Abstract:
A metal cutting insert incorporates a polycrystalline diamond or a polycrystalline cubic boron nitride material as a pre-formed discrete cutting tip which wraps around the nose of the insert. The insert may further incorporate an integral chipbreaker.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates generally to cutting inserts and, more particularly to a cutting insert used in metalworking operations incorporating a discrete cutting tip made of a material such as polycrystalline diamond or cubic boron nitride. Additionally, the cutting insert may include a chip breaker.  
         BACKGROUND OF THE INVENTION  
         [0002]    It is a continuing goal in the metalcutting industry to provide metalcutting inserts with sharp cutting edges that stay sharp longer even when machining non-ferrous and abrasive materials. To this end it has been known to incorporate polycrystalline diamond (PCD) materials and polycrystalline cubic boron nitride (CBN) materials on a carbide substrate to provide an improved cutting edge. U.S. Pat. No. 4,854,784 and U.S. Pat. No. 4,946,319, both assigned to the assignee of the present application and both hereby incorporated by reference, teach a cutting insert having a discrete PCD or CBN cutting tip secured within an existing slot in the insert substrate. However, in the design disclosed in each of these patents, a significant portion of the cutting tip is embedded within the slot and this embedded portion acts only as structural material to retain the tip within the slot and does not contact the workpiece.  
           [0003]    Relative to the cost of a typical cemented carbide substrate, the cost of PCD or CBN materials used as a substrate is very high.  
           [0004]    An object of this invention is to reduce the amount of PCD or CBN used for such discrete cutting tips, thereby reducing the overall cost of cutting inserts utilizing such tips.  
         SUMMARY OF THE INVENTION  
         [0005]    In accordance with the subject invention, a cutting insert comprises a polygonal body with a central axis, said body comprising:  
           [0006]    a) a top surface and a bottom surface  
           [0007]    b) at least two sides and a nose between the top surface and bottom surface,  
           [0008]    c) wherein the nose  
           [0009]    i) connects two sides and  
           [0010]    ii) has a side contour,  
           [0011]    e) a recess within the nose, wherein the recess follows the side contour and wherein the recess has a depth and two ends defining a recess length and wherein the depth of the recess anywhere across the length is less than one-half the distance of a line connecting the respective ends at the sides of the body,  
           [0012]    f) a pre-formed discrete tip conforming to the shape of, and secured within, the recess, wherein the tip has a top and a front wall that intersect to form a cutting edge.  
           [0013]    In yet another embodiment, the cutting insert additionally has a chip breaker adjacent to the land. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The above as well as other features and advantages of the invention will become apparent through consideration of the detailed description and connection with the several drawings in which:  
         [0015]    [0015]FIG. 1 is an exploded isometric view of a cutting insert in accordance with the subject invention;  
         [0016]    [0016]FIG. 2 is a plan view of the cutting insert illustrated in FIG. 1 in an assembled configuration;  
         [0017]    [0017]FIG. 3 is a side view of the cutting insert illustrated in FIG. 1 in an assembled configuration;  
         [0018]    [0018]FIG. 4 is a partial cross-sectional view of the cutting insert illustrated in FIGS.  1 - 3  taken along arrows  4 - 4  in FIG. 2;  
         [0019]    [0019]FIG. 5 and  6  are partial cross-sectional views similar to that illustrated in FIG. 4 but demonstrating different rake angles;  
         [0020]    [0020]FIG. 7 is an exploded isometric view of a variation of the cutting insert illustrated in FIG. 1 but in a fully assembled configuration.  
