The ratchet allows {HEAD ~ the mill} to move away from the object when {TAIL ~ the drill string} is rotated in the first direction and lifted relative to the mandrel 
The ratchet allows { HEAD ~ the mill } to move away from the object when { TAIL ~ the drill string } is rotated in the first direction and lifted relative to the mandrel
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH