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Can trussrods "run out" of turns?

Discussion in 'Hardware, Setup & Repair [BG]' started by IronLung1986, Oct 4, 2013.

  1. so i'm not sure if this is a dumb question but here goes...

    about once or twice a year i notice a little too much relief in the neck of my P bass. it gets uncomfortable to play and i have to tighten the truss rod just a little bit. i almost never need to loosen it, which made me think: if i'm mostly tightening it year after year won't there come a time when it's as tight as it can get? will it be screwed at that point? literally and figuratively :D

    i've never heard of anyone maxing out a trussrod in the way that i described, but i would appreciate any insight you guys could offer!
  2. Epitaph04

    Epitaph04 Always overcompensating Supporting Member

    Jul 5, 2010
    I had that happen to me with a second hand Bongo that had a seemingly faulty neck. I did eventually run out of truss rod adjustment (quite quickly, actually) so I had it sent to a tech who reset the neck. It was fine for about a year until I once again ran out of truss rod adjustment, so yes it can happen.
  3. dedpool1052


    Jan 10, 2011
    Seattle, WA
    IIRC, a truss rod can run out of threads, but on a fender, you're most likely to run out of room with the truss nut, in which case you will need to remove it and put in a couple shims to give you more travel with the nut.
  4. THand


    Jun 9, 2008
    I may be wrong, but I'm pretty sure you can take the nut off the truss rod and then slide a little washer or two onto the truss rod, and then put the nut back on.
    This may give you a few extra years by forcing the truss rod to start bending sooner.
    What "may" be happening in the OP's example is, the wood may be compressing under the nut when the rod is tightened, making you always tighten it to get the same result.
    Besides forcing the rod to bend sooner, the washers should disperse the pressure when the nut is tightened and stop the nut from sinking into the neck and eventually making you run out of threads.
  5. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Actually, that's a very common problem with the truss rods in Fender necks. The Fender truss rod installation is weak at both ends; the amount of surface area of the contact between the wood and metal is marginal. Over time and load, the wood will start slowly crushing behind the washer at the adjusting nut, and in front of the anchor. As the neck ages, it may start bowing forward, and you keep correcting it by tightening the truss rod. And the wood keeps slowly crushing at the two ends, allowing the neck to creep into forward bow again.

    Yes, eventually you will run out of threads. The nut will bind up on the rod and you'll feel it spring back when try to turn it. If you keep trying to turn it, you'll snap off the rod. That's the sequence of how almost all Fender truss rods get broken.

    A common quick fix is to remove the adjusting nut and add a washer or two under it. This spaces the nut back and gives the rod a few more threads to turn. But that isn't going to fix the real problem.

    Remember, the reason that a Fender truss rod runs out of threads is that it has been tightened beyond what it was designed for, and it has internally crushed the wood. That is, you are asking it to straighten out a neck bow beyond what it is capable of doing. Giving it more threads doesn't reduce the load. If you tighten it back up to the same level, it most likely will continue to slowly crush the wood. Sooner or later, the bow will be back. Keep tightening it, and something will eventually break.

    If you break the truss rod, and have someone just replace it, that won't really fix the problem either.

    The problem isn't the truss rod. The problem is that the neck has bowed beyond what the truss rod can handle. That's what the poor truss rod is trying to tell you! It's crying out for mercy.

    The correct fix is to pull the frets, recut the fingerboard to flatten it, and refret it. Then the truss rod can do its job.
  6. SactoBass

    SactoBass A retired civil engineer who likes all-tube amps! Supporting Member

    Would just buying and installing a new neck be another viable option? (assuming a bolt-on neck of course)
  7. chuck norriss

    chuck norriss Banned

    Jan 20, 2011
    I maxed out a truss rod it snapped dun do eet
  8. megafiddle


    May 25, 2011
    If the neck wood were so soft as to continually compress, I would replace the neck.

    Good hard maple shouldn't fail like that.

  9. uhhh yikes...! ok well thanks guys. i've heard of maxed out trussrods before but i was under the impression that it was pretty rare and usually due to some defect; i didn't think it could just happen one day through normal use.

    i appreciate all the feedback, this has been very informative and a liiiittle scary! additional ideas on preventing/resolving the eventual death of my trussrod are welcome!
  10. megafiddle


    May 25, 2011
    How much have you actually been having to turn the adjusting nut?

    Some necks are very stable. Other necks will move noticablly with seasonal humidity changes,
    but those necks also reverse seasonanly. Adjustment is back and forth.

    Or the wood may be very gradually moving.
    If the movement (and required adjustment) is slight, it may stabilize eventually.

  11. BillyRay

    BillyRay Supporting Member

    Jan 20, 2008
    Some necks do give in and bow under string pressure due to the nature of the wood or the construction: you never need to loosen the nut to correct the back bow because the neck is slowly folding forward. Seasonal changes in temperature in humidity only accelerate the process.

    It's my experience that any bass that needs constant adjustement to get the relief right will probably have the neck fail, wether because of excessive bow that cannot be corrected with the truss rod or twisting.
  12. it's only a very small amount each time - less than a quarter turn is all it takes to get it perfect. the bass is a 2011 american special, so it's pretty new. what is the total number of turns you typically get out of these things?
  13. when you say "constant" do you mean once or twice a year or like every couple months?
  14. megafiddle


    May 25, 2011
    Depending on the initial starting point of the truss rod nut, you could have several complete turns of adjustment
    before you run out of threads.

    The bigger concern is if this is a movement in the neck that is progressing steadily. If the movement is tapering off,
    requiring less and less adjustment, or less frequent adjustment, it may be stabilizing. Anyway though, at that rate
    of adjusment, you probably have a long way to go before running out of threads.

    If it's not tapering off, it could be as Bruce Johnson said, the wood crushing at the truss rod ends.

    Are actually measuring the relief when the adjustment is needed? The neck is actually bowing?
    (I suspect it is; you would have wound up with a backbow by now otherwise)
    But if it might be the action height changing, aside from neck relief, make sure the neck screws
    are tight. Not likely from the desciption, but easy enough to check.

  15. no sadly i haven't invested in any decent setup tools so i really can't measure things too well. it would be great to have a record of measurements and adjustments over time. i'm pretty good at eyeballing it though, and i can usually get it back to the right amount of relief without overshooting. the bass has no ostensible problems, plays great and adjusts easily. for the moment this is just me learning what might happen someday. but it's my favorite so sometimes i worry about its longevity, you know how it is!
  16. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    It isn't that the maple is soft. The problem is with Fender's truss rod design, which was compromised to squeeze it into the narrow "skunk stripe" type rear installation. At both ends of the truss rod, the metal parts only have a very small surface area of wood to push against. Both the washer under the adjusting nut and the shoulder of the anchor are only about 5/16" diameter. It isn't enough area to handle the load. Tighten the truss rod too much, and the wood crushes.

    I've machined out and replaced many, many truss rods in Fender necks. I've seen examples where the anchor end has been pulled into the neck almost 3/8". Usually, the wood just crushes, but sometimes the anchor will "part" the wood and cause the neck to split. The washers at the adjustment end can also get pushed in real deep. You can tell which end has done the crushing by measuring from the heel surface to the end of the rod. Usually, both ends crush some amount.

    On new necks that I build for other Luthiers, which use a skunk-stripe style truss rod, I use a much stronger design for the anchors at both ends, which has far more surface area contacting the wood. The anchor end uses an offset aluminum block set into a milled slot, and the adjustment end has a round aluminum slug that insets in from the heel surface.

    The factory Fender truss rod can only straighten the neck a small amount. More than that, and it will fail. Like trying to lift a 3 ton car with a 1 ton jack.
  17. P Town

    P Town

    Dec 7, 2011
    I saw a post in another thread warning that putting oil on the threads of a truss rod will soften the wood where the rod applies pressure, thus causing the wood to be more easily deformed. I put a small amount of oil on the threads of all my basses, and guitars when I acquired them, (including two new Fender Am Dlx basses, and a real nice Gibson SG guitar), and I hope that it takes a lot more oil than I used to soften the wood. Has anyone seen oil on a truss rod cause problems?
  18. 96tbird

    96tbird PLEASE STAND BY

    Yes it can soften wood. A tiny drop that can't make it's way to the wood is fine but you have to be careful. Use pencil lead rubbed on threads, a cheap paraffin candle wax or Vaseline as lube instead.
  19. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Yes, it sure can if it soaks the wood below the washer. I normally use a little smear of automotive wheel bearing grease. It's slippery and sticky, and will stay right on the metal parts. And if some does touch the wood, it doesn't tend to soak in.

    Like 96Tbird says, paste wax and Vaseline will work too. A sticky paste, not a drippy oil.

    If you just put a drop of oil on the threads, you're probably okay. Unfortunately when you say to oil the threads, some guys like to pour it on....
  20. dedpool1052


    Jan 10, 2011
    Seattle, WA
    Bruce, is the truss rod on fenders only a problem with the "skunk-stripe" type truss rods where they're inserted from the back or is it a problem with the bi-flex truss rods used on the american standard/deluxe models where it's inlayed into the front of the neck and covered up by the fretboard?

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