here are a few of my ( maybe ) stupid questions

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I am trying to silver solder a few boiler fittings. and things are not going to my liking. Before I continue I would like to get some advise.
I heat the whole up with 3 burners ( acetylene / oxy ) and propane to a temperature I think is right . Two small bushings went wel but he third not. I noticed that the flux for the third one was partly gone . Burned away maybe ?

Question :
===========
1 ) Can I ad flux while the boiler is hot ?
2 ) To fill a few suspected pinholes can I just fluxed again ( after cleaning of course ) and ad solder to it ?
3 ) What action do you guy's take to avoid by heating the boiler tube bushings and avoiding the already soldered in place fall out .

I thank Mr. Google with the spelling ( English is not my mother tongue ) so please have mercy.

And to those who respond a Big thank you in advance,

Gerard
 

ThomasSK

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1 ) Can I ad flux while the boiler is hot ?
Yes, you can add flux while the boiler is hot, but its more common to do it while its cold. If you use propper flux for your soldering method, it will not boil off too early. You will not have any good experience using plumbers flux for silver soldering, nor silver soldering flux for tin soldering.
2 ) To fill a few suspected pinholes can I just fluxed again ( after cleaning of course ) and ad solder to it ?
Yes, but you heating it up may cause more problems than leaving it alone. Make sure you have it well cleaned before trying to solder, cleanliness is the most important part.
3 ) What action do you guy's take to avoid by heating the boiler tube bushings and avoiding the already soldered in place fall out .
Try to avoid the solder being the only attachment method, pinning it or holding it together with bolts as well as solder help. Screen the part you have soldered, either with a plumbers mat or a piece of Kaowool. There is also different temperature solders available, going down to a melting point as low as 80C. This way you can stage the soldering if necessary.
 
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Thanks for the quick reply Thomas and advice .
For the record : I am not a newbie in regards to silver soldering but my experience in this matter is soldering nuts and bolts only.
I have a nice workshop , clean as a whistle and work clean also. The parts to be soldered are very clean and even cleaned and flux with rubbing alcohol before adding the torch to it.
I have to look in to your advice with regards to the flux with various melting points . Have no idee were to get that. I live in the boondox here in Canada with no specific knowledge around.

Have a nice weekend,

Gerard
 

John Antliff

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Hi Gerard - I have just finished making my first copper boiler - see
and I learnt several important lessons.
1) Make fittings/assemblies self supporting i.e. they hold together mechanically such that heat (expansion) will not loosen them. This allows you to apply flux and silver solder without disturbing the setup.
2) Use a high temperature flux i.e. Johnson Mathey Tenacity 5. The No. 1 reason for failing to get a good braze is overheating the flux. You need to heat the assembly evenly and slowly - I avoid using oxy/acetylene because it is too hot a flame, a propane/butane torch with a wide flared flame is better even if it takes a lot longer to get up to the required heat. This will avoid hot spots and the possibility that the flux will have exhausted it's oxide absorbing capability by the time the solder reaches it's melting temperature. Use Kaowool as an insulator to prevent loss of heat and cold drafts which will cause incomplete brazing. Remember, the silver solder moves towards the heat and in addition, gravity can be used to encourage the direction of flow!
3) Avoid exposing the silver solder to direct flame as this may very easily cause the silver solder to melt before the base metals are at the required brazing temperature. Exposing the silver solder to direct flame can cause the alloy to separate before brazing takes place - avoid it if at all possible!
4) Keep your joint tolerances/gaps to less than 5 thousandths of an inch as silver solder is not a good gap filler. Accurate joints are a must but do not expect the braze to flow through interference fits. In the case of a tube passing through a plate, ensure penetration by using a triangular file to put a couple of shallow grooves in the sides of the hole so that the solder can flow from one side to the other.
5) Existing silver solder joints will have a slightly higher re-melt temperature called it's solidus temperature and for 45% silver solder this is typically 50 C higher than at the first melt temperature. This allows you to revisit brazed joints to add or modify and if you avoid lesson 3) then you can use this fact to your advantage.
6) Cleanliness of mating surfaces is essential. Oil and grease in even small quantities will cause failure. Surface oxide is not so important to remove manually as the flux is designed to do this for you when the temperatures reach the required level. Different fluxes have different operating temperature ranges - the flux mentioned in 2) has a range of 600 - 900 C and most silver solders melt around 600 C and above depending on their silver content. So that flux is good for most silver solders you would normally use.
7) I use whenever possible, "pallets" to braze small items together. A pallet is a small piece of silver solder laid onto the surface of a pre-fluxed joint - just enough to fill the joint and then I heat the joint/assembly from below. Remember any copper in the joint will conduct away the heat far far faster than other metals and so the torch may need to be directed more onto the copper section than the other metal to ensure both parent metals reach the required brazing temperature AT THE SAME TIME.
8) Despite the clamour from the H&S fraternity these days about workplace safety, I always use a silver solder that contains Cadmium because in my opinion the "Cadmium Free" solders do not flow as well. I know it is not easy today to buy the cadmium silver solder but if you get the choice then if I was you I would opt for the cadmium one. I always ensure good ventilation whenever I am soldering whether it's got cadmium in it or not!
I hope this is useful information and that your brazing experiences improve accordingly.
 
