Project: "Turboyota" (Tur-BRO-yota would probably be more accurate)

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Mar 29, 2017
Time: 5 hours
1/16” tig rods consumed: 18
Tungsten sharpening time: 15 minutes
Music: NOFX
Footwear: flip flops
Shorts: Dickies
Shirt: Black (naturally)
Bro: True

After welding on the backside of steel, and carefully grinding, sanding, and cleaning the topside, why does the arc jump around and the material melt & flow all weird? What material property gets altered that produces such shoddy weld characteristics?

And Brent installed Lowe’s dynamat for me! What a swell guy!!! Thanks buddy! He said it acts exactly like the KilMat he bought for the Mobza.


the bodj

1st post pg805
Mar 4, 2010
I usually see what you're experiencing with hot rolled steel that I use a flapper disk to remove the millscale. I'm not sure if it's just crappy metal, contamination from the flapper disk, etc. Something else to consider is if there is a magnet nearby.

Edit: just reread what you wrote. This is happening on metal that you already welded on the backside. You might have cooked it when you initially welded the backside. Are you sanding it back with a clean pad and then wiping with acetone? I find I get poor results when I don't do that. The top guys are doing multiple passes, so it's doable lol
Mar 29, 2017
You’re probably right Bodj, there is a good chance the problem is substandard cleaning, but I still get arc wandering and weird melting characteristics even when the metal has been sanded bright and shiny. If I use a large torch angle—like 45 degrees—it seems to help a little.

The areas that were NOT mig welded on the inside welded fairly decent for being hot rolled steel.

I should whip out the stick welder, melt those puppies in, and then paint them to match the Tiger Wagon...
May 14, 2004
Easton, KS
Back side of the NIG weld is unshielded. If you had a way to shield the backside you would not have these issues. I just tack the inside, TIG the outside then go back and get crazy with the squirt gun.

Even if you were TIGing the inside you would still have issues without some sort of shielding. On stainless shit that had to be welded inside and out, we would put a piece of angle over the outside of the corner. It usually held enough gas in to make the outside weld nice when you go there. Without wasting shitloads of C25, I don't see a way around this unless you weld the outside first. NIG welder in the inside don't care if it's sloppy seconds.
Likes: Turboyota

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