Roof drilling improvements

Abstract

The invention is embodied in a heavy duty drill bit for hard/soft rock drilling comprising a high fatigue resistant, high alloy steel bit body having a PCD cutter element of super hard material and an enlarged shank portion constructed to accommodate torsional forces at high thrust pressures, and reamer means for compensating the effect of bore hole rifling. The invention further involves the method of forming a roof bolting matrix in extremely hard rock formations having a compression strength up to about 50,000 psi using PCD wafers on a high tensile strength steel body coupled by a heavy duty shank through high fatigue resistant reamer means to a high strength drive steel member.

1 . A heavy duty drill tool for performing a sequential series of roof boring operations for a roof bolting matrix in metal/non-metal mines, comprising: 
 a drill bit section having a high fatigue resistant steel body constructed and arranged with PCD cutter members having a bore hole diameter up to 2 inches, and said steel body including a heavy duty shank constructed for connecting the drill bit section; and    a reamer section having a high fatigue resistant steel body constructed and arranged with a cutting insert and being secured to the heavy duty shank to thereby form a coupler means for connecting the drill bit section to a drilling apparatus set at optimum drilling parameters for hard/soft rock formations.    
   
   
       2 . The heavy duty drill tool of  claim 1 , in which said high fatigue resistant steel body of the drill bit section has a tensile strength in the range of 175,000 to 225,000 psi.  
   
   
       3 . The heavy duty drill tool of  claim 1 , in which said high fatigue resistant steel body of the drill bit section has a tensile strength in a preferred range of 209,500 to 211,000 psi.  
   
   
       4 . The heavy duty drill tool of  claim 3  in which the drill bit steel body has a tensile strength of about 210,000 psi.  
   
   
       5 . The heavy duty drill tool of  claim 1 , in which said high fatigue resistant steel body of at least one of said drill bit section and said reamer section is formed of a high nickel/chromium alloy characterized by a tensile strength in the range of 209,500 to 211,000 psi and a yield strength in the range of 135,000 to 145,000 psi.  
   
   
       6 . The heavy duty drill tool of  claim 1 , in which the steel bodies of both said drill bit section and said reamer section are formed of 4340 stainless steel having a tensile strength of about 210,000 psi and a yield strength of about 141,000 psi.  
   
   
       7 . The heavy duty drill tool of  claim 1 , in which said PCD cutter members are constructed and arranged to form a bore hole in the range of 1⅛ to 2 inches, and said heavy duty shank has a drill bit connecting dimension in range of 9/16 to ¾ inches.  
   
   
       8 . The heavy duty drill tool of  claim 7 , in which the shank connecting dimension is about ⅝ inch.  
   
   
       9 . The heavy duty drill tool of  claim 1 , in which said PCD cutter inserts are disc-shaped and have a thickness in the range of 9/16 to ¾ inches.  
   
   
       10 . The heavy duty drill tool of  claim 9 , in which the PCD inserts present front wear surfaces facing in the direction of rotation, and have upper arcuate cutting edges, and means for delivering flushing fluid across said wear faces to the cutting edges.  
   
   
       11 . The heavy duty drill tool of  claim 10 , in which said steel body is constructed and arranged to support said PCD cutter insert against maximum compressive drilling forces exerted thereon.  
   
   
       12 . The heavy duty drill tool of  claim 11 , in which the margins of said PCD cutter inserts have lower margins opposite to said cutting edges, and said steel body is formed with support ledges to seat the lower margins of the PCD cutter inserts in opposition to the compressive drilling forces exerted against the upper cutting edges.  
   
   
       13 . The heavy duty drill tool of  claim 10 , in which said means for delivering flushing fluid comprises a vertically-oriented flute formed along the side of the shank and an angularly related channel in the side of the head portion in fluid communication with the flute and being angled toward a front wear surface.  
   
   
       14 . The heavy duty drill tool of  claim 1 , in combination with a drilling drive steel member to which the reamer section is removably connected, and said drive steel member being formed of high fatigue resistant steel.  
   
