Drill Collar Sizes & Make up torque Tables & Charts
API Drilling Collar Selections

Woods and Lubinski pointed out that using an unstabilized Drilling Bit and small OD drill collar size can cause an undersized hole, making it difficult for Casing Running. They determined that the actual drift, oruseful diameter, of the hole would be equal to the bit diameter plus the drill collar diameter, divided by two,

The above equation can be rewritten to determine the minimum drill collar OD which would insure passage of the larger Casing 
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