Abstract:
The invention relates to an indexable insert ( 1 ) for fitting in supporting tools ( 5 ) for the machining of workpieces, with an upper side ( 2 ) and an underside ( 3 ), on which clamping recesses are arranged, and with a circumferential geometry ( 4 ) joining the upper side ( 2 ) and the underside ( 3 ), wherein cutting corners and cutting edges ( 6 ) are arranged at the transition from the upper side ( 2 ) and the underside ( 3 ) to the circumferential geometry ( 4 ). In order that the clamping situation during machining is improved significantly, and at the same time the introduction of the clamping recesses is made easier, it is proposed that the clamping recess consists of grooves ( 10 ) which are arranged on two crossing straight lines ( 11 ), wherein the two straight lines ( 11 ) run at right angles in relation to each other and all the grooves ( 10 ) are arranged at the same distance from the center axis or longitudinal axis ( 12 ) of the indexable insert ( 1 ), and the crossing point ( 13 ) of the two straight lines ( 11 ) lies on the center axis or longitudinal axis ( 12 ) of the indexable insert ( 1 ).

Description:
This application is a §371 of PCT/EP2010/070467 filed Dec. 22, 2010 and claims priority from DE 10 2009 060 436.7 filed Dec. 22, 2009. 
     BACKGROUND OF THE INVENTION 
     The invention relates to an indexable insert for mounting in carrier tools for machining workpieces, having a top side and a bottom side on which clamping depressions are situated, and a circumferential geometry which joins the top side and the bottom side, wherein cutting corners and/or cutting edges are situated at the transition from the top side and the bottom side to the circumferential geometry. 
     This type of indexable insert is known from WO 2008/155331 A1. 
     OBJECTS OF THE INVENTION 
     The object of the present invention is to improve an indexable insert in such a way that the clamping situation during machining is significantly improved, and at the same time the introduction of the clamping depressions is simplified. 
     SUMMARY OF THE INVENTION 
     According to the invention, this object is achieved in that the clamping depression is composed of grooves which are situated on two intersecting straight lines, the two straight lines extending at right angles to one another, and all grooves being situated at the same distance from the center axis or longitudinal axis of the indexable insert, and the point of intersection of the two straight lines lying on the center axis or longitudinal axis of the indexable insert. The indexable insert is thus uniformly clamped in the mounted state; i.e., the clamping forces uniformly press the indexable insert onto a carrier tool. The indexable insert is not subjected to load on one side, thus significantly improving the clamping situation. In addition, grooves allow greater ease of introduction than the customary clamping depressions. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a cylindrical indexable insert according to the invention. 
         FIG. 2  shows a clamping claim according to the invention. 
         FIG. 3  shows a cylindrical indexable insert according to the invention having two grooves. 
         FIG. 4 . Shows a clamping claw according to the invention. 
         FIG. 5  shows a clamping claw according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In one embodiment of the invention, four grooves are situated on each top side and bottom side, two grooves being situated on each of the straight lines. 
     This embodiment results in excellent distribution of the clamping forces on the indexable insert since the grooves are uniformly distributed, and therefore the indexable insert is uniformly clamped in the mounted state. As a result of the mentioned four grooves, for a cylindrical indexable insert the top and bottom sides are divided into four circle segments having a segment angle of 90 degrees. Each circle segment has a groove, so that in the mounted state each circle segment is also clamped. This embodiment is described in greater detail below with reference to  FIG. 1 . However, the indexable insert may also have a cuboidal design, with a square top side and bottom side. 
     In an alternative embodiment of the invention, two grooves are situated on each top side and bottom side, a single groove being situated on each straight line, and the two grooves intersecting on each top side and bottom side and forming a cross groove whose midpoint lies on the center axis or longitudinal axis of the indexable insert. This embodiment, shown in  FIG. 3 , has the advantage that only two grooves must be introduced, and the resulting clamping force lies exactly on the center axis or longitudinal axis of the indexable insert, thus improving the clamping situation. 
     In a preferred refinement of the invention, the circumferential geometry has circumferential positive open spaces on both sides beneath the cutting corners and/or cutting edges which are recessed with respect to the cutting corners and/or cutting edges, thus providing a positive clearance angle on both sides, and a collar which is raised relative to the lowest points of the open spaces is situated between two open spaces which are oppositely situated, in relation to the top side and bottom side, on the circumferential geometry, the surface of the collar being used as a bearing surface in carrier tools. 
