Brazing Stainless Lugs - Setup and Heating

[False Flats]

Hi Everyone,

Apologies if this has been discussed previously and I missed the thread when searching.

Looking for some input from those who have experience brazing stainless. I've built a dozen bikes over the past few years, but only one with stainless lugs. That build went ok, but I did struggle with heat control while brazing - things seemed to go from not ready to way too hot in an instant.

I was using Fillet Pro and Stainless Light flux, an imitation Victor 0 tip and the Oxy/Acetylene both at 5psi. Prior to fluxing, lugs were sanded with new 80 grit and wiped clean with isopropyl alcohol. Same process for the tubes. Went about heating things up the same way I would with a mild steel lug - medium/small neutral flame, repeated sequence of movements around the joint to heat while watching for flux to become glassy/transparent. Frame was brazed in a Bringheli Jig.

Any suggestions/improvements for setup and preheating would be greatly appreciated.
I'm looking for people's opinions on the best methods to prep the joint, get it up to temp and keep it there.

Just getting started on a new bike with stainless lugs using same filler/flux/torch. Happy to post photos as things progress if it helps move the discussion along.

Thanks in advance.

[e-RICHIE]

Have you tried lining up a row of SS lugs and some mitered pipes and brazing them, so as to develop a sense of what is happening and what is different with the material? I would suggest making the investment in parts, and use some off-cuts from pipe you already have. Also, I use at least a #2 tip on all my joints and would suggest that a #0 is too small. A cigarette lighter throws a bigger flame! PS You never want to do more than a small tack when the frame is fixture-ed. After that, braze it free hand without any clamps constricting its movement.

[Jonathan]

Were you really using fillet pro? Is that a typo?

[False Flats]

Richard - Thanks for the suggestions. I have some extra stainless lugs I'm not going to be using for this bike. I'll line them up and give it a try.

With regards to tacking, I'm assuming that I would run a sequence similar to what you would do for fillets, e.g. obtuse ctr, acute ctr, 3 o'clock, 9 o'clock?

Jonathan - Nope, not a typo. Did some practice joints beforehand and got things to flow ok. Realize that 56 Pro or similar would be more suitable. Will switch over to 56 Pro for future joints.

[e-RICHIE]

On the tacking - it all depends on what's being held, and where.
On the lugs - great to read.
Good luck there.
PS turn up the heat and show the fukcer who's boss.
The worse thing you can do is be timid.

[afwalker]

Is fillet pro not good for stainless? Maybe it won't flow far enough so it works for fillets so is 56 pro better?
I've only done a stainless crown on a fork with columbus max blades and the fillet pro worked fine, but I was using a #2 tip.
I had some questions on using SSL flux and fillet pro on those darn stainless water bottle bosses that I kept scorching, so I asked Wade at Cycledesign how to do better and here was his reply, maybe some of it pertains to the heat control you seek:
"
Hi Andy,

The issue is likely to be both your cleaning procedure, and torch technique.

Stainless Steel develops a thin, high temperature chromium oxide layer
on its surface. This layer prevents the filler from flowing.
It needs to be removed by physical means. Usually it is sanded off.
after the surface is mechanically abraded, it needs to be re-cleaned.
An alcohol, or acetone wipe usually works well.
Brazing should take place within a short time of cleaning, less than
an hour would be preferable. Clean both the inside and outside of the
braze area as best as possible.
Flux should be allowed to stay on the surface for a few minutes, to
allow it to chemically remove any remaining oxides.

The next problem is the shape of the boss. It sticks out. Any time
you have a surface that sticks out, it catches the heat of the flame.
Keep the tip of your torch so the heat angles away from the boss, not
towards it as would seen sensible.
With a neutral flame (not oxidizing, it will ruin everything), heat
the area around the boss. Stainless dissipates heat faster than
steel, so it takes a bit more heat.
More heat requires a larger tip, or flame, and not moving the torch in closer.

The flux has 5 stages- paste, fluffy, fluffy with dark speckles,
globby liquid, thin liquid. You are up to temperature when the flux
changes from globby liquid to thin liquid.
At this point the stainless should just start to develop a red tint.
To dark a red tint, and everything will burn. Once the flux goes
thin, place your filler on the intersection between the tube and boss.
Flick the flame onto the silver, and it should melt and flow around
the joint. You may need to quickly move the flame around the boss to
get silver flow and penetration all of the way around.


So in general, you are overheating the boss, when the tube is not yet
recepitive to the silver. Clean everything well, check your flame,
and heat the area around the braze first.

Brazing stainless is difficult, but not impossible.
You can get some inexpensive practice materials at the hardware store.
A few nuts and bolts are great to practice with.

Let me know how everything goes, and don't hesitate to send more
photos, or call.

Thanks,
Wade"

I was pretty impressed with his timely and helpful reply, I bet you can ask him directly and he'll help you out:)
cheers
andy

[Jonathan]

Set aside the fillet pro. It's the wrong stuff.

[Kumo Cycles]

Keep that torch moving!

