The work that I do is uncommon, exciting and rewarding, not to mention lots of fun. Metalwork however, is not without its downsides, which include the very dirty messes created from it.
Frustrated with this, my shop mates have requested that I take the most obnoxious parts of my work outside to be done in our small courtyard.
Fair is fair, but the courtyard does not have any usable surfaces to work on. Luckily, the previous tenants had left a large rack of various materials and I was able to find enough stuff on it to scab this table together. Now I have a solid work surface, plenty of ventilation and my shop mates are happy.
Here is how I made it:
With help from my shop mate, we precariously yanked this 1/2" thick steel plate out from under our material rack. Steel plate is 20 lbs/sq ft. @ .5" thick. This plate was 2.5' x 9'. Do the math.
Once the plate was free, I used soap stone to do some simple layout. Then I cut two equal 2' x 4' sections out of the plate with my Oxy / Acetylene torch.
While the plate was cooling, I pulled this 1/4" x 8" channel from the rack. I divided it into four equal 3' lengths and cut them out with 45 degree miters.
Once cut and ground I assembled the channels into a square and tack welded them together. I also cut four 23" lengths from a 3" schedule 40 pipe. These became the legs, which I then placed on the square frame and tack welded into position.
(It is worth noting that all of this material had been outside for years and was covered with rust, oil and paint. All of this had to be removed from the areas to be welded as to not contaminate the welds. This was a VERY toxic process, and should you ever find yourself in a similar position, you should NOT do this without the proper respiratory equipment.)
With the legs now attached, the square frame was now upside down, and so I took the opportunity to firm up the legs by adding stretcher bars.
With everything being held in the right place with tack welds, it was time to commit with full weld beads down all the seams.
Steel can warp when it is heated which can cause great frustration. It is important then to assemble as many parts with small tack welds as possible before welding the whole thing up.
Now, with the base completed, it was time for the table top pieces to be added.
As I mentioned in the previous step, steel can warp when it is heated and these plates were no different. Each one curled up on both sides while I was cutting them creating a subtle potato chip shape. Normally, this is not a big deal as steel is flexible and can be coaxed back into shape with proper leverage and clamping. The problem here was that the table top was 4' sq and the frame it sat on was 3' sq. Since the major warping was on the edges of the plate, there was nothing underneath to clamp them to for correction.
To remedy this I had to add two short sections of I-beam to the square frame where the warping was the worst. I welded the I-beam sections flush with the top of the frame, which extended the plane out to the ends of the top plates. Then I clamped one end down and tack welded it to the I-beam.
Next I used my largest clamp to bring the opposite end of the plate down to be flat and flush with the frame and tack welded. I repeated this process with the second plate.
Once the plates were in position and tack welded, there was only a little bit of fussing that was still needed to achieve total flatness on the table top. I welded in a few gussets along the square frame in strategic spots and used the big clamp to suck the plate down as needed. Now, with everything locked in place with good tack welds, I burned in full welds down all the seams.
Next, I ground and sanded the seams flush with the surface and the table was finished.
Now I have a solid surface to work on outside which makes my workspace cleaner and safer.
As pointed out in the comments, I neglected to include the process of checking for squareness and level. These are steps of paramount importance and should be done throughout the process. Measuring corner to corner of a square and achieving the same dimension will result in squareness. Leveling a four legged object is a little trickier than a three legged object, but making sure your parts (legs) are all cut to within the same tolerances will go a long way in helping you get level. The condition of the floor, well that is another matter all together. Installing adjustable leveling feet can be one of the smartest things you can do if you are building a shop, or any large object where maintaining level is important.