Abstract:
The invention relates to a cutting insert having two working surfaces facing away from each other and having a through hole extending between the working surfaces for receiving a fastening bolt, having a peripheral cutter rim having a cutting edge on each working surface and a central recess surrounded annularly by the cutter rim, having a number of segment-like molded parts corresponding to the number of different cutter positions of a working surface, for positioning the cutting insert in the corresponding cutting position.

Description:
BACKGROUND OF THE INVENTION 
     a) Field of the Invention 
     The present invention relates to an indexable cutting insert, an insert seat for an indexable cutting insert and a cutting tool having an insert seat and an indexable cutting insert. 
     b) Description of the Related Art 
     Such indexable cutting inserts can be of one-sided or double-sided design. In a one-sided indexable cutting insert, as is known, for example, from WO 2007/127109 A1, a main face of the indexable cutting insert is configured as a working surface. The working surface has a plurality of cutting edges at its rim. If the effective cutting edge has become worn after a predetermined number of machining operations, the cutting insert is rotated in the insert seat, such that the next lip is used. Such indexable cutting inserts can be designed to be, for example, triangular, square or hexagonal and then correspondingly have three, four or six lips, which are used one after the other. 
     As a further embodiment, double-sided indexable cutting inserts are known, for example from WO 2007/037733 A1. In these indexable cutting inserts, both insert surfaces are designed as working surfaces and each have cutting edges at their rims. During the machining, first of all the one working surface forms the active machining surface, while the surface facing away from this machining surface is inactive and rests on the supporting surface of the insert seat. First of all, in these indexable cutting inserts, the cutting edges of the active machining surface become worn one after the other as in a one-sided indexable cutting insert. If the lips of the active machining surface have become worn, the indexable cutting insert is rotated by 180° in the insert seat, such that the worn machining surface rests on the supporting surface and the inactive surface resting previously on the supporting surface becomes the active machining surface. The cutting edges of this active machining surface also become worn one after the other. 
     Finally, a further double-sided indexable cutting insert is known from WO 2007/104275 A1. This cutting insert has a lip rim having a positive rake angle, said lip rim adjoining the cutting edge. Adjoining the lip rim is a falling surface which extends conically about the central through-hole. The advantage of this indexable cutting insert lies in the fact that inaccuracies when tightening the fastening bolt can be compensated for by the conical region. 
     With such double-sided indexable cutting inserts there is the problem of configuring the insert seat in such a way that the indexable cutting insert rests securely and fixedly in the insert seat and can be securely clamped there, but without damaging the cutting edges facing the supporting surface or those regions of the inactive working surface of the indexable cutting insert which are near the lip, said working surface facing the supporting surface of the insert seat. In particular, it is desirable to be as free as possible with regard to the configuration of the geometry of the cutting edges and of the chip breakers. 
     The object of the present invention is therefore to design an indexable cutting insert which can be positioned and clamped in the insert seat in an effective and dimensionally accurate manner and whose lip geometry and whose regions near the lip can be designed as freely as possible and so as to be adapted to the respective application. 
     SUMMARY OF THE INVENTION 
     The indexable cutting insert according to the invention first of all has a circumferential lip rim. A cutting edge is formed on the lip rim. In addition, the lip rim can have chip breakers or similar cutting aids. 
     A hollow is provided inside the circumferential lip rim. This hollow is provided with a number of segment-like molded bodies corresponding to the number of the different cutting positions of a working surface. Finally, a through-hole passes through the working surface. A fastening bolt, preferably a fastening screw, with which the indexable cutting insert can be fixed and clamped to the tool in the insert seat, can be inserted into the through-hole. The indexable cutting insert according to the invention has two working surfaces, facing away from one another, of the type mentioned at the beginning on the main faces of its parent body. 
     The molded bodies can be designed, on the one hand, as hollow bodies, that is to say as recesses, and, on the other hand, as solids, that is to say as projections. They thus form a negative or positive relief. Corresponding molded body receptacles designed to be at least partly complementary to the molded bodies must be provided on the insert seat. For example, it is possible to configure the molded bodies as prismatic projections. It then suffices to provide corresponding walls on the insert seat, and side walls of the prismatic projections bear against said walls in order to securely position the indexable cutting insert in its respective cutting position. The molded bodies then serve solely for the positioning and as a supporting surface of the indexable cutting insert, such that the actual lips can be designed completely independently of these positioning aids. 
     It is advantageous for each of the molded bodies to be of identical configuration and to attach them like a relief ring to the surface of the hollow. In this way, the molded bodies arranged next to one another form a structure like a spur gear which has a constant pitch. If a molded body adjacent to a molded body in engagement with the molded body receptacle is brought into engagement with the molded body receptacle, the indexable cutting insert is indexed, as it were, by one pitch interval and thus the next lip is activated. 
