Frame Forum: Fillet Brazing- tips, tricks, and info share

[Todd Mosley]

Am I doing this right? I'm using straight gauge 4130, 1mm wall. The main tube failed just after the edge of the fillet.

[sam]

Im not a pro so I wont give you any feedback on your work, but I will give you my thought on practice tubing. When I was first starting to practice I found that anything with that kind of wall thickness took a while to heat up and took a while to cool down, and often my fillets did not come out well. On practice pieces on .8 it would react to the torch much faster, and I could quickly see my errors, after just a few practice pieces on thinner stuff I could then go back to the thicker stuff and get much better results because I better understood what my torch was doing.

So im not saying to practice on thinner wall, but I am suggesting trying a couple on thinner wall for the experience

[Curt Goodrich]

Todd,

One thing that I'll add, while practicing the torch side of the fillet brazing equation is important, filing and sanding the fillets smooth is equally important. Laying a nice fillet isn't that difficult. Filing and sanding fillets to aesthetically pleasing radii without undercutting the tubes is where the real skill and learning curve lies. Keep up the practicing and don't focus solely on the torch skills.

[Brian Chapman]

Hi Todd,

What Curt said is important because as you file fillets, you'll realize what you can let go and what will need to be smoothed or wetted out with the torch. I also recommend practicing on .035" stock at first. It's thick but not too thick. Your joint looks a bit cold. Could probably have used some more flux too. And read the advice in this post:
http://www.velocipedesalon.com/forum...1-a-31373.html

And these videos can't hurt either:



Good luck!
Brian

[Todd Mosley]

I've watched those videos but they don't show a lot of close up work. I've scoured youtube, etc., but most of the videos I've found you can't see they detail of what's happening with the joint.

[ToddFarr]

I watched those videos and learned I've been holding the torch way to far away. I'm used to silver I guess, Ritchey is right up in there with that thing!

As for much else, I like to just practice, practice, practice. Try different things and pay attention to what works and what doesn't, you will have some ah-hah moments. I try to NOT read as much as I can. The pioneers had to figure this stuff out on there own by trial and error, I kinda like that idea too! I'm not saying you have to start completely from scratch, but just keep working it and watching how the metal behaves.

[Todd Mosley]

I try to NOT read as much as I can. The pioneers had to figure this stuff out on there own by trial and error...

Along those lines... even though I am by nature a perfectionist, I can accept that fillet brazed frame #1 won't be aesthetically perfect. Lugged frame #1 definitely was not. But, are the joints I'm making now structurally sound? I've got an itchy trigger finger and I'm eager to jump into my next frame build.

[Curt Goodrich]

The pioneers had to figure this stuff out on there own by trial and error, I kinda like that idea too!

I think this is a false assumption. Most builders learned from other builders either by working directly with them or through informal information exchanges. This notion of figuring it out on one's own is a recent change is framebuilding. And if I may editorialize, it's not a positive change.

[EricKeller]

I pretty much figured it out by myself, but the guys that were cleaning up the brazing would give feedback if you weren't doing a good job. My motto is "no file"

[ToddFarr]

I think this is a false assumption. Most builders learned from other builders either by working directly with them or through informal information exchanges. This notion of figuring it out on one's own is a recent change is framebuilding. And if I may editorialize, it's not a positive change.

Curt I was talking about brazing in general not in regards to frame building. Some guy at some point had to figure out you can "glue" two metals together with another metal. He had to test methods, had to text different metals and had to think-on, act-on, and feel what was happening when he did certain movements. I know there are a few framwbuilding eras and I know there are a couple sets of pioneers but the craft had to start somewhere. It's like everything in this world that builds on itself. The guy who made the first lathe probably had no idea what cutting speed to run different alloys of steel at. Introduce new materials and you have to prove your formulas again, or develop new ones of those don't work.

[shiggy]

Along those lines... even though I am by nature a perfectionist, I can accept that fillet brazed frame #1 won't be aesthetically perfect. Lugged frame #1 definitely was not. But, are the joints I'm making now structurally sound? I've got an itchy trigger finger and I'm eager to jump into my next frame build.

I use short sections of scrap tubing for brazing practice because it is cheap and I can easily look at the inside of the joins. Sometimes cut through the join to check for voids and flow.

[edoz]

I think this is a false assumption. Most builders learned from other builders either by working directly with them or through informal information exchanges. This notion of figuring it out on one's own is a recent change is framebuilding. And if I may editorialize, it's not a positive change.

