Well, I learned something today. You get some very fine advice on this forum! Thank you so much.
I don't know exactly what happened previously, (bad technique, I'd guess) but when you "chase" the thread with a Vee, and then thread with the Acme, it comes out fairly well. I still have an undersized lathe for this kind of work, but, I learned the technique. I had the lathe spindle motor stall at the very end on the last cut, which was ambitious for being near the end. (I took 0.005" full form.) But no harm to the work piece. The VFD on my lathe has little torque at it's lowest speed. I had to really pay attention for 5 TPI, things happen pretty quickly at 100 RPM. Would be nice to drop the speed to 50, guess I would need to make a pulley for that.
Now this looks like an acme thread form. It's not useful for me, (wrong diameter and material) as it was just a test piece, but it was an invaluable lesson in technique! Thank you all for your help.
I used my original acme tool I ground with 15 degree relief angles on all cutting edges. Didn't even hone the tool, just straight off the belt grinder (36 grit ceramic). I'll probably grind another, better (smoother) tool sometime soon.
Same ELS, thread TPI as before, but it came out much much better, at least in terms of the thread form. Surface finish? Well, I'm going slow, with minimal lube, on a small lathe that is rated for 8 TPI stock, using roughly ground HSS tooling. Still, pretty pleased with doing this.