welding holes closed: largest size practical

thinking of welding shut trim holes, and wondering for practical purposes just how large a hole can be filled by wire alone without a plug of some kind? i know i'll need a thick piece of copper to back up the hole while welding, and i probably can't fill very much in one pass without putting too much heat in the panel. tips and ideas?
also, along with a number of neatly punched round holes, there's a few square ones as well; any special trick for those that i need to know? i'm already thinking i'll need a bunch of filler pieces.....

 

I've plugged dime sized holes using a strip of copper for backup. I work my way around the edge of the hole with small welds allowing each to cool completely between welds. It takes a while. I use a TIG welder so I can hammer and dolly when finished.

 

my way to fill trim holes

Ever how big of nail head you can find.

 

wat he said nails. they work great and you can grind them to be square.

 

i hold a penny on the back side for under 7/16" any bigger use something to fill it

 

Where did you get the plugs?

 

All good advice ... also get a spoon. On those square holes ... I find using the square wire makes it a breeze.

 

the plugs in the red box were in the scrap bin at a fab place. they are a little thick, but not bad.

I bought the yellow ones from Covell but I don't think he sells them anymore???? anyone know?

 

I'm not sure about american ones but the penny trick does't work with Canadian pennys. I ended up with a couple pennys welded to the inside of my hood.

 

I sometimes use scrap copper water pipe. Hammer the ends closed and now you have a backup and a handle. Works good.

 

Aluminum works well for a back up also...be sure and skip around to different holes as far apart as possible allowing them to cool as to limit warpage.

 

Welded up roughly100 trim holes on my 41 Chevy. Not a big deal welding wise but gets real old, real fast, grinding them.

 

Doesn't Harbor Freight has that .025 square wire?....

 

I've not filled anything larger than a dime without making a plug.
But with a copper backer, I've filled a lot of holes.
As someone else said, a piece of scrap pluming tubing with an end flattened works great. After hammering the end shut, I ground the corners round so it fits in tighter areas.
A couple of these wouldn't be bad... one with a pointed end, the other with a gentle radius on the paddle to back the crown of a roof or hood, the other end with a more pronounced radius.

The key to mine is the lightening holes drilled in it, between the head and where your hand holds it.

They're actually heat diffuser holes... I can weld with that all day long, without wearing a glove, and never burn my hand. Without the heat diffuser holes, the tubing gets too hot to hold fairly quickly.

-Brad

 

:d lol.

 

If you're going to use a Penny make sure it's a 1981 or older... Starting in the middle of 1982 they're copper plated Zinc.

 

A block of copper behind hole and MIG weld, spot by spot for smaller holes then grind and linish smooth. Larger holes require filler pieces cut and tacked in with a MIG, a quick grind and linish before TIG'ing them up. I lost count of the number of holes in my '46 Olds firewall. 60+ It would have been easier to replace firewall with a flat sheet however I love the OEM pressings.

 

When I got my 32 roadster it had some rather big holes cut with a torch in the front frame rails. It's pretty easy to weld up 3/8" bolt holes but the big hole for the through the frame shock absorber (a Doan Spencer shock style) was a challenge. Just for shits and giggles I accepted the challenge and welded up the 1 1/2" hole strictly with weld. It took a while but I did it.

So it can be done but I wouldn't recommend it for novice welders. For large holes, patches are the answer.

 

I use a cheap metal hand punch to make my plugs and tig them shut. A wire feed welder tries to push out the material in the hole.

 

You must have a lot of old pennies. They have been 97.5% zinc since 1983.

 

HF sell a neat and handy welding spoon to be used for a backer, also commercial roofing companies have copper flashing that is very handy for a welding backer.

 

Good Idea about the diffuser holes will have to do that to mine.

 

I agree with mgtstumpy on the OEM Olds firewalls. Pretty neat stampings, but looking from the inside out it looks like someone emptied a shotgun with double 0 buckshot. I was amazed at the number of factory holes in my 39 Olds. Lots of welding ahead of me also.

 

I made my copper backers out of some recycled copper buss bar, that came out of a commercial / industrial electrical cabinet. It's 1/4"x2" and about 6' long. I've made several
each made to do a different job. Each has a shaped welding surface with a tang and I used a file handle on them so I don't burn my hand. All work well and makes filling holes an easy job.

..............Jack

 

Quite a bit of heat involved to weld up a 1/2" hole with no plug. One thing on a firewall but on a flat panel would likely mean potentially a lot of distortation. Either way take it slow and let things cool completely. I also use flattened copper pipe.

 

I like to weld from the inside of the panel if it's accessible...with a copper backer on the outside of the panel, Alot less to grind that way.

 

I'll sometimes use a washer for a plug, there are some nice fender washers that will do the job on bigger holes. Fill the hole and then leave a length of rod welded to the washer so you have a means to hold the washer in the hole.

 

excellent tips; gotta get a roll of square wire, too.... hahahaha!

i'm not sure how many i'm going to close up; i may keep the lower trim intact and ditch the upper loop.

my GrandDad would have brazed them all.... big fan of brazing, he was...

 

I've got one of the HF backers... they made the handle aluminum, and put a rubber/plastic handgrip on it.
Copper and aluminum... can anyone say "heat sink"?
That's why I made mine... holy shit that thing gets hot if you're using it for more than a few tacks!
Not paying attention, just buzzing away, and the next thing you know it's that "hot thru the glove that doesn't go away when you throw the glove off" kind of hot.

-Brad