4) The bowl

Prepare the bowl by cutting down the nipple to one segment, a little over 1/8". The brass diameter is a little oversized. Now you can just screw it into the iron. It's tight, so I needed to use a wrench and pliers to thread it in. It helped to put a little oil in first to help cut the threads. The metal in the soldering iron is harder than the brass, so it will cut threads into the brass. Be careful not to screw it on too hard or it'll break the brass nipple off.