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Warped neck fix.

Discussion in 'Hardware, Setup & Repair [BG]' started by David A. Davis, Nov 29, 2012.

  1. Ok, so I bought a bass on CL for $50. It's a P-bass knock off. The action was pretty high, when I got it home I found that the truss rod nut was stripped. I had a friend machine another nut for me. Even after adjusting the action is still way high, so I've got a warped neck. I've thought about it, and I'd like to try and repair (straighten) the neck. I have access to an environmental oven ( basically I can control the heat and humidity).
    Here comes the onslaught of question I've for you guys.
    1. How do I clamp this thing up? I know I need a straight edge to clamp along the fret board, should I remove the frets or can I do it with them in?
    2. Should I remove all tension on the truss rod?
    3. At what temperature should I set this at and for how long?
    4. Should I use humidity? If so what level?

    If I'm correct with my research the wood will move more with higher humidity. What I was thinking was to run it at about 75% humidity 160 F for 12 to 18 hours then reduce the humidity, same temp for about 6 hours, Then take it out of the "oven" and let it sit at ambient temp and humidity for 48 hours, then unclamp.

    I'm only in this thing for $50, so if I screw it up it's not a big deal. Any experienced suggestions are much welcomed.
  2. Are you sure it's warped and not bowed? My understanding of warped is "twisted" with one end going left and the other going right. If it's bowed, the truss rod is not countering the tension of the strings enough. The way you described it, the neck looks more bowed than warped. If the truss rod snapped, then you'll have to take the fretboard out and replace the truss rod. If it's just the threads on the truss rod that's problem, you might be able to save it. There's this contraption from StewMac that might help:


    Hope that helps.
  3. Thanks Jaco D, it's not twisted, it's bowed. But, I've adjusted as much on the truss rod that I dare. I even added a washer behind it, still not enough.
  4. Smilodon

    Smilodon Supporting Member

    Feb 18, 2012
    First of all, are you sure you know how to set up a bass properly and how the different settings affect things like string height?

    What is the reason for the truss rod "not working"?

    If the truss rod is maxed out in it's adjustment a few washers behind the nut should help.

    Also check that your frets are perfectly level (all of them, and over their entire surface!) and check bridge height and neck angle.

    The way you describe the problem I don't think sticking the neck in a oven will do anything at all.


    Try forcing the neck towards the shape you need it to be by hand while you tighten the truss rod. (This is to help the truss rod a bit). You may need an extra pair of hands for this.
  5. I'll try adding more washers, then the forcing of the neck idea.
  6. MMMMM....maybe, maybe not. Can you measure the relief? Do you know how? Start there, bearing in mind that 'action' comes from a combination of things. Once proper relief is achieved, action can be adjusted with the bridge and/or shimming the neck pocket.
  7. ctmullins

    ctmullins fueled by beer and coconut Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    Have you done a setup before? If not, I highly encourage you to do some research before going any further.

    IMHO, here's what you need to do:
    1. Remove the strings (I'm assuming you've done this, but I don't like to assume too much...).
    2. Slacken the truss rod nut.
    3. Using a straightedge, assess how straight the neck is when it is under zero pressure. You may want to wait a few days after relieving the string and truss rod pressure before you take this measurement. Also, try to ignore the frets in this process, because they may be wonky...
    4. If - and only if - the neck is reasonably straight - no more than about 1.5 mm of bow either direction (again IMHO) - then it's probably usable as is, and you can proceed to try and adjust the truss rod the correct way:

    4a. Snug up the truss rod nut, so that it's not slack, but not tight either.
    4b. String up the bass and tune it to pitch.
    4c. Check your relief. If you need to remove relief from the neck, then the truss rod needs to be tightened, but don't just go at it with a wrench. Clamp the ends of the neck down to a work table, with a block of wood in the center, such that the clamps are exerting the pressure on the neck, taking out the bow. Once the neck is already in this position, with the right amount of relief, only then tighten the truss rod nut.
    4d. Release the clamps and check relief again. Repeat the procedure if needed.

    5. If you find after step 4 that the neck is indeed excessively bowed, then you may proceed with the oven, or whatever crazy stuff you have in mind. It's only $50, after all. :)
  8. Crazy? Noooo, not me:bag:
    I've done everthing you've mention, i just completed step 4 after I installed 2 more washer behind the nut. Man, this neck has got ALOT of flex in it. I'm at the point now of running out of thread on the truss rod if I add more washers. It seems to be better, but not great. I'm going to leave it as is overnight.
  9. Smilodon

    Smilodon Supporting Member

    Feb 18, 2012
    Just adding washers doesn't do anything by itself. You need to tighten the nut as well. ;)

    Seriously, though, do you know how much force you can use?

    Go to a hardware store and buy a bolt and a nut the same size as the truss rod. Use the same tool as you use to tighten the truss rod to tighten the nut/bolt you just bought. Tighten it until it breaks to get a feel on how much force it can really handle.

    (get some with 4.6 or 5.8 grade bolts. 8.8 could be stronger than your truss rod)

    I'm not saying that you should try to tighten the truss rod to the same tension. This is just to give you a feel for the forces you are working with. You may find that you are only tightening the nut to 10% of what it can safely handle.
  10. 1. I don't want to strip the nut.
    2. I've been doind my own setups for 25 years, I've learned a thing or two.
    3. If I were to go as far as to take a guess and do what you suggest with buying more bolts for a break test, I would use a torque wrench to measure the force neccesary to break the bolt. But, i'm not going to do that, I may be crazy but I'm not dumb.