Tool for machining a workpiece, machine tool and method for machining a workpiece

Abstract

Tool (5) for machining a workpiece (4), comprising: - a tool shank (12) rotatable about a rotary axis (10), - a cutting device (13) arranged on the tool shank (12) with: - at least one pre-cutting element (14) and - at least one post-cutting element (15),- a first slide unit (8) for displacing the at least one pre-cutting element (14) relative to the tool shank (12) with -- a first output body (25) connected to the at least one pre-cutting element (14) and -- a first drive body (23) interacting with the respective first output body (25) via a first drive surface (24) and - a second slide unit (9) displaceable relative to the first slide unit (8) for displacing the at least one re-cutting element (15) relative to the tool shank (12) with -- a second output body (29) connected to the at least one re-cutting element (15) and -- a second drive body (27) interacting with the respective second output body (29) via a second drive surface (28), wherein the first drive surface (24) and the second drive surface (28) overlap each other in an orthogonal projection onto a transverse plane to the axis of rotation (10), thereby characterizedthat a maximum feed path (s1, s2) of at least two of the output bodies (25, 29) is different.

Description

[0001] The invention relates to a tool for machining a workpiece and to a machine tool with such a tool. Furthermore, the invention relates to a method for machining a workpiece.

[0002] From DE 10 2010 002 019 A1, a machine tool is known with a machine frame and a tool rotatably connected to it, wherein the tool comprises a set of first tool elements and a set of second tool elements for two-stage machining, in particular of cylindrical bores, of a workpiece. The first tool elements and the second tool elements are arranged spaced apart from each other along a rotational axis of the tool and can be displaced radially to the rotational axis by means of a sliding unit. The installation space occupied by the sliding units is particularly large, especially in the radial direction to the rotational axis, which means that only workpieces whose bores have a certain minimum diameter can be machined.

[0003] The invention is based on the objective of creating an improved tool for multi-stage machining of workpieces, which enables the machining of workpieces, in particular small diameter bores, in an economical manner.

[0004] This problem is solved by a tool with the features of claim 1. According to the invention, it was found that the first drive surface of the first slide unit and the second drive surface of the second slide unit must overlap each other in orthogonal projection onto a transverse plane to the axis of rotation in order to create a tool that enables the economical machining of small-diameter bores. Because the first drive surface and the second drive surface overlap in orthogonal projection onto a transverse plane to the axis of rotation, the respective first output body connected to the at least one pre-cutting element and the respective output body connected to the at least one post-cutting element can be arranged particularly close to the axis of rotation of the tool. The transverse plane is a plane extending perpendicular to the axis of rotation.The tool, in particular the first slide unit and / or the second slide unit, can therefore have a particularly small radial dimension. The installation space required for mounting the at least one first drive body and the at least one second drive body, especially in the radial direction, can thus be reduced. The mounting of the drive bodies on the tool shank is therefore particularly stable and has minimal play, even with a small radial extent of the tool.

[0005] The maximum first stroke of the at least one pre-cutting element and / or the maximum second stroke of the at least one re-cutting element can therefore be particularly large, especially due to the small radial dimensions of the slide units. This increased stroke enhances the tool's flexibility and can also extend its service life. Because of the reduced dimensions of the slide units, the at least one pre-cutting element and / or the at least one re-cutting element can have a particularly large, especially radial, extension. This allows the wear limit of the at least one pre-cutting element and / or the at least one re-cutting element to be raised, resulting in longer tool life. Consequently, machining the workpiece can be performed with exceptional efficiency.For example, the radial extent of a bearing assembly for supporting the output elements on the tool shank can be made particularly large. This results in a mechanically robust and low-backlash bearing arrangement for the output elements.

[0006] The term "pre-cutting element" refers to the cutting element that engages with the workpiece in a first machining step. The term "re-cutting element" refers to the cutting element that engages with the workpiece in a second machining step. The tool according to the invention thus enables two machining steps to be performed without a tool change. According to one aspect of the invention, the at least one pre-cutting element is designed for rough machining of the workpiece, and the at least one re-cutting element is designed for fine machining of the workpiece. Machining of the workpiece can also be performed alternately with the at least one re-cutting element and with the at least one pre-cutting element.

[0007] The cutting elements can have a geometrically defined and / or a geometrically undefined cutting edge. For example, the pre-cutting element can have a geometrically undefined cutting edge and the post-cutting element a geometrically defined cutting edge, or vice versa. The at least one pre-cutting element and / or the at least one post-cutting element can therefore be designed, for example, as a friction element or as a grinding element.

[0008] Preferably, the cutting device comprises several pre-cutting elements and several post-cutting elements. For example, the cutting device can comprise at least two, in particular at least three, and in particular at least six pre-cutting elements and / or post-cutting elements. Preferably, the number of pre-cutting elements corresponds to the number of the first output bodies. The number of post-cutting elements can correspond to the number of the second output bodies. According to a preferred embodiment, the number of pre-cutting elements can correspond to the number of post-cutting elements. Alternatively, the number of pre-cutting elements can be different from the number of post-cutting elements. The ratio between the number of pre-cutting elements and the number of post-cutting elements can thus be designed according to the loads acting on them and according to the wear of the tool, in particular the cutting elements.

[0009] The at least one pre-cutting element is preferably detachably connected to the at least one first drive body. The at least one post-cutting element can be detachably connected to the at least one second drive body, in particular by frictional and / or positive locking. This advantageously ensures that the cutting elements designed as pre-cutting and post-cutting elements are easily replaceable. Alternatively, the at least one pre-cutting element and / or the at least one post-cutting element can be materially bonded to the respective drive body. The at least one pre-cutting element and / or the at least one post-cutting element can each be connected to the respective drive body via a cutting element receptacle. The at least one pre-cutting element and / or the at least one post-cutting element each form a cutting edge together with one of the drive bodies.

[0010] Preferably, the first slide unit and the second slide unit, in particular the first drive body and the second drive body and / or the first drive surface and the second drive surface and / or the at least one first output body and the at least one second output body, are arranged overlapping each other along the axis of rotation on the tool shank. This advantageously results in a particularly small axially compact installation space occupied by the tool. Preferably, the at least one pre-cutting element and the at least one post-cutting element extend over an identical length along the axis of rotation. The workpiece can thus be machined with an unchanged penetration depth by either the at least one pre-cutting element or the at least one post-cutting element.

[0011] Preferably, the tool comprises at least one spring element that interacts with the cutting device. For example, a compression spring and / or a tension spring can be operatively connected to the cutting device via the first slide unit and / or via the second slide unit. According to a preferred embodiment, a compression spring is arranged between the first drive body and the tool shank, and another between the second drive body and the tool shank. The compression springs can be arranged on the tool shank such that they are tensioned in the direction of the workpiece when the first drive body or the second drive body is moved along the axis of rotation. The at least one pre-cutting element and / or the at least one post-cutting element can be operatively connected to at least one ring spring.Preferably, the at least one ring spring is arranged on the cutting elements in such a way that it is tensioned outwards when the cutting elements are moved in a radial direction.

[0012] To reposition the at least one pre-cutting element and / or the at least one post-cutting element relative to the tool shank, in particular in the direction of the axis of rotation, in particular into a return position, the tool may have magnets.

[0013] The tool shank can be made of multiple parts. Preferably, the tool shank is composed of several parts along the axis of rotation, which are particularly detachably connected to one another. This makes the assembly of the tool, especially the slide units and the spring elements that interact with them, particularly easy.

[0014] The first slide unit and / or the second slide unit may have a pair of sliding bearings on the first drive surface and / or in the area of ​​the second drive surface. The drive bodies and / or the driven bodies may have a hardened material in the area of ​​the drive surfaces.

[0015] The first drive surface and / or the second drive surface can be flat. According to a preferred embodiment, the drive surfaces are curved, in particular conical, and in particular sector-shaped with a frustoconical face. The drive elements and the output elements of the first and second slide units can thus interact with each other with particularly low friction.

[0016] Preferably, the first slide unit and / or the second slide unit and / or the tool shank comprises a damping material.

[0017] The tool can incorporate active damping elements. This reliably prevents chatter marks from forming during machining of the workpiece.

[0018] According to another aspect of the invention, the tool can have wear sensors. The tool can have electrical and / or optical wear sensors. Alternatively, the tool can have fluid channels for wear determination that open as wear increases.

[0019] A tool according to claim 2 can be manufactured particularly economically and, especially in the radial direction, can be designed to be particularly compact. By mounting the first drive body on, and especially within, the second drive body, an additional, space-consuming bearing arrangement can be dispensed with. Preferably, the first drive body is connected to the second drive body in a rotationally fixed manner, particularly by a positive locking connection. The second drive body can be connected to the tool shank in a rotationally fixed manner, particularly by a positive locking connection. The drive bodies thus interact with the respective output bodies in a particularly reliable and low-friction manner.

[0020] A tool according to claim 3, particularly in the radial direction, can be designed to be especially space-saving. Preferably, the second drive body has at least one, in particular slot-shaped, recess that penetrates the second drive body in the radial direction. The first drive body can penetrate the at least one recess. Alternatively, the at least one recess can be penetrated by the at least one first output body.

[0021] A tool according to claim 4 ensures particularly flexible and economical machining of the workpiece. The circumferential overlap refers to an arrangement, at least partially, in the same area along the axis of rotation. Due to the circumferential overlap of the at least one pre-cutting element and the at least one post-cutting element around the axis of rotation, these elements are arranged particularly compactly on the tool shank along the axis of rotation. The space required by the tool in the axial direction is therefore particularly small. Preferably, all pre-cutting elements and all post-cutting elements extend over the same section along the axis of rotation.

[0022] A tool according to claim 5 has a particularly small installation space requirement in the axial direction. Preferably, the first drive surface and the second drive surface are also arranged overlapping each other along the axis of rotation on the tool shank.

[0023] A tool according to claim 6 ensures particularly precise machining of the workpiece. Because the first drive body interacts with the at least one first output body and / or the second drive body interacts with the at least one second output body via several axially spaced first drive surfaces and / or second drive surfaces, the bearing of the output bodies on the tool shank is particularly stable. Preferably, each output body is connected via at least two drive surfaces of the respective drive body. This allows, in particular, a very precise adjustment of the angle between the axis of rotation and the respective drive body. Preferably, a portion of the respective cutting element interacting with the workpiece is oriented parallel to the axis of rotation.

[0024] A tool according to claim 7 has a particularly long service life and can be operated particularly economically. The pre-cutting edge height is defined by the radial extent of the at least one pre-cutting element together with the first output body associated therewith. The post-cutting edge height is defined by the radial extent of the at least one post-cutting element together with the second output body associated therewith.

[0025] Preferably, the radial extensions of the cutting edge bearings, in which the cutting elements are guided, differ according to the design of the pre-cutting edge height and the post-cutting edge height. This allows the cutting edge bearings to be dimensioned according to the forces acting during machining of the workpiece.

[0026] A tool according to claim 8 ensures a particularly long service life and is especially economical in operation. The maximum feed stroke of the respective output body can, for example, be adapted to the wear of the associated pre-cutting or post-cutting element. Preferably, the maximum feed stroke of the at least one first output body is not equal to the maximum feed stroke of the at least one second output body.

[0027] A tool according to claim 9 is particularly robust in operation. The cross-sectional area of ​​the cutting edge bearing is understood to be the area that extends tangentially to the axis of rotation and is surrounded by the cutting edge bearing. Preferably, the cutting edge bearings of the first output bodies differ from the cutting edge bearings of the second output bodies. The cutting edge bearings can thus be dimensioned independently of one another for the at least one first output body and the at least one second output body, according to the forces acting on the output bodies. The tool can thus be designed to be particularly robust, material-efficient, and compact.

[0028] A tool according to claim 10 is particularly robust and economical in operation. The bearing surfaces are understood to be those surfaces of the respective cutting edge bearing that are in contact with the cutting edges, in particular the drive bodies and / or the cutting elements. The cutting edge bearings can therefore be designed to be particularly wear-resistant and compact.

[0029] A tool according to claim 11 ensures particularly precise centering relative to the workpiece and thus very precise workpiece machining. Due to the alternating arrangement of the multiple pre-cutting elements and the multiple post-cutting elements around the circumference of the tool, the forces transmitted between the workpiece and the tool are also distributed evenly in the circumferential direction. This reliably ensures the centering of the tool. Chatter marks on the workpiece can be reliably prevented.

[0030] A tool according to claim 12 is particularly simple and robust in its construction. By arranging several pre-cutting elements and / or several post-cutting elements side by side or directly following one another in the circumferential direction, the first slide unit and / or the second slide unit can be designed to be simple and robust. For example, the first drive body can thus interact with several first output bodies via a single recess, in particular a penetration, of the second drive body.

[0031] A tool according to claim 13 has a high wear limit, a high feed rate of the cutting elements, and a particularly small installation space requirement, especially in the radial direction. Using the tool, which is designed as a honing tool, bores, especially cylindrical ones, with a particularly small bore diameter can be machined. Preferably, the at least one pre-cutting element is designed as a roughing element and the at least one finishing element is designed as a surface honing element.

[0032] The invention is further based on the objective of creating a machine tool that is particularly flexible in use, has a long service life and can therefore be operated in a particularly economical manner.

[0033] This problem is solved by a machine tool with the features of claim 14. The advantages of the machine tool according to the invention correspond to the advantages of the tool already described. The machine tool can be designed as a multi-axis machine. Preferably, the tool is rotatably mounted on the machine frame and can be driven by means of the drive unit. The drive unit can comprise a motor, in particular an electric motor and / or a hydraulic motor.

[0034] The selection device preferably comprises a first selection drive for providing a first selection force and a second selection drive for providing a second selection force. To transmit the first selection force to the first slide unit, the tool may have a first push rod with a first selection force surface for interaction with the first selection drive. The second selection drive may transmit the second selection force via a second selection force surface to a second push rod of the tool, which is connected to the second slide unit.

[0035] The invention is further based on the objective of creating a method that enables the machining of a workpiece, especially when the workpiece has small dimensions, in a particularly economical manner.

[0036] This problem is solved by a method with the features of claim 15. The advantages of the method according to the invention correspond to the advantages of the tool according to the invention already described. In particular, the method can also be further developed with the features mentioned in connection with the tool, especially with the features of at least one of claims 1 to 14.

[0037] Further features, advantages, and details of the invention will become apparent from the following description of two exemplary embodiments. These show: Fig. 1 A schematic representation of a machine tool with a machine frame, a tool mounted on the machine frame for machining a workpiece, a drive device and a selection device for actuating a first slide unit and a second slide unit of the tool, Fig. 2 a side view of the tool in Fig. 1 with a tool shank and a cutting device arranged thereon, which comprises several pre-cutting elements and several post-cutting elements, wherein three pre-cutting elements and three post-cutting elements are arranged alternately on the tool shank in the circumferential direction, Fig. 3 a front view of the tool in Fig. 2 comprising a first sliding unit for repositioning the multiple pre-cutting elements relative to the tool shank and a second sliding unit for repositioning the multiple post-cutting elements relative to the tool shank, wherein the pre-cutting elements and the post-cutting elements are arranged in a return position, Fig. 4. A section view along the section line IV-IV . in Fig. 3 through a rotational axis of the tool, Fig. 5 a sectional view along the section line V-V in Fig. 2 with the multiple pre-cutting elements, the multiple post-cutting elements and guide elements arranged between them, Fig. 6 a front view of the tool in Fig. 1, wherein the multiple pre-cutting elements and the multiple post-cutting elements are arranged in a delivery position, Fig. 7 a sectional view along the cutting line VII-VII in Fig. 6 with the multiple pre-cutting elements and multiple post-cutting elements arranged in the delivery position, Fig. 8 a side view of a tool for machining a workpiece according to a further embodiment with a tool shank and a cutting device arranged thereon, which comprises several pre-cutting elements and several post-cutting elements, wherein the pre-cutting elements and the post-cutting elements are arranged alternately on the tool shank in the circumferential direction, Fig. 9 a side view of a first drive body of a first slide unit and a second drive body of a second slide unit of the tool slidably mounted therein in Fig. 8, wherein the first drive body penetrates the second drive body in a radial direction, Fig. 10 a sectional view along the section line X-X in Fig. 8, wherein the multiple pre-cutting elements and the multiple post-cutting elements are arranged in a reset position and Fig. 11 a sectional view of the tool according to Fig. 8, in contrast to the section view in Fig. 10 unchanged position relative to the tool shank, wherein the several pre-cutting elements and the several post-cutting elements are arranged in a feed position radially outwards relative to the axis of rotation.

[0038] The following is based on the Fig. 1 to Fig. 7 describes a first embodiment of the invention. A machine tool 1 includes a machine frame 2 with a workpiece holder 3 for clamping a workpiece 4 The workpiece 4 has several boreholes 4a on the machine frame 2 is a tool 5 for processing the workpiece 4 Rotatably mounted. For rotating the tool. 5 The machine tool includes 1 one with the machine frame 2 connected drive unit 6 The machine tool 1 It also features a tool 5 Interconnected selection device 7 to actuate a first slide unit 8 and a second slide unit 9 , as in Fig. 4 shown, on. The tool 5 is along a rotation axis oriented parallel to the vertical direction10 linearly movable on the machine frame 2 stored. One attached to the machine frame 2 arranged bearing drive 11 is for repositioning the workpiece holder 3 and the associated workpiece 4 relative to the machine frame 2 formed in a horizontal direction.

[0039] The Fig. 2 shows the tool 5 from the side. The tool 5 includes a tool shaft 12 as well as one on the tool shaft 12 arranged cutting device 13 with several pre-cutting elements 14 and several recutting elements 15 The tool shaft 12 includes a tool connection 16 for the rotationally fixed connection of the tool 5 with a tool holder 17 the machine tool 1 . About the tool holder 17 is the tool 5rotationally fixed to the drive unit 6 tied together.

[0040] At the tool connection 16 are hydraulic connections 18 to supply the tool 5 Provided with coolant. For rotating the tool. 5 The tool connection includes 16 a drive flange 19 . For cooperation with the selection committee 7 The tool connection includes 16 a first selection force area 20 and a second selection force area 21 .

[0041] The Fig. 3 shows the tool 5 in a front view. Between the pre-cutting elements 14 and the recutting elements 15 are guide elements 22 on the tool shaft 12 arranged. The first slide unit 8 penetrates the front area of ​​the tool 5The second slide unit in a radial direction. The first slide unit 8 includes a concentric axis to the axis of rotation 10 arranged first drive body 23 , which has a first propulsion surface 24 with several first drive bodies 25 is connected. For relocating the pre-cutting elements 14 relative to the tool shaft 12 There is a first drive body in each case. 25 in conjunction with each of the pre-cutting elements 14 The pre-cutting elements 14 Each has a cutting element holder 26 on the first drive bodies 25 appropriate.

[0042] The second slide unit 9 is relative to the first slide unit 8 on the tool shaft 12 attached. The second sliding unit 9 includes a second drive unit 27 , which has a second propulsion surface 28with several second drive bodies 29 interacts. For repositioning the recutting elements 15 relative to the tool shaft 12 is one of the second driven bodies 29 via one cutting element holder each 26 each with a recutting element 15 tied together.

[0043] The first drive bodies 25 and the second drive bodies 29 are each located at a storage area 30 of the tool shaft 12 radial to the axis of rotation 10 The tool shaft is mounted on a sliding bearing. 12 The tool shank is made of a metallic material. 12 is in the area of ​​storage areas 30 hardened.

[0044] The Fig. 4 shows the tool 5 in a longitudinal section. In the tool shank 12 is concentric to the axis of rotation 10 first push rod arranged 31arranged. The first push rod 31 The first selection force area 20 up. Concentric to the axis of rotation 10 is the second push rod 32 in the tool shaft 12 arranged. The second push rod 32 The second selection force area includes 21 The first push rod 31 is along the axis of rotation 10 in the second push rod 32 The second push rod is mounted so that it can slide linearly. 32 is in the tool shaft 12 along the axis of rotation 10 linearly movable mounting.

[0045] The first push rod 31 stands above one with the first drive body 23 connected control pin 33 in conjunction with the first slide unit 8 . Between the control pin 33 and the first drive unit 23 is a first compression spring 34arranged, which causes the control pin to shift 33 and the first push rod 31 towards the first selection area 20 causes.

[0046] The second push rod 32 is above one with the second drive unit 27 connected control sleeve 35 with the second slide unit 9 in connection. Between the control sleeve 35 and the tool shaft 12 A second compression spring is also active 36 The second compression spring 36 results in a direction towards the second selection force area. 21 oriented force for moving the control sleeve 35 and the second push rod 32 .

[0047] The tool shaft 12 It is designed in two parts and has a machine-side connection shaft. 37 and a workpiece-side headstock 38 up. The affiliation 37 is with the headstock 38positive locking via a shaft nut 39 tied together.

[0048] The first thrust surface 24 is just like the second thrust surface 28 in two along the axis of rotation 10 subdivided into spaced-apart sub-surfaces. The first drive unit 23 and the second drive unit 27 They thus interact with the respective first drive elements via two bearing points each. 25 and the second drive bodies 29 together.

[0049] The first thrust surface 24 and the second thrust surface 28 overlap each other in an orthogonal projection onto a transverse plane to the axis of rotation 10 The first drive unit 23 and the second drive unit 27 overlap each other circumferentially around the axis of rotation 10 Similarly, the multiple first drive bodies overlap each other. 25 and the several second drive bodies 29circumferentially around the axis of rotation 10 The multiple pre-cutting elements 14 and the multiple recutting elements 15 overlap each other circumferentially around the axis of rotation 10 The pre-cutting elements 14 and the recutting elements 15 extend along the axis of rotation 10 over the same length.

[0050] As can be seen in particular from the Fig. As can be seen from 5, the first drive body 23 circumferentially around the axis of rotation 10 positively locking and therefore rotationally fixed with the second drive body 27 connected. The guide elements 22 show exit openings 40 for the application of cooling lubricant, which is routed via pipes 41 with the hydraulic connections 18 are connected.

[0051] The several pre-cutting elements 14 and the multiple recutting elements 15are in relation to the tool shaft 12 moved back and thus positioned in a reset position. The first drive unit 23 and the second drive unit 27 are in the direction of the tool connection 16 relocated. The tool 5 is in a basic position.

[0052] In the Fig. 6 and Fig. 7 is the tool 5 Shown in a machining position. In the machining position, the several pre-cutting elements are 14 and the multiple recutting elements 15 arranged in a delivery position in which they are opposite the tool shaft 12 protrude. The first drive unit 23 and the second drive unit 27 are in the direction of the workpiece 4 relocated.

[0053] The pre-cutting elements 14 are in relation to the tool shaft 12 to achieve a first maximum delivery routes1 Displaceable in a radial direction. The recutting elements 15 are in relation to the tool shaft 12 to create a second maximum delivery route s2 Displaceable in a radial direction. The second maximum delivery path s2 is larger than the first maximum delivery route s1 .

[0054] The pre-cutting strips 14 and the first drive bodies 25 extend together with the first drive bodies 25 , in a radial direction to the axis of rotation 10 , via a pre-cutting strip height H V The recutting elements 15 and the second drive bodies 29 extend together, in a radial direction to the axis of rotation 10 , via a trimming strip height H N The pre-cutting strip height Hv is greater than the post-cutting strip height. H N .

[0055] The several pre-cutting elements 14and the multiple recutting elements 15 are designed as honing cutting elements. The tool 5 is a honing tool.

[0056] How the machine tool works 1 or the tool 5 for machining a workpiece 4 is as follows: The machine tool 1 is in a resting position in which the tool 5 out of contact with the workpiece 4 The tool is standing. 5 is arranged in the home position. The workpiece 4 is at the workpiece holder 3 appropriate.

[0057] By means of the bearing drive 11 The workpiece holder 3 and the workpiece placed on it 4 under the tool 5 arranged. In particular, the borehole 4a concentric to the axis of rotation 10 arranged. The drive unit 6is activated and the workpiece 5 It is rotary-driven. By means of the drive unit 6 will the workpiece 5 along the axis of rotation 10 into the bore 4a introduced. Via the hydraulic connections 18 Coolant is added to the tool 5 guided. The tool 5 will be in the bore 4a about the guide elements 22 guided.

[0058] A first selection officer will be appointed via the selection institution. F1 on the first selection area 20 exercised. The first push rod 31 , the control pin 33 and the first drive unit 23 are in the direction of the workpiece 4 relocated. The first compression spring 34 It is compressed in the process. The first drive body 23 acts via the first shoot surface 24 on the first drive bodies 25 The first drive elements 25This causes them to rotate in a radial direction relative to the axis of rotation. 10 shifted outwards. The pre-cutting elements 14 are in the delivery position and the tool 5 is arranged in a first processing position.

[0059] The rotary-driven tool 5 attached pre-cutting elements 14 come into contact with a wall of the borehole 4a The workpiece 4 is being processed and the machine tool 1 is in a working position.

[0060] For further processing of the workpiece 4 will be applied to the first selection area 20 effective first selection force F1 withdrawn. The first compression spring 34 causes a change in the control pin 33 Force acting in the direction of the tool connection 16 The control pin 33 , the first drive unit 23and the first push rod 31 will be directed towards the first selection area 20 Retracted. For retracting the cutting elements. 14 , 15 , the first driven body 25 and the second drive body 29 in the direction of the axis of rotation 10 The tool indicates 5 Ring spring elements 42 on, which are in ring spring grooves 43 the first drive body 25 and the second drive body 29 are mounted. The ring spring elements 42 are in the delivery position of the cutting elements 14 , 15 tensioned and in the return position of the cutting elements 14 , 15 relaxed. By moving the first drive unit back. 23 will the pre-cutting elements 14 by means of the ring spring elements 42 moved back into the reset position.

[0061] By means of the selection mechanism 7A second selection committee will be appointed. F2 to the second selection area 21 deployed. The second push rod 32 is parallel to the axis of rotation 10 in the direction of the cutting device 13 displaced. The one over the control sleeve 35 with the second push rod 32 connected second drive body 29 is directed towards the cutting device 13 displaced. The second compression spring 36 is being tensioned. The second drive unit 27 acts via the second propulsion surface 28 with the driven bodies 29 together, thereby causing the axial displacement of the second drive body 27 a radial displacement of the second output bodies 29 caused by the second driven body. 29 connected re-cutting elements 15 are in the delivery position. The tool 5is arranged in a second machining position. The wall of the bore 4a is achieved by means of the recutting elements 15 machined by machining.

[0062] By activating the selection device 7 will be the second substitute F2 withdrawn. The second compression spring 36 causes a change in the control sleeve 35 in the direction of the tool connection 16 acting force. The control sleeve 35 , the associated second drive unit 27 and the second push rod 32 are directed towards the tool connection 16 displaced. The several second drive bodies 29 and the recutting elements arranged on it 15 are achieved by means of the ring spring elements 42 radially in the direction of the axis of rotation 10 relocated. The recutting elements 15 are in the reset position and the tool 5is arranged in the basic position.

[0063] Based on the Fig. 8 to Fig. Figure 11 is a further embodiment of the tool according to the invention. 5 described. In contrast to the previous embodiment, a pre-cutting element is alternately positioned in the circumferential direction. 14 and a recutting element 15 on the tool shaft 12 arranged. As in Fig. As shown in 9, the first slide unit indicates this. 8 and the second slide unit 9 a modified design. A first drive unit 23 the first slide unit 8 is in a second drive unit 27 the second slide unit 9 in the direction of the axis of rotation 10 Slidingly mounted. The first drive unit 23 penetrates the second drive body 27 in the radial direction exactly once per first output body 25 .

[0064] The first drive bodies 25 and the second drive bodies 29 are each in cutting strip bearings 44 of the tool shaft 12 The cutting edge bearings are slidably mounted. 44 exhibit a cross-sectional area extending perpendicular to the radial direction A1 , A2 up. The cutting edge bearings 44 for storing the first drive bodies 25 the first cross-sectional areas A1 up. The cutting edge bearings 44 for storing the second output bodies 29 the second cross-sectional areas A2 on. The second cross-sectional areas A2 are larger than the first cross-sectional areas A1 .

[0065] How the tool works 5 According to the second embodiment, the tool functions as follows: 5according to the first embodiment. The alternating arrangement of the pre-cutting elements. 14 and the recutting elements 15 ensures a particularly even effect of the pre-cutting elements 14 or the recutting elements 15 on the drilling 4a of the workpiece 4 .

