lazylathe you make some good points. I agree with what you say. I found when working and high speed production shops that parting tool with was dependent on the stock , for 6" you want a 1/4" parting tool. too small a tool is as bad as too big. Parting 4 inch you might want 3/16" 2 inch 1/8" wide tool works good. For 1 inch or under you can do fine with a 1/16" parting tool. When I started working fixing screw machines I saw the guys making parting tools on the surface grinder. I thought their tool geometry was way wrong but I was the one who was wrong, so I shut my mouth and watched the tools in action and got an education from some non college guys. The tools they made left little to no burrs. some guys set up tools that would go way down a bore and put a champher then pull out before the part was parted off. No burr and the internal champher was done. I learned alot there the boss had 3 nitro funny cars so that ate up half my time, when the car has a parachute you know its not a toy for little boys. It was cool to have a boss make me work on the cars. I'm rambling but anyway parting can suck, do it as close the the chuck as you can and get it done. its not magic and you dont need a live center.