Mirror hole repair options

[Ohiotinkerer]

I've got 2 mirror holes in the door I'm prepping to replace a bad drivers door that are about 1/2 inch in diameter and have gotten multiple suggestions on how to fill them. I want to brace a piece of brass behind them and slowly tack them shut but my dad says I should tack a piece of metal inside and then fill them. Another one was to glue a piece of metal behind them and then fill.....one I've never heard of and don't know what kind of glue to use if I did that. What do y'all recommend as the best way to do it?............

[tsherry]

Gluing in metal and then covering with bondo will result in a failure with temperature change (BTDT).
Tacking in metal from behind will work, but if there is ANY exposed metal on the patch, like between the door skin and the patch, rust can start and cause problems later (big problem in saltier/ wetter environments, and again BTDT).
That said, I had identical issues with my '67, with no fewer than 10 mirror holes per door. Some bondo'd, some tacked, some open. I used a home made copper spoon, held in place, and filled the hole with my wire-feed. Once the outside was welded up and filed/ground smooth, a tiny amount o filler was needed, and the inside of the door was cleaned as much as I felt prudent, and then I sprayed the **** out of it with rustproofing paint and undercoat.

I think it's six or seven years since I painted it--the truck lives outside, and other than oxidation, no issues with the work.

[Ranchero50]

Ditto. Weld them shut but don't overheat the panels doing it. Patience grasshopper. Tack and wait, tach and wait.

[Busboy]

LIsten to your father!

[cep62]

I guess it depends on how good of a welder you are.
For a big hole you can trim a patch to fit with very little overlap on the inside.

Less overlap means less space to trap moisture.
You can tack a nail or wire to the patch to hold it while you weld , then grind it off.

You can draw a hole closed , but a half inch can test your patience .
Either way you'll need to coat the back of the repair with paint or rustproofing ,(or both).

[Ohiotinkerer]

LIsten to your father!

Problem is I've proven him wrong a couple times.......

Thanks all for the advice - I can do pretty decent with a welder but that damn Hobart welder my dad has is the problem - may have to make a trip to my buddy's garage and use his Miller instead......

[jamesdfo]

Drill the hole(s) out to make them ROUND. cut a piece of the same gage sheetmetal, then, using tinsnips and a file, file the plug to make it fit flush in the hole with zero airgap around the patch piece.
Clean the front AND backside of the doorskin to bare metal beyond the weld area(s).
If you're using a mig, best results will be with 0.023 hard wire & shielding gas, flux core is not the hot setup for autobody sheetmetal. (Tig is even better, but not everyone has ALL the toys;)
Place the plug in the hole, and place a couple tacks on it. Knock the "proud" off the front AND back of the panel where it was tacked. Then, backing up the panel with a dolly, give it a few "on dolly" hammer blows to stretch the HAZ (heat affected zone).
Repeat this procedure, overlapping the last tack(s) until you have fully welded the plug. Then it's on to the next one:)
If you have a vixen file, you can file the panel to help determine highs/lows and work out as much as possible, then it's on to epoxy and filler if required....

**any time you weld, you shrink, so that's why you need to stretch the HAZ to get the panel back into shape.

** doing lap welded patches or plugs is never my first choice, as it makes it next to impossible to "work" the panel, and the backside of the overlapped area is susceptible to rust between the two layers. (unless you go to great lengths to prevent it)

**if your mig is set up for flux core, and not capable of running hard wire with shielding gas, then definitely go use your buddys mig;)

EDIT: Forgot to mention, any time you're welding or grinding, you need to protect the glass, otherwise, you'll end up with pitting on your glass from the hot sparks off the grinder and/or the teeny little slag balls off the mig. (one more reason I like my tig so much;)

HTH
James