Thor, or should that be Zeus?

[Boyan Silyavski]

The way i see it, if you go with high speed spindle, fixed gantry would be better, if you go with servo motor and Bt30, the VMC shape will be better. So at the end there is not so much to consider which shape you go.

With that size bearings and rails length, overhang will be irrelevant. You could try to make it small, just for a designers satisfaction though, but its not necessary.

[Robin Hewitt]

I cannot claim any "experience" making super routers, but I have made a few tables and converted a couple of milling machines. But enough of the X, here are my thoughts on the Z.
With a knee mill you have 2 controls for the Z, you can lift the table of lower the quill. A round column mill is similarly adjustable. When you CNC it you probably motorise the quill and use the other, heavy duty adjustment, to optimise the quill travel and get maximum support on a job by job basis. You would be lost without this double control of the Z and yet nobody puts it in a home build.
I suggest you make the entire gantry moveable in the Z with some big bolts so you can lock it in the optimum position. I do have expertise in this because when the locking bolts went on my mill everything went to hell in a hand basket PDQ

[Davek0974]

That's quite a neat idea there Robin, have never seen that applied yet.

I guess it depends on the intended use of the monster mill, spindle power and speed could dictate smaller (<10mm) cutters which would then indicate that smaller workpieces would be used - no use tickling a 300kg lump with a 3mm end mill I think.

That being said, a dual position gantry maybe offering the tool a 0 - 150mm and 150 - 300mm range could be useful, would need an assisted method of raising/lowering the gantry though - two trapezoidal leadscrews might work along with some heavy clamping method when in position.