Hi 49shep,
I recently had a stainless steel shower trim part custom made for a bathroom renovation. Fortunately I have a high school friend who is a highly skilled and trained welder - straight up welding magician intuitively skilled on all welding technologies and watching him work out and decide what methods to use while making my part was something you could make a television show out of.
Anyway, he described that if you do or don’t want a gap between the two parts depends how you feel you want to weld it
Thin as this job sounds seems similar to the 0.0625 stainless we were butt welding
He decided no gap - tig would yield a good polishable weld and he was correct
However some post folding and bending joints left about a 1/32 to 1/16 gap which needed a filler mig wire placed in the crack to resume tig without filler rod
He backed every spot with a lot of aluminum scraps to sink heat
And jumped from opposite sides of the work to allow heat to dissipate
Also some of the aluminum blocks got a bit too warm so we would put those aside and get fresh off the floor cold ones
Once A tack weld is done it might be a bit proud or bumpy that tiny extra material is holding stress, just flattening the first tack welds restored flatness and makes a difference
Once the part is tacked up and the tacks are dressed to return flatness at cold then you proceed to more tacks between the first set
Repeat
All extra metal from the weld is pulling (shrink) so removing the excess to flat helps a lot
After it’s flat gently tapping on the welds at the right place will return the panels to completely flat
Don’t weld too much on a warped panel unless you know for sure the two edges are uniformly warped at that instant and the natural flatness would keep those two edges uniform in the end - if the edges are offset from their true position due to intermediate work the welded position will lock in the warpness.
