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Bending aluminum plate without cracking it?

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  • 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
    anneal it its the only way


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


    Stuart

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    • #3
      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

      Comment


      • #4
        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

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        • #5
          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

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          • #6
            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, 12:20 PM.

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            • #7
              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.
              Home, down in the valley behind the Red Angus
              Bad Decisions Make Good Stories​

              Location: British Columbia

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              • #8
                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

                Comment


                • #9
                  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.

                  Comment


                  • #10
                    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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                    • #11
                      The OP might want to consider getting some aluminum of known alloy.
                      Some 5052 or 3003 will bend with little problems.
                      3003 is used in heating and A/C applications.
                      Something to think about. Good luck.
                      JIM : You don't get a 2nd chance to make a 1st impression.

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                      • #12
                        Do the soap trick
                        or
                        Use a magic marker and lay down an inkline on the bend
                        or
                        Use a candle and smoke the bend area.

                        If you heat the bend area with a torch, the aluminum will not melt.
                        You heat until the smoked area or the markers ink starts to disappear.( This is the annealing temperature )
                        Let cool and then bend
                        It occurs around 500 degrees, and some paints can withstand such a temp !
                        you may also want to use an electric stove burner.

                        I would mark the bare side with a line of ink
                        Lay a steel plate on either side of the line about 1/4 to 3/8" apart and then
                        go down the 'slot" with a focused MAPP or acetylene torch flame.
                        This should happen fairly quickly with little effect on the rest of the piece
                        Green Bay, WI

                        Comment


                        • #13
                          Originally posted by KINGWELD
                          The OP might want to consider getting some aluminum of known alloy.
                          Some 5052 or 3003 will bend with little problems.
                          3003 is used in heating and A/C applications.
                          Something to think about. Good luck.
                          This Kingweld has the right Idea.

                          Comment


                          • #14
                            I say Rich wins.

                            Comment


                            • #15
                              You got one of these handy in your shop?

                              http://www.youtube.com/watch?v=ZhGHALB4_hQ
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                              Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

                              It is true, there is nothing free about freedom, don't be so quick to give it away.

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