The cutters arrived ... and they're excellent! Not measured the diameter yet as my sister has borrowed my micrometer (long story).

I've only used one so far, and on aluminium. Cut some lots of parts from 4mm aluminium sheet with 0.5mm depth of cut and no coolant at 550mm/min ... no problems and left a good finish. I used a spiral path, so no plunging.

Also used one to cut two spindle mounts from 5/8" aluminium, again pretty good finish this time with 0.7mm depth of cut and cutting fluid. The swarf is ejected much better as expected.