Neck Angle Jig
For both mortise-and-tenon bolt-on and dovetail glue-on necks, I use a bench-mounted router jig that simplifies cutting the desired neck angle at the heel. The fixture, manufactured by Chris Klumper of luthiertool.com, clamps a neck with a centered truss rod slot to a vertical plate, neck heel pointing up. Two (2) perfectly centered locating pins accurately position the neck, while a dial indicator, juxtaposed to an adjustable horizontal plate that will support a hand held router, lets me calculate and dial in the precise angle needed to mate the neck heel to the body, as well as cut the tenon, be it straight or dovetail. It accomplishes this by letting me compensate for the (desired) offset between the plane of the fretboard and the height of the bridge. As I am constantly altering guitar designs, not having to stop to think in terms of angles is of tremendous benefit to me.
Recently, I set out to modify my jig with an option to reference the edge (side) of the neck, instead of the center, as I had added a carbon fiber Dragonplate D-Tube to the neck. If you are interested, you can view the article on the D-Tube install here. The D-Tube neatly occupies the center position in a neck blank, and I wanted to come up with an alternative to drilling into the carbon fiber in order to make use of the neck angle jig's centering pins. I would need to rely on the outside edge(s) of the neck for referencing the center position, and that meant *no longer* violating the perfectly squared sides of the neck blank as I had been doing, prior. To this end I added a self-centering clamp, a relatively inexpensive Panavise 376. I chose to bolt this vise to the center of the backside of the vertical plate of the jig. The fixed center block of the vise had limited space for drilling, which helped determine where to countersink two (2) slightly oversized through holes in the vertical plate.
The next step was to locate, drill and tap two (2) holes in the Panavise.
Mounting the vise to backside of the plate restricts it's travel, shortening the throw of the vise. I addressed this by replacing the two (2) pieces of 90° angle iron that shipped with the Panavise with a pair of wooden extension blocks. Each block will press up against it's respective side of the neck, extending the reach of the Panavise across the face of the vertical plate, to assist in positioning the neck relative to center.
One last modification was required, and that involved relocating the neck angle jig's hold down clamps in order to accommodate a wider neck (blank). Up until now, I would reduce my rough neck blanks in width in order to fit between the jig's hold down clamps.
I have to laugh at myself, here. It is humorous to me how these inefficient idiosyncrasies can develop in a workflow... When I first obtained this jig several years ago, I encountered the narrow space between the pre-positioned hold-down clamps. If I remember the discussion I had with myself back then, I determined that as I was positioning that first neck relative to it's centerline (truss rod slot), it would be easier to just saw the neck blank a little thinner than to tear the jig apart and relocate the clamps. Several years and many, many necks later I was still (re)sawing my neck blanks to fit between the narrowly spaced clamps.
This is reminiscent of that great kitchen cooking story, where a perfectly good roast gets seriously trimmed prior to being put into the oven. When asked why, mom says, 'That's how grandma always did it'. Only after going to grandma did the truth come out: 'That was so it would fit into my small pan!'
I determined to bring my own silliness to an end!
I drilled and tapped a pair of holes for both the upper and lower DESTACO clamps, relocating them as far apart from each other as the vertical plate will allow. I could have done this years ago and saved all that sawdust.