Marking out: Nut and tuning pin positions

Some weeks ago I cut the soundboard to its final shape: this was as easy as clamping it to the frame of the harpsichord and routing all around it with a laminate trimmer.

With the final shape established and the board clamped in place again, the process of marking out the locations of the nut pins and tuning pins commenced. Once again, the registers that were made many months ago acted as the marking stick that determines the positions of key elements.

Before marking out, I had to calculate where to locate the leftmost string in order that the string band be centered on the instrument. This is determined by subtracting the width of the string band from the interior width of the instrument and dividing the answer in half. Back in the autumn, when determining the bentside curvature, I estimated this would be something like 35 mm; it turned out to be 37 mm, which is close enough.

The string band width comes directly from the distance between the first and last register slot, with one caution: a harpsichord with two registers has left-facing and right-facing jacks with strings on either side. Therefore the lowest string is left-facing but the highest string is right-facing. Marking out with the register gives the position of all strings belonging to one register only, not the other. The final right-facing string is located one more register slot to the right of the final left-facing string (a distance of 13.75 mm), minus the string spacing between narrow pairs (which I have decided will be 3 mm), giving a position of 10.75 mm to the right of the final left-facing string.

I clamped one of the registers in place along the back edge of the register gap, making sure the first slot was 37 mm from the left edge. With a pencil I made a little tick mark on the soundboard along the edge of each register slot:


I also put a tick mark for the final right-facing string based on the calculations above. Next, I drew a line on the wrestplank to mark the nut position, which has its centre at 46 mm from the front edge of the wrestplank. With a square, I transferred the first set of tick marks to this line. Then, with a compass set to a width of 3 mm, I marked the position of all the remaining right-facing strings:


Finally, I drew parallel lines 13 and 26 mm from the front of the wrestplank and, using a bevel gauge set to 10 degrees, I drew lines from each tick mark on the nut to intersect these two lines: each left-facing string the first line, each right-facing string the second. The intersection points mark the tuning pin positions, which are shifted 10 degrees to the right of each nut pin. I pricked these holes into the wrestplank surface, shifting pins that represented accidentals slightly forward to make visual identification of the pins easier:


The next step will be to use a large T-square and tape measure to mark out the string sounding lengths on the soundboard, which will locate the bridge, and to determine the hitch pin positions along the bentside.