An apparatus for checking {HEAD ~ the diameter} of a cylindrical part in orbital motion about a geometrical axis in {TAIL ~ a numerical control grinding machine}, said apparatus comprising: 
An apparatus for checking { HEAD ~ the diameter } of a cylindrical part in orbital motion about a geometrical axis in { TAIL ~ a numerical control grinding machine } , said apparatus comprising :
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH