Brazing technique for fillets
 

Trying to learn fillet brazing, found this vid while searching around for info. Although he's using fluxed rod the movement of the torch shows the In/out off/on liquid/soild sequence close up, something I've not seen before on brazing vids, they're usually much further away so you can't clearly see the movement. The brazing starts at 4:30 in if you want to skip the intro. There is also a vid on this site practice brazing by building a "brass tree". Any input and all input welcome.

thanks, Brian

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edit: removed brass tree vid, doesn't have much to do with the torch/flame movement shown in the 1st vid, that is the point of my post

Thanks for posting this. I have been looking for this type of video for a while as well. Makes more sense now. I may go find the filler he is using. That would be handy for a couple of house projects.

this is the only time that flux covered rod is any good for anything. When I made one of those trees, I only had powder, it's always a pain. But I don't think paste flux would be very useful.

I suggest brazing fillets on offcuts instead of this, much more educational. You can just move the filler around and learn a lot from doing that

!00% agree, thats what I've been doing, moving the brass around, playing with it. Think I've done around thirty fillets and lots of laying rod along the tubes. I got 40' of 1 1/8 .035 so when I'm done at least I'll have a better feel for the process. Using propane for the first time. Using a mill/drill to cut the miters, I use tubing blocks to hold a 24" length of tube and get 6 4" pieces with miters on both ends, them cut those in half on an old HF horizontal bandsaw into 2" pieces, clean up the miters with a half round to get a decent fit.

regards, Brian

https://i.imgur.com/70kmVZs.jpg

https://i.imgur.com/B2X8xE5.jpg

​​​​​​https://i.imgur.com/iBtRXnX.jpg

​​​​​​https://i.imgur.com/jCp9srU.jpg

that's good. I suggest you cut some miters at 60 degree angles to get the hang of that inside corner

Brian, congratulations on doing a nice job of practicing fillet brazing! I have a couple of simple suggestions to help you with your journey. I’m guessing that you might want to move the long stem tube around more to keep the walls of both tubes at an equidistant angle from straight up. This means the melted brass will flow towards the crease instead of away from it. This allows you to keep the mass melted just a hair longer so it flows out more and becomes a bit smoother (just before you have to flick the flame off to keep it from running away). Eventually you will be working at keeping the width of the fillet consistent. I also recommend cutting off the used end of your tree so nothing gets in the way of your flame.

If your tubes are both the same size I recommend getting a smaller tubing diameter for the short stubs so it is easier to keep the area around the ears of the miter from getting away. Once you have mastered the technique with an easier braze you can graduate to a bigger stub. I also 2nd Eric’s suggestion of mitering the stubs at angles to get a more realistic practice braze. You might start with 73s before going to the slightly more difficult 60.
The advantage of having a long tube is that it serves as a handle to keep constantly moving the joint to the best angle for fillet brazing. Of course to do this your tube holder has to be tightened to that sweet spot between tight/free where it will move without much effort with your non-torch hand but will stay put when it is in the right position without having to adjust the vise handle. My oldest most beat up wooden tube blocks work best. New blocks that haven’t been broken in can be a bit sticky to move easily.

Eric and Doug, thanks for the input, I'll start making some stubs with angles(60-73ish). I got all the same size tubes(1 1/8 .035) because that size is quite inexpensive compared to other sizes(at Wicks). Being the same size the ears of the fillet on the main tube are the most difficult for me, I just consider that area to be a different skill to develop, I try to look at it like I'm brazing along the top of the tube same as my practice runs along the top, probably will get different sizes next time I order. All my tubes were shipped as 4' lengths(less $ shipping), I cut those in half and make fillet stubs from one and the other for attachment, but from now on I'll start using a 4' tube to braze onto, makes more sense.

regards, Brian

one of my big goals when brazing fillets is avoiding anything I'm going to have to work hard to file away. "No file" is my motto. The tricky part is the edges. I hate having to file a lip at the edge of the fillet because it's so difficult to keep the file off of the tube.

Here's another vid, from Chapman cycles, showing process he uses to tin the tubes prior to building a fillet(a two pass method) by pulling a small amount of brass around/into the joint with heat. This is also helpful(for me) seeing the heat/color of the tubing relative to flowing the brass.

