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  1. #1
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    explain filet brazed

    Can someone please explain what filet brazed entitles and its benefits as it pertains to frame building?

  2. #2
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    Quote Originally Posted by thebronze
    Can someone please explain what filet brazed entitles and its benefits as it pertains to frame building?
    Fillet brazing is the method used to join STEEL tubes without lugs. Sometimes it's called "lugless" construction.

    Brass is the joining metal. (When using lugs, silver is the joining metal)

    The "fillet" refers to the radiused bronze material that the builder creates to smooth the transition between the tubes. The cleaner the fillet, the nicer the braze, and USUALLY the better the joint.

    As to advantages... well, I'm not gonna waste your time on this, I'd suggest you go read Don Ferris's web page, he's done more to flesh out the subject than I will. Basically, there are no real functional differences between lugged, lugless, and welded joints IF THEY ARE DONE CORRECTLY.

    Here's the Don Ferris (Anvil Bikeworks) web page discussion: 411 on Joining Methods

  3. #3
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    Idea! Also check out the framebuilders' list

    Quote Originally Posted by gonzostrike
    Fillet brazing is the method used to join STEEL tubes without lugs. Sometimes it's called "lugless" construction.

    Brass is the joining metal. (When using lugs, silver is the joining metal)

    The "fillet" refers to the radiused bronze material that the builder creates to smooth the transition between the tubes. The cleaner the fillet, the nicer the braze, and USUALLY the better the joint.

    As to advantages... well, I'm not gonna waste your time on this, I'd suggest you go read Don Ferris's web page, he's done more to flesh out the subject than I will. Basically, there are no real functional differences between lugged, lugless, and welded joints IF THEY ARE DONE CORRECTLY.

    Here's the Don Ferris (Anvil Bikeworks) web page discussion: 411 on Joining Methods
    I've been lurking on the framebuilders list for a while and learned a lot about joining methods and other framebuilding topics. Many well-known builders post regularly. Go to
    http://search.bikelist.org/ to read the archived posts.

    I'm waiting for my fillet-brazed Curtlo S3 road frame to be painted, now. I had Doug Curtis send it to me unpainted, and it was cool to be able to see his work. Maybe next year I'll have him build me a cross frame or something. His fillet brazed frames are less expensive than most builders' tig bikes; other builders usually charge extra for fillet brazed.

    Tig welding, fillet-brazing, and lugged construction are the most common joining methods, and all work well. Lugged is somewhat limiting as far as tube diameters and joint angles. Tig and fillet-brazing allow pretty much any configuration of tubes. Most anyone would say that fillet-brazed frames look better than tig, but they also require more finishing work. Fillet brazing requires the tubing to be heated to a lower temperature than tig, but that doesn't seem to matter with the newer steels, or with the tube wall thicknesses generally required for MTB frames.

    -David
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  4. #4
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    Quote Originally Posted by gonzostrike
    The "fillet" refers to the radiused bronze
    Thanks gonzo, I was hoping to get your opinion.
    I had always heard that brazing yielded better welds due to the lower materials putting less stress on the tubes. Interesting that with the new line of tubes they can handle higher temps without the haz. Can you elaborate on the "finishing" required with brazing?
    Is it just cleaning up the welds with a file?
    I would love to see some pics of the process.
    I've never welded anything in my life.

  5. #5
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    S3, eh David? oughta be nice 'n' light. don't go riding it on the Shore like Lance did in his commercial for Nike...

    thebronze,

    finish work can be emery cloth, files, die grinders, dynafiles, you name it. basically it's to smooth the radius of the fillets. there's no structural reason for the finish work. it's purely cosmetic. Cannondale's been doing finish work on its TIG welds for quite some time, and as far as I know they're the only company that does such finish work on welds.

    The hard part is working the abrasive into the small spaces, and keeping the radius consisitent. It's definitely artisan work - and some might even say artistic. It requires patience greater than many can muster. That's the primary reason for higher prices on fillet brazed frames, I'd bet.

    Also, truly fine detail work is required of those that do finish prep on lugged frames. The more elaborate the lugging, the more detailed the work.

    As to pictures of the process, I don't have any, but honestly, I don't think they'd illustrate the point very well.

  6. #6
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    Quote Originally Posted by thebronze
    Thanks gonzo, I was hoping to get your opinion.
    I had always heard that brazing yielded better welds due to the lower materials putting less stress on the tubes. Interesting that with the new line of tubes they can handle higher temps without the haz. Can you elaborate on the "finishing" required with brazing?
    Is it just cleaning up the welds with a file?
    I would love to see some pics of the process.
    I've never welded anything in my life.

    The newer series of air hardening tubes are primairily designed to cope with TIG welding. This methode creats a very concentrated spot of heat in the tubes. This means they can get the tubes with shorter butt lenghts (thus in some cases a bit lighter). This should be taken in mind when choosing material and construction methode. With fillet brazing you spread the heat more, more material will be heated and the stresses on the finall joint have a slight different pattern. If you braze with silver solder, you do not need as much heat as with 'traditional' brazing agents. The air hardening tubes need to get heated beyond a certain temperature, to get the 'air hardening' proces working. TIG welding triggers it, as well as the 'traditional' brazing methodes. Using silver alloyed brass will not work in this cases.

    In some cases silver solder ís the material to choose. For instance for soldering on braze ons (cable stops). You wont have to heat up the tubes as much on places were it is not wanted (half way a tube for instance).

    A just layed fillet brazing joint is rough and can be described as fairly big droplets of molten brass, stapled on top, just like a TIG weld, only bigger. This joint will be filed down and sanded to create a super smooth transition of the joined tubes. This is a very labour intensive job.

    Some steels are not at all suitable for fillet brazing. For instance, Dedacciai has (had) tube sets that have some sort of heat treatment that gives the tubes outedge a sort of layer hardening. If you fillet braze these tubes and sand them, you will take away some of this layer and signicantly weaken the tube. Dedacciai does not permite these tubes to be joint other than by TIG welding.

    These are some of the variables that should take in account for, when choosing your tube material and joining methode.

    There are some very nice examples of the fillet brazing process somewhere online. Have seen them and was sure I had them on my harddisk.. cannot find them now. Will continue my search for them. Pictures say more than words.


    JB
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    "...though a lot of marijuana was smoked in the early days of mountain bike development, not all of the riders were potsmoking hippies... " Frank J. Berto

    Who's that f#$king Doug Lexington?!

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