Welding and Metalworking - Stainless Home Brew Help

I am trying to make a 3 tier system for home brewing. It consists of 3, 1/2 bbl stainless steel beer kegs. I need to have the tops removed and a total of 4 bungs welded. 3 of the bungs need to be 5/8 threaded, internal diameter and one 1/2 threaded, internal diameter. The slugs will need to be polished inside the kegs for food grade quality. I spoke with a welder and he said that plasma cutting the tops is not a good idea as it would ruin the surface inside the kegs and they would need a pile of work. As for the bungs I would like to take care as much of the non-welding parts as possible because I do not have the $70.00+ per keg. Does anyone have any suggestions on how I should proceed in this little project? Feel free to ask more detailed questions if you want

Thanks
Alan

use a skill type saw and a metal cutting blade to remove the tops that will give you minimal clean up. why do you need the bungs welded? are you adding bungs or just closeing them up?

life begins when the kids leave home and the dog dies

I need the threaded bungs so I can attach ball-valves. One will be in the center bottom of the Mash-Tun as it will not take any direct heat. The others are on the bottom-side.

you might be able to use bungs that have inner and outer flangs and don't need welding, look around and see what you can find. good luck.

are you going to cowboy up or just lay there and bleed?

Yeah I think that I can use stainless pipe couplings, and cut them to fit. I was thinking of using a stainless nut for the 1/2 in section, which is for the thermometer...?

most oil field equipment suppliers sell high quality stainless thermometers in ranges from 0 - 100 f. to 1000 f, that have pipe threads on them prices are reasonable for low range. how about a bung designed for a poly tank, would be a type of plastic but you are not talking high heat are you? those are designed to be placed into a existing hole and a threaded collar goes on the inside and then tighten counter clockwise so that any nipples or valves screwed into them tighten them when installed.

life begins when the kids leave home and the dog dies