Nosing Around

[Brian Trout]

Hi Jeannie,

Happened upon your post about nose bolts, and thought maybe I'd offer a
thought or two, more or less off the cuff.

The nose bolts provide points at which the plate is anchored to the
underbelly, the wooden structure of the piano.  The outer plate bolts tie
the outside edge of the plate to the inner rim, the pinblock screws tie the
plate web to the pinblock (and perhaps a bit more indirectly to the
stretcher and again to the rim), and the nose bolts give the plate support
at various points throughout the inner parts of the plate.

Acoustically, fastening the plate solidly to the wooden structure of the
piano effectively adds mass and stiffness to the whole assembly, and helps
to contribute to even more solid string termination points.

Those nose bolts, when well placed, will help the plate to resist distorting
under the weight of all of those tons of string tension, and plates do bend
and distort, more so than some might imagine.

For the most part, when I'm setting a plate in a piano, I want it to sit
solidly on whatever support is around the perimeter.  Up in the front,
that's the pinblock.  Around the other edges, it's usually either sitting on
dowels or bolts or something similar.  When those points are set and solid,
so that the plate won't have to be 'bending' into position when the bolts
are tightened down, then I'll set the nose bolts.  (Up until this point, the
nose bolts are wound down at least part way so that the plate is not being
supported by them in any fashion.)  Now, one by one, I'll bring the nose
bolts up so that they will just come in contact with the plate.  I don't
want to bend the plate upwards or to put pressure on the plate.  The goal is
simply to have the plate sitting unflexed upon all of the points it is
supported by.  And then, it's ready to be tightened down.  I can't give an
exact measurement of torque readings that I'd use, but it needn't be so
tight that no man will ever be able to loosen them again.  I go a fair bit
past finger tight, but no large wrenches either.

The only one I can think of that is perhaps an exception is the single
Steinway bolt that runs down through the plate in the treble end, the one
that goes down into the "tone bell".  Most all of the other nose bolts you
encounter have a larger portion of the bolt that does not go through the
plate which provides a lip that the various points of the plate sit on, and
then the smaller threaded portion which normally comes up through the plate
and gets the nut put on it.  On the "tone bell" bolt, there is no lip on it.
It is normally set so that it's just past finger tight when the piano is not
under tension.  Once there is tension on the piano, you will need a wrench
to move that bolt.  This is another one that I believe is there to stiffen
the plate by tying it to the underbelly, effectively providing a more solid
termination point on that end of the treble sting section, which now that I
think about it, might be the upper part of the 'killer octave' range.
(Plenty more to ponder there...)

Hmmm...  the mind is drawing a blank again.  I'm sure there are other things
to be added, maybe even some corrections to be made.  But those are the
thoughts that came to mind just now.

Amazing the things that we muse over while tuning, huh?

Have a good day,

Brian Trout
Quarryville, PA
btrout@desupernet.net