EP0555285B1 - Process for machining the inner surfaces of bores - Google Patents

Abstract

According to a process for machining bores of workpieces, a honing tool provided with an abrasive coating and radially pressed against the wall of the bore carries out simultaneous rotary and reciprocal movements. In addition to the reciprocal and rotary movements (2, 3), the honing tool (1, 100) vibrates with a high-frequency, short-hub natural vibration (31, 22) excited by ultrasonic oscillation in the range between 16 and 40 KHz.

Description

The invention relates to a method and a device for machining the inner surfaces of bores in workpieces, in which a tool coated with an abrasive coating simultaneously executes a rotary movement, an axial lifting movement and which also carries out an ultrasonic oscillation superimposed on the movements mentioned.

Such a device is known from the publication "Frequency honing for high removal rates" from the journal Werkstatt und Betrieb 118 (1985 (7), pages 393-395 (cf. in particular page 394, section 4.1). There, the rotation movement and axial stroke movement formed helical basic movement of the honing process overlaid an oscillating relative movement. This increases the cutting speed (for the forward stroke) and self-sharpening the honing stones (for the reverse stroke). The oscillation is generated by two hydraulic cylinders. From this, although more precise details have not been given in the cited publication, it can be concluded that this third movement component is a movement with a frequency of at most a few 100 Hz. The honing stones are pressed hydromechanically with constant pressure.

From US Pat. No. 2,939,250 a method known as "resonance honing" has become known which works with a honing tool, the honing stones covered with cutting agent coating are adjustable in the radial direction in that their inclined infeed surfaces interact with correspondingly oblique infeed surfaces of an infeed rod. The delivery rod is now exposed to an oscillating electromagnetic field by a coil surrounding it, which as a result of magnetostriction leads to corresponding periodic shortening or lengthening of the delivery rod. This results in corresponding radial reciprocating movements of the honing stones via the adjustment mechanism mentioned. A second embodiment, which is described in the same document, generates a vibration between the inner surface of the bore and the stones of the Abrasive coating of the tool in that the platform on which the workpiece is attached is set in a rapid up and down movement. For this purpose, the platform is provided with a vibration excitation device which has a coil excited with an electromagnetic oscillation. In both variants of US Pat. No. 2,939,250, this oscillation is said to lead to the collapse of abrasive grains and thus to the self-sharpening of the cutting surface. No information is given on the frequency; due to the mechanical conditions, however, it can be assumed that in this case too it is around 100 Hz. The adjustment mechanism shown (FIG. 2) or the platform with workpiece (FIG. 3) would be too slow for higher frequencies.

In US Pat. No. 2,939,251, also with the aim of constantly self-sharpening the cutting surface, a method is described in which the workpiece (see FIG. 2) or the tool (see FIG. 9) is given a third vibration which is in the range of 20-100,000 Hz, preferably above the audible range, in order to avoid disturbing noises for the environment. However, these are also electromagnetically excited vibrations that are generated with the aid of coils that move the tool or workpiece holder back and forth accordingly. However, the tool or workpiece holder does not vibrate naturally, but acts as a rigid means of transmitting vibrations from the vibration exciter to the tool or workpiece.

In the so-called superfinishing (also: external honing) in a continuous process, the rotationally symmetrical workpieces are given a rotary movement, while a honing stone sits on the outer surface, which is given a high-frequency oscillating movement parallel to the axis of rotation of the workpiece (DE 35 33 082 A1). The vibrations that are used generally have frequencies of up to 3000 vibrations per minute, i.e. up to 50 Hz. To improve workpiece removal, an attempt was made in the process according to the document mentioned to proceed step by step and between the individual steps, each after a certain forced delivery route, let the superfinishing stone fire.

In the context of superfinishing, i.e. the processing of the outer surfaces of rotationally symmetrical workpieces, attempts have also already been made to use ultrasonic waves for cleaning the honing stones (cf. DE-AS 24 35 848). However, the ultrasonic vibration is not forced onto the tool, but rather to promote blasted or broken grains into the surface between the tool and the workpiece via the detergent-liquid medium.