   
       15 . The heavy duty drill tool of  claim 14 , in which said high fatigue resistant steel of the drive steel member is a high NiCr alloy.  
   
   
       16 . The method of drilling a sequential series of roof boring operations for a roof bolting matrix in metal/non-metal mines, comprising: 
 forming a heavy duty drill tool having a drill bit section made of a high fatigue resistant steel body with PCD cutter members constructed and arranged to form a bore hole diameter up to 2 inches, and said steel body including a heavy duty shank constructed for connecting the drill bit section;    forming a reamer section having a high fatigue resistant steel body constructed and arranged with a cutting insert and being secured to the heavy duty shank to thereby form coupler means for connecting the drill bit section to a drilling apparatus, and setting the optimum drilling parameters for hard/soft rock formations.    
   
   
       17 . The method of  claim 16 , in which said high fatigue resistant steel body of the drill bit section is formed to have a tensile strength in the range of 175,000 to 225,000 psi.  
   
   
       18 . The method of  claim 16 , in which said high fatigue resistant steel body of the drill bit section is formed to have a tensile strength in a preferred range of 209,500 to 211,000 psi.  
   
   
       19 . The method of  claim 16 , in which said high fatigue resistant steel body of at least one of said drill bit section and said reamer section is formed of a high nickel/chromium alloy characterized by a tensile strength in the range of 209,500 to 211,000 psi and a yield strength in the range of 135,000 to 145,000 psi.  
   
   
       20 . The method of  claim 16 , in which the steel bodies of both said drill bit section and said reamer section are formed of 4340 stainless steel having a tensile strength of about 210,000 psi and a yield strength of about 141,000 psi.  
   
   
       21 . The method of  claim 16 , including using said PCD cutter members to form a bore hole in the range of 1⅛ to 2 inches, and sizing said heavy duty shank to have a drill bit connecting dimension in range of 9/16 to ¾ inches.  
   
   
       22 . The method of  claim 21 , in which the shank connecting dimension is about ⅝ inch.  
   
   
       23 . The method of  claim 16 , including constructing and arranging the cutter inserts of said reamer section to form an under-reamer operating in tandem with the PCD cutter members to reduce the effect of bore hole rifling caused thereby.  
   
   
       24 . The method of  claim 20 , including connecting the drill bit section and reamer section together to form a uniform drilling system connection to a drive steel member of a roof bolting apparatus.  
   
   
       25 . The method of  claim 24 , in which said drive steel is formed of high fatigue resistant, high NiCr alloy steel having a tensile strength of about 210,000 psi and a yield strength of about 141,000 psi.  
   
   
       26 . The method of drilling multitudinous bore holes in hard/soft rock formations as in metal/non-metal mines for establishing a rock bolting reinforcement matrix, comprising the steps of: 
 1. Setting rotational drilling parameters that call for thrust forces in the upper range of 4500 to 60000 psi;    2. Providing a heavy duty drilling system that includes 
 a. a coring drill bit section having a main steel body formed from a high nickel/chromium alloy steel having a tensile strength in the range of 175,000 to 225,000 psi, and being constructed and arranged with PCD cutting members having PCD inserts layers with a thickness in the range of 0.275 to 0.300 and tungsten carbide support layers whereby to form said PCD wafers having an increased mass, and the PCD layers having outer cutting edges arranged to bore a hole with a diameter of between  1⅛ inch and  2 inches; and  
 b. a reamer section having a main steel body formed from a high nickel/chromium alloy steel having a tensile strength in the range of 175,000 to 225,000 psi, and having at least two radially outwardly projecting non-PCD inserts defining thereacross a predetermined rock boring under-reamer diameter smaller than the bore hole diameter across the outer cutting edges; and  
 c. said drill bit and reamer sections having axially aligned coupling means comprising a heavy duty shank formed on the steel body of the drill bit section and a complementary shank-receiving opening in the steel body of the reamer section; and  
   connecting the drill bit and reamer sections in tandem to form a unitary system and mounting the system on a drilling apparatus and operating such apparatus at thrust forces up to 5000 pounds to sequentially drill a multitude of bore holes.