Pinblock question

[Doug Hershberger]

Del,
   Thank you for this excellent explanation and food for thought regarding
pinblock drilling. I tried to just include one section of your message in my
reply but my E-mail program(outlook) does not seem to want to let me. I
particulalry liked the idea about the extreme angle of the pin causing the
never ending falling coils. There is no way to keep the coils tight on these
pianos that exhibit what you are talking about. I have seen it happen on
brand new high quality pianos. I believe it causes tuning instability as
well. Doug Hershberger, RPT
----- Original Message -----
From: Delwin D Fandrich <pianobuilders@olynet.com>
To: <pianotech@ptg.org>
Sent: Saturday, July 24, 1999 3:40 PM
Subject: Re: Pinblock question


>
> ----- Original Message -----
> From: <ETomlinCF3@AOL.COM>
> To: <pianotech@ptg.org>
> Sent: Saturday, July 24, 1999 11:12 AM
> Subject: Pinblock question
>
>
> > List,
> >
> > ... I know it needs to be modified to allow a 7 degree angle ...
> >
> > Ed
> >
> --------------------------------------------------
>
> Ed,
>
> Before you drill this pinblock, let's think about this a bit.  Where did
the
> 7º specification come from?  What is the rational for it?  I expect that
> part of this might have originated with early 3-ply pinblocks that had a
bit
> more give in them than do modern multi-laminate pinblocks, but that is
pure
> speculation on my part.
>
> There are no definitive specifications for tuning pin back angles on
>  "modern" pianos.  It varies from one piano to the next.  And, although
it's
> rarely drilled this way, the correct pin angle may well vary within the
> compass of a single piano.  That is, the correct angle may be different in
> the bass section than it is in the tenor.  And may be yet some other angle
> for the treble sections.  In other words, there are no absolute
> specifications....
>
> As far as the tuning pin is concerned it really doesn't matter what the
> drilling angle is in the pinblock.  This is not a structural issue.  The
pin
> is not going to pull out of the block if the angle is too little.  And
it's
> not going to be more stable if it is extreme.  What does matter is the
angle
> that the string makes with the tuning pin.  The string should make a 90º
to
> 92º angle with the centerline of the pin relative to the bottom of the
pin.
> That is the string should leave the pin at no less than 0º and no more
than
> 2º from perpendicular to the centerline of the pin.  With the pin driven
in
> to its correct height and the string at pitch it should bear up very
> slightly against the coil as the tuning pin is turned clockwise-as in
> raising the pitch.  Remember, this applies to string tensions appropriate
to
> the modern piano.  Not harpsichords or even fortepianos.  I suspect that
> greater angles probably wouldn't be as dangerous at the considerably lower
> tensions found on these strings.
>
> Boring for the tuning pins to achieve these angles depends on the plate
> design and the string termination arrangement used.  And, of course, on
the
> diameter of the wire, the number of coils of wire on the pin, on how far
the
> pin is driven into the block, etc.
>
> For example, through the tenor section of an unmodified Steinway B the
> string may well leave the counterbearing felt just barely above the plate
> surface-1 to 3 mm is not uncommon.  In this case the pin angle shouldn't
be
> much at all.  In fact it would probably be best to bore straight through
> this section.  I've seen some pianos in which the pins really should have
> been installed with something of a forward angle.  Moving to the treble
> sections the string passes over a set of counterbearing bars that vary in
> height along their length and that place the strings at some variable
> distance above the plate.  But, overall, they will be somewhat higher than
> they are in the tenor-about 3 to 6 mm.  Here the ideal tuning pin back
angle
> might be anywhere from about 1º to 3º.  Finally, depending on the height
of
> the bass counterbearing bar, the correct tuning pin back angle through the
> bass section might be anywhere from 2º to 5º.  These angles are drawn from
> memory but you get the idea.  For the most part we compromise and bore to
> some average back angle that we anticipate will work reasonably well
> throughout the scale.  Although in some cases I have varied the bore angle
> from the bass to the tenor section.  Especially in vertical pianos with
> fairly tall agraffe panels and very short string segments between
> V-bar/agraffe and the tuning pin.
>
> I frequently hear of pinblocks being drilled at what I consider to be both
> extreme and excessive back angles -- 5º to 7º, occasionally even more.
What
> the purpose of this is in the modern piano, I don't know.  If the back
angle
> is excessive the string will work its way down the pin as the piano is
tuned
> and the technician will be faced with a constant -- and losing -- struggle
> to keep the coils tight.
>
> So, for the modern piano at least, we have to look to the string angle
> relative to the tuning pin to tell us what the bore angle for the tuning
pin
> should be and not just rely on some arbitrary standard we may have heard
> about.
>
> Regards,
>
> Del
>
>
>
>