Bookcases again.

Worst case: a 30" long shelf in a cabinet with all fixed shelves, all
glued and dadoed. The bookcase will have a back and a face frame.

My dado jig works nicely so far (I even whipped up a miniature
"bookcase" to try out the system http://www.flickr.com/photos/gdguarino/8311879665/
), but the pattern bit I have can only do 1/4" depth. I can't think of
a way that such a joint could easily come apart, but 3/8" "feels" like
the right depth for 3/4 ply. Should I spring for a bit with greater
cutting depth, or is 1/4" enough?

"Greg Guarino" wrote:

Bookcases again.

Worst case: a 30" long shelf in a cabinet with all fixed shelves,
all
glued and dadoed. The bookcase will have a back and a face frame.

My dado jig works nicely so far (I even whipped up a miniature
"bookcase" to try out the system
http://www.flickr.com/photos/gdguarino/8311879665/
), but the pattern bit I have can only do 1/4" depth. I can't think
of
a way that such a joint could easily come apart, but 3/8" "feels"
like
the right depth for 3/4 ply. Should I spring for a bit with greater
cutting depth, or is 1/4" enough?
---------------------------------------------------------------------
Mikey likes 1/4" deep dados for 3/4" thick shelves.

Cut shelves 1/16" short thus allowing 1/32" per side.

SFWIW, the shelves are strictly in shear at the dado end points.

As far as a router bit is concerned, don't you already have a
shelf space reserved for that new bit?

Lew

On 12/26/2012 6:51 PM, Greg Guarino wrote:
I can't think of
a way that such a joint could easily come apart, but 3/8" "feels" like
the right depth for 3/4 ply. Should I spring for a bit with greater
cutting depth, or is 1/4" enough?

Suit yourself ... almost all of the dadoes/rabbets I cut in ply are 1/4"
in depth, but 3/8" is fine in 3/4" thick ply also.

I usually use 1/4" for one overriding reason ... almost without
exception I prefer to cut all dadoes/rabbets with one machine setup, as
it fosters consistency, which fosters fit and square, and 1/4 allows
that, even with dividers and shelves that are back to back.

--
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Wood Shop: www.e-WoodShop.net
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KarlCaillouet@ (the obvious)

On 12/26/12 6:51 PM, Greg Guarino wrote:
Bookcases again.

Worst case: a 30" long shelf in a cabinet with all fixed shelves, all
glued and dadoed. The bookcase will have a back and a face frame.

My dado jig works nicely so far (I even whipped up a miniature
"bookcase" to try out the system http://www.flickr.com/photos/gdguarino/8311879665/
), but the pattern bit I have can only do 1/4" depth. I can't think of
a way that such a joint could easily come apart, but 3/8" "feels" like
the right depth for 3/4 ply. Should I spring for a bit with greater
cutting depth, or is 1/4" enough?


That's plenty deep, quit worrying so much. :-)


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

On Dec 26, 8:40*pm, "Lew Hodgett" wrote:
"Greg Guarino" wrote:
Bookcases again.

Worst case: a 30" long shelf in a cabinet with all fixed shelves,
all
glued and dadoed. The bookcase will have a back and a face frame.

My dado jig works nicely so far (I even whipped up a miniature
"bookcase" to try out the system
http://www.flickr.com/photos/gdguarino/8311879665/
), but the pattern bit I have can only do 1/4" depth. I can't think
of
a way that such a joint could easily come apart, but 3/8" "feels"
like
the right depth for 3/4 ply. Should I spring for a bit with greater
cutting depth, or is 1/4" enough?

---------------------------------------------------------------------
Mikey likes 1/4" deep dados for 3/4" thick shelves.

Cut shelves 1/16" short thus allowing 1/32" per side.

I'm not sure I get this last bit. Could you flesh it out a little?

SFWIW, the shelves are strictly in shear at the dado end points.

As far as a router bit is concerned, don't you already have a
shelf space reserved for that new bit?

You mean, inside the micro-bookshelf?

On Dec 26, 10:25*pm, -MIKE- wrote:
On 12/26/12 6:51 PM, Greg Guarino wrote:

Bookcases again.

