I have some offcuts from cast part ends. Material is EN-GJS-500-7 (GRP500) Spheroidal graphite cast iron. Nominally it should be very nice material to machine. I have mixed experience with it. These are ends of the cast bosses and are cut off during manufacture. Some are porous at the very end, or are hardened. Some are pretty nice to turn, but milling seems to be a little harder.
http://www.steelnumber.com/en/steel_composition_eu.php?name_id=1522Material number is 5.3200. Nominally Brinell hardness (HBW): 150 - 230, but it feels harder than that.
I would like to mill T-groves to them and having a little trouble choosing to buy T-grove milling cutter. It should be good enough,butnot overly expensive.
I haven't tried it yet. One friend tried, made 10 mm slot witha a mill, but strugled to make T-slot.
I am looking proper size for M6 T-nuts. 10 mm groove, 15-16 mm wide bottom.

Suggestions? Easy or not?