I would like to make a 6" refractor. I was thinking about hand grinding but ran across an old article about Tom Waineos' Desktop Grinding/Polishing Machine. Has anyone made one of these? A similar machnine? How much time should one expect (in hours) to finish a lense by hand and/or by machine? What are the pros and cons of using a machine vs doing it by hand? Any other info you think would be helpful is welcome.