Overs Piano modifications: agraffes

[David Love]

Thanks.  I hope to see your work in Reno.

David Love


>From: Overs Pianos <sec@overspianos.com.au>
>Reply-To: pianotech@ptg.org
>To: pianotech@ptg.org
>Subject: Re: Overs Piano modifications:  agraffes
>Date: Tue, 20 Mar 2001 07:47:45 +1100
>
>David and list,
>
>Sorry for the delay in responding, yesterday was one of those days
>where everything happened and nothing got done.
>
>David wrote;
>
>>Related to this subject, some years ago I saw a modification on a
>>Steinway D done by a highly reputable local technician (now
>>deceased) in which the agraffes were replaced with a much deeper
>>profile agraffe (not unlike a Bechstein agraffe).   The idea was
>>that the larger and more stable agraffe prevented any leakage or
>>vibration through this termination point and resulted in increased
>>clarity and power.
>
>Interesting.
>
>>Have you done any research in this area?
>
>  Yes, we've done quite a number of experiments. In 1997, I built a
>set of agraffes (for a D rebuild) from 1040 carbon steel (with an
>Electroless Nickel Plated coating for corrosion protection). Took a
>whole week to make them on the lathe with the milling attachment. The
>electroless nickel process lays down a uniform plating thickness,
>even in the holes. We had 0.002" (0.05 mm) laid down. It deposits
>with an as plated hardness of just over 40 on the Rockwell C scale
>and can be hardened to around 60 by heating to 240 degrees C for four
>hours. Nice stuff. While the 1040 agraffes sounded quite good, they
>were pretty difficult to machine, and I wasn't totally smitten by the
>tone.
>
>We are presently developing a new string termination technology which
>is showing lots of promise, but we won't have it ready for our Reno
>exhibit piano, No. 003.
>
>>Any idea on the reasoning behind the design differences in agraffe
>>depth by these two manufacturers?  Are the effects of these
>>differences quantifiable?
>
>Most OEM agraffes seem to be between 4 to 5 mm in thickness. While
>most use the 4 mm variety, there is likely little tonal difference
>between the two, since free machining brass is basically a lousy
>termination material for piano wire. It deforms under the cutting
>action of the wire during tuning. The agraffes with the steel pin
>insert are not much better, since the pin hardness is only about 19
>Rockwell C.
>
>We have inserted hardened pins into steel pin agraffes as an
>experiment, but the wire tends to skid across to the edge of the
>hole, only to produce as much string noise as any other poor agraffe.
>
>The latest Kawai agraffes seem to be better than average even though
>they are brass. While I have no inside information, they appear to be
>forging the string holes. If this is the case, it would explain the
>performance improvement, since forged brass will have a work hardened
>surface which will resist the string cutting action a little better.
>You can probably guess our agraffe source for piano No. 003.
>
>Regards,
>
>Ron O
>--
>
>_________________________
>
>Website:  http://www.overspianos.com.au
>Email:      mailto:ron@overspianos.com.au
>_________________________

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