WO2005105351A1

WO2005105351A1 - Interface for a cutting tool

Info

Publication number: WO2005105351A1
Application number: PCT/EP2005/051800
Authority: WO
Inventors: Günter Schweighöfer; Peter Müller
Original assignee: Günther & Co. GmbH
Priority date: 2004-04-29
Filing date: 2005-04-22
Publication date: 2005-11-10
Also published as: DE102004021190A1

Abstract

The invention relates to a cutting tool comprising a cutting portion and a shank portion (1) and at least one channel (2), extending within the cutting tool, for supplying a coolant and/or lubricant from the shank portion (1) to the cutting portion. The end surface of the shank portion (1) is provided with a recess (3) in which at least one inlet opening of at least one channel (2) for supplying a coolant and/or lubricant is located. The aim of the invention is to provide a cutting tool and/or an interface for a cutting tool of the aforementioned type which has improved flow and sealing properties as compared to the prior art, and which is easy to produce. For this purpose, the recess (3) is rotationally symmetric.

Description

Günther & Co. GmbH

Interface for a cutting tool

The present invention relates to a cutting tool, e.g. a drill or milling cutter with a cutting part, e.g. a drilling part, and a shaft part and at least one channel running within the cutting tool for the supply of coolant and / or lubricant from the shaft part to the cutting part. Such cutting tools have been known for a long time.

Even if the present invention can be used in principle for all possible types of cutting tools, it will be explained below for the sake of simplicity using the example of a drill.

The drill has a drill part that carries the major and minor cutting edges that come into contact with the workpiece during machining and a shank part that is generally intended to be used in a tool chuck, e.g. a drill chuck, and therefore an interface between the cutting tool or the drill on the one hand and the machine tool, e.g. the drilling machine. During machining, there is considerable heat development in the area of the cutting edges. It has therefore long been common practice to cool the cutting edges. For this purpose, a coolant is fed to the cutting edges. In addition, it can be advantageous for some applications if, alternatively or in combination with the coolant, a lubricant is made available.

For some years now, attempts have been made to replace the machining with cooling lubricant, which has been customary up to now, by dry machining with suitable cutting geometries and suitable material combinations. So far, however, a completely dry machining for various machining operations, such as not possible in practice for reaming and thread cutting processes, for deep bores and for machining materials that tend to stick to the tool. The reason for this is generally less the lack of cooling, since modern cutting materials and possibly used coatings can withstand the higher temperatures without loss of quality, but rather the lack of lubrication.

For this reason, so-called "quasi-dry" machining is often carried out, ie so-called "minimal quantity lubrication" takes place. In general, an oil-air Mixture generated and fed to the tool - as with conventional machining with cooling lubricant - either from the outside or through the inside of the cutting tool.

It has been shown in practice that, particularly in series production, the internal feed via the shaft part is of great advantage.

To ensure this, the cutting tool or the drill has at least one channel running inside the cutting tool for the supply of coolant and / or lubricant from the shaft part to the cutting part. For cutting tools with several main cutting edges, e.g. in the case of twist drills, several such channels can also be provided, each of which transports the oil-air mixture to one of the cutting edges involved.

The minimal quantity lubrication via the inner channels, however, poses various physical and technical problems. In particular, it is not trivial to transport the oil-air mixture on the long way through the spindle and tool, sometimes with very small channel cross-sections, while maintaining an adequate flow and preventing segregation of the oil-air mixture.

In principle, the mixture is formed in two different ways. On the one hand, so-called single-channel systems are known in which the corresponding mixture (aerosol) is formed before it enters the machine spindle. Here it is necessary that very fine oil droplets are formed in order to segregate during the long way to the point of exit. prevent. On the other hand, so-called two-channel systems are known, in which oil and air are first transported separately into the tool in two different channels, oil being then injected into the air stream that is carried past at the tool-side end of the spindle.

