[pianotech] Pinblock expensive experiment

[David Love]

Don 't know about the bowing as not having the before measurements and not
having glued up these laminated blocks myself I can't say what happened
there.  Blocks do arrive with some bowing sometimes and a small bit of
bowing is not that big a deal as once you tighten the pin block screws it
will pull the block snug to the plate.  I try to keep that to a minimum, of
course, and 10 mm seems like a fair amount but others may comment on this.
I've never really tested the limits of what can be done there.  On shimming
the board up at the ends to achieve the required plate height, there's
nothing wrong with doing that, I do it all the time.  It's a hell of lot
easier than planning down the entire block and certainly more acceptable
than taking material off the inner rim and lowering the bottom of the block
below the level of the stretcher.  

 

David Love

www.davidlovepianos.com

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Duane McGuire
Sent: Sunday, April 04, 2010 10:32 AM
To: pianotech at ptg.org
Subject: [pianotech] Pinblock expensive experiment

 

I think that my first grand pinblock replacement has become an expensive
experiment. 

I wanted to do the multi-lam capped with delignit block that Ron Nossaman
described at Grand Rapids and was documented in the journal.   I resawed the
delignit and planed a 9mm cap for the block. 

Before gluing up I noted that the multi-lam  (Schaff) was not exactly flat,
but I did not measure its degree of bow (I believe this is the root an
expensive mistake). I selected a clamping caul with a compensating bow, and
glued the assembly up, thinking that it would tend to flatten out.  

After unclamping and planing the multilam to final thickness per the
original block,  I find that the bow in the board is just plain awful.
Total deflection measured at the midpoint of the board is 10 mm!  I'm
thinking I have some more firewood for next winter. 

By the way, the original block measures 39.6 mm, and from my look at the
suppliers, Bulduc's 1-5/8 is the only material that will match that
thickness.   At the same time, I do suppose a person could place blocking at
the ends, and use a somewhat thinner board.  From my starting, I didn't find
that idea appealing, but I'm looking at this from every direction now. 

Right now my thought is that tomorrow I order a Bolduc pinblock and get on
with it.   

But rather than just reacting to my own self-pity, I'd appreciate your
input, before my wallet gets even thinner.   In the category of self
recrimination, I expect that I should have measured the bow in that
multi-lam and shipped it back when I found the degree of deflection that was
present. 

Thoughts? 


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

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