EP3085492B1 - Grinding tool - Google Patents

Description

The invention relates to a grinding tool according to the preamble of claim 1, a set of a first and a second grinding tool according to the preamble of claim 2, the use of a grinding tool according to the invention or one of the two grinding tools of the set according to the invention in a machining process of the inner surface of a cylinder bore in one Workpiece, as well as a CNC machine with at least one grinding tool according to the invention or at least one of the two grinding tools of the set according to the invention and a control program, which is designed to perform the machining process automatically.

It has been found that the cylinders deform in internal combustion engines in the operating state due to a spatially uneven heating to the effect that in the operating state is deviating from the ideal cylindrical shape shape. This results in an increased fuel consumption, which is problematic in view of the limits to be complied with for the emission of the amount of CO ₂ per kilometer of route.

To solve this problem, a honing process was developed that does not have the cylindrical bore shape as its goal, but already takes into account the anticipated distortions in terms of production, so that quasi-cylindrical bore surface areas are established under operating conditions. This makes it possible to reduce the piston ring voltage. The result is a lower friction, a lower fuel consumption and thus a reduced CO ₂ emission.

A disadvantage of this honing method, however, is that it is associated with a relatively high amount of time, since the honing tool in an oscillating Movement in the cylinder bore is moved back and forth. In addition, it would be desirable to further improve the precision over this method.

The DE 24 62 847 C2 and the WO 2013/11 45 27 A1 each show a honing tool, which is used for machining the inner surface of a cylinder bore in a workpiece. In both cases, the grinding tool has a cylindrical and an adjoining conical region.

The object of the present invention is therefore to provide a grinding tool or a set of a first and a second grinding tool, which makes it possible to edit the inner surface of a cylinder bore in a workpiece very quickly and with high precision to the effect that the inner surface of the Machining has a shape that transforms under operating conditions into a quasi-cylindrical shape. Another object of the invention is to provide a use of a grinding tool in a machining process of the inner surface of a cylinder bore in a workpiece, as well as a CNC machine with at least one grinding tool according to the invention.

These objects are solved by the features of independent claims 1, 2, 16 and 17.

With respect to the grinding tool according to the invention, it is thus provided that the grinding tool has a free end and an opposite end and the conical grinding area is disposed adjacent to the free end of the grinding tool, and at the opposite end a fastening means for attachment of the grinding tool to a machining head a CNC machine or an associated one Adapter, preferably HSK adapter, is provided, wherein the fastening means is preferably designed as a flange.

A machining process of the inner surface of a cylinder bore in a workpiece, e.g. an engine block, could thus look like that the grinding tool is introduced with its cylindrical and then conical tapered grinding area in the cylinder bore, is brought to the inner surface of the cylinder bore, at least once in a circle on the inner surface of the cylinder bore along it, where it rotated about its axis of rotation, is lifted from the inner surface of the cylinder bore and is led out of the cylinder bore again. As a result, following the machining process, the inner surface of the cylinder bore has taken a shape that is initially cylindrical, and has the shape of an opening cone where the conical grinding region has become effective. If a cylinder bore machined in this way expands unevenly due to the fact that a higher heat development takes place in the cylindrical region than in the region of the cone opening, a quasi-cylindrical bore surface area arises.

The fact that the cylinder bore can be processed by the grinding tool in a single operation reduces the time required for machining. In addition, the precision in the shaping increases because the grinding tool during the machining process does not have to be moved back and forth in the direction of the depth of the cylinder bore, as is the case with honing tools.

Advantageous embodiments of the grinding tool according to the invention are defined in the dependent claims 5 to 15.

With respect to the kit according to the invention, it is provided that the second grinding tool of the set has a free end and an opposite end and the conical grinding portion is disposed adjacent to the free end on the second grinding tool of the set, and at the opposite end a fastening means for fixing the second grinding tool of the set to a machining head of a CNC machine or an adapter connected thereto, preferably HSK adapter, is provided, wherein the fastening means is preferably formed as a flange.

