[CAUT] Hammer Alignment

[Don Mannino]

Wim,
 
I would submit to you that the glue never lets go or moves - I think
that when you heat the glue joint and twist the hammer, you are actually
twisting the shank wood.  Unless you have just glued the shanks on in
the past few hours, there is not enough moisture in the glue or shank to
soften the glue up enough.
 
The tip of the shank is usually the thinnest point, so the hammer is
easiest to twist at this location, which I think is why it feels like
the hammer is spinning on the shank.  When heating the full shank
length, though, the twisting is spread out over a longer area.  I don't
have any kind of definitive test results that say heating the full shank
is more stable, but that has been my impression.
 
If you have a suitable test hammer I'd be interested in hearing if you
can continue to rotate the hammer - If I am wrong about this I'd like to
know, as I have tried loosening hammer glue joints with heat alone and
have never succeeded.  If the glue has actually loosened enough to allow
the hammer to spin, then there would be nothing stopping it from
spinning on around.  Give it a try.  Also, try a thumb nail into the
glue collar after you heat it - does it feel soft?  Wood glues might.
 
My understanding is that heating the wood temporarily softens the resins
in the wood, allowing it to twist.  Once it cools back down the resins
harden again, and the fibers are locked into place.  Humidity swings can
affect the results, of course, but then humidity swings can affect the
shanks in any case, whether they have been twisted or not.  If the
fibers have been seriously twisted (more than 5 degrees??) it seems
logical that they would be exerting more restoring force, and the wood
resins might allow creep during high temperature / high humidity
conditions.  Over-heating the shanks to the point where they begin to
turn black is a bad thing - the resins are cooked, and will not be as
resilient, changing the shank flexibility and strength.
 
Don Mannino RPT
 


On Mar 29, 2006, at 6:38 PM, Wimblees at aol.com wrote:



In a message dated 3/29/2006 1:17:00 PM Central Standard Time,
garym at PIANOSERVICE.BIZ writes:

I used to heat the glue joint to align hammers, until I found out that
Titebond begins to break down at about 120 degrees, and loses half its
strength at about 150 degrees. I got this info from a technician named
Tom Patten in his class concerning fire damage to pianos. My
understanding is he got this information from Franklin, the makers of
Titebond. I assume this applies to other glues as well.

It would be interesting to see how hot the glue joint becomes. I use a
Weller heat gun, and put the nozzle about 2" or 3" from the glue joint.
Then I do as Ed does, although I don't hold on to the shank with pliers.
I sort of "swipe" at the glue joint until I can feel the hammer move.
After all, in most cases, we're only talking moving the hammer one or
two degrees, so it is not going to take much heat to loosen the glue
joint. 
 
Wim 


-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://www.moypiano.com/ptg/caut.php/attachments/20060330/b8328cb1/attachment-0001.html