String breakage

[Danny Moore]

KUANG wrote:

  I think loose pin problems could be avoided.  I believe pin holes
  wear out
  because of unnecessary forces excerted by the pin holes (don't they
  only
  wear as result of years of tunings?).

This has certainly not been my experience.  I frequently see pianos with
loose tuning pins that may not have been tuned 10 times in 50 years.
The biggest factor I see contributing to loose pins is the natural
drying out of the wood pin block and the resultant shrinkage of the
wood.  The next biggest factor (on the Texas gulf coast) is delamination
of the pin block.  Remember, most older pianos have maple blocks
laminated with animal hyde glue.  This organic form of glue is
succeptable to attack by bacteria.  After a while, the bacteria eat
enough glue to allow the block to begin to come apart.  When that
happens, the block can no longer grip the pin.

  If you only apply force ( _not_ torque), then the pin hole wall must
  apply an opposite force unless your pin is not stationary (here
  comes Newton's law of mechanics).  However, if you apply a _torque_,
  then the pin hole wall wouldn't have to oppose any force at all
  (well, except some friction).

A very good definition of force and torque.  I submit to you, however,
that there is a great and constant force applied to the wall of the hole
- somewhere between 150 lbs (high treble on a low tension scale) to
approaching 300 lbs (low bass on a high tension scale) - the force
applied by the wire itself.  The tuner must exert enough force on the
pin to overcome the force of the string before the torque can be
applied.

  If you constantly apply forces only on a pin, then the diameter of
  the hole at the top is going to increase (the diameter at the bottom
  probably won't change at all).

This is true, however, those forces WILL be applied as long as there are
240 strings pulled up to pitch.

I am not discounting the damage than can be done by a careless tuner.
We have all seen that.  It's just that tuning stability is virtually as
important as tuning accuracy.  There are many more factors involved than
just turning a pin in a hole.  The pin must be "set" in such a way that
will minimize movement due to the environment, and the string tension
must be equalized across its termination points.

Just a little more food for thought.

Danny Moore
Houston Chapter