Abstract:
A combination of a cutting insert and a shim. The cutting insert and shim have two opposing end surfaces, two identical opposing major side surfaces and two identical opposing minor side surfaces. Each end surface of the insert has a shim abutment surface for contacting the shim. One end surface of the shim has an insert abutment surface for contacting the insert. The abutment surfaces contact each other along an entire length of the cutting insert and shim 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 
       [0001]    In general, the invention relates to a cutting insert and a cutting tool, and in particular to a cutting insert 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 
       [0002]    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. 
         [0003]    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 
       [0004]    In one aspect of the invention, a cutting insert comprises two opposing end surfaces, two opposing minor side surfaces extending between the two opposing end surfaces, and two opposing major side surfaces extending between the end surfaces and the minor side surfaces. Each end surface has four corners including two lowered corners and two raised corners. The two lowered corners are diagonally opposite each other, and the two raised corners are diagonally opposite each other. The cutting insert further includes two opposing major edges formed at an intersection of each end surface and the major side surfaces, two opposing minor edges formed at an intersection of each end surface and the minor side surfaces, and two opposing corner edges formed at an intersection of each the corner side surfaces and the major side surfaces. The cutting insert further includes a major cutting edge formed at an intersection of each major edge and the end surface, and a minor cutting edge formed at an intersection of each minor edge and the end surface, and a corner cutting edge formed at an intersection of the major and minor cutting edges. Each end surface includes a shim abutment surface that extends from one lowered corner to the diagonally opposite lowered corner. 
         [0005]    In another aspect, a combination cutting insert and a 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, and two opposing major side surfaces extending between the end surfaces and the minor side surfaces. Each end surface has four corners including two lowered corners and two raised corners. The two lowered corners are diagonally opposite each other, and the two raised corners are diagonally opposite each other. Each end surface includes a shim abutment surface that extends from one lowered corner to the diagonally opposite lowered corner. The shim comprises two opposing end surfaces, two opposing minor side surfaces extending between the two opposing end surfaces. Two opposing major side surfaces extend between the end surfaces and the minor side surfaces. One end surface has four corners comprising two lowered corners and two raised corners. The two lowered corners are diagonally opposite each other, and the two raised corners are diagonally opposite each other. One of the end surfaces of the shim has an insert abutment surface that extends entirely from one raised corner to the diagonally opposite raised corner of the shim for contacting the shim abutment surface of the cutting insert. 
         [0006]    In another aspect, a milling cutter comprises a plurality of insert pockets, wherein the cutting insert and the shim of the invention are seated in each of the plurality of insert pockets. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    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. 
           [0008]      FIG. 1  is an isometric view of an exemplary embodiment of a cutting insert of the invention; 
           [0009]      FIG. 2  is an end view of the exemplary embodiment of the cutting insert of  FIG. 1 ; 
           [0010]      FIG. 3  is a top view of the exemplary embodiment of the cutting insert of  FIG. 1 ; 
           [0011]      FIG. 4  is a front view of the exemplary embodiment of the cutting insert of  FIG. 1 ; 
           [0012]      FIG. 5  is a cross-sectional view of the exemplary embodiment of the cutting insert taken along line  5 - 5  of  FIG. 3 ; 
           [0013]      FIG. 6  is a cross-sectional view of the exemplary embodiment of the cutting insert taken along line  6 - 6  of  FIG. 3 ; 
           [0014]      FIG. 7  is an isometric view of an exemplary embodiment of a shim of the invention; 
           [0015]      FIG. 8  is another isometric view of an exemplary embodiment of the shim of  FIG. 7 ; 
           [0016]      FIG. 9  is an end view of the exemplary embodiment of the shim of  FIG. 7 ; 
           [0017]      FIG. 10  is another end view of the exemplary embodiment of the shim of  FIG. 7 ; 
           [0018]      FIG. 11  is a side view of the exemplary embodiment of the shim of  FIG. 7 ; 
           [0019]      FIG. 12  is a cross-sectional view of an exemplary embodiment of the cutting insert and the shim; and 
           [0020]      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. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Referring now to  FIGS. 1-6 , 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 A1 passing through the two end surfaces  12 , each minor side surface  14  has 180° rotational symmetry about a second central axis A2 passing through the two minor side surfaces  14 , and each major side surface  16  has 180° rotational symmetry about a third central axis A3 passing through the two major side surfaces  16 . The second central axis A2 is perpendicular to the first central axis A1, and the third central axis A3 is perpendicular to the first central axis A1 and to the second central axis A2. 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 . 
         [0022]    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 A2 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 . 
         [0023]    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  14  and extends along 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 shown in  FIG. 4 . Because the cutting insert  10  is symmetric about all three axes, A1, A2 and A3, the cutting insert  10  has a total of four major cutting edges  38 , four minor cutting edges  40  and four corner cutting edges  42 . 
         [0024]    Referring now to  FIGS. 3 ,  5  and  6 , one aspect of the invention is that each end surface  12  of the cutting insert  10  has a shim abutment surface  30  for contacting a shim  60  ( FIG. 7 ) that extends entirely from one lowered corner  20  to the diagonally opposite lowered corner  20  of the cutting insert  10 . In the illustrated embodiment, the shim abutment surface  30  is in the form of a U-shaped groove having side support walls  30   a ,  30   b , and a bottom wall  30   c  formed between the two side support walls  30   a ,  30   b  with a radius R. The two side support walls  30   a ,  30   b  extend from the bottom wall  30   c  to the surface  26  of each raised member  24 , as shown in  FIG. 3 . 
         [0025]    As shown in  FIG. 5 , the two side support walls  30   a ,  30   b  are formed at an angle  48  with respect to the second central axis A2. That is, the two side support walls  30   a ,  30   b  are non-parallel to the third central axis A3 of the cutting insert  10 , unlike conventional cutting inserts. The angle  48  can be greater than zero (0) degrees and less than ninety (90) degrees. In the illustrated embodiment, the angle  48  is about sixty (60) degrees. However, it will be appreciated that the invention is not limited by the magnitude of the angle  48 , and that the invention can be practiced with any desirable angle between the two side support walls  30   a ,  30   b  to provide sufficient contact between the insert  10  and the shim  60 . In an alternate embodiment, the radiused bottom wall  30   c  can be omitted and the abutment surface  30  can have a substantially V-shaped profile with only the side supports surfaces  30   a ,  30   b , rather than a substantially U-shaped profile of the illustrated embodiment. 
         [0026]    As shown in  FIGS. 5 and 6 , a distance  50  between the bottom wall  30   c  and the third central axis A3 remains constant across the entire length of the abutment surface  30 . In other words, the bottom wall  30   c  of the shim abutment surface  30  is substantially coplanar along its entire length from one lowered corner  20  to the diagonally opposite lowered corner  20 . 
         [0027]    As shown in  FIG. 3 , the bottom wall  30   c  has a substantially constant width along its entire length from one lowered corner  20  to the diagonally opposite lowered corner  20 . On the other hand, the side support walls  30   a ,  30   b  have a continuously varying width  52  along their entire length from one lowered corner  20  to the diagonally opposite lowered corner  20 . Specifically, the width  52  of the side support walls  30   a ,  30   b  are inversely proportional to each other. For example, the width of the side support wall  30   a  is a minimum, while the width  52  of the side support wall  30   b  is a maximum at the lowered corner  20 , and the width  52  of the side support wall  30   a  is a maximum, while the width  52  of the side support wall  30   b  is a minimum at the diagonally opposite lowered corner  20 . It is noted that the width  52  of each side support wall  30   a ,  30   b  is approximately equal to each other at a point where the first central axis A1 and the third central axis A3 intersect each other, as shown in  FIG. 3 . 
