Now getting back to the top ring. This shows the detent mechanism still in place but I had removed it by now. The ring needs to be machined down in thickness from the back end forwards. Namely the "wall" must be removed and even the metal ring needs to be thinned to a level slightly below that of the top of the screw heads that will again hold it in place on the back of the lens. I started to do just this but as I removed metal I noticed that the gap where the detent mechanism was eventually would disappear and I could no longer hold the ring on the latheÕs turret