Abstract:
A tool includes a parent body ( 12 ) and at least two cutting inserts ( 14 ) fastened directly or indirectly to the parent body ( 12 ). A central clamping device ( 30 ) is configured to clamp the cutting inserts ( 14 ) in an oriented position relative to the parent body ( 12 ). An assembly includes the tool ( 10 ) and a jig ( 32 ), which can accommodate the tool ( 10 ) in such a way that the cutting insert ( 14 ) is located in a desired position on the tool ( 10 ) and can be clamped in the desired position by actuating the clamping device ( 30 ). A method for fastening at least one cutting insert ( 14 ) to the parent body ( 12 ) includes fitting the parent body ( 12 ) with the cutting insert ( 14 ); arranging the parent body ( 12 ) in a jig ( 32 ); bringing the cutting insert ( 14 ) into a desired position; and clamping the cutting insert ( 14 ) in the desired position.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a tool for machining, comprising a parent body and at least two cutting inserts which are fastened directly or indirectly to the parent body. The invention also relates to an assembly comprising such a tool and a jig which serves to orient the cutting inserts on the parent body. Finally, the invention relates to a method for fastening cutting inserts to a parent body of such a tool. 
       BACKGROUND OF THE INVENTION 
       [0002]    The tool according to the invention is a milling cutter, drill or reaming tool in the widest sense, that is to say a tool which is set in rotation and is used for stock removal by machining. To machine the material to be cut, a plurality of cutting inserts are provided on the parent body of the tool. Said cutting inserts are usually made of sintered materials or of cutting materials produced by a metallurgical melting process and have at least one cutting edge. In order to ensure a long service life of the cutting inserts used and a high quality of the machined surface of the workpiece, it is important that the cutting edges of all the cutting inserts of a tool are correctly oriented. If the cutting edges acting on the workpiece are not exactly oriented axially and/or radially, a uniform surface is not obtained. If some of the cutting inserts project further in the direction of the surface of the workpiece than other cutting inserts, the cutting edges which project further are prematurely worn. 
         [0003]    It is known from the prior art to attach each cutting insert to the parent body in an individually adjustable manner. This enables the user of the tool to correctly orient the cutting inserts individually. From the multiplicity of known designs, US 2007/0127992 A1 and US 2008 0107493 A1 may be mentioned as examples. Shown in the first-mentioned document is a milling cutter in which each cutting insert is attached to a holder, which is arranged in turn in a receptacle of the parent body of the milling cutter. An adjusting screw is provided behind the rear side, facing away from the cutting insert, of each holder, by means of which adjusting screw the position of each holder can be set individually in the axial direction. The second document mentioned discloses an adjusting device which can be used in drilling tools, milling cutters and lathe tools. Here, too, a holder to which the corresponding cutting insert is attached is used. The holder is fastened to the tool at its end remote from the cutting insert and is provided with a bending region, such that the end provided with the cutting insert can be adjusted outward in the radial direction. Provided for the adjustment is an adjusting screw which is provided with an eccentric surface and which can displace an adjusting slide provided with a wedge surface, a pressure piece bearing in turn against the wedge surface of the adjusting slide, this pressure piece interacting with the holder. A common feature of these solutions and the other known solutions from the prior art is that each individual cutting insert has to be adjusted manually. The effort involved here is also quite considerable when two cutting inserts are attached to a holder; in this case, too, complicated manual adjustment must be carried out. 
         [0004]    As an alternative to the manual adjustment of each individual cutting insert, it is known to use cutting inserts which are produced with high precision and which are arranged in receptacles which are likewise produced with corresponding precision. In this way, the manual adjustment of each individual cutting insert can be avoided. However, the close tolerances which have to be maintained during both the production of the cutting inserts and the production of the tool require a very high production outlay, which leads to high production costs. 
       SUMMARY OF THE INVENTION 
       [0005]    The object of the invention is to provide a tool and a method for fitting a tool with cutting inserts which is distinguished by low production costs for the tool and the cutting inserts and in addition permits precise adjustment of all the cutting inserts with little effort. 
         [0006]    To achieve this object, a central clamping device is provided according to the invention in a tool of the type mentioned at the beginning, by means of which central clamping device the cutting inserts can be secured or clamped in an oriented position relative to the parent body. The tool according to the invention is based on the basic idea of first orienting all the cutting inserts relative to the parent body and of then clamping a plurality of cutting inserts simultaneously in their desired position in one operation. This enables cutting inserts having standard production tolerances to be used and also enables simply the normal tolerances to be maintained during the production of the parent body. This results in low production costs. The requisite precision of the tool is obtained by each individual cutting insert being located individually in its desired position. Through the use of the central clamping device, however, the effort involved in having to clamp each individual cutting insert in its position is not required. 
