Cutter pocket having reduced stress concentration

Abstract

A method for forming a drag bit using displacements having a rounded end that creates a cutter pocket having a rounded rear portion. The displacement may comprise an insert on the rounded end that remains in the drag bit during and after formation. A cutter element may then be attached to the upper portion of the insert. The rounded shape of the insert provides a more even force distribution.

1 . A method of forming a bit body for an earth boring drill bit comprising:
 combining bit body raw materials and a displacement having a rounded end into a bit body casting form;   orienting the rounded end of the displacement to extend into the bit body materials; and   processing the materials in the casting form to form a bit body, wherein the presence of the displacement extending into the bit body raw materials during the step of processing the materials forms a cutter pocket in the bit body.   
     
     
         2 . The method of  claim 1  further comprising, removing the displacement from the cutter pocket. 
     
     
         3 . The method of  claim 1 , wherein the displacement comprises an insert portion not removable from the bit. 
     
     
         4 . The method of  claim 1 , wherein the displacement comprises a portion formed from an erodible material and an insert portion comprising the rounded end. 
     
     
         5 . The method of  claim 4 , wherein the insert is integrally formed in the bit body, the method further comprising removing the removable portion, and affixing a cutting element to the insert. 
     
     
         6 . The method of  claim 1 , wherein the raw materials comprise tungsten and a binder. 
     
     
         7 . The method of  claim 2  further comprising, affixing a cutting element into the cutter pocket. 
     
     
         8 . The method  claim 1 , further comprising combining a plurality of displacements into the casting form to thereby form a plurality of cutter pockets. 
     
     
         9 . The method of  claim 1 , wherein the cutter pocket rounded bottom end has a shape selected from the group consisting of hemispherical, elliptical, and frusto-conical. 
     
     
         10 . The method of  claim 1 , wherein the displacement comprises an erodible material. 
     
     
         11 . The method of  claim 10 , wherein the displacement comprises material selected from the group consisting of graphite and silicone carbide, refractory materials, compressed particles, and combinations thereof. 
     
     
         12 . The method of  claim 1  further comprising, removing at least a portion of the displacement from the formed bit body, affixing a cutting element within the cutter pocket, coupling the bit body with insert to a drill pipe, boring a wellbore with the bit body and drill pipe. 
     
     
         13 . An earth boring bit formed using a casting process, the b it attachable to a drill string for forming a subterranean wellbore, the bit comprising:
 a bit body;   a blade extending from the bit body; and   a cutter pocket having a rounded bottom end formed in the blade during the casting process, wherein the rounded bottom end is formed using a displacement having a rounded end.   
     
     
         14 . The earth boring bit of  claim 13 , wherein the displacement is formed using an erodible material. 
     
     
         15 . The earth boring bit of  claim 13 , wherein the displacement comprises an insert on the rounded end. 
     
     
         16 . The earth boring bit of  claim 13 , wherein the displacement comprises a mid section and a rear portion having a rounded end. 
     
     
         17 . The earth boring bit of  claim 13 , wherein the displacement rounded end is orientable in a bit body casting mold to form a cutter pocket having a rounded bottom. 
     
     
         18 . The earth boring bit of  claim 16 , wherein the displacement mid section and rear portion comprises an erodible material. 
     
     
         19 . The earth boring bit of  claim 13 , wherein the displacement comprises material selected from the group consisting of graphite and silicone carbide, refractory materials, compressed particles, and combinations thereof. 
     
     
         20 . The earth boring bit of  claim 13 , wherein the rounded end has a shape selected from the group consisting of hemispherical, elliptical, and frusto-conical.