brass vs silver lugs

Discussion in 'General Bike Discussion' started by Sunlover, Jun 14, 2009.

  1. Sunlover

    Sunlover Guest

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    I have heard lots of debate about this topic, but I'm not exactly sure who is correct...

    Most people I've talked to feel brass brazing a lug is not the same quality as silver brazing a lug.

    So is this true? Does the higher temp. w/ brass damage the tubing, or is that just rumor, so to speak?

    I was hoping some of you pros could give some insight on whats really going on here.

    Thanks
     
  2. Bluedog

    Bluedog New Member

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    This is how I understand it. Most (if not all) brazed or welded joints fail outside the brazed area. The braze or weld almost never fails if it is done correctly. The reason for this is because the "mother" material is effected by the heat generated during the process, this is called the "heat effected area". Silver brazing happens at about 1250 degrees F., and brass brazing at about 1650 degrees F. Less heat means less effect. I have heard no convincing arguments that silver brazing is weaker than brass when used with a lug. Silver is a weaker material than brass but when used properly with a lug it is in my opinion stronger than a brass brazed joint. Done properly, both are superior methods of building a frame with steel.

    Hope this helps.
    Darrell
     

  3. Kurt

    Kurt Guest

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    Good info Darrell, he said it all for me!
     
  4. Cranky

    Cranky New Member

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    First of all, how are you defining "quality" of brazing in this context? It's important to get full penetration with the filler material, no matter what that material is. Most people who use silver probably use cadmium-free 56% which flows pretty well, although not as well as the old 45% with cadmium. Brass can also be made to flow, but it just takes greater heat control. Done properly, either one can make a sound, ("quality") robust joint.

    A lug that's been overfilled with brass is more difficult to clean up than one that's been overfilled with silver. Again, it's just a matter of heat control. The finished lugged joint need to be aesthetically pleasing ("quality").

    I've built a few frames using both brass and silver, and once they're painted, you can't tell one from the other.

    As far as damaging the tubing when using brass as opposed to silver, done properly, there's no reason it should happen. Many times the same tubesets that are used for lugged frames are used for brass brazed luggless frames.

    That being said, without good heat control you can cook the tubes and lugs while using silver and compromise the joint. It all comes down to technique and a sound brass or silver lugged joint will not fail before the tubing material will.

    Cranky
     
  5. tfbh

    tfbh New Member

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    The heat is in the torch, not the filler. The heat is controlled by the builder.
    It doesn't matter if the melting point of the filler is 500 of 1500c, if a joint is overcooked, its overcooked.
    Whether silver or brass is used, it will do nothing to prevent a poorly brazed join if the guy holding the torch lacks basic framebuilding skills. The use of silver is no guarantee of competence or quality.