Worst case: a 30" long shelf in a cabinet with all fixed shelves, all
glued and dadoed. The bookcase will have a back and a face frame.

My dado jig works nicely so far (I even whipped up a miniature
"bookcase" to try out the systemhttp://www.flickr.com/photos/gdguarino/8311879665/
), but the pattern bit I have can only do 1/4" depth. I can't think of
a way that such a joint could easily come apart, but 3/8" "feels" like
the right depth for 3/4 ply. Should I spring for a bit with greater
cutting depth, or is 1/4" enough?

That's plenty deep, quit worrying so much. * :-)

Glad to hear it.

I wrote:

Mikey likes 1/4" deep dados for 3/4" thick shelves.

Cut shelves 1/16" short thus allowing 1/32" per side.

"Greg Guarino" wrote:

I'm not sure I get this last bit. Could you flesh it out a little?
---------------------------------------------------------------
If the inside distance between the verticals is 30",
then using 1/4" deep dados, the distance from bottom of dado
to bottom of dado is 30-1/2" and the shelf would be 30-7/16"
allowing 1/32" per side for slop.

Lew

Lew Hodgett wrote:
I wrote:

Mikey likes 1/4" deep dados for 3/4" thick shelves.

Cut shelves 1/16" short thus allowing 1/32" per side.
"Greg Guarino" wrote:

I'm not sure I get this last bit. Could you flesh it out a little?
---------------------------------------------------------------
If the inside distance between the verticals is 30",
then using 1/4" deep dados, the distance from bottom of dado
to bottom of dado is 30-1/2" and the shelf would be 30-7/16"
allowing 1/32" per side for slop.

Lew




If instead the dados were intended for vertical inserts(structural),
would you anticipate some *slop* in forcing the joints square (and thus
rely on an additional mechanism, such as screws or dowel-joinery for
more strength). or would you not expect this to be an issue, with
plywood. If so, would you (really) add 1/32" to a 1/4" dado cut in 3/4"
ply to help account for this? My guess is no, but you raised my
curiosity about the way that you approach achieving the desired
results--exactitude in the desired height, for instance, the sort of
perfection that Swingman has preached to me about!

Bill

Greg Guarino wrote:

Bookcases again.

Worst case: a 30" long shelf in a cabinet with all fixed shelves, all
glued and dadoed. The bookcase will have a back and a face frame.

My dado jig works nicely so far (I even whipped up a miniature
"bookcase" to try out the system
http://www.flickr.com/photos/gdguarino/8311879665/ ), but the pattern
bit I have can only do 1/4" depth. I can't think of a way that such a
joint could easily come apart, but 3/8" "feels" like the right depth
for 3/4 ply. Should I spring for a bit with greater cutting depth, or
is 1/4" enough?

A quarter will be fine in 3/4 ply if your fitting a back and framed
front .

Lew Hodgett wrote:
I wrote:

Mikey likes 1/4" deep dados for 3/4" thick shelves.

Cut shelves 1/16" short thus allowing 1/32" per side.

"Greg Guarino" wrote:

I'm not sure I get this last bit. Could you flesh it out a little?
---------------------------------------------------------------
If the inside distance between the verticals is 30",
then using 1/4" deep dados, the distance from bottom of dado
to bottom of dado is 30-1/2" and the shelf would be 30-7/16"
allowing 1/32" per side for slop.

I would do that for shelves with one or two shoulders but definitely not for
shelves without shoulders. With shoulders, the distance between them end to
end determines the shelf width and you want the tongue fully within the
dado; making the tongues a skosh short assures that the shoulders will be
touching the uprights and that tells you visually when the tongues are all
the way in.

Without shoulders - I rarely do this - you want all the shelves to bottom
out so I make the dados slightly sloppy so that the shelves are an easy fit.


--

dadiOH
____________________________

Winters getting colder? Tired of the rat race?
Taxes out of hand? Maybe just ready for a change?
Check it out... http://www.floridaloghouse.net

On Dec 27, 2:40*am, "Lew Hodgett" wrote:
I wrote:
Mikey likes 1/4" deep dados for 3/4" thick shelves.

