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Soldering work

jrintaha

Senior Member
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283
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Helsinki, Finland
I have an old Conn 6D F/Bb French horn in need of a bit of soldering work. Two of the tuning slides have one of the solder joints, which connect the two pieces of tubing to the "U" bend at the end of the slide, broken off.

What kind of flux or solder wire or paste do you recommend for work like this? Is it soft solder or silver solder? If the latter is the case, I guess I can kiss the lacquer at the joint goodbye. I suppose some kind of paste would be the easiest since I can spread the right amount inside the tube (as the joint is on the inside, not the outside of the tube). Or what's the correct way to do it?
 

saxismyaxe

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Native of the Lone Star state.
I use a very fine silver solder, paste flux, and a micro butane torch to do such repairs. For larger areas, I use a Bernzomatic torch set to a lower, fine flame.
 

jbtsax

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Typically braces and tubing connections on brass instruments are soft soldered. Heating the part(s) to the temperatures required to "silver solder" (also called brazing) is just asking for trouble. Parts nearby can come unsoldered, lacquer can be burned, and you can even melt through the brass tube if it is thin enough.

There is a product that is called "low temp silver solder" which is really a lead solder with a bit of silver added. It is stronger than regular solder but melts at a much lower temperature than true silver solder. The most important part of soldering is the preparation work. All of the parts must be removed and spotlessly cleaned where they are to be joined. Then they are reassembled and clamped or wired into the correct position. Braces nearby are either wired in place or wrapped with a damp cloth so they do not come apart even when using soft solder. You don't want to make the job bigger than it already is.

If you have any reservations, it is best to let an experienced professional do the work---especially on good quality instruments. There are lots of junker horns on ebay and in pawn shops to practice on.
 
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Colin the Bear

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Burnley bb9 9dn
As said, cleanliness is the key. The flux keeps the metal from oxidising while the heat is applied and the solder will run wherever the flux is. Many soft solders come with the flux embedded in them. I like to use one without flux and add my own.

Clean all parts to a fine shine right before doing the job. Any oxidation will cause problems.

Depending on what job you're undertaking, parts can be tinned first. Which means cleaning, fluxing ,heating them up and applying a thin coat of solder and allowing to cool before clamping them.

I was taught that the clamping or wiring should be solid. No movement. This will give best results.

Allow parts to cool naturally, no blowing or quenching.

The thing to remember with soft solder is that it is a glue. The strength of a joint comes from the bonded surfaces not the surrounding area. If it's done right you can't see any excess around the parts.

The expression "less is more" is very apt when soldering. As is "practice makes perfect"

A handy tool to have is a solder sucker. A minature vacuum cleaner that can whisk away any excess while it's hot and before it runs where it's not wanted.
 

jrintaha

Senior Member
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283
Locality
Helsinki, Finland
Fortunately in this case it's the tuning slides that require work, and they can be pulled out of the main tubing of the instrument, so there's no risk of harming any other parts - other than the lacquer which is already half gone as this is an old instrument that's seen a lot of use.

I don't think I have fluxless solder, all the other stuff (except for silver solder) I have, as I used to do a fair bit of tinkering with electronics at home and at work. I fix worn guitar electronics etc. every now and then.

Will lead-free or leaded solder make a difference here? I usually don't use lead-free solder as it's generally more difficult to work with, at least with printed circuit boards.
 

kevgermany

ex Landrover Nut
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The flux in cored solder sold for electrical work isn't really suitable. Make sure you wash the flux off properly after soldering.. Lead shouldn't make a difference.

I'd follow Mike's suggestion to use silver solder. Much stronger. Comes in different melting points, so you can solder something, then use a lower melting point solder later and solder again without losing the original join. Can be problematic if you use low melting point and someone solders close to it with higher melting point solder - your bits fall off before their solder melts. :w00t:
 

