Modernizing the Ancient

A traditional flamenco guitar came in with the complaint of imprecise tuning. Like many ancient and romantic instruments, flamenco guitars are fitted with friction tuning pegs. These are made of a hard wood such as ebony or boxwood, and are tapered so as to jam in the peg-hole to hold tune. This is a grim proposition, as small adjustments are seldom possible and often necessary. Here we will slot the existing headstock for conventional geared tuners, like a modern classical guitar would have. 

First we will measure the headstock in detail to make sure that, I don't know, the whole headstock isn't off center by a full degree. Oh good it is. This strange geometry will need to be accounted for if the slots are to look right and the tuners are to appear even. Small discrepancies can cause unsightly asymmetries that draw the eye and are difficult to fix. Fore-warned is fore-armed. The slots will be indexed off the sides of the headstock, rather than any center line.

The first holes drilled are in the sides for the string rollers to pass through. These are done before the slots so as to avoid any chip-out into the empty space. Whereas the drill bit would have blown through into the slot, taking chunks of mahogany with it, this way the router will cut the slot from the top, right through the side hole, resulting in a factory clean appearance.

A custom router template is made for both slots. It will be adhered to the front of the headstock, and a flush trim router will trace and cut the shape into the wood. This all is very delicate, and a lot could go wrong quickly. It is paramount that the template be sturdy and well attached. It's position checked and re-checked 346 times.

Once the template is well placed, the shape is scribed into the surface for easy realignment later. My rule with routing is to put as little strain on the cutter and template as possible. This means removing material well inside the scribed area with more efficient, but less precise tools, and then finishing it off with the router. Again, worried about chip-out as I gleefully drill through the headstock, I have clamped a spoiler board to the back to remove any shock as the bit passes through the headstock. It continues immediately into the spoiler board with no gap, and thus no room for a chip out. Here you can see the left side finished and the right side still being roughed out.

Nice and clean, still waiting for interior roller holes to be drilled and for relief to be cut from the nut to each slot. This will ensure the strings don't drag or vibrate against the headstock.

Before and after. Now the tuners are fitted and the system is working perfectly. A much more practical flamenco guitar! 

Material is carefully removed with a finely beveled flat chisel. Notice how I take an angle to the grain: the thickness of shavings can be keenly adjusted by the cutting direction. Just a little bit, and then to check again.

The whole time we are shaving and checking for a snug fit, we must also be monitoring the neck's angle in two planes: from side to side and front to back. Too far to the left or right will result in string centering issues or maybe an asymmetrical look. Too far forward or back will create action adjustment issues in either extreme. Here you can see that I use a taught length of dental floss to check the neck straightness.

Now this is what we hope to see as the neck is nearly fit. An even gap all the way around the neck block. With a little sanding the eventual joint should disappear. Notice the bent Koa sides are cut a bit long where they attach to the neck block. This way we can knock them down gradually and get a really nice tight fit. 

Here the side will be carefully trimmed first with a chisel...

...and a snug fit is achieved. This picture does a better job of illustrating just how strange the neck geometry is on a semi hollow carved top.

Now the neck is trimmed to shape and the guitar looks, well, much more guitar-y. A tight-fitting hand-hewn mortise and tenon joint is quite strong, certainly intended to stand the test of time.