I have done similar a few times. You haven't run a cnc machine until you have done similar Those carbide router bits have no trouble cutting steel. I have crashed and cut clean through some steel toggle clamps a couple times. Once without breaking the bit.
I have cut quite a bit of aluminum on purpose with my router.
Just yesterday I was using a new Onsrud router bit for some polycarbonate. I bought it as a 3/16" bit. I have to cut 3/16" dados in some of this. After the first run, the dado was indeed too narrow. Check the bit diameter. It is .176" rather than .1875". That is a big difference for a brand new bit. Maybe it's metric or something, but marked as 3/16" too. OOOPs. So, lesson learned. Always measure rather than assume the bit size.