This (thin) nut is screwed down and tightened up in the normal way. The thick nut is then screwed down on top of it, to within a few degrees of its limit. THEN THE THIN NUT IS UNSCREWED BACK UP TO THE TOP NUT. Alan, Obviously that "expert" method of tightening nuts was written by someone who had no practical experience in the process at all. Reminds me of our "educators" who are gradually canceling all manual arts vocational programs because "everyone needs to go to college". Jesse the Redneck Tennesseean . MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.