Mon, Feb 6, 2006, 1:16pm (dnoyeB) doth admit:
snipI set them on the basement floor leaning up against the wall.
Eventhough the cement floor is sealed, I am assuming the wood absorbed
moisture from it? Because it was not bowed when I brought it into the
basement, but its bowed now snip

Simple. You leaned it. It bowed. If you'd laid it flat, it
wouldn't have bowed.



JOAT
Don't believe everything you think.

I made part of my box for the in-wall stereo cabinet last night.

First problem is that the plywood was bowed. These started out as 4'x4'
3/4" plywood when I brought it in the house. I set them on the basement
floor leaning up against the wall. Eventhough the cement floor is
sealed, I am assuming the wood absorbed moisture from it? Because it
was not bowed when I brought it into the basement, but its bowed now
Anyway, The show must go on... The sides are 4'x1'6", the top and
bottom are 1'5.5"x1'6". The sides are still bowed. I think I will glue
a stationary shelf in the middle to remove the bowing.

Second question is, the cut at the lumberyard (1-4x8 into 2-4x4)was kind
of off since someone appearantly hit the guys saw with their vehicle.
How do I square this edge? (wouldnt fit into subaru without a cut)

third question is how does one cut 1/4" off a 2'x4' piece? When I cut
the two sides, one was about 1/4" shorter than the other. Table saw
didn't seem a good strategy since the fence cant get that close. I have
an old B&D circular saw my dad re-found in the basement of a house he
was selling. But teh motor housing is so big, It wouldnt clear the
clamps I tried to use to clamp a straight piece of wood to the panel to
cut that 1/4" off. I could have used the saber saw, but this end will
be receiving the glue and I was scared the edge would be nasty!? I
ended up just cutting another side piece on the tablesaw and it came out
better.



--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

Do you have a router? That would be your best bet. Use a flush
cutting router bit with the factory end of one of the other pieces of
plywood as a template.

Chuck

First problem is that the plywood was bowed. These started out as 4'x4'
3/4" plywood when I brought it in the house. I set them on the basement
floor leaning up against the wall. Eventhough the cement floor is
sealed, I am assuming the wood absorbed moisture from it?

You can wick moisture through concrete. I doubt this is the problem
though. The plywood was probably wetish to begin with and is warping as
it dries.

I think I will glue
a stationary shelf in the middle to remove the bowing.

That could fix it. You may want to screw through the outside panels
into the center shelf to add some strength. Even if you dado the shelf
into the uprights, the glue joint won't be that strong. If it were me,
I'd spend $30 and pick up another sheet of plywood at home depot.

How do I square this edge? (wouldnt fit into subaru without a cut)

Most of us make panel cutting sleds that ride in the miter slot.
Baring that, I'd pick up a framing square.

third question is how does one cut 1/4" off a 2'x4' piece? When I cut
the two sides, one was about 1/4" shorter than the other. Table saw
didn't seem a good strategy since the fence cant get that close.

Don't do what you're describing, it's dangerous. The way to cut 1/4"
off is to run the large piece between the fence and blade, with the
1/4" piece to the left of the blade. Trapping the 1/4" piece between
the blade and fence is a recepe for kickback. Doing it right will make
you account for the blade kerf correctly also.

brian

brianlanning wrote:
First problem is that the plywood was bowed. These started out as 4'x4'
3/4" plywood when I brought it in the house. I set them on the basement
floor leaning up against the wall. Eventhough the cement floor is
sealed, I am assuming the wood absorbed moisture from it?


You can wick moisture through concrete. I doubt this is the problem
though. The plywood was probably wetish to begin with and is warping as
it dries.



It was stored outside so that is likely true. Any way to avoid this?

I think I will glue
a stationary shelf in the middle to remove the bowing.


That could fix it. You may want to screw through the outside panels
into the center shelf to add some strength. Even if you dado the shelf
into the uprights, the glue joint won't be that strong. If it were me,
I'd spend $30 and pick up another sheet of plywood at home depot.


I keep forgetting im going to put a 1/2" backing on this box. Ill use
one clamp to bring in the bow, then glue the square back on. That
should square it up. This is getting clamp crazy though. Last night I
had planned on using 2 clamps on the top and 2 clamps on the bottom
piect, but I ended up using 4 clamps to glue in the top, and ill have to
glue in the bottom tonight since 2 clamps didnt cover the 18" too well.

