Teflon post

[Avery Todd]

It's almost too late but I heard from Del today and with his permission,
thought some of you might like to read this from Jan. 2000! Yeah, what
goes around comes around. Again and again! :-)

Avery

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Dear list:

I used this Teflon bushing subject to motivate me to save (to floppy disk -
it still comes in handy sometimes) some of the files on my modem-defunct home
computer.  Was able to find Del's post, so here it is - thanks, again, Del!

(This is my preceding post, for context...)

 > 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..?
 >
 > 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 hammer shank 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 in
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. Gluesize the
hole if necessary. I used diluted 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 secret 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