GB1597298A - Apparatus for stroke reversal in honing machines - Google Patents

Description

(54) APPARATUS FOR STROKE REVERSAL IN HONING MACHINES (71) We, NAGEL MASCHINEN UND WERKZEUGFABRIK GMBH, a German company of P.O. Box 508, 7440 Nuertingen, Federal Republic of Germany do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to apparatus for effecting stroke reversal in a honing machine having a honing spindle which can be moved backwards and forwards.

The reversal of the honing spindle stroke movement takes place conventionally by way of limit switches and stops the relative positions of which can be adjusted. The setting of these switches and stops must be made manually when the machine is set up.

A control by way of a machine programme is not possible and any intervention during machining is almost excluded.

An aim of the present invention is to create an apparatus of the kind mentioned initially which operates with great accuracy and makes possible easy adjustment and programming as well as good control capabilities, particularly in dependence upon measuring stations.

According to the present invention there is provided apparatus for effecting stroke reversal in a honing machine having a spindle which can be moved backwards and forwards, comprising a measuring station containing a measuring device for monitoring the shape of a workpiece, and adjusting means actuable by a regulating mechanism for adjusting the stroke threshold positions of the honing spindle in dependence upon workpiece shape information supplied to said regulating mechanism from said measuring station.

Due to the fact that the stroke path travelled is determined digitally and transmitted to the control mechanism, the error at all stroke lengths is constant and small and independent of any external interference value. By means of corresponding fine division of the digital counting the error can be reduced as desired without the costs of production or operation thereby being substantially increased.

A manual or -preprogrammable input device can be provided advantageously for setting the reversal count. The setting of upper and lower reversal points can thereby take place, for example, by way of digital adjusters. These may operate digitally but it is however also possible to operate with adjusting devices which operate in an analogue manner and whose value is then converted to a digital form. Accuracy does not suffer thereby because a digital control unit can be provided.

The setting of the reversal count can however also take place advantageously and automatically dependent upon measuring and control procedures. Just as for the connection of the control mechanism to a machine programme which is, for example, stored on magnetic tape, or the like, the digital form is especailly well suited for adaptation to measuring or regulating mechanisms which can operate digitally.

Thus the bore shape can, for example, be measured (deviation from, for example, the desired cylindrical shape) by means of a measuring station which can be disposed in front of, on or behind the honing machine and dependent thereupon the reversal count can be varied during operation in stages or continuously so that the error in shape can be corrected by differentially greater overrun of the honing tool at the bore ends.

The incremental/digital converter is preferably at least one contactless pulse generator which co-operates with a lined gauge rod which may be mounted on the honing spindle. The gauge rod can take any suitable form e.g. metal comb, optical line gauge etc. Two pulse generators are preferably provided whose signals are displaced relative to each other for the purposes of stroke direction recognition by an amount unequal to n x t/2 (n is a whole number; t = pitch or spacing between identical characteristics on the lined gauge).

The control mechanism preferably alters the set or input reversal count by a value which corresponds to the overrun of the honing spindle at the stroke end and is dependent upon the honing speed. An overrun of the honing spindle, i.e. the path between the initiation of reversal and the actual reversal in stroke direction, occurs particularly in hydraulic arrangement, and also in mechanical stroke drives. The overrun is thus dependent on the honing speed.

The control mechanism is in accordance with the feature described, set up for the purpose of determining the overrun in each case automatically from the stroke speed, which it preferably determines itself from the signals of the incremental/digital converter. The control mechanism then introduces the reversal at a count value which lies above or below the adjusted or input value by the corresponding overrun-count value.

Due to inaccuracies in the shape of the workpiece to be machined, for example the workpiece bore which is to be honed, or due to inaccuracies in the tool (for example due to uneven wear) errors in shape often occur in the case of finished machined workpieces which have a disadvantageous effect on the characteristics of the machined workpiece.

In some cases, however, a certain shape is deliberately to be produced which deviates from that of a cylinder. In each case it is difficult in practice to meet these requirements and maintain them dependent upon the characteristics of the tool and the material characteristics of the workpiece.

