On May 23, 7:36 pm, Tom Watson wrote:
...
I usually make a dado that is in width from a
third to a half of the nominal thickness of the ply. Then I cut a
tongue in the other piece to match that width.
...
The offset tongue should be made on the bottom face of the shelf so
that the laminations of the shelf ply are loaded in compression,
rather than being under tension.

I usually make thelength of the tongue very slightly shorter than the
depth of the dado, so that the glue has somewhere to go when you clamp
up. By 'very slighty' I mean no more than the thickness of a sheet of
paper.

That makes good sense, but I would be inclined to make
the tongue more like 2/3 to 3/4 of the thickness. I don't see
any advantage to making it less.

If it is less than half, the some of the veneers that
aren't glued into the dado will be in tension.

--

FF