Schilling & Sons Pinblock Work

February 14, 2020

As noted in the previous post, the pinblock in this piano had separated from the back posts.  Previously, a repair had been attempted by boring through the pinblock and bolting the block to the back posts.   While the piano was unstrung, I used the existing bolts  to close the gap further, and then inserted low-viscosity epoxy into the gap for a solid composite construction.

Showing the closed gap and epoxy fill after sanding

This was the first time for me to do this procedure, and a bit of a learning experience, because epoxy ran in directions I did not anticipate.  While working at the back of the piano and monitoring drips there, I did not anticipate epoxy running out through the tuning pin holes.  The photo below shows my corrective actions after discovering the mess.   I first inserted ear plugs, then realized that the old tuning pins would also stem the flow.

Note to self: Next time, do the epoxy application before removing the tuning pins!

The epoxy flowing through the tuning pin holes wasn’t really a big issue, since it was my intention to restore this pinblock by filling pinblock holes with epoxy and then re-boring. This also was a process I had not previously used.  In theory this will result in tight fitting pins of uniform torque, without resorting to oversized pins — or replacing the pinblock.  I’m pleased to be using this technique for this piano, since I’ll be seeing the piano regularly in the future: this is an unpaid project for the family.   I feel free to experiment!  The photo below shows the pinblock with this epoxy fill complete.

Pinblock holes filled with epoxy

Following the fill of epoxy, I let it cure for a week before reboring.  To achieve uniform results, I chose to use a double-boring technique.   Initially, I bored with a 1/4″ drill bit (0.250″).   Within that process, it became clear that double boring was a good idea.  The epoxy was brutal.  While boring the 200+ holes, the drill bit was good for 15 to 20 holes, and then required re-sharpening.  The photo below shows my setup for boring at a uniform 7 degrees.

Initial boring of the pinblock with an undersized drill bit.  The drill guide has detents at 5 degree increments.   The guide was set to 10 degrees.   The base, riding on the pinblock and v-bar was set to -3 degrees for a net 7 degree bore angle.

After the initial boring, the pinblock was sanded and re-lacquered.   Final boring was done with a letter J drill bit (0.276″).  This boring was very smooth and easy-going.  I completed these bores freehand just following the initial bore.   Number 2 tuning pins were tested in the first two bores with good results:  smooth turning pins with 120 1b-in of torque.  I’m encouraged by the result.  I’ll know more later!

Open faced pinblock: bored, lacquered, and ready for restringing.

 

After all that, it’s nice to see stringing complete.