Pinning the nut

At least one register pair needs to be in place to pin the nut. I've installed one and wedged it place so it doesn't shift from side to side:



Here are the tools needed to pin the nut:


From top left: 1.2 mm bridge/nut pins, Dremel Stylus with #57 drill bit installed, marking awl made from a nut pin installed into a dowel, and a marking jack with two pencil lines showing the proper string spacing for the wide string pairs (10.75 mm).

With the exception of the marking jack, the exact same tools were used to pin the bridge.

Pinning the nut starts by installing the first nut pin a known distance from the case edge. When pinning the bridge, I put the lowest bridge pin 37 mm rightward of the spine, so the first nut pin must match that position. Here it is:


The leftmost string is now in the correct position.

Next, the marking jack is dropped into the leftmost register slot and the wedge is adjusted until the side-to-side position of the register brings the left pencil line on the jack into alignment with the leftmost string. Now the register position and marking jack together will ensure the correct spacing of the remainder of the string band. Since the spacing of the register slots is 13.75 mm, and the pencil lines on the marking jack are 10.75 mm apart, the narrow string pairs end up 3 mm apart, as desired.

Each register slot can be used to pin two strings by matching them with the left and right pencil line positions, respectively. Pinning is as simple as catching the string with the marking awl and pushing it leftward until it matches up with the appropriate line, as shown in the next two photos:



When the string position is satisfactory, the awl is used to make a dimple in the nut:


Since the awl uses an actual nut pin, the thickness of the pin is automatically taken into account.

Next, a hole is drilled at the dimpled location and a nut pin is installed with the same pushing tool used when pinning the bridge. The tool automatically leaves a few millimetres exposed:


All that's left is to lift the string over the nut pin. Obviously the strings are pretty loose at this point to make them easy to manipulate: they've been tightened just enough to eliminate any visible slack.

Here is an overhead view of the process. Correctly pinned strings are to the left, unpinned strings and mess from drilling lots of holes are to the right:


Not only do the strings end up spaced correctly, but the string band is now parallel to the spine. Previously the strings all sloped slightly to the right as they reached the tuning pins. This was done to ensure they would gain some sidebearing once the nut was pinned.

A method such as this, done purely by eye, will yield some very slight inconsistencies in the string spacing, but this is accounted for when the plectra are cut to length and voiced.

When the nut pinning was complete, the position of the two gap spacers was rechecked. In order to keep out of the way of the jacks, each spacer must lie exactly below a close pair of strings. I moved one of them a little bit; the other appears to be correct. The spacers were made 3 mm wide to match the close pair string spacing.