The trick, then, is to find a structure that takes advantage of that strength while retaining some visual delicacy. Mr. Ban has experimented with several ways of joining his tubes, and, following his research, I chose to bolt through with quarter-inch bolts, which is simple, straightforward, and strong. The top is made from PolyGal, a corrugated industrial plastic used in architectural applications, such as greenhouses.
I salvaged all the tubes for free, as well as the plastic for the top; I spent maybe fifteen dollars on hardware, nuts, washers, etc. The table was built with simple hand tools -- drill, hacksaw, wrench, and screwdriver. It took about ten to fifteen hours to make. It is strong enough to stand on, yet light enough to lift with one hand, and one hundred percent recyclable at the end of its life.
Step 1: The "X"
I also reinforced the notches by gluing a scrap of tube on the inside of each notch. This isn't strictly necessary, but be forewarned that once you take a big chunk out of the middle of the tube, they are likely to bend and crease when handled if you aren't careful. Treat them gently until bolted together.
Lay one of the "X" tubes with two full tubes as legs coming off from it as shown in the last picture. Cut two short, 18" braces for the legs, each with a 3" slot in both ends. Move the tubes around on the floor until the angles look ok; the goal is to have the end of the legs come slightly past the end of the "X" piece. This provides a wide enough stance for stability while maximizing knee and leg space for the user.
Step 2: Legs!
Attach the braces the same way; start flush at the end of the "X" tube, pin, then pivot down until you hit the leg. Clamp, drill, glue, and bolt. You may want to scribe the tab cuts on the braces to fit more tightly against the legs. All the compound curves and conic sections involved in cutting cylinders can be tricky, so just do your best with a pencil, a box cutter, and your eye.
Repeat until all four legs are attached and you have two identical frames with two legs, two braces, and one cross-piece each. Lay the saddle joints across one another and bolt through. Hand-tighten the "X" bolt, as it will need to be removed later in the process.
Step 3: Finishes
Step 4: Top
The top works as a brace for the whole structure, locking the legs together. It has to be stiff to achieve this; in that vein, I made the cuts so the corrugations would lie diagonally across the the "X" structure for maximum stiffness. An even better approach would be to layer two pieces of PolyGal together, with the corrugations running perpendicular to one another.
Measure and make bolt holes in the top in an X shape. Scribe and make corresponding holes in the tubes. Take out the "king" bolt at the center of the legs. Attach one set of legs. I used regular and neoprene washers to make sure the top was tight to the structure, yet protected from crushing. Again, don't over-tighten the bolts, as it will dimple the plastic and crush the tubes.
The second set of legs will actually be a little bit lower than the first, because of the saddle notching. Make up the difference in height between the top of the tubes and the underside of the PolyGal with some washers and a nut as a shim.
Step 5: Braces
To trim the feet, flip the table up on its legs. Shim under the feet that are high. Use a piece of cardboard or wood to transfer the line of the floor onto the tubes, several inches up. Cut. If the feet still don't lie flat, there is a considerable amount of adjustment in the threaded rods; by tightening and loosening those, you can pull the legs in or out until the table sits flat.