Bechstein hammer bore

[John Delacour]

At 22:37 +0100 15/2/08, Richard Brekne wrote:

>...I have to admit I have never taken into consideration the angle 
>of the strings to the key bed... I pretty much stick with a 
>perpendicular to shank hammer... tho I am most willing to listen to 
>reason why I should rather choose hammer perpendicular to string.

It is most important, in the extreme treble especially, to have the 
hammer strike the string exactly at a right angle in both planes, 
otherwise there will be loss of energy.  On many grands the strings 
in the top section are at a considerable angle to the horizontal. 
The Bechstein C I am working on surprised me by being an exception to 
the rule, but the angle has to be measured and factored into the bore.

>I also tend to go for a constant rake ( 90 degrees to shank)...

Why? That is by no means standard.  Many pianos require a 2 degree 
outward rake and some older models require an inward rake.  With a 
Bechstein you can mess about with the rest rail but that doesn't mean 
you're not introducing errors in the geometry.  On pianos with 
individual rest cushions things have to be just right.

>  ...and vary hammer bore to match string distance to keybed.


Well, as I hope I've made clear, that's not good enough.  You'll get 
away with it through most of the scale but in the treble not only is 
it critical to have a right angle but if you don't measure the slope 
of the strings you won't be able to calculate it so that you do get a 
right angle.  It's a very common omission and it's the reason why so 
many people can't get the treble right, especially on Bechsteins and 
Blüthners.  Now if you're lucky to have a piano with the strings 
perfectly horizontal in the extreme treble, well and good, but it has 
to be known.

On most pianos the slope of the strings diminishes to an 
insignificant amount by the time you get to the top break, but by 
that time, you're out of trouble anyway.

JD