Summary of Fluxes and Fillers for Brass and Silver Brazing

I compiled the following for my welding teacher here in Boone, NC, Steve Ward.  Steve's taught me a lot about all kinds of welding & fabrication.  He teaches a little brazing with flux-coated low-fuming bronze rods.  He's the kind of guy who's always looking for the best tools and supplies, so I compiled this summary of the brazing supplies I've used and heard of, so he can order some of the really nice stuff in the future.

These are but the humble opinions of one brazing nerd.  Please comment freely.

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Brass brazing flux:

- The blue flux I have is Gasflux brand Type B.  Excellent stuff.  I have bought small quantities (1-2 lbs) in the past year+ directly from Gasflux, but was told during my last order that that would no longer be possible and that I should order from an Airgas dealer in the future.  Details here: http://www.gasflux.com/paste.html

- If that's not an option, there is some even more obscure stuff called Brazage LFB Light flux, produced and sold by a bike framebuilding old-timer, Freddy Parr.  Freddy's stuff is well-regarded by some of the big names in the bike building world.  I've not used it, but I expect it is superb, based on his silver flux:  http://www.cycledesignusa.com/lfblight.htm

Brass brazing fillers:

I like 3/32" diameter best but 1/16" is fine for many things, and gives you more rods per lb.

- The stuff I like best if Gasflux C-04 nickel bronze.  This stuff flows much better than anything I've ever used, especially on stainless.  $9/lb for my last order, which was over a year ago.  Again, I've bought 1 or 2 lb quantities from Gasflux directly, but was directed to Airgas last time.  http://www.gasflux.com/brazing.html

- All-State 11 nickel silver.  I've used several pounds of this, unfortunately in 18" lengths.  They were samples that sat in the back room of a welding store in Richmond for years until I called up asking about brazing rod and someone offered me them for free.  They were flux-coated but the flux was stale so I soaked most of it off.  Very strong stuff, 85 kpsi, but a little less fluid than low-fuming bronze, and harder to file/machine post-braze. Makes small fillets.  http://www.esabna.com/euweb/as_handbook/596as5_2.htm Here it is for sale from Airgas: http://airgas.com/browse/productDetail.aspx?Category=10&product=ESA69063020

- Again, Freddy Parr offers a rod that is presumably excellent: http://www.cycledesignusa.com/brazage_lfb.htm

- Bare low-fuming bronze (LFB).  Any welding store should be able to order some.  Harris or whatever brand they have should be fine.  LFB may not be as consistent quality-wise or as quick to wet out as some of the higher-end stuff, but it gets the job done nicely in the right hands.  I've seen some beautiful fillets laid down with plain LFB.

Silver brazing flux:

- Hands-down the best I've ever used is Stainless Light from Freddy Parr.  Protects beautifully and washes off quickly.  This is the grey flux that inspired my friends & I to start mixing fluxes: http://www.cycledesignusa.com/stainlesslight.htm

- Harris Stay-Silv white flux and black flux.  These are the workhorses of silver brazing fluxes.  It's easier to see what's happening with the white flux, but the black flux remains effective at temperatures 200 F hotter, so is more tolerant of overheating. http://www.harrisproductsgroup.com/en/Products/Alloys/Brazing/Fluxes/Stay-Silv-White-Flux.aspx and http://www.harrisproductsgroup.com/en/Products/Alloys/Brazing/Fluxes/Stay-Silv-Black-Flux.aspx

- Gasflux Type U white flux and Type H black flux.  This is good stuff, but I haven't used it in a while.  From what I remember, the Gasflux washes off faster than the equivalent Harris, but it's also harder to buy.  http://www.gasflux.com/paste.html

- Mixing white and black flux is pretty straightforward.  Once you've added water to both your white and black fluxes to make them into pastes, spoon some of each into a baby food jar.  We've had good luck with something like 3 parts white to 1 part black, but it's not super critical.  Adding more black flux will make it more opaque but more resistant to higher temps.

Silver brazing fillers:
- 56% silver is the "runniest" and most expensive of the silver fillers mentioned here.  Requires tight fitups, but goes liquid at low temps.  It'll join steel to stainless if everything is squeaky clean and the heat is just right.  50N is a better choice for stainless if those conditions can't be met consistently.
- 50N has higher nickel content, which enables it to wet out onto stainless really well.  From what I remember it has about the same "runniness" as 45%.
- 45% works best with relatively loose fitups.  Brazing temps are slightly higher than 56%, and it's noticeably less runny.  Never tried it on stainless.
- I've only used Harris brand silver fillers, and always been satisfied.

A thought on safety

Tools
are like guns
and are ideally treated as such.

Now I'm talking about guns used in a certain way, like by a gun collector or a hunter. I'm not a big fan of guns, but if there must exist guns, I'd prefer they all get treated the way these guys treat their guns.
And I'm talking about tools like a plasma cutter, an oxy-acetylene torch, that kinda real powerful high-energy kinda tool. Well, all tools, but those especially.

