[CAUT] stack fit to keyframe

[David Ilvedson]

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.   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...

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

David Ilvedson, RPT
Pacifica, CA  94044


----- Original message ----------------------------------------
From: "John Delacour" <JD at Pianomaker.co.uk>
To: pianotech at ptg.org,  caut at ptg.org
Received: 9/9/2006 2:33:36 PM
Subject: Re: [CAUT] stack fit to keyframe


>At 1:49 pm -0700 9/9/06, David Ilvedson wrote:

>>When I come across a grand action stack that doesn't fit flush to 
>>the keyframe, I have typically thought the keyframe should 
>>beÊshimmed to fit...
>>
>>What I'm concerned about:   This action/keyframe is perfectly mated 
>>to the keybed as it is...I'm wondering if I might not change 
>>something not necessarily for the better...????

>Any shimming or shaving you do is unlikely to change the mating of 
>the key-frame to the key-bottom.  The main question is whether the 
>line of the hammer-centres (and of the lever-centres) is straight and 
>parallel to the key-bottom, or the underside of the wrestplank, which 
>ought to amount to the same thing.  Then there is the question of the 
>height of the hammer-centre line, the differential boring of the 
>hammer-heads etc.  It is quite easy to get things wrong unless the 
>whole geometry of the action and the strings is taken into account 
>and the best makers are not guaranteed to get it right in the first 
>place once the drawing board fades into history.  I recently had to 
>make significant adjustments to a Hamburg Steinway of 1923 which can 
>never have been properly set up.

>JD