Rock Maple Hammer Cores

[Delwin D Fandrich]

> -----Original Message-----
> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On
> Behalf Of Phillip Ford
> Sent: February 11, 2004 1:03 PM
> To: pianotech@ptg.org
> Subject: Re: Rock Maple Hammer Cores
>
>
> Andre O wrote:
> >
> >I have nothing against maple for many uses in piano manufacture, but I
> >believe there are more suitable woods for hammer cores.
> >...
> >My early experience with Hornbeam cored Imadagawa hammers put me off
using
> >hard core wood for hammer cores. You could voice these things forever and
> >they still screamed at you, similar to the early series Kawai KG hammers.
> >I understand that hammer manufacturers have to be very careful when
> >pressing up hammers made with lighter cores such as Walnut or Mahogany. I
> >suspect that when using maple (or hornbeam) cores, it is possible to load
> >them up to the max. in the press without fear of damaging the core-wood.
> >Furthermore, you can imagine how much compressional pressure there must
be
> >right at the apex of the core. A softer core wood provides for a level
> >of 'give' under the highly compressed hammer felt. This may go some way
> >towards explaining why hammers with maple or hornbeam cores are generally
> >so bright.
> >
> >Ron O.
> >--
>
> Some time ago I saw a Bluthner piano with hammers having softwood cores
(it
> appeared to be some sort of pine).  Also the nose of the core was not a
> sharp point, as is typical now, but a blunt rounded end.  The piano had a
> beautiful tone.  I assumed that the reason we do not see softwood cores
> these days was because of strength issues when pressing the hammers.
Would
> there be other reasons?  Also, what's the point of the point on the nose
of
> the core?  Is it tonal, or is it to help in keeping the felt from moving
> around when the hammers are pressed (or some other reason)?
>
> Phil Ford
> ----------



I've been hearing about the tonal characteristics of the various species of
wood used for hammer moldings for something over four decades now. And,
still, I remain unconvinced.

Molding wood is chosen for a variety of reasons, mass being only one of
them. And that is a very minor consideration, indeed. If you actually weigh
hammer moldings of approximately equal strength and stiffness -- especially
once they are all tapered, coved, curved, etc. -- you'll find that the any
mass differences are so slight as to be virtually non-existent.

One of the most significant factors in this choice is how much compression
and shear stress the wood (obviously, with the grain) can bear without
bending and/or breaking. Denser and thicker hammer felt requires higher
press pressures and stronger and tougher wood moldings must be used. Hence,
in hammers like (but certainly not limited to) the very hard Imadagawa's --
which use a lot of dense felt and relatively high press heat and pressure --
we see molding woods like hornbeam or maple being used. (Hammer press
alignment and the skill of the press operator can also be factors -- a press
in poor alignment places more shear stress on the molding as does a
misaligned felt strip.

It would be nice to be able to make a general rule about this: maple molding
= dense and heavy hard-pressed hammers; walnut or mahogany moldings =
lighter, softer and more resilient hammers. Unfortunately, such
generalizations are not accurate, even though we often see them. One hammer
maker might use the great strength of maple to make a slender, beautifully
tapered hammer molding that is both stronger and less massive than another's
thick and chunky mahogany molding. If the felt pressed on these maple
moldings is of reasonable density and texture and is pressed using
reasonable temperatures and pressures the resulting hammers will outperform
those chunky mahogany hammers in all respects. Personally, I like maple
moldings because the seem to hold a good backcheck surface longer and they
It's all a balancing act.

Blaming the species of wood used in the hammer molding for the mass, density
and character of the felt is a bit like blaming the horse for the
uncomfortable saddle. Dense, hard-pressed hammers get that way because of
the characteristics of the felt coupled with the heat and pressure of the
press, not because of the species of wood used in the moldings. Woods like
hornbeam or maple are required in these hammers only because they are strong
enough to stand up to the physical abuse the moldings are subjected to
during the press cycle. They have little or nothing to do with the aural
abuse we are subjected to by the hammers made this way.

Del