"Mike Marlow" wrote in message
...

"George" george@least wrote in message
...


The movement numbers are for expansion and contraction of wood fiber
with
changes in RH. If they compress against frame members and blow them
apart -
what could happen if the lower shelf isn't allowed a relief at the ends,
and
always happens with mitered solid stock, it's shaky table. If
restrained
at
either end and seeking relief from lower moisture, the board splits and
becomes unsightly.

Since it's easily prevented, it seems almost ridiculous not to
anticipate
and allow. As I said earlier, that's what woodworking is about - the
wood.




What about things like production tables, etc. then George? The
construction that toller posted the pic of is common place construction.
--

Imagine if you look you'll see this is not the case. For instance, the
lower shelf of Toller's sofa table, made with a single board of butternut,
if tightly held between the legs has a 50/50 chance of popping or loosening
the joinery as it expands beyond its ability to compress what holds it and
itself. Simple remedy is good woodworking, either pinning center on the
cross-grained rail and floating both ends with a sixteenth gap by making
oversize holes for the pocket screws, or realizing that there will be a
front - where the drawers open - and a rear, pinning flush to the leg at the
front, floating the center and rear, allowing the full eighth expansion
where it's not noticeable.

Using your example of frame and panel construction, which, I assume, you
know is designed to maintain virtually constant exterior dimension through
changes in MC, you always want to finish the panels prior to framing them,
because they can shrink and reveal bare wood at their edges. If made too
large when dry, they can find the weakest glue joint in the frame and
destroy it, or finding themselves the weaker, compression set their fiber
and develop a rattle. A competent woodworker anticipates and compensates
for all these.

I'm sure you've seen your share of tables with split tops (and chairs with
split seats) which were restrained without regard for wood movement, as well
as those with ears from having well-varnished tops and virtually finish-free
bottoms. Then there are the open corners on mitered wood ... the list is
endless. It's never been my objective in woodworking to emulate the shoddy
manufacturing processes of commercial work. Therefore I use techniques
designed to accommodate future movement.