Zero clearance inserts and riving knife

[Steve Demuth]

Just out of curiosity, how do you all cut the slot for a riving knife when making zero clearance table saw inserts? I always manage to get the job done, but haven't hit on a method that seems right - it's just an awkward cut on a small piece of wood. Too wide to do neatly with handsaws, and a lousy fit for most power tools.

[Andy Giddings]

Last one I made, I drilled holes at the ends and joined them together with a coping saw. As long as the riving knife clears the slot, it doesn't have to be a close fit

[Mark Carlson]

I use my tablesaw with a gripper and turn the saw off when the saw has cut a large enough slot.

[John Lankers]

I make several passes with a 1/8" spiral bit in my trim router to cut the slot for the riving knife - it's a PITA, but what do you do.

[Lee Schierer]

As long as the riving knife clears the slot, it doesn't have to be a close fit

Exactly, the blade does all the cutting at the front of the insert, the back can be a wider opening with no problem.

[David Helm]

I've always done it on the band saw.

[Jim Becker]

I've always done it on the band saw.

The challenge with a riving knife is that properly installed, it's right up near the back of the blade and it moves up and down with the blade. So you have to pre-cut for it since it's not going to cut for itself. You can't just do a slot at the back of the insert like you used to be able to do with a traditional splitter than didn't move with the blade because that would result in the insert being almost spit in half once you raise the blade up to cut the zero-clearance slot for the cutter. So using a router to "drop down" on to the cut and make a captive slot for the back half of the blade and riving knife is about the best way to do it... While you "can" use the bandsaw, you'd have to glue in some material to close up the kerf at the back of the insert to keep its integrity.

[John Ziebron]

I take my riving knife out with a new, blank insert and raise the blade all the way up to make the slot for the blade. Then I put in an old, or the original insert and, with the blade up I set the new insert on top in position with the blade going through it. Then move your fence over to the right edge of the new insert. Lower the blade and move the new insert a bit toward the front of the machine. Put a scrap piece of wood on the front part of the new insert and use a clamp on the fence to hold it down. Start the saw and slowly raise the blade til the slot is almost to the rear of the insert and you are done.

[Steve Demuth]

Thanks all. As I suspected, lots of different ways, none that anybody really loves.