Using diamond coated inserts on stainless steel at 57rc, would you use air or coolent.
The air is cool because it's real clean, it helps setting up part to part. Other than that I see no difference. But...It might keep the temp stabilized to hold the 2 tenths?
Disclaimer: Iv'e already roughed these parts before heat treat, so we are talking .005/side approx material. I would call it "hard finishing".