     Mounting in conventional clamping holders is thus made possible without sacrificing the features and advantages of a positive open space. When, for a cylindrical indexable insert, the collar has a peripheral design on the circumferential geometry, the bearing surface is maximized, and mounting may be carried out in any possible orientation. 
     A clamping claw for clamping an indexable insert according to the invention in a carrier tool for machining is characterized in that the clamping claw has cams at its end facing the indexable insert which are directly or indirectly adapted to the grooves in the indexable insert. In the present context, “directly” means that the cams have a one-piece design with the clamping claw. “Indirectly” means that a pressure plate or the like is fastened to the clamping claw, and the cams are situated on this pressure plate instead of being situated directly on the clamping claw. 
     In one embodiment the cams form a cross cam. 
     The invention therefore relates to an indexable insert for mounting in carrier tools for machining workpieces, having a top side and a bottom side, and a circumferential geometry which joins the top side and the bottom side, in one preferred embodiment cutting corners and/or cutting edges being situated at the transition from the top side and the bottom side to the circumferential geometry, and the circumferential geometry having circumferential positive open spaces on both sides beneath the cutting corners and/or cutting edges which are recessed with respect to the cutting corners and/or cutting edges, thus providing a positive clearance angle on both sides. 
     According to the prior art, ceramic cutting inserts are generally manufactured with a clearance angle α of 0° or with a clearance angle α&gt;0°. 
     If the clearance angle α=0°, the cutting insert may be used on both sides, and cutting corners and cutting edges on the top side and the bottom side are available. For a rectangular cutting insert, for example four cutting edges and/or cutting corners are situated in each case on the top side and bottom side; i.e., a total of eight cutting edges and/or cutting corners are available. 
     If the clearance angle α&gt;0°, the cutting insert may be used on only one side, thus reducing the number of usable cutting corners and/or cutting edges by half compared to the design in which the clearance angle α=0°. 
     An indexable insert is known from U.S. Pat. No. 3,490,117, which has circumferential positive open spaces on the circumferential geometry on both sides beneath the cutting corners and cutting edges which are recessed with respect to the cutting corners and cutting edges, thus providing a positive clearance angle on both sides. A disadvantage herein is that this indexable insert for clamping onto carrier tools requires a plate seat which is adapted to the circumferential geometry of the cutting insert, so that it is not mountable in conventional clamping holders. The exchangeability and use are thus limited and made more difficult. 
     One preferred embodiment according to the invention is characterized in that a collar which is raised relative to the lowest points of the open spaces is situated between two open spaces which are oppositely situated, in relation to the top side and bottom side, on the circumferential geometry, the surface of the collar being used as a bearing surface in carrier tools. Mounting in conventional clamping holders is thus made possible without sacrificing the features and advantages of a positive open space. 
     In one embodiment, the collar has a peripheral design on the circumferential geometry, thus maximizing the bearing surface and allowing mounting to be carried out in any possible orientation. 
     In one preferred design, the indexable insert is made of a ceramic. An extremely long service life for the cutting insert results in particular with ceramics. 
     In one design according to the invention, the length of the open spaces is less than one-half the thickness of the indexable insert. As a result, the collar may be centrally located on the circumferential geometry and also have a sufficient width. 
     To reinforce the cutting edges and/or cutting corners, in one embodiment the open spaces are provided at essentially right angles to the top side and bottom side of the indexable insert in the contact area directly adjoining the cutting edges and/or cutting corners. The cutting insert may thus lie against bearing surfaces in the carrier tool via the two contact areas as well as via the raised collar. At the same time, this contact area reinforces the cutting corners and/or cutting edges. 
     In one embodiment of the invention, the surface of the collar is at the same or greater radial height than the cutting edges and/or cutting corners in relation to the longitudinal axis of the indexable insert. The cutting insert may thus lie against bearing surfaces in the carrier tool in any desired manner. 
     In one embodiment of the invention, the contact area of the open spaces and the surface of the collar are at the same radial height in relation to the longitudinal axis of the indexable insert, or the radial height of the surface of the collar is greater than the radial height of the contact area of the open spaces in relation to the longitudinal axis of the indexable insert. 
     In one embodiment the open spaces are introduced by peripheral grinding. In another embodiment, the open spaces are introduced by appropriate pressing of the green body and subsequent sintering. 
