As mentioned using the flanges will get you a connection for the legs. You will probably find them in the electrical fittings area of your hardware store. For a decent looking job I would use carrage bolts with the round tops countersunk just enough to fit flush with the topside of your table. Some areas have them both in galv. and SS. IF you have a Forstner bit set this is easily done, use your flange as a template, set the holes where you want them then mark them. Then using the Forstner bit just drill down about 1/8" or so, then drill through with the proper sized bit for your bolts. IF you use the Forstner first it will, or should give you a clean edges around the hole on topside.
On the actual legs, if you want them to be pointed on the ends there are also a couple of options. One use the welded points on the caps, however this isn't going to give you any way to level it on uneven hard ground. Another is to use threaded pieces with a locking nut to enable you to level it up and lock it in place reasonably quick. An easy way to do this is to get a threaded coupling that fits your legs. Get a reducing bushing which is the same size as your pipe but reduced down to 1/4" or 1/8" pipe depending on what your using for the pointed part. This will allow you to drill out and tap the hole to the size and thread of your actual foot. You can use several things from this point on to accomplish a decent foot, I would suggest 1/2" all thread rod. This can be found at your hardware store in several lengths and is easily worked with. You can also find wing nuts that will fit it and make locking them in place quick and easy. Tap the reducer bushing out to 1/2"-13tpi and your set. Then all you would need to do is gring a point on the ends and screw them in. You should only need about a foot for each leg but even that might be too much. The more you have out the more shakey it will be.
Another option is if you have a friend who is an electrical contractor or if you can get hold of some aluminum conduit. I have found that the 1" will perfectly slide into the 1-1/4" makeing a very stable lightweight adjustable section. If you went this route you could simply drill a set of say six 1/4" or 3/8" holes an inch apart through both pieces and use them for a major adjustment (use the spring clips like for tractor attachments for the pins) and then have the all thread on the bottoms for minor adjustments. You could also set a couple of the small bulls eye levels in the top if you wanted to get that particular with it as well.
Mike / Tx
"Heck why would I lie, most folks don't believe the truth when I tell them"