650 



Subsurface Geologic Methods 



tration rate and maximum footage in drilling medium-soft formations re- 

 ferred to above. 



The interfitting of teeth into grooves of mating cones is embodied 

 in the OSQ-2 rock bit to retain the desirable features of mechanical clean- 

 ing: long chisel-shaped teeth; a safe thickness of cone-shell; and a strong 

 bearing. As in the OSC series, the teeth are hard-faced with tungsten car- 

 bide to prolong their cutting life, and the same arrangement of water- 

 course nozzles insures an effective flushing action of the drilling fluid. 

 The main difference in the types OSC and OSQ-2 is the increased amount 

 of cutting surface on the OSQ-2 bit. 



Figure 346. Hughes 9-inch type OWS tricone bit. 



Medium-Hard to Hard, Nonabrasive Formation Bits 

 The OWS Tricone 



The OWS rock bit (fig. 346) is designed to drill formations having 

 a compressive strength of a magnitude somewhat greater than that noted 

 in medium-hard formations, which are economically drilled with the 

 OSQ-2. Formations classed as medium-hard to hard, nonabrasive include 

 hard rock interbedded with waxy, tough shales; hard lime; hard anhy- 

 drite; dolomitic lime; hard shale; slate; and dolomite. These formations 

 respond to a drilling action combining twisting-tearing and chipping- 

 crushing by the cutter teeth acting on bottom. 



The OWS tricone provides teeth with a larger included angle to resist 



