I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Been a long time since I've done this, so can't remember if I can
route that wide a slot (3/4") -- just 1/4" deep or even less, just
enough to fit another piece of 3/4" plywood into.

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? (yuk).

thanks

mkr5000 wrote:
I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Been a long time since I've done this, so can't remember if I can
route that wide a slot (3/4") -- just 1/4" deep or even less, just
enough to fit another piece of 3/4" plywood into.

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? (yuk).

Sure assuming your router is up to the task.

Altho w/ today's ply you'll more than likely want a 23/32" bit
specifically for the purpose.

Even there you'll want to make a test cut and see if that matches the
specific piece sufficiently well.

So, all in all, you may well want to consider one of two options -- use
the narrower bit and make the cut in a couple of passes to ensure the
proper fit or,

b) cut a rabbet on the inset piece of a specific thickness and use the
proper bit size for it instead.

--

On Jan 16, 1:12*pm, mkr5000 wrote:
I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Been a long time since I've done this, so can't remember if I can
route that wide a slot (3/4") -- just 1/4" deep or even less, just
enough to fit another piece of 3/4" plywood into.

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? *(yuk).

thanks

You can buy a router bit for plywood, it's 23/32 as is 3/4 plywood.
Always good for me.

On 1/16/2010 12:12 PM, mkr5000 wrote:
I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Been a long time since I've done this, so can't remember if I can
route that wide a slot (3/4") -- just 1/4" deep or even less, just
enough to fit another piece of 3/4" plywood into.

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? (yuk).

Plywood is not 3/4" thick, and yes, there are bits that are sized for
the thickness of modern plywood, generally around 23/32 for 3/4" plywood.

However, using a jig and a piece of the actual ply to set up the jig,
can give you the exact dado size for a much better fit.

Leon has a jig that is excellent for cutting the dado to the exact fit,
but I can't remember where the file is located.

I'm sure someone will jump in here with a url to it.

--
www.e-woodshop.net
Last update: 10/22/08
KarlC@ (the obvious)

On Jan 16, 11:12*am, mkr5000 wrote:
I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Been a long time since I've done this, so can't remember if I can
route that wide a slot (3/4") -- just 1/4" deep or even less, just
enough to fit another piece of 3/4" plywood into.

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? *(yuk).

thanks

They're all right about the nominal vs. actual thickness of ply.
Bits ... here ... among other sources:

http://www.mlcswoodworking.com/shops...s/setstrgt.htm

On Sat, 16 Jan 2010 12:26:35 -0600, Swingman wrote:


Leon has a jig that is excellent for cutting the dado to the exact fit,
but I can't remember where the file is located.

I've posted a dado jig to ABPW.

"mkr5000" wrote in message
...
I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Been a long time since I've done this, so can't remember if I can
route that wide a slot (3/4") -- just 1/4" deep or even less, just
enough to fit another piece of 3/4" plywood into.

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? (yuk).

thanks

As mentioned, Leon... Oh that's me. I have designed a jig to route a slot
to be exactly the width of any thickness piece of wood that you would want
to fit the dado.

But! If you simply want to do the deed and be done you can use the
principal that my jig uses and be done with it pronto.

What you will need,

1. A "Top Bearing" straight cut pattern bit. I was able to pick up cheap
ones 1/2" in diameter for around $5-6 each a few years ago.
2. Two straight edges the length of the dado you want to cut and preferably
at least 1/2" thick. Plywood works well for this.

What to do.

1. Clamp one straight edge exactly where you want the edge of the dado to
be located.
2. Use a piece of the actual material that is going to fit in the dado and
stand it on edge next to the board you just clamped.
3. Clamp the second straight edge up next to that piece of scrap.
Basically what you end up with are two straight edges defining exactly where
the dado will be and exactly the width of the material that will fit in the
dado.
4. Remove the scrap material.
5. With the top bearing bit in your router plunge down between the straight
edges until the bearing is below the top surface of the straight edge. Use
both straight edges to guide your cut. The top bearing will ride along the
inside edges of the straight edges. You will have to make a couple passes
but do not move the straight edges until the dado is complete. When
finished the scrap should fit perfectly into the dado.

On Sat, 16 Jan 2010 12:26:35 -0600, Swingman wrote:

Plywood is not 3/4" thick, and yes, there are bits that are sized for
the thickness of modern plywood, generally around 23/32 for 3/4" plywood.

