[pianotech] Hammer felt etc. [was ...]

John Delacour JD at Pianomaker.co.uk
Tue Feb 17 14:56:53 PST 2009


At 14:48 -0500 17/2/09, erwinspiano at aol.com wrote:

>Assuming that would rob you of missing some hammers with great 
>potential. Often time & even with the weickert felt the tone may 
>seem slightly under but thisÊis simply a need in most cases for some 
>filing.  The felt is quite dense & strongly springyÊin the weickert 
>hammers & and I would caution all participants from using very much 
>hardening solution of any kind anyÊwhere & certainly not strong 
>solutions.
>
>The fact is a hammer is a felt spring, & sometime that niceÊstrong 
>spring has a radical gradation or uniqual springyness, meaning that 
>in the case where the sound is initially a bit soft,Êthe hammer 
>top/crownÊhasÊtoo dis-similar a spring rate as the felt under 
>itÊcouple mm or so down.

Well it does depend a lot on how the hammer is made.  As I have made 
clear, I now use almost exclusively Abel hammers and most sets I get 
are made to special order with the felt of my choosing, which at 
present is almost always Wurzen AA felt.  I have not yet tried their 
"natural" felt but will do.  My experience seems quite similar to 
Paul Williams':


At 10:43 -0600 16/2/09, Paul T Williams wrote:

>The "raw" hammers are suprisingly nice and round. ÊAfter a very 
>light paddle filing over the top (they're not very cupped right out 
>of the box!) the clarity and "bite", if you will, begins to sing 
>out. ÊI follow that up with some tone building and sustain building 
>with some light needling on the mid shoulders ala Wally style.

I'm not familiar with Wally style but the main needling I do is done 
with a jabbing action radially.  I use always a single needle, with 
the hammer, or a group of hammers supported on a special rosewood 
tray.  I won't bore the list with every detail of what I do.  The 
point is that nowadays the Abel hammer is a lot different from 20 
years ago when the Abels left Renner and set up making hammers in 
very much the old Renner style.  These hammers _were_ cupped and not 
only that; when the hammer heads were cut apart there was contraction 
round the edges so that the width at the crown and round the 
perimeter was less than the width of the moulding.  These hammers 
needed quite a lot of preliminary work to release this tension and 
get rid of the concavity of the crown.

The hammers I get from Abel now are quite different and in the past 
couple of years I have found the preliminary work needed diminished 
almost to nothing.  On thing I guess they do now, and this in only a 
guess based on what I would do myself to get rid of these defects, is 
to compress the felt length lengthwise before gluing.  Other special 
devices have been developed to clean up and relieve the surface of 
the hammers where they have been pressed against the cauls.  The bad 
way to do this is to sandpaper the whole strip to shape, as one 
luckily shortlived hammer maker did, to my horror.  I think you will 
get a hint of how Abels do this from a very small picture at their 
site.  However it is done the result is excellent.  For many years I 
did not use Abel because I was not impressed with their consistency 
and could never be sure not to get a soft set. (I used mainly special 
Imadegawa hammers). Besides that their glue was unreliable.  The Abel 
hammers I get now are a completely different beast and my recent 
experience has been thoroughly satisfactory.

I have made it clear that I am all for Wurzen felt from what I have 
tried, but the same felt differently applied to the hammer will not 
behave the same, and there is a lot more to hammer-making than has 
been suggested by some postings on this topic.  It has been suggested 
that there is an old way of making hammers with one felt, which is 
good and a 1990s way of making hammers with another felt that is bad 
and that we now have the second coming of the good old way with the 
good old felt.  This is pure nonsense.  The variety of felts, methods 
and machines used 100 years ago was vast.  Pianos were big business 
and there were dozens of excellent hammer makers and a good variety 
of fine felt makers.  When I started out in the trade we used to do a 
lot of hammer refacing both on uprights and grands and that was a 
good way to get familiar with the variety of textures and qualities 
of felt and how they behave.  The felt that always surprises me most 
is the felt on the old Bechsteins.  How it worked at all I don't 
know.  Felts that feel and look completely different and are 
obviously of different textures can be made to produce equally fine 
results.

JD









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