Abstract:
An indexable milling insert has a parallelepipedic shape. The cutting insert includes a mounting hole placed centrally in the cutting insert, a first support side and a second support side, which support sides are parallel with each other and act as alternating support sides. The cutting insert is provided with main cutting edges, which are orientated perpendicularly to the centre axis of the mounting hole as well as provided in such a way that a rotation of the cutting insert around the centre axis of the mounting hole to an alternative insert seat alternatively a turning of the cutting insert to an alternative insert seat provides an identical location of the main cutting edges in relation to a piece to be machined. A milling tool equipped with such milling inserts is also provided. The cutting insert can include four identical sides for chip removing machining, the sides extending between the parallel support sides, and each side has exactly two cutting edge areas.

Description:
BACKGROUND AND SUMMARY 
       [0001]    The present invention relates to a cutting insert and a tool for chip removing machining, especially a milling insert and a milling tool. The milling insert is indexable in the milling tool. The milling tool is an end mill having 90° setting angle. 
         [0002]    By each one of WO 2003/101655 and WO 2004/050283, a tangential cutting insert as well as a milling tool are previously known. The cutting inserts comprise four cutting corners, which are distributed on two sides for chip removing machining, i.e., each side has two cutting corners. 
         [0003]    WO/0002693 shows a milling system having tangentially mounted cutting inserts where each cutting insert has eight cutting corners, which are distributed on two sides for chip removing machining, i.e., each side has four cutting corners. However, four of these cutting corners are intended for clockwise rotary machining and four cutting corners are intended for anticlockwise rotary machining. This means that only four cutting corners can be utilized in. one and the same milling tool and that the passive minor cutting edges may be worn during the machining. U.S. Pat. No. 4,597,695 shows another multi-edged cutting insert. 
         [0004]    It is desirable to provide a cutting insert and a tool for chip removing machining of the kind defined by way of introduction, the cutting insert being provided with a greater number of cutting corners, which in this case are eight. 
         [0005]    It is also desirable to provide the cutting insert with clearances between the cutting corners so that the inactive cutting corners do not interfere with the active cutting corner. 
         [0006]    It is also desirable that all cutting corners should be possible to be used for one and the same direction of rotation. 
         [0007]    According to an aspect of the present invention, 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Below a preferred embodiment of the invention will be described, reference being made to the accompanying drawings, where: 
           [0009]      FIG. 1  shows a perspective view of a first embodiment of a cutting insert according to the present invention; 
           [0010]      FIG. 2  shows a side view of a milling tool according to the present invention, equipped with cutting inserts according to  FIG. 1 ; 
           [0011]      FIG. 3  shows an enlargement of the dash-dotted circle A in  FIG. 2 ; 
           [0012]      FIG. 4  shows a planar view of the milling tool according to  FIG. 2 ; 
           [0013]      FIG. 5  shows an enlargement of the dash-dotted circle B in  FIG. 4 ; 
           [0014]      FIG. 6  shows a perspective view of a second embodiment of a cutting insert according to the present invention; 
           [0015]      FIG. 7  shows an end view of the cutting insert according to  FIG. 6 ; 
           [0016]      FIG. 8  shows a planar view of the cutting insert according to  FIG. 6 ; 
           [0017]      FIG. 9  shows a side view of a milling tool according to the present invention, equipped with cutting inserts according to  FIG. 6 ; and 
           [0018]      FIG. 10  shows an enlargement of the dash-dotted circle E in  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The cutting insert  1  for chip removing machining shown in  FIG. 1  constitutes a milling insert, which is four-sided, i.e., it has four active sides. The cutting insert  1  has a parallelepipedic basic shape and is manufactured from pressed or injection moulded cemented carbide. With “cemented carbide”, reference is here made to WC, TiC, TaC, NbC etc., in sintered combination with a binder metal such as, for instance, Co or Ni. The cutting insert  1  is preferably at least partly covered with a layer of, e.g., Al203, TiN and/or TiCN. In certain cases, it may be justified that the cutting edges comprise or consist of soldered superhard materials such as CBN or PCD. 