In accordance with a particularly preferred feature of the present invention the measuring station contains a measuring device for measuring the shape of the workpiece and an adjusting device, which can be actuated by the regulating mechanism dependent upon the shape of the workpiece, is provided for adjusting the stroke threshold positions of the honing spindle, i.e. for adjusting the limit positions of the spindle.

If the measuring station is a remeasuring station, i.e. located downstream of the honing machine, account is automatically taken of both an error in shape during the rough work as well as an error in the shape of the tool and in each case this error is compensated for in the next workpiece.

Since it is to be assumed that the rough work on the workpieces is also performed on automatic machines and thus the errors in successive workpieces happen to be identic al, a complete elimination of errors in shape can therefore take place. In any case this is always so when the honing machine is part of an automatic production line.

It is however also possible that the measuring station is a premeasuring station, i.e. located upstream of the honing machine, which thus measures the shape of the workpiece surface which has yet to be machined. This embodiment is advantageous if it is not certain that the workpieces fed to the honing machine all have the same error in shape. A solution which is more expensive but which takes into account all the facts is the one which includes both a pre- and a remeasuring station where account is then also taken of the remaining influences, especially those originating from the inaccuracy of shape of the honing tool, which errors cannot be taken into account automatically by means of one premeasuring station alone.

It would also be possible to operate using a measuring station which measures the shape of the workpiece during machining or during pauses in machining. Here account could be taken of all erroneous influences, but this arrangement is difficult and the pauses in honing required for the measurement extend the operating time. Ideally this solution can however be employed if the honing tool itself contains a measuring mechanism.

The overrun of the honing tool beyond the workpiece surface which is too be machined, can be adjusted preferably by means of the regulating mechanism and the adjusting device. Whilst, for example, in the case of a cylindrical bore and cylindrical tool, i.e. without any error in shape, an overrun of approx. 1/3 of the honing tool length on each side gives the best results in the majority of cases, the overrun can be reduced in the case of a bore which broadens out towards the edge, whilst it can be enlarged in the case of a bore which narrows in towards the edge. Let it be noted here that by means of the honing machine in accordance with the present invention not only errors in shape with respect to the cylindricality of the workpieces can be removed but also deviations in shape can be deliberately produced, for example, a slight taper, barrel shape or the like. Furthermore the invention can be used in internal honing machines (for bores) and external honing machines (for external diameters).

If the readjustment of the overrun of the honing tool is not sufficient to achieve the desired shape of the workpiece, then in an advantageous development of the present invention the regulating mechanism can be constructed for the purposes of initiating short strokes at the bore ends dependent upon the size of the deviation from the desired shape of the workpiece. Mention has already been made of the fact that manual or preprogrammed adjustment of short strokes at bore ends has already become known from German Patent Specification No. 1 963 233. In accordance with the present advantageous feature, however, the short strokes can be regulated in their stroke length and/or stroke count or duration dependent upon the measurement.

The measuring mechanism which preferably operates pneumatically but can also do so electrically or mechanically, preferably possesses several measuring points axially spaced apart from each other. It is, however, also possible to move the measuring tool during measurement along the workpiece axis and to determine the variation in the measuring value during this measuring stroke. In this case it would be possible to manage with, for example, one measuring point.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows, in part in a block diagram, a honing machine and its stroke control unit, constructed according to the present invention; Fig. 2 shows a diagrammatic representation of a honing machine having a remeasuring station and the associated regulating mechanisms, in the form of block circuit diagrams; and Fig. 3 shows a representation in accordance with Fig. 2 of a honing machine having a premeasuring station.

Fig. 1 shows diagrammatically a honing machine 11 having a honing spindle 12 which can be moved upwards and downwards by means of a hydraulic stroke drive 13. The honing spindle 12 is also driven rotatably in a conventional manner by a rotary drive 18. The honing spindle carries a honing tool 14 which, in the example shown, machines the bore 15 of a workpiece 16.

An incremental/digital converter 17 for the stroke movement of the honing spindle is connected to the honing spindle. In the present embodiment the converter 17 comprises two pulse generators 19 which are constructed as contactless proximity switches and which co-operate with a lined gauge rod 20 which in the present embodiment is mounted on the honing spindle. This lined gauge rod is a part which is arranged longitudinally of the stroke path and has an alternately varying characteristic, such variations preferably being abrupt. The nature of the gauge rod is dependent on the nature of the pulse generator. The gauge rod can, for example, comprise a metal comb which co-operates with inductive sensors, an optical line gauge, which cooperates with optical or infra-red sensors, a gauge coated with ferromagnetic stripes, which co-operate with magnetic heads, or - the like. It is also possible, dependent on the design of the machine, to mount the pulse generators on the honing spindle and the gauge rod on a fixed part of the machine.

