Fred -
The little experimenting that I've already done produced the same
results - either too tight or too loose. I already have the Mannino
reamers, and had wondered if it might be worth experimenting with them
as well (now that I've just dropped over $200 on S&S's "kit" plus
reamers :-(
You are also right about the friction coming from more than just the
centers. A bit of prolube on the keypins and capstans, and some teflon
powder on the BR holes, knuckles, wip cushions and key bushings each
remove another 2g or so. Adding that to the 10-12g of extra friction at
the centers gets me down to the mid to upper fifties. Additionally, the
FW at #40 is only about 65% of Stanwood's published maximums, so I could
probably even add another small lead to get me right onto spec.
Thanks,
- Mark Dierauf
Fred Sturm wrote:
> <div class="moz-text-flowed" style="font-family: -moz-fixed"> Well,
> I won't claim to be an expert, but I have done a fair amount of work
> with teflon, mostly the early, thinner bushings. They can be
> troublesome to get "just right."
> With wool bushings we have a lot of options: remove material
> (ream); pack the felt (burnish, using different sizes of burnishers,
> create enough friction to heat up the fibers or not; sizing pin and
> wetting agent, with or without heat); and lubrication.
> With teflon, there is only the option of removing material. This
> needs to be done with a parallel tool, and the fluted reamers Steinway
> provides are good for that. But the problem is that the reamers and
> the pins are precisely the same size (precisely within our realm of
> measurement), and, in my experience, the result of reaming with a
> .050" reamer for a .050" pin is somewhere around 6 - 10 grams of
> friction, which is generally too much.
> So how do you get that friction down? You have to remove a little
> more material. I experimented with those "half size" reamers Pianotek
> used to provide (maybe still does), graduated by .0005" (midway
> between the .001" increments of the Steinway ones), and the result is,
> in my experience, 0-2 gms, too little friction, and a wee bit of
> wobble. There isn't anything between those sizes, to my knowledge. So
> I have tried using "modified technique" of reaming with the standard
> sized reamers, pressing against the sides, trying to make it even all
> the way around the circumference of the bushing. I had some success
> with that, but it's a little iffy.
> What I have ended up with is initially sizing the bushing with the
> fluted reamer, then following with a Mannino style reamer,
> experimenting with size and amount of reaming. George Defebaugh used
> to recommend rolling a centerpin on a table with a file to scuff it
> up, and using that. That works, but doesn't last too long, as the
> material of the pin is soft. The Mannino reamers are essentially piano
> wire given the same treatment, with a segment roughed up. This raises
> some filings around the circumference of the wire that act as cutting
> surfaces, but making them is inexact (the precise size will vary - and
> with teflon we are wanting to be within .0001 - .0003"), and they wear
> down with use. (you can re-rough them with a file as needed). With
> felt, it is more forgiving to use one of these. With teflon, you have
> to be more careful and experiment.
> One thing I have thought about but haven't actually looked into is
> the possibility that metric sizes might be "just right" as an in
> between size, and produce just the right friction with the fluted
> reamer. If you have some, it might be worthwhile experimenting.
> Standard pins (as opposed to Steinway's which are smooth both ends and
> already the right length) work just fine in teflon (in removing a
> standard pin, press it out from the side that wasn't cut, as the cut
> side would score the teflon during removal).
> In the end, once you figure out what will work for the particular
> application, teflon is very easy to deal with, or can be. It's very
> predictable, if you use precise tools and techniques.
> Your 80g DW probably includes other sources of friction, though.
> Key bushings, wipp cushions, capstans, knuckles, etc. The teflon
> probably only accounts for about 10g or so. (And, of course, there is
> the question of how much might be friction, and how much geometry, but
> let's not go there for now <G>).
> Regards,
> Fred Sturm
> University of New Mexico
> fssturm at unm.edu
>
>
>
> On Dec 5, 2008, at 6:57 PM, Mark Dierauf wrote:
>
>> Well, I managed to survive 30 years in business without having to
>> deal with these by simply replacing teflon vintage parts, but now
>> I've got an L action on the bench that needs sprucing up to ready for
>> sale. Some of the keys are at 80g DW(!), and quite a bit of that
>> excess seems to be in the hammer flanges. So I've gotten the "kit"
>> from Steinway, but now I'd like to hear from the experts on the best
>> way to proceed. My 1972 S&S Service Manual isn't much help ("ream the
>> bushing accordingly", with a target of "3 to 6 grams"). This is one
>> of the later teflon pianos, with the improved (ribbed) bushings. Any
>> takers?
>>
>> Thanks,
>>
>> Mark Dierauf
>>
>>
>
>
>
> </div>
>
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