I removed the stuck gasket (likely made of annealed copper) from a 10" to 4.5" reducing flange on the side of an LFC Vacuum Cube with the smallest of the 4 locking pliers I cleaned. I didn't try the other 3 locking pliers. I think I very lightly scuffed the inside of the vacuum area, but the knife edge looked good. I added a new 4.5" copper gasket and 4.5" blank flange and tightened the screws.