Japanese patent application J 02 212 069-A describes a method for machining workpieces from a Aluminum-silicon carbide alloy that performs an axial movement, a rotating movement and an expanding movement. It is stated that the workpiece or tool vibrates at high frequency (ultrasonic). However, no further details can be found in this publication. In particular, it is not apparent in what way shape corrections on the workpiece can be achieved by increased material removal.

Technologically, the so-called "ultrasonic eroding" does not concern the machining of the inner surfaces of bores, but rather the drilling of bores at all by means of ultrasonic-excited machining heads. This method has also been combined with drilling machines (see US Pat. Nos. 3,614,484 and 4,828,052). This makes it possible to drill holes in materials that are too hard for normal drilling. However, it is not a matter of reworking the inner surfaces of existing holes.

From DE-C 584 199 a honing tool is known, in which the cutting surface is attached to a shaft, which can be elastically expanded by an expansion piece, and in which the expansion piece can be inserted into a recess in the shaft. This tool is made of hard tissue or hard paper by mechanical processing from wound and, if necessary, pressed tubes or plate material manufactured in order to obtain variable and, at the same time, finely adjustable expansions that can be varied within wide diameter limits. The grinding or polishing mandrels thus obtained serve as carriers for loose grinding and polishing agents. They are not suitable for improving the known methods described in the sense of an improved shape correction through higher material removal.

The invention is based on the object of further improving the method and the device of the type mentioned at the outset, on the one hand in such a way that a greater removal of material can be achieved and on the other hand in that better form corrections are possible.

This object is achieved by the features of claims 1 and 10 respectively.

Advantageous developments of the invention are defined in the subclaims.

The invention now surprisingly shows up not only increased material removal compared to the prior art, but also better shape corrections of the bore are possible with it. There is also a "new" one, characterized by a large number of small pockets Surface. These pockets (see FIG. 10) are used to hold lubricant. This is particularly important when it comes to achieving an otherwise extreme accuracy and shape of the surface to ensure lubrication in cooperation with other components, especially when it comes to the inner surfaces of cylinder bores in automobile engines or control bores in valves. In principle, a new surface and a method for its production are given.

The new process enables in particular high machining allowances with relatively fine grain sizes with fine machining surfaces. With the achievable surface qualities, the previous quality limits of conventional honing are exceeded. Previously, values around 0.6 µm R _z were the limit for hardened steel. This surface quality could be significantly improved with the method according to the invention. The high frequency honing according to the invention results in relatively low machining forces. The consequence of this is only an extremely small formation of burrs. A new surface structure is created with a particularly high proportion of load. According to the kinematics, a periodic surface pattern is created with regular "troughs" or "pockets", which, as mentioned, are particularly suitable for holding lubricants.

Figur 1

ein Schema zur Erläuterung;

Figur 2

ein Steuerschema für die Bearbeitung einer Bohrung mit dem erfindungsgemäßen Verfahren;

Figur 3

den Schwingungsverlauf eines Schleifmittelkorns an der Wand einer Bohrung;

Figur 4

ein Schema zur Erläuterung der Kornüberdeckung;

Figur 5

eine Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens;

Figur 6

ein erstes Ausführungsbeispiel eines Honwerkzeugs zur Durchführung des erfindungsgemäßen Verfahrens;

Figur 7

die Kontur des Schleifmittelbelags 40 im Werkzeug 1 nach Figur 6;

Figur 8

ein zweites Ausführungsbeispiel eines Honwerkzeugs zur Durchführung des erfindungsgemäßen Verfahrens;

Figur 9

eine schematische Darstellung der elastischen Verformung der Kontur und der Länge des Werkzeugs 1 bei Durchführung der Eigenschwingung;

Figur 10

eine Oberflächenaufnahme einer mit dem erfindungsgemäßen Verfahren bearbeiteten Bohrung;

Figur 11

ein Schema zur Erläuterung der mit dem erfindungsgemäßen Verfahren erreichbaren Honzugaben;

Figur 12

eine zeichnerische Darstellung zur Zuordnung der Form des Werkzeuges 8 zur Lage der radialen Schwingung und Schwingung in Längsrichtung der Eigenschwingung;

Figur 13

eine Abwandlung von Figur 9 derart, daß bei maximaler Amplitude der radialen Komponente der eigenfrequenten Schwingung des Werkzeuges 1 eine zylindrische Form des Werkzeuges entsteht.