         [0028]    Referring now to  FIGS. 7-11 , 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 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 minor side surface  64  is asymmetric about a second central axis A2 passing through the two minor side surfaces  64 , and each major side surface  66  has 180° rotational symmetry about a third central axis A3 passing through the two major side surfaces  66 . The second central axis A2 is perpendicular to the first central axis A1, and the third central axis A3 is perpendicular to the first central axis A1 and to the second central axis A2. 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 . 
         [0029]    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 A2 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 a 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 surface  76  extends entirely from one raised corner  72  to the diagonally opposite raised corner  72  of the shim  60 . As seen in  FIG. 7 , the insert abutment surface  76  is planar and perpendicular to the first central axis A1, and parallel to both the second central axis A2 and the third central axis A3. 
         [0030]    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 . 
         [0031]    As shown in  FIG. 10 , another aspect of the invention is that one of the end surfaces  62  of the shim  60  has an insert abutment surface  76  that extends entirely from one raised corner  72  to the diagonally opposite raised corner  72  of the shim  60  for contacting the shim abutment surface  30  of the cutting insert  10 . In the illustrated embodiment, the insert abutment surface  76  is in the form of a U-shaped protrusion having substantially planar side support walls  76   a ,  76   b , and a substantially planar top wall  76   c  formed between the two side support walls  76   a ,  76   b . The two side support walls  76   a ,  76   b  extend from the top wall  76   c  to the surface  80  of each lowered member  78 , as shown in  FIG. 10 . 
         [0032]    As shown in  FIGS. 7 ,  9  and  10 , the two side support walls  76   a ,  76   b  are formed at an angle  88  with respect to the second central axis A2. That is, the two side support walls  76   a ,  76   b  are non-parallel to the second central axis A2 of the shim  60 , unlike conventional shims. The angle  88  can be greater than zero (0) degrees and less than ninety (90) degrees. In the illustrated embodiment, the angle  88  is about sixty (60) degrees. However, it will be appreciated that the invention is not limited by the magnitude of the angle  88 , and that the invention can be practiced with any desirable angle between the two side support walls  76   a ,  76   b  to provide sufficient contact between the insert  10  and the shim  60 . In one embodiment, the angle  88  is approximately equal to the angle  52  of the side support walls  30   a ,  30   b  of the shim abutment surface  30  of the cutting insert  10 . Similar to the bottom wall  30   c  of the shim abutment surface  30 , the top wall  76   c  of the insert abutment surface  76  has a constant width. 
         [0033]    Referring now to  FIG. 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 side support walls  30   a ,  30   b  of the shim abutment surface  30  of the cutting insert  10  engage the side support walls  76   a ,  76   b  of the insert abutment surface  76  of the shim  60  along the entire length of the cutting insert  10  and the shim  60 , thereby increasing the contact area between the cutting insert  10  and the shim  60 . It is noted that the bottom surface  30   c  of the shim abutment surface  30  of the cutting insert  10  does not contact the top surface  76   c  of the insert abutment surface  76  of the shim  60 . In addition, the diagonal opposite engagement of the cutting insert  10  and the shim  60  along the entire length aids in centering the cutting insert  10  with respect to the shim  60 . Further, the large contact area between the cutting insert  10  and the shim  60  is located in an area where high cutting forces occur during heavy machining applications. Because the cutting insert  10  and the shim  60  contact each other in the area 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. 
         [0034]    Referring now to  FIG. 13 , a milling cutter  100  is shown according to an embodiment of the invention. The milling cutter  100  has an axis of rotation  101 , and a cutter body  102  with a plurality of insert pockets  104 . In each insert pocket  104 , the cutting insert  10  and the 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 . 
         [0035]    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 shim abutment surface  36  on the end surface  12  of the cutting insert  10  engages the insert abutment surface  76  of the shim  60  to permit proper seating and reduced rotation of the cutting insert  10  during heavy machining operations. 
         [0036]    The patents and publications referred to herein are hereby incorporated by reference. 
         [0037]    Having described presently preferred embodiments the invention may be otherwise embodied within the scope of the appended claims.