I'm making a cart made of 1 1/2" steel angle 1/8" thick...I've started with the base that has a 4' X 1' dimension. I've cut the connections into 45 degree angles(some of them do not meet properly(gaps), probably from the chop saw) I used one of those magnetic angle holders as well...my problem is that after welding the pieces together I ended up with different dimensions across the length...the middle ended up slightly smaller than the 1'...what is the best method for clamping all the pieces together so that I get a perfect rectangle.
should I also clamp some type of block at the other corners I'm not welding? what I did was tack weld each piece one at a time...should I have clamped all the pieces together first before tack welding?
another problem that i was getting was burn-through at the edges
I recently made up several dollies for file cabinets and I wanted a nice close fit to the cabinet. What worked good for me was to take a scrap piece of plywood and make a fixture. First I laid out the perimeter of the rectangle. You can check the diagonals of each corner point to make sure your layout is square. I then screwed blocks on all four sides to locate each piece of angle and clamped them to the blocks. After tacking all the corners I removed the frame from the jig. Then I clamped a copper block into each inside corner and welded them up from the outside. It would be harder to grind the inside surface flush and that is why I used the copper backing block. My welds came out nice and flush with the inside surface. Then I disc sanded the outside welds where necessary and screwed a dollie wheel to each corner. After a coat of paint to match the cabinets they looked like they had come with the cabinets.