The one-channel system has the advantage that, due to the use of very fine droplets, the risk of segregation is very low, so that the lubricant mixture is relatively insensitive to centrifugation at very high speeds. However, only a relatively limited proportion of oil can be achieved with this system. In addition, it is very difficult to meter oil and air separately.

The two-channel system has the advantage that large amounts of oil are also possible. In addition, oil and air can be set separately. The larger droplets formed in this system compared to the single-channel system make the lubricant mixture susceptible to segregation. In fact, at least partial segregation inevitably occurs, so that part of the oil flows along the channel walls. In order to provide the best possible minimum quantity lubrication, it is therefore necessary in particular to carefully carry out all interfaces on the way of transferring the minimum quantity lubrication mixture, since they can represent dead spaces and loss points.

On the one hand, dead spaces represent turbulence points that hinder the flow of the mixture. On the other hand, they also increase the response time of the lubricant supply, which is generally switched off and on frequently with every tool change and even when the tool spindle is moved. In order to ensure effective lubrication, the lubricant mixture should ideally emerge from the tool as soon as it is switched on. Any dead spaces, however, prevent this since they first have to be filled with the required mixture. Even if the exact physical-technical process in the presence of dead spaces is still not understood, a clear increase in the response time can still be observed. In addition, dead spaces lead to oil losses, which generally have to be blown out when changing tools and not only increase oil consumption, but also contaminate the inside of the machine with an oil film.

In principle, it is also of crucial importance that the interfaces are as tight as possible so that no further dead spaces form outside the tool.

The present invention relates to improving the interface between the tool on the one hand and the chuck on the other.

Especially for drills, the chuck generally has a screw in the chuck that is used for the length adjustment. With the help of the screw, length manufacturing tolerances and length losses due to regrinding can be compensated. When assembled, the screw head rests directly on the face of the shaft part. In order to provide an interface between the chuck or screw on the one hand and the shank part on the other hand, hollow machining of grub screws is used in conventional machining with cooling lubricant and a slot is provided in the shaft end of the tool in order to establish a connection to the cooling channels.

However, this type of interface is completely unsuitable for minimum quantity lubrication. For minimum quantity lubrication, it is necessary to achieve a fluidically favorable transition from the central channel in the screw to the cooling channels, to achieve the best possible seal between the screw and the shaft end to the dead space in the chuck and the dead space in the transition from the screw to the chuck as small as possible. For minimum quantity lubrication, it has therefore already been proposed to use a screw with an inner taper and to make the tool shaft end tapered with a transverse groove. However, this embodiment shows inadequate sealing behavior in the area of the transverse groove. In addition, no optimal flow behavior is observed. Furthermore, this solution can only be used for tools with one or two cooling channels.

Furthermore, the applicant has already proposed a tool shaft end which has an essentially mold-shaped depression. However, this embodiment also does not show optimal sealing and flow behavior.

Starting from this prior art, it is therefore an object of the present invention to provide a cutting tool or an interface for a cutting tool with a cutting part and a shaft part and at least one channel running within the cutting tool for the supply of coolant and / or lubricant from the shaft part to the cutting part, the end face of the shaft part having a recess in which at least one inlet opening for at least one channel for the supply of coolant and / or lubricant is arranged, to provide the flow properties which are improved compared to the prior art and shows an improved sealing behavior, the cutting tool should be easy to manufacture.

According to the invention the object is achieved in that the depression is rotationally symmetrical. Surprisingly, it has been shown that the formation of the recess in a rotationally symmetrical manner significantly improves the flow behavior, so that overall there is minimal quantity lubrication with a shorter response time.

The depression is advantageously designed to be rotationally symmetrical to the longitudinal axis of the cutting tool. This ensures that the recess can be made easily. In addition, with the interface geometry according to the invention, cutting tools can be realized with almost any number of channels for the supply of coolant and / or lubricant. The interface can therefore be used universally.

Basically, the depression can have any rotationally symmetrical shape. However, it has been shown that the surfaces formed by the depression are advantageously curved, since additional dead spaces are thereby largely avoided and a favorable flow ratio is ensured.

