BLUEBOOK OF PIANOS
PIANO
CONSTRUCTION AND SCALE DESIGN
ACTIONS
(Click on image to see how an
action functions)
THE
ACTION
Briefly
stated, the way a piano action works is that the down
pressure on a key is converted to a forward motion of
the hammer towards the strings. The hammer travels
five times as far and approximately four times as
fast as the front end of the key does, the key travel
being only about 3/8 of an inch at its front edge.
This is accomplished through a remarkable system of
levers and pivots which, for a quality piano, must be
adjusted to the utmost accuracy, making the action so
responsive to the player's touch on the keys that
there is almost no limit to the musical effects
obtainable. For a better, more natural leverage,
piano keys slope slightly downward towards the back
and become level when the key is depressed.
A piano action
would be a fairly simple mechanism if, when you
depressed a key, it just had to push the hammer
against the string. But if it worked that way, there
would not be much tone because the hammer would stay
against the string and, acting as a muffler, would
stop it from vibrating. Thus, it would not have had
time to return to its starting position after you
released it.
Consider
the manufacturing problem created by the fact that
thousands of the parts in a piano are moving parts,
that many are very small and that on some of them a
variation of a thousandth of an inch will affect
their performance. Not only is the utmost precision
required in making and assembling the parts, but they
must operate quietly and resist friction, wear and
loss of accuracy under long and strenuous use. The
materials used today for the best piano actions are
largely wood, felt, woolen bushing cloth and leather.
Like all products of nature, these items are inclined
to be unstable when exposed to varying climatic
conditions, although this hazard is greatly reduced
in the better pianos by use of the highest quality
materials and by superior workmanship.
If metal could be
used, it would simplify the manufacturing problems
and substantially reduce the cost; however, metal
(not being noiseless without frequent lubrication and
adjustment) does not lend itself to the purpose and
very little of it is employed. Many other materials,
including all kinds of synthetics, have been tried,
but, with few exceptions, have not proved success,
imagine a hinge or bearing that would work smoothly
and silently for fifty years or more without
lubrication or constant adjustment. Every pivot in a
piano action must do this and they do it because
these moving parts are held in a circle of specially
made material called bushing cloth. Action hinges or
pivots are made by boring holes in wooden parts,
lining the holes with this bushing cloth, then
connecting the adjoining parts with German Silver
center pins which will rotate in these cloth bearings
indefinitely without attention unless exposed to the
most abnormal climatic conditions. This cloth, among
its many other properties, must be uniform in
thickness to an unbelievable degree. The makers allow
a tolerance of 2 one-thousandths of an inch, plus or
minus, which is less than one-half the thickness of
an ordinary business card and is an incredible
measurement for such material. It requires a total of
ninety-six different operations in the felt mill to
produce the superior grades of this cloth used in
actions.
To summarize the
story about piano actions, good performance is not
only a question of superior materials. but also
involves skill, experience and the willingness of the
piano manufacturer to spend the extra money to have
these important hidden parts as accurate and
dependable as it is possible to make them.
***NOTE:
Hi there, I'm writing from Carnes Piano Co. in San Mateo, Ca.
I've read most of the info given at your site and it is excellent.
Although I would like to kindly suggest a correction to your PIANO ACTION section.
I guess Kawai's ABS components deserve some credit. Based on most people in the industry,
the actions made with ABS parts have high performance quality and they had proven to be
reliable; in some cases better than some actions with wood components.
I hope you'll find this statement adequate and also helpful for your site
visitors.
Carnes Piano Company 11/8/03
Correction noted:
Mr. Fred Carnes is a very knowledgeable and highly respected music merchant in the San Francisco Bay
area. We would like to enter this correction and totally agree with the statement by his company.
ABS action parts are a lot better than wood in every respect as many years of use and tests have proven.
Bob Furst - Author
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