When using a part off tool make certain it is absolutley square to the work axis. Set the heigth a few thou lower than center, it will leave a tiny nub but it will cut easier. Also LOW RPM when parting. And do not ever use a tailstock when trying to part off a tool. As for finish, find a tool with a nice small nose radius and watch your feedrate. You should know what it is in inches per revolution and play with it a bit to get the best finish. And remember RIGIDITY is king. The stiffer and more solid your setup the better, Have any direct questions ask away. I have 30 years machine shop experience.