Mike,
Go to Foils Metal Salvage on Hwy 49 in Harrisburg. They have used and new steel, stainless, aluminum, and other metals and their prices are very reasonable. You can look at it and know the price before accepting it. You will do better if you buy a piece that's slightly too big if you can cut it down yourself. For a welding table, I would go much thicker, so it doesn't warp and will soak up heat better without warping. One inch thick makes a great welding table, but it is unreasonable when just starting out. 3/8 inch thickness won't break the budget, yet should stay fairly flat if you don't torch heat it too much. The 3/8" top will quickly warp from just welding something close to it if you get it too hot. With thicker tables it's common for welders to tack pieces of scrap to it when needed for clamping and shaping something and then just grind it off later. You can't do this with a table thinner than about 1" or it will distort. For starters on a thiner table (as thick as you can afford) just plan on mechanical clamping and keep the heat away from it as much as possible. Those welding tables from Northern and Harbor Freight will almost warp from just leaving them out in the Sun, but you could add a 1/4 or 3/8 piece of steel to them and make a fair welding table, although quite small.
A few fire bricks or a Kaolin board placed under things that need to be heated will extend your table's life and flatness. An extra small hole or two in a used piece of steel can reduce the price significantly while adding character to your table, They are sometimes handy to have too. Lowes has fire bricks and you will only need a few.
My offer still stands if you want any demonstrations or help. PM me if you want to get together.
Charley
