Is there any rule of thumb about how deep to cut a rabbit or dado? I
have typically cut them to half the thickness of the stock, but I'm
wondering if this may be overkill. Does the strength of the joint
increase with the depth of cut?
Certainly depth makes a difference. Cut a 1/32" deep dado then jump on
the joint. (Did it hold?) It's also possible to go too deep. Cut a
N-31/32" dado then rock the joint. (Did it hold?) When each piece is
the same thickness, I use the same rule as you: half the thickness of
The deeper you go, the stronger the joint is, but the weaker the side piece
It is all a compromise; the depth depends on the particular piece. If an
adequately deep dado will make the side too weak, I have used a shallow dado
with either biscuits or pocket screws.
This article doesn't give a 'standard' depth but it does explain how
to cut a 'standardized' dado and end up with a joint that appears easy
to cut and could be stronger in some situations.
As far as your original question I go somewhere between 1/3 to 1/2
deep depending on what 'feels' right for that joint.
> Is there any rule of thumb about how deep to cut a rabbit or dado?
Rule 1: It's a matter of convenience.
Rule 2: It's a matter of "What looks good in the shower".
Will try to explain those, what might appear to be, rather flip remarks.
Rule 1: The deeper the dado, the easier the assembly, especially if you
are single handling the project.
Keeping the dado joints assembled while getting the clamps in place can
be a hassle, unless like Norm, you grab the damn nail gun all the time.
Deeper dadoes help with this problem.
Rule 2: The depth of the dado is often chosen based on what is appealing
to the eye.
You might use a 3/8 deep dado in a 3/4 side call for case goods such as
a chest of drawers which translates into a 50% dado.
You will probably use a 1/4 deep dado for a loose fitting 1/4 drawer
bottom which translates into a 100% dado.
From a strength stand point, a dado joint is basically in shear load.
Wood has a relatively high shear load capability so you don't need much
surface area in shear to carry the load, thus the depth of a dado is
usually not critical.
Since most dado joints are secured with a modern adhesive, the member
which has the dado cut in it is reinforced by a good adhesive bond and
the part that is inserted into it, thus strength usually is not a major
Thus, my comment, "What looks good in the shower".
Partially true, should have read:
From a strength stand point, a dado joint is basically in compression
as well as a shear load.
The depth of the dado determines the surface area in compression.
Since wood has very good compression characteristics, a shallow dado
usually provides more than adequate compression area.
Considerations other than strength usually apply to the determination of
a dado depth.
Sorry for the confusion.
I know your post concerned the depth of dadoes and rabbets. Other
posts have handled your question very adequately. I add my $0.02 worth
concerning width of the dado with respect to 3/4" sheet goods which
vary all over the lot. I use the stacked dado set. I leave out one
1/8" chipper ( do install the 1/16" chipper) and add enough shims
between the blades to reach the fit you deisire. Usually a couple of
playing cards with holes cut in them surfices. You can acheive a good
fit regardless of the precise thickness of the shelf.
If the side and the shelf are of equal thickness, let's say 3/4" and
the material left by the dado forms a rectangle
3/4 x X, the ratio of that rectangle would benefit from the 1 : 1.6
In other words 0.75/1.6 = a touch under 1/2". That means letting in
the dado 1/4" (or 1/3 ).
Whilst picking nits, that really should be about .28 instead of .25
for that 'optimum look'.
When using 1" sides and shelves:
1.0/1.6 = 0.625; the dado should be 0.375 deep. Again, just a solid
Scandinavian C-hair more than 1/3.
Hey, I don't make the rules....and... to stave off a flood of nit-
pickers... it really should be 1.0 : 1.61... unless you use the
Schlebotnik Translation from Greek.
A rule of thumb seems to be 1/4 to 1/3 the thickness of the piece it's cut
into. With plywood, always try to avoid matching with a layer-joint. I use
whichever calculates easiest in my head; never had any problems. If half
the depth is needed, I'd say that means the piece isn't thick enough.
"The depth of the rabbet is usually at least one half of the width,
and the deeper it is made the less end grain will be visible. Taken
to an extreme, the depth can be such that only a thin veneer strip
remains to cover the width of the mating board, but then the joint
is almost a butt joint <Butt.aspx> since the rabbet lip no longer
provides structural support, only an aesthetic veneer to cover end
As an avid malware fighter, I checked that out but didn't see anything
untoward happening. I never left the main page though, once I saw that the
post was actually a shameless attempt to promote a business site on a
newsgroup. No probes, no pushes, no error messages in any of my logs, etc..
Perhaps the push you noticed came from a site you'd recently visited? Or
he removed whatever was there or it's buried in the inner pages or he's been
hacked. Lots of possibilities.
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