I have an old beveled pyrex blank, 8 inches, F 4.35. Good polish, nice sphere. The last couple of mm are turned down. I had a good edge until I started figuring. 1After losing the edge, I have spent about two hours tool on top, pressure on outside edge of six inch tool, small W stroke on the edge of mirror. I cannot get more than the dimmest of diffraction rings on far side, and the Ronchi's take the slightest turn at the very end.
Should I go figure, and then when done turn the mirror over on a piece of glass and fine grind the edge, or fine grind the edge now, and then figure, or put in more time trying to get the edge back with the stroke I have been using? Is there a better stroke to try?
Alex
Should I go figure, and then when done turn the mirror over on a piece of glass and fine grind the edge, or fine grind the edge now, and then figure, or put in more time trying to get the edge back with the stroke I have been using? Is there a better stroke to try?
Alex