         [0020]    As is seen in  FIG. 1 , the cutting insert  1  comprises four sides S 1 , S 2 , S 3 , S 4 , which are intended for chip removing machining. In  FIG. 1 , only two sides S 1  and S 2  are visible. The cutting insert  1  has also two opposite support sides ST 1  and ST 2 , which are parallel with each other. Only the first support side ST 1  is visible in  FIG. 1 . For mounting the cutting insert I in an insert seat of a milling body, the cutting insert  1  is provided with a mounting hole  3 , which is provided centrally in the cutting insert  1  in respect of the support sides ST 1  and ST 2 . The mounting hole  3  penetrates both the first support side ST 1  and the second support side ST 2 . A centre axis C of the mounting hole  3  defines the axial direction of the milling insert  1 . 
         [0021]    Each one of the four sides S 1 -S 4  has two cutting edge areas and in total the cutting insert  1  accordingly has eight cutting edge areas SEO 1 , SEO 2 , SEO 3 , SEO 4 , SEO 5 , SEO 6 , SEO 7 , SEO 8 . Each one of the four sides S 1 -S 4  also has a support surface STY 1 , STY 2 , STY 3 , STY 4 . The support surfaces STY 1 -STY 4  have a rectangular shape and adjacent support surfaces STY 1 -STY 4  are interconnected so that they form a “band”, which extends around the cutting insert  1 . 
         [0022]    Each cutting edge area SEO 1 -SEO 8  has a main cutting edge H 1 , H 2 , H 3 , H 4 , H 5 , H 6 , H 7 , H 8  as well as a minor cutting edge B 1 , B 2 , B 3 , B 4 , B 5 , B 6 , B 7 , B 8 . Four of the main cutting edges H 1 , H 2 , H 3 , H 4  are situated adjacent to the first support side ST 1 , while the four other main cutting edges H 5 , H 6 , H 7 , H 8  are situated adjacent to the second support side ST 2 . The cutting edges connect to chip surfaces and clearance surfaces, the clearance surface of a cutting edge area, for example SEO 1 , having been provided essentially transversely to the clearance surface of an adjacent cutting edge area, SEO 6 . 
         [0023]    The main cutting edges H 1 -H 8  and associated minor cutting edges B 1 -B 8  are connected by means of nose cutting edges N 1 , N 2 , N 3 , N 4 , N 5 , N 6 , N 7 , N 8 , the first nose cutting edge N 1 , the second nose cutting edge N 2 , the fifth nose cutting edge N 5  and the sixth nose cutting edge N 6  of which are shown in  FIG. 1 . 
         [0024]    To each main cutting edge H 1 -H 8  and minor cutting edge B 1 -B 8 , a chip breaking countersunk recess U 1 , U 2 , U 3 , U 4 , U 5 , U 6 , U 7 , U 8  connects, the first U 1 , the second U 2 , the fifth U 5  and the sixth U 6  of which recesses are shown in  FIG. 1 . These recesses U 1 -U 8  are countersunk in relation to the cutting edges and give the cutting edges a positive rake angle in order to easily cut in a piece to be machined. 
         [0025]    In  FIG. 2 , a side view of a milling tool  10  according to the present invention is shown, a number of milling inserts  1  according to the present invention being tangentially mounted in insert seats of a milling body  11  of the milling tool  10 . With “tangentially mounted”, reference is made to a fixing screw being radially or axially screwed into the tool body but not tangentially screwed into the tool body. For the cutting insert, “tangentially mounted” relates to the mounting hole extending essentially parallel with the minor cutting edges of the cutting insert. A support side, e.g., ST 2  and two support surfaces S 1  and S 4  of the milling insert  1  co-operate with the appurtenant insert seat. The milling inserts  1  are anchored in the milling body  11  by screws, which extend through the mounting hole  3  of the respective milling insert  1  and into threaded holes of the milling body  11 . 
