Scale Length

Discussion in 'Luthier's Corner' started by mahrous, Nov 14, 2005.

  1. mahrous


    Aug 13, 2005
    i have recently talked to a fellow luthier who is specialized in acoustic guitar building. he told me that the 'correct' way of measuring a scale length is by measure from the nut to the 12th fret then doubling that distance to get the correct placement of your bridge.

    while i have always known and as i read in books and online literature that the scale length is measured from the nut to the bridge.

    which method do you guys use? or is it preferable to use my method in electric building because we have our moving saddles to compensate for any differences in scale lengths?
  2. It is double the distance from the nut to the 12th fret, typically. I don't think that the nut to bridge distance would be terribly useful as it should be different for every string if the instrument is correctly intonated.

    Everyone I know of uses double the nut to 12th fret distance, with the possible exception of Gibson. I would say that the nut to 12th fret measurement makes the most sense as it is the same for every string (except for multiscale instruments) and it tells what the fret spacing is.
  3. Scott French

    Scott French Dude Supporting Member

    May 12, 2004
    Grass Valley, CA
    Measuring from the nut to the 12th and doubling it still isn't going to give you the correct bridge position. During building you slot your fingerboard to whatever scale length then measure that out and add compensation to get your bridge/saddle position. If you are trying to figure out the scale length of an already built instrument measure from the nut to the 12th and double it. If you measure from the nut to a saddle you're going to get the scale length + compensation (different for every string).
  4. Just out of curiosity, could it ever be scale length minus compensation?

    I know it isn't usually, but could it be?

    Josh D
  5. Gawd I hope not! I position my bridges based on the assumption that the saddles will always be adjusted to flatten the notes from the perfect scale length. It seems to me the additional tension from fretting would preclude any other way.
  6. Thats that I figured. It was more concerned with compensation for different strings. Or is the contribution of the string always going to be sufficiently small in comparison to the contribution of action?
  7. So long as fretting the string increases the tension of the string, the actual string length will have to be longer than the scale length. Since I know of no way decrease the tension by fretting, this is pretty much a law of building stringed instruments with this system.
  8. ahhhh physics....don't you just love physics

    when I put together my first bass, I had an inkling of what scale length was, so I measure 17" from the 12 fret (I put the neck on first) and moved the saddles on my BAII bridge back about 1/2"...I then ran some cotton string through my nut in the E and G positions and connected these to the bridge...I then aligned the bridge to the neck, placed the bridge of the body where the 17" mark was approx, = to the saddles, and I taped her down (then I drilled some pilot holes and screwed her down).

    It worked out perfectly...took all of about 10mins to do...
  9. Suburban


    Jan 15, 2001
    lower mid Sweden
    What's the difference? As far as I know, 1/2+1/2=1. I may be wrong... :(

    Whatever you do, you measure the theoretical scale length (which is actually a good thing). Then, when you strring up, you will have to compensate. Theoretically, you need to compensate with a proportional part of the string diameter, which is pretty correct IRL. For a bass, IRL, it means that all bridges will be moved to a longer scale. For a treble guitar, IRL, it's less obvious; some experienced luthiers say that it would be a great idea to give the bridge a few mm compensation options to shorter scale. Saves some redrilling for some instruments, they say. NOTE that this is not shared by all T.G. builders!
    But, for a bass, whether you measure from the nut or 12th fret, placing the bidges frontmost position on the theor scale length is good.