> 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".