         [0026]    Each one of the minor cutting edges B 1  -B 8  is provided with a primary chamfer  5 , see  FIG. 3 , where the primary chamfer  5  of the minor cutting edge B 2  is shown, wherein the primary chamfer  5  of the minor cutting edge B 2  may essentially be situated in the plane of the paper in  FIG. 3 , while the corresponding primary chamfer of the adjacent minor cutting edge extends transversely to the plane of the paper in  FIG. 3 . In this connection, it should be pointed out that  FIG. 3  accordingly shows the milling insert  1  in the mounted state thereof in the milling tool according to  FIG. 2 . This entails that in the front view of the cutting insert  1  according to the present invention shown in  FIG. 3 , the minor cutting edge situated next to the minor cutting edge B 2  will be positioned on a higher level than the minor cutting edge B 2  in the position of the cutting insert  1  shown in  FIG. 3 . This level difference is illustrated by means of the distance “δ” in  FIG. 3 . Normally, the distance δ is in the order of 0.05 mm. Stated another way, an imaginary extension line L of a minor cutting edge B 2 ; B 102  for a chosen cutting edge area SEO 2 ; SEO 102  is spaced by a distance δ from an adjacent additional minor cutting edge B 7 ; B 107  while the adjacent additional minor cutting edge is comprised in a cutting edge area SEO 7 ; SEO 107  that faces away from the chosen cutting edge area SEO 2 . These two cutting edge areas may be perpendicular to each other. The main cutting edge H 2  and the minor cutting edge B 2  are the active cutting edges, while the adjacent minor cutting edge is inactive by the level difference described above.  FIG. 3  illustrates how the cutting insert  1  carries out end milling by 90° setting angle. The main cutting edge H 2  and the appurtenant minor cutting edge B 2  are in a common plane, wherein accordingly also the primary chamfer  5  of the minor cutting edge B 2  may be positioned in this plane. The corresponding applies to other main cutting edges and the appurtenant minor cutting edges. 
         [0027]      FIG. 4  shows a planar view of a milling tool  10  according to the present invention. In  FIG. 5 , an enlarged detail of  FIG. 4  is shown. The dash-dotted curved line D symbolizes the effective diameter of the tool, which the cutting tool according to the present invention generates during milling. By the fact that the nose cutting edges N 1 -N 8  have been given a convenient radius of curvature, the nose cutting edge N 1  of the cutting edge area SEO 1  will be situated inside the main cutting edge H 2 , as seen in the views according to  FIGS. 3 and 5 . The distance between the main cutting edge H 2  and the nose cutting edge N 1  is designated ε in  FIG. 5 . The distance e is normally in the order of 0.05 mm. 
         [0028]    In  FIG. 5  it is also seen that the cutting insert  1  according to the present invention is mounted in the milling body  11  in such a way that there is formed a wedge-shaped clearance W between the cutting insert  1  and the effective diameter D of the milling tool  10 . 
         [0029]    In  FIGS. 6-8 , an alternative embodiment of a milling insert  101  according to the present invention is shown, this milling insert  101  also having a parallelepipedic basic shape having four sides S 101 , S 102 , S 103 , S 104 , which are intended for chip removing machining. The cutting insert  10  also has two opposite support sides ST 101  and ST 102 , which are parallel with each other. For mounting the cutting insert  101  in an insert seat of a milling body, the cutting insert  101  is provided with a mounting hole  103 , which is provided centrally in the cutting insert  101  in respect of the support sides ST 101  and ST 102 . The mounting hole  103  penetrates both the first support side ST 101  and the second support side ST 102 . A centre axis C of the mounting hole  103  defines the axial direction of the milling insert  101 . 
         [0030]    The cutting insert  101  has also eight cutting edge areas SEO 101 , SEO 102 , SEO 103 , SEO 104 , SEO 105 , SEO 106 , SEO 107 , SEO 108 , which each one comprises a main cutting edge H 101 , H 102 , H 103 , H 104 , H 105 , H 106 , H 107 , H 108 , an appurtenant minor cutting edge B 101 , B 102 , B 103 , B 104 , B 105 , B 106 , B 107 , B 108  as well as an appurtenant nose cutting edge N 101 , N 102 , N 103 , N 104 , N 105 , N 106 , N 107 , N 108 . 
