Following on Doug and Bill's advice to Jay,

It is important to keep the bottom hole on a key free to the point that 
the key will drop back onto the frame when lifted, they do tend to close 
up!   I use a thin rat-tail file to adjust that operation though I was 
taught in my Broadwood days to use a tapered awl.   The problem with a 
tapered awl is it compresses the wood and it returns with humidity to 
its original state.   Any friction drag from a key will badly effect its 
balance and working efficiency.  

When setting up and balancing a key on a new keyboard I always tap the 
balance pin slightly forward until the key is working completely free 
without any noticeable friction or drag.   Because I am that fussy about 
keyboards, I do not traditionally cut and punch my balance mortise but 
bore a clearance hole from the top of the key and make a lime chase to 
ceate the mortise.   I pinched that from Derek Adlam thirty years ago 
and it has served me well.   Having made so many instruments now for 
institutions and academies which get tremendous use, it is easy to fit 
new chases when them come in for a major service and get the keyboard 
wear back to new.

I remember way back in the seventies Bob van Asperen bringing his double 
back to me, upside down in the back of a Renault 5, because the 
repetition had gone.   It had been in a very damp Church for a week or 
so and suffered.   The interesting point was his cure;  selotaped  lead 
weights on top of all the keys and what a bloody mess that was to clean off.

M

-- 
www.michaeljohnsonharpsichords.co.uk