1/2 punching

[David C. Stanwood]

>What is the thinking on cutting the balance rail punching in half, i.e on 
>the backside of the key only?
>
>David Ilvedson, RPT

Hi David

Sorry to jump in on this so late...  this is a trick that the Precision 
TouchDesign installers group has been using for about a decade.  It makes 
the action dynamically lighter by lowering the overall ratio or heavier if 
you cut off the back half of the punching and heavier if you cut off the 
front half.  Chris Solliday presented the half cut punching method in the 
two day action regulation class in Rochester.  The method came to me in the 
mid 90's when I had been working on an action that had been in a very wet 
storehouse for many months...  After thoroughly drying out the action I 
repinned, lubricated keybushings, etc... friction friction friction I 
thought..  I live on an island and I was putting the action together to 
take it to the client and my boat was leaving in 2 hours... well when I got 
the stack on and ran my fingers across the keys it felt heavy... I had 
ASS-U-MEd that friction was the only problem... I did a quick check on the 
strike weight ratio and found it to be above 6.0.  TOO HIGH!  The necessity 
of having to catch my ferry kicked inventiveness into gear and I put a 
little glue on the bottom of the key just in back of the balance hole and 
put the key down on the key pin.  When the glue dried I took off the key 
and cut the front half of the punching.  I found that the overall ratio 
dropped by about 0.4, Enough to significantly lighten the dynamic feel of 
the action.  I treated all the keys this way, made my ferry boat, and the 
client was happy!

I shared the technique with my PTD installers group but we were 
trepidatious about the punchings coming unglued when fictitious technicians 
in the future had the keys off the frame for maintenance.  In 2004 Steve 
Willis at the Callahan piano shop in Oakland, came up with a more 
transparent method of using a veneer shim on the balance rail.

http://www.stanwoodpiano.com/RatioShim.htm

The trade off is that you get a slight movement of the key on the pin and 
one might think this will lead to problems of chucking in the long run but 
we have not seen this.  I have seen 100 year old Ivers and Pond 
uprights  that have balance rails set up like a bridge pin with the rail 
cut away to the center of the balance rail pin.  The key rocks on the rail 
behind the pin with slight movement on the pin.  These 100 year old pianos 
exhibit no enlargement of the hole from the slight movement.  So we don't 
consider that to be a problem so long as the pin is shining and smooth.

I noticed in Rochester that Jurgen Goering at Piano Forte Supply in Canada 
was selling cloth balance rail punchings cut just to the edge of the 
hole,.... enough to reduce the ratio while leaving something to keep the 
punching on the pin.  His feeling was that the punching would have no 
reason to rotate once in place and said it was an old technique.

Maybe Jurgen can share some of his history with the technique.

Regards,

David Stanwood