Foundry Castings

[Paul Chick (EarthLink)]

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Alan
My dad ran a machine shop that catered to repairs for industrial =
equipment which included several foundries. I worked for him for about =
11 years.   "Jerry" was the foreman for one of these foundries.  We =
watched him unloading used cast to be recycled for new cast.  He'd set =
the piano plates aside because they were "pig," first pour iron  He'd =
add some nickel to cast to give it a "little flex."  Brom's Foundry =
would add chromium to the mix to add hardness and pour "nyhard" (sp) =
castings for government contracts.  It was very hard, and hard on =
equipment.  Brittle cast was for low stress, low cost castings.  I'm =
sorry I can't relate any specific formulas.    Some cast machined very =
well, while other parts were a head ache.  They had hard spots and =
cavities.  Until epoxies came along, we had to bore out and press a =
steel sleeve in the bearing journal to make some repairs. We regularly =
junk old pianos and are amazed how difficult it is to break up the =
plates.

Paul Chick
  ----- Original Message -----=20
  From: Alan R. Barnard=20
  To: pianotech@ptg.org=20
  Sent: Tuesday, August 27, 2002 6:57 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. 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

  I understand that cast aluminum was tried back in the 40's or so. It =
would sure be nice to find a different, lighter, less brittle =
material--then you wouldn't need such a heavy wood frame either. Every =
time I move a piano, my thoughts stray in this direction ...

  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

  Alan R. Barnard
  Salem, MO
    ----- Original Message -----=20
    From: Delwin D Fandrich=20
    To: pianotech@ptg.org=20
    Sent: Tuesday, August 27, 2002 1:16 PM
    Subject: Re: Foundry Castings


    And If I haven't created enough confusion yet, I'll toss out another =
one:

    Just why do we think gray iron is the best of all possible materials =
to use for piano plates anyway? What is it about gray iron that is so =
special?=20

    We say it is extremely rigid -- but it is not. It's brittle. Is this =
an advantage?

    We say it has excellent internal damping characteristics -- but is =
this an advantage? Why?

    Right off hand I can think of only two characteristics that make it =
a particularly good choice for piano plates: [1] It is easy to machine =
and [2] it is cheap. Neither of these has anything to do with its =
performance in the piano.

    Del=20




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