Welding Tips and Tricks

Quick question for the forum. I am getting ready to weld/braze in floor panel reproductions I made and was planning on TIG brazing them in with butt welds for the joints. While doing some research, I found a couple references that cautioned against brazing a butt joint. The comments were that the joint would crack later in use. The panels are 18 gauge steel on a unit body construction. I have not cut the panels to fit yet, so I can still pivot to lap joints, but then would be concerned about trapped areas for corrosion.

I would appreciate your thoughts based on experience/knowledge.

DoubleA

Brazing is more like glue. It only bonds to the surface. In a but joint there’s only a small surface for the braze to bond to. Then there’s the matter of the braze material that fills the space between the two parent metals is usually more brittle so it doesn’t handle flexing stress very well.

It doesnt have the kind of set and forget strentgh you would be after. It is good for sealing, strengthening welded panels i.e if they are welded intermittently or spotted, than brazing can take a bit of the vibration and stress away from smaller welds.
I have been tuning my hand in with sibronze for this reason. But if you installing a new piece, I would lap if possible. Even if you were comfortable to stitch weld with steel filler both sides of lap and then seal with bronze. Strength and minimal distortion. hence the wide uses of bronze in auto world. Silicon bronze is not a big seller at my LWS but I usually have to compete with an older panel beater for the sticks on the shelf depends on which one gets it the other one waits a week for restock
Its so commonly used by these top end restorers for bog alternatives and stitch support etc.
Asking those guys for advice is variable though, some of them would never share technique. Do some break tests if you can just to get a feel for it.

I will say I’ve done lots of brazing and lots of welding. But I guess I never thought about combining spot welds and then brazing a lap joint. That is a great idea. One I plan on trying in the future.

@Poland308 & @Gdarc21,

Thank you for the replies and information. It does make sense for the brazing to be used as a "filler". I did see a reference to a high end restorer using it in place of seam sealer for a cleaner look on the appearance surfaces in engine rooms, etc. I will run a couple test joint panels and let you know how it goes.

Again, thanks for your insights.
DoubleA

Also a little side note if your looking towards brazing.


Eastwood makes a panel prep tool (pretty sure they have a vise grip style and a pneumatic style)

It rolls the edge of the sheet metal down slightly so a butt weld becomes more of a groove weld so you have more material in the joint once ground flush for bodywork.


Might be a handy tool for you to look into for bodywork.

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Silicon Bronze has a tensile strength of 51, 000 lbs. Jody has done a number of videos where he has welded joints that were not lap joints (so no real capillary action) and demonstrated how strong the joints were. I think for floor pans, TIG brazing a butt weld would be fine, so long as you aren't trying to sand and blend the joints. If you want to lap weld it, just braze both sides and you should have no problems with trapped areas.

https://www.youtube.com/watch?v=wf-Cq5eQmt0