Milling tool having an adjustable insert seat

A milling tool includes insert seats in which respective cutting inserts are disposed. Positioned in each seat is a wedge plate which is adjustable relative to the tool body in a direction of wedge adjustment. A cutting insert is supported on the wedge plate and secured directly to the tool body. The wedge plate is wedge shaped such that when the wedge plate is adjusted relative to both the tool body and the cutting insert, the cutting insert is displaced in a direction perpendicular to the direction of wedge adjustment.

This application is based on and claims priority under 37 U.S.C. § 119 with respect to Patent Application No. 103 40 493.7 filed in Germany on Sep. 3, 2003, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a milling tool which has at least one adjustably supported cutting insert.

In milling tools intended for performing particularly accurate machining operations, it is frequently a desideratum to adjust the position of the individual cutting inserts in such a manner that the cutting edges of a plurality of cutting inserts working on the same surface define a common plane upon rotation of the milling tool. For example, circumferentially spaced cutting edges disposed on the cylindrical outer periphery of a cylindrical miller or a disk miller should lie in the same cylindrical plane. Also, cutting edges which lie at an end face of the tool body should, as far as possible, lie in a common plane oriented perpendicular to the axis of rotation.

It is known to adjustably support cutting inserts on a tool body, for example, by means of adjustable cassettes, such as described in European Patent No. 0 499 280 B1. The adjustable cutting insert is supported in a respective, approximately square cassette. For receiving the cassette, the tool body is provided with a cassette seat having an inclined bottom surface. In case the cassette seat is arranged at an end face of a disk-shaped tool body (i.e., an end-face cassette seat), the cassette bottom is inclined toward the end face. If, however, the cassette seat is arranged at the outer periphery of the disk-shaped tool body (i.e., a peripheral cassette seat), the bottom of the cassette seat is inclined toward the tangent of the tool body. Shifting a cassette in an end-face cassette seat thus results in an axial adjustment of the cutting insert, whereas shifting a cassette in a peripheral cassette seat results in a radial adjustment of the cutting insert. The cassette is secured to the tool body by a fastening screw which may be released as required. A cassette shift is effected by a wedge which is pressed against a terminus of the cassette and is actuated by its own setscrew.

Cassettes have a substantial spatial requirement, as a result of which a minimum distance must be observed between consecutive cutting inserts. Such a requirement limits the number of teeth.

A large number of teeth is a significant consideration in developing efficient chip-breaking tools. On the other hand, a high machining precision is sought after, particularly as concerns surfaces which are exposed to finish-machining during the milling process. Also, as concerns a uniform wear of the cutting inserts and the cutting edges, an accurate setting of those cutting edges which do not participate in the finish-machining is desired, so that, as much as possible, all participating cutting inserts remove the same chip thickness.

It is accordingly an object of the invention to provide a milling tool having a large number of teeth and further having adjustable cutting inserts.

SUMMARY OF INVENTION

The above object is achieved with a milling tool which comprises a tool body in combination with at least one cutting insert mounted thereon. The tool body defines an axis of rotation and includes at least one insert seat on which the at least one insert is mounted. The at least one insert seat includes a wedge-plate seating surface. A wedge plate is disposed in the at least one insert seat and is adjustable relative to the body in a direction of wedge adjustment. The wedge plate includes a base surface movably disposed on the wedge-plate seating surface, and an insert seating surface on which the at least one insert is supported. The base surface and the insert seating surface form an acute angle therebetween as viewed in a direction perpendicular to the direction of wedge adjustment. A setting device operably engages the wedge plate and is arranged to move the wedge plate in the direction of wedge adjustment relative to both the insert and the wedge-plate seating surface for adjusting the insert in a direction of insert adjustment oriented substantially perpendicularly to the direction of wedge adjustment.

Another aspect of the invention pertains to the milling tool independent of the cutting inserts.

