Truss rod problem

Discussion in 'Hardware, Setup & Repair [BG]' started by hdracer, Sep 29, 2010.

  1. hdracer


    Feb 15, 2009
    Elk River, MN.
    I just got a bass that had a rounded out truss rod adjusting nut (bullet allen type). I got the allen nut off the rod and repaired it buy putting it in my lathe & turning off the hex part. I then ran a tap through it and cut down a allen screw just so there was a couple of threads left. I screwed it into the nut and tig welded it together, turned it smooth and polished it.
    When I screwed it back on the truss rod it felt like it was bottoming out on the rod. I then made some spacer shims on the lathe 3- .050 & 3-.100 thick. I put a .100 on the rod and brought the nut down. It felt good as I put some tension on it and let it sit for a hour. I checked the relief , it was .035 @ the 7th to 9th fret. I gave it another 1/3 turn and let it sit. When I checked the relief it was .030. I tried to give another turn on the nut and it felt like it was bottoming again so I took the nut off and put another .100 shim on the rod. I adjusted it up again and the same thing. .030 relief. It feels like the nut is bottoming out but it isn't. The nut is sticking out of the neck more then it was. There is .700 of threads in the nut and only .250-.300 of rod. When I try and tighten the nut and it feels like it is bottoming, I can feel the rod twisting if I put pressure on it. If I leave the nut off and tune the bass it has .035 relief so that tells me the truss rod is not doing anything.

    I back off on all the strings during the adjustments.

    I can't figure out what is happening.
  2. Slowgypsy

    Slowgypsy 4 Fretless Strings

    Dec 12, 2006
    NY & MA
    What brand/model instrument?

    I've encountered this situation before and it turned out to be the truss rod channel. A truss rod is in a bowed channel, and when tightened it tries to make itself straight, which in the process bends the neck accordingly. The bass I encountered this with had a channel that was not cut with enough bow, which means the truss rod had almost no wood to push against and counter-bend the neck.

    It took removing the fret board to find this out, and I did the repair mainly out of curiosity to see if I could do it. But the instrument was not worth the time spent... this was just one of those things I did for the experience.

    Not saying that's what's causing your problem, but it might be.
  3. hdracer


    Feb 15, 2009
    Elk River, MN.
    Thanks, That is along the lines of what I was thinking. I think I will pull the fretboard. This is a cool old bass I picked up very cheap because the nut was stripped out. I got it for a winter project, just didn't think it was going to be this big. I have been on the Stew-Mac site adding up everything it will take to fix it and make it better. It will be a good opportunity to learn something on a bass that is old and cool but isn't worth that much.
  4. Hi.

    What Slowgypsy said.

    On some older Japanese copies the TR channel was cut straight, and the necessary bow was done with just a block of wood between the TR and the fretboard. Sometimes the block collapsed or was otherwise inadequate for the job, and symptoms You described were the result. Some necks had no block in the first place and were usually set up much like Rics to get 'em sold. That's just a temporary gimmick to get the action bearable of course.

  5. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

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