{HEAD ~ A central part shaft} 2 of {TAIL ~ the shaft} 2 a has a reduced diameter as shown 
of
{ HEAD ~ A central part shaft } 2 of { TAIL ~ the shaft } 2 a has a reduced diameter as shown
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH