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Neck Shim Question

Discussion in 'Hardware, Setup & Repair [BG]' started by Rusty G String, Sep 25, 2013.

  1. Rusty G String

    Rusty G String

    Mar 19, 2013
    I've read differing opinions on whether a neck shim. "Strategically" placed can eliminate fret buzz. Others say it is only a good option if bridge saddles are too high. That is how I feel, also. Us there a real benefit from placing a shim under 2 acres of the neck that would eliminate fret buzz? It seams geometrically illogical.
  2. dedpool1052


    Jan 10, 2011
    Seattle, WA
    never heard that one before. the main reason for shims is either correcting the neck angle due to a neck pocket being cut wrong, or if the string saddles are bottomed out and the action is still not low enough.
  3. I've only had to shim one of my basses. It was a now long gone Epiphone P bass copy. No matter how many times I tried to get it as playable as I wanted; the saddles were bottomed out, there was no relief in the neck, and the action was still too high for my taste. I finally shimmed and it was perfect after.

    I used pressboard (similar to business card thickness) and only shimmed a half-inch closest to the pickup.

    As far as the geometry goes, if the tongue* of the neck pocket isn't at the right angle, there's no way to get it set up right without shimming or going all out and attempting to re-slope the tongue*.

    *Use of the term "tongue" for lack of a better word. I'm a dummy.
  4. walterw

    walterw Supportive Fender Gold Supporting Member

    Feb 20, 2009
    no, fretboard "tongue" is indeed the right word for that last bit that's over the body.

    as for the OP's question, shims are for changing the neck angle when the saddles run out of adjustment room either up or down; they don't do anything else.
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  6. JLS

    JLS Supporting Member

    Sep 12, 2008
    Emeryville, Ca
    I setup & repair guitars & basses
    I've read differing opinions on whether a neck shim.

    "Strategically" placed can eliminate fret buzz.


    Others say it is only a good option if bridge saddles are too high.


    When saddles are too low, and your action's still too high.
  7. Rusty G String

    Rusty G String

    Mar 19, 2013
    That's just what I thought. There's posts that claim shims have eliminated fret buzz, but I couldn't figure out how that could even be possible. Bottomed out saddles was the only thing I thought a shim could fix.
  8. 202dy

    202dy Supporting Member

    Sep 26, 2006
    False assumption.

    Insert shim.
    Perform necessary setup.
    Guitar now plays well.

    Mistaking the shim instead of the set up as the reason for eliminating buzz is understandable in a neophyte. Shimming seems a much larger event that doing a set up.

    As stated above, shims are inserted to change the geometry of the guitar. Anything else that happens is purely coincidental.
  9. deeptubes


    Feb 21, 2011
    It pushes the headstock back, lowering the strings, allowing one to raise the saddles, with the side effect of increasing the gap between the strings and body. I like low neck action but higher over the body. I tend to wedge my thumb under the E when focusing on the upper register. The micro-tilt on my basses does this perfectly for me. Took a really long time to figure that one out for myself.
  10. mongo2


    Feb 17, 2008
    Da Shaw
    I usually prefer to use a flat shim to raise the neck without changing the geometry of the neck/body relationship.
  11. claudel

    claudel Supporting Member

  12. JustForSport


    Nov 17, 2011
    re: "Others say it is only a good option if bridge saddles are too high.
    If the saddles are too high with the proper relief dialed in and the strings are still buzzing in the higher registers, a shim in the front of the pocket can help.
    This situation is rarely seen, tho.
  13. 202dy

    202dy Supporting Member

    Sep 26, 2006
    If the saddles are too high, lower the saddles.
  14. walterw

    walterw Supportive Fender Gold Supporting Member

    Feb 20, 2009
    the thing about that is you need a huge, thick shim to accomplish what a far thinner shim at the body end would do.
  15. 202dy

    202dy Supporting Member

    Sep 26, 2006
    Placing a shim in the neck pocket changes the geometry of the guitar.
  16. dannster

    dannster Supporting Member

    Aug 20, 2000
  17. RSBBass


    Jun 11, 2011
    A shim can change the neck angle as well as lift the neck further from the face of the bass. In some cases either or both may be desired. I prefer, when possible, to make a full pocket shim that is flat on one side and has the desired angle on the other. This keeps a good fit for the neck in the pocket.
  18. walterw

    walterw Supportive Fender Gold Supporting Member

    Feb 20, 2009
    interesting, but he's making a very complicated full-length tapered shim, on the theory that a shim just at one end warps the neck from the pressure; thing is, you never see that!

    when you find a neck with the dreaded "ski-ramp" problem of the rising tongue over the body, you'll see that the "kink" happens where the neck transitions from round in back to square to fit the body, nowhere near any shims.

    what's way easier and probably just as solid is to use a strip of whatever thickness you need for a shim at one end, then find a strip of something thinner to put in the middle of the pocket, so as to take the pressure of the screws and provide more support and solidity.

    after putting in the "primary shim", just lay a straightedge against it and the other end of the pocket, then slide your thinner "secondary" shim along until it hits the straightedge; a spot of superglue to lock it in place and you're done, with the neck safely supported in the middle between the screws.
  19. megafiddle


    May 25, 2011
    When your neck needs to be shimmed because the saddles are too high, it doesn't mean
    that the action is too high. It means that the action is correct, but the saddles had to be raised
    unusually high in order to achieve that correct action height.

    The solution is a shim at the outer edge of the neck pocket to change the angle of the neck with
    respect to the body (and the bridge). The saddles will now have to be lowered in order to restore
    the correct action height. But they will also now be well within their allowable adjustment range.

    More commonly, a neck will need a shim because because the saddles have to be set too low
    in order to reach the desired action height, or can't be lowered enough. A shim at the inner end
    of the neck pocket corrects this.

    It's important to realize that the only thing that changes when you shim a neck is the angle of the
    neck in relation to the body and bridge. The bow (or relief) does not change directly as a result of
    changing the neck angle. If the action height is maintained, the relief will not change. If the action
    was ridiculously high, the relief might change when the action is lowered after shimming. But that
    is a result of lowering the string height, not changing the neck angle.

    It's all simply relational between the saddles and the neck. When you can't position the saddles
    where you want them in relation to the neck, you move the neck instead.

  20. megafiddle


    May 25, 2011
    That's exactly the way I like to add shims. I would say that the mechanical integrety Is virtually as good
    as any full length tapered shim (or flat unshimmed pocket for that matter).

    I also use "fish paper" for shim material. That's the fiber based plastic resin composite that's been used
    as an electrical insulator for ages. McMaster Carr has it in 0.005, 0.010, 0.015, etc up to 0.030 thicknesses.
    The 0.005 and 0.010 sizes give you "business card" and "half business card" thicknesses.
    Fish paper is also less slippery than paper card stock (business card).

  21. walterw

    walterw Supportive Fender Gold Supporting Member

    Feb 20, 2009
    hmm; with that nice consistent increase in thicknesses, it becomes easy to make "stairstep" shim sets that are good and straight.

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