Corner welding 1/16th aluminum plate

by Tim
(Las Vegas, NV)

I am a beginner in tig welding, but am decent at just laying a bead on flat plate. I have a Lincoln Precision Tig 225, I am trying to weld 1/16th aluminum diamond plate to make a fuel tank for an ATV. I have tried 1/16th 2% thorium and 3/32 2% and pure 3/32, and tried 1/16th and 3/32 filler. I'm using a number 5 cup for the 1/16th tungsten and 7 for the 3/32. I'm running around 60-70 amps, and 15 cfh of pure argon. I'm practicing with scrap aluminum identical to what im going to be welding later.

Now that you know my setup, here is my problem. Ive tried for a good 2 hours and can NOT get the surface tension to break between the two sheets before it melts away and leaves me with a big hole. Like I said I'm a just another damn noob, but this is frustrating. -
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try the 7 cup with 3/32 2% thor tungsten tapered a little less sharp than you would for steel.
make sure your joint has no gap.

light up and let the cleaning action dance for a few seconds and then puddle making sure the arc is directed so that both pieces start to puddle...if only one piece puddles, back off on the amperage to where you lose the puddle, redirect your arc more to the other piece and increase amperage again until you get both corners to puddle a little bit.
now jab the tip of your rod in to join both puddled areas...dont increase amperage much at all until you get them joined.

another way is to make good and sure you have no gap in the place you are going to tack, prop the cup on the corner joint with the electrode really close, and give it full pedal and let off as quickly as you can...if there is no gap, and if your arc length is tight, it will tack , then you can easily go back and add some filler to keep the fused tack from cracking.

it takes a little more than one amp per thousandths of thickness for aluminum to do this and it will require some testing and practice on scrap like you are already doing...but it works great .

good luck,
jody