I am very new to woodworking. This question seems so basic, that I am
probably missing the obvious.



Here is the question.



How does one create a cut that is 90 degrees from purchased lumber?





For example if I buy a 2'x 4' sheet of wood and there is not a perfect 90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?



I hope I am making sense.



Thanks



Scott

"Scott Willett" wrote in message
I am very new to woodworking. This question seems so basic, that I am
probably missing the obvious.

For example if I buy a 2'x 4' sheet of wood and there is not a perfect 90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?

For "practical" purposes the 'factory' edges of sheet goods are considered
"square" ... and are generally "square enough" for woodworking purposes.

--
www.e-woodshop.net
Last update: 11/06/04

"Swingman" wrote in message
...

"Scott Willett" wrote in message
I am very new to woodworking. This question seems so basic, that I am
probably missing the obvious.

For example if I buy a 2'x 4' sheet of wood and there is not a perfect
90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?

For "practical" purposes the 'factory' edges of sheet goods are considered
"square" ... and are generally "square enough" for woodworking purposes.

As long as you manage to get new sheet, that is. If you've got someone's
slightly trimmed bargain leftover you'll still face this problem. One way I
dealt with this was to tack an auxilliary straight edge to the sheet so it
hangs over the sheet's edge and can slide along the fence. The straigth
edge can even be a series of blocks if they line up with one another.
You're free to position this edge at any angle you like, of course. Once
you've got one straight side, use whatever tools you have (such as a square)
to line it up a second time at 90 degrees to the straight side. It's work,
but it works.

- Owen -

As a previous poster said, factory edges are considered to be straight and
this is generally true for plywood and particle board. For other materials,
seasonal movement might cause the edges to warp.. Corners are a different
issue. Plywood and particle board corners are generally "straight enough,"
as has been posted but don't count on the corners of dimensional lumber
because of the gain/loss of moisture.

Assuming that your table saw's blade and fence are accurately aligned, it
will make cuts that are precisely parallel to the edge that rides against
the fence, if the edge is perfectly straight. This is a given and something
you can count on.

For square corners (perfect right angles), it is up to you to supply the
precision. Don't rely on the miter gauge that came with your saw unless you
have verified its alignment. This is something you can do with an accurate
framing square. But the miter gauge is only useful for small workpieces
(not more than a few inches wide and a couple feet long). For squaring
larger workpieces, you will have to construct something called a crosscut
sled. You can find details of this device posted here frequently, on many
of the woodworking web sites and periodically in the woodworking magazines.

Good luck...work safely.

"Scott Willett" wrote in message
...
I am very new to woodworking. This question seems so basic, that I am
probably missing the obvious.



Here is the question.



How does one create a cut that is 90 degrees from purchased lumber?





For example if I buy a 2'x 4' sheet of wood and there is not a perfect 90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?



I hope I am making sense.



Thanks



Scott

"Owen Lawrence" wrote in message

"Swingman" wrote in message

For "practical" purposes the 'factory' edges of sheet goods are
considered
"square" ... and are generally "square enough" for woodworking purposes.

As long as you manage to get new sheet, that is. If you've got someone's
slightly trimmed bargain leftover you'll still face this problem.

?? ... then obviously you are NOT dealing with a 'factory' edge, are you?

--
www.e-woodshop.net
Last update: 11/06/04

You do the basic geometry of 3,4,5 to check for square. Or check with
a good 2 foot framing square. If it is not square then square it up.
Remember high school math where they said a square triangle has a
sides of 3 and 4 and the hypotenuse is 5. A (3) squared plus B (4)
squared equals C (5) squared. I square up with a router or circular
saw run against a straight edge on that square line I just drew.

"Scott Willett" wrote:

I am very new to woodworking. This question seems so basic, that I am
probably missing the obvious.



Here is the question.



How does one create a cut that is 90 degrees from purchased lumber?





For example if I buy a 2'x 4' sheet of wood and there is not a perfect 90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?



I hope I am making sense.



Thanks



Scott

Thanks so much for the replies. This helps. My second project is going to
be a cross cut sled. I will then use the factory edge perpendicular to the
blade. Thanks again fro answering such a basic question.

"Chuck Hoffman" wrote in message
m...
As a previous poster said, factory edges are considered to be straight and
this is generally true for plywood and particle board. For other
materials,
seasonal movement might cause the edges to warp.. Corners are a different
issue. Plywood and particle board corners are generally "straight
enough,"
as has been posted but don't count on the corners of dimensional lumber
because of the gain/loss of moisture.

