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Need PERMANENT threadlock product for truss rod nut

Discussion in 'Hardware, Setup & Repair [BG]' started by Tim Skaggs, Sep 29, 2017.


  1. Tim Skaggs

    Tim Skaggs

    Sep 28, 2002
    I have a 1998 Carvin LB75 with a two way truss rod that needs a nut "glued" back on the end of the adjusting rod so there is a way to turn the adjusting rod. This is kinda complicated to explain, but I'll do my best.

    The two way truss rod does not have a nut that turns on the end of the rod. The entire rod itself turns and its threaded into two metal blocks imbedded in the neck under the fingerboard. There is also a static rod between the two blocks. The adjusting rod has opposite threads on each end (right handed and left handed) so it pulls the blocks together or pushes the blocks apart depending on which way it is turned. The static rod holds the blocks from moving so both rods bow as pressure is applied.

    Since the adjustment rod is just a threaded rod, most have a socket or nut brazed on the end of the rod so there is a way to turn the rod. My truss rod HAD a 1/4" nut brazed on the end of the rod that has left hand threads, accessible under a cover on the headstock as typical on many basses.

    My problem is that the braze holding the nut on the end of the rod broke loose and since the nut is left handed threads, when trying to tighten the truss rod, the nut simply screws off the rod.

    I have tried to use two types of RED thread locker to "lock" the nut back on the adjustment rod. I tried Permatex and another non-Loctite brand, but have had no success yet. When I try to tighten the truss rod, the thread lock compound breaks loose and the nut threads off the rod. I'm looking for a way to get the nut seized on the adjusting rod so the ROD will turn and not the nut.

    I attached a picture to illustrate how a two way rod looks. This one is not for a bass, but is designed exactly the same way. The rod in the pic appears to have a socket brazed on the adjustable rod so an Allen / hex key can be used to turn the adjusting rod.
    IMG_0018.JPG
     
  2. BadExample

    BadExample

    Jan 21, 2016
    Injiana
    600 series, both parts must be absolutely clean, degreased, no residue and you must choose the product that matches the gap between parts.
    A bit difficult, but that is how it works. Hit Loc-Tite website for specs and details.
     
  3. Low viscosity ("thick", or consistency like putty) epoxy?
     
  4. BadExample

    BadExample

    Jan 21, 2016
    Injiana
    Might work as well, but still, absolute clean parts or it won't stick.

    600 Series as I mentioned takes heat to remove. It, and nothing else will stick to oil.
     
  5. Tim Skaggs

    Tim Skaggs

    Sep 28, 2002
    I've been carousing the loctite web site, but haven't found anything referring to 600 series. Looks like 263 is what I'll try next.
     
  6. BadExample

    BadExample

    Jan 21, 2016
    Injiana
    It seems like 670 was one of two I used, but another series may be more appropriate for threads.
     
  7. GIBrat51

    GIBrat51 Innocent as the day is long Supporting Member

    Mar 5, 2013
    Lost Wages, Nevada
    Red Permatex. This stuff, maybe, or red Loctite 271...maybe. Neither was really intended for the use you're going to put them to - gluing a nut to a threaded rod, and turning the rod with the nut. Against considerable resistance... My inclination would be to (somehow) get hold of some of the aerospace adhesive they use to glue jet fighters (and Aston Martins) together, and give that a try. Unless someone knows how to braze the nut back on, in situ...:thumbsup:
     
  8. BadExample

    BadExample

    Jan 21, 2016
    Injiana
    If there's room, that can be accomplished by two nuts jammed together. Just don't jam too hard, because it's tough on the threads.
     
  9. Tim Skaggs

    Tim Skaggs

    Sep 28, 2002
    If this stuff requires 500 degree heat to release, it should hold well above the touque required to turn the rod, and it's specifically designed to glue a nut to a rod / bolt to a nut. The wrench I use to adjust the truss rod on this bass is 3 inches long, so the torque applied to the truss rod isn't extreme. Torque values are inch-pounds. If it doesn't hold, the "heat & specialty tools required for disassembly" is apparently a sales pitch.

    I tried the red Permatex, but it didn't hold. I suspect the rod and nut may have not been clean enough. I also had a few people tell me to use the "Loctite" brand for. best results I found through further research that Loctite has a new product which replaces 271, its 263. It will cure & hold even with contaminates on the metal parts. It's also designed to work with non-active metals such as stainless steel. I have some on order.

    As for brasing or double nutting: the end of this truss rod is in a hole in the headstock that extends down behind the string nut and is just large enough for a 1/4" socket to fit down over the nut. Open flame brasing is totally out of the question. A friend suggested wire welding the nut onto the rod, but we couldn't get a ground on the nut or rod. There's no way to double nut because there's no way to get to the bottom nut. The nut I'm trying to glue on the rod is like a coupling nut, but still only about 3/8" in long & I have about the same length of rod to work with.

    I do appreciate the suggestions, but some are not possible due to the location of the rod and access to it.
     
