What's the largest gap you have moved a weld pool across?

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I'm big on filler pieces for the truck i'm working on just because it looks nicer But I bought these sheet metal clamps from Eastwood's and there great but I started experimenting with just moving the weld pool across the gap and holding on the other side to maintain penetration. So I started fooling around with some practice pieces and then started fooling with cooper backings and you can tell where this went. But my main concern was proper penetration. So My question is what is the recommended length on a gap between two pieces of metal you could safely move a weld pool across. Whew...... Or better yet what has been the biggest gap you have done to date and maintained good penetration on your sheet metal edges?Weld-Pak 100 Mig. New to welding and melting anything metal
Reply:Cuople of thoughts come to mind here. On automotive sheet metal I don't think penetration is as much a problem as blowing a hole. Even if you did grind and find a cold lap or crack you could hit it quick and burn it in. The hard part, the gap, has been bridged. I can't really say on sheet cuzz I don't get into it if at all possible. My guess is that 1/8 gap would be  a huge leap. I've done two different things on thicker. One is short beads no more than it takes to create one bridge, then another and another and so-on till I've done the section. Then grind it down and weld back along the whole thing to fill it in. Flip it over, gouge it out and weld from the back side. You'd have to be a lot more gentle than that with sheet metal of course, and then I wanna see ya flip that cab over too.  The other is the copper backing plate, but again on thicker. Just yesterday I did two pieces of 3/16ths in an "L" configuration with a good 1/4 gap. Sprayed my copper with anti-spatter and went for it. Flipped it over, gouged it out and filled it in. Came out good.
Reply:biggest gap i've filled is probably around two inches just for fun.. lol
Reply:I've been practicing with the Eastwood clamps and find they leave way too big a gap for my abilities.  They measure 0.040 and leave a gap of the same size.I find that sheet metal (20 ga.) is easier to weld (mig) the closer the gap is - no gap being the best.   I'm an amateur so chime in if I'm being stupid.  I made new "blades" for the clamp using 20 ga. and find it much easier to bridge the gap without blowing holes.Another approach is to file a 0.040 relief in one side of the sheet metal to be butt welded so that the gap is zero.  Then go back and bridge weld the relieved area."Bridging the gap" is useful as the metal thickness increases but on 20 ga. it gives me hives!Paul
Reply:Seems like you can fill any gap if you have enough filler.  Just keep building up until the two pieces meet.  But, if you have an alternative, I'd use it.  The Golden Gate Bridge is just a gap filler, but I'd hate to try to build it entirely out of wire or 7018 rod (both slow and costly).  In general, it's a whole lot easier to just push the two pieces together, or put in a third piece, when the two original pieces of metal (or land masses) are immobile. With thin sheet metal, it would seem better to cut a piece to fit the gap.  A neat sheet metal trick that a friend showed me (so I can't take credit for either how good or bad it works in practice) was to find another piece that covers the gap entirely, clamp the snot out of it (to the first piece, that is), then use a plasma cutter (or, a reciprocating saw would work ok to) to cut around the original gap through both pieces at the same time.  I've done this with wood, but for some reason it had never registered with me that it would work for metal just as well.  He did this while I was watching, and even though his hands were not steady at all, the resulting cover piece fit like a jigsaw piece into the new larger hole/gap.  He was fixing the rusted floor of an old VW bug.  The resulting gap around the edge was probably less than 1/16 inch.  The welds werent straight, by any means.  He did it one-handed while smoking a cigarette and talking to me...but with more patience the lines could have been much straighter.  I have never had a need for that trick yet, but ya never know when that will be just the thing to do.  Like Sandy, I personally try to avoid thin sheet metal or use rivets first.Last edited by smithboy; 10-10-2005 at 03:18 PM.Smithboy...if it ain't broke, you ain't tryin'.