Thread: Mig'ing sheet metal

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One day... I want to have a real shop, and begin some actual work on my 36. Until then, any chance to work some sheet metal is 'practice'.

The latest practice, is to make some chain guards for the machines at work. Dirty, nasty location, they don't have to be pretty, and I'm not trying to make them perfect. Just good industrial quality guards, hopefully about 10% better than most of the chain guards you would see.

Unfortunately, the only steel I have at my disposal is some 20ga galvanized. Now, welding galvanized presents some intresting troubles. Causes the MIG to splatter, generally fouls the weld, and of course: it's deadly. SO.. I keep the fan to my back, and hold my helmet as to create a clean air draft into the helmet to displace any of the fumes.

anyway.. I have some questions for ya. my guards always seem to warp, and the top of the guard becomes convex from the shrinkage around the edges. Would this be eliminated if I were to induce some bend into the face before welding? If I started with it concave, would the warpage cause it to be flat when done? Is it better to try to shrink the metal in the center after welding?

Not that it matters for the guards. No one really cares if they 'hump' up a tad, and I actually like the look. BUT.. the day will come when I have to make something which actually has to be flat. I'm pretty sure that if I were to spot weld instead of continuous bead weld it wouldn't happen. But, that makes for a weaker joint, and I like full welds when joining pieces.

From my experience, warpage is the biggest problem to welding steel.

anyone got tips? Thanks

I don't think I would do it. If your employer can't buy some ungalvanized stuff they are putting you in jeopardy. I know galvanizing isn't as dangerous as spraying 2 part epoxy without the proper mask, but it isn't the best either.

You are a young guy, what you do today will be with you for a long time. Maybe I'm overly cautious, but there are a lot of guys suffering whose bosses told them it was ok to mess with asbestos and stuff like that.


Don

On top of what Itoldyouso said, you are eliminating the advantages of inert gas welding when you work in front of a fan.

yeah, two good points.

I forgot to mention: I also wear my respirator, so any chance of the zinc fumes are pretty negligable, when coupled together with the fan. And the breeze blowing away the gas shield is a pretty big factor too, probably part of why the welds aren't as clean as they could be.

I'll order in a half sheet of ungalvanized 20 ga tomorrow. Just seems like I never think of it till I need to make a guard, then it's too late...

meanwhile, about these shrink issues?

The shrink and warpage comes from getting the metal too hot while you are welding. When doing tin work with a mig, you should only weld a series of tacks, not try to run a bead. Keep your tacks an inch or so apart, let the metal cool then some more tacks. Keep the procedure going til the welds are finished.

I won't allow galvanized metal in my shop.Got one dose years ago,and can still feel it. 20 ga.is too thin to run a bead on,do as Dave said and tack,and go back. The other choice is to make the guard out of heavier material. Once again,Do Not Even Heat Galvanized Metal. Hank