Bdshull@AOL.COM wrote: > Del, > > I defer to your experience on the durability of the teflon bushings. I am > sure you have serviced many more than I have. Maybe you are right; the > problem was not the expansion and contraction of the wood around the bushings, > but instead it was the result of improper reaming and fitting techniques. Do > you have anything to add to the Steinway bulletin regarding servicing teflon > bushings? There are still quite a number of teflon actions in service. > Would you mind being more specific about the various techniques - types of > reamers, the acceptability (or not) of the centerpin rolled in a file, etc? > > I am interested in the comments of others who have serviced a considerable > number of these actions also - do you mind speaking up here? Thanks - > > Bill Shull > U of Redlands, La Sierra University ------------------------------------------------------- Bill, I'll do my best, keeping in mind that I haven't serviced one of these actions since 1981. I'm assuming that you have a clicker and must do something to make the noise go away. Or you have a high-friction center and must free up the action. I'm also assuming that the action has the larger, ribbed bushings in the hammershank flanges. If it has the smaller bushings either replace the shanks or drill them out and replace the bushings with the larger, ribbed bushings. 1) Fit the pin to the tongue. Make sure that the pin size you want to use will fit tightly into the hole in the tongue of the center. If it is loose either choose a larger pin or gluesize the hole. I didn't bother with the blunt pins sold at a frightful cost by S&S. I used standard pins -- they thread easier and cause less damage to the second bushing as they pass through -- and cut them with a sharp flush cutting side cutter. Contrary to popular belief the residual burr won't cause any trouble at all. It doesn't cause any trouble with felt bushings either, but I'm sure it will take more than facts to convince anyone of that. 2) Fit the bushings to the fork. The bushings must fit snugly into the hole in the wood fork. If they are even slightly loose they will click. Glue size the hole if necessary. I used dilute white glue, it does not make the wood fiber as hard and rigid as does hide glue sizing. Also the slightly sticky texture seems to help hold the bushing tighter and makes it a bit less susceptible to changes in the wood moisture content. It is usually not necessary to replace both bushings. One side is often tight -- frequently excessively so -- and the other side can be so loose that it will click. Usually this was due to poor factory fitting -- remember I was working on new pianos at the time -- or they had been damaged at some point during manufacture. Replace just the loose bushing. 3) Ream the bushings. This is the most critical step of the whole procedure. And the secrete is in having the proper reamers. Do NOT use a knurled center pin, it will simply make your problem worse. It does wear away a bit of the Teflon, but mostly it just temporarily compresses it. This will give you the illusion that you have obtained a proper fit but the center WILL tighten up on you later. You must actually cut the hole to the proper size. I had my reamers custom made -- The name Johnson Carbide comes to mind, but remember I had these made some 25+ years ago. As I recall the set cost me about $90. -- of solid carbide in 0.0005" increments from whatever to whatever. I think the smallest was the diameter of a #18 pin or a #19 pin. There were seven of them. They had five flutes and they were ground in a "reverse" spiral. This kept the tendency to chatter down and made it easier to cut a nice clean hole in the Teflon. The flutes were only 4 mm long. I could carefully press the cutting end of the reamer all the way through the first bushing and cut the second bushing using the first as a guide to keep the hole straight. I would then -- again, very carefully -- pull the reamer out, turn the fork over and repeat the process cutting the first bushing. I would then verify the fit and friction of the pin before assembly. Make sure that you have the same amount of friction in each bushing. With just a bit of practice this became a one-shot operation. Once you have verified this you can assemble the center. Check overall friction of the center and trim the pin. Don't worry about the slight burr. The resulting bushing was solid, quiet and trouble free. And durable. Yes, you can voice hammers without damaging the Teflon bushings if you properly support the hammer tails and hold the hammer firmly with one hand. You might want to work on your needling technique a bit -- the idea is to use the needles on the hammer, not your thumb. Don't ask... The Teflon bushing was and is a much maligned development. In fact, it was a potentially good and useful innovation that was killed off by a lack of proper product development and support both from the factory and from within the service community. It was not tested adequately before it was released. The small, smooth bushing should never have reached production. Even the small, ribbed bushing was marginal. The larger bushing -- the final version -- worked quite well when it was assembled properly at the factory or carefully re-fitted in the field -- both of which were astonishingly rare occurrences at the time. It is true that they were introduced as a cost cutting measure replacing another problematic part, the felt bushing. There is nothing inherently wrong with that. Piano manufacturers should be constantly looking for ways to reduce their costs. What got lost somewhere along the line was that just as much care was required to properly install and fit the Teflon bushing as was needed with the felt bushing. Sadly they never received this kind of manufacturing attention. Once it became obvious that these parts were having trouble in the field Steinway became very defensive about them and was very slow in developing any kind of servicing techniques for them. When servicing procedures finally were developed they caused about as many additional problems as they solved. The Teflon bushing has now gone into history as a terribly bad idea along with the general use of plastic in piano actions. Too bad, I remain convinced that the Teflon bushing was really quite a good idea and handled properly -- and with some further development work -- might well have freed the industry from the problematic felt bushing. Regards, Del
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