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  1. #1
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    Default Help with Chair design

    I am a woodworker but would like to use metal for the legs for a project I am working on. I have attached a picture of the frame of the chair and the curve I would like to use for the legs/arms out of metal. How difficult would it be to bend 1/2 to 5/8 round metal stock to a curve like this? Would this be easier to do with flat stock?

    FYI - There will be supports running between each leg and under the chair. I realize it will need more support than I have drawn. However, I am more concerned with how easy it would be to do the bending on the leg/arms that I have drawn. This would not be a large production but just a handful as a prototype. I have access to a simple bender but I am not sure how many dyes are available or what this would take.
    Attached Images Attached Images

  2. #2
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    Hi and Welcome to a TOP FORUM.
    I think your design is great, my concern would be that the round tubing that you'd like to use is on the small side. I presume that it's tubing and not solid bar???
    To make a former, you'll need some ply to make the main shape, (the area inside the legs)
    some more ply for the lower support, you could use the offcuts to make them. Then you'll need some more to hold the tube in place. Unfortunately I'm not great on the computer, so I can't really draw how to do it.
    Wooden former.jpg
    https://www.youtube.com/watch?v=YvMoWcs1Fz4
    https://www.instructables.com/id/How-to-bend-tubing/

    Hope this helps you.
    Kryn
    To grow old is mandatory, growing up is optional.

  3. #3
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    You may have to heat your steel to red heat if you don't want to have to work too hard to bend the steel - I would think almost certainly for 5/8" bar.
    Flat or round probably does not make too much difference in the long run. For steel the same thickness, flat will be stronger but also harder to bend.

    Michael

  4. #4
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    For the question.

    1/2" = 12mm round bar doesn't require very much.
    It can even be bent with this kind of vise mounted bender.

    https://youtu.be/aHfRvcw_C1c


    It all depends from the desired bending radius. Larger radius doesn't require so much power to be made than tighter one.

  5. #5
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    Thanks for the help

    Sent from my SM-A520F using Tapatalk

  6. #6
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    Quote Originally Posted by hobbyhack View Post
    Thanks for the help

    Sent from my SM-A520F using Tapatalk
    And..

    For that kind of design, i would try this kind of way..


    Rod would be heated to red before bending, and right after the bends are made, cooled in mineral motor oil to harden the curve.

    Then re-heated to blue and cooled in water.

    This way you would get bends and hardening at the same time.

    If hardening cold formed curves, usually those tend to "open" a little when heating and curve changes its shape.
    That's why i would do bending rather red heated. ( in this kind of purpose and material thickness.

    Same if using flat bar. After hardening it would return its shape, even that it leans little in use.

    1/2" is little thin otherwise.. I think. But that's just what i think.

    16mm pipe with 2mm wall would be good choose, if little bigger diameter doesn't matter.

  7. #7
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by Tuomas Soikkeli View Post
    A Rod would be heated to red before bending, and right after the bends are made, cooled in mineral motor oil to harden the curve.
    Then re-heated to blue and cooled in water.
    This way you would get bends and hardening at the same time. .
    Just a reminder that this would only work for some higher carbon steels - not all steel is like this and so may not be able to be hardened this way.

  8. #8
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    Quote Originally Posted by BobL View Post
    Just a reminder that this would only work for some higher carbon steels - not all steel is like this and so may not be able to be hardened this way.
    Actually. Mild steel hardens in oil too. Only surface tought, but that still makes curve little stronger.
    It doesn't get really hard, but surface comes 30-40 % harder than it originally was.

    It sounds little complex. But, like i said, that was just my toughts.
    If heat is used for bending, i would use that way. Otherwise thicker material or different desing.

  9. #9
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    What a great and helpful forum! A friend is going to give me a basic welding intro in a few weeks. You have given me the comfort level to go ahead and build the chair portion to be ready to experiment with the arms and legs.

    The main chair frame will be covered with a thin, leather covered cushion layer. So the entire chair frame and cushion is less than 2" thick. I am trying to keep the legs as minimal asthetically as possible. I was planning on using rod or flat stock instead of tube or pipe for that reason.

    I like the current curves but I might bring that front arm more straight down to avoid the potential stress of having that tighter angle under the chair. I also might separate the legs from the arms and make the legs straight and directly under the rails of the chair.

    Thanks again for the advice! I will keep checking in if you have any more thoughts.

    Sent from my SM-A520F using Tapatalk

  10. #10
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    Hello and welcome,
    I'll leave the bending technique to others more knowledgeable, but I can say with almost 100% certainty that " solid bar will not be stiff enough for this application. Sit a 100kg (220lb) person in that chair and the legs will splay badly. ⅝" might be OK.

    Also, the armrests look very uncomfortable. Flat bar might improve the comfort somewhat.
    Chris

  11. #11
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    Thanks for the comments. There will be wood and leather pass over the armrests. This is just the frame. I haven't figured out supports yet but I was thinking stretchers connecting all 4 legs.

    Sent from my SM-A520F using Tapatalk

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