I had the same issue. What is holding it still in place after removing the screw is the rough drill/tap metal that wasn't cleaned off. They just slammed the knob on. After so many year, the plastic knob may have shrunk a bit and or the rough side of the drill hole rusted a bit. I used a torch pointed away from the knob on the metal handle and it came right off. Yes, I did file away that metal around the hole and it slid right on and off after that.

Jim