Abstract:
A milling cutter having a plurality of on-edge cutting inserts mounted within pockets about the peripheral wall of the cutter body includes angled pockets which not only permit a greater number of pockets to accept inserts but furthermore permits relatively easy access to insert and remove mounting screws for securing each insert within a pocket.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to milling cutters and, more specifically, to a plunge milling cutter having angled pockets with a chip clearance groove to permit a greater number of inserts to be mounted within the cutter. 
     2. Description of Related Art 
     A goal of most metalworking operations is to perform a given machining task in the least amount of time and in a manner that will not result in premature tool failure. In particular, in a milling operation, it is well-known that the cutting forces upon, and the tool wear of, individual inserts within a milling cutter will be diminished if the cutting load is evenly distributed among many inserts in the milling cutter. However, in the past, milling cutter body designs have limited the maximum number of cutting inserts to be placed in the body. Utilizing a cutter with the maximum number of inserts is especially important for the machining of cam lobes on cam shafts of internal combustion engines. 
     U.S. Pat. No. 5,820,308 is directed to a milling cutter having a plurality of on-edge inserts mounted about the periphery of the cutter. The orientation of these on-edge inserts limits the number of inserts that will fit within the cutter body. 
     An object of this invention is to provide a plunge milling cutter having a greater number of cutting inserts about its periphery to minimize the force and to maximize the tool life of each insert in the milling cutter while at the same time providing effective chip clearance. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a plunge milling cutter comprising a cutter body rotatable about a central axis, a peripheral wall on the cutter body, and insert pockets located in the peripheral wall. Each pocket is spaced from an adjacent pocket by a lug and each pocket has support surfaces including a bottom surface adapted for positioning a rectangular insert within a predefined rectangular envelope within the pocket. Each rectangular envelope has a front and back and four sides therebetween, including a top side, a bottom side and a radially inward side. Each lug has a radial width, a front face extending upwardly from the pocket bottom to the top of the lug, an axial face extending downwardly from the top of the lug to a height below the top of the lug; and a rear face extending from the axial face downwardly to the bottom surface of an adjacent pocket. The support surfaces of the pocket are defined by the lug front face, the bottom surface, the lug rear face of an adjacent lug, and a pocket wall positioned radially inwardly from the peripheral wall and connecting adjacent lugs. The lug axial face is sloped downwardly across the entire lug width from the top of the lug to the lug rear face, thereby providing a chip clearance groove across the entire width of the lug. Furthermore, the lug front face extends over the entire back of the insert envelope. 
     The invention is further directed to a plunge milling cutter assembly comprising a milling cutter as described above and including inserts within each pocket of the milling cutter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a perspective view of a milling cutter in accordance with the subject invention; and 
     FIG. 2 illustrates an enlarged view from a slightly different perspective view of a portion of the cutter in FIG. 1, however, with a cutting insert retracted from a pocket and a phantom insert envelope introduced for illustrative purposes. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a milling cutter  10  having a cutter body  12  rotatable about a central axis  14 . A plurality of cutting inserts  16  may be mounted about the peripheral wall  18  within pockets  20  (FIG. 2) therein. The cutting inserts  16  are identified as lay-down inserts. 
     A lay-down cutting insert is one where the cutting face of the insert is located on the largest seating surface of the insert. On the other hand, an on-edge cutting insert is one where the cutting face of the insert is located on a side of the insert perpendicular to the largest seating surface for the insert. A milling cutter with lay-down inserts, not on-edge inserts, is the subject matter of the present application. Using lay-down cutting inserts, the inventors have discovered a design that permits more inserts to be installed in the milling cutter than if they were to use on-edge cutting inserts. 
     The milling cutter  10  may be used for plunge milling operations and, more particularly, may be used for the machining of cam lobes on cam shafts used for automotive equipment. 
     Reference will be made to top and bottom with respect to the elements of FIG. 2, however it should be understood that these terms are used only to describe the relative location of these elements. 
     For clarity reference will also be made to a single pocket  20  and a single lug  25  with the understanding that each pocket and lug is identical to other pockets and lugs in the cutter body  12 . However, separate reference will be made to adjacent pockets  20 A,  20 B and adjacent lugs  25 A,  25 B to better describe pocket  20  and lug  25 . 
     Directing attention to FIG. 2, insert pocket  20  is spaced from an adjacent pocket  20 B by a lug  25  and is defined, in large part, by two lugs  25 ,  25 A. 
     Each pocket  20  has support surfaces including a bottom surface  27 . Furthermore, the pocket  20  is adapted for positioning a rectangular insert  16  conforming to a predefined rectangular envelope  30  in the pocket  20 . Although the insert envelope  30  is actually located within the pocket  20 , for clarity in illustration, the envelope  30  has been extracted as shown in FIG.  2 . 
     The rectangular envelope  30  has a front  32 , a back  34 , and four sides including a top side  36 A, a bottom side  36 B, a radially inward side  36 C, and a radially outward side  36 D. Additionally the cutting insert  16  has a front  132 , a back  134 , and four sides including a top side  136 A, a bottom side  136 B, a radially inward side  136 C, and a radially outward side  136 D. At the intersection of the front  132  and each of the sides  136 A,  136 B,  136 C and  136 D of the insert  16  there are cutting edges  137 A,  137 B,  137 C and  137 D respectively. However, it is possible for certain insert designs to include only cutting edges  137 A and  137 B. 
