Part 6: Compound Radius Fretboard
Thor’s fretboard has compound radius, with a radius of 304 mm (12″) at the nut and 456 mm (18″) at the 24th fret. Typical fretboards have a uniform radius, which is less than ideal for low action because the strings must be parallel to each other for consistent string height. But they are not. The fretboard is tapered. The strings are closer together at the nut and wider apart at towards bridge.
Compound radius fretboards follow a conical surface, as opposed to cylindrical. This allows for lowest action without string buzz. This article on Stewmac goes into greater detail: Compound Radius: Explained.
Of course, we made our own jig for precise compound radius shaping of the fretboard. The jig saves time and ensures consistent results without the need for tedious sanding with a sanding block.
A router guide (top) swivels along an axis supported by two pillow blocks, one end 304 mm (12′′) below the fretboard’s top and the other 456 mm (18′′).
Here’s a quick video of the jig in action:
And the result, after fret and nut slotting (coming up next!):