Kyle where do you put the upper limit for "small gauge stuff"? Just to know, I'll surely never consider welding big stuff.
Depends on what it is, which isn't really helpful i know. You commonly see stitch welds on stuff 1/4 inch on down, 3/8 rarely, but on occasion. Bigger than that you usually see stuff welded out, because it's stiff enough to tear unless it has been fully welded. Remember proper welds will actually warp the material, because they have actually penetrated and when they cool, they pull. You can easily ruin a bucket by welding it to much and warping it (small mini bucket, the bigger machines use wayyyyyyyyyy thicker materials).
Another thing to keep in mind is that certain objects can't be welded on without ruining their structural integrity. For example, i beams have 2 flanges, and a web connecting them. You can weld in the web, you can weld end plates on, you can weld on the edges of the flanges, but you can't weld across the flanges because it greatly weakens them, because it adds stress and warping on the part that has to be straight and carries the load. You can however weld stiffners on the inside, because that actually helps it keep its shape. If you need a welded connection off of the flange, you usually weld an extra plate on first, along the edges of the flange, and then weld to that.
For a fillet weld (a tee or lap joint), a rule of thumb is a full strength weld will be the size of the smaller of the two plates. So if you are welding a 1/4 in plate onto a half inch plate, a quarter inch weld on one side would be as strong as the material itself. So if you are going to weld both sides, a quarter inch weld size, stitch welded so it's the same as welding one side, would be bordering on over welding because welding on both sides is way stronger than just one side because of shear loading. So you usually see even more spacing.
