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Advice for pipe or tubing for project

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  • Advice for pipe or tubing for project

    I work quite a bit on pump cans that are made of thin drawn steel, about 5 1/4" diameter and about 6" deep. These can are often bent and dented and I would like to come up with a quick and easy way to take out the dents and creases and restore the original round contour.

    I figure the easiest way would be to have a metal piece inside the can that has the correct contour to it, and another matching piece on the outside just a hair different to allow for the metal thickness. By compressing these two parts together over the dent, it should very easily bring the metal can back to its original shape.

    The pieces need not be the full circumference of the can, since most dents are not that large. About 30-degrees or so would be enough to fix most dents. The pieces also need not be the full 6" deep, and 4" would be fine. It would probably be best to start with a full round piece, machine it to size, then section it as needed.

    I can also take pieces like this and grind other bevels and edges into them to repair other damaged features such as the outer lip edges and rounded corners.

    Obviously, to make a couple of pieces like this machined from metal would cost a fortune. I figure there may be a steel or cast iron pipe that can be turned inside or out to the needed diameter, then sectioned as required. After turning to size, the piece has to be thick enough to hold its shape while forming the can, so thin-wall wouldn't work as well.

    Short of searching through a salvage yard, can anyone recommend a source for a short section of piping that would work for this project?

  • #2
    The way they take dents out of musical instrument tubing is to press the right sized ball through. If you can turn a ball of the right size, it should be straightforward to push it through with hydraulics.

    metalmagpie

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    • #3
      A section of 2-3" steel pipe suitably clamped and an "auto body hammer" tapped on the outside should fairly quickly reduce the dent. Another option used by
      sheet metal shapers is a sandbag inside the can and then hammer the outside to the desired contour. Youtube should have some videos of this if you
      rummage around under autobody repair and sheet metal shaping. Access to a 50# or up anvil would do as well. Search your area for blacksmith. I think
      if you approach it as an autobody problem and not a machinist problem it will be simple to fix.
      Last edited by sch; 05-09-2014, 04:54 PM.
      Steve

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      • #4
        metalmagpie - Even if I had the money and capability to turn a 5 1/4" diameter ball, I would not be able to push it through the can because there is a back wall. The ball would not even go far enough into the can to get to the dented area.

        sch - I know it can be done like an "auto body man", and I have been doing it this way for years, but I am a rebuilder, and need a method that is both quick and will produce a better repair and finish than my hammer work. Effectively "clamping" the walls of the can between two properly contoured pieces will almost instantly remove the dent and will look better as well.

        A lot of the pump cans I get in have a significant dent in one particular area from where people pry against the pump with a baseball bat in order to tighten the belt. A fixture like I envision should fix this in seconds and provide a nice finish after smooth paint is laid down.

        It is only a machinist problem in so far that I am looking for a suitable material to start with that I can machine to fit my exact purpose.

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        • #5
          What the hell is a " pump can"? How 'bout a little more info? Bob.

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          • #6
            I fix musical instruments for a living...among other things. A suitable tube or bar slightly smaller than the can slid into the inside of the dented tube and gentle taps on the outside with a leather hammer is the way we do it. Or if we don't have good results with the leather hammer, we use a concave curved roller for putting pressure on the outside of the can to iron the dent out between the roller and the mandrel inside. On dents that come from the outside in, we have rollers that just fit inside the can and you just roll it back and forth and it will push it back out. Check out this website:
            http://www.ferreestools.com/brasswin...t-rollers.html

            Lots of the time, the dent stretches the metal and just pushing it back into the plane it was in again won't be enough to make it stay straight. Sometimes you need to shrink the metal to its old size and shape.

            How thick is the metal? That make a difference.--Mike.

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            • #7
              Take a look at how paintless dent repair is done on vehicles. It sounds to me like you could do something similar.

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              • #8
                I have repaired antique brass bases that have similar problems.
                Two methods
                1; Oak block formed to radius and a leather mallet
                2; Get some Cerro casting alloy and pour molds ( inside and outside) in the "good" areas . Works good and can be used over and over again

                Using a die will not remove the crease , takes a mallet to do that, as you have extra metal in the stretched area
                Rich
                Green Bay, WI

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                • #9
                  The "can" I am talking about is the reservoir canister that fits most 1965-1977 Ford power steering pumps.



                  The dents and creases are not major bad, but when you do a nice rebuild, you want the pump to look as good as possible. After the can is blasted down to bare metal and painted nicely, the little dents show up even more, and big dents look awful.

                  I think if I have two curved surfaces to clamp down simultaneously on both sides of the defect, it will flatten out well enough that it will look presentable after painting, and without much time spent on "body work".

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                  • #10
                    I know it can be done like an "auto body man", and I have been doing it this way for years, but I am a rebuilder, and need a method that is both quick and will produce a better repair and finish than my hammer work. Effectively "clamping" the walls of the can between two properly contoured pieces will almost instantly remove the dent and will look better as well.
                    While I think I understand what you are after, I am not sure I agree with your statement.
                    If there is a dent (going out or going in does not matter) there has been some stretching of the material. That has to be accounted for somehow...and somewhere. In the case of autobody, if the "extra" material is sufficient, you will need to shrink it by some method.

                    What I am envisioning is having a very close fitting and slightly longer than full length interior and a very close fitting exterior and "drawing" the exterior down the full length of the can...what I don't see is how the "extra" from the dent will be accounted for by this unless there was enough force and a tight enough fit that the can was actually stretched some small amount in the length direction...this could effectively "pull" all of the dents out (and leave the can that smidgin longer)

                    Edit: scratch the above idea, we were typing at the same time...yeah, I agree with you, its all those little "tap, tap, tap" marks that look even worse, what you propose maybe enough to shift the dents to a smoother look effectively hiding the issue...to me, still same issue of needing to shrink stretched metal however
                    Last edited by RussZHC; 05-09-2014, 08:31 PM.

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                    • #11
                      Metal on metal will stretch the part. A wood block inside, with a close or somewhat smaller radius than the can and a wooden mallet will shrink the dent/metal. If you don't have a wooden or plastic mallet, use a section from a hammer handle and hit it wit your metal hammer. Done with care using a lot of hammer strokesyou should not be able to see either hammer marks or the dent. If needed finish with some abrasive paper and automobile sanding primer.

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                      • #12
                        This is off the wall but maybe some thing like a small english wheel ?
                        Richard

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                        • #13
                          Pipe sources

                          You ask, "Short of searching through a salvage yard, can anyone recommend a source for a short section of piping that would work for this project?"

                          Try your local water well driller. Five inch well casing is 5.563 OD. Most of them will have short sections in the scrap pile. If you place your location in the file it helps.
                          Byron Boucher
                          Burnet, TX

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                          • #14
                            Bead roller with plain steel or plastic even wheels
                            http://img.photobucket.com/albums/v2...a/Dsc00778.jpg

                            Mark

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                            • #15
                              My thought would be to roll a piece of sheet metal wrap it around the can and clamp with hose clamps then either add air to the can or put water in and let it freeze to pop out the dent.

                              Mike

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