bmwpower said:
How small should I go and still be useful? What dimensions?
I want to add a vise to the table.
The table will be contructed of a steel plate top (what thickness is good?) and some sort of metal legs.
The table will be mounted on casters so I can move it around, maybe with some sort of system to raise the casters off the ground or bring securing feet down to keep the table stable on the floor.
I assume you've seen mine. It is 3X4 and has two small casters and adjustable feet on the other two. The casters don't move up as you suggested on mine as I thought it was too expensive and not necessary for my kind of welding. If you use casters, be sure to select a wheel that won't burn when it rolls over a piece of hot slag, and don't choose casters that will mar whatever floor you choose. Test your design for stability as well, especially the caster and or foot design. My table works well as a stable platform on which to weld, hammer, etc.
My belief is that small tables can be useful, but they need space around them (or the ability to move them to the center of the work area as needed). Mine is about as small as I could make it and still feel useful.
You should give some thought to the height of the table surface. If you are tall, for example, you should make it higher than the "normal" cabinet height. One way to get to your optimum height is to try different surfaces in your house to see how you'd like working on that surface height as a welding table. The welding process you will primarily use also affects optimum height: for TIG, you will want something that is a bit higher than you might need for MIG (this is because of the size and way that the different torches or guns are typically used). Consider that most weldors want to be braced somehow when they are welding so they can concentrate on controlling the weld puddle instead of their balance. That means that the best working height is also partly a function of whatever stool you will want to use while welding. It should go without saying that the stool should have fabric, or worse, plastic, on the seating area.
I used a 1/4" steel top for mine, which was about all I wanted to afford at the time. Bigger is better, but too thick means it will be impossible to move around easily on small casters, and will get stuck outside in the gravel if you ever need to move it out there. Some people like the "acorn" style which has square holes in the top to make fixturing easier. You'd have to buy or make special fixtures to make these work, and the top and fixtures are pretty pricey. I think they also make dust go more places, but if I had to fixture more I might think differently.
Put your vise on the outside corner and make sure it is one that rotates so you can use it to hold weldments in a variety of ways that make the welding job easier. The best welds will always result from a weldment that is positioned correctly to weld. Choose a vise that will withstand the hammering it will get.
You'll find it useful to have a drawer or two dedicated to the welder(s) and that area as part of the table. Plan your design accordingly. Plan for a place to store wire as well, either in spools or as lengths or rods, depending on the process you select. I built my table with integrated holders for the 5-lb containers of welding wire I tend to buy. The tops of each container are color coded, so I know just by looking which ones to pull up if I need aluminum, stainless, etc. You'll also want to plan for where to store your welding helmets, magnetic holders, welding blankets, etc. For example, if your table is 4 feet deep and you are going to store your helmets above the table, reaching them is going to be am issue unless you are really NBA material. My point is that the table can be designed to store these things, and moving the table will also mean that the necessary tools you'll need will be traveling with you.
Painting or powdercoating the table makes cleanup easier, and, if painted in the right colors, makes the table seem more integrated with the rest of the garage. I believe Lista sells touchup paint for their cabs- you could take some of that and get a match at the local powder coater. Only the top surface should remain unpainted, preferably still in the mill finish it came with. If you end up welding things to the table and grinding them off later, you'll need to plan for managing rust on the surface; avoid that if possible.
Plan what you want to store underneath the table and design accordingly. My plan was always to store the TIG welder under the table so I could weld without even moving the welder. If you will need access to the welder front panel, design it so you can see the controls but so that they will tend not to be bumped by passersby. Mine is oriented (by design) on the side that is relatively open by sees no traffic so it's accessible but hard to bump.
Plan to place the welding table where you are going to weld. That implies that power is or will be near the area. You can use extension cords as needed (we made a 6-gauge 50-amp cord for our welder so we'd have lots of flexibility when we wanted to weld farther from the power outlet.)
Understand your welding process. If you are using TIG, you don't need a lot of protection for nearby things. If you are MIG welding, spatter will be a problem and flooring, nearby cabinets and anything else will need to be protected. A similar precaution applies to the inevitable grinding that every welding area has. Understand where the grinding dust will go so cleanup will be easier. For example, don't plan to place a welding table near a part of the garage that has your newly painted BMW M1 in the next stall without a plan to move it out of the way when doing even a quick job. Same goes for any area that will be hard to reach to clean.
Plan for proper grounding in advance. You might weld on a couple of studs on the bottom of the top for a ground clamp to use. Be sure they are masked off when painting or powdercoating.
A welding table is usually the first project one undertakes with a new welder (it was mine, anyway!), so have fun with it!
-Will
PS: if you use the hitch receiver idea, be sure you try it out with actual pieces you might weld. Locating the vise below the normal top height (as it would be if mounted underneat the top) may make the vise too low for your requirements.
that was the only space I had to back use then, better than in the bedroom I guess... The brown blanket is a welding tarp and was sliding off in the picture. In my own garage will have much more space with exhaust fan etc 
And I pretty much don't have card board boxes.