He did say pioneers, and by definition, pioneers had no one to learn from because they were...wait for it...pioneers;)

[mayan42]

Couple of shots of my first fillet braze, using sifbronze filler and flux; some old scrap tubes (the practice bottom bracket is approx 1.5mm and the seat tube is approx 0.8mm)

Any general comments are welcome (and please dont hold back!) but 2 specific points I'd like some feedback on-
1) Is the fillet big enough? I've seen a couple of comments saying the fillet should 3x the tube thickness, is anything more than that purely for asethetics? Is there a minimum "safe" size?
2) The holes - I'm guessing this is contamination where I didnt clean the tubes properly first?

thanks

https://picasaweb.google.com/mayan42...eat=directlink

[Doug Fattic]

I'm never sure how to respond to these threads asking for advice on how to brass fillet braze (or do any kind of braze) because a few pointers aren't nearly enough. In your case mayan42 you made so many basic mistakes it is hard to know where to begin. Really if one wants to be good at brazing they should go learn from an expert. Because a number of factors are in play at the same time, it can be difficult by oneself to figure out what those problems are and how to correct all of them.

Good brazing starts with the selection of the right materials that are the most likely to give success. This includes the joint materials (joining a heavy bb to lighter tubing isn't a great place to start), filler rod and flux and the kind of equipment used. Next hand positions holding both the rod and torch need to be established. Then the hand motions can be choreographed. Rookies tend to make similar mistakes and understanding what those mistakes are and how to correct them can really speed up the learning curve. Only after those basics are established can some refinements be pointed out.

In your case mayan42 you need to keep the heat on your joint just beyond the melting temperature of brass. You control where the brass flows by adding and subtracting heat. There is an acceptable temperature window that you control with the motions of your flame. You got it way too hot probably because you didn't flick off your flame often enough (to control joint temperature) while adding the brass. If you want to be good, you'll need more instruction than what can be provided by internet advice.

Doug Fattic
NIles, Michigan

[Eric Estlund]

We've had a bit of discussion on fillet brazing lately. To help make life a little easier for the new folks looking for info, and to help the older guys from having to re-write info we have this clearing house for all things fillet brazing.

[mayan42]

Thanks Doug,
I understand your point about learning from an expert, but for various reasons, that really isnt possible for me right now. This is not intended to be a new career for me, just a bit of fun. So, in the absence of any expert tution, I'm gonna just have to practice on my own, learning what I can through my own mistakes, but any pointers would be appreciated.

You say I got the joint way too hot, which I can understand, and part of that was definitely from trying to get the thicher tube up to temperature, but how can you tell it got too hot? ie how do i know next time?
And are the pits or holes caused by contaminants ? not enough flux?

[Eric Estlund]

Did you do the brazing in that fixture? If so, don't. Use it to tack, but see the heat sink discusssion- the massive cones (while better then a tube sink) will take a more effort to heat up.

If you see filler rushing to one tube and not the other, there is a heat imbalance that needs to be corrected. Remember that pulling the fire back doesn't take the heat off, turning the torch off the work does.

If there is a local community college or art metal program, see if you can hook up for some classes. You asked about how you know if the tube is too hot- part of this is just repetition of doing a bunch of joints and getting a feel for how your hands motions are influencing filler flow and outcome. Do 20 (arbitrary) samples, take notes, and vary your technique slightly between each. Practice, practice, practice. The specific questions, in a vacuum of experience, won't be very helpful at this point.

[mayan42]

Just tacked in the fixture, then held loosely in a clamp so I could turn and twist it by hand.
Yep, the thinner tube definitely attracted all the wet filler, I have some more tubing, so I'll do some even sized joints.

Thanks for the tips, I'll just get out there and practice practice practice.

[Will Neide]

Have you put it in the vise and tried to break the joint?

[shand]

Have you put it in the vise and tried to break the joint?

Why?

I see this time and time again and it's (almost) meaningless. It's incredibly difficult to NOT to fillet braze 2 tubes together and pass that test. Bicycles don't fail in that way. And if they do, they probably would have, no matter how good the join. There's exceptions to this of course (mostly joins that are waaay too cold) but it really is a waste of time.

The pics below show someone who visited our workshop for a day. He'd never even held a torch before and this was the first and only braze he did. It was on the unbutted section of 2 scrap tubes (0.7) and the miter was done in about 45 seconds with a hacksaw and file. There was a 4mm gap on the miter on one side! It passed the vice test. We had to put a 3 foot cheater bar on it to break it. It proves nothing.

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