a 4 or 5 degree is a good gentle inlet, that is what I use and it keeps the case centered.
My Sheldon Lathe is down and that thread gear box is a nightmare to get back in time again. I'm about ready to part it out and get a small bench Lathe if I can find one that has at least a one inch spindle bore, 3/4" just won't do for the die projects I like to make.
This is about as close as I can come for a small hobby lathe I can use foe my small projects but I'm not sure the Chinese tools hold a close enough tolerance I need.