Hammers with no inner felt.

[Delwin D Fandrich]

----- Original Message -----
From: "Phil Bondi" <tito@philbondi.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: July 25, 2002 1:49 AM
Subject: Hammers with no inner felt.


>
> Does anyone know what kind of hammer is manufactured with no inner felt?
> They sounded fine on new wire(they need a poke here and there), but I
could
> not tell what kind of hammer they are.
>
> Anyone?


Underfelt is used to build out the size of the wood molding and provide a
basic shape for the hammer thereby reducing the thickness of outer felt
required to yield the final size and shape of hammer desired. A thinner
outer felt sheet is desirable to reduce the tensile stress on the wool
fibers running around the outer surface of the hammer when it is pressed
into the shaped caul.

The most resilient hammers are made with felt that is not overly hard
(dense), not overly moist when pressed, and not subjected to much heat
during pressing. Such a hammer will have an outer felt layer that is nicely
compressed around the wood molding and/or the inner felt and will be
stretched rather tightly around the outer face. It will bounce nicely away
from the string without rattling a lot. Unfortunately, this outer felt, if
too thick, can easily tear (crack) as it is pressed into the caul. Thick
felt can be pressed without a lot of steam and heat, but it takes much time
and care.

With modern hammer making techniques--very moist felt, lots of steam and
heat--cracking is less of a problem and thicker felt can more easily be
used. Considerable resilience is lost in the process but this no longer
seems to be a desirable characteristic for piano hammers.

Regards,

Anyone