     In one embodiment the cutting insert has a cylindrical design, the top side and bottom side forming the end faces, and the side surfaces forming the peripheral surface of the cylinder. In another advantageous embodiment the cutting insert has a cuboidal design. 
     The clamping claw, also referred to as a clamping finger, has a cross cam at its end facing the culling insert which is adapted to the cross groove. The cross cam may also be situated on a pressure plate which is fastened to the clamping finger. For clamping, the cross cam engages in the cross groove in a clamping manner. 
     A carrier tool for machining has a cutting insert according to the invention which is held in a holder by a clamping finger according to the invention. 
     The cutting insert is preferably made of a ceramic, preferably cubic boron nitride (CBN). 
     In contrast to existing systems, this indexable insert is pulled against the seat via a positive-fit cross groove and corresponding bevels in the holder by means of a clamping finger. The clamping finger has the shape of the negative of the cross groove. 
     The invention is explained in greater detail below with reference to five figures. 
       FIG. 1  shows a cylindrical indexable insert  1  according to the invention, in each case having a circular top side  2  and a circular bottom side  3 , and a circumferential geometry  4  which joins these sides. The respective edges of the sides  2 ,  3  with respect to the circumferential geometry  4  are designed as cutting edges  6 . 
     In this embodiment, four grooves  10  are introduced on each side  2 ,  3 . The grooves  10  are located on two imaginary straight lines  11  which extend on the surface of the sides  2 ,  3  and which are situated at right angles to one another. All grooves  10  are situated at the same distance, namely, the distance  0 , from the center axis or longitudinal axis  12  of the indexable insert  1 , and the point of intersection  13  of the two straight lines  11  lies on the center axis or longitudinal axis  12  of the indexable insert  1 . Due to this configuration of the grooves  10 , the indexable insert is subjected to uniform load in the mounted state, thus optimizing the clamping situation. 
     The circumferential geometry  4  has circumferential positive open spaces  7   a ,  7   b  on both sides beneath the cutting edges  6  which are recessed with respect to the cutting corners and cutting edges  6 , thus providing a positive clearance angle on both sides. A collar  8  which is raised relative to the lowest points of the open spaces  7   a ,  7   b  is situated between two open spaces  7   a ,  7   b  which are oppositely situated, in relation to the top side  2  and bottom side  3 , on the circumferential geometry  4 , the surface  9  of the collar being used as a bearing surface in carrier tools  5  (see  FIG. 2 ). 
     All indexable inserts described herein are made of a ceramic. Due to its hardness, cubic boron nitride (CBN) is preferred. 
       FIG. 2  shows a clamping claw  15  according to the invention which is fastened to a carrier tool  5  via a screw  18 , and which presses an indexable insert  1  according to the invention into its plate seat on a support plate  19 . On its side facing the indexable insert  1 , the clamping claw  15  has cams which are adapted to the grooves  10  in the indexable insert  1 . The cams are described in greater detail below with reference to another embodiment. 
       FIG. 3  shows a cylindrical indexable insert  1  according to the invention, in each case having a circular top side  2  and a circular bottom side  3 , and a circumferential geometry  4  which joins these sides  2 ,  3 . The respective edges of the sides  2 ,  3  with respect to the circumferential geometry  4  are designed as cutting edges  6 . 
     In this embodiment, two grooves  10  are introduced on each side  2 ,  3 . The grooves  10  are located on two imaginary straight lines  11  which extend on the surface of the sides  2 ,  3  and which are situated at right angles to one another. All grooves  10  are situated at the same distance, namely, the distance  0 , from the center axis or longitudinal axis  12  of the indexable insert  1 , and the point of intersection  13  of the two straight lines  11  lies on the center axis or longitudinal axis  12  of the indexable insert  1 . 
     According to the invention, in this embodiment a single groove  10  is situated on each straight line  11 , the two grooves  10  intersecting and forming a cross groove  14  whose midpoint lies on the center axis or longitudinal axis  12  of the indexable insert  1 . The circumferential geometry  4  has a design as described for  FIG. 1 . 
       FIGS. 4 and 5  show a clamping claw  15  according to the invention which, as shown in  FIG. 2 , fastens the indexable insert  1  to the carrier tool. For clamping the indexable insert  1  on the carrier tool, the clamping claw has cams  16  at its end facing the indexable insert which are directly or indirectly adapted to the grooves in the indexable insert. In the embodiment according to  FIG. 3 , one cross cam  17  composed of two intersecting cams  16  is required.