Silver solder for custom bike frames?
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  1. #1
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    Silver solder for custom bike frames?

    Just wondering why silver solder - as opposed to, say, bronze brazing rod - is used for joining tubular frame pieces (socket joints) in expensive custom bicycle frames. Can someone tell me why this is preferred?

  2. #2
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    Re: Silver solder for custom bike frames?

    Silver solder like regular tin/led solder will migrate or suck into the joint but is stronger. Brazing is like putty and will only lie on the outside and is hard to get a clean look. Another advantage is silver solder comes in strips and can be inserted into the bore or wrapped around the tube and put together. Then after the bike is put together and aligned all they need to do is heat the joints or place in an oven at the proper temp. No real "Welding Skill Involved"
    Mike

  3. #3
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    Re: Silver solder for custom bike frames?

    don't know. I want want my frame welded.
    Tough as nails and damn near as smart

  4. #4
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    Re: Silver solder for custom bike frames?

    Quote Originally Posted by Machinereaper View Post
    Silver solder like regular tin/led solder will migrate or suck into the joint but is stronger. Brazing is like putty and will only lie on the outside and is hard to get a clean look. Another advantage is silver solder comes in strips and can be inserted into the bore or wrapped around the tube and put together. Then after the bike is put together and aligned all they need to do is heat the joints or place in an oven at the proper temp. No real "Welding Skill Involved"
    Mike
    Brazing does use capallary (sp) action like soldering and also can be done in a furnace.
    Tough as nails and damn near as smart

  5. #5
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    Re: Silver solder for custom bike frames?

    Does the silver solder flow at a lower temp?

  6. #6
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    Re: Silver solder for custom bike frames?

    Brazing does have some capallary action but requires more heat depending on the alloy. Silver soldering is actually considered brazing. Sorry I did not clarify

  7. #7
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    Re: Silver solder for custom bike frames?

    Quote Originally Posted by flatbustedbroke View Post
    Does the silver solder flow at a lower temp?
    yes it does
    Tough as nails and damn near as smart

  8. #8
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    Re: Silver solder for custom bike frames?

    So depending on the alloy could that make a difference?

  9. #9
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    Re: Silver solder for custom bike frames?

    Quote Originally Posted by flatbustedbroke View Post
    So depending on the alloy could that make a difference?
    Alloys and materials in general make a differance

  10. #10
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    Re: Silver solder for custom bike frames?

    Guess what I should have posted was With the use of alloys(chrome molly) in bike frames wouldn't the lower heat needed for silver solder be an asset?

  11. #11
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    Re: Silver solder for custom bike frames?

    Quote Originally Posted by flatbustedbroke View Post
    Guess what I should have posted was With the use of alloys(chrome molly) in bike frames wouldn't the lower heat needed for silver solder be an asset?
    I see where you're going but don't buy it. Aircraft parts like engine baskets are welded chrome moly, nobody with a license would dream of soldering or brazing them. Sure there are bike frames made from more exotic metals but they don't silver solder. if it is a heat treated or normalized frame that well with in the size range of heat treating or normalizing the whole frame after welding. Don't know why someone would heat treat a bike frame.
    Tough as nails and damn near as smart

  12. #12
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    Re: Silver solder for custom bike frames?

    AFAIK silver solder first started being used with Reynolds 753 tubing which is the 'heat treated' version of 531 (both are a manganese moly alloy). While 531 was typically brazed (lugged cappilary joints or fillet brazed/bronze welded) the temperatures involved would destroy the properties of 753. Because 753 was so temperature sensitive Reynolds would only sell this tubing to builders after completion of a test coupon

    Given the cost of silver solder many builders only use it when they have to but as high end lugged road frames have an 'artwork' factor to them, silver solder can be good marketing.

    Many of the alloys used for tubing these days are designed to be welded or brazed so issues like those with 753 don't really exist any more, stainless fittings (dropouts etc) are becoming more popular though...

    Some more on the subject... http://desperadocycles.com/The_Lowdown_On_Tubing/About_Steel_Tubing_page4.htm

  13. #13
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    Re: Silver solder for custom bike frames?

    From my understanding - and I'm not a pro - brazed joints made with bronze rod are stronger than silver-soldered ("hard" solder). Is that right?

    But I take it that a good hard-soldered socket-type joint in a bike frame can be very strong (or at least, strong enough for the task).

    Anybody care to discuss strength of hard-soldered joints?

  14. #14
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    Re: Silver solder for custom bike frames?

    Just to be clear, are you talking about the brazed-lug style construction method? If so then both silver and copper based alloys have been used for years with that process. Brazed-lug is one of the oldest methods of joining thin wall tubing for structures, it pre-dates fusion welding. In the early years of the teens, people were having trouble fusion welding some of the "new" high strength steels due to what would be later learned was poorly controlled sulphur levels. However brazing worked well, so they seemed to use that process on motorcycles, bicycles, and aircraft to about 1918-1920 until the issues with the metals were resolved for fusion welding. Bicycle companies seemed to carry this method on for many years after, along with fillet brazing ( schwinn ), perhaps just as tradition or ease of production assembly in jigs. Its light, proven, and very traditional and professional. In fact it actually allows a slightly lighter frame over fusion welding, as the requirements for wall thickness decrease due to lower specific loading it the areas of conection. It shows up quite a bit in modern car construction, however its more stampings brazed together rather than tube. 45% silver brazing alloy is a common choice.

  15. #15
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    Re: Silver solder for custom bike frames?

    Quote Originally Posted by makoman1860 View Post
    Just to be clear, are you talking about the brazed-lug style construction method?
    Yeah. What's called 'slip,' 'flow' or lugged' brazing.

  16. #16
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    Re: Silver solder for custom bike frames?

    And still curious to learn: anyone know the strength of silver-soldered joints, as compared with say brass/bronze brazing or welding?

  17. #17
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    Re: Silver solder for custom bike frames?

    I would say that with a bicycle frame's sweat soldered tube and socket joints, braze and silver would show no difference in strength. Without checking, it seems like the yield of both solders is in the 30,000 PSI range. That number might include the Denrep 50% safety factor.

    My gut says that for a joint without any other mechanical connection, braze would be superior to silver.

    Good Luck
    Last edited by denrep; 07-15-2009 at 11:25 AM.

  18. #18
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    Re: Silver solder for custom bike frames?

    Ed Conley
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  19. #19
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    Re: Silver solder for custom bike frames?

    Quote Originally Posted by denrep View Post
    I would say that with a bicycle frame's sweat soldered tube and socket joints, braze and silver would show no difference in strength. Without checking, it seems like the yield of both solders is in the 30,000 PSI range. That number might include the Denrep 50% safety factor.

    My gut says that for a joint without any other mechanical connection, braze would be superior to silver.

    Good Luck
    Years ago, running a bike shop in MA and building custom frames, we preferred silver solder over braze. Having the solder flow into the lug 'filled' the gap between the OD of the tube and the ID of the lug, making a joint with less flex. A brazed connection creates a hinge point at the outer edges of the lug sockets. If there is any gap between the tube and lug, the constant flex will eventuallly fatigue the joint.

    That said, I rode and raced a Raleigh International w/ a brazed 731 frame for over 10 years with no problems.

    My personal favorite was to build 'Vitus' frame sets that were pressed and glued together with a type of crazy glue. As the glue set up, the frame would actualy squeak.
    There are no small projects

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