Pinblock Separation Repair & Pitch Change

[Richard Strang]

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Thanks for the info, Terry. I have to go make that very repair to a piano
shortly and was contemplating whether or not to lower the pitch first. It
this case, the separation is about 1/2"  in the bass and about 1/4" in the
treble. Those pesky little termites are in there, too. I think they are
causing the problem. They are not in the pinblock, though, so the piano is
in tune, though 200 cents flat.
   I was also wondering what size bolts to use, 1/4", 3/8"? What do you
recommend?
Thanks.

Richard
  -----Original Message-----
  From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On
Behalf Of Farrell
  Sent: Thursday, October 30, 2003 8:09 AM
  To: pianotech@ptg.org
  Subject: Pinblock Separation Repair & Pitch Change


  Differing opinions regarding the benefit of lowering pitch prior to
drawing a pinblock/backpost separation back together have been expressed on
this list. I am one that generally feels more comfortable lowering pitch. I
thought it might be of benefit to put some numbers on potential pitch
changes.

  Yesterday I did one of these repairs on a late model (1980s) Baldwin
Acrosonic console. It had an approximate 1/4-inch separation between the
pinblock and the backposts and deadwood back assembly. The separation had
been "repaired" in the past with something that appeared to be silicone
bathtub adhesive - surprisingly (?) the separation appeared to have widened
since the application of the silicone. The piano was tuned at that time (and
presumably tuned at standard pitch).

  Prior to my repair the piano was fairly uniformly 75 cents flat. I dropped
the pitch to between 200 and 250 cents flat prior to any clamping. I yucked
in West System epoxy thickened with #403 Microfibers. (A fine fiber blend,
is used as a thickening additive with resin/hardener to create a
multi-purpose adhesive, especially for bonding wood. Epoxy thickened with
microfibers has good gap-filling qualities while retaining excellent
wetting/penetrating capability.)  I drew the gap closed slowly going back
and forth among the six 3/4" pipe clamps (of which two got bent pretty
good!). The separation appeared to close very close to 100%.

  I then checked pitch again. Piano was fairly uniformly about 75 cents
flat. Therefore, it appears that closing the 1/4-inch gap resulted in a
pitch increase of approximately 150 cents.

  I will be going back to the job on Friday morning to install a few through
bolts, remove clamps, pitch raise and tune. If there is anyone out there
that perhaps has not seen this repair done (or whoever for whatever reason)
wants to see a few photos, I will take them Friday morning. Let me know.

  Terry Farrell

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