In the case of the set, a machining process of the inner surface of a cylinder bore in a workpiece, eg, an engine block, could look like that the second abrasive tool having the conical grinding portion is first inserted into the cylinder bore, brought to the inner surface of the cylinder bore, at least once in a circle the inner surface of the cylinder bore is guided along, wherein it rotates about its axis of rotation, is lifted from the inner surface of the cylinder bore and is led out of the cylinder bore again. In a subsequent step, the first grinding tool with the cylindrical grinding portion is inserted into the cylinder bore, guided to the inner surface of the cylinder bore, at least once guided in a circle on the inner surface of the cylinder bore, thereby rotating about its axis of rotation, from the inner surface of the cylinder bore lifted and led out of the cylinder bore again. As a result, following the machining process, the inner surface of the cylinder bore has taken a shape that is initially cylindrical, and has the shape of an opening cone where the conical grinding region has become effective. If a cylinder bore machined in this way expands unevenly due to the fact that a higher heat development takes place in the cylindrical region than in the region of the cone opening, a quasi-cylindrical bore surface area arises.

The two processing steps by means of the first and the second grinding tool can also be carried out in the reverse order.

The variant with the machining of the inner surface of a cylinder bore by means of the set has the disadvantage over the variant with the machining of the inner surface of a cylinder bore by means of the grinding tool, which has both the cylindrical and the conical abrasive coating, that two processing steps are necessary, however These two processing steps are performed with less driving force, since a smaller grinding surface per processing step is effective.

Advantageous embodiments of the kit according to the invention are defined in the dependent claims 3 to 7 and 9 to 15.

It should be noted in particular that it is provided according to a particularly preferred embodiment of the grinding tool or the inventive set that the diameter of the conical grinding area over the length of the conical grinding area in the axial direction relative to the diameter of the cylindrical grinding area by 50 to 110 microns , preferably by 80 microns, increases, ie that the cone shape is not visible to the naked eye. Nevertheless, in the processing of the inner surface of a cylinder bore already the desired technical effect in an advantageous manner.

The cone angle of the conical grinding area is - measured with respect to an axis parallel to the axis of rotation - preferably 0.014 ° to 0.039 °, particularly preferably 0.025 °.

Furthermore, it should be noted that it can be provided that the cylindrical and the conical grinding area uniform with the same Abrasive, preferably CBN, are occupied. It is therefore desirable in this case that the two grinding areas produce substantially the same grinding performance. In this context, it should be noted that the coating with the abrasive is favorably galvanic.

The embodiments defined in claims 12 to 15 enable a highly efficient cooling of the grinding tool or grinding tools, which also contributes to the fact that the inner surface of the cylinder bore can be machined very precisely.

A fundamental advantage of the grinding tool according to the invention or of the grinding tools of the set according to the invention is also that the machined material is removed very quickly from the grinding area.

As already mentioned protection is desired for use of a grinding tool according to claim 1 or one of claims 5 to 15, or one of the two grinding tools of the set according to one of claims 2 to 4 or 5 to 7 or 9 to 15 in a machining process of the inner surface of a Cylinder bore in a workpiece, wherein the grinding tool or the one of the two grinding tool of the set is introduced in the course of the machining process in the cylinder bore, is brought to the inner surface of the cylinder bore, at least once guided in a circle on the inner surface of the cylinder bore, wherein it rotated about its axis of rotation, is lifted from the inner surface of the cylinder bore and is led out of the cylinder bore again.

In addition, protection is desired for a CNC machine having at least one grinding tool according to the invention or at least one set according to the invention and a control program which is designed to automatically carry out the described machining process of the inner surface of a cylinder bore in a workpiece, ie at least one grinding tool or the first of the two grinding tools of the set and in a subsequent step to introduce the other of the two grinding tools of the set respectively in a cylinder bore in a workpiece to introduce it to the inner surface of the cylinder bore, at least once in a circle on the Run along the inner surface of the cylinder bore, wherein it rotates about its axis of rotation, to lift it from the inner surface of the cylinder bore and bring it out of the cylinder bore again.

Fig. 1

das Schleifwerkzeug gemäß einer bevorzugten Ausführungsform in einer perspektivischen Ansicht,

Fig. 2a und 2b

eine Querschnittsdarstellung des Schleifwerkzeugs in Längsrichtung,

Fig. 3

eine Querschnittsdarstellung durch den konischen Schleifbereich des Schleifwerkzeugs,

Fig. 4

die Kombination aus dem Schleifwerkzeug und einem HSK Adapter,

Fig. 5

eine Prinzipdarstellung zur Veranschaulichung des zylindrischen und sich daran axial anschließenden konischen Schleifbereichs,

Fig. 6a bis 6f

eine schematische Darstellung des Bearbeitungsprozesses der Innenfläche einer Zylinderbohrung in einem Werkstück mittels des erfindungsgemäßen Schleifwerkzeugs,

Fig. 7a und 7b

das erste Schleifwerkzeug des erfindungsgemäßen Sets in einer bevorzugten Ausführungsform, und zwar in einer Seitenansicht mit Adapter (Fig. 7a) und in einer Querschnittsdarstellung (Fig. 7b), und

Fig. 8a und 8b

das zweite Schleifwerkzeug des erfindungsgemäßen Sets in einer bevorzugten Ausführungsform, und zwar in einer Seitenansicht mit Adapter (Fig. 8a) und in einer Querschnittsdarstellung (Fig. 8b).

Further details and advantages of the present invention will be explained in more detail below with reference to the description of the figures with reference to the drawings. Show:

Fig. 1

the grinding tool according to a preferred embodiment in a perspective view,

Fig. 2a and 2b

a cross-sectional view of the grinding tool in the longitudinal direction,

Fig. 3

a cross-sectional view through the conical grinding region of the grinding tool,

Fig. 4

the combination of the grinding tool and a HSK adapter,

Fig. 5

a schematic representation of the cylindrical and axially adjacent conical grinding area,

Fig. 6a to 6f

a schematic representation of the machining process of the inner surface of a cylinder bore in a workpiece by means of the grinding tool according to the invention,

Fig. 7a and 7b

the first grinding tool of the set according to the invention in a preferred embodiment, in a side view with adapter ( Fig. 7a ) and in a cross-sectional representation ( Fig. 7b ), and

Fig. 8a and 8b

the second grinding tool of the set according to the invention in a preferred embodiment, in a side view with adapter ( Fig. 8a ) and in a cross-sectional representation ( Fig. 8b ).

In FIG. 1 the abrasive tool 1 according to the invention according to a preferred embodiment is shown schematically in a perspective view. It is essentially rotationally symmetrical about an axis of rotation 4 which extends in the longitudinal direction 26. The grinding tool 1 has a free end 14 and an opposite end 15 to which a fastening means 16 in the form of a flange for attachment of the grinding tool 1 to a machining head of a CNC machine or an adapter connected thereto (see. Fig. 4 ) is provided. In the mounting flange 16 six recesses 24 are provided for receiving screws offset by 60 °.

The grinding tool 1 has a base body 11 made of steel, which comprises the fastening flange 16, as well as a component protruding therefrom, on the lateral surface of which a cylindrical 5 and cylindrical conical grinding area 6 adjoining it with respect to the rotation axis 4 are arranged. In this case, the cylindrical grinding area 5 adjacent to the fastening means 16 and the conical grinding area 6 are arranged adjacent to the free end 14 of the grinding tool 1. The transition between cylindrical 5 and conical grinding area 6 is indicated by a dashed line. The cylindrical 5 and the conical grinding portion 6 are uniformly coated with the same abrasive, namely CBN (cubic drilled nitrite). The assignment is galvanic. In the work area a total of seven grooves 23 are arranged, which extend over the cylindrical 5 and conical grinding area 6 and substantially in the longitudinal direction 26 of the grinding tool 1. In these grooves 23 open channels 21, which have a diameter of 2 mm. A total of 42 such channels 21 are provided, wherein the channels 21st are arranged spirally, namely so that in each case two adjacent channels 21 are rotated by an angle of 50 ° and axially offset by 3 mm.

In the FIGS. 2a and 2b Cross-sectional views of the grinding tool along a central cutting plane parallel to the axis of rotation 4 and to the longitudinal direction 26. It shows FIG. 2a ) the section in a perspective view and FIG. 2b ) the same section viewed from a direction perpendicular to the cross-sectional plane.

It can be seen from these illustrations that the grinding tool 1 also has a central bore 18 parallel to the axis of rotation 4, the bore 18 having a diameter 19 of 12 mm and a length 20 of 170 mm. Between the bore 18 and the cylindrical 5 and the conical grinding region 6 extend the channels 21, which - as already described - open into the grooves 23. The bore 18, the channels 21, as well as the grooves 23 together form a coolant guide which enables a centrally fed coolant to be efficiently directed to the working area, i. to guide the cylindrical 5 and conical grinding area 6 and distribute there.

