Drill stem and method

Abstract

A drill stem segment and method of manufacture are shown. Drill stem segment and methods are shown that greatly strengthen the weld joint using sleeves. reinforced butt joints are shown in selected examples where sleeves and drill stem tubes are welded to connections such as tapered thread connections. Using methods described, the drill stem segments are also inexpensive to manufacture.

1 . A drill stem segment, comprising:
 a hollow shaft;   a sleeve fitted around an external surface of the hollow shaft at a shaft end wherein the sleeve aligns with the shaft end; and   a threaded connection welded to the shaft end and the sleeve.   
   
   
       2 . The drill stem segment of  claim 1 , wherein the threaded connection is butt welded to the shaft end and the sleeve. 
   
   
       3 . The drill stem segment of  claim 1 , wherein the hollow shaft includes a 1.5 inch outer diameter hollow shaft. 
   
   
       4 . The drill stem segment of  claim 3 , wherein the hollow shaft includes a 0.25 inch wall thickness. 
   
   
       5 . The drill stem segment of  claim 4 , wherein the hollow shaft includes a 4130 steel hollow shaft. 
   
   
       6 . The drill stem segment of  claim 5 , wherein the 4130 steel hollow shaft includes a Rockwell hardness C scale of approximately 28-30. 
   
   
       7 . The drill stem segment of  claim 1 , wherein the sleeve includes a 1.875 inch outer diameter and a 0.1875 inch wall thickness. 
   
   
       8 . The drill stem segment of  claim 7 , wherein the sleeve includes a Rockwell hardness C scale of approximately 28-30. 
   
   
       9 . A drill stem segment, comprising:
 a hollow steel shaft, including
 a 1.5 inch outer diameter; 
 a 0.25 inch wall thickness; 
 a Rockwell hardness C scale of approximately 28-30; 
   a pair of sleeves fitted around an external surface of hollow shaft on each end of the shaft wherein the sleeves align with the ends of the hollow shaft; and   a pair of threaded connections butt welded to each end of the shaft and to the respective sleeves.   
   
   
       10 . The drill stem segment of  claim 9 , wherein the hollow shaft includes a 4130 steel hollow shaft. 
   
   
       11 . The drill stem segment of  claim 9 , wherein the sleeve includes a 1.875 inch outer diameter and a 0.1875 inch wall thickness. 
   
   
       12 . The drill stem segment of  claim 11 , wherein the sleeve is 4130 steel, and includes a Rockwell hardness C scale of approximately 28-30. 
   
   
       13 . The drill stem segment of  claim 11 , wherein the pair of threaded connections each include a 1.875 inch outer diameter. 
   
   
       14 . The drill stem segment of  claim 13 , wherein the pair of threaded connections each include a Rockwell hardness C scale of approximately 30-34. 
   
   
       15 . A method of making a drill stem segment, comprising:
 fitting a sleeve over an external surface of a hollow shaft at a shaft end; and   welding a threaded connection to both the hollow shaft and the sleeve.   
   
   
       16 . The method of  claim 15 , wherein welding a threaded connection to both the hollow shaft and the sleeve includes butt welding the threaded connection. 
   
   
       17 . The method of  claim 15 , wherein fitting the sleeve over the external surface of the hollow shaft includes interference fitting the sleeve. 
   
   
       18 . The method of  claim 16 , further including fitting a second sleeve over the external surface of the hollow shaft at a second shaft end, and welding a second threaded connection to both the hollow shaft and the second sleeve at the second shaft end. 
   
   
       19 . The method of  claim 18 , wherein both a male threaded connection and a female threaded connection are welded to the hollow shaft.