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  1. #1
    Join Date
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    melb
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    Default Which join method gives Strongest bond?

    Which of the following two welds give strongest bond/join for each of the 4 sides? Is there any real difference? Im about to make a rectangular tube out of 3mm sheet cut pieces with my little 130a arc welder, it has to be a specific size & there are no stock tubes close enough. It can't be welded inside the tube, but a few mm of sides isn't an issue. Thanks.

  2. #2
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    Hi, for max strength I would do similar to the first sketch but make the corners touch as in a V. You would gain max penetration, and have a neat finish on your welded tube. How long will the piece be? As welding it, could be a problem with distortion, if not done correctly.
    Kryn

  3. #3
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    Default

    +1 for the outside fillet if you want max strength. The catch is the metal at the root of the join will be quite thin (or open depending on fit-up), which might prove a challenge in avoiding blow-through.

  4. #4
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    As others have mentioned, outright strength is but one factor in choosing a joint. A bit more information about dimensions and actual application would assist in giving you the best answer. For exanple, your second joint design would excell if no internal penetration were allowed and would be the easiest to maintain dimensional tolerances while giving excellent strength, but it is a somewhat ugly and clunky looking joint in comparison to a well executed outside corner joint.

  5. #5
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    Only issue with trying to do the outside corner joint as being discussed above is that arc welding the 3mm material will test your skills. Depending on the application #1 or #2 from your drawing might actually be a better option just from a practicality/frustration point of view.
    How long does the tube need to be? and how straight does the tube need to be after you've finished welding it? Does the tube need to have continuously welded seams? If you haven't already - consider distortion and how you're going to keep it all straight.
    what dimensions are we talking about? Can you join 2 bits of angle iron and halve the amount of welding?
    Cheers
    - Mick

  6. #6
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    Jul 2013
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    from my experience the fillet weld would come out more consistent and possibly stronger.

    good little shelf to run a bead along : )

    my fillets always look better than flat /horizontals/ vertical butts
    Attached Images Attached Images

  7. #7
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    Aug 2013
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    melb
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    Default

    Quote Originally Posted by KBs PensNmore View Post
    Hi, for max strength I would do similar to the first sketch but make the corners touch as in a V. You would gain max penetration, and have a neat finish on your welded tube. How long will the piece be? As welding it, could be a problem with distortion, if not done correctly.
    Kryn
    Hi, its about a 25cm long. 6x3.5cm tube.



    As for what its for, hard to describe exactly, its a stand on a tripod holding some weight. As long as its strength is close to a stock 3mm tube.

  8. #8
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    Quote Originally Posted by Tegmark View Post
    Hi, its about a 25cm long. 6x3.5cm tube.



    As for what its for, hard to describe exactly, its a stand on a tripod holding some weight. As long as its strength is close to a stock 3mm tube.
    Any sliding fits? If not, then a simple corner to corner joint would be the go, provided your welding skills are up to it. Overlapping the root of the weld by a mm or so will help greatly.

  9. #9
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    My vote is for outside corner. But realistically any of those joints should be more than strong enough for a little fabbed tube like that. For neatness' sake if you don't want to try an outside corner I'd go with your original butt. You could even (part) bevel the join so that the weld sat more or less flush with the surface and get more strength too.

    I reckon if you tacked all over and then staggered a bunch of short welds well you could get by with minimal distortion.

    When you say "it has to be a specific size", is 65mm x 35mm tube too far removed from what you need?

  10. #10
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    Quote Originally Posted by Legion View Post
    My vote is for outside corner. But realistically any of those joints should be more than strong enough for a little fabbed tube like that. For neatness' sake if you don't want to try an outside corner I'd go with your original butt. You could even (part) bevel the join so that the weld sat more or less flush with the surface and get more strength too.

    I reckon if you tacked all over and then staggered a bunch of short welds well you could get by with minimal distortion.

    When you say "it has to be a specific size", is 65mm x 35mm tube too far removed from what you need?
    Hi, That size would work I guess. cheers

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