# Which is better?  Brazing rods with flux  Or without flux



## mickri (Jan 22, 2021)

Looks like I am going to try some brazing.  Is it better to use rods with flux?  Or have the flux and rod separate.  I will be brazing .065 wall exhaust tubing.  I know nothing about brazing and have never done it.


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## FOMOGO (Jan 22, 2021)

If you've never done it before the coated rod may be a little easier, as you will have a little less to pay attention to. Other than that not a whole lot of difference. On heavier work I like being able to apply flux directly to the prepped area before adding filler, but on your thin wall material it should be a non issue. Mike


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## Norseman C.B. (Jan 23, 2021)

I personally prefer using bare rod and common 20 mule team borax for flux
more bang fer the bux....................


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## C-Bag (Jan 23, 2021)

I have better luck with the non fluxed rod. Just got to remember to dip your heated rod in the flux all the time. Brazing is a great way to go. It’s a lot stronger than you think if it’s done right. It’s all about prep and getting it to flow. My first project in metal shop was to take two 3/8 thick plates, v them and braze them together. Then you had to bend them in the press until the ends touched without the weld breaking. Got an A on that one.


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## Cooter Brown (Jan 23, 2021)

I like the Harris Bare low Fuming Bronze 15 filler with the Black Stay-Silv Flux.........You will need .030-1/16" diameter filler rod for brazing .065 material..... The larger filler needs to get to hot and you burn though the base metal before the filler ever melts....

I actually like using galvanized bicycle spokes as filler for Gas Welding sheet metal it works great for me.....


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## matthewsx (Jan 23, 2021)

Brazing is a cool art to learn, especially for owners of LBC's (little British cars). I did a bunch of brazing on my Triumph TR4 and don't think those repairs could have been done any other way.

I'm with @FOMOGO here, don't really think it makes too much difference except for cost. Just make sure you practice plenty on the scrap from building your header so you know exactly how much heat that metal can take before you blow a hole in it.

John


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## mickri (Jan 23, 2021)

I have leaks where the exhaust tubes slips into the collector that I have not been able to fix.  The leaks are where the tubes are right next to each other. This is not to try to actually weld the tubes together.  I am just hoping to plug the leaks.  I have a 1 3/8 OD exhaust tube that is slipped into a 1 3/8 ID collector tube.  There is between 1/2" to 1" overlap.  Silver solder would probably work because I don't think that the collector gets that hot.  The problem is that when the header is ceramic coated it will be baked at up to 700* to 1400* to cure the ceramic coating.  That would melt the silver solder causing who knows what kind of problems.  From the videos that I have watched it seams like the bronze filler flows down into the joint.  That is what I would like to happen.


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## matthewsx (Jan 23, 2021)

You're on the right track. The only thing I might suggest is rather than ceramic coating you just wrap the header. Ceramic may make it difficult or impossible to repair when need arises, it also costs a lot. Header wrap is relatively cheap, effective, and IMHO looks just as good or better.

John


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## G-ManBart (Jan 23, 2021)

If you can make a similar joint out of scrap to practice on you'll be way ahead of the game.  I have both coated an uncoated rods and think it's easier to use the coated rods for someone starting out.  After you get a bit of practice it shouldn't matter either way.


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## Cooter Brown (Jan 23, 2021)

You need safety-silv 56 for this project..... Melts at about 1500°F....

Bronze filler melts at much lower temps... Bronze also doesn't wick down into the joint as well as silver does...Bronze does build up easily but it's not great at being a thin layer down inside the joint like you want....


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## Dhal22 (Jan 23, 2021)

Cooter Brown said:


> You need safety-silv 56 for this project..... Melts at about 1500°F....
> 
> Bronze filler melts at much lower temps... Bronze also doesn't wick down into the joint as well as silver does...Bronze does build up easily but it's not great at being a thin layer down inside the joint like you want....




Agree,  very strong way way to assemble tubing.   Here's some of my work on .035 wall steel tubing.   My test joints were almost unbreakable.


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## mickri (Jan 23, 2021)

I looked at the spec for safety-silv 56.  It melts at 1205*.  Don't think that will work if the header is baked at 1400* to cure the ceramic coating as a local company claims on their website.  If I go with VHT spray on then the header gets heated to 700*.  My only reason for the ceramic coating is for rust prevention.  Otherwise I would leave it as is.  Not thinking about trying to control heat radiating off the header.  I have used heat wrap on the exhaust on my sailboat.  So I am familiar with it.

I have used Harris silver solder.  It melts at 435*.  One thing that I really like about it is that I can put a small piece and flux where I want it.  Then heat the surrounding area until it melts and flows into the joint.  I don't over heat or under heat this way.  Will the safety silv 56 and the other safety silv's do the same thing?

I can do some practice pieces.  This stuff is expensive at $8 to $10 per rod.


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## Ulma Doctor (Jan 23, 2021)

For lower strength brazing pre-fluxed LFB is my goto
When i need more strength i got bare silicon bronze and 20 mule team borax


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## mickri (Jan 23, 2021)

What is "LFB"?  I tried searching for it and didn't get any hits.


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## matthewsx (Jan 23, 2021)

Rust prevention on a car like this is probably a non issue. You’re going to be working on it all the time and can keep an
eye out for any problems.

It’s way more likely you’ll need to repair a crack than a rust hole. Ask the coating place what you’ll need to do for any future repairs, maybe they can give you a scrap piece to practice on so you’ll know what to expect.

John


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## Technical Ted (Jan 23, 2021)

mickri said:


> What is "LFB"?  I tried searching for it and didn't get any hits.



Google LFB brazing rod. Here's the first one that popped up:






						Harris LFB-FC Low Fuming Bronze Brazing Rod 015FC500POP
					






					store.cyberweld.com
				




Looks like "low fuming bronze". 

Ted


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## Ulma Doctor (Jan 24, 2021)

mickri said:


> What is "LFB"?  I tried searching for it and didn't get any hits.


Low Fuming Bronze


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## Logan Novice (Feb 2, 2021)

I think it's worthwhile to note that the filler follows the flux.  As long as I can generate the heat I need where it's needed and get it clean, and get flux into the opening, I can braze it.


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## mickri (Mar 5, 2021)

Bought some Safety Silv 56 and flux off ebay.  Should get it sometime next week.


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## aliva (Mar 5, 2021)

Use the coated rod till you get proficient. Easier and quicker for the beginner. Then experiment with bare rod, just be sure to clean the bare rod with steel wool before welding to get the oxidation off. I use bare silver solder wire and it must be clean prior to use.


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