Al - Steinway's spec for key dip is between .390" and .420" so,at 10mm (.394") you're well within range. The only reason I mentioned dip was relating to the jack binding the rep lever window butt felt. If that's not happening, there would be no reason to play with the dip. I think Mike Spaulding's image of the self-locking taper is the paradigm to use as you look at your piano again. I had another Steinway this morning on which I had done the action some years ago. The treble checking was OK but I was having some trouble in the bass. I noticed that the convergence angle of the tail and check was a tiny bit too severe, so I gently sanded the tail a bit flatter (less radius) and slightly more angle, so that the convergence was more congruent, and it worked fine, even without re-roughing. Good luck tomorrow. David Skolnik At 08:24 AM 3/16/2008, you wrote: >David, > >These are all original parts and I did check jack clearance, which is good. > >One thing you mentioned is very interesting. In order to get the >proper after touch, I had to set the key dip at 10mm which is a >little more than Steinway recommends. If all else fails, I will >reset the touch to Steinway specs in the bass to see if that helps >any, but I'm sure the problem is elsewhere. > >I also agree; >(snip) >"the buckskin & felt on the newer checks offer almost no resilience >the profile at the top of the backcheck face forces the tail to >bounce off, as you describe in your post" > >Al Guecia > > >----- Original Message ----- >From: "David Skolnik" ><<mailto:davidskolnik at optonline.net>davidskolnik at optonline.net> >To: "Pianotech List" <<mailto:pianotech at ptg.org>pianotech at ptg.org> >Sent: Sunday, March 16, 2008 1:02 AM >Subject: Re: Steinway M Backcheck Problem > > > Mike - > > I think the self-locking taper image is an apt analogy. I had > > occasion this afternoon to be working on a recent vintage Steinway D > > which has what I think is the same condition that Al has described, > > and I would just add a few details to my previous summary: > > - the buckskin & felt on the newer checks offer almost no resilience > > - the profile at the top of the backcheck face forces the tail to > > bounce off, as you describe in your post. > > - one other regulating parameter can have a significant impact on > > checking: if either the dip is excessive, or if the particular > > combination of parts employed in rebuilding force the jack to firmly > > contact the butt felt in the rep lever window, the resulting friction > > can absorb enough energy from the hammer rebound to compromise checking. > > > > As for the particular version of the problem in the low bass, the > > requisite stiff, heavier spring might have something to do with > it. Or not. > > > > David Skolnik > > > > > > At 10:45 AM 3/15/2008, you wrote: > >>David, > >> > >>Good comprehensive summary of the issues, and I agree with you on > >>all points, particularly the folly of roughing the tails or check leather. > >>If roughing improves checking, there is an unresolved problem somewhere. > >> > >>I like to think of the backchecks and tails as a self-locking taper. > >>This is the same mechanism that keeps the chuck in your drill > >>press. As long as there is some amount of friction, no matter how > >>small, there is a taper angle below which the taper will lock, and > >>above which it will fall apart. In the context of backchecks, if > >>the check is laid way back then adjusted to contact near the tip of > >>the tail, the hammer will bounce off the check. Go to the other > >>extreme, with the check near vertical and contacting up near the > >>shank, and the hammer will check, but not at a consistent height: > >>the harder you play, the lower it will check. Somewhere in between > >>is the optimum, where the hammer will reliably check, and will be > >>difficult to push further down. > >>Admittedly, there are pianos where this sweet spot is not easy to > >>find, especially in the low bass. > >> > >>Mike > > > > > > >No virus found in this incoming message. >Checked by AVG. >Version: 7.5.519 / Virus Database: 269.21.7/1330 - Release Date: >3/15/2008 2:36 PM -------------- next part -------------- An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/20080316/3f281c24/attachment.html
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