Gram weighing of parts

[David C. Stanwood]

Hi Terry,

Techs and dealers too often overlook key bushing friction and there is a 
lot of misunderstanding about it.  (I'm going to being spending a good 
amount of time the subject during my new class on Friction at Rochester and 
so is Bob Marinelli in his two day class.)  Near zero without slop is an ok 
test.  To answer your question.. one may measure key bushing friction by 
putting a back check weight on the keystick on the frame, measuring up/down 
and applying the friction formula (D-U)/2.  I would rate low as 1g-3g, 
medium as 3g-5g, and anything above 6g as high...  Low or medium is fine so 
long as it's consistent, that's the trick...  I don't recommend doing this 
test for each key unless you have a government grant or your in school 
doing research....  It's a good teaching tool especially for learning how 
to judge balance rail bushings... often the key will drop on the pin but 
still be to tight.  You learn to feel the difference in the weight of the 
key as it drops onto the bushing...  etc etc....

David Stanwood

>What do you recommend for key bushing friction? Minimal/near-zero without 
>inducing slop? Some number of grams friction? What are the advantages to 
>having near-zero and having some amount? Thanks.
>
>Terry Farrell