Wrestplank: Gluing together

The wrestplank (or pinblock) is also an important structural component in all harpsichords. Not only must it hold all the tuning pins tightly—although not so much that they can't be turned when the instrument is being tuned—but it must resist the pull of the strings and not get dragged backward towards the tail of the instrument.

The original Trasuntino has a walnut wrestplank 1.75" thick. Quarter-sawn wood would be helpful here, because its grain orientation allows the pinblock to expand and contract in the same direction as various other structural parts of the instrument.

Walnut doesn't seem to be available anywhere quarter-sawn, or perhaps only by special order, but that's not a problem. My friendly harpsichord maker told me to just saw up a bunch of slabsawn strips, stand them on edge and glue them up that way. Here are the raw materials:



The net result will be a block made of 2"-wide sections standing on edge. After planing to final thickness, the block will be covered with a veneer of soundboard material, as often is the case with many instruments, so the patchwork appearance of the multiple strips will be completely hidden.

I glued the strips up with polyurethane glue, which is quite strong and supposedly won't "creep" (i.e. shift slowly under prolonged stress) like conventional woodworking glues. This was my first time using it. It seems to work well, but has this habit of foaming dramatically as it cures. Not long after clamping everything, this beige sauce-like stuff starts oozing out of all the joints. It's supposed to scrape off easily when dry. I glued things up in two sets to start out:


Note that the leftmost set has strips of different lengths. This wrestplank is trapezoidal, not rectangular, so one end is wider than the other. It was more economical of material to not make all the strips full width. I used the same technique as I did for the baseboard in making these strips, by laying them down on the drawing right onto the outline of the wrestplank.

The final glue-up of both sets of strips:

By the way, the polyurethane glue does indeed scrape off when dry: a chisel seems to be the best tool to get it off, but it took a fair bit of work. You can see from the photo immediately above that I learned to apply it more sparingly the second time around. The squeeze-out I experienced the first time was a bit much. I have to say I'd be leery of using this glue on joints that would be easily visible in the finished product because the foam spreads out sideways much more than squeeze-out from regular glue.

After scraping the glue off, the wrestplank was planed on both sides to its final thickness, and the left edge was cut cleanly. I've left it long on the right side for now.



A straight taper will be cut along the back edge.