TIG welding aluminum tubing???

Discussion in 'Painting, Welding, Bending and Gas Tanks' started by Happy Valley, Jun 5, 2009.

  1. Happy Valley

    Happy Valley Active Member

    Any experience hereabouts with 7000 series and TIG repairs?
    Got a bike with a crack at the binder lugs on the the seattube that I'd hate to trash. I need to find out if it's doable, what kind or prep is necessary, which filler alloy to use, etc.
    Thanks for any help.
    Last edited: Jun 5, 2009

  2. layboomo

    layboomo New Member

  3. Happy Valley

    Happy Valley Active Member

    Yeah, thought of that but a seatpost clamp by itself isn't going to do it. I'd have to cut the tube off, drill a hole and saw the tube to the hole to create a new pinch slot. Problem, there is not enough tube.


    Weld it's gotta be I think.
  4. mlcorson

    mlcorson Member

    From experience, (I own a TIG machine) I can tell you welding aluminum requires a great deal of skill. I would only recommend a professional welder tackle the project. The strength of the weld should be as good as the original, or better. I would expect that the inside of the tube may pick up some oxidation from the welding process and perhaps a little overfill of the weld. You should be prepared to ream out the tube to the correct size to fit your seat post. Soldering or brazing this part will not be strong enough.
  5. Happy Valley

    Happy Valley Active Member

    Thanks Mike.
    I got some great feedback on a mountain biking forum I belong to from a bike welder in CA and it seems while a repair like this is doable it is somewhat involved. Not sure if anyone is interested but for welding 7000 series tubing he suggests the following.
    He uses an expanding, steel mandrel inserted into the seat tube to keep the flow of filler from entering the tube and to keep distortion to a minimum.
    He suggested I do the prep and bring it to the welder. Prep is removing the powdercoat from the area, grinding off the the binder lugs and slightly grooving the edges of the crack with a dremel.
    He was adamant enough about only using 5356 alloy filler rod for the TIG repair on 7005 aluminum that he is sending me a stick. He said the actual welding shot should be only about 10 to 15 seconds, not enough to cause annealing problems with the tube but I should let it relax for maybe a month.
    I saw some pics of his work that I won't eat up bandwidth here with but it is great.
  6. Mountainman

    Mountainman Active Member

    yes as mentioned before around here somewhere
    I was a pretty fair welder (((at one time)))

    then after many years away from the rod
    a buddy was making aluminum ((custom)) wheel chairs
    he was showing me the tricks needed to know so as to weld those THINGS

    it was what I would call dang dong hard to weld -- just perfect

    good advice -- find a true pro for this job !! ---------------------MM
  7. Axlerod

    Axlerod Member

    Weld Repair 7005 AL

    Yo HV: Good advice on the 5356 rod. I have made many simular repairs on bike frames & wheel chairs. Seat binders are highly stressed especially if seat post is extended so only a short part is inserted in frame. Your only ~ 100 mi from me. I'd be glad to weld it up. May we could ride too.
    Yours Truly Gt reynolds
  8. Happy Valley

    Happy Valley Active Member

    Axelrod 'sup?

    You do the TIG thing then mon?
    Wouldn't happen to have a 27.2mm steel mandrel kicking around would ya?
    lol :D

    I hear ya on the seat post, luckily the one I have is a long, 400mm and my setting leaves about 250mm in the tube. My other bud advised taking the binder lugs right off and then going with a seat tube clamp.

    Ironically this break didn't happen from riding stress but happened when this bike was moved in a truck and the load shifted. :confused:

    I shoot ya a PM, live free or die!
  9. Axlerod

    Axlerod Member


    HV, I have something better than a mandrel, a seat tube reamer. Gtr
  10. fetor56

    fetor56 Guest

    Sounds like you've got a pretty descent plan there & i'de be interested to see the weld after it's done.
  11. Mountainman

    Mountainman Active Member

    high tec tools being used here !!!

    sounds like a high tec THING tool -- as used by doctors at times also

    be careful with that THING !!!
  12. Happy Valley

    Happy Valley Active Member

    Really. That is tech and a great remedy to prevent seatpost from freezing I bet.

    No, no, MM....not that kind of THING.....unless your seatpost has been getting frozen. :devilish: