Abstract:
A combination of a cutting insert and a shim. The cutting insert and shim have two opposing end surfaces with two identical opposing major side surfaces and two identical opposing minor side surfaces extending between the minor side surfaces. Each end surface of the insert has two lowered abutment members, each having a shim abutment surface for contacting the shim. One end surface of the shim has two raised abutment members, each having an insert abutment surface for contacting the insert. The abutment surfaces contact each other in an area where high cutting forces occur so as to help distribute the loads encountered in the cutting operation, as well as provide protection of the insert pocket in case of insert failure.

Description:
FIELD OF THE INVENTION 
     In general, the invention relates to a cutting insert and a cutting tool, and in particular to a combination of a cutting insert and shim for a milling cutter that contact with each other in an area where high cutting forces occur so as to help distribute the loads (stresses) encountered in the cutting operation, as well as provide protection of the insert pocket in case of insert failure. 
     BACKGROUND OF THE INVENTION 
     One problem encountered with conventional tool holders is that of holding the cutting insert securely in the pocket of the tool holder. At the beginning of a cutting operation, the sudden transition from no load to extreme pressure load on the insert can cause the insert to shift position in the holder and thereby affect the accuracy of the planned cut. At the end of the cutting operation, the sudden disengagement of the cutting insert from the workpiece causes the pressure load suddenly to be removed from the insert. This sudden change in load can cause the insert to shift and distress any repeatable dimensional accuracy, which is essential for most tool holders, especially cutting inserts used in Numerically Controlled machines, to meet. 
     During the cutting operation, loads of up to 35,000 pounds may be encountered on the cutting insert which, if the insert is not precisely located and firmly held in the holder to begin with, can also cause shifting of the insert during the cutting operation. It is, therefore, important to provide a tool holder that can precisely and securely seat a cutting insert and then securely hold the cutting insert in location during all phases of the heavy duty cutting operation. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention, in combination, a cutting insert and shim for heavy machining operations. The cutting insert comprises two opposing end surfaces, two opposing minor side surfaces extending between the two opposing end surfaces, two opposing major side surfaces extending between the end surfaces and the minor side surfaces, each end surface having four corners including two lowered corners and two raised corners, each end surface provided with two raised abutment members and two lowered abutment members, each lowered abutment member having a shim abutment surface, wherein the shim abutment surfaces are diagonally opposite each other with respect to the second, central axis of the cutting insert. The shim comprises two opposing end surfaces, two opposing minor side surfaces extending between the two opposing end surfaces, two opposing major side surfaces extending between the end surfaces and the minor side surfaces, one end surface having four corners including two lowered corners and two raised corners, the one end surface being provided with two raised abutment members and two lowered abutment members, each raised abutment member having an insert abutment surface, wherein the insert abutment surfaces are diagonally opposite each other with respect to the second, central axis of the shim. The shim abutment surfaces of the cutting insert engage the insert abutment surfaces of the shim when the cutting insert and shim are mounted within an insert pocket of a cutting tool. 
     In another aspect, a milling cutter comprises a plurality of insert pockets, and the combination of a cutting insert and a shim seated in each of the plurality of insert pockets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While various embodiments of the invention are illustrated, the particular embodiments shown should not be construed to limit the claims. It is anticipated that various changes and modifications may be made without departing from the scope of this invention. 
         FIG. 1  is an isometric view of an exemplary embodiment of a cutting insert of the invention; 
         FIG. 2  is another isometric view of the exemplary embodiment of the cutting insert of  FIG. 1 ; 
         FIG. 3  is an end view of the exemplary embodiment of the cutting insert of  FIG. 1 ; 
         FIG. 4  is another end view of the exemplary embodiment of the cutting insert of  FIG. 1 ; 
         FIG. 5  is a side view of the exemplary embodiment of the cutting insert of  FIG. 1 ; 
         FIG. 6  is an isometric view of an exemplary embodiment of a shim of the invention; 
         FIG. 7  is another isometric view of an exemplary embodiment of the shim of  FIG. 6 ; 
         FIG. 8  is an end view of the exemplary embodiment of the shim of  FIG. 6 ; 
         FIG. 9  is another end view of the exemplary embodiment of the shim of  FIG. 6 ; 
         FIG. 10  is a side view of the exemplary embodiment of the shim of  FIG. 6 ; 
         FIG. 11  is an isometric view of an exemplary embodiment of the combination cutting insert and shim; 
         FIG. 12  is a side view of the exemplary embodiment of the combination cutting insert and shim; 
         FIG. 13  is an isometric view of an exemplary embodiment of a milling cutter with the combination cutting insert and shim seating in insert pockets; and 
         FIG. 14  is a side view of the exemplary embodiment of the milling cutter of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIGS. 1-5 , a cutting insert  10  is shown according to an embodiment of the invention. In general, the cutting insert  10  is tangential and indexable. The cutting insert  10  is typically manufactured by form-pressing and sintering carbide powders using methods well-known in the art. The cutting insert  10  is generally rectangular in shape and has two identical opposing end surfaces  12 , two identical opposing minor side surfaces  14  extending between the two opposing end surfaces  12 , two identical opposing major side surfaces  16  extending between the end surfaces  12  and the minor side surfaces  14 . Each end surface  12  has 180° rotational symmetry about a first central axis A 1  passing through the two end surfaces  12 , each minor side surface  14  has 180° rotational symmetry about a second central axis A 2  passing through the two minor side surfaces  14 , and each major side surface  16  has 180° rotational symmetry about a third central axis A 3  passing through the two major side surfaces  16 . The second central axis A 2  is perpendicular to the first central axis A 1 , and the third central axis A 3  is perpendicular to the first central axis A 1  and to the second central axis A 2 . The cutting insert  10  also includes four opposed corner side surfaces  18  between the minor and major side surfaces  14 ,  16  and the end surfaces  12 . 
