Optimized central cutter and method

Abstract

A central cutting structure for use with a drill bit includes a plurality of cutters, of which at least one overlaps the center of a supporting member from which the cutters extend. Each cutter has a side rake angle that provides an overlapping relationship with at least one other cutter to provide an aggressive cutting surface for penetrating hard formations.

1 . A central cutting structure for a drill bit, the central cutting structure comprising:
 a base member having a surface; and   a plurality of cutters secured to the surface, wherein each of said cutters comprises a cutting surface having an inner edge, wherein the inner edge of each of said cutters extends away from the surface and proximate to the inner edge of each other of said cutters to define an apex, and wherein the cutting surface of each of said cutters has a side rake angle that provides an overlapping relationship with the cutting surface of at least one other of the cutters to provide an aggressive cutting structure for penetrating hard formations.   
     
     
         2 . The central cutting structure of  claim 1 , wherein the cutting surface of at least one of said cutters overlaps a center of the base member. 
     
     
         3 . The central cutting structure of  claim 1 , wherein the cutting surface of each of said cutters further comprises a base edge extending from a center of the surface toward an edge of the surface. 
     
     
         4 . The central cutting structure of  claim 1 , wherein the plurality of cutters comprises at least three cutters. 
     
     
         5 . The central cutting structure of  claim 1 , wherein the side rake angle ranges from −15 degrees to 15 degrees. 
     
     
         6 . The central cutting structure of  claim 1 , wherein the cutting surface of at least one of said cutters further comprises an outer surface extending from an edge of the surface to the apex. 
     
     
         7 . The central cutting structure of  claim 1 , further comprising an attachment member disposed on a side of the base member opposite the surface, wherein the attachment member is configured for engagement with a bit face of the drill bit. 
     
     
         8 . The central cutting structure of  claim 7 , wherein the attachment member is configured for removable engagement with the bit face of the drill bit. 
     
     
         9 . The central cutting structure of  claim 7 , wherein the attachment member is configured for fixed engagement with the bit face of the drill bit. 
     
     
         10 . The central cutting structure of  claim 7 , wherein the attachment member comprises a cylindrical body configured for engagement within a complementary receptacle within the bit face. 
     
     
         11 . A drill bit for forming boreholes in subterranean formations, the drill bit comprising:
 a drill bit body having a bit face with a center;   a central cutting structure secured to the center of the bit face, wherein the central cutting structure comprises:
 a base member having a first side, a second side, a center, and an edge; 
 an attachment member extending from the first side and engaged with the center of the bit face; 
 a plurality of cutters extending from the second side, wherein each of said cutters comprises a cutting surface having an inner edge, wherein the inner edge of each of said cutters extends away from the second side proximate to the inner edge of each other of said cutters to define an apex, and wherein the cutting surface of each of said cutters has a side rake angle that provides an overlapping relationship with the cutting surface of at least one other of the cutters to provide an aggressive cutting structure for penetrating hard formations. 
   
     
     
         12 . The drill bit of  claim 11 , wherein the central cutting structure is removably engaged with the bit face. 
     
     
         13 . The drill bit of  claim 11 , wherein the central cutting structure is fixedly engaged with the bit face. 
     
     
         14 . The drill bit of  claim 11 , wherein the plurality of cutters comprise polycrystalline diamond compact cutters. 
     
     
         15 . The drill bit of  claim 11 , wherein the attachment member comprises a cylindrical body configured for engagement within a complementary receptacle within the bit face. 
     
     
         16 . The drill bit of  claim 11 , wherein the cutting surface of at least one of said cutters overlaps a center of the base member. 
     
     
         17 . The drill bit of  claim 11 , wherein the cutting surface of each of said cutters further comprises a base edge extending from the center of the base member the edge of the base member. 
     
     
         18 . The drill bit of  claim 11 , wherein the plurality of cutters comprises at least three cutters. 
     
     
         19 . The drill bit of  claim 11 , wherein the side rake angle ranges from −15 degrees to 15 degrees. 
     
     
         20 . The drill bit of  claim 11 , wherein the cutting surface of at least one of said cutters further comprises an outer surface extending from the edge of the base member to the apex. 
     
     
         21 . A method for penetrating a hard or abrasive formation with a drill bit, the method comprising the steps of:
 providing a central cutting structure to a center of a bit face of a drill bit, wherein the central cutting structure comprises a plurality of cutters extending therefrom, wherein each of said cutters comprises a cutting surface having an inner edge, and wherein the inner edge of each of said cutters extends away from the bit face and proximate to the inner edge of each other of said cutters to define an apex; and   contacting the hard or abrasive formation with the central cutting structure, wherein the cutting surface of each of said cutters has a side rake angle that provides an overlapping relationship with the cutting surface of at least one other of the cutters to provide an aggressive cutting structure for penetrating the hard or abrasive formation.