Replaceable cutting means substantially encircle {HEAD ~ the rolling cutter shell} for contacting {TAIL ~ the formations} and forming a hole therein 
Replaceable cutting means substantially encircle { HEAD ~ the rolling cutter shell } for contacting { TAIL ~ the formations } and forming a hole therein
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH