Foundry Castings

[Delwin D Fandrich]

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  ----- Original Message -----=20
  From: Alan R. Barnard=20
  To: pianotech@ptg.org=20
  Sent: August 27, 2002 4:57 PM
  Subject: Re: Foundry Castings


  Cast iron IS brittle but it will not deform nor compress under stress =
and tension the way steel, aluminum, and other metals do.=20
Yes, it does. It bends rather easily up to a point. Then it breaks.


  Nor does it expand and contract with changing temperatures as much as =
other metals. The key point is that it holds its shape and, most =
important, the critical string length dimensions.=20
The difference in thermal expansion and contraction between gray iron =
and the steel used to make piano wire is nominal.


  I'm guessing that a lot of the metal in the casting is just to make =
the plate "beefier" so it doesn't break so easily.=20
That, and it's just easier. You don't have to 'design' it--you just =
throw extra iron at it. As well, piano plate foundries have not been =
noted for their consistency in casting.

Del



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