Cut shelves 1/16" short thus allowing 1/32" per side.
"Greg Guarino" wrote:

I'm not sure I get this last bit. Could you flesh it out a little?
---------------------------------------------------------------
If the inside distance between the verticals is 30",
then using 1/4" deep dados, the distance from bottom of dado
to bottom of dado is 30-1/2" and the shelf would be 30-7/16"
allowing 1/32" per side for slop.

Lew

That's what I figured you meant, and that's why I'm confused. Whatever
length I cut the shelves, won't the shelves of necessity bottom out in
the dadoes during glue-up, whether held in place by clamps or screws?
Are you suggesting that the glue will take some extra space, or will
swell the wood such that the shelves expand a hair (lengthwise)?

On 12/27/2012 2:17 AM, Bill wrote:

If instead the dados were intended for vertical inserts(structural),
would you anticipate some *slop* in forcing the joints square (and thus
rely on an additional mechanism, such as screws or dowel-joinery for
more strength). or would you not expect this to be an issue, with
plywood. If so, would you (really) add 1/32" to a 1/4" dado cut in 3/4"
ply to help account for this? My guess is no, but you raised my
curiosity about the way that you approach achieving the desired
results--exactitude in the desired height, for instance, the sort of
perfection that Swingman has preached to me about!


That is a holdover from days of yore that is no longer operable in most
situations, particularly the one under discussion.

Cut it the exact/proper project dimension and be done with it ... if you
don't batch cut, or if you use only hand tools, you will have at least a
1/32 variance in part dimensions, so it is a moot point and you best be
fitting each individual part in that case.

If you are working with modern tool and take reasonable care to properly
use consistent reference edges and proper machines techniques, and
unless there is a specific reason and/or you are simply that damned
sloppy, there is generally NO need to build in any "slop" into a
dimension in the circumstance under discussion.

*If you don't attempt perfection in every step, you will achieve it in
none!*

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://plus.google.com/114902129577517371552/posts
KarlCaillouet@ (the obvious)

On 12/27/2012 8:55 AM, Greg Guarino wrote:

... and that's why I'm confused.

Lots of "French model" advice on the Internet these days confusing you
.... beware, and bawn jyour.

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://plus.google.com/114902129577517371552/posts
KarlCaillouet@ (the obvious)

"Greg Guarino" wrote in message
...
On Dec 26, 10:25 pm, -MIKE- wrote:
On 12/26/12 6:51 PM, Greg Guarino wrote:

Bookcases again.

Worst case: a 30" long shelf in a cabinet with all fixed shelves, all
glued and dadoed. The bookcase will have a back and a face frame.

My dado jig works nicely so far (I even whipped up a miniature
"bookcase" to try out the
systemhttp://www.flickr.com/photos/gdguarino/8311879665/
), but the pattern bit I have can only do 1/4" depth. I can't think of
a way that such a joint could easily come apart, but 3/8" "feels" like
the right depth for 3/4 ply. Should I spring for a bit with greater
cutting depth, or is 1/4" enough?

That's plenty deep, quit worrying so much. :-)

Glad to hear it.

For years I have used 1/8" deep, with proper gluing these joints have held
up for over 40 years with no failure in fir ply, particle board and hardwood
plywood, some joints had a rough life in a workbench which is till going.

On Thu, 27 Dec 2012 06:55:22 -0800 (PST), Greg Guarino
wrote:

On Dec 27, 2:40*am, "Lew Hodgett" wrote:
I wrote:
Mikey likes 1/4" deep dados for 3/4" thick shelves.

Cut shelves 1/16" short thus allowing 1/32" per side.
"Greg Guarino" wrote:

I'm not sure I get this last bit. Could you flesh it out a little?
---------------------------------------------------------------
If the inside distance between the verticals is 30",
then using 1/4" deep dados, the distance from bottom of dado
to bottom of dado is 30-1/2" and the shelf would be 30-7/16"
allowing 1/32" per side for slop.

Lew

That's what I figured you meant, and that's why I'm confused. Whatever
length I cut the shelves, won't the shelves of necessity bottom out in
the dadoes during glue-up, whether held in place by clamps or screws?
Are you suggesting that the glue will take some extra space, or will
swell the wood such that the shelves expand a hair (lengthwise)?

