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Thread: Bending aluminum plate without cracking it?

  1. #1
    Join Date
    Apr 2003
    Location
    Ottawa Ontario Canada
    Posts
    167

    Default Bending aluminum plate without cracking it?

    Hello all,
    Is there a trick to bending 0.0625" thick aluminum plate without it cracking? I have a piece that is 5.5" long and 3.75" wide. I need to bend a 0.75" wide by 5.5" long tab to 45 degrees on each side of the 3.75" dimension. The plate is cracking every time I do this. Alloy and temper of the material is unknown. Would heating it up reduce its tendancy to crack? I have avoided doing this test as one side of the plate is painted.
    Thanks for any input you may have.
    Greg

  2. #2
    Join Date
    Mar 2005
    Location
    Tilchestune
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    199

    Default

    anneal it its the only way


    put some household soap on it and heat till the soap turns brown then let it cool


    Stuart

  3. #3
    Join Date
    Aug 2002
    Location
    Columbus, OH
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    136

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    There is a definate grain to sheet goods. Look closely at the surface, you'll see the grain.

    The best way to bend is perpendicular to the grain, so the grain lines cross the bend. In your case, you'd want the grain to run the 3.75" direction, so you can bend the edges against the grain.


    The other thing to look at is the radius of the bend. For most aluminum sheet, the inside radius of the bend should at least be equal to the sheet thickness. If the alloy is higher strength and/or heat treated, the radius goes up to double the thickness (or more). Bending along the grain makes these radii even more important. You may find that you have to go to a 1/4" radius to keep from cracking.

    Are you bending the sheet with sharp cornered vise jaws? If so, swap in a piece of wood with a slight radius on the corner and see how that works.
    Mike P
    1919 13" South Bend Lathe
    1942 Bridgeport M-head Mill

  4. #4
    MuellerNick Guest

    Default

    It depends on the alloy! If it is painted (not by you) on one side and is not a factory made part, then chances are very high that it is easy to bend.
    But! That depends on your bending radius and also it makes a difference wether you bend lengthwise to the rolling direction (cracks) or not.

    I'm too lazy to convert those odd inches to reasonable millimeters.


    Nick

  5. #5
    Join Date
    Sep 2004
    Location
    Brisbane, CA
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    442

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    Its probably 6061 or a similar alloy that has been heat treated. Heating it to anneal it will definitely make it bend more easily, but the problem is you have to get it pretty hot, 700 to 800 degrees F or so, if you do have a way to get it that hot the paint will have to come off first. The panel won't be as strong after this annealing.

    Paul T.
    www.power-t.com

  6. #6
    gary350 Guest

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    Aluminum melts at 659.6 degree F or 660 degrees. Do not heat it hotter than about 600 deg.

    Boiling point is 2327 degrees F.

    Pouring temperature in a foundry is about 1800 degrees F.

    Aluminum will not vaporize but aluminum dust is easily ignited and will explode.

    Aluminum reacts with HCl, H2SO4, KOH, NaOH.
    Last edited by gary350; 08-17-2010 at 01:20 PM.

  7. #7
    Join Date
    Oct 2005
    Location
    British Columbia
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    3,751

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    Quote Originally Posted by gary350
    Aluminum melts at 659.6 degree F or 660 degrees. Do not heat it hotter than about 600 deg.

    Boiling point is 2327 degrees F.

    Pouring temperature in a foundry is about 1800 degrees F.

    Aluminum will not vaporize but aluminum dust is easily ignited and will explode.

    Aluminum reacts with HCl, H2SO4, KOH, NaOH.


    That would be 660 Celsius, or about 1220 F.

  8. #8
    Join Date
    Jun 2010
    Posts
    133

    Smile bending

    basicly what all has said dito

    the min bend radii is approx. 1 to 1-1/2 x the thickness of the sheet.

    direction of grain flow is important.
    if it cracks increase the bend radii
    if it still cracks purchase aluminum that is in the annealed condition.
    then bend it.
    then have it aged at a heat treat facility.(minimum charge)
    clean it
    then paint it.

    leesr

  9. #9
    Join Date
    Dec 2008
    Posts
    362

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    If it's one of the stronger alloys, eg 2024, heating it up may cause a phenomena called 'inter granular corrosion'. The heat causes the alloyed metals to precipitate out within the structure, and it will eventually exfoliate, actually shed flakes of corroded aluminum. The bending radius is the trick.

    here's a link to the sheetmetal section of an aircraft repair manual:

    http://www.lotus-europa.com/manuals/...apter%2004.pdf

    scroll down to pg 14-15 & look for 'table 4-6' . This stuff is, of course related to aircraft repair, but it's good information.

  10. #10
    gary350 Guest

    Default

    Quote Originally Posted by Willy
    That would be 660 Celsius, or about 1220 F.

    I looked this up in the Merck Index it says, melting point 660 degree, boiling point 2327 degrees. Page 44 Ninth Edition.
    I assumed it was F because it does not say F or C.

    This link says, mp 660 deg C 1220 deg F.

    http://en.wikipedia.org/wiki/Aluminium

    Another link says 659.6 deg.

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