said {HEAD ~ core} having a central axis which coincides with {TAIL ~ said axis} of said surrounding ferrous cylindrical case, 
said { HEAD ~ core } having a central axis which coincides with { TAIL ~ said axis } of said surrounding ferrous cylindrical case ,
OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH