Flanging a Plate

Following,  are the steps to flanging a plate. Flanging plates was really a fun process for building the boiler. Annealed copper is like lead and can be shaped almost any way you want, given the right former. The former is made to the dimension of the inside of the plate with a radius on the corner the copper is to go around. The copper plate is positioned between the former and a clamping piece. The clamping piece is just a little smaller than the former so the forming hammer can get around the radius well. The clamping piece also assures that the plate being flanged remains flat. The copper is first annealed by bringing it to a dull red color with a torch. The copper is then clamped between the former and the clamping piece. The edges are beaten with a hard plastic or rawhide mallet. Do not use a metal hammer as it will thin the copper where struck. As the copper is worked with the hammer, it will stiffen as it work hardens. Re-anneal the copper and repeat. The annealing process will have to be done several times before the copper reaches the finished shape.
Here's the flat plate to be flanged along with the drawing, former and clamping piece.
The flanging process has begun.  It's of benefit to remove extra material from the corners. 
The clamps must be re-positioned as you hammer your way around the plate.
Another view of the shape left by the former.
To bring the flanged edge of the plate to a uniform length, a fly cutter is run around the edge of the plate.
Another view of the fly cutter going around the edge of a flanged plate.
The annealed copper is positioned between the former and clamping piece.
After the first round of forming, you can start to see the shape of the former appear.      
The edge of the plate is slowly going over the edge of the former.
The edge of the plate is nearing completion.
Here, the edge of the plate has been beaten tight against the former.
Here's the hard plastic hammer that I flanged all of my plates with. To the right is a former and the plate that was flanged with it.
The finished flanged plate after trimming the edge and cleaning up in the acid bath.
Here's some of the other plate formers. The round one at the top is for the smoke box tube plate. The two towards the bottom are for the double flanged throat plate.