[CAUT] Reverse Torque tuning pins & reverse crown

[Don Mannino]

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
>