That kinda tool can mess you up right good and real quick, if you don't handle it right. You could die because of being just a little bit wrong.
On the other hand, you treat the tool with respect, you take care of it, you can go your life using it every day and be just fine. In fact, there's lots of people doing it.

And--big bonus compared to guns--it's a lot less likely someone is going to pick up a plasma cutter and threaten your life with it. You control these tools your own damn self. Any problems, you usually got just yourself to blame.

This is scary to a lot of people. It's a big responsibility. It takes courage to know that this thing in your hand could hurt you real bad, and then to go ahead and use it anyways.

Shop Skills I Possess

Know-how and good sense are the shibboleths of the shop; they are inadequately conveyed in writing. But here goes.

Notes
- I'm a designer, prototyper, troubleshooter, and problem-solver.
- I love designing and fabricating one-off solutions to complex problems.
- I love teaching to interested students.
- I learn new skills quickly.
- Steel is my favorite material.  Aluminum, copper, brass, and hardwoods are nice, too.  I know little about plastics and composites.

Introductory Level
Small gas engine maintenance and repair
Automobile maintenance
Oxy-acetylene welding
CNC machining

Some Experience
Stick welding
Advanced machining (e.g. lathe-cut threads, high-precision work)
Sheet metal work (bending brake, shear)
Blacksmithing/forging steel
Epoxies (wood, metal, plastics)
Tube bending, especially thin-wall steel
Fine woodworking
Table saw (wood)
Wood and metal finishing

Lots of Experience
TIG welding
MIG welding
Brazing steel, with brass or silver filler
Copper pipe (cutting, sweating, brazing to steel)
Basic machining (turning and milling)
Drilling and tapping
Horizontal and vertical band saws (wood and metal)
Power sanders, grinders, chop saws, miter saws
Precision layout and measurement to .001 inch or .1 mm
Bicycle maintenance, repair, assembly
Bondo (applying, shaping)
AutoCAD (2D)
AutoCAD Inventor (parametric solid modeling)

Relevant Coursework:
Welding Techniques, Caldwell Community College, Boone, NC
Computer-Aided Drafting II, J. Sargent Reynolds Community College, Richmond, VA
Small Gasoline Engines, J. Sargent Reynolds Community College, Richmond, VA
Machine Shop Practices, John Tyler Community College, Richmond, VA

Machine Blueprint Reading, John Tyler Community College, Richmond, VA
Intro to Digital Drafting, Corcoran College of Art + Design, Washington, DC
Furniture Fundamentals, Corcoran College of Art + Design, Washington, DC

Relevant Work History
Graduate Assistant, Department of Technology, Appalachian State University, Boone, NC
Volunteer, Appropriate Infrastructure Development Group, Quetzaltenango, Guatemala
Technical Consultant, MARZ Industries, Richmond, VA
Journeyman Framebuilder, Tektonics Design Group, Richmond, VA
Student Shop Foreman, Machine Shop, School of Engineering, Virginia Commonwealth University, Richmond, VA
President and Co-Founder, Bike Fabricators at VCU, Richmond, VA
Shop Assistant, CNK Machine Manufacturing, Richmond, VA
Intern, Fabrication and Model Shop units, Office of Exhibits Central, Smithsonian Institution, Washington, DC
Lab Technician, Sculpture Department, Corcoran College of Art + Design, Washington, DC

Why the Shop

I spend a lot of time in a shop. I consider myself a shop person.  But most of the people in my life are not shop people, with only a few exceptions.

I often think about how to relate to non-shop people about the shop. "Why do you spend so much damn time down there?", they ask. "You always come home filthy." "What's so exciting about screw threading of all things?"  "What's the point of endlessly tinkering?"

It's especially difficult to discuss, perhaps, because the shop is not generally a place I go to accomplish a specific thing. I might go there to work on one problem but end up working on the shop itself. Sometimes the tool I need is broken, so I spend an afternoon making a new one, or fixing the old one. The work is often non-linear; I work on what needs to be worked on.

Not many places are ambiguous in this way. A kitchen is for cooking; a classroom is for learning; a theater is for seeing shows. A shop can be for doing anything, and its purpose can change momentarily.  A shop is for working on things, but that includes the shop itself and everything in it.

Working in a shop can have a wonderfully self-reflexive feeling, of constantly re-examining the tools, the process, the shop--even the people in the shop, including yourself.

A shop is a place where all variables are in flux. A mill, for example, is so versatile that it could be used to produce a copy of itself*. When you're standing in front of a mill, the question is not "What is possible?" but now "What do I want to do?".
In the shop, the only limitation is you. It's up to you to decide what deserves your time and effort. It's a nice metaphor for growing up.

But why machine tools and screw threads and such?  What dispassionate things to study and to have strong opinions about.

