Fillet brazing: Material and passes

[Christoph]

Hello

I am a hobby frame builder and am currently working on my fourth frame. I always braze in two passes: First a basic seam of nickel-silver and then the fillet of bronze or 20% silver.
It works well so far, but I stress the tubes by applying high temperatures twice.
Hence my question: Do I need the first pass at all? Or is it enough to braze once, but then with bronze? How do you do it?

The materials I use:
From https://www.sonderlote.de/
Fontargen AF210, A102 and A303

Best regards,
Christoph

[steve garro]

it is enough to braze once with bronze?

Yes
- Garro.

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[Andrew R Stewart]

My understanding is that as long as you can end up with the tube to tube interface flowed, don't deform or warp the tubes from poor heat placement or show burned flux/boiled off filler you are Ok with either method. When I began my fillet phase (still in it) I would do two passes, a flowing one and then the fillet build up one. Recently I am practicing a one pass method if only to get more skilled and perhaps reduce the time at temp (which is another aspect that I have heard effects the tube's strength).

Have you tried on a practice joint or 10 yet? Andy

[Christoph]

Sure. And both methods work well. My concerns for the one pass method was not to bring enough metall in the gap between the tubes and to produce more unwanted warping due to the larger amount of material pulling at the tubes.
I assume the warping issue is a matter of a good frame jig and the right brazing order.

Thanks, Christoph

[Andrew R Stewart]

"I assume the warping issue is a matter of a good frame jig and the right brazing order." Christoph

I might put tight miters and good fit up ahead of a jig. Andy