Assuming the OP is not using cabinet grade plywood you are correct.
However, if the project does involve cabinet grade plywood then a 3/4"
piece of plywood is 3/4" thick.

Gordon Shumway

Our Constitution needs to be used less as a shield
for the guilty and more as a sword for the victim.

"Gordon Shumway" wrote in message
...
On Sat, 16 Jan 2010 12:26:35 -0600, Swingman wrote:

Plywood is not 3/4" thick, and yes, there are bits that are sized for
the thickness of modern plywood, generally around 23/32 for 3/4" plywood.

Assuming the OP is not using cabinet grade plywood you are correct.
However, if the project does involve cabinet grade plywood then a 3/4"
piece of plywood is 3/4" thick.

After working with probably 50 sheets of cabinet grade 3/4" plywood in the
last few years, specifically Oak veneer plywood, I can tell you that 3/4"
cabinet grade plywood is not 3/4" thick. It is very close to 23/32" as
witnessed by my tape measure just now. At least in Texas it is that way
and had been for years.

Now I will say that recently I have seen cabinet grade 1/4" oak veneer
plywood that appeared to be a full 1/4" thick at Lowe's. I was shocked.

On 1/16/2010 2:14 PM, Gordon Shumway wrote:
On Sat, 16 Jan 2010 12:26:35 -0600, wrote:

Plywood is not 3/4" thick, and yes, there are bits that are sized for
the thickness of modern plywood, generally around 23/32 for 3/4" plywood.

Assuming the OP is not using cabinet grade plywood you are correct.
However, if the project does involve cabinet grade plywood then a 3/4"
piece of plywood is 3/4" thick.


Actually, there is no "grade" of plywood termed "cabinet grade".

--
www.e-woodshop.net
Last update: 10/22/08
KarlC@ (the obvious)

On Sat, 16 Jan 2010 14:34:13 -0600, Swingman wrote:

On 1/16/2010 2:14 PM, Gordon Shumway wrote:
On Sat, 16 Jan 2010 12:26:35 -0600, wrote:

Plywood is not 3/4" thick, and yes, there are bits that are sized for
the thickness of modern plywood, generally around 23/32 for 3/4" plywood.

Assuming the OP is not using cabinet grade plywood you are correct.
However, if the project does involve cabinet grade plywood then a 3/4"
piece of plywood is 3/4" thick.


Actually, there is no "grade" of plywood termed "cabinet grade".

Touché.

Gordon Shumway

Our Constitution needs to be used less as a shield
for the guilty and more as a sword for the victim.

On 1/16/2010 2:48 PM, Gordon Shumway wrote:
On Sat, 16 Jan 2010 14:34:13 -0600, wrote:

On 1/16/2010 2:14 PM, Gordon Shumway wrote:
On Sat, 16 Jan 2010 12:26:35 -0600, wrote:

Plywood is not 3/4" thick, and yes, there are bits that are sized for
the thickness of modern plywood, generally around 23/32 for 3/4" plywood.

Assuming the OP is not using cabinet grade plywood you are correct.
However, if the project does involve cabinet grade plywood then a 3/4"
piece of plywood is 3/4" thick.


Actually, there is no "grade" of plywood termed "cabinet grade".

Touché.

I buy a _lot_ of plywood.

As an example, the last 3/4" "hardwood plywood" I bought for a large
kitchen project was "A-1 grade" Red Oak and was just a tad over 23/32"
thick (.73) ... on a good day.

Since hardwood ply varies in thickness from lot to lot, even from the
same manufacturer, I try to buy plywood for a full sized kitchen all at
one time, and from the same stack, so that I can at least try to get an
even average thickness.

AAMOF, and Leon will verify this, I ALWAYS carry a "project dado guide"
in my truck for the projects that are currently in progress ... this is
nothing more than cutoff stile with the project dado size cut in it that
matched the thickness of the first lot of plywood bought for that
particular project:

http://www.e-woodshop.net/files/projectdado.jpg

That way, and because I make all the face frames first, I can insure
that any extra plywood that needs to be bought, from a different lot,
stack, or retailer, will actually fit the pre-cut dadoes in the face
frames already made up.

I do wish that this thickness variable wasn't in play, but it must be
taken into account when doing any production type fabrication.

