I consider it a useful feature of the g0704 that one of the gears in the drive train is plastic. When I was pushing that big face mill across a piece of old railroad track, I kept encountering "tough patches" in the steel. Work hardened by the action of wheels rolling over the rail, I imagine. I was trying to be careful, but I kept crashing it. My mill just didn't have enough power to push that big face mill through that gnarly piece of track. It was a stupid project, but I was stubborn, and I plowed through.
If it hadn't been for those sacrificial plastic gears, who knows what I would have broken instead. Something a lot more expensive, I imagine.