thereafter accurately machining said blank to form said {HEAD ~ opening} of {TAIL ~ said rotor} means 
of
thereafter accurately machining said blank to form said { HEAD ~ opening } of { TAIL ~ said rotor } means
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH