Burn-through at edge


Old 03-06-05, 09:22 PM
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Burn-through at edge

I'm a rookie, but have practiced enough to mig-weld 20 ga steel successfully using .024 wire and Argon/CO2. However when I reach the end of a butt-weld seam (edge of the metal), it invariably burns through right at the edge. If I stop soon enough before the edge, there's no burn through, but the last bit of the seam isn't joined. What's the trick here? Should I be using a backing plate at the edges?
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Old 03-07-05, 04:54 AM
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Run-off tab

You're on the right track. Add a short tab of metal at the end of the seam and finish the weld once you are on it. Then cut the tab free and grind back to the finished edge.
Old 03-07-05, 11:08 PM
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you could also put a tack there at the end. that way you wouldn't have to grind off the tab. i do this all the time.

Old 03-08-05, 07:53 AM
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Thanks guys. I'll practice some more both ways. The extra tab does work; would a copper tab work better since it won't stick? My tacks without the tab are still a bit too hot yet (metal shrinks back at the edge); I'll try tacking side-to-side instead of in-line with the seam.
Old 03-08-05, 08:01 AM
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I have always kept a thin piece of copper or brass (1/8 to 1/4") in the tool box for thin metals. Especially for filling holes. It takes up some of the heat and won't stick. Good luck.
Old 03-10-05, 06:57 PM
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A side-to-side (across the seam) tack at the metal edge works pretty well with no tab if I don't linger on the trigger. After some practice I can do it just about every time. Thanks for the advice.
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