Two very common tig welding repairs are:
In this video, we are doing both.
Its common to need to weld a mis drilled hole, a worn rivet hole, or a hole with damaged threads.
For welding a hole in aluminum sheet metal, it helps to clean the hole first. A slightly larger drill bit in a cordless drill is one easy quick way.
For filling holes in aluminum I usually let the cleaning action of the AC arc clean the area before I actually melt the aluminum.
Then, I gradually add filler metal using just enough amperage to move the puddle along.
After I make it around once, I add a little amperage and keep going in circles until the hole is completely filled.
To avoid a crater crack, I slowly taper off amperage while I keep the arc moving around.
Whether its a tank, a pontoon, or a media blast cabinet, a doubler patch is a common repair.
Some industries like general aviation have standard practices or codes that specify doubler thickness, dimensions, radius, and procedure.
Its never a bad idea to radius the corners on an aluminum doubler patch because sharp corners can be a stress riser where cracks might form in service.
I cut the patch out of a piece of scrap tubing the same exact diameter and thickness as the piece I was patching.
I used some Stronghand Tools long locking c clamps to hold the doubler while I put 4 tack welds on it.
Since the doubler was .070” (1.7mm) thick I only needed 4 tacks but if I was welding on thinner aluminum, I might have tack welded every inch or so.
I was using a CK worldwide mt200 ac dc machine and this machine has all the sweet spot settings highlighted in blue on the knobs and that is exactly how I set the machine.
There is a whole lot of discussion on what is the best tig cup for aluminum.
I used a #8 furick pro clear cup for this video but mainly because it helps everyone see the puddle better.
Its a great cup for aluminum but some people prefer using a standard #5 cup with standard collet body.
The video below shows tig welding aluminum with a standard #5 cup.
Both gas lens cups and standard cups have their place for tig welding aluminum...
it mostly just depends on the application or personal preference.