Assuming that your table saw's blade and fence are accurately aligned, it
will make cuts that are precisely parallel to the edge that rides against
the fence, if the edge is perfectly straight. This is a given and
something
you can count on.

For square corners (perfect right angles), it is up to you to supply the
precision. Don't rely on the miter gauge that came with your saw unless
you
have verified its alignment. This is something you can do with an
accurate
framing square. But the miter gauge is only useful for small workpieces
(not more than a few inches wide and a couple feet long). For squaring
larger workpieces, you will have to construct something called a crosscut
sled. You can find details of this device posted here frequently, on many
of the woodworking web sites and periodically in the woodworking
magazines.

Good luck...work safely.

"Scott Willett" wrote in message
...
I am very new to woodworking. This question seems so basic, that I am
probably missing the obvious.



Here is the question.



How does one create a cut that is 90 degrees from purchased lumber?





For example if I buy a 2'x 4' sheet of wood and there is not a perfect 90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?



I hope I am making sense.



Thanks



Scott

On Sun, 2 Jan 2005 13:22:20 -0500, "Scott Willett"
wrote:

I am very new to woodworking. This question seems so basic, that I am
probably missing the obvious.



Here is the question.



How does one create a cut that is 90 degrees from purchased lumber?

Assuming your edges are straight [and you don't then need an
auxilliary piece], then you need only one 90 degree angle. That is
because a rectangle is a parallelogram, and having one angle 90 will
make the others 90 if the sides are parallel. So, make your first cut
using the miter guide [an extension, and perhaps clamping jig would
hold it better to the miter.] Mark the cuts and the miter sideas now
having a 90 degree angle.

Now cut the other two edges using the fence.

"Scott Willett" wrote in message
...
I am very new to woodworking. This question seems so basic, that I am
probably missing the obvious.


As a final check, after you cut a panel measure the diagonals. When a
panel's sides are parallel (they will be after ripping against the fence)
and the panel is square, the diagonals will be equal. I always do this
final check.

Frank

"Scott Willett" wrote in message


For example if I buy a 2'x 4' sheet of wood and there is not a perfect 90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?



I hope I am making sense.

Yes, sort of. The cut will be parallel to the fence and will be no better
or no worse than the original corners. Assuming your miter is set up
properly, you can then cut the ends and make it 90 degrees.

Also, be sure you square is really square.

"Scott Willett" wrote in message
...
that is exactly the qs that I was getting at. The fence is great but only
replicates the edge in relation to the others.

Is this what jointers do?. Do they in essence help you get that first
straight edge? Then you go from there.


Jointers take wood that is warped, twisted, cupped, wavy or otherwise not
perfect and make it flat and one edge straight. Other tools take it from
there.

Chances are, that piece of plywood is near perfect as most from the factory
are pretty good. But what if it isn't? You mentioned you have a 24 x 48
piece. Let's say you want a cut off that is perfectly square and measures
10 x 42.

Step one is to set the fence at a little over at 10 1/4". Turn on the saw
and rip the wood 10 1/4" wide. No you have one perfect edge. Set the fence
to 10", turn the board around and now cut the other edge parallel to it In
most cases you don't have to do this, but there is also a chance the sheet
goods had a ding on the side and now it is cut off.

Take the piece and cross cut it, taking off just enough of the end to be
sure it is square. Turn the board around, measure and mark the 42" you want
and make the cut. assuming your saw is set up properly, the finished piece
should be perfect. This is wood though, don't expect the same precision at
you get on a $500,000 machine making jet engine parts.

Plywood does not require a jointer and it would not be wise to use one on
it. Rough cut lumber is another story and another lesson.
--
Ed
http://pages.cthome.net/edhome/

On Sun, 2 Jan 2005 12:56:27 -0600, "Swingman" vaguely
proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

"Owen Lawrence" wrote in message

"Swingman" wrote in message

For "practical" purposes the 'factory' edges of sheet goods are
considered
"square" ... and are generally "square enough" for woodworking purposes.

As long as you manage to get new sheet, that is. If you've got someone's
slightly trimmed bargain leftover you'll still face this problem.

?? ... then obviously you are NOT dealing with a 'factory' edge, are you?

Actually the OP was talking lumber. Lots of that out there way off
straight or square.

"Old Nick" wrote in message
...


Actually the OP was talking lumber. Lots of that out there way off
straight or square.

