I have not seen these kinds of problems with Kawai actions here in the Chicago area. I agree with some of the observations that Dave Renaud has made. A couple of years ago, I wrote an article for the Partial Post, the newsletter of the North Shore Chapter. This is more controversial a thing than I would normally like to post, but here it is: The Weird Stuff: The Hole Truth By Bruce Dornfeld, RPT Do you think about holes? If you work on pianos, you deal with them all the time. Those tuning pin holes are great when they’re the right size, but too tight and work is much harder, too loose and tuning may be impossible without a lot of repairs. How does humidity change holes? Those tuning pins feel tighter in high humidity, so they must shrink then. Do other piano holes act the same? A pinblock is quite unique; it is made of multiple laminations of very dense wood. It is also fitted in such a way that it cannot expand in all directions as it would if it was leaning up against your shop wall. Do you want the hole story? What about other holes? How about the key’s balance rail hole? What time of year do they tend to bind more? They are worse in the winter. When the key shrinks with dryness, the hole does too. This is more typical of wood. As the whole piece gets smaller, so does any hole in it. Wood type and grain orientation can make the effects of humidity change greater or lesser as well. What about action centers? Do the holes get bigger or smaller with dryness? How does the felt act? First, let’s look at an action center with no felt, with a bushing that does not change dimensions with humidity. The best known example of this is the Steinway & Sons Permafree™ action, best known from the Teflon™ bushing. The Teflon bushing does not change at all with humidity, so changes in tightness are from changes in the hole alone. The most common problem we see in the field related to the Teflon bushing is clicking. It clicks when the hole in the hammer flange gets a bit too big for the bushing. One thing that makes this very different from other action clicks is that it tends to get worse in the summer. When high humidity makes the flange screws tighter, because the wood gets bigger, the hole for the action center gets bigger too. It gets big enough to make the bushing too small. We then replace it with a new Teflon bushing and normally this will be tight and will not click. Usually this is a long lasting repair. The traditional action center is more likely to bind in the summer. But, why? The type of wood, maple or something like it, is not much different from the Steinway Permafree action part. The hole gets bigger in high humidity, but the felt expands too. The wool felt will just get bigger in whatever direction it can; grain does not apply here, but quality and density do. Cheaper action manufacturers have and will continue to make shortcuts when they can. The two shortcuts that we notice in the field most are cheaper bushing cloth and poor fit. Cheaper cloth is not as dense and is less stable. Poor fit often is the result of pinning without reaming or proper sizing. Some manufacturers have relied on a lubricant to keep the action free and pinning into too tight of a bushing. Sometimes a shrinking solution, such as 50%/50% water and alcohol, can have long lasting results. Other times repinning and properly reaming the centers is the only thing that will keep it playing for years. Lubricants may help for a while, but their effects will not last. I do not believe anything above is controversial or anything that an experienced technician would disagree with. What follows here is more speculative and not based on anything I have seen written about or discussed to any extent, just observation and logic. A traditional wooden action center will have an optimum size for the hole. That hole will expand and contract with humidity changes, in high humidity it gets larger, which would tend to make the pin looser. The felt bushing has the opposite effect; it also gets larger in high humidity, but this tends to make the pin tighter. To say it another way, the wood moves away from the pin, but the felt expands toward it. If the hole is the optimum size and the felt is of a good quality, sized (or shrunk) properly, and if the felt is reamed for the correct fit for the pin, this will be a very stable feeling action. Normal humidity changes will not make the friction go outside of an acceptable range. One trend in piano manufacturing in recent decades involves using plastic action parts. There are many benefits to good quality plastic parts such as Kawai uses. Consistent dimensions, weight, and texture are real advantages over wood. The plastic jack will not have too much roughness where it contacts the knuckle or hammer butt. It will not change in length, changing the hammer line or lost motion. It will not break. Most plastic action parts still use wool bushings. The plastic does not change, but the felt will. The way I see it, action centers will be less stable this way. I do not know what companies like Kawai do to stabilize their felt. On an occasional mishap, I have filled a bushing with CA glue, it was stable but it didn’t really act like a felt bushing any more. A manufacturer might try just using less felt, but too little and the noise factor is likely to increase. When Don Mannino from Kawai was in Chicago recently, he mentioned to us that engineers from Kawai were considering Teflon bushings. Don discouraged the idea. From a marketing point of view, he is undoubtedly right. Steinway had three big problems with their Teflon bushings. One was that they were in wood which changed dimensions and consequently deformed the bushings. Two, it was a problem getting parts and service instructions to technicians in a timely way. When Virgil Smith gave a technical to the Chicago Chapter on Teflon bushings, it was about the time Steinway went back to felt bushings, 1981. Third, the bad press that Steinway got was a big part of the demise of Teflon bushings. There is good information about this in Larry Fine’s The Piano Book. Tokai built pianos in Japan in the early eighties with plastic parts, but without felt bushings. Instead of a bushing, they simply fit the pins directly into the plastic, (was it nylon?) flange. We can presume that they reamed or fitted the pin in the flange in some way. One Tokai grand that I saw over a period of years had a heavy action when I first saw it, which got worse with time. In desperation I tried Protek CLP; it made a slight improvement for a little while. The Protek may have made it worse in the long run. When my client sold the piano, the only way it could have been made playable was complete repinning. I suspect it would have tightened up again in a few years time. Until piano makers come up with an action center that never needs service, we should keep a few things in mind. Most holes get bigger when humidity goes up. In the well-made wooden action center, good felt will compensate and keep the friction from changing much. This assumes the slow gradual climate changes that are normal, not radical changes. A quick change is more likely to change the felt first. When you repin, do not make the hole that holds the bushing bigger unless you are sure it should be. Use a high quality dense bushing cloth like the Hainsworth cloth that Schaff sells. Before reaming it to fit, size the bushing and let it dry overnight if possible. This should give you trouble free action centers for many seasons. To the best of my knowledge, this is the hole truth and I thought you wood like to know. I know there are many parts of this line of thought that many will disagree with. I have never seen this issue examined in the Journal or on this list. I suppose I should go out now and find me one of them flame suits. Bruce Dornfeld, RPT bdornfeld at earthlink.net North Shore Chapter -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech_ptg.org/attachments/20090103/d1b33526/attachment.html>
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