"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.