tuning pins and changes in humidity

Carl Teplitski koko99@shaw.ca
Fri, 06 Sep 2002 14:51:05 -0500


Wooden doors  become hard to open and close when it has been raining for a few
days, I suspect that the gap left for the door to meet the frame has narrowed.
I would suspect that it has become smaller because the wood has taken on
moisture and expanded, thus eliminateing the necessary gap ( lost motion ) for
the door to pass the frame easily. I think if we could measure the thickness of
a piece of wood before and after an increase in humidity, we would find that
the particular piece of wood would be larger, as it has taken on moisture. Same
should hold true for a balance rail hole in a key, should get smaller, that way
holding the pin tighter. I suppose that the wood in the key has expanded in all
directions, but the one concerning us , is the expansion towards the hole. My
bathroom door only works properly for a small percentage of time during
the year. Sometimes it closes with difficulty, other times it closes very
easily. It's always when
the humidity is high or low for a prolonged period of time. I understand that
A/C takes moisture
out of the air, so it shouldn't make a difference what the humidity outside is,
but the A/C can't
usually keep up with the changes fast enough. Takes time for the wood to expand
or shrink.
How a hole could get bigger with high humidity escapes me, but stanger things
do happen,
don't they??

Carl / Winnipeg

Don wrote:

> Hi Terry,
>
> I agree tuning pins appear to become "loose" under low humidity conditions
> sometimes. There are exceptions--in particular the old Canadian Bell pianos
> appear to become loose under high humidity--or else don't change much at
> all. I still remember with some embarressment telling an owner of one Bell
> that the torque on the tuning pins would go up, and when I measured it a
> year later--it was lower. I believe it has to do with how the pinblock is
> installed and what material it is--is it a multilaminate or a solid block?
>
> I think multilaminate blocks feel looser because while the hole is getting
> smaller the wood fibres that create the resistance to turning are *also*
> getting smaller so there is less "surface" touching the tuning
> pin--therefore lower torque, even though the hole is smaller. Further the
> wood cells around the tuning pin are almost certainly "ruptured" and so
> would loose moisture very  much more quickly than the surrounding undamaged
> wood.
>
> Any other theorys of how this happens out there?
>
> At 07:23 AM 9/6/02 -0400, you wrote:
> >"Holes in wood get smaller as humidity goes down..."
> >
> >I have heard this before. Believe me, I am not trying to start an
> arguement - just trying to understand. If a hole gets smaller, then why do
> tuning pins get more loose with lower humidity?
> >
> >Terry Farrell
> >
> >----- Original Message -----
> >From: "Don" <pianotuna@accesscomm.ca>
> >To: <pianotech@ptg.org>
> >Sent: Thursday, September 05, 2002 10:51 AM
> >Subject: Re: removing key pins
> >
> >
> >> Hi Keith,
> >>
> >> Holes in wood get smaller as humidity goes down, unless there are
> >> contraints of some kind that don't allow the wood to shrink.
> >>
> >SNIP.
> >>
> >> Regards,
> >> Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T.
> >>
> >> mailto:pianotuna@accesscomm.ca
> >>
> >> http://us.geocities.com/drpt1948/
> >>
> >> 3004 Grant Rd.
> >> REGINA, SK
> >> S4S 5G7
> >> 306-352-3620 or 1-888-29t-uner
> >
> >
> >
>
> Regards,
> Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T.
>
> mailto:pianotuna@accesscomm.ca
>
> http://us.geocities.com/drpt1948/
>
> 3004 Grant Rd.
> REGINA, SK
> S4S 5G7
> 306-352-3620 or 1-888-29t-uner



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