Sweat Soldering Help

jbtsax

jbtsax

Distinguished Member
Distinguished Member
Does anyone have any tips or tricks to "sweat solder" parts together. Specifically my challenge is to solder posts, neckstrap rings, guard feet, and thumb hooks to silver instruments and have it look professional.

When feeding the solder from outside the part, it is very easy to have the solder flow to the exposed areas around the part. This is why I am hoping to get good at sweat soldering.

What happens when I try to sweat solder putting a flattened piece of solder and flux under the part, the solder refuses to flow and leaves gaps around the edge of the part. Any advice would be appreciated.
 
John,

I do limited soldering on horns (I do mostly clarinet work 'ya know) but the occasional sax or brass horn comes in. Plus I used to do plumbing and this is a basic plumbing technique.

Of course practice makes perfect.

Thus, I recommend practice on pieces of brass, etc with specific sized items to emulate a thumbhook base, etc

you can buy flat sheets of brass/copper at a hardware or hobby store, or instrument supplier (for patchwork).

One of the keys is maintaining the heat of the pieces and the flame has to be pulled away as the pressure can easily push the solder away. You don't want to heat it too much as that bubbles the flux too quickly.

Thus the temperature is key, which I why I recommend practicing on plumbing first or flat sheets first

Once you start you can quickly "zap" the piece from above with the heat to maintain the temp to add add'l solder.

If you need to adjust something you have to just "zap" it until you can adjust it. Don't just hold the flame against it.

This will teach you the "feel" of heat and solder flow on something before you try it on an instrument. And you can try it again and again and again.

The heat temps are higher but the technique takes some getting used to. With plumbing it is normally deeper with sockets, thus using flat/curved plates is more ideal.

once you master the technique then it is more easily transferrable to the sax

Also, do not use a thick gauge of solder, I've always worked best with thin gauge solder (except on plumbing where alot of quantity sweating in is needed).

I'll check too on the silver/lead content of the solder as that can make it easier too, but also the softer the easier the flow but it can also break off easier (though many simply don't have issues).

My hardest part of it is keeping the post base against the horn while I do all of this. I used bases that have those tweezer clamps and such but can't ever seem to get it 100% correct without manual fixes.

I've tried the super flat piece of solder under the foot and have come across the same problem.

My solution was to hammer the piece thinner and larger.
But then I've good at just sweating it in too. It can (and will) create some lacquer damage. I haven't had any problem with nickel, but haven't tried it on a silverplated horn.

I should also add that I've found It's easier with the right type of flame. Don't use a flame that is weak. It needs a strong focused, adjustable nozzled flame.
 
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Try fluxing and getting solder to flow on the entire surface of the post or foot first. Then flux that solder and the body location, position, and heat. Obviously, it is of paramount importance that nothing moves once the solder melts.
 
MartinMods said:
Try fluxing and getting solder to flow on the entire surface of the post or foot first. Then flux that solder and the body location, position, and heat. Obviously, it is of paramount importance that nothing moves once the solder melts.
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That's how I learned it too. It pays to pre-heat, flux and tin the body's soldering spot as as well before applying the post.

Prior to fluxing and tinning, make sure the post's "foot plate" matches the shape of the mating part *perfectly*. Then you need actually very little solder and what's on either thusly primed part is sufficient.
 
That's all well and good, but...

...when I was occasionally occupied with doing plumbing work that involved heat-related processes (like sweating, or (shudder) the dreaded process of 'lead wiping'), the single most important factor that I found to merit attention was the one that addressed all of these: practice.

Like any skill only occasionally used, getting yourself up to speed on sweat soldering best responds to repetition. You're dealing with fire, with alignment, with a material that doesn't (in many cases) want to adhere without special preparation, and is relatively demanding in prior surface and contour preparation. Mistakes can not only cost you your time; they can cost you money, and ruin a costly instrument. In the worst form with heat related stuff, they can cost you physical pain - ask me how I know...

Push comes to shove, you are going to end up making mistakes, so it's best to make them on a practice piece before moving on to that Mark VI.

This line of thought set me off on an extended essay on "the one perfect thing". I'll recast it, work it up over the next week or so, and then post it in the Music Business area.
 
tictactux said:
That's how I learned it too. It pays to pre-heat, flux and tin the body's soldering spot as as well before applying the post.
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This seems to be the most difficult part. Solder LOVES silver plated surfaces. Is there a way to keep the solder confined to the "footprint" on the body when tinning this side?

Groovekiller said:
I can't believe you have trouble doing this. Practice.
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You must be misoverestimating my soldering skills. :) Actually I am getting quite good at soldering parts back on to lacquered instruments, since the solder doesn't wander like it does on silver plate.
 
jbtsax said:
This seems to be the most difficult part. Solder LOVES silver plated surfaces. Is there a way to keep the solder confined to the "footprint" on the body when tinning this side?
...
You must be misoverestimating my soldering skills. :) Actually I am getting quite good at soldering parts back on to lacquered instruments, since the solder doesn't wander like it does on silver plate.
Click to expand...
Actually, you have just answered your own question: You can lacquer the surrounding area, for instance with nail varnish which is comparably easy to remove after the job. (there's special solder-stop varnish sold in electronics shops.) I'm not sure how much heat it can stand, so a bit of experimenting might be necessary. If lacquer doesn't work, a bit of plaster (used for filling screw holes in walls, comes pre-mixed in squeeze tubes) should.
 
Doesn't the whiteout "thinner" (or whatever solvent is used) damage the laquer?

It's been a while, but I think that the "thinner" (which was hard to find, the last time I mounted a search for it in local office supply outlets) is some form of dry cleaning fluid.
 
SOTW member Chu-Jerry posted some great examples of his restoration work and his soldering technique was impressive.

Here's the thread showing off one of his projects:
http://www.saxontheweb.net/vbulletin/showthread.php?63147-soldering-a-silver-plated-sax

And at the bottom of this thread, he explains his technique:

http://forum.saxontheweb.net/showthread.php?63147-soldering-a-silver-plated-sax

Here's a picture of a couple of posts that he re-soldered:

solderpost.jpg
 
Beautiful horn! Did he do the gold plating and/or bead blasting as well?
 
He touched up the plating on the neck and around the strap ring, but the rest is original. He did bead blast it as well. It has signs of dent removal and wear, but very nice for its age, especially for a bari.
 
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