Compound Radius Fretboard Jig

Here are some pictures of the jig I built for routing a compound radius on fretboards (12" radius at the nut end and 20" radius at the soundhole end). The original designer of this type of jig is Mario Proulx (of Proulx Guitars fame) who has a brief description and some photos of it on his website. My version of this jig occupies the left hand end of a mobile work unit that will also have a Fleischman type binding routing jig on it. The work unit will eventually have a set of 8 or 10 drawers for luthier tools and supplies.

The jig works by virtue of a stainless steel shaft that runs in four spherical bearings, one pair on the sides of the work bench and the other pair on the sides of a swinging router guide. The shaft is set at an angle to the work surface such that the radius of the swing is exactly 12" at the nut end of the work piece and exactly 20" at the soundhole end of the work piece. The shaft forces the router guide to swing in a compound arc, tracing the surface of a section of a cone.

The swinging router guide subscribes exactly the right compound arc, per the calculations! It has plenty of free swing to route the widest fretboard I'm ever likely to want (over 4" wide!). The swinging router guide binds on the sides of the work unit at its extremes. Some aluminum angle was added to set the router path straight and stiffen the top plate. I added a couple of locking knobs (using modified straight box stays) front and back to hold the swinging platform steady during routing. It's incredibly smooth in operation and works extremely well.

Please feel free to contact me and ask any questions you have about it.