I'm trying to rabbet the trim to fit over the 5/16" wainscotting in the DR. I am making two cuts, stock flat 1st & on edge second. My on edge cuts aren't coming out square. Trying to make a 5/16 by 1/2 rabbet.

Any technique tips? I'm following the instructions in Cliff's tables saw book. Will a zero clearance throat plate help? Should I suck it up and lay out the $$$$$ for a dado head?

Thanks!!!