Brazing with TIG torch

[le Cadre custom bicycles]

I have used my Tig-set with a brons filler material to braze steel furniture and some interior window frames and doors for clients. I liked the idea of brazing, since I have done this a lot in the past (some 50 frames) and clients liked the color of the joints.

Has anybody tried to Tig braze bicycle tubing?

At this moment I don't have a shop. I would have tried it if I could.

Post edit:
just found an article on the subject:
https://www.weldability-sif.com/medi...2035-45%20amps.

[shand]

This is on my list to dig into. I'd love to start doing the parts I normally braze (bosses/guides/bridges) with a tig torch instead of oxy/fuel torch.

[progetto]

[shand]

I'll try and find the video I've seen previously where the process is much more like silver brazing than that video lined above. Rather than treating the rod similar to a tig weld rod, the emphasis is more in getting the joint up to temp with a less focussed arc and getting the filler to flow into the joint rather than 'sitting' on it.

[hampco]

I played with it back in my welding days and I think the issue is that it's not quite strong enough to hold bicycle tubes together. Furniture, yes; structures that your life depends on, possibly not.

But i may be wrong on this.

[shand]

I played with it back in my welding days and I think the issue is that it's not quite strong enough to hold bicycle tubes together. Furniture, yes; structures that your life depends on, possibly not.

But i may be wrong on this.

You're probably right. I'm not sure I'd look to be fully brazing frames together but if I could silver bottle bosses etc then I'm all over it. I suspect that the heat source is too tight and focused but I'm going to have a play around and look at the results.

[Alistair]

TIG brazing has been a subject of discussion a few times over the years in the framebuilding world. The first time I saw the technique demonstrated was in a Jody Collier Welding Tips and Tricks video, maybe 10 years or so ago? From what I recall from those discussions, TIG brazing is much more suited to statically loaded structures. Not so good for dynamically loaded ones, like bike frames.

The issue is that it is difficult to get the weld puddle hot enough to get good adhesion through the toes of the weld, but not so hot that the base metal melts. The latter scenario results in bronze inclusions in the steel, which leads to stress risers. Not such a big deal in a sculpture, or a piece of furniture, but a real problem in a bike frame.

There was a US builder some years ago who used TIG brazing to attach tabs for disc brake calipers and ended up having to deal with customers who ultimately had fork failures.

Anyway, it's been quite some time since I read those discussions but from what I remember my take away was always that it is a risky technique to use for bicycle construction.


Alistair

[bulgie]

I suspect TIG brazing could be strong enough if you made the fillets large enough. Quite a bit larger than welding with steel filler, like 3-4 times larger?

The jargon on this isn't fully settled or agreed on but you might be better calling this "bronze welding" since, at least by some people's definition, brazing requires penetration of the braze filler via capillary action between tightly spaced parts. British framebuilders always used bronze welding for what we in the States mostly called fillet brazing. Others reserve the use of "weld" to mean when the filler has the same melting point as the parent metal. Neither definition is wrong BTW, just coming from different spheres of jargon.

But even British style bronze welding with a gas torch does get some capillary penetration, and even (usually) a small inside fillet. Hard to tell without sawing one up, but I bet normal TIG-brazing gets almost none of that. Maybe more heat will get you more penetration but unless you purge the inside of the frame with argon, oxides will form on the hot steel inside almost immediately and prevent the filler from wetting out there.

Even with gas fillet-brazing, to be stronger than the tube, the fillet needs to be substantially larger than a steel TIG bead. Any joint that comes apart is a bad bad thing, even if it took a crash to do it — the tubing should always fail first, or ipso facto the joint was defective. If you don't know for sure that your joints are stonger than your tubes, that is gross negligence.

[le Cadre custom bicycles]

Yes I was tiding up my desk the other day and came across your business card and wondered how you were doing and if you were able to continue making frames. We met about 20 years ago at a town that had some kind of manor house or castle that kept peacocks on the grounds. Our project to continue our charity bicycle project in Ukraine has been interrupted thanks to the Russians. Our shop was located on a college campus in the town of Bucha that was in the news back when the invasion started. Lots of terrible things happened there. The Russians did break into our bike/frame shop and stole all of our general tools but thankfully not bicycle specific equipment. What a mess

I hope the people didn't get hurt and this war ends sooner than later. If the project gets started again please let me know if you need a hand.

I stopped making frames after 10 years of trying to get a market. Back then I was kind of ahead of the wave. By the time the market was created I was burned out on building. So I spend the last 10 years on my career (QC Engineer for a Notified Body and now as an independent contractor). By now I want to build something again, for myself.

unless you purge the inside of the frame

I spoke to an older Engineer from the UK once that had been building copper heath exchangers for submarines in the 80's. He told me they back purged to have better penetration of the capilary. I always wondered if framebuilders would also try this. I have recently bought an argon regulator with two flow tubes to try this on lugs. Still need to modify my jig first.

[progetto]

I hope the people didn't get hurt and this war ends sooner than later. If the project gets started again please let me know if you need a hand.

I stopped making frames after 10 years of trying to get a market. Back then I was kind of ahead of the wave. By the time the market was created I was burned out on building. So I spend the last 10 years on my career (QC Engineer for a Notified Body and now as an independent contractor). By now I want to build something again, for myself.



I spoke to an older Engineer from the UK once that had been building copper heath exchangers for submarines in the 80's. He told me they back purged to have better penetration of the capilary. I always wondered if framebuilders would also try this. I have recently bought an argon regulator with two flow tubes to try this on lugs. Still need to modify my jig first.

Don't over think it, it is a bicycle. Just because you can melt bronze with a TIG, doesn't mean you should.

[Apollo]

Here is a PDF that mentions TIG brazing lugged bicycle frames, using a certain British TIG brazing alloy the company sells.

https://www.weldability-sif.com/medi...ig_brazing.pdf

The British company describes the brazing alloy as, "aluminum bronze."

It looks like it might be commonly used to TIG braze cast iron, seeing this web page.

https://www.weldingtipsandtricks.com...derskills.html

That was using AC TIG, which is interesting.

[hampco]

ipso facto

Mark, gettin' all fancy with his Latin American...

[bulgie]

Mark, gettin' all fancy with his Latin American...

illegitimi non carborundum, y'all.

[claritycycler]

illegitimi non carborundum, y'all.

Another phrase I had to look up: illegitimi non carborundum = "Don't let the bastards grind you down", the phrase has no meaning in Latin, originated during WWII.