moisture in wool or wood.

[Richard Brekne]

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I think what Dan is trying to describe to you is simply that if
the "hole" wasnt there... then what would happen to the same area
of wood around that hole ? Why should that react differently, or
why shouldnt it ? Think about that as well when you drill your
test piece tommorrow. :)

In returning a bit to the starting point for this thread, it
seems we have reached a consensus that this problem about keybeds
and lost motion is probably more related to felt being affected
by humidity changes then to wood related concerns ??



Farrell wrote:

> Your position is consistent with many others. It is likely I
> who is hard/thick headed. I just may go out to the shop
> tomorrow morning and drill me a hole in some maple and see what
> happens. Just does not make sense to me.  :-)  I'll report
> back! Terry Farrell
> Piano Tuning & Service
> Tampa, Florida
> mfarrel2@tampabay.rr.com
>
>      ----- Original Message -----
>      From: Donald Mannino
>      To: pianotech@ptg.org
>      Sent: Monday, January 01, 2001 10:56 PM
>      Subject: Re: moisture in wool or wood.
>       Terry Farrell wrote:
>
>     > I have heard/read this many times, so I suppose it
>     > is true. But, intuitively, it makes no sense to me.
>     > If you drill a hole in a piece of wood and expose
>     > it to high humidity, the wood will swell - and
>     > swell much more across the grain (perpendicular to
>     > the grain direction) than with the grain. So why
>     > doesn't the hole tend to close a bit - on the two
>     > sides of the whole where the tangents are parallel
>     > to the wood grain.
>
>
>      Because the whole piece of wood swells, and the hole
>      becomes larger along with the piece of wood.  As I
>      wrote in my last post, imagine the plug of wood which
>      used to be in the hole.  The hole behaves the same as
>      the plug of wood that was taken out.
>
>      Do the hole and rod test.   Just pick a small piece
>      of maple or something, soak it in water for a while,
>      then drill a hole in it with a spare drill.  After
>      drilling, put the drill back in the hole, then dry
>      the wood in the oven!  That drill will be really
>      nasty tight in the hole!  You'll have to soak the
>      wood again to get it out.
>
>      There are some exceptions to this behavior:
>      1. In some situations the surface fiber swelling in
>      the hole exceeds the change in shape of the wood.
>      Key balance holes are examples of this, where high
>      humidity sometimes tightens the fit.  The wood
>      thickness is small, and the wood fibers are large and
>      sometimes made of more reactive wood.
>      2. Cross-laminated wood is more dimensionally stable,
>      and the surface fibers will again have more affect on
>      the hole size than the dimensional changes of the
>      wood.  This is what happens in pinblocks.
>      3. If the hole was made by compression of the fibers
>      instead of by drilling and removing wood (like with a
>      nail) then the grip on the nail is tighter during
>      humid times.  All surface fiber effect, no hole to
>      swell.
>
>      Don Mannino RPT
>
>
--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:Richard.Brekne@grieg.uib.no


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