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Threadlocker For Metal Nut On Plastic Screw

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  • #16
    For an engineered product that won't hurt many plastics, I suggest Vibra-Tite. McMaster number 75145A69 for example. Definitely avoid most Loctite and cyanoacrylate on acrylic, polycarbonate and Ultem, maybe some other plastics. It crazes and destroys the plastic. If that image doesn't show, search Vibra Tite. My experience is that it stays sticky and you can still move the screw, but it's a different animal than Loctite.


    • #17
      Sounds like a nice idea if I were making the parts from scratch. But I am not going to make a nut when they are already supplied with the jacks. Perhaps I can bend one out of round just a bit. That should do the same thing. Or crack it: they are awful slender and bending it is hard to control.

      Originally posted by Toolguy View Post
      I make a lot of parts out of Acetal. One threadlocking method that works well is to have the external thread smaller than the internal thread. For example, when drilling and tapping the plastic for a metal screw, I grind the points off of the tap and make it flat crested. This makes the plastic part a "Nylock type" fastener that can be reused several times and is very secure because the plastic is gripping the entire thread engagement.

      In your case, you could make nuts (single point) that are a bit undersize to provide the same function and not have to worry about any liquid additives.
      Paul A.
      SE Texas

      And if you look REAL close at an analog signal,
      You will find that it has discrete steps.


      • #18
        Little tidbit about loctite that I learned from a call to the manufactuers tech support. Loctite is catylized by metal ions which is why it cures in a threaded joint and not in the plastic bottle.


        • #19
          I thought it was lack of air
          bottle is porous

          BUT then again what the heck do I know
          George from Conyers Ga.
          The early bird gets the worm, BUT it's the second mouse that gets the cheese.


          • #20
            It is partly lack of air. That's why a new bottle is only partly full. The air in the other part keeps it from getting hard.
            Kansas City area


            • #21
              I don't think the threads in the plastic are strong enough for the locknut idea- plus there probably isn't room for two nuts, and it wouldn't look good either. Me, I'd use a small dab of 5 min epoxy on it. It will fill the pores in the plastic but probably won't stick to it very well. That should make it removable, but keep it from loosening by itself. This is probably a job for dollar store epoxy- one of few things that it might actually be good for.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-