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

  1. #21
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    Default Re: Fillet brazing - newbie advice

    Quote Originally Posted by shand View Post
    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.

    Attachment 52919

    Attachment 52920
    Thanks! Good to know. It just seems like standard operating procedure to test your first joints. I'm guessing the guy in your shop had your watchful eye and I'm guessing you set up the torch for him. It would seem that Mayan is flying solo, so all the pre brazing steps are unsupervised as well. If anything it would be a boost of confidence, or affirmation, and that's not such a bad thing.
     
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  2. #22
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    Default Re: Fillet brazing - newbie advice

    Quote Originally Posted by shand View Post
    Why?

    I see this time and time again and it's (almost) meaningless.
    Thanks!
    I totally agree.
    An overcooked fillet will pass that test no prob only to crack at the HAZ within two years if ridden.
    - Garro.
    Steve Garro, Coconino Cycles.
    Frames & Bicycles built to measure and Custom wheels
    Hecho en Flagstaff, Arizona desde 2003
    www.coconinocycles.com
    www.coconinocycles.blogspot.com
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  3. #23
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    Default Re: Fillet Brazing Practice

    Quote Originally Posted by edoz View Post
    He did say pioneers, and by definition, pioneers had no one to learn from because they were...wait for it...pioneers;)
    On the other hand, the brazing was used way before bicycles. People joined metals together for over 1000 years, and were experimenting with different alloys for that long as well. In a similar vein, the first cast engine block was not the first attempt at casting. Technology and process come from many sources.
     
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  4. #24
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    Default Re: Fillet Brazing Practice

    Regarding the structural integrity of the steel:

    http://www.velocipedesalon.com/forum...ing-31851.html
     
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    Default Re: Fillet Brazing Practice

    I havent tested that joint in the vice, but I have tested a few other bits, which I've managed to break, but not the joint - just fold the tubing around the joint, if that makes sense. I had wondered if it was a fair test of the join, and if the stresses were representative of a bike. So I guess its good to know that its not worth doing. I have cut open the other joints to see what it looks like - I think thats proabably a better way to learn about the "sucess" of a joint.

    And, yep, I'm flying solo all the way, so any tips are more than welcome, it seems the best tip of all is practice, practice, practice.
     
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  6. #26
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    Default Re: Fillet Brazing Practice

    Great intel. I'm moving this to the eff'builder wiki for easy reference.
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    Default Re: Fillet Brazing Practice

    Quote Originally Posted by Brian Chapman View Post
    It's Could probably have used some more flux too. And read the advice in this post:
    I used a lot more flux and got much smoother edges before filing/sanding. At first I was practicing with the information to use flux only where you want the bronze to be - this is clearly not the case. Directing the flame ensured it only went near where I wanted it.



     
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  8. #28
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    Default Re: Fillet Brazing Practice

    Just an update for this thread- seemed like as good a place for any for this.

    At Bespoked I was given a sample of Sif Bronze (not sure if it's 101 or #1) from one of the UK distributors, and I told him I'd post up a side by side. I generally use RBCuZn-B, first Gas Flux Co4, now Aufhauser.

    Here is that side by side:


    Sif:


    RBCuZn-B:


    Both frames have the same tubes mitered to the same angles, and are brazed with GF Type B and in-line flux.

    Wet out flash happened a little more quickly with the Sif, but both were generally comparable. I am looking forward to trying a sample on lugs to see if the wet out translates to easier pull through. For fillets I like both- though I still maintain rod consistency between batches are still more important then small differences in flow rate.
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  9. #29
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    Default Re: Fillet Brazing Practice

    Any major changes in technique when transitioning to Fillet Pro for stainless?
     
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  10. #30
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    Default Re: Fillet Brazing Practice

    Quote Originally Posted by Velo Wilco View Post
    Any major changes in technique when transitioning to Fillet Pro for stainless?
    Answering my own question based on a few practice fillets with Fillet Pro. Smaller tip helped. Went with a 1-TEN since i'm oxy/propane. The stuff moves fast if you get carried away with the heat. Just like LFB but with a lot less heat needed. Always keep your work on the top side because gravity will definitely pull this stuff toward the floor. Just feed the rod directly into the pool, not swipe back and forth like with LFB (at least that's how I do it).

    Starting to really like it. Frustrated me at first until I got the smaller tip on and heat turned way down. Now it's great!
     
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  11. #31
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    Default Re: Fillet brazing - newbie advice

    A some noob questions on flux.

    Bought the Cycles Design LFB flux and rod, on my third practice joint, using a Nova 28.6 top tube.

    My torch set-up is an oxygen concentrator and propane, Uniweld 71 handle, UN-J mixer and TEN-2 tip all per Doug's amazing info in the acetylene vs propane thread. Pretty sure I have a neutral flame with a nice small 5-7mm inner cone.

    Now to the actual flux questions.

    I slather on lots of flux but it doesn't really seem to spread out in a nice even layer. I've been using a clean rag, will a small paint brush change this so I get a consistent even layer? As it is now I have sections that have thick globs and sections that are pretty thin.

    As soon as I wave the torch across the flux I immediately get small black burnt bubbles. With any heat the thin sections instantly get these black bubbles. My tube prep is to sand them with ememry cloth then wipe down with mineral spirits.

    If my burnt flux due to not getting an even thick layer of flux? As I've typed all this out I feel I am answering my own question. A nice even layer of flux a couple mm thick would prevent the bubbles...

