Device for machining hollow cylindrical workpieces having any desired contour in diameter

Abstract

The invention relates to a device for machining by turning hollow cylindrical workpieces (17), wherein the device has an outer tool (1.1, 1.2) and an inner tool (10), wherein a free installation space for receiving the workpiece (17) to be machined is formed between the outer contour of the inner tool (10) and the inner contour of the outer tool (1.1, 1.2). The invention addresses the problem of providing a technical solution by means of which workpieces can also be machined which have undercut diameter regions in the outer contour in the feed direction or enabling outer diameters to be machined which are both larger and smaller than the penetration diameter at the start of the cutting operation. This problem is solved in that at least one of the inwardly directed cutting edges (13.1, 13.2) arranged on the outer tool (1.1, 1.2) is designed to be adjustable radially with respect to the axis of rotation (12) of the workpiece (17).

Description

[0001] Device for machining hollow cylindrical shapes

[0002] Workpieces with any contour and diameter

[0003] The invention relates to a device for machining hollow cylindrical workpieces by turning, wherein the device comprises an outer tool with at least one inwardly directed cutting edge and a bore for supplying process aids, and an inner tool with at least one outwardly directed cutting edge and a bore for supplying process aids, and wherein the outer tool and the inner tool are arranged coaxially to each other with respect to the axis of rotation of a hollow cylindrical workpiece to be machined, wherein the outer tool is designed as a stationary tool or a tool that can be displaced along the axis of rotation and has a hollow cylindrical base body.on which several inwardly directed cutting edges are arranged distributed around the circumference and which has several openings in its cylindrical surface, and wherein the inner tool is designed as a tool rotating about the axis of rotation, on which several outwardly directed cutting edges are arranged distributed around the circumference, and which is arranged within the hollow cylindrical base body of the outer tool in such a way that a free installation space for receiving the workpiece to be machined is formed between the outer contour of the inner tool and the inner contour of the outer tool.

[0004] In the machining of thin-walled hollow cylindrical workpieces with a machining allowance on all sides, the outer and inner contours are currently machined sequentially using tools for the inner diameter, outer diameter, and end faces. To meet dimensional accuracy requirements and ensure accessibility for the machining process, it is necessary to reclamp the workpiece between successive machining steps. Furthermore, mechanical vibration due to the workpiece's natural frequencies in the clamping position or during the machining process itself is problematic when machining such thin-walled hollow cylindrical workpieces. This negatively impacts the achievable surface finish.

[0005] To avoid reclamping between successive machining steps in such turning operations, various technical solutions have already been proposed.

[0006] From DE 1 978461 A, a device for the simultaneous external and internal turning of long, rotationally symmetrical hollow bodies is known. Such hollow bodies are required, for example, in apparatus engineering, the textile industry, or plastics technology. The simultaneous machining of the external and internal surfaces is carried out using two separate tools, designed as an external turning support and a boring bar.

[0007] The subject matter of DE 3942 543 C1 is a device for the simultaneous machining of the outer and inner surfaces of drying cylinders for paper machines. Here, two separate tools are used: an external turning support and an internal turning support.

[0008] WO 2018 / 170 611 A1 describes a tool holder for a machine tool that has two mounts for separate tools for machining a rotating workpiece. This allows various turning operations to be performed on a single workpiece in a single setup using a combined tool. However, simultaneous internal and external turning is not possible.

[0009] To reduce machining time during internal machining, tools with multiple cutting edges around the circumference can be used. In this case, the clamping device must transmit a multiple of the torque to the workpiece. However, this makes the workpiece unstable, resulting in an increased tendency to vibrate. To prevent such instabilities, damping elements are known that are applied to the workpiece via the clamping device or during setup. However, such clamping devices are complex and leave clearly visible clamping marks on the workpiece. Furthermore, these measures for vibration damping and workpiece clamping only achieve a reduction in machining time for internal machining.

[0010] DE 10 2021 003700 A1 describes a device and a method for the simultaneous machining of external and internal hollow cylindrical workpieces, in which the external tool and the internal tool are arranged coaxially to each other with respect to the axis of a workpiece to be machined, wherein the external tool is designed as a stationary tool or a tool that can be displaced along a tool axis and has a hollow cylindrical base body on which several inwardly directed cutting edges are arranged distributed around the circumference and which has several openings in its cylindrical surface, and wherein the internal tool is designed as a tool that rotates about the tool axis on which several outwardly directed cutting edges are arranged distributed around the circumference and which is arranged within the hollow cylindrical base body by the external tool in such a way thatthat a free space is formed between the outer contour of the inner tool and the inner contour of the outer tool to accommodate the workpiece to be machined. The inner and outer contours of the rotating workpiece are machined simultaneously by the cutting edges arranged on the outer and inner tools. The inner tool and the workpiece rotate in the same direction, and the rotational speed of the inner tool is higher than the rotational speed of the workpiece by the necessary cutting speed.

[0011] This solution has proven successful and is to be further improved by a development in such a way that hollow cylindrical workpieces which have undercut diameter areas in the outer contour in the feed direction during machining can also be machined.

[0012] The object of the invention is therefore to provide a technical solution that enables simultaneous external and internal machining of hollow cylindrical workpieces, ensuring high vibration damping and workpiece clamping during machining, thus overcoming the known disadvantages of vibration tendency and clamping marks. Furthermore, the solution should also allow the machining of workpieces with undercut diameter areas in the feed direction along the outer contour, or the machining of outer diameters that are both larger and smaller than the initial plunge diameter. Additionally, it should enable the machining of different outer diameters with one and the same external tool.

[0013] This task is solved by means of a device design in which at least one of the inwardly directed cutting edges arranged on the outer tool is adjustable radially to the axis of rotation of the workpiece. The radial adjustment of the cutting edges takes place in the macroscopic range, i.e., on the order of a few millimeters.

[0014] Thus, the object of the invention is fulfilled, namely to create a technical solution with which simultaneous external and internal machining of hollow cylindrical workpieces is possible, and with which, in addition to the prior art, external diameters can also be machined that are both larger and smaller than the plunge diameter at the beginning of the cutting process.

[0015] In a particularly advantageous embodiment, at least one of the inwardly directed cutting edges arranged on the outer tool is adjustable during machining. This means that while the machining tool is engaged with the workpiece, the cutting edge moves radially to the axis of rotation of the workpiece or the machining spindle, thus changing the outer diameter of the workpiece accordingly. In this way, any desired shoulders and radii can be machined.

[0016] For various reasons, it can be advantageous to equip the external tool with two or more cutting edges, for example, to increase machining speed and thus productivity, or to minimize vibrations generated during the machining process. The cutting edges can be arranged with a symmetrical or asymmetrical pitch around the circumference. The radial adjustment of these cutting edges is synchronized with each other.

[0017] Another particularly advantageous embodiment of the device according to the invention provides that two or more external tools are arranged coaxially to an axis of rotation and parallel to each other perpendicular to this axis. In a further embodiment, the two or more external tools can be connected to each other.

[0018] For the efficient machining of highly complex workpiece geometries, it is advantageous to combine several external tools into a single machining fixture. The individual external tools are aligned coaxially and, depending on requirements, operated separately or permanently mounted together. Each external tool can be controlled independently of the other(s), enabling the simultaneous machining of different geometries. Furthermore, this design allows for different machining operations, such as roughing and finish turning, to be performed in a single setup without tool changes. Another advantage of this configuration is that different diameter ranges can be accommodated by the varying adjustment ranges of the individual external tools.

[0019] An advantageous embodiment of the device according to the invention provides that an adjustment kinematic mechanism, integrated into or attached to the hollow cylindrical base body of the outer tool, is configured for radial adjustment of at least one inwardly directed cutting edge relative to the axis of rotation of the workpiece. This adjustment kinematic mechanism serves to adjust the cutting edge of the outer tool radially to the axis of rotation of the hollow cylindrical workpiece and the inner tool during machining, so that different outer diameters can be produced.

[0020] When a workpiece, particularly a cylindrical hollow body, has multiple diameter steps, the cutting edges are adjusted via the drive mechanism's adjustment kinematics. This allows different diameters on the workpiece to be machined in steps or continuous transitions by adjusting the tool position superimposed on the workpiece's axial feed movement. Undercuts and grooves can also be machined by adjusting the cutting edges during the cut. The machinable outside diameters can be larger or smaller (undercuts) than the plunge diameter. Furthermore, it is possible to perform combinations of grooving and turning complex external contours on cylindrical hollow bodies.

[0021] A further advantageous embodiment provides that the adjustment kinematics of the at least one inwardly directed cutting edge comprises at least one numerically controllable adjustment drive, wherein the numerically controllable adjustment drive is designed to be interpolable with other axes. This embodiment makes it possible to continuously adjust the cutting edges during machining. The cutting edge adjustment can thus be integrated, for example, as a superimposed movement into the entire CNC machining program. CNC technology (Computerized Numerical Control) allows automated machining with several simultaneously controlled axes. In the embodiment of the device according to the invention, the at least one numerically controllable adjustment drive represents one of these simultaneously controllable axes.The adjustment drive can be designed as an electric, hydraulic or pneumatic axis, or as a combination of several axes.

[0022] Examples of numerically controllable adjustment drives suitable for the design of a device according to the invention include, among others, rack and pinion systems, worm and rack systems or spindle and nut systems.

[0023] An advantageous embodiment of the device according to the invention provides that the adjustment kinematics integrated into the hollow cylindrical base body of the outer tool comprise at least one drive, one drive pinion, one synchronizing ring, and one actuating element. The drive sets the drive pinion into a rotary motion, which in turn moves the actuating element, for example a toothed ring segment or a gear, and, via this, the synchronizing ring, in such a way that a cam guide moves a cutting tool holder, and thus an inwardly directed and backlash-free clamped cutting edge attached to it, linearly radially to the axis of rotation of the workpiece. In this embodiment, the basic principle of the adjustment kinematics is based on the conversion of the rotary motion of a drive into a linear motion of the cutting tool holder and thus of the cutting tool.Alternatively, other drive variants are also conceivable, for example the use of linear direct drives for the linear movement of the cutting tool holders, or an arrangement in which two or more synchronous rings are adjusted to each other without backlash via mechanical or fluidic coupling elements.

[0024] An advantageous embodiment provides that the inwardly directed cutting edges each have at least one cutting tool holder. Typically, replaceable cutting inserts or adjustable cutting insert carriers are used as cutting tools. Preferably, openings or bores for supplying process aids, such as cooling lubricants, are arranged directly adjacent to the cutting inserts.

[0025] Another embodiment provides that the cutting tool holder is designed as an interchangeable indexable insert carrier that is adjustable in the radial cutting direction. Typically, indexable inserts with multiple cutting edges are used as cutting inserts, which are rotated or flipped when worn. To achieve the required accuracy, the indexable insert carrier must be adjustable in the radial cutting direction.

[0026] The device according to the invention for machining hollow cylindrical workpieces by turning is explained below with reference to the drawings. Fig. 1 shows the basic structure of the device.

[0027] Fig. 2 shows the basic setup of the device with a workpiece,

[0028] Fig. 3 shows an embodiment of the adjustment kinematics,

[0029] Fig. 4 shows a sectional view of the device with the workpiece in forward machining.

[0030] Fig. 5 shows a sectional view of the device with the workpiece in forward machining,

[0031] Fig. 6 shows a sectional view of the device with the workpiece in reverse machining and

[0032] Fig. 7 shows a sectional view of the device with the workpiece in reverse machining.

[0033] Figures 1 and 2 show the basic structure of an embodiment of the device according to the invention for machining hollow cylindrical workpieces by turning, wherein it is a design with two external tools 1.1, 1.2 fixedly connected to each other. Figure 1 shows the device without a workpiece 17; Figure 2 shows the device with a workpiece 17. The device has a front external tool 1.1 and a rear external tool 1.2 for external machining, as well as an internal tool 10 for internal machining of the workpiece 17. Typically, the spindles of machine tools are equipped with mechanically or pneumatically clampable workpiece and / or tool holders, so that the operator can manually change the workpiece and / or the machining tool.Automated machine tools have differently designed tool magazines in which various machining tools are stored and can be automatically inserted and removed from the tool holders depending on the machining step. The external tool 1.1. 1.2 of the device according to the invention also has a corresponding interface to a tool holder 2 of the associated machining unit, here a machine spindle 3 of a machine tool (not shown).

[0034] The external tools 1.1, 1.2, which are rigidly connected to each other, are arranged coaxially to a rotational axis 12 and perpendicular to it, parallel to each other. Depending on the length of the workpiece to be machined, the hollow cylinder base of the external tool 1.1, 1.2, together with the tool holder 2, which encloses the workpiece, extends to the machine spindle 3. The hollow cylindrical base of the tool holder 2 has openings to allow chips and process fluids to drain away. A housing cover 16 closes the front of the external tool 1.1, 1.2.