An embodiment of the invention and its advantageous Further developments are described below with reference to the accompanying drawings. They represent:

Figure 1

a diagram for explanation;

Figure 2

a control scheme for machining a hole with the inventive method;

Figure 3

the course of vibration of an abrasive grain on the wall of a bore;

Figure 4

a diagram to explain the grain coverage;

Figure 5

a device for performing the method according to the invention;

Figure 6

a first embodiment of a honing tool for performing the method according to the invention;

Figure 7

the contour of the abrasive coating 40 in the tool 1 according to FIG. 6;

Figure 8

a second embodiment of a honing tool for performing the method according to the invention;

Figure 9

a schematic representation of the elastic deformation of the contour and the length of the tool 1 when performing the natural vibration;

Figure 10

a surface photograph of a bore machined with the method according to the invention;

Figure 11

a diagram for explaining the achievable honing with the inventive method;

Figure 12

a graphic representation to assign the shape of the tool 8 to the position of the radial vibration and vibration in the longitudinal direction of the natural vibration;

Figure 13

a modification of Figure 9 such that at maximum amplitude of the radial component of the natural frequency vibration of the tool 1, a cylindrical shape of the tool is formed.

FIG. 1 shows a honing tool 1. The usual honing movement that results in the cross-section is the sum of a rotary movement (corresponding to arrow 2) and a periodic back and forth Movement (lifting movement). According to the invention, a third movement, namely a short-stroke ultrasonic oscillation of the tool, is superimposed on these two movement components, which leads to a natural oscillation of the tool in the natural resonance range. The excitation by a vibration exciter takes place in the axial direction parallel to the stroke movement 3. This inherently resonant vibration of the tool leads to elastic deformations of the tool and thus to movements of the individual areas of the tool both in the axial and in the radial direction, as indicated by the arrows 32 and 33 indicated. In one exemplary embodiment, the oscillation takes place at a frequency of 21.7 kHz with an amplitude that could be set to a maximum of 15 μm.

The workpiece 4 has a bore 5, the inner surface of which is to be machined. The honing tool 1 is - as known per se - designed as a mandrel honing tool and provided with a conical cutting zone 6, the rear larger diameter D 1 of which is slightly larger than the smallest diameter of the bore 5 not yet machined with the honing tool 1. The front smaller diameter D 2 allows the introduction of the tool 1. With the stroke in the direction of the arrow, the conical cutting zone 6 moves into the bore 5 and works off the material which corresponds to a bore diameter of less than D 1. Following the conical cutting zone 6, the honing tool 1 is cylindrical, so that it is in the Hole is inserted. The machining is preferably carried out with an axial double stroke.

With additional excitation of the honing tool 1 with a high-frequency, short-stroke ultrasonic vibration in the axial direction, there is the unexpected effect that much more material can be removed, and thus more than ever since, shape errors in the bore can be corrected. There is also a new type of surface, which is characterized by a large number of small pocket-like depressions. This surface is shown in Fig. 10 as a photograph.

FIG. 2 shows the control diagram of the stroke movement 3 at (a), the rotary movement 2 at (b) and the ultrasound excitation at (c) in their temporal association with one another and as a function of time. The broader line at (c) indicates the amplitude of the ultrasonic vibration. The residence time dt at (a) is adjustable. Points A, B, C, D can also be set, ie the start and the beginning of the rotary movement and the high-frequency vibration. A machine for performing the method according to the invention, taking into account the control diagram according to FIG. 2, was designed with the following data on a trial basis:

The movement path of a tip of an abrasive grain 7 as a function of time is shown in a range from 0 to 300 μsec in FIG. 2. The upper and lower boundary lines, which each represent a rising path, correspond to the oblique course of the grooves in conventional honing.

If one imagines that the individual abrasive grains 7 lie along this high-frequency oscillation path with a certain area on the surface to be machined, then it depends on how the duration of an oscillation (oscillation period) and its amplitude are matched to the peripheral speed of the honing tool 1 is one of the two situations shown in Figure 4. With (a), that is to say with relatively "narrow" vibration in relation to the surface area of the cutting agent grains 7, it follows that an abrasive grain 7 sweeps over a certain area during a first ultrasonic stroke, which in part also swept again during the next ultrasonic stroke taking place in the opposite direction becomes. That means: The same surface is processed several times, depending on the choice of these parameters, so that it leads to a "sparking" effect is coming. By choosing these parameters differently, as in (b), it can be achieved that this effect is limited to areas in the vicinity of the vibration peaks. In general, the choice of parameters is more advantageous, so that the course according to (a) results.

Figure 5 shows an apparatus for performing the method.

The honed to the dimensions D₁ and D₂ and contour honing tool 1 is received with its tool receiving cone 8 in a conical receiving opening 8 'of the sound transmission body 9. The sound transmission body 9 has two flanges 10, 11, which are provided at the points 10 ', 11' in the depicted manner with grooves, so that thin points 10 ', 11' arise, which have the effect of an articulated suspension, so that an axial high-frequency ultrasonic vibration, which the sound transmission body 9 carries out, is not transmitted to the housing 12. The sound transmission body 9 is made of titanium, for example. The housing 12 consists of the cylindrical part 13, the lower cover 14 and the upper cover 15. The upper cover 15 has in the middle a bore 16 provided with an internal thread, into which the threaded pin 17 projects, which is fixed with the receiving hub 18 connected is. Housing cover 15 and receiving hub 18 are thus firmly screwed together, the disc 19 being clamped in between. In this way rotates the housing 12 with the receiving hub 18, which in turn is driven in the direction of rotation via toothed belt wheel 20 and toothed belt 21. The entire unit, as shown in FIG. 5, including a motor (not shown) can be moved up and down to produce the lifting movement, as is known per se from conventional honing machines, so that a more detailed description of the structural details is provided here Connection can be dispensed with.

The actual ultrasonic vibration exciter 25, which in the exemplary embodiment is formed by two piezoelectric elements (quartz crystals) 26 and 27, is located on the top of the sound transmission body 9, with a disk 28 representing an oscillating mass being arranged above the ultrasonic vibration exciter 25 for tuning the vibration system. The entire arrangement is firmly clamped by the clamping screw 29, which is screwed into the sound transmission body 9. The centering takes place by means of centering sleeve 29 '. A coolant channel 30 passes through the sound transmission body 9 and the clamping screw 29. The interior of the housing, the line 31 and the openings in the disk 19 and in the cover 15, a cooling medium can be supplied.

The supply of electrical energy to the ultrasonic vibration exciter 25 takes place in the illustrated Way through slip rings 35 arranged on the cover 15 and slip rings 36 attached to a non-rotating part of the mentioned unit. FIG. 6 shows the simplest form of a honing tool 1 as a fixed mandrel with fixed, non-adjustable external dimensions. The cutting surface has the contour 40, as shown in detail in FIG. 7, namely an insertion zone 37 over approximately less than 10% of its length, followed by the cutting zone 6 already mentioned, which is approximately over a little less than half of the total Length of the cutting agent covering extends, as does the cylindrical guide zone 38 thereafter.

