Key Pin Friction - was Heavy Playing S&S C

[Richard Brekne]

Hi Terry... have never actually tried to measure directly friction on key pins
myself. I always find that if you polish them (replace if rusted) well enough
and coat them with proteck..then they are as good as you can get them...and that
means I gotta deal with whatever that is. As far as bushings are concerned and
sizeing the balance pin hole... well the same kinda thing applies. Too loose and
the keys are wobbly... any tighter then just loose enough to avoid wobbly (grin)
is too tight. Gotta love those Spurlock rebushing cauls in this regard... I also
use teflon powder in the key bushings.


I suppose if you first were going to measure the friction in the key pins...
you'd have to somehow be dealing with a "zeroed" start condition. Perhaps a
perfect balanced key over the balance rail to start with... then 10 grams dead
weight on one end and measure weight on the other end...??? hadnt really thought
of this before.. Might be nice to know if it didnt cost too much time to find
out.

Farrell wrote:

> > Carefully polish the key pins, front and center.
>
> And then how do techs evaluate key pin friction? I have never seen anything
> in print regarding any definitive procedures to evaluate key pin friction.
> The gal that does my key bushing jobs for me says to just push down the end
> that is up (usually the back of the key) and see if the key returns.
> Hmmmmmmmmmmm. I think that only tells you if the friction is less than some
> large amount - like maybe ten or 20 grams. I sure feel the need to be more
> accurate than that. Is there some great method used that I am not aware of?
>
> What I have done in the past is to place weights on top of the capstan so
> that the back end of the key is just touching in the down position (or as
> close as I can get - take a gram off and it rises - this example is
> obviously for a key that is front-heavy). One can measure the friction in
> the key pins (I'm assuming - or I make sure - here that the center rail pin
> hole is eased properly and the key is not rubbing on a neighbor) by placing
> a weight on the front end of the key. If it takes a ten gram weight on the
> front of the key to make the key front go down, then I guess there is about
> ten grams of friction lost in the key pins. I've only done this once or
> twice, but it seems like two or three grams of key pin friction is about
> right - if you go down to one gram or less, you seem to end up with too much
> play in the key pin bushings. Then I ease the key bushings until I get to
> whatever my target key pin friction is.
>
> Does anyone else use a similar procedure? Is there a better way?
>
> Terry Farrell
> Piano Tuning & Service
> Tampa, Florida
> mfarrel2@tampabay.rr.com
>
> ----- Original Message -----
> From: "Newton Hunt" <nhunt@optonline.net>
> To: <pianotech@ptg.org>
> Sent: Monday, April 30, 2001 12:56 PM
> Subject: Re: Heavy Playing S&S C
>
> > Most bang for the time is reduce the friction even more.
> >
> > Are you doing new hammers?   Then go for a lighter set, just two or three
> grams.
> >
> > Without running the numbers the rest seems in the ball park.
> >
> > Carefully polish the key pins, front and center.  Polish the capstans.
> Carefully
> > lubricate all the centers then regulate and take new measurements.
> >
> > Let us know how it comes out.
> >
> > Newton

--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no