I am going to show you how to make a ring from a 3/8" washer
Step 1: Find Washer and Tools
I used a galvanized 3/8 flat washer, but you can use any other washer as long as it is wider than your finger.
You will need: a stepper drill bit, a file or a dremel tool and a small hammer.
Step 2: Start Hammering
Start rotating the washer on its edge. Simultaneously, tap the washer on its edge with a hammer.
Step 3: Keep Hammering
The edge of the ring should start to bow out from the hammer blows and the diameter of the washer should be getting smaller.
Note: I didn't hammer the edge of the washer enough.
Step 4: Widening
Once the diameter of the washer reaches the right size, you can use the stepper bit to widen the hole in the center of the washer.
Step 5: Inspecting
Once your done with the stepper bit the washer should start looking like a ring.
Step 6: Widen Some More
Using a dremel tool, or a file, finish up the inside of the ring.
Step 7: Finished Product
This is what you should get when you are finished although to be honest, mine is too big.