[0066] A machine tool 1 with a tool 5 According to one of the embodiments described above, for a given machining diameter D of the tool 5 a particularly long first delivery route s1 the pre-cutting elements 14 and a particularly large second delivery route s2 the re-cutting elements 15 up. The cutting edge bearings 44 the tools 5 They also exhibit a particularly large radial extent, which makes the first driven bodies 25 and the second drive bodies 29especially stable, particularly free of play, on the tool shaft 12 are stored. This reliably prevents the formation of chatter marks. Due to the increased delivery distances. s1 , s2 is the service life of the tools described above 5 also for small machining diameters D of the tool 1 or diameter of the bores 4a of the workpiece 4 especially high. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 102010002019 A1

[0002]

Claims

[1] Tool for machining a workpiece, comprising - a tool shaft (12) that can be rotated about a rotary axis (10), - a cutting device (13) arranged on the tool shaft (12) with -- at least one pre-cutting element (14) and -- at least one recutting element (15), - a first slide unit (8) for repositioning the at least one pre-cutting element (14) relative to the tool shank (12) with -- each a first drive body (25) connected with at least one pre-cutting element (14) and -- a first drive body (23) interacting with the respective first output body (25) via a first drive surface (24) and - a second slide unit (9) which can be displaced relative to the first slide unit (8) for displacing the at least one recutting element (15) relative to the tool shank (12) with -- each a second drive body (29) connected with at least one recutting element (15) and -- a second drive body (27) which interacts with the respective second output body (29) via a second drive surface (28), characterized by , that the first drive surface (24) and the second drive surface (28) overlap each other in an orthogonal projection onto a transverse plane to the axis of rotation (10). [2] Tool according to claim 1, characterized by , that the first drive body (23) is mounted linearly displaceable on the second drive body (27). [3] Tool according to claim 1 or 2, characterized by , that the first drive body (23) penetrates the second drive body (27) in a radial direction. [4] Tool according to any of the preceding claims, characterized by , that the at least one pre-cutting element (14) and the at least one post-cutting element (15) overlap each other in the circumferential direction around the axis of rotation (10). [5] Tool according to any of the preceding claims, characterized by , that the first drive body (23) and the second drive body (27) and / or the at least one first output body (25) and the at least one second output body (29) overlap each other in the circumferential direction around the axis of rotation (10). [6] Tool according to any of the preceding claims, characterized by , that the first drive body (23) interacts with the at least one first output body (25) and / or the second drive body (27) interacts with the at least one second output body (29) via axially spaced drive surfaces (24, 28). [7] Tool according to any of the preceding claims, characterized by , that a radial pre-cutting edge height (Hv) of at least one of the pre-cutting elements (14) together with the respective associated first drive body (25) is not equal to a radial re-cutting edge height (H N) of at least one of the recutting elements (15) together with each associated second drive body (29). [8] Tool according to any of the preceding claims, characterized by , that a maximum delivery route (s1, s2 ) is different from at least two of the drive bodies (25, 29). [9] Tool according to any of the preceding claims, characterized by , that the tool shank (12) has at least two cutting edge bearings (44) with different cross-sectional areas (A1, A2). [10] Tool according to any of the preceding claims, characterized by , that the tool shank (12) has at least one cutting edge bearing (44) with a hardened bearing surface (30). [11] Tool according to any of the preceding claims, characterized byseveral pre-cutting elements (14) and several post-cutting elements (15), wherein a pre-cutting element (14) and a post-cutting element (15) are arranged alternately on the tool shank (12) in the circumferential direction. [12] Tool according to any one of claims 1 to 10, characterized by several pre-cutting elements (14) and several post-cutting elements (15), wherein at least two pre-cutting elements (14) and / or at least two post-cutting elements (15) are arranged successively on the tool shank (12) in the circumferential direction. [13] Tool according to any of the preceding claims, characterized by , that the at least one pre-cutting element (14) and / or the at least one post-cutting element (15) are designed as honing cutting elements, wherein the tool (5) is a honing tool. [14] Machine tool comprising - a machine frame (2), - a tool (5) rotatably mounted on the machine frame (2) according to one of claims 1 to 13, - a drive device (6) for rotating the tool (5) and - a selection device (7) operatively connected to the tool (5) for actuating the first slide unit (8) and the second slide unit (9). [15] Method for machining a workpiece comprising the steps: - Providing a tool (5) according to any one of claims 1 to 13, - Arranging the tool (5) in a home position in which the at least one pre-cutting element (14) and the at least one post-cutting element (15) are arranged in a return position and are moved back relative to the tool shank (12), - Rotary drive of the tool (5), - Moving the tool (5) into a machining position in which the at least one pre-cutting element (14) or the at least one post-cutting element (15) is arranged in a feed position and protrudes from the tool shank (12) and - separating machining of the workpiece (4) with the at least one pre-cutting element (14) or post-cutting element (15) arranged in the feed position.