I was trying to get the servo's working on my Excello mill and managed to get the z axis stuck all the way down. Normally I can connect a 12v battery charger and move the axis but it wont' work now (and I don't have the axis working properly yet under control..) Any ideas on what it takes to free it?
I normally use a wrench on the bottom or top of the ball screw, on the tensioning nut. If is is stuck so tight that the wrench won't work, then you may have to loosen the attaching bolts on anything you can get to. Tapping the nut with a hammer while you are turning may help. As an absolute last resort, vice grips or channel locks applied to the unused part of the threads at the very top may work, as I said, absolute last resort.