I also find the insert cutters good for dealing with castings that may have hard spots not just covering large areas quickly as the carbide will survive where HSS will quickly blunt. They are also more durable when dealing with mill scale on "black" bar.
I have 40, 50, 63 and 80mm but have not used the largest on iron or steel apart from initially trying them out.
I run them at the high end of the right speed but adjust chip load(feed) and DOC to suit my X3 and SX2.7
For brass I use the 80mm one with the sharper inserts for Non ferrous and recent tests have shown that these inserts work well on ferrous much like the **GT ones do on smaller lathes.. Recent thread about facemills has the video
As for shape with the smaller DOC the smaller machines can take it won't make a lot of difference as you will probably be at or below the corner radius
Edited By JasonB on 09/10/2022 06:35:48