Monday, April 13, 2009

Bass Nut

The nut of the bass is carved from a rectangular block of ebony wood. I start with a piece that is tall enough so that it extends between 1/16" to 1/8" above the fingerboard. It also has to be long enough that it covers the entire width of the pegbox at the fingerboard. (Hopefully, this makes sense. It's hard to describe.) I started with a piece of ebony that was about 3/4" tall X 2-1/2" long X 1/2" thick. I made sure that the ebony fit tightly and squarely against the fingerboard. If it doesn't, then I have to keep sanding and filing until it does. Since the strings will be going across this, it has to be a perfect fit against the fingerboard.

With the nut blank in place, I use a pencil to draw the contour of the fingerboard end on the blank. I also mark the ends where I need to cut off the length. I cut the ends off the blank after they are marked, and then I file and sand the contour. I keep checking the fit as I go to make sure I haven't deviated from my original markings, and also in case I didn't mark something very accurately. You can always take more away, but you can't add back!!!!

Once the fit is very close, I use hide glue to adhere the nut to the bass. I let it dry for at least several hours so that it won't work loose when I start filing it. All of the final fitting is done after the nut is glued into place. That is when I set the string height and the contour of the back of the nut. The back of the nut has to be rounded and smooth so that they strings don't break too sharply as they go across the nut. Otherwise, you'll get broken and frayed strings here.

I mark the string positions with pencil, and then I use a small, round file to put the grooves in the nut. Interestingly enough, the space between the nut and peghead box was originally cut uneven on this bass, so the second picture of the nut looks like the nut is crooked. It's not the nut -- it's the peghead box! It won't hurt a thing, and it's hardly noticeable after the instrument is strung up.

I use sandpaper and eventually 0000 steel wood & olive oil on the nut to make it perfectly smooth and shiny. This is also the time to get rid of any excess glue.

Now I can do the final fitting of the bridge and the nut. The strings have to be in place for this. I start by making sure the soundpost hasn't fallen. That's pretty easy to tell because you can hear it rolling around inside if it has! Bass soundposts are pretty big, so they make lots of noise when they are loose. I check to see that the grooves are the correct width and height for each string, and then I check the overall height of the strings and adjust the bridge according to how high or low I would like the the strings to be. Although there is a "correct" height for all of this, I have found that most bluegrass players have their own preference.

When all is done, you are ready to tune up and play!

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