Two Part Drill Bit Assembly

Abstract

A two part drill bit assembly and to the two drill bits that form the assembly. The drill bits are releasably engageable, to form the assembly, via compatible spiral grooved surfaces on each bit with one of the drill bits being re-useable and the other intended for single use or being made otherwise disposable.

1 - 37 . (canceled) 
     
     
         38 . A first drill bit for a two part drill bit assembly, the first drill bit having:
 (a) a leading end;   (b) a trailing end; and   (c) an annular bit body comprising:
 (i) a first cutting part disposed at the leading end of the first drill bit; 
 (ii) a spiral grooved inner surface; and 
 (iii) an outer surface; 
   
       wherein the first drill bit is adapted to be releasably received on a shaft defined by a second drill bit via said inner surface. 
     
     
         39 . The first drill bit according to  claim 38 , wherein the spiral grooved inner surface is tapered. 
     
     
         40 . The first drill bit according to  claim 38 , wherein the spiral grooved inner surface tapers towards the leading end of the drill bit. 
     
     
         41 . The first drill bit according to  claim 38 , wherein the outer surface of the annular drill bit body tapers towards the trailing end of the drill bit. 
     
     
         42 . The first drill bit according to  claim 38 , wherein the outer surface of the annular drill bit body includes at least one groove extending between the leading and trailing end of the drill bit. 
     
     
         43 . The first drill bit according to  claim 42 , wherein the groove is spiral shaped. 
     
     
         44 . The first drill bit according to  claim 42 , wherein the groove tapers towards its trailing end. 
     
     
         45 . The first drill bit according to  claim 38 , wherein the leading end defines an opening adapted to fit the leading end of the other part of the two part drill bit assembly such that the leading ends of each part of the two part drill bit together form a cutting surface. 
     
     
         46 . The first drill bit according to  claim 45 , wherein the opening has an outer cross sectional shape that defines a reuleaux polygon. 
     
     
         47 . A second drill bit for a two part drill bit assembly, the second drill bit having:
 (a) a leading end;   (b) a trailing end; and   (c) a bit body comprising:
 (i) a second cutting part disposed at its leading end; 
 (ii) a shaft member with a spiral grooved outer surface; and 
 (iii) a means for operably attaching the drill bit to a drill string assembly, 
   
       wherein the drill bit is adapted to releasably receive a first drill bit according to  claim 38  via said shaft member. 
     
     
         48 . The second drill bit according to  claim 47 , wherein the spiral grooved outer surface is tapered. 
     
     
         49 . The second drill bit according to  claim 47 , wherein the spiral grooved outer surface tapers towards the leading end of the drill bit. 
     
     
         50 . The second drill bit according to  claim 47 , wherein the shaft member has an outer cross sectional shape that defines a reuleaux polygon. 
     
     
         51 . A two part drill bit assembly comprising:
 (a) a first drill bit according to  claim 38 ; and   (b) a second drill bit having a leading end, a trailing end; and a bit body comprising (i) a second cutting part disposed at its leading end, (ii) a shaft member with a spiral grooved outer surface; and (iii) a means for operably attaching the drill bit to a drill string assembly,   
       wherein the first drill bit is adapted to be releasably received on the second drill bit via said inner surface of the first drill bit and said outer surface of the second drill bit. 
     
     
         52 . The two part drill bit assembly according to  claim 51 , wherein the interface between the shaft bit body and the shank member defines an abutment surface that is adapted to abut with the trailing end of the first drill bit. 
     
     
         53 . A drill assembly comprising a first drill bit according to  claim 38 , or a two part drill bit comprising the first drill bit and a second drill bit having a leading end, a trailing end; and a bit body comprising (i) a second cutting part disposed at its leading end, (ii) a shaft member with a spiral grooved outer surface; and (iii) a means for operably attaching the drill bit to a drill string assembly, wherein the first drill bit is adapted to be releasably received on the second drill bit via said inner surface of the first drill bit and said outer surface of the second drill bit. 
     
     
         54 . The drill assembly according to  claim 53 , comprising a friction bolt defining a longitudinal axial passage.