Saturday, May 26, 2012

Archtop Guitar Build - Fingerboard and Neck Extension

The neck for this guitar is made from a single piece of maple so there are a few aspects of this type of construction that I will take advantage of.  The neck was planed square, the headstock angle was cut and a channel was made for the truss rod.  I am using a Stewart Mac "Hot Rod" dual action truss rod for this guitar.  I purchased a spiral cut router bit that was exactly the same size as the truss rod width so the fit would be perfect. A dovetail was cut into the end of the neck to connect it to the body.

The fingerboard extension was something that I thought about long and hard.  The plans call for cutting a 5/8 inch rabbet into the end of the neck and then trimming away about half of the material to thin it out enough to allow the neck to sit low enough to allow a distance of 3/4 of an inch to be obtained if a straightedge is held over the fingerboard and extended over the body to where the bridge sits.  The problem with this way of attaching the neck extension is that you remove a perfectly cut dove tail with the rabbet and then have to re-cut that dove tail into the bottom of the fingerboard extension and this entails carving into a blind corner.  I thought about this and came up with this alternative.  A dovetail could be cut into fingerboard extension instead and this strong joint could be used to attach the extension.  This would allow you to fit the neck into the body and remove the fingerboard extension for frequent trimming of the extension to get the fit just right.  This is what the neck and fingerboard extension joint looked like.  The truss rod is also in place.

The fingerboard was run though my model making table saw to cut the fret slots and the taper was also cut into the sides.  Plastic binding material was run around the edges and mother of pearl inlays were prepared.  I really liked the inlays shown on the plans but when I looked around, I couldn't find ones that matched them.  I bought a set of generic block inlays (like on a Les Paul Custom) and cut scallops into the edges to make them "hour glass" shaped.  I then cut them at a 66.6 degree angle and fitted ebony strips between the two pieces and super glued the three pieces together so I had to only make one recess for the inlay rather than two.  These were glued in using epoxy with a couple of drops of amber and black Stew Mac Color Tone dye added.  This makes the epoxy "ebony" colored and any imperfections in the routs are magically hidden.  The finger board was set in place and a couple of pieces of fine wire were drilled though two fret slots to act as indexes for the glue up.  I used hide glue for this so that if I ever needed to replace the fingerboard, I could steam it off.  Here is the glue up.
The fingerboard is a uniform 1/4 inch thick so a 12 inch radius must be cut into the surface of it.  I bought a 12 inch Stewart Mac radius block from Bob Gaffney (be sure to check out his very well done archtop blog) and installed two shooting boards into the sides of the neck block.  This is one place where altering the neck building process from that described in the book works out well.  By leaving the block intact I can easily mount it in a workmate, hold the fingerboard in its final position and also mount the shooter boards with screws so that the radius block always travels straight down the fingerboard with no deviation left or right.  Here is the neck and fingerboard after 100 grit sanding to a 12 inch radius.

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