A particularly preferred embodiment provides a recess which has the shape of a spherical cap or spherical cap. Experiments have shown that this form of depression ensures favorable flow properties of the minimum quantity lubricant. About that In addition, this geometry can be produced simply and inexpensively, for example by grinding with a grinding wheel.

The geometry according to the invention has proven itself in particular in the case of hard metal cutting tools or even solid carbide cutting tools, since tool machining is very complex in this type of tool, so that only simple geometries can be used for cost reasons. With the geometry according to the invention, a balanced compromise is thus made between good sealing properties and good flow properties on the one hand and simple, inexpensive producibility on the other.

In order to achieve the best possible seal against the adjusting screw of the tool chuck, an expedient embodiment provides that the end surface of the shaft part has a sealing surface which is arranged surrounding the recess. In the clamped tool, the sealing surface then engages with the preferably conical inner surface of the adjusting screw.

Another particularly preferred embodiment provides that the sealing surface is essentially conical. The conical arrangement of the sealing surface effectively increases the sealing surface, so that the sealing function is improved.

Advantageously, the end surface of the shaft part is essentially frustoconical, the sealing surface being formed by the outer surface of the truncated cone. It is particularly expedient if the sealing surface is inclined perpendicular to the longitudinal axis of the cutting tool with respect to an imaginary plane. The angle of inclination a, i.e. the angle which the imaginary plane and the sealing surface enclose are greater than 15 °, preferably greater than 30 ° and particularly preferably between approximately 45 ° and approximately 60 °.

It has also been demonstrated in numerous experiments that the sealing surface is advantageously made relatively large. It is particularly expedient if, in a plan view of the end surface of the shaft part, the width b of the sealing surface is at least 3% and preferably at least 5% of the shaft diameter d.

Furthermore, it has been shown that, in a particularly preferred embodiment, the depression has a maximum depth in relation to the shank end surface which is at least 3%, preferably at least 5%, particularly preferably at least 7% of the cutting tool diameter.

For some applications, it may be advantageous to provide an essentially flat circular ring surface between the sealing surface and the recess. Further advantages, features and possible uses of the present invention will become clear from the following description of preferred embodiments and the associated figures. Show it:

1 shows a top view and a sectional view of a first embodiment of the shank part according to the invention of a drill, FIG. 2 shows a top view and a sectional view of a second embodiment of the shank part according to the invention, FIG. 3 shows a top view and a sectional view of a third embodiment of a shank part according to the invention and

Figure 4 is a sectional view of the first embodiment together with a corresponding adjusting screw in the clamped state.

1 shows a first embodiment of a shaft part according to the invention in a plan view of the shaft end face and a partial sectional view. The partial sectional view shown in the lower part of FIG. 1 shows the shank part of the cutting tool with two channels 2 for coolants and / or lubricants. The partial shaft end face, which is oriented downward in the sectional view shown in FIG. 1, has a recess 3 which is designed in the form of a spherical cap. The two channels 2 each end in the depression 3. The depression 3 is arranged rotationally symmetrically about the central cutting tool axis 6. A circular sealing surface 4 is arranged on the outer sides of the shaft partial end surface, which is inclined in such a way that the surfaces enclose an angle of approximately 45 ° with an imaginary plane that runs perpendicular to the longitudinal axis 6 of the cutting tool.

Between the recess 3 and the sealing surface 4, a narrow circular ring surface 5 is provided, which lies essentially in an imaginary plane that is perpendicular to the longitudinal axis 6 of the cutting tool.

In principle, the number of cooling channels 2 is arbitrary. Therefore, two further embodiments of the shaft part according to the invention are shown in FIGS. 2 and 3, which have three or a cooling channel 2.

As shown by way of example in FIG. 2, the high tightness of the connection between the shaft part 1 and the adjusting screw 7 is achieved by the relatively wide sealing surface 4. In the sectional views shown in FIGS. 1 to 4, the sealing surface 4 has a width b that makes up approximately 10% of the diameter d of the shaft part 1. Finally, FIG. 4 shows an example of the embodiment of the shaft part 1 known from FIG. 1 in engagement with the adjusting screw 7 of the tool chuck. The adjusting screw 7 has a head with an inner cone 8. The shaft part 1 is now brought into contact with the adjusting screw 7 such that the conical or frustoconical sealing surface 4 of the shaft part 1 comes into contact with the inner cone 8 of the adjusting screw 7. Because the sealing surface 4 is not, as is occasionally the case in the prior art, partially interrupted by a transverse groove, a very tight connection between the shaft part 1 on the one hand and the adjusting screw 7 on the other hand is achieved.

In the embodiment shown in FIG. 4, the lubricant mixture can then be supplied via the tool chuck into which the adjusting screw 7 is screwed, via the central channel in the adjusting screw 7. Due to the spherical cap shape of the recess 3 of the shaft part 1, there is a very even flow through the space, which is formed on the one hand by the inner cone 8 of the adjusting screw 7 and on the other hand by the spherical cap-shaped recess 3 of the shaft part 1. Overall, a very direct minimum quantity lubrication metering with a very short response time and a very small dead space volume can be achieved by the configuration of the shaft part 1 according to the invention.

LIST OF REFERENCE NUMERALS

1 shaft part

2 cooling and / or lubrication channels

3 deepening

4 circular sealing surface

5 circular surface

6 central cutting tool axis

7 adjusting screw

8 inner cones

Claims

PATENT CLAIMS

1. Cutting tool with a cutting part and a shaft part (1) and at least one channel (2) running inside the cutting tool for the supply of coolant and lubricant from the shaft part (1) to the cutting part, the end face of the shaft part (1) being one Has recess (3), in which at least one inlet opening of at least one channel (2) for the supply of coolant and / or lubricant is arranged, characterized in that the recess (3) is rotationally symmetrical.

2. Cutting tool according to claim 1, characterized in that the recess (3) is rotationally symmetrical to the longitudinal axis (6) of the cutting tool.

3. Cutting tool according to claim 1 or 2, characterized in that the surfaces formed by the recess (3) are curved.

4. Cutting tool according to one of claims 1 to 3, characterized in that the recess (3) has the shape of a spherical cap or spherical cap.

5. Cutting tool according to one of claims 1 to 4, characterized in that the end surface of the shaft part (1) has a sealing surface (4) which is arranged surrounding the recess (3).

6. Cutting tool according to claim 5, characterized in that the sealing surface (4) is substantially conical.

7. Cutting tool according to claim 5 or 6, characterized in that the end surface of the shaft part (1) is substantially frustoconical, the sealing surface (4) being formed by the outer surface of the truncated cone.

8. Cutting tool according to one of claims 5 to 7, characterized in that the sealing surface (4) is inclined relative to an imaginary plane perpendicular to the longitudinal axis (6) of the cutting tool, wherein the angle of inclination a, ie the angle that the imaginary plane and enclose the sealing surface (4), is greater than 15 °, preferably greater than 30 ° and particularly preferably between approximately 45 ° and approximately 60 °.

9. Cutting tool according to one of claims 1 to 8, characterized in that the cutting tool is a hard metal cutting tool, preferably a solid carbide cutting tool.

10. Cutting tool according to one of claims 7 to 9, characterized in that the width (b) of the sealing surface (4) is at least 3% and preferably at least 5% of the shaft diameter (d).

11. Cutting tool according to one of claims 1 to 10, characterized in that the recess (3) has a maximum depth relative to the shaft end surface, which is at least 3%, preferably at least 5%, particularly preferably at least 7% of the cutting tool diameter.

12. Cutting tool according to one of claims 5 to 11, characterized in that an essentially flat circular ring surface (5) is provided between the sealing surface (4) and the recess (3).

13. Cutting tool according to one of claims 1 to 12, characterized in that the cutting tool is a drill.