[BrandonSpringle]

Hello everyone.
So last time I posted on here I was having trouble with horizontal. Now I'm having trouble with overhead.
Vertical was a piece of cake.
Mild steel to mild steel T joint. 1/4" thick base metals. Using 2% thoriated tungsten and 3/32 70s filler metal. 100% argon gas. TurboTorch. And weld machine is on 155. Argon pressure is at 25-30psi.
I have to put down a single pass 1/4inch bead. The dual pass 3/8's bead. Then triple pass 5/8's bead.
So every time I try to put down a 1/4 inch bead I get undercut to the top base metal. And every time I put the second or third pass on my 3/8's and 5/8's I get undercut.
Any advice or ideas on how to prevent the undercut will help a lot.
Thanks.

[AKweldshop]

Here's Jody's video on it.

Hope this helps,

~John

http://welding-tv.com/tig-welding-overh ... -overhead/

[blaz]

I have found that torch angle is a big reason for under cut.

[BrandonSpringle]

I'm thinking it's angle too but can not figure out what angle will work.

[MinnesotaDave]

Does under-cut mean under-fill in this case?

I've noticed that whatever process I use, stick/tig/mig, if it's undercut, often I have traveled too fast to fill the cut it (mig/stick) or just didn't fill enough (tig).

[Mongol]

Do you have any wiggle room on those parameters? 155 amps is kind of a lot for 3/32" filler and is probably a contributing factor in your undercut. I'd switch to 1/8" at that amperage.

And are you letting it cool any in between passes? Undercut is simply melting material without replacing it, and getting it too hot is a good way to melt a lot of material really fast.