         [0007]    A plurality of receptacles, in which a respective cutting insert is arranged, are preferably provided on the parent body. The use of individual receptacles for each cutting insert results in high strength of the tool with high precision. 
         [0008]    Depending on the requirements, each cutting insert can either be inserted directly into the receptacle or alternatively can be attached to a holder, which is then inserted in turn in the corresponding receptacle. If the cutting insert is to be inserted directly into the receptacle, a certain minimum size is required so that the cutting insert can be reliably clamped. This leads to somewhat greater use of material during the production of the cutting insert. Instead, however, the effort required to attach the cutting insert to a holder is not required. On the other hand, if a holder is used, the actual cutting insert can be made very much smaller. This saves material during the production of the cutting insert, but requires attachment to the holder. 
         [0009]    The cutting insert is preferably displaceable and rotatable in the receptacle in the axial and/or radial direction when the clamping device is not actuated. This enables all the cutting inserts (if need be with their holders) to be correctly oriented on the parent body and clamped in the desired position after the orientation. 
         [0010]    According to a preferred embodiment, the receptacle is designed like a pocket having a base surface, a top surface and at least one side surface. Such a receptacle encloses the cutting insert (and if need be the holder used) very tightly, such that good guidance of the cutting insert in the parent body is ensured. 
         [0011]    In order to ensure precise orientation of the cutting inserts, the clamping device clamps the cutting insert against a reference surface or a plurality of reference surfaces. This reference surface can be, in particular, the base surface or the top surface of the receptacle. It is also possible for the reference surfaces to be formed by one or more side surfaces and a base surface or top surface of the receptacle. This configuration is suitable if only axial orientation of the cutting inserts is necessary, as is the case in face milling. 
         [0012]    Pressure means which attempt to push the cutting insert out of the receptacle are preferably provided. The pressure means ensure that each cutting insert, in the initial state, is located in a position “outside” the desired position. This is the precondition required for all the cutting inserts to be pushed simultaneously into their desired position by very simple means, for example a jig, into which the parent body is inserted. The cutting inserts can then be clamped in the desired position by actuating the clamping device. 
         [0013]    The pressure means can be formed, for example, by at least one spring, for example a leaf spring, or also by a plurality of elastomer elements, in particular rubber elements. 
         [0014]    The clamping device can be a mechanical clamping device. In this case, the clamping device can have in particular a clamping element which can be adjusted axially with a thread. This enables the requisite clamping forces to be applied by tightening the clamping element. Alternatively or additionally, it is possible for the clamping device to have a clamping wedge. This also enables the requisite clamping forces to be easily produced. 
         [0015]    Alternatively, the clamping device can be a hydraulic clamping device. In this case, the clamping device in particular has an expansion chamber. Such a configuration is known in principle from expansion chucks. 
         [0016]    The aforesaid object is also achieved by an assembly comprising a tool and a jig which can accommodate the tool in such a way that the at least one cutting insert is located in a desired position on the tool and can be clamped in the desired position by actuating the clamping device. The task of the jig is to bring the cutting inserts from their initial position, in which they are originally located “temporarily” on the parent body, into the desired position. If pressure means are used in the parent body, the task of the jig is in particular to press the cutting inserts simultaneously into their desired position in the axial and/or radial direction. In this position, they can then be clamped on the parent body by actuating the clamping device. 
         [0017]    If no pressure means are provided on the tool, the task of the jig is also to pull the cutting inserts into their desired position in the axial and/or radial direction. Holding means, for example magnets or holding arms, can be provided for this purpose. 
         [0018]    The aforesaid object is also achieved by a method for fastening cutting inserts to a parent body of a tool for machining, in which method first of all the parent body is fitted with the cutting inserts. The parent body is then arranged in a jig, the jig bringing the cutting inserts into their desired position. Finally, each cutting insert is clamped in its desired position on the parent body. In this method, the precise orientation of all the cutting inserts is carried out in a single step, namely by the simple arrangement of the parent body in a jig, said parent body being fitted with the cutting inserts. It is not necessary to orient each cutting insert individually. 