         [0021]    [0021]FIG. 8 is a partial exploded isometric view of a cutting insert having a discrete tip and an associated individual chipbreaker;  
         [0022]    [0022]FIG. 9 is a partial isometric view of a cutting insert in accordance with an alternate embodiment of the subject invention, whereby the chipbreaker has an undulating shape;  
         [0023]    [0023]FIG. 10 is a plan view of the insert shown in FIG. 9;  
         [0024]    [0024]FIG. 11 is a cross sectional view along arrows XI-XI in FIG. 10;  
         [0025]    [0025]FIG. 12 is a cross-sectional view along arrows XII-XII in FIG. 11;  
         [0026]    FIGS.  13 - 18  are alternate insert configurations to which the subject invention may be applied;  
         [0027]    [0027]FIG. 19 is an isometric view of a cutting insert in accordance with an alternative embodiment, whereby the discrete cutting tip connects two sides of the insert;  
         [0028]    [0028]FIG. 20 is a plan view of the insert shown in FIG. 19;  
         [0029]    [0029]FIG. 21 is a side view of the insert illustrated in FIG. 19;  
         [0030]    [0030]FIG. 22 is an end view of the cutting insert illustrated in FIG. 19;  
         [0031]    [0031]FIG. 23 is an isometric view of a cutting insert in accordance with yet another embodiment; and  
         [0032]    [0032]FIG. 24 is an isometric view of a cutting insert in accordance with yet another embodiment;  
         [0033]    [0033]FIG. 25 is a plan view of the insert shown in FIG. 24; and  
         [0034]    [0034]FIG. 26 is a side view of the insert shown in FIG. 24. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]    [0035]FIG. 1 is a cutting insert  10 , having a polygonal body  15 , having a central axis A extending therethrough. The body  15  is comprised of a top surface  20  and a bottom surface  25 . Between the top surface  20  and the bottom surface  25  are sides  30 , 35 ,  40 , 45 . Between each pair of sides is a nose  50 , 55 , 60 , 65  extending between the top surface  20  and the bottom surface  25 . A nose  50  may be symmetric about a line L, which is equidistant between the two sides  30 , 35 . The nose  50  has a side contour  70 . The nose  50  has a recess  75  which follows the side contour  70 . As illustrated in FIG. 1, the recess  75  has a floor  77 , a back wall  79 , and end walls  80 , 82 .  
         [0036]    Directing attention to FIG. 2, the recess  75  has a depth D and a line L 1  with a recess length defined by the side contour  70  and the ends  80 , 82  of the recess  75 . The depth D of the recess  75  at any point on the recess  75  is less than one-half the length of a line L 2  connecting the respective ends  80 , 82  at the sides  30 , 35  of the body  15 . The depth D may be less than one-third the length of the line L 2  and furthermore, less then one-fourth the length of the line L 2 .  
         [0037]    A pre-formed discrete tip  85  (FIG. 1) has a bottom surface  87  and a top surface  89  with a front wall  91  therebetween, and an opposing back wall  93 . The top surface  89  and front wall  91  intersect to form a cutting edge  95 .  
         [0038]    The body  15  may be comprised of cemented carbide and may be fabricated by molding such that the recess  75  is molded into the insert body  15 . In the alternative, the recess  75  may be generated after the insert body  15  is fabricated by any number of commercial techniques for grinding or removing material from a cemented carbide substrate.  
         [0039]    The tip  85  may be comprised of a support layer  100 , and a cutting layer  105  deposited upon the support layer  100 . The cutting layer  105  may be comprised of PCD, which is a common material typically used for non-ferrous applications or, in the alternative, may be comprised of CBN which is a common material used for hardened non-ferrous application.  
         [0040]    The support layer  100  of the tip  85  may be comprised of cemented carbide. Additionally, the insert body  15  may be comprised of cemented carbide and manufactured in any number of conventional processes known in the art. However, at least one embodiment of the subject invention is directed to a substrate manufactured by molding.  
         [0041]    The tip  85  may be secured within the recess  75  by brazing the support layer  100  of the tip  85  within the recess  75 .  
         [0042]    Again directing attention to FIG. 2, lines L 3  and L 4  extend perpendicular from the front wall  91  at each end  80 , 82  and form a wraparound angle WA of not greater than 180 degrees.  
         [0043]    Directing attention to FIG. 4, the tip  85  may have a land  110 , which defines a rake angle RA with a line RL parallel to the top  20  of the insert body  15 . As illustrated in FIGS.  4 - 6 , the land  110  may define a rake angle RA with a line RL parallel to the top  20  of the insert body 15 of between minus 15 degrees and plus 25 degrees.  
         [0044]    [0044]FIG. 7 illustrates an isometric view of the cutting insert  10  in FIG. 1 in an assembled configuration and without the chipbreaker  115 .  
         [0045]    The discussion so far has been directed to a cutting insert without a chipbreaker. Although it is entirely possible to fabricate an insert in accordance with the subject invention without a chipbreaker, it is also possible to include a chipbreaker with the current design.  
