Wednesday, September 5, 2012

The Triple Nut Extension - Continued

Previously, when I made triple nut or swan-neck extensions I used a drill press to remove the excess material and then trued the edges and finished the bottom of the excavation with various chisels. Using the drill press for this process makes me nervous. There is the risk of something slipping and ruining my work and it is generally rough work. So this time I decided to do the entire procedure with chisels - one pegbox per day.
I laid out the boundaries of the smallest cavity (you can see several reference lines) and proceeded to partially  excavate a small area with various sizes of chisels. Working like this it becomes obvious how to proceed: truing the edges, then deepening the recess, lengthening it a little and then truing again. I found that the work went quickly and neatly.

Of course, this pegbox was the easiest to do. The middle one requires working under the over-hanging nut support. It is made even more difficult because of the limited space for the six peg holes. The last hole for this rank of strings goes far under the over-hang. Here I am using a "skew" chisel to reach the rear of the recess. Note that I am using a waste portion of the original block as a support. Later, this cut-off along with the others will go in the wood stove this winter.

The first pegbox is a little more complicated in that the treble side has several crooks and curves. I lay these out with generous side cheeks which provide strength and stability. Here I am using a front bent chisel to clear the bottom of the recess. I like to leave more than six millimeters of wood thickness  in the bottom of this pegbox for strength. I can achieve this even with the relatively low profile of the pegbox by drilling the holes off center and closer to the top edge by a millimeter and a half. Although I found this work pleasing I still felt I needed some aesthetic gratification. I reamed out several peg holes in the finished pegboxes and inserted temporary pegs to see what the final product would look like.

One feature of this design puts the chantrelle in its own recess. This allows the string a straight run over the nut and into the pegbox cheek at an angle that is far less likely to break it. I drill a pilot hole and enlarge and square the recess with small chisels.

This photo also demonstrates how I clamp any of the types of  extensions that I make. I tie two wound bass string of the same size in the appropriate holes in the bridge at one end and on pegs in the pegbox. When these strings are brought up to equal tension the extension is pulled back into the neck joint in proper alignment. Two spring clamps hold it firmly against the bottom of the neck.

The back of the extension that over-laps the neck can then be contoured. Visible in this photo is the skewed angle of the rear of the extension. I leave a little more room on the treble side for the player's thumb to comfortably grasp the first fret position.

Next time I'll show photos of the finished lute and describe a surprising historical varnishing process.

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