Pinning the nut

Now that all of the strings are in place it is time to pin the nut.

The "nut" is the bridge which sits on top of the wrest plank between the tuning pins and the bridge.

It is the pins on the nut and on the bridge attached to the soundboard that control the exact position of each string, and it is really critical that they are in exactly the right place because there is essentially no margin for error if all of the strings are going to end up in the right place relative to the jacks.

Since this instrument has two registers there are pairs of strings each of which sound the same note. These pairs of strings fall on opposites sides of the jacks for each note and the jacks face in opposite directions. The front jack plucks the string on its right and the back one plucks the strings on its left.

The size of an octave on this instrument's keyboard is about 162 mm which only leaves 13.5 mm per note into which we have to fit the width of the jack (about 4 mm) and two strings (which range from about 0.25 mm to 0.5 mm in diameter). What that means is that the pair of strings for each note ends up having a width of about 10 mm, centered on the 4 mm jack leaving about 3 mm between the jack and the strings. That leaves us another 3 mm separating the string pairs for adjacent notes. (and yes, there is another 0.5 mm in there somewhere that you can put wherever you need to in order to make things fit ...)

To make it easier to get the strings into the correct position we use a marking gauge which drops into each jack slot in the register and which has lines marked on it indicating exactly where the strings should be. Once you have that in place all you have to do is to insert a pin into the nut at the correct place. The catch is that you don't just want to get the string into the correct position at a single point - you want it to cross the registers at right angles and maintain the same distance from both sets of jacks - and that can only work (especially in the treble where the strings are very short) if the pins that have already been inserted into the bridge are also in exactly in the right place.

Before doing anything else I went used the marking gauge to go through all of the strings looking for any obvious problems - everything seemed to be OK, but it looked as if I was going to have to take about 1.5 mm of the right hand end of the registers to get everything to line up correctly. I was pretty sure about this but also a little worried because the parts in this kit have all been cut amazingly accurately and the registers already looked as if they fit perfectly.

However, when all else fails, try reading the instructions ...

The instructions were to set the rightmost string into a specific position (1 19/32" from the inside edge of the case), and use that in conjunction with the marking gauge to determine the correct position of the register. Amazingly enough, when I actually followed the instructions, I determined that the back register needed to be in exactly the position that I thought it needed to be in - about 1.5 mm to the right of where it was. So, I took about 2.5 mm off the end of the register (an extra 1 mm to allow for future adjustments) and set it back in place with some shims at either end to fix it in the correct position.

By the way, this instrument has what is, for an Italian harpsichord, a distinctly inauthentic but very practical feature - a hole in the spine of the instrument covered by a removable plate which allows the registers to be removed without the need to also remove most of the strings ...

Once everything was in place the actual drilling of the holes and inserting the pins was quite easy.

The result looks like this:



Here is the marking gauge being used to check strings that have already been pinned.

The distances involved are so small that you have to be very careful to look directly down on the string when checking the alignment. Here the camera angle makes it look as if the right hand string is slightly to the left of the mark but in fact both of these strings are lined up in exactly the right place.

In the end everything went very well and I only made one mistake (at least, only one that I have found so far).

There were three pins that didn't quite end up in the right place. They weren't out by much and I could probably have just gotten away with bending the pins a lot to force the strings into the right place - but that would have left me with no possibility of doing any fine adjustment on those strings and since everything else appeared to be "just right" I decided to go back and fix them.

This was really quite easy and didn't even take very long to do.

First I removed the three offending pins and drilled the holes out slightly to 1/16".


Then I plugged the holes with small pieces of cherry which I had whittled down from a spare piece of soundboard molding. This is exactly the same way that I plugged the holes left by the nails that were used to position the nut when it was being glued down. In fact you can see one of those plugs right in the middle of this picture.


Once the glue dried I cut the plugs off flush with the nut and sanded carefully with a small piece of sandpaper.


After redrilling the holes and inserting the pins you really can't tell that anything was done (except for that fact that the pins are now in the correct position ...)