The milling tool according to the invention has a tool body on which a plurality of cutting inserts are supported. The cutting inserts are mounted preferably as lateral inserts or tangential inserts, that is, their securing bore is oriented either approximately in the axial direction (lateral insert) or in the radial direction (tangential insert). A wedge plate, shiftable transversely to the securing bore, is arranged between the base surface of the cutting insert, to which the securing bore of the cutting insert is perpendicularly oriented, and a wedge plate seating surface of the tool body. By shifting the wedge plate, the distance between the base surface of the cutting insert and the wedge plate seating surface, and thus the position of the cutting edge of the cutting insert may be changed. Thus, in case of tangential inserts a radial adjustment of the cutting inserts is effected, while in case of lateral cutting inserts an axial adjustment of the cutting inserts is carried out. The change of position of the cutting insert is limited to an adjustment in the direction of the securing bore. Otherwise the cutting insert remains in place relative to the tool body.

Only a small space is needed between consecutive cutting inserts for shifting the wedge plates. Consequently, the distance between the cutting inserts may be maintained very small, resulting in a large number of teeth. Supporting the lateral surfaces of the cutting inserts may be effected directly by cleats of the tool body.

A significant advantage of a cutting edge adjustment by means of wedge plates shiftable relative to cutting inserts and the tool body resides in a repetitive accuracy, for example, in case of inverting an invertible cutting insert: The cutting insert may be released from its seat and again mounted thereon without the need for a new adjustment. In case of sufficiently accurately manufactured cutting inserts even a replacement of a cutting insert may be effected without a new adjustment of the wedge plate. The concept of an adjustable wedge plate situated between the base surface of the cutting insert and the seating surface of the wedge plate and the otherwise direct engagement of the lateral surfaces of the cutting insert with the seating surfaces of the tool body result in a high degree of repetitive accuracy upon tightening the cutting inserts.

Advantageously, both the cutting insert and the wedge plate are provided with an opening through which a single tightening screw passes. The tightening screw clamps the cutting insert against the wedge plate and also clamps the latter against the wedge plate seating surface. An adjustment of the wedge plate may be effected only after the tightening screw has been slightly loosened. If the screw is tightened, both the cutting insert and the wedge plate are firmly clamped.

The wedge plate seating surface is inclined preferably a few degrees (for example, 1° to 10°) to an imaginary reference surface to which the securing bore is oriented perpendicularly and which extends parallel to the base surface of the cutting insert. The acute angle corresponds to the wedge angle of the wedge plate whose shift results in a height adjustment of the cutting insert. The range of adjustment of the cutting insert is preferably between 20 and 30 micron. If required, however, larger or smaller adjustment ranges may be set.

The base surface of the cutting insert and the seating surface of the wedge plate are preferably planar. If required, however, they may be provided with a profile, such as ribs or grooves, extending parallel to the adjusting direction of the wedge plate. Similar considerations apply to the base surface of the wedge plate and the wedge plate seating surface of the tool body. Planar surfaces are preferred because of the resulting uniform pressure distribution.

The engagement surfaces serving for a lateral support of the cutting insert are preferably directly formed on the tool body. Such an arrangement results, on the one hand, in a very rigid support of the cutting inserts and, on the other hand, in a small distance between inserts and thus in a large number of teeth.

The wedge plate is shifted preferably in a direction which is oriented parallel to the cutting edge to be adjusted. In this manner particularly small cutting insert distances may be achieved. As setting devices for a specified adjustment of the wedge plate, for example, differential threaded screws may be used which are positioned with one thread in the wedge plate and with another thread in the tool body. In case of unlike thread pitches, turning of the screw results in a shift of the wedge plate. The direction of shift is preferably transverse to the cutting insert. It is to be understood that a simple securing screw may be used instead which, upon tightening, can shift the wedge plate only in one direction. In the two cases noted above, the respective screw extends longitudinally to the wedge plate. It is furthermore feasible to orient the screw transversely to the wedge plate and, for example, to provide the screw with an eccentric head which shifts the wedge plate.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1illustrates a milling tool1which is formed as a disk miller and which has a large number of tangentially arranged cutting inserts2. The milling tool includes a disk-shaped tool body or base body3which is centrally provided with a securing device, such as a receiving bore4for accommodating a spindle. The cutting inserts2are arranged on the outer periphery of the tool body3in respective, identically structured insert seats5shown inFIGS. 2 to 6to which reference will be made below. The illustrated cutting insert2has a base surface6(FIG. 3), a top surface7essentially parallel to the base surface6and side surfaces8,9,10,11(FIG. 5). Between the side surface9and the top surface7a cutting edge12is formed which extends, for example, axially and whose radial distance from the axis of rotation is to be set. A securing bore13passes through the cutting insert2perpendicularly to the base surface6and the top surface7for receiving a securing screw14shown only as a dash-dot line15inFIG. 3.

