Help filling holes please

Hi Guys, (and Gals?)
I would like some advise please, on filling some 1/2 " bolt holes in the doors of my 54 Chevy Pickup. It had some bulky mirrors bolted on that I removed. I'm not worried about the paint, but the doors are perfect and I don't need to warp them, and honestly I just don't know how best to do this..
I have a Harbor Frieght "Dual Mig" 35 - 110 amp, 220v welder. In the past on another project, I tried tacking in a washer as filler with only limited success.
I know this is kindergarden stuff for you guys, but I appreciate any suggestions. I apologise if its already been addressed elsewhere, I searched but didn't find it.

Thanks

If they are 1/2 inch round holes, I would use 1/2 inch round stock. Cut off a 3/8 piece with the band or chop saw, use a magnet to hold it in place, flat with the sheet metal, and take my time spotting it in. The 110 side of your machine is plenty. Practice with a 1/2 round piece, and some sheet metal until you are comfortable.

Another method. Use a backing block/plate (copper, brass or aluminum) pressed tight to the backside. Spot, spot, spot, until the hole closes. Take plenty of time between spots to reduce/eliminate warpage.

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That would be my approach....

MHO

either one will work, i keep a wet rag handy and quench after each weld, dends to keep it shrunk up and flat, good luck.
Take your time[

I've used the copper or brass backing trick quite a bit before with great results.
G to your local big box hardware store and buy a short chunk of copper plumbing tube. Hammer it flat (the flatter the better) and hold that behind your hole. Tack the edge, let it cool to the touch, tack again, cool, tack, cool, then once it's all filled in, lightly grind the weld away with a medium grit flap wheel on your grinder.
Take your time on the flap wheel too! That'll get it hot enough to warp. If it starts turning colors (blue) your too hot and/or too thin.
Take your time here since you don't want to warp.
Realistically though, unless your a pro with metal, you'll end up needing filler anyways if your going to paint.
Good luck!

magnet under holes

Lots of good ideas for small holes. But anything bigger than 1/4 inch you should have a steel plug the same gauge as to what you are working on. I use a magnet to hold it flat for tacking and then remove it for final wellding. I hope this helps you. Good luck and remember were all:rolleyes in this together.

I have had pretty good success with holding a washer from the back side a drywall screw slid through the center to hold onto while tack welding.The key is to take your time and keep it cool with a wet rag.