Capo-hardening

[jolly roger]

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>
>
> Regardless of what folks claim, our tests have shown that V plates are
softer
> - at least for Kawai, Samick and Yamaha. This is what one would expect since
> V plates have a longer freeze time. The big advantage of V plates is that
the
> longer freeze time results in plates with less distortion and internal
> stresses. These plates can be 'stuck' into a piano (which is usually how
they
> are installed) without any need for de-stressing.


Hi Ron,
            I am either mis reading you, or dis agreeing?   Having spent time
in the Yamaha foundry.  The V Pro plate is cooled and ready to work in 40mins
flat.  The sand cast plate is left in the mold with electrical heating for
24hrs approx.  The slow cooling gives the stress relief required to prevent
distortion.   The rate of cooling also effects the structure of the free
carbon
crystals.  I have heard stories about aging plates, out side in the elements
for extended periods, for further stress relief.   This may be sales smoke and
mirrors.
The water in the sand, quenches the melt on contact, and case hardens the
material to a depth of about 1mm.   So the skin of a sand cast plate is much
harder.
It's the addatives in V Pro that enables the material to be cooled this
rapidly.  Unless you know the composition, there is no way to look up Brinell
or Rockwell hardness tables to verify this.   My gut feel is that the skin of
sand cast is much harder, but if over grinding has taken place, to bite into
the raw grey iron, then the reverse may be true.

Regards Roger

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