Things Along the Way: Radius Block

Things Along the Way: Radius Block

In the last post, I discussed how I might add the dots to the neck’s fret board. I might also bind the neck, which might sound restrictive, but is actually just adding a decorative/protective strip along each edge of the fret board. Below is an unbound neck on the left and a bound one on the right.

I’ll no doubt dedicate a post to that eventually, but once that’s decided on and done, the fret board will have to be radiused. “Radiused?” you might be thinking?

Well, while some stringed instruments have flat fret boards (think ukuleles, classical/spanish guitars…), most guitars, especially electrics, have a fret board radius, or curve, to them.:

The above is shamelessly stolen from somebody else’s better site, and it shows the fret board (or fingerboard) radius very clearly. The value of the radius varies among guitar manufacturers and models, and generally varies from just over 7″ to 14″ or more. Tighter radiuses (radii?) are easier/more comfortable to play, as the curve of the fret board follows the natural curve of your hand holding the neck, and wider/flatter radiuses (radii??) are better for precise picking (think of shredding a metal solo, or the aforementioned classical picking). This is a simplistic explanation, but hey – I’m simple…

So, the Danelectro electric style I’m building uses either a 12″ or 14″ radius, depending on which year they built ’em. There are other parts of the guitar that have to match the fret board radius, those being the bridge and the nut, and I’ll post about those eventually, but the upshot is that I have already bought them for this project and they are both for a 12″ fret board, so 12″ it is!

Now, actual guitar shops and bonafide luthiers will have fancy equipment like radiusing jigs and CNC machines to pound out many necks per day, but for one-off projects, we do it the harder way, by hand-sanding the flat fret board down using a ‘radiusing block’, which is basically a long flat board with a concave curve matching the radius you want cut into it: you attach sandpaper of various grits to it as you sand the fret board down to match.

I’ll jump to the spoiler: here is my completed radiusing block, which should make the above clear:

Clear, except for the fuzzy background.

Doesn’t look like much of a curve, but that is precisely 12″ in radius.

Making that, of course, is a story in itself. There are many ways to skin this cat, and I went with a hanging jig for one of my routers. This would be a table that allows me to swing the router like a pendulum, with the length from the pivot to the end of the router bit being 12″ exactly.

Above is the swinging part; it ‘bolts’ on to a fixed base that I repurposed from an old project that doesn’t deserve to be spoken about:

I cut off the top half of that, figured out the correct pivot placement and used a cheap bolt and hammer-in nut from an IKEA-ish table I scavenged from when I threw it out a while back.Actually works great as a pivot, and with the addition of a couple of rails under the jig, I was able to slide the soon-to-be radius block under the jig while swinging the router to and fro, resulting in the finished block!

Unfortunately, no pics during the radiusing as I needed all three hands to keep everything in line…