I would make a rectangular "box" (with no top and bottom) with inside
dimensions that match your table top, i.e. 40" by 3/4". Slip it over your
tabletop, clamp it down (add some ears for clamping) and use that to guide
for your router. One setup will allow you to route both faces of your
tenon, and it should come out perfect.

Jay Knepper

"George Nachman" wrote in message
om...
Hi all,

I'm building my first tabletop with breadboard ends and have a bit of
a quandry. The tabletop is 40" wide by 60" long, and I'd like to put
3" breadboard ends on it.

From reviewing the rec.woodworking archives, most people say that the
tongue should be be between 1-2 inches long. This makes intuitive
sense, and would be aesthetically sound.

My dilemma is this: I can't find tongue-and-groove router bits that
will cut a tenon an inch deep. Best I could find was just over 1/2".
Some folks have suggested using a dado blade on the table saw to cut
the tenon, but that's unworkable for me (would be very hard to get a
precise cut--the top is just too unwieldy). The only remaining
suggestion I've seen is a straight bit with an edge guide. That would
require making two cuts, one on the top, and one on the bottom.
Ideally, those cuts would be perfectly aligned with each other. Any
error (out of parallel or one being deeper than the other) would be
very apparent. It seems remarkably difficult to get this right. Does
anyone have suggestions on how I can get this right?

Thanks,
George