         [0019]    In this case, it is in principle possible to clamp each cutting insert using an individual clamping device. However, a clamping device which clamps more than one cutting insert is preferably used in order to make it easier to fasten the cutting inserts. In particular, a central clamping device is used, with which all the cutting inserts can be clamped simultaneously. In this way, minimum effort is required for fastening the cutting inserts. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The invention is described below with reference to various embodiments which are shown in the attached drawings, in which: 
           [0021]      FIG. 1  shows a tool according to the invention in a schematic, perspective view; 
           [0022]      FIG. 2  shows, in a schematic sectional view, a receptacle in the tool with cutting insert arranged therein according to a first embodiment, the tool being arranged in a jig; 
           [0023]      FIG. 3  shows a sectional view perpendicular to the sectional view of  FIG. 2 ; 
           [0024]      FIG. 4  schematically shows the tool in  FIGS. 1 to 3  when being inserted into the jig; 
           [0025]      FIG. 5  shows a view corresponding to  FIG. 2 , a second embodiment being shown; 
           [0026]      FIG. 6  shows the second embodiment in a view corresponding to  FIG. 3 ; 
           [0027]      FIG. 7  shows a tool having a mechanical clamping device in a schematic sectional view; and 
           [0028]      FIG. 8  shows a tool having a hydraulic clamping device in a schematic view. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0029]    A tool  10  for machining which has a parent body  12  is shown schematically in 
         [0030]      FIG. 1 . Attached to the parent body are a plurality of cutting inserts  14  which, in the exemplary embodiment shown here, project both in the radial direction beyond the circumferential surface U and in the axial direction beyond an end face S of the parent body  12 . In the exemplary embodiment shown here, the tool  10  is a milling cutter. The way in which the cutting inserts  14  are attached to the parent body  12  can be applied in principle to any other tool for machining in which a plurality of cutting inserts are to be attached in a certain position, for example drilling tools. 
         [0031]    Here, each cutting insert  14  is attached to a holder  16  (see also  FIGS. 2 and 3 ) which is arranged in each case in a pocket-like receptacle  18  of the parent body  12 . Each receptacle  18  is formed by a base surface  20 , a top surface  22  opposite the base surface  20 , and two side surfaces  24 ,  26 , which connect the base surface  20  to the top surface  22 . 
         [0032]    The dimensions of the receptacle  18  are such that the holder  16  together with the cutting insert  14  can be inserted with clearance into the corresponding receptacle  18 . For this reason, each holder  16  is displaceable in the receptacle  18  in both the axial direction A and the radial direction R. In addition, the holder  16  and thus the cutting insert  14  can be rotated about an axis which is perpendicular to the base surface  20  (see arrow D in  FIG. 2 ). Three pressure means  28 , which are designed here as rubber elements, are arranged between the side surfaces  24 ,  26  of the receptacle  18  and the edges of the holder  16  that are opposite said side surfaces. Said pressure means  28  displace the holder  16  and thus the cutting insert  14  both in axial direction A and in radial direction R outward from the receptacle  18 . 
         [0033]    A clamping device  30  which can displace the holder  16  against the base surface  20  is arranged on that side of the receptacle  18  which is opposite the base surface  20 . When the clamping device  30  is activated, the holder  16  is firmly restrained against the base surface  20 , which then acts as a reference surface for the orientation of the cutting insert. 
         [0034]    According to a development (not shown), provision can be made for the cutting inserts and/or the receptacles for the cutting inserts to be geometrically shaped in such a way that they cannot leave the tool receptacle radially if the clamping force of the clamping device decreases undesirably during operation. 
         [0035]    A jig  32  in which the parent body  12  can be arranged is used for orienting and adjusting the cutting inserts  14  in the parent body  12 . The jig  32  is provided with centering structures  38  which are indicated in  FIG. 2  and which ensure that the parent body  12  comes to lie both in a centered manner in the radial direction and at the correct height in the axial direction in the jig  32 . To position the cutting inserts, the jig  32  has an axial bearing surface  34  and a radial bearing surface  36 . 
         [0036]    The jig is made of a material which virtually rules out damage to the cutting edges of the cutting inserts, but at the same time ensures the precise positioning. Suitable materials are aluminum, plastics with high rigidity, and hardwood. 
         [0037]    It will now be explained with reference to  FIG. 4  how the jig  32  brings the cutting inserts  14  into their desired position. The pressure means  28  ensure that, in the initial position, the cutting insert  14  together with the holder  16  project outward beyond the desired position in the radial direction and in the axial direction. In this initial position, the cutting insert  14 , when the parent body is pushed into the jig  32 , first of all runs against a sloping insertion surface  40 . When pushed in further, the cutting insert  14  is pushed radially inward by the insertion surface  40  until said cutting insert  14  reaches the radial bearing surface  36 . When the parent body  12  is put onto the centering structure  38 , the cutting insert  14  also comes into contact with an axial bearing surface  34 . Both bearing surfaces  34 ,  36  cause the cutting insert  14  together with its holder  16  to be displaced into the receptacle  18  in the radial direction and axial direction against the action of the pressure means  28 . In the process, the pressure means  28 , which are shown as leaf springs in  FIG. 4  as an alternative configuration, ensure that the cutting edges of the cutting insert  14  bear in their correct orientation against the axial bearing surface  34  and the radial bearing surface  36 . The pressure means  28  are adapted with regard to their pressure force and their direction of action in such a way that undesirable tilting of the cutting insert  14  about one of its corners is prevented. Therefore, the cutting insert  14 , as can be seen in  FIG. 2 , bears with its two cutting edges against the axial bearing surface  34  and the radial bearing surface  36 . This position corresponds to the desired position of the cutting insert  14  relative to the parent body  12 . 
