Help with a ring roller

[bullchuck]

So I decided to build a ring roller to make MY OWN rings. I have it completed and now I just need to fine tune it. The two bottom rollers are driven together. When I put the metal in and put pressure on it , then turn the handle the rollers just slip on the metal and will not feed. The rollers are very smooth.The only thing I can think of doing is to have the rollers knurled, to help feed the metal. dose any body have any other suggestions.
any help would be great.