The usual radial expansion, as is known for the adjustment of honing tools, presents certain difficulties in the present case, since there is a risk that individual parts which are adjustable against one another and which are not in a vibration node rub against one another at high frequency, so that excessive heating occurs can occur. In addition, it must be ensured that no parts come loose despite the high-frequency vibration. In this respect, specially designed honing tools are advantageous. Such a honing tool 100 is shown in FIG. 8. The cutting surface 40, which has the contour according to FIG. 8, is applied to a shaft 101 which can be elastically expanded by means of an expansion piece 102. This is the case, for example, when the recess 103 in the shaft 101, on the one hand, and the expansion piece 102, on the other hand, are conical, so that Axial displacement of the expansion piece results in an elastic expansion of the shaft in the radial direction, which, however, is designed as a solid body without grooves and without slots to ensure particular stability. The required elastic radial widenings can also be achieved in this way. In the axial direction following the expansion piece 102 there is a pressure piece 104, which is interchangeably inserted in the recess 103. It rests with its right end on the pressure surface 105 of the receiving part 106, which in turn is then inserted with the right end into the tool receiving cone 8 of the sound transmission body 9. The cutting agent covering 40 can therefore be elastically expanded by using pressure pieces 104 of different lengths. The longer the pressure piece 104, the more the shaft 101 is expanded radially.

The tool 1 carries out a natural vibration, preferably in the resonance range. This means that the tool 1 does not act as a rigid transmission element of the high-frequency ultrasonic oscillation, but rather is itself the medium of the ultrasonic oscillation, ie the longitudinal and transverse waves triggered by the excitation. As already mentioned above, this means that the tool 1 itself carries out elastic vibrations in the axial and radial directions with the natural (resonance) frequency excited by the ultrasonic vibration and periodically changes its contour. To a cheap coupling of the To reach ultrasound energy from the ultrasound vibration exciter 25 into the tool 1, the ultrasound vibration exciter 25 must have a frequency that is as close as possible to the natural resonance of the tool 1. If the natural resonance of the tool deviates too far from that of the stimulating system (vibration exciter 25, sound transmission body 9), the tool does not vibrate. In order to optimally design the transmission of the ultrasound energy from the vibration exciter 25 to the tool 1, the sound wave resistance of the vibration exciter must also be as equal as possible to that of the tool 1.

The natural frequency of the tool 1 is determined by the dimensions (length, diameter), the modulus of elasticity of the material and the speed of sound given in the material. For steel, the modulus of elasticity is approx. 21,000 daN / mm² and the speed of sound is 5,960 m / sec. at 21.7 kHz, this gives half a wavelength equal to 187 cm. This is the free tool length from the clamping cone. FIG. 9 shows how the natural vibration of the tool 1 is represented geometrically. The diameter of the tool at (a) has its greatest value D _max , while the length L has the minimum value L _min . At (b), the zero crossing of the vibration in the longitudinal direction, the average diameter D₀ and the average length L₀ result. At (c), the minimum diameter D _min and the maximum length L _max . In Figure 9, the individual amplitudes are assigned to the situations according to (a), (b) and (c).

As shown in (a) in FIG. 9, there is indeed a movement component 32 in the axial direction and a movement component 33 in the radial direction for each grain of the cutting agent covering 40. Both components are subject to the natural frequency.

The movement component 33 in the radial direction is the reason why 40 small individual pockets are introduced in the radial direction into the inner surface of the machined bores during the circulation of an abrasive grain of the cutting agent coating.

Figure 10 shows, as a photograph - since it cannot be represented otherwise - this novel surface, a distance, which in reality corresponds to 30 µm, is shown in the photograph to clarify the scale. It has now surprisingly been found that along the oblique grooves which result in the cross-grinding pattern during classic honing, troughs or pockets, which are practically "hammered" or "chiseled in" during the circulation, practically arise at short intervals due to the superimposed high-frequency vibration with radial and axial components , whereby - as can easily be seen from this photograph - burr-free, flat load-bearing areas are created between the troughs, which other components can carry. The pockets or depressions serve as an oil reservoir for lubricants in the inner surfaces of the bores. This is especially so of the utmost importance if otherwise a surface of extremely good quality is achieved. The material is removed evenly and a surface pattern is created that is periodic in accordance with the kinematics. It is of course heavily dependent on the set parameters. At a low speed, for example, the cutting tracks created by the high-frequency oscillation are very close together. At a high speed, these cutting marks are stretched accordingly and result in a somewhat less favorable bearing component. The load share was approximately 30% in a test series with a cutting depth of approx. 0.2 µm.

