Hi there!
I've written a free mini-tutorial on making glass discs using Grace's Disc Shaper, a tool made by Graceful Customs. I am not affiliated with the company, other than I really like their tools!
The tut came about after I ordered a custom disc shaper, with a slot for 3/16-inch to 1/4-inch mandrels. (Which will probably be available soon as a production tool.) I was letting them know how much I loved it, and they asked me how I used it. I got a little carried away, and this little tutorial was born. The same techniques apply whether you are using the original tool with the smaller mandrel slot, or the larger-slot version.
I will be making some updates and edits, but the original version is at
http://www.greywillow.com/p/using-gr...-graceful.html
There is a link to the printable pdf version in the middle of the page, as well as image files of the two pages that should also be printable. If you have issues and can't print either one, please let me know.
Please feel free to let me know if you see any typos or other issues!