A few years ago I submitted this as a tip to one of the woodworking periodicals. I tried to be very thorough and provided pictures. Yes, I was disappointed that it was not chosen and published, but I was even more disappointed that they didn't at least send me a message back thanking me for my submission. So I thought I'd offer it up to this forum and see what you folks think about it. I will say up front that this project involves some drilling and tapping in your table saw and so it will likely not appeal to everyone. I've always had an issue with zero clearance inserts, especially for my Grizzly. Other brand saw ones are easier to find but they are all on the pricey side. And I think there are two reasons for this; the material (either hard phenolic or some kind of plastic) and the fact that they all involve labor to have four set screws installed to allow for surface adjustment. So I reversed that. I decided to drill and tap four holes, one in each of the tabs on my table saw that the insert rests on. I then put a set screw in each location. That way I can make a bunch of my own inserts and not have the laborious job of drilling and tapping and adding set screws to all those inserts. I used 1/2 inch MDF for the insert material. Here's the process. You'll want to drill the holes fairly perpendicular in the tabs. The reason for this is that it is better for the insert to sit flush on the tops of the set screws. You could drill by eye, but I used one of those little plastic drill guides with different size bushings. Speaking of size, I used 1/4-20 set screws. I just felt this is a good size for the job but you can go bigger or smaller. Cast iron drills very easy and you might want to use a shop vac if you don't want the small metal chips mixed in with your wood dust. The holes need to be chamfered on top and remember to use a little oil when running the tap through. For the inserts I used one of the metal inserts that came with the saw as a pattern and I also made some using a purchased insert as a pattern (more on that later). Take your piece of 1/2 inch MDF and rip some strips the same width as your pattern insert. Then cut them to rough length. By hand, hold down the pattern insert on each piece of MDF and draw the rounded ends. I used my miter saw set at 45 degrees to chop the corners off close to each rounded line. One at a time put a piece of double sided tape on the pattern insert and fasten it to a piece of MDF (you will, of course, have to use a new piece of tape for each insert). Then it's off to the router table with a pattern bit in place. After making as many inserts as you want set up your router table with a cove bit to make the undercut where the blade comes up. The location of the undercut will vary depending on your brand of TS. If you use a couple of stop blocks this part goes quickly. I was able to make 18 inserts in a little over an hour. You will also want to drill a hole (I used 3/4 inch) in each insert for a finger hole to easily remove the insert. Lastly, there needs to be a way to prevent the insert from rising at the back end when the blade comes up. Many manufacturers use a pin inserted at a slight angle in the back edge of the insert. I made some this way and used a section of finishing nail with the head cut off. Be sure to drill a pilot hole though. One of my pattern inserts used a nub at the back which was part of the material itself. But it needs to be pared down part way. I also made some inserts like this. MDF is a nice flat material but it is not always the same thickness from sheet to sheet. So I suggest making all your initial inserts from from the same sheet. The other advantage now is that your set screws don't have to be readjusted for each MDF insert. BTW, you should use a bit of thread locker on each set screw so it doesn't move with vibration. Remember to break the edges of each insert and chamfer the finger hole. And even like a purchased insert, if you have a riving knife you will have to extend the cut from the blade by hand to accommodate it. You can still use the metal inserts that came with your saw but you may have to readjust their set screws if they contact one of the ones you've just installed.
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Originally Posted by John Ziebron
