[pianotech] 1098 Hammer Bore

[Roger@Integra.net]

Greg,
Measuring the string to center pin distance and subtracting the blow 
distance is not always the correct method to determine bore distance. Many 
pianos have a "rake" (less than 90 degrees) designed into action geometry 
and that method would never produce a "rake" -- you would always have a 90 
degree angle with the shank to hammer molding. The rake is sometimes needed 
to ensure that the hammer returns securely. A no-rake condition can cause, 
under certain conditions, the hammer assembly to get "stuck" against the 
string on a light blow because there isn't enough mass behind the 
perpendicular from the center pin when the hammer strikes the string. The 
older Steinway uprights are an example where an extreme rake is designed 
into the geometry. Some Yamaha grands have a reverse rake in the bass 
section -- without it, the hammers wouldn't clear the pin block when 
removing the action.
Roger Gable

-----Original Message----- 
From: Greg Newell
Sent: Thursday, February 14, 2013 5:40 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] 1098 Hammer Bore

Jon,
Although it's a bunch more work, I would plug and re-drill. Who
cares what the stock bore is? Don't you measure from the string to center
pin and subtract the blow distance? I thought that was it. Please correct me
if I'm wrong.

Best,

Greg Newell
Greg's Piano Forte
216-226-3791 (office)
216-470-8634 (mobile)
www.gregspianoforte.com
gpf at ameritech.net




-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Jon Page
Sent: Thursday, February 14, 2013 8:28 AM
To: pianotech at ptg.org
Subject: [pianotech] 1098 Hammer Bore

I was handed a project that another tech could not finish due to a family
illness. New hammers are in the offing but I have a few concerns.
First, the shanks mic .210" but the hammers were bored to .218" (7/32).
That is way too loose. Could a paper shim be glued in on the non-string side
of the molding without causing a problem down the line? Secondly, the
hammers are bored close to the same length as these old, worn ones and there
are shims under the hammer rail already. What is a stock bore
for a S&S 1098?   Maybe I should plug these holes and rebore to bring
the action parameters to original specs.

Regards,

Jon Page