wood movement

Vic wrote: Recently saw pix of a telephone stand made from maple with a
mahogany top.
The top was about 18" square - couldn't tell if it was one piece or a
glue
up but it was solid wood. It sat in rabbets notched in the tops of the
legs
and was glued ( doweled?) in the corners.


With two different species of wood and the top anchored to the legs,
wouldn't that top be a candidate for splitting?


I'm thinking of building one. Usually I attach table tops in different
ways,
all so that it can move freely

Recently saw pix of a telephone stand made from maple with a mahogany
top.
The top was about 18" square - couldn't tell if it was one piece or a
glue
up but it was solid wood. It sat in rabbets notched in the tops of the
legs
and was glued ( doweled?) in the corners.


With two different species of wood and the top anchored to the legs,
wouldn't that top be a candidate for splitting?

I'm thinking of building one. Usually I attach table tops in different
ways,
all so that it can move freely

http://www.woodzone.com/properties.htm Certain species of
mahogany are pretty darn stable. An 18 inch panel may move very little.
I'd still allow for movement, just 'cause it's a good practice. Tom

"Art Greenberg" <[email protected]> wrote in message
news:[email protected]...
> On Wed, 15 Jun 2005 00:41:09 GMT, Doug Miller wrote:
>> In article <[email protected]>, "toller"
>> <[email protected]> wrote:
>> >My guidebook (Wood - The best of Fine Woodworking) says that maple moves
>> >..3/12" and mahogany moves .2/12"
>> >
>> >You said it is 18", so the differential motion is a max of 0.15".
>>
>> Check your math. 0.2 per 12" is 0.3 per 18", not 0.15.
>
Hey, is that you AlphaTurd! (No one else says I am wrong just to be
obnoxious.) Is your problem with math or reading?

You sure the corners are actually doweled?
Could have a screw in a slot to allow for
movement and capped with a plug. Screws
INTO end grain aren't the best way to go
but for a small, light table ...

charlie b

"Vic Baron" <[email protected]> wrote in message
news:[email protected]...
> Recently saw pix of a telephone stand made from maple with a mahogany top.
> The top was about 18" square - couldn't tell if it was one piece or a glue
> up but it was solid wood. It sat in rabbets notched in the tops of the
legs
> and was glued ( doweled?) in the corners.
>
> With two different species of wood and the top anchored to the legs,
> wouldn't that top be a candidate for splitting?
>
> I'm thinking of building one. Usually I attach table tops in different
ways,
> all so that it can move freely.
>

If it's doweled perpendicular to the grain on the top - safe. It moves, and
presumably floats in the groove in the other direction. The wood moves
across the grain.

"Doug Miller" <[email protected]> wrote in message
news:[email protected]...
> In article <[email protected]>, "Vic Baron"
<[email protected]> wrote:
> >Recently saw pix of a telephone stand made from maple with a mahogany
top.
> >The top was about 18" square - couldn't tell if it was one piece or a
glue
> >up but it was solid wood. It sat in rabbets notched in the tops of the
legs
> >and was glued ( doweled?) in the corners.
> >
> >With two different species of wood and the top anchored to the legs,
> >wouldn't that top be a candidate for splitting?
>
> You don't mention any aprons between the legs. If there are none - and the
> only thing connecting the legs together is the top - then I don't see how
> there could be any wood movement issues. As the top changes size, the legs
> would move with it.
>
> OTOH, if the legs *are* connected by aprons - thus fixing the legs at a
> constant separation from each other - then it's only a matter of time
before
> something breaks.


Good catch, Doug! I didn't mention that in the post. Yes, there is an apron
about 3/4 down the legs. Couldn't tell how it was attached.

Vic

In article <[email protected]>, "Vic Baron" <[email protected]> wrote:
>Recently saw pix of a telephone stand made from maple with a mahogany top.
>The top was about 18" square - couldn't tell if it was one piece or a glue
>up but it was solid wood. It sat in rabbets notched in the tops of the legs
>and was glued ( doweled?) in the corners.
>
>With two different species of wood and the top anchored to the legs,
>wouldn't that top be a candidate for splitting?

You don't mention any aprons between the legs. If there are none - and the
only thing connecting the legs together is the top - then I don't see how
there could be any wood movement issues. As the top changes size, the legs
would move with it.

OTOH, if the legs *are* connected by aprons - thus fixing the legs at a
constant separation from each other - then it's only a matter of time before
something breaks.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?

In article <[email protected]>, "toller" <[email protected]> wrote:
>My guidebook (Wood - The best of Fine Woodworking) says that maple moves
>..3/12" and mahogany moves .2/12"
>
>You said it is 18", so the differential motion is a max of 0.15".

Check your math. 0.2 per 12" is 0.3 per 18", not 0.15.

> If they
>were cut at mid-moisture, are varnished, or in an air-conditioned/humidified
>room, it could be much less.
>
>I don't see that as a problem, even if fully glued.

Even if your math was right, your conclusion is still wrong - 0.15" is more
than enough shrinkage to break a panel that's not been attached in a way that
allows it to move freely.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?

Thanx all - good points to consider!

Vic

My guidebook (Wood - The best of Fine Woodworking) says that maple moves
.3/12" and mahogany moves .2/12"

You said it is 18", so the differential motion is a max of 0.15". If they
were cut at mid-moisture, are varnished, or in an air-conditioned/humidified
room, it could be much less.

I don't see that as a problem, even if fully glued.

"Vic Baron" <[email protected]> wrote in
news:[email protected]:

...
>
> Good catch, Doug! I didn't mention that in the post. Yes, there is an
> apron about 3/4 down the legs. Couldn't tell how it was attached.

Any chance you can point us to a picture of this table?

On Wed, 15 Jun 2005 00:41:09 GMT, Doug Miller wrote:
> In article <[email protected]>, "toller" <[email protected]> wrote:
> >My guidebook (Wood - The best of Fine Woodworking) says that maple moves
> >..3/12" and mahogany moves .2/12"
> >
> >You said it is 18", so the differential motion is a max of 0.15".
>
> Check your math. 0.2 per 12" is 0.3 per 18", not 0.15.

OK. The maple is 0.3 per 12 inches, and mahogany is 0.2 per 12 inches. They
will move in the same way (both expanding, or both contracting). Doesn't that
mean that the *relative* motion over 12 inches is the *difference*, or 0.1
inch? Then, over 18 inches, it would be 0.15 inch. This assumes two pieces are
pinned at on one side, free to move at the other.

Do I misunderstand?

--
Art Greenberg
artg AT eclipse DOT net

"charlie b" <[email protected]> wrote in message
news:[email protected]...
> You sure the corners are actually doweled?
> Could have a screw in a slot to allow for
> movement and capped with a plug. Screws
> INTO end grain aren't the best way to go
> but for a small, light table ...
>
> charlie b

Good point Charlie - I "assumed" a dowel but it could be a plug.

Vic b ( no relation :) )

In article <[email protected]>, [email protected] wrote:
>On Wed, 15 Jun 2005 00:41:09 GMT, Doug Miller wrote:
>> In article <[email protected]>, "toller" <[email protected]>
> wrote:
>> >My guidebook (Wood - The best of Fine Woodworking) says that maple moves
>> >..3/12" and mahogany moves .2/12"
>> >
>> >You said it is 18", so the differential motion is a max of 0.15".
>>
>> Check your math. 0.2 per 12" is 0.3 per 18", not 0.15.
>
>OK. The maple is 0.3 per 12 inches, and mahogany is 0.2 per 12 inches. They
>will move in the same way (both expanding, or both contracting). Doesn't that
>mean that the *relative* motion over 12 inches is the *difference*, or 0.1
>inch? Then, over 18 inches, it would be 0.15 inch. This assumes two pieces are
>pinned at on one side, free to move at the other.
>
>Do I misunderstand?

My fault, I misunderstood. My main point still stands, though: 0.15" movement
is more than enough to break a joint.


--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?