Well, it depends on the size of the key pin. The balance rail bushing, in my opinion, should not be "snug" meaning there should be virtually no friction there at all-certainly no squeezing. Nor should it be snug enough to wear a small indention where the balance rail pin contacts the bushing. Have you done a weigh off (up and down weight) measuring with a "snug" fitting and one that is relatively frictionless? You might be surprised at how much excess friction can be created there. Do you mean that Yamaha specifies that the width of the bushed mortise is .008 wider than the BRP? That's fine but that's not snug, that's free by a factor of .008". Having done many weigh-offs with both UW and DW and calculated friction and then going back to find the culprit I often find that the balance rail bushing is responsible. The Spurlock cauls when fitted with the proper cloth produce a perfect fit if you follow his instructions about how tight the dry fit should be which is tight enough to be able to lift the key gently but loose enough to be pulled out with relative ease. After the hot glue sizes the bushing with water present in the glue the caul should come out very easily as it's only o/s by about what you mention (maybe less actually-don't recall). One thing to be careful of with the dry fit is that the caul is not binding on the ends of the mortise so that what feels like a snug fit when dry fitting is actually the caul hitting the ends of the mortise and not representative of the fit with the bushing cloth-can happen. After I remove the cauls I go through with a single caul and test the fit through the entire set. The caul, in my view, should slip in and out of the mortise easily with virtually no binding (and no slop either). The insures that you actually have the play that you need there. Afterwards you can also then dust the bushing with dry Teflon powder to help with wear-and don't forget to polish the keypins (what fun). David Love www.davidlovepianos.com From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Ryan Sowers Sent: Friday, April 02, 2010 4:02 PM To: pianotech at ptg.org Subject: Re: [pianotech] FW: re: Rebushing keys, was ...VS Profelt I would answer by saying "just enough". When I say snug I mean "not loose". If you let a balance rail bushing dry with a standard .146 caul it will come out too loose. Yamaha specifies .008" for the balance rail. That's not a lot. On Fri, Apr 2, 2010 at 3:32 PM, David Love <davidlovepianos at comcast.net> wrote: What's too loose? A "snug" balance rail bushing may not cause a sticking key but it sure can cause a lot of excess friction. David Love www.davidlovepianos.com On Apr 2, 2010, at 1:38 PM, Ryan Sowers <tunerryan at gmail.com> wrote: The other thing about keybushing that I don't here discussed much is how to make the balance rail snug enough. If you leave regular cauls in until they are completely dry they will be way too loose for my taste. I actually ordered a set of cauls from BiIl that are not oversized (the regular cauls are .148"). Even so, I remove the cauls after about 15 minutes so they can swell slightly. Otherwise they are too loose. A snug balance rail bushing rarely causes a sticky key, and it will correct a lot of key squaring issues making key leveling easier an quicker. -- Ryan Sowers, RPT Puget Sound Chapter Olympia, WA www.pianova.net -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100402/cdd8d80c/attachment.htm>
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