Quote:
Originally Posted by murrmac123
I am about to commence the shaping the fretboard for my first "proper" (I hope) guitar, and I am planning on doing a conical radius (or "compound radius" if you prefer) .
I rather like the idea that John Arnold mentioned on here some time ago ... he said that he shaped his boards starting with a defined radius at the nut, and maintains a constant center thickness and a constant edge thickness. I seem to recall that Charles Tauber said that was his preferred method as well.
Am I right in thinking that doing it this way, there is one, and only one end radius which satisfies these conditions for any given nut width, end width, and nut radius ? ie if you start off with a given radius at the nut, then the radius at the end is predetermined ?
I am 99.99 % sure that such is the case, but just wanted confirmation from those who have actually done it.
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Murray, you are correct in your assumption. [a quote from Mel Brooks, BTW]
But--John and Charles are
describing a conical surface fretboard. They are not giving a method of construction. It would be impractical to construct the board by repeatedly measuring the sagitta and side wall height and adjusting them to remain equal over the length of the board. The method of construction should be a mechanical jig that will yield a conic surface, or a hand method that will do the same. One such mechanical system can be seen on Grizzly Industrial's site--look for their fretboard radius sander.
While the hand methods (there are a few different ones) may lack mechanical precision and be impractical for a factory (which does not want to rely on individuals' hand skills), they are every bit as good for a skilled hand builder. This is so because the deviations produced from the ideal surface will vary by no more than a couple of thousandths of an inch, which is greater accuracy than you achieve when installing the frets. You will still level the frets along the string paths, and any deviation in the board's surface will be eliminated in that process.
Moreover, the ideal conical surface is not the only one that works, for both theoretical and practical reasons. You can deviate from it while maintaining a board that is perfectly straight under each string path, if you allow variation in the board's side height. This can be up to several thousandths of an inch and never be seen or cared about.
You can also improved the playability of a guitar that will be used for bent ("choked" in some sources' terminology) by increasing the radius more than the taper of the board would dictate as you go toward the body. That will decrease the sagitta if the side height is maintained, which allows the bent notes to not fret out (by bending, the string is no longer over a level fret top path--it starts lower down on the curve, and can buzz against the next fret or two). Or you can decrease both sagitta and side height toward the body end to give clearance for bent notes. I find that the decrease in sagitta is necessary for good electric guitar setup.
And last, you may want a bit of dropoff on an acoustic guitar to provide a cushion against the eventual change in neck angle. That will depend on player preferences and how much the upper frets are to be used.