The descriptions on the tack store sites say that it rusts. The rust is what's making it bind. You probably have to remove or smooth out a bit of rust somewhere to free it up. You can use steel wool. Or maybe a Dremel tool with appropriate bit. If the whole thing is rusted, you can boil it in cola (Any brand, diet or regular) but that will darken the whole bit, or at least any place on it where plating has rubbed off. The acid in the cola eats rust.