     As already stated, it is possible with the invention to provide chip breakers or similar cutting aids in the region of the lip rim. For example, a ring consisting of a CBN or PCD cutting material can be brazed or adhesively bonded in place as a cutting aid. The possibility of also providing the indexable cutting insert with two differently configured working surfaces is especially advantageous, such that various cutting tasks or, for example, a rough machining operation and a subsequent finish machining operation can be realized with the same indexable cutting insert. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail with reference to the exemplary embodiment shown in the figures. In the drawing: 
         FIG. 1  shows the plan view of a working surface of an indexable cutting insert according to the invention, 
         FIG. 2  shows the perspective view of the indexable cutting insert shown in  FIG. 1 , 
         FIG. 3  shows a sectional view through the circumference of the indexable cutting insert shown in  FIG. 1 , 
         FIG. 4  shows a view of the insert seat, 
         FIG. 5   a  shows an indexable cutting insert resting in the insert seat, 
         FIG. 5   b  shows the section V-V in  FIG. 5   a,    
         FIG. 6   a  shows an indexable cutting insert resting in an insert seat, 
         FIG. 6   b  shows the section VI-VI from  FIG. 6   a,    
         FIG. 7   a  shows an indexable cutting insert resting in the insert seat, 
         FIG. 7   b  shows the section VII-VII shown in  FIG. 7   a,    
         FIG. 8  shows a sectional illustration of a first embodiment of an indexable cutting insert resting in the insert seat, 
         FIG. 9  shows a sectional illustration of a second embodiment of an indexable cutting insert resting in the insert seat. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The indexable cutting insert shown greatly enlarged in  FIG. 1  has first of all the circumferential lip rim  1  and a hollow  2 . In the exemplary embodiment, the lip rim  1  is defined by a virtually circular line which forms a circumferential cutting edge  3 . Six trapezoidal molded bodies  4  are provided next to one another like a relief in the hollow  2 . The molded bodies  4  are exactly the same size and project from the hollow  2 . As a result of their constant pitch, the molded bodies  4  form indexing for the indexable cutting insert in the insert seat. Chip breakers of various configuration or, for example, a ring of CBN or PCD cutting material that is adhesively bonded or brazed in place can be provided as a cutting aid in the region of the lip rim  1 . 
     The through-hole  5  passing through the parent body of the cutting insert can be seen especially clearly in  FIG. 2 . The through-hole  5  extends concentrically to its center line  22 , which can be seen in the illustration in  FIG. 3 . In the final fitted state of the indexable cutting insert, a fastening bolt preferably configured as fastening screw  6  is pushed through the through-hole  5  for fixing the indexable cutting insert in the insert seat. The fastening screw  6  then runs concentrically to the center line  22  of the through-hole  5 . In the exemplary embodiment, the flat surfaces of the molded bodies  4  are arranged in one plane and extend at an angle of 90° to the center line  22  of the through-hole  5 . 
     It can be seen in the exemplary embodiment that the indexable cutting insert is configured as a cylindrical body, but this need not necessarily be the case. Here, the two top surfaces of the cylinder are configured as working surfaces. The working surface resting on the supporting surface  7  of the insert seat forms the inactive positioning surface  8  of the indexable cutting insert. The machining surface  9  faces diametrically away from this positioning surface  8  of the indexable cutting insert. During the cutting operation, the machining surface  9  is in engagement with the workpiece, while the indexable cutting insert rests with the positioning surface  8  on the supporting surface  7  of the tool seat. 
     The use of the molded bodies  4  may be explained with reference to  FIG. 1 . In the illustration in  FIG. 1 , this is to be explained with reference to the molded body  4  in the “two o&#39;clock position” and to the molded body  4  in the “ten o&#39;clock position” opposite the molded body  4  in the “two o&#39;clock position”. The molded bodies  4  are of roughly trapezoidal configuration with a long trapezoid side effective as bearing strip  10 . The bearing strip  10  is in each case depicted as reference sign only on the molded bodies  4  explained here in the “two o&#39;clock position” and “ten o&#39;clock position”, respectively. 
     The section VI-VI through the bearing strip  10  of the molded body  4  in the “two o&#39;clock position” or “ten o&#39;clock position” is shown in  FIG. 6   a . In  FIG. 6   b , firstly the supporting surface  7  on the insert seat for the indexable cutting insert is shown. The supporting surface  7  is defined in each case by stop edges  12 . Either the bearing strips  10  ( FIG. 9 ) or the bearing surfaces  20  ( FIG. 8 ) bear against these stop edges  12  in the insert seat and therefore secure the indexable cutting insert against rotation and also form the indexing for the indexable cutting insert. 
     To activate the next part of the cutting edge  3  in each case, the bearing surface  20  of the molded body  4  adjacent to the respectively active molded body  4  is brought into engagement with the mating bearing surface  12 . This ensures that the respectively active region of the cutting edge  3  always has the same relative position relative to the insert seat and thus also relative to the workpiece during the machining. 
