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Busted truss rod help!!

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by kurtsstuff, Jan 31, 2008.

  1. kurtsstuff

    kurtsstuff Member

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    I have a 74/75 Gibson EB3 bass with a busted truss rod and wondering if anybody can refer me to someone that can fix such a thing??? Thabnks!!
     
  2. David Collins

    David Collins Member

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    It all depends on how and where it's busted. Sometimes you can bore a bit deeper in to access the rod if it's broken right up at the washer. Sometimes you can pull a small section of board up at the heel to re-anchor it. The last EB-3 truss rod I repaired though, I had to pull the board and replace it completely if I recall correctly.

    Looks like you're not far from Palo Alto - take it in to Frank Ford at Gryphon.
     
  3. kurtsstuff

    kurtsstuff Member

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    Hi Dave!
    Sheared off right at the washer....I'll hit up Frank....Thanks!!!:AOK
     
  4. David Collins

    David Collins Member

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  5. paulg

    paulg Supporting Member

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    He probably won't work on it. He hates electrics. I'm sure they have other repairpeolpe to fix it.
     
  6. David Collins

    David Collins Member

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    No, you're right that he probably won't be personally interested in that job. Still, you can certainly trust any of the other people he has working with him.
     
  7. kurtsstuff

    kurtsstuff Member

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    I was thinking about getting one of those "Truss rod rescue kits" from Stew-Mac....Which is essentially what Frank is doing in the pictures cept..He made his own...:dude
     
  8. David Collins

    David Collins Member

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    I think Frank gave StewMac the idea originally. Years back I'd made a plug cutter to expose more threads on a broken rod, but had never made a tap to cut more threads if they ended. It's really a great idea that Frank had.

    There's limitations to how successful a repair it can be though. The catch is that most rods (including most eras of Gibsons) have rolled threads rather than cut threads. The difference is that with a cut thread you would start with a 3/16" rod, then cut the threads either in a lathe or with a tap, leaving you with a 10-32 thread. With a rolled thread however, you start with a rod of a smaller diameter than the 3/16" (aka, #10 rod) and a the threads are shaped with a roller die. This forces metal up, leaving you with a full proper 3/16" outer diameter of the threads from a smaller rod. Metal does have a grain, and a rolled thread will offer much better strength than a cut thread.

    So then there's a problem when you want to now cut a thread in to a smaller diameter rod that was intended for a rolled thread. Since you can only remove metal and not reshape it you end up essentially with about 2/3 to 3/4 the thread depth of a full 10-32. It's the equivalent of taking a screw and filing off the outer third of the threads - you end up with less surface area to bear the load.

    Now for most truss rods, this shouldn't be much of a problem. If this rod snapped because it was stressed to it's limits though, this may be enough to push it over the edge and snap again. They could possibly cut a new truss rod nut with a longer thread length to compensate for this, but it's a tough call. They would have to make recommendations when they see it.

    Then again, I'm not entirely sure Gibson used rolled thread rods in the 70's. It may very well be a cut thread, in which case all that blabber above would be irrelevant. I'm also having flash backs to the last EB rod I replaced, and keep picturing a non-typical rod, something more like an old Gretsch system, but I may be thinking of a totally different instrument - it's been a while. They'll be able to give you a better opinion when they see it.
     

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