Open face vs. closed face pin blocks

[Phillip L Ford]

I checked my notes.  This is not from a handout but from a note that
I wrote down myself.  Gray iron 35 ksi.  I could have made a mistake.

I checked a couple of engineering references.  Representative numbers
are:

ASTM A 48  Class 20 to Class 60 with tensile strengths of
20000 to 60000 psi.

So, 35000 psi is certainly well within this range.  It would depend on the
specific 'recipe' that Kelly is using.  Also, I don't know if they use the
same recipe for everyone's plates.  The different classes have different
microstructure with some changes in various properties that certain
manufacturers may want.  For instance, I believe damping capacity and
machinability increase as you move down in class and strength, stiffness,
and wear resistance go up as you move up in class.

A couple of references if you are interested:

http://www.ironcasting.org/Gray%20Iron%20-%20A%20Unique%20Material.htm

http://www.castingsource.com/tech_art_grayiron.asp

Phil
---
Phillip Ford
Piano Service & Restoration
1777 Yosemite Ave
San Francisco, CA  94124

On Wed, 15 Aug 2001 13:47:18  
 Delwin D Fandrich wrote:
>
>----- Original Message -----
>From: "Phillip L Ford" <fordpiano@lycos.com>
>To: <pianotech@ptg.org>
>Sent: August 15, 2001 6:11 PM
>Subject: Re: Open face vs. closed face pin blocks
>
>
>> ---
>> Yes, the front flange does work as a beam.  More on that later.  Cast iron
>> does in fact have tensile strength.  How much depends on the specific
>> iron that is being used.  At the convention, I went to the Boesendorfer
>> class and they mentioned that they use 35000 PSI iron.  This refers to the
>> tensile strength (breaking strength) of the material.  While not high by
>> high strength steel standards it is still a respectable number, even by
>> metal standards.  Also, the iron is capable of giving (deflecting) as
>every
>> tuner knows.  One of the reasons it takes several tunings to stabilize a
>> piano is because the plate is deflecting under the increased load.
>> ---
>
>I wonder about the 35,000 psi figure. When I was dealing with O.S. Kelly
>from the mid-1980s through the mid-1990s they were using iron and a casting
>process that tested at 24,000 to 26,000 psi tensile strength. Unless I'm
>mistaken--and I could well be--O.S. Kelly is casting at least some of the
>Bosendorfer plates.
>
>Del
>
>


Get 250 color business cards for FREE!
http://businesscards.lycos.com/vp/fastpath/