         [0046]    Briefly returning to FIG. 1, the cutting insert  10  may include a chipbreaker  115  having a top  120  and a contact wall  125 . Although as illustrated in FIG. 1- 6  the top  20  of the insert is identical to the top  120  of the chipbreaker  115 , it is entirely possible for the chipbreaker to be selectively placed only in the region of the nose  50 , 55 , 60 , 65  to which it is associated. This feature is illustrated in the exploded isometric view of FIG. 8. Additionally, while a single cutting tip  85  has been discussed with respect to a single nose  50 , it should be appreciated that a cutting tip  130 , 135 , 140  may be associated with noses  55 , 60 , 65 , respectively as shown in FIG. 1.  
         [0047]    Directing attention to FIG. 3, the chipbreaker contact wall  125  is positioned adjacent to the land  110 , and away from the cutting edge  95 . The contour of the chipbreaker wall  125  may be similar to that of the nose  50  in that it is symmetric about the line L equidistant distant between the two sides  30 , 35  (FIG. 2). Although the form of the chipbreaker wall  125  may be any of a variety of forms known in the art to promote the formation of chips, FIGS. 2 and 3 illustrate a preferred embodiment in which the chipbreaker contact wall  125  has a constant profile angle PA relative to the top  20  of the insert body  15  over the length L 1  adjacent to the cutting tip  85 . In particular, the profile angle PA may have a range between 5-45 degrees.  
         [0048]    The depth of the land  110 , between the cutting edge  95  and the contact wall  125 , may be the same as the depth D of the recess  75 . Additionally, the contact wall  125  extends above the level of the cutting edge  95 .  
         [0049]    [0049]FIG. 3 illustrates a chipbreaker wall  125  having a constant profile angle PA. Directing attention to FIG. 9, a chipbreaker wall  125  has an undulating profile such that the profile angle PA, defined in FIG. 3, varies along the recess length L 1  of the line L 1  along the recess  75 . FIG. 10 is a plan view of the isometric view shown in FIG. 9, and sections XI-XI and XII-XII illustrated in FIGS. 11 and 12 respectively indicate the manner in which the profile angle PA varies along the recess length L 1  of the cutting tip  140 . The profile angle PA may have a value ranging between 5-45 degrees. When the profile angle PA is constant over the length L of the chipbreaker wall  125 , the angle PA may have a value between 5-45 degrees, while when the profile angle varies over the length L of the chipbreaker wall  125 , the profile angle may have a value of between 5-45 degrees for the portion of the profile having the smallest angle and between 15-45 degrees for the portion of the chipbreaker wall  145  having the greatest profile angle.  
         [0050]    As previously mentioned, the profile of the chipbreaker wall does not necessarily require a constant profile angle or an undulating profile and it should be understood that a variety of other chipbreaker walls are available and known to those skilled in the art.  
         [0051]    A method of fabricating a cutting insert having a discrete cutting tip and having a polygonal body with a central axis and a top surface and a bottom surface with at least two sides and a nose between the top surface and bottom surfaces and a nose connecting the two sides, wherein the nose is symmetric about a line equidistant between the two sides, wherein the method comprises the steps of:  
         [0052]    a) forming the polygonal body with a recess within the nose following the side contour of the nose, wherein the recess has a depth and two ends defining a length and wherein the depth of the recess anywhere across the length is less than one half the distance of a line connecting the respective ends at the sides of the body,  
         [0053]    b) positioning a pre-formed discrete tip conforming to the shape of the recess within the recess, wherein the tip has a top and a front wall that intersect to form a cutting edge and  
         [0054]    c) securing the tip within the recess.  
         [0055]    What has been discussed so far is a cutting insert  10  having a square shape, and a cutting tip  85  is secured to a corner recess  75  in one nose  50 . It should be appreciated that such a cutting tip  85  may exist in recesses in any of the other noses  55 , 60 , 65 . Just as before, the depth D may be less than one-third the length of the line L 2  and furthermore, less than one-fourth the length of the line L 2 .  
         [0056]    The subject invention should not be limited to a cutting insert  10  having a square shape. In particular. FIGS.  13 - 18  show a variety of applications of the present invention and inserts of various configurations. In these several figures, each insert is generally indicated by the reference character  210  and the cutting tip is indicated by the reference character  285  while the chipbreaker is indicated generally by the reference character  215 . However, just as before, it should be appreciated that the subject may or may not include a chipbreaker.  
