Speeking from experience, it's not how thick your top is as much as ,..how level it is..from left to right and ect.. Over hang is a huge consideration.. Meaning,.u need to be able to clamp the metal down using a common c clamp without bs frame issues. The best table I have ever used was framed out of 2x6 oak. And caped with 1/8 plate steel.
I don't care what you intend to do with any work table...it should have a slab of thick steel about 10x20" x1"thick that you can maneuver around the work top...something you can hammer on,..drill on,..paint on,..pound your head on,..What ever,...personally,..I don't pound on my benches...I pound on the piece of Slab steel that's 1" thick.. So don't consern yourself with how thick your table needs to be ,..If your
Gona Beat The **** Outa It..be smart and use a 1" plate of steel that you can abuse and move around
And I also need to add,..that you can do wonders when you need to straighten a piece of steel, if you have this moveable flat piece of anvil plate. And the fact that you can pick it up and set it aside,..leaving your welding table completely flat is priceless.. A flat level 1/4 " table is thick enough if you use a 1" thick moveable slab like I have described. To each his own....kubotakid USA