     Each end surface  12  has four corners; two diagonally opposite lowered corners  20  and two diagonally opposite raised corners  22 . The lowered corners  20  are closer to the second central axis A 2  than the raised corners  22 . Each corner side surface  18  extends between the raised corner  22  of one of the two opposing end surfaces  12  and the lowered corner  20  of the other one of the two opposing end surfaces  12 . Each end surface  12  is provided with two raised members  24 , each raised member  24  having a surface  26 , and two lowered abutment members  28 , each lowered abutment member  28  having a shim abutment surface  30  for contacting the shim  60 . The shim abutment surfaces  30  are diagonally opposite each other with respect to the second central axis A 2 . As seen in  FIGS. 2 and 3 , the shim abutment surfaces  30  are substantially coplanar with each other and are substantially parallel with both the second central axis A 2  and the third central axis A 3 . 
     Two opposing major edges  32  are formed at the intersection of each end surface  12  and the major side surfaces  16 , two opposing minor edges  34  are formed at the intersection of each end surface  12  and the minor side surfaces  14 , and two opposing corner edges  36  are formed at the intersection of each the corner side surfaces  18  and the major side surfaces  16 . A major cutting edge  38  is formed at the intersection of each major edge  32  and the end surface  12  and extends along substantially the entire length of its associated major edge  32 . A minor cutting edge  40  is formed at the intersection of each minor edge  34  and the end surface and extends along at least half of the length of its associated minor edge  34 . A corner cutting edge  42  is formed at the intersection of the major and minor cutting edges  38 ,  40 . The section of the major cutting edge  38  proximate the raised corner  22  constitutes a leading end  44  of the major cutting edge  38 , whereas the section of the major cutting edge  38  proximate the lowered corner  20  constitutes a trailing end  46  of the major cutting edge  38 . 
     As seen in  FIG. 3 , the minor edge  34  is divided into three substantially straight sections; a first section  48  extending from the raised corner  22  to approximately one-half the distance to the central axis A 1 ; a second section  50  extending from the first section  48  to approximately the central axis A 1 ; and a third section  52  extending from the central axis A 1  to the lowered corner  20 . As seen in  FIG. 3 , the minor edge  34  is generally L-shaped when viewed from the side of the cutting insert  10 . That is, the first section  48  and the third section  52  are substantially parallel to each other and to the third central axis A 3 . In other words, the first and third sections  48 ,  52  do not overlap and do not lie on a common straight line when viewed from the side of the cutting insert  10 . 
     Referring now to  FIGS. 6-10 , a shim  60  is shown according to an embodiment of the invention. In general, the shim  60  is generally rectangular in shape and has two identical opposing end surfaces  62 , two identical opposing minor side surfaces  64  extending between the two opposing end surfaces  62 , two identical opposing major side surfaces  66  extending between the end surfaces  62  and the minor side surfaces  64 . Each end surface  62  has 180° rotational symmetry about a first central axis A 1  passing through the two end surfaces  62 , each minor side surface  64  is asymmetric about a second central axis A 2  passing through the two minor side surfaces  64 , and each major side surface  66  has 180° rotational symmetry about a third central axis A 3  passing through the two major side surfaces  66 . The second central axis A 2  is perpendicular to the first central axis A 1 , and the third central axis A 3  is perpendicular to the first central axis A 1  and to the second central axis A 2 . The cutting insert  10  also includes four opposed corner side surfaces  68  between the minor and major side surfaces  64 ,  66  and the end surfaces  62 . 
