are formed at both ends of the damper 11, and the male screw portion 12A located on the tip side of the male screw portions 12A and 12B is formed in the damper mounting screw hole 10 of the head 4. It is screwed on.

Further, in the damper 11, the male screw portion 12B located on the proximal end side of the damper 11 is projected from the proximal end surface of the shank 1 when the male screw portion 12A is screwed into the damper mounting screw hole 10. It is set. A nut 13 is screwed onto the male screw portion 12B, and the tip end surface of the nut 13 is brought into close contact with the base end surface of the shank 1. Therefore, in the boring bar having the above structure, the damper 11 has the male screw portions 12A, 1 formed at both ends thereof.
2B is screwed to the head 4 and the nut 13, respectively. By properly rotating the nut 13, the damper 11 acts on the damper 11 because the male screw portion 12A at the tip thereof is pulled to the base end side while being screwed to the head 4. The tension changes, and the degree of contact between the damper 11 and the insertion hole 2 of the shank 1 also changes.

In the boring bar having such a structure, the vibration generated in the cutting edge 8 of the throw-away tip 7 during cutting propagates to the shank 1 and the damper 11 via the head 4. Here, in this embodiment, the shank 1 and the damper 11 are provided.
Are formed from different materials, and the inner peripheral surface of the insertion hole 2 formed in the shank 1 and the outer peripheral surface of the damper 11 into which the insertion hole 2 is inserted are formed in a tapered surface shape in close contact with each other. The shank 1 and the damper 11
A large frictional resistance occurs due to the friction of the two surfaces being rubbed against each other due to the vibrations propagated to the above, and the above-mentioned vibrations are absorbed by this friction. As a result, the vibration propagating from the head 4 consumes the vibration energy as frictional heat and is attenuated and suppressed. Therefore, such vibration causes chattering or the like on the boring bar. This can be prevented in advance.
Therefore, according to the boring bar having the above structure, it is possible to increase the stability limit against vibration, prevent deterioration of the machined surface due to chattering even in cutting under high cutting conditions, and perform deep hole machining. Even if the protrusion length of the shank is large, stable cutting can be performed.

Further, in this embodiment, the damper 1
Reference numeral 1 denotes a damping alloy such as a damping steel material, or a material having a vibration absorbing property as compared with a cemented carbide that constitutes the shank 1 such as aluminum or copper. That is, in the present embodiment, since the damper 11 itself has a large vibration damping rate and has an action of damping and suppressing the propagating vibration, the stability limit against the vibration is further increased and the resistance against chattering etc. is further improved. It is possible.

Further, in the boring bar of this embodiment,
By appropriately rotating the nut 13 as described above,
It is possible to change the tension of the damper 11, which changes the degree of adhesion between the inner peripheral surface of the insertion hole 2 of the shank 1 and the outer peripheral surface of the damper 11, that is, the magnitude of the pressing force acting between the two surfaces. be able to. As a result, the strength of the damping action of the damper 11 can be appropriately adjusted according to the vibration generated during cutting, so that the above configuration can easily cope with a wide range of cutting conditions and the like. It is possible to provide a boring bar that can effectively suppress vibration.

In this embodiment, the inner peripheral surface of the insertion hole 2 and the outer peripheral surface of the damper 11 are formed as the above-described tapered surfaces over their entire length. However, a part of the insertion hole 2 and the damper 11 on the tip side is formed. Only such a tapered surface may be used.

Further, in the present embodiment, the both surfaces are tapered surfaces that expand in diameter toward the tip end side in the axis O direction, but conversely, they are tapered surfaces that expand in diameter toward the base end side in the axis O direction. You can also For example, FIGS. 6 and 7 show another embodiment of the present invention. However, in FIG. 6, the same parts as those in the embodiment shown in FIGS. 1 to 5 are designated by the same reference numerals. In this embodiment, the inner peripheral surface of the insertion hole 22 of the shank 21 is formed into a tapered surface shape whose diameter increases toward the base end side in the direction of the axis O over the entire length thereof, and the outer peripheral surface of the damper 23 also covers the entire length thereof. The damper 1 is formed in a tapered surface shape whose diameter increases toward the base end side in the axis O direction.
1 is screwed to the head 4.

Also in the present embodiment, the taper of these surfaces is appropriately set within the range of 1/100 to 1/2. Further, in the present embodiment, since the insertion hole 2 and the base end side of the damper 11 are expanded in diameter, it is possible to change the tension acting on the damper 11 by rotating the damper 11 itself. Therefore, instead of the male screw portion 12A and the nut 13 in the above embodiment, an engaging portion 24 that can be engaged with a spanner, a box wrench, or the like is formed at the base end portion of the damper 11.

Even in the boring bar having such a structure, the vibration propagating from the cutting edge 8 to the head 4 is transmitted to the damper 23, and friction is caused by the contact friction between the outer peripheral surface of the damper 23 and the inner peripheral surface of the insertion hole 22. It is converted into heat and its vibration energy is consumed. As a result, the stability limit against vibration can be increased and the occurrence of chattering can be suppressed, and the same effect as that of the embodiment shown in FIGS. 1 to 5 can be obtained. Further, since the strength of the damping action of the damper 23 can be adjusted by rotating the engaging portion 24 to change the tension acting on the damper 23, it is the same as that of the nut 13 of the above embodiment. The effect can be achieved.

Even in this case, the inner peripheral surface of the insertion hole 22 and the outer peripheral surface of the damper 23 do not necessarily have the tapered surfaces as described above over the entire length thereof, but only a part of these surfaces on the base end side. May be formed so as to increase in diameter toward the base end side.

[0019]

As described above, according to the present invention, the inner peripheral surface of the insertion hole of the shank and the outer peripheral surface of the damper inserted into the shank are tapered surfaces that are in close contact with each other, and are used during cutting. Since the generated vibration is consumed by the contact friction of these surfaces, such vibration can be attenuated and suppressed, and chattering and the like can be prevented. And this
It is possible to prevent deterioration of the machined surface due to such vibration and to enable stable machining even under high cutting conditions or deep hole machining.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view showing an embodiment of the present invention.

FIG. 2 is a side view of the tip portion of the embodiment shown in FIG.

FIG. 3 is a front view of the embodiment shown in FIG. 1 from the front end side.

FIG. 4 is a ZZ sectional view of the embodiment shown in FIG.

5 is a rear view from the base end side of the embodiment shown in FIG.

FIG. 6 is a partially cutaway plan view showing another embodiment of the present invention.

7 is a rear view from the base end side of the embodiment shown in FIG.

[Explanation of symbols]

 1,21 Shank 2,22 Insertion hole 4 Head 7 Throw-away tip 8 Cutting edge 10 Damper mounting screw hole 11,23 Damper 12A, 12B Male screw part of damper 11 13 Nut 24 Engaging part O Axis

Claims (1)

[Claims] 1. A boring bar in which a head having a cutting blade is attached to the tip of a shaft-shaped shank, wherein the shank is formed with insertion holes that open at both ends of the shank along the axial direction thereof. At least a part of the insertion hole is a tapered portion that expands in diameter toward the tip end side or the base end side in the axial direction, and the insertion hole is made of a material different from the material forming the shank. A boring bar, characterized in that a damper having a tapered outer peripheral portion that is in close contact with the tapered portion is inserted by screwing the tip of the damper into the head.