Filling small holes without welding

I have read in the past that you can fill small holes (like trim deleting) with solder and not have to mess with welding. Anyone done this and if so, does paint stick to it ok? I dont have a welder but do have some maybe 1/8" holes that need filled. Was figuring just using bondo but some metal filler sounds better.

THX

I have not done the soldering method, but have used JB weld to fill over a hole or two and have had reasonable success. Short strand fiberglass would be ok too.

If the soldering method uses acid core solder I would proceed with caution, if you do not get all of the flux removed/cleaned it can make issues with corrosion later on, which would be less than ideal.

I would advise against bondo, or polyester filler over holes, it is porous and will absorb moisture from behind and will cause bubbling, or delamination, and it has relatively little strength to be free floating a gap.

If you start with something like JB weld or short strand, then polyester filler on top then there should not be an issue.

I got an idea?

Sand the bondo too much, and it and the paint covering it will fall out. Welding is preferable, lead is the old way, yet still widely used by restoration shops.
However, you can use almost anything,lead, bondo, epoxy, etc if you do 1 of 2 things, with long lasting results--dimple in the outer surface, so there is a surface still holding the material after sanding, OR sand the backside and use a backer--screen, fiberglas, etc.
Be aware there is special solder for body work, and lead free solder, and special fluxes, Now, i don't know the differences. Have seen the dimple and bondo done on vans where roof racks were removed, and lasted many years.

I know the few articles I've seen on it, they always say to avoid the acid core. I've always had questions about the flux issue - would you apply it around the holes? IIRC the main thing was to preheat the area just enough to melt the solder but not warp or damage anything.

PO had alot of hooks and tie downs on this truck - all the holes are 1/8 - 3/16 and slightly concave (from tightening them down)....<1/8". Thought about the JB Weld but again, didn't know how well it would handle paint.

SquareRoot said:

I got an idea?

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Dare I ask?

My buddy asked me if I could weld up some 3/16 holes in the trunk of his 69 442 this weekend. I have a 120V mig welder that I use 99% of the time. I told him I could but I didn't want to. I know how finiky welding thin sheet metal can be. It's not hard to make a 3/16th hole into a 1/2 inch hole in seconds. If someone would gift me a tig welder, it would be different.

If you've got an oxy acetylene outfit I'd braze them shut.

Use some copper or aluminum to back the area up, works as a heat sink and helps with bridging a gap.

Larger holes a Whitney Jensen hand punch or equivalent to make little discs to weld in:

A friend of mine came by about a year ago - he'd been welding 40+yrs - and couldn't stop from turning small holes into bigger ones on the firewall using a Miller 110 welder I had - found out later the welder's wiring was bad so he (apparently) couldn't turn it down enough. He died in a house fire last winter, so I dont know anyone locally at this point who can even weld.

Eastwood sells a solder 'kit' for a brazillian dollars - I only need to fill about 20 holes, most all 1/8 (maybe smaller). Cab is going to be stripped (again) Monday AM so would kind of like to get them filled beforehand. Maybe JB Weld? Dunno. Its always something.

Robert Bare said:

Sand the bondo too much, and it and the paint covering it will fall out. Welding is preferable, lead is the old way, yet still widely used by restoration shops.
However, you can use almost anything,lead, bondo, epoxy, etc if you do 1 of 2 things, with long lasting results--dimple in the outer surface, so there is a surface still holding the material after sanding, OR sand the backside and use a backer--screen, fiberglas, etc.
Be aware there is special solder for body work, and lead free solder, and special fluxes, Now, i don't know the differences. Have seen the dimple and bondo done on vans where roof racks were removed, and lasted many years.

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I tried my hand at some lead repair. Been a while but believe I had the right lead(solder) and flux. That sht wouldn’t stick to save my life!
I’d 1000% advise against it for amateurs.
Agree, if you’re going to use only bondo then you have to make it worse to make it better. Seems counterproductive to me. Especially for an OCD over the top restoration like @Doppleganger is doing.
Makes no sense why you’d skimp in that situation.
Only way I’d consider bondo over welding holes is if you patched the backside first somehow with something moisture proof (fiberglass or bond a plastic or metal patch over the back side of the hole).

And after you do all that it won’t be as good as welding and welding will take like 69 sec per hole! And you don’t have to know how to weld to do spot weld fills like that. Only need to know how to crudely adjust the knobs on the welder and when to let go of the trigger.
I’m not a good welder and welded up better part of 100 holes in the blue truck, blind. (Didn’t have a decent welding hood so just closed my eyes and squeezed the trigger.)
It’s by far the easiest and quickest method imo.

Doppleganger said:

A friend of mine came by about a year ago - he'd been welding 40+yrs - and couldn't stop from turning small holes into bigger ones on the firewall using a Miller 110 welder I had - found out later the welder's wiring was bad so he (apparently) couldn't turn it down enough. He died in a house fire last winter, so I dont know anyone locally at this point who can even weld.

Eastwood sells a solder 'kit' for a brazillian dollars - I only need to fill about 20 holes, most all 1/8 (maybe smaller). Cab is going to be stripped (again) Monday AM so would kind of like to get them filled beforehand. Maybe JB Weld? Dunno. Its always something.

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Just weld them up. You’re chasing your tail with other methods.
Assuming you don’t own a welder, borrow, rent, or buy a cheapo one. That’s all you need.
And PS, anyone who welded for “40 years” and couldn’t goober up some sheetmetal holes (the sheetmetal is thick on those old trucks too. Makes it easier) and couldn’t identify he was blowing them out with way too much amperage or couldn’t circumvent that just can’t weld.
If you’re not willing to tackle it then find someone who will do it. 20 little holes is like 20 min for someone with a welder. Or an hour if they weld em all up and then smash a couple beers before the hour is up.

Agreed on the welding for the small holes. If its rusty then it might blow out to a bigger area and have to stack in a bit more weld to cover. Be patient between tacks and let it cool, the hotter it is the more it will warp/burnout larger holes. Other "hack" option is to peen in the hole a little, smash something on the backside of the hole if possible and fill with short strand fiberglass filler. Will probably need to go over it with some glazing putty for the air holes that will appear when sanding it out. Then you need to use a good epoxy primer sealer on it before your final paint job. I have been reserving the short strand process mainly for holes bigger than a nickel and smaller than a quarter or a 50 cent piece, bigger than that I usually weld in something as a filler.

Grit dog said:

Just weld them up. You’re chasing your tail with other methods.
Assuming you don’t own a welder, borrow, rent, or buy a cheapo one. That’s all you need.
And PS, anyone who welded for “40 years” and couldn’t goober up some sheetmetal holes (the sheetmetal is thick on those old trucks too. Makes it easier) and couldn’t identify he was blowing them out with way too much amperage or couldn’t circumvent that just can’t weld.
If you’re not willing to tackle it then find someone who will do it. 20 little holes is like 20 min for someone with a welder. Or an hour if they weld em all up and then smash a couple beers before the hour is up.

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Maybe the guy was practicing welding holes while closing his eyes because he didn't have a helmet. How do you think he started the house on fire and ended up dead? Poor guy.

My friend had a sugar issue. Would crash and he'd pass out. Happened at the wrong time when an electrical socket in his bedroom (original wiring - 1946) started to burn. No bad fire but lots of smoke. Thats what killed him. Didn't help he smoked like a train so his lungs were already compromised.

The welder I had was defective - the heat setting would not stay consistent. Guy who bought it said the whip was bad - ?! Maybe he's a fking idiot too?

I figured how to fix the holes, so never mind.