# Brazing Passes



## karavshin (Mar 20, 2004)

[tried to post this earlier, but it seems to have disappeared]

I'm nearly done with my second and third fillet-brazed frames. Iteratively, each bike improves in miters, alignment, etc. I'm not convinced I'm doing myself favors in how I braze the frame, though. I just spent a nearly-fruitless evening staring at awful youtube brazing videos trying to get some idea of how to improve.

So how I presently braze a junction would be to tack sides first, then the obtuse angle, then the acute angle (as per paterek suggests). After that I tried to build up a thick blob (fillet) of brass on some point around the circumference. Then start trying to melt and flow that into a properly-shaped fillet.

I think the result is slow, results in a lot of inconsistent heating, a lot of uncessarily long heating, which I think leads to more filth and ugly brazes, and probably a crappier joint.

When I watched youtube videos today of guys brazing butt joints, they brazed very much like I'd tig weld: get a molten pool, dip filler rod, advance, repeat. They werent' melting little towers of brass filler and then trying to manipulate it with the torch.

I'm wondering if I should be doing the same sort of thing with my fillet joints? Just start walking the filler/torch around the circumference of the miter joint (maybe hopping around noon-three, six-nine, three-four, nine-midnight or something).

Furthermore, I'm wondering, do I make this circumference in a single pass, or do I lay escalating levels of fillet on consecutive passes, like you might see in a MIG textbook showing build-ups of a fillet joint.

And a little sidenote......... I bought some sifbronze coated brazing rods from Ceeway to replace the standard cheap raw brass rods from the local welders' supply. I guess overall it seems a bit better (cleaner, mostly), but I will confess I sometimes have a hard time distinguishing the murky black flux from the brass in the midst of a joint. As in "there's a puddle of something -- is it brass or molten flux?" Any tricks/tips on using sifbronze coated rods? I bought two diameters. 1.6 and 2.4 (I think!). I never have brazed with 2.4, I thought maybe it would help me layer bigger fillets quicker.

Regards


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## Walt (Jan 23, 2004)

*I am a cruddy fillet brazer...*

But for what it's worth, I do it as if I'm TIG welding. I think that's pretty much standard.

-Walt


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## karavshin (Mar 20, 2004)

Walt said:


> But for what it's worth, I do it as if I'm TIG welding. I think that's pretty much standard.
> 
> -Walt


Sorry, so does that mean a single pass?

When I weld "normal" non-bike stuff, it's generally a single pass. When I was talking to ?Black Sheep? (might have the wrong name) guys at NAHBS, they were saying they did multiple passes on their titanium frames, the last one being, I think, for cosmetics.


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## Linnaeus (May 17, 2009)

Yea, Ti is different than other materials. I've never done it personally, but it seems they do a fusion pass and then come back and do a cosmetic pass. 

Hopefully Garro will weigh in on some brazing tips, he does real nice work.


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## unterhausen (Sep 28, 2008)

for what it's worth, I do it in one pass after tacking. I keep the brass in the flame so that it's easy to add. I see no reason to make little towers of brass and then flow them out, that's a waste of time and may actually raise the temperatures considerably because brass flows a lot better the first time. I'd rather not have dimes as in tig because I don't want to have to finish those. With brass, you can keep things pretty smooth. 

I did recently see someone talking about brazing uphill which is something I had never heard before. That really does allow me more freedom to control the rest of the process. The main difficulty for me is to keep edges smooth at the fillet/tube transition, I find those really hard to finish. I'm not sure how much this will help. Practice is the most important thing.

Some people do a tinning pass, and then a finish pass. I don't really think that is necessary.

As far as discriminating between brass and flux, I know where I put the brass so if there is a pile of flux I already know it's not brass. Takes some practice, plus I use ACE glasses so that I can see the colors a lot better. I can braze using #3 shaded glasses, but I can see how beginners would have problems with doing that. Of course, that's an investment of $130.

I am using 1/8" rod, a little over 3mm. I like it better. I've heard that beginners might not like to deal with it. I don't have any problems with 1/16" rod.


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## Winter Bicycles (Jun 8, 2008)

After tacking (you'll figure out a sequence that works for you) :

- Preheat the joint. I do a general "warming", but at a modest distance with a soft flame.

