Hollow steel rod strength?

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  • Cochese
    Veteran Member
    • Jun 2010
    • 1988

    Hollow steel rod strength?

    For this project I'm tackling I was in need of 3/4" steel rod. Of course, I would have prefered solid, but all I could source was hollow (1/16" wall thickness). I did find 5/8" threaded rod that fit perfectly inside the rod, so I thought I could work with that.

    Unfortunately, the rod length I needed was about 25.5" or so and my threaded rod is 24". I didn't quite grasp that problem until the project was assembled, and while I could make a correction it would take some doing. The rod sits in a bushing and will be holding about 10-15lbs of plywood and about 135-140lbs of tools.

    Basically, I'm trying to figure out if I need to bite the bullet now and add that length of threaded rod to support the hollow rod at the bushings, or will the steel take that kind of weight.

    If you couldn't figure it out, I made a flip-top stand for my planer and sander.
    I have a little blog about my shop
  • dbhost
    Slow and steady
    • Apr 2008
    • 9209
    • League City, Texas
    • Ryobi BT3100

    #2
    Uh. How is it you are unable to source up 3/4" steel rod? Are you far from a Home Depot?
    Please like and subscribe to my YouTube channel. Please check out and subscribe to my Workshop Blog.

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    • Cochese
      Veteran Member
      • Jun 2010
      • 1988

      #3
      That was where I went. I thought I had bought some previously, but it had been awhile.

      I may need to try Lowes if it is determined I need to supplement the strength.
      I have a little blog about my shop

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      • cwsmith
        Veteran Member
        • Dec 2005
        • 2737
        • NY Southern Tier, USA.
        • BT3100-1

        #4
        I don't see an answer to your question as being easy.

        Very much will depend on the type of steel, it's temper, etc., I would think. Also, how the load is applied and distributed across the rod. Is this just simply and axle of sorts or are you using it as a support on which you are stacking tools and materials?

        I took a course a very long time ago in Strength of Materials... I passed, but that was too long ago to remember much of anything beyond basics. Looking in my 25th edition of the Machinist Handbook tells me only that I need a lot more education on the subject and certainly conderably more Algebra and Trig.

        Sorry!
        Think it Through Before You Do!

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        • greenacres2
          Senior Member
          • Dec 2011
          • 633
          • La Porte, IN
          • Ryobi BT3000

          #5
          I'm able to buy threaded rod in 36" length at Ace Hardware--so in the absence of an educated answer, how about cutting down a longer section of 5/8" threaded?

          earl

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          • Tom Slick
            Veteran Member
            • May 2005
            • 2913
            • Paso Robles, Calif, USA.
            • sears BT3 clone

            #6
            I'm not sure what the answer is, it all depends on shear load and moment. If it's normalized 4130 then it's plenty strong but if it's HREW A500 then maybe not but then again it's a static load of only 150 lbs...
            Opportunity is missed by most people because it is dressed in overalls and looks like work. - Thomas Edison

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            • Tom Slick
              Veteran Member
              • May 2005
              • 2913
              • Paso Robles, Calif, USA.
              • sears BT3 clone

              #7
              You also need to look at failure mode. A solid bar is more flexible and will bend further before a slow failure. A tube is more rigid and will support more weight with less bend until it fails rapidly...

              Without seeing the design nobody can answer the question except to err on the side of caution and use the design's intended material. In the proper application a 1/4" bolt can hold 150 lbs but if a 3/4" thin wall tube across 24" span is supported only at the unrestrained ends and 150+ lbs is applied to the center, that low carbon steel tube could fail.
              Last edited by Tom Slick; 01-13-2014, 11:22 PM.
              Opportunity is missed by most people because it is dressed in overalls and looks like work. - Thomas Edison

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              • Cochese
                Veteran Member
                • Jun 2010
                • 1988

                #8
                This is a rod sandwiched between two layers of 3/4 ply sitting in steel bushings inbedded in more 1.5" ply. It is a flippable surface that will support two stationary tools.

                I think I will just go grab some more threaded rod.

                Sent from my HTC One using Tapatalk
                I have a little blog about my shop

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                • LinuxRandal
                  Veteran Member
                  • Feb 2005
                  • 4889
                  • Independence, MO, USA.
                  • bt3100

                  #9
                  You might look up welding supply places, for future metal purchases. I have had better luck looking them up, then the Borg or Blowes.
                  She couldn't tell the difference between the escape pod, and the bathroom. We had to go back for her.........................Twice.

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                  • capncarl
                    Veteran Member
                    • Jan 2007
                    • 3564
                    • Leesburg Georgia USA
                    • SawStop CTS

                    #10
                    If you are building a flip top table like I would think it was designed, the load will be real close to the supporting bushings, in which 3/4 round tube will support a suprising amount of weight. (1/2" emt conduit will hold what you are describing). If you was to put the weight closer to the center of the round bar then the planer may end up on your feet. Your rotating platform with the planer attached will be very ridgid so in fact your weight footprint is only on the round tube nearest the bushings. If you are really concerned with the round tube buckling you can put another support in the center of the roatating platform to prevent it from buckling, but that should not be necessary. As far as support is concerned the threaded rod inside is doing little more than taking up space that could be used by dirt daubers. Bushings are a nice touch but do little for support, mainly offer some precision to the table, a drilled hole through a 2x4 will do just as well with a touch of grease, and will be there long after we are gone with no signs of wear. Wagon axles hauled tons since the invention of the wheel with no bearings. The problems that I see with most flip tops is the small footprint on the casters make them prone to turn over. Mabe that is why they call them flip tops, they flip over on top of you.
                    capncarl

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                    • JimD
                      Veteran Member
                      • Feb 2003
                      • 4187
                      • Lexington, SC.

                      #11
                      The hollow tube is plenty strong enough. I googled up a calculator for bending deflection in hollow tubes. Using 24 inch span and 200 lb load, I got .0078 inch deflection (about 1/128 or half of 1/64) and 1833psi (yield for mild steel is about 36,000psi). So I think your tube is fine. The deflection would be even less for a solid rod but I don't see how you would see it in the tube. And this calculation is conservative because the support of the tube by the shelf is not considered. It's really more of a shear load.

                      Google is your friend. I have the text books and the background to solve this but why when a handy calculator is a search away?

                      It takes a few days for things to arrive but I often source this kind of thing from McMaster Carr.

                      Comment

                      • eezlock
                        Senior Member
                        • Feb 2006
                        • 997
                        • Charlotte,N.C.
                        • BT3100

                        #12
                        hollow steel rod strength?

                        Sounds as if you are building a flip top or rotating top machinery stand...?
                        You can use a piece of 3/4" steel water pipe or a piece of steel re-bar
                        and accomplish the same task. Those materials are very strong especially
                        in short lengths like this project would require, and are pretty easily obtained
                        and not hard to work with either.

                        Comment

                        • Cochese
                          Veteran Member
                          • Jun 2010
                          • 1988

                          #13
                          I just dropped an additional length of the threaded rod in for insurance. It was actually very easy to get it out, too easy in fact. Put some PVC spacers in so it wouldn't walk.

                          Got the project almost ready for pictures.
                          I have a little blog about my shop

                          Comment

                          • capncarl
                            Veteran Member
                            • Jan 2007
                            • 3564
                            • Leesburg Georgia USA
                            • SawStop CTS

                            #14
                            I found an old photo of the Craftsman rotary work bench. Lots of folks talk bad about them but it seems like a real space saver.
                            It doesn't appear that they are using much of an axle.
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