Function of Riving Knives for Table Saws

I can never say enough about safety on the table saw. It's a power tool that you use all the time. You wanna make sure that you've got everything in place to make the tool as safe as possible. So what I wanna talk about here are riving knives. And there's some questions about this. Not everybody really understands. What's a splitter? What's a riving knife? Let's talk about a splitter first. Behind the table saw are blade. Now, I've got this one on plug, so I can get up close and personal to the blade here. Behind the blade, I wanna have a piece of steel. I want that steel there, so that as my material comes by, that piece of steel can fill into the curve made by the saw blade. Couple of reasons for this safety is huge. If I show you this board, this is a piece of pine. And as I cut this, what happened is that you can see down at this end, this is the standard curve for the saw blade on this saw. Out here, look at how much wider it is. So as I cut into this, the board is reacting and it's opening up. Sometimes they open up, sometimes they close. They pinch back in. In the absence of some form of splitter or riving knife behind the blade, when they pinch back in, they can actually pinch here on the back of the blade. And as they pinch on the back of the blade, the blade is doing this, causes the board to climb up off the table. And pretty soon you're eating wood for dinner, it throws the board back at you. It's called kickback on the table saw. So along with that piece of steel which acts as a wedge to fill in the curve, commonly, you'll see these on the splitter. These are called pawls or anti-kickback pawls. It's a one-way deal. Once these are engaged on here, the wood can pass under, but the teeth on them would prevent them from coming back. So in this case, we've kind of got a belt and suspenders because the splitter itself, the riving knife, is helping prevent the wood from pinching in. Even if something does go astray, we've got our anti-kickback pawls on here, that are gonna prevent the wood from being able to travel back toward the operator. None of this takes the place of a guard. So you should always have the guard in place on the saw whenever you can use it. Let's come back to that riving knife idea. We've talked about splitters. Now, if we were just looking at a splitter here, what would happen when I lower the saw blade, is that the blade itself would get progressively further from this shark-fin. What happens there, is that this gap behind the blade, between the blade and the fin, opens up bigger and bigger and bigger. And what can happen then, is that we're cutting a piece. It starts to pinch in on itself, it gets here behind the blade, but in front of the splitter pinches in, you can't continue forward, because now that pinch has closed up and it's actually bumping against the front of the splitter. One of the great things about a riving knife is that, I can keep it in close proximity to the blade, because that's how they're set up to work, regardless of how high or how low a blade is in the table it's always equidistant. The other thing that's nice about the splitter, when it's set up like this, like a riving knife, is that I can set it so that I can get the riving knife down here. In this position, I can make that curve cut. And again, it's not cutting all the way through. As the board comes past the saw blade, it's gonna travel on either side of my riving knife, again, supporting the cut, making sure that that curve, that slot, can't pinch back in on my saw blade. So riving knives have been around for a long time. Only, fairly recently become a big deal here in the United States. And it's great to see them even on portable saws, like this one here.