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Dear John,

I owe you extensive salutes for the lessons ( I learned ) and the time you took to write this . You did a amazing job on your boiler.
Much appreciated here in the neck of the woods.

Sincerely yours,

Gerard Hengeveld
 

John Antliff

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Thanks Gerard. The photo below shows the components I made yesterday to make a double steam cock for my boiler. If you look carefully you will see that each joint has an embedded ferule so that the components can be pressed together just prior to silver soldering. Just to ensure that the assembly does not come apart I use a jubilee clip around the two cock bodies and hold the entire assembly vertical using the threaded portion that will be the connection to the boiler. In this situation I flux around each joint (it's not necessary to assemble the joints with flux in between but one can) and lay a small piece of silver solder on each joint. The bottom joint will have to have solder poked at it when the brazing temperature is reached.
Hope this gives you some ideas.

John A.
 

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foden

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Hi John
thanks for the terrific video . just one question did you drill and tap straight through the outer rapper to bolt on the fire door ?
 

John Antliff

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Hi Foden. No, I inserted 4 bronze bushes approximately 6mm thick by 6mm diameter into the shell which were blind tapped to about 3mm deep. These bushes were silver soldered in at the time the firehole ring outer flange was brazed. See in the video at 4:40 a photograph which shows the 4 tapped bronze inserts. I have read that others drill and tap the shell and rely on calking the threads but I was not happy with anything that penetrated the shell that was not brazed or had a considerable area of thread!
 

bikerbaker

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Just watched your video. Was impressed especially by the band. As I play soprano cornet, I would like to know the name of the band/orchestra.
 

Blogwitch

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I am not nit picking at all, just trying to get the terminology correct In John Antliff's very good write up above

"I use whenever possible, "pallets" to braze small items"

In fact "pallets" is incorrect, it should be "pallions".

Like John, I use Tenacity 5 or 4A, both are very good fluxes, designed mainly for joining stainless, but works fantastically on all materials you can normally silver solder.

For my pallions I tend to use very thin sheet easy flo silver solder to actually surround or put in between parts to be soldered, but for ease of use at times, I also use 0.5mm easy flo solder wire, wrapped in a coil around the part to be soldered.

Here are a few pics of what I mean


Rings of solder and flux

finish13.JPG


After heating up by playing torch on main body part

finish14.JPG


Again, wire coils used

finish15.JPG


Torch played onto largest part

finish16.JPG


All joints done to perfection by letting heat build up in main part

finish17.JPG


BTW, I NEVER feed the solder in by hand as it is too wastefull plus you tend to deplete the flux by heating it up for too long.


I hope this explains a few things

John
 
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dkwflight

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Hi

I don't think any one mentioned overheating.
If the parts are over heated the solder won't flow and stick.
I used to watch my Dad do solder pipe joints and the finish was a wipe down with a damp rag. I have seen small jobs wiped with w wet brush, same idea.
The fix for an over heated joint is to let is cool and clean to bright finish and start again
Good luck
Dennis
 

SmithDoor

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For my pumping work I use AC type silver solder it melts at higher temperature.
I also for silver solder for steel it melts at higher temperature than AC silver solder and is stronger

You will need acetylene.

Dave
 

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