If you ignore Lew you will be better off.

"Greg Guarino" wrote:

That's what I figured you meant, and that's why I'm confused. Whatever
length I cut the shelves, won't the shelves of necessity bottom out in
the dadoes during glue-up, whether held in place by clamps or screws?
Are you suggesting that the glue will take some extra space, or will
swell the wood such that the shelves expand a hair (lengthwise)?
--------------------------------------------------------
Not if you factor in my brain fart.G

Forgot to include description of "shoulder" on end of shelf.

See dadiOH post for explantion.

Lew

On 12/27/2012 8:55 AM, Greg Guarino wrote:
On Dec 27, 2:40 am, "Lew Hodgett" wrote:
I wrote:
Mikey likes 1/4" deep dados for 3/4" thick shelves.

Cut shelves 1/16" short thus allowing 1/32" per side.
"Greg Guarino" wrote:

I'm not sure I get this last bit. Could you flesh it out a little?
---------------------------------------------------------------
If the inside distance between the verticals is 30",
then using 1/4" deep dados, the distance from bottom of dado
to bottom of dado is 30-1/2" and the shelf would be 30-7/16"
allowing 1/32" per side for slop.

Lew

That's what I figured you meant, and that's why I'm confused. Whatever
length I cut the shelves, won't the shelves of necessity bottom out in
the dadoes during glue-up, whether held in place by clamps or screws?
Are you suggesting that the glue will take some extra space, or will
swell the wood such that the shelves expand a hair (lengthwise)?



Simple question to ask yourself. Would you force a 1/32" glue gap
between two board edges when making a wider plank? Then why on a dado?

On 12/27/2012 10:29 AM, Swingman wrote:
On 12/27/2012 8:55 AM, Greg Guarino wrote:

... and that's why I'm confused.

Lots of "French model" advice on the Internet these days confusing you
... beware, and bawn jyour.

Mair Cee Bo Koo.

On 12/27/2012 3:34 PM, Leon wrote:
On 12/27/2012 8:55 AM, Greg Guarino wrote:

That's what I figured you meant, and that's why I'm confused. Whatever
length I cut the shelves, won't the shelves of necessity bottom out in
the dadoes during glue-up, whether held in place by clamps or screws?
Are you suggesting that the glue will take some extra space, or will
swell the wood such that the shelves expand a hair (lengthwise)?



Simple question to ask yourself. Would you force a 1/32" glue gap
between two board edges when making a wider plank? Then why on a dado?

I figure myself for a fairly bright guy, and one of the things fairly
bright guys do (on those chance occasions when their egos don't get in
the way) is consider that other people may know things that we don't. So
no, I couldn't think of a reason why one would leave a gap, and in fact,
couldn't figure how it might even be accomplished. Hence my puzzlement,
and my question.

I try to weigh the advice I get here against my own sense of how things
work. I also weigh responses against each other. So fear not, my
cabinets will not be 1/16" too narrow. My mistakes are seldom that small.

On 12/28/2012 9:14 AM, Greg Guarino wrote:
On 12/27/2012 10:29 AM, Swingman wrote:
On 12/27/2012 8:55 AM, Greg Guarino wrote:

... and that's why I'm confused.

Lots of "French model" advice on the Internet these days confusing you
... beware, and bawn jyour.

Mair Cee Bo Koo.

Quick, TradeMark that before some RAP group locks onto it, then used to
name a future NFL running back ...

--
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Wood Shop: www.e-WoodShop.net
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KarlCaillouet@ (the obvious)

On 12/28/2012 9:24 AM, Greg Guarino wrote:

I try to weigh the advice I get here against my own sense of how things
work. I also weigh responses against each other.

Responses are easy to come by ... responses with actual hands-on
experience factored in, not necessarily. Some folks even try to make it
easy for you to take that into account.

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://plus.google.com/114902129577517371552/posts
KarlCaillouet@ (the obvious)

Greg Guarino wrote:


I try to weigh the advice I get here against my own sense of how
things work. I also weigh responses against each other. So fear not,
my cabinets will not be 1/16" too narrow. My mistakes are seldom that
small.

