To make a steel BBQ pit, first either purchase a food grade steel barrel, or weld one from sheets of non-galvanized steel. To do the latter, employ a sheet metal shop to cut, roll and weld the main barrel, its door and a smaller firebox to place on the side. The shop can also construct a steel support to hold the barrel and drum before sending it home to have customized trim added.
Use piano hinge on the doors of both the barrel and firebox to maintain a tight seal when cooking. Apply them with either rivets or sheetmetal screws. Add wooden handles to all doors with 5/16-inch bolts and brass spacers. The spacers keep the handles away from the metal, therefore making them safe to touch bare-handed while cooking. Sand the handle, and wax it if desired. Add metal handles to both ends of the barrel to make it easy to transport.
Smoke management pathways must be installed in a steel BBQ pit. Drill a hole in the side of the barrel furthest from the firebox to accommodate a 3-inch diameter chimney pipe. Insert the pipe securely in the hole so that the smoke from the barrel is guided up and toward the back of the pit. Use a similar drilling process to provide the firebox with a damper made from the end of a soup can.
Connect the firebox and barrel by drilling a hole in the side of each to accommodate 2-inch diameter water pipe. It should fit snugly between the two and be held in place by a bolt and wingnut.
Once the BBQ pit is assembled, build a fire in the firebox to heat the metal and eliminate any remaining mill scale or oil. After cooling, clean it, and apply vegetable oil.