Posted by Keith I Washington [172.68.57.164] on Tuesday, April 27, 2021 at 17:23:12 :
In Reply to: Other Subject posted by Scott [172.69.170.49] on Sunday, April 25, 2021 at 22:02:33 :
I have spent hours welding over so many holes. Once you get the knack it’s not hard. The biggest thing is to minimize and control the heat you apply. I like tig and mig welding as you can control the heat better.
I have found that clamping a flattened piece co copper pipe on the back side of the hole really helps control heat and gives a surface to weld against. It also makes the back of your weld flat. I have welded so many rust holes in the metal wraps around my Carryall windows. Using copper to back my welds gives me a flat smooth surface that matches the existing surface. I only need to grind on the weld side. Without doing this there is no way to rebuild these irreplaceable parts.
The key is to weld without warpage is to weld a little area at a time then let it cool before welding more. Once done get your grinder out and clean up the excess weld. Be careful not to grind hard and heavy as you can build up heat and warp the metal. When you are done you may have a small dimple just use a shrinking hammer and dolly. When welding a patch in I weld a1/4” then move to the other side of the patch keep moving across the patch and come back to a previous weld only after it has cooled. Never weld working down one side as the metal will heat up and walk on you and then you have a mess. If you look at a patch your welding in it should look like just a bunch of dots holding it in until your done. I will also clamp or use clecos to hold flattened copper pipe behind my patch welds.
I only use bondo to cover surface imperfections. Alway seal the metal with epoxy primer like DP. Then apply bondo sand smooth. I will often spay coats of DP primer after sanding and putting another skim coat of bondo to cover any metal sanding exposed. Then cover the bondo with DP primer again to seal the bondo when you are totally done with sanding and shaping. Bondo can absorb moisture and will cause the metal under it to rust if not sealed on both sides. Don’t use bondo to fill holes as it will come out with time. I like to keep bondo under an 1/8” and keep the thicker areas really small. Do the body work and keep the bondo to basically a skim layer to cover minor imperfections.