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Homemade dc tig welder out of mig question

858 Views 2 Replies 2 Participants Last post by  TiminMb
I'm thinking about trying to use my mig welder as a power source for a low amp dc tig. My little mig is a Cebora (Pocket mig) unit. Output of 30-110 amps.

I opened the welder up to look at how easy it might be to tap into the power and it looks a cinch. The manual says the contactor is not live at all times. But I don't see a relay in between the transformer or rectifier and the two main leads. How does the contactor get connected when you squeeze the trigger on a mig? Is there a connection made inside the gun? If so, I can just cut into the two obvious leads that go to the gun and ground cable.

Also, wondering what polarity a gas mig operates on. It looks like the ground clamp is in fact ground. So I was planning to put two welder lugs on the side of the case so I can switch ground to whatever polarity I choose, as I understand on DC tig you run negative on the tungsten electrode. Also, what size and type of electrode and gas nozzle / funnel thingy would work best for welding light gauge stainless and mild steel (around 100 thou or less)? Do I run pure argon, or do I run a body shop type mix for mild steel and stainless?
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Wire feed power supplies are constant voltage. If the tip of the wire gets a little closer to the puddle, the CV power supply increases the current to hold the voltage constant, and the additional current burns the wire a little faster. That's what holds the distance from the wire to the puddle constant.

TIG power supplies are constant current. You would have a heck of a time trying to weld if the current were bouncing up and down with every tiny change in distance from the electrode to the puddle.

Back to the drawing board.
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