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Bending 1 1/2" aluminium Tube

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  • Bending 1 1/2" aluminium Tube

    I want to bend a 1 1/2" aluminium tube to about a 3 1/2" radius. I guess it can be done. I seen a very nice little tool for doing a 2" radius so a 3 1/2" should be doable. Here is a link: I wonder if I can get away with making a hardwood mandrel on the wood lathe. And also a roller that I can "pull" around the bend?

    I can get 6061 T6 locally. 6061 0 would be better I think. I can anneal the T6 though.

    Any ideas. I only need one of these at the moment. I don't think I could find a shop to do just one.


  • #2
    To bend that tight a radius, you may have to buy some of that metal which is solid at room temperature but melts at water boiling point. Use it to fill he bend area, let it solidify, and bend the tube. The solid metal inside will keep the walls from collapsing,. Then you heat the tube in hot water and pour the metal out.
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada


    • #3


      • #4
        Maybe pack it with sand then bend?
        Sole proprietor of Acme Buggy Whips Ltd.
        Specialty products for beating dead horses.


        • #5
          Beazld--Let me ask you a question. Have you ever personally bent a pipe that way successfully, or are you just suggesting "something you heard about"? I have heard that suggestion for 40 years now, and never seen it work successfully without the pipe going all oval shaped and weird at the bend, regardless of how the sand was packed in there.------Brian
          Brian Rupnow
          Design engineer
          Barrie, Ontario, Canada


          • #6
            The link explains the solution. There is an internal mandrel with a bullet nose that keeps the pipe from collapsing. Some Lanolin on the mandrel will help. You will need the alum. in condition 0 (completely annealed) to bend it. T6 will not bend well.

            I was a toolmaker at a chair factory for 6 years and we bent tubes like that day in and day out on Pines hydraulic benders. I've made dies and mandrels for round, square and rhombic shaped tubing.

            Hardwood blocks of maple or something else close grained might work. If not, you will have to go with mild steel. We used tool steel for the high production environment.
            Last edited by Toolguy; 01-18-2014, 10:00 AM.
            Kansas City area


            • #7
              Brian, I agree with you if it is a tight bend having tried it several times. The only time that was succesful was a piece of 1-1/4 steel handrail. The radius was 24 inches in the tight parts of the bend and we used dry sand and quite a bit of heat. The pipe was 21 feet long with several bends in different planes as it was handrail for a stairway with two half- round landings and some straight sections.


              • #8
                First constructive use I've heard for the expression "Go pound sand."
                Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                ~Practitioner of the Electromechanical Arts~


                • #9
                  Originally posted by brian Rupnow View Post
                  I have heard that suggestion for 40 years now, and never seen it work successfully without the pipe going all oval shaped and weird at the bend, regardless of how the sand was packed in there.------Brian
                  Aw, dang it. We were hoping you'd show us how it's done and post nice pics!

                  Or maybe a video of one of your awesome little engines powering a tube bender?

                  I did see a nice video on forming sand-filled PVC pipe into snow shoes using steam. It was for a boy scout troop that needed a bunch of them. The forming went very well, but I'm not sure how the PVC handles stress when frozen.


                  • #10
                    Sand will be of "doubtful" practicality. I use that particular word because, if the sand has rounded grains, ie alluvial, it will shift in the tube. On the other hand if the sand grains are angular, they lock in place. The problem is, how does one tell? In Brian's case, the sand is almost certainly alluvial. He lives "downstream" from the retreating ice sheet, and virtually ALL sand and gravel pits in his area were created by glacial outwash.
                    Cerrobend would sure work, but has anyone calculated the cost? They dont give it away and it is fairly dense; it would take a couple of kilos to fill a 11/2" tube for a foot.
                    Salt would work very well. It has angular grains, locks in place, is cheap, and when it jams in the tube, water will diassolve it out.
                    Duffy, Gatineau, Quebec


                    • #11
                      I have successfully bent small dia brass tubing by filling the tube with lead. On a "How do they do it?" Episode brass tubing for musical instruments was bent on arbors after filling the tubes with molten pitch.whichever method you use, you will still need an appropriate arbor and shoe. Bob.


                      • #12
                        I dont think a bend like that is even possible on a mandrel bender, you will get wrinkling, buckling and orange peel, you could however make it in two parts and weld together, imagine a bagel split in two, you then cut into quaters, stick two together and weld the seam, ive done it on steel for big exhaust pipes but not ali, ali would probably be easier to form with sandbag and bossing mallet, or over a hardwood former.


                        • #13
                          I have never bent 6061 T6, and don't think it will bend very well.
                          I would use this:
                          before I would try to bend to that radius.

                          An internal mandrel bender will be very expensive. If you were to support the ID before bending I think you would need something like this:


                          I use their 105 bender for steel tubing down to .625", they have been great to talk to and it's a great tool, if you need to bend them yourself call these folks and ask them what they think of the possibility.

                          ARS W9PCS

                          Esto Vigilans

                          Remember, just because you can doesn't mean you should...
                          but you may have to


                          • #14
                            I have read of a guy that made his copper coils by filling copper tubing with water and freezing it. Then he simply wrapped it into a coil and had no kinks.


                            • #15
                              You don't say what the wall thickness is and that has a large affect on minimum radius, regardless of what method (die, mandrel, or filled tube). And the hardness and ductility of the material has an affect. 6061 is gonna be a problem.

                              There is a good discussion of tube bending at