         [0038]    When the parent body  12  is inserted together with the cutting inserts arranged in the receptacles, not only is the cutting insert  14  shown by way of example in  FIGS. 2 to 4  brought into its desired position, but rather all the cutting inserts are brought into their desired position simultaneously. As soon as the parent body  12  of the tool is located in the jig  32  and all the cutting inserts are thereby brought into their desired position automatically, the clamping device  30  is actuated, such that all the cutting inserts  14  are simultaneously clamped (indirectly via their holders  16 ) in the corresponding receptacle  18 . The tool is then ready for use. 
         [0039]    As an alternative to the described jig having sloping insertion surfaces, a jig which consists of a plurality of parts and which can be pushed together from an open position into a closed position can also be used. In such an embodiment, (virtually) no displacement of the cutting edges of the cutting inserts on the surface of the jig occurs, which prevents both chipping of the cutting edges and wear of the jig. 
         [0040]    It can be seen that the jig can be reused. Thus, every new tool which is to be fitted with cutting inserts can be adjusted in the corresponding, matching jig, and a tool with cutting inserts already fitted can be readjusted with the matching jig by the tool being inserted into the jig, by the clamping device  30  being released, such that the pressure means  28  can press the cutting inserts against the bearing surfaces  34 ,  36  again, and then by the clamping device being reactivated. 
         [0041]    It is also possible to use a standardized parent body, into which various receptacles or cutting inserts are inserted, which are then oriented by means of different jigs. 
         [0042]    An alternative configuration is shown in  FIGS. 5 and 6 . The same designations are used for the components known from the first embodiment and reference is made in this respect to the above explanations. 
         [0043]    The essential difference between the first embodiment and the second embodiment consists in the fact that, in the second embodiment, the cutting insert  14  is attached directly in the corresponding receptacle  18 . No holder is used, and so the cutting insert  14  is pressed by the clamping device  30  directly against the base surface  20  acting as reference surface. 
         [0044]    Shown schematically in  FIG. 7  is a mechanical clamping device  30  which has a clamping ring  42  having a wedge surface  44  and a clamping screw  46 . Bearing against the wedge surface  44  is a clamping ball  48  which is guided in the parent body  12 . The clamping ring  42  is adjusted in the parent body  12  in a clamping direction S by tightening the clamping screw  46 , such that the clamping ball  48  is displaced radially outward. The clamping ball  48  presses directly against the holder  16  or the cutting insert  14 , such that said holder  16  or cutting insert  14  is clamped against the base surface of the corresponding receptacle  18 . 
         [0045]    A tool having a hydraulic clamping device  30  is shown in  FIG. 8 . The clamping device  30  uses an expansion chamber  50  which is arranged “behind” the top surface  22  of the corresponding receptacle. The top surface  22  is deformed toward the base surface  20  by applying a hydraulic pressure P to the expansion chamber  50 , such that the holder  16  or the cutting insert  14  is clamped between the base surface  20  and the top surface  22 . The pressure supply for the expansion chamber  50  and the way in which the hydraulic pressure is generated and controlled is already known in principle from expansion chucks and is not explained in any more detail here. 
         [0046]    Instead of the pressure means  28  which press the holder  16  or the cutting insert  14  out of the receptacle  18 , other means which ensure that the cutting edges of the cutting insert  14  bear in linear contact against the bearing surfaces  34 ,  36  can also be used. For example, magnetic repelling forces could be used between parent body and cutting insert  14  or holder  16 , or magnetic attraction forces could be used between the jig  32  and the cutting insert  14  or the holder  16 . Depending on the respective spatial orientation, it could also be sufficient to use solely the force of gravity in the axial direction in order to ensure that the cutting inserts bear against the axial bearing surface  34 . It is also conceivable in principle to provide mechanical means in the jig  32 , for example holding arms. 
         [0047]    In deviation from the embodiment shown, the receptacle  18  can also have a shape different from a rectangular shape. The side surfaces need not be rectilinear, but rather can run in a curved manner. Nor do two side surfaces need to be used, but rather a single side surface can also be used.