The gauge has a pitch t, which determines the accuracy of the stroke reversal.

A limit switch 21 of any suitable design is also provided for triggering a switching pulse at one end of the stroke spindle movement.

In the embodiment shown, a measuring station 22 is also provided and contains a measuring tool 23 and a measuring device 24. The measuring device 24 is designed to measure the shape of the workpiece, and for this purpose the measuring tool 23 operates, for example, pneumatically and possesses several (e.g. three) pairs of measuring noz zles which lie one after the other in the axial driection of the bore and measure a devia tion of the bore 15 from the desired shape (for example a cylindrical shape). A devia tion, however, from a preset conical, barrel shape or the like can also be measured. This measuring tool 23 is, in the embodiment shown, disposed below the bore and accor dingly measures the bore shape either be fore or after machining or during pauses in operation. Here however, a pre- or re measuring station can also be provided.

The hydraulic stroke drive 13 is controlled by a hydraulic control device 115 having solenoid valves 25 and 26 for the upward and downward stroke and its relay coils 27, 28 are controlled by a control device 30.

The control device 30 is a digitally operat ing electronic device having the basic design and function described hereinbelow: The two pulse generators 19 are disposed opposite the lined gauge rod 20 so that a directional recognition for the stroke move ment is possible. They can thus be displaced or out of phase with respect to each other by any amount which is not equal to a multiple of the half pitch t/2. The phase displacement is preferably t/4. Thereby it is of course also possible to use two lined gauge rods offset or out of phase with respect to each other in place of or in addition to the phase displace ment of the pulse generators. One should further note concerning the incremental/ digital converter 17 that it is constructed preferably so that the resolution is equal to half the pitch in that the pulse generators respond to every change in condition.

The signals of the pulse generators 19 are fed to a phase-dependent pulse evaluation circuit 31 which feeds the counting pulses and the counting direction further to a forward/backward counter 32. This controls a digital display 33 from which can be read (actual display) therefore in each case the stroke position of the honing spindle, with out inertia and digitally, for example in millimetre steps.

A determination device for the stroke speed 34, for example, a differentiator, also obtaines its signals from the main counter.

The stroke speed in each case and/or the mean speed is indicated on a display 35. An overrun-correction calculator 36 determines therefrom a speed-dependent correction of the reversal point or the reversal count.

The stroke drive of the honing spindle, whether it be hydraulic or mechanical, does not operate in an inertialess manner, i.e. a certain time elapses and thus a certain stroke path takes place between the reversal signal and the actual reversal point. Because of the mass inertia this overrun is speeddependent and thus increases with the speed of the stroke movement. The corresponding correction value is determined in the correction calculator 36 and fed to a desired values store 37. All the inputs for the upper and lower reversal points are fed thereto, including those from a manual input 38 which contains a keyboard 39 and a digital display for the upper and lower reversal point, i.e.

the reversal count. An input 40 for the length, position, count and possibly periodicity of a short stroke honing is also provided. The principle of short stroke honing is explained in greater detail in German Patent Specification No. 963233. It is employed not only for honing bores having internal restrictions or blind bores but also for equalising deviations from the cylindrical shape or for deliberately producing them. The keyboard of the input 40 can be replaced by the keyboard 39, the latter being connected differently only for the input of the short stroke honing values.

The control device and particularly the two inputs 38 and 40 can be connected to a programme input device 41 by means of which, data which is stored for example on magnetic tape and which relates to reversal points and any possible short honing, is fed in. The desired values store 37 is also connected to a regulating device 42 which determines the reversal and/or short stroke data dependent upon the indication of the measuring device 24 which measures the shape of the workpiece 16. The inputs determine in each case the upper and lower reversal points as well as the short stroke data at the lower and upper reversal points.

