teflon flange & bushing??

[Phillip Ford]

> I've often wondered, since teflon is uneffected
> by humidity/temp, why BOTH 
> the flange AND bushing isn't made from teflon.
> Just curious.
> 
> 
> Terry Peterson 
> 
> 
> Teflon is not effected by humidity, but the
> wood around it is. That is why the Teflon
> bushing didn't last. When the wood shrinks, the
> Teflon doesn't, which caused them to click. If
> we had Teflon pins inside Teflon bushings, even
> though the pins would not be effected, the wood
> would snhrink, and you get the clock. 
> 
> The only way to stop all the expansion is to
> make all the wood parts out of ABS, including
> the shanks. But I wonder if an ABS shanks would
> be flexible enough to withstand the force of a
> hammer hitting a string?
> 
> Wim

	I've never understood why flanges are still made out of wood.  The moving
parts of the action I can understand.  You want a material that is strong
enough and easy to machine but also light, so that the action is playable. 
Wood fits the bill well.  Plastics will as well but some manufacturers are
reluctant to use plastics because of their image problem in the piano trade. 
However, in the case of the flanges, weight is not an issue.  They are not
part of the moving weight of the action.  They could be plastic.  They could
be metal.  They could be just about anything that's strong enough.  It also
seems desirable that they be stable - which wood is not.  The shrinking and
swelling cause problems with the tightness of the centers and also with the
tightness of the flange screws.  Plastics or metal seem superior choices to
me.  I might be reluctant to use plastics in a piano that was meant to last a
long time since I don't believe there is yet a track record for longevity with
the plastics available now.  But metal seems a good choice.  Either with
teflon bushings or felt, if you insist on felt.  They will be more expensive
than wooden flanges but, at least on an expensive piano, I imagine that the
cost differential would be insignificant.
	In regard to the question of teflon flanges with teflon bushings - if you're
making the flange out of teflon why do you even need a bushing?  Just drill or
ream the hole to the proper size for the pin.  This would seem to speed things
up in the assembly process.  There would be no need for reaming felt bushings
to account for differences in the felt bushings and wooden flanges.  Just use
pins made to close tolerance and drill the holes to give the desired
clearance.  I'm surprised some manufacturer hasn't thought of this already
(maybe they have and I don't know about it).
	As to the comment that all wood parts would have to be made of ABS (or other
plastic), why?  Why can't you mix?  Some parts could be plastic and some parts
wood, as seems appropriate.  Doesn't Yamaha (and some others - Fandrich I
think) use plastic jacks with other parts being wood?
	About the Kawai actions with ABS parts?  I have not seen one of these yet. 
What sort of bushings do these use?

Phil F




Phillip Ford
Piano Service & Restoration
1777 Yosemite Ave - 215
San Francisco, CA  94124