Perfect!

--

-Mike-

On 12/28/12 10:04 AM, Swingman wrote:
On 12/28/2012 9:24 AM, Greg Guarino wrote:

I try to weigh the advice I get here against my own sense of how things
work. I also weigh responses against each other.

Responses are easy to come by ... responses with actual hands-on
experience factored in, not necessarily. Some folks even try to make it
easy for you to take that into account.


+1

--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

On 12/28/2012 10:33 AM, Swingman wrote:
On 12/28/2012 9:14 AM, Greg Guarino wrote:
On 12/27/2012 10:29 AM, Swingman wrote:
On 12/27/2012 8:55 AM, Greg Guarino wrote:

... and that's why I'm confused.

Lots of "French model" advice on the Internet these days confusing you
... beware, and bawn jyour.

Mair Cee Bo Koo.

Quick, TradeMark that before some RAP group locks onto it, then used to
name a future NFL running back ...

I prefer to envision the overseer of a town in Senegal (wait for it)
"Mayor Siboku"

Greg Guarino wrote:

I prefer to envision the overseer of a town in Senegal (wait for it)
"Mayor Siboku"



--

dadiOH
____________________________

Winters getting colder? Tired of the rat race?
Taxes out of hand? Maybe just ready for a change?
Check it out... http://www.floridaloghouse.net

On 12/28/2012 10:53 AM, Greg Guarino wrote:
On 12/28/2012 10:33 AM, Swingman wrote:
On 12/28/2012 9:14 AM, Greg Guarino wrote:
On 12/27/2012 10:29 AM, Swingman wrote:
On 12/27/2012 8:55 AM, Greg Guarino wrote:

... and that's why I'm confused.

Lots of "French model" advice on the Internet these days confusing you
... beware, and bawn jyour.

Mair Cee Bo Koo.

Quick, TradeMark that before some RAP group locks onto it, then used to
name a future NFL running back ...

I prefer to envision the overseer of a town in Senegal (wait for it)
"Mayor Siboku"

LOL ... and, by the time he immigrated here that be spelled "Mercy Buckets".

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://plus.google.com/114902129577517371552/posts
KarlCaillouet@ (the obvious)

On Wednesday, December 26, 2012 6:51:13 PM UTC-6, Greg Guarino wrote:
Bookcases again.



Worst case: a 30" long shelf in a cabinet with all fixed shelves, all

glued and dadoed. The bookcase will have a back and a face frame.



My dado jig works nicely so far (I even whipped up a miniature

"bookcase" to try out the system http://www.flickr.com/photos/gdguarino/8311879665/

), but the pattern bit I have can only do 1/4" depth. I can't think of

a way that such a joint could easily come apart, but 3/8" "feels" like

the right depth for 3/4 ply. Should I spring for a bit with greater

cutting depth, or is 1/4" enough?

I usually dado to 3/8" depth in 3/4" material whether it is solid or plywood. Why? No analytical reason - that is the way I have always done it and it seems to work.

On Fri, 28 Dec 2012 14:13:20 -0800 (PST), RonB
wrote:

On Wednesday, December 26, 2012 6:51:13 PM UTC-6, Greg Guarino wrote:
Bookcases again.



Worst case: a 30" long shelf in a cabinet with all fixed shelves, all

glued and dadoed. The bookcase will have a back and a face frame.



My dado jig works nicely so far (I even whipped up a miniature

"bookcase" to try out the system http://www.flickr.com/photos/gdguarino/8311879665/

), but the pattern bit I have can only do 1/4" depth. I can't think of

a way that such a joint could easily come apart, but 3/8" "feels" like

the right depth for 3/4 ply. Should I spring for a bit with greater

cutting depth, or is 1/4" enough?

I usually dado to 3/8" depth in 3/4" material whether it is solid or plywood. Why? No analytical reason - that is the way I have always done it and it seems to work.

What do you do if there are dados on both sides? I generally use 1/4"
dados and get nervous if there are dados on both sides, even if
they're not opposing.

On 12/29/2012 1:33 PM, wrote:
What do you do if there are dados on both sides? I generally use 1/4"
dados and get nervous if there are dados on both sides, even if
they're not opposing.

