hammers rubbing

[John Delacour]

richard.ucci at att.net wrote:
> List , Kranich & Bach baby grand, ca: 1964 , e and f 5 are catching on 
> the plate after shift pedal is engaged. I have filed off some felt on 
> the under side of the hammer shoulder, but still sticking. Does not 
> seem to be any space to push action in further. Any solutions?
I have the same problem right now with a 1924 Bechstein Model C.   What 
appear to be original hammer-heads, worn, to be sure but not really 
badly, seem to have been hitting the iron frame under the agraffes 
(Bechstein has agraffes right to the top) since the piano was new, and 
at least a dozen hammers are badly chewed up at the front in the top two 
sections.  When I first reported on the piano I remarked that the tone 
overall was excellent but that the top treble was weak and woolly.

I am now almost decided on how to proceed.  I calculate that the hammer 
bore was 50 mm when it ought to have been 52 mm given the strike height 
and the bore angle.  For one thing, therefore, the hammers have always 
over-centred.  Since the action is a tied action, it might be possible 
to raise the action 2 mm, provided the drop screws have head-room, or I 
may bore the new hammers 2mm longer.  Nevertheless I suspect that they 
will still hit the frame.

The casting is generally lumpy in the offending area with some hardened 
runs of paint.  I will be looking closely at the problem next week with 
bright lights and mirrors and it is almost certain I shall grind down 
the iron using a die grinder.

Pushing the action in further is no solution at all, since I would then 
lose the strike line and get even worse tone for different reasons.  
Besides, there is then the risk on this piano of the hammers hitting the 
far side!

I shall bore sample hammers from spares and get them hitting the strings 
at a right angle exactly on the strike line and set them up for the best 
obtainable tone.  I will then remove 2 mm or so from the nose of the 
hammers to account for future wear and work out how much iron I need to 
grind off for the hammers to clear the frame.  So far I don't foresee 
any problems with the job.  I have seen pianos, probably Bechsteins, 
that were ground away at the factory so that the shank of the agraffes 
is partly flattened off and exposed, and from the look of it this is not 
the case (YET) with this piano.

JD