Marv-- thats simple but ingenious and I am grateful for the tip. I have that on a long list of tooling to make. I was going to make about 3-4 traditional looking chuck spacers but this could cut the work immensely and make it easy to make a custom thickness as needed by merely making another set of spacer buttons.
I have seen an idea for a sort of spindle plug with an adjustable center rod shown here before. What other means do you guys use for say facing off cut washers? It would be neat to see some of the variety of ways of hanging on to and holding parallel various thin objects. I've seen round magnetic chucks....are these really a viable option for holding something you want to face off like that? A lathe makes a lot of force compared to say a grinder.