The first time that I tried to remove cranks, with a puller, I managed to strip the threads (my fault entirely). My only option was brute force of some kind. It took me about two weeks using a variety of tools, pieces of wood, hammers and mallets, to get the crank off, and nothing was technically ruined by the process. I chose not to install the crank again, because I knew I'd have to go through the same BS should I want to remove them in the future and they weren't worth going the helicoil route. The point is, sometimes you can't use a crank puller.