- I get in close with a small flame and start in on the joint. Keep the filler in the flame. As it starts to wet out I use it and the torch to do a "stitching" or painting motion for the width of the braze. Add filler to the root,and use the flame to paint it out. Doing this helps feather the edges (assuming a decent and maintained preheat).

- If things start running away pull the flame OFF the work, not back from the work. Off turns off the heat, back just lessens the heat (and you already have to much).

- Your puddle should start walking away from the flame to follow the heat. If that is happening to fast, slow down and work slightly uphill.

- I move the torch up the rod to pull down filler. This is different then adding the rod into the flame. Pulling down adds a lot of brass that is at temp and avoids the dab-dab-dab cold dimes.

Heat is your friends, but so is speed. If things are to hot or to fast back off for a bit and try again.

These are single pass. I occasionally to a tinning pass, but that is more of a heavy tack then a "first layer" to be built upon. Try to get it in one go if you can.


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## themanmonkey (Nov 1, 2005)

Winter Bicycles said:


> - Preheat the joint. I do a general "warming", but at a modest distance with a soft flame.


This I think is the real key to good fillets. You get that flux nice and ready just before glassy flow and you can move really quick around the joint without causing a lot of distortion. I've found that if you don't preheat you really should braze the joint in quarters to minimize distortion and pull.


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## karavshin (Mar 20, 2004)

Kept forgetting to bring my camera.


Click for full size

Anyway, I tried two test passes after I wrote the original email. The first one (with 1.8mm sifbronze) didn't seem to leave a big enough fillet after one pass.

Then I tried again with the 2.4mm sifbronze rod on a single pass and got a better (is it good enough?) fillet.


Click for full size

The differences wasn't entirely due to the thicker rod (which with a #2 tip ONLY just managed to melt -- I had to make busy, whirling circles to get it to melt and flow), but also that I figured out I could use the blast of the torch to push away excess flux, in order to distinguish where the brass ended and the flux began.

Since then, I have brazed more stuff and changed my technique a bit more -- someone on a forum said to "draw" the brass off the rod with the torch. So I run the torch up and down the rod a few cm and I get a nicer flow of brass onto the fillet.


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## bobbotron (Nov 28, 2007)

Well, the cool thing is you can test your joint strength. Do another one of those with a foot or two of bar on one side. After it's done brazing, attach the one side to a VERY well secured vise (or equivalent), stick a breaker bar near the end of the other side, and break it. If the joint is good, the tube will bend/break/fail and the joint will remain.

Anyway, I would say the pin hole bubbles in your example indicate... something - overheating?

If you want to deposit more brass in one pass, try something like this: heat the joint up first, running the torch all around it. Once it's red (er, through #4 goggles?) and your flux gets glossy and wet looking start applying the brass. Once it starts to melt, instead of continuing on, try to feed the brass rod into the molten puddle to build it up a little more - draw back/remove the torch as needed to keep things from getting too hot.

Are you tack-brazing the tubes before you start?

Another fun thing to practice is T joints, using 1/16 (or 1/32") mild steel. Cheap, easy practice, takes way less time to prepare than a tube too. You could also practice welding with that, which I think everyone should try with an O/A setup (yeah, it will be ugly without filler.)

Making metal sculptures out of random dead steel things is also great brazing practice, and fun!


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## Brad Bedell (Apr 18, 2009)

bobbotron said:


> Anyway, I would say the pin hole bubbles in your example indicate... something - overheating?


+1 Either overheating or potentially unclean filler rod,base material/etc. A very common mistake that I still make after welding for 10 years is not being clean enough before firing up the torch.


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## karavshin (Mar 20, 2004)

Brad Bedell said:


> +1 Either overheating or potentially unclean filler rod,base material/etc. A very common mistake that I still make after welding for 10 years is not being clean enough before firing up the torch.


It's probably more likely overheating, then.... On these samples, I sanded down the metal and scrubbed it with a sponge-thing with detergent before I covered it in flux paste.

The brazing rods were straight from the case, so they couldn't have been dirty.

The parts become quite orange when I'm brazing them. Not yellowish orange when they start sparking and spitting, but definitely brightly colored. I guess I should be aiming for a lower temperature.


