Tools & Materials:
Carbide Router Bit
Head Block Shelf for Classical Guitar:
This may seem like a trivial subject to cover, but come to think about it, one one of my first guitars, I didn’t pay enough attention to this matter and I had to do a lot of back-tracking to make things come out right.
Shave Down The Head Block:
The Head Block, which is part of the neck and foot assembly and they are all glued together as one piece.
When gluing the sides of the Classical Guitar into the side “Let-In” channels as I call them, provisions should be made for the top to be glued over the upper portion of the Head Block, on top of the Head Block.
This area is shaded in the tan coloring in the diagram above. You should have your entire top plate thickness sanded and all of the bracing attached and sanded to it as well.
The first step is to accurately measure your guitar top. This only way that is accurate enough for this is to use a Vernier Calipers
with a dial or digital readout.
Set Up The Router and Bit:
Next, set up a router (I prefer to use a Bosch Colt for this). You can use this router with a single hand and have much greater control over this task.
About the best bit you can use for this is a Down-Cutting Spiral Bit. These are usually used in CNC machines, but work equally well in a router. Transfer the cutting depth from the Calipers to the router and adjust it’s depth setting exactly.
Do a Dry Run of Scrap Wood First:
When everything is set, I prefer to do a trial run on a scrap piece of lumber. Hold the top plate over the routed test spot and run your finger over it or check with a straight edge. Adjust as necessary until the depth setting is perfect.
If you haven’t already, trim the top to the exact contour of the the guitar shape – at least in the area we are work with here. Also, if you rout out everything except the two corners of the head block opposite to the sides, you will be much more accurate in the routing depth. The last corners can be filed or sanded off. Finally, finish sand with a sanding stick and test fit the top to the head block to check the accuracy of your work.
Tip: If you are to error in depth, it is best to error with too shallow of a shelf cut as the top can be sanded a bit after the top is glued in place. If you cut too deep you will have to fill in with wood veneer – not the mark of an excellent guitar maker.