Miscellaneous Subsurface Methods 



509 



been done in the Rocky Mountain area with 5^- and T^-inch whipstocks. 

 The diamond-core bit, because of its superior cutting qualities in very hard 

 formations, has justified its greater cost over that of a standard oil-well 

 rock bit. Figure 240 illustrates one of these special bits. 



The Eastman full-gauge removable whipstock was especially designed 



Figure 240. Diamond 

 whipstock bit. 



to use a bit larger than that used with the conventional removable whip- 

 stock. The new hole made below the whipstock is slightly smaller in 

 diameter than the hole in which the whipstock is set. Figure 238B shows a 

 full-gauge whipstock equipped with a rock bit. This tool has a much thin- 

 ner section than the conventional whipstock. Data on size, length, etc., 

 are shown on table 26. 



Figure 241 illustrates the operation of an Eastman full-gauge whip- 

 stock, which is almost the same as that of the conventional tool, except 

 that the "rathole" need not be reamed. After the whipstock has been with- 