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## unterhausen (Sep 28, 2008)

First off, it looks like you don't have far to go before you are making good joints.

straight from the case doesn't mean the rods aren't oxidized. However, it doesn't really look like the pits you generally see from that. On the other hand, it seems to me that you generally get bigger pits from overheating. I realize that it has been sandblasted, but the surface doesn't really look right to me.

The copper indicates you are overheating, hard to know how much. Show us some new joints that haven't been sandblasted.

It's possible to overheat and underheat the same joint. I'm wondering if the pits aren't related to local cold areas. You can go overboard in heating the brass.



karavshin said:


> The differences wasn't entirely due to the thicker rod (which with a #2 tip ONLY just managed to melt -- I had to make busy, whirling circles to get it to melt and flow), but also that I figured out I could use the blast of the torch to push away excess flux, in order to distinguish where the brass ended and the flux began.


The only manipulation of flux I've ever done is to pull more into the area where I was brazing because I took longer than I thought to braze something. Not sure about your problem seeing with the flux there, seems like something is not quite right. My brazing motion is a little spastic, waving the torch back and forth. Sometimes I get self-conscious about it, but the important thing is getting the right amount of heat and no more. It's best to slow down and relax.


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## karavshin (Mar 20, 2004)

unterhausen said:


> First off, it looks like you don't have far to go before you are making good joints.
> 
> straight from the case doesn't mean the rods aren't oxidized. However, it doesn't really look like the pits you generally see from that. On the other hand, it seems to me that you generally get bigger pits from overheating. I realize that it has been sandblasted, but the surface doesn't really look right to me.
> 
> The copper indicates you are overheating, hard to know how much. Show us some new joints that haven't been sandblasted.


Do these help?

I just sent two frames to the powder coat today, so maybe I have some time tomorrow to try some more sets of joints.



fullsize: 
https://www.flickr.com/photos/karavshin/sets/72157624141109786/


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## Schmitty (Sep 7, 2008)

Dude, get some real product from Henry James or some of Fred Parrs stuff.

-Schmitty-


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## unterhausen (Sep 28, 2008)

I think he's in the UK


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## Smokebikes (Feb 2, 2008)

This is a great read from an old post about brazing...........worth a look. :thumbsup:

_Hello All,

This is an extension of the "fillet BB" thread in the Eye candy section. I've been asked for some fillet tips from a number of folks so thought I'd make a general post. There are a number of things that can make or break the whole fillet thing. I'll break this into three sections - prep, laying fillets, and finish work. FWIW this is just the way I'm comfortable doing this and by no mean the "only" way or the "right" way to do this. I've seen plenty of very nice fillets that didn't go by this recipe.

Prep -

1) Clean the tubes. I dip the tubes into my can of acetone and then wipe clean with a clean rag. I then use new, fresh, 80 grit emery and sand each end. I then dip the tube into the acetone again to get any dust off and wipe with rag again.
2) Clean the rod. This is very important. The brass rod lies around for months getting tarnished and dirty and it will work much, much better if you clean it. I wipe it down with a rag wet with acetone. You'll be amazed how dirty the rod was.
3) I use a Gasflux machine and I like it. I know many do not and that is cool. But I use one and I always check the flux level before starting. It's a bummer to run out mid-fillet.
4) I use a Victor torch with a #2 tip. In fact I use it for everything not just fillets.
5) So everything is clean and ready to go - I flux everything up before putting it in the jig to tack. I flux a good two inches up into the tube. Might sound silly but it does a very good job of preventing heated up oils inside the tube from running into the joint. It provides a barrier if you will.
6) I tack each tube in four places.