[0035] The external tools 1.1, 1.2 and the internal tool 10 are also arranged coaxially with respect to the axis of rotation 12 of the hollow cylindrical workpiece 17 to be machined. The axis of rotation 12 is the common axis of rotation 12 of the external tools 1.1, 1.2, the internal tool 11 and the workpiece 17.

[0036] The external tools 1.1, 1.2 can be designed as stationary tools, as shown in Fig. 1, or as tools arranged perpendicular to the axis of rotation 12 and parallel to it in a feed direction 20 along the axis of rotation 12, as shown in Fig. 2. The internal tool 10 is arranged within the hollow cylindrical base body of the external tool 1.1, 1.2 such that a free space for receiving the workpiece 17 is formed between the outer contour of the internal tool 10 and the inner contour of the external tool 1.1, 1.2.

[0037] On a hollow cylindrical base body of the outer tool 1.1, 1.2, which has several openings (not shown) in its outer surface, several inwardly directed cutting tool holders 6.1, 6.2 with cutting tools 13.1, 13.2 are arranged symmetrically or asymmetrically around the circumference. In the illustrated embodiment, each of the two outer tools 1.1, 1.2 has four cutting tool holders 6.1, 6.2, each with four cutting tools 13.1, 13.2. On these cutting tool holders 6.1, 6.2, bores for supplying process aids 14 (not shown) are arranged directly adjacent to the cutting tools 13.1, 13.2.

[0038] Figures 1 and 2 show an embodiment of the device according to the invention, in which the inwardly directed cutting tools 13.1, 13.2 arranged on the outer tool 1.1, 1.2 are adjustable in working engagement by a radial displacement of one or more cutting tool holders 6.1, 6.2 in an adjustment direction 9. The cutting tool adjustment is effected by moving the cutting tool holders 6.1, 6.2 by means of an adjustment kinematic mechanism integrated into or attached to the outer tool 1.1, 1.2. The adjustment kinematics of the embodiment shown in Fig. 1 and Fig. 2 respectively has a numerically controllable adjustment drive 4.1, 4.2 which, via the movement (rotation) of a drive pinion 5.1, 5.2, moves an actuating element 7.1, 7.2, here designed as a toothed ring segment, such that, via suitable transmission elements (not shown here), the cutting tool holder 6.1, 6.2 and thus also the cutting tool 13.1, 13.2 radially adjusted.

[0039] In the illustrated embodiment, four cutting tool holders 6.1, 6.2 are arranged in an axial plane on the end face of the cylindrical contour section of the outer tool 1.1, 1.2, both on the front outer tool 1.1 and on the rear outer tool 1.2. These four cutting tool holders 6.1, 6.2 of an outer tool 1.1, 1.2 are moved synchronously via the associated adjustment kinematics, so that several cutting tools 13.1, 13.2 are simultaneously engaged on a target diameter on the workpiece 17.

[0040] The inner tool 10 is designed as a tool rotating about the axis of rotation 12 in the direction of rotation 15, on which several, in the embodiment shown in Figs. 1 and 2, four outwardly directed cutting edges 11 with a circumferentially symmetrical division are arranged in recesses on the circumferential surface, these cutting edges 11 acting in the opposite direction to the cutting direction of the outer tool 1.1, 1.2. In the recesses on the circumferential surface of the inner tool 10, bores for the supply of process aids 14 are arranged directly adjacent to the cutting edges 11.

[0041] The cutting edges 13.1, 13.2 of the outer tool 1.1, 1.2 are arranged in the opposite direction to the cutting edges 11 of the inner tool 10. Furthermore, both the cutting edges 13.1, 13.2 of the outer tool 1.1, 1.2 and the cutting edges 11 of the inner tool 10 are preferably designed as cutting inserts and are each individually replaceable. This design allows, for example, the use of indexable inserts.

[0042] The cutting edges 11 of the internal tool 10 can also have radially adjustable cutting tool holders (not shown) as an alternative to the fixed arrangement shown in Fig. 1 and Fig. 2.

[0043] Figure 2 also shows that the workpiece 17 is driven in a direction of rotation 19 that corresponds to the direction of rotation 15 of the internal tool 10. The rotational speed of the internal tool 10 is higher than the rotational speed of the workpiece 17. The difference in rotational speed is large enough to achieve the required cutting speed for the internal tool 10. The machining feed is carried out in a feed direction 18 through the workpiece 17, or in a feed direction 20 through the internal tool 10 and external tools 1.1, 1.2 along the axis of rotation 12, or by the superposition of several feed movements.

[0044] Simultaneous machining by internal tool 10 and external tool 1.1, 1.2 results in a reduction of the clamping force required for machining due to the at least partially canceling reaction forces resulting from the opposing cutting forces on the workpiece 17. This avoids visible clamping marks on the component surface, and workpiece clamping can also be performed on smaller diameters. A further advantage is that the resulting torque at the workpiece 17 clamping point is lower than when machining the inner or outer diameter separately, because the cutting forces are opposing.

[0045] Fig. 3 shows an embodiment of the adjustment kinematics for the synchronous radial adjustment movement of the outer tools 1.1, 1.2. The following description refers only to the front outer tool 1.1. The design and function of the rear outer tool 1.2 are identical.

[0046] The adjustment kinematics feature a numerically controlled adjustment drive 4.1, which, via the movement (rotation) of the toothed drive pinion 5.1, moves an actuating element 7.1, implemented here as a toothed ring segment, which is connected to a synchronizing ring 22, such that the cutting tool holder 6.1, and thus also the cutting edge 13.1, is radially adjusted. The cutting tool holder 6.1 is linearly guided in the base body of the external tool 1.1 to enable movement towards the axis of rotation 12 in the positioning direction 9. The synchronizing ring 22 has a correspondingly shaped cam guide 23 into which a drive pin 21, fixedly connected to the cutting tool holder 6.1, engages. The radial bearing of the synchronizing ring 22 is provided at its inner diameter (not shown) by the base body of the external tool 1.1. The position detection of the cutting edges 13.1 can be done either via the motor measuring system of the adjustment drive 4.1 or via a linear measuring system (not shown) integrated into the base body of the external tool 1.1 for position detection of the cutting tool holders 6.1.

[0047] The device according to the invention enables two different feed movements or machining directions, namely forward machining and reverse machining. The figures described below show, in sectional view, an embodiment of the device in forward machining (Figs. 4 and 5) and reverse machining (Figs. 6 and 7), respectively.

[0048] Figures 4 and 5 show an embodiment of the device according to the invention for machining hollow cylindrical workpieces 17 by turning, for forward machining, wherein the feed direction 18 of the workpiece 17 into the machining device, which has an outer tool 1.1 and an inner tool 10, is shown as a feed movement in the direction Z+. The workpiece 17 has an undercut 17.1 on its outer contour.

[0049] To machine a workpiece 17 with such an undercut 17.1, it is moved into the machining device in the feed direction 18 in Z+, while the cutting tool holders 6.1 are moved radially outwards in a positioning direction 9 with respect to the axis of rotation 12 until the maximum diameter range of the workpiece 17 can pass through, see Fig. 4. After the undercut geometry of the workpiece 17 has reached the contour of the cutting tool holders 6.1, the cutting tool holders 6.1 with the cutting edges 13.1 are moved radially inwards in the positioning direction 9 until the undercut outer contour of the workpiece 17 can be machined, see Fig. 5.

[0050] The radial movement of the cutting tool holders 6.1, and thus of the cutting edges 13.1, is effected by the adjusting drive 4.1 and the adjusting kinematics of the outer tool 1.1 via the drive pins 21 engaging in the synchronizing ring 22 (not shown here), synchronously for all cutting edges 13.1, as also shown in Fig. 3. The cutting edges 13.1 can also be adjusted to further required diameters along the workpiece axis 12 during the feed of the workpiece 17. After the required machining length of the workpiece 17 has been reached, the cutting edges 13.1 are cleared by moving the cutting tool holders 6.1, so that the workpiece 17 can be moved out of the machining device 1.1, 10 in the Z-direction without collision.

[0051] Figures 6 and 7 show an embodiment of the device according to the invention for machining hollow cylindrical workpieces 17 by turning in reverse, wherein the feed movement in feed direction 18 takes place in Z+ for internal machining and in Z- for external machining. For machining the inner contour of the workpiece 17 with the internal tool 10, the workpiece 17 is moved in feed direction 18 in Z-. The cutting edges 13.2 of the external tool 1.2 are not engaged; they are retracted far enough so that the workpiece 17 can move towards the internal tool 10 in the Z+ direction without collision, see Figure 6. During the subsequent retraction movement 18 of the workpiece 17 from the internal tool 10, the cutting tool holders 6.2 with the cutting edges 13.2 are positioned in working engagement with the outer contour, see Figure 7.

