I have always shaped the back of a guitar neck using a couple of different rasps, a spokeshave and sandpaper. The last couple of necks I've checked the work in progress using some profile templates I drew, then printed on paper and cut out. The results have been ok, but not as consistent as I prefer. Inspired by another thread, I decided to try making a neck shaping jig. The concept is to mount the neck in a jig, fingerboard down, and have a router slide on top of radius templates.
The neck shape profile was drawn at the first, sixth and fifteenth frets and then offset by the distance the router bit extends beneath the router base. I decided on three radius templates because using only two seemed as though it would make for a very large router base plate that would be difficult to control and subject to more deflection. The starting thickness of the neck, including fingerboard, and width are taken into account as well. The shape profiles and neck plan view of the neck are printed and then mounted to some ½” MDF using spray-mount. The high-strength spray mount was way too thick for this purpose, but, it was the only kind I had at the moment.
Everything is cut out and sanded to shape.
Screw holes for holding the radius templates are drilled, then the screws are threaded in so far as the tips barely poke through, then the radius templates are aligned and pushed on to the screw tips, marking the location for the screw hole. Note the vertical line on the radius template (beneath and between the letters “b” and “a”) is used to align the radius template to the neck.
Using a wooden screw clamp to hold the radius template makes it easy to drill the screw hole.
Test fitting the radius templates to the neck board.
A test neck was made from a scrap 2x4 and placed into the jig.
The router was mounted to a piece of ½” MDF. The base needs to be at least twice as wide as the distance from radius template to radius template so that it is always supported by two points. If I were to make another base, I would incorporate some kind of bushing around the router bit so I don’t have to worry about the bit cutting into the MDF accidentally. I would also mount some handles at the ends of the base for better control.
Then neck and jig are clamped to a sawhorse…but…now the clamps are in the way! Hmmm…
Once again, bicycle inner tubes to the rescue!
Set the router bit depth to take off only about 1/8” at a time.
Slide the router and base perpendicular and parallel to the radius templates and neck to cut the neck profile, keeping the bit perpendicular to the radius of the radius template.
Wear a face shield when routing because you will get hit with bits and chunks of wood.
Remove the neck from the jig…
…and remove the remaining chunks with a chisel, rasp, spokeshave or sandpaper.
Do some shaping and smoothing with some sandpaper…
…and check with the paper templates.
I love seeing build reports!