JPH05162006A - Cutting tool for turning machine and installation thereof - Google Patents

Abstract

PURPOSE:To prevent a main spindle from galling by forming the top end part of a cutting tool of ceramic for preventing excessive force from being applied to the main spindle of a turning machine. CONSTITUTION:A cutting tool 23 for a turning machine is constituted of a shank 24 which is clamped and fixed to a tool holder 21, and a tip 25 for cutting which is installed at the top end of the shank 24. At least the part of the shank 24 which is exposed from the tool holder 21 to the top end is formed from ceramic. When the tool 23 collides with a work or a work chuck impact force which exceeds a prescribed value, the top end part of the shank 24 which is made of ceramic is immediately broken. Since excessive impact force is not applied to the main shaft of the turning machine, it is possible to prevent the main spindle from being caught.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to a lathe tool for supporting a main shaft by a non-contact bearing such as a hydrostatic bearing and performing super-precision cutting, and a method of mounting the same.

[0002]

BACKGROUND OF THE INVENTION In a lathe for performing ultra-precision cutting of a work piece, a work chuck for holding and fixing one side of a work piece as a work piece is provided on a spindle that makes a rotational motion without vibration. .. Further, the other side of the work attached to the work chuck is center-supported by a tailstock shaft as necessary, so that the work is stably rotated. Cutting is performed by bringing a bite into contact with a rotating work by manual operation or NC control.

When performing ultra-precision machining which requires a machining accuracy of about 0.1 micron on such a lathe, the spindle for supporting the work is made of a pneumatic or hydraulic pressure which has an extremely small friction coefficient and does not cause wear. The bearings are supported by non-contact bearings such as hydrostatic bearings or magnetic bearings, which allows the spindle to rotate in a very smooth and vibration-free state.

By the way, in such a lathe, a tool may collide with a work or a work chuck due to an operator's operation being difficult, or in an NC lathe, an error in a machining program. As a result, an impact force due to a collision acts on the main spindle, causing the main spindle and the bearing portion of the main spindle to come into contact with each other, causing rubbing of the main spindle or dents on the bearing portion, and as a result, the performance of the bearing is deteriorated and the lathe There is a problem in that the accuracy of is reduced.

In order to solve such a problem, the tool rest of the lathe may be provided with a mechanism as shown in FIGS. 3 and 4. In this mechanism, a tool rest 2 is provided with a base plate 2a and a pivot plate 3 on which a tool base 5 is rotatable, and an upper plate 2b to which a tool holder 5 for a cutting tool 4 is fixed.
It consists of An L-shaped member 6 is provided on the left side of the substrate 2a.
Is provided in the L-shaped member 6, and a cap screw 7 having a ball 9 biased by a spring 8 is provided.
It is pressed and fixed by a ball 9 of a cap screw 7 that engages with a U-shaped hole formed in a stepped portion of the upper plate 2b provided below the character-shaped member 6.

Therefore, when the cutting tool 4 collides with a work or the like and the impact force due to the collision exceeds the locking force due to the pressing of the ball 9, the ball 9 is pushed out from the U-shaped hole of the step portion of the upper plate 2b. Then, the upper plate 2b is rotated integrally with the cutting tool 4 on the substrate 2a about the pivot 3 in the horizontal direction.
As a result, the impact force due to the collision is absorbed by the movement of the upper plate 2b and is not transmitted to the spindle of the lathe, so that the problem of galling of the spindle is prevented.

However, in the examples shown in FIGS. 3 and 4, since the position of the cutting tool 4 and the position of the sliding surface of the upper plate 2b are different in the horizontal direction, the impact force applied to the cutting tool 4 due to the collision. Also acts as a moment force to lift the upper plate 2b, increasing the friction between the substrate 2a and the upper plate 2b, and when the bite 4 collides, the upper plate 2b moves around the pivot 3 as described above. Therefore, it could not be said that it is not necessarily suitable as a gall prevention mechanism for the spindle.

