The Stovebolt Site Forums The Shop Area Paint and Body Shop lap weld Vs. Rust and other stuff

I have been dreaming way ahead of my actuall project progress and have been thinking about the misc. tools and such that I will need as well as parts.
I have some panels to weld in so obviously I need a welder and some panels.

Question:

If I understand correctly a lap weld is only welded on one side. What keeps the water/rust and stuff from giving me problems on the opposite side?

When the lap weld is complete what is the common way to even out the bump from the overlap? Flange tool?

hmmm.

Normally the flange tool is used first, then the lap weld is performed and filler is used to level it up. The only thing protecting it from moisture is the weld itself.

I'm pretty sure that in pro shops lap welds are only used for glued panels, and the glue does a good job of keeping the moisture out.

If you are actually welding, butt joints are the best, since they require the least amount of filler when all the work is done.

At the Hot Rod shop I work at occasionally, all lap welds are coated with seam sealer. Most of the laps are done on the interior where they are not seen. You can get this product from most body work suppliers.

Lap welds are sorta like "utility" welds. Not really finish work. Can be done yet not the best or final way to go. Not only a butt weld, but a hammer weld is by far the best and most accurate approach. This is done by backing up the weld area with a dolly and spotting the panel in place one weld at a time. While each weld is "red" it`s tapped with a hammer against the dolly to ward off warping the panel when the weld itself shrinks...in essence you "stretch" the weld. This takes practice to get the eel of how hard to hit, and in many instances takes a helper to hold the dolly behind the panel. When you have the process down to a science, very little filler is needed and routine rust prevention is all that's required.

Highlander, that is a BEAUTIFUL way to discribe the lap weld, "Utility", I will be using that if you don't mind.

Guys, this is how I see it. The ENTIRE truck, EVERY SINGLE CAR made for many, many decades is a lap/pinch weld. Let me say that agian. There is not one single butt weld on 99.9% of the cars made all over the world in the last half century or more.

Your ENTIRE truck is held together with lap/pinch welds. Sooooo, to add another is not a big deal. It is however as Highlander pointed out not the end all for custom or super high quality work. If you "can" butt weld, then by all means do it.

Only you can say whether you have the skill to butt weld, it does require more skill,that is a fact.
My way of thinking is, I much rather see you do a lap weld, finish the truck and see your smiling face behind the wheel down the road. I feel that is a better way to go than to be all stressed out over a failed butt weld attempt.

The average collision repair shop lap or "Butt with backing" EVERY single weld on repairs. This is the standard industry accepted method. It is recommended by most all industry organizations such as ICAR and ASE.

However, that and doing high quality restoraton or hot rod work are two different things. Butt welding is always preferred in these circumstances.