--
www.e-woodshop.net
Last update: 10/22/08
KarlC@ (the obvious)

On Jan 16, 10:12*am, mkr5000 wrote:
I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Do they even make a 3/4" bit

If you can get to it, mark the slot and hog out some of the midsection
with
Forstner bits on a drill press. Then (with suitable guides clamped
to the work) route full-depth with a smaller bit (maybe 1/2").

It's easier to get the bit into the cut if you dont have to plunge-cut
(and you can use non-spiral bits), it's easier on the ears to remove
the bulk of the wood with a Forstner bit, and the heat buildup (and
wear) on the expensive router bit is minimized if you just clean up
the edges with it.

On Sat, 16 Jan 2010 10:12:33 -0800 (PST), mkr5000
wrote:

I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Been a long time since I've done this, so can't remember if I can
route that wide a slot (3/4") -- just 1/4" deep or even less, just
enough to fit another piece of 3/4" plywood into.

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? (yuk).

thanks

I wonder the length of your board. A dado blade in the table saw will
work and is accurate but you will need to chisel out the end(s).

Another method that works well... Clamp on a straight-edge and make a
hardwood strip that is taped to the straight edge. Make the first
pass with a 1/2" , remove the strip, make the second pass. You may
need 3 or 4 test tries to get the groove width you need. After the
gauge strip is correct, the setup is repeatable.

A router sled jig is another consideration, good or not depending on
your setup.

I have not seen a 3/4" straight router bit, but that sounds hefty
(probably pricey), and you may need better at a slower speed.

"Phisherman" wrote in message
...

I have not seen a 3/4" straight router bit, but that sounds hefty
(probably pricey), and you may need better at a slower speed.

I got one in a cheap set of bits at Harbor Freight awhile back. I recently
used it to make dadoes for 3/4" shelves in a bookcase made of poplar, worked
fine despite not being el primo quality.

On Sat, 16 Jan 2010 14:26:30 -0600, "Leon"
wrote:

After working with probably 50 sheets of cabinet grade 3/4" plywood in the
last few years, specifically Oak veneer plywood, I can tell you that 3/4"
cabinet grade plywood is not 3/4" thick. It is very close to 23/32" as
witnessed by my tape measure just now. At least in Texas it is that way
and had been for years.

I haven't used 50 sheets of plywood in these last years, but I can
tell you that's it's been well over 30 years since I've actually seen
plywood that's exactly 3/4" thick. Between imperial and metric
measurements, plywood in Canada has been every conceivable thickness
except 3/4".

"Swingman" wrote in message
...
On 1/16/2010 2:14 PM, Gordon Shumway wrote:
On Sat, 16 Jan 2010 12:26:35 -0600, wrote:

Plywood is not 3/4" thick, and yes, there are bits that are sized for
the thickness of modern plywood, generally around 23/32 for 3/4"
plywood.

Assuming the OP is not using cabinet grade plywood you are correct.
However, if the project does involve cabinet grade plywood then a 3/4"
piece of plywood is 3/4" thick.


Actually, there is no "grade" of plywood termed "cabinet grade".


Seems like Hardwood Products refers to cabinet quality and paint grade.

wrote:

I haven't used 50 sheets of plywood in these last years, but I can
tell you that's it's been well over 30 years since I've actually
seen
plywood that's exactly 3/4" thick. Between imperial and metric
measurements, plywood in Canada has been every conceivable thickness
except 3/4".

Around here, 5x5 Finnish birch comes off the pile in 3/4" sheets.

Lew

"Lew Hodgett" wrote in message
...

wrote:

I haven't used 50 sheets of plywood in these last years, but I can
tell you that's it's been well over 30 years since I've actually seen
plywood that's exactly 3/4" thick. Between imperial and metric
measurements, plywood in Canada has been every conceivable thickness
except 3/4".

Around here, 5x5 Finnish birch comes off the pile in 3/4" sheets.


Actual 3/4? What I get is typically closer to 18-19 mm IIRC.

"Leon" wrote:

Actual 3/4? What I get is typically closer to 18-19 mm IIRC.

Yes, actual 3/4" for 13 ply.

Also, 1/4", 1/2" (9 ply) and 5/8" (11 ply).

All bets off on 4x8 shts.

Lew

"Lew Hodgett" wrote in message
...

"Leon" wrote:

Actual 3/4? What I get is typically closer to 18-19 mm IIRC.

Yes, actual 3/4" for 13 ply.

Also, 1/4", 1/2" (9 ply) and 5/8" (11 ply).

All bets off on 4x8 shts.

Lew


Cool..All I can find is actual metric.

In article ,
mkr5000 wrote:
I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Been a long time since I've done this, so can't remember if I can
route that wide a slot (3/4") -- just 1/4" deep or even less, just
enough to fit another piece of 3/4" plywood into.

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? (yuk).


routing to that depth is _no_ problem, assuming you've got an 'adequate' router.

_I_ would use a narrower bit, and do two passes -- that way I can guarantee
an exact fit for 'whatever' thickness the nominal 3/4" ply is. I've had some
that would _not_ fit in an exact 3/4" slot and others that were loosey-goosey
in a 23/32nds slot.

The type/class of the plywood, the manufacturer, the humidity it's been exposed
to, can all make a difference. And they're all -guaranteed- to be in the
direction that you'd rather -not- have them go. wry grin

This is especially important since you've ruled out the optimum solution of
cutting a slot with a Freud 60-tooth blade. Which, as reported in another
thread herein -- according to Freud's own advertising -- "always cuts to the
correct length."

On Sun, 17 Jan 2010 19:53:53 -0700, Robert Bonomi wrote
(in article ):

In article
,
mkr5000 wrote:
I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Been a long time since I've done this, so can't remember if I can
route that wide a slot (3/4") -- just 1/4" deep or even less, just
enough to fit another piece of 3/4" plywood into.

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? (yuk).

I've gone the router route ;^)

Problem with a dado set is you must make sure the wood is _firmly_ forced
against the table or the resulting bump in the bottom of the groove will
throw everything off. Also consider cutting more than a foot into the center
of a board (side shelf supports). Either you need a really long miter gauge
or a good panel sled setup.

-Bruce

On 16 Jan, 18:12, mkr5000 wrote:

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? *(yuk).

Good guide rail, and do it in two full-depth plunges, one for each
side.

If you've got a really good guide rail, you could do it in one pass
(for 1/4" depth) or multi-depth passes, cutting both sides
simultaneously. That's a hateful process though, as the forces are
pushing you both ways simultaneously, so are far harder to control.

On 17 Jan, 14:43, "Lew Hodgett" wrote:

Around here, 5x5 Finnish birch comes off the pile in 3/4" sheets.

Same here, although it's actually just enough below 3/4" that it fits
a 3/4" dado just nicely, merely needing the edge broken. Another reson
to use the good stuff.

I don't use cheap ply much, certainly not for making cabinets out of.
Repeatable results like this are just one reason. The only ply I've
used lately has been some cheap Chinese stuff (sorry) for dy-lining
the refurbed workshop, and the thickness of that wasn't even
consistent from one end of the board to the other.

Don't try to get to the thickness of the plywood.

Cut a rabbet to a "known" thickness(1/2" is good)
and then route a slot using a 1/2" bit.

Using this method, you can really get very close
and not worry about weird sized plywood.

Actually, I would make my dado and sneak up with
the rabbet.

You can do this with a table saw or a router table.

mkr5000 wrote:
I really need to route it because I need to plunge into it and don't
want the slot the total length of the board.

Been a long time since I've done this, so can't remember if I can
route that wide a slot (3/4") -- just 1/4" deep or even less, just
enough to fit another piece of 3/4" plywood into.

Do they even make a 3/4" bit or would I have to do multiple passes for
both the width and depth? (yuk).

thanks

On Jan 18, 2:44*pm, Pat Barber wrote:
Don't try to get to the thickness of the plywood.

Cut a rabbet to a "known" thickness(1/2" is good)
and then route a slot using a 1/2" bit.

Using this method, you can really get very close
and not worry about weird sized plywood.

Actually, I would make my dado and sneak up with
the rabbet.

You can do this with a table saw or a router table.

I've used that method when I've pre-finished the components. The
rabits and dados then expose unfinished wood for the glue to bond to.

"Pat Barber" wrote in message
...
Don't try to get to the thickness of the plywood.

Cut a rabbet to a "known" thickness(1/2" is good)
and then route a slot using a 1/2" bit.

Using this method, you can really get very close
and not worry about weird sized plywood.

Actually, I would make my dado and sneak up with
the rabbet.

You can do this with a table saw or a router table.