Moreover, since it is necessary to allow the sliding of the upper plate 2b, the pressing force of the ball 9 against the upper plate 2b cannot be made too strong. Therefore, the upper plate 2b should be firmly fixed to the substrate 2a. However, when heavy cutting is performed, the fixing screw 10 of the L-shaped member 6 is loosened due to microvibration during cutting, and the position of the ball 9 is displaced, so that the position of the cutting tool 4 may be displaced during the operation of the lathe. There is a possibility that the bite 6 cannot be accurately positioned.

Further, in an NC lathe in which a cutting tool is moved by numerical control to perform cutting, there is a possibility that the cutting tool may collide with a work or the like due to a mistake in creating a machining program.
As a countermeasure against such a case, the area where the cutting tool may collide with the work is defined as the interference area, and when the cutting tool enters this interference area, the cutting tool is forced to move from the rapid feed speed to the cutting speed. Measures to slow down may be taken.

However, in such a measure, the interference area must be wide on the safe side in order to set the interference area for all of the assumed work shapes, which requires a lot of play time and cutting. It takes a lot of time, which in turn leads to soaring production costs. Further, depending on the type of the cutting tool, the cutting tool may collide with a position other than the position of the work being cut. In such cases,
The measures by the interference area described above are not effective, and the main shaft may be gnawed.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems of the prior art. Even if the cutting tool strongly collides with a work or the like due to a malfunction or a program mistake, the spindle can be chewed. It is an object of the present invention to provide a turning tool for lathes and a method for mounting the turning tools, which can prevent the bearings of the lathes and protect the bearings of the lathes.

[0012]

SUMMARY OF THE INVENTION To achieve the above object, a lathe tool according to claim 1 of the present invention comprises a shank which is sandwiched and fixed to a tool holder, and a tip for cutting which is attached to the tip of the shank. In the lathe bite consisting of and, at least the portion of the shank exposed from the tool holder and extending to the tip is formed of ceramics.

Since the part of the cutting tool protruding from the tool holder is made of ceramics as described above, when the cutting tool collides with a work or a work chuck by an impact force exceeding a predetermined value, the shank made of ceramics is immediately removed. The tip breaks. Therefore, a large impact force is not applied to the main shaft of the lathe, and galling of the main shaft can be prevented.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The lathe turning tool and its mounting method according to the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a tool rest 40 of a lathe equipped with a turning tool according to an embodiment of the present invention. On the tool rest 40, a tool holder 21 having a U-shaped cross section is provided in a protruding manner. A recess 22 is formed in the tool holder 21. The lathe tool 23 includes a shank 24 having a rectangular cross section and a tip 25 attached to the tip of the shank 24. The shank 24 according to the present invention is made of Al
It is made of ceramics such as ₂ O ₃ . Shank 2
At a position protruding from the tool holder 21 of No. 4, a groove-shaped notch 29 extending in the vertical direction in the attached state is formed on the feed side of the cutting tool.

In the shank 24 thus formed, an elastic body 26 such as urethane rubber having a hardness of about 60 to 80 and a steel plate 27 are interposed in the recess 22, and the portion where the notch 29 is formed is the tool holder 21. The two holders 21 are sandwiched by the two holders 21 by screws 28, 28 which are arranged so as to project from the above and press the steel plate 27 from above.

Now, it is assumed that a part of the turning tool 23 collides with a work or a work chuck. Then, the impact force is applied to the shank 24. But shank 24
Is made of ceramics, and ceramics is
Compared to cutting tool materials such as high speed steel, it is weak against bending stress (particularly tensile stress generated on the upper surface), has low toughness, and is easily broken when subjected to a strong impact. Moreover, in the present embodiment, since the notch 29 is provided on the feed side of the shank 24, the impact force due to the impact becomes a bending stress and the stress is concentrated in the notch 29, and the shank 24 is removed from the notch. It is easily broken. As a result, the impact force due to the collision is absorbed and hardly transmitted to the main shaft of the lathe.