         [0031]    The most obvious difference in comparison with the embodiment described above is the formation of the support surfaces and the recesses, which are integrated with each other. Such as most clearly is seen in  FIGS. 6 and 7 , the four support surfaces STY 101 , STY 102 , STY 103 , STY 104  extend generally diagonally in a side surface S 101 -S 104 , the support surfaces STY 101 -STY 104  al so forming a part of the recesses U 101 , U 102 , U 103 , U 104 , U 105 , U 106 , U 107 , U 108  belonging to each cutting edge area SEO 101 -SEO 108 . The fact that the support surfaces and the recesses are integrated with each other has as a consequence that the cutting insert  101  has a smaller extension in the axial direction C 1  than the cutting insert  1  in the embodiment described above. Also here it is seen that the cutting edges connect to chip surfaces and clearance surfaces, the clearance surface of a cutting edge area, for example SE 01 O 1 , having been provided essentially transversely to the clearance surface of an adjacent cutting edge area, SE 01 O 6 . 
         [0032]    In  FIG. 9 , a side view of a milling tool  110  according to the present invention is shown, a number of milling inserts  101  according to the present invention being tangentially mounted in insert seats of a milling body  111  of the milling tool  110 . In that connection, a support side ST 101 , ST 102  and two support surfaces S 101 -S 104  of the milling insert  101  co-operate with the appurtenant insert seat. The milling inserts  101  are anchored in the milling body  111  by screws, which extend through the mounting hole  103  of the respective milling insert  101  and into threaded holes of the milling body  111 . 
         [0033]    Correspondingly as in the embodiment described above, each one of the minor cutting edges B 101 -B 108  is provided with a primary chamfer  105 , see  FIG. 10 , where the primary chamfer  105  of the minor cutting edge B 102  is shown, the primary chamfer  105  of the minor cutting edge B 102  being essentially situated in the plane of the paper in  FIG. 10 , while the corresponding primary chamfer of the adjacent minor cutting edge extends transversely to the plane of the paper in  FIG. 10 . In this connection, it should be pointed out that  FIG. 10  accordingly shows the milling insert  101  in the mounted state thereof in the milling tool according to  FIG. 9 . This entails that in the front view of the cutting insert  1  according to the present invention shown in  FIG. 10  the minor cutting edge situated next to the minor cutting edge B 102  will be positioned on a higher level than the minor cutting edge B 102  in the position of the cutting insert  101  shown in  FIG. 9 . This level difference is illustrated by means of the distance “δ” in  FIG. 10 . Normally, the distance  6  is in the order of 0.05 mm. The main cutting edge H 102  and the minor cutting edge B 102  are the active cutting edges, while the adjacent minor cutting edge is inactive by the level difference described above.  FIG. 10  illustrates how the cutting insert  1  carries out end milling by 90° setting angle. The main cutting edge H 102  and the appurtenant minor cutting edge B 102  are in a common plane. The corresponding applies to other main cutting edges and the appurtenant minor cutting edges. 
         [0034]    As for the distance ε described above which is shown in  FIG. 5  the milling insert  101  has the corresponding distance ε, this distance normally being in the order of 0.05 mm. 
         [0035]    In the tangential mounting of the milling inserts  101  in the milling body  111 , the cutting inserts  101  obtain a corresponding wedge-shaped clearance W as has been described above in connection with  FIG. 5 . 
         [0036]    In a milling insert  1 ;  101  according to the present invention, all eight cutting edge areas SEO 1 -SEO 8 ; SEO 101 -SEO 108  can be indexed forward for one and the same direction of rotation of the milling tool  10  according to the present invention. 
         [0037]    In the embodiments described above distance ε is provided by the fact that the nose cutting edges N 1 -N 8  are given a convenient curvature. However, within the scope of the present invention it is conceivable that the distance is provided by the fact that the nose cutting edges N 1 -N 8  are in the form of chamfers.