Sunday, July 26, 2009

Fitting the Nut

Sunday, July 26, 2009

Not having parts and then having to make yet another unanticipated business trip have really slowed down progress this week, but I have been able to get a little bit done.

As you might recall, one of the last things I did last week was to seal my test soundboard with a mildly diluted hide glue formula. After it dried for a couple days, I spent about two hours hand-sanding it off to what looks like bare wood. It is my understanding that the goal here is to “clog” the otherwise open pores of the wood with the hide glue to prevent the stain from soaking in too much without inhibiting the stain from getting to the majority of the wood fibers. From what I have read of other people’s attempts at this, its almost impossible to sand it off too much. So, armed with my trusty 80 grit paper followed by some 120 and then 220 grit paper, I sanded off the dry hide-glue layer. Here is what it looks like.

One of the interesting things I found while sanding the glue off was that this is a really good opportunity to find and correct many of the imperfections in the contour of the top. The hide-glue dries just a little bit darker than the color of the raw spruce so each dip and valley, regardless of how shallow, shows up. I was quite surprised at the number of irregularities I found. I believe using this will really help the appearance of the finished mandolin.

With the fretboard now in place, it was time to install the nut. But before I could do that, I realized I needed a padded block to go under the neck while the mandolin is laying on its back to prevent hold the peghead off of the workbench. For this I picked a scrap piece of wood that measured about 1-1/2” x 3” x 4”, cut a shallow wedge in the center of the 4” long face, and glued a piece of soft leather to it. Here is how it looks.

NOW it was time to install the nut.

I started by measuring the width of my slot with my digital calipers. I measured both edges to make sure they were about the same, and much to my surprise, they were within .001” of each other.

I then measured my nut blank (bone - ordered and received way back).

Since the difference between the two was almost half the thickness of the nut blank, I decided to use my drill-press-drum-sander to get it roughly to size. (I used a piece of scrap would to verify the thickness before committing to the nut itself).

Once run through the drum sander, I measured again.

With less than 1/10th of an inch remaining to trim, I stopped there and finished sizing by hand.

I already new that the height of the blank would need to be trimmed but before I could do that, I needed to be able to mark the correct fret height on the nut and this could most easily be done once the nut was correctly sized to fit the slot.

Now to find a way to mark it.

I read somewhere that somebody had taken a wooden pencil, cut it down the center to create a “half” pencil and used this to mark the fret height - so that is what I did. Rather than try to cut the pencil, though, I used my drum sander again to sand away the unwanted half of the pencil.

Using my drum sander once again, I removed all but about 0.30 inches of material above the fret line and then hand-contoured it to shape before gluing it into the slot with Titebond. Here is how it looks now.

As you can see on the top photo above (if you look really hard, anyway) you can see I have marked where the notches for my strings will.

My brother-in-law read my last post where I wrote about buying and using feeler gauges for saws and offered up an old set that he had (and no longer used) for creating my “saws”. Not being one to look a gift horse in the mouth, I accepted and found that this set has a much wider selection of thicknesses.

And, last but not least, the remainder of my parts finally arrived late this week. Now that they are here and assuming I get to stay home a bit more this week, I should be able to get the rest of my binding on and try my hand at staining. I am really looking forward to the staining - if I am lucky, I may get to even try it on the mandolin, not just the test piece.

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