Besides tooling and machine rigidity material quality is an important factor in getting a good finish.
Is your hot rolled steel to a proper specification from from an engineering materials supplier or just a lump from a steel stockholder primarily providing materials to the structural community. If its the latter you could be in for a nasty shock when trying to machine it.
If it is at all dubious odds are the only way you have a hope of getting a good finish is to turn it in a four jaw. If you have any offcuts experiment first.
Cautionary tale
Due to placing an order with brain disengaged I ended up with 9 metres of nominal 25 mm by 300 mm steel bar that is exceedingly difficult to cut and seriously hard work to get a decent finish on it. Cutting is an abrasive disk job and machining needs coolant, a respectably stiff machine and sharp high quality cutters able to run at a decent speed.
My shaper leaves a finish like a ploughed field and its not terribly impressed by a flycutter.
Fortunately I have ex-industrial machinery and can afford higher end HSS milling cutters for the Bridgeport but the finish quality barely makes it to "hafta do".
After a lot of work and creative language.
It does turn reasonably well given good inserts or super-sharp HSS and appropriate feed.
Seriously impressed by the Chronos Little Hogger milling cutter which comes close to a properly decent finish if pushed hard. Kills the inserts tho'. A bigger shell mill with Maydown inserts works OK ish.
Lord knows what the stuff is but it certainly isn't to the specification discussed when I ordered. Frankly I should have left it on the lorry when I saw the invoice had no specification numbers. Supporting my local(ish) small guy kept delivery costs down and I got 9 m for the price of 3 m delivered from more engineering focused folk but false economy in retrospect. Thats the second time I've ended up with crazy stuff from him so won't be buying there again.
Application is totally undemanding so I just wanted "steel". Bad mindset when spending over a months pension in one hit!
Clive