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wall thickness safety factor

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  • wall thickness safety factor

    Is there a general rule regarding wall thickness regarding fittings etc for plumbing or anything in general when it comes to threads so that its safe. I often machine a fitting in brass and wonder if it will fail because it has an inside thread and outside thread and its hard to measure the wall thickness between them.
    I have come across commercially made threads that have cracked because of this same problem. They can cause immense damage and would not like to take a chance. I always aim at as thick as possible but sometimes a purpose made thread leaves me feeling uncomfortable.

  • #2
    Plunger, that's why there are engineers. They do the calculations. Then there are tests. Failures and more calculations and tests. And insurance.

    If you have to ask, then you probably should not make the part if there is danger to life or limb if it fails. You could be libel.
    Paul A.

    Make it fit.
    You can't win and there is a penalty for trying!


    • #3
      I think that the problem is complicated more today by the range of alloys that are called "brass." For example, "cartridge brass," (I have no idea the alloy number,) was developed over a long time for its ability to withstand tremendous drawing forces, and incidentally, the pressure inside a gun chamber, but only once!
      The "ornamental brass" in inexpensive Indian brassware has so much zinc in it that it is only faintly yellow, while "leaded brass" has, as it says, lead added soley to increase the machineability, (read production speed.)
      A long time ago when things were simple, "red brass," described an alloy that had a minimum of zinc together with a bit of tin. It was, (and is,) tough, corrosion resistant, (in both a marine and urine environment,) and has only so-so machining properties. Metalurgical "tinkerers" have added other stuff to increase machinability and castability, (read profitability,) with various effects on the alloy properties.
      All this to say, you probably have to be VERY CAREFUL machining brass fittings for uncertain uses, especially if you are not sure what exactly the "yellow stuff" is that you are machining.
      Duffy, Gatineau, Quebec