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Thread: Fret board slotting

  1. #1

    Default Fret board slotting

    If I were to cut an already slotted fretboard at the first fret location to shorten the scale, I would assume I would need to shim the nut half the width of the slot since I cut it flush with the bridge side of the slot? If I were to cut it at the second fret, would I need to shim the nut by half or the full width of the slot? Would the distance compound as I move up the fretboard? I bought some fretboards and I think that the boards were slotted from a larger fretboard template and I'm having some issues with intonation. I'm hoping I can shim them instead of replacing the boards. I'm hoping that I just need to shim .0115 for a .023 slot.

  2. #2
    Teacher, luthier
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    Default Re: Fret board slotting

    Measure everything at least twice and cut once. You need to figure out [a] if the slots are accurate to the desired scale in relationship to each other, and [b] if any correction needs to be made at the end of the board.

    What I do when I work on a mandolin with intonation problems is measure everything from the nut, and see how far each fret deviates from its correct position. If they are all off by approximately the same amount in the same direction, I can add a shim [or shorten the nut end] as necessary. 0.01" of deviation is probably not worth losing sleep over.

    Now. if the boards were slotted using an antique Gibson board as a reference, you might have a problem.

    Stew-mac's on-line fret calculator can be of great help.

  3. #3
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    Default Re: Fret board slotting

    A zero fret would make things much simpler; no shimming required. Also slotting the nut is much easier since it is only a string spacer. Some folks like zero frets & some don't. I started using them a while back & wouldn't think about changing. But that's just me........

  4. #4
    Adrian Minarovic
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    Default Re: Fret board slotting

    Forget shimming. Many folks (and perhaps even the pre-cut boards from suppliers) use zero fret slot on their boards and trim the board right through that slot. The tiny amount of wood missing actually helps intonation in the lower positions. Basic rule of thumb is that shortening scale at nut lowers all the notes by same (per)centage (cents can be estimated by percentage of missing wood from the first fret to nut distance), the compensation at bridge lowers the more the higher up the neck you are.
    Adrian

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  6. #5
    Teacher, luthier
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    Default Re: Fret board slotting

    Measure the distance from where you want the fingerboard end to be to the slot 12 frets above. Multiply this number by 2. This will be your scale length.

    Look up the fret positions with Stew-mac's fret calculator. Measure the slots in your board and compare them with the Stew-mac results.
    An error of .01" is within acceptable tolerances.

    When you locate your bridge, the initial location for the front of the saddle should be roughly .06" greater than the scale length for the E string, and about .12" for the G string.

    The saddle location for guitars will be the scale length plus 2.5 mm. for the first string, and scale plus 5 mm. for the sixth string.

    My guess is that your problems are due either to a mis-located bridge or an inaccurately slotted board. Measure, check, then measure again and double check.

  7. #6

    Default Re: Fret board slotting

    I get what you're saying and I ran this idea through my head just a few days ago. I have an X/Y table on my drill press and I was making templates for fret slotting. The idea was to make long scale templates and find the scale lengths within that long scale by starting on frets other than the one calculated.

    I would rather shim if I discovered a problem than need to remove wood.

    The most useful position for actual edge of the nut isn't always in the math as there is the Buzz Feiten thing along with players who can't fret the first two frets without choking the neck. I myself wouldn't worry about .010 and if it was discovered to be a problem, it could be addressed fairly invisibly.

  8. #7
    Mandolin & Mandola maker
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    Default Re: Fret board slotting

    What HoGo says. Shortening the fretboard at the nut a tad does help intonation. If you want to go into more details on that then read the book by Australian luthiers Trevor Gore and Gerard Gilet. It is all explained in detail in the first book for guitars, but the principles are the same for all fretted instruments.
    Peter Coombe - mandolins, mandolas and guitars
    http://www.petercoombe.com

  9. #8
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    Default Re: Fret board slotting

    Peter, when you say a tad how much are we talking about?
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

  10. #9

    Default Re: Fret board slotting

    Kinda related ...
    Shortening the distance between the nut and the 1st fret is the general idea of the Buzz Feiten system which is targeted toward guitars. You can Google it if you're curious. I'm an authorized installer and I've done a few -- about five instruments in the last ten years. There are fans and there are folks who consider it smoke and mirrors. As far as guitars are concerned, if you experience the problems the concept is designed to address, it works. However, there are a number of things that an honest tech will rule out before the modification is done. A number of manufacturers employ the math used by the system to determine the distance between the nut and the first fret. Earvana techs use proprietary software calculators to determine the length of the shelf by entering instrument specs into the Earvana software. The typical mod involves the installation of a shelf nut. Earvana is another intonation band-aid idea for guitar.

    I have an octave mandolin that when I set the 12th fret intonation position, the first two fret positions of the 4th string are sharp enough to require intervention. The accuracy of the fretwork and the adjustment of the nut slots are correct. The situation mimics the typical problem of the 3rd string of a guitar when playing a D-chord the 3rd string sounds sharp. Its a mix of the player fretting with too much force and the fact that a sharp 5th in any chord is very dissonant and noticeable. Choking the neck when fretting is just a bad habit developed early when learning to play and very difficult to overcome. The solution on my octave mandolin was to install a tiny extension to the nut using a .015" sliver of bone and CA. Its held up for years as bone bonded to bone with CA is very strong.

  11. #10
    Mandolin & Mandola maker
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    Default Re: Fret board slotting

    Peter, when you say a tad how much are we talking about?
    You would need to do the maths from the Gore Gilet book to work that out for mandolin. I don't know because I have not done it, but it is not much.
    Peter Coombe - mandolins, mandolas and guitars
    http://www.petercoombe.com

  12. #11
    Registered User amowry's Avatar
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    Default Re: Fret board slotting

    Quote Originally Posted by pops1 View Post
    Peter, when you say a tad how much are we talking about?
    0.01” is about right, so half of the fret slot works just fine.

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