dimensional tolerances (and implications)

[peter havriluk]

Curious about allowable tolerances in fretboard shaping. Width, no problem, same for scale length, fret spacing, and longitudinal flatness. Where I get shaky is in the fretboard radius: it ain't particularly easy to sand the crown into the fretboard dead level so that the edges of the fretboard wind up at the same height. I know that sanding the crown into the fretboard results in a small bit of a sixteen-inch-diameter circle, but I suspect playability is impacted by deviations. I think it's also possible to sand a twist into the crown, so that the axis of the fretboard doesn't align with the axis of the neck.
Thoughts, explanations, and suggestions will be much appreciated.

Thanks, folks.

[John Parchem]

I think it is important to have the fretboard level along the string paths, otherwise the you will need to spend more time leveling the frets to avoid buzzing. Not as big of an issue if the fret board has a very slight tilt (the edges of the fretboard wind up at slightly different height) You will fix it in the nut and saddle as you are setting the action. I put a 1 mm tilt in my classical guitar fretboards so the string height from the top is more consistent bass to treble.

On my latest guitar I put a constant radius on the fretboard but after I glue it on the neck, I level the fret board with a long narrow sanding bar following the string paths. With a consistent radius the fretboard will drop away as the outside strings go from the narrow nut side to the wider side of the fretboard toward the saddle. The outside strings start out higher on the crown. You may be able to get lower buzz free action if you level the paths.

[peter havriluk]

John, thanks for answering. Your comments addressed my concerns very well.