I have a PM25 which is the same size as the G704 and have buried a 3/8" carbide corn-cob (rougher) in 1" thick mild steel. I don't suggest doing this as a normal course of use, but it was all I had at the time. I'm just repeating this as an example of what the mill can do at the extremes.
I just looked that machine up on the net. Very interesting- it looks a lot like the Grizzly G0704 that I am considering. Since I live within a day's driving distance of Grizzly's Eastern location, I could drive out there and pick one up at their facility if I settle on that model. By the way, I can content myself with a machine like these that can take say, maybe a .200" cut in mild steel if need be. Yes, I might have to make more passes to get the project to size but I have time. Thanks for posting about the capabilities of you machine- that is the kind of helpful info I was hoping for.