Making zero clearance table saw inserts can be quite easy, depending on the model of saw you own. Some of the portable saws and less expensive saws this is not the case, but the techniques used in this methodology can also be applied to other situations so there is value even if at this time, you don't own a table saw that can easily have different inserts made for it.
Watch it on Youtube: https://youtu.be/Fze5KP8F-0k
The main purpose for having a zero clearance insert is to be able to bring the saw blade close to the sides of the insert and this is done for 2 reasons ...
1) - in the case of dado blades, to make them safer to use
2) - in the case of single saw blades, to prevent very thin pieces of wood that are being cut, from dropping into the base of the saw through the opening between the saw and the insert.
Editor's note: Some will also claim that a zero clearance insert will help to prevent or at least reduce "tear-out" of wood fibers on the underside of wood that is being cut, but in all my testing I have found that zero clearance inserts do at best very little, but more often may no difference to tear-out. What does make a difference to tear-out is better quality saw blades.
To start off with you will need a good quality plywood, like Baltic Birch, or some other high quality plywood that will remain straight and flat, and in my case 1/2 plywood, with the laminate attached is slightly too thick, but I can plane this down to a proper thickness after the laminate is has been attached by planing off the underside of the insert.
First, you need to attach some laminate material to the plywood. Laminate can be cut in many different ways but the one of the quickest and easiest is to use a laminate knife.
After the laminate is cut, it needs to be glued, with contact cement to the Baltic birch plywood. The water-based versions of contact cement have far fewer fumes and odors and works just fine. Make sure you stir them well are read the instructions.
Once the laminate is attached to the plywood, next you need to cut out the outline of the insert. In my case, I made a plastic template many years ago, but it is often possible to use your existing table saw insert as a template. If it is steel, just make SURE it will not be coming into contact with the carbide edges of your router bit.
Cutting the insert blank to the correct outline is easy with a wood router table using either a trim bit or a template bit. The only real difference is whether your template will be above or below the laminate blank you will be routing, otherwise, both work well. To attach your template to the blank, I use good quality double sided tape. One of my favorites is one that is sold in most automotive supply stores, that is used for attaching the trim to cars, but don't use a lot of it, it sticks very well, as you can see in the video, I only used 4 small squares on the corners.
For this application, I used the Templating bit in my router table and carefully went around the whole area until I had a duplicate of the outside of the table saw insert.
Next, you will need to cut a slot for the table saw blade to run through but before you get to that you will need to check to make sure the insert is slightly below the level of your table saw top. If it is not, plane off, or joint off a layer thin enough that the insert will fit just slightly below the base of your table saw top.
Now is the time to apply some painters tape to the tabs that hold your table saw insert in place. On the front tabs, one-piece so painters tape is probably enough, on the back tabs I usually put 3 layers or tape (usually 2 of which will be removed later to give the insert a slight angle so the wood will not catch on the insert as it is passed by the saw blade.
On top of each of the 4 bits of painters tape, I will drop a small amount of hot melt glue then immediately drop the table saw insert onto to the glue then make sure the insert is leveled with a couple of small pieces of or wood that will make the insert level with the top of the table saw.
In a couple of minutes when the glue has hardened, you can take the insert out and remove the tape on the front and at least 2 of the pieces on each of the back tabs. This should allow the insert to sit at a slight angle that will not catch on wood being pushed through the saw blade.
Making the slot for the blade is easy, simply hold the insert down with any secure piece of wood, and wind the blade up through the insert and now you have a custom made a table saw insert with a laminate top that will give you many, many years of excellent use.
Copyright Colin Knecht