Bore lengths

[Richard Brekne]

Hi folks..


just got through double checking a measurement for borelengths on a 
Petrof grand and noticed a rather large discrepancy between on bench 
measurements and in piano measurements... and ended up with the 
following observation resulting in the accompanying question.

Measuring the distance between strings and keybed, then hammer centers 
and keybed yeilded a near 2 mm difference when done on the bench visa vi 
done in the piano. At first I thought that well..... its a bit clumsy to 
measure in the piano.... so....  But then I got to thinking about 
bedding issues and decided to double check very closely in the piano and 
came up with very close to the same results.  Obviously in this 
particular example, the bedding screws accounted for a quite significant 
difference in the height of  hammer centers. This of course is directly 
reflected in the bore length one decides on, so its kind of important to 
get the darned thing right.

I ususally go about deciding bore length in a different fashion, but 
have lately wanted to try out this <<formula based>> method and stumped 
on this right off.

So what do you folks do here ?  Go with a bench figure, compensate for 
the bedding on the bench, or simply measure in the piano ?  If the 
bedding screws are taken into account... do you always make sure of 
optimal bedding first ?..

I'd like a bit more detailed description of what you all do in 
conjunction with this on the surface simple measurement.

Cheers
RicB