Purchase a nut-cutter from amazon.It will cut off nuts without damaging the threads.Saves a lot of time and trouble on otherwise stuck or cold welded nuts.About $8 or so.Worth it if you do much mechanical work on anything.There will always be one that is stubborn.
Metal Nut Splitter Cracker 12-16mm Manual Pressure Remove Rusty Nut Cracker Nut Removing Splitting Tool Heavy Duty Nut Splitter for Damaged Nut Remover