[pianotech] Determining Bore Angles

[Mike Spalding]

Steven,

I've not done a C7, so I can't confirm or deny the 9 degrees.  For 
comparison, most Steinway grands are less than that...  I always measure 
the string angles, and compare them to the hammer angles, also observe 
the string grooves in the hammers, as a verification.   If the hammer 
angle isn't equal to the string angle, then the difference should show 
up as string grooves not parallel to the hammers.  Then you've got to 
decide whether to duplicate the original hammers, or get closer to 
parallel to the strings...My goal is to get the hammers as close to 
parallel to the strings as possible, without getting such a large angle 
that they interfere with each other.  Most pianos that means a max angle 
of 10 to 12 degrees.  But I'm working on a Schiedmayer grand right now 
where the top bass hammer angle is 15 degrees, and the hammers are 
spaced widely enough that it's not a problem.

Mike

On 9/2/2011 9:43 PM, Steven Hopp wrote:
> Hello,
>
> I have begun to do my own hammer work.  I am challenged at this point 
> by determining bore angles from the original hammers.
>
> I am boring for a Yamaha C-7 and have found the bass angle to be 9 
> degrees.
>
> Does this seem correct?
>
> Also, if anyone has the angles for this piano I would appreciate it so 
> I can practice reading my angle guide knowing what I should be expecting.
>
> I am sure that these are the original hammers.
>
> Any help is greatly appreciated.
>
> Thanks,
>
> Steven Hopp
> Midland, TX