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