EP2049294A2

EP2049294A2 - Crankshaft milling cutter

Info

Publication number: EP2049294A2
Application number: EP07787706A
Authority: EP
Inventors: Berthold Schaupp
Original assignee: Walter AG
Current assignee: Walter AG
Priority date: 2006-07-24
Filing date: 2007-07-18
Publication date: 2009-04-22
Also published as: US20100047031A1; CN101495261A; JP2009544478A; WO2008012254A3; KR20090064527A; DE102006034673A1; WO2008012254A2

Abstract

The present invention relates to a method for machining journals, with a first step for the rough machining and with a second step for the fine machining, wherein the journal is roughed with a crankshaft milling cutter in the first step and the journal is smoothed with a crankshaft milling cutter in a second step. In order to provide a method and a milling cutter, together with an indexable insert for this milling cutter, which make it possible to machine crankshaft journals more quickly, inexpensively and with at least the same quality as in the prior art, it is proposed according to the invention that the method for the fine machining exclusively comprises the second step, which concludes the dimension-changing machining of the journals.

Description

crankshaft cutters

The present invention relates to a method for machining journal, roughing in a first step and fine machining in a second step, wherein in the first step, the pin is roughed with a crankshaft cutter and in the second step, the pin is finished with a crankshaft cutter.

Moreover, the invention relates to a cutter or a cutter segment, which are rotatable about a cutter axis, for finishing machining journals with at least one cutting board holder, wherein the Schneidplattenhaiter forming a part of the insert seat flat surface and a sliding wedge for adjusting the radial distance of the cutting edge of a Cutting insert from the axis of rotation of the milling tool, wherein the wedge has a substantially perpendicular to the flat surface stop surface for a side surface of the cutting plate.

Furthermore, the present invention relates to an indexable insert for a milling cutter for the finishing machining of bearing journals with an upper and a lower surface as well as circumferential fenden side surfaces which connect the upper and lower surfaces with each other, wherein the edges between the upper and lower surface and the side surfaces form the cutting edges, wherein the side surfaces form clamping surfaces adjoining the cutting edges.

In the standard production of crankshafts is usually resorted to forged or cast waves. Here and in the following under a crankshaft is generally understood a machine element that converts linear movements in rotating or rotating in linear movements. These are in particular crankshafts and camshafts of internal combustion engines. The modern engine design places ever greater demands on the performance and smoothness of crankshafts. In addition, the cost of production should be reduced.

The cast or forged rough shafts must be further processed in the area of the journals for the main and stroke bearings, so that these areas of the waves meet the demands placed on them in terms of dimensional stability, concentricity and surface finish. For this purpose, from the prior art, for example DE 102 18 630 A1, methods for milling crankshafts with external cutters are known. In most cases, side milling cutters with a diameter of, for example, about 700 mm and with, for example, up to 300 indexable inserts are used. The journals are machined in the prior art milled in two steps. First, a roughing by roughing and then a finishing by finishing milling. In order to achieve the surface finish required for the journals, the surfaces of the trunnions are reground in the prior art after completion of the milling operations, so that for the preparation of each pin a total of three steps, roughing, finishing trimming and grinding are required in succession. Since these three processing steps are done with very different tools and machines, the processing of the journals of a crankshaft is time- and kosteπinteπsiv.

In contrast, the present invention has for its object to provide a method and a cutter and an indexable insert for this cutter, which make it possible to work crankshaft journals faster, cheaper and at least in the same quality as in the prior art.

According to the present invention there is therefore provided a method of machining trunnions, comprising a first roughing step and a second step of

Fine machining, in each case by machining by means of defined Cutting in a milling process, wherein in the first step, the pin is scrubbed with a crankshaft fraser and in the second step, the pin is finished with a crankshaft, the method for finishing only the second step, which completes the Maßverandernde processing of the journals on In this way, the method for producing the bearing journals or the outer surfaces of the journals can be reduced to a single fine-machining step, namely the aforementioned sizing nose

For the purposes of this application, a change in machining is understood to mean a machining in which material is targeted to achieve a nominal diameter with the aid of geometrically defined cutting edges, for example by turning, milling or broaching, or by means of geometrically undefined cutting edges, for example by grinding However, under the definition used here, these dimensional changes do not fall within the scope of a change in the surface texture, for example by coating or blasting. These processes may also change the dimensions of the work piece, but these changes are minimal usually negligible, or they are, if necessary, taken into account in the machining by means of defined cutting beyond that is not the change of the measure in these here not regarded as Maßverandernd machining In contrast, grinding or filing is regarded as a dimensionally altering treatment which, according to the invention, should be dispensed with after finishing, since the aim is to produce a final dimension by removing material, but not by means of defined cutting

It is particularly expedient if the inventive method has exactly two steps d h first a roughing for grooving the pins and then a final sizing for fine machining of the pins

In a particularly preferred embodiment of the invention, in the second step of finishing machining the trunnions are operated at a cutting speed of more than 250 m per minute, preferably more than 270 m per minute, and more preferably more than 300 m per minute

It is preferably carried out at a feed rate of 1000 mm / min to 2000 mm / min, which corresponds to a feed of about 0.2 mm per blade in a preferred embodiment To carry out the method according to the present invention, a side milling cutter or disc cutter segment rotatable about a cutter axis for finishing machining journals with at least one insert holder, the insert holder forming a first planar surface forming part of the insert seat and a slidable wedge for adjusting the radial Distance of the main cutting edge of the cutting insert from the cutter axis, said wedge having a substantially perpendicular to the flat surface stop surface for a side surface of the cutting plate, and wherein the wedge is movable in a direction substantially parallel to the flat surface.

The cutter according to the invention or the cutter segment, i. e.g. a cassette with one or more cutting board holders that can be attached to a substantially rotationally symmetrical base body, allows a fine adjustment of the radial distance of the active cutting edge of each cutting insert from the axis of rotation of the milling tool.

For this purpose, the flat surface of the insert seat is tilted relative to a tangent in the region of an active cutting edge on a circle around the cutter axis in such a way that the advancing in the direction of rotation portion of this surface of the cutter axis has a greater distance than the trailing portion of this surface. The lateral stop surface for the cutting insert is formed by a wedge, which is displaceable in a direction substantially parallel to the flat surface of the insert seat. Depending on the position of the wedge, the position of the cutting insert circumferentially changes on the flat surface of the insert seat tilted with respect to the tangent so that upon movement of the wedge the radial distance of the active cutting edge from the axis of rotation of the milling tool changes.

In this way, the same radial distance of the cutting edges of the individual cutting inserts from the axis of rotation of the milling tool can be set for all cutting inserts of a milling cutter or cutter segment. Thus, a high quality of the surface condition of the bearing pins after finish milling with an average roughness depth of the surface of less than or equal to 3.2 μm, preferably of less than or equal to 1.6 μm, is ensured. The average roughness R _{z is defined} in the sense of DIN 4768. Since the wedge for fine adjustment of the cutting plate on the milling cutter in a direction parallel to the flat surface of the insert seat and thus to the cutter axis direction, each cutting insert of the milling cutter can be configured as an indexable insert with four or more cutting edges without the wedge with one of the cutting edges in Intervention comes and this damaged. For this purpose, the cutting insert is supported in one Area of a side surface between the non-active upper and lower cutting edges on the stop surface of the wedge from

It is expedient if the stop surface of the wedge in a direction perpendicular to the flat surface of the insert seat and parallel to the Fraserachse a width of 0.5 mm to 5 mm, preferably from 1 mm to 3 mm and more preferably from 1, 5 mm having

In a particularly preferred embodiment of the invention, the cutting plate holder is provided for receiving trapezoidal cutting inserts. In a preferred embodiment, the stop surface of the wedge forms an angle with the axis of rotation of the cutter. This included angle is expediently between 1 ° and 15 °, preferably 12 °, and a side surface of the milling cutter preferably points from a perpendicular to the baseline of the trapezoid by twice the angle

It is advantageous if the side surface of the cutting insert in the installed state is not perpendicular to the axis of rotation, but with respect to the axis of rotation perpendicular to an angle between 1 ° and 3 °, preferably inclined by 2 ° in this way is between the side surface of the Cutting insert and the Werkstuckflache formed a clearance angle

In a particularly preferred embodiment, the fine adjustment allows an adjustment range of the cutting edge of the cutting plate of 0.05 mm The screw for mounting the wedge is chosen such that the cutter allows adjustment of the concentricity of the milling cutter of less than 0.005 mm

