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Gas welding the big stuff


Well-Known Member
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Jun 12, 2007
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Seattle, WA
So I tried to weld up that spring bending jig the other day, and scared myself half to death with the process. I just couldn't get a good puddle to form in the thick steel, it took a ton of heat. I'm using OA, which I realize is not the best choice, but it's what I've got.

I only got one side done, and by the time I was finished, the AW209 tip on my Smith Airline was distinctly not copper colored any more. Looks like it was overheating, and the detonations I got while I was welding suggested the same thing. I had the regulators set to 10 PSI each, but I have technique questions.

1. When turning on the acetylene, my usual method (with the tiny AW200 tip) is to look for 1-2 inches of smooth flame before it starts feathering. Is this still a valid practice to find the right gas flow with the big tip?

2. I'm using the little lightweight kevlar hoses. They seem very skinny, but they're also very short. Are they likely to be restricting gas flow enough to cause problems with the big tips?

3. I'm trying to weld 3/8" mild steel to 1/4" mild steel. The Smith chart I can find says the AW209 is the right tip, but I have an AW210 available as well -- should I switch to that one, or is it just a gas flow problem I've got?

4. Related to point 3, is the Airline just the wrong/too-small torch for this job?

I appreciate any thoughts you guys have. Steel of this size is outside my previous experience, and I don't want to mess up my equipment with bad technique.

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