At 12:02 PM -0500 8/26/02, Conrad Hoffsommer wrote:
>>Do you have any technical reference for this? I've been trying to track down
>>solid information on the subject for some time--but to no avail. It's long
>>been assumed and talked about--at least within the piano industry--but I'm
>>after specific details. What 'strength' parameters change over time?
>>Stiffness? Impact strength? Compression strength? What?
>>
>>Del
>
>I don't know about strength, but the speil I got at S&S was that
>that "curing" time was to allow for relief >of internal stresses.
>Don't ask me how, or just what stresses they were. dat's jus whut i
>heared.
That's a matter of stabilizing it dimensionally before they do any
critical machining on it. It's not that the casting actually shrinks
during this cure time, it's the warpage. Machine tools also need to
be free of the warpage which result from the internal stresses
relieving themselves, before you can start milling and grinding the
reference and working surfaces into them.
But I'd never heard that the cast iron pickled up strength. Only that
any close tolerance work you might do on them would be wasted while
they continue to warp. Sort of like expecting to do a concert grade
tuning on fresh wire barely chipped that afternoon.
Bill Ballard RPT
NH Chapter, P.T.G.
"I'll play it and tell you what it is later...."
...........Miles Davis
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