they make butt clamps for welding that will hold your sheet metal together while you spot weld your way around it.

 

interesting. i've been using the magnets.

claims look like they might create gap?

 

you need a little bit of a gap for the weld

 

i've heard that, but what i've experienced is that it blows through with a gap. better to have it touching. no gap, in my limited experience, works better.

if you do no gap, then you cant grind it all the way down, obviously (or maybe not so obviously)

 

i'm not great at welding, so i'm not talking down to you, but it sounds like you just need more practice. i'm pretty sure that gap is needed for maximum strength.

 

need more practice, that is true for sure.

if you are going to grind it down the gap is needed. If not, its just as strong both ways, gap and no gap

 

The professionals leave a little gap, it allows the metal to expand and contract without buckling. It can be treacherous to cut your patch panels planning for a gap though because you may end up really short on the other side of your patch panel. That's why I like the method above from youtube cutting at a 45 degree angle so your panel fits the repair perfectly.

 

I've seen pros recommend both ways

I tried the 45 degree method. It takes a steady hand and a very thin cut off disk. I got some areas where gaps were created with that method because I did not cut perfectly straight. In tight places its hard to cut straight, know what am sayin

Also, you then have to push the piece down into place as you cut out the back piece. It was a mess. Did not line up, burned through…

Had more luck tracing the patch piece and cutting it out all at once. Like this dude:

 

my latest attempt. i overlaped by a few mm. i would then prep the metal and put sealer on top and bottom, followed by the standard paint process

do yall think this level of quality would work or should i keep practicing? be frank.

 

what do you plan to weld? if you're replacing rusty body panels, i don't want to beat a dead horse, but you're gonna want to butt-weld them instead of overlap.

also, i would suggest getting some thicker pieces to practice welding. sheet metal can be tricky. you have to tack weld repeatedly vs trying to get a bead working.

 

it will be a patch in the floor pan. 4 inch by 4 inch patch. 18ga. thats it.

practicing with 18 ga. figure i'll need to be able to weld that, so practicing with that.

butt weld is the right way, i get that. i'm not very concerned with appearance because it will not be visible. Covered by epoxy, sealer, primer, paint

I do want it to last

 

I would think that overlapping would invite space for that to start rusting on the backside of the patch. Maybe weld it up on both sides if possible. Definitely do something to address the back to prevent future rust.

 

good thought. I'm going to give it another go with the butt weld also

last time i tried the butt weld was with 20 ga. harder to manage

 

tried again. this time a butt weld. something that I learned this time is to start the weld on the edge of another cool spot weld. less burn through that way.

where it did burn through in three spots I was able to use a copper backer to fill the holes

let me post some pics

 

front side, before grinding down the welds

 

Front side, after a bit of grinding

 

back side. no grinding

 

warpage

 

i don't think i'm really giving new information, but that looks like you're getting it too hot. maybe give it longer to cool between spot welds?

 

yeah i struggle with waiting. i think your right tho. its getting too hot

i had the air gun right there and was spraying air on it after each set of welds (4 at a time)

 

haha i hear that on being impatient

 

im going to try again. maybe turn it up even more (and do shorter spot welds)

really dont want to warp the floor pan and cause an issue for the seat bracket mount points (is that a risk?). seems like it might be

maybe i could install the seat brackets and then weld in the patch. the bracket would hold things in place somewhat, no?

 

Man... I'm not the one to his advice on that. But I would think doing tack welds all the way around is the way to go

 

tack weld and not a spot weld? come again.

 

that's probably a misuse of terms on my part...in my mind, spot weld just meant welding in one spot. but that to me is the same as tack welding, which is welding in just one spot.

but, i looked it up and actually spot welding is a term for something different.

what i was suggesting is just doing tack welds on alternating sides of the your work area so it doesn't get hot and warp. i watch a ton of tv shows where people are restoring cars or fabricating things for cars, and they always say to just hit small welds (not trying to run a bead) and letting it cool so you don't warp your metal. i apologize if i was unclear or sounding like i'm changing what i'm saying.