What is the proper thickness of a true riving knife in relation to the thickness of the blade being used?
Richard Jones: The same thickness, or a tad more, as the blade plate, which is just a hair less than the saw kerf.
Carol Reed: Riving knives are often tapered from front to back. The thickest part is slightly less than the thickness of your saw blade. In America, sheet metal splitters are the norm. I have never really measured mine, but I do know that it is marginally too thick for a thin-kerf blade.