Glassing the block

[Farrell]

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Re: Glassing the blockRon Overs wrote:

"....our pianos have a flange either side of the pin block (front and =
rear). Since we epoxy fit the plank to both flange faces..."

Do you have some sort of system for moisture content of the block at =
time of installation? Is there a concern of the block expanding and =
causing damage? Is there a concern of the block contracting and =
compromising the fit between the two flanges?

Ron went further to say:

"....West System (which we use for other uses such as gluing up our =
multi-laminated bridge caps)."

Do you clamp your bridge cap laminations together (obviously the only =
way I can imagine the process)? If so, my understanding of epoxy is that =
it requires a gap between the things being bonded together. Would not =
hide glue, Titebond, resorsinol, Weldwood, etc. be a better choice for =
this application? I'm sure you have researched this. But this seems to =
be a different application for epoxy. Please help me understand as I =
would like someday to epoxy an entire piano together (just kidding) - =
it's such wonderful stuff!

Terry Farrell

  ----- Original Message -----=20
  From: Ron Overs=20
  To: pianotech@ptg.org=20
  Sent: Friday, January 04, 2002 5:44 PM
  Subject: Re: Glassing the block


  Terry, Del and all,


      ----- Original Message -----
      From: Terry Farrell


      Hello Del. When you wax your plate flange, you must use some thin, =
wipe-on type of wax, such that it doesn't fill small depressions that =
may be present in the plate flange surface - or is that not really a big =
deal? What do you do.


  We grind the plate flanges to remove the small depressions before =
applying the release agent, otherwise there is a risk of the epoxy =
keying the pinblock to the plate. While this will be less of a problem =
with single flanged plates, our pianos have a flange either side of the =
pin block (front and rear). Since we epoxy fit the plank to both flange =
faces (before the plank is fitted to the case - while screwed to the =
plate), we would run a big risk of gluing it in for keeps, unless the =
plate flanges are free of depressions.


       How thick do you make your epoxy mixture - peanut butter?


  We use an Australian made paste-like industrial epoxy which has =
similar strength properties to West System (which we use for other uses =
such as gluing up our multi-laminated bridge caps).


       Also, when you put your epoxy mixture in, what is your exact =
procedure in order to avoid having excess epoxy migrate to the area =
between the pinblock top and the plate web bottom and thus impair the =
fit. Do you screw the pinblock to the plate first and then mooosh epoxy =
into any small gaps between the pinblock and flange? Or do you put a =
bead of epoxy on the flange edge of the pinblock and draw it into the =
flange somehow? Thanks.


    The wax is standard floor wax.

  Ditto.

     Others use a spray-on mold release. Either works.

    The consistency is about like peanut butter.

    The pinblock is shaped for a good wood-to-flange fit first. Then the =
epoxy matrix is troweled on to the pinblock (front) surface with a =
suitable putty knife and the pinblock is screwed in place. There may be =
some migration up over the top because there is inevitably some space =
between the top of the pinblock and the bottom of the plate tuning pin =
panel. Unless, of course, you've done a perfect fit along the top as =
well. I've never managed to do that quite. The excess will clean off. =
When the epoxy has cured, disassemble the pinblock and clean it up. =
Knock off the squeeze-out along the edges, etc. I go over the whole =
thing with 60-grit sandpaper lightly to smooth of the roughness from the =
casting but not enough to alter the fit.

    There are other procedures that probably work just as well. This is =
mine. I use the epoxy matrix to improve an already good =
pinblock-to-plate fit. Others simply hack out the block on a bandsaw and =
use the epoxy matrix to mate the whole thing. That seems to work as well =
but I've never been comfortable with the idea of it.

    Del


  This has been my experience too Del. Epoxy should not be used as a fix =
for a poorly fitted block, it should be used to make a well fitted block =
near perfect. If used in this way, you will never have a problem with =
the paste type epoxy running around to the top face of the pin block.


  I'm sold on this idea of epoxy fitting blocks. It really helps tuning =
stability.


  Regards,


  Ron O
  --=20
                   OVERS PIANOS
         Grand Piano Manufacturers
  _____________________________

  Web:    http://www.overspianos.com.au
  Email:  mailto:ron@overspianos.com.au
  _____________________________

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