re- fortepiano key "bushing

[Allen Wright]

I thought I'd mention an interesting and useful material I've found for
shimming the frontrail holes in the keys of a McCobb fortepiano (Graf copy)
here. This instrument is 15 years or more old, and the keys produced
considerable clacking noise because of excessive play on the front pins. I
should mention that the keys have what I suppose might be termed "key shoes"
(as opposed to recessed "plates") made of hardwood, U-shaped, and glued to the
bottoms of the keys around the frontrail hole. I assume these were installed
in the hope that the hole would stay the proper size for a longer time, but
these are also ultimately what caused the problem of clacking. Because once
they've worn enough to allow for any play whatsoever then there can be plenty
of noise introduced. In a recital here a couple of years ago the noise could
be heard clearly from the audience.
So my problem was to find a thin enough material to use as a shim, or
"bushing", in order to eliminate the play between the key and pin. There was
very little play, really, so at first I tried using superglue, and it worked -
but the difficulty of trying to get any kind of consistency of thickness,
having to file away the excess, etc. made it rather tedious. What did work
well, however, was linen tape (any art frame shop has it, used for mounting
art works to matts, etc.) - it's gum backing glues it quite strongly in place.
I cut small pieces and glued a piece as a shim on one side of the  key hole (
the tape is only .006" thick, and still I had to file away with little pieces
of emery board as files in order to allow for enough play that the keys
weren't binding on the pins!) In other words, only about .003" of play was
enough (because of the hardwood shoes) to allow for lots of noise in these
keys. I don't know how long these shims will last, but I'm hoping that because
they have some cloth content that they'll hang in there for awhile. An sort of
unusual and specialized problem, I know, but for others of you who work on
fortepianos, perhaps this is a useful material to keep in mind - has anyone
else out there used it? It might have other purposes - shimming hammer flanges
on modern pianos? although it might stick TOO well for that purpose. Once it's
on and dried it's pretty tough to get it off.

Allen Wright, RPT
Oberlin Conservatory