Originally Posted by Pilotgeek
I could definitely see welding up an xchamber and then pumping water to get it to round out a bit. I could most easily see this done to make neat looking gas tanks, though.
So what happens when part of the pipe you don't want to change balloons out and you've lost your dimensions? Not to mention the thousands of PSI you'll need to actually bend metal. Sorry, but while this alleged forming technique may work in Internet Fantasy Land, it worthless, expensive, and dangerous in the real world.