[CAUT] Reverse Torque tuning pins & reverse crown

[David Skolnik]

Thanks Don -
So I assume that, in rebuilding, the issue of 'reverse torque' pins 
would be secondary to getting the fit right in the first place.
Are you aware of which pin makers use the various methods?

Re reverse crown, Perzina is apparently employing this design on 
their uprights.  I've heard one, which I thought sounded surprisingly 
good.  Any thoughts as to what allows it to work, if it does?  It 
seems to run counter-intuitive to the idea of compressive loading.

David Skolnik



At 09:55 AM 4/4/2007, you wrote:
>David,
>
>Reverse Torque Tuning Pins is a marketing term (read, misnomer) for the
>concept of 'cutting' the threads into the tuning pins after plating, as
>opposed to rolling the threads into the pins or plating over the threads
>after cutting.  This cutting process causes the threaded portion of the
>pins to be slightly rough in one direction, but smooth in the other.
>The rough surface increases the pin torque in the pitch lowering
>direction (counter-clockwise), but it is smooth in the pitch raising
>direction (clockwise).  The result is that the effort in turning the
>pins is closer to being the same up or down in pitch, because the
>variation in torque is the opposite of the string tension.
>
>The relative benefit for tuning feel is, of course, a trade-off with
>longevity, as the rough pin does tend to chew at the wood a bit.  Since
>our actual rotation during tuning is small it's not much of an issue,
>but when changing strings it certainly can be.
>
>Reverse crowned soundboards are those in which the board is (for a grand
>piano) bowed down instead of up in the soundboard press.  A few piano
>makers have tried this design over the years.
>
>Or, in the case of a tired out old piano, a soundboard which has failed
>and is bowing down in response to the string pressure is sometimes
>called "reverse crown" by piano techs.  Not uncommonly this is also
>caused by a someone having added excess downbearing during a restringing
>in an effort to 'improve' the tone.
>
>Don Mannino
>
>
> > -----Original Message-----
> > From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On
> > Behalf Of David Skolnik
> > Sent: Wednesday, April 04, 2007 7:40 AM
> > To: pianotech List; caut at ptg.org
> > Subject: [CAUT] Reverse Torque tuning pins & reverse crown
> >
> > List(s) -
> > Can anyone tell me about or direct me to information about reversed
> > torque tuning pins and the use of reverse crown soundboards?   Thanks
> >
> > David Skolnik
> > Hastings on Hudson, NY
> >