In a preferred embodiment of the invention, two circumferentially adjacent cutting board seats are arranged such that they overlap each other in the circumferential direction of the cutter considered in this way can be a large cutting width at high Qualltat the Werkstuckbearbeitung reach

With respect to the indexable insert, the present object is also achieved by providing an indexable insert for a milling cutter for finishing of journal with an upper and a lower surface and peripheral side surfaces connecting the upper and lower surfaces with the edges between the upper and lower surfaces. The bottom edges and the side surfaces form the cutting edges, the side surfaces forming clamping surfaces adjoining the cutting edges, wherein the chip surfaces of the upper and lower cutting edges are separated by a web which protrudes from the chip surfaces, wherein the web forms a lateral contact surface of the indexable insert.

Such designed indexable insert may be equipped with four or more cutting edges, since it is supported in the installed state with the web as a bearing surface against the abutment surface of the movable wedge of the milling cutter, so that the stop surface facing cutting edges of the indexable insert not with the insert seat or the wedge engage.

Preferred is an embodiment of the inventive insert, in which the upper and the lower surface have at least one corner with a large angle of 90 °. Corresponds to this angle minus 90 ° the angle of the stop surface of the wedge of the cutter relative to the axis of rotation of the cutter, it is possible to attach the cutting insert on the cutter so that one of its side surfaces is always perpendicular to the axis of rotation.

It is particularly expedient if the upper and the lower surface of the indexable insert are substantially trapezoidal, preferably isosceles trapezoidal. In this way, an indexable insert with four available cutting edges can be provided

The cutting edges are advantageously arranged along the base side or long side and the short side of the trapezoid parallel thereto. Accordingly, it is expedient for the milling cutter or cutter segment according to the invention to have two different types of cutting plate holders, a first, which is used to receive a turning cutting plate is provided so that a cutting edge of the base side of the trapezoid actively engages the workpiece and a second, which is provided for receiving a reversible cutting plate, so that a cutting edge of the short, parallel to the base side of the trapezoid active with the In this manner, the two long cutting edges of the indexable insert can be successively used in a plate holder of the first type, and the two short cutting edges successively in a plate holder of the second type

It is advantageous if the edges of the cutting insert running perpendicular to the base side and the short side of the trapezoid form secondary cutting edges Particularly preferred is an embodiment of the invention, in which the surface of the web lies outside the plane which is spanned by the cutting edges of one side of the indexable insert. It is expedient for the surface of the web to be opposite the plane in which the cutting edges of one side of the web Have indexable insert projecting between 0.01 mm and 0.5 mm, preferably by 0.05 mm

In order to be able to use the cutting insert according to the invention for finishing, which replaces the grinding step known from the prior art, it is expedient for the cutting edges of the indexable insert to have a PVD (plasma vapor deposition) Al ₂ O ₃ coating as the cutting material

Further advantages, features and possible uses of the present invention will become apparent from the following description of a preferred embodiment and the accompanying figures

FIG. 1 shows a three-dimensional view of a cassette with cutting inserts of the milling cutter according to the invention

Figure 2 shows a view of the cartridge of Figure 1 from above

FIG. 3 shows a side view of the cassette from FIG. 1

FIG. 4 shows a top view of an indexable insert according to the invention

FIGS. 5a and 5b show lateral views of the indexable insert according to the invention

FIG. 6 shows a lateral sectional view of the indexable insert of FIGS. 4 and 5a, 5b

FIG. 1 shows a three-dimensional oblique view from above of a cassette with four cutting inserts for a crankshaft fraser. A fraser axis 30 extends at a radial distance R to a peripheral surface which is jointly spanned by all active cutting edges 5, 6. The cassette can be attached to the tool holder The receptacles 2 for indexable inserts 3 are clearly visible in the segment of the crankshaft cutter shown in FIG. 1. Each receptacle 2 consists of a plate seat 4, which is formed by a flat bearing surface. The course of the flat surfaces 4 is that the surface 4 is opposite the tangent of the crankshaft sers at the location of the active cutting edges 5, 6 of the cutting inserts 3 are arranged at an angle but parallel to the axis 30. In addition, each insert holder has a wedge 9 which is secured by means of an adjusting screw 10 on the segment 1. The adjusting screw 10 is a fine thread single screw in the illustrated embodiment.