If I get another sheet of plywood im scared it will just do the same
thing. perhaps I should shop at indoor lumber yards during the winter
months? Or when I bring it in, sit a bunch of weights on it for a week?



How do I square this edge? (wouldnt fit into subaru without a cut)


Most of us make panel cutting sleds that ride in the miter slot.
Baring that, I'd pick up a framing square.

I had the thought, but that would be one HUGE sled. I really need to
make a full table for this so I can get a fence out that far. Or stop
making bad cuts...



third question is how does one cut 1/4" off a 2'x4' piece? When I cut
the two sides, one was about 1/4" shorter than the other. Table saw
didn't seem a good strategy since the fence cant get that close.


Don't do what you're describing, it's dangerous. The way to cut 1/4"
off is to run the large piece between the fence and blade, with the
1/4" piece to the left of the blade. Trapping the 1/4" piece between
the blade and fence is a recepe for kickback. Doing it right will make
you account for the blade kerf correctly also.

brian



OK, so I should always put the larger piece against the fence? Or just
never put small pieces against the fence? I better read the rest of the
cutting sections in my books.


--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

On Mon, 06 Feb 2006 13:16:56 -0500, dnoyeB
wrote:

I made part of my box for the in-wall stereo cabinet last night.

First problem is that the plywood was bowed. These started out as 4'x4'
3/4" plywood when I brought it in the house. I set them on the basement
floor leaning up against the wall. Eventhough the cement floor is
sealed, I am assuming the wood absorbed moisture from it? Because it
was not bowed when I brought it into the basement, but its bowed now
Anyway, The show must go on... The sides are 4'x1'6", the top and
bottom are 1'5.5"x1'6". The sides are still bowed. I think I will glue
a stationary shelf in the middle to remove the bowing.

When the box is assembled won't this take out the bow? If not glue
some 1x2" cleats on the side that won't show.

Second question is, the cut at the lumberyard (1-4x8 into 2-4x4)was kind
of off since someone appearantly hit the guys saw with their vehicle.
How do I square this edge? (wouldnt fit into subaru without a cut)

A hand plane or jointer will square the edge.


third question is how does one cut 1/4" off a 2'x4' piece? When I cut
the two sides, one was about 1/4" shorter than the other. Table saw
didn't seem a good strategy since the fence cant get that close. I have
an old B&D circular saw my dad re-found in the basement of a house he
was selling. But teh motor housing is so big, It wouldnt clear the
clamps I tried to use to clamp a straight piece of wood to the panel to
cut that 1/4" off. I could have used the saber saw, but this end will
be receiving the glue and I was scared the edge would be nasty!? I
ended up just cutting another side piece on the tablesaw and it came out
better.

If I understand correctly, put the larger piece against the fence so
that the 1/4" is trimmed off on the other side. The side put against
the fence MUST be straight and square. Also, set up a featherboard.
Use strong (1/16" more) cuts and smooth with a plane or jointer.

Instead of clamps you can use a larger straight edge that won't hit
the motor housing or consider using double-sided carpet tape or hot
glue instead of the clamps.

Woodchuck34 wrote:
Do you have a router? That would be your best bet. Use a flush
cutting router bit with the factory end of one of the other pieces of
plywood as a template.

Chuck


I was looking at them today. My brother has a router and Ill try to
borrow that from him. That idea about using another sheet of plywood
with the factory end is genious.

--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

J T wrote:
Mon, Feb 6, 2006, 1:16pm (dnoyeB) doth admit:
snipI set them on the basement floor leaning up against the wall.
Eventhough the cement floor is sealed, I am assuming the wood absorbed
moisture from it? Because it was not bowed when I brought it into the
basement, but its bowed now snip

Simple. You leaned it. It bowed. If you'd laid it flat, it
wouldn't have bowed.



JOAT
Don't believe everything you think.


Does wood have to be so picky. I thought i was being nice bringing it
in our of the cold.

I just have this urge to get to work. Yet everytime I do I end up
realizing I should have finished reading the whole chapter. Thanks for
the tip, next time Ill lay it flat.


--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

It was stored outside so that is likely true. Any way to avoid this?

Don't store it outside? :-) Wood is like a sponge. It will aclimate
to the relative humidity in the environment. And as it dries, it will
warp and check. Plywood would just warp.

This is getting clamp crazy though

I have about $800 just in clamps, and I would use more.

If I get another sheet of plywood im scared it will just do the same
thing. perhaps I should shop at indoor lumber yards during the winter
months? Or when I bring it in, sit a bunch of weights on it for a week?

At places like home depot, they're indoors, stored flat, and stored in
large stacks which helps to keep them flat. They'll also be aclimated
to the indoor environment. I buy 3/4" 4x8 sheets of chinese birch
plywood and I never have warping problems. The thinner stuff warps
sometimes.

I had the thought, but that would be one HUGE sled. I really need to
make a full table for this so I can get a fence out that far. Or stop
making bad cuts...

Woodworking stores have this special clamp. It's made of aluminum and
comes in various lenghs. The one I have is maybe 6' long. It has a
black clamping mechanism built in. You could use a framing square to
line up a clamp like this, the clamp it in place. Then you could use a
circular saw with the shoe riding along the edge of the clamp. If you
have a really straight board or something, you could clamp it in place
and use it with teh circular saw the same way.

OK, so I should always put the larger piece against the fence? Or just
never put small pieces against the fence? I better read the rest of the
cutting sections in my books.

You want to avoid trapping things between the fence and the blade. As
the piece you're cutting gets thinner, the ganger goes up a lot. If
you're ripping a 2" piece into two 1" pieces, it's not so bad. But if
you're trying to cut less than an inch off a larger panel, it's better
to have the smaller piece falling off and the larger piece against the
fence.

brian

On Mon, 06 Feb 2006 14:55:01 -0500, dnoyeB wrote:
I just have this urge to get to work.

I've learned a lot of things about woodworking, by diving in and doing it. One
of the most important things I learned is patience. A little of that goes a
long way, and you can never have too much of it.

--
Art

I disagree. It's 3/4" plywood that's been leaning for a few days.
There's no way it should bow in that time simply from gravity.

I have pieces of plywood that have leaned against walls in my shop for
months and months and they're still straight as an arrow. On the other
hand, I've had pieces that I laid flat on a concrete floor that cupped
up in just a day or two. I've also had pieces that I kept in my humid
basement that curled up like a potato chip when one side was exposed to
the sun for a few days.

This is a moisture issue.

Josh wrote:
I disagree. It's 3/4" plywood that's been leaning for a few days.
There's no way it should bow in that time simply from gravity.

I have pieces of plywood that have leaned against walls in my shop for
months and months and they're still straight as an arrow. On the other
hand, I've had pieces that I laid flat on a concrete floor that cupped
up in just a day or two. I've also had pieces that I kept in my humid
basement that curled up like a potato chip when one side was exposed to
the sun for a few days.

This is a moisture issue.

Which way did it cup? I suspect the moisture takeup is from the air,
the board being a cooler temperature by conduction from the concrete.

The direction of the cup would tell.

er
--
email not valid

"Enoch Root" wrote in message
...
This is a moisture issue.

Which way did it cup? I suspect the moisture takeup is from the air,
the board being a cooler temperature by conduction from the concrete.

The direction of the cup would tell.

Yep, the concrete floor is colder - higher RH - and with less movement. The
corners come up from the floor.

Outdoors in the sun, same-o, only it's loss from lower RH in the heat that
makes the down side seem like it's gaining.

Enoch Root wrote:
Josh wrote:

I disagree. It's 3/4" plywood that's been leaning for a few days.
There's no way it should bow in that time simply from gravity.

I have pieces of plywood that have leaned against walls in my shop for
months and months and they're still straight as an arrow. On the other
hand, I've had pieces that I laid flat on a concrete floor that cupped
up in just a day or two. I've also had pieces that I kept in my humid
basement that curled up like a potato chip when one side was exposed to
the sun for a few days.

This is a moisture issue.


Which way did it cup? I suspect the moisture takeup is from the air,
the board being a cooler temperature by conduction from the concrete.

The direction of the cup would tell.

er

It cupped in a sagging direction, along the grain. The grain was going
vertically as the wood was standing long. But the bow was so small,
perhaps 1/2" in a 4 foot board, and they were practically vertical that
I doubt if it was really weight, but could have been a combination of
factors. The cement floor is sealed with waterproofing too.

Its true that the concerete is likely a few degrees colder than the air
but the bow was even along the whole board.

--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

I still think it's because the outward side of the plywood dried more
quickly than the side facing the wall. That would cause the outside to
shrink faster than the inside.