I certainly treat plywood panels with opposing 1/4" dadoes with care
until they're filled with the partitions/shelves, but it is remarkable
how strong that 1/4" of plies remains.

Luckily, never had one break in all these years ... even with Murphy and
the shop dummy in attendance.

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://plus.google.com/114902129577517371552/posts
KarlCaillouet@ (the obvious)

On 12/29/2012 2:33 PM, wrote:
On Fri, 28 Dec 2012 14:13:20 -0800 (PST), RonB
wrote:

On Wednesday, December 26, 2012 6:51:13 PM UTC-6, Greg Guarino wrote:
Bookcases again.



Worst case: a 30" long shelf in a cabinet with all fixed shelves, all

glued and dadoed. The bookcase will have a back and a face frame.



My dado jig works nicely so far (I even whipped up a miniature

"bookcase" to try out the system http://www.flickr.com/photos/gdguarino/8311879665/

), but the pattern bit I have can only do 1/4" depth. I can't think of

a way that such a joint could easily come apart, but 3/8" "feels" like

the right depth for 3/4 ply. Should I spring for a bit with greater

cutting depth, or is 1/4" enough?

I usually dado to 3/8" depth in 3/4" material whether it is solid or plywood. Why? No analytical reason - that is the way I have always done it and it seems to work.

What do you do if there are dados on both sides? I generally use 1/4"
dados and get nervous if there are dados on both sides, even if
they're not opposing.

So here's the neat thing about dados, if you build them tight, you are
filling the void left behind. So while you lose a little strength, most
of it is gained back by filling it back in.

AGAIN AS LONG AS THEY ARE TIGHT, not sloppy loose.

So like Swingman said, just be careful while you are not all assembled.
Once you are, you should be good maybe a 5% loss in strength(pulling
that out of my ASS so beware).

On Sat, 29 Dec 2012 21:03:53 -0500, tiredofspam nospam.nospam.com
wrote:

On 12/29/2012 2:33 PM, wrote:
On Fri, 28 Dec 2012 14:13:20 -0800 (PST), RonB
wrote:

On Wednesday, December 26, 2012 6:51:13 PM UTC-6, Greg Guarino wrote:
Bookcases again.



Worst case: a 30" long shelf in a cabinet with all fixed shelves, all

glued and dadoed. The bookcase will have a back and a face frame.



My dado jig works nicely so far (I even whipped up a miniature

"bookcase" to try out the system http://www.flickr.com/photos/gdguarino/8311879665/

), but the pattern bit I have can only do 1/4" depth. I can't think of

a way that such a joint could easily come apart, but 3/8" "feels" like

the right depth for 3/4 ply. Should I spring for a bit with greater

cutting depth, or is 1/4" enough?

I usually dado to 3/8" depth in 3/4" material whether it is solid or plywood. Why? No analytical reason - that is the way I have always done it and it seems to work.

What do you do if there are dados on both sides? I generally use 1/4"
dados and get nervous if there are dados on both sides, even if
they're not opposing.

So here's the neat thing about dados, if you build them tight, you are
filling the void left behind. So while you lose a little strength, most
of it is gained back by filling it back in.

AGAIN AS LONG AS THEY ARE TIGHT, not sloppy loose.

So like Swingman said, just be careful while you are not all assembled.
Once you are, you should be good maybe a 5% loss in strength(pulling
that out of my ASS so beware).

Right. The problem is splitting the dados when their being cut. A
void in the wrong place can be a disaster. If you cut everything at
the same time, now you're out a piece. A real bummer.

wrote:

Right. The problem is splitting the dados when their being cut. A
void in the wrong place can be a disaster. If you cut everything at
the same time, now you're out a piece. A real bummer.
-----------------------------------------------------
That's why epoxy and micro-balloons exist.

Lew

On 12/29/2012 8:03 PM, tiredofspam wrote:

So here's the neat thing about dados, if you build them tight, you are
filling the void left behind. So while you lose a little strength, most
of it is gained back by filling it back in.

AGAIN AS LONG AS THEY ARE TIGHT, not sloppy loose.

