im getting ready to finish my boatsiding project now that i have a nice warm garage to work in. my question is about welding thin sheet metal to thicker steel. im making sort of a rockslider/rocker deal and am having trouble welding it up. even with the welder at a low enough setting to get any penetration into the thicker metal im burning through the sheet metal of the body. the truck is an 88 chevy cut to the body line. the welder is an older lincoln sp-125 using 110v on a 20 amp breaker if that means anything. im using .035 (.35?) flux core welding wire. the welder has a hookup for shielding gas but i just cant afford it right now. should i switch to a thinner wire? any tips?

i double posted this in general 4x4 cause im not sure were to put it. the mods can delete whichever one is in the wrong spot. sorry.

My .02 but be warned I am not and official trained welder I just fuck about a lot in the shop:

Shielding gas will probably help a ton, I could never weld thin stuff for shit with flux core but I have never been sire if that was the wire or the fact I was rather novice at that point.

Shielded or not when I have to weld tin to structural thickness stuff I set the welder a little cooler then I normally would for the thicker material and then start and keep most of my pool on the thick material, like you where not even planing on welding the thin material, and then pull the heat up to the edge of the thin material and quickly back to the thick piece. Because you are spending more 'time' on the thick material you are still getting good enough penetration plus when you think about it does it really matter if you get full penetration on the thick material as long as you do not have a completely cold weld and you penetrate deeper then the sheet metal is thick your weld is still not the weak link in the chain.

This usually gives a wider bead then many consider best but I find it cleans up nicely with a flap disc.

ahh. to run the mig wire though wouldnt i need to get the shielding gas? i cant afford that right now.

If you've got a torch try preheating the thicker metal as much as possible, and leaving the thin at ambient temp.

It's still not going to be easy with flux core.

ive got maybe a total of 1.5 foot of welding to do to the thinner stuff. im going to try some methods posted in this topic and the twin topic in gen 4x4. might have to go to smaller wire though. im just a hobby welder so when things dont work out it throws me for a loop :)

ahh. to run the mig wire though wouldnt i need to get the shielding gas? i cant afford that right now.

I use co2 as a welding gas it is cheap bottle and gas is cheap. I do have mixed gas and try to save it for exactly what you are doing. co2 is better then the shield wire by a lot. can you do a rossette weld with a hole in the sheet metal that you weldup to the thicker metal. ED

not to sound dumb but what is a rosette weld? i tried focusing the bead on the thicker metal and quickly pulling it into the thinner metal but i still burned through. i think im going to get some thinner wire and try that before i tap out my resourse for solid core wire and shielding gas.

not to sound dumb but what is a rosette weld? i tried focusing the bead on the thicker metal and quickly pulling it into the thinner metal but i still burned through. i think im going to get some thinner wire and try that before i tap out my resourse for solid core wire and shielding gas.

a rosette is when you drill out the outer material and fuse the inner material to the outside it ends up like a spot weld. if you were to put rod in a shaft and drilled the outer hollow shaft and welded the inner rod to the outside solid shaft. Ed get the thinner wire first and try that. good luck let us know what happens. ED

I would get your self a bottle of c25 it isn't really that expensive, and will help a ton in the long run. The bottle i have was 175 filled, and it is the largest one you can buy. The smaller bottles are way cheaper, and you could even use just co2, and then it would serve dual purposes.

im going to try the thinner wire first. unless it cost 20 bucks then i cant afford it right now.

still having trouble. i wish i could afford to swap everything over to mig but funds are tight right now. im thinking of cutting my shit welds,grinding everything down smooth and using some strips of 3/16th's plate rosette welded into the b pillar. then weld the "rocker"to that. would that be strong enough? does it make any sense?

im just getting hella frustrated and am past the point of no return as far as cutting and everything goes.

Try getting the way smaller wire and first run a bead on the thin metal only. Once you have a bead ran on the thin metal, you can then switch back to the larger wire. As you are running your bead now you will still concentrate the heat on the thicker metal and wash the bead onto the the thinner metal that has the extra thickness on it from the first bead that you ran. Hope that makes since. :grinpimp:

i think i may have got it. FINALLY:smokin: i was able to get good penetration on the thicker metal while still penetrating the thinner metal but not burning through. i was hopping on it earlier and it wasnt flinching so im happy. thanks for all the advice folks. it was really helpful.:grinpimp:

How much penetration do you really need anyway?

My rule of thumb - although only being a holiday inn expert - is no deeper than the thinest material I am working with.

If I'm welding .095" to 3/4" I'll only look for that .095" of penetration in the thick material.

i wasnt looking to get alot but enough for me to feel comfortable. i achieved that so i am happy. im just not going to adjust the welder till i get the other "rocker" welded up. then ill put the larger wire back in for the thicker stuff.

I agree w/ TW, and better still, so do the welding manuals I have. You only need enough penetration for the thinnest piece you are joining.