OK, what happened?

Posted by Vincent Cuenca on July 8, 2013 at 11:44am

Just finished my first full-scale build.  I had planned to use a 25-inch scale length with a zero fret.  I downloaded a template from one of those generator sites, laid out everything nice and neat, put my bridge 25 inches away from that zero fret... and the intonation was way off.  I had to move the bridge in almost a full inch.  The scale length is closer to 24 inches.  All the notes are correct, no quarter-tones or other oddnesses, but the bridge is right in the middle of the box top.  Weird.

 

Any ideas what might cause this?

 

Thanks in advance,

 

Vince

 

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Replies

  • Tim LaFave July 10, 2013 at 2:28pm

    Essentially you must put the bridge the same distance from the 12th fret as the 12th fret is from the nut in order to have correct tuning. If your template was marketed as a "25" scale", you should have 12 1/2" from the nut marking to the 12th fret marking. Then you must measure another 12 1/2" from the 12th fret to place your bridge. If it was another figure, then that's the figure you must duplicate.

  • QGolden July 9, 2013 at 10:12am
    If bridge placement is the only issue, I think your interpretation of a "zero fret" might got you off track. If the pitch is off all the way down the neck, you might have a stack tolerance issue. Did you layout from the nut down, or did you measure from fret to fret for your layout?

    If moving the bridge back allows you to tune it then don't worry, just play it the way it is.
  • Jeff McFadden July 8, 2013 at 11:12pm

    Let me second what William McCauley said: Google a conversion from your chosen scale length in inches to metric, go to StewMac and enter your metric number from Google for your scale length to get your fret measurements.  Then buy a metric "yard stick" from Lowe's (it's yellow, mm on one edge and inches on the other) and lay out your fingerboards from scratch in mm.  Works for me.

    The reason to go metric is that mm's are smaller than 16ths of an inch.  Closer to 26ths of an inch.  (A 13 mm wrench fits a half inch bolt head real well.)  The chart tells you to put the next fret whatever, say 56.254 mm, and that's an even 56 + a half a pencil line.  Inches are just too big and awkward.

  • Jeff McFadden July 8, 2013 at 11:03pm

    What's a zero fret?  Did your bridge move come out to be about the same as, say, the distance from the nut to your first fret?

    • wormil > Jeff McFadden July 9, 2013 at 11:01am
      Zero fret is just using a fret in place of a nut.
  • Mark Kortuem July 8, 2013 at 5:40pm

    I use a 25" scale. The calculator I use is from Stewart Macdonald. I usually have to move the bridge back, but only

    1/8-1/4 ". I would redo the numbers through the calculator and try to find an error. If it still plays, It's a good guitar.

     

  • Tony Brown July 8, 2013 at 12:47pm

    All I did for my 1st and subsequent builds was lay a 1" wide thin wooden Batten (an off cut) on the fretboard of a normal guitar and mark a line on the Batten at all the Guitars frets from Nut Center to the 24th fret.

    Lay the Batten on your CBGs neck and mark the fret positions.

    Put the bridge at 25.5 "  from the nut and its always an octave at the 12th fret.

  • William McCauley July 8, 2013 at 12:40pm

    I prefer to use the chart from Stew-Mac and lay out my own fret locations. 

  • Richard Holmes July 8, 2013 at 11:54am

    Which generator site? Maybe they just were wrong.

    Another possibility: If what the site gave you was a graphic, which you then printed, are you certain your printer printed it at exactly 100% scale?

    How far is the 12th fret from the zero fret?

    • Vincent Cuenca > Richard Holmes July 8, 2013 at 4:22pm

      I think you may have at least part of the answer there.  The site did give me a graphic.  It also asked me for a number of other measurements that I didn't quite understand (amount of taper, slot width at the bridge, bridge height, eyelash thickness...) and that may have thrown things off.  I didn't have a normal guitar to copy, so I went with a template.  I may have to borrow my brother-in-law's guitars for the next ones. :-)

      I'll get a measurement this evening and get back to you.

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