We are rebuilding a Steinway D and someone suggested drilling the tuning pin block for 1/0 tuning pins as opposed to the usual 2/0 size. The pianos I am familiar with that come with 1/0 tuning pins from the manufacturer either have tuning pin plate bushings or an open window pin block (no plate webbing over the tuning pin field).
My guess is that, in these instances, the greater flexibility of 1/0 pins compared to 2/0 is mitigated by the bottom of the coils being closer to the terra firma of either the plate bushing or the block itself. If that is correct, then the problem with using 1/0 pin in pianos without either an open window pin block or tuning pin plate bushings might be that thy are too flexible if the coil bottom is a few millimeters above the plate webbing, which imposes an additional few millimeters before the spot where the pin enters the block.
But that is pure conjecture on my part. Has anyone out there either done this themself or know of anyone else that has?
I am all in favor of experimentation, but do not relish the thought of possibly having to re-pin a freshly strung piano.
I would not do it. I would use 2/0. For the very reasons you pointed out.
Peter Grey Piano Doctor
Thanks very much for your input, Matteo! From what I gather, you are hardly alone in this.