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This is on a Vimeo vid by Steve Bilenky showing a bb he tinned, ready for building a fillet:

https://i.imgur.com/BHisJmm.png

regards, Brian

I think of "tinning" to be coating a work piece with a thin layer of filler BEFORE joining to another work piece. What has been mentioned is what I call a "flow braze" of the joint, suggesting the filler was flowed inside to create an internal fillet during the first pass. This is what I do. Andy

Do you use a different filler rod for the flow pass?

No. Not sure why I would want to. I use Gasflux CO4 low fuming bronze and their B flux. Andy

David Kirk from a list of his tips on fillet brazing:

2) “Tin” the joint. This is in effect tacking the entire joint. This is the real structure of the fillet and will make sure that the bike is still together after your death. Tin it well and flow brass into the joint evenly all round

I guess I am taking my meaning from the soldering world. One would tin the surfaces prior to joining to insure good wet out. Andy

Which way do people recommend you braze when doing fillets?

I started by beginning at the ears and working towards the deepest section of the fillet but have found that I get much better results going the other way

I think the ears are the hard part. I generally tack at the top and bottom where the tubes are at the sharpest angle. And then start moving around from somewhere away from the centerlines where the tubes are still at a sharp angle

I know people that tack away from the centerlines.

Tacking and/or starting the full brazing along the tube/frame centerlines is generally thought to reduce the heat distortions that can lead to a twisted frame. By applying the heat at the center line and then trapping the tube together with a tack or the beginning of a full brazing traps/keys the tubes with less side ways uneven heat expansion (distortion). Once the centerlines are linked then working down and away from the centerline, a bit on one side then the other side, is the attempt to reduce the distortions and trying to be consistent WRT the heat applied on the tube sides. Andy

probably with a big iron heated by a propane burner :)

Another fillet technique, he calls it bronze welding, but it is brazing as the parent material is not melting.
​​​​​​ end result, "stack of dimes", lots of filing/sanding if you want a smooth fillet, he obviously doesn't.

similar technique, different guy:
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Both using a gasfluxer, no flux visible. These vids are from older posts on this forum.

regards, Brian

Brian- That's just fillet brazing without an initial flow/tinning step. All be it very nice fillet work indeed. Andy

Yeah bronze welding is the correct term in England, at least in the bike biz (I don't know about general industrial usage). A few Americans call it that too. The idea is that brazing involves the filler sucking into a gap by capillary action, so making a fillet is not brazing by that definition.

In America the same thing is more commonly called fillet brazing. It's definitely brazing by my definition. As long as you know the terms are interchangeable, communication doesn't suffer.

I also call the filler brass, not bronze, but I'm not dogmatic about it; I think either are OK in the jargon of brazing. Many will tell you bronze is more correct but I don't care, I am old and not gonna change so don't bother!

Mark B in Seattle

I was at a local welding supply store and asked for some 1/16” bare brass rod. The old guy behind the counter snarled at me and said “You mean bronze rod!”

I would be surprised if the people at my LWS would know the difference. I always called it brass because I didn't know any better. Now I'm more careful because there might be pedants around.

I asked the LWS person if they sold brass flux and they pointed at the stay-silv. Wonder how many people they have screwed over with that bad information. I understand it almost works

I'm curious how much penetration you can get with the stack of dimes fillet style of brazing.

Yeah not everyone is agnostic about that!
Again I'm not saying brass is right and bronze is wrong, but look up the dictionary definitions:Then look up the AWS designation of, say, C-04 bronze: RBCuZn-B. CuZn means copper and zinc. QED.

The following is from brazing.com (Aufhauser):

Q: WHAT ARE DIFFERENCES BETWEEN BRASS AND BRONZE?

• Composition
  • Brass: Copper and Zinc alloy
  • Bronze: Copper and Tin alloy
• Properties
  • Brass: Higher Malleability
  • Bronze: Hard and brittle <- [does this sound like braze filler to you?]
• Melt Point
  • Brass: Lower (~900°C); flows when melted <- [C-04 solidus is 866° C, Liquidus is 882° C.]
  • Bronze: Higher (~950°C) depending on Tin quantity <- [higher than any CuZn braze filler]

Again, if you want to call C-04 bronze, you're in good company and you are not wrong.

So we were right BITD to call it brass. Not that it really matters