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Loctite and plastic parts.

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  • Loctite and plastic parts.

    It comes to our attention at Motion RC on occasion that people use Loctite on plastic parts when assembling a model. Loctite should NEVER be used on any plastic parts. It is stated on the Loctite packaging NOT to be used on plastic parts. The reason is this. As Loctite cures it also expands in the threads and this is how it locks metal threaded parts together. If it is used on plastic, the plastic will break as the Loctite expands as it dries out. This may or may not be apparent at first but it will at some point when the parts fail. Loctite can also have a chemical reaction to some plastics and again they joint between the steel screw and the plastic will fail.

    You do not need to use Loctite on any of the plastic parts on electric models, there is no vibration to speak of that would warrant the use of any form of thread lock. If a thread lock is required it will be stated in the instructions for the relevant model. The vibration level is nothing like that of an IC powered model. The natural friction of the plastic against the metal screw is sufficient to prevent it from coming loose in an electric model.

    I hope this helps.

    Martin.

  • #2
    Made this mistake.Although it wasn't plastic I was loctiteing. It was the two control wires that operate the elevators. The Mig 15 has separate elevator wires, (one for each side). Could never seem to get the locking mechanism tight. (The wires kept slipping) So I decided to loctite the connection. What a mistake. The loctite dripped onto the plastic control horns and ate through both of them. After replacing the control horns, I used a small amount of super glue to lock the mechanism to the control wires. I also glued the wire to the locking mechanism at the servo end under the canopy. They haven't slipped ever since I glued them.

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    • #3
      I don't even bother with Loctite on metal to metal nuts/bolts anymore on models. I use FoamTac on the threads and it works just as good. Holds tight, resists vibration and can be undone later when needed.

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      • #4
        Originally posted by xviper View Post
        I don't even bother with Loctite on metal to metal nuts/bolts anymore on models. I use FoamTac on the threads and it works just as good. Holds tight, resists vibration and can be undone later when needed.
        Right On ;)
        Warbird Charlie
        HSD Skyraider; FlightLine: Sea Fury; FMS 1400: P-40B, P-51, F4U, F6F, T-28, P-40E, 1700 F4U & F7F and a Fox glider; Freewing: A-6, P-51; VQ: P-39; Dynam: ME-262, FW-190, Waco; ASM A-26; ESM F7F-3; LX PBJ-1 EFL CZ T-28, C-150

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        • #5
          Thanks for posting that! Sometimes we forget that folks brand new to modeling visit these pages for advice, tips, and tricks.

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          • #6
            Originally posted by xviper View Post
            I don't even bother with Loctite on metal to metal nuts/bolts anymore on models. I use FoamTac on the threads and it works just as good. Holds tight, resists vibration and can be undone later when needed.
            That's funny, just did this the other day because I ran out of locktite and happy to see it's more common and I shouldn't run into uneceunnece trouble. Seems to work like a charm.

            Foam tac is the nector of the RC gods

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            • #7
              To add a little more - I see people put Loctite on metal screws that screw into metal inserts sorrounded by plastic. Even this often ends badly. If any loctite spills out onto the plastic, and it often does, the plastic becomes weak, brittle, cracked, and will eventually fail causing the metal insert to tear out of the plastic along with the screw sill attached. I've seen many spinners blow up mid air because of this. Be careful! The only real place I'd use Loctite on most planes is screwing the motor to the metal X mount. Do not use loctite to screw the X mount to the firewall.

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              • #8
                there is a loctite made for plastic screws and plastic to metal connections.. https://www.henkel-adhesives.com/us/...ctite_425.html

                I come from the RC racing scene. loctite is a must for us. I like the paste stick loctite. it seems to work better than the liquid kind. remember, you MUST shake the stuff up to mix it before you use it. if it's not working for you try the paste. another brand that works very well is made by Pro Seal. https://www.grainger.com/product/PRO...Strength-3HHH9 it actually seemed to work better than permatex thread loc I was using. now i use loctite sticks. https://www.henkel-adhesives.com/us/...ctite_248.html

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                • #9
                  Originally posted by serpentracer View Post
                  there is a loctite made for plastic screws and plastic to metal connections.. https://www.henkel-adhesives.com/us/...ctite_425.html

                  I come from the RC racing scene. loctite is a must for us. I like the paste stick loctite. it seems to work better than the liquid kind. remember, you MUST shake the stuff up to mix it before you use it. if it's not working for you try the paste. another brand that works very well is made by Pro Seal. https://www.grainger.com/product/PRO...Strength-3HHH9 it actually seemed to work better than permatex thread loc I was using. now i use loctite sticks. https://www.henkel-adhesives.com/us/...ctite_248.html
                  That is some good info regarding the Loctite 425........never was aware that Loctite made a plastic safe locker............still really like the Foam Tac as my all-around modeling adhesive.
                  Just would like to point out that your other 2 links(ie...Loctite 248 and Pro Seal Ana-Lok 42) are not plastic safe thread lockers so that other community members don't get confused with that info being in this thread.
                  Warbird Charlie
                  HSD Skyraider; FlightLine: Sea Fury; FMS 1400: P-40B, P-51, F4U, F6F, T-28, P-40E, 1700 F4U & F7F and a Fox glider; Freewing: A-6, P-51; VQ: P-39; Dynam: ME-262, FW-190, Waco; ASM A-26; ESM F7F-3; LX PBJ-1 EFL CZ T-28, C-150

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                  • #10
                    serpentracer OV10 Thanks for the info and the clarification, guys. A helpful PSA to always triple-check the bottle of Loctite before applying it.

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                    • #11
                      I bought this for my motorcycles. I think it will last a while haha

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                      • #12
                        Originally posted by OV10 View Post
                        still really like the Foam Tac as my all-around modeling adhesive.
                        Same with me. I don't like having to read the label on a different product to see if it'll be safe for this or will it hold for this? Is it permanent or is it temporary? I don't think I've used Loctite on anything for a very long time. I may occasionally use epoxy for special applications. I haven't even used CA for a long time either. I pick up the FoamTac and I just know it'll work for foam, plastic, metal threads, glass, wood, even teflon type threads. Oh, and I'll use hot glue sometimes on certain things. I have previously opened containers of this and that and some of them have dried out and become useless. FoamTac seems to have a long "opened" shelf life.

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