< 90 degrees at impact

[Jurgen Goering]

Ed:
It is my understanding that on uprights, the hammers should 
under-center.  I was taught that the amount should about 5 mm (= .200", 
just less than one hammer shank thickness).  This helps the hammer 
rebound off the string better. The piano will not play properly if the 
distance: string to center pin is the same as the hammer bore.

I know this is how  European upright actions (Renner, Langer, etc.) are 
designed.

I seriously doubt that the 1/16" more under-centering will be a 
problem, neither at the hammer rest rail nor at the strike line.  If 
you feel compelled to compensate, you could do that by adjusting the 
action bolts.


Jurgen Goering
Piano Forte Supply
(250) 754-2440
info at pianofortesupply.com
http://www.pianofortesupply.com


On Nov 18, 2006, at 11:00, pianotech-request at ptg.org wrote:
>
> I am installing new butts, shanks, and hammers into an old Knabe 
> upright. The replacement butts I bought are Tokiwa. I didn't think 
> much about the fact that these butts are made in Japan, and Knabe is 
> an American upright.
...snip
>
> I lined a new Tokiwa butt and shank up in the action, side by side, 
> next to the old butt/shank/hammer. It turns out that the placement of 
> the shank-hole in the  new Tokiwa butt is a little over 1/16th of an 
> inch closer to the strings than the old butt. This puts the hammer and 
> shank at a different pitch resting on the hammer rail, and more 
> importantly at impact with the strings.
>
> With these new butts, the hammer will make impact with the strings 
> just BEFORE is reaches a 90 degree angle (assuming the original 
> geometry of the butt/shank/hammer to string dimensions did so). Will 
> this be a problem?????
>
> Your input is greatly appreciated.
> Ed
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