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HowTo: do Fanned Fretboards

Discussion in 'Luthier's Corner' started by The Insane, Apr 2, 2009.

  1. The Insane

    The Insane

    Jul 12, 2007
    Hi everybody,

    after successfully completing my first fanned fret bass I want to share the technique I used to get the angles on the fretboard right.

    Get the exact measurements of:
    -Distance Nut<->Middle of Fret for every fret
    -Angle of each fret

    You can do this with CAD or let FretFind (http://www.fretfind.ekips.org/ do the work for you.
    Here's the result for my 6-string with a 34-37" fan from FretFind: The columns of interest are "angle" and "mid to nut"

    Then we have to prepare the fretboard: I'm demonstrating this on a piece of scrapwood because I don't have a build going on at this moment :ninja:
    The two sides of the fretboard have to be perfectly straight and parallel . Then draw a centerline, again perfectly parallel to the sides:

    Now I use a tape measure that has a sticky surface on the bottom and glue it right at the centerline so you can barely see the line

    Ok, now we're ready for the tricky part. Get yourself a smooth and perfectly rectangular (I use a laminated) piece of wood. Glue another tape measure right at the edge and draw a line at 0 perpendicular to the side. Then mark a distance that can be easy worked with, something like 10 or 20cm. The longer the better (but not too long, will explain later). I used 15, so mark the distance of 15 on the perpendicular line. Lets call this point A

    Now that we've got the exact angles for the fret we can use the tangens:
    In our case side a is the side with 15cm length and b is the side with the tape measure. If we've got the right angle we can calculate side b

    Now I use a great tool, a sliding bevel. Hold it firmly against the side and adjust it so it connects the point A with the tape measure at that point where it reads the value of side b!
    Example: For the zero fret the angle is ~29,4° so side b is 8,45cm. Then connect Point A with 8,45cm at the tape measure. I hope a pic will explain this procedure:

    If you're using FretFind, be sure to take the right angles (sometimes you have to substract the angle from 180°, sometimes add).
    Tighten the sliding bevel and hold it to your fretboard. Slide it up and down until you reach the point where the middle of the fret has to be (Distance Nut<->Middle of Fret). On the side with the center line of course. I start with the zero fret at 0:

    Then I use this sharp thing:

    and scribe the correct angle on the fretboard

    Well done! We got the correct angle for our first fanned fret! Now move on to the next one. Calculate side b again and transfer it on your fretboard

    If you do this for all frets you should end up like this:

    Well done! Our fretboard is ready for slotting. Now any common fretsaw will do the job and it's easy to slot it because we did cut the upper fibers of the wood already. Cut the fret slots, then taper, or taper first, then slot or glue on the neck first just as normal. With woods like Wenge it can be better to taper first because the fret slots might splinter or tear out when tapering.
    It is absolutely essential to have a good centerline that's parallel to the sides of the fretboard and the sides of the fretboard itself being parallel.
    Make up your mind about what is side a and side b, e.g be careful not to measure on the wrong side of the tape measure. If you look at the picture again, side a is the 15cm starting at the right side of the tape measure

    Of course there will be many other ways to do it. E.g. you don't need to use a glued down tape measure, just mark the middle of each fret and then draw the angles. But I think it works quite well, the intonation on my build was spot on. Just take your time and enjoy :smug:
  2. vbasscustom


    Sep 8, 2008
    so, whats that pine fretboard gonna be used on? :p
  3. jordan_frerichs


    Jan 20, 2008
    wow. now it actually seems doable! Too bad i will be doing frettless basses after my current 2 are done, because i will not have access to all the tools i do now
  4. Thanks! That's a nice tutorial and I think it's a really clever way to do this, although your first fret line doesn't exactly look 'precise' (but than again, this is a test piece just to show us).

    On more or less off-topic question: how is it to play a 37" scale on the lower frets? Any problems or just fine?
  5. zagnut


    Jan 4, 2009
    Back in Detroit
    I love "sharp things".
    Seriously though, awesome thread.
  6. Bocete

    Bocete My E string is 36 1/4" long

    Sep 30, 2006
    Great job.

    However, one question: instead of measuring angles, wouldn't it be better if you drew the nut-to-bridge polygon on a huge piece of paper, and independantly found the points where the frets end by recursively dividing each side length by a 12th root of 2; then applied the template? I hope I've explained it right. I'm no luthier, but some geometry I know and this method should (IMO) work, and be easier to do.
  7. Yvarg

    Yvarg Gold Supporting Member

    Mar 10, 2007
    Irvine, CA
    Great Howto! My only question: why not print out a template if you're already using fretfind?
  8. scottyd

    scottyd Commercial User

    Nov 17, 2006
    Waco Tx
    Builder/owner Redeemer Basses
    One thing I've found recently is that if you use a template check and re-check the measurements. Not all printers print the same.
  9. Yvarg

    Yvarg Gold Supporting Member

    Mar 10, 2007
    Irvine, CA
    Yeah, definitely, but if it's correct then you should be fine, right?
  10. The Insane

    The Insane

    Jul 12, 2007
    Mmh, what do you mean with "then applied the template" exactly? Drawing a huge template works also but I wanted to get as less inaccuracies as possible. If you do something wrong on a drawing it might reproduce itselfs. With this method I have (theoretically) only the inaccuracy of me adjusting the sliding bevel and its positioning which gets resetted for every fret again.

    Scotty already pointed that out, it's not easy to prevent your printer from scaling the template. And I don't want to glue 4 sheets of paper together for a template, which is again very inaccurate. You could find a copyshop how could print this to full scale on one page but I found paper to be highly sensitive to humdity and temperature. It shrinks and warps very very easy from my experience.

    Yeah, I didn't really care and took a serious measuring, but this fret line got very sloppy because I was holding the camera, sliding bevel and the "sharp thing" ;) with my hands simultaneously
    I definately had to get used to the 37" scale, but I have small hands. It might be quite a bit harder to do some fast runs on the low notes (which I neither want to do nor can ;) ) but it's nothing that shouldn't be able to solve by practicing
  11. Bocete

    Bocete My E string is 36 1/4" long

    Sep 30, 2006
    True. The errors made while using the method I proposed stack. It can be fine in a CAD environment, but it wouldn't be in the real world :p

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