We will be making a ring out of your average quarter.
What you need:
Hard Metal Surface
Get your hard surface and put the quarter on top. Tap softly on the quarter while slowly spinning it and after about 15 minutes it should look pretty fat and round.
Drill a hole into the quarter (the size has to be big enough to fit the dremel inside).
Then take your dremel and carefully drill out the inside. After about 30 minutes it should look like the photo. Also if you want you can add polisher to the inside and outside. To make it 90% silver try to find a quarter from 1964 or below if it isn't it will still work but is made of much less silver.