Feeds and speeds are crucial for turning hot rolled low carbon steel. I find that fairly low surface ace speed and a significant depth of cut with a moderate feed rate give a very nice finish on my big monarch. On A36 it’s something like 70-100 sfpm a 150 thou radial depth of cut and 6 thou feed per rev. Dry with a CCMT insert. Finish is clean no tearing. On my smaller 10EE which is still quite rigid I get best results with high positive tooling like a vcgt insert. Similar speeds. Much smaller depth, maybe only 20 thou and a slower feed 2-4 thou. For small lathes that struggle with power and rigidity, grind up a HSS shear tool. These work wonders finishing HR with a 1-2 thou depth of cur and a tiny feed rate. I have a couple and also a huge one I finish soft steel with on the 24”Cincinnati shaper. For milling, high quality dead sharp end mills, again you’ll need to find that feed speed combo that does it. I just got a Haas 3” high positive face mill that does a very nice job. For those guys running high speed modern machines with flood coolant this advice is likely all wrong.
Keep trying, finishes won’t likely ever be as nice as 4140HT but a little scotchbrite does wonders.