Each insert seat5includes a recess having a wedge-plate seating surface19. Disposed in the insert seat is a wedge plate16which has a preferably planar seating surface17facing the cutting insert2. On the lower side of the wedge plate16a base surface18is formed which also is preferably planar and which lies against the wedge plate seating surface19.

As will be explained hereafter, the wedge plate16is axially adjustable, i.e., in a direction of wedge adjustment extending parallel to the tool's axis of rotation, (a right-left direction inFIG. 7). Such axial adjustment of the of the wedge plate produces an adjustment of the insert in a direction of insert adjustment oriented perpendicular to the direction of wedge adjustment (i.e., radially with reference to the axis of rotation, due to the particular configuration of the wedge plate described below). When viewing the wedge plate16in a direction perpendicular to the direction of wedge adjustment (i.e., when viewing the wedge plate16inFIG. 7), it can be seen that the seating surface17and the base surface18together form an acute angle of a few degrees, for example 3° The seating surface17is oriented preferably perpendicularly to the axis of the securing bore13, while the base surface18(and thus the wedge plate seating surface19), defines an angle other than 90°(i.e., it defines an oblique angle) with the axis of the securing bore13.

The wedge plate16is an overall flat plate whose thickness is less than the height of the cutting insert2. The wedge plate16serves only to provide for a height-adjustable seating surface for the cutting insert2. The wedge plate16, as may be well observed particularly inFIG. 4, its seating surface17supports the base surface6of the insert, whereas engagement surfaces21,22of the insert seat5support respective side surfaces of the insert. The wedge plate16and its seating surface17extend beyond the side surface9of the cutting insert2, whereby the seating surface17forms the bottom of a chip space23which adjoins, preferably in a stepless manner, a curved surface24of the tool body3.

The wedge plate16further has a throughgoing opening25formed as a slot as shown inFIG. 6. The long dimension of the opening25extends approximately parallel to the cutting edge12, that is, parallel to the adjusting direction of the wedge plate16. The securing screw14passes through the opening25and is screwed into a threaded bore26of the base body3.

For performing a specified shifting or adjusting the wedge plate16, a setting device27is provided which is arranged preferably underneath the chip space23, that is, externally of a wedge plate region which is firmly clamped by the tightening screw14. The setting device27comprises a tubular portion28which is an integral part of the wedge plate16and which is situated essentially externally of a region of the wedge plate covered by the cutting insert2. Stated differently, the wedge plate seating surface19has essentially the same size as the base surface6of the cutting insert2. As viewed in the tool's direction of rotation, indicated by the arrow P, disposed ahead of the wedge plate seating surface19is a groove-like recess which receives the tubular portion28with only a small play. Further, a setscrew29is held in the portion28which, for this purpose, is provided with a bore, for example, a threaded bore. In alignment with such a bore a further threaded bore31is formed in the tool body3for receiving the setscrew29. The thread in the portion28and the thread provided in the bore31preferably have different pitches. Likewise, the setscrew29has two threads whose pitches correspond to the pitches in portion28and the bore31, respectively. A rotation of the setscrew29thus effects an axial displacement of the wedge plate16.

A setting of the radial position of the cutting edge12and thus the radial setting of the cutting inserts2is effected as follows.

After providing the base body3with the cutting inserts2, the securing screws14are first slightly (that is, not too firmly) tightened. Thereafter the base body3is received in a measuring device, and the cutting inserts2are consecutively set as follows. The cutting edge12is sensed and its distance from the rotary axis determined. If such a distance deviates from a desired value, the setscrew29is turned in the appropriate direction for axially shifting the wedge plate16relative to the cutting insert2and the base body3. Shifting the wedge plate16to the left as viewed inFIG. 7adjusts the insert radially outwardly, resulting in an enlargement of the cutting radius, whereas shifting the wedge plate16to the right as viewed inFIG. 7causes a reduction of the cutting radius. When the desired value is reached, the securing screw14is firmly tightened. This process is repeated for each cutting insert2until the required accurate positioning of the cutting edges is reached, whereupon the milling tool1is ready for use. As may be seen inFIG. 1, the milling tool1is capable of a high chip breaking performance due to the small distances between the cutting inserts2. The distances between the cutting inserts2are less than the length of one cutting insert. The distances are determined solely by the size of the required chip spaces23and the minimum width of the cleats32which are formed on the base body3and which carry the engagement surfaces21. Thus, between two cutting inserts2there are situated only one chip space23and one cleat32.