     Each lug  25  has a radially outward surface  40  and a radially inward surface  42  defining therebetween a radial width W which for clarity is shown on an adjacent lug  25 B. Each lug  25  furthermore has a front face  45  extending upwardly from the pocket bottom  27  to the top  47  of the lug  25 . Each lug  25  furthermore has an axial face  49  extending downwardly from the top  47  of the lug  25  to a height H (See lug  25 B) which is less than the height L of the lug. Each lug  25  furthermore has a rear face  51  extending downwardly from the axial face  49  of an adjacent lug  25 A to the bottom surface  27  of pocket  20 . 
     The support surfaces of pocket  20  are defined by the lug front face  45 , the pocket bottom surface  27 , the lug rear face  51  of lug  25 A, and a pocket wall  53  positioned radially inwardly from the peripheral wall  18  whereby the pocket wall  53  connects adjacent lugs  25 ,  25 A. The lug axial face  49  is sloped downwardly across the entire lug width W from the top  47  of the lug  25  to the lug rear face  51 . By doing so, a chip clearance groove  55  is provided across the entire width W of the lug  25 . 
     To provide maximum support to the cutting insert  16  within the pocket  20 , the lug front face  45  extends over the entire back side  134  of the insert  16 . 
     To maximize the size of the clearance groove  55 , the lug rear face  51  preferably extends from the bottom surface  27  to a distance H which is no higher than half way up the side of the insert  16 , when the insert is mounted within the pocket  20 . To further enhance the chip clearance groove  55 , the lug axial face  49  has a planar portion  57  which may be generally perpendicular to the lug front face  45 . 
     Each lug front face  45  has a bore  60  therethrough to accept a mounting screw  62  that is designed to extend within a mounting bore  70  through the cutting insert  16  and to secure the insert  16  within the pocket  20 . Furthermore, each pocket  20  is angled about the central axis  14  (FIG. 1) by an axial rake angle X which may be between 20-30° and preferably is 25° to permit multiple inserts  16  to be mounted in the cutter body  12  and furthermore to provide access for inserting and removing the mounting screw  62 . Each lug  25  furthermore has an access groove  64  (FIG. 2) within the lug front face  45  and the lug axial face  49  to permit greater access to the mounting screw  62  secured within the lug front face  45 . Although the access groove  64  is illustrated as curved, this is only a matter of convenience. 
     The lug rear face  51 , as previously mentioned, extends upwardly from the bottom surface  27 . This not only determines the size of the chip clearance groove  55  but furthermore, in conjunction with the bottom surface  27 , protects the bottom edge  136 B of the cutting insert  16  that is mounted within the pocket  20 . 
     To protect the side cutting edge  137 C of a cutting insert  16 , the pocket wall  53  may further include at least one recessed groove  66  parallel to the lug front face  45 . It is entirely possible that the cutting insert  16  has a cutting edge on side  136 C but opposite cutting edge  137 C. Under the circumstances, a second recessed groove  68  may exist such that, together, recessed grooves  66 ,  68  protect the cutting edge  137 C and a cutting edge on the opposite side of  136 C. These recesses  66 ,  68  also provide relief for the cutting edges positioned within the recesses  66 ,  68 . 
     It should be noted that the pocket wall  53  extends only partially to the top  47  of the lug  25 . In one embodiment the pocket wall  53  extends no more than 0.350 inches from the top  27  of the lug  25 . The purpose of this shortened height is to provide clearance during a cam lobe milling operations such that the cutter body  12  does not interfere with adjacent lobes on a cam shaft that are not currently being machined by the cutter  10 . In one embodiment, the pocket wall  53  may extend upwardly to a point which is a distance of at least 0.350 inch from the top  47  of the lug  25 . 
     From inspection of FIG. 1, one comer  17  of each of the inserts  16  is protruding and foremost in the cutter body  12  such that during a plunge milling operation this corner will be the first to engage a workpiece. The bottom surface  27  of the pocket  20  is oriented to position the rectangular insert  16  such that this corner  17  of the insert  16  protrudes beyond the cutter body  12 . In particular, the pocket bottom surface  27  is angled to provide a bevel angle Y of between 10-20° and preferably 15°. 
     Finally, the lug front face  45  may be oriented at a radial rake angle relative to a radial line extending from the central axis  14  to form an angle of between 5-15° and is preferably 10°. Radial rake angles are well known by those skilled in the art of metalworking and for that reason the radial rake angle is not illustrated in FIG.  1 . 
     It should be appreciated that the insert  16  suitable for the pockets  20  discussed herein has been described as rectangular and it is entirely possible that such a rectangle may be a square. 
     While the subject invention so far has been directed to a milling cutter  10  having a body  12  with reference to a cutting insert  16  mounted within a pocket  20 , it should be appreciated that he invention may be directed to the milling cutter body  12  alone without cutting inserts  16  mounted therein. However, under these circumstances, the insert envelope  30 , which is a predetermined shape based upon an insert for which the cutter body  12  was designed, will define the shape of the pocket  20 . 
     While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. The presently preferred embodiments described herein are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.