No, he specifically mentioned sheet good. See Quote below:

For example if I buy a 2'x 4' sheet of wood and there is not a perfect 90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?

"Scott Willett" wrote in
:

How does one create a cut that is 90 degrees from purchased lumber?

For example if I buy a 2'x 4' sheet of wood and there is not a perfect
90 angle on at least one angle, will not all my cuts that are up
against my fence on the table saw be off?

Cuts against the fence just create a parallel cut edge to the fence.
So, if you are cutting sheet lumber and it's not square to begin with,
and you are only using the tablesaw fence, then the cut faces will be
likewise out of square.

Most sheet goods are cut pretty close to square, though.

To verify whether it's 90 degrees, there are a couple of ways:

1. You can use a try square that's accurate. To test whether your
square is accurate, you can do the double line test -- placing it on a
flat edge, draw a line perpindicular to the edge, flipping the square
over, and draw a second line in the same spot. A good square ought to
produce an overlaid single line.

2. Measure the diagonals on the sheet. They ought to be equal.

3. Measure a 3-4-5 square ... e.g., measure 3 units from a corner on
one side, 4 units from the same corner on an adjacent side, and test
that the marks are 5 units apart (if you're on a 2'x4' sheet you can
divide by two, e.g., 1.5', 2', 2.5')

If it's not square, then you have to square it by any one of several
methods:

1. On a tablesaw, using either a miter gauge set to 90 degres or a
crosscut sled.
2. By hand, saw along a marked square line using either a handsaw or a
bandsaw.
3. With a circular saw, using a straight fence clamped square to an
edge.

Probably lots of other ways as well ...

p.s. If you are buying at one of the Borg stores (like Home Depot) then
they will cut it the large sheets on their panel saws, which are
(usually) darned close to square.

On Mon, 03 Jan 2005 04:35:32 GMT, "Edwin Pawlowski"
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email


"Old Nick" wrote in message
.. .


Actually the OP was talking lumber. Lots of that out there way off
straight or square.

No, he specifically mentioned sheet good. See Quote below:

For example if I buy a 2'x 4' sheet of wood and there is not a perfect 90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?



and quote below

How does one create a cut that is 90 degrees from purchased lumber?

On Mon, 03 Jan 2005 04:35:32 GMT, "Edwin Pawlowski"
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

In the end I suppose it's the definition of lumber that matters. I
have always thought of lumber as timber, not made sheet goods. But a
couple of searches said "timber prepared for the building trade"
etc.....


"Old Nick" wrote in message
.. .


Actually the OP was talking lumber. Lots of that out there way off
straight or square.

No, he specifically mentioned sheet good. See Quote below:

For example if I buy a 2'x 4' sheet of wood and there is not a perfect 90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?

In article ,
says...
I am very new to woodworking. This question seems so basic, that I am
probably missing the obvious.



Here is the question.



How does one create a cut that is 90 degrees from purchased lumber?





For example if I buy a 2'x 4' sheet of wood and there is not a perfect 90
angle on at least one angle, will not all my cuts that are up against my
fence on the table saw be off?



I hope I am making sense.



Thanks



Scott


Hi Scott

From your post I have to make the assumption you are talking about sheet
goods rather then solid stock.

If you do get a sheet that is not square enough for your use and wish to
rectify the problem you can attach, double sided tape, hot glue, brads,
nails, screws, what ever is appropriate, a straight edge guide to one
side. Affix it so that when you run the piece through your table saw
with the guide against the fence you get a 90 degree side.

A router with a guide bushing or flush cut bit will also accomplish the
task.



--
Mike G.
Heirloom Woods

www.heirloom-woods.net

1. You can use a try square that's accurate. To test whether your
square is accurate, you can do the double line test -- placing it on a
flat edge, draw a line perpindicular to the edge, flipping the square
over, and draw a second line in the same spot. A good square ought to
produce an overlaid single line.

One additional method for checking your square from Euclid-

Use a compass (this can be a good string tied to a nail and a pencil
if you don't have one) to draw a circle on something. Bisect the
circle in any direction (just draw a line through the center hole made
by your compass) Mark any point on the circle, and draw a line from
where the diameter line crosses the circle to that point on each side
of the circle. The resulting angle is always 90 degrees (assuming
your geometric layout isn't sloppy, that is)

I always like this better than the 3-4-5 method or flipping the
square, myself.

Aut inveniam viam aut faciam