Adding a riving knife to a zero-clearance insert

Zero-clearance board on top of tablesaw with blade protruding threw slot in board.
Use the blade to position the zero-clearance insert, then bring up the rip fence until it just kisses the edge of the insert.

Q:

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:

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.

Tablesaw is cutting the end of the zero-clearance insert board to join earlier cut.
Guide the insert along the rip fence until you reach the previously cut opening. Turn the saw off and let the blade come to a stop before backing out of the cut.

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.

Boards being clamped together that have a spacer between then to allow for an opening in insert.

Zero-clearance board on top of tablesaw with blade protruding threw slot in board.
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