Solder and flux.

[the elephant]

The micro butane silver solders small stuff very well, but takes more time. I usually silver-solder with my air/acetylene rig, but I used to own a large oxy/acetylene rig for that. It was very expensive, and I seldom used it, so I sold the torch and returned the tank to our local welding supply store. Pity, as it was a marvelous cutting torch, and I need one of those right now. <sigh>

What I want is a Goss GA-32 tip (.750" flame width) for an acetylene torch, for use on disassembly/reassembly work. I have used one of them in the past, and they are wonderful. They are like the torches used to braze tube seams at the factory, and they make quick work of evenly heating the large ferrules of a tuba for disassembly or reassembly work.

What I want and what I need, though, are not the same things, unfortunately, and one of these is a lot of money for how often it will get used…

https://imsbolt.com/goss-go-ga-32-tip/? ... agx4W0pZdi

[gocsick]

Bernzomatic Oxy-propane or Oxy-Mapp Pro is convenient but expensive. The small oxygen bottles run out really quickly and are about $15 at my local ace. It does give a nice concentrated high heat flame... so it worked really well for hard silver solder or other braze materials for things like bicycle frames... but realistically I didn't use mine very much. I actually traded my setup to a friend for a larger older American made bench vise.

[bloke]

Ace is expensive though. I've always thought of it as a hardware convenience store.

[ghmerrill]

Ace is expensive though. I've always thought of it as a hardware convenience store.

Yeah, but their fastener and small parts sections typically continue to contain stuff that just isn't there in other stores. Traditional local hardware stores have pretty much disappeared. There's one in Raleigh that I know continues to hang in there, but otherwise the best you can find is Ace and TruValue around here. Also, a lot of Ace stores have gone "fully suburban" and don't closely resemble real hardware stores. There used to be two good hardware stores in town here, but they've been gone for at least a couple of decades now.

A few years ago, years after the truly local hardware stores had disappeared, a new "Hardware General" (which is an "independently owned True Value dealer") opened up. In part they're making it because they immediately opened a UPS Store in one corner -- which does a huge amount of business owing to the USPS up the street becoming next to useless. Their small parts/fasteners section is actually quite good, though not in general as good as the nearest Ace, and oddly not as good in some areas as the local Lowes (if you're willing to buy quantities you don't really want in small plastic bags). The hardware situation has become dire, and I often find myself ordering stuff from Amazon that I'd much rather I could get locally.

[bloke]

I go to eBay to buy most specialty/goofball stuff.
By the time I might find myself able to leave here and GO to Ace (35 minutes r/t minimum) where they MIGHT have something (for a high-ass price), I can just get it from an eBay seller (phone's browser) and it's here (probably three days) by the time I would have EVENTUALLY gone to Ace to SEE IF they have what I need.

not eBay but "the internet"...
I found that one of these A/C systems needed a new A-coil...did research...discovered that I had to have THE ONE (Rheem, Fort Smith, AR) and no generic would do...

Sadly, it was $6XX PLUS TAX PLUS SHIPPING ($8XX), but I got it for c. the "licensed installer" price.
Then I called my (unlicensed) buddy (who has all the $h!t to do it - he got tired of being raped by all the HVAC peeps, so he went through all the training...he owns a bunch of rental properties), and I gave him $500 to help me cut out the old one and do all the jazz needed to hook in the new one...

...That's generally how I approach things (whereby I need BOTH specialty stuff PLUS expertise). I don't just pay retail+ and call the people who advertise on TV.

addendum:
All three of this place's HVAC units are the age of the house (26 years old), all have been repaired several times, and are all working A-OK.
oh yeah...My friend (who is now an HVAC expert)...I taught him how to silver-braze. LOL

[ghmerrill]

Is there a benefit to the acetylene?

Yes, depending on the size of what you're soldering and what type of solder you're using. The temperature of air-acetylene torches will often be twice that of air-propane torches, and air-propane produces a broader heat profile. This means that you can more quickly solder a joint (particularly a large or difficult joint much more quickly with the acetylene than with the propane -- which can avoid overheating problems (and possibly softening/loosening nearby joints, and effects on finish) by using the acetylene.

So, yeah, you can use the propane to solder joints. But the joints -- at least in some significant circumstances -- will come out better with the hotter gas that takes less time to do that job and so doesn't affect surrounding areas so much. And if you're using harder solder, the acetylene can make a significant difference as well. You can also braze effectively with acetylene while (at least in my experience) using propane for brazing is really iffy.

Whether there's an overall benefit to you for using acetylene vs. propane (which includes the difference in the cost of the tank, regulator, getting the tank filled, etc.) is another question.

[arpthark]

Is there a benefit to the acetylene?

