The dremel engraver is not at all powerful enough.
A normal dremel can mill one, if you go very slowly, and very patiently, and are willing to sacrifice a number of drill bits.
I am currently milling my water block with a model 395 dremel, and it is very hard, and taking a very long time.
Right now I can't work on it, I broke the brushes on the dremel.
I would be done by now if I had taken it slow, but I tried to go fast, which hurt it.
The engraver though, won't dent it. .02 amps. That won't get more than 1/2mm deep.