[pianotech] Hammer Cant Angle, was D Hammers

[George F Emerson]

Of course hammer shanks have been burned almost as long as there have been 
pianos.  Mostly, to my knowledge, it has been done to correct alignment of 
the hammers as they lie in a straight line.  Burning shanks to center a 
raised hammer tail between its neighbors, at rest, is quite another thing. 
I'll take your work for this being a long standing European factory 
procedure.  On the surface, it makes perfect sense to do so.  It would seem 
reasonable to think that centering the hammer tail of a raised hammer 
between its neighbors at rest, would only serve to refines a perfectly 
vertically oriented hammer with no cant.  However, centering the tip of the 
hammer tail between neighboring heads does, in fact, result in a slight cant 
angle; it's unavoidable.  Maybe it's not enough to matter, but that is not 
quite what I am talking about.  Maybe what you are talking about is not a 
different means to the same end, after all.

This may be where the difference lies.  For me, it's not a matter of 
centering the tip of the hammer tail between the neighboring heads; it is to 
position the hammers such that there is equal clearance on both sides, to 
the extent that this is possible.  On one side it is the tip of the tail 
that comes closest to interference; on the other side the greatest risk of 
interference is closer to where the shank enters the hammer molding.  I 
prefer a larger cant angle for the purpose of getting closer to equal 
clearance on both sides, not centering the tip of the tail.  In fact the tip 
is deliberately off center a bit, to relieve the closer clearance problem on 
the opposite side.  Any significant cant angle necessitates one of two 
things, an action scale offset from the strike point scale in an amount 
anticipating the cant angles of the hammers, or a misalignment of action 
parts to get the hammers centered back under the strings despite the offset 
of the cant angle in those instruments where the strike point scale exactly 
matches the action scale.

Frank Emerson