Changing Toilet Seat Cover?

I have an old style Villeroy Boch toilet seat cover I want to change out. The screw (butterfly screw?) is underneath. I managed to loosen it up and unscrew it 1/3 way down a very, very long bolt. Then it just stops even though I can keep spinning. Does this mean the threads are stripped? It doesn't make sense that I can keep spinning the plastic part but it doesn't continue to travel down the threaded bolt. I don't have a bolt cutter so how can I proceed to remove this toilet seat?