Abstract:
A cutting tool for machining a workpiece. The cutting tool comprises a holder and at least two cutting inserts which are separated from each other by a spacer element. The cutting tool may be used to produce two or more bevels (and/or joints and/or grooves) at precisely defined spacings in only one operation. Through the use of spacer elements of different lengths, it is possible to produce bevels at different spacings. The spacer element preferably has an interface which comprises only radial contact surfaces, which run parallel to a longitudinal axis of the spacer element, and a substantially flat axial contact surface, which runs transverse to the longitudinal axis. The length of the spacer element can therefore be shortened on the rear side of the spacer element without destroying said interface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of international patent application PCT/EP2011/070811, filed on Nov. 23, 2011 designating the U.S., which international patent application has been published in German language and claims priority from German patent application DE 10 2010 054 392.6, filed on Dec. 7, 2010. The entire contents of these priority applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The disclosure relates to a cutting tool for machining a workpiece. Further, the disclosure relates to a cutting insert for such a cutting tool. Still further, the disclosure relates to a spacer element for such a cutting tool. 
         [0003]    DE 102 22 446 A1 shows an exemplary cutting tool and corresponding cutting insert of this type. Such tools are used, for example, for the milling of bevels. In metal working, in particular, the deburring or beveling of a surface is of great importance. In beveling, the sharp edges of workpieces are chamfered, whereby the risk of injury is reduced. A variety of cutting inserts can be used to create bevels. A frequent objective in the creation of bevels is that a bevel should be produced both on the top side and on the bottom side of a workpiece. Since traditional cutting tools generally have only one cutting insert, the bevels on the top and bottom side of the workpiece have hitherto had to be produced in two operations. The effort involved in creating two opposite-situated bevels is thus significantly greater than the effort involved in creating just one bevel. The same applies to the creation of grooves and joints. Another frequent objective is that bevels, grooves or joints should be made on a plurality of stackable workpieces. 
       SUMMARY OF THE INVENTION 
       [0004]    It is therefore an object to provide a cutting tool with which two or more bevels, grooves and/or joints can be produced simultaneously. In addition, it is an object to provide a spacer element and a cutting insert for such a cutting tool. 
         [0005]    In view of this object, there is provided a cutting tool for machining a workpiece, comprising:
       a holder having a central holder bore that extends along a longitudinal axis, and having a first interface that is arranged at a front end of the holder;   a first cutting insert having a second interface, which is arranged at a rear side of the first cutting insert and corresponds to the first interface, for coupling the first cutting insert to the holder, and having a third interface that is arranged at a top face of the first cutting insert opposite the rear side of the first cutting insert;   a spacer element having a fourth interface, which is arranged at a rear side of the spacer element and corresponds to the third interface, for coupling the spacer element to the first cutting insert, and having a fifth interface that is arranged at a top face of the spacer element opposite the rear side of the spacer element,   a second cutting insert having a sixth interface, which is arranged at a rear side of the second cutting insert and corresponds to the fifth interface, for coupling the second cutting insert to the spacer element;   at least one fastening element for fastening together the two cutting inserts, the spacer element and the holder, wherein each of the first cutting insert, the second cutting insert and the spacer element have a central bore, coaxial to the central holder bore, for the reception of the at least first fastening element;
 
wherein the fourth interface is configured to engage the third interface with at least one radial contact surface, which runs parallel to the longitudinal axis and is configured to fix the spacer element in radial direction, and with a substantially flat axial contact surface, which runs transverse to the longitudinal axis and fixes the spacer element in axial direction, such that the spacer element can be shortened at its rear side, and yet the fourth interface continues to correspond to the third interface.