So like Swingman said, just be careful while you are not all assembled.
Once you are, you should be good maybe a 5% loss in strength(pulling
that out of my ASS so beware).

All of what you say makes perfect sense. However, I question the last
one that you pulled out of that dark placeg

Under some circumstances you may be correct but when you stop and think
about it and consider what really happens when you use a TIGHT dado...

What I'm thinking of is along these lines.

A piece of 3/4" plywood each 5' long.

Lay it horizontal across supports either end 12" off the ground and put
a 50 lbs weight in the middle. How much deflection do you see?

Now cut a 3/4" x 3/8" dado in the midpoint of the same piece and reapply
the weight. What happens is just what we expect and fear: extreme
deflection or it breaks due to the removal of the wood.

Now do the same thing and glue another piece of 3/4" plywood into the
dado, extended vertically 12 3/8" to keep it level and apply the weight.
Now how much deflection?

I think this runs true in all applications employing a dado. Properly
cut and assembled, you will not lose strength, you will only gain
strength. Doesn't matter in which direction the forces are applied, the
dadoed assembly will always be stronger.

Unassembled? Handle like eggsg

On 12/30/2012 8:44 AM, Unquestionably Confused wrote:
On 12/29/2012 8:03 PM, tiredofspam wrote:

So here's the neat thing about dados, if you build them tight, you are
filling the void left behind. So while you lose a little strength, most
of it is gained back by filling it back in.

AGAIN AS LONG AS THEY ARE TIGHT, not sloppy loose.

So like Swingman said, just be careful while you are not all assembled.
Once you are, you should be good maybe a 5% loss in strength(pulling
that out of my ASS so beware).

All of what you say makes perfect sense. However, I question the last
one that you pulled out of that dark placeg

Under some circumstances you may be correct but when you stop and think
about it and consider what really happens when you use a TIGHT dado...

What I'm thinking of is along these lines.

A piece of 3/4" plywood each 5' long.

Lay it horizontal across supports either end 12" off the ground and put
a 50 lbs weight in the middle. How much deflection do you see?

Now cut a 3/4" x 3/8" dado in the midpoint of the same piece and reapply
the weight. What happens is just what we expect and fear: extreme
deflection or it breaks due to the removal of the wood.

Now do the same thing and glue another piece of 3/4" plywood into the
dado, extended vertically 12 3/8" to keep it level and apply the weight.
Now how much deflection?

I think this runs true in all applications employing a dado. Properly
cut and assembled, you will not lose strength, you will only gain
strength. Doesn't matter in which direction the forces are applied, the
dadoed assembly will always be stronger.

Unassembled? Handle like eggsg


I think you have assumed a dado for a vertical piece.
In this case I am considering a dado for a horizontal piece.
And I don't believe it to be stronger, but I also don't consider it to
be appreciably weaker.

In the case (you present) of that dado supporting a vertical piece, it
certainly adds to the strength.

BTW an overly tight dado will weaken the structure just as much as a
loose dado, perhaps even more, since you risk breaking the fibers of
remaining structure left, and are no relying on glue to hold it all
together, but the glue is not where the broken fibers are.


If you don't have a side rabbet plane, I would just sand or plane the
piece that fits into the dado for fitting. You can control it much better.

On 12/30/2012 11:41 AM, tiredofspam wrote:

I think you have assumed a dado for a vertical piece.
In this case I am considering a dado for a horizontal piece.
And I don't believe it to be stronger, but I also don't consider it to
be appreciably weaker.

Six of one, half dozen of the other, really. I think the point that
each of us is trying to make is that once PROPERLY assembled, any
weakening of the wood by the dado is negligible and, in most instances,
is offset by the fact that the piece is strengthened by the dado.

Okay.. Take the side of a bookcase (what you perhaps are speaking of
when you refer to the horizontal dado vs. what I stated) in that
instance a dado cut in the side to insert a fixed shelf would only
weaken the side with regard to lateral forces and then, only until the
cabinet was assembled. Once assembled, it's strength with regard to
lateral forces would be increased in every situation that I can think of
and, again, PROPERLY cut dado and assembly, would have almost no
measurable effect on the vertical strength. (i.e. Vertical forces
pushing down on the side from the top)