Ca pin block repair-broken tuning pin

[Susan Kline]

Hi, Tom

It might have been okay. Might the pin with the bronze bushing have
been okay without the CA, too?

Have you ever tried to find out _HOW LITTLE_ CA will still get the piano
tunable? Focus on the worst notes, leave the okay ones, see how little
will get the bad ones to hold, etc.? Since in small amounts CA sets up
so quickly, you can treat some "offenders" and try them out a few minutes
later. And if you come back in six months, and find some more loose pins,
or find that the ones you have treated with just a few drops are a little
bit loose, you can just add a little bit more. In my experience, using
minimal amounts of CA on loose pins is a repeatable repair -- though
I have hardly needed to repeat it.

I think that we are still approaching this job as if it were the old
pinblock treatment: tilting the upright or removing the action of
the grand, and flooding the whole pinblock area with glycerin and
alcohol. Since this job was such a mess, and since the piano needed
to sit for a week before we could tune it, we had to do the whole
process at one sitting, and we'd put in as much as we could get
the pinblock to accept, and then a little extra, which we had to
clean up.

CA is different. We can use it without tilting, on individual pins, and tune
the notes a half hour later. If a pin later gets loose again, we can slip
a few more drops in. Since CA follows cracks, if the pin is loose, the
CA can creep around it and and find the open space. This means that we 
don't have
to do an all-or-nothing job. I think we might consider just what we want
to end up with, as well. Do we want a wooden pinblock where the pins are
still basically contacting wood (most of them, anyway) but where the
cracks and delaminations have been sort of stuck back together, or do
we want a kind of a resin pinblock, where the whole thing is saturated with
CA? Do we want to turn a block into a kind of hard plastic?

It's true that all the other tuning pins didn't break: but just one is
a major pain. I was tuning a 1970's Steinway B this summer and
only one agraffe broke, too, but if I had installed them, I
wouldn't have called it a successful job.

Best,

Susan



At 01:19 PM 9/14/2003 -0400, you wrote:
>Susan,
>         Second question first: I usually do two passes with the thin CA
>as long as it is "draining" past the bushing. If the stuff pools up in
>my opinion it's not going to help. As to the approx amount I usually
>apply about 2 oz.  Question 2: I swabbed the hole after the pass with
>the drill bit because I scraped up the hole by driving the mangled pin
>through. Courage? Not really. 234 pins did not seize up with CA so this
>hole W/O  bronze bushing figured to react normally. Maybe the 3/0 pin
>would have been fine without the CA.
>         Tom Driscoll RPT