Thank you Pat. I have been watching this same question for a long time now,
and have wondered why people make so much of such a simple thing. Measure
what you have on hand - cut to fit that measurement - glue it up. Good
Lord - why does it have to be so complicated?

--

-Mike-

"Mike Marlow" wrote:

Good Lord - why does it have to be so complicated?

Think mid "January", think "Bored", "Cabin Fever".

Lew

"Lew Hodgett" wrote in message
...

"Mike Marlow" wrote:

Good Lord - why does it have to be so complicated?

Think mid "January", think "Bored", "Cabin Fever".


****... I thought that was what sex was for. Damned, are you telling me I
have to come up with a new line to convince the wife that it's time again?


--

-Mike-

"Mike Marlow" wrote in message
...

"Pat Barber" wrote in message
...
Don't try to get to the thickness of the plywood.

Cut a rabbet to a "known" thickness(1/2" is good)
and then route a slot using a 1/2" bit.

Using this method, you can really get very close
and not worry about weird sized plywood.

Actually, I would make my dado and sneak up with
the rabbet.

You can do this with a table saw or a router table.


Thank you Pat. I have been watching this same question for a long time
now, and have wondered why people make so much of such a simple thing.
Measure what you have on hand - cut to fit that measurement - glue it up.
Good Lord - why does it have to be so complicated?

I really do not see much of an advantage doing it this way. You either cut
the dado to be a precise fit or you cut a dado a specific size then measure
and make a precice cut on the board to fit the dado. IMHO 6 of one, half
dozen of the other except if you cut the shelf to fit the dado you are
making 2 cuts instead of 1.

"Leon" wrote in message
...

"Mike Marlow" wrote in message
...

"Pat Barber" wrote in message
...
Don't try to get to the thickness of the plywood.

Cut a rabbet to a "known" thickness(1/2" is good)
and then route a slot using a 1/2" bit.

Using this method, you can really get very close
and not worry about weird sized plywood.

Actually, I would make my dado and sneak up with
the rabbet.

You can do this with a table saw or a router table.


Thank you Pat. I have been watching this same question for a long time
now, and have wondered why people make so much of such a simple thing.
Measure what you have on hand - cut to fit that measurement - glue it up.
Good Lord - why does it have to be so complicated?

I really do not see much of an advantage doing it this way. You either
cut the dado to be a precise fit or you cut a dado a specific size then
measure and make a precice cut on the board to fit the dado. IMHO 6 of
one, half dozen of the other except if you cut the shelf to fit the dado
you are making 2 cuts instead of 1.


True Leon - on the point of two cuts instead of one. For me, I make my
dado's with a router for the most part. I find it faster than installing a
dado blade and setting it up to a proper size cut. Since I don't own every
router bit known to man, I have to default to selecting the closest size,
and then making the board fit the slot. This by the way, I generally do
with a router also. Sometimes with the table saw. I'll confess that my
technique is based more on my preference for tool set up/use, and the ways
that seem more convenient to me, than anything else. I don't think I could
defend my techniques against others, as being a better way.

--

-Mike-

On Jan 16, 1:12*pm, mkr5000 wrote:
Do they even make a 3/4"

Yes, they do make a 3/4" bit designed for plywood rabbits. And, if
you're intending to do a lot of them, maybe it's worth the $$.

Otherwise, multiple passes.

On Jan 16, 1:12*pm, mkr5000 wrote:


The response "b) cut a rabbet on the inset piece of a specific
thickness and use the
proper bit size for it instead. "

is they way I did it last time. It's forgiving and hides the joint
nicely.

"Mike Marlow" wrote in message
...


True Leon - on the point of two cuts instead of one. For me, I make my
dado's with a router for the most part. I find it faster than installing
a dado blade and setting it up to a proper size cut. Since I don't own
every router bit known to man, I have to default to selecting the closest
size, and then making the board fit the slot. This by the way, I
generally do with a router also. Sometimes with the table saw. I'll
confess that my technique is based more on my preference for tool set
up/use, and the ways that seem more convenient to me, than anything else.
I don't think I could defend my techniques against others, as being a
better way.


Understood. The dado blade can be a PIA however if you route the slot like
I mentioned above you can cut an exact fit dado to any stock you wish
regardless of thickness, 5/8", 11/16", 23/32" with only a 1/2" bit. And
it only takes a couple of moments extra to use that method.
BUT we use the method which we are most comforatble with . LOL