Question about tuning pins and strings

[Delwin D Fandrich]

----- Original Message -----
From: "jstuart1" <jstuart1@pdq.net>
To: "pianotech" <pianotech@ptg.org>
Sent: August 06, 2001 1:27 AM
Subject: Question about tuning pins and strings


> While tuning a couple of the pianos I have, I noticed that some of the
> strings in the trebble unisons touch thier neighbors in the vicinity of
> the tuning pins. After further investigation, this seems to be the case
> on all 6 of the pianos I have. I am curious as to why. It appears that
> the tuning pins were set to close together in this area. How does this
> affect sound and tuning of the pianos? Are most/ all pianos this way?
> Even the baby grand I have is like this.
>
> Thanks
> Judy
> -----------------------------------------------------------

This occurs most frequently in very short pianos--whether they be grand or
vertical--and typically toward the lower tenor section, but I've encounter
it some relatively large instruments as well. It occurs most often in pianos
using plates that are drilled to either a drilling pattern or to plate
dimples.

First the problem with short pianos--
For a variety of reasons most designers of short pianos use rather high
string angles toward the low tenor. This flare is centered around the hammer
strike line where adequate unison spacing must be maintained to provide
hammer and action clearance. This means that the strings will diverge toward
the foot, or bottom, of the piano and converge toward the front, or top, of
the piano. For reasons that have never been adequately explained all of this
flare typically takes place through just the tenor section with the strings
through the treble section(s) running roughly parallel to each other. At
least the center strings of each unison are usually more-or-less parallel to
the center string of the adjacent unison through the treble section(s).
There is nearly always at least some string divergence within the unison
itself--the two outside strings angle away from the center string somewhat.
And in the bi-chord string section the unison center is actually an
imaginary line between the two string which themselves are diverging toward
the foot (or bottom) of the piano.

This means that all of the strings are converging toward themselves
somewhere in front of (or above) the piano. All of this makes the
side-to-side spacing of the tuning pins very tight, especially as they get
squeezed together--fore-and-aft (in the grand) and up-and-down (in the
vertical)--toward the low end of the tenor section. In some exceptionally
tight scales strings will often touch each other no matter how carefully the
tuning pin field is laid out..

Next, the problem of erratic plate drilling--
Piano plates made before the advent of numerically controlled drilling
machinery (whether that control be by paper tape or by computer
program--i.e., CNC machining) were drilled either to a hardened steel
pattern or to dimples cast in the plate surface. In both cases there was
considerable room for error. If the tuning pin drilling is off even slightly
strings will rub together. Even if the tuning pin field was once carefully
laid out, pattern and template maintenance over the years allowed errors to
creep in. In some cases these errors have been perpetuated through the
transition to CNC machining. There are at least a couple of plates in
current production that are now drilled on CNC equipment using x,y
coordinates taken from existing drilled plates. The new plates coming off of
these machines still exhibit exactly the same drilling mistakes that were
present in those existing plates, the out-of-place drilling coordinates
having been faithfully ported over to the computer based controller.

If you're interested, there's some discussion of action center spacing
problems in my PTJ articles on small vertical piano design, The Problem of
Small Pianos, Part I--July, 1997 and Part II--April, 1998.

Perhaps the more important question is: "Does it really matter?" Unless the
strings are actually binding to the extent that it adversely affects you
ability to tune the piano, no. On the other hand, it does look sloppy and
with careful design it can nearly always be avoided except in the tightest
of scales.

Even manufacturers of very high-end pianos allowed themselves to become a
little sloppy over the years and simply let this stuff happen. I remember a
"Piano Quality Comparison Chart" that was circulated by a Yamaha dealer in
the mid- to late- 70s that had pictures of this in a Steinway grand and
comparing it with a comparably-sized Yamaha grand. It made a dramatic, if
mis-leading, point.

Del