I am using a zero clearance insert from Infinity Tools on a SawStop cabinet saw. It is made from aluminum, with an easily replaced MDF inner throat plate for the blade. I bought it ($110) when I saw the price of genuine SawStop zero clearance inserts ($50 each). Infinity Tools sells a wide range of similar inserts for many brands of table saw, left and right tilt. You can buy additional inner throat plates or make your own. For my saw, throat plates are 4 for $14. I bought one set with my order, but plan to make my own after that. The specs are on their website. Here is the model I bought for my SawStop:
Before I bought it, I thought about making my own insert plates. SawStop has a thin hook-shaped lockdown on the front of their inserts. At the time, I was not sure whether a homemade insert without the lock would stay down. I did not realize it when I ordered it, but the Infinity Tools product does not have a front hook. They must assume that the aluminum plate is heavy enough on its own. (In retrospect, I have seen other table saw inserts without lockdowns in the front, and they work fine.)
It is great to have different inner throat plates for different dado widths. I have them for regular kerf and thin kerf blades. I have them for different blade angles as well. I mark the back of the throat plates to remember which is which.
I like the Infinity Tools zero clearance insert and use it, but there are very
annoying issues with it:
* Anti-kickback Pawls Snag and Leave Sharp Points
The anti-kickback pawls on my table saw guard snag on the powder coated aluminum when you lower the blade. When that happens, it can leave sharp raised points that can scratch your wood. You must raise the anti-kickback pawls before lowering the blade. When I forget, I use a small file to knock down the sharp points and smooth the surface. I can live with it, but I don't have to like it. I wrote to the inventor, and he knows about the issue but says that he does not have a solution. To me, it indicates that the design focus was on dados, not regular blades. Dumb.
* Slot "Fingers" Have a "Pinch" Issue
If you use the insert with standard blades, you will need to extend the slot to the end of the throat plate so that the riving knife fits. The problem is that the throat plate has "fingers" of MDF on each side of the extended slot are thin and not well supported by the zero clearance insert. They want to curve in at the tips and potentially "pinch" the blade. That statement reads far more alarming than it really is. The aluminum zero clearance insert frame includes two screw holes underneath the ends of the fingers. In theory, you can anchor the fingers in place with screws from underneath. In practice, the MDF is too thin to take the screws, and MDF doesn't take screws very well anyway. In practice, I have found that I can ignore the issue, and it seems safe. Once the blade is raised, it holds the MDF fingers apart and keeps them in their slots. The MDF is soft enough that any rubbing goes away quickly and it doesn't interfere with the cuts.
* Included Screw Was the Wrong Size (!!)
Infinity Tools includes a single screw for holding down one of the "fingers." Unfortunately, the screw they provided was too long and it protruded through the top of the throat plate "finger". The "finger" broke off, ruining that throat plate.
I like having lots of zero clearance inserts for individual table saw blades and uses. The Infinity Tools zero clearance insert is a heavy, solid replacement for the expensive SawStop inserts. The removeable/replaceable throat plates make it economical to have as many different zero clearance inserts as you want. The throat plates are inexpensive to buy and easy to make.
Unfortunately the design has several very
annoying flaws, which should have been addressed before putting the product on the market. Despite the design flaws, I like it and use it because it is way more economical than buying many SawStop inserts. Knowing what I know now, I might have considered making my own SawStop inserts out of hardwood (or Baltic Birch?) without a front lockdown instead, but this one works for me.
* Infinity Tools ZCI Top:
Note the tiny filed-off shiny aluminum dings from the anti-kickback pawls. I cut the end of the slot using a stopped cut and the rip fence (... and a different insert). Notice how the long slot leaves only a tiny structure on the right side to keep the throat plate from "pinching" together.
* Infinity Tools ZCI Bottom:
Note the two "white" screw holes on the left side, for anchoring the throat insert "fingers" and prevent pinching. Frankly, the MDF is soft and the blade itself fills the space and keeps the "fingers" in their slots, preventing pinching from becoming a real issue, in my opinion.