[0052] This radial adjustment of the cutting edges 13.2 is carried out synchronously for all cutting edges 13.2 via the adjusting drive 4.2 and the adjusting kinematics of the outer tool 1.2 via the drive pins 21 and the synchronizing ring (not shown).

[0053] Reference numeral list: front external tool, rear external tool, tool holder, machine spindle, adjusting drive front cutting edges, adjusting drive rear cutting edges, drive pinion front, adjusting kinematics, drive pinion rear, adjusting kinematics, front cutting tool holder, rear cutting tool holder, actuating element front, adjusting element rear, adjusting kinematics, direction of actuating element front, adjusting direction, actuating element rear, adjusting kinematics, direction of actuating element rear, cutting tool holder, internal tool, cutting edge, internal tool, axis of rotation, front cutting tool; front cutting edge, rear cutting tool; rear cutting edge, bore for supplying process aids, direction of rotation, internal tool, housing cover, workpiece, undercut, feed direction, workpiece, direction of rotation, workpiece, feed direction, external tool, drive pin, adjusting kinematics, synchronizer ring, cam guide

Claims

Patent claims 1. Device for machining hollow cylindrical workpieces (17) by turning, wherein the device comprises an outer tool (1.1, 1.2) with at least one inwardly directed cutting edge (13.1, 13.2) and a bore for supplying process aids (14) and an inner tool (10) with at least one outwardly directed cutting edge (11) and a bore for supplying process aids (14), and wherein the outer tool (1.1, 1.2) and the inner tool (10) are arranged coaxially to each other with respect to the axis of rotation (12) of a hollow cylindrical workpiece (17) to be machined, wherein the outer tool (1.1, 1.2) is designed as a stationary tool or a tool displaceable along the axis of rotation (12) and has a hollow cylindrical base body on which several inwardly directed cutting edges (13.1, 13.2) are distributed around the circumference.2) are arranged and which has several openings in its cylindrical surface and wherein the inner tool (10) is designed as a tool rotating about the axis of rotation (12), on which several outwardly directed cutting edges (11) are arranged distributed around the circumference and which is arranged within the hollow cylindrical base body of the outer tool (1.1 , 1.2) such that a free installation space for receiving the workpiece (17) to be machined is formed between the outer contour of the inner tool (10) and the inner contour of the outer tool (1.1 , 1.2), characterized in that at least one of the inwardly directed cutting edges (13.1 , 13.2) arranged on the outer tool (1.1 , 1.2) is designed to be adjustable radially to the axis of rotation (12) of the workpiece (17).

2. Device according to claim 1, characterized in that at least one of the inwardly directed cutting edges (13.1, 13.2) arranged on the outer tool (1.1, 1.2) is adjustable in the working engagement.

3. Device according to one of the preceding claims, characterized in that two or more external tools (1.1 , 1.2) are arranged coaxially to an axis of rotation (12) and perpendicular to it and parallel to each other.

4. Device according to claim 3, characterized in that the two or more external tools (1.1 , 1.2) are configured to be connected to each other.

5. Device according to one of the preceding claims, characterized in that an adjustment kinematics integrated into the hollow cylindrical base body of the external tool (1.1 , 1.2) or attached to the hollow cylindrical base body of the external tool (1.1 , 1.2) is designed for the radial adjustment of the at least one inwardly directed cutting edge (13.1 , 13.2) to the axis of rotation (12) of the workpiece (17).

6. Device according to claim 5, characterized in that the adjustment kinematics of the at least one inwardly directed cutting edge (13.1 , 13.2) has at least one numerically controllable adjustment drive (4.1 , 4.2).

7. Device according to claim 6, characterized in that the adjustment drive (4.1 , 4.2) is designed as an electric or a hydraulic or a pneumatic axis.

8. Device according to claim 6, characterized in that the numerically controllable adjustment drive (4.1 , 4.2) is designed to be interpolable with other axes.

9. Device according to claim 5, characterized in that the adjustment kinematics integrated into the hollow cylindrical base body of the external tool (1.1 , 1.2) comprises at least one drive (4.1 , 4.2 ), a drive pinion (5.1 , 5.2 ), a synchronizing ring (22 ) and an actuating element (7.1 , 7.2 ).

10. Device according to claim 1 characterized in that each of the inwardly directed cutting edges (13.1 , 13.2) has at least one cutting tool holder (6.1 , 6.2).

11. Device according to claim 10 characterized in that the cutting tool holder (6.1 , 6.2) is designed as an interchangeable indexable insert carrier that is adjustable in the radial cutting direction.

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