Lots of mirror holes - best fill practices?

[ItWillBeSlow]

Im stripping down my doors to get ready for epoxy and fixing the bad stuff.

My doors have 10 holes each. I put 3 of them in with my reproduction DG4(ish) mirrors. I am not sure exactly what the others are - (4) small ones and (3) large ones. I think the truck originally had DG4 mirrors.

My question is what is the best method to fill the large ones. The holes are at least 3/8" in diameter. I can get copper behind them but wanted to verify trying to fill them with a copper backer is the best method with something this large.

Thoughts?

[Mike C]

Weld 'em up. I bet I fixed twice that many on the donor doors for my kids Jimmy. Start with the small ones and learn how to do it then you can even weld the bigger ones without filler pieces.

[HotWheelsFan]

With larger holes, you may need to weld a tab of metal to help fill the hole. Seen holes welded up both ways...

Body filler used to plug holes will not last, as the body filler will attract water from the back side and expand.

[Grumpy old man]

Use a copper backing plate ,The weld won't stick to it . You can buy the fancy ones like in this video or just flatten a piece of copper pipe . cool your welds with a wet rag or air gun to prevent warping

https://www.youtube.com/watch?v=huPdLOIA438

[Peanut74]

I have done it two ways. One just fill it in with weld using a copper backing. A the second a filler plug welded in. I liked the filler plug method best because I had less issues getting the hole filled. I'm still working on my welding skills and when I tried to fill the hole with weld it looked like a wad of gum stuck to the door.

[blazer2007]

could use a large nail head for filler then cut off the rest off the nail

[BigBird05]

2X on the filler plug method. Thats how I did my fire wall.

[kwmech]

I use a brass hammer for backing up if I am going to weld them. Gives me a nice handle so I don't burn my hand. the nail idea works really well if you can get to nail part later and smooth the protrusion out

[Big Kev-O]

I just started learning MIG and managed to fill those holes with a copper backing tool I made from a copper pipe cap.

This method looks fairly easy too:
https://www.youtube.com/watch?v=-DvzUkMQGlk

[Caddylackn]

Make sure that your new holes will not be in the same place as the old holes. If so, you want a sheet metal patch there and not a big clump of wire behind the panel. If the entire hole is filled with welding wire, it will be extremely hard to drill out again and get a nice clean hole. I bought a set of used doors that were filled by somebody else. I had to put a new mirror hole over a welded up hole and it was a nightmare. The wire they used was hard as hell and very hard to drill. There was also a big slag of metal on the back side which made bolting the mirror difficult and it made the drill bit wander. There was no way to grind this down inside the door.

For a 3/8" hole I would weld in 3/8" round sheet metal patches tacked to the end of a coat hanger, using the coat hanger as a handle. A washer could work also. Then slowly tack weld the perimeter in stages criss crossing. You want to avoid adding too much heat filling a large hole with only wire filler or you will create warpage in the surrounding panel. The warpage can be subtle but it will show when painted. If you do fill the hole with only wire, do it in 3 or 4 passes allowing it to cool some between passes. Use the copper plate to keep from getting a slag pile on the other side of the metal. A piece of coat hanger also makes good filler material for big gaps.

[89AKurt]

I wanted to ask this question.

[LS short box]

I had to fill similar holes on my 68. I have a body shop guy as car buddy and had me do the following.
1. Bigger holes make a filler piece of similar thickness and weld in.
2. Smaller holes as said above use a copper backer weld slowly to keep the heat down.
3. Then fiber glass filler over the holes. Body guy said it's waterproof unlike regular filler.
4. On the inside of door where the holes used to be smear some two part epoxy to water proof (I used JB Weld) over each hole to completely seal the inside of the door.

[ItWillBeSlow]

thanks for the replies everyone.

I realized today my 3/8" spot cutter bit will probably cut a perfect circle patch for the larger holes. I am going to give this a try tomorrow, and will use my magnetic copper backer to back the hole and lay the patch in. Should make for an easy weld job with minimal wire mess.

I am not as concerned with the smaller ones, I can get my copper to each one of them and have filled a few smaller ones with this method on the truck so far.

[Wikid61]

Hose the backside of the filled hole w/rust preventative/epoxy/paint.