I run a couple swiss lathes. The tooling I inherited is so so and im ordering some new stuff but I'd like to use the stick tools that I already have. I my main turn tool is a CCMT21.50.5 (80* .250 ic .008 Rad insert TiN coated). .008 is the smallest corner rad that insert is offered in. otherwise id order a .002 or .004 rad in the same insert. It works pretty well and the only real complaint I have is that most prints want shoulders with a <.005" corner rad so I end up cleaning up the corner with a groove tool that has a sharp edge. so, I want something with a .001-.004 corner radius for light-medium turning which is a lot of what I do.

Im looking at a Mitsubushi CCET21.5V3RWSN which is a 80*, .250 ic, .0012 rad insert with a wiper. Here's my question: I was looking at the chip breaker geometry and the cutting edge has a 20* positive rake. I mostly cut 303 stainless and 12L14. Is 20* too much for 303? let me rephrase: I know 20* is too much but will I notice really fast edge wear or chipping? how much performance will I sacrifice? also, Ive seen 4-12* recommended rake for 303. whats your opinion of the ideal rake?

If it is, can you recommend an insert with a .001-.002 corner rad? Its for a Swiss lathe so DOC is usually .020-.200" but most often towards the low end of that. mitsubishi is preferable but it can be from almost anyone.