Glides and after touch

[Jim_Harvey@yca.ccmail.compuserve.com]

I have done this... under duress, and knowing better. While working
for a large dealership (that was also paying my salary), I
occasionally had to do this when said dealer refused to buy
much-needed replacement hammers on trade-in pianos, and the existing
hammers were too short to permit regulation (proper or otherwise).

Note: this 'operation' was usually performed on the same pianos that
were painted white before being put on the sales floor.

Since the keyframe is "fixed" at the front by the key blocks, the
keyframe will pivot on the now taller glides and rise at the back.
While keyframe strength does enter the picture, both the strength of
and the amount of rise are governed by the dags. If excessive, either
the dag or a chunk of the keyframe will break off. Otherwise, the
limit indicator for this 'scab' operation will be a noticeable
increase in the amount of friction while shifting the action!

Jim Harvey, RPT
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        I have heard of some very respected Techs who will set the glides a
little extra deep to increase dip and after touch.  My question is how far
can we go with this?   Assuming that the glides are set correctly in the
first place, would an increase of 1.5mm key height be too much?  What are
the dangers of doing this? (Please don't tell I'll know I've gone too far
when I have buried the hammer flange screws into the pinblock)  Does the
brand of piano make a difference? (i.e. sturdiness vs. flexabilty of key
frame) How does weather changes affect these setting?