<html> Hi Ron,               I would not be surprised if there was a poor pin block to flange fit.  Particularly if it's a newer instrument. Regards Roger At 09:52 PM 8/14/02 -0500, you wrote: <blockquote type=cite class=cite cite>I don't have any information specific to the Petrof, but in general... <blockquote type=cite class=cite cite>Stability seems to be a problem.  This piano has an open faced pin block which means that the pins stand upright and do not lean back as in a conventional design.  The coils stand 1/4" - 3/8" above the block.  The hypothesis is that the pins may be bending excessively due to the high coils, making setting the pins more difficult. A possible cure would be to simply set the pins deeper into the block,  although this is speculative theory, (particularly since this is how it was designed).  Additionally this would add friction to the pins which may contribute or create a new problem.</blockquote> I wasn't aware that open face meant the pins stand upright instead of leaning back, but there are a lot of things I don't know and that isn't the problem in any case. Is the problem really with tuning stability, or getting a solid tuning in the first place? These are entirely different things, and driving pins won't improve tuning stability. It will, however, give you a little better control for getting the string settled in. An open face block with the coil 3/8" above the block shouldn't tune any differently than a piano with a non-bushed plate with the coil 1/8" above the 1/4" thick webbing, so if you don't characteristically have trouble with that very common type, the Petrof shouldn't be a problem either - unless that's not the problem. How tight are the pins already? What's unstable about the tuning? Unisons, overall pitch drift in certain specific areas? Do the strings render well across the bearing points while you're tuning? Hot lights? Ron N </blockquote> </html>