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Old 06-01-2012, 10:31 AM
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Originally Posted by S10 Racer
I think I would turn the heat & wire speed down a little. Try trimming the wire before each tack and see if it helps. It don't look like undercut, what is happening is the welds are "sinking". This is why I suggest turning the heat down. It looks like some welds are wanting to fall out due to heat, creating a crater.
I'll play with the wire speed on some scraps. I've tried with the heat setting on 1 and there just doesn't seem to be adequate penetration with this 20ga. Sometimes I will do two tacks one right after the other when dealing with a longer gap, so maybe that is putting too much heat into it like you mention. I'll start trimming the wire before each tack as well.

Welcome SRT. I too use a Hobart Handler and like it a lot. I do set my flow meter to 30 cfm. I find I get a little cleaner weld with the higher setting. How about taking some scrap metal and set your flow meter higher then work your way down and see at what point it begins to deteriorate. When you trim the wire you allow the purge gas to displace the oxygen before the arc is struck also. One last thought. How clean is the bottom side of the metal. Could you be getting some contamination from the underside of the panel.

John L
I will turn up the gas flow and see how that works. I used to keep the gas at 17-18 CFH with the trigger pulled but upped it to 20 in an attempt to get rid of these pinholes. I've heard of too much gas flow causing turbulence and causing problems as well though, so I didn't go up much with it. That's a good point about trimming the wire so it doesn't obstruct the gas flow. I clean both the top and bottom sides with a clean and strip roloc disc before any welding and after each round of tacks I clean both sides with a wire brush.

Any suggestions on how to treat the current pinholes in preparation for epoxy and paint? Should I drill them out and weld up the holes? Will the epoxy be sufficient to fill these in? Or should I put a skim coat of filler over them after epoxy? I'm new to the paint and bodywork side of cars.
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