[pianotech] tightening balance hole was Bouncing Bostons

William Monroe bill at a440piano.net
Sun Aug 1 19:56:30 MDT 2010


Jim,

I won't speak for JD, but when I do this job, I use a similar process, but
use 1/4 sawn poplar for the insert.  Then, when the job is done, the through
hole is made "funnel shaped" enough simply by rocking the key back and forth
on a jig with a clean balance rail pin installed on it.  The jig allows the
key to rock perhaps 3/4", rougly twice normal key travel.  Once or twice is
all that is needed.  I suspect if you simply place the keys on their
keyframe when done, with no back rail felt or front punchings, you'd have it
too.  Maybe even with punchings.  I don't know, never tried it.

William R. Monroe

SNIP

you simply say run the drill backward to center on the pilot hole and drill
through the hornbeam.

This will give you a hole the thickness of the hornbeam bushing. If it fits
the pin precisely it cant pivot freely, so the hornbeam has to be relieved
from the inside of the mortise.

1  How are you relieving the hornbeam from the inside to create a "funnel"
shaped hole

2 (This is question that's tripping me up) in creating that funnel shaped
hole, in order keep the hole at the bottom of the key a true circle fit
precisely to the pin, the hole has to have no depth, ie the funnel has to
come to a point at the bottom of the key.  I don't think this is what you
are doing as the hole would be elongated in quick order.  On the other hand,
if you leave the sides of the hole straight for 1-mm or some amount to give
the hole some meat before it is relieved, then you have to introduce slop
into the hole to let the key pivot. slop = clicks.

how are you achieving the necessary freedom of movement and the snug-ish
hole?


Jim I
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