Each cutting insert 3 is screwed to the segment 1 by means of a Torx screw 11. From the side view in Figure 3, the arrangement of the cutting inserts 3 on the segment or the cassette 1 of the milling cutter can be seen particularly clearly. In particular, the inclination of the flat surfaces of the insert seats 4 with respect to the tangent of the milling cutter is shown at the point of the active cutting edges 5, 6.

The geometric shape of the indexable inserts 3 used is shown in detail in Figures 4, 5a and b and 6. In plan view of the indexable insert in Figure 4 can be clearly seen that the inserts have an isosceles trapezoidal basic shape. Each of the cutting inserts has a total of four cutting edges, two long 5 and two short 6 on. The side surfaces adjoining the cutting edges 5, 6 each form a rake face 7 for each of the cutting edges. Each of the clamping surfaces 7 is provided as a concave depression in the side surfaces and is used when inserting the insert as Spanablauffläche and thus for chipbreaking. Between two adjacent clamping surfaces 7, for example, the long upper and lower cutting edges 5, a web 8 is provided, which forms a raised contact surface with respect to the concave depressions of the clamping surfaces 7. The surface 8 of the web is in the illustrated embodiment in a slightly greater distance from the lowest point of the clamping surfaces 7 than the plane of the cutting edges 5 and 6 respectively.

In the illustrated embodiment, the trapezoid angle of the cutting insert is 15 °, the length of the base side is 14 mm, and the width (defined as the distance between the base side and the short side) is 8.5 mm. The thickness of the cutting insert is 5 mm. The cutter has a diameter of 700 mm and is designed to hold 48 cutting inserts.

The mode of operation of the interaction between the plate holders 2 according to the invention and the indexable inserts 3 can be seen particularly clearly from FIGS. 2 and 3. FIG. 2 shows a view from above onto the segment 1 of the crankshaft cutter according to the invention shown in FIG. 1. The radial spacing of the active cutting edges 5, 6 of the indexable inserts 3 can be adjusted with the aid of the inclined plate seats 4 and the adjustable wedges 9. In this case, the Torxschraube 11 has sufficient lateral clearance The wedges 9 have a stop surface 12 inclined with respect to their direction of movement. By including an angle between the direction of movement of the wedges 9 and the stop surface 12, the position of the stop surface 12 becomes circumferential changed by translation of the wedge 9

The web 8 of each cutting insert 3 is supported against the abutment surface 12 of the corresponding wedge 9. If the position of the abutment surface 12 changes in circumferential direction, the position of the cutting insert 3 accommodated in the respective plate holder 2 also changes in circumferential direction since the insert seat or whose flat surface 4 is inclined relative to the tangent of the cutter at the location of the cutting edge 5, 6, this displacement of the insert 3 in Umfangsnchtung leads to a change in the radial distance of the cutting edge 5, 6 from the axis of rotation of the crankshaft

The inclination of the flat surface 4 amounts to 12 ° in the illustrated embodiment with respect to the tangent at the point of the active cutting edge

Since the upper and the lower surface of the cutting insert are formed mirror-inverted and parallel to each other, the inclination of the seat surface 4 with respect to a tangent at the same time defines the required clearance angle

In the installed state, only one cutting edge 5, 6 of each cutting insert 3 is active, ie it engages with the workpiece. If the service life of the cutting edge, for example the short cutting edge 6 of the left cutting insert of FIG. 2, is reached, then the indexable insert can be rotated Is also the life of the second short cutting edge 6 is reached, the trapezoidal inserts 3 of the crankshaft cutter between adjacent cutting plate holders 2 of the cutter are replaced, for example, the two left indexable inserts 3 off Thus, the two long cutting edges 5 of the left cutting insert 3 successively become the active cutting edge on the right cutting edge holder 2, and the short cutting edges 6 of the right cutting insert 3 shown by both become active cutting edges on the l inken of the two illustrated cutting plate holders. 2

The insert seat has a recess in the flat surface 4 in the region of the cutting edges, so that the cutting edges do not engage with the insert seat DIΘ use of four cutting edges on the indexable inserts 3 successively is possible in that the indexable inserts by means of the webs 8 at the stop surfaces

Thus, the cutting edges 5, 6, even when installed, do not come into contact with the insert holder 2, ie neither with the wedge 9 nor with the flat surface 4, so that the cutting edges experience only a load and wear when they Therefore, active cutting edges engage the workpiece. The seat surface 4 therefore expediently has an undercut (not shown) in the area of the stop surface 12 of the wedge 9

