I had two steel table legs fabricated for a dining table. It is made from flat steel of size 80mm x 8mm (3.15in x 0.3in). It looks like a rounded square and the size of each leg is 700mm x 700mm (27.5in x 27.5in) . When I tried to attach a wooden table top, I noticed a bit of wobble. The wooden table top is around 1500mm x 800mm x 50mm (59 x 31 x 2 in)and weighs around 30kg (66lbs). I was thinking of adding three cross supports to prevent this wobble. Would this be a way to do it? Or can someone perhaps suggest a better type of support for connecting both legs? Many thanks!
You have to think in terms of triangles when resolving issues like this. The upper inside corners of your leg frames want triangle type corner braces. You also want to have triangle braces from each leg frame up to the underside of the table. Done properly this will eliminate all of the wobble.
This might upset your design, but if you skewed the legs a small amount (say, +10 degrees, -10 degrees) off of perpendicular, it might provide enough triangulation to prevent the wobble. (This assumes the wobble is in the long direction...)