Support radius shelf from underneath with attachment to metal table legs

john a bit more info on the legs might be helpful. Are they straight round tube/pipe? tapered? metal wall thickness. A rather simplistic approach might be to create a ring out if wood and thru bolt or split the ring and clamp using two bolts if the wall thickness of the tube will support that.

From designs like that one that I’ve put together for people, the bottom leg often has a threaded bolt coming out of it while the bottom of the top leg is drilled out at and tapped. Usually they’re assembled upside down. So the legs thread into the top, the shelf is put on and the bolt in the next leg goes through it to thread into the other leg. This sandwiches the self between the two legs so there is no extra hardware; the shelf is only drilled just enough to let the bolt through. The process continues till you hit the bottom shelf and the bolt in the foot goes through the bottom shelf and tightens into the leg. All the ones I’ve dealt with have it so the threaded rod is at the top when they’re right side up so that the top is screwed down by the legs and they can finish with the feet and no hardware shows anywhere.
The hardware then would be a threaded insert for the top and the bottom of each foot and those double sided bolts for the top of each leg where they are a coarse thread on one end meant to screw directly into wood and the other end is fine threaded to thread into the inserts.
http://www.woodcraft.com/product/2001048/2806/brass-threaded-inserts-832-10-pack.aspx
http://www.woodcraft.com/product/2001069/3148/51618--x-3-hanger-bolt-10piece.aspx

-- --Rev. Russ in NY-- A posse ad esse

Thanks for the help. The legs are 16 gauge metal and rated to support 250lbs each. One other idea I was kicking around was placing a wood cylinder inside that roughly matched the tube diameter so any screws would have something to grab on to but I don’t have a lathe.They are straight tubes(one piece counter height length and not tapered at all.

-- john

john, just a thought, 16 gauge is approx 1/16”. Will you will be using a 2 3/8” diameter hole saw to drill the hole for the leg to shelf penetration? I’m thinking that a 2 3/8” diameter hole saw would leave a drill core + or – 2 1/8” diameter and add the 1/16” wall thickness times 2. Might not the core from drilling the hole be your wood cylinder? Additionally you could consider taking a piece of hardwood drill a 2 3/8” hole and make a sort of wooden washer, drill thru the washer, tube stock, and perhaps the inner wood drill core cylinder, bolt or screw. the one shown in the drwg I show cut in half and bolted. I realize that there are many ways and perhaps better ways but if you want to use the tube stock you have this is one way. I really do not see it needing to be that strong if the wood to wood joints are done right. It is a middle shelf with limited space so how much load will it see.

Hope my thoughts make sense, I had a few pints earlier today.

That will work. I was trying to figure a way to get a wood insert the right size and never even thought about the plug using the circle cutter. That should be the exact size. It will take some manipulation to get it to the middle of the tube and stay where I want it but very doable. By cutting the square collar and splitting it , the loss of wood from the kerf should make it just enough gap between the 2 pieces for a snug bolt down fit. Thanks for the great graphic. Working on the cylinder drawing probably caused your craving for the pints.
Thanks again, John

-- john

I would just drill a 2-3/8 dia hole through the shelf, drill a hole in the edge, and drive a sheet metal screw into the tube (after drilling a pilot hole). The edge banding will cover the hole in the shelf edge.

john, I know how I am when I get an idea stuck in my head, lol. As the hole saw plug will have a pilot hole you could take any square stock cut-off that will go into the tube and drive a pin (larger dia. nail with head removed) and sort of use the stick to the index depth. If you marked the center line of the plug and pre-drilled the tube you might also have a usable visual indicator. good luck with your build.