There's a feeling I get after I've been using a lathe for a while. I don't mean any lathe, I mean one specific lathe, because each one is a little different. When I first start using it, I take my time flipping every lever, making sure I don't make some catastrophic mistake. But over time the lathe and I come to an understanding. I learn her idiosyncrasies, and she lets me know when I'm pushing her too far. After a few weeks, I'm flipping levers left and right. I know every control without taking an eye off the workpiece. I like to use the words sensual and intimate in describing this feeling. It's a little like raising a dog.

My old machining teacher liked to refer to using a machine tool like driving a car, e.g. "How do I drive this daggone mill?".  For my part I think of it more like flying an airplane.  It's more complicated than driving a car, but the possibilities are greater.  Pilots are an elite, sometimes cocky bunch, much like machinists.  Among those in the know, what they do inspires awe.

Machine tools are anything but cold. It honors me to include myself in a tradition that bears the mark of so many great people, including a few of my ancestors. It brings me closer to a history I don't fully understand yet. It gives me something in common with everyone who's ever made something well.

It's by learning to apply tools well that we have advanced our human condition. Our survival depends on knowing how to manipulate our world with tools, and on continuing to pass on that knowledge.

And by the way:
Besides being essential to everything we do, screw threads are, in one sense, a culmination of all human experiences. Their development is the result of many tiny decisions made by many people over many centuries. The most recent decisions were based on older decisions, which were based on yet older ones. That legacy goes back to the earliest humans. And without exaggerating, it can be said that screw threading standards have made fortunes and lost them.

In fact, every modern tool is a permutation of some simple, primitive tool. It was when we first started using these simple tools that we became technological--that we began a period of ever-increasing improvement upon what came before.

*This is theoretically true, but it's not something that happens often. It would require almost fantastical quantities of metal and time.  Some of the tools used to make machine tools are friggin' huge.

On Grinder Safety

Here was the most interesting part of my day (so far):

I work as a 'Student Shop Foreman' in the machine shop of an engineering school.
A guy came in today who's been in pretty regularly in the few weeks I've been working here. He cut up some stainless sheet on the vertical band saw. No big deal.
Then he wanted to use the grinder to remove the burrs.
The only utility grinder we have is monstrous, like 12" wheels.
Sure, I say, just be careful 'cuz that thing can take your hand off.
So I walk away. And before he's even really gotten started, the plate gets snagged and wedges between the grinder support and the grinding wheel. Turned out the gap was set too big. Coulda happened to anybody.
All of us who had been chatting gathered around to watch the grinder spin down, partly out of curiosity, partly out of concern that the situation not get any more interesting.
And then he shows me his hand, which is bleeding from the thumb, cut pretty deep, but thankfully it was the burr that got him, not the grinding wheel.
First aid kit. Alochol wipes, sanitizing spray, gauze, bandages, anitbiotic ointment. Sink. Wash for a few minutes.
He's telling me about how he hates blood and needles and going to the doctor. He's pale in the face. Got him sitting down. He wants the trash can next to him. Turns down water but I send for some anyways.
At this point I'm running worst-case scenarios through my head while I keep pressure on his thumb. It's not a life-threatening cut, but if he passes out, things get more complicated. He could go into shock, and I don't remember exactly how to deal with shock (a blanket over them and call for an ambo maybe).
He ralphs into the trash for a couple minutes, while I change the gauze and maintain pressure. Then he picks his head up, color in his face now, he's back amongst the living, 100% fine.
That's one way to learn how to use a grinder.

Be careful, folks. Mind the grinder gap.

Shop Class Journalism

In last month's WIRED magazine, Clive Thompson reminds us why shop class is important, especially for "my" generation.

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Shop Class as Soulcraft is the tentative title of a forthcoming book by Matthew B. Crawford.
In the article upon which it is based, published in The New Atlantis two years ago, Crawford brings together a lot of the themes I've been blogging about here for the past year.

[A]n engineering culture has developed in recent years in which the object is to “hide the works,” rendering the artifacts we use unintelligible to direct inspection. Lift the hood on some cars now (especially German ones), and the engine appears a bit like the shimmering, featureless obelisk that so enthralled the cavemen in the opening scene of the movie 2001: A Space Odyssey. Essentially, there is another hood under the hood. This creeping concealedness takes various forms. The fasteners holding small appliances together now often require esoteric screwdrivers not commonly available, apparently to prevent the curious or the angry from interrogating the innards. By way of contrast, older readers will recall that until recent decades, Sears catalogues included blown-up parts diagrams and conceptual schematics for all appliances and many other mechanical goods. It was simply taken for granted that such information would be demanded by the consumer.

This guy gets it!

Bonus points awarded because Crawford used to run a motorcycle shop here in Richmond, VA--and because he turned me on to local machine tool dealer Dempsey and Co.