Therefore, it is possible to surely prevent the bearing and the main shaft from coming into contact with each other and the main shaft from being galled by the collision. However, although the ceramic material has low toughness and is easily broken as compared with the metal material as described above, for example, comparing the case where the ceramic material is formed of Al ₂ O ₃ described above and the case where the ceramic material is formed of SCM440,
Since the bending strength decreases only to about 2/3, under normal cutting load, the same shank diameter as the conventional one or a shank diameter one size larger can be used, but the impact value is about 1/10. It is understood that shanks made of ceramic are easier to break as compared to shanks of metallic materials, due to the reduction of the shank.

In the present embodiment, the notch 29 is provided on the feed side of the cutting tool. However, the notch 29 may be provided on the upper surface of the cutting tool, and the notch 29 is not essential and may not be provided. .. In this case as well, since the shank 24 is made of ceramics, it can be reliably broken by a sufficiently small impact force as compared with a shank made of a metal material at the time of collision with a work or the like, and galling of the spindle can be prevented. ..

As described above, since ceramics are weak in stress concentration, in this embodiment, an elastic body 26 such as urethane rubber and a steel plate 27 are interposed between the screws 28, 28 for pressing the shank 24 and the shank 24. In order to disperse the stress applied to the shank 24 and surely fix the shank 24, an elastic body is also interposed on the lower surface of the shank 24 to disperse the stress concentration on the lower surface.

FIG. 2 shows another embodiment of the present invention, in which the same elements as those in FIG. 1 are designated by the same symbols. In this embodiment, instead of forming the entire shank of ceramics as described above, only the portion 30 protruding from the tool holder 21 to the tip is made of ceramics, and the remaining portion 31 is made of metal. Even with the lathe turning tool 32 formed in this way, the lathe turning tool 23
The stress concentration due to the collision is concentrated in the notch 29, and the shank 24 is broken from the notch, which has the same effect and effect.

Therefore, similarly, it is possible to surely prevent the bearing and the main shaft from coming into contact with each other due to a collision and the main shaft is galled, and the remaining portion 31 of the shank 24 is made of a metal material, so that the screws 28, 28 are sufficient. Can be firmly fixed.

Although each embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention. For example, in the above embodiments, the groove-shaped recess 29 is provided on one side of the shank 24, but this recess may be provided one on each side.
The position to be arranged is not limited to the above embodiment, and may be another part.

In the embodiment shown in FIG. 2, the boundary between the metal part and the ceramic part is arranged in the tool holder 21, but this part is aligned with the end surface of the tool holder. Alternatively, it may be at a position protruding from the end surface of the tool holder.

Further, when a diamond single crystal is used as a bite tip, a highly tough material such as glass fiber is integrated along the longitudinal direction of the ceramic shank in order to prevent the expensive diamond tip from being damaged. When the shank is broken, the tip of the cutting tool is prevented from dropping and the dropped tip collides with the structural portion of the lathe to damage the tip.

[0026]

As described above, according to the turning tool according to the present invention, since the periphery of the tip of the cutting tool is made of ceramics, when the cutting tool accidentally collides with the work or the work chuck. Immediately, the tip of the ceramic shank breaks. Therefore, an excessive force is not applied to the spindle of the lathe, and galling of the spindle can be prevented.

[Brief description of drawings]

FIG. 1 is a perspective view showing a turning tool and a tool shank according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a turning tool and a tool shank according to another embodiment of the present invention.

FIG. 3 is a perspective view showing a conventional example.

4 is a partially cutaway perspective view of FIG. 3. FIG.

[Explanation of symbols]

 21 Tool Holder 23 Lathe Tool Bit 24 Shank 25 Tip 27 Elastic Body 29 Notch Part 30 Part Protruding from Tool Holder to Tip 32 Lathe Tool Bit

Claims (3)

[Claims] 1. A lathe tool comprising a shank that is sandwiched and fixed to a tool holder, and a cutting tip that is attached to the tip of the shank, wherein the shank protrudes from at least the tool holder to the tip. A lathe tool bit whose parts are made of ceramics. 2. The turning tool for lathe according to claim 1, wherein at least one notch is formed in a portion of the shank formed of ceramics. 3. The method for mounting a lathe tool according to claim 2, wherein the shank of the lathe tool formed of the ceramics is sandwiched by a tool holder with an elastic body interposed therebetween.