Am I able to make a wooden Zero Clearance Insert for my tablesaw?

Question

After watching more videos about table saws I got excited and wanted to make a ZCI. When I looked at my saw the current insert gave way too much room. I had lost some wood down there on one occasion and was worried about kickback.

I took off the cheap flimsy plastic, that was starting to bow, only to find this:

^{Note: The "tab" on the right looks more recessed than it actually is}

The place where the potential ZCI would rest is between 1/8th - 3/16ths of an inch from the table (both tabs are not equal distances from the table). That would mean for a very thin piece of the board at those locations. That would likely snap when it got some pressure. Also the side of the gap facing the blade (that you cant see in this picture) tapers at a 45 degree angle. I could see sawdust or, if nothing else, debris getting in there.

All the good ZCI's that I see are one unit and I don't see how I could do that with this setup.

Can I safely make a wooden ZCI for this table saw? Would I need to mill one from metal to get the same effect?

Answer 1

You can make the bulk of the ZCI thicker for rigidity, then rabbet the edges and recess the other interference points to fit. If the existing throat plate was plastic and it was starting to bow, I wouldn't consider a wooden replacement any more dangerous.

A better alternative to wood would be UHMW plastic; otherwise metal would also be rigid enough.

For a metal throat plate it may not be necessary, but for other materials I would still suggest designing the throat plate to be thicker, if possible. From your picture, it appears the blade is well below the throat plate supports, but if there isn't much clearance it will be tricky to cut your zero-clearance slot on a thicker throat plate with rabbeted edges.

Note that if you intend to make a metal throat plate, the process is different than that for making a wood, MDF, or plastic throat plate. You will need to use a non-ferrous metal as your material, and a carbide-tipped blade with a negative rake angle to cut it. If your saw has a flesh-detective active safety system similar to SawStop or REAXX, you'll need to temporarily disable it to cut metal. A typical zero-clearance metal throat plate itself is not zero-clearance but has replaceable plastic or MDF inserts held in place with a long groove or sliding dovetail, similar to the Infinity Tools ZCI Throat Plate. If cutting the slot on a table saw, use a sled to cut all the way from the back of the throat plate to an inch or so past the furthest forward point that the blade would reach if it were fully raised.

Another solution is to forget messing with making an insert for the existing slot. Clamp a piece of plywood or MDF to the top of your saw and raise the blade--instant zero-clearance auxiliary top, similar to the one shown in How To Turn a Crappy Table Saw into a Good One. You'll lose some depth of cut capacity, but that may be an acceptable tradeoff. Remember to also extend the slot behind the blade so you can still use your riving knife.

Or you can replace the existing top entirely.

Answer 2

Another solution, for some cuts at least, is a crosscut sled; that can act as a moving near-zero-clearance plate. Here's a picture of one:

Answer 3

You can certainly make your own insert. I usually use 1/2" MDF for these, and I make several at a time so that I don't have to stop and make another when the first needs replacing.

The insert should fit in the saw with very little play. If you have an existing insert that fits well, use it as a template for your new one. Cut a blank that's slightly oversize, attach the existing insert to the blank with double-stick carpet tape (the thin stuff, not the foam tape), and use a pattern bit in your router to copy the insert's shape exactly. Mark the areas that need to be removed to make space for the blade and insert supports and use a router to quickly remove the extra material there.

Answer 4

How about solid surface? I prefer MDF, but I have a couple of solid surface plates around.

Whats nice about ss in your application is that in addition to being supremely easy to machine, it will give you an extra bit of tensile strength over those screw-down-flanges.