Okay, it looks like it worked. I sawed a brass 1/4 pipe coupling in half, rather than using a half-nipple, That way, I have lots of area, for strength. I filed a clean spot on my kettle, and filed the edge of the brass half-coupling clean. Then brazed it on, using a slightly oxidizing flame, to burn off any oils. I haven't drilled the center hole yet- until I leak tested it with a quick-disconnect screwed in, and spray any-damn-soapy-stuff. It's tight, I'll go ahead and buy a valve, Vana. Not as neat as regular braze, it didn't seem to want to flow as well. Next time, I'll try some silver SOLDER. probably neater, nearly as strong? I may put the valve on with a steet Ell, to keep it in close to minimize the sticky-out-ness. Oh, this was on my shop built stainless 9 gallon pot, 16ga, 48" circumfrence by 15 deep, because that's how big the cut off was, 20 years ago when I needed a big pot of beans.
Or should I put the valve on a stright piece of pipe, to get it away from the fire? Who has burnt up a valve?