thereafter machining said end faces on said blank while orienting said machining operation by use of {HEAD ~ the previously formed opening} of {TAIL ~ said rotor means}; and 
of
thereafter machining said end faces on said blank while orienting said machining operation by use of { HEAD ~ the previously formed opening } of { TAIL ~ said rotor means } ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH