Thanks for all the good info. Once this goes into full production, I'll have more time to dial it in. Hopefully, the few inserts I ordered to test will get me through this prototype run. On my list of things to try are flat top inserts, CBN, and ceramic inserts. This will be a repeat job, so finding the right tool will be worth it.
The one thing I'm worried about on this part is that on the OD with all the interruptions, there are these thin "fingers". I'm afraid of snapping one off while turning. I guess I have to find the right balance between pushing hard enough so that the tool cuts like it's supposed to and not pushing so hard as to snap those little guys off. There's only one way to find out, right?
I'm just remembering now that the foundry that made these said that they held some parts back in case I needed some annealed. Like I said before, I don't have much experience with cast iron. Is it not very machinable in the un-annealed state? I'm confused about this.