Originally Posted by silverbear
Now Dan needs to cut the bottom piece which will close off the gas tank. He measures carefully so that there is an additional 1/8" or so of lip showing on the side pieces flanges to give more surface area for the solder to flow into. I forget the name of this cutting machine, but it is a little like a big paper cutter except that the blade cuts through the metal evenly all at once, else the metal would want to curl if it cut like a paper cutter. He marks the length and cuts off the excess. Then he marks the two spots with an awl where the mounting bolts will attach to the tank. Acorn nuts will be soldered from the inside, so the holes need to be bigger than the bolt and smaller than the outside edge of the acorn nut. You and I would use a drill probably, but the problem with a drill bit is that it can grab the metal and want to tear it. Dan uses a metal hole punch instead of drilling. You can see the blue box next to the tank which holds different sizes of punches which fit inside the punching tool. Pretty slick.
I have a Leslie shear I use for trimming that works well and I like his old Whitney punch. My personal opinion would be to use a regular threaded female bung with a lip on them and solder them into holes from the outside so that they can be repaired if the develop a leak or break loose from vibration later.