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  • I need to expand a thin wall tube.

    I have a piece of thin wall tubing that I need to expand the end on. It is actually a piece of 22ga.(.030") mild steel that was rolled and seam welded. I need to expand one end of it about .035" around .600" deep, the ID of the tube is around 1.500". I was thinking about heating the end up red and hammering a slug turned to the proper diameter in. Any other suggestions before I do the heat and beat? I have 3 of these I need to do. Thanks.

  • #2
    One method, make a flat tool about quarter inch thick and 1.535" wide and round the edges off. Flatten the end of the tube enough to slip this tool in the required 0.6". Now work the tool back and forth thereby stretching the metal until you can freely make a full revolution.

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    • #3
      Don't heat it- insert a solid bar about .6 inches and slowly roll it around on an anvil while hammering on the bar. You will be able to stretch the metal enough to raise the diameter that amount.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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      • #4
        Originally posted by The Artful Bodger View Post
        One method, make a flat tool about quarter inch thick and 1.535" wide and round the edges off. Flatten the end of the tube enough to slip this tool in the required 0.6". Now work the tool back and forth thereby stretching the metal until you can freely make a full revolution.
        Will this actually stretch it out, or since it is so thin just keep making the "oval" as it goes around?

        Originally posted by darryl View Post
        Don't heat it- insert a solid bar about .6 inches and slowly roll it around on an anvil while hammering on the bar. You will be able to stretch the metal enough to raise the diameter that amount.
        darryl, I don't quite under stand what you are saying. What diameter bar?

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        • #5
          The ID of the tube is about 1.5 inches- a bar say 3/4 to 1 inch diameter should work. Lay the tube on the anvil with the solid bar partway into it. You may want to support the other end of the bar so it sits level. As you hammer on the side of the bar near your tube, it will pinch the material thus stretching it. If you roll it all around you will be pinching the material all around the tube. Once around a couple of times, you should be able to see a slight bulging of the tube
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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          • #6
            I am guessing the part of the tube that is getting stretched hangs off the end of the anvil?

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            • #7
              Buy a "Tail Pipe Expander" or similar from an autoparts or online store. Insert, wind bolt and like magic - the pipe expands...


              http://www.amazon.com/s?ie=UTF8&page...ipe%20expander

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              • #8
                I have thought about the tailpipe expanders, do they work when they go in part way or do they have to be full inserted into the tube? (I know sounds bad, lol)

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                • #9
                  You could go to a local muffler shop and ask them if they would put it on their pipe machine. A Box O Joe will help ensure success.

                  Rick

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                  • #10
                    Yeah, lakeside53 has the easy solution, and inexpensive.

                    But I've used the method darryl described many times when it was get it done now, no expander available and to long a wait to get one. It works quite well and doesn't take all that long --thin metal like that stretches pretty easy (which is why the expanders are cheap and work).

                    I own a couple of the expanders, but I seem to end up at my buddies muffler shop, talking shop, while somebody uses a real machine to expand the pipe. Always seems like the easiest way to get it done --time permitting.

                    Zero.

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                    • #11
                      I have done this with Electrical Metal Tubing. I took 1" EMT and flared it by driving a machined mandrel the size I needed less the wall thickness just support the tubing and drive it in with a BFH ! It works fine. Mine was for a depth of 2" the biggest problem was getting the mandrel out without stretching the EMT more. I ended up using 1/2" EMT to drive the mandrel out.

                      Mr fixit for the family
                      Chris

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                      • #12
                        Originally posted by Mr Fixit View Post
                        I have done this with Electrical Metal Tubing. I took 1" EMT and flared it by driving a machined mandrel the size I needed less the wall thickness just support the tubing and drive it in with a BFH ! It works fine. Mine was for a depth of 2" the biggest problem was getting the mandrel out without stretching the EMT more. I ended up using 1/2" EMT to drive the mandrel out.
                        We use this method quite often when we need to expand a tube by a small amount--usually the wall thickness. Muffler shop type expanders are hard to control to such tight tolerances. Machine your mandrel with a slight taper to get it started and then machine a straight section of the require diameter and length. No need to heat and it works great.

                        You can also do the reverse if you need to shrink a thin wall tube...
                        Keith
                        __________________________
                        Just one project too many--that's what finally got him...

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                        • #13
                          Oxford, the part of the tube getting expanded doesn't hang off the end of the anvil, it lays right on it. Imagine if instead of a tube it was a ring, say 2 ft in diameter. You lay the OD against the anvil and pound on the inside with a hammer. If you pound on it all around, you will find it has stretched and become a larger diameter.

                          Another way to look at the process- say you mount a piece of solid bar in a vise with an inch or so sticking out one side. Place your tubing over that and whack it with a hammer from the OD. Rotate the tubing so you distribute the blows around the entire circumference. The end result is the same, except the solid rod held in the vise won't have the same inertial resistance that an anvil would have.
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                          • #14
                            Thanks darryl, I got it now.

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                            • #15
                              Originally posted by oxford View Post
                              Will this actually stretch it out, or since it is so thin just keep making the "oval" as it goes around?
                              Yes, the "oval" will move around but as it does so it stretches a little each time around.

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