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Threadlocker For Metal Nut On Plastic Screw

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  • Threadlocker For Metal Nut On Plastic Screw

    I am building a control that will have a phone jack in the rear for connecting to external buttons. The phone jacks that I have ordered, Switchcraft part# RA49B14B, are made from "black thermoplastic polyester 94V0" which is the description from the data sheet. The nuts are "nickel plated brass", again quoted from the data sheet. I do not have any further information on either material. It will be installed in a 3/8" hole in a 0.040" aluminum panel but I do not think that matters.

    In the past I have just grabbed whatever thread locking compound that was handy, but I am wondering just what would be the best for this combination of materials. I would want a removable compound, not a permanent one.
    Paul A.
    SE Texas

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

  • #2
    Loctite has lots of online data that might mention which ones are compatible with that combo.

    A simple, low tech solution is nail polish, assuming that there are not stresses that would loosen the nut. It relies on mechanical bonding to the surface imperfections and it's brittle so it's removable.

    Dan
    At the end of the project, there is a profound difference between spare parts and left over parts.

    Location: SF East Bay.

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    • #3
      Loctite or permatex blue removable thread locker. Nailpolish will work but might be a bear for future removals. if the project is subject to vibration a couple dots of hot glue to hold the body to the back of the panel is recommended by 9 out of 10 OCD service techs ( the tenth guys uses 2 part epoxy.... )

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      • #4
        I would think the answer depends on what kind of plastic the screw is made of.
        Location: Long Island, N.Y.

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        • #5
          Just a thought... A second nut used as a lock nut might work nicely here. If you do ever need to service your device, it just takes a second or two to release the additional nut and there's no threadlocker to reapply later.

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          • #6
            Call Loctite support. They are very helpful. You are right to be concerned. Many types of Loctite eat plastic. I had a similar situation after I rebuilt a fish tank air pump. The nut was originally secured with a dab of paint. I used Loctite and the area of the case around the nut turned to mush. I believe locctite makes a suitable product. You could also try a cyanoacrylate ( crazy glue), RTV (silicone sealer) or Goop which I have used on plastic with no solvent action

            Sent from my SM-G900V using Tapatalk

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            • #7
              Blue Permatec is not suggested for plastics, and I don't have blue Loctite in front of me now to check.

              There are two things you may consider if Loctite reps have no suggestions for you (which is unlikely): Poly-Zap and Loctite Plastics Bonding System. I don't know how easy it will be to unscrew the fasteners though. You may try it. In the worst case scenario, you'll have a good plastics adhesive at home. Poly-Zap is especially unique in terms of bonding poorly bondable plastics.
              Mike
              WI/IL border, USA

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              • #8
                I gave all the information on that that I have in the first post.

                "black thermoplastic polyester 94V0" is word for word from the Switchcraft data sheet. For more than that I would have to contact them.



                Originally posted by RichR View Post
                I would think the answer depends on what kind of plastic the screw is made of.
                Paul A.
                SE Texas

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

                Comment


                • #9
                  Originally posted by Paul Alciatore View Post
                  I gave all the information on that that I have in the first post.

                  "black thermoplastic polyester 94V0" is word for word from the Switchcraft data sheet. For more than that I would have to contact them.
                  Sorry, I thought that just referred to the jack. I didn't realize it meant the screw too. It could have been nylon but not mentioned in the description.
                  Last edited by RichR; 05-26-2017, 09:40 AM.
                  Location: Long Island, N.Y.

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                  • #10
                    A smear of bathroom silicone sealant on the threads works well and doesn't affect many plastics

                    Sent from my Nexus 6 using Tapatalk

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                    • #11
                      I can't help with a suggestion, but to add fuel to the Loctite fire:

                      I know for a fact that many (most/all?) formulations of loctite are ESC agents (environmental stress cracking). This was discovered when I did some vibration testing on a plate made from polycarbonate (the plate was bolted to the vibration table, and the nuts were loctited). The test had to be terminated early because the amorphous polymer, plus ESC agent, plus fatigue loading of vibe table equaled bad news. Live and learn. Not sure how polyester would react, but free useless advice from somebody who learned the hard way.

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                      • #12
                        I presume that the black thermoplastic body of the jack has threads that match the nut you're referring to? I've put in many plastic 3/8" jack fittings, and most of them have a simple star washer included that will fit between the chassis and the nut - so you won't need any loctite - the loctite will likely have bad effect on the plastic whatever type it is

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                        • #13
                          Originally posted by RichR View Post
                          Sorry, I thought that just referred to the jack. I didn't realize it meant the screw too. It could have been nylon but not mentioned in the description.
                          There is no "screw" as such. The jack itself has a threaded spigot.

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                          • #14
                            To clear up any confusion, the external thread is molded into the plastic used for the body of the jack. The internal thread is in the metal nut. There was no lock washer supplied with it, only a thin, flat washer.

                            I think I will try the silicone sealer. I have plenty of that and it will only take a little dab.
                            Paul A.
                            SE Texas

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

                            Comment


                            • #15
                              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.
                              Kansas City area

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