       
 
         [0011]    According to a further aspect, there is provided a cutting insert for a cutting tool, said cutting tool having a holder with a first interface that is arranged at a front end of the holder, the cutting insert comprising:
       a second interface, which is arranged at a rear side of the cutting insert and corresponds to the first interface of the holder, for coupling the cutting insert to the holder;   a third interface, which is arranged at a top face of the cutting insert opposite the rear side of the cutting insert, for coupling the cutting insert to a corresponding fourth interface;   a central through bore that extends along a longitudinal axis; and   at least one cutting element arranged on a periphery of the cutting insert;
 
wherein the third interface comprises at least one radial contact surface, which runs parallel to the central through bore, and a substantially flat axial contact surface, which is arranged perpendicular to the longitudinal axis.
       
 
         [0016]    According to a still further aspect, there is provided a spacer element for a cutting tool, said cutting tool having a holder, a first and a second cutting insert, wherein the holder has a first interface that is arranged at a front end of the holder, wherein the first cutting insert has a second interface, which is arranged at a rear side of the first cutting insert and corresponds to the first interface of the holder, and a third interface that is arranged at a top face of the first cutting insert opposite the rear side of the first cutting insert, and wherein the second cutting insert has a sixth interface, which is arranged at a rear side of the second cutting insert, the spacer element comprising:
       a fourth interface, which is arranged at a rear side of the spacer element and corresponds to the third interface, for coupling the spacer element to the first cutting insert;   a fifth interface that is arranged at a top face of the spacer element opposite the rear side of the spacer element, for coupling the spacer element to the second cutting insert; and   a central through bore that extends along a longitudinal axis;
 
wherein the fourth interface comprises at least one radial contact surface, which runs parallel to the longitudinal axis, and a substantially flat axial contact surface, which runs transverse to the longitudinal axis, such that the spacer element can be shortened at its rear side, and yet the fourth interface continues to correspond to the third interface.
       
 
         [0020]    The spacer element with its two oppositely disposed interfaces enables the torque to be relayed from the holder via the first cutting insert and the spacer element to the second cutting insert, and further enables the second cutting insert to be guided at an exactly defined distance from the first cutting insert and coaxially to the first cutting insert. It is thus hereby possible to produce two or more bevels (and/or joints and/or grooves) at precisely defined spacings in one operation. It is also an advantage of the cutting tool that, through the use of spacer elements of different lengths, it is possible to produce bevels at different spacings. A further advantage is that, by coupling a plurality of coupling plates and spacer elements, it is also possible to produce more than two bevels in one operation. In addition, it is possible for the spacer element to be removed and for only the second cutting insert be attached directly to the holder. 
         [0021]    Since the fourth interface of the spacer element comprises only radial contact surfaces, which run parallel to the longitudinal axis, and a substantially flat axial contact surface, which runs transverse to the longitudinal axis, the length of the spacer element can be shortened on the rear side of the spacer element, and yet the fourth interface continues to correspond to the third interface. It is hereby possible, even if spacer elements are mass produced only in certain lengths, for the spacer elements to be shortened individually, for instance by turning. As a result, optional spacings between the cutting inserts are realizable. 
         [0022]    In a refinement, the first and the fifth interface are configured to be substantially the same. It is thereby possible for traditional cutting inserts, which can be mounted directly onto the holder, to be coupled to the presented spacer element and thus to be used, in the presented cutting tool as a second cutting insert. Previously known holders can likewise be used for the presented cutting tool. “Substantially the same” should thus be taken to mean that the interfaces themselves do not have to be of perfectly identical configuration, but rather those elements of the interface which are relevant to the force transmission and to the coupling of the components to be coupled together, such as, for instance, the number, position and orientation of ribs and thereto corresponding joints. 
         [0023]    Alternatively, in a further refinement, the first interface does not correspond to the fifth interface. It is hereby possible for the first and fifth interface to be adapted to a particular requirement of the first and second cutting insert. For example, the second cutting insert could be a three-edged cutting insert, and the first cutting insert a five-edged cutting insert. These cutting inserts could require different corresponding interfaces, which would be possible in this refinement. 
         [0024]    In a further refinement, the first and fifth interface are placed twisted relative to each other about the holder longitudinal axis. In this refinement, the cutting elements of the first and second cutting insert are arranged mutually offset in the radial direction. 
