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How to flatten sheet metal?

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  • How to flatten sheet metal?

    In this particular case, SS. I squished it in the vise, but there is still about 10-20 thou of curvature that won't come out.

  • #2
    In order to straighten it, you have to bend it slightly beyond flat. Try putting a shim on each end of the piece on one side with another shim in the middle on the other side.
    Any products mentioned in my posts have been endorsed by their manufacturer.


    • #3
      SS is famous for having a LOT of spring back and needs to be bent well beyond the desired final shape.
      Free software for calculating bolt circles and similar: Click Here


      • #4
        You can "planish" it..... once sheet has a spring in it, you have ea heck of a time getting it out....

        You have to stress the material more than the residual stress to get rid of the bend. pressing it flat cannot do it, you can't exceeed the condition you want if you do that, but you HAVE to exceed it to un-bend it.

        One way used commercially is to press flat with platens having small dimples in them... these stress teh surface more than the original residual bend, and relieve it . You may see pieces done that way in products, looks like "diamond plate", but the "bumps" go IN.

        Another way is stretching....

        neither of those is home-shop-friendly

        You'll have to reverse-bend just enough... Watch out that you don't stretch spots, or you'll have "cans" (circular bumps like an oil can bottom) that you will never remove, because the metal is stretched relative to the metal around it..

        Keep eye on ball.
        Hashim Khan


        • #5
          English Wheel

          I understand than using an English Wheel is one way of
          getting a panel straight.

          Another is proper use use of a correctly shaped dolly
          and hammer.

          I have not done either. But have seen it on DVDs and read
          on posts on metal shaping type boards.



          • #6

            Originally posted by beanbag
            In this particular case, SS. I squished it in the vise, but there is still about 10-20 thou of curvature that won't come out.
            How about a little more informaiton regarding the size, alloy and thickness?


            • #7
              Sheet metal that won't flatten could have had an area of it expanded. If so it will not flatten by bending. If that is the case then this video may show how to use heat to flatten it:



              • #8
                Iv read about methods of using heat to remove expanded sections (outward dents basicly), by heating with a torch and then rapidly cooling with a damp rag.
                3M also puts out a type of disk designed for this.. I forget the name however.
                Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


                • #9
                  Originally posted by dp
                  If that is the case then this video may show how to use heat to flatten it:
                  apparently it'll also harden the steel


                  • #10
                    Flat steel plate and a nearly flat body hammer. Difficulty will depend on how big the part is and whether you can tolerate marks. With a smooth plate and hammer, marking will be minimal. I do this all the time with mild steel. Works with stainless too just won't move as easily.

                    Similar to but not the same as straightening bent nails with a hammer.


                    • #11
                      Don't know about flattening, but I found that sand- or bead blasting one side of sheet aluminum will put a bow in the metal, bowing toward the blasted side. Put a nice matte finish on the piece but it wasn't flat anymore.
                      Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                      ~Practitioner of the Electromechanical Arts~


                      • #12
                        Depends how thick it is, you can flatten thicker stuff of around 1/8 by rolling, less is harder, you need to temper roll then anneal, then flatten.
                        small bits can be done in a press.


                        • #13
                          one piece is .036 x 1 x .5. It got a bend in it from trying to cut it with a shear.

                          Some other pieces are .09 x 3 x 4.


                          • #14
                            If it is that small, you may be able to flatten it by placing it on a somewhat soft surface and running a roller over it. Soft surface = several layers of cloth on top of work bench. Or a thin sheet of rubber on work bench. You may have to experiment with the thickness of the soft material and the diameter of the roller.
                            Paul A.
                            SE Texas

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


                            • #15
                              Originally posted by Mcgyver
                              apparently it'll also harden the steel
                              That probably won't matter if it's a chip tray he's building. Even a chocolate chip tray