In the illustrated embodiment, the geometric arrangement of the wedge 9 allows an adjustment of the cutting edge of 0.05 mm, whereby an adjustment of the concentricity of the milling cutter of less than 0.005 mm is made possible

In the illustrated preferred embodiment of the invention, the cutting inserts 3 are trapezoidal, so that when a displacement of the cutting inserts 3 in the circumferential direction, a side surface always parallel to the side surfaces 13 of the cutter (or the cassette 1) remains this is the angle between which the stop surface 12th of the wedge 9 and the side surface

13 of the cutter, equal to the large angle of the trapezoid described by the upper and lower surfaces of the cutting inserts 3

In alternative embodiments, however, the inclination of the stop surfaces 12 of the wedges 9 may be configured such that the side surfaces of the cutting inserts 3 with respect to the vertical axis to the rotation side surfaces 13 of the cutter include a clearance angle of preferably 2 °

In the illustrated embodiment, the full cutting width of the crankshaft cutter is achieved by the interaction of two circumferentially adjacent cutting inserts 3 clearly seen in Figure 2, for example, only by the interaction of a short cutting edge 6 and a long cutting edge 5 of two cutting inserts 3 a cutting width A short 6 and a long 5 cutting edge of adjacent inserts 3 overlap one another in the circumferential direction. The active cutting edges 5, 6 of the cutting inserts 3 are shown in FIG Embodiment inclined relative to the axis of rotation of the milling cutter, so that the individual sections of each cutting edge 5, 6 nachein- engages the workpiece In this way, the force acting on each cutting insert at a given time is reduced

With the crankshaft cutter according to the invention, even hardened waves can be machined

Since the cutting edges are also slightly inclined relative to the axis 30 due to the inclination of the wedge surfaces 12, the cutting edges may be slightly convex so that they lie exactly in a (common) Zyhndermantelflache

For purposes of the original disclosure, it is to be understood that all such features as will become apparent to those skilled in the art from the present description, drawings, and claims, even though they have been specifically described in connection with certain further features, both individually and separately any combinations with other of the features or feature groups disclosed herein are combinable, as far as this was not explicitly excluded or technical conditions make such combinations impossible or pointless on the comprehensive explicit representation of all conceivable Merkmaiskombinationen is omitted here for brevity and legibility of the description

LIST OF REFERENCE NUMBERS

1 cutter, cutter segment, cassette

2 cutting board holder, holder

3 indexable insert, cutting insert

4 insert seat, flat surface

5, 6 cutting edge

7 chip surface

8 footbridge

9 wedge

10 adjustment screw

11 Torx screw

12 stop surface

13 side surface

30 cutter axis

Claims

claims

1 method for machining journal, with a first step for roughing and with a second step for finishing, wherein in the first step of the 5 pin is scrubbed with a crankshaft and in the second step of the

Pin is finished with a crankshaft cutter, characterized in that the method for finishing exclusively has the second step, which completes the Maßverandemde machining of the bearing pin

A method according to claim 1, characterized in that it has exactly the two steps of roughing and barbecuing

3. The method according to claim 1 or 2, characterized in that the outer step of the pin is defined in the first step substantially

15

4. The method according to any one of claims 1 to 3, characterized in that in the second step of Schhotfrasens with a cutting speed of more than 250 m / mιn, preferably more than 270 m / min and more preferably worked by more than 300 m / mm becomes

20

5. The method according to any one of claims 1 to 4, characterized in that in the second step of the Schhntfrasens with a feed rate of 1000 mm / min to 2000 mm / min is used

1.5 6 Method according to one of claims 1 to 5, characterized in that the sizing the machining of the bearing pin with an average roughness of the surface of the bearing pin of less than or equal 3.2 microns, preferably less than or equal to 1, 6 microns, concludes

30 7 Process according to one of claims 1 to 6, characterized in that the bearing pins, preferably a crankshaft or a camshaft, are processed

8. The method according to claim 7, characterized in that the pins of the main bearings are processed. 5 9 The method according to claim 7, characterized in that the pins of the stroke bearings are processed

10. The method according to any one of claims 1 to 7, characterized in that a milling cutter according to one of claims 12 to 19 is used

