Trim hole filler
 

What could be used to fill trim holes other than welding?

While welding is preferred, I suspect you could install stainless steel screws and then grind them down ( I have not tried this personally). Many many years ago, on a few very small trim holes, I used some JB Weld. 15 years later it has held up fine.

I used a tool that knocks out small holes for riveting (usually 3/16" diameter). I then took those small metal discs or plugs and either tack weld them in place and use JB Weld or use JB Weld exclusively. Both work fine.

Stainless is dissimilar and expands at a different rate than steel. I would use some PBA with a backer. Sand and finish

fender body moulding panel holes?

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What is PBA?

If I wasn't going to weld it I would scuff the area around each hole to about the diameter of a dime or so, then indent the area that you just scuffed to a shallow depth of maybe 1/8 inch or just enough to be below the surrounding surface.... Then just fill it with your favorite body filler. Epoxy it after sanding and finishing.
I'm just a driveway tinkerer though...

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Greg, I have seen some of your finished products and you are far better than a driveway tickerer. Beautiful cars.

This is true but given a limited temperature change (hot to cold) and the size of the hole involved, the coefficient of expansion/contraction may not be an issue...but it certainly is a valid concern. If I get some time this summer I might try it on a piece of scrap to satisfy my curiosity. Welding is obviously the best approach as even a filler would likely have a different rate of expansion/contraction.

Panel Bonding Adhesive

When I de-chromed my '47 Ford (back in 1957!) I countersunk the trim holes (using a larger drill bit) and installed flathead 1/4" bolts & nuts, then ground the heads down flush. It worked great.

Trying to fill a hole with just body filler isn't going to cut it. I know. I tried this in 1980 on my 55 Chevy. Many years down the road you can see the ring of the trim holes where I filled with filler. Around 2010 when I was finishing a frame off resto on it, I welded small plugs (3/16") in the door trim and fender trim holes. Painted it in 2013 and now ten years later still good as new. The bad? Filler absorbs water and it's hard to coat that from the back side on many panels. Filler also shrinks over time. If you plan on painting and want it to look good, do it right so your paint can look good without showing deteriation around those quick filled holes.

PBA does Not Shrink. And only a tiny skim coat of putty would be needed.
OR.. put a backer on it ( anything) and use UV curing paint or glue, which you can cure INSTANTLY. no shrink..

If it needs paint as a result of the holes then welding is a no-brainer. I've done both. The filler only was as a young fella, but removed giant body moulds and replaced with thin adhesive type that covered any shoddy work.
Did we ever get confirmation or just assumed this was the task being discussed?

Welding is first choice and done properly would require minimal grinding., assuming of course it’s an emblem hole on a fender. Where I live, you can’t get away with much body filler. JB weld and adhesives will work but I’ve seen the metal rust away around those as well. Lots of rain and salty ocean air here.

JB Marine Weld.

Cut up a plastic baggie then tape the plastic in place (stretched smooth) on either side of the hole. Over the plastic, lay a piece of sheet metal over the hole holding in place by clamps. Be sure to allow enough room to spread the JB Weld without interference from the clamps, or I suppose you could also use tape to hold the sheet metal in place if you don't have access to clamps.

JB will not stick to the plastic. You can also use sheet metal on both sides after applying the JB Weld sandwiched with plastic to the other side as well. The clamps will squeeze the JB Weld into the entire void and then some.

JB Weld is hard to sand but easier than sanding welds!

I've used fiberglass cloth and resin on the backside of panel before. Proper preparation of the metal and some epoxy paint afterwards keeps the rust away. Epoxy primer with a skim coat of filler with a seal primer on the exterior before painting.

I've used fiberglass mat on the outside. Indent the area around the hole, lay epoxy impregnated mat in the low area, sand flush, repeat until the depression is filled. Skim coat of filler followed by epoxy.

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That hole need to be welded....end of story.

The good thing about JB Marine Weld is that if you ever change your mind, just heat up the panel with a torch to 400 degrees and voila, you have your holes back with no damage to the metal.