gladsaxisme

Try Hard Die Hard
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manchester
Here is a strange thing that I don't understand about flux and solder and tallow and completely off subject but some may find interesting.I started my working life as an apprentice plumber so was involved in wiping joints on old lead piping, now when doing this you used a flux to keep the surfaces to be joined clean and enable the solder to adhere to the pipe you used a small square of heavy cloth called a moleskin to shape the hot solder around the pipe, this moleskin you kept liberally covered in tallow which stopped the hot solder from sticking to it whilst shaping the solder, now this is all well and good the flux helps adhesion the tallow stops it, then when watching a program on the tell about renovating properties there is a piece about leaded windows where they went into how they cut the glass to size with lead beading between the glass and then soldered the joints together for a rigid finish , now here comes the rub when they were doing this soldering they said that the secret was to rub tallow on the joints before soldering as this allows the solder to flow and fill the joints.Now this to me goes against everything I have learnt about soldering in that it should in fact stop any adhesion between the parts being joined and the solder but for some strange reason it apparently doesn't any of our technically minded know why this is ....John
 

griff136

Well-Known Member
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I live in Exmouth Devon.
I would use soft solder, make sure the parts fit together snugly and are clean, flux both parts, assemble, cut a small piece of solder and place it onto the join, add a little flux, heat and watch the solder run around the joint.

this method requires less "clean up" afterwards.

I would also assemble the tuning slide and place it into the instrument before you solder it together - that way it will fit! if you solder it off the instrument your asking for trouble.

once completed, give the tuning slide a good wash and scrub with an old toothbrush, followed by a good rinse to neutralise the acidity in the flux.

good luck
 

aldevis

Surrealist Contributor.
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when they were doing this soldering they said that the secret was to rub tallow on the joints before soldering as this allows the solder to flow and fill the joints.Now this to me goes against everything I have learnt about soldering in that it should in fact stop any adhesion between the parts being joined and the solder but for some strange reason it apparently doesn't any of our technically minded know why this is

Interesting! I guess they don't want adhesion to have the solder to flow.
On the other hand, telly is even less trustworthy that the interweb.
 

jbtsax

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Beautiful Springville, Utah USA
I agree completely with Griff. Silver solder is great for repairing broken keys and attaching key arms to hinge tubes and key cups. Soldering tuning slide tubes does not require this type of strength. Soft solder is more than adequate. Most failed solder joints are due to a poor soldering job in the first place at the factory---not because soft solder was used.

Flow temperatures of common "silver" solders
Extra easy.....1300° F - 705° C
Easy.............1325 °F - 719° C
Medium.........1390 °F - 755° C
Hard.............1475 °F - 802° C

Flow temperatures of common "soft" solders
Typical 60/40 tin/lead "soft" solder.......................411° F - 211° C
Stay Brite (low temp "silver bearing soft solder").....430° F - 222° C

As you can see there is a great difference between the two.
 
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Colin the Bear

Well-Known Member
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14,662
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Burnley bb9 9dn
Just to be completely nerdy about it I've looked up the melting point of brass.

900 to 940 °C, 1652 to 1724 °F,

Using a hard solder runs the risk of over heating and your instrument becoming a puddle on the workbench.
 

jbtsax

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Ok, I'm envious. How do you type the small raised circle to denote degrees? I'm not smart enough to no how two doo that. :confused:
 

Colin the Bear

Well-Known Member
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14,662
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Burnley bb9 9dn
Me neither. Copied and pasted it from elsewhere. It's something to do with superscript innit?
 

sushidushi

Mine's an espresso
Messages
651
I can do it on my mobile phone (that's a cell phone to jbtsax :p ).

Look: 100° :cool:

The phone is generally rather easier and more versatile than the computer.

サキソホーンが好きです。
 

saxismyaxe

Honored SOTW Ambassador
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556
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Native of the Lone Star state.
A wee bit shorter code on a PC based computers is pressing ALT + 248, which will also produce the symbol i.e. °.
 

johnboy

Senior Member
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1,179
Locality
ISLE OF WIGHT, UK
Use JB Weld, it will do the job perfectly! If you aren't happy with the results ( and I doubt that you won't be), no damage is done!!
I have used it for similar jobs and wouldn't use any other method.

John :):);}
 

saxismyaxe

Honored SOTW Ambassador
Messages
556
Locality
Native of the Lone Star state.
Use JB Weld, it will do the job perfectly! If you aren't happy with the results ( and I doubt that you won't be), no damage is done!!
I have used it for similar jobs and wouldn't use any other method.

John :):);}

The professional techs here are likely going to shudder at the thought of this. I used J&B back when I was just starting out repairing horns for myself, but most repair technicians don't advise using epoxy based products in this manner.

But now that I've brought that up we'll see what is said about it.;}
 
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