So what is Gasflux GF-72?

[JBanderob]

Hey guys,

I took a frame building course a few years back where we used GF-72 Nickel Silver for tacking tubes and an initial joint which was then covered with brass filler.

I really enjoyed working with nickel silver, but whenever I go to do an order from BFS or other places it is sold out, being in Canada I would rather not do an entire order just for some filler.

So my question to you guys, is what exactly it is? It is impossible to find anything with a similar make up from any of my usual brazing suppliers up here. I have recently read about Aufhauser A-56T, which doesnt look to be the same but the properties description sounds very much like it.

Hoping to get some more generic terms to search for, the welding suppliers don't seem to be too much help in finding out an alternative.

Thankyou for any help!

JB

[e-RICHIE]

With little experience past the course itself, I'd suggest not fixating on the rod alone, or itself, and simply get some brass. I'm assuming this is for lugless frame building. I've never heard of using two separate and different filler metals on the same task. I use the C-04® exclusively. For lugged joints, it's the BAg-7 alloys for me.

[JBanderob]

Thanks Richie,

I have been getting by with just generic brass rod for the last frames / forays into brazing, its more just trying to get my hands on it for the sake of having some around.

I was however able to get some good leads on it over the past couple hours of digging through some catalogues, it looks like it is the same as Harris Alloys 170 or Aufhauser C773. That being said none of the suppliers are willing to get less than 50 lbs of the stuff for me.

[e-RICHIE]

Thanks Richie,

I have been getting by with just generic brass rod for the last frames / forays into brazing, its more just trying to get my hands on it for the sake of having some around.

I was however able to get some good leads on it over the past couple hours of digging through some catalogues, it looks like it is the same as Harris Alloys 170 or Aufhauser C773. That being said none of the suppliers are willing to get less than 50 lbs of the stuff for me.

hmm must be a canada thing.

i've never bought 50 pounds of anything.
50 ounces of silver, yeah.

[rellis]

The only problem with the nickel silver is that some folks report developing an allergic reaction to the nickel in the filing and sanding finishing procedures.

I have used both the Gasflux and Cycle Design rods and flux. All worked as expected.

These suppliers will sell you a pound of bronze or flux.

https://www.bikefabsupply.com in Arizona carries Gasflux rod and flux (on vacation this week)

https://framebuildersupply.com/ in Portland carries the C-04 bronze and blux from Gasflux (also on vacation this week)

https://www.cycledesignusa.com/ Sells there own line of bronze, nickel silver and silver.

Ceeway in the UK also sells the Cycle Design line

[Doug Fattic]

One of my framebuilding colleagues tig tacked his frames with spots of steel rod before fillet brazing. The idea I suppose was that the frame would move less (or the spot would not break) when the brass was being applied.

[Eric Estlund]

GF-72 is their in house designation for RBCuZn-D, which is UNS C77300. Ask your local folk for those later terms. The gasflux bronze rod that everyone seems to love is RBCuZn-B, which is also high nickel bearing, and may be easier to find. Most major alloy suppiers will offer their version. It's a more widely used alloy in bikes than RBCuZn-D, and will work for everything save stainless. Nickel silver will work with some stainless, but both are picky with heat and flux, and most people have better success there with real silver bearing alloys.

In the past I've done fillet and lug tests with RBCuZn-B and -C back to back, and both worked fine for me. -C is regular low fuming broze, and some folks prefer it to sweat joints. As Richard mentioned, at this stage it's more about learning heat control than the particulars of the filler. Nickel Silver, Nickel Bronze and Low Fuming Bronze are all close enough in working temp and flow characteristics that, provided you have decent flux and heat control and are working on regular steel, can all be substituted with a moment to get a feel for the rod in hand. Buy a couple lbs of one, and get it worked out. Good luck!

[JBanderob]

When I was doing the aftermentioned course I tried this as well, by the time you got it all setup it was quicker just to tack with whatever you were going to be using to fillet braze.