How to make a coal forge fire pot?
The best solution for a fire pot is to buy a cast steel one from www.centaurforge.com or www.piehtoolco.com or www.blacksmithsdepot.com or www.nfap.ca all have good quality fire pots that will last a long time. They are expensive.
It is cheaper to weld up your own but don't expect it to least near as long. It is esentially a flat bottomed rectangle with tappering sides with a lip around the edge. General size top opening 10 by 8 inches, bottom size 6 inches by 4 inches with a 2.5 inch hole in the centre. Depth top to bottom 4 inches with tapering sides down to the bottom to fit. The lip around the edge about 1 inch wide.
You will need to add a grate in the bottom that is removeable. I have used one with 9, half inch (1/2") holes in it arranged in a grid pattern that fits over the 2.5 inch hole. This grate will get burned up but you can make another one easily. I have used 1/2 inch thick plate for this.
The plate thickness for the walls and the floor and the lip of the fire pot should be 1/2 inch thick or a minimum of 3/8 thick.
I think if you dig around www.anvilfire.com they may have some more information and diagrams.
Hope this helps. Really you are farther ahead to buy a cast one and spend the $200 or so. Save you a ton of time and much better product.