Count me in as another vote for
The Amateur's Lathe. After that, I've also found value in the
Workshop Practice series, mostly written by some of the big names in the British modelmaking scene. I don't know if there was a comparable phase in the US but in the pre-WW2 UK there was a boom in the production of small lathes for amateur use, so they are well-documented, and quite well-supported into the present for the manufacturers that lasted later into the century. I have (in bits) a 50s Myford ML7 which is a pretty typical 3 1/2 inch English lathe (7" by US standards); a lathe of this sort of size is excellent for bike-scale work, apart from its very restrictive through-bore. I really should put it back together. I could never have gotten started making frames without it; there have been countless jig bits and bike parts I've made with it.
There are also a number of simple guides (some lathe model-specific) made for the US Army; this is a general one (and, I think, the one I have printed out at home, covered in oil):
https://archive.hnsa.org/doc/pdf/lathe.pdf
Moving into the 21st century I subscribe to This Old Tony on YouTube and always learn something as well as having fun.
I have personally resisted the urge to do all my tube fit up with machine tools; I've found it not only satisfying but productive too - at the rate that you and I are making frames, the time spent learning how to mitre tubes accurately with hand tools has a better payoff than machine setup and fixturing. Machines are always far more repeatable than hand work but not necessarily meaningfully more accurate, easy or time effective. You can do a lot with a small lathe, a small mill, and a good selection of excellent hand files.
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