I have a King drill press, model KC-18BP, 3/4 hp. The chuck arbor keeps falling our of the spindle. There is a threaded screw, with a slot end one the left side (when facing the drill press), screwed into the quill head. this screw has a nut which tightens onto two lock washers. I'm presuming (wrongly or rightly) that the screw holds or releases the chuck arbor, but the screw cannot be turned when the nut is loosened. I don't want to force the screw, so am looking for advice. Jack.