Router Fixture For Radiusing Guitar Fretboards

finger board radius cutter

Unless you’ve been up close and personal with a guitar, it’s easy to miss that the fretboard (where a guitar player presses on the strings) is not flat. There is a slight curve, the amount of which varies with the type and brand of guitar. There are even guitars with fretboards that have a compound radius that changes from one end to the other.

finger board radius cutter

[Mike] is a guitar builder and needed a way to radius his own fretboards. He did what any other DIYer would, he designed and built a tool to do exactly what he needed. The fretboard radius cutting fixture consists of a new large router base that has a curved bottom. This base rests on two metal pipes and can slide both back and forth in addition to along the new base’s curve. The flat fretboard blank is secured to the fixture below the router and is slowly nibbled away at using a standard straight flute router bit. A little sanding later and [Mike] will be able to keep moving forward on his guitar builds.

18 thoughts on “Router Fixture For Radiusing Guitar Fretboards

    1. The other day my sister called my mom to tell me I should bring my router but we couldn’t figure out which one she meant as my sister knows the one I have is broken and she still have my dad’s. After an hour we called her and said I needed to bring her the internet router I had laying around I’d said I’d bring.

  1. A luthier (/ˈluːtiər/ LOO-ti-ər) is someone who makes or repairs string instruments. The term originally referred specifically to makers of lutes. The term is used interchangeably with any term that refers to a specific, or specialty, type of stringed instrument, such as violin maker, guitar maker, lute maker, etc.

  2. This would be even better if he had realized that instead of using different arcs for different target radii, he might as well allow for vertical adjustment of the router position.

    1. Most routers (including the trim router he’s using) have the ability to adjust the depth that the router bit will contact the materials to be machined. I’m not sure how building the adjustability into the rig would be superior to using the adjustment already available in the router.

      1. Using the bit depth adjustment only would produce a surface with a series of flat cuts of varying depths requiring further (and imprecise) machining with a belt sander to end with a curved surface. Not to mention the tediousness of having to adjust the bit depth after every cut. Using a jig like this allows the router to cut along a curved path from the start without having to readjust the bit after every cut resulting in a surface that only requires fine sanding to achieve the finished surface.

    2. he could achieve different effects with either of two simple modifications to the fixture

      1) allow the parallel bars to be adjusted so that they diverge or converge at either end, which would have the effect of slowly raising or lowering, respectively, the router mounted in it’s circular jig as it traverses the length of the fret board

      2) have a height adjustable bed down the middle of the jig upon which the fret board sits, which allows vertical adjustment at either end, again, altering the depth of cut on the fret board with respect to its longitudinal axis

      3) an ellipsoidal, rather than circular section, router holding jig, in combination with diverging or converging bars would allow for even more subtle effects along the length of the fret board, but figuring out what would work would be tricky.

  3. Nicely done Mike!

    PS, the “he should have done it a different way!!” comments are getting old. The spirit of a “hack” is to solve a problem with the skills and materials that you have at hand and Mike did that.

    Having different jigs for different radii makes sense and if you’ve tried to accurately and repeatedly adjust the depth of one of these routers, you’d understand Mike’s solution. Way easier to build multiple jigs.

  4. Cool stuff! I’ve just just gone to town with a radiused sanding block for the fretboards on the guitars that I’ve built, but having something like this would be a big time saver.

  5. One suggestion, as the true radius is measured from the cutter, the far end of the pipes could be adjustable separation. This would allow a compound radius by bring the far end closer together you would end up with a smaller radius on that end

    1. No you wouldn’t. not with a curved template on the router. Changing the width will only change the depth of cut. If the template on the router has straight edges riding on the pipes it will cut different radii. Google “long Compass”

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