{HEAD ~ A ratchet} allows the mill to move toward the object relative to the mandrel and prevents {TAIL ~ the mill} from moving away from the object relative to the mandrel 
{ HEAD ~ A ratchet } allows the mill to move toward the object relative to the mandrel and prevents { TAIL ~ the mill } from moving away from the object relative to the mandrel
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH