I replied to your other post about my convo with 1F and why the 50mm diameter rail isn’t an option for the machinist model.
In regard to milling aluminum, here are some examples done on my machinist model. Now, in an apartment or balcony etc, if you are into milling aluminum your neighbours are going to love you 
As far a titanium, steel etc. this isn’t the machine to do those. Aluminum, brass, no problem.
