Adding a riving knife to a zero-clearance insert
I just got a new tablesaw wth a riving knife, and I need to make some new zero-clearance inserts for it. But this is my first saw with a riving knife, and I don't know how to allow for that when making the inserts.
—Gary Rowe, Woodland Hills, Calif.
A zero-clearance insert is a must-have accessory for making splinter-free cuts on the tablesaw, Gary. Creating the opening for the blade is pretty straightforward. But making the opening for a riving knife is a little more involved.
Start by creating the zero-clearance slot for the blade. Lower the blade below the tablesaw top and fit the uncut insert into the opening. (If your blade doesn't drop low enough to clear the insert, try using a smaller-diameter blade, such as the outer blade from a dado set.) Clamp a scrap board over the insert, or position your rip fence so it just covers one edge of the insert (but isn't directly over the blade). Turn the saw on and slowly raise the blade through the insert to cut the opening.
To create the opening for the riving knife, reinstall your factory-supplied tablesaw insert. Raise the blade 1" or so and fit the zero-clearance insert over it and aligned with the factory insert, flush all around. Now butt the rip fence against the edge of the zero-clearance insert [opening photo] and lock it in place.
Lift the zero-clearance insert off the blade, turn the saw on, and slide the insert along the rip fence to lengthen the slot [Photo B, below]. The two cuts should align perfectly.
To prevent the slot from closing up around the blade and riving knife, glue a kerf-wide spacer into the end of the slot, making sure there's still adequate clearance for the riving knife [Photo C, below]. You now have a zero-clearance insert with a perfectly matched opening for your riving knife.