The cutting inserts2are replaceably supported. For a replacement, merely the securing screws14need to be removed, whereupon the cutting inserts2may be exchanged. In case of a sufficiently accurate manufacture of the cutting inserts (for example, if they originate from the same batch), no new adjustment is necessary. In case the cutting inserts2are of the invertible type as shown inFIG. 8, their inversion is feasible without a new adjustment of the respective wedge plate16. The cutting insert2ofFIG. 8is an invertible cutting insert, whose lateral surfaces8,10have an identical inclination to the base surface6. The individual insert seats are radially adjusted after providing the base body3with the cutting inserts2, so that all cutting edges lie on the same diameter. In case the cutting edges are worn down, the securing screws14are released, and each cutting insert2is inverted in its seat and again tightened. A new adjustment is not needed, even if the individual cutting inserts2could not be replaced among one another without a new adjustment due to their manufacturing tolerances.

According to a simplified embodiment of the milling tool1, instead of the setscrew29having unlike threads (FIG. 6), a setscrew with only a single thread could be provided which passes through the tubular portion28with “play” and which is screwed into the threaded bore31. By tightening such a setscrew, an adjustment of the wedge plate16may be effected in one direction and such adjustment ends upon reaching the desired magnitude. A backward motion of the wedge plate16is possible only by fully releasing the securing screw14and by manually pushing back the wedge plate16. Such a simplified embodiment would be sufficient for almost all applications.

The present invention can also be employed to effect an axial adjustment of a cutting insert disposed on an end face of a milling tool. In that regard,FIG. 9illustrates a milling tool1awhere a cutting insert2formed as an axially adjustable lateral insert is provided. The insert seat5provided for such a cutting insert is disposed at the flat side (end face) of the base body3. The seat includes a wedge plate16for adjusting the height position (in this case the axial position) of the cutting insert2. In other aspects, reference is made to the foregoing description and the same reference numerals.

According to the earlier described embodiments the wedge plate16was adjusted by a setscrew29extending essentially parallel to the wedge and situated adjacent the wedge portion of the wedge plate. Alternatively, a setting device may be arranged in alignment ahead of or behind the wedge portion of the wedge plate16. According to the embodiment shown inFIG. 10, where parts or elements which are structurally or functionally identical to those as described earlier, are provided with the same reference numerals, the wedge plate16A is configured for a dovetail-type guidance. The direction of the thickness increase is again oriented transversely to the direction of motion and the cutting edge of the cutting insert (not shown). The direction of motion determined by the rotation of the base body3is indicated by an arrow33inFIG. 10. In the base body3, next to the dovetail shaped insert seat5A proper, a well34is formed into which projects an extension35of the wedge plate16. The extension35, which undercuts the lateral engagement surface22, is provided with a slot36oriented transversely to the adjusting direction37of the wedge. The slot36is associated with a setscrew29A provided with an eccentric head38. In the installed state the eccentric head38sits in the slot36and has a diameter which corresponds to the width of the slot36measured in the adjusting direction37. Turning the setscrew29thus causes a longitudinal adjustment of the wedge plate16in the direction37and thus a height adjustment of the seating surface17. The radial or axial position of the cutting insert is accordingly changed, dependent on whether the cutting insert is used as a tangential insert or a lateral insert.

In accordance with the invention there is provided a milling tool of good precision having a large number of teeth, includes insert seats5,5A whose seating surface17is formed on a wedge plate16,16A. The wedge plate is adjustable within the insert seat with respect to the tool body3and the cutting insert2. A securing screw14passes through the cutting insert2and the wedge plate and clamps them both against the tool body3. A setscrew29,29A serves for a specified adjustment of the wedge plate and thus for a height adjustment of the cutting insert2and its cutting edge12.