         [0057]    [0057]FIG. 13 shows the use of a cutting tip  285  with a triangle metal cutting insert having the chipbreaker  215 . FIG. 14 shows the use of this invention with a rectangular insert with a chipbreaker  215 . It should be noted that each of the inserts of FIGS. 13, 14 and  15  have a centrally disposed hole  290  therein which can be used by a securing means for retaining the insert onto a tool holder. FIG. 15 shows a similarly configured diamond shaped insert with a chipbreaker  215 .  
         [0058]    FIGS.  16 - 18  show another embodiment of the present invention in which the metal insert body does not include a hole therein for securing a metal cutting insert to a tool. Rather, the metal cutting insert is retained in the tool by a clamping mechanism, which securely retains the insert within the tool. Additionally, the inserts illustrated in FIGS. 17 and 18 incorporate a pair of integral notches  220 , which are engaged by a clamping arrangement such as that taught in U.S. Pat. No. 3,754,309 which is assigned to the assignee of the present invention and which is incorporated herein by reference. In all other respects, however, the inserts  210  shown in FIGS.  16 - 18  incorporate the chipbreaker  215  in combination with the cutting tip  285 .  
         [0059]    What has so far been described are cutting inserts having two sides which converge to define a nose. However, it is entirely possible for the two sides to be parallel and act as a bridge between these two sides, thereby providing a recess to accept a cutting tip.  
         [0060]    FIGS.  19 - 22  disclose an insert similar to that disclosed in U.S. Pat. No. 4,946,319, which is assigned to the assignee of the present invention and is hereby incorporated by reference. In particular, FIGS.  19 - 22  illustrate a cutting insert  310 , comprised of a polygonal body  315  with a central axis A. The body  315  is comprised of a top surface  320  and bottom surface  325 . At least two side surfaces  330 , 335  and a nose  350  extend between the top surface  320  and bottom surface  325 . The nose  350  connects the two sides  330 , 335  and is symmetric about a line L equidistant distant between the two sides  330 , 335 . In this embodiment, the line L is superimposed over the central axis A. Additionally, the nose  350  has a side contour  370 . The body  315  further has a recess  375  within the nose  350  wherein the recess  375  follows the side contour  370 . Furthermore, the recess  375  has a depth D and two ends  380 , 382  defining a length L 1 . The depth D of the recess  375  anywhere along the length L 1  is less then one-half the distance of a line L 2  connecting the respective ends  380 , 382  at the sides  330 , 335  of the body  315 . A pre-formed discrete tip  385  conforms to the shape of and is secured within the recess  375 . The tip  385  has a top surface  389 , and a front wall  391  that intersect to form a cutting edge  395 . The depth D may be less than one-third the length of the line L 2  and furthermore, less than one-fourth the length of the line L 2 .  
         [0061]    Just as before, the body  315  may be fabricated by molding and the recess  375  may be imparted to the insert body  315  during such molding. In the alternative, the recess  375  may be generated after the insert body  315  is fabricated. With respect to the composition of the tip  385 , the previous discussion directed to tip  85  may be applied.  
         [0062]    The tip  385  may be secured within the recess  375  by brazing.  
         [0063]    The tip  385  has a first end  386 , a second end  387 , and a front wall  391 . Lines extending perpendicular from the outer side of each end  386 , 387  intersect to form a wraparound angle WA of not greater than  180  degrees. As illustrated in FIG. 20 the wraparound angle WA is approximately  180  degrees. Furthermore, as illustrated in FIG. 19 and in FIG. 20, the tip  385  is U-shaped. The insert  315  further has a chipbreaker  415 .  
         [0064]    The insert  310  has a mounting surface  397  and a clamping surface  398 . The mounting surface  397  rests within a conforming pocket in a toolholder, while a toolholder clamp contacts the clamping surface  398  to urge the insert  310  within the pocket.  
         [0065]    The method for producing such an insert comprises the steps of forming the polygonal body  15 , with a recess  75  within the nose  50  following the side contour  70  of the nose  50 . The recess  75  has a depth D and two ends  80 , 82  defining length L. The depth D of the recess  75  at any point across the length is less than one-half the distance of a line L 1  connecting the respective ends  80 , 82  at the sides  30 , 35  of the body  15 . The method further comprises the steps of positioning a pre-formed discrete tip  85  conforming to the shape of the recess  75  within the recess  75 . The tip  85  has a top surface  89  and a front wall  91  that intersect to form a cutting edge  95 . Finally, the tip  85  is secured within the recess  75 .  
