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4130 .035 Wall on Aircraft Fuselage

by Charlie
(Oshkosh, WI, USA)

Any suggestions on getting into the really tight acute angles I run into on my aircraft fuselage?

All my welds are good where I can get access but I struggle in this area. It is often a "bridge weld" since I cannot get all the way down into the base of the angle. Sometime it will "bubble" and look terrible with porosity. Sometimes it will work fine. I try to keep the tungsten stick out to 1/2 inch and pre purge by tapping the foot pedal before sticking the arc.

Today I tried putting some aluminum foil on the backside to "catch argon", I tap the foot pedal to pre purge.

I'm running a gas lens with 1/16th tungsten, argon at 15CFH.
I wire brush everything so there is no mill scale. I've tried it with a standard cup #4 without any better results.

If you want to see the project, visit

Thanks for the help. Great website.


CNI makes a #12 cup that lets you extend the electrode almost an inch

I use either scotchbrite diffuser or a fine wire screen for a diffuser.

you are also on the right track with the foil to trap gas...thats a very good idea.

you can see the cup here...

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