A. Michael Dresdner: "Your problem is the type of dado blade you are using. Adjustable dados, known colloquially as "wobble washers" are famous for tear out in plywood. If you want a clean dado in plywood, you will have to invest in a stacked dado set with outside teeth that are ground with a negative rake. A negative rake tooth will leave a smooth exit cut on the bottom of the board. Better dado stack sets, such as the Forrest Dado King, which have negative rake teeth, will give you clean dados, even in cross grain plywood."

A. Rob Johnstone: "The problem is you are cutting across a thin piece of veneer with a dado head ... oops, did I say that out loud? You would be better served by plowing dados that cross the grain on a plywood panel with a router and straight router bit. You will get much less tear out. You can do reasonably well on a table saw with a stacked dado set if you take the time to create a zero clearance insert for the cut you are making. But even then you are tempting fate."