Re: Lead Loading
Posted: Fri Jul 19, 2013 1:07 am
Some fairly recent Chrysler cars used a process called spray braze to seal the joint between the rear quarter panel and the C-pillar. VW uses some laser weld joints on decklids. The key to success in both these processes is robotics to limit the time and area exposed to high heat.
In the old days ('60s and back), lead was used primarily because there wasn't any good, durable body filler available. The old body filler would tend to separate from the steel and/or crack, since it was fairly brittle. If you wanted a good lifetime repair, lead was the way to go.
On newer cars, the exterior sheetmetal is much thinner, and higher strength (to recover some dent resistance). This new thin gauge high strength steel doesn't like heat. When you put the torch to it long enough to work the lead, it will deform in ugly ways. I tried it about 10 years ago on some FB test panels, and it was a total failure.
The good news is that modern body fillers are very good. If applied properly, you'll never know there was a repair.
In the old days ('60s and back), lead was used primarily because there wasn't any good, durable body filler available. The old body filler would tend to separate from the steel and/or crack, since it was fairly brittle. If you wanted a good lifetime repair, lead was the way to go.
On newer cars, the exterior sheetmetal is much thinner, and higher strength (to recover some dent resistance). This new thin gauge high strength steel doesn't like heat. When you put the torch to it long enough to work the lead, it will deform in ugly ways. I tried it about 10 years ago on some FB test panels, and it was a total failure.
The good news is that modern body fillers are very good. If applied properly, you'll never know there was a repair.