Best way to cut dado across width of plywood sheet

[stoppy]

I’m working on a rolling lumber cart and I need to cut a dado the full width of a sheet of plywood. I figured the easiest way would be to clamp pieces of wood and slide the router between them rather than making a jig like was described in the bookcase thread. Am I right in still thinking that?

[sweensdv2]

That's probably how I would do it. Simple, easy and quick.

[K. L. McReynolds]

First time I did that, I used plywood router bits.

The second and subsequent times, I used regular bits and made two passes.

Why? Plywood is almost never the thickness of the dedicated plywood bits---either thinner or thicker. Making one pass and the ply is floppy sucks!!

[mike4244]

I’m working on a rolling lumber cart and I need to cut a dado the full width of a sheet of plywood. I figured the easiest way would be to clamp pieces of wood and slide the router between them rather than making a jig like was described in the bookcase thread. Am I right in still thinking that?

I have done a lot of wide width dados and rabbits. I found the easiest way for me was to elevate the sheet vertically about 18". I use one straight edge and position it to the right of the dado. I set the depth and rout from the top of the sheet down. One pass for a 3/8" or less depth of cut.
I lean the sheet against the wall as it sits on two low trestles with a scrap screwed to each trestle to keep the sheet from kicking out. 
Very difficult for me to reach across a sheet 4'-0" wide, that's why I prefer to rout from top to bottom.
mike

[JohnnyEgo]

I run continuous dadoes down the length of plywood sheets fairly frequently, so that I know I will end up with the dado in consistent locations when I subsequently chop them up. I use the back-side of a long Festool track that I clamp my Dewalt 618 to. I also follow the same approach as K.L in doing a two pass cut with a narrower bit, because plywood sizes are truly random these days.

[fredhargis]

One more vote for the 2 pass method, since plywood is now variable thickness. As for technique, anything mentioned above will work very well including your original approach.

[bhh]

The best way I've seen is to make two wooden "T-squares" and put one on each edge of the piece you want to dado.   Insert the plywood you want to fit in the dado and slide them together.   Then put a top-bearing flush cutting router bit a size smaller than the plywood (e.g., 1/2" for a 'nominal' 3/4" ply).   Run up one side and back the other (left to right on the bearing side).   The T-square provides accurate dado width and provides some protection against chip-out.

[handi]

I built a Saw track and included a sled for the router. The router sled can be adjusted in and out to align bits of different sizes exactly to the edge. I do have the plans for sale on my site.

But for a one-off, your two board plan is perfectly adequate.

[Halfathumb]

If your outfeed table for the TS is long enough. That's the way I do it. Not bragging, just glad I have the space & outfeed support. But the way you describe is good also.

[stoppy]

Out feed table is not long enough. When I get a little better at this flat stock wood working I’ll remedy that.