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  1. #1
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    Default silver soldering

    I know I should run a search, but my problem is fairly specific. Today I broke a brass fitting on my compressor. I thought I'd whip home and silver solder it. I've never done silver soldering before, but I assumed it's like lead soldering, where you heat up whatever is to be joined until the solder melts into the joint.

    So I set this brass fitting up by joining it in the vyce, and cleaned it, and applied some flux, and aimed a propane blowtorch at it for ages. The silver solder wouldn't met, so I aimed another one at the same spot and had two running at once and aimed at the one spot for a good ten minutes. The silver solder only just started to melt, but wouldn't stick to the brass. I gave up.

    What's going on?

  2. #2
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Rossluck View Post
    I know I should run a search, but my problem is fairly specific. Today I broke a brass fitting on my compressor. I thought I'd whip home and silver solder it. I've never done silver soldering before, but I assumed it's like lead soldering, where you heat up whatever is to be joined until the solder melts into the joint.

    So I set this brass fitting up by joining it in the vyce, and cleaned it, and applied some flux, and aimed a propane blowtorch at it for ages.
    I'm no pro but have done a bit successfully in my time with a MAPP torch so here's my two peneth worth. What do you mean by "cleaned", and what sort of flux did you use. It's very easy to overcook the flux and then the silver solder won't flow at all. Also did you really get it hot enough. I find that you get better heat control by using a small fire brick castle/surround to really get it hot enough and holding it in a vice can be just another way for the heat to be conducted away, sometimes using a small clamp or multi grips surrounded by a couple of fire bricks are better.

  3. #3
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    There are various formulations of hard solder and a lot don't contain silver at all. Used appropriately they have much superior strength to soft (lead based) solders. However they all have much higher melting points and hence need higher temperature torches, with a reasonable heat output.

    LPG/OXY and Acceteline/Oxy rigs with appropriate burners are needed, and operate at higher temperatures than an LPG free air torch.

  4. #4
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    I'm a relative newcomer to silversoldering and I was quite nervous after reading all the information I could lay my hands on describing how difficult it was. Most of the difficulties arise from not getting the piece hot enough. I'm fortunate in that I have a small oxy acetylene kit, and found it almost too easy! I make sure the edges to be joined are bright off a file and well coated with Comweld Silver Brazing Flux #2, then heat to a dull red heat and apply the rod. Bingo. If the flux gets spread too far, then the solder will flow everywhere, so wipe up any excess that is where you don't want the solder.
    Cheers
    Graeme

  5. #5
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    You will need to use an oxy setup.
    You will also need to use the correct solder which is available from any plumbers supply outlet. A stick of 5% SS is what you should use. %% will wet the joint easier than 2%. 15% will wet easier, but is not as strong, which is why I suggest using 5%.

    Use fluride flux, after cleaning the joint. Heat up the job to cherry red hot, but be careful not to heat too much more or the brass will collapse.

    Can you just replace the fitting? That course would be safer all round, considering the damaged fitting is under a decent ammount of pressure.

  6. #6
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    Silver Soldering is an art, requires clean joints and I mean clean, even a fingerprint can contaminate a joint.

    Correct flux must be used for brass

    Here's a link to some tips

    Another thing too is some of you have said to heat it up to cherry red, this is too hot. When the flux becomes opaque it is getting very close to the correct temperature.
    Cheers

    DJ


    ​ADMIN

  7. #7
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    Rossluck,
    Making some assumptions here, but if you are holding the part in the vise, close in its probably acting as a heatsink. Depending on the size of the part, silver soldering can be done with a gas torch, MAP or oxy, all will work. Oxy is the best as it heats the part quickly but as has been said you can get it too hot quickly. As others have said clean and correct flux into the joint, ss wicks well. If you need to hold something in the vise while soldering I have used a set of hard jaws liners made from jarrah, slow to burn.