     Similar to the cutting insert  10 , one of the end surfaces  62  has four corners; two diagonally opposite lowered corners  70  and two diagonally opposite raised corners  72 . Unlike the cutting insert  10 , the other end surface  62  is substantially planar for engaging the rear wall of the insert pocket, as described below. The lowered corners  70  are closer to the second central axis A 2  than the raised corners  72 . Each corner side surface  68  extends between the raised corner  72  of one of the two opposing end surfaces  62  and the lowered corner  70  of the other one of the two opposing end surfaces  62 . One of the end surfaces  62  is provided with two raised abutment members  74 , each raised abutment member  74  having an insert abutment surface  76  for contacting the insert  10 , and two lowered members  78 , each lowered member  78  having a surface  80 . The insert abutment surfaces  76  are diagonally opposite each other with respect to the second central axis A 2 . As seen in  FIGS. 6 and 8 , the insert abutment surfaces  76  are substantially coplanar with each other. In addition, the insert abutment surfaces  76  are substantially parallel with both the second central axis A 2  and the third central axis A 3 . 
     Two opposing major edges  82  are formed at the intersection of each end surface  62  and the major side surfaces  66 , two opposing minor edges  84  are formed at the intersection of each end surface  62  and the minor side surfaces  64 , and two opposing corner edges  86  are formed at the intersection of each the corner side surfaces  68  and the major side surfaces  66 . 
     As seen in  FIG. 8 , the minor edge  84  is divided into three substantially straight sections; a first section  88  extending from the raised corner  72  to approximately one-half the distance to the central axis A 1 ; a second section  90  extending from the first section  88  to approximately the central axis A 1 ; and a third section  92  extending from the central axis A 1  to the lowered corner  70 . As seen in  FIG. 8 , the minor edge  84  is generally L-shaped in the side view, similar to the minor edge  34  of the cutting insert  10 . That is, the first section  88  and the third section  92  are substantially parallel to each other and to the third central axis A 3 . In other words, the first and third sections  88 ,  92  do not overlap and do not lie on a common straight line when viewed from the side of the shim  60 . 
     Referring now to  FIGS. 11 and 12 , the insert  10  and the shim  60  interact with each other to provide additional support to permit proper seating and reduce rotation of the cutting insert  10  during heavy machining applications, as compared to conventional cutting inserts and shims. Specifically, the diagonally opposite shim abutment surfaces  26  on the end surface  12  of the cutting insert  10  engage the diagonally opposite insert abutment surfaces  76  of the shim  60 . This diagonally opposite engagement of the cutting insert  10  and the shim  60  is located in an area  94  where high cutting forces occur during heavy machining applications. Because the cutting insert  10  and the shim  60  contact each other in the area  94  where high cutting forces (and high stress) occur, additional support to permit proper seating and reduced rotation of the cutting insert  10  is provided by the cutting insert  10  and shim  60  of the invention. 
     Referring now to  FIGS. 13 and 14 , a milling cutter  100  is shown according to an embodiment of the invention. The milling cutter  100  has an axis of rotation R, and a cutter body  102  with a plurality of insert pockets  104 . In each insert pocket  104 , the cutting insert  10  and shim  60  of the invention is tangentially mounted to the cutter body  102  by means of a clamping screw  106 ,  108 , respectively. As can be seen, each cutting insert  10  is seated so that there is a clearance between a workpiece (not shown) and the minor side surface  14  of the cutting insert  10 , the minor side surface  64  of the shim  60  and the face  110  of the milling cutter  100 . 
     The insert pocket  104  includes a side wall  112  and a rear wall  114  generally transverse to a bottom wall  116 . Each wall  112 ,  114 ,  116  is generally planar. When seated in the insert pocket  104 , one of the minor side surfaces  14  of the cutting insert  10  is adjacent and engages the side wall  112 , and one of the major side surfaces  16  of the cutting inset  10  is adjacent and engages the bottom wall  116  of the insert pocket  104 . Similarly, one of the minor side surface  64  of the shim  60  is adjacent and engages the side wall  112 , and one of the major side surfaces  66  of the shim  60  is adjacent and engages the bottom wall  116  of the insert pocket  104 . In addition, the diagonally opposite shim abutment surfaces  26  on the end surface  12  of the cutting insert  10  engages the diagonally opposite insert abutment surfaces  76  of the shim  60  to permit proper seating and reduced rotation of the cutting insert  10  during heavy machining operations. 
     The patents and publications referred to herein are hereby incorporated by reference. 
     Having described presently preferred embodiments the invention may be otherwise embodied within the scope of the appended claims.