Abstract:
An insert having a cutting segment of a polycrystalline diamond or cubic boron wafered between two layers of a hard metal carbide is bonded into a pocket in a standard insert and machined to form a chip breaker having a clearance surface and expose the cutting edge of polycrystalline material integral with the cutting segment.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to chip control inserts having diamond segments or other polycrystalline segments adhered thereto to provide excellent cutting, longevity of tool life, and good chip control. 
     The present invention further relates to an insert having a pocket at its forward end and extending at least partially through the body substrate. A cutting means is interfaced between two wafers of bondable material and bonded into the pocket at one wafer and the other wafer is ground away to form a chip breaker. 
     2. Description of the Prior Developments 
     Murray et al., U.S. Pat. No. 4,854,784 discloses a diamond tipped chip control insert which incorporates a polycrystalline diamond or cubic boron nitride material therein as a cutting edge material. The insert substrate includes integral chip control features which eliminate the need for the use of separately attached mechanical chip breakers. 
     Murray et al differs from the present invention because Murray et al first form a chip breaker from a solid insert, then at one nose portion the insert is provided with a slot which accommodates a polycrystalline diamond material. The diamond is then bonded to the insert in the slot. In the present invention, the chip breaker is formed in the wafer comprised of tungsten carbide/polycrystalline diamond/tungsten carbide after it is bonded to the insert substrate. 
     Jurgens, U.S. Pat. No. 4,498,549 discloses a cutting member for a rotary drill bit comprised of a substrate to which is bonded a polycrystalline material. The drill does not have any chip breaking features and neither does it utilize the tungsten carbide/polycrystalline diamond/tungsten carbide wafer of the present invention. 
     Bibbs, Jr. et al., U.S. Pat. No. 4,605,343 discloses a sintered polycrystalline diamond compact having an integral metallic heat sink bonded to and covering at least the outer diamond surface. The metallic heat sink is used to increase compact life when the compact is used for material removal without fluid coolant. The present invention does not require a metallic heat sink to achieve dry cutting and further includes a chip breaker which is absent from Bibbs Jr. et al. 
     Slutz et al., U.S. Pat. No. 4,899,922 disclose a brazed, thermally stable polycrystalline diamond compact having a network of interconnected empty pores dispersed throughout the compact and bonded to a substrate by a brazing filler metal which may be an alloy having a liquidus above about 700 degrees centigrade. Slutz relates to a manner of bonding the polycrystalline diamond to a substrate. There is no showing in Slutz of using a polycrystalline diamond compact as a metal cutting insert with built in chip control features. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a cutting insert, comprising a substrate having an upper surface, a lower surface and a side wall extending substantially unbroken there between, wherein the upper surface has a pocket, extending at least partially through the insert body, to define a floor and, preferably, at least one wall. A cutting means, such as a polycrystalline diamond composite wafered between two layers of tungsten carbide, is adapted to be mounted and bonded into the floor of the pocket and preferably abutting the aforementioned wall to present a tight fit in the pocket. Those skilled in the art recognize that the polycrystalline segment could be adhered to the upper surface of the insert without the need to provide a pocket in the insert. The inset segment is then subjected to grinding to remove some of the tungsten carbide upper wafer and expose the polycrystalline diamond. The removal of tungsten carbide presents a chip breaker and exposes some diamond for cutting. The present invention avoids the shortcomings of the prior art, and especially Murray et al, in that the composite is brazed or bonded along the floor and wall of the pocket. Murray requires that the polycrystalline diamond composite be bonded along at least three sides, and, because of the brazing techniques available, will not allow a uniform product insofar as the location of the polycrystalline diamond within the pocket is concerned. 
     Moreover, the present invention allows the formation of the chipbreaker integrally with the polycrystalline diamond composite, thereby reducing manufacturing costs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top perspective view of the insert of the present invention. 
     FIG. 2 is a detail of the nose portion of the insert showing the pocket and polycrystalline diamond composite wafer. 
     FIG. 3 is a detail of the nose portion of the insert showing the polycrystalline composite bonded into the pocket. 
     FIG. 4 is a side sectional view of the polycrystalline diamond composite wafer taken along line 4--4 showing the different layers to its construction. 
     FIG. 5 is a side sectional detail of the polycrystalline diamond composite section showing the chipbreaker formed therein. 
     FIG. 6 is a detail of portion 6 of FIG. 5 showing the chip breaker in greater detail. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now to the figures, wherein like numerals depict like structures, FIG. 1 depicts a top perspective view of the polygonal shaped chip control insert 10 of the present invention showing upper surface 12, lower surface 14 and sidewall 16 extending substantially unbroken therebetween to define a body 18 of the insert. The insert body is comprised of a cemented carbide such as tungsten carbide or any other hard composite or alloyed sintered metallic composite, such as are well known to those skilled in the art. A composite cutting means 20, such as a polycrystalline diamond composite or a cubic boron composite material is positioned and bonded within a pocket 22 at nose portion 24 of the insert. The pocket has a floor 26, and at least one wall 28. Those skilled in the art recognize that the pocket may have two or more walls, such as a diamond shaped pocket. Those skilled in the art recognize that the pocket may also be any shape, as long as the inset is retained therein. Also, the pocket may be eliminated and the polycrystalline wafer may be brazed directly to the upper surface of the insert. 
     Turning to FIG. 3, there is shown a detailed side perspective of the insert in place on the nose portion of the insert. Note that the pocket is of such depth that the cutting means segment, when placed in the pocket and bonded in place such by brazing, the upper surface 30 of the segment is coplanar with the upper surface of the insert, and the sides 32 and 34 of the segment are coplanar with the sidewalls of the insert body. Thus, the cutting means segment is seen to fill the pocket and correspond to the configuration of the insert body. 
     Turning to FIG. 4, there is seen a cross section of the segment in place in the pocket taken along line 4--4 of FIG. 3. The segment is bonded against the floor of the insert body substrate 36. The segment has a polycrystalline diamond composite or a polycrystalline cubic boron composite to which are bonded two wafers of tungsten carbide or other similar hard metals, 38 and 40, respectively to present a sandwich construction of the segment. The segment is bonded into place onto the substrate of the body at the floor of the pocket by brazing or by other means such a epoxy, such as are well known by those skilled in the art. 
     Turning now to FIG. 5, there is shown therein the chipbreakers which are formed in the upper surface of the segment after it is bonded into place in the pocket. Specifically, chipbreaker 42 is ground into the upper surface of the segment thereby exposing the cutting means at the chip breaker groove 44 to present a cutting edge 46, as seen in FIG. 6. The chip breaker is seen as being concave so as to present at least one clearance surface in close proximity to the cutting edge. Those skilled in the art recognize that any manner of chip breaker may be formed. 
     The cutting means is preferably a polycrystalline diamond composite, generally available as DRILpax , from Mega Diamond, a division of Smith International, Inc., of Provo, Utah. The entire insert may be adapted to be clamped or otherwise suitable held within a tool holder or blade in the manner which are well known to those skilled in the art. 
     Those skilled in the art recognize that many modifications are possible to the above described invention without departing from the scope and spirit of the invention as claimed.