{HEAD ~ a reference device} for cooperating with the cylindrical part in orbital motion and defining {TAIL ~ a checking condition} of said apparatus 
for defining
{ HEAD ~ a reference device } for cooperating with the cylindrical part in orbital motion and defining { TAIL ~ a checking condition } of said apparatus
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH