Thought I'd share this since I'm very pleased with the results. Welding on ~1mm stainless is a daunting proposition.
This is a dirt cheap and very solid way to add stainless 1/2" NPT fittings to your stills, fermenting vessels, pot lids, etc. Everything is either SS or teflon so it's also very safe.
Yes I know I've just basically reinvented the 'bulkhead' fitting, but brew houses charge 5x as much for them and they come with silicone O-rings which will need to be replaced anyway.
These teflon gaskets cost $2 for a pack of 20.
The hole was drilled with a step bit, but you can also use a regular drill bit (of smaller diameter) and clean up the messy hole with a dremel.
SS 304 3/4" NPT Lock nut ($2.00)
SS 304 3/4" NPT male x 1/2" NPT female adapter ($0.75)
29x24x2mm PTFE Flat Washer ($0.10)
So under $3 each. Parts can be found all over ebay or AE and perhaps locally (although I had no luck with SS fittings at local plumbing shops).
The 24mm ID teflon gasket was about 1mm to tight, but if you rub them between your hands for a minute to heat them up they easily slip over the fitting. I also applied teflon tape to the threads when assembling.
Note: the big nut goes on the *inside* of the vessel.