I am using a Hobart handler 140 with gas and .023 wire. With minimal gap at most spaces, determined by my cutting ability and patience to take my time to get it right, for the most part my spot welds and small 1/2" to 1 inch beads get good penetration and are pretty flat. But then all of a sudden and at total random intervals I will blow out a nice size hole and then being I am not a totally experienced welder, have a helluva time fixing what happened. If it was I was always blowing out the new sheet metal or the old sheet metal I might be able to see what I am doing wrong but it can happen to either or both at any time or place. If it happened when my gap was too far away or too close I might see something but it can happen at either or both also. It can happen at lowest heat setting or at an ramped up one on the same metal. I have tried to vary my setting on scrap to see any patterns but it doesnt seem to have one, its totally random.

My buddy who has quite a bit more experience welding than I do says he doesnt see anything wrong with my technique, torch position, speed or anything. He kinda in a sorta way said after he watched me that I was better at it than I should be with not having much experience till I bought the welder I have.

Can anyone give me some tips on how to keep blow thoughs from happening, I was thinking about making a heat sink using scraps of brass or copper from work and attaching to a piece of metal stock to use as a handle or maybe rig it to one of them 21 inch vise grips so I dont have to hold it. I am not totally sure if this would even work, I have tried to research buying something like what I have imagined in my head but havent seen anything anywhere. Anyone know where I could buy something like that if that would help or is there some other trick for not blowing through.

I am welding floor pans and inner rockers now then trunk next. I understand that it might take more practice and experience to get better but I might be missing some important information also. My buddy mostly welds big stuff and has almot no experience with thin sheetmetal so he doesnt know what I should do.


Any help is appreciated.

Thanks

Tim

I would suggest turning your welder down but, you say you have tried this.
Based on your welds being flat, I suggest turning up your wire speed.
Also, to me a 3/4" or 1" bead, would be getting the metal quite molten (I guess so, you're blowing through). With practice, you will be able to see when you are about to burn through.
When you're filling a blow through, try to build up the edges with weld starting on the far side and work your way in, letting each "tack" cool a bit, if you know what I mean.
Good luck, don't get frustrated!

Filling in a blow out is a real pain, I usually wound up with a big mound of weld to grind off later. I'm not sure on how to prevent it, but I know this works for me.

When you blow a hole through it, just leave it and go to the next one, then when your done go back and grind off the slag on the blow outs, then cut your self some little pieces of metal the same thickness or a tad thicker if anything.

They don't have to be round just kind of round, tin snips will work good.

I use a stud welder to weld a stud to the little piece of metal so I can hold it over the hole, but you can hit it with the mig and just snip the wire, either or.

Now hold the new metal over the hole, turn the current up pretty good and wire feed a little over 1/2 speed. You concentrate your weld on the edge of the new piece so it runs into the old metal.

Like your only welding the edge of your little piece but kind of getting into the old one at the same time.

You will have a nice flat weld, and save your self a whole lot of time and grinding off excess weld.

also if you are doing 1" circular welds on thin metal, like mentioned above, it is getting pretty hot. try doing it in stages... you know... zap (wait) zap (wait) zap. that way it will cool a bit and keep from blowing your puddle out the back of the metal. using some copper scraps like you said as a back up works good if you have a way to hold it in place. might not be so easy on floor pans.

All great suggestions above, and I use the same approach as Rob outlined for fixing a blowout.
My concern comes from the fact that you used the term "bead". If butt welding thin material you should not be running a bead at all. The correct method is to simulate a bead by lining up many little tacks until you have completed the seam. You should be contantly moving to different parts of the panel to make sure that the welded areas stay cooler. It's very difficult to muster the patience required...you'll wish you could just blast out a bead and be done with it, but you simply can't. Not with a butt weld. By the way, what sort of gap do you have between the panels and is it consistent?Copper or even aluminum backup helps A TON. I use exactly the same welder as you and with the same wire size. I assume your buddy helped you to insure that the welder was set up properly? (the feed roll has to be flipped to run .023 vs. the .030 that it came with)
What thickness material are you using? I can try to simulate this weekend and reply with pictures and the exact machine settings I used.
Post back...we'll get this figured out!
Tom

I just glanced over everyones posts being I am late for work. :) But one thing may be that where you are blowing thru the metal may simply be "warmer" a tad from a previous near by weld. I find that the warmth of the metal is in direct relation to if I blow thru.

"Tapping" the trigger with the wire hitting on the SIDE of the opening of a hole will greatly reduce the "mound" of weld when done. Technically, you could fill a 1" hole with the MIG welder!

Brian

Tim I'm not a expert like MartinSR but I have found problems welding because of the ground clamp not good enough or the work had oil or dirt on it, or the sheilding gas flow rate was wrong or wind blowing on it. The two pieces have to be tight together, no gaps.

Just to add to what others have said...Metal must be clean on both sides if possible. Let the welds cool and don't try to weld too much at once. If you do blow through try to put some copper behind the weld. The weld won't stick to it and it will help you to fill in the larger gap or hole you have created (i just take some copper pipe and flatten it out for this use). Blow through happens to the best of us...

If you are having problems trying to figure out how to hold a piece of copper to help fill the holes check out the eastwood company, they have small copper sheets with magnets in them just for welding check them out it might be helpful, either just buying one or helping you figure out how to make your own.

Thanks for all the great replies everyone. Now I just have to wait till sunday to get back at it 8). I was running a bead but it was a very small one, the blow through would also happen during a tack weld sometimes also. I do hear ya when you say its difficult to go slow using only tacking it and keeping the metal cool. I would get antsie and run small beads but I was working in the kick panel area which I did first to get used to welding there being it gets covered up. I am moving on to floor sections and it will be seen so thats why i posted to try and curb it and any bad habbits i may have developed.

I will keep all this in mind and take some pics when I get some pieces in and post them up.

Thanks again

Tim

The last time I did a series of plug welds it was in a new trunk floor.

Heres what worked for me.

I used a stool maybe a little under two feet tall, then I put a five gallon bucket on top of that, filled it three quarters full of water, and went in and stole one of the brides bath towels.

I also set a step ladder right beside me with the bucket right there also.

I would do a plug weld then lay the mig welder on the step ladder, then grab the wet towel and put it on the weld immediately, then keep turning the towel over real fast and put it on the weld, then after some of that I would take the wet towel and rub all around the weld, like the surrounding metal, so it was all cooled down.

Before I did a plug weld I would rinse the towel then wring it out a little but it would still be dripping pretty good.

You will get wet doing this but the trunk sheet metal is perfectly straight, I'll get a picture up of it.

Heres the bottom. They were drilled and panel glued first, the I drilled out the tops of the drilled holes and mig welded them full, both sides.



http://www.1969supersport.com/rest13.jpg

Heres another one before I blasted them.



http://www.1969supersport.com/sb26.jpg

I can't find my good picture, but heres one of the inside, where you can see how flat they are with out any warpage.

http://www.1969supersport.com/rest16.jpg

I can't find my good picture, but heres one of the inside, where you can see how flat they are with out any warpage.

http://www.1969supersport.com/rest16.jpg