Brazing v.s. silver solder / silver brazing

He has a bunch of amazing vids but his repair of a Sousaphone that looked like it been sat on by a sumo wrestler was like magic. He has quite the arsenal of cool tools too. But a whole lot of it is heating and annealing while working it just right. I wouldn’t say he make look easy, but it makes me want to mess with something like that. Of course only if it was a cheap no name junk destined for the dump……
 
He has a bunch of amazing vids but his repair of a Sousaphone that looked like it been sat on by a sumo wrestler was like magic. He has quite the arsenal of cool tools too. But a whole lot of it is heating and annealing while working it just right. I wouldn’t say he make look easy, but it makes me want to mess with something like that. Of course only if it was a cheap no name junk destined for the dump……
He’s amazing to watch!
Excellent craftsmanship
 
I've been subscribed to him for a long time. I don't watch often but it is so satisfying to watch him. I've played every major brasswind at some point so that makes it close to my heart.
 
Nutfarmer is so right! The hobby “silver soldering” kits that come with a small roll of solder and a little bottle of flux are no better than electronics solder. The flux is great but the solder has a melting point lower than electronics solder.
I use Harris Stay Silv 15
 
I use Harris Stay Silv 15
The liquidus point is way too high for model airplane use. It would anneal the music wire used for landing gear. I've found electronics solder combined with Harris Stay-Clean flux to be sufficiently strong since much of the strength is from binding the music wire pieces with bare copper wire before soldering.

In my volunteer work I have to braze bronze occasionally. I'm trying to convince them to let me use a brazing material that will wick with capillary action. Common brazing rod has a liquidus point very close to the bronze base metal which makes using it very stressful.
 
Last time I purchased silver solder, it was Brazetec 5507 55% 1mm rods. Wicked well too. Used the last of it about 2 months ago.

Had to braize a small extension on the rack for the lathe I am rebuilding a few days ago (just so it was done and ready to fit). Got that done without issue using C2 Silicon Bronze rod. Not sure it was the best rod to use, but it got the job done.

I do find the thinner rods pool and wick better than the larger rods, though that may just be my personal experience.
 
I build lugged bicycle frames as a hobby, using silver brazing rod to join the pieces. "Silver soldering" is sort of a misnomer, since most joining work using silver is actually "brazing." To my knowledge, silver soldering is more of a water pipe thing.

I use oxy-acetylene and, typically, 56% silver brazing rod. A paste flux is needed. Warm the joint to a dull red, then feed in the silver. It will suck into the joint, and you can further move the silver using the "follow the heat" methodology. Once you get the hang of it, it's great fun. I don't pretend to be a skilled welder by any means, but my bike frames have held up just fine over the years...

P1040129 by nessism, on Flickr
That's exactly the result I'm hoping to obtain.
 
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I strongly recommend the use of oxygen concentrators for brazing instead of bottled O2. Much safer, and other than the little bit of electricity they use, you have unlimited free O2 from then on. OK there is the initial cost of the concentrator (they're stupidly expensive when new, so buy used) and some maintenance costs if parts wear out — nothing on mine has yet. It cost $200 when I got it a few years ago and sometimes I see them even cheaper. They're medical devices so they tend to be well made. They're often available cheap because the patient died and the family just wants rid of it. Ignore the small/portable ones; they're expensive due to miniaturazation and ability to run off a battery, so the bigger 120V AC ones are cheaper.

Your competition, the other people likely to buy it before you get there, tends to be lampworkers or glass-blowers.

Mine puts out 5 liter per minute at somewhere upward of 90% pure O2. It keeps up with the torch tip sizes I tend to use, short of a rosebud.
10 l/min devices exist, but 5 l/min is much more common. 10 l/min ones tend to sell for lots more, like over double, so if you want to run a rosebud it's probably better to buy two 5 l/min units and run them in parallel with a Y hose adapter.

I use a standard 20 lb propane bottle, available at the grocery down the street. No more trips to the welding supply for bottled gas! And it shouldn't make your insurance company lose their excrement.

You do pretty much need propane-specific tips, because the flame detaches and blows out if you use acetylene tips. There are workarounds but the best tips I've found are from Paige tools. They make a pointy concentrated flame not too different from an O/A torch, and they never blow out. I use them with a Smith AW1, a classic "aircraft" style welding torch, and with a Meco Midget, but Paige makes adapters for several other torch types, like Victor, Harris, and clones thereof. No affiliation, just a satisfied customer.

Where I'm comin' from, like why should you believe me? Over 20 years of brazing every day (silver and brass) in a production environment. Not an expert, as in I didn't get an advanced degree in the science of it or anything, but 20 years of practice did give me some clue as to what's going on. Most of that time I used both acetylene and propane, like evey day, so I'm very familiar with the differences between them. Propane, with the right tips, now suffices for everything acetylene can do, short of gas-welding of steel, which I never do. (If I want to weld, I have TIG.) I now believe there's no good reason for anyone to use acetylene anymore, though YMMV.
I appreciate the well intended cautionary advice here on O2 bottles. Scares me and I will take the steps to mitigate any hazards (like storing them outside in the shade) Some years ago, a former chain smokin coworker who had retired for health reasons found himself on an 02 generator. While sitting in his living room (confined space) he continued to smoke until one day fate struck.
I don't think I disagreed with that, and I'm pretty sure I did say that I keep one for that reason. It is 1.03 times as hot after all..... The number of times that .03 difference actually makes a difference, it doesn't warrant paying three plus times as much for a fuel gas that you're already buying in (almost) the most expensive way possible.



A leaking fuel gas bottle (within reason) presents a fire hazard, as it could be lit on fire. A leaking oxygen bottle, that has the potential to make everything around it a fire hazard, including "flame proof" and "fire proof" things start to either spontaneously combust, or to "touch off" from normal operation, when otherwise that might not happen. A good whiff through the furnace, the clothes dryer, light switches... Everything becomes a risk. At lower quantities where we're talking about (rough math) 10 cubic feet in the bottle once it's released, a more likely scenerio is that it's a slow leak, where it'll raise the oxygen content in a full basement, under an average sized house, by a few percent. Because fire spread geometrically, that little "kick" at the beginning will happily take an unrelated fire from burning the shop, garage, barn, house down, to burning it down so fast that nobody can react. Insurance companies want nothing to do with it. (or they charge a premium). And regulatory bodies have their rules written in blood. (Even if it was the blood of stupid people). It raises costs in property losses and loss of life way, way more than fuel gasses do. (Like for like of course, comparing comparable volumes).
I appreciate the cautionary advice on O2 bottles & generators. Scares ther hell out of me. Steps will be taken to mitigate any hazards (like storing them outside in the shade) Some years ago, a former chain smokin coworker who had retired for health reasons found himself on an 02 generator. One day and while sitting in his living room (confined space) he lit up a cigarette............horrible outcome as described above. The internet is loaded with O2 related fires. Thanks for the reminder.
 
As @Ulma Doctor pointed out back in post #6 the difference between brazing and soldering is the temperature of 842°F (450°C). Some one at some point in time drew a line in the sand and picked this specific temperature to separate the 2 processes.

I do some of all (solder, Silver solder, brazing and silver brazing) and they each have their place.
One thing that applies to all of the non welding methods of joining metal is that there are a number of different alloys to choose from with one significant difference being the melting temperature. Yes there is also significant other characteristics like viscosity while molten, ideal joint clearance, strength, color..... Some times when you need to attach multiple parts to the same place you can put the first one on with a higher temp material and then add the second using a lower temp so that the first ones joint does not melt and fall off. You need to be able to control your heat for this to work. Like everything else just takes practice.
Almost all soldering and brazing requires the use of a flux that is correct for the alloy of the filler metal as well as the materials being joined.
The only one I know of off hand is a silver solder alloy that contains phosphorus and it used in HVAC for joining copper pipe/tube in the refrigeration section and is considered self fluxing so there is way less clean up required after the joint is made.

Electrical solder, sometimes called soft solder: is yup, for electronics. It is very soft so has the least strength, and melts at the lowest temperature. Not to say it has no structural strength it can and is often be used for many mechanical joints. Plumbers solder is considered a soft solder. Plumber solder will melt with a soldering iron but it would take a really big iron to heat the mass of a pipe joint so a torch is usually used, not for the temperature of the flame but for the speed of heating the joint.

Silver solder, sometimes referred to as silver bearing solder: The more silver it contains the higher the melting point, the harder the solder is and also the higher the strength of the joint. It is more electrically conductive that soft solder so is sometimes used in electronics where the resistance of the joint matters. Most silver bearing solder can still be melted with a soldering iron. Most of my silver soldered joints are made with an iron.

Silver brazing often incorrectly called silver soldering: It is used at temperatures higher that most any soldering iron can reach so is usually used with a torch of some kind depending on size of the joint and alloy chosen. There is a vast choice of alloys with all kinds of characteristics with all kinds of silver contents. You have to do some research to find which is best for your application. You can usually boil it down to one or 2 that will cover most of what you do as it can be a bit pricey.

Brazing or bronze brazing: This is the highest temp and will usually require an oxy/fuel torch to get hot enough. It is used at temps not real far from the melting point of steel.

For instance if you had to solder in a part that was heat treated you would not want to heat it to a dull red hot for bronze brazing as it would end up getting annealed in the process and re heat treating will melt the joint causing it to fall apart. in a case like this you might opt for a soft solder with a very low melting temp and try to design the joint with more area to get the strength needed. Soldering can also be used to join different materials where welding might be near impossible and a fastener is just not going to get the job done.

Each of these methods and materials have a range of temps that they work in. To hot is just as bad as not hot enough.
 
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Low priority, but I've been considering a small jewelers torch set. I don't have the space or need for a full size oxy / acetylene torch set.

For a small torch and small projects, not cutting is going oxy / propane likely to be regretted?

When I took a welding class we mostly did oxy / propane, only using acetylene for cutting.

Propane is much simpler for acquisition, storage and safety particularly if left sitting for extended periods.
 
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