Pinblock Separation Repair & Pitch Change

[John Ross]

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Hi Richard,
At 200 cents flat, I don't drop the pitch.
I used to use 1/2" carriage bolts, but in a discussion on the list, that was considered overkill. So 3/8" will be good enough.
We don't have a termite problem up here (Canada), but I think I would check out the piano further, for a termite problem.
Someone had brought a piano up from the US, with a termite problem in the keys. They appeared to have just a little hole, but in fact had been hollowed out in places. Much more damage than indicated.
Regards,
John M. Ross
Windsor, Nova Scotia, Canada
jrpiano@win.eastlink.ca
  ----- Original Message ----- 
  From: Richard Strang 
  To: 'Pianotech' 
  Sent: Thursday, October 30, 2003 5:50 PM
  Subject: RE: Pinblock Separation Repair & Pitch Change


  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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