Laying fillets -

1) Preheat the entire joint. Take your time and don't be in a hurry to lay down the fillet. By heating the entire joint you minimize the amount of distortion of the tubes. This is very important on head tubes and BB's where ovalizing can cause real issues in machining. I heat the bottom of the BB and the front of the head tube just as much as the part I'm laying the fillet on. This will make your life much easier down the road.
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.
3) Once the joint is tinned I start laying the fillets. Turn the torch way, way down. I use a flame that is about the same size as I use doing bottle bosses. Small. When laying the fillet ALWAYS work away from the torch. I'm right handed and hold the torch in my right hand&#8230;&#8230;&#8230;.so I work from right to left. This will assure that you are preheating the spot you want to lay down the next bead of fillet and also make sure you aren't melting the stuff you just put down. This is super important to me. Lay the fillet in beads like a TIG welder does. Overlapping beads. If the fillet starts to get away from you and is getting sloppy back off and let it cool some. Do not rush. Back off and take a few long breaths before going back in. It will still be there. The few seconds of time this cost you here will save you hours later in finish work. Go slow.
4) Do everything you can to NOT go back over the work to reheat and smooth things out. This can get away from you in a hurry and you'll end up with the fillet on your foot.
5) I have the frame in a Park stand so I can rotate it and get the angle I want for each bead. Take the time to get the frame is a good position. Do not try to work around a corner. Take you time and move the frame so you can get at it properly. See the trend?&#8230;&#8230;..take your time.

Finish work -

1) Soak the frame in very hot water to get the flux off. Don't waste your time with warm water. If the water cools down replace it with really hot water. It will go much faster this way. Soak ALL the flux off before trying to do anything else. Finishing with glass hard flux is a waste of time.
2) This is a bit of a diversion - I check the alignment before doing any finish work. On the 1 in a 1000 chance that the alignment is crap you won't waste you time doing the finish work.
3) All finish work should be done from the middle of the fillet out toward the tubes. This will assure that the fillet is a quarter circle shape and not have a flat in it. So work from the middle.
4) I start with a 10" round file and take off the high spots. Don't touch the file to the steel&#8230;&#8230;..ever.
5) I then wrap the same file with 80 grit emery and sand the joint.
6) I then rip the emery into narrow strips about 8mm wide and sand with those&#8230;&#8230;..working from the center and blending into the tubes.
7) Lastly I use an abrasive brush wheel to buff the joint. This makes it shiny which is fun but the real purpose is that it will highlight defects. File marks and low spots will stick out in a big way once you use the wheel. When you first to it you will be bummed but you'll learn a lot about where you leave poorly finished stuff. Once you use the brush you'll have to go back in and refinish some stuff that wasn't right.

My aim is to make a straight bulletproof bike with pretty joints that will need no putty. Anyone can lay down joints that will hold the tubes together but look like ass and then putty them into shape. Take the extra step and you'll be proud of your putty free work. This takes lots of practice and you won't master it quickly. Be patient and methodical and it will come around. Over the years I've done many thousands of fillet bikes and they go like clockwork now but it wasn't always that way. Practice makes perfect.

I hope that helps and answers your questions. Thanks for reading.

Dave

--------------------

David Kirk
Kirk Frameworks Co.
329 Little Wolf Road
Bozeman, MT 59715
USA
(800) 605 5475
www.kirkframeworks.com_


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## karavshin (Mar 20, 2004)

unterhausen said:


> I think he's in the UK


...more obscure: Singapore

Ceeway is easier for me to order from - website vaguely more complete and they respond to emails fast. Henry James is 12 hours out of synch with my timezone and difficult to contact.


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## karavshin (Mar 20, 2004)

Smokebikes said:


> This is a great read from an old post about brazing...........worth a look. :thumbsup:


That sure is interesting, thanks.

This afternoon I did a couple more joints for fun. Another boring set of results posted here
https://www.flickr.com/photos/karavshin/sets/72157624022821225/



Things I noted:

** Where I tacked the two corners (the 90-degree) the brass never penetrated under the tube. This isn't good I think. Means I didn't have the tubing hot enough?

** I had way fewer pinholes on the braze than earlier.

** I was using a #5 this time, not the #2. Maybe I should go back to using the #2 as per your note above?

Most clues are indicating heat control. Same rod, flux, joint with a #2 I got pinholes. With a #5 I didn't. Brass tacks didn't flow. etc.

In the archived thread quoted above, the one thing you don't talk about is how you tell when the joint is hot enough. I'm not sure how to describe the spectrum of tubing color I see. Basically gray, orange, bright orange, sparking white. Now I know that the white sparks means the tube is way too hot. I don't know where in the "orange to bright orange" spectrum I should be though. Any suggestions on that?


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