In the specific embodiment, the grinding tool 1 has the following dimensions: the cylindrical grinding area 5 has a diameter 8 of 65 mm. The diameter 7 of the conical grinding area 6 increases by 80 μm over the length 9 of the conical grinding area in the axial direction 26 relative to the diameter 8 of the cylindrical grinding area 5. Here, the cylindrical grinding portion 5 has a length 13 of 50 mm and the conical grinding portion 6 has a length 9 of 90 mm. The thickness of the cylindrical and the conical grinding area is 300 μm.

These dimensions are each adapted to the workpiece to be ground (engine block). It is important that the total length of cylindrical and conical grinding area at least the depth of Cylinder bore corresponds, so that the grinding process can be done in one step, without the grinding tool must be offset in the direction of the depth of the cylinder bore during the machining process.

FIG. 3 shows a further cross-sectional view of the grinding tool 1 along a plane in which one of the channels 21 between the central bore 18 and one of the grooves 23 extends.

In FIG. 4 the combination of a grinding tool 1 and a so-called HSK adapter 17 is shown, which makes it possible in a simple manner to attach the grinding tool 1 to a machining head of a CNC machine. The connection between the grinding tool 1 and the HSK adapter 17 via six screws 25 which are arranged in the recesses of the mounting flange 16 and engage in threads which are provided on the adapter 17. The CNC machine can be a conventional three-axis machine.

Since, on the grinding tool 1 according to the above-described embodiment, the geometry of the cylindrical 5 and of the adjoining conical grinding area 6 can not be seen with the naked eye, this geometry is shown in FIG FIG. 5 once more exaggerated: The effective grinding area is composed of a cylindrical grinding area 5 with a length 13 and a diameter 8 and an axially adjoining conical grinding area 6 with a length 9 and a diameter 7, starting from the cylindrical grinding area 5 in axial direction 26 relative to the diameter 8 of the cylindrical grinding area 7 increases. The total increase of the diameter 7 of the conical grinding area 6 at the free end 14 corresponds to twice the drawn distance 10. The cone angle of the conical grinding area 6 is provided with the reference numeral 32.

The sequence of FIGS. 6a) to 6f ) serves to illustrate an advantageous machining process of the inner surface 2 of a cylinder bore 3 in a workpiece, for example a motor block. Schematically represented are respectively the views perpendicular to the cylinder bore and that of the side, which is the side from which the grinding tool 1, 27 or 28 (see FIGS. 7a, 7b . 8a and 8b ) is inserted into the bore opposite. So look at the free end of the grinding tool 1, 27 or 28.

In a first step (transition from sub-figure a) to sub-figure b)), the grinding tool 1, 27 or 28 is inserted substantially centrally and with the cylindrical and / or conical grinding area in the cylinder bore 3. Subsequently, the grinding tool 1, 27 or 28 is brought to the inner surface 2 of the cylinder bore 3, which is shown in part figure c). Thereafter, the grinding tool 1, 27 or 28 is guided at least once in a circle along the inner surface 2 of the cylinder bore 3, wherein it rotates about its axis of rotation 4. It should be noted that the grinding tool 1, 27 or 28 can also be set in rotation before or after the actual grinding process.

After the grinding process, the grinding tool 1, 27 or 28 is lifted from the inner surface 2 of the cylinder bore 3 again, i. brought into an approximately central position with respect to the cylinder bore 3 (see Part Figure e)) and finally led out of the cylinder bore 3 (transition between the subfigures e) and f)).

In the subfigure d), arrows indicate a specific direction of movement of the grinding tool 1, 27 or 28 along the inner surface 2 of the cylinder bore 3 and a specific direction of rotation of the grinding tool 1, 27 or 28 about the axis of rotation 4. Basically, both directions of rotation are possible for these movements.

In general, it should be noted that this machining operation in the case of metallic workpieces both directly on the untreated surface and on a coated, e.g. LDS-coated, surface can be made. In this case, LDS stands for arc-wire spraying, which is a special plasma-phase coating process.

The FIGS. 7a, 7b . 8a and 8b show advantageous embodiments of the inventive set, wherein in the FIGS. 7a and 7b the first grinding tool 27 and in the FIGS. 8a and 8b the second grinding tool 28 is shown - in the FIGS. 7a and 8a each together with an adapter 17 which is connected to a fastening means 16 in the form of a flange.

The first grinding tool 27 has a cylindrical grinding area 5 with a diameter 8 that is cylindrical relative to the axis of rotation 4.

The second grinding tool 28 has a grinding area 6 conical with respect to the rotation axis 4, wherein the diameter 7 of the conical grinding area 6 increases in the axial direction 26 starting from a smallest diameter 29 which corresponds to the diameter 8 of the cylindrical grinding area 5 of the first grinding tool 27.

In addition, the second grinding tool 28 has a grinding agent-free region 30. This is cylindrical with respect to the axis of rotation 4 with a reduced by 3 mm with respect to the smallest diameter 29 of the conical grinding portion 6 diameter 31.

The length of the abrasive-free region 30 of the second grinding tool 28 corresponds to the length 13 of the cylindrical grinding region 5 of the first grinding tool 27.

The total length of the second grinding tool 28 corresponds to the total length of the grinding tool 1, which has both the cylindrical grinding area 5 and the conical grinding area 6.

Both the first grinding tool 27 and the second grinding tool 28 have a central bore 18, which in each case extends almost over the entire grinding tool 27 or 28. The lengths of the bore 18 is provided with the reference numerals 33 and 20, respectively.

As with the grinding tool 1, which has both the cylindrical grinding area 5 and the conical grinding area 6, the first grinding tool 27 and the second grinding tool 28 of the set have channels 21, which between the central bore 18 and the cylindrical grinding area 5 and the conical Grinding area 6 run. In the abrasive-free region 30 of the second grinding tool 28, no such channels 21 are provided.

Claims (17)

1. A grinding tool (1) for machining the inside surface (2) of a cylinder bore (3) in a workpiece, having an axis of rotation (4), wherein the grinding tool has a grinding region (5) which is cylindrical with respect to the axis of rotation and a conical grinding region (6) axially adjoining the cylindrical grinding region and the diameter (7) of the conical grinding region (6) increases starting from the cylindrical grinding region (5) in the axial direction (26) with respect to the diameter (8) of the cylindrical grinding region (5), characterized in that the grinding tool (1) has a free end (14) and an opposite end (15) and the conical grinding region (6) is arranged adjoining the free end (14) on the grinding tool (1), and provided at the opposite end (15) is a fixing means (16) for fixing the grinding tool (1) to a machining head of a CNC machine or an adaptor (17) connected thereto, preferably an HSK adaptor, wherein the fixing means (16) is preferably in the form of a flange.
2. A set comprising a first grinding tool (27) and a second grinding tool (28) for machining the inside surface (2) of a cylinder bore (3) in a workpiece, wherein the two grinding tools (27, 28) each have a respective axis of rotation (4), wherein the first grinding tool (27) has a grinding region (5) which is cylindrical with respect to the axis of rotation (4) and which is of a diameter (8) and the second grinding tool (28) has a grinding region (6) which is conical with respect to the axis of rotation (4), wherein the diameter (7) of the conical grinding region (6) increases in the axial direction starting from a smallest diameter (29) which corresponds to the diameter (8) of the cylindrical grinding region (5) of the first grinding tool (27), characterized in that the second grinding tool (28) of the set has a free end (14) and an opposite end (15) and the conical grinding region (6) is arranged adjoining the free end (14) on the second grinding tool (28) of the set, and provided at the opposite end (15) is a fixing means (16) for fixing the second grinding tool (28) of the set to a machining head of a CNC machine or an adaptor (17) connected thereto, preferably an HSK adaptor, wherein the fixing means (16) is preferably in the form of a flange.
3. The set pursuant to claim 2 wherein the second grinding tool (28) has a grinding agent-free region (30).
4. The set pursuant to claim 3 wherein the grinding agent-free region (30) is cylindrical with respect to the axis of rotation (4), preferably, and the grinding agent-free region (30) is of a diameter (31) which is reduced with respect to the smallest diameter (29) of the conical grinding region (6) by between 1 mm and 5 mm, preferably 3 mm.
5. The grinding tool (1) pursuant to claim 1 or the set pursuant to one of the claims 2 to 4 wherein the conical grinding region (6) has a taper angle (32) of between 0.014° and 0.039°, preferably 0.025°.
6. The grinding tool (1) pursuant to claim 1 or 5, or the set pursuant to one of the claims 2 to 4 or claim 5 wherein the cylindrical grinding region (5) is of a diameter (8) of between 60 and 70 mm, preferably 65 mm.
7. The grinding tool (1) pursuant to claim 1, 5 or 6, or the set pursuant to one of the claims 2 to 4 or claim 5 or claim 6 wherein the diameter (7) of the conical grinding region (6) increases in the axial direction (26) over the length of the conical grinding region (6) with respect to the diameter (8) of the cylindrical grinding region (5) by between 50 and 110 µm, preferably by 80 µm.
8. The grinding tool (1) pursuant to claim 1 or one of the claims 5 to 7 wherein the cylindrical grinding region (5) and the conical grinding region (6) are arranged on an integrally provided main body (11), the main body preferably comprising steel.
9. The grinding tool (1) pursuant to claim 1 or one of the claims 5 to 8, or the set pursuant to one of the claims 2 to 4 or claims 5 to 7 wherein the cylindrical grinding region (5) and the conical grinding region (6) are coated uniformly with the same grinding agent, preferably CBN.
10. The grinding tool (1) pursuant to claim 1 or one of the claims 5 to 9, or the set pursuant to one of the claims 2 to 4 or claims 5 to 7 or claim 9 wherein the cylindrical grinding region (5) and the conical grinding region (6) are of a thickness (12) of between 100 and 600 µm, preferably 300 µm.
11. The grinding tool (1) pursuant to claim 1 or one of the claims 5 to 10, or the set pursuant to one of the claims 2 to 4 or claims 5 to 7 or claim 9 or claim 10 wherein the cylindrical grinding region (5) is of a length (13) of between 40 and 60 mm, preferably 50 mm, and the conical grinding region (6) is of a length (9) of between 80 and 100 mm, preferably 90 mm.
12. The grinding tool (1) pursuant to claim 1 or one of the claims 5 to 11, or the set pursuant to one of the claims 2 to 4 or claims 5 to 7 or claims 9 to 11 wherein the grinding tool (1) or, respectively, the two grinding tools (27, 28) of the set have a central bore (18) parallel to the axis of rotation (4) wherein the bore (18) is preferably of a diameter (19) of between 10 and 14 mm, particularly preferably 12 mm, and/or are preferably of a length (20) of between 150 and 190 mm, particularly preferably 170 mm.
13. The grinding tool (1) pursuant to claim 12, or the set pursuant to claim 12 wherein a plurality of passages (21) are provided which are extending between the central bore (18) and the cylindrical grinding region (5) and the conical grinding region (6), wherein the passages (21) are preferably of a diameter (22) of between 1 and 3 mm, particularly preferably 2 mm..
14. The grinding tool (1) pursuant to claim 12 or 13, or the set pursuant claim 12 or 13 wherein the passages (21) are arranged in a spiral form, wherein each two adjacent passages (21) are rotated through an angle of between 40° and 60°, preferably 50°, and are axially displaced by between 2 and 4 mm, preferably 3 mm.
15. The grinding tool (1) pursuant to claim 1 or one of the claims 5 to 14, or the set pursuant to one of the claims 2 to 4 or 5 to 7 or 9 to 14 wherein provided in the cylindrical grinding region (5) and the conical grinding region (6) are grooves (23) which extend substantially in the longitudinal direction (26) of the grinding tool (1) or, respectively, the grinding tools (27, 28) of the set and into which the passages (21) open.
16. Use of a grinding tool (1) pursuant to claim 1 or one of the claims 5 to 15, or the set pursuant to one of the claims 2 to 4 or 5 to 7 or 9 to 15 in a machining process for the inside surface (2) of a cylinder bore (3) in a workpiece, wherein the grinding tool (1) or, respectively, at first one of the two grinding tools (27, 28) of the set and in a further step the other one of the two grinding tools (27, 28) in the course of the machining process is introduced into the cylinder bore (3), moved to the inside surface (2) of the cylinder bore (3), guided at least once in a circle along the inside surface (2) of the cylinder bore (3), in which case it rotates about its axis of rotation (4), is lifted off the inside surface (2) of the cylinder bore (3) and is again passed out of the cylinder bore (3).
17. The CNC machine having at least one grinding tool (1) pursuant to claim 1 or one of the claims 5 to 15, or at least one set pursuant to one of the claims 2 to 4 or 5 to 7 or 9 to 15 and a control program which is adapted to introduce the at least one grinding tool (1) or, respectively, each, at first one of the two grinding tools (27, 28) of the set and in a further step the other one of the two grinding tools (27, 28) into a cylinder bore (3) in a workpiece, move it to the inside surface (2) of the cylinder bore (3), guide it at least once in a circle along the inside surface (2) of the cylinder bore (3), in which case it rotates about its axis of rotation (4), lift it off the inside surface (2) of the cylinder bore (3) and move it out again of the cylinder bore (3).

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