[CAUT] stack fit to keyframe

[John Delacour]

At 2:59 pm -0700 9/9/06, David Ilvedson wrote:

>When the action is on the stack the ends are mated but in the middle 
>there is a slight space...it could very well be the back of the keys 
>holding it up...I haven't pulled the keys and check, which would be 
>the correct way I imagine.

I would always make these adjustments with the keys removed, though 
it's most unlikely the keys are holding anything up, otherwise they'd 
be very audibly knocking the lever rail!

>   Then measuring the hammer centerpin heights as is and when the 
>stack is pushed down.   A thin ruler in between action parts seems 
>to measure that well as long as it doesn't sit on the keyframe...

I first check to see how reliable the underside of the plank is as a 
datum by measuring from the key-bottom to the plank, at the level of 
the hammer rail.  Next I screw the action to the key-frame, slide it 
in and place a card vertically against the hammer-rail and touching 
the underside of the plank.  At the level of each standard I mark the 
card with a knife.  However you choose to do it, the aim is to shim 
under the standards, or remove wood, to achieve a straight line 
parallel to the key-bottom.

>Is there a spec of some sort for action height?   I suppose it has 
>to do with the magic line etc...

There are hundreds of different actions and set-ups.  You can only 
work out the original specs by measuring and calculating and there is 
often room for improvement of the original set-up, especially in the 
case of less careful makers.  One very important thing for me is, 
having once got all the hammer-centres lined up, to bore the hammers 
correctly taking into account not only the varying height of the 
strike line but also the angle the strings make with the horizontal 
(specially significant in the high treble) in order that each hammer 
strike the string at a right angle.  This also requires careful 
measurement and calculation.  The use of ready-bored hammers is 
almost certain to lead to endless problems and fudges.

JD