11. The method according to any one of claims 1 to 8, characterized in that an indexable insert according to one of claims 21 to 28 is used

12 cutter or Frasersegment (1) which are rotatable about a Fraserachse (30), for finishing machining of bearing journals with at least one Schneiattehalter (2), wherein the cutting insert holder (2) forming a part of the insert seat first flat surface (4) and a displaceable wedge (9) for adjusting the radial distance of the cutting edge (5, 6) of an insert (3) of the Fraserachse, wherein the wedge (9) has a substantially to the flat surface (4) perpendicular stop surface (12) for a Side surface of the cutting plate, characterized in that the wedge (9) in a direction substantially parallel to the flat surface (4) is movable

13 cutter according to claim 12, characterized in that the cutting plate holder (2) for receiving trapezoidal, preferably isosceles trapezoidal Schneideinsatze

(3) is designed

A milling cutter according to claim 13, characterized in that it comprises a butt seat of a first type adapted to receive the cutting insert so that a cutting edge of the long base side of the trapezoid engages the workpiece and a butt seat of a second type which is adapted to receive the cutting insert so that a cutting edge of the short side parallel to the base side of the trapezoid engages the workpiece

15 cutter according to one of claims 12 to 14, characterized in that the stop surface (12) of the wedge (9) is arranged at an angle to the axis of rotation of the milling cutter

16 cutter according to one of claims 12 to 15, characterized in that the stop surface (12) of the wedge (9) at an angle of 5 ° -10 °, preferably from 7 ° to

Movement direction of the wedge (9) is arranged

17. Milling cutter according to one of claims 12 to 16, characterized in that the wedge (9), the wedge angle and the inclination of the seat surface (4) are dimensioned so that they have an adjustment of the cutting edge of the insert in the radial direction with respect to the Allow cutter axis (30) of 0.05 mm.

18. Milling cutter according to one of claims 12 to 17, characterized in that the wedge (9) allows adjustment of the concentricity of less than 0.005 mm.

19. Milling cutter according to one of claims 12 to 18, characterized in that each two adjacent cutting plate holder (2) are arranged such that the therein recordable cutting plates (3) overlap one another viewed in the direction of rotation of the milling cutter.

20. Milling cutter according to one of claims 12 to 19, characterized in that the abutment surface (12) of the wedge (9) in a direction perpendicular to the flat surface (4) of the

Platter seat has a width of 0.5 mm to 5 mm, preferably from 1 mm to 3 mm and more preferably of 1.5 mm.

21. indexable insert (3) for a milling cutter for machining trunnions having upper and lower surfaces and peripheral side surfaces interconnecting the upper and lower surfaces, the edges between the upper and lower surfaces and the side surfaces containing the cutting edges (5 , 6), wherein the side surfaces on the cutting edges (5, 6) subsequent clamping surfaces (7) form, characterized in that the rake surfaces (7) of the upper and lower cutting edges (5, 6) by a web (8 ) are separated, which protrudes relative to the rake surfaces (7), wherein the web (8) forms the lateral contact surface of the cutting insert.

22. indexable insert (3) according to claim 21, characterized in that the upper and the lower surface have at least one corner with an angle greater than 90 °.

23. indexable insert (3) according to claim 21 or 22, characterized in that the upper and the lower surface are substantially trapezoidal and preferably isosceles trapezoidal.

24. indexable insert (3) according to any one of claims 21 to 23, characterized in that it comprises four cutting edges which extend along parallel sides of the cutting insert.

25. indexable insert (3) according to any one of claims 21 to 24, characterized in that the surface of the web (8) lies outside the plane which is spanned by the cutting edges of one side of the cutting insert.

26. indexable insert (3) according to claim 25, characterized in that the surface of the web (8) relative to the plane by 0.01 mm to 0.5 mm, preferably to

0.05 mm protrudes.

27. Indexable insert (3) according to any one of claims 21 to 26, characterized in that the cutting edges (5, 6) are provided with a PVD-Al ₂ O ₃ coating as a cutting material.

28 indexable insert (3) according to any one of claims 21 to 27, characterized in that they have a concave chip surface (7) for chip-forming.

29. Use of a milling cutter according to one of claims 12 to 20 for finishing machining of journal of a crankshaft.

30. Use according to claim 29, characterized in that a turning cutting plate (3) according to one of claims 21 to 28 is used.