I just bought a nice late model Series I bridgeport. It will be delivered in a few weeks. The trouble is that it will be delivered on a truck with a lift-gate, and I don't have any means of wheeling it into the garage besides rolling it on pipes. The driver may have a pallet jack, so maybe I could use that. But anyways -
I was going to design and build a mobile carrier for it, and bought 4 750 lb rated casters for it. I have two different designs in mind, and which one I go with will depend on the answer to this question:
Can the 4 machine bolt-down holes in the base support the full weight of the machine? If they will, I will design something that will hang over the machine base like a gantry, and then will pull the machine off the ground by bolts through the bolt-down holes. Then once it's rolled into place, I can drop the machine back down to the ground and remove the carrier.
If those holes can also be used for leveling bolts, then they would work for that design.
If they can't be used for leveling bolts because they would overstress the base, then I can go with a second design that will have to go under the base. The trouble then is getting the base out from under the machine. I know I can make or buy prybars and jacks to do it with, but would rather not have to.
And no matter which design I go with, it will be built of probably 2"x4"x 1/4" wall rectangular tubing that will be welded together and could likely support two machines.
I've only found two examples of people building mobile carts for their mills, and neither of them used the bolt holes to support the machine when in transit.