    Last edited: Oct 1, 2017
  10. tlc1976

    tlc1976

    Aug 2, 2016
    Michigan
    Lots of good ideas. Only other thing I can think of is to file notches into the threads so the threadlocker has something additional to stop rotation. Or file hex flats and use a 1/4" socket to turn it. Or file a groove like for a keyway, and make your own matching wrench to turn it.

    Of course aside from having a luthier pull the fingerboard and brazing it back on (preferably pinning it as well). But I wonder what broke the braze to begin with?

    Whatever you do for a threadlocker, I'd keep the neck a little down until it dries so no chance of it running down into the threads at the block. That would probably be the time it would work the best.
     
  11. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    know nothing about wire welding, but it strikes me you could drill a little hole through the fretboard down into the neck until you hit the rod and then run a connection, then fill the hole with a matching wood plug when it was all said and done.
     
  12. tlc1976

    tlc1976

    Aug 2, 2016
    Michigan
    Not a bad idea. If the string nut pops off easily and the location is right, you could drill the hole under it too so you'd never notice. If at all possible I'd drill a hole thru the nut once it's screwed onto the thread, and pin it. Premake the pin the same length as the nut diameter, heck even predrill one half of the nut first. Assemble, drill the rest thru, and drive the pin thru. When I made the custom truss rod on my 6 string, I pinned a socket head cap screw that went thru a block and was threaded into the main rod. I used a 3/32 dia roll pin and never had any problems with it. Due to my design I torqued on it pretty good too.
     
    Last edited: Oct 2, 2017
  13. Bruce Johnson

    Bruce Johnson Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    I would do what tlc1976 is suggesting, but using a 2mm steel dowel pin. It would be a tricky job, but it could be done. You'd have to carefully locate the hole, then drill a 2mm hole down through the wood, the nut, the rod, and the other side of the nut. Then drive the pin down through the nut, the rod, and the other side of the nut, stopping it at the right depth. A one-shot deal. Then plug the little 2mm hole in the wood.

    I make my own truss rods here all the time, and I use 2mm pins to lock anchors onto 3/16" rods. I did a bunch of experimenting, and a 2mm pin is the optimal strength, in terms of the diameter of the pin vs the metal removed from the rod by drilling the hole in it.
     
    tlc1976 likes this.
  14. Tim Skaggs

    Tim Skaggs

    Sep 28, 2002
    No possible way I know to get a file to the threads. There's about 1/8 inch clearance around the rod.

    The rod is about 10-28 , so if I could file flats on it, it would be much smaller than 1/4". The nut that threads on the rod is 1/4.
     
  15. Tim Skaggs

    Tim Skaggs

    Sep 28, 2002
    This might actually work. The ground being away from the nut would give full access to the end of the rod & nut. I can leave the nut up some creating a "bowl" on the end of the rod & nut into which I can stick the wire of the wire-feed welder. I'll have to do some serious measuring looking and measuring.
     
  16. Tim Skaggs

    Tim Skaggs

    Sep 28, 2002
    This also might work, but I'm leaning more toward drilling down to make contact with the rod for a ground and welding the top of the rod to the nut. Thanks for out of the box ideas.
     
  17. Ross W. Lovell

    Ross W. Lovell

    Oct 31, 2015

    Low viscosity, water is thinner than a high viscosity, molasses.

    Meanwhile, red LocTite 262 is what you are looking for BUT......if you are unscrewing that LH thread out because the adjusting nut can't be loosened, you need to fix that first.

    Either double LH nut the rod after you pull it out OR........just replace it with a new rod from McMaster Carr.

    Find out first if it's metric.

    Buy the rod, cut and dress the ends to facilitate threading. Buy a couple of nuts to fit new rod.

    ISO alcohol the end you are going to LocTite. Let it dry 24 Hrs. Understand LocTite is anaerobic, meaning it will cure in the absence of air, not much flow in threads, good thing.

    Those of you that like it for bridge screws, LocTite makes a specific small screw threadlocker 222.

    Good luck.
     
  18. You are correct.

    I swapped my intended term, (low) for the viscosity (high) that I meant to suggest.

    (I do know the difference. I have actually done repairs on some electronic viscosity measuring instruments a few years ago and had to understand the theory of operation, which included understanding some of the science behind fluid dynamics).

    In my defense, children's toys were painted with lead paint when I was a little kid, rendering my ability to think clearly limited on some occasions.
     
    Last edited: Oct 2, 2017
    walterw likes this.
  19. Tim Skaggs

    Tim Skaggs

    Sep 28, 2002
    Rod can't be removed. It's a double action rod threaded through two metal blocks imbedded in the neck under the fingerboard. One end has LH threads, the other end (not accessible) has RH threads. I have to get the nut seized on the rod to act as a "head" to turn the rod. I have some Loctite 263 ordered. It's new, doesn't require primer or even totally clean threads....according to Loctite.
     
    Last edited: Oct 2, 2017
  20. I don't think any thread locking compound will be effective. That is why I suggested epoxy.
     

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