     In the section shown in  FIG. 6   a  and  FIG. 6   b , the effective stop edges  12  of the insert seat are situated well inside the insert seat with respect to the tool.  FIG. 7   a  and  FIG. 7   b  show a section with stop edges  12  which are arranged well to the outside on the tool with respect to the body of the tool. The section VII-VII runs through the bearing strip  10  of the molded body  4  or through the bearing surface  20  of the indexable cutting insert in the “four o&#39;clock position” or “eight o&#39;clock position”. The insert seat again has the supporting surface  7  with the stop edges  12 . Either the bearing strips  10  ( FIG. 9 ) or the stop surfaces  20  ( FIG. 8 ) bear against these stop edges  12 . In addition to the supporting surface  7 , a clearance portion  18  for accommodating the cutting edge  3  of the indexable cutting insert can be seen on the insert seat in both  FIG. 6   b  and  FIG. 7   b.    
     The machining surface  9  of the indexable cutting insert is tilted relative to the center longitudinal axis  13  of the tool in a preferred embodiment. In this case, the axial angle  14  of the machining surface  9  relative to the center longitudinal axis  13  is of the order of magnitude of 3° to 10°. A tilt angle  14  of 7° is especially preferred. The fastening screw  6  has a screw-in angle  16  within the range of 0° to 10°, preferably 8°, relative to the normal  15  of the center longitudinal axis  13 . 
     The position angle  17  of the insert seat relative to the center longitudinal axis  13  is within the range of 10° to 50°, preferably 30°. 
       FIG. 8  shows a sectional illustration of a first exemplary embodiment of an indexable cutting insert according to the invention resting in the insert seat. The positioning surface  8  and the machining surface  9  of the indexable cutting insert shown in  FIG. 8  are designed to be identical, for which reason the reference numerals applicable to both surfaces are only marked on the machining surface  9  for the sake of better readability. It can be seen from the illustration in  FIG. 8  that the indexable cutting insert, with its hollow  2 , completely bridges that region of the supporting surface  7  which runs horizontally in  FIG. 8 . Consequently, with its bearing surfaces  20 , which run obliquely from the lip rim  1  in the direction of the hollow  2 , the indexable cutting insert bears against that region of the supporting surface  7  which runs out into the clearance portions  18 . In this embodiment shown in  FIG. 8 , the lip rim is preferably configured as a chip breaker. 
       FIG. 9  shows a second exemplary embodiment in which a relief-like projection  21  is provided in the hollow  2 . The relief-like projection  21  has the bearing strips  10  on the indexable cutting insert on its obliquely running side ends. The supporting surface  7  in the insert seat is of bowl-like configuration, such that the projection  21  rising from the positioning surface  8  can engage in the supporting surface  7  of bowl-like configuration. The bearing strips  10  of the indexable cutting insert then bear against the stop edges  12  which form the rims of the bowl-like supporting surface  7 . 
     A plurality of fixing variants are possible with the indexable cutting insert according to the invention. In a first variant ( FIG. 8 ), the positioning surface  8  of the indexable cutting insert covers the entire supporting surface  7  of the insert seat, such that the indexable cutting insert bears with its bearing surface  20  against the stop edges  12  of the insert seat. In a second variant ( FIG. 9 ), the positioning surface  8  of the indexable cutting insert only partly covers the supporting surface of the insert seat, and the bearing strip  10  of the molded body  4  of the indexable cutting insert bears against the associated stop edge  12  of the insert seat. These two aforementioned variants can each be combined with two different insert seat variants: in the first insert seat variant ( FIG. 6   a / FIG. 6   b ), the molded bodies ( FIG. 9 ) or the associated bearing surfaces  20  ( FIG. 8 ) of the indexable cutting insert which are arranged, in the final fitted state, in the “two o&#39;clock position”, on the one hand, and in the “ten o&#39;clock position”, on the other hand, are active for the fixing. Here, the stop strips  10  and bearing surfaces  20 , respectively, in the “two o&#39;clock position” and at the same time in the “ten o&#39;clock position” are active. This is the embodiment with fixing of the indexable cutting insert that is effective well inside the tool body. The second insert seat variant relates to fixing of the indexable cutting insert that is arranged well to the outside with respect to the tool body. Here ( FIG. 7   a / FIG. 7   b ), the molded bodies  4  ( FIG. 9 ) or the associated bearing surfaces  20  ( FIG. 8 ) of the indexable cutting insert which are arranged, in the final fitted state, in the “four o&#39;clock position” and in the “eight o&#39;clock position” are active. With the indexable cutting insert according to the invention, therefore, a comparatively large number of insert seat configurations of the indexable cutting inserts can be realized, such that a high degree of flexibility is ensured with regard to the application.