    I know a local course is likely the best option, but it's either course or purchase the equipment and learn on my own. I chose the learn on my own route, I have zero aspirations of making a living or ever selling any frames, this is for personal and family bikes. Maybe I need to see if I can just do a single day/evening with Paul Brodie instead of doing his whole course as it's not in the finances. I live in North Vancouver so he's the closest local building doing any courses/instruction.
     
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  12. #32
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    Default Re: Fillet brazing - newbie advice

    I don't think what you're seeing is burnt flux. I had a similar problem with the black bubbles appearing and contacted Wade (the CycleDesign guy). He said :

    Hi Steve,

    The short answer is "don't worry, its normal", but that would be a
    really boring answer to a good question.

    I don't think this has anything to do with your cleaning procedures.
    It is likely a chemical change in the flux itself.

    I am making the probably true assumption that you are not using a
    carburizing flame.
    If you were, the wet flux would pick up carbon soot from the torch and
    discolor, leaving a glossy, but blackened flux.
    This color would go away fairly quickly as the carbon is burnt off.

    From the picture it does not appear that you are overheating the flux,
    burning a bit, and leaving a mix of burnt and unburnt flux. This
    would be what happens when you bring the torch too close, and the flux
    burns (this isn't happening in the photo)

    What is more likely happening is that there is a chemical change in
    the one of the boron compounds in the flux. The boron salts in the
    flux are a white color. As some of the deoxidation potential of the
    compounds are used up, it would result in a small amount being
    converted to pure elemental boron which would be released in the flux.
    Pure boron is a very dark black color, and even a tiny amount (a
    fraction of a percent) would make the flux change to a black color.
    This can be differentiated from burning by the glossiness of the flux.
    Burnt flux is flat black, not glossy. This is not the same as flux
    gradually darkening due to picking up oxides. This would usually
    result in a brown (or red/green/blue) color depending on the
    particular oxide that is dominant.

    The flux will continue to be active, and will work fine. The dark
    color could go away on its own, or if you either added more flux, or
    stirred the existing flux.

    Adding cool flux to a hot joint can result in cracking. A better way
    is to either sprinkle on some powder flux, which will stick to the
    joint, or to heat some paste flux on a stainless steel spoon, until it
    goes clear, then pour a bit on the desired area."
    My issue was that the flux looked like this :

    flux_issue.jpg
    Steven Shand
    www.shandcycles.com
    Bicycle Manufacture - Scotland, UK
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  13. #33
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    Default Re: Fillet brazing - newbie advice

    That is what mine looks like. The second I put flame to it I get those same dark ball/bubbles.

    So I'll just ignore it and not worry, good to know.
     
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  14. #34
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    Default Re: Fillet brazing - newbie advice

    Some shots of my first practice brazes.





     
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  15. #35
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    Default Re: Fillet brazing - newbie advice

    Too much black...looks like you are using the high temp silver flux.
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  16. #36
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    Default Re: Fillet brazing - newbie advice

    Quote Originally Posted by shand View Post
    I don't think what you're seeing is burnt flux. I had a similar problem with the black bubbles appearing and contacted Wade (the CycleDesign guy). He said :



    My issue was that the flux looked like this :

    flux_issue.jpg
    My latest batch of LFB for CD does this as well. My last batch didn't though. It also seems more "sticky" this time. I like the texture better on what I have now (creamier and stickier), but the black bubbles threw me off at first. Still works fine and it all soaks off.
     
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  17. #37
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    Default Re: Fillet brazing - newbie advice

    Quote Originally Posted by Chauncey Matthews View Post
    Too much black...looks like you are using the high temp silver flux.
    Kinda frustrating for a noob, I specifically bought Low Fuming Bronze flux from Cycles Design because I figured it would be the right stuff for the right application. With the right stuff it would be easier to learn.

    Unless it's labelled wrong it's a 1 pound tub of this flux.
     
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  18. #38
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    Default Re: Fillet brazing - newbie advice

    I would give Wade at cycle design a call. Super nice guy and I'm sure he will help you get sorted out. That looks exactly like mine when I was using the wrong flux.
     
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  19. #39
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    Default Re: Fillet brazing - newbie advice

    There is a difference between the black that is right up against the filler (carbon precipitation) and the black flux further away. I don't think that "looks good after brazing" is one of the top priorities for most flux manufacturers. At brass brazing temps you get some carbon precipitation that is normally carried away from the joint by the flux. The copper and the carbon precipitation (that wasn't moved away by the flux) show that the joint was overheated.
     
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  20. #40
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    Default Re: Fillet brazing - newbie advice

    Quote Originally Posted by seankanary View Post
    I would give Wade at cycle design a call. Super nice guy and I'm sure he will help you get sorted out. That looks exactly like mine when I was using the wrong flux.
    Wade was a great to work with on the original order. The first shipment he sent out went MIA in the mail and he sent a replacement.

    Quote Originally Posted by EricKeller View Post
    There is a difference between the black that is right up against the filler (carbon precipitation) and the black flux further away. I don't think that "looks good after brazing" is one of the top priorities for most flux manufacturers. At brass brazing temps you get some carbon precipitation that is normally carried away from the joint by the flux. The copper and the carbon precipitation (that wasn't moved away by the flux) show that the joint was overheated.
    I'll back off on the heat on the next practice joint.

    I don't really care if it looks pretty after brazing, I just want to ensure I've got the right stuff and using it correctly. Will capture more photo's in process on the next joint to see if we can clarify if there is something wrong with the flux or it's just my noob ways.
     
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