         [0066]    The step of forming the polygonal body  15  is further comprised of molding the body  15  and including the recess  75  within the mold. The step of forming the polygonal body  15  may also be comprised of molding the polygonal body  15  and then separately removing material to form the recess  75 .  
         [0067]    The step of forming the polygonal body  15  may further include forming a chipbreaker  115  on the insert body  15 . The step of securing the tip  85  within the recess  75  may be comprised of brazing the tip  85  within the recess  75 .  
         [0068]    [0068]FIG. 23 shows yet another insert embodiment whereby an insert  510  has an insert body  515  with a recess  575  to accommodate a U-shaped tip  585 . The subject insert has a mounting surface  597  and a clamping surface  598  that may be secured within a tool holder in a manner similar to that of the insert described in FIGS.  19 - 22 .  
         [0069]    What has so far been described are cutting inserts having a nose which connects two sides, and is symmetric about a line equidistant between the two sides. It is also possible for the nose to connect two sides and to be asymmetric about a line equidistant between the two sides.  
         [0070]    FIGS.  24 - 26  disclose an insert having such features. In particular, FIGS.  24 - 26  illustrate a cutting insert  610  comprised of a body  615 , with a central axis A. The body  615  is comprised of top surface  620 , and bottom surface  625 . At least two side surfaces  630 ,  635  and a nose  650  extend between the top surface  620  and bottom surface  625 . The nose  650  connects the two sides  630 ,  635  and is located about a line L, between the two sides  630 ,  635 . Additionally, the nose  650  has a side contour  670 . The body  615  further has a recess  675 , which follows the side contour  670 . Furthermore, the recess  675  has a depth D and two ends  680 ,  682  defining a length L 1 . The depth D of recess  675  anywhere along the length Li is less than one-half the distance of a line L 2 , connecting the respective ends  680 ,  682  at the sides  630 ,  635  of the body  615 . A pre-formed discrete tip  685 , conforms to the shape of, and is secured within the recess  675 . The tip  685  has a top surface  689 , and a front wall  691  that intersect to form a cutting edge  695 . The depth D may be less than one-third the length of the line L 2  and furthermore, less than one-fourth the length of the line L 2 .  
         [0071]    Just as before the body  615  may be fabricated by molding and the recess  675  may be imparted to the insert body  615  during such molding. In the alternative, the recess  675  may be generated after the insert body  615  is fabricated. With respect to the composition of the tip  685 , the previous discussion directed to tip  685  may be applied.  
         [0072]    The tip  685  may be secured within the recess  675  by brazing. The tip  685  has the first end  686 , a second end  687 , and a front wall  691 . Lines extending perpendicular from the outer side of each end  686 ,  687  intersect to form a wrap-around angle (WA) of not greater than 180 degrees. Furthermore, the insert  615 , may have a chip breaker, similar to that illustrated in the previous embodiments of this invention.  
         [0073]    The insert  610 , has a mounting surface  697 , comprised of the bottom surface  625 , and a rail  699  which may fit within mating groove in a conforming pocket in a toolholder. As illustrated, a bore  700  extending through the insert body  615  may accept a mounting screw which is threadably engaged within a toolholder body to secure the insert body  615  within the pocket of the toolholder. However, it should be appreciated that the insert  610  may not have a bore  700 , but may have a continuous top surface suitable for the application of a clamp against the insert  610 , thereby holding the insert within a conforming pocket of the toolholder.  
         [0074]    The method for producing such an insert is similar to the method previously described further embodiments.  
         [0075]    Throughout this discussion, inserts having a variety of shapes and configurations for holding such inserts have been presented. It should be appreciated any shape of insert may be secured within a toolholder, using any of a number of different configurations, whether it be a hold down screw extending into a bore through the insert body and threaded into the toolholder pocket, or a clamp holding the insert within the pocket of a toolholder. Therefore, the manner of holding inserts, and the modifications to an insert body necessary for such holding discussed in this application should not be interpreted as a limitation upon the scope of the subject inventor.  
         [0076]    It is thought the present invention and many of its intended advantages will be understood from the foregoing description and that it will be apparent that various changes may be made in the form construction an arrangement of the parts thereof, without departing from the spirit and scope of the invention, or sacrificing all of its material advantages, the form herein before described merely preferred or exemplary embodiments thereof.