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Thread: Bending aluminum to make an 85 deg. angle

  1. #1
    Join Date
    Aug 2013
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    Default Bending aluminum to make an 85 deg. angle

    Hello, I have a project where I need some angles on the outside of a box made of ABS plastic, used both as a drain tray for water (there is a bulkhead fitting with a hose for drainage) and access panel. The box wall's are sloped 5 deg. outward from 90, so I need 4x 85 deg. angles with about 1-1/2" legs and 1/2"-3/4" width. The angles will be fastened to the box with machine screws and nuts, and have captive thumbscrews on the other legs for easy removal of the panel.

    I would use steel but corrosion may be an issue because of the water and stainless is too expensive for the budget so I wanted to use aluminum.

    I know aluminum can fracture/weaken when bent so making the angles from flat stock will probably not work. But if I take a 90deg angle and just bend it 5 deg. will that be ok? The smallest thickness I can find commercially for aluminum angles is 1/16", but a machinist buddy of mine told me I should get thinner if possible like 1/32", but can't find it the places I have looked. Thanks for any input.

  2. #2
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    Some alloys tolerate bending better than others. Look up aluminum alloys in Mc Master Carr, it will give you some info as to the better choices. There is also a "grain" to consider, most will bend best across the grain than with it. Don't take this as gospel, just my own experience. Bob.

  3. #3
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    Aug 2013
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    Thank you for the tip, Bob. I was planning to get 6061 but McMaster lists its "workability/bendability" at Fair. Alloys 6063 and 2024 are also offered at 1/16" thick but have Fair bendability.

    I could get angles made of alloy 5086 which have Good bendability, but the min. thickness McMaster offers (on their website) on these angles is 1/4". I checked Grainger and MSC Direct also but couldn't find a thin 5086 angle. Maybe I'm looking at the wrong places?

    The bending tool I was planning to use has a maximum thickness of 60 thousandths of an inch, so just less than 1/16", I believe the machinist said. I don't think I'd have the strength to bend a 1/4" angle though anyway.

    Perhaps I could get a flat stock of alloy 1100 or 5052 which have "Excellent" bendability and just bend them 85 degrees? But these are also "Poor" in the machinability category. We will need to drill some clearance holes for 6-32 screws, but don't need to tap them.
    Last edited by John_29; 08-26-2013 at 09:36 PM. Reason: more info

  4. #4
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    3003 if you don't need high strength.
    I just need one more tool,just one!

  5. #5
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    It doesn't sound like you need much- stainless can't be that expensive if you buy is as sheet, then cut and bend it yourself. I much prefer it over aluminum, once I got used to not babying it when cutting and drilling. You won't get far cutting it with a carbon blade though-

  6. #6
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    Quote Originally Posted by wierdscience View Post
    3003 if you don't need high strength.
    That is the preferred alloy for metal shapers.

  7. #7
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    I have bent aluminum up to 1/8" thick successfully with primitive tools, like a vise and hammer. At the 1/8" thickness you will get some cracking at the surface, but it will be solid enough for most purposes. Even at 1/4" thick, I find the bent aluminum still useful for most purposes. At 1/16" thickness there are almost no noticeable problems.

    1/32" (0.031" or 0.040" sounds like it would be ideal for what you are doing. These thicknesses should bend OK in just about any alloy that you will find sheets sold in.

    I would not use preformed angle as it is extruded and the alloys they use tend to be harder (for strength?). I would expect it to crack more when bent, even by a small angle. When you try to change (lessen) the 90 degree angle of the extruded angle to 85 degrees, you will put a high amount of stress at the inside corner and it may crack there.

    For what you are doing you could probably buy an aluminum cookie sheet and cut that up and bend it.

    The trick is to use a bender that leaves a slight internal radius on the bend, perhaps 1/32". That will go a long way toward preventing any cracks. If you are using primitive methods, like a vise, then cut some lengths of steel angle to put in the jaws. ROUND the outside edge of these steel angles t provide that radius. I find that after clamping aluminum in a vise with these rounded jaws, a hammer (2 pound is nice) and a piece of hard wood is good for making the bend. Put the end grain of the wood against the point of bending and hit it with the hammer. Rotate the wood as the bend proceeds until you have the angle you want. This works well for me when I do not have access to a proper brake.
    Paul A.

    Make it fit.
    You can't win and there is a penalty for trying!

  8. #8
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    We bend aluminum all the time. If you're starting with sheet you can use--in order of softness and bendability--3003, 5052 or 5086. All three will bend fine, especially if you keep the bend radius up a bit. My choice would be 5052 as it's a good compromise between 3003 (which is really soft) and 5086 which is more than you need. If you're using flat bar then you should find 6063 alloy; it will form just fine.

    Where are you? (I don't understand why people don't put a location in their profile.) On the off chance that you're close I'd be happy to bend up a few pieces for you...
    Keith
    __________________________
    Just one project too many--that's what finally got him...

  9. #9
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    Draw a line with a felt tip pen (Sharpie) where you will bend the aluminum ( 6061 OK)
    Heat the sheet up with a propane torch along this line, and when the black mark disappears (about 475)
    You have annealed the aluminum and you can cold bend it with out cracking.
    Try to do this in under 24 hours, as Aluminum re-hardens it self in 30 days

    Rich

  10. #10

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    Make a form out of foam, and lay it up with fiberglass. Add reinforcement where/if necessary.

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