Key Friction

[David Love]

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A very simple approach that I found works well is to first ease balance
rail hole (not the bushing) so that the key slides slowly down the pin,
and the front bushing to have just the slightest movement at the bottom
of the key when moved from side to side.  Do this after polishing and
lubricating the key pins.  Then install the keys without the stack.
>From your gram weight set, get a 30 and a 26 (or a 50 and a 46, or a 20
and a 16), two weights that are four grams apart and will represent 2
grams worth of friction when downweight and upweight are achieved using
these two (f = (d-u)/2.  Set the 30g weight on the front of the key and
using a couple of jiffy leads move them around on the key until the key
just goes down.  Take the 30 g weight off and replace it with the 26g
weight.  If the key doesn't go up, ease slightly at the balance rail
bushing and check again-since that's the only likely remaining variable
and the hardest one to see movement and free play on.   You can get a
sense of how much additional friction over the 2 grams exists by sliding
the 26g weight back toward the balance rail until the key rises.  
David Love
davidlovepianos@comcast.net 
 
 
> Actually... Terry turned me on to this idea... you do it the same way
as 
> you take balance weight... except the stack is off so there is nothing

> on the keys.  I like to put about 50 grams of weight on the back of
the 
> key and then just take up and downweight measurements.
> 
> Cheers
> RicB
> 
> Barbara Richmond wrote:
> 
> > Ric,
> >
> > I haven't gotten that far in my studies.  How do you measure that?  
> > I've just always adjusted keys the "old" way--by touch--how the key 
> > slides down the balance pin and the fit of the bushings.
> >
> > Barbara Richmond
> > (I wanna be a touchweight freak.)

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