A little late, I know. But that's me, a day late and a dollar short.
I butt in here to bring up an old technique used in Gingery's first book on the lathe. He uses a mold around the leadscrew and casts a babbit half nut set, or three. It is involved what all is necessary. Candle smoke on a greasless screw is the least of the set-ups. But done with a lot of hard work and a chunk of babbit and a fire. Could just as well use lead or tin(shorter life) or any other low melting point metal such as bismuth, et al. As I recall, the extra pair I acquired for my 12" Craftsman was of babbit. They're still on the shelf, sitting around just in case.
I have some stuff for my models that melts below the boiling point of water. A bismuth
alloy that I don't know how long it would stand up. But a starting point, once you find the book. I had a set but gave it to a maker's group a while back. Could maybe run it down but I haven't been active for a couple of years. And Gingery is retired, or maybe even deceased. Who knows? Some of his books are still around, at
www.yotb.com or somesuch. Your Old Time Bookstore is the English name for the place. A maybe worst case solution, but I'm proud that my memory still works that good. Just wish the rest of me was in that shape.
Bill Hudson
Edit: The link didn't work. Best look it up with a search engine. BH