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I need an advice on silver-soldering of older style wire "rat cage" keyguard. It was broken at the point where 3 wires are joined together in the middle. Well, it's supposed to be one solid brace to which a side wire is attached (see the picture if it sounds confusing). However the solid wire broke in two at an attemt to straighten a badly smashed keyguard. Now it's three separate wires that meet in the middle.

I need to join all three pieces together with silver solder. I've got proper silver solder from Votaw. It flows at 652 deg.C. However I can't find proper silver solder flux locally.
What can I use for the job alternatively? Can I use a lower temperature paste flux?
I've got fittings flux. It is grey thick paste. It has no specs on it but it is probably not supposed to be used for high-temp silver soldering.
Anyway, it seems I'm in trouble.
View attachment 194425
 

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I need an advice on silver-soldering of older style wire "rat cage" keyguard. It was broken at the point where 3 wires are joined together in the middle. Well, it's supposed to be one solid brace to which a side wire is attached (see the picture if it sounds confusing). However the solid wire broke in two at an attemt to straighten a badly smashed keyguard. Now it's three separate wires that meet in the middle.

I need to join all three pieces together with silver solder. I've got proper silver solder from Votaw. It flows at 652 deg.C. However I can't find proper silver solder flux locally.
What can I use for the job alternatively? Can I use a lower temperature paste flux?
I've got fittings flux. It is grey thick paste. It has no specs on it but it is probably not supposed to be used for high-temp silver soldering.
Anyway, it seems I'm in trouble.
View attachment 194425
No, do not use regular plumbing flux for silver soldering. It will just scorch and make a mess at silver soldering temperatures. The standard is probably Harris Stay-Silv white flux which, if you can't find a local source, is easily available on line. I would try a supply house that serves HVAC repair people. Even a commercial plumbing supply house may have brazing supplies. Also, most cities of any decent size have a welders' supply house.
 

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Take it to someone that knows how to do the job. If you overheat the parts during the repair, the feet will come loose at the body.
 

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Take it to someone that knows how to do the job. If you overheat the parts during the repair, the feet will come loose at the body.
Yeah, I was assuming the OP knew how to do this and was just looking for flux.

Honestly, I have done several repairs to wire type keyguards; I have also added pieces to them on occasion when the original design didn't adequately keep my clothing from interfering. In all cases I have just soft soldered and have never had any issue. I would probably just make a little splint (a piece of thin brass sheet, wrapped around the broken bits) and soft solder it down, and declare victory.

By the way, any time I do any kind of soldering on the body of a horn, unless it's truly VERY FAR AWAY from any other soldered joints, I wire down everything that could even conceivably get too hot and shift. There is always the possibility that I could make a mistake and I do not want a moment's inattention to cause - say - the post that holds the whole lower stack - to fall off just because for a second there I lost focus. I would much rather wire everything down unnecessarily a hundred times, than not do so one time and have a small job inadvertently turn into a large job.
 

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One other thing that occurred to me is that if you do silver solder the break, first of all you may not be able to keep the soft soldered joints at the feet from coming loose no matter what you do; and then you are probably going to want to take the thing off the horn anyway to clean it up, much more of which is going to be required than with soft solder.
 

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Discussion Starter #6
One other thing that occurred to me is that if you do silver solder the break, first of all you may not be able to keep the soft soldered joints at the feet from coming loose no matter what you do; and then you are probably going to want to take the thing off the horn anyway to clean it up, much more of which is going to be required than with soft solder.
Thanks, I got your message.
I soft soldered the joint after soft soldering the feet to the body. It was a hard job for me. I didn't tell it but the feet were actually separated from the sax. I had to figure out the proper set angle for each one so they met exactly in the middle. Since the cage was initially badly smashed I had very hard time adjusting the parts back and forth and constantly making minute bending adjustments until they were more or less mating properly while taking the original position at the feet.
It would probably be easier to make a new cage for a nicer look and silver plate it but that's beyond my budget. When assembled and soldered together the cage feels solid. However I understand that the middle joint is the weakest point of the whole assembly now. It will not break though unless given a good kick. Better not.
 

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If you cannot access a proprietary silver-soldering flux then you could consider making your own. It is borax based.

And note that what silversmiths use for what they call silver-soldering, or silver brazing, may not be suitable, because they solder with rods (actually by cutting chips off a sheet) of a higher silver content and higher melting point in order to better match the colour of sterling silver.

Each flux is designed for a certain temperature range.

https://www.ehow.com/how_6006005_make-silver-soldering-flux.html
 

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Discussion Starter #8
Thanks Gordon, you are a little late but your advice is always appreciated.

What they sell over here for silver-soldering (brazing) is Borah (yes) and similar stuff in a dry flour (powder) form. I don't like the idea because what I see on YT is some kind of paste flux, not powder. I can't imagine how I can properly apply powder to such a joint I consider in this thread. The powder flux particles will simply fall down, they won't stay in the joint.

If you cannot access a proprietary silver-soldering flux then you could consider making your own. It is borax based.
...
https://www.ehow.com/how_6006005_make-silver-soldering-flux.html
 

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If you mix the powder with a little water you have paste.

I use powder. I heat the brazing rod until close to red hot, then dip it in the flux. A heap of powder sticks to the rod. When the work is hot, apply that to the work, and it sticks then flows on the work, at a temperature somewhat below that at which the rod melts.

If you use paste, you have the added complication of it bubbling all over the place and possibly dripping off while the water is boiling off.
 

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Discussion Starter #10
If you mix the powder with a little water you have paste.

I use powder. I heat the brazing rod until close to red hot, then dip it in the flux. A heap of powder sticks to the rod. When the work is hot, apply that to the work, and it sticks then flows on the work, at a temperature somewhat below that at which the rod melts.

If you use paste, you have the added complication of it bubbling all over the place and possibly dripping off while the water is boiling off.
Thank you Gordon. I'll give it a try. Need to practice this skill of course.
 
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