[pianotech] Pinblock expensive experiment

[Greg Newell]

Duane,

                Have you considered vacuum clamping as a solution to the
inherent unevenness of clamps and pressure bars? While I haven’t purchased
my system yet it seems that this would be as even as it gets and also allow
the glue to work into the pores of the wood as much as possible making for a
stronger glue up. I’d love to hear your thoughts.

 

Greg Newell

Greg's Piano Forté

www.gregspianoforte.com

216-226-3791 (office)

216-470-8634 (mobile)

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Duane McGuire
Sent: Wednesday, April 07, 2010 9:49 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Pinblock expensive experiment

 

Good questions, and good thoughts.   I think you are correct that my
original glue up process enhanced the bow of the multi-lam.  I didn't take
before measurements.  I just know that the after measurement was extreme and
unacceptable to me. 

I think that the gluing setup needs refinement also.   As to the original, I
clamped up without a bottom caul, and with a top caul of 6/4 maple that had
a bow opposite the bow in the multilam.    So I am thinking that the current
glue up is better, but not ideal.  By the way, prior to this glue-up I
removed the original delignit cap which did not relieve the bowing in any
way.  After resawing the multilam, the two pieces bowed to an even more
extreme.  In this glue up, they went back together with the bows opposing.  

I acknowledge your observation about unequal clamping pressure.   The cauls,
however, are 60 - 80 mm oak, so the issue may not be as extreme as you
perceive.  I also used whatever bow was present in the cauls to advantage
and placed the convex edge down.   

The table is extremely rigid and flat, which of course why I used it this go
around. 

Last night after doing this glue-up I did some searching of prior posts on
hybrid boards here.  I saw some gluing setups that are far superior to what
I used -- both vacuum and mechanical.  It's great to have all the input
available.  The experience of others is invaluable. 

Experimental results and observations will be available tonight! 

In any event, for the next pinblock, I don't expect to have such an
adventure. 

Duane McGuire
801-830-5858
http://blog.duanemcguire.com



On Wed, Apr 7, 2010 at 6:32 AM, jimialeggio <jimialeggio at gmail.com> wrote:

I was thinking about your original glueup problem...I would bet that a good
part of what happened was caused by the way you clamped your stock.  
1- did you clamp the multi-lam and delignit together without flat cauls top
and bottom
2- looking at the clamp setup in your new glueup, the clamping cauls
reaching across that wide presumably flat table are exerting unequal
pressure, ie lots of pressure at the edges and considerably less in the
center.  As well, the clamps reaching over that wide distance will tend to
deform (cup) the previously flat gluing table. The clamp pressure above and
below should be right on the piece not offset.

Just some thoughts..hope its helpful

Jim I -- 

Jim Ialeggio
grandpianosolutions.com
978- 425-9026
Shirley, MA





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