Brian25

Hi, I've finally run out of bronze brazing flux and I'd like to know what other frame builders prefer to use for lugged construction, to get the best results. There are likely going to be different preferences, so let's keep this civil. Thank you.

A clarification: I am asking about the best flux for brass rod brazing for a frame with lugs.
(not silver brazing or silver soldering). Silver wire has become more expensive, so I was planning on using brass for this particular frame.

A separate question: what size silver wire do you guys use, and where do you get it? I have done silver soldering/ brazing; I used to install s&s couplers, and have built a number of frames with silver as well. When I had done silver solder/braze, I used a thin .6mm silver wire. But I'd like to know what other options are available.

Andrew R Stewart 

GasFlux products have been my standard for decades. Andy

Live Wire 

dsaul

Gasflux Type B for brass, Cycle Design System 48 for silver.

BigPoser

In my limited experience, I really love Cycle Design for silver.

Andrew R Stewart 

These replies follow the reports I've read of for a number of years (since Freddy started the Cycle Design efforts). But flux is one more tool and can be abused or work out well, dependent on the guy holding that flame. I'll add that the GasFlux type B flux is far easier to soak off with hot water then any local welding shop stuff I've tried. This is why I have stayed with it for so long.

Not asked but I'll also add that some (like me) use their CO4 bronze rod for sleeves and lugs as needed. Andy

Doug Fattic 

One reason to choose Gasflux type G (not to be confused with their Type U) or Cycle Design Stainless Light flux is because they have a higher temperature range up to 1700º while most other silver white fluxes from those companies or what is available at the welding supply store go only up to 1600º. For those just learning this extra protection can be important. This is why i use those fluxes for my frame building classes.

It takes a different technique to evaporate the water out of the flux for each manufacturer's flux. Gasflux gets runny quick and you have to figure out how to stop the runs before it is on the floor. Stainless light gets puffy and will explode in sheets off of the joint unless it is heated more slowly and generally 1st.

Nessism

I'm back to building after a pretty long lay off and first joint, using freshly purchased Gasflux U, and the flux was running off on the floor just like you state here. I backed off the heat and tried to get the water to flash off before moving the heat back in with earnest. In the end the joint turned out fine but there were a couple of spots on the outside of the BB shell that had dark spots from burned flux. Open to suggestions on how you do it.

Doug Fattic 

I turn the heat up so it dries more quickly and have the flame close to the joint, start at the bottom so the dried flux acts as a dam and point the flame up so the pressure of the gas counters the flow of the flux. I go after the "runners" aggressively. If you move the flame too fast the flux dries too slow and runs away.

The Blue Angels were just flying over my shop making a huge racket practicing for the Notre Dame/Michigan game Saturday where they will do a flyover. it is hard to see them because the noise is behind where they are in the sky.

Brian25

Are you writing about using the Gasflux U with brass rod welding or are you writing about silver brazing? I have been using the Gasflux b for brass brazing but admit that I am too lazy to go out and see what I use for silver. brazing.

Nessism

Sorry for the thread drift...I'm talking about the U for silver.

I wouldn't have thought of using high gas flow and blowing the flux uphill. Going to have to practice that one...

Oh, and regarding airplanes flying overhead...there is a small airport in my town that is popular for the vintage pilots to fly into. There are regular runs of WWII vintage stuff flying over and I always run outside anytime I hear one. Just love that sort of thing!

Brian25

I am in the middle of a "lazy attack" I was too lazy to look up the application for the Gas flux U. Doh-- it's for silver. Regardless when I silver brazing or brass brazing, I always do some preheating of the shell before starting in on the brazing, but of coarse there is a limit. I do not want to start to burn the flux. (Doug)l is so much better at describing the process than me.

Doug Fattic 

It is better not too put flux on too thick and spread it out up the tube. This way there is more room and time to stop the runs. It is a common rookie mistake to put a bunch right by the joint but then it goes below the shoreline when it starts to melt where it does no good.

Students also have trouble brushing flux on so the right amount is left on the tube. It can't be brushed on, it needs to be rolled on. Brushing leaves too thin of a layer.

i keep a pound of Gasflux type G powder ready so it can be applied while the joint is hot. I also have a metal flat stick available to reposition melted flux to where I want it to be. If necessary I will dip that stick in the tub of flux and then heat it with my flame before applying it to a hot joint.

Brian25

For silver, I have been using 24 gauge (.6mm) silver wire. Would you mind letting us know what size silver you prefer?

JohnDThompson 

For brass, my vote is for Gasflux type B paste. Works really well, and comes off easily with hot water and a wire brush.

Doug Fattic 

I use 1/16" 56% silver when brazing lugs because it is conveniently available. Whether smaller diameter wire works as well depends on the coordination of the person brazing. Some decent percentage of my frame building class students have trouble having their hands do different motions at the same time. If they are moving the flame with their right hand, their left hand freezes and if they are moving their left hand to keep the silver in the right place as it melts, their right hand with the flame freezes (assuming they are right handed). The most successful brazers can move their hands independent of each other. So because smaller diameter silver requires more hand motion to keep the silver in the right place, it creates more problems for people with average or less hand coordination.

Here is an exercise to try to see how independent your hands can move. It is similar to pat your head while making circles around your tummy. Point a finger from your left and right hand towards each other. Now make a circle with one finger around the other. Once you get that circle started, do a circle in the opposite direction with the other finger. 90% of people can't do this at 1st. The 2 fingers will go in the same direction like pursuit cyclists on a track. If and when they can go in different directions their circles will be more like ovals. Try it and see. This lack of independent hand motion is at the foundation of problems learning to braze.

David Tollefson

Well, now I feel like a totally uncoordinated putz...

unterhausen

apparently, passing Doug's test isn't necessary to be facile at brazing, because I have never had any problem at all with independent hand movements. And I have always moved my torch around like a monkey with palsy. Would be difficult to braze if the filler rod was moving in concert.

I have always used Gasflux for bronze. I keep meaning to try the Cycles Designs stuff, and particularly the nickel silver flux. My LWS tried to tell me that silver flux was good for bronze, I was hard-pressed not to say something insulting. I'm sure there are lots of good bronze fluxes by other companies that we don't know about.

I'm pretty happy with the Harris silver fluxes. I use the black flux a lot, it is hard to see what you are doing, but it sticks around a long time. I usually use it on stainless. I need to get more white flux. With good heat control, silver flux will remain active for a very long time.

calstar 

Reading some older threads(like this one) and don't know how "rolling on" flux is done, anyone? Is it using a small spatula to spread it on? Using Gasflux B.

thanks, Brian

unterhausen

I don't know, I use a brush. It's easy to put it on too thin that way though

I just noticed that framebuilder supply sells Gasflux silver flux. I'll have to try it.

Doug Fattic 

I actually do know what I meant when I wrote that . I'll see if I can be more clear. I'm talking about how to unload the flux on a brush once it has been dipped into the jar of flux. A brushing motion (like painting something) tends to leave a thin layer on the surface of the work as the brush moves along. Instead, if you leave the bristles of the brush in one place and then rotate the handle (but don't otherwise move the brush), more flux will come off the bristles and stay in one place (since the brush isn't moving). This loads up flux in one spot. This is more useful for brass flux since it is much harder to remove and you don't want to randomly spread it around where it isn't needed. But this motion works for silver flux too when you want more in just one local area.

Andrew R Stewart 

I also will dab with a flux brush or the Al "tongue depressor" I use. Like Doug, I have a tub of type B flux in powder. I'll sprinkle some on the joint if I want more flux. Andy

JohnDThompson 

You can also just heat the rod up and stick it in the flux powder. It will come out coated with flux.

Andrew R Stewart 

I do that too. I also clean off my filler rod with steel wool before using. Andy

unterhausen

Didn't know type b came in powder. In the rare case I want more flux, I just brush some more on. It's wasteful, but some does get on there. Love the smell of burning horse hair from the brush.