Hi everyone!
I’m a relatively new framebuilder and was hoping to get some pointers about fillet brazing. I have some experience with cromo, regular brass, and nickel silver; I was hoping to get into stainless-and-silver.
Some questions about materials:
I’m in the EU and don’t have good access to Gasflux, Cycle Design, etc. It’s all Fontargen over here.
About brass and nickel silver:
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I’ve been using Fontargen’s F 120, which is a powder that is mixed with distilled water to form a paste. Datasheet says it’s good to 1100°C / 2012°F, but I find that I consistently overheat it (turns black and flat, sticks to filler and makes pinholes or messes with the general consistency / quality of the fillet). Is there a trick to this or a better alternative? I make it work, but repeatedly replacing cooked flux can’t be the way.
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I’ve been told Castolin is worth looking at but I can’t seem to find anything they have that’s rated to a higher temperature. I did see they have a 1000°C product, but with nickel silver melting in the 900s that’s an even smaller margin than with Fontargen.
About stainless and silver:
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I’ve been struggling quite hard with Fontargen’s F 300 H Ultra NT. It’s supposedly good to 800°C, which is sufficient for any silver filler on paper, but I’m definitely going over temperature on it before I reach flowing temp for silver rod. I’ve also tried F 300 HM (brown paste) which is good to 850°C but I didn’t like, and F 300 H Ultra BF (grey paste), good to 930°C, which worked well on my test pieces but I still ended up overheating when I tried joining heavy things to light things (for example, integrated flat mount dropout to chainstay). Any tips on material or technique here?
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I’ve also found filler selection difficult. I’ve been mostly working with A 340 (40% silver) and A319 (34% silver). I find that the 40% flows great (almost indistinguishable from 55%) but can’t build up much of a radius (is this a limitation of the material or a lack of skill on my part?), and the 34% can build up a pretty nice fillet* but melts at a higher temperature than 40% so can’t go on top of it. If i try to flow the 34% into the joint, I usually end up overheating everything. Any advice here?
*even here I’m not satisfied. I can “get close” to what I can achieve with brass, but it’s always so close to tipping over into overheat and it happens so quickly. How do I get huge silver fillets like David Kirk does?
- I’ve heard that stainless is quite intolerant of being overheated, that stuff precipitates to the surface that hinders wicking and adhesion. I did have problems with wetting the steel with filler at some point, and did notice a grey discolouration (although I didn’t get the usual heat stain on the bare metal that wasn’t covered by flux). Is that what is happening, or is that something going wrong with the flux? Even after sanding this layer off, I struggled to get filler to stick again. Are some steels more tolerant of heat than others? XCr vs 931?
General questions:
- What are peoples’ favourite torches that are available in EU? I’ve tried the Greggersen Ergomax but found the valves rather sloppy and imprecise. I’ve tried the Messer Minitherm, which was great but got hot in my hand rather quickly and I wonder if I’m doing something wrong there.
I’d be super grateful for any expertise / knowledge that anyone can share!
Cheers