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What can I do to block this hole?

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  • What can I do to block this hole?

    You may have seen the thread where weighing a shipping container was being discussed and WeirdScience (?)**** suggested a hydraulic load cell.

    So I started making the bits, the piston is 20mm thick plate of 113mm diameter and I carved out a matching 'cylinder' from some much thicker steel, right at the end of this process I found a void in the metal!

    I know how it got there, these pieces are scraps from a plasma cutting place and the original 'round' had a slot in it from where the plasma cutter had started, I thought I had welded it up but obviously not good enough.

    So what can I fill it with, expoxy? Soft solder? Drill it out and Loctite a bit of rod into the hole?

    The hole does not extend to the outside and the O-ring will not pass over it.

    BTW, the piston size is chosen to read 100Bar at 10 tonnes, I dont expect to be going that heavy, least I hope not! (100Bar is 1450PSI)


    ****[Later] It was Camdigger.
    Last edited by The Artful Bodger; 10-11-2010, 05:33 PM.

  • #2
    When ever I have had a student remove too much metal I generally sent him or her looking for a metal stretcher.

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    • #3
      Originally posted by Dr Stan
      When ever I have had a student remove too much metal I generally sent him or her looking for a metal stretcher.
      Left or right handed version?
      This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
      Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
      Plastic Operators Dot Com

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      • #4
        Originally posted by Liger Zero
        Left or right handed version?
        Either, I was not too picky.

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        • #5
          Ohhhhhh, I am feeling sorry I asked!

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          • #6
            Id drill it out, Countersink the hell out of it, then fill it up with my mig welder and hope I did'nt warp the hell outta everything else nearby.
            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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            • #7
              Originally posted by Black_Moons
              Id drill it out, Countersink the hell out of it, then fill it up with my mig welder and hope I did'nt warp the hell outta everything else nearby.
              Yes, I agree and that was my first inclination however the machining is now at the finished size and I am afraid I would have difficulty machining true without becoming oversize.

              I guess the crux of my question, does epoxy get attacked by hydraulic oil? What about Loctite?

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              • #8
                The hole does not extend to the outside and the O-ring will not pass over it.
                Is it a big enough void to cause a stress riser that would cause the cylinder to fail? Is it deep enough to result in a thin spot that might blow out under pressure? If the answer is no to both of these, leave it as is.

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                • #9
                  JB Weld ???

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                  • #10
                    When working to hold in oil, weld the hole.
                    CCBW, MAH

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                    • #11
                      oring type seals of that size are very forgiving. . . . weld it. . . . .

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                      • #12
                        Perhaps you could drill and tap the hole? Wind in a screw w/LocTite, then cut off the end of the screw.

                        That pressure isn't super-high as far as hydraulics go.

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                        • #13
                          The hole does not extend to the outside and the O-ring will not pass over it.
                          Drill it out, tap it and put in a setscrew with some pipe dope (as per Jim). Call it a bleeder.
                          Free software for calculating bolt circles and similar: Click Here

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                          • #14
                            How?

                            AB.

                            I'd be more concerned about the small diameter to depth ratio (113:20 = 5.65).

                            If the load and its axis is not precisely on and normal to the centre/axis of the piston, the piston will be inclined to tilt and if it jams in the bore you will have a new set of problems.

                            The "rod" in most hydraulic cylinders attends to this matter as it keeps the piston parallel to the cylinder bore.

                            How much piston travel does the 113mm bore allow for?

                            How are you going to bleed the air from the oil under the piston?

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                            • #15
                              Good points OT.

                              I am putting a 'knob' on the centre of the piston, about 20mm diameter, to take care of any tendency to tip.

                              The piston travel should be minimal, just enough to operate the gauge, stretch the hose and maybe compress any air, I expect a couple of mm.

                              I will be putting the hose connection on one side of the cylinder and a bleed screw on the other, as Clamdigger showed. I might even be able to use the troublesome void as a point for one or the other (as Evan suggests).

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