         [0025]    A peripherally offset (twisted) positioning of the cutting elements of the first and second cutting insert has the advantage that a better force distribution is achieved. This can be achieved by virtue of the fact that the two cutting inserts have a different offset relative to the interfaces. Alternatively, the cutting elements can be equally positioned relative to the interfaces of the cutting inserts, and the offset can be achieved by a mutually twisted, radial alignment of the interfaces. 
         [0026]    In a further refinement, the holder bore has an internal thread, the fastening element is a screw having a corresponding external thread, and all bores are through bores. The first cutting insert, the second cutting insert and the spacer element can hence be fastened in a particularly simple and stable manner with a screw. Similarly, a simple exchange of the spacer element is possible. 
         [0027]    In a further refinement, the cutting tool has precisely one spacer element. This has the advantage that the second cutting insert can be fastened with particularly high precision relative to the first cutting insert, since tolerances of a plurality of spacer elements are not added together. 
         [0028]    In a further refinement, the cutting tool has alternately a plurality of spacer elements and a plurality of first cutting inserts. It is hereby possible for more than two cutting inserts to be able to be fitted at defined spacings, and thus for also more than two bevels, joints and/or grooves to be able to be produced simultaneously. 
         [0029]    In a further refinement, the fifth interface of the spacer element corresponds to the fourth interface, so that a plurality of spacer elements can be coupled to one another. In much the same way as with plug-in modular components, different spacings can thus be realized by the simple attachment of spacer elements. By combining spacer elements of different length, it is thus possible to realize optional spacings between the cutting inserts by simple plugging together. 
         [0030]    In a further refinement, the third interface has three radial faces, which form an angle of 60° to one another. This enables particularly stable fastening. 
         [0031]    In a further refinement, the fastening element has an inner bore for the supply of coolant and/or for the lead-through of a fastening element. Advantageously, radially disposed openings in the fastening element can be used to supply coolant to different cutting inserts. 
         [0032]    It is to be understood that the aforementioned features and the following features which are yet to be described can be used not only in the respectively stated combination, but also in other combinations, or in isolation, without departing from the spirit of the invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0033]    Exemplary embodiments are illustrated in the drawings and will be ex-plained in greater detail in the following description. In the drawings: 
           [0034]      FIG. 1  shows an exploded representation of an embodiment of the cutting tool comprising holder, first cutting insert, spacer element, second cutting insert and fastening element, 
           [0035]      FIG. 2  shows an exploded representation similar to  FIG. 1  from another perspective, 
           [0036]      FIG. 3  shows a representation of the assembled cutting tool, 
           [0037]      FIG. 4  shows a representation of the assembled cutting tool from another perspective, 
           [0038]      FIG. 5  shows a representation of the assembled cutting tool, viewed from the side facing toward the workpiece, 
           [0039]      FIG. 6  shows a view of that side of the spacer element which is facing toward the workpiece, and 
           [0040]      FIG. 7  shows a view of that side of the spacer element which is facing away from the workpiece. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0041]      FIGS. 1 and 2  show the cutting tool  10 , which has a holder  12 , a first cutting insert  14 , a spacer element  16 , a second cutting insert  18  and a fastening element  20 . The holder  12  here comprises a holder base part  22  and a soldered-on part  24 , but can also in principle be configured in one piece. The soldered-on part  24  has a plurality of holes  26  for the supply of coolant. At that end of the soldered-on part which is nearest to the workpiece is disposed, on the end face, a first interface  28 . The axially parallel holder bore  30  runs axially through the holder. At that end of the axially parallel holder bore, which is nearest to the workpiece, an internal thread  32  is disposed, so that the fastening element  20 , which is realized as a screw and has an external thread  34 , can be screwed to the holder  12 . In this example, the first interface  28  is configured to be the same as the fifth interface  50 , which is shown in detail in  FIG. 7 . 
         [0042]    The first cutting insert  14  has a second interface  36  on the side facing toward the holder. Said second interface  36  corresponds to the first interface  28 . A third interface  38  is arranged on the side of the first cutting insert  14  that faces away from the holder  12 . Further, the first cutting insert  14  comprises a plurality of cutting elements  40 , which extend in radial direction and which are distributed over the periphery of the first cutting insert  14 . In this embodiment a cutting insert  14  having six cutting elements  40  is shown, but the number can be chosen differently according to the desired machining. Running through the cutting insert  14  is a bore  42  coaxial with the holder bore  30 . The third interface  38  has three radial contact surfaces  44  which are directed in a radially outward direction. The radial contact surfaces  44  stand at an angle of 60° to one another. The third interface  38  further comprises an axial contact surface  45 . 
         [0043]    A fourth interface  46  is arranged on the side of the spacer element  16  that faces toward the holder  12 . The fourth interface  46  has three inwardly directed radial contact surfaces  48 , running in the direction of the holder longitudinal axis. The inwardly directed radial contact surfaces  48  likewise stand at an angle of 60° to one another. On the side of the spacer element  16  which is facing away from the holder  12 , a fifth interface  50  is provided. Since the second interface  36  corresponds to the fifth interface  50 , a further cutting insert of the type of the first cutting insert, and a further spacer element, can be inserted between the spacer element  16  and the second cutting insert  18 . Through the addition of further first cutting inserts and spacer elements, a cutting tool  10  for the simultaneous performance of a plurality of cutting operations (for example creation of more than two bevels, joints and/or grooves) can thus be formed. 
         [0044]    Unlike the cutting tool shown in the figures, the fourth and fifth interface  46 ,  50  of the spacer element can also be designed such that they correspond to each other. A plurality of such spacer elements can thus be coupled to one another and greater spacings between the first and second cutting insert  14 ,  18  can be realized. 
         [0045]    On the side of the second cutting insert  18  which is facing toward the holder  12 , a sixth interface  52  is provided. Distributed in the peripheral direction, cutting elements  40 ′ are found on the second cutting insert  18 . These are arranged offset relative to the cutting elements  40  of the first cutting insert  14 . This is achieved by virtue of the fact that the fifth interface  50  (corresponding to the first interface  28 ) is twisted in comparison to the first interface  28  correspondingly in the peripheral direction. A contact surface  54  is arranged on the side facing away from the holder  12 . Against this contact surface  54 , the head  56  of the fastening element  20  can be placed. 
         [0046]    The screw (the fastening element)  20  comprises an external thread  34 . The screw  20  is sufficiently long that it can be guided through the bores, coaxial with the holder bore  30 , of the first cutting insert  14 , spacer element  16  and second cutting insert  18  and can be screwed to the internal thread  32  of the holder bore  30 . For this purpose, at that end of the screw  20  which is nearest to the workpiece a tool engagement member  58 , for example for a Torx wrench, is provided. 
         [0047]      FIG. 3  and  FIG. 4  show two lateral views of an inventive cutting tool  10  in the assembled state. In addition to the component parts already illustrated in  FIGS. 1 and 2 , the grooves  66  of the first interface  28  and of the second interface  36 , as well as the complementarily configured ribs  78  of the second and sixth interface  36 ,  52 , are here represented. The first and the fifth interface  28 ,  50  are of the same design, as are the thereto corresponding second and sixth interface  28 ,  52 . The first interface  28  is here, however, arranged slightly twisted relative to the fifth interface  50  about the holder longitudinal axis. The result is that also the second and sixth interface  36 ,  52 , and thus the first and second cutting insert  14 ,  18 , are arranged twisted relative to each other about the holder longitudinal axis. 
         [0048]      FIG. 5  shows a top view of the cutting tool  10  from the side facing toward the workpiece. It can be seen that the cutting elements  40 ,  40 ′ of the first and second cutting insert  14 ,  18  have an offset relative to each other. The mutually offset arrangement of the cutting elements  40 ,  40 ′ is a preferred embodiment, since a more even force distribution is obtained during the machining It is equally also conceivable, however, that in another embodiment the first and the fifth interface  28 ,  50  are not twisted relative to each other, and that the cutting elements of the first and second cutting insert  14 ,  18  thus also have no offset. 
         [0049]      FIG. 6  shows the side of the spacer element  16  which is facing toward the holder  12 . The fourth interface  46 , shown at the top in the figure, has three inwardly directed radial contact surfaces  48  (only one of which is visible in the figure). The three radial contact surfaces  48  are connected to one another by three rounded corner pieces  60 . Moreover, the fourth interface  46  has an inner axial surface  62  and an outer axial surface  64 . The supporting of a further interface coupled to the fourth interface  46  is here realized via the outer axial surface  64 . 
         [0050]    The transition between the inwardly directed radial contact surfaces  48  and the outer axial surface  64  is configured in the form of a beveled surface (bevel)  76 , which extends also along the round corner piece  60 . The bevel  76  facilitates the coupling with a corresponding interface, but is otherwise not fundamental to the interface characteristics of the fifth interface. 
         [0051]    On the side facing toward the holder  12 , the spacer element  16  can be shortened in length in the axial region  74  (for example rubbed down, turned or sawn off) without the interface characteristics of the fourth interface  46  being substantially changed thereby. The axial extent of the axial region  74  is here dependent on the axial extent of the region in which the interface has only radial faces. 
         [0052]    The third interface  38  corresponding to the fourth interface  46  has three axially projecting, outwardly directed radial contact surfaces  80  (shown in  FIG. 1 ). The height of these contact surfaces  80  in the axial direction is here less than the height of the inwardly directed radial contact surfaces  48  of the fourth interface  46 . In the assembled state, the inwardly directed contact surfaces  48  thus fully enclose the outwardly directed contact surfaces  80 . 
         [0053]      FIG. 7  shows the side of the spacer element  16  which is facing away from the workpiece. The fifth interface  50 , visible in the figure, has three grooves  66 , three secondary grooves  68  and three axial surfaces  82 . Each groove  66  has inclined side faces  70 ,  72 , the side faces  72  being more steeply inclined and being provided as torque driving surfaces. An interface corresponding to the fifth interface  50  has three corresponding ribs  78  (represented in  FIG. 2 ). 
         [0054]    The axial surfaces  82  are not necessarily intended for contact with a corresponding surface of the sixth interface  52 . The load-bearing regions are instead formed merely by part- surfaces on the side walls of the grooves  66  of the fifth interface  50 . A small gap thus remains between the axial surface  82  and an opposite axial surface  84  on the sixth interface  52 . This simplifies production because, unlike a full-faced contact against the axial surface  82 , only the smaller load-bearing regions on the grooves  66  have to be produced within narrow tolerances. In other words, the accuracy of the coupling realized with the fifth and sixth interface  50 ,  52  is not compromised by surface defects which may arise outside the limited load-bearing regions, should such faults be present on the axial surfaces  82  lying outside the load-bearing regions. Corresponding considerations apply to the opposite axial surface  84  on the sixth interface  52 . These considerations are of particular importance in the production process, because the sintered blanks which form the hard metal cutting inserts are laborious to machine. The considerations which are here set out in relation to the fifth and sixth interface  50 ,  52  apply correspondingly, for example, to a first and second interface  28 ,  36 . 
         [0055]    In summary, a tool is presented which is simple to produce and easy to operate and with which double or multiple machinings can be made in one operation with high accuracy. With just two new components (a first cutting insert having two interfaces and a spacer element), an innovative tool which offers a significant work saving in the conductance of a plurality of, in particular similar, machining operations is obtained. With the proposed tool, a single workpiece can here be machined. It is also suitable, however, for simultaneously machining a plurality of workpieces, in that these are machined stacked in a pack. In addition, the tool can be constituted both by a rotary and by a stationary metal-cutting tool.