Stainless will develop hot spots very quickly so you need to make sure you are moving the torch more than usual so you heat the whole piece evenly and not just cook one spot

[False Flats]

Andy, thanks for posting that email from Wade. I've had great support from Cycle Design with all the products I've ordered from them.

Wade got in touch with me after seeing this post and confirmed Jonathan's recommendation that Fillet Pro is not an optimal choice for stainless lugs.

I ordered some 56 Pro and System 48 to try out. Will post pics of practice joints when the stuff arrives.

[afwalker]

Ok, this is why vsalon rocks. I apparently haven't thought through why fillet pro is not good for lugs. Ok for braze-ons, so please share what Wade told you, and Jonathan and Eric know, but maybe me and others don't yet. 56 pro works best with stainless lugs because....
thanks
andy

[Will Neide]

......56 pro works best with stainless lugs because....
thanks
andy

As I'm sure you already know, it just flows better. Fillet pro will work, it's just "gummier" and less optimal. I've used Fillet Pro to do a bunch of sleeves and it worked fine. If I were doing a complete lugged bike, or did lugs all the time I would use 56.

[Jonathan]

56 pro works best with stainless lugs because....
thanks
andy

It flows. Do you remember when you started brazing and you'd heat too much tube up and 56 would just go everywhere? We see newbs just make a mess with the stuff. Fillet pro resists that but the with lugs you really want flow, especially if the experience is lacking. Add in the learning curve of stainless and I'd be very surprised if a noob could braze a safe lugged joint with fillet pro. It's why I thought there may have been a typo. I thought the name of the filler was all one needed to know.

[afwalker]

Thanks all, especially Rob for the thread. (see how without anonymity we all just get along;)
I really never messed with 56, just went straight to cycledesign products and now i know more!
So does everyone use 56 for lugs, stainless and steel?
I had a heck of a time with my last lugged steel S&S touring bike, took a lot of cleanup, hmmm maybe I should use 56!
cheers
andy

[cicli polito]

I personally use 50n for any/all stainless to stainless and stainless to non-stainless brazed joints on a bike frame (lugs, small fillets, couplers, braze-ons, etc) and believe several other builders do as well. In my experience, it flows great and wets onto the stainless "better-to-my-eye" on account of the high nickel content. I will say that 50n is very skill dependent though for stainless, as it requires a louder flame and a quicker brazing cycle.

For "regular" lugs, 56 for me.

[e-RICHIE]

I am 100 pecent 56Ag from Prince & Izant and wouldn't trade it for anything, and I have used most everything.
Big hot flame with a #2 Victor tip and more flux than ten of you use in a week.
Here: Brazing & Soldering Products | Prince & Izant Co. - Silver Braze 56

These shots are from the afternoon shift atmo:

[duanedr]

Richard,
What flux are you using?

[e-RICHIE]

Richard,
What flux are you using?

The white paste from The GasFlux Compnay atmo.

[Doug Fattic]

As I understand it, 50N silver (which Henry James sells and uses in the rings they supply with their dropouts) is designed to work better brazing stainless steel. Gasflux makes several white fluxes for brazing with silver. Type U is what Henry James sells. I asked Gasflux which of their fluxes would work best brazing stainless steel and they recommended their Type G flux. This is particularly true for beginners because its higher temperature range is less likely to burn off. Type G has a working temperature up to 1700 degrees F and Type U, 1600. Of course my favorite flux for any kind of silver brazing with any kind of steel is Stainless Light from Cycle Design. This is what I recommend my students use in class.

Gasflux silver fluxes have a tendency to run away as it is heated so some thought should be given to how to dry the flux so as much as possible stays on the joint. Rookies have a tendency to start heating at the top pointing the flame down - which is the opposite of what they should do. They also move around too fast and have the flame too far away giving the flux more runny time so it ends up on the floor. In my classes I put a drip plate on the ground to catch this run off. Cycle Design’s Stainless Light flux doesn’t run away nearly as easily. As it is heated it does have a tendency to flake off some before it starts to melt. Gasflux’s Type T flux acts more like Stainless Light and doesn’t run away like its cousins. How to dry flux to keep as much as possible on the joint is an art beginners must learn.

Most pros can use almost any kind of flux with a variety of brazing rods. Their experience allows them to keep the joint at just the right temperature window for their chosen brazing material. I can use just about anything on hand. Rookies however need all the help they can get (particularly with stainless) so getting the best flux and rod is important.

[EricKeller]

I like to use the Harris Stay Silv black flux for stainless or in other cases where I might take a long time to finish brazing. It will last forever at heat as long as you don't overheat it. It does have the disadvantage that it is harder to see through. I resolve to use the Cycle Design stainless flux, but inertia on things like this is hard to overcome.

I like to have a reserve of flux near the joint in case I manage to cook the flux. Doesn't happen often, but it's not really possible to add flux to a hot joint, so it's worth wasting a little flux

[duanedr]

Rookies however need all the help they can get ....

This pretty much sums up every question I ask...

In fact, I may start all of my posts with
"Since rookies need all the help then can get, how do you ...?"

Thanks again...