<html> <body> Hi, Ron, At 01:46 PM 10/12/2005, you wrote: <blockquote type=cite class=cite cite="">Hi Mike and all, There have been some good posts on this thread. <blockquote type=cite class=cite cite="">. . .  I don't think any hard-fast rule is going to suffice. -Mike Jorgensen</blockquote> With the exception of the final jack position relative to the roller, I agree.</blockquote> Yes - exactly. <blockquote type=cite class=cite cite="">The jack position (relative to the roller) at full key dip (with the hammer in check) is probably the only hard-fast rule when it comes to key dip/hammer blow considerations. Since the hammer/key ratio varies so widely, as others have also mentioned, even within the one brand/model of instrument, there will need to be an adjustment from the standard spec of dip and/or blow in many situations. Increasing the blow distance on a high-ratio action will tend to place the already ordinary-relationship of the jack roller contact even further away from its line of centers. Reducing the blow distance in the case of a low ratio action will tend to improve it.</blockquote> ...which problem is exacerbated in what might be called "mixed" actions containing parts with mis-matching geometries. <blockquote type=cite class=cite cite="">If the dip is insufficient for a given action ratio, the lack of jack/roller clearance at check may cause the action to blubber at let-off, particular when played softly. If the dip is set so deep as to cause considerable clearance between the jack and roller at check it will slow repetition.</blockquote> ...especially if the performer also wants the check height set lower than spec (in hopes of achieving more power on repetition). <blockquote type=cite class=cite cite="">The much mentioned problem of the hammer/key ratio varying so much with the US S&S pianos got me thinking about the problem again recently when retro-fitting one of my actions to another factory piano (the instrument in question seemed to have a plate position problem which was accommodated in the original action by fitting the hammers 3 mm short of 130 mm. When I fitted my action I followed suit and hung the hammers short also, since I wanted to keep my action stack at the correct position with respect to the keyboard (to preserve the action ratio I wanted - 5.7:1). The shorter hammer position will reduce the hammer/key ratio, but only by a small amount.</blockquote> Yes. <blockquote type=cite class=cite cite="">In the factory situation, if the plate is not positioned according to the standard specification, I believe it is inappropriate to shift the action stack relative to the keyboard, in an attempt to shift the strike position (line). If a piano is built with the plate out of position, it should be a simple matter to tolerate a small adjustment in the hammer position along the hammer shank. A 3 mm + or - adjustment of a hammer from say a standard 130 mm standard distance from the hammer center pin will allow for an out-of-position plate to be accommodated without turning the action geometry into a disaster.</blockquote> What you have described here was the S&S factory method used until (at least) the late 80's, changing only slowly after the introduction of the Kluge keysets.  What was known as "forefinishing" was done largely in compensation of/for whatever errors had preceded in manufacture.  It does not matter if this is right or wrong.  What matters is that this is how things were done and explains why it is so important to take exceptionally careful measurements of just about everything in sight before beginning major action work.  Over the years, it was much more likely to find plates installed too high than too low; but this happened, as well.  <blockquote type=cite class=cite cite="">If an action stack is moved only 2 mm relative to the keyboard it will have a major influence on the hammer/key ratio, which will cause major headaches at regulation time (if the regulator is aiming to obtain a workable regulation with standard specifications). The truth is we often need to bend the specs somewhere, to get real-world actions working at their optimum level.</blockquote> Absolutely. Best. Horace <blockquote type=cite class=cite cite="">Ron O. <pre>-- </pre> OVERS PIANOS - SYDNEY    Grand Piano Manufacturers _______________________ Web <a href="http://overspianos.com.au" eudora="autourl"> http://overspianos.com.au</a> <a href="mailto:ron@overspianos.com.au" eudora="autourl"> mailto:ron@overspianos.com.au</a> _______________________</blockquote></body> </html>