I've got a pretty big problem with this bath tub. The ring was completely corroded and the cross in the middle was gone. So I used an internal wrench to try and screw it out and the whole thing just crumbled, leaving me with a ring of the old flange attached to the inside of the piping (image). Its extremely stubborn and theres a lot of old plumbers putty sticking it to the threading.
Any ideas on how I could chip this away and clean off the putty or get off the old drain flange altogether would be greatly appreciated.