  8. #8
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    Guys
    Here is some info I have put together in earlier posts.

    http://www.woodworkforums.ubeaut.com...=Silver+solder

    and

    http://www.woodworkforums.ubeaut.com...=Silver+solder

    Ross there is more technique to it than beginners realize.
    An Important thing is your heat source which should ideally be a pin point type as heat control is usually critical.

    The window in which "correct" temperature is arrived at is fairly narrow and that is what makes it difficult for some.
    The metal must be at the right temperature to take the silver deposit.Too cold it won't take,too hot it vaporises the liquid zinc out of the molten solder.

    Another point is to obtain equal temps in the pieces to be joined.Therefore one heats the big bit first and manipulates the torch so that the little bit does not overheat.

    To summarize
    • Spotlessly clean
    • Correct Temperature Window
    • Balance the Temperature of the joined Components


    Djstimber is spot on when he says the opaque colour is an indicator of temperature.

    Not knowing anything further it is difficult to advise past this point.


    Grahame

  9. #9
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    Thanks for the advice everyone. I basically chucked the towel in. I feel that I need an Oxy torch for the fairly hefty pieces I'm trying to solder. It all seemed so simple until I tried doing it (don't laugh Grahame).

    I'll try it again some day .....

  10. #10
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    Default Don't give up

    Ross ,

    No one is laughing believe me!

    There are some Non acetylene fueled torches available that will handle certain silver solder tasks.

    I don't enough about them so maybe a talk with a plumbers supply type guy may yield better results.

    There are no failures, just unsuccessful practice attempts.
    Never give up and never give in.

    Grahame

  11. #11
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    Another thing too is some of you have said to heat it up to cherry red, this is too hot.
    I disagree. Cherry colour is the correct indicator for 5% silver solder when soldering thicker materials such as the air fitting described. I use 5% frequently for plumbing work..... soldering breaches. 2% is the standard for copper to copper, but 5% is much better for the breaches because of the lower temp required when soldering the cast breach fittings, where hotter temps will collapse or blow open the fitting.

    Mabey you have cherry confused with the colour of boiled carrots, which is way too hot.

    Grahame describes the other issues well.... flames setting. I find that a too agressive falme doesn't work so well with brass. Less oxygen, with approx 3/4" blue point to the flame works well.

  12. #12
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    Ah this forum just amazes me type in the right required search and you'll find what your after.

    I have done Silver Soldering in past years far to many ago. Thought I still had some rod left LOML picked it and a new pot of GP Silver Brazing Flux up has 101 stamped on it Silver Rod is 15% the highest they had.

    Task at hand to Silver solder a Fishing pole ring to the top of a screw (its for a spinning wheel to allow fibre feed).

    Clean Clean clean got that!! Temp easy does it,

    My question I guess would be after fluxing do I lay a strip into the grove of the head of the screw heat and place the ring onto it ???

    OR

    place the ring on then heat and feed silver rod in???

    Ray

  13. #13
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    [QUOTE=
    My question I guess would be after fluxing do I lay a strip into the grove of the head of the screw heat and place the ring onto it ???

    OR

    place the ring on then heat and feed silver rod in???

    Ray[/QUOTE]

    Probably "place the ring on then heat and feed silver rod" but I'd assume that the screw and the ring are fairly small? How big is the stick of solder? If its not fine you will have to stick a bit of heat into it as well. The trick is to get the job hot enough to melt the solder rather than use the heat from the torch to melt the solder (if that makes sense) Once the job is hot enough the solder will flow into the joint. On something fine like I assume this job is you will have to be real careful with the heat that you don't over do it and melt the job. Also be careful that you don't run solder or flux into the thread.regardsbollie7

  14. #14
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    Thanks Bollie7

    Yep fine screw ring being attached is same as a loop on a fishing rod about 15mm dia dia of silver rod is 3mm head of screw about 4mm dia.

    A job for a day where steady hands keen eyes are needed.

  15. #15
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    Default

    have used MAPP gas torch for silver soldering brass fittings with good results no failures.

    Also silver soldered (with 45% silver sticks) bandsaw blades with propane. Only issue with it not working was not cleaning the blade enough.

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