Well, I attempted lead body solder for the first time today. Now, I can add "old school body man" to my repertoire.
It was interesting to learn the process. Comments and critique are welcome.
Eastwood sells a lead body filler kit for $109.00. I'm too cheap for that, so I found a 1 lb 70% lead / 30% tin rod on amazon for about $8 and bought Eastwood tinning butter for $20. I used a scrap piece of wood for my spreading paddle....lubed up with some ski wax I had laying around to prevent the lead from sticking to the wood.
The process I used in a nutshell. (disclaimer!!!!! I am a total amateur at this so take anything I say with a grain of salt)
1) Clean the metal! I de-greased, used a wire wheel on the grinder, and de-greased again. Ended up with a nice clean shiny surface.
2) Brush on a thin layer of tinning butter to cover a larger area than the dent. Tinning butter is 75% flux, and 25% lead.
3) Tin the area with a MAP torch using a small to medium flame. I found it best to keep the flame moving over the surface in a kind of fanning motion. As you are heating the surface, you can first see the acid flux liquify, and then the lead flows shortly after. When it is hot enough, it turns a silver color. Have a wet clean cloth available to cool the surface and wipe off any excess flux. Work small areas at a time.
4) After the metal cools, you need to neutralize the acid from the flux. I did this by scrubbing the surface with a baking soda and water mixture. Then I rinsed with plain water and dried.
5) de-greased again with acetone.
6) Now the fun begins. Time to melt the lead and somehow get it to stay on the metal. There is a fine line between not hot enough to work the lead, and too hot. If you get it too hot, it will puddle and just run off the surface. Once again, using a MAP torch, I heated the tank and the lead bar. Most of the time is spent heating the bar because it is fairly thick. The actual surface of the tank heats up pretty quick. I built up the lead in the dent until it appeared to be higher than the surrounding area. It was trial and error to find just the right heat.
7) Next, I worked the area with heat and the wood stick. I heated the lead again while trying to spread it around like butter. I ended up getting it shaped somewhat to the curves of the tank. Again, trial and error. It is a challenge to get just the right consistency to form the lead.
8. The final part involves cold shaping the lead. None of this is to be done with power tools in order to minimize lead dust in the air. First, I used a rasp to get it roughed out. Then, I used regular files, and finally I used sandpaper with a sanding pad. This is a much slower process than plastic fillers as the lead is much harder to work. Also, you only get one shot at the repair
. If you have any low spots, or you take too much off, you have to start all over or accept what you have and finish up with a little bondo. (which I will end up doing
After attempting to spread the lead with the wood stick. The area with the arrow pointed to it is ever so slightly too low. I did not find this out until I was almost finished filing and sanding.
Filing and sanding. getting there! What a pain in my you know what.
Here it is, as good as I am going to get it. I will need a very thin layer of plastic filler on the bottom half of the dent on the front, as well as a small amount of filler near the emblem mount bar. I accomplished what I set out to do. That is, make sure there will be no leaks and to use as little plastic filler as possible. No filler would have been better, but I will take this for a first try.