Most china WN flanges are cut from thick sheets of brass and sanded flat before assembly. A light sanding in a hand-held electric sanding attachment will remove some of the fine finishes so it's important to keep the flange straight during assembly. We use an external hand-held electric sanding, but if using a standard sanding attachment on a drill press, the process is the same.

Most china WN flanges are cut from 1/8" thick, brass plated brass-coated steel - but brass flanges do not have a thin, shiny finish like stainless. They are usually cut with a chisel.Flanges are typically 4 to 10 inches long. They typically weigh 2 to 5 pounds. 

One need not fear the flange on the rear of the flange and butt-on-flange. One do not want to remove a lot of metal. The flange will need to keep the heat off the welds on all surfaces. If you want to add a new flange, you will need to put a pair of new rivets through the main (in front) and the reverse top rivets. The "reverse" is a set to be worn along with the original ones for the flange. If you are adding a butt weld, you can put a new rear flange through the butt weld. The rear flange needs to be removed, and a pair of old rivets, and new rear and top rivets welded.
Be sure the WN flange is properly welded. A low price WN flange can cause damage to the fuel supply. Do not add additional fuel-air gaskets or add more cinder blocks if there is no low ground. Always ground the flange to the same ground as the fuel tank.Also be sure the fuel tank is clean and dry. A wet flange may result in loss of fuel flow.Always use clean fuel, preferably fuel from a reputable fueling supplier or you will find that the fuel has gone to waste.