Method and apparatus for retaining polycrystalline diamond cutters in a drill bit body of matrix or steel

Abstract

As a more friendly, environmentally sounder replacement process for retaining PDC cutters in drill bits, compared to the known high temperature metallic brazing processes, a process is described for using a low temperature resin which cures in the range of 350° F. to 450° F., while having a melting point below 1250° F., to prevent degradation to the PDC cutters usually occurring at 1250° F. in the drill bit repair cycle.

1 . A method for retaining a PDC cutter in a drill bit body, comprising the steps of:
 at least partially coating the interior surfaces of cutter pocket formed in a drill bit body, with a resin-based glue having a melting point below 1250° F. once the glue has been cured;   at least partially coating the exterior surfaces of the PDC cutter with said glue;   placing said PDC cutter in said pocket;   curing said glue to thereby retain said PDC cutter in said pocket.   
   
   
       2 . A method for retaining and removing a PDC cutter in a drill bit body, comprising the steps of:
 at least partially coating the interior surfaces of a cutter pocket formed in a drill bit body, with a resin-based glue having a melting point below 1250° F. once the glue has been cured;   at least partially coating the exterior surfaces of the PDC cutter with said glue;   placing said PDC cutter in said pocket;   curing said glue to thereby retain said PDC cutter in said pocket;   heating said glue at the melting point of said glue; and   removing said PDC cutter from the said pocket.   
   
   
       3 . The method according to  claim 2 , comprising the additional steps of:
 replacing the said PDC cutter in said pocket but at in a position rotated from the position in the pocket as said cutter was originally place in said pcket.   
   
   
       4 . The method according to  claim 1 , wherein the melting point of said glue is 1150° F. for less. 
   
   
       5 . A method for retaining a plurality of PDC cutters in a drill bit body, comprising the steps of:
 at least partially coating the interior surfaces of a plurality of cutter pockets formed in a drill bit body, with a resin-based glue having a melting point below 1250° F. once the glue has been cured;   at least partially coating the exterior surfaces of said PDC cutters with said glue;   placing said PDC cutters in said sockets, respectively; and   curing said glue to thereby retain said PDC cutters in said pockets, respectively.   
   
   
       6 . The method according to  claim 5 , wherein the melting point of said glue is 1150° F. or less. 
   
   
       7 . A method for retaining and removing a plurality PDC cutters in a drill bit body, comprising the steps of:
 at least partially coating the interior surfaces of a plurality of cutter pockets formed in a drill bit body, with a resin-based glue, and a melting point below 1250° F. once the glue has been cured;   at least partially coating the exterior surfaces of a plurality of PDC cutters with said glue;   placing said plurality of PDC cutters in said pocket, respectively;   curing said glue to thereby retain said PDC cutters in said pockets;   heating said glue to the melting point of said glue; and   removing at least one of said PDC cutters from at least one of said pockets, respectively.   
   
   
       8 . The method according to  claim 7 , comprising the additional steps of:
 replacing said at least PDC cutter in said at least one pocket but in a position rotated from the position in the pocket as said at least one cutter was originally placed in said at least one pocket.   
   
   
       9 . A method for retaining a PDC cutter in a drill bit body, comprising the steps of:
 at least partially coating the interior surfaces of cutter pocket formed in a drill bit body, with a resin-based glue having a melting point below 1250° F. once the glue has been cured;   at least partially coating the exterior surfaces of the PDC cutter with said glue;   placing said PDC cutter in said pocket;   heating said glue to one or more temperatures in the range of 300° F. to 450° F. to thereby retain said PDC cutter in said pocket.   
   
   
       10 . A method for retaining a PDC cutter in a drill bit body, comprising the steps of:
 at least partially coating the interior surfaces of a cutter pocket formed in a drill bit body, with a resin-based glue having a glue strenght of at least 3000 psi and a melting point below 1250° F. once the glue has been cured;   at least partially coating the exterior surfaces of the PDC cutter with said glue;   placing said PDC cutter in said pocket; and   curing said glue to thereby retain said PDC cutter in said pocket.   
   
   
       11 . A method for retaining and removing a plurality PDC cutters in a drill bit body, comprising the steps of:
 at least partially coating the interior surfaces of a plurality of cutter pockets formed in a drill bit body, with a resin-based glue, and a melting point below 1250° F. once the glue has been cured;   at least partially coating the exterior surfaces of a plurality of PDC cutters with said glue;   placing said plurality of PDC cutters in said pocket, respectively;   curing said glue to thereby retain said PDC cutters in said pockets;   heating said glue to the melting point of said glue; and   removing at least one of said PDC cutters from at least one of said pockets, respectively; and   placing said at least PDC cutter in at least one of said pockets but in a position rotated from the position in the pocket as said at least one cutter was originally placed in said at least one pocket.