Yes, depending on the size of what you're soldering and what type of solder you're using. The temperature of air-acetylene torches will often be twice that of air-propane torches, and air-propane produces a broader heat profile. This means that you can more quickly solder a joint (particularly a large or difficult joint much more quickly with the acetylene than with the propane -- which can avoid overheating problems (and possibly softening/loosening nearby joints, and effects on finish) by using the acetylene.

So, yeah, you can use the propane to solder joints. But the joints -- at least in some significant circumstances -- will come out better with the hotter gas that takes less time to do that job and so doesn't affect surrounding areas so much. And if you're using harder solder, the acetylene can make a significant difference as well. You can also braze effectively with acetylene while (at least in my experience) using propane for brazing is really iffy.

Whether there's an overall benefit to you for using acetylene vs. propane (which includes the difference in the cost of the tank, regulator, getting the tank filled, etc.) is another question.

I’ve brazed plenty of stuff with the propane torch, but I guess I’ve just learned to do it despite the issues you describe. It is definitely a big honkin’ flame. Most recently a handful of broken braces on an old Holton euph.

[ghmerrill]

I’ve brazed plenty of stuff with the propane torch, but I guess I’ve just learned to do it despite the issues you describe.

Yeah, I guess you can braze thin metal with a propane torch, though the acetylene would make it quicker. I was thinking more of brazing steel with typical brazing rod -- but I think that's not the kind of application you're interested in. I do have a little oxy-propane torch I've used for brazing, but I don't feel very comfortable with it. ... which reminds me that at some point there's a part on my tractor blade I need to try to braze and see how well that fixes it. But it may need welding. On the other hand, it's been like it is for ten years or more.

[bloke]

@arpthark

Your problem is that you don't understand the court's definition of "reasonable doubt". You only think you're using propane to silver braze. The other 11 people telling you that you're not doing it... You need to listen to them.

[gocsick]

Given the thermal conductivity of brass at ~ 110 W/m·K

According to my welding processes textbook here- Net Power Transferred: A propane torch can produce up to 2,000 Watts (6,700 BTU/hr) of raw chemical energy, the heat transfer efficiency into a flat plate is poor. Most of the heat escapes via bouncing exhaust gas, leaving only about 15% to 25% actually absorbed by the metal (300 to 500 Watts)

We need to get to about 677°C for silver solder to flow

That means there is a practical limit of about 1/8" thickness of brass that can be heated to brazing temps with a propane air torch. After that the rate at which heat is conducted away will exceed the rate at which is heat is supplied by the torch. That is assuming a large flat plate. Repairing braces which are not on the instrument or attaching rings to flanges etc.. you are effectively heating the whole thing and you can easily get it up to temp.

Flame temperature of propane and butane are about the same - 1,980°C (3,596°F). Butane has more chemcial engergy than propane but you run into the limits of an air torch... butane oxygen would burn significantly hotter than propane oxygen. Acetylene air gets you 2,200°C (3,990°F) versus 3,150°(5,700°F) for oxy acetylene.

[bloke]

Years ago, it became apparent that I needed a longer 3/4" threaded rod than I had.

I went to the scrap yard and found a 4 ft piece of that stuff that was remarkably straight and bought it for very little money.

I got home, drilled into the end of it, tapped up 1/2 x 13 thread into the hole that I drilled, screwed in a screw, silver brazed that screw into that hole, cleaned up the male threads down to the end of that rod with a die, and then cut off the bolt, leaving about 9/16 inch of threads.

That was a lot less expensive than ordering a rod like that from repair supply place (in addition to the shipping of would have cost).

Finally, I decided to put that rod between a double tree trunk and barely put a bend in it - so that I could put that rod and a vise with a threaded ball sort of tilting uphill to make up for downward pressure, but whatever on that detail.

I don't know what the point of this reply is, other than I used propane to braze that bolt into that 3/4 inch steel.

[ghmerrill]

@arpthark
You only think you're using propane to silver braze

I'm kind of inclined to put it that way myself, but to be fair, ...

The generally accepted meaning of welding is quite clear: it melts both workpieces and the filler, fusing them into a single solid piece upon cooling.

The generally accepted meaning of soldering is also clear: it melts only a filler metal without melting the base workpieces.

The generally accepted meaning of brazing is quite fuzzy: it melts only a filler metal (hmmm, like soldering), and without melting the base workpieces, but ...

And then what follows the "but ..." is vaguely worded except that it typically mentions a specific temperature boundary of 840 degrees F.

This leaves you in the situation where it's not totally unreasonable to view soldering as "low temperature brazing" or brazing as "high temperature soldering". But I think the real issue is the "filler material" (which is what the 840 deg F condition is really getting at).

There are "hard" silver "solders" that can still be melted with a common air propane torch (with a "working temperature" of 1,100 deg F to 1,250 deg F). And that -- technically -- would be brazing.

So you can silver braze with a propane torch. Whether you are brazing with a propane torch depends on your "brazing material".

[arpthark]

Okay, I assumed that, since we were talking about band instrument repair on the tuba forum, it would be understood that by “brazing” I meant silver brazing, or silver soldering, or hard soldering, or whatever you’d like to call it, on band instruments. :-)

[bloke]

I was just goofing around with rhetoric, because it appeared that that's what everyone else had decided to do, since the topic was talked out.

[catgrowlB]

I always thought of 'welding' as being utilized on aluminum, steel, and iron. Very high temperatures. Brazing being a brass paste that fuses two brass or copper-alloyed metals together into one. And 'solder' being a filler metal that melts at a lower temp than the two base metal pieces being joined together.

But Yamaha, for example, uses what they call a 'plasma weld' on the bells of their marching brass, and maybe the student and intermediate brass (since they are all made at the same facility). It is a high tech plasma weld that melts and fuses the very edges of the bell flare to the stem or stack. I've noticed the bell on the YSH-411 sousa is somewhat reminiscent of the old HN White sousa bells, where the bell elbow was brazed onto the bell flare and finished. On other sousas, the bell flare and elbow are soldered together with a ferrule joining them.

So I guess some of these terms are used a little differently sometimes

[bloke]

I've stuck a lot of things together - that are made of steel - with silver solder. I consider that to be "brazing", because I'm melting the silver solder and I'm not melting any steel. (How wrong am I to use that term in relation to these operations?)

[ghmerrill]

I've stuck a lot of things together - that are made of steel - with silver solder. I consider that to be "brazing", because I'm melting the silver solder and I'm not melting any steel

But why is that "brazing" rather than "soldering"? Especially since -- as you point out -- you did it with "solder".

I've stuck steel things (including parts of tractor implements) together with brass or bronze brazing rod. For years I've been thinking of doing that to an old cast iron school bell I've got that has a crack in it. Nobody would call that "soldering".

The whole soldering/brazing distinction is pretty arbitrary. It seems to get that way mostly at the point that you move from lead as the primary component for the joint to silver or some other harder metal. But it's a real slippery slope, and particularly when you start mixing different percentages of a harder metal in with your lead.

[gocsick]

I don't know what the point of this reply is, other than I used propane to braze that bolt into that 3/4 inch steel.

And that's the difference between engineering and practice... I calculated that it wouldn't work.. but was proven wrong.

[bloke]

If it's hard solder (where by the materials being stuck together have to get red hot) I believe I tend to call it brazing, and if the temperature required is only a few hundred degrees, I probably am going to call it soldering (even though a name for a type of hard solder is called silver solder.) it's pretty confusing because the soft solder (a few hundred degrees) that is now required for plumbing has no lead in it and actually has a little bit of silver in it. (Some people call that low temperature silver solder. I tend to call it plumbing solder.)

I've also lead soldered (a few hundred degrees, lead and tin) things together made of steel...
Those tended to be things that only had to be together for a few minutes.

so here are my personal made-up definitions:
- soldering is a few hundred degrees
- brazing is red hot
- welding is usually melting (liquefying) the materials themselves

I'm not claiming that these are correct, but simply how I use those words.

random info:
I just finished replacing an A-coil (evaporator coil) in a central air conditioning system. If you try to lead solder the pipes to your system's pipes, the freon will leak out. You have to silver braze the copper pipes. (Thankfully, I knew this.)

[gocsick]

The generally accepted meaning of soldering is also clear: it melts only a filler metal without melting the base workpieces.

The generally accepted meaning of brazing is quite fuzzy: it melts only a filler metal (hmmm, like soldering), and without melting the base workpieces, but ...

And then what follows the "but ..." is vaguely worded except that it typically mentions a specific temperature boundary of 840 degrees F.

The American Welding Society has very clear technical definitions of soldering and brazing. The 450C (840 F) designation had to due with melting points of metals. If you sort all the metals we know by meeting temperature you have a bunch of low melting temp metals like tin (232C) lead (327C) and Zn(420 C) then a big gap between this and higher melting point metals. The lowest of these higher melting point metals is aluminum which melts at 660C. 450C was chosen because it was a nice round number rthat was in between the melting points of Zn and Al. basically to distinguish solder as filler metal made from lower melting point metals and braze as filler metal made from this other group of higher melting point metals.

That is it.. from a metallurgical point of view there is absolutely no difference between soldering and brazing... You have a molten metal glue joint that gets it's strength from partially diffusing into the base metal. Formally... silver soldering is brazing and not soldering.