Dumb question. I made a TP special knife out of a hundred layers of flat drain snake alternated with starrett band saw blades. I normalized it twice and gritted it down. It seems to be a pretty hard flexible blade at it normal state without hardening. A mill file cuts it but barely. SO what would the hardness be at normal state compared to hardened and tempered back to straw color?

Id post photos but can't figure how

An air hardening steel will be a bit hard to cut with a file and some of them will have a bit of flex to them. The only way to know for sure with your steel is to anneal it and see if it is softer, Prediction of anything else is Not something I can do.

I'm inclined to leave it normal and not harden it at all. Would the grain be to big to take an ok edge?

Ok I'm gonna cut some extra material off the handle area and do some tests. Annealing and oil quench to see what happens

Is it a sharp mill file?

Even if the BSB is air hardening, I very much doubt that the drain snake is. So I don't expect those layers will have hardened through normalizing. (Carbon migrates pretty quickly during forge welding, but the other elements that make a steel air-hardening basically don't migrate. They do in theory, but it happens so slowly that it's meaningless for practical purposes.)