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Need to flatten thinwall pipe ends for structural use. Ideas on methods?

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  • Need to flatten thinwall pipe ends for structural use. Ideas on methods?

    I am looking for the best way to flatten the end of thin wall pipe such as "conduit", (EMT). I need initially to flatten it so that the flat is in line not with the center, but to the OD, so that if laid down on a flat surface, the flat would be touching the surface along with the OD of the pipe.

    I figured to make a die to accomplish that, since I have had recurring needs for it. I will also want one that puts the flat on-center.

    Anyone have good tips on the method or the die?
    1601 2137 5683 1002 1437

    Keep eye on ball.
    Hashim Khan

    If you look closely at a digital signal, you find out it is really analog......

  • #2
    I built a lot of pipe panels with the ends flattened. I just made a tall jaw for a heavy duty vise I had. That put the flat on one side. For the centered flats I just used normal vise jaws.
    Location: The Black Forest in Germany

    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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    • #3
      For thinner stuff, if you can sleeve the tubing on the inside you will make a stronger end. Also, from examples I've seen before, a rounded or V-shaped die gives you a better transition from flat to round. I see this on all of the older motorcycle subframes I work with. Newer subframes tend to have welded-on lugs at the ends.

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      • #4
        Like so: https://www.youtube.com/watch?v=g9Kr2tSTVew

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        • #5
          I had a need to do just this, with conduit, to make hangers for a shelf in the garage. I found a chunk of steel scrap that happened to already have a large radius on one edge. I sandwiched the end of the conduit between this and a larger flat piece in the hydraulic press, and the results were fine. You could probably use a sturdy vise in place of the press.

          Dave

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          • #6
            Arbor/hydraulic press?
            21" Royersford Excelsior CamelBack Drillpress Restoration
            1943 Sidney 16x54 Lathe Restoration

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            • #7
              In a sense this is similar to a tubing notcher- something grips the tubing, then an operation is performed on the end. In this case you would need a top and bottom die to grip the tubing- probably clamped with a big C clamp- then a shoe to press with. The shoe would have a bend to allow the tubing to crush flat at the end, but with a consistent shape between the flat and the original round. A jig would allow you to position the bottom die and the shoe so the operation goes the same every time. It would be relatively easy to make the flat part line up with one side of the tube because the tube doesn't move as the bending is done. It's all in the holding jig.

              For a roughly centered tab you would still press the end, but with a top and bottom shoe in an alignment jig, and you hold the tubing by hand so it can move as the flattening is done.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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              • #8
                If you take a hole saw or mill about the dia of the tube
                and cut a shallow angle notch in one (or both if centered) of the plates
                max depth at edge of press block about the hight of the tube off the surface of the flat
                you can get a nice compound curve bubble or crown leading to the flattened part that
                will not have that nasty stress riser you get with a straight line crimp.Click image for larger version  Name:	tube_flattener.png Views:	0 Size:	3.5 KB ID:	1893652
                Last edited by Astronowanabe; 08-19-2020, 08:43 PM. Reason: oooh pictures
                --
                Tom C
                ... nice weather eh?

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                • #9
                  As mentioned above, build dies and a clamping device.
                  As roughly pictured below, the tooling will take some tweaking in production.

                  A clamping device that opens far enough to extract the finished part.
                  An internal mandrel, this keeps the part of the work that needs to remain round from distorting, the mandrel is inserted before the press operation then extracted.
                  An upper die and a lower die, in order to switch between flatening on the diameter and the center just change the lower die height. This requires a press that moves both dies at the same time or a holding device that moves with the upper die.
                  Last edited by Bented; 08-19-2020, 08:42 PM.

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                  • #10
                    Thanks,

                    That's mostly what I figured, but no mandrel can be used, the pipe will be closed at both ends, which would trap any mandrel.

                    Originally posted by The Metal Butcher View Post
                    Arbor/hydraulic press?
                    Naturlich....
                    Last edited by J Tiers; 08-19-2020, 08:14 PM.
                    1601 2137 5683 1002 1437

                    Keep eye on ball.
                    Hashim Khan

                    If you look closely at a digital signal, you find out it is really analog......

                    Comment


                    • #11
                      You prolly want to do it nice and clean but I have have great success with the vise. JR
                      My old yahoo group. Bridgeport Mill Group

                      https://groups.yahoo.com/neo/groups/...port_mill/info

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                      • #12
                        Originally posted by JRouche View Post
                        You prolly want to do it nice and clean but I have have great success with the vise. JR
                        How does one control the offset with a vice?

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                        • #13
                          Originally posted by J Tiers View Post
                          Thanks,

                          That's mostly what I figured, but no mandrel can be used, the pipe will be closed at both ends, which would trap any mandrel.
                          Naturlich....

                          Well almost any mandrel... how about frozen water then a pin hole to steam it out
                          --
                          Tom C
                          ... nice weather eh?

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                          • #14
                            Originally posted by Bented View Post

                            How does one control the offset with a vice?
                            Check post #2. Simple and it should pretty much work, aside from the straight "fold" it makes. I will make an angled die more like post 8, that will make the tube end stronger and better supported, without the stress riser of the fold.

                            Two half dies for the centered one.
                            1601 2137 5683 1002 1437

                            Keep eye on ball.
                            Hashim Khan

                            If you look closely at a digital signal, you find out it is really analog......

                            Comment


                            • #15
                              When I built my Kenbota front end loader, I used a piece of angle iron welded to the end of 2" pipe. There was no need to "smash" anything and it looked better. I can't post pictures any more so you'll have to wing it.

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