The control device 30 also contains a comparator 44 which compares the actual value from the counter 32 with the desired value in each case from the desired value store 37 and when the digital values agree transmits a control signal to a signal amplifier and converter 45 which actuates the relay coils 27, 28 and thus the solenoid valves 25 and 26 for the stroke reversal. An operating- and switch board 46 is associated with the signal amplifier and converter 45, by means of which board 46 the other operating functions can be controlled either manually or in a preprogrammed manner, (for example, setting the honing machine in operation, moving the honing tool into and out of the workpiece or the like).

The device 30 also contains advantageously a determination device 47 for the overcutting angle of the honing tracks which is important for the characteristics of the workpiece surface (oil retaining ability etc.).

This overcutting angle is related to the pitch angle of the path of travel of the individual honing stones and such pitch angle, is determined, dependently upon the stroke speed (from the corresponding differentiator 35) and an input 48 for the rotational speed of the honing tool, as a quotient and is indicated on a display device 49.

The apparatus shown in Fig. 1 operates in the following manner. After the honing tool has been moved into the workpiece bore 15 the stroke drive is driven by the hydraulic pump 50. Previously upper and lower reversal points were set, for example, manually at the input 38. The incremental/digital converter 17 now determines, whilst recognising the direction, by means of the phasedependent pulse evaluation circuit 31, the actual digital value in each case of the stroke position of the honing spindle, which value is indicated on the digital display 33.

Moreover the stroke speed and the associated overrun correction value are determined by way of the components 34 and 36 and are transmitted to the desired value store 37 where these values are subtracted from or added to the upper and lower reversal counting value. When the counting values in the counter 32 and in the desired value store 37 agree, the comparator 44 transmits the reversal signal by way of the signal amplifier 45 and the stroke direction is reversed. The limit switch 21 serves the purpose of setting the counter 32 at one extreme stroke position, for example the maximum upper stroke position, to the value zero in order to have an unambiguous starting value.

If the input 40 for short honing is actuated simultaneously then instead of a backwards and forwards movement between the two extreme reversal points a short stroke value of a certain preset length is transmitted to the desired value store 37 so that the short stoke then moves in the region of the lower reversal point, without however exceeding it. All these functions can, as has already been noted, also be fed in by way of programme input 41 and/or dependent on regulating procedures by way of the regulating mechanism 42. The overrun correction 36 also operates during short stroke honing.

A particular advantage of the present invention is that the overrun in each case of the honing tool beyond the end of the bore can be easily altered automatically dependent upon the measurement of the bore shape by means of the regulating mechanism.

The determination of the overcutting angle by means of the device 47 offers the advantage that a regulation of the overcutting angle can take place by means of a correction of the stroke speed and/or speed of the honing tool.

Fig. 2 shows diagrammatically a honing machine 11 whose honing spindle 12 carries a honing tool 14 at its lower end. The honing spindle is rotably driven and possesses an expanding mechanism, which is not shown, for the honing tool 14. A hydraulic cylinder 13 provides the axial stroke movement of the honing spindle.

The hydraulic cylinder 13 is supplied with hydraulic fluid and controlled by a control mechanism 115. The reversal of the hydraulic cylinder 13 is controlled by a control mechanism 30a which corresponds to that in Fig. 1.

The workpieces 16a which are to be machined, or have been machined, are automatically moved past the honing machine gradually in the direction of conveying 123 (from left to right), the honing machine 11 in this case, being part of an automatic operating process. In the embodiment shown, a remeasuring station 22a is located downstream of the honing machine, i.e. one conveying step after the machining position, and contains a measuring tool 23a, similar to that in Fig. 1, which can be moved into the bore 15, the measuring tool 23a being constructed for the purpose of generating signals which represent the shape of the bore 15. In addition to a display device 127 for the three diameters the signals of the pneumatic measuring device are fed to a regulating mechanism 42 which is connected to control mechanism 30a corresponding to that in Fig. 1. The signals of the measuring station are converted into signals which alter the stroke threshold positions by means of a programme which is fed in by way of a programme input 41.

The honing machine in Fig. 2 operates in accordance with the following method: Let it be assumed that the workpiece 16a prior to machining has a widened portion in the direction of the two bore ends or a constriction in the centre, as is shown in a highly exaggerated manner. In practice errors in shape are of the order of magnitude of hundredths, at most tenths of a millimetre.

If an error in shape occurs during machining then, for example, the central of the three measuring jets of the measuring tool 23a detects a somewhat smaller diameter than the two outer measuring jets. This value is fed by way of the regulating mechanism 42 to the control mechanism 30a which generates in its evaluation and calculating device an output signal by means of the programme which has been fed in, which signal actuates the control device 115.

The stroke threshold position of the honing tool 13 is thus altered. Up to this point the reversal of the honing tool took place with a normal overrun of about one third of the honing tool length. Now the honing tool reverses at an overrun of, for example, one quarter of the honing tool length, the overrun being to the same extent at each end of the tool movement, this being necessary in order to obtain uniform widening at both ends of the workpiece bore.

In the event that the error in shape is not removed by the first adjustment and displacement of the tool then during the next remeasuring a small error in shape of the same tendency is detected and the adjusting device is further readjusted in the same direction. The same occurs if the error in the shape of the crude workpiece or of the tool is aggravated in the same direction.

If the error in shape is however removed by the alteration in the stroke threshold position (state shown in Fig. 2) then the measuring station 25 no longer measures any error in shape and the present state is retained, i.e. in the present case the overrun remains only slightly adjusted. In a manner of speaking the correction associated with the error is thereby stored. Alternatively, if the error in the crude workpiece or the tool is reduced and an error in shape is detected by the remeasuring station 22a, which is so small that it lies far below the tolerances and is barrel-shaped, the regulating circuit then shifts the limit switches away from each other to thus produce an enlargement of the stroke and the overrun of the workpiece.

In mass-production operations the fact that a slight error must always first appear at the remeasuring station before it can be corrected for the following workpieces, is in practice of no importance. The measuring tools operate so accurately that the workpieces are still always within the required tolerances. If desired, the first workpiece, which in any case even in other operating methods, would be purely a test workpiece, could have larger than normally expected, deviations in desired dimensions. It is however, also possible to provide instead of a remeasuring station, a measuring station 22 as per Fig. 1, which measures the workpiece directly during machining or during the pauses therein. In this embodiment no finished machined workpiece need have even only the smallest inaccuracy of shape.

The measurement in this case could, for example, take place during the short pauses in machining from the side remote from the honing spindle.

Whilst in the embodiment in Fig. 1, the regulated position of the upper and lower reversal points remains constant, in this embodiment the stroke threshold position however can be altered in each case dependent upon, amongst other factors, the measurement which is to be undertaken several times during machining, in order to be able to achieve greater accuracy of shape.

Let it also be noted that the programme which forms the basis of the calculating device does not have to definitely be altered for every workpiece or every kind of tool.

The calculating device will convert only the signals from the evaluation device with the following meaning. "The stroke is to be lengthened at the end at which there is a constriction" and "the stroke is to be shortened at the end where there is a widened portion". This can happen symmetrically (Fig. 2) or also assymmetrically (Fig. 3). The programme input serves only to readjust the sensitivity in order to arrive at an optimum result in as few operating steps as possible. This is dependent on the workpiece and on the kind and size of the tool. Moreover the basic adjustment of the stroke threshold positions for each workpiece can be undertaken by way of the programme input.

The same reference numerals are also used in the embodiment in Fig. 3 for the same parts. The honing machine 11b comprises a mechanical stroke drive 13b in place of the hydraulic stroke drive 13. The mechanical stroke drive 13b has a motor which is fed by an electrical control device 115b. The adjusting device 17b operates by means of a pulse generator 19b, located on the honing spindle, the pulse generator 19b cooperating with an elongate gauge 20b which is comb-shaped to transmit a pulse when it moves past each of the teeth of the gauge, which pulse is fed to the control mechanism 30 which is constructed as per Fig. 1.

In the present case the measuring station 22b is a pre-measuring station. The measuring tool 23b can be a per se known electric measuring tool which is moved into the bore in the workpiece by a drive in the measuring mechanism 24b and is moved through up to its end. Whilst it is being moved through the bore several measurements can be taken either continuously or at certain points so that the one measuring tool delivers the required measuring values one after the other to establish the inaccuracy of shape.

Thus a separate measuring tool does not therefore need to be available for each length of bore 15b. The signals of the measuring station 22b are fed by way of the regulating mechanism 42 to the control mechanism 30.

The manner of operation of the embodiment in Fig. 3 is distinguished from that in Fig. 2 as follows: In the embodiment shown in Fig. 3, the measuring tool 23b detects a downwards conical constriction on the workpiece 16b which is to be machined. Accordingly the digital values for the stroke threshold lengths, which are fed into the regulating mechanism, are altered by way of the regulating mechanism 42 described in such a manner that the stroke threshold position is displaced downwards. The honing tool is thereby moved further at every stroke from the lower narrower bore end than from the upper end so that a greater amount of material is removed at the lower bore end.

If an inaccuracy of shape is detected above a certain threshold value, then the short strokes at the lower bore end are initiated by the regulating mechanism. The stroke of the honing tool 17 is thereby limited to the region of the lower bore end. A series of short strokes can be initiated dependent on requirements in the course of one or more maching operations and the short strokes can be advantageously of differing length.

Thus a series of short strokes in the vicinity of the lower bore end can, for example, come to an end by their bcoming increasingly longer until they have once again reached the length of the normal stroke.

WHAT WE CLAIM IS: 1. Apparatus for effecting stroke reversal in a honing machine having a spindle which can be moved backwards and forwards, comprising a measuring station containing a measuring device for monitoring the shape of a workpiece, and adjusting means actuable by a regulating mechanism for adjusting the stroke threshold positions of the honing spindle in dependence upon workpiece shape information supplied to said regulating mechanism from said measuring stat

Claims (22)

**WARNING** start of CLMS field may overlap end of DESC **. in machining from the side remote from the honing spindle. Whilst in the embodiment in Fig. 1, the regulated position of the upper and lower reversal points remains constant, in this embodiment the stroke threshold position however can be altered in each case dependent upon, amongst other factors, the measurement which is to be undertaken several times during machining, in order to be able to achieve greater accuracy of shape. Let it also be noted that the programme which forms the basis of the calculating device does not have to definitely be altered for every workpiece or every kind of tool. The calculating device will convert only the signals from the evaluation device with the following meaning. "The stroke is to be lengthened at the end at which there is a constriction" and "the stroke is to be shortened at the end where there is a widened portion". This can happen symmetrically (Fig. 2) or also assymmetrically (Fig. 3). The programme input serves only to readjust the sensitivity in order to arrive at an optimum result in as few operating steps as possible. This is dependent on the workpiece and on the kind and size of the tool. Moreover the basic adjustment of the stroke threshold positions for each workpiece can be undertaken by way of the programme input. The same reference numerals are also used in the embodiment in Fig. 3 for the same parts. The honing machine 11b comprises a mechanical stroke drive 13b in place of the hydraulic stroke drive 13. The mechanical stroke drive 13b has a motor which is fed by an electrical control device 115b. The adjusting device 17b operates by means of a pulse generator 19b, located on the honing spindle, the pulse generator 19b cooperating with an elongate gauge 20b which is comb-shaped to transmit a pulse when it moves past each of the teeth of the gauge, which pulse is fed to the control mechanism 30 which is constructed as per Fig. 1. In the present case the measuring station 22b is a pre-measuring station. The measuring tool 23b can be a per se known electric measuring tool which is moved into the bore in the workpiece by a drive in the measuring mechanism 24b and is moved through up to its end. Whilst it is being moved through the bore several measurements can be taken either continuously or at certain points so that the one measuring tool delivers the required measuring values one after the other to establish the inaccuracy of shape. Thus a separate measuring tool does not therefore need to be available for each length of bore 15b. The signals of the measuring station 22b are fed by way of the regulating mechanism 42 to the control mechanism 30. The manner of operation of the embodiment in Fig. 3 is distinguished from that in Fig. 2 as follows: In the embodiment shown in Fig. 3, the measuring tool 23b detects a downwards conical constriction on the workpiece 16b which is to be machined. Accordingly the digital values for the stroke threshold lengths, which are fed into the regulating mechanism, are altered by way of the regulating mechanism 42 described in such a manner that the stroke threshold position is displaced downwards. The honing tool is thereby moved further at every stroke from the lower narrower bore end than from the upper end so that a greater amount of material is removed at the lower bore end. If an inaccuracy of shape is detected above a certain threshold value, then the short strokes at the lower bore end are initiated by the regulating mechanism. The stroke of the honing tool 17 is thereby limited to the region of the lower bore end. A series of short strokes can be initiated dependent on requirements in the course of one or more maching operations and the short strokes can be advantageously of differing length. Thus a series of short strokes in the vicinity of the lower bore end can, for example, come to an end by their bcoming increasingly longer until they have once again reached the length of the normal stroke. WHAT WE CLAIM IS:

1. Apparatus for effecting stroke reversal in a honing machine having a spindle which can be moved backwards and forwards, comprising a measuring station containing a measuring device for monitoring the shape of a workpiece, and adjusting means actuable by a regulating mechanism for adjusting the stroke threshold positions of the honing spindle in dependence upon workpiece shape information supplied to said regulating mechanism from said measuring station.

2. Apparatus as claimed in claim 1, in which the two stroke threshold positions can be altered independently of each other.

3. 3. Apparatus as claimed in claim 1 or 2, in which the stroke threshold positions can be altered during a machining process.

4. Apparatus as claimed in any one of claims 1 to 3, comprising an incremental/ digital converter which transmits the stroke path travelled by the honing spindle in digital form to a control mechanism arranged to trigger the stroke reversal at a preset upper and lower reversal count.

5. Apparatus as claimed in any one of claims 1 to 4, in which the measuring station is a remeasuring station.

6. Apparatus as claimed in any one of claims 1 to 4, in which the measuring station is a remeasuring station.

7. Apparatus as claimed in any one of

claims 1 to 4, in which the measuring station is disposed in the vicinity of the honing tool and measures the shape of the workpiece at the site where it is machined.

8. Apparatus as claimed in any one of claims 1 to 7, in which the overrun of the honing tool beyond the workpiece surface to be machined, can be adjusted by means of the regulating mechanism and the control mechanism.

9. Apparatus as claimed in any one of claims 1 to 7, in which the measuring device for measuring the shape of the workpiece, has several measuring points spaced axially from one another.

10. Apparatus as claimed in any one of claims 1 to 7, in which the measuring device operates pneumatically.

11. Apparatus as claimed in claim 4, in which a manual or preprogrammable device is provided for setting the desired reversal count.

12. Apparatus as claimed in claim 4 or claim 11, in which the setting of the reversal count takes place automatically dependent upon measuring or regulating procedures.

13. Apparatus as claimed in claim 4, claim 11 or claim 12, in which the in cremental/digital converter contains at least one contactless pulse generator arranged to cooperate with a part which alternately alters its characteristics periodically along the honing spindle stroke movement.

14. Apparatus as claimed in claim 13, in which two pulse generators are provided whose signals, for the purposes of stroke direction recognition, are displaced relative to each other by an amount which is not equal to n x t/2(n is a whole number; t = interval between identical characteristics of said part).

15. Apparatus as claimed in claim 14, in which the displacement is t/4.

16. Apparatus as claimed in claim 4 or in any one of claims 11 to 15, in which the control mechanism alters the adjusted or input reversal count by a value which corresponds to the overrun of the honing spindle at the stroke end and is dependent upon the stroke speed.

17. Apparatus as claimed in claim 16, in which the control mechanism determines the stroke speed from the signals of the incremental/digital converter.

18. Apparatus as claimed in claim 4 or in any one of claims 11 to 17, in which the control mechanism contains a short stroke honing device which initiates a short honing procedure in the region of at least one of the bore ends at a signal which is fed in manually by a program or by said regulating mechanism.

19. Apparatus as claimed in claim 18, in which the length of the short honing stroke can be altered with regard to time and, if desired, dependent upon the measuring value of the measuring device.

20. Apparatus as claimed in claim 4 or in any one of claims 11 to 19, in which a stroke speed display is connected to the control mechanism.

21. Apparatus as claimed in claim 4 or in any one of claims 11 to 20, in which a display for the overcutting angle of the honing tracks is connected to the control mechanism.

22. Apparatus for effecting stroke reversal in a honing machine having a honing spindle which can move backwards and forwards, constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.