Journeyman Wood Butcher
Join Date: Feb 2008
Location: Central Illinois
a riving knife is a fixed, curved blade or shank that closely matches the contour of the table saw blade. It rides up and down with it, and it is precisely the same width as the blade. Its purpose is to keep the material tight against the rip fence, so that on the outfeed side of the blade, your material won't ride away from the fence, and have the oppertunity to climb the back of the blade and create a kickback.
As long as you have one straight edge, I'm with Cabinetman...do it on the table saw. Don't reinvent the wheel.