Miscellaneous Subsurface Methods 



651 



breaking and battering forces encountered in drilling dolomite, hard lime, 

 and hard shale. The chipping and crushing action is obtained from the 

 sturdy, closer-spaced teeth that support the load applied on the bit. 



The twisting-tearing action is retained but to a lesser degree than in 

 the OSC series and the OSQ-2 design. This twisting-tearing action of the 

 teeth penetrating the formation is desirable when softer, tough shales, 

 gypsum, and the like are interbedded with hard rock and when factors 

 such as deviation control prevent the application of weight required to es- 

 tablish the most effective chipping and crushing action. 



Oftentimes layers of soft, sticky shale are encountered in medium-to- 



Figure 347. Hughes 9-inch type W? tricone bit. 



hard-rock drilling. The interfitting rows of teeth of the OWS bit mechan- 

 ically clean the cutting surfaces of sticky formations, help prevent balling 

 up, and retain a good penetration rate. Also, the interfitting teeth provide 

 the additional space needed for effective depth of teeth, thickness of cone 

 shell, and a strong bearing. 



Modifications of the OWS, Type OWC 



In an area where hard rock such as dolomite or hard limestone pre- 

 dominates, there may be a tendency for the gage point to break down 

 or round off. The OWC rock bit has a T-shaped structure milled where 

 the crest of the heel teeth and the gage surface intersect to fortify this 

 strategic point against wear or breakdown. Otherwise, the OWC bit is 

 identical to the OWS. 