The new surface results in an extreme improvement of the wearing properties. If, for example, a specific bore is machined in two machining stages with grit D46 and D15 (according to the FEPA definition; see VDI guidelines VDI 3394 from June 1980), the bore geometry (straightness, roundness) is less than 0.5 µm reachable. This was carried out on a trial basis for workpieces which were conventionally pre-honed to a diameter of 6.955 to 6.965 mm and were finished in two further processing steps using the method according to the invention. The surface roughness was initially 0.7 µm R _z and could be improved to less than 0.4 µm R _z with increasing numbers. Diamond was used as the grain.

In general, superabrasive materials are considered, in addition to Diamond cubic boron nitride (CBN), possibly for bores made of soft material (e.g. aluminum) also ruby, sapphire, corundum.

The machining forces that occur are of particular importance for the application of the method according to the invention. When adding 10 µm (difference in the diameter of the unfinished bore compared to the final dimension desired by machining) using the fixed mandrel with the D46 grit, an axial force of 1.0 N and a torque of 1.120 Ncm were determined. A direct comparison with a machining process in which the same tool would have been used without high-frequency exposure was not possible, since it would not be possible to add more than 4 µm without the high-frequency oscillation. If you want to remove more material with one stroke without HF oscillation, the tool seizes up. But even with an addition of 4 µm without high-frequency oscillation, i.e. with an addition reduced by more than 50%, the axial force was still 2.4 N and the torque 1.3 Ncm. It can therefore be assumed that the process according to the invention can remove 2 to 3 times the addition in a double stroke, and that the axial force and torque are even lower than in conventional processes.

It also follows that the method described here causes very little burr formation. In the case of workpieces machined on a trial basis, as in FIG clearly visible, no burr formation at all.

FIG. 11 finally shows the honing addition dz (in micrometers) as a function of the grain k (according to the FEPA definition) in the comparison between the - known - mandrel honing (lower bar with a grain size D15 to D181) compared to the high-frequency honing ( black filled area). The workpiece was hardened steel with a hardness of more than 60 HRc.

The vibration ratios over the length of the tool 1 result from FIG. 12 in the event that the length of the tool 1 is equal to half the wavelength of the ultrasonic vibration. In general, a prerequisite for the occurrence of a natural vibration is that the length of the tool 1 from the clamping cone, which lies in the "restraining plane", is a very large multiple (including 1 times) of half the wavelength. In this case, the vibration in the radial direction, the component 33, and the vibration in the axial direction, the component 32, are entered to the left of the tool and related to the length of the workpiece 1.

A particularly advantageous embodiment of the invention results from FIG. 13. This representation corresponds essentially to FIG. 9, but with the difference that the shape the tool in the idle state (zero crossing (b)) is not cylindrical, but has a convex contour. It then follows that in the state in the greatest radial expansion according to (a), ie at D _max and L _min, the tool has a cylindrical shape.

The addition of the diameter depends on the input amplitude. With a change in the amplitude of the ultrasonic vibration, by which the natural vibration of the tool 1 is excited, the amplitude of the axial vibration component 33 and thus also D _{max can also be} set. These parameters also directly influence the quality of the machined hole. The roughness depth R _Z decreases in an essentially linear dependence on the amplitude and frequency.

Claims (15)

1. Process for machining the inner surfaces of bores in workpieces, in which a tool provided with an abrasive coating simultaneously carries out a rotary movement (2), an axial reciprocal movement (3) and furthermore ultrasonic oscillation superimposed upon the said movements (2, 3), characterised in that the ultrasound excites natural oscillation of the tool (1) in the range of 16-40 kHz and that the free length of the tool (1) from the point at which it is clamped on to a sound transmission element (9) is an integral multiple of half the wavelength of the natural oscillation of the tool.
2. Process according to claim 1, characterised in that the contour of the tool (1) is determined in such a manner that the shape of the tool (1) with a maximum amplitude (D_max) of the radial component (33) of the natural oscillation of the tool (1) is cylindrical.
3. Process according to claim 1 or claim 2, characterised in that the ultrasonic oscillation by the oscillation exciter (25) acts on the tool (1) in the axial direction of the bore.
4. Process according to claim 1 or one of the following claims, characterised in that machining is effected in only one double stroke and that the honing tool is provided in the manner known per se with a conical cutting zone (6), the rear larger diameter (D₁) of which in the direction of the axial reciprocal movement (3) has an oversize of more than 4 µm compared to the diameter of the unmachined bore.
5. Process according to claim 3, characterised in that the exciting ultrasonic oscillation has a frequency of 20 to 24 kHz.
6. Process according to claim 1 or one of the following claims, characterised in that the frequency of the exciting ultrasonic oscillation is essentially equal to the natural frequency of the tool (1).
7. Process according to claim 1, characterised in that an abrasive agent (lapping abrasive) is added in suspension to the coolant used.
8. Process according to claim 1 or one of the following claims, characterised in that, in order to obtain a spark-out effect, the speed of rotation of the honing tool, the feed of the honing tool in the axial direction (reciprocation speed), and the amplitude and frequency of the ultrasonic oscillation of the honing tool are determined in such a manner that the surfaces coated with the abrasive grit during an ultrasonic stroke are partially coated once again during the subsequent ultrasonic stroke in the opposite direction.
9. Process according to claim 1 or one of the following claims, characterised by the use of super-abrasive grit.
10. Device for carrying out the process according to claim 1 or one of the following claims, with a honing tool for machining the inner surfaces of bores, the honing tool (1, 100) being accommodated in the lower end (8) of a sound transmission element (9) acted upon from above by an ultrasonic oscillation exciter (25), characterised in that the free length of the tool (1) from the point at which it is clamped on to a sound transmission element (9) is an integral multiple of half the wavelength of the natural oscillation of the tool, and that the sound transmission element is suspended in a housing at least in a plane situated in the nodal region of the ultrasonic oscillation by fixing means (10′, 11′) in such a manner that it (9) can carry out ultrasonic oscillation relative to the housing (12), while the housing does not take part in the oscillation, that the housing (12) is driven in rotation (20, 21) and that the unit for producing the axial reciprocal movement formed by the housing (12), the sound transmission element (9), the honing tool (1, 100) and the rotary actuator (20, 21) is vertically adjustable in a manner known per se.
11. Device according to claim 10, characterised in that electrical energy is supplied to the ultrasonic oscillation exciter (25) via slip rings (35, 36).
12. Device according to claim 10, characterised in that the ultrasonic oscillation exciter (25) is fixed to the upper end of the sound transmission element (9) by oscillator crystals.
13. Process according to one of claims 1 to 9 using a honing tool, characterised in that the cutting coating (40) is applied to a shank (101) which can be expanded elastically by an expansion piece (102) which can be inserted into a recess (103) in the shank (101), and that an exchangeable thrust piece (104) acting on the expansion piece (102) in the axial direction is accommodated in the recess (103) and the shank (101) is screwed on to a receiving part (106) in such a manner that a contact surface (105) of the receiving part presses the thrust piece and the expansion piece firmly against the inner surface of the shank in a position resulting in the desired expansion of the shank as a function of the length of the thrust piece.
14. Process according to claim 13, characterised in that the receiving part is screwed on to the shank in the region of an oscillation node.
15. Process according to claim 13, characterised in that the shank is an unslotted solid body.

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