Brass Rail Repairs

[BSimon1234@AOL.COM]

Mr. Fox:

You might not be a metallurgist, but you do seem to have a darn good handle on
alloys, work-hardening and such.  Your statement;

<< I am very sure that the brass started out in an annealed condition.  >>

makes a lot of sense. Decades later, work hardening through playing made the
brass very hard and breakage occurs! I wonder if there isn't some component of
crystallization, like in pot metal, where simply aging crystallizes and swells
the metal.  ( probably not in good brass?) 

It sounds to me as though  you hit upon the right explanation. 

Thanks for the input.  I am putting your post into my personal pianotech
archive.

Bill Simon
Phoenix

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
wrote:

<<
On Sun, 21 Mar 1999 07:14:59 EST BSimon1234@AOL.COM writes:

>I was wondering, however, why the piano companies did not anneal the 
>original
>rails. As you have shown, they easily could have, and I cannot imagine 
>that
>they did not know about it.

Bill,
	work hardening of the metal is a gradual process. I 'm not a
metallurgist but I am very sure that the brass started out in an annealed
condition.   Annealing is merely the creating of a stress free condition
at the molecular level in a substance.  The opposite is tempering. 
Tempering is done by heating the subject material and purposely
introducing stress by cooling the material quickly.  The thinner the
material the faster the quench necessary.   I believe that heating the
entire rail at the same time would be a better approach,  even if that
can only be accomplished by sweeping the heat source back and forth on
the brass.  The brass should then be allowed to cool very slowly.  Slower
the better.

 Do you think that over time continuous 
>impact
>stresses from playing might bend the annealed tabs out of line? You 
>are
>gaining a ductility and losing hardness.    Do you foresee any downside 
>risk?

It is when the material looses it's softness that it becomes prone to
breakage.   Again,  I am no metallurgist but it seems to me that as the
tabs go out of line they are becoming work hardened (Breaking).   Please,
anyone with better insight feel free to jump in here.   Until work
hardening occurs the brass is able to take the punishment just fine.;   I
agree that it would be nice if all engineering materials had an infinite
life span but then we wouldn't have anything to fix for a living.

>
>I have not yet duplicated a rail on my mill, but I always thought that 
>should
>I need to do so I would try to use copper, hoping that it would be 
>stronger,
>and get away from the brass annealing question.

Copper (unalloyed) is extremely ductile and would deform with the
minimal pressures needed to screw on the butt plate.   Copper/zinc or tin
alloys (also sometimes called brass)  do not exhibit this tendency.  
Brass with more than 62% copper can be worked cold but is notoriously
weak.   Most brass screws and bolts are made of this type brass.  Brasses
with more zinc are less ductile and stronger and are used for faucets and
sprinklers.  Add tin and it becomes salt water resistant.  Lead (Pb) 
makes it more machinable.  Nickel (Ni) makes it silverish in color.  

Less than 55% copper and it is not workable.  This form is used in
brazing applications.

 It would be easier to 
>work
>than steel, but still be a step up in longevity from the brass, which 
>I am
>sure was used because of cost and ease of cutting.

I'm not so sure that it wasn't used because it was the best choice.  
Steel and brass center pins would not be a good mix if you are
considering longevity of the piano.

JMHO
Dale Fox
Foxpiano@Juno.com