I know that level is not that critical, but not having a 2000# rocking horse is what I really want to accomplish. Solidly mounted machine tools cut better in my opinion....plus I am just anal and hate to work on rickety stuff.
I agree that tripod mounting would probably be the best provided the three points were in correct orientation with what I will call the moments of inertia (God forbid it ever really rotates ) of the mill. The thing is a rather unwieldy shape and its balance changes as it is used, further making having a stable mounting useful. I am not sure the relatively small base footprint on this mill really makes it a good candidate for tripod mounting, however.
The base of the Bridgeport has 4 "high spots", one at each corner that are unfortunately several inches wide. The trouble with shims as I have been using them is that because each corner is actually a long contact area that wraps around in two dimensions in a plane, there is no good place to stick a shim and not make the whole works a little tippy in yet another direction. Forget square and plumb....you still end up chasing the ability to rock the whole thing, around in a circle, as you insert a shim in a new location. The problem exists because the shims are not tapered to exactly fit the pretty much unmeasurable tapered gap at the corners....and because it is four point contact instead of three. I think this is the reason that mortar is often used on these once they are positioned.
Mcgyver's three point barstock wedges (if I understand it correctly) is probably the wisest way to deal with this, but I will likely go ahead and drill and tap the existing bolt-down holes and use the bolts minimally to just make the whole works stable. I was just paranoid about having the mill standing on what amount to 5-6 inches of unsupported bolt. They have to be that long due to the thickness of the hollow base. I don't even have the thing fully assembled, and already I have moved it a small amount three times to make it better fit its space. The ability to quickly re-stabilize it as it occupies a different section of uneven floor will be nice.
thanks for all the help!