Moving bridge back for proper intonation

Discussion in 'Luthiery, Modifications & Customizations' started by nkri, Jun 22, 2012.

  1. nkri

    nkri SS.org Regular

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    I'm in the process of refinishing my 7621 (pics coming soon), and I usually tune this guitar to A standard. The saddle for the low A doesn't move back far enough (even after removing the spring that keeps the saddle in place), so I'm planning to install the bridge farther back on the body to achieve proper intonation with low strings.

    My question is, how far back should I move it? I want it far back enough that I could correctly intonate a .062 in A (and maybe .068 in G) but still be able to move the treble saddles forward enough to intonate properly in standard tuning. So how far back should I move the bridge? 0.25"? 0.5"? More/less?
    Thanks,
    Dan

    PS: I'm not trying to change the scale length here, since that's determined by the distance between the nut and 12th fret...just want enough clearance with the saddles to intonate everything the way it should be.
     
  2. bob123

    bob123 Banned

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    God this is gonna be a painful experience.

    How far off is the intonation? what size strings are you using?

    You may just need to adjust bridge angle back not necessarily the whole thing.
     
  3. nkri

    nkri SS.org Regular

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    lol, painful experience? How so? I'd estimate it was off by somewhere between a quarter tone and half step, so it's not like I need an extra inch or something. I was thinking (and hoping) 0.25" should be ok, just concerned about the high strings when I'm back in standard. In B, I use 10-46 + 58; in A, 11-49 + 62.

    I'd rather adjust the whole bridge than the angle...aside from it looking pretty goofy, I don't wanna be bending the strings over the saddles at a weird angle...i.e., the strings are supposed to go parallel to the saddles, but if I changed the angle of the bridge, the saddles would be diagonal while the strings would be straight with the neck...that would create issues with setup and string breakage that I don't even wanna think about dealing with.
     
  4. BlackMastodon

    BlackMastodon \m/ (゚Д゚) \m/ Contributor

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    Hmmm not sure how far back you will need to move it but I do highly recommend you tune the guitar to standard (or the highest tuning you will use with it) and intonate it with that tuning and see how much you would be able to get away with from there.

    Another thing my guitar tech told me when I asked him about a similar problem was that you can add a small shim in the neck pocket to push the neck forward a bit and then intonate it from there, but I think this method is more for if you are just a smidge off from being properly intonated. What you're describing will probably need more.
     
  5. schecter4life

    schecter4life Banned

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    if your bridge is a flat-mount with 4 screws holding it in, pop a couple washers under the bridge for the 2 screws closest to the bridge pickup, re adjust your action, and that slight angle of the bridge may be enough to correct your intonation, i have NO idea if this will work, but in my minds logic it seems like it would.. i would give this idea a shot before potentially ruining the playability of a perfectly fine instrument
     
  6. geeman8

    geeman8 SS.org Regular

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    You know....Caparison did something similar to what you are trying to accomplish. I forget the name for the particular series of guitars, but they intentionally placed the bridge further back. These guitars came in drop B tuning I believe. They only changed the positioning of the bridge by a few millimeters though...nothing too drastic.
     
  7. skeels

    skeels ..to pay the beels

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    ^ this. Only a slight change is needed.

    Look at hipshots with short saddles on the low strings.
     
  8. espman

    espman Is beardless....

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    That was the HGS series, they moved the bridge back by 3mm, tuned to B standard.
     
  9. WiseSplinter

    WiseSplinter SS.org Regular

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    I've heard of people removing the saddle of the low string and grinding it down a little at the rear, thereby allowing it to move slightly further back.
    Not sure if this would work for your particular bridge but it might be worth it to check before doing anything more drastic.
    The thought of cutting new holes in the top gives me the chills...

    :2c:
     
  10. nkri

    nkri SS.org Regular

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    Cutting holes is the part I'm least worried about. I'm veneering the top anyway, and it's very easy to fill holes with wood filler so it's not a big deal. This project goes much deeper than simply moving the bridge...I'm veneering the top/back/headstock, rewiring it with a 3-way switch and no tone pot, and replacing the inlays with abalone. So it's not a big deal to drill a few holes in the body. I decided to move the bridge back 0.25", and I'll just replace the treble saddle screws with longer ones if the saddles can't move forward far enough :yesway:
     
  11. loki

    loki Banned

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    exactly...

    i could be mistaken but i believe the position of each fret is calculated by the total length of the scale. moving the neck back is going to throw off that calculation. you might achieve intonation at the 12th fret but your other frets will be thrown off. you would need a new neck to match the new scale length.

    modifying the bridge while maintaining the same scale length is the only realistic option.
     
  12. VBCheeseGrater

    VBCheeseGrater not quite a shredder

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    I was thinking this too, but the more i think about it, maybe not. If the 12th fret is in the exact middle of nut/saddle (meaning perfectly intonated), the frets should line up perfectly. The frets are laid out with the assumption that the 12th fret is dead center, so it should be good i'm thinking - someone correct me if i'm wrong.
     

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