Per the accepted answer above, here is a picture of the old and new harps with their respective bases. I originally saw the old harp as "welded to the lamp" but in fact it was welded to its own base that was attached to the lamp in the usual way, and it was easily replaced as shown here.
I was excited to develop my non-existent brazing skills as ...
First - "edge molding" or "rubber trim" comes in a variety of sizes, types, hardness, shapes, and prices. Here are just two examples taken from many from one of many vendors - not a recommendation
Second - depending on the application some type of tape (duct tape, weatherproofing tape etc.) might work folded over the edge.
I second Nate's comment that folding the edges is your best bet - it'll give you a small, slightly rounded edge, instead of a sharp edge, and it will stiffen your panel. The drawback is that you probably need a sheet-metal brake to make this happen in anything resembling a neat, time efficient fashion, especially for 200 copies.
This is a small portable ...
I think that part of your problem is your use of the super economy installation tool. With that kind of tool it is difficult to hold the rivet nut very firmly into the hole.
I use this type tool for installing rivet nuts and have had good luck with its use. The tool allows you to press down firmly on the rivet nut while at the same time folding the handles ...
It is welded . The only rational way to remove it is with a portable grinder ,probably an angle grinder. It will be a significant job and require repainting the bare steel and possible the whole table for a professional job.
Your first consideration has to be evaluating the value of the lamp. There are various factors that would need to enter into the decision equation as to whether to repair or replace:
Part of a set of lamps
Cost of repair
If you land on the side of repair then I can see a number of possible options.
Take the whole ...
Picture 2 shows it's held on to the legs by a pretty crappy weld. My first thought is "hit it with a hammer" because that weld should be reasonably easy to break; but you run a risk for